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Prepubertal Testicular Tumors in Korea: A Single Surgeon’s Experience of More Than 20 Years
백경돈,강민용,박광진,최황 대한비뇨의학회 2013 Investigative and Clinical Urology Vol.54 No.6
Purpose: To present clinical and histological features of prepubertal testicular tumors through the analysis of the long-term experiences of a single surgeon. Materials and Methods: The charts of 48 children treated for testicular tumors from 1986 to 2010 were retrospectively reviewed. All patients underwent radical orchiectomy. The patients’ ages, clinical presentations, histopathological findings, kinetics of tumor markers, and outcomes were recorded. Results: The patients’ median age at the initial diagnosis was 19.5 months (range, 3to 84 months). All patients presented with either a palpable mass (76%) or scrotal size discrepancy (24%). Compared with a palpable mass, scrotal size discrepancy led to delay in diagnosis by 5 months. Regarding histology, yolk sac tumors and teratomas accounted for 53% and 36% of the tumors, respectively. The mean preoperative alpha-fetoprotein (AFP) level was significantly higher in patients with yolk sac tumors than in those with teratomas (4,600 ng/mL vs. 6.3 ng/mL), and only one patient with a teratoma had a preoperative AFP value higher than 20 ng/mL. Following radical orchiectomy,72%, 8%, and 16% of patients with a yolk sac tumor showed normalization, persistent elevation, and relapse after transient lowering of AFP, respectively. Preoperative AFP was greater in patients with non-normalization than in those with normalization. Five of six patients with non-normalization showed evidence of either vascular invasion or endolymphatic tumor emboli. Conclusions: We found a higher number of yolk sac tumors than teratomas in patients with prepubertal testicular tumors. AFP was the most useful marker in the diagnosis and follow-up of childhood yolk sac tumors. Relapsed yolk sac tumors often showed pathological evidence of aggressiveness.
산전 초음파검사에서 본 제대탈추 및 횡경막결손을 동반한 심장이소증의 1 예
백경돈,김상갑,지정희,최영주,이흥섭,하부수 대한산부인과학회 1992 Obstetrics & Gynecology Science Vol.35 No.7
본원 산부인과에서는 분만전 초음파검사에 의해 제대탈출, 심장이소증 및 횡경막결손의 기형을 가진 태아 1예를 경험하였기에 간단한 문헌고찰과 함께 보고하는 바이다. Omphalocele is a defect in the umbilical ring from which protrudes a sac, and into which abdominal contents have typically herniated. Ectopic cordis was first reported in 1671 by Stensen, which means that the heart is partially or totally outside the thorax. We have experienced a case of omphalocele and ectopia cordis with diaphragmatic defect. We report the case and review with literature briefly.
고분자 연료전지 스택에서 질소 크로스오버 특성에 관한 연구
백경돈,김민수 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.03
Crossover of nitrogen from cathode to anode is inevitable in typical membranes used in PEM fuel cells. This crossovered nitrogen normally accumulates in the hydrogen recirculation system at anode side channels. Excessive buildup of nitrogen in the anode side lowers the relative hydrogen concentration and finally affects the performance of fuel cell stack. So it is very important to analysis the nitrogen gas crossover at various operating conditions. In this study, characterization of nitrogen gas crossover in PEM fuel cell stack was investigated. The mass spectroscopy (MS) has been applied to measure the amount of the crossovered nitrogen gas at the anode exit. Results show that nitrogen gas crossover rate was affected by current density, anode and cathode stoichiometric ratio and operating pressure. Current density, anode stoichiometric ratio and anode operating pressure do not affect nitrogen crossover rate but anode exit concentration of nitrogen. Cathode pressure and stoichiometric ratio largely affect the nitrogen crossover rate.
고분자 연료전지 스택에서 질소 크로스오버 특성에 관한 연구
백경돈(Kyung Don Baik),김민수(Min Soo Kim) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.3
Crossover of nitrogen from cathode to anode is inevitable in typical membranes used in PEM fuel cells. This crossovered nitrogen normally accumulates in the hydrogen recirculation system at anode side channels. Excessive buildup of nitrogen in the anode side lowers the relative hydrogen concentration and finally affects the performance of fuel cell stack. So it is very important to analysis the nitrogen gas crossover at various operating conditions. In this study, characterization of nitrogen gas crossover in PEM fuel cell stack was investigated. The mass spectroscopy (MS) has been applied to measure the amount of the crossovered nitrogen gas at the anode exit. Results show that nitrogen gas crossover rate was affected by current density, anode and cathode stoichiometric ratio and operating pressure. Current density, anode stoichiometric ratio and anode operating pressure do not affect nitrogen crossover rate but anode exit concentration of nitrogen. Cathode pressure and stoichiometric ratio largely affect the nitrogen crossover rate.
