• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.689-694
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• 2003

An iterative modal analysis approach is developed to determine the effect of transverse open cracks on the dynamic behavior of simply supported pipe conveying fluid subject to the moving mass. The equation of motion is derived by using Lagrange's equation. The influences of the velocity of moving mass and the velocity of fluid flow and a crack have been studied on the dynamic behavior of a simply supported pipe system by numerical method. The presence of crack results in higher deflections of pipe. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments i.e. the crack is modelled as a rotational spring. Totally, as the velocity of fluid flow and the crack severity are increased, the mid-span deflection of simply supported pipe conveying fluid is increased. The time which produce the maximum dynamic deflection of the simply supported pipe is delayed according to the increment of the crack severity.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.713-718
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• 2001

This paper describes an attempt to develop a new equation to calculate deflection for reinforced concrete deep beams(a/d<2.5). The main idea incorporated with this equation is the internal force state factor($\alpha$)which is able to express global state of internal force flow in cracked reinforced concrete beams subjected to shear and bending. A new equation for deflection calculation using internal force state factor($\alpha$)provides more exact result of deflection in reinforced concrete deep beams than the equation predicted by the current code provisions.

• Wind and Structures
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• 제5권2_3_4호
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• pp.329-336
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• 2002

The along-wind response of a surface-mounted elastic fence under the action of wind was investigated numerically. In the computations, two sets of equations, one for the simulation of the unsteady turbulent flow and the other for the calculation of the dynamic motion of the fence, were solved alternatively. The resulting time-series tip response of the fence as well as the flow fields were analyzed to examine the dynamic behaviors of the two. Results show that the flow is unsteady and is dominated by two frequencies: one relates to the shear layer vortices and the other one is subject to vortex shedding. The resulting unsteady wind load causes the fence to vibrate. The tip deflection of the fence is periodic and is symmetric to an equilibrium position, corresponding to the average load. Although the along-wind aerodynamic effect is not significant, the fluctuating quantities of the tip deflection, velocity and acceleration are enhanced as the fundamental frequency of the fence is near the vortex or shedding frequency of the flow due to the occurrence of resonance. In addition, when the fence is relatively soft, higher mode response can be excited, leading to significant increases of the variations of the tip velocity and acceleration.

• 전자공학회논문지
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• 제50권11호
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• pp.108-116
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• 2013

네트워크 온 칩(Network on Chip)의 라우터에서 사용되는 입력버퍼는 온 칩 네트워크 플로우 컨트롤 및 가상채널 구성을 통해 네트워크의 성능을 좌우하는 중요한 요소이다. 하지만 네트워크 크기 증가에 따른 입력버퍼의 면적 및 전력 소모 증가 문제가 심화됨에 따라 입력버퍼를 제거한 버퍼리스 디플렉션(Bufferless Deflection) 라우팅 기법이 등장하였다. 그러나 버퍼리스 디플렉션 라우터는 통신량이 많은 네트워크에서 성능이 급격히 감소하기 때문에 이를 해결하기 위해 소량의 사이드 버퍼(side buffer)와 디플렉션 라우팅 기법을 결합하는 연구들이 등장하였다. 이러한 기법들은 전송시간 등에 의한 단순 우선순위에 따라 출력 포트에 할당할 데이터를 결정하는 방식을 사용함으로 인해 출력포트에서의 패킷 충돌이 빈번해져 네트워크의 성능을 제한한다. 본 논문에서는 데이터의 위치 정보를 이용한 변형된 디플렉션 라우팅 기법을 제안하고 이에 부합하는 라우터 구조를 제시하였다. 모의실험 결과 제안한 방식은 기존의 사이드 버퍼를 사용하는 디플렉션 라우터에 비해 3%의 면적이 증가하지만 처리량이 12% 향상되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.202-205
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• 1995

Developed controller is the part of deflection yoke winding machine which controls the power to form the deflection yoke coil into desired shape after winding. So as to form the deflection yoke coil, it is needed to melt the bonding material which is spreaded on the coil. The heat melt the bonding material which is produced by flowing the current through the winded coil. Therefore, at first it is needed to peel off the enamel from the winded coil so as to flow the current, and then supply the power to produce the heat which form the winded coil into desired shape. Naturally developed controller is composed of the peeling part and the conduction and forming part. All of them consist of the inverter structure and control the output current. The peeling is achieved by low voltage and high AC current, the conduction and forming is by DC current. Developed controller also has a function that detect the resistance of the deflection yoke coil to prevent the damage of the load which is produced by poor peeling.

