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Two-machine robotic cell scheduling problem with sequence-dependent setup times

COMPUTERS & OPERATIONS RESEARCH 2013年第5期40卷 1420-1434页

作者： Zarandi, M. H. Fazel Mosadegh, H. Fattahi, M. Amirkabir Univ Technol Dept Ind Engn & Management Syst Tehran *** Iran

In this paper, we introduce a new and practical two-machine robotic cell scheduling problem with sequence-dependent setup times (2RCSDST) along with different loading/unloading times for each part. Our objective is to simultaneously determine the sequence of robot moves and the sequence of parts that minimize the total cycle time. The proposed problem is proven to be strongly NP-hard. Using the Gilmore and Gomory (GnG) algorithm, a polynomial-time computable lower bound is provided. Based on the input parameters, a dominance condition is developed to determine the optimal sequence of robot moves for a given sequence of parts. A mixed-integer linear programming (MILP) model is provided and enhanced using a valid inequality based on the given dominance condition. In addition, a branch and bound (BnB) algorithm is exploited to solve the problem, and due to the NP-hardness, an improved simulated annealing (SA) algorithm is proposed to address large-sized test problems. All the solution methods are evaluated using small-, medium- and large-sized test problems. The numerical results indicate that the optimal solution of the MILP model is attained for the medium- and some large-sized test problems, and the proposed SA, tuned using the Taguchi technique, provides an acceptable, near-optimal solution with markedly reduced CPU time. Moreover, the lower bound is observed to be significantly near the optimal solution. Thus, this lower bound is exploited to validate the results of the SA algorithm for large-sized test problems. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Robotic cell scheduling Sequence-dependent setup times mixed-integer linear programming Simulated annealing Branch and bound Taguchi

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Modelling disruptions and resolving conflicts optimally in a railway schedule

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COMPUTERS & INDUSTRIAL ENGINEERING 2013年第1期64卷 469-481页

作者： Narayanaswami, Sundaravalli Rangaraj, Narayan Higher Coll Technol Abu Dhabi U Arab Emirates Indian Inst Technol Bombay 400076 Maharashtra India

Resolving disruptions, by dispatching and rescheduling conflicting trains is an NP-complete problem. Earlier literature classify railway operations as: (i) tactical scheduling, (ii) operational scheduling, and (iii) rescheduling. We distinguish the three based on operational criticality. Existing optimisation models do not distinguish precisely between scheduling and rescheduling based on constraints modelling;the only difference is in their objective function. Our model is the first of its kind to incorporate disruptions in an MILP model and to include conflicts-resolving constraints in the model itself. The major advantage of such a formulation is that only those trains which are disrupted are rescheduled and other nonconflicting trains retain their original schedules. Our model reschedules disrupted train movements on both directions of a single track layout with an objective to minimise total delay of all trains at their destinations. Using a small sized data it is proved that all possible conflicts out of a disruption are resolved. Apart from achieving optimal resolutions, we infer through experimental verification that a non-standard dispatch ordering is a requisite for global optimality, as cogitated by other authors. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Disruption Conflicts Optimal resolution Single-track railway mixed-integer linear programming

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A mixed-integer LP model for the optimal allocation of voltage regulators and capacitors in radial distribution systems

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INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS 2013年第1期48卷 123-130页

作者： Franco, John F. Rider, Marcos J. Lavorato, Marina Romero, Ruben Univ Estadual Paulista UNESP Fac Engn Ilha Solteira Dept Elect Engn Ilha Solteira SP Brazil

This paper presents a mixed-integer linear programming model to solve the problem of allocating voltage regulators and fixed or switched capacitors (VRCs) in radial distribution systems. The use of a mixed-integer linear model guarantees convergence to optimality using existing optimization software. In the proposed model, the steady-state operation of the radial distribution system is modeled through linear expressions. The results of one test system and one real distribution system are presented in order to show the accuracy as well as the efficiency of the proposed solution technique. An heuristic to obtain the Pareto front for the multiobjective VRCs allocation problem is also presented. Crown Copyright (c) 2012 Published by Elsevier Ltd. All rights reserved.

