• 제목/요약/키워드: Numerical Differentiation Method

검색결과 78건 처리시간 0.028초

Delay Performance of Multi-Service Network with Strict Priority Scheduling Scheme

  • Lee, Hoon
    • 한국통신학회논문지
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    • 제30권2B호
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    • pp.11-20
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    • 2005
  • Strict priority scheduling scheme is a good candidate for the implementation of service differentiation in an Internet because of simplicity in implementation and the capability to guarantee the delay requirement of the highest class of traffic. However, it is also blown that strict priority starves the lower-class traffic at the cost of prioritizing the higher-class traffic. The purpose of this work is to propose an analytic method which can estimate the average delay performance of Diffserv service architecture and shows that strict priority scheme does not sacrifice the lower class traffic over a diverse condition of the load. From the numerical experiments for three-class Diffserv network we validate our argument that strict priority scheme may be applied to a service differentiation scheme for the future Internet.

상용 차량의 축거 예견 제어를 위한 미지 입력 관측기 설계 (Design of unknown input observer of wheelbase preview control of commercial vehicles)

  • 노현석;박영진
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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    • pp.892-895
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    • 1996
  • An unknown input observer is proposed that can be used in wheelbase preview control of commercial vehicles. The preview and state information, required to calculate actuator force, are reconstructed from the measurement variables such as heave and pitch acceleration. Gain matrix of observer is optimally selected so that influence of system and measurement noises on the estimation error can be minimized. Estimated preview information requires low pass filtering to eliminate high frequency components resulting from differentiation of noisy output signals. Effectiveness of the proposed method is demonstrated by numerical simulation of half car model.

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전달함수합성법을 이용한 민감도 해석 (Sensitivity Analysis using FRF-based Substructuring Method)

  • 이두호;황우석;김찬묵
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 추계학술대회논문집A
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    • pp.602-606
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    • 2000
  • A general procedure for the design sensitivity analysis of structural dynamic problems has been presented in frame of the FRF-based substructuring formulation. In the procedure, the direct differentiation method is used for the sensitivity formula. For a system response function, the proposed method gives a parametric design sensitivity formula in terms of the partial derivatives of the connection element properties and the transfer matrix of the subsystems. The derived design sensitivity formula is applied to a numerical example. The comparison of sensitivities derived by the proposed method and the finite difference method shows that the proposed method is efficient and accurate.

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반해석적 방법을 이용한 고유치 문제의 형상 설계 민감도 향상에 관한 연구 (A study on the improvement of shape design sensitivity in eigenvalue problems using semi-analytical method)

  • 김현기;조맹효
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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    • pp.159-166
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    • 2001
  • Structural optimization often requires the evaluation of design sensitivities. The Semi Aanalytic method(SAM) for computing sensitivity is popular in shape optimization because this method has several advantages. But when relatively large rigid body motions are identified for individual elements, the SA method shows severe inaccuracy. In this paper, the improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes. Moreover, the error of the SA method caused by numerical difference scheme is alleviated by using a series approximation for the sensitivity derivatives and considering the higher order terms. Finally, this paper shows that the refined SA method including the iterative method improves the results of sensitivity analysis in dynamic problems.

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혼합 요소에서의 개선된 민감도 계산법 (The calculation of refined semi-analytic sensitivity based on the hybrid element)

  • 조맹효;김현기
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집A
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    • pp.686-691
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    • 2001
  • Structural optimization often require the evaluation of design sensitivities. The Semi Analytic method(SAM) is popular for shape optimization because this method has several advantages. But when relatively large rigid body motions are identified for individual elements, the SA method shows severe inaccuracy. In this paper, the improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes. Moreover, the error of the SA method caused by numerical difference scheme is alleviated by using a series approximation for the sensitivity derivatives and considering the higher order terms.

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반복계산에 의한 고유치 해석 알고리즘의 2차 뉴튼랩슨법으로의 정식화 (A Formulation of Iterative Eigenvalue Analysis Algorithm to the Second Order Newton Raphson Method)

  • 김덕영
    • 대한전기학회논문지:전력기술부문A
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    • 제51권3호
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    • pp.127-133
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    • 2002
  • This paper presents an efficient improvement of the iterative eigenvalue calculation method of the AESOPS algorithm. The intuitively and heuristically approximated iterative eigenvalue calculation method of the AESOPS algorithm is transformed to the Second Order Newton Raphson Method which is generally used in numerical analysis. The equations of second order partial differentiation of external torque, terminal and internal voltages are derived from the original AESOPS algorithm. Therefore only a few calculation steps are added to transform the intuitively and heuristically approximated AESOPS algorithm to the Second Order Newton Raphson Method, while the merits of original algorithm are still preserved.

