A New Possibility of Dynamical Study on Solid State Ionic Materials by Inelastic Neutron Scattering

A new technique of inelastic neutron scattering measurement utilizing the multiple incident energies is applied to the dynamical study of vitreous silica. A wide variety of extracted information from a series of two-dimensional maps of dynamical structure factor with multiple different incident energies are greatly valuable. The applicability and its expected contribution of new experimental technique into the further progress of scientific activities in solid state ionic materials are discussed.Received: 30 September 2010; Revised: 25 October 2010; Accepted: 26 October 201

Anharmonic vs. relaxational sound damping in glasses: II. Vitreous silica

The temperature dependence of the frequency dispersion in the sound velocity and damping of vitreous silica is reanalyzed. Thermally activated relaxation accounts for the sound attenuation observed above 10 K at sonic and ultrasonic frequencies. Its extrapolation to the hypersonic regime reveals that the anharmonic coupling to the thermal bath becomes important in Brillouin-scattering measurements. At 35 GHz and room temperature, the damping due to this anharmonicity is found to be nearly twice that produced by thermally activated relaxation. The analysis also reveals a sizeable velocity increase with temperature which is not related with sound dispersion. This suggests that silica experiences a gradual structural change that already starts well below room temperature.Comment: 13 pages with 8 figure

Enhancements to linear least squares localization through reference selection and ML estimation

Linear least squares (LLS) estimation is a low complexity but sub-optimum method for estimating the location of a mobile terminal (MT) from some distance measurements. It requires selecting one of the fixed terminals (FTs) as a reference FT for obtaining a linear set of expressions. However, selection of the reference FT is commonly performed arbitrarily in the literature. In this paper, a method for selection of the reference FT is proposed, which improves the location accuracy compared to a fixed selection of the reference FT. Moreover, a covariancematrix based LLS estimator is proposed in line of sight (LOS) and non-LOS (NLOS) environments which further improves accuracy since the correlations between the observations are exploited. Simulation results prove the effectiveness of the proposed techniques. © 2008 IEEE

Effect of Injector Exit Geometry on Atomization of a Liquid-Liquid Double Swirl Coaxial Injector using Non-Invasive Laser, Optical, and X-ray Techniques

The spray characteristics of a liquid-liquid double swirl coaxial injector were studied using non-invasive optical, laser, and X-ray diagnostics. Phase Doppler interferometry was used to characterize droplet statistics and non-dimensional droplet parameters over a range of inlet conditions and for various fluids allowing for a study on the role of fluid properties on atomization. Based on the atomization statistics and observed trends from high-speed images, a description of breakup regimes over a range of Reynolds and Weber numbers was created. Next, X-ray computed tomography scans revealed that the spray cone was distinctively non-uniform and comprised of several pockets of increased mass concentration which varied with injection pressure. Finally, a parametric study of injector exit geometry demonstrated that spray breakup time, breakup type, and sheet stability could be controlled with exit geometry. Implications for these data on injector stability and atomization efficiency are discussed considering the desired performance characteristics of liquid-liquid rocket injectors

Anharmonic vs. relaxational sound damping in glasses: I. Brillouin scattering from densified silica

This series discusses the origin of sound damping and dispersion in glasses. In particular, we address the relative importance of anharmonicity versus thermally activated relaxation. In this first article, Brillouin-scattering measurements of permanently densified silica glass are presented. It is found that in this case the results are compatible with a model in which damping and dispersion are only produced by the anharmonic coupling of the sound waves with thermally excited modes. The thermal relaxation time and the unrelaxed velocity are estimated.Comment: 9 pages with 7 figures, added reference

Proton Microprobe and Particle Induced X-Ray Emission (PIXE) Analysis for Studies of Pathological Brain Tissue

Particle Indiced X-ray Emission and proton microprobe analyses have been applied for the investigation of regional elemental distributions in connection with various pathological states in the brain. Malignant brain tumours and adjacent histologically intact tissue removed during surgery were analysed with PIXE. Systematic elemental variations, e.g., for calcium and selenium, were observed in the tumour front. The proton microprobe was applied to study the Ca and K concentrations in various cell strata in hippocampus following transient ischaemia in rat brain. Significant increases in the Ca level occurred in selectively vulnerable cells within 48 h after the ischaemia