• Structural Engineering and Mechanics
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• 제59권4호
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• pp.653-669
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• 2016

Recent earthquakes worldwide show that a significant portion of the earthquake shaking happens in the vertical direction. This phenomenon has raised significant interests to consider the vertical ground motion during the seismic design and assessment of the structures. Strong vertical ground motions can alter the axial forces in the columns, which might affect the shear capacity of reinforced concrete (RC) members. This is particularly important for non-ductile RC frames, which are very vulnerable to earthquake-induced collapse. This paper presents the detailed nonlinear dynamic analysis to quantify the collapse risk of non-ductile RC frame structures with varying heights. An array of non-ductile RC frame architype buildings located in Los Angeles, California were designed according to the 1967 uniform building code. The seismic responses of the architype buildings subjected to concurrent horizontal and vertical ground motions were analyzed. A comprehensive array of ground motions was selected from the PEER NGA-WEST2 and Iran Strong Motions Network database. Detailed nonlinear dynamic analyses were performed to quantify the collapse fragility curves and collapse margin ratios (CMRs) of the architype buildings. The results show that the vertical ground motions have significant impact on both the local and global responses of non-ductile RC moment frames. Hence, it is crucial to include the combined vertical and horizontal shaking during the seismic design and assessment of non-ductile RC moment frames.

• Structural Engineering and Mechanics
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• 제82권6호
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• pp.735-745
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• 2022

The suspension thyristor valve can generate tremendous vertical acceleration responses in layers and large tension forces in hangers. A shaking table test of a scaled-down model of thyristor valves suspended on a hall building is performed to qualify the risk of vertical uplift of two representative types of valves, the chain valve and the rigid valve. Besides, an analytical model is established to investigate the source of the slackening of hangers. The test results show that the valves frequently experience a large vertical acceleration response. The soft spring joint can significantly reduce acceleration, but is still unable to prevent vertical uplift of the chain valve. The analytical model shows a stiffer roof and inter-story connection both contribute to a higher risk of vertical uplift for a rigid valve. In addition, the planar eccentricity and short hangers, which result in torsional motion of the valve, increase the possibility of vertical uplift for a chain valve. Therefore, spring joints with additional viscous dampers and symmetric layout in each layer are recommended for the rigid and chain valve, respectively, to prevent the uplift of valves.

• 한국운동역학회지
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• 제19권3호
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• pp.457-466
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• 2009

본 연구는 현대무용 아라베스크 동작 시 팔의 사용 유.무에 따라 아라베스크 동작 바로직후의 턴으로 이어지는 동작에 영향을 미치는 운동역학적 변인을 분석하여 무용 동작에 대한 과학적 근거를 마련하고자 하는 연구의 목적이 있다. 상지를 이용하지 않은 아라베스크 턴 동작이 상지를 이용한 아라베스크 턴 동작 보다 머리의 회전력과 몸통의 회전력을 더 사용 하였고, 오른쪽 어깨를 이용한 회전력을 얻었다. 상지를 이용한 아라베스크 턴 동작은 왼쪽의 고관절 범위와 왼쪽 발끝의 위치변화가 수직축으로 크게 상승되어 있고, 상지를 이용하지 않는 아라베스크 턴 동작은 발끝의 위치가 이벤트별 아래로 떨어졌다. 신체중심 변위에서는 상지를 이용한 아라베스크 턴 동작이 회전하는 축으로 더 크게 이동하였고, 상지를 이용하지 않은 아라베스크 턴 동작의 신체중심이 낮게 위치하였다. 또한 최대 수직지면반력의 결과 상지를 이용한 아라베스크 턴 동작이 상지를 이용하지 않은 동작보다 낮은 값으로 나타나, 상지를 이용하지 않은 아라베스크 턴 동작이 상지를 이용한 동작보다 하지의 체중부하를 더 사용한다는 것으로 나타났다.

• 한국통신학회논문지
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• 제28권4C호
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• pp.406-412
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• 2003

움직이는 여러 개 물체의 속도를 추정하능 방법으로 피리오도그램(periodogram)을 사용하는 방법이 있다. 이는 영상 시퀀스를 프레임별로 수직과 수평 방향으로 투사를 한 후 시간축 FFT를 실행한다. 차원 주파수 도메인에서 원점을 지나는 직선상의 화소들의 에너지를 합하여 움직이는 물체의 속도를 추정하게 된다. 물체가 두 개 이상일 경우에는 각각의 움직이는 속도에 해당하는 여러 개의 피크 값들을 검출하게 된다. 이 피크 값들을 짝지어 주게 되면 물체 각각의 속도가 나오게 된다. 본 논문의 방법은 기존의 수평, 수직 투사이외에, 투사의 방향을 추가하여 수평 수직 방향 속도 성분을 짝지워줬다. 기존의 논문들에 비해 간단한 계산으로 움직이는 물체의 속도를 효과적으로 짝지울 수 있다.

