250 research outputs found

    Assessing the Effects of Enhanced Supply Chain Visibility Through RFID

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    The majority of RFID implementations can be traced back either to mandates issued by companies or institutions with significant market power like Wal-Mart or the U.S. Department of Defense, or to the replacement of existing Auto-ID technologies like barcodes. Only sporadically is RFID being used to derive superior information about current processes in order to create supply chain visibility. In this contribution, we examine the visibility potentials of RFID technology within the context of SCM and we propose a four-step approach to assessing the results that can be achieved through visibility

    Complex Radio Spectral Energy Distributions in Luminous and Ultraluminous Infrared Galaxies

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    We use the Expanded Very Large Array to image radio continuum emission from local luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in 1 GHz windows centered at 4.7, 7.2, 29, and 36 GHz. This allows us to probe the integrated radio spectral energy distribution (SED) of the most energetic galaxies in the local universe. The 4-8 GHz flux densities agree well with previous measurements. They yield spectral indices \alpha \approx -0.67 (where F_\nu \propto \nu^\alpha) with \pm 0.15 (1\sigma) scatter, typical of nonthermal (synchrotron) emission from star-forming galaxies. The contrast of our 4-8 GHz data with literature 1.5 and 8.4 GHz flux densities gives further evidence for curvature of the radio SED of U/LIRGs. The SED appears flatter near \sim 1 GHz than near \sim 6 GHz, suggesting significant optical depth effects at the lower frequencies. The high frequency (28-37 GHz) flux densities are low compared to extrapolations from the 4-8 GHz data. We confirm and extend to higher frequency a previously observed deficit of high frequency radio emission for luminous starburst galaxies.Comment: 7 pages, 3 figures, 1 table, accepted for publication in the EVLA Special Issue of ApJ Letter

    Evidence for an interaction between the Galactic Center clouds M0.10-0.08 and M0.11-0.11

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    We present high-resolution (~2-3"; ~0.1 pc) radio observations of the Galactic center cloud M0.10-0.08 using the Very Large Array at K and Ka band (~25 and 36 GHz). The M0.10-0.08 cloud is located in a complex environment near the Galactic center Radio Arc and the adjacent M0.11-0.11 molecular cloud. From our data, M0.10-0.08 appears to be a compact molecular cloud (~3 pc) that contains multiple compact molecular cores (5+; <0.4 pc). In this study we detect a total of 15 molecular transitions in M0.10-0.08 from the following molecules: NH3, HC3N, CH3OH, HC5N, CH3CN, and OCS. We have identified more than sixty 36 GHz CH3OH masers in M0.10-0.08 with brightness temperatures above 400 K and 31 maser candidates with temperatures between 100-400 K. We conduct a kinematic analysis of the gas using NH3 and detect multiple velocity components towards this region of the Galactic center. The bulk of the gas in this region has a velocity of 51.5 km/s (M0.10-0.08) with a lower velocity wing at 37.6 km/s. We also detect a relatively faint velocity component at 10.6 km/s that we attribute to being an extension of the M0.11-0.11 cloud. Analysis of the gas kinematics, combined with past X-ray fluorescence observations, suggests M0.10-0.08 and M0.11-0.11 are located in the same vicinity of the Galactic center and could be physically interacting.Comment: Accepted for publication in the Astrophysical Journa

    Bayesian optimisation for quality diversity search with coupled descriptor functions

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    Quality Diversity (QD) algorithms such as the Multi- Dimensional Archive of Phenotypic Elites (MAP-Elites) are a class of optimisation techniques that attempt to find many high performing points that all behave differently according to a userdefined behavioural metric. In this paper we propose the Bayesian Optimisation of Elites (BOP-Elites) algorithm. Designed for problems with expensive fitness functions and coupled behaviour descriptors, it is able to return a QD solution-set with excellent performance already after a relatively small number of samples. BOP-Elites models both fitness and behavioural descriptors with Gaussian Process surrogate models and uses Bayesian Optimisation strategies for choosing points to evaluate in order to solve the quality-diversity problem. In addition, BOP-Elites produces high quality surrogate models which can be used after convergence to predict solutions with any behaviour in a continuous range. An empirical comparison shows that BOP-Elites significantly outperforms other state-of-the-art algorithms without the need for problem-specific parameter tuning

    Evidence of a Cloud-Cloud Collision from Overshooting Gas in the Galactic Center

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    The Milky Way is a barred spiral galaxy with "bar lanes" that bring gas towards the Galactic Center. Gas flowing along these bar lanes often overshoots, and instead of accreting onto the Central Molecular Zone, it collides with the bar lane on the opposite side of the Galaxy. We observed G5, a cloud which we believe is the site of one such collision, near the Galactic Center at (l,b) = (+5.4, -0.4) with the ALMA/ACA. We took measurements of the spectral lines 12^{12}CO J=2-1, 13^{13}CO J=2-1, C18^{18}O J=2-1, H2_2CO J=303_{03}-202_{02}, H2_{2}CO J=322_{22}-221_{21}, CH3_{3}OH J=422_{22}-312_{12}, OCS J=18-17 and SiO J=5-4. We observed a velocity bridge between two clouds at ∼\sim50 km/s and ∼\sim150 km/sin our position-velocity diagram, which is direct evidence of a cloud-cloud collision. We measured an average gas temperature of ∼\sim60 K in G5 using H2_2CO integrated intensity line ratios. We observed that the 12^{12}C/13^{13}C ratio in G5 is consistent with optically thin, or at most marginally optically thick 12^{12}CO. We measured 1.5 x 109^9 cm−2^{-2}(K km/s)−1^{-1} for the local XCO_{CO}, 10-20x less than the average Galactic value. G5 is strong direct observational evidence of gas overshooting the Central Molecular Zone (CMZ) and colliding with a bar lane on the opposite side of the Galactic center.Comment: Accepted to ApJ. 27 pages, 19 figure
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