Enhanced visible light photocurrent generation at surface-modified TiO2 nanotubes

Photoelectrodes consisting of TiO₂ nanotube layers with different thicknesses (0.5 μm, 1.7 μm, 3 μm, 6 μm, 9 μm, and 18 μm) were prepared by anodization of titanium substrates and subsequent surface modification by a heat treatment at 400 °C in the presence of urea pyrolysis products. In contrast to unmodified TiO₂ nanotubes, the modified photoelectrodes exhibit photocurrents under visible light irradiation down to 750 nm. Photocurrent transients indicate enhanced recombination unless a suitable hole-scavenger, like iodide, is present since the photogenerated holes do not oxidize water efficiently. In the visible light the photoconversion efficiency increases significantly with nanotube length. The maximum incident photon-to-current efficiency (IPCE) was observed for tubes with the length of 6-9 μm (IPCE ∼4.5% and 1.4% at 450 nm and 550 nm, respectively) and the photocurrent enhancement with increasing tube length is found to be stronger at longer irradiations wavelengths.     

Changes in Older Europeans’ Health Across Two Waves of SHARE: Life-Course and Societal Determinants

Building on recent research investigating the role of life-course factors (including childhood conditions) and societal context in older Europeans health status, this study investigates the determinants of changes in elders’ health across two waves of the Survey of Health Ageing and Retirement in Europe (SHARE). Controlling for individuals’ current living conditions at baseline, our analysis provides evidence for long-term associations between childhood conditions (SES, health, cognition) and health dynamics in older age. Moreover, our findings suggest that income inequality tends to increase elders’ risk of experiencing negative health changes (decreases their chance to recover from poor health, respectively). Our study underlines the importance of accounting for both life-course and societal determinants of later life health dynamics.     

采用硬件加速可以让MicroBlaze发挥更为强劲的处理能力

在实际应用中,有许多算法可以转化为纯硬件来加速您的处理器.平均标准偏差算法、给定时间内创建最小值或最大值、滤波器以及FFT均属于可轻松移植到硬件上的典型算法.不过诸如位反转等一些不常见的算法可采用合适的硬件加速器也能移植到硬件上.     

Aluminium foam–polymer composites: processing and characteristics

Dissemination of closed cell metal foam unique properties (low density, efficient energy absorption, high vibration/sound attenuation) in real life products has often been difficult to realise. With advanced pore morphology (APM) aluminium foam–polymer hybrids a new and simplified process route targeted at application in foam-filled structures (e.g. automotive A-pillar) has been introduced. APM foams are made from spherical, small volume foam elements joined to each other in a separate process step. Joining the aluminium foam elements by adhesive bonding delivers composite foam with approximately 80–95 wt.% aluminium foam and 5–20 wt.% adhesive (polymer). Setting up cellular structures from spherical foam elements allows for automatic part production, good pore morphology control and cost effective aluminium foam application. An automated production line is displayed and discussed. Mechanical properties of APM aluminium foam–polymer hybrids are similar to other closed cell aluminium foams. Integration of APM foams in profiles resulted in significantly improved properties as observed for conventional closed cell aluminium foam fillings. The unique properties of APM composite foams make them an attractive alternative as a cost effective and easily applicable material of construction with targeted uses such as energy absorbing reinforcement of composite structures.     

Energy efficient office buildings with passive cooling – Results and experiences from a research and demonstration programme

To gain access to information on energy use in office buildings, the German Federal Ministry for Economy launched an intensive research and demonstration programme in 1995. In advance of the 2002 EU energy performance directive a limited primary energy coefficient of about 100 kW h m⁻² a⁻¹ as a goal for the complete building services technology was postulated (HVAC + lighting) for all demonstration buildings to be supported. A further condition was that active cooling be avoided. Techniques such as natural or mechanical night ventilation or heat removal by slab cooling with vertical ground pipes as well as earth-to-air heat exchangers in the ventilation system were applied. An accompanying research was established to keep track of the results and the lessons learned from about 22 demonstration buildings realized and monitored until the end of 2005. As one outcome this paper summarises the energy performance of a selection of characteristic buildings together with an overview on the summer thermal comfort situations achieved. The research program will proceed during the next five years. Detailed reports and future results may be downloaded from the internet: www.enbau-monitor.de.     

CO Oxidation on Pd(100) Versus PdO(101)-(\sqrt{5}\times \sqrt{5})R27^{\circ}: First-Principles Kinetic Phase Diagrams and Bistability Conditions

We present first-principles kinetic Monte Carlo (1p-kMC) simulations addressing the CO oxidation reaction at Pd(100) for gas-phase conditions ranging from ultra-high vacuum to ambient pressures and elevated temperatures. For the latter technologically relevant regime there is a long-standing debate regarding the nature of the active surface. The pristine metallic surface, an ultra-thin $(\sqrt{5}\times \sqrt{5})R27^{\circ}$ PdO(101) surface oxide, and thicker oxide layers have each been suggested as the active state. We investigate these hypotheses with 1p-kMC simulations focusing on either the Pd(100) surface or the PdO(101) surface oxide and intriguingly obtain a range of (T, p)-conditions where both terminations appear metastable. The predicted bistability regime nicely ties in with oscillatory behavior reported experimentally by Hendriksen et al. (Catal Today 105:234, 2005). Within this regime we find that both surface terminations exhibit very similar intrinsic reactivity, which puts doubts on attempts to assign the catalytic function to just one active state.     

Experimental validation of high-order time integration for non-linear heat transfer problems

An accurate prediction of the temperature distribution in space and time plays an important role in many industrial applications, in particular when phase transformations are involved. In this article the thermo-physical properties of steel 51CrV4 (SAE 6150) are determined and used in numerical simulations. For the simulation of the temperature field a semi-discrete approach is used, consisting of a finite element approximation in space and a high order Runge– Kutta integration in time. Several adaptive high-order time integration method (stiffly accurate diagonally implicit Runge–Kutta methods) are applied and their computational efficiency is investigated. The theoretical rates of convergence are achieved for all problems, including the non-linear case. Whereas the second order accurate method of Ellsiepen with time adaptive step-size control proves to be most efficient. Further, the influence of the material model on the simulation results is studied and the numerical results are verified by experiments. The best correlation of the simulation and experimental data is achieved using temperature-dependent parameters.     

Volatilization of organotin species from municipal waste deposits: novel species identification and modeling of atmospheric stability

Organotin compounds are used as pesticides and fungicides as well as additives in plastics. This study identifies the de novo generation of novel volatile organotins in municipal waste deposits and their release via landfill gas. Besides tetramethyltin (Me(4)Sn), a strong neurotoxin, and 5 previously reported organotins, 13 novel ethylated, propylated, and butylated tetraalkyltin compounds were identified. A concentration of 2-4 μg of Sn m(-3) landfill gas was estimated for two landfill sites in Scotland. The atmospheric stability of Me(4)Sn and methylated tin hydrides was determined empirically in a static atmosphere in the dark and under UV light to simulate night- and daytime conditions. Theoretical calculations were carried out to help predict the experimentally obtained stabilities and to estimate the relative stabilities of other alkylated species. Assuming first-order kinetics, the atmospheric half-life for Me(3)SnH was found to be 33 ± 16 and 1311 ± 111 h during day- and nighttime conditions, respectively. Polyalkylation and larger alkyl substitutes tend to reduce the atmospheric stability. These results show that substantial concentrations of neurotoxic organotin compounds can be released from landfill sites and are sufficiently stable in the atmosphere to travel over large distances in night- and daytime conditions to populated areas.