6,668 research outputs found
Anomalous Thermoluminescent Kinetics of Irradiated Alkali Halides
Anomalous thermoluminescent kinetics of irradiated alkali halide
An Energy-conscious Transport Protocol for Multi-hop Wireless Networks
We present a transport protocol whose goal is to reduce power consumption without compromising delivery requirements of applications. To meet its goal of energy efficiency, our transport protocol (1) contains mechanisms to balance end-to-end vs. local retransmissions; (2) minimizes acknowledgment traffic using receiver regulated rate-based flow control combined with selected acknowledgements and in-network caching of packets; and (3) aggressively seeks to avoid any congestion-based packet loss. Within a recently developed ultra low-power multi-hop wireless network system, extensive simulations and experimental results demonstrate that our transport protocol meets its goal of preserving the energy efficiency of the underlying network.Defense Advanced Research Projects Agency (NBCHC050053
Fatigue delamination behaviour of unidirectional carbon fibre/epoxy laminates reinforced by Z-Fiber® pinnin
-Pin reinforced carbon-fibre epoxy laminates were tested under Mode I and Mode
II conditions, both quasi-statically and in fatigue. Test procedures were
adapted from existing standard or pre-standard tests. Samples containing 2% and
4% areal densities of carbon-fibre Z-pins (0.28mm diameter) were compared with
unpinned laminates. Quasi-static tests under displacement control yielded a
dramatic increase of the apparent delamination resistance. Specimens with 2% pin
density failed in Mode I at loads 170N, equivalent to an apparent GIC of 2kJ/m2.
Fatigue testing under load control showed that the presence of the through-
thickness reinforcement slowed down fatigue delamination propagation
Zero Temperature Thermodynamics of Asymmetric Fermi Gases at Unitarity
The equation of state of a dilute two-component asymmetric Fermi gas at
unitarity is subject to strong constraints, which affect the spatial density
profiles in atomic traps. These constraints require the existence of at least
one non-trivial partially polarized (asymmetric) phase. We determine the
relation between the structure of the spatial density profiles and the T=0
equation of state, based on the most accurate theoretical predictions
available. We also show how the equation of state can be determined from
experimental observations.Comment: 10 pages and 7 figures. (Minor changes to correspond with published
version.
Absolute Calibration of the Radio Astronomy Flux Density Scale at 22 to 43 GHz Using Planck
The Planck mission detected thousands of extragalactic radio sources at
frequencies from 28 to 857 GHz. Planck's calibration is absolute (in the sense
that it is based on the satellite's annual motion around the Sun and the
temperature of the cosmic microwave background), and its beams are well
characterized at sub-percent levels. Thus Planck's flux density measurements of
compact sources are absolute in the same sense. We have made coordinated VLA
and ATCA observations of 65 strong, unresolved Planck sources in order to
transfer Planck's calibration to ground-based instruments at 22, 28, and 43
GHz. The results are compared to microwave flux density scales currently based
on planetary observations. Despite the scatter introduced by the variability of
many of the sources, the flux density scales are determined to 1-2% accuracy.
At 28 GHz, the flux density scale used by the VLA runs 3.6% +- 1.0% below
Planck values; at 43 GHz, the discrepancy increases to 6.2% +- 1.4% for both
ATCA and the VLA.Comment: 16 pages, 4 figures and 4 table
The Bayesian Decision Tree Technique with a Sweeping Strategy
The uncertainty of classification outcomes is of crucial importance for many
safety critical applications including, for example, medical diagnostics. In
such applications the uncertainty of classification can be reliably estimated
within a Bayesian model averaging technique that allows the use of prior
information. Decision Tree (DT) classification models used within such a
technique gives experts additional information by making this classification
scheme observable. The use of the Markov Chain Monte Carlo (MCMC) methodology
of stochastic sampling makes the Bayesian DT technique feasible to perform.
However, in practice, the MCMC technique may become stuck in a particular DT
which is far away from a region with a maximal posterior. Sampling such DTs
causes bias in the posterior estimates, and as a result the evaluation of
classification uncertainty may be incorrect. In a particular case, the negative
effect of such sampling may be reduced by giving additional prior information
on the shape of DTs. In this paper we describe a new approach based on sweeping
the DTs without additional priors on the favorite shape of DTs. The
performances of Bayesian DT techniques with the standard and sweeping
strategies are compared on a synthetic data as well as on real datasets.
Quantitatively evaluating the uncertainty in terms of entropy of class
posterior probabilities, we found that the sweeping strategy is superior to the
standard strategy
Planck Observations of M33
We have performed a comprehensive investigation of the global integrated flux
density of M33 from radio to ultraviolet wavelengths, finding that the data
between 100 GHz and 3 THz are accurately described by a single modified
blackbody curve with a dust temperature of = 21.670.30 K
and an effective dust emissivity index of = 1.350.10,
with no indication of an excess of emission at millimeter/sub-millimeter
wavelengths. However, sub-dividing M33 into three radial annuli, we found that
the global emission curve is highly degenerate with the constituent curves
representing the sub-regions of M33. We also found gradients in
and across the disk of M33, with both
quantities decreasing with increasing radius. Comparing the M33 dust emissivity
with that of other Local Group members, we find that M33 resembles the
Magellanic Clouds rather than the larger galaxies, i.e., the Milky Way and M31.
In the Local Group sample, we find a clear correlation between global dust
emissivity and metallicity, with dust emissivity increasing with metallicity. A
major aspect of this analysis is the investigation into the impact of
fluctuations in the Cosmic Microwave Background (CMB) on the integrated flux
density spectrum of M33. We found that failing to account for these CMB
fluctuations would result in a significant over-estimate of
by 5 K and an under-estimate of by 0.4.Comment: Accepted for publication in MNRA
Semantic Transformation of Web Services
Web services have become the predominant paradigm for the development of distributed software systems. Web services provide the means to modularize software in a way that functionality can be described, discovered and deployed in a platform independent manner over a network (e.g., intranets, extranets and the Internet). The representation of web services by current industrial practice is predominantly syntactic in nature lacking the fundamental semantic underpinnings required to fulfill the goals of the emerging Semantic Web. This paper proposes a framework aimed at (1) modeling the semantics of syntactically defined web services through a process of interpretation, (2) scop-ing the derived concepts within domain ontologies, and (3) harmonizing the semantic web services with the domain ontologies. The framework was vali-dated through its application to web services developed for a large financial system. The worked example presented in this paper is extracted from the se-mantic modeling of these financial web services
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