Indian Journal of Pure and Applied Physics

http://www.niscair.res.in

 

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VOLUME 40 NUMBER 10 OCTOBER 2002

CODEN:IJOPAU 40(10) 679-758(2002) ISSN: 0019-5596

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CONTENTS

 

Electromagnetism, Optics, Acosutics, Heat Transfer, Classical Mechanics and Fluid Dynamics

Effect of ammonium halides on the temperature of sound velocity maximum of water

G Venkata Ramana, E Rajagopal & N Manohara Murthy

683

Squeezed states in third harmonic generation

Jawahar Lal*, R M P Jaiswal & B S Rajput

690

Induced twist grain boundary phase in the binary mixtures of cholesteryl caprylate and
nonyloxybenzoic acid

Ravindra Dhar*, A K Srivastava & V K Agrawal

694

Field-dependent sound attenuation in barium titanate, strontium titanate and potassium tantalate type

perovskites

D S Lingwal*, U C Naithani & B S Semwal

701

MHD free convective flow through a porous medium between two vertical parallel plates

Atul Kumar singh

709

Design and development of an inexpensive novel OTDR type system for detection of fiber cracks
and breaks

S Kher*, S Chaubey, A L Chkraborty, V Bhanage & T P S Nathan

750

Condensed Matter: Structure, Mechanical and Thermal Properties

Lattice dynamics of thorium using semi-nonlocal pseudopotential

J K Baria, P N Gajjar & A R Jani*

 

714

Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties

Integrating communication with sensing micro-bending of multi-mode optical fibre

H K Sardana*, Gaurav Julka & J K Chhabra

 

720

Electrical Properties of boron delta-layers in silicon

M O Hakim* & M Mozibur Rahman

726

Interdisicplinary Physics and Related Areas of Science and Technology

Analytical models for the angular distributions of filter generated scatter in diagnostic radiology

A A Okunade*, F O Ogundare & L A Hussain

732

Geophysics, Astronomy and Astrophysics

Empirical scaling relationships between earthquake magnitudes, epicentral distances and amplitudes of

radon anomalies in N-W Himalaya

Vivek Walia, H S Virk* & Puneet Kumar

743

News Scan

New reliable sensors for magnetic field measurement using silver chalcogenides

Tarun Banerjee

 

754

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*The corresponding author has been indicated by (*) mark in case of papers with more than one author

 

Indian Journal of Pure & Applied Physics

Vol. 40, October 2002, pp. 683-689

Effect of ammonium halides on the temperature of sound velocity maximum of water

G Venkata Ramana, E Rajagopal & N Manohara Murthy

Effect of ammonium halides on the temperature of sound velocity maximum (TSVM) of water has been studied by determining the ultrasonic velocity with an accuracy of 0.003 % using single-crystal variable-path interferometer working at 3 MHz. The velocity measurements were carried out at @ 2 C intervals over a range of 5 C to either side of the TSVM of the solutions. The accuracy in fixing the TSVM is 0.2 C. The shift in TSVM of water due to the addition of the NH4Cl, DTobs, is found to be positive up to w @ 3.4 10-2 and negative thereafter, where w represents weight fraction of the solute. The shifts in TSVM of water due to the addition of the NH4Br and NH4I are found to be negative throughout the concentration range. The structural contribution to the shift in TSVM of water, DTstr, is found to be positive for NH4Cl and increases with increase in the concentration nonlinearly. DTstr for NH4Br is almost zero up to w @ 3 10-2 and thereafter becomes negative. DTstr for NH4I is found to be negative throughout the concentration range. The results are explained in terms of the structure, making and breaking nature of anions and cations present in the solutions.

Indian Journal of Pure & Applied Physics

Vol. 40, October 2002, pp. 690-693

Squeezed states in third harmonic generation

Jawahar Lal, R M P Jaiswal & B S Rajput

Field amplitude squeezing of the third harmonic mode in a non-linear crystal has been investigated and it has been shown that the squeezing occurs for selective phase values of the fundamental mode of the incident light when calculated up to fourth power of the interaction time. It is also shown that, the squeezing occurs with Poissonian photon-statistics of the field.

