• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.756-759
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• 2005

Dynamic force microscopy utilizes the dynamic response of a resonating probe tip as it approaches and retracts from a sample to measure the topography and material properties of a nanostructure. We present recent ideas based on proper orthogonal decomposition (POD) and detailed experiments that yield new perspectives and insight into AFM. A dynamic cantilever model with Lennrad-Jones interaction Potential which includes attractive and repulsive van der Waals demonstrates the resonable tapping mode response in time and frequency.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.3117-3129
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• 2022

Deeply understanding the phase change of thin liquid sodium film inside wick pore is very important for further studying high-temperature sodium heat pipe's heat transfer. For the first time, the evaporation and condensation of thin liquid sodium film are investigated by the Lennard-Jones potential of molecular dynamics. Based on the startup and normal operation of the sodium heat pipe, three different cases are simulated. First, the equilibrium is achieved and the Mass Accommodation Coefficients of the three cases are 0.3886, 0.2119, 0.2615 respectively. Secondly, the non-equilibrium is built. The change of liquid film thickness, the number of gas atoms, the net evaporation flux (J_net), the heat transfer coefficient (h) at the liquid-gas interface are acquired. Results indicate that the magnitude of the J_net and the h increase with the basic equilibrium temperature. In 520-600 K (the startup of the heat pipe), the h has approached 5-6 W m^-2 K^-1 while liquid film thickness is in 11-13 nm. The fact shows that during the initial startup of the sodium heat pipe, the thermal resistance at the liquid-gas interface can't be negligible. This work is the complement and extension for macroscopic investigation of heat transfer inside sodium heat pipe. It can provide a reference for further numerical simulation and optimal design of the sodium heat pipe in the future.

• 오토저널
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• 제6권1호
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• pp.46-54
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• 1984

We applies Molecular Dynamics simulation technics to a system of Lennard-Jones potential interacting Argon liquid to study shear flow behavior. The thermodynamic state of the system is .rho.=35.54 Kg, mole/m$^{3}$, T=86.5.deg. K which is the triple point of Argon liquid. We applies shear rate : .epsilon.=9.26*10$^{9}$ 1/sec in the system. We find the response function, shear viscosity changes, and shear rate build-up as a function of time. We also find the thermal conductivity in a soft-sphere system.

• 반도체디스플레이기술학회지
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• 제9권1호
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• pp.5-10
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• 2010

Among a variety of cleaning processes, the cryogenic carbon dioxide ($CO_2$) cleaning has merits because it is highly efficient in removing very fine particles, innoxious to humans and does not produce residuals after the cleaning, which enables us to extend its area of coverage in the semi-conductor fabrication society. However, the cryogenic carbon dioxide cleaning method has some technical research issues in aspect to particles' adhesion and removal. To resolve these issues, performing an analysis for the identification of particle adhesion mechanism is needed. In this study, a research was performed by a theoretical approach. To this end, we extended the G-T (Greenwood-Tripp) model by applying the JKR (Johnson-Kendall-Roberts) and Lennard-Jones potential theories and the statistical characteristics of rough surface to investigate and identify the contact, adhesion and deformation mechanisms of soft or hard particles on the rough substrate. The statistical characteristics of the rough surface were taken into account through the employment of the normal probability distribution function of the asperity peaks on the substrate surface. The effects of surface roughness on the pull-off force for these particles were examined and discussed.

• 대한화학회지
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• 제34권3호
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• pp.267-279
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• 1990

Amberlite XAD-2 및 XAD-7 수지에 대한 페놀과 그 할로겐 일치환체들에 대한 흡착성을 분포계수를 측정하여 조사하였다. XAD 수지에 대한 페놀의 흡착은 Langmuir 등온흡착으로 설명될 수 있었으며, 이 때의 흡착은 분자의 크기에 따르는, 즉 분산상호작용에 기인하는 전형적인 물리흡착임을 알았다. 고분자 합성수지에 대한 페놀류의 흡착에너지는 Lennard-Jones potential로 계산하였다. 이 때 고분자 수지의 반지름은 수지의 최소기본단위의 van der Waals 부피로부터 계산하였으며 페놀류의 분자 반지름도 같은 방법으로 구하였다. 페놀유도체들의 흡착성은 각 수지에 대한 시료의 Stacking factor (F)-고분자 수지와 페놀류사이의 van der Waals 부피로부터 구한 평형거리의 보정인자-로부터 흡착에너지를 구하고 뱃치법으로 측정한 흡착엔탈피값과 비교함으로써 설명할 수 있었다. 각 수지에 대한 페놀이온의 흡착엔탈피는 쌍극자 작용력이나 하전-쌍극자 상호작용보다 분산상호작용이 주 요인인 것으로 나타났다.

