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- Multi-device Notifications: a comparison between MQTT and CoAPPublication . Silva, Luis; Mello, Gabriel de; Silva, Bruno Alves da; Villarrubia Gonzalez, Gabriel; Santana, Juan da Paz; Prata, Paula; Leithardt, ValderiNew devices generate, send, and display messages about their status, data retrieval, and device information. An increase in the number of notifications received, tends to reduce their tolerance . This article sets out a notification management system focused on user profiles and environments. The solution involves transferring notifications in a multi-device scenario using MQTT and CoAP technologies, while also adopting privacy criteria. It consists of three modules, the first of which was prototype and evaluated using real devices.
- Computing Topics on Multiple Imputation in Big Identifiable Data Using R: An Application to Educational ResearchPublication . Ferrão, Maria Eugénia; Prata, PaulaThis article shows how to conduct multiple imputation in big identifiable data for educational research purposes. The R statistical package and procedures to handle missing data applied for the purpose of this study were “Bay-lorEdPsych” and “mi”. Firstly, we checked that every dataset rejected the null hypothesis for Missing Completely At Random (MCAR), using the function “LittleMCAR”. Simulated and real data analyses were conducted. Results sug-gest that the improvement of the quality of imputation requires alternative methods to be developed.
- Web application for the analysis of assessment testsPublication . Prata, Paula; Duarte, Luís; Ferrão, Maria EugéniaIntroduction: An assessment test enables the evaluation of an individual’s competence or ability. Such tests are important for both teaching and professional training institutions, as well as for the recruiting of human resources in the enterprise. Objectives: The present paper introduces the “Evaluate” web application, for the analysis of assessment tests. Methods: The design and implementation of the application is described, which allows the management of assessment items, used to constitute evaluation tests, upon which results the main descriptive statistic values used under the classical test theory in the analysis of assessment tests are calculated. The application was developed in Python, within the Django framework, and tested with real assessment tests. Results: Scores are assigned to each assessment item, and various statistics — such as difficulty and discrimination index, point-biserial correlation, test internal consistency coefficient — can be obtained upon the answers of the subjects, as well as a graphic analysis of the performance of each subject on each assessment item, as well as on the test as a whole. Conclusion: The “Evaluate” application makes a meaningful contribution to a better knowledge of assessment tools used in competence evaluation, by allowing the detection of inconsistencies and the consequent improvement in the process.
- Estratégias de Tolerância a Falhas em Computação Móvel na NuvemPublication . Catumbela, Euclides; Prata, PaulaApesar de os periféricos móveis possuírem cada vez mais capacidade de computação e armazenamento, a ligação da computação móvel com a computação na núvem (cloud) é também, cada vez mais, forte. Aplicações móveis que processem ou partilhem grandes quantidades de dados usam a nuvem para superar a limitação de recursos imposta por smartphones e tablets. Estes sistemas trazem novos desafios em termos de tolerância a falhas. Por um lado funcionam com baterias cuja carga tem duração limitada e por outro lado, a mobilidade do utilizador pode dificultar a obtenção de conectividade contínua e com largura de banda invariável como seria desejável. Neste trabalho propomos e avaliamos mecanismos de tolerância a falhas para dois tipos de falhas comuns em computação móvel na nuvem: Falha da carga da bateria e falhas na ligação à rede.
- Mobile Cloud Computing - Building High Availability ApplicationsPublication . Prata, Paula; Catumbela, EuclidesMobile Computing seems to spread to all aspects of our life, from light entertainment to health or finance apps. Cloud services appear as the common solution to be used as backend of mobile applications. In complex applications the cloud can even be used as an additional computational resource. Mobile cloud computing applications raise new reliability and availability challenges that result namely from the device mobility and from the limited battery charge. In this work, fault tolerant mechanisms for connection problems and for low battery charge are proposed and studied. The execution time overhead of those mechanisms is evaluated and compared with the offline support existent in two common cloud platforms: Firebase and Azure.
- Performance Assessment of the Canonical Genetic Algorithm: a Study on Parallel Processing Via GPU ArchitecturePublication . Fazendeiro, Paulo; Prata, PaulaGenetic Algorithms (GAs) exhibit a well-balanced operation, combining exploration with exploitation. This balance, which has a strong impact on the quality of the solutions, depends on the right choice of the genetic operators and on the size of the population. The results reported in the present work shows that the GPU architecture is an efficient alternative to implement population-based search methods. In the case of heavy workloads the speedup gains are quite impressive. The reported experiments also show that the two-dimensional granularity offered by the GPU architecture is advantageous for the operators presenting functional and data independence at the population+genotype level.