• Title/Summary/Keyword: approximation technique

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An Overview of Optimization of Structures Subjected to Transient Loads (동하중을 받는 구조물의 최적화에 관한 연구동향)

  • Park Gyung-Jin;Kang Byung-Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.3 s.234
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    • pp.369-386
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    • 2005
  • Various aspects of structural optimization techniques under transient loads are extensively reviewed. The main themes of the paper are treatment of time dependent constraints, calculation of design sensitivity, and approximation. Each subject is reviewed with the corresponding papers that have been published since 1970s. The treatment of time dependent constraints in both the direct method and the transformation method is discussed. Two ways of calculating design sensitivity of a structure under transient loads are discussed - direct differentiation method and adjoint variable method. The approximation concept mainly focuses on re- sponse surface method in crashworthiness and local approximation with the intermediate variable Especially, as an approximated optimization technique, Equivalent Static Load method which takes advantage of the well-established static response optimization technique is introduced. And as an application area of dynamic response optimization technique, the structural optimization in flexible multibody dynamic systems is re- viewed in the viewpoint of the above three themes

Approximate analysis of the serial production lines (분할기법을 이용한 직렬 생산라인의 근사화 해석)

  • 서기성;강재현;이창훈;우광방
    • 제어로봇시스템학회:학술대회논문집
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    • 1990.10a
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    • pp.406-410
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    • 1990
  • This paper presents an approximate analysis of the serial production lines using decomposition technique. A serial production line consists of a series of unreliable machines separated by finite buffers. The serial production line is evaluated by approximation method, the results of which are compared with those examined by the discrete time event simulation, based on this approximation method, a gradient technique is proposed, which improves the efficiency of an operation of production line through the re-allocation of buffers.

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Moment-Based Density Approximation Algorithm for Symmetric Distributions

  • Ha, Hyung-Tae
    • Communications for Statistical Applications and Methods
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    • v.14 no.3
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    • pp.583-592
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    • 2007
  • Given the moments of a symmetric random variable, its density and distribution functions can be accurately approximated by making use of the algorithm proposed in this paper. This algorithm is specially designed for approximating symmetric distributions and comprises of four phases. This approach is essentially based on the transformation of variable technique and moment-based density approximants expressed in terms of the product of an appropriate initial approximant and a polynomial adjustment. Probabilistic quantities such as percentage points and percentiles can also be accurately determined from approximation of the corresponding distribution functions. This algorithm is not only conceptually simple but also easy to implement. As illustrated by the first two numerical examples, the density functions so obtained are in good agreement with the exact values. Moreover, the proposed approximation algorithm can provide the more accurate quantities than direct approximation as shown in the last example.

IMPLICIT DIFFERENCE APPROXIMATION FOR THE TWO-DIMENSIONAL SPACE-TIME FRACTIONAL DIFFUSION EQUATION

  • Zhuang, Pinghui;Liu, Fawang
    • Journal of applied mathematics & informatics
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    • v.25 no.1_2
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    • pp.269-282
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    • 2007
  • In this paper, we consider a two-dimensional fractional space-time diffusion equation (2DFSTDE) on a finite domain. We examine an implicit difference approximation to solve the 2DFSTDE. Stability and convergence of the method are discussed. Some numerical examples are presented to show the application of the present technique.

VISCOSITY METHODS OF APPROXIMATION FOR A COMMON SOLUTION OF A FINITE FAMILY OF ACCRETIVE OPERATORS

  • Chen, Jun-Min;Zhang, Li-Juan;Fan, Tie-Gang
    • East Asian mathematical journal
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    • v.27 no.1
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    • pp.11-21
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    • 2011
  • In this paper, we try to extend the viscosity approximation technique to find a particular common zero of a finite family of accretive mappings in a Banach space which is strictly convex reflexive and has a weakly sequentially continuous duality mapping. The explicit viscosity approximation scheme is proposed and its strong convergence to a solution of a variational inequality is proved.

