• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2554-2557
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• 2008

Effect of a particle's spin is investigated numerically by considering the effect of lift occurring due to difference of rotations of a particle and of fluid such as the Saffman lift and Magnus force. These lift forces have been neglected in many previous works on particle-laden turbulence. The trajectory of particles can be changed by the lift forces, resulting in significant modification of the stochastic characteristics of heavy particles. Probability density functions and autocorrelations are examined of velocity, acceleration of solid particle and acceleration of fluid at the position of solid particle. Changes in velocity statistics are negligible but statistics related with acceleration are a little bit changed by particle's rotation. When a laden particle encounters with coherent structures during the motion, the particle's rotation might significantly affects the motion due to intermittently large fluid acceleration near coherent structures.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.2 no.1
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• pp.39-49
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• 1996

The techniques of joint mobilization and traction are used to improve joint mobility or to decrease pain by restoring accessory movements to the shoulder joints and thus allowing full, nonrestriced, pain-free range of motion. In the glenohumeral joint, the humeral head would be the convex surface, while the glenoid fossa would be the concave surface. The medial end of the clavicle is concave anterioposteriorly and convex superioinferiorly, the articular surface of the sternum is reciprocally curved. The acromioclavicular joint is a plane synovial joint between a small convex facet on lateral end of the clavicle and a small concave facet on the acromion of the scapula. The relationship between the shape of articulating joint surface and the direction of gliding is defined by the convex-concave rule. If the concave joint surface is moving on a stationary convex surface, gliding occur in the same direction as the rolling motion. If the convex surface is moving on a stationary concave surface, gliding will occur in an opposite direction to rolling. Hypomobile shoulder joint are treated be using a gliding technique.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.275-283
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• 1999

To predict the dynamic behavior of the cylindrical liquid storage tank subjected to seismic ground motion three dimesional analysis with liquid-structure interaction must be performed, In this study a three dimensional dynamic analysis method over the frequency domain using FE-BE coupling technique which combines the efficiency of the boundary elements for liquid with the versatility of the finite shell elements for tank. The liquid region is modeled using boundary elements which can counter the sloshing effect at free surface and the structure region the tank itself is modeled using the degenerated finite shell elements. At the beginning of the procedure the equivalent mass matrix of the liquid is generated by boundary elements procedure. Then this equivalent mass matrix is combined with the mass matrix of the structure to produce the global mass matrix in the equation of the motion of fluid-structure interaction problem In order to demonstrate the accuracy and validity of the developed method the numerical results re compared with the previous studies. Finally the effects of the fluid-structure interaction on the natural frequency and dynamic response of the system are analyzed.

• Bulletin of the Society of Naval Architects of Korea
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• v.19 no.4
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• pp.47-52
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• 1982

The present paper gives numerical results of 2-D hydrodynamic forces on twin cylinders oscillating on a free surface in a deep water. The singularity distribution method is applied to determine a stream function. Based on the 2-D results the vertical motion responses of a catamaran model(ASR 5061) moving in regular head seas are estimated by using Ordinary Strip Method(O.S.M.). Numerical results show in general good agreements with Jones' theoretical and experimental results except those the resonance frequency.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.7
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• pp.809-822
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• 1992

A mathematical approach to solving the time-varying obstacle avoidance problem is pursued. The mathematical formulation of the problem is given in robot joint space(JS). View-time concept is used to deal with time-varying obstacles. The view-time is the period in which a time-varying obstacles. The view-time is the period in which a time-varying obstacle is viewed and approximated by an equivalent stationary obstacle. The equivalent stationary obstacle is the volume swept by the time-varying obstacle for the view-time. The swept volume is transformed into the JS obstacle that is the set of JS robot configurations causing the collision between the robot and the swept volume. In JS, the path avoiding the JS obstacle is planned, and a trajectory satisfying the constraints on robot motion planning is planned along the path. This method is applied to the collision-free motion planning of two SCARA robots, and the simulation results are given.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.174-180
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• 2002

