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김경완 ( Kyungwan Kim ),이영진 ( Youngjin Lee ),강두선 ( Doosun Kang ),김영화 ( Younghwa Kim ) 한국농공학회 2013 한국농공학회 학술대회초록집 Vol.2013 No.-
전통적으로 농업용 급수시설은 개수로의 형태가 대부분이었으나 유지보수 및 운영의 효율이 낮은 문제점이 있어, 최근 용수공급 측면에서 보다 안정적이고 효율적인관수로 시스템으로의 전환이 이루어지고 있다. 최근 다양한 최적화 기법들을 활용한 농업용 관수로 시스템의 최적설계가 이루어지고 있다. 하지만, 결정변수가 많은 대규모 시스템의 경우에는 계산효율이 떨어져 전역해(global optima)를 발견하지 못하는 경우가 대부분이다. 본 연구에서는 관망 수리해석 프로그램인 EPANET모형과 비선형 최적화 기법인 유전자 알고리즘(Genetic Algorithm)을 연계하여 농업용 관수로 시스템의 최적관경 결정을 위한 모형을 제안하였다. 제안된 모형은 유전자 알고리즘의 초기해(Initial Population)를 단순히 무작위해(Random Solution)로 사용하는 대신, 관망 수리해석을 통해 계산된 관내 유속을 기준으로 초기전략해(Warm Initial Population)를 구성함으로써 유전자 알고리즘의 계산효율을 높이고 전역해(global optima)에 근접한 최적설계가 가능하도록 하였다. 개발된 모형을 국내 대규모 농업단지에 적용하여 최적설계를 실시하였으며, 관망형태(분기형 혹은 망형)에 상관없이 향상된 결과를 보여줌을 알 수 있었다. 본 연구에서는 초기전략해를 활용한 농업용 관수로 최적화기법을 상세히 설명하고, 그 적용절차 및 결과를 발표함으로써 향후 실무에서 적극 활용될 수 있도록 할 계획이다.
김기현(Kihyun Kim),구경완(Kyungwan Koo),김필규(Pilkyu Kim) 대한전기학회 2021 전기학회논문지 Vol.70 No.10
Jeju island has unique weather such as strong and salty wind. Thus, it is necessary to select stronger PV modules and system components because of Jeju island own harsh weather conditions. To secure safety against harsh weather, more severe tests were carried out for selections of PV. Actually, only test-passed-PV-modules were installed. Lastly, A option of PV mount rotation was added to protect against winds. Herein we will introduce its outdoor test results and guidelines for Jeju application.
김기현(Kihyun Kim),이재각(Jaegak Lee),유봉조(BongJo Ryu),김지환(Jiwhan Kim),구경완(Kyungwan Koo) 대한전기학회 2021 대한전기학회 학술대회 논문집 Vol.2021 No.5
육지부 지열의 지중열교환기 타입은 수직밀폐형, 지중수평형, 에너지파일형, 스탠딩컬럼웰형 네가지 방식으로 구분되어지며, 각 타입별 성능평가 방식은 한국에너지공단 신 · 재생에너지 설비의 지원 등에 관한 지침 중 별표1의 신 · 재생에너지 설비 원별 시공기준(제7조제1항 관련)을 적용하여 KOLAS 인증기관으로부터 별표3의 ‘1. 지중열전도도 측정기준’[1]에 따라 측정한 열전도도 값을 지열이용검토서 작성기준에 맞게 적용하여 설계한다. 그러나 제주도의 지열 지중열교환기 타입은 평가 방법이 없는 상황이다. 이에 본 연구에서는 제주형 지중열교환기 성능 평가 방법을 제안하고자 한다.
이민호(Lee, Minho),김성우(Kim, Sungwoo),김정환(Kim, Jeonghwan),김기호(Kim, Kiho),정충섭(Jung, Choongsub),노경완(Rho, Kyungwan),장광식(Jang, Kwangsik) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.11
The fuel economy estimates essentially serve two purposes : to provide consumers with a basis on which to compare the fuel economy of different vehicles, and to provide consumers with a reasonable estimate of the range of fuel economy they can expect to achieve. The current fuel economy label values utilize measured fuel economy over city driving cycles. However, this test driving mode can not be evaluated the variety factor of the real-world. These factors include differences between the way vehicles are driven on the road and over the test cycles, air conditioning use, widely varying ambient temperature and humidity, widely varying trip lengths, wind, precipitation, rough road conditions, hills, etc. The purpose of this paper is to account for three of these factors on the fuel economy : 1) on-road driving patterns (i.e. higher speeds and more aggressive driving (higher acceleration rates)), 2) air conditioning, and 3) colder temperatures. The new test methods will bring into the fuel economy estimates the test results from the five emissions tests in place today : CVS-75, HWFET, US06, SC03 and Cold CVS-75. Based on these new test methods, this paper discusses the characteristics of driving condition on Hybrid electric vehicle (HEV). And this paper assesses the fuel economy label of HEV.
