The generation maintenance scheduling problem faced by a power producer aims at defining the optimal time intervals for the maintenance of each generating unit. The planning horizon is typically mid-term (year-ahead)....
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ISBN:
(纸本)9781467308328;9781467308342
The generation maintenance scheduling problem faced by a power producer aims at defining the optimal time intervals for the maintenance of each generating unit. The planning horizon is typically mid-term (year-ahead). In this paper, the annual maintenance scheduling problem of a thermal producer is solved with respect to economic and technical security criteria. The aim is to maximize yearly profit, while simultaneously satisfying the operating constraints of the producer's generating units. Specific constraints regarding unit maintenance are also taken into consideration, such as avoiding the simultaneous planned outage of generating units that belong to the same power station, and maintenance intervals that must be scheduled whenever a specific number of operating hours is completed. The generation maintenance scheduling problem is formulated and solved as a mixed-integer linear programming problem using commercial software (GAMS/CPLEX).
This paper addresses the design of joint source-channel variable-length codes with maximal free distance for given codeword lengths. While previous design methods are mainly based on bounds on the free distance of the...
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ISBN:
(纸本)9780769546568
This paper addresses the design of joint source-channel variable-length codes with maximal free distance for given codeword lengths. While previous design methods are mainly based on bounds on the free distance of the code, the proposed algorithm exploits an exact characterization of the free distance. The code optimization is cast in the framework of mixed-integer linear programming and allows to tackle practical alphabet sizes in reasonable computing time.
Cross-docking plays an important role in supply chain and can reduce delivery lead times, inventory holding and transportation costs. However, the advantages of cross-docking would be reduced without an efficient vehi...
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Cross-docking plays an important role in supply chain and can reduce delivery lead times, inventory holding and transportation costs. However, the advantages of cross-docking would be reduced without an efficient vehicle routing. This paper considers a split vehicle routing problem (SVRP) with capacity constraint for multi-product cross-docks. In VRP with split deliveries (pickups) customers (suppliers) are willing to receive (send) goods in multiple shipments and each node can be served by more than one vehicle. The problem is formulated as a mixed-integer linear programming (MILP) model in the GAMS software to determine the best vehicle routes and the optimal number of utilized vehicles.
The concerns of regulatory authority for the cost efficiency and service quality of distribution utilities has led them to implement monetary schemes, such as penalty/reward mechanism (PRM). PRM provides explicit fina...
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The concerns of regulatory authority for the cost efficiency and service quality of distribution utilities has led them to implement monetary schemes, such as penalty/reward mechanism (PRM). PRM provides explicit financial incentives for distribution system operators (DSO) to maintain or improve their efficiency and quality of service. Although the effectiveness of the PRM is proven, analytical tools that can handle the complex decision-making process faced by decision makers to respond to PRM are scarce. This paper presents an approach for distribution system maintenance management in the presence of the PRM. The proposed approach tailors the maintenance plans by taking into account the equipment condition in terms of failure rate, cost of planned and unplanned outage, as well as labor and material cost in conjunction with the incentives provided by PRM. New insights are also gained regarding the effects of PRM on the process of decision making by DSO.
One of the most challenging tasks in today's food industry is controlling the product quality throughout the food supply chain. In this paper, we integrate food quality in decision-making on production and distrib...
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One of the most challenging tasks in today's food industry is controlling the product quality throughout the food supply chain. In this paper, we integrate food quality in decision-making on production and distribution in a food supply chain. We provide a methodology to model food quality degradation in such a way that it can be integrated in a mixed-integer linear programming model used for production and distribution planning. The resulting model is applied in an illustrative case study, and can be used to design and operate food distribution systems, using both food quality and cost criteria. (C) 2009 Elsevier B.V. All rights reserved.
We consider a production planning problem known as the discrete lot-sizing and scheduling problem (DLSP) and study a variant of the DLSP involving several identical parallel resources. We show how to solve the resulti...
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We consider a production planning problem known as the discrete lot-sizing and scheduling problem (DLSP) and study a variant of the DLSP involving several identical parallel resources. We show how to solve the resulting discrete optimisation problem as a mixed-integerlinear program using a commercial MIP solver. To achieve this, we exhibit a family of strong valid inequalities for which the associated separation problem is efficiently solvable. Our computational results show that the proposed solution algorithm is capable of providing optimal solutions for medium-sized instances.
