2013
Authors
Queiros, RB; Guedes, A; Marques, PVS; Noronha, JP; Sales, MGF;
Publication
SENSORS AND ACTUATORS B-CHEMICAL
Abstract
Using low cost portable devices that enable a single analytical step for screening environmental contaminants is today a demanding issue. This concept is here tried out by recycling screen-printed electrodes that were to be disposed of and by choosing as sensory element a low cost material offering specific response for an environmental contaminant. Microcystins (MCs) were used as target analyte, for being dangerous toxins produced by cyanobacteria released into water bodies. The sensory element was a plastic antibody designed by surface imprinting with carefully selected monomers to ensure a specific response. These were designed on the wall of carbon nanotubes, taking advantage of their exceptional electrical properties. The stereochemical ability of the sensory material to detect MCs was checked by preparing blank materials where the imprinting stage was made without the template molecule. The novel sensory material for MCs was introduced in a polymeric matrix and evaluated against potentiometric measurements. Nernstian response was observed from 7.24 x 10(-10) to 1.28 x 10(-9) M in buffer solution (10 mM HEPES, 150 mM NaCl, pH 6.6), with average slopes of -62 mV decade(-1) and detection capabilities below 1 nM. The blank materials were unable to provide a linear response against log(concentration), showing only a slight potential change towards more positive potentials with increasing concentrations (while that of the plastic antibodies moved to more negative values), with a maximum rate of +33 mV decade(-1). The sensors presented good selectivity towards sulphate, iron and ammonium ions, and also chloroform and tetrachloroethylene (TCE) and fast response (<20 s). This concept was successfully tested on the analysis of spiked environmental water samples. The sensors were further applied onto recycled chips, comprehending one site for the reference electrode and two sites for different selective membranes, in a biparametric approach for "in situ" analysis.
2013
Authors
Bahubalindruni, P; Tavares, VG; de Oliveira, PG; Barquinha, P; Martins, R; Fortunato, E;
Publication
2013 IEEE INTERNATIONAL CONFERENCE OF ELECTRON DEVICES AND SOLID-STATE CIRCUITS (EDSSC)
Abstract
A high-gain amplifier topology, with all single n-type enhancement transistors, is proposed in this paper. This type of circuits are essential in transparent TFT technologies, such as GIZO and ZnO that lack complementary type transistor. All circuits were simulated using BSIM3V3 model of a 0.35 mu m CMOS technology, due to the absence of a complete electrical model for the TFTs. Results reveal that the proposed circuit promise more gain, lower power consumption and higher bandwidth than the existing solutions under identical bias conditions.
2013
Authors
Fátima Teles, Md; de Sousa, JF;
Publication
EWG-DSS
Abstract
Companies are increasingly including their corporate social responsibility into their business strategy. The environmental issues assume here a priority role. In order to get a balance in economic, social and environmental trade-offs, companies need to consider multiple objectives, namely related to the allocation of resources and investments, which can cause contradictory opinions among diverse stakeholders. Companies should incorporate into the decision-making process tangible and intangible elements, identifying and structuring objectives in a consistent way, in order to choose sustainable options for the company and create compromises between stakeholders. The main motivation of this paper is to present a methodology or framework to support decision-making and appraisal of corporate environmental strategies and subsequent management approaches. In order to gain a closer view over the proposed approach, we will present the preliminary results illustrated with examples from an ongoing case study within a public passenger transport company. © Springer International Publishing Switzerland 2014.
2013
Authors
Almeida, JB; Barbosa, M; Pinto, JS; Vieira, B;
Publication
SCIENCE OF COMPUTER PROGRAMMING
Abstract
Formal verification of cryptographic software implementations poses significant challenges for off-the-shelf tools. This is due to the domain-specific characteristics of the code, involving aggressive optimizations and non-functional security requirements, namely the critical aspect of countermeasures against side-channel attacks. In this paper, we extend previous results supporting the practicality of self-composition proofs of non-interference and generalizations thereof. We tackle the formal verification of high-level security policies adopted in the implementation of the recently proposed NaCl cryptographic library. We formalize these policies and propose a formal verification approach based on self-composition, extending the range of security policies that could previously be handled using this technique. We demonstrate our results by addressing compliance with the NaCl security policies in real-world cryptographic code, highlighting the potential for automation of our techniques.
2013
Authors
Pontes, MJ; Coelho, TVN; Carvalho, JP; Santos, JL; Guerreiro, A;
Publication
8TH IBEROAMERICAN OPTICS MEETING AND 11TH LATIN AMERICAN MEETING ON OPTICS, LASERS, AND APPLICATIONS
Abstract
This work discusses remote fiber sensors enabled by optical amplification. Continuous wave numerical modeling based on the propagation of pumps and signal lasers coupled to optical fibers explores Raman amplification schemes to predict the sensor's behavior. Experimental analyses report the results to a temperature remote optical sensor with 50 km distance between the central unit and the sensor head. An electrical interrogation scheme is used due to their low cost and good time response. Different architectures in remote sensor systems are evaluated, where diffraction gratings are the sensor element. A validation of calculated results is performed by experimental analyses and, as an application, the noise generated by Raman amplification in the remote sensors systems is simulated applying such numerical modeling. The analyses of sensors systems based on diffraction gratings requires optical broadband sources to interrogate the optical sensor unit, mainly in long period gratings that shows a characteristic rejection band. Therefore, the sensor distance is limited to a few kilometers due to the attenuation in optical fibers. Additional attenuation is introduced by the sensor element. Hence, to extend the distance in the optical sensor system, the optical amplification system is needed to compensate the losses in the optical fibers. The Raman amplification technology was selected mainly due to the flexibility in the gain bandwidth. The modeling can be applied to sensor systems that monitor sites located at long distances, or in places that the access is restricted due to harsh environment conditions in such cases conventional sensors are relatively fast deteriorated.
2013
Authors
Madeira, S; Goncalves, J; Bastos, L;
Publication
JOURNAL OF COASTAL CONSERVATION
Abstract
A Mobile Mapping System (MMS) is composed by a set of sensors placed on a mobile platform whose main objective is to obtain attitude and position over time of a referential in the platform together with the image of the objects surrounding the platform. The acquired data allows to obtain georeferenced positions of object points captured by the object sensors. This paper describes a methodology to automatically extract accurate Digital Terrain Models (DTM) of sand beach areas using a Terrestrial Mobile Mapping System (TMMS). The main goal of the presented TMMS is to obtain accurate 3D models of sand beaches. A very important consequence of this will be the abbility to track spatial and temporal changes in coastal geomorphology. The presented methodology has several advantages over more classical approaches: the overall cost, flexibility for regular surveys or at the most convenient epoch, such as after storms. Besides one of the major constraints in Mobile Mapping, that is poor GNSS (Global Navigation Satellite Systems) observation conditions, is usually not present in these areas. The TMMS uses two progressive colour video cameras and can work with any type of direct georeferencing system, which obvoiusly has impact in the final accuracy of the derived DTM. For the results herein reported, a dual frequency GNSS receiver and a low grade type of IMU (Inertial Measurement System) were used. The moving platform where the system was installed is a moto quad. The developed methodology for the DTM generation relies on an automatic choice of terrain points whose three-dimensional coordinates are calculated using a presented image matching technique. A cloud of points obtained in a nearly regular grid pattern is the base for the DTM. The proposed methodology was applied on a sector of the Vila Nova de Gaia Coast, in northern Portugal, and the results presented here show that it is possible with this methodology to produce DTMs with a precision of a few centimetres.
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