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초음속 기저부 유동에서 ${\kappa}-{\varepsilon}$ 난류 모델에 대한 와점성 계수의 영향
박수형,사정환,김지웅,권장혁,김창주,Park, Soo-Hyung,Sa, Jeong-Hwan,Kim, Jee-Woong,Kwon, Jang-Hyuk,Kim, Chang-Joo 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.3
A supersonic base flow is computed to investigate the effect of the eddy viscosity coefficient to the linear ${\kappa}-{\varepsilon}$ turbulence models. Slight modifications to the eddy viscosity coefficient, which are based on the realizability condition, are given to the Launder-Sharma turbulence model so that present models satisfy the realizability condition. Numerical results for supersonic base flow show that turbulence models with the weaky-nonlinear eddy viscosity coefficient can lead to reasonable enhancements in the prediction of the velocity and turbulent kinetic energy profiles.
양측 슬와동맥 혈전 폐색증에서 성공적인 내혈관 치료 1예
박수형 ( Soo Hyung Park ),장원영 ( Won Young Jang ),현학준 ( Hak Jun Hyun ),최성지 ( Seong Ji Choi ),김민정 ( Min Jung Kim ),나승운 ( Seung-woon Rha ) 대한내과학회 2018 대한내과학회지 Vol.93 No.4
The popliteal artery is a relatively short vascular structure, but acute occlusion can decrease blood flow into the lower extremities and cause subsequent critical limb ischemia, amputation, and even mortality. Further, peripheral artery disease patients frequently have combined cardio-cerebrovascular disease. Here, we report a rare case of sudden bilateral thrombotic total occlusion in the popliteal arteries of a patient with dilated cardiomyopathy and left ventricular thrombi. This patient has been successfully managed by endovascular therapy and subsequent intra-arterial thrombolytic therapy. (Korean J Med 2018;93:393-397)
박수형(Soo Hyung Park),성춘호(Chun-ho Sung),권장혁(Jang Hyuk Kwon),이승수(Seungsoo Lee) 한국전산유체공학회 2002 한국전산유체공학회지 Vol.7 No.4
An efficient implicit multigrid method is presented for the Navier- Stokes and k-ω turbulence equations. Freezing and limiting strategies are applied to improve the robustness and convergence of the multigrid method. The eddy viscosity and strongly nonlinear production terms of turbulence are frozen in the coarser grids by passing down the values without update of them. The turbulence equations together with the Navier-Stokes equations, however, are consecutively solved on the coarser grids in a loosely coupled fashion. A simple limit for k is also introduced lo circumvent slow down of convergence. Numerical results for the unseparated and separated transonic airfoil flows show that all computations converge well without any robustness problem and the computing time is reduced to a factor of about 3 by the present multigrid method.
HLLE+와 LU-AF를 이용한 극초음속 화학적 비평형 유동장 해석
박수형(Soo-Hyung Park),권장혁(Tang Hyuk Kwon) 한국전산유체공학회 2000 한국전산유체공학회지 Vol.5 No.2
A robust Navier-Stokes code has been developed to efficiently predict hypersonic flows in chemical nonequilibrium. The HLLE + flux discretization scheme is used to improve accuracy and robustness of hypersonic flow analysis. An efficient LU approximate factorization method is also used to solve the flow equations and species continuity equations in fully coupled fashion to implicitly treat stiff source terms of chemical reactions. The HLLE+ scheme shows lower grid dependency for the wall heating rates than other schemes. The developed code has been used to compute chemical nonequilibrium air flow through expanding hypersonic nozzle and past two and three dimensional blunt-nosed bodies. The results are in good agreement with existing numerical and experimental results.
박수형(Park, Soo Hyung) 한국정치학회 2016 한국정치학회보 Vol.50 No.1
이 논문은 반부패 정치 개혁의 대표적 사례 가운데 하나인 2004년 개정 정치관계법을 소재로 그와 같은 개혁을 뒷받침한 주장의 오류와 그것이 가져온 결과를 분석한다. 2004년 개정 정치관계법은 부패 정치 해소, 고비용 정치 구조 개선을 위해 정당과 단체의 정치·선거 활동 자유를 폭넓게 제한했지만, 이를 뒷받침하는 가정에는 중요한 오류들이 있었다. 첫째, 한국 정치·선거 활동에 너무 많은 비용이 소요된다는 가정은 경험적으로 증명하기 어렵고 평가 기준에 따라 다르게 볼 수 있는 문제이다. 둘째, 정치 자금이 선거 결과를 결정한다는 가정 또한 경험적으로 증명되지 않았을 뿐 아니라 논리적으로 그렇지 않을 가능성이 높다. 셋째, 과다한 정치 자금 수요와 음성적인 정치 자금 기부가 부패를 낳는다는 가정 또한 강력한 조직과 확고한 사회적 기반을 가진 정당의 부패 방지 효과를 고려하지 않은 오류를 범했다. 마지막으로 정당 조직 축소와 정당 활동 제한이 고비용 정치 문제를 해결해준다는 가정은 그것이 가져올 부작용을 고려하지 않은 채 전형적인 반정당 담론에 부응해 자기 대안을 정당화하는 데만 몰두했다. 2004년 정치관계법 개정의 결과 또한 기대와 다른 것으로 나타났다. 우선 애초 목표와 달리 정치 부패를 줄이지 못했다. 다음으로 제3정당의 발전 경로를 차단함으로써 기존 정당 체계를 온존시키는 데 기여했다. 마지막으로 정당 간 경쟁이 사회의 기능 이익에 기반하기보다 도덕·법률 위반 문제를 중심 이슈로 삼아 상대방의 존재 가치를 부정하는 방향으로 나가도록 하는 데 일조했다. This study analyzes fallacies of the arguments upholding 2004 revision of the election and party laws and consequences of the revision. In order to reduce political corruption and to reform high-cost political structure, 2004 revision of the election and party laws has exclusively limited freedom of political activity. The argument upholding this revision has significant fallacies in its assumptions. First, the assumption that the cost of Korean political/election activity is high is difficult to be empirically substantiated and has an equivocal ground. Second, the assumption that money wins elections is neither empirically substantiated nor logically coherent. Third, the assumption that the excessive demand of political money and hidden political funding leads to corruption makes an error in disregarding the corruption prevention effect of a party with a well-established organization and a strong social base. Lastly, the assumption that downsizing of party organization and constraining party activity resolves the problem of high-cost politics is self-legitimizing based on the anti-party discourse without considering its side effects. Also consequences of 2004 revision of election and party laws has turned out to be different from the expected results of the revision. First it has not reduced political corruption as its initial anticipation. Next, the revision has contributed to maintaining the existing political party system while preventing the third party development. Lastly, instead of promoting the party competition to be based on functional interests, the revision has let the party competition develop into gainsaying others’ value of existence by pursuing charges of others’ moral and legal violations.