Primal-dual variable neighborhood search for the simple plant-location problem

Copyright @ 2007 INFORMSThe variable neighborhood search metaheuristic is applied to the primal simple plant-location problem and to a reduced dual obtained by exploiting the complementary slackness conditions. This leads to (i) heuristic resolution of (metric) instances with uniform fixed costs, up to n = 15,000 users, and m = n potential locations for facilities with an error not exceeding 0.04%; (ii) exact solution of such instances with up to m = n = 7,000; and (iii) exact solutions of instances with variable fixed costs and up to m = n = 15, 000.This work is supported by NSERC Grant 105574-02; NSERC Grant OGP205041; and partly by the Serbian Ministry of Science, Project 1583

Improvements and comparison of heuristics for solving the uncapacitated multisource Weber problem

Copyright @ 2000 INFORMSThe multisource Weber problem is to locate simultaneously m facilities in the Euclidean plane to minimize the total transportation cost for satisfying the demand of n fixed users, each supplied from its closest facility. Many heuristics have been proposed for this problem, as well as a few exact algorithms. Heuristics are needed to solve quickly large problems and to provide good initial solutions for exact algorithms. We compare various heuristics, i.e., alternative location-allocation (Cooper 1964), projection (Bongartz et al. 1994), Tabu search (Brimberg and Mladenovic 1996a), p-Median plus Weber (Hansen ct al. 1996), Genetic search and several versions of Variable Neighbourhood search. Based on empirical tests that are reported, it is found that most traditional and some recent heuristics give poor results when the number of facilities to locate is large and that Variable Neighbourhood search gives consistently best results, on average, in moderate computing time.This study was supported by the Department of National Defence (Canada) Academic Research; Office of Naval Research Grant N00014-92-J-1194, Natural Sciences and Engineering Research Council of Canada Grant GPO 105574 and Fonds pour la Formation des Chercheurs et l’Aide a la Recherche Grant 32EQ 1048; and by an International Postdoctoral Fellowship of the Natural Sciences and Engineering Research Council of Canada, Grant OGPOO 39682

Constructive Heuristics for the Minimum Labelling Spanning Tree Problem: a preliminary comparison

This report studies constructive heuristics for the minimum labelling spanning tree (MLST) problem. The purpose is to find a spanning tree that uses edges that are as similar as possible. Given an undirected labeled connected graph (i.e., with a label or color for each edge), the minimum labeling spanning tree problem seeks a spanning tree whose edges have the smallest possible number of distinct labels. The model can represent many real-world problems in telecommunication networks, electric networks, and multimodal transportation networks, among others, and the problem has been shown to be NP-complete even for complete graphs. A primary heuristic, named the maximum vertex covering algorithm has been proposed. Several versions of this constructive heuristic have been proposed to improve its efficiency. Here we describe the problem, review the literature and compare some variants of this algorithm

Solving the minimum labelling spanning tree problem using hybrid local search

Given a connected, undirected graph whose edges are labelled (or coloured), the minimum labelling spanning tree (MLST) problem seeks a spanning tree whose edges have the smallest number of distinct labels (or colours). In recent work, the MLST problem has been shown to be NP-hard and some effective heuristics (Modified Genetic Algorithm (MGA) and Pilot Method (PILOT)) have been proposed and analyzed. A hybrid local search method, that we call Group-Swap Variable Neighbourhood Search (GS-VNS), is proposed in this paper. It is obtained by combining two classic metaheuristics: Variable Neighbourhood Search (VNS) and Simulated Annealing (SA). Computational experiments show that GS-VNS outperforms MGA and PILOT. Furthermore, a comparison with the results provided by an exact approach shows that we may quickly obtain optimal or near-optimal solutions with the proposed heuristic

