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      Volume 78, Issue 2

      February 2012,   pages  165-1

    • Octonionic Lorenz-like condition

      Murat Tanişli Bernard Jancewicz

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      In this study, the octonion algebra and its general properties are defined by the Cayley–Dickson’s multiplication rules for octonion units. The field equations, potential equations and Maxwell equations for electromagnetism are investigated with the octonionic equations and these equations can be compared with their vectorial representations. The potential and wave equations for fields with sources are also provided. By using Maxwell equations, a Lorenz-like condition is newly suggested for electromagnetism. The existing equations including the photon mass provide the most acknowledged Lorenz condition for the magnetic monopole and the source.

    • Preferred states of the apparatus

      Anu Venugopalan

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      A simple one-dimensional model for the system–apparatus interaction is analysed. The system is a spin-1/2 particle, and its position and momentum degrees constitute the apparatus. An analysis involving only unitary Schrödinger dynamics illustrates the nature of the correlations established in the system–apparatus entangled state. It is shown that even in the absence of any environment-induced decoherence, or any other measurement model, certain initial states of the apparatus – like localized Gaussian wavepackets – are preferred over others, in terms of measurementlike one-to-one correlations in the pure system–apparatus entangled state.

    • Solutions of several coupled discrete models in terms of Lamé polynomials of order one and two

      Avinash Khare Avadh Saxena

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      Coupled discrete models abound in several areas of physics. Here we provide an extensive set of exact quasiperiodic solutions of a number of coupled discrete models in terms of Lamé polynomials of order one and two. Some of the models discussed are: (i) coupled Salerno model, (ii) coupled Ablowitz–Ladik model, (iii) coupled saturated discrete nonlinear Schrödinger equation, (iv) coupled $\phi^4$ model and (v) coupled $\phi^6$ model. Furthermore, we show that most of these coupled models in fact also possess an even broader class of exact solutions.

    • Coupled-channel analysis for 20.4 MeV energy of p-^{64}Zn inelastic scattering

      Harun Yücel Müşfik Taşan

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      In this study, a coupled-channel (CC) analysis of the elastic and the inelastic scattering of 20.4 MeV polarized protons from a 64Zn target leading to the deformed 2+, $3^−$, $2^+_2$ states was performed. The CC potential parameters and the deformation parameters of the excited states corresponding to the best fit to the experimental differential cross-sections and the analysing powers data were determined. For $2^+_2$ excited state, a mixed type was used and a good fit to the data was provided. The CC calculation results were compared to the pure distorted wave Born approximation (DWBA) calculation results which were calculated using the new parameters. All calculations were conducted using the computer code ECIS06.

    • Origin of inertia in large-amplitude collective motion in finite Fermi systems

      Sudhir R Jain

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      We argue that mass parameters appearing in the treatment of large-amplitude collective motion, be it fission or heavy-ion reactions, originate as a consequence of their relation with Lyapunov exponents coming from the classical dynamics, and, fractal dimension associated with diffusive modes coming from hydrodynamic description.

    • Analysis of shape isomer yields of ${}^{237}$Pu in the framework of dynamical–statistical model

      Hadi Eslamizadeh

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      Data on shape isomer yield for $\alpha +^{235}$U reaction at $E^{\text{lab}}_$\alpha = 20–29$ MeV are analysed in the framework of a combined dynamical–statistical model. From this analysis, information on the double humped fission barrier parameters for some Pu isotopes has been obtained and it is shown that the depth of the second potential well should be less than the results of statistical model calculations.

    • Energy of vanishing flow in heavy-ion collisions: Role of mass asymmetry of a reaction

      Varinderjit Kaur Suneel Kumar

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      We aim to understand the role of Coulomb interactions as well as different equations of state on the disappearance of transverse flow for various asymmetric reactions leading to the same total mass. For the present study, the total mass of the system is kept constant (A_{\text{TOT}} = 152) and mass asymmetry of the reaction is varied between 0.2 and 0.7. The Coulomb interactions as well as different equations of state are found to affect the balance energy significantly for larger asymmetric reactions.

