• Title/Summary/Keyword: Grid points

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Application of a Parallel Asynchronous Algorithm to Some Grid Problems on Workstation Clusters

  • Park, Pil-Seong
    • Ocean and Polar Research
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    • v.23 no.2
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    • pp.173-179
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    • 2001
  • Parallel supercomputing is now a must for oceanographic numerical modelers. Most of today's parallel numerical schemes use synchronous algorithms, where some processors that have finished their tasks earlier than others must wait at synchronization points for correct computation. Hence, the load balancing is a crucial factor, however, it is, in general, difficult to achieve on heterogeneous workstation clusters. We devise an asynchronous algorithm that reduces the idle times of faster processors, and discuss application of the algorithm to some grid problems and implementation on a workstation cluster using Message Passing Interface (MPI).

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Finite Difference Numerical Solutions for Isotropic Rectangular Thin Elastic Plates with Three Edges Clamped and the Other Free (등방성 직사각형의 3변 고정 1변 자유 얇은 탄성판에 대한 유한차분법의 수치해)

  • Seo Seung-Nam
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.18 no.3
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    • pp.225-240
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    • 2006
  • In order to calculate bending moments of rectangular plates with three edges clamped the other free subjected to both a uniform load and a triangular load, a finite difference equation for the non-dimensional governing equation are presented and numerical solutions with different aspect ratios and/or number of grid points are analyzed. The finite difference solutions are obtained by use of grid points up to 11,520 and the optimum grid points according to aspect ratios of the plate are presented as well. The obtained numerical solutions are shown to satisfy the given x moment boundary condition at the free edge, which can not be satisfied in Levy's analytical solutions and peculiar behaviour of the calculated moments is observed around the corners between the free edge and fixed ones. The numerical solutions of bending moments subjected to both a uniform load and a triangular load are compared with the corresponding analytical solutions which are shown in very good agreement on the solution domain except the neighborhood of the free edge.

Control Gain Optimization for Mobile Robots Using Neural Networks and Genetic Algorithms (신경회로망과 유전알고리즘에 기초한 이동로봇의 제어 이득 최적화)

  • Choi, Young-kiu;Park, Jin-hyun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.20 no.4
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    • pp.698-706
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    • 2016
  • In order to move mobile robots to desired locations in a minimum time, optimal control problems have to be solved; however, their analytic solutions are almost impossible to obtain due to robot nonlinear equations. This paper presents a method to get optimal control gains of mobile robots using genetic algorithms. Since the optimal control gains of mobile robots depend on the initial conditions, the initial condition range is discretized to form some grid points, and genetic algorithms are applied to provide the optimal control gains for the corresponding grid points. The optimal control gains for general initial conditions may be obtained by use of neural networks. So the optimal control gains and the corresponding grid points are used to train neural networks. The trained neural networks can supply pseudo-optimal control gains. Finally simulation studies have been conducted to verify the effectiveness of the method presented in this paper.

Extraction of Ground Points from LiDAR Data using Quadtree and Region Growing Method (Quadtree와 영역확장법에 의한 LiDAR 데이터의 지면점 추출)

  • Bae, Dae-Seop;Kim, Jin-Nam;Cho, Gi-Sung
    • Journal of Korean Society for Geospatial Information Science
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    • v.19 no.3
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    • pp.41-47
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    • 2011
  • Processing of the raw LiDAR data requires the high-end processor, because data form is a vector. In contrast, if LiDAR data is converted into a regular grid pattern by filltering, that has advantage of being in a low-cost equipment, because of the simple structure and faster processing speed. Especially, by using grid data classification, such as Quadtree, some of trees and cars are removed, so it has advantage of modeling. Therefore, this study presents the algorithm for automatic extraction of ground points using Quadtree and refion growing method from LiDAR data. In addition, Error analysis was performed based on the 1:5000 digital map of sample area to analyze the classification of ground points. In a result, the ground classification accuracy is over 98%. So it has the advantage of extracting the ground points. In addition, non-ground points, such as cars and tree, are effectively removed as using Quadtree and region growing method.

Computation of Bessel Coordinates of the Cadastral Control Points by Trilateration Adjustment of GPS Baseline Measurements (GPS 관측기선의 삼변망 조정계산에 의한 우리나라 지적측량기준점의 베셀성과 산출)

  • Yang, Chul-Soo;Kang, Sang-Gu;Jung, Rea-Jung;Kim, Yong-Ho;Lee, Min-Seok
    • Journal of Korean Society for Geospatial Information Science
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    • v.15 no.3
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    • pp.41-49
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    • 2007
  • In this study, the software to compute Bessel coordinates by trilateration adjustment was developed, and the software was used to determine coordinates of the cadastral control points over the southern Korean peninsula. The baseline measured by GPS was reduced to the distance on geoid surface by applying PNU95 geoid model, and the distance on geoid surface was reduced to the plane grid distance by applying scale factor of map projection of Bessel coordinates. Using the plane grid distance, Bessel coordinates of 32 CORS (Continuously Operating Reference Station) were computed by free adjustment at first, and then the coordinates of the cadastral control points were computed by joining the control points to adjacent CORS. The result shows a possibility of construction of highly accurate and consistent cadastral survey network with coordinate error less than 1ppm of distance, when newly computing the coordinates of the control points by using distances measured by GPS.

