Millimeter wave attenuation in relation to rain rate distribution over a tropical station

Rain, perhaps, is the worst offender for utilising Millimeterwaves in practice. This paper describes the rain rate distribution from which millimeterwave attenuation distribution have been attempted. Results reveal that in our location (Calcutta: lat 23°N long 88.5°E) the rain rate distribution fits well with normal distribution. The cumulative distribution of rain rate also prompted the present authors to find out rain attenuation cumulative distribution for both terrestrial and earth-space paths in millimeterwave band.     

Universality in the effective pair interaction ofd-shell metals — Compressibility and vacancy formation energy of 3d-liquid metals

Like liquid alkali metalsd-shell liquid metals show scaling behaviour in structure and interaction potentials. A realistic interaction potential model, properly parametrized can reasonably describe the universality in the isothermal compressibility and vacancy formation energy of 3d-liquid metals in electron ion plasma model.     

On the effect of cure cycle parameters and dopants on pre and post irradiation annealing response of CR-39 track detectors

The effect of additives and cure cyle parameters on pre and post irradiation annealing characteristics of CR-39 detectors has been investigated. Effect of pre and post irradiation annealing on bulk etch rate, sensitivity, track diameter and etching behaviour of various CR-39 detectors has been investigated.     

Effective intermolecular potential energy function. Hydrogen-bonded structure of water

The average effective pair potential energy function between two neighbouring molecules has been computed from the centre structure factor data of water and this shows an unusual feature at short range due to strong hydrogen bonding. The effective potential is highly temperature dependent and at elevated temperature it turns out to be approximately like that for simple liquids. The effective potential can be represented satisfactorily by the square well model.     

On the derived length of units in group algebra

Let G be a finite group G, K a field of characteristic p ≥ 17 and let U be the group of units in KG. We show that if the derived length of U does not exceed 4, then G must be abelian.     

Synthesis,characterization, and catalytic activity of a polymer-supported copper(II) complex with a thiosemicarbazone ligand

A thiosemicarbazone Cu(II) complex anchored to a polystyrene framework has been synthesized and characterized by analytical and spectroscopic techniques. The complex was found to be a highly active catalyst for the oxidation of various organic substrates including alkenes and alcohols using H₂O₂ as oxidant. The reaction conditions were optimized with respect to temperature, solvent, oxidant, catalyst amount, and substrate to peroxide ratio. The heterogeneous catalyst was reused five times without significant loss of activity. A comparison between the catalytic activities of this polymer-supported Cu(II) complex and its homogeneous analogue was carried out.     

Gold-catalyzed 1,2-difunctionalizations of aminoalkynes using only N- and O-containing oxidants

We report two viable routes for the 1,2-difunctionalization of aminoalkynes using only oxidants. In the presence of a gold catalyst, nitrones enable the oxoamination of aminoalkynes 1 to form 2-aminoamides 2. With a suitable gold catalyst, nitrosobenzenes implement an alkyne/nitroso metathesis of the same substrates to give 2-oxoiminylamides 3. These two novel oxidations also provide 1,2-aminoalcohols with opposite regioselectivity via NaBH(4) reduction in situ.     

Low-temperature magnetization relaxation in magnetic molecular solids

The low temperature relaxation of the magnetization in molecular magnetic solids such as Fe₈ is studied using Monte Carlo simulations. A set of rate equations is then developed to understand the simulations, and the results are compared. The simulations show that the magnetization of an initially saturated sample deviates as a square-root in time at short times, as observed experimentally, and this law is derived from the rate equations analytically.     

An estimation of S/N degradation at millimeter waves during rain events

The use of Ka Band (20/30 GHz) for future satellite communications has been addressed. The exploitation of Ka band with a bandwidth of 2500 MHz seems to represent the largest significant achievement in satellite communications potential, so far. The problems associated with the use of this frequency band such as attenuation and receiver noise temperature (floor) variation with rain has been addressed. The receiver noise floor variation with rain has so far been ignored. Therefore, in view of propagation and noise study over this Ka Band, both signal attenuation and receiver noise floor variations with rain rate are estimated using dual frequency radiometers operating at 22.235 and 31.4 GHz over a tropical station, Calcutta, India.     

Amplitude-frequency characteristics of non-linear vibrations of clamped elliptic plates carrying a concentrated mass

The influence of a concentrated mass on the amplitude-frequency characteristics of large amplitude-transverse vibrations of an isotropic clamped elliptic plate has been investigated by the application of the von Karman equations.