• Volume 64, Issue 2

      February 2005,   pages  159-304

    • Exact periodic wave solutions to the generalized Nizhnik-Novikov-Veselov equation

      Yan-Ze Peng

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      The extended mapping method with symbolic computation is developed to obtain exact periodic wave solutions to the generalized Nizhnik-Novikov-Veselov equation. Limit cases are studied and new solitary wave solutions and triangular periodic wave solutions are obtained. The method is applicable to a large variety of non-linear partial differential equations, as long as odd-and even-order derivative terms do not coexist in the equation under consideration.

    • The Pondicherry interpretation of quantum mechanics: An overview

      U Mohrhoff

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      An overview of the Pondicherry interpretation of quantum mechanics is presented. This interpretation proceeds from the recognition that the fundamental theoretical framework of physics is a probability algorithm, which serves to describe an objective fuzziness (the literal meaning of Heisenberg’s term ‘Unschärfe’, usually mistranslated as ‘uncertainty’) by assigning objective probabilities to the possible outcomes of unperformed measurements. Although it rejects attempts to construe quantum states as evolving ontological states, it arrives at an objective description of the quantum world that owes nothing to observers or the goings-on in physics laboratories. In fact, unless such attempts are rejected, quantum theory’s true ontological implications cannot be seen. Among these are the radically relational nature of space, the numerical identity of the corresponding relata, the incomplete spatio-temporal differentiation of the physical world, and the consequent top-down structure of reality, which defies attempts to model it from the bottom up, whether on the basis of an intrinsically differentiated space-time manifold or out of a multitude of individual building blocks.

    • Bianchi Type-IX viscous fluid cosmological model in general relativity

      Raj Bali Mahesh Kumar Yadav

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      Bianchi Type-IX viscous fluid cosmological model is investigated. To get a deterministic model, we have assumed the conditiona = bm(m is a constant) between metric potentials andηθ whereη is the coefficient of shear viscosity andθ the scalar of expansion in the model. The coefficient of bulk viscosity (ς) is taken as constant. The physical and geometrical aspects of the model are also discussed.

    • Unusually low-amplitude anisotropic wave-train events of cosmic ray intensity during 1981–1994

      Rajesh K Mishra Rekha Agarwal Mishra

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      Investigation has been made for unusually low-amplitude anisotropic wave train events (LAE) for cosmic ray intensity data of Deep River neutron monitoring station during the period 1981–94. It has been observed that the phase of diurnal anisotropy remains in the same co-rotational direction for most of the LAEs while the phase shifts to early hours for some of the LAEs in diurnal anisotropy. During minimum solar activity, LAEs have been observed to be dominant. Solar wind plasma (SWP) parameters, inter-planetary magnetic field and various features at solar disk have also been studied. The amplitude remains low continuously for most of the days while the phase shifts to earlier hours. Occurrence of LAE is independent of the nature of interplanetary magnetic field (IMF).

    • Exploring effective interactions through transition charge density study of70,72,74,76Ge nuclei

      A Shukla P K Raina P K Rath

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      Transition charge densities (TCD) for 0+ → 21+ excitation have been calculated for70,72,74,76Ge nuclei within microscopic variational framework employing 2p3/2, 1f5/2, 2p1/2 and 1g9/2 valence space. The calculated TCDs for different monopole variants of Kuo interaction are compared with available experimental results. Other systematics like reduced transition probabilitiesB(E2) and static quadrupole momentsQ(2) are also presented. It is observed that the transition density study acts as a sensitive probe for discriminating the response of different parts of effective interactions.

    • Angular momentum transfer in incomplete fusion

      B S Tomar K Surendra Babu K Sudarshan R Tripathi A Goswami

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      Isomeric cross-section ratios of evaporation residues formed in 12C+93Nb and 16O + 89Y reactions were measured by recoil catcher technique followed by off-line 𝛾-ray spectrometry in the beam energy range of 55.7-77.5 MeV for 12C and 68-81 MeV for 16O. The isomeric cross-section ratios were resolved into that for complete and incomplete fusion reactions. The angular momentum of the intermediate nucleus formed in incomplete fusion was deduced from the isomeric cross-section ratio by considering the statistical de-excitation of the incompletely fused composite nucleus. The data show that incomplete fusion is associated with angular momenta slightly smaller than critical angular momentum for complete fusion, indicating the deeper interpenetration of projectile and target nuclei than that in peripheral collisions.

    • Time-gated optical imaging through turbid media using stimulated Raman scattering: Studies on image contrast

      K Divakar Rao H S Patel B Jain P K Gupta

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      In this paper, we report the development of experimental set-up for time-gated optical imaging through turbid media using stimulated Raman scattering. Our studies on the contrast of time-gated images show that for a given optical thickness, the image contrast is better for sample with lower scattering coefficient and higher physical thickness, and that the contrast improves with decreasing value of anisotropy parameters of the scatterers. These results are consistent with time-resolved Monte Carlo simulations.