• International Journal of Aeronautical and Space Sciences
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• 제10권2호
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• pp.95-105
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• 2009

The flow fields around the HARTII rotor were numerically investigated using a viscous flow solver on adaptive unstructured meshes. An overset mesh and a deforming mesh technique were used to handle the blade motion including blade deflection, which was obtain from the HARTII experimental data. A solution-adaptive mesh refinement technique was also used to capture the rotor wake effectively. Comparison of the sectional normal force and pitching moment at 87% radial station between the two cases, with and without the blade deflection, showed that the blade loading is significantly affected by blade torsion. It was found that as the mesh was refined, the strength of tip vortex is better preserved, and the magnitude of high frequency blade loading, caused by blade-vortex interaction (BVI), is further magnified. It was also found that a proper time step size, which corresponds to the cell size, should be used to predict unsteady solutions accurately. In general, the numerical results in terms of the unsteady blade loading and the rotor wake show good agreement with the experimental data.

• 한국정밀공학회지
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• 제20권5호
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• pp.66-72
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• 2003

In case of hollow cylinder extrusion using porthole die, the effects of extrusion parameters-temperature, the speed of extrusion, the shape of the die and mandrel-on metal flow in porthole die extrusion of aluminum have been investigated. However, there have been few studies about condenser tube extruded by porthole die. Original metal flow of condenser tube by porthole die extrusion is similar to hollow cylinder extrusion but the estimation of metal flow for extrusion parameters is different. For example, variation of chamber length in hollow extrusion only affects the welding pressure, however, the welding chamber length in condenser tube extrusion influences to the welding pressure as well as the deflection of mandrel. This study was designed to evaluate metal flow, welding pressure, extrusion load, tendency of mandrel deflection according to angular variation in the bottom of chamber in porthole die. Estimation was carried out using finite element method in as non-steady state. Analytical results can provide useful information the optimal design of porthole die.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.1999-2010
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• 2023

Undesirable flapping motion of discs can cause the failure of swing check valves in nuclear passive safety systems. Time-resolved particle image velocimetry (PIV) was employed to investigate the flow characteristics around a free-to-rotate plate and the motion response, with the Reynolds numbers, based on the hydraulic diameter of the channel, from 1.32 × 10⁴ to 3.95 × 10⁴. Appreciable flapping motion (±3.52°) appeared at the Reynolds number of 2.6 × 10⁴ with the frequency of 5.08 Hz. In the low-Reynolds-number case, the plate showed negligible flapping. In the high-Reynolds-number case, the deflection angle increased with reduced flapping amplitude. The torque from the fluid determined the flapping amplitude. In the low-Reynolds-number case, Karman vortices were absent. With increasing Reynolds numbers, Karman vortices developed behind the plate with larger deflection angles. Strong interaction between the wake flow from the leading and trailing edge of the plate was observed. Based on power spectrum density (PSD) analysis, the vortex shedding frequency coincided with the flapping frequency, and the amplitude was positively correlated to the strength of the vortices. Proper orthogonal decomposition (POD) modes evince that, in the case of appreciable motion, coherent structures exhibited a larger spatial scale, enhancing the magnitude of the external torque on the plate.

• International Journal of Aeronautical and Space Sciences
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• 제14권3호
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• pp.210-214
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• 2013

The sensitivity of transonic flow past a Whitcomb airfoil to deflections of an aileron is studied at free-stream Mach numbers from 0.81 to 0.86 and vanishing or negative angles of attack. Solutions of the Reynolds-averaged Navier-Stokes equations are obtained with a finite-volume solver using the $k-{\omega}$ SST turbulence model. The numerical study demonstrates the existence of narrow bands of the Mach number and aileron deflection angles that admit abrupt changes of the lift coefficient at small perturbations. In addition, computations reveal free-stream conditions in which the lift coefficient is independent of aileron deflections of up to 5 degrees. The anomalous behavior of the lift is explained by interplay of local supersonic regions on the airfoil. Both stationary and impulse changes of the aileron position are considered.

• 한국가시화정보학회지
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• 제21권1호
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• pp.40-46
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• 2023

For application to drag-based propulsion system, the dynamics of a segmented structure with multiple hinges undergoing oscillatory motion are investigated. The side flaps are connected to a centre rod with elastic plates acting as hinges. The hinges bend to only one direction so that the structure behave asymmetrically between the power stroke and the recovery stroke. An analytical model is proposed, which estimates the asymmetric deformation of the segmented structure coupled with hinges. Using the proposed model, the effects of key geometric and kinematic parameters on the dynamics of the structure are analyzed.