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Optimal Set (optimal + set)
Selected AbstractsTabu Search Strategies for the Public Transportation Network Optimizations with Variable Transit DemandCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 7 2008Wei Fan A multi-objective nonlinear mixed integer model is formulated. Solution methodologies are proposed, which consist of three main components: an initial candidate route set generation procedure (ICRSGP) that generates all feasible routes incorporating practical bus transit industry guidelines; a network analysis procedure (NAP) that decides transit demand matrix, assigns transit trips, determines service frequencies, and computes performance measures; and a Tabu search method (TSM) that combines these two parts, guides the candidate solution generation process, and selects an optimal set of routes from the huge solution space. Comprehensive tests are conducted and sensitivity analyses are performed. Characteristics analyses are undertaken and solution qualities from different algorithms are compared. Numerical results clearly indicate that the preferred TSM outperforms the genetic algorithm used as a benchmark for the optimal bus transit route network design problem without zone demand aggregation. [source] Design and implementation of a process optimizer: a case study on monitoring molding operationsEXPERT SYSTEMS, Issue 1 2005H.C.W. Lau Abstract: To cope with the requirements of high dimensional accuracy for injection molding components, it is important to optimize the process parameters in order to sustain the high level dimensional quality of the molded parts. In this respect, a study in the domain of process optimization is of paramount importance in terms of determining the optimal set of injection molding parameters. To this end, a methodology to establish an integrated model which consists of both fuzzy logic reasoning and a genetic algorithm is proposed. These two artificial intelligence techniques can complement each other to form an integrated model which capitalizes on the merits and at the same time offsets the pitfalls of the involved technologies. To validate the feasibility of the proposed model, a case study related to injection molding optimization is also covered in this paper. [source] Parameter estimation in semi-distributed hydrological catchment modelling using a multi-criteria objective functionHYDROLOGICAL PROCESSES, Issue 22 2007Hamed Rouhani Abstract Output generated by hydrologic simulation models is traditionally calibrated and validated using split-samples of observed time series of total water flow, measured at the drainage outlet of the river basin. Although this approach might yield an optimal set of model parameters, capable of reproducing the total flow, it has been observed that the flow components making up the total flow are often poorly reproduced. Previous research suggests that notwithstanding the underlying physical processes are often poorly mimicked through calibration of a set of parameters hydrologic models most of the time acceptably estimates the total flow. The objective of this study was to calibrate and validate a computer-based hydrologic model with respect to the total and slow flow. The quick flow component used in this study was taken as the difference between the total and slow flow. Model calibrations were pursued on the basis of comparing the simulated output with the observed total and slow flow using qualitative (graphical) assessments and quantitative (statistical) indicators. The study was conducted using the Soil and Water Assessment Tool (SWAT) model and a 10-year historical record (1986,1995) of the daily flow components of the Grote Nete River basin (Belgium). The data of the period 1986,1989 were used for model calibration and data of the period 1990,1995 for model validation. The predicted daily average total flow matched the observed values with a Nash,Sutcliff coefficient of 0·67 during calibration and 0·66 during validation. The Nash,Sutcliff coefficient for slow flow was 0·72 during calibration and 0·61 during validation. Analysis of high and low flows indicated that the model is unbiased. A sensitivity analysis revealed that for the modelling of the daily total flow, accurate estimation of all 10 calibration parameters in the SWAT model is justified, while for the slow flow processes only 4 out of the set of 10 parameters were identified as most sensitive. Copyright © 2007 John Wiley & Sons, Ltd. [source] Groundwater parameter estimation via the unsteady adjoint variable formulation of discrete sensitivity analysisINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 6 2002C. O. E. Burg Abstract Discrete sensitivity analysis (DSA) is a method that efficiently estimates the derivatives of a numerically approximated objective function with respect to a set of parameters at a fraction of the cost of using finite differences. Coupled with an optimization algorithm, this method can be used to locate the optimal set of parameters for the objective function. The time dependent adjoint variable formulation of discrete sensitivity analysis is derived and applied to a time-dependent, two-dimensional groundwater code. The derivatives agreed with finite difference derivatives to between 6 and 8 significant digits, at approximately , the computational cost. Using the BFGS optimization algorithm to update the parameters, the parameter estimation technique successfully identified