We report and analyze the results of our computational testing of branch-and-cut for the complementarity-constrained optimization problem (CCOP). Besides the MIP cuts commonly present in commercial optimization softwa...
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We report and analyze the results of our computational testing of branch-and-cut for the complementarity-constrained optimization problem (CCOP). Besides the MIP cuts commonly present in commercial optimization software, we used inequalities that explore complementarity constraints. To do so, we generalized two families of cuts proposed earlier by de Farias, Johnson, and Nemhauser that had never been tested computationally. Our test problems consisted of linear, binary, and general integer programs with complementarity constraints. Our results on the use of complementarity cuts within a major commercial optimization solver show that they are of critical importance to tackling difficult CCOP instances, typically reducing the computational time required to solve them tremendously.
In this paper, we investigate resource allocation strategies for a point-to-point wireless communications system with hybrid energy sources consisting of an energy harvester and a conventional energy source. In partic...
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In this paper, we investigate resource allocation strategies for a point-to-point wireless communications system with hybrid energy sources consisting of an energy harvester and a conventional energy source. In particular, as an incentive to promote the use of renewable energy, we assume that the renewable energy has a lower cost than the conventional energy. Then, by assuming that the non-causal information of the energy arrivals and the channel power gains are available, we minimize the total energy cost of such a system over N fading slots under a proposed outage constraint together with the energy harvesting constraints. The outage constraint requires a minimum fixed number of slots to be reliably decoded, and thus leads to a mixed-integer programming formulation for the optimization problem. This constraint is useful, for example, if an outer code is used to recover all the data bits. Optimal linear time algorithms are obtained for two extreme cases, i.e., the number of outage slot is 1 or N - 1. For the general case, a lower bound based on the linear programming relaxation, and two suboptimal algorithms are proposed. It is shown that the proposed suboptimal algorithms exhibit only a small gap from the lower bound. We then extend the proposed algorithms to the multi-cycle scenario in which the outage constraint is imposed for each cycle separately. Finally, we investigate the resource allocation strategies when only causal information on the energy arrivals and only channel statistics is available. It is shown that the greedy energy allocation is optimal for this scenario.
The master surgery scheduling problem involves the development of a master surgical schedule, a cyclic timetable that determines the patient category associated with each block of operating room time. A myriad of vari...
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ISBN:
(纸本)9781479964109
The master surgery scheduling problem involves the development of a master surgical schedule, a cyclic timetable that determines the patient category associated with each block of operating room time. A myriad of variants of the problem has been addressed in literature. Here we focus on two major variants, arising during cooperation with Karmoze hospital, a non-profit hospital located in Alexandria, Egypt. The first variant asks for balancing both beds and nurses daily requirements, whereas the second for considering surgeons preferences. To cope with these problems we introduce a new mixedinteger formulation. The objective function minimizes the weighted sum of peaks in the daily bed occupancy and nurse daily workloads. The results show that our model provides a more leveled daily bed occupancy and nurse requirements. Furthermore, our model reduces both the daily bed occupancy and nurse workloads.
We consider a scenario with two firms determining which products to develop and introduce to the market. In this problem, there exists a finite set of potential products and market segments. Each market segment has a ...
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We consider a scenario with two firms determining which products to develop and introduce to the market. In this problem, there exists a finite set of potential products and market segments. Each market segment has a preference list of products and will buy its most preferred product among those available. The firms play a Stackelberg game in which the leader firm first introduces a set of products, and the follower responds with its own set of products. The leader's goal is to maximize its profit subject to a product introduction budget, assuming that the follower will attempt to minimize the leader's profit using a budget of its own. We formulate this problem as a multistage integer program amenable to decomposition techniques. Using this formulation, we develop three variations of an exact mathematical programming method for solving the multistage problem, along with a family of heuristic procedures for estimating the follower solution. The efficacy of our approaches is demonstrated on randomly generated test instances. This article contributes to the operations research literature a multistage algorithm that directly addresses difficulties posed by degeneracy, and contributes to the product variety literature an exact optimization algorithm for a novel competitive product introduction problem. (C) 2009 Wiley Periodicals, Inc. Naval Research Logistics 56: 714-729, 2009
This paper proposes a solution to mixed-integer programming by using a gradient system and searching for multiple equilibrium points in the system. The method is available when the objective function of a problem is c...
