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201.
We study a nonlinear fourth order evolution equation arising in the context of sand ripple dynamics. We analyse the set of stationary solutions and travelling waves in order to recover the observed phenomenology such as different wavelengths ripples, travelling waves, coarsening and time scales. Moreover, we construct an approximate solution which describes the early stages of the dynamics and which suggests the existence of coarsening and of time scales with different dynamical behaviour. 相似文献
202.
Explicit Traveling Wave Solutions and Their Dynamical Behaviors for the Coupled Higgs Field Equation 下载免费PDF全文
In this paper, we focus on the traveling wave solutions of the coupled Higgs field equation from the perspective of dynamical systems. Through the phase portraits, in addition to periodic wave solutions and solitary wave solutions, we also obtain explicit periodic singular wave solutions, singular wave solutions and kink wave solutions, which were not found in the previous works. The dynamical behavior of these solutions and their internal relations are revealed through asymptotic analysis. The results will help supplement the study of field equation. 相似文献
203.
C. E. I. Carneiro M. J. de Oliveira W. F. Wreszinski 《Journal of statistical physics》1995,79(1-2):347-376
We show rigorously that the ground state of a quantum chain with competing ferromagnetic nearest and antiferromagnetic next nearest interactions undergoes a transition from ferromagnetic to helical type, in the isotropic case, for a certain value of the relevant ratio of coupling constants. Boundaries of the phase diagram are also determined in the anisotropic case. The stability of a special quantum state (corresponding to a classical modulated phase of =/3) is analyzed by an extension of Holstein-Primakoff arguments, along a line of constant ratio of couplings, showing in particular a sequence of (instability) gaps. Finally, a natural adaptation of a variational wave function due to Huse and Elser is used to study several portions of the phase diagram, with very good agreement with previous theoretical results. 相似文献
204.
Prospecting for oil and gas resources poses the problem of determining the geological structure of the earth's crust from indirect measurements. Seismic migration is an acoustic image reconstruction technique based on the inversion of the scalar wave equation. Extensive computation is necessary before reliable information can be extracted from large sets of recorded data. In this paper a collection of industrial migration techniques, each giving rise to a data parallel algorithm, is outlined. Computer simulations on synthetic seismic data illustrate the problem and the approach. 相似文献
205.
Aleksandr V. Prichodko Evgenii V. Shatkovski Sergei G. Yastrebov 《International Journal of Infrared and Millimeter Waves》1994,15(3):579-584
Photostimulated changes in thin carbon films deposited onto fused silica substrates by reactive magnetron sputtering and irradiated by the light of the first (1060nm) and the second (530nm) harmonics of a QW-switched Nd3+ AVG laser were investigated. The changes are supposed to be connected with the reordering of chemical bounds. 相似文献
206.
M. Slemrod 《Journal of statistical physics》1996,83(5-6):1067-1108
A discrete-velocity Boltzmann model is introduced. It is based on two principles: (i) clusters of particles move in 3 with seven fixed momenta; (ii) clusters may gain or lose particles according to the rules of Becker-Döring cluster equations. The model provides a kinetic representation of evaporation and condensation. The model is used to obtain macroscopic fluid equations which are valid into the metastable fluid regime,
, where is any positive number, is the inelastic Knudsen number, and
s
is the saturation density. 相似文献
207.
LIZHIBIN SHIHE 《高校应用数学学报(英文版)》1996,11(1):1-6
Abstract. We consider the following simplified model for the Belousou-Zhabotinskii(B-Z)reaction: 相似文献
208.
Jeffrey Bub 《Foundations of Physics Letters》1993,6(1):21-35
Elby (1993) has raised certain problems that appear to be devastating for modal interpretations of quantum mechanics, but do not arise for Bohm's pilot wave theory. Here I show that the features Elby identifies as objectionable in my version of the modal interpretation have their counterpart in Bohm's theory. To the extent that Bohm's theory works as a no collapse solution to the measurement problem - and I think it does - so does my modal interpretation. 相似文献
209.
Transient propagation of weak pressure perturbations in a homogeneous, isotropic, fluid saturated aquifer has been studied. A damped wave equation for the pressure in the aquifer is derived using the macroscopic, volume averaged, mass conservation and momentum equations. The equation is applied to the case of a well in a closed aquifer and analytical solutions are obtained to two different flow cases. It is shown that the radius of influence propagates with a finite velocity. The results show that the effect of fluid inertia could be of importance where transient flow in porous media is studied.List of symbols
b
Thickness of the aquifer, m
-
c
0
Wave velocity, m/s
-
k
Permeability of the porous medium, m2
-
n
Porosity of the porous medium
-
p(
,t)
Pressure, N/m2
-
Q
Volume flux, m3/s
-
r
Radial coordinate, m
-
r
w
Radius of the well, m
-
s
Transform variable
-
S
Storativity of the aquifer
-
S
d(r, t)
Drawdown, m
-
t
Time, s
-
T
Transmissivity of the aquifer, m2/s
-
(
,t)
Velocity of the fluid, m/s
-
Coordinate vector, m
-
z
Vertical coordinate, m
-
Coefficient of compressibility, m2/N
-
Coefficient of fluid compressibility, m2/N
-
Relaxation time, s
-
(r, t)
Hydraulic potential, m
-
Dynamic viscosity of the fluid, Ns/m2
-
Dimensionless radius
-
Density of the fluid, Ns2/m4
-
(, )
Dimensionless drawdown
-
Dimensionless time
-
, x
Dummy variables
-
0,
1
Auxilary functions 相似文献
210.
We propose a new approach for high-throughput continuous titration based on a flow ratiometry. The method was applied to potentiometric titrations of acids and bases. A base solution, the flow rate FB of which was varied in response to controller output voltage Vc, was merged with an acid solution under constant total (acid + base) flow rate. Downstream, the pH of the mixed solution was measured with a flow-through glass electrode. Initially, Vc, and thus FB was increased linearly. At the instant the equivalence point (EP) was sensed, the ramp direction of Vc was reversed from upward to downward. The direction was reversed to upward when EP was sensed again. Such the feedback-based operation gives a triangular waveform of Vc, because there is a delay corresponding mainly to the transit time of merged solutions to reach the sensor. The value of Vc that gives EP composition, VE, was estimated by averaging the most recent maximum and minimum values of Vc. Next, fixed triangular waves of Vc was used to control FB. The amplitude and the scan rate of the waves were fixed narrower and faster, respectively, than those in the feedback-based operation in order to improve the throughput rate. The EP can be located as long as the scan range covers VE. These automated processes limited the titration to just the narrow range around EP, and thus realized extremely high throughput rate of maximally 17.6 titrations per minute (=3.4 s per titration) at R.S.D. = 0.35%. 相似文献