ESTG - Capítulos de livros
Permanent URI for this collection
Browse
Recent Submissions
- Comparing Metaheuristic Algorithms for Error Detection in Java ProgramsPublication . Chicano, Francisco; Ferreira, Marco; Alba, EnriqueModel checking is a fully automatic technique for checking concurrent software properties in which the states of a concurrent system are explored in an explicit or implicit way. The main drawback of this technique is the high memory consumption, which limits the size of the programs that can be checked. In the last years, some researchers have focused on the application of guided non-complete stochastic techniques to the search of the state space of such concurrent programs. In this paper, we compare five metaheuristic algorithms for this problem. The algorithms are Simulated Annealing, Ant Colony Optimization, Particle Swarm Optimization and two variants of Genetic Algorithm. To the best of our knowledge, it is the first time that Simulated Annealing has been applied to the problem. We use in the comparison a benchmark composed of 17 Java concurrent programs. We also compare the results of these algorithms with the ones of deterministic algorithms.
- A Face Attention Technique for a Robot Able to Interpret Facial ExpressionsPublication . Simplício, Carlos; Prado, José; Dias, JorgeAutomatic facial expressions recognition using vision is an important subject towards human-robot interaction. Here is proposed a human face focus of attention technique and a facial expressions classifier (a Dynamic Bayesian Network) to incorporate in an autonomous mobile agent whose hardware is composed by a robotic platform and a robotic head. The focus of attention technique is based on the symmetry presented by human faces. By using the output of this module the autonomous agent keeps always targeting the human face frontally. In order to accomplish this, the robot platform performs an arc centered at the human; thus the robotic head, when necessary, moves synchronized. In the proposed probabilistic classifier the information is propagated, from the previous instant, in a lower level of the network, to the current instant. Moreover, to recognize facial expressions are used not only positive evidences but also negative.
- Using ICT for Tacit Knowledge Preservation in Old AgePublication . Marcelino, Isabel; Góis, José; Laza, Rosalía; Pereira, AntónioAs the world population is aging, numerous challenges were raised. How to maintain a sustainable aging? How to increase the active role of older adults in society? How to promote healthy aging along with the improvement of social and technological inclusion and enhance emotional well-being? How to preserve the vast tacit knowledge existent in seniors? Pervasive computing can giving an enormous contribution to overcome this issues. In the present paper we introduce eService platform as a novel service ecosystem mainly developed for senior population, including life experiences and knowledge record service. We have researched and selected the most relevant accessibility guidelines concerning senior population and made a low fidelity prototype, followed by both fidelity prototypes, one with and one without guideline application. Finally we conducted usability tests and semi structured interviews with 6 individuals to validate our work. The experimental results demonstrated that the proposed guideline checklist was validated, well accepted and easy to use by seniors. They also validate the extreme importance of knowledge preservation.
- Complexity Analysis of HEVC Decoding for Multi-core PlatformsPublication . Cordeiro, Paulo J.; Assunção, Pedro; Gómez-Pulido, Juan A.The High Efficiency Video Coding (HEVC) is the latest standard, providing the same quality as its predecessor H.264/AVC at about half of the bit-rate. An increasing demand for higher quality and better resolutions in mobile applications require the use of more efficient video codecs, but the high computational complexity of HEVC poses problems to resource-constrained devices and portable equipment with limited batery-life. Despite the fact that video coding complexity is much higher than decoding, in most user devices, video decoding is used more often than encoding, thus particular attention must also be given to HEVC decoders. This paper presents an experimental study and complexity analysis of the HEVC decoder’s behaviour when decoding 4k ultra high definition (UHD) and HD video sequences on multi-core platforms, such as those of the most recent mobile devices. It is shown that when tile partitioning is used, different tiles have different decoding complexities. These findings are relevant for devising dynamic tile partitioning schemes capable of achieving load balancing in video decoders running on multi-core platforms.
- Adaptive Evolutionary Testing: An Adaptive Approach to Search-Based Test Case Generation for Object-Oriented SoftwarePublication . Ribeiro, José Carlos Bregieiro; Zenha-Rela, Mário Alberto; de Vega, Francisco FernándezAdaptive Evolutionary Algorithms are distinguished by their dynamic manipulation of selected parameters during the course of evolving a problem solution; they have an advantage over their static counterparts in that they are more reactive to the unanticipated particulars of the problem. This paper proposes an adaptive strategy for enhancing Genetic Programming-based approaches to automatic test case generation. The main contribution of this study is that of proposing an Adaptive Evolutionary Testing methodology for promoting the introduction of relevant instructions into the generated test cases by means of mutation; the instructions from which the algorithm can choose are ranked, with their rankings being updated every generation in accordance to the feedback obtained from the individuals evaluated in the preceding generation. The experimental studies developed show that the adaptive strategy proposed improves the test case generation algorithm's efficiency considerably, while introducing a negligible computational overhead.
