[en] The evolutions of grain growth in ceramics with ABO₃ type structure were simulated at atomistic level by the Monte Carlo method with Visual C++ language. Several parameters, such as initial seed number, seed activation coefficient, sintering temperature and time, were incorporated. Realistic images in series were monitored and quantitative data were obtained, including the fractal dimensions of grain boundaries during the kinetic evolution of grain growth. The resulted kinetic exponents of grain growth were variable during the process of simulation, being smaller (∼1.8) at early period and larger (∼5.5) at later stage. It was in good agreement with the experimental result of practical (Ba_0.9Sr_0.1)TiO₃ ceramics

[en] Silicon nanowires have large aspect-ratio to keep high absorption along the incident direction, so nanowire arrays are one of potential structures for trapping light. To further enhance absorption in silicon nanowire arrays, thin blocks are arranged on the silicon substrate. It numerically demonstrates that additional blocks not only have few negative influence on absorption of nanowire arrays in the visible range, but also excite extra resonances in the near-infrared range, which make grading absorption and enhancement in the nanostructures. These excited resonances are finely examined and attributed to surface plasmon polaritons, guided modes and their coupled modes. The enhancement mechanism is further revealed by the electromagnetic fields and theoretical analysis for corresponding two-dimensional structures. The nanostructures can achieve higher absorption in silicon nanowire arrays, and grading absorption in the nanostructures will facilitate the development of other devices as novel filters, photoelectronics and so on. - Highlights: • Absorption enhancement in silicon nanowires with thin blocks are investigated. • Grading absorption is found when the width of nanowires is small. • The enhancement mechanism caused by thin blocks is revealed. • Grading absorption and enhancement is validated to achieve by dielectric blocks.

[en] 'Certain high level wastes (HLW) in the US contain components such as phosphates, heavy metals, and halides which make them poorly suited for disposal in borosilicate glasses. Iron phosphate glasses appear to be a technically feasible alternative to borosilicate glasses for vitrifying these HLWs. The iron phosphate glasses mentioned above and their nuclear wasteforms are relatively new, so little is known about their atomic structure, redox equilibria, structure-property relationships, and crystallization products and characteristics. The objective of this research is to gain such information for the binary iron-phosphate glasses as well as iron phosphate wasteforms so that a comprehensive scientific assessment can be made of their usefulness in nuclear waste disposal. This report summarizes the work undertaken and completed in the first 20 months of a three year project. Approximately 250 samples, binary iron phosphate glasses and iron phosphate glasses containing one or two common nuclear waste components such as UO₂ , Na₂O, Bi₂O₃ , Cs₂O, SrO, and MoO₃, have been prepared. Weight loss has been used to measure the chemical durability and the redox equilibria between Fe(II) and Fe(III) has been investigated using Moessbauer spectroscopy. The atomic structure has been investigated using a variety of techniques including Mossbauer, Raman, X-ray absorption (XAS), and X-ray photoelectron (XPS) spectroscopies and neutron/high energy X-ray scattering. Glass forming and crystallization characteristics have been investigated using differential thermal analysis (DTA). In addition, information necessary for glass manufacturing such as suitable refractories and Joule heating parameters also have been obtained.'

[en] The recycling of laser beams in the focal region of non-resonant multipass optical cavities has been investigated as a means of providing a high intensity of photons for weak interaction experiments. Ray-tracing simulations and measurements with an Ar-ion laser have been carried out to examine the intensity profiles of the laser field in different 2-mirror geometries. In particular, the use of such cavities in the generation of X-rays by inverse Compton scattering is considered. X-ray yields are calculated for electron beams of 0.05, 0.1, 0.2 and 0.5 mm diameter yielding enhancement factors of 10-200 compared to a free space laser interaction

No abstract available

[en] In this study, the pulsed laser ablation of RuO₂ and SrRuO₃ (SRO) is investigated by observing the fluorescence from excited atoms in the plume by using a framing streak camera. Vaporization, phase explosion and boiling are suggested to play the main roles in the processes for the interaction between the laser beam and target. Collisions and adiabatic expansion are also suggested before particles move forward with shifted Maxwellian spatial distribution. In O₂ pressure, numerous collisions between fast and slow atoms occur and result in the exchange of speeds. The structural and electrical (conductivity and work-function) properties of RuO₂ and SRO thin films are measured. Epitaxial SRO growth was obtained at growth temperatures down to 350 C. Ferroelectric and high- dielectric thin-film capacitors with RuO₂ or SRO thin film electrode are also studied. (orig.)

[en] Measurements of absolute cross sections for the single electron detachment (σ_-1,0) in collisions between H^- and Ar in the energy range 5-50 keV are reported. A well-collimated H^- ion beam is directed toward an Ar gas target and all three of the exiting scattered beam components (i.e. H⁰, H⁺ and H^-) are measured simultaneously. Using the closure relation among the collision beam components, (H⁰, H^- and H⁺) the neutral detection efficiencies are determined at each energy and thereby we are able to report absolute single detachment cross sections. The single detachment cross sections σ_-1,0 exhibit a broad maximum with a value of 1.78 x 10^-15 cm² at an impact energy of 25 keV

[en] Absolute total cross sections for the double electron detachment σ_-1,1 in collisions between H^- and Ne have been measured in the 5 - 50 keV energy range. A well-collimated H^- beam components of the collision products (i.e, H^O, H⁺ and H^-) are magnetically analyzed and directed into appropriately-biased Faraday cups for detection. The cross sections are determined by a quadratic least squares fit of the H⁼ fraction as a function of the target thickness in the growth curve analysis of the data. The double-electron detachment cross sections increase monotonically with impact energy over the energy region covered in this experiment. The values of σ_-1,1 range from 1.02 x 10^-17cm² at 5.0 keV to 5.54 x 10^-17 cm² at 50 keV

[en] Nd-Fe-B hard magnetic materials have been investigated intensively in recent years because of their high coercivities and maximum energy products. In this study we have examined the properties of the quaternary alloy Nd-Dy-Fe-B. Experiments revealed the underlying magnetic properties of these samples and these have been related to a theoretical model of the magnetization process. Samples were prepared in the form of particles either in the free state, in a randomly oriented state or in a field-oriented state obtained from solidification under an external field. Modeling results and microstructure analysis showed that compacting process strongly influenced the final magnetic properties through the change in the coupling coefficient resulting from one- or two-dimensional couplings among the particles which were totally different from those of the same materials in bulk state. (orig.)

[en] We investigate differential cross sections for single and double ionization and ratios of double to single ionization of He by proton projectiles at a few MeV/amu. A factor-of-two difference is found in the T-matrix at large deflection angles, with the target nucleus-electron interaction in the final state turned on and off. The differential cross sections for single ionisation, calculated in the first Born approximation with the effect of nuclear deflection of the projectile included, are in good agreement with the experimental data. The shakeoff mechanism is calculated on an s-wave basis. The two-hard-hit mechanism, in which two energetic recoiling electrons are produced, is also calculated and a sharp peak in the ratio is found. The magnitude of the calculated peak is discussed. The ratio calculated by combining different mechanisms is compared to the experimental data and discussed. (orig.)