Aging effects of nanoscale ceria in ceria–platinum composite electrodes for direct alcohol electro-oxidation

Nanocrystalline Pt/CeO₂ composite electrodes were fabricated to study the electrochemical oxidation of methanol and ethanol. The performance of the electrodes was tested as the ceria solutions aged over time. It was observed that the performance oscillated with time, suggesting that the catalytic behavior towards alcohol oxidation was greatly dependent on the aging of the particles. These results point to a great dependence of the catalytic effect on the redox state of the ceria particles.     

橡树林中的小教堂 智利Junquillos小教堂

这是一个简单而朴实的教堂设计项目,它坐落在智利南部边远地区的一个小树林中。与很多教堂建设项目一样,建造这个小教堂的预算并不多。但幸运的是,接手这个项目的建筑师Claudio Baladron与Diego Grass成功地向我们展示了如何用最小的预算去建造最具有品质的经典项目。小教堂位于一片幽静的橡树林中,地理     

A simple procedure to improve the pressure evaluation in hydrodynamic context using the SPH

In literature, it is well know that the Smoothed Particle Hydrodynamics method can be affected by numerical noise on the pressure field when dealing with liquids. This can be highly dangerous when an SPH code is dynamically coupled with a structural solver. In this work a simple procedure is proposed to improve the computation of the pressure distribution in the dynamics of liquids. Such a procedure is based on the use of a density diffusion term in the equation for the mass conservation. This diffusion is a pure numerical effect, similar to the well known artificial viscosity originally proposed in SPH method to smooth out the shock discontinuities. As the artificial viscosity, the density diffusion used here goes to zero increasing the number of particles recovering consistency and convergence of the final numerical scheme adopted. Different artificial density diffusion formulas have been studied, paying attention to prevent unphysical changes of the flows. To show the improvements of the new scheme proposed here, a suitable set of examples, for which reference solutions or experimental data are available, has been tested.     

Applied studies in solar photocatalytic detoxification: an overview

The technical feasibility and performance of photocatalytic degradation of four water-soluble pesticides (diuron, imidacloprid, formetanate and methomyl) have been studied at pilot scale in two well-defined systems which are of special interest because natural-solar UV light can be used for them: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. The pilot plant is made up of compound parabolic collectors specially designed for solar photocatalytic applications. The initial concentration tested with imidacloprid, formetanate and methomyl was 50 and 30 mg/l with diuron, and the catalyst concentrations were 200 mg/l and 0.05 mM with TiO₂ and iron, respectively. Total disappearance of the parent compounds, 90% mineralisation and toxicity reduction below the threshold (EC₅₀) have been attained with all pesticides tested. All these results have contributed to an evaluation of photocatalytic treatment capacity and comments on the main parameters of TiO₂ and Fe separation from the treated water.     

Production of volatile compounds in the fermentation of chardonnay musts inoculated with two strains of Saccharomyces cerevisiae with different nitrogen demands

This paper studies the behaviour of two strains of Saccharomyces cerevisiae with different nitrogen requirements in the production of esters and higher alcohols during alcoholic fermentation. To carry out the study a chardonnay must with a high content of nitrogen compounds was used. The results showed that the strain with the highest nitrogen demand produced a higher concentration of esters during fermentation and gave rise to a wine with a somewhat lesser content of higher alcohols. The formation of volatile compounds was probably related to the consumption of nitrogen by the strains as the nitrogen nutrients act as precursors in the synthesis of esters and alcohols and regulate their production.     

Forecasting airborne pollen concentration time series with neural and neuro-fuzzy models

Forecasting airborne pollen concentrations is one of the most studied topics in aerobiology, due to its crucial application to allergology. The most used tools for this problem are single lineal regressions and autoregressive models (ARIMA). Notwithstanding, few works have used more sophisticated tools based in Artificial Intelligence, as are neural or neuro-fuzzy models. In this work, we applied some of these models to forecast olive pollen concentrations in the atmosphere of Granada (Spain). We first studied the overall performance of the selected models, then considering the data segmented into intervals (low, medium and high concentration), to test how they behave on each interval. Experimental results show an advantage of the neuro-fuzzy models against classical statistical methods, although there is still room for improvement.¹     

