1,561 research outputs found
A compact spectroradiometer for solar simulator measurements
Compact spectral irradiance probe has been designed and built which uses wedge filter in conjunction with silicon cell and operational amplifier. Probe is used to monitor spectral energy distribution of solar simulators and other high intensity sources
Compact spectroradiometer
Development and characteristics of spectroradiometer with wedge filters to eliminate adverse effect of pinholes in filter
Velocity Statistics in the Two-Dimensional Granular Turbulence
We studied the macroscopic statistical properties on the freely evolving
quasi-elastic hard disk (granular) system by performing a large-scale (up to a
few million particles) event-driven molecular dynamics systematically and found
that remarkably analogous to an enstrophy cascade process in the decaying
two-dimensional fluid turbulence. There are four typical stages in the freely
evolving inelastic hard disk system, which are homogeneous, shearing (vortex),
clustering and final state. In the shearing stage, the self-organized
macroscopic coherent vortices become dominant. In the clustering stage, the
energy spectra are close to the expectation of Kraichnan-Batchelor theory and
the squared two-particle separation strictly obeys Richardson law.Comment: 4 pages, 4 figures, to be published in PR
A New Android Malware Detection Approach Using Bayesian Classification
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Mobile malware has been growing in scale and complexity as smartphone usage continues to rise. Android has surpassed other mobile platforms as the most popular whilst also witnessing a dramatic increase in malware targeting the platform. A worrying trend that is emerging is the increasing sophistication of Android malware to evade detection by traditional signature-based scanners. As such, Android app marketplaces remain at risk of hosting malicious apps that could evade detection before being downloaded by unsuspecting users. Hence, in this paper we present an effective approach to alleviate this problem based on Bayesian classification models obtained from static code analysis. The models are built from a collection of code and app characteristics that provide indicators of potential malicious activities. The models are evaluated with real malware samples in the wild and results of experiments are presented to demonstrate the effectiveness of the proposed approach
Nuclear Magnetic Resonance and Hyperfine Structure
Contains reports on four research projects
Binary black hole merger in the extreme mass ratio limit
We discuss the transition from quasi-circular inspiral to plunge of a system
of two nonrotating black holes of masses and in the extreme mass
ratio limit . In the spirit of the Effective One Body
(EOB) approach to the general relativistic dynamics of binary systems, the
dynamics of the two black hole system is represented in terms of an effective
particle of mass moving in a (quasi-)Schwarzschild
background of mass and submitted to an
radiation reaction force defined by Pad\'e resumming high-order Post-Newtonian
results. We then complete this approach by numerically computing, \`a la
Regge-Wheeler-Zerilli, the gravitational radiation emitted by such a particle.
Several tests of the numerical procedure are presented. We focus on
gravitational waveforms and the related energy and angular momentum losses. We
view this work as a contribution to the matching between analytical and
numerical methods within an EOB-type framework.Comment: 14 pages, six figures. Revised version. To appear in the CQG special
issue based around New Frontiers in Numerical Relativity conference, Golm
(Germany), July 17-21 200
Nuclear Magnetic Resonance and Hyperfine Structure
Contains reports on six research projects
Fluctuation dynamo and turbulent induction at low magnetic Prandtl numbers
This paper is a detailed report on a programme of simulations used to settle
a long-standing issue in the dynamo theory and demonstrate that the fluctuation
dynamo exists in the limit of large magnetic Reynolds number Rm>>1 and small
magnetic Prandtl number Pm<<1. The dependence of the critical Rm_c vs. the
hydrodynamic Reynolds number Re is obtained for 1<Re<6700. In the limit Pm<<1,
Rm_c is ~3 times larger than for Pm>1. The stability curve Rm_c(Re) (and, it is
argued, the nature of the dynamo) is substantially different from the case of
the simulations and liquid-metal experiments with a mean flow. It is not as yet
possible to determine numerically whether the growth rate is ~Rm^{1/2} in the
limit Re>>Rm>>1, as should be the case if the dynamo is driven by the
inertial-range motions. The magnetic-energy spectrum in the low-Pm regime is
qualitatively different from the Pm>1 case and appears to develop a negative
spectral slope, although current resolutions are insufficient to determine its
asymptotic form. At 1<Rm<Rm_c, the magnetic fluctuations induced via the
tangling by turbulence of a weak mean field are investigated and the
possibility of a k^{-1} spectrum above the resistive scale is examined. At low
Rm<1, the induced fluctuations are well described by the quasistatic
approximation; the k^{-11/3} spectrum is confirmed for the first time in direct
numerical simulations.Comment: IoP latex, 27 pages, 25 figures, 3 tables. Accepted by New J. Physic
Dynamics of a small neutrally buoyant sphere in a fluid and targeting in Hamiltonian systems
We show that, even in the most favorable case, the motion of a small
spherical tracer suspended in a fluid of the same density may differ from the
corresponding motion of an ideal passive particle. We demonstrate furthermore
how its dynamics may be applied to target trajectories in Hamiltonian systems.Comment: See home page http://lec.ugr.es/~julya
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