교류 임피던스 측정법을 이용한 고분자 전해질 연료전지의 성능특성 분석

서상헌,이창식 한국수소및신에너지학회 2009 한국수소 및 신에너지학회논문집 Vol.20 No.4

This study focuses on the performance characteristics of polymer electrolyte membrane fuel cell (PEMFC) using the AC impedance technique. The experiment was carried out to investigate the optimal operating conditions of PEMFC such as cell temperature, flow rate, humidified temperature and backpressure. The fuel cell performance was analyzed by DC electronic-loader with constant voltage mode and expressed by voltage-current density. Additionally, AC impedance was measured to analysis of ohmic and activation loss and expressed by Nyquist plot. The results showed that the cell performance increased with increase of cell temperature, air flow rate, humidified temperature and backpressure. Also, the activation loss decreased as the increase of cell temperature, air flow rate, humidified temperature and backpressure.

Antiapoptotic Effect of Paricalcitol in Gentamicin-induced Kidney Injury

서상헌,이고은,박정우,김인진,김옥,김창성,최준석,배은희,마성권,이종은,김수완 대한약리학회 2013 The Korean Journal of Physiology & Pharmacology Vol.17 No.5

While the anti-apoptotic effect of paricalcitol has been demonstrated in various animal models, it is not yet clear whether paricalcitol attenuates the apoptosis in gentamicin (GM)-induced kidney injury. We investigated the effect of paricalcitol on apoptotic pathways in rat kidneys damaged by GM. Rats were randomly divided into three groups: 1) Control group (n=8), where only vehicle was delivered,2) GM group (n=10), where rats were treated with GM (150 mg/kg/day) for 7 days, 3) PARI group (n=10), where rats were co-treated with paricalcitol (0.2 μg/kg/day) and GM for 7 days. Paricalcitol attenuated renal dysfunction by GM administration in biochemical profiles. In terminal deoxynucleotidyl transferase dUTP nick end labeling staining, increased apoptosis was observed in GM group,which was reversed by paricalcitol co-treatment. Immunoblotting using protein samples from rat cortex/outer stripe of outer medulla showed increased Bax/Bcl-2 ratio and cleaved form of caspase-3in GM group, both of which were reversed by paricalcitol. The phosphorylated Jun-N-terminal kinase (JNK) expression was increase in GM, which was counteracted by paricalcitol. The protein expression of p-Akt and nitro-tyrosine was also enhanced in GM-treated rats compared with control rats, which was reversed by paricalcitol co-treatment. Paricalcitol protects GM-induced renal injury by antiapoptotic mechanisms, including inhibition of intrinsic apoptosis pathway and JNK.

촉매량 변화에 따른 직접 메탄올 연료전지의 성능 특성에 관한 연구

서상헌,이창식 한국수소및신에너지학회 2008 한국수소 및 신에너지학회논문집 Vol.19 No.6

This study is to investigate the influence of catalyst loading quantity on the direct methanol fuel cell (DMFC) performance. In this paper, Pt-Ru and Pt-black loading as the catalyst were varied from 1 to 4mg/cm2 at the anode and cathode, respectively. The experiment was conducted with single fuel cell consisted of 5cm2 effective electrode area, serpentine type flow pattern and Nafion 117 membrane. Also, AC impedance and methanol crossover current were measured to investigate the performance loss precisely. As a result, the performance of fuel cell was significantly increased with the increase of cathode catalyst loading. However, the performance did not increase further above a certain Pt-Ru catalyst loading as the increase of anode catalyst loading.

Gender-specific association of adiponectin with coronary artery calcification progression in CKD

서상헌 대한내과학회 2021 대한내과학회 추계학술대회 Vol.2021 No.1

Dyslipidemia in Patients with Chronic Kidney Disease: An Updated Overview

서상헌,김수완 대한당뇨병학회 2023 Diabetes and Metabolism Journal Vol.47 No.5

Dyslipidemia is a potentially modifiable cardiovascular risk factor. Whereas the recommendations for the treatment target of dyslipidemia in the general population are being more and more rigorous, the 2013 Kidney Disease: Improving Global Outcomes clinical practice guideline for lipid management in chronic kidney disease (CKD) presented a relatively conservative approach with respect to the indication of lipid lowering therapy and therapeutic monitoring among the patients with CKD. This may be largely attributed to the lack of high-quality evidence derived from CKD population, among whom the overall feature of dyslipidemia is considerably distinctive to that of general population. In this review article, we cover the characteristic features of dyslipidemia and impact of dyslipidemia on cardiovascular outcomes in patients with CKD. We also review the current evidence on lipid lowering therapy to modify the risk of cardiovascular events in this population. We finally discuss the association between dyslipidemia and CKD progression and the potential strategy to delay the progression of CKD in relation to lipid lowering therapy.

$SF_6$ 가스의 전리 및 부착계수에 관한 연구

서상헌,유회영,김상남,하성철,Seo, Sang-Hyeon,Yu, Heoi-Young,Kim, Sang-Nam,Ha, Sung-Chul 한국조명전기설비학회 1996 조명.전기설비 Vol.10 No.6

