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- 저자 : 서정천(Suh, J.-C.) (검색결과 43 건)
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서정천(J. C. Suh) 한국전산유체공학회 1998 한국전산유체공학회지 Vol.3 No.1
A vorticity-based method for the numerical solution of the two-dimensional incompressible Navier-Stokes equations is presented. The governing equations for vorticity, velocity and pressure variables are expressed in an integro-differential form. The global coupling between the vorticity and the pressure boundary conditions is fully considered in an iterative procedure when numerical schemes are employed. The finite volume method of the second order TVD scheme is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition. The velocity field is obtained by using the Biot-Savarl integral. The Green's scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well established for potential flow analysis. The present formulation is validated by comparison with data from the literature for the two-dimensional cavity flow driven by shear in a square cavity. We take two types of the cavity flow: (i) driven by non-uniform shear on top lid and body forces for which the exact solution exists, and (ii) driven only by uniform shear (of the classical type).
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서정천(J.-C. Suh) 한국전산유체공학회 1998 한국전산유체공학회 학술대회논문집 Vol.1998 No.-
As an alternative for solving the incompressible Navier-Stokes equations) we present. a vorticity integro-differential formulation for vorticity) velocity and pressure variables. One of the most difficult problems encountered in the vorticity-based methods is the introduction of the proper value of vorticity or vorticity flux at the solid surface. A practical computational technique toward solving this problem is presented in connection with the coupling between the vorticity and the pressure boundary conditions. Numerical schemes based on an iterative procedure are employed to solve the governing equations with the boundary conditions for the three variables. A finite volume method is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition. The velocity field is obtained by using the Biot-Savart integral derived from the mathematical vector identity. Green)s scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well-established for potential flow analysis. The calculated results with the present method for two test problems are compared with data from the literature in order for its validation. The first. test problem is one for the two-dimensional square cavity flow driven by shear on the top lid. Two cases arc considered here: (i) one driven both by the specified non-uniform shear on the top lid and by the specified body forces acting through the cavity region, for which we find the exact solution, and (ii) one of the classical type (I.e.) driven only by uniform shear). Secondly, the present method is applied to deal with the early development of the flow around an impulsively started circular cylinder.
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서정천(J. C. Suh) 한국전산유체공학회 1998 한국전산유체공학회지 Vol.3 No.1
A vorticity-based method for the numerical solution of the two-dimensional incompressible Navier-Stokes equations is presented. The governing equations for vorticity, velocity and pressure variables are expressed in an integro-differential form. The global coupling between the vorticity and the pressure boundary conditions is fully considered in an iterative procedure when numerical schemes are employed. The finite volume method of the second order TVD scheme is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition. The velocity field is obtained by using the Biot-Savarl integral. The Green's scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well established for potential flow analysis. The present formulation is validated by comparison with data from the literature for the two-dimensional cavity flow driven by shear in a square cavity. We take two types of the cavity flow: (i) driven by non-uniform shear on top lid and body forces for which the exact solution exists, and (ii) driven only by uniform shear (of the classical type).
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경주지역에서 식물제제에 의한 급성 간손상 환자의 임상적 고찰
천우정(Woo Jung Chun),윤병구(Byung Gu Yoon),김남일(Nam Il Kim),이구(Goo Lee),양창헌(Chang Heon Yang),이창우(Chang Woo Lee),서정일(Jeong Ill Suh) 대한내과학회 2002 대한내과학회지 Vol.63 No.2
