• Title/Summary/Keyword: GRID

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A Near-tip Grid Refinement for the Effective and Reliable Crack Analysis by Natural Element Method (효율적이고 신뢰성있는 자연요소 균열해석을 위한 균열선단 그리드 세분화기법)

  • Cho, Jin-Rae
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.32 no.3
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    • pp.183-190
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    • 2019
  • This paper introduces a near-tip grid refinement and explores its usefulness in the crack analysis by the natural element method(NEM). As a sort of local h-refinement in finite element method(FEM), a NEM grid is locally refined around the crack tip showing high stress singularity. This local grid refinement is completed in two steps in which grid points are added and Delaunay triangles sharing the crack tip node are divided. A plane strain rectangular plate with symmetric edge cracks is simulated to validate the proposed local grid refinement and to examine its usefulness in the crack analysis. The crack analysis is also simulated using a uniform NEM grid for comparison. Unlike the uniform grid, the refined grid provides near-tip stress distributions similar to the analytic solutions and the fine grid. In addition, the refined grid shows higher convergence than the uniform grid, the global relative error to the total number of grid points.

A Study on the Usefulness of VGR (Virtual Grid Role) Algorithm for Elevation of Image Quality in DR System (DR 시스템에서 화질 개선을 위한 VGR 알고리즘의 유용성에 관한 연구)

  • Yang, Hyun-Jin;Han, Dong-Kyoon
    • Journal of the Korean Society of Radiology
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    • v.14 no.6
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    • pp.763-772
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    • 2020
  • During X-ray examinations in the DR system, the scattered X-rays physically generated by the patient cause image blurring in poor quality. Although X-rays to increase the contrast of images, this increases the patient's exposure dose and is likely to result in grid induced artifacts. Therefore, the purpose of this study is obtain images similar to those of real-grid with non-grid level conditions using a VGR (Virtual Grid Role) algorithm that serves as a virtual grid. Comparing MTF, SNR and CNR of non-grid and VGR algorithm images obtained with 70% exposure conditions of real-grid images showed that the MTF0.5 differed from 0.265 to 0.350 and the MTF0.1 from 0.412 to 0.467 and the SNR, CNR were also different. In addition, comparing MTF, SNR and CNR of VGR algorithm and real-grid images showed that the MTF0.5 differed from 0.350 to 0.367 and the MTF0.1 from 0.467 to 0.483 and the SNR, CNR by little.

A Study on the Construction and Deconstruction of the 'Grid' : The Historical Context and Interpretation ('그리드'(Grid)의 형성과 해체 -서양회화의 사적맥락과 그 해석을 중심으로 -)

  • Kim Jai-Kwan
    • Journal of Science of Art and Design
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    • v.1
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    • pp.125-164
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    • 1999
  • The Grid, a lattice structure adapted in paintings, is one of thesimplest plastic structures based on the intersection of horizontal and perpendicular lines. Though mankind has, from the pre-history to the present day, put it to good use in everyday life as a traditional practice or a magical, esoteric, religious emblem in the case of the teciform of primitve art, it was in the paintings of Piet Mondrian that the Grid showed its modern, artistic transformation. As we suggest in the title, before I state the Grid as a plastic construction of modern painting, this dissertation inquires the Grid structure that extends over paintings through the ages as a painterly conept, especially focused on their formation and deconstruction. To begin with, my dissertation investigates, as a historical background, a general idea of the geometrical structure and phases of its transition in art, prior to dealing with the Grids as plastic strures in modern painting. the core of my study on formal Grids is permeated through the third chapter. The first chapter concentrates on, firstly, difining the notion of the Grid and geometrical structure, secondly, searching for a historical backgrounb with whict the so- called modern Grid-paintings come in, inquiring into the formation of the illusion-Grid as aresult of discovering the linear perpective and the situation of the conflict and reconciliaton between reality and illusion. Based on these considerations, the second cecond chapter will examine the various sitations of formation and adaptation of the paintery Grids in the Literalism-Grid, as we have already seen in the chapter one. And the cardinal third chapter devotes itself to the process of the formation of the so-called Object-Grid and Literal-Grid in the Literalism or Minimalism as its logical extension of the Painterly Grid. With it we can get to an interpretation and understanding of the meaning and qualites of Grid dwelt in Modernism thst transformed the structure of Painterly Grid originally as a plane concept to the third dimentionl structure. And then, the fourth chapter, we try to draw a new meaning andre-interpretation of the Formal-Grid as a representatuinnal structure appeared in the post-modernist paintings, going with its deconstructional situation. Therefore, we can, in our study on Grids, see the various points of view in the interpretation of them as illusion-structure, as plane-structure, and as cubic-structure; its concept differs form times, oscillating between its formation and deconstruction. The Grid, as we have seen in my dissertation, contains various problems and significations in art that deserve to investigate throughly, including some important plastic problem such as space and plane, and, in the case of do-grid, time. We may expect new concepts of it that will have difference meanings. 1 hope my study makes some contributions to understanding the coordination of the abstruse modern and contemporary art.

