• Structural Engineering and Mechanics
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• 제54권1호
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• pp.135-148
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• 2015

The present investigation is concerned with a study effect of magnetic field and non-homogenous on the elastic stresses in rotating orthotropic infinite circular cylinder. A certain boundary conditions closed form stress fields solutions are obtained for rotating orthotropic cylinder under initial magnetic field with constant thickness for three cases: (1) Solid cylinder, (2) Cylinder with a circular hole at the center, (3) Cylinder mounted on a circular rigid shaft. Analytical expressions for the components of the displacement and stress fields in different cases are obtained. The effect of rotation and magnetic field and non-homogeneity on the displacement and stress fields are studied. Numerical results are illustrated graphically for each case. The effects of rotating and magnetic field and non-homogeneity are discussed.

• 대한기계학회논문집B
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• 제21권5호
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• pp.700-712
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• 1997

The flowfield generated by a 2-D rotating cylinder on a plane moving at freestream velocity was experimentally investigated in a wind tunnel to simulate aerodynamic characteristics of rotating wheels of an automobile. In the flowfield around a rotating cylinder at 3*10$^{3}$ < Re$_{d}$<8*10$^{3}$, unique mean flow and turbulence characteristics were confirmed by hot-wire measurements as well as frequency analysis, which was supported by flow visualization. In the vicinity of a rotating cylinder, a unique turbulence structure on .root.over bar u'$^{2}$ profiles was formed in hump-like shape at 1 < y/d < 3. A peak frequency which characterized the effect of a rotating cylinder had the same value of the rotation rate of a cylinder. In case of cylinder rotation, the depths of mean velocity -defect and turbulent-shear regions were thickened by 20-40% at 0 < x/d < 10 compared with the case of cylinder stationary. Far downstream beyond x/d > 10, the flowfield generated by a rotating cylinder showed self-similarity in the profiles of mean velocity and turbulence quantities. The effect of a rotating cylinder was independent of its rotation rate and Reynolds number in the measurement range.

• 한국자동차공학회논문집
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• 제14권1호
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• pp.31-38
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• 2006

Cylinder liner rotation is a new concept for reducing piston assembly friction in the internal combustion engine. The purpose of cylinder liner rotation is to reduce the occurrence of boundary and mixed lubrication friction in the piston assembly. This paper reports the results of experiments to quantify the potential of the rotating liner engine. A GM Quad-4 SI engine was converted to single cylinder operation and modified for cylinder liner rotation. The hot motoring method was used to compare the friction loss between the baseline engine and the rotating liner engine. Additionally, tear-down tests were used to measure the contribution of each engine component to the total friction torque. The cycle-averaged motoring torque of the RLE represents a $23\~31\%$ friction reduction compared to the baseline engine for hot motoring tests. Through tear down tests, it was found that the piston assembly friction of the baseline engine is reduced from $90\%$ at 1200 rpm to $71\%$ at 2000 rpm through liner rotation.

• 대한기계학회논문집B
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• 제26권4호
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• pp.515-523
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• 2002

Effects of rotary oscillation on unsteady laminar flow past a circular cylinder have been investigated in this study. Numerical simulations are performed for the flow at Re=100 in the range of 0.2<$\Omega$<2.5 and 0.02<$St_f$<0.8, where $\Omega$ and $St_f$ are, respectively, the maximum rotation velocity and rotation frequency normalized by the free-stream velocity and cylinder diameter. Results show that rotary oscillation has significant effects on the flow. When the rotation frequency is near the natural vortex-shedding frequency, lock-on occurs and the lock-on frequency range becomes wider as the rotation velocity increases. In a certain range of the rotation frequency and velocity, modulations in the velocity, lift and drag signals occur and this modulation frequency is expressed as a linear combination of the rotation frequency and vortex-shedding frequency. The mean drag and amplitude of the lift fluctuations show local minima near the boundary between the lock-on non and lock-on regions.

• 대한기계학회논문집B
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• 제21권3호
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• pp.436-444
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• 1997

Three-dimensional conjugate heat transfer and particle deposition on a circular cylinder in the OVD process are numerically investigated. Flow and temperature fields are obtained by an iterative method, and thermophoretic particle deposition is simulated. Effects of the heat conduction in the cylinder, the rotation speed of the cylinder, and the traversing speed of torch on the deposition are studied. Effects of variable properties are also included. As the conductivity of the cylinder decreases, particle deposition rate and deposition efficiency greatly decrease due to the reduced temperature gradient. The rotation of the cylinder has no significant effect on the deposition due to the small diameter of the cylinder and low speed of rotation. Since the increase of the torch speed keeps the surface low temperature, the particle deposition increases with the traversing speed.

