The Euclidean Steiner tree problem (ESTP) in R-n is to find a shortest network interconnecting p given points in n-dimensional Euclidean space. The problem was first described in the plane and an algorithm with very g...
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The Euclidean Steiner tree problem (ESTP) in R-n is to find a shortest network interconnecting p given points in n-dimensional Euclidean space. The problem was first described in the plane and an algorithm with very good practical efficiency has been proposed to solve this particular case. The generalization for higher dimensions was proposed in the 19th century, however the numerical solution of the problem remains very challenging when n >= 3. We give an overview of the exact algorithms presented in the literature for the ESTP when n >= 3 and discuss their common and distinguished features, their advantages and drawbacks, and some possible directions for improvement toward the numerical solution of large instances of the problem.
We propose a method for solving mixed-integernonlinear programmes (MINLPs) to global optimality by discretization of occurring nonlinearities. The main idea is based on using piecewise linear functions to construct m...
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We propose a method for solving mixed-integernonlinear programmes (MINLPs) to global optimality by discretization of occurring nonlinearities. The main idea is based on using piecewise linear functions to construct mixed-integer linear programme (MIP) relaxations of the underlying MINLP. In order to find a global optimum of the given MINLP, we develop an iterative algorithm which solves MIP relaxations that are adaptively refined. We are able to give convergence results for a wide range of MINLPs requiring only continuous nonlinearities with bounded domains and an oracle computing maxima of the nonlinearities on their domain. Moreover, the practicalness of our approach is shown numerically by an application from the field of gas network optimization.
This paper examines a practical tactical liner ship route schedule design problem, which is the determination of the arrival and departure time at each port of call on the ship route. When designing the schedule, the ...
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This paper examines a practical tactical liner ship route schedule design problem, which is the determination of the arrival and departure time at each port of call on the ship route. When designing the schedule, the availability of each port in a week, i.e., port time window, is incorporated. As a result, the designed schedule can be applied in practice without or with only minimum revisions. This problem is formulated as a mixed-integernonlinear nonconvex optimization model. In view of the problem structure, an efficient holistic solution approach is proposed to obtain global optimal solution. The proposed solution method is applied to a trans-Atlantic ship route. The results demonstrate that the port time windows, port handling efficiency, bunker price and unit inventory cost all affect the total cost of a ship route, the optimal number of ships to deploy, and the optimal schedule. (C) 2014 Elsevier Ltd. All rights reserved.
In this study, we have introduced a fuzzy decision-making approach to design a multi-objective optimal design problem of a multiproduct batch chemical plant. In the crisp decision-making approach, the designer is firs...
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In this study, we have introduced a fuzzy decision-making approach to design a multi-objective optimal design problem of a multiproduct batch chemical plant. In the crisp decision-making approach, the designer is first to solve the multi-objective optimization problem, and then to check whether each optimal objective function value satisfies the rigid preference goal. In real world application, the preference goal for each objective function is an interval bound not a rigid value so that the problem becomes a fuzzy goal optimization problem. A monotonic increasing or decreasing membership function is used to define the degree of satisfaction for each objective function so that the fuzzy goal optimization problem is then represented as an augmented minimax problem formulated as mixed-integer nonlinear programming (MINLP) models. To obtain a unique solution, we have introduced the mixed-integer hybrid differential evolution (MIHDE) to solve the MINLP problems. The MIHDE can straightforwardly solve the problem without any mathematical model transformation. Two examples were used to illustrate the applicability of the proposed interactive algorithm. (C) 2002 Elsevier Science Ltd. All rights reserved.
Cryogenic distillation cascades are proposed to be used today to separate hydrogen isotopes in the fuel cycle of a fusion reactor, It is necessary to design these cascades so that their tritium inventory, is minimal. ...
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Cryogenic distillation cascades are proposed to be used today to separate hydrogen isotopes in the fuel cycle of a fusion reactor, It is necessary to design these cascades so that their tritium inventory, is minimal. We have thus developed optimization tools in order to simultaneously optimize the structure and the operating parameters of these distillation sequences. This leads to the implementation of a mixed-integer nonlinear programming procedure in a process simulator The application concerns the International Thermonuclear Experimental Reactor (ITER) isotope separation system. Successive simulation and optimization studies have been carried out which show the accuracy of the simulation and lead to the suggestion of a new arrangement of units for the cascade, with a higher number of columns.
In this article, we investigate methods to solve a fundamental task in gas transportation, namely the validation of nomination problem: given a gas transmission network consisting of passive pipelines and active, cont...
