• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.723-724
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• 2012

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.296-299
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• 2015

$MoS_2$ 단일층에 단축 방향으로 스트레인을 가해 Mo와 S 사이의 거리를 변화시키면서 밴드 구조의 변화를 밀도 범함수 이론에 기반해 계산했다. $MoS_2$ 단일층의 전자 구조는 스트레인에 민감하게 변화하여 밴드갭의 감소와 직접 밴드갭에서 간접 밴드갭으로 밴드갭의 특성이 변화함을 확인했다. 이러한 전자 구조의 변화는 스트레인에 의한 전하 분포의 변화와 로컬 오비탈의 상호작용에 의한 영향으로 해석된다.

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.354-363
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• 2011

Quantum-chemistry study was explored to investigate the electronic structures, absorption and phosphorescence mechanism, as well as electroluminescence (EL) properties of three red-emitting Ir(III) complexes, $(fpmqx)_2Ir$(L) {fpmqx=2-(4-fluorophenyl)-3-methyl-quinoxaline; L=triazolylpyridine (trz) (1); L=picolinate (pic) (2) and L=acetylacetonate (acac) (3)}. The calculated results show that the HOMO distribution for 1 is mainly localized on trz moiety due to its stronger ${\pi}$-electron acceptor ability, and HOMO for 2 and 3 is the combination of Ir d- and phenyl ring ${\pi}$-orbital. The higher phosphorescence yields and differences among 1-3 are investigated in this paper. In addition, the reasons of higher EL efficiency of 2 than 1 and 3 have been rationalized.

• Journal of Power System Engineering
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• v.14 no.2
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• pp.71-77
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• 2010

This paper was studied on microstructure, mechanical properties and corrosion characteristics of 316L stainless steel pipe welds was fabricated by orbital welding process. S-Ar specimen was fabricated by using Ar purge gas and S-$N_2$ specimen was fabricated by using $N_2$ purge gas. Ferrite was not detected in weld metal of S-$N_2$ specimen but the order of 0.13 Ferrite number(FN) was detected in weld metal of S-Ar specimen. Oxygen and Nitrogen concentration of S-$N_2$ specimen was higher than S-Ar specimen on HAZ and inner bead. The welds microstructural characteristics of S-Ar and S-$N_2$ specimens are similar. The microvickers hardness values of S-Ar and S-$N_2$ specimens welds were similar and average values of each regions were in the range of 174~194. The microstructures of S-Ar and S-$N_2$ weld metal were full austenite by primary austenite solidification. The Solidification structures of S-Ar and S-$N_2$ weld metal were formed directional dendrite toward bead center. The potentiodynamic polarization curve of STS 316L pipe welds exhibited typical active, passive, transpassive behaviour. Corrosion current density$(I_{corr.})$ and corrosion rate values of S-Ar specimen in 0.1M HCl solution were $0.95{\mu}A/cm^2$ and $0.31{\mu}A$/year respectively. The values of S-$N_2$ specimen were $1.4{\mu}A/cm^2$ and $0.45{\mu}m$/year.

• Journal of the Korean Chemical Society
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• v.50 no.4
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• pp.291-297
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• 2006

The equilibrium structures, relative energies and NBO analyses for the possible conformations and transition states which can exist on the internal rotation of CPDFB and CPCFB molecules have been investigated using DFT and ab initio methods with various basis sets. The interaction between bonding orbital ((C1-C3, C2-C3)) and antibonding orbital (n*(B9) and *(B9-Cl11)) was the main characteristic hyperconjugation in both molecules. In addition, the stabilization energy of CPDFB was 6.63kcal/mol and that of CPCFB was 6.97(E-form)/6.79(Z-form) kcal/mol for each conformation. The rotational barriers by internal rotation of BF2- and BFCl- functional groups were evaluated to be 5.3~6.7kcal/mol and 5.7~6.5kcal/mol respectively, which showed good agreement with the experimental values reported by previous dynamic NMR study. Finally, Z-form was more stable than E-form by 0.2 kcal/mol in CPCFB molecule and therefore Z-form was confirmed as global minimum.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.26-26
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• 2009

