Service capacity pooling in M/G/1 service systems

International audienceWe study the cost-sharing problem among independent service providers in a service capacity pooling system. The effective improvement of such pooling system can be achieved by reducing the resource idleness in case of congestion. In this paper, we model both the service provider and the cooperative coalition as a single server queue. We attempt to answer the following questions: (i) which coalition strategy should be used; and (ii) which allocation rule should be selected in order to maintain the stability of the coalition? In particular, we consider the service pooling with a fixed service capacity for M/G/1 service systems. The benefit of the pooling system is due to the shortened waiting queue in the overall system. We develop the corresponding cooperative game with transferable utility, and analyze the core allocations. Although it is difficult to express a core allocation explicitly for the game, we prove the non-emptiness of the core. We give a reasonable expression of Equal Profit Method to distribute the cost for our game, and investigate a number of cost allocation rules under three typical situations to evaluate the gain of the service pooling strategy for each service provider. The numerical results show that the cost allocation rule proposed gives a reasonable cost-sharing result considering the contribution of each participant

Equivalence, reversibility and symmetry properties in fork/join queueing networks with blocking

In this paper we study quantitative as well as qualitative properties of Fork/Join queueing networks with blocking (FJQN/B's). Specifically, we prove theorems regarding the equivalence of the behavior of a FJQN/B and that of its duals of a circuit-free FJQN/B, and a strongly connected marked graph. In addition, we obtain general conditions that must be satisfied by the service times to guarantee the existence of a long term throughput and its independence on the initial configuration. We also establish conditions under which the reverse of a FJQN/B has the same throughput as the original network. Last, by combining the equivalence results for duals and the reversibility results, we establish a symmetry property for the throughput of a FJQN/B

Manufacturing flow line systems: a review of models and analytical results

The most important models and results of the manufacturing flow line literature are described. These include the major classes of models (asynchronous, synchronous, and continuous); the major features (blocking, processing times, failures and repairs); the major properties (conservation of flow, flow rate-idle time, reversibility, and others); and the relationships among different models. Exact and approximate methods for obtaining quantitative measures of performance are also reviewed. The exact methods are appropriate for small systems. The approximate methods, which are the only means available for large systems, are generally based on decomposition, and make use of the exact methods for small systems. Extensions are briefly discussed. Directions for future research are suggested.National Science Foundation (U.S.) (Grant DDM-8914277

Modelling home care organisations from an operations management perspective

Home Care (HC) service consists of providing care to patients in their homes. During the last decade, the HC service industry experienced significant growth in many European countries. This growth stems from several factors, such as governmental pressure to reduce healthcare costs, demographic changes related to population ageing, social changes, an increase in the number of patients that suffer from chronic illnesses, and the development of new home-based services and technologies. This study proposes a framework that will enable HC service providers to better understand HC operations and their management. The study identifies the main processes and decisions that relate to the field of HC operations management. Hence, an IDEF0 (Integrated Definition for Function Modelling) activity-based model describes the most relevant clinical, logistical and organisational processes associated with HC operations. A hierarchical framework for operations management decisions is also proposed. This analysis is derived from data that was collected by nine HC service providers, which are located in France and Italy, and focuses on the manner in which operations are run, as well as associated constraints, inputs and outputs. The most challenging research areas in the field of HC operations management are also discussed

Extending the Scope of Analytical Methods for Performance Evaluation of Manufacturing Flow Systems

Manufacturing flow systems consisting of machines separated by buffers of finite capacity have been studied a lot in the literature because systems of this type are widely encountered in industry. The basic assumptions are that the processing time of each machine is deterministic and machines are subject to random failures. Failure and repair times of each machine are characterized by probabilistic distributions. The corresponding model is referred to as the asynchronous model. The basic configuration that has been widely studied is the so-called production lines. Analytical methods for performance evaluation of production lines have been developed for two different models: the synchronous model and the continuous flow model. For the range of parameters usually encountered in practical applications, the behavior of either model is close to that of the asynchronous model, and therefore, these models can be used as approximations of asynchronous models. Moreover, for both models, efficie..

A Performance Comparison Of Pull Type Control Mechanisms For Multi-Stage Manufacturing

With the emergence of Just-in-Time manufacturing, production control mechanisms that react rapidly to actual occurrences of demand are gaining importance. Several pull type control mechanisms have been proposed to date, but it is usually difficult to quantify how good these mechanisms are, as well as understanding the structural properties that make them desirable. By using a two stage model and an optimal control framework, we study some of these issues here. Our framework permits quantifying the performance of classical mechanisms such as base stock and kanban and more complex mechanisms such as generalized and extended kanban. We also analyze the tradeoffs between single versus multiple control points and service level constraints on the backorders. 1 Introduction The emergence of Just-in-Time manufacturing approach has underlined the importance of production control and coordination mechanisms that react to actual occurrences of demand rather than future demand forecasts. This ..

