Search results for "MATEMATICA APLICADA"

Survival analysis of author keywords: An application to the library and information sciences area

2020

[EN] Our purpose is to adapt a statistical method for the analysis of discrete numerical series to the keywords appearing in scientific articles of a given area. As an example, we apply our methodological approach to the study of the keywords in the Library and Information Sciences (LIS) area. Our objective is to detect the new author keywords that appear in a fixed knowledge area in the period of 1 year in order to quantify the probabilities of survival for 10 years as a function of the impact of the journals where they appeared. Many of the new keywords appearing in the LIS field are ephemeral. Actually, more than half are never used again. In general, the terms most commonly used in the …

The Hierarchical Mixed Rural Postman Problem: Polyhedral analysis and a branch-and-cut algorithm

2017

[EN] The Hierarchical Mixed Rural Postman Problem is defined on a mixed graph where arcs and edges that require a service are divided into clusters' that have to be serviced in a hierarchical order. The problem generalizes the Mixed Rural Postman Problem and thus is NP-hard. In this paper, we provide a polyhedral analysis of the problem and propose a branch-and-cut algorithm for its solution based on the introduced classes of valid inequalities. Extensive computational experiments are reported on benchmark instances. The exact approach allows to find the optimal solutions in less than 1 hour for instances with up to 999 vertices, 2678 links, and five clusters.

Group Extensions and Graphs

2016

A classical result of Gaschütz affirms that given a finite A-generated group G and a prime p, there exists a group G# and an epimorphism phi: G# ---> G whose kernel is an elementary abelian p-group which is universal among all groups satisfying this property. This Gaschütz universal extension has also been described in the mathematical literature with the help of the Cayley graph. We give an elementary and self-contained proof of the fact that this description corresponds to the Gaschütz universal extension. Our proof depends on another elementary proof of the Nielsen-Schreier theorem, which states that a subgroup of a free group is free.

Updating the OSPF routing protocol for communication networks by optimal decision-making over the k-shortest path algorithm

2019

Internet routing protocols such as Routing Information Protocol (RIP) pre-compute all the shortest paths by Dijkstra's algorithm (shortest path first, SPF) based on the number of hops between one node and another. Every time any communication is intended, RIP looks-up for the optimal choice in a routing table. This is a high speed method in the decision-making process but not necessary fast for data traffic as it does not take into account any real-time measure of route congestion. Open Shortest Path First (OSPF) presents a dynamic version of this problem by computing the shortest paths taking into account network features such as bandwidth, delay and load. OSPF thereby maintains link-state…

The inverse eigenvalue problem for a Hermitian reflexive matrix and the optimization problem

2016

The inverse eigenvalue problem and the associated optimal approximation problem for Hermitian reflexive matrices with respect to a normal {k+1}-potent matrix are considered. First, we study the existence of the solutions of the associated inverse eigenvalue problem and present an explicit form for them. Then, when such a solution exists, an expression for the solution to the corresponding optimal approximation problem is obtained.

Characterizations of {K,s+1}-Potent Matrices and Applications

2012

Recently, situations where a matrix coincides with some of its powers have been studied. This kind of matrices is related to the generalized inverse matrices. On the other hand, it is possible to introduce another class of matrices that involve an involutory matrix, generalizing the well-known idempotent matrix, widely useful in many applications. In this paper, we introduce a new kind of matrices called {K,s+1}-potent, as an extension of the aforementioned ones. First, different properties of {K,s+1}-potent matrices have been developed. Later, the main result developed in this paper is the characterization of this kind of matrices from a spectral point of view, in terms of powers of the ma…

A personality mathematical model of placebo with or without deception: an application of the Self-Regulation Therapy

2019

Self-Regulation Therapy to Reproduce Drug Effects:A Suggestion Technique to Change Personality and theDRD3Gene Expression

2013

This study proposes a strategy, based on self-regulation therapy, to change personality and its biological substrate, the DRD3 gene expression. It has been demonstrated that acute doses of stimulating drugs, like methylphenidate, are able to change personality and the expression of certain genes in the short term. On the other hand, self-regulation therapy has been proven to reproduce the effects of drugs. Thus, it is feasible to hope that self-regulation therapy is equally effective as methylphenidate in changing personality and the gene expression. This is a preliminary study with a single-case experimental design with replication in which 2 subjects participated. The results and potentia…

The effects of age and emotional valence on recognition memory: An ex-Gaussian components analysis

2014

[EN] The aim of this work was to study the effects of valence and age on visual image recognition memory. The International Affective Picture System (IAPS) battery was used, and response time data were analyzed using analysis of variance, as well as an ex-Gaussian fit method. Older participants were slower and more variable in their reaction times. Response times were longer for negative valence pictures, however this was statistically significant only for young participants. This suggests that negative emotional valence has a strong effect on recognition memory in young but not in old participants. The tau parameter, often related to attention in the literature, was smaller for young than …

Analysing the effect of public health campaigns on reducing excess weight: a modelling approach for the Spanish Autonomous Region of the Community of…

2012

Abstract Excess weight is fast becoming a serious health concern in the developed and developing world. The concern of the public health sector has lead to the development of public health campaigns, focusing on two-fold goals: to inform the public as to the health risks inherent in being overweight, and the benefits of a change in nutritional behaviour. Recent studies indicate that the effects of the average public health campaign on the target community is around 5%. In this study we aim to quantify the effect of different public health campaigns on lifestyle behaviour in the target populations in order to bring about weightloss in a significant number of people over the next few years. T…