Indian Journal of Pure and Applied Physics

 

Total visitors: 1,146  since 11-12-06

 

Volume 44                                                        Number 11     NOVEMBER 2006

CODEN: IJOPAU 44 (11) 795-880                      ISSN: 0019-5596

 

 

CONTENTS





Review Article

 

Laser power meter: A simple optoelectronic set-up

D Choudhury*, M Devi & A K Barbara

801

General

 

Unsteady two-dimensional flow of a radiating and chemically reacting MHD fluid with time-dependent suction

J Prakash* & A Ogulu

805

Atomic and Molecular Physics

 

Non-radiative energy transfer between Eu3+ and Er3+ ions in zinc phosphate glass

B C Joshi*, Charu Ch Dhondiyal, D K Upreti & Bhawana Khulbey

811

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

 

Ultrasonic investigation of induced dipole-induced dipole interactions in binary liquid mixtures at 298K

V Kannappan* & R Jaya Santhi

815

Amplitude distribution analysis of acoustic emissions and investigation of the development of brittle fracture in rock

M V M S Rao* & K J Prasanna Lakshmi

820

Physics of Gases, Plasmas and Electric Discharges

 

Analysis of disruptive instabilities in Aditya tokamak discharges

Asim Kumar Chattopadhyay*, Arun Anand, C V S Rao*, Shankar Joisa

826

Kinetic model of Alfven wave in dusty plasma

Nidhi Shukla, Ruchi Mishra, P Varma & M S Tiwari*

834

Condensed Matter: Structure, Mechanical and Thermal Properties

 

Study of attractive hard – core Yukawa fluids of variable range

D K Dwivedee & K N Khanna*

845

Kinetic theory of Shubnikov-de Hass oscillations in GaAs/AlGaAs

S Fujita*, S Horie, A Suzuki & D L Morabito

850

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

 

Dielectric relaxation phenomena of some aprotic polar liquids under giga hertz electric field

A Karmakar, U K Mitra, K Dutta, S K Sit & S Acharyya

856

Gas sensing properties of undoped and antimony doped tin oxide films prepared by spray pyrolysis and electron beam evaporation method

K S Shamala, L C S Murthy & K Narasimha Rao*

867

Interdisciplinary Physics and Related Areas of Science and Technology

 

Low-voltage CCII based all-pass/notch filter

Susheel Sharma, S S Rajput, K Pal, L K Mangotra & S S Jamuar*

871

 

___________

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


 

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 801-804

 

Laser power meter: A simple optoelectronic set-up

D Choudhury, M Devi & A K Barbara

Department of Physics, Gauhati University, Guwahati, Assam 781 014

Received 16 December 2005; revised 8 May 2006; accepted 2 August 2006

 

The development and working of an optoelectronic set-up have been described and the reliability of this system for use as a laser power meter mainly for CW operation has been examined and adopted it as a field model. Subsequently, its performance in measurement of pulsed lasers in limited cases is also presented.

Keywords: Optical detectors, Laser power, Optoelectronic

IPC Code: H01L

 

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 805-810

 

Unsteady two-dimensional flow of a radiating and chemically reacting
MHD fluid with time-dependent suction

 

J.Prakash*

Department of Mathematics, University of Botswana, Gaborone, Botswana

*E-mail: prakashj@mopipi.ub.bw

and

A. Ogulu

School of Physics, Westville Campus, University of KwaZulu-Natal, Durban, South Africa

Received 23 January 2006; revised 10 July 2006; accepted 6 September 2006

The study considers the problem of unsteady two-dimensional, laminar, boundary layer flow of a viscous, incompressible, electrically conducting fluid along a semi-infinite vertical plate in the presence of thermal and concentration buoyancy effects. A time-dependent suction is assumed and the radiative flux is described using the differential approximation for radiation. Asymptotic series expansion about a small parameter e, is performed to obtain the flow fields. Our results show that when the thermal and solutal Grashof numbers increase, the thermal and concentration buoyancy effects are enhanced and so the fluid velocity increases. Furthermore, when the Prandtl and Schmidt numbers increase, the thermal and concentration levels decrease resulting in reduced fluid velocity. We, further, found that the skin-friction coefficient increases due to increase in the thermal and concentration buoyancy effects, while it decreases as a result of increase in the Schmidt number. The Nusselt number decreases as the Prandtl number increases just like the Sherwood number decreases with increase in the Schmidt number. These results are in good agreement with results from the literature.

