Remarks on the existence of solutions to the average cost optimality equation in Markov decision processes

Necessary conditions are given for the existence of a bounded solution to the optimality equation arising in Markov decision processes, under a long-run, expected average cost criterion. The relationships of some of our results to known sufficient conditions are also shown.     

The demand for residential electricity in South Africa

This paper examines the residential demand for electricity in South Africa as a function of real gross domestic product per capita, and the price of electricity during the period 1978–2005. We make use of the bounds testing approach to cointegration within an autoregressive distributed framework, suggested by Pesaran et al. [2001. Bounds testing approaches to the analysis of level relationships. Journal of Applied Econometrics 16(3) 289–326]. Following the literature, we use a linear double-logarithmic form using income and price as independent variables in the empirical analysis. In the long run, we find that income is the main determinant of electricity demand, while electricity price is insignificant.     

Fabrication and Testing of Oxide/Oxide Microcomposites with Monazite and Hibonite as Interlayers

Oxide/oxide microcomposites were fabricated and tested to evaluate the effectiveness of monazite (LaPO₄) and hibonite (CaAl₁₂O₁₉) as interlayers in sapphire-reinforced Al₂O₃-matrix composites. For interlayer thicknesses of 0.3-0.5 µm, both interlayers showed evidence of crack deflection; however, debond lengths in hibonite-coated specimens were limited to just a small fraction of the fiber diameter. Monazite-coated specimens showed multiple matrix cracks and extensive debonding at the coating/matrix interface. Composite strengths were relatively high for both coatings, considering the fiber strength degradation during processing. The strengths were greater than the calculated matrix cracking stresses. However, the mean strengths were not significantly different from those of the control specimens, although coated composites had higher Weibull moduli. The lack of difference in strength is attributed to porosity in the matrix. The results imply that matrix density needs to be >85% to evaluate novel interface strategies reliably.     

Coupling active and passive techniques to control the flow past the square back Ahmed body

Several active and passive control techniques are used to reduce the drag coefficient of the square back Ahmed body. The results are carefully analyzed and compared to each other. The final goal of this paper is to show that it is possible to couple passive and active control techniques to improve the flow control. In the present study, a drag reduction of 30% is achieved, almost corresponding to the goal of automotive industry.     

Viscoelastic properties and morphological characterization of silica/polystyrene nanocomposites synthesized by nitroxide-mediated polymerization

Polystyrene (PS) chains with molecular weights comprised between 15,000 and 60,000 g/mol and narrow polydispersities were successfully grown from the surface of silica nanoparticles by nitroxide-mediated polymerization (NMP). Small angle X-ray scattering was used to characterize the structure of the interface layer formed around the silica particles, and at a larger scale, dynamic light scattering was used to determine the hydrodynamic diameter of the functionalized silica suspension. In a second part, blends of PS-grafted silica particles and pure polystyrene were prepared to evaluate the influence of the length of the grafted PS segments on the viscoelastic behavior of the so-produced nanocomposites in the linear viscoelasticity domain.Combination of all these techniques shows that the morphology of the nanocomposite materials is controlled by grafting. The steric hindrance generated by the grafted polymer chains enables partial destruction of the agglomerates that compose the original silica particles when the latter are dispersed either in a solvent or in a polymeric matrix.     

Is numerical comparison digital? Analogical and symbolic effects in two-digit number comparison.

Do Ss compare multidigit numbers digit by digit (symbolic model) or do they compute the whole magnitude of the numbers before comparing them (holistic model)? In 4 experiments of timed 2-digit number comparisons with a fixed standard, the findings of J. V. Hinrichs et al (see record 1982-07073-001) were extended with French Ss. Reaction times (RTs) decreased with target-standard distance, with discontinuities at the boundaries of the standard's decade appearing only with standards 55 and 66 but not with 65. The data are compatible with the holistic model. A symbolic interference model that posits the simultaneous comparison of decades and units can also account for the results. To separate the 2 models, the decades and units digits of target numbers were presented asynchronously in Experiment 4. Contrary to the prediction of the interference model, presenting the units before the decades did not change the influence of units on RTs. Pros and cons of the holistic model are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Corrosion of aluminium alloy A6061-T6 members embedded in alkaline materials

Owing to the corrosive conditions in coastal areas, aluminium alloy railings and similar structures are normally used on infrastructure works such as bridges and roads located in such areas because aluminium alloys are inherently corrosion resistant. However, to achieve rigid support, aluminium alloy members are often embedded in concrete. Consequently, the embedded parts undergo corrosion caused by the alkaline content of the cement used in the concrete. This research was carried out to study the corrosion behaviour on both the embedded and unembedded sides of aluminium alloy A6061-T6 members embedded in the concrete and also to investigate the ability of a combined coating of anodic oxide and organic film to inhibit corrosion. Additionally, the influence of scratch damage on the performance of this coating material was evaluated.     

Ultrathin PECVD epitaxial Si solar cells on glass via low‐temperature transfer process

Fabrication of high‐quality ultrathin monocrystalline silicon layers and their transfer to low‐cost substrates are key steps for flexible electronics and photovoltaics. In this work, we demonstrate a low‐temperature and low‐cost process for ultrathin silicon solar cells. By using standard plasma‐enhanced chemical vapor deposition (PECVD), we grow high‐quality epitaxial silicon layers (epi‐PECVD) from SiH₄/H₂ gas mixtures at 175 °C. Using secondary ion mass spectrometry and transmission electron microscopy, we show that the porosity of the epi‐PECVD/crystalline silicon interface can be tuned by controlling the hydrogen accumulation there. Moreover, we demonstrate that 13–14% porosity is a threshold above which the interface becomes fragile and can easily be cleaved. Taking advantage of the H‐rich interface fragility, we demonstrate the transfer of large areas (∽10 cm²) ultrathin epi‐PECVD layers (0.5–5.5 µm) onto glass substrates by anodic bonding and moderate annealing (275–350 °C). The structural properties of transferred layers are assessed, and the first PECVD epitaxial silicon solar cells transferred on glass are characterized. Copyright © 2016 John Wiley & Sons, Ltd.