Constructions of ideal lattices with full diversity

In this paper, we present new constructions of ideal lattices for the Rayleigh fading channel in Euclidean spaces with full diversity. These constructions are through totally real subfields of cyclotomic fields, obtained by endowing their ring of integers. With this method we reproduce rotated versions of algebraic lattices where the performance in terms of minimum product distance is related with the field determinant.

Nanodisplacement measurements of piezoelectric flextensional actuators using a new interferometry homodyne method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Algebraic constructions of densest lattices

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Extensive computation of albedo contrast between martian dust devil tracks and their neighboring regions

We have developed a method to compute the albedo contrast between dust devil tracks and their surrounding regions on Mars. It is mainly based on Mathematical Morphology operators and uses all the points of the edges of the tracks to compute the values of the albedo contrast. It permits the extraction of more accurate and complete information, when compared to traditional point sampling, not only providing better statistics but also permitting the analysis of local variations along the entirety of the tracks. This measure of contrast, based on relative quantities, is much more adequate to establish comparisons at regional scales and in multi-temporal basis using imagery acquired in rather different environmental and operational conditions. Also, the substantial increase in the details extracted may permit quantifying differential depositions of dust by computing local temporal fading of the tracks with consequences on a better estimation of the thickness of the top most layer of dust and the minimum value needed to create dust devils tracks. The developed tool is tested on 110 HiRISE images depicting regions in the Aeolis, Argyre, Eridania, Noachis and Hellas quadrangles. As a complementary evaluation, we also performed a temporal analysis of the albedo in a region of Russell crater, where high seasonal dust devil activity was already observed before, comprising the years 2007-2012. The mean albedo of the Russell crater is in this case indicative of dust devil tracks presence and, therefore, can be used to quantify dust devil activity. (C) 2014 Elsevier Inc. All rights reserved.

Nano-displacement measurements of a new piezoelectric flextensional actuator by using a high dynamic range interferometry homodyne method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Interferometric measurements of nanometric displacements in a Piezoelectric Flextensional Actuator by using the new J1...J5 method

In this work, nanometric displacement amplitudes of a Piezoelectric Flextensional Actuator (PFA) designed using the topology optimization technique and operating in its linear range are measured by using a homodyne Michelson interferometer. A new improved version of the J1...J4 method for optical phase measurements, named J1...J5 method, is presented, which is of easier implementation than the original one. This is a passive phase detection scheme, unaffected by signal fading, source instabilities and changes in visibility. Experimental results using this improvement were compared with those obtained by using the J1... J4, J1...J6(pos) and J1...J 6(neg) methods, concluding that the dynamic range is increased while maintaining the sensitivity. Analysis based on the 1/f voltage noise and random fading show the new method is more stable to phase drift than all those methods. © 2012 IEEE.

Lattices from subfields of Q (xi n)

In this paper we present a method for evaluating the center density of algebraic lattices from subfields of Q(xi n), where n is a positive integer. This method allows to reproduce rotated versions of dense lattices in some dimensions. Constellations on algebraic lattices with high packing density have been proposed for use in communications in Gaussian channels and also in Rayleigh fading channels in case they have high diversity.

Analysis of linearity and frequency response of a novel piezoelectric flextensional actuator using a homodyne interferometer and the J(1)-J(4) method

Piezoelectric transducers are widely used in high-resolution positioning systems. This paper reports the experimental analysis of a novel piezoelectric flextensional actuator (PFA), which is designed by using the topology-optimization method through a low-cost homodyne Michelson interferometer. By applying the J(1) - J(4) method for signal demodulation, which provides a linear and direct measurement of dynamic optical phase shift independent of fading, the nanometric displacements of the PFA were determined. Linearity and frequency response of the PFA were evaluated up to 50 kHz. PFA calibration factor and amplification rate were determined for the PFA operating in the quasi-static regime. To confirm the observed frequencies of resonance, an impedance analyzer is also utilized to measure the magnitude and phase of the PFA admittance.

As cortinas que cerram o Vale: religião e secularização na diocese de Limoeiro do Norte/CE (1940-1980)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Detecção automática e análise temporal de slope streaks na superfície de Marte

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)