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Abstract This paper presents a comparison of commercially used German and Russian reactor pressure vessel steels from the positron annihilation spectroscopy (PAS) point of view, having in mind knowledge obtained also from other techniques from the last decades. The second generations of Russian RPV steels seems to be fully comparable with German steels and their quality enables prolongation of NPP operating lifetime over projected 40 years. The embrittlement of CrMoV steel is very low due to the dynamic recovery of radiation-induced defects at reactor operating temperatures.

Abstract In this work, we propose an acoustic energy harvesting metamaterial consisting of an array of silicone rubber pillars and a PZT patch deposited on an ultrathin aluminum plate with several holes based on locally resonant mechanism. The resonance is formed by removing four pillars, drilling a few of holes and attaching the PZT patch on the aluminum plate. The strain energy originating from an incident acoustic wave is centralized in the resonant region, and the PZT patch is used to convert the elastic strain energy into electrical power. Numerical analysis and experimental results show that the proposed millimeter-scale harvester with holes obviously improves the effect of acoustic energy harvesting while performing at the subwavelength scale for sonic low-frequency environment (less than 1150 Hz). In addition, the experimental results demonstrate that the maximum output voltage and power of the proposed acoustic energy harvesting system with 16 holes of 2 mm radius are 3 and 10 times higher than those without holes at the resonant mode for 2 Pa of incident acoustic pressure. Both the number and size of holes have a significant effect on the performance of acoustic energy harvesting. The advantages of the proposed structure are easy-to-machine and full of practicality, and it can be used in broad applications for low-frequency acoustic energy harvesting.

AbstractNiNb2O6‐BaTiO3 ceramics were prepared using a solid‐state reaction method, and the effects of the addition of NiNb2O6 on the dielectric properties and energy‐storage characteristics of BaTiO3 were investigated systematically. We used XRD to show that the obtained NiNb2O6‐BaTiO3 ceramics possess a single perovskite structure. The addition of NiNb2O6 improves the energy density efficiency and leads to a decrease of the dielectric loss to less than 1 %. Moreover, optimum performances of the BaTiO3 ceramics can be achieved by the addition of 1.0 mol % NiNb2O6, at which content the obtained ceramic satisfies the X7R specification. The addition of NiNb2O6 stabilizes the crystalline lattice, which enhances the temperature stability of the dielectric properties accordingly.

AbstractThis paper presents a numerical model, which quantitatively demonstrates that ablation and partial recondensation of the dopant precursor layer are some of the dominating physical processes in laser doping (LD) of crystalline silicon. Our pulsed LD process uses a line focused laser beam, enabling the creation of solar cell emitters without the generation of dislocations, if the width w of the short axis of the line focus is w < 10 μm. The concentration profiles of the dopant atoms strongly depend on the pulse energy density Ep, the pulse to pulse separation Δx and the number of laser scans Ns. By comparing measured with modeled concentration profiles, we are able to evaluate the ablation width as well as the amount of the ablated precursor layer. In case of a sputtered phosphorus precursor layer, the ablation width wa is wa = 6 μm, whereas the width of the molten silicon layer wm is wm = 5 μm. The model also explains the dependence of experimental dopant concentration profiles on the number of subsequent laser scans Ns and pulse to pulse separation Δx. Copyright © 2010 John Wiley & Sons, Ltd.

Abstract As promising candidates for thermophotovoltaic energy conversion systems, epitaxial thin film III–V cells have gained increasing attention due to their potential for reduced weight. However, few studies have been done to date to enhance the performance of epitaxial single crystal GaSb thin film cells. In this work, the internal quantum efficiencies of epitaxial single crystal GaSb thin film cells with Zn-diffused and epitaxial p–n junctions were predicted with models verified using the corresponding experimental results. The results are the first to indicate that, for the former, when the base region thickness is approximately equal to minority carrier diffusion length, the maximal IQE can be obtained and it is notably higher than the IQE of GaSb bulk cell at wavelengths from 800 to 1700 nm. Reducing bottom surface recombination velocity and increasing hole Shockley–Read–Hall lifetime could also increase the IQE. While for the latter, the results demonstrated that the optimal base region thickness is also approximately equal to minority diffusion length, and reducing emitter region thickness will increase the IQE when the base region is optimized. The comparison of the two optimized GaSb thin film cells showed that the GaSb thin film cell with epitaxial p–n junction has a higher IQE.

A new approach for the electromagnetic control and propulsion of a current carrying electric arc plasma ring is described. The essence of the approach is to form and manipulate the arc plasma outside rather than inside a magnetic field producing coil so that pulsed plasma thrusts can be produced in a choice of different directions. The interaction of the electric arc, formed in atmospheric pressure air, with such a magnetic field has been investigated. It has been shown that a stable azimuthal plasma ring can be rapidly produced by the simple process of separating two annular contacts. Pulsed plasma propulsion is obtained when the arc plasma and B-field sustaining current is reduced to zero whereby the constraining electromagnetic forces are removed and, as a consequence, the resulting plasma ring expands radially outwards. Several different measurement techniques have been deployed for investigating the behavior of the plasma ring. These include electrical probing, B-field probing and high-speed plus video photography. The results suggest that the plasma control and propulsion is governed by a combination of effects including ablation of the material around which the plasma ring is formed and self-pressurization related to the device geometry, as well as the electromagnetic forces. Preliminary results indicate that through the use of appropriate device geometries, the arc plasma may be propelled in axially opposite directions as well as radially.

Abstract Optimal technology conditions, infrared absorption (IR) spectra, variation of optical gap ( E opt ) with x , measurement results of ESCA and ESR of a-Si x C 1− x :H films prepared by glow-discharge decomposition of silane-ethane mixtures have been studied. Preliminary discussions about these experimental results have been made in this paper.

The detected variety in chemistry and circumstellar shell morphology of the limited sample of Galactic post-AGB stars is so large that there is no consensus yet on how the different objects are linked by evolutionary channels. The evaluation is complicated by the fact that their distances and hence luminosities remain largely unknown. Via cross-correlation of the Spitzer SAGE catalogue with optical catalogues we selected a sample of LMC post-AGB candidates based on their [8]-[24] colour index and estimated luminosity. We determined the fundamental properties of the central stars of 105 of these objects using low-resolution, optical spectra that we obtained at Siding Spring Observatory and SAAO, and constructed a catalogue of 70 high probability and 1337 candidate post-AGB stars that is available at the CDS. The sample forms an ideal testbed for stellar evolution theory predictions of the final phase of low- and intermediate-mass stars, because the distance and hence luminosity and also the current and initial mass of these objects is well constrained. About half of the objects in our sample of post-AGB candidates show a spectral energy distribution (SED) that is indicative of a disc rather than an expanding and cooling AGB remnant. Like in the Galaxy, the disc sources are likely associated with binary evolution. Important side products of this research are catalogues of candidate young stellar objects, candidate supergiants with circumstellar dust, and discarded objects for which a spectrum was obtained. These too are available at the CDS.