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Chang-Bock Chung,In-Su Han,Sang-Kyun Park 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.11
The effect of gas diffusion layer (GDL) compression on the polarization curves of a polymer electrolyte membrane fuel cell was analyzed using a polarization curve-fitting model. The polarization curves measured at four different GDL compression ratios were fitted with the model and were decomposed into an open circuit voltage and three over-voltages resulting from activation, ohmic, and mass-transport losses, respectively. The model fitting was excellent enough to use the model in the subsequent analysis of the GDL compression effect. The relationship between the over-voltages and the compression ratio was investigated by analyzing the estimated model parameters, and an optimal compression ratio was determined for the fuel cell. The proposed analysis method based on the polarization curve-fitting model can be applied to identifying quantitative differences of polarization curves under various operating conditions and designs for fuel cells.
SENSITIVITY BEHAVIOR ANALYSIS IN DISTRIBUTED PARAMETER ESTIMATION
Chung, Chang Bock 한국화학공학회 1991 Korean Journal of Chemical Engineering Vol.8 No.4
This paper is concerned with sensitivity analysis for the distributed parameter estimation problem arising in the modeling process for fluid flow in underground porous media. An efficient algorithm was constructed using variational calculus techniques for the evaluation of sensitivity gradient curves which describe variations of system outputs resulting from variations of a spatially-varying parameter in nonlinear partial differential equations. For a test problem of estimating transmissivity of a one-dimensional ideal gas reservoir, sensitivity behavior was analyzed under various reservoir conditions, and the results were applied to devising a parameter discretization scheme which will yield improved parameter estimates.
ESTIMATION OF A STATE - DEPENDENT MODEL PARAMETER
Chung, Chang Bock,Chung, Young Sun 한국화학공학회 1995 Korean Journal of Chemical Engineering Vol.12 No.3
A numerical algorithm was developed which estimates a state-dependent model parameter on the basis of transient state observation data. The algorithm was presented for the problem of estimating the temperature dependence of thermal diffusivity in a one-dimensional heat equation. The estimation problem was converted into a finite dimensional optimization problem by the least-squares formulation and B-splines representation of the parameter. Numerical experiments were performed using simulated observation data as well as the actual observation data obtained in a heat conduction experiment on rubber compound layers. The performance of the algorithm was discussed in relation to the effect of the parameter representation scheme, the quality and quantity of the data.
Estimation of a State - Dependent Model Parameter
Chung, Chang Bock,Chung, Young Sun 한국화학공학회 1995 NICE Vol.13 No.5
A numerical algorithm was developed which estimates a state-dependent model parameter on the basis of transient state observation data. The algorithm was presented for the problem of estimating the temperature dependence of thermal diffusivity in a one-dimensional heat equation. The estimation problem was converted into a finite dimensional optimization problem by the least-squares formulation and B-splines representation of the parameter. Numerical experiments were performed using simulated observation data as well as the actual observation data obtained in a heat conduction experiment on rubber compound layers. The performance of the algorithm was discussed in relation to the effect of the parameter representation scheme, the quality and quantity of the data.
Sensitivity Behavior Analysis in Distributed Parameter Estimation
Chung, Chang Bock 한국화학공학회 1992 NICE Vol.10 No.1
This paper is concerned with sensitivity analysis for the distributed parameter estimation problem arising in the modeling process for fluid flow in underground porous media. An efficient algorithm was constructed using variational calculus techniques for the evaluation of sensitivity gradient curies which describe variations of system outputs resulting from variations of a spatially-varying parameter in nonlinear partial differential equations. For a test problem of estimating transmissivity of a one-dimensional ideal fas reservoir, sensitivity behavior was analyzed under various reservoir conditions, and the results were applied to devising a parameter discretization scheme which will yield improved parameter estimates.
