• Volume 62, Issue 4

      April 2004,   pages  803-981 and L983-L991

    • On the Bohmian quantum friction

      Fatimah Shojai Ali Shojai

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      The problem of quantum friction in the framework of Bohmian quantum mechanics is studied. The appropriate equations for such a system is written and solved exactly for some cases. Also two approximate solutions are found which represent the transition of a system from an upper state to the ground state caused by the friction. The physical nature of these solutions are examined.

    • Soliton dynamics in a modified Yakushevich model

      P C Dash M Panigrahi

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      We study a modified Yakushevich model with different disc diameters representing different bases and find two new in-phase solitonic solutions. We also discuss here the effect of helical structure which acts as perturbation on soliton centre of mass.

    • Shape change in Hf, W and Os-isotopes: A non-relativistic Hartree-Fock versus relativistic Hartree approximation

      Z Naik B K Sharma T K Jha P Arumugam S K Patra

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      We have investigated the ground-state structures of even-even Hf, W and Os isotopes within the framework of a deformed non-relativistic Hartree-Fock and a relativistic mean field formalism. A majority of the nuclei are predicted to be prolate in shape in the relativistic calculations. On the other hand, contrary to the relativistic results, we predict a shape change in a cyclic order in the non-relativistic calculations. However, in both the cases, the magnitude of the quadrupole deformation parameter agrees well with the experimental data. We also evaluated the hexadecapole deformation parameter for Hf, W and Os isotopes and irrespective of the shape change in quadrupole moments, we find a cyclic change in hexadecapole shape from positive to negative and vice versa in both the relativistic and non-relativistic formalisms.

    • Potential energy surfaces forN =Z,20Ne-112Ba nuclei

      M S Mehta T K Jha S K Patra Raj K Gupta

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      We have calculated the potential energy surfaces forN = Z,20Ne-112Ba nuclei in an axially deformed relativistic mean field approach. A quadratic constraint scheme is applied to determine the complete energy surface for a wide range of the quadrupole deformation. The NL3, NL-RA1 and TM1 parameter sets are used. The phenomenon of (multiple) shape coextistence is studied and the calculated ground and excited state binding energies, quadrupole deformation parameters and root mean square (rms) charge radii are compared with the available experimental data and other theoretical predictions.

    • Effect of environmental conditions on radon concentration-track density calibration factor of solid-state nuclear track detectors

      A El-Sersy M Mansy A Hussein

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      In this work, the effect of environmental conditions viz., temperature (T) and relative humidity (RH) on the track density-radon concentrations calibration factor (K) has been studied for CR-39 and LR-115 track detectors. The factorK was determined using a reference radon chamber in the National Institute for Standards (NIS) in Egypt. Track detectors were etched at the recommended optimum etching conditions.

      It is found that, the calibration factorK varies with bothT and RH, so they should be considered for the sake of uncertainty reduction. Good agreement is found between the calculated and measured values ofK and the compatibility between them is in the range of experimental uncertainty.

    • Statistical fluid theory for associating fluids containing alternating heteronuclear chain molecules

      Dinesh Kumar Singh K N Khanna

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      Statistical associating fluid theory of homonuclear dimerized chain fluids and homonuclear monomer-dimer mixture chain fluids are extended to fluids containing alternating heteronuclear chain molecules separately. The proposed models account for the appropriate site-site correlation functions at contact. The modified equations of state show a good agreement with generalized Flory dimer theory and MD simulation data for small and medium size ratio of hard sphere diameters.

    • Selective excitation of vibrational modes of polyatomic molecule

      N Singhal V Prasad M Mohan

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      Mode-selective dynamics of triatomic molecule in the electronic ground state under continuous wave laser pulse is investigated for the discrete vibrational bound states. A non-perturbative approach has been used to analyse the vibrational couplings and dynamics of the molecule.

    • Gain clamping in double-pass L-band EDFA using a broadband FBG

      Sulaiman Wadi Harun Harith Ahmad

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      A highly efficient gain-clamped L-band EDFA with improved noise figure characteristic is demonstrated by simply adding a broadband C-band FBG in double-pass system. The combination of the FBG and optical circulator has created laser in the cavity for gain clamping. By adjusting the power combination of pumps 1 and 2, the clamped gain level can be controlled. The amplifier gain is clamped at 28.1 dB from −40 to −25 dBm with a gain variation of less than 0.5 dB by setting the pumps 1 and 2 at 59.5 and 50.6 mW, respectively. The gain is also flat from 1574 nm to 1604 nm with a gain variation of less than 3 dB. The corresponding noise figure varies from 5.6 to 7.6 dB, which is 0.8 to 2.6 dB less than those of unclamped amplifier.

    • Kelvin-Helmholtz instability in a rotating ideally conducting inhomogeneous plasma

      Vinod Kumar K M Srivastava Nagendra Kumar Himanshu Sikka

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      The Kelvin-Helmholtz instability in sheared magnetohydrodynamic flow of an ideally conducting rotating inhomogeneous compressible plasma is investigated. The asymptotic behaviour inx of the Kelvin-Helmholtz eigenfunctions for the case of finite compressibility in the presence of rotation is discussed and instability condition is derived. In the incompressible limit, a dispersion relation is derived which has been solved numerically and discussed in detail. It is found that the inhomogeneous system is unstable in an incompressible plasma.

