Browsing by Issue Date, starting with "2019-02-01"
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- Optical and photoconductive properties of indium sulfide fluoride thin filmsPublication . Vygranenko, Yuri; Vieira, Manuela; Lavareda, G.; Carvalho, C. Nunes de; Brogueira, Pedro; Amaral, A.; Pessoa Barradas, Nuno; Alves, E.This work reports on transparent semiconducting indium sulfide fluoride (ISF) thin-films exhibiting high sensitivity to ultraviolet radiation. The films were deposited on fused silica and silicon substrates using a radiofrequency plasma-enhanced reactive thermal evaporation system. The deposition was performed evaporating pure indium in SF6 plasma at a substrate temperature of 423 K. Rutherford backscattering measurements were used to determine the chemical composition of the films deposited on silicon substrates. The surface morphology was studied using scanning electron microscopy technique. The film characterization includes electrical, optical, and photoconductivity measurements. The synthesized compound is highly-resistive (similar to 700 M Omega-cm at 300 K) and exhibits an evident semiconducting behavior. The activation energy of 0.88 eV is deduced from the temperature dependence of electrical resistivity. The indirect band energy gap of 2.8 eV is determined from transmittance spectra of the ISF films. The photoconductivity band is centered at 345 nm wavelength. The photoconductivity spectrum also shows the Urbach tail with a characteristic energy of 166 meV. ISF is a promising candidate for a buffer layer in chalcogenide-based solar cells.
- Synthesis and bactericide activity of nanofiltration composite membranes - Cellulose acetate/silver nanoparticles and cellulose acetate/silver ion exchanged zeolitesPublication . Beisl, Stefan; Monteiro, Silvia; Santos, Ricardo; Figueiredo, Ana Sofia; SANCHEZ-LOREDO, MARIA GUADALUPE; Lemos, Maria Amélia; Lemos, Francisco; Minhalma, Miguel; De Pinho, Maria NorbertaThe present work addresses the synthesis of nanofiltration composite membranes with bactericide properties. The cellulose acetate based membranes with polyvinylpyrrolidone coated silver nano particles, silver ion-exchanged beta-zeolite and beta-zeolite are casted by the phase inversion technique and subjected to an annealing post-treatment. They are characterized in terms of the nanofiltration permeation performance and antibacterial properties. The incorporation of silver nanoparticles produces a threefold increase in the membrane hydraulic permeability when compared to the silver-free membranes and the incorporation of silver ion loaded zeolite resulted in a 56.3% increase in hydraulic permeability. In contrast to the influence of silver presence, either in nanometric or in the ionic form, the presence of zeolite does not significantly influence the hydraulic permeability. The rejection coefficients to salts range from 83% to 93% for the silver ion-exchanged zeolite membrane and from 84% to 97% for the polyvinylpyrrolidone coated silver nanoparticles membrane. They are higher for sulfate salts than for chloride salts. The antibacterial properties of the membranes were evaluated against Escherichia coli. The results have shown that the silver ion-exchanged beta-zeolite membrane was effective in inactivating Escherichia coli after just 210 min of contact time. No bacterial activity was detected following 24 h of contact time with the membrane containing polyvinylpyrrolidone coated silver nanoparticles. A reduction of more than 6-log, in the number of Escherichia coli, was achieved for both membranes. The different patterns of bactericide activity are associated to the silver speciation in metallic or ionic form. The high flux nanofiltration composite membranes with bactericidal properties represent a strong asset in water treatment biofouling control.
- Domain specific language generation based on a XML schemaPublication . Duarte, Luís Carlos da Silva; Carvalho, Fernando Miguel Gamboa deThe use of markup languages is recurrent in the world of technology, with HyperText Markup Language (HTML) being the most prominent one due to its use in theWeb. The requirement of tools that can automatically build well formed documents with good performance is clear. Yet, the most used solution is template engines, which neither ensures well-formed documents nor presents good performance, due to the use of external text files. To tackle the first issue we propose to define HTML templates as first-class functions instead of using text files. To that end, these HTML template functions use a Java Domain Specific Language (DSL) to write HTML. Our main goal is to create the required tools that automatically generate that DSL based on its language definition from an eXtensive Markup Language Schema Definition (XSD) file. The resulting DSL should enforce the restrictions of the given language which are specified in the XSD file. By removing the use of text files we are also suppressing the file load overhead and reducing String manipulation, which in turn increases the overall performance and solves the second issue. My proposal, named xmlet, includes a set of tools that are able to: 1) parse and extract the rules from a XSD file, 2) generate the adequate classes and methods to define the DSL that reflects the language rules, 3) handle the use of the resulting DSL through the implementation of the Visitor pattern. Finally we validated this solution not only for the HTML language, but also with the Android layouts and the regular expressions languages. By comparing the developed solution to some state-of-art solutions, including template engines and some other solutions with specific innovations, we obtained very favorable results with the suggested solution being the best performancewise in all the tests we performed. These results are important, specially considering that apart from being a more efficient solution it also introduces validations of the language usage based on its syntax definition.
- A review on methods for random motion detection and compensation in bio-radar systemsPublication . Gouveia, Carolina; Vieira, José; Pinho, PedroThe bio-radar system can measure vital signals accurately, by using the Doppler effect principle, which relates the received signal properties to the distance change between the radar antennas and the subject chest-wall. These systems have countless applications, from short range detection to assist in rescue missions, to long-term applications as for the continuous sleeping monitoring. Once the main applications of these systems intend to monitor subjects during long periods of time and under noisy environments, it is impossible to guarantee the patient immobilization, hence its random motion, as well as other clutter sources, will interfere in the acquired signals. Therefore, the signal processing algorithms developed for these applications have been facing several challenges regarding the random motion detection and mitigation. In this paper, an extended review on the already implemented methods is done, considering continuous wave radars. Several sources of random motion are considered, along with different approaches to compensate the distortions caused by them.