关键词： Distribution system optimization Optimal allocation of voltage regulators and capacitor mixed-integer linear programming

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An approach to optimization of airport taxiway scheduling and traversal under uncertainty

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART G-JOURNAL OF AEROSPACE ENGINEERING 2013年第G2期227卷 273-284页

作者： Anderson, Ross Milutinovic, Dejan Univ Calif Santa Cruz Santa Cruz CA 95060 USA

Airport runways and taxiways have been identified as a key source of system-wide congestion and delay in the over-strained commercial air traffic system. To combat this growing problem, we present a novel approach for taxiway scheduling and traversal. Aircraft must traverse a taxiway, represented by a graph, from gates to their respective runways and arrive at their scheduled times while adhering to safety separation constraints. We describe a combinatorial mixed-integer linear program to determine the push-back time windows, aircraft speeds, stopping times, and in particular, traversal paths for a given graph and an imposed flight schedule as part of a single optimization problem. Safety and scheduling constraints are made robust to probabilistic deviations from the prescribed schedule and aircraft motion, and multiple objective functions are considered to examine the trade-off between taxi times and the probability of safety separation violation. Several scenarios are presented to demonstrate improvements gained from the method and possible uses for this approach.

关键词： Taxiway optimization airport scheduling mixed-integer linear programming

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Multi-parametric disaggregation technique for global optimization of polynomial programming problems

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JOURNAL OF GLOBAL OPTIMIZATION 2013年第2期55卷 227-251页

作者： Teles, Joao P. Castro, Pedro M. Matos, Henrique A. Unidade Modelacao & Optimizacao Sistemas Energet Lab Nacl Energia & Geol P-1649038 Lisbon Portugal Inst Super Tecn Dept Engn Quim & Biol P-1049001 Lisbon Portugal

This paper discusses a power-based transformation technique that is especially useful when solving polynomial optimization problems, frequently occurring in science and engineering. The polynomial nonlinear problem is primarily transformed into a suitable reformulated problem containing new sets of discrete and continuous variables. By applying a term-wise disaggregation scheme combined with multi-parametric elements, an upper/lower bounding mixed-integer linear program can be derived for minimization/maximization problems. It can then be solved to global optimality through standard methods, with the original problem being approximated to a certain precision level, which can be as tight as desired. Furthermore, this technique can also be applied to signomial problems with rational exponents, after a few effortless algebraic transformations. Numerical examples taken from the literature are used to illustrate the effectiveness of the proposed approach.

关键词： Polynomial Signomial Optimization mixed-integer linear programming Parameterization

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Redundant Observability PMU Placement in the Presence of Flow Measurements Considering Contingencies

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IEEE TRANSACTIONS ON POWER SYSTEMS 2013年第4期28卷 3765-3773页

作者： Esmaili, Masoud Gharani, Kiarash Shayanfar, Heidar Ali Islamic Azad Univ Dept Elect Engn West Tehran Branch Tehran Iran Iran Univ Sci & Technol Ctr Excellence Power Syst Automat & Operat Tehran Iran

Phasor measurement units (PMUs) have made it possible to observe and control wide-area power systems. In this paper, a new redundant observability method as a mixed-integer linear programming (MILP) is presented for optimal PMU placement. Redundant observation of buses enhances measurement reliability. The proposed method improves observability redundancy by a new objective function while using the same number of PMUs as the existing methods. Because of using MILP, the global optimal integer solution is achieved with a zero optimality gap. In addition, a systematic novel approach is proposed to incorporate already installed branch flow measurements in the PMU placement problem leading to a reduced number of PMUs required for system observability. This approach is able to handle both single and multiple flow measurements incident to a bus. PMU placement in case of PMU failure or branch outage is also studied. The proposed method along with an existing method is tested on four IEEE and Polish 3375-bus test systems. Obtained results, discussed in detail, show the efficiency of the proposed method in both speed and accuracy.

关键词： Flow measurement mixed-integer linear programming observability redundancy phasor measurement unit

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Forecasting flexibility in electricity demand with price/consumption volume signals

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ELECTRIC POWER SYSTEMS RESEARCH 2013年 95卷 200-205页

作者： Gorria, C. Jimeno, J. Laresgoiti, I. Lezaun, M. Ruiz, N. Univ Pais Vasco UPV EHU Dept Appl Math Stat & Operat Res Leioa 48940 Spain Tecnalia Energy Unit Derio 48160 Spain

The introduction of renewable energy sources, particularly wind power, is limited by their dependence on weather conditions and by the difficulty of storing surplus energy for use at times when production is low. One effective way of tackling the energy storage problem is to minimise the need for storage, i.e. to switch from a system based on producing electricity in response to the unpredictable whims of demand to one in which consumption adapts to supply. Demand can be managed indirectly via the sending of price/consumption volume signals. This paper presents a mathematical model for forecasting the aggregated electricity demand of a group of domestic consumers signed up to an incentive-based demand management programme. Under this programme consumers receive signals that offer financial incentives for limiting their volume of consumption at time intervals when system peak demand is forecast. The resulting optimisation model is a mixed-integer linear programming problem implemented in JAVA and solved using free software. This model is applied to a case study in which the objective is to limit consumption by a population of 15932 consumers from 15:00 to 17:45 on a specific summer day. The responses to two different incentive amounts are shown. (c) 2012 Elsevier B.V. All rights reserved.

