Showing papers by "Instituto Superior Técnico published in 2005"
TL;DR: A new method for unsupervised endmember extraction from hyperspectral data, termed vertex component analysis (VCA), which competes with state-of-the-art methods, with a computational complexity between one and two orders of magnitude lower than the best available method.
Abstract: Given a set of mixed spectral (multispectral or hyperspectral) vectors, linear spectral mixture analysis, or linear unmixing, aims at estimating the number of reference substances, also called endmembers, their spectral signatures, and their abundance fractions. This paper presents a new method for unsupervised endmember extraction from hyperspectral data, termed vertex component analysis (VCA). The algorithm exploits two facts: (1) the endmembers are the vertices of a simplex and (2) the affine transformation of a simplex is also a simplex. In a series of experiments using simulated and real data, the VCA algorithm competes with state-of-the-art methods, with a computational complexity between one and two orders of magnitude lower than the best available method.
2,422 citations
TL;DR: In this article, the authors proposed a new correlation between the heating value and dry ash content of biomass (in weight percent, wt%) (i.e. HHV (MJ/kg) = 19.914-0.2324 Ash) to estimate the HHV from proximate analysis.
Abstract: The heating value is one of the most important properties of biomass fuels for design calculations or numerical simulations of thermal conversion systems for biomass. There are a number of formulae proposed in the literature to estimate the higher heating value (HHV) of biomass fuels from the basic analysis data, i.e. proximate, ultimate and chemical analysis composition. In the present paper, these correlations were evaluated statistically based on a larger database of biomass samples collected from the open literature. It was found that the correlations based on ultimate analysis are the most accurate. The correlations based on the proximate data have low accuracy because the proximate analysis provides only an empirical composition of the biomass. The correlations based on the bio-chemical composition are not reliable because of the variation of the components properties. The low accuracy of previous correlations is mainly due to the limitation of samples used for deriving them. To achieve a higher accuracy, new correlations were proposed to estimate the HHV from the proximate and ultimate analyses based on the current database. The new correlation between the HHV and dry ash content of biomass (in weight percent, wt%) (i.e. HHV (MJ/kg) = 19.914–0.2324 Ash) could be conveniently used to estimate the HHV from proximate analysis. The new formula, based on the composition of main elements (in wt%) C, H, and O (i.e. HHV ( MJ / kg ) = - 1.3675 + 0.3137 C + 0.7009 H + 0.0318 O * ), is the most accurate one, with more than 90% predictions in the range of ± 5 % error.
800 citations
TL;DR: In this paper, a simple generalization of the Kohlrausch decay law that eliminates unphysical aspects of the original form is introduced and fully characterized, and general results concerning the relation between decay law and distribution of rate constants are also obtained.
528 citations
TL;DR: In this paper, a nanostructured hybrid sol-gel coatings doped with cerium ions were investigated as pre-treatments for the AA2024-T3 alloy.
483 citations
TL;DR: Several strategies that can be used for recombinant protein secretion in E. coli are presented and their advantages and limitations depending on the characteristics of the target protein to be produced are discussed.
482 citations
TL;DR: In this article, the incorporation of nanoparticles in the hybrid sol-gel systems increases the corrosion protection properties due to lower porosity and lower cracking potential along with enhancement of the mechanical properties.
Abstract: Sol–gel derived films exhibit a high potential as substitutes for the environmentally unfriendly chromate metal-surface pre-treatment methods. Inorganic sol–gel derived films offer good adhesion between metals and organic paint. However, they cannot provide adequate corrosion protection due to their high crack-forming potential. Introduction of an organic component to an inorganic sol–gel system leads to the formation of thicker, more flexible and functionalized films with enhanced compatibility to different organic top coatings. Incorporation of nanoparticles in the hybrid sol–gel systems increases the corrosion protection properties due to lower porosity and lower cracking potential along with enhancement of the mechanical properties. Furthermore, the incorporation of inorganic nanoparticles can be a way to insert corrosion inhibitors, preparing inhibitor nanoreservoirs for “self-repairing” pre-treatments with controlled release properties.
467 citations
24 Feb 2005
TL;DR: This paper compares two popular redundancy schemes: replication and erasure coding, and concludes that in some cases the benefits from coding are limited, and may not be worth its disadvantages.
Abstract: High availability in peer-to-peer DHTs requires data redundancy. This paper compares two popular redundancy schemes: replication and erasure coding. Unlike previous comparisons, we take the characteristics of the nodes that comprise the overlay into account, and conclude that in some cases the benefits from coding are limited, and may not be worth its disadvantages.