Application of the first-order perturbation method to optimal structural design

  • Lee, Byung Woo;Lim, O Kaung
    • Structural Engineering and Mechanics
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    • 제4권4호
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    • pp.425-436
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    • 1996
  • An application of the perturbation method to optimum structural design with random parameters is presented. It is formulated on the basis of the first-order stochastic finite element perturbation method. It also takes into full account the stress, displacement and eigenvalue constraints, together with the rates of change of the random variables. A method for calculating the sensitivity coefficients in regard to the governing equation and the first-order perturbed equation has been derived, by using a direct differentiation approach. A gradient-based nonlinear programming technique is used to solve the problem. The numerical results are specifically noted, where the stiffness parameter and external load are treated as random variables.

강체모드분리와 급수전개를 통한 고유치 문제에서의 준해석적 설계 민감도 개선에 관한 연구(II) -동적 문제 - (A Refined Semi-Analytic Sensitivity Study Based on the Mode Decomposition and Neumann Series Expansion in Eigenvalue Problem(II) - Eigenvalue Problem -)

  • 김현기;조맹효
    • 대한기계학회논문집A
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    • 제27권4호
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    • pp.593-600
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    • 2003
  • Structural optimization often requires the evaluation of design sensitivities. The Semi Analytic Method(SAM) fur computing sensitivity is popular in shape optimization because this method has several advantages. But when relatively large rigid body motions are identified for individual elements. the SAM shows severe inaccuracy. In this study, the improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes. Moreover. the error of the SAM caused by numerical difference scheme is alleviated by using a series approximation for the sensitivity derivatives and considering the higher order terms. Finally the present study shows that the refined SAM including the iterative method improves the results of sensitivity analysis in dynamic problems.

이산형 변수를 이용한 뼈대구조물의 다단계 최적설계 (Multi-Level Optimization for Steel Frames using Discrete Variables)

  • 조효남;민대용;박준용
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2000년도 가을 학술발표회논문집
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    • pp.115-124
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    • 2000
  • An efficient multi-level (EML) optimization algorithm using discrete variables of framed structures is proposed in this paper. For the efficiency of the proposed algorithm multi-level optimization techniques using a decomposition method that separates both system-level and element-level are incorporated in the algorithm In the system-level, to save the numerical efforts an efficient reanalysis technique through approximated structural responses such as moments and frequencies with respect to intermediate variables is proposed in the paper. Sensitivity analysis of dynamic structural response is executed by automatic differentiation (AD) that is a powerful technique for computing complex or implicit derivatives accurately and efficiently with minimal human effort. In the element-level, to use AISC W-sections a section search algorithm is introduced. The efficiency and robustness of the EML algorithm, compared with a conventional multi-level (CML) algorithm and single-level genetic algorithm is successfully demonstrated in the numerical examples.

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박판 구조물의 방사 소음에 대한 크기설계 민감도 해석 및 최적 설계 (Sizing Design Sensitivity Analysis and Optimization of Radiated Noise from a Thin-body)

  • 이제원;왕세명
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2003년도 춘계학술대회논문집
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    • pp.1038-1043
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    • 2003
  • There are many industrial applications including thin-body structures such as fins. For the numerical modeling of radiation of sound from thin bodies, the conventional boundary element method (BEM) using the Helmholtz integral equation fails to yield a reliable solution. Therefore, many researchers have tried to solve the thin-body acoustic problems. In the area of the design sensitivity analysis (DSA) and optimization methods, however, there has been just a few study reported. Especially fur the thin-body acoustics, however, no further study in the DSA and optimization fields has been reported. In this research, the normal derivative integral equation is adopted as an analysis formulation in the thin-body acoustics, and then used for the sizing DSA and optimization. Since the gradient-based method is used for the optimization, it is important to have accurate gradients (design sensitivities) of the objective function and constraints with respect to the design variables. The DSA formulations are derived through chain-ruled derivatives using the finite element method (FEM) and BEM by using the direct differentiation and continuum variation concepts. The proposed approaches are implemented and validated using a numerical example.

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