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Mössbauer Spectroscopy (MS) was applied to study the occurrence and behavior of the iron-sulfur-containing minerals in coal and coal fractions obtained by different separation methods: hydrocyclonic, flotation and chemical removal process. Samples of one high sulfur coal from Guachinte mine (Valle, Colombia) and three low sulfur coals from the El Salitre zone (Paipa-Boyacá, Colombia) were analyzed. MS evidenced only the presence of pyrite in Esmeralda and Las Casitas coals, while it identified pyrite and siderite on Cerezo coal. MS and SEM- EDX confirm the inorganic sulfur removal on Guachinte coal submitted to hydrocyclonic removal process. MS of the precipitated coal fraction from Las Casitas mine obtained by flotation in water showed the presence of ferrous sulfate because of coal-weathering process. Treatment with hot diluted HNO3 equal to 27 acid on raw coal sample from Las Casitas mine showed that almost all of the pyrite in raw coal was removed. [ABSTRACT FROM AUTHOR]

This paper proposes vision-based techniques for localizing an unmanned aerial vehicle (UAV) by means of an on-board camera. Only natural landmarks provided by a feature tracking algorithm will be considered, without the help of visual beacons or landmarks with known positions. First, it is described a monocular visual odometer which could be used as a backup system when the accuracy of GPS is reduced to critical levels. Homography-based techniques are used to compute the UAV relative translation and rotation by means of the images gathered by an onboard camera. The analysis of the problem takes into account the stochastic nature of the estimation and practical implementation issues. The visual odometer is then integrated into a simultaneous localization and mapping (SLAM) scheme in order to reduce the impact of cumulative errors in odometry-based position estimation approaches. Novel prediction and landmark initialization for SLAM in UAVs are presented. The paper is supported by an extensive experimental work where the proposed algorithms have been tested and validated using real UAVs. [ABSTRACT FROM AUTHOR]

The localization problem is usually solved in aerial robotics by means of GPS, Inertial Measurement Units (IMUs) and compass sensors, which are fused to provide UAV position estimation in a global frame. However, GPS estimates are often subject to inaccuracies and errors related to GPS failure or degradation. Also, GPS cannot be directly used for relative positioning of a UAV with respect to other objects, as for example for landing on mobile platforms or for wall following in building inspection. [ABSTRACT FROM AUTHOR]

Experimental data on the electrophoretic mobility of cholesterol particles in aqueous NaCl and NaCl + bile salt solutions are employed for the estimation of the zeta potential (ζ) of the particles in these media. The results obtained through the use of the well known Smoluchowski formula are compared with those deduced from a more elaborate treatment [11] so as to study the relative influence of the relaxation and electrophoretic effects for these systems. The use of the parameter ζ2x−1 (x−1 being the double layer thickness) allows us to correlate the electrokinetic properties of cholesterol with its tendency to coagulate in suspension. The influence of pH and NaCl concentration on this parameter is first discussed. Furthermore, the zeta potential of cholesterol in the presence of a series of bile salts is used to study the stability conditions of such suspensions, the results being discussed in terms of the characteristics of the different bile salts in solution. [ABSTRACT FROM AUTHOR]