共查询到20条相似文献,搜索用时 15 毫秒
1.
N. Moussa 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):193-196
Using computer simulations, we show that metastable states still
occur in two-lane traffic models with slow to start rules.
However, these metastable states no longer exist in systems where
aggressive drivers (which do not look back before changing
lanes) are present. Indeed, the presence of only one aggressive
driver in the circuit, triggers the breakdown of the high flow
states. In these systems, the steady state is unique and its
relaxation dynamics should depend on the lane changing probability
pch and the number of aggressive drivers present in the
circuit. It is found also that the relaxation time τ diverges
as the form of a power-law: τ∝pch
-β, β=1.
89.40.+k 相似文献
2.
R. Jiang M.-B. Hu B. Jia R. Wang Q.-S. Wu 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):197-206
In this paper, we have investigated the effects of adaptive cruise
control (ACC) vehicles in a mixture with manually-controlled
(manual) vehicles. The manual vehicles are simulated by using the
modified comfortable driving model, which can describe
synchronized traffic flow. The phase transition probabilities from free
flow to synchronized flow and from synchronized flow to jams are
studied. The impact of ACC vehicles on the flow rates in free flow
and synchronized flow and on the propagation velocity of the
downstream front of jams are investigated. The dependence of
microscopic properties of traffic flow, including the
spatiotemporal patterns and the velocity distribution, is
explored. Our results are expected to be useful for developing ACC
systems. 相似文献
3.
We present extensive computational results for the effective temperature,
defined by the fluctuation-dissipation relation between the mean square
displacement and the average displacement of grains, under the action of
a weak, external perturbation, of a sheared, bi-disperse granular packing
of compressible spheres. We study the dependence of this parameter on the
shear rate and volume fractions, the type of particle and the observable
in the fluctuation-dissipation relation. We find the same temperature
for different tracer particles in the system. The temperature becomes
independent on the shear rate for slow enough shear suggesting that it is
the effective temperature of the jammed packing. However, we also show
that the agreement of the effective temperature for different observables
is only approximate, for very long times, suggesting that this defintion
may not capture the full thermodynamics of the system. On the other hand,
we find good agreement between the dynamical effective temperature and a
compactivity calculated assuming that all jammed states are equiprobable.
Therefore, this definition of temperature may capture an instance
of the ergodic hypothesis for granular materials as proposed by theoretical
formalisms for jamming. Finally, our simulations indicate
that the average shear
stress and apparent shear viscosity follow the usual relation with the shear
rate for complex fluids. Our results show that the application of
shear induces jamming in packings whose particles interact
by tangential forces. 相似文献
4.
P. Fronczak A. Fronczak J. A. Hołyst 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):133-139
We study a model of network with clustering and desired node
degree. The original purpose of the model was to describe optimal
structures of scientific collaboration in the European Union. The
model belongs to the family of exponential random graphs. We show
by numerical simulations and analytical considerations how a very
simple Hamiltonian can lead to surprisingly complicated and
eventful phase diagram. 相似文献
5.
E.G. Campari G. Levi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(2):245-251
Highway traffic as simulated with a simple cellular automata model has been analysed in a search for self-similarity in the
behaviour of car density and car flow as a function of space. Fractal dimensions between 1.5 and 1.6, depending on the simulation
characteristics, have been measured with a box counting algorithm. The self-similarity spans over about 2 orders of magnitude.
A comparison with experimental data is suggested.
Received 23 April 2001 and Received in final form 28 September 2001 相似文献
6.
W. Hichri A. Kirman 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(2):149-159
In physical models it is well understood that the aggregate behaviour of a system is not in one to one correspondence with
the behaviour of the average individual element of that system. Yet, in many economic models the behaviour of aggregates is
thought of as corresponding to that of an individual. A typical example is that of public