A millimetre wavelength absorption in soda lime silica glass

Dispersive Fourier transform determinations of the optical constants of soda lime silica glass below 20 cm^-1 at 293 K have allowed the presence of a broad, discrete absorption feature centred on 9 cm^-1 to be inferred. The feature is tentatively linked to a similar feature previously seen in the spectrum of fused silica.     

Different shapes of tracks in phlogopite, biotite and soda lime glass

Etched track opening geometries in Biotite, Phlogopite and soda-lime glass irradiated with swift heavy ions [¹⁹⁷Au(11.64 MeV/n), ¹³⁶Xe(11.56 MeV/n), ⁵⁸Ni(11.56 MeV/n)] at different angle of incidence have been studied using appropriate chemical etching technique. Different geometries (Hexagonal, irregular polygon, triangular in case of Biotite and Phlogopite, and circular & elliptical in case of soda lime glass detector) of heavy ion tracks are reported in the present investigations using optical microscope. The different shapes of these heavy ions track geometries are found to be related with various target-projectile parameters (viz: type of projectiles, energy, stopping power, angle of incidence of the projectile, density of defects and its reactivity with etchant, etching conditions and chemical structure of the detectors). The dependence of different shapes of heavy ion tracks in isotropic and anisotropic medium on the variation of radiation damage densities along the ion trajectories have also been discussed in the present paper.      

X-ray photoemission study of a sodalimesilica glass

A comparison is made between the X-ray photoemission spectra of the core levels and the valence band of a high purity sodalimesilica glass (21.3 wt.% Na₂O5.2 wt.% CaO73.5 wt.% SiO₂) with those for fused silica. In the valence band of fused silica three peaks are observed whereas in the compound glass an additional peak is found above the high binding energy edge of the valence band. The presence of non-bridging oxygen in the sodalimesilica glass not only broadens the oxygen core level asymmetrically to lower binding energy, but also broadens the lowest energy peak in the valence band. It is this latter broadening which certainly contributes to the shift in the fundamental optical absorption edge to lower energy in this glass with respect to pure SiO₂. An energy-level model is proposed for this glass. The diffusion of Na⁺ ions to the surface is also observed.     

Structure and properties of soda lime silicate glass doped with rare earth

Soda-lime-silicate glasses doped with different rare-earth oxides (La₂O₃, CeO₂, Nd₂O₃, Gd₂O₃ and Y₂O₃) of 1 mol% content were prepared with the traditional melting-quenching methods. In order to reveal the effects of rare-earth elements on the behavior of soda-lime-silicate glass, the structure of soda-lime-silicate glasses doped with different rare-earth oxides were determined with Fourier transform infrared spectrometer using the KBr method, and viscosity of glass melts were measured by the rotating crucible viscometer, the melting temperature of the studied glasses were derived on the basis of Arrhenius Equation, moreover the density, bending strength and molar volume were measured and calculated. The effect of rare-earth dopants on the structure of soda-lime-silicate was analyzed by a shift of peak position and variation in the full-width at half-maximum. The effect of doping rare-earth oxides into glass on the viscosity, density and bending strength was interpreted by changing in structure of soda-lime-silicate glasses doped with rare-earth oxides.     

Shock wave propagation in gases under subatmospheric pressure

In the present paper the results of the experiments on the shock wave dynamics under subatmospheric pressure in neutral gases are presented. The characteristics of spherical and plane configuration shock wave excitation and propagation are studied in the pressure region 1 torr<p<760 torr. It is shown that whenp=3 torr it is still possible to fix successfully the shock wave appearance and propagation in various neutral gases. The pressure dependence of the shock wave propagation velocity and amplitude is determined experimentally. It is shown that when the pressure decreases the shock wave amplitude decreases and an increase of the Mach number takes place. In the case of plane shock wave the Mach number reaches the valueM=5.2 under the pressurep=3 torr.     

X-ray-assisted formation of gold nanoparticles in soda lime silicate glass: suppressed Ostwald ripening

The in situ formation of gold nanoparticles in soda lime silicate glass under constant x-ray irradiation is compared with the ex situ formation in preirradiated glasses. The ASAXS measurements confirm that pure Au particles are formed. The comparison shows that the number of particles nucleated under irradiation is about an order of magnitude higher than of those nucleated with preirradiation. The radius, R, remains slightly below 1 nm under in situ conditions and the Ostwald ripening stage is slowed down. Under ex situ conditions Ostwald ripening is clearly observed and R grows up to 3 nm.     

