This paper studies a variant of the three-dimensional bin packing problem (3D-BPP), where the bin height can be adjusted to the cartons it packs. The bins and cartons to be packed are assumed rectangular in shape. The...
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This paper studies a variant of the three-dimensional bin packing problem (3D-BPP), where the bin height can be adjusted to the cartons it packs. The bins and cartons to be packed are assumed rectangular in shape. The cartons are allowed to be rotated into any one of the six positions that keep the carton edges parallel to the bin edges. This greatly increases the difficulty of finding a good solution since the search space expands significantly comparing to the 3D-BPP where the cartons have fixed orientations. A mathematical (mixed integer programming) approach is modified based on [Chen, C. S., Lee, S. M., Shen, Q. S., 1995. An analytical model for the container loading problem. European journal of Operational Research 80 (1), 68-761 and numerical experiments indicate that the mathematical approach is not suitable for the variable bin height 3D-BPP. A special bin packing algorithm based on packing index is designed to utilize the special problem feature and is used as a building block for a genetic algorithm designed for the 3D-BPP. The paper also investigates the situation where more than one type of bin are used and provides a heuristic for packing a batch of cartons using the genetic algorithm. Numerical experiments show that our proposed method yields quick and satisfactory results when benchmarked against the actual packing practice and the MIP model with the latest version of CPLEX. (C) 2009 Elsevier B.V. All rights reserved.
In this paper we introduce flexible models for capacitated discrete location problems. We describe three different points of view of a location problem in a logistics system. Different mathematical programming formula...
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In this paper we introduce flexible models for capacitated discrete location problems. We describe three different points of view of a location problem in a logistics system. Different mathematical programming formulations are presented, illustrated by examples and compared using a battery of test problems. Extensive computational tests are done showing the potentials and limits of this kind of resolution approach. (C) 2009 Elsevier B.V. All rights reserved.
The problem of allocation of orders for custom parts among suppliers in make to order manufacturing is formulated as a single- or multi-objective mixedinteger program. Given a set of customer orders for products, the...
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The problem of allocation of orders for custom parts among suppliers in make to order manufacturing is formulated as a single- or multi-objective mixedinteger program. Given a set of customer orders for products, the decision maker needs to decide from which supplier to purchase custom parts required for each customer order. The selection of suppliers is based on price and quality of purchased parts and reliability of on time delivery. The risk of defective or unreliable supplies is controlled by the maximum number of delivery patterns (combinations of suppliers delivery dates) for which the average defect rate or late delivery rate can be unacceptable. Furthermore, the quantity or business volume discounts offered by the suppliers are considered. Numerical examples are presented and some computational results are reported. (C) 2009 Elsevier Ltd. All rights reserved.
Optimizing production planning has tremendous economic impact for many industrial production systems. In this paper, the planning problem of a class of production systems with hybrid dynamics and constraints is consid...
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Optimizing production planning has tremendous economic impact for many industrial production systems. In this paper, the planning problem of a class of production systems with hybrid dynamics and constraints is considered with practical background of power generation planning and other applications. The problem is solved within the Lagrangian relaxation framework, with the system wide demand and resource limit constraints relaxed by Lagrange multipliers. A new method is developed in this paper to obtain the exact optimal solutions to the subproblems with hybrid dynamics and constraints efficiently without discretizing the continuous production levels or introducing intermediate levels of relaxation. A novel definition of the discrete state associated with a consecutive time span is introduced so that solving each subproblem is converted into solving a number of continuous optimization problems and a discrete optimization problem separately. An efficient double dynamic programming (DP) method is developed to solve these subproblems and the principle of optimality is guaranteed for both the continuous and discrete problem. The production levels in a consecutive running span with non-convex piecewise linear cost functions are determined in a DP forward sweep without discretization. The DP method is then applied to determine the optimal discrete operating states across time efficiently. Numerical testing results demonstrate that the new method is efficient and effective for optimization based production planning with the complex hybrid dynamics and constraints.
Infinite group relaxations of integer programs (IP) were introduced by Gomory and Johnson (Math Program 3:23-85, 1972) to generate cutting planes for general IPs. These valid inequalities correspond to real-valued fun...
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Infinite group relaxations of integer programs (IP) were introduced by Gomory and Johnson (Math Program 3:23-85, 1972) to generate cutting planes for general IPs. These valid inequalities correspond to real-valued functions defined over an appropriate infinite group. Among all the valid inequalities of the infinite group relaxation, extreme inequalities are most important since they are the strongest cutting planes that can be obtained within the group-theoretic framework. However, very few properties of extreme inequalities of infinite group relaxations are known. In particular, it is not known if all extreme inequalities are continuous and what their relations are to extreme inequalities of finite group problems. In this paper, we describe new properties of extreme functions of infinite group problems. In particular, we study the behavior of the pointwise limit of a converging sequence of extreme functions as well as the relations between extreme functions of finite and infinite group problems. Using these results, we prove for the first time that a large class of discontinuous functions is extreme for infinite group problems. This class of extreme functions is the generalization of the functions given by Letchford and Lodi (Oper Res Lett 30(2):74-82, 2002), Dash and Gunluk (Proceedings 10th conference on integerprogramming and combinatorial optimization. Springer, Heidelberg, pp 33-45 (2004), Math Program 106:29-53, 2006) and Richard et al. (Math Program 2008, to appear). We also present several other new classes of discontinuous extreme functions. Surprisingly, we prove that the functions defining extreme inequalities for infinite group relaxations of mixedinteger programs are continuous.