지역 간 특성에 따른 소매점의 효율성 차이 및 결정요인 분석
고경완 ( Kyungwan Ko ),김대철 ( Dae Cheol Kim ) 한국생산성학회 2016 生産性論集 Vol.30 No.1
This study analyzes the relative efficiency of chain stores according to regional characteristics and identifies its factors. In this study, the efficiency of 321 chain stores is measured by DEA model and its factors are identified by Tobit regression model. Three inputs(store size, number of items, and number of employees) and two outputs(sales and number of customers) are used for the DEA model. As a result, only 3 ∼6% of the stores are efficient and the average technical efficiency score is 0.5968 and the average pure technical efficiency score is 0.6457. The efficiency of metropolitan stores is higher than that of small town stores and the efficiency of residential and commercial area stores is higher than that of residential area stores. In Tobit regression model, the DEA efficiency scores are used as dependent variables and five variables, namely store age, number of items per store size, number of items per employee, trade area index, and number of competitors are used as independent variables. The results show that store age, number of items per employee, trade area index, and number of competitors play a significant role in influencing stores` efficiency. All of five variables are statistically significant in metropolitan stores, but in small town stores so are two variables, namely store age and number of items per store size. In residential area stores number of items per store size, number of items per employee, and trade area index are statistically significant, but number of items per store size is not statistically significant in residential and commercial area stores. Managerial implications of the study are discussed.
DEA 모형을 활용한 소매점의 효율성 및 결정요인 분석
고경완(Kyungwan Ko),김대철(Daecheol Kim) 한국경영과학회 2014 經營 科學 Vol.31 No.4
This paper analyzes the operational efficiency of 91 individual retail stores in Seoul by a two-step procedure. In the first step, a data envelopment analysis (DEA) model is used to identify the efficiency scores. Three inputs (store size, number of items, and number of employees) and two outputs (sales and number of customers) are used for the efficiency measurement. In the second step, a Tobit regression model is used to identify the drivers of efficiency. DEA efficiency scores are used to test hypotheses on the impact of five independent variables, namely store age, number of items per store size, number of items per employee, trade area index, and number of competitors. Results of the Tobit analysis show that number of items per store size, number of items per employee, and number of competitors play a significant role in influencing the operational efficiency of retail stores. Managerial implications of the study are discussed.
Terahertz spectroscopy of high temperature superconductors and their photonic applications
Seo Choongwon,Kim Jeonghoon,Eom Seonhye,Kim Kyungwan,Park Hyeong-Ryeol 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.6
Development of the ultrashort pulse lasers made it possible to realize the terahertz (THz) generation and detection in a broad frequency range between 0.1 and 30 THz. Extensive studies of the superconducting materials have been performed from basic sciences to the photonic applications because the THz frequencies span the gap in the electromagnetic spectrum between the electronic and the photonic technologies. Especially, the ultrashort pulses allow us to monitor the non-equilibrium dynamics of the superconductors and develop the ultrafast switching. Starting from a brief overview of the cuprate superconductor, we review the basic optical properties and photonic applications of the superconductors in a wide range of THz frequencies. It should be noted that numerous equilibrium and non-equilibrium THz spectroscopic measurements of the high temperature superconductors demonstrated the existence of the superconducting gap and its recovery dynamics and also terahertz electromagnetic wave modulation combined with the concept of metamaterials. These superconducting metamaterials will pave the way for better understanding of the new material properties and giving new ideas in application aspects.
A Study on Development of Maintenance Skill Training Simulator for Railway Vehicle
Jung, NoGeon,Kim, BoSung,Lee, JaeBong,Lee, SangMoon,Koo, KyungWan,Kim, JaeMoon The Institute of Internet 2015 International Journal of Internet, Broadcasting an Vol.7 No.2
Generally, in the railway vehicle the driving force of gravity happens by the high-speed running and the repetitive impulse cause the degradation and the malfunction phenomenon shows differently because the durability of each component changes according to the internal and external causes. The maintenance of propulsion control device which is played the very important role as to the stable service of the railway vehicle is greatly important among them. Therefore maintenance training propulsion control device simulator is needed to maximize learning through repetition and improve the maintenance practical skills training. This paper designed the railway vehicle running device with a miniature for the railway vehicle maintenance training and developed a propulsion control device simulator equipped the imitation steering wheel.