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Author Alvarez-Miranda, E.; Pereira, J. doi  openurl
  Title On the complexity of assembly line balancing problems Type
  Year 2019 Publication Computers & Operations Research Abbreviated Journal Comput. Oper. Res.  
  Volume 108 Issue Pages 182-186  
  Keywords Line balancing; Complexity; Bin packing  
  Abstract (up) Assembly line balancing is a family of combinatorial optimization problems that has been widely studied in the literature due to its simplicity and industrial applicability. Most line balancing problems are NP-hard as they subsume the bin packing problem as a special case. Nevertheless, it is common in the line balancing literature to cite [A. Gutjahr and G. Nemhauser, An algorithm for the line balancing problem, Management Science 11 (1964) 308-315] in order to assess the computational complexity of the problem. Such an assessment is not correct since the work of Gutjahr and Nemhauser predates the concept of NP-hardness. This work points at over 50 publications since 1995 with the aforesaid error. (C) 2019 Elsevier Ltd. All rights reserved.  
  Address [Alvarez-Miranda, Eduardo] Univ Talca, Dept Ind Engn, Curico, Chile, Email: jorge.pereira@uai.cl  
  Corporate Author Thesis  
  Publisher Pergamon-Elsevier Science Ltd Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0305-0548 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000471733300014 Approved  
  Call Number UAI @ eduardo.moreno @ Serial 1015  
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Author Pereira, J.; Ritt, M.; Vasquez, O.C. pdf  doi
openurl 
  Title A memetic algorithm for the cost-oriented robotic assembly line balancing problem Type
  Year 2018 Publication Computers & Operations Research Abbreviated Journal Comput. Oper. Res.  
  Volume 99 Issue Pages 249-261  
  Keywords Line balancing; Cost-oriented line balancing; Robotic assembly line; Hybrid algorithms  
  Abstract (up) In order to minimize costs, manufacturing companies have been relying on assembly lines for the mass production of commodity goods. Among other issues, the successful operation of an assembly line requires balancing work among the stations of the line in order to maximize its efficiency, a problem known in the literature as the assembly line balancing problem, ALBP. In this work, we consider an ALBP in which task assignment and equipment decisions are jointly considered, a problem that has been denoted as the robotic ALBP. Moreover, we focus on the case in which equipment has different costs, leading to a cost-oriented formulation. In order to solve the problem, which we denote as the cost-oriented robotic assembly line balancing problem, cRALBP, a hybrid metaheuristic is proposed. The metaheuristic embeds results obtained for two special cases of the problem within a genetic algorithm in order to obtain a memetic algorithm, applicable to the general problem. An extensive computational experiment shows the advantages of the hybrid approach and how each of the components of the algorithm contributes to the overall ability of the method to obtain good solutions. (C) 2018 Elsevier Ltd. All rights reserved.  
  Address [Pereira, Jordi] Univ Adolfo Ibanez, Fac Engn & Sci, Av Padre Hurtado 750,Off C216, Vina Del Mar, Chile, Email: jorge.pereira@uai.cl;  
  Corporate Author Thesis  
  Publisher Pergamon-Elsevier Science Ltd Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0305-0548 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000442059400019 Approved  
  Call Number UAI @ eduardo.moreno @ Serial 907  
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Author Pereira, J. pdf  doi
openurl 
  Title The robust (minmax regret) assembly line worker assignment and balancing problem Type
  Year 2018 Publication Computers & Operations Research Abbreviated Journal Comput. Oper. Res.  
