183,581 research outputs found
On the Statistical Errors of RADAR Location Sensor Networks with Built-In Wi-Fi Gaussian Linear Fingerprints
The expected errors of RADAR sensor networks with linear probabilistic location fingerprints inside buildings with varying Wi-Fi Gaussian strength are discussed. As far as we know, the statistical errors of equal and unequal-weighted RADAR networks have been suggested as a better way to evaluate the behavior of different system parameters and the deployment of reference points (RPs). However, up to now, there is still not enough related work on the relations between the statistical errors, system parameters, number and interval of the RPs, let alone calculating the correlated analytical expressions of concern. Therefore, in response to this compelling problem, under a simple linear distribution model, much attention will be paid to the mathematical relations of the linear expected errors, number of neighbors, number and interval of RPs, parameters in logarithmic attenuation model and variations of radio signal strength (RSS) at the test point (TP) with the purpose of constructing more practical and reliable RADAR location sensor networks (RLSNs) and also guaranteeing the accuracy requirements for the location based services in future ubiquitous context-awareness environments. Moreover, the numerical results and some real experimental evaluations of the error theories addressed in this paper will also be presented for our future extended analysis
Laplace deconvolution on the basis of time domain data and its application to Dynamic Contrast Enhanced imaging
In the present paper we consider the problem of Laplace deconvolution with
noisy discrete non-equally spaced observations on a finite time interval. We
propose a new method for Laplace deconvolution which is based on expansions of
the convolution kernel, the unknown function and the observed signal over
Laguerre functions basis (which acts as a surrogate eigenfunction basis of the
Laplace convolution operator) using regression setting. The expansion results
in a small system of linear equations with the matrix of the system being
triangular and Toeplitz. Due to this triangular structure, there is a common
number of terms in the function expansions to control, which is realized
via complexity penalty. The advantage of this methodology is that it leads to
very fast computations, produces no boundary effects due to extension at zero
and cut-off at and provides an estimator with the risk within a logarithmic
factor of the oracle risk. We emphasize that, in the present paper, we consider
the true observational model with possibly nonequispaced observations which are
available on a finite interval of length which appears in many different
contexts, and account for the bias associated with this model (which is not
present when ). The study is motivated by perfusion imaging
using a short injection of contrast agent, a procedure which is applied for
medical assessment of micro-circulation within tissues such as cancerous
tumors. Presence of a tuning parameter allows to choose the most
advantageous time units, so that both the kernel and the unknown right hand
side of the equation are well represented for the deconvolution. The
methodology is illustrated by an extensive simulation study and a real data
example which confirms that the proposed technique is fast, efficient,
accurate, usable from a practical point of view and very competitive.Comment: 36 pages, 9 figures. arXiv admin note: substantial text overlap with
arXiv:1207.223
Predictions for the frequency and orbital radii of massive extrasolar planets
We investigate the migration of massive extrasolar planets due to
gravitational interaction with a viscous protoplanetary disc. We show that a
model in which planets form at 5 AU at a constant rate, before migrating, leads
to a predicted distribution of planets that is a steeply rising function of log
(a), where a is the orbital radius. Between 1 AU and 3 AU, the expected number
of planets per logarithmic interval in orbital radius roughly doubles. We
demonstrate that, once selection effects are accounted for, this is consistent
with current data, and then extrapolate the observed planet fraction to masses
and radii that are inaccessible to current observations. In total, about 15
percent of stars targeted by existing radial velocity searches are predicted to
possess planets with masses 0.3 M_Jupiter < M_p sin (i) < 10 M_Jupiter, and
radii 0.1 AU < a < 5 AU. A third of these planets (around 5 percent of the
target stars) lie at the radii most amenable to detection via microlensing. A
further 5-10 percent of stars could have planets at radii of 5 AU < a < 8 AU
that have migrated outwards. We discuss the probability of forming a system
(akin to the Solar System) in which significant radial migration of the most
massive planet does not occur. About 10-15 percent of systems with a surviving
massive planet are estimated to fall into this class. Finally, we note that a
smaller fraction of low mass planets than high mass planets is expected to
survive without being consumed by the star. The initial mass function for
planets is thus predicted to rise more steeply towards small masses than the
observed mass function.Comment: MNRAS, in pres
Mesoscopic real space structures in aging spin-glasses: the Edwards-Anderson model
Isothermal simulational data for the 3D Edwards-Anderson spin glass are
collected at several temperatures below and, in analogy with a
recent model of dense colloidal suspensions,interpreted in terms of clusters of
contiguous spins overturned by quakes, non-equilibrium events linked to record
sized energy fluctuations. We show numerically that, to a good approximation,
these quakes are statistically independent and constitute a Poisson process
whose average grows logarithmically in time. The overturned clusters are local
projections on one of the two ground states of the model, and grow likewise
logarithmically in time. Data collected at different temperatures can be
collapsed by scaling them with , a hitherto unnoticed feature of the
E-A model, which we relate on the one hand to the geometry of configuration
space and on the other to experimental memory and rejuvenation effects. The
rate at which a cluster flips is shown to decrease exponentially with the size
of the cluster, as recently assumed in a coarse grained model of dense
colloidal dynamics. The evolving structure of clusters in real space is finally
sssociated to the decay of the thermo-remanent magnetization.
Our analysis provides an unconventional coarse-grained description of spin
glass aging as statistically subordinated to a Poisson quaking process and
highlights record dynamics as a viable common theoretical framework for aging
in different systems.Comment: 13 pages, 6 figs. Revised text and notation, several typos correcte
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