Performance Evaluation of CORBA Concurrency Control Service Using Stochastic Petri Nets

The interest in performance evaluation of middleware systems is increasing. Measurement techniques are still predominant among those used to carry out performance evaluation. However, performance models are currently being defined due to their flexibility, precision and facilities to carry out capacity planning activities. This paper presents stochastic Petri net models for performance evaluation of the CORBA Concurrency Control Service (CCS), which mediates concurrent access to objects. In order to validate the proposed models, CCS performance results obtained using those models are then compared against ones obtained through actual measurements.The interest in performance evaluation of middleware systems is increasing. Measurement techniques are still predominant among those used to carry out performance evaluation. However, performance models are currently being defined due to their flexibility, precision and facilities to carry out capacity planning activities. This paper presents stochastic Petri net models for performance evaluation of the CORBA Concurrency Control Service (CCS), which mediates concurrent access to objects. In order to validate the proposed models, CCS performance results obtained using those models are then compared against ones obtained through actual measurements

DEP–DM: Uma Abordagem baseada em Ensemble Regression para o Diagnóstico de Problemas Educacionais

Este artigo apresenta a abordagem DEP-DM, baseada em modelos Ensemble Regression para o diagnóstico do problema do desempenho escolar dos estudantes das escolas públicas de Pernambuco. O estudo baseou-se em informações do SAEB do ano de 2013. O conhecimento foi extraído por meio da abordagem proposta, sendo possível identificar os fatores associados e estabelecer as relações de causa e efeito com o problema do desempenho escolar. Por fim, foram aplicados modelos de regressão paramétricos e não paramétricos para a previsão desse desempenho. Os resultados e diagnóstico apresentam que os fatores relacionados a infraestrutura da escola, ensino e familiares, exercem forte influência sobre o desempenho escolar

Educational DataMining: A Study of the Factors That Cause School Dropout in Higher Education Institutions in Brazil

Context:In Brazil, there is a high dropout rate in higher education institutions. Thus, it is clear that evasion is a frequent problem and that it is necessary to analyze the factors that cause it to enable solutions that can mitigate/ reduce this problem. Objetive: (1)perform a correlation analysis (Pearson and Spearman) of the educational factores of the School Census; (2)propose school dropout prediction models taking into account educational and economic factors using regression methods (linear, robust, ridge, lasso, clusterwise regression). Methodology: used the phases of the CRISP-DM methodology. Results: the factors related to not allowing financial assistance are related to as evasion, namely: food, permanence, didactic material, transportation. There are also factors related to the study period. The regression robust and linear regression show fewer errors. Conclusion: the correlations used present the selection of factors in a similar way, thus following a linear distribution. This study can help to create more investment in public policies, as it ratifies factors are related to this dropout problem

Performance Evaluation of CORBA Concurrency Control Service Using Stochastic Petri Nets

Abstract. The interest in performance evaluation of middleware systems is increasing. Measurement techniques are still predominant among those used to carry out performance evaluation. However, performance models are currently being defined due to their flexibility, precision and facilities to carry out capacity planning activities. This paper presents stochastic Petri net models for performance evaluation of the CORBA Concurrency Control Service (CCS), which mediates concurrent access to objects. In order to validate the proposed models, CCS performance results obtained using those models are then compared against ones obtained through actual measurements.

Identification and measurement of Requirements Technical Debt in software development:a systematic literature review

Abstract Context: Requirements Technical Debt are related to the distance between the ideal value of the specification and the actual implementation of the system, which are consequences of strategic decisions for immediate gains, or unintended changes in context. To ensure the evolution of the software, it is necessary to to manage TD. Identification and measurement are the first two stages of the management process; however, they are poorly explored in academic research in requirements engineering. Objective: We aimed to investigating which evidence helps to strengthen the TD requirements management process, including identification and measurement. Method: We conducted a Systematic Literature Review through manual and automatic searches considering 7499 studies from 2010 to 2020, and including 66 primary studies. Results: We identified some causes related to Technical Debt requirements, existing strategies to help in the identification and measurement, and metrics to support the measurement stage. Conclusion: The studies on Requirements Technical Debt are still preliminary, especially regarding management software. Yet, however, the interpersonal aspects that prove difficult in the implementation of such activities are not sufficiently addressed. Finally, the provision of metrics to help measure technical debt is part of the contribution of this search, providing insights into the application in its requirements context

The Role of Condensed Tannins in the In Vitro Rumen Fermentation Kinetics in Ruminant Species: Feeding Type Involved?

Animal feeding behavior and diet composition determine rumen fermentation responses and its microbial characteristics. This study aimed to evaluate the rumen fermentation kinetics of domestic ruminants feeding diets with or without condensed tannins (CT). Holstein dairy cows, Nelore beef cattle, Mediterranean water buffalo, Santa Inês sheep and Saanen goats were used as inoculum donors (three animals of each species). The substrates were maize silage (Zea mays), fresh elephant grass (Pennisetum purpureum), Tifton-85 hay (Cynodon spp.) and fresh alfalfa (Medicago sativa). Acacia (Acacia molissima) extract was used as the external CT source. The in vitro semi-automated gas production technique was used to assess the fermentation kinetics. The experimental design was completely randomized with five inoculum sources (animal species), four substrates (feeds) and two treatments (with or without extract). The inclusion of CT caused more severe effects in grazing ruminants than selector ruminants

Mitochondrial Population Genomics Supports a Single Pre-Clovis Origin with a Coastal Route for the Peopling of the Americas

It is well accepted that the Americas were the last continents reached by modern humans, most likely through Beringia. However, the precise time and mode of the colonization of the New World remain hotly disputed issues. Native American populations exhibit almost exclusively five mitochondrial DNA (mtDNA) haplogroups (A–D and X). Haplogroups A–D are also frequent in Asia, suggesting a northeastern Asian origin of these lineages. However, the differential pattern of distribution and frequency of haplogroup X led some to suggest that it may represent an independent migration to the Americas. Here we show, by using 86 complete mitochondrial genomes, that all Native American haplogroups, including haplogroup X, were part of a single founding population, thereby refuting multiple-migration models. A detailed demographic history of the mtDNA sequences estimated with a Bayesian coalescent method indicates a complex model for the peopling of the Americas, in which the initial differentiation from Asian populations ended with a moderate bottleneck in Beringia during the last glacial maximum (LGM), around ∼23,000 to ∼19,000 years ago. Toward the end of the LGM, a strong population expansion started ∼18,000 and finished ∼15,000 years ago. These results support a pre-Clovis occupation of the New World, suggesting a rapid settlement of the continent along a Pacific coastal route