  Volume 93 Issue Pages 27-40  
  Keywords Production; Line balancing; Robust optimization; Minmax regret  
  Abstract (up) Line balancing aims to assign the assembly tasks to the stations that compose the assembly line. A recent body of literature has been devoted to heterogeneity in the assembly process introduced by different workers. In such an environment, task times depend on the worker performing the operation and the problem aims at assigning tasks and workers to stations in order to maximize the throughput of the line. In this work, we consider an interval data version of the assembly line worker assignment and balancing problem (ALWABP) in which it is assumed that lower and upper bounds for the task times are known, and the objective is to find an assignment of tasks and workers to the workstations such that the absolute maximum regret among all of the possible scenarios is minimized. The relationship with other interval data minmax regret (IDMR) problems is investigated, the inapplicability of previous approximation methods is studied, regret evaluation is considered, and exact and heuristic solution methods are proposed and analyzed. The results of the proposed methods are compared in a computational experiment, showing the applicability of the method and the theoretical results to solve the problem under study. Additionally, these results are not only applicable to the problem in hand, but also to a more general class of problems. (C) 2018 Elsevier Ltd. All rights reserved.  
  Address [Pereira, Jordi] Univ Adolfo Ibanez, Dept Sci & Engn, Av Padre Hurtado 750,Off C216, Vina Del Mar, Chile, Email: jorge.pereira@uai.cl  
  Corporate Author Thesis  
  Publisher Pergamon-Elsevier Science Ltd Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0305-0548 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000427339800003 Approved  
  Call Number UAI @ eduardo.moreno @ Serial 838  
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Author Rezakhah, M.; Moreno, E.; Newman, A. pdf  doi
openurl 
  Title Practical performance of an open pit mine scheduling model considering blending and stockpiling Type
  Year 2020 Publication Computers & Operations Research Abbreviated Journal Comput. Oper. Res.  
  Volume 115 Issue Pages 12 pp  
  Keywords Stockpiling; Linear and integer programming; Mine planning; Open pit mining; Software  
  Abstract (up) Open pit mine production scheduling (OPMPS) is a decision problem which seeks to maximize net present value (NPV) by determining the extraction time of each block of ore and/or waste in a deposit and the destination to which this block is sent, e.g., a processing plant or waste dump. Spatial precedence constraints are imposed, as are resource capacities. Stockpiles can be used to maintain low-grade ore for future processing, to store extracted material until processing capacity is available, and/or to blend material based on single or multiple block characteristics (i.e., metal grade and/or contaminant). We adapt an existing integer-linear program to an operational polymetallic (gold and copper) open pit mine, in which the stockpile is used to blend materials based on multiple block characteristics, and call it ((P) over cap (la)). We observe that the linear programming relaxation of our objective function is unimodal for different grade combinations (metals and contaminants) in the stockpile, which allows us to search systematically for an optimal grade combination while exploiting the linear structure of our optimization model. We compare the schedule of ((P) over cap (la)) with that produced by (P-ns) which does not consider stockpiling, and with ((P) over tilde (la)), which controls only the metal content in the stockpile and ignores the contaminant level at the mill and in the stockpile. Our proposed solution technique provides schedules for large instances in a few seconds up to a few minutes with significantly different stockpiling and material flow strategies depending on the model. We show that our model improves the NPV of the project while satisfying operational constraints. (C) 2019 Elsevier Ltd. All rights reserved.  
  Address [Rezakhah, Mojtaba] Tarbiat Modares Univ, Engn Dept, POB 14115411, Tehran, Iran, Email: m.rezakhah@modares.ac.ir;  
  Corporate Author Thesis  
  Publisher Pergamon-Elsevier Science Ltd Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0305-0548 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000514218600009 Approved  
  Call Number UAI @ eduardo.moreno @ Serial 1161  
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Author Pereira, J. pdf  doi
openurl 
  Title The robust (minmax regret) single machine scheduling with interval processing times and total weighted completion time objective Type
  Year 2016 Publication Computers & Operations Research Abbreviated Journal Comput. Oper. Res.  
  Volume 66 Issue Pages 141-152  
  Keywords Scheduling; Single machine; Uncertainty; Robust optimization; Branch-and-bound  
  Abstract (up) Single machine scheduling is a classical optimization problem that depicts multiple real life systems in which a single resource (the machine) represents the whole system or the bottleneck operation of the system. In this paper we consider the problem under a weighted completion time performance metric in which the processing time of the tasks to perform (the jobs) are uncertain, but can only take values from closed intervals. The objective is then to find a solution that minimizes the maximum absolute regret for any possible realization of the processing times. We present an exact branch-and-bound method to solve the problem, and conduct a computational experiment to ascertain the possibilities and limitations of the proposed method. The results show that the algorithm is able to optimally solve instances of moderate size (25-40 jobs depending on the characteristics of the instance). (c) 2015 Elsevier Ltd. All rights reserved.  
