20,755 research outputs found
Subjective and Objective Measures of the Extent of Governmental Regulations
In recent years, three different quantitative studies measuring the extent of regulation in OECD nations have appeared. One analysis is based on an extensive review and quantification of laws and regulations; the other two are based on opinion data of those familiar with these regulations. Despite their very different methodologies and coverage of particular types of governmental regulation, the results of the three studies are significantly correlated, even though they differ in detail. The advantages and disadvantages of each of the three approaches are discussed.Regulatory Reform, Other Topics
Performance of MMSE MIMO Receivers: A Large N Analysis for Correlated Channels
Linear receivers are considered as an attractive low-complexity alternative
to optimal processing for multi-antenna MIMO communications. In this paper we
characterize the performance of MMSE MIMO receivers in the limit of large
antenna numbers in the presence of channel correlations. Using the replica
method, we generalize our results obtained in arXiv:0810.0883 to
Kronecker-product correlated channels and calculate the asymptotic mean and
variance of the mutual information of a MIMO system of parallel MMSE
subchannels. The replica method allows us to use the ties between the optimal
receiver mutual information and the MMSE SIR of Gaussian inputs to calculate
the joint moments of the SIRs of the MMSE subchannels. Using the methodology
discussed in arXiv:0810.0883 it can be shown that the mutual information
converges in distribution to a Gaussian random variable. Our results agree very
well with simulations even with a moderate number of antennas.Comment: Invited article at the IEEE Vehicular Technology Conference,
Barcelona 200
A Semantic Web Annotation Tool for a Web-Based Audio Sequencer
Music and sound have a rich semantic structure which is so clear to the composer and the listener, but that remains mostly hidden to computing machinery. Nevertheless, in recent years, the introduction of software tools for music production have enabled new opportunities for migrating this knowledge from humans to machines. A new generation of these tools may exploit sound samples and semantic information coupling for the creation not only of a musical, but also of a "semantic" composition. In this paper we describe an ontology driven content annotation framework for a web-based audio editing tool. In a supervised approach, during the editing process, the graphical web interface allows the user to annotate any part of the composition with concepts from publicly available ontologies. As a test case, we developed a collaborative web-based audio sequencer that provides users with the functionality to remix the audio samples from the Freesound website and subsequently annotate them. The annotation tool can load any ontology and thus gives users the opportunity to augment the work with annotations on the structure of the composition, the musical materials, and the creator's reasoning and intentions. We believe this approach will provide several novel ways to make not only the final audio product, but also the creative process, first class citizens of the Semantic We
A Search for Radio Emission at the Bottom of the Main Sequence and Beyond
We have used the VLA to conduct a deep search for 3.6 cm radio emission from
nearby very low mass stars and brown dwarfs. The Gudel-Benz relation is used to
predict radio luminosities for some very low mass stars and candidate brown
dwarfs with measured X-ray fluxes. The predicted radio fluxes are quite small,
whereas the measured radio flux from the brown dwarf candidate Rho Oph GY 31 is
relatively strong. In light of our new observations, this object remains an
anomaly. We present upper limits for our measured radio fluxes at 3.6 cm for
our targets.Comment: 10 pages, no figures. Accepted for publication in A
Spectroscopic Probe of the van der Waals Interaction between Polar Molecules and a Curved Surface
We study the shift of rotational levels of a diatomic polar molecule due to
its van der Waals (vdW) interaction with a gently curved dielectric surface at
temperature , and submicron separations. The molecule is assumed to be in
its electronic and vibrational ground state, and the rotational degrees are
described by a rigid rotor model. We show that under these conditions
retardation effects and surface dispersion can be neglected. The level shifts
are found to be independent of , and given by the quantum state averaged
classical electrostatic interaction of the dipole with its image on the
surface. We use a derivative expansion for the static Green's function to
express the shifts in terms of surface curvature. We argue that the curvature
induced line splitting is experimentally observable, and not obscured by
natural line widths and thermal broadening.Comment: 8 pages, 2 figures, version accepted for publication in Phys. Rev.
Velocities of Venus clouds derived from VIRTIS observations
Retrograde superrotation is a well known feature of the atmosphere of Venus, with Venus’ cloud tops rotating in only 4.4 days, much faster than the 243-day rotation period of the solid globe. A good characterization of the circulation of the venusian atmosphere is essential in order to understand the mechanisms controlling superrota- tion. VIRTIS, onboard ESA’s Venus Express, is one of the most flexible instruments for such a characterization. The VIRTIS-M imaging spectrometer, operating in the range 0.25 to 5 micrometers, has acquired images of Venus’ clouds from the cloud tops, in visible wavelengths, to the lower cloud layer, close to 40 km, at infrared wavelengths. We present velocity determinations from automated cloud tracking in the night side at 1.74, 2.3 and 5 micrometers, from high to mid latitudes in the south- ern hemisphere. The method is based on a digital correlator which compares two or more consecutive images and identifies patterns by maximizing correlations between image blocks (Luz, Berry and Roos-Serote, 2008, New Ast. 13, 224). Notable features are the variability of the winds and the detection of a clear transition region between 75S and 80S. The meridional component is suggestive of a polar Hadley cell. Wave motions are detected at the transition latitudes with wavenumbers 3 and 8 for the zonal and meridional components. We estimate the contribution from the subsolar to antisolar-point wind component to be higher than 10 m/s
Lifetime of the superconductive state in short and long Josephson junctions
We study the transient statistical properties of short and long Josephson
junctions under the influence of thermal and correlated fluctuations. In
particular, we investigate the lifetime of the superconductive metastable state
finding the presence of noise induced phenomena. For short Josephson junctions
we investigate the lifetime as a function both of the frequency of the current
driving signal and the noise intensity and we find how these noise-induced
effects are modified by the presence of a correlated noise source. For long
Josephson junctions we integrate numerically the sine-Gordon equation
calculating the lifetime as a function of the length of the junction both for
inhomogeneous and homogeneous bias current distributions. We obtain a
nonmonotonic behavior of the lifetime as a function of the frequency of the
current driving signal and the correlation time of the noise. Moreover we find
two maxima in the nonmonotonic behaviour of the mean escape time as a function
of the correlated noise intensity.Comment: 12 pages, 9 figure
Spin squeezing and entanglement for arbitrary spin
A complete set of generalized spin-squeezing inequalities is derived for an
ensemble of particles with an arbitrary spin. Our conditions are formulated
with the first and second moments of the collective angular momentum
coordinates. A method for mapping the spin-squeezing inequalities for spin-1/2
particles to entanglement conditions for spin-j particles is also presented. We
apply our mapping to obtain a generalization of the original spin-squeezing
inequality to higher spins. We show that, for large particle numbers, a
spin-squeezing parameter for entanglement detection based on one of our
inequalities is strictly stronger than the original spin-squeezing parameter
defined in [A. Sorensen et al., Nature 409, 63 (2001)]. We present a coordinate
system independent form of our inequalities that contains, besides the
correlation and covariance tensors of the collective angular momentum
operators, the nematic tensor appearing in the theory of spin nematics.
Finally, we discuss how to measure the quantities appearing in our inequalities
in experiments.Comment: 18 pages including 3 figures, revtex4; v2: references added, typos
corrected; v3: typos corrected, published versio
- …