• Title/Summary/Keyword: Loop Operators

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Quadrilateral Mesh Generation on Trimmed NURBS Surfaces

  • Chae, Soo-Won;Kwon, Ki-Youn
    • Journal of Mechanical Science and Technology
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    • v.15 no.5
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    • pp.592-601
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    • 2001
  • An automatic mesh generation scheme with unstructured quadrilateral elements on trimmed NURBS surfaces has been developed. In this paper NURBS surface geometries in the IGES format have been employed to represent geometric models. For unstructured mesh generation with quadrilateral elements, a domain decomposition algorithm employing loop operators has been modified. As for the surface meshing, an indirect 2D approach is proposed in which both quasi-expanded planes and projection planes are employed. Sampled meshes for complex models are presented to demonstrate the robustness of the algorithm.

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The Minimization of Generator Output Variations by Impulse Chamber Pressure Control during Turbine Valve Test (터빈 밸브시험 중 충동실 압력제어에 의한 발전기 출력변동 최소화)

  • Choi, In-Kyu;Kim, Jong-An;Park, Doo-Yong;Woo, Joo-Hee;Shin, Jae-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.1
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    • pp.152-159
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    • 2010
  • This paper describes the actual application of a feedback control loop as a means for minimizing turbine impulse chamber pressure variation during the turbine steam valve tests at a 1,000 MW nuclear power plant. The chamber pressure control loop was implemented in the new digital control system which was installed as a replacement for the old analog type control system. There has been about 40MW of the generator output change during the steam valve tests, especially the high pressure governing valve tests, because the old control system had not the impulse chamber pressure control so the operators had to compensate steam flow drop manually. The process of each valve test consists of a closing process and an reopening process and the operators can make sure that the valves are in their sound conditions by checking the valves movement. The control algorithm described in this paper contributed to keep the change in megawatt only to 6MW during the steam valve tests. Thereby, the disturbance to reactor control was reduced, and the overall plant control system's stability was greatly improved as well.

Automatic Generation of Triangular Ginite Element Meshes on Three-Dimensional Surfaces (3차원 곡면에서 삼각형 유한요소망의 자동생성)

  • 채수원;손창현
    • Korean Journal of Computational Design and Engineering
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    • v.1 no.3
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    • pp.224-233
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    • 1996
  • An automatic mesh generation scheme with triangular finite elements on three-dimensional surfaces has been developed. The surface triangulation process is performed as follows. To begin, surfaces with key nodes are transformed to two-dimensional planes and the meshes with triangular elements are constructed in these planes. Finally, the constructed meshes are transformed back to the original 3D surfaces. For the mesh generation, an irregular mesh generation scheme is employed in which local mesh densities are assigned by the user along the boundaries of the analysis domain. For this purpose a looping algorithm combined with an advancing front technique using basic operators has been developed, in which the loops are recursively subdivided into subloops with the use of the best split lines and then the basic operators generate elements. Using the split lines, the original boundaries are split recursively until each loop contains a certain number of key nodes, and then using the basic operators such as type-1 and type-2, one or two triangular elements are generated at each operation. After the triangulation process has been completed for each meshing domain, the resulting meshes are finally improved by smoothing process. Sample meshes are presented to demonstrate the versatility of the algorithm.

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Automatic Blood Pressure Control Using PI Controller with $H_{\infty}$ Loop-Shaping

  • Han, Jeong-Yup;Lee, Sang-Kyung;Park, Hong-Bae
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.326-329
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    • 2004
  • In this paper, we show a new form of blood pressure controller combined PI control with $H_{\infty}$ loop-shaping. Hypertensive patients or post-operative patients need to maintain normally blood pressure. Exact regulation of blood pressure is needed for maintaining variable blood pressure of preventing complications. The regulation of blood pressure is achieved by injecting drugs, and usually sodium nitroprusside is used as those kinds of drugs. It is necessary to control the infusion rate sodium-nitroprusside carefully to achieve the desired blood pressure. It has been known that regulation of blood pressure by automatic controller is more effective than regulation of blood pressure by human operators. The control of blood pressure has many constraints and uncertainties. Most of biological system has the time-varying variables and the side effects such as increased risk of sepsis and organ failure. To solve such a problem, we design a new robust PI controller using $H_{\infty}$ loop-shaping to decrease noise effects that come out from human body and errors for time delay. The system with designed controller shows more stable control of mean blood pressure and more robust performance for uncertainties. Validation methods for the control performance are confirmed to computer simulations.

