Effect of the three-body force on triton asymptotic normalization constants by the hyperspherical harmonics expansion method

We investigate the change in the calculated value of asymptotic normalization constant (ANC) by the hyperspherical harmonics expansion method with the inclusion of three nucleon force (3BF) in addition to two nucleon force. We see that ANC does not change very much with the inclusion of 3BF indicating that the 3BF does not alter the asymptotic behaviours of HHE wavefunction significantly.     

Laser induced air breakdown using 0.355, 0.532, and 1.06 µm radiation

Studies of breakdown threshold intensity for air at various pressures in the range of 24–760 torr using 0.355, 0.532 and 1.06 μm radiation are reported. We observep ^−0.8 scaling ofI _th at 1.06 μm and a weak scaling ofp ^−0.4 at 0.532 and 0.355 μm radiation. Strong dependence of breakdown spot size on laser power but weak dependence on air pressure is observed.     

A numerical study of an unsteady laminar flow in a doubly constricted 3D vessel

Unsteady flow dynamics in doubly constricted 3D vessels have been investigated under pulsatile flow conditions for a full cycle of period T. The coupled non‐linear partial differential equations governing the mass and momentum of a viscous incompressible fluid has been numerically analyzed by a time accurate Finite Volume Scheme in an implicit Euler time marching setting. Roe's flux difference splitting of non‐linear terms and the pseudo‐compressibility technique employed in the current numerical scheme makes it robust both in space and time. Computational experiments are carried out to assess the influence of Reynolds' number and the spacing between two mild constrictions on the pressure drop across the constrictions. The study reveals that the pressure drop across a series of mild constrictions can get physiologically critical and is also found to be sensitive both to the spacing between the constrictions and the oscillatory nature of the inflow profile. The flow separation zone on the downstream constriction is seen to detach from the diverging wall of the constriction leading to vortex shedding with 3D features earlier than that on the wall in the spacing between the two constrictions. Copyright © 2002 John Wiley & Sons, Ltd.     

Temperature sensors and optical sensors

The dependence of temperature on the fluorescence lifetime and fluorescence intensity ratio using Stark sublevels and thermally coupled (close lying) levels in triply ionized rare earth ions, doped into a variety of glasses and fibers, have been reviewed. Also, it is claimed that not only for the two closely lying levels of triply ionized rare earth ion of the same kind, but also for two different triply ionized rare earth ions, having their excited levels very close to each other, may be used to monitor the temperature. PACS 42.70.Ce     

Self-organized ZnAl2O4 nanostructures grown on -sapphire

Self-organized ZnAl₂O₄ nanostructures with the appearance (in SEM) of high aspect ratio horizontal nanowires are grown on uncatalysed c-sapphire by vapour phase transport. The nanostructures grow as three equivalent crystallographic variants on c-sapphire. Raman and cathodoluminescence spectroscopy confirm that the nanostructures are not ZnO and TEM shows that they are the cubic spinel, zinc aluminate, ZnAl₂O₄, formed by the reaction of Zn and O with the sapphire substrate.     

The case of missing incommensurate smectic A phases

Two binary mixtures of polar liquid crystal materials were previously reported to exhibit three incommensurate smectic A phases predicted for such materials on the basis of phenomenological theory. Results of our recent high-resolution X-ray scattering experiments show that no incommensurate phases exist in the two systems. Wide coexistence regions are found at first order transitions between various frustrated smectic phases of these mixtures. These regions were previously identified as the incommensurate smectic A phases. The phase diagrams of the two systems determined with high-resolution X-ray technique are shown to be in excellent agreement with Baroisa-Prost-Lubensky theory.     

A novel scheme for protection of power semiconductor devicesagainst short circuit faults

Power semiconductor devices find wide application in modern power electronic converters. Protection of these devices against overload/short circuit conditions is of paramount importance. Present day protection topologies employing different circuits have invariably one main drawback in that the fault current reaches the set value before action is initiated to trip the system. This poses a severe stress on the device. Hence an adequate safety margin has to be necessarily provided to prevent excessive device stresses and care has to be taken to see that the device is operated well within its safe operating areas. The present paper proposes a method wherein the slope or rate of rise of the fault current is detected and once the slope exceeds the set reference, action is initiated to trip the system much before the fault current reaches dangerous levels. The method provides a fast means of detection of overload and short circuit currents and can be conveniently adopted for the protection of devices in power transistor/IGBT based inverters against short circuited load conditions or shoot through faults. The possible reduction of stresses in the power devices are also highlighted     

Study of the effect of swift heavy Ni ion irradiation on ruby single crystal by using the XANES and EXAFS techniques

We have made the XAFS measurements at the Cr–K-edge on natural Indian ruby single crystals (corundum) and its two irradiated samples with fluence 1×10¹² Ni⁶⁺ and 5×10¹² Ni⁶⁺ ions/cm². Irradiated samples show interesting changes in their physical appearance. XANES measurements show progressive decrease in Δ_oct value on increase of Ni fluence in irradiated samples. EXAFS measurements on these samples show decrease in Cr–O distance on increase of Ni fluence. Lowering of Δ_oct value is correlated with the increase of Cr–O distance.