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Lifting the knapsack cover inequalities for the knapsack polytope

OPERATIONS RESEARCH LETTERS 2020年第5期48卷 607-611页

作者： Letchford, Adam N. Souli, Georgia Univ Lancaster Dept Management Sci Lancaster LA1 4YX England Univ Lancaster STOR I Ctr Doctoral Training Lancaster LA1 4YR England

Valid inequalities for the knapsack polytope have proven to be very useful in exact algorithms for mixed-integer linear programming. In this paper, we focus on the knapsack cover inequalities, introduced in 2000 by Carr and co-authors. In general, these inequalities can be rather weak. To strengthen them, we use lifting. Since exact lifting can be time-consuming, we present two fast approximate lifting procedures. The first procedure is based on mixed-integer rounding, whereas the second uses superadditivity. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Knapsack problems Lifted cover inequalities Polyhedral combinatorics mixed-integer linear programming

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Short-term planning of a work shift for open-pit mines: A case study

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COGENT ENGINEERING 2023年第1期10卷 Article: 2168172页

作者： Silva-Junior, Ademar L. Martins, Aldrin G. Pantuza-Jr, Guido Cota, Luciano P. Souza, Marcone J. F. Inst Tecnol Vale BR-354000000 Ouro Preto MG Brazil Univ Fed Ouro Preto Programa Posgrad Instrumentacao Controle & Automac BR-35400000 Ouro Preto Brazil Inst Tecnol Vale BR-35400000 Ouro Preto Brazil Vale SA BR-35900900 Itabira Brazil Fed Inst Minas Gerais Dept Min BR-36415000 Congonhas MG Brazil Themat Network Mat Engn REDEMAT Grad Program Mat Engn BR-35000000 Ouro Preto Brazil Fed Inst Minas Gerais BR-35057760 Governador Valadares Brazil Univ Fed Ouro Preto Dept Comp BR-35400000 Ouro Preto Brazil

This work deals with the short-term planning problem of a work shift for open-pit mines. The problem involves ore and waste fronts, shovels, heterogeneous truck fleets, and discharge points. The allocation of trucks is dynamic to allow multiple routes to be assigned to each truck. The problem consists of deciding which fronts must be mined and establishing the number of trucks, their routes, and the amount of material transported by them to each discharge point, satisfying a stripping ratio at the desired level. The objectives are to minimize the deviations from the targets for production, chemical grade, and particle size range of each control parameter at each plant and reduce the number of trucks needed for the process. To solve the problem, we developed a mixed-integer linear goal programming model and tested it using real data from an iron ore mine. The results showed that the proposed approach supports decision-makers in the sizing and allocation of truck fleets and in meeting the production and control parameter targets required by the ore processing plants according to the daily scenario, such as low availability of shovels and trucks, flexibility in ore quality, and need for increased production.

关键词： Short-term planning open-pit mining blending truck allocation mixed-integer linear programming goal programming

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Reorganization of a medical service network to manage pandemic waves: A real case study

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OPERATIONS RESEARCH FOR HEALTH CARE 2023年 39卷

作者： Ahadian, Sajjad Pishvaee, Mir Saman Jahani, Hamed Iran Univ Sci & Technol Sch Ind Engn Tehran Iran RMIT Univ Sch Accounting Informat Syst & Supply Chain Melbourne Australia

During Covid-19, medical service networks (MSNs) faced new challenges, such as an impressive increase in hospital visits, a shortage of hospital beds and staff, and insufficient information to estimate the number of mild and critical cases. In addition, governments were encountered to implement appropriate quarantine policies. Dealing with these problems became more complex and challenging when a new wave of disease occurred. This study develops a mixed-integer linear programming model for reorganizing an MSN to manage future pandemic waves. The model aims at reallocation medical staff to prevent a shortage of hospital beds. A fuzzy approach is employed to estimate the uncertain number of patients in each period. As a result, direct hospital visits are decreased by 60% on average, and shortages of beds are avoided by adding the fewest beds possible in each period. The model can also optimize several performance ratios, e.g., the ratio of hospitalized patients to the specialized personnel assigned to each hospital, which is decreased by approximately 40% in our case.

关键词： Pandemic control Medical service network Staff management Post-disaster casualty management Fuzzy approach mixed-integer linear programming

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Reducing waste in manufacturing operations: bi-objective scheduling on a single-machine with coupled-tasks

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INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH 2020年第23期58卷 7130-7148页

作者： Le Hesran, Corentin Agarwal, Aayush Ladier, Anne-Laure Botta-Genoulaz, Valerie Laforest, Valerie Univ Lyon DISP Lab EA 4570 INSA Lyon Villeurbanne France Univ Lyon CNRS EMSE UMR EVS 5600 St Etienne 2 France

This study addresses a scheduling problem involving a single-machine with coupled-tasks and bi-objective optimisation considering simultaneously inventory and environmental waste. A mixed integer linear Program representing the problem is first developed. Subsequently, a Genetic Algorithm (GA) is presented, followed by numerical experiments on multiple instances. Pareto fronts are determined using the epsilon-constraint and weighted sum methods, and a trade-off point is selected according to a distance criterion. Numerical experiments on both small and large instances show near-optimal results for small instances, and considerably reduced computing times for large ones when using the GA. The results show that a compromise can be found, with a decrease in setup-related waste up to 36% for an increase of inventory of 12%. This will help decision-makers to better consider the environmental aspect when designing schedules, as well as reduce their production environmental impact and waste-management costs.

