• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.27-27
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• 1998

제트에 있어서 유동특성은 제트초기의 생성되는 불안정성이 하류에서의 와류성장에 영향을 끼치게 되기 때문에 중요하게 되며, 와류의 조절을 통해 충돌면에의 열전달 효과의 변화를 가져올 수 있게 된다 따라서 본 연구에서는 FFT를 이용하여 제트의 와류생성과 병합의 주파수 특성을 연구하고, 이에 적절한 주파수로 와류를 여기 하여 자유제트의 유동특성 변화와 이에 따른 충돌 면에서의 충돌제트의 유동 및 열전달 특성을 고찰하였다. 제트의 음향을 통한 여기를 함으로써 생성되는 와류형성 및 병합 특성 변화는 연기열선법(smoke-wire method)과 속도 및 난류강도 특성 결과를 통해 확인 할 수 있었는데, 이는 자연적으로 생성되는 와류의 주파수(고유 주파수)와 관련하여 고유주파수의 조화성분 또는 부조화성분의 주파수를 가함으로써 와류의 병합을 촉진시키거나 억제하는 효과를 나타내기 때문이다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1495-1502
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• 1991

본 연구에서는 동일 작업 공간내에서 두대의 로봇이 각각의 토크의 제한 조건 과 충돌 회피 조건을 만족하면서 근사 최소 시간에 지정된 경로를 주행하기 위한 궤적 계획법을 제안하고자 한다. 이때, 동작 우선도에 의하여 한 대의 로봇은 주 로봇, 다른 한 대의 로봇은 종 로봇으로 지정되는데 주 로봇은 입력 토크의 제한조건을 만족 하며 주어진 경로를 최소 시간에 움직이도록 궤적 계획을 하였으며, 종 로봇은 주 로 봇과의 충돌을 피하고 입력 토크의 제한 조건을 만족하며 주어진 경로를 근사 최소 시 간에 움직이도록 하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.716-718
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• 2016

본 연구는 차량이 정차해 있거나 차량을 후진하여 이동시키고자 할 때 운전자의 시야에 보이지 않는 차량의 후방 좌 우측에서 접근하는 차량 또는 보행자와 같은 움직임을 가지는 물체와 충돌을 회피하기 위한 방법에 관한 연구이다. 해당 물체와 충돌을 피하기 위해서는 후방의 영상을 획득하여 움직임을 가진 물체를 식별하고 차량과의 거리, 속도 및 충돌 가능성을 계산할 수 있어야 한다.

• Journal of Korean Port Research
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• v.14 no.2
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• pp.219-231
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• 2000

In this paper a complicated structural behavior in collision and its effects of energy translation to the collision bulkhead was examined through a methodology of the numerical simulation to obtain a ideal bow construction and a location of collision bulkhead against head on collision. In the present the bow structure is normally designed in consideration of its specific structural arrangements and internal and external loads in these area such as hydrostatic and dynamic pressure, wave impact and bottom slamming in accordance with the Classification rules, and the specific location of collision bulkhead by SOLAS requirement. By these studies the behavior of the bow collapse due to collision was synthetically evaluated for the different size of tankers and its operational speed limits, and by the results of these simulation it provides the optimal design concept for the bow construction to prevent the subsequent plastic deformation onto or near to the collision bulkhead boundary and to determine the rational location of collision bulkhead.

• Journal of Korea Multimedia Society
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• v.9 no.5
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• pp.554-563
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• 2006

We present a linear-time algorithm for treating collision response of articulated rigid bodies in physically based modeling. By utilizing the topology of articulated rigid bodies and the property of linear equations, our method can solve in linear time the system of linear equations that is crucial for treating collision response. We also present several new joint condition equations for articulated rigid bodies composed of various joints.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1369-1375
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• 2011

Shot ball impacts to materials cause residual compressive stress on their surfaces. Improving the fatigue strength of a material that has this residual compress stress is the purpose of the shot peening process. A numerical study was performed to evaluate the effect of the strain rate sensitivity and hardness of the shot ball on the residual compressive stress. We calculated the residual compressive stress due to multiple impact shot peening using ABAQUS 6.9-1. AISI 4340 steel was the material used in this study. We compared the effects of high strain rate sensitivities and low strain rate sensitivities and found that when the material's sensitivity to the strain rate increased, the residual compressive stress decreased. In addition, the residual compressive stress of low-hardness material is higher than that of high-hardness material.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.593-599
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• 2016

