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1.
We give a multiresolution partition of pure point parts of diffraction patterns of one-dimensional aperiodic sets. When an aperiodic set is related to the Golden Ratio, denoted by
, it is well known that the pure point part of its diffractive measure is supported by the extension ring of
, denoted by
. The partition we give is based on the formalism of the so called
-integers, denoted by
. The set of
-integers is a selfsimilar set obeying
,
. The pure point spectrum is then partitioned with respect to this Russian doll like sequence of subsets
. Thus we deduce the partition of the pure point part of the diffractive measure of aperiodic sets.Received: 24 March 2004, Published online: 12 July 2004PACS:
61.44.Br Quasicrystals - 61.10.Dp Theories of diffraction and scattering 相似文献
2.
We study the stationary properties and the state transition of the tumor cell growth model (the logistic model) in presence of correlated noises for the case of nonzero correlation time. We derived an approximative Fokker-Planck equation and the stationary probability distribution (SPD) of the model. Based the SPD, we investigated the effects of both correlation strength (
) and correlation time (
) of cross-correlated noises on the SPD, the mean of the tumor cell population and the normalized variance (
) of the system, and calculated the state transition rate of the system between two stable states. Our results indicate that: (i)
and
play opposite roles in the stationary properties and the state transition of the system, i.e. increase of
can produce a smaller mean value of the cell population and slow down the state transition, but increase of
can produce a larger mean value of the cell population and enhance state transition; (ii) For large
, there a peak structure on both
-
plot and
-
plot. For the small
,
increases with increasing
, but
increases with decreasing
.Received: 26 June 2004, Published online: 30 September 2004PACS:
87.10. + e General theory and mathematical aspects - 05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion - 02.50.Ey Stochastic processes 相似文献
3.
Surface structures in the Te/Ni(111) system are revealed by using reflection high-energy electron diffraction combined with X-ray and ultraviolet photoelectron spectroscopies. At a 0.33 mono-layer (ML)-Te/Ni(111) surface, a reversible structural phase transition is observed with a transition temperature Tc of 380
C. The diffraction pattern from the low temperature phase is accompanied by streaks. The high and low temperature phases are characterized by
and
rectangle, respectively. The mechanism of the phase transition is explained by the order-disorder transition with a rumpled chain model. Both 0.51 ML- and 0.44 ML-Te/Ni(111) surfaces exhibit the complex diffraction patterns accompanied by diffuse streaks. These surface structures are characterized by the
rectangle and
, respectively. All diffuse streaks obtained at the above surfaces are consistently interpreted in the view of the ill-ordered arrangements of the well-ordered
linear chains. It is shown that the
linear structure is the key in the Te/Ni(111) system.Received: 1 December 2003, Published online: 20 April 2004PACS:
61.14.Hg Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED) - 68.65.-k Low-dimensional, mesoscopic, and nanoscale systems: structure and nonelectronic properties - 64.60.Cn Order-disorder transformations; statistical mechanics of model systems 相似文献
4.
Granular films of Co-cluster/C60 mixtures have been prepared by the co-deposition of well defined Co clusters (mean diameter
4.5 nm) and C60 fullerenes onto a cold (
35 K) substrate. Films having a Co cluster volume fraction
show a resistivity
, typical for tunneling with a Coulomb barrier. The tunneling magnetoresistance (TMR) has a value of TMR (
% for
and is decreasing by almost one order of magnitude going to
. We explain this unusual decrease of the TMR with increasing
as caused by electron-doping of the C60 fullerenes due to the known charge transfer process occurring between transition metal surface and C60. Increasing electron doping may lead to an increasing probability for spin-flip processes within the tunneling barrier, resulting in a decrease of the TMR.Received: 17 March 2004, Published online: 3 August 2004PACS:
75.47.-m Magnetotransport phenomena; materials for magnetotransport - 73.40.Gk Tunneling - 73.40.Rw Metal-insulator-metal structures 相似文献
5.
