Showing papers on "Optimal design published in 1998"
TL;DR: A functional approximation to earlier exact results is shown to have excellent agreement with the exact results and one can use it easily without intensive numerical computation.
Abstract: A method is developed to calculate the required number of subjects k in a reliability study, where reliability is measured using the intraclass correlation rho. The method is based on a functional approximation to earlier exact results. The approximation is shown to have excellent agreement with the exact results and one can use it easily without intensive numerical computation. Optimal design configurations are also discussed; for reliability values of about 40 per cent or higher, use of two or three observations per subject will minimize the total number of observations required.
1,795 citations
TL;DR: In this article, the application of a new genetic algorithm for the optimal design of large distribution systems, solving the optimal sizing and locating problems of feeders and substations using the corresponding fixed costs as well as the true nonlinear variable costs, is presented.
Abstract: This paper presents the application of a new genetic algorithm for the optimal design of large distribution systems, solving the optimal sizing and locating problems of feeders and substations using the corresponding fixed costs as well as the true nonlinear variable costs. It can be also applied to single stage or multistage distribution designs. The genetic algorithm has been tested with real size distribution systems achieving optimal designs in reasonable CPU times compared with respect to the dimensions of such distribution systems. On the other hand, these distribution systems present significantly larger sizes than the ones frequently found in the technical literature about the optimal distribution planning. Furthermore, original operators of the genetic algorithm have been developed in order to obtain global optimal solutions, or very close ones to them. An integer codification of the genetic algorithm has also been used to include several relevant design aspects in the distribution network optimization.
279 citations
TL;DR: An automated procedure is used to formulate a constrained non-linear optimization model, whose solution provides a measure of the fitness of each candidate HEN generated by the GA, and the obtained solutions are compared with those available in literature.
167 citations
01 Nov 1998
TL;DR: This work presents a method for optimizing and automating component and transistor sizing for CMOS operational amplifiers, and shows how the method can be applied to six common op-amp architectures, and gives several example designs.
Abstract: We present a method for optimizing and automating component and transistor sizing for CMOS operational amplifiers. We observe that a wide variety of performance measures can be formulated as posynomial functions of the design variables. As a result, amplifier design problems can be formulated as a geometric program, a special type of convex optimization problem for which very efficient global optimization methods have recently been developed. The synthesis method is therefore fast, and determines the globally optimal design; in particular the final solution is completely independent of the starting point (which can even be infeasible), and infeasible specifications are unambiguously detected. After briefly introducing the method, which is described in more detail by M. Hershenson et al., we show how the method can be applied to six common op-amp architectures, and give several example designs.
152 citations
TL;DR: A method for including inventory costs within a fixed-charge facility location model, allowing such a model to be used more effectively for the development of optimal system designs is described.
Abstract: An important question in the design of efficient logistics systems is the identficaton of locations for distribution centers. Optimal designs should be based on consideration of inventory, transportation, construction and operating costs. This paper describes a method for including inventory costs within a fixed-charge facility location model, allowing such a model to be used more effectively for the development of optimal system designs. A realistic application of the model is discussed.
144 citations
TL;DR: A generalized sensor network design algorithm for finding the optimal placement of sensors in a linear mass flow process has been developed and implemented and application to a steam-metering network of a methanol plant demonstrates the versatility of this method.
122 citations
TL;DR: This work presents a new formulation of the problem of minimizing the initial cost of a structure subject to a minimum reliability requirement, expressed in terms of the so-called design points of the first-order reliability theory, i.e., points on limit-state surfaces that are nearest to the origin in a transformed standard normal space.
Abstract: We present a new formulation of the problem of minimizing the initial cost of a structure subject to a minimum reliability requirement, expressed in terms of the so-called design points of the first-order reliability theory, i.e., points on limit-state surfaces that are nearest to the origin in a transformed standard normal space, as well as other deterministic constraints. Our formulation makes it possible to use outer approximations algorithms for the solution of such optimal design problems, eliminating some of the major objections associated with treating them as bilevel optimization problems. A numerical example is presented that illustrates the reliability and efficiency of the algorithm.