• 대한조선학회논문집
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• 제49권4호
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• pp.296-303
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• 2012

The captive model test of submerged body using CPMC(Computerized Planar Motion Carriage) was carried out at the Ocean Basin of KORDI/MOERI. The target model is a submarine with general hullform. The forces and moments acting on the submerged body were measured by 6-axis waterproof gage. The oblique motion test and turning test were carried out in horizontal and vertical planes of the model. Maneuvering coefficients and derivatives were obtained from the test results. The stability indices in horizontal and vertical planes were obtained by using maneuvering derivatives. In this paper the introduction of test equipment and test results are presented.

• 대한기계학회논문집
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• 제19권4호
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• pp.1095-1101
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• 1995

Numerical analysis of vertical solidification process allowing solid-liquid density change is performed by a hybrid method between a winite volume method (FVM) and a finite element method (FEM). The investigation focuses on the influence of solid-liquid density change and cooling rates on the motion of solid-liquid interface, solidified mass fraction, temperatures and thermal stresses in the solid region. Due to the density change of pure aluminium, solid-liquid interface moves more slowly but the solidified mass fraction is larger. The cooling rate of the wall is shown to have a significant influence on the phase change heat transfer and thermal stresses, while the density change has a small influence on the motion of the interface, solidified mass fraction, temperature distributions and thermal stresses. As the cooling rate increases, the thermal stresses become higher at the early stage of a solidification process, but it has small influence on the final stresses as the steady state is reached.

• 대한기계학회논문집A
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• 제26권3호
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• pp.487-496
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• 2002

Hydrodynamic behavior and response of vertical-cylindrical liquid-storage tank is considered. The equation of the liquid motion is shown by Laplace's differential equation with the fluid velocity potential. The solution of the Laplace's differential equation of the liquid motion is expressed with the modified Bessel functions. Only rigid tank is studied. The equivalent masses and heights for the tank contents are presented for engineering design model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.228-230
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• 2005

In this paper, we address an active vibration control system, which suppresses the vibration engaged by magnetically levitated stage. The stage system consists of a levitating platen with four permanent magnetic linear synchronous motors in parallel. Each motor generates vertical force for suspension against gravity and propulsion force horizontally as well. This stage can generate six degrees of freedom motion via the vertical and horizontal forces. In the stage system, which represents the settling-time critical system, the motion of the platen vibrates mechanically. We designed an active vibration control system for suppressing vibration due to the stage moving. The command feedforward with inertial feedback algorithm is used for solving stage system's critical problems. The components of the active vibration control system are accelerometers for detecting stage tables's vibrations, a digital controller with high precise signal converters. and electromagnetic actuators.

• 한국소음진동공학회논문집
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• 제22권9호
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• pp.889-895
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• 2012

A vertical launching system(VLS) is a system for holding and firing missiles on surface ships. When a missile is launched in VLS, relative motion between canister and missile and drag force induced by wind can cause initial unstability of a missile. Thus dynamic analysis of initial behavior of vertically launched missile should be performed to prevent collision with any structure of a ship. In this study, dynamic analyses of initial behavior of vertically launched missile are performed using Monte-Carlo simulation, which relys on random sampling and probabilistic distribution of variables. Each parameter related with dynamic behavior of a missile is modeled with probability variables and Recurdyn, a commercial software for multi body dynamic analysis, is used to perform Monte-Carlo simulation. As a result, initial behavior of a missile is evaluated with respect to various performance indexes in a probabilistic sense and sensitivity of the each parameters is calculated.

• Wind and Structures
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• 제31권5호
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• pp.459-472
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• 2020

This study focused on the non-synoptic, tornado-like wind-induced effects on flexible horizontal structures that are extremely sensitive to winds. More specifically, the nonuniform, intensive vertical wind-velocity and transient natures of tornado events and their effects on the global behavior of a long-span bridge were investigated. In addition to the static part in the modeling of tornado-like wind-induced loads, the motion-induced effects were modeled using the semi-empirical model with a two-dimensional (2-D) indicial response function. Both nonlinear wind-induced static analysis and linear aeroelastic analysis in the time domain were conducted based on a 3-D finite-element model to investigate the bridge performance under the most unfavorable tornado pattern considering wind-structure interactions. The results from the present study highlighted the important effects due to abovementioned tornado natures (i.e., nonuniform, intensive vertical wind-velocity and transient features) on the long-span bridge, and hence may facilitate more appropriate wind design of flexible horizontal structures in the tornado-prone areas.