東北大学研究者紹介

オハラ　タク

小原　拓

Taku Ohara

所属

流体科学研究所　ナノ流動研究部門　分子熱流動研究分野

職名

教授

学位

工学博士（東京大学）

researchmap

https://researchmap.jp/read0168550

J-GLOBAL ID

200901060199729129

経歴 3

2006年1月～継続中

東北大学　流体科学研究所　教授
1995年4月～ 2005年12月

東北大学　流体科学研究所　助教授
1991年4月～ 1995年3月

東北大学　流体科学研究所　助手

学歴 3

東京大学　工学系研究科　機械工学専攻

1986年4月～ 1991年3月
東京大学　工学部　機械工学科

1984年4月～ 1986年3月
東京大学　教養学部　理科Ⅰ類

1981年4月～ 1984年3月

委員歴 70

日本機械学会　理事

2022年4月～継続中
International Journal of Heat and Mass Transfer　Editor

2019年1月～継続中
Asian Union of Thermal Science and Engineering　Executive Board Member

2015年～継続中
日本伝熱学会　副会長

2022年5月～ 2023年5月
Asian Union of Thermal Science and Engineering　Secretary in General

2020年10月～ 2022年9月
日本機械学会熱工学部門　部門長

2021年4月～ 2022年3月
日本機械学会熱工学部門　副部門長

2020年4月～ 2021年3月
日本熱物性学会　会長

2020年1月～ 2020年12月
日本流体力学会　理事

2018年4月～ 2020年2月
日本伝熱学会　理事

2015年～ 2017年
JSME Mechanical Engineering Letters　副編集委員長

2015年～ 2017年
日本熱物性学会　副会長（事務局）

2014年1月～ 2016年12月
日本機械学会東北支部　庶務幹事

2013年～ 2015年
日本伝熱学会　東北支部副支部長

2012年～ 2014年
日本伝熱学会　理事

2012年～ 2014年
日本機械学会　熱工学部門運営委員

2012年～ 2014年
Scientific World Journal　Editorial Board Member

2012年～ 2014年
日本伝熱学会　東北支部副支部長

2012年～ 2014年
日本機械学会　熱工学部門運営委員

2012年～ 2014年
日本機械学会　東北支部幹事

2012年～ 2013年
日本機械学会　東北支部幹事

2012年～ 2013年
日本流体力学会　代議員

2011年～ 2012年
日本機械学会　表彰部会委員

2011年～ 2012年
日本流体力学会　代議員

2011年～ 2012年
日本機械学会　表彰部会委員

2011年～ 2012年
日本伝熱学会　評議員

2010年～ 2012年
日本伝熱学会・編修委員会　委員

2010年～ 2012年
ISRN Mechanical Engineering　エディター

2010年～ 2012年
日本伝熱学会　評議員

2010年～ 2012年
日本伝熱学会・編修委員会　委員

2010年～ 2012年
日本機械学会　商議員

2010年～ 2011年
日本機械学会　商議員

2010年～ 2011年
日本伝熱学会Thermal Science and Engineering編集委員会　委員（Editor）

2005年～ 2011年
日本伝熱学会Thermal Science and Engineering編集委員会　委員（Editor）

2005年～ 2011年
日本機械学会計算力学部門運営委員会　委員

2009年～ 2010年
日本機械学会・計算力学部門運営委員会　委員

2009年～ 2010年
日本機械学会計算力学部門運営委員会　委員

2009年～ 2010年
日本機械学会・計算力学部門運営委員会　委員

2009年～ 2010年
日本機械学会学会誌編集部会　委員

2008年～ 2009年
日本機械学会学会誌編集部会　委員

2008年～ 2009年
日本機械学会熱工学部門Journal of Thermal Science and Technology編集委員会　委員

2005年～ 2009年
Editorial Board, Journal of Thermal Science and Technology　Editor

2005年～ 2009年
日本機械学会熱工学部門運営委員会　委員

2007年～ 2008年
日本機械学会熱工学部門運営委員会　委員

2007年～ 2008年
日本機械学会熱工学部門出版委員会　委員

2006年～ 2007年
日本機械学会熱工学部門出版委員会　委員

2006年～ 2007年
日本熱物性学会　評議員

2003年～ 2005年
日本熱物性学会　評議員

2003年～ 2005年
日本伝熱学会　評議員

2002年～ 2005年
日本伝熱学会　評議員

2002年～ 2005年
日本機械学会　代表会員

2012年～
日本機械学会　代表会員

2012年～
Scientific World Journal　Editorial Board Member

2012年～
日本機械学会・熱工学部門学会賞委員会　委員長

2010年～
日本機械学会・学会賞委員会　委員

2010年～
日本機械学会・熱工学部門学会賞委員会　委員長

2010年～
日本機械学会・学会賞委員会　委員

2010年～
ISRN Mechanical Engineering　Editor

2010年～
日本機械学会熱工学部門学会賞委員会　委員

2009年～
日本機械学会熱工学部門学会賞委員会　委員

2009年～
日本伝熱学会・表彰選考委員会　委員

2008年～
日本伝熱学会・表彰選考委員会　委員

2008年～
日本機械学会熱工学部門学会賞委員会　委員

2007年～
日本機械学会熱工学部門学会賞委員会　委員

2007年～
日本伝熱学会表彰選考委員会　委員

2005年～
日本機械学会熱工学部門学会賞委員会　幹事

2005年～
日本伝熱学会表彰選考委員会　委員

2005年～
日本機械学会熱工学部門学会賞委員会　幹事

2005年～
日本機械学会熱工学部門年鑑委員会　委員長

2004年～
日本機械学会熱工学部門年鑑委員会　委員長

2004年～

︎全件表示 ︎最初の5件までを表示

所属学協会 28

日本流体力学会
日本熱物性学会
日本伝熱学会
日本機械学会
日本機械学会熱工学部門年鑑委員会
日本伝熱学会表彰選考委員会
日本機械学会熱工学部門出版委員会
日本機械学会熱工学部門運営委員会
日本伝熱学会・表彰選考委員会
Journal of Thermal Science and Technology
Editorial Board
日本機械学会学会誌編集部会
日本機械学会熱工学部門学会賞委員会
日本機械学会計算力学部門運営委員会
日本機械学会・計算力学部門運営委員会
日本機械学会・熱工学部門学会賞委員会
日本機械学会・学会賞委員会
日本伝熱学会Thermal Science and Engineering編集委員会
日本伝熱学会・編修委員会
日本機械学会東北支部
Japan Society of Thermophysical Engineering
ISRN Mechanical Engineering
Scientific World Journal
JSME Mechanical Engineering Letters
Asian Union of Thermal Science and Engineering
日本流体力学会
日本熱物性学会
日本伝熱学会

︎全件表示 ︎最初の5件までを表示

研究キーワード 10

熱抵抗
固液界面
分子動力学
エネルギー
流体
ナノスケール
Molecular Dynamics
Energy
Fluid
Nano-scale

研究分野 2

ものづくり技術（機械・電気電子・化学工学） / 流体工学 /
ものづくり技術（機械・電気電子・化学工学） / 熱工学 /

受賞 15

Fellow

2021年7月　Asian Union of Thermal Science and Engineering
学術賞

2019年5月　日本伝熱学会　分子スケール熱伝搬解析に基づく液体の熱伝導メカニズムと分子構造との関係の解明
フェロー

2019年2月　日本流体力学会
日本機械学会創立120周年記念功労表彰

2017年11月
日本機械学会熱工学部門講演論文表彰

2014年3月　架橋を有するアモルファスポリマー材料における熱輸送機構の解明
日本伝熱学会学術賞

2013年5月　脂質二重膜の構造と熱伝導特性
日本機械学会フェロー

2012年
日本熱物性学会論文賞

2011年11月　長鎖ポリマー液体の熱伝導率：分子間及び分子内エネルギー伝搬の寄与についての分子動力学的研究
日本機械学会熱工学部門賞（業績賞）

2011年3月　熱工学、とりわけ分子熱流体、界面、液膜流などの分野における顕著な研究業績
日本機械学会論文賞

2009年4月　固体壁面間でせん断を受ける極薄液膜の分子動力学的研究（固液界面におけるエネルギー・運動量伝搬に及ぼす固体結晶面の影響）
日本機械学会熱工学部門講演論文表彰

2009年3月　SAM－溶媒界面における界面熱抵抗特性の分子論的研究
日本伝熱学会学術賞

2004年5月　バイオ分子解析のためのラチェット式電気泳動マイクロチップ
日本流体力学会竜門賞

2001年2月　Intermolecular energy transfer in liquid water and its contribution to heat conduction: A molecular dynamics study
日本機械学会論文賞

1993年4月　回転円盤上の薄膜形成
機器研究会研究奨励賞

1993年1月　回転円盤上の薄膜形成

︎全件表示 ︎最初の5件までを表示

論文 234

Molecular dynamics study on the effect of surface ionization on the interfacial heat transfer between silica and water 査読有り

Haiyi Sun, Donatas Surblys, Shukai Cheng, Taku Ohara

Applied Thermal Engineering　244　122762-122762　2024年5月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.applthermaleng.2024.122762 　

ISSN：1359-4311
A molecular dynamics study on the solid–liquid polymer interface: insight into the effect of surface roughness scale and polymer chain length on interfacial thermal resistance 査読有り

Qing-Yao Luo, Donatas Surblys, Hiroki Matsubara, Taku Ohara

Molecular Physics　2024年2月26日
出版者・発行元：Informa UK Limited
DOI： 10.1080/00268976.2024.2321311 　

ISSN：0026-8976

eISSN：1362-3028
Degrees of freedom of atoms in a rigid molecule for local temperature calculation in molecular dynamics simulation 査読有り

Hiroki Matsubara, Donatas Surblys, Taku Ohara

Molecular Simulation　49　(13-14)　1365-1372　2023年7月17日
出版者・発行元：Informa UK Limited
DOI： 10.1080/08927022.2023.2232466 　

ISSN：0892-7022

eISSN：1029-0435
Molecular dynamics study on the role of hydrogen bonds and interfacial heat transfer between diverse silica surfaces and organic liquids 査読有り

Haiyi Sun, Donatas Surblys, Hiroki Matsubara, Taku Ohara

International Journal of Heat and Mass Transfer　208　14091　2023年3月

DOI： 10.1016/j.ijheatmasstransfer.2023.124091 　
Molecular Dynamics Study of Energy Transport Mechanism in Nanofluids: Spatial and Component Decompositions of Effective Thermal Conductivity 査読有り

Yoshitaka Ueki, Yukihiro Yamamoto, Taku Ohara, Masahiko Shibahara

International Journal of Heat and Mass Transfer　202　123746-123746　2023年3月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.ijheatmasstransfer.2022.123746 　

ISSN：0017-9310
Enhancing mechanism of CNT-CNT interface by metal nanoparticle and nanowire effect on the inside and outside of CNT 査読有り

Hanying Zou, Yanhui Feng, Xinxin Zhang, Taku Ohara, Lin Qiu

International Journal of Thermal Sciences　185　108094-108094　2023年3月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.ijthermalsci.2022.108094 　

ISSN：1290-0729
One-dimensional harmonic chain model of vibration-mode matching in solid-liquid interfacial thermal transport 査読有り

Hiroki Matsubara, Donatas Surblys, Taku Ohara

Physical Review E　107　(2)　024103　2023年2月1日
出版者・発行元：American Physical Society (APS)
DOI： 10.1103/physreve.107.024103 　

ISSN：2470-0045

eISSN：2470-0053
Molecular dynamics study on the thermal conductivity of a single polyethylene chain: Strain dependence and potential models’ effect 査読有り

Tsuyoshi Ito, Hiroki Matsubara, Donatas Surblys, Taku Ohara

AIP Advances　12　(10)　105223-105223　2022年10月1日
出版者・発行元：AIP Publishing
DOI： 10.1063/5.0095975 　

eISSN：2158-3226

詳細を見る詳細を閉じる

The thermal conductivity of a single polymer chain, which is an important factor in the rational design of polymer-based thermal management materials, is strongly affected by the strain state of the chain. In the present study, using non-equilibrium molecular dynamics simulations, the thermal conductivity of a single polyethylene chain, representing a typical polymer chain, was calculated as a function of strain. To investigate the effect of different modeling of covalent bonds, the results were compared for reactive and non-reactive potential models, the AIREBO and NERD potentials, respectively. When the strain ε was as small as ε < −0.03, i.e., under slight compression, the thermal conductivity values were similar regardless of the potential model and increased with increasing strain. However, the two potential models showed qualitatively different behaviors for larger strains up to ε < 0.15: the thermal conductivity calculated by the non-reactive potential continually grows with increasing strain, whereas that by the reactive potential model is saturated. The analysis of internal stress and vibrational density of states suggested that the saturation behavior is due to the weakening of the covalent bond force as the C–C bond elongates, and thus, the result of the reactive model is likely more realistic. However, for ε > 0.1, the reactive potential also produced unphysical results due to the effect of the switching function, describing the formation and breaking of covalent bonds. The present results indicate that careful selection of the potential model and deformation range is necessary when investigating the properties of polymers under tensile strain.
Computing the Work of Solid–Liquid Adhesion in Systems with Damped Coulomb Interactions via Molecular Dynamics: Approaches and Insights 査読有り

Donatas Surblys, Florian Müller-Plathe, Taku Ohara

The Journal of Physical Chemistry A　126　(32)　5506-5516　2022年8月18日
出版者・発行元：American Chemical Society (ACS)
DOI： 10.1021/acs.jpca.2c03934 　

ISSN：1089-5639

eISSN：1520-5215
Prediction of nanoscale thermal transport and adsorption of liquid containing surfactant at solid–liquid interface via deep learning 国際誌査読有り

Yuting Guo, Gaoyang Li, Takuya Mabuchi, Donatas Surblys, Taku Ohara, Takashi Tokumasu

Journal of Colloid and Interface Science　613　587-596　2022年5月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.jcis.2022.01.037 　

ISSN：0021-9797

詳細を見る詳細を閉じる

HYPOTHESIS: Recent advances in deep learning (DL) have enabled high level of real-time prediction of thermophysical properties of materials. On the other hand, molecular dynamics (MD) have been long used as a numerical microscope to observe detailed interfacial conditions but require separate simulations that are computationally costly. Hence, it should be possible to combine MD and DL to obtain high resolution interfacial details at a low computational cost. EXPERIMENT: We proposed a novel DL encoding-decoding convolutional neural network (CNN) coupled with MD to realize the mapping from micro solid-liquid interface geometry to molecular temperature and density distribution of liquid containing surfactant. A multi-nanoscale optimization scheme was further proposed to reduce the uncertainty of DL prediction at the expense of local details to obtain more resilient predictors. FINDINGS: The statistical results showed that the proposed CNN had high prediction accuracy and could reproduce the heat transfer and adsorption phenomena under the influence of various factors including liquid composition, wettability, and solid surface roughness, while the computational efficiency was greatly improved. Our DL method with the support of multi-nanoscale learning strategies can achieve the fast and accurate visualization and prediction of various interfacial properties of liquid and assist for interfacial material design.
Prediction of the adsorption properties of liquid at solid surfaces with molecular scale surface roughness via encoding-decoding convolutional neural networks 査読有り

Gaoyang Li, Yuting Guo, Takuya Mabuchi, Donatas Surblys, Taku Ohara, Takashi Tokumasu

Journal of Molecular Liquids　349　118489-118489　2022年3月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.molliq.2022.118489 　

ISSN：0167-7322

詳細を見る詳細を閉じる

Molecular dynamics (MD) simulation can effectively analyze the transport properties of liquid at the solid surface with different nanoscale roughness, while high computational costs are required. Herein, a deep learning encoding-decoding convolutional neural network is proposed to predict the adsorption density distribution of atomic and organic liquids under different molecular scale surface roughness. Compared with the previous deep learning studies focusing on simple macro adsorption parameters, our deep learning method realizes the prediction and visualization of micro scale adsorption behavior with very high accuracy. The data-driven deep learning algorithm replaces the MD extensive sampling and simplifies the operation process, which improves the computational efficiency of a single model 36000-fold. This study proves the good coupling between MD and deep learning method, which is helpful for designing surface geometry to obtain desirable interfacial transport properties of molecular liquid and complementing the nanoscale model system enabling the interactive visualization.
Molecular dynamics study on vibration-mode matching in surfactant-mediated thermal transport at solid–liquid interfaces 査読有り

Hiroki Matsubara, Donatas Surblys, Yunhao Bao, Taku Ohara

Journal of Molecular Liquids　347　118363-118363　2022年2月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.molliq.2021.118363 　

ISSN：0167-7322

eISSN：1873-3166

詳細を見る詳細を閉じる

Surfactants have attracted attention as a means of enhancing thermal transport across solid-liquid interfaces. In the present study, non-equilibrium molecular dynamics simulation was used to study the effect of surfactants on interfacial thermal transport at solid-liquid interfaces, from the viewpoint of vibration-mode matching. The solid atom, surfactant molecule, and solvent molecule were all represented by a single atom. The vibrational characteristics of surfactant molecules were altered by changing surfactant mass m(srf), surfactant concentration c(srf), and the interaction strength between solid atoms and surfactant molecules, epsilon(sld-srf). For given values of c(srf) and epsilon(sld-srf), the interfacial thermal resistance (ITR) between the solid and surfactant solution exhibited a minimum as a function of m(srf). This minimum was found to result from the mutual interference of interparticle heat transfer among atoms in the solid surface layer, and surfactant and solvent molecules in the first and second adsorption liquid layers. The amount of interparticle heat transfer was only partly correlated with the traditionally used overlap of vibrational density of states and with the matching of the characteristic frequencies associated with the spring constant of potential of mean force, proposed here. From this result, we conclude that ITR at solid-liquid interfaces can be minimized by optimizing the vibrational characteristics of surfactant molecules, but the theory of vibration-mode matching should be refined in order to fully identify the condition under which the best vibrational matching occurs between solid, surfactant, and solvent. (C) 2021 The Authors. Published by Elsevier B.V.
Excellent heat transfer and phase transformation performance of erythritol/graphene composite phase change materials 査読有り

Xiaoxin Yan, Haibo Zhao, Yanhui Feng, Lin Qiu, Lin Lin, Xinxin Zhang, Taku Ohara

Composites Part B: Engineering　228　109435-109435　2022年1月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.compositesb.2021.109435 　

ISSN：1359-8368
Methodology and meaning of computing heat flux via atomic stress in systems with constraint dynamics 招待有り査読有り

Donatas Surblys, Hiroki Matsubara, Gota Kikugawa, Taku Ohara

Journal of Applied Physics　130　(21)　215104-215104　2021年12月7日
出版者・発行元：AIP Publishing
DOI： 10.1063/5.0070930 　

ISSN：0021-8979

eISSN：1089-7550
The effect of surface roughness and solvent polymer chain-length on solid-liquid interfacial Thermal Resistance

Qing-Yao Luo, Yining Li, Surblys Donatas, Hiroki Matsubara, Taku Ohara

Proceedings of the International Conference on Flow Dynamics, 2021　2021年11月
Obtaining heat flux via atomic stress in systems with many-body interactions and constrained dynamics 査読有り

Donatas Surblys, Hiroki Matsubara, Gota Kikugawa, Taku Ohara

Proceedings of the 2nd Asian Conference on Thermal Sciences　20321　2021年10月
Effect of molecular structure and molecular scale interaction on thermal conductivity of fluorocarbon liquids: A molecular dynamics study 査読有り

Shinsuke Kokubo, Hiroki Matsubara, Donatas Surblys, Gota Kikugawa, Taku Ohara

Proceedings of the 2nd Asian Conference on Thermal Sciences　20322　2021年10月
Thermal conduction over PEG-terminated SAM/water interface with different SAM chain lengths 査読有り

Gota Kikugawa, Leton Chandra Saha, Takashi Yagi, Yuichiro Yamashita, Masahide Sato, Taku Ohara

Proceedings of the 2nd Asian Conference on Thermal Sciences　20312　2021年10月
Molecular-scale insights into the heat transfer enhancement at solid-liquid interfaces by surfactants: Effect of vibrational properties of surfactant molecules 査読有り

Hiroki Matsubara, Donatas Surblys, Yunhao Bao, Taku Ohara

Proceedings of the 2nd Asian Conference on Thermal Sciences　20314　2021年10月
A molecular dynamics study of the effect of functional groups and side chain on adsorption of alcoholic surfactant and interfacial thermal transport 査読有り

Yuting Guo, Donatas Surblys, Hiroki Matsubara, Taku Ohara

Journal of Molecular Liquids　335　116243-116243　2021年8月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.molliq.2021.116243 　

ISSN：0167-7322
Comparison of molecular heat transfer mechanisms between water and ammonia in the liquid states 査読有り

Hiroki Matsubara, Gota Kikugawa, Taku Ohara

International Journal of Thermal Sciences　161　106762-106762　2021年3月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.ijthermalsci.2020.106762 　

ISSN：1290-0729
Effect of the in-plane aspect ratio of a graphene filler on anisotropic heat conduction in paraffin/graphene composites 査読有り

Hiroki Matsubara, Taku Ohara

Physical Chemistry Chemical Physics　23　(21)　12082-12092　2021年
出版者・発行元：Royal Society of Chemistry (RSC)
DOI： 10.1039/d1cp00556a 　

ISSN：1463-9076

eISSN：1463-9084

詳細を見る詳細を閉じる

<p>The analysis of molecular-scale heat transfer in paraffin/graphene composite based on molecular dynamics simulation suggests an important effect of the in-plane aspect ratio of a graphene filler on the effective thermal conductivity of the composite.</p>
Molecular Dynamics Study on the Effect of Long-Chain Surfactant Adsorption on Interfacial Heat Transfer between a Polymer Liquid and Silica Surface 査読有り

Yuting Guo, Donatas Surblys, Hiroki Matsubara, Yoshiaki Kawagoe, Taku Ohara

The Journal of Physical Chemistry C　124　(50)　27558-27570　2020年12月17日
出版者・発行元：American Chemical Society (ACS)
DOI： 10.1021/acs.jpcc.0c08940 　

ISSN：1932-7447

eISSN：1932-7455
Output density quantification of electricity generation by flowing deionized water on graphene 査読有り

Kei Kuriya, Kotaro Ochiai, Golap Kalita, Masaki Tanemura, Atsuki Komiya, Gota Kikugawa, Taku Ohara, Ichiro Yamashita, Fumio S. Ohuchi, M. Meyyappan, Seiji Samukawa, Katsuyoshi Washio, Takeru Okada

Applied Physics Letters　117　(12)　123905-123905　2020年9月21日
出版者・発行元：AIP Publishing
DOI： 10.1063/5.0018862 　

ISSN：0003-6951

eISSN：1077-3118
Cross-Plane and In-Plane Heat Conductions in Layer-by-Layer Membrane: Molecular Dynamics Study 査読有り

Yoshiaki Kawagoe, Donatas Surblys, Hiroki Matsubara, Gota Kikugawa, Taku Ohara

Langmuir　36　(23)　6482-6493　2020年6月16日
出版者・発行元：American Chemical Society (ACS)
DOI： 10.1021/acs.langmuir.0c00845 　

ISSN：0743-7463

eISSN：1520-5827
Erratum to “A molecular dynamics study of thermal boundary resistance over solid interfaces with an extremely thin liquid film” (International Journal of Heat and Mass Transfer (2020) 147, (S0017931019306490), (10.1016/j.ijheatmasstransfer.2019.118949)) 査読有り

Xiao Liu, Donatas Surblys, Yoshiaki Kawagoe, Abdul Rafeq Bin Saleman, Hiroki Matsubara, Gota Kikugawa, Taku Ohara

International Journal of Heat and Mass Transfer　150　2020年4月

DOI： 10.1016/j.ijheatmasstransfer.2020.119307 　

ISSN：0017-9310

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© 2020 Elsevier Ltd The publisher regrets that Fig. 7 was published incorrectly. The correct version of Fig. 7 is indicated below and has been updated on the original article online. [Figure presented] The publisher would like to apologise for any inconvenience caused.
Evaluation of thermal conductivity and its structural dependence of a single nanodiamond using molecular dynamics simulation 査読有り

Hiroki Matsubara, Gota Kikugawa, Takeshi Bessho, Taku Ohara

Diamond and Related Materials　102　107669　2020年2月

DOI： 10.1016/j.diamond.2019.107669 　

ISSN：0925-9635

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© 2019 Elsevier B.V. In the present study, we investigated thermal conductivity and its structural dependence of a spherical nanodiamond with 2.5 nm in diameter using molecular dynamics simulation. We briefly discussed the difficulty of computing the thermal conductivity of a free nanoparticle using conventional methods and here we derived it from the non-equilibrium molecular dynamics simulation of a composite system where a nanodiamond is sandwiched between two solid blocks. The structural dependence was examined by applying this method based on a composite system to the 2.5 nm nanodiamonds having different ratios of 3- and 4-coordinate carbons (termed sp2-like and sp3-like carbons, respectively), which were obtained from annealing at different temperatures. The thermal conductivity of the nanodiamond decreased from 28 to 10 W/(m·K) with decreasing ratio of sp3-like carbons until the number of sp2-like bonds exceeded that of sp3-like bonds. When sp2-like bond became richer than sp3-like bond, the thermal conductivity was less sensitive to further increase of the ratio of sp2-like carbons. Based on the consideration of the heat transfer associated with a single C[sbnd]C bond, we interpreted that this structural dependence reflects the heat transfer characteristics of sp3- or sp2-like bond, whichever is more abundant. This interpretation, as well as the methodology, is helpful for understanding thermal conductivity of nanodiamonds and other carbon nanomaterials.
A molecular dynamics study of thermal boundary resistance over solid interfaces with an extremely thin liquid film 査読有り

International Journal of Heat and Mass Transfer　147　118949-118949　2020年2月
出版者・発行元：None
DOI： 10.1016/j.ijheatmasstransfer.2019.118949 　

ISSN：0017-9310

eISSN：1879-2189
Thermal conductivity of nanofluids: A comparison of EMD and NEMD calculations 査読有り

K. Fujiwara, M. Daimo, Y. Ueki, T. Ohara, M. Shibahara

International Journal of Heat and Mass Transfer　144　118695-118695　2019年12月
出版者・発行元：Elsevier BV
DOI： 10.1016/j.ijheatmasstransfer.2019.118695 　

ISSN：0017-9310
A molecular dynamics study of heat transfer over an ultra-thin liquid film with surfactant between solid surfaces 査読有り

Yuting Guo, Donatas Surblys, Yoshiaki Kawagoe, Hiroki Matsubara, Taku Ohara

Journal of Applied Physics　126　(18)　185302　2019年11月14日

DOI： 10.1063/1.5123583 　

ISSN：0021-8979

eISSN：1089-7550

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© 2019 Author(s). Using molecular dynamics simulation, we investigated the mechanism by which the intercalation of a surfactant solution reduces the contact thermal resistance of two solid surfaces. We constructed a model system where two solid surfaces with a gap were immersed in a surfactant solution, and the gap was filled with permeating molecules to form a molecular thin film. By varying the concentration of the surfactant and the distance between the confining surfaces, factors affecting the intersolid heat transfer were explored. It was demonstrated that the overall thermal resistance of the present system was determined by interfacial thermal resistance between the solid and the solution and can be reduced by increasing the surfactant concentration. The surface separation, i.e., the distance between the two solid surfaces, had a significant impact on interfacial thermal resistance, whether or not surfactant molecules were involved. Interfacial thermal resistance was an oscillatory function of the surface separation and displayed minimum values not at the most adsorption amount of liquid molecules but when the density profile of liquid molecules showed a sharp peak, i.e., when the surface separation was commensurable with the size of the solvent molecule. This tendency was most remarkably seen when the liquid film was composed of a single molecular layer. The findings in this study provide helpful insights into the reduction of interfacial thermal resistance utilizing surfactant solutions.
Construction of polydisperse polymer model and investigation of heat conduction: A molecular dynamics study of linear and branched polyethylenimine 査読有り

Yoshiaki Kawagoe, Donatas Surblys, Hiroki Matsubara, Gota Kikugawa, Taku Ohara

Polymer　180　121721　2019年10月10日

DOI： 10.1016/j.polymer.2019.121721 　

ISSN：0032-3861

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© 2019 Elsevier Ltd Molecular dynamics (MD) simulation is a powerful tool for investigating the molecular mechanism of heat conduction in polymers. However, existing MD studies are mostly on monodisperse polymers and the effect of polydispersity, which typically occurs in commercial polymers, remains to be clarified. In this work, various types of polydisperse polyethylenimine (PEI) composed of molecules having different molecular weights and branching structures were constructed by in silico step-growth polymerization. The effect of the polydispersity and molecular structure on heat conduction in PEI was investigated using all-atom MD simulations. The number and weight fraction distributions of the polydisperse purely-linear PEI agreed well with the Flory-Schulz distributions, and therefore it can be concluded that the in silico polymerization used in this work reasonably mimics the step-growth-like polymerization observed in the actual synthesis of PEI. Thermal conductivity increased with increase in the radius of gyration dependent on the degree of branching of the molecules. In addition, thermal conductivity of a polydisperse PEI exhibited a similar value to that of a monodisperse PEI of a representative polymer chain in the polydisperse system. By analyzing in detail the thermal energy transfer among and inside molecules, their microscopic mechanisms could be understood and it was discovered that the average molecular weight is a critical factor in determining heat conduction.
A molecular dynamics study on the effect of surfactant adsorption on heat transfer at a solid-liquid interface 査読有り

Yuting Guo, Donatas Surblys, Yoshiaki Kawagoe, Hiroki Matsubara, Xiao Liu, Taku Ohara

International Journal of Heat and Mass Transfer　135　115-123　2019年6月

DOI： 10.1016/j.ijheatmasstransfer.2019.01.131 　

ISSN：0017-9310

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© 2019 The Authors Molecular dynamics simulations of a liquid layer between solid surfaces under a temperature gradient were performed to investigate the mechanism by which solid-liquid interfacial heat transfer is affected by adsorption of surfactant on solid surfaces with various concentrations of surfactant. The surfactant and solvent were chosen to be single-atom molecules with a contact angle of 0 and 180 degrees to the solid surface, respectively. Density distributions showed that the surfactant molecules formed a layer on the solid surface. The heat flux across the solid-liquid interface and between two adsorption layers closest to the surface was decomposed into energy transport terms based on molecular motions and inter-molecular interactions to examine the molecular mechanism of heat transfer. The interfacial thermal conductance (ITC) was also evaluated, and the molecular mechanism contributing to it was analyzed. It was found that the surfactant molecules that were adsorbed onto the solid surface decreased the interfacial thermal resistance, causing an increase in the heat flux, where the heat path from the solid to the solvent molecules via surfactant molecules became dominant as compared with the direct path from the solid to solvent molecules. It resulted in the temperature of surfactant being closer to the temperature of the solid than that of solvent in the vicinity of the solid surfaces. This indicated that in order to increase heat transfer via surfactants, not only the surfactant affinity with solid surface, but also the surfactant-solvent affinity must be considered. The contribution of each surfactant molecule to the ITC was greater than that of each solvent molecule, and both were proportional to their intermolecular potential with the solid atoms. Also, the contributions of a single surfactant and solvent molecule to the ITC were independent of their concentrations in the adsorption layer.
Application of atomic stress to compute heat flux via molecular dynamics for systems with many-body interactions 査読有り

Donatas Surblys, Hiroki Matsubara, Gota Kikugawa, Taku Ohara

Physical Review E　99　(5)　051301(R)　2019年5月14日

DOI： 10.1103/PhysRevE.99.051301 　

ISSN：2470-0045

eISSN：2470-0053

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© 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Although the computation of heat flux and thermal conductivity either via Fourier's law or the Green-Kubo relation has become a common task in molecular dynamics simulation, contributions of three-body and larger many-body interactions have always proved problematic to compute. In recent years, due to the success when applying to pressure tensor computation, atomic stress approximation has been widely used to calculate heat flux, where the lammps molecular dynamics package is the most prominent propagator. We demonstrated that the atomic stress approximation, while adequate for obtaining pressure, produces erroneous results in the case of heat flux when applied to systems with many-body interactions, such as angle, torsion, or improper potentials. This also produces incorrect thermal conductivity values. To remedy this deficiency, by starting from a strict formulation of heat flux with many-body interactions, we reworked the atomic stress definition which resulted in only a simple modification. We modified the lammps package accordingly to demonstrate that the new atomic stress approximation produces excellent results close to that of a rigid formulation.
All- and one-particle distribution functions at nonequilibrium steady state under thermal gradient 査読有り

Hiroki Matsubara, Gota Kikugawa, Taku Ohara

Physical Review E　99　(5)　052110　2019年5月10日

DOI： 10.1103/PhysRevE.99.052110 　

ISSN：2470-0045

eISSN：2470-0053

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© 2019 American Physical Society. We provide a concrete expression for the phase-space distribution function at nonequilibrium steady state under a constant thermal gradient, which is a typical system of the nonequilibrium molecular dynamics simulation of heat conduction. First, the phase-space distribution function of all particles in a local volume is formulated. Our formulation explicitly takes into account the entropy production due to the change in equilibrium thermodynamic variables in addition to the traditional entropy production described by the spatial gradients and fluxes of equilibrium thermodynamic variables. This treatment is necessary to explain the nonequilibrium response of a quantity that has no equilibrium correlation with mass and heat fluxes and is essential to correctly deduce one-particle distribution functions from the all-particle one. From the all-particle distribution function, we derive the Green-Kubo relations that express the one-particle distribution functions of density and velocity in terms of equilibrium correlation functions and verify these expressions using the molecular dynamics simulation of a Lennard-Jones liquid. These nonequilibrium one-particle distribution functions are sufficiently tractable for practical use, such as for the analytical evaluation of the nonequilibrium average of physical quantities.
Molecular dynamics investigation of surface roughness scale effect on interfacial thermal conductance at solid-liquid interfaces 査読有り

Donatas Surblys, Yoshiaki Kawagoe, Masahiko Shibahara, Taku Ohara

The Journal of Chemical Physics　150　(11)　114705-114705　2019年3月21日
出版者・発行元：AIP Publishing
DOI： 10.1063/1.5081103 　

ISSN：0021-9606

eISSN：1089-7690
Molecular dynamics study on thermal energy transfer in bulk polyacrylic acid 査読有り

Yoshiaki Kawagoe, Donatas Surblys, Gota Kikugawa, Taku Ohara

AIP Advances　9　025302　2019年2月

DOI： 10.1063/1.5080432 　
Data Analysis of Multi-Dimensional Thermophysical Properties of Liquid Substances Based on Clustering Approach of Machine Learning 査読有り

Chemical Physics Letters　728　109-114　2019年
A molecular dynamics study on the thermal rectification effect at the solid-liquid interfaces between the face-centered cubic (FCC) of gold (Au) with the surfaces of (100), (110) and (111) crystal planes facing the liquid methane (CH4) 査読有り

Abdul Rafeq, bin Saleman, Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

Molecular Simulation　45　(1)　68-79　2018年10月

DOI： 10.1080/08927022.2018.1535177 　
Kinetic model for molecular transport of liquid mixtures in the vicinity of solid-liquid interfaces 査読有り

Mamoru Hirasawa, Gota Kikugawa, Takeo Nakano, Taku Ohara

Proceedings of the 16th International Heat Transfer Conference　IHTC16-22176　2018年8月
Microscopic picture of heat conduction in liquid ethylene glycol by molecular dynamics simulation: Difference from the monohydric case 査読有り