119 citations
TL;DR: In this article, a non-probabilistic ellipsoidal convex model is established for considering the uncertainties using three different criteria, i.e., structural volume, joint displacements, and stresses.
Abstract: The optimal design of trusses subjected to loads considered to be uncertain in both magnitude and direction is investigated. A non-probabilistic ellipsoidal convex model is established for considering the uncertainties using three different criteria. The convex model is described as a set of constraints on the upper and lower limits of the load magnitudes and directions. The optimal design of the trusses is performed using two different optimization objectives. The first objective function to be minimized is the structural volume; constraints are imposed on the stresses and buckling loads of the members and on the joint displacements. Another objective function to be minimized is a selected displacement; constraints are implemented on the stresses and buckling loads of the members and on the structural volume. The presented method yields optimal designs that violate stress, displacement, and buckling constraints with less frequency than the assumed worst load condition. This method offers an alternative t...
98 citations
TL;DR: In this article, the optimal design method of piezocomposite microstructures proposed in the previous work was extended to three dimensional (3D) topologies, considering static applications such as hydrophones.
94 citations
TL;DR: A simple and facile design algorithm is proposed to solve the structure-specified H/sup /spl infin// optimization problem via genetic searching approach from suboptimal perspective and is very suitable for practical control systems.
Abstract: A robust H/sup /spl infin// optimal design problem under a structure-specified controller is investigated for systems with parameter variations and disturbance uncertainties. A simple and facile design algorithm is proposed to solve the structure-specified H/sup /spl infin// optimization problem via genetic searching approach from suboptimal perspective. The proposed design method is very suitable for practical control systems. Therefore, the gap between the theoretical H/sup /spl infin// control and practical engineering designs can be filled up. Two examples involving a single input-single output (SISO) phase-locked-loop motor speed system with a lead/lag type controller and an MIMO supermaneuverable F18/HARV fighter aircraft system with a PID-type controller are given to illustrate the design procedure and exhibit the performance of the proposed method.
94 citations
TL;DR: The aim of this paper is to show the advantage of a deterministic global-optimization method in the optimal design of electromechanical actuators with original and unexpected results in this optimal design.
Abstract: The aim of this paper is to show the advantage of a deterministic global-optimization method in the optimal design of electromechanical actuators. The numerical methods classically used are founded either on nonlinear programming techniques (i.e., augmented Lagrangian, sequential quadratic programming) or on stochastic approaches which are more satisfactorily adapted to global optimum research (i.e., genetic algorithm, simulated annealing). However, the latter methods only guarantee reaching this global optimum with some probability. The present paper proposes a deterministic branch and bound algorithm associated with interval arithmetic which is then applied to the dimensioning of a slotless permanent magnet machine. The problem is formulated as a multiobjective-optimization problem with mixed variables. Original and unexpected results in this optimal design are obtained, and comparisons with previous works are presented.
TL;DR: In this article, a computer-aided optimal design system was developed to improve the performance of a cooling system for injection molding by minimizing a weighted combination of the uniformity of the part temperature and the cooling time.
Abstract: A computer-aided optimal design system was developed to improve the performance of a cooling system for injection molding. This was done by minimizing a weighted combination of the uniformity of the part temperature and the cooling time. The CONMIN algorithm was adopted to obtain the optimal design using the special boundary integral formulation and a corresponding design sensitivity analysis formulation. Design variables related to the processing conditions (i.e., inlet coolant temperature and volumetric flow rate of each cooling channel) and mold cooling system design (radius and location of each cooling channel) were considered. Three different optimization strategies are suggested, and three sample problems were solved to demonstrate the efficiency and the usefulness of this optimization procedure.
TL;DR: In this paper, general sufficient and necessary conditions for minimax design are reconsidered in a form allowing application in various optimal design problems, such as estimating the maximum point of a quadratic response function with intercept.
