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Indian Journal of Pure and Applied Physics

 

 ISSN: 0019-5596  

CODEN:IJOPAU 41(7) 505-584(2003) 

VOLUME 41  NUMBER 7  

  JULY 2003

                                                                                                                                                 

CONTENTS

 

 

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

Hydromagnetic free convection & mass transfer flow past a porous plate with temperature
gradient dependent heat source

Ajay Kumar Singh

 


509

Finite time thermodynamic optimization of irreversible Rankine cycle heat pump system
P K Bhardwaj*, S C Kaushik & Sanjeev Jain

515

Effect of magnetic field on viscosity of ferroconvection in an anisotropic sparsely distributed  porous medium

A Ramanathan* & P Surendra


522

Physics of Gases, Plasmas, and Electric Discharges

Experimental lifetimes of some 3p5 5p levels of ArI

M B Das* & K Karmakar

 

527

Condensed Matter: Structure, Mechanical and Thermal Properties

Influence of solvents and temperature on the photophysical characteristics of flavanones

Rajesh Giri* & Yatendra Tiwari

 

530

Domain formation in ferroelectric Ba5Ti2O7Cl4

S G Ingle & N M Patil*

538

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

Charge density waves induced superconductivity in LaSrCuO with intra-layer interactions

Dinesh Varshney*, G S Patel & R K Singh

 

542

Interdisciplinary Physics and Related Areas of Science and Technology

Three input and one output voltage mode universal filter

N A Shah*, M F Rather & S Z Iqbal


556

Geophysics, Astronomy, and Astrophysics

Characterization of iron bearing minerals from Dagsheri and study of their decomposition behaviour during combustion using 57Fe Mossbauer spectroscopy

Roshan Lal & N D Sharma*

 


559

Concentration of radon and its progeny near the surface of the earth at a continental station
Pune (18N, 74 E)

K Nagaraja*, B S N Prasad, M S Madhava & L Paramesh


562

Nuclear Physics

Measurement of mass attenuation coefficients of gamma-rays for various elements through
aqueous solution of salts in the energy range 0.511-1.33 MeV

M T Teli*, C S Mahajan, S S Malode & R Nathuram

 


570

Temperature dependence of anti-stokes luminescence in ZBLAN:Pr3+

S Sengar, S J Dhoble*, D S Raghuvanshi & B P Chandra

575

Current-mode active-only universal filter

N A Shah* & S Z Iqbal

578

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

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 509-514

 

 

Hydromagnetic free convection & mass transfer flow past a porous plate with temperature gradient dependent heat source

Ajay Kumar Singh

Department of Mathematics, C L Jain (PG) College, Firozabad 283 203

 

Received 23 September 2002; revised 31 March 2003; accepted  13 May 2003

 

 

The present paper deals with numerical solution of the unsteady free convection and mass transfer flow of an incompressible, electrically conducting, viscous fluid, past an infinite vertical porous flat plate. The flow is considered under the influence of constant suction velocity and temperature gradient dependent heat source. Implicit finite difference method is used to solve the equations governing the flow. The constant suction and the uniform magnetic field are considered normal to the plate. The results for the velocity field, the temperature field, the concentration field and the skin-friction are investigated and discussed for different values of the parameters encountered into the equations of the problem.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 515-521]

 

 

Finite time thermodynamic optimization of irreversible
Rankine cycle heat pump system

P K Bhardwaj1, S C Kaushik1 & Sanjeev Jain2

1Centre for Energy Studies, Indian Institute of Technology, New Delhi 110 016

2Department of Mechanical Engineering, Indian Institute of Technology, New Delhi 110 016

E-mail: kaushiksc@hotmail.com, kaushik@ces.iitd.ernet.in

 

Received: 15 May 2002; accepted 22 October 2002

 

 

This paper presents finite time thermodynamic optimization of a Rankine cycle heat pump system affected by both, external and internal irreversibility. For a given input heat transfer rate in the boiler (heat source), work output of the heat engine is maximized and for a given heating load, work input to the heat pump cycle is minimized. The optimal bounds for the coefficient of performance (COP) and working fluid temperatures are determined, at a given heating load. The parametric study gives the variation of the coefficient of performance with operating variables (viz. inlet temperature of heat reservoirs, finite heat capacitance of external fluid, effectiveness of the heat exchangers and internal irreversibility parameters). Parametric study shows internal irreversibility is more responsible for performance reduction than external irreversibility.

