Search results for "MATEMATICA APLICADA"
showing 10 items of 277 documents
A generalization to Sylow permutability of pronormal subgroups of finite groups
2020
[EN] In this note, we present a new subgroup embedding property that can be considered as an analogue of pronormality in the scope of permutability and Sylow permutability in finite groups. We prove that finite PST-groups, or groups in which Sylow permutability is a transitive relation, can be characterized in terms of this property, in a similar way as T-groups, or groups in which normality is transitive, can be characterized in terms of pronormality.
On $p$-Dunford integrable functions with values in Banach spaces
2018
[EN] Let (Omega, Sigma, mu) be a complete probability space, X a Banach space and 1 X. Special attention is paid to the compactness of the Dunford operator of f. We also study the p-Bochner integrability of the composition u o f: Omega->Y , where u is a p-summing operator from X to another Banach space Y . Finally, we also provide some tests of p-Dunford integrability by using w*-thick subsets of X¿.
Frames and representing systems in Fréchet spaces and their duals
2014
[EN] Frames and Bessel sequences in Fr\'echet spaces and their duals are defined and studied. Their relation with Schauder frames and representing systems is analyzed. The abstract results presented here, when applied to concrete spaces of analytic functions, give many examples and consequences about sampling sets and Dirichlet series expansions.
QR-Factorization Algorithm for Computed Tomography (CT): Comparison With FDK and Conjugate Gradient (CG) Algorithms
2018
[EN] Even though QR-factorization of the system matrix for tomographic devices has been already used for medical imaging, to date, no satisfactory solution has been found for solving large linear systems, such as those used in computed tomography (CT) (in the order of 106 equations). In CT, the Feldkamp, Davis, and Kress back projection algorithm (FDK) and iterative methods like conjugate gradient (CG) are the standard methods used for image reconstruction. As the image reconstruction problem can be modeled by a large linear system of equations, QR-factorization of the system matrix could be used to solve this system. Current advances in computer science enable the use of direct methods for…
The impact factor as a measuring tool of the prestige of the journals in research assessment in mathematics
2016
The (2-year) Impact Factor of Thomson-Reuters (IF) has become the fundamental tool for analysing the scientific production of academic researchers in a lot of countries. In this article we show that this index and the ordering criterion obtained by using it are highly unstable in the case of mathematics, to the extent that sometimes no reliability can be assigned to its use. We explain the reasons of this behaviour by the specific properties of the mathematical journals and publications, attending mainly the point of view of the researchers in pure mathematics. Using the Journal Citation Report list of journals as a source of information, we analyse the stability in the position of the math…
Advances in the general factor of personality dynamics
2018
This paper presents a dynamical integro-differential equation to reproduce the dynamical response of the General Factor of Personality (GFP) to a stimulus dose, particularly to a stimulant drug dose. The model is called in the past authors publications as response model. We refer to it as the old response model, due to a new response model presented here that solves partially the problem of the model validation: how to forecast the GFP dynamical response from a previous model calibration. The application case presented is an individual ABC experimental design where the stimulus used is methylphenidate.
A genetic algorithm to calibrate dynamical systems: Confidence intervals for parameters and residuals
2018
This paper presents a genetic algorithm to calibrate dynamical systems that is able to calculate confidence intervals for the parameters of the system. As an application case is used to calibrate the system that reproduces the dynamical response of the General Factor of Personality (GFP) to a given stimulus, particularly to a stimulant drug dose. The model is called in Literature as the response model and includes an integro-differential equation. The presented application case is a single case ABC experimental design where the stimulus is methylphenidate.
Assessing supply chain risks in the automotive industry through a modified MCDM-based FMECA
2020
Supply chains are complex networks that receive assiduous attention in the literature. Like any complex network, a supply chain is subject to a wide variety of risks that can result in significant economic losses and negative impacts in terms of image and prestige for companies. In circumstances of aggressive competition among companies, effective management of supply chain risks (SCRs) is crucial, and is currently a very active field of research. Failure Mode, Effects and Criticality Analysis (FMECA) has been recently extended to SCR identification and prioritization, aiming at reducing potential losses caused by lack of risk control. This article has a twofold objective. First, SCR assess…
Explaining the rising precariat in Spain
2020
[EN] Spanish GDP indicator figures recover while the risk of poverty has not stopped increasing since 2007 given the continuous austerity policies adopted by Governments, while labour and welfare conditions have worsened. A new phenomenon is emerging: the flattening of the Spanish middle class. This study proposes a model to quantify the number of individuals according to their level of precariousness in Spain. The model allows us to predict the behaviour of society in Spain given the mimetic nature of humans by constructing a discrete finite epidemiological model that classifies and quantifies the population in Spain according to its risk of precariousness. Our results show a rise in the p…
Spectral study of {R, s + 1, k}- and {R, s + 1, k, *}-potent matrices
2020
[EN] The {R, s +1, k}- and {R, s +1, k, *}-potent matrices have been studied in several recent papers. We continue these investigations from a spectral point of view. Specifically, a spectral study of {R, s + 1, k} -potent matrices is developed using characterizations involving an associated matrix pencil (A, R). The corresponding spectral study for {R, s+ 1, k, *}-potent matrices involves the pencil (A*, R). In order to present some properties, the relevance of the projector I - AA(#). where A(#) is the group inverse of A is highlighted. In addition, some applications and numerical examples are given, particularly involving Pauli matrices and the quaternions.