Keywords: Buoyancy effects, Radiative flux, Suction/blowing

IPC Code: G01N

 

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 811-814

 

Non-radiative energy transfer between Eu3+ and Er3+ ions in zinc phosphate glass

B C Joshi, Charu Ch Dhondiyal, D K Upreti & Bhawana Khulbey

Department of Physics, Kumaun University, S S J Campus, Almora (Uttaranchal), India

Received 20 March 2006; revised 28 August 2006; accepted 8 September 2006

 

A study of non-radiative energy transfer in Eu3+-Er3+ has been done by observing the steady state emission of Eu3+ with varying concentration of Er3+ in zinc phosphate glass at room temperature. It has been observed that Eu3+ ion emission intensity decreases with increasing Er3+ concentration resulting in a non-radiative energy transfer from Eu3+ to Er3+. The energy transfer mechanism for Eu-Er system is mainly found electric dipole-dipole in nature. Various parameters necessary for quantitative study e.g. energy transfer efficiencies, transfer probabilities etc. between Eu3+ and Er3+ have been computed.

Keywords: Zinc phosphate glass, Non-radiative energy transfer

IPC Code: G01J 3/12

 

 

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 815-819

 

 

 

Ultrasonic investigation of induced dipole-induced dipole interactions in binary liquid mixtures at 298K

V Kannappan# & R Jaya Santhi

#Postgraduate and Research Department of Chemistry, Presidency College, Chennai
Department of Chemistry, Auxilium College, Vellore

Received 4 July 2005; revised 18 October 2005; accepted 4 September 2006

 

Induced dipole-induced dipole interactions have been studied in binary liquid mixtures of benzene, n-hexane, carbon tetra chloride and p-xylene with cyclohexane by ultrasonic velocity (U), density (ρ) and viscosity (η) measurements at 298K and at different mole fractions. Acoustical parameters such as adiabatic compressibility (β), free volume (Vf) internal pressure (πi), intermolecular free length (Lf), available volume (va), cohesive energy (CE) Rao constant (R) and molecular interaction parameter (χU) were calculated from the experimental data. The ultrasonic investigations on four binary liquid systems reveal that in the liquid mixture containing non-polar liquids, there exist weak induced dipole-induced dipole attractions. The strength of this type of intermolecular attraction depends on the polarizability of molecules of the components present in the mixture.

Keywords: Interactions, Induce dipole, Mole fractions, Polarizability, Adiabatic Compressibility, Ultrasonics, Binary liquid mixtures

IPC Code: B01J 19/10

 

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 820-825

 

 

Amplitude distribution analysis of acoustic emissions and investigation of the development of brittle fracture in rock

 

M V M S Rao & K J Prasanna Lakshmi

National Geophysical Research Institute, Hyderabad 500 007

Received 7 June 2005; revised 12 July 2006; accepted 3 August 2006

Materials undergoing brittle failure produce large number of acoustic emissions (AE) of varying amplitudes. The most useful way to describe and analyse the AE amplitude distribution is by computing the b-value (slope of the log-linear frequency-magnitude distribution of AE). Conventionally, the b-value of AE is calculated using the methods adopted in seismology since many similarities exist between AE and seismic waves. The b-value is usually obtained either from the cumulative frequency distribution or the discrete frequency distribution of earthquake magnitudes and the same principles hold good for the AE data also. We have carried out the AE amplitude distribution analysis using advanced software (Mistras-2001) and computed the AE b-value using the Gutenberg-Richter relationship for the cumulative frequency distribution data and Aki’s method for the discrete distribution data. The results obtained by both these methods to evaluate the fracture process in a granite rock are compared and discussed as a case study in this paper. Useful inferences about the fractal distribution of crack lengths leading to the dynamic failure of the test rock could also be obtained using the AE b-value data.

Keywords: Microcracking, AE b-value, Rock fracture, Fractals

IPC Code: G10K11/16

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 826-833

 

Analysis of disruptive instabilities in Aditya tokamak discharges

 

Asim Kumar Chattopadhyay*, Arun Anand, C V S Rao, Shankar Joisa & Aditya team

Institute for Plasma Research, Bhat, Gandhinagar 382 428

*E-mail: asim@ipr.res.in

Received 8 February 2006; accepted 8 September 2006

 

Major disruptions and sawteeth oscillations (internal disruptions) are routinely observed in ohmically heated Aditya tokamak discharges and their characteristics have been investigated with the help of soft X-ray (SXR) tomography along with other diagnostics. The SXR tomography is carried out with the help of single array of detectors assuming rigid rotation of the modes to analyse the mode structure of sawtooth internal disruptions. Coupling of m/n=2/1 and m/n=1/1 modes could be the main mechanism for the major disruption. Sawteeth periods were measured and compared with the scaling laws and found to be in good agreement.

