Showing papers by "Instituto Superior Técnico published in 2011"

Unveiling the biometric potential of finger-based ECG signals

Abstract: The ECG signal has been shown to contain relevant information for human identification. Even though results validate the potential of these signals, data acquisition methods and apparatus explored so far compromise user acceptability, requiring the acquisition of ECG at the chest. In this paper, we propose a finger-based ECG biometric system, that uses signals collected at the fingers, through a minimally intrusive 1-lead ECG setup recurring to Ag/AgCl electrodes without gel as interface with the skin. The collected signal is significantly more noisy than the ECG acquired at the chest, motivating the application of feature extraction and signal processing techniques to the problem. Time domain ECG signal processing is performed, which comprises the usual steps of filtering, peak detection, heartbeat waveform segmentation, and amplitude normalization, plus an additional step of time normalization. Through a simple minimum distance criterion between the test patterns and the enrollment database, results have revealed this to be a promising technique for biometric applications.

Bioaugmentation and biostimulation strategies to improve the effectiveness of bioremediation processes.

Abstract: Bioremediation, involving bioaugmentation and/or biostimulation, being an economical and eco-friendly approach, has emerged as the most advantageous soil and water clean-up technique for contaminated sites containing heavy metals and/or organic pollutants. Addition of pre-grown microbial cultures to enhance the degradation of unwanted compounds (bioaugmentation) and/or injection of nutrients and other supplementary components to the native microbial population to induce propagation at a hastened rate (biostimulation), are the most common approaches for in situ bioremediation of accidental spills and chronically contaminated sites worldwide. However, many factors like strain selection, microbial ecology, type of contaminant, environmental constraints, as well as procedures of culture introduction, may lead to their failure. These drawbacks, along with fragmented literature, have opened a gap between laboratory trials and on-field application. The present review discusses the effectiveness as well as the limitations of bioaugmentation and biostimulation processes. A summary of experimental studies both in confined systems under controlled conditions and of real case studies in the field is presented. A comparative account between the two techniques and also the current scenario worldwide for in situ biotreatment using bioaugmentation and biostimulation, are addressed.

Optimal Location of Charging Stations for Electric Vehicles in a Neighborhood in Lisbon, Portugal:

Abstract: Growing concerns about environmental issues have led to the consideration of alternatives to current mobility. Electric mobility is one such alternative that is receiving a great deal of attention in Europe. In particular, a new legal framework for the introduction of an electric mobility system in Portugal has recently been set up by the government. A key issue in this system is recharging the batteries and, consequently, the location of charging stations. This paper presents a study on the location of electric-vehicle charging stations for an area of Lisbon, the capital city of Portugal, characterized with a strong concentration of population and employment. This type of area is appropriate for slow charging because vehicles stay parked for several hours within a 24-h period. The methodology used here is based on a maximal covering model to optimize the demand covered within an acceptable level of service and to define the number and capacity of the stations to be installed. The results clearly indicate...

Music and emotions in the brain: familiarity matters

Abstract: The importance of music in our daily life has given rise to an increased number of studies addressing the brain regions involved in its appreciation. Some of these studies controlled only for the familiarity of the stimuli, while others relied on pleasantness ratings, and others still on musical preferences. With a listening test and a functional magnetic resonance imaging (fMRI) experiment, we wished to clarify the role of familiarity in the brain correlates of music appreciation by controlling, in the same study, for both familiarity and musical preferences. First, we conducted a listening test, in which participants rated the familiarity and liking of song excerpts from the pop/rock repertoire, allowing us to select a personalized set of stimuli per subject. Then, we used a passive listening paradigm in fMRI to study music appreciation in a naturalistic condition with increased ecological value. Brain activation data revealed that broad emotion-related limbic and paralimbic regions as well as the reward circuitry were significantly more active for familiar relative to unfamiliar music. Smaller regions in the cingulate cortex and frontal lobe, including the motor cortex and Broca's area, were found to be more active in response to liked music when compared to disliked one. Hence, familiarity seems to be a crucial factor in making the listeners emotionally engaged with music, as revealed by fMRI data.

