Movlab – Laboratory of Technologies for Interactions and Interfaces

URI permanente desta comunidade:

http://hdl.handle.net/10437/11004

Navegar

Percorrer Movlab – Laboratory of Technologies for Interactions and Interfaces por título

A mostrar 1 - 20 de 39
  • Item
    Agentes ou Jogadores? Os monstros estranhamente reais dos jogos de computadores
    (Cetac, 2008) Luz, Filipe Costa; Abrantes, João M. C. S.
    Pretendemos mostrar como os sistemas de motion capture permitem transpor para avatares movimentos de pessoas reais para, com o auxílio do processamento gráfico e dos incrementos em Inteligência artificial, criar as planícies de Masahiro Mori, o uncanny valley. Acreditamos que, num futuro próximo, será possível emocionar jogadores se o realismo das interacções no jogo apresentar consistência semelhante às experiências no mundo real.
  • Item
    Algorithms for Estimating the Location of Remote Nodes Using Smartphones
    (IEEE, 2019) Pedro, Dario; Tomic, Slavisa; Bernardo, Luís; Beko, Marko; Oliveira, Rodolfo; Dinis, Rui; Pinto, Paulo; Amaral, Pedro
    Locating the position of a remote node on a wireless network is becoming more relevant, as we move forward in the Internet of things and in autonomous vehicles. This paper proposes a new system to implement the location of remote nodes. A new prototype Android application has been developed to collect real measurements and to study the performance of several smartphone's sensors and location algorithms, including an innovative one, based on the second order cone programming (SOCP) relaxation. The application collects theWiFi access points information and the terminal location. An internal odometry module developed for the prototype is used when Android's service is unavailable. This paper compares the performance of existing location estimators given in closed form, an existing SOCP one, and the new SOCP location estimator proposed, which has reduced complexity. An algorithm to merge measurements from non-identical terminals is also proposed. Cooperative and terminal stand-alone operations are compared, showing a higher performance for SOCP-based ones, that are capable of estimating the path loss exponent and the transmission power. The heterogeneous terminals were also used in the tests. Our results show that the accurate positioning of static remote entities can be achieved using a single smartphone. On the other hand, the accurate real-time positioning of the mobile terminal is provided when three or more scattered terminal nodes cooperate sharing the samples taken synchronously.
  • Item
    Augmented Reality for Games
    (ACM - Association for Computing Machinery, 2008) Luz, Filipe Costa; Bila, Vasco; Dinis, José Maria
    In this text, we intend to explore augmented reality as a means to visualise interactive communication projects. With ARToolkit, Virtools and 3ds Max applications, we aim to show how to create a portable interactive platform that resorts to the environment and markers for constructing the game’s scenario. We plan to show that the realism of simulation, together with the merger of artificial objects with the real world, can generate interactive empathy between players and their avatars.
  • Item
    Bayesian methodology for target tracking using combined RSS and AoA measurements
    (Elsevier, 2017) Tomic, Slavisa; Beko, Marko; Dinis, Rui; Tuba, Milan; Bacanin, Nebojsa
    This work addresses the target tracking problem based on received signal strength (RSS) and angle of arrival (AoA) measurements. The Bayesian methodology, which integrates the information given by observations with prior knowledge extracted from target motion model in order to enhance the estimation accuracy was employed. First, by converting the considered highly non-linear measurement model into a linear one, i.e., a novel linearization technique of the measurement model is proposed. The derived model is then merged with the prior knowledge, and a novel maximum a posteriori (MAP) estimator whose solution is given in closed-form is proposed. It is also shown that the Kalman filter (KF) can be directly applied on top of the linearized observation model, which results in a proposal of a novel KF algorithm. Furthermore, to the best of authors’ knowledge, this paper premierly presents the application of the extended KF (EKF) and the unscented KF (UKF) to the considered tracking problem, by applying first-order linearization technique to the original non-linear model, and by applying the unscented transformation to carefully selected sample points, respectively. Finally, importance weights are computed for a large number of randomly selected sample points to render a well-known particle filter (PF) solution. Simulation results show that the proposed algorithms perform better than a naive one which uses only information from observations. They also confirm the effectiveness of the proposed linearization technique in comparison with the existing one, reducing the estimation error for about 25%.