• Macromolecular Research
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• 제15권7호
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• pp.682-687
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• 2007

The equation of state developed herein is predicated on a hard-sphere reference with perturbations introduced via a potential function to account for electrostatic forces and for attraction between protein particles. During this process, the generalized Lennard-Jones (GLJ) pair potential function is employed. The GLJ pair potential function is employed to represent the protein-protein interaction in two-protein systems. Via the use of the relation between the equation of state and the chemical potential, the phase behavior in the aqueous two-protein system can be estimated. The partition coefficients can be obtained via these processes. The calculated values of the coefficients agree fairly well with the experimental data in the given pH and ionic strength range, with no additional adjustable model parameters.

• Macromolecular Research
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• 제17권10호
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• pp.763-769
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• 2009

A chromatographic method is used to measure interactions between dissimilar proteins in aqueous electrolyte solutions as a function of ionic strength, salt type, and pH. One protein is immobilized on the surface of the stationary phase, and the other is dissolved in electrolyte solution conditions flowing over that surface. The relative retention of proteins reflects the mean interactions between immobile and mobile proteins. The osmotic cross second virial coefficient calculated by assuming a proposed potential function shows that the interactions of unfavorable proteins depend on solution conditions, and the proposed model shows good agreement with the experimental data of the given systems.

• Journal of Advanced Marine Engineering and Technology
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• 제29권1호
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• pp.34-41
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• 2005

An experimental study of molecular motions on a liquid-vapor interface is limited due to micro-scale characteristics of a system with an angstrom or a nanometer size Therefore, in recent, many studies for micro-scale systems have been conducted by a computer simulation because it is free from experimental limitations. In this study, through the molecular dynamic (MD) method. molecular behavior was clarified on a liquid-vapor interface and a criterion to distinguish between liquid and vapor was suggested by a potential energy and the number of neighboring molecules. At an interface. the potential energy of a molecule was increased but the number of neighboring molecules was decreased when the molecule moved into a vapor region from a liquid region, and vice versa.

• Elastomers and Composites
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• 제35권1호
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• pp.29-37
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• 2000

본 연구에서는 elastomer의 기초 연구로써 두개의 침투할 수 없는 평판사이로 국한시킨 용융상태에서 두개의 다른 사슬 길이를 가진 고분자의 거동에 대한 결과를 보여 주었다. 입방 격자시뮬레이션은 reptation과 crankshaft bond flip 이동의 조합에 따른 방법으로 유도되었다. 10개의 구슬로 엮어진 544개의 짧은 사슬과 160개의 구슬로 엮어진 136개의 긴 사슬로 구성된 전체 680개의 사슬은 20개의 격자 충에 투입되었다. 공유결합으로 연결된 구슬사이의 energetic 상호인력은 없고 반면에 모든 다른 이웃들은 truncated 6-12 Lennard-Jones 포텐셜로서 상호작용하고 있다고 가정하였다. 수치모사 결과의 분석으로부터 순수한 entropic 효과로 인하여 짧은 사슬이 우선적으로 표면에 도달하는 것을 보여 주었다 또한 짧은 사슬의 질량밀도중심은 표면근처에서 최고값을 보여주었다. 이것은 긴 사슬의 경우와 상반되는 현상이다. 그러나 짧은 사슬과 긴 사슬의 segment는 결합 정렬에 있어서는 큰 변화를 주지 않았다.

• 에너지공학
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• 제23권2호
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• pp.7-12
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• 2014

탄소나노튜브의 수소 저장소로써의 가능성을 평가하기 위한 분자 모사를 수행하였다. 일정한 온도와 압력에서 Grand canonical Monte Carlo 방법을 적용하여 탄소나노튜브에 수소가 흡착된 평형 상태를 구현하였다. Lennard-Jones 퍼텐셜 모델로부터 탄소나노튜브와 수소 분자 간 상호 작용 에너지를 계산 한 결과에 의하면 수소 분자는 나노튜브 외부보다 내부에 많은 양이 흡착되는 반면 흡착 강도는 외부가 높은 것으로 나타났다. 여러 가지 온도와 압력에 대해 흡착율을 검토하였으며, 200 K와 200 bar의 저온 고압 조건에서 약 2.5wt%의 흡착율을 나타내었다.