Sliding Mode Controller Design Considering Weight (가중치를 고려한 슬라이딩 모드 제어기 설계)

  • 임동균;서병설
    • Proceedings of the KIPE Conference
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    • 1998.11a
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    • pp.73-77
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    • 1998
  • The conventional sliding mode controller (SMCr) approach is often impractical or difficult when applied to high order process because the number of tuning parameters in the SMCr increases with the order of the plant. Camacho(1996) proposed the design of a fixed structure sliding mode controller based on a first order plus dead time approximation to the higher-order process. But, there are such problems as overshoot, settling time and command following. They are mainly due to the approximation errors of the time delay term by Taylor series. In this paper, in order to improve Camcho's method, a new Taylor approximation technique considering a weight is proposed.

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APPROXIMATION-SOLVABILITY OF A CLASS OF A-MONOTONE VARIATIONAL INCLUSION PROBLEMS

  • Verma, Ram U.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.8 no.1
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    • pp.55-66
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    • 2004
  • First the notion of the A-monotonicity is applied to the approximation - solvability of a class of nonlinear variational inclusion problems, and then the convergence analysis is given based on a projection-like method. Results generalize nonlinear variational inclusions involving H-monotone mappings in the Hilbert space setting.

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Order Based Performance Evaluation of a CONWIP System with Compound Poisson Demands (복합포아송 수요를 갖는 CONWIP 시스템의 주문관점에서의 성능평가)

  • Park, Chan-Woo;Lee, Hyo-Seong
    • Journal of the Korean Operations Research and Management Science Society
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    • v.32 no.1
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    • pp.137-146
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    • 2007
  • In this study we consider a CONWIP system studied in Park and Lee [1] in which the processing times at each station follow a Coxian distribution and the demands for the finished products arrive according to a compound Poisson process. The demands that are not satisfied Immediately are either backordered or lost according to the number of demands that exist at their arrival instants. For this system using the results in [1] we develop an approximation method to calculate order based performance measures such as the mean time of fulfilling a customer order and the mean number of customer orders. To test the accuracy of the approximation method, the results obtained from the approximation method are compared with those obtained by simulation. Comparisons with simulation have shown that the approximate method provides fairly good results.

Seat Allocation Model for Single Flight-leg using Linear Approximation Technique (선형근사 기법을 이용한 단일비행구간의 좌석할당 모형)

  • Song, Yoon-Sook;Lee, Hwi-Young
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • 2008.10a
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    • pp.65-75
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    • 2008
  • Over the last three decades, there are many researches focusing on the practice and theory of RM in airlines. Most of them have dealt with a seat assignment problem for maximizing the total revenue. In this study, we focus on a seat assignment problem in airlines. The seat assignment problem can be modeled as a stochastic programming model which is difficulty to solve optimally. However, with some assumptions on the demand distribution functions and a linear approximation technique, we can transform the complex stochastic programming model to a Linear Programming model. Some computational experiments are performed to evaluate out model with randomly generated data. They show that our model has a good performance comparing to existing models, and can be considered as a basis for further studies on improving existing seat assignment models.

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Design of Initial Billet using the Artificial Neural Network for a Hot Forged Product (신경망을 이용한 열간단조품의 초기 소재 설계)

  • Kim, D.J.;Kim, B.M.;Park, J.C.
    • Journal of the Korean Society for Precision Engineering
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    • v.12 no.11
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    • pp.118-124
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    • 1995
  • In the paper, we have proposed a new technique to determine the initial billet for the forged products using a function approximation in neural network. A three-layer neural network is used and a back propagation algorithm is employed to train the network. An optimal billet which satisfied the forming limitation, minimum of incomplete filling in the die cavity, load and energy as well as more uniform distribution of effective strain, is determined by applying the ability of function approximation of the neural network. The amount of incomplete filling in the die, load and forming energy as well as effective strain are measured by the rigid-plastic finite element method. This new technique is applied to find the optimal billet size for the axisymmetric rib-web product in hot forging. This would reduce the number of finite element simulation for determining the optimal billet of forging products, further it is usefully adopted to physical modeling for the forging design

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