Sanjay Kumar
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 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 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 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 0007 Research Article
NILANJAN SIL NIBEDITA DARIPA ACHINT KAPOOR SANJAY KUMAR DEY
In the present paper, we have studied the binding energy of the shallow donor hydrogenic impurity, which is confined in an inhomogeneous cylindrical quantum dot (CQD) of $\rm{GaAs-Al_{x}Ga_{1−x}As}$. Perturbation method is used to calculate the binding energy within the framework of effective mass approximation and taking into account the effect of dielectric mismatch between the dot and the barrier material. The ground-state binding energy of the donor is computed as a function of dot size for finite confinement. The result shows that the ground-state binding energy decreases with the increase in dot size. The result is compared with infinite dielectric mismatch as a limiting case. The binding energy of the hydrogenic impurity is maximum for an on-axis donor impurity.
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 97 All articles Published: 3 January 2023 Article ID 0016 Research Article
Effect of thermal radiation on Bodewadt flow in the presence of porous medium
SUNIL DEEPIKA GARG VIMAL KUMAR JOSHI KUSHAL SHARMA SANJAY KUMAR
In this manuscript, the heat transport phenomena have been studied on time-dependent Bodewadt flow of magnetic nanofluids in the porous medium under the effect of thermal radiation. The governed modelled equations are solved using a finite difference scheme followed by the shooting techniques. To cover a wide range of nanofluids, we took the Prandtl number from 12.3 to 176.4. The impacts of geothermal viscosity, permeability parameter, ferrohydrodynamics (FHD) interaction parameter and thermal radiation on flow behaviour have beendiscussed. It is observed that the heat transport rate enhanced significantly due to the thinner thermal boundary layer thickness for higher radiation parameter. Also, an enhancement of 268% in heat dissipation is noted for themagnetic nanofluids with high Prandtl values.
Volume 97, 2023
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