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A Three-Phase Zero-Voltage and Zero-Current Switching DC–DC Converter for Fuel Cell Applications
Hyungjoon Kim,Changwoo Yoon,Sewan Choi IEEE 2010 IEEE transactions on power electronics Vol.25 No.2
<P>In spite of having many advantages, such as low switch voltage and easy implementation, the voltage-fed dc-dc converter has been suffering from problems associated with large transformer leakage inductance due to high transformer turn ratio when it is applied to low-voltage, high-current step-up application such as fuel cells. This paper proposes a new three-phase voltage-fed dc-dc converter, which is suitable for low-voltage, high-current applications. The transformer turn ratio is reduced to half owing to ¿-Y connection. The zero-voltage and zero-current switching (ZVZCS) for all switches are achieved over wide load range without affecting effective duty cycle. A clamp circuit not only clamps the surge voltage but also reduces the circulation current flowing in the high-current side, resulting in significantly reduced conduction losses. The duty cycle loss can also be compensated by operation of the clamp switch. Experimental waveforms from a 1.5 kW prototype are provided.</P>
( Hyung Joon Kim ),( Wan Long Chuang ),( Kosh Agarwal ),( Jae Seok Hwang ),( Florin Caruntu ),( Florence Wong ),( Hie Won Hann ),( John Flaherty ),( Audrey Lau ),( Anuj Gaggar ),( Vithika Suri ),( Shu 대한간학회 2017 춘·추계 학술대회 (KASL) Vol.2017 No.1
Aims: In Phase 3 studies in CHB patients the efficacy of TAF was found smaller changes in renal parameters compared with TDF treatment. This benefit was particularly evident in patients with risk factors for renal impairment.Here, we present renal safety results after 96 weeks of treatment. Methods: In Phase 3 studies (HBeAg positive patients [N=873] and HBeAg negative patients [N=425]), patients were randomized 2:1 to TAF 25 mg QD or TDF 300 mg QD, and treated for 144 weeks. Renal parameters including estimated glomerular filtration rate (eGFR) calculated by the Cockcroft-Gault method were evaluated. Chronic kidney disease (CKD) staging was categorized by the National Kidney Foundation KDOQI guidelines. Evaluated risk factors for kidney disease included older age (age ≥ 50), female gender, renal impairment (eGFR <90mL/min) and presence of comorbidities (hypertension, cardiovascular disease and diabetes). Urine markers of renal glomerular dysfunction (urine protein and albumin to creatinine ratio) and tubular dysfunction (retinol binding protein (RBP) and beta-2 microglobulin [B2M] to creatinine ratio) were serially assessed. Results: Patients treated with TAF continued to show smaller changes in serum creatinine (p=0.001) and eGFRCG (p<0.001) at 96 weeks. Similarly, median percentage changes in renal tubular markers, were also smaller in TAF-treated patients compared with TDF patients at Week 96; RBP/Cr (p<0.0001) and B2M/Cr (p<0.0001). A lower percentage of patients experienced ≥1 stage worsening in NKF CKD stage when treated with TAF compared with TDF at Week 96 overall and when evaluated by risk factors for kidney disease.Furthermore, CKD stage progression increased disproportionately in the TDF group in patients with ≥2 risk factors (Table). Conclusions: Treatment with TAF for 96 weeks continued to be associated with smaller changes in renal parameters compared with TDF treatment. The benefits of TAF are particularly evident in patients with risk factors for kidney disease.
Hyung-Joon Kim,Pyungho Choi,Kwangsoo Kim,Byoungdeog Choi 대한전자공학회 2013 Journal of semiconductor technology and science Vol.13 No.6
The effect of fluorine ions, which can be reacted with boron in high-doped BPSG, is investigated on the contact sidewall wiggling profile in semiconductor process. In the semiconductor device, there are many contacts on p+/n+ source and drain region. However these types of wiggling profile is only observed at the n+ contact region. As a result, we find that the type of plug implantation dopant can affect the sidewall wiggling profile of contact. By optimizing the proper fluorine gas flow rate, both the straight sidewall profile and the desired electrical characteristics can be obtained. In this paper, we propose a fundamental approach to improve the contact sidewall wiggling profile phenomena, which mostly appear in high-doped BPSG on nextgeneration DRAM products.
Analysis of 17th National Assembly Election Outcomes in Korea
Hyung Joon Kim,김도종 한국학술연구원 2004 Korea Observer Vol.35 No.4
This analysis uses aggregate data on Koreas 17th National Assembly election results to explore the impact of a new one-man-two-votes electoral process on such critical factors as voter turnout; parties vote share won by constituents direct vote for their candidates (district vote share) and by constituents proportional support for their party (party vote share, or PR share), that is, by each aspect of one-man-two-votes; candidates political experience; and incumbents re-election rates. Findings indicate, first, general election voter turnout rose for the first time since the 12th general election (1985). Second, the new electoral system facilitated entry of the third party and independents into the legislature, by, for instance, providing the Democratic Labor Party 10.5-21.9 percent of party vote share in 16 cities and provinces even though it won only 4.3 percent of district seats. Third, the systems PR provision favored the largest party and key opponent party, yielding them far more seats than other parties than their district votes would support. Fourth, the massive influx of new faces among winning candidates -- 70 percent among majority Uri Party victories -- holds out the prospect of a new era in Korean politics, although it could compromise the ability of the legislature to effectively check presidential power.By popular consensus, Korean politics need to change. If a change of players suffices, the general election was a success. However, being new does not alone guarantee that lawmakers will conduct the National Assembly in more productive or effective fashion, as previous assemblies have demonstrated. Of particular concern is the chronic dependence of politicians on regional support, which attenuates their ability to act independently in the interest of the entire nation. Absent such independence true change in Korean politics remains doubtful.
