Automatic offensive language detection from Twitter data using machine learning and feature selection of metadata

The popularity of social networks has only increased in recent years. In theory, the use of social media was proposed so we could share our views online, keep in contact with loved ones or share good moments of life. However, the reality is not so perfect, so you have people sharing hate speech-related messages, or using it to bully specific individuals, for instance, or even creating robots where their only goal is to target specific situations or people. Identifying who wrote such text is not easy and there are several possible ways of doing it, such as using natural language processing or machine learning algorithms that can investigate and perform predictions using the metadata associated with it. In this work, we present an initial investigation of which are the best machine learning techniques to detect offensive language in tweets. After an analysis of the current trend in the literature about the recent text classification techniques, we have selected Linear SVM and Naive Bayes algorithms for our initial tests. For the preprocessing of data, we have used different techniques for attribute selection that will be justified in the literature section. After our experiments, we have obtained 92% of accuracy and 95% of recall to detect offensive language with Naive Bayes and 90% of accuracy and 92% of recall with Linear SVM. From our understanding, these results overcome our related literature and are a good indicative of the importance of the data description approach we have used

Lógica de organização territorial Guarani: concepções do modo de ser

O objetivo da pesquisa é demonstrar que a cultura Guarani possui uma lógica de organização territorial estreitamente relacionada com as características do território. Parte-se do conceito de Paisagem Cultural para reconhecer essa lógica, e se valora como ao longo da história se produzem sucessivas intenções de aculturação, que fundamentalmente se baseiam na pretensão de impor modelos urbanos como meio civilizatório. Apesar de todo o processo de aculturação, se pretende demonstrar que os Guaranis ainda preservam traços de sua antiga organização, servindo como suporte para manter suas tradições e seu modo de vida. Neste artigo, apresentamos os padrões culturais dos seus assentamentos, baseando-se principalmente nas narrativas de jesuítas, para depois comparar com a legislação portuguesa de 1755, que inicia um sistema de urbanização utilizando a população indígena como meio de organização e defesa do território.The main research objective is to demonstrate that the Guarani’s culture has an organization pattern closely linked to the territorial features. We use the concept of Cultural Landscape to recognize this logic, and we try to show how successive attempts of acculturation happen along the time, based on the intention to impose a different urban model as a means of civilization. However we want to show how the Guaranis still try to defend traces of their old organization, serving as a basis to maintain their traditions and their way of life. In this article we present the cultural patterns of their settlements, based mainly in the narratives of the Jesuits, comparing them with the Portuguese legislation of 1755, which starts a settlement system and requires the formation of cities as the unique alternative to the territorial native organization

An Empirical Evaluation of an Evolutionary Game Theory Model of the Labor Market

In this paper we intend to perform an empirical evaluation of the evolutionary game theory model of the labor market developed by Araujo and Souza (2010). In order to accomplish this task we focus on the Brazilian labor market by using data from the National Household Sampling Survey – PNAD/IBGE, from 1995 to 2008. We used four different methodologies: the OLS, Pseudo-panel with fixed effects, Instrumental Variables and the Heckman Selection Model. Results indicate that the main difference between the 1995-2002 and 2003-2008 period is the impact of education over wages. According to these findings, investments in education were more profitable for the 2003-2008 period. However, all wage gaps between formal and informal markets reduced considerably.formal and informal and labor market, evolutionary game theory.

