• Title/Summary/Keyword: structure-sensitivity

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Eigenderivative Analysis of the Damped Structurure due to Modification of Mass and Stiffness (질량과 강성 변경 따른 감쇠구조물의 동특성 변화 해석)

  • Lee, Jung-Youn
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.14 no.4
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    • pp.7-12
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    • 2005
  • This study predicts the modified eigenvectors and eigenvalues of the damped structure due to the change in the mass, damping and stiffness of structure by calculation of the sensitivity coefficient using the original dynamic characteristic. The method is applied to examples of the damped 3 degree of freedom system by modifing the mass, damping and stiffness. The predicted dynamic characteristics are in good agreement with these from the structural reanalysis using the modified mass, damping and stiffness.

A Study on the Sensitivity of Influencing Parameters on Axial Force in CWR on a Viaduct (교량상 장대레일의 축력 영향인자의 민감도 분석에 관한 연구)

  • Chun, Hee-Kwang;Choi, Jin-Yu;Choi, Il-Yun;Yang, Shin-Chu;Jeong, Jang-Yong
    • Proceedings of the KSR Conference
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    • 2008.11b
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    • pp.1043-1049
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    • 2008
  • Trouble by excessive axial stress in CWR layed on a bridge is frequently happen, and this problem is induced from lack of considering on the track/structure interface on preliminary design stage. In this study, the sensitivity evaluation for the major influencing parameters, that is, expansion length of span, stiffness of super structure, arrangement of bearing, and strength of sub-structure, to the axial force in CWR on a bridge is conducted. From the sensitivity study, the guideline to reduce axial force efficiently in CWR for bridge engineer was suggested. The suggested guideline may not applicable for every case, but it is helpful for preliminary design of bridge.

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Application of sensitivity analyses in premixed combustion within a porous ceramic burner (다공 세라믹 연소기 속에서의 예혼합연소에 대한 민감도 해석의 적용)

  • Im, In-Gwon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.2
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    • pp.162-172
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    • 1998
  • A numerical study of premixed combustion within a porous ceramic burner (PCB) is performed to understand flame behavior with respect to various model parameters. Basic flame structure within the porous ceramic burner and species profiles such as NO and CO are examined. Sensitivity analysis of flame speed, gas and solid temperature, NO and CO emission from the burner with respect to reaction steps and various physical properties of the ceramic material is applied to find the most significant parameters in selection of porous materials for the porous ceramic burner. Effects of thermal conductivity, extinction coefficient and scattering albedo on the burner characteristics are studied through the sensitivity analysis. The results of sensitivity study reveal the order of importance in ceramic material properties to get suitable burner performance. Scattering albedo, which governs the ratio of absorbed energy by the ceramic material to total radiative energy transferred, is one of the most important parameters in the material properties since it affects the actual absorbed radiation rate and thus it largely affects the flame structure. Through the study, it is found that the sensitivity study can be used to estimate the flame behavior within the porous ceramic burner more effectively.

A Study on the Stochastic Sensitivity Analysis in Dynamics of Frame Structure (프레임 구조물의 확률론적 동적 민감도 해석에 관한 연구)

  • 부경대학교
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.35 no.4
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    • pp.435-447
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    • 1999
  • It is main objective of this approach to present a method to analyse stochastic design sensitivity for problems of structural dynamics with randomness in design parameters. A combination of the adjoint variable approach and the second order perturbation method is used in the finite element approach. An alternative form of the constant functional that holds for all times is introduced to consider the time response of dynamic sensitivity. The terminal problem of the adjoint system is solved using equivalent homogeneous equations excited by initial velocities. The numerical procedures are shown to be much more efficient when based on the fold superposition method: the generalized co-ordinates are normalized and the correlated random variables are transformed to uncorrelated variables, whereas the secularities are eliminated by the fast Fourier transform of complex valued sequences. Numerical algorithms have been worked out and proved to be accurate and efficient : they can be readily adapted to fit into the existing finite element codes whose element derivative matrices can be explicitly generated. The numerical results of two cases -2 dimensional portal frame for the comparison with reference and 3-dimensional frame structure - for the deterministic sensitivity analysis are presented.

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Sensor selection approach for damage identification based on response sensitivity

  • Wang, Juan;Yang, Qing-Shan
    • Structural Monitoring and Maintenance
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    • v.4 no.1
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    • pp.53-68
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    • 2017
  • The response sensitivity method in time domain has been applied extensively for damage identification. In this paper, the relationship between the error of damage identification and the sensitivity matrix is investigated through perturbation analysis. An index is defined according to the perturbation amplify effect and an optimal sensor placement method is proposed based on the minimization of that index. A sequential sub-optimal algorithm is presented which results in consistently good location selection. Numerical simulations with a two-dimensional high truss structure are conducted to validate the proposed method. Results reveal that the damage identification using the optimal sensor placement determined by the proposed method can identify multiple damages of the structure more accurately.