Keywords: Tokamak, MHD instabilities, Tomography

IPC Code: H05H

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 834-844

 

Kinetic model of Alfven wave in dusty plasma

Nidhi Shukla, Ruchi Mishra, P Varma & M S Tiwari*

Department of Physics & Electronics,

Dr H S Gour University Sagar (M P) 470 003

Received 28 September 2005; accepted 25 July 2006

The kinetic Alfven waves are investigated for the dusty plasma using Maxwell-Boltzmann-Vlasov equations. The dispersion relation and damping rate are derived including the effect of negatively charged dust grain in the magnetized plasma. The effect of ion-gyro radius is included in the analysis for both the regions  and , where  the perpendicular wave number is and  is the ion-gyro radius. The wave frequency and damping rate are numerically analyzed for auroral acceleration region. It is observed that dust grains modify the wave frequency and damping rate. The effect of dust particle is to increase the wave frequency and enhance the damping rate. It is predicted that energy carried by kinetic Alfven wave observed in plasma sheet boundary layer by different satellites is dissipated in the auroral acceleration region accelerating auroral particle responsible to the auroral emission processes.

Keywords:  Dusty plasma, Kinetic Alfven wave, Plasma sheet boundary layer, Auroral acceleration region

IPC Code: H05H

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 845-849

 

 

Study of attractive hard-core Yukawa fluids of variable range

 

D K Dwivedee & K N Khanna*

Department of Physics VSSD College, Kanpur

*E-mail: knkhanna@rediffmail.com

Received 13 October 2005; accepted 29 June 2006

The thermodynamic and structural properties of purely attractive hard-core Yukawa particles in the fluid state are determined in the high-temperature expansion of the mean spherical solution (MSA-HTE) to the Ornstein-Zernike equation. The radial distribution function at contact of attractive hard-core Yukawa particles is reported by introducing second order perturbation term, thus improving its accuracy. Further, systems of particles with Yukawa screening length λ = 1.8, 3.0 and 4.0 are examined and compared with the results obtained by simulation.

Keywords : Attractive Yukawa fluid, Screening length, Mean-spherical approximation

IPC Code : G01K

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 850-855

 

Kinetic theory of Shubnikov-de Hass oscillations in GaAs/AlGaAs

S Fujita

Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA

and

S Horie & A Suzuki

Institute of Pure and Applied Physics, Graduate School of Science, Tokyo University of Science

Shinjiuku-ku, Tokyo 162-8601, Japan

and

D L Morabito

Department of Physics, Rochester Institute of Technology, Rochester, New York 14623, USA

Received 20 December 2005; accepted 2 May 2006

 

A quantum theory is developed for the Shubnikov-de Haas oscillation in GaAs/AlGaAs. The envelope of the oscillation for the magnetoresistance is shown to arise from the thermal average of the sinusoidal density of states with the Fermi distribution function for the field-dressed electrons (guiding centers). It is proportional to , where M* is the magneto-transport mass. Comparison between theory and experiment directly gives the M*-value: M*=0.30 m which is 4.5 times the cyclotron mass m*=0.067 m. The carriers are likely to be the c-fermions, each electron with two flux quanta. The theory avoids the use of the Dingle temperature arising from the Landau level damping. The magneto-conductivity  for the center of oscillations is given by , where n is the carrier density and  is the relaxation rate. This useful formula is obtained by applying kinetic theory (and the Boltzmann equation method) to the motion of the dressed electrons.

Keywords: Magnetoresistance, Shubnikov-de Hass oscillations, Quantum Hall effect, Magneto-transport mass

IPC Code: H01F1/40

 

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 856-866

 

Dielectric relaxation phenomena of some aprotic polar liquids
under giga hertz electric field

A Karmakar, U K Mitra, K Dutta, S K Sit & S Acharyya

Department of Physics, Raiganj College (University College), P.O. Raiganj, Dist: Uttar Dinajpur (West Bengal)

 

