Oscar Gualdron

Instituto de Investigación de Recursos Biológicos Alexander von Humboldt

Dentro de este articulo se presenta las caracteristicas de desempeno del estandar IEEE802.11 en enlaces punto a punto de largo alcance sobre emplazamientos rurales en Colombia. Para explicar este desempeno primero se realiza una descripcion detallada del comportamiento de la capa fisica y MAC en el despliegue de redes de largo alcance, esto se real...

Este documento describe la experiencia de diseño, implementación y pruebas de campo de un enlace de largo alcance, alimentado con energía solar, utilizando radios Wi-Fi modificando parámetros de su MAC. El sistema es una alternativa para la conectividad de zonas rurales. Se utilizó el simulador RadioMobile durante el proceso de diseño. Se evaluó el...

La verificación automática de la firma es un área de investigación bien establecida y activa, con numerosas aplicaciones. En contraste, la identificación automática de la firma se le ha dado poca importancia, aunque exista una amplia gama de aplicaciones potenciales que podrían usar la firma como herramienta de identificación. Este trabajo describe...

A method in order to carry out the verification of handwritten signatures is described. The method keeps in mind global features and local features that encode the shape and the dynamics of the signatures. Signatures are recorded with a digital tablet that can read the position and pressure of the pen. Input patterns are considered time and space d...

A procedure inside the context of artificial vision that estimates the weight in bovine livestock was developed and designed. The input data to the system are images obtained by a videotape camera to color. These images are digitized and preprocessing using filters of elimination of noise; later are implemented and evaluated different segmentation...

A method in order to carry out the verification of handwritten signatures is described. The method keeps in mind global features and local features that encode the shape and the dynamics of the signatures. Signatures are recorded with a digital tablet that can read the position and pressure of the pen. Input patterns are considered time and space d...

A procedure inside the context of artificial vision that estimates the weight in bovine livestock was developed and designed. The input data to the system are images obtained by a videotape camera to color. These images are digitized and preprocessing using filters of elimination of noise; later are implemented and evaluated different segmentation...

The accuracy and flexibility of the technique proposed by Davis et al. [Appl. Opt. 35, 2488 (1996)] for the encoding of the amplitude and the phase of a filter onto a single liquid-crystal spatial light modulator operating in a phase-only regime has been exploited to implement several filter designs in a convergent optical correlator. We have selec...

Recently, the use of three-dimensional correlation for multichannel pattern recognition has been introduced. In this work we propose the use of circular harmonic components with this new technique to obtain invariance under target rotations. The differences between this method and the previous use of circular harmonic filters for multichannel image...

The general objective of this work is to establish a procedure standardized for the measure and monitoring the change in the optic transmittance of circuits and communication devices with optic fiber. This procedure allows to determine, with a reduced degree of uncertainty, the form like changes the transmittance in elements of optic fiber communic...

RESUMEN Se presentan los resultados de la implementación de un arreglo óptico que permite sintetizar filtros de fase para reconocimiento de patrones; el arreglo está basado en un cristal fotoeléctrico BSO. La capacidad de discriminación de patrones fue el criterio de desempeño valorado. Se presentan resultados experimentales. ABSTRACT The results o...

Optical correlation is a powerful tool for visual automatic inspection, because it offers high speed, non-destructive test and on-line inspection. W. Liu et al, proposed a hybrid optical/digital linear joint transform correlator (JTC) for the detection Of defects in optical fibers. Based in this work we have introduced some modifications allowing a...

The TIA and the EIA have developed a set of standardized test procedures for optical loss of fiber, cables, connectors and splices under many varying environmental conditions called FOTPs. We have implemented the experimental setup corresponding to four of these FOTPs. The firs test allows to measure the change in optical transmittance for devices...

Presents a prototype of a virtual shared environment in which several users can interact inside a three dimensional scene. Actions of a user are visible to others thanks to a protocol of transmission parameters of the scene. The communications are managed under a protocol of distributed objects, the visualization as well as the user interface use m...

