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On compact groups with Engel-like conditions.
(2023) Bastos Júnior, Raimundo de Araújo; Silveira, Danilo Sanção da
Let G be a compact Hausdorff group. We show that if for every element x∈G
there exists a positive integer q=q(x)
such that xq is Engel, then G is locally virtually nilpotent. Furthermore, we show that if G is a finitely generated compact Hausdorff group in which any commutator [x,y]
in G is Engel, then the commutator subgroup G′
is locally nilpotent.
Non-singular derivations of solvable Lie algebras in prime characteristic.
(2019) Lima, Marcos Goulart; Schneider, Csaba
We study solvable Lie algebras in prime characteristic p that
admit non-singular derivations. We show that Jacobson’s
Theorem remains true if the quotients of the derived series
have dimension less than p. We also study the structure of Lie
algebras with non-singular derivations in which the derived
subalgebra is abelian and has codimension one. The paper
presents some new examples of solvable, but not nilpotent,
Lie algebras of derived length 3 with non-singular derivations.
A network-driven study of hyperprolific authors in computer science.
(2024) Vieira, Vinicius da Fonseca; Ferreira, Carlos Henrique Gomes; Almeida, Jussara Marques de; Moreira, Edré; Laender, Alberto Henrique Frade; Meira Júnior, Wagner; Gonçalves, Marcos André
Scientific authors’ collaborations are influenced by various factors, such as their field, geographic region, and institutional role. Here we focus on a group of authors whose patterns of publications greatly deviate from the average, previously referred as hyperprolific authors. Prior studies have investigated the emergence of hyperprolific authors and their productivity. In this article, we focus on the role of coauthorships in the hyperprolific authors’ publication profiles. Based on a network model that represents researchers as nodes and weighted edges as the number of collaborations between a pair of researchers, we argue that not all network edges have the same importance to characterize the existence of hyperprolific authors. As such, we filter out “sporadic” coauthorships, revealing an underlying structure composed only of edges representing consistent and repetitive collaborations, named as the network backbone. Our network-oriented methodology was applied to a dataset of Computer Science publications extracted from DBLP, covering an 11-year period from 2010 to 2020. Our experiments reveal significant topological differences between the full coauthorship networks and backbones, concerning only authors with very off-the-pattern profiles. We also show that hyperprolific authors are consistently more likely to exhibit off-the-pattern coauthorships and that an author’s probability of being present in the backbone substantially increases with her topological proximity to a hyperprolific author. Finally, we investigate how authors’ hyperprolific profiles correlate to their presence in the backbone.
Evaluating testing strategies for resource related failures in mobile applications.
(2023) Marinho, Euler Horta; Ferreira, Fischer; Diniz, João P.; Figueiredo , Eduardo
Mobile applications have been used for multiple purposes from entertainment to critical domains. As a consequence, the quality of mobile applications has become a crucial aspect, for instance, by promoting the use of testing as a quality assurance practice. The diversity of mobile platforms is pervaded by several resources related to communication capabilities, sensors, and user-controlled options. As a result, applications can present unexpected behaviors and resource interactions can introduce failures that manifest themselves in specific resource combinations. These failures can compromise the mobile application quality and harm the user experience. We evaluate the failure-detection capability and effectiveness of five sampling testing strategies (Random, One-Enabled, One-Disabled, Most-Enabled-Disabled, and Pairwise) in the context of resource related failures in 15 mobile applications. We focus on 14 common resources of the Android platform and analyze the resource interactions more likely to cause failures. Random had great percentages of failing test cases, followed by One-Enabled, Most-Enabled-Disabled, and Pairwise. We observe that One-Enabled and One-Disabled are the most effective testing strategies for six and four applications, respectively. Surprisingly, resource pairs have more influence on failures than other resource combinations, varying widely among the applications.
Recebimento de sucata para o processo Shredder : uma análise de cenários por meio da simulação computacional.
(2024) Reis, Beatriz Mendanha; Gomes, Helton Cristiano; Guimarães, Irce Fernandes Gomes; Gomes, Helton Cristiano; Guimarães, Irce Fernandes Gomes; Murta, Jorge Luiz Brescia; Queiroz, Rhelman Rossano Urzedo
A produção de aço em Forno Elétrico a Arco (FEA) ganhou destaque
significativo nas usinas siderúrgicas após a Segunda Guerra Mundial (1939-1945),
devido à capacidade de controlar com precisão a composição química, a possibilidade
de utilização de sucata de aço viabilizando a reciclagem e a crescente disponibilidade de
energia elétrica (Matsuura; Fruehan, 2009). No mundo, aproximadamente 28% do aço é
produzido via FEA baseado em utilização de sucata na composição da carga fria
(Worldsteel, 2022). Nesse processo, as matérias-primas essenciais incluem o ferro gusa,
fundentes e a sucata de aço. A quantidade de sucata de aço disponível está
intrinsecamente ligada à taxa de reciclabilidade em diferentes economias (mundial,
mista, política e industrial) de desenvolvimento. Em 2021, a taxa de retorno de sucata
obsoleta é de aproximadamente 85%, com previsão de aumentar para cerca de 100%
nos próximos 30 anos. Neste sentido, a simulação de eventos discretos (SED), aplicada
ao processo de reciclagem de sucata de aço, tem sido uma ferramenta eficaz para
estudar o comportamento dos sistemas em diversas condições. Nesse trabalho, a
simulação de eventos discretos foi utilizada como ferramenta para simular o fluxo de
recebimento e estocagem da sucata de aço em uma usina siderúrgica para o processo
Shredder com o objetivo de quantificar a demanda de trabalho do recurso escavadeira
para o recebimento de sucata de aço, levando em conta fatores como volume diário de
recebimento, tempos e movimentos da atividade de descarga, tipo de sucata a ser
recebida e distribuição de chegada das carretas para diferentes cenários com
recebimento mensal de 20.000 t de sucata. Foram simulados quatro cenários variando a
quantidade de horas disponíveis do recurso escavadeira e a proporção entre os dois tipos
de sucata resultando na escolha do cenário em que o atendimento à demanda médio foi
de 79% com a quantidade de duas escavadeiras com disponibilidade diária de 24 horas e
8 horas, respectivamente, e ocupação média de 71%.