The single-item lot sizing problem under a periodic energy limitation is considered in this paper. Identical and parallel capacitated machines constitute the production system, each one consuming a certain amount of e...
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The single-item lot sizing problem under a periodic energy limitation is considered in this paper. Identical and parallel capacitated machines constitute the production system, each one consuming a certain amount of energy when being switched on, when reserved, and when producing. We consider a cost for starting-up the machines, a reservation cost to keep the machines ready for production, in addition to classical lot sizing costs, such as, joint setup cost, unit production cost and unit holding cost, all being time-dependent. Besides the classical lot sizing decisions of how much and in which periods to produce, we have to decide the number of machines to switch on and to switch off in each period. We show that this problem is NP-hard even under restricted conditions. In contrast, assuming stationary energy parameters, we propose two polynomialtime dynamic programming algorithms to solve the problem to optimality. The first algorithm is proposed for the case with null setup cost, null reservation cost and null reservation energy consumption, and runs in O ((MT4)-T-5) time, with M being the number of machines and T the number of periods. We show that we can extend this algorithm to solve the generalized version of the problem in time complexity O ((MT6)-T-6).
In this paper, we deal with two variants of graph matching, the graph isomorphism with restriction and the prefix set of graph isomorphism. The former problem is known to be NP-complete, whereas the latter problem is ...
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In this paper, we deal with two variants of graph matching, the graph isomorphism with restriction and the prefix set of graph isomorphism. The former problem is known to be NP-complete, whereas the latter problem is known to be GI-complete. We propose polynomialtime exact algorithms for these problems on partial k-trees.
This paper addresses the single-item uncapacitated lot sizing problem with batch ordering under the buyback contract between a retailer and a supplier. The form of this type of contract consists in returning all the u...
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This paper addresses the single-item uncapacitated lot sizing problem with batch ordering under the buyback contract between a retailer and a supplier. The form of this type of contract consists in returning all the unused products at the end of every w periods (with w >= 1) to the supplier. This problem is studied with only full batches (OFB), which means that the procurement in each period is restricted to a multiple of a constant batch size, where each demand is satisfied without backlogging and all cost parameters are time-dependent. In this extension, we consider a stepwise discontinuous procurement cost structure due to the fixed cost per batch replenished, incurred by the retailer, in addition to the classical lot sizing costs. Several properties of the optimal solution are proposed to develop an efficient dynamic programming algorithm performed in time complexity O(Tw). (C) 2018, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
The (un-weighted) vertex cover problem in general graphs is a classical NP-hard problem, but it is polynomialtime solvable in bipartite graphs. This paper considers two combinatorial optimization problems. One is the...
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ISBN:
(纸本)9781538677438
The (un-weighted) vertex cover problem in general graphs is a classical NP-hard problem, but it is polynomialtime solvable in bipartite graphs. This paper considers two combinatorial optimization problems. One is the weighted vertex cover problem and the other is the so-called maximum edge packing problem. We proved that in bipartite graphs, maximum edge packing problem can be viewed as the dual of the weighted vertex cover problem, and hence these two problems are polynomialtime solvable. We explored the relationships between these two problems in bipartite graphs and some structural results are obtained accordingly. Furthermore, a new efficient algorithm for the weighted vertex cover problem in bipartite graphs is also derived. Our method generalized some previous algorithms for un-weighted vertex cover in bipartite graphs.
In this paper, we introduce the problem of transmitting particles to a target point by the effect of a repulsion actuator (RA). In this problem, we are given a polygonal domain P and a target point t inside it. Also, ...
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ISBN:
(纸本)9783030046514;9783030046507
In this paper, we introduce the problem of transmitting particles to a target point by the effect of a repulsion actuator (RA). In this problem, we are given a polygonal domain P and a target point t inside it. Also, there is a particle at each point of P. The question is which particles can get to the target point t by activating a RA in P. We present the first polynomial time algorithm to solve this problem.
We consider a version of parallel machine scheduling with rejection. There are m machines and n jobs, and each job is either accepted and then processed by one of the machines, or rejected and then a rejected fee is p...