FPT algorithms to recognize well covered graphs

Given a graph $G$, let $vc(G)$ and $vc^+(G)$ be the sizes of a minimum and a maximum minimal vertex covers of $G$, respectively. We say that $G$ is well covered if $vc(G)=vc^+(G)$ (that is, all minimal vertex covers have the same size). Determining if a graph is well covered is a coNP-complete problem. In this paper, we obtain $O^*(2^{vc})$-time and $O^*(1.4656^{vc^+})$-time algorithms to decide well coveredness, improving results of Boria et. al. (2015). Moreover, using crown decomposition, we show that such problems admit kernels having linear number of vertices. In 2018, Alves et. al. (2018) proved that recognizing well covered graphs is coW[2]-hard when the independence number $\alpha(G)=n-vc(G)$ is the parameter. Contrasting with such coW[2]-hardness, we present an FPT algorithm to decide well coveredness when $\alpha(G)$ and the degeneracy of the input graph $G$ are aggregate parameters. Finally, we use the primeval decomposition technique to obtain a linear time algorithm for extended $P_4$-laden graphs and $(q,q-4)$-graphs, which is FPT parameterized by $q$, improving results of Klein et al (2013).Comment: 15 pages, 2 figure

On some geometric inverse problems for nonscalar elliptic systems

In this paper, we consider several geometric inverse problems for linear elliptic systems. We prove uniqueness and stability results. In particular, we show the way that the observation depends on the perturbations of the domain. In some particular situations, this provides a strategy that could be used to compute approximations to the solution of the inverse problem. In the proofs, we use techniques related to (local) Carleman estimates and differentiation with respect to the domain

Characterizing videos, audience and advertising in Youtube channels for kids

Online video services, messaging systems, games and social media services are tremendously popular among young people and children in many countries. Most of the digital services offered on the internet are advertising funded, which makes advertising ubiquitous in children's everyday life. To understand the impact of advertising-based digital services on children, we study the collective behavior of users of YouTube for kids channels and present the demographics of a large number of users. We collected data from 12,848 videos from 17 channels in US and UK and 24 channels in Brazil. The channels in English have been viewed more than 37 billion times. We also collected more than 14 million comments made by users. Based on a combination of text-analysis and face recognition tools, we show the presence of racial and gender biases in our large sample of users. We also identify children actively using YouTube, although the minimum age for using the service is 13 years in most countries. We provide comparisons of user behavior among the three countries, which represent large user populations in the global North and the global South

Inverse problems for linear parabolic equations using mixed formulations -Part 1 : Theoretical analysis

We introduce in this document a direct method allowing to solve numerically inverse type problems for linear parabolic equations. We consider the reconstruction of the full solution of the parabolic equation posed in Ω × (0, T)-Ω a bounded subset of R N-from a partial distributed observation. We employ a least-squares technique and minimize the L 2-norm of the distance from the observation to any solution. Taking the parabolic equation as the main constraint of the problem, the optimality conditions are reduced to a mixed formulation involving both the state to reconstruct and a Lagrange multiplier. The well-posedness of this mixed formulation-in particular the inf-sup property-is a consequence of classical energy estimates. We then reproduce the arguments to a linear first order system, involving the normal flux, equivalent to the linear parabolic equation. The method, valid in any dimension spatial dimension N , may also be employed to reconstruct solution for boundary observations. With respect to the hyperbolic situation considered in [10] by the first author, the parabolic situation requires-due to regularization properties-the introduction of appropriate weights function so as to make the problem numerically stable

A mixed formulation for the direct approximation of L2-weighted controls for the linear heat equation

This paper deals with the numerical computation of null controls for the linear heat equation. The goal is to compute approximations of controls that drive the solution from a prescribed initial state to zero at a given positive time. In [Fernandez-Cara & Münch, Strong convergence approximations of null controls for the 1D heat equation, 2013], a so-called primal method is described leading to a strongly convergent approximation of distributed control: the controls minimize quadratic weighted functionals involving both the control and the state and are obtained by solving the corresponding optimality conditions. In this work, we adapt the method to approximate the control of minimal square integrable-weighted norm. The optimality conditions of the problem are reformulated as a mixed formulation involving both the state and its adjoint. We prove the well-posedeness of the mixed formulation (in particular the inf-sup condition) then discuss several numerical experiments. The approach covers both the boundary and the inner situation and is valid in any dimension.Coordenação de aperfeiçoamento de pessoal de nivel superiorMinisterio de Ciencia e Innovació