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The incremental connected facility location problem

COMPUTERS & OPERATIONS RESEARCH 2019年 112卷 104763-000页

作者： Arulselvan, Ashwin Bley, Andreas Ljubic, Ivana Univ Strathclyde Dept Management Sci Glasgow Lanark Scotland Univ Kassel Inst Math Kassel Germany ESSEC Business Sch Paris IDS Dept Paris France

We consider the incremental connected facility location problem (incremental ConFL), in which we are given a set of potential facilities, a set of interconnection nodes, a set of customers with demands, and a planning horizon. For each time period, we have to select a set of facilities to open, a set of customers to be served, the assignment of these customers to the open facilities, and a network that connects the open facilities. Once a customer is served, it must remain served in subsequent periods. Furthermore, in each time period the total demand of all customers served must be at least equal to a given minimum coverage requirement for that period. The objective is to minimize the total cost for building the network given by the investment and maintenance costs for the facilities and the network summed up over all time periods. We propose a mixed integer programming approach in which, in each time period, a single period ConFL with coverage restrictions has to be solved. For this latter problem, which is of particular interest in itself, new families of valid inequalities are proposed: these are set union knapsack cover (SUKC) inequalities, which are further enhanced by lifting and/or combined with cut-set inequalities, which are primarily used to ensure connectivity requirements. Details of an efficient branch-and-cut implementation are presented and computational results on a benchmark set of large instances are given, including examples of telecommunication networks in Germany. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： mixed integer programming Facility location Branch-and-cut Multi-period network design Incremental network design

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One-dimensional stock cutting resilient against singular random defects

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COMPUTERS & OPERATIONS RESEARCH 2023年第1期157卷

作者： Arbib, Claudio Marinelli, Fabrizio Pferschy, Ulrich Ranjbar, Fatemeh K. Univ Aquila Dipartimento Ingn Sci Informaz & Matemat Laquila Italy Univ Politecn Marche Dipartimento Ingn Informaz Ancona Italy Karl Franzens Univ Graz Inst Operat & Informat Syst Graz Austria

When industrial components are obtained by cutting bars of raw material (stocks), production volumes and values can be affected by random defects in the stocks. To deal with this inconvenience, we propose to design reconfigurable cutting patterns that can be adjusted so that defects fall, as far as possible, in the residual area that is normally discarded. In this situation, a trade-off arises between the amount of this scrap area and the probability that there exists a reconfiguration with no loss of items. We define mathematical models for the expected economic value produced with a single stock, or with all the stocks cut to obtain the required items. We then introduce the relevant optimization problems, discuss their complexity and devise various solution algorithms, comprising dynamic programming and integer Linear programming. The effectiveness of our algorithms is finally illustrated by computational tests on sample problems derived from the literature.

关键词： Cutting stock Bin packing Recoverable defects Dynamic programming mixed integer programming

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A two-stage decomposition method for integrated optimization of islanded AC grid operation scheduling and network reconfiguration

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INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS 2022年 136卷 107647-107647页

作者： Damgacioglu, Haluk Celik, Nurcin Univ Miami Dept Ind Engn Coral Gables FL 33146 USA

A restructuring of electricity systems promises energy resilience, prosperity, and sustainability for communities. In particular, Reconfigurable networks, such as distribution systems or microgrids, as smart electricity systems are more controllable and flexible compared to traditional systems. In this study, we integrate network reconfiguration decisions into a multi-period grid operation scheduling problem to minimize the operational costs while taking into account both technical and inter-temporal constraints for distributed energy resources, physical constraints on alternating current (AC) network, and system reliability constraints. We develop a comprehensive optimization model for the grid operation planning problem by taking into account the operation scheduling and economic dispatch decisions from earlier cycles and grid operational constraints while determining the optimal network topology. Due to the NP-hard nature of the problem, we introduce a two-stage decomposition algorithm where the solution of the operation scheduling problem (without switching variables) feeds the network reconfiguration problem embedding the dispatch problem for each time period. The performance of the proposed two-stage decomposition algorithm is demonstrated on three different available IEEE testbeds against CPLEX and COUENNE solvers for benchmarking purposes. The selected IEEE testbeds have been widely adopted by previous literature for the aforementioned grid operation planning problem due to their capability in reproducibility. The proposed decomposition algorithm outperforms CPLEX in terms of both solution quality and computational times, particularly our algorithm provides 0.5% and 3.17% better solutions in mid-size and large-size networks, respectively.