Color center formation in soda lime glass and NaCl single crystals with femtosecond laser pulses

The high instantaneous powers associated with femtosecond lasers can color many nominally transparent materials. Although the excitations responsible for this defect formation occur on subpicosecond time scales, subsequent interactions between the resulting electronic and lattice defects complicate the evolution of color center formation and decay. These interactions must be understood in order to account for the long term behavior of coloration. In this work, we probe the evolution of color centers produced by femtosecond laser radiation in soda lime glass and single crystal sodium chloride on different time scales, from microseconds to hundreds of seconds. By using an appropriately chosen probe laser focused through the femtosecond laser spot, we can follow the changes in coloration due to individual or multiple femtosecond pulses, and follow the evolution of that coloration for a long time after femtosecond laser radiation is terminated. For the soda lime glass, the decay of color centers is well described in terms of bimolecular annihilation reactions between electron and hole centers. Similar processes appear to operate in single crystal sodium chloride. PACS 82.50.Pt; 78.55.Qr; 78.55.Fv; 78.47.+p     

Shock wave and detonation propagation through U-bend tubes

The objective of the research outlined in this paper is to provide experimental and computational data on initiation, propagation, and stability of gaseous fuel–air detonations in tubes with U-bends implying their use for design optimization of pulse detonation engines (PDEs). The experimental results with the U-bends of two curvatures indicate that, on the one hand, the U-bend of the tube promotes the shock-induced detonation initiation. On the other hand, the detonation wave propagating through the U-bend is subjected to complete decay or temporary attenuation followed by the complete recovery in the straight tube section downstream from the U-bend. Numerical simulation of the process reveals some salient features of transient phenomena in U-tubes.     

Structure functions for optical wave propagation in underwater medium

The features of the wave structure function (WSF) derived for spherical excitation in turbulent water are investigated. It is found that as the rate of the dissipation of turbulent kinetic energy ? decreases, WSF increases. The rate of dissipation of the mean-squared temperature X_T is observed to be proportional to the WSF value. Deviation from the source and the receiver axis reveals greater turbulence effect. Salinity driven turbulence gives greater WSF values compared to the temperature driven turbulence. As expected, WSF is found to increase as the propagation distance increases.     

Time-domain observation of optical pulse propagation in whispering-gallery modes of glass spheres

We report picosecond time-resolved measurements of optical pulse propagation in dielectric spheres (8, 10, and 26 mm in diameter) for which the pulse duration ( approximately 2 ps) was short compared with the equatorial round-trip time within the sphere. A size-independent buildup of the leakage intensity in terms of the number of round trips was observed for each of the spheres, as were damped low-frequency oscillations superimposed upon the pulse ringdown envelope. These features of the data are interpreted as resulting from perturbative coupling of eigenmodes of the sphere and trajectory precession near the observation region.     

Dynamic imaging and hydrodynamics study of high velocity, laser-accelerated thin foil targets using multiframe optical shadowgraphy

The main aim of the study of thin target foil–laser interaction experiments is to understand the physics of hydrodynamics of the foil acceleration, which is highly relevant to inertial confinement fusion (ICF). This paper discusses a simple, inexpensive multiframe optical shadowgraphy diagnostics developed for dynamic imaging of high velocity laser-accelerated target foils of different thicknesses. The diagnostic has a spatial and temporal resolution of 12 μm and 500 ps respectively in the measurements. The target velocity is in the range of 10⁶–10⁷ cm/s. Hydrodynamic efficiency of such targets was measured by energy balance experiments together with the measurement of kinetic energy of the laser-driven targets. Effect of target foil thickness on the hydrodynamics of aluminum foils was studied for determining the optimum conditions for obtaining a directed kinetic energy transfer of the accelerated foil. The diagnostics has also been successfully used to study ablatively accelerated targets of other novel materials.     