Received 17 October 2005; revised 27 June 2006; accepted 5 July 2006

The two relaxation times t1 and t2 due to rotations of the flexible parts and the whole molecules of some aprotic polar liquids (j) like N, N-dimethyl sulphoxide (DMSO); N, N-dimethyl formamide (DMF), N, N-dimethyl acetamide (DMA) and N, N-diethyl formamide (DEF) in benzene (i) are estimated from the measured real cij¢ and imaginary cij² part of hf complex dielectric orientational susceptibility cij* and low frequency susceptibility coij at different weight fractions wj’s of solute at various experimental temperatures [Saha et al., J Phys. D: Appl Phys, 27 (1994) 596]. The relative contributions c1 and c2 due to t1 and t2 are calculated from Fröhlich’s equations and graphical technique. All the c’s are positive from Fröhlich’s equations while some c2’s are negative from graphical method. The dipole moments m2 and m1 in Coulomb-metre (C.m) measured from the slope β’s of cij¢wj curves are compared with those of conductivity sij measurements using t’s from the ratio of individual slope of (dcij²/dwj)wj®o and (dcij¢/dwj)wj®o, linear slope of cij²cij¢ along with Gopalakrishna’s method [Trans Faraday Soc, 53 (1957) 767]. The estimated m1’s agree with the measured and reported m’s to indicate that the flexible part of the molecule is rotating under GHz electric field. The theoretical dipole moment mtheo’s are obtained in terms of available bond moments of the substituent polar groups attached to the parent molecules acting as pusher or puller of electrons due to inductive, mesomeric and electromeric effects in them under hf electric field. The variation of m1 with temperature suggests the elongation of bond moments. The energy parameters such as enthalpy of activation ΔHt, free energy of activation ΔFt and entropy of activation ΔSt’s are obtained for DMSO only assuming dielectric relaxation as a rate process to know the molecular dynamics. The variation of ln(t1T) against 1/T of DMSO reveals that it obeys Eyring rate theory unlike ln(t2T) against 1/T curve.

Keywords: Dielectric relaxation, Aprotic polar liquids, Dipole moment

IPC Code: G01R27/26

 

 

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 867-870

 

Gas sensing properties of undoped and antimony doped tin oxide films prepared by spray pyrolysis and electron beam evaporation method

 

K S Shamala & L C S Murthy

Department of Physics, Jnanabharathi, Bangalore University, Bangalore 560 056

and

K Narasimha Rao*

Department of Instrumentation, Indian Institute of Science, Bangalore 560 012

Received 16 November 2005; revised 1 August 2006; accepted 17 August 2006

The thin films of undoped and antimony doped tin oxide films were prepared on glass substrates by spray pyrolysis and electron beam evaporation techniques. The substrate temperature was varied between 300 and 370°C in case of spray pyrolysis and 200°C in case of electron beam evaporation. The films were tested as gas sensors in the presence of liquid petroleum gas (LPG) and compressed natural gas (CNG). Undoped and antimony doped tin oxide films prepared by spray pyrolysis were more sensitive to LPG. Sensitivity of spray deposited ATO film in the presence of 1000 PPM of LPG was found to be 0.86 at an operating temperature of 400°C and it was 0.23 for undoped film. Undoped tin oxide films prepared by electron beam evaporation showed a maximum sensitivity of 0.79 at an operating temperature of 375°C on its exposure to 1000 PPM of LPG. The performance of the sensor has been explained on the basis of the structure and conduction mechanism of the tin oxide film.

Keywords: Tin oxide films, Spray pyrolysis, Vacuum evaporation, Gas sensors

IPC Code: C30B

 

Indian Journal of Pure & Applied Physics

Vol. 44, November 2006, pp. 871-874

 

Low-voltage CCII based all-pass/notch filter

Susheel Sharma1, S S Rajput2, K Pal3, L K Mangotra1 & S S Jamuar4

1Department of Physics & Electronics, University of Jammu, Jammu 180 006

2National Physical Laboratory, Dr K S Krishnan Marg, New Delhi 110 012

3Department of Earthquake Engineering, Indian Institute of Technology, Roorkee

4Department of Electrical & Electronic Engineering, University Putra Malaysia, Malaysia

Received 1 September 2005; revised 13 February 2006; accepted 8 September 2006

 

A second order low-voltage (± 0.75 V) second-generation current conveyor (CCII) based filter circuit has been presented which can realize dual filter functions (all-pass/notch) depending on the resistance ratio. The gain of the filter is independently controlled by a resistance. The circuit employs almost all grounded components (except one resistor), thus enables its implementation with standard CMOS technologies. Theoretical results have been verified by PSpice simulations using 0.5 mm technology parameters.

Keywords: Low voltage circuit, Floating-gate MOSFET, Current conveyor, Active filter

IPC Code: H03H