422 citations
TL;DR: In this paper, a review of metal-mediated hydration of organonitriles is presented, focusing on unusual conversions of RCN species, yet underdeveloped and non-systematic, which involve hydrolysis and lead to compounds of synthetic or pharmacological significance.
364 citations
TL;DR: In this article, the 1,2,4-triazole, 3-amino, 1, 2, 4 triazole and 2-mercaptobenzothiazole were evaluated as corrosion inhibitors for protection of the AA2024 alloy in neutral chloride solutions.
320 citations
TL;DR: In this article, a drop-on-demand ink-jet printer was used to print a silver-organic solution onto glass substrates and conductive silver tracks were obtained by heat treatment of the inkjet printed deposits at temperatures ranging from 125°C to 200°C in air.
Abstract: Summary: A drop-on-demand ink-jet printer has been used to print a silver-organic solution onto glass substrates. Conductive silver tracks were obtained by heat treatment of the ink-jet printed deposits at temperatures ranging from 125 °C–200 °C in air. Resistivity values were found to have dropped to two to three times the theoretical resisitivity of bulk silver after temperatures of 150 °C and above were used.
Resistivity values of a silver-based ink.
317 citations
TL;DR: In this article, the main characteristics of such aggregates as well as those of the fresh and hardened concrete made with them are presented and compared with those of conventional materials (primary stone aggregates and the concretes made exclusively with them), within a larger experimental investigation to maximize the reuse and reutilization of construction and demolition waste.
Abstract: In order to reduce the volume of ceramic waste from the construction industry, it is possible, among other applications, to use it as aggregates in the production of non-structural concrete artefacts. The main characteristics of such aggregates as well as those of the fresh and hardened concrete made with them (after a standardized pre-saturation procedure) are presented here and compared with those of conventional materials (primary stone aggregates and the concretes made exclusively with them), within a larger experimental investigation to maximize the reuse and reutilization of construction and demolition waste. The results show that there is a potential for the use of these ceramic aggregates in elements in which the primary requirement is not compressive strength but tensile strength and abrasion resistance, such as for concrete pavement slabs.
12 Sep 2005
TL;DR: The experience of constructing the application FearNot!
Abstract: We discuss the experience of constructing the application FearNot! (Fun with Empathic Agents Reaching Novel Outcomes in Teaching), an application of virtual drama to anti-bullying education inspired by Forum Theatre. An appraisal-driven agent architecture is presented as a mechanism for generating an emergent, that is, unscripted, narrative. A small-scale evaluation is discussed and the lessons learned are described.
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TL;DR: In this paper, the authors present a technical process, multi-criteria portfolio analysis, for balancing the conflicting elements of the problem, and a social process, decision conferencing, which engages all the key players during the modelling process, ensuring their ownership of the model and subsequent implementation.
Abstract: Managers in both for-profit and not-for-profit organisations continually face the task of allocating resources by balancing costs, benefits and risks and gaining commitment by a wide constituency of stakeholders to those decisions. This task is complex and difficult because many options are present, benefits and risks are rarely expressed as single objectives, multiple stakeholders with different agendas compete for limited resources, individually optimal resource allocations to organisational units are rarely collectively optimal, and those dissatisfied with the decisions taken may resist implementation. We first explain three current approaches to resource allocation taken from corporate finance, operational research and decision analysis, and we identify a common mistake organisations make in allocating resources. The paper then presents a technical process, multi-criteria portfolio analysis, for balancing the conflicting elements of the problem, and a social process, decision conferencing, which engages all the key players during the modelling process, ensuring their ownership of the model and the subsequent implementation. This socio-technical process improves communication within the organisation, develops shared understanding of the portfolio and generates a sense of common purpose about those projects that will best realise the organisation’s objectives. The paper concludes with lessons we have learned from actual practice.
TL;DR: In this article, a model where non-commutativity of both configuration and momentum spaces is considered is proposed and the problem of the two-dimensional gravitational quantum well is analyzed.
Abstract: We study noncommutative geometry at the quantum mechanics level by means of a model where noncommutativity of both configuration and momentum spaces is considered. We analyze how this model affects the problem of the two-dimensional gravitational quantum well and use the latest experimental results for the two lowest energy states of neutrons in the Earth's gravitational field to establish an upper bound on the fundamental momentum scale introduced by noncommutativity, namely, $\sqrt{\ensuremath{\eta}}\ensuremath{\lesssim}1\text{ }\mathrm{meV}/c$, a value that can be improved in the future by up to $3$ orders of magnitude. We show that the configuration space noncommutativity has, in leading order, no effect on the problem. We also analyze some features introduced by the model, especially a correction to the presently accepted value of Planck's constant to $1$ part in ${10}^{24}$.
