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유기금속화학증착법으로 유리기판 위에 성장된 산화아연 하이브리드 구조의 광학적 전기적 특성
김대식,강병훈,이창민,변동진,Kim, Dae-Sik,Kang, Byung Hoon,Lee, Chang-Min,Byun, Dongjin 한국재료학회 2014 한국재료학회지 Vol.24 No.10
A zinc oxide (ZnO) hybrid structure was successfully fabricated on a glass substrate by metal organic chemical vapor deposition (MOCVD). In-situ growth of a multi-dimensional ZnO hybrid structure was achieved by adjusting the growth temperature to determine the morphologies of either film or nanorods without any catalysts such as Au, Cu, Co, or Sn. The ZnO hybrid structure was composed of one-dimensional (1D) nanorods grown continuously on the two-dimensional (2D) ZnO film. The ZnO film of 2D mode was grown at a relatively low temperature, whereas the ZnO nanorods of 1D mode were grown at a higher temperature. The change of the morphologies of these materials led to improvements of the electrical and optical properties. The ZnO hybrid structure was characterized using various analytical tools. Scanning electron microscopy (SEM) was used to determine the surface morphology of the nanorods, which had grown well on the thin film. The structural characteristics of the polycrystalline ZnO hybrid grown on amorphous glass substrate were investigated by X-ray diffraction (XRD). Hall-effect measurement and a four-point probe were used to characterize the electrical properties. The hybrid structure was shown to be very effective at improving the electrical and the optical properties, decreasing the sheet resistance and the reflectance, and increasing the transmittance via refractive index (RI) engineering. The ZnO hybrid structure grown by MOCVD is very promising for opto-electronic devices as Photoconductive UV Detectors, anti-reflection coatings (ARC), and transparent conductive oxides (TCO).
농촌그린빌리지 조성을 위한 일별 잠재적 태양광발전량의 적정확률분포형 추정 - 서산지역을 중심으로 -
김대식,구승모,남상운,Kim, Dae-Sik,Koo, Seung-Mo,Nam, Sang-Woon 한국농공학회 2008 한국농공학회논문집 Vol.50 No.6
Photovoltaic power generation is currently being recognized as one of the most popular sources for renewable resources over the country. Although it is also being adapted to rural area for may reasons, it is important to estimate the magnitudes of power outputs with reliable statistical methodologies, while applying historical daily solar energy data, for correct feasibility analysis. In this study, one of the well-known statistical methodologies is employed to define the appropriate probability distributions for monthly power outputs for the selected rural area, county of Seo-san, province of Chungnam. The results imply that the assumption of normal distributions for several months may lead to incorrect decision-making and therefore lead to the unreliable feasibility analysis. Generalized beta and triangular distributions were found to be superior to normal distribution, when describing monthly probability distributions for daily photovoltaic power. Based on the appropriate distributions resulted from this study, Monte Carlo simulation technique was also applied to provide additional flexible information for the relevant decision makers. This study found out new finding that the probability distributions should be considered to make planning of the photovoltaic power system in rural village unit, in order to give reasonable economic analysis to the decision makers.
선박충돌 위기상황에서 선박운항자가 지각한 충돌위험도 분석
김대식,임정빈,Kim, Dae Sik,Yim, Jeong Bin 대한인간공학회 2017 大韓人間工學會誌 Vol.36 No.5
Objective: The purpose of this study is to present the basic guidelines for preventing human error by measuring and analyzing the risk of collision perceived by the ship operator in the collision risk situation by using Korea Coast Guard patrol ships. Background: In the last 5 years, 97.5% of the causes of ship collision occurred at the sea was caused by human factors. However, the rate of marine accidents due to human error has not been reduced yet. Experiments and researches on the ship operators using the ships in actual operation are rarely performed. Method: Using two K.C.G Ships on the sea, the ship measured by 30 persons who are the subject of the ship (ship operator) when both ships approach and the relative distance gradually decreases in four encounter situations, perceived ship collision risk (PSCR) data were analyzed by statistical analysis. Results: The age and boarding career of the ship operator in the situation of ship collision risks encountered a negative impact on perceived collision risk in all four opposing encounter situations S1 ($000^{\circ}$), S2 ($045^{\circ}$), S3 ($090^{\circ}$) and S4 ($135^{\circ}$) respectively. That is, the higher the age of the ship operator, the lower the perceived risk of collision and the lower the age, the higher the risk of collision. Also, there was a difference between the average of group A (20~30 years) and group B (40~50 years) according to age of the ship operators at $000^{\circ}$, $045^{\circ}$ and $090^{\circ}$ and there was no difference at $135^{\circ}$. The mean difference of the experience of boarding career was also significantly different between group A (less than 4 years) and group B (more than 5 years), but there was no significant difference at $135^{\circ}$. Conclusion: The results showed that age and boarding career of the ship operators had negative impact on perceived collision risk and there was a difference in perceived risk of collision according to age and abundance of boarding career. As a result, by focusing on the ship operators who are in the age group of 20~30 years old and have less than 4 years of experience in boarding the ship. It is expected that the effect of prevention of marine accidents can be expected by avoiding collision avoidance. Application: The results of this study can be used as policy data of related organizations to prevent human error of ship operators and as training data of training institutes.
농촌 그린빌리지 계획을 위한 일별 풍력발전량의 적정확률분포형 추정
김대식,구승모,남상운,Kim, Dae-Sik,Koo, Seung-Mo,Nam, Sang-Woon 한국농공학회 2008 한국농공학회논문집 Vol.50 No.6
This study aims to estimate the optimal probability distribution of daily electricity generation by wind power, in order to contribute in rural green-village planning. Wind power generation is now being recognized as one of the most popular sources for renewable resources over the country. Although it is also being adapted to rural area for may reasons, it is important to estimate the magnitudes of power outputs with reliable statistical methodologies while applying historical daily wind data, for correct feasibility analysis. In this study, one of the well-known statistical methodology is employed to define the appropriate statistical distributions for monthly power outputs for specific rural areas. The results imply that the assumption of normal distributions for many cases may lead to incorrect decision-making and therefore lead to the unreliable feasibility analysis. Subjective methodology for testing goodness of fit for normal distributions on all the cases in this study, provides possibilities to consider the other various types of statistical distributions for more precise feasibility analysis.
김대식,권용대,Kim, Dae-Sik,Kwon, Yong-Dae 한국농공학회 2009 한국농공학회논문집 Vol.51 No.3
This study tried to develop a tentative evaluation system on greentourism potentials(GTP) of rural villages. The GTP evaluation system consisted of 45 detail criteria within three kinds of large scale criteria, which are human resources of residents capability, amenity resources of tourists attraction, and income resources through exchange activity between rural and urban areas. The evaluation criteria were adapted from several decades existing studies considering the hardware(facility and amenity resources) and software(human resources and programs on tourism)resources in rural villages. Two kinds of test study areas, which are subdivisions of county in a typical rural area(Boori) and an suburbanized area surrounding a big city(Chooboo), located on Keumsan county in Chungnam province, were selected to test the GTP evaluation system. The results showed that the average GTP values of each village in Boori are higher than those of Chooboo, due to higher values in criteria on amenity resources and income resources, which the typical rural area may have higher value in such criteria.