The 3D information of an object increases the discrimination ability of a pattern recognition system. A new digital procedure based on the correlation between range images is described. The results of synthesis of a 3D phase-only filter are presented. A range image represents a topography of a free-form surface in a 3D scene. All the possible 3D co...

This communication introduces the Optics and Signal Processing Group from Universidad Industrial de Santander at Bucaramanga, Colombia. First, a brief description of how the group was formed, its strategic importance and also some of its more important achievements are presented. Then, the main scientific domains where the group carries out its res...

This paper presents a digital implementation of an out-of- plane target location system by means of a joint transform correlator (JTC). A sequence of images of the 3D scene is coded into a single performing an integration of each frame in the vertical sense. The coded sequence is used as the input plane of the JTC after binarization, Fourier transf...

Two objective speckle patterns are obtained - one before and one after the object has been moved - and are placed in the input plane of an optoelectronic nonlinear joint transform correlator. Nonlinear transformation of the joint power spectrum permits a sharper correlation peak and a high signal-to-noise ratio. The autocorrelation peak coordinates...

We present some recent results in invariant pattern recognition, including methods that are invariant under two or more distortions of position, orientation and scale. There are now a few methods that yield good results under changes of both rotation and scale. Some new methods are introduced. These include locally adaptive nonlinear matched filter...

Some important concepts of neural networks are similarity, generalization, invariance and training. Some neural networks are supposed to be able to classify objects according to hidden similarities. All of those concepts are put into question by the consideration first put forward by Watenabe that from a purely logical point of view, similarity is...

We introduce an optimum matched filter for rotation-invariant pattern recognition in scenes with disjoint noise. The optimum filter maximizes the ratio between the correlation-peak intensity and the correlation-output energy; in order to ensure rotation invariance, we assume the filter to take the form of a circular-harmonic function. The performan...

We study the discrimination ability of a recently introduced optimum rotation invariant filter for disjoint noise. The discrimination ability of a sub-optimum filter related to the preceding one but where the non-target images are involved is also studied. The performance of both filters has been tested by computer simulations with a variety of nat...

We study the discrimination ability of a recently introduced optimum rotation invariant filter for disjoint noise. The discrimination ability of a sub-optimum filter related to the preceding one but where the non-target images are involved is also studied. The performance of both filters has been tested by computer simulations with a variety of nat...

A comparison of the performance of Locally Nonlinear Filters (LNMFs) and Optimal Tradeoff Filters (OTFs) for the recognition of single images has been carried out. The comparison is done using several performance criteria such as Signal to Noise Ratio, Peak to Correlation Energy Ratio and Optical Efficiency. A strong similarity between the whitenin...

A new rotation invariant correlation filter with superior performance, based on the circular harmonic expansion is introduced. The filter is obtained from one circular harmonic component of the phase of the Fourier transform of the target. Among the properties of this filter are full rotation invariance, good peak sharpness and discrimination abili...

A new matched filter for pattern recognition is introduced. Previous researchers have introduced matched filters that are nonlinear functions of the spectrum, for which the classical matched filter is divided by some power m of the spectrum of interest. We further generalize this filter by making the power m a function of the spatial frequency; thi...

Phase-only filters generally have better discrimination ability than normal filters. Rotation-invariant Circular harmonic (CH) filters that use only one component of the target generally don’t have sufficient discrimination to classify complex objects, unless they are realized as phase-only filters.

Resumen Con el objeto de determinar la capacidad de un cable de fibra óptica para resistir simultáneamente flexión y torsión; se hicieron medidas de transmitancia óptica, siguiendo la normativa TIA/EIA/FOTP-91, donde se plantea un procedimiento secuencial de toma de datos, antes y después de someter el cable sobre un montaje mecánico diseñado para...

Résumé en anglais et en français. Thèse (Ph. D.)--Université Laval, 1995. Bibliogr.: f. 88-91.