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서정천,Seo, Jeong-Cheon 선박안전기술공단 2001 선박안전 Vol.7 No.-
소형 어선의 조업 환경을 개선하고자 하는 선주와 어민 입장에서 연안에서 번번히 발생하는 그물 걸림이나 충돌시 손상이 적은 추진장치를 저렴하게 공급받기를 원한다. 어선의 고속화 및 낚시전용선 개발 추제에 부응하여 어선용 소형 물제트 추진장치의 특성을 파악하고, 시스템의 개념 설계, 시제품 제작과 시운전 시험을 통하여 실용화 가능성을 검토하였다. 어선의 저항 감소, 캐비테이션 억제 등과 관련된 한계 기술을 개발하는 후속 연구가 진행되고 있다.
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서정천,이창섭,Seo, Jeong-Cheon,Lee, Chang-Seop 한국기계연구원 1984 기계연구원소보 Vol.11 No.-
The MAU-series propellers were designed and tested in japan. This report presents the polynomial coefficients of open water Characteristics for each standard MAU-series propellers, obtained by multiple polynomial regression analysis in terms of pitch-diameter ratio and advance coefficient. The limitation of applicability and the accuracy of the regression polynomial are also discussed.
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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 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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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
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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난류 모델이 적용된 VIC 방법의 2차원 날개 단면 해석 및 검증
김명수,서정천,김기섭,김광수,김유철 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.11
A vortex-in-cell (VIC) method for resolved-scale turbulent flow in wake of two-dimensional hydrofoils is presented. As a turbulence modeling, the Smagorinsky model is used to resolve the eddies. The well-established panel method is used together with the Lagrangian approach for solving the vorticity transport equation in time-marching analysis. Besides the irrotational velocity component obtained by the panel method, the rotational velocity component is calculated from the Poisson equation representing relationship between vorticity and vector streamfunction. In numerical implementation of the Poisson equation, we take Fast Fourier Transform scheme coupled with concept of the immersed boundary method using uniformly rectangular grids. With the calculated irrotational and rotational velocity components, we apply the no-penetration boundary condition on the body surface as well as the no-slip condition. By comparison with computing results for laminar version of VIC method and with the corresponding turbulent version results, we support the validation of the present turbulent modeling for VIC method. And using the filter size variation, the residual stress computing results are presented.
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