A virtual reality technology for multipurpose numerical simulation is developed to reproduce and investigate a variety of ocean environmental problems in a 3D-Numerical Wave Tank. The governing equations for solving incompressible fluid motion are Navier-Stokes equation and continuity equation, and the Marker-Density function technique is adopted to implement the fully-nonlinear free-surface kinematic condition. The marine environmental situations, i.e. waves, currents, wind, etc., are reproduced by use of multi-segmented wavemaker on the basis of the so-called "snake-principle". In this paper, some numerical reproduction techniques for regular and irregular waves, multi-directional waves, Bull's-eye wave, wave-current, and solitary wave are presented, and a model test in motion with large amplitude of roll angle is conducted in the developed 3D-NWT, using a overlaid grid system.

• IE interfaces
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• v.16 no.1
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• pp.85-93
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• 2003

The purposes of this study are to investigate perceived discomfort for static joint motions, and to propose rankings for the joint motions based on the perceived discomfort. The perceived discomfort was measured through an experiment using the free modulus method of the magnitude estimation, in which ten healthy college-age female students participated. The results showed that joints, joint motions and their levels significantly affected the perceived discomfort at $\alpha$=0.01, and that the interaction of joints and joint motion levels was also significant. Based on the experimental results, three rankings were proposed by joint and joint motions, by joints and by joint motions, which were very different from the existing ones. Especially, the proposed rankings were different from the males' published before in their order and magnitude. These rankings can be used as a valuable tool for better understanding potentially adverse effects of poor working postures in industrial sites, and as basic data for developing the postural classification scheme.

• The Journal of Korea Robotics Society
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• v.1 no.1
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• pp.46-57
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• 2006

It is well known that mathematical solutions for multi-agent planning problems are very difficult to obtain due to the complexity of mutual interactions among multi-agent. Most of the past research results thus are based on the probabilistic completeness. However, the practicality and effectiveness of the solution from the probabilistic completeness is significantly reduced by heavy computational burden. In this paper, we propose a practically applicable solution technique for multi-agent planning problems, which assures a reasonable computation time and a real world application for more than 3 multi-agents for the case of general shaped paths in agent movement. First, to reduce the computation time, a collision map is utilized for detecting potential collisions and obtaining collision-free solutions for multi-agents. Second, to minimize the maximum of multi-agent task execution time, a method is developed for selecting an optimal priority order. Simulations are finally provided for more than 20 agents to emphasize the effectiveness of the proposed interactive approach to multi-agent planning problems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.730-735
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• 2013

This paper contains various vibration analysis of multi-stage shaft shape such as the bending, torsional and axial vibration. The shaft system is modeled as Timoshenko beam with the transverse shear and rotary inertia effect and the equation of motion is derived by Hamilton's principle with considering clamped-free boundary condition. Then, eigenvalue problem of discrete equation of motion for multi-stage shaft model is solved and got results of the natural frequency through the numerical analysis. Obtained numerical analysis results through Matlab program were compared with those of FEM analysis to verify the results. This study suggests that design of shaft system be consider torsional and axial vibration as well as bending vibration.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.05b
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• pp.559-562
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• 2003

본 논문에서는 실시간 마커프리 모션캡쳐 시스템으로 캡쳐된 동작자의 Root와 End-effector 위치 데이터를 이용하여 가상 캐릭터의 동작을 생성하는 방법에 0해 기술한다. 동작자의 신체중심이 되는 Root와 머리, 손, 발과 같은 End-effector의 위치 데이터는 동작자의 전방 좌, 우에 위치한 동기화된 2대의 컬러 CCD 카메라를 이용하여 3차원 위치를 캡쳐한다. 영상으로부터 추출되지 않은 중간관절의 위치를 생성하기 위해 Root와 End-effector의 3차원 위치값들을 IK( Inverse Kinematics) 알고리듬에 적용하고, 생성된 위치값들에 다양한 신체의 제약조건을 고려하여 정밀하게 계산한다. 이러한 과정을 거치므로 서 20개 관절의 위치값을 생성할 수 있으며, 생성된 관절의 위치값을 가상 캐릭터에 적용하므로 서 캐릭터의 움직임을 실시간으로 생성할 수 있다.