• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.1-7
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• 2016

Triphenylsulfonium 양이온(TPS)은 잘 알려진 광산 생성자(photoacid generator, PAG)중 하나로 양이온성 중합반응(cationic polymerization)의 개시제로 널리 사용됐으며, 유기발광다이오드의 활성층, 폴리머 발광다이오드의 전자주입층을 구성하는 재료로도 사용되고 있다. TPS는 200nm 주변의 빛을 흡수하면 탄소-황 결합이 끊어져 페닐 라디칼과 diphenylsulfonium 양이온 라디칼로 분해되는 것이 알려져 있다. 본 연구에서는 밀도범함수이론과 시간의존 밀도범함수이론을 이용 triphenylsulfonium 이온의 광학적 특성을 조사하였다. 가장 안정한 구조를 기준으로 자외선 흡광 스펙트럼을 계산하였고, 실험값에 잘 맞는 것을 확인하였다. TPS의 빛에 의한 해리 과정을 알아보기 위해 페닐-황 결합 길이를 변화시키며 TPS의 흡광 스펙트럼을 계산, 여기상태 포텐셜 에너지 곡선을 구할 수 있었다. 결합의 분해에 이용되는 상태들은 주로 점유 분자 오비탈에서 최저준위 비점유 분자 오비탈(LUMO)로 들뜨는 성분을 가지고 있었는데, 이는 LUMO가 반결합성 오비탈이기 때문이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.316-316
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• 2011

제일원리 계산으로 Fe/Pt (001) 표면의 표면상태도를 계산하고 표면상태도로 부터 얻어진 평형 Fe/Pt (001) 표면구조의 자기이방성에너지를 계산하였음. 계산된 표면상태도로 부터 Fe-rich $L1_2$ 구조와 수직 $L1_0$ 구조가 가장 안정한 표면 Fe/Pt (001) 구조임이 밝혀졌음. 제일원리로 계산 된 두 구조의 자기이방성에너지를 관측하여 두 구조의 자기용이축이 모두 [001] 방향으로 정렬 됨을 확인하였다. 자기이방성에너지가 격자 변화와 표면 형성 중 어떤 원인에 의해 발생하는지 판단하기 위해서 표면구조, 벌크구조, 및 표면구조와 동일한 격자상수를 가진 벌크구조를 비교 하였다. 비교 결과에 의해 자기이방성에너지의 주 원인은 표면 형성임이 밝혀졌으며 이를 좀 더 명확히 하기위해 상태밀도함수를 계산하였다. 상태밀도함수 계산 결과 Fe 원자의 $3d_{z2}$ 오비탈의 페르미 준위 아래에서의 상태가 표면이 형성되면서 증가하는 것을 관측하였으며 이는 [001] 방향으로의 자기이방성을 증가시키는 오비탈이므로 표면 형성에 따른 자기이방성에너지 증가는 Fe 원자의 $3d_{z2}$ 오비탈에 의함이 판명되었다.

• Journal of the Korean Magnetics Society
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• v.20 no.2
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• pp.68-74
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• 2010

Nuclear Magnetic Resonance (NMR) is a very useful tool for magnet study because it provides information on local spin environment. The valence of magnetic ions, spin canting angle, orbital state can be measured by NMR and the information on the position of the ions and the change of domains and domain walls can be obtained. The principle of operation is discussed with corresponding application examples.

• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.179-186
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• 2002

A molecular orbital analysis based on the extended Huckel calculations has been carried out to study the OH bond activation of water on the $TiO_2$(110) surface. $H_2O$ binds with its axis perpendicular to the surfac on top of the five-coordinate $Ti^{4+}$ atom via its $3a_1$ orbital. In this bonding situation, the two-coordinated bridging $O^{2-}$ atom ($O_b$, basic site) on $TiO_2$(110) is too distant from an H atom of water to form hydrogen-bondig interactions with water that facilitate O-H bond cleavage. It has been elucidated that the O-H bond is appreciably weakened when the water molecule is tilted to give a hydrogen bond with the $O_b$ atom. This mechanism includes mutual transfer of electron density from the $3a_1$ orbital of the water molecule to the $Ti^{4+} 3d_{z2}$ orbital and from the $O_b$ P orbitals to the $2b_1$ of the adsorbed water molecule This should result in lengthening of the O-H bond in the surface complex and the subsequent dissociation into the fragments OH and H.

