• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1207-1212
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• 2004

A model for the phonon dispersion relationship for cubic zinc sulfide structure, for example SiC, is developed in terms of two unknown force constants. Born model that incorporates bond bending and bond stretching, is used for the force constants. The force constants are determined by fitting to experimental data. Using only the nearest-neighbor coupling results in $6{\times}6$ sized dynamic matrix. The eigenvalues of dynamics matrix for each wavenumber in 3-D ${\kappa}$ space correspond to frequencies, 3 for optical phonon and 3 for acoustic phonon, which is so-called dispersion relation (${\kappa}$-${\omega}$). The density of state is determined by counting the states for each frequency bin, and the properties such as specific heat and thermal conductivity can be obtained. The specific heat is estimated on this model and compared with experiment and other models, i.e. Debye model, Einstein model and combined Debye-Einstein model. In spite of the simple bond potential model, reasonable agreements are found.

• 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.

• 한국재료학회지
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• 제16권8호
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• pp.473-478
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• 2006

The coherent interface energies and misfit strain energies of Fe/XN (X=Ti, Zr, Hf) systems were calculated by first principles method. The interface energies in Fe/TiN, Fe/ZrN and Fe/HfN systems were 0.343, 0.114, and 0.030 $J/m^2$, respectively. Influence of bond energy was estimated using the discrete lattice plane/nearest neighbor broken bond(DLP/NNBB) model. It was found that the dependence of interface energy on the type of nitride was closely related to changes of the bond energies between Fe, X and N atoms before and after formation of the Fe/XN interfaces. The misfit strain energies in Fe/TiN, Fe/ZrN, and Fe/HfN systems were 0.239, 1.229, and 0.955 eV per 16 atoms(Fe; 8 atoms and XN; 8 atoms). More misfit strain energy was generated as the difference of lattice parameters between the bulk Fe and the bulk XNs increased.

• Bulletin of the Korean Chemical Society
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• 제19권4호
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• pp.422-428
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• 1998

In the present paper, we report a molecular dynamics (MD) simulation of non-rigid zeolite-A framework only as the base case for a consistent study of the role of intraframework interaction on several zeolite-A systems using the same technique in our previous studies of rigid zeolite-A frameworks. Usual bond stretching, bond angle bending, torsional rotational, and non-bonded Lennard-Jones and electrostatic interactions are considered as intraframework interaction potentials. The comparison of experimental and calculated structural parameters confirms the validity of our MD simulation for zeolite-A framework. The radial distribution functions of non-rigid zeolite-A framework atoms characterize the vibrational motion of the framework atoms. Mean square displacements are all periodic with a short period of 0.08 ps and a slow change in the amplitude of the vibration with a long period of 0.53 ps. The displacement auto-correlation (DAC) and neighbor-correlation (DNC) functions describe the up-and-down motion of the framework atoms from the center of α-cage and the back-and-forth motion on each ring window from the center of each window. The DAC and DNC functions of the framework atoms from the center of α-cage at the 8-ring windows have the same period of the up-and-down motion, but those functions from the center of 8-ring window at the 8-ring windows are of different periods of the back-and-forth motion.

• 한국조경학회지
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• 제42권6호
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• pp.39-49
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• 2014

혐오시설은 인근 지역의 생활환경에 부정적인 영향을 미치는 시설로 인식되어 지역주민들로부터 기피되었으나, 최근 부정적 인식 개선을 위해 혐오시설 공원화사업이 진행되었고, 지역주민의 만족도가 상당히 높게 나타났다. 또한 혐오시설 공원화 사업은 보다 쾌적한 생활환경을 제공하고, 지역주민의 삶의 질 향상을 도모하여 지역주민 간 갈등을 해소하고, 상호 친밀감을 조성하는 등 커뮤니티의식에 일정부분 영향을 미치고 있는 것으로 보인다. 본 연구는 혐오시설이 공원화됨에 따라 지역주민의 만족도가 커뮤니티 의식변화에 어떻게 영향을 미치는지 규명하고자 수행되었으며, 이를 위해 대표적인 혐오시설인 하수처리장을 복개 후 공원으로 조성한 서울특별시 강남구의 마루공원 방문객을 대상으로 설문조사를 시행하였다. 분석결과에 따르면, 과거 탄천 물 재생센터가 마루공원으로 조성된 후 만족도는 매우 높은 편이었다. 방문객이 느끼는 커뮤니티 의식도 대체로 높은 편이었으나, '정주의식 및 소속감'에 비해 '연대의식 및 주민유대'는 다소 낮은 수준이었다. 방문객의 만족도가 커뮤니티 의식에 미치는 상대적 영향을 알아보기 위해 위계적 회귀분석을 한 결과, '정주의식 및 소속감'항목에는 생태적 건강도 만족도가 가장 큰 영향력을 미쳤고, 다음으로 경관미 만족도인 것으로 나타났으며, 청결미만족도는 영향관계가 없는 것으로 분석되었다. '연대의식 및 주민유대' 항목은 청결도, 생태적 건강도, 경관미 만족도 모두 영향을 미치지 않는 것으로 분석되었다. 이 같은 결과로 볼 때, 혐오시설이 공원화 됨에 따라 '정주의식 및 소속감'은 긍정적인 변화가 나타났지만, 영향이 미치지 않는 '연대의식 및 주민유대'를 고취하기 위해서는 주민들의 의식변화를 위한 적절한 시설과 이용프로그램 제공이 마련되어야 한다고 판단된다.