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991.
In this paper we consider an ignition-temperature zero-order reaction model of thermo-diffusive combustion. This model describes the dynamics of thick flames, which have recently received considerable attention in the physical and engineering literature. The model admits a unique (up to translations) planar travelling wave solution. This travelling wave solution is quite different from those usually studied in combustion theory. The main qualitative feature of this travelling wave is that it has two interfaces: the ignition interface where the ignition temperature is attained and the trailing interface where the concentration of deficient reactants reaches zero. We give a new mathematical framework for studying the cellular instability of such travelling front solutions. Our approach allows the analysis of a free boundary problem to be converted into the analysis of a boundary value problem having a fully nonlinear system of parabolic equations. The latter is very suitable for both mathematical and numerical analysis. We prove the existence of a critical Lewis number such that the travelling wave solution is stable for values of Lewis number below the critical one and is unstable for Lewis numbers that exceed this critical value. Finally, we discuss the results of numerical simulations of a fully nonlinear system that describes the perturbation dynamics of planar fronts. These simulations reveal, in particular, some very interesting ‘two-cell’ steady patterns of curved combustion fronts. 相似文献
992.
Implementing of photonic sampling and quantizing analog-to-digital converters (ADCs) enable us to extract a single binary word from optical signals without need for extra electronic assisting parts. This would enormously increase the sampling and quantizing time as well as decreasing the consumed power. To this end, based on the concept of successive approximation method, a 4-bit full-optical ADC that operates using the intensity-dependent Kerr-like nonlinearity in a two dimensional photonic crystal (2DPhC) platform is proposed. The Silicon (Si) nanocrystal is chosen because of the suitable nonlinear material characteristic. An optical limiter is used for the clamping and quantization of each successive levels that represent the ADC bits. In the proposal, an energy efficient optical ADC circuit is implemented by controlling the system parameters such as ring-to-waveguide coupling coefficients, the ring’s nonlinear refractive index, and the ring’s length. The performance of the ADC structure is verified by the simulation using finite difference time domain (FDTD) method. 相似文献
993.
Between many prominent contributions of Markus Büttiker to mesoscopic physics, the scattering theory approach to the electron transport and noise stands out for its elegance, simplicity, universality, and popularity between theorists working in this field. It offers an efficient way to theoretically investigate open electron systems far from equilibrium. However, this method is limited to situations where interactions between electrons can be ignored, or considered perturbatively. Fortunately, this is the case in a broad class of metallic systems, which are commonly described by the Fermi liquid theory. Yet, there exist another broad class of electron systems of reduced dimensionality, the so-called Tomonaga–Luttinger liquids, where interactions are effectively strong and cannot be neglected even at low energies. Nevertheless, strong interactions can be accounted exactly using the bosonization technique, which utilizes the free-bosonic character of collective excitations in these systems. In the present work, we use this fact in order to develop the scattering theory approach to the bosonization of open quasi-one dimensional electron systems far from equilibrium. 相似文献
994.
Granular flows in a rotating drum: the scaling law
between velocity and thickness of the flow 总被引:1,自引:0,他引:1
The flow of dry granular material in a half-filled rotating drum is studied. The thickness of the flowing zone is measured
for several rotation speeds, drum
sizes and beads sizes (size ratio between drum and beads ranging from 47
to 7400). Varying the rotation speed, a scaling law linking
mean velocity vs. thickness of the flow, v∼hm, is deduced for each couple
(beads, drum). The
obtained exponent m is not always equal to 1, the value previously reported for a drum in litterature, but varies with the
geometry of the system.
For small size ratios, exponents higher
than 1 are obtained due to a saturation of the flowing zone thickness.
The exponent of the power law decreases with the size ratio, leading
to exponents lower than 1 for high size ratios. These exponents imply that
the velocity gradient of a dry granular flow in a rotating drum
is not constant. More fundamentally, these results show that the flow of a
granular material in a rotating drum is very sensible to the geometry, and that
the deduction of the “rheology” of a granular medium flowing in such a
geometry is not obvious. 相似文献
995.
Pica Ciamarra M Coniglio A Nicodemi M 《The European physical journal. E, Soft matter》2007,22(3):227-234
We overview the physics of a granular mixture subject to horizontal oscillations,
recently investigated via experiments and molecular dynamics simulations.
First we discuss the rich phenomenology exhibited by this system, which encompasses
both segregation and dynamical instabilities.
Then we show that the phenomenology can be explained
via an effective interaction approach, by which the driven,
non-thermal, granular mixture in mapped into a monodispersed thermal
system of particles interacting via an effective potential.
After determining the effective interaction we discuss its
microscopic origin and investigate how it induces the observed
phenomenology. Finally, as much as in thermal fluids, from the
effective interaction we derive a Cahn-Hilliard dynamics equation,
which appears to capture the essential characteristics of the dynamics
of the granular mixture. 相似文献
996.
