• Title/Summary/Keyword: Optimum Modification Method

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The Optimum Modification of Dynamic Characteristics of Stiffened Plate Structure Including the Number of Stiffener (보강재의 수를 포함한 보강판 구조물의 동특성의 최적변경)

  • 박성현;고재용
    • Journal of the Korean Institute of Navigation
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    • v.25 no.4
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    • pp.461-469
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    • 2001
  • The purpose of this paper is the optimum modification of dynamic characteristics of stiffened plate structure including the number of stiffener. This paper shows the optimum structural modification method by dynamic sensitivity analysis and quasi-least squares method and considers it's validity. In the method of the optimization, finite element method, sensitivity analysis and optimum structural modification method are used. The change of natural frequency and total weight are made to be an objective function. Thickness of plate, the number of stiffener and cross section moment of stiffener become a design variable. The dynamic characteristics of stiffened plate structure is analyzed using finite element method. Next, rate of change of dynamic characteristics by the change of design variable is calculated using the sensitivity analysis. Then, amount of change of design variable is calculated using optimum structural modification method. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate structure including the number of stiffener.

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Study on the Optimum Modification and Modal Analysis of Stiffened Plate of Ship Hull Structure (신체의 Stiffened Plate 구조물의 모우드해석과 최적변경법에 관한 연구)

  • 박성현;박석주;고재용
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2000.10b
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    • pp.51-58
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    • 2000
  • The purpose of this study is the optimum modification of dynamic characteristics of stiffened plate structure. In the method of the optimization ,finite element method (FEM), sensitivity analysis and optimum structural modification method are used. To begin with, using FEM, the dynamic characteristics of stiffened plate structure is analyzed. Next, rate of change of dynamic characteristic by the change of design variable is calculated using the sensitivity analysis. Then, amount of change of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of plate and cross section moment become a design variable. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate structure.

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The optimum structural modification by shape changes (형상변경에 의한 최적구조변경법)

  • 오창근;박석주
    • Journal of Advanced Marine Engineering and Technology
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    • v.19 no.3
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    • pp.42-49
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    • 1995
  • In this study, the optimum structural modification of the L-type structure by shape changes is suggested. The vibration characteristics of L-type structure are analyzed by the sub-structure synthesis method, and the coordinte sensitivities of each sub-structure are calculated and the change quantities of the positions to be modified are suggested by using the coordinate sensitivities. The results obtained are as follows : 1. The sensitivities of the natural frequency could be calculated by the sensitivity analysis. 2. The change quantities of the position to be modified could be suggested by the optimum structural modification method. 3. The developed program could reduce the process and time of computation, since the sensitivity was directly calculated by differential method, not finite difference method.

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A Study on the estimation of an equivalent system of a local vibration system of a huge structure and the Optimum Structural Modification Method (거대 구조물의 국부진동계의 등가계 산출과 이를 이용한 최적구조변경법)

  • 박석주;황문주;오창근;김성우
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 1998.04a
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    • pp.120-127
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    • 1998
  • It is very difficult to execute the vibration analysis of a huge strucutre, which takes up much time and expense. In this paper we intend to make the equivalent system of a local vibration system of a huge structure with a view to improving the dynamic characteristics and reducing time and expense. First of all, upper deck structure model is maded. And we perform the vibration analysis by the Substructure Synthesis Method and execute the exciting test for the upper deck structure model, and observe the coincidences of two results to confirm the reliability of the analyzing tools used. To make the equivalent system, we give boundary condition to sub-structure that want to be modified and execute the Sensitivity Analysis Method and the Optimum Structural Modification Method. And we execute the structural modification of the equivalent system.. The following can be found from this study. 1. The analytical results are generally coincident with each other. 2. The equivalent system of the superstructure model can be easily obtained using the sensitivity analysis metho and the optimum structural modification method. 3. The structural modification using the equivalent system can be obtained good results above 90% of object value.

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A Study on the Optimum Modification of Dynamic Characteristics of Stiffened Plate Structure of Ship (선박의 보강판 구조물의 동특성의 최적 변경법에 관한 연구)

  • 박성현;박석주;고재용
    • Journal of the Korean Institute of Navigation
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    • v.25 no.1
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    • pp.45-52
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    • 2001
  • The purpose of this study is the optimum modification of dynamic characteristics of stiffened plate structure. In the method of the optimization, finite element method(FEM), sensitivity analysis and optimum structural modification method are used. To begin with, using FEM, the dynamic characteristics of stiffened plate structure is analyzed. Next, rate of change of dynamic characteristics by the change of design variable is calculated using the sensitivity analysis. Then, amount of change of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of plate and cross section moment become a design variable. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate structure.