배경: B형 간염 백신의 도입 이후 우리나라에서는 바이러스에 의한 급성 간손상은 감소하는 추세에 있는 반면에 식물제제나 건강식품에 의한 약인성 간손상이 증가하고 있는 추세이나, 급성 간손상에 대한 일치된 진단방법과 원인평가의 기준이 없는 실정이다. 이에 저자들은 경주 인근지역의 급성 간손상의 분포와 특성, 식물제제에 의한 급성 간손상의 빈도와 원인물질, 임상양상 등을 알아보고, 원인평가기준으로 제시된 CIOMS 진단점수표와 Maria & Victorino 진단점수표를 비교, 분석하였다. 대상 및 방법: 1997년 4월부터 2001년 3월까지 급성 간손상으로 동국대 경주병원에 입원한 150예의 환자 중에서 이전 간질환의 병력이나 상습적인 음주력, 대사성 간질환 및 간담도 질환, 바이러스성 간염과 자가면역성 간염을 제외한 78예를 대상으로 하였으며, 명확한 약제의 복용력이 있으면서 ALT, ALP, Total bilirubin 중 한 가지 이상이 정상범위 상한의 2배(2N) 이상이며, 약제복용 중단후 특별한 치료없이 간검사가 정상으로 회복된 경우만을 대상으로 선택하였으며, 각각의 예에 대해 복용약제, 간손상의 양상, 약제 중단 후 회복기간, 음주력, 다른 간담도질환의 존재 여부, 의심되는 약제의 재투여 여부, 바이러스성 간염 표지자, AST, ALT, TB, ALP 등을 후향적으로 조사하였고, 각 예를 식물제제에 의한 군과 양약제에 의한 군으로 구분하여 두 군간의 특성을 비교하였다. 또한 CIOMS 진단 점수표와 M&V 진단 점수표의 유용성과 일치성을 비교하였다. 결과: 4년 동안 급성 간손상으로 입원한 환자는 150예였고, 그 중 약인성 간손상이 78예(52.0%)로 가장 높은 빈도를 보였다. 원인약제로는 양약이 39예(50.0%)였으며, 식물제제와 건강식품 또한 39예(50.0%)였다. 그 중 한약제가 23예(58.9%)였고, 환약 5예(12.8%), 인진쑥 3예(7.7%), 사슴 액기스 3예(7.7%), 키토산이 2예(5.1%), 호박소주, 잉어, 풀뿌리 등이 각 1예(2.6%)였다. 간손상의 양상은 간세포성 간손상이 48예(61.5%)로 가장 많았고 두 군간에 유의한 차이는 없었다(p>0.1). CIOMS와 M&V 진단점수표 간에 등급이 일치하는 경우는 2예(2.6%)에 불과하여 kappa값을 이용한 카이제곱 검정으로 계산이 되지 않을 만큼 매우 낮은 일치율을 보였다. 결론: 급성 간손상으로 입원한 환자들에게서 약인성 간손상의 빈도가 증가하고 있고, 그 중 식물제제에 의한 간손상의 비중이 높음을 확인할 수 있었으며, 간손상의 가능성이 있는 양약제 및 식물제제의 무분별한 남용에 대해 사회적 경각심을 고취시켜야 할 것으로 생각된다. 또한 식물제제에 의한 간손상의 빈도가 높은 한국적 특성에 맞는 새로운 진단 점수표가 필요할 것으로 생각된다. Background: The prevalence of acute viral liver injury is decreasing, but drug induced liver injury by herbal medicine and health foods is on an increasing trend after introduction of vaccination. Nevertheless, there is no consensus of diagnostic method and causality assessment for acute liver injury. Therefore, the cause, clinical features, prevalence and pattern of acute liver injury caused by herbal medicine and health foods in Gyeongju area were analyzed. Moreover, Council for International Organization of Medical Science (CIOMS) scale and Maria and Victorino (M&V) scale, clinical scales for causality assessment in hepatotoxicity were compared. Methods: 78 patients in whom there was definite evidence of taking medicine and there was one more increase of over 2N (upper limit of the normal range) in alanine aminotransferase (ALT) or total bilirubin (TB) or alkaline phosphatase (ALP) and self-remitted after drug stop were selected excluding patients with previous liver disease history and history of alcohol, metabolic liver disease and hapatobiliary disease and viral, autoimmune, unknown origin hepatitis among 150 patients of admission due to acute liver injury, from April 1997 to March 2001. Each case was investigated retrospectively about taken medicine, the pattern of liver injury, recovery period after drug stop, history of alcohol, other hepatobiliary disease, pregnancy, recent hypotension, rechallenge and viral markers of hepatitis, aspartate aminotransferase (AST), ALT, TB, ALP. Also, herbal medicine and western medicine groups were compared and consistency with CIOMS scale and M&V scale were investigated. Results: For four years, among 150 cases, drug-induced liver injury were 78 cases (52.0%), occurred the highest prevalence. In taken medicine, western medicine were 39 cases (50.0%), herbal medicine and health foods were 39 cases (50.0%), too. Among those cases, herbal medication were 23 cases (58.9%), pellet 5 cases (12.8%), In-jin-ssuk 3 cases (7.7%), deer extract 3 cases (7.7%), kitosan 2 cases (5%) and pumpkin extract, carp, plant roots was 1 case (2.5%) respectively. In the pattern of liver injury, hepatocellular liver injury were 48 cases (61.5%), occurred the highest prevalence. Between CIOMS and M&V scale, best correlation were only 2 cases (2.6%), therefore, their agreement was very low. Conclusion: The prevalence of drug induced liver injury is on an increasing trend in Gyeongju area and acute liver injury caused by herbal medicine and health foods had very high incidence was ascertained. Therefore, we should attend to indiscreet use of herbal medicine and health foods and should give a warning to our society. And a new clinical scale suitable for characteristic of our country that had high prevalence of liver injury caused by herbal medicine and health food is needed. (Korean J Med 63:141-150, 2002)
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Hybrid Particle-Mesh 방법에 적합한 다중영역 방법
이승재(Seung-Jae Lee),서정천(Jung-Chun Suh) 한국전산유체공학회 2014 한국전산유체공학회지 Vol.19 No.2
A hybrid particle-mesh method as the combination between the Vortex-In-Cell (VIC) method and penalization method has been achieved in recent years. The VIC method, which is based on the vorticity-velocity formulation, offers particle-mesh algorithms to numerically simulate flows past a solid body. The penalization method is used to enforce boundary conditions at a body surface with a decoupling between body boundaries and computational grids. The main advantage of the hybrid particle-mesh method is an efficient implementation for solid boundaries of arbitrary complexity on Cartesian grids. However, a numerical simulation of flows in large domains is still not too easy. In this study, a multi-domain approach is thus proposed to further reduce computation cost and easily implement it. We validate the implementation by numerical simulations of an incompressible viscous flow around an impulsively started circular cylinder.
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