2015
Autores
Freire, HF; de Moura Oliveira, PBD; Solteiro Pires, EJS; Bessa, M;
Publicação
CONTROLO'2014 - PROCEEDINGS OF THE 11TH PORTUGUESE CONFERENCE ON AUTOMATIC CONTROL
Abstract
Proportional, integral and derivative controller tuning can be a complex problem. There are a significant number of tuning methods for this type of controllers. However, most of these methods are based on a single performance criterion, providing a unique solution representing a certain controller parameters combination. Thus, a broader perspective considering other possible optimal or near optimal solutions regarding alternative or complementary design criteria is not obtained. Tuning PID controllers is addressed in this paper as a many-objective optimization problem. A Multi-Objective Particle Swarm Optimization algorithm is deployed to tune PID controllers considering five design criteria optimized at the same time. Simulation results are presented for a set of four well known plants.
2015
Autores
Matos, A; Rocha, T; Cabral, L; Bessa, M;
Publicação
PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON SOFTWARE DEVELOPMENT AND TECHNOLOGIES FOR ENHANCING ACCESSIBILITY AND FIGHTING INFO-EXCLUSION
Abstract
In this paper we present a study about multi-sensory content within the context of learning activities aimed at people with intellectual disability. A story was prepared together with traditional stimulus (audio and visual) and multisensory (audio, video, tactile and smell). Knowing that people with intellectual disability, due to their cognitive limitation, have multiple learning difficulties, namely in areas such as: communication, reading/writing and attention [1], it is really important to create innovative and pedagogically effective solutions that may motivate them and assist their learning process. Therefore, this study presents Preliminary results showing an overall improvement regarding the participant's memory when using the very multi-sensory contents. (C) 2015 The Authors. Published by Elsevier B.V.
2016
Autores
Mukherjee, R; Debattista, K; Bashford Rogers, T; Vangorp, P; Mantiuk, R; Bessa, M; Waterfield, B; Chalmers, A;
Publicação
SIGNAL PROCESSING-IMAGE COMMUNICATION
Abstract
A number of High Dynamic Range (HDR) video compression algorithms proposed to date have either been developed in isolation or only-partially compared with each other. Previous evaluations were conducted using quality assessment error metrics, which for the most part were developed for qualitative assessment of Low Dynamic Range (LDR) videos. This paper presents a comprehensive objective and subjective evaluation conducted with six published HDR video compression algorithms. The objective evaluation was undertaken on a large set of 39 HDR video sequences using seven numerical error metrics namely: PSNR, logPSNR, puPSNR, puSSIM, Weber MSE, HDR-VDP and HDR-VQM. The subjective evaluation involved six short-listed sequences and two ranking-based subjective experiments with hidden reference at two different output bitrates with 32 participants each, who were tasked to rank distorted HDR video footage compared to an uncompressed version of the same footage. Results suggest a strong correlation between the objective and subjective evaluation. Also, non-backward compatible compression algorithms appear to perform better at lower output bit rates than backward compatible algorithms across the settings used in this evaluation.
2016
Autores
Rocha, Tania; Bessa, Maximino; Cabral, Luciana;
Publicação
Proceedings of the XVII International Conference on Human Computer Interaction, Interacción 2016, Salamanca, Spain, September 13 - 16, 2016
Abstract
With this study we aim at assessing if a mini iPad device is a usable option for digital interaction to perform selection, manipulation, and insertion tasks by people with intellectual disabilities. This study builds on previous studies where usability was evaluated for universal tasks using the keyboard and a mouse input device [1]. This allowed us to assess the usability of a small mini iPad and compare it with other two input devices, namely keyboards and the mouse. For usability assessment we registered the following variables: successful conclusion of activities, type of difficulties found, errors and satisfaction indicators. The results showed that this group was much motivated to learn how to handle with the iPad, several asked to repeat the task and no one quit any task requested. Despite the number of errors as registered in their interaction, they always knew how to overcome the error and never showed frustration or demotivation. Furthermore, they had a good performance (relation between variables: time to conclude the task, number of errors and difficulties felt) with the mini iPad device, however when compared with the keyboard and mouse, their performance increased. © 2016 ACM.
2016
Autores
Melo, M; Rocha, T; Barbosa, L; Bessa, M;
Publicação
2016 23RD PORTUGUESE MEETING ON COMPUTER GRAPHICS AND INTERACTION (EPCGI)
Abstract
The sense of presence and cybersickness are keyfactors to have into account when referring to Virtual Environments (VE). To achieve high levels of presence and minimize cybersickness, it is important to ensure that the user's stimulation is coherent with the contents that are being delivered. In this paper, it is presented a pilot study addressing the usage of both objective and subjective metrics to measure the sense of presence and cybersickness in VE in order to study possible correlations between these two evaluation approaches. On top of that, the pilot study includes two body positions to allow evaluating if the stimulation of the vestibular study has impact on the sense of presence and cybersickness. To evaluate presence and cybersickness, it was developed a VE that consists in a hill where participants ride a bicycle. To broaden the scope of the study, there were studied two body positions: standing and sitting on the bicycle. The equipment EMOTIV epoc+ was used to register the objective metrics. The subjective metrics were registered using the Igroup Presence Questionnaire (IPQ) and the Simulator Sickness Questionnaire (SSQ). To complement the collected data, the levels of fatigue and stress before and after the experience were also registered through self-evaluation. Results show that objective metrics Interest and Stress and the subjective metrics Realism, Fatigue and Stress have a positive interaction regarding the sense of presence. Results further suggest that there is a positive interaction between the objective metric Focus and the subjective metric Involvement.
2016
Autores
Rocha, T; Paredes, H; Barroso, J; Bessa, M;
Publicação
COMPUTERS HELPING PEOPLE WITH SPECIAL NEEDS, PT II (ICCHP 2016)
Abstract
In this paper an accessible Web application that uses icons instead of text to performed YouTube video search, called SAMi, is presented. With this iconic interaction Web application (SAMi), we aimed to develop universal access on the Web, by presenting an alternative way of Web search (without using text); to be a starting point for the definition of an accessible interaction metaphor, based on universal design iconography for digital environments; and ultimately, to contribute to the democratization of access to the Web for all users, regardless of the degree of literacy. The main results obtained with the user test evaluation were: first-rate performance, higher satisfaction and total autonomy in their interaction with SAMi.
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