• Title/Summary/Keyword: effective modification method

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A direct modification method for strains due to non-conforming modes

  • Choi, Chang-Koon;Chung, Keun-Young;Lee, Tae-Yeol
    • Structural Engineering and Mechanics
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    • v.11 no.3
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    • pp.325-340
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    • 2001
  • This paper addresses an efficient modification method that eliminates the undesirable effects of strains due to various non-conforming modes so that the non-conforming element can pass the patch test unconditionally. The scheme is incorporated in the element formulation to establish new types of non-conforming hexahedral elements designated as NHx and NVHx for the regular element and variable node element, respectively. Non-conforming displacement modes are selectively added to the ordinary (conforming) element displacement assumptions to improve the bending behavior of the distorted solid element. To verify the validation of proposed direct modification method and the improvement of element behavior, several numerical tests are carried out. Test results show that the proposed method is effective and its applications to non-conforming solid elements guarantee for the element to pass the patch test.

Adaptive local histogram modification method for dynamic range compression of infrared images

  • Joung, Jihye
    • Journal of the Korea Society of Computer and Information
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    • v.24 no.6
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    • pp.73-80
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    • 2019
  • In this paper, we propose an effective dynamic range compression (DRC) method of infrared images. A histogram of infrared images has narrow dynamic range compared to visible images. Hence, it is important to apply the effective DRC algorithm for high performance of an infrared image analysis. The proposed algorithm for high dynamic range divides an infrared image into the overlapped blocks and calculates Shannon's entropy of overlapped blocks. After that, we classify each block according to the value of entropy and apply adaptive histogram modification method each overlapped block. We make an intensity mapping function through result of the adaptive histogram modification method which is using standard-deviation and maximum value of histogram of classified blocks. Lastly, in order to reduce block artifact, we apply hanning window to the overlapped blocks. In experimental result, the proposed method showed better performance of dynamic range compression compared to previous algorithms.

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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A Study on Noise Reduction of a HDD by Structural moification of Cover (Cover의 구조변겨을 통한 HDD의 소음 저감에 관한 연구)

  • 이성진;유성우;홍순교;이장무
    • Journal of KSNVE
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    • v.10 no.5
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    • pp.859-864
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    • 2000
  • An effective and new method of reducing the noise of a HDD by structural modification of cover was investigated in this study. The correlation between the noise characteristics of the HDD and the vibration characteristics of the cover, which is the main source of the HDD noise, is found from experiments. A theoretical analysis is performed to find the modification method of the cover, and this modification method is applied the real cover of the HDD. The modification reduces the vibration of the cover transferred from driving motor. The effect of the modification is verified through noise tests.

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An Improvement for Determining Response Modification Factor in Bridge Load Rating (응력보정계수 산정 방법 개선)

  • Koo, Bong-Kuen;Shin, Jae-In;Lee, Sang-Soon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.5 no.1
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    • pp.169-175
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    • 2001
  • Bridge load rating calculations provide a basis for determining the safe load capacity of bridge. Load rating requires engineering judgement in determining a rating value that is applicable to maintaining the safe use of the bridge and arriving at posting and permit decisions. Load testing is an effective means in calculating the rating value of bridge. In Korea, load carrying capacity of bridge is modified by response modification factor that is determined from comparisons of measured values and analysis results. The response modification factor may be corrupted by vehicle location error that is defined as the gap of test vehicle location between load testing and analysis. In this study, the effects of vehicle location error to structural response and response modification factor are investigated, and a new method for evaluating response modification factor is proposed. The random data analysis shows that the proposed method is less sensitive to vehicle location error than the present method.

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Experimental Structural Dynamic Modification of Fixture for Environmental Vibration Test Control (환경진동시험제어를 위한 치구의 실험적 구조변경 설계)

  • 김준엽;정의봉
    • Journal of KSNVE
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    • v.6 no.3
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    • pp.317-323
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    • 1996
  • This paper proposes the method of experimental structural dynamic modification of fixture for environmental vibration test control. This method can predict the responses at any points on the fixture utilizing the experimental data, and structural dynamic modification of fixture is made using the predicted responses for the spectra at the specimen attachment points to meet the specified reference spectrum. From the results of controlling the fixture before and after modification by conventional control method and optimal reference spectrum, which has been previously reported by the authors, the proposed method is shown to be an effective one.

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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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Lateral stiffness of reinforced concrete flat plates with steps under seismic loads

  • Kim, Sanghee;Kang, Thomas H.K.;Kim, Jae-Yo;Park, Hong-Gun
    • Earthquakes and Structures
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    • v.7 no.5
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    • pp.891-906
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    • 2014
  • The purpose of this study is to propose a modification factor to reflect the lateral stiffness modification when a step is located in flat plates. Reinforced concrete slabs with steps have different structural characteristics that are demonstrated by a series of structural experiment and nonlinear analyses. The corner at the step is weak and flexible, and the associated rotational stiffness degradation at the corner of the step is identified through analyses of 6 types of models using a nonlinear finite element program. Then a systematic analysis of stiffness changes is performed using a linear finite element procedure along with rotational springs. The lateral stiffness of reinforced concrete flat plates with steps is mainly affected by the step length, location, thickness and height. Therefore, a single modification factor for each of these variables is obtained, while other variables are constrained. When multiple variables are considered, each single modification factor is multiplied by the other. Such a method is verified by a comparative analysis. Finally, a complex modification factor can be applied to the existing effective slab width.

A Robust Input Modification Approach for High Tracking Control Performance of Flexible Joint Robot

  • Park, Min-Kyu;Lee, Sang-Hun;Hur, Jong-Sung;Yim, Jong-Guk;Park, Jong-Hyeon
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.1249-1253
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    • 2004
  • A robust input modification approach to the control of flexible joint robot is presented. In our previous study, we developed an observer based state feedback control for the suppression of residual vibration of a robot. The control was very effective in suppressing the inherent vibration of a flexible joint robot. However it did not meet high performance requirements under high speed motion and model uncertainties. As a solution of the problem, we present an input modification method with robustness against parametric uncertainties. The main idea of the proposed input modification method is to generate a modified reference position command for fast and accurate motion of the robot. Using this proposed method we can reduce the servo delay and settling time by about 60% and substantially improve the path accuracy.

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Experimental Approach Method for Strcutural Dynamic Modification of Vibration Test Fixture (진동시험치구의 구조변경을 위한 실험적 접근법)

  • 김준엽;정의봉
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1996.04a
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    • pp.100-105
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    • 1996
  • This paper proposes the method of experimental structural dynamic modification of fixture for environmental vibration test control. This method can predict the responses at any points on fixture utilizing the experimental data, and structural dynamic modification of fixture is made using the predicted responses for the spectra at the speciment attachment points to meet the specified reference spectrum. From the results of controlling the fixture before and after modification by conventional control method and optimal reference spectrum, which has been previously reported by the authors, the proposed method is shown to be an effective one.

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