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A semi-continuous MIP model for the irregular strip packing problem

INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH 2016年第3期54卷 712-721页

作者： Leao, Aline A. S. Toledo, Franklina M. B. Oliveira, Jose Fernando Carravilla, Maria Antonia Univ Sao Paulo Inst Ciencias Matemat & Comp BR-13560 Sao Carlos Brazil Univ Porto INESC TEC Fac Engn Rua Campo Alegre 823 P-4100 Oporto Portugal

Solving nesting problems involves the waste minimisation in cutting processes, and therefore it is not only economically relevant for many industries but has also an important environmental impact, as the raw materials that are cut are usually a natural resource. However, very few exact approaches have been proposed in the literature for the nesting problem (also known as irregular packing problem), and the majority of the known approaches are heuristic algorithms, leading to suboptimal solutions. The few mathematical programming models known for this problem can be divided into discrete and continuous models, based on how the placement coordinates of the pieces to be cut are dealt with. In this paper, we propose an innovative semi-continuous mixed-integer programming model for two-dimensional cutting and packing problems with irregular shaped pieces. The model aims to exploit the advantages of the two previous classes of approaches and discretises the [GRAPHICS] -axis while keeping the [GRAPHICS] -coordinate continuous. The board can therefore be seen as a set of stripes. Computational results show that the model, when solved by a commercial solver, can deal with large problems and determine the optimal solution for smaller instances, but as it happens with discrete models, the optimal solution value depends on the discretisation step that is used.

关键词： mixed-integer programming irregular strip packing problem nesting irregular pieces cutting and packing

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A NEW MATHEMATICAL programming MODEL FOR LOAD PLANNING PROBLEMS IN INTERMODAL LOGISTICS NETWORKS

JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GA...

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JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY 2016年第2期31卷 383-394页

作者： Baykasoglu, Adil Subulan, Kemal Dokuz Eylul Univ Muhendislik Fak Enduuhendisligi Bolumu Izmir Turkey

Recently, there has been a growing attention to load planning problems in intermodal logistics networks by global logistics sector. However, most of the studies in the literature were concentrated on single mode problems from the perspectives of logistics companies/production firms. Since increasing importance of intermodal transportation, the problem need to be solved by handling various complex decisions simultaneously (i.e., transportation mode selection, load allocation, outsourcing and sizing of maritime and railway cruises), which makes the problem much more complex. In this study, a mixed-integer programming model is developed for a multi-objective, multi-mode and multi-period load planning problem from the perspective of freight forwarders. In the proposed model, both import/export transport demands of the customers are considered. In addition to minimize overall transport costs, it is also aimed to minimize total transit time and environmental impact resulted from CO2 emissions. In order to handle these conflicting objectives and to provide compromise solutions under uncertainty, a fuzzy goal programming approach is used. According to the computational results, effective/efficient load plans can be generated in terms of economic and environmental issues.

关键词： Intermodal transportation load planning mixed-integer programming fuzzy goal programming

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Optimizing Flow Thinning Protection in Multicommodity Networks with Variable Link Capacity

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OPERATIONS RESEARCH 2016年第2期64卷 273-289页

作者： Pioro, Michal Fouquet, Yoann Nace, Dritan Poss, Michael Warsaw Univ Technol Inst Telecommun PL-00665 Warsaw Poland Lund Univ Dept Elect & Informat Technol S-22100 Lund Sweden Univ Technol Compiegne Univ Paris 04 UMR CNRS Heudiasyc 7253 F-60203 Compiegne France Univ Montpellier UMR CNRS LIRMM 5506 161 Rue Ada F-34392 Montpellier 5 France

Flow thinning (FT) is a concept of a traffic routing and protection strategy applicable to communication networks with variable capacity of links. In such networks, the links do not attain their nominal (maximum) capacity simultaneously, so in a typical network state only some links are fully available whereas on each of the remaining links only a fraction of its maximum capacity is usable. Every end-to-end traffic demand is assigned a set of logical tunnels whose total capacity is dedicated to carry the demand's traffic. The nominal (i.e., maximum) capacity of the tunnels, supported by the nominal (maximum) link capacity, is subject to state-dependent thinning to account for variable capacity of the links fluctuating below the maximum. Accordingly, the capacity available on the tunnels is also fluctuating below their nominal levels and hence the instantaneous traffic sent between the demand's end nodes must accommodate to the current total capacity available on its dedicated tunnels. The related multi-commodity flow optimization problem is NP-hard and its noncompact linear programming formulation requires path generation. For that, we formulate an integer programming pricing problem, at the same time showing the cases when the pricing is polynomial. We also consider an important variant of FT, affine thinning, that may lead to practical FT implementations. We present a numerical study illustrating traffic efficiency of FT and computational efficiency of its optimization models. Our considerations are relevant, among others, for wireless mesh networks utilizing multiprotocol label switching tunnels.