  Address [Pereira, Jordi] Univ Adolfo Ibanez, Fac Sci & Engn, Vina Del Mar, Chile, Email: jorge.pereira@uai.cl  
  Corporate Author Thesis  
  Publisher Pergamon-Elsevier Science Ltd Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0305-0548 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000366779900013 Approved  
  Call Number UAI @ eduardo.moreno @ Serial 558  
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Author Alvarez-Miranda, E.; Pereira, J. pdf  doi
openurl 
  Title Designing and constructing networks under uncertainty in the construction stage: Definition and exact algorithmic approach Type
  Year 2017 Publication Computers & Operations Research Abbreviated Journal Comput. Oper. Res.  
  Volume 81 Issue Pages 178-191  
  Keywords Network design; Network construction; Two-stage robust optimization; Exact algorithms  
  Abstract (up) The present work proposes a novel Network Optimization problem whose core is to combine both network design and network construction scheduling under uncertainty into a single two-stage robust optimization model. The first-stage decisions correspond to those of a classical network design problem, while the second-stage decisions correspond to those of a network construction scheduling problem (NCS) under uncertainty. The resulting problem, which we will refer to as the Two-Stage Robust Network Design and Construction Problem (2SRNDC), aims at providing a modeling framework in which the design decision not only depends on the design costs (e.g., distances) but also on the corresponding construction plan (e.g., time to provide service to costumers). We provide motivations, mixed integer programming formulations, and an exact algorithm for the 2SRNDC. Experimental results on a large set of instances show the effectiveness of the model in providing robust solutions, and the capability of the proposed algorithm to provide good solutions in reasonable running times. (C) 2017 Elsevier Ltd. All rights reserved.  
  Address [Alvarez-Miranda, Eduardo] Univ Talca, Dept Ind Engn, Curico, Chile, Email: ealvarez@utalca.cl  
  Corporate Author Thesis  
  Publisher Pergamon-Elsevier Science Ltd Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0305-0548 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000394079400015 Approved  
  Call Number UAI @ eduardo.moreno @ Serial 706  
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Author Wanke, P.; Ewbank, H.; Leiva, V.; Rojas, F. pdf  doi
openurl 
  Title Inventory management for new products with triangularly distributed demand and lead-time Type
  Year 2016 Publication Computers & Operations Research Abbreviated Journal Comput. Oper. Res.  
  Volume 69 Issue Pages 97-108  
  Keywords Approximation of functions; Bisection method; Kernel method; Kullback-Leibler divergence; Monte Carlo method; (Q, r) model; R software; Statistical distributions  
  Abstract (up) This paper proposes a computational methodology to deal with the inventory management of new products by using the triangular distribution for both demand per unit time and lead-time. The distribution for demand during lead-time (or lead-time demand) corresponds to the sum of demands per unit time, which is difficult to obtain. We consider the triangular distribution because it is useful when a distribution is unknown due to data unavailability or problems to collect them. We provide an approach to estimate the probability density function of the unknown lead-time demand distribution and use it to establish the suitable inventory model for new products by optimizing the associated costs. We evaluate the performance of the proposed methodology with simulated and real-world demand data. This methodology may be a decision support tool for managers dealing with the measurement of demand uncertainty in new products. (C) 2015 Elsevier Ltd. All rights reserved.  
  Address [Wanke, Peter; Ewbank, Henrique] Univ Fed Rio de Janeiro, COPPEAD Grad Sch Business, BR-21941 Rio De Janeiro, Brazil, Email: victorleivasanchez@gmail.com  
  Corporate Author Thesis  
  Publisher Pergamon-Elsevier Science Ltd Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0305-0548 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000370908300009 Approved  
  Call Number UAI @ eduardo.moreno @ Serial 586  
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