Gamma-rays from harmonically resonant betatron oscillations in a plasma wake

Abstract: The radiation produced when an intense laser interacts with a solid target could provide a cheaper source of X-rays to synchrotrons and free-electron lasers. But they can also produce short bursts of gamma rays, whereas synchrotrons do not.

Sodium borohydride as a fuel for the future

Abstract: In a time of unprecedented change in environmental, geopolitical and socio-economic world affairs, the search for new energy materials has become a topic of great relevance. Sodium borohydride, NaBH 4 , seems to be a promising fuel in the context of the future hydrogen economy. NaBH 4 belongs to a class of materials with the highest gravimetric hydrogen densities, which has been discovered in the 1940s by Schlesinger and Brown. In the present paper, the most relevant issues concerning the use of NaBH 4 are examined. Its basic properties are summarised and its synthesis methods are described. The general processes of NaBH 4 oxidation, hydrolysis, and monitoring are reviewed. A comprehensive bibliometric analysis of the NaBH 4 publications in the energy field opens the discussion for current perspectives and future outlook of NaBH 4 as an efficient energy/hydrogen carrier. Despite the observed exponential increase in the research on NaBH 4 it is clear that further efforts are still necessary for achieving significant overchanges.

The influence of curing conditions on the mechanical performance of concrete made with recycled concrete waste

Abstract: Research on the use of Construction and Demolition Waste (CDW) as recycled aggregate (in particular crushed concrete) for the production of new concrete has by now established the feasibility of this environmentally-friendly use of otherwise harmful waste. However, contrary to conventional concrete (CC), no large applications of concrete made with recycled concrete have been made and there is still a lack of knowledge in some areas of production and performance of recycled aggregate concrete (RAC). One issue concerns curing conditions: these greatly affect the performance of concrete made on site and some potential users of RAC wonder how RAC is affected by far-from-ideal curing conditions. This paper shows the main results of experiments to determine the influence of different curing conditions on the mechanical performance of concrete made with coarse recycled aggregate from crushed concrete. The properties analyzed include compressive strength, splitting tensile strength, modulus of elasticity, and abrasion resistance. The general conclusion in terms of mechanical performance is that RAC is affected by curing conditions roughly in the same way as CC.

On the planning and analysis of Integrated Community Energy Systems: A review and survey of available tools

Abstract: Highly Integrated Community Energy Systems (ICES) greatly but not solely dependent on combined heat and power (CHP) sources are a viable approach for dealing effectively with the new set of global threats which Mankind is facing, such as Climate Change, Global Warming and Extreme Poverty. ICES are capable of delivering sustainable electricity, heat and cold to small communities and of working as grid-connected or islanded microgrids, adding technical, economical, environmental and social benefits to populations. The impacts of introducing ICES in current distribution networks can be analyzed at different scales due to the wide range of influence exerted not only at the local but also at regional and global levels. For these reasons, there is increased need for appropriate modeling of ICES for the vital purposes of planning and analysis of these systems. An overview on the available bottom-up tools for the optimization planning and analysis of ICES is done in this paper. The survey shows that DER-CAM can be considered an appropriate tool for the purpose of ICES design modeling due to the robust and flexible three-level optimization algorithm, hourly time step and other scale considerations but particularly due to the several successful applications with modeling microgrid systems. Additionally there is research experience on expanding the objective function for environmental concerns and also with EV battery storage interactions. Finally, GAMS DER-CAM's base language, is a widely known package for allowing changes to be made in model specifications simply and safely. In that sense, there is potential in exploring such tool for the design of ICES. Furthermore, it is found that MARKAL/TIMES, also a GAMS/CPLEX based tool, has scale flexibility which enables it for analyzing the long-term deployment of ICES in time. There is opportunity in this field for further work exploring the sustainability-sound modeling for optimal design of ICES and deployment scenario options evaluation, through long-term time horizons consideration.

