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한상훈(Sang-Hoon Han),김명호(Myeong-Ho Kim),최정열(Jeong-Yeol Choi) 한국항공우주학회 2007 韓國航空宇宙學會誌 Vol.35 No.3
이차원 범프 유동에 대한 다양한 예조건화 행렬의 수렴 특성을 살펴 Choi와 Merkle의 예조건화 행렬을 선택하여, 압축성 및 예조건화 Roe의 Riemann 해법의 수치 소산항을 수학적으로 비교하였다. 이 결과 코드의 구조는 동일하게 유지한 채, 고유치의 작은 수정만으로 압축성 해법을 예조건화 해법으로 이전할 수 있는 방법을 알 수 있었다. 아울러 점성 유동 영역에서의 안정성 및 정확성을 향상시키기 위하여 von Neumann 안정 조건 및 점성 자코비안을 고려하였으며, 개발된 코드는 표준 검증 문제에 적용하여 검증을 수행하였다. Comprehensive mathematical comparison of numerical dissipation vector was made for a compressible and the preconditioned version Roe's Riemann solvers. Choi and Merkle type preconditioning method was selected from the investigation of the convergence characteristics of the various preconditioning methods for the flows over a two-dimensional bump. The investigation suggests a way of migration from a compressible code to a preconditioning code with a minor changes in Eigenvalues while maintaining the same code structure. Von Neumann stability condition and viscous Jacobian were considered additionally to improve the stability and accuracy for the viscous flow analysis. The developed code was validated through the applications to the standard validation problems.
지방정부의 정치적 이념과 정책선호: 개발정책과 복지정책에 대한 영향 비교
최정열 ( Jeong Yeol Choi ),박석희 ( Sauk Hee Park ) 한국지방행정연구원 2014 地方行政硏究 Vol.28 No.4
본 연구는 기초자치단체 수준에서 보수와 진보로 표현되는 지방정부의 정치적 이념이 정책선호에 미치는 영향을 분석하는 데 목적이 있다. 이를 위해 본 연구는 지방정부의 정치적 이념을 보수성향과 진보성향으로 이분하였고, 기초의회 의원에 대한 정당공천이 실시된 민선 4기와 5기를 중심으로 2009~2012년의 기간 중 단체장의 당적과 지방의회 과반의석 확보 정당이 동일했던 102개 기초자치단체를 분석대상으로 하였다. 지방정부의 정책 선호는 개발지향정책과 복지지향정책의 두 가지 측면에서 분석하였고, 이는 당해 지방정부 예산에서 경제개발비와 사회보장비의 비중을 통해 측정하였다. 분석 결과 경제개발비는 지방정부의 정치적 이념이 보수적일 경우 증가하는 것으로 나타난 반면, 사회보장비의 경우 지방정부의 정치적 이념에 따른 차이가 없는 것으로 나타났다. 이는 복지정책에 대한 높은 사회적·정책적 수요를 반영함과 동시에 기초자치단체가 주로 주민들의 일상생활과 복리에 관한 사무를 수행한다는 점에서 기초자치단체는 정치적 이념과 무관하게 복지업무를 중시하지 않을 수 없는 현실을 반영한다. This article analyzes the extent to which the political ideology of primary local governments affects their policy preference. To achieve this, it divides political ideology into the conservative and progressive inclination based on both the party affiliation of local government`s head and a political party securing majority seats in the primary local council, and classifies policy preference into the development-oriented and welfare-oriented policy, which is respectively assessed by the proportion of economic development budgets and welfare budgets in local government budgets. The results reveal that while the proportion of economic development budgets is likely to be higher in conservative local governments, the proportion of welfare budgets rarely differs between conservative and progressive local governments. This implies that because they have a responsibility for works related to daily life of citizens, particularly welfare services, primary local governments can not help put an emphasis on welfare services irrespective of political inclinations.
Viscous and Diffusion Effects in the Numerical Simulation of Highly Unstable Detonation Phenomena
최정열(Jeong-Yeol Choi),조덕래(Deok-Rae Cho) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.42
The effect of Reynolds number and grid resolution is investigated in this study. A series of numerical simulations are carried out for wide range of Reynolds number using coarse and fine grid system. The role of diffusion and the effect of grid resolution are clearly understood in the aspect of detonation structures and stabilities in the present study. It is considered that the numerical damping increase the mixing and combustion leading to the completion of combustion. Therefore it is recommended to introduce some sort of mathematical modeling that can account for the physical process of turbulence mixing and combustion in the highly unstable detonation structures.
RDE의 연소동역학 및 액체 로켓 연소 불안정과 연관성에 대한 고찰
최정열(Jeong-Yeol Choi) 한국연소학회 2012 KOSCOSYMPOSIUM논문집 Vol.- No.45
Detonative combustion is considered as a promising combustion mechanism for improving thermodynamic efficiency of power generation systems as a PGC, as well as high-speed propulsion systems. Among the various types of detonative combustion, RDE is fascinated by many researchers because of the simplicity and continuos operation characteristics. Present paper is an introduction to the physical and operational concept of RDE with a brief history of RDE researches and recent development activities. Additional discussions will devoted to the relevance to the tangential mode instabilities in liquid rocket engines and improvement of liquid rocket performance.
최정열(Jeong-Yeol Choi),Vigor Yang 한국전산유체공학회 2003 한국전산유체공학회 학술대회논문집 Vol.2003 No.-
A series of computational simulations have been carried out for supersonic flows in a scramjet engine with and without a cavity. Transverse injection of hydrogen, a simplest form of fuel supply, is considered in the present study with the injection pressure varying from 0.5 to 1.5 ㎫. The corresponding equivalence ratios are 0.167 - 0.50. The work features detailed resolution of the flow dynamics in the combustor, which was not typically available in most of the previous studies. In particular, oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms, Much of the flow unsteadiness is related not only to the cavity, but also to the intrinsic unsteadiness in the flowfield. The interactions between shock waves and shear layer may cause a large excursion of flow oscillation. The role of the cavity and injection pressure are examined systematically