• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.827-832
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• 2001

A multi-level optimum design algorithm for prestressed concrete (PSC) box girders is proposed in this paper. To save the numerical efforts, a multi-level optimization technique using model coordination method that separately utilizes both tendon profile design and section design is incorporated. And also, a reduced basis technique for the efficient tendon profile optimization is proposed in this paper. From the numerical investigations, it may be positively stated that the optimum design of PSC box girder based on the new approach proposed in this study will lead to more rational and economical design compared with the currently available designs.

• Structural Engineering and Mechanics
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• v.8 no.1
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• pp.73-84
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• 1999

This paper is concerned with shape optimization problems by the boundary element method (BEM) emphasizing the use of a reduced basis reanalysis technique proposed recently by the author. Problems of this class are conventionally carried out iteratively through an optimizer; a sequential quadratic programming-based optimizer is used in this study. The iterative process produces a succession of intermediate designs. Repeated analyses for the systems associated with these intermediate designs using an exact approach such as the LU decomposition method are time consuming if the order of the systems is large. The newly developed reanalysis technique devised for boundary element systems is utilized to enhance the computational efficiency in the repeated system solvings. Presented numerical examples on optimal shape design problems in electric potential distribution and elasticity show that the new reanalysis technique is capable of speeding up the design process without sacrificing the accuracy of the optimal solutions.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.235-242
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• 2001

An optimization algoriam for the optimum design of prestressed concrete (PSC) box girder bridges is proposed in this paper. In order to optimize the tendon profile efficiently, a reduced basis technique is introduced. The optimization algorithm which includes the tendon profile, tendon size and concrete dimensions optimization problem of the PSC box girder bridges is verified on the Genetic algorikhm (GA) from the numerical examples. it may be positively stated that the optimum design of the PSC box girder bridges based on the new approach proposed in this study will lead to more rational and economical design compared with the currently available designs.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.13 no.2
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• pp.141-159
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• 2009

In this article, we consider a weighted CVT-based reduced-order modelling for Burgers equation. Brief review of the CVT (centroidal Voronoi tessellation) approaches to reduced-order bases are provided. In CVT-reduced order modelling, we start with a snapshot set just as is done in a POD (Proper Orthogonal Decomposition)-based setting. So far, the CVT was researched with uniform density ($\rho$(y) = 1) to determine the basis elements for the approximatin subspaces. Here, we shall investigate the technique of CVT with nonuniform density as a procedure to determine the basis elements for the approximating subspaces. Some numerical experiments including comparison of two CVT (CVT-uniform and CVT-nonuniform)-based algorithm with numerical results obtained from FEM(finite element method) and POD-based algorithm are reported.

• Journal of the Korean Society of Safety
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• v.12 no.3
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• pp.120-131
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• 1997

This paper presents an approximate reanalysis methods of structures based on substructuring for an effective optimization of large-scale structural systems. In most optimal design procedures the analysis of the structure must be repeated many times. In particular, one of the main obstacles in the optimization of structural systems are involved high computational cost and expended long time in the optimization of large-scale structures. The purpose of this paper is to evaluate efficiently the structural behavior of new designs using information from previous ones, without solving basic equations for successive modification in the optimal design. The proposed reanalysis procedure is combined Taylor series expansions which is a local approximation and reduced basis method which is a global approximation based on substructuring. This technique is to choose each of the terms of Taylor series expansions as the basis vector of reduced basis method in substructuring system which is one of the most effective analysis of large -scale structures. Several numerical examples illustrate the effectiveness of the solution process.

• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.1
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• pp.97-106
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• 2016

3D virual reality technique develop rapidly such as parts of education, health, national defense, etc. This paper implements an education contents utilizing 3D virtual reality based on HMD. In this paper, contents make up Changdeokgung Palace using to 3Dmax and Unity program, it shows on implemented Helmet Mounted Display. HMD obtain dynamic image from the target source of smart phone. Also, contents consist of service senerio through divided palace position and King's a day's journey especially. Above all, this paper indicate improving performance according to reduced cybersickness and immersion enlargement. And memory capacity reduced by various technique such that file type, compressed file, minimized resource. Proposed technique can obtain dynamic 3D image by HMD implementation at real time basis so that it is possible to use simultaneously multi-source. From the various and practical experiment, it is confirm that proposed 3D VR education system is useful for experience of virtual reality practically.

• East Asian mathematical journal
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• v.34 no.5
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• pp.661-681
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• 2018

In this paper, we discuss a reduced-order modeling for the Benjamin-Bona-Mahony-Burgers (BBMB) equation and its application to a distributed feedback control problem through the centroidal Voronoi tessellation (CVT). Spatial distcritization to the BBMB equation is based on the finite element method (FEM) using B-spline functions. To determine the basis elements for the approximating subspaces, we elucidate the CVT approaches to reduced-order bases with snapshots. For the purpose of comparison, a brief review of the proper orthogonal decomposition (POD) is provided and some numerical experiments implemented including full-order approximation, CVT based model, and POD based model. In the end, we apply CVT reduced-order modeling technique to a feedback control problem for the BBMB equation.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.3
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• pp.62-70
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• 1989

For the conduct of optimum design for such complicated and large structures as ship structure by direct structural analysis such as finite element method, it is very important problem that the process needs much computational efforts due to the repeated structural analysis. In this study, the reanalysis technique based on the modified reduced basis method is applied in the process to reduce the computing time required in repeated structural analysis. Numerical examples to simple grillage and actual ship structure are performed and applicability of reanalysis technique to structural optimization process is discussed.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.1
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• pp.54-62
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• 1983

This paper presents structural analyses performed on the white body of vehicle using the most competitive analyzer, Finite Element Method, and attempts to obtain design criteria of body. By applying the substructure and restart technique to structural model, computation time is reduced. The synthetic processing from modelling to graphic visualization is accomplished by several subprograms, viz., various pre-post processors. On the basis of home-made vehicle modeling, typical cases of accident and service load is analyzed and discussed. The results obtained will guide the designer to design the structure optimally.

• Structural Engineering and Mechanics
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• v.21 no.5
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• pp.539-551
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• 2005

Finite elements based on isoparametric formulation are known to suffer spurious stiffness properties and corresponding stress oscillations, even when care is taken to ensure that completeness and continuity requirements are enforced. This occurs frequently when the physics of the problem requires multiple strain components to be defined. This kind of error, commonly known as locking, can be circumvented by using reduced integration techniques to evaluate the element stiffness matrices instead of the full integration that is mathematically prescribed. However, the reduced integration technique itself can have a further drawback - rank deficiency, which physically implies that spurious energy modes (e.g., hourglass modes) are introduced because of reduced integration. Such instability in an existing stiffness matrix is generally detected by means of an eigenvalue test. In this paper we show that a knowledge of the dimension of the solution space spanned by the column vectors of the strain-displacement matrix can be used to identify the instabilities arising in an element due to reduced/selective integration techniques a priori, without having to complete the element stiffness matrix formulation and then test for zero eigenvalues.