• Title/Summary/Keyword: Frequency Weight Function

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Truss Size Optimization with Frequency Constraints using ACO Algorithm (개미군락 최적화 알고리즘을 이용한 진동수 구속조건을 가진 트러스구조물의 크기최적화)

  • Lee, Sang-Jin;Bae, Jungeun
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.35 no.10
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    • pp.135-142
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    • 2019
  • Ant colony optimization(ACO) technique is utilized in truss size optimization with frequency constraints. Total weight of truss to be minimized is considered as the objective function and multiple natural frequencies are adopted as constraints. The modified traveling salesman problem(TSP) is adopted and total length of the TSP tour is interpreted as the weight of the structure. The present ACO-based design optimization procedure uses discrete design variables and the penalty function is introduced to enforce design constraints during optimization process. Three numerical examples are carried out to verify the capability of ACO in truss optimization with frequency constraints. From numerical results, the present ACO is a very effective way of finding optimum design of truss structures in free vibration. Finally, we provide the present numerical results as future reference solutions.

Vibration Analysis of Micro Speaker Diaphragm (마이크로 스피커 다이어프램의 진동해석)

  • Hong, D.K.;Woo, B.C.;Ahn, C.W.;Han, G.J.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.551-554
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    • 2005
  • This study uses a characteristic function to explain correlations between the objective function and design variables. Analysis of means and table of orthogonal array were carried out. The change of shape of diaphragm, thickness of diaphragm and voice coil weight based on the table of orthogonal array is made. Therefore this study carried to decide shape of diaphragm, voice coil weight and thickness of diaphragm for minimizing 1st natural frequency and maximizing 2nd natural frequency of diaphragm using design of experiments and characteristic function with constraints. we showed improved design factors that minimized 1st natural frequency and maximized 2nd natural frequency of diaphragm.

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Estimation of Pump Induced Vibration Force by Frequency Response Function (진동수응답함수 측정에 따른 펌프 가진력 산정)

    • Journal of the Earthquake Engineering Society of Korea
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    • v.3 no.1
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    • pp.103-112
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    • 1999
  • This is study to estimate the pump induced vibration in time and frequency domain by frequency response function between two points in case of 20Hp and 50Hp centrifugal pumps. The frequency response function has real and imaginary information of signals, and response function has also real and imaginary information. So the vibration force can be obtained from the response function and frequency response function by complex calculation. And it is compared with the theoretically estimated values and it is suggested that the amplitude of vibration with main frequency is about 10~25% of pump and motor weight, and the magnitude of unbalanced mass is about 30~60% of pump and motor weight to estimated vibration force in time domain. There are the other kinds of vibration components with different frequency values of 2~3 times of its main frequency, and these kinds of information are used to control the tuning ratio between operating frequency of pump and structural frequency of concrete slab.

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A Study on the Weight Minimization of an Automobile Engine Block by Optimum Structural Modification (최적구조변경법에 의한 자동차 엔진 블록의 중량최소화에 관한 연구)

  • 길병래
    • Journal of Advanced Marine Engineering and Technology
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    • v.22 no.4
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    • pp.560-568
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    • 1998
  • Recently to develop an automobile with better properities many researches and investments have been executed. In this paper we intend to improve the automobile properties by reducing the weight of the engine without changing the dynamic characteristics. At first the vibration analysis by the Substructure Synthesis Mehtod and the exciting test of the engine model performed to confirm the reliability of the analyzing tools. And the weight minimiza-tion is performed by the Sensitivity Analysis and the Optimum Structural Modificationl. To decrease the engine weight ideally the weight of the parts with the low sensitivity is to cut mainly and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with the high sensitivity. As actually the mathematical unique solution for the homogeneous problem(i. e. 0 object func-tion problem)does not exist we redesign the engine block with much thinner initial thickness and recover the natural frequencies and natural modes of original structure by the sensitivity analy-sis and then observe the Frequency Response Function(FRF) for the interesting points. In this analysis the original thickness of the engine model is 8mm and the redesigned initial thicknesses are 5mm and 6mm, And the number of the interesting natural frequencies are 1, 2, 3, 4 and 5 respectively.

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Topology Optimization of Plane Structures using Modal Strain Energy for Fundamental Frequency Maximization

  • Lee, Sang-Jin;Bae, Jung-Eun
    • Architectural research
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    • v.12 no.1
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    • pp.39-47
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    • 2010
  • This paper describes a topology optimization technique which can maximize the fundamental frequency of the structures. The fundamental frequency maximization is achieved by means of the minimization of modal strain energy as an inverse problem so that the strain energy based resizing algorithm is directly used in this study. The strain energy to be minimized is therefore employed as the objective function and the initial volume of structures is used as the constraint function. Multi-frequency problem is considered by the introduction of the weight which is used to combine several target modal strain energy terms into one scalar objective function. Several numerical examples are presented to investigate the performance of the proposed topology optimization technique. From numerical tests, it is found to be that the proposed optimization technique is extremely effective to maximize the fundamental frequency of structure and can successfully consider the multi-frequency problems in the topology optimization process.

