250 research outputs found
Assessing the Effects of Enhanced Supply Chain Visibility Through RFID
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
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
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
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
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 CO J=2-1, CO J=2-1, CO J=2-1, HCO
J=3-2, HCO J=3-2, CHOH
J=4-3, OCS J=18-17 and SiO J=5-4. We observed a velocity bridge
between two clouds at 50 km/s and 150 km/sin our position-velocity
diagram, which is direct evidence of a cloud-cloud collision. We measured an
average gas temperature of 60 K in G5 using HCO integrated intensity
line ratios. We observed that the C/C ratio in G5 is consistent
with optically thin, or at most marginally optically thick CO. We
measured 1.5 x 10 cm(K km/s) for the local X, 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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