TIG 용접은 고품질이고 용접인자의 제어가 쉽고 정확하다는 장점이 있지만, 얕은 용입과 낮은 생산성과 같은 단점이 있다. TIG 오비탈 용접에서는 용입의 한계 때문에 작은 루트면과 넓은 그루브를 가공하여 다층 용접을 하며, 루트패스에서는 파이프 진원도에 의한 핏업 시 단차의 문제가 자주 발생하여 많은 현장에서 루트갭을 만들어 수동 용접하는 실정이다. 따라서 생산성이 낮으며 생산 단가가 높고 용접 품질이 작업자에 따라 다르게 된다. 이러한 문제점을 해결하여 자동 오비탈 용접을 위해 단차를 흡수 할 수 있는 용접 공정 개발이 필요하다. 본 연구의 목적은 TIG 용접에서 단차에 따른 용접성을 검토하여 이를 맞대기 용접에 적용했을 때 균일한 이면비드를 얻는 공정을 개발하는 것이다. 따라서 본 연구는 아래보기 자세에서 단차에 따른 용입 특성을 이면비드 및 단면으로 비교 분석하였다. 단차 없이 아크길이만 1mm, 2mm, 3mm로 변경하여 실험한 결과 아크길이가 짧아질수록 표면비드 폭은 좁아졌고 이면비드 폭은 증가하는 경향을 나타내어 아크길이가 짧아질수록 용융효율이 증가하는 것을 확인하였다. 단차 1mm에서 아크길이 3mm를 제외하고 표면비드 및 이면비드가 미려하였다. 하지만 단차 2mm에서는 아크길이 1mm, 2mm, 3mm 전부 이면비드가 생성되지 않았다. 이는 단차로 인해 아크길이가 증가하여 용융효율이 낮아졌기 때문이라 판단된다. 이면비드가 생성되지 못한 시험편을 백 베벨링(0.5mm, 1.0mm, 1.5mm, 2.0mm)하여 실험한 결과 단차 2mm, 아크길이 1-3mm 백 베벨링 2.0mm 적용한 시험편에서 양호한 이면비드를 얻을 수 있었다.

• Journal of the Korean Chemical Society
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• v.26 no.4
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• pp.195-204
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• 1982

Semi-empirical MO calculations, EHT, CNDO/2, MINDO/3, and MNDO met hods, were performed on various geometries of n-butane, n-alkyl radical and tetramethylene diracal (triplet) in order to compare eigenvalue and eigenvector properties with those obtained by STO-3G method. All methods predicted the same relative order of stabilities of various geometries for n-butane; geometrical preferences were found to be dominated by one-electron factor, ${\pi}$-orbital energy changes being more impotant in the semi-empirical methods. The hyperconjugative energy changes accompanying structural changes from $(n-{\sigma}{\ast})_{trans}$ to (n-{\sigma}{\ast})cis were underestimated in the EHT, CNDO/2 and MINDO/3, whereas those were overestimated in the MNDO. The net destabilizing effect of $(n-{\sigma}{\ast})_{trans}$ structure was mainly due to the large internuclear energy involved in the structure. Through-space interaction between $n_1$ and $n_2$ orbitals of diradical caused energy gap narrowing of ${\Delta}E_{sp}$ and ${\Delta}{\varepsilon}={\varepsilon}_0$-${\varepsilon}_{av}$; through-space interaction had opposing effect to that of through-bond interaction. Due to the less severe neglect of differential overlaps in the MNDO, this energy gap narrowing effect appeared amplified in the MNDO. In general orbital properties were found to be reproduced satisfactorily, but eigenvalue properties were not, in all the semi-empirical methods especially when ${\sigma}-{\sigma}{\ast}$ and n-$n-{\sigma}{\ast}$interactions were involved.

