Semi-Huber potential function for image segmentation

In this work, a novel model of Markov random field is presented, named Semi-Huber potential function, applied to image segmentation in presence of noise. The main difference with respect to other models that have been taken as a reference, is that the number of parameters in the proposed model is significatively smaller. The idea is to choose adequate parameter values heuristically for a good segmentation of the image. In that sense, experiment results show that the proposed model allows a faster and easier parameter adjustment with razonable computation times

Foucault test: shadowgram modeling from the physical theory for quantitative evaluations

The physical theory of the Foucault test has been investigated to represent the complex amplitude and irradiance of the shadowgram in terms of the wavefront error; however, most of the studies have limited the treatment for the particular case of nearly diffraction-limited optical devices (i.e., aberrations smaller than the wavelength). In this paper we discard this restriction, and in order to show a more precise interpretation from the physical theory we derive expressions for the complex amplitude and the irradiance over an optical device with larger aberrations. To the best of our knowledge, it is the first time an expression is obtained in closed form. As will be seen, the result of this derivation is obtained using some properties of the Hilbert transform that permit representing the irradiance in a simple form in terms of the partial derivatives of the wavefront error. Additionally, we briefly describe from this point of view a methodology for the quantitative analysis of the test

Bayesian nonparametric mrf and entropy estimation for robust image filtering

We introduce an approach for image filtering in a Bayesian framework. In this case, the probability density function (pdf) of the likelihood function is approximated using the concept of non-parametric or kernel estimation. The method is complemented using Márkov random fields, for instance the Semi-Huber Markov random field (SHMRF), which is used as prior information into the Bayesian rule, and the principal objective of it is to eliminate those effects caused by the excessive smoothness on the reconstruction process of signals which are rich in discontinuities. Accordingly to the hypothesis made for the present work, it is assumed a limited knowl- edge of the noise pdf, so the idea is to use a non-parametric estimator to estimate such a pdf and then apply the entropy to construct the cost function for the likelihood term. The previous idea leads to the construction of new Maximum a posteriori (MAP) robust estimators, and considering that real systems are always exposed to continuous perturbations of unknown nature. Some promising results have been obtained from two new MAP entropy estimators (MAPEE) for the case of robust image filtering, where such results have been compared with respect to the classical median image filter

La tecnología MEMS como auxiliar en el posicionamiento GPS a bajo costo

Hoy en día la navegación por GPS es una herramienta cotidiana muy útil para la humanidad, gracias a esta tecnología las personas pueden desplazarse por lugares en los cuales no han estado antes con cierto grado de precisión. La ubicación de un punto sobre la superficie terrestre se hace por medio de un satélite transmisor y un receptor que se ubica por medio del principio de Triangulación. Los Sistemas-Micro-Electro-Mecánicos o MEMS, son una tecnología que, en su forma más general puede ser definida como elementos electro mecánicos miniaturizados que se realizan con técnicas de micro-fabricación

LA TECNOLOGÍA MEMS COMO AUXILIAR EN EL POSICIONAMIENTO GPS A BAJO COSTO

Hoy en día la navegación por GPS es una herramienta cotidiana muy útil para la humanidad, gracias a esta tecnología las personas pueden desplazarse por lugares en los cuales no han estado antes con cierto grado de precisión. La ubicación de un punto sobre la superficie terrestre se hace por medio de un satélite transmisor y un receptor que se ubica por medio del principio de Triangulación. Los Sistemas-Micro-Electro-Mecánicos o MEMS, son una tecnología que, en su forma más general puede ser definida como elementos electro-mecánicos miniaturizados que se realizan con técnicas de micro -fabricación.Las unidades de medición inercial o IMU, son dispositivos que miden aceleración y orientación, que implementados con algún procesador o sistema de cómputos permiten crear un sistema de navegación inercial o INS. El enfoque de esta investigación es crear un sistema de bajo costo que permita fusionar los datos provenientes de los sistemas IMU/GPS mediante un filtro Kalman, esto con la finalidad de aprovechar las características propias de cada sistema y mejorar la precisión del posicionamiento por GPS. Con el uso de este sistema mediante sensores comerciales de bajo costo se hace posible mejorar la precisión del posicionamiento GPS con hasta un 3.03%

MAP entropy estimation: Applications in robust image filtering

We introduce a new approach for image filtering in a Bayesian framework. In this case the probability density function (pdf) of the likelihood function is approximated using the concept of non-parametric or kernel estimation. The method is based on the generalized Gaussian Markov random fields (GGMRF), a class of Markov random fields which are used as prior information into the Bayesian rule, which principal objective is to eliminate those effects caused by the excessive smoothness on the reconstruction process of images which are rich in contours or edges. Accordingly to the hypothesis made for the present work, it is assumed a limited knowledge of the noise pdf, so the idea is to use a non-parametric estimator to estimate such a pdf and then apply the entropy to construct the cost function for the likelihood term. The previous idea leads to the construction of Maximum a posteriori (MAP) robust estimators, since the real systems are always exposed to continuous perturbations of unknown nature. Some promising results of three new MAP entropy estimators (MAPEE) for image filtering are presented, together with some concluding remarks

Acoustic individual identification in birds based on the band-limited phase-only correlation function

A new technique based on the Band-Limited Phase-Only Correlation (BLPOC) function to deal with acoustic individual identification is proposed in this paper. This is a biometric technique suitable for limited data individual bird identification. The main advantage of this new technique, in contrast to traditional algorithms where the use of large-scale datasets is assumed, is its ability to identify individuals by the use of only two samples from the bird species. The proposed technique has two variants (depending on the method used to analyze and extract the bird vocalization from records): automatic individual verification algorithm and semi-automatic individual verification algorithm. The evaluation of the automatic algorithm shows an average precision that is over 80% for the identification comparatives. It is shown that the efficiencies of the algorithms depend on the complexity of the vocalizations

Phase Unwrapping using Chebyshev Polynomials

Phase unwrapping is an intermediate step for interferogram analysis. The phase associated with an interferogram can be estimated using a curve mesh of functions. Each of these functions can be approximated by a linear combination of basis functions. Chebyshev polynomials in addition to being a family of orthogonal polynomials can be defined recursively. In this work a method for phase unwrapping using Chebyshev polynomials is proposed. Results show good performance when applied to synthetic images without noise and also to synthetic images with noise

Chlorophyll fluorescence emission of tomato plants as a response to pulsed light based LEDs

The effects of pulsed light based-LEDs at eleven frequencies (0.1, 1, 10, 50, 100, 500 Hz, 1, 5, 10, 50 and 100 kHz) programmed at 50 % duty cycle were analyzed, obtaining important parameters of the fluorescence emission of chlorophyll such as: maximum fluorescence (Fm0), minimum fluorescence, the fluorescence emission in steady state, maximum efficiency of PSII (Fv0/Fm0), the fraction of PSII centers that are open, photochemical quenching, nonphotochemical quenching (NPQ), quantum efficiency of photosystem II (UPSII), electron transport rate (ETR) and quantum yield of CO2 assimilation (/CO2). For the study and validation of the results obtained in the experiments, the analysis of variance (ANOVA) was applied 0for each parameter with confidence intervals of 95 %. The results show that the frequencies of pulsed light had positive and negative effects on the fluorescence parameters with respect to the control treatment (continuous light). The frequencies that generated the best performance of Fv0/Fm0, NPQ, UPSII, ETR, /CO2 in tomato plants were 0.1, 1, 100 Hz, and 1 kHz. The increase obtained in these parameters can represent an optimal growth and productivity conditions for optimal energy consumption