    • Physics design of a CW high-power proton Linac for accelerator-driven system

      Rajni Pande Shweta Roy S V L S Rao P Singh S Kailas

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      Accelerator-driven systems (ADS) have evoked lot of interest the world over because of their capability to incinerate the MA (minor actinides) and LLFP (long-lived fission products) radiotoxic waste and their ability to utilize thorium as an alternative nuclear fuel. One of the main subsystems of ADS is a high energy (∼1 GeV) and high current (∼30 mA) CW proton Linac. The accelerator for ADS should have high efficiency and reliability and very low beam losses to allow hands-on maintenance. With these criteria, the beam dynamics simulations for a 1 GeV, 30 mA proton Linac has been done. The Linac consists of normal-conducting radio-frequency quadrupole (RFQ), drift tube linac (DTL) and coupled cavity drift tube Linac (CCDTL) structures that accelerate the beam to about 100 MeV followed by superconducting (SC) elliptical cavities, which accelerate the beam from 100 MeV to 1 GeV. The details of the design are presented in this paper.

    • Induced photonuclear interaction by Rhodotron-TT200 10 MeV electron beam

      Farshid Tabbakh Mojtaba Mostajab Aldaavati Mahdieh Hoseyni Khadijeh Rezaee Ebrahim Saraee

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      In this paper the photonuclear interaction induced by 10 MeV electron beam generating high-intensity neutrons is studied. Since the results depend on the target material, the calculations are performed for Pb, Ta and W targets which have high 𝑍, in a simple geometry. MCNPX code has been used to simulate the whole process. Also, the results of photon generation has been compared with the experimental results to evaluate the reliability of the calculation. The results show that the obtained neutron flux can reach up to 1012 n/cm2 /s with average energies of 0.9 MeV, 0.4 MeV and 0.9 MeV for these three elements respectively with the maximum heat deposited as 3000 W/c3,4500 W/c3 and 6000 W/c3.

    • Formation of multiple dark photovoltaic spatial solitons

      Yuhong Zhang Keqing Lu Jianbang Guo Xuewen Long Xiaohong Hu Kehao Li

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      We theoretically study the formation of multiple dark photovoltaic soliton splitting in the quasi-steady-state and steady-state regimes under open-circuit conditions. We find that the initial width of the dark notch at the entrance face of the crystal is a key parameter for generating an even (or odd) number sequence of dark coherent photovoltaic solitons. If the initial width of the dark notch is small, only a fundamental soliton or Y-junction soliton pair is generated. As the initial width of the dark notch is increased, the dark notch tends to split into an odd (or even) number of multiple dark photovoltaic solitons, which realizes a progressive transition from a low-order soliton to a sequence of higher-order solitons. The soliton pairs far away from the centre have bigger width and less visibility. In addition, when the distance from the centre of the dark notch increases, the separations between adjacent dark stripes become slightly smaller.

    • A comparative study of the ionic keV X-ray line emission from plasma produced by the femtosecond, picosecond and nanosecond duration laser pulses

      V Arora P A Naik B S Rao P D Gupta

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      We report here an experimental study of the ionic keV X-ray line emission from magnesium plasma produced by laser pulses of three widely different pulse durations (FWHM) of 45 fs, 25 ps and 3 ns, at a constant laser fluence of $\sim 1.5 \times 10^4$ J cm-2. It is observed that the X-ray yield of the resonance lines from the higher ionization states such as H- and He-like ions decreases on decreasing the laser pulse duration, even though the peak laser intensities of $3.5 \times 10^{17}$ W cm-2 for the 45 fs pulses and $6.2 \times 10^{14}$ W cm-2 for the 25 ps pulses are much higher than $5 \times 10^{12}$ W cm-2 for the 3 ns laser pulse. The results were explained in terms of the ionization equilibrium time for different ionization states in the heated plasma. The study can be useful to make optimum choice of the laser pulse duration to produce short pulse intense X-ray line emission from the plasma and to get the knowledge of the degree of ionization in the plasma.