  • Item
    A bisection-based approach for exact target localization in NLOS environments
    (Elsevier, 2017) Tomic, Slavisa; Beko, Marko
    This work addresses the range-based target localization problem in adverse non-line-of-sight (NLOS) en- vironments. We start by deriving the maximum likelihood (ML) estimator from the measurement model, since it is asymptotically efficient. However, this estimator is highly non-convex and difficult to solve di- rectly. Hence, we convert the localization problem into a generalized trust region sub-problem (GTRS) framework. Although still non-convex in general, the derived estimator is strictly decreasing over a read- ily obtained interval, and thus, can be solved exactly by a bisection procedure. In huge contrast to exist- ing algorithms, which either require the knowledge about the magnitude of the NLOS bias or to a priori distinguish between line-of-sight (LOS) and NLOS links, the new one does not require such prerequi- sites. Also, the computational complexity of the proposed algorithm is linear in the number of reference nodes, unlike the majority of existing ones. Our simulation results show that the new algorithm possesses a steady NLOS bias mitigation capacity and that it represents an excellent alternative in the sense of the trade offbetween accuracy and complexity. To be more specific, it not only matches the performance of existing methods (majority of which significantly more computationally complex) but outperforms them in general. Moreover, the performance of the proposed algorithm is validated through real-indoor exper- imental data.
  • Item
    Uma certa imagem de um mundo : estereoscopia e educação visual no início do século XX; uma investigação a partir da coleção Pestalozzi (MIMO)
    (ICNOVA - Nova Institute of Communication, 2017) Peixoto, Rodrigo
    No século XVIII surgiu um novo paradigma na educação, que ficou conhecido sob o nome de educação visual. Na sua origem estão as ideias de Pestalozzi. Esta mudança na estrutura do modo de lecionar está intimamente ligada à fundação de uma sociedade moderna assente na tecnologia como forma de aceder ao conhecimento. Este ímpeto visual veio encontrar na fotografia e na estereoscopia, primeiro, e no cinema, depois, os veículos para a formação de gerações de estudantes, criando uma relação de visibilidade com a matéria lecionada, visibilidade que era olhada como equivalente ao contacto com um objeto a estudar, transformando a noção de ilustração ou documento, e esquecendo a mediação tecnológica. Através do estudo da coleção Pestalozzi (158 cartões estéreo em depósito no Museu de Imagem em Movimento (MIMO) de Leiria, pelo projeto Stereo Visual Culture apoiado pela FCT (PTDC/IVC-COM/5223/2012), e dos guias de leitura das coleções educacionais da Keystone View Co., pretendemos analisar a industrialização deste novo paradigma e a sua influência na criação de uma ideia hierarquizada, sistematizada, e apoiada em «evidências» visuais, de uma organização do mundo (no momento em que o surgimento do cinema ameaçava esta indústria). Um mundo que se pretendia objetivado nas imagens estéreo.
  • Item
    ColorShapeLinks: A board game AI competition for educators and students
    (Elsevier, 2021-02-23) Fachada, Nuno
    ColorShapeLinks is an AI board game competition framework specially designed for students and educators in videogame development, with openness and accessibility in mind. The competition is based on an arbitrarily-sized version of the Simplexity board game, the motto of which, “simple to learn, complex to master”, is curiously also applicable to AI agents. ColorShapeLinks offers graphical and text-based frontends and a completely open and documented development framework built using industry standard tools and following software engineering best practices. ColorShapeLinks is not only a competition, but both a game and a framework which educators and students can extend and use to host their own competitions. It has been successfully used for running internal competitions in AI classes, as well as for hosting an international AI competition at the IEEE Conference on Games.
  • Item
    Como a vontade de ser arte da fotografia do final do século XIX expulsou a estereoscopia
    (LabCom - Universidade da Beira Interior, 2015) Peixoto, Rodrigo
    As razões para o desaparecimento da fo-tografia estereoscópica do quotidiano dacultura ocidental, e o seu consequenteapagamento das histórias da Fotografia,têm sido estudadas por vários autores. Osprincipais argumentos para este aconteci-mento parecem ser o triunfo da fotogra-fia monoscópica (Anne Maxwell, 2000),o aparato necessário para a visualizaçãoe a subjetividade da imagem estéreo (Jo-nathan Crary, 1990), ou a sua utiliza-ção por industrias moralmente condená-veis como a pornografia (AA.VV, 2013,p.183). Mas o papel do ímpeto artísticoe da utilização da Fotografia como Arte(e a desadequação da estereoscopia a estepropósito) terá ficado esquecido.Neste texto procuramos encontrar uma li-gação causal entre o surgimento dos mo-vimentos fotográficos de expressão artís-tica da segunda metade do século XIX,nomeadamente o Pictorialismo em Ingla-terra e nos Estados Unidos, e o caminhopara o desuso da estereoscopia. Atravésda análise de imagens estereoscópicas decoleções públicas portuguesas, possibili-tada pelo projeto Stereo Visual Culture(PTDC/IVC-COM/5223/2012), e a in-vestigação em textos da época de autoresligadosaosmovimentospictorialistas, foipossível encontrar especificidades com-positivas e temáticas que corroboram atese de que também a vontade de promo-ção da Fotografia ao mundo da “Grande”Arte terá contribuído para a queda da fo-tografia estereoscópica.