• Journal of the Korean Chemical Society
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• v.35 no.4
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• pp.316-323
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• 1991

We calculated a difference between the YBa$_2Cu _3O_{7-x}$ superconductor (123 system) of critical temperature, 95 K and the YBa$_2Cu_4 O_8$ superconductors (124 system) of critical temperature, 80 K in Y-system superconductors using Extended Huckel Theory (EHT). The valence electron population (VEP), reduced overlap population (ROP) and net charge for the charged cluster models relating to the layer and the chain in 123 and 124 systems were compared. The VEPs of Cu atom in the layer of 123 and 124 systems populated d$_{z^2}$ orbital more than d$_{x^2-y^2}$ orbital, and in the chain of 123 and 124 systems populated d$_{y^2-z^2}$ orbital more than d$_{z^2}$ orbital. The ROP of the Cu(1)-O(1) in the layer of 123 system was larger than the value of the Cu(1)-O(2), but the ROP of the Cu(1)-O(2) in the layer of 124 system was larger than the value of the Cu(1)-O(1). The ROP of Cu(2)-O(4) in the chain of 123 and 124 systems were larger than the value of the Cu(2)-O(3). In 123 system the net charge values of the Cu in the layer was larger than the value of the Cu in the chain. However, in 124 system the net charge value of the Cu in the chain was larger than the value in the layer.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.118-127
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• 2017

형광화학센서는 형광분자의 화학적으로 유도된 형광의 소광 또는 증광을 통해 생체 등에서 특정 물질을 관찰할 수 있기에 그 활용도가 높다. 본 연구에서는 두 개의 서로 다른 킬레이트 결합자리를 가지는, 파이렌 이중체를 발색단의 형광분자(Pyex)를 이용하여, PET (photoinduced electron transition)와 AID (absorbance intensity decreasing)의 형광 소광 원리에 집중하여, 전자구조계산과 TD (time-dependent) 계산을 근거로 금속 양이온의 형광 소광 원리를 분류하고, 더불어 그에 관여하는 금속 양이온의 원자오비탈까지 탐색하였다. 그 결과 Pyex와 그 칼륨이온 복합체에서는 실험값과 일치하는 형광이, 납과 은 이온 복합체에서는 소광이 나타났다. 구체적으로는 납 이온의 경우 PET를 주된 원인으로 AID와 함께 작용하여 소광을 발생시키고, 은 이온의 경우는 AID에 의해 소광이 일으키는 것으로 밝혀졌다. 또한 납 이온의 p 오비탈이 소광에 관여하는 것으로 볼 수 있는 결과도 나타났다.

• Journal of the Korean Chemical Society
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• v.50 no.4
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• pp.281-290
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• 2006

The electronic structure and properties of the 1H-indene and mono-sila-1H-indene series have been investigated using basis set of 6-31G(d, p) and hybrid density functional theory. Basic measures of aromatic character derived from structure, molecular orbitals, a variety of magnetic criteria (magnetic isotropic and anisotropic susceptibilities) are considered. Energetic criteria suggest that In(Si7) enjoy conspicuous stabilization. However, by magnetic susceptibility isotropic this system are among the least aromatic of the family: Within their isomer series, In(Si4) is the most aromatic using this criteria. Natural bond orbital (NBO) analysis method was performed for the investigation of the relative stability and the nature of the 8-9 bonds in 1H-indene and mono-sila-1H-indene compounds. The results explained that how the p character of natural atomic hybrid orbital on X8 and X9 (central bond) is increased by the substitution of the C8 and C9 by Si. Actually, the results suggested that in these compounds, the X8-X9 bond lengths are closely controlled by the p character of these hybrid orbitals and also by the nature of C-Si bonds. The magnitude of the molecular stabilization energy associated to delocalization from X8-X9 and to * X8-X9 bond orbital were also quantitatively determined. Molecular orbital (MO) analysis further reveal that all structure has three delocalized MOs and two delocalized MOs and therefore exhibit the aromaticity.