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증례(症例) : 동맥경화성 뇌혈관변화를 보인 환자에서 혈액학적 이상에 의한 뇌경색
양태호 ( Tae Ho Yang ),오선영 ( Sun Young Oh ),정슬기 ( Seul Ki Jung ),서만욱 ( Man Wook Seo ),김영현 ( Young Hyun Kim ),신병수 ( Byoung Soo Shin ) 전북대학교 의과학연구소 2007 全北醫大論文集 Vol.31 No.1
Background: Anemic hypoxia is characterized by reduced hemoglobin content with normal arterial oxygen tension and saturation. Healthy individual could tolerate profound, short term decrease in hemoglobin level, but patients with severe atherosclerotic narrowing in brain lack the reserve capacity to preserve tissue oxygenation. Aims of study: we evaluate the effect of anemia in severe atherosclerosis narrowing in cerebral vasculature which leading to focal or permanent neurological deficits. Methods: we present five patients with severe atherosclerotic lesion who developed transient or permanent neurological deficits occurred during a severe anemia and recovered or improved after transfusion. Results and conclusion: Iron deficiency should be considered in the differential diagnosis of vascular events and treated as a preventive measure in reducing the risk of stroke in the severe atherosclerotic narrowing in cerebral vasculature.
비정렬 격자계에서 연속체 및 천이 영역 유동 해석을 위한 2차원 Gas-Kinetic BGK 해석자 개발
양태호(T.H. Yang),권오준(O.J. Kwon) 한국전산유체공학회 2014 한국전산유체공학회지 Vol.19 No.2
In the present study, 2-D gas-kinetic flow solver on unstructured meshes was developed for flows from continuum to transitional regimes. The gas-kinetic BGK scheme is based on numerical solutions of the BGK simplification of the Boltzmann transport equation. In the initial reconstruction, the unstructured version of the linear interpolation is applied to compute left and right states along a cell interface. In the gas evolution step, the numerical fluxes are computed from the evaluation of the time-dependent gas distribution function around a cell interface. Two-dimensional compressible flow calculations were performed to verify the accuracy and robustness of the current gas-kinetic approach. Gas-kinetic BGK scheme was successfully applied to two-dimensional steady and unsteady flow simulations with strong contact discontinuities. Exemplary hypersonic viscous simulations have been conducted to analyze the performances of the gas-kinetic scheme. The computed results show fair agreement with other standard particle-based approaches for both continuum part and transitional part.
유한체적법 기반의 격자 볼츠만 해석 기법을 이용한 이차원 압축성 점성 유동 해석
양태호(T.H. Yang),권오준(O.J. Kwon) 한국전산유체공학회 2018 한국전산유체공학회지 Vol.23 No.2
This paper presents a finite-volume based lattice Boltzmann method for simulation of full compressible flows with flexible Prandtl number. The equilibrium distribution function is replaced with circular function where all mass, momentum, and energy is equally distributed along a circle. Two different density distribution functions are newly introduced to develop lattice Boltzmann model for compressible viscous flows. The equilibrium distribution function for the evolution equations can be derived from the integration of the Lagrangian interpolation polynomial, which depends on the configurations of the lattice model in the velocity phase space. Two-dimensional compressible flows in a shock tube were investigated to verify the accuracy of the current lattice Boltzmann method. The lattice Boltzmann method based on circular function was successfully adopted to two-dimenstional unsteady simulations with strong contact discontinuities. The present lattice Boltzmann code is applied to the subsonic laminar flow over an NACA0012 airfoil, and the computed results show fair agreement with the Navier-Stokes solution. The hypersonic flow passing through a cylinder is selected as a test case to verify the performances of the current lattice Boltzmann approach. The present solver gives a reasonable agreement with the continuum-based simulation results for flows including detached normal shock wave near the leading edge. Our results imply that the replacement of the Maxwellian distribution function with circular function may be the suitable approach for the evaluation of compressible viscous flows.
2차원 천이 영역 유동 해석을 위한 비정렬 격자 기반의 Gas-Kinetic BGK 기법
양태호(T. H. Yang),권오준(O. J. Kwon) 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.5
In the present study, 2-D gas-kinetic flow solver on unstructured meshes was developed for flows from continuum to transitional regimes. The gas-kinetic BGK scheme is based on numerical solutions of the BGK simplification of the Boltzmann transport equation. In the initial reconstruction, the unstructured version of the linear interpolation is applied to compute left and right states along a cell interface. In the gas evolution step, the numerical fluxes are computed from the evaluation of the time-dependent gas distribution function around a cell interface. Two-dimensional compressible flow calculations were performed to verify the accuracy and robustness of the current gas-kinetic approach. Gas-kinetic BGK scheme was successfully applied to two-dimensional steady and unsteady flow simulations with strong contact discontinuities. Exemplary hypersonic viscous simulations have been conducted to analyze the performances of the gas-kinetic scheme. The computed results show fair agreement with other standard particle-based approaches for both continuum part and transitional part.
주퇴력 저감을 위한 연식 주퇴 메커니즘의 매개변수에 관한 연구
양태호(Tae Ho Yang),이영신(Young-Shin Lee),이규섭(Kyu-Sub Lee),전상배(Sang-Bae Jun),강국정(Kuk-Jeong Kang) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.7
연식주퇴 메커니즘은 전방 운동량으로 주퇴력을 감소시키는 메커니즘이다. 연식주퇴 메커니즘에 영향을 미치는 매개변수는 사격 각도, 복좌기의 초기 압력, 발사위치등과 같이 다양하게 존재한다. 이런 매개변수들은 연식주퇴 메커니즘에서 전방 운동량을 결정짓는 요소가 된다. 연식주퇴 메커니즘의 설계를 위해 몇 가지 적당한 조건들을 고려하여 전방 운동량에 영향을 미치는 매개변수들에 대해 연구하였다. 여러 가지 매개변수들 중에서 복좌기의 초기 압력과 사격 위치가 전방 운동량에 영향을 미치는 중요한 요소로 확인하였다. 복좌기의 초기 압력이 180 일 때, 주퇴력이 가장 낮은 값을 가진다. The soft recoil mechanism was an effective mechanism for reducing the recoil force by forwarding momentum. There were some parameters such as the fire angle, firing position, and initial pressure of the recuperator, which influenced the forwarding momentum. These parameters affected the generation of the forwarding momentum in the soft recoil mechanism. To design for the mechanism, the parameters affecting momentum were studied to consider some reasonable conditions. Among the various parameters, the initial pressure of the recuperator and firing position was confirmed as a key factor to have affected the momentum. It was determined that the recoil force had a minimum value when the initial pressure of the recuperator was 180.