http://hdl.handle.net/2117/3626 2013-05-20T00:48:01Z http://hdl.handle.net/2117/17129 Title: Multiperiod location-routing with decoupled time scales Authors: Albareda Sambola, Maria; Fernández Aréizaga, Elena; Nickel, Stefan Abstract: This paper focuses on a multiperiod discrete facility location problem where transportation costs are considered together with location costs to design the operating facility pattern along a time horizon. The problem captures the difference in the scope of the location and routing decisions by considering different scales within the time horizon. Thus, solutions to this problem reflect the stability of locational decisions along time. The high complexity of this problem makes it impossible to be solved in practice with commercial software. For this reason, an approximation based on replacing vehicle routes by spanning trees is proposed, and its capability for providing good quality solutions is assessed in a series of computational experiments. 2012-12-13T16:16:36Z http://hdl.handle.net/2117/16396 Title: General network design : a unified view of combined location and network design problems Authors: Contreras Aguilar, Iván; Fernández Aréizaga, Elena Abstract: This paper presents a unified framework for the general network design problem which encompasses several classical problems involving combined location and network design decisions. In some of these problems the service demand relates users and facilities, whereas in other cases the service demand relates pairs of users between them, and facilities are used to consolidate and re-route flows between users. Problems of this type arise in the design of transportation and telecommunication systems and include well-known problems such as location-network design problems, hub location problems, extensive facility location problems, tree-star location problems and cycle-star location problems, among others. Relevant modeling aspects, alternative formulations and possible algorithmic strategies are presented and analyzed. 2012-08-28T11:02:51Z http://hdl.handle.net/2117/16394 Title: Minimizing the maximum travel time in a combined model of facility location and network design Authors: Contreras Aguilar, Iván; Fernández Aréizaga, Elena; Reineltc, Gerhard Abstract: This paper presents a combined Facility Location/Network Design Problem which simultaneously considers the location of facilities and the design of its underlying network so as to minimize the maximum customer-facility travel time. The model generalizes the classical p-center problem and has various applications in regional planning, distribution, telecommunications, emergency systems, and other areas. Two mixed integer programming formulations are presented and compared. Several valid inequalities are derived for the most promising of these formulations to strengthen its LP relaxation bound and to reduce the enumeration tree. Numerical results of a series of computational experiments for instances with up to 100 nodes and 500 candidate links are reported. 2012-08-28T10:21:34Z http://hdl.handle.net/2117/15894 Title: Modeling and solving a variant of the mixed-model sequencing problem with work overload minimisation and regularity constraints. An application in Nissan’s Barcelona Plant Authors: Bautista Valhondo, Joaquín; Cano Pérez, Alberto; Alfaro Pozo, Rocío Abstract: In this paper, we present an extension to the mixed-model sequencing problem with work overload minimisation (MMSP-W) for production lines with serial workstations and parallel homogeneous processors. The extension is intended to meet the industrial need to sequence various products so that the work required and completed at the workstations over time is as constant as possible. Several approaches are proposed to formulate the problem, giving rise to different models. Four models are selected, and their performances are compared after running the Gurobi solver, using instances from the literature and a case study of the Nissan powertrain plant in Barcelona. 2012-05-18T11:02:07Z http://hdl.handle.net/2117/15277 Title: A scatter search based hyper-heuristic for sequencing a mixed-model assembly line, Journal of Heuristics Authors: Cano-Belman, J; Ríos-Mercado, Roger Z.; Bautista Valhondo, Joaquín Abstract: We address a mixed-model assembly-line sequencing problem with work overload minimization criteria.We consider time windows in work stations of the assembly line (closed stations) and different versions of a product to be assembled in the line, which require different processing time according to the work required in each work station. In a paced assembly line, products are feeded in the line at a predetermined constant rate (cycle time). Then, if many products with processing time greater than cycle time are feeded consecutively, work overload can be produced when the worker has insufficient time to finish his/her job. We propose a scatter search based hyper-heuristic for this NP-hard problem. In the low-level, the procedure makes use of priority rules through a constructive procedure. Computational experiments over a wide range of instances from the literature show the effectiveness of the proposed hyper-heuristics when compared to existing heuristics. The relevance of the priority rules was evaluated as well. 2012-02-21T11:50:57Z http://hdl.handle.net/2117/14734 Title: Multiobjective memetic algorithms for time and space assembly line balancing Authors: Chica, Manuel; Cordon, Oscar; Damas, Sergio; Bautista Valhondo, Joaquín Abstract: This paper presents three proposals of multiobjective memetic algorithms to solve a more realistic extension of a classical industrial problem: time and space assembly line balancing. These three proposals are, respectively, based on evolutionary computation, ant colony optimisation, and greedy randomised search procedure. Different variants of these memetic algorithms have been developed and compared in order to determine the most suitable intensification–diversification trade-off for the memetic search process. Once a preliminary study on nine well-known problem instances is accomplished with a very good performance, the proposed memetic algorithms are applied considering real-world data from a Nissan plant in Barcelona (Spain). Outstanding approximations to the pseudo-optimal non-dominated solution set were achieved for this industrial case study. 