the target values, for problems with small number of parameters. Copyright © 2002 John Wiley & Sons, Ltd. [source] The pure parsimony haplotyping problem: overview and computational advancesINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 5 2009Daniele Catanzaro Abstract Haplotyping estimation from aligned single-nucleotide polymorphism fragments has attracted more and more attention in recent years due to its importance in analysis of many fine-scale genetic data. Its application fields range from mapping of complex disease genes to inferring population histories, passing through designing drugs, functional genomics, and pharmacogenetics. The literature proposes a number of estimation criteria to select a set of haplotypes among possible alternatives. Usually, such criteria can be expressed under the form of objective functions, and the sets of haplotypes that optimize them are referred to as optimal. One of the most important estimation criteria is the pure parsimony, which states that the optimal set of haplotypes for a given set of genotypes is that having minimal cardinality. Finding the minimal number of haplotypes necessary to explain a given set of genotypes involves solving an optimization problem, called the pure parsimony haplotyping (PPH) estimation problem, which is notoriously -hard. This article provides an overview of PPH, and discusses the different approaches to solution that occur in the literature. [source] Application of local and global particle swarm optimization algorithms to optimal design and operation of irrigation pumping systems,IRRIGATION AND DRAINAGE, Issue 3 2009M. H. Afshar stations de pompage; conception et exploitation; optimisation par essaims particulaires locale et globale Abstract A particle swarm optimization (PSO) algorithm is used in this paper for optimal design and operation of irrigation pumping systems. An irrigation pumping systems design and management model is first introduced and subsequently solved with the newly introduced PSO algorithm. The solution of the model is carried out in two steps. In the first step an exhaustive enumeration is carried out to find all feasible sets of pump combinations able to cope with a given demand curve over the required period. The PSO algorithm is then called in to search for optimal operation of each set. Having solved the operation problem of all feasible sets, the total cost of operation and depreciation of initial investment is calculated for all the sets and the optimal set and the corresponding optimal operating policy is determined. The proposed model is applied to the design and operation of a real-world irrigation pumping system and the results are presented and compared with those of a genetic algorithm. Two global and local versions of the PSO algorithm are used and their efficiencies are compared to each other and that of a genetic algorithm (GA) model. The results indicate that the proposed model in conjunction with the PSO algorithm is a versatile management model for the design and operation of real-world irrigation pumping systems. Copyright © 2008 John Wiley & Sons, Ltd. Un algorithme d'optimisation par essaims particulaires (PSO en anglais) est employé dans cet article pour la conception et l'exploitation optimale des systèmes d'irrigation avec pompages. Un modèle de conception et de gestion du système est d'abord présenté et ensuite résolu avec le nouvel algorithme PSO. La solution du modèle est effectuée dans deux étapes. Dans la première étape une énumération exhaustive est effectuée pour trouver toutes les combinaisons possibles de pompes capables de répondre à une courbe de demande donnée pendant la période souhaitée. L'algorithme d'optimisation par essaims particulaires est alors utilisé pour rechercher la gestion optimale de chaque ensemble. Ayant résolu le problème de gestion de toutes les combinaisons possibles, le coût d'exploitation et d'amortissement de l'investissement initial est calculé pour chacune et la combinaison optimale et sa stratégie de gestion optimale est déterminée. Le modèle proposé est appliqué à la conception et l'exploitation d'un système irrigué réel et les résultats sont présentés et comparés à ceux d'un algorithme génétique. Deux versions globales et locales de l'algorithme PSO sont employées et leurs efficacités sont comparées entre eux et avec celles d'un modèle à algorithme génétique. Les résultats indiquent que le modèle proposé associé à l'algorithme d'optimisation par essaims particulaires est un modèle souple pour la conception et l'exploitation systèmes irrigués réels avec pompage. Copyright © 2008 John Wiley & Sons, Ltd. [source] Design of a thermally balanced membrane reformer for hydrogen productionAICHE JOURNAL, Issue 10 2008David S. A. Simakov Abstract Hydrogen production by autothermal methane steam reforming in a catalytic fixed bed membrane reactor has been analyzed and simulated. The two-compartment reactor indirectly couples the endothermic steam reforming with methane oxidation, while hydrogen is separated by a permselective Pd membrane. Simulations of the reactor, using published kinetics, map the acceptable domain of operation and the optimal set of operating parameters. The simulations exhibit slow-moving thermal fronts and the steady-state operation domains bounded by stationary fronts, separating domains of upstream and downstream-moving fronts. Front velocity depends on thermal coupling and hydrogen separation. An analytical approximation for the thermal front velocity in a thermally balanced reactor has been developed. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Molecular markers of circulating melanoma cellsPIGMENT CELL & MELANOMA RESEARCH, Issue 2 2007Sandra Medic Summary Of all skin cancers, cutaneous malignant melanoma (CMM) is the most aggressive and the life expectancy of patients with lymphatic or systemic metastases is dramatically reduced. Understandably therefore, scientists and clinicians have focused on improving diagnostic and prognostic techniques. Of these, perhaps the most promising are multimarker real-time RT-PCR and microarray for detection of circulating CMM cells in peripheral blood. While the optimal set of markers is still to be identified that can accurately assess disease severity and progression at all clinical stages of the disease, recent progress has been dramatic. Here we provide an exhaustive review of recent studies in which a variety of markers are assessed. Moreover, the efficacy of the markers relative to clinical stage is discussed in light of experimental findings. From these studies, it is apparent that researchers are now much closer to defining a set of markers of circulating cells that can be utilized in routine diagnostic tests. [source] Multiobjective optimization of polymerization reaction of vinyl acetate by genetic algorithm technique with a new replacement criterionPOLYMER ENGINEERING & SCIENCE, Issue 5 2008Maryam Sadi A multiobjective optimization procedure based on genetic algorithm has been developed to determine optimum operational conditions of polymerization reaction. In this article by using a new selection criterion to choose the next generation members with better quality, optimization efficiency is improved and the number of generations to obtain Pareto optimal set reduced. In this proposed method a novel replacement criterion based on ranking level information and proximity of solutions to the Pareto optimal front is used to choose the next generation members. The polymerization of vinyl acetate has been chosen as an example. Two objective functions, which used in this study, are maximization of the weight average molecular weight up to the desired value and minimization of the residual initiator concentration. A Pareto optimal set of objective functions has been obtained by application of a Pareto set filter operator. Furthermore, the influence of genetic algorithm parameters on the efficiency and convergence of genetic algorithm is studied by changing cross over and mutation probabilities. Because of the flexibility and generality of genetic algorithm, this optimization method is a useful technique with lots of potentials in determination of optimum value of operation parameters. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] The Economics of Controlling Infectious Diseases on Dairy FarmsCANADIAN JOURNAL OF AGRICULTURAL ECONOMICS, Issue 3 2002Junwook Chi Cost-effective disease control on the dairy farm can enhance productivity and subsequently profitability. Previous economic studies on animal disease have focused on production losses and evaluation of disease eradication programs and have provided little guidance on the optimal prevention action. This paper presents a theoretical model on the economics of livestock disease and develops an empirical model to determine the optimal set of control strategies for four production-limiting cattle diseases: bovine viral diarrhea (BVD), enzootic bovine leukosis (EBL), Johne's Disease (JD) and neosporosis. Control functions indicating the prevalence of infection with each of the four diseases for each of the 10 strategies are estimated. The optimal strategies that minimize total disease cost (direct production losses and control expenditures) are provided for each disease on the basis of farm survey results from the maritime provinces. The results emphasize the importance of introduction checks before new animals enter the herd and adequate vaccination protection as cost-effective control strategies. Lutter contre la maladie d'une manière rentable dans les élevages de bovins laitiers peut déboucher sur un meilleur rendement et des profits plus élevés. Les études économiques antérieures s'intéressant à cet aspect portaient essentiellement sur les pertes de production et l'évaluation des programmes d'éradication. Elles donnaient peu d'indications sur la solution idéale au niveau de la prévention. Cet article présente un modèle théorique de l'économique des maladies du bétail et aboutit à un modèle empirique permettant d'établir le jeu optimal de moyens pour lutter contre quatre maladies réduisant la production animale : la diarrhée à virus des bovins (DVB), la leucose bovine enzootique (LBE), la paratuberculose et la néosporose. Les auteurs estiment les fonctions qui indiquent la prévalence d'une infection pour chacune des quatre maladies retenues, dans le cadre des dix stratégies examinées. Ensuite, ils présentent les meilleures stratégies, à savoir celles qui minimisent le coût total de la maladie (pertes de production directes et dépenses associées à la lutte contre la maladie), pour chaque maladie en fonction des résultats d'un sondage auprès des éleveurs des provinces de l'Atlantique. Tout indique que les méthodes de lutte les plus rentables sont l'examen de l'animal avant son addition au troupeau et une vaccination qui protègera les bêtes de manière adéquate. 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