共查询到20条相似文献,搜索用时 15 毫秒
1.
In this paper, we study the cyclic scheduling problem for electroplating lines where products are loaded into the system at
one end and unloaded at the other end. The electroplating jobs must be processed within a given time window in each tank.
There is no buffer between tanks. Two hoists sharing a common track are used to move products between the tanks in the production
line. The objective is to minimize the production cycle time through scheduling hoist moves. A solution procedure is proposed
in this study. The production line is first divided into two non-overlapping zones with a hoist assigned to each zone. Then
a mixed integer linear programming model is developed for scheduling hoist moves. Computational results on a benchmark example
problem are given in the paper to demonstrate the application of the proposed method. 相似文献
2.
Rupert L. Frank Elliott H. Lieb Robert Seiringer Lawrence E. Thomas 《Publications Mathématiques de L'IHéS》2011,113(1):39-67
We resolve several longstanding problems concerning the stability and the absence of multi-particle binding for N≥2 polarons. Fröhlich’s 1937 polaron model describes non-relativistic particles interacting with a scalar quantized field with coupling \(\sqrt{\alpha}\), and with each other by Coulomb repulsion of strength U. We prove the following: (i) While there is a known thermodynamic instability for U<2α, stability of matter does hold for U>2α, that is, the ground state energy per particle has a finite limit as N→∞. (ii) There is no binding of any kind if U exceeds a critical value that depends on α but not on N. The same results are shown to hold for the Pekar-Tomasevich model. 相似文献
3.
Alex Shenfield Peter J. Fleming Visakan Kadirkamanathan Jeff Allan 《Annals of Operations Research》2010,180(1):213-231
The emerging paradigm of Grid Computing provides a powerful platform for the optimisation of complex computer models, such
as those used to simulate real-world logistics and supply chain operations. This paper introduces a Grid-based optimisation
framework that provides a powerful tool for the optimisation of such computationally intensive objective functions. This framework
is then used in the optimisation of maintenance scheduling strategies for fleets of aero-engines, a computationally intensive
problem with a high-degree of stochastic noise, achieving substantial improvements in the execution time of the algorithm. 相似文献
4.
Some existence and multiplicity results are obtained for periodic solutions of the ordinary p-Laplacian systems: $$\left\{\begin{array}{@{}l@{\quad{}}l}(|u'(t)|^{p-2}u'(t))'=\nabla F(t,u(t)),&\mbox{a.e. }t\in[0,T],\\[4pt]u(0)-u(T)=u'(0)-u'(T)=0\end{array}\right.$$ by using the Saddle Point Theorem, the least action principle and the Three-critical-point Theorem. 相似文献
5.
Generalised ‘join the shortest queue’ policies for the dynamic routing of jobs to multi-class queues
P S Ansell K D Glazebrook C Kirkbride 《The Journal of the Operational Research Society》2003,54(4):379-389
Jobs or customers arrive and require service that may be provided at one of several different stations. The associated routing problems concern how customers may be assigned to stations in an optimal manner. Much of the classical literature concerns a single class of customers seeking service from a collection of homogeneous stations. We argue that many contemporary application areas call for the analysis of routing problems in which many classes of customer seek service provided at a collection of diverse stations. This paper is the first to consider routing policies in such complex environments which take appropriate account of the degree of congestion at each service station. A simple and intuitive class of policies emerges from a policy improvement approach. In a numerical study, the policies were close to optimal in all cases. 相似文献
6.
One decoupling method for multiphysics, multiscale, multidomain applications involves partitioning the problem via explicit
time discretizations in the coupling terms. Specialized, problem-specific techniques are needed for the resulting partitioned
methods to avoid time step restrictions which make long time calculations costly. This report studies unconditionally stable,
uncoupled time stepping methods for a model problem sharing mathematical structure akin to the coupled atmosphere-ocean system.
Three decoupled time stepping algorithms are introduced and their stability and consistency are rigorously examined. Numerical
experiments are performed that study their stability and convergence properties. 相似文献
7.