고분자 전해질 막 연료전지에서 수소 크로스오버 특성에 관한 연구
백경돈(Baik Kyung Don),공임모(Kong Im Mo),정애리(Jung Aeri),김민수(Kim Min Soo) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
In this study, the effects of operating parameters including temperature, relative humidity, hydrogen pressure and membrane thickness on hydrogen crossover have been investigated. It is found that hydrogen crossover increases proportionally to the increase in both temperature and relative humidity for all membrane samples. The increase in hydrogen crossover is also observed with increasing hydrogen pressure. A comparison among all of the operating parameters on hydrogen crossover is analyzed using a multiple linear regression analysis. The results indicate that the main factors causing increase in hydrogen crossover are in the order of membrane thickness, hydrogen pressure, RH, and temperature.
백경돈(Kyung Don Baik),김성일(Sung Il Kim),공임모(Im Mo Kong),김민수(Min Soo Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Gas crossover through the membrane is well known phenomena in PEM fuel cells. Characterization of oxygen crossover which represents the permeation was investigated in this study. Oxygen crossover from the cathode side to the anode side causes the carbon corrosion which affects the fuel cell durability. Thus it is important to analyze the characterization of oxygen crossover in PEM fuel cells at various conditions such as different cell temperature and relative humidity of supplying gases. In this study, mass spectrometer has been applied at anode exit stream to measure the amount of oxygen crossover at OCV condition. Instead of supplying hydrogen gas, helium gas was supplied at anode side because helium gas does not react with oxygen gas at anode side. Results show that temperature and relative humidity affect the oxygen crossover. As temperature increases, anode exit concentration of oxygen decreases due to the change of oxygen concentration at cathode side.
고분자 연료전지 스택에서 질소 크로스오버 특성에 관한 연구
백경돈(Kyung Don Baik),김민수(Min Soo Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
Crossover of nitrogen from cathode to anode is inevitable in typical membranes used in PEM fuel cells. This crossovered nitrogen accumulates in anode recirculation system and excessive buildup of nitrogen in the recirculating anode gas lowers the hydrogen concentration and finally affects the performance of fuel cell stacks. In this study, characterization of nitrogen gas crossover was investigated in PEM fuel cell stacks. The mass spectroscopy (MS) has been applied to measure the amount of the crossovered nitrogen at the exit of anode. Results show that anode and cathode stoichiometric number (SR<SUB>c</SUB>) have a big effect of nitrogen crossover.
고분자 전해질 연료전지의 GDL 이방성이 채널로의 GDL 침투에 미치는 영향에 관한 연구
백경돈(Kyung Don Baik),홍보기(Bo Ki Hong),김민수(Min Soo Kim) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
The effects of the metallic bipolar plate (MBP) structure on the performance of polymer electrolyte membrane fuel cells with gas diffusion layers (GDLs) having anisotropic bending stiffness have been investigated. The Ⅰ-Ⅴ performances of the fuel cells with 90˚ GDLs, whose directions of higher stiffness are perpendicular to the direction of the major flow field, were higher than those with 0˚ GDLs, whose directions of higher stiffness are parallel with the direction of the major flow field. As the land/channel width ratio increased (i.e., wider land width), the Ⅰ-Ⅴ performances of both 0˚ and 90˚ GDL cells increased, presumably due to less GDL intrusion and more intimate contact. However, an excessively large land width greatly decreased the Ⅰ-Ⅴ performances because of the reduced channel width for mass transport. As the land/channel width ratio increased, the high frequency resistance (HFR) values of the cells decreased due to better contact, but the air pressure differences of cathode increased due to the reduced channel width. The differences of Ⅰ-Ⅴ performances and HFR values between the 0˚ and 90˚ GDL cells gradually reduced with increasing land/channel width ratio, because of the reduced anisotropic stiffness effects of the GDLs due to the better support by the MBPs with wider lands.