    • A new approach of binary addition and subtraction by non-linear material based switching technique

      Archan Kumar Das Partha Pratima Das Sourangshu Mukhopadhyay

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      Here, we refer a new proposal of binary addition as well as subtraction in all-optical domain by exploitation of proper non-linear material-based switching technique. In this communication, the authors extend this technique for both adder and subtractor accommodating the spatial input encoding system.

    • Full-wave solution of short impulses in inhomogeneous plasma

      Orsolya E Ferencz

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      In this paper the problem of real impulse propagation in arbitrarily inhomogeneous media will be presented on a fundamentally new, general, theoretical way. The general problem of wave propagation of monochromatic signals in inhomogeneous media was enlightened in [1].

      The earlier theoretical models for spatial inhomogeneities have some errors regarding the structure of the resultant signal originated from backward and forward propagating parts. The application of the method of inhomogeneous basic modes (MIBM) and the complete full-wave solution of arbitrarily shaped non-monochromatic plane waves in plasmas made it possible to obtain a better description of the problem, on a fully analytical way, directly from Maxwell’s equations. The model investigated in this paper is inhomogeneous of arbitrary order (while the wave pattern can exist), anisotropic (magnetized), linear, cold plasma, in which the gradient of the one-dimensional spatial inhomogeneity is parallel to the direction of propagation.

    • Structures and autocorrelation functions of liquid Al and Mg modelled via Lennard-Jones potential from molecular dynamics simulation

      G A Adebayo O Akinlade L A Hussain

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      The structures and autocorrelation functions of Al and Mg in the liquid state are investigated through the pair distribution functiong(r), the diffusion coefficients as well as the shear viscosity via the Green-Kubo and Einstein relations. From the structure and the Enskog relation we determined the frequency of collisions of atoms in the first shell ofg(r) in the systems. We also discovered that the packing fraction of Lennard-Jones liquids should be approximately half the reduced density value. This approximation is accurate to within 99%. The temperature dependence of the pair distribution function and the atomic mean square displacement are investigated by performing simulations at various experimental temperatures and corresponding densities. The structures of the systems are affected by temperature via movements of atoms in the first minimum ofg(r).

      The Lennard-Jones model shows that density dependence of the shear viscosity is in agreement with what is expected of simple liquids in the range of investigated temperatures and densities. In the gas limit, the Stoke-Einstein relation =KBT/2πσ is grossly overestimated by Lennard-Jones model. This could not be attributed to deficiencies in the model, as other investigators using first principle method could not obtain the gas limit of the Stoke-Einstein relation.

    • Phase changes in Fe72−xAl28Crx (x = 0,2,4,6) alloys due to mechanical strain

      Brajesh Pandey H C Verma

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      Fe72−xAl28Crx (x = 0,2,4,6) are made by arc melting a mixture of constituent elements in stoichiometric proportion, in argon atmosphere. The ingots so obtained are filed to make powder samples thereby giving them substantial mechanical deformation. It is observed that as-powdered samples show hyperfine field distribution typical of α-phase, where the atoms are randomly distributed on the available sites. Annealing at 900°C for 60 h leads to preferential occupation of lattice sites by the atoms and this results in better defined groups of hyperfine magnetic field (HMF) which can be associated with specific configuration in the neighbourhood of probe iron atoms. The average HMF is found to decrease sharply with increasing Cr concentration even though the net chromium concentration remains low (≤6 at%). The results show that cold working on samples is very important in changing the atomic ordering and must be taken into account if properties of equilibrium phases are probed.

    • Liesegang patterns: Complex formation of precipitate in an electric field

      István Lagzi

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      Formation of 1D Liesegang patterns was studied numerically in precipitation and reversible complex formation of precipitate scenarios in an electric field. The Ostwald’s supersaturation model reported by Buki, Kárpáti-Smidróczki and Zrínyi (BKZ model) was extended further. In the presence of an electric field the position of the first and the last bands (Xn) measured from the junction point of the outer and the inner electrolytes can be described by the functionXn =a1τn1/2 +a2τn +a3, where τn is the time elapsed until the nth band formation,a1,a2 anda3 are constants. The variation of the total number of bands with different electric field strengths (ε) has a maximum. For higher ε one can observe a moving precipitation zone that becomes wider due to precipitation and reversible complex formation.

    • Lattice vibrational properties of transition metal carbides (TiC, ZrC and HfC)

      K S Upadhyaya Ajay Kumar Singh Atul Pandey S N Pathak A K Singh

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      Lattice vibrational properties of transition metal carbides (TiC, ZrC and HfC) have been presented by including the effects of free-carrier doping and three-body interactions in the rigid shell model. The short-range overlap repulsion is operative up to the second neighbour ions. An excellent agreement has been obtained between theory and experiment for their phonon dispersion curves and Debye temperature variations. It is concluded that the contributions of free-carrier doping and three-body interactions are essential for the description of the lattice dynamics of these carbides.

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