• 한국진공학회지
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• 제9권3호
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• pp.273-278
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• 2000

본 연구에서는 분자동력학 방법을 사용하여 알루미늄 덩어리 증착에 관하여 연구하였다. 다양한 크기의 덩어리 충돌에서 기판의 온도와 비정렬 원자수 변화를 관찰하여 알루미늄 덩어리 증착시 덩어리내의 원자들 상호간의 상관충돌이 기판으로의 에너지전달과 원자 재배열과정에 큰 영향을 미치는 것을 발견하였다. 덩어리 크기가 클수록 상관충돌 효과는 커지는 것을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제3권2호
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• pp.44-49
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• 1982

Dynamic and equilibrium structures of a polymer chain immersed in solvent molecules have been investigated by a molecular dynamic method. The calculation employs the Lennard-Jones potential function to represent the interactions between two solvent molecules (SS) and between a constituent particle (monomer unit) of the polymer chain and a solvent molecule (CS) as well as between two non-nearest neighbor constituent particles of the polymer chain (CC), while the chemical bond for nearest neighbor constituent particles was chosen to follow a harmonic oscillator potential law. The correlation function for the SS, CS and CC pairs, the end-to-end distance square and the radius of gyration square were calculated by varying the chain length (= 5, 10, 15, 20). The computed end-to-end distance square and the radius of gyration square were found to be in a fairly good agreement with the corresponding results from the random-flight model. Unlike earlier works, the present simulation rsesult shows that the autocorrelation function of radius of gyration square decays slower than that of the end-to-end distance square.

• Bulletin of the Korean Chemical Society
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• 제18권5호
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• pp.478-484
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• 1997

In a recent paper[Bull. Kor. Chem. Soc. 17, 735 (1996)] we reported results of molecular dynamic (MD) simulations for the thermodynamic and structural properties of liquid n-alkanes, from n-butane to n-heptadecane, using three different models. Two of the three classes of models are collapsed atomic models while the third class is an atomistically detailed model. In the present paper we present results of MD simulations for the dynamic properties of liquid n-alkanes using the same models. The agreement of two self-diffusion coefficients of liquid n-alkanes calculated from the mean square displacements (MSD) via the Einstein equation and the velocity auto-correlation (VAC) functions via the Green-Kubo relation is excellent. The viscosities of n-butane to n-nonane calculated from the stress auto-correlation (SAC) functions and the thermal conductivities of n-pentane to n-decane calculated from the heat-flux auto-correlation (HFAC) functions via the Green-Kubo relations are smaller than the experimental values by approximately a factor of 2 and 4, respectively.

• Bulletin of the Korean Chemical Society
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• 제19권10호
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• pp.1068-1072
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• 1998

We present results of molecular dynamic (MD) simulations for the segmental motion of liquid n-butane as the base case for a consistent study for conformational transition from one rotational isomeric state to another in long chains of liquid n-alkanes. The behavior of the hazard plots for n-butane obtained from our MD simulations are compared with that for n-butane of Brownian dynamics study. The MD results for the conformational transition of n-butane by a Poisson process form the total first passage times are different from those from the separate t-g and g-t first passage times. This poor agreement is probably due to the failure of the detailed balance between the fractions of trans and gauche. The enhancement of the transitions t-g and g-t at short time regions are also discussed.

• Bulletin of the Korean Chemical Society
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• 제20권10호
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• pp.1129-1135
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• 1999

Free energy perturbation and molecular dynamics simulations were carried out to investigate the relative binding affinities of [17] ketonand (1) toward alkali metal cations in methanol. The binding affinities of 1 toward the alkali metal cations were calculated to be in the order Li+ > Na+ > K+ > Rb+ > Cs+, whereas our recent theoretically predicted and experimentally observed binding affinities for [18]starand (2) were in the order K+ > Rb+ > Cs+ > Na+ > Li+. The extremely different affinities of 1 and 2 toward smaller cations, Li + and Na+ , were explained in terms of the differences in their ability to change the conformation to accommodate cations of different sizes. The carbonyl groups constituting the central cavity of 1 can reorganize to form a cavity with the optimal M+ -O distance, even for the smallest Li+, without imposing serious strain on 1. The highest affinity of 1 for Li+ was predominantly due to the highest Coulombic attraction between the smallest Li+ and the carbonyl oxygens of 1.