TL;DR: The electrochemical behavior of passive films formed on one austenitic stainless steel and one ferritic stainless steel (AISI 446) in solutions with pH between 0.6 and 8.4 was studied by capacitance measurements and photocurrent spectroscopy.
TL;DR: In this article, the stability constants of proton (hydron) and metal complexes for seven complexones of particular biomedical and environmental interest were evaluated using available experimental data on stability constants.
Abstract: Available experimental data on stability constants of proton (hydron) and metal complexes for seven complexones of particular biomedical and environmental interest: iminodiacetic acid (2,2'-azanediyldiacetic acid, IDA); (methyl-imino)diacetic acid (2,2'-(methylazanediyl)diacetic acid, MIDA); 2,2',2",2'''-{[(carboxymethyl)azanediyl]bis[(ethane-l,2-diyl)nitrilo]}tetraacetic acid (DTPA); 3.6,9,12-tetrakis(carboxymethyl )-3,6,9,12-tetraazatetradecanedioic acid (TTHA); 2,2',2"-(l,4,7-triazanonane-l,4,7-triyl)triacetic acid (NOTA); 2,2',2",2'''-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (DOTA); 2,2',2",2'''-(1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetrayl)tetraacetic acid (TETA), published in 1945-2000, have been critically evaluated. Some typical errors in stability constant measurements for particular complexones are summarized. Higher quality data are selected and presented as "Recommended" or "Provisional".
TL;DR: In this article, a thermo-kinetic LPD model coupling finite element heat transfer calculations with transformation kinetics and quantitative property-structure relationships is presented. And the results show that the thermal history and, hence, the microstructure and properties of the final part depend significantly on these parameters.
TL;DR: In the first year of the Supernova Legacy Survey (SNLS) as mentioned in this paper, a new technique called SN photo-z was proposed to improve the efficiency of supernova classification at high redshift.
Abstract: We present new techniques for improving the efficiency of supernova (SN) classification at high redshift using 64 candidates observed at Gemini North and South during the first year of the Supernova Legacy Survey (SNLS). The SNLS is an ongoing 5 year project with the goal of measuring the equation of state of dark energy by discovering and following over 700 high-redshift SNe Ia using data from the Canada-France-Hawaii Telescope Legacy Survey. We achieve an improvement in the SN Ia spectroscopic confirmation rate: at Gemini 71% of candidates are now confirmed as SNe Ia, compared to 54% using the methods of previous surveys. This is despite the comparatively high redshift of this sample, in which the median SN Ia redshift is z = 0.81 (0.155 ≤ z ≤ 1.01). These improvements were realized because we use the unprecedented color coverage and light curve sampling of the SNLS to predict whether a candidate is a SN Ia and to estimate its redshift, before obtaining a spectrum, using a new technique called the SN photo-z. In addition, we have improved techniques for galaxy subtraction and SN template χ2 fitting, allowing us to identify candidates even when they are only 15% as bright as the host galaxy. The largest impediment to SN identification is found to be host galaxy contamination of the spectrum—when the SN was at least as bright as the underlying host galaxy the target was identified more than 90% of the time. However, even SNe in bright host galaxies can be easily identified in good seeing conditions. When the image quality was better than 055, the candidate was identified 88% of the time. Over the 5 year course of the survey, using the selection techniques presented here, we will be able to add ~170 more confirmed SNe Ia than would be possible using previous methods.
TL;DR: This paper reviews the state of the art on ethanol determination based on AOX sensors, using either electrochemical electrodes or immobilised enzyme reactors, and proposes different types of electrodes for the detection of ethanol.
TL;DR: In this article, the electrochemical behavior of galvanized steel (GS) substrates pre-treated with bis-triethoxysilylpropyl tetrasulfide silane (BTESPT) doped with cerium nitrate was evaluated by electrochemical impedance spectroscopy (EIS) and by the scanning vibrating electrode technique (SVET).
TL;DR: In this paper, the authors investigated the long-time evolution of magnetic fields generated by the two-stream instability at ultra-and subrelativistic astrophysical collisionless shocks.
Abstract: We investigate the long-time evolution of magnetic fields generated by the two-stream instability at ultra- and subrelativistic astrophysical collisionless shocks. Based on three-dimensional particle-in-cell (PIC) simulation results, we introduce a two-dimensional toy model of interacting current filaments. Within the framework of this model, we demonstrate that the field correlation scale in the region far downstream of the shock grows nearly as the light crossing time, λ(t) ~ ct, thus making the diffusive field dissipation inefficient. The obtained theoretical scaling is tested using numerical PIC simulations. This result extends our understanding of the structure of collisionless shocks in gamma-ray bursts and other astrophysical objects.
