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이중강압 DC-DC 컨버터를 이용한 새로운 LED 전류 밸런싱 기법
김기수(Kisu Kim),도 득 뜨완(Do Duc Tuan),김흥근(Heung-Geun Kim),차헌녕(Honnyong Cha) 대한전기학회 2017 전기학회논문지 Vol.66 No.10
This paper presents a new LED current balancing scheme using double-step-down dc-dc converter. With the proposed structure, the two channel LED currents are automatically balanced without using any dedicated control or auxiliary circuit. In addition, switching loss of the switching devices in the proposed LED driver is lower than that of the conventional buck LED driver. To verify the operation of the proposed LED driver, a hardware prototype is built and tested with different number of LED.
하프-브리지 구조 DAB 컨버터를 위한 새로운 전압 밸런서
김기수(Kisu Kim),차헌녕(Honnyong Cha) 대한전기학회 2020 전기학회논문지 Vol.69 No.6
This paper proposes an application of artificial neural networks for analyzing electricity market that has insufficient information for calculating equilibrium. Neural networks are constructed and trained on two representative cases in the electricity market. One is for calculating equilibrium price in perfect competition market and the other is for determining whether the transmission congestion occurs. The neural network uses a multilayer structure and learns with backpropagation algorithms for training. The neural networks trained in the case studies calculate the market price with a high probability and also determines an occurrence of the transmission congestion accurately.
김기수(Kisu Kim),신춘식(Choonsik Shin),윤성민(Sungmin Yoon),박창규(Changkyu Park),강경훈(Kyeonghoon Kang) 한국추진공학회 2011 한국추진공학회 학술대회논문집 Vol.2011 No.11
군에서 사용하는 탄약의 보관 및 취급상 발생할 수 있는 외형결함을 가정하여 그것이 사거리에 미치는 영향을 예측하였다. 외형결함은 탄체두부의 오자이브 형상에 각 1.5mm, 3.3mm의 축대칭 함몰부가 생기는 것으로 가정하였다. FLUENT를 사용하여 마하수 별 항력계수를 해석하였고, 탄도해석 프로그램인 PRODAS에 항력계수 데이터를 입력하여 탄도해석을 하였다. 공력해석결과 1.5mm, 3.3mm 함몰 탄체의 항력증가율은 정상탄체와 비교했을 때 아음속 영역에서는 큰 차이를 보이지 않았으나, 초음속 영역에서 각각 평균 3%, 9% 의 증가율을 보였다. 최대 사거리는 포구속도 650m/s를 기준으로 각각 1%, 3% 감소한 결과를 보였다. Projectile can be damaged during the storage and handling. Maximum range calculation of the ammunition was performed on the assumption that each projectiles have 1.5mm/3.3mm axisymetric dent on the surface. Drag coefficient for trajectory calculation was delivered from CFD using commercial software FLUENT. In the result of CFD, damaged projectiles those have 1.5mm/3.3mm axisymetric dent have similar drag coefficient compare with normal projectile in the region of subsonic. But, in supersonic region, drag coefficient was increased 3%, 9% each in average. In the result of trajectory calculation, Maximum rage was decreased 1%, 3% each.