Hiroki Matsubara, Gota Kikugawa, Mamoru Ishikiriyama, Seiji Yamashita, Taku Ohara

International Journal of Heat and Mass Transfer　121　1033-1038　2018年6月

DOI： 10.1016/j.ijheatmasstransfer.2018.01.060 　

ISSN：0017-9310

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© 2018 Elsevier Ltd The present study investigates the molecular-scale heat transfer in the liquid of ethylene glycol, which is widely used as heat transfer media. First, by combining existing molecular models, we developed a new united atom model of ethylene glycol, and showed that this model reasonably reproduces the experimental thermal conductivity. Using the non-equilibrium molecular dynamics simulations with this model, we characterized the heat transfers due to different kinds of inter- and intramolecular interactions on the basis of a picture that a single pair interaction is a path of heat transfer. These characteristics were compared with those of ethanol (Matsubara et al., 2017) to elucidate the molecular mechanism which realizes an enhanced thermal conductivity because of an additional hydroxylation on ethanol. The results indicate that the thermal conductivity enhancement occurs because the additional heat paths provided by the second hydroxyl group increases the amount of heat conduction owing to all of the van der Waals, Coulomb, and covalent interactions. In particular, the increase in the number of the paths associated with the intermolecular Coulomb interaction between the non-hydrogen bonding hydroxyl groups is prominent and consequently the Coulomb interaction, which is an efficient heat carrier, performs the largest amount of heat conduction in ethylene glycol. Although the second hydroxyl group also increases the number of hydrogen bonds, the direct heat transfer via the hydrogen bonds accounts for only a small portion of the total heat conduction. On the other hand, this augmentation of hydrogen bond, since it keeps a dense molecular packing against the increase in molecular volume, is indispensable in increasing the density of heat paths.
Molecular dynamics study of thermal resistance of solid-liquid interface in contact with single layer of nanoparticles 査読有り

Yoshitaka Ueki, Yasuhiro Miyazaki, Masahiko Shibahara, Taku Ohara

International Journal of Heat and Mass Transfer　120　608-623　2018年5月1日
出版者・発行元：Elsevier Ltd
DOI： 10.1016/j.ijheatmasstransfer.2017.12.061 　

ISSN：0017-9310

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In a nanoscale system, thermal resistance at a solid-liquid interface can be considerable. Nanoparticle deposition on the solid-liquid interface is able to influence the solid-liquid interfacial thermal resistance (ITR). The influence of the nanoparticle layer on the thermal resistance can be critical, for an example, in a heat transfer of nanoparticle suspension fluids. In the present study, by means of non-equilibrium classical molecular dynamics (MD) method, we numerically investigated changes in the solid-liquid ITR, liquid density near the interface, heat flux components through single layer of carbon nanoparticles. Under the present conditions, the carbon nanoparticle layers on the solid-liquid interface influenced the liquid density and the heat transport near the solid-liquid interface, and the ITR. The ITR decreased, as the liquid density in the nanoparticle layer increased. The change in the liquid density near the solid-liquid interface was one of significant factors that affected the ITR. When the nanoparticle layer significantly decreased the ITR, the energy transport from the wall to the nanoparticles was enhanced, and the energy transfer inside the nanoparticles increased. Therefore, the nanoparticles were able to extract and store the thermal energy from the solid wall, which decreased the ITR.
A molecular dynamics study on thermophysical and transport properties of fluorinated alkane liquids 査読有り

Gota Kikugawa, Naoki Minami, Yingping Fang, Mitsuru Nemoto, Hiroki Matsubara, Taku Ohara

International Heat Transfer Conference　2018-August　7019-7024　2018年

ISSN：2377-424X

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© 2018 International Heat Transfer Conference. All rights reserved. Thermophysical and transport properties of heat media, which are extensively utilized in heat transfer devices such as refrigerating and air-conditioning equipment, are inherently determined from microscopic components like molecular interactions and molecular-scale structure of liquid. An essential understanding of these microscopic information are of critical importance for designing and exploring liquid materials having desired properties. Here we performed molecular dynamics (MD) simulation on fluorocarbon liquids, which are prevailing as typical coolants in industrial products, in order to examine thermophysical properties such as a liquid-vapor phase change property and thermal conductivity at the bulk liquid state. In the present study, we have developed a new transferable potential model for fluorocarbon and hydrofluorocarbons by modifying partial charges of the OPLS-AA force field based on the ab initio molecular orbital calculation. We demonstrated that our developed potential models well reproduce experimental data of a liquid-vapor phase change property and thermal conductivity for several fluorocarbons having different chain lengths. Not only physical property itself, but the underlying molecular-scale mechanism was also examined, i.e., the microscopic mechanism to realize the thermal conductivity was precisely investigated by decomposing macroscopic thermal conductivity into microscopic building blocks.
Thermal boundary conductance and energy transfer modes over the interfaces of various self-assembled monolayers and solvents: A molecular dynamics study 査読有り

Gota Kikugawa, Mitsuru Nemoto, Taku Ohara

Proceedings of the 9th JSME-KSME Thermal and Fluids Engineering Conference　2017年10月
A molecular dynamics study on the thermal energy transfer and momentum transfer at the solid-liquid interfaces between gold and sheared liquid alkanes 査読有り

Abdul Rafeq bin Saleman, Hari Krishna Chilukoti, Gota Kikugawa, Masahiko Shibahara, Taku Ohara

INTERNATIONAL JOURNAL OF THERMAL SCIENCES　120　273-288　2017年10月
出版者・発行元：ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
DOI： 10.1016/j.ijthermalsci.2017.06.014 　

ISSN：1290-0729

eISSN：1778-4166

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Solid-liquid (S-L) interfaces of linear alkane liquids contacting two parallel solid walls of gold with three types of face-centered cubic (FCC) of (100), (110) and (111) crystal planes were examined using nonequilibrium molecular dynamics simulations (NEMD). The liquid alkanes were sheared by the two parallel solid walls sliding at a constant speed and in opposite directions, which generates viscous heating in the liquid. The effect of the molecular length of the linear alkane liquids, methane, butane, octane, and tetracosane, was investigated in terms of the thermal energy transfer and momentum transfer at the S-L interfaces. The gap distance between the surface layer of the solid atoms and the adsorption layer of the liquid molecules was measured as a key feature of the interface. The slip length, which was defined as the extrapolated velocity of liquid into the solid walls where the tangential velocity vanishes, was measured and the mechanism that determines its magnitude was examined. The gap distance and the slip length were correlated with the molecular length of the liquid alkanes. The thermal boundary resistance at the S-L interfaces was measured and it was also correlated with the gap distance and molecular length of liquid alkanes. It was found that the differences in the surface structure of the solid walls between the three types of crystal planes affect the slip length at the S-L interfaces. The present results suggest that the factors affecting the thermal energy transfer and momentum transfer at the S-L interfaces were the gap distance, which differs significantly depending on the molecular length of liquid, and the surface structure of the solid walls. (C) 2017 Elsevier Masson SAS. All rights reserved.
Equivalence of the EMD- and NEMD-based decomposition of thermal conductivity into microscopic building blocks 査読有り

Hiroki Matsubara, Gota Kikugawa, Mamoru Ishikiriyama, Seiji Yamashita, Taku Ohara

JOURNAL OF CHEMICAL PHYSICS　147　(11)　114104　2017年9月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4990593 　

ISSN：0021-9606

eISSN：1089-7690

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Thermal conductivity of a material can be comprehended as being composed of microscopic building blocks relevant to the energy transfer due to a specific microscopic process or structure. The building block is called the partial thermal conductivity (PTC). The concept of PTC is essential to evaluate the contributions of various molecular mechanisms to heat conduction and has been providing detailed knowledge of the contribution. The PTC can be evaluated by equilibrium molecular dynamics (EMD) and non-equilibrium molecular dynamics (NEMD) in different manners: the EMD evaluation utilizes the autocorrelation of spontaneous heat fluxes in an equilibrium state whereas the NEMD one is based on stationary heat fluxes in a non-equilibrium state. However, it has not been fully discussed whether the two methods give the same PTC or not. In the present study, we formulate a Green-Kubo relation, which is necessary for EMD to calculate the PTCs equivalent to those by NEMD. Unlike the existing theories, our formulation is based on the local equilibrium hypothesis to describe a clear connection between EMD and NEMD simulations. The equivalence of the two derivations of PTCs is confirmed by the numerical results for liquid methane and butane. The present establishment of the EMD-NEMD correspondence makes the MD analysis of PTCs a robust way to clarify the microscopic origins of thermal conductivity. Published by AIP Publishing.
Understanding the chain length dependence of thermal conductivity of liquid alcohols at 298 K on the basis of molecular-scale energy transfer 査読有り

Hiroki Matsubara, Gota Kikugawa, Takeshi Bessho, Seiji Yamashita, Taku Ohara

FLUID PHASE EQUILIBRIA　441　24-32　2017年6月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.fluid.2016.12.019 　

ISSN：0378-3812

eISSN：1879-0224

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Many of the specifics of microscopic energy transfer in liquids are not sufficiently understood in spite of their importance in controlling heat transport in practical devices. The present study aims to clarify the details of microscopic energy transfer in associated liquids with the aid of non-equilibrium molecular dynamics (NEMD) simulations on the liquids of linear alcohols from ranging ethanol to decanol at normal conditions. The NEMD simulations reasonably reproduce the experimentally observed chain length dependence of thermal conductivity. The microscopic energy transfer corresponding to each type of interatomic interactions are analyzed in relation to the liquid structures and molecular morphologies. Our analysis shows that the heat transfer by the Coulomb interaction has only a limited contribution to the alcohol thermal conductivity. Molecular morphology also has little effect. Rather, the chain length dependence of the thermal conductivity is determined by the result of the competition between the intermolecular and intramolecular energy transfers. The new insights obtained in the present study are a step towards a molecular theory of the thermal conductivity of liquids. (C) 2016 Elsevier B.V. All rights reserved.
Molecular dynamics study on the role of hydroxyl groups in heat conduction in liquid alcohols 査読有り

Hiroki Matsubara, Gota Kikugawa, Takeshi Bessho, Seiji Yamashita, Taku Ohara

INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER　108　749-759　2017年5月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/j.ijheatmasstransfer.2016.12.045 　

ISSN：0017-9310

eISSN：1879-2189

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On the basis of non-equilibrium molecular dynamics (NEMD) simulation for alcohols from ethanol to tetracosanol, the present study analyzes the molecular-level energy transfer in associated liquids for the first time. Direct evaluation of the energy transfer by each interatomic interaction reveals a counter-intuitive result that in liquid alcohols the Coulomb interaction does not transfer heat more than the van der Waals interaction even for short chain species like ethanol. In addition, by comparing the NEMD analysis on alcohols with those of alkanes, we discuss a molecular mechanism by which alcohol has a higher thermal conductivity than alkane in view of molecular heat transfer. It is shown that hydroxyl OH, not only provides heat paths for the Coulomb interaction, but also increases the number of heat paths for the vdW and the intramolecular interactions. Consequently, the part of the heat transfer by the vdW interaction is replaced with more efficient transfers by the Coulomb and intramolecular interactions, and therefore a higher thermal conductivity occurs. The insights obtained from the present study update the view of microscopic heat transfer in associated liquid towards the molecular theory of thermal conductivity of liquids, which is currently immature in comparison with those of gases and solids. (C) 2016 Elsevier Ltd. All rights reserved.
Molecular Dynamics Study on Influence of Nanoparticles on Thermal Resistance Over a Solid-Liquid Interface 査読有り

M. Shibahara, Y. Miyazaki, Y. Ueki, T. Ohara

2017年3月
Thermal energy transport over the solvent interface of self-assembled monolayers with different fluorination 査読有り

Gota Kikugawa, Mitsuru Nemoto, Taku Ohara

Proceedings of the Asian Conference on Thermal Sciences 2017　2017年3月
Thermal rectification effects on solid-liquid interfaces between face-centered cubic (FCC) lattice and a simple liquid 査読有り

Abdul Rafeq, bin Saleman, Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

Proceedings of the Asian Conference on Thermal Sciences 2017　2017年3月
A molecular dynamics study on the thermal transport properties and the structure of the solid-liquid interfaces between face centered cubic (FCC) crystal planes of gold in contact with linear alkane liquids 査読有り

Abdul Rafeq Bin Saleman, Had Krishna Chilukoti, Gota Kikugawa, Masahiko Shibahara, Taku Ohara

INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER　105　168-179　2017年2月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/j.ijheatmasstransfer.2016.09.069 　

ISSN：0017-9310

eISSN：1879-2189

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Solid-liquid (S-L) interfaces of liquid alkane in contact with three types of face-centered cubic (FCC) of gold with the surfaces of (100), (110) and (111) crystal planes facing with linear alkane liquids were examined using nonequilibrium molecular dynamics (NEMD) simulations where constant heat flux was applied. The effect of molecular length of the linear alkane liquids, which are methane (CH4), butane (C4H10), octane (C8H18), hexadecane (C16H34) and tetracosane (C24H50), with respect to the thermal boundary resistance (TBR) of the S-L interfaces, were investigated. It was found that on the solid wall surface of (110) crystal plane, where lattice-scale corrugation exists, molecules of the liquid alkanes are adsorbed into the corrugation. This tendency is obvious at low temperatures and it fades at higher temperatures. The gap distance between the surface layer of atoms of the solid walls and the adsorption layer of liquid alkanes molecules was correlated with the length of liquid alkane molecules and the number density of solid atoms at the surface layer. The TBR over each S-L interfaces were obtained based on the temperature jump at the interfaces and the heat flux, and it was found that the TBR is influenced by the length of liquid alkane molecules, the number density of solid atoms at the surface layer and the gap distance. It is concluded that the TBR is influenced by the gap distance of the S-L interfaces and the number density of solid atoms at the surface layer, which varies depending on the length of liquid alkane molecules. (C) 2016 Elsevier Ltd. All rights reserved.
6.3.1 脂質二重膜中の熱エネルギー伝搬特性招待有り

小原拓, 中野雄大, 菊川豪太

佐藤岳彦他編, 高度物理刺激と生体応答, 第6章計測・予測と応用, 6.3 数値解析, 養賢堂　170-173　2017年
液体・界面の熱輸送特性発現機構－分子設計を志向して招待有り査読有り

松原裕樹, 菊川豪太, 小原拓

伝熱　56　(236)　17-24　2017年
Molecular thermal energy transfer in binary mixture of simple liquids 査読有り

Yingping Fang, Gota Kikugawa, Hiroki Matsubara, Takeshi Bessho, Seiji Yamashita, Taku Ohara

FLUID PHASE EQUILIBRIA　429　293-300　2016年12月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.fluid.2016.09.013 　

ISSN：0378-3812

eISSN：1879-0224

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Molecular thermal energy transfer in liquid mixtures was investigated using non-equilibrium molecular dynamics (NEMD) simulations of heat conduction in a series of binary mixture liquids with various compositions. Mixtures of argon and krypton were selected as simple liquids which were modeled using the Lennard-Jones (LJ) interaction potential. Thermal conductivities for these mixtures in a saturated state at a constant temperature (127 K) were compared with respect to mixture composition, i.e., molar fraction of each component. According to the molecular energy transfer mechanism, microscopic heat conduction flux can be decomposed into two molecular-scale contributions: one from self transportation, which includes transport of kinetic energy and potential energy by molecular motion, and the other via the contribution of intermolecular energy transfer based on intermolecular interaction. The intermolecular energy transfer, which is the dominant source of macroscopic heat conduction flux in liquids, can be decomposed into contributions from various pair interactions, which in the present study are energy transfers via the paths Ar-Ar, Ar-Kr, and Kr-Kr. The above contributions to heat conduction were evaluated quantitatively. It was found that the composition dependence of the first self transportation contribution is mostly caused by the differences of their thermodynamic states, and the variation of total thermal conductivity with the composition is dominated by the second intermolecular energy transfer contribution, which accounts for about 80% of the total. The contributions of individual interaction paths were analyzed with our new concept of atomistic heat path [Matsubara et al., J. Chem. Phys., 142 (2015), 164509]. It was found that these contributions are mostly affected by the number densities of the interaction paths in the first neighbor shell. The molecular-scale internal structure of the liquid is changed by changes in composition, which affects the efficiency of the energy transfer by a single intermolecular interaction. A sensitivity analysis of LJ cross-molecular parameters was done using various combining rules. We found that the decomposed energy transfer contribution of interaction paths, Ar-Ar and Kr-Kr may be affected by changing the LJ parameters of Ar-Kr. (C) 2016 Elsevier B.V. All rights reserved.
Non-equilibrium molecular dynamics simulation as a method of calculating thermodynamic coefficients 査読有り

Hiroki Matsubara, Gota Kikugawa, Takeshi Bessho, Seiji Yamashita, Taku Ohara

FLUID PHASE EQUILIBRIA　421　1-8　2016年8月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.fluid.2016.03.019 　

ISSN：0378-3812

eISSN：1879-0224

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A method is proposed in the present study, by which the specific heat at constant pressure, c(p), and the thermal expansion coefficient, alpha(p), at different temperatures along an isobar can be derived from a single run of non-equilibrium molecular dynamics (NEMD) at using a steady temperature gradient. This study aims to demonstrate the method and examine its validity in the NEMD simulation. For Lennard-Jones fluids, it is shown that the c(p) and alpha(p) obtained from the NEMD simulations are in good agreement with those calculated in a traditional manner from the equilibrium fluctuations. The results of the present study suggest that a NEMD simulation with heat conduction is useful not only to measure thermal conductivity but also to determine these thermodynamic coefficients. In particular, there is a possibility that the present method is applicable even to heterogeneous systems, to which the standard method is difficult to apply. (C) 2016 Elsevier B.V. All rights reserved.
Structure and Mass Transport Characteristics at the Intrinsic Liquid Vapor Interfaces of Alkanes 査読有り

Had Krishna Chilukoti, Gota Kikugawa, Taku Ohara

JOURNAL OF PHYSICAL CHEMISTRY B　120　(29)　7207-7216　2016年7月
出版者・発行元：AMER CHEMICAL SOC
DOI： 10.1021/acs.jpcb.6b05332 　

ISSN：1520-6106

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In this paper, an instantaneous interface definition has been used to study the intrinsic structure and self-diffusion coefficient in the vicinity of the liquid vapor interfaces of decane and tetracosane at three different temperatures using molecular dynamics simulations, and the results have been compared with those obtained on the basis of the conventional Gibbs dividing surface (time- and space-averaged interface). The alkane molecules were modeled using the united atom NERD force field. Partial layered structures of alkane molecules at the liquid vapor interface are observed as a pinned structure of alkane liquids based on the intrinsic interface. This kind of characteristic has not been observed in the density profiles obtained based on the Gibbs dividing surface. By examining the orientation order parameter and radius of gyration of the alkane molecules, it was observed that the alkane molecules were preferentially oriented to be more parallel to the intrinsic interface than to the Gibbs dividing surface, and the shape of the alkane molecules is slightly changed in the vicinity of the liquid vapor interfaces. The self-diffusion coefficient parallel to the intrinsic interface was examined using the Green Kubo relation, where the projection of the velocity in the parallel direction to the local intrinsic interface is used in the velocity correlation function. It was found that the self-diffusion coefficient in the direction parallel to the intrinsic interface changes as the position approaches the interface in a more obvious manner as compared with the self-diffusion coefficient obtained with respect to the Gibbs dividing surface. These results suggest that the use of an instantaneous interface definition allowed us to capture sharp variations in transport properties which are originating due to steeper structure at the liquid vapor interfaces.
Mechanism of thermal energy transfer in Nanoscale Solid-Liquid Systems

Masahiko Shibahara, Gota Kikugawa, Hari Krishna Chilukoti, Taku Ohara

Proceedings of The Sixteenth International Symposium on Advanced Fluid Information　84-85　2016年
Molecular Transport Phenomena of Liquids Confined in the Nanoscopic Structures

Gota Kikugawa, Yoichi Naruke, Jo Suzuki, Takeo Nakano, Taku Ohara

Proceedings of Thirteenth International Conference on Flow Dynamics　418-419　2016年
Molecular-Scale Structure of Liquid Alkane Mixtures in the Vicinity of α-Quartz Substrate

Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

Proceedings of Thirteenth International Conference on Flow Dynamics　416-417　2016年
Mass transport and structure of liquid n-alkane mixtures in the vicinity of α-quartz substrate 査読有り

Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

RSC (Royal Society of Chemistry) Advances　6　(102)　99704-99713　2016年
出版者・発行元：None
DOI： 10.1039/c6ra22398b 　

ISSN：2046-2069
Self-diffusion Coefficient and Structure of Binary n-Alkane Mixtures at the Liquid-Vapor Interfaces 査読有り

Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

JOURNAL OF PHYSICAL CHEMISTRY B　119　(41)　13177-13184　2015年10月
出版者・発行元：AMER CHEMICAL SOC
DOI： 10.1021/acs.jpcb.5b07189 　

ISSN：1520-6106

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The self-diffusion coefficient and molecular-scale structure of several binary n-alkane liquid mixtures in the liquid-vapor interface regions have been examined using molecular dynamics simulations. It was observed that in hexane-tetracosane mixture hexane molecules are accumulated in the liquid-vapor interface region and the accumulation intensity decreases with increase in a molar fraction of hexane in the examined range. Molecular alignment and configuration in the interface region of the liquid mixture change with a molar fraction of hexane. The self-diffusion coefficient in the direction parallel to the interface of both tetracosane and hexane in their binary mixture increases in the interface region. It was found that the self-diffusion coefficient of both tetracosane and hexane in their binary mixture is considerably higher in the vapor side of the interface region as the molar fraction of hexane goes lower, which is mostly due to the increase in local free volume caused by the local structure of the liquid in the interface region.
Hydrodynamic consideration of the finite size effect on the self-diffusion coefficient in a periodic rectangular parallelepiped system 査読有り

Gota Kikugawa, Takeo Nakano, Taku Ohara

JOURNAL OF CHEMICAL PHYSICS　143　(2)　024507　2015年7月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4926841 　

ISSN：0021-9606

eISSN：1089-7690

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In the present study, we use molecular dynamics (MD) simulations to provide an insight into the system size effect on the self-diffusion coefficient of liquids in the periodic rectangular parallelepiped system, from the hydrodynamic perspective. We have previously shown that in the rectangular box system, the diffusivity exhibits anomalous behaviors, i.e., the diffusion tensor appears to be anisotropic despite the bulk liquid simulation and the diffusion component in the direction along the short side of rectangular box with a high aspect ratio exceeding the diffusivity in the infinite system [Kikugawa et al., J. Chem. Phys. 142, 024503 (2015)]. So far, the size effect on the diffusivity has been intensively studied in the cubic system and has been interpreted quite well by the theoretical considerations employing the hydrodynamic interaction. Here, we have extended the hydrodynamic theory to be applied to periodic rectangular box systems and compared the theoretical predictions with MD simulation results. As a result, the diffusivity predicted by the hydrodynamic theory shows good agreement with the MD results. In addition, the system size effect was examined in a rod-shaped rectangular box in which the two shorter side lengths were equivalent and a film-type rectangular box in which the two longer side lengths were equivalent. It is of interest that we found that the aspect ratio, at which the diffusivity coincides with that in the infinite system, is a universal constant independent of the cross-sectional area for the rod system or the thickness for the film system. By extracting the universal structure in the hydrodynamic description, we also suggested a simplified approximate model to accurately predict the size effect on the diffusivity over a practical range of aspect ratios. (C) 2015 AIP Publishing LLC.
Local thermal conductivity of liquid alkanes in the vicinity of α-quartz solid surfaces and thermal resistance over the interfaces: A molecular dynamics study 査読有り

Hari Krishna Chilukoti, Gota Kikugawa, Masahiko Shibahara, Taku Ohara

Physical Review E　91　(5)　052404　2015年5月20日
出版者・発行元：None
DOI： 10.1103/PhysRevE.91.052404 　

ISSN：1550-2376 1539-3755
Local thermal transport of liquid alkanes in the vicinity of alpha-quartz solid surfaces and thermal resistance over the interfaces: A molecular dynamics study 査読有り

Hari Krishna Chilukoti, Gota Kikugawa, Masahiko Shibahara, Taku Ohara

PHYSICAL REVIEW E　91　(5)　2015年5月
出版者・発行元：AMER PHYSICAL SOC
DOI： 10.1103/PhysRevE.91.052404 　

ISSN：2470-0045

eISSN：2470-0053

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Thermal transport in liquid n-alkanes in the vicinity of alpha-quartz substrates and thermal boundary resistance between the liquid n-alkanes and the alpha-quartz substrates have been investigated using nonequilibrium molecular dynamics simulations. The study considers two liquid alkanes, methane and decane, and three crystal orientations of a-quartz substrate terminated with -H or -OH groups. The local thermal conductivity (LTC), defined in the same manner as with macroscopic thermal conductivity, is used to measure the efficiency of thermal energy transport of the liquids in the vicinity of the solid surface. The variations in the LTC of the liquid alkanes in the layered region next to the surface of the substrate were examined. The modeled LTC values of the alkanes were found to oscillate in the solid-liquid interface region. These fluctuations were typically proportional to the oscillations in the local density profile. The correlation between the thermal conductivity and density was linear in the bulk liquid region. The correlation between LTC and local density in the first adsorption layer is not a straightforward extension of that of the bulk liquid, which is mostly due to the specific molecular-scale ordering structure that occurs in the liquids formed by the proximity of the solid substrate. Thermal boundary resistance between the liquid alkanes and the quartz substrate was also evaluated. It was observed that thermal boundary resistance is relatively large when the in-plane molecular-scale structure in the first adsorption layer is sparse, and is lower when the liquid structure is dense in the adsorption layer.
A molecular dynamics study on mass transport characteristics in the vicinity of Si02-water/IPA interfaces 査読有り

Yoichi Naruke, Shuichi Kosaka, Takeo Nakano, Gota Kikugawa, Taku Ohara

INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER　84　584-591　2015年5月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/j.ijheatmasstransfer.2015.01.051 　

ISSN：0017-9310

eISSN：1879-2189

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Mass transport in the vicinity of solid-liquid interfaces exhibits anomalous characteristics that differ from those in bulk liquids. These anomalous transport properties play a crucial role in recent nanoscale applications such as wet processing in semiconductor fabrication, surface modification by chemical treatment, and dynamic coating. In the present study, interfaces between solid Si02 and liquid water or isopropyl alcohol (IPA), which are typically used in the semiconductor industry, were investigated using molecular dynamics (MD) simulations. The molecular-scale structures of the adsorption layers of water or IPA molecules were examined, and self-diffusion coefficients of these liquids related to migration of molecules in the direction parallel to the interfaces were calculated. Both H- and OH-terminated SiO2 surfaces were investigated in this study. It was found that layered structures of water and IPA molecules form near the interfaces, and were influenced by the crystal plane orientation. To examine the influences of these structures on molecular transport, local self-diffusion coefficients of water and IPA were derived via MD simulation using two methods based on the mean square displacement and on the velocity auto correlation function. The present study focused on a system of two solid walls with a spacing on the order of 10 nm with the liquids confined in between. It was found that the self-diffusion coefficients of water and IPA are reduced in the vicinity of the interfaces. The self-diffusion coefficient of water approaches its bulk value when separated from the solid wall by approximately 2-3 nm, while in the case of IPA, the solid wall influences the liquid properties more deeply into the liquid phase. o 2015 Elsevier Ltd. All rights reserved.
Influence of computational domain shape in molecular dynamics simulations on self-diffusion coefficient of bulk liquids 査読有り

Gota Kikugawa, Jo Suzuki, Yoichi Naruke, Takeo Nakano, Taku Ohara

Proceedings of the Fourth International Symposium on Micro and Nano Technology　2015年5月
Effects of molecular structure on microscopic heat transport in chain polymer liquids 査読有り

Hiroki Matsubara, Gota Kikugawa, Takeshi Bessho, Seiji Yamashita, Taku Ohara

JOURNAL OF CHEMICAL PHYSICS　142　(16)　164509　2015年4月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4919313 　

ISSN：0021-9606

eISSN：1089-7690

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In this paper, we discuss the molecular mechanism of the heat conduction in a liquid, based on nonequilibrium molecular dynamics simulations of a systematic series of linear- and branched alkane liquids, as a continuation of our previous study on linear alkane [T. Ohara et al., J. Chem. Phys. 135, 034507 (2011)]. The thermal conductivities for these alkanes in a saturated liquid state at the same reduced temperature (0.7T(c)) obtained from the simulations are compared in relation to the structural difference of the liquids. In order to connect the thermal energy transport characteristics with molecular structures, we introduce the new concept of the interatomic path of heat transfer (atomistic heat path, AHP), which is defined for each type of inter-and intramolecular interaction. It is found that the efficiency of intermolecular AHP is sensitive to the structure of the first neighbor shell, whereas that of intramolecular AHP is similar for different alkane species. The dependence of thermal conductivity on different lengths of the main and side chain can be understood from the natures of these inter-and intramolecular AHPs. (C) 2015 AIP Publishing LLC.
Analysis of molecular transport in the solid-liquid interface region based on the kinetic model

Jo Suzuki, Gota Kikugawa, Takeo Nakano, Taku Ohara

Proceedings of the 12th International Conference on Flow Dynamics　446-447　2015年
Atomistic heat path analysis of heat transfer in chain polymer liquids

Hiroki Matsubara, Gota Kikugawa, Takeshi Bessho, Seiji Yamashita, Taku Ohara

Proceedings of the 12th International Conference on Flow Dynamics　454-455　2015年
Interfacial properties of binary n-alkane mixtures at the liquid-vapor interfaces

Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

Proceedings of the 12th International Conference on Flow Dynamics　456-457　2015年
Molecular dynamics study on thermal resistance of solid-liquid interfaces

Masahiko Shibahara, Taku Ohara, Gota Kikugawa

Proceedings of the Fifteenth International Symposium on Advanced Fluid Information　88-89　2015年
Kinetic model for transport of liquid molecules in the solid-liquid interface region: a molecular dynamics view 査読有り

Jo Suzuki, Gota Kikugawa, Takeo Nakano, Taku Ohara

JSME Mechanical Engineering Letters　1　15-00353　2015年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/mel.15-00353 　

ISSN：2189-5236

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Liquid molecules form ordered structures in the vicinity of the solid-liquid interface. Mass transport in the ordered structure exhibits decidedly different characteristics from the ordinary diffusion property governed by Ficks law. In order to analyze mass transport at this nanoscopic scale, we have monitored the PMF (potential of mean force) obtained from the number density of liquid molecules, which corresponds to the free energy change with respect to the molecular migration. Using this PMF profile, the kinetic process model to describe the molecular mobility inside these ordered structures was developed in this study. In order to verify whether the suggested kinetic model works correctly, molecular dynamics (MD) simulations of the liquid-solid interface system were performed. In a simple system consisting of a LJ liquid and flat solid walls, which are modeled by the continuum media interacting with liquid molecules, molecular adsorption and desorption phenomena were observed. In each process in which molecules migrate to the neighboring adsorption layer, the height of the free energy barrier was calculated using the PMF distribution. It was found that the PMF has a dominant influence on the molecular transport perpendicular to the wall and that the developed kinetic model can accurately predict the molecular mobility over the free energy barrier due to the adsorption and desorption process.
熱流体工学における分子動力学シミュレーション招待有り査読有り

小原拓, 菊川豪太

アンサンブル分子シミュレーション研究会　17　(1)　35-43　2015年
出版者・発行元：分子シミュレーション研究会
DOI： 10.11436/mssj.17.35 　

ISSN：1884-5088 1884-6750

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機械工学において流体中の熱・物質輸送現象を解明しその応用を図るのが熱流体工学である．近年，この分野に分子動力学シミュレーションが取り入れられ，界面現象や熱物性値の研究に成果を上げている．分子熱流体と呼ばれるこの分野における研究を紹介するのが，本稿の目的である．
Effect of the computational domain size and shape on the self-diffusion coefficient in a Lennard-Jones liquid 査読有り

Gota Kikugawa, Shotaro Ando, Jo Suzuki, Yoichi Naruke, Takeo Nakano, Taku Ohara

JOURNAL OF CHEMICAL PHYSICS　142　(2)　024503　2015年1月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4905545 　

ISSN：0021-9606

eISSN：1089-7690

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In the present study, molecular dynamics (MD) simulations on the monatomic Lennard-Jones liquid in a periodic boundary system were performed in order to elucidate the effect of the computational domain size and shape on the self-diffusion coefficient measured by the system. So far, the system size dependence in cubic computational domains has been intensively investigated and these studies showed that the diffusion coefficient depends linearly on the inverse of the system size, which is theoretically predicted based on the hydrodynamic interaction. We examined the system size effect not only in the cubic cell systems but also in rectangular cell systems which were created by changing one side length of the cubic cell with the system density kept constant. As a result, the diffusion coefficient in the direction perpendicular to the long side of the rectangular cell significantly increases more or less linearly with the side length. On the other hand, the diffusion coefficient in the direction along the long side is almost constant or slightly decreases. Consequently, anisotropy of the diffusion coefficient emerges in a rectangular cell with periodic boundary conditions even in a bulk liquid simulation. This unexpected result is of critical importance because rectangular fluid systems confined in nanospace, which are present in realistic nanoscale technologies, have been widely studied in recent MD simulations. In order to elucidate the underlying mechanism for this serious system shape effect on the diffusion property, the correlation structures of particle velocities were examined. (C) 2015 AIP Publishing LLC.
A molecular dynamics analysis of water/IPA liquid displacement in the vicinity of silica interface 査読有り

Takeo Nakano, Shuichi Kosaka, Gota Kikugawa, Jo Suzuki, Yoichi Naruke, Taku Ohara

Proceedings of the Fourth International Symposium on Micro and Nano Technology　2015年
Structure and transport properties of liquid alkanes in the vicinity of α-quartz surfaces 査読有り

Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

International Journal of Heat and Mass Transfer　79　846-857　2014年12月
出版者・発行元：None
DOI： 10.1016/j.ijheatmasstransfer.2014.08.089 　

ISSN：0017-9310

eISSN：1879-2189
A molecular dynamics study on heat conduction characteristics inside the alkanethiolate SAM and alkane liquid 査読有り

Gota Kikugawa, Taku Ohara, Tohru Kawaguchi, Ikuya Kinefuchi, Yoichiro Matsumoto

INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER　78　630-635　2014年11月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/j.ijheatmasstransfer.2014.07.040 　

ISSN：0017-9310

eISSN：1879-2189

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In the present study, we performed molecular dynamics (MD) simulations of the self-assembled monolayer (SAM) and alkane solvent interface. In particular, 1-dodecanethiol (C12H25S-) SAM chemisorbed on a gold substrate contacting with n-dodecane (C12H26) solvent was examined to compare the heat transfer mechanisms inside both the SAM and solvent phases from a microscopic viewpoint. The nonequilibrium MD (NEMD) simulation, in which a constant heat flux across the SAM interface was imposed, was performed. Here, we introduced the novel approach to clarify the molecular-scale mechanism on heat conduction in both SAM and alkane solvent. This approach enables us to decompose the macroscopic heat flux into the microscopic "building blocks", i.e., the contribution of energy transfer associated with molecular motion and those of energy exchange by intermolecular (nonbonded) and intramolecular (covalent bond) interactions. Interestingly, we have obviously demonstrated that inside the SAM layer, almost all of the energy is transferred by the intramolecular interaction along the alkyl chain. On the other hand, inside the alkane liquid, the intramolecular and intermolecular interactions have similar contributions to the total heat flux in spite of the same molecular structure and alkyl chain length as the SAM molecules. This striking difference in heat conduction mechanism originates from the ordering structure of alkyl chains in the SAM layer. (C) 2014 Elsevier Ltd. All rights reserved.
A Molecular Dynamics Study on Heat Transfer Characteristics Over the Interface of Self-Assembled Monolayer and Water Solvent 査読有り

