Constructive updating/downdating of oblique projectors: a generalization of the Gram-Schmidt process

A generalization of the Gram-Schmidt procedure is achieved by providing equations for updating and downdating oblique projectors. The work is motivated by the problem of adaptive signal representation outside the orthogonal basis setting. The proposed techniques are shown to be relevant to the problem of discriminating signals produced by different phenomena when the order of the signal model needs to be adjusted.Comment: As it will appear in Journal of Physics A: Mathematical and Theoretical (2007

Nonlinear non-extensive approach for identification of structured information

The problem of separating structured information representing phenomena of differing natures is considered. A structure is assumed to be independent of the others if can be represented in a complementary subspace. When the concomitant subspaces are well separated the problem is readily solvable by a linear technique. Otherwise, the linear approach fails to correctly discriminate the required information. Hence, a non extensive approach is proposed. The resulting nonlinear technique is shown to be suitable for dealing with cases that cannot be tackled by the linear one.Comment: Physica A, in pres

Measurements design and phenomena discrimination

The construction of measurements suitable for discriminating signal components produced by phenomena of different types is considered. The required measurements should be capable of cancelling out those signal components which are to be ignored when focusing on a phenomenon of interest. Under the hypothesis that the subspaces hosting the signal components produced by each phenomenon are complementary, their discrimination is accomplished by measurements giving rise to the appropriate oblique projector operator. The subspace onto which the operator should project is selected by nonlinear techniques in line with adaptive pursuit strategies

Constructive approximations to the q=1/2 maximum entropy distribution from redundant and noisy data

An approach adopted to consider the problem of constructing the q=1/2 maximum entropy distribution from redundant and noisy data was discussed. The advantage of this generalized approach, when dealing with very noisy data was illustrated by a numerical simulation. A strategy was proposed that evolved through different steps such as independent constraints were first preselected by recourse to a data independent technique. A backward approach was also proposed for reducing the parameters of such distributions. It was found that the sub-optimal strategies could be utilized in a broad range of situations

Cross-coupled doa trackers

A new robust, low complexity algorithm for multiuser tracking is proposed, modifying the two-stage parallel architecture of the estimate-maximize (EM) algorithm. The algorithm copes with spatially colored noise, large differences in source powers, multipath, and crossing trajectories. Following a discussion on stability, the simulations demonstrate an asymptotic and tracking behavior that neither the EM nor a nonparallelized tracker can emulate.Peer ReviewedPostprint (published version

Tecnología de información & productividad en América latina (Information technology & production in Latin America)

Se investiga en que grado el total de gastos de Tecnología de información y las inversiones de software/hardware, tienen impacto sobre la productividad en países de Latinoamérica, se pretende averiguar como la productividad puede ser aumentada en respuesta a estas variables. Aunque literaturas anteriores hayan investigado en países desarrollados las preguntas respecto a si la Tecnología de Información tiene impacto sobre la productividad de un pais, en países con economía emergente han sido pocas las investigaciones. Un mejor entendimiento de cómo la productividad de una nación es afectada por la tecnología de información puede ayudar a los políticos a inventar mejores estrategias de promover el crecimiento. Es importante para empresas multinacionales en economías de mercado emergente, saber cuando invertir en tecnología de información para alcanzar los niveles mas eficientes de producción. La relación postulada entre la Tecnología de Información y la productividad de un país es examinada usando el método estadístico de regresión linear, dónde las variables Dependientes son representadas por: El Producto Interno Bruto y la Inversión del Gobierno; las variables independientes las representan: La Información, Comunicación y Tecnología, la inversión de Tecnología de Información en Educación y en Software/Hardware en los países seleccionados. The purpose of this investigation its whether total ICT spending, Software/Hardware spending, and IT variables have varying degrees of impact on country productivity in Latin American. I predict that productivity could be increased in response to any of these variables. Although previous literature has investigated these questions for developed countries, questions of whether information technology has any impact on a country’s productivity has received little attention in emerging market economies. A better understanding of how productivity of a nation is affected by information technology can help policymakers devise better strategies to promote high and stable economic growth. It is also important for multinational companies operating in emerging market economies to know how much to invest in information technology in order to achieve the most efficient levels of production. Yearly information technology data are obtained from Digital Planet of the Global Research organization, the productivity indicators are obtained from the international Financial Statistics publications of the international Monetary fund. The postulated relationship between IT and country productivity is examined using a linear regression method

Phase only transmit beamforming for spectrum sharing microwave systems

This paper deals with the problem of phase-only transmit beamforming in spectrum sharing microwave systems. In contrast to sub-6 GHz schemes, general microwave systems require a large number of antennas due to its huge path loss. As a consequence, digital beamforming needs a large number of computational resources compared to analog beamforming, which only needs a single radio-frequency chain, results the less computational demanding solution. Analog schemes are usually composed by a phase shifter network whose elements transmit at a certain fixed power so that the system designer shall compute the phase values for each element given a set of directions. This approach leads to non-convex quadratic problems where the traditional semidefinite relaxation fails to deliver satisfactory outcomes. In order to solve this, we propose a nonsmooth method that behaves well in several scenarios. Numerical evaluations in different spectrum sharing scenarios, which show the performance of our method, are provided.Peer ReviewedPostprint (author's final draft

Subspace modelling for structured noise suppression

The problem of structured noise suppression is addressed by i)modelling the subspaces hosting the components of the signal conveying the information and ii)applying a nonlin- ear non-extensive technique for effecting the right separation. Although the approach is applicable to all situations satisfying the hypothesis of the proposed framework, this work is motivated by a particular scenario, namely, the cancellation of low frequency noise in broadband seismic signals