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Search Results: 1 - 10 of 297624 matches for " J. Selva "
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Efficient Sampling of Band-limited Signals from Sine Wave Crossings
J. Selva
Mathematics , 2010,
Abstract: This correspondence presents an efficient method for reconstructing a band-limited signal in the discrete domain from its crossings with a sine wave. The method makes it possible to design A/D converters that only deliver the crossing timings, which are then used to interpolate the input signal at arbitrary instants. Potentially, it may allow for reductions in power consumption and complexity in these converters. The reconstruction in the discrete domain is based on a recently-proposed modification of the Lagrange interpolator, which is readily implementable with linear complexity and efficiently, given that it re-uses known schemes for variable fractional-delay (VFD) filters. As a spin-off, the method allows one to perform spectral analysis from sine wave crossings with the complexity of the FFT. Finally, the results in the correspondence are validated in several numerical examples.
FFT Interpolation from Nonuniform Samples Lying in a Regular Grid
J. Selva
Mathematics , 2014,
Abstract: This paper presents a method to interpolate a periodic band-limited signal from its samples lying at nonuniform positions in a regular grid, which is based on the FFT and has the same complexity order as this last algorithm. This kind of interpolation is usually termed "the missing samples problem" in the literature, and there exists a wide variety of iterative and direct methods for its solution. The one presented in this paper is a direct method that exploits the properties of the so-called erasure polynomial, and it provides a significant improvement on the most efficient method in the literature, which seems to be the burst error recovery (BER) technique of Marvasti's et al. The numerical stability and complexity of the method are evaluated numerically and compared with the pseudo-inverse and BER solutions.
Signal Estimation from Nonuniform Samples with RMS Error Bound -- Application to OFDM Channel Estimation
J. Selva
Mathematics , 2014,
Abstract: We present a channel spectral estimator for OFDM signals containing pilot carriers, assuming a known delay spread or a bound on this parameter. The estimator is based on modeling the channel's spectrum as a band-limited function, instead of as the discrete Fourier transform of a tapped delay line (TDL). Its main advantage is its immunity to the truncation mismatch in usual TDL models (Gibbs phenomenon). In order to assess the estimator, we compare it with the well-known TDL maximum likelihood (ML) estimator in terms of root-mean-square (RMS) error. The main result is that the proposed estimator improves on the ML estimator significantly, whenever the average spectral sampling rate is above the channel's delay spread. The improvement increases with the spectral oversampling ratio.
Regularized sampling of multiband signals
J. Selva
Mathematics , 2010, DOI: 10.1109/TSP.2010.2057248
Abstract: This paper presents a regularized sampling method for multiband signals, that makes it possible to approach the Landau limit, while keeping the sensitivity to noise at a low level. The method is based on band-limited windowing, followed by trigonometric approximation in consecutive time intervals. The key point is that the trigonometric approximation "inherits" the multiband property, that is, its coefficients are formed by bursts of non-zero elements corresponding to the multiband components. It is shown that this method can be well combined with the recently proposed synchronous multi-rate sampling (SMRS) scheme, given that the resulting linear system is sparse and formed by ones and zeroes. The proposed method allows one to trade sampling efficiency for noise sensitivity, and is specially well suited for bounded signals with unbounded energy like those in communications, navigation, audio systems, etc. Besides, it is also applicable to finite energy signals and periodic band-limited signals (trigonometric polynomials). The paper includes a subspace method for blindly estimating the support of the multiband signal as well as its components, and the results are validated through several numerical examples.
Efficient Maximum Likelihood Estimation of a 2-D Complex Sinusoidal Based on Barycentric Interpolation
J. Selva
Mathematics , 2011,
Abstract: This paper presents an efficient method to compute the maximum likelihood (ML) estimation of the parameters of a complex 2-D sinusoidal, with the complexity order of the FFT. The method is based on an accurate barycentric formula for interpolating band-limited signals, and on the fact that the ML cost function can be viewed as a signal of this type, if the time and frequency variables are switched. The method consists in first computing the DFT of the data samples, and then locating the maximum of the cost function by means of Newton's algorithm. The fact is that the complexity of the latter step is small and independent of the data size, since it makes use of the barycentric formula for obtaining the values of the cost function and its derivatives. Thus, the total complexity order is that of the FFT. The method is validated in a numerical example.