For Hamiltonian systems with non-canonical structure matrix a new class of numerical integrators is proposed. The methods
exactly preserve energy, are invariant with respect to linear transformations, and have arbitrarily high order. Those of optimal
order also preserve quadratic Casimir functions. The discussion of the order is based on an interpretation as partitioned
Runge–Kutta method with infinitely many stages. 相似文献
8.
In the past decades, resource parameters have been introduced in project scheduling literature to measure the scarceness of
resources of a project instance. In this paper, we incorporate these resource scarceness parameters in the search process
to solve the multi-mode resource constrained project scheduling problem, in which multiple execution modes are available for
each activity in the project. Therefore, we propose a scatter search algorithm, which is executed with different improvement
methods, each tailored to the specific characteristics of different renewable and nonrenewable resource scarceness values.
Computational results prove the effectiveness of the improvement methods and reveal that the procedure is among the best performing
competitive algorithms in the open literature. 相似文献
9.
Mihai Popescu 《Journal of Applied Mathematics and Computing》2008,27(1-2):393-409
We consider the controlled systems where the non-linear term is multiplied by a small scalar parameter ε. In the class of these quasi-linear systems, we shall determine the control and optimal trajectory which minimizes the index of performance represented by quadratics functionals. The initial and final conditions are specified and the final time is free. The presence of the small parameter leads to an approximate solution of the formulated problem of optimum. Thus, the zeroth-order solution is obtained for ε=0. The first order solution results by using the sweep method which determines the perturbation of the control and of the state variable on the optimal neighboring trajectory. 相似文献
10.
Guojing Ren 《Journal of Difference Equations and Applications》2013,19(12):1289-1302
This paper is concerned with asymptotic behaviour of solutions of perturbed dynamic systems on time scales. A time scale version of the Hartman–Wintner theorem is established for a class of time scales. 相似文献
11.
An aggregate deformation homotopy method for min-max-min problems with max-min constraints 总被引:1,自引:0,他引:1
In this paper, the constrained min-max-min problem, which is an essentially nonsmooth and nonconvex problem, is considered.
Based on a twice aggregate function with a modification, an aggregate deformation homotopy method is established. Under some
suitable assumptions, a smooth path from a randomly given point to a solution of the generalized KKT system is proven to exist.
By numerically tracing the smooth path, a globally convergent algorithm for some solution of the problem is given. Some numerical
results are given to show the feasibility of the method. 相似文献
12.
A system consisting of a number of servers, where demands of different types arrive in bursts (modelled by interrupted Poisson
processes), is examined in the steady state. The problem is to decide how many servers to allocate to each job type, so as
to minimize a cost function expressed in terms of average queue sizes. First, an exact analysis is provided for an isolated
IPP/M/n queue. The results are used to compute the optimal static server allocation policy. The latter is then compared to four heuristic
policies which employ dynamic switching of servers from one queue to another (such switches take time and hence incur costs).
This work was carried out in the framework of the collaborative project DOPCHE (Dynamic Operative Policies for Commercial
Hosting Environments), funded by the UK Engineering and Physical Sciences Research Council under its E-Science programme.
The support of the Network of Excellence EuroNGI, funded by the EU, is also acknowledged. 相似文献
13.
José Fernando Gonçalves Mauricio G. C. Resende Jorge J. M. Mendes 《Journal of Heuristics》2011,17(5):467-486
This paper presents a biased random-key genetic algorithm for the resource constrained project scheduling problem. The chromosome
representation of the problem is based on random keys. Active schedules are constructed using a priority-rule heuristic in
which the priorities of the activities are defined by the genetic algorithm. A forward-backward improvement procedure is applied
to all solutions. The chromosomes supplied by the genetic algorithm are adjusted to reflect the solutions obtained by the
improvement procedure. The heuristic is tested on a set of standard problems taken from the literature and compared with other
approaches. The computational results validate the effectiveness of the proposed algorithm. 相似文献
14.
Martin Bohner Kenzhegaly Kenzhebaev Oleksandr Stanzhytskyi 《Journal of Difference Equations and Applications》2017,23(7):1161-1189
In this work, an analogue of Pontryagin’s maximum principle for dynamic equations on time scales is given, combining the continuous and the discrete Pontryagin maximum principles and extending them to other cases ‘in between’. We generalize known results to the case when a certain set of admissible values of the control is not necessarily closed (but convex) and the attainable set is not necessarily convex. At the same time, we impose an additional condition on the graininess of the time scale. For linear systems, sufficient conditions in the form of the maximum principle are obtained. 相似文献
15.