One-dimensional infinite group problems have been extensively studied and have yielded strong cutting planes for mixedinteger programs. Although numerical and theoretical studies suggest that group cuts can be signif...
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One-dimensional infinite group problems have been extensively studied and have yielded strong cutting planes for mixedinteger programs. Although numerical and theoretical studies suggest that group cuts can be significantly improved by considering higher-dimensional groups, there are no known facets for infinite group problems whose dimension is larger than two. In this paper, we introduce an operation that we call sequential-merge. We prove that the sequential-merge operator creates a very large family of facet-defining inequalities for high-dimensional infinite group problems using facet-defining inequalities of lower-dimensional group problems. Further, they exhibit two properties that reflect the benefits of using facets of high-dimensional group problems: they have continuous variables' coefficients that are not dominated by those of the constituent low-dimensional cuts and they can produce cutting planes that do not belong to the first split closure of MIPs. Further, we introduce a general scheme for generating valid inequalities for lower-dimensional group problems using valid inequalities of higher-dimensional group problems. We present conditions under which this construction generates facet-defining inequalities when applied to sequential-merge inequalities. We show that this procedure yields some two-step MIR inequalities of Dash and Gunluk.
In Andersen et al. (Lecture Notes in Computer Science, vol. 4513, Springer, Berlin, pp. 1-15, 2007) we studied a mixed-integer set arising from two rows of a simplex tableau. We showed that facets of such a set can be...
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In Andersen et al. (Lecture Notes in Computer Science, vol. 4513, Springer, Berlin, pp. 1-15, 2007) we studied a mixed-integer set arising from two rows of a simplex tableau. We showed that facets of such a set can be obtained from lattice point free triangles and quadrilaterals associated with either three or four variables. In this paper we generalize our findings and show that, when upper bounds on the non-basic variables are also considered, further classes of facets arise that cannot be obtained from triangles and quadrilaterals. Specifically, when exactly one upper bound on a non-basic variable is introduced, stronger inequalities that can be derived from pentagons involving up to six variables also appear.
A new multi-generation of cuts algorithm is presented in this paper to improve the efficiency of Benders decomposition approach for the cases that optimality cuts are difficult to be achieved within the iterations of ...
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A new multi-generation of cuts algorithm is presented in this paper to improve the efficiency of Benders decomposition approach for the cases that optimality cuts are difficult to be achieved within the iterations of the algorithm. This strategy is referred to as maximum feasible subsystem (MFS) cut generation strategy. In this approach in each iteration of the Benders algorithm an additional cut is generated that has the property to restrict the value of the objective function of the Benders master problem. To illustrate the efficiency of the proposed strategy, it is applied to a scheduling problem of multipurpose multiproduct batch plant. Two different partitioning alternatives are tested in order to show the importance of the way that a problem is decomposed upon the efficiency of the Benders algorithm. The application of the proposed acceleration procedure results in substantial reduction of CPU solution time and the total number of iterations in both decomposition alternatives. (C) 2009 Elsevier Ltd. All rights reserved.
In this article we deal with deadlock prevention problems for S4PR, a class of generalised Petri nets, which can well model a large class of flexible manufacturing systems where deadlocks are caused by insufficiently ...
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In this article we deal with deadlock prevention problems for S4PR, a class of generalised Petri nets, which can well model a large class of flexible manufacturing systems where deadlocks are caused by insufficiently marked siphons. We present a deadlock prevention methodology that is an iterative approach consisting of two stages. The first one is called siphon control, which is to add for each insufficiently marked minimal siphon a control place to the original net. Its objective is to prevent a minimal siphon from being insufficiently marked. The second one, called control-induced siphon control, is to add a control place to the augmented net with its output arcs connecting to the source transitions, which assures that there are no new insufficiently marked siphons generated. At each iteration, a mixed integer programming approach is adopted for generalised Petri nets to obtain an insufficiently marked minimal siphon from the maximal deadly siphon. This way complete siphon enumeration is avoided that is much more time-consuming for a sizeable plant model than the proposed method. The relation of the proposed method and the liveness and reversibility of the controlled net is obtained. Examples are presented to demonstrate the presented method.
In wireless communication systems, the interference between links results in a challenging scheduling problem. A K-hop interference model is defined as one for which no two links within K-hops can successfully transmi...
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In wireless communication systems, the interference between links results in a challenging scheduling problem. A K-hop interference model is defined as one for which no two links within K-hops can successfully transmit at the same time (note that IEEE 802.11 DCF corresponds to a 2-hop interference model). For a given K, a throughput-optimal scheduler needs to solve a maximum weighted matching problem subject to the K-hop interference constraints. Previous work has mainly focused on developing scheduling algorithms with performance guarantees for the primary interference model (K = 1). For K >= 2, the problem is NP-Complete and cannot be approximated within a constant factor by any polynomial time algorithm. Our algorithm achieves at least a constant fraction (1/3) of the capacity region under any K-hop interference model. The simplicity of the solution and low control complexity makes it highly amenable for practical implementation. Simulation results show that when the communication overhead is taken into account, the delay characteristics of the proposed scheme may be better than the ideal optimal scheduler (given the prices at all the links, the ideal scheduler computes the optimal schedule instantaneously). (C) 2009 Elsevier B.V. All rights reserved.
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