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.     

A procedure for quantitative 13c-n.m.r. application to the characterisation of the naphtha fraction of petroleum crude

A method for optimising the conditions for the quantitative ¹³C-n.m.r. measurement is suggested and has been applied to the compositional studies of naphtha fractions (50–100°C and 100–150°C) of Darius crude oil. The novelty of the method is that we can pre-estimate the pulse repetition time for unknown samples. It has been shown that the various compositional parameters thus obtained are in satisfactory agreement with those obtained from the elemental analysis, fluorescent indicator adsorption (FIA) and ¹H-n.m.r. spectrometry.     

Burden of organochlorine pesticides in blood and its effect on thyroid hormones in women

Man has utilized a wide variety of pesticides to combat the crop pests and vectors of human diseases. However, in this process, he has overlooked the darker side of these noxious chemicals, the concentrations of which have reached the environment and pose serious threats, such as mutagenesis, teratogenesis, carcinogenesis and endocrine dysfunction in various components of the ecosystem. The present study was planned to assess the burden of organochlorine pesticides and their influence on thyroid function in women. The study included a total of 123 women from Jaipur City who visited the Thyroid clinic in SMS Medical College and Hospital. One hundred women showed normal thyroid hormone levels while the remaining 23 women had depleted T4 and high TSH levels. The qualitative and quantitative estimation of organochlorine pesticides was carried out by gas chromatography. Out of the analyzed pesticides, the concentration of p,p'-DDT and its metabolites was higher in all the subjects, but dieldrin was found to be significantly high in the hypothyroid women. The correlation analysis for dieldrin and depleted T4 levels in hypothyroid women elicited an inverse relationship between them.     

Robust optimization of Random Early Detection

Random Early Detection (RED) is the most widely used Adaptive Queue Management (AQM) mechanism in the internet. Although RED shows better performance than its predecessor, DropTail, its performance is highly sensitive to parameter settings. Under non-optimum parameter settings, the performance degrades and quickly approaches that of DropTail gateways. As the network conditions change dynamically and since the optimum parameter settings depend on these, the RED parameters also need to be optimized and updated dynamically. Since the interaction between RED and TCP is not well understood as analytical solutions cannot be obtained, stochastic approximation based parameter optimization is proposed as an alternative. However, simulation based approaches may yield a sub-optimal solution since for these to work, the network needs to be accurately simulated which is, however, infeasible with today’s internet. In this paper, we present an optimization technique for optimizing RED parameters that makes use of direct measurements in the network. We develop a robust two-timescale simultaneous perturbation stochastic approximation algorithm with deterministic perturbation sequences for optimization of RED parameters. A proof of convergence of this algorithm is provided. Network simulations, using direct implementation of the algorithm over RED routers, are carried out to validate the proposed approach. The algorithm presented here is found to show better performance as compared to a recently proposed algorithm that adaptively tunes a RED parameter.