Missions with high combinatorial complexity involving several logical and temporal constraints often arise in cooperative control of multiple Uninhabited Aerial Vehicles. In this paper, we propose a new class of probl...
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Missions with high combinatorial complexity involving several logical and temporal constraints often arise in cooperative control of multiple Uninhabited Aerial Vehicles. In this paper, we propose a new class of problems that generalizes the standard Vehicle Routing Problem (VRP) by addressing complex tasks and constraints on the mission, called the 'mission specifications', expressed in a high-level specification language. In the generalized problem setup, these mission specifications are naturally specified using the linear Temporal Logic language LTL-X. Using a novel systematic procedure, the LTL-X specification is converted to a set of constraints suitable to a mixed-integer linear programming (MILP) formulation, which in turn can be incorporated into two widely-used MILP formulations of the standard VRP. Solving the resulting MILP provides an optimal plan that satisfies the given mission specification. The paper also presents two mission planning applications. Copyright (C) 2011 John Wiley & Sons, Ltd.
In this work, a series of novel formulations for a commercial territory design problem motivated by a real-world case are proposed. The problem consists on determining a partition of a set of units located in a territ...
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In this work, a series of novel formulations for a commercial territory design problem motivated by a real-world case are proposed. The problem consists on determining a partition of a set of units located in a territory that meets multiple criteria such as compactness, connectivity, and balance in terms of customers and product demand. Thus far, different versions of this problem have been approached with heuristics due to its NP-completeness. The proposed formulations are integer quadratic programming models that involve a smaller number of variables than heretofore required. These models have also enabled the development of an exact solution framework, the first ever derived for this problem, that is based on branch and bound and a cut generation strategy. The proposed method is empirically evaluated using several instances of the new quadratic models as well as of the existing linear models. The results show that the quadratic models allow solving larger instances than the linear counterparts. The former were also observed to require fewer iterations of the exact method to converge. Based on these results the combination of the quadratic formulation and the exact method are recommended to approach problem instances associated with medium-sized cities.
This paper proposes a new unit commitment (UC) formulation for a power system with significant levels of wind generation. The proposed scheme departs from existing unit commitments in that it explicitly models the day...
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This paper proposes a new unit commitment (UC) formulation for a power system with significant levels of wind generation. The proposed scheme departs from existing unit commitments in that it explicitly models the day-ahead predicted residual demand probability density function (PDF) including the effect of wind power curtailment. This PDF is then used to define a constraint on the probability of the residual demand exceeding the scheduled reserve, which is imposed in addition to the standard N-1 deterministic security criterion. This hybrid probabilistic/deterministic form maintains the mixed-integerlinear structure that makes the proposed UC compatible with highly efficient commercially available solvers. Numerical examples illustrate the economical and technical benefits obtained by systematically including wind curtailment as decisions variables in the UC. In addition, the paper computes the hourly day-ahead UC schedule over the course of one year for a typical power system to illustrate the impact of wind power penetration on measures such as operation costs, incremental costs, emission levels, on/off unit switching operations, and reserve levels.
This work addresses the scheduling of continuous single stage multiproduct plants with parallel units and shared storage tanks. Processing tasks are energy intensive and we consider time-dependent electricity pricing ...
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This work addresses the scheduling of continuous single stage multiproduct plants with parallel units and shared storage tanks. Processing tasks are energy intensive and we consider time-dependent electricity pricing and availability together with multiple intermediate due dates, handled as hard constraints. A new discrete-time aggregate formulation is proposed to rapidly plan the production levels. It is combined with a continuous-time model for detailed scheduling as the essential part of a rolling-horizon algorithm. Their computational performance is compared to traditional discrete and continuous-time full-space formulations with all models relying on the Resource-Task Network (RTN) process representation. The results show that the new models and algorithm can generate global optimal schedules much more efficiently than their counterparts in problems involving unlimited power availability. Under restricted power, the aggregate model underestimates the electricity cost, which may cause the rolling-horizon approach to converge to a suboptimal solution, becoming the discrete-time model a better approach. (c) 2010 Elsevier Ltd. All rights reserved.
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