A decomposition algorithm for robust lot sizing problem with remanufacturing option

In this paper, we propose a decomposition procedure for constructing robust optimal production plans for reverse inventory systems. Our method is motivated by the need of overcoming the excessive computational time requirements, as well as the inaccuracies caused by imprecise representations of problem parameters. The method is based on a min-max formulation that avoids the excessive conservatism of the dualization technique employed by Wei et al. (2011). We perform a computational study using our decomposition framework on several classes of computer generated test instances and we report our experience. Bienstock and Özbay (2008) computed optimal base stock levels for the traditional lot sizing problem when the production cost is linear and we extend this work here by considering return inventories and setup costs for production. We use the approach of Bertsimas and Sim (2004) to model the uncertainties in the input

Coordination in closed-loop supply chain with price-dependent returns

This paper proposes two Closed-loop Supply Chain (CLSC) games in which a manufacturer sets some green activity programs efforts and a retailer sets the selling price. Both strategies influence the return rate, which is a state variable. The pricing strategy plays a key role in the identification of the best contract to achieve coordination as well as in achieving environmental objectives. The pricing strategy influences the return rate negatively, as consumers delay the return of their goods when the purchasing (and repurchasing) price is high. We then compare a wholesale price contract (WPC) and a revenue sharing contract (RSC) mechanism as both have interesting pricing policy implications. Our result shows that firms coordinate the CLSC through a (WPC) when the sharing parameter is too low while the negative effect of pricing on returns is too severe. In that case, the low sharing parameter deters the manufacturer to accept any sharing agreements. Further, firms coordinate the CLSC when the sharing parameter is medium independent of the negative impact of pricing on returns. When the sharing parameter is too high the retailer never opts for an RSC. We find that the magnitude of pricing effect on returns determines the contract to be adopted: For certain sharing parameter, firms prefer an RSC when the price effect on return is low and a WPC when this effect is high. In all other cases, firms do not have a consensus on the contract to be adopted and coordination is then not achieved

Ablative Z-Pinch Pulsed Plasma Thruster

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77148/1/AIAA-4362-652.pd

Static Testing of Propulsion Elements for Small Multirotor Unmanned Aerial Vehicles

The growing use of small multirotor aircraft has increased the interest in having better performance results especially with the propulsion system. The size of the propellers used on these aircraft operate at low Reynolds numbers that are typically less than 200,000. Static performance testing of ten propeller pairs (tractor and pusher) were completed and is the beginning of a systematic test of propellers used on multirotor systems. The propellers chosen for this initial set of tests were selected from four popular quadrotors. Besides testing the propellers provided with the aircraft, propellers that are sold as replacements from third-party companies were also tested. Both the 3D Robotics Solo and DJI Phantom 3 had multiple propellers tested and a method to compare the resulting endurance is discussed

SOSORT 2012 consensus paper: reducing x-ray exposure in pediatric patients with scoliosis

This 2012 Consensus paper reviews the literature on side effects of x-ray exposure in the pediatric population as it relates to scoliosis evaluation and treatment. Alternative methods of spinal assessment and imaging are reviewed, and strategies for reducing the number of radiographs are developed. Using the Delphi technique, SOSORT members developed consensus statements that describe how often radiographs should be taken in each of the pediatric and adolescent sub-populations

Recovery decisions of a producer in a legislative disposal fee environment

Due to copyright restrictions, the access to the full text of this article is only available via subscription.The main objectives of the environmental legislation originating from extended producer responsibility (EPR) principle are to lead producers to undertake recovery initiatives for their end-of-use products and to promote environmentally desirable product design. It is still controversial whether current implementations of EPR principle are effective in attaining these objectives. This study seeks to answer the following questions: (1) What is the impact of EPR legislation on the product recovery decisions of producers? (2) How do the redesign opportunities (i.e., design for disassembly) affect the willingness of producers for product recovery? (3) How do the investment needs to start recovery practices and the reluctance of producers to allocate sufficient funds for this purpose affect the optimal recovery decisions? We use stylized economic models to represent the implementation in practice and solving our models we obtain closed form and numerical solutions that help us to see the impact of various parameters on the optimal decisions of a producer. Our findings indicate that redesign opportunities encourage producers for more recovery, however the reluctance of producers to cover the initial investments may substantially reduce the effectiveness of the legislation and the recovery amounts.TÜBİTA