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In this article, we investigate methods to solve a fundamental task in gas transportation, namely the validation of nomination problem: given a gas transmission network consisting of passive pipelines and active, controllable elements and given an amount of gas at every entry and exit point of the network, find operational settings for all active elements such that there exists a network state meeting all physical, technical, and legal constraints. We describe a two-stage approach to solve the resulting complex and numerically difficult nonconvex mixedintegernonlinear feasibility problem. The first phase consists of four distinct algorithms applying mixedinteger linear, mixedintegernonlinear, nonlinear, and methods for complementarity constraints to compute possible settings for the discrete decisions. The second phase employs a precise continuous nonlinearprogramming model of the gas network. Using this setup, we are able to compute high-quality solutions to real-world industrial instances that are significantly larger than networks that have appeared in the mathematical programming literature before.
We study the acquisition policy decision problem for a supply network involving one manufacturer and multiple suppliers. The manufacturer produces multiple products under uncertain demands and each supplier provides p...
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We study the acquisition policy decision problem for a supply network involving one manufacturer and multiple suppliers. The manufacturer produces multiple products under uncertain demands and each supplier provides price discounts. The problem is to determine the manufacturer's acquisition policy and production levels so as to maximise the manufacturer's expected profit, subject to both the manufacturer's and suppliers' capacities. We present a mixedintegernonlinearprogramming (MINLP) formulation of the problem, for both single- and multiple-sourcing procurement policies. General algebraic modeling system (GAMS) and its solvers, combining external integration functions, are employed to solve the complex MINLP problem. The preliminary computation results and managerial analysis are reported.
Focusing on the energy -conservation train operation issues, this paper proposes an effective real-time train regulation scheme for metro systems with energy storage devices. Specifically, to minimize train timetable ...
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Focusing on the energy -conservation train operation issues, this paper proposes an effective real-time train regulation scheme for metro systems with energy storage devices. Specifically, to minimize train timetable deviation, passenger waiting and energy consumption, we formulate a mixed -integernonlinearprogramming model to generate energy -efficient train regulation strategies. This model explicitly considers the train traffic, passenger load and storage, immediate and delayed uses of regenerative energy. Carefully tailored to the proposed model, we devise an efficient decomposition algorithm to split the original problem into small-scale subproblems. In the algorithm, specific values of binary variables, passenger -flow estimates and logic -based cuts are consecutively identified and updated. Besides, bound contraction and bilinear -specific warming start procedures are particularly designed for further acceleration. Numerical experiments are conducted to validate the proposed model and method. Our energyefficient train regulation strategies can improve train departure punctuality, headway regularity, reduce passenger waiting times, and achieve energy savings. Furthermore, the solution algorithm exhibits promising computational efficiency in real -world experiments, thereby facilitating an online implementation.
Polygeneration, typically involving co-production of methanol and electricity, is a promising energy conversion technology which provides opportunities for high energy utilization efficiency and low/zero emissions. Th...
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Polygeneration, typically involving co-production of methanol and electricity, is a promising energy conversion technology which provides opportunities for high energy utilization efficiency and low/zero emissions. The optimal design of such a complex, large-scale and highly nonlinear process system poses significant challenges. In this article, we present a multiobjective optimization model for the optimal design of a methanol/electricity poly generation plant. Economic and environmental criteria are simultaneously optimized over a superstructure capturing a number of possible combinations of technologies and types of equipment. Aggregated models are considered, including a detailed methanol synthesis step with chemical kinetics and phase equilibrium considerations. The resulting model is formulated as a non-convex mixed-integer nonlinear programming problem. Global optimization and parallel computation techniques are employed to generate an optimal Pareto frontier. (C) 2009 American Institute of Chemical Engineers AIChE J, 56: 1218-1234, 2010
We consider a multi-period revenue maximization and pricing optimization problem in the presence of reference prices. We formulate the problem as a mixedintegernonlinear program and develop a generalized Benders'...
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We consider a multi-period revenue maximization and pricing optimization problem in the presence of reference prices. We formulate the problem as a mixedintegernonlinear program and develop a generalized Benders' decomposition algorithm to solve it. In addition, we propose a myopic heuristic and discuss the conditions under which it produces efficient solutions. We provide analytical results as well as numerical computations to illustrate the efficiency of the solution approaches as well as some managerial pricing insights. (C) 2019 Elsevier B.V. All rights reserved.
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