Characterization and carbonylic hydrogenation of methyl oleate over Ru-Sn/Al2O3: Effects of metal precursor and chlorine removal

Hydrogenation of methyl oleate to oleyl alcohol was evaluated over Ru-Sn/Al₂O₃ catalysts, prepared from different precursors, at 270 °C and 5.0 MPa. Two kinds of metal precursors were employed: chlorine-free precursors and inorganic chlorides. In addition, several methods for chlorine removal of metal-chloride-based catalysts were studied. Catalysts were characterized by EDX, XRF, DRX, BET and TPR analyses. Selectivity toward unsaturated alcohol was higher with the bimetallic catalyst based on chlorine-free precursors than with the catalyst based on metal chlorides, owing that chlorine avoids, at certain extent, an effective interaction between ruthenium and tin species. However, the most selective catalyst was the bimetallic one based on chloride precursors and reduced with NaBH₄, due to elimination of residual chlorine and higher dispersion of Ru-Sn species.     

Nonlinear control of the doubly-fed induction generator in wind power systems

This paper describes the models of a wind power system, such as the turbine, generator, power electronics converters and controllers, with the aim to control the generation of wind power in order to maximize the generated power with the lowest possible impact in the grid voltage and frequency during normal operation and under the occurrence of faults. The presented work considers a wind power system equipped with the doubly-fed induction generator and a vector-controlled converter connected between the rotor and the grid. The paper presents comparative results between proportional-integral controllers and neural networks based controllers, showing that better dynamic characteristics can be obtained using neural networks based controllers.     

Value of security: modeling time-dependent phenomena and weather conditions

Deterministic security criteria provide a degree of security that may be insufficient under some operating conditions and excessive for others. To determine an appropriate level of security, one should perform a probabilistic cost/benefit analysis that balances the cost of the security margin against its benefits, i.e., the expected societal cost of the avoided outages. This paper shows how a previously published method based on Monte Carlo simulation can be enhanced to take into account time-dependent phenomena (TDP) such as cascade tripping of elements due to overloads, malfunction of the protection system, and potential power system instabilities. In addition, the importance of using failure rates that reflect the weather conditions is discussed. Studies based on the South-Western part of the transmission network of England and Wales demonstrate the validity of the models that have been developed.     

Overexpression of human superoxide dismutase inhibits oxidation of low-density lipoprotein by endothelial cells

Oxidation of LDL in the subendothelial space has been proposed to play a key role in atherosclerosis. Endothelial cells produce superoxide anions (O2.-) and oxidize LDL in vitro; however, the role of O2.- in endothelial cell-induced LDL oxidation is unclear. Incubation of human LDL (200 microg/mL) with bovine aortic endothelial cells (BAECs) for 18 hours resulted in a 4-fold increase in LDL oxidation compared with cell-free incubation (22.5+/-1.1 versus 6.3+/-0.2 [mean+/-SEM] nmol malondialdehyde/mg LDL protein, respectively; P<0.05). Under similar conditions, incubation of LDL with porcine aortic endothelial cells resulted in a 5-fold increase in LDL oxidation. Inclusion of exogenous copper/zinc superoxide dismutase (Cu/ZnSOD, 100 microg/mL) in the medium reduced BAEC-induced LDL oxidation by 79%. To determine whether the intracellular SOD content can have a similar protective effect, BAECs were infected with adenoviral vectors containing cDNA for human Cu/ZnSOD (AdCu/ZnSOD) or manganese SOD (AdMnSOD). Adenoviral infection increased the content and activity of either Cu/ZnSOD or MnSOD in the cells and reduced cellular O2.- release by two thirds. When cells infected with AdCu/ZnSOD or AdMnSOD were incubated with LDL, formation of malondialdehyde was decreased by 77% and 32%, respectively. Two other indices of LDL oxidation, formation of conjugated dienes and increased LDL electrophoretic mobility, were similarly reduced by SOD transduction. These data suggest that production of O2.- contributes to endothelial cell-induced oxidation of LDL in vitro. Furthermore, adenovirus-mediated transfer of cDNA for human SOD, particularly Cu/ZnSOD, effectively reduces oxidation of LDL by endothelial cells.     

Characterization of Cr(VI) binding and reduction to Cr(III) by the agricultural byproducts of Avena monida (oat) biomass

Chromium contamination of the environment has become an important issue due to the potential health threat it poses. Conventional technologies to clean up heavy metal ions from contaminated waters have been utilized, but these technologies are not cost-effective. However, the use of agricultural waste byproducts for the removal of Cr(VI) from contaminated waters may be a new cost-effective alternative. Oat byproducts from the Juarez Valley in Mexico were studied for the ability to bind Cr(VI) under different temperature and time conditions. The metal binding ability of oat byproducts was calculated from experimental data collected at temperatures of 8, 26, and 54°C, and time exposures of 1, 6, 24, 48, and 72 h at each temperature. These results showed that the binding of Cr(VI) to oat biomass increased as time and temperature increased. The bound chromium was recovered from the oat biomass by treatment with 0.2 M HCl. Through the use of X-ray absorption spectroscopy, the reduction of Cr(VI) to Cr(III) was determined to occur by the oat byproducts. These results indicate that the use of agricultural waste byproducts could be a better alternative for the removal and subsequent reduction of Cr(VI) to Cr(III) from contaminated waters.     

Optical and structural properties of ZnO + Zn<Subscript>2</Subscript>TiO<Subscript>4</Subscript> thin films prepared by the sol–gel method

ZnO + Zn₂TiO₄ thin films were obtained by the sol–gel method using precursor solutions with different Ti/Zn ratios in the 0.18–2.13 range. The films were deposited on glass substrates and annealed in an open atmosphere at 550 °C. The oxide was characterized by X-ray diffraction and photoacoustic (PA) spectroscopy. The films were constituted of polycrystalline ZnO for the lowest Ti/Zn ratio (0.18), polycrystalline Zn₂TiO₄ for the 0.70 and 1.0 ratios, and mixes of both oxides for the intermediate ratios (0.32 and 0.50). For the highest ratios studied (1.44 and 2.13), the films were amorphous. The energy band gap (E_g) values were determined from optical absorption spectra, measured by means of the PA technique spectra. E_g varied in the 3.15 eV (ZnO) to 3.70 eV (Zn₂TiO₄) range.     

An approach to integrate manufacturing process information in part design phases

Design for Manufacturing (DFM) is the integrated practice of designing components while considering their manufacture (O’Driscoll, M., 2002. Design for manufacture. Journal of Material Processing Technology, 122, 318–321). The benefits of this practice have been widely acknowledged in the industry. Several techniques fall under the umbrella of Design for Manufacturing, and their implementation depends heavily on the context in which they will be applied. How to enhance their use by designers is still an issue. The use of a formalized design process, in which a software application is used to bring manufacturing knowledge to the forefront, would improve DFM implementation. In such a context, a fundamental issue is to define the manufacturing information that should be presented to the designer.This work addresses the capture and documentation of essential DFM information to make design decisions. Essential manufacturing information is that which can affect the fulfilment of functional requirements and product constraints. The proposed approach combines DFM techniques and principles of Axiomatic Design (AD) theory. The manufacturing information is represented by the concepts of Process Property (PP) and process Execution Variable (EV). The ultimate aim of the approach is to define manufacturing knowledge structures and develop a knowledge-based application for DFM.The approach was applied to a case study in which a connecting rod was the part to de designed and manufactured. The manufacturing processes selected were forging and powder metallurgy. The DFM information about these manufacturing processes, related to the connecting rod, was identified and formalized in a table-based data structure.