Sanjay
Articles written in Pramana – Journal of Physics
Volume 23 Issue 2 August 1984 pp 235-243 Atomic And Molecular Physics
Computer calculation of positron drift velocities in He, Ne and Ar
P S Grover Sanjay Kumar K V Sinha
The drift velocities of positrons in rare gases, He, Ne and Ar have been calculated at various temperatures. The drift velocity depends quite sensitively on the strength of the electric field and temperature.
Volume 34 Issue 5 May 1990 pp 415-422
Cosmological models consistent with supersymmetric compactiflcation of superstring theories
Sanjay Kumar S Mahajan A Mukherjee N Panchapakesan R P Saxena
The compactification of 10-dimensional supergravity, coupled to super Yang-Mills theory, to curved 4-dimensional spacetimes is investigated. The requirement of unbroken supersymmetry leads to a set of consistency conditions. These are fairly restrictive, but nevertheless permit some nontrivial solutions, including the Milne universe. More general time-dependent metrics are also not ruled out.
Volume 48 Issue 2 February 1997 pp 737-748 Applications
Some recent applications of cell dynamical modelling to phase ordering dynamics
We study experimentally relevant effects in phase ordering dynamics using Cell Dynamical System (CDS) models. In particular, we present representative numerical results for phase ordering in random magnets and phase separation in binary fluids.
Volume 53 Issue 1 July 1999 pp 37-51 Liquid Crystals And Other Soft Materials
Surface adsorption and collapse transition of linear polymer chains
Yashwant Singh Sanjay Kumar Debaprasad Giri
The critical behaviour of surface adsorption and collapse transition of a flexible self-attracting self-avoiding polymer chain is examined. Depending upon the underlying lattice and space dimensionality, phase diagrams that exhibit many different universality domains of critical behavior are found. We discuss these phase diagrams and the values of the critical exponents found from different theoretical methods.
Volume 54 Issue 6 June 2000 pp 827-844
Swaralipi Ghosh Sanjay Sen SS Bhattacharyya Samir Saha
Polarization effects on population transfer by stimulated Raman transition using overlapping time dependent pump and Stokes laser pulses from the ground
Volume 54 Issue 6 June 2000 pp 863-870
Multifractal behaviour of
Sanjay Kumar Debaprasad Giri Sujata Krishna
We study the asymptotic behaviour of resistance scaling and fluctuation of resistance that give rise to flicker noise in an
Volume 60 Issue 3 March 2003 pp 433-441
Bianchi type I string cosmologies
By making use of Letelier’s form of energy—momentum tensor for a cloud of stringdust we present some classes of solutions of general relativistic field equations which describe cosmological string-dust models in Bianchi type I space-time. Some of the classes of models obey Takabayashi’s equation of state whereas a class of models exhibits inflation in the initial stage. Two of the classes presented here have Kasner’s space-time as past asymptote
Volume 62 Issue 3 March 2004 pp 695-698
Alok Kumar Rashmi R Nayak Sanjay
We show the existence of classical solutions of
Volume 64 Issue 6 June 2005 pp 881-892
Wetting and phase separation at surfaces
We study the problem of
Volume 76 Issue 1 January 2011 pp 183-188 Brief Report
Thermoelastic properties of minerals at high temperature
Sanjay Upadhyay Hem Chandra Meenakashi Joshi Deepika P Joshi
The knowledge of elasticity of the minerals is useful for interpreting the structure and composition of the lower mantle and also in seismic studies. The purpose of the present study is to discuss a simple and straightforward method for evaluating thermoelastic properties of minerals at high temperatures. We have extended the Kumar’s formulation by taking into the account the concept of anharmonicity in minerals above the Debye temperature ($\theta_D$). In our present study, we have investigated the thermophysical properties of two minerals (pyrope-rich garnet and MgAl_{2}O_{4}) under high temperatures and calculated the second-order elastic constant ($C_{ij}$) and bulk modulus ($K_T$) of the above minerals, in two cases ﬁrst by taking Anderson–Gruneisen parameter ($\delta_T$) as temperature-independent and then by treating $\delta_T$ as temperature-dependent parameter. The results obtained when $\delta_T$ is temperature-dependent are in close agreement with experimental data.