    • Nonlocal Coulomb interaction in the two-dimensional spin-1/2 Falicov–Kimball model

      S K Bhowmick N K Ghosh

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      The two-dimensional (2D) extended Falicov–Kimball model has been studied to observe the role of nonlocal Coulomb interaction ($U_{\text{nc}}$) using an exact diagonalization technique. The f-state occupation ($n^f$), the f–d intersite correlation function ($c_{\text{fd}}$), the specific heat (𝐶), entropy (𝑆) and the specific heat coefficient (𝛾) have been examined. Nonlocal Coulomb interaction-induced discontinuous insulator-to-metal transition occurs at a critical f-level energy. More ordered state is obtained with the increase of $U_{\text{nc}}$. In the specific heat curves, two-peak structure as well as a singlepeak structure appears. At low-temperature region, a sharp rise in the specific heat coefficient 𝛾 is observed. The peak value of 𝛾 shifts to the higher temperature region with $U_{\text{nc}}$.

    • Dielectric relaxation and hydrogen bonding studies of 1,3-propanediol–dioxane mixtures using time domain reflectometry technique

      Madhukar N Shinde Ravindra B Talware Pravin G Hudge Yogesh S Joshi Ashok C Kumbharkhane

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      The complex permittivity, static dielectric constant and relaxation time for 1,3-propanediol, 1,4-dioxane and their mixtures have been studied using time domain reflectometry (TDR). The excess permittivity, excess inverse relaxation time and Kirkwood correlation factor have also been determined at various concentrations of dioxane. Hydrogen bonded theory was applied to compute the correlation terms for the mixtures. The Bruggeman model for the nonlinear case has been fitted to the dielectric data for mixtures.

    • Optical characterization of a-Se$_{85−x}$Te15Zn$_x$ thin films

      S Shukla S Kumar

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      Thin films of Se$_{85−x}$Te15Zn$_x$ ($x = 0$, 2, 4, 6 and 10) glassy alloys have been deposited onto a chemically cleaned glass substrate by thermal evaporation technique under vacuum. The analysis of transmission spectra, measured at normal incidence, in the spectral range of 400–2500 nm helped us in the optical characterization of thin films under study. From the analysis of transmission spectra, the optical parameters such as refractive index (𝑛), extinction coefficient (𝑘), absorption coefficient (𝛼), real and imaginary dielectric constants ($\epsilon'$ and $\epsilon"$) have been calculated. It is observed that the parameters 𝑛, 𝑘, $\epsilon'$, $\epsilon"$ and 𝛼 decrease with increase in wavelength (𝜆) and increase with Zn content. Optical band gap ($E_g$) has also been calculated and found to decrease with Zn content in Se$_{85−x}$Te15Zn$_x$ glassy system which could be correlated with increase in the density of defect states.

    • Synthesis and nanostructural investigation of TiO2 nanorods doped by SiO2

      M Riazian A Bahari

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      TiO2 Nano rods can be used as dye-sensitized solar cells, various sensors and photocatalysts. These nanorods are synthesized by a hydrothermal corrosion process in NaOH solution at $200^\circ$C using TiO2 powder as the source material. In the present work, the synthesis of TiO2 nanorods in anatase, rutile and Ti7O13 phases and synthesis of TiO2 nanorods by incorporating SiO2 dopant, using the sol–gel method and alkaline corrosion are reported. The morphologies and crystal structures of the TiO2 nanorods are characterized using field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) study. The obtained results show not only an aggregation structure at high calcination temperatures with spherical particles but also Ti–O–Si bonds having four-fold coordination with oxygen in SiO4-.

    • Reply to the comment on: “Corrosion behaviour of low energy, high temperature nitrogen ion-implanted AISI 304 stainless steel”

      Ali Shokouhy

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