关键词： coupled-tasks bi-objective optimisation scheduling genetic algorithm waste prevention mixed-integer linear programming

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Optimal Design and Dispatch of Electrically Driven Heat Pumps and Chillers for a New Development Area

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ENVIRONMENTAL AND CLIMATE TECHNOLOGIES 2020年第3期24卷 470-482页

作者： Pieper, Henrik Ommen, Torben Elmegaard, Brian Volkova, Anna Brix Markussen, Wiebke Tallinn Univ Technol Ehitajate Tee 5 EE-19086 Tallinn Estonia Tech Univ Denmark Nils Koppels alle Bldg 403 DK-2800 Lyngby Denmark

Large-scale heat pumps (HPs) and refrigeration plants are essential technologies to decarbonise the heating and cooling sector. District heating and cooling (DHC) can be supplied with low carbon footprint, if power generated from renewable energy sources is used. The simultaneous supply of DHC is often not considered in energy planning, nor the characteristics of the heat source and sink. Simplified approaches may not reveal the true potential of HPs and chillers. In this paper, different heat sources and sinks and their characteristics were considered for the simultaneous supply of DHC based on large-scale HPs and refrigeration plants. An optimization model was developed based on mixed-integer linear programming. The model is able to identify ideal production and storage capacities, heat sources and sinks based on realistic hourly operation profiles. By doing so, it is possible to identify the most economical or sustainable supply of DHC using electricity. The optimization model was applied to the Nordhavn area, a new development district of Copenhagen, Denmark. The results show that a combination of different heat sources and sinks is ideal for the case study. A HP that uses the district cooling network as a heat source to supply DHC was shown to be very efficient and economical. Groundwater and sewage water HPs were proposed for an economical supply of district heating. The Pareto frontier showed that a large reduction in annual CO2 emissions is possible for a relatively small increase in investments.

关键词： District cooling district heating energy planning heat source heat sink large-scale heat pump mixed-integer linear programming optimization

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Combinatorial optimization applied to VLBI scheduling

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JOURNAL OF GEODESY 2020年第2期94卷 1-22页

作者： Corbin, A. Niedermann, B. Nothnagel, A. Haas, R. Haunert, J. -H. Univ Bonn Inst Geodesy & Geoinformat Nussallee 17 D-53115 Bonn Germany Univ Bonn Inst Geodesy & Geoinformat Meckenheimer Allee 172 D-53115 Bonn Germany Chalmers Univ Technol Dept Space Earth & Environm Observ Vagen 90 S-43992 Onsala Sweden TU Wien Dept Geodesy & Geoinformat Wiedner Hauptstr 8 A-1040 Vienna Austria

Due to the advent of powerful solvers, today linear programming has seen many applications in production and routing. In this publication, we present mixed-integer linear programming as applied to scheduling geodetic very-long-baseline interferometry (VLBI) observations. The approach uses combinatorial optimization and formulates the scheduling task as a mixed-integer linear program. Within this new method, the schedule is considered as an entity containing all possible observations of an observing session at the same time, leading to a global optimum. In our example, the optimum is found by maximizing the sky coverage score. The sky coverage score is computed by a hierarchical partitioning of the local sky above each telescope into a number of cells. Each cell including at least one observation adds a certain gain to the score. The method is computationally expensive and this publication may be ahead of its time for large networks and large numbers of VLBI observations. However, considering that developments of solvers for combinatorial optimization are progressing rapidly and that computers increase in performance, the usefulness of this approach may come up again in some distant future. Nevertheless, readers may be prompted to look into these optimization methods already today seeing that they are available also in the geodetic literature. The validity of the concept and the applicability of the logic are demonstrated by evaluating test schedules for five 1-h, single-baseline Intensive VLBI sessions. Compared to schedules that were produced with the scheduling software sked, the number of observations per session is increased on average by three observations and the simulated precision of UT1-UTC is improved in four out of five cases (6 mu saverage improvement in quadrature). Moreover, a simplified and thus much faster version of the mixed-integer linear program has been developed for modern VLBI Global Observing System telescopes.