Synthesis of the State-space Digital Filter with Minimum Statistical Cofficient Sensitivity (최소총계적계수 감도를 갖는 상태공간 디지틀 필터의 합성)

  • 문용선;박종안
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.13 no.6
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    • pp.510-520
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    • 1988
  • In this paper, the output error variance due to the differential vcariation of the state-space coefficient [ABCD], which is the coefficient quentization error, is normalized on the variance for cases that infinite wordlength state-space digital filter is realized by the finite one. That is, defining S as the statistical sensitivity and extending controllability gramian, observability gramian, and 2nd order mode analysis method to the state space digital filter, we synthesize the realization structure with the minimum statistical sensitivity and prove the effecency of the minimum statistical sensitivity structure synthesis by the simulation.

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Analysis of Fatigue Strength in Expansion Joint Weldment of Bridge (교량 신축이음창치 용접부의 피로강도 해석)

  • 이용복;정진성;박영근;김태윤;김호경;박상흡
    • Journal of Welding and Joining
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    • v.16 no.4
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    • pp.73-82
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    • 1998
  • This paper is especially concerned with the weldment between support beam and square bar that plays important roles in control box of Expansion Joint as a brdige structure. Fatigue strength ({TEX}$$\sigma$_{ult}${/TEX}) of the weldment is dependent on notch factor ({TEX}$K_{f}${/TEX}) become important factors to predict fatigue life. The fatigue notch sensitivity (η) for metals can be divided into two types ; high and low notch sensitivity. In this work, the Expansion Joint weldment was found to have low notch sensitivity. The maximum strain distribution during static loading is similar to the FEM analysis. Fatigue test of real structure was performed up to {TEX}$10^{6}${/TEX} cycles to be compared with predicted endurance limit.

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Structural Modification for Vehicle Interior Noise Reduction Using Vibration Response Sensitivity Analysis

  • Park, Yong-Hwa;Cheung, Wan-Sup;Park, Youn-Sik
    • The Journal of the Acoustical Society of Korea
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    • v.19 no.3E
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    • pp.3-11
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    • 2000
  • A structural modification technique for reducing structure-borne noise of vehicles using a sensitivity analysis is suggested. To estimate the noises generated by the vibration response, a semi structure-acoustic coupling analysis was exploited. As a result of the coupling analysis, severe noise generating positions are identified whose vibrations should be cured through structural modifications. Formulation for the sensitivity analysis of those severe vibration responses with respect to the design changes is derived to enhance the vibration response. Special attention is given in this paper to the use of the experimentally measured vibration responses in the sensitivity analysis. As a result of the proposed method, the structural modifications can be peformed accurately by using experimental data instead of using the finite element method though the higher vibration modes are considered as long as the vibration measurement and acoustic mode calculations are accurate. Effectiveness of this method was examined using an example model by experiments.

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Design Sensitivity Analysis and Optimal Design to Control Forced Harmonic Vibration of Structure (구조물 진동제어를 위한 설계 민감도해석 및 최적설계)

  • J.H. Lee;K.H. Lee
    • Journal of the Society of Naval Architects of Korea
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    • v.32 no.4
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    • pp.64-72
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    • 1995
  • Sizing design sensitivity analysis of structures subjected to the harmonic vibration is performed using adjoint variable method. Constraint is the stress and sizing design variables are thickness, bending moment of inertia, and cross-sectional area of structures. Accurate sensitivities are computed and plotted sensitivity can be used as a design guidance tool. The accuracy of sensitivities is verified by the finite difference values. Also, optimal design of three-bar structure is performed using the computed sensitivity and feasible direction method while satisfying constraints and obtaining the minimum weight.

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Optical waveguide structure design of Non-dispersive Infrared (NDIR) CO2 gas sensor for high-sensitivity (이산화탄소 검출을 위한 고감도 비분산 적외선 가스센서의 광도파관 구조 설계)

  • Yoon, Jiyoung;Lee, Junyeop;Do, Namgon;Jung, Daewoon
    • Journal of Sensor Science and Technology
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    • v.30 no.5
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    • pp.331-336
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    • 2021
  • The Non-dispersive Infrared (NDIR) gas sensor has high selectivity, measurement reliability, and long lifespan. Thus, even though the NDIR gas sensor is expensive, it is still widely used for carbon dioxide (CO2) detection. In this study, to reduce the cost of the NDIR CO2 gas sensor, we proposed the new optical waveguide structure design based on ready-made gas pipes that can improve the sensitivity by increasing the initial light intensity. The new optical waveguide design is a structure in which a part of the optical waveguide filter is inclined to increase the transmittance of the filter, and a parabolic mirror is installed at the rear end of the filter to focus the infrared rays passing through the filter to the detector. In order to examine the output characteristics of the new optical waveguide structure design, optical simulation was performed for two types of IR-source. As a result, the new optical waveguide structure can improve the sensitivity of the NDIR CO2 gas sensor by making the infrared rays perpendicular to the filter, increasing the filter transmittance.