• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.355-355
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• 2010

We studied the dependence of the performance of schottky barrier metal-oxide-field effect transistors(SB MOSFETs) on the work function of source/drain metals. A strong impact of the various work functions and the light wavelengths on the transistor characteristics is found and explained using experimental data. We used an insulator of a high thickness (100nm) and back gate issues in SOI substrate, subthreshold swing was measured to 300~400[mV/dec] comparing with a ideal subthreshold swing of 60[mV/dec]. Excellent characteristics of Al/Si was demonstrated higher on/off current ratios of ${\sim}10^7$ than others. In addition, extensive photoresponse analysis has been performed using halogen and deuterium light sources(200<$\lambda$<2000nm).

• Proceedings of the Korean Society for Cognitive Science Conference
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• 2000.06a
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• pp.303-308
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• 2000

본 논문에서는 영한기계번역 시스템에서 한국어 문장을 생성할 때 올바른 한국어 어순 규칙을 제안한다. 한국어 생성은 영한기계번역의 최종 단계로서 이전단계에서 얻어진 정보를 가지고 목적 언어인 한국어 문장을 만드는 곳이다. 본 논문에서 제안하는 계층적 어순 생성 규칙은 한국어 의존구조를 기본으로 하며 규칙 적용은 4가지 함수를 단계적으로 적용시킨다. 인터넷의 발들은 언어 장벽이라는 새로운 문제를 부각시켰으며 이를 위해서 기계번역은 활발히 연구가 진행되고 있는 분야이다. 한국어 문장에 대하 올바른 어순 생성 규칙은 번역 결과의 품질을 증가시키며, 기계 번역뿐만 아니라 한국어 생성을 필요로 하는 모든 시스템에 적용할 수 있다.

• Annual Conference on Human and Language Technology
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• 2000.10d
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• pp.303-308
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• 2000

본 논문에서는 영한기계번역 시스템에서 한국어 문장을 생성할 때 올바른 한국어 어순 규칙을 제안한다. 한국어 생성은 영한기계번역의 최종 단계로서 이전단계에서 얻어진 정보를 가지고 목적 언어인 한국어 문장을 만드는 곳이다. 본 논문에서 제안하는 계층적 어순 생성 규칙은 한국어 의존구조를 기본으로 하며 규칙 적용은 4가지 함수를 단계적으로 적용시킨다. 인터넷의 발달은 언어 장벽이라는 새로운 문제를 부각시켰으며 이를 위해서 기계번역은 활발히 연구가 진행되고 있는 분야이다. 한국어 문장에 대한 올바른 어순 생성 규칙은 번역 결과의 품질을 증가시키며, 기계 번역뿐만 아니라 한국어 생성을 필요로 하는 모든 시스템에 적용할 수 있다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.372-372
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• 2007

유기 발광 소자에서의 내장 전압을 변조 광전류를 이용하여 측정하였다. 내장 전압은 양극의 일함수와 음극의 일함수 차이에 해당한다. 실험적으로는 유기 발광 소자에 500W Xenon light(ORIEL Instruments 66021)로부터 나온 빛을 chopper(Stanford Research SR540)를 통해 유기 발광 소자에 조사시키면 소자에서 발생한다. 변조 광전류를 lock-in amplifier(Stanford Research SR530)를 이용하여 변조 광전류의 크기와 위상을 측정할 수 있다. 이때 변조 광전류 크기가 최소가 될 때의 외부 인가 전압을 내장 전압이라고 한다. 본 연구에서 사용한 소자의 구조는 양극/$Alq_3$/음극 구조이며, 양극으로는 ITO 혹은 ITO/PEDOT:PSS를 사용하였고, 음극으로는 Ba/Al을 사용하였다. 발광 층으로는 $Alq_3$(150nm)를 사용하였다. Ba층의 두께는 0nm에서 3nm까지 변화시켰다. Ba이 금속의 역할을 하기 위해서는 두께가 20nm 이상은 되어야 한다. 그러나 본 연구에서는 Ba의 두께가 최대 3nm이므로 금속의 역할은 하지 않을 것으로 예상되며, 음극의 일함수에 약간의 영향을 주었을 것으로 생각된다. 내장 전압은 ITO/$Alq_3$(150nm)/Ba/Al 소자 구조에서 1V를 얻었고, ITO/PEDOT:PSS/$Alq_3$(150nm)/Ba/Al 소자 구조에서는 2V로 나타났다. ITO와 Ba/Al 전극 사이에 PEDOT:PSS 층을 주입함으로써 내장 전압은 약 1V 증가하였다. 이것으로, Ba의 두께가 얇으면 음극의 전자 주입 장벽에 영향을 거의 미치지 않는다는 것을 알 수가 있다.

• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.290-294
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• 2010

We performed a density functional theory study to investigate the intercalation voltage and lithium ion conduction in lithium cobalt oxide for lithium ion battery as a function of the lithium concentration. There were two methods for the intercalation of lithium ions; the intercalation of a lithium ion at a time in the individual layer and the intercalation of lithium ions in all the sites of one layer after all the sites of another layer. The average intercalation voltage was the same value, 3.48 V. However, we found the former method was more favorable than the latter method. The lattice parameter c was increased as the increase of the lithium concentration in the range of x < 0.25 while it was decreased as increase of the lithium concentration in the range of x > 0.25. The energy barrier for the conduction of lithium ion in lithium cobalt oxide was increased as the lithium concentration was increased. We demonstrated that the decrease of the intercalation voltage and increase of the energy barrier as the increase of the lithium concentration caused lower output voltage during the discharge of the lithium ion battery.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.2015-2020
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• 2012

The subthreshold characteristics has been analyzed to investigate the effect of two gate in Double Gate MOSFET using impact factor based on scaling theory. The charge distribution of Gaussian function validated in previous researches has been used to obtain potential distribution in Poisson equation. The potential distribution was used to investigate the short channel effects such as threshold voltage roll-off, subthreshold swings and drain induced barrier lowering by varying impact factor for scaling factor. The impact factor of 0.1~1.0 for channel length and 1.0~2.0 for channel thickness are used to fit structural feature of DGMOSFET. The simulation result showed that the subthreshold swings are mostly effected by impact factor but are nearly constant for scaling factors. And threshold voltage roll-off and drain induced barrier lowering are also effected by both impact factor and scaling factor.

• 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.

• Journal of the Korean Chemical Society
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• v.34 no.3
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• pp.239-247
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• 1990

The gas-phase S_N2$ reactions can be classified into neutral bimolecular, solvated, and ionic reactions; the neutral bimolecular reaction proceeds via retention mechanism whereas the ionic reaction produces inversion products. In the reaction of solvated nucleophile with one solvent molecule, a six-center transition state (TS) is formed and the two processes i.e., retention and inversion, are found to compete with a favored path depending on the electronic effect of the nucleophile and substituents in the substrate and on the steric requirement. In the ionic reaction, the difference in the energy barrier between the two processes reduces to a small value when the substrate methyl group is made bulky, leaving ability of the leaving group is improved and at the same time the negative charge of the nucleophile is dispersed. When the reaction center atom in the $S_N2$ reaction is changed to a larger sized second row elements, the activation barrier decreases since the steric crowding in the penta-coordinated TS is relieved. However within the same row, the barrier was found to increase as the atomic size decreased. For the boron, B, the barrier height was the least since in addition to the relatively large atomic size compared to C and N, it forms tetra-coordinated TS so that the steric crowding becomes nearly negligible.

• Journal of the Korean Data and Information Science Society
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• v.25 no.2
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• pp.403-410
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• 2014

Binary logistic regression analysis is a statistical technique that explains binary response variable by quantitative or qualitative explanatory variables. In the binary logistic regression model, the probability that the response variable equals, say 1, one of the binary values is to be explained as a transformation of linear combination of explanatory variables. This is one of big barriers that non-statisticians have to overcome in order to understand the model. In this study, an educational tool is developed that explains the need of the binary logistic regression analysis using Excel VBA. More precisely, this tool explains the problems related to modeling the probability of the response variable equal to 1 as a linear combination of explanatory variables and then shows how these problems can be solved through some transformations of the linear combination.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.6
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• pp.556-561
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• 2022

Computational material science as an application of Density Functional Theory (DFT) to the discipline of material science has emerged and applied to the research and development of energy materials and electronic materials such as semiconductor. However, there are a few difficulties, such as generating input files for various types of materials in both the same calculating condition and appropriate parameters, which is essential in comparing results of DFT calculation in the right way. In this tutorial status report, we will introduce how to create crystal structures and to prepare input files automatically for the Vienna Ab initio Simulation Package (VASP) and Gaussian, the most popular DFT calculation programs. We anticipate this tutorial makes DFT calculation easier for the ones who are not experts on DFT programs.