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  • 2000-2004  (158)
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  • 1
    ISSN: 1572-9532
    Keywords: quantum Cosmology ; Quantum Gravity ; Time ; Minisuperspace ; Wavefunction of the Universe PACS No. - 04.60, 98.80 Hw
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We start from the classical Hamiltonian constraint of general relativity to obtain the Einstein–Hamiltonian–Jacobi equation. We obtain a time parameter prescription demanding that geometry itself determines the time, not the matter field, such that the time so defined being equivalent to the time that enters into the Schrödinger equation. Using a semiclassical approximation we obtain an equation for quantum gravity in Schrödinger form containing time. We restrict ourselves to a minisuperspace description. Unlike matter field equation our equation is equivalent to the Wheeler–DeWitt equation in the sense that our solutions reproduce also the wavefunction of the Wheeler–DeWitt equation provided one evaluates the normalization constant according to the wormhole dominance proposal recently proposed by us.
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  • 2
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Measurements of two-components of velocity in the wake of a square cylinder using a hot-wire anemometer are reported. Two Reynolds numbers, namely 8700 and 17,625, have been considered. The measurements were carried out in a low-speed, low-turbulence wind tunnel. Benchmark experiments at much lower Reynolds numbers show good agreement between the present experiments and published results. At higher Reynolds numbers, the experimental data reveal anticipated trends in terms of wake recovery and turbulence decay. Both velocity and velocity fluctuations show symmetry about the wake axis. The experimental data have been compared with the large eddy simulation (LES) calculation reported by Wang et al. [University of Illinois at Urbana – Champaign (1996) Report CFD 96-03] and LDV measurements of Lyn et al. [J Fluid Mech (1995) 304: 285–319]. The agreement among the three sets is generally acceptable in terms of the time-averaged velocity components, but not the velocity fluctuations. The turbulence fluctuations in the present experiments are seen to be lower than in the referred work. The differences have been traced to factors such as the aspect ratio, blockage ratio and upstream turbulence. Experiments with increased upstream turbulence did show a reduction in the discrepancy between the present experiments and the published data. An assessment of the experimental data in terms of physical mechanisms revealed that (a) streamwise normal stresses were correlated with the vortex centers, and (b) the turbulence kinetic energy profiles are similar to the turbulence shear stress. Spectral analysis of the velocity signals was carried out in the present work. Energy transfer from the mean flow to the streamwise velocity fluctuation was confirmed in the near wake. A redistribution of the kinetic energy between the streamwise and transverse components of velocity over a longer distance downstream was subsequently observed.
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  • 3
    ISSN: 1434-601X
    Keywords: PACS. 25.70.Jj Fusion and fusion-fission reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Fission fragment mass and energy distributions and their correlations have been measured for the 16O and 19F + 209Bi reactions over a wide range of excitation energies ( E * = 30-50 MeV). It is observed that in the case of 16O + 209Bi reaction, the average total fragment kinetic energy, 〈TKE〉 is nearly independent of the bombarding energy. However, in the case of 19F + 209Bi reaction, the average total kinetic energy of the fission fragments shows a peaking behaviour near the barrier. The variation in 〈TKE〉 at near barrier energies in the 19F + 209Bi system seems to be correlated with corresponding strong variation in the variance of the fragment mass distribution. The present results may imply certain dynamical effects leading to compact scission configurations in the fission of 19F + 209Bi system at near barrier bombarding energies.
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  • 4
    ISSN: 1434-601X
    Keywords: PACS: 27.70.+q 150 〈 A 〈 189 – 21.10.Re Collective levels – 25.70.Gh Compound nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Measurements of fission fragment yields and neutron multiplicities have been carried out for the Mo-Ba fragment pairs in the spontaneous fission of 252Cf, using the γ-ray spectroscopy technique to analyze γ-γ-γ coincidence data. Prompt γ -ray multiplicities were also measured as a function of the number of neutrons emitted in the fission process leading to the Mo-Ba partition. We do not observe the enhancement in the yields of events with high neutron emission multiplicity (νn 〉 7) that has been associated to a second fission mode leading to the production of hyperdeformed Ba fragments, as reported in some earlier studies. The average γ-ray multiplicity is found to be rather weakly dependent on the number of neutrons emitted in the fission process.
