Search results for " posterior"
showing 10 items of 221 documents
Fast Estimation of Diffusion Tensors under Rician noise by the EM algorithm
2016
Diffusion tensor imaging (DTI) is widely used to characterize, in vivo, the white matter of the central nerve system (CNS). This biological tissue contains much anatomic, structural and orientational information of fibers in human brain. Spectral data from the displacement distribution of water molecules located in the brain tissue are collected by a magnetic resonance scanner and acquired in the Fourier domain. After the Fourier inversion, the noise distribution is Gaussian in both real and imaginary parts and, as a consequence, the recorded magnitude data are corrupted by Rician noise. Statistical estimation of diffusion leads a non-linear regression problem. In this paper, we present a f…
Modelling by Statistic in Research of Mathematics Education
2008
Summary. The aim of this paper is to study the quantitative tools of the research in didactics. We want to investigate the theoretical-experimental relationships between factorial and implicative analysis. This chapter consists of three parts. The first one deals with the didactic research and some fundamental tools: the a priori analysis of a didactic situation, the collection of experimental data and the statistic analysis of data. The purpose of the second and the third section is to introduce the experimental comparison between the factorial and the implicative analysis in two researches in mathematics education.
Exploring Multiobjective Optimization for Multiview Clustering
2018
We present a new multiview clustering approach based on multiobjective optimization. In contrast to existing clustering algorithms based on multiobjective optimization, it is generally applicable to data represented by two or more views and does not require specifying the number of clusters a priori . The approach builds upon the search capability of a multiobjective simulated annealing based technique, AMOSA, as the underlying optimization technique. In the first version of the proposed approach, an internal cluster validity index is used to assess the quality of different partitionings obtained using different views. A new way of checking the compatibility of these different partitioning…
Localized forms of the LBB condition and a posteriori estimates for incompressible media problems
2018
Abstract The inf–sup (or LBB) condition plays a crucial role in analysis of viscous flow problems and other problems related to incompressible media. In this paper, we deduce localized forms of this condition that contain a collection of local constants associated with subdomains instead of one global constant for the whole domain. Localized forms of the LBB inequality imply estimates of the distance to the set of divergence free fields. We use them and deduce fully computable bounds of the distance between approximate and exact solutions of boundary value problems arising in the theory of viscous incompressible fluids. The estimates are valid for approximations, which satisfy the incompres…
Split Bregman Method for Gravitational Wave Denoising
2014
This paper presents a progress report in our aim to develop a Total Variation algorithm for denoising of gravitational waves. These algorithms, are routinely employed in the context of image processing and they do not need any a priori information on the signals. We apply our method to two different types of numerically-simulated gravitational wave signals, namely burst produced from the core collapse of rotating stars and waveforms from binary black hole mergers, and present a preliminary assessment of its capabilities.
Calculation and inversion of two-dimensional gravity in the vicinity of Lake Tuz, Turkey
2000
Abstract An example of gravity inversion and interpretation is presented which demonstrates how a priori information can be used to derive reliable, though complex models. In this case, the geometry of the studied model profile has been constructed on the basis of seismic and geological data. The densities used in the forward calculations were obtained from laboratory measurements of drill cores, from density-velocity relationships, and from Nettleton’s method of fitting gravity and topography. In the seismic section 21 ‘formations’ are distinguished leading to a very complex gravity model. What is called ‘formations’ here, are two-dimensional bodies which are distinguished from each other …
Spatules de Thierry ou forceps : comparaison des morbidités materno-fœtales
2016
Resume Objectif Comparer la morbidite materno-fœtale immediate lors d’une l’extraction par forceps ou par spatules de Thierry. Methodes Etude retrospective, descriptive, monocentrique de 2006 a 2012. Les extractions etaient realisees par spatules ou forceps pour defaut de progression du mobile fœtale, sur singleton, en presentation cephalique, a terme, sans anomalies du rythme cardiaque fœtal et sans pathologie gravidique associee. Resultats Notre serie comprenait 65 extractions par spatules contre 77 par forceps. Nos populations etaient comparables. Au niveau maternel, on retrouvait davantage de perinees intacts (5,19 % versus 15,38 %, p = 0,04), autant de dechirures vaginales et moins de …
Remote Photoplethysmography measurement using constrained ICA
2017
Remote Photoplethysmography (rPPG) is a technique that consists in estimating physiological parameters such as heart rate from live or recorded video sequences taken by conventional camera or even webcams. This technique is increasingly used in many application fields thanks to its simplicity and affordability. The basic idea is that the arterial blood flow shows regularity due to the heartbeat. This regularity is manifested by very small periodic variations in the color of the skin, which can be isolated and quantified by signal and image processing methods. In this context, Independent Component Analysis (ICA) is largely used to separate the signal due to arterial flow from signals from o…
Epidural hematoma after cochlear implantation in a 2.5-year-old boy.
2005
OBJECTIVE Report a case of an epidural hematoma after cochlear implantation in a 2.5-year-old boy, the diagnostic and therapeutical emergency management, as well as the postinterventional course and rehabilitation of the child. STUDY DESIGN Retrospective case review. PATIENT Two and a half-year-old boy, suffering from early onset, profound sensorineural hearing loss had been diagnosed at an age of 1.5 years, which had been more severe on the right side initially, but had progressed to bilateral deafness. INTERVENTION AND COMPLICATION: Cochlear implantation on the left side, followed up by an extensive epidural hematoma, causing intracranial compression with a midline shift of 15 mm to the r…
Uncertainty and Equifinality in Calibrating Distributed Roughness Coefficients in a Flood Propagation Model with Limited Data
1998
Monte-Carlo simulations of a two-dimensional finite element model of a flood in the southern part of Sicily were used to explore the parameter space of distributed bed-roughness coefficients. For many real-world events specific data are extremely limited so that there is not only fuzziness in the information available to calibrate the model, but fuzziness in the degree of acceptability of model predictions based upon the different parameter values, owing to model structural errors. Here the GLUE procedure is used to compare model predictions and observations for a certain event, coupled with both a fuzzy-rule-based calibration, and a calibration technique based upon normal and heteroscedast…