关键词： Grid operation scheduling Network reconfiguration Radial networks mixed integer programming

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Application of demand response to improve voltage regulation with high DG penetration

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ELECTRIC POWER SYSTEMS RESEARCH 2020年 189卷 106722-106722页

作者： Chandran, Chittesh Veni Basu, Malabika Sunderland, Keith Pukhrem, Shivananda Catalao, Joao P. S. TU Dublin Dublin Ireland Univ Porto Fac Engn Porto Portugal INESC TEC Porto Portugal

The ability of a consumer friendly demand response based voltage control (DR-VC) program to improve the voltage regulation in a low voltage distribution network (LVDN) with high penetration of DG is investigated. The use of active and reactive power management to regulate the nodal voltage in a distribution network with simple incremental reduction algorithm, in conjunction with DR, is proposed as a solution for over voltage and undervoltage issues in the LVDN. The algorithm micromanages the load and generation in the network enabling the operator to utilize grid resources economically and efficiently while maintaining fairness between consumers with minimum inconvenience. The algorithm is tested on a representative. 74-load radial urban distribution network (Dublin, Ireland) using consumer load and DG generation profiles. The system is modelled and analysed using COM interface between OpenDSS and MATLAB. The DR is modelled through a mixed integer linear programming (MILP), implemented in CVX, such that consumer inconvenience is prioritized. The DR-VC algorithm is capable of regulating load and generation within normal operation limits during undervoltage and overvoltage scenarios.

关键词： Demand response DG penetration mixed integer programming Voltage stability Voltage quality

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Express shipment service network design with complex routes

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COMPUTERS & OPERATIONS RESEARCH 2020年 114卷 104810-000页

作者： Perez, Jose Miguel Quesada Tancrez, Jean-Sebastien Lange, Jean-Charles Catholic Univ Louvain CORE Chaussee Binche 151 B-7000 Mons Belgium

The Express Shipment Service Network Design (ESSND) problem consists in defining a network of flights that enables the overnight flow of express packages from their origins to their destinations at minimum cost. This problem is normally solved considering only one-leg, multi-leg and ferry routes. Assessing the value of more complex route types is an open question of academic and practical importance. In this article, we present a mixed integer programming model that includes five types of complex routes: two-hub, transload, direct, inter-hub and early routes. We assess their economic impact by performing many experiments built from an instance provided by FedEx Express Europe. Inter-hub and early routes have the best performance, with significant average savings (from 0.5% to 3.5%). (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Service network design Express integrator Multiple hubs Flexible hub assignment mixed integer programming Complex routes

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Adaptive large neighborhood search for the time-dependent profitable dial-a-ride problem

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COMPUTERS & OPERATIONS RESEARCH 2022年 147卷

作者： Zhao, Jingyi Poon, Mark Zhang, Zhenzhen Gu, Ruixue Natl Univ Singapore Dept Ind Syst Engn & Management Singapore 117576 Singapore Amazon Seattle WA 98109 USA Tongji Univ Sch Econ & Management Shanghai 200092 Peoples R China

