An exact algorithm for the mixed-model level scheduling problem

The Monden Problem, also known as the Output Rate Variation Problem, is one of the original formulations for mixed-model assembly line-level scheduling problems in a just-in-time system. In this paper, we develop a new branch-and-bound procedure for the problem that uses several new and previously proposed lower and upper bounds. The algorithm also includes several dominance rules that leverage the symmetry in the problem as well as a new labelling procedure that avoids repeated exploration of previously examined partial solutions. The branching strategy exploits the capabilities of current multiprocessor computers by exploring the search tree in a parallel fashion. The algorithm has been tested on several sets of instances from the literature and is able to optimally solve problems that are double the size of those addressed by other procedures previously reported in the literature.Preprin

Allocating refuse bins for selective waste collection, a case study

One of the problems found in Municipal Waste Management is the allocation of refuse bins to different collection areas where waste (glass, paper, plastic, organic material) is left by the citizens. The relationship between the studied problem and the apportionment of seats in a parliament is tackled and it is used to develop an ant algorithm approach to solve the problem. The algorithm is then compared to an exact procedure for a real life instance found in the metropolitan area of Barcelona.Postprint (published version

Equilibrado de la línea de montaje del motor del modelo Pathfinder en la planta de NISSAN de Barcelona

Postprint (published version

Diseño de rutas de recogida de residuos sólidos urbanos en el área metropolitana de Barcelona

Los problemas aso ciados a la recogida de residuos sólidos urbanos son muy variados. En este traba jo se presenta el problema de diseño de itinerarios de recogida y se muestran los resultados ofrecidos p or un pro cedimiento basado en colonias de hormigas a la recogida en un núcleo urbano del Área Metrop olitana de Barcelona.Postprint (published version

Solving an Urban Waste Collection Problem Using Ants Heuristics

This paper describes the methodology that we have applied for the solution of an urban waste collection problem in the municipality of Sant Boi de Llobregat, within the metropolitan area of Barcelona (Spain). The basic nature of the considered problem is that of a capacitated arc routing problem, although it has several specific characteristics, mainly derived from trafic regulations. We present the model that we have built for the problem, which results after an appropriate transformation of the problem into a node routing one. We also present the ant colonies heuristics that we have used to obtain the solutions to the problem. These combine constructive methods, based on nearest neighbor and on nearest insertion, with a local search that explores various neighborhoods. The application of the proposed methods gives results that improve considerably the ones that were previously used in the municipality.Peer Reviewe

Comparativa de las fases constructivas de las metaheurísticas ACO y GRASP para el problema CARP

En los años 80 y 90 han aparecido diversas metaheurís ticas para la resolución de problemas de optimización. Entre ellas, la metaheurística GRASP, Greedy Randomized Adaptive Search Procedure, y los algoritmos de hormigas, ACO An t Colony Optimization, comparten un esquema similar dividido en una fase constructiva que pe rmite la generación de soluciones distintas mediante la incorporación de un factor de azar, se guidas por una fase de mejora de éstas. En el presente trabajo se comparan los resultados ofr ecidos por las fases constructivas de ambas metaheurísticas para un problema en concreto, el diseño de itinerar ios con servicio asociado a los arcos y restricciones de capacidad de los vehículosPostprint (published version

A new model for supply chain network design with integrated assembly line balancing decisions

Supply chain network design aims at the integration of the different actors of a supply chain within a single framework in order to optimise the total profit of the system. In this paper, we consider the integration of line balancing issues within the tactical decisions of the supply chain, and we offer a novel model and a solution approach for the problem. The new approach decomposes the problem into multiple line balancing problems and a mixed integer linear model, which is easier to solve than the previously available non-linear mixed integer formulation. The results show that the new method is able to solve previously studied models within a fraction of the reported running times, and also allows us to solve larger instances than those reported in earlier works. Finally, we also provide some analysis on the influence of the cost structure, the demand and the structure of the assembly process on the final configuration of the assemblies and the distribution network.Postprint (author's final draft

Models and procedures for electric energy distribution planning. A review

Distribution system planning is a key component to accomplish the service in a fast growing demand market, both from a technical point of view and from the economic costs management. In the near future, electric companies will need faster and cheaper planning tools to evaluate different scenarios and their consequences for the rest of the system and provide their clients whit safe reliable and economic energy. The objective of this paper is to review different articles about this subject trying to continue the previous work from Gonen and Ramírez-Rosado in 1986 (Gönen,1986).Postprint (published version

Aplicación de la CLP al problema de secuencias regulares con restricciones en una cadena de montaje de automóviles

Líneas de producción, secuencias regulares, Justo a TiempoLas líneas de montaje de automóviles presentan problemas de diseño y programación cada vez más complejos generados por la diversificación del producto mediante opciones ofertadas sobre un modelo base. El problema de secuenciación de unidades mixtas en una única línea de producción con el objetivo de atenuar las variaciones de las tasas de consumo de recursos (componentes y cargas de trabajo) ha recibido atención creciente durante los últimos años. En el presente trabajo se presenta una visión de distintos enfoques recogidos en la literatura y se establece una generalización parcial de algunas variantes del problema mediante el CORV ( constrained output rate variation problem ) que parece adaptarse con mayor fidelidad que otros enfoques a la concepción de dichos problemas en la industria de automoción. Se resuelve el problema mediante Propagación Lógica de restricciones (CLP) y se comparan resultados con los ofrecidos por la Programación Dinámica Acotada (BDP)Postprint (published version

Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio