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Munar-Vivas O.,National University of Colombia | Morales-Osorio J.G.,National University of Colombia | Castaneda-Sanchez D.A.,Jaime Isaza Cadavid Colombian Polytechnic
Crop Protection

Ralstonia solanacearum (formerly Pseudomonas solanacearum) causes large losses in more than 200 different cultivated plant species. Banana and plantain " Moko" disease is caused by R. solanacearum race 2. Moko disease may cause 100% loss if prompt control measures are not applied. Although a number of investigations have been carried out, many ecological and epidemiological aspects of R. solanacearum race 2 are still unknown, particularly in the tropics. Bacteria dispersion occurs by infested tools, soil, water, insects, domestic animals and agricultural labourers. Alternative hosts have been described which may contribute to inoculum availability in crop fields. In banana crops, cable-ways are routinely used to transport fruit and materials inside plantations. In most humid tropical areas, drainage channels are made to evacuate excess soil water. It is thought that agricultural activities associated with drainage channels and cable-ways may play a role in bacteria dispersion but individual contributions have not yet been quantified. In this work we have used field-integrated information in geographical information systems (GIS)-based maps to evaluate Moko presence in the Urabá region of Colombia, during three different time periods. A previously described risk index (RI) and losses throughout the three periods were quantified. A regression model was developed to quantify the relationship between infested area and distance from every Moko focus to the nearest cable-way and drainage channels. Farms were grouped into four different profiles according to the RI. Parameters calculated using the regression model showed that 76% of Moko foci detected during the three time periods were associated with cable-ways used for transport of fruit and consumables. This finding has important implications for disease management since bacteria spread in these ways may be prevented by simple measures taken inside plantations. © 2010 Elsevier Ltd. Source

Mateus S.,Jaime Isaza Cadavid Colombian Polytechnic | Branch J.,National University of Colombia
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

This paper describes a Virtual Environment with Intelligent Agents, using an agent-oriented methodology called Prometheus. This technique was incorporated in the perception and reasoning of a character in the Intelligent Virtual Environment (IVE), in order to react intelligently to given warning signs. The main objective of the character in the developed IVE is finding the optimum path without having to do extra shifts. The used technique achieves an optimal solution using only probability calculations, without requiring additional data to be supplied. This solution is obtained given the repetitions and the number of ants in the character agent. The virtual environment was created with the UDK tool to identify warning signs in a work environment. UDK is used because of its importance in the development of world-renowned games. © Springer International Publishing Switzerland 2016. Source

Mateus S.,Jaime Isaza Cadavid Colombian Polytechnic | Branch J.,National University of Colombia
Communications in Computer and Information Science

In this article, two artificial intelligence techniques such as Artificial Neural Networks and Genetic Algorithms were incorporated into a 3D working environment and turned into a game engine, which simulates a working environment in order to obtain possible warning signs to different hazards. These techniques were incorporated in the perception and reasoning of a character in the virtual environment, in order to react intelligently to given warning signs. © Springer International Publishing Switzerland 2015. Source

Gomez J.A.,Pontifical Bolivarian University | Gomez J.A.,Jaime Isaza Cadavid Colombian Polytechnic | Lorduy G. H.,Pontifical Bolivarian University | Salazar A.,Pontifical Bolivarian University
Optics Communications

In this work, the dependence on the speckle size in the performance of a micro displacement sensor based on fiber specklegrams stored in a photorefractive BSO (Bi 12SiO 20) crystal is experimentally demonstrated. In our experimental setup, a plastic optical fiber (POF) was used to generate a subjective speckle pattern which was recorded in the crystal by using a four-wave mixing arrangement in transmission geometry. The speckle size was controlled by modifying the diameter of a pupil aperture adjacent to a lens producing the image of the speckle. The signal speckle beam was mixed into the crystal with two counter propagating pump beams to generate a fourth beam which is proportional to the conjugate of the original speckle beam. Real time fringe patterns were obtained at the output of the system by producing micro displacements of the fiber output end. Increases of the phase conjugation reflectivity and the visibility of the fringe patterns were appreciated when the speckle length was increased by decreasing the pupil aperture diameter. This behavior allowed recovering the autocorrelation functions of fringe patterns associated to micro displacements that initially led to decorrelation, and therefore, to improve the dynamic range of the metrological system. Until the best of our knowledge this is the first report about the influence of the speckle size on fiber specklegrams sensors recorded on photorefractive materials by four-wave mixing. © 2010 Elsevier B.V. All rights reserved. Source

Gomez J.A.,Jaime Isaza Cadavid Colombian Polytechnic | Gomez H.L.,Pontifical Bolivarian University | Salazar A.,Pontifical Bolivarian University
Optics Communications

We present a novel procedure based on an improved physical model and a versatile numerical fitting technique, to simultaneously determinate the Debye screening length and electro-optic coefficient using a thick sample of an optically active photorefractive crystal Bi12SiO20 (BSO). For the computation, experimental data of gain vs. grating spacing were obtained by a two-beam coupling arrangement. Unlike former calculation models, in our work, the general expression for the diffraction efficiency in the presence of self-diffraction is considered, and the influence of the optical activity in the coupling parameters is had into account for the calculation of the gain values. The fitting of the experimental data to the predicted theoretical behavior by our model is achieved by finding the closest theoretical curve to a set of data sampled from a spline-smoothed curve of the experimental data. Both, the Debye screening length ls and the electro-optic coefficient r41 are used as fitting parameters by searching in a rather wide range for each one of the parameters, so that, the estimation of their values is obtained in a more reliable and direct way from the same experiment. The calculations are performed in diffusion regimen and the procedure leads to ls = 0.22 μm and r41 = 4.5 × 10-12m/V. Because the optical activity can alter the maximum gain and self-diffraction effects influence the energy exchange, the procedure reveals to be physically appropriated for the simultaneous determination of these physical parameters when thick photorefractive crystals with high optical activity are considered. © 2010 Elsevier B.V. All rights reserved. Source

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