Academia Militar

Lisbon, Portugal

Academia Militar

Lisbon, Portugal
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Gomes R.D.F.R.,Academia Militar | Martins M.J.,Academia Militar | Baptista A.,University of Lisbon | Torres J.P.N.,University of Lisbon
Optical and Quantum Electronics | Year: 2017

Nowadays, communications are moving to the optical frequencies, due to the extended bandwidth available, and the saturation of the RF spectrum. The dimensions of the antennas decrease with the operating wavelength. Therefore, in the optical domain, building an antenna may imply the design of a device with dimensions of several nanometers. The development of nanotechnology has enabled the development of these new devices, known as nanoantennas or optical antennas. New phenomenology has appeared with these new devices. In 2006 it was discovered that the transmission of light through arrays of subwavelength holes in a metal, gives rise to the phenomenon of extraordinary optical transmission, or in other words the amount of optical energy appearing on the other side of the metal is much greater than was expected by theoretical studies. The applications of these new antennas are fascinating, and are present in a very broad range of areas from biophotonics to quantum communication, data processing or optical wireless communications. This paper aims at studying and characterizing, in a classical perspective, an optical antenna formed by an array of subwavelength holes in a metal sheet that could be integrated in the transmitter or receiver ends of an intersatellite optical communication system. © 2017, Springer Science+Business Media New York.

Torres J.A.,Academia Militar | Torres J.A.,Telecommunications Institute of Portugal | Freire J.C.,University of Lisbon | Freire J.C.,Telecommunications Institute of Portugal
Integration, the VLSI Journal | Year: 2015

The study of monolithic integration of active inductors (AI) on a 0.25μm SiGe BiCMOS technology with 4 metal layers and HBTs with f T =120GHz is presented. Two topologies are presented and their performance discussed. Q values higher than 30 were obtained on a 3.4GHz bandwidth at 28GHz and maximum values as high as 100. Active inductors can be biased with low power, such as 2V with a nominal DC current of 0.6mA. The inductance value is controlled by external bias voltages and adjustments up to 40% were measured. Simple gyrators topologies with only 2 transistors are used for low power consumption and good performance at K Band is proved. The internal parameters of small signal model of HBT were studied and the crucial parameter to enhance the negative resistance and so the Q of the AI was identified. © 2015 Elsevier B.V.

Jose Antonio T.L.,Academia Militar | Catalao J.,University of Lisbon
Iberian Conference on Information Systems and Technologies, CISTI | Year: 2013

In this paper, a new methodology is presented for contour line generalization. The methodology is based on the combination of artificial neural network, decision tree and classification & regression tree algorithms into an auction schema where the 'best' parameter for contour line generalization is selected. The contour lines are generalized using a tension parameter locally adapted to a selection set of line characteristics. The proposed methodology determines the tension to be applied to the curve in function of the contour line characteristics (fractal dimension, the length and others). A test is performed over a 1:25k scale map. The resulting 1:50k scale contour lines were compared with contour lines generalized interactively with the same algorithm and a global precision of 81% was achieved. © 2013 AISTI.

Seghar D.,University dras | Thandapani E.,University dras | Pinelas S.,Academia Militar
Tamkang Journal of Mathematics | Year: 2015

In this paper we obtain some new oscillation criteria for the neutral difference equation (equation presented) where 0 ≥ pn ≥ p < 1, qn > 0 and l and k are positive integers. Examples are presented to illustrate the main results. The results obtained in this paper improve and complement to the existing results.

Grace S.R.,Cairo University | Pinelas S.,Academia Militar | Agarwal R.P.,Texas A&M University-Kingsville
International Journal of Dynamical Systems and Differential Equations | Year: 2012

We shall establish some new criteria for the oscillation of neutral delay dynamic equations on an arbitrary time-scale. © 2012 Inderscience Enterprises Ltd.