2012-01-23T11:58:29Z http://hdl.handle.net/2117/14056 Title: Solving the Fm|block|Cmax problem using bounded dynamic programming Authors: Bautista Valhondo, Joaquín; Cano Pérez, Alberto; Companys Pascual, Ramón; Ribas Vila, Immaculada Abstract: We present some results attained with two variants of Bounded Dynamic Programming algorithm to solve the Fm|block|Cmax problem using as an experimental data the well-known Taillard instances. We have improved the best known solutions for 17 of Taillard's instances, including the 10 instances from set 12. 2011-11-24T11:23:49Z http://hdl.handle.net/2117/14000 Title: A dynamic programming based heuristic for the assembly line balancing problem Authors: Bautista Valhondo, Joaquín; Pereira Gude, Jordi Abstract: The simple assembly line balancing problem is the simplification of a real problem associated to the assignment of the elementary tasks required for assembly of a product in an assembly line. This problem has been extensively studied in the literature for more than half a century. The present work proposes a new procedure to solve the problem we call Bounded Dynamic Programming. This use of the term Bounded is associated not only with the use of bounds to reduce the state space but also to the reduction of such space based on heuristics. This procedure is capable of obtaining an optimal solution rate of 267 out of 269 instances, which have been used in previous works, thus obtaining the best-known performance for the problem. These results are an improvement from any previous procedure found in the literature even when using smaller computing times. 2011-11-22T09:06:58Z http://hdl.handle.net/2117/13482 Title: The Windy clustered prize-collecting arc-routing problem Authors: Corberan, Angel; Fernández Aréizaga, Elena; Franquesa Niubó, Carles; Sanchis, Jose Maria Abstract: This paper introduces the windy clustered prize-collecting arc-routing problem. It is an arc-routing problem where each demand edge is associated with a profit that is collected once if the edge is serviced, independent of the number of times the edge is traversed. It is further required that if a demand edge is serviced, then all the demand edges of its component are also serviced. A mathematical programming formulation is given and some polyhedral results including several facet-defining and valid inequalities are presented. The separation problem for the different families of inequalities is studied. Numerical results from computational experiments are analyzed. 2011-10-11T11:15:19Z http://hdl.handle.net/2117/12653 Title: ‘Low-cost educational videos’ for engineering students: a new concept based on video streaming and YouTube channels Authors: Garriga Garzón, Federico; Rajadell Carreras, Manuel; García-Almiñana, Daniel; Suñé Torrents, Albert; Fernández Alarcón, Vicenç; Simó Guzmán, Pep; Algaba Joaquín, Inés María; Albareda Sambola, Maria; Salán Ballesteros, Maria Núria; Amante García, Beatriz; Enache, Cristina Mihaela; Bravo Ibarra, Edna Rocío Abstract: There are many papers that present the problems of educational videos: need of a high number of resources to create them, excess of information in the majority of videos, gaps of information between videos and the rest of materials of the courses, etc. This paper introduces the concept ‘low-cost educational video’, which attempts to solve to a large extent the problems that have been identified in the educational videos. To this end, an empirical research is conducted with 487 students and various lecturers and professors in three undergraduate degrees: Mechanical Engineering, Industrial Engineering and Management (in face-to-face as well as semi-distance modalities), and Aeronautical Engineering at the Universitat Politècnica de Catalunya (Spain). In order to achieve this goal, we introduce the process and the required resources for the creation and the diffusion of these low-cost educational videos. The results are analysed taking a literature-based questionnaire as a starting point and within the principles of good practice in higher education framework. The main research findings revealed an improved student motivation and an increase of the perceived efficiency in the learning and teaching processes, without substantially raising costs. 