Gota Kikugawa, Taku Ohara, Tohru Kawaguchi, Ikuya Kinefuchi, Yoichiro Matsumoto

JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME　136　(10)　102401　2014年10月
出版者・発行元：ASME
DOI： 10.1115/1.4027910 　

ISSN：0022-1481

eISSN：1528-8943

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We performed molecular dynamics (MD) simulations of the interface which is comprised of self-assembled monolayer (SAM) and water solvent to investigate heat transfer characteristics. In particular, local thermal boundary conductance (TBC), which is an inverse of so-called Kapitza resistance, at the SAM-solvent interface was evaluated by using the nonequilibrium MD (NEMD) technique in which the one-dimensional thermal energy flux was imposed across the interface. By using two kinds of SAM terminal with hydrophobic and hydrophilic properties, the local TBCs of these interfaces with water solvent were evaluated, and the result showed a critical difference due to an affinity between SAM and solvent. In order to elucidate the molecular-scale mechanism that makes this difference, microscopic components contributing to thermal energy flux across the interface of hydrophilic SAM and water were evaluated in detail, i.e., the total thermal energy flux is decomposed into the heat transfer modes such as the contribution of molecular transport and that of energy exchange by molecular interactions. These heat transfer modes were also compared with those in the bulk water.
Thermal Resistance between Nano-Structured Surfaces and Liquids

Taku Ohara, Masahiko Shibahara, Gota Kikugawa, Hari Krishna Chilukoti

Proceedings of the 14th International Symposium on Advanced Fluid Information　134-135　2014年
Thermal Transport in Lipid Bilayers

Taku Ohara, Takeo Nakano, Gota Kikugawa

Proceedings of the Eleventh International Conference on Flow Dynamics　2014年
Molecular dynamics study on the influences of nanostructure on the thermal energy transport at a liquid-solid interface 査読有り

R. Toda, Y. Ueki, M. Shibahara, T. Ohara

Proceedings of the 25th International Symposium on Transport Phenomena　2014年
Structure and transport properties at the liquid-vapor interfaces of binary n-alkane mixtures 査読有り

Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

Proceedings of the 25th International Symposium on Transport Phenomena　2014年
Molecular dynamics study on influences of surface structural characteristics on thermal energy transport over liquid-solid interfaces 査読有り

Masahiko Shibahara, Ryohei Toda, Sho Murakami, Taku Ohara

Proceedings of the 15th International Heat Transfer Conference　2014年
出版者・発行元：None
DOI： 10.1615/ihtc15.mlt.008513 　
Investigation of Thermal Resistance and Heat Conduction at α-Quartz-Liquid Alkane Interfaces Using Nonequilibrium Molecular Dynamics Simulations 査読有り

Hari Krishna Chilukoti, Gota Kikugawa, Masahiko Shibahara, Taku Ohara

Proceedings of the 15th International Heat Transfer Conference　2014年
HEAT TRANSFER CHARACTERISTICS OVER THE INTERFACE OF ALKANETHIOLATE SAM AND ALKANE LIQUID 査読有り

Gota Kikugawa, Taku Ohara, Tohru Kawaguchi, Ikuya Kinefuchi, Yoichiro Matsumoto

PROCEEDINGS OF THE ASME SUMMER HEAT TRANSFER CONFERENCE - 2013, VOL 1　CD-ROM　2014年
出版者・発行元：AMER SOC MECHANICAL ENGINEERS
DOI： 10.1115/HT2013-17607 　

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In the present study, we performed molecular dynamics (MD) simulations of the self-assembled monolayer (SAM) interface system in order to investigate heat transfer characteristics over the SAM/alkane solvent interface. 1-dodecanethiol (C12H25S-) SAM chemisorbed on a gold substrate contacting with n-dodecane (C12H26) solvent was examined to compare the microscopic heat transfer mechanisms inside both the SAM and solvent phases. The direct nonequilibrium MD (NEMD) simulation, in which a constant heat flux across the SAM interface was imposed, was performed. The heat flux through the system was decomposed into the microscopic "building blocks", i.e., the contribution of energy transfer associated with molecular motion and that of energy exchange by intermolecular (nonbonded) and intramolecular (covalent bond) interactions. Interestingly, inside the SAM layer, almost all of the energy is transferred by the intramolecular interaction along the alkyl chain. On the other hand, in the alkane liquid phase, the intramolecular and intermolecular interactions have comparable contributions to the total heat flux in spite of the same molecular structure and alkyl chain length as the SAM molecules. This difference in the heat transfer mechanism implies the relation between the ordering structure of alkyl chains and thermal conductivity in organic materials.
Effect of crosslink formation on heat conduction in amorphous polymers 査読有り

Gota Kikugawa, Tapan G. Desai, Pawel Keblinski, Taku Ohara

JOURNAL OF APPLIED PHYSICS　114　(3)　034302　2013年7月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.4813505 　

ISSN：0021-8979

eISSN：1089-7550

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We performed molecular dynamics (MD) simulations on amorphous polyethylene (PE) and polystyrene (PS) in order to elucidate the effect of crosslinks between polymer chains on heat conduction. In each polymer system, thermal conductivities were measured for a range of crosslink concentration by using nonequilibrium MD techniques. PE comprised of 50 carbon atom long chains exhibited slightly higher conductivity than that of 250 carbon atom long chains at the standard state. In both cases for PE, crosslinking significantly increased conductivity and the increase was more or less proportional to the crosslink density. On the other hand, in the PS case, although the thermal conductivity increased with the crosslinking, the magnitude of change in thermal conductivity was relatively small. We attribute this difference to highly heterogeneous PS based network including phenyl side groups. In order to elucidate the mechanism for the increase of thermal conductivity with the crosslink concentration, we decomposed energy transfer into modes associated with various bonded and non-bonded interactions. (C) 2013 AIP Publishing LLC.
Molecular Heat Transfer in Lipid Bilayers With Symmetric and Asymmetric Tail Chains 査読有り

Takeo Nakano, Gota Kikugawa, Taku Ohara

JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME　135　(6)　1-061301　2013年6月
出版者・発行元：ASME
DOI： 10.1115/1.4023572 　

ISSN：0022-1481

eISSN：1528-8943

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Intramolecular energy transfer in polymer molecules plays a dominant role in heat conduction in polymer materials. In soft matter where polymer molecules form an ordered structure, the intramolecular energy transfer works in an anisotropic manner, which results in an anisotropic thermal conductivity. Based on this idea, thermal energy transfer in lipid bilayers, a typical example of soft matter, has been analyzed in the present study. Non-equilibrium molecular dynamics simulations were carried out on single component lipid bilayers with ambient water. In the simulations, dipalmitoyl-phosphatidyl-choline (DPPC), dilauroyl-phosphatidyl-choline (DLPC), and stearoyl-myristoyl-phosphatidyl-choline (SMPC), which have two alkyl chains with 16C atoms for each, 12C atoms for each, and 18 and 14C atoms, respectively, were used as lipid molecules. The thermal energy transfer has been decomposed to inter-and intramolecular energy transfer between individual molecules or molecular sites, and its characteristics were discussed. In the case of heat conduction in the direction across the membranes (cross-plane heat conduction), the highest thermal resistance exists at the center of the lipid bilayer, where lipid alkyl chains face each other. The asymmetric chain length of SMPC reduces this thermal resistance at the interface between lipid monolayers. The cross-plane thermal conductivities of lipid monolayers are 4.8-6.5 times as high as the ones in the direction parallel to the membranes (in-plane) for the cases of the tested lipids. The overall cross-plane thermal conductivities of the lipid bilayers are reduced to be approximately half of those of the monolayers, due to the thermal resistance at the interfaces between two monolayers. The lipid bilayer of SMPC with tail chains of asymmetric length exhibits the highest cross-plane thermal conductivity. These results provide detailed information about the transport characteristics of thermal energy in soft matter, which are new materials with design flexibility and biocompatibility. The results lead to their design to realize desired thermophysical properties and functions.
A molecular dynamics study on transport properties and structure at the liquid-vapor interfaces of alkanes 査読有り

Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER　59　144-154　2013年4月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/j.ijheatmasstransfer.2012.12.015 　

ISSN：0017-9310

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In this paper, self-diffusion and structure in the vicinity of liquid vapor interfaces of several species of n-alkanes are examined using molecular dynamics simulations. The united atom NERD force field was utilized to model the alkane molecules, and the obtained properties were validated by the reported experimental results. Surface tension was calculated based on the averaged pressures, and tail corrections were implemented based on the molecular virial formulae. Present surface tension results for butane, hexane and decane are in good agreement with experimental and other simulated values. Molecular orientation and chain conformation in the interface region were examined by observing the ordering parameter and radius of gyration for decane and tetracosane. In the interface region, molecules are preferentially oriented parallel to the interface and shape of the molecules is slightly flattened in the z-direction for both decane and tetracosane. With an increase in temperature, molecules are preferentially less parallel to the interface. The Einstein relation modified for confined regions was used to obtain the self-diffusion coefficient according to migration of molecules parallel to the interface. Self-diffusion coefficient increases in the interface region for both decane and tetracosane. This increase in self-diffusion coefficient has a correlation with decrease in density. The dependency of self-diffusion coefficient on density is nonlinear in the liquid and vapor side of the interface region and is linear in between the above two regions. Influence of chain length of the alkane molecules has been studied by comparing the physical and structural quantities of decane, tetracosane and hexatriacontane at the same reduced temperature. At the same reduced temperature, self-diffusion coefficient decreases with an increase in chain length in the interface region as well as in the bulk liquid region. All three alkanes show similar tendency of ordering and chain conformation at the interface at the same reduced temperature. (C) 2012 Elsevier Ltd. All rights reserved.
Preface 査読有り

Shigenao Maruyama, Taku Ohara

Journal of Thermal Science and Technology　8　(2)　336　2013年

DOI： 10.1299/jtst.8.336 　

ISSN：1880-5566
Crosslinking Effect in Amorphous Polymers on Heat Transfer Characteristics

Gota Kikugawa, Pawel Keblinski, Taku Ohara

Proceedings of the Thirteenth International Symposium on Advanced Fluid Information　194-195　2013年
Surface Termination Effect on Structure of Decane Liquid in the Vicinity of Alpha-Quartz Surfaces

Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

Proceedings of the International Conference on Flow Dynamics 2013　2013年
Thermal Transport Characteristics over the Interface of Alkanethiol SAM on a Copper Substrate and Water Solvent 査読有り

Yoichi Naruke, Gota Kikugawa, Takeshi Bessho, Satoshi Takata, Taku Ohara

Proceedings of the 12th International Symposium on Fluid Control, Measurement and Visualization (FLUCOME2013)　CD-ROM　2013年
Study of Alkane Chain Length Influence on Structure and Dynamic Properties at Intrinsic Liquid-Vapour Interfaces 査読有り

Hari Krishna Chikukoti, Gota Kikugawa, Taku Ohara

Proceedings of the 12th International Symposium on Fluid Control, Measurement and Visualization (FLUCOME2013)　CD-ROM　2013年
Molecular Dynamics Study on the Influences of Nanochannel Geometry on the Energy Transport Mechanism at Liquid-Solid Interfaces 査読有り

Masahiko Shibahara, Sho Murakami, Taku Ohara

Proceedings of the 4th International Symposium on Micro and Nanotechnology　CD-ROM　2013年
A Molecular Dynamics Study on Effect of Temperature on Diffusion in the Vicinity of an Alpha-Quartz Surface/Alkane Interfaces 査読有り

Hari Krishna Chikukoti, Gota Kikugawa, Taku Ohara

Proceedings of the 4th International Symposium on Micro and Nanotechnology　CD-ROM　2013年
Molecular dynamics mechanism of thermal energy transport in liquid methane 査読有り

Joji Haneda, Gota Kikugawa, Taku Ohara

Proc. 4th International Symposium on Micro and Nanotechnology　CD-ROM　2013年
A molecular dynamics study on mass transport properties in the vicinity of SiO2-water/IPA interfaces 査読有り

Yoichi Naruke, Shuichi Kosaka, Takeo Nakano, Gota Kikugawa, Taku Ohara

Proceedings of the 4th International Symposium on Micro and Nanotechnology　CD-ROM　2013年
Heat Conduction in Amorphous Polymers with Crosslink Formation 査読有り

Gota Kikugawa, Pawel Keblinski, Taku Ohara

Proceedings of the 4th International Symposium on Micro and Nanotechnology　CD-ROM　2013年
MASS TRANSPORT CHARACTERISTICS OF WATER/IPA AT SILICA-LIQUID INTERFACES 査読有り

Takeo Nakano, Shuichi Kosaka, Gota Kikugawa, Taku Ohara

PROCEEDINGS OF THE 11TH INTERNATIONAL CONFERENCE ON NANOCHANNELS, MICROCHANNELS, AND MINICHANNELS, 2013　CD-ROM　2013年
出版者・発行元：AMER SOC MECHANICAL ENGINEERS
DOI： 10.1115/ICNMM2013-73195 　

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Molecular dynamics simulations were performed in order to investigate the impact of temperature on molecular structure and mass transport properties in the vicinity of silica-water and/or iso-propyl alcohol (IPA) liquid film interfaces. Each of water and IPA liquid molecules form layered structures in the vicinity of the solid. Although temperature has an insignificant effect on the first layer from the solid, the layered structure at higher temperature decays farther away from the second layer comparing with that at lower temperature for both silica-water and silica-IPA systems. Moreover, interfusion of water and IPA molecules between silica substrates was simulated and molecular coverage on the substrates are analyzed for temperatures of 300 K and 350 K.
Investigation of interfacial properties at α-quartz/alkane interfaces using molecular dynamics simulations 査読有り

Hari Krishna Chikukoti, Gota Kikugawa, Taku Ohara

International Journal of Advanced Research in Engineering & Technology　4　(3)　68-76　2013年
Molecular dynamics study on the influences of nanostructure geometry on the energy transport and the local non-equilibrium behavior at the liquid-solid interface 査読有り

Sho Murakami, Masahiko Shibahara, Taku Ohara

Proceedings of the 8th KSME-JSME Thermal and Fluids Engineering Conference　CD-ROM　2012年3月
Preface 査読有り

Shigenao Maruyama, Taku Ohara

Journal of Thermal Science and Technology　7　(2)　350　2012年

DOI： 10.1299/jtst.7.350 　

ISSN：1880-5566
Molecular Dynamics Simulation of Thermal and Fluid Phenomena 査読有り

Taku Ohara

JOURNAL OF JAPANESE SOCIETY OF TRIBOLOGISTS　57　(8)　547-553　2012年
出版者・発行元：JAPAN SOC TRIBOLOGISTS
ISSN：0915-1168
熱流体現象の分子動力学シミュレーション招待有り査読有り

小原拓

トライボロジスト　57　(8)　547-553　2012年
出版者・発行元：日本トライボロジー学会
ISSN：0915-1168
Molecular Dynamics Study on the Influences of Nanostructure Geometry on the Energy Transport and Local Non-Equilibrium Behavior at Liquid-Solid Interfaces 査読有り

S. Murakami, M. Shibahara, T. Ohara

Proceedings of the 23rd International Symposium on Transport Phenomena　CD-ROM　2012年
Molecular Dynamics Simulation of Liquid-Vapor Interfacial Properties of n-Alkanes 査読有り

Hari Krishna Chikukoti, G. Kikugawa, T. Ohara

Proceedings of the 3rd International Forum on Heat Transfer　2012年
A Molecular Dynamics Study on Molecular Scale Structure and Mass Transport Properties in the Vicinity of SiO2-Water/IPA Interfaces 査読有り

S. Kosaka, G. Kikugawa, T. Nakano, T. Ohara

Proceedings of the 3rd International Forum on Heat Transfer　2012年
Energy dissipation in non-isothermal molecular dynamics simulations of confined liquids under shear 査読有り

Hassan Berro, Nicolas Fillot, Philippe Vergne, Takashi Tokumasu, Taku Ohara, Gota Kikugawa

JOURNAL OF CHEMICAL PHYSICS　135　(13)　134708　2011年10月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3644938 　

ISSN：0021-9606

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Energy is commonly dissipated in molecular dynamics simulations by using a thermostat. In non-isothermal shear simulations of confined liquids, the choice of the thermostat is very delicate. We show in this paper that under certain conditions, the use of classical thermostats can lead to an erroneous description of the dynamics in the confined system. This occurs when a critical shear rate is surpassed as the thermo-viscous effects become prominent. In this high-shear-high-dissipation regime, advanced dissipation methods including a novel one are introduced and compared. The MD results show that the physical modeling of both the accommodation of the surface temperature to liquid heating and the heat conduction through the confining solids is essential. The novel method offers several advantages on existing ones including computational efficiency and easiness of application for complex systems. (C) 2011 American Institute of Physics. [doi:10.1063/1.3644938]
Heat conduction in chain polymer liquids: Molecular dynamics study on the contributions of inter- and intramolecular energy transfer 査読有り

Taku Ohara, Tan Chia Yuan, Daichi Torii, Gota Kikugawa, Naohiro Kosugi

JOURNAL OF CHEMICAL PHYSICS　135　(3)　034507　2011年7月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3613648 　

ISSN：0021-9606

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In this paper, the molecular mechanisms which determine the thermal conductivity of long chain polymer liquids are discussed, based on the results observed in molecular dynamics simulations. Linear n-alkanes, which are typical polymer molecules, were chosen as the target of our studies. Non-equilibrium molecular dynamics simulations of bulk liquid n-alkanes under a constant temperature gradient were performed. Saturated liquids of n-alkanes with six different chain lengths were examined at the same reduced temperature (0.7T(c)), and the contributions of inter- and intramolecular energy transfer to heat conduction flux, which were identified as components of heat flux by the authors' previous study [J. Chem. Phys. 128, 044504 (2008)], were observed. The present study compared n-alkane liquids with various molecular lengths at the same reduced temperature and corresponding saturated densities, and found that the contribution of intramolecular energy transfer to the total heat flux, relative to that of intermolecular energy transfer, increased with the molecular length. The study revealed that in long chain polymer liquids, thermal energy is mainly transferred in the space along the stiff intramolecular bonds. This finding implies a connection between anisotropic thermal conductivity and the orientation of molecules in various organized structures with long polymer molecules aligned in a certain direction, which includes confined polymer liquids and self-organized structures such as membranes of amphiphilic molecules in water. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3613648]
Preface 査読有り

Shigenao Maruyama, Taku Ohara

Journal of Thermal Science and Technology　6　(2)　203　2011年

DOI： 10.1299/jtst.6.203 　

ISSN：1880-5566
Effects of the Nanostructural Geometry at a Liquid-Solid Interface on the Interfacial Thermal Resistance and the Liquid Molecular Non-Equilibrium Behaviors 査読有り

Masahiko Shibahara, Taku Ohara

JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY　6　(2)　247-255　2011年
出版者・発行元：JAPAN SOC MECHANICAL ENGINEERS
DOI： 10.1299/jtst.6.247 　

ISSN：1880-5566

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The effects of the structural geometry at the nanometer scale on the thermal resistance at a liquid molecule-solid interface, as well as the interfacial energy transport mechanism of liquid molecules, were investigated directly by the nonequilibrium classical molecular dynamics simulations. The 12-6 Lennard-Jones potential energy functions for liquid molecules and the channel structure at the nanometer scale are employed so as to discuss the effects of the surface geometry at the nanometer scale on the interfacial thermal resistance in comparison with a flat surface. The thermal resistance between solid and liquid molecules was calculated by the temperature discontinuity at the liquid-solid interface and the energy flux that was added or subtracted by the Langevin method per unit area so as to maintain a constant boundary temperature of solid walls. The substantial interfacial thermal resistance reduction depending on the interaction parameters between solids and liquid molecules was observed in the case of the nanostructure surface in comparison with the flat surface. The liquid-solid interfacial thermal resistance reduction in the case of nanostructure surface relates to the energy transport mechanism change at the liquid-solid interface and the surface area magnification.
Interfacial Heat Transfer Characteristics over the Self-Assembled Monolayer and Solvent Interfaces

G. Kikugawa, T. Ohara, T. Kawaguchi, I. Kinefuchi, Y. Matsumoto

7th US-Japan Joint Seminar on Nanoscale Transport Phenomena - Science and Engineering -　44-44　2011年
GPUを用いた適応的粒子系可視化査読有り

小田川雅人, 竹島由里子, 藤代一成, 菊川豪太, 小原拓

日本機械学会論文集B編　77　(781)　1767-1778　2011年

DOI： 10.1299/kikaib.77.1767 　

ISSN：0387-5016
液体中の熱伝導：分子動力学による一描像招待有り査読有り

小原拓

伝熱　50　(211)　37-43　2011年
Momentum and Heat Transport in Nanoscale Lubrication of Alkane Thin Film Sheared by Self-Assembled Monolayer Surfaces 査読有り

G. Kikugawa, N. Yamamoto, T. Ohara

Proceedings of the 4th International Conference on Heat Transfer and Fluid Flow in Microscale　CD-ROM　2011年
A MOLECULAR DYNAMICS STUDY ON HEAT TRANSFER CHARACTERISTICS OVER THE INTERFACE OF SELF-ASSEMBLED MONOLAYER AND WATER SOLVENT 査読有り

Gota Kikugawa, Taku Ohara, Toru Kawaguchi, Ikuya Kinefuchi, Yoichiro Matsumoto

PROCEEDINGS OF THE ASME/JSME 8TH THERMAL ENGINEERING JOINT CONFERENCE 2011, VOL 3　405-+　2011年
出版者・発行元：AMER SOC MECHANICAL ENGINEERS

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We performed molecular dynamics simulations of the interface which is comprised of self-assembled monolayer (SAM) and water solvent to investigate heat transfer characteristics. In particular, local thermal boundary conductance (TBC), which is an inverse of so-called Kapitza resistance, at the SAM solvent interface was evaluated by using the nonequilibrium MD (NEMD) technique in which the one-dimensional thermal energy flux was imposed across the interface. By using two kinds of SAM terminal with hydrophobic and hydrophilic properties, the local TBCs of these interfaces with water solvent were evaluated, and the result showed a critical difference due to an affinity between SAM and solvent. In order to elucidate the reason for this difference, microscopic components contributing to thermal energy flux across the interface were evaluated in detail, i.e., the total thermal energy flux is decomposed into the contribution of molecular transport and that of energy exchange by molecular interactions.
EFFECT OF ALKYL CHAIN LENGTH ON MOLECULAR HEAT TRANSFER CHARACTERISTICS IN LIPID BILAYERS 査読有り

Takeo Nakano, Gota Kikugawa, Taku Ohara

PROCEEDINGS OF THE ASME/JSME 8TH THERMAL ENGINEERING JOINT CONFERENCE 2011, VOL 3　397-403　2011年
出版者・発行元：AMER SOC MECHANICAL ENGINEERS

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Nonequilibrium molecular dynamics simulations are carried out on single component lipid bilayers with ambient water in order to investigate the effect of acyl chain length on heat transport characteristics along and across the membranes. In this study, dipalmitoyl-phosphatidyl-choline (DPPC), dilauroyl-phosphatidyl-choline (DLPC), and stearoyl-myristoyl-phosphatidyl-choline (SMPC) which has two acyl chains of both sixteen C atoms, both twelve C atoms, and eighteen and fourteen C atoms, respectively, were used as lipid molecules. In the direction along the membranes, thermal conductivity corresponds with that of each membrane. On the other hand, in the direction across membrane, the highest thermal resistance exists at the center of lipid bilayer where lipid acyl chains face each other However asymmetric chain length reduces thermal resistance at the interface between lipid monolayers. Therefore, thermal conductivity across the membrane which consists of asymmetric chain length is higher than those which consist of symmetric chain length.
EFFECTS OF THE NANOSTRUCTURAL GEOMETRY AT A LIQUID-SOLID INTERFACE ON THE INTERFACIAL THERMAL RESISTANCE AND THE LIQUID MOLECULAR NON-EQUILIBRIUM BEHAVIORS 査読有り

Masahiko Shibahara, Taku Ohara

PROCEEDINGS OF THE ASME/JSME 8TH THERMAL ENGINEERING JOINT CONFERENCE 2011, VOL 3　6　(2)　497-+　2011年
出版者・発行元：AMER SOC MECHANICAL ENGINEERS
DOI： 10.1299/jtst.6.247 　

ISSN：1880-5566

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The effects of the structural geometry at the nanometer scale on the thermal resistance at a liquid molecule-solid interface, as well as the interfacial energy transport mechanism of liquid molecules, were investigated directly by the nonequilibrium classical molecular dynamics simulations. The 12-6 Lennard-Jones potential energy functions for liquid molecules and the channel structure at the nanometer scale are employed so as to discuss the effects of the surface geometry at the nanometer scale on the interfacial thermal resistance in comparison with a flat surface. The thermal resistance between solid and liquid molecules was calculated by the temperature discontinuity at the liquid-solid interface and the energy flux that was added or subtracted by the Langevin method per unit area so as to maintain a constant boundary temperature of solid walls. The substantial interfacial thermal resistance reduction depending on the interaction parameters between solids and liquid molecules was observed in the case of the nanostructure surface in comparison with the flat surface. The liquid-solid interfacial thermal resistance reduction in the case of nanostructure surface relates to the energy transport mechanism change at the liquid-solid interface and the surface area magnification.
Thickness uniformity of spin coated film influenced by nonuniform temperature of substrates 査読有り

Taku Ohara, Shinichiro Matsubara, Hirotoshi Kadowaki, Gota Kikugawa, Kazuhiro Takeshita, Tomoko Hamada

International Journal of Emerging Multidisciplinary Fluid Sciences　2　(4)　215-232　2010年12月1日

DOI： 10.1260/1756-8315.2.4.215 　

ISSN：1756-8315

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The film thinning process in the spin coating has been analyzed by finite difference computational simulations. The coating liquid was assumed to be a solution of polymer solute and volatile organic solvent, for which Newtonian viscosity was given as a function of solute concentration. The flow of the coating liquid film that covers the entire substrate surface was analyzed where heat and mass transfer due to evaporation of solvent and heating/cooling by the substrate surface were taken into consideration. The whole process until all the solvent evaporates off the coating liquid and a dry coating film of the solute is left on the substrate was solved, and then the final film thickness was determined. Especially, influences of nonuniform substrate temperature on the profile of the final film thickness have been focused, for which three dimensional computational simulations have been performed. The case where the substrate is at rest and coating is processed only by drying the liquid film after a certain amount of solution liquid is deposited has also been analyzed and it was found that the final film thickness is larger at the local region of substrate with a higher temperature, exhibiting somewhat complicated thickness profiles.
A molecular dynamics study on heat conduction characteristics in DPPC lipid bilayer 査読有り

Takeo Nakano, Gota Kikugawa, Taku Ohara

JOURNAL OF CHEMICAL PHYSICS　133　(15)　154705　2010年10月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3481650 　

ISSN：0021-9606

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In this paper, nonequilibrium molecular dynamics simulations were performed on a single component 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine lipid bilayer in order to investigate the thermal conductivity and its anisotropy. To evaluate the thermal conductivity, we applied a constant heat flux to the lipid bilayer along and across the membrane with ambient water. The contribution of molecular interaction to the heat conduction was also evaluated. Along the bilayer plane, there is little transfer of thermal energy by the interaction between lipid molecules as compared with the interaction between water molecules. Across the bilayer plane, the local thermal conductivity depends on the constituents (i.e., water, head group, and tail group of lipid molecule) that occupy the domain. Although the intramolecular transfer of thermal energy in the tail groups of lipid molecules works efficiently to promote high local thermal conductivity in this region, the highest thermal resistance appears at the center of lipid bilayer where acyl chains of lipid molecules face each other due to a loss of covalent-bond and low number density. The overall thermal conductivities of the lipid bilayer in the directions parallel and perpendicular to the lipid membrane have been compared, and it was found that the thermal conductivity normal to the membrane is higher than that along the membrane, but it is still smaller than that of bulk water. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3481650]
自己組織化単分子膜のための粒子配置設計支援システム招待有り

竹島由里子, 新坂拓真, 菊川豪太, 小原拓, 藤代一成

第38回可視化情報シンポジウム講演論文集　30　(1)　277-280　2010年7月21日
出版者・発行元：可視化情報学会
T0501-1-2 酸化物固体-溶媒界面における溶質移動に関する2次元自由エネルギー曲面([T0501-1]マイクロ・ナノスケールの熱流体現象(1))

菊川豪太, 加藤惇平, 小原拓

年次大会講演論文集　2010　71-72　2010年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmemecjo.2010.8.0_71 　

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In this paper, we investigated mass transfer of Fe^<2+> ions adjacent to the magnetite (Fe_3O_4) solid surface from the microscopic viewpoint by using the molecular dynamic simulations. Not only mass transfer characteristic across the interface, but also that along the interface has to be elucidated in order to predict the strict transport path and diffusion process of ions in the vicinity of the interface. Therefore, we here evaluated two-dimensional free energy surface along the interface according to the ion translation. With Fe^<2+> ions fixed at a certain surface separation distance (SSD), the umbrella sampling/WHAM (weighted histogram analysis method) procedure which can be applied to two-dimensional space was adopted for free energy calculations. As a result, it was found that the free energy surface is significantly influenced by the surface charge distribution of the magnetite surface.
T0501-1-1 自己組織化膜修飾が固液界面熱抵抗に与える諸影響の分子論的解析([T0501-1]マイクロ・ナノスケールの熱流体現象(1))

川口暢, 菊川豪太, 杵淵郁也, 八束真一, 小原拓, 松本洋一郎

年次大会講演論文集　2010　69-70　2010年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmemecjo.2010.8.0_69 　

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We studied the influential factors on heat transfer at Au-toluene interface modified by dodecanethiol self-assembled monolayer (SAM). The thermal boundary conductance was calculated for different temperatures using nonequilibrium molecular dynamics simulation. As a result, the overall thermal boundary conductance at Au-SAM-toluene interface decreases as the temperature increases. We analyzed the temperature dependence of SAM structure and discussed the relation between SAM structure and thermal boundary conductance.
T0501-2-1 せん断流中における脂質二重膜の運動量伝搬特性に関する分子動力学的研究([T0501-2]マイクロ・ナノスケールの熱流体現象(2))

中野雄大, 菊川豪太, 小原拓

年次大会講演論文集　2010　81-82　2010年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmemecjo.2010.8.0_81 　

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Nonequilibrium molecular dynamics simulations were conducted for lipid bilayers with ambient water under two directions of shear flow along the bilayer plane to investigate mechanisms of momentum transfer characteristics in the membranes. Under a shear flow parallel to the bilayer plane, intermolecular interaction contributes to momentum flux positively in the lipid tail area, while negative flux due to intramolecular interaction arises. In the lipid head area, positive and negative contributions of each interaction invert. Under a shear flow perpendicular to the bilayer plane, the largest fraction to total momentum flux in the lipid bilayer is in the lipid head groups. This indicates that the contribution of the head group is the most dominant to surface shear viscosity in the lipid bilayer.
Molecular-Scale Mechanism of Thermal Resistance at the Solid-Liquid Interfaces: Influence of Interaction Parameters Between Solid and Liquid Molecules 査読有り

Daichi Torii, Taku Ohara, Kenji Ishida

JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME　132　(1)　2010年1月
出版者・発行元：ASME-AMER SOC MECHANICAL ENG
DOI： 10.1115/1.3211856 　

ISSN：0022-1481

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The solid-liquid interfacial thermal resistance is getting more and more important as various solid-liquid systems are utilized in nanoscale, such as micro electro-mechanical systems/nano electro-mechanical systems (MEMS/NEMS) with liquids and nanoparticle suspension in liquids. The present paper deals with the transport of thermal energy through the solid-liquid interfaces, and the goal is to find a molecular-scale mechanism that determines the macroscopic characteristics of the transport phenomena. Nonequilibrium molecular dynamics simulations have been performed for systems of a liquid film confined between atomistic solid walls. The two solid walls have different temperatures to generate a steady thermal energy flux in the system, which is the element of macroscopic heat conduction flux. Three kinds of liquid molecules and three kinds of solid walls are examined, and the thermal energy flux is measured at the control surfaces in the liquid film and at the solid-liquid interfaces. The concept of boundary thermal resistance is extended, and it is defined for each degree of freedom of translational motion of the molecules. It is found that the interaction strength between solid and liquid molecules uniformly affects all boundary thermal resistances defined for each degree of freedom; the weaker interaction increases all the resistances at the same rate and vice versa. The boundary thermal resistances also increase when the solid and liquid molecules are incommensurate, but the incommensurability has a greater influence on the boundary thermal resistances corresponding to the molecular motion parallel to the interface than that for the normal component. From these findings it is confirmed that the thermal resistance for the components parallel to the interface is associated with the molecular-scale corrugation of the surface of the solid wall, and that the thermal resistance for the component normal to the interface is governed by the number density of the solid molecules that are in contact with the liquid.
Heat Transfer Characteristics at the SAM Interface of Self-Assembled Monolayer with Hydrophobic and Hydrophilic Termini and Solvent

G. Kikugawa, T. Ohara, T. Kawaguchi, I. Kinefuchi, Y. Matsumoto

Proc. 7th International Conference on Flow Dynamics　370-371　2010年
Molecular Momentun Transfer Characteristics of Liquid Behaviors in Shear Flows

T. Nakano, G. Kikugawa, T. Ohara

Proc. 7th International Conference on Flow Dynamics　368-369　2010年
Assesment of Different Thermostating Techniques in the Simulation of Molecular Lubrication

H. Berro, T. Tokumasu, T. Ohara, G. Kikugawa, N. Fillot, P. Vergne

Proceedings of the 10th International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　128-129　2010年
非平衡分子動力学法を用いた親水性末端基を有する自己組織化膜と水の界面熱抵抗の解析査読有り

川口暢, 菊川豪太, 杵淵郁也, 八束真一, 小原拓, 松本洋一郎

日本機械学会論文集C編　76　(768)　1936-1938　2010年
出版者・発行元：None
DOI： 10.1299/kikaic.76.1936 　

ISSN：0387-5024
長鎖ポリマー液体の熱伝導率：分子間及び分子内エネルギー伝搬の寄与についての分子動力学的研究査読有り

タンチアユアン, 鳥居大地, 小杉直央, 菊川豪太, 小原拓

熱物性　24　(3)　134-140　2010年
出版者・発行元：JAPAN SOCIETY OF THERMOPHYSICAL PROPERTIES
DOI： 10.2963/jjtp.24.134 　

ISSN：0913-946X

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長鎖状ポリマー分子からなる液体中の熱伝導を決定する分子スケールのメカニズムについて，分子動力学シミュレーションによる観察結果に基づいて議論する．典型的なポリマー分子として直鎖アルカンを選択し，そのバルク液体に一定の温度勾配及び熱流束を誘起させる非平衡分子動力学シミュレーションを行った．鎖長が異なる6種類の直鎖アルカン分子からなる対臨界温度0.7の飽和液を対象として，熱流束の構成要素である分子間・分子内相互作用によるエネルギー伝搬の大きさを観測した．その結果，分子の鎖長が長いほど，分子内エネルギー伝搬がなす寄与が分子間エネルギー伝搬と比較して大きくなり，長鎖ポリマー液体中では分子内の強固な結合に沿った熱エネルギーの空間中の移動が熱伝導流束を構成する主な因子であることが明らかになった．
MOLECULAR DYNAMICS STUDY OF INTERFACIAL THERMAL RESISTANCE OF MERCAPTO-ALKANOL SELF-ASSEMBLED MONOLAYER AND WATER 査読有り

Touru Kawaguchi, Gota Kikugawa, Ikuya Kinefuchi, Taku Ohara, Shinichi Yatuzuka, Yoichiro Matsumoto

MNHMT2009, VOL 2　217-221　2010年
出版者・発行元：AMER SOC MECHANICAL ENGINEERS

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The interfacial thermal resistance of 11-mercaptoundecanol (-S(CH2)(11)OH) self-assembled monolayer (SAM) adsorbed on Au(111) substrate and water was investigated using nonequilibrium molecular dynamics simulations. The interfacial thermal resistance was found to be a half of that in the system which consists of 1-dodecanthiol (-S(CH2)(11)CH3) SAM adsorbed on Au(111) and toluene [Kikugawa G. et al., J. Chem. Phys. (2009)]. The effective thermal energy transfer originates from hydrogen-bond structure between the SAM and water molecules in spite of weak structurization of water molecules near the SAM surface.
A molecular dynamics study on heat transfer characteristics at the interfaces of alkanethiolate self-assembled monolayer and organic solvent 査読有り

Gota Kikugawa, Taku Ohara, Toru Kawaguchi, Eiichi Torigoe, Yasumasa Hagiwara, Yoichiro Matsumoto

JOURNAL OF CHEMICAL PHYSICS　130　(7)　074706　2009年2月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3077315 　

ISSN：0021-9606

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In this paper, we present molecular dynamics (MD) simulations of interfaces composed of self-assembled monolayers (SAMs) and solvents in order to investigate the heat transfer characteristics at the interface. Two typical normal alkylthiolate SAMs with different chain lengths, i.e., 1-propanethiol C(3)H(7)SH and 1-dodecanethiol (C(12)H(25)SH) chemically adsorbed on Au(111) substrate surfaces, were used, and toluene was adopted as the organic solvent. In addition to the SAM systems, an interface composed of the bare solid substrate and solvent (without SAMs) was analyzed for comparison. Nonequilibrium MD simulations, in which a temperature gradient perpendicular to the interface was imposed, were performed and the difference in thermal boundary resistance in the interface systems was discussed. We observed that the SAM interfaces have smaller thermal resistance when compared with that of the bare solid interface. In order to understand the mechanisms of the small resistance at the SAM-solvent interfaces, the vibrational character of molecules in each phase, which contacted each other at the interface was analyzed and a detailed adsorbed structure of solvent molecule in the interface region was extracted. As a result, a clear difference in these characters was found between the SAM interfaces and bare solid interface.
T0501-1-5 ポリマー液体の熱輸送特性に及ぼす分子内エネルギー伝搬の影響(マイクロ・ナノスケールの熱流体現象(1))

タンチアユアン, 小杉直央, 鳥居大地, 菊川豪太, 小原拓

年次大会講演論文集　2009　103-104　2009年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmemecjo.2009.8.0_103 　

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Molecular dynamics simulations have been performed to investigate the effects of intramolecular energy transfer on heat conduction characteristics in bulk liquids of n-alkanes with several chain lengths. A simulation system which consists of a rectangular basic cell, where the periodic boundary condition is applied in all directions, is filled with n-alkane molecules. Artificially 'hot' and 'cold' slabs are placed at the middle and at both sides of the cell to generate constant heat energy flux in the system. Contributions of molecular motion and molecular interaction to thermal energy flux are measured in detail by applying a mathematical expression for thermal energy flux in molecular dynamic system which is extended to many-body potentials. The results show that the contribution of intramolecular energy transfer to the total thermal energy flux in n-alkane liquids increases with the extension of the molecular length when compared at the same reduced temperature and the saturation densities.
T0501-4-3 コーティング液膜流れの3次元数値解析(マイクロ・ナノスケールの熱流体現象(4))

門脇宏宗, 松原慎一郎, 菊川豪太, 小原拓

年次大会講演論文集　2009　135-136　2009年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmemecjo.2009.8.0_135 　

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The transient process of a liquid film flow that covers a rotating substrate in the spin coating process was analyzed by a 3-D computational simulation using the finite difference method. Evaporation of solvent and change of thermophysical properties such as viscosity was taken into account The case of nonuniform temperature distribution of the substrate was analyzed applying ring-like and spot-like high temperature region on the substrate, and it was concluded that hot ring/spot on the substrate results in large final film thickness on those ring/spot. As a special case of the spin coating, the drying process of the coating liquid on a substrate that was not rotating was also simulated, and it was found that the hot range on the substrate produces complicated profiles of the final film thickness.
T0501-1-3 固体表面近傍の水中における物質輸送特性(マイクロ・ナノスケールの熱流体現象(1))

加藤惇平, 菊川豪太, 小原拓, チアユアンタン

年次大会講演論文集　2009　99-100　2009年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmemecjo.2009.8.0_99 　

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Molecular dynamics simulations of the magnetite-water interface with eluted ions(Fe^<2+>, Fe(OH)_2 ) were performed in order to estimate free energy profile of the ions across the interface. The purpose of examining the free energy profile is to discuss mass transfer characteristics in the vicinity of interface. The free energy profile was calculated by using the umbrella sampling and WHAM procedure. From the calculation, we show that in the case of Fe^<2+> ion, a high free energy barrier exist at the solvent surface. On the other hand, in the case of Fe(OH)_2, the free energy barrier is not recognized because the strong coulomb interaction between hydroxyl group of Fe(OH)_2 and the magnetite surface contributes decrease of the energy barrier.
T0501-1-6 SAM内部およびSAM界面における熱輸送特性の分子動力学的研究(マイクロ・ナノスケールの熱流体現象(1))

菊川豪太, 持丸孝人, 小原拓, 川口暢, 松本洋一郎

年次大会講演論文集　2009　105-106　2009年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmemecjo.2009.8.0_105 　

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In this paper, we focused on heat transfer characteristics in the self-assembled monolayer (SAM) system with elucidating the dominant contribution of the molecular interactions to the heat transfer in each constituent phase, i.e., the alkanethiolate SAM phase, the interface of SAM and solvent, and alkane solvent phase. By using direct nonequilibrium molecular dynamics simulations, in which the temperature gradient was imposed across the SAM interface, each component of heat flux vector, which is transferred by molecular interactions including intra- and intermolecular interactions, were separately measured. Moreover, in order to investigate the effect of the SAM modification on thermal boundary resistance of the solid-liquid interface, the bare solid interface without the SAM was examined as well. As a result, the thermal boundary resistance at the SAM interface is much lower than that at the bare solid interface.
T0501-1-2 せん断流動場における脂質二重膜の運動量輸送特性の異方性に関する分子動力学的研究(マイクロ・ナノスケールの熱流体現象(1))

中野雄大, 菊川豪太, 小原拓

年次大会講演論文集　2009　97-98　2009年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmemecjo.2009.8.0_97 　

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Nonequilibrium molecular dynamics simulations were performed for lipid bilayers with ambient water under two shear flows along the bilayer plane to investigate mechanisms of heat generation and momentum transfer characteristics in the membranes. Under parallel shear flow to the bilayer, temperature rises by viscous heating in water layer and by frictional heating at the interface between two lipid monolayers. In the lipid tail area, intermolecular interaction contributes to momentum flux positively, while negative flux due to intramolecular interaction arises. In the lipid head area, positive and negative contributions of each interaction inverts. Under perpendicular shear flow to the bilayer, temperature of lipid is higher than that of water because of the difference of heat production by viscous heating and thermal conductivity. Momentum is dominantly transferred by intra- and intermolecular interaction between lipids. From the both simulations, friction coefficient at the interface of lipid acyl chains and surface shear viscosity of lipid are evaluated.
The Effect of Different Thermostating Techniques on Friction and Dissipation in Molecular Dynamics Simulations of Confined Lubrication Films

Hassan Berro, Nicoas Fillot, Philippe Vergne, Takashi Tokumasu, Taku Ohara, Gota Kikugawa

Proc. of the World Tribology Congress 2009　622　2009年
Heat Transfer Characteristics inside the SAM layer and at the SAM interface

Gota Kikugawa, Taku Ohara, Toru Kawaguchi, Ikuya Kinefuchi, Yoichiro Matsumoto

Proc. 6th International Conference on Flow Dynamics　534-535　2009年
Thermal conductivity of silicon nanowire by nonequilibrium molecular dynamics simulations 査読有り

Shuai-chuang Wang, Xin-gang Liang, Xiang-hua Xu, Taku Ohara

JOURNAL OF APPLIED PHYSICS　105　(1)　14316　2009年1月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3063692 　

ISSN：0021-8979

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The thermal conductivity of silicon nanowires was predicted using the nonequilibrium molecular dynamics method using the Stillinger-Weber potential model and the Nose-Hoover thermostat. The dependence of the thermal conductivity on the wire length, cross-sectional area, and temperature was investigated. The surface along the longitudinal direction was set as a free boundary with potential boundaries in the other directions. The cross-sectional areas of the nanowires ranged from about 5 to 19 nm(2) with lengths ranging from 6 to 54 nm. The thermal conductivity dependence on temperature agrees well with the experimental results. The reciprocal of the thermal conductivity was found to be linearly related to the nanowire length. These results quantitatively show that decreasing the cross-sectional area reduces the phonon mean free path in nanowires. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3063692]
SAM–溶媒界面の界面熱抵抗に関する分子動力学的研究査読有り

菊川豪太, 小原拓, 川口暢, 鳥越栄一, 萩原康正, 松本洋一郎

日本機械学会論文集B編　75　(749)　146-154　2009年
出版者・発行元：日本機械学会
DOI： 10.1299/kikaib.75.749_146 　

ISSN：0387-5016

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In this paper, we perform molecular dynamics (MD) simulations of the interfaces composed of the self-assembled monolayer (SAM) and organic solvent in order to investigate the interfacial heat transfer characteristics of SAMs from the microscopic viewpoint. Archetypal SAMs, i.e., alkanethiol molecules chemically adsorbed on Au (111) substrate, and toluene solvent are adopted for the computational system. Two alkanethiols with different chain lengths, that is, 1-propanethiol (C_3H_7SH) and 1-dodecanethiol (C_<12>H_<25>SH), are used for SAM interface systems. In addition to the SAM interfaces, bare solid substrate without SAM are examined for comparison of the heat transfer characteristics. Nonequilibrium MD (NEMD) simulations in which a temperature gradient is imposed across the interface are performed and the interfacial thermal resistance in each system is discussed. As a result, it is shown that the SAM-solvent interfaces have the smaller thermal resistance as compared with that at the bare Au interface. In order to investigate the mechanisms of the small resistance at SAM-solvent interface, a vibrational character of molecules in the interface region and an adsorbed structure of solvent molecules are discussed.
Heat transfer characteristics inside the SAM layer and at the SAM interfaces with organic solvents 査読有り

Gota Kikugawa, Takahito Mochimaru, Taku Ohara, Toru Kawaguchi, Yoichiro Matsumoto

Proceedings of 2nd Asian Symposium on Computational Heat Transfer and Fluid Flow　CD-ROM　225-229　2009年
A molecular dynamics Study on lipid bilayers in shear flows 査読有り

Takeo Nakano, Gota Kikugawa, Taku Ohara

Proceedings of 2nd Asian Symposium on Computational Heat Transfer and Fluid Flow　CD-ROM　220-224　2009年
数万オーダ粒子系のイメージベース可視化招待有り

小田川雅人, 竹島由里子, 藤代一成, 菊川豪太, 小原拓

第３６回可視化情報シンポジウム講演論文集　28　(1)　73-74　2008年7月
出版者・発行元：可視化情報学会
ISSN：0916-4731
Molecular-scale heat transfer in liquids and at liquid-solid interfaces: Toward the quality evaluation of heat flux 招待有り査読有り

Taku Ohara

JOURNAL OF COMPUTATIONAL AND THEORETICAL NANOSCIENCE　5　(2)　175-186　2008年2月
出版者・発行元：AMER SCIENTIFIC PUBLISHERS
ISSN：1546-1955

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Molecular mechanism of heat conduction in liquids and at solid-liquid interfaces, which is getting important recently especially in the field of micro/nanofluidics and biodevices, is discussed based on the results of the authors' molecular dynamics (MD) simulations. The concept of intermolecular energy transfer (IET) is introduced as a view of molecular-scale mechanism of heat conduction in liquids focusing attention on the liquid structure that transfers thermal energy. Characteristics of various types of IET are examined. Heat conduction flux is a sum of IET and in that sense, heat conduction flux is a product assembled with various types of IET as "parts." In case of heat conduction in highly nonequilibrium thermal state, only some types of IET constitute particular contribution to macroscopic heat conduction flux. A case of a solid-liquid interface through which high heat flux exists is reported as an example. In this case, a type of IET passes through the interface with a low thermal boundary resistance and other types do with a high resistance. The overall thermal boundary resistance of a solid-liquid interface depends on the types of IET of which the heat flux consists. For example, high thermal resistance is resulted if the heat flux consists of "high-resistance type" IET On the other hand, heat flux consisting of "low-resistance type" IET can pass through the interface with a small temperature drop. A sort of "quality" of heat flux, which is determined by IET as its "parts" can thus be defined.
505 アルカン液体の固液界面におけるエネルギー・運動量伝搬特性(T07-1 流体及び界面におけるナノ構造と流動特性(1),大会テーマセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

タンチアユアン, 鳥居大地, 菊川豪太, 小原拓

年次大会講演論文集　2008　209-210　2008年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmemecjo.2008.8.0_209 　

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Molecular dynamics simulations have been performed on ultra-thin liquid film which is sheared between two solid surfaces to clarify the mechanisms and characteristics of momentum and thermal energy transfer at solid-liquid interface. Four types of crystal plane of FCC lattice were examined for the surface of platinum solid wall and four types of n-alkane were employed as liquid. It was found that transfer characteristics of thermal energy and momentum at the solid-liquid interfaces were significantly influenced by the types of crystal plane of the solid surface and the length of the n-alkanes.
507 SAM-溶媒界面における界面熱抵抗特性の分子論的研究(T07-2 流体及び界面におけるナノ構造と流動特性(2),大会テーマセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

菊川豪太, 小原拓, 川口暢, 鳥越栄一, 萩原康正, 松本洋一郎

年次大会講演論文集　2008　213-214　2008年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmemecjo.2008.8.0_213 　

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In this paper, we perform molecular dynamics simulations of self-assembled monolayer (SAM) and solvent interfaces in order to elucidate the microscopic mechanisms of interfacial heat transfer at the SAM interfaces. Archetypal SAM systems, i.e., n-alkanethiol chemically adsorbed on Au (111), and toluene solvent are employed in our simulations. By using nonequilibrium molecular dynamics technique, a temperature gradient is imposed perpendicular to the interface, and interfacial heat transfer characteristics are analyzed. In addition to the SAM systems, a bare solid substrate and solvent system is examined to compare thermal boundary resistances at the SAM-modified interface and non-modified one. As a result, we find a significant decrease of the thermal boundary resistance at the SAM-toluene interface as compared to that of the bare Au interface. In order to explain this effect, we focus on the adsorption structure of toluene in the vicinity of the interface.
Contribution of inter- and intramolecular energy transfers to heat conduction in liquids 査読有り

Daichi Torii, Takeo Nakano, Taku Ohara

JOURNAL OF CHEMICAL PHYSICS　128　(4)　44504　2008年1月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2821963 　

ISSN：0021-9606

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The molecular dynamics expression of heat flux, originally derived by Irving and Kirkwood [J. Chem. Phys. 18, 817 (1950)] for pairwise potentials, is generalized in this paper for systems with many-body potentials. The original formula consists of a kinetic part and a potential part, and the latter term is found in the present study to be expressible as a summation of contributions from all the many-body potentials defined in the system. The energy transfer among a set of sites for which a many-body potential is defined is discussed and evaluated by the rate of increase in the kinetic energy of each site due to the potential, and its accumulation over all the potentials in the system is shown to make up the potential part of the generalized expression. A molecular dynamics simulation for liquid n-octane was performed to demonstrate the applicability of the new expression obtained in this study to measure the heat flux and to elucidate the contributions of inter- and intramolecular potentials to heat conduction.
Study on Molecular Thermal Energy Transfer in a Lipid Bilayer 査読有り

Takeo Nakano, Taku Ohara, Gota Kikugawa

JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY　3　(3)　421-429　2008年
出版者・発行元：JAPAN SOC MECHANICAL ENGINEERS
DOI： 10.1299/jtst.3.421 　

ISSN：1880-5566

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Recently, lipid bilayers attract a great deal of interest as a material with nanoscale structure. Various devices utilizing lipid bilayers, which include some kinds of sensors and molecular sorting devices, have been proposed. Understanding of thermal energy transfer in the lipid bilayers is important for utilizing the lipid bilayers as a new material for NEMS with nano structures. In this study, we have investigated the energy transfer along and across the bilayer membrane by molecular dynamics simulations of the lipid bilayer in liquid water. We found that along the bilayer membrane, thermal energy flux in the lipid bilayer is much smaller than that in the water layer. On the other hand, in case of thermal energy transfer across the membrane, total thermal resistance of the lipid bilayer-water system is composed of thermal resistances of various parts of the system, including water layer, head group of lipid, and tail hydrocarbon chain of lipid, which exhibit different magnitude of values. It is found that the tail hydrocarbon chains of lipid have the highest thermal resistance.
A Molecular Dynamics Study on the Local Structure of Liquid-Vapor Interface of Water and L-J Fluid 査読有り

Gota Kikugawa, Shu Takagi, Yoichiro Matsumoto, Taku Ohara

JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY　3　(2)　234-240　2008年
出版者・発行元：JAPAN SOC MECHANICAL ENGINEERS
DOI： 10.1299/jtst.3.234 　

ISSN：1880-5566

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Microscopic structures of a liquid-vapor interface are investigated by molecular dynamics simulations. In the previous studies, we proposed the local and instantaneous definition of the interface at the molecular level, which can capture the thermal fluctuation of the interface. By using this definition, the layering structure of water molecules at the interface was found, in other words, the structurization phenomena of water at the molecular level were clearly seen as usually found at the liquid-solid interface. In this study, we investigated the liquid-vapor interface of Lenard-Jones fluid. The effect of well depth of L-J potential parameter on the structure was also studied. Although the structurization was found at the L-J fluid as well as water, characteristic of this structure was clearly different from that of water. We consider that the difference is ascribed to the intrinsic structure of liquid and associative trend of molecules. We also discussed the anisotropic characteristics of the molecular diffusion at the interface. The anisotropy of the translational diffusion at the interface of water is stronger than that of the L-J fluid.
Ion transport by the thermally rectified Brownian ratchet 査読有り

Taku Ohara, Takeo Nakano, Daichi Torii

NANOSCALE AND MICROSCALE THERMOPHYSICAL ENGINEERING　12　(2)　144-153　2008年
出版者・発行元：TAYLOR & FRANCIS INC
DOI： 10.1080/15567260802171911 　

ISSN：1556-7265

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The Brownian ratchet is a mechanism that is effective in nanoscale for ion transport and molecular motor, in which isotropic thermal diffusion of charged particles such as ions is rectified by some asymmetric ratcheting and net mass flux in a certain direction is generated. The principle is important for future design of novel devices for particles separation, molecular motors, and ion pumps. In the present article, it is demonstrated that the combination of a nonuniform temperature field and a spatially symmetric ratchet, either of which induces no net mass transport when being applied alone, works to rectify the thermal mass diffusion and generate net mass flux of charged particles. This finding is important in the following two points: It adds a new mode of the Brownian ratchet to rectify the diffusion of particles and suggests a new method to transport particles utilizing a preexisting temperature gradient.
Molecular dynamics study on lipid-bilayer membranes in shear flow 査読有り

T. Nakano, G. Kikugawa, T. Ohara

Proc. The Seventh JSME-KSME Thermal and Fluids Engineering Conference　CD-ROM　2008年
Thermal boundary resistance at the interface of self-assembled monolayers 査読有り

G. Kikugawa, T. Kawaguchi, T. Ohara, E. Torigoe, Y. Hagiwara, Y. Matsumoto

Proc. The Seventh JSME-KSME Thermal and Fluids Engineering Conference, Sapporo　CD-ROM　2008年
Molecular dynamics study on ultrathin liquid water film sheared between platinum solid walls: Liquid structure and energy and momentum transfer 査読有り

Daichi Torii, Taku Ohara

JOURNAL OF CHEMICAL PHYSICS　126　(15)　154706　2007年4月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2719699 　

ISSN：0021-9606

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Molecular dynamics simulation has been performed on a liquid film that is sheared in between solid surfaces. As a shear is given to the liquid film, a Couette-like flow is generated in the liquid and energy conversion occurs from the macroscopic flow to the thermal energy, which is discharged back to the solid walls. In such a way, momentum and thermal energy fluxes are present simultaneously. And all these thermal and fluid phenomena take place in highly nonequilibrium state where thermal energy is not distributed equally to each degree of freedom of molecular motion in the vicinities of the solid-liquid interface. In the present paper, platinum and water are employed as solid and liquid, respectively. First, the structure and orientation of water molecules in the vicinities of the solid surfaces are analyzed and how these structure and orientation are influenced by the shear is considered. Based on this result, momentum and thermal energy transfer in the vicinities of and at the solid-liquid interfaces are investigated in detail. Results are compared with those of our previous study, in which monatomic and diatomic molecules are employed as liquid. (c) 2007 American Institute of Physics.
Molecular scale mechanism of thermal resistance at solid-liquid interfaces (influence of interaction parameters between solid and liquid molecules) 査読有り

Daichi Toril, Taku Ohara, Kenji Ishida

PROCEEDINGS OF THE ASME/JSME THERMAL ENGINEERING SUMMER HEAT TRANSFER CONFERENCE 2007, VOL 1　132　(1)　23-31　2007年
出版者・発行元：AMER SOC MECHANICAL ENGINEERS

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Nonequilibrium molecular dynamics simulations have been performed for systems of a liquid film confined between atomistic solid wails. The two solid walls have different temperatures to generate a steady thermal energy flux in the system, which is the element of macroscopic heat conduction flux. Three kinds of liquid molecules and three kinds of solid walls are examined, and the thermal energy flux is measured at control surfaces in the liquid film and at the solid-liquid interfaces. By analyzing the thermal energy flux in detail by decomposing it into several molecular-scale contributions, influence of interaction parameters between solid and liquid molecules and the spacing of molecular alignment on the surface of the solid wall are clarified, and the molecular-scale mechanisms that govern the thermal resistance at a solid-liquid interface are elucidated.
Molecular heat conduction in liquid alkane: Contribution of inter- and intramolecular energy transfer 査読有り

Daichi Torii, Taku Ohara, Takehiro Matsuzaka

Proc. 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics　CD-ROM　2007年
A molecular dynamics study on the local structure of liquid-vapor interface of water and L-J fluid 査読有り

Gota Kikugawa, Shu Takagi, Yoichiro Matsumoto, Taku Ohara

PROCEEDINGS OF THE ASME/JSME THERMAL ENGINEERING SUMMER HEAT TRANSFER CONFERENCE 2007, VOL 1　CD-ROM　91-96　2007年
出版者・発行元：AMER SOC MECHANICAL ENGINEERS
DOI： 10.1115/HT2007-32722 　

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Microscopic structures of the liquid-vapor interface are investigated by molecular dynamics simulations. In previous studies, we proposed the local and instantaneous definition of the interface at the molecular level, which can capture the thermal fluctuation of the interface. By using this definition, the layering structure of water molecules at the interface is found, in other words, the structurization phenomena of water at the molecular level are clearly seen as usually found at the liquid-solid interface. In this study, we also investigated the liquid-vapor interface of Lenard-Jones fluid. Well depth of L-J potential parameter was somewhat changed and the effect on the structure was studied. Although the structurization was also found at the L-J fluid as well as water, characteristic of this structure is clearly different from that of water. We consider that the difference is ascribed to the intrinsic structure of liquid and associative trend of molecules. We also discussed the anisotropic character of the molecular diffusion at the interface. The anisotropy of the translational diffusion at the interface of water is stronger than that of the L-J fluid.
Study on molecular thermal energy transfer in a lipid bilayer 査読有り

Takeo Nakano, Taku Ohara, Gota Kikugawa

PROCEEDINGS OF THE ASME/JSME THERMAL ENGINEERING SUMMER HEAT TRANSFER CONFERENCE 2007, VOL 1　CD-ROM　59-63　2007年
出版者・発行元：AMER SOC MECHANICAL ENGINEERS
DOI： 10.1115/HT2007-32635 　

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In recent studies, lipid bilayers attract a great deal of interest as a material for nanoscale structure. Some devices utilizing lipid bilayers, which include various kinds of sensors and molecular sorting devices, have been proposed. Understanding of thermal energy transfer in the lipid bilayers plays an important role in developing such devices with nano structures. In this study, we have investigated the energy transfer along and across the bilayer membrane by molecular dynamics simulations of the lipid bilayer in liquid water. We found that along the bilayer, the thermal energy is transferred by the interaction principally between water molecules and barely between lipid molecules. On the other hand, in the latter case, total thermal resistance of the lipid bilayer structure is composed of the thermal resistance of the structure's various parts, including water, head group of lipid, and tail hydrocarbon chain of lipid, which show different values. It is found that the tail hydrocarbon chains have the highest thermal resistance.
Molecular scale mechanism of thermal resistance at solid-liquid interfaces (influence of interaction parameters between solid and liquid molecules) 査読有り

Daichi Toril, Taku Ohara, Kenji Ishida

PROCEEDINGS OF THE ASME/JSME THERMAL ENGINEERING SUMMER HEAT TRANSFER CONFERENCE 2007, VOL 1　CD-ROM　23-31　2007年
出版者・発行元：AMER SOC MECHANICAL ENGINEERS
DOI： 10.1115/HT2007-32391 　

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Nonequilibrium molecular dynamics simulations have been performed for systems of a liquid film confined between atomistic solid wails. The two solid walls have different temperatures to generate a steady thermal energy flux in the system, which is the element of macroscopic heat conduction flux. Three kinds of liquid molecules and three kinds of solid walls are examined, and the thermal energy flux is measured at control surfaces in the liquid film and at the solid-liquid interfaces. By analyzing the thermal energy flux in detail by decomposing it into several molecular-scale contributions, influence of interaction parameters between solid and liquid molecules and the spacing of molecular alignment on the surface of the solid wall are clarified, and the molecular-scale mechanisms that govern the thermal resistance at a solid-liquid interface are elucidated.
液体／固液界面／気液界面の構造と輸送招待有り査読有り

小原拓, 菊川豪太

フルードパワーシステム　38　(5)　233-238　2007年
多体ポテンシャルによる液体中の熱伝導（分子内及び分子間エネルギー伝搬の寄与）査読有り

鳥居大地, 中野雄大, 小原拓

日本機械学会論文集B編　73　(734)　2122-2199　2007年

DOI： 10.1299/kikaib.73.2122 　
Transport of ions by the thermally anisotropic Brownian ratchet microchip 査読有り

Taku Ohara, Takeo Nakano, Daichi Torii

International Journal of Transport Phenomena　9　41-53　2007年
Transport of ions by the thermally anisotropic Brownian ratchet microchip 査読有り

Taku Ohara, Takeo Nakano, Daichi Torii

Proc. 17th Internatioinal Symposium on Transport Phenomena　CD-ROM　2006年
Solid-liquid boundary resistance: A molecular dynamics study on intermolecular energy transfer at solid-liquid interfaces 査読有り

Daichi Torii, Taku Ohara, kenji Ishida

Proc. 13th International Heat Transfer Conference　CD-ROM　2006年
Molecular thermal phenomena in an ultrathin lubrication liquid film of linear molecules between solid surfaces 査読有り

T Ohara, D Torii

MICROSCALE THERMOPHYSICAL ENGINEERING　9　(3)　265-279　2005年7月
出版者・発行元：TAYLOR & FRANCIS INC
DOI： 10.1080/10893950500196386 　

ISSN：1089-3954

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Molecular dynamics simulation has been performed on an ultra-thin lubrication liquid film, where the liquid film of diatomic molecules having a thickness of molecular scale (several nanometers) is sheared by two parallel solid walls moving at different speeds. The Couette-like flow is generated and energy conversion from the macroscopic flow energy to thermal energy, which is the viscous heating in a macroscopic sense, occurs in the liquid film. It was observed in the present simulations that the thermal phenomena in the liquid film are far from the macroscopically expected ones; thermal energy is not distributed evenly to each degree of freedom of molecular motion, and energy transfer in the liquid adjacent to the solid surface is contributed by molecular motion in a manner different from those in a bulk liquid.
Molecular dynamics study of thermal phenomena in an ultrathin liquid film sheared between solid surfaces: The influence of the crystal plane on energy and momentum transfer at solid-liquid interfaces 査読有り

T Ohara, D Torii

JOURNAL OF CHEMICAL PHYSICS　122　(21)　214717　2005年6月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.1902950 　

ISSN：0021-9606

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A molecular dynamics study has been performed on a liquid film sheared between moving solid walls. Thermal phenomena that occur in the Couette-like flow were examined, including energy conversion from macroscopic flow energy to thermal energy, i.e., viscous heating in the macroscopic sense, and heat conduction from the liquid film to the solid wall via liquid-solid interfaces. Four types of crystal planes of fcc lattice were assumed for the surface of the solid wall. The jumps in velocity and temperature at the interface resulting from deteriorated transfer characteristics of thermal energy and momentum at the interface were observed. It was found that the transfer characteristics of thermal energy and momentum at the interfaces are greatly influenced by the types of crystal plane of the solid wall surface which contacts the liquid film. The mechanism by which such a molecular scale structure influences the energy transfer at the interface was examined by analyzing the molecular motion and its contribution to energy transfer at the solid-liquid interface. (c) 2005 American Institute of Physics.
熱伝導の「質」についての一考察招待有り査読有り

小原拓

熱物性　19　(3)　181-184　2005年
固体壁面間でせん断を受ける極薄液膜の分子動力学的研究（固液界面におけるエネルギー・運動量伝搬に及ぼす固体結晶面の影響）査読有り

鳥居大地, 小原拓

日本機械学会論文集B編　71　(710)　2507-2514　2005年
出版者・発行元：None
DOI： 10.1299/kikaib.71.2507 　

ISSN：0387-5016
Molecular thermal and fluid phenomena in an ultrathin lubrication liquid film 査読有り

Taku Ohara, Daichi Torii

Proc. 1st International Symposium on Micro & Nano Technology, the Pacific Center of Thermal-Fluids Engineering　CD-ROM　2004年
Transport of biomolecules in the ratcheting electrophoresis microchip (REM) 査読有り

T Ohara, D Torii, A Majumdar, K Dunphy

JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING　46　(4)　593-599　2003年11月
出版者・発行元：JAPAN SOC MECHANICAL ENGINEERS
DOI： 10.1299/jsmeb.46.593 　

ISSN：1340-8054

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Ratcheting electrophoresis microchip (REM) is a novel concept of a microfluidic device proposed by the authors for the electrophoretic separation of macromolecules such as DNA and proteins in aqueous solution. In the present report, a new type of REM is proposed. The first prototype of the REM, which consists of a microchannel and an array of thousands of parallel linear microelectrodes with a width of similar to 2 mum and a pitch of similar to 10 mum embedded in the wall of the microchannel, has some problems: dispersion of analyte molecules is large when they leave the surface of the electrodes in the direction parallel to the surface, and the small width of the microelectrodes that are needed to minimize the dispersion of molecules makes the chip susceptible to the Debye screening. To solve these problems, the crosswise migration type is proposed here, where electrophoretic migration is driven as crossing the microchannel, which results in minimized dispersion of analyte molecules and effective electric field over the whole channel that is free from the Debye screening. Computational simulation has been performed and satisfactory results were obtained.
Effect of molecular elongation on the thermal conductivity of diatomic liquids 査読有り

T Tokumasu, T Ohara, K Kamijo

JOURNAL OF CHEMICAL PHYSICS　118　(8)　3677-3685　2003年2月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.1540089 　

ISSN：0021-9606

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The effect of molecular elongation on the thermal conductivity of diatomic liquids has been analyzed using a nonequilibrium molecular dynamics (NEMD) method. The two-center Lennard-Jones model was used to express the intermolecular potential acting on liquid molecules. The simulations were performed using the nondimensional form of the potential so that the molecular elongation, d/sigma, was the only parameter varied in the simulation. The simulations were performed for five values of this parameter. First, the equation of state of each liquid was obtained using equilibrium molecular dynamics simulation, and the critical temperature, density, and pressure of each liquid were determined. Then, NEMD simulations of heat conduction in the five liquids were performed using values for temperature and density which were identical among the five liquids when they were reduced by their respective critical temperature and density (T=0.7 T-cr and rho=2.24 rho(cr)). Obtained thermal conductivities were reduced by the critical temperature, density, and molecular mass of each compound, and these values were compared with each other. It was found that the reduced thermal conductivity increased as molecular elongation increased. Detailed analysis of the molecular contribution to the thermal conductivity revealed that (a) the contribution of the heat flux caused by energy transport and by translational energy transfer to the thermal conductivity is independent of the molecular elongation, and (b) the contribution of the heat flux caused by rotational energy transfer to the thermal conductivity increases with the increase in the molecular elongation. (C) 2003 American Institute of Physics.
分子動力学法による二原子分子液体の熱伝導率の検討査読有り

徳増崇, 小原拓, 上條謙二郎

日本機械学会論文集B編　69　(683)　1644-1650　2003年
出版者・発行元：None
DOI： 10.1299/kikaib.69.1644 　

ISSN：0387-5016
Energy and momentum transfer in an ultrathin liquid film under shear between solid surfaces 査読有り

T Ohara, T Yatsunami

MICROSCALE THERMOPHYSICAL ENGINEERING　7　(1)　1-13　2003年1月
出版者・発行元：TAYLOR & FRANCIS INC
DOI： 10.1080/10893950390150412 　

ISSN：1089-3954

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Molecular dynamics study has been performed on ultra-thin liquid film sheared between two solid surfaces, which has a direct relation to lubrication. Energy and momentum transfer in the liquid film and at the solid-liquid interface accompanied by viscous heating are analyzed. The system consists of liquid film where molecules are modeled by the Lennard-Jones (12-6) potential and two parallel solid walls having a spacing of several nanometers. The solid walls have a constant temperature and move at a velocity in the opposite directions to each other, which causes a shear in the liquid film. A layered structure has been formed in the liquid by the effect of interaction with solid molecules, in which highly nonequilibrium distribution of thermal energy among the degrees of freedom for molecular motion is observed.
Shock wave relation containing lane change source term for two-lane traffic flow 査読有り

A Sasoh, T Ohara

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN　71　(9)　2339-2347　2002年9月
出版者・発行元：PHYSICAL SOC JAPAN
DOI： 10.1143/JPSJ.71.2339 　

