• 전자공학회논문지SC
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• 제44권3호
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• pp.45-50
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• 2007

1550nm의 파장대를 이용하는 자동 위상보정 양자암호 시스템을 소개한다. 양자키 분배 시스템에서 자동위상보정된 양자키 분배를 위한 메인 컨트롤보드와 phase modulator를 제어할 수 있는 보드를 제작하였고, 단일광자검출기를 위한 dark count당 photon count, quantum key distribution rate($R_{sift}$)와 quantum bit error rate(QBER)값을 측정하였다. 이 시스템은 25km의 광섬유상에서 quantum bit error rate(QBER) 3.5%의 결과값을 얻었고, 이는 상용화가 가능할 것으로 예상된다.

• 전기학회논문지
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• 제62권4호
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• pp.467-473
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• 2013

The addition of disconnect switches to a distribution feeder or the replacement of the manual switches with the automatic switches do, in general, increase reliability by decreasing the duration of the outage of many to the customers on the feeder and reducing the outage section. However, the improvement of reliability in power distribution system causes an increase of the investment cost, for example, replacement costs, labor costs, and so on. For this reason - the balance between investment and reliability improvement - many studies about the appropriate level of investment have been conducted. In this paper, we suggest the algorithm for determining the reasonable switch automation rate in the power distribution system. We evaluate the customer interruption cost and reliability for several cases - these cases relate with the switch automation rate - in the domestic metropolitan power distribution system, estimate the effectiveness of changing the manual switch to automatic switch quantitatively. These results can help the determining on the disconnect switch's automation rate.

• 전기학회논문지
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• 제63권3호
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• pp.331-337
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• 2014

The Korean distribution system consists of overhead ground wire (OHGW), phase conductors and neutral wire. Especially, OHGW is installed over the phase conductors to protect distribution system from the lightning surge. The flashover rate and the magnitude of lightning overvoltage on distribution system can be affected by grounding condition of OHGW such as grounding resistance and grounding interval. In this paper, we conduct an analysis of lightning overvoltage and flashover rate according to the grounding condition of OHGW. The distribution system and lightning surge are modeled by using ElectroMagnetic Transient Program (EMTP). Also, the Monte Carlo method is applied to consider random characteristics of lightning, and the flashover rate is calculated based on IEEE std. 1410. The simulations are performed by changing the grounding resistance and interval of OHGW and the simulation results are analyzed.

• 대한기계학회논문집
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• 제14권6호
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• pp.1561-1567
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• 1990

본 연구에서는 고강도 알루미늄합금 A12024-T3재의 통계적시험에 의하여 시험 편두께가 피로크랙 진전속도의 분포에 미치는 영향을 밝히고자 하며, 또한, 통계적시 험의 능률화 및 일관성을 꾀하기 위하여 개발한 새로운 유형의 자동화 다단식 피로시 험기의 개략을 밝힌다.

• 대한기계학회논문집
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• 제19권8호
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• pp.1940-1949
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• 1995

A numerical study for a two dimensional multi-jet with crossflow of the spent fluid has been carried out. Three different distributions of mass-flow rate at 5 jet exits were assumed to see their effects upon the flow characteristics, especially in the jet-flow region. For each distribution, various Reynolds numbers ranging from laminar to turbulent flows were considered. Results show that a fully developed laminar flow exists above a certain Reynolds number whose exact value depends upon the mass flow rate distribution. AS the Reynolds number increases, the flow becomes transitional from downstream and finally a fully developed turbulent flow forms in the jet-flow region. The critical Reynolds number where the fully developed turbulent flow forms is quite dependent upon the distribution of mass-flow rate. One interesting result is that the distribution of the skin friction coefficient along the inpingement plate in the jet-flow region shows a consistent dependency on the Reynolds number, i.e. inversely proportional to the square root of the Reynolds number, regardless of flow regime.