A memetic algorithm based on a NSGAII scheme for the flexible job-shop scheduling problem 总被引:1,自引:0,他引:1
Mariano Frutos Ana Carolina Olivera Fernando Tohmé 《Annals of Operations Research》2010,181(1):745-765
The Flexible Job-Shop Scheduling Problem is concerned with the determination of a sequence of jobs, consisting of many operations, on different machines, satisfying several parallel goals. We introduce a Memetic Algorithm, based on the NSGAII (Non-Dominated Sorting Genetic Algorithm II) acting on two chromosomes, to solve this problem. The algorithm adds, to the genetic stage, a local search procedure (Simulated Annealing). We have assessed its efficiency by running the algorithm on multiple objective instances of the problem. We draw statistics from those runs, which indicate that this Memetic Algorithm yields good and low-cost solutions. 相似文献
16.
In this paper we are interested in the fast and efficient solution of nm×nm symmetric positive definite ill-conditioned Block Toeplitz with Toeplitz Blocks (BTTB) systems of the form T
nm
(f)x=b, where the generating function f is a priori known. The preconditioner that we propose and analyze is an extension of the one proposed in (D. Noutsos and
P. Vassalos, Comput. Math. Appl., 56 (2008), pp. 1255–1270) and it arises as a product of a Block band Toeplitz matrix and matrices that may belong to any trigonometric
matrix algebra. The underlying idea of the proposed scheme is to embody the well known advantages characterizing each component
of the product when used alone. As a result we obtain spectral equivalence and a weak clustering of the eigenvalues of the
preconditioned matrix around unity, ensuring the convergence of the Preconditioned Conjugate Gradient (PCG) method with a
number of iterations independent of the partial dimensions. Finally, we compare our method with techniques already employed
in the literature. A wide range of numerical experiments confirms the effectiveness of the proposed procedure and the adherence
to the theoretical analysis. 相似文献
17.
This paper deals with a multi-class priority queueing system with customer transfers that occur only from lower priority queues
to higher priority queues. Conditions for the queueing system to be stable/unstable are obtained. An auxiliary queueing system
is introduced, for which an explicit product-form solution is found for the stationary distribution of queue lengths. Sample
path relationships between the queue lengths in the original queueing system and the auxiliary queueing system are obtained,
which lead to bounds on the stationary distribution of the queue lengths in the original queueing system. Using matrix-analytic
methods, it is shown that the tail asymptotics of the stationary distribution is exact geometric, if the queue with the highest
priority is overloaded.
相似文献
18.
Best trigonometric approximation in L
p
, 1≦p≦∞, is characterized by a modulus of smoothness, which is equivalent to zero if the function is a trigonometric polynomial
of a given degree. The characterization is similar to the one given by the classical modulus of smoothness. The modulus possesses
properties similar to those of the classical one. 相似文献
19.
We consider a Markov-modulated fluid queue with a finite buffer. It is assumed that the fluid flow is modulated by a background
Markov chain which may have different transitions when the buffer content is empty or full. In Sakuma and Miyazawa (Asymptotic
Behavior of Loss Rate for Feedback Finite Fluid Queue with Downward Jumps. Advances in Queueing Theory and Network Applications,
pp. 195–211, Springer, Cambridge, 2009), we have studied asymptotic loss rate for this type of fluid queue when the mean drift of the fluid flow is negative. However,
the null drift case is not studied. Our major interest is in asymptotic loss rate of the fluid queue with a finite buffer
including the null drift case. We consider the density of the stationary buffer content distribution and derive it in matrix
exponential forms from an occupation measure. This result is not only useful to get the asymptotic loss rate especially for
the null drift case, but also it is interesting in its own light. 相似文献
20.
Daniel M. Oberlin 《Journal of Geometric Analysis》2010,20(2):422-438
We study lower bounds for the Minkowski and Hausdorff dimensions of the algebraic sum E+K of two sets E,K⊂ℝ
d
. 相似文献