We propose a general hierarchical procedure to address real-life job shop scheduling problems. The shop typically produces a variety of products, each with its own arrival stream, its own route through the shop and a given customer due date. The procedure first determines the manufacturing lot sizes for each product. The objective is to minimize the expected lead time, and therefore we model the production environment as a queueing network. Given these lead times, release dates are set dynamically. This in turn creates a time window for every manufacturing order in which the various operations have to be sequenced. The sequencing logic is based on an Extended Shifting Bottleneck Procedure. These three major decisions are next incorporated into a four-phase, hierarchical, operational implementation scheme. A small numerical example is used to illustrate the methodology. The final objective however is to develop a procedure that is useful for large, real-life shops. We therefore report on a real-life application.Queueing Networks, Leadtime Estimation, Lot Size, Multimachine Scheduling

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This research was supported by the Environmental Report for Flanders (VMM), the Science Foundation of Flanders (FWO-project G.0063.98) and BOF fund of UFSIA. 2 The authors like to thank Ilse Bilsen and Ruth Creten for their contribution.

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This paper analyses the effectiveness of policy measures aimed at triggering a modal shift in the freight transport market. The analysis is based on the inventory-theoretic framework that studies modal choice from a business logistics viewpoint. The crux of the inventory-theoretic approach lies in the fact that explicit attention is paid to all costs in the supply chain that are affected by the choice of transport mode. After a brief literature review on the inventory-theoretic framework, the framework is used to calculate the market shares of different freight transport modes for a hypothetical transport market. In a second step, the impact of some policy measures on the market shares of the transport modes is calculated. By way of illustration, the analysis is applied to the market for container transport from a seaport to its hinterland. It is shown that a combination of certain policy measures can lead to significant modal shifts from road transport to intermodal transport.

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In this paper, an overview of different analytic queueing models for traffic on road networks is presented. In the literature, it has been shown that queueing models can be used to adequately model uninterrupted traffic flows. This paper gives a broad review on this literature. Moreover, it is shown that the developed published methodologies (which are mainly single node oriented) can be extended towards queueing networks. First, an extension towards queueing networks with infinite buffer sizes is evaluated. Secondly, the assumption of infinite buffer sizes is dropped leading to queueing networks with finite buffer sizes. The impact of the buffer size when comparing the different queueing network methodologies is studied in detail. The paper ends with an analytical application tool to facilitate the optimal positioning of the counting points on a highway.

Access to immunization varies greatly across the world. In order to increase vaccine coverage, the required vaccines need to be able to reach the targeted population. However, in low-and middleincome countries, this often turns out to be a challenging task. This article provides a literature review on vaccine distribution chains in low-and middle-income countries and consists of two main parts. The first part elaborates on the characteristics and challenges inherent to such distribution chains. In order to obtain a complete overview, both quantitative and qualitative papers are included. In the second part, relevant operations research and operations management literature is structured according to seven classification criteria: decision level, methodology, part of the vaccine distribution chain modelled, uncertainties and characteristics covered, performance measures, real-life applicability, and countries and vaccines covered. Throughout these classifications, a comparison is made between the issues reported in practice and those investigated in the operations research and operations management literature. Based on this analysis, we identify trends and conclude that several gaps exist, providing a promising avenue for future research.