• 산업경영시스템학회지
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• 제28권3호
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• pp.26-35
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• 2005

This paper is intended to compare the hazard rate estimations from Bayesian approach and maximum likelihood estimate(MLE) method. Hazard rate frequently involves unknown parameters and it is common that those parameters are estimated from observed data by using MLE method. Such estimated parameters are appropriate as long as there are sufficient data. Due to various reasons, however, we frequently cannot obtain sufficient data so that the result of MLE method may be unreliable. In order to resolve such a problem we need to rely on the judgement about the unknown parameters. We do this by adopting the Bayesian approach. The first one is to use a predictive distribution and the second one is a method called Bayesian estimate. In addition, in the Bayesian approach, the prior distribution has a critical effect on the result of analysis, so we introduce the method using computerized-simulation to elicit an effective prior distribution. For the simplicity, we use exponential and gamma distributions as a likelihood distribution and its natural conjugate prior distribution, respectively. Finally, numerical examples are given to illustrate the potential benefits of the Bayesian approach.

• 방사선산업학회지
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• 제4권1호
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• pp.85-89
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• 2010

The radioactive experiments are carried out for diagnosis of a variety of industrial processes in terms of the operation condition and the efficiency by measuring the residence time distribution. However, it is not easy to interpret the residence time distribution using the conventional methods when the flow rate is not constant and a number of processes are coupled in a complicated manner. In these cases, they can be analyzed by describing the system with mathematical models that can be defined with the state-space equations. In this paper, the residence time distribution of sludge was measured with a radiotracer, $^{46}Sc-EDTA$, in the digester of which the flow rate varies with time. The digester was assumed as a linear time variant system since the flow rate changed during the experiment and the operation efficiency of the digester was calculated by applying the state-spae equations.

• 산경연구논집
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• 제7권4호
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• pp.17-31
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• 2016

Purpose - The purpose of this study is to discuss problems and propose the direction of the current international university placement program in the country by deriving the concept of and developing questionnaires for 'service satisfaction'. Research design, data, and methodology -The SERVQUAL scale was used to measure the quality of services. In this study reliability, empathy, and assurance are used to measure the quality of the international university placement system, considering the characteristics of the education environment. The survey data is based on responses from 280 students who either have completed the international university placement system and currently studying abroad, or are studying the domestic part of the program. Cronbach's Alpha value was calculated. To verify the hypothesis, the multiple regression analysis was conducted. Results - According to the study, the satisfaction rate of the domestic learning process is heavily relied on reliability and empathy; particularly empathy on the curriculum of the international placement program. The study also found that to make students to feel a high sense of achievement, the satisfaction rate is a priority which should be improved. Conclusions - The results from the analysis of the hypothesis shows that the satisfaction rate of students who are taking the domestic part of the international university placement program should be increased.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.34-37
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• 1998

Signal Attenuation in the design of satellite channel is due mostly to rain. In this paper, the rain rate characteristics based on the recent year(1994-1996) data for Changwon-Masan were approximated to Moupfouma distribution, and the parameters of distribution were calculated from a simple conversion method of 1-h rate to 1-min rain rate data. From rain rate characteristics, the rain attenuation was estimated and compared with CCR model, Global model and SAM model.

• 수산해양기술연구
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• 제28권3호
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• pp.243-251
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• 1992

The author examined the response of File fish, Stephanolepis Cirrhifer (TEMMINCK et SCHLEGEL) to the surface attracting lamps(0.5W, 0.8W, 1W) line in the experimental water tank (550L$\times$58W$\times$73H cm). the attracting rate was investigated in accordance with the interval of lighting and putting out hour (1, 5 minute)when each of the attracting lamps was gradually switched off after they were switched on all at once. The results are as follows: 1. Total distribution rate of fish in the illuminated section was 96.9%(mean 19.4%) in case of 1 minute interval, and 98.4%(mean 19.7%) in case of 5 minutes interval. 2. Mean distribution rate of fish at the illuminated section: \circled1 Distribution rate at interval of 1 minute were 19.9% in 0.8W, 19.3% in 1W and 18.9% in 0.5W respectively. \circled2 Distribution rate at interval of 5 minutes were 19.8% in 1W, 19.8% in 0.8W, and 19.5% in 0.5W respectively. 3. Attracting rate of the last section showed increasing as illuminating time elapse without interval and lighting source. 4. Attracting rate of fish in only last section switched on: \circled1 Attracting rate at interval in case of 1 minute were 98.0% in 1W, 97.0% in 0.5W and 83.0% in 0.8W respectively. \circled2 Attracting rate at interval in case of 5 minutes were 99.3% in 1W, 97.3% in 0.5W and 93.3% in 0.8W respectively.