Development of a Dynamic Virtual Reality Model of the Inner Ear Sensory System as a Learning and Demonstrating Tool
P. Selva,J. Morlier,Y. Gourinat
Modelling and Simulation in Engineering , 2009, DOI: 10.1155/2009/245606
Abstract: In order to keep track of the position and motion of our body in space, nature has given us a fascinating and very ingenious organ, the inner ear. Each inner ear includes five biological sensors—three angular and two linear accelerometers—which provide the body with the ability to sense angular and linear motion of the head with respect to inertial space. The aim of this paper is to present a dynamic virtual reality model of these sensors. This model, implemented in MATLAB/Simulink, simulates the rotary chair testing which is one of the tests carried out during a diagnosis of the vestibular system. High-quality 3D animations linked to the Simulink model are created using the export of CAD models into Virtual Reality Modeling Language (VRML) files. This virtual environment shows not only the test but also the state of each sensor (excited or inhibited) in real time. Virtual reality is used as a tool of integrated learning of the dynamic behavior of the inner ear using ergonomic paradigm of user interactivity (zoom, rotation, mouse interaction, etc.). It can be used as a learning and demonstrating tool either in the medicine field—to understand the behavior of the sensors during any kind of motion—or in the aeronautical field to relate the inner ear functioning to some sensory illusions.
Bargmann-Michel-Telegdi equation and one-particle relativistic approach
A. Della Selva,J. Magnin,L. Masperi
Physics , 1995, DOI: 10.1007/BF02749016
Abstract: A reexamination of the semiclassical approach of the relativistic electron indicates a possible variation of its helicity for electric and magnetic static fields applied along its global motion due to zitterbewegung effects, proportional to the anomalous part of the magnetic moment.
A weak Local Linearization scheme for stochastic differential equations with multiplicative noise
J. C. Jimenez,C. Mora,M. Selva
Mathematics , 2015,
Abstract: In this paper, a weak Local Linearization scheme for Stochastic Differential Equations (SDEs) with multiplicative noise is introduced. First, for a time discretization, the solution of the SDE is locally approximated by the solution of the piecewise linear SDE that results from the Local Linearization strategy. The weak numerical scheme is then defined as a sequence of random vectors whose first moments coincide with those of the piecewise linear SDE on the time discretization. The rate of convergence is derived and numerical simulations are presented for illustrating the performance of the scheme.
O ENSINO DE HISTóRIA EM ESCOLAS NO MEIO RURAL BRASILEIRO
Astrogildo Fernandes Silva Júnior,Selva Guimar?es Fonseca
Eccos Revista Científica , 2010,
Abstract: In this text are shown the results from the Master thesis "Knowledge and practices of the History teaching in rural schools (a study performed in the City of Araguari, MG, Brazil), developed during Master in Education in the Pos-graduate program in Education from Universidade Federal de Uberlandia (PPGE/UFU), articulated to the research project "Teacher formation, knowledge and practice of History teaching" supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico -CNPq. Here the objectives were to characterize history teaching in rural schools education in the last decades and to analyze the knowledge and curricular practices from the History teaching in rural schools. We concluded that the History teaching and education in the Brazilian rural area underwent transformation in the last decades, and the knowledge and practices are built during the education experience in schools that are multicultural spaces, where distinct subjects play.
QUESTIONING AN “ICON OF CHANGE”: THE NURUOSMANIYE COMPLEX AND THE WRITING OF OTTOMAN ARCHITECTURAL HISTORY
Selva SUMAN
Middle East Technical University Journal of the Faculty of Architecture , 2011,
Abstract:
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