    • Surface morphology changes of poly(ethyleneterephthalate) fabrics induced by cold plasma treatments

      G Poletti F Orsini A Raffaele-Addamo C Riccardi E Selli

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      Some selective cold plasma processing modify specific surface properties of textile polymeric materials such as their dyeability, wettability and hydrorepellence. To correlate the sample surface changes with the acquired surface properties allows one to obtain information on the chemical and physical processing involved in plasma treatment. In this work, atomic force microscopy (AFM) has been applied to investigate the morphological and topographical surface modifications induced by RF cold plasma processing of poly(ethyleneterephthalate) (PET) fabrics. Rms surface roughness and surface area of the samples are measured before and after the treatments. The morphology changes have been analysed as a function of the treatment time and air gas pressure. Measurements have been performed also using plasmas produced by different gases such as He, Ar, SF6 and CF4. The PET shows different behaviour with different gas plasmas. In the case of air, He and Ar gases the sample surface modifications seem to be mainly due to etching effects, while the fluorine atoms grafting probably is responsible for surface rearrangement process using SF6 and CF4 gases. As a consequence different surface properties are produced in the plasma treated samples.

    • Impulse coupling in laser-driven microtargets

      P Bhargava M Kumar H Kumar P Pandit R Pandey A K Nath

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      We have studied about the thrust imparted to targets of different materials by pulsed TEA CO2 laser and chopped CW CO2 laser in air and its dependence on different parameters such as laser intensity and pulse duration. We estimated the impulse-coupling coefficient and compared it with the published results. The mechanism of generation of thrust by laser incident on targets in air is, in effect, combination of those involved in laser ablation in vacuum and laser-induced air detonation.

    • Exact periodic wave solutions to the coupled Schrödinger-KdV equation and DS equations

      Yan-Ze Peng

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      The exact solutions for the coupled non-linear partial differential equations are studied by means of the mapping method proposed recently by the author. Taking the coupled Schrödinger-KdV equation and DS equations as examples, abundant periodic wave solutions in terms of Jacobi elliptic functions are obtained. Under the limit conditions, soliton wave solutions are given.

    • Real solution of monochromatic wave propagation in inhomogeneous media

      Cs Ferencz

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      The earlier phenomenological descriptions of the propagation of signals in inhomogeneous media — except the mirror-type, scattering-type descriptions — have an inherent misunderstanding and therefore these methods are wrong except the non-coupled WKB approximation. The cause of the problem is the wrong physical concept about the structure of the signals propagating in inhomogeneous media. Using a better physical concept of the signal structure propagating in inhomogeneous media and the method of inhomogeneous basic modes (MIBM) it was possible to derive correct full-wave solutions for propagating signals. The investigated example is a monochromatic plane wave propagating in an isotropic, inhomogeneous, linear media parallel to the gradient of the one-dimensional inhomogeneity. However, a generalization of the process for more complex inhomogeneities is possible.

    • Cluster radioactivity in xenon isotopes

      K P Santhosh Antony Joseph

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      Half-life time and branching ratio for cluster decay from various xenon isotopes are studied taking Coulomb and proximity potentials as interacting barrier. Inclusion of proximity potential reduces the height of potential barrier, which closely agrees with the experiments. It is found that4He,8Be,12C and16O emissions are well within the present upper limit for measurements (T1/2 1030 s). Our predicted half-life time values lie close to those values reported by Gupta and collaborators based on preformed cluster model (PCM) and also with those values reported by Poenaruet al based on ASAFM. The calculated half-life time shows that8Be from108Xe and110Xe are most favourable for emission (T1/2 ≈ 108 s). LowestT1/2 value for8Be emission from108Xe stress the role of doubly magic100Sn daughter in cluster decay process. The logarithm of half-life time calculated for4He emission from110Xe is −0.39 s which is in good agreement with experimental value which is −0.40 s. Geiger-Nuttall plots for all clusters are studied and are found to be linear. Nuclear structure effect and shell effect are evident from the observed variation in slope and intercept of Geiger—Nuttall plots. It is found that neutron excess in the parent will slow down the cluster decay process.

    • EinsteinA-coefficients for rotational transitions in the ring-chain isomer of C5H2

      Suresh Chandra S A Shinde

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      Laboratory formation of four isomers of C5H2 molecule is reported and detection of the ring-chain isomer (isomer 1) of C5H2 in cosmic objects has been suggested. For identification of a molecule in cosmic objects, one of the required input data is EinsteinA-coefficients (radiative transition probabilities) for the molecule. Here, we report EinsteinA-coefficients for electric dipole transitions in the ring-chain isomer of C5H2 among the rotational levels of the ground electronic and ground vibrational states up to 21 cm−1.

    • Dielectric relaxation studies of aqueous sucrose in ethanol mixtures using time domain reflectometry

      C G Akode K S Kanse M P Lokhande A C Kumbharkhane S C Mehrotra

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      Time domain reflectometry method has been used in the frequency range of 10 MHz to 10 GHz to determine dielectric properties of aqueous sucrose in ethanol. The dielectric parameters, i.e., static dielectric constant and relaxation time were obtained from the complex permittivity spectra using the non-linear least squares fit method. The Luzar theory is applied to compute the cross-correlation terms for the mixtures. It adequately reproduces the experimental values of static dielectric constants. The Bruggeman model for the non-linear case has been fitted to the dielectric data for mixtures.

    • A time-dependent Fourier grid Hamiltonian-based formulation of time-dependent multi-configuration Hartree method

      Kaushik Maji S P Bhattacharyya

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