• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.49-55
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• 2003

When a body with slant angle after its shoulder is moving at high speed, the turbulent motion around the afterbody is generally associated with the flaw separation and determines the normal component of the drag. By changing the slant angle of afterbody, there exists a critical angle at which the drag coefficients change drastically. Understanding and control of the turbulent separated flows are of significant importance for the design of optimal configuration of the moving bodies. In the present paper, a new Large Eddy Simulation technique has been developed to investigate turbulent vortical motions around the afterbodies with slant angle. By basis of understanding the structure of turbulent flaw around the body, the new configuration of afterbodies are designed to reduce the drag of body and the nonlinear effects due to the interaction between the body configuration and the turbulent separated flows are investigated by use of the developed LES technique.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.234-239
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• 1993

Most of the control problem is for the redundant manipulators use the pseudo-inverse control, thit is, the redundancy is resolved by the pseudo-inverse of the Jacobian matrix and then the controller is designed based on this resolution. However, this pseudo-inverse control has some problems when the redundant robot repeats the cyclic tasks. This is because the pseudo-inverse resolution is a local solution that generates the different configurations of the robot arm for the same hand position. Therefore it is necessary to find the global solution that maintains the optimal configuration of the robot for the repetitive tasks. In this paper, we want to propose a redundancy resolution method by the optimal theory that uses the calculus of variation. The problem formulations are : first to convert the optimal resolution problem to an optimal control problem and then to resolve the redundancy using the necessary conditions of optimal control.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.95-109
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• 1993

In this study, the optimal configuration of arch structure has been tested by a decomposition technique. The object of this study is to provide the method of optimizing the shapes of both two hinged and fixed arches. The problem of optimal configuration of arch structures includes the interaction formulas, the working stress, and the buckling stress constraints on the assumption that arch ribs can be approximated by a finite number of straight members. On the first level, buckling loads are calculated from the relation of the stiffness matrix and the geometric stiffness matrix by using Rayleigh-Ritz method, and the number of the structural analyses can be decreased by approximating member forces through sensitivity analysis using the design space approach. The objective function is formulated as the total weight of the structures, and the constraints are derived by including the working stress, the buckling stress, and the side limit. On the second level, the nodal point coordinates of the arch structures are used as design variables and the objective function has been taken as the weight function. By treating the nodal point coordinates as design variable, the problem of optimization can be reduced to unconstrained optimal design problem which is easy to solve. Numerical comparisons with results which are obtained from numerical tests for several arch structures with various shapes and constraints show that convergence rate is very fast regardless of constraint types and configuration of arch structures. And the optimal configuration or the arch structures obtained in this study is almost the identical one from other results. The total weight could be decreased by 17.7%-91.7% when an optimal configuration is accomplished.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.8-13
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• 2008

In this study, an adaptive node generation procedure in the radial point interpolation method is proposed. Since we set the initial configuration of nodes by subdivision of background cell, abrupt changes of inter-nodal distance between higher and lower error regions are unavoidable. This unpreferable nodal spacing induces additional errors. To obtain the smoothy nodal configuration, it's regenerated by local Delaunay triangulation algorithm This technique was originally developed to generate a set of well-shaped triangles and tetrahedra. To demonstrate the performance of proposed scheme, the results of making optimal nodal configuration with adaptive refinement method are investigated for stress concentration problems.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.7
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• pp.2356-2366
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• 1996

High-power electronic chips have been advanced to such an extent that the heat dissipation capability of a system design has become one of the primary limiting factors. Therefore, thermal design must be considered in the early stage of the electronic system development. In present paper, the results of an experimental study on the forced convection cooling are presented to evaluate cooling performance of an electronic cabinet which in generally used for telecommunication system. Temperatures and thermal resistances are applied to compare the heat transfer characteristics for various locations of a fan unit as well as various configuration of non-uniform powering modules. As a result, the optimal configuration of a fan unit and powering configuration is suggested for the effective thermal design of telecommunication system.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.67-75
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• 2002

A study to investigate the influence of combustion chamber shape, especially piston top face configuration, on the combustion stability is presented with CFD analysis and single cylinder GDI engine test. Initial configuration of the piston bowl was designed with CFD analysis and further parametric studies of the design factors on the piston top face were carried out through the single cylinder GDI engine test. It was found that both the geometry of piston top face and the compression ratio have great influences on the combustion stability. Of interest is that the design factors of the GDI piston to prevent mixture diffusion out of the piston bowl have important roles for the stable combustion at the stratified mixture condition. Also the relationship between spray impingement and flow pattern in a GDI piston bowl should be considered to design an optimal bowl configuration for stable stratified combustion.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.4
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• pp.31-38
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• 2012

In this paper, requirements of GNSS receiver station installation are derived for optimizing the performance of network based GNSS precise positioning by concern of international organization(IGS, NGS) recommendation. Also a analysis method of network based GNSS precise positioning is suggested in order to evaluate the availability depending on various network configurations. To evaluate network candidates, a performance evaluation method is proposed for positioning of users according to a geometric configuration and the baseline distance. After the proposed method is used to Ochang region that is a the test area 6 network candidates are derived and the performance of positioning was analyzed. Finally, Ansung, Gongju, Eumsung, Boeun network configuration was selected as the best positioning performance. An optimal Receiving station network was selected using the proposed method.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.16 no.4
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• pp.1-11
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• 2008

This research presents a study for the knowledge-based configuration design development of a RC (remote control) helicopter. Parametric design and knowledge based design concepts are introduced for rapid design changes and analyses using commercial CAD software, CATIA(R) Knowledgeware module. It is crucial for RC helicopter design because it enables rapid conceptual design through instant configuration changes. Positions and dimensions of RC helicopter parts were used as design parameters. As an example, positions of CG(center of gravity) points were traced and plotted as the configuration changes. Further research should be performed in areas of user interfaces and web-based multi-user environments instead of using Excel data sheets.

• International Journal of Control, Automation, and Systems
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• v.4 no.4
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• pp.486-494
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• 2006

In this paper, we present the complete isotropy analysis of a caster wheeled omnidirectional mobile robot (COMR) with nonredundant/redundant actuation. It is desirable for robust motion control to keep a COMR close to the isotropy but away from the singularity as much as possible. First, with the characteristic length introduced, the kinematic model of a COMR is obtained based on the orthogonal decomposition of the wheel velocities. Second, a general form of the isotropy conditions of a COMR is given in terms of physically meaningful vector quantities which specify the wheel configuration. Third, for all possible nonredundant and redundant actuation sets, the algebraic expressions of the isotropy conditions are derived so as to identify the isotropic configurations of a COMR. Fourth, the number of the isotropic configurations, the isotropic characteristic length, and the optimal initial configuration are discussed.

• Journal of Korean Institute of Industrial Engineers
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• v.28 no.4
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• pp.425-434
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• 2002

Mobility of service users makes location update and paging (L/P) procedures indispensable features in mobile communication networks. Importance of optimizing the configuration of L/P areas has been increased by the growth of L/P related signaling. In this study, we deal with the L/P configuration which an LA (Location Area) may contain multiple PAs (Paging Areas). Given the network topology, L/P related parameters, and traffics generated by each cell, is provided the problem of finding optimal LA/PA configuration minimizing the amount of L/P related signaling. The optimization problem is solved using a simulated annealing, and detailed computational results are conducted to capture the effects of mobility, call arrival patterns and boundary crossing rate on the LA and PA configurations.