• Title, Summary, Keyword: Selective Element Method

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Development of a Structural Shape Optimization Scheme Using Selective Element Method (선택적 요소방법을 이용한 구조 형상최적 설계기법의 개발)

  • 심진욱;박경진
    • 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.

The performance analysis of the selective element encryption method (선택적 요소 암호화 방식에 대한 성능 분석)

  • Yang, Xue;Kim, Ji-Hong
    • 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.

Development of Shape Optimization Scheme Using Selective Element Method (Application to 2-D Problems) (선택적 요소방법을 이용한 형상 최적 설계 기법 개발)

  • Shim, J.W.;Shin, J.K.;Park, G.J.
    • Proceedings of the KSME Conference
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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.

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Comparisons of RCS Characteristic of Spherical Frequency Selective Surfaces with FSS Element Arrangement (FSS 단위셀 배열구조에 따른 구형 주파수 선택 구조의 RCS 특성비교)

  • Hong, Ic-Pyo;Lee, In-Gon
    • 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.

Design of a Multiband Frequency Selective Surface

  • Kim, Dong-Ho;Choi, Jae-Ick
    • 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.

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hp-Version of the Finite Element Analysis for Reissner-Mindlin Plates (Reissner-Mindlin 평판의 hp-Version 유한요소해석)

  • 우광성;이기덕
    • Proceedings of the Computational Structural Engineering Institute Conference
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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.

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A Finite Element Model of Melt Pool for the Evaluation of Selective Laser Melting Process Parameters (선택적 레이저 용융 공정의 공정변수 평가를 위한 용융풀 유한요소 모델)

  • Lee, Kanghyun;Yun, Gun Jin
    • 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.

Rotation-Free Plate Element Based on the Natural Element Method (자연요소법에 기초한 회전자유도가 없는 평판요소)

  • Cho, Jin-Rae;Choi, Joo-Hyoung;Lee, Hong-Woo
    • Proceedings of the Computational Structural Engineering Institute Conference
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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.

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Development of 2D Structural Shape Optimization Scheme Using Selective Element Method (선택적 요소 방법을 이용한 2차원 구조물의 형상 최적설계 기법 개발)

  • 심진욱;신정규;박경진
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.4
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    • pp.599-607
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    • 2002
  • During the shape optimization, 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 lot 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. In each cycle, the method allots real properties to the elements inside the structure and nearly zero to ones outside. The performance of the method is evaluated through two examples with displacement and frequency constraints.

Image Segmentation Improvement by Selective Application Structuring Element of Mathematical Morphology (수리 형태학의 선택적 구조요소 적용에 의한 영상 분할의 성능 개선)

  • 오재현;김성곤;김종협;신홍규;김환용
    • Proceedings of the IEEK Conference
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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.

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