A Demand Side Requirements Model to Forecast C-17 Mobility Aircraft Availability

Current aircraft forecasting methods of the Air Mobility Command (AMC) Directorate of Logistics are reliant on the experience of personnel and lead to after the fact, labor-intensive analysis. These deficiencies led AMC to the development of a Mobility Aircraft Availability Forecasting (MAAF) model. The purpose of the MAAF model is threefold: predict aircraft availability in order to provide the Tanker Airlift Control Center (TACC) with a forecast of aircraft that will be available for AMC mission requirements, provide what if capabilities that analyze the effects of tasking and policy changes, and to provide foresight into problems associated with aircraft availability (Briggs, 2003b). This research uses Arena simulation to model C-17 aircraft generation at a major enroute location to determine how significant the factors of crew chief manning and spares levels affect aircraft throughput and turn-times. From the simulation, ANOVA statistical techniques are applied to determine factor significance. In addition, a hierarchical structure of aircraft generation is generated to include the variability of unscheduled maintenance actions. This provides a more precise analysis of expected turn-time duration, which leads to overall throughput of the system. Ultimately, this research provides a key input to the MAAF project that will enable AMC to predict aircraft availability and provide the TACC with a monthly forecast of the number of aircraft that will be available to fulfill AMC mission requirements

Evolution of the Density of States Gap in a Disordered Superconductor

It has only recently been possible to study the superconducting state in the attractive Hubbard Hamiltonian via a direct observation of the formation of a gap in the density of states N(w). Here we determine the effect of random chemical potentials on N(w) and show that at weak coupling, disorder closes the gap concurrently with the destruction of superconductivity. At larger, but still intermediate coupling, a pseudo-gap in N(w) remains even well beyond the point at which off-diagonal long range order vanishes. This change in the elementary excitations of the insulating phase corresponds to a crossover between Fermi- and Bose-Insulators. These calculations represent the first computation of the density of states in a finite dimensional disordered fermion model via the Quantum Monte Carlo and maximum entropy methods.Comment: 4 pages, 4 figure

The Reverse Logistics Process in the Supply Chain and Managing Its Implementation

Increased competition caused by globalization and rapid technological advances has driven organizations to address and make efforts to improve efficiency in their supply chain. Increasing efficiency in reverse logistics processes such as the recovery of the returned products or disposal of end-of-life products is one way in which firms attempt to maintain and increase competitiveness and market share. The volume and monetary value of product flowing in the reverse direction within the supply chain has been and continues to be increasing, particularly as environmental, legal, and customer service requirements increase throughout the marketplace (Guide Jr, Souza et al. 2006). It has been reported that the value of product returns in the commercial sector have exceeded $100 billion annually (Stock, Speh et al. 2002; Guide Jr, Souza et al. 2006). This process of returning products back through the supply chain is the reverse logistics process and it may encompass several different logistics activities. This research effort is actually a compilation of three related research efforts. The first study focuses on the status of the reverse logistics field across multiple disciplines; logistics, operations management, information systems, environmental economics, and business management. The state of the field then provides the structure for a Delphi study on the key factors in a reverse logistics process. This Delphi ranking highlights possible shortcomings in the framework and provides insight into the priorities of practitioners. The second paper analyzes the impact information systems, technologies, and innovation has on the reverse logistics process. It analyzes the information technology capabilities, compatibilities and technologies utilized in the organization and their relationship with reverse logistics performance in the areas of two measures, cost effectiveness and process effectiveness. The final research paper addresses reverse logistics performance metrics within an organization. There is a lack of empirical research regarding reverse logistics metrics, especially in the area of determining if the metrics currently being utilized by practitioners are meeting the information needs of the organizations and the managers who make the resource allocation decisions. There is a need to assess the information reporting abilities of the key reverse logistics metrics in an organization and what aspect of information reporting are they providing. When the three research projects are brought together, they represent one, unique research effort. This effort analyzes various key aspects of the reverse logistics process to include effectiveness of metrics, information systems impact on performance, and practitioners input on key factors impacting reverse logistics processes and how well they compare with the established reverse logistics framework

Reshoring of Service Operations: Evidence from a Delphi Study

Part 20: Data-Driven Manufacturing and Services Operations ManagementInternational audienceThe reshoring phenomenon has been explored mainly in the context of manufacturing, while research on business service still appears lacking behind. To address this gap, the article explores the reshoring phenomenon relevance in the context of business services. The research applies a Delphi method developed along three rounds involving a panel of 18 experts. The results show that, although still being in its infancy, the reshoring phenomenon will impact significantly business services in the next future, but with its own specificity, thus deserving dedicated future research streams. Particularly the experts highlight that the main drivers leading to business service reshoring are quite different with respect to ones identified in manufacturing reshoring literature. Moreover, this study indicates that service reshoring will be fundamental in all the business services in which the technology cannot be considered as the main driver for service delivery and that requires a strong human relationship

Planning of waste electrical and electronic equipment (WEEE) recycling facilities: MILP modelling and case study investigation

Waste electrical and electronic equipment (WEEE) consist of many different substances some of which contain hazardous components and valuable materials. The recovery of WEEE plays a key role on environmental sustainability because it minimizes the negative effects of hazardous materials and helps the efficient use of world's limited resources. Recovery strategies enable companies to collect reusable components and to recycle the material content of WEEE by using operations like sorting, disassembly and bulk recycling. Usually companies associated with municipals collect WEEE from end-users and/or collection points. Then they sell these items to WEEE recycling facilities through bidding. For recycling facilities, it is important to generate the best operational level decisions to receive and handle WEEE. This study contributes to the fulfillment of this need by presenting a mixed integer linear programming model to determine the maximum bid price offer while determining the best operation planning strategies. In order to demonstrate the potential of the proposed model, a real life case study along with several scenarios is studied. The findings of the case study indicate that the model has the potential to enable the decision maker to come with stronger decisions related to both bidding process and operational strategies of the facility.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [111M428]The authors are indebted to the anonymous referees and the Editor for several suggestions, which substantially improved the paper. This research is partially funded by the Scientific and Technological Research Council of Turkey (TUBITAK) under the Grant Number 111M428. The authors wish to acknowledge this valuable support