A network approach to topic models

One of the main computational and scientific challenges in the modern age is to extract useful information from unstructured texts. Topic models are one popular machine-learning approach which infers the latent topical structure of a collection of documents. Despite their success --- in particular of its most widely used variant called Latent Dirichlet Allocation (LDA) --- and numerous applications in sociology, history, and linguistics, topic models are known to suffer from severe conceptual and practical problems, e.g. a lack of justification for the Bayesian priors, discrepancies with statistical properties of real texts, and the inability to properly choose the number of topics. Here we obtain a fresh view on the problem of identifying topical structures by relating it to the problem of finding communities in complex networks. This is achieved by representing text corpora as bipartite networks of documents and words. By adapting existing community-detection methods -- using a stochastic block model (SBM) with non-parametric priors -- we obtain a more versatile and principled framework for topic modeling (e.g., it automatically detects the number of topics and hierarchically clusters both the words and documents). The analysis of artificial and real corpora demonstrates that our SBM approach leads to better topic models than LDA in terms of statistical model selection. More importantly, our work shows how to formally relate methods from community detection and topic modeling, opening the possibility of cross-fertilization between these two fields.Comment: 22 pages, 10 figures, code available at https://topsbm.github.io

Sampling motif-constrained ensembles of networks

The statistical significance of network properties is conditioned on null models which satisfy spec- ified properties but that are otherwise random. Exponential random graph models are a principled theoretical framework to generate such constrained ensembles, but which often fail in practice, either due to model inconsistency, or due to the impossibility to sample networks from them. These problems affect the important case of networks with prescribed clustering coefficient or number of small connected subgraphs (motifs). In this paper we use the Wang-Landau method to obtain a multicanonical sampling that overcomes both these problems. We sample, in polynomial time, net- works with arbitrary degree sequences from ensembles with imposed motifs counts. Applying this method to social networks, we investigate the relation between transitivity and homophily, and we quantify the correlation between different types of motifs, finding that single motifs can explain up to 60% of the variation of motif profiles.Comment: Updated version, as published in the journal. 7 pages, 5 figures, one Supplemental Materia

Memória e suas relações com Cronos e Kariós

The article intends to show the vibrant and constant relationship between memory and the experience of the present; taking care to bring memory, truth and justice closer to the contemporary assumptions of human rights. Based on an analysis of the resurgence of an ultra-conservative ideology in Brazil in the last decade, we seek to demonstrate the importance of not forgetting the recent past in the country to point out relevance and paths that expand our network of meanings, and help us to recognize the risk of present and future experiences that attempt to suppress political and civil rights.O artigo tem a intenção de mostrar a relação viva e constante entre a memória e a experiência do presente; cuidando para aproximar a memória, a verdade e a justiça dos pressupostos contemporâneos dos direitos humanos. Buscamos, a partir de uma análise do recrudescimento de uma ideologia ultra-conservadora nesta última década no Brasil, demonstrar a importância do não esquecimento do passado recente no país para se apontar relevâncias, caminhos e percursos que ampliemnossa rede de significados, e nos ajudem a reconhecer o risco de experiências presentes e futuras que intentem em suprimir direitos políticos e civis

A utilização do composto de marketing para um evento: caso show Jorge Ben Jor: 15 de Abril/ Brasília

Este trabalho tem como objetivo de estudo analisar a utilização do composto de marketing em eventos culturais. Mais especificamente, como os conceitos de produto, preço, praça e promoção podem ser usados para resultar no sucesso de um evento. No caso, o show do artista Jorge Ben Jor, realizado dia 15 de abril de 2006 em Brasília. Ressalta-se que este estudo não tem o intuito de explicar o funcionamento de um evento, apenas reconhecer como os 4 P’s de marketing podem influenciar na viabilidade do projeto

O programa Inovar-Auto : uma análise com a teoria da economia internacional e os acordos da OMC

Monografia (graduação)—Universidade de Brasília, Faculdade de Administração, Economia e Contabilidade, Departamento de Economia, 2016.Em janeiro de 2013 entrou em vigor no Brasil o programa INOVAR-AUTO que, segundo o Ministério do Desenvolvimento, Indústria e Comércio Exterior, visa melhorar a indústria automotiva nacional. Este programa oferece incentivos fiscais com créditos do IPI para empresas já com fábricas nacionais, que pretendem abrir novas fábricas ou que pretendem apenas comercializar automóveis dentro do Brasil em troca de elas investirem em determinados seguimentos no setor automotivo brasileiro. Mesmo sendo discutíveis os reais benefícios gerados na economia nacional, a União Europeia e o Japão alegam que ele não está em sintonia com acordos mundiais. Estes países acusam o Brasil de gerar, por meio do programa, uma concorrência desleal entre os veículos nacionais e os importados. O presente trabalho analisará se programa realmente negligencia estes acordos além de verificar se ele está em sintonia com as teorias do comércio internacional como as de Ricardo e de Hecksher-Ohlin que afirmam que o livre comércio é sempre mais benéfico do que um comércio com barreiras.In January 2013 came into force in Brazil the INOVAR-AUTO program aimed at improving the national automotive industry. This program offers tax incentives with IPI credits to companies already with domestic factories, those intend to open new plants or intend to only sell cars within Brazil in exchange for them to invest in certain segments of the Brazilian automotive industry. Even though the real benefits generated in the national economy is debatable, the European Union and Japan claim that it is not in line with global agreements. These countries accuse Brazil of generating, through the program, unfair competition between domestic and imported vehicles. This study will examine whether the program actually neglects these agreements and to verify if it is in line with the theories of international trade such as Ricardo and Heckscher-Ohlin who claim that free trade is always more beneficial than a trade hurdles