In this paper, we study B-spline curve interproximation with different energy forms and parametrization techniques, and present an interproximation scheme for B-spline surfaces. It shows that the energy form has a muc...
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In this paper, we study B-spline curve interproximation with different energy forms and parametrization techniques, and present an interproximation scheme for B-spline surfaces. It shows that the energy form has a much bigger impact on the generated curve than the parametrization technique. With the same energy form, different parametrization techniques generate relatively small difference on the corresponding curves. With the same parametrization technique, however, different energy forms make significant difference on the shape and smoothness of the resulting curves. Furthermore, interproximating B-spline curves generated by minimizing approximated energy forms are far from being good approximations to the optimal curves. They tend to generate flatter regions and sharper turns than curves generated by minimizing the exact energy form. The interproximation scheme for surfaces is aimed at generating a smooth surface to interpolate a grid of data which could either be a point or a region. This is achieved by minimizing a strain energy based on squared principal curvatures for bicubic B-spline surfaces. The surface interproximation process is also studied with different energy forms and parametrization techniques. The test results of the surface interproximation process also show the same conclusion as the curve interproximation process. (C) 1997 Elsevier Science Ltd.
This paper explores the Kuhn-Tucker conditions and convexity issues in a non-linear DEA model for the joint determination of efficiencies developed by Mar Molinero. It is shown that the usual convexity conditions that...
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This paper explores the Kuhn-Tucker conditions and convexity issues in a non-linear DEA model for the joint determination of efficiencies developed by Mar Molinero. It is shown that the usual convexity conditions that apply to linearprogramming problems are satisfied in this case. First order Kuhn-Tucker conditions are derived and interpreted. Estimation strategies are suggested. Some empirical work is reported.
作者：
Nikolic, ZMihanovic, A
(Faculty of Civil Engineering University of Split Croatia)
(Faculty of Civil Engineering University of Split Croatia)
Presents a non-linear numerical model for the computations of post-tensioned plane structures. Generally curved prestressing tendons and reinforcing bars are embedded into the concrete and they are modelled independen...
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Presents a non-linear numerical model for the computations of post-tensioned plane structures. Generally curved prestressing tendons and reinforcing bars are embedded into the concrete and they are modelled independently of the concrete mesh using one-dimensional curvilinear elements. Among the losses which influence the decrease in the prestress force, it is possible to compute the losses caused by friction between tendons and the concrete, the losses which result from the concrete deformation and the losses in the anchorage zone. The computation for posttensioned structures is organized in phases: the phase preceding prestressing (Phase I), the prestressing phase (Phase II) and the phase following prestressing (Phase III). The load is applied incrementally until failure. The model is tested on a number of examples.
Pooling is usually present throughout an oil refinery right from the processing of raw crudes through to the blending of petroleum products. Pooling occurs when two or more crudes, each with specific properties such a...
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Pooling is usually present throughout an oil refinery right from the processing of raw crudes through to the blending of petroleum products. Pooling occurs when two or more crudes, each with specific properties such as cost, sulphur content and unique distillation yields, are processed through distilling units simultaneously to yield downstream fractions. The decisions required in this problem are to select the quantities of each crude to be processed in each crude distiller and to select the best cut points which produce the desired fractions while minimising total cost of crude. Cut points are temperatures in the distillers at which different output streams are separated. In the proposed model, we introduce the use of cumulative functions for the distillation yields which enables a detailed description of the process in a mathematical model. Preliminary numerical results at the New Zealand Refining Company show that the non-linear model accurately describes the pooling problem and simultaneously is efficiently solvable.
Mathematical models for controlling multi-echelon inventory and production levels have been developed for entire interconnected systems rather than myopically for each point in the inventory or production system. With...
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Mathematical models for controlling multi-echelon inventory and production levels have been developed for entire interconnected systems rather than myopically for each point in the inventory or production system. With such models come the additional burden of considering the lead times and delays associated with the movement of items through the network. The delays develop when a backorder state occurs and are often considered in models by approximating the mean delay by an application of Little's Law and without consideration of the delay variation. In this article a general methodology for incorporating the variation of the delay is derived and incorporated into a backorders optimisation model. The result of incorporating delay variation into the model is a tolerance interval for order quantities that may be utilised for tighter inventory control.
Tolerance assignment plays a vital role in reducing the manufacturing cost, and most optimization models for assigning the tolerances lend to ignore the process capability of the machine. Therefore, the quality loss d...
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Tolerance assignment plays a vital role in reducing the manufacturing cost, and most optimization models for assigning the tolerances lend to ignore the process capability of the machine. Therefore, the quality loss due to nonconforming parts can be unacceptably high. Proposes a non-linear mathematical programming model for determining the component tolerances by simultaneously formulating the component's manufacturing cost, the machine's process capability and scrap rate. Includes a comparison between the results obtained by the proposed model and the traditional method.
This paper deals with the thermal diagnosis on a D.C. motor working with steady or variable speed. This supervision is performed by means of parameter identification of a thermal model with parameters depending on ang...
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This paper deals with the thermal diagnosis on a D.C. motor working with steady or variable speed. This supervision is performed by means of parameter identification of a thermal model with parameters depending on angular speed. The model parameter is estimated by minimizing the output error by means of a nonlinearprogramming according to the Marquardt algorithm. The method used allows characterizing and distinguishing several thermal behaviours.
This paper addresses capacity planning in manufacturing and computer networks. More specifically, given a manufacturing or computer system modeled as a network of queues, we consider the minimum cost selection of capa...
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This paper addresses capacity planning in manufacturing and computer networks. More specifically, given a manufacturing or computer system modeled as a network of queues, we consider the minimum cost selection of capacity levels from a discrete set of choices such that a single system performance constraint is satisfied. We focus on settings where the cost of obtaining capacity is a concave function, allowing fixed charges and economies of scale to be handled. To solve this class of capacity planning problems, we present a branch and bound algorithm that globally minimizes a concave cost function over a single convex nonlinear performance constraint and lower and upper bounds on the discrete capacity variables. We also present reoptimization procedures that allow the subproblems to be solved more efficiently. Computational results with the algorithm are reported.
The objective of this study is to apply the differential dynamic programming (DDP) technique of optimal control to heating, ventilating and air-conditioning (HVAC) systems and to compare its performance with a non-lin...
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The objective of this study is to apply the differential dynamic programming (DDP) technique of optimal control to heating, ventilating and air-conditioning (HVAC) systems and to compare its performance with a non-linear programming (NLP) technique using the sequential quadratic programming method. The DDP technique is briefly described and studied. Limitations of the technique are noted. Three cases of a system that has been treated previously in the literature are optimized by the two techniques and the computational times compared, The study shows DDP to be efficient compared with NLP for the example problems. NLP is, however, more robust and general and can treat constraints on the state variables directly. Further investigation is needed for larger-scale problems to fully explore the features of the two methods.
Under production economies of scale, the trade-off between production and transportation costs will create a tendency towards a decentralized decision-making process. First, reviews previous approaches suggested in th...
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Under production economies of scale, the trade-off between production and transportation costs will create a tendency towards a decentralized decision-making process. First, reviews previous approaches suggested in the literature for solving the production-distribution problem Then offers a non-linear programming model of the transportation problem under production economies of scale to illustrate the computational complexity of the problem. Discusses and proves the convergence of the ''tangent line approximation procedure''. Finally, introduces and solves a numerical example.
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