• Proceedings of the Korean Society of Crop Science Conference
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• 2002.10a
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• pp.58-58
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• 2002

• Korean Journal of Materials Research
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• v.4 no.6
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• pp.687-694
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• 1994

Heteroepitaxial InP/GaAs layers were grown using the selective liquid phase epitaxy (SLPE) technique. It was observed that the optimum LPE conditions were $660^{\circ}C$ growth temperature, $5^{\circ}C$ supercooling, and $0.4^{\circ}C$/min cooling rate. Maximum expitaxial layer overgrowth (ELO) of 110-160$\mu \textrm{m}$ was obtained when the seed was aligned along (112) orientation. Initial melt-back of the substrate was observed but limited to the seed region so that flat In-Ga-As-P layers were grpwn throughout the GaAs substrates. The InP/GaAs heteroepitaxial structure could be obtained by growing an additional InP layer on top of the In-Ga-As-P layer.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2165-2170
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• 2007

At nanoscales, the Boltzmann transport equation (BTE) can best describe the behavior of phonons which are energy carriers in crystalline materials. Through this study, the phonon transport in some micro/nanoscale problems was simulated with the Monte Carlo method which is a kind of the stochastic approach to the BTE. In the Monte Carlo method, the superparticles of which the number is the weighted value to the actual number of phonons are allowed to drift and be scattered by other ones based on the scattering probability. Accounting for the phonon dispersion relation and polarizations, we have confirmed the one-dimensional transient phonon transport in ballistic and diffusion limits, respectively. The thermal conductivity for GaAs was also calculated from the kinetic theory by using the proposed model. Besides, we simulated the electrostatic discharge event in the NMOS transistor as a two-dimensional problem by applying the Monte Carlo method.

• Proceedings of the KIEE Conference
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• 1999.11a
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• pp.43-51
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• 1999

The power flow calculations(PFc) are the most important and powerful tools in power systems engineering. The conventional power flow problem is solved generally with numerical methods such as Newton-Raphson(NR). The conventional numerical method generally have some convergency problem, which is sensitive to initial value, and numerical stability problem concerned with jacobian matrix inversion. This paper presents a new PFc algorithm based on the improved genetic algorithm (IGA) which can overcome the disadvantages mentioned above. The parameters of GA, with dynamical hierarchy of the coding system, are improved to make GA a practical algorithm in the problem of real system. Some case studies with test bus system also present to show the performance of proposed algorithm. The results of proposed algorithm are compared with the results of PFc obtained using a conventional NR method.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.350-353
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• 2000

This paper presents an algorithm for Optimal Reactive Power Dispatch(ORPD) problem based on genetic algorithm. Optimal reactive power dispatch is particularized to the minimization of transmission line losses by suitable selection of generator reactive power outputs and transformer tap settings. To reduce system loss and improve voltage profile, two methods, Loss Re-Distribution Algorithm (LRDA) and Voltage Dependent Load Model (VDLM), are applied to ORPD. The proposed methods have been evaluated on the IEEE 30 bus system. Each of results have been compared with result of load flow.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.214-217
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• 2002

The chromosomes of Genetic Algorithm(GA) are classified to be good or not to be by Support vector machines(SVM), and then the only good chromosomes are adopted to the evolution process. By this way, computational load becomes low, so the evolution speed of Genetic Algorithm modified by SVM can be much accelerated than the conventional GA.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.52-54
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• 2019

본 논문에서는 Anyplace Induction Cooktop 시스템의 설계 방안을 제시한다. 다수의 워킹코일이 적용된 Anyplace 시스템은 전력밀도 향상을 위해 고주파 동작이 필요하다. 따라서 시뮬레이션 및 수학적 계산을 통한 동작 주파수, 전력 반도체 소자 조건 별 시스템의 손실 및 부피 간 Trade-off 분석이 필요하다 따라서 분석 결과를 토대로 각 전력반도체 소자 기반 시스템의 적합한 동작 주파수 영역 및 공진 네트워크 설계 방안을 제시한다.

• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.237-242
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• 2006

Nowadays, LEDs has been applied to the luminescent devices of various fields because of the invention of high efficient blue chip. Recently, especially, the white LEDs composed of InGaN blue chips and a yellow phosphor (YAG:Ce3+) have been investigated extensively. With the exception of YAG:Ce3+ phosphor, however, there are no reports on yellow phosphor that has significant emission in the 450~470 nm excitation range and this LED system is the rather low color rendering index due to their using two wavelength. Hence, we have attempted to synthesize thiogallate phosphors that efficiently under the long wavelength excitation range in the present case. Among those phosphors, we have synthesized Sr2Ga2S5:Eu2+ phosphor by change the host material of SrGa2S4:Eu2+ which is well known phosphor and we investigated the luminescent properties. In order to obtain the harmlessness and simplification of the synthesis process, sulfide materials and mixture gas of 5 % H2/95 % N2 were used instead of the CS2 or H2S gas. The prepared phosphor shows the yellow color peaking at the 550 nm wavelength and it possible to emit efficiently under the broad excitation band in the range of 300~500 nm. And this phosphor shows high luminescent intensity more than 110 % in comparison with commercial YAG:Ce3+ phosphor and it can be applied for UV LED due to excitation property in UV region.

• Korean Journal of Medicinal Crop Science
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• v.23 no.5
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• pp.379-384
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• 2015

Background : Considerable time and effort is required to develop new Panax ginseng varieties. Ginseng breeders have been developing techniques to shorten the breeding cycle to resolve this problem. In this study, we investigated the effects of adding $GA_3$ and alternating temperature (AT, $2^{\circ}C{\rightarrow}-2^{\circ}C{\rightarrow}2^{\circ}C$) on breaking bud dormancy in the varieties (Chungsun and Sunun) of ginseng root. Methods and Results : The $GA_3$ soaking treatment and AT were applied to one year old roots, which greatly accelerated the emergence of new buds. In one year old roots, new buds emerged from the 4th day post transplanting and after breaking dormancy with $GA_3$ and AT treatments. The emergence of new buds was completed within two weeks. The rate of bud emergence for Chungsun was 60% - 98% over 15 - 60 days after the AT and $GA_3$ treatments. The emergence rate of Sunun was 46% - 92%. Normal growth of the ginseng seedling was observed in spite of the early breaking of bud dormancy by combined $GA_3$ and AT treatments. Conclusions : $GA_3$ and AT treatments shortened the dormancy period and facilitated the stable emergence of ginseng seedlings. However, some plants suffered deformities and early sprouting owing to the combined $GA_3$ and AT treatments. Early sprouting was free from dormancy after leaf fall from the of aerial part of the plant.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.7
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• pp.567-571
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• 2009

Polycrystalline ZnO and Ga doped ZnO (GZO) films are deposited on glass substrate by RF magnetron sputtering at room temperature. The characteristics of ZnO and GZO films are investigated with X-ray diffraction measurement, UV-VIS-NIR spectrophotometer $(250{\sim}1200nm)$ and hall measurement. The post-growth thermal treatment of these films is carried out in N2 ambient at $500^{\circ}C$ for 30 min and an hour. ZnO and GZO films have different changing behavior of structural and optical properties by annealing. To use transparent conductive films for solar cell, films should have not only high transmittance but also good electrical property. Although as deposited GZO films have electrical properties than ZnO films, GZO films have not good transmittance properties. Consequently, we succeed that the high transmittance of GZO films is improved by annealing process.