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Publications

2016

Car safety: A statistical analysis for marketing management

Authors
Moreira, AC; Gouveia, M; Macedo, P;

Publication
Handbook of Research on Intelligent Techniques and Modeling Applications in Marketing Analytics

Abstract
Car safety is an essential feature of marketing strategies for automobile companies. In this work, a statistical analysis on crash tests is conducted based on data available from European New Car Assessment Programme (Euro NCAP). The research work developed in this chapter presents a statistical analysis of the information produced by Euro NCAP, using the SPSS and MATLAB software, and seeks to answer the following research questions: - are there statistically significant differences on adult occupant safety in the six years under study? - are there statistically significant differences among the best-selling car classes regarding safety in frontal collisions? - are electric and hybrid automobiles less secure than their traditional counterparts with respect to frontal collisions?

2016

Simulation Models for IEC 61850 Communication in Electrical Substations Using GOOSE and SMV Time-critical Messages

Authors
Leon, H; Montez, C; Stemmer, M; Vasques, F;

Publication
2016 IEEE WORLD CONFERENCE ON FACTORY COMMUNICATION SYSTEMS (WFCS)

Abstract
IEC 61850 is a communication standard for electrical Substation Automation Systems (SAS). It defines both the information model and services used for communication between Intelligent Electronic Devices (IEDs) in a substation. The adoption of this standard brings several advantages for the design and operation of substations. The abstract data models defined in IEC 61850 can be mapped upon application protocols, such as MMS, GOOSE or SMV. These protocols can run upon TCP/IP networks or upon specific high speed Ethernet LANs, in order to match the timing requirements associated to protective relaying mechanisms. For the specific case of GOOSE messages, the standard specifies the use of VLANs (Virtual LANs) with priority tagging (IEEE 802.1q) to implement separate virtual networks with the appropriate message priority levels, in order to ensure the specified response times. The lack of adequate simulation models that enable the response time assessment of both SMV and GOOSE messages is one of the shortcomings of available simulation tools. In this paper, we propose simulation models for the IEC 61850 communication standard, targeting application that use GOOSE and SMV messages. This simulation models has been built upon OMNeT++/INET. The simulation results obtained from a typical IEC 61850 communication scenario show the effectiveness of the developed models. Some of these results have been experimentally validated.

2016

Novelty detection in data streams

Authors
Faria, ER; Gonçalves, IJCR; de Carvalho, ACPLF; Gama, J;

Publication
ARTIFICIAL INTELLIGENCE REVIEW

Abstract
In massive data analysis, data usually come in streams. In the last years, several studies have investigated novelty detection in these data streams. Different approaches have been proposed and validated in many application domains. A review of the main aspects of these studies can provide useful information to improve the performance of existing approaches, allow their adaptation to new applications and help to identify new important issues to be addresses in future studies. This article presents and analyses different aspects of novelty detection in data streams, like the offline and online phases, the number of classes considered at each phase, the use of ensemble versus a single classifier, supervised and unsupervised approaches for the learning task, information used for decision model update, forgetting mechanisms for outdated concepts, concept drift treatment, how to distinguish noise and outliers from novelty concepts, classification strategies for data with unknown label, and how to deal with recurring classes. This article also describes several applications of novelty detection in data streams investigated in the literature and discuss important challenges and future research directions.

2016

Virtual Atmosphere, Emotions, Attitudes and Real Use

Authors
Moreira, AC; Ferreira, MM; Macedo, P;

Publication
Advances in Marketing, Customer Relationship Management, and E-Services - Managing Public Relations and Brand Image through Social Media

Abstract
This study involves several theories, namely: the theory of reasoned action, the technology acceptance model, the theory of planned behavior and the internet banking acceptance model. It aims to understand the relationships between the virtual atmosphere and emotional states, how the individual characteristics (social identity, altruism and telepresence) and emotional states influence attitudes, and how attitudes, past experience and trust influence actual use of a site. To this end, the authors developed three conceptual models explaining the relationships among the above-mentioned variables. Methodologically, descriptive statistics, exploratory factor analysis and the generalized maximum entropy estimator are used to test the three models in a wedding site. Of the eight hypotheses proposed, one can only partially validate hypotheses h1, h2, h3 and h6, while hypothesis h7 is accepted and the remaining are rejected.

2016

Simulation of the operation of hydro plants in an electricity market using Agent Based Models - introducing a Q Learning approach

Authors
Sousa, JC; Saraiva, JT;

Publication
2016 13TH INTERNATIONAL CONFERENCE ON THE EUROPEAN ENERGY MARKET (EEM)

Abstract
The restructuring of power systems with the introduction of electricity markets and decentralized structures increased the number of participating entities. This is particularly true in generation and retailing which are now provided under competition. Accordingly, it is important to develop models to simulate the behavior of these agents and to optimize their participation in electricity markets. Among them, it is essential to adequately model generation agents namely in countries having a large share of hydro stations. This paper describes an agent-based approach to model the day-ahead electricity market having a particular emphasis on hydro generation. Apart from the characterization of the agents, the paper details the introduction of the Q-Learning algorithm in the model as a way to enhance the performance of generation agents. This paper also presents some preliminary results taking the Portuguese generation system as an example.

2016

InGaZnO TFT behavioral model for IC design

Authors
Bahubalindrun, P; Tavares, V; Barquinha, P; de Oliveira, PG; Martins, R; Fortunato, E;

Publication
ANALOG INTEGRATED CIRCUITS AND SIGNAL PROCESSING

Abstract
This paper presents a behavioral model for amorphous indium-gallium-zinc oxide thin-film transistor using artificial neural network (ANN) based equivalent circuit (EC) approach to predict static and dynamic behavior of the device. In addition, TFT parasitic capacitances (C-GS and C-GD) characterization through measurements is also reported. In the proposed model, an EC is derived from the device structure, in terms of electrical lumped elements. Each electrical element in the EC is modeled with an ANN. Then these ANNs are connected together as per the EC and implemented in Verilog-A. The proposed model performance is validated by comparing the circuit simulation results with the measured response of a simple common-source amplifier, which has shown 12.2 dB gain, 50 mu W power consumption and 85 kHz 3-dB frequency with a power supply of 6 V. The same circuit is tested as an inverter and its response is also presented up to 50 kHz, from both simulations and measurements. These results show that the model is capable of capturing both small and large signal behavior of the device to good accuracy, even including the harmonic distortion of the signal (that emphasizes the nonlinear behavior of the parasitic capacitance), making the model suitable for IC design.

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