A Study on the Vibration Analysis of a Power Transmission by Substructure Synthesis Method (부분구조합성에 의한 동력전달기의 진동해석에 관한 연구)

  • 박석주;박성현;박영철
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11a
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    • pp.161-166
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    • 2001
  • This study intends to reduce the weight of structure without changing the dynamic characteristics. At first, the Vibration analyses by the Substructure Synthesis Method and FEM using the ANSYS are performed for the engine speed converter to confirm the reliability of the analyzing tools. Weight minimization is performed by the Sensitivity Analysis and the Optimum Structural Modification. To decrease the converter weight ideally, the parts with low sensitivity are to be cut mainly, and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with high sensitivity. As the unique mathematical solution for the homogeneous problem( i.e. 0 object function problem) does not exist, the converter is redesigned with much thinner initial thickness. The goal of this study is to recover the dynamic characteristics of redesigned structure to those of the original one. To say in the other words, the modified structure has the same dynamic characteristics and the more lighter weight to compare with the original one. In this analysis, the modification was performed with the redesigned initial thickness of 60 mm and 70 mm. And the numbers of the interesting natural frequencies are 1, 2, 4 respectively. Consequently 27% of weight reduction effects were earned.

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A Study on the Vibration Analysis of a Power Transmission Converter by Substructure Synthesis Method (부분구조합성법에 의한 동력전달 변화기의 진동해석에 관한 연구)

  • 박석주;왕지석;박성현;오창근;박영철
    • Journal of Advanced Marine Engineering and Technology
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    • v.24 no.3
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    • pp.52-57
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    • 2000
  • This study intends to reduce the weight of structure without changing the dynamic characteristics. At first, the Vibration analysis by the Substructure Synthesis Method and FFM using the ANSYS are performed for the engine speed converter to confirm the reliability of the analyzing tools. Weight minimization is performed by the Sensitivity Analysis and the Optimum Structural Modification. To decrease the converter weight ideally, the parts with low sensitivity are to be cut mainly, and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with high sensitivity. As the unique mathematical solution for the homogeneous problem(i.e. 0 object function problem) does not exist, the converter is redesigned with much thinner initial thickness. The goal of this study is to recover the dynamic characteristics of redesigned structure to those of the original one. To say in the other words, the modified structure has the same dynamic characteristics and the more lighter weight to compare with the original one.

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Comparison of X-ray Image Quality Between Multi-Function Device(MFD) and Weight Bearing Platforms(WBPs) (다기능 보조기구와 체중부하검사 보조기구의 X선 화질 비교)

  • Gil, Jong-Won;Lee, Kwang-Sung
    • Journal of the Korean Society of Radiology
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    • v.13 no.4
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    • pp.605-611
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    • 2019
  • The purpose of this study is to manufacture a multi-function device (MFD) which can be applied to various types of weight-bearing view of the lower leg, and to compare the results with the images from the existing weight-bearing platforms (WBPs), thereby suggesting a clinical utilization. The MFD was manufactured, by considering the minimum adjustable heights of the platform for weight-bearing foot/ankle, platform for hindfoot alignment view, and X-ray tube of the X-ray device. A foot/ankle phantom was used to take the images of weight-bearing lateral foot in MFD and WBPs to compare the resolutions of the X-ray images using a quick modulation transfer function (MTF) program. Between both the images taken from the MFD and WBPs, there was no statistically significant difference found in the mean cycles per pixel (C/P) and the lines per image height (LPH) of the 50%-Contrast Spatial Frequency (MTF50), and 10-90% of Maximum Energy Rise Distance (10-90%), where p>0.05. The MFD is suggested for its clinical trial as a useful positioning device that can secure the patient's safety and manifoldly perform various inspections. Also, the recommendation of the positioning device as a policy can activate dedicated manufacturers, while also improving the quality of medical services.

Estimation of Pump Induced Vibration Force Using Transfer Function (전달함수를 이용한 펌프(50Hp)의 진동가진력 산정)

  • 노병철
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1998.10a
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    • pp.157-162
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    • 1998
  • Dynamic loads may arise from rotating parte of pump if they are insufficiently balanced. The magnitude of pump induced vibrations varies according to the weight, eccentricity, and unbalanced mass of pump. This is a study to estimate the pump induced vibration in time and frequency domain by transfer function. The transfer function has real and imaginary information of signals, and response function has also real and imaginary information. So the vibration force can be obtained from the response and transfer function by complex calculation. The amplitudes and components of 50Hp pump vibration force are suggested.

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Non-destructive weight measurement by using a vibration model

  • Tsuruoka, Hisashi
    • 제어로봇시스템학회:학술대회논문집
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    • 1988.10b
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    • pp.777-781
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    • 1988
  • A method for weighing fruits without separating them from stem is proposed. The base of stem is fixed and a fruit or a cluster of fruits is forced to vibrate. The approximated vibration model is constructed by the use of Transfer Matrix Method. The natural frequency (w) in this model can be represented as a function of weight elements, and the length and stiffness of branch elements of stem. With this function, only w is possible to measure. However, several small weights whose weights are known are attached to weight elements in various combinations. From these equations, unknown parameters are determined so that the weight of each fruit can be obtained by a non-destructive method.

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