  • Item
    Computational Programming as a Tool in the Teaching of Electromagnetism in Engineering Courses: Improving the Notion of Field
    (MDPI, 2019) Marques, Pedro Carmona; Nogueira, João; Alves, Ricardo Gaio
    In this study we have attempted, firstly, to describe programming protocols developed for the teaching of an Electromagnetism course in the university degrees of Electrical Engineering and Energy Engineering, and secondly, to evaluate students’ satisfaction with the simulation practices through MATLAB®programming. The main objective of the protocols is to allow students to model and visualize the electric field and magnetic field (both static) and understand the approximation that is made when considering certain distributions of electric charges and electric currents. To evaluate the usefulness of this computational methodology, eighteen students from the two engineering degrees answered a questionnaire with seven questions related to the Electromagnetism course and to the benefits of using computer programming. Their answers are measured by a Likert scale. From the analysis of the results, we can conclude, in a general way, that the use of this methodology has positive effects in the learning of Electromagnetism in these two degrees.
  • Item
    Democracia e populismo na Europa e na América : equilíbrio instável
    (Instituto D. João de Castro, 2018) Pinto, José Filipe
    O populismo é um fenómeno antigo, uma vez que acompanha a demo‑ cracia desde o seu berço grego, embora a sua teorização só tenha sido iniciada por Herzen no século XIX na Rússia dos czares. No entanto, foi no século XX que o populismo conheceu protagonismo, uma vez que os regi‑ mes que marcaram a vida política, designadamente o sovietismo, o fascismo e o nazismo, eram populistas. Um protagonismo que pareceu esmorecer após a II Guerra Mundial, mas que voltou a emergir no final do século passado e no início do atual. Esta comunicação reflete sobre as realidades populistas na União Europeia e nos Estados Unidos da América e mostra que o populismo não representa uma alternativa coerente para o exercício do Poder, razão pela qual não existe democracia sem populismo, mas pode haver populismo sem democracia
  • Item
    Design Digital: Do traço ao pixel
    (COFAC, 2005) Luz, Filipe Costa
    Neste artigo pretende-se compreender a aversão que designers (e arquitectos, inclusive) sentem verdadeiramente em relação “ao computador”. Se de um modo ele é um excelente parceiro aceite por todos, simultaneamente, é com muita apreensão que se programam currículos de disciplinas universitárias para que os alunos aprendam as características projectuais do design, desenvolvam capacidade criativa (inteligência no uso de recursos para a produção de conceitos ou objectos) usando o computador sistematicamente, ou seja, não apenas como uma ferramenta de desenho, mas também de projecto (design). Os automatismos continuam a ser os monstros de hoje, porém, como aqui defendemos, os computadores sempre projectaram sombra humana, são “apenas” máquinas hipermédias que recorrem a existentes tecnologias para, supostamente, criarem novas mais transparentes na relação homem-máquina.
  • Item
    Dissimilar Metals LaserWelding between DP1000 Steel and Aluminum Alloy 1050
    (MDPI, 2019) Marques, Pedro Carmona; Pereira, António; Cabrinha, Ana; Rocha, Fábio; Fernandes, Fábio A. O.; Sousa, Ricardo
    The welding of dissimilar metals was carried out using a pulsed Nd: YAG laser to join DP1000 steel and an aluminum alloy 1050 H111. Two sheets of each metal, with 30 14 1 mm3, were lap welded, since butt welding proved to be nearly impossible due to the huge thermal conductivity differences and melting temperature differences of these materials. The aim of this research was to find the optimal laser welding parameters based on the mechanical and microstructure investigations. Thus, the welded samples were then subjected to tensile testing to evaluate the quality of the joining operation. The best set of welding parameters was replicated, and the welding joint obtained using these proper parameters was carefully analyzed using optical and scanning electron microscopes. Despite the predicted difficulties of welding two distinct metals, good quality welded joints were achieved. Additionally, some samples performed satisfactorily well in the mechanical tests, reaching tensile strengths close to the original 1050 aluminum alloy.