ISSN：0031-9015

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The shock wave relation for two-lane traffic flow with lane changes has been formulated. The post-shock condition is obtained by adding a source term which accounts for the lane changes to the continuity equation. The shock velocity, and the corresponding post-shock conditions are obtained from matching relation between the lanes. The source term is affected by the transverse velocity for the lane change. If the lane to which cars intend to change is not crowded and lane change is permitted without restriction, the source term linearly increases with increasing the transverse velocity. However, if the lane change motion is limited due to crowded traffic, the lane change rate is decreased; the traffic flow gets involved in more complicated shock wave dynamics. In any case, shock polar analysis eases the derivation and the comprehension of the matched shock relation.
Rapid separation and manipulation of DNA by a Ratcheting Electrophoresis Microchip (REM) 査読有り

Katherine Dunphy, Veljko Milanovic, Samantha Andrews, Taku Ohara, Arun Majumdar

ASME International Mechanical Engineering Congress and Exposition, Proceedings　419-423　2002年
出版者・発行元：American Society of Mechanical Engineers (ASME)
DOI： 10.1115/IMECE2002-33564 　

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The Ratcheting Electrophoresis Microchip (REM) is a microfluidic device for electrophoretic separation of biomolecules such as DNA and proteins. By using thousands of electrodes along the length of a microchannel, the REM separates molecules using low applied voltages (∼1 V) in short times (&lt 1 minute). This paper describes the microfabriation of the REM and initial testing results. Parallel arrays of platinum electrodes are fabricated on a silicon chip with a pitch of 10 μm. Two types of channels are fabricated: silicon nitride channels fabricated on the chip and poly(dimelthylsiloxane) (PDMS) channels fabricated separately and attached to the chip. Initial testing shows partial success with the PDMS channels and promising results for the silicon nitride channels. Copyright © 2002 by ASME.
二原子分子流体の熱物性に回転自由度が及ぼす影響

徳増崇, 上條謙二郎, 小原拓, 松本洋一郎

日本機械学会2002年度年次大会講演論文集(IV)　2002　33-34　2002年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmemecjo.2002.4.0_33 　

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In this paper the effect of rotational degree of freedom on the properties of liquid is analyzed by the Molecular Dynamics (MD) Method. Oxygen is assumed as the liquid and molecules are assumed as both monatomic and diatomic one. 2 center Lennard-Jones (2CLJ) potential is assumed as the intermolecular potential for diatomic molecules and Lennard-Jones (LJ) potential is used for monatomic molecule. Simulations are performed at various combinations of density and temperature and an Equation of State (EOS) of each liquid is obtained by using these results. The parameters of each potential are determined so that the critical temperature and density are consistent with each other. The properties of liquid such as, latent heat, specific heat, thermal conductivity and surface tension are compared with each other and the effect of rotational degree of freedom on the properties of liquid is investigated.
熱流体工学における分子動力学（第4回）招待有り査読有り

徳増崇, 小原拓

日本数値流体力学会誌　10　41-46　2002年
二原子分子流体の熱物性に関する分子動力学的研究（分子の回転自由度の物性に及ぼす影響）査読有り

徳増崇, 上條謙二郎, 小原拓, 松本洋一郎

日本機械学会論文集(B編)　68　(668)　1227-1234　2002年
出版者・発行元：None
DOI： 10.1299/kikaib.68.1227 　

ISSN：0387-5016
Intermolecular momentum transfer in a simple liquid and its contribution to shear viscosity 査読有り

T Ohara, D Suzuki

MICROSCALE THERMOPHYSICAL ENGINEERING　5　(2)　117-130　2001年4月
出版者・発行元：TAYLOR & FRANCIS INC
DOI： 10.1080/108939501750397463 　

ISSN：1089-3954

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Momentum transfer in a sheared liquid is analyzed with a focus on the intermolecular momentum transfer (IMT). The IMT, which determines shear viscosity of liquids, is examined based on the result of molecular dynamics (MD) simulations for a simple liquid modeled by the Lennard-Jones (12-6) potential. Distortion of liquid structure, which is characterized by spherical symmetry breaking in the pair distribution of molecules, is reproduced by the MD simulation and its effect on the characteristics of the IMT, which includes a negative momentum transfer in a certain range of intermolecular distance, is discussed. The appearance of negative IMT depends on characteristics of the intermolecular potential, and it is predicted that the IMT will show a different response for repulsive soft-sphere liquids.
G214 マイクロチップによるバイオ分子のラチェット式電気泳動(オーガナイズドセッション11 : マイクロ熱流体システム)

小原拓, Majumdar Arun

熱工学講演会講演論文集　2001　631-632　2001年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmeptec.2001.0_631 　

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A ratcheting electrophoresis microchip (REM), a novel microdevice that can separate biomolecules such as DNA and proteins in aqueous solution using low applied voltages as low as 1 V, is introduced in the present report. The device consists of several thousands of parallel linear electrodes with a pitch of 10 μm typically, which is produced easily by the microlithography technique. A spatial saw-tooth potential distribution is generated by the electrode array, which works to drive charged analyte molecules to migrate in the electrophoresis fashion. Results of simple 1-D simulations suggest the REM can function as a molecular filter through which only molecules having mobility larger than a desired threshold can pass. The REM can also be programmed to separate molecules to create a molecular profile, much like conventional electrophoresis. 2-D simulations for a real device, which consider molecular diffusion, transient development of diffuse-electric double layers near the electrodes as well as electrophoretic migration of analyte molecules, are also performed and feasibility of this chip is proved.
Ratcheting electrophoresis microchip (REM) for programmable transport and separation of macromolecules 査読有り

Taku Ohara, Arun Majumdar

Proc. ASME International Mechanical Engineering Congress and Exposition, MEMS　3　619-628　2001年
熱流体工学における分子動力学（第3回）招待有り査読有り

徳増崇, 小原拓

日本数値流体力学会誌　9　177-182　2001年
熱流体工学における分子動力学（第2回）招待有り査読有り

徳増崇, 小原拓

日本数値流体力学会誌　9　122-127　2001年
熱流体工学における分子動力学（第1回）招待有り査読有り

徳増崇, 小原拓

日本数値流体力学会誌　9　89-94　2001年
液体水における分子間エネルギー伝搬とその熱伝導への寄与に関する分子動力学的研究招待有り

小原拓

ながれ　20　159-164　2001年
「拡散項３兄弟」を考える招待有り査読有り

小原拓

伝熱　40　(160)　38-43　2001年
出版者・発行元：The Heat Transfer Society of Japan
DOI： 10.11368/htsj1999.40.38 　

ISSN：0910-7851
バイオ分子解析のためのラチェット式電気泳動マイクロチップ査読有り

小原拓, Arun Majumdar

Thermal Science and Engineering　9　(3)　37-47　2001年
Molecular dynamics study in microscale thermophysical engineering: Current activities and future in Japan 招待有り査読有り

T Ohara

MICROSCALE THERMOPHYSICAL ENGINEERING　4　(4)　213-221　2000年10月
出版者・発行元：TAYLOR & FRANCIS INC
ISSN：1089-3954

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Molecular dynamics (MD) studies have been playing a major role ill this fast expanding research field of microscale thermophysical engineering in Japan. MD simulation is very effective for setting up a simplified ideal situation to examine the fundamental mechanism of thermal phenomena. On the other hand, when researchers try to solve complex problems at the stage of practical application, they face difficulties that are coming from the scale gap between the phenomena and the molecular system that can be treated by MD. In the present article, efforts that are being made to overcome these difficulties are discussed along,with an overview of current hot topics in Japanese MD research.
Intermolecular energy transfer at a solid-liquid interface 査読有り

T Ohara, D Suzuki

MICROSCALE THERMOPHYSICAL ENGINEERING　4　(3)　189-196　2000年7月
出版者・発行元：TAYLOR & FRANCIS INC
ISSN：1089-3954

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It is known that a temperature jump appears at a solid-liquid interface where high heat pur is applied. The molecular mechanism of this thermal resistance at the interface was analyzed in the present study based on the concept of the intermolecular energy transfer (IET) proposed by the present author. A molecular dynamics simulation has been performed for a system of a liquid layer between two parallel solid walls at different temperatures and the IET characteristics at the interface were examined. It was found that at the interface, intermolecular energy transfer reverse to the macroscopic heat flux occurs in a wide range of the intermolecular distance, which reduces the macroscopic heat flux.
Molecular dynamics study on the cluster structure of the 2-D LJ fluid and water 査読有り

Taku Ohara, Toru Watanabe

Heat Transfer - Asian Research　29　(3)　218-232　2000年

DOI： 10.1002/(SICI)1523-1496(200005)29:3<218::AID-HTJ6>3.0.CO;2-6 　

ISSN：1099-2871

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A molecular dynamics simulation has been performed for a two-dimensional Lennard-Jones (12-6) fluid. A saturated liquid at low temperature, compressed liquid, and fluid at supercritical temperatures with various densities were analyzed. Number of bonds per molecule, lifetime of bonds, connectivity of molecules to form clusters, stability of clusters, and their responses to temperature and density are compared with those of a hydrogen bond in water. (C) 2000 Scripta Technica, Heat Trans Asian Res, 29(3): 218-232, 2000.
Molecular dynamics study on molecule-to-molecule energy transfer in fluid water 査読有り

Taku Ohara, Hiroshi Odagiri

International Journal of Heat and Technology　18　31-36　2000年
Contribution of intermolecular energy transfer to heat conduction in a simple liquid 査読有り

T Ohara

JOURNAL OF CHEMICAL PHYSICS　111　(21)　9667-9672　1999年12月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.480338 　

ISSN：0021-9606

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Heat conduction in a low-temperature liquid is mainly caused by interaction between molecules. The intermolecular energy transfer (IET), which contributes to macroscopic heat conduction flux, is discussed in the present paper. Intermolecular energy transfer is examined using the results of molecular dynamics (MD) simulations for a simple liquid, which is modeled using the Lennard-Jones (LJ) (12-6) potential. The intermolecular energy exchange rate (IEER) is defined as the product of the intermolecular forces acting between two molecules and the velocities of the molecules. A probability distribution of the magnitude of the IEER was obtained in an ordinary equilibrium MD simulation; such a distribution was well correlated to the intermolecular distances. The substantial contribution of the IET to heat conduction flux, which is called the intermolecular energy transfer rate (IETR) here, is given by a time average of the IEER. A model is introduced to evaluate the contribution of the IET to heat conduction flux, based on an assumption that the IETR is proportional to the magnitude of the IEER itself. To verify this model, MD simulations of heat conduction in the LJ liquid under a constant temperature gradient were performed and the IETR was obtained directly. It was found that the IETR had a strong correlation with the IEER. The direct observation of the IETR by the simulation of heat conduction also showed that energy transfer in the direction opposite to the macroscopic heat flux appears in certain regions of intermolecular distances periodically. The negative energy transfer is observed between a center molecule and molecules in the inner half shell of the second and further neighbor shells The appearance of negative energy transfer reduces the net contribution of energy transfer between molecules separated by longer distances, and consequently heat conduction in a liquid is effected only by the IET between first neighbor molecules. (C) 1999 American Institute of Physics. [S0021-9606(99)50145-1].
Intermolecular energy transfer in liquid water and its contribution to heat conduction: A molecular dynamics study 査読有り

T Ohara

JOURNAL OF CHEMICAL PHYSICS　111　(14)　6492-6500　1999年10月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.480025 　

ISSN：0021-9606

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Intermolecular energy transfer (IET) is a dominant factor in heat conduction in liquid. The IET in liquid water and its contribution to macroscopic heat conduction under a temperature gradient were analyzed by a molecular dynamics simulation utilizing the extended simple point charge (SPC/E) potential model. Intermolecular energy exchange rates (IEERs) for both the translational and rotational motion of molecules were defined and their characteristics examined. The IEER of hydrogen-bonded molecules and nonbonded molecules have different characteristics. The IEER oscillates with a high amplitude and its time average, which is much smaller than the magnitude of the IEER, gives the effective rate of the IET that contributes to macroscopic heat conduction. In the present study, the effective rate of the IET was assumed to be proportional to the magnitude of the IEER. Based on the characteristics of the IEER and the above supposition, contributions of the translational and rotational IET between hydrogen-bonded molecules and nonbonded molecules to macroscopic heat conduction were evaluated. The evaluated results were compared with the results of a molecular dynamics (MD) simulation of heat conduction under a constant temperature gradient, and good qualitative agreement between the predicted value and the simulated result was found. The rotational IET was found to be dominant as compared with the translational IET, and the contribution of hydrogen-bonded molecules to heat conduction was found to be relatively small. The possibility of a mechanism that cancels the IET between distant molecules and the development of a precise model for this mechanism were also discussed. (C) 1999 American Institute of Physics. [S0021-9606(99)50138-4].
Molecular mechanism of energy and momentum transfer in liquids 査読有り

Taku Ohara, Daigo Suzuki

Thermal Science and Engineering　7　(6)　1-8　1999年
Molecular dynamics study on structure of water around an ion 査読有り

Taku Ohara, Toru Watanabe

Proc. 5th ASME-JSME Thermal Engineering Joint Conference　CD-ROM　1999年
熱伝導の機構をさぐる招待有り査読有り

小原拓

熱物性　13　(2)　102-112　1999年
Transition from boiling to free convection in supercritical fluid 査読有り

J Tamba, T Takahashi, T Ohara, T Aihara

EXPERIMENTAL THERMAL AND FLUID SCIENCE　17　(3)　248-255　1998年7月
出版者・発行元：ELSEVIER SCIENCE INC
DOI： 10.1016/S0894-1777(97)10062-0 　

ISSN：0894-1777

eISSN：1879-2286

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Observations of abnormal convection similar to boiling in supercritical fluids have been reported for many years. Recently, a molecular dynamics study performed by the authors clarified that even at the supercritical pressure, an interface accompanied with interfacial tension exists in fluids under a temperature gradient. Such findings have led us to think that the abnormal convection observed slightly above the critical point, which has been called the boiling-like phenomenon, is nothing but a boiling phenomenon, Here we report from this point of view, an experimental observation of the transition from boiling at subcritical pressure to ordinary free convection far above the critical pressure. Visual observation and measurement of the critical heat Bur shows that with pressure elevation the phenomenon changes gradually and continuously from boiling to free convection with no drastic changes. The point at which boiling characteristics disappear lies slightly above the critical pressure. (C) 1998 Elsevier Science Inc. All rights reserved.
Molecular dynamics study on molecule-to-molecule energy transfer in fluid water 査読有り

Taku Ohara, Hiroshi Odagiri

Proc. Eurotherm Seminar No.57, Microscale Heat Transfer　121-127　1998年
二次元LJ流体と水のクラスタ構造に関する分子動力学的研究査読有り

小原拓, 渡辺徹

日本機械学会論文集B編　64　(626)　3414-3422　1998年

DOI： 10.1299/kikaib.64.3414 　
Analysis of particle motion in a very shallow fluidized bed 査読有り

U Schaflinger, T Aihara, T Gruber, U Weingerl, T Ohara, W Schneider

INTERNATIONAL JOURNAL OF MULTIPHASE FLOW　23　(3)　455-471　1997年6月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/S0301-9322(96)00082-1 　

ISSN：0301-9322

eISSN：1879-3533

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It is well known that heat transfer characteristics can be improved by immersing the heat exchanger tubes into a fluidized bed. However, conventional fluidized beds are rather unstable and the comparatively large bed height causes a high pressure drop. To address this problem, one of the authors developed a very shallow fluidized bed heat exchanger which is composed of a horizontal array of tubes and a special designed multislit distributer that produces several two-phase jets. The solid particles carried in the jet impinge against the tubes and cause continuous defrosting by abrading ice formation. Here we shall present theoretical predictions for the flow properties within the jet, the impingement rate against the tube and calculations of the granular flow of particles on the inclined bottom chute that feeds the solids back into the jet. The theoretical models are based on experimental observations and data which we also present here. (C) 1997 Elsevier Science Ltd.
Heat-transfer and defrosting characteristics of a horizontal array of cooled tubes immersed in a very shallow fluidized bed 査読有り

T Aihara, T Ohara, T Shimoyama, H Kitano

INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER　40　(8)　1807-1815　1997年5月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/S0017-9310(96)00258-X 　

ISSN：0017-9310

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Heat transfer and defrosting characteristics of a horizontal single-row array of cooled tubes immersed in a gas-solid fluidized bed, have been studied experimentally. The fluidized bed produces gas-solid particle impinging jets to effectively remove frost layers on the tube surface. It has been verified that Frost-free running of the cooled tubes is possible under the conditions of inlet air temperature - 7 degrees C, tube-surface temperature - 17 degrees C and relative humidity 80%. The local contact frequency of particles onto the tube surface was measured by an optical sensing system and the defrosting mechanism of impinging solid particles was observed in detail with a visualization technique. (C) 1997 Elsevier Science Ltd.
A turbulent two-phase jet in a very shallow fluidized bed 査読有り

T Gruber, U Schaflinger, T Aihara, T Ohara

ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK　77　S107-S108　1997年
出版者・発行元：AKADEMIE VERLAG GMBH
ISSN：0044-2267
MD study on microscopic structure of water in bulk liquid and liquid-vapor interface regions 査読有り

Taku Ohara, Toshio Aihara

Proc. JSME Centennial Grand Congress, International Conference on Fluid Engineering　3　1491-1496　1997年
MD study on dynamic structure of water 査読有り

Taku Ohara, Toshio Aihara

Proc. International Center for Heat and Mass Transfer (ICHMT) Symposium on Molecular and Microscale Heat Transfer in Materials Processing and Other Applications　1　75-84　1997年
MD study on interfacelike phenomena in supercritical fluid 査読有り

J Tamba, T Ohara, T Aihara

MICROSCALE THERMOPHYSICAL ENGINEERING　1　(1)　19-30　1997年1月
出版者・発行元：TAYLOR & FRANCIS INC
ISSN：1089-3954

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An interfacelike structure observed during heat transfer in fluid near the critical point has been analyzed using a molecular dynamics (MD) method for a simple fluid modeled by the Lennard-Jones (12-6) potential. Under the condition that a temperature gradient exists, MD simulations at supercritical pressure reproduced a structure which is similar to the normal liquid-vapor interface observed at subcritical pressure. Some characteristics of the interfacelike structure, such as density profile, interface thickness, and interfacial tension, are compared with those of a subcritical liquid-vapor interface. The predicted value of the supercritical interfacial tension is compared with the value that was estimated using a theory of hydrodynamic instability due to the interfacial tension.
液体ヘリウムにおける水平被覆ストリップからの急速過渡沸騰熱伝達査読有り

小村昭義, 岡田定五, 相原利雄, 小原拓, 山本広衛

低温工学　32　(2)　66-72　1997年
出版者・発行元：低温工学協会
DOI： 10.2221/jcsj.32.66 　

ISSN：0389-2441
Augumentation of free-convection heat transfer between vertical parallel plates by inserting an auxirialy plate 査読有り

Toshio Aihara, Taku Ohara, Akira Sasago, Motoyuki Ukaku, Fabio Gori

Proc. 2nd European Thermal-Sciences and 14th UIT National Heat Transfer Conference　2　731-738　1996年
Overall performance of heat sink - fan/pump unit and its optimum design 査読有り

Toshio Aihara, Taku Ohara, Akira Sasago

Proc. 3rd KSME/JSME Thermal Engineering Conference　1　483-488　1996年
極浅層流動層中におかれた水平冷却管群の伝熱と除霜特性に関する研究査読有り

相原利雄, 小原拓, 下山利幸, 北野仁

日本機械学会論文集B編　62　(598)　2406-2413　1996年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/kikaib.62.2406 　

ISSN：0387-5016

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Heat transfer and defrosting characteristics of a horizontal single-row array of cooled tubes immersed in a gas-solid fluidized bed have been studied experimentally. The test fluidized bed with a low static bed height of l0mm produced excellent fluidization and effective gas-solid particle impinging jets for defrosting through the use of a newly developed cornice-type multislit distributor, in spite of very low pressure loss. The measured local heat-transfer coefficients and their transient behavior were discussed by consideration and comparison with these defrosting mechanisms. The defrosting limit when utilizing the present fluidized bed was also examined. It has been verified that frost-free running of the cooled tubes is possible with the use of this fluidized bed system under the conditions of inlet air temperature of -7℃, tube-surface temperature of -17℃, and relative humidity of 80%. Local contact frequency of particles onto the tube surface was measured by an optical sensing system and the defrosting mechanism of impinging solid particles was observed in detail by a visualization technique.
Free-convection heat-transfer from a step- and pulse-heated wire in supercritical fluid 査読有り

Toshio Aihara, Jun Tamba, Taku Ohara

Proc. 4th ASME/JSME Thermal Engineering Joint Conference　1　179-184　1995年
Molecular Dynamics Study on Hydrogen Bond and Cluster formation in Water 査読有り

Taku Ohara, Toshio Aihara

Proc. 4th ASME-JSME Thermal Engineering Joint Conference　2　549-556　1995年
ヒートシンクとファンないしポンプの組合せ総合特性とその最適設計査読有り

相原利雄, 小原拓, 笹子晃

日本機械学会論文集（B編）　61　(584)　1528-1533　1995年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/kikaib.61.1528 　

ISSN：0387-5016

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Performance of a forced-convection-cooling fin array in practical use should be evaluated taking its pressure-loss characteristics into account. On the other hand, the influence of the pressure loss on the cooling performance of a fin array is strongly dependent on the pressure-rise characteristics of fans/pumps driving the cooling fluid. From this poing of view, total performance of a forced-convection fin-array is analyzed in the present report considering its pressure loss and the performance of applied fan simultaneously. Based on this result, the optimum design method for forced-convection-cooling fin arrays is presented.
数値解析を援用したカーボンペイスト塗膜による急速過度沸騰熱伝達の計測査読有り

相原利雄, 小村昭義, 岡田定五, 小原拓, 黒田邦茂, 山本広衛

低温工学　30　(9)　420-430　1995年

DOI： 10.2221/jcsj.30.420 　

ISSN：0389-2441
水平着霜管群の衝突噴流熱伝達査読有り

小原拓, 相原利雄, 北野仁, 下山利幸

空気調和・衛生工学会論文集　20　(58)　103-109　1995年
出版者・発行元：公益社団法人空気調和・衛生工学会
DOI： 10.18948/shase.20.58_103 　

ISSN：0385-275X

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従来の管群熱交換器に衝突噴流を組み合わせて熱交換器の高性能化を図り,さらに着霜環境下での実用化を行う観点から,衝突噴流中の冷却管について,その着霜特性および熱伝達特性を実験的に解析した.まず,衝突噴流中の加熱円管についてその熱伝達率を比較することにより,顕著な熱伝達の向上が得られた.さらに,衝突噴流中に置かれた着霜を伴う冷却円管の局所熱伝達特性について詳細な実験を行い,冷却管周りの霜層による熱抵抗の増大が着霜による潜熱放出などに勝る結果,熱伝達率は低下する過程を明らかにし,また,霜層表面と空気間の熱抵抗と,霜層の熱抵抗も含む管表面と空気間の全熱抵抗の比を表す実験式を提示した.
水の水素結合に関する分子動力学的研究(第2報、水素結合ネットワークの解析) 査読有り

小原拓, 相原利雄

日本機械学会論文集（B編）　61　(583)　1107-1113　1995年

DOI： 10.1299/kikaib.61.1107 　
水の水素結合に関する分子動力学的研究(第1報,結合数及び寿命の温度・密度依存性) 査読有り

小原拓, 相原利雄

日本機械学会論文集（B編）　61　(582)　592-598　1995年
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/kikaib.61.592 　

ISSN：0387-5016

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A molecular dynamics study has been performed for water over wide ranges of temperature and density. The Carravetta-Clementi intermolecular potential model was applied for a system of 256 molecules. The liquid-vapor coexistence, near-critical and supercritical regions, and the region of compressed liquid having high density were extensively studied. The behavior of hydrogen bonds is analyzed in the present report. The number of bonds per molecule, their lifetime, and temperature-and density-dependences are presented in detail.
RAPID TRANSIENT HEAT TRANSFER OF NEAR-CRITICAL CARBON DIOXIDE 査読有り

T AIHARA, T OHARA, J TAMBA

HEAT TRANSFER 1994 - PROCEEDINGS OF THE TENTH INTERNATIONAL HEAT TRANSFER CONFERENCE, VOL 5　(135)　13-18　1994年
出版者・発行元：INST CHEMICAL ENGINEERS
Molecular Dynamics Study on Structure of Near-Critical Water 査読有り

Taku Ohara, Toshio Aihara

Thermal Science and Engineering　2　(1)　132-137　1994年

ISSN：0918-9963
Heat transfer and defrosting characteristics of a horizontal tube array evaporator immersed in a very shallow fluidized bed 査読有り

Toshio Aihara, Taku Ohara, Hitoshi Kitano

Proc. CFCs, THE DAY AFTER International Conference　599-606　1994年
「臨界点近傍の二酸化炭素の急速非定常熱伝達」査読有り

小原拓, 丹波純, 相原利雄

日本機械学会論文集（B編）　60　(572)　1370-1377　1994年

DOI： 10.1299/kikaib.60.1370 　
「水のクラスタ構造の分子動力学的研究(クラスタサイズ及びその確率分布の温度・密度依存性)」査読有り

小原拓, 相原利雄

日本機械学会論文集（B編）　60　(570)　496-503　1994年

DOI： 10.1299/kikaib.60.496 　

ISSN：0387-5016
「液体ヘリウムにおける鉛直被覆ストリップからの急速過渡沸騰熱伝達」査読有り

相原利雄, 小村昭義, 岡田定五, 黒田邦茂, 小原拓, 山本広衛

低温工学　29　(1)　2-11　1994年
出版者・発行元：CRYOGENICS AND SUPERCONDUCTIVITY SOCIETY OF JAPAN
DOI： 10.2221/jcsj.29.2 　

ISSN：0389-2441

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In order to simulate an insulated superconductor in practical use, a 20-μm-thick stainless steel strip, both surfaces of which were coated with a PVF film and a carbon-paste film, was used as a test piece in the present experiment. Rapid transient (up to approx. 5, 000K/s) and steady-state boiling heat transfer from this vertical test strip, which was heated stepwise in saturated liquid helium-4 at atmospheric pressure, has been studied. In steady-state boiling, thermal resistance of the coating shifts the nucleate boiling curve to a higher wall-superheat region and suppresses burnout and a quick transition; consequently, heat transfer data were well correlated with a single boiling curve with smooth and continuous transition from nucleate boiling to film boiling. In the case of stepwise heating with a heat flux below the steady-state CHF, the wall superheat suddenly increases to a value corresponding to the Kapitza resistance just as the thermal wave reaches the test piece surface; steady-state nucleate boiling is attained within a very short time after rapid increase in the wall temperature. In the case of a heat flux above the steady-state CHF, just after the transition from transient nucleate boiling to film boiling, the wall heat flux sharply dips once; then steady-state film boiling is attained within a very short time. A rapid transient boiling curve has also been obtained.
液体をミクロに見れば招待有り査読有り

小原拓, 相原利雄

日本機械学会誌　96　(892)　180-183　1993年
遷臨界域の水の分子動力学的研究(微視的構造の検討) 査読有り

小原拓, 相原利雄, 小竹進

日本機械学会論文集（B編）　59　(561)　1658-1663　1993年

DOI： 10.1299/kikaib.59.1658 　
FILM THINNING PROCESS ON A ROTATING-DISK 査読有り

T OHARA, Y MATSUMOTO, H OHASHI

ROTATING MACHINERY : TRANSPORT PHENOMENA　209-224　1992年
出版者・発行元：HEMISPHERE PUBL CORP
RESIST FILM FORMATION IN SPIN COATING 査読有り

T OHARA, Y MATSUMOTO, H OHASHI

INTERSOCIETY CONFERENCE ON THERMAL PHENOMENA IN ELECTRONIC SYSTEMS　281-288　1992年
出版者・発行元：I E E E
Cooling performance of compact heat sinks with semimicrochannels 査読有り

Taku Ohara, Toshio Aihara, Chihiro Hayashi

Proc. 1992 Joint ASME/JSME Conference on Electronic Packaging　1　249-252　1992年
回転円盤上の液膜形成

小原拓, 他

日本の伝熱研究　20　(1)　36-55　1991年
回転円盤上の薄膜形成査読有り

小原拓, 大橋秀雄, 松本洋一郎

日本機械学会論文集（B編）　57　(543)　3807-3814　1991年

DOI： 10.1299/kikaib.57.3807 　
PRESSURE WAVE PHENOMENA IN BUBBLY LIQUID 査読有り

Y MATSUMOTO, H NISHIKAWA, T OHARA, H OHASHI

CURRENT TOPICS IN SHOCK WAVES　208　837-842　1990年
出版者・発行元：AIP PRESS
THE FILM FORMATION DYNAMICS IN SPIN COATING 査読有り

T OHARA, Y MATSUMOTO, H OHASHI

PHYSICS OF FLUIDS A-FLUID DYNAMICS　1　(12)　1949-1959　1989年12月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.857520 　

ISSN：0899-8213
NUMERICAL-ANALYSIS AT THE INITIAL-STAGE - LIQUID-FILM FORMATION ON A ROTATING-DISK 査読有り

Y MATSUMOTO, T OHARA, TERUYA, I, H OHASHI

JSME INTERNATIONAL JOURNAL SERIES II-FLUIDS ENGINEERING HEAT TRANSFER POWER COMBUSTION THERMOPHYSICAL PROPERTIES　32　(1)　52-56　1989年2月
出版者・発行元：JAPAN SOC MECHANICAL ENGINEERS SANSHIN HOKUSEI BLDG
DOI： 10.1299/jsmeb1988.32.1_52 　

ISSN：0914-8817
回転円盤上における液膜形成過程(第2報，熱・物質移動を伴う薄膜化過程の数値解析) 査読有り

小原拓, 松本洋一郎, 島本憲夫, 大橋秀雄

日本機械学会論文集（B編）　55　(514)　1640-1648　1989年
出版者・発行元：The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaib.55.1640 　

ISSN：0387-5016

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The unsteady flow of a liquid film and the surrounding gas on a rotating disk, which is related to a spin-coating technique to form a thin uniform film on a plate, is simulated numerically with emphasis on the heat and mass transfer at the interface. The full governing equations and boundary conditions are formulated and a newly developed calculation method is applied. The numerical results reveal that the liquid film thickness decreases mainly by convection in the middle stage. The radial and azimuthal velocities are proportional to the radius, and other values are independent of it. According to these results, one-dimensional calculation models for both phases are developed. The results show that the increased viscosity due to the evaporation of the solvent has considerable effects on the film formation process when the film is sufficiently thin. The liquid film thins mainly because of evaporation in the last stage.
回転円盤上における液膜形成過程(第1報，初期過程の数値解析) 査読有り

松本洋一郎, 小原拓, 照屋功, 大橋秀夫

日本機械学会論文集（B編）　54　(499)　569-574　1988年
出版者・発行元：The Japan Society of Mechanical Engineers
DOI： 10.1299/kikaib.54.569 　

ISSN：0387-5016

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Unsteady liquid film flow on a rotating disk, which is related to a spin coating technique to form a thin uniform film on a plate, is calculated numerically. Vewly developed calculation method, where the surface tension on the liquid surface can be taken into account, is applied. The numerical results reveal the followings : The hemi-spherical liquid on the disk, which starts to rotate impulsively from rest, spreads by a gravitational force at the first stage. The development of the distribution of radial and azimuthal velocities is affected complicatedly by the Coriolis force, viscous force and centrifugal force. The liquid spreads mainly by centrifugal force and forms a uniforml thin film on the disk at the last stage. The surface tension has a little influence on the spreading process only at the first stage.

