Behaviour of organised disturbances in fully developed turbulent channel flow

In our earlier work we have shown the relevance of stability theory in understanding the sustenance of turbulence in turbulent boundary layers. Here we adopt the same model to study the evolution of organised disturbances in turbulent channel flow. Since the dominant modes are wall modes we find that the stability characteristics in the two flows are nearly identical although the boundary conditions (at the edge of the boundary layer and at the centre of the channel) are different. Comparisons with the experiments of Hussain and Reynolds are also presented.     

Effects of DC testing on AC breakdown strength of XLPE insulatedcables subjected to laboratory accelerated aging

The results of a study performed on crosslinked polyethylene (XLPE) insulated cables tested in the laboratory under accelerated conditions are described. URD-type cables rated at 15 kV were aged at 60 Hz, 6 kV/mm, (150 V/mil) and load cycled daily to 90°C conductor, with water inside the pipe and outside of the samples, for periods of up to 3 years. DC testing was performed before and during the aging. An anticipated significant reduction in the AC breakdown strength is observed in control cables (not DC tested), from 44 kV/mm (1100 V/mil) for unaged cables, to 10 kV/mm (250 V/mil), for aged cables. However, there was no further reduction in the AC breakdown strength of cables subjected to DC testing as compared to those that are not tested with DC. It is concluded that AC breakdown strength is not an effective diagnostic tool for determining the effect of DC testing of URD cables aged under the conditions described     

Lack of effect of food on the steady state pharmacokinetics of BMS-181101, an antidepressant, in healthy subjects

An annual atmospheric pollen survey was performed for 14 consecutive years in the autumn at Sakado city, Saitama prefecture. The survey was performed on the transition of pollen dispersion of major allergen plants: ragweed (Ambrosia spp.), Humulus japonicus, Artemisia spp. and Gramineae. 1. Annual total pollen count of ragweed showed marked increases beginning from 1991. Total pollen count in 1991 was 8.8 times and that in 1996 was 18.6 times that in 1983. This increase is probably caused by marked proliferation of giant ragweed which is left without mowing as it is on a dry riverbed, and consequently produces much more pollen than short ragweed. 2. Annual increases in total pollen counts of other major plants which disperse their pollen in the same season as ragweed were 0.95 times in 1991 and 0.5 times in 1996 that in 1983 for Humulus japonicus, 0.68 times in 1991 and 1.5 times in 1996 that in 1983 for Artemisia spp. and 1.3 times in 1991 and 1.4 times in 1996 that in 1983 for Gramineae. None of these species showed a marked increase of pollen dispersion although they showed some annual variation. The above findings suggest that changes in the proliferous state of various allergenic plants due to environmental change should be considered with respect to characteristics of pollen allergy.     

Edge passivation and related electrical stability in silicon powerdevices

Factors governing long-term stability of silicon power devices are discussed with particular reference to a major failure mechanism observed in a thyristor device. The device failure was due to electrical instability during an electrical and thermal stability storage test, wherein it was observed that the reverse blocking voltage deteriorated under applied bias at the rated maximum junction temperature. The major cause of this failure was identified as lack of exhaust during the edge passivation and curing process due to which excessive chemical deposits are retained in the bevel region of the silicon element. This contributes to surface leakage current and, hence, a rapid degradation of the off-state characteristics. An orthogonal array experiment was employed to optimize the process factors and levels. The manufacturing process was then modified by incorporating an effective exhaust system in the passivant curing oven. This resulted in marked improvements in the electrical stability and manufacturing yield of this device     

Magnetic and transport properties of Laves phase Dy1−xMmxCo2 (x = 0–0.5) alloys

The influence of Mm substitution (Mm = mischmetal) on structural, transport and magnetic properties of (Dy_1?xMm_x)Co₂ (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) alloys has been investigated by means of X-ray diffraction (XRD), temperature dependent electrical resistivity (ρ(T)), ac susceptibility (χ(T)) and thermopower (S(T)). XRD patterns show the formation of solid solutions crystallizing with cubic Laves (C15) type structure at room temperature. The pronounced discontinuities in the resistivity and thermopower at Curie temperature (T_C) are explained based on the suppression of the spin-fluctuation contribution. The gradual decrease in T_C and sharpness of discontinuities in ρ(T) and S(T) with increasing Mm substitution has been discussed.     

Peristaltic transport in an asymmetric channel with heat transfer — A note

The problem of heat transfer for the motion of a viscous incompressible fluid induced by travelling sinusoidal waves has been analytically investigated for a two-dimensional asymmetrical channel. The channel asymmetry is produced by choosing the peristaltic wave train on the walls to have different amplitudes and phase. The flow is investigated in a wave frame of reference moving with the velocity of the wave. The momentum and energy equations have been linearized under long-wavelength and low-Reynolds number assumptions and closed form expressions for temperature and coefficient of heat transfer have been derived. The effect of Hartmann number, Eckert number, width of the channel and phase angle on temperature and coefficient of heat transfer are discussed numerically and explained graphically.     

An Efficient,Stable and Reusable Palladium Nanocatalyst: Chemoselective Reduction of Aldehydes with Molecular Hydrogen in Water

Palladium nanoparticles (Pd‐BNP) stabilized by a binaphthyl‐backbone can be efficiently used for the chemoselective reduction of aldehydes in the presence of hydrogen at room temperature in water. The Pd‐BNP catalyst is easily recovered and reused for five catalytic cycles.