• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.12
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• pp.2101-2109
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• 2003

Structural shape optimization offers engineers with numerous advantages in designing shapes of structures. However, excessive relocation of nodes often cause distortion of elements and eventually result in degrade of accuracy and even halts of processes. To overcome these problems, an effective method, Selective Element Method(SEM), has been developed. This paper describes the basic concept of SEM and processes to implement into real-world problem. 2-D and 3-D shape optimization problems have been chosen to show the performance of the method. Though some limitations have been found, it was concluded that SEM can be useful in general shape optimization and even in some special cases such as decision of optimal weld line location.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.848-854
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• 2015

There are a lot of encryption methods to secure database proposed recently. Those encryption methods can protect the sensitive data of users effectively, but it deteriorates the search performance of database query. In this paper, we proposed the selective element encryption method in order to complement those drawbacks. In addition, we compared the performance of the proposed method with that of tuple level encryption method using the various queries. As a result, we found that the proposed method, which use the selective element encryption with bloom filter as a index, has better performance than the other encryption method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1601-1610
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• 1991

본 연구에서는 3차원 스트레칭 문제의 2차원화가 가능한 주요 단면에 대해서 박막요소와 적층 셸(degenerated shell) 요소를 혼합하여 사용하는 선택적 M/S 방법을 이용하여 2차원 문제로 해석하였다. M/S변환 조건으로는 변형형상의 기하학적 조건 을 고려하였다.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.1972-1975
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• 2003

Video segmentation is an essential part in region-based video coding and any other fields of the video processing. Among lots of methods proposed so far, the watershed method in which the region growing is performed for the gradient image can produce well-partitioned regions globally without any influence on local noise and extracts accurate boundaries. But, it generates a great number of small regions, which we call over segmentation problem. Therefore we proposes image segmentation improvement by selective application structuring element of mathematical morphology.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.531-536
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• 2001

The structural shape optimization is a useful tool for engineers to determine the shape of a structure. During the optimization process, relocations of nodes happen successively. However, excessive movement of nodes often results in the mesh distortion and eventually deteriorates the accuracy of the optimum solution. To overcome this problem, an efficient method for the shape optimization has been developed. The method starts from the design domain which is large enough to hold the possible shape of the structure. The design domain has pre-defined uniform fine meshes. At every cycle, the method judges whether all the elements are inside of the structure or not. Elements inside of the structure are assigned with real material properties, however elements outside of the structure are assigned with nearly zero values. The performance of the method is evaluated through various examples.

• Journal of IKEEE
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• v.16 no.4
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• pp.328-334
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• 2012

In this paper, we analyzed the electromagnetic characteristics of the spherical frequency selective surface with different arrangement of crossed dipole slot elements for reducing the RCS(radar cross section). The three dimensional MOM(method of moment) with RWG basis is used to analyze the proposed structure. To reduce the simulation time, we applied the BiCGSTab(Biconjugate Gradient Stabilized) algorithm as an iterative method and presented the comparison results with Mie's theoretical results for PEC sphere to show the validity of this paper. From the simulation results, the different arrangement of elements array showed the difference RCS that cannot be negligible. The arrangement method of element in frequency selective surface will be one of variables for the design of curved frequency selective structures.

• ETRI Journal
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• v.28 no.4
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• pp.506-508
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• 2006

A frequency selective surface (FSS), whose unit cell consists of a ternary tree loop loaded with a modified tripole, is proposed to block multiple frequency bands. Target frequency bands correspond to Korean personal communication services, cellular mobile communication, and 2.4 GHz industrial, scientific, and medical bands. Through the adjustment of inter-element and inter-unit cell gaps, and adjustment of the length of elements, we present an FSS design method that makes the precise tuning of multiple resonance frequencies possible. Additionally, to verify the validity of our approach, simulation results obtained from a commercial software tool and experimental data are also presented.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.10a
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• pp.39-44
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• 1992

This paper is concerned with formulations of the hierarchical $C^{o}$-plate element on the basis of Reissner-Mindlin plate theory. On reason for the development of the aforementioned element is that it is still difficult to construct elements based on h-version concepts which are accurate and stable against the shear locking effects. An adaptive mesh refinement and selective p-distribution of the polynomial degree using hp-version of the finite element method we proposed to verify the superior convergence and algorithmic efficiency with the help of the clamped L-shaped plate problems.s.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.3
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• pp.195-203
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• 2020

Selective laser melting(SLM) is one of the powder bed fusion(PBF) processes, which enables quicker production of nearly fully dense metal parts with a complex geometry at a moderate cost. However, the process still lacks knowledge and the experimental evaluation of possible process parameter sets is costly. Thus, this study presents a finite element analysis model of the SLM process to predict the melt pool characteristics. The physical phenomena including the phase transformation and the degree of consolidation are considered in the model with the effective method to model the volume shrinkage and the evaporated material removal. The proposed model is used to predict the melt pool dimensions and validated with the experimental results from single track scanning process of Ti-6Al-4V. The analysis result agrees with the measured data with a reasonable accuracy and the result is then used to evaluated each of the process parameter set.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.513-518
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• 2007

A polygon-wise constant curvature natural element approximation is presented in this paper for the numerical implementation of the abstract Kirchhoff plate model. The strict continuity requirement in the displacement field is relaxed by converting the area integral of the curvatures into the boundary integral along the Voronoi boundary. Curvatures and bending moments are assumed to be constant within each Voronoi polygon, and the Voronoi-polygon-wise constant curvatures are derived in a selective manner for the sake of the imposition of essential boundary conditions. The numerical results illustrating the proposed method are also given.