1,680 research outputs found
On the second moment of the number of crossings by a stationary Gaussian process
Cram\'{e}r and Leadbetter introduced in 1967 the sufficient condition
to have a
finite variance of the number of zeros of a centered stationary Gaussian
process with twice differentiable covariance function . This condition is
known as the Geman condition, since Geman proved in 1972 that it was also a
necessary condition. Up to now no such criterion was known for counts of
crossings of a level other than the mean. This paper shows that the Geman
condition is still sufficient and necessary to have a finite variance of the
number of any fixed level crossings. For the generalization to the number of a
curve crossings, a condition on the curve has to be added to the Geman
condition.Comment: Published at http://dx.doi.org/10.1214/009117906000000142 in the
Annals of Probability (http://www.imstat.org/aop/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Rice formulae and Gaussian waves
We use Rice formulae in order to compute the moments of some level
functionals which are linked to problems in oceanography and optics: the number
of specular points in one and two dimensions, the distribution of the normal
angle of level curves and the number of dislocations in random wavefronts. We
compute expectations and, in some cases, also second moments of such
functionals. Moments of order greater than one are more involved, but one needs
them whenever one wants to perform statistical inference on some parameters in
the model or to test the model itself. In some cases, we are able to use these
computations to obtain a central limit theorem.Comment: Published in at http://dx.doi.org/10.3150/10-BEJ265 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
Estimation in models driven by fractional Brownian motion
Let be the fractional Brownian motion with
parameter . When , we consider diffusion equations of the type
In different particular models where
or and or ,
we propose a central limit theorem for estimators of and of based
on regression methods. Then we give tests of the hypothesis on for
these models. We also consider functional estimation on in the
above more general models based in the asymptotic behavior of functionals of
the 2nd-order increments of the fBm.Comment: Published in at http://dx.doi.org/10.1214/07-AIHP105 the Annales de
l'Institut Henri Poincar\'e - Probabilit\'es et Statistiques
(http://www.imstat.org/aihp/) by the Institute of Mathematical Statistics
(http://www.imstat.org
Estimation for Stochastic Damping Hamiltonian Systems under Partial Observation. II Drift term
International audienceThis paper is the second part of our study started with \citet*{CLP}. For some ergodic hamiltonian systems we obtained a central limit theorem for a non-parametric estimator of the invariant density, under partial observation (only the positions are observed). Here we obtain similarly a central limit theorem for a non-parametric estimator of the drift term. This theorem lies on the previous result for the invariant density
1D Convolutional Neural Network for Detecting Ventricular Heartbeats
This paper shows a novel approach for detecting ventricular heartbeats using a 1D Convolutional Neural Network (1D-CNN). The algorithm input is the raw ECG signal, i.e., no signal pre-processing nor feature extraction are involved. The output of the 1D-CNN is filtered using a combination of linear and nonlinear filters to produce the final output. The MIT-BIH arrhythmia database was used for both algorithm training/tuning and evaluation. The assessment methodology followed the interpatient paradigm, where the algorithm was trained and evaluated using independent subsets. The performance of the proposed method was evaluated for two tasks; QRS detection, and heartbeat classification. QRS detection resulted in a sensitivity of 99.0% and a positive predictivity of 96.5%. The performance assessment of the ventricular ectopic beat detection resulted in a sensitivity of 85.8% and a positive predictivity of 64.5%. Although there is still room for improvement, the results suggest that convolutional neural networks are a promising approach for building heartbeat classifiers
Draft Genome Sequence of the Moderately Halophilic Bacterium Pseudoalteromonas ruthenica Strain CP76
Pseudoalteromonas ruthenica strain CP76, isolated from a saltern in Spain, is a moderately halophilic bacterium belonging to the Gammaproteobacteria. Here we report the draft genome sequence, which consists of a 4.0-Mb chromosome, of this strain, which is able to produce the extracellular enzyme haloprotease CPI
La prótesis de cadera con recubrimiento de vidrio Primeros resultados con 2 años de evolución
El presente trabajo analiza los primeros resultados clínicos y radiográficos de un
estudio con la prótesis de cadera no cementada con recubrimiento «de vidrio» a nivel metafísario
(prótesis CRM). La casuística comprende 80 artroplastias totales implantadas desde 1991 a 1994
con un seguimiento mínimo de 2 años. La evolución clínica, valorada según el sistema de Harris
modificado, ha sido satisfactoria en el 90% de los enfermos. La observación radiográfica ha mostrado
buena fijación y orientación de los componentes femorales en 72 casos. La conclusión de
este análisis preliminar permite apreciar que el recubrimiento protésico con cerámica de vidrio
supone un mecanismo de seguridad en la fijación primaria y secundaria de la prótesis de cadera.This work analizes the first clinical and radiological results of a cementless hip
prosthesis with glass coating at metaphyseal level (CRM prosthesis). A total of 80 arthroplasties implanted
since may 1991 to 1994 were studied with a two year follow-up. The clinical assesment was
done by the modified Harris score, being satisfactory in 90% of the patients. The radiological study
demonstrated good fixation and orientation of the prosthetic compounds in 72 cases. The prosthetic
model studied provides a security mechanism both for primary and secondary fixation of the
femoral stem and acetabular cup
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