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  • 5
    ISSN: 1434-6036
    Keywords: PACS. 75.30.Vn Colossal magnetoresistance – 61.72.-y Defects and impurities in crystals; microstructure – 72.15.Gd Galvanomagnetic and other magnetotransport effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A structural study has been performed on the La0.8Sr0.2FexCo1-xO3 (x = 0.025 to 0.3) system displaying large magnetoresistance (MR) at room temperature. A detailed analysis of the crystal structure and microstructure was done by X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM). The atomic resolution TEM images and the appearing superreflections in the corresponding SAED patterns revealed that a superstructure is formed due to the presence of iron. The correlation between the ordered microstructure and the observed large MR ratio is discussed. 57Fe Mössbauer spectroscopy was utilized to gain information on the valence state of iron in the sample with x = 0.3. The lattice parameters of Fe- doped La0.8Sr0.2FexCo1-xO3 compounds were found to increase monotonously with increasing Fe content. The valence state of iron was found to be Fe3+.
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  • 6
    ISSN: 1434-4475
    Keywords: Keywords. Cyclizations; 5,6-Fused quinolones; Heterocycles; Sigmatropic rearrangement.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  A simple and efficient synthesis of the hitherto unreported ring systems pyrano[3,2-f]quinolin-2(7H)-one and furo[3,2-f]quinolin-2-one was accomplished via a thermal [3,3]-sigmatropic rearrangement.
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  • 7
    ISSN: 1434-601X
    Keywords: PACS. 25.70.Jj Fusion and fusion-fission reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The pre- and post-scission neutron multiplicities have been determined from the fragment-neutron angular-correlation measurements in 19F + 209Bi reaction at bombarding energy of 108 MeV. The average pre-scission neutron multiplicity ( νpre) is significantly larger than that calculated on the basis of the statistical model. The excess in νpre value is used to estimate the dynamical delay in the fusion-fission time scale for the 228U compound system. For a level density parameter a n = A/10 MeV-1 and a n = a f, the fusion-fission dynamical time was established to be 120 ± 10 × 10-21 s. We also observe that νpre is higher for asymmetric mass splits as compared to symmetric mass splits. The enhancement in the νpre for the asymmetric region could be due to strong variations in the fragment mass distribution at different stages in multiple chance fission at medium excitation energies.
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  • 8
    ISSN: 1061-0421
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Economics
    Notes: One main concern regarding the use of reference prices in advertisements relates to the possibility of deception due to consumers' positive response towards exaggerated or implausible claims. This paper examines the moderating roles of a contextual variable-market price dispersion for a product category, and that of an individual level variable-need for cognition, in influencing consumer evaluation of reference prices across two experiments. The results support the hypothesized effects of need for cognition and demonstrate that, for low need, for cognition individuals, increasing the level of reference price results in positive effects on value perception and shopping intention.
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  • 9
    ISSN: 1061-0421
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Economics
    Notes: This paper examines the effects of resource dependency and contract exclusivity on the attitudes and intentions of consumers in brand alliances. Findings indicate that attitudes of the brands before the alliance (pre-attitudes) have a positive effect on the attitude toward the alliance, which has a positive effect on perceived quality of the alliance, willingness to pay a premium price and purchase intention. Further, attitudes toward the brands after the alliance (post-attitudes) reveal a positive spillover effect for both the host and ally brands. Interestingly, the moderating effects of dependency and exclusivity differ based on whether the brand serves as the host or the ally brand in the alliance. Analyses conducted after controlling for the effects of familiarity of the ally brands revealed consistent results.
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  • 10
    ISSN: 1420-8989
    Keywords: 47A57 ; 47A20 ; 47B35
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this note, we prove a harmonic-type maximal principle for the Schur parametrization of all contractive interpolants in the three chains completion problem (see [4]), which is analogous to the maximal principle proven in [2] in case of the Schur parametrization of all contractive intertwining liftings in the commutant lifting theorem.
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