A concern for public safety on the roads, cost pressures from global competition and a need to find more energy efficient forestry practices are driving forest companies to develop new transport management systems and...
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A concern for public safety on the roads, cost pressures from global competition and a need to find more energy efficient forestry practices are driving forest companies to develop new transport management systems and novel approaches to using trucking resources. A 0/1 integerlinearprogramming truck route-scheduling model was developed and tested in two medium-sized New Zealand forest companies. One company indicated that truck fleet size could be reduced by 25 to 30%. The other company indicated that a reduction in fleet size of 50% was possible. Substantial cost savings were also identified. In practice, it is expected that the reductions in fleet size and cost savings would not be quite as large as those indicated because of a number of simplifying assumptions included in the models. Results and solution times would be suitable for using the model as a tactical planning tool for small to medium sized problems. It would not be suitable as an aid for dispatching log trucks or for use with large and complex transport operations.
This paper proposes a constrained optimal power dispatch algorithm (COPD) for electricity and ancillary services auctions. The problem is decomposed into social welfare maximization subproblem which is solved by the m...
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This paper proposes a constrained optimal power dispatch algorithm (COPD) for electricity and ancillary services auctions. The problem is decomposed into social welfare maximization subproblem which is solved by the mixed integer linear programming (MILP) and real power loss minimization subproblem which is solved by the quadratic programming (QP). The proposed COPD is tested on the modified IEEE 30 bus system with six generator companies (GenCos) bidding to sell the electricity and ancillary services. The social welfare of the proposed competitive electricity and ancillary services price scheme is higher than the competitive electricity price scheme and the constrained down payment (CDP) scheme adopted by the future Thailand power pool, thereby leading to a lower average electricity price. With the spot price including the marginal electricity price and marginal ancillary services prices, the correct price signal could be sent to all market participants. In addition, using the proposed scheme, the individual generator congestion gaming is not effective. (C) 2003 Elsevier Science B.V. All rights reserved.
A number of open loop indicators for the determination of the disturbance rejection capability of a system have been proposed in the literature in the last decade. These tools are useful in screening regulatory proces...
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A number of open loop indicators for the determination of the disturbance rejection capability of a system have been proposed in the literature in the last decade. These tools are useful in screening regulatory process control structures in an early design stage since they are based on minimum modelling requirements. This paper presents mixed-integerlinearprogramming formulations for the efficient determination of the disturbance rejection measures proposed by Skogestad and Wolff (IFAC Workshop on Interactions between Process Design and Process Control (1992) Oxford: Pergamon). Furthermore, an extension of these disturbance rejection measures to nonlinear systems is presented. A close relation between the ideas of steady state flexibility test and index problems (AICHE J 24 (1978) 1021;Comput. Chem. Eng. 11 (1987) 319) and the disturbance rejection measures proposed by Skogestad and Wolff (IFAC Workshop on Interactions between Process Design and Process Control (1992) Oxford: Pergamon) is shown to exist. (C) 2002 Published by Elsevier Science Ltd.
A hoist controlled by a computer is widely used for moving electroplates which is chemically treated in a sequence of tanks. The hoist scheduling directly affects the throughput of a production system. The objective o...
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A hoist controlled by a computer is widely used for moving electroplates which is chemically treated in a sequence of tanks. The hoist scheduling directly affects the throughput of a production system. The objective of the hoist scheduling problem is to schedule the moves to maximize the throughput. This paper investigates the hoist scheduling problem, a specific material handling issue, in a manufacturing environment. The scope of the study is in the area of single hoist cyclic scheduling with multiple tanks. The purpose of the study is to develop a mixed integer linear programming model that can be used to schedule multiple tanks and improve throughput in a process industry. Specifically, a method has been proposed to estimate the processing time in a bottleneck stage with multiple tanks. (C) 2002 Elsevier Science Ltd. All rights reserved.
We present a framework for solving logical topology design (LTD) problems in a constrained amount of computation time. Our framework uses a search space dimensionality (SSD) reduction technique that exploits a tradeof...
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We present a framework for solving logical topology design (LTD) problems in a constrained amount of computation time. Our framework uses a search space dimensionality (SSD) reduction technique that exploits a tradeoff between computation time and solution quality. We have demonstrated that our framework offers improved solution quality in comparison to an existing SSD reduction technique reported in the literature.