关键词： Electricity demand Demand management Optimisation mixed-integer linear programming

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Reversing port rotation directions in a container liner shipping network

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TRANSPORTATION RESEARCH PART B-METHODOLOGICAL 2013年 50卷 61-73页

作者： Wang, Shuaian Meng, Qiang Univ Wollongong Sch Math & Appl Stat Wollongong NSW 2522 Australia Natl Univ Singapore Dept Civil & Environm Engn Singapore 117576 Singapore

Reversing port rotation directions of ship routes is a practical alteration of container liner shipping networks. The port rotation directions of ship routes not only affect the transit time of containers, as has been recognized by the literature, but also the shipping capacity and transshipment cost. This paper aims to obtain the optimal port rotation directions that minimize the generalized network-wide cost including transshipment cost, slot-purchasing cost and inventory cost. A mixed-integer linear programming model is proposed for the optimal port rotation direction optimization problem and it nests a minimum cost multi-commodity network flow model. The proposed model is applied to a liner shipping network operated by a global liner shipping company. Results demonstrate that real-case instances could be efficiently solved and significant cost reductions are gained by optimization of port rotation directions. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Liner shipping network design Port rotation directions Multi-commodity network flow mixed-integer linear programming

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A mixed-integer LP model for the reconfiguration of radial electric distribution systems considering distributed generation

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ELECTRIC POWER SYSTEMS RESEARCH 2013年 97卷 51-60页

作者： Franco, John F. Rider, Marcos J. Lavorato, Marina Romero, Ruben Univ Estadual Paulista UNESP FEIS DEE Sao Paulo Brazil

The problem of reconfiguration of distribution systems considering the presence of distributed generation is modeled as a mixed-integer linear programming (MILP) problem in this paper. The demands of the electric distribution system are modeled through linear approximations in terms of real and imaginary parts of the voltage, taking into account typical operating conditions of the electric distribution system. The use of an MILP formulation has the following benefits: (a) a robust mathematical model that is equivalent to the mixed-integer non-linear programming model;(b) an efficient computational behavior with exiting MILP solvers;and (c) guarantees convergence to optimality using classical optimization techniques. Results from one test system and two real systems show the excellent performance of the proposed methodology compared with conventional methods. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.

关键词： Reconfiguration of electric distribution systems Active power losses reduction Distributed generation mixed-integer linear programming

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A Stochastic Optimization Formulation of Unit Commitment With Reliability Constraints

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IEEE TRANSACTIONS ON SMART GRID 2013年第4期4卷 2200-2208页

作者： Xiong, Peng Jirutitijaroen, Panida Natl Univ Singapore Dept Elect & Comp Engn Singapore 119077 Singapore

This paper proposes a new formulation for a stochastic unit commitment (UC) problem that incorporates two major and common sources of uncertainty in short-term generation scheduling, namely, unavailability of generators and load uncertainty. The objective is to minimize operating cost and expected loss of load cost subject to reliability constraints in terms of loss of load probability. The problem is first formulated as a two-stage recourse model in stochastic programming framework where generator unavailability is expressed by a discrete set of outage scenarios and system demand is set to be a nominal value in power balance equations. Then, load uncertainty is represented as a continuous random variable in loss of load probability constraint, which is approximated by a mixed-integer piecewise linear function and integrated to the second stage problem. As a result, the UC problem has a much smaller dimension as compared to the original two-stage recourse model. The proposed formulation can be solved in a timely manner even though the formulation requires some extra binary decision variables. Although loss of load probability constraint is approximated in the optimization problem, simulation results show that the optimal solutions yield desired reliability performance. Several case studies are conducted to examine the impact of reliability requirements and system uncertainties on UC decisions.

关键词： mixed-integer linear programming reliability stochastic programming uncertainty unit commitment

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