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A Review on the Grid-Connected Technology of the Distributed Energy Resources (분산형전원의 계통연계기술 리뷰)

  • Lee, Kyungsoo
    • Proceedings of the KIPE Conference
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    • 2014.07a
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    • pp.371-372
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    • 2014
  • This review focuses on grid-connected technology for distributed energy resources(DER). The grid-connected technology is categorized into three classifications: 1) protection function; 2) power quality improvement function; 3) grid stabilization fuction. Grid codes comparison of Japan, USA, EU and Korea is also described in the paper.

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A study on the development of PCB automatic routing system using the mixing method of non-grid and grid (논-그리드와 그리드 혼합 방식을 이용한 PCB 자동 배선 시스템 개발)

  • Choe, Yeong-Gyu;Lee, Cheon-Hui
    • The Transactions of the Korea Information Processing Society
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    • v.2 no.4
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    • pp.592-602
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    • 1995
  • Non-grid and grid method are used for modeling the routing region of the automatic routing system. In this study, we develop the automatic routing system by mixing the methods of non-grid and grid to improve the speed of routing. Grid method has a demerit which decreases the automatic routing speed because it is required a lot of memory by the limitation of the size of board and grid, although the electrical and physical elements are insufficient on the PCB, But non-grid is spent gurite less memory than grid method by using a shape-based patterns. Therefore, we used the methods of non-grid and grid altogether in this paper, In the former method, it is attributed to the improvement of speed, the latter one is applied only the connection of the failed routing in the former one, and it performs the complete automatic routing. This system was developed with C++language under the Windows NT environment of IBM 486DX2-66 Computer.

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BPF-based Grid Voltage Feedforward Control of Grid-connected Converters for Improving Robust Stability

  • Yang, Shude;Tong, Xiangqian;Yin, Jun;Wang, Haiyan;Deng, Yaping;Liu, Le
    • Journal of Power Electronics
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    • v.17 no.2
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    • pp.432-441
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    • 2017
  • Grid voltage feedforward is extensively used for controlling grid-connected converters. However, the conventional voltage feedforward control reduces the stability margins of the converter connected to a high-impedance grid. The effect mechanism of voltage feedforward on the grid-connected converter control under high-inductive conditions of the grid impedance is clearly explained in this study using the equivalent transformations of control block diagrams. Results show that the delay produced by the digital control is the root cause of this effect. An improved voltage feedforward strategy, in which a bandpass filter (BPF) is introduced into the feedforward path, is proposed to strengthen the converter's robust stability against grid impedance variations. The selection method of the BPF's bandwidth is also provided considering the tradeoff between the response speed to the grid voltage sag and the system's robust stability. The converter can work stably over a wide range of the grid impedance through the proposed approach. Simulation and experimental results fully verify the effectiveness of the BPF-based voltage feedforward strategy.

