非同类机极小化最大完工时间的保密排序问题

提出并研究了一类非同类机的极小化最大完工时间的保密排序问题Rm||Cmax.该问题的模型参数分为若干组,每个组都由一个不愿意共享或公开自己数据的单位所拥有.基于随机矩阵变换构造了一个不泄露私有数据且与原问题等价的安全规划模型,求解该安全模型可以获得问题的最优解,而且各单位的隐私数据仍然保持不被泄露.     

Job sequencing rules for minimizing the expected makespan in flexible machines

We consider scheduling of a deteriorating flexible machine that is capable of processing a number of diverse jobs with negligible setup times between jobs. Specifically, we develop rules for sequencing N jobs on such a machine such that its expected makespan (sum of all job processing times and machine down-time) is minimized. Using the Weibull distribution to characterize machine failures in our model, we permit different jobs to contribute to machine deterioration (and hence its failure) at different failure rates, and do not require these rates to remain constant with machine-use time. We validate the effectiveness of these job sequencing rules for different cases, using extensive simulation tests.     

A hybrid imperialist competitive algorithm for minimizing makespan in a multi-processor open shop

In this paper a new mixed-integer linear programming (MILP) model is proposed for the multi-processor open shop scheduling (MPOS) problems to minimize the makespan with considering independent setup time and sequence dependent removal time. A hybrid imperialist competitive algorithm (ICA) with genetic algorithm (GA) is presented to solve this problem. The parameters of the proposed algorithm are tuned by response surface methodology (RSM). The performance of the algorithm to solve small, medium and large sized instances of the problem is evaluated by introducing two performance metrics. The quality of obtained solutions is compared with that of the optimal solutions for small sized instances and with the lower bounds for medium sized instances. Also some computational results are presented for large sized instances.     

An improved max-flow-based lower bound for minimizing maximum lateness on identical parallel machines

In this paper, we introduce a new concept of semi-preemptive scheduling and we show how it can be used to derive a maximum-flow-based lower bound for the P|r_j|L_max which dominates the well-known preemptive lower bound. We show that, in some cases, the proposed bound strictly dominates the preemptive one while having the same complexity.     

A heuristic for minimizing the expected makespan in two-machine flow shops with consistent coefficients of variation

The paper deals with the classical problem of minimizing the makespan in a two-machine flow shop. When the job processing times are deterministic, the optimal job sequence can be determined by applying Johnson’s rule. When they are independent and exponential random variables, Talwar’s rule yields a job sequence that minimizes the makespan stochastically.Assuming that the job processing times are independently and Weibull distributed random variables, we present a new job sequencing rule that includes both Johnson’s and Talwar’s rules as special cases. The proposed rule is applicable as a heuristic whenever the job processing times are characterized by their means and the same coefficient of variation. Simulation results show that it leads to very encouraging results when the expected makespan is minimized.     

A global MILP model for FMS scheduling

Flexible manufacturing systems (FMS) require intelligent scheduling strategies to achieve their principal benefit — combining high flexibility with high productivity. A mixed-integer linear programming model (MILP) is presented here for FMS scheduling. The model takes a global view of the problem and specifically takes into account constraints on storage and transportation. Both of these constrained resources are critical for practical FMS scheduling problems and are difficult to model. The MILP model is explained and justified and its complexity is discussed. Two heuristic procedures are developed, based on an analysis of the global MILP model. Computational results are presented comparing the performance of the different solution strategies. The development of iterative global heuristics based on mathematical programming formulations is advocated for a wide class of FMS scheduling problems.     

An algorithm for minimizing Boolean functions

The Cranfield method of minimizing Boolean functions is examined, and it is shown that the method does not always produce all the minimal sums. An algorithm is given which produces all the minimal sums and uses the Cranfield method as a first stage in the minimization procedure.     

An improved model averaging scheme for logistic regression

Recently, penalized regression methods have attracted much attention in the statistical literature. In this article, we argue that such methods can be improved for the purposes of prediction by utilizing model averaging ideas. We propose a new algorithm that combines penalized regression with model averaging for improved prediction. We also discuss the issue of model selection versus model averaging and propose a diagnostic based on the notion of generalized degrees of freedom. The proposed methods are studied using both simulated and real data.     

Iterative algorithms for part grouping and loading in cellular reconfigurable manufacturing systems

A reconfigurable manufacturing system (RMS), one of state-of-the-art manufacturing system technologies, is the one designed at the outset for rapid changes in its hardware and software components in order to quickly adjust its production capacity and functionality in response to market or system changes. In this study, we consider a cellular RMS with multiple reconfigurable machining cells (RMCs), each of which has numerical control machines, a setup station, and an automatic material handling and storage system. Each machine within the RMC has an automatic tool changer and a tool magazine of a limited capacity. Two important operational problems, part grouping and loading, are considered in this study. Part grouping is the problem of allocating parts to RMCs, and loading is the problem of allocating operations and their cutting tools to machines within the RMC. An integer programming model is suggested to represent the two problems at the same time for the objective of balancing the workloads assigned to machines. Then, due to the complexity of the problem, we suggest two iterative algorithms in which the two problems are solved repeatedly until a solution is obtained. Computational experiments were done on various test instances and the results are reported.     