Calado L.M.,New University of Lisbon | Cordas C.M.,New University of Lisbon | Sousa J.P.,Academia Militar
Analytical and Bioanalytical Electrochemistry | Year: 2013

In the present work, mercury thin film modified carbon microelectrodes were tested towards detection of the pharmacological compounds acemetacin and indomethacin. The compounds were characterized electrochemically by adsorptive stripping differential pulse and square wave voltammetry (AdSDPV and AdSSWV). Best results were obtained via AdSDPV for both compounds (Acemetacin: LOD=1.05×10-7 M, LOQ=3.51× 10-7 M; Indomethacin: LOD=1.34× 10-7 M, LOQ=4.47× 10-7 M). These results are comparable to earlier reports using classical hanging drop mercury electrodes, but with environmental advantages due to the limited mercury amount that is used and the easy way to recover it. Detection and quantification limits are lower than the obtained with currently used analytical techniques. © 2013 by CEE.

Valdez M.T.,Polytechnic Institute of Coimbra | Ferreira C.M.,Polytechnic Institute of Coimbra | Martins M.J.M.,Academia Militar | Barbosa F.P.M.,INESC Porto
2015 International Conference on Information Technology Based Higher Education and Training, ITHET 2015 | Year: 2015

3D Virtual Labs are the support of learning, a tool of education in the future. Learning in a 3D environment allows greater interaction with contents in a unique way as students perceive it as being really there. Simulations are being designed, a combination of real-world environment with the information supplied by devices, where measurements can be replicated and data analyzed. This study presents a virtual scenario of a Measurements and Instrumentation laboratory. © 2015 IEEE.

Valdez M.T.,Polytechnic Institute of Coimbra | Ferreira C.M.,Polytechnic Institute of Coimbra | Martins M.J.M.,Academia Militar | Barbosa F.P.M.,INESC Porto
Proceedings of the 25th International Conference on European Association for Education in Electrical and Information Engineering, EAEEIE 2014 | Year: 2014

Virtual labs are more likely to offer a user friendly environment as well as greater flexibility, allowing students to carry out experiments and repeat them as often as necessary. Nevertheless, they do not discard the need for a conventional system as traditional labs are a valuable asset. In this context, the student is the centre of the whole process , taking on the main role and is responsible for his/her own learning process, although there may be an extra support through in-class sessions in order to keep him/her in contact with the system, to offer guidance and motivation for the challenges ahead. One of the advantages of virtual experimentation is the opportunity of using a lab in situations which might be impossible otherwise, allowing students to take part in lab sessions; another one is related with its use to improve learning results. Virtual experimentation labs create flexible learning environments suitable for different types of learners, allowing the interactive and systematic development of competences in the various areas of learning and can be used to complement the conventional type of lectures. VEMA is a practical asynchronous software tool devised to meet the needs of students who can't be present in regular lab classes in the Electrical Engineering Department of ISEC (Instituto Superior de Engenharia de Coimbra). © 2014 IEEE.

Martins M.J.M.,Academia Militar | Barbosa F.P.M.,INESC Porto | Ferreira C.M.,Polytechnic Institute of Coimbra | Valdez M.T.,Polytechnic Institute of Coimbra
Proceedings of the 25th International Conference on European Association for Education in Electrical and Information Engineering, EAEEIE 2014 | Year: 2014

Nowadays, education extends beyond the field of formal education delivered in universities and colleges, and is increasingly based on new technological developments. Long Life Learning (LLL) is a fundamental tool in today's world in order to remain competitive in the market. The ease of access to the Internet and computer technologies has turned into a new field for developing applications which can be distributed worldwide in an almost instantaneous manner, but must be appropriately designed in order to achieve their goals. Quality e-Iearning courseware requires several aspects to be covered in order to achieve its purposes. These include a thorough knowledge of the content as well as methods of delivery and learning theory. These requirements were taken into account in the development of a virtual-lab environment, named VEMA, developed by one of the authors and used in the Bachelor and Master's classes. © 2014 IEEE.

Travassos Valdez M.,Polytechnic Institute of Coimbra | Machado Ferreira C.,Polytechnic Institute of Coimbra | Martins M.J.M.,Academia Militar | Maciel Barbosa F.P.,University of Porto
ITHET 2014 - 13th International Conference on Information Technology Based Higher Education and Training | Year: 2014

3D worlds provide excellent platforms to achieve performance results when designed for the needs of students, helping them to improve acquisition and allowing greater interaction with contents in a unique way. © 2014 IEEE.

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