The results of first-principles theoretical study of the structural, electronic and optical properties of beryllium monochalcogenides BeTe, BeSe and BeS, performed using the full potential linearized augmented plane wave (FP-LAPW) method are presented. The calculated structural parameters and band gaps compare very well with previous theoretical results. The trends of the band gap pressure coefficients and volume deformation potentials for these II-VI compounds are investigated. The linear pressure coefficients for the
X and
band gaps increase with decrease in anion atomic weight. The dependence of the direct and indirect band gaps on the relative change of lattice constant are found to follow almost the same type of trends in each of these compounds. The volume deformation potential (
) for the direct (
) and indirect (
) gaps are positive, but negative for the indirect (
) gap. Furthermore,
, for
transitions decreases with increase in anion atomic number whereas
, increases. The optical properties have also been calculated. From the reflectivity spectra, the compounds will be useful for optical applications. The variation of the band gaps with respect to the application of pressure and the origin of some of the peaks in the optical spectra are discussed in terms the calculated electronic structure.Received: 26 September 2003, Published online: 18 June 2004PACS:
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.) - 71.15.Mb Density functional theory, local density approximation, gradient and other corrections - 71.20.Nr Semiconductor compounds 相似文献
6.
D. Bensimon R. Zeyher 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(2):141-150
Phase fluctuations of a d-wave superconducting order parameter are
theoretically studied in the context of high-Tc cuprates. We consider
an extended t-J model describing electrons in a layer which also contains
long-range Coulomb interactions. The constraint of having at most singly
occupied sites is enforced by an additional Hubbard term. The Heisenberg interaction is decoupled by a d-wave order parameter
in the particle-particle channel. Assuming first that the equilibrium state has long-range phase order, the effective action
is derived perturbatively for small fluctuations within a path integral formalism, in the presence of the
Coulomb and Hubbard interaction terms. In a second step, a more general
derivation of
is performed in terms of a gradient
expansion which only assumes that the gradients of the order parameter are
small whereas the value of the phase may be large. We show that in the
phase-only approximation the resulting
reduces in
leading order in the field gradients to the perturbative one which thus allows to treat also the case without long-range phase
order or vortices. Our result generalizes previous
expressions for
to the case of interacting electrons,
is explicitly gauge invariant, and avoids problematic singular
gauge transformations. 相似文献
7.
The effects of the open boundaries on the dynamical behavior of the optimal velocity traffic flow models with a delay time
allowing the car to reach its optimal velocity is studied using numerical simulations. The particles could enter the chain with a given injecting rate probability
, and could leave the system with a given extracting rate probability
. In the absence of the variation of the delay time
, it is found that the transition from unstable to metastable and from metastable to stable state occur under the effect of the probabilities rates
and
. However, for a fixed value of
, there exist a critical value of the extraction rate
above which the wave density disappears and the metastable state appears and a critical value
above which the metastable state disappears while the stable state appears.
and
depend on the values of
and the variation of the delay time
. Indeed
and
increase when increasing
and/or decreasing
. The flow of vehicles is calculated as a function of
,
and
for a fixed value of
. Phase diagrams in the (
) plane exhibits four different phases namely, unstable, metastable, stable. The transition line between stable phase and the unstable one is curved and it is of first order type. While the transition between stable (unstable) phase and the metastable phase are of second order type. The region of the metastable phase shrinks with increasing the variation of the delay time
and disappears completely above a critical value
.Received: 23 July 2003, Published online: 8 December 2003PACS:
05.50. + q Lattice theory and statistics (Ising, Potts, etc.) - 64.60.Cn Order-disorder transformations; statistical mechanics of model systems - 75.30.Kz Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.) - 82.20.Wt Computational modeling; simulation 相似文献
8.