Volume 82 Issue 2 February 2014 pp 373-377 Contributed Papers
Smita Chaubey Sanjay Kher Jai Kishore S M Oak
We have developed high sensitivity long-period fibre gratings (LPGs) in B–Ge codoped fibre for strain sensing application. These LPGs are shortest grating period (180 𝜇m) LPGs inscribed in B–Ge co-doped fibre using CO_{2} laser-based grating inscription set-up. Strain sensitivity of 1.77 dB/mε has been obtained for attenuation band corresponding to the turnaround point mode. TAP operation of LPG facilitates intensity-based detection using simple optical power meter instead of wavelength-based detection.
Volume 87 Issue 2 August 2016 Article ID 0021 Research Article
Brief report: Volume dependence of Grüneisen parameter for solids under extreme compression
SANJAY KUMAR S K SHARMA O P PANDEY
The Nie expression is amended in such a way that the expression follows the infinite pressure behaviour, i.e., P → ∞or V → 0. A new empirical relationship is developed to predict the values of volume dependence of Grüneisen parameter. NaCl and ε-Fe have been employed to test the suitability of the expression.The results obtained reveal that the relationship is reliable as there is a good agreement between the calculated and the experimental data
Volume 90 Issue 1 January 2018 Article ID 0013 Research Article
Study of chaos in chaotic satellite systems
In this paper,we study the qualitative behaviour of satellite systems using bifurcation diagrams, Poincaré section, Lyapunov exponents, dissipation, equilibrium points, Kaplan–Yorke dimension etc. Bifurcation diagrams with respect to the known parameters of satellite systems are analysed. Poincaré sections with different sowing axes of the satellite are drawn. Eigenvalues of Jacobian matrices for the satellite system at different equilibrium points are calculated to justify the unstable regions. Lyapunov exponents are estimated. From these studies, chaosin satellite system has been established. Solution of equations of motion of the satellite system are drawn in the form of three-dimensional, two-dimensional and time series phase portraits. Phase portraits and time series display the chaotic nature of the considered system.
Volume 91 Issue 4 October 2018 Article ID 0049 Research Article
Analysis and time-delay synchronisation of chaotic satellite systems
In this paper, we analyse the chaotic satellite system using dissipativity, equilibrium points, bifurcation diagrams, Poincare section maps, Lyapunov exponents and Kaplan–Yorke dimension. We obtain the equilibrium points of chaotic satellite system and at each equilibrium point, we obtain the eigenvalue of Jacobian matrix of the satellite system to verify the unstable region.We calculate the Kaplan–Yorke dimension, which ensures the strange behaviour of the system. We observe closely the three-dimensional (3D) phase portraits of the satellite system at different parameter values. We plot the Lyapunov exponent graphs corresponding to every 3D phase portrait of satellite systems, to verify the chaoticity of satellite systems. We establish time-delay synchronisation for twoidentical satellite systems. The simulated and qualitative results are in an excellent agreement.
Volume 92 Issue 2 February 2019 Article ID 0020 Research Article
KAMAL KUMAR GULATI SANJAY GULIA NITESH KUMAR ANIL KUMAR SWARAN KUMARI VIJAYETA GAMBHIR M N REDDY
A transportable, trolley-mounted stand-off explosive material detection system based on the time-gated Raman spectroscopy was developed and tested in our laboratory. This system is capable of identifying the explosives and improvised explosive materials located up to a distance of 30 m. A frequency tripled Nd:YAG, nanosecond pulsed laser (355 nm, 6 ns) operated at 10 Hz was used as an excitation source to induce Raman spectra of explosive materials under investigation. A reflected type 200 mm aperture telescope designed using Zemax opticaldesign software was used to collect the backscattered Raman signals. Raman signals were recorded using the gated intensified charge coupled device (ICCD) spectrograph. A LabVIEW-based data acquisition and analysis software for real-time identification of materials was developed and used. It gives audio as well as text alarm to the operatorabout threat identification.
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