Development of One Dimensional Kinetics Program
Chan Bock Lee,Chang Hyun Chung,Bub Dong Chung Korean Nuclear Society 1986 Nuclear Engineering and Technology Vol.18 No.2
원자로 노심을 축방향으로 일차원 해석을 하고, 가입경수로형원자로의 안전성 해석에 적용할 수 있는 중성자 동특성프로그램 BIK를 개발하였다. BIK프로그램내에서 공간변수에 대해서는 유한차분법이, 시간변수에 대해서는 $\theta$-시간적분법이 채택되었다. 또한 도플러 및 감속재 궤환과 제어봉구동 등을 자세히 묘사하는 모델들이 포함되었다 핵모델의 검증은 ANL검증문제를 통해 이루어졌고, 고리 1호기의 제어봉 인출사고시의 노심출력 변화를 계산하였다. 이상의 계산결과 BIK동특성프로그램이 노심의 중성자 속 변화를 일차원해석의 한계내에서 비교적 정착하게 묘사할 수 있으며, 가압경수로형 원자로의 안전성 해석에 유용하게 사용될 수 있다는 것이 증명되었다. A one dimensional neutron kinetics program, BIK which is applicable to the safety analyses of PWR's is developed to analyze the reactor core in axial dimension. The BIK employs the finite difference technique in space and $\theta$-time integration method in time. Detailed models for the Doppler and moderator feedbacks and control rod motion are included. The benchmark of the nuclear model is carried out through the ANL benchmark problem and the time dependent nuclear power change in the rod ejection accident of KNU1 is calculated by BIK code. The results indicate that the BIK can predict the neutron dynamics with fair accuracy within the limits of one dimensional analysis and it is useful for the safety analyses of PWR's.
자궁 경부암 환자의 림파선 폐 전이 1례 보고 : A Case Report
장병우,임옥경,박미혜,신효경,김향미,손영수,우복희,정호인,서정수 梨花女子大學校 醫科大學 醫科學硏究所 1994 EMJ (Ewha medical journal) Vol.17 No.1
Diffuse pulmonary Iymphangitic involvement secondary to cervical carcinoma is a rare form of pulmonary metastatic disease. A patient with recurrent squamous cell carcinoma of cervix presented with rapid deterioration with marked respiratory symptoms suggestive of pulmonary embolism and right heart faiure, with which the disease is often confused. Pulmonary Iymphangitic spread of the cancer was found postmortem. The pathogenesis of pulmonary Iymphangitic carcinomatosis is reviewed and diagnostic evaluation discussed.
( Chang Hoon Kim ),( Seung Min Bang ),( Kyung Ho Song ),( Jeong Youp Park ),( Tae Joo Jeon ),( Sung Pil Hong ),( Jae Bock Chung ),( Seung Woo Park ),( Si Young Song ) 대한소화기학회 2007 Gut and Liver Vol.1 No.1
Background/Aims: Obstruction of the main pancreatic duct (MPD) has been considered one of the major causes for pain in chronic pancreatitis (CP). In this study, we evaluated the efficacy of MPD stenting in painful CP, and tried to determine a guideline for stent removal. Methods: Sixteen patients with painful CP who underwent MPD stenting were included. Follow up ERCP was performed 3 months after stenting in all patients. Stents were removed in patients who achieved pain relief, complete stone clearance, and decreased MPD diameter after 3 months. Results: Before stenting, ERCP showed MPD stricture in 11 cases, MPD dilatation by stone in 1 case, concomitant stricture and stone in 4 cases. After stenting, complete pain relief was achieved in 13 patients (81.3%) and partial pain relief was achieved in 3 patient (18.7%). There was no patient whose pain was not relieved. Stents were removed in 7 patients who achieved pain relief, complete stone clearance, and decreased MPD diameter after 3 months. Decrease of MPD diameter was significantly greater in patient who could remove stent than those who could not (72.9% vs. 127.9% of initial MPD diameter, p=0.008). Conclusions: If partial or full pain relief is achieved after MPD stenting and follow up ERCP after 3 months shows decreased MPD diameter compared to the initial one, stent removal might be considered. (Gut and Liver 2007;1:63-67)