 

  

   

Indian J Pure & Applied Physics

Vol. 41, July 2003, pp. 522-526

 

 

Effect of magnetic field on viscosity of ferroconvection in an anisotropic sparsely distributed porous medium

A Ramanathan & P Surendra

Department of Mathematics, Kanchi Mamunivar Centre for Postgraduate Studies, Pondicherry 605 008

 

Received 28 June 2002; revised 30 December 2002; accepted 20 March 2003

 

 

The effect of magnetic field dependent viscosity on ferroconvection saturating an anisotropic porous medium has been investigated using Brinkman model. Liner theory is being employed. The effect of anisotropy is found to destabilize the system whereas the viscosity stabilizes the system. The magnetization tends to destabilize as in earlier analysis.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 527-529

 

 

Experimental lifetimes of some 3p5 5p levels of ArI

M B Das1 & S Karmakar2

1Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700 064

2Department of Physics, Kandi College, Kandi, Murshidabad 742 137

E-Mail: mbd@niss.saha.ernet.in, Fax: +91-33-3374637

 

Received 13 September 2002; accepted 24 April 2003

 

 

Lifetime of nine levels belonging to the 3p55p configuration of neutral argon have been measured by high frequency deflection technique with a delayed coincidence single photon counting arrangement. The measurements have been performed under conditions where the pressure dependent effects are negligible. The results have been compared with other experimental and theoretical values.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 530-537

 

 

Influence of solvents and temperature on the photophysical characteristics of flavanones

Rajesh Giri

Department of Physics, Rajdhani College (Delhi University), New Delhi 110 015

and

Yatendra Tiwari

Institute of Technology & Management, (MD University, Rohtak), Sector 23A, Gurgaon, Haryana

 

Received 11 October 2002; accepted 16 April 2003

 

 

The absorption and fluorescence emission spectra of substituted flavanones viz., flavanone (I), 6-methyl flavanone (II) and 6-methyl-4'-methoxy flavanone, have been reported in various polar and non-polar organic solvents. The values of excited state dipole moments of these flavanones have been calculated, using solvatochromic data. The values of excited state dipole moments for all these molecules investigated, are higher than their corresponding values in the ground state. It is also observed that, the excited state dipole moment of 6-methyl-4'-methoxy flavanone > 6-methyl flavanone > flavanone. Further, the values of percentage polarization of these molecules in various solvents of different polarity have been obtained and interpreted in terms of Perrin's theory as well as dipole-dipole interaction. Also, the effect of temperature on fluorescence intensity in water and a non-polar solvent have been observed. The variations in the fluorescence intensity have been discussed in terms of the positions of 1(p p*) and 3(n p*) energy levels of the molecules studied.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 538-541

 

 

Domain formation in ferroelectric Ba5Ti2O7Cl4

S G Ingle & N M Patil

Kavikulguru Institute of Technology and Science, Ramtek, Nagpur, Maharashtra 441 106

[Email: naresh_patil2000@yahoo.com]

 

Received 8 October 2002; revised 18 February 2003; accepted 14 April 2003

 

 