An improved model for noise barriers in a moving fluid

We study a problem of diffraction of a cylindrical acoustic wave from an absorbing half plane in a moving fluid introducing Myers' condition [M.K. Myers, On the acoustic boundary condition in the presence of flow, J. Sound Vibration 71 (1980) 429] and present an improved form of the analytic solution for the diffracted field. The importance of the work lies in the fact that Myers' condition (a generalization of Ingard's impedance condition) is now the accepted form of the boundary condition for impedance barriers with flow and hence yields a correct form of the field. The method of solution consists of Fourier transform, Wiener-Hopf technique and the modified method of stationary phase.     

An effective heuristic for minimising makespan on unrelated parallel machines

Scheduling independent tasks on unrelated machines is a relatively difficult and challenging problem. In this paper, we develop a tabu search based heuristic for minimising makespan for the above problem that can provide good quality solutions for practical size problems within a reasonable amount of computational time. Our adaptation of this tabu search uses hashing to control the tabu restrictions of the search process and requires fewer critical parameters than many of the common tabu search approaches employed for combinatorial optimisation. Hashing is simple to implement and very effective in providing a near-optimal solution. Computational results are presented to demonstrate the effectiveness of the proposed heuristic.     

New algorithms and complexity status of the reducibility problem of sequences in open shop scheduling minimizing the makespan

We consider the problem of minimizing the makespan in open shop scheduling. The decision problem whether a given sequence in open shop scheduling is irreducible has already been considered, however, has not been solved yet. A sequence is an acyclic orientation of the Hamming graph K _n ×K _m . Irreducible sequences in open shop are the local optimal elements. We present two variants of algorithms based on the specific properties of the H-comparability graph. The first is polynomial whereas the second is exponential. The irreducibility is co-NP. The stated properties argue whether it belongs to P. The complexity status of the considered decision problem is updated.     

An improved decision support model for scheduling production in an engineer-to-order manufacturer

4OR - This paper outlines a mathematical model to solve a scheduling problem for a company engineering and producing propellers to order. Nonås and Olsen (Comput Oper Res...     

一种改进的几何活动轮廓模型

针对传统的几何活动轮廓模型在分割具有凹形边界时,演化曲线不能准确定位的缺点,提出了一种改进的几何活动轮廓模型,该模型通过在原模型的演化方程中增加一个正的常数项,使得演化曲线在未到达目标边界时,加速曲线演化,而在到达边界附近时,该加速项逐渐减小为零,从而能够很好的完成对凹形边界的分割.实验证明,该方法不仅能够分割具有凹形边界的目标,还能够使演化过程加速,提高几何活动轮廓模型的分割速度.     

An improved model of age-structured population dynamics

The classical model of age-dependent population dynamics is improved. Instead of the traditional renewal equation, a new approach is developed to describe the reproduction process of the population. The composition of a population is redefined to contain the pre-birth individuals, and the disadvantages of the classical model avoided. Moreover, the improved model turns out to be an initial value problem, which is mathematically more convenient to deal with. Existence and uniqueness results for the nonlinear nonautonomous system of model equations are obtained. It is shown that the classical model and its time delay generalization are two degenerate cases of the improved model.     

An MILP for scheduling problems in an FMS with one vehicle

This paper concerns the mathematical formulation and optimal solutions for the Flexible Manufacturing Systems Scheduling Problem (FMSSP) with one vehicle. This linear formulation differs from the previously published ones as it takes into account the maximum number of jobs allowed in the system, limited input/output buffer capacities, empty vehicle trips and no-move-ahead trips simultaneously. Our objective is to propose optimal solutions for small and medium-sized instances and to examine a number of commonly used assumptions and heuristics. Computational experiments are carried out on instances adapted from Bilge and Ulusoy [Bilge, Ü., Ulusoy, G., 1995. A time window approach to simultaneous scheduling of machines and material handling system in an FMS. Operations Research 43, 1058–1070] and the following heuristics are evaluated: FIFO (First In First Out) rules for input/output buffer management; and FIFO, SPT (Shortest Processing Time), STT (Shortest Travel Time) and MOQS (Maximum Outgoing Queue Size) rules concerning the vehicle. The consequences of classical assumptions are also studied: ignoring empty trips, ignoring no-move-ahead constraints, and ignoring vehicle-disjunction constraints. The numerical experiments provide a set of optimal solutions and allow to evaluate the performances of heuristic search schemes.     

An improved reservoir simulation model in the petroleum industry

Sensible prediction of petroleum production from a well reliesheavily on the accurate determination of reservoir constantsduring pressure drawdown or build-up tests. Models for simulatinga fractured reservoir have been developed to accommodate theslope changes in the measured pressure curves. This paper presentsa modification to Barenblatt et al.s (1960) prototype, suitablefor the simulation of a fractured reservoir. The modificationis intended to provide an improved interpretation of fluid flowin fractured porous media, as compared to the traditional conceptualization.The significant differences in terms of reservoir pressure predictionbetween this model and the one suggested by Warren & Root(1963) are identified and shown to depend on the compressibilitymagnitudes of fractures and matrix blocks. The analytical solutionsof this improved model have been obtained for both the caseof radial flow with quasi-steady matrix flow, and for the caseof one-dimensional linear flow where transient matrix flow isretained.