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Improvement of LBW quality of Zircaloy-4 Spacer Grids for PWR Fuel Assembly (경수로 원전연료용 지르칼로이-4 지지격자 레이저용접품질 개선)

  • Kim, Soo-Sung;Song, Kee-Nam;Han, Hyoung-Jun
    • Journal of Welding and Joining
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    • v.24 no.5
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    • pp.22-28
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    • 2006
  • A spacer grid assembly, which is an interconnected array of slotted grid straps and is welded at the intersections to form an egg crate structure, is one of the main structural components of the nuclear fuel assembly for Pressurized Water Reactors (PWRs). The weld quality of spacer grids in PWRs fuel is extremely important for the fuel assembly performance in the nuclear renter. The spacer grid welds are currently evaluated mainly by the metallographic examination although it reveals only cross-points which are welded by the laser beam. This experiment is also to compare the weldability of Zircaloy-4 spacer grids using by the GTA and LB. The effect of node geometries of spacer grids for the GTAW and LBW has been studied and optimum conditions of spacer grid welding have been found. Microstructures and micro-hardness of the GTA and LB welded zones have been also compared.

Flexible Voltage Support Control with Imbalance Mitigation Capability for Inverter-Based Distributed Generation Power Plants under Grid Faults

  • Wang, Yuewu;Yang, Ping;Xu, Zhirong
    • Journal of Power Electronics
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    • v.16 no.4
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    • pp.1551-1564
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    • 2016
  • The high penetration level of inverter-based distributed generation (DG) power plants is challenging the low-voltage ride-through requirements, especially under unbalanced voltage sags. Recently, a flexible injection of both positive- (PS) and negative-sequence (NS) reactive currents has been suggested for the next generation of grid codes. This can enhance the ancillary services for voltage support at the point of common coupling (PCC). In light of this, considering distant grid faults that occur in a mainly inductive grid, this paper proposes a complete voltage support control scheme for the interface inverters of medium or high-rated DG power plants. The first contribution is the development of a reactive current reference generator combining PS and NS, with a feature to increase the PS voltage and simultaneously decrease the NS voltage, to mitigate voltage imbalance. The second contribution is the design of a voltage support control loop with two flexible PCC voltage set points, which can ensure continuous operation within the limits required in grid codes. In addition, a current saturation strategy is also considered for deep voltage sags to avoid overcurrent protection. Finally, simulation and experimental results are presented to validate the effectiveness of the proposed control scheme.

형상보건을 이용한 유한요소 격자생성

  • Lee, Won-Yang;Choi, Young;Cho, Sung-Wook
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1994.10a
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    • pp.298-302
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    • 1994
  • A three dimensional FE mesh generation scheme based on mapping approach is proposed in this study. A volume in Euclcdian space is represented by composite hyperpatches which are piecewise cubic functions with parameters u,v,w. A key idea in the proposed approach is that sampled grid data points only on the boundary surfaces are needed for the shape representation. Inner points which are necessary of form a hyperpatch are internally generated by Coons patches. This approach is most appropriate for the shapes which are compositions of hexahedron-like shapes and also severely curved.

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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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Determining 3D-shape of specular objects by using an encoded grid pattern light source

  • Ye, Xiongying;Fujimura, Sadao
    • 제어로봇시스템학회:학술대회논문집
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    • 1991.10b
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    • pp.1758-1763
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    • 1991
  • This paper describes a new method to determine the 3D-shape of objects consisting of specular planar surfaces. This method exploits a light source which is made of a diffuse plane with a grid pattern encoded in an M-sequence and uses a single image of the light source reflected by the objects to acquiring orientations and positions of the surfaces of the objects. When grid lines of the light source are reflected by a specular planar surface and perspectively projected on an image plane, a set of lines vanishing at a point are obtained on the image plane. The orientation of the specular planar surface is determined by using the vanishing point, and the position is determined by using the correspondence between lines on the image and lines on the light source, which is obtained by employing a characteristic regularity of the M-sequence. Before the vanishing points are calculated, the lines on the image are classified and correlated with the surfaces of objects by using slopes and positions of the lines and the regularity of the M-sequence. This method requires only a single image.

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