This paper is motivated by a non-emergency ambulance transportation service provider that picks up and drops off patients while considering both the time window for medical appointments and the maximum ride-time constraint for each patient. Varying travel times based on departure times further complicates the feasibility evaluation of a given route under both constraints. This problem aims to maximize the net profit which is calculated as the collected reward of serving the selected requests minus the total travel cost of the designed route. The problem is modeled as a time-dependent profitable dial-a-ride problem (TD-PDARP) with a single -vehicle using a mixed-integer linear programming (MILP) model. We propose a tailored feasibility evaluation procedure to handle the complicated maximum ride-time constraint under the time-dependent travel time model, which is then embedded in a hybrid algorithm to solve the proposed problem. This hybrid algorithm leverages an adaptive large neighborhood search (ALNS) for large-scale exploration together with local search (LS) techniques to exploit local regions comprehensively. We evaluate the performance of the proposed algorithm on newly generated TD-PDARP instances. The experiments show that our ALNS-LS algorithm can solve large instances that cannot be solved by commercial solvers in a reasonable time. Furthermore, for all instances that can be solved by the solver within 12 h, our proposed heuristic algorithm is able to obtain the optimal solutions and takes only 1.03% of the average run time required by the solver.

关键词： Routing Time-dependent travel time Dial-a-ride problem Meta-heuristics mixed integer programming

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Uma abordagem estocástica para aumento de produtividade em linhas de montagem: o problema de balanceamento de produção

Uma abordagem estocástica para aumento de produtividade em ...

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作者： Souza, Yuri Prado Universidade Estadual Paulista

Neste trabalho propõe-se uma abordagem para o Problema de Balanceamento de Linhas de Montagem (do inglês, Assembly Line Balancing Problem - ALBP) para aumentar a eficiência de uma indústria montadora de veículos. O ALBP caracteriza-se como um problema de sequenciamento de tarefas em estações de trabalho classificado como um problema de Otimização Combinatória NP-difícil e, portanto, a solução exata do problema em ambientes reais geralmente implica em elevado custo computacional. Para resolver o ALBP, foram formulados um modelo matemático de otimização inteira mista para obtenção de soluções determinísticas e um modelo estocástico com recurso que considera a incerteza dos tempos de execução das tarefas pelos operadores. A motivação para o desenvolvimento do presente trabalho decorre da observação de interrupções constantes do fluxo de produção nesta indústria, atribuídas às mais diversas naturezas, e que causavam transtornos e elevados níveis de estresse aos trabalhadores. Ambos os modelos, determinístico e estocástico, aumentaram a capacidade de produção de 196 unidades/dia para 245 e 233 unidades/dia, respectivamente. O modelo estocástico aumentou o tempo de ciclo CT em 5,6% quando comparado ao modelo determinístico, embora diminua a capacidade efetiva em 4,8% Porém, não considerar a incerteza no tempo de execução das tarefas pode diminuir a quantidade produzida em até 10,6%. Contrariamente ao entendimento comum em linhas de montagem, este trabalho conclui que reduzir os tempos de ociosidade aos níveis mínimos é prejudicial à produtividade de linhas de montagem. Isto se deve ao fato de que uma parcela do tempo atribuído à ociosidade dos operadores, na verdade contêm um tempo adicional gerado pela incerteza do tempo de execução das tarefas. Os resultados sugerem que a abordagem do ALBP sob incerteza contribui para o aumento dos índices de capacidade operacional da empresa. Devido ao grande esforço computacional necessário para a solução dos modelos de otimização pro

关键词： Problema de Balanceamento de Linhas de Montagem Programação Inteira Mista Programação Estocástica Modelo estocástico com recurso Heurística Assembly line balancing problem mixed integer programming Stochastic programming Stochastic model with reco

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Slot assignment for outbound containers in storage space limited container terminal

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OCEAN & COASTAL MANAGEMENT 2024年 256卷

作者： Wang, Yu Tan, Caimao Wu, Hao Shanghai Maritime Univ Logist Engn Coll Shanghai Peoples R China Shanghai Maritime Univ China Inst FTZ Supply Chain Shanghai Peoples R China

For coping with the storage stacking demand of outbound container, this paper explores the yard slot assignment problem for resourced limited container terminal. Based on the penalty method proposed in this paper, a mixed integer programming and a heuristic algorithm are presented. In numerical experiments, instances combined with practical port operation are designed to verify the effectiveness the proposed heuristic algorithm and stacking strategy. In addition, some scenario experiments designed to analyze the affect of container weight grades and available stack space on yard slot assignment. Experimental results show the model and algorithm proposed in this paper can increase the utilization of yard space resource and decrease container reshuffle effectively, and it can provide an effective decision support for the terminal manager.