Indian J Pure & Applied Physics

Vol. 40, October 2002, pp. 694-700

Induced twist grain boundary phase in the binary mixtures of cholesteryl caprylate and nonyloxybenzoic acid

Ravindra Dhar and A K Srivastava & V K Agrawal

Binary mixtures of cholesteryl caprylate (ChC) and nonyloxybenzoic acid (NOBA) having different mole ratios have been studied using differential scanning calorimeter (DSC) and polarizing microscope (PM). ChC has monotropic chiral nematic (N*) mesophase in the cooling cycle whereas, NOBA has enantiotropic nematic (N) and smectic C (SmC) mesophases. Transition temperatures and enthalpies of these mixtures have been determined with the help of DSC, whereas different mesophases have been identified by their typical textures as viewed under polarizing microscope. Addition of NOBA in ChC induces smectic A (SmA) and twist grain boundary A (TGBA) phases between two critical concentrations.

Indian Journal of Pure & Applied Physics

Vol. 40, October 2002, pp. 701-708

Field-dependent sound attenuation in barium titanate, strontium titanate and potassium tantalate type perovskites

D S Lingwal, U C Naithani & B S Semwal

A theoretical expression for attenuation constant in para-electric phase is described. Taking electric field as parameter, variation of attenuation constant with frequency and temperature is also discussed by considering third and fourth order anharmonic interactions. The attenuation constant increases with increasing temperature and frequency in presence of an electric field. In the vicinity of the Curie temperature, the attenuation constant increases anomalously. The results obtained are compared with the results of others.

Indian Journal of Pure & Applied Physics

Vol. 40, October 2002, pp. 709-713

MHD free convective flow through a porous medium

between two vertical parallel plates

Atul Kumar Singh

Free convective flow of a viscous, incompressible, electrically conducting fluid through a porous medium between two vertical parallel plates which are heated or cooled uniformly, under a pressure gradient in presence of uniform transverse magnetic field has been studied. The governing equations are solved to obtain approximate analytical solutions for velocity field and temperature distribution for small values of Rayleigh number, using regular perturbation technique. Two physical situations, namely, steady heating of ascending cold fluid (SHACF) and steady cooling of ascending hot fluid (SCAHF) have been investigated. The effect of various parameters on velocity field, temperature distribution, mass flow rate ratio, friction factor ratio and heat transfer rate has been discussed.

 

Indian Journal of Pure & Applied Physics

Vol. 40, October 2002, pp. 750-753

NOTE

Design and development of an inexpensive, novel OTDR type system for detection of fiber cracks and breaks

S Kher, S Chaubey, A L Chakraborty, V Bhanage & T P S Nathan

The optical time domain reflectometry signature of few fibers has been recorded using different lasers having different pulse energy. The signature corresponds to the light scattered back by the fiber towards the input end, versus time. One of the fiber signatures, obtained using nitrogen laser as light source, clearly displays few spikes corresponding to minor cracks in it. Suitability of this laser for OTDR applications has been tested.

Indian Journal of Pure & Applied Physics

Vol. 40, October 2002, pp. 714-719

Lattice dynamics of thorium using semi-nonlocal pseudopotential

J K Baria, P N Gajjar & A R Jani

A semi-nonlocal pseudopotential is proposed to calculate lattice dynamics of fcc thorium. A unique technique is suggested to determine the parameter of the potential. A new criterion for the selection of screening function is suggested, for the first time, to incorporate exchange and correlation effects in the pseudopotential form factor. The present calculations have produced relatively better theoretical values compared to earlier reports for phonon dispersion curves, C11, C12, B and the propagation velocities of elastic waves.