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MISC 125

様々な水モデルを用いた分子動力学シミュレーションによる各種熱物性の再現性評価

田村双, 松原裕樹, SURBLYS Donatas, 小原拓

第42回日本熱物性シンポジウム講演論文集　B212　2021年10月
構造制御されたポリアクリル酸/ポリエチレンイミン相互積層膜の熱伝導率

佐藤正秀, 伊藤晴美, 的場優仁, 山下雄一郎, 八木貴志, 川越吉晃, Surblys Donatas, 松原裕樹, 菊川豪太, 小原拓

第42回日本熱物性シンポジウム講演論文集　B311　2021年10月
SiO2結晶表面近傍における液体水/IPAの物質輸送特性

佐藤大雅, 早坂裕真, SURBLYS Donatas, 松原, 裕樹, 中野雄大, 菊川豪太, 小原拓

日本機械学会2021年度年次大会　J52-06　2021年9月
表面微細構造をもつ加熱基板近傍に置かれた物体に誘起される接線方向クヌッセン力の源

オティッククリントジョン, 小原拓, 米村茂

日本機械学会2021年度年次大会　J52-11　2021年9月
ナノ粒子を含む液体のエネルギー輸送機構に関する分子動力学的研究

芝原正彦, 山本幸宏, 藤原邦夫, 植木祥高, 小原拓

第58回日本伝熱シンポジウム講演論文集　2021年5月
多体ポテンシャルを有する系の原子応力による熱流束算出

Surblys Donatas, 松原裕樹, 菊川豪太, 小原拓

第58回日本伝熱シンポジウム講演論文集　2021年5月
パラフィン/屈曲グラフェン複合材料のフィラー分散性および熱伝導率に関する分子動力学解析

松原裕樹, 小原拓

第58回日本伝熱シンポジウム講演論文集　2021年5月
フルオロカーボン系熱媒の熱伝導機構と熱伝導率の関係に関する分子動力学的研究

小久保信佑, 松原裕樹, Surblys Donatas, 菊川豪太, 小原拓

第58回日本伝熱シンポジウム講演論文集　2021年5月
分子接合されたグラフェンの熱伝導特性に関する分子動力学的研究

伊藤豪志, 松原裕樹, Surblys Donatas, 小原拓

第58回日本伝熱シンポジウム講演論文集　2021年5月
自己組織化単分子膜表面上の液滴接触状態に関する分子動力学的研究

菊川豪太, 新田則佳, Surblys Donatas, 小原拓

第58回日本伝熱シンポジウム講演論文集　2021年5月
ナノ粒子懸濁液のエネルギー輸送機構に関する分子動力学的研究

山本幸宏, 藤原邦夫, 植木祥高, 小原拓, 芝原正彦

熱工学コンファレンス講演論文集　2019　(0)　24-24　2019年10月
出版者・発行元：一般社団法人日本機械学会
DOI： 10.1299/jsmeted.2019.0024 　

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<p>In the present study, we conducted nonequilibrium molecular dynamics simulations in order to investigate influences of the adsorption layers of the liquid around a nanoparticle on the effective thermal conductivity of liquid with nanoparticle suspension. We adopted liquid systems with nanoparticle suspension between two solid walls and obtained the effective thermal conductivity based on the Fourier's law imposing a temperature difference between the two solid walls. Contributions of the adsorption layer to the effective thermal conductivity were investigated quantitatively, and the results showed that the thermal conductivity in the adsorption layer increases with the increase of the interaction intensity between the nanoparticle and the liquid.</p>
ナノ粒子が液体のエネルギー輸送機構に与える影響に関する分子動力学的研究

大茂昌史, 藤原邦夫, 植木祥高, 小原拓, 芝原正彦

日本伝熱シンポジウム講演論文集(CD-ROM)　56th　ROMBUNNO.D324　2019年

ISSN：1346-1532
ナノノスケール微細構造における熱交換機構に関する分子動力学解析

SURBLYS Donatas, 川越吉晃, 芝原正彦, 小原拓

2018年12月
ナノ粒子による液体の熱伝導率変化に関する分子動力学的研究

大茂昌史, 藤原邦夫, 植木祥高, 芝原正彦, 小原拓

日本伝熱シンポジウム講演論文集(CD-ROM)　55th　ROMBUNNO.P1420　2018年

ISSN：1346-1532
101 フルオロカーボンSAM界面の熱輸送特性に関する分子動力学的研究

根本充, 菊川豪太, 別所毅, 山下征士, 小原拓

講演論文集　2016　(51)　3-4　2016年
出版者・発行元：一般社団法人日本機械学会
108 Molecular Thermal Energy Transfer in Binary Mixture of Simple Liquids

Fang Yingping, Kikugawa Gota, Matsubara Hiroki, Bessho Takeshi, Yamashita Seiji, Ohara Taku

講演論文集　2016　(51)　15-16　2016年
出版者・発行元：一般社団法人日本機械学会
A molecular dynamics study on molecular diffusion in liquids of water and IPA in the vicinity of solid surfaces and in liquid mixture

Y. Naruke, J. Suzuki, T. Nakano, G. Kikugawa, T. Ohara

Proceedings of the First Pacific Rim Thermal Engineering Conference　2016年
Molecular dynamics study on influences of slit structures on thermal resistance and energy transport mechanism at a liquid-solid interface

M. Shibahara, R. Toda, Y. Ueki, T. Ohara

Proceedings of the First Pacific Rim Thermal Engineering Conference　2016年
Molecular dynamics mechanism of heat conduction in 1-butyl-3-methylimidazolium ionic liquid

Joji Haneda, Gota Kikugawa, Taku Ohara

Proceedings of the 11th Asian Thermophysical Properties Conference　2016年
Molecular mechanism of heat conduction in linear alcohol liquids: Effect of chain length

Hiroki Matsubara, Gota Kikugawa, Takeshi Bessho, Seiji Yamashita, Taku Ohara

Proceedings of the 11th Asian Thermophysical Properties Conference　2016年
Molecular thermophysical properties toward the design of liquids and soft matters

Taku Ohara, Gota Kikugawa, Hiroki Matsubara

Proceedings of the 11th Asian Thermophysical Properties Conference　2016年
Molecular dynamics mechanism to determine viscosity of thermal medium liquids

Satoru Harada, Gota Kikugawa, Taku Ohara

Proceedings of the 4th International Forum on Heat Transfer　2016年
Molecular mechanism for thermal boundary conductance over fluorinated SAM-solvent interfaces

Mitsuru Nemoto, Gota Kikugawa, Takeshi Bessho, Seiji Yamashita, Taku Ohara

Proceedings of the 4th International Forum on Heat Transfer　2016年
Thermal rectification over solid-liquid interfaces of gold (Au) contacting liquid methane (CH4)

Abdul Rafeq Saleman, Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

Proceedings of the 4th International Forum on Heat Transfer　2016年
C214 1-ブチル-3-メチルイミゾダリウム塩系イオン液体中の熱エネルギー伝搬機構に関する分子動力学シミュレーション(OS-13:分子シミュレーション(1))

羽田城司, 菊川豪太, 小原拓

熱工学コンファレンス講演論文集　2015　"C214-1"-"C214-2"　2015年10月23日
出版者・発行元：一般社団法人日本機械学会

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The molecular level mechanism of thermal energy transfer is important in thermal engineering or understanding the factors that determine macroscopic thermal conductivity, which enables design of thermal medium having desired thermophysical properties. This is a report of non-equilibrium molecular dynamics (MD)simulation of heat conduction in ionic liquids, which attract attentions in various engineering fieldsrecently. MD simulations were performed for 1-butyl-3-metyhlimidazolium ionic liquids at 323 K and 1×10^5 Pa by using the united atom model in three systems which have different size of anions (F^-, Cl^- and Br^-). Thecontributions of molecular migration and intra/intermolecular interactions to heat flux has been analyzed.
J0540304 壁面近傍のナノスケール液体における物質輸送特性

鈴木城, 菊川豪太, 中野雄大, 小原拓

年次大会 : Mechanical Engineering Congress, Japan　2015　"J0540304-1"-"J0540304-3"　2015年9月13日
出版者・発行元：一般社団法人日本機械学会

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Mass transport in ordered structures of a liquid which are formed in the vicinity of a solid-liquid interface exhibits decidedly different characteristics from the ordinary diffusion. Using the PMF (potential of mean force) profile obtained from the number density of liquid molecules, the kinetic process model to describe the molecular mobility inside these ordered structures was developed in this study. From the result obtained from molecular dynamics (MD) simulations, it was found that the developed kinetic model can accurately predict the molecular mobility over the free energy barrier.
スリット状微細構造が固液界面エネルギー輸送に及ぼす影響に関する分子動力学的研究

芝原正彦, 戸田亮平, 植木祥高, 小原拓

日本伝熱シンポジウム講演論文集(CD-ROM)　52nd　ROMBUNNO.H235　2015年

ISSN：1346-1532
分子動力学計算系におけるバルク液体の自己拡散係数に対する計算系形状の影響

鈴木城, 菊川豪太, 安藤翔太郎, 成毛陽一, 小原拓

計算力学講演会講演論文集　2014　(27)　711-713　2014年11月22日
出版者・発行元：一般社団法人日本機械学会
ISSN：1348-026X

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In the present study, molecular dynamics (MD) simulations on simple liquids like monatomic Lennard-Jones and water bulk liquids in periodic boundary systems were performed to clarify the effect of the system size and shape on self-diffusion coefficient. So far, in the previous publications, the system size effect in cubic computational domains has been reported, and these studies showed that the diffusion coefficient becomes smaller as the system size decreases. Here we examined the system size effect not only in the cubic cell systems, but also in the rectangular cell systems which were created by changing one side length of the cubic cell with the system density kept constant. It is found that the diffusion coefficient in the direction perpendicular to the long side of the rectangular cell significantly increases more or less linearly as the side length increases for both liquids. On the other hand, the diffusion coefficient in the direction along the long side is almost constant. In consequence, anisotropy of the diffusivity appears in the rectangular cell with a periodic boundary condition even though the diffusion property of bulk liquids is examined.
分子動力学法による鎖状アルカン液体の熱伝導解析 : 分岐鎖の影響

松原裕樹, 菊川豪太, 別所毅, 山下征士, 小原拓

計算力学講演会講演論文集　2014　(27)　714-715　2014年11月22日
出版者・発行元：一般社団法人日本機械学会
ISSN：1348-026X

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This paper investigates how the details of molecular structure affect the thermal properties of liquids. We carried out the nonequilibrium molecular dynamics simulations for the liquids of a systematic series of branched-alkanes. In the simulations, the thermal conductivity as well as the corresponding heat flux were calculated. Particularly, the heat transfer by way of side chain was analyzed in detail. It is shown that the heat flux associated with one side chain atom is not significantly different for the different alkane species, and thus the total heat flux of side chain is proportional to the number density of side chain atoms.
B222 固液界面近傍におけるアルカン液体の局所的熱伝導率

チルコティハリクリシュナ, 菊川豪太, 小原拓

熱工学コンファレンス講演論文集　2014　"B222-1"-"B222-2"　2014年11月8日
出版者・発行元：一般社団法人日本機械学会

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In this paper, thermal conductivity of liquid n-alkanes in the vicinity of three crystal planes of a-quartz substrate terminated with H and OH-groups have been investigated using nonequilibrium molecular dynamics simulations. Methane and decane molecules are considered as alkane molecules in this study. It is found that the thermal conductivity fluctuates in an oscillating manner in the solid-liquid interface region. These fluctuations are typically in proportion to the oscillations in the density profile.
J0550304 Lennard-Jonesおよび水バルク液体の自己拡散係数に対する計算系形状の影響([J055-03]マイクロ・ナノスケール熱流体現象(3))

菊川豪太, 安藤翔太郎, 鈴木城, 成毛陽一, 中野雄大, 小原拓

年次大会 : Mechanical Engineering Congress, Japan　2014　"J0550304-1"-"J0550304-5"　2014年9月7日
出版者・発行元：一般社団法人日本機械学会

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In the present study, molecular dynamics (MD) simulations on monatomic Lennard-Jones and water bulk liquids in the periodic boundary system were performed in order to elucidate the effect of the system size and shape on self-diffusion coefficient. So far, the system size effect in cubic computational domains has been intensively investigated and these studies showed that the diffusion coefficient becomes smaller as the system size decreases. We examined the system size effect not only in the cubic cell systems, but also in the rectangular cell systems which were created by changing one side length of the cubic cell with the system density kept. As a result, the diffusion coefficient in the direction perpendicular to the longer side of the rectangular cell significantly increases more or less linearly as the side length increases for both liquids. On the other hand, the diffusion coefficient in the direction along the longer side is almost constant or slightly decreases. Consequently, anisotropy of diffusion coefficient appears in the rectangular cell with a periodic boundary condition even in the case of bulk liquids.
G131 SiO_2固体壁近傍における水およびIPAの物質輸送特性に関する分子動力学的研究(OS-7:マイクロ・ナノ熱工学(3))

成毛陽一, 小坂秀一, 中野雄大, 菊川豪太, 小原拓

熱工学コンファレンス講演論文集　2013　215-216　2013年10月18日
出版者・発行元：一般社団法人日本機械学会

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Mass transport in the vicinity of solid-liquid interfaces exhibits complicated characteristics and an essential understanding of their mechanism is of critical importance. The interfaces between SiO_2 and water or IPA (iso-propyl alcohol) are typical system in the semiconductor industry. In the present study, we investigated molecular-scale structures of the adsorption layers of liquid molecules and molecular transport characteristics by using molecular dynamics (MD) simulations in order to clarify the mass transport in the vicinity of the interfaces between SiO_2 and liquids. As typical terminations of SiO_2 surfaces, H- and OH- terminated ones were used and self-diffusion coefficients in the direction parallel to the interface were measured and the mass transfer properties were discussed.
J053013 架橋を有するアモルファスポリマー材料における熱輸送機構の解明(〔J053-01〕マイクロ・ナノスケールの熱流体現象(1))

菊川豪太, KEBLINSKI Pawel, 小原拓

年次大会 : Mechanical Engineering Congress, Japan　2013　"J053013-1"-"J053013-5"　2013年9月8日
出版者・発行元：一般社団法人日本機械学会

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In the present study, molecular dynamics (MD) simulations on two typical amorphous polymers, polyethylene (PE) and polystyrene (PS) were performed in order to elucidate the effect of crosslinks between polymer chains on heat conduction. Direct nonequilibrium MD techniques were used to evaluate thermal conductivities in both polymeric systems with varying a crosslink concentration. In the PE systems, the effect of crosslinking on thermal conductivity is significant and the thermal conductivity more or less linearly increases with the crosslink concentration. On the other hand, the change of thermal conductivity in the PS systems is insignificant. We guess that this striking difference is due to highly heterogeneous PS based network including phenyl side groups in terms of molecular interactions and molecular conformation. In order to elucidate the molecular-scale mechanism on the increase of thermal conductivity with the crosslink concentration for PE, we monitored microscopic energy transfer modes associated with various bonded and non-bonded interactions. The results show that crosslinking plays a role in creating new thermal paths to increase thermal conductivity.
日本伝熱学会学術賞を受賞して

中野雄大, 菊川豪太, 小原拓

伝熱 : journal of the Heat Transfer Society of Japan　52　(220)　6-6　2013年7月1日

ISSN：1344-8692
Molecular Dynamics Mechanism of Thermal Energy Transport in Liquid Methane Reproduced by All-Atom and United-Atom Models

Joji Haneda, Gota Kikugawa, Taku Ohara

Proceedings of the 4th International Symposium on Micro and Nanotechnology　2013年
OS1-1-6 SiO_2-水/IPA界面近傍における液膜中の構造と物質輸送に対する温度の影響(OS1 マルチスケ-ル現象のシミュレーション技術(1))

中野雄大, 小坂秀一, 菊川豪太, 小原拓

マイクロ・ナノ工学シンポジウム　2012　(4)　129-130　2012年10月21日
出版者・発行元：一般社団法人日本機械学会

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Molecular dynamics simulations are performed in order to investigate an impact of temperature on molecular structure and mass transport properties in the vicinity of silica-water and/or iso-propyl alcohol (IPA) liquid film interfaces. Water and IPA liquid molecules form layer structure in the vicinity of the solid, respectively. Although temperature has an insignificant effect on the first layer from the solid, the layer structure at higher temperature decays farther away from the second layer comparing with lower temperature for both silica-water and silica-IPA systems. Moreover, interfusion of water and IPA molecules between silica substrates is simulated and coverage molecules on the substrates are analyzed for temperatures of 300K and 350K.
J053026 ナノメートルスケールの微細構造が固液界面の熱抵抗とエネルギー輸送機構に与える影響に関する分子動力学的研究

芝原正彦, 村上翔, 松本拓也, 小原拓

年次大会 : Mechanical Engineering Congress, Japan　2012　"J053026-1"-"J053026-5"　2012年9月9日
出版者・発行元：一般社団法人日本機械学会

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The influences of the nanostructures adherent to a surface on the macroscopic thermal resistance and the molecular energy transport mechanism at a liquid-solid interface were investigated directly by the nonequilibrium classical molecular dynamics simulations. There was a negative correlation between the interfacial liquid molecular density and the macroscopic interfacial thermal resistance in the case of the same nanostructure adherent surface. The increase of the heat flux through the nanostructures was observed when the macroscopic interfacial thermal resistance was reduced by the nanostructures in the case of the same nanostructure adherent surface.
J053034 直鎖アルカン飽和液中の熱エネルギー伝搬機構に関するAll-Atom分子動力学シミュレーション

羽田城司, 菊川豪太, 小原拓

年次大会 : Mechanical Engineering Congress, Japan　2012　"J053034-1"-"J053034-3"　2012年9月9日
出版者・発行元：一般社団法人日本機械学会

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This report mentions non-equilibrium molecular dynamics (MD) simulation of heat conduction in alkane liquids. In the previous study, the authors have analyzed the molecular mechanism of heat conduction in liquid n-alkanes ofvarious molecular lengths by utilizing the united-atom model. Although the results were satisfactorily reasonable, the influence of C-H bonds was not clarified because the bonds were ignored in the united atom model. To analyze the influence, a non-equilibrium MD simulation was performed in the present study for heat conduction in liquid n-alkanes applying an all-atom model. The influence of the presence of H sites and the contributions of the C-H bond were examined.
日本熱物性学会賞論文賞を受賞して

小原拓, ユアンタンチア, 鳥居大地, 小杉直央, 菊川豪太

熱物性 : Japan journal of thermophysical properties　26　(1)　4-4　2012年2月29日

ISSN：0913-946X
G114 親水性および疎水性SAMと水溶媒の界面における熱輸送機構の詳細解析(一般講演(1))

菊川豪太, 小原拓, 川口暢, 杵淵郁也, 松本洋一郎

熱工学コンファレンス講演論文集　2011　159-160　2011年10月28日
出版者・発行元：一般社団法人日本機械学会

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In the present paper, molecular dynamics simulations of the interface system comprised of self-assembled monolayers (SAMs) and water solvent were performed in order to investigate heat transfer characteristics. Here we focused on the effect of hydrophobicity of SAMs on interfacial heat transfer. Two types of SAM terminal groups, i.e., methyl (CH3-) and hydroxyl (OH-) terminals which have hydrophobic and hydrophilic characters, respectively, were adopted. Nonequilibrium molecular dynamics simulations, in which a constant heat flux was imposed across the SAM interface, were performed to evaluate thermal boundary conductances (TBCs). The result demonstrated that the TBC at the OH-terminated SAM interface is one order of magnitude larger than that at the methyl-terminated SAM interface. Moreover, possible reasons for this significant difference were explored.
4-4 マグネタイト-水溶媒界面におけるイオン移動の自由エネルギー分布(セッション4:OS1-1 マルチスケール・シミュレーションとナノ計測)

菊川豪太, 加藤惇平, 小原拓

マイクロ・ナノ工学シンポジウム　2011　(3)　43-44　2011年9月25日
出版者・発行元：一般社団法人日本機械学会

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In the present paper, we investigated mass transfer characteristics of Fe^<2+> ions over the magnetite (Fe_3O_4) substrate/water solvent interface by using the molecular dynamics simulations. In addition to the transfer perpendicular to the interface, that along the interface has to be elucidated in order to understand the precise transport properties and diffusion process of ions in the vicinity of the interface with complicated surface structure. Therefore, we here evaluated two-dimensional free energy surface along the interface according to the ion translation with umbrella sampling/WHAM (weighted histogram analysis method) technique. Additionally, actual ion trajectories adjacent to the interface were traced to compare those with the probable transport paths predicted from the free energy surface. As a result, it was found that the free energy surface is significantly influenced by the surface charge distribution of the magnetite surface, and the trajectories show a good correlation with the free energy profiles.
J054051 微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響([J05405]マイクロ・ナノスケールの熱流体現象(5))

村上翔, 芝原正彦, 小原拓

年次大会 : Mechanical Engineering Congress, Japan　2011　"J054051-1"-"J054051-5"　2011年9月11日
出版者・発行元：一般社団法人日本機械学会

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The influences of the structural geometry at the nanometer scale on the thermal resistance at a liquid molecule-solid interface, as well as the interfacial local non-equilibrium behaviors of liquid molecules, were investigated directly by the non-equilibrium classical molecular dynamics simulations. A liquid molecular region confined between the solid walls, of which the interparticle potential was Lennard-Jones model or SPC/E model, was employed as a calculation system. The interfacial thermal resistance was dependent on the surface geometry at the nanometer scale and the interaction parameters between the solid atoms and the liquid molecules. The interfacial thermal resistance at the liquid-solid interface related to the interfacial local non-equilibrium behaviors of the liquid molecules regardless of liquid molecular degrees of freedom. The energy transport mechanism at the liquid-solid interface was changeable depending on the surface geometry at the nanometer scale under the present calculation conditions and it might relate to the variations of the interfacial thermal resistance and the local non-equilibrium behaviors of the liquid molecules at the liquid-solid interface.
B214 親水性および疎水性末端基を持つSAM-溶媒界面の熱輸送特性(OS-4:マイクロ・ナノ熱工学(III))

菊川豪太, 小原拓, 川口暢, 杵淵郁也, 松本洋一郎

熱工学コンファレンス講演論文集　2010　259-260　2010年10月29日
出版者・発行元：一般社団法人日本機械学会

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In this paper, we investigated the heat transfer characteristics over the interface of self-assembled monolayers (SAMs) and water solvent by using molecular dynamics simulations. Two types of SAM terminal groups, i.e., methyl (CH_3-) and hydroxyl (OH-) which have a hydrophobic and hydrophilic property, respectively, were applied to elucidate the effect of the affinity between the SAM and solvent. By nonequilibrium molecular dynamics simulations, a constant heat flux was imposed across the SAM interface and the resultant temperature distribution was obtained. Thereby, thermal boundary conductances (TBC) were evaluated at the both SAM interfaces. The result demonstrated that the TBC at the OH-terminated SAM interface is one order of magnitude larger than that at the methyl-terminated SAM interface.
B221 微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響(OS-4:マイクロ・ナノ熱工学(IV))

芝原正彦, 小原拓

熱工学コンファレンス講演論文集　2010　261-262　2010年10月29日
出版者・発行元：一般社団法人日本機械学会

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The influences of the structural geometry at the nanometer scale on the thermal resistance at a liquid molecule-solid interface, as well as the interfacial energy transport mechanism of liquid molecules, were investigated directly by the nonequilibrium classical molecular dynamics simulations. The interfacial thermal resistance is dependent on the surface geometry at the nanometer scale and the interaction parameters between solids and liquid molecules. The energy transport mechanism at a liquid-solid interface can be varied by the surface geometry at the nanometer scale under some specific conditions.
MNM-5A-4 脂質二重膜の熱輸送特性に対するアルキル鎖界面の影響(セッション 5A ナノ・マイクロ異相界面センシングと制御)

中野雄大, 菊川豪太, 小原拓

マイクロ・ナノ工学シンポジウム　2010　(2)　201-202　2010年10月12日
出版者・発行元：一般社団法人日本機械学会

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Nonequilibrium molecular dynamics simulations are carried out on single component lipid bilayer membranes with ambient water in order to elucidate influence of alkyl chain length on characteristics of heat transfer along and across the membranes. It was found that thermal conductivity along membrane corresponds with that of each membrane despite different lipid species. On the other hand, in the direction perpendicular to the membrane, the highest thermal resistance exists at the center of lipid bilayer where lipid acyl chains face each other. However, asymmetric chain length increases interface thermal conductance at the center of lipid bilayer compared with symmetric chain length. Thereby, overall thermal conductivity of across the membrane which consists of asymmetric chain length is higher than that which consists of symmetric chain length.
MNM-5A-6 自己組織化単分子膜を修飾した固液界面における界面熱コンダクタンスの温度依存性の分子論的研究(セッション 5A ナノ・マイクロ異相界面センシングと制御)

川口暢, 杵淵郁也, 菊川豪太, 小原拓, 松本洋一郎

マイクロ・ナノ工学シンポジウム　2010　(2)　205-206　2010年10月12日
出版者・発行元：一般社団法人日本機械学会

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We studied influential factors in heat transfer characteristics at the Au-toluene interface modified by dodecanethiol self-assembled monolayer (SAM) using nonequilibrium molecular dynamics simulation. The thermal boundary conductances of Au-SAM-toluene interface for different temperature were evaluated. As a result, the overall thermal boundary conductance tends to decrease as the temperature increases. This is partly because the depth of the hollow on the SAM surface becomes small and the probability density of toluene at the hollow site becomes lower as the temperature increases.
マイクロ/ナノ国際会議〔ISMNT-3 & MECT-2010〕報告

小原拓

伝熱 : journal of the Heat Transfer Society of Japan　49　(208)　85-85　2010年7月1日

ISSN：1344-8692
大規模粒子系の対話的可視化による分子配置に関するパラメータスタディ支援

新坂拓真, 竹島由里子, 菊川豪太, 小原拓, 藤代一成

情報処理学会第72回全国大会講演論文集　4　321-322　2010年3月9日
出版者・発行元：情報処理学会
脂質二重膜の熱輸送特性に対する脂質分子種の影響(分子スケール(3),一般講演)

中野雄大, 菊川豪太, 小原拓

日本流体力学会年会講演論文集　2010　111-111　2010年
出版者・発行元：日本流体力学会

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Nonequilibrium molecular dynamics simulations are performed on single component DPPC, DLPC, and SMPC lipid bilayer membranes with ambient water in order to investigate the effect of molecular species on heat transport characteristics along and across the membranes. Thermal conductivity along membrane corresponds with that of each membrane monolayer. On the other hand, in the direction across membrane, the highest thermal resistance exists at the center of lipid bilayer where lipid acyl chains face each other. However, asymmetric chain length reduces thermal resistance at the interface between lipid monolayers. Thus, thermal conductivity across the membrane which consists of asymmetric chain length is higher than those which consist of symmetric chain length.
自己組織化単分子膜の水溶媒界面における熱輸送特性(分子スケール(3),一般講演)

菊川豪太, 小原拓, 川口暢, 杵淵郁也, 松本洋一郎

日本流体力学会年会講演論文集　2010　110-110　2010年
出版者・発行元：日本流体力学会

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Molecular dynamics simulations of the interface of self-assembled monolayer (SAM) with two kinds of terminal group and water were performed in order to investigate heat transfer characteristics over the SAM interfaces. Particularly, thermal boundary conductance (TBC) at these interfaces was evaluated and the effect of hydrophobic/hydrophilic property of SAM terminal was discussed. As a result, it was found that the local TBC at the hydroxyl-terminated SAM interface is an order of magnitude larger than that at the methyl-terminated SAM interface. In order to elucidate the reason for this large TBC, components contributing to thermal energy flux across the interface were evaluated in detail, i.e., the total thermal energy flux is decomposed into the contribution of molecular transport and that of energy exchange by molecular interactions.
Heat Transfer Characteristics at the SAM Interface with Water and Alkane Solvents

Gota Kikugawa, Taku Ohara, Toru Kawaguchi, Ikuya Kinefuchi, Yoichiro Matsumoto

Proceedings of Joint International Symposia on 3rd Micro & Nano Technology and Micro/Nanoscale Energy Conversion & Transport - 2010　116-118　2010年
C141 親和性および非親和性溶媒を用いたSAM界面熱輸送特性の分子動力学解析(マイクロ・ナノスケールの熱輸送現象II)

菊川豪太, 小原拓, 川口暢, 杵淵郁也, 松本洋一郎

熱工学コンファレンス講演論文集　2009　83-84　2009年11月6日
出版者・発行元：一般社団法人日本機械学会

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The present paper focuses on the difference of thermal boundary resistances at the interface of alkanethiolate self-assembled monolayer (SAM) with hydrophobic and hydrophilic solvents. By using nonequilibrium molecular dynamics simulations, a temperature gradient was imposed across the SAM interface and thermal boundary resistance was evaluated at the both interfaces. It was found that the resistance between hydrophobic SAM and hydrophilic solvent is much larger than that at the hydrophobic SAM and hydrophobic solvent. As one of the influential factors in this difference, the matching of vibrational spectrums of molecules at the interface region was examined.
M3-13 分子動力学法を用いた親水性SAMと水の界面熱抵抗の解析(M3 熱流体デバイス)

川口暢, 杵淵郁也, 松本洋一郎, 菊川豪太, 小原拓, 八束真一

マイクロ・ナノ工学シンポジウム　2009　(1)　69-70　2009年10月15日
出版者・発行元：一般社団法人日本機械学会

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The interfacial thermal resistance at the interface of 11-mercapoundecanol (-S(CH_2)_<11>OH) self-assembled monolayer (SAM) adsorbed on Au(111) substrate and water was investigated using nonequilibrium molecular dynamics simulations. As a result, the interfacial thermal resistance was found to be a half of that in the system that consists of 1-dodecanthiol (-S(CH_2)_<11>OH) SAM adsorbed on Au(111) and toluene [Kikugawa, G., et al., J. Chem. Phys. (2009)]. Also the local thermal resistance between SAM and water was found to be very small. We consider that hydrogen bonds between SAM terminal and water contribute the effective thermal energy transfer from SAM to water. The detailed analysis of heat transport phenomena at the interface was performed and the influence of the bonding structure of water molecules near the interface on the thermal resistance was discussed.
Thermal energy transfer in liquids with ordered/random structures

Taku Ohara, Gota Kikugawa

Proc. 6th International Conference on Flow Dynamics, Sendai　578　2009年
Transport Phenomena at Nano-Structured Interfaces

Taku Ohara, Masahiko Shibahara, Gota Kikugawa

Proc. 9th International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration, Sendai　82-83　2009年
Thermal energy transfer in liquids with ordered/random structures

Taku Ohara, Gota Kikugawa

Proc. 6th International Conference on Flow Dynamics, Sendai　578　2009年
Transport Phenomena at Nano-Structured Interfaces

Taku Ohara, Masahiko Shibahara, Gota Kikugawa

Proc. 9th International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration, Sendai　82-83　2009年
A molecular dynamics study on heat conduction characteristics in lipid bilayer

T. Nakano, G. Kikugawa, T. Ohara

Proc. The Second International Forum on Heat Transfer　2008年
A molecular dynamics study on the heat transfer characteristics at a SAM-solvent interface

G. Kikugawa, T. Kawaguchi, T. Ohara, E. Torigoe, Y. Hagiwara, Y. Matsumoto

Proc. The Second International Forum on Heat Transfer　2008年
A molecular dynamics study on heat transfer characteristics in lipid membranes

T. Nakano, G. Kikugawa, T. Ohara

Proc. The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
Interfacial heat transfer characteristics at the interface of self-assembled monolayers and organic solvent

G. Kikugawa, T. Ohara, T. Kawaguchi, E. Torigoe, Y. Hagiwara, Y. Matsumoto

Proc. The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
Point sprite-based visualization of large-scale particle systems

M. Odagawa, Y. Takeshima, I. Fujishiro, G. Kikugawa, T. Ohara, Y. Terada, M. Tokuyama

Proc. The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
A molecular dynamics study on heat conduction characteristics in lipid bilayer

T. Nakano, G. Kikugawa, T. Ohara

Proc. The Second International Forum on Heat Transfer　2008年
A molecular dynamics study on the heat transfer characteristics at a SAM-solvent interface

G. Kikugawa, T. Kawaguchi, T. Ohara, E. Torigoe, Y. Hagiwara, Y. Matsumoto

Proc. The Second International Forum on Heat Transfer　2008年
A molecular dynamics study on heat transfer characteristics in lipid membranes

T. Nakano, G. Kikugawa, T. Ohara

Proc. The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
Interfacial heat transfer characteristics at the interface of self-assembled monolayers and organic solvent

G. Kikugawa, T. Ohara, T. Kawaguchi, E. Torigoe, Y. Hagiwara, Y. Matsumoto

Proc. The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
Point sprite-based visualization of large-scale particle systems

M. Odagawa, Y. Takeshima, I. Fujishiro, G. Kikugawa, T. Ohara, Y. Terada, M. Tokuyama

Proc. The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
D245 アルカンチオールSAM膜界面の構造と熱輸送特性のMD解析(分子動力学2)

菊川豪太, 川口暢, 小原拓, 鳥越栄一, 萩原康正, 松本洋一郎

熱工学コンファレンス講演論文集　2007　321-322　2007年11月23日
出版者・発行元：一般社団法人日本機械学会

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In this paper, molecular structure and heat transfer properties at the interface of alkanethiol SAMs (self-assembled monolayers) adsorbed on Au surface and toluene solvent are investigated by using molecular dynamics simulations. Heat transfer properties at the solid-liquid interface have not fully been understood as compared to the solid-solid interface because the phonon-based theoretical framework breaks down. In this study, we focus on the SAM-solvent interfaces on the solid substrate which are widely used not only in the industrial devices, but also in the biomaterials and biodevices. By molecular dynamics simulations of SAM-solvent systems, the molecular structures of toluene and SAM molecules are obtained and the difference of the heat transfer property between the SAM-modified interface and the bare solid-lquid interface (Au-toluene) is discussed.
固液界面の熱抵抗に関する分子動力学的研究

鳥居大地, 小原拓

理論応用力学連合会講演論文集　131-132　2007年
気液界面における水分子およびL-J流体の微視的構造とダイナミクス

菊川豪太, 高木周, 松本洋一郎, 小原拓

第44回日本伝熱シンポジウム講演論文集　III　585-586　2007年
アルカン液体中における熱エネルギー伝搬特性

鳥居大地, 小原拓, 松坂岳廣

第44回日本伝熱シンポジウム講演論文集　III　583-584　2007年
脂質二重膜の熱エネルギー伝搬特性

中野雄大, 小原拓, 菊川豪太

第44回日本伝熱シンポジウム講演論文集　III　581-582　2007年
Molecular dynamics study on thermal resistance at solid-liquid interfaces

Daichi Torii, Taku Ohara

理論応用力学連合会講演論文集　131-132　2007年
Heat conduction in liquids due to many-body potential (Contributions of intra- and intermolecular transfer)

Daichi Torii, Takeo Nakano, Taku Ohara

Trans. JSME, Ser. B　73　(734)　2122-2199　2007年
Microscopic structure and dynamics of water and L-J liquids at gas-liquid interfaces

Gota Kikugawa, Shu Takagi, Yoichiro Matsumoto, Taku Ohara

Proc. 44th National Heat Transfer Conference　III　585-586　2007年
Thermal energy transfer characteristics in alkane liquids

Daichi Torii, Taku Ohara, Takehiro Matsuzaka

Proc. 44th National Heat Transfer Conference　III　583-584　2007年
Thermal energy transfer characteristics of lipid bilayer

Takeo Nakano, Taku Ohara, Gota Kikugawa

Proc. 44th Nationa Heat Transfer Conference　III　581-582　2007年
Structure of liquids, solid-liquid/gas-liquid interfaces and their transport characteristics

Taku Ohara, Gota Kikugawa

Fluid Power System　38　(5)　233-238　2007年
Structure of liquids and solid-liquid/gas-liquid interfaces and transport characteristics

Taku Ohara, Gota Kikugawa

Fluid Power System　38　(5)　233-238　2007年
Thermophysics

小原拓

伝熱 : journal of the Heat Transfer Society of Japan　45　(193)　22-22　2006年10月1日

ISSN：1344-8692
AM06-20-002 極薄液膜内のクエット流れにおける運動量・エネルギー伝搬特性(分子スケールの流れ(1),一般講演)

鳥居大地, 小原拓

日本流体力学会年会講演論文集　2006　292-292　2006年
出版者・発行元：日本流体力学会

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The Couette flow of an ultra-thin liquid film between solid surfaces has been studied by molecular dynamics simulations. Water molecules were assumed as liquid and platinum was employed as solid wall in the present report. For the first half of this paper, the characteristics of flow profile and structure and orientation of water molecules adjacent to the solid surfaces were studied. It was revealed that there is little velocity slip at the boundary even the shear stress is as high as the order of 10^2MPa and that the orientation of water molecule is strongly influenced by the application of a shear. For the latter half, transfer of energy and momentum both in liquid film and at the solid-liquid interface was analyzed.
Thermally driven ion transport by the spatially symmetric Brownian ratchet

Taku Ohara, Takeo Nakano, Daichi Torii

Proc. 2nd International Symposium on Micro and Nano Technology　390-393　2006年
Thermally driven ion transport by the spatially symmetric Brownian ratchet

Taku Ohara, Takeo Nakano, Daichi Torii

Proc. 2nd International Symposium on Micro and Nano Technology　390-393　2006年
C131 固液界面における熱伝導の分子熱工学的研究(OS-11 ナノスケール伝熱III)

鳥居大地, 石田健児, 小原拓

熱工学コンファレンス講演論文集　2005　109-110　2005年11月2日
出版者・発行元：一般社団法人日本機械学会

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Molecular dynamics simulation has been performed to clarify the mechanism and characteristics of the energy transfer at the solid-liquid interfaces. The system consists of a pair of parallel solid walls and a liquid film in between. The solid walls have different temperatures in order to generate a constant thermal energy flux, and three kinds of crystal planes that contact the liquid are employed. Investigating the intermolecular energy transfer at the solid-liquid interfaces, the characteristics of the energy transfer are found to be greatly influenced by the molecular surface configuration of the solid walls and the mechanism of the energy transfer is clarified.
AM05-06-002 ナノスケールクエット流における固体壁面性状の影響(分子スケールの流れ1,一般講演)

小原拓, 鳥居大地

日本流体力学会年会講演論文集　2005　96-96　2005年
出版者・発行元：日本流体力学会

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The Couette flow of an ultra-thin liquid film between solid surfaces has been studied by a molecular dynamics simulation. A liquid of diatomic molecules and liquid water were assumed for the film liquid, and transfer of energy and momentum both in liquid film and at the solid-liquid interface was analyzed. It was revealed that the flow has peculiar characteristics when shear at high rate is given to the liquid. Highly nonequilibrium energy distribution occurs in the liquid just close to the solid surface in the process of energy conversion from flow to thermal one, i.e., viscous heating in a macroscopic sense, and energy transfer among degrees of freedom for rotational motion of molecules and translational one. Influence of the molecular scale structure of the solid surface is revealed in the present study.
Energy and momentum transfer in an ultra-thin liquid water film sheared between solid surfaces