Abstract: General sufficient and necessary conditions for minimax design are here reconsidered in a form allowing application in various optimal design problems. In combination with the Elfving theorem they are used to find maximin efficient designs for a two-dimensional linear extrapolation, and to find the optimum design for estimating the maximum point of a quadratic response function with intercept. An alternative proof of a recently published relation between D-optimality and maximin efficiency is given. It is shown that for exponential growth curve models with one parameter, maximin efficient designs can not be one point designs. A similar result is obtained for growth curve models with two parameters.
01 Aug 1998
TL;DR: The proposed optimization setup can handle any type of loading condition and neither makes any restriction on the type of hydraulic components in the network nor does it need analytical cost functions for the pipes.
Abstract: This paper presents an approach to the optimal design of pipe networks for water distribution. Design is important it often comprises major part of the whole investment in such a system. The problem is solved using a global optimization tool with various random search algorithms and a network simulation model that can handle both static and dynamic loading conditions. An appropriate interface between the two tools performs the decoding of the potential solutions into pipe networks for construction and calculates the corresponding network costs. Two algorithms, adaptive cluster covering and genetic algorithm, yielded promising solutions enabling a choice between accuracy and required computer time. The proposed optimization setup can handle any type of loading condition and neither makes any restriction on the type of hydraulic components in the network nor does it need analytical cost functions for the pipes.
TL;DR: In this article, an application of the Chebyshev's criterion to the optimal design of the damped dynamic vibration absorber is presented, and the results are summarized in ready-to-use computational graphs.
TL;DR: In this paper, an optimization-based, integrated concurrent design method is applied to the modelling, analysis, and design of a transportation fuel cell system, and a general optimal design model considering both functional performance and production costs is first introduced.
TL;DR: In this article, a method of optimal design of the excitation coil for an electromagnetic flow meter is presented, the main goal is to form an algorithm which will be able to deal with natural channels of any shape with conductive beds/banks.
Abstract: A new method of optimal design of the excitation coil for an electromagnetic flow meter is presented, The main goal is to form an algorithm which will be able to deal with natural channels of any shape with conductive beds/banks. The presented method allows an engineer to design an optimal coil to obtain homogeneity of the special weight vector W. This homogeneity provides that the voltage measured between the electrodes of the flow meter will be proportional to the mean velocity of the liquid in the channel. The optimization of the coil shape is carried out through minimization of an objective function defined on the basis of a finite element method 2D model of the cross-section of the channel.
TL;DR: In this paper, the Gamma-limit of a rescaled version of an optimal material distribution problem for a cylindrical two-phase elastic mixture in a thin three-dimensional domain is explicitly computed.
Abstract: Abstract The Gamma-limit of a rescaled version of an optimal material distribution problem for a cylindrical two-phase elastic mixture in a thin three-dimensional domain is explicitly computed. Its limit is a two-dimensional optimal design problem on the cross-section of the thin domain; it involves optimal energy bounds on two-dimensional mixtures of a related two-phase bulk material. Thus, it is shown in essence that 3D-2D asymptotics and optimal design commute from a variational standpoint.
TL;DR: In this paper, a general framework to obtain analytical design sensitivities for steady-state nonlinear systems where special emphasis is given to design variables that define prescribed boundary conditions is presented, and the sensitivities are derived for a general response functional using both the direct and adjoint methods and compared to show that the two sensitivity analysis methods yield identical expressions.
TL;DR: In this paper, it was shown that the optimal design problem for trigonometric regression models is equivalent to the problem of optimal design for discriminating between certain homo-and heteroscedastic polynomial regression models.
Abstract: For the Fourier regression model, we determine optimal designs for identifying the order of periodicity. It is shown that the optimal design problem for trigonometric regression models is equivalent to the problem of optimal design for discriminating between certain homo- and heteroscedastic polynomial regression models. These optimization problems are then solved using the theory of canonical moments, and the optimal discriminating designs for the Fourier regression model can be found explicitly. In contrast to many other optimality criteria for the trigonometric regression model, the optimal discriminating designs are not uniformly distributed on equidistant points.