Boiler combusting large soya straw bales for heating the greenhouses complex

U jednoj od najvećih kompanija koje se bave poljoprivrednom proizvodnjom u Srbiji pod zasadom soje se nalazi preko 2000 ha, i svake godine se proizvede oko 4000 t balirane sojine slame. Planirano je da se sojina slama koristi za grejanje plastenika, ukupne površine 5 ha. Zbog toga, u Laboratoriji za termotehniku i energetiku Instituta za nuklearne nauke 'Vinča' je učinjen napor da se razvije tehnologija za korišćenje krupne balirane biomase za proizvodnju energije. U prvoj fazi, razvijeno je demonstraciono eksperimentalno postrojenje - ložište za sagorevanje bala sojine slame. Ložište je izgrađeno i termotehnički ispitano, da bi se utvrdio kvalitet sagorevanja. Kako su rezultati ispitivanja bili veoma zadovoljavajući, u drugoj fazi razvoja, vrelovodni kotao sličnih karakteristika (koji sagoreva bale sojine slame dimenzija 0,7 x 1,2 x 2,7 m) je projektovan, i trenutno je u fazi izgradnje.In one of the largest agricultural companies in Serbia with over 2000 ha of soya plantations there is 4000 t/year of baled soya straw production. Soya straw biomass is planned to be used as renewable energy source for heating the greenhouses, with 5 ha in area. Therefore, efforts have been made to develop a technology for utilizing large bales of soya straw for energy production. In the first phase, a demo energy production facility - furnace was developed and built. The facility was tested in order to examine the quality of combustion of large soya straw bales. Since the experimental results obtained by testing of this facility proved to be very satisfactory in the second phase of development, the hot water boiler of similar characteristics (burning soya straw bales, with dimensions 0.7 x 1.2 x 2.7 m) was designed

Boiler combusting large soya straw bales for heating the greenhouses complex

U jednoj od najvećih kompanija koje se bave poljoprivrednom proizvodnjom u Srbiji pod zasadom soje se nalazi preko 2000 ha, i svake godine se proizvede oko 4000 t balirane sojine slame. Planirano je da se sojina slama koristi za grejanje plastenika, ukupne površine 5 ha. Zbog toga, u Laboratoriji za termotehniku i energetiku Instituta za nuklearne nauke 'Vinča' je učinjen napor da se razvije tehnologija za korišćenje krupne balirane biomase za proizvodnju energije. U prvoj fazi, razvijeno je demonstraciono eksperimentalno postrojenje - ložište za sagorevanje bala sojine slame. Ložište je izgrađeno i termotehnički ispitano, da bi se utvrdio kvalitet sagorevanja. Kako su rezultati ispitivanja bili veoma zadovoljavajući, u drugoj fazi razvoja, vrelovodni kotao sličnih karakteristika (koji sagoreva bale sojine slame dimenzija 0,7 x 1,2 x 2,7 m) je projektovan, i trenutno je u fazi izgradnje.In one of the largest agricultural companies in Serbia with over 2000 ha of soya plantations there is 4000 t/year of baled soya straw production. Soya straw biomass is planned to be used as renewable energy source for heating the greenhouses, with 5 ha in area. Therefore, efforts have been made to develop a technology for utilizing large bales of soya straw for energy production. In the first phase, a demo energy production facility - furnace was developed and built. The facility was tested in order to examine the quality of combustion of large soya straw bales. Since the experimental results obtained by testing of this facility proved to be very satisfactory in the second phase of development, the hot water boiler of similar characteristics (burning soya straw bales, with dimensions 0.7 x 1.2 x 2.7 m) was designed

An oil pipeline design problem

Copyright @ 2003 INFORMSWe consider a given set of offshore platforms and onshore wells producing known (or estimated) amounts of oil to be connected to a port. Connections may take place directly between platforms, well sites, and the port, or may go through connection points at given locations. The configuration of the network and sizes of pipes used must be chosen to minimize construction costs. This problem is expressed as a mixed-integer program, and solved both heuristically by Tabu Search and Variable Neighborhood Search methods and exactly by a branch-and-bound method. Two new types of valid inequalities are introduced. Tests are made with data from the South Gabon oil field and randomly generated problems.The work of the first author was supported by NSERC grant #OGP205041. The work of the second author was supported by FCAR (Fonds pour la Formation des Chercheurs et l’Aide à la Recherche) grant #95-ER-1048, and NSERC grant #GP0105574

Pooling problem: Alternate formulations and solution methods

Copyright @ 2004 INFORMSThe pooling problem, which is fundamental to the petroleum industry, describes a situation in which products possessing different attribute qualities are mixed in a series of pools in such a way that the attribute qualities of the blended products of the end pools must satisfy given requirements. It is well known that the pooling problem can be modeled through bilinear and nonconvex quadratic programming. In this paper, we investigate how best to apply a new branch-and-cut quadratic programming algorithm to solve the pooling problem. To this effect, we consider two standard models: One is based primarily on flow variables, and the other relies on the proportion. of flows entering pools. A hybrid of these two models is proposed for general pooling problems. Comparison of the computational properties of flow and proportion models is made on several problem instances taken from the literature. Moreover, a simple alternating procedure and a variable neighborhood search heuristic are developed to solve large instances and compared with the well-known method of successive linear programming. Solution of difficult test problems from the literature is substantially accelerated, and larger ones are solved exactly or approximately.This project was funded by Ultramar Canada and Luc Massé. The work of C. Audet was supported by NSERC (Natural Sciences and Engineering Research Council) fellowship PDF-207432-1998 and by CRPC (Center for Research on Parallel Computation). The work of J. Brimberg was supported by NSERC grant #OGP205041. The work of P. Hansen was supported by FCAR(Fonds pour la Formation des Chercheurs et l’Aide à la Recherche) grant #95ER1048, and NSERC grant #GP0105574