2011-05-25T16:32:15Z http://hdl.handle.net/2117/11202 Title: Travel time forecasting and dynamic origin-destination estimation for freeways based on bluetooth traffic monitoring Authors: Barceló Bugeda, Jaime; Montero Mercadé, Lídia; Marquès, Laura; Carmona, Carlos Abstract: From the point of view of the information supplied by an ATIS to the motorists entering a freeway of one of the most relevant is the Forecasted Travel Time, that is the expected travel time that they will experience when traverse a freeway segment. From the point of view of ATMS the dynamic estimates of time dependencies in OD matrices is a major input to dynamic traffic models used for estimating the current traffic state and forecasting its short term evolution. Travel Time Forecasting and Dynamic OD Estimation are two of the key components of ATIS/ATMS and the quality of the results that they could provide depend not only on the quality of the models but also on the accuracy and reliability of the measurements of traffic variables supplied by the detection technology. The quality and reliability of the measurements produced by traditional technologies, as inductive loop detectors, is not usually the required by real-time applications, therefore one wonders what could be expected from the new ICT technologies as for example Automatic Vehicle Location, License Plate Recognition, detection of mobile devices and so on. The main objectives of this paper are: to explore the quality of the data produced by the Bluetooth detection of mobile devices equipping vehicles for Travel Time Forecasting and its use to estimate time dependent OD matrices. Ad hoc procedures based on Kalman Filtering have been designed and implemented successfully and the numerical results of the computational experiments are presented and discussed. 2011-01-25T15:15:22Z http://hdl.handle.net/2117/10873 Title: An integrated GPS/PDA/GIS telegeoprocessing system for traffic & environment Authors: Ramos, Ana Luísa; Vasconcelos Ferreira, José; Barceló Bugeda, Jaime Abstract: The development of sustainable urban transport networks is a present priority for world leaders, national governors and local authorities. The challenge is to increase mobility reducing the adverse impacts of transport. The potential of Intelligent Transportation Systems (ITS) to provide solutions for the 21st century sustainable urban transport system has already been demonstrated in several piecewise applications. An integrated framework that addresses the needs of municipal authorities, that integrates the data spread through different sources, that supports the intelligent traffic & environment operations, and that provides information to the citizens steering their involvement and commitment is of critical importance and can be the enabler towards the creation of more efficient, safety, and environmental-friendly transport networks that promote the citizens’ quality of life. This work describes an integrated GPS (Global Positioning System) / PDA (Personal Digital Assistant) / GIS (Geographical Information System) system which is part of the mentioned framework. The system includes prototypes for mobile urban traffic data acquisition, with a GPS -equipped vehicle, a PDA application and wireless communications, and for a geodatabase with a related Web application for urban traffic & environment. Their integrated operation is exemplified for a real urban transport system. 2011-01-03T09:05:33Z http://hdl.handle.net/2117/10438 Title: Including different kinds of preferences in a multi-objective ant algorithm for time and space assembly line balancing on different Nissan scenarios Authors: Chica, Manuel; Cordon, Oscar; Damas, Sergio; Bautista Valhondo, Joaquín Abstract: Most of the decision support systems for balancing industrial assembly lines are designed to report a huge number of possible line configurations, according to several criteria. In this contribution, we tackle a more realistic variant of the classical assembly line problem formulation, time and space assembly line balancing. Our goal is to study the influence of incorporating user preferences based on Nissan automotive domain knowledge to guide the multi-objective search process with two different aims. First, to reduce the number of equally preferred assembly line configurations (i.e., solutions in the decision space) according to Nissan plants requirements. Second, to only provide the plant managers with configurations of their contextual interest in the objective space (i.e., solutions within their preferred Pareto front region) based on real-world economical variables. We face the said problem with a multi-objective ant colony optimisation algorithm. Using the real data of the Nissan Pathfinder engine, a solid empirical study is carried out to obtain the most useful solutions for the decision makers in six different Nissan scenarios around the world. 2010-11-29T10:39:59Z http://hdl.handle.net/2117/10424 Title: Multiobjective constructive heuristics for the 1/3 variant of the time and space assembly line balancing problem: ACO and random greedy search Authors: Chica, Manuel; Cordon, Oscar; Damas, Sergio; Bautista Valhondo, Joaquín 2010-11-26T15:08:12Z http://hdl.handle.net/2117/10177 Title: The multi-period incremental service facility location problem Authors: Albareda Sambola, Maria; Fernández Aréizaga, Elena; Hinojosa, Yolanda; Puerto, Justo Abstract: In this paper we introduce the multi-period incremental service facility location problem where the goal is to set a number of new facilities over a finite time horizon so as to cover dynamically the demand of a given set of customers. We prove that the coefficient matrix of the allocation subproblem that results when fixing the set of facilities to open is totally unimodular. This allows to solve efficiently the Lagrangean problem that relaxes constraints requiring customers to be assigned to open facilities. We propose a solution approach that provides both lower and upper bounds bt combining subgradient optimization to solve a Lagrangean dual with an ad hoc heuristic that uses information from the Lagrangean subproblem to generate feasible solutions. Numerical results obtained in the computational experiments show that the obtained solutions are very good. In general, we get very small percent gaps between upper and lower bounds with little computation effort. 2010-11-08T14:51:37Z