• Bulletin of the Korean Chemical Society
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• 제20권9호
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• pp.1067-1072
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• 1999

Structures of unprotonated [(NH3)n+(n = 1-6)] and protonated [NH4+(NH3)n-1(n = 1-6)] ammonia cluster cations have been optimized with ab initio Hartree-Fock (HF) and second-order MФller-Plesset (MP2)/6-31+G ** levels and the harmonic vibrational frequencies have also been evaluated. In unprotonated cluster cations, NH3+ forms as a central core of the first ammonia solvation shell. In protonated cluster cations, NH4+ forms as a central core. In unprotonated dimer and trimer cations, there are two types of isomers (hydrogen-bonded and head-to-head interactions). In both cluster cations, the hydrogen-bonded isomers are more stable. In the hydrogen-bonded dimer cation, the proton transfer reaction takes place from (NH3-HN+H2) to (NH4+-NH2). But in the other unprotonated cluster cations, the proton transfer does not take place. In unprotonated pentamer and hexamer, a NH3+ core has both interactions in a complex. On the other hand, in unprotonated tetramer a core has only the hydrogen-bonded type combined with neutral ammonia molecules. With increasing cluster cation size, the bond lengths [R(NN)] between two nitrogen atoms and the distances [R(N ...H)] of the hydrogen-bond increase reg-ularly. In the calculated infra-red absorption bands for ammonia cluster cations, the characteristic peaks of the bridged NH vibration of the hydrogen-bonded clusters appear near 2500 cm-1 . With increasing size, the peaks shift from 2306 cm-1 to 2780 cm-1 .

• Structural Engineering and Mechanics
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• 제72권4호
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• pp.469-477
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• 2019

The understanding of tool-rock interaction mechanism is of high essence for improving the rock breaking efficiency and optimizing the drilling parameters in mechanical rock breaking. In this study, the tool-rock interaction models of indentation and cutting are carried out by employing the discrete element method (DEM) to examine the rock failure modes of various brittleness rocks and critical indentation and cutting depths of the ductile to brittle failure mode transition. The results show that the cluster size and inter-cluster to intra-cluster bond strength ratio are the key factors which influence the UCS magnitude and the UCS to BTS ratio. The UCS to BTS strength ratio can be increased to a more realistic value using clustered rock model so that the characteristics of real rocks can be better represented. The critical indentation and cutting depth decrease with the brittleness of rock increases and the decreasing rate reduces dramatically against the brittleness value. This effort may lead to a better understanding of rock breaking mechanisms in mechanical excavation, and may contribute to the improvement in the design of rock excavation machines and the related parameters determination.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2595-2602
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• 2009

Hexamer cluster of N,N-dimethylformamide(DMF) based on the crystal structure was investigated for the equilibrium structure, the stabilization energies, and the vibrational properties in the density functional force field. The geometry (point group $C_i$) of fully optimized hexamer clustered DMF shows quite close similarity to the crystal structure weakly intermolecular hydrogen bonded each other. Stretching force constants for intermolecular hydrogen bonded methyl and formyl hydrogen atoms with nearby oxygen atom, methyl C–H${\cdots}$O and formyl C–H${\cdots}$O, were obtained in 0.055 $\sim$ 0.11 and $\sim$ 0.081 mdyn/$\AA$, respectively. In-plane bending force constants for hydrogen bonded methyl hydrogen atoms were in 0.25 $\sim$ 0.33, and for formyl hydrogen $\sim$ 0.55 mdynÅ. Torsion force constants through hydrogen bonding for methyl hydrogen atoms were in 0.038 $\sim$ 0.089, and for formyl hydrogen atom $\sim$ 0.095 mdynÅ. Calculated Raman and infrared spectral features of single and hexamer cluster represent well the experimental spectra of DMF obtained in the liquid state. Noncoincidence between IR and Raman frequency positions of stretching C=O, formyl C–H and other several modes was interpreted in terms of the intermolecular vibrational coupling in the condensed phase.

• Bulletin of the Korean Chemical Society
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• 제29권10호
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• pp.1951-1959
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• 2008

Pentamer cluster of azodicarbonamide (ADA) based on the crystalline structure was investigated for the equilibrium structure, the stabilization energies, and the vibrational properties at various levels of the density functional theory. Stretching force constants of N${\cdot}{\cdot}{\cdot}$H or O${\cdot}{\cdot}{\cdot}$H, and angle-bending force constants of N-H${\cdot}{\cdot}{\cdot}$N or N-H${\cdot}{\cdot}{\cdot}$O for intermolecular hydrogen bonds in the pentamer cluster were obtained in 0.2-0.5 mdyn/$\AA$ and 1.6-2.0 mdyn$\AA$, respectively. The geometry of central ADA molecule fully hydrogen bonded with other four molecules shows good coincidence to the crystalline structure except the bond distances of N-H. Calculated Raman and infrared spectra of central ADA molecule in cluster represent well the experimental spectra of ADA obtained in the solid state compared to a single molecule. Detailed structural and vibrational properties of central ADA molecule in the pentamer cluster are presented.

• Coupled systems mechanics
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• 제6권3호
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• pp.369-376
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• 2017

Intermolecular interaction energies and conformer geometries of the hydrogen bonded acrylamide dimers have been studied by using the second-order Møller-Plesset (MP2) perturbation theory and the density functional theory (DFT) with 17 density functionals. Dunning's correlation consistent basis sets (up to aug-cc-pVTZ) have been used to study the basis set effects. The DFT calculated interaction energies are compared to the reference energy data calculated by the MP2 method and the coupled cluster method at the complete basis set (CCSD(T)/CBS) limit in order to determine the relative performance of the studied density functionals. Overall, dispersion-energy-corrected density functionals outperform uncorrected ones. The ${\omega}B97XD$ density functional is particularly effective in terms of both accuracy and computational cost in estimating the reference energy values using small basis sets and is highly recommended for similar calculations for larger systems.

• 공업화학
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• 제21권1호
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• pp.81-86
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• 2010

실리카 지지 루테늄과 철의 합금($Ru/Fe-SiO_2$) 시료에 일산화탄소(CO)를 흡착시켰을 때 Ru/Fe의 몰비 9/1 이상에서 다섯 적외선 흡수띠($2138.7{\sim}2142.5cm^{-1}$, $2067.3{\sim}2073.1cm^{-1}$, $1976.7{\sim}2017.2cm^{-1}$, $1737.9{\sim}1799.3cm^{-1}$, $1625.7cm^{-1}$)를 관찰했고, Ru/Fe의 몰비 8/2 이하에서 두 적외선 흡수띠($1934.0{\sim}1990.2cm^{-1}$, $1625.7cm^{-1}$)를 관찰했다. $2138.7{\sim}2142.5cm^{-1}$ 흡수띠, $2067.3{\sim}2073.1cm^{-1}$ 흡수띠, $1976.7{\sim}2017.2cm^{-1}$흡수띠는 Ru/Fe 뭉치 표면의 Ru 원자에 선형결합한 CO의 신축진동에 의한 것으로, $1774.2{\sim}1799.3cm^{-1}$ 흡수띠는 Ru/Fe 뭉치 표면의 Ru 원자와 다리결합하거나 높은 지수 평면에 있는 Ru 원자에 결합한 CO의 신축진동에 의한 것으로, $1934.0{\sim}1990.2cm^{-1}$ 흡수띠는 Ru/Fe 뭉치 표면의 Fe 원자에 선형결합한 CO의 신축진동에 의한 것으로 제시할 수 있다. $Ru/Fe-SiO_2$에서 CO를 흡착시켰을 때 Ru/Fe 몰비가 8/2 이하에서 증가할 때 CO가 Fe에 선형결합하여 생긴 $1934.0{\sim}1990.2cm^{-1}$ 흡수띠의 흡광도가 증가하였는데, 이 현상은 Ru/Fe 몰비가 8/2 이하에서 증가할 때 Ru/Fe 뭉치 표면에서 시료의 함량과 비교하여 Fe 농도가 증가했고 $Fe-SiO_2$ 시료와 비교하여 표면적이 Ru/Fe 몰비의 증가에 따라 점차 증가했기 때문으로 설명할 수 있다.

• 대한화학회지
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• 제64권6호
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• pp.350-353
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• 2020

물 분자내의 OH 신축진동(stretching vibration) 운동을 나타내는 정규모드(normal mode)와 국소모드(local mode) 진동수들을 비교하여 수소결합한 물 분자에 대한 국소모드에 기반한 계산의 타당성을 조사하였다. 물 분자의 단량체, 이합체, 삼량체에 대한 계산을 수행하여 분자 클러스터 크기가 커짐에 따라 국소모드 진동수, 국소모드의 비조화성, 그리고 국소모드와 정규모드 진동수들의 유사성이 어떤 경향성을 보이는지 순이론적 양자화학 계산 방법으로 연구하였다. 단량체에서 삼량체로 분자의 갯수가 증가할수록 OH 결합의 비조화성은 증가하며 국소모드와 정규모드 진동수 간의 차이는 줄어드는 것으로 나타났다. 따라서, 응축상에 존재하는 물 분자들의 OH 신축 진동수의 이론적 계산은 비조화성을 쉽게 다룰 수 있는 국소모드에 기반한 방식이 적절할 수 있음을 확인하였다.

