This paper presents an efficient and compact Matlab code to solve three-dimensional topology optimization problems. The 169 lines comprising this code include finite element analysis, sensitivity analysis, density fil...
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This paper presents an efficient and compact Matlab code to solve three-dimensional topology optimization problems. The 169 lines comprising this code include finite element analysis, sensitivity analysis, density filter, optimality criterion optimizer, and display of results. The basic code solves minimum compliance problems. A systematic approach is presented to easily modify the definition of supports and external loads. The paper also includes instructions to define multiple load cases, active and passive elements, continuation strategy, synthesis of compliant mechanisms, and heat conduction problems, as well as the theoretical and numerical elements to implement general non-linear programming strategies such as SQP and MMA. The code is intended for students and newcomers in the topology optimization. The complete code is provided in Appendix C and it can be downloaded from http://***.
This paper extended the concept of the technique for order preference by similarity to ideal solution (TOPSIS) to develop a methodology for solving multi-level non-linear multi-objective decision-making (MLN-MODM) pro...
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This paper extended the concept of the technique for order preference by similarity to ideal solution (TOPSIS) to develop a methodology for solving multi-level non-linear multi-objective decision-making (MLN-MODM) problems of maximization-type. Also, two new interactive algorithms are presented for the proposed TOPSIS approach for solving these types of mathematical programming problems. The first proposed interactive TOPSIS algorithm includes the membership functions of the decision variables for each level except the lower level of the multi-level problem. These satisfactory decisions are evaluated separately by solving the corresponding single-level MODM problems. The second proposed interactive TOPSIS algorithm lexicographically solves the MODM problems of the MLN-MOLP problem by taking into consideration the decisions of the MODM problems for the upper levels. To demonstrate the proposed algorithms, a numerical example is solved and compared the solutions of proposed algorithms with the solution of the interactive algorithm of Osman et al. (2003)141. Also, an example of an application is presented to clarify the applicability of the proposed TOPSIS algorithms in solving real world multi-level multi-objective decision-making problems. (C) 2013 Elsevier Inc. All rights reserved.
In-vitro fertilization (IVF) is one of the highly pursued assisted reproductive technologies (ARTs) worldwide. Superovulation is the most crucial stage in IVF, since it involves injection of hormones externally to sti...
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In-vitro fertilization (IVF) is one of the highly pursued assisted reproductive technologies (ARTs) worldwide. Superovulation is the most crucial stage in IVF, since it involves injection of hormones externally to stimulate development and maturation of multiple oocytes. A model for the follicular dynamics as a function of injected hormones and patient characteristics has been developed and validated in our previous studies. Using the same model as a predictive tool along with the application of optimal control principles;the optimal dose and frequency of medication customized for each patient is predicted. The objective of successful superovulation is to obtain maximum number of mature oocytes/follicles within a particular size range, which is translated into mathematical form by using concepts from normal distribution. The problem is solved by different optimal control methods like the maximum principle and discretized non-linear programming. The results from both the approaches are compared and their advantages are discussed. (C) 2014 Elsevier Ltd. All rights reserved.
In this paper, the two mixed refrigerant refrigeration cycles were proposed to be replaced by pure ethylene cycle in the olefin plant of the Tabriz petrochemical complex. Both these components composition of refrigera...
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In this paper, the two mixed refrigerant refrigeration cycles were proposed to be replaced by pure ethylene cycle in the olefin plant of the Tabriz petrochemical complex. Both these components composition of refrigerant and the compressor operations pressures are the key design parameters in the mixed refrigerant refrigeration systems. The purpose of the paper is to present a systematic method based on a combination of mathematical methods and thermodynamic viewpoint to optimize mixed refrigerant cycles parameters. Particle swarm optimization and non-linear programming techniques were employed to optimize the parameters of cycles. Results show that the particle swarm optimization is superior to the NLP optimization techniques in finding the values of optimizing variables. (C) 2014 Elsevier B.V. All rights reserved.
Deriving the optimal operational rules for a multi-reservoir system serving various purposes like irrigation, multiple hydropower plants and flood control are complex. In the present study, such a multi-reservoir syst...
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Deriving the optimal operational rules for a multi-reservoir system serving various purposes like irrigation, multiple hydropower plants and flood control are complex. In the present study, such a multi-reservoir system with multiple hydropower plants are optimized for maximizing the hydropower production and satisfying the irrigation demands using a non-linear programming (NLP) technique. The developed NLP model has been applied to Koyna Hydro-Electric Project (KHEP) for maximizing the hydropower production and solved for three different dependable inflow scenarios under various operating policies. The complexity of the problem is such that the power releases and irrigation releases are in opposite direction and are non-commensurate. The total annual power production, monthly power production and the end of the month storage plots are compared for different inflows and operating policies. From the study, it is found that hydropower production can be increased to a minimum of 22% by slightly relaxing the tribunal constraint on releases towards the western side. The optimal releases from Policy 3 are further evaluated using a simulation model. The simulation result shows that the optimal releases have performed satisfactorily over long period of operation.
Several existing revenue management (RM) models are based on some simplifying assumptions. One of these is that passengers, who do not get the fare they want, book and travel on other airlines or they do not travel at...
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Several existing revenue management (RM) models are based on some simplifying assumptions. One of these is that passengers, who do not get the fare they want, book and travel on other airlines or they do not travel at all. In reality, many customers are not necessarily lost to the airline but they buy-up, i.e. buy a more expensive ticket. We model network RM which incorporates buy-up using dynamic programming (DP). Due to the curse of dimensionality, the DP model is analytically and computationally intractable. Thus, to provide a valuable support for the decision-making process, different approximate models are presented and their solutions are used to define several capacity-control schemes based on partitioned booking limits and bid prices. The schemes are compared in a computational study showing that a significant increase in revenue is obtainable even when the buy-up probability is relatively small. The booking limits for high-fare products, as well as the bid prices for all itineraries, are likely to increase in the buy-up probability.
Enhancing the quality of the product has always been one considerable concern of production process management, and this subject gave way to implementing so many methods including robust design. In this paper, robust ...
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Enhancing the quality of the product has always been one considerable concern of production process management, and this subject gave way to implementing so many methods including robust design. In this paper, robust design utilizes response surface methodology (RSM) considering the mean and variance of the response variable regarding system design, parameter design, and tolerance design. In this paper, customer requirements and robust design are regarded simultaneously to achieve enriched quality. Subsequently, with a non-linear programming, a novel method for integrating RSM and quality function deployment has been proposed to achieve robustness in design. The customer requirements are regarded in every stage of product development process meaning system design, parameter design and tolerance design. To validate the applicability of the proposed approach, it has been implemented in a real case of chemical industry. Research findings show that the proposed method is much better than other existing methods including MSE and dual response methods. According to this method, the resulted mean is better than MSE method, and more importantly, the variance of the process is approximately 14% and 10% lesser than dual response and MSE method. Copyright (c) 2013 John Wiley & Sons, Ltd.
Bio-invasions occur in management mosaics where local control affects spread and damage across political boundaries. We address two obstacles to local implementation of optimal regional control of a bio-invasion that ...
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Bio-invasions occur in management mosaics where local control affects spread and damage across political boundaries. We address two obstacles to local implementation of optimal regional control of a bio-invasion that damages public and private resources across jurisdictions: lack of local funds to protect the public resource and lack of access to protect the private resource. To evaluate these obstacles, we develop a spatial-dynamic model of the optimal control of emerald ash borer (EAB) in the Twin Cities metropolitan area of Minnesota, USA. We focus on managing valuable host trees with preventative insecticide treatment or pre-emptive removal to slow EAB spread. The model includes spatial variation in the ownership and benefits of host trees, the costs of management, and the budgets of municipal jurisdictions. We develop and evaluate centralized strategies for 17 jurisdictions surrounding the infestation. The central planner determines the quantities of trees in public ownership to treat and remove over time, to maximize benefits of surviving trees net costs of management across public and private ownerships, subject to constraints on municipal budgets, management activities, and access to private trees. The results suggest that centralizing the budget across jurisdictions rather than increasing any one municipal budget does more to increase total net benefits. Strategies with insecticide treatment are superior to ones with pre-emptive removal because they reduce the quantity of susceptible trees at lower cost and protect the benefits of healthy trees. Increasing the accessibility of private trees to public management substantially slows EAB spread and improves total net benefit. (C) 2013 Elsevier B.V. All rights reserved.
This article surveys optimization of simulated systems. The simulation may be either deterministic or random. The survey reflects the author's extensive experience with simulation-optimization through Kriging (or ...
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This article surveys optimization of simulated systems. The simulation may be either deterministic or random. The survey reflects the author's extensive experience with simulation-optimization through Kriging (or Gaussian process) metamodels, analysed through parametric bootstrapping for deterministic and random simulation and distribution-free bootstrapping (or resampling) for random simulation. The survey covers: (1) simulation-optimization through 'efficient global optimization' using 'expected improvement' (EI);this EI uses the Kriging predictor variance, which can be estimated through bootstrapping accounting for the estimation of the Kriging parameters;(2) optimization with constraints for multiple random simulation outputs and deterministic inputs through mathematical programming applied to Kriging metamodels validated through bootstrapping;(3) Taguchian robust optimization for uncertain environments, using mathematical programming-applied to Kriging metamodels-and bootstrapping to estimate the variability of the Kriging metamodels and the resulting robust solution;(4) bootstrapping for improving convexity or preserving monotonicity of the Kriging metamodel.
In this paper, we present an extension of the semi-definite programming formulation of the optimal rate code design in single link Binary Erasure Channel (BEC) proposed by the authors to the Binary Erasure Multiple Ac...
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ISBN:
(纸本)9781479953592
In this paper, we present an extension of the semi-definite programming formulation of the optimal rate code design in single link Binary Erasure Channel (BEC) proposed by the authors to the Binary Erasure Multiple Access Channel (BE-MAC) with two sources correlation. This new way can be easily extended to the multiple access senders. Simulation results show the efficiency and effectiveness of the new approach in practice.
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