Initial Solution (initial + solution)

Distribution by Scientific Domains

Selected Abstracts

Hybrid Meta-Heuristic Algorithm for the Simultaneous Optimization of the O,D Trip Matrix Estimation

Antony Stathopoulos
These include a genetic algorithm (GA), a simulated annealing (SA) algorithm, and a hybrid algorithm (GASA) based on the combination of GA and SA. The computational performance of the three algorithms is evaluated and compared by implementing them on a realistic urban road network. The results of the simulation tests demonstrate that SA and GASA produce a more accurate final solution than GA, whereas GASA shows a superior convergence rate, that is, faster improvement from the initial solution, in comparison to SA and GA. In addition, GASA produces a final solution that is more robust and less dependent on the initial demand pattern, in comparison to that obtained from a greedy search algorithm. [source]

Self evolution algorithm to minimize earliness and tardiness penalties with a common due date on a single machine

Wei Weng Non-member
Abstract Earliness and tardiness penalties are designed for such scheduling problems where the popular Just-In-Time (JIT) concept is considered to be of significant importance. In this paper, a self evolution (SE) algorithm is proposed to solve the problem of single-machine total earliness and tardiness penalties with a common due date. Up to now, no specific attention has been paid to straddling V-shaped schedules of such problems, which may be better than pure V-shaped schedules for the early due date cases; and no specific discussions have been made on the start time setting of the first job in a schedule. Therefore, in this research, efforts have been made on digging out the straddling V-shaped schedules, improving the efficiency of setting the start time of a schedule, and reducing the execution time. In addition, a new RHRM approach is proposed to create the initial solution for evolution, which helps in achieving the fast contingency of the algorithm. The performance of the proposed algorithm has been tested on 280 benchmark instances ranging from 10 to 1000 jobs from the OR Library, and the results show that the proposed SE algorithm delivers much higher efficiency in finding optimal or near-optimal solutions with both better results in total penalties and significant execution time reduction. Copyright 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

On the solution of the nonlinear Korteweg,de Vries equation by the homotopy perturbation method

Ahmet Yildirim
Abstract In this paper, the homotopy perturbation method is used to implement the nonlinear Korteweg,de Vries equation. The analytical solution of the equation is calculated in the form of a convergent power series with easily computable components. A suitable choice of an initial solution can lead to the needed exact solution by a few iterations. Copyright 2008 John Wiley & Sons, Ltd. [source]

Evidence of partial unfolding of proteins at the ice/freeze-concentrate interface by infrared microscopy

J. Jeff Schwegman
Abstract The goal of this research was to use infrared spectroscopy in combination with a freeze drying stage to gain a better understanding of the mechanism of loss of protein integrity due to the stresses associated with freezing. Infrared spectra were collected in triplicate for the interstitial space between ice crystals and through ice crystals in a partially frozen system. Spectra were collected for lactate dehydrogenase (LDH) and human immune globulin (IgG) both in the presence and absence of an added surfactant (polysorbate 80). Spectra collected in the interstitial space, distant from the surface of ice crystals, were very similar to spectra collected from the initial solution regardless of the presence of a surfactant. Spectra collected through ice crystals, without added surfactant, were significantly different than spectra collected from the initial solution. An increase in bands characteristic of intermolecular ,-sheet structures (main component of aggregates) were present in these spectra. The presence of surfactant in both protein formulations resulted in a decrease in intermolecular ,-sheet signals in spectra of the proteins on the ice crystal surface. Additionally, much of the native state structure of LDH initially lost on the surface of ice crystals returned when surfactant was added to the formulation prior to freezing. 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3239,3246, 2009 [source]

Application of semi definite relaxation and variable neighborhood search for multiuser detection in synchronous CDMA

Abdel Lisser
Abstract In this article, a detection strategy based on variable neighborhood search (VNS) and semidefinite relaxation of the multiuser model maximum likelihood (ML) is investigated. The VNS method provides a good method for solving the ML problem while keeping the integer constraints. A SDP relaxation is used as an efficient way to generate an initial solution in a limited amount of time, in particular using early termination. The SDP resolution tool used is the spectral bundle method developed by Helmberg. We show that using VNS can result in a better error rate, but at a cost of calculation time. 2009 Wiley Periodicals, Inc. NETWORKS, 2010 [source]