The mechanism of domain formation in the ferroelectric Ba5Ti2O7Cl4 has been studied. It is found that, when the crystal is subjected to mechanical stress, domain structures are produced in the crystal. When these domain structures are observed under reflected light, the domain regions show linear arrays of etch pits on them. It is concluded that, the etch pits are at sites of point defects that carry appreciable strain energy with them. The arrangement of these point defects is on account of this strain energy. The ordered point defects can then reduce their strain energy by nucleation of domains around them. These nucleated micro-domains can further join each other end-to-end through piezoelectric interaction. This mechanism produces macro-domain structures in the crystal. The geometry of the micro-domain structures and the overall mechanism of domain formation is exactly similar to that observed by Ingle and co-workers in KNbO3 and PbNb2O6.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 542-555

 

 

Charge density waves induced superconductivity
in LaSrCuO with intra-layer interactions

Dinesh Varshney1, G S Patel1 & R K Singh2

1School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452 017

2M P Bhoj (Open) University, Shivaji Nagar, Bhopal, MP 462 016

 

Received 15 July 2002; revised 6 November 2002; accepted 26 November 2002

 

 

An effective two-dimensional dynamic interaction is developed which incorporates screening of holes by charge density fluctuations and by optical phonons to discuss the nature of the pairing mechanism leading to superconductivity in layered La-based cuprates. The authors treat the La-Sr-CuO system as an ionic solid containing layers of holes as carriers and a model dielectric function is set up which fulfils the appropriate sum rules on the electronic and ionic polarizabilities. Estimate of the Coulomb pseudo-potential (m*=0.22), describing the screening effects on superconductivity is due to reduced carrier density and large value of the optical dielectric constant as well as the effective mass of holes. The hole-phonon coupling constant (l) is evaluated as 1.5, which infers strong strength of coupling. Following strong coupling theory, the superconducting transition temperature of optimally doped La-Sr-CuO is estimated as 42 K. The isotope exponent, coherence length and magnetic penetration depth are also estimated. The implications of the model and its analysis are discussed.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 556-558

 

 

Three input and one output voltage-mode universal filter

N A Shah, M F Rather & S Z Iqbal

Postgraduate Department of Electronics and Instrumentation Technology, University of Kashmir,

Hazratbal, Srinagar 190 006

 

Received 30 October 2002; accepted 20 March 2003

 

 

A three-input and one output voltage-mode (VM) universal biquadratic filter using a single current-feedback amplifier (CFA), a single operational transconductance amplifier (OTA), a single resistor and two capacitors is presented. The circuit without requiring component matching is capable of realizing from the same configuration all the standard filtering responses viz. lowpass (LP), highpass (HP), bandpass (BP), notch (BR), and allpass (AP). The cut off frequency w0 and bandwidth w0/Q are independently tuneable. The low sensitivity figures is the additional advantage of the circuit. The circuit has been simulated using personal computer-simulation program with integrated circuit emphasis (PSPICE) and results are found to be in close conformity with theoretical analysis.

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 559-561

 

 

Characterization of iron bearing minerals from Dagsheri and
study of their decomposition behaviour during combustion
using 57Fe Mössbauer spectroscopy

Roshan Lal & N D Sharma*

Department of Physics, Kurukshetra University, Kurukshetra 136 119

 

Received 3 Feb 2003; revised 23 April 2003; accepted 24 April 2003

 

 

57Fe Mössbauer spectroscopy has been used to characterize the iron-bearing minerals from Dagsheri (Himachal Pardesh, India). An interesting feature of this sample is, the presence of large amount of haematite and small amount of Jarosite, which decompose into oxide phase, i.e. into haematite, which is likely to have volcanic origin. The decomposition behaviour of these minerals on combustion is studied by Mössbauer technique, after heating the samples at different temperatures. The decomposition route is significantly different from that normally observed in coal samples.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 562-569

 

 

Concentration of radon and its progeny near the surface of the earth at a continental station Pune (18 N, 74 E)

K Nagaraja, B S N Prasad, M S Madhava & L Paramesh

DOS in Physics, University of Mysore, Manasagangotri, Mysore 570 006

 

Received 14 November 2002; revised 22 April 2003; accepted 25 April 2003

 

 

