Multi-item capacitated lot-sizing problems with setup times and pricing decisions

We study a multi-item capacitated lot-sizing problem with setup times and pricing (CLSTP) over a finite and discrete planning horizon. In this class of problems, the demand for each independent item in each time period is affected by pricing decisions. The corresponding demands are then satisfied through production in a single capacitated facility or from inventory, and the goal is to set prices and determine a production plan that maximizes total profit. In contrast with many traditional lot-sizing problems with fixed demands, we cannot, without loss of generality, restrict ourselves to instances without initial inventories, which greatly complicates the analysis of the CLSTP. We develop two alternative Dantzig–Wolfe decomposition formulations of the problem, and propose to solve their relaxations using column generation and the overall problem using branch-and-price. The associated pricing problem is studied under both dynamic and static pricing strategies. Through a computational study, we analyze both the efficacy of our algorithms and the benefits of allowing item prices to vary over time. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2010Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65027/1/20394_ftp.pd

A computational analysis of lower bounds for big bucket production planning problems

In this paper, we analyze a variety of approaches to obtain lower bounds for multi-level production planning problems with big bucket capacities, i.e., problems in which multiple items compete for the same resources. We give an extensive survey of both known and new methods, and also establish relationships between some of these methods that, to our knowledge, have not been presented before. As will be highlighted, understanding the substructures of difficult problems provide crucial insights on why these problems are hard to solve, and this is addressed by a thorough analysis in the paper. We conclude with computational results on a variety of widely used test sets, and a discussion of future research

Central nervous system corticotropin releasing factor (CRF) systems contribute to increased anxiety-like behavior during opioid withdrawal : an analysis of neuroanatomical substrates

Increased release of the stress neurotransmitter corticotropin-releasing factor (CRF) in the extended amygdala mediates ethanol withdrawal signs such as anxiety -like behaviors. The present study determined whether anxiety-like consequences of naloxone-precipitated withdrawal from morphine dependence also involves CRF hyperactivity in the extended amygdala, by selectively infusing antalarmin, an antagonist that selectively blocks CRF 1 receptors, into the nucleus accumbens shell (NAC) or the central amygdala (CeA). Anxiety-like behavior was assessed as a reduction in willingness to explore the open arms of an elevated plus maze. Male Wistar rats were implanted with bilateral cannulae in the NAC shell or the CeA. Dependence was induced by daily injections of 10 mg/ kg of morphine over a period of 4 days (non-dependent controls received vehicle in place of morphine). Eight hours after morphine injection on the fourth day, withdrawal was precipitated by naloxone (0.33 mg/kg; controls received vehicle in place of naloxone. Bilateral infusion of the CRF-1 receptor antagonist antalarmin (1.0, 3.3, or 10.0nmol) or vehicle preceded naloxone by 10 min. Naloxone administered after morphine but not vehicle reduced the relative time spent in, and number of entries into, the open vs. closed arms of the maze. Antalarmin dose-dependently attenuated these morphine withdrawal anxiety-like signs when infused in the NAC shell but not CeA. The same dose of intra-NAC antalarmin that attenuated anxiety-like signs antalarmin reduced activity (number of closed arm entries), suggesting that blunting CRF's arousing effects in the NAC may result in a reduction of morphine withdrawal anxiet