TL;DR: In this article, the authors describe recent developments in the application of mathematical and computational techniques to the problem of designing binary gratings on top of a multilayer stack in such a way that the propagating modes have a specified intensity or phase pattern for a chosen range of wavelengths or incidence angles.
TL;DR: In this paper, the authors extend these results to the nonlinear model classified as power-law clasticity, and show that the proportionality between elastic strain energy density and elastic stress energy density implies localized sensitivity analysis for the total elastic energy.
Abstract: Recent results on optimal design with anisotropic materials and optimal design of the materials themselves are in most cases based on the assumption of linear clasticity. We shall extend these results to the nonlinear model classified as powerlaw clasticity. These models return proportionality between elastic strain energy density and elastic stress energy density. This is shown to imply localized sensitivity analysis for the total elastic energy, and for a number of optimal design problems this immediately gives practical, general results.
TL;DR: In this paper, a numerical design tool is presented for minimizing radiated sound power from a vibrating shell structure using a material tailoring approach, where a finite element method using shell elements is used to predict the vibration response of the shell.
TL;DR: In this paper, an expert enumerative algorithm is coupled with an evolutionary search to obtain optimal composite plates for the in-plane problem, where material and geometrical properties are distributed around their nominal value.
TL;DR: This correspondence deals with the problem of designing planar shapes for subpixel image registration, and basic theoretical considerations are shown to lead to a lower bound on location accuracy.
Abstract: This correspondence deals with the problem of designing planar shapes for subpixel image registration. Basic theoretical considerations are shown to lead to a lower bound on location accuracy. Optimal registration marks achieving this bound are discussed. These optimal designs, however, require very high printing or etching resolution and are inherently very sensitive to variations in the image sampling model (like scaling of grid size and rotation). More robust, optimal and suboptimal "topology-preserving" registration marks are then introduced and analyzed.
TL;DR: In this paper, a new approach to process optimal design in non-isothermal, non-steady-state metal forming is presented, which is formulated on the basis of the integrated thermo-mechanical finite element process model.
Abstract: A new approach to process optimal design in non-isothermal, non-steady-state metal forming is presented. In this approach, the optimal design problem is formulated on the basis of the integrated thermo-mechanical finite element process model so as to cover diverse objective functions and design variables, and a derivative-based approach is adopted for conducting optimization. The process model, the formulation for process optimal design, and the schemes for the evaluation of the design sensitivity, and an iterative procedure for optimization are described in detail. The validity of the schemes for the evaluation of the design sensitivity is examined by performing a series of numerical tests. The capability of the proposed approach to deal with diverse process parameters and objective functions is demonstrated through applications to some selected process design problems. © 1998 John Wiley & Sons, Ltd.
TL;DR: In this paper, a simple evolutionary method for minimizing the weight of structures subject to displacement constraints is presented, where sizing design variables are discrete and sensitivity numbers for element size reduction are derived using optimality criteria methods.
02 Sep 1998
TL;DR: In this article, the incorporation of structural optimization into the crashworthiness design of automotive structures is discussed, and a very efficient response surface method is presented. But closed loop software for the optimization of structures with nonlinear behavior such as known for linear statics is not available currently.
Abstract: Consideration of the crashworthiness of a design requires nonlinear structural analysis. Analysis codes for such problems are based on explicit integration schemes. Parameter changes are derived from the results of the analysis to improve the design in order to meet the requirements of regulations and design goals. Today, the usual approach is a trial-and-error search that is very expensive with respect to labor costs. Optimization methods can be used to automate the search for the optimum design. Closed loop software for the optimization of structures with nonlinear behavior such as known for linear statics is not available currently. Usually addons to the non-linear codes based on response surface methods or finite difference sensitivity analysis are used. The paper discusses the incorporation of optimization into the crashworthiness design of automotive structures. A very efficient response surface method is presented. Some examples show practical applications of structural optimization in the development of motor vehicles. The use of structural optimization reduces the manual effort to search for an optimal design considerably.