• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.757-761
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• 2008

The aerostat dynamic equation of motion has been built including the tether cable dynamic effects. A numerical program to solve the derived equation of motion has been developed. The dynamic motion of the 32m aerostat has been analyzed under discrete gust and continuous turbulence. The aerostat behaviors under discrete gust which represents a deterministic approach for determining design loads for manned aircraft are solved to verify the effect of aerostat mechanical properties on the aerostat dynamic behavior. Continuous turbulences are simulated for each given altitude, translational mean wind velocity and gust intensity. Dynamic behaviors of the 32m aerostat are simulated for each continuous turbulence conditions. Translational and vertical velocity and pitching behavior and tether reaction force are monitored for each simulation.

• Journal of Mechanical Science and Technology
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• 제20권6호
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• pp.882-895
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• 2006

Surface and interfacial waves in two superposed horizontal inviscid fluids of finite depths are studied. The flow is induced by translating a vertical rigid plate with a prescribed velocity. Analytical solutions that accurately predict the motion of the free surface and the interface are obtained by using a small-Froude-number approximation. Three different velocities of the plate are considered, while flows induced by any arbitrary motion of the plate can be easily analyzed by a linear superposition of the solutions obtained. It is shown that pinching of the upper layer can occur for a sufficiently thin upper layer, which leads to its rupture into small segments. Other interesting phenomena, such as primary and secondary wiggles generated on the interface near the wavemaker, are discussed.

• 한국해양공학회지
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• 제35권2호
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• pp.99-112
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• 2021

The prediction of maneuverability is very important in the design process of an underwater vehicle. In this study, we predicted the steady turning ability of a symmetrical underwater vehicle while considering interactions between the yaw rate and drift/rudder angle through a simulation-based methodology. First, the hydrodynamic force and moment, including coupled derivatives, were obtained by computational fluid dynamics (CFD) simulations. The feasibility of CFD results were verified by comparing static drift/rudder simulations to vertical planar motion mechanism (VPMM) tests. Turning motion simulations were then performed by solving 2-degree-of-freedom (DOF) equations with CFD data. The turning radius, drift angle, advance, and tactical diameter were calculated. The results show good agreement with sea trial data and the effects on the turning characteristics of coupled interaction terms, especially between the yaw rate and drift angle.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 추계 학술발표회논문집
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• pp.403-410
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• 2003

This paper presents the results of experimental studies on the equipment isolation effect in the nuclear containment. For this purpose, shaking table tests were performed. The isolation system, known as Friction Pendulum System (FPS), combines the concepts of sliding bearings and pendulum motion was selected. Peak ground acceleration, bidirectional motion, effect of vertical motion and frequency contents of selected earthquake motions were considered. Finally, it is presented that the FPS systems are effective for the small equipment isolation. Key word equipment isolation, nuclear containment, shaking table test, Friction Pendulum System (FPS)

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.125-130
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• 1999

A flowfields around a NACA0012 airfoil pitching about a 1/4 chord and plunging in vertical displacement are analyzed by solving two-dimensional compressible Navier-Stokes equations. A steady solution was solved first as a validation of the code used and the results were compared with experimental data. Then as a unsteady case, the oscillatory airfoil was solved to compare the results with experimental data. Oscillating rate of pitching and plunging motion was set to have analogy and the magnitude of plunging was set using the magnitude of pitching angle of attack. Finally combined pitching and plunging motion was solved to show the effect of 2 different types of oscillating motion of the airfoil.

• 전자공학회논문지S
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• 제34S권2호
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• pp.33-42
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• 1997

In this paper, a video coding method in wavelet transformed multi-resolution image using variable block sized motion estimation and multi-codebook is proposed. In the propoed method, the accuracy of motion estimation is increased by using variable block matching algorithm based on edge type of blocks which estimation is increased by using variable block matching algoritm based on edge type of blocks which is classified accoridng to the magnitude of wavelet coefficients in vertical subband and horizontal subband of the highest layer. Also, we increased the flexibility of bit allocation and decreased vector quantization error for motion compensated error transmission by using importance of each subband. Some experimental results confirm that he proposed mothod has fine reconstructed images without blocking effect at low bit rate, and especially reconstructs edges well to which human eyes are sensitive.

• 한국전자통신학회논문지
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• 제8권6호
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• pp.831-837
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• 2013

MEMS 가속도계는 운동측정을 위하여 가속도신호를 해석하는 저비용의 방안이다. 이론적으로 변위는 가속도신호를 두 번 적분함으로서 계산될 수 있으나 실제적으로는 실제 존재하는 여러 가지 원인에 의해서 이 방법으로는 계산 될 수가 없다. 본 실험은 실제적인 가속도신호를 획득하여 저주파 운동해석을 위하여 처리하는 과정에 대하여 보여준다.

• 대한조선학회논문집
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• 제48권1호
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• pp.23-32
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• 2011

Numerical analysis of hydrodynamic performance of a movable submerged breakwater was carried out as an eco-friendly marine structure for coastal and harbor protection. Using boundary elements method with two-dimensional frequency-domain reflection and transmission coefficients and wave forces acting on the submerged flat plate were calculated with various submerged depths and respective motion allowable modes. The movable breakwater was found to be more efficient in wave-blocking than the fixed structure. Variation of reflection coefficients was significantly influenced by vertical motion of the body.

• 한국자동차공학회논문집
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• 제8권3호
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• pp.171-180
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• 2000

This paper deals with the whole-body vibration and ride quality evaluation in the vertical direction. The responses of the floor, hip, back, and head in four subjects were measured for various seats when the floor was excited by random vibration with r.m.s of 1.2m/s2 in the vertical direction. In the transmissibility between the hip and floor, the fundamental mode is observed at 4.4 Hz. In the transmissibility between the head and floor, the fundamental mode at 4.4Hz and the second mode at 7.6Hz are observed. It is shown that the head motion is 41% larger than the hip motion and the response of female subject is larger than that of male subject. The response without backrest also was compared with that with backrest. From these human responses ride quality of five seats were evaluated by the ride value such as transfer ration having frequency weighting function is the statistical sense. It is observed that the seat having high damping property can reduce the most acceleration exposed to hip in the statistical sense for all ride valves, while the seat having different seat spring doesn't show statistical difference.

• 대한조선학회지
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• 제12권1호
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• pp.47-58
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• 1975

The effect of the bow shape on the ship motion response among longitudinal regular waves, is investigated employing the strip theory. The two dimensional hydrodynamic forces such as added mass and damping are calculated by the integral equation method for arbitrary sections. Nine ship models are selected for investigation. They are U, UV and V bow ship forms of different block coefficient of 0.6, 0.7 and 0.8 with constant after body. The heave amplitude of the V bow ship is smaller than that of the U bow ship in the whole range of wave length except extremely short wave as were stated by the earlier investigators. This results holds also in the case of bow vertical motions such as vertical relative displacement, velocity and acceralation. As to the pitch amplitudes, the V bow ship gives smaller value in long waves but larger value in short waves. However, heave and pitch phase angles are practically not influenced by the form of the fore body sections. In the bow motions, a little difference in phase angle is appeared in the vicinity of the wave which has same ship length. With respect to the wave exiting force and moment unfovourable effects could be expected in V bow ships. And these tendency hold also in the wave bending moment.