Optical properties of Se1−x Sb x thin films (0<x<0.5)

The energy gap (E _g) of approximately 100 nm thick films of the Se_1–x Sb _x system has been investigated using an optical transmission method. E _g is found to decrease linearly with increasing Sb concentration in Se_1–x Sb _x films. No anomalous behaviour in E _g is observed at x = 0.4 as reported earlier by Wood et al.     

Semi-dry pressed tiles from alluvial deposits of northern India

Drying problems are greatly reduced when shaping tiles in semi-dry conditions write J.B. Bhatnagar, R.B. Hajela and R.K. Goel, of the Research Institute at Roorkee, where testing shows that better dimensional accuracy and finish can be achieved compared to traditionally made clay tiles at plastic or stiff plastic consistency.     

Roofing finishes

Scientists at the Central Building Research Institute, CBRI, at Roorkee conclude, in a detailed study as part of their normal research programme, that good-quality roofing tiles possessing adequate breaking strength and durability can be produced from properly blended and processed clay, either on a potter's wheel or on a tile-moulding table.     

Synthesis and performance evaluation of O, O-dialkylphosphorodithioic disulphides as potential antiwear, extreme-pressure and antioxidant additives

The ashless antiwear/EP additives based on phosphorodithioic acids are preferred to their heavy metal complexes, due to operational problems and enviromental restrictions being enforced in many countries. Four O, O-dialkylphosphorodithioic disulphides with varying alkyl chain length from C5 to C10 have been synthesized and their antiwear, EP and antioxidant performance examined vis-à-vis a commercial ZDDP in a mineral base oil. The synthesized products have been found to exhibit appreciable antiwear and antioxidant properties and mild EP performance, which are comparable to that of commercial ZDDP.     

High Data Rate Alamouti Code From Field Extension

Alamouti code is the only known Orthogonal Space Time Block Code (OSTBC) with rate-1. All other known orthogonal codes have rate less than unity. The orthogonal property of OSTBCs reduces the decoding complexity to a large extent. High data rate Space Time Block Codes for arbitrary number of transmit antennas were recently proposed based on Division Algebras. But these STBCs are not orthogonal. Therefore their decoding complexity is very high. In this paper we propose high data rate Alamouti codes from field extensions for two transmit antennas. Our codes have better coding gain than the both high rate codes from division algebra and the rate-1 Alamouti code. Vishwanath R was born in Hyderabad, India in 1982. He did his B.E. in Electronics and Communications Engineering from Birla Institute Of Technology, Ranchi, India in 2002 and Master of Technology in Communications Engineering in 2005 from Indian Institute of Technology Delhi, India.. Currently he is pursuing PhD from Indian Institute of Technology Delhi, India. His research interests include Routing in Optical Networks, Signal Processing, Wireless Communications and Image Processing. He is a member of the IEEE. Bhatnagar Manav R was born in Moradabad, India in 1976. He did his B.E. in Electronics in 1997 and Master of Technology in Communications Engineering in 2005 from Indian Institute of Technology Delhi, India. He has worked as lecturer in Moradabad Institute of Technology, Moradabad, India from 1998–2003. He is currently pursuing PhD from Indian Institute of Technology Delhi, India. His research interests include Routing in Optical Networks, Signal Processing in Wireless Communications and Image Processing. He is a member of the IEEE.     

Effect of optical turbulence in the dye medium on the bandwidth of a narrowband, high-repetition-rate dye laser

An analysis of turbulence in the dye medium of a high-repetition-rate narrowband dye laser is presented, and it is shown that the output bandwidth is proportional to the turbulence length scale, which depends on the Reynolds number. The length scale and the bandwidth both first decrease and then increase as the Reynolds number is increased from -200 to -20,000. The observed bandwidth, as we report and as in the published literature, confirms the validity of the analysis. A Rhodamine 6G grazing-incidence grating, stable dye laser transversely pumped by a copper-vapor laser was used in the experiments.     

Spectral measurements of gamma radiation streaming through ducts

The paper presents the spectral measurements of gamma radiation streaming through multi-legged rectangular concrete ducts for cesium-137 and cobalt-60 sources. Effect of lead lining the inner surface of the duct on the streaming radiation spectrum and optimization of liner thickness for minimum streaming radiation dose have been studied.For three-legged ducts, a comparative analysis of lead lining the entire duct as against lining any one or both the corners of the duct is reported. It is seen that lead lining any one of the corners would reduce the streaming radiation dose by a factor of 5 to 12. Lining both the corners which is nearly as effective as lining the entire duct reduces the dose by a factor of 16 to 60 depending on the source energy and duct dimensions.     

Analysis of a noncavity laser with magnifying optics in front ofthe high-reflectivity mirror

The behavior of a noncavity laser with a magnifying optical element placed in front of the high-reflectivity mirror is analyzed. Using ray matrix analysis, a general formula for estimating the divergence is derived. It is shown that the formula can be applied to lasers with a telescope or a prism placed in front of the high-reflectivity curved or plane mirror at one end. The various noncavity configurations are applied to a copper vapor laser (CVL) and divergence is measured. The calculated and the experimentally observed divergence values are found to be in good agreement     

Slow viscoelastic fluid flow past a rotating sphere

The problem of axially symmetric flow of a particular type of non-Newtonian fluid past a rotating sphere due to a uniform stream at infinity is investigated. The presence of a region of reversed flow is found under certain conditions depending on the angular velocity of the sphere, the speed of the uniform stream and radius of the sphere. This region which is attached to the rear portion of the sphere is found to depend strongly on the viscoelasticity of the fluid. The vortex is seen to move towards the sphere as the viscoelastic parameter increases while the other parameters are kept fixed. As this viscoelastic parameter approaches a critical value, the vortex is found to disappear.