Supply optimization for a pulp and paper mill network

A real case of procurement planning of wood fiber between a paper mill and fiber suppliers, e.g. sawmills, is modelled and validated. Several sourcing options are available to the paper mill (in-house sawmills, external sawmills, trading sawmills, and partners). The model optimizes the choice of suppliers, determines the supply option (contract or spot market) and decides the quantities to order for each period as well as the contractual annual volume guarante

Engineering process for capacity-driven web services

This paper presents a novel approach for the engineering of capacity-driven Web services. By capacity, we mean how a Web service is empowered with several sets of operations from which it selectively triggers a set of operations with respect to some run-time environmental requirements. Because of the specificities of capacity-driven Web services compared to regular (i.e., mono-capacity) Web services, their engineering in terms of design, development, and deployment needs to be conducted in a complete specific way. Our approach define an engineering process composed of five steps: (1) to frame the requirements that could be put on these Web services, (2) to define capacities and how these capacities are triggered, and last but not least link these capacities to requirements, (3) to identify the processes in term of business logic that these Web services could implement, (4) to generate the source code, and (5) to generate the capacity-driven Web Services Description Language (c-WSDL)

No-wait scheduling of a two-machine flow-shop to minimize the makespan under non-availability constraints and different release dates

International audienceIn this paper, we consider the two-machine no-wait flow-shop scheduling problem, when every machine is subject to one non-availability constraint and jobs have different release dates. The non-availability intervals of the machines overlap and they are known in advance. We aim to find a non-resumable schedule that minimises the makespan. We propose several lower bounds and upper bounds. These bounding procedures are used in a branch-and-bound algorithm. Computational experiments are carried out on a large set of instances and the obtained results show the effectiveness of our method

RETRATO SIN IDENTIFICAR [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Constraint handling strategies in Genetic Algorithms application to optimal batch plant design

Optimal batch plant design is a recurrent issue in Process Engineering, which can be formulated as a Mixed Integer Non-Linear Programming(MINLP) optimisation problem involving specific constraints, which can be, typically, the respect of a time horizon for the synthesis of various products. Genetic Algorithms constitute a common option for the solution of these problems, but their basic operating mode is not always wellsuited to any kind of constraint treatment: if those cannot be integrated in variable encoding or accounted for through adapted genetic operators, their handling turns to be a thorny issue. The point of this study is thus to test a few constraint handling techniques on a mid-size example in order to determine which one is the best fitted, in the framework of one particular problem formulation. The investigated methods are the elimination of infeasible individuals, the use of a penalty term added in the minimized criterion, the relaxation of the discrete variables upper bounds, dominancebased tournaments and, finally, a multiobjective strategy. The numerical computations, analysed in terms of result quality and of computational time, show the superiority of elimination technique for the former criterion only when the latter one does not become a bottleneck. Besides, when the problem complexity makes the random location of feasible space too difficult, a single tournament technique proves to be the most efficient one

Clustering problems in optimization models

We discuss a variety of clustering problems arising in combinatorial applications and in classifying objects into homogenous groups. For each problem we discuss solution strategies that work well in practice. We also discuss the importance of careful modelling in clustering problems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44350/1/10614_2004_Article_BF00121636.pd

Centralized and distributed algorithms for on-line synthesis of maximal control policies under partial observation

This paper deals with the on-line control of partially observed discrete event systems (DES). The goal is to restrict the behavior of the system within a prefix-closed legal language while accounting for the presence of uncontrollable and unobservable events. In the spirit of recent work on the on-line control of partially observed DES (Heymann and Lin 1994) and on variable lookahead control of fully observed DES (Ben Hadj-Alouane et al. 1994c), we propose an approach where, following each observable event, a control action is computed on-line using an algorithm of linear worst-case complexity. This algorithm, called VLP-PO , has the following additional properties: (i) the resulting behavior is guaranteed to be a maximal controllable and observable sublanguage of the legal language; (ii) different maximals may be generated by varying the priorities assigned to the controllable events, a parameter of VLP-PO ; (iii) a maximal containing the supremal controllable and normal sublanguage of the legal language can be generated by a proper selection of controllable event priorities; and (iv) no off-line calculations are necessary. We also present a parallel/distributed version of the VLP-PO algorithm called DI-VLP-PO . This version uses several communicating agents that simultaneously run (on-line) identical versions of the algorithm but on possibly different parts of the system model and the legal language, according to the structural properties of the system and the specifications. While achieving the same behavior as VLO-PO, DI-VLP-PO runs at a total complexity (for computation and communication) that is significantly lower than its sequential counterpart.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45126/1/10626_2005_Article_BF01797138.pd

Developing control and integration software for flexible manufacturing systems

The slow growth of computer-integrated manufacturing is attributed to the complexity of designing and implementing their control and integration software. This article expands on a methodology for designing and implementing this software that was introduced in [16]. The goal of this methodology is to build flexible and resuable control and integration software for computer-integrated manufacturing systems. It hinges upon the concepts of software/hardware components, their assemblages, a distributed common language environment, formal models, and generic controllers. Major sources of flexibility are obtained by decoupling process plan models from the model of the factory floor and by using a generic controller. Reusability is achieved by building selfcontained software/hardware components with general, possibly parametrized, interfaces. The interplay between simulated and actual hardware internals of software/hardware components is used as the basis of a testing strategy that performs off-line simulation followed by on-line testing.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43095/1/10952_2005_Article_BF02265064.pd