Topin V Delenne JY Radjai F Brendel L Mabille F 《The European physical journal. E, Soft matter》2007,23(4):413-429
Cemented granular materials (CGMs) consist of densely packed solid particles and a pore-filling solid matrix sticking to the
particles. We use a sub-particle lattice discretization method to investigate the particle-scale origins of strength and failure
properties of CGMs. We show that jamming of the particles leads to highly inhomogeneous stress fields. The stress probability
density functions are increasingly wider for a decreasing matrix volume fraction, the stresses being more and more concentrated
in the interparticle contact zones with an exponential distribution as in cohesionless granular media. Under uniaxial loading,
pronounced asymmetry can occur between tension and compression both in strength and in the initial stiffness as a result of
the presence of bare contacts (with no matrix interposed) between the particles. Damage growth is analyzed by considering
the evolution of stiffness degradation and the number of broken bonds in the particle phase. A brutal degradation appears
in tension as a consequence of brittle fracture in contrast to the more progressive nature of damage growth in compression.
We also carry out a detailed parametric study in order to assess the combined influence of the matrix volume fraction and
particle-matrix adherence. Three regimes of crack propagation can be distinguished corresponding to no particle damage, particle
abrasion and particle fragmentation, respectively. We find that particle damage scales well with the relative toughness of
the particle-matrix interface with respect to the particle toughness. This relative toughness is a function of both matrix
volume fraction and particle-matrix adherence and it appears therefore to be the unique control parameter governing transition
from soft to hard behavior. 相似文献
997.
Regtmeier J Eichhorn R Duong TT Reimann P Anselmetti D Ros A 《The European physical journal. E, Soft matter》2007,22(4):335-340
We demonstrate the proof-of-principle of a new separation concept for micrometer-sized particles in a structured microfluidic
device. Under the action of externally applied, periodic
voltage-pulses two different species of like-charged polystyrene beads are observed to simultaneously migrate into opposite
directions. Based on a theoretical model of the particle motion in the microdevice that shows good agreement with the experimental
measurements, the underlying separation mechanism is identified and explained. Potential biophysical applications, such as
cell sorting, are briefly addressed. 相似文献
998.
J.-B. Liu J.-H. Li X.-Y. Lü A. Zheng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):601-606
In this paper, we investigate the geometric phase of a composite system which is composed of two spin-
particles driven by a
time-varying magnetic field. Firstly, we consider the special case that only one subsystem driven by time-varying magnetic
field. Using the quantum jump
approach, we calculate the geometric phase associated with the adiabatic evolution of the system subjected to decoherence.
The results show that the lowest
order corrections to the phase in the no-jump trajectory is only quadratic in decoherence coefficient. Then, both subsystem
driven by time-varying magnetic
field is considered, we show that the geometric phase is related to the exchange-interaction coefficient and polar angle of
the magnetic field. 相似文献
999.
J.-H. Huang S.-Y. Zhu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):557-575
The normalized second-order
correlation of the emission fields from a driven four-level atomic
ensemble is investigated theoretically by using the state vector
method. The violation of Cauchy-Schwarz inequality, which indicates
the establishment of non-classical correlation between two emission
fields, has been found. The effects of various decays and time delay
on the correlation are discussed in detail, which are helpful in
finding the ways to obtain high non-classical correlation. This
technique for the generation of non-classical light is operable
based on the current experimental technology and will lead to some
potential applications in quantum information science. 相似文献
1000.
J. B. Satinover D. Sornette 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(3):369-384
Human beings like to believe they are in control of their
destiny. This ubiquitous trait seems to increase motivation and persistence,
and is probably evolutionarily adaptive [J.D. Taylor, S.E. Brown, Psych. Bull. 103, 193 (1988); A. Bandura,
Self-efficacy: the exercise of control (WH Freeman, New
York, 1997)]. But how good really is our
ability to control? How successful is our track record in these areas? There
is little understanding of when and under what circumstances we may
over-estimate [E. Langer, J. Pers. Soc. Psych. 7, 185 (1975)] or even lose our ability to control and optimize outcomes,
especially when they are the result of aggregations of individual
optimization processes. Here, we demonstrate analytically using the theory
of Markov Chains and by numerical simulations in two classes of games, the
Time-Horizon Minority Game [M.L. Hart, P. Jefferies, N.F. Johnson, Phys. A 311, 275 (2002)] and the Parrondo Game
[J.M.R. Parrondo, G.P. Harmer, D. Abbott, Phys. Rev. Lett.
85, 5226 (2000); J.M.R. Parrondo, How to cheat a bad mathematician (ISI, Italy, 1996)], that agents
who optimize their strategy based on past information may actually perform
worse than non-optimizing agents. In other words, low-entropy (more
informative) strategies under-perform high-entropy (or random) strategies.
This provides a precise definition of the “illusion of control” in certain
set-ups a priori defined to emphasize the importance of optimization.
An erratum to this article is available at . 相似文献