Modification of poly(ethylene terephthalate) surface with attached dextran macromolecules

Yurij Stetsyshyn
Abstract BACKGROUND: Peroxidation of a poly(ethylene terephthalate) (PET) surface clears the path to the formation of biospecific polymeric layers on it. The goal of this work was the modification of a PET surface with oligoperoxides with further grafting of dextran macromolecules to this peroxidated surface. RESULTS: Novel oligoperoxides with a good affinity to PET were synthesized. They are capable of attaching to the PET surface, due to the decomposition of peroxide groups via the formation of free radicals. The alterations in surface energy and its components as a result of surface modification as well as changes in topography of the PET surface were determined. The degree of modification of the PET surface can reach 68% and depends on the following: the method of oligoperoxide and dextran deposition; the concentration of both oligoperoxide and dextran in the initial solution; and the temperature at which the modification is carried out. CONCLUSION: A new method of PET surface activation has been developed. The attachment of dextran macromolecules to modified PET surfaces is confirmed. Copyright 2009 Society of Chemical Industry [source]

Pseudosymmetry, high copy number and twinning complicate the structure determination of Desulfovibrio desulfuricans (ATCC 29577) flavodoxin

Megan Guelker
The crystal structure of oxidized flavodoxin from Desulfovibrio desulfuricans (ATCC 29577) was determined by molecular replacement in two crystal forms, P3121 and P43, at 2.5 and 2.0, resolution, respectively. Structure determination in space group P3121 was challenging owing to the presence of pseudo-translational symmetry and a high copy number in the asymmetric unit (8). Initial phasing attempts in space group P3121 by molecular replacement using a poor search model (46% identity) and multi-wavelength anomalous dispersion were unsuccessful. It was necessary to solve the structure in a second crystal form, space group P43, which was characterized by almost perfect twinning, in order to obtain a suitable search model for molecular replacement. This search model with complementary approaches to molecular replacement utilizing the pseudo-translational symmetry operators determined by analysis of the native Patterson map facilitated the selection and manual placement of molecules to generate an initial solution in the P3121 crystal form. During the early stages of refinement, application of the appropriate twin law, (,h, ,k, l), was required to converge to reasonable R -factor values despite the fact that in the final analysis the data were untwinned and the twin law could subsequently be removed. The approaches used in structure determination and refinement may be applicable to other crystal structures characterized by these complicating factors. The refined model shows flexibility of the flavin mononucleotide coordinating loops indicated by the isolation of two loop conformations and provides a starting point for the elucidation of the mechanism used for protein-partner recognition. [source]

Upper bounds for single-source uncapacitated concave minimum-cost network flow problems

Dalila B. M. M. Fontes
Abstract In this paper, we describe a heuristic algorithm based on local search for the Single-Source Uncapacitated (SSU) concave Minimum-Cost Network Flow Problem (MCNFP). We present a new technique for creating different and informed initial solutions to restart the local search, thereby improving the quality of the resulting feasible solutions (upper bounds). Computational results on different classes of test problems indicate the effectiveness of the proposed method in generating basic feasible solutions for the SSU concave MCNFP very near to a global optimum. A maximum upper bound percentage error of 0.07% is reported for all problem instances for which an optimal solution has been found by a branch-and-bound method. 2003 Wiley Periodicals, Inc. [source]

Local search with perturbations for the prize-collecting Steiner tree problem in graphs

S. A. Canuto
Abstract Given an undirected graph with prizes associated with its nodes and weights associated with its edges, the prize-collecting Steiner tree problem consists of finding a subtree of this graph which minimizes the sum of the weights of its edges plus the prizes of the nodes not spanned. In this paper, we describe a multistart local search algorithm for the prize-collecting Steiner tree problem, based on the generation of initial solutions by a primal-dual algorithm using perturbed node prizes. Path-relinking is used to improve the solutions found by local search and variable neighborhood search is used as a post-optimization procedure. Computational experiments involving different algorithm variants are reported. Our results show that the local search with perturbations approach found optimal solutions on nearly all of the instances tested. 2001 John Wiley & Sons, Inc. [source]