• 한국기계기술학회지
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• 제13권4호
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• pp.1-7
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• 2011

The paper concerns numerical study of fully developed laminar flow of a Newtonian water and non-Newtonian fluids, 0.2% aqueous of sodium carboxymethyl cellulose(CMC) solution in eccentric annuli with combined bulk axial flow and inner cylinder rotation. Pressure losses and skin friction coefficients have been measured when the inner cylinder rotates at the speed of 0~200 rpm. A numerical analysis considered mainly the effects of annular eccentricity and inner cylinder rotation. The present analysis has demonstrated the importance of the drill pipe rotation and eccentricity. In eccentricity of 0.7 of a Newtonian water, the flow field is recirculation dominated and unexpected behavior is observed. it generates a strong rotation directed layer, that two opposing effects act to create two local peaks of the axial velocity. The influences of rotation, radius ratio and working fluid on the annular flow field are investigated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2095-2100
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• 2003

This Experimental study concerns the characteristics of vortex flow in a concentric annulus with a diameter ration of 0.52, whose outer cylinder is stationary and inner one is rotating. Pressure losses and skin-friction coefficients have been measured for fully developed flow of bentonite-water solution(5%) when the inner cylinder rotates at the speed $0{\sim}400rpm$. The results of present study reveal the relation of the bulk flow Reynolds number Re and Rossby number $R_o$ With respect to the skin friction coefficients. The effect of rotation on the skin friction coefficient is significantly dependent on the flow regime. In all flow regime, the skin friction coefficient is increased by the inner cylinder rotation. The critical (bulk flow) Reynolds number $Re_c$ decreases as the rotational speed increases. Thus, the rotation of the inner cylinder promotes the onset of transition due to the excitation of Taylor vortices.

• 인지과학
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• 제16권4호
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• pp.243-254
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• 2005

Pulfrich 효과는 운동정보를 처리하는 기제가 깊이정보도 처리할 가능성을 시사하는데, 다양한 신경생리학적 결과들이 이러한 가능성을 지지한다. 대표적인 깊이정보인 양안부등을 처리하는 기제가 Pulfrich 효과도 처리할 것이라는 가능성이 제기되어 왔지만, 두 가지 정보원이 하나의 자극 내에 공존하는 경우에 두 정보원의 상호작용 특성을 규명하기 위한 정신물리학적 연구는 없었다. 본 연구는 양안부등과 Pulfrich 효과를 이용하여 회전하는 무선점 반투명 원통체의 회전반향과 깊이를 일관되게 (일치조건) 또는 일관되지 않게 정의하는 조건 (불일치 조건)에서의 원통체의 지각된 깊이와 회전방향을 측정하였다. 일치조건에서 지각된 원통체의 깊이는 양안부등 또는 Pulfrich효과 단독에 의하여 정의된 원통체의 지각된 깊이보다 컸다. 흥미롭게도 불일치 조건에서 원통체의 지각된 회전방향은 양안부둥과 Pulfrich효과의 상대적인 강도에 의하여 조절되었다. 이러한 실험결과는 양안부등과 Pulfrich효과가 하나의 처리기제를 공유함을 함의한다.

• 한국통신학회논문지
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• 제29권8A호
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• pp.962-971
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• 2004

본 논문에서는 모드매칭법을 이용하여 구형 도파관 내부에 금속의 Half cylinder에 의한 산란 특성을 해석하는 수치적 해석법을 제시하였고, Half cylinder의 반경 변화와 회전에 따른 산란 특성을 계산하였다. 또한, 제안된 방법이 일반산란계수법과 연계되었을 때 여러 개의 Half cylinder가 위치한 경우에도 적용 가능함을 보였다. 2 pole 필터의 계산 결과로부터 Half cylinder의 회전에 따라 공진 주파수의 조정이 가능함을 알 수 있었다. 계산 결과는 HFSS의 결과와 비교하여 잘 일치하였다. 본 논문에서 제시한 구조와 해석법은 튜닝 소자로 금속의 Half cylinder를 사용하는 도파관 관련 부품의 설계에 쉽게 이용될 수 있다.

• 대한기계학회논문집
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• 제18권5호
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• pp.1310-1321
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• 1994

Turbulent coherent structures in the intermediate wake of a stationary and rotating cylinder, spin rate S=0.7, situated in a uniform were experimentally investigated using a conditionalphase average technique. Measurements were carried out at a section of 8.5 diameters downstream form the center of cylinder and a Reynolds number of $Re=6.5{\times}10^{3}.$/TEX> The phase averaged velocity and velocity vector fields, contours of vorticity, turbulent intermittency function and velocity fluctuation energy are presented and discussed in relation to the large scale coherent structures by Karman vortices that shed periodically from the cylinder. Coherent wake structures of the rotating cylinder is almost identical with stationary cylinder, but the lateral displacement and shrinkage of turbulent wake region is occured by rotation. Rotation of the cylinder result in that the deflection of wake center to deceleration region(Y/D${\simeq}-0.3)$ and the decrease of mean velocity defect(10%), vorticity strength of large scale structures(19%), total velocity fluctuation energy(12%).