CAC Procedures For Delay-constrained VBR Sources

In this paper, we apply the Network Calculus approach to the problem of deriving CAC procedures for leaky bucket constrained sources having arbitrary delay constraints. We compare the relative efficiency of resource allocation disciplines in this context, showing that Generalized Processor Sharing can outperform Complete Partitioning schemes under a judicious choice of the weights allocated to the sources. 1 Motivation Several approaches are presently considered for the design and dimensioning of broadband networks with Quality of Service (QoS) guarantees. The main approach consists in assigning stochastic behaviors to the traffic sources. Then, an analysis based upon queueing models is used to derive performance figures. The CAC procedure is able to provide only "statistical" QoS guarantees, the validity of which depends moreover on the assumptions on the sources. Another approach is gaining attention, which attempts to provide deterministic bounds on QoS criteria, and especially delay. The analysis proceeds by assuming that each source is characterized by some traffic descriptor, to which it is conforming. Then the worst-case sources are derived from which delay bounds are derived. This approach has been initiated by R. Cruz [3, 4]. See also [1]. In this paper we discuss some issues related with Call Acceptance Control (CAC) procedures aiming at providing delay guarantees. We show that, depending on the values of the constraints, traffic has to be accommodated according to Complete Partitioning (CP) or Complete Sharing (CS) schemes. Then, we give a comparison of these FIFO schemes with the Generalized Processor Sharing (GPS) algorithm. Especially, we show that this last performs better than CP, if the weights associated with the sources are optimally derived. 2 Probl..

Optimisation de la chaine logistique avec prise en compte de critères de développement durable (Un focus sur les modèles de gestion de stock)

Les problématiques liées au développement durable modifient fortement les habitudes des consommateurs ainsi que les stratégies des entreprises. Dans ce contexte, l optimisation de la chaîne logistique avec prise en compte de critères de développement durable devient un défi majeur. Néanmoins, les travaux scientifiques basés sur des modèles quantitatifs sont encore rares. Nous contribuons donc à cette littérature en revisitant des modèles classiques d optimisation de gestion de stock en prenant en compte des critères de développement durable. Nous sommes convaincus que les différents aspects du développement durable ne devraient pas être réduits à un seul objectif. Nous proposons donc une approche basée sur l optimisation multi-objectif pour revisiter les modèles economic order quantity en mono- et multi-échelon. Ces modèles sont ensuite utilisés pour analyser les impacts de la coopération client-fournisseur ou de l investissement dans des technologies vertes sur les performances de la chaîne logistique. Par ailleurs, les entreprises deviennent de plus en plus proactives vis-à-vis du développement durable. Nous proposons donc d utiliser des méthodes d aide multicritère à la décision au lieu de considérer le développement durable comme une contrainte dans les modèles. Dans cette optique, l entreprise peut fournir des informations sur les compromis désirables entre les dimensions économiques, environnementales et sociales du développement durable afin d obtenir rapidement une solution satisfaisante.Sustainability concerns are increasingly shaping customers behavior as well as companies strategy. In this context, optimizing the supply chain with sustainability considerations is becoming a critical issue. However, work with quantitative models is still scarce. Our research contributes by revisiting classical inventory models taking sustainability concerns into account. We believe that reducing all aspects of sustainable development to a single objective is not desirable. We thus reformulate single and multi-echelon economic order quantity models as multi-objective problems. These models are then used to study several options such as buyer-supplier coordination or green technology investment. We also consider that firms are becoming increasingly proactive with respect to sustainability. We thus propose to apply multiple criteria decision aid techniques instead of considering sustainability as a constraint. In this sense, the firm may provide preference information about economic, environmental and social tradeoffs and quickly identify a satisfactory solution.CHATENAY MALABRY-Ecole centrale (920192301) / SudocSudocFranceF

Moments of First Passage Times in General Birth-Death Processes

Submitted for publicationWe consider ordinary and conditional first passage times in a general birth-death process. Under existence conditions, we derive closed-form expressions for the $k$th order moment of the defined random variables, $k\geq1$. We also give an explicit condition for a birth-death process to be ergodic degree 3. To the best of our knowledge, the results of this paper are new, except for some already known quantities as we shall mention. Based on the obtained results, we next analyze some interesting applications for markovian queueing systems. In particular, we compute for some non-standard markovian queues, the moments of the busy period duration, the busy cycle duration, and the state-dependent waiting time in queue