Metastable zoning in cordierite-based glass-ceramics

When phase-separated TiO₂-bearing glasses having compositions in the cordierite primary phase volume of the CaO-Al₂O₃-SiO₂-MgO system are crystallised at 1000°–1100°C, a zoned microstructure is often seen in the glass-ceramic products by scanning electron microscopy. X-ray microanalysis by the energy dispersive method has produced evidence of large-scale atomic segregation in these zones, particularly involving calcium and magnesium atoms. It is suggested that zoning has a markedly deleterious effect on some of the physical properties of these materials, particularly their strength.     

Solar cells consisting of phenazine dyes in polymer matrix

We have constructed p−n heterojunction solar sandwich cells with phenazine dyes in a thin film of polyvinyl alcohol placed between a conducting glass coated with indium oxide and a platinum foil. The current-voltage relations of the cells have been measured in the dark and light under both forward and reverse biases.     

Whirl instability of externally pressurized gas-lubricated porous journal bearings

A study of the whirl instability of externally pressurized gas-lubricated porous journal bearings was made. The theoretical analysis was obtained using a quasi-static assumption. The stability characteristic of a particular journal bearing is given for various supply pressures, design dimensions and feeding parameters. Experimental data confirm the theoretically obtained results.     

Effects of chronic vanadium pentoxide administration on L-ascorbic acid metabolism in rats: influence of L-ascorbic acid supplementation

1. Rats toxicated with vanadium pentoxide showed drastic retardation in growth rate and supplementation of L-ascorbic acid to these rats could not reverse this effect. The urinary excretion of L-ascorbic acid and D-glucuronic acid was decreased in the toxicated group of rats. 2. Considerable lowering of L-ascorbic acid content of the liver tissues of rats was observed under vanadium toxicated conditions. Supplementation of L-ascorbic acid to this group raised the tissue Vitamin C reserve considerably. 3. The normal histological patterns of the liver and kidney tissues of rats were severely disturbed under vanadium toxicated conditions. L-ascorbic acid supplementation to this group of rats showed marked signs of restoration in this respect. 4. Vanadium pentoxide treatment brought about a significant reduction in the biosynthetic capacity of L-ascorbic acid, along with an enhanced utilization of this vitamin. Subsequent supplementation of L-ascorbic acid to the toxicated group of rats was found to be effective in reversing these effects almost to the basal level.     

Zero-load stability of a rigid rotor supported on pressurized porous gas bearings

A theoretical and experimental investigation of stability characteristics of a rigid rotor mounted on externally expressurized gas-lubricated porous bearings in made. The hydrodynamic fluid film forces of an unloaded journal which undergoes steady whirl are obtained to find limits of the stable region. The results are compared with experimental data and with a similar solution using Galerkin's method. The effect of a feeding parameter, supply pressure, thickness of porous bushing and porosity of bushing material on stability characteristics is also investigated.     

Generation of waves by a moving oscillatory source in magnetohydrodynamics

The two-dimensional linear gravity waves created by a moving oscillatory source in an incompressible, inviscid, electrically conducting fluid of infinite depth where a constant magnetic field acts outside the air-water interface are considered. To determine the unsteady asymptotic waves, Bleistien's method had been applied to the Fourier transform solution. Several physically interesting results about the four waves generated, together with their fronts, are found and also the effect of magnetic force on the gravity waves has been studied.     

Fundamental Oseen solution for the 2-dimensional flow of a micropolar fluid

The steady, incompressible flow of a micropolar fluid in 2 dimensions is considered. The Oseen linearization of the convective operator is introduced, and the associated problem for the fundamental solution is formulated. Solution of the fundamental problem is obtained in explicit form under a certain restriction on the physical parameters of the problem. Utilization of the fundamental solution in the investigation of general flow problems is discussed.     

Plane vibration characteristics of multired externally pressurized oil journal bearings

Externally pressurised oil journal bearings are often subjected to dynamic loading and vibration. A theoretical analysis of the dynamic behaviour of orifice compensated bearings is presented and a design procedure outlined. The analysis assumes that the journal undergoes plane harmonic vibration about its mean steady state position in the absence of shaft rotation. The lubricant is assumed to be isovicous and incompressible. Stiffness and damping characteristics are presented.     

Laboratory-simulation experiment for optical communication through low-visibility atmosphere using a diode laser

A laboratory-simulation experiment has been performed to determine the feasibility of exploiting the scattered (in addition to the unscattered) radiation to improve optical communication through low-visibility atmosphere. A multiple field-of-views (FOV) (0.043-0.945degfull angle) optical receiver was designed which utilizes a narrow-band interference filter (Deltalambda sim 15Å) for background-light suppression. The laser transmitter was a CW GaAlAs laser diode (lambda = 0.8486 mum) capable of emitting ∼ 7 mW power output of 15° divergent beam. Both polydisperse (particle diameters,din the range ofsim0.2-5.17 mum) and monodisperse (d sim 0.2 mum andd = 3.01 mum) latex spheres in water were used for simulating haze, fog, etc. Results include signal-to-noise ratio (SNR) and scattered-to-unscattered signal ratio as a function of field-of-view of reception for various optical thickness of the medium. Also, SNR is plotted as a function of optical thickness for various FOV's. The unique feature of this simulation is that it can simulate worst case solar background where the sun enters the FOV of receiver. Finally a new technique of estimating forward-scattering efficiency and root-mean-square forward scatter angle has also been presented with examples.