High Multiplicity Scheduling with Switching Costs for few Products

We study a variant of the single machine capacitated lot-sizing problem with sequence-dependent setup costs and product-dependent inventory costs. We are given a single machine and a set of products associated with a constant demand rate, maximum loading rate and holding costs per time unit. Switching production from one product to another incurs sequencing costs based on the two products. In this work, we show that by considering the high multiplicity setting and switching costs, even trivial cases of the corresponding "normal" counterparts become non-trivial in terms of size and complexity. We present solutions for one and two products.Comment: 10 pages (4 appendix), to be published in Operations Research Proceedings 201

Cyclic Lot-Sizing Problems with Sequencing Costs

We study a single machine lot-sizing problem, where n types of products need to be scheduled on the machine. Each product is associated with a constant demand rate, maximum production rate and inventory costs per time unit. Every time when the machine switches production between products, sequencing costs are incurred. These sequencing costs depend both on the product the machine just produced and the product the machine is about to produce. The goal is to find a cyclic schedule minimizing total average costs, subject to the condition that all demands are satisfied. We establish the complexity of the problem and we prove a number of structural properties largely characterizing optimal solutions. Moreover, we present two algorithms approximating the optimal schedules by augmenting the problem input. Due to the high multiplicity setting, even trivial cases of the corresponding conventional counterparts become highly non-trivial with respect to the output sizes and computational complexity, even without sequencing costs. In particular, the length of an optimal solution can be exponential in the input size of the problem. Nevertheless, our approximation algorithms produce schedules of a polynomial length and with a good quality compared to the optimal schedules of exponential length

Toward a comprehensive water-quality modeling of Barnegat Bay : development of ROMS to WASP coupler

Author Posting. © Coastal Education and Research Foundation, 2017. This article is posted here by permission of Coastal Education and Research Foundation for personal use, not for redistribution. The definitive version was published in Journal of Coastal Research SI78 (2017): 34-45, doi:10.2112/SI78-004.1.The Regional Ocean Modeling System (ROMS) has been coupled with the Water Quality Analysis Simulation Program (WASP) to be used in a comprehensive analysis of water quality in Barnegat Bay, New Jersey. The coupler can spatially aggregate hydrodynamic information in ROMS cells into larger WASP segments. It can also be used to resample ROMS output at a finer temporal scale to meet WASP time-stepping requirements. The coupler aggregates flow components, temperature, and salinity in ROMS output for input to WASP via a hydrodynamic linkage file. The coupler was tested initially with idealized cases designed to verify the water mass balance and conservation of constituent mass using one-to-one and one-to-many connectivity options between segments. A realistic example from the Toms River embayment, a subdomain of Barnegat Bay, was used to demonstrate the functionality of the coupling. A WASP eutrophication model accounting for dissolved oxygen (DO), nitrogen, and constant phytoplankton concentrations was applied to explore the distribution and trends in DO and nitrogen in the embayment for the period of July–August 2012. Results of DO modeling indicate satisfactory agreement with measurements collected at in-bay stations and also indicate that this coupled approach, despite substantial differences in spatiotemporal discretization between the models, provides adequate predictive capabilities.Funding was provided by the NJDEP and the Coastal and Marine Geology Program of the USGS

Assessing Spiritual Development in Business Students: Lessons Learned and a Suggested Process

As Christian higher education institutions increasingly engage in continuous quality improvement and outcome measurement, research on spiritual development is filtering down to undergraduate business programs. This paper presents lessons learned from a pilot cross-sectional survey of Abilene Christian University undergraduate business students who completed the Faith Maturity Scale (Benson, Donahue & Erickson, 1993) and responded to other questions about faith development. Based on the results, a number of helpful observations were made for the ACU business program. A method and process for assessing spiritual development at multiple Christian colleges is proposed

A Major Asymmetric Dust Trap in a Transition Disk

The statistics of discovered exoplanets suggest that planets form efficiently. However, there are fundamental unsolved problems, such as excessive inward drift of particles in protoplanetary disks during planet formation. Recent theories invoke dust traps to overcome this problem. We report the detection of a dust trap in the disk around the star Oph IRS 48 using observations from the Atacama Large Millimeter/submillimeter Array (ALMA). The 0.44-millimeter-wavelength continuum map shows high-contrast crescent-shaped emission on one side of the star originating from millimeter-sized grains, whereas both the mid-infrared image (micrometer-sized dust) and the gas traced by the carbon monoxide 6-5 rotational line suggest rings centered on the star. The difference in distribution of big grains versus small grains/gas can be modeled with a vortex-shaped dust trap triggered by a companion.Comment: 25 pages, 7 figures (accepted version prior to language editing

Sovereign Rating Changes - Do They Provide New Information for Stock Markets?