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A Gate Modification Method Using the Input Vector Maximizes the Number of Gates in WLS within the Optimum Range (최적 범위내에서 WLS인 게이트 수가 최대가 되는 입력 벡터를 이용한 게이트 수정 기법)

  • Sung, Bang-Hyun;Park, Hyae-Seong;Kim, Seok-Yoon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.4
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    • pp.745-750
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    • 2007
  • In this paper, we propose a new gate modification method using the input vector maximizes the number of gates in WLS within the optimum range of the minimum leakage power. We prove that MLV is not always the optimal solution, and that the leakage power and area can decrease when modifying the gates using the input vector for which the number of gates in WLS is maximized within the optimum range of the minimum leakage power for the circuits applying the IVC technique and gate modification method. Using the proposed method, the gate-level description circuit can be converted to the modified circuit which reduces the leakage power by chip designer, and the modified circuit can be applied without any modification in design flow.

A Study on the Structural Modification of the Open Box Type Structure by Using the Stiffener (보강재를 이용한 열린 상자형 구조물의 구조변경법에 관한 연구)

  • 박석주;최창우;오창근;왕지석;정재현
    • Journal of KSNVE
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    • v.6 no.1
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    • pp.57-64
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    • 1996
  • The objectiv of this paper is to offer the method of the optimum structural modification by fixing the stiffener on the structure. The vibrational characteristics of a open box type structure are analyzed by the sub-structure synthesis method and sensitivies of each sub-structure are calculated by sensitivity analysis method. The positions to modify are found and the quantities to change are obtained by optimization techniques. As the result, it was found that; (1) The sensitivites of the natural frequency could easily be calculated by the sensitivity analysis method and the optimum position to fix stiffeners could be found. (2) The exact size of stiffeners could be calculated by the optimum structural modification method and the natural frequency could be easily shifted to the objective value. (3) It could be confirmed that the stiffener is a effective tool for accomplishing structural modification.

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A Study on Optimum Modification of Dynamic Characteristics of Stiffened Plate Using Simplified Equation of Natural Frequency (고유진동수의 간이 추정식을 이용한 보강판 구조물의 동특성의 최적변경에 관한 연구)

  • 박성현;남정길
    • Journal of Advanced Marine Engineering and Technology
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    • v.26 no.1
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    • pp.48-58
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    • 2002
  • There is a purpose of this study for the proposal of the optimum technique utilized for the vibration design initial step. The stiffened plate structure for the ship hull is made for analysis model. To begin with, dynamic characteristics of stiffened plate structure is analysed using FEM. Main vibrational mode of the structure is decided in the analytical result of FEM. The simplified equation on the natural frequency of the main vibrational mode is induced. Next, sensitivity analysis is carried out using the simplified equation, and rate of change of dynamic characteristics is calculated. Then, amount of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of panel, cross section moment of stiffener and girder become a design variable. The validity of the optimization method using simplified equation is examined. It is shown that the result effective in the optimum modification for natural frequency of the stiffened plate structure.

A study on the weight minimization of an engine block (엔진 블록의 중량 최소화에 관한 연구)

  • 오창근;박석주;박영범
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1996.10a
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    • pp.231-236
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    • 1996
  • Recently to develope an automobile with better properties, much researches and investments are executed in many countries. In this paper, the weight of an engine block intend to minimize without changing the natural frequency. The weight minimization of an engine block is started from much less initial thickness than original thickness of the model and performed by using the sensitive analysis method and the optimum structural modification method. It can be considered that the weight minimization is completed through this process, because the optimum structural modification method includes the constraint of minimum changing quantity.

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Study on Optimum Modification Method of Dynamic Charcteristics of Ship Structures by Multi-level Optimization (다단계최적화방법에 의한 선박구조물의 동특성의 최적변경법에 관한연구)

  • 박석주
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.4
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    • pp.574-582
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    • 1999
  • This paper discusses the multi-level optimization method in dynamic optimization problems through stiffened plate of ship structures. In structural optimization the computational cost increases rapidly as the number of design variables increases. And we need a great amount of cal-culation and time on problems of modified dynamic characteristics of large and complicated struc-tures. In this paper the multi-level optimization is proposed which decreases computational time and cost. the dynamic optimum designs of stiffened plate that control the natural frequency and minimize weight subjected to constraints condition are derived. The way to apply the multi-level optimization methods in this study follow: In the first step the dynamic characteristics is controlled for the two-dimensional model of stiffened plate by sensitivity analysis and quasi-least squares methods. In the second step the cross-section of the stiffener is decided so that the weight is minimized under needed constraints by the steepest descent or ascent method. In the third the three-dimensional model is made based on the results of the first step and the second step confirmation and finer tuning of the objective function are carried out. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate.

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