Automatic analysis of affective postures and body motion to detect engagement with a game companion

Abstract: The design of an affect recognition system for socially perceptive robots relies on representative data: human-robot interaction in naturalistic settings requires an affect recognition system to be trained and validated with contextualised affective expressions, that is, expressions that emerge in the same interaction scenario of the target application. In this paper we propose an initial computational model to automatically analyse human postures and body motion to detect engagement of children playing chess with an iCat robot that acts as a game companion. Our approach is based on vision-based automatic extraction of expressive postural features from videos capturing the behaviour of the children from a lateral view. An initial evaluation, conducted by training several recognition models with contextualised affective postural expressions, suggests that patterns of postural behaviour can be used to accurately predict the engagement of the children with the robot, thus making our approach suitable for integration into an affect recognition system for a game companion in a real world scenario.

Optimal and Approximate Q-value Functions for Decentralized POMDPs

Abstract: Decision-theoretic planning is a popular approach to sequential decision making problems, because it treats uncertainty in sensing and acting in a principled way. In single-agent frameworks like MDPs and POMDPs, planning can be carried out by resorting to Q-value functions: an optimal Q-value function Q* is computed in a recursive manner by dynamic programming, and then an optimal policy is extracted from Q*. In this paper we study whether similar Q-value functions can be defined for decentralized POMDP models (Dec-POMDPs), and how policies can be extracted from such value functions. We define two forms of the optimal Q-value function for Dec-POMDPs: one that gives a normative description as the Q-value function of an optimal pure joint policy and another one that is sequentially rational and thus gives a recipe for computation. This computation, however, is infeasible for all but the smallest problems. Therefore, we analyze various approximate Q-value functions that allow for efficient computation. We describe how they relate, and we prove that they all provide an upper bound to the optimal Q-value function Q*. Finally, unifying some previous approaches for solving Dec-POMDPs, we describe a family of algorithms for extracting policies from such Q-value functions, and perform an experimental evaluation on existing test problems, including a new firefighting benchmark problem.

Toward a clinical-grade expansion of mesenchymal stem cells from human sources: a microcarrier-based culture system under xeno-free conditions.

Abstract: The immunomodulatory properties of mesenchymal stem cells (MSCs) make them attractive therapeutic agents for a wide range of diseases. However, the highly demanding cell doses used in MSC clinical trials (up to millions of cells/kg patient) currently require labor intensive methods and incur high reagent costs. Moreover, the use of xenogenic (xeno) serum-containing media represents a risk of contamination and raises safety concerns. Bioreactor systems in combination with novel xeno-free medium formulations represent a viable alternative to reproducibly achieve a safe and reliable MSC doses relevant for cell therapy. The main goal of the present study was to develop a complete xeno-free microcarrier-based culture system for the efficient expansion of human MSC from two different sources, human bone marrow (BM), and adipose tissue. After 14 days of culture in spinner flasks, BM MSC reached a maximum cell density of (2.0 –0.2) ·10 5 cells$mL -1 (18 –1-fold increase), whereas adipose tissue-derived stem cells expanded to (1.4 –0.5) ·10 5 cells$mL -1 (14 –7-fold increase). After the expansion, MSC expressed the characteristic markers CD73, CD90, and CD105, whereas negative for CD80 and human leukocyte antigen (HLA)-DR. Expanded cells maintained the ability to differentiate robustly into osteoblast, adipocyte, and chondroblast lineages upon directed differentiation. These results demonstrated the feasibility of expanding human MSC in a scalable microcarrier-based stirred culture system under xeno-free conditions and represent an important step forward for the implementation of a Good Manufacturing Practices‐ compliant large-scale production system of MSC for cellular therapy.