The affective priming of aesthetic estimates

Резиме: У три од четири експеримента, чији су резултати приказани у овом раду, је експериментална парадигма репетиционог афективног примовања била комбинована са парадигмом коју су увели Мишкин и Форгајс (Mishkin & Forgays, 1952), а која омогућава упућивање иконичког материјала на превасходну обраду у леву или десну хемисферу. Ово је учињено како би се испитало да ли се ефекти афективног примовања мењају уколико се позитивно и негативно афективно валентни примови излажу у десно или лево визуелно поље, чиме се осигурава да првенствено буду обрађени у левој односно десној хемисфери. Стимулуси су били приказивани на компјутерском екрану величине 21.5'', а удаљеност испитаника од монитора износила је 80 cm. Испитанику је наложено да гледа у фиксациону тачку која је била у центру екрана, и испитаници су били снимљени камером како би се из анализе искључили они који нису поштовали инструкцију. Време експозиције примова у свим експериментима је било 16.67ms, а мета 1500ms, осим првог које је било 500ms и последњег излагања које је трaјало 15000ms. Свака од пет мета у свим експерименталним ситуацијама је била примована са пет различитих примова, а за време последњег излагања мете, које је највљивао звучни сигнал, испитаник је процењивао колико му се мета допада на седмостепеној скали. Примови су били преузети из IAPS-a, позитивно и негативно валентни примови су били уједначени према нивоу побуђености (ароусал). Мете су биле слике фрактала које су предходно уједначене према проценама које им испитаници дају у погледу њихове лепоте. У току експеримента је регистрована вредност електродермалне активности (ЕДА) испитаника помоћу полиграфа, с тим да је на крају употребом одговарајуће софтверске функције израчунавана просечна вредност ЕДА за сваку експерименталну ситуацију. У свим експериментима број испитаника је био 32, са подједнаком заступљеношћу особа оба пола.Abstract This paper describes the results from four experiments. In the three of which the experimental paradigm of repetitive affective priming was combined with the paradigm introduced by Mishkin and Forgays (Mishkin & Forgays, 1952), and which enables sending of the iconic material to the primary processing in the left and right hemisphere. This was done in order to examine whether the effects of affective priming change if the positive and negative affective valence primes аrе exposed to the right or left visual field, ensuring that they are initially processed in the left or right hemisphere respectively. A participant sat 80 cm away from the 21.5" computer screen on which stimuli were presented. Respondents were asked to look at the fixation point, which was at the center of the screen, and they were filmed with a camera in order to exclude from the analysis those who did not abide the instruction. The exposure time in all experiments was 16.67 ms for the primes, and 1500 ms for the targets, except the first that lasted 500ms and the last target exposure that lasted 15000ms. Each of the five targets in all experimental situations was primed with five different primes, and during the last exposure of the target, which was announced by a beep, a respondent assessed his aesthetic preference of the target on the seven - point scale. The primes were taken from the IAPS, the positive and negative valence primes were equalized according to the level of arousal. The targets were pictures of fractals equalized according to the estimates of their beauty given by respondents in the previous study. During the experiment, the value of a respondent’s EDA (Electro Dermal Activity) was registered with polygraph, but in the end the average EDA value for each experimental situation was calculated with an appropriate software function. The number of respondents in all experiments was 32, with equal representation of both genders

Mejora de la exploración y la explotación de las heurísticas constructivas para el MLSTP

En este trabajo se proponen dos mejoras para aumentar la explotación y la exploración del clásico algoritmo constructivo MVCA para el problema del árbol generador etiquetado mínimo (Minimum Labelling Spanning Tree Problem; MLSTP). Se describe la aplicación de contrastes de hipótesis no paramétricos para contrastar tales mejoras. En el MLSTP se parte de un grafo conexo con aristas de distinto tipo y se trata de encontrar el árbol generador con las aristas más parecidas posible. Cada tipo de arista viene identificado por un color o etiqueta y el árbol generador óptimo es aquel que usa el menor número de colores. Los tiempos y soluciones obtenidas son comparables a los mejores resultados aparecidos en la literatura para el MLSTP