关键词： survivable network design multiple partial link failures mixed-integer programming multicommodity flows path generation robust optimization

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Combining spatiotemporal corridor design for reindeer migration with harvest scheduling in Northern Sweden

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SCANDINAVIAN JOURNAL OF FOREST RESEARCH 2016年第7期31卷 655-663页

作者： St John, Rachel Ohman, Karin Toth, Sandor F. Sandstrom, Per Korosuo, Anu Eriksson, Ljusk Ola Univ Washington Ind & Syst Engn Seattle WA 98195 USA Swedish Univ Agr Sci Dept Forest Resource Management Umea Sweden Univ Washington Sch Environm & Forest Sci Seattle WA 98195 USA Int Inst Appl Syst Anal Ecosyst Serv & Management Program Laxenburg Austria

Reindeer husbandry and commercial forestry seek to co-exist in the forests of Northern Sweden. As interwoven as the two industries are, conflicts have arisen. Forest practices have reduced the distribution of lichen, the main winter diet for reindeer. Forest practices have also increased forest density, compromising the animals' ability to pass through forested areas on their migration routes. In an attempt to reduce impacts on reindeer husbandry, we present a spatially explicit harvest scheduling model that includes reindeer corridors with user-defined spatial characteristics. We illustrate the model in a case study and explore the relationship between timber revenues and the selection and maintenance of reindeer corridors. The corridors are not only to include sufficient lichen habitat, but they are also supposed to ensure access for reindeer by connecting lichen areas with linkages that allow unobstructed travel. Since harvest scheduling occurs over a planning horizon, the spatial configuration of corridors can change from one time period to the next in order to accommodate harvesting activities. Our results suggest that maintaining reindeer corridors in harvest scheduling can be done at minimal cost. Also, we conclude that including corridor constraints in the harvest scheduling model is critical to guarantee connectivity of reindeer pastures.

关键词： mixed-integer programming forest management wildlife conservation reindeer husbandry spatial optimization

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Annual block scheduling for family medicine residency programs with continuity clinic considerations

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IIE TRANSACTIONS 2016年第9期48卷 797-811页

作者： Bard, Jonathan F. Shu, Zhichao Morrice, Douglas J. Leykum, Luci K. Poursani, Ramin Univ Texas Austin Dept Mech Engn Operat Res & Ind Engn Austin TX 78712 USA Univ Texas Austin Dept Mech Engn Austin TX 78712 USA Univ Texas Austin McCombs Sch Business Operat Management Austin TX 78712 USA Univ Texas Austin McCombs Sch Business Univ Texas Supply Chain Management Ctr Excellence Austin TX 78712 USA Univ Texas Hlth Sci Ctr San Antonio Sch Med Med San Antonio TX 78229 USA Univ Texas Hlth Sci Ctr San Antonio Sch Med Dept Family & Community Med San Antonio TX 78229 USA

This article presents a new model for constructing annual block schedules for family medicine residents based on the rules and procedures followed by the Family Medicine Department at the University of Texas Health Science Center in San Antonio (UTHSC-SA). Such residency programs provide 3years of specialty training for recent medical school graduates. At the beginning of each academic year, each trainee is given an annual block schedule that indicates his or her monthly assignments. These assignments are called rotations and include a variety of experiences, such as pediatric ambulatory care, the emergency room, and inpatient surgery. An important requirement associated with a subset of the rotations is that the residents spend multiple half-day sessions a week in a primary care clinic treating patients from the community. This is a key consideration when constructing the annual block schedules. In particular, one of the primary goals of most residencies is to ensure that the number of residents in clinic each day is approximately the same, so that the number of patients that can be seen each day is also the same. Uniformity provides for a more efficient use of supervisory and staff *** difficulty in achieving this goal is that not all rotations allow for clinic duty and that the number of patients that can be seen by a resident each session depends on his or her year of training. When constructing annual block schedules, two high-level sets of variables are available to the program coordinator. The first is the assignment of residents to rotations for each of the 12 blocks, and the second is the (partial) ability to adjust the days on which a resident has clinic duty during each rotation. In approaching the problem, our aim was to redesign the current rotations while giving all residents a 12-month schedule that concurrently (i) balances the number of patients that can be seen in the clinic during each half-day session and (ii) minimizes the number of ad

关键词： Resident scheduling block scheduling medical rotations soft constraints mixed-integer programming

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A reactive decision-making approach to reduce instability in a master production schedule

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INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH 2016年第8期54卷 2394-2404页

作者： Herrera, Carlos Belmokhtar-Berraf, Sana Thomas, Andre Parada, Victor Univ Concepcion Dept Ingn Ind Concepcion Chile Ecole Super Ingn Elect & Electrotech Syst Engn Dept Noisy Le Grand France Univ Henri Poincare Ctr Rech Automat Nancy Nancy France Univ Santiago de Chile Dept Ingn Informat Santiago Chile

One of the primary factors that impact the master production scheduling performance is demand fluctuation, which leads to frequently updated decisions, thereby causing instability. Consequently, global cost deteriorates, and productivity decreases. A reactive approach based on parametric mixed-integer programming(MIP) is proposed that aims to provide a set of plans such that a compromise between production cost and production stability is ensured. Several stability measures and their corresponding MIP model are proposed. An experimental study is performed to highlight the effectiveness of the reactive approach with regard to the proposed performance measures. It is observed that an improvement in stability does not mean a significant increase in the total production cost. Furthermore, the procedure yields a set of plans that in practice would enable flexible management of production.