Daichi Torii, Taku Ohara

Proc. Engineering Conference International, Heat Transfer and Fluid Flow in Microscale　CD-ROM　2005年
Energy and momentum transfer in an ultra-thin liquid water film sheared between solid surfaces

Daichi Torii, Taku Ohara

Proc. Engineering Conference International, Heat Transfer and Fluid Flow in Microscale　CD-ROM　2005年
Molecular dynamics study on ultrathin liquid film sheared between solid surfaces

Daichi Torii, Taku Ohara

Trans. JSME, Ser. B　71　(710)　2507-2514　2005年
Thinking about "quality" of heat conduction flux

Taku Ohara

Thermophysical Properties　19　(3)　181-184　2005年
固体壁間でせん断を受ける極薄膜液体水の分子動力学シミュレーション(OS15b 熱流体の分子シミュレーション)

鳥居大地, 小原拓

計算力学講演会講演論文集　2004　(17)　537-538　2004年11月17日
出版者・発行元：一般社団法人日本機械学会
ISSN：1348-026X
固液界面におけるエネルギー・運動量伝搬 : 固体結晶面の影響(オーガナイズドセッション10 ナノ・マイクロスケール伝熱)

鳥居大地, 小原拓

熱工学コンファレンス講演論文集　2004　139-140　2004年11月10日
出版者・発行元：一般社団法人日本機械学会

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Molecular dynamics simulation has been performed on pairs of solid walls and liquid films in between. As a shear is given to the liquid film by moving the solid walls, the Couette-like flow is generated in the liquid film and energy conversion occurs from the macroscopic flow to the thermal one, i.e., viscous heating in the macroscopic sense. In such a way, momentum transfer and thermal energy transfer are present simultaneously. At the solid-liquid interfaces, there exist large velocity and temperature jumps due to the large momentum and heat fluxes. It has been revealed in our present study that the characteristics of the energy and momentum transfer at the interfaces are greatly influenced by the crystal plane of the solid walls which contacts to the liquid film.
日本伝熱学会学術賞を受賞して

小原拓, MAJUMDAR Arun

伝熱 : journal of the Heat Transfer Society of Japan　43　(181)　5-5　2004年7月1日

ISSN：1344-8692
B234 摺動面間におけるナノスケール液膜のクエット流れに関する研究(B-23 分子スケールの流れ(1),一般講演)

小原拓, 鳥居大地

日本流体力学会年会講演論文集　2004　292-293　2004年
出版者・発行元：日本流体力学会

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The Couette flow of an ultra-thin liquid film between solid surfaces has been studied by a molecular dynamics simulation. A liquid of diatomic molecules and liquid water were assumed for the film liquid, and transfer of energy and momentum both in liquid film and at the solid-liquid interface was analyzed. It was revealed that the flow has peculiar characteristics when shear at high rate is given to the liquid due to velocity difference between the two solid walls. Highly nonequilibrium energy distribution occurs in the liquid just close to the solid surface in the process of energy conversion from flow to thermal one, i.e., viscous heating in a macroscopic sense, and energy transfer among degrees of freedom for rotational motion of molecules and translational one.
321 潤滑薄液膜中のエネルギー・運動量伝搬

小原拓

計算力学講演会講演論文集　2003　(16)　213-214　2003年11月22日
出版者・発行元：一般社団法人日本機械学会
ISSN：1348-026X
H114 固液界面のエネルギー・運動量伝達

小原拓, 芝原正彦

熱工学コンファレンス講演論文集　2003　297-298　2003年11月10日
出版者・発行元：一般社団法人日本機械学会

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Energy and momentum transfer at a solid-liquid interface has peculiar characteristics when shear at high rate is applied to the liquid by the moving solid wall. It has been showed in the previous report of ours on this problem for a monatomic liquid film that highly nonequilibrium energy distribution occurs in the liquid just close to the solid surface in the process of energy conversion from flow to thermal one, i.e., viscous heating in the macroscopic sense. This phenomenon will be more complicated for the case with polyatomic liquid, where degree of freedom in rotational motion plays an important role in energy transfer. The present report is on the molecular dynamics study of this phenomenon, in which diatomic molecules are applied for the sheared liquid.
611 潤滑液膜の分子動力学的研究

小原拓

計算力学講演会講演論文集　2002　(15)　599-600　2002年10月30日
出版者・発行元：一般社団法人日本機械学会
ISSN：1348-026X
Molecular Dynamics in Thermofluid Engineering

Takashi Tokumasu, Taku Ohara

日本数値流体力学会誌,日本数値流体力学会　10　41-46　2002年
マイクロチップによるDNAの分離解析

小原拓

伝熱研究 = News of HTSJ　40　(165)　7-7　2001年11月1日

ISSN：0910-7851
A002 液体水における分子間エネルギー伝搬とその熱伝導への寄与に関する分子動力学的研究

小原拓

日本流体力学会年会講演論文集　2001　5-8　2001年
出版者・発行元：日本流体力学会
ISSN：1342-8004

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Intermolecular energy transfer (IET) is a dominant factor in heat conduction in liquid. The IET in liquid water and its contribution to macroscopic heat conduction under a temperature gradient was analyzed by a molecular dynamics simulation. Intermolecular energy exchange rates (IEERs) for both the translational and rotational motion of molecules were defined and their characteristics examined. The IEER of hydrogen-bonded molecules and non-bonded molecules have different characteristics. In the present study, the effective rate of the IET was assumed to be proportional to the magnitude of the IEER that oscillates with a high amplitude. Based on the characteristics of the IEER, contributions of the translational and rotational IET between hydrogen-bonded molecules and non-bonded molecules to macroscopic heat conduction were evaluated. The evaluated results were compared with the results of a MD simulation of heat conduction under a constant temperature gradient, and good qualitative agreement between the predicted value and the simulated result were found. The rotational IET was found to be dominant as compared with the translational IET, and the contribution of hydrogen-bonded molecules to heat conduction was found to be relatively small. The possibility of a mechanism that cancels the IET between distant molecules and the development of a precise model for this mechanism was also discussed.
Ratcheting Electrophoresis Microchip for Analysis of Biomolecules

OHARA Taku

Thermal Science and Engineering　9　(3)　37　2001年
固液界面近傍における分子間エネルギー伝搬

OHARA Taku

8　(3)　19　2000年
液体中の熱伝導の分子動力学シミュレーション

小原拓

年会一般講演　18　339-340　1999年7月29日

ISSN：1342-8004
伝熱シンポジウム「気になる研究」物質移動, エネルギー有効利用, 分子スケール関連

小原拓

伝熱研究 = News of HTSJ　38　(151)　10-10　1999年7月1日

ISSN：0910-7851
液体中の熱伝導における分子間エネルギー伝搬特性

OHARA Taku

Thermal science and engineering　7　(1)　53-61　1999年
出版者・発行元：Heat Transfer Society of Japan
ISSN：0918-9963
Intermolecular Energy Transer Characteristics of Simple Liquid Heat Conduction

OHARA Taku

Thermal Science and Engineering　7　(1)　53-61　1999年
Microscopic Insight into Heat Conduction

OHARA Taku

熱物性　13　(2)　102-112　1999年
水の分子間エネルギー伝搬に関する分子動力学的研究

OHARA Taku

6　(4)　1-8　1998年
Molecular Dynamics Study on Intermolecular Energy Transfer in Water

OHARA Taku

Thermal Science and Engineering　6　(4)　1-8　1998年
密閉セル中の超臨界圧流体の非定常熱伝達に関する数値解析

小原拓, 相原利雄, 本木一郎

東北大学流体科学研究所報告　8　17-24　1997年3月
出版者・発行元：東北大学
ISSN：0916-2860
気液界面における液体水の構造

小原拓, 他

第34回日本伝熱シンポジウム講演論文集　3　671-672　1997年
液体ヘリウムにおける水平被覆ストリップからの急速過渡沸騰熱伝達

小村昭義, 岡田定五, 相原利雄, 小原拓, 山本広衛

低温工学　32　(2)　66-72　1997年
出版者・発行元：低温工学協会
ISSN：0389-2441
Structure of Liquid Water at the Liquid-Vapor Interface Region

OHARA Taku

第34回日本伝熱シンポジウム講演論文集　3　671-672　1997年
Molecular Dynamics Study on Phase Change and Cluster Formation in Fluids

OHARA Taku

Proc. Symposium on Molecular Thermo Fluid Dynamics　104-109　1995年
Molecular Dynamics Study on Phase Change and Cluster Formation in Fluids

OHARA Taku

Thermal Science and Engineering　3　(3)　7-13　1995年
Molecular Dynamics Study on Phase Change and Cluster Formation in Fluids

OHARA Taku

Proc. Symposium on Molecular Thermo Fluid Dynamics　104-109　1995年
水平着霜管群の衝突噴流熱伝達

小原拓, 北野仁, 相原利雄, 下山利幸

空気調和・衛生工学会論文集　20　(58)　103-109　1995年
出版者・発行元：公益社団法人空気調和・衛生工学会
DOI： 10.18948/shase.20.58_103 　

ISSN：0385-275X

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従来の管群熱交換器に衝突噴流を組み合わせて熱交換器の高性能化を図り,さらに着霜環境下での実用化を行う観点から,衝突噴流中の冷却管について,その着霜特性および熱伝達特性を実験的に解析した.まず,衝突噴流中の加熱円管についてその熱伝達率を比較することにより,顕著な熱伝達の向上が得られた.さらに,衝突噴流中に置かれた着霜を伴う冷却円管の局所熱伝達特性について詳細な実験を行い,冷却管周りの霜層による熱抵抗の増大が着霜による潜熱放出などに勝る結果,熱伝達率は低下する過程を明らかにし,また,霜層表面と空気間の熱抵抗と,霜層の熱抵抗も含む管表面と空気間の全熱抵抗の比を表す実験式を提示した.
Molecular Dynamics Study on Phase Change and Cluster Formation in Fluids

OHARA Taku

Thermal Science and Engineering　3　(3)　7-13　1995年
[Molecular Dynamics Study on cluster Structure of Water]

OHARA Taku

Trans. JSME, Ser. B　60　(570)　496-503　1994年
水分子のクラスター形成の可視化

小原拓, 他

可視化情報　13　(1)　107-108　1993年
出版者・発行元：The Visualization Society of Japan
DOI： 10.3154/jvs.13.Supplement1_107 　

ISSN：0916-4731

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Huge amount of information about velocities and locations of individual molecules is derived in the molec-ular dynamics calculation. On the other hand it is difficult to understand from these results how molecules behave. The authors have been studying about microscopic structure of water in a wide range of temperature and density, including liquid-gas coexistence region and near the critical point. The motion of 256 water molecules in a cubic cell is analyzed by molecular dynamics calculations. Visualization of molecules' location and animation of molecules' motion are successfully performed in the present report to see how molecular structure is formed.
液体をミクロに見れば

小原拓, 相原利雄

日本機械学會誌　96　(892)　180-183　1993年
出版者・発行元：一般社団法人日本機械学会
ISSN：0021-4728
27 水分子のクラスター形成の可視化

小原拓, 相原利雄

可視化情報学会誌　13　(1)　107-108　1993年
出版者・発行元：The Visualization Society of Japan
DOI： 10.3154/jvs.13.Supplement1_107 　

ISSN：0916-4731

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Huge amount of information about velocities and locations of individual molecules is derived in the molec-ular dynamics calculation. On the other hand it is difficult to understand from these results how molecules behave. The authors have been studying about microscopic structure of water in a wide range of temperature and density, including liquid-gas coexistence region and near the critical point. The motion of 256 water molecules in a cubic cell is analyzed by molecular dynamics calculations. Visualization of molecules' location and animation of molecules' motion are successfully performed in the present report to see how molecular structure is formed.
Liquid Film Formation on a Rotating Disk

OHARA Taku

Heat Transfer Japanese Research　20　(1)　36-55　1991年
Liquid Film Formation on a Rotating Disk (Numerical Analysis at the Initial Stage)

MATSUMOTO Y., OHARA Taku, TERUYA Isao, OHASHI Hideo

JSME Int. J. Series II　32　52-52　1989年
出版者・発行元：一般社団法人日本機械学会
ISSN：0914-8817

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Unsteady liquid film flow on a rotating disk which is related to a spin coating technique to form a uniform thin film on a plate is calculated numerically. A newly developed calculation method which takes the surface tension on the liquid surface into account is applied. The numerical results reveal the following : the hemispherical liquid on the disk, which starts to rotate impulsively from rest, spreads by gravitational forces at the first stage. The development of the distribution of radial and azimuthal velocities is affected complicatedly by the Coriolis forces, viscous forces and centrifugal forces. The liquid spreads mainly by centrifugal forces and forms a uniform thin film on the disk at the last stage. The surface tension only show a little influence on the spreading process at the first stage.
Liquid Film Formation on a Rotating Disk (2nd Report)

OHARA Taku

Trans. of Japan Society of Mechanical Engineers　55　(514)　1989年
粒子の流れ場に対する追従性に関する数値解析

李英浩, 小原拓, 松本洋一郎

東京大学工学部総合試験所年報　(47)　p163-166　1988年9月
出版者・発行元：東京大学工学部総合試験所
ISSN：0371-3067

︎全件表示 ︎最初の5件までを表示

書籍等出版物 16

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マイクロ・ナノ熱工学の進展

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マイクロ・ナノ熱工学の進展

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Capter 4, Transport phenomena in nanoscale solid-liquid structures

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環境と省エネルギーのためのエネルギー新技術大系

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Experiment in Heat Transfer and Thermodynamics

Toshio Aihara, Taku Ohara

Cambridge University Press　1994年
Molecular Dynamics Study on Structure of Near Critical Water

1994年
Liquid Film Formation on a Rotating Disk

1990年

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ASME 2013 Summer Heat Transfer Conference　2013年
架橋を有するアモルファスポリマー材料における熱輸送機構の解明

日本機械学会2013年度年次大会　2013年
Heat Conduction in Amorphous Polymers with Crosslink Formation

4th International Symposium on Micro and Nanotechnology　2013年
Molecular Dynamics Study on the Influences of Nanochannel Geometry on the Energy Transport Mechanism at Liquid-Solid Interfaces

4th International Symposium on Micro and Nanotechnology　2013年
SiO2固体壁近傍における水およびIPAの物質輸送特性に関する分子動力学的研究

日本機械学会熱工学コンファレンス2013　2013年
Molecular Dynamics Mechanism of Thermal Energy Transport in Liquid Methane Reproduced by All-Atom and United-Atom Models

4th International Symposium on Micro and Nanotechnology　2013年
A Molecular Dynamics Study on Effect of Temperature on Diffusion in the Vicinity of an Alpha-Quartz Surface/Alkane Interfaces

4th International Symposium on Micro and Nanotechnology　2013年
A molecular dynamics study on mass transport properties in the vicinity of SiO2-water/IPA interfaces

4th International Symposium on Micro and Nanotechnology　2013年
Study of Alkane Chain Length Influence on Structure and Dynamic Properties at Intrinsic Liquid-Vapour Interfaces

12th International Symposium on Fluid Control, Measurement and Visualization (FLUCOME2013)　2013年
Thermal Transport Characteristics over the Interface of Alkanethiol SAM on a Copper Substrate and Water Solvent

12th International Symposium on Fluid Control, Measurement and Visualization (FLUCOME2013)　2013年
Surface Termination Effect on Structure of Decane Liquid in the Vicinity of Alpha-Quartz Surfaces

Hari Krishna Chilukoti, Gota Kikugawa, Taku Ohara

International Conference on Flow Dynamics 2013　2013年
微細構造が固液界面エネルギー輸送機構に及ぼす影響に関する分子動力学的研究

第27回数値流体力学シンポジウム　2013年
Heat Effect of Cross-Linking on Heat Conduction of Amorphous Polymers

MRS (Materials Research Society) Spring Meeting 2013　2013年
アモルファスポリマー内の架橋による熱伝導特性への影響

第50回日本伝熱シンポジウム　2013年
ナノメートルスケールの微細構造が固液界面エネルギー輸送機構に及ぼす影響

第50回日本伝熱シンポジウム　2013年
気液瞬時界面近傍における液体アルカンの構造

第50回日本伝熱シンポジウム　2013年
銅基盤上のアルカンチオールSAMの構造と熱輸送特性

第50回日本伝熱シンポジウム　2013年
Mass Transport Characteristics of Water/IPA at Silica-Liquid Interfaces

ASME 2013 11th International Conference on Nanochannels, Microchannels and Minichannels　2013年
Intrinsic Structure and Diffusion at the Liquid-Vapor Interfaces of Alkanes by Molecular Dynamics Simulation

ASME 2013 Summer Heat Transfer Conference　2013年
架橋を有するアモルファスポリマー材料における熱輸送機構の解明

日本機械学会2013年度年次大会　2013年
Heat Conduction in Amorphous Polymers with Crosslink Formation

4th International Symposium on Micro and Nanotechnology　2013年
Molecular Dynamics Study on the Influences of Nanochannel Geometry on the Energy Transport Mechanism at Liquid-Solid Interfaces

4th International Symposium on Micro and Nanotechnology　2013年
SiO2固体壁近傍における水およびIPAの物質輸送特性に関する分子動力学的研究

日本機械学会熱工学コンファレンス2013　2013年
Molecular Dynamics Mechanism of Thermal Energy Transport in Liquid Methane Reproduced by All-Atom and United-Atom Models

4th International Symposium on Micro and Nanotechnology　2013年
A Molecular Dynamics Study on Effect of Temperature on Diffusion in the Vicinity of an Alpha-Quartz Surface/Alkane Interfaces

4th International Symposium on Micro and Nanotechnology　2013年
A molecular dynamics study on mass transport properties in the vicinity of SiO2-water/IPA interfaces

4th International Symposium on Micro and Nanotechnology　2013年
Study of Alkane Chain Length Influence on Structure and Dynamic Properties at Intrinsic Liquid-Vapour Interfaces

12th International Symposium on Fluid Control, Measurement and Visualization (FLUCOME2013)　2013年
Thermal Transport Characteristics over the Interface of Alkanethiol SAM on a Copper Substrate and Water Solvent

12th International Symposium on Fluid Control, Measurement and Visualization (FLUCOME2013)　2013年
微細構造が固液界面エネルギー輸送機構に及ぼす影響に関する分子動力学的研究

第27回数値流体力学シンポジウム　2013年
Structure and Transport Characteristics at Liquid-Vapor Interfaces of Alkanes

第49回日本伝熱シンポジウム　2012年
微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響

第49回日本伝熱シンポジウム　2012年
SiO2－水/IPA界面近傍における液膜中の構造と物質輸送に関する分子動力学的研究

第49回日本伝熱シンポジウム　2012年
All-atomモデルによる各種アルカン飽和液中の熱伝導に関する分子動力学シミュレーション

第49回日本伝熱シンポジウム　2012年
Thermal Resistance between Nano-Structured Surfaces and Liquids

M. Shibahara, T. Ohara, G. Kikugawa

9th International Conference on Fluid Dynamics, IFS Collaborative Research Forum (AFI/TFI-2012)　2012年
Molecular Dynamics Study on Effect of Chain Length on Liquid-Vapor Interfacial Properties of alkanes

Hari Krishna Chikukoti, G. Kikugawa, T. Ohara

9th International Conference on Fluid Dynamics　2012年
直鎖アルカン飽和液中の熱エネルギー伝搬機構に関するAll-Atom分子動力学シミュレーション

日本機械学会2012年度年次大会　2012年
ナノメートルスケールの微細構造が固液界面の熱抵抗とエネルギー輸送に与える影響に関する分子動力学的研究

日本機械学会2012年度年次大会　2012年
SiO2－水/IPA界面近傍における液膜中の構造と物質輸送に対する温度の影響

日本機械学会第4回マイクロ・ナノ工学シンポジウム　2012年
A Molecular Dynamics Study on Molecular Scale Structure and Mass Transport Properties in the Vicinity of SiO2-Water/IPA Interfaces

3rd International Forum on Heat Transfer　2012年
SiO2-水/IPA界面近傍での液膜構造と物質輸送に関する分子動力学的研究

日本機械学会熱工学コンファレンス2012　2012年
Molecular Dynamics Simulation of Liquid-Vapor Interfacial Properties of n-Alkanes

3rd International Forum on Heat Transfer　2012年
Molecular Dynamics Study on the Influences of Nanostructure Geometry on the Energy Transport and Local Non-Equilibrium Behavior at Liquid-Solid Interfaces

23rd International Symposium on Transport Phenomena　2012年
流体の熱輸送を支配する分子動力学機構

大阪大学機械工学系第63回技術交流会　2012年
SiO2-水/IPA界面近傍における物質輸送に関する分子動力学的研究（吸着層内での分子の挙動とエネルギー状態）

第26回数値流体力学シンポジウム　2012年
Structure and Transport Characteristics at Liquid-Vapor Interfaces of Alkanes

第49回日本伝熱シンポジウム　2012年
微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響

第49回日本伝熱シンポジウム　2012年
SiO2－水/IPA界面近傍における液膜中の構造と物質輸送に関する分子動力学的研究

第49回日本伝熱シンポジウム　2012年
All-atomモデルによる各種アルカン飽和液中の熱伝導に関する分子動力学シミュレーション

第49回日本伝熱シンポジウム　2012年
直鎖アルカン飽和液中の熱エネルギー伝搬機構に関するAll-Atom分子動力学シミュレーション

日本機械学会2012年度年次大会　2012年
ナノメートルスケールの微細構造が固液界面の熱抵抗とエネルギー輸送に与える影響に関する分子動力学的研究

日本機械学会2012年度年次大会　2012年
SiO2－水/IPA界面近傍における液膜中の構造と物質輸送に対する温度の影響

日本機械学会第4回マイクロ・ナノ工学シンポジウム　2012年
A Molecular Dynamics Study on Molecular Scale Structure and Mass Transport Properties in the Vicinity of SiO2-Water/IPA Interfaces

3rd International Forum on Heat Transfer　2012年
SiO2-水/IPA界面近傍での液膜構造と物質輸送に関する分子動力学的研究

日本機械学会熱工学コンファレンス2012　2012年
Molecular Dynamics Simulation of Liquid-Vapor Interfacial Properties of n-Alkanes

3rd International Forum on Heat Transfer　2012年
Molecular Dynamics Study on the Influences of Nanostructure Geometry on the Energy Transport and Local Non-Equilibrium Behavior at Liquid-Solid Interfaces

23rd International Symposium on Transport Phenomena　2012年
流体の熱輸送を支配する分子動力学機構

大阪大学機械工学系第63回技術交流会　2012年
SiO2-水/IPA界面近傍における物質輸送に関する分子動力学的研究（吸着層内での分子の挙動とエネルギー状態）

第26回数値流体力学シンポジウム　2012年
A Molecular Dynamics Study on Heat Transfer Characteristics over the Interface of Self-Assembled Monolayer and Water Solvent

ASME/JSME 2011 8th Thermal Engineering Joint Conference　2011年
Effect of Alkyl Chain Length on Molecular Heat Transfer Characteristics in Lipid Bilayers

ASME/JSME 2011 8th Thermal Engineering Joint Conference　2011年
Effects of the Nanostructural Geometry at a Liquid-Solid Interface on the Interfacial Thermal Resistance and the Liquid Molecular Non-Equilibrium Behaviors

ASME/JSME 2011 8th Thermal Engineering Joint Conference　2011年
SiO2－水界面近傍における分子スケール構造と物質輸送に関する分子動力学的研究

第48回日本伝熱シンポジウム　2011年
自己組織化膜修飾界面によるアルカン極薄液膜のせん断に関する分子動力学シミュレーション

第48回日本伝熱シンポジウム　2011年
微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響

第48回日本伝熱シンポジウム　2011年
Momentum and Heat Transport in Nanoscale Lubrication of Alkane Thin Film Sheared by Self-Assembled Monolayer Surfaces

4th International Conference on Heat Transfer and Fluid Flow in Microscale　2011年
微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響

日本機械学会2011年度年次大会　2011年
SiO2－水／IPA界面近傍における構造と物質輸送に関する分子動力学的研究

熱工学コンファレンス　2011年
親水性および疎水性SAMと水溶媒の界面における熱輸送特性の詳細解析

熱工学コンファレンス2011　2011年
液体メタンの熱伝導を支配する分子動力学機構

第32回日本熱物性シンポジウム　2011年
All-atomモデルによるアルカン飽和液中の熱伝導に関する分子動力学シミュレーション

第25回数値流体力学シンポジウム　2011年
微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響

第25回数値流体力学シンポジウム　2011年
The midle way: Transport Phenomena in Soft Matters

7th NSF-JSPS US-Japan Joint Seminar on Nanoscale Transport Phenomena - Science and Engineering -　2011年
A Molecular Dynamics Study on Heat Transfer Characteristics over the Interface of Self-Assembled Monolayer and Water Solvent

ASME/JSME 2011 8th Thermal Engineering Joint Conference　2011年
Effect of Alkyl Chain Length on Molecular Heat Transfer Characteristics in Lipid Bilayers

ASME/JSME 2011 8th Thermal Engineering Joint Conference　2011年
Effects of the Nanostructural Geometry at a Liquid-Solid Interface on the Interfacial Thermal Resistance and the Liquid Molecular Non-Equilibrium Behaviors

ASME/JSME 2011 8th Thermal Engineering Joint Conference　2011年
SiO2－水界面近傍における分子スケール構造と物質輸送に関する分子動力学的研究

第48回日本伝熱シンポジウム　2011年
自己組織化膜修飾界面によるアルカン極薄液膜のせん断に関する分子動力学シミュレーション

第48回日本伝熱シンポジウム　2011年
微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響

第48回日本伝熱シンポジウム　2011年
Momentum and Heat Transport in Nanoscale Lubrication of Alkane Thin Film Sheared by Self-Assembled Monolayer Surfaces

4th International Conference on Heat Transfer and Fluid Flow in Microscale　2011年
微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響

日本機械学会2011年度年次大会　2011年
SiO2－水／IPA界面近傍における構造と物質輸送に関する分子動力学的研究

熱工学コンファレンス　2011年
親水性および疎水性SAMと水溶媒の界面における熱輸送特性の詳細解析

熱工学コンファレンス2011　2011年
液体メタンの熱伝導を支配する分子動力学機構

第32回日本熱物性シンポジウム　2011年
All-atomモデルによるアルカン飽和液中の熱伝導に関する分子動力学シミュレーション

第25回数値流体力学シンポジウム　2011年
微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響

第25回数値流体力学シンポジウム　2011年
The midle way: Transport Phenomena in Soft Matters

7th NSF-JSPS US-Japan Joint Seminar on Nanoscale Transport Phenomena - Science and Engineering -　2011年
Heat Transfer Characteristics at the SAM Interface with Water and Alkane Solvents

Joint International Symposia on 3rd Micro & Nano Technology and Micro/Nanoscale Energy Conversion & Transport - 2010　2010年
SAM-溶媒界面の熱輸送特性に対する親水性・疎水性の影響

第47回日本伝熱シンポジウム　2010年
脂質二重膜の熱伝導特性に対する炭化水素鎖長による影響

第47回日本伝熱シンポジウム　2010年
自己組織化単分子膜のための粒子配置設計支援システム

第38回可視化情報シンポジウム　2010年
脂質二重膜の熱輸送特性に対する脂質分子種の影響

日本流体力学会年会2010　2010年
自己組織化単分子膜の水溶媒界面における熱輸送特性

日本流体力学会年会2010　2010年
せん断流中における脂質二重膜の運動量伝搬特性に関する分子動力学的研究

日本機械学会2010年度年次大会　2010年
酸化物固体－溶媒界面における溶質移動に関する2次元自由エネルギー局面

日本機械学会2010年度年次大会　2010年
自己組織化膜修飾が固液界面熱抵抗に与える諸影響の分子論的解析

日本機械学会2010年度年次大会　2010年
界面における熱流体輸送現象の分子動力学解析

第１２回分子シミュレーションのトライボロジーへの応用研究会　2010年
親水性および疎水性末端基を持つSAM－溶媒界面の熱輸送特性

日本機械学会熱工学コンファレンス2010　2010年
微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響

日本機械学会熱工学コンファレンス2010　2010年
Effects of Nanostructural Geometry at a Liquid-Solid Interface on the Interfacial Thermal Resistance and Liquid Molecular Non-Equilibrium Behaviors

M. Shibahara, T. Ohara

7th International Conference on Flow Dynamics　2010年
Heat Transfer Characteristics at the SAM Interface of Self-Assembled Monolayer with Hydrophobic and Hydrophilic Termini and Solvent

G. Kikugawa, T. Ohara, T. Kawaguchi, I. Kinefuchi, Y. Matsumoto

7th International Conference on Flow Dynamics　2010年
Molecular Momentun Transfer Characteristics of Liquid Behaviors in Shear Flows

T. Nakano, G. Kikugawa, T. Ohara

7th International Conference on Flow Dynamics　2010年
Transport Phenomena at Nano-Structured Interfaces

IFS Collaborative Research Forum (AFI/TFI-2010)　2010年
Heat Transfer Characteristics at the SAM Interface with Water and Alkane Solvents

Joint International Symposia on 3rd Micro & Nano Technology and Micro/Nanoscale Energy Conversion & Transport - 2010　2010年
SAM-溶媒界面の熱輸送特性に対する親水性・疎水性の影響

第47回日本伝熱シンポジウム　2010年
脂質二重膜の熱伝導特性に対する炭化水素鎖長による影響

第47回日本伝熱シンポジウム　2010年
自己組織化単分子膜のための粒子配置設計支援システム

第38回可視化情報シンポジウム　2010年
脂質二重膜の熱輸送特性に対する脂質分子種の影響

日本流体力学会年会2010　2010年
自己組織化単分子膜の水溶媒界面における熱輸送特性

日本流体力学会年会2010　2010年
せん断流中における脂質二重膜の運動量伝搬特性に関する分子動力学的研究

日本機械学会2010年度年次大会　2010年
酸化物固体－溶媒界面における溶質移動に関する2次元自由エネルギー局面

日本機械学会2010年度年次大会　2010年
自己組織化膜修飾が固液界面熱抵抗に与える諸影響の分子論的解析

日本機械学会2010年度年次大会　2010年
界面における熱流体輸送現象の分子動力学解析

第１２回分子シミュレーションのトライボロジーへの応用研究会　2010年
親水性および疎水性末端基を持つSAM－溶媒界面の熱輸送特性

日本機械学会熱工学コンファレンス2010　2010年
微細構造によって誘起された局所非平衡性が固液界面エネルギー輸送に及ぼす影響

日本機械学会熱工学コンファレンス2010　2010年
Transport Phenomena at Nano-Structured Interfaces

IFS Collaborative Research Forum (AFI/TFI-2010)　2010年
せん断流中における脂質二重膜の運動量伝搬特性

第46回日本伝熱シンポジウム　2009年
マグネタイト－水界面における溶出分子の物質輸送特性

第46回日本伝熱シンポジウム　2009年
SAM内部およびSAM界面における熱輸送特性の分子動力学的研究

日本機械学会2009年度年次大会　2009年
コーティング液膜流れの3次元数値解析

日本機械学会2009年度年次大会　2009年
せん断流動場における脂質二重膜の運動量輸送特性の異方性に関する分子動力学的研究

日本機械学会2009年度年次大会　2009年
ポリマー液体の熱輸送特性に及ぼす分子内エネルギー伝搬の影響

日本機械学会2009年度年次大会　2009年
固体表面近傍の水中における物質輸送特性

日本機械学会2009年度年次大会　2009年
A molecular dynamics Study on lipid bilayers in shear flows

Takeo Nakano, Gota Kikugawa, Taku Ohara

2nd Asian Symposium on Computational Heat Transfer and Fluid Flow, Jeju　2009年
Heat transfer characteristics inside the SAM layer and at the SAM interfaces with organic solvents

Gota Kikugawa, Takato Mochimaru, Taku Ohara, Toru Kawaguchi, Yoichiro Matsumoto

2nd Asian Symposium on Computational Heat Transfer and Fluid Flow, Jeju　2009年
SAM修飾による固液界面の界面熱抵抗低減特性

第30回日本熱物性シンポジウム　2009年
ポリマー液体の熱伝導率に対する分子内エネルギー伝搬の寄与

第30回日本熱物性シンポジウム　2009年
脂質二重膜の熱伝導特性に関する分子動力学解析

第30回日本熱物性シンポジウム講演論文集　2009年
Thermal energy transfer in liquids with ordered/random structures

6th International Conference on Flow Dynamics, Sendai, GCOE, IFS-Tsinghua University Joint Workshop　2009年
Transport Phenomena at Nano-Structured Interfaces

9th International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration, Sendai　2009年
親和性および非親和性溶媒を用いたSAM界面熱輸送特性の分子動力学解析

日本機械学会熱工学コンファレンス2009　2009年
Molecular Dynamics Study of International Thermal Resistance of Mercapto-Alkanol Self-Assembled Monolayer and Water

ASME 2009 2nd Micro/Nanoscale Heat & Mass Transfer　2009年
せん断流中における脂質二重膜の運動量伝搬特性

第46回日本伝熱シンポジウム　2009年
マグネタイト－水界面における溶出分子の物質輸送特性

第46回日本伝熱シンポジウム　2009年
SAM内部およびSAM界面における熱輸送特性の分子動力学的研究

日本機械学会2009年度年次大会　2009年
コーティング液膜流れの3次元数値解析

日本機械学会2009年度年次大会　2009年
せん断流動場における脂質二重膜の運動量輸送特性の異方性に関する分子動力学的研究

日本機械学会2009年度年次大会　2009年
ポリマー液体の熱輸送特性に及ぼす分子内エネルギー伝搬の影響

日本機械学会2009年度年次大会　2009年
固体表面近傍の水中における物質輸送特性

日本機械学会2009年度年次大会　2009年
SAM修飾による固液界面の界面熱抵抗低減特性

第30回日本熱物性シンポジウム　2009年
ポリマー液体の熱伝導率に対する分子内エネルギー伝搬の寄与

第30回日本熱物性シンポジウム　2009年
脂質二重膜の熱伝導特性に関する分子動力学解析

第30回日本熱物性シンポジウム講演論文集　2009年
Thermal energy transfer in liquids with ordered/random structures

6th International Conference on Flow Dynamics, Sendai, GCOE, IFS-Tsinghua University Joint Workshop　2009年
Transport Phenomena at Nano-Structured Interfaces

9th International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration, Sendai　2009年
親和性および非親和性溶媒を用いたSAM界面熱輸送特性の分子動力学解析

日本機械学会熱工学コンファレンス2009　2009年
Molecular Dynamics Study of International Thermal Resistance of Mercapto-Alkanol Self-Assembled Monolayer and Water

ASME 2009 2nd Micro/Nanoscale Heat & Mass Transfer　2009年
膜・界面の輸送現象

日本機械学会RC225分科会「マイクロ・ナノフルイディクス調査研究分科会」　2008年
SAM膜－溶媒界面における熱輸送特性の分子動力学解析

第45回日本伝熱シンポジウム　2008年
脂質二重膜界面における熱輸送特性

第45回日本伝熱シンポジウム　2008年
数万オーダ粒子系のイメージベース可視化

第36回可視化情報シンポジウム　2008年
Thermal energy transfer in membranes and at liquid-solid interfaces

