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Publications

Publications by Carlos Bragança Oliveira

2014

Distributed simulation framework

Authors
De Oliveira, CB; Brito, AC;

Publication
Modelling and Simulation 2014 - European Simulation and Modelling Conference, ESM 2014

Abstract
The performance of a company depends on the quality of its strategic decisions but depends also on how those decisions are implemented. Companies are composed of different units that can be geographically distributed with different levels of autonomy and local resources. Due to the complexity of the problem many companies use simulation to analyse the performance of critical sectors based on a number of scenarios. This reality requires new approaches that, taking advantage of existing models enables their integration with new models, facilitate their upgrade and allow a distributed execution. In this work we developed a Framework to integrate distributed agent-based simulators (ABMS) with a mechanism of communication TCP/IP to exchange synchronization messages and business messages based on the OASIS standard. The XML standard format was used for coding of all the messages. The communication mechanism of the Framework was developed in order to benefit from distributed computing.

2013

DISTRIBUTED AGENT BASED SIMULATION FRAMEWORK

Authors
de Oliveira, CB; Brito, AC;

Publication
EUROPEAN SIMULATION AND MODELLING CONFERENCE 2013

Abstract
Industrial companies are faced today with strong competition and fast changing markets. To reduce the risk and evaluate alternatives, simulation is often considered to be an adequate tool. Industrial companies' simulation models must have enough internal detail to be useful but, at the same time, must take into account the external environmental behaviour. Distributed simulation has specific characteristics to allow the integration of these models but its complexity limits its use in industry as stated in the literature. To overcome these difficulties, a framework is proposed, using Agent-based Modelling and Simulation (ABMS) technique and offering communication and synchronization mechanisms, which allow the integration of simulation models in the industrial area. To promote semantic interoperability, a business language is also proposed based on the OASIS Universal Business Language (UBL). To validate the framework a prototype was developed. The experiments made with the prototype shows that a distributed simulation can be more efficient than a single computer simulation as the number of agents increases in the model.

2014

Preface

Authors
Brito, AC; Tavares, JMRS; De Oliveira, CB;

Publication
Modelling and Simulation 2014 - European Simulation and Modelling Conference, ESM 2014

Abstract

2018

Utilização do sucesso acadêmico para prever o abandono escolar de estudantes do ensino superior: um caso de estudo

Authors
Sousa, ACCd; Oliveira, CABd; Borges, JLCM;

Publication
Educação e Pesquisa

Abstract
Resumo O abandono escolar é um problema complexo que afeta a maioria dos programas de graduação pós-secundária, em todo o mundo. O curso de engenharia industrial do Instituto ISVOUGA, localizado em Santa Maria da Feira, Portugal, não é exceção. Este estudo usou um conjunto de dados contendo informações gerais dos estudantes e suas notas para as unidades curriculares já avaliadas. A partir deste conjunto de dados, foram selecionados dezessete preditores potenciais: cinco intrínsecos (gênero, estado civil, situação profissional, idade e regime de dedicação aos estudos – integral ou parcial) e doze extrínsecos (as notas em todas as doze unidades curriculares ministradas durante os dois primeiros semestres do curso). O objetivo principal desta investigação foi prever a probabilidade de um estudante abandonar o curso com base nos referidos preditores. Foi usada uma regressão logística binária para classificar os estudantes como tendo uma probabilidade alta ou baixa de não se reinscreverem no curso. Para validar se a metodologia utilizada é apropriada para o estudo em causa, a precisão obtida com o modelo de regressão logística foi comparada, por via de uma validação cruzada com cinco partições, com a precisão obtida pela utilização de três métodos muito utilizados em data mining: One R, K Nearest Neighbors e Naive Bayes. O modelo de regressão logística identificou quatro variáveis significativas na previsão do abandono escolar (as classificações nas unidades curriculares de ciência dos materiais, eletricidade, cálculo 1 e química). Os dois preditores mais influentes do abandono dos estudantes são não conseguir aprovação nas unidades curriculares menos exigentes: ciência dos materiais e eletricidade. Ao contrário do que seria de supor antes desta investigação, descobrimos que a não aprovação em unidades curriculares mais exigentes, como física ou estatística, não tem influência significativa no abandono escolar.

2018

ESTIMATION OF DAILY MEAN TEMPERATURES: AN ACCURATE METHOD FOR THE DOURO VALLEY

Authors
Real, AC; Borges, J; Oliveira, CB;

Publication
CIENCIA E TECNICA VITIVINICOLA

Abstract
Air temperature data from many locations worldwide are only available as series of daily minima and maxima temperatures. Historically, several different approaches have been used to estimate the actual daily mean temperature, as only in the last two or three decades automatic thermometers are able to compute its actual value. The most common approach is to estimate it by averaging the daily minima and maxima. When only daily minima and maxima are available, an alternative approach, proposed by Dall'Amico and Hornsteiner in 2006, uses the two daily extremes together with next day minima temperature and a coefficient related to the local daily astronomical sunset time. Additionally, the method uses two optimizable coefficients related to the region's temperature profile. In order to use this approach it is necessary to optimize the region's unknown parameters. For this optimization, it is necessary a dataset containing the maxima, minima, and the actual daily mean temperatures for at least one year. In this research, for the period 2007-2014, we used three datasets of minima, maxima and actual mean temperatures obtained at three automatic meteorological stations located in the Douro Valley to optimize the two unknown parameters in the Dall'Amico and Hornsteiner approach. Moreover, we compared the actual mean daily temperatures available from the three datasets with the correspondent values estimated by using i) the usual approach of averaging the daily maxima and minima temperatures and ii) the Dall'Amico and Hornsteiner approach. Results show that the former approach overestimates, on average, the daily mean temperatures by 0.5 degrees C. The Dall'Amico and Hornsteiner approach showed to be a better approximation of mean temperatures for the three meteorological stations used in this research, being unbiased relative to the actual mean values of daily temperatures. In conclusion, this research confirms that the Dall'Amico and Hornsteiner is a better approach to estimate the mean daily temperatures and provides the optimized parameters for three sites located at each of the three sub-regions of the Douro Valley (Baixo Corgo, Cima Corgo and Douro Superior).

2011

MULTI-HIERARCHICAL AGENT BASED MODELLING SIMULATION FRAMEWORK

Authors
de Oliveira, CB; Brito, AC;

Publication
EUROPEAN SIMULATION AND MODELLING CONFERENCE 2011

Abstract
The performance of a company depends on its strategic decisions but also on the efficiency of how those decisions are implemented by all of its sectors. In any company there are different sectors or groups, probably physically distributed, with different levels of autonomy, each one controlling local resources and interacting with the others. Many companies use simulation software to analyze critical sectors based in a number of scenarios, in order to estimate the efficiency of the different configurations. The process of simulate alternative solutions can be time consuming. Depending on the software used it may be necessary to generate new simulation models for each solution, develop new applications or change existing ones. This paper describes a simulation framework where each element is modelled using the discrete-event approach and interoperability between elements is achieved by the combination of web services and Agent-based modelling and simulation (ABMS). The use of ABMS in this framework provides an easier way to evaluate alternative solutions. Each sector or group is an agent that can be added or removed from the model to build different configurations. A multi-hierarchical simulation executive is proposed in order to enable the use of different time intervals in each level. This increases the autonomy of the simulation agents and promotes the use of parallel or distributed solutions.

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