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This paper proposes a solution to mixed-integer programming by using a gradient system and searching for multiple equilibrium points in the system. The method is available when the objective function of a problem is continuous and differentiable. In order to find feasible Solutions of a mixed-integer programming problem by gradient systems, discrete decision variables are treated as continuous ones. We demonstrate a systematic way to build the kind of gradient systems in which equilibrium points are embedded at feasible solutions of a mixed-integer problem. For numerical computation, the multiple equilibrium points search method we have already proposed is available and its adjustments to improve efficiency and certainly for mixed-integer programming are also proposed in this paper. Results for some problems show the effectiveness of our method: high ability of thorough search and high quality of derived solutions. (C) 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(8): 53-63, 2009;Published online in Wiley InterScience (***). DOI 10.1002/ecj.10037
This study is concerned with an original traffic restoration strategy for wide-area communication networks called Elastic Rerouting (ER). ER aims at alleviating the trade-off between the network cost and traffic resto...
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ISBN:
(纸本)9781479970407
This study is concerned with an original traffic restoration strategy for wide-area communication networks called Elastic Rerouting (ER). ER aims at alleviating the trade-off between the network cost and traffic restoration complexity observed in existing solutions. We present the strategy, provide a mathematical formulation for the ER related optimization problem, and discuss an approach to its resolution. We also report results of a numerical illustrating effectiveness of ER in terms of the link capacity cost.
Optimal transmission switching (OTS) has become a research focus in recent years as a new operational method for power systems. OTS is modeled as a mixed-integer programming (MIP) problem and it is difficult to solve ...
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ISBN:
(纸本)9781479964154
Optimal transmission switching (OTS) has become a research focus in recent years as a new operational method for power systems. OTS is modeled as a mixed-integer programming (MIP) problem and it is difficult to solve it within short time horizon. Current acceleration heuristics cannot guarantee both the computational accuracy and efficiency. In this paper, a new concept called auxiliary induce function (AIF) is proposed. Based on the result of the relaxation problem, the coefficients of integer variables are strategically decided in AIF. Then the AIF algorithm is proposed, which properly adds the AIF function into the objective function of the OTS model. AIF algorithm is able to speed up the solving process for OTS while achieving exactly the same optimal solution. Case study on the IEEE 118-bus system shows that the AIF algorithm can improve 5 times as much the computation speed while obtaining the same optimal solution. Another case study on the IEEE 662-bus system indicates that the AIF algorithm is also capable of further improving the computational efficiency of current acceleration heuristics.
Based on the day-ahead forecast of system load and wind power output. A joint operation of pumped storage and wind power plants model is built with the purpose of minimizing the system operation cost. In order to achi...
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ISBN:
(纸本)9781479941254
Based on the day-ahead forecast of system load and wind power output. A joint operation of pumped storage and wind power plants model is built with the purpose of minimizing the system operation cost. In order to achieve the higher system flexibility and reduce the impact of volatility of wind power, pumped-storage units are incorporated into the unit commitment (UC) problem with wind power. The UC problem of the joint operation of pumped-storage and wind power plants is formulated as the mixedinteger convex program, which is optimized by Cplex. Conducted on a ten-unit system simulation, we can get the conclusion that the joint operation of pumped-storage and wind power plants is effective to reduce the impact of volatility of wind power on the power grid operation. At the same time, economic benefit is remarkable.
Managing uncertainty has been a challenging task for market operations. This paper first reviews the current practice of managing uncertainties at MISO. A framework of using robust optimization based approach on MISO ...
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ISBN:
(纸本)9781479964154
Managing uncertainty has been a challenging task for market operations. This paper first reviews the current practice of managing uncertainties at MISO. A framework of using robust optimization based approach on MISO Look-Ahead commitment (LAC) is then introduced. The numerical results show that this type of approaches are promising and yet with challenges to overcome in order to be practical for real world application.
The unit commitment (UC) problem is a well-known combinatorial optimization problem arising in operations planning of power systems. It involves deciding both the scheduling of power units, when each unit should be tu...
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ISBN:
(数字)9783319100463
ISBN:
(纸本)9783319100456
The unit commitment (UC) problem is a well-known combinatorial optimization problem arising in operations planning of power systems. It involves deciding both the scheduling of power units, when each unit should be turned on or off, and the economic dispatch problem, how much power each of the on units should produce, in order to meet power demand at minimum cost while satisfying a set of operational and technological constraints. This problem is typically formulated as nonlinear mixed-integer programming problem and has been solved in the literature by a huge variety of optimization methods, ranging from exact methods (such as dynamic programming and branch-and-bound) to heuristic methods (genetic algorithms, simulated annealing, and particle swarm). Here, we discuss how the UC problem can be formulated with an optimal control model, describe previous discrete-time optimal control models, and propose a continuous-time optimal control model. The continuous-time optimal control formulation proposed has the advantage of involving only real-valued decision variables (controls) and enables extra degrees of freedom as well as more accuracy, since it allows to consider sets of demand data that are not sampled hourly.
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