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이승표,김형관,김용진,오세일,손대원 한국심초음파학회 2014 Journal of Cardiovascular Imaging (J Cardiovasc Im Vol.22 No.2
Background: Although rarefaction of myocardial angiogenesis has been shown to be associated with left ventricular (LV)systolic dysfunction in animal models of ventricular hypertrophy, this relationship has not been investigated in depth norvalidated in humans. We aimed to analyze the relationship of myocardial angiogenesis with various functional and structuralventricular remodeling parameters in moderate to severe aortic stenosis (AS) patients with normal LV ejection fraction (LVEF). Methods: A total of 38 moderate or severe AS patients with LVEF > 50% were enrolled for the current study and all patientsunderwent LV endomyocardial biopsy at the septum during aortic valve replacement. The biopsy specimens were stained forplatelet endothelial cell adhesion molecule-1 (CD31) to analyze the density of blood vessels in the myocardium. Results: The degree of myocardial angiogenesis tended to increase with worse myocardial systolic function, LV filling pressure andprogressed ventricular hypertrophy (Spearman’s ρ = -0.388, p = 0.016 for LVEF; Spearman’s ρ = 0.442, p = 0.007 for E/e’; Spearman’sρ = 0.424, p = 0.008 for LV mass index). The degree of myocardial angiogenesis was also significantly associated with the degree ofaortic valve stenosis (Spearman’s ρ = -0.368, p = 0.023). There was significant difference in the degree of myocardial angiogenesisaccording to the LV geometry (p = 0.016 for mean difference between different LV geometry groups by analysis of variance). Significant predictors of myocardial blood vessel density were LV mass index (β = 0.398, p = 0.010) and LVEF (β = -0.313, p = 0.028). Conclusion: There is a close relationship between myocardial angiogenesis and LV remodeling in moderate to severe ASpatients with normal LVEF, with angiogenesis increasing with LV hypertrophy. Further studies to demonstrate the mechanismunderlying this phenomenon is warranted.
이승표,강기원,장세명,이장호,Lee, Seung-Pyo,Kang, Ki-Weon,Chang, Se-Myong,Lee, Jang-Ho 한국생산제조학회 2010 한국생산제조학회지 Vol.26 No.2
In recent years, wind energy has been the world's fastest growing source of energy. This paper describes the structural design and analysis of composite blade for 2 kW-level HAWT (horizontal axis wind turbine). The aerodynamic design and force, which are required to design and analyze a composite blade structurally, are calculated through BEMT(blade element momentum theory) implemented in public code PROPID. To obtain the equivalent material properties of filament wound composite blades, the rule-of-mixture is applied using the basic material properties of fiber and matrix, respectively. Lay-up sequence, ply thickness and ply angle are designed to satisfy the loading conditions. Structural analysis by using commercial software ABAQUS is performed to compute the displacement and strength ratio of filament wound composite blades.
초탄성 및 점탄성 물성을 고려한 자동차용 휠 베어링 실의 드래그 토크 예측
이승표 한국트라이볼로지학회 2019 한국윤활학회지(윤활학회지) Vol.35 No.5
Wheel bearings are important automotive parts that bear the vehicle weight and translate rotation motion; in addition, their seals are components that prevent grease leakage and foreign material from entering from the outside of the bearings. Recently, as the need for electric vehicles and eco-friendly vehicles has been emerging, the reduction in fuel consumption and CO2 emissions are becoming the most important issues for automobile manufacturers. In the case of wheel bearings, seals are a key part of drag torque. In this study, we investigate the prediction of the drag torque taking into consideration the hyperelastic and viscoelastic material properties of automotive wheel bearing seals. Numerical analysis based on the finite element method is conducted for the deformation analyses of the seals. To improve the reliability of the rubber seal analysis, three types of rubber material properties are considered, and analysis is conducted using the hyperelastic material properties. Viscoelastic material property tests are also conducted. Deformation analysis considering the hyperelastic and viscoelastic material properties is performed, and the effects of the viscoelastic material properties are compared with the results obtained by the consideration of the hyperelastic material properties. As a result of these analyses, the drag torque is 0.29 Nm when the hyperelastic characteristics are taken into account, and the drag torque is 0.27 Nm when both the hyperelastic and viscoelastic characteristics are taken into account. Therefore, it is determined that the analysis considering both hyperelastic and viscoelastic characteristics must be performed because of its reliability in predicting the drag torque of the rubber seals.