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991.
S. Duhot R. Mélin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(3):289-296
A Cooper pair from a s-wave superconductor (S) entering a conventional charge density wave (CDW) below the Peierls gap dephases
on the Fermi wavelength while one particle states are localized on the CDW coherence length ξCDW. It is thus practically impossible to observe a Josephson current through a CDW. The paths following different sequences
of impurities interfere destructively, due to the different electron and hole densities in the CDW. The same conclusion holds
for averaging over the conduction channels in the ballistic system. We apply two microscopic approaches to this phenomenon:
(i) a Blonder, Tinkham, Klapwijk (BTK) approach for a single highly transparent S-CDW interface; and (ii) the Hamiltonian
approach for the Josephson effect in a clean CDW and a CDW with non magnetic disorder. The Josephson effect through a spin
density wave (SDW) is limited by the coherence length ξSDW, not by the Fermi wave-length. A Josephson current through a SDW might be observed in a structure with contacts on a SDW
separated by a distance ξSDW. 相似文献
992.
The paper discusses the basic design of the critical facility, whose main purpose is the physics validation of AHWR. Apart
from moderator level control, the facility will have shutdown systems based on shutoff rods and multiple ranges of neutron
detection systems. In addition, it will have a flux mapping system based on 25 fission chambers, distributed in the core.
We are planning to use this reactor for experiments with a suitable source to simulate an ADS system. Any desired sub-criticality
can be achieved by adjusting the moderator level. Apart from perfecting our experimental techniques, in simple configurations,
we intend to study the one-way coupled core in this facility. Preliminary calculations, employing a Monte Carlo code TRIPOLI,
are presented.
相似文献
993.
A. B. Shapoval M. G. Shnirman 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(3):399-403
This paper considers a one-parameter family of sand-piles.
The family exhibits the crossover
between the models with deterministic and stochastic relaxation.
The mean pile height is used to describe the crossover.
The height densities corresponding to the models with relaxation
of both types approach one another as the parameter increases.
Relaxation is supposed to deal
with the local losses of grains by a fixed amount.
In that case the densities show a step-like behaviour
in contrast to the peaked shape
found in the models with the local loss of grains down
to a fixed level
[S. Lübeck, Phys. Rev. E 62, 6149 (2000)].
A spectral approach based on the long-run properties of the pile height
considers the models with deterministic and random relaxation
more accurately and
distinguishes between the two cases for admissible parameter values. 相似文献
994.
文章全面、系统地介绍了近藤效应、近藤问题、近藤共振现象的起源和研究历史的发展过程,提供了一个清晰而准确的近藤物理问题的图像.同时,文章还讨论了近年来近藤共振现象在各种低维电子关联系统中的实现. 相似文献
995.
A new type of combined magnetic focusing–electrostatic deflection systems whose orientation of deflection field is rotated synchronously with the beam electrons is proposed. This rotation deflection field can be formed by twistification of tube wall electrode (TWE) deflectors. Formulae are derived for the first-order optical properties, third-order geometrical aberrations and first-order chromatic aberrations of this system. A program was written in FORTRAN for numerical computation. An example is given; the computation results show that compared to the conventional systems, the proposed new system has lower deflection aberration coefficients. 相似文献
996.
J. Adam K. Katovsky A. Balabekyan V. G. Kalinnikov M. I. Krivopustov H. Kumawat A. A. Solnyshkin V. I. Stegailov S. G. Stetsenko V. M. Tsoupko-Sitnikov W. Westmeier 《Pramana》2007,68(2):201-212
Target-blanket facility ‘Energy + Transmutation’ was irradiated by proton beam extracted from the Nuclotron Accelerator in
Laboratory of High Energies of Joint Institute for Nuclear Research in Dubna, Russia. Neutrons generated by the spallation
reactions of 0.7, 1.0, 1.5 and 2 GeV protons and lead target interact with subcritical uranium blanket. In the neutron field
outside the blanket, radioactive iodine, neptunium, plutonium and americium samples were irradiated and transmutation reaction
yields (residual nuclei production yields) have been determined using γ-spectroscopy. Neutron field's energy distribution
has also been studied using a set of threshold detectors. Results of transmutation studies of 129I, 237Np, 238Pu, 239Pu and 241Am are presented.
相似文献
997.
For efficient progress, model properties and measurement needs can adapt to oceanic events and interactions as they occur. The combination of models and data via data assimilation can also be adaptive. These adaptive concepts are discussed and exemplified within the context of comprehensive real-time ocean observing and prediction systems. Novel adaptive modeling approaches based on simplified maximum likelihood principles are developed and applied to physical and physical–biogeochemical dynamics. In the regional examples shown, they allow the joint calibration of parameter values and model structures. Adaptable components of the Error Subspace Statistical Estimation (ESSE) system are reviewed and illustrated. Results indicate that error estimates, ensemble sizes, error subspace ranks, covariance tapering parameters and stochastic error models can be calibrated by such quantitative adaptation. New adaptive sampling approaches and schemes are outlined. Illustrations suggest that these adaptive schemes can be used in real time with the potential for most efficient sampling. 相似文献
998.
G. A. Miller 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):578-584
The discovery more than twenty years ago, by the EMC Collaboration, that the deep-inelastic-scattering DIS structure functions
are influenced by the nuclear environment stunned the nuclear physics community and brought quarks and gluons into the field
with great impact. A great length of time has passed, but despite a semi-infinite number of papers on the subject, there is
no explanation that is universally accepted. Many models (related in one way or another to QCD) have been successful in reproducing
data for deep inelastic scattering on nuclear targets, but fewer have described both the DIS and nuclear Drell-Yan experiments.
Although there are some positive indications, no model has been used to predict correctly and unambiguously new independent
phenomena. We review the history and discuss the best experimental prospects for future discovery. 相似文献
999.
V. Wagner A. Krása M. Majerle F. Křížek O. Svoboda A. Kugler J. Adam V. M. Tsoupko-Sitnikov M. I. Krivopustov I. V. Zhuk W. Westmeier 《Pramana》2007,68(2):297-306
The set-up ‘energy plus transmutation’, consisting of a thick lead target and a natural uranium blanket, was irradiated by
relativistic proton beams with the energy from 0.7 GeV up to 2 GeV. Neutron field was measured in different places of this
set-up using different activation detectors. The possibilities of using the obtained data for benchmark studies are analyzed
in this paper. Uncertainties of experimental data are shown and discussed. The experimental data are compared with results
of simulation with MCNPX code.
相似文献
1000.
Nathan L. Harshman 《International Journal of Theoretical Physics》2007,46(8):1929-1946
The notion that elementary systems correspond to irreducible representations of the Poincaré group is the starting point for
this paper, which then goes on to discuss how a semigroup for the time evolution of unstable states and resonances could emerge
from the underlying Poincaré symmetry. Important tools in this analysis are the Clebsch-Gordan coefficients for the Poincaré
group. 相似文献