High luminosity, slow ejecta and persistent carbon lines: SN 2009dc challenges thermonuclear explosion scenarios

Abstract: Extended optical and near-IR observations reveal that SN 2009dc shares a number of similarities with normal Type Ia supernovae (SNe Ia), but is clearly overluminous, with a (pseudo-bolometric) peak luminosity of log (L) = 43.47 (erg s^(−1)). Its light curves decline slowly over half a year after maximum light [Δm_(15)(B)_true= 0.71], and the early-time near-IR light curves show secondary maxima, although the minima between the first and the second peaks are not very pronounced. The bluer bands exhibit an enhanced fading after ~200 d, which might be caused by dust formation or an unexpectedly early IR catastrophe. The spectra of SN 2009dc are dominated by intermediate-mass elements and unburned material at early times, and by iron-group elements at late phases. Strong C ii lines are present until ~2 weeks past maximum, which is unprecedented in thermonuclear SNe. The ejecta velocities are significantly lower than in normal and even subluminous SNe Ia. No signatures of interaction with a circumstellar medium (CSM) are found in the spectra. Assuming that the light curves are powered by radioactive decay, analytic modelling suggests that SN 2009dc produced ~1.8 M_⊙ of ^(56)Ni assuming the smallest possible rise time of 22 d. Together with a derived total ejecta mass of ~2.8 M_⊙, this confirms that SN 2009dc is a member of the class of possible super-Chandrasekhar-mass SNe Ia similar to SNe 2003fg, 2006gz and 2007if. A study of the hosts of SN 2009dc and other superluminous SNe Ia reveals a tendency of these SNe to explode in low-mass galaxies. A low metallicity of the progenitor may therefore be an important prerequisite for producing superluminous SNe Ia. We discuss a number of possible explosion scenarios, ranging from super-Chandrasekhar-mass white-dwarf progenitors over dynamical white-dwarf mergers and Type I(1/2) SNe to a core-collapse origin of the explosion. None of the models seems capable of explaining all properties of SN 2009dc, so that the true nature of this SN and its peers remains nebulous.

A Brief History of Fluorescence and Phosphorescence before the Emergence of Quantum Theory

Abstract: Fluorescence and phosphorescence are two forms of photoluminescence used in modern research and in practical applications The early observations of these phenomena, before the emergence of quantum theory, highlight the investigation into the mechanism of light emission In contrast to incandescence, photoluminescence does not require high temperatures and does not usually produce noticeable heat Such a “cold light” was the object of an interesting controversy in the 19th century: does it fit into thermodynamics? The early applications, such as the fluorescent tube, fluorescence analysis, and fluorescent tracers, are described

Thermal stability and oxidation resistance of laser clad TiVCrAlSi high entropy alloy coatings on Ti–6Al–4V alloy

Abstract: TiVCrAlSi high entropy alloy coatings were deposited on Ti–6Al–4V alloy by laser cladding. SEM, XRD and EDS analyses show that, the as-clad coating is composed of (Ti,V) 5 Si 3 and a BCC solid solution. After annealing at 800 °C for 24 h under vacuum, the coating is composed of (Ti,V) 5 Si 3 , Al 8 (V,Cr) 5 , and a BCC solid solution. The temperature-dependent phase equilibrium for the coating material calculated by using the CALPHAD method, indicates that above 880 °C the stable phases existing in the coating material are a BCC solid-solution and (Ti,V) 5 Si 3 . When the temperature is below 880 °C, the stable phases are (Ti,V) 5 Si 3 , Al 8 (V,Cr) 5 , and a BCC solid solution. In order to validate the calculation results, they were compared with TiVCrAlSi alloy samples prepared by arc melting, encapsulated in quartz tubes under vacuum, annealed at 400–1100 °C for 3 days and water-quenched. XRD analysis shows that the experimental phase composition agrees with the thermodynamic calculations. After vacuum annealing, there is a small increase of hardness for the laser clad TiVCrAlSi coating, which is due to the formation of Al 8 (V,Cr) 5 . The oxidation tests show that the TiVCrAlSi coating effectively improves the oxidation resistance of Ti–6Al–4V at 800 °C in air. The formation of a dense and adherent scale consisting of SiO 2 , Cr 2 O 3 , TiO 2 , Al 2 O 3 and a small amount of V 2 O 5 is supposed to be responsible for the observed improvement of the oxidation resistance.