6th NSF-ONR US-Japan Seminar on Nanoscale Transport Phenomena　2008年
SAM-溶媒界面における界面熱抵抗特性の分子論的研究

日本機械学会2008年度年次大会　2008年
アルカン液体の固液界面におけるエネルギー・運動量伝搬特性

日本機械学会2008年度年次大会　2008年
せん断流中における脂質二重膜の分子動力学的研究

日本機械学会2008年度年次大会　2008年
A molecular dynamics study on heat conduction characteristics in lipid bilayer

The Second International Forum on Heat Transfer　2008年
A molecular dynamics study on the heat transfer characteristics at a SAM-solvent interface

The Second International Forum on Heat Transfer　2008年
Molecyular dynamics study on lipid-bilayer membranes in shear flow

The Seventh JSME-KSME Thermal and Fluids Engineering Conference　2008年
Thermal boundary resistance at the interface of self-assembled monolayers

The Seventh JSME-KSME Thermal and Fluids Engineering Conference　2008年
熱工学におけるナノ

日本機械学会熱工学部門活性化のためのワークショップ　2008年
A molecular dynamics study on heat transfer characteristics in lipid membranes

The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
Interfacial heat transfer characteristics at the interface of self-assembled monolayers and organic solvent

The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
Point sprite-based visualization of large-scale particle systems

The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
膜・界面の分子熱流動

2008流体工学シンポジウム　2008年
膜・界面の輸送現象

日本機械学会RC225分科会「マイクロ・ナノフルイディクス調査研究分科会」　2008年
SAM膜－溶媒界面における熱輸送特性の分子動力学解析

第45回日本伝熱シンポジウム　2008年
脂質二重膜界面における熱輸送特性

第45回日本伝熱シンポジウム　2008年
数万オーダ粒子系のイメージベース可視化

第36回可視化情報シンポジウム　2008年
Thermal energy transfer in membranes and at liquid-solid interfaces

6th NSF-ONR US-Japan Seminar on Nanoscale Transport Phenomena　2008年
SAM-溶媒界面における界面熱抵抗特性の分子論的研究

日本機械学会2008年度年次大会　2008年
アルカン液体の固液界面におけるエネルギー・運動量伝搬特性

日本機械学会2008年度年次大会　2008年
せん断流中における脂質二重膜の分子動力学的研究

日本機械学会2008年度年次大会　2008年
A molecular dynamics study on heat conduction characteristics in lipid bilayer

The Second International Forum on Heat Transfer　2008年
A molecular dynamics study on the heat transfer characteristics at a SAM-solvent interface

The Second International Forum on Heat Transfer　2008年
Molecyular dynamics study on lipid-bilayer membranes in shear flow

The Seventh JSME-KSME Thermal and Fluids Engineering Conference　2008年
Thermal boundary resistance at the interface of self-assembled monolayers

The Seventh JSME-KSME Thermal and Fluids Engineering Conference　2008年
熱工学におけるナノ

日本機械学会熱工学部門活性化のためのワークショップ　2008年
A molecular dynamics study on heat transfer characteristics in lipid membranes

The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
Interfacial heat transfer characteristics at the interface of self-assembled monolayers and organic solvent

The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
Point sprite-based visualization of large-scale particle systems

The Eighth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration　2008年
膜・界面の分子熱流動

2008流体工学シンポジウム　2008年
Thermally driven ion transport by the Spatially Symmetric Brownian Ratchet

2nd International Symposium on Micro and Nano Technology　2006年
Solid-liquid boundary resistance: A molecular dynamics study on intermolecular energy transfer at solid-liquid interfaces

13th International Heat Transfer Conference　2006年
Transport of ions by the thermally anisotropic Brownian ratchet microchip

17th International Symposium on Transport Phenomena　2006年
Ion pump by the thermally anisotropic Brownian ratchet microchip

International Conference of Flow Dynamics 2006　2006年
Molecular scale governing factor on characteristics of thermal energy transfer at solid-liquid interfaces

International Conference of Flow Dynamics 2006　2006年
Thermally driven ion transport by the Spatially Symmetric Brownian Ratchet

2nd International Symposium on Micro and Nano Technology　2006年
Solid-liquid boundary resistance: A molecular dynamics study on intermolecular energy transfer at solid-liquid interfaces

13th International Heat Transfer Conference　2006年
Transport of ions by the thermally anisotropic Brownian ratchet microchip

17th International Symposium on Transport Phenomena　2006年
Ion pump by the thermally anisotropic Brownian ratchet microchip

International Conference of Flow Dynamics 2006　2006年
Molecular scale governing factor on characteristics of thermal energy transfer at solid-liquid interfaces

International Conference of Flow Dynamics 2006　2006年

︎全件表示 ︎最初の5件までを表示

共同研究・競争的資金等の研究課題 43

液体熱物性の予測・設計を志向した分子動力学データ基盤の確立

小原拓

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

研究種目：Grant-in-Aid for Scientific Research (C)

研究機関：Tohoku University

2020年4月～ 2023年3月

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液体の熱伝導率を決定している分子スケールのメカニズムを分子間・分子内の力学的エネルギーの伝搬に求め、このエネルギー伝搬を分子動力学シミュレーションにより定量的に観測する独自の解析法を用いて、様々な液体中で生じている分子間・分子内エネルギー伝搬の大きさと発生密度（頻度）を網羅的に調べるのが本研究の計画である。液体種として、比較的単純な分子によるものから複雑なもの、実用上重要なものにデータ蓄積を進め、さらにパラフィンなどPCM（相変化物質）として重要なソフトマターまでを対象とする。得られた分子間・分子内エネルギー伝搬の定量データを特徴的な原子団（官能基）ごとに分類し、加算性に注意しながら整理することにより、液体分子の原子団構成と液体に発現する熱伝導率との間に機序を見出す。物性値が既知の物質についてこの手法を確立し、未知の物質の熱伝導率予測や所望の熱伝導率をもつ液体の分子設計を可能にするデータ基盤を確立することを目的とする。本年度は、まず、以前から予備的に解析を開始していた水とアンモニアのバルク液体に対する解析をまとめた。それぞれ水素結合をもつ会合性の液体で、比較的高い熱伝導率をもつ液体であるが、クーロン相互作用が分子間エネルギー伝搬においてなすマクロ熱輸送（熱伝導率）への寄与など、基本的な特性における差異を明らかにすることができた。また、冷媒として重要なフルオロカーボンに研究を進め、計算系の構築を開始した。
新しい熱媒体材料を志向したナノ固液界面複合系における熱輸送特性の解明と制御

小原拓

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (C)

研究機関：Tohoku University

2017年4月1日～ 2020年3月31日

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厚さ0.3～10nmの固体層・液体層が重畳した系など、固液界面のみから成るマクロ媒体を構成して、固液界面において生じる特異な（バルク液体・固体とは異なる）熱輸送特性を積極的に利用した新しい熱媒体を創成するための学理を確立する基礎研究として、大規模な分子動力学シミュレーションにより、固液界面や固体壁面に挟まれた液膜の熱輸送特性を解析した。液膜厚さ、固体表面の結晶スケール構造、固体表面近傍に吸着した液体分子の密度など様々な要因により熱輸送特性が大きく変化し、これらをパラメータとして現象を制御する可能性を示した。
分子界面修飾とナノ熱界面材料による固体接合界面熱抵抗低減競争的資金

小原拓

提供機関：Japan Science and Technology Agency

制度名：CREST

2017年11月～
生体界面プラズマ流の極限時空間制御による標的遺伝子群発現誘導機構

佐藤岳彦, 城倉浩平, 小原拓, 金澤誠司, 宮原高志, 小宮敦樹, 大谷清伸, 吉野大輔

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (A)

研究機関：Tohoku University

2012年4月1日～ 2015年3月31日

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本研究では，高速高圧電源の開発，高時空間分解能を有する可視化システムの構築，高精度プラズマ特性同期計測システムの構築により，自己保存プラズマ流の生成制御および観察法の開発・製作に成功した．自己保存プラズマ流は，電圧印加後数百ナノ秒後に電極先端に微細な気泡群を構成し，突起状気泡の先端から秒速2 km程度でパルス状の放電電流と同期して断続的に進展を開始することを明らかにした．遺伝子群発現誘導については，弱いプラズマ刺激に対し，プラズマ刺激の主要因となる過酸化水素と異なる代謝，免疫，再生などの機能を有する遺伝子群が発現することを網羅的遺伝子解析により明らかにした．
熱媒流体の分子設計競争的資金

2013年～
Molecular design of thermofluid 競争的資金

制度名：The Other Research Programs

2013年～
ポリマー液体及びソフトマター中に発現する構造と熱エネルギー伝搬特性競争的資金

小原拓

2012年～
ナノスケール固液複合システムの物質輸送特性競争的資金

2012年～
Mass transport characteristics of nanoscale solid-liquid complex systems 競争的資金

制度名：The Other Research Programs

2012年～
生体反応プラズマ流生成輸送制御による細胞活性化の促進抑制機構

佐藤岳彦, 小原拓, 城倉浩平, 宮原高志

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (A)

研究機関：Tohoku University

2009年～ 2011年

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生体反応プラズマ流の化学輸送機構について, 放電時に形成される高温気流が水面上に広がり水中に流れが誘導され化学輸送を担うことを実験・数値解析から明らかにした. また, ラジカルから変化した安定化学種の中で, 過酸化水素がHeLa細胞の不活化作用を有することを, 形態変化, カタラーゼによる細胞毒性の消滅, 遺伝子発現解析などから明らかにした. さらに, 細胞膜のエネルギー輸送は輸送方向と細胞膜分子種に依存することを示した.
液体およびその界面における分子スケールヘテロ構造と熱・運動量・物質輸送特性競争的資金

小原拓

2009年～
ナノ熱流体システムの構築を志向した液膜及び固液界面における熱・物質移動の基礎研究競争的資金

小原拓

2006年～
ポリマーの反応性を考慮した非ニュートンリミングおよびコーティング流れの解析的研究

FOMIN Sergei, 福西祐, 小原拓

2003年～ 2004年

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エリスおよびベキ乗則流体のリミング流れに関する流出条件を導出した。流出条件を満足することで、定常状態での溶解の存在を証明することができた。これらの条件より想定されるリミング流れの範囲内において、フィルムの厚さは継続的な溶解を可能にし、それは臨界前および臨界状態での流れ則を用いた予備値と一致することを示した。また、臨界状態での流れ則において、不連続な溶解挙動が予測された。エリスおよびベキ乗則流体における衝撃位置と高さに関する検討をするにあたり、定常状態理論は有効であることが示された。ベキ乗則モデルについて、流れのフィルム厚さに関する定常状態方程式の理論的解の導出に成功し、エリスモデルについて演算処理を実行した。このモデルについて解析的な漸近解が陽な形式で得られ、演算処理の結果と比較することができた。これらの解より、コーティング流れの正確なシミュレーションを行うためのエリスおよびベキ乗則の方程式におけるパラメーター値を最適化することが可能になり、流れが超臨界状態にある時に起こる定常水位急上昇の大きさと位置について、種々の流れパラメーターにおける解も決定できた。これにより、異なる多因子の溶解のための、エリスおよびベキ論の流動学的モデルの較正を呈示した。上述した方程式の高次近似解析のための数値的アルゴリズムを導出した。高次数における流れの安定性についてのより詳細な判定法を定め、主な次数方程式から導出される結果と比較した。長波理論の枠組みにおいて、二軸回転シリンダー上の非ニュートン流れについてのリミング流れの数学的3Dモデルを導出した。3D支配方程式の安定性解析を実施し、流れの安定性に対する二軸回転成型の影響を解析した。さらに、フィルムの一様性に対する微小重力の影響を明らかにした。
複雑媒体中の衝撃波現象の解明と学際応用

井小萩利明, 高山和喜, 林一夫, 佐宗章弘, 齋藤務, 小原拓, 谷口宏充, 井小萩利明, 樋口博

2000年～ 2004年

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特別推進研究「複雑媒体中の衝撃波現象の解明とその学際応用」では、(1)複雑組成の媒体中の衝撃波現象、(2)化学変化、相変化を伴う媒体中の衝撃波現象、(3)複雑境界を過ぎる衝撃波、また、極低温および高温境界を過ぎる衝撃波、および(4)きわめて大きな時間変動を伴う衝撃波現象を解明し、その成果を医療、地球物理など学際領域研究に発展させ、また、産業応用への展開の基盤技術の確立を目指した。また、この本研究拠点が国内外に衝撃波学際応用研究センターとなることを目標に研究を推進した。ここに、過去および最近5年間の衝撃波研究の成果が体系化され、本拠点活動が国内の衝撃波研究会活動を支援するばかりでなく、平成17年3月に国際衝撃波学会(International Shock Wave Institute)の設立に結びついたこと述べ、特別推進研究「衝撃波」を総括する。主な研究成果は: i)基礎的研究くさびを過ぎる衝撃波反射に粘性効果に起因する遷移遅れを実験と精緻な数値模擬結果との対比から、始めて実証した。この現象が凹面および凸面さらに円錐面にも現れることを明らかにし、流体力学の教科書を書き直すに足る事実を見いだしている。また、大型縦型衝撃波管内に加速度計を内蔵した球を吊し衝撃波を負荷するという巧妙な実験で、衝撃波負荷での球の非定常抗力を実測し、衝撃波ないし爆風負荷での各種形状物体の非定常抗力計測に始めて成功している。この結果は数値模擬法との組み合わせで、粉塵気体中の衝撃波伝播に非定常抗力の効果明らかにしている。縦型無隔膜衝撃波管、大型無隔膜衝撃波管などを設計法を開発して、衝撃波の実験研究の精度を飛躍的に向上させ、また、衝撃波研究に微小爆薬の爆発を導入するなど、独創的な衝撃波実験法を発展させている。高性能の二段式軽ガス銃を設備し、弾道飛行実験装置の機能を加えて、高速飛行および高速衝突の動力学の体系化に成功している。直径1mのシュリーレン鏡を導入して大視野で、高レイノルズ数流れの二重露光ホログラフィー干渉計測定法を確立し、さらに、これを位相変位ホログラフィー干渉計法を展開し、音波に近い非常に弱い衝撃波の計測に成功している。気体、液体、混相媒体中の衝撃波現象の解明に適した数値模擬法を開発している。 ii)水中衝撃波現象の解明とその医療応用医学部の共同者と衝撃波の医療応用を推進し、衝撃波医療システムが構築されようとしている。水中でパルスレーザー光照射でのマイクロ衝撃波発生の物理を解明し、成果を種々の医療装置開発に結びつけることに成功している。カテーテル内でのレーザー光照射で気泡と衝撃波を発生し、カテーテル先端から直径0.1mm、速度20m/s程度の水ジェットを制御して噴出させ、これを空気中で用いて生体軟組織の切開装置を試作し、また、これを血管内で用いて低侵襲的な脳血栓血行再建術装置を試作している。これら装置での基礎実験、動物実験を終了させて現在臨床実験を開始しようとしている。また、衝撃波と細胞の相互作用を組織学的にまた生化学的に解明するための、医学と工学の連携研究が進行中である。パルスレーザー光を金属膜に作用させ発生するレーザーアブレージョンでの金属膜の高速変形を用いて微粒子を高速で打ち出す過程を詳細に解明して独創性の高いドラッグデリベリー法を開発している。この原理は微粒子分布と貫通深さを制御した物理的遺伝子導入法の開発に拡張され、現在、実用研究が進行中である。 iii)地球物理、火山学への応用地球物理学者との連携で研究を推進し、地球進化史に巨大隕石衝突が重要な役割を果たし、そのとき固体および水中衝撃波が激変の素過程となっていることを、アナログ実験と数値模擬により様々の角度から実証している。また、火山の爆発的な噴火では短時間のエネルギー解放が重要な素過程となり、同様に衝撃波の関与が重要となっていることを実証している。特に、マグマの微粒化の動力学的機序をアナログ実験で解明した。 iv)産業応用爆発騒音、自動車排気騒音およびトンネルソニックブームの機序を解明し、防止あるいは低減法を提案している。また、レーザー光を用いる新しい海底岩盤掘削法開発の基礎を確立した。 v)学会活動5年間の拠点形成過程を通じて日本衝撃波研究会事務局を、また、Shock Wave International Journalの編集長と編集事務を担当し、さらに、拠点活動の一環として平成13年アジア太平洋衝撃波研究会を発足させ、これを平成17年3月国際衝撃波学会(International Shock Wave Institute)の設置に発展させている。
極限的液体潤滑の分子熱工学的研究競争的資金

小原拓

2003年～
流体のエネルギー・運動量輸送特性を支配する分子間伝搬機構の解明競争的資金

小原拓

2001年～
コーティング及び潤滑の液膜流れ競争的資金

2001年～
Liquid Film Flow in Coating and Lubrication 競争的資金

2001年～
リアルタイム分子膜厚分布計測装置の開発

圓山重直, 岡田繁信, 小原拓

1998年～ 1999年

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本研究は位相シフト技術を駆使し、リアルタイムで分子膜厚の計測を行えるシステムを確立するもので、平成10年から平成11年度の研究期間で以下に示す研究成果を得ることができた。 (1)既存のマッハツェンダー干渉計に位相シフト技術を導入し、本研究の予備実験として各種物質の濃度拡散場を観察した。得られたディジタル画像から解像度の検証を行い、同時に物質拡散係数の推定を行った。その結果、現在のシステムではアナログデータをディジタルデータに変換し、さらに圧縮処理を施しているので、分子膜を観察するには更なる解像度の向上が必要であることが確認できた。また、高精度な画像を取得するためには、ノイズの影響も無視できないことが分かった。 (2)上記知見より、波面分割精度を高精度化するため、高精度の偏光光学素子を使用して位相シフト画像を得るようにした。また、データ処理過程におけるA/D変換をなくすため、アナログ用のCCDセンサーに代わってディジタル用を使用し、初めてディジタル位相シフトカメラを開発した。 (3)また高解像度の画像データを記録するために、新たな記録装置を開発した。この装置は電子ノイズの影響を考慮して10ビットの精度でデータを記録し、1秒間に60フレームの割合で画像データを得る。この画像記録装置とディジタル位相シフトカメラを組み合わせることで、高精度なリアルタイム画像を非圧縮処理で取り込むことができた。 (4)位相シフト技術とエリプソメータの原理を応用して、位相シフトエリプソメータの原理を導き、観察セルを開発した。ペルチェ素子を用いてセル内のアルミ蒸着板を高精度温度制御することにより、水の分子膜生成に成功し、観察することができた。以上をまとめると、平成10年から平成11年度の研究期間中に、成果報告書に記載した内容を得るとともに、本研究の目的をほぼ達成した。
バイオ分子分離用マイクロチップ競争的資金

1999年～
Microchip for separation of biomolecules 競争的資金

1999年～
流体中の分子スケールエネルギー伝搬過程競争的資金

1998年～
Molecular Process of Energy Transfer in Fluids 競争的資金

制度名：Grants and Funding

1998年～
流体の動的構造に関する分子熱工学的研究競争的資金

小原拓

1997年～
遷臨界域流体の急速過渡伝熱特性を利用した伝熱制御に関する研究

相原利雄, 印南幸夫, 宇角元亨, 小原拓

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (B)

研究機関：Tohoku University

1994年～ 1996年

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本研究は、超臨界圧流体が示す特異な熱伝達特性を利用して、熱伝達を能動的に制御する手法を確立しようとするものである。以下に3年間にわたる研究の成果を要約する。まず、急速過渡熱伝達特性に関する基礎的な熱伝達と流動の特性を明らかにするために、臨界点近傍の亜臨界圧および超臨界圧の二酸化炭素中の水平白金細線をステップ状に加熱する非定常実験を行い、超臨界圧条件で、定常状態では見られない半球状の気泡類似な流体塊(擬似気泡)を観察した。次に、能動的伝熱制御のための応用研究として、超臨界圧二酸化炭素中の水平白金細線をパルス状に加熱する実験を行った。時間平均の熱流束が一定であっても、流体の臨界点近傍の熱物性と、パルス周波数との組み合わせにより、伝熱面温度を任意に制御できることを明らかにし、新たな伝熱制御の手法を示した。さらに、このような能動的伝熱制御法の確立のためには必要不可欠となる、遷臨界域における熱流動メカニズムの解明のための研究を行った。まず、亜臨界圧から超臨界圧に至る広い圧力範囲の二酸化炭素について、定常熱伝達実験を行い、熱伝達および流動の特性が、連続的に遷移する様子を詳細に明らかにした。さらに、超臨界圧における沸騰類似現象が界面張力(擬似界面張力)に支配されているものとして、従来の限界熱流束の推算式を適用し、この擬似界面張力を逆算した。ここで推算した擬似界面張力の発生メカニズムに関して、分子動力学解析を行った。その結果、流体に温度勾配を与えた場合には、超臨界圧においても極めて大きな密度勾配をもつ擬似界面領域が存在し、ここに擬似界面張力が作用することが明らかとなった。これらの結果は、先に行った実験の結果と一致しており、超臨界圧流体における擬似界面張力という新たな視点から、沸騰類似現象の統一的な解釈を提出した。以上の解析により、遷臨界域流体の急速非定常伝熱・流動特性を解明し、これを用いた能動的伝熱制御に関する基盤を確立した。
衝突噴流式流動層による熱伝達と着霜の制御に関する共同研究

相原利雄, UWE Schaflin, WILHELM Schn, 印南幸夫, 小原拓, 山田雅彦, 横迫尚一郎

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for international Scientific Research

研究機関：TOHOKU UNIVERSITY

1994年～ 1995年

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1.東北大学においては、 (1)前年度に引き続き、低温の単列管群における局所熱・物質伝達率を詳細に測定し、また、着霜状況の周方向分布を目視観察により調べた。 (2)固体粒子の衝突頻度の光学的計測を行った。すなわち、固体粒子の接近による反射光を検出する光学プローブを管表面に埋設することにより、前淀み点から後淀み点に至る管表面各位置での固体粒子の衝突頻度を計測した。更に反射鏡とビデオシステムを用いて、低温の管表面における霜層の形成や粒子衝突による霜層の剥離挙動を観測記録した。 (3)これらの結果を局所熱伝達率分布や着霜状況と併せて解析した結果、粒子衝突による除霜効果は、衝突頻度だけではなく、衝突の性質にも大きな影響を受けることを明らかにした。すなわち、本衝突噴流式流動層中の冷却管において、管側面の衝突頻度は最も高いものの、衝突は擦過的であるため除霜効果は大きくない。これに対し、淀み点近傍では、粒子衝突が与える力積が大きいため、衝突頻度は小さいにもかかわらず良く除霜されている。以上に述べた衝突噴流式流動層の除霜メカニズムと除霜特性、並びに後述のオーストリア側の固気衝突噴流の理論解析結果とを考慮し、様々な改良を加えた結果、管表面温度-17℃における連続無着霜運転の新記録を達成できた。これらの結果は、寒冷地における高性能蒸発器の開発にブレークスルーを与えるものである。 2.北海道大学においては、 (1)流動層内におかれた垂直冷却面および水平冷却管群まわりの着霜現象について実験的検討を行った結果、(1)垂直冷却面上の着霜特性は、粒子層の局所的挙動と密接な関係がある。(2)濃厚層では薄い氷層が、遷移層では厚い霜層が、希薄層では薄い霜層が成長する。(3)水平冷却管群の場合、一般流動層と本流動層における最小流動化速度の差は、粒子径の減少とともに増大する。(4)除霜および熱伝達特性は、粒子径に最も依存する。(5)表面に凹凸を有する石英粒子が、滑らかな表面を有するガラス球より除霜特性が優れている。などが明らかにされた。 (2)固・気・液三相流動層(流動液状氷)内におかれた水平加熱管群まわりの融解熱伝達について実験的検討を行った結果、(1)本三相流動層の熱伝達は、熱流束・空気速度の増加および初期水溶液濃度の減少とともに増大する。(2)本三相流動層の熱伝達は、流動化のために約10%の付加エネルギーを使用することにより、約27倍に増大する。(3)三相流動層による冷熱回収法は、制御の面で工業的に非常に有効である。などが明らかとなった。Schaflinger助教授は、1995年12月11日〜12月16日北海道大学に滞在し、流動化のためのエネルギーの評価法に対して新しいアイデアを提供し、これにより研究が飛躍的に進展した。 3.ウィーン工科大学においては、東北大学で開発した蛇腹状分散板による固気衝突噴流の形成から冷却管表面への衝突までの過程について、詳細な理論解析を行った。これに関する議論、データの交換、本研究の計画全体の推進調整等のため、研究代表者の相原教授が1995年9月23日から10月25日までウィーン工科大学を訪問した。また、Schaflinger助教授が1995年12月1日から12月20日まで来日し、解析の最終的な総括を東北大学と共同で行った。これにより、粒子の速度分布や密度分布、管表面への衝突頻度などの現象を支配する因子を明らかにし、粒子の衝突による除霜効果が顕著な固気衝突噴流を形成するための重要なデータを得た。本研究の実績を総括すると、東北大学においては、本研究計画の最終的な目標である衝突噴流式流動層について、設計・製作とその熱伝達及び除霜特性の実験的解析を行い、北海道大学においては、基礎データの取得を目的として、流動層による熱伝達及び除霜特性のより一般化した実験的解析、ウィーン工科大学では、東北大学の衝突噴流式流動層における固気衝突噴流の理論解析を行い、実験への効果的な指標を与えた。以上、広範な学術課題を包含する本研究について、有機的な研究組織を構成し、積極的な検討を重ねた結果、予定以上の研究成果をあげたものと考える。
流体の相変化と遷臨界現象の分子動力学的研究競争的資金

小原拓

1995年～
遷臨界域流体のクラスタ構造に関する分子動力学的研究競争的資金

小原拓

1994年～
超電導破壊の早期予測と超電導コイルの高度安定化に関する熱工学的研究

相原利雄, 小原拓, 谷順二, 高橋秀明, 金柱均

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for General Scientific Research (B)

研究機関：Tohoku University

1991年～ 1993年

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本研究の目的は、強制冷却型および浸漬冷却型超電導コイルにおけるクエンチ発生機構を解明し、常電導転移の早期予測法に関する理論を確立し、クエンチ抑制に優れた超電導コイルの高度安定化法を確立することである。以下に3年間にわたる本研究で得られた成果を要約する。 1.平成3年度は、強制冷却型および浸漬冷却型超電導コイルのクエンチ発生機構と過渡安定性の数値解析を行った。関連諸因子の影響を定量的に明らかにし、常電導転移とクエンチ発生の早期予測法の基礎を構築した。 2.平成4年度では、超電導破壊(クエンチ)の早期予測に関して、以下の成果が得られた。 (1)液体ヘリウム中で浸漬冷却さらるパンケーキ巻き超電導コイルについて、クエンチの高速伝播を可視化した結果、常電導転移域の伝播に先駆けた、クエンチが誘起する熱衝撃による圧力波の発生が明らかとなった。この熱衝撃による圧力波を検知することによって、常電導転移をその前段状態で検出できる可能性を示唆した。 (2)超電導体の熱的安定性を精密に解析するためには、冷却剤である液体ヘリウムの急速過渡沸騰熱伝達特性について、信頼性の高いデータを得ることが必要である。そこで、実用超電導導線に近い状態を実現するため、ステンレス箔ヒータにPVF絶縁層及び温度測定用カーボンペーストを被覆したテストピースを作成し、過渡沸騰熱伝達特性について実験を行った。得られた測定値を数値解析し、被覆層の熱容量と温度分布も考慮した補正を加え、ヒータにステップ状の熱入力を印加した場合の急速過渡沸騰熱伝達特性を詳細に明らかにした。 3.今年度においては、平成3、4年度に行った理論計算と実験の結果を分析し、超電導コイルにおける常電導転移を初生段階で早期予測し、超電導マグネットを安全に運転するための熱的安定化法の基礎を固めた。
遷臨界域の流体の微視的構造に関する分子動力学的研究競争的資金

小原拓

1993年～
超臨界圧流体中の微細構造体からの非定常熱伝達と伝熱制御に関する研究

相原利雄, 小原拓

1992年～ 1992年

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平成3年度に製作した超臨界非定常伝熱実験装置を用い、容積約6x10^<-4>m^3の円筒形超臨界圧チャンバ中に水平に設置されたφ100μmの白金加熱細線にコンピューター制御されたさまざまなステップ高さの熱入力を加え、亜臨界非定常沸騰熱伝達実験及び超臨界非定常自由対流熱伝達実験を行った作動流体にはCO_2(臨界温度304.2K,圧力7.383MPa)を用いた、得られた結果は以下のとおりである。 (1)亜臨界沸騰実験の結果、熱伝導域を離脱後、非定常沸騰曲線は速やかに(10ms程度で)定常沸騰曲線に漸近することが確認された。印加熱入力が大きい場合は、加熱開始直後から膜沸騰状態となるが、約30ms後には比較的低い印加熱入力の場合は、加熱開始直後は核沸騰状態にあり、やがて膜沸騰に遷移する。この場合、加熱初期の核沸騰により細線の温度上昇を大幅に遅延させることができる。過熱度の経時変化は当初の核沸騰域においては緩やかで、膜沸騰への遷移に伴って急激になり、やがて変曲点を生じつつ再び緩やかになり、定常状態に漸近する。 (2)超臨界自由対流熱伝達の場合は、亜臨界における核沸騰から膜沸騰への遷移現象が存在しないことから、過熱度の経時変化曲線に変曲点は存在せず、曲線は定常値に向けて速やかに漸近する。超臨界圧流体の場合、加熱度や熱流速はステップ高さや流体圧力により容易に制御できることから現在これらを応用した伝熱制御法について解析を行っている。超急速な非定常熱伝達に際しては物質固有の性質が現象を支配する。このような観点から水を例にとって、分子動力学の数値解析により、遷臨界域の流体の微視的構造を解析した。臨界点を中心とした広い範囲の温度、密度に対して数値計算を行い、水分子のダイマー・クラスター形成に関する解析を行った。この結果、ダイマーの個数及び寿命やクラスターのサイズに関して、その温度・密度依存性を明らかにした。
伝熱制御式・長尺クライオプローブの試作に関する研究

相原利雄, 藤間克己, 笠原敬介, 鈴木和弥, 小原拓, 藤間克巳, 笠原啓介, 鈴木和也, 金柱均

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Developmental Scientific Research (B)

研究機関：TOHOKU UNIVERSITY

1990年～ 1992年

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本研究の目的は、非切開的に癌や腫瘍を局所的に凍結外科治療して患者の苦痛や危険性を軽減させるため、内視鏡内に設けられた生検鉗子用チャンネルに挿入して用いることができる極細径(3.1mm)かつ長尺1mのクライオプローブを開発することである。本研究で開発したクライオプローブは、本体を3重管で構成し、その先端に冷却端子を設け、外管と中管の環状部を真空断熱したもので、デュワー瓶内で加圧された液体窒素は、直径1mmの内管を通ってプローブ先端部に到達し、内管から噴出して冷却端子の内面に衝突し、冷却端子を高熱流束で冷却するものである。以下に本研究で得られた成果を年度別に示す。 (1)平成2年度に行った極細径・長尺クライオプローブの定常冷却実験により、液体窒素の衝突噴流の質量流量や冷却端子の内面形状などがプローブの冷却性能に及ぼす影響を明らかにし、最大冷却性能として約1.5MW/m^2を達成した。 (2)平成3年度に行った本クライオプローブの断熱性能実験と非定常冷却実験により、真空断熱層の真空度とスペーサの形状が断熱層を介しての漏洩熱量に及ぼす影響を明らかにし、また冷却端子に働く熱負荷、デュワー圧力、液体窒素の流量などが冷却曲線(冷却速度)に及ぼす影響を明らかにした。 (3)平成4年度では、平成3年度までの研究成果に基づき、極細径・長尺クライオプローブの伝熱性能(冷却性能)の制御をデュワー圧力制御方式として、コンピュータによるオンラインシステムを構築し、動的に冷却能力を制御する手法を確立し、研究計画を終了した。以上述べたように、本研究の目標は、ほぼ達成されたということができる。なお本研究の成果の一部は、平成3年11月7日付の新聞4誌によって全国的に紹介されたことを付記する。
超臨界圧流体中の微細構造体からの非定常熱伝達と伝熱制御に関する研究

相原利雄, 金柱均, 小原拓

1991年～ 1991年

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本研究において、超臨界圧伝熱実験装置を新たに考案・設計・製作した。これは作動流体の圧力調整部、伝熱実験を行う高圧テストチャンバ、恒温油槽並びに計測システムの制御系で構成される。この装置を用いた第一段階の実験として、超臨界圧のCO_2中における白金細線からの定常自由対流熱伝達について計測を行ない、以下の結果を得た。 (1)加熱細線温度と作動流体のバルク温度との間に(擬)臨界点が存在するときは、臨界点近傍での比熱、プラントル数等の物性値の著しい変化により、自由対流熱伝達が最大7倍まで促進される。 (2)この自由対流熱伝達の促進は、流体圧力が臨界点に近く、また、細線及び流体の温度差が小さいほど大きい。また、実験と並行して、臨界点近傍の流体中を充填した2次元セル内の非定常伝熱について数値計算を行い、以下の点を明らかにした。 (3)伝熱面のステップ加熱開始後、各位置での温度は時間経過と共に上昇して行くが,臨界点近傍では定圧比熱が大きくなるため温度上昇が遅れ、温度分布にも明確な屈折点が生じる。 (4)作動流体の温度は、臨界点近傍で長時間一定値を保つが、臨界域から離脱するにつれて急激に減少し、温度勾配が大きくなる。これらの影響により、臨界点近傍では温度と圧力条件の設定により、1.5〜4倍の熱伝達率の向上が得られる。 (5)超臨界点近傍での物性値変化を利用して、作動流体の圧力・温度と臨界点・擬臨界点との関係をコントロ-ルすることにより、熱伝達特性や温度分布特性を能動的に制御できる。以上のごとく、総合的な自己評価により、本年度の研究目標はほぼ達成されたものと考えられる。
分子設計による熱媒液体・相変化蓄熱媒体の開発競争的資金
固液／気液界面熱抵抗の制御競争的資金
ナノスケール液体中の熱・物質輸送競争的資金
ナノ構造体／ナノコンポジットの熱的特性競争的資金
高機能流体潤滑競争的資金
シリコンウェハのコーティング及び洗浄競争的資金
DNA分離用マイクロチップ競争的資金
極限流体潤滑現象の分子スケール解析競争的資金
Coating and Cleaning of Silicon Wafer 競争的資金
DNA Separation Microchip 競争的資金

︎全件表示 ︎最初の5件までを表示

Works（作品等） 8

細胞選別用マイクロフルイディクスチップの開発

2010年～ 2015年
細胞選別用マイクロフルイディクスチップの開発

2010年～ 2015年
熱媒流体の設計を志向した液体中における分子熱輸送の機序解明

2014年～
熱媒流体の設計を志向した液体中における分子熱輸送の機序解明

2014年～
ウェットプロセスの分子熱流動

2010年～
ウェットプロセスの分子熱流動

2010年～
ナノ構造化界面における輸送現象

2009年～
Transport Phenomana on Nano-Structured Interfaces

2009年～

︎全件表示 ︎最初の5件までを表示

社会貢献活動 1

学会活動支援・学術普及

2016年8月～継続中