Uncertainty Cases in Economic Evaluation of Back-End Nuclear Fuel Cycle
Hyung-Joon Kim,Chun-Hyung Cho,Kyung-Ku Lee 한국방사성폐기물학회 2008 방사성폐기물학회지 Vol.6 No.2
후행 핵연료주기 경제성 평가는 추정 비용의 불확실성, 평가 대상기간의 장기성, 적용 할인율에 따른 계산결과의 변동성 등 많은 불확실성을 내포하고 있기 때문에 평가기관 또는 평가자에 따라 그 결과가 서로 상이하다. 본고에서는 지금까지 수행된 주요 경제성 평가 연구들을 조사/분석하여 그 특징과 한계를 알아봄으로써 현재 국내에서 추진되고 있는 사용후핵연료 공론화 및 후행 핵연료주기 정책 연구 추진에 기초자료로 활용될 수 있도록 하고자 하였다. 분석 결과 사용후핵연료 재활용 옵션에 비해 직접처분 옵션이 유리하나, 입력 자료로 사용된 파라미터 값에 따라 결과의 불확실성이 많이 나타나 이 부분에 대한 추가적인 연구가 필요하다는 사실을 알 수 있었다. Due to the uncertainties resulting from cost projection, evaluation over long term period, and adequacy of applied discount rate, the economic assessment for back-end fuel cycle is different from each organizations or individuals. In this paper, the features and limitations of some noticeable economic evaluations were investigated and analysed to contribute for the public participation and back-end fuel cycle policy related researches. As a result of analysis, we found that the reprocess and recycling is more economical than direct disposal option, but the result includes high uncertainty that depends on the input parameters.
( Hyung Joon Kim ),( Young-Suk Lim ),( Ki Tae Yoon ),( Won Young Tak ),( Sang Hoon Ahn ),( Jae-Seok Hwang ),( Henry LY Chan ),( Scott Fung ),( Wai Kay Seto ),( Wan-Long Chuang ),( Chi-Yi Chen ),( Aric 대한간학회 2016 춘·추계 학술대회 (KASL) Vol.2016 No.1
Aims: Tenofovir alafenamide (TAF), a novel prodrug of tenofovir (TFV),is more stable in plasma and enhances delivery of TFV into hepatocyteswhile lowering circulating levels of TFV by approximately 90% comparedto tenofovir disoproxil fumarate (TDF).Methods: In this Phase 3 study, patients with HBeAg-positive chronichepatitis B (CHB) were randomized 2:1 to TAF 25 mg QD or TDF300 mg QD and treated for 96 weeks. After Week 96, patients receiveopen label TAF for 48 weeks. The primary efficacy analysis was thepercent of patients with HBV DNA <29 IU/mL at Week 48. Key secondarysafety endpoints were assessed sequentially: changes in hip andspine bone mineral density (BMD), changes in serum creatinine (sCr),and dipstick proteinuria. Markers of bone formation and resorption,and renal tubular function were also assessed.Results: 873 patients were randomized and treated at 164 sites in19 countries. Baseline characteristics included: mean age 38 years,83% males, 82% Asians; 47% had HBV DNA ≥ 8 log10 IU/mL, and26% were treated previously with nucleos(t)ides. At Week 48, TAFwas non-inferior in efficacy to TDF with virologic response rates of63.9% with TAF and 66.8% with TDF. A greater percentage of patientstreated with TAF achieved normalization of serum ALT values.Patients on TAF experienced significantly less declines in hip and spineBMD, and a smaller increase in sCr than TDF; eGFRCG, and renaltubular markers also changed less with TAF. No viral resistance wasobserved in 22/581 (3.8%) and 11/292 (3.8%) of TAF and TDF patients,respectively, who qualified for testing.Conclusions: Compared to TDF 300 mg, the efficacy of TAF 25 mgin patients with HBeAg-positive CHB was noninferior. Safety wasalso improved, with less change in bone and renal parameters.
Hyung Joon Kim,Duk Kyung Kim,Sang Chul Lee,Soon Ha Yang,Jung Hyun Yang,Won Ro Lee 대한내과학회 1998 The Korean Journal of Internal Medicine Vol.13 No.2
Pheochromocytoma in pregnancy is very rare but it is associated with very high maternal and fetal mortality. Therefore, it is important to include pheochromocytoma in the differential diagnosis of hypertension associated with pregnancy. It is difficult to