2,502 research outputs found
Non destructive evaluation of absorbing materials using microwave stimulated infrared thermography
The electromagnetic wave nondestructive evaluation methods that appeared some years ago are attractive because many materials can absorb hyperfrequency energy. Nevertheless, generally the detections are achieved point by point which is highly time consuming for NDE of extended structures. We developed a global method which associates electromagnetic stimulation and a detection by an IR camera (EMIR method). For others applications, this method has been used over the past several years [1,2]. The aim of this paper is to give the first results about the possibilities of this new method for NDE
Service Platform for Converged Interactive Broadband Broadcast and Cellular Wireless
A converged broadcast and telecommunication
service platform is presented that is able to create, deliver, and
manage interactive, multimedia content and services for consumption
on three different terminal types. The motivations of
service providers for designing converged interactive multimedia
services, which are crafted for their individual requirements, are
investigated. The overall design of the system is presented with
particular emphasis placed on the operational features of each
of the sub-systems, the flows of media and metadata through the
sub-systems and the formats and protocols required for inter-communication
between them. The key features of tools required for
creating converged interactive multimedia content for a range of
different end-user terminal types are examined. Finally possible
enhancements to this system are discussed. This study is of particular
interest to those organizations currently conducting trials
and commercial launches of DVB-H services because it provides
them with an insight of the various additional functions required
in the service provisioning platforms to provide fully interactive
services to a range of different mobile terminal types
The High-Metallicity Explosion Environment of the Relativistic Supernova 2009bb
We investigate the environment of the nearby (d ~ 40Mpc) broad-lined Type Ic
supernova SN 2009bb. This event was observed to produce a relativistic outflow
likely powered by a central accreting compact object. While such a phenomenon
was previously observed only in long-duration gamma-ray bursts (LGRBs), no LGRB
was detected in association with SN 2009bb. Using an optical spectrum of the SN
2009bb explosion site, we determine a variety of ISM properties for the host
environment, including metallicity, young stellar population age, and star
formation rate. We compare the SN explosion site properties to observations of
LGRB and broad-lined SN Ic host environments on optical emission line ratio
diagnostic diagrams. Based on these analyses, we find that the SN 2009bb
explosion site has a very high metallicity of ~2x solar, in agreement with
other broad-lined SN Ic host environments and at odds with the low-redshift
LGRB host environments and recently proposed maximum metallicity limits for
relativistic explosions. We consider the implications of these findings and the
impact that SN 2009bb's unusual explosive properties and environment have on
our understanding of the key physical ingredient that enables some SNe to
produce a relativistic outflow.Comment: 7 pages, 4 figures, 1 table; accepted for publication in ApJ Letters
(replaced to include missing figure
Rotational Diffusion in a Chain of Particles
We study the coupled rotational diffusion in a two-particle chain on the
basis of a Smoluchowski equation and calculate time-correlation functions that
are measurable in an experiment. This might be used to explore hydrodynamic
interactions in the limit where lubrication theory is valid.Comment: 7 pages, 2 figures, to be published in J. Phys.: Condens. Matte
Compilability of Abduction
Abduction is one of the most important forms of reasoning; it has been
successfully applied to several practical problems such as diagnosis. In this
paper we investigate whether the computational complexity of abduction can be
reduced by an appropriate use of preprocessing. This is motivated by the fact
that part of the data of the problem (namely, the set of all possible
assumptions and the theory relating assumptions and manifestations) are often
known before the rest of the problem. In this paper, we show some complexity
results about abduction when compilation is allowed
Focused Local Search for Random 3-Satisfiability
A local search algorithm solving an NP-complete optimisation problem can be
viewed as a stochastic process moving in an 'energy landscape' towards
eventually finding an optimal solution. For the random 3-satisfiability
problem, the heuristic of focusing the local moves on the presently
unsatisfiedclauses is known to be very effective: the time to solution has been
observed to grow only linearly in the number of variables, for a given
clauses-to-variables ratio sufficiently far below the critical
satisfiability threshold . We present numerical results
on the behaviour of three focused local search algorithms for this problem,
considering in particular the characteristics of a focused variant of the
simple Metropolis dynamics. We estimate the optimal value for the
``temperature'' parameter for this algorithm, such that its linear-time
regime extends as close to as possible. Similar parameter
optimisation is performed also for the well-known WalkSAT algorithm and for the
less studied, but very well performing Focused Record-to-Record Travel method.
We observe that with an appropriate choice of parameters, the linear time
regime for each of these algorithms seems to extend well into ratios -- much further than has so far been generally assumed. We discuss the
statistics of solution times for the algorithms, relate their performance to
the process of ``whitening'', and present some conjectures on the shape of
their computational phase diagrams.Comment: 20 pages, lots of figure
Unusually High Thermal Conductivity of Carbon Nanotubes
Combining equilibrium and non-equilibrium molecular dynamics simulations with
accurate carbon potentials, we determine the thermal conductivity of
carbon nanotubes and its dependence on temperature. Our results suggest an
unusually high value ~W/mK for an isolated
(10,10) nanotube at room temperature, comparable to the thermal conductivity of
a hypothetical isolated graphene monolayer or diamond. Our results suggest that
these high values of are associated with the large phonon mean free
paths in these systems; substantially lower values are predicted and observed
for the basal plane of bulk graphite.Comment: 4 pages 3 figures (5 postscript files), submitted for publicatio
Staying hot to fight the heat-high body temperatures accompany a diurnal endothermic lifestyle in the tropics
Much of our knowledge of the thermoregulation of endotherms has been obtained from species inhabiting cold and temperate climates, our knowledge of the thermoregulatory physiology of tropical endotherms is scarce. We studied the thermoregulatory physiology of a small, tropical mammal, the large treeshrew (Tupaia tana, Order Scandentia) by recording the body temperatures of free-ranging individuals, and by measuring the resting metabolic rates of wild individuals held temporarily
in captivity. The amplitude of daily body temperature (~4 °C) was higher in treeshrews than in many homeothermic eutherian mammals; a consequence of high active-phase body temperatures (~40 °C), and relatively low rest-phase body temperatures (~36 °C). We hypothesized that high body temperatures enable T. tana to maintain a suitable gradient between ambient and
body temperature to allow for passive heat dissipation, important in high-humidity environments where opportunities for evaporative cooling are rare. Whether this thermoregulatory phenotype is unique to Scandentians, or whether other warm climate
diurnal small mammals share similar thermoregulatory characteristics, is currently unknown
A framework for explaining query answers in dl-lite
An Ontology-based Data Access system is constituted by an ontology, namely a description of the concepts and the relations in a domain of interest, a database storing facts about the domain, and a mapping between the data and the ontology. In this paper, we consider ontologies expressed in the popular DL-Lite family of Description Logic, and we address the problem of computing explanations for answers to queries in an OBDA system, where queries are either positive, in particular conjunctive queries, or negative, i.e., negation of conjunctive queries. We provide the following contributions: (i) we propose a formal, comprehensive framework of explaining query answers in OBDA systems based on DL-Lite; (ii) we present an algorithm that, given a tuple returned as an answer to a positive query, and given a weighting function, examines all the explanations of the answer, and chooses the best explanation according to such function; (iii) we do the same for the answers to negative queries. Notably, on the way to get the latter result, we present what appears to be the first algorithm that computes the answers to negative queries in DL-Lite
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