Passive microwave remote sensing of the atmosphere and ocean

The microwave remote sensing experiments conducted during the last decade using airborne and spaceborne sensors are now evolving as operational spacecraft observation systems. Microwave sounding unit (MUS) onboard TIROS-N regularly provides global atmospheric temperature profile required for numerical weather prediction. The monitoring of composition profile and geophysical parameters from space platform is now a reality and holds a great promise for future meteorological and oceanographic research. This review paper summarises the recent advances and future opportunities in passive microwave radiometry. Indian microwave remote sensing programme and achievements to date are also described.     

Qualitative percolation study of free-radical cross-linking polymerization

Summary Simulations of a conceptually simple model for free-radical cross-linking polymerization have been performed in relation to experimental indications for (temporary) microgel particles. Many qualitative features ascribed to microgels show up in the simulation. In particular this model yields qualitative agreement with experiments on the conversion dependence of the number of pendant double bonds.     

Analysis and modelling of edm parameters

Metal removal in electro-discharge machining (edm) is basically a thermal erosion process where the heat transfer is predominantly through conduction. In this paper, a two-dimensional heat transfer model, assuming the plasma channel to be a disc heat source, has been employed to study the effects of edm input parameters, such as pulse duration, pulse energy and material properties, on metal removal and crater shape. Reasons for somewhat poor correlation between theoretical and experimental data are discussed.     

Theoretical evaluation of ultrasonic velocity in molten electrolytes

Significant structure theory and Flory theory are successfully applied for evaluating the ultrasonic velocity in five molten alkali halides (NaCl, NaBr, KCl, KBr, and KI). Later theory provides better estimates and the theoretical results are in fairly good agreement with experimental findings. Hard sphere models and cellular hole theory were also attempted. The results are not encouraging.     

On threshold and flat-band voltages for MOS devices with polysilicon gate and nonuniformly doped substrate

Expressions for the flat-band voltage V_FB and threshold voltage V_T for MOS devices with polysilicon gate and nonuniformly doped substrate are given. The role of metal-semiconductor contacts and the assumptions involved in the analysis are discussed. Both V_FB and V_T have three extra terms over the conventional expressions, two terms result from nonuniform doping and one is due to a voltage drop in the gate produced by space charge. Contrasts are made to devices with metal gates and uniformly doped substrates. The commonly used expression for mobile channel charge in terms of gate voltage is clarified.     

Mechano and thermoluminescence of gamma-irradiated CaSO4:Dy phosphor

In order to have a better idea of the interaction of the defect centres produced by y-irradiation with dislocation in the processes of deformation destruction, mechanoluminescence (ML) and thermoluminescence (TL) of gamma-irradiated CaSO4:Dy, these phosphors have been investigated. CaSO4:Dy phosphors were prepared by dissolving CaSO4.2H2O in sulphuric acid and evaporating the excess acid around 300 degrees C. ML was excited impulsively by dropping a load on to the sample. Two peaks have been observed in the ML intensity against time curve. The total light output, i.e. integrated ML intensity, increases with concentration of dopant, strain rate and with irradiation doses. The TL glow curves of CaSO4:Dy phosphors at different concentrations of dopant and irradiation doses were also recorded. Studies of the influence of post-irradiation annealing on the ML of CaSO4:Dy show that with the removal of the TL dosemetric peak (approximately 210 degrees C) the ML intensity decreases markedly. A spectroscopic study of ML and TL has also been carried out to elucidate the mechanism of ML. Correlation between ML and TL has also been found.     

A Scheduling Scheme for Controlling Allocation of CPU Resources for Mobile Programs

There is considerable interest in developing runtime infrastructures for programs that can migrate from one host to another. Mobile programs are appealing because they support efficient utilization of network resources and extensibility of information servers. In this paper, we present a scheduling scheme for allocating resources to a mix of real-time and non real-time mobile programs. Within this framework, both mobile programs and hosts can specify constraints on how CPU should be allocated. On the basis of the constraints, the scheme constructs a scheduling graph on which it applies several scheduling algorithms. In case of conflicts between mobile program and host specified constraints, the schemes implements a policy that resolves the conflicts in favor of the host. The resulting scheduling scheme is adaptive, flexible, and enforces both program and host specified constraints.     

Evaluation of sound velocity in binary molten electrolytes

A comparison of sound velocity evaluated from Nomoto's relation, ideal mixing relation Jacobson's free length theory and Schaaffs' collision factor theory has been made in six binary molten electrolytes (NaClKCl, NaClRbCl, NaClCsCl, KClLiCl, KClRbCl, KClKBr) at 800°C. The agreement between theoretical and experimental values is quite satisfactory. Discrepancies in the sound velocity values are maximum in the case of the NaClCsCl system where maximum interactions are observed. Non-ideality in the mixtures has been discussed in terms of sound velocity.