• 한국의류학회지
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• 제24권8호
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• pp.1242-1253
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• 2000

The purpose of this study was to find out the shopping motive factors of clothing and to classify consumer groups according to clothing shopping motives, and also to analyze demographic characteristics, conspicuous consumption and clothing purchase behavior among consumer groups. The subjects were 329 women in their twenties living in Seoul. For data analysis, mean, Factor Analysis, Cluster Analysis, $\chi$$^2$-test, ANOVA, Duncan test were conducted. The results are as follows; 1. Three factors of clothing shopping motives were identified: fashion/leisure pursuit, economic, and personal motive. Consumer groups are classified into the following four subdivisions: personalizing group, apathetic group, fashion/leisure pursuit group, economic group. 2. Among consumer groups, there were significant differences in demographic characteristics according to age, occupation of the subjects. 3. Among consumer groups, there were significant differences in conspicuous consumptions according to factors such as brand intention, status symbol intention. 4. Among consumer groups, there were significant differences in clothing purchase behavior according to use of information sources. Regardless of clothing shopping motives, consumer preferred department stores in purchasing formal dress, and preferred haberdashery.bonded store in purchasing casual wear.

• Bulletin of the Korean Chemical Society
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• 제16권7호
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• pp.634-641
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• 1995

The metal-carbon σ-bond cluster complexes 1-Mn(CO)5-2-R-1,2-C2B10H10 (R=CH3 Ia, C6H5 Ib) have been prepared in good yields from readily available carboranyl lithium complexes, 1-Li+-2-R-1,2-C2B10H10- (R=CH3, C6H5), by direct reaction with (CO)5MnBr. These manganese metal complexes are rapidly converted to the corresponding manganese metal carbene complexes, 1-[(CO)4Mn=C(OCH3)(CH3)]-2-R-1,2-C2B10H10 (R=CH3 IIIa, C6H5 IIIb), via alkylation with methyllithium followed by O-methylation with CF3SO3CH3. The crystal structure of IIIb was determined by X-ray diffraction. Thus, complex IIIb crystallizes in the orthorhombic space group P212121 with cell parameters a=15.5537(5), b=19.0697(5), c=7.4286(3) Å, V=2203.4(1) Å3, and Z=4. Of the reflections measured a total of 3805 unique reflections with F2>3σ(F2) was used during subsequent structure refinement. Refinement converged to R1=0.053 and R2=0.091. Structural studies showed that the manganese atom had a slightly distorted pseudo-octahedral configuration about the metal center with the carbene and ortho-carborane occupying the equatorial plane cis-orientation to each other.

• 한국전산구조공학회논문집
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• 제24권6호
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• pp.715-722
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• 2011

본 논문에서는 항공기 충돌에 의한 원전 격납건물의 거동을 병렬해석을 통해 수행하였다. 지금까지의 원전 격납건물에 대한 항공기 충돌관련 연구는 항공기의 경우, Riera의 충격하중-시간함수를 이상화하여 대상 구조체의 일정영역에 대해 충격하중으로 적용하는 방법을 사용해 왔고 충돌대상 구조체의 경우, 단순 철근콘크리트 벽체나 빌딩에 머물러 왔다. 하지만 본 논문에서는 항공기(Boeing-767, http://www.boeing.com)와 가상의 원전 격납건물을 실제와 유사하게 모델링하여 해석을 수행하였으며, 항공기모델은 충돌평가 가이드인 NEI 07-13(2009)에서 허용하는 Riera의 식에 따른 충돌하중이력곡선과 비교하는 방법으로 검증되었다. 또한, 일반적으로 고속 충돌해석은 짧은 시간동안 두 개 이상의 물체가 접촉하고 동적 대변형을 일으키는 비선형성이 강한 문제로 많은 계산시간이 요구되기 때문에 이를 효과적으로 다루기 위해서는 단일 CPU만으로는 한계가 있다. 따라서 본 논문에서는 해석의 효율성을 향상시키기 위해 자체 구축한 리눅스 클러스터 시스템을 이용하여 Message-Passing MIMD 형태의 병렬해석을 수행하였고 병렬성능에 대한 평가를 위해 무근콘크리트(Plain Concrete, PC), 철근콘크리트(Reinforced Concrete, RC), 내부 Liner Plate를 부착한 철근콘크리트(RC with Containment Liner Plate, CLP), SC구조(Steel-Plate Concrete, SC)등 4가지 경우에 대한 수치해석 효율성이 비교 검토되었다.