• Journal of the Korean Chemical Society
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• v.49 no.1
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• pp.35-46
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• 2005

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.417-418
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• 2013

• Journal of the Mineralogical Society of Korea
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• v.30 no.2
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• pp.59-70
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• 2017

$SiO_2$ is one of the most abundant constituents of the Earth's crust and mantle. Probing its electronic structures at high pressures is essential to understand their elastic and thermodynamic properties in the Earth's interior. The in situ high-pressure x-ray Raman scattering (XRS) experiment has been effective in providing detailed bonding transitions of the low-z materials under extreme compression. However, the relationship between the local atomic structures and XRS features at high pressure has not been fully established. The ab initio calculations have been used to overcome such experimental difficulties. Here we report the partial density of states (PDOS) of O atoms and the O K-edge XRS spectra of ${\alpha}-quartz$, ${\alpha}-cristobalite$, and $CaCl_2$-type $SiO_2$ phases calculated using ab initio calculations based on the full-potential linearized augmented plane wave (FP-LAPW) method. The unoccupied O PDOSs of the $CaCl_2$-type $SiO_2$ calculated with and without applying the core-hole effects present significantly distinctive features. The unoccupied O p states of the ${\alpha}-quartz$, ${\alpha}-cristobalite$ and $CaCl_2$-type $SiO_2$ calculated with considering the core-hole effect present similar features to their calculated O K-edge XRS spectra. This confirms that characteristic features in the O K-edge XRS stem from the electronic transition from 1s to unoccupied 2p states. The current results indicate that the core-hole effects should be taken in to consideration to calculate the precise O K-edge XRS features of the $SiO_2$ polymorphs at high pressure. Furthermore, we also calculated O K-edge XRS spectrum for $CaCl_2$-type $SiO_2$ at ~63 GPa. As the experimental spectra for these high pressure phases are not currently available, the current results for the $CaCl_2$-type $SiO_2$ provide useful prospect to predict in situ high-pressure XRS spectra.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.7
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• pp.595-600
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• 2016

An orbital grinding system uses a special motion to machine crankshafts in ships. When a crankshaft is operated, eccentric pins rotate and a grinding wheel moves in order to grind the pins. Thermal error caused by heat generated in the grinding process decreases the quality of the final product. In this study, the thermal error of an orbital grinding system caused by heat generation was investigated in order to predict the extent of thermal error that can occur during the grinding process. Since the machine position changes during orbital grinding, the pin part is divided into 30 degree intervals and heat is generated. Total thermal error was measured by summing the thermal errors associated with the pin and the grinding wheel. Total thermal error was found to reach a maximum at 60 degrees and a minimum at 210 degrees because of the shape of the crankshaft.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.57-62
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• 2015

A large variety of pipe flanges are required in the marine and construction industry. Pipe flanges are usually welded or screwed to the pipe end and are connected with bolts. This approach is very simple and has been widely used for a long time; however, it results in high development costs and low productivity, and the products made through this approach usually have safety problems in the welding area. In this research, a new approach for forming pipe flanges based on cold forging and the floating die concept is presented. This innovative approach increases the effectiveness of the material usage and saves time and costs compared with the conventional welding method. To ensure the dimensional accuracy of the final product, finite element analysis (FEA) was carried out to simulate the process of cold forging, and orthogonal experiment methods were used to investigate the influence of four manufacturing factors (stroke of distance, pin die angle, forming of pipe diameter, and speed of the die) and predict the best combination of them. The manufacturing factors were obtained through numerical and experimental studies, which show that the approach is very useful and effective for the forming of pipe flanges and could be widely used in the future.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.23-23
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• 2009

우수한 용접부 품질 때문에 TIG를 이용한 오비탈 용접은 파이프 용접에 널리 사용되고 있다. 하지만 루트갭이 없고 루트페이스가 큰 맞대기 오비탈 용접의 위보기 및 경사상진자세에서는 오목한 이면비드가 형성되기 쉽지만, 이러한 문제를 극복하기 위한 연구는 희박한 실정이다. 본 연구에서는 위보기 및 경사상진자세에서 볼록한 이면비드의 형성을 연구하기위해서 용융지의 제어 방법을 적극적으로 검토하였다. 4mm 두께의 SS400 시편을 위보기 및 경사상진자세에서 각각 Bead-on-plate 용접하고, 이 때 비드성형기의 사용에 따른 비드 형상 변화를 관찰하였다. 텅스텐 전극과 비드 성형기간의 거리(Tip To Former Distance, 이하 TTFD)를 4.5mm에서 7.5mm로 1mm단위로 변경시켜 실험하였으며, TTFD가 증가할수록 위보기 및 경사상진자세에서 이면비드 높이가 감소하였으며 표면비드의 처짐이 증가하였다.