On the performance of heterogeneous MANETs

Recent decades have witnessed the birth of major applications of wireless communication technology, further supported by the increasing capabilities of portable devices, low cost and ubiquitous presence. Despite radio technology diversity, a great deal of existing research focuses on a single and isolated wireless technology at a time, where homogeneous elements are identified by IP addresses. This work presents a heterogeneous technology routing (HTR) Framework, targeted towards scenarios where the heterogeneity of devices and networking technologies is present. Our contribution is many fold. It consists of a framework, which encompasses a process for bootstrapping networks, a routing protocol capable of dealing with multiple network interfaces, and a tuning with multipath extensions. We evaluate the performance of the bootstrap, routing and multipath mechanisms by way of simulation and an actual testbed implementation. The multipath evaluation simulates HTR networks with WiMAX, 3GPP LTE and Wi-Fi support. Results show that our proposal can effectively improve the data delivery ratio for ad-hoc networks and that it reduces the end-to-end delay without major impact on network energy consumption. As part of HTR tuning, we investigate next the impacts of tuning the HELLO refresh interval timer on route convergence and its subsequent energy consumption reduction during this phase. We also compare our tuned HTR with the widely used optimized link state routing protocol. Results show that varying the HELLO refresh interval can improve the convergence time and reduce the energy consumption without major impact on network behavior. Our proposal also includes a new distributed address allocation algorithm, namely, the dynamic node configuration protocol (DNCP). This paper conducts a comparative analysis between the Prime, Prophet and the DNCP schemes using static and dynamic topologies in terms of network setup time, energy consumption and control message overhead. Results show that the DNCP had a lower battery power consumption and less control message overhead while it slightly suffers with regard to setup.

     

Theoretical efficiencies of angular-selective non-concentrating solar thermal systems

This paper explores the thermodynamic limits of solar thermal systems using absorber surfaces with high angular selectivity. It shows that theoretical considerations regarding the behavior of non-concentrating solar thermal systems are not enough in themselves to rule out their use in high-temperature applications. In fact, the paper demonstrates that the maximum theoretical thermal efficiency of a non-concentrating system may equal that of a concentrating system if the monochromatic directional emittance of its absorbing surface is sufficiently restricted. It is thus confirmed that the fundamental parameter that determines the ability of a solar-energy system to operate at high temperatures is not optical concentration, but angular selectivity of emittance.     

Effect of electrodeposition current density on the microstructure and the degradation of electroformed iron for degradable stents

Pure iron has become one of the most interesting candidate materials for degradable metallic stents due to its high mechanical properties and moderate degradation. In this work we studied the effect of electrodeposition current density on microstructure and degradation of pure iron films electrodeposited on Ti alloy substrate for degradable metallic stent application. Iron sheets were produced by electrodeposition using four different current densities 1, 2, 5 and 10 A dm⁻². The films were then studied by SEM (scanning electron microscope) and EBSD (electron backscatter diffraction) to observe the surface morphology, grain size and orientation. Potentiodynamic polarization and static immersion tests were used to determine the corrosion rate and to study the degradation behavior of iron films, respectively. The current density was found to significantly influence the texture, the grain size and the grain shape of the electrodeposited iron. At current densities of 1, 5 and 10 A dm⁻², weak textures corresponding to 〈1 0 1〉, 〈1 1 1〉 and 〈1 1 2〉 in the normal (electrodeposition) direction were obtained, respectively. At these current densities, average grain sizes smaller than 3 μm were also obtained. However, at 2 A dm⁻², a strong 〈1 1 1〉//ND texture with density of 7.4 MUD was obtained with larger average grain size of 4.4 μm. The microstructure of iron samples changed after annealing at 550 °C because of the induced recrystallization. Different corrosion rates were obtained from potentiodynamic polarization curves of iron films deposited at different current densities because of their microstructures. Fe-2 showed the lowest corrosion rate due to its larger grains size and its texture. The corrosion rates of all iron samples decreased after annealing. Static degradation showed lower corrosion rates for iron because of the formation of a degradation layer on samples surface which reduced the degradation reaction rate. The degradation morphology was uniform for Fe-2 due to its strong texture. On the other hand, microscopic pits were found for Fe-1, Fe-5 and Fe-10.