关键词： production planning and control stability mixed-integer programming manufacturing systems master production schedule

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Mitigating hard capacity constraints with inventory in facility location modeling

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IIE TRANSACTIONS 2016年第2期48卷 120-133页

作者： Maass, Kayse Lee Daskin, Mark S. Shen, Siqian Univ Michigan Dept Ind & Operat Engn Ann Arbor MI 48109 USA

Although the traditional capacitated facility location model uses inflexible, limited capacities, facility managers often have many operational tools to extend capacity or to allow a facility to accept demands in excess of the capacity constraint for short periods of time. We present a mixed-integer program that captures these operational extensions. In particular, demands are not restricted by the capacity constraint, as we allow for unprocessed materials from one day to be held over in inventory and processed on a following day. We also consider demands at a daily level, which allows us to explicitly incorporate the daily variation in, and possibly correlated nature of, demands. Large problem instances, in terms of the number of demand nodes, candidate nodes, and number of days in the time horizon, are generated from United States census population data. We demonstrate that, in some instances, optimal locations identified by the new model differ from those of the traditional capacitated facility location problem and result in significant cost savings.

关键词： Capacitated facility location inventory control inventory mixed-integer programming

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Resource-constrained scheduling with hard due windows and rejection penalties

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ENGINEERING OPTIMIZATION 2016年第9期48卷 1515-1528页

作者： Garcia, Christopher Univ Mary Washington Coll Business Fredericksburg VA 22401 USA

This work studies a scheduling problem where each job must be either accepted and scheduled to complete within its specified due window, or rejected altogether. Each job has a certain processing time and contributes a certain profit if accepted or penalty cost if rejected. There is a set of renewable resources, and no resource limit can be exceeded at any time. Each job requires a certain amount of each resource when processed, and the objective is to maximize total profit. A mixed-integer programming formulation and three approximation algorithms are presented: a priority rule heuristic, an algorithm based on the metaheuristic for randomized priority search and an evolutionary algorithm. Computational experiments comparing these four solution methods were performed on a set of generated benchmark problems covering a wide range of problem characteristics. The evolutionary algorithm outperformed the other methods in most cases, often significantly, and never significantly underperformed any method.

关键词： resource-constrained order acceptance evolutionary algorithm mixed-integer programming Meta-RaPS

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Workforce planning and financing on a production/capital discrete-time model

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INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH 2016年第3期23卷 507-538页

作者： Martins, Pedro Quelhas, Ana Paula Polytech Inst Coimbra ISCAC Coimbra Portugal Univ Lisbon Fac Sci Operat Res Ctr CMAF CIO P-1699 Lisbon Portugal

Traditionally, companies have considered production planning and financial commitments separately. Production planning involves planning when to produce how much of a product, while the financial commitment considers which loans to take and how to repay them. In the current difficult financial environment with new challenges and with different opportunities, such as short-term flexible loans for paying salaries, these related problems must be considered together. In this paper, we model the two processes (production and cash flows) in a single framework, using a mixed-integer programming discrete-time formulation. When taken individually, each of the problems has been thoroughly discussed in the literature, while the combined version that also incorporates labor financial costs and workforce sizing is more scarce. The main contribution of the paper involves new strategies for financing labor costs in strong agreement with the company's production plan and financial commitments. The new strategy relates credit ceiling with employment funding, using a sequence of flexible short-term loans. We consider applications and propose mathematical programming based tools that can be used by companies' managers for conducting their own solutions analysis, following their own findings and discussion of alternative scenarios.

关键词： discrete-time financial planning production planning labor financing mixed-integer programming

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Inclusive multi-objective PMU placement in power systems considering conventional measurements and contingencies

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INTERNATIONAL TRANSACTIONS ON ELECTRICAL ENERGY SYSTEMS 2016年第3期26卷 609-626页

作者： Esmaili, Masoud Islamic Azad Univ Dept Elect Engn West Tehran Branch Tehran Iran

Phasor measurement units (PMUs) are becoming vital parts of modern state estimation systems in smart grids because of their outstanding abilities. In this paper, an inclusive optimal PMU placement (OPP) is proposed as a mixed-integer programming with objective functions of minimizing the number of PMUs and maximizing measurement redundancy. Fuzzy memberships are used to transform differently scaled objective functions into the same range in order to ensure Pareto optimality of the solution. The properties of zero injection buses (ZIBs) are used to make buses observable in the network as a whole using the system of equations instead of focusing on each individual ZIB property. This can be beneficial in handling multiple ZIBs connected to each other. Also, conventional measurements are modeled in the proposed method, and a formulation is introduced for inclusion of multiple branch flow measurements (FMs) adjacent to a bus. In addition, changes in ZIB and FM sets after outage of a branch are considered in the proposed OPP for a more realistic solution. Results from testing the proposed OPP method are discussed and compared with previous methods. Copyright (c) 2015 John Wiley & Sons, Ltd.

关键词： Flow measurement mixed-integer programming measurement redundancy optimal placement phasor measurement unit zero injection bus

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