In the atmosphere, above the surface of the Earth, the concentrations of radon and its progeny are measured along with the meteorological parameters from December 1997 to December 2000 for a continental location, Pune (18 N, 74 E), India. The concentrations show a maxima in the early morning hours when the turbulence mixing is minimum and a minima in the afternoon when the turbulence mixing is maximum. The median values of concentration are 9.70 Bq m–3 and 2.84 Bq m–3 respectively, for radon and its progeny, during the observation period. Ionization rates in the atmosphere are derived for the same period. It is found that, the ionization rate exhibits a median value of 5.48 ion-pairs cm–3 s–1. The diurnal and seasonal variations in the concentrations of radon and its progeny, and the ionization rate due to radioactivity are found to exhibit correlation with relative humidity, and anti-correlation with temperature. Radioactivity measurements and the derived ion pair production rates are important in modelling the atmospheric electrical conductivity near the Earth’s surface.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 570-574

 

 

NOTE

 

Measurement of mass attenuation coefficients of gamma-rays for various elements through aqueous solution of salts in the energy range 0.511-1.33 MeV

M T Teli, C S Mahajan, S S Malode & R Nathuram*

Nuclear Research Laboratory, Department of Physics,

Dr Babasaheb Ambedkar Marathwada University, Aurangabad 431 004

*Radiation Safety System Division, Bhabha Atomic Research Centre, Mumbai 400 085

 

Received 11 November 2002; revised 22 April 2003; accepted 23 April 2003

 

 

In continuation of an earlier study, demonstrating measurement of attenuation coefficients of gamma-rays for various compounds and elements [Indian J Pure & Appl Phys, 39 (2001) 816], values for an additional nine elements B, Ca, V, Se, Mo, Cd, Rh, In, W are presented in this communication. This is done through the measurements of mass attenuation coefficients for their compounds– boric acid, calcium chloride, ammonium metavanadium, selenium dioxide, ammonium molydbenum, cadmium acetate, rhodanin-N, indium (III) nitrate and sodium tungstate hydrated. The measurements agree with theoretical values of Hubbell and Seltzer [NISTR, 5632, 1995].

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 575-577

 

NOTE

 

Temperature dependence of  anti-stokes luminescence in ZBLAN: Pr3+

S Sengar, S J Dhoble*, D S Raghuvanshi & B P Chandra†

Department of Physics, Government Model Science College, Pachpedhi, Jabalpur, Madhya Pradesh 482 001

*Kamla Nehru College, Sakkardara Square, Nagpur, Maharashtra 440 009

†Pt Ravishankar Shukla University, Raipur, Chhatisgarh 492 010

 

Received 20 September 2002; revised 17 February 2003; accepted 25 April 2003

 

 

The effect of temperature on the intensity of anti-stokes luminescence in Pr3+-doped ZBLAN fluoride phosphor has been investigated in the temperature range 30-240 °C. Initially, as the temperature is raised, an increase in emission is observed and after a particular value of temperature, the emission intensity decreases rapidly. The increase in the intensity of blue phosphorescence with increasing temperature is due to an increase in the probability of the non-resonant multi-phonon relaxation process.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, July 2003, pp. 578-580

 

 

NOTE

 

Current-mode active-only universal filter

N A Shah & S Z Iqbal

Department of Electronics & Instrumentation Technology, University of Kashmir, Srinagar 190 006

Email:zaffer121@rediffmail.com

 

Received 30 January 2003; revised 8 April 2003; accepted 25 April 2003

 

 

A new current-mode active-only universal filter based on and employing two OA's and three DO-OTAs is presented. The circuit is capable of realizing all the five generic filter characteristics viz. Lowpass, bandpass, highpass, notch and allpass without changing the circuit topology or nature of components, or additional component besides, no component matching conditions is required. The filter parameters w0 and Q are electronically tunable in an orthogonal manner through separate transconductances of OTAs. The circuit has low sensitivity performance and is ideal for production in IC form as it is devoid of external passive components.