Indian Journal of Pure & Applied Physics

Vol. 40, October 2002, pp. 720-725

Integrating communication with sensing

micro-bending of multi-mode optical fibre

H K Sardana, Gaurav Julka & J K Chhabra

Environment perturbations on a multi-mode fibre lead to changes in intensity at the output due to bending induced losses. A carrier signal has been modulated in a form such that, the amplitude of the light signal is not affected, which is left for sensing light intensity variations due to micro-bending. Pulse frequency modulation has been suggested for this purpose using a voltage-to-frequency converter. This information is again decoded at the receiver end using frequency-to-voltage conversion. In this manner, a fibre link, which is acting as a perturbation sensor, also acts as a communication link without affecting the sensing capability as long as the link is not damaged due to perturbation. It is known that, the multi-mode fibre can be used to sense any form of environment perturbation, such as strain, pressure, force, position, acceleration, temperature etc1-3. The proposed approach is applicable in all these situations with integrated communication capability.

Indian Journal of Pure & Applied Physics

Vol. 40, October 2002, pp. 726-731

Electrical properties of boron delta-layers in silicon

M O Hakim & M Mozibur Rahman

Electrical properties of MBE grown boron d-layer in Si have been investigated in the temperature range 10-300 K and a comparative study with their uniform doping counterpart has been presented. Various boron doping levels from 1012-1014 cm-2 in the d-layer show that, with the fall of temperature from 300 to 50 K, Hall mobility first increases followed by a rapid decrease, and at temperature 50 K, it becomes almost constant. Higher doping level in the sample grossly lowers the value of Hall mobility but its variations with temperature are almost similar to each other. Existence of the dominant carrier scattering mechanism has also been reported. In all the samples, freeze-out of carriers have been clearly noticed below 100 K. Existence of a Mott metal-non-metal transition in the sample has been observed at low temperature region when the doping concentration exceeds a critical high value of 61013 cm-2, and this has been found consistently with the other observations like zero activation energy and negative TCR. The value of minimal metallic conductance for the samples has also been reported.

Indian Journal of Pure & Applied Physics

Vol. 40, October 2002, pp. 732-742

Analytical models for the angular distributions of

filter-generated scatter in diagnostic radiology

A A Okunade, F O Ogundare & L A Hussain

Analytical models for describing large volume of data on angular distributions of photons that have undergone Compton & Rayleigh interactions while passing through spectrally equivalent filter materials commonly considered useful in diagnostic radiology have been developed. The comparison of the results of simulation of scatter data from these filter materials, using Monte Carlo techniques with those from the models developed, are in reasonable agreement.

Indian Journal of Pure & Applied Physics

Vol. 40, October 2002, pp. 743-749

Empirical scaling relationships between earthquake magnitudes, epicentral distances and amplitudes of
radon anomalies in N-W Himalaya

Vivek Walia, H S Virk & Puneet Kumar

Radon data accumulated during the time-window (1992-1999) in the grid (30-34oN, 74-78oE) in N-W Himalaya has been analysed vis-a-vis seismic data recorded in the same area, supplied by Indian Meteorological Department (IMD) network. In general, there is a positive correlation between total radon emission and the micro-seismicity in the area under investigation. The earthquake magnitude has moderate positive correlation with epicentral distance and low positive correlation with amplitude of radon precursory signal, whereas, both show low negative correlation between them. Empirical scaling relations are proposed using the best-fit straight line from the log-linear graphs between magnitude of the events (M) and log of the product of amplitude of radon anomaly (A) and epicentral distance (D). The error between recorded and the calculated magnitude is also taken into account. The number of points lying within 25 % limit is 74 out of the total 142 cases, on which the test is applied. The error range is higher at lower epicentral distances and magnitudes, which shows that, the local geology and tectonics have predominant influence on radon signals.

Indian Journal of Pure & Applied Physics

Vol. 40, October 2002, pp. 754-754

News Scan

New reliable sensors for magnetic field measurement using silver chalcogenides

With the advancement of technology, the demand of scientists entering new frontiers of research such as, investigation of novel quantum states, magnetic resonance imaging, etc., for a steady magnetic field of higher and yet higher value has been realized. Today, compact magnets with a steady magnetic field of 20 T and a pulsed field of 40 T, are routinely produced. Pulsed fields in the range 50-300 T from 108 to 106 s pulses have also been achieved. The problem faced however is, measurement of such high magnetic fields with accuracy and consistency, thus requiring a magnetic field sensor that works over a wide range of magnetic field and is insensitive to temperature