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Simple, cost-effective, and reproducible devices have been prepared for the detection of H 2 at room temperature. Pd, Cu and bimetallic Cu-Pd nanoparticles (prepared by the reduction-by-solvent method) have been loaded on a MWCNT deposit avoiding the use of surfactants or complicated techniques. The devices based on pure Pd nanoparticles have shown a high H 2 sensitivity in the studied H 2 concentration range with low response and recovery times. However, the addition of Cu in the metallic nanoparticles does not result in a considerable improvement. Furthermore, the Pd and Cu-Pd/MWCNTs-based sensors have kept part of their H 2 sensitivity when they have been tested in an O 2 -depleted atmospheres, which is an altogether new finding compared to Pd-based systems. Through these experiments it has been possible to conclude how the main H 2 detection mechanism is the electron transfer from the nanoparticles (when the PdH x is formed) to the carbon nanotubes. [ABSTRACT FROM AUTHOR]

In the propylene epoxidation reaction with Fe-SiO 2 catalysts the presence of iron oxide particles has a detrimental effect due to the total combustion of propylene on these iron species. Thus, the complete elimination of the iron oxide particles is presented as a preliminary strategy in order to increase the selectivity towards propylene oxide in iron-based catalysts. In this sense, a simple post-treatment of the catalysts with alkali or alkaline-earth elements (such as K or Ca, respectively) has proven effective in the total elimination of these iron oxide particles. Furthermore, the addition of K and Ca has modified the physico-chemical properties of the catalysts, decreasing their superficial acidity and (for higher K or Ca loadings) masking/blocking the active sites responsible for the catalytic reaction. With all this, it is shown that K has a higher efficiency removing the iron oxide particles compared with Ca (for the same molar ratios) and that a higher amount of K (compared to Fe) is required for the complete elimination of the iron oxide particles. A considerable propylene oxide selectivity enhancement (up to 65%) has been obtained for the K-promoted Fe 0.005 SiO 2 and Fe 0.01 SiO 2 catalysts using O 2 as sole oxidant. [ABSTRACT FROM AUTHOR]

Abstract: Pd and bimetallic Ni50Pd50 nanoparticles protected by polyvinylpyrrolidone (PVP) have been synthesized by the reduction-by-solvent method and deposited on single wall carbon nanotubes (SWCNTs) to be tested as H2 sensors. The SWCNTs were deposited by drop casting from different suspensions. The Pd nanoparticles-based sensors show a very reproducible performance with good sensitivity and very low response times (few seconds) for different H2 concentrations, ranging from 0.2% to 5% vol. H2 in air at atmospheric pressure. The influence of the metal nanoparticle composition, the quality of SWCNTs suspension and the metal loading have been studied, observing that all these parameters play an important role in the H2 sensor performance. Evidence for water formation during the H2 detection on Pd nanoparticles has been found, and its repercussion on the behaviour of the assembled sensors is discussed. The sensor preparation procedure detailed in this work has proven to be simple and reproducible to prepare cost-effective and highly efficient H2 sensors that perform very well under real application conditions. [Copyright &y& Elsevier]

The main purpose of this paper is to estimate 2D and 3D transformation parameters. All the group transformations are represented in terms of their Lie algebra elements. The Lie algebra approach assures to follow the shortest path or geodesic in the involved Lie group. For the estimation of the Lie algebra parameters, we take advantage of the theory of system identification. Two experiments are presented to show the potential of the method. First, we carry out the estimation of the affine or projective parameters related to the transformation involved in monocular region tracking. Second, we develop a monocular method to estimate 3D motion of an object in the visual space. In the latter, the six parameters of the rigid motion are estimated based on measurements of the six parameters of the affine transformation in the image. [Copyright &y& Elsevier]

In this paper, an embedded design for implementing a real-time photovoltaic (PV) system emulator with user-defined environmental conditions is proposed. The design implemented on a Sitara Cortex 9 ARM processor allows the evaluation of PV cells in a low-cost, portable and affordable system. This embedded PV emulation system uses an LCD screen to establish a human-system interface (HSI), and it contains an extensible database of commercial PV cells with their manufacturer’s datasheet parameters. Based on the accurate two-diode model, the proposed design allows the generation of high precision I – V , P – V characteristic curves with the embedded ARM, which represents an affordable and simple solution. Experimental results demonstrate the accuracy of the real-time embedded system for different solar cells and environmental conditions. [ABSTRACT FROM AUTHOR]