The purpose of this paper is to examine the impact of sovereign rating changes on international financial markets using a comprehensive database of 42 countries, covering the major regions in the world over the period 1995-2003. In general, we find that rating agencies provide stock and foreign exchange markets with new tradable information. Specifically, rating upgrades (downgrades) significantly increased (decreased) USD denominated stock market returns and decreased (increased) volatility. Whereas the mean response is contributed evenly by the local currency stock returns and exchange rate changes that make up the USD returns, only the foreign exchange volatility was behind the USD denominated return volatility. In addition, we find significant asymmetric effects of rating announcements. The market responses - both return and volatility - are more pronounced in the cases of downgrades, foreign currency debt, emerging market debt, and during crisis periods. This study has important policy implications for international investors' asset allocation plans and for regulatory bodies such as the Basel Committee who increasingly rely upon Moody's, Standard and Poor's and Fitch's ratings for their regulatory regimes

Contrasting vulnerability of drained tropical and high-latitude peatlands to fluvial loss of stored carbon

Carbon sequestration and storage in peatlands rely on consistently highwater tables. Anthropogenic pressures including drainage, burning, land conversion for agriculture, timber, and biofuel production, cause loss of peat-forming vegetation and exposure of previously anaerobic peat to aerobic decomposition. This can shift peatlands from net CO2 sinks to large CO2 sources, releasing carbon held for millennia. Peatlands also export significant quantities of carbon via fluvial pathways, mainly as dissolved organic carbon (DOC). We analyzed radiocarbon (14C) levels of DOC in drainage water from multiple peatlands in Europe and Southeast Asia, to infer differences in the age of carbon lost from intact and drained systems. In most cases, drainage led to increased release of older carbon from the peat profile but withmarked differences related to peat type. Very low DOC-14C levels in runoff from drained tropical peatlands indicate loss of very old (centuries to millennia) stored peat carbon. High-latitude peatlands appear more resilient to drainage; 14C measurements from UK blanket bogs suggest that exported DOC remains young (500 year) carbon in high-latitude systems. Rewetting at least partially offsets drainage effects on DOC age

A Systematic Review of Patients’ Values, Preferences, and Expectations for the Treatment of Metastatic Prostate Cancer

Peer reviewedPublisher PD

Metformin Preconditioning Improves Hepatobiliary Function and Reduces Injury in a Rat Model of Normothermic Machine Perfusion and Orthotopic Transplantation

Background. Preconditioning of donor livers before organ retrieval may improve organ quality after transplantation. We investigated whether preconditioning with metformin reduces preservation injury and improves hepatobiliary function in rat donor livers during ex situ normothermic machine perfusion (NMP) and after orthotopic liver transplantation. Methods. Lewis rats were administered metformin via oral gavage, after which a donor hepatectomy was performed followed by a standardized cold storage period of 4 hours. Graft assessment was performed using NMP via double perfusion of the hepatic artery and portal vein. In an additional experiment, rat donor livers preconditioned with metformin were stored on ice for 4 hours and transplanted to confirm postoperative liver function and survival. Data were analyzed and compared with sham-fed controls. Results. Graft assessment using NMP confirmed that preconditioning significantly improved ATP production, markers for hepatobiliary function (total bile production, biliary bilirubin, and bicarbonate), and significantly lowered levels of lactate, glucose, and apoptosis. After orthotopic liver transplantation, metformin preconditioning significantly reduced transaminase levels. Conclusions. Preconditioning with metformin lowers hepatobiliary injury and improves hepatobiliary function in an in situ and ex situ model of rat donor liver transplantation