  • Item
    Distributed localization with complemented RSS and AOA measurements : theory and methods
    (Applied Sciences, 2019) Tomic, Slavisa; Beko, Marko; Matos, Luís M. Camarinha de; Oliveira, Luís Bica
    Remarkable progress in radio frequency and micro-electro-mechanical systems integrated circuit design over the last two decades has enabled the use of wireless sensor networks with thousands of nodes. It is foreseen that the fifth generation of networks will provide significantly higher bandwidth and faster data rates with potential for interconnecting myriads of heterogeneous devices (sensors, agents, users, machines, and vehicles) into a single network (of nodes), under the notion of Internet of Things. The ability to accurately determine the physical location of each node (stationary or moving) will permit rapid development of new services and enhancement of the entire system. In outdoor environments, this could be achieved by employing global navigation satellite system (GNSS) which offers a worldwide service coverage with good accuracy. However, installing a GNSS receiver on each device in a network with thousands of nodes would be very expensive in addition to energy constraints. Besides, in indoor or obstructed environments (e.g., dense urban areas, forests, and canyons) the functionality of GNSS is limited to non-existing, and alternative methods have to be adopted. Many of the existing alternative solutions are centralized, meaning that there is a sink in the network that gathers all information and executes all required computations. This approach quickly becomes cumbersome as the number of nodes in the network grows, creating bottle-necks near the sink and high computational burden. Therefore, more effective approaches are needed. As such, this work presents a survey (from a signal processing perspective) of existing distributed solutions, amalgamating two radio measurements, received signal strength (RSS) and angle of arrival (AOA), which seem to have a promising partnership. The present article illustrates the theory and offers an overview of existing RSS-AOA distributed solutions, as well as their analysis from both localization accuracy and computational complexity points of view. Finally, the article identifies potential directions for future research.
  • Item
    Elephant Herding Optimization for Energy-Based Localization
    (MDPI, 2018) Correia, Sérgio; Beko, Marko; Cruz, Luís Alberto da Silva; Tomic, Slavisa
    This work addresses the energy-based source localization problem in wireless sensors networks. Instead of circumventing the maximum likelihood (ML) problem by applying convex relaxations and approximations, we approach it directly by the use of metaheuristics. To the best of our knowledge, this is the first time that metaheuristics are applied to this type of problem. More specifically, an elephant herding optimization (EHO) algorithm is applied. Through extensive simulations, the key parameters of the EHO algorithm are optimized such that they match the energy decay model between two sensor nodes. A detailed analysis of the computational complexity is presented, as well as a performance comparison between the proposed algorithm and existing non-metaheuristic ones. Simulation results show that the new approach significantly outperforms existing solutions in noisy environments, encouraging further improvement and testing of metaheuristic methods.
  • Item
    Energy-based acoustic localization by improved elephant herding optimization
    (IEEE Access, 2020) Correia, Sérgio; Beko, Marko; Tomic, Slavisa; Cruz, Luís Alberto da Silva
    The present work proposes a new approach to address the energy based acoustic localization problem. The proposed approach represents an enhanced version of evolutionary optimization based on Elephant Herding Optimization (EHO), where two major contributions are introduced. Firstly, instead of random initialization of elephant population, we exploit particularities of the problem at hand to develop an intelligent initialization scheme. More precisely, distance estimates obtained at each reference point are used to determine the regions in which a source is most likely to be located at. Secondly, rather than letting elephants to simply wander around in their search for an update in the source location, we base their motion on a local search scheme which is found on a discrete gradient method. Such a methodology significantly accelerates the convergence of the proposed algorithm, and comes at a very low computational cost, since discretization allows us to avoid the actual gradient computations. Our simulation results show that the enhanced algorithm significantly outperforms the standard EHO method for low noise and matches its performance for high noise, in terms of localization accuracy. Moreover, they show that the proposed enhanced version requires significantly less number of iterations to converge.