关键词： Combinatorial optimization mixed-integer linear programming Geodetic VLBI Scheduling Local sky coverage VGOS

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Optimization operation model of electricity market considering renewable energy accommodation and flexibility requirement

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Global Energy Interconnection 2021年第3期4卷 227-238页

作者： Jinye Yang Chunyang Liu Yuanze Mi Hengxu Zhang Vladimir Terzija Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education(Shandong University) Jinan 250061ShandongP.R.China The Center for Energy Science and Technology Skolkovo Institute of Science and TechnologyMoscowRussia

The renewable portfolio standard has been promoted in parallel with the reform of the electricity market,and the flexibility requirement of the power system has rapidly *** promote renewable energy consumption and improve power system flexibility,a bi-level optimal operation model of the electricity market is proposed.A probabilistic model of the flexibility requirement is established,considering the correlation between wind power,photovoltaic power,and load.A bi-level optimization model is established for the multi-markets;the upper and lower models represent the intra-provincial market and inter-provincial market models,*** efficiently solve the model,it is transformed into a mixed-integer linear programming model using the Karush–Kuhn–Tucker condition and Lagrangian duality *** economy and flexibility of the model are verified using a provincial power grid as an example.

关键词： Renewable energy accommodation Renewable portfolio standards Flexibility requirement Optimization operation mixed-integer linear programming

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Valid inequalities for mixed-integer programmes with fixed charges on sets of variables

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OPERATIONS RESEARCH LETTERS 2020年第3期48卷 240-244页

作者： Letchford, Adam N. Souli, Georgia Univ Lancaster Dept Management Sci Lancaster LA1 4YX England Univ Lancaster STOR I Ctr Doctoral Training Lancaster LA1 4YR England

We consider mixed 0-1 linear programmes in which one is given a collection of (not necessarily disjoint) sets of variables and, for each set, a fixed charge is incurred if and only if at least one of the variables in the set takes a positive value. We derive strong valid linear inequalities for these problems, and show that they generalise and dominate a subclass of the well-known flow cover inequalities for the classical fixed-charge problem. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Polyhedral combinatorics Branch-and-cut mixed-integer linear programming

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Analysing the impact of collaborations between airlines and maintenance service company under MRO outsourcing mode: Perspective from airline?s operations

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JOURNAL OF AIR TRANSPORT MANAGEMENT 2023年第1期109卷

作者： Qin, Yichen Ng, Kam K. H. Shanghai Maritime Univ Sch Econ & Management Shanghai 201306 Peoples R China Hong Kong Polytech Univ Dept Aeronaut & Aviat Engn Hung Hom Hong Kong Peoples R China

The practice of Aircraft Maintenance Repair and Overhaul (MRO) outsourcing has changed airline companies' decision-making processes in both operational and tactical levels. Specifically, the aircraft heavy maintenance service provided by an independent maintenance service company alleviates airlines' fixed-asset investments and daily operations regarding maintenance. On the other hand, the fluctuations in MROs service capability, availability and service level also affect airlines' fleet management and daily operations if their maintenance demands cannot be met in a timely manner. In this regard, the impact of the collaborations between airlines and maintenance service company is investigated from the perspective of airline's operations, by studying the maintenance planning problem at operational level. Afterwards, to examine and investigate the impact of col-laborations between the two parties have on airline's operational performance, aircraft maintenance routing problems under 'airlines-service company' non-collaborative and collaborative contexts are investigated and formulated. The computational results demonstrate the effectiveness of the MRO collaboration under outsourcing mode, in view of airline company's overall operational revenue and flexibility while carrying out maintenance routing for individual aircraft in its fleet.

关键词： Aircraft maintenance routing Aircraft maintenance Repair and overhaul MRO Outsourcing Collaborative MRO mixed-integer linear programming

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Embedding reservoirs in industrial models to exploit their flexibility

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SN APPLIED SCIENCES 2020年第12期2卷 2171页

作者： Cuvelier, Thibaut Cent Supelec L2S Lab Signaux & Syst Gif Sur Yvette France

In the context of energy transition, industrial plants that heavily rely on electricity face more and more price volatility. To continue operating in these conditions, the directors become continually more willing to increase their flexibility, i.e. their ability to react to price fluctuations. This work proposes an intuitive methodology to mathematically model electro-intensive processes in order to assess their flexibility potential. To this end, we introduce the notion of reservoir, a storage of either material or energy, that allows models based on this paradigm to have interpretations close to the physics of the processes. The design of the reservoir methodology has three distinct goals: (1) to be easy and quick to build by an energy-sector consultant;(2) to be effortlessly converted into mixed-integer linear or nonlinear programs;(3) to be straightforward to understand by nontechnical people, thanks to their graphic nature. We apply this methodology to two industrial case studies, namely an induction furnace (linear model) and an industrial cooling installation (nonlinear model), where we can achieve significant cost savings. In both cases, the models can be quickly written using our method and solved by appropriate solver technologies.

关键词： Electro-intensive industrial process Electricity-price volatility mixed-integer linear programming Global optimisation

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