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소프트스위칭의 연료전지용 고효율 멀티레벨 DC-DC 컨버터
김춘성(Chun-Sung Kim),김세민(Se-Min Kim),김광헌(Kwang-Heon Kim),박성준(Sung-Jun Park),정병환(Byong-Hwan Jeong),최규하(Gyu-Ha Choe) 전력전자학회 2009 전력전자학술대회 논문집 Vol.2009 No.1
This paper presents a high voltage resonant DC power converter that is using ZCS soft-switching method for fuel cells. Many converters secondary of transformer connect 3 series to input area. Resulting the converter operate high boost ratio and high efficiency. Also it is combined each filter in secondary of transformer to decrease the elements. A capacitor substitute the part of rectification diode in secondary of transformer. That is operated soft-switching with ZCS. Proposed resonant multi-level DC/DC converter verified by simulation.
전압 불평형 조건에서 스위칭 소자의 전류용량을 고려한 MMC-HVDC 순환전류 제어기법
김춘성(Chun-Sung Kim),정승환(Seung-Hwan Jung),황정구(Jung-Goo Hwang),박성미(Seong-Mi Park),박성준(Sung-Jun Park) 한국조명·전기설비학회 2016 조명·전기설비학회논문지 Vol.30 No.1
This paper proposed a new control method which is capable of controlling circulating current considering current capacity of switching device. In the unbalanced voltage conditions, active power and reactive power have double line frequency. Thus, in order to provide active power without ripple, it is necessary to inject the negative sequence current components. However, when the negative current components is injected, it increases the total current flowing in the Arm, and in the Sub-module(SM) the current more than rated is impressed, which leads to destroy the system. Also, in impressing the circulating current reference of each arm, conventional control method impressed applicable i<SUB>dck</SUB>/3 in the case of balanced voltage conditions. In the case of unbalanced conditions, as arm circulating current of three phase show difference due to the power impressed to each arm, reference of each arm is not identical. In this study, in the case of unbalanced voltage, within permitted current, the control method to decrease the ripple of active power is proposed, through circulating current control and current limitations. This control method has the advantage that calculates the maximum active power possible to generate capacity and impressed the current reference for that much. Also, in impressing circulating current reference, a new control method proposes to impress the reference from calculating active power of each phase. The proposed control method is verified through the simulation results, using the PSCAD/EMTDC.
김춘성(Chun-Sung Kim),이상혁(Sang Hyeok Lee),이용재(Yong-Jae Lee),이상훈(Sang Hun Lee),박성준(Sung Jun Park) 전력전자학회 2010 전력전자학술대회 논문집 Vol.2010 No.7
현재 학계에서는 신재생 에너지에 관한 연구가 활발히 진행 되고 있으며, 그 중 태양광과 풍력이 큰 비중을 차지하고 있다. 본 논문에서는 Push-Pull 컨버터를 기초한 전류형 PWM 인버터를 제안하고 계통 연계가 가능한 회로로의 타당성을 검증 하였다. 스위칭 소자 중 Push-Pull컨버터부의 두 개의 스위치만 PWM(Pulse Width Modulation)을 행하고 계통과 연결된 Full-Bridge의 스위치는 계통의 극성을 판단하여 Auto-ZCS (Zero Current Switching)가 가능하도록 설계하였다.
A Fibrinolytic Enzyme from the Medicinal Mushroom Cordyceps militaris
Jae-Sung Kim,Kumar Sapkota,Se-Eun Park,최봉석,김승,Nguyen Thi Hiep,김춘성,Han-Seok Choi,Myung-Kon Kim,Hong-Sung Chun,Yeal Park,Sung-Jun Kim 한국미생물학회 2006 The journal of microbiology Vol.44 No.6
In this study we purified a fibrinolytic enzyme from Cordyceps militaris using a combination of ion-exchange chromatography on a DEAE Sephadex A-50 column, gel filtration chromatography on a Sephadex G-75 column, and FPLC on a HiLoad 16/60 Superdex 75 column. This purification protocol resulted in a 191.8-fold purification of the enzyme and a final yield of 12.9%. The molecular mass of the purified enzyme was estimated to be 52 kDa by SDS-PAGE, fibrin-zymography, and gel filtration chromatography. The first 19 amino acid residues of the N-terminal sequence were ALTTQSNV THGLATISLRQ, which is similar to the subtilisin-like serine protease PR1J from Metarhizium anisopliae var. anisopliase. This enzyme is a neutral protease with an optimal reaction pH and temperature of 7.4 and 37°C, respectively. Results for the fibrinolysis pattern showed that the enzyme rapidly hydrolyzed the fibrin α-chain followed by the γ-γ chains. It also hydrolyzed the β-chain, but more slowly. The Aα, Bβ, and γ chains of fibrinogen were also cleaved very rapidly. We found that enzyme activity was inhibited by Cu2+ and Co2+, but enhanced by the additions of Ca2+ and Mg2+ ions. Furthermore, fibrinolytic enzyme activity was potently inhibited by PMSF and APMSF. This enzyme exhibited a high specificity for the chymotrypsin substrate S-2586 indicating it’s a chymotrypsin-like serine protease. The data we present suggest that the fibrinolytic enzyme derived from the edible and medicinal mushroom Cordyceps militaris has fibrin binding activity, which allows for the local activation of the fibrin degradation pathway.
Resveratrol Induces Apoptosis of KB Human Oral Cancer Cells
Seong-Hoon Kim,김흥중,이명화,유선경,김춘성,국중기,전홍성,Euteum Park,Sook-Young Lee,김수관,Hye Ryun Kim,김도경 한국응용생명화학회 2011 Applied Biological Chemistry (Appl Biol Chem) Vol.54 No.6
Resveratrol (trans-3,4',5,-trihydroxystilbene), a phytoalexin present in grape skin and red wine, suppresses many types of cancers by regulating cell proliferation and apoptosis through a variety of mechanisms. However, the effects of resveratrol on oral cancer are not completely understood. Thus, effects of resveratrol on cell growth and apoptosis induction were examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, DNA fragmentation, immunoblotting, and determination of caspase activation in KB human oral cancer cells. Treatment with resveratrol induced inhibition of cell growth depending on the resveratrol treatment time and concentration in KB cells. Treatment with resveratrol induced DNA ladder formation in KB cells and promoted proteolytic cleavage of procaspase-3 and procaspase-7 with increases in the amount of cleaved caspases-3 and -7. Proteolytic processing of caspase-9 in KB cells was increased by resveratrol treatment. Activation of caspase-3/-7 was detected in living KB cells by fluorescence microscopy. These results suggest that the resveratrol can suppress cell growth and induce cell apoptosis in KB human oral cancer cells, and may have potential as an anti-cancer drug.