Incheon Bridge is 13.38 km long with an 800 m span, connecting Incheon International Airport and Songdo International City, Per hour 73.8 vessels navigate this space. The purpose of this study was to suggest a safe passing speed based on the displacement of a vessel based on the safety criteria of Incheon Bridge's anti-collision fence, which was designed during its initial construction. As AASHTO LRFD suggested, vessel collision energy, vessel collision velocity, and the hydrodynamic mass coefficient were considered to derive a safe vessel traffic speed. Incheon Bridge's anti-collision fence was designed so that 100,000 DWT vessels can navigate at a speed of 10 knot. This research suggests a safe speed for vessel traffic through a comparative analysis of an experimental ship's (300,000 DWT) speed and cargo conditions, regulation speed has been calculated according to the collision energy under each set of conditions. Additionally, safe traffic vessel's safe speed was analyzed with reference to tidal levels. Results from the experimental ship showed that a vessel of maximum 150,000 DWT is able to pass Incheon Bridge at a maximum of 7 knots with an above average water level, and is able to pass the bridge with a maximum of 8 knots under ballast conditions.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.3_4
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• pp.247-256
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• 2004

This paper presents an efficient collision detection algorithm the performance of which is independent of animation speed. Most of the previous collision detection algorithms are incremental and discrete methods, which find out the neighborhood of the extreme vertex at the previous time instance in order to get an extreme vertex at each time instance. However, if an object collides with another one with a high torque, then the angular speed becomes faster. Hence, the candidate by the incremental algorithms may be farther from the real extreme vertex at this time instance. Therefore, the worst time complexity nay be $O(n^2)$, where n is the number of faces. Moreover, the total time complexity of incremental algorithms is dependent on the time step size of animation because a smaller time step yields more frequent evaluation of Euclidean distance. In this paper, we propose a new method to overcome these drawbacks. We construct a spherical extreme vertex diagram on Gauss Sphere, which has geometric properties, and then generate the distance function of a polyhedron and a plane by using this diagram. In order to efficiently compute the exact collision time, we apply the interval Newton method to the distance function.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.3
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• pp.179-186
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• 2016

A study is to research crash barriers for vehicles that prevent road breakaway of vehicles and protect car passengers and pedestrians as absorbing impulse. Protection performance tests on vehicle passengers were simulated by using a LS-DYNA program. Through repetitive simulation on various speed and angles, passenger protection performance according to different impact condition was contemplated. Variable setting for the simulation was calculated as the mean weight of domestic car sales. By analyzing NASS (National Automotive Sampling System) of NHTSA (National Highway Traffic Safety Administration) of the U.S., the actual speed and collision angle section of accidents were computed. As a result, we confirmed that THIV (Theoretical Head Impact Velocity) and PHD (Post-impact Head Deceleration) are increased according to the impact speed and angle. Also, when the vehicle hit the guardrail post, we could be confirmed that the passenger protection performance greatly decreased.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.291-297
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• 2008

The solid particle erosion behaviour of unidirectional carbon fiber reinforced plastic (CFRP) composites was investigated. The erosive wear of these composites was evaluated at different impingement angles ($30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $90^{\circ}$), different impact velocities (40, 55, 60, 70m/s) and at three different fiber orientations ($0^{\circ}$, $45^{\circ}$, $90^{\circ}$). The erodent was SiC sand with the size $50-100{\mu}m$ of irregula. shapes. The result showed ductile erosion behaviour with maximum erosion rate at $30^{\circ}$ impingement angle. The fiber orientations had a significant influence on erosion. The erosion rate was strongly dependent on impact velocity which followed power law $E{\propto}\;V^n$. Based on impact velocity (V), impact angle (${\alpha}$) and fiber orientation angle (${\beta}$), a method was proposed to predict the erosion rate of unidirectional fiber reinforced composites.