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991.
YANG Guo-Hui GAO Wen-Bin ZHOU Ling SONG He-Shan 《理论物理通讯》2007,48(3):453-456
The thermal entanglement of a two-qubit anisotropic Heisenberg XYZ chain under an inhomogeneous magnetic field b is studied. It is shown that when inhomogeneity is increased to a certain value, the entanglement can exhibit a larger revival than that of less values of b. The property is both true for zero temperature and a finite temperature. The results also show that the entanglement and threshold temperature can be increased by increasing inhomogeneous external magnetic field. 相似文献
993.
Stability related to theoretical model for catastrophic weather prediction, which includes non-hydrostatic perfect elastic model and anelastic model, is discussed and analyzed in detail. It is proved that non-hydrostatic perfect elastic equations set is stable in the class of infinitely differentiable function. However, for the anelastic equations set, its continuity equation is changed in form because of the particular hypothesis for fluid, so "the matching consisting of both viscosity coefficient and incompressible assumption" appears, thereby the most important equations set of this class in practical prediction shows the same instability in topological property as Navier-Stokes equation, which should be avoided first in practical numerical prediction. In light of this, the referenced suggestions to amend the applied model are finally presented. 相似文献
994.
A group of asymmetric difference schemes to approach the Korteweg-de Vries(KdV)equation is given here.According to such schemes,the full explicit difference scheme and the fun implicit one,an alternating segment explicit-implicit difference scheme for solving the KdV equation is constructed.The scheme is linear unconditionally stable by the analysis of linearization procedure,and is used directly on the parallel computer. The numerical experiments show that the method has high accuracy. 相似文献
995.
996.
997.
A series of non-Noether conservative quantities and Mei symmetries of nonconservative systems 下载免费PDF全文
In this paper Mei symmetry is introduced for a nonconservative system. The necessary and
sufficient condition for a Mei symmetry to be also a Lie symmetry is
derived. It is proved that the Mei symmetry leads to a non-Noether
conservative quantity via a Lie symmetry, and deduces a Lutzky conservative
quantity via a Lie point symmetry. 相似文献
998.
The ground state of a two-dimensional square superconducting π
ring array has been investigated. The circulating currents of the
π ring array will spontaneously magnetize to the
`antiferromagnetic' arrangement with directions of the
nearest-neighbouring currents circulating oppositely in the absence
of an external magnetic field. It is found that the external magnetic
field could destroy the anti-parallel configuration effectively. The
external magnetic field needed to destroy the anti-parallel
configuration is related to the superconducting \pi ring's
inductance parameter β=2\pi L Ic/\phi0. For a small β
the anti-parallel configuration, which is the lowest-energy ground
state of the system, will be fully destroyed and changed to the
configuration that the circulating currents have the same direction
and parallel to the external magnetic field when the magnetic flux
reaches \phi0/4 in each ring. Moreover, the magnetic field needed
to destroy the anti-parallel configuration will be very small when
β is large enough. 相似文献
999.
In this paper an efficient quantum secure direct communication (QSDC) scheme with
authentication is presented, which is based on quantum entanglement and
polarized single photons. The present protocol uses Einstein--Podolsky--Rosen
(EPR) pairs and polarized
single photons in batches. A particle of the EPR pairs is retained
in the sender's station, and the other is transmitted forth and back
between the sender and the receiver, similar to the `ping--pong'
QSDC protocol. According to the shared information beforehand, these
two kinds of quantum states are mixed and then transmitted via a
quantum channel. The EPR pairs are used to transmit secret messages
and the polarized single photons used for authentication and
eavesdropping check. Consequently, because of the dual contributions
of the polarized single photons, no classical information is needed.
The intrinsic efficiency and total efficiency are both 1 in this
scheme as almost all of the instances are useful and each EPR pair
can be used to carry two bits of information. 相似文献
1000.
Temperature or strain induced adjustable-chirp characteristics of uniform fibre grating with tapered metal coating 下载免费PDF全文
Temperature and strain characteristics of uniform fibre grating with
tapered metal coatings have been analysed theoretically, by which
adjustable chirp characteristics of such gratings are shown.
Electroplating is adopted to fabricate such gratings, and the tapered
metal coating is obtained by gradually drawing the fibre grating out
of the solution during the process of electroplating. The gradually
changing cross-sectional area of the metal coating is calculated by a
newly suggested numerical method. By combining the theoretical and
numerical simulation analyses, the gratings' characteristics are
given at various temperatures and strains. The results obtained using
such a method are also testified by experiments. 相似文献