Matrix Completion for Multi-label Image Classification

Abstract: Recently, image categorization has been an active research topic due to the urgent need to retrieve and browse digital images via semantic keywords. This paper formulates image categorization as a multi-label classification problem using recent advances in matrix completion. Under this setting, classification of testing data is posed as a problem of completing unknown label entries on a data matrix that concatenates training and testing features with training labels. We propose two convex algorithms for matrix completion based on a Rank Minimization criterion specifically tailored to visual data, and prove its convergence properties. A major advantage of our approach w.r.t. standard discriminative classification methods for image categorization is its robustness to outliers, background noise and partial occlusions both in the feature and label space. Experimental validation on several datasets shows how our method outperforms state-of-the-art algorithms, while effectively capturing semantic concepts of classes.

Lucy in the sky without diamonds: Stealing confidential data in the cloud

Abstract: Cloud Computing is a recent paradigm that is creating high expectations about benefits such as the pay-per-use model and elasticity of resources. However, with this optimism come also concerns about security. In a public cloud, the user's data storage and processing is no longer done inside its premises, but in data centers owned and administrated by the cloud provider. This may be a concern for organizations that deal with critical data, such as medical records. We show that a malicious insider can steal confidential data of the cloud user, so the user is mostly left with trusting the cloud provider. The paper achieves this goal by showing a set of attacks that demonstrate how a malicious insider can easily obtain passwords, cryptographic keys, files and other confidential data. Additionally, the paper shows that recent research results that might be useful to protect data in the cloud, are still not enough to deal with the problem. The paper is a call to arms for research in the topic.

Global Social Identity and Global Cooperation

Abstract: This research examined the question of whether the psychology of social identity can motivate cooperation in the context of a global collective. Our data came from a multinational study of choice behavior in a multilevel public-goods dilemma conducted among samples drawn from the general populations of the United States, Italy, Russia, Argentina, South Africa, and Iran. Results demonstrate that an inclusive social identification with the world community is a meaningful psychological construct that plays a role in motivating cooperation that transcends parochial interests. Self-reported identification with the world as a whole predicts behavioral contributions to a global public good beyond what is predicted from expectations about what other people are likely to contribute. Furthermore, global social identification is conceptually distinct from general attitudes about global issues, and has unique effects on cooperative behavior.

How to achieve a 100% RES electricity supply for Portugal?

Abstract: Portugal is a country with an energy system highly dependent on oil and gas imports. Imports of oil and gas accounted for 85% of the country's requirements in 2005 and 86% in 2006. Meanwhile, the share of renewable energy sources (RES) in the total primary energy consumption was only 14% in 2006. When focusing only on electricity production, the situation is somewhat better. The share of RES in gross electricity production varies between 20% and 35% and is dependent on the hydropower production in wet and dry years. This paper presents, on a national scale, Portugal's energy system planning and technical solutions for achieving 100% RES electricity production. Planning was based on hourly energy balance and use of H 2 RES software. The H 2 RES model provides the ability to integrate various types of storages into energy systems in order to increase penetration of the intermittent renewable energy sources or to achieve a 100% renewable island, region or country. The paper also represents a stepping-stone for studies offering wider possibilities in matching and satisfying electricity supply in Portugal with potential renewable energy sources. Special attention has been given to intermittent sources such as wind, solar and ocean waves that can be coupled to appropriate energy storage systems charged with surplus amounts of produced electricity. The storage systems also decrease installed power requirements for generating units. Consequently, these storages will assist in avoiding unnecessary rejection of renewable potential and reaching a sufficient security of energy supply.

Foreword to the Special Issue on Spectral Unmixing of Remotely Sensed Data

Abstract: The 19 papers in this special issue focus on the state-of-the-art and most recent developments in the area of spectral unmixing of remotely sensed data.