A fluid EOQ model of perishable items with intermittent high and low demand rates

We consider a stochastic fluid EOQ-type model with demand rates that operate in a two-state random environment. This environment alternates between exponentially distributed periods of high demand and generally distributed periods of low demand. The inventory level starts at some level q, and decreases linearly at rate a during the periods of high demand, and at rate b <a at periods of low demand. The inventory level is refilled to level q when level 0 is hit or when an expiration date is reached, whichever comes first. We determine the steady-state distribution of the inventory level, as well as other quantities of interest like the distribution of the time between successive refills. Finally, for a given cost/revenue structure, we determine the long-run average profit, and we consider the problem of choosing q such that the profit is optimized

A compound Poisson EOQ model for perishable items with intermittent high and low demand periods

We consider a stochastic EOQ-type model, with demand operating in a two-state random environment. This environment alternates between exponentially distributed periods of high demand and generally distributed periods of low demand. The inventory level starts at some level q, and decreases according to different compound Poisson processes during the periods of high demand and of low demand. The inventory level is refilled to level q when level 0 is hit or when an expiration date is reached, whichever comes first. We determine various performance measures of interest, like the distribution of the time until refill, the expected amount of discarded material and of material held (inventory), and the expected values of various kinds of shortages. For a given cost/revenue structure, we can thus determine the long-run average profit

Operational Research: Methods and Applications

Throughout its history, Operational Research has evolved to include a variety of methods, models and algorithms that have been applied to a diverse and wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first aims to summarise the up-to-date knowledge and provide an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion. It should be used as a point of reference or first-port-of-call for a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order

Improving Logistics Processes in a Global Spares Supply Organization

This thesis studies logistics processes related to balancing of the inventories between supply channels. Balancing operations are based on lateral transshipments, which are a recent field of studies and have been on the focus of the optimization studies during the past few years. The findings of the study model current processes and material flows, reveals issues related to processes, studies cost figures and provides alternative solutions for improvement. The main objective of the study is to provide a construction that makes it possible to improve decision-making related to inventory balancing between the distribution centers of the organization. This study answers three main questions: How does the existing inventory network look like? What kind of issues and development areas are there? How is it possible to improve current inventory pooling operations? This study is a single case study carried out in a global spares supply organization willing to improve their logistics processes. To achieve the objects of the study, several methods were needed: literature survey on logistics models, sourcing methods and logistics cost models, qualitative information through interviews in the case company, study of the existing process descriptions and contract terms in addition to several quantitative analyses on the performance of the operations. Due to multiple methods, reliability and validity is increased as is the extent of the study. Findings of this study demonstrate that the expansion of the company on Asian markets is in its infancy and that the processes lack standardization and appropriate tools. Asian Distribution Center is highly dependent on European suppliers. Despite the strategic aspect of Asian supplier markets, supplier base does not yet provide a comprehensive alternative for balancing transshipments from Europe. This underlines the importance of processes on inventory balancing as they provide significant cost reductions against local sourcing in Asia at the moment. It is recommended to continue balancing using European supply chains, but to set up ocean deliveries for major flows and to focus sourcing efforts on establishing local suppliers for materials that have the highest importance by their total value. Future studies should provide more detailed information on quality and sourcing related costs to improve cost analysis and comparisons in addition to benchmarking values and ratios. /Kir1

Special Issue of the Manufacturing Engineering Society (MES)

This book derives from the Special Issue of the Manufacturing Engineering Society (MES) that was launched as a Special Issue of the journal Materials. The 48 contributions, published in this book, explore the evolution of traditional manufacturing models toward the new requirements of the Manufacturing Industry 4.0 and present cutting-edge advances in the field of Manufacturing Engineering focusing on additive manufacturing and 3D printing, advances and innovations in manufacturing processes, sustainable and green manufacturing, manufacturing systems (machines, equipment and tooling), metrology and quality in manufacturing, Industry 4.0, product lifecycle management (PLM) technologies, and production planning and risks

Operational research:methods and applications

Throughout its history, Operational Research has evolved to include a variety of methods, models and algorithms that have been applied to a diverse and wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first aims to summarise the up-to-date knowledge and provide an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion. It should be used as a point of reference or first-port-of-call for a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order