We present a new formulation of the truss topology problem that results in unique design and unique displacements of the optimal truss. This is reached by adding an upper level to the original optimization problem and...
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We present a new formulation of the truss topology problem that results in unique design and unique displacements of the optimal truss. This is reached by adding an upper level to the original optimization problem and formulating the new problem as an MPCC (Mathematical Program with Complementarity Constraints). We derive optimality conditions for this problem and present several techniques for its numerical solution. Finally, we compare two of these technique's on a series of numerical examples.
An algorithm was developed to select an optimum model among several neural network (NN) models using the Manhattan and Euclidean metric measures. The algorithm was implemented to find an optimum NN prediction model ba...
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An algorithm was developed to select an optimum model among several neural network (NN) models using the Manhattan and Euclidean metric measures. The algorithm was implemented to find an optimum NN prediction model based on simultaneous comparison of five performance parameters. Weighted coefficients were given to each performance parameter based on their significance for specific condition. The associated weighted coefficients were optimised using two optimisation techniques: (i) genetic algorithm;and (n) linear programming. The algorithm performed satisfactorily in determining acceptable models and selecting an optimum NN model. The radial basis function NN model based on green vegetation index texture yielded an average prediction accuracy of 92(.)1% for predicting leaf nitrogen content under field conditions. (c) 2006 IAgrE. All rights reserved. Published by Elsevier Ltd.
This article presents a new approach to minimize the losses in electrical power systems. This approach considers the application of the primal-dual logarithmic barrier method to voltage magnitude and tap-changing tran...
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This article presents a new approach to minimize the losses in electrical power systems. This approach considers the application of the primal-dual logarithmic barrier method to voltage magnitude and tap-changing transformer variables, and the other inequality constraints are treated by augmented Lagrangian method. The Lagrangian function aggregates all the constraints. The first-order necessary conditions are reached by Newton's method, and by updating the dual variables and penalty factors. Test results are presented to show the good performance of this approach.
A class of optimal control problems for semilinear elliptic equations with mixed control-state constraints is considered. The existence of bounded and measurable Lagrange multipliers is proven. As a particular applica...
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A class of optimal control problems for semilinear elliptic equations with mixed control-state constraints is considered. The existence of bounded and measurable Lagrange multipliers is proven. As a particular application, the Lavrentiev-type regularization of pointwise state constraints is discussed. Here, the existence of associated regular multipliers is shown, too.
This paper extends an exponential reliability growth model to determine the optimal number of test cases to be executed for various use case scenarios during the system testing of software. An example demonstrates a p...
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This paper extends an exponential reliability growth model to determine the optimal number of test cases to be executed for various use case scenarios during the system testing of software. An example demonstrates a practical application of the optimization model for system test planning.
Simulation response optimization has wide applications for management of systems that are so complicated that the performance can only be evaluated by using simulation. This paper modifies the quasi-Newton method used...
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Simulation response optimization has wide applications for management of systems that are so complicated that the performance can only be evaluated by using simulation. This paper modifies the quasi-Newton method used in deterministic optimization to suit the stochastic environment in simulation response optimization. The basic idea is to use the estimated subgradient calculated from different replications and a metric matrix updated from the Broyden-Fletcher-Goldfarb-Shanno (BFGS) formula to yield a quasi-Newton search direction. To avoid misjudging the minimal point, in both the line search and the quasi-Newton iterations, due to the stochastic nature, a t-test instead of a simple comparison of the mean responses is performed. It is proved that the resulting stochastic quasi-Newton algorithm is able to generate a sequence that converges to the optimal point, under certain conditions. Empirical results from a four-station queueing problem and an (s,S) inventory problem indicate that this method is able to find the optimal solutions in a statistical sense. Moreover, this method is robust with respect to the number of replications conducted at each trial point. (c) 2005 Elsevier B.V. All rights reserved.
An interior-point method for nonlinear programming is presented. It enjoys the flexibility of switching between a line search method that computes steps by factoring the primal-dual equations and a trust region method...
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An interior-point method for nonlinear programming is presented. It enjoys the flexibility of switching between a line search method that computes steps by factoring the primal-dual equations and a trust region method that uses a conjugate gradient iteration. Steps computed by direct factorization are always tried first, but if they are deemed ineffective, a trust region iteration that guarantees progress toward stationarity is invoked. To demonstrate its effectiveness, the algorithm is implemented in the Knitro [6,28] software package and is extensively tested on a wide selection of test problems.
Multiwavelength laser exposures pose unique safety challenges for both laser experts and users of laser systems. We describe two methods of optimizing optical density requirements for multiwavelength laser exposures. ...
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Multiwavelength laser exposures pose unique safety challenges for both laser experts and users of laser systems. We describe two methods of optimizing optical density requirements for multiwavelength laser exposures. The problem is first formulated and solved using standard mathematical programming techniques, and the results are compared to those from a simplified algorithm. The result is a method that can be efficiently integrated into existing laser modeling and hazard analysis software. As an example, overall visible light transmittance is maximized while maintaining eye-safe viewing conditions during a multiwavelength exposure, simultaneously minimizing the total optical density required for sufficient laser eye protection. This optimization formulation helps laser system users determine the proper laser eye protection for safe viewing in multiwavelength laser environments. (c) 2006 Laser Institute of America.
The aim of this study is to expand the application of the nonlinear softened truss model for membrane elements on beam-column joints. The softened truss model employs three equations for equilibrium, three for compati...
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The aim of this study is to expand the application of the nonlinear softened truss model for membrane elements on beam-column joints. The softened truss model employs three equations for equilibrium, three for compatibility and four equations for the constitutive laws of materials. The constitutive equations for both the concrete and steel are based on the actually observed stress-strain relationships. The model has three important attributes. The first is the nonlinear association of stress and strain. The second, and conceivably more noteworthy, is the softening of concrete in compression due to tensile strains in the perpendicular direction. The third is that the influence of the concrete tensile stresses between cracks on the average stress-strain relationship for reinforcing steel and the influence of orthogonal tensile stresses on the compression stress-strain relationship for concrete can be considered in the model. For beam-column joints, one of the most important factors influencing the behaviour is certainly the bond conditions of the beam bars. In this study, the softened truss model is expanded to take into account the influence of this important factor into account. In the revised version of the model, full strain compatibility does not exist between the steel reinforcement and the surrounding concrete and thus the factors influencing the bond-slip between concrete and reinforcement is adequately considered. The improved softened truss model is applied on 51 exterior beam-column joint tests. It is apparent from the results that the revised model gives very accurate predictions of the shear strength of joints and is an improvement on the existing version of the model proposed by Hsu. (c) 2005 Elsevier Ltd. All rights reserved.
Global convergence to first-order critical points is proved for a variant of the trust-region SQP-filter algorithm analyzed in (Fletcher, Gould, Leyffer and Toint). This variant allows the use of two types of step str...
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