• Journal of the Korean Chemical Society
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• v.28 no.5
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• pp.279-283
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• 1984

${\beta}$-Substituent effect on the reactivity of retro-ene decarboxylation of but-3-enoic acid was investigated theoretically. It was found that charge effect is important not only through ${\pi}$-electron transfer as has been claimed to rationalize experimental results but also through polarization as found for the $CH_3$ substituent. The reactivity was not determined by the charge effect alone but the HOMO-LUMO energy gap was also found to affect the reactivity. In general it was confirmed that the greater the ${\pi}$-electron donating power of the substituent, the greater is the reactivity.

• Journal of the Korean Chemical Society
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• v.35 no.4
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• pp.335-342
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• 1991

The effect of pressure and temperature on the stabilities of the charge transfer complexes of 1,3,5-trinitrobenzene, tetrachloro-p-benzoquinone and tetracyanoethylene with hexamethylbenzene in carbon tetrachloride has been investigated by spectrophotometric measurements. The equilibrium constants for the formation of the complexes were obtained at various temperature and pressure, and thermodynamic parameters for the formation of the charge transfer complexes are calculated from these values. The relative stabilities of charge transfer complexes with hexamethylbenzene increase in the order; 1,3,5-trinitrobenzene < tetrachloro-p-benzoquinone < tetracyanoethylene. This may be regarded as an order of relative acidity of these compounds in complexation with hexamethylbenzene and is explained in terms of the negative inductive effect of the ${\pi}$ acceptors. The red-shift at higher pressure, the blue-shift at higher temperature and the relation between pressure and oscillator strength are discussed on the basis of thermodynamic functions.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.219-220
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• 2006

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2004.11a
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• pp.170-178
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• 2004

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.1 no.2
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• pp.74-81
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• 1987

The reduction in dielectric strength of insulating polymer material when applying electric field is known to be substantial due to the trapped carrier effect. In this study, the carrier property of Biaxially-Drawn polypropylene, which has superior heat-resistance compared to ordinary one, is examined to improve electrical characteristics by measuring TSC spectra as a function of electric field applied to a sample of ($50{\mu}m$) thickness film. The TSC spectra in the temperature range of 303-413(K) and electric field of 2-80(MV/m) have shown no observable effect below 12(MV 1m) but TSC currents of Hetero-and Homo-peaks formed from trapped space charger and space charger injected from electrode have been observed above that point, which seems eventually lead to dielectric breakdown. Finally, this study has shown the superior dielectric proporty of Biaxially-Drawn polypropylene film compared to the non-oriented one for electrical insulation.

• Journal of IKEEE
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• v.20 no.4
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• pp.432-434
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• 2016

In conventional SIDO(Single Inductor Dual Output) boost converter, charging time is changed by load power consumption. In this case, if the power consumption of one load is changed to such a degree that switching frequency of the boost converter must be changed, another load charge time is also changed, which this causes cross regulation. In this paper, the charge copy technique is proposed to reduce cross regulation. When the switching frequency is changed to an integer ratio, another load charge time is also changed to integer ratio. Simulation result shows that proposed method reduces the 10.24mV cross regulation and 39.118us recover-time compared with conventional method.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.210-213
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• 2013

실리콘 나노선 전계 효과 트랜지스터(Field Effect Transisor: FET)의 특성을 시뮬레이션을 통해 연구하였다. 일반적인 트랜스컨덕턴스(transconductance) 값을 이용하여 소자의 전계 효과 이동도(field effect mobility)를 추출했고, Y-function 방법을 이용하여 저전계 이동도(low field mobility)와 문턱전압(threshold voltage)를 구했다. 채널길이가 10nm로 매우 짧을 때와 100nm의 일반적인 길이 일 때의 전하 이동도 특성을 비교하여 Si 나노선 FET의 쇼트 채널 효과(short channel effect)를 보았다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.446-446
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• 2013

유기태양전지는 가벼운 무게와 우수한 유연성을 가져 플렉서블 태양전지 및 롤투롤(Roll-to-roll) 인쇄 공정에 대한 적용 가능성 때문에 많은 연구가 이루어지고 있다. 하지만 이종접합 유기태양전지를 상용화하기 위해서는 낮은 전력 변환 효율 (PCE)을 증진하는 연구가 필요하다. 본 연구에서는 간단한 용액공정을 통해 poly (3-hexylthiophene) (P3HT) 나노구조층을 사용하여 indium-tin-oxide 양극 전극/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) 정공수송층/P3HT 나노구조층/P3HT 복합체로 제작한 나노구조층/C60 전자수송층 /lithium quinolate 전자주입층/Al 음극 전극 구조의 유기태양전지를 제작하였다. 전류밀도-전압 곡선 결과는 P3HT 복합체 이용한 나노구조층를 가진 유기태양전지의 구조는 평면층을 가진 유기태양전지에 비해서 PCE가 향상됨이 관찰되었다. 유기태양전지는 짧은 엑시톤의 확산거리가 PCE 감소의 주요 원인이 된다. P3HT 복합체를 사용한 나노구조층을 가지는 유기태양전지는 광활성층과 전자수송층 사이의 계면이 넓어지는 효과를 가진다. 계면이 넓어지는 효과를 통해 생성된 엑시톤을 효율적으로 분리할 뿐만 아니라 더 많은 양의 전하를 생성할 수 있기 때문에 전하의 양이 증가되고 더 높은 전류를 생성하여 PCE를 효과적으로 높일 수 있다.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.1
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• pp.61-68
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• 2010

Purpose: This article attempted to determine the factors affecting the preload and screw loosening. Methods: Available clinical studies from 1981 to 2008 from the PUBMED that presented screw loosening data and review articles regarding screw joint stability were evaluated. Eleven studies dealing the biomechanical principles of the screw mechanics were reviewed. Moreover, the results of our data were included. Results: The frequency of screw loosening was consequently reduced due to the advancement in torque tightening with torque wrench, screw material, coating technique for reducing the frictional force, and thread design, etc. If preload in the screw falls below a critical level, joint stability may be compromised, and the screw joint may fail clinically. The types of fatigue failure of screw were divided to adhesive wear, plastic deformation, and screw fracture. Conclusion: An optimum preload is essential to the success of the implant-abutment complex. To maintain optimum preload, using a torque wrench and re-tightening at recall time were needed.

• Journal of the Korean Chemical Society
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• v.39 no.8
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• pp.598-603
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• 1995

Kinetics for the reaction of para-substituted benzyl bromides with 3-picoline have been studied with the changes of substituent, pressure and temperature. The activation parameters and the Hammett ρ-values were determined from the values of rate constants. The results of these studies showed that the positive charge developed in the reaction center and bond cleavage was greater than bond formation. The reaction rate and the ability of charge transfer were increased with elevating pressure. The effect of pressure for the charge transfer was more enhanced at low temperatures.