Engineering equations of state (EOS) deal with the majority of fluids of interest in process and equipment design in the chemical industries. Accuracy and universality are two desirable features the engineering EOS re...
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Engineering equations of state (EOS) deal with the majority of fluids of interest in process and equipment design in the chemical industries. Accuracy and universality are two desirable features the engineering EOS require, however, both of them cannot be simultaneously obtained without some degree of compromise. Therefore a simultaneous optimization algorithm is proposed to develop an accurate but compact engineering EOS for wide range of fluids with one single functional form. The algorithm is based on a simulated annealing method, and operates on different fluids at the same time to achieve the best average results. A 14-term EOS is developed based on this algorithm that has good accuracy for selected non-polar and polar fluids. The resulting equation is compared with two different 12-term EOS developed by Span and Wagner, one for polar fluids, the other for non-polar fluids. The new 14-term EOS also gives good predictions for some associating fluids such as alcohols and water. (C) 2004 Elsevier B.V. All rights reserved.
optimization of heterogeneous composite aerospace structures that operate in a range of temperatures is considered. It is observed that heterogeneous composite plates optimized to operate at a fixed service temperatur...
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optimization of heterogeneous composite aerospace structures that operate in a range of temperatures is considered. It is observed that heterogeneous composite plates optimized to operate at a fixed service temperature may perform poorly when that temperature is varied, that is, those plates may be highly sensitive to thermal loadings. A strategy is presented to obtain optimal designs of heterogeneous composite plates that operate within a given temperature range and under arbitrary mechanical loading, such that the significant and undesired sensitivity of these optimal designs to both thermal and mechanical loadings are effectively suppressed. It is assumed that the mechanical loading distribution is arbitrarily piecewise linear and that the operating temperature is within a specified range. Hence, the applied loadings are uncertain or not fixed in nature. Results for heterogeneous composite plates demonstrate the effectiveness of the strategy proposed and the danger of utilizing composite designs sensitive to variations in the thermal and mechanical loadings.
As more research centers embark on sequencing new genomes, the problem of DNA fragment assembly for shotgun sequencing is growing in importance and complexity. Accurate and fast assembly is a crucial part of any seque...
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ISBN:
(纸本)1932415432
As more research centers embark on sequencing new genomes, the problem of DNA fragment assembly for shotgun sequencing is growing in importance and complexity. Accurate and fast assembly is a crucial part of any sequencing project and many algorithms have been developed to tackle it. Since the DNA fragment assembly problem is NP-hard, exact solutions are very difficult to obtain. In this work, we present four heuristic algorithms, which we designed, implemented and tested. We compare the algorithms and the data structures of the four heuristics and present results of our experiments. We also compare our results with the assemblies produced by the well-known packages: PHRAP and CAP3.
This paper discusses the problem of optimizing the utilization of communication satellite capacity. The modem fixed satellite service provider seeks improved methods to optimize the amount of service demand that is ac...
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ISBN:
(纸本)097445592X
This paper discusses the problem of optimizing the utilization of communication satellite capacity. The modem fixed satellite service provider seeks improved methods to optimize the amount of service demand that is accommodated by capacity available on its satellite network. A mixed-integer programming (MIP) model is proposed for the solution of the problem, as part of a decision support tool. Such a tool integrates three system components, which are: a mathematical optimization model, an optimization algorithm, and a graphical user interface. This paper will discuss the design process associated with each component of the system and will conclude with preliminary results obtained from sample optimization runs.
The frequency response characteristics of surface acoustic wave (SAW) filters are governed primarily by their geometrical structures, i.e., the configurations of interdigital transducers (IDTs) and grating reflectors ...
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ISBN:
(纸本)0780386620
The frequency response characteristics of surface acoustic wave (SAW) filters are governed primarily by their geometrical structures, i.e., the configurations of interdigital transducers (IDTs) and grating reflectors fabricated on piezoelectric substrates. In the process of designing optimal structures for SAW filters, computer-aided design techniques utilize theoretical model of IDT for estimating their performances. In this paper, considering dispersion of uncertain parameters included in IDT's model, the robust design of SAW filters is formulated as a constrained optimization problem. Then, a new penalty function method combined with a variable neighborhood search (VNS) is applied to the optimization problem. Computational experiments conducted on a practical design of SAW filter demonstrate the usefulness of the proposed robust design approach.
A new approach to the multiobjective constrained design of aerodynamic shapes is suggested. The approach employs genetic algorithms (GA) as an optimization tool in combination with a reduced-order-models method based ...