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Implementation of Topological Operators for the Effective Non-manifold CAD System (효율적인 복합다양체 CAD 시스템 위상 작업자 구현)

  • 최국헌
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2004.10a
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    • pp.382-387
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    • 2004
  • As the increasing needs in the industrial filed, many studies for the 3D CAD system are carried out. There are two types of 3D CAD system. One is manifold modeler, the other is non-manifold modeler. In the manifold modeler only 3D objects can be modeled. In the non-manifold modeler 3D, 2D, 1D, and 0D objects can be modeled in a unified data structure. Recently there are many studies on the non-manifold modeler. Most of them are focused on finding unknown topological entities and representing all kinds of topological entities found. In this paper, efficient data structure is selected. The boundary information on a face and an edge is included in this data structure. The boundary information on a vertex is excluded considering the frequency of usage. Because the disk cycle information is not required in most case of modeling. It is compact. It stores essential non-manifold information such as loop cycle and radial cycle. A suitable Euler-Poincare equation is studied and selected. Using the efficient data structure and the selected Euler-Poincare equation, 18 basic Euler operators are implemented. Several 3D models are created using the implemented modeler. A non-manifold modeling can be carried out using the implemented 3D CAD system. The results of this paper could be used in the further studies such as an implementation of Boolean operators, and a translation of 2D CAD drawings to 3D models.

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Automatic Mesh Generation with Quadrilateral Finite Elements (사각형 유한요소망의 자동생성)

  • 채수원;신보성;민중기
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.12
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    • pp.2995-3006
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    • 1993
  • An automatic mesh generation scheme has been developed for finite element analysis with two-dimensional, quadrilateral elements. The basic strategies of the method are to transform the analysis domain into loops with key nodes and the loops are recursively subdivided into subloops with the use of best split lines. Finally by using the basic loop operators, the meshes are completed. In this algorithm an eight-node loop operator is proposed, which is useful in the area where the change of element size is large and the splitting criteria for subdividing the loops have also been modified to the existing algorithms. Lines, arcs, and cubic spline curves are used to define the boundaries of analysis domain. Sample meshes for several geometries are presented to demonstrate the robustness of the algorithm.

Automatic Generation of Quadrilateral Meshes on Trimmed Surfaces (트림 곡면상에서 사각형 요소망의 자동 생성)

  • 김형일;채수원
    • Korean Journal of Computational Design and Engineering
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    • v.4 no.2
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    • pp.153-161
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    • 1999
  • An atomatic mesh generation scheme with unstructured quadrilateral elements on trimmed surfaces has been developed. Trimmed surfaces are often encountered in modeling of structures with complex shapes such as aircrafts, automobile structures, pressure vessels and etc. For unstructured mesh generation with quadrilateral elements, a domain decomposition algorithm employing loop operators has been used. Mesh generation on trimmed surface is performed in three steps. First, trimmed surfaces with holes or cuts are transformed to th largest projection planes in which the meshes are constructed. The constructed meshes are transformed to the u-v parametric plane and then finally to the original 3D surfaces. Th exact locations of holes or cuts in projection planes are determined by the Newton-Raphson method. Sample meshes are constructed to demonstrate the effectiveness of the proposed algorithm.

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On Robustness of Linear Quadratic State Feedback Regulators for Infinite Dimensional systems (무한차원 시스템을 위한 선형 이차상태 궤한 제어기의 견인성에 관한 연구)

  • Seo, Jin-Heon
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.37 no.7
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    • pp.490-497
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    • 1988
  • This paper is concerned with the robust stability of linear quadratic state feedback regulators for infinite dimensional systems in the presence of system uncertainties Several robustness results ensuring the asymptoitc stability and exponential stability of the perturbed closed loop system are derived for a class of nonlinear perturbations of the system and input operators satisfying the matching condition. For the case where the input space is finite dimensional, some robust properties of the state feedback regulator designed on the basis of the linear quadratic regulator for finite dimensional unstable modes are also discussed seperately.

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A Study on the Railway Control by Creation of the Causal Loop Diagram- - Centering on railroad safety management system technical standards 11.7 - (인과순환지도(CLD) 작성을 통한 철도관제업무에 관한 연구 - 철도안전관리체계 기술기준 11.7 철도관제를 중심으로 -)

  • Park, Jung Soo;Lee, Sang Oh
    • Journal of The Korean Society For Urban Railway
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    • v.6 no.4
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    • pp.287-298
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    • 2018
  • This research is intended to understand and make practical suggestions on various aspects of the railroad traffic controllers focusing on railroad control of the railroad safety management system's technical standards. The method of analysis is using the causal loop diagram, which is the soft method of System Dynamics. Content of analysis is about the system. 11.7 of the work of the railroad control system. In addition, we compared and analyzed railroad controllers by four railroad operators, suggesting the importance of railroad control and future practical improvement plans.