3,626 research outputs found

    Quick Response Practices at the Warehouse of Ankor

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    In the warehouse of Ankor, a wholesaler of tools and garden equipment, various problems concerning the storage and retrieval of products arise. For example, heavy products have to be retrieved prior to light products to prevent damage. Furthermore, the layout of the warehouse differs from the layout generally assumed in literature. The goal of this research was to determine storage locations for the products and a routing method to obtain sequences in which products are to be retrieved from their locations. It is shown that despite deviations from the "normal" case, similar savings in route length can be obtained by adapting existing solution techniques. Total labor savings are far less than expected on basis of assumptions made in literature. With a minimum of adaptations to the current situation the average route length can be decreased by 30 %. There is no need for complex techniques.storage;warehousing;optimization;case study;routing

    Tetragonal CuO: A new end member of the 3d transition metal monoxides

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    Monoclinic CuO is anomalous both structurally as well as electronically in the 3dd transition metal oxide series. All the others have the cubic rock salt structure. Here we report the synthesis and electronic property determination of a tetragonal (elongated rock salt) form of CuO created using an epitaxial thin film deposition approach. In situ photoelectron spectroscopy suggests an enhanced charge transfer gap Δ\Delta with the overall bonding more ionic. As an end member of the 3d transition monoxides, its magnetic properties should be that of a high TNT_N antiferromagnet

    Tendency Bias Correction in Coupled and Uncoupled Global Climate Models with a Focus on Impacts over North America

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    We revisit the bias correction problem in current climate models, taking advantage of state-of-the-art atmospheric reanalysis data and new data assimilation tools that simplify the estimation of short-term (6 hourly) atmospheric tendency errors. The focus is on the extent to which correcting biases in atmospheric tendencies improves the models climatology, variability, and ultimately forecast skill at subseasonal and seasonal time scales. Results are presented for the NASA GMAO GEOS model in both uncoupled (atmosphere only) and coupled (atmosphereocean) modes. For the uncoupled model, the focus is on correcting a stunted North Pacific jet and a dry bias over the central United States during boreal summerlong-standing errors that are indeed common to many current AGCMs. The results show that the tendency bias correction (TBC) eliminates the jet bias and substantially increases the precipitation over the Great Plains. These changes are accompanied by much improved (increased) storm-track activity throughout the northern midlatitudes. For the coupled model, the atmospheric TBCs produce substantial improvements in the simulated mean climate and its variability, including a much reduced SST warm bias, more realistic ENSO-related SST variability and teleconnections, and much improved subtropical jets and related submonthly transient wave activity. Despite these improvements, the improvement in subseasonal and seasonal forecast skill over North America is only modest at best. The reasons for this, which are presumably relevant to any forecast system, involve the competing influences of predictability loss with time and the time it takes for climate drift to first have a significant impact on forecast skill

    Fast thermistor string observations at the slope of Great Meteor Seamount

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    International audienceA very fast thermistor string has been built to accommodate the scientific need to accurately monitor fast and vigorous internal wave and overturning processes above sloping bottoms in the ocean. The thermistors and their custom designed electronics can register temperature at an estimated precision of about 1mK with a response time faster than 0.25 s down to depths of 6000 m. The present string holds 128 synoptically measuring sensors at 0.5 m intervals, which are all read-out within 0.5 s. When sampling at 1Hz, the batteries and the memory capacity of the recorder allow for deployments of up to 2 weeks. Detailed examples of the first field observations are presented, which show overturning and very high-frequency (Doppler-shifted) internal waves besides occasionally large turbulent bores moving up the sloping side of Great Meteor Seamount, Canary Basin, North-Atlantic Ocean

    High sampling rate thermistor string observations at the slope of Great Meteor Seamount

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    International audienceA high sampling rate (1 Hz) thermistor string has been built to accommodate the scientific need to accurately monitor high-frequency and vigorous internal wave and overturning processes in the ocean. The thermistors and their custom designed electronics can register temperature at an estimated precision of about 0.001° C with a response time faster than 0.25 s down to depths of 6000 m. With a quick in situ calibration using SBE 911 CTD an absolute accuracy of 0.005° C is obtained. The present string holds 128 sensors at 0.5 m intervals, which are all read-out within 0.5 s. When sampling at 1 Hz, the batteries and the memory capacity of the recorder allow for deployments of up to 2 weeks. In this paper, the instrument is described in some detail. Its performance is illustrated with examples from the first moored observations, which show Kelvin-Helmholtz overturning and very high-frequency (Doppler-shifted) internal waves besides occasionally large turbulent bores moving up the sloping side of Great Meteor Seamount, Canary Basin, North-Atlantic Ocean

    Preparation and properties of amorphous MgB2_2/MgO superstructures: A new model disordered superconductor

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    In this paper we introduce a novel method for fabricating MgB2_2/MgO multilayers and demonstrate the potential for using them as a new model for disordered superconductors. In this approach we control the annealing of the MgB2_2 to yield an interesting new class of disordered (amorphous) superconductors with relatively high transition temperatures. The multilayers appear to exhibit quasi-two-dimensional superconductivity with controlled anisotropy. We discuss the properties of the multilayers as the thickness of the components of the bilayers vary.Comment: 7 pages, 8 figure

    Electronic properties of buried hetero-interfaces of LaAlO3 on SrTiO3

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    We have made very thin films of LaAlO3 on TiO2 terminated SrTiO3 and have measured the properties of the resulting interface in various ways. Transport measurements show a maximum sheet carrier density of 1016 cm-2 and a mobility around 104 cm2 V-1 s-1. In situ ultraviolet photoelectron spectroscopy (UPS) indicates that for these samples a finite density of states exists at the Fermi level. From the oxygen pressure dependence measured in both transport as well as the UPS, we detail, as reported previously by us, that oxygen vacancies play an important role in the creation of the charge carriers and that these vacancies are introduced by the pulsed laser deposition process used to make the heterointerfaces. Under the conditions studied the effect of LaAlO3 on the carrier density is found to be minimal.Comment: 19 pages, 6 figure

    A Modeling Study of the On-Going Drought and Heat Wave over the United States

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    Ensembles of AGCM experiments have been conducted to examine the causes of the on-going drought and heat wave affecting much of the United States. The results show that the drought and hot temperatures that have been especially severe over Texas and parts of Mexico since late 2010 are the result of a combination of SST forcing from both the tropical Pacific and the tropical Atlantic, with the latter playing a particularly important role during later half of the summer of 2011, and the warm SSTs off the East Coast contributing to the warm conditions along the East Coast. An extension of the model simulations into the summer of 2012 suggests that the warm conditions are again primarily driven by SST forcing - despite the return of the tropical Pacific to neutral conditions. The results of additional experiments currently being conducted to separate the influences of the 2012 SST anomalies in the various ocean basins will be discussed
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