Brovchenko I. Geiger A. Oleinikova A. 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,44(3):345-358
The phase behavior of fluids near weakly attractive substrates is studied by computer simulations of the coexistence curve of a Lennard-Jones (LJ) fluid confined in a slitlike pore. The temperature dependence of the density profiles of the LJ fluid was used to study the surface critical behavior. A universal critical behavior of the local order parameter, defined as the difference between the local densities of the coexisting liquid and vapor phases at some distance
from the pore walls,
, is observed in a wide temperature range and found to be consistent with the surface critical behavior of the Ising model. Near the surface the dependence of the order parameter on the reduced temperature
obeys a scaling law ~1 with a critical exponent 1 of about 0.8, corresponding to the
surface transition. A crossover from bulk-like to surface-like critical behavior occurs, when the distance to the surface is about twice the correlation length at the given temperature. Relations between the
and
transitions in Ising systems and the surface critical behavior of fluids are discussed. 相似文献
9.
J. Voigt E. Kentzinger U. Rücker W. Schweika D. Wermeille W. Schmidt Th. Brückel 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(4):441-451
We have investigated the structural and magnetic properties of
Er|Tb
multilayers by different scattering methods. Diffuse X-ray scattering under
grazing incidence reveals the interface structure in
Er|Tb
bilayers and trilayers, indicating vertically correlated roughness between the Er and Tb interfaces. The magnetic properties
of
ErnEr|TbnTb
superlattices have been studied as a function of the superlattice composition (indices denote the number of atomic layers).
Coupled ferromagnetic structures exist in all investigated samples. The phase transition temperature varies with the Tb layer
thickness.
Modulated magnetic order is short range for all samples beside the
Er20|Tb5
superlattice, the sample with the smallest Tb layer thickness.
We observe dipolar antiferromagnetic coupling between single ferromagnetic Tb layers in all samples, with the onset of this
ordering depending on the Tb layer thickness. Due to competing interactions, exchange coupling is limited to the interface
near region. Therefore long range modulated magnetic order is observed in the
Er20|Tb5
superlattice only, where the interface regions overlap.
The distinct differences to the magnetic structure of an Er0.8Tb0.2
alloy film are explained by a highly anisotropic arrangement of neighbouring
atoms due to the correlated roughness. 相似文献
10.
The quantum dynamics, both non-equilibrium and equilibrium, of the dissipative two-level system is studied by means of the perturbation approach based on a unitary transformation. It works well for the whole parameter range
and
and our main results are: the coherence-incoherence transition is at
; for
the non-equilibrium correlation
; the susceptibility
is of a double peak structure for
and the Shibas relation is exactly satisfied; at the transition point
the equilibrium correlation
in the long time limit.Received: 14 October 2003, Published online: 8 June 2004PACS:
72.20.Dp General theory, scattering mechanisms - 05.30.-d Quantum statistical mechanics 相似文献
11.
Noiret I. Schamps J. Danede F. Odou G. Lamiot J. 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,41(1):23-30
Structural properties of two RbCdCl3 samples grown either from the melt or from aqueous solution are studied via X-ray diffraction over a closed temperature cycle between 20
C and 300
C. During cooling step (300
C), the crystal grown from the melt undergoes a phase transition at 110
C that drives it from the cubic structure into a tetragonal structure that still persists at 20
C. It undergoes exactly the reverse phase transition at the same temperature during the heating (
C) step that immediately follows. The other crystal grows from aqueous solution at 20
C in an orthorhombic structure (i.e. not tetragonal as that of the crystal grown from the melt and cooled down to this temperature). During the heating (
C) step, it undergoes a direct orthorhombic-cubic phase transition at 240
C (without passing through the tetragonal phase) whereas, during subsequent cooling (300
C), it does not exhibit the corresponding reverse phase transition but rather exhibits exactly the same cubic-tetragonal phase transition at 110
C as the crystal grown from the melt. However, for both crystals, this tetragonal phase observed at room temperature is unstable and slowly converts into an orthorhombic phase over the course of time. Complementary Differential Scanning Calorimetry (D.S.C.) and Thermo Gravimetric Analysis (T.G.A.) measurements have been carried out over the range (
)
C in order to interpret diffraction experiments.Received: 19 May 2004, Published online: 30 September 2004PACS:
61.10.Nz X-ray diffraction - 64.70.Kb Solid-solid transitions - 65.40.Ba Heat capacity 相似文献
12.