  • Item
    A era das “fake news”: o digital storytelling como promotor do pensamento crítico
    (Universidade de Aveiro, 2018) Brites, Maria José; Amaral, Inês; Catarino, Fernando
    Neste artigo, consideramos que o contexto mediático e informacional atual constitui por si só um ambiente importante e a ter em conta na forma como os cidadãos se posicionam e protegem face às notícias falsas. Neste sentido, apresentamos uma base teórica e crítica da qual nos socorremos para pensar e implementar um projeto Europeu de educação para os media (Media In Action), no âmbito do qual está a ser preparada uma ação de formação para professores. Esta formação tem como objetivo contribuir para que professores e alunos possam usufruir de maiores capacidades para compreenderem e atuarem no atual ecossistema mediático. Refletimos sobre algumas questões, como quais as melhores metodologias para atuar no âmbito escolar e qual o papel dinâmico que o digital storytelling pode ter no trabalho com crianças e jovens. Apontamos para a necessidade de trabalharmos com metodologias dinâmicas e participativas e ainda para o cruzamento do digital storytelling com as ferramentas mais ligadas ao jornalismo.
  • Item
    Estimating Directional Data From Network Topology for Improving Tracking Performance
    (MDPI, 2019) Tomic, Slavisa; Beko, Marko; Dinis, Rui; Montezuma, Paulo
    This work proposes a novel approach for tracking a moving target in non-line-of-sight (NLOS) environments based on range estimates extracted from received signal strength (RSS) and time of arrival (TOA) measurements. By exploiting the known architecture of reference points to act as an improper antenna array and the range estimates, angle of arrival (AOA) of the signal emitted by the target is first estimated at each reference point. We then show how to take advantage of these angle estimates to convert the problem into a more convenient, polar space, where a linearization of the measurement models is easily achieved. The derived linear model serves as the main building block on top of which prior knowledge acquired during the movement of the target is incorporated by adapting a Kalman filter (KF). The performance of the proposed approach was assessed through computer simulations, which confirmed its effectiveness in combating the negative effect of NLOS bias and superiority in comparison with its naive counterpart, which does not take prior knowledge into consideration.
  • Item
    Exact Robust Solution to TW-ToA-Based Target Localization Problem With Clock Imperfections
    (IEEE, 2018) Tomic, Slavisa; Beko, Marko
    This letter addresses the problem of target localization based on two-way time of arrival (TW-ToA) measurements with clock imperfections. In addition to the target location, the turn-around times and clock skews are considered unknown. Since an optimal estimator for this problem cannot be tackled directly, we approximate it by a suboptimal, robust one, formulated as a generalized trust region subproblem. Even though nonconvex in general, exact solution of the derived estimator can be obtained by just a bisection procedure. Simulation results validate the effectiveness of the proposed technique, matching the performance of the state of the art with significantly lower computational complexity.
  • Item
    Exploiting orientation information to improve range-based localization accuracy
    (IEEE Access, 2020) Tomic, Slavisa; Beko, Marko; Tuba, Milan
    This work addresses target localization problem in precarious surroundings where possibly no links are line of sight. It exploits the known architecture of available reference points to act as an irregular antenna array in order to estimate the azimuth angle between a reference point and a target, based on distance estimates withdrawn from integrated received signal strength (RSS) and time of arrival (TOA) observations. These ctitious azimuth angle observations are then used to linearize the measurement models, which triggers effortless derivation of a new estimator in a closed-form. It is shown here that, by using xed network geometry in which target orientation with respect to a line formed by a pair of anchors can be correctly estimated, the localization performance can be signi cantly enhanced. The new approach is validated through computer simulations, which corroborate our intuition of pro ting from inherent information within a network.
  • Item
    A geometric approach for distributed multi-hop target localization in cooperative networks
    (IEEE Transactions on Vehicular Technology, 2020) Tomic, Slavisa; Beko, Marko
    This work addresses target localization problem in cooperative distributed sensor networks, in which all sensors are capable of measuring Received Signal Strength (RSS), but only some are appropriately equipped to measure Angle Of Arrival (AOA) of the received signal. A novel approach based on simple geometry and multi-hopping is proposed, which allows for natural conversion of the problem into a Generalized Trust Region Sub-Problem (GTRS). The proposed algorithm comprises three main steps, each of them with linear computational cost in the number of neighbors, making it suitable for real-time applications. Our simulation results validate the performance of the new algorithm, surpassing some significantly more complex ones, and almost achieving a lower bound set by an existing algorithm which uses some (unrealistic) assumptions in its favor.