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91.
This paper presents the results of developing a branch and price algorithm and an ejection chain method for nurse rostering problems. The approach is general enough to be able to apply it to a wide range of benchmark nurse rostering instances. The majority of the instances are real world applications. They have been collected from a variety of sources including industrial collaborators, other researchers and various publications. The results of entering these algorithms in the 2010 International Nurse Rostering Competition are also presented and discussed. In addition, incorporated within both algorithms is a dynamic programming method which we present. The algorithm contains a number of heuristics and other features which make it very effective on the broad rostering model introduced. 相似文献
92.
The paper deals with an as yet unexplored combinatorial optimization problem concerning balancing complex transfer lines in the machining/process environment. In contrast to similar problems for assembly lines, in transfer line balancing, tasks are grouped into blocks. All tasks of each block are executed simultaneously (in parallel) by one piece of equipment (spindle head). For the transfer lines considered in this paper, spindle heads at each station are activated in serial-parallel order. The set of all available spindle heads is known beforehand. Precedence, cycle time, compatibility, and parallelism constraints for the blocks and tasks are given. The line investment cost is estimated by the sum of block and station costs. The problem is to assign all tasks (using the available blocks) such that all constraints are respected and line investment cost is at a minimum. This paper focuses on solving the problem via a branch-and-bound algorithm. An approach for obtaining an efficient lower bound is offered, based on a reduction of the initial problem to a set partitioning problem. Computational experiments reveal that the proposed approach is efficient mathematically and can be used to solve practical transfer line design problems of a medium size. 相似文献
93.
This paper presents an efficient branch and bound algorithm for globally solving sum of geometric fractional functions under geometric constraints, which arise in various practical problems. By using an equivalent transformation and a new linear relaxation technique, a linear relaxation programming problem of the equivalent problem is obtained. The proposed algorithm is convergent to the global optimal solution by means of the subsequent solutions of a series of linear programming problems. Numerical results are reported to show the feasibility of our algorithm. 相似文献
94.
Marina Ville 《Geometriae Dedicata》2009,140(1):145-162
Branch points of a real 2-surface Σ in a 4-manifold M generalize branch points of complex curves in complex surfaces: for example, they can occur as singularities of minimal surfaces.
We investigate such a branch point p when Σ is topologically embedded. It defines a link L(p), the components of which are closed braids with the same axis up to orientation. If Σ is closed without boundary, the contribution
of p to the degree of the normal bundle of Σ in M can be computed on the link L(p), in terms of the algebraic crossing numbers of its components and of their linking numbers with one another.
相似文献
95.
The aim of this paper is to discuss different branch and bound methods for solving indefinite quadratic programs. In these
methods the quadratic objective function is decomposed in a d.c. form and the relaxations are obtained by linearizing the
concave part of the decomposition. In this light, various decomposition schemes have been considered and studied. The various
branch and bound solution methods have been implemented and compared by means of a deep computational test.
相似文献
96.
In a mixed-model assembly line, varying models of the same basic product are to be produced in a facultative sequence. This results to a short-term planning problem where a sequence of models is sought which minimizes station overloads. In practice – e.g. the final assembly of cars – special sequencing rules are enforced which restrict the number of models possessing a certain optional feature k to rk within a subsequence of sk successive models. This problem is known as car sequencing. So far, employed solution techniques stem mainly from the field of Logic and Constraint Logic Programming. In this work, a special Branch & Bound algorithm is developed, which exploits the problem structure in order to reduce combinatorial complexity. 相似文献
97.
本文讨论FlowShop排序问题Fm|prmu|∑ωjCj给出了求解该问题的一个分枝定界法. 相似文献
98.
In this paper, we study the zero-inventory production and distribution problem with a single transporter and a fixed sequence
of customers. The production facility has a limited production rate, and the delivery truck has non-negligible traveling times
between locations. The order in which customers may receive deliveries is fixed. Each customer requests a delivery quantity
and a time window for receiving the delivery. The lifespan of the product starts as soon as the production for a customer’s
order is finished, which makes the product expire in a constant time. Since the production facility and the shipping truck
are limited resources, not all the customers may receive the delivery within their specified time windows and/or within product
lifespan. The problem is then to choose a subset of customers from the given sequence to receive the deliveries to maximize
the total demand satisfied, without violating the product lifespan, the production/distribution capacity, and the delivery
time window constraints. We analyze several fundamental properties of the problem and show that these properties can lead
to a fast branch and bound search procedure for practical problems. A heuristic lower bound on the optimal solution is developed
to accelerate the search. Empirical studies on the computational effort required by the proposed search procedure comparing
to that required by CPLEX on randomly generated test cases are reported. 相似文献
99.
Airport management: taxi planning 总被引:4,自引:0,他引:4
Ángel G. Marín 《Annals of Operations Research》2006,143(1):191-202
The Taxi Planning studies the aircraft routing and scheduling on the airport ground. This is a dynamic problem, which must be updated almost every time that a new aircraft enters or exits the system. Taxi Planning has been modelled using a linear multicommodity flow network model with side constraints and binary variables. The flow capacity constraints are used to represent the conflicts and competence between aircrafts using a given airport capacity. The “Branch and Bound” and “Fix and Relax” methodologies have been used. The computational tests have been run at the Madrid-Barajas airport, using actual data from the airport traffic. 相似文献
100.
本文提出了一种求解带二次约束和线性约束的二次规划的分支定界算法.在算法中,我们运用Lipschitz条件来确定目标函数和约束函数的在每个n矩形上的上下界,对于n矩形的分割,我们采用选择n矩形最长边的二分法,同时我们采用了一些矩形删除技术,在不大幅增加计算量的前提下,起到了加速算法收敛的效果.从理论上我们证明了算法的收敛性,同时数值实验表明该算法是有效的. 相似文献