Search results for "multivariate"
showing 10 items of 1520 documents
Robust estimation of partial directed coherence by the vector optimal parameter search algorithm
2009
We propose a method for the accurate estimation of Partial Directed Coherence (PDC) from multichannel time series. The method is based on multivariate vector autoregressive (MVAR) model identification performed through the recently proposed Vector Optimal Parameter Search (VOPS) algorithm. Using Monte Carlo simulations generated by different MVAR models, the proposed VOPS algorithm is compared with the traditional Vector Least Squares (VLS) identification method. We show that the VOPS provides more accurate PDC estimates than the VLS (either overall and single-arc errors) in presence of interactions with long delays and missing terms, and for noisy multichannel time series. ©2009 IEEE.
Error bounds for a convexity-preserving interpolation and its limit function
2008
AbstractError bounds between a nonlinear interpolation and the limit function of its associated subdivision scheme are estimated. The bounds can be evaluated without recursive subdivision. We show that this interpolation is convexity preserving, as its associated subdivision scheme. Finally, some numerical experiments are presented.
Adaptive Gaussian particle method for the solution of the Fokker-Planck equation
2012
The Fokker-Planck equation describes the evolution of the probability density for a stochastic ordinary differential equation (SODE). A solution strategy for this partial differential equation (PDE) up to a relatively large number of dimensions is based on particle methods using Gaussians as basis functions. An initial probability density is decomposed into a sum of multivariate normal distributions and these are propagated according to the SODE. The decomposition as well as the propagation is subject to possibly large numeric errors due to the difficulty to control the spatial residual over the whole domain. In this paper a new particle method is derived, which allows a deterministic error…
MCR-ALS on metabolic networks: Obtaining more meaningful pathways
2015
[EN] With the aim of understanding the flux distributions across a metabolic network, i.e. within living cells, Principal Component Analysis (PCA) has been proposed to obtain a set of orthogonal components (pathways) capturing most of the variance in the flux data. The problems with this method are (i) that no additional information can be included in the model, and (ii) that orthogonality imposes a hard constraint, not always reasonably. To overcome these drawbacks, here we propose to use a more flexible approach such as Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) to obtain this set of biological pathways through the network. By using this method, different constraint…
Matrix Shuffle- Exchange Networks for Hard 2D Tasks
2021
Convolutional neural networks have become the main tools for processing two-dimensional data. They work well for images, yet convolutions have a limited receptive field that prevents its applications to more complex 2D tasks. We propose a new neural model, called Matrix Shuffle-Exchange network, that can efficiently exploit long-range dependencies in 2D data and has comparable speed to a convolutional neural network. It is derived from Neural Shuffle-Exchange network and has O(log N) layers and O(N ^ 2 log N) total time and O(N^2) space complexity for processing a NxN data matrix. We show that the Matrix Shuffle-Exchange network is well-suited for algorithmic and logical reasoning tasks on …
Predicting sediment deposition rate in check-dams using machine learning techniques and high-resolution DEMs
2021
Sediments accumulated in check dams are a valuable measure to estimate soil erosion rates. Here, geographic information systems (GIS) and three machine learning techniques (MARS-multivariate adaptive regression splines, RF-random forest and SVM-support vector machine) were used, for the first time, to predict sediment deposition rate (SR) in check-dams located in six watersheds in SW Spain. There, 160 dry-stone check dams (~ 77.8 check-dams km−2), accumulated sediments during a period that varied from 11 to 23 years. The SR was estimated in former research using a topographical method and a high-resolution Digital Elevation Model (DEM) (average of 0.14 m3 ha−1 year−1). Nine environmental-to…
An undergraduate thesis training course for faculty reduces variability in student evaluations
2020
Abstract Background The undergraduate thesis evaluation process is one of the most prevalent weak points in universities; the literature indicates the need to orient undergraduate thesis evaluators through specific training initiatives. Objectives The aim of this study was to analyze the discrepancies between the grades awarded by undergraduate thesis supervisors and by the panel of faculty examiners, and the effect of training targeted to faculty members. Design and methods A cross-sectional study was performed during the 2015–2016 academic year in a Spanish Nursing School. Settings and participants We analyzed the mean grades from undergraduate thesis evaluation rubrics and the effects of…
Quality of School Life in the Finnish Comprehensive School: a comparative view
1996
Abstract The article attempts to answer the questions of how Finnish students experience the quality of school life as a whole and how students’ well‐being and social interaction in the Finnish comprehensive school compare with some other countries on the basis of extensive international comparative data. First, the concept ‘quality of school life’ and the self‐assessment instrument are described. Second, the validity of the instrument is explored. Next, the results of the assessment are first discussed from the national and then from the international perspective, comparing the data collected as a sub‐survey of the IEA Study of Reading Literacy in March 1991. The Finnish school is contrast…
Phytosociological analysis of the Genista sp. pl. garrigues of the Cisto-Lavanduletea and Rosmarinetea officinalis classes in the South-Tyrrhenian ar…
2015
The study reviews the Genista sp. pl. garrigues ascribable to the classes Cisto-Lavanduletea (acidophilous communities on volcanics and quartzarenites) and Rosmarinetea officinalis (basiphilous communities on calcareous and calcareous-dolomite substrates), in the southern territories of the Italo-Tyrrhenian Province. The floristic-synecological characterization of the identified coenoses led to the description and/or redefinition of various new syntaxa. They are distributed in the two new suballiances Calicotomo villosae–Genistenion tyrrhenae and Genisto aristatae–Calicotomenion infestae of the class Cisto- Lavanduletea (Lavanduletalia stoechadis and Calicotomo villosae–Genistion tyrrhenae)…
Education modulates the association of the FTO rs9939609 polymorphism with body mass index and obesity risk in the Mediterranean population
2012
Objective To define whether the rs9939609 FTO (fat mass and obesity associated) single nucleotide polymorphism (SNP) is associated with anthropometric measurements and its modulation by educational level in a Mediterranean population. Methods We studied 3 independent adult samples: a random sample (n = 1580) from the general population (GP), obese hospital patients (OHP) (n = 203) and elderly subjects (n = 1027) with high cardiovascular risk (HCR). Weight and height were directly measured. Education and physical activity (PA) were measured using questionnaires. Results The rs9939609 presented heterogeneous associations with BMI. In the GP, the minor A-allele was significantly associated wit…