Evaluation of optical propagation and radiation in optical waveguide using a numerical method

We introduce a mathematical model based on a concept of intrinsic mode in order to analyse and synthesise optical wave propagation and radiation occurring in a non-uniform optical waveguide used in integrated optics as optical coupler. The model is based on numerical evaluation of electromagnetic wave by applying an intrinsic field integral to evaluate the field behaviour inside the optical waveguide. To analyse the field distribution inside the non-uniform waveguide and predict the beam propagation of optical energy involved in the propagation process, it is necessary to track the motion of any observation point along the tapered waveguide itself. Physically, the rays of the spectrum undergo reflections on the waveguide boundaries until the cut-off occurs and the phenomena of radiation begin. The numerical results show good agreement with those obtained by classical methods of evaluation used bv other works.     

Microwave propagation in two dimensional structures using lossy cylindrical glass rods

Two dimensional microwave band gap structures have been constructed using lossy cylindrical glass samples ( and ). The power transmission spectra observed between 10 and 20 GHz for both square and triangular structures with three different lattice spacing (2.5, 1.4 and 0.9 cm) are explained in terms of the lattice spacing, filling fraction and loss tangent. The experimental results and the theoretical values agree well for the structures having higher filling fraction. Also, the values predicted from the scaling procedure agree well with the experimental values. The appearance of acceptor modes due to the introduction of defects in these structures is also reported.Received: 26 April 2004, Published online: 12 October 2004PACS: 41.20.Jb Electromagnetic wave propagation; radiowave propagation - 42.25.Fx Diffraction and scattering     

Relation between different formalisms describing partially incoherent wave propagation in nonlinear optical media

It is shown that the Wigner formalism for describing propagation of partially incoherent waves in nonlinear media with slow medium response is equivalent to previously established methods based on coherent density theory, self-consistent multi-mode theory and the mutual coherence function approach.     

The effect of disorder on the wave propagation in one-dimensional periodic optical systems

The influence of disorder on the transmission through periodic waveguides is studied. Using a canonical form of the transfer matrix, we investigate the dependence of the Lyapunov exponent γ on the frequency ν and magnitude of the disorder σ. It is shown that in the bulk of the bands γ?～?σ², while near the band edges it has order γ?～?σ^2/3. This dependence is illustrated by numerical simulations.     

Effect of γ-irradiation on the electrical conductivity of some soda lime silicate glass containing blast furnace slag

The effect of electric field strength on conduction in soda lime silicate glass doped with blast furnace slag with different concentration was studied and the value of jump distance was calculated. The structure and the mixed anion effect in the conductivity have been examined by measuring the electrical conductivity of glass samples at temperature ranging between 20 and 250 °C. The results showed that the electrical conductivity of the examined glasses are divided into three ranges depending on the temperature range. The first is from room temperature to about 49.5 °C, the second is at a temperature range of 60.3–104 °C where the glass shows a decrease in its conductivity with the increase in temperature. This was followed by another increase in the electrical conductivity with the increase in temperature. The results also showed that the glass becomes more insulating as the slag content increased. The effect of irradiation was also studied by exposing glass samples to two different irradiation doses. It can be noticed that irradiation causes an increase in the electrical conductivity, especially at high temperature. The results were discussed and correlated according to the molecular structure of the prepared glass.     

Modeling wave propagation in realistic heart geometries using the phase-field method

We present a novel algorithm for modeling electrical wave propagation in anatomical models of the heart. The algorithm uses a phase-field approach that represents the boundaries between the heart muscle and the surrounding medium as a spatially diffuse interface of finite thickness. The chief advantage of this method is to automatically handle the boundary conditions of the voltage in complex geometries without the need to track the location of these boundaries explicitly. The algorithm is shown to converge accurately in nontrivial test geometries with no-flux (zero normal current) boundary conditions as the width of the diffuse interface becomes small compared to the width of the cardiac action potential wavefront. Moreover, the method is illustrated for anatomically realistic models of isolated rabbit and canine ventricles as well as human atria.     

Simulation of extended phase screens in problems of optical wave propagation through the atmosphere

Turbulent medium in problems of optical wave propagation through the atmosphere is usually nodeled as a set of statistically independent plane screens with a random two-dimensional field of phase progress. In this paper, we develop methods for the formation of nonperiodic phase screens infinitely extended in a certain direction, which are required in problems of dynamic simulation of wave propagation. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 1, pp. 21–34, January 2006.