关键词： Container terminal Slot assignment mixed integer programming Heuristic algorithm Penalty method

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Decision support for healthcare cyber security

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COMPUTERS & SECURITY 2022年 122卷

作者： Sonmez, Ferda Ozdemir Hankin, Chris Malacaria, Pasquale Imperial Coll Inst Secur Sci & Technol South Kensington Campus London London SW7 2AZ England Queen Mary Univ London Sch Elect Engn & Comp Sci Mile End Rd London E1 4NS England

The pandemic has demonstrated that healthcare systems are prime targets for attackers. Finding an optimal security control set is a constant challenge for health organizations, where cost is a major consideration. The purpose of this paper is to demonstrate a healthcare cost optimization system as well as a case study based on two IT setup configurations that have been evaluated by medical experts as well as IT experts. These configurations would aid in conveying the complexity of the decision parameters and demonstrating how CySecTool handles this difficulty. In the study, 64 different security controls were linked to 70 vulnerabilities that could occur at any level of a hospital system dealing with both internal and external attacks/risks. The study also includes a novel visualization scheme that allows for the observation of vulnerabilities and also their subcategories based on Microsoft's STRIDE categorization. Crown Copyright (c) 2022 Published by Elsevier Ltd. This is an open access article under the CC BY license ( http://***/licenses/by/4.0/ )

关键词： Healthcare Cyber Security Optimization CySecTool Visualization Attack Graph mixed integer programming

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Scheduling consecutive days off: A case study of maritime pilots

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COMPUTERS & INDUSTRIAL ENGINEERING 2021年 155卷 107192-107192页

作者： Lorenzo-Espejo, Antonio Munuzuri, Jesus Onieva, Luis Cortes, Pablo Univ Seville Dept Org Ind & Gest Empresas 2 Escuela Tecn Super Ingn Cm Descubrimientos S-N Seville 41092 Spain

Pilots are essential for the operation of maritime ports and an efficient piloting workforce management is critical to provide quality service to incoming vessels, to comply with the strict labor regulations associated with piloting and to avoid penalties due to delays in service. However, designing labor schedules that meet workforce demand and fulfill both labor requirements and workers' preferences at once can become an arduous task. This paper presents two general days-on and days-off scheduling mixed integer linear programming models, which aim to configure extended breaks for each staff member. The first model produces schedules with two long breaks of bounded durations for each worker and minimizes the difference between the employees' workloads. Having the option to modify the minimum lengths of each of the two types of breaks allows managers to comply with the workers' desired rest patterns, while at the same time exploiting the flexibility gained by constraining the off-periods with a lower bound and achieving fair schedules in terms of break lengths and workloads. On the other hand, the second model assigns breaks as extended as possible and minimizes the difference between the rest accumulated by the workers. Its novel formulation allows maximizing the length of the workers' breaks, an objective rarely found in the literature, and can be adjusted to prioritize the overall duration of the off-periods or the fairness of the distribution of breaks. Results of the application of these models to the piloting workforce in a Spanish port are shown, as well as a sensitivity analysis performed in order to assess the behaviour of the models when dealing with longer planning horizons and greater workforce sizes. Additionally, an ad-hoc model is developed for the assignment of special-maneuvering turns to the pilots.

关键词： Personnel scheduling Days-off scheduling mixed integer programming Maritime transportation

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