District heating plants are becoming more common in European cities. These systems make it possible to furnish users with warm water while locating the production plants in the outskirts having the double benefit of l...
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District heating plants are becoming more common in European cities. These systems make it possible to furnish users with warm water while locating the production plants in the outskirts having the double benefit of lowering the impact of pollution on the center of the city and achieving better conversion performances. In order to amortize the costs throughout the year, the system often includes a combined heat and power (CHP) plant, to exploit the energy during the summer as well, when the demand for warm water decreases. A linearprogramming model for the optimal resource management of such a plant is presented and some results for a real case are reported. A distribution network design problem is also addressed and solved by means of mixed integer linear programming.
The authors solve the deep space optimal dual-spacecraft reconfiguration problem in the presence of a collision avoidance requirement. The approach is distinguished by its reliance on the necessary optimality conditio...
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The authors solve the deep space optimal dual-spacecraft reconfiguration problem in the presence of a collision avoidance requirement. The approach is distinguished by its reliance on the necessary optimality conditions, similar in spirit to the Euler-Lagrange equations. In this venue, the collision avoidance guarantee is identified as a state inequality constraint in the corresponding optimal control problem. This modification significantly changes the solution characteristic of the optimal control and involves the introduction of the nonsmooth multiplier, which dynamically monitors the violation of the state constraints. The time evolution of this multiplier essentially determines the switching times, which in turn, lead to the characterization of the optimal relative state trajectory. At the same time, we recognize that the extension of the proposed approach to more than two spacecraft scenarios involves expressions for the control parameters that are not easy to solve. However, the proposed scheme can be employed to obtain nontrivial upper bounds for the general optimal multiple spacecraft reconfiguration by reducing it to a sequence of two-at-a-time collision-free reconfigurations. (CSA)
This paper considers the Modular Capacitated Location Problem ( MCLP) which consists of finding the location and capacity of the facilities, to serve a set of customers at a minimum total cost. Each customer has an as...
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This paper considers the Modular Capacitated Location Problem ( MCLP) which consists of finding the location and capacity of the facilities, to serve a set of customers at a minimum total cost. Each customer has an associated demand and the capacity of each potential location must be chosen from a finite and discrete set of available capacities. Practical applications of this problem can be found in the location of warehouses, schools, health care services or other types of public services. For the MCLP different mixed integer linear programming models are proposed. The authors develop upper and lower bounds on the problem's optimal value and present computational results with randomly generated tests problems.
The economic viability of the modern day mine is highly dependent upon careful planning and management. Declining trends in average ore grades, increasing mining costs and environmental considerations will ensure that...
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The economic viability of the modern day mine is highly dependent upon careful planning and management. Declining trends in average ore grades, increasing mining costs and environmental considerations will ensure that this situation will remain in the foreseeable future. The operation and management of a large open pit mine having a life of several years is an enormous and complex task. Though a number of optimization techniques have been successfully applied to resolve some important problems, the problem of determining an optimal production schedule over the life of the deposit is still very much unresolved. In this paper we will critically examine the techniques that are being used in the mining industry for production scheduling indicating their limitations. In addition, we present a mixed integer linear programming model for the scheduling problems along with a Branch and Cut solution strategy. Computational results for practical sized problems are discussed.
The economic viability of the modern day mine is highly dependent upon careful planning and management. Declining trends in average ore grades, increasing mining costs and environmental considerations will ensure that...
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The economic viability of the modern day mine is highly dependent upon careful planning and management. Declining trends in average ore grades, increasing mining costs and environmental considerations will ensure that this situation will remain in the foreseeable future. The operation and management of a large open pit mine having a life of several years is an enormous and complex task. Though a number of optimization techniques have been successfully applied to resolve some important problems, the problem of determining an optimal production schedule over the life of the deposit is still very much unresolved. In this paper we will critically examine the techniques that are being used in the mining industry for production scheduling indicating their limitations. In addition, we present a mixed integer linear programming model for the scheduling problems along with a Branch and Cut solution strategy. Computational results for practical sized problems are discussed.
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