Efficient Resource Management Framework on Grid Service (그리드 서비스 환경에서 효율적인 자원 관리 프레임워크)

  • Song, Eun-Ha;Jeong, Young-Sik
    • Journal of KIISE:Computer Systems and Theory
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    • v.35 no.5
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    • pp.187-198
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    • 2008
  • This paper develops a framework for efficient resource management within the grid service environment. Resource management is the core element of the grid service; therefore, GridRMF(Grid Resource Management Framework) is modeled and developed in order to respond to such variable characteristics of resources as accordingly as possible. GridRMF uses the participation level of grid resource as a basis of its hierarchical management. This hierarchical management divides managing domains into two parts: VMS(Virtual Organization Management System) for virtual organization management and RMS(Resource Management System) for metadata management. VMS mediates resources according to optimal virtual organization selection mechanism, and responds to malfunctions of the virtual organization by LRM(Local Resource Manager) automatic recovery mechanism. RMS, on the other hand, responds to load balance and fault by applying resource status monitoring information into adaptive performance-based task allocation algorithm.

Ontology-based Grid Resource Selection System (온톨로지 기반의 그리드 자원선택 시스템)

  • Noh, Chang-Hyeon;Jang, Sung-Ho;Kim, Tae-Young;Lee, Jong-Sik
    • Journal of the Korea Society of Computer and Information
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    • v.13 no.3
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    • pp.169-177
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    • 2008
  • Grid resources are composed of various communication networks and operation systems. When a grid system searches and selects grid resources, which meet requirements of a grid user, existing grid resource selection systems are limited due to their storage methods for resource information. In order to select grid resources suitable for requirements of a grid user and characteristics of data, this paper constructs an ontology for grid resources and proposes an ontology-based grid resource selection system. This system provides an inference engine based on rules defined by SWRL to create a resource list. Experimental results comparing the proposed system with existing grid resource selection systems, such as the Condor-G and the Nimrod-G, verify the effectiveness of the ontology-based grid resource selection system with improved job throughput and resource utilization and reduced job loss and job processing time.

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A Study on Image Change according to Grid Ratio in Digital Radiography (디지털 방사선에서 격자 비에 따른 영상변화에 관한 연구)

  • Sung-Hun Jeong
    • Journal of radiological science and technology
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    • v.46 no.2
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    • pp.89-97
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    • 2023
  • With the introduction of the D.R system, the grid with high removal rate of scattered radiation is selected and used without considering the grid performance evaluation. Despite the high removal rate of scattered radiation belonging to high grid ratio, it is also possible to see the cut-off phenomenon in which the primary ray involved in the formation of image could be removed as well. Thus, the purpose of this study is to provide the basic data for researches on the usefulness of using the grid by presenting the appropriate grid ratio in the D.R system through the measurement of image in grid such as non-grid, 6:1, 8:1, 10:1, 12:1. The equipments used for this study were radiation generator with grid in 12:1, 10:1, 8:1, 6:1, indirect-type detector, and acryl phantom. As the study for image evaluation, this study measured the SNR, PSNR, MSE, and Entropy. In the results of this study, the PSNR was the highest in 6:1 and the lowest in 8:1. The SNR was high in 6:1 and 8:1, and the lowest in 12:1. In case of Entropy, it was high in 8:1 and 10:1, and the lowest in 12:1. Therefore, when the grid is used, it would be more proper to choose the grid in 8:1 or 10:1 with less loss in information content of primary ray rather than the high grid ratio showing the increased patient exposure dose.

Single Sign On between Grid Portal and Web applications on MGrid (MGrid에서 그리드 포털과 웹 어플리케이션의 통합인증)

  • Heo, Dae-Young;Hwang, Dae-Bok;Hwang, Sun-Tae
    • Journal of the Korea Society of Computer and Information
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    • v.14 no.12
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    • pp.1-8
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    • 2009
  • Grid services offer SSO(single sign-on) mechanism using GSI(grid security infrastructure) based on X.509. However. portal applications in web environment use ID and password model for single sign-on. Grid portals means a system which provides grid services by integrating portlet contents on single web interface. In existing research such as GAMA and PURSE, SSO for a whole grid portal is figured out in the way that user is authenticated by ID and password in front and call grid service via GSI at back-end. Other types of web applications outside of portlet framework cannot unfortunately access grid service in SSO way in the existing researches, because the SSO mechanism is developed for portlet framework only. In this paper, we suggest a SSO mechanism based on ID and password model, which forwards authentication information and a GSI token for grid access among portlets and grid-enabled web applications. This mechanism is applied to MGrid for SSO, which consists of applications of java web start, applet, servlet, and etc. as also as portlets.