본 논문은 저자들에 위해 결정된 전자충돌단면적을 사용하여 몬테칼로 시뮬레이션 볼쯔만 방정식법에 의해 E/N:150∼180[Td] 범위에서 계산된 {{{{ { SF}_{ 6} }}}}가스의 전자수송 특성과 TOF법에서 구한 전자군 파라미터 값들을 나타냈다. 전자이동 속도 전자전력 또는 부착계숙, 종·횡방향 확산계수 등의 전자군 파라미터 값들은 E/N범위에서 실험치와 이론치가 일치하였다. 전자사태의 특성은 전자에너지의 비평형영역에서 고려되었다. 전자에너지 분포함수 는 평균에너지의 평형영역에 대하여 E/N:150∼180[Td]에서 해석하였다. 그 결과의 타당성은 TOF법에 의해 입증되었다. This paper describes the electron transport characteristics in SF6 gas calculated for range of E/N values from 150~ 800[Td) by the Monte Carlo simulation and Boltzmann equation method using a set of electron collision cross sections detennined by the authors and the values of electron swarm parameters are obtained by TOF method. The results gRined that the values of the electron swarm parameters such as the electron drift velocity, the electron ionization or Rttachment coefficients, longitudinal and transverse diffusion coefficients agree with the experimental and theoretical for a range of E/N. The properties of electron avalanches is concerned electron energy non--equilibrium region. The electron energy distributions function were analysed in sulphur hexafluoride at E/N : 500~800[Td) for a case of non-equilibrium region in the mean electron energy. The validity of the results obtained has been confilll1ed by a TOF method.

Acute Kidney Injury in Patients with Sepsis and Septic Shock: Risk Factors and Clinical Outcomes

서상헌,김창성,최준석,배은희,마성권,김수완 연세대학교의과대학 2013 Yonsei medical journal Vol.54 No.4

Purpose: The aim of this study was to investigate clinical characteristics and risk factors of acute kidney injury (AKI) in patients with sepsis and septic shock. Additionally,we explored whether the severity of AKI affects on the clinical outcomes. Materials and Methods: Data were collected retrospectively in a single center. Among 5680 patients who visited emergency department from January to December 2010, 992 patients with sepsis and septic shock were enrolled. Patients were divided into two groups, patients who developed AKI or not, to compare the baseline characteristics, and laboratory and physiologic data. Patients with AKI were subdivided according to its stages for survival analysis. Results: AKI was developed in 57.7% of patients. Multivariable logistic regression analysis revealed that development of septic AKI was associated with older age, pre-existing chronic kidney disease, use of angiotensin converting enzyme inhibitor or angiotensin receptor blocker, presence of shock, positive blood culture results, and low white blood cell and platelet counts. Hospital mortality was higher in AKI group. Crude Kaplan-Meier survival curves demonstrated reduced 30-day survival rate was significantly associated with the severity of acute kidney injury. Conclusion: The development of septic AKI was associated with poor clinical outcomes. Furthermore, the severity of AKI was associated with increased mortality.

메탄올 및 에탄올을 이용한 직접 알코올 연료전지의 성능 특성

서상헌(Sang Hern Seo),이창식(Chang Sik Lee) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4

This paper describes the performance characteristics of direct alcohol fuel cell utilized methanol and ethanol experimentally. In this experiment, Pt-Ru(4㎎/㎠) and Pt-black(4㎎/㎠) were used as the anode and cathode catalysts, respectively, and the N-115 was used as the membrane. The ohmic loss and activation loss were measured by the AC impedance spectrometer. Also, to investigate the methanol and ethanol permeation from then anode to the cathode through the membrane, the crossover current density was measured by power supply. It was revealed that the performance of direct methanol fuel cell(DMFC) was much higher than that of direct ethanol fuel cell(DEFC) because the ohmic loss and activation loss of DMFC were smaller than those of DEFC. However, methanol shows the higher crossover current than ethanol.

작동 조건 변화에 따른 직접 메탄올 연료전지의 성능 특성

서상헌(Sang Hem Seo),이도연(Do Youn Lee),이창식(Chang Sik Lee) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

In this work, the characteristics of a direct methanol fuel cell (DMFC) were investigated under changes of various operating conditions in order to understand the behaviors of the single fuel cell and find the optimal operating conditions. The operating parameters included the operating temperature. methanol concentration, flow rate, cathode humidification temperature, and so on. The membrane electrode assembly(MEA), with a Pt-Ru(4㎎/㎠) anode catalyst and Pt-black(4㎎/㎠) cathode catalyst, was used for methanol oxidation and oxygen reduction. The methanol in water solution was used as the fuel and the air was used as the oxidant in all experiments. The cell performance was analyzed based on the measurement of the current-voltage and current-power density characteristics expressed by polarization curve. The results showed that performance of the single cell was enhanced by increasing cell temperature, air flow rate, cathode back-pressure. but the temperature effect of cathode preheater was almost negligible. When cathode backpressure was increased up to 200kPa, the highest single cell power density of 0.178W/㎠ was achieved with 1M methanol feed at 80°C of cell temperature. From this experimental study, it was revealed that changing various conditions can be an important role in suitable operation of DMFC.

디메틸에테르와 에탄올을 이용한 고분자 전해질 연료전지의 성능 특성

서상헌(Sang Hern Seo),이창식(Chang Sik Lee) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11

This study conducted an experiment on the performance characteristics of polymer electrolyte membrane fuel cell using dimethyl ether and ethanol and investigated on the ohmic loss, activation loss and crossover loss. A blend of dimethyl ether(DME) and ethanol pressurized to 5 bar was supplied to serpentine flow field of anode. Membrane electrode assembly (MEA) consists of Nafion 115, anode catalyst loading Pt-Ru(4㎎/㎠) and cathode catalyst loading Pt-black(4㎎/㎠). Also, the impedance test was carried out to analysis performance losses such as ohmic loss and activation loss precisely. Fuel crossover from anode to cathode through the membrane was measured by using nitrogen gas at the cathode and power supply. It was found from the result that the performance of using a blend of DME and ethanol was more increased than that of using ethanol because the activation loss was decreased. Moreover, the open circuit voltage (OCV) and over