- Citizens@City Mobile Application for Urban Problem ReportingPublication . Ribeiro, António Miguel; Costa, Rui Pedro; Marcelino, Luís; Silva, CatarinaUrban problems, such as holes in the pavement, poor accesses to wheelchairs or lack of public lighting, are becoming pervasive. Despite the fact that most of these problems directly affect life quality and sometimes even safety, not everyone has the readiness or initiative to report them to the proper authorities. This fact makes these “black spots” difficult to identify and the repairing process slow. Citizens@City is an Android mobile application that allows the general population to play a more active role in the identification of these problems by reporting them to the proper authorities in a simple and fast way. Moreover, citizens will have the possibility to follow the identification and repairing processes, and know at a given moment its status (e.g. identified, repairing scheduled, solved). Additionally, it will also allow the proper authorities to identify and manage the reported problems, from their identification until they are solved.
- An innovative algorithm for circumventing numerical stiffness in time-domain simulation of strongly nonlinear multirate RF circuitsPublication . Oliveira, Jorge F.; Pedro, José C.This paper proposes an innovative computer-aided design tool especially conceived for the efficient numerical simulation of strongly nonlinear RF circuits whose state variables are all fluctuating in a rapidly changing time scale, but evidence disparate rates of change in a slow envelope time scale. The proposed numerical technique is able to circumvent numerical stiffness and can be seen as a mixed mode algorithm that results from a combination of the method of lines based on multirate Runge-Kutta (MRK) schemes and the envelope transient over shooting technique. Simulation tests conducted in an illustrative example reveal promising results in terms of computational effort, over previous methods recently proposed for the simulation of the same category of circuits.
- A Maximum Likelihood Estimator for the Prevalence Rate Using Pooled Sample TestsPublication . Martins, João Paulo; Santos, Rui; Felgueiras, MiguelSince Dorfman’s seminal work, research on methodologies involving pooled sample tests has increased significantly.Moreover, the use of pooled samples refers not only to the classification problem (identifying all the infected individuals in a population), but also refers to the problem of estimating the prevalence rate p, as Sobel and Elashoff stated. The use of compound tests is not restricted to hierarchical algorithms where the most common example is Dorfman’s two-stage procedure. Matrix schemes such as the square array algorithm or multidimensional matrices schemes in certain cases outperform Dorfman’s procedure. Maximum likelihood estimates are quite difficult to compute when a procedure does not classify all individuals. This paper presents two innovative methods to compute maximum likelihood estimates in both type of procedures.
- Senior Potential Analysis: A Challenge that Contributes to Social SustainabilityPublication . Guarda, Teresa; Mota Pinto, Filipe; Cordova, Juan Pablo; Augusto, Maria Fernanda; Mato, Fernando; Quiña, Geovanni NinahualpaPopulation aging is one of the greatest triumphs of humanity, also is both a major challenge. The number of older workers in the European Union (EU) will increase over the next decades, the active population of the EU points to a growth of approximately 16.2% of the age group of 55-64 years between 2010 and 2030, being contrary to tendency of other age groups, with a reduction of 4% to 5%. This demographic change is due to the decline in fertility rates and increased life expectancy. The labor force in Europe will reach age levels never before registered in that older workers represent more than 30% of the active population. In this paper, based on the questionnaire results, brought out by "harnessing the potential senior", which was applied in enterprises in Portugal. It is intended to address some of the concerns related to the aging population and the use of senior potential, facing this problem as a challenge that contributes to social sustainability. Thus, the senior potential should be seen as a very important contribution. In this paper, we intend extract the survey data from data bases, for knowledge discovery and analysis using the data mining tool Weka.
- The Efficient and Stable Charging of Electric Vehicle Batteries: Simplified Instantaneous RegulationPublication . Medeiros, Rui; Valtchev, Stanimir; Valtchev, SvilenThe future charging of the growing fleet of Electric Vehicles (EV) requires new solutions that guarantee a better efficiency and widely spread chargers. Both in fast charging and in slow charging of the electric vehicle (EV) and hybrid electric vehicle (HEV), the wireless charger is the better choice. The wired charger is limited by its cabling and relatively lower output voltage, while the contactless charger can be more universal and safe. What rests to be discovered is the more efficient energy transfer that would have a stable operation. The strategy is based on guaranteeing the correct portion of energy transported by the resonant tank to the load. Some results are shown from this implementation of the instantaneous energy control.