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ZnSe/GaAs 이종접합 구조에서의 광전류에 관한 연구
조현준,배인호,손정식 한국물리학회 2007 새물리 Vol.55 No.5
The properties for the interface barrier of a ZnSe/GaAs heterojunction structure grown by using molecular beam epitaxy were investigated using photocurrent spectroscopy. The derivative photocurrent (DPC) at 300 K indicated that the band-gap energies of GaAs and ZnSe were 1.38 and 2.66 eV, respectively. The effect of the interface barrier between ZnSe and GaAs was relaxed gradually with increasing forward bias. The low-temperature result showed that the defect states increased the conduction current or acted as a trapping level decreasing the conduction current as the direction of conduction The dependence of the light power on indicated that the photocurrent under a low bias voltage flowed in a direction opposite to that of the conduction current and that the conduction current decreased. 반절연성 GaAs 위에 molecular beam epitaxy (MBE)법으로 성장시킨 ZnSe/GaAs 이종접합 구조에서 계면장벽에 의한 특성을 광전류 분광법 (photocurrent spectroscopy)으로 조사하였다. 1차 미분 광전류 (derivative photocurrent) 스펙트럼을 이용하여 구하여진 상온에서의 GaAs와 ZnSe의 띠 간격 에너지는 각각 1.38, 2.66 eV 이었다. 순방향으로 인가된 바이어스 전압이 증가할 수록 ZnSe층과 GaAs층 사이의 계면장벽이 점차 완화되었다. 저온 실험으로부터 계면에서의 불순물 준위가 전도전류의 방향에 따라 전도전류에 기여하거나 약화시키는 트랩준위로 작용하였다. 그리고 작은 인가 바이어스 전압에 대하여 입사광 세기 의존성을 측정한 결과 광전류가 전도전류와 반대방향으로 흐르게 되어 전도전류를 감소시켰다.
과학자의 과학적 탐구과정에서 나타나는 귀추적 추론 분석틀 개발
조현준,정선희,양일호 한국지구과학회 2008 한국지구과학회지 Vol.29 No.7
The purpose of this study was to identify the scientists' abductive reasoning in three stages of hypothetical-deductive inquiry process; generating hypothesis, designing, and interpreting data and to suggest new analytic coding frames on abductive reasoning in each of the stages. For this purpose, the interview protocols collected through in-depth interviews with eight scientists were analyzed by the early frame with sub-elements derived from the literature reviews. The need of a new frame of analysis beyond the previously established elements arose from the result of this analysis because the processes of abductive reasoning were found in all three stages. Based on scientists’ interview data, this study then designed a new frame of analytic coding frames on the abductive reasoning in each of the stages. The content validity index from four experts was 0.90, and these frames showed a good fit to analyze the scientists' real process of abduction in three stages of hypothetical-deductive inquiry process. 본 연구의 목적은 과학자의 가설-연역적 탐구과정에서 가설설정단계, 실험설계단계, 결과해석단계에서 귀추적 추론이 나타나는지를 확인하고, 각각의 단계에서의 귀추적 추론과정을 분석하기 위한 분석틀을 제안하는 데 목적이 있다. 이를 위해, 8명의 과학자들과의 심층면담을 통해 얻은 프로토콜을, 기존 문헌에서 추출한 귀추적 추론과정의 하위요소로 분석해 보았다. 그 결과, 과학자의 귀추적 추론이 세 단계 모두에서 나타나고 있어 기존요소에 의한 분석틀을 벗어난 새로운 분석틀이 요구되었다. 그 결과 과학자들과의 심층면담을 통해 탐구의 각 단계에서 나타나는 귀추적 추론 분석틀을 새롭게 개발하였다. 이 틀을 과학교육전문가로부터 타당성 확인 결과, 내용타당도 지수 0.90을 얻어 타당한 것으로 인정되었으며, 실제로 과학자의 탐구과정에서 나타나는 귀추적 추론과정을 분석한 결과 매우 적절한 것으로 확인되었다.
A Study on Soil Suitability Criteria for Adzuki Bean
조현준,현병근,손연규,허승오,신국식 한국토양비료학회 2014 한국토양비료학회지 Vol.47 No.6
Soil properties and yields of red been were investigated to establish soil suitability of Korean adzuki bean at166 farms in Korea. The soil morphological and physical properties were investigated by 1:5,000 scaleaverage yield of 2~3 years. The impact factors to the adzuki bean yields and soil properties were selected basedon standard error of each factor. The yields of adzuki bean showed the greatest values when the morphologywas alluvial plains, the drainage was well or moderately well, the slope was 2~7%, the texture was fine loamy,the gravel content was less than 15% and the available soil depth was more than 100 cm. Contribution factorsof soil properties to the yields were 0.18 of morphology, 0.18 of drainage level, 0.23 of slope, 0.20 of texture,0.11 of gravel content and 0.10 of available soil depth, respectively. Soil suitability levels were set as the bestsuitable land if score was greater than 90, suitable land if score ranged from 89 to 85, the possible land if thescore ranged from 79 to 84 and low productive land if score was less than 78. According to the criteria 37.5%of the production area was the best suitable land, 29.4% was suitable land, 22.3% was possible land and 10.8%was low productive land. The best and suitable lands were total of 66.9% in Gyeongju, Gyeosangbuk-do.
A comparative study of teaching-learning-self-study algorithms on benchmark function optimization
조현준,Faisal Ahmed,김태영,김범석,여영구 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.3
In typical optimization problems, the number of design variables may be large and their influence on the specific objective function can be complicated; the objective function may have some local optima while most chemical engineers are interested only in the global optimum. For any new optimization algorithms, it is essential to validate their performance, compare with other existing algorithms and check whether they provide the global optimum solutions, which can be done effectively by solving benchmark problems. In this work, seven typical optimization algorithms including the newly proposed TLBO (Teaching-learning-based optimization) based algorithms such as the TLSO (Teaching-learning-self-study optimization) algorithm have been reviewed and tested by using a set of 20 benchmark functions for unconstrained optimization problems to validate the performance and to assess these optimization algorithms. It was found that the TLSO algorithm shows the fastest convergence speed to the optimum and outperforms other algorithms for most test functions.