TL;DR: In this paper, the standing wave difference method (SWDM) is applied to several configurations of pipe systems with different leak locations and sizes to identify the leak frequencies and estimate the approximate location.
Abstract: The current paper focuses on leakage detection in pipe systems by means of the standing wave difference method (SWDM) used for cable fault location in electrical engineering. This method is based on the generation of a steady-oscillatory flow in a pipe system, by the sinusoidal maneuver of a valve, and the analysis of the frequency response of the system for a certain range of oscillatory frequencies. The SWDM is applied to several configurations of pipe systems with different leak locations and sizes. A leak creates a resonance effect in the pressure signal with a secondary superimposed standing wave. The pressure measurement and the spectral analysis of the maximum pressure amplitude at the excitation site enable the identification of the leak frequencies and, consequently, the estimation of the leak approximate location. Practical difficulties of implementation of this technique in real life systems are discussed.
TL;DR: Results provide strong support for a genotoxic mechanism of AA carcinogenicity in rodents and the kinetic/biomarker approaches described here may represent a meaningful way to extrapolate cancer risks to actual human exposures from food, which are much lower.
Abstract: Acrylamide (AA) is an important industrial chemical that is neurotoxic, mutagenic to somatic and germ cells, and carcinogenic in chronic rodent bioassays. Recent findings of AA in many common starchy foods have sparked renewed interest in determining toxic mechanisms and in understanding the cancer, neurotoxicity, and reproductive risks from typical human exposures. Dosing mice and rats with AA (50 mg/kg) led to presence of glycidamide (GA) in serum and tissues. Furthermore, GA-derived DNA adducts of adenine and guanine were formed in all tissues examined, including both target tissues identified in rodent carcinogenicity bioassays and in non-target tissues. Dosing rats and mice with an equimolar amount of GA typically produced higher levels of DNA adducts than observed with AA. Kinetics of DNA adduct formation and accumulation were measured following oral administration of a single dose of AA (50 mg/kg) or from repeat dosing (1 mg/kg/day), respectively. The formation of these DNA adducts is consistent with previously reported mutagenicity of AA and GA in vitro, which involved reaction of GA with adenine and guanine bases. These results provide strong support for a genotoxic mechanism of AA carcinogenicity in rodents. The kinetic/biomarker approaches described here may represent a meaningful way to extrapolate cancer risks to actual human exposures from food, which are much lower.
TL;DR: In this article, the authors demonstrate the possibility to use the zirconia nanoparticles as a reservoir for the storage and prolonged release of the corrosion inhibitor, which not only reinforce the hybrid matrix but also absorb inhibitors ions releasing them during contact with moisture offering the effective self-healing properties.
TL;DR: The issue of empathy as one desirable aspect of the affective interaction between learners and synthetic characters is focused on and some results achieved are reported in the evaluation executed with 127 children and 95 adults on the FearNot!.
Abstract: Virtual environments (VEs) are now becoming a promising new technology to be used in the development of interactive learning environments for children. Perhaps triggered by the success of computer games, VEs are seen as an emergent and engaging new way by which children can learn experimental sciences and other disciplines. Inhabiting these IVEs can be agents or intelligent characters that are responsible for events that happen in the environment and make it not predictive or completely controlled. However, to build such environments, in particular, if populated by synthetic characters, one needs to carefully address the problem of how do the learners respond to the characters in the virtual environment. Do learners like the characters? Do learners identify themselves with characters in virtual environments? This relation between learners and characters in virtual environments can be studied in several perspectives. In this paper, we will focus primarily on the issue of empathy as one desirable a...
TL;DR: The acetic acid-induced prolongation of the lag phase of unadapted cell populations lacking HAA1 or TPO3, compared with wild-type population, was correlated with the level of the acid accumulated into the stressed cells.
TL;DR: The specificity of pDNA purification and the consequent limitations to the performance of chromatography are described.
TL;DR: Both [AO7] and TOC removal efficiencies were found to be similar (approximately 70%), which is indicative of AO7 mineralization.
TL;DR: In this paper, an apparatus where individual bubbles are kept stationary in a downward liquid flow was adapted to simultaneously follow mass transfer to/from a single bubble as it inevitably gets contaminated; follow its shape; and periodically measure its terminal velocity.