• Bulletin of the Korean Chemical Society
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• 제19권11호
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• pp.1217-1221
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• 1998

We present results of molecular dynamic (MD) simulations for the segmental motion of liquid n-heptadecane in order to investigate conformational transitions from one rotational isomeric state to another. The behavior of the hazard plots for n-heptadecane obtained from our MD simulations are compared with that for polymer of Brownian dynamics (BD) study. The transition rate at the ending dihedrals of the n-heptadecane chain is much higher than that at the central dihedrals. In the study of correlation between transitions of neighboring dihedrals, the large value of c2 implies that some 30% of the transitions of the second neighbors can be regarded as following transitions two bonds away in a correlated fashion. Finally the analysis of multiple transitions and the number of times occurred in the initial 0.005 ns are discussed.

• Coupled systems mechanics
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• 제4권2호
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• pp.137-155
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• 2015

This paper presents a simple procedure to obtain a substitute, homogenized mechanical response of single layer graphene sheet. The procedure is based on the judicious combination of molecular mechanics simulation results and homogenization method. Moreover, a series of virtual experiments are performed on the representative graphene lattice. Following these results, the constitutive model development is based on the well-established continuum mechanics framework, that is, the non-linear membrane theory which includes the hyperelastic model in terms of principal stretches. A proof-of-concept and performance is shown on a simple model problem where the hyperelastic strain energy density function is chosen in polynomial form.

• Nuclear Engineering and Technology
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• 제51권5호
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• pp.1398-1405
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• 2019

We use a molecular dynamics simulation to explore thermal transport in oxide nuclear fuels with point defects. The effect of vacancy and substitutional defects on the thermal conductivity of plutonium dioxide and uranium dioxide is investigated. It is found that the thermal conductivities of these fuels are reduced significantly by the presence of small amount of vacancy defects; 0.1% oxygen vacancy reduces the thermal conductivity of plutonium dioxide by more than 10%. The missing of larger atoms has a more detrimental impact on the thermal conductivity of actinide oxides. In uranium dioxide, for example, 0.1% uranium vacancies decrease the thermal conductivity by 24.6% while the same concentration of oxygen vacancies decreases the thermal conductivity by 19.4%. However, uranium substitution has a minimal effect on the thermal conductivity; 1.0% uranium substitution decreases the thermal conductivity of plutonium dioxide only by 1.5%.

• Bulletin of the Korean Chemical Society
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• 제17권3호
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• pp.245-253
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• 1996

A topological theory has been introduced to explain and evaluate the fractional volumes of system materials, the change of the weight and concentration of monomer molecules, molecular weight distribution, and interaction functions of polymer-polymer and polymer-oligomer, etc. for dispersion polymerization. The previous theory of Lu et al. has offered only an incomplete simulation model for dispersion polymer systems, whereas our present one gives a general theoretical model applicable to all the polymerization systems. The theory of Lu et al. considered only the physical property term caused by interaction between matters of low molecular weight (i.e., diluent, monomer, and oligomer) and polymer particles without dealing with physical properties caused by the structure of polymer networks in polymer particles, while our theory deals with all physical effect possible, caused by the displacement of not only entangled points but also junction points in polymer particles. The theoretically predictive values show good agreement with the experimental data for dispersion polymerization systems.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(2)
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• pp.306-309
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• 2000

In this work, we investigated A1 cluster deposition on Al (100) surface using molecular dynamics simulation. A result of simulations showed that large cluster with low energy was proper for good surfaced-films without craters at the low temperatures. We investigated the maximum substrate temperature and the time taken for substrate temperature to reach its maximum as a function of cluster size in the case of the same total energy and in the case of the same energy Per atom. The correlated collisions play an important role in interaction between energetic cluster and surface, and as cluster size and cluster energy increases, the correlated collisions effect affects interaction between energetic cluster and surface.