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A new approach to the multiobjective constrained design of aerodynamic shapes is suggested. The approach employs genetic algorithms (GA) as an optimization tool in combination with a reduced-order-models method based on linked local databases obtained by full Navier-Stokes computations. The method was applied to the problem of multiobjective transonic profile optimization with nonlinear constraints. The results demonstrated that the method retains high robustness of conventional GAs while keeping computational-fluid-dynamics computational volume to an acceptable level as a result of a limited use of full Navier-Stokes computations. A significant computational time saving (in comparison with optimization tools fully based on Navier-Stokes computations) allowed the algorithm to be used in a demanding engineering environment.
A multi-objective, multidisciplinary design optimization methodology for mathematically modeling the distributed satellite system conceptual design problem as an optimization problem has been developed. The tradespace...
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A multi-objective, multidisciplinary design optimization methodology for mathematically modeling the distributed satellite system conceptual design problem as an optimization problem has been developed. The tradespace for distributed satellite systems can be enormous, too large to enumerate, analyze, and compare all possible architectures. The seven-step methodology enables an efficient search of the tradespace for the best families of architectures during the conceptual design phase. Four classes of optimization techniques are investigated, Taguchi, heuristic, gradient, and univariate methods. The heuristic simulated annealing algorithm found the best distributed satellite system architectures with the greatest consistency due to its ability to escape local optima within a nonconvex tradespace. The conceptual design problem scope is then broadened by expanding from single-objective to multiobjective optimization problems, and two variant multi-objective simulated annealing algorithms are developed. Finally, several methods are explored for approximating the true global Pareto boundary with only a limited knowledge of the full design tradespace. In this manner, the methodology serves as a powerful, versatile systems engineering and architecting tool for the conceptual design of distributed satellite systems.
CPU times and memory requirements for a commonly used solver are compared to that of a state-of-the-art, parallel, sparse solver. The sparse solver is then used in conjunction with three optimization methodologies (ge...
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CPU times and memory requirements for a commonly used solver are compared to that of a state-of-the-art, parallel, sparse solver. The sparse solver is then used in conjunction with three optimization methodologies (genetic algorithm, contour deformation, and Davidon-Fletcher-Powell) to assess the usefulness of these methodologies for designing optimized nonaxisymmetric liners. This assessment is performed using a multimodal noise source in a finite length rectangular duct without flow. The sparse solver is found to reduce memory requirements by a factor of 5 and processing time by a factor of 11 when compared with the commonly used solver. All three optimization techniques give nearly the same optimum impedance for uniform liners, and this impedance approaches the Cremer optimum impedance at low frequency where only the plane wave mode is cuton. For nonaxisymmetric liners, the genetic algorithm gives improvements in optimum attenuation over the other optimization methodologies because of the presence of multiple local optima. Another important result is the discovery that, when optimized, a spanwise segmented liner with two segments gives attenuations equal to or substantially greater than an optimized axially segmented liner with the same number of segments.
Collaborative optimization is examined with a focus on its consistency equality constraints and the effect of their vanishing gradients. Attempts are made to enhance its analytical and computational performance. Gener...
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Collaborative optimization is examined with a focus on its consistency equality constraints and the effect of their vanishing gradients. Attempts are made to enhance its analytical and computational performance. General theoretical investigation and specific analytical study show that when system-level variables satisfy the consistency equality constraints, system-level optimization generally will encounter no-solution and convergence difficulties if it depends on Lagrange multipliers in the Karush-Kuhn-Tucker necessary conditions. Thus, to avoid such difficulties, algorithms and methods that need no Lagrange multipliers at all are used. Alternatively, to avoid multiplier troubles in applying the Karush-Kuhn-Tucker conditions, the consistency constraints are replaced by other constraints that are not sums of squared differences. Specific computational study shows that enhanced application of the penalty-function method can yield approximate solutions very close to the solution of the predecomposed problem. Convergence is obtained with little difficulty when only the least of the freedom allowable by collaborative optimization is taken in using or producing variants of the targets.
作者:
Puri, RIBM Corp
TJ Watson Res Ctr Yorktown Hts NY 10598 USA
Power dissipation is becoming the most challenging design constraint in nanometer technologies. Among various design implementation schemes, standard cell ASICs offer the best power efficiency for high-performance app...
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ISBN:
(纸本)0780385284
Power dissipation is becoming the most challenging design constraint in nanometer technologies. Among various design implementation schemes, standard cell ASICs offer the best power efficiency for high-performance applications. The flexibility of ASICs allow for the use of multiple voltages and multiple thresholds to match the performance of critical regions to their timing constraints, and minimize the power every where else. We explore the trade-off between multiple supply voltages and multiple threshold voltages in the optimization of dynamic and static power. The use of multiple supply voltages presents some unique physical and electrical challenges. Level shifters need to be introduced between the various voltage regions. The physical layout needs to be designed to ensure the efficient delivery of the correct voltage to various voltage regions. More flexibility can be gained by using appropriate level shifters.
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