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ISBN:
(纸本)9781450365673
We consider a version of parallel machine scheduling with rejection. There are m machines and n jobs, and each job is either accepted and then processed by one of the machines, or rejected and then a rejected fee is paid. The goal is to find a way of partitioning the set of jobs into two subsets, the subset of accepted and the subset of rejected jobs, the subset of accepted and the subset of rejected jobs, and to schedule all the accepted jobs to m machines such that the sum of the makespan and the total rejection fees of the rejected jobs is minimized. In this paper, we focus on a special case of this NP-hard problem where the processing time of each job is a power of 2. We show that if one more condition is satisfied, namely, if the ratio of rejection fee and processing time of each job can be indexed in the same way as the order of processing time, then the problem is polynomialtime solvable. We therefore present an efficient algorithm for this case. Our result is also applicable to the case in which the processing times are the powers of q, where q is a positive integer.
This paper addresses the stochastic lot-sizing problem with quantity discounts. In particular, we examine the uncapacitated finite-period economic lot-sizing problem in which the parameters in each period are random a...
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This paper addresses the stochastic lot-sizing problem with quantity discounts. In particular, we examine the uncapacitated finite-period economic lot-sizing problem in which the parameters in each period are random and discrete. When an order is placed, a fixed cost is incurred and an all-unit quantity discount is awarded based on the quantity ordered. The lead time is zero and the order is delivered immediately. First we study the case with overstocks by which the excess inventory incurs a holding cost. The objective in this case is to minimize the expected total cost including ordering and holding costs. The stochastic dynamics is modeled with a scenario tree. We characterize properties Of the optimal policy and propose a polynomial time algorithm with complexity O(n(3)) for single discount level, where n is the number of nodes in the scenario tree. We extend the results to cases allowing stockout and multi-discount levels. Numerical experiments are conducted to evaluate the performance of the algorithm and to gain the management insights. (C) 2016 Elsevier Ltd. All rights reserved.
This paper considers a single machine scheduling problem in which each job is assigned an individual due date based on a common flow allowance (i.e. all jobs have slack due date). The goal is to find a sequence for jo...
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This paper considers a single machine scheduling problem in which each job is assigned an individual due date based on a common flow allowance (i.e. all jobs have slack due date). The goal is to find a sequence for jobs, together with a due date assignment, that minimizes a non-regular criterion comprising the total weighted absolute lateness value and common flow allowance cost, where the weight is a position-dependent weight. In order to solve this problem, an O (n log n) timealgorithm is proposed. Some extensions of the problem are also shown.
In this paper, we study the single-item lot sizing problem under a capacity reservation contract. A manufacturer is replenished by an external supplier with batch deliveries and a certain capacity is reserved at the s...
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In this paper, we study the single-item lot sizing problem under a capacity reservation contract. A manufacturer is replenished by an external supplier with batch deliveries and a certain capacity is reserved at the supplier level with an advantageous cost. In addition to the classical ordering and inventory holding costs, for each batch ordered under the reserved capacity a fixed cost per batch is incurred;and for batches exceeding this capacity a higher fixed cost per batch is paid, typically through the purchase from the spot market. We identify various NP-hard cases, propose a pseudo-polynomialtime dynamic programming algorithm under arbitrary parameters, show that the problem admits an FPTAS and give polynomial time algorithms for special cases. We finally state a list of open problems for further research. (C) 2016 Elsevier B.V. All rights reserved.
We consider the problem of clique coloring, that is, coloring the vertices of a given graph such that no (maximal) clique of size at least two is monocolored. It is known that interval graphs are 2-clique colorable. I...
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We consider the problem of clique coloring, that is, coloring the vertices of a given graph such that no (maximal) clique of size at least two is monocolored. It is known that interval graphs are 2-clique colorable. In this paper we prove that B-1-EPG graphs (edge intersection graphs of paths on a grid, where each path has at most one bend) are 4-clique colorable. Moreover, given a B1-EPG representation of a graph, we provide a linear timealgorithm that constructs a 4-clique coloring of it. (C) 2017 Elsevier B.V. All rights reserved.
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