Search results for "multivariate"
showing 10 items of 1520 documents
Outlier analysis and principal component analysis to detect fatigue cracks in waveguides
2009
Ultrasonic Guided Waves (UGWs) are a useful tool in structural health monitoring (SHM) applications that can benefit from built-in transduction, moderately large inspection ranges and high sensitivity to small flaws. This paper describes a SHM method based on UGWs, discrete wavelet transform (DWT), outlier analysis and principal component analysis (PCA) able to detect and quantify the onset and propagation of fatigue cracks in structural waveguides. The method combines the advantages of guided wave signals processed through the DWT with the outcomes of selecting defectsensitive features to perform a multivariate diagnosis of damage. The framework presented in this paper is applied to the de…
A Mesh-free Particle Method for Transient Full-wave Simulation
2007
A mesh-free particle method is presented for electromagnetic (EM) transient simulation. The basic idea is to obtain numerical solutions for the partial differential equations describing the EM problem in time domain, by using a set of particles, considered as spatial interpolation points of the field variables, arbitrarily placed in the problem domain and by avoiding the use of a regular mesh. Irregular problems geometry with diffused non-homogeneous media can be modeled only with an initial set of arbitrarily distributed particles. The time dependence is accounted for with an explicit finite difference scheme. Moreover the particle discretization can be improved during the process time ste…
Air conditioning and heat-related mortality: a multi-country longitudinal study
2020
Background: Air conditioning has been proposed as one of the key factors explaining reductions of heat-related mortality risks observed in the last decades. However, direct evidence is still limited. Methods: We used a multi-country, multi-city, longitudinal design to quantify the independent role of air conditioning in reported attenuation in risk. We collected daily time series of mortality, mean temperature, and yearly air conditioning prevalence for 311 locations in Canada, Japan, Spain, and the USA between 1972 and 2009. For each city and sub-period, we fitted a quasi-Poisson regression combined with distributed lag non-linear models to estimate summer-only temperature–mortality associ…
Predictive factors for sustained virological response after treatment with pegylated interferon α-2a and ribavirin in patients infected with HCV geno…
2014
BackgroundPrevious trials have often defined genotype 2 and 3 patients as an "easy to treat" group and guidelines recommend similar management.AimsThe present study looks for differences between the two genotypes and analyzes predictive factors for SVR.MethodsProspective, community-based cohort study involving 421 physicians throughout Germany. The analysis includes 2,347 patients with untreated chronic HCV genotype 2 (n = 391) and 3 (n = 1,956) infection treated with PEG-IFN α-2a plus ribavirin between August 2007 and July 2012.ResultsWhen compared with genotype 2 patients, those with genotype 3 were younger, had a shorter duration of infection, lower values of total cholesterol, LDL chole…
Drug-drug interactions in a cohort of hospitalized elderly patients
2013
Purpose The aim of this study is to assess the prevalence of patients exposed to potentially severe drug–drug interactions (DDIs) at hospital admission and discharge and the related risk of in-hospital mortality and adverse clinical events, readmission, and all-cause mortality at 3months. Methods This cross-sectional, prospective study was held in 70 Italian internal medicine and geriatric wards. Potentially severe DDIs at hospital admission and discharge; risk of in-hospital mortality and of adverse clinical events, readmission, and all-cause mortality at 3-month follow-up. Results Among 2712 patients aged 65years or older recruited at hospital admission, 1642 (60.5%) were exposed to at le…
Early alterations of the behavioural structure of mice affected by Duchenne muscular dystrophy and tested in open-field
2020
Present study has been carried out to assess whether early alterations of the behavioural structure may be detected in mice affected by Duchenne muscular dystrophy (DMD). To this purpose, both quantitative and T-pattern analysis (TPA) were used to analyse the behaviour of two groups of male, two months old mice, 18 MDX and 18 normal as control, tested in an open-field apparatus. T-pattern analysis is a multivariate technique able to reveal hidden structural features of behaviour and, in particular, its temporal characteristics. As to quantitative analyses, mean durations evidenced a significant increase of Walking, Modified Climbing and Rearing and a significant reduction of Immobile-Sniffi…
A CLASS OF MULTIVARIATE TRANSFORMED-EXPONENTIAL DISTRIBUTIONS
2013
In finance it is commonly accepted that heavy-tailed distributions are appropriate for modelling financial asset return variables and part of the financial literature has recently focused on them. Much less attention has been dedicated to the construction of joint models of asset returns unable to describe an adequate dependence structure between all these variables. In this paper we propose a procedure for constructing multivariate distributions with given heterogeneous heavy-tailed marginal distributions as a possible (under certain conditions) alternative to the copula approach. The procedure bases on the marginal transformation method and, for given plausible specifications of the margi…
Small Mammals in Forests of Romania: Habitat Type Use and Additive Diversity Partitioning
2021
Small mammals are key components of forest ecosystems, playing vital roles for numerous groups of forest organisms: they exert bottom-up and top-down regulatory effects on vertebrate and invertebrate populations, respectively
The effectiveness of rural versus urban nonprofit organisations in the Democratic Republic of Congo
2017
The Democratic Republic of Congo (DRC) is a country with high natural resources, but it has suffered from decades of civil wars and social turmoil, being heavily aid-dependent. In the DRC, several Nonprofit Organisations (NPOs) are major players in fighting poverty and enhancing welfare. This research aims to analyse the effectiveness of small NPOs in improving poor peoples’ lives through health, education, and economic activities. Two NPOs working in the DRC, one in a rural and the other in an urban area, are compared by researching the aid sites and surveying 201 households (aid beneficiaries). Our case observations and the survey results facilitate analysing the mission accomplishment, e…
Weak versus strong dominance of shrinkage estimators
2021
We consider the estimation of the mean of a multivariate normal distribution with known variance. Most studies consider the risk of competing estimators, that is the trace of the mean squared error matrix. In contrast we consider the whole mean squared error matrix, in particular its eigenvalues. We prove that there are only two distinct eigenvalues and apply our findings to the James–Stein and the Thompson class of estimators. It turns out that the famous Stein paradox is no longer a paradox when we consider the whole mean squared error matrix rather than only its trace.