The laser ion source has been used for the study of the isotope shifts of neutron-deficient Eu isotopes. The extension of the region of applicability of the method by using the
- and
-radiation detection is reported. We have measured the isotope shifts of the europium optical line 576.520 nm for
. To increase the laser ion source efficiency an axial magnetic field (350 gauss) was applied. Nearly a twofold rise of the ionization efficiency for Eu was observed. By using the effect of optical ion bunching an increase of the selectivity was obtained. The isotope shift data for
are in agreement with the previously measured isotope shifts for these nuclides. The new data for
and refined data for
point to a gradual increase of the deformation for these isotopes. Comparisons with microscopic-macroscopic calculations and calculations in the framework of the Hartree-Fock model were performed.Received: 10 November 2003, Revised: 28 April 2004, Published online: 19 October 2004PACS:
29.25.Rm Sources of radioactive nuclei - 42.62.Fi Laser spectroscopy - 21.10.-k Properties of nuclei; nuclear energy levels - 21.10.Ft Charge distribution 相似文献
13.
The kinetics of aggregate growth through reversible migrations between any two aggregates is studied. We propose a simple model with the symmetrical migration rate kernel
at which the monomers migrate from the aggregates of size k to those of size j. The results show that for the
case, the aggregate size distribution approaches a conventional scaling form; moreover, the typical aggregate size grows as
in the
case and as
in the
case. We also investigate another simple model with the asymmetrical rate kernel
(
), which exhibits some scaling properties quite different from the symmetrical one. The aggregate size distribution satisfies the conventional scaling form only in the case of
and
, and the typical aggregate size grows as
.Received: 14 October 2003, Published online: 23 December 2003PACS:
82.20.-w Chemical kinetics and dynamics - 68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation - 89.75.Da Systems obeying scaling laws 相似文献
14.
A. Bartl K. Hohenwarter-Sodek T. Kernreiter H. Rud 《The European Physical Journal C - Particles and Fields》2004,36(4):515-522
We consider the process
at a linear collider with transverse
beam polarization. We investigate the influence of the CP phases on azimuthal asymmetries in
with subsequent two-body decays
and
. We show that triple product correlations involving the transverse
beam polarization vanish if at least one subsequent chargino decay is not observed. We derive this result within the minimal supersymmetric standard model (MSSM) with complex parameters; however, it holds also in the general MSSM with SUSY flavor violation.Received: 29 March 2004, Published online: 30 July 2004 相似文献
15.
Numerical simulations of the field dependence of the isothermal remanent moment (IRM) and the thermoremanent moment (TRM) are presented, based on a Preisach formalism which decomposes the free energy landscape into an ensemble of thermally activated, temperature dependent, double well subsystems, each characterized by a dissipation field H
d
and a bias field H
s
. The simulations show that the TRM approaches saturation much more rapidly than the corresponding IRM and that, as a consequence, the characteristics of the IRM are determined primarily by the distribution of dissipation fields, as defined by the mean field
and the dispersion
, while the characteristics of the TRM are determined primarily by a mixture of the mean dissipation field
and the dispersion of bias fields
. The simulations also identify a regime
, where the influence of
on the TRM is negligible, and hence where the TRM and the IRM provide essentially independent scans of the Preisach distribution along the two orthogonal H
s
and H
d
directions, respectively. The systematics established by the model simulations are exploited to analyze TRM and IRM data from a mixed ferromagnetic perovskite Ca0.4Sr0.6RuO3, and to reconstruct the distribution of characteristic fields H
d
and H
s
, and its variation with temperature.Received: 16 April 2004, Published online: 12 August 2004PACS:
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects - 75.60.-d Domain effects, magnetization curves, and hysteresis 相似文献
16.
We have investigated, in the framework of proximity effect theory, the interface transparency
of superconducting/normal metal layered systems which consist of Nb and high paramagnetic Pd deposited by dc magnetron sputtering. The obtained
value is relatively high, as expected by theoretical arguments. This leads to a large value of the ratio
although Pd does not exhibit any magnetic ordering.Received: 12 December 2003, Published online: 20 April 2004PACS:
74.45. + c Proximity effects; Andreev effect; SN and SNS junctions - 74.78.Fk Multilayers, superlattices, heterostructuresS.L. Prischepa: Permanent address: State University of Computer Science and RadioElectronics, P. Brovka street 6, 220600, Minsk, Belarus 相似文献
17.
It was shown recently [1] that the structural
-relaxation time
of supercooled o-terphenyl depends on a single control parameter
, which is the product of a function of density
, by the inverse temperature T
-1. We extend this finding to other fragile glassforming liquids using light scattering data. Available experimental results do not allow to discriminate between several analytical forms of the function
, the scaling arising from the separation of density and temperature in
. We also propose a simple form for
, which depends only on three material-dependent parameters, reproducing relaxation times over 12 orders of magnitude.Received: 16 July 2004, Published online: 23 December 2004PACS:
66.20. + d Viscosity of liquids; diffusive momentum transport - 78.35. + c Brillouin and Rayleigh scattering; other light scattering - 64.70.Pf Glass transitions 相似文献
18.
C.-M. Ghim E. Oh K.-I. Goh B. Kahng D. Kim 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,38(2):193-199
We investigate a problem of data packet transport between a pair of vertices on scale-free networks without loops or with a small number of loops. By introducing load of a vertex as accumulated sum of a fraction of data packets traveling along the shortest pathways between every pair of vertices, it is found that the load distribution follows a power law with an exponent
. It is found for the Barabási-Albert-type model that the exponent
changes abruptly from
for tree structure to
as the number of loops increases. The load exponent seems to be insensitive to different values of the degree exponent
as long as
.Received: 4 February 2004, Published online: 14 May 2004PACS:
89.75.Fb Structures and organization in complex systems - 05.65. + b Self-organized systems - 02.10.Ox Combinatorics; graph theory 相似文献
19.
We present an analysis of the longitudinal
polarization in ultrarelativistic heavy-ion collisions. The polarization of
s coming from the decay chain
exhibits a very well differentiated behavior depending on the production region of the primordial
s. This effect reflects the different values of the
ratio in the QGP region, where nucleon-nucleon interactions take place in a hot and dense environment, and the peripherical region, in which ordinary nucleon-nucleon interactions occur. An increase in the longitudinal
polarization signals a strangeness enhancement which is thought of as a property of the QGP phase.Received: 21 September 2004, Revised: 25 October 2004, Published online: 17 December 2004 相似文献
20.
K. Christensen N. Farid G. Pruessner M. Stapleton 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):331-336
We derive general properties of the finite-size scaling of
probability density functions and show that when the apparent
exponent
of a probability density is less than 1, the
associated finite-size scaling ansatz has a scaling exponent τ
equal to 1, provided that the fraction of events in the universal
scaling part of the probability density function is non-vanishing in
the thermodynamic limit.
We find the general result that τ≥1 and
.
Moreover, we show that if the scaling function
approaches a
non-zero constant for small arguments,
, then
.
However, if the scaling function vanishes for small arguments,
, then τ= 1, again assuming a
non-vanishing fraction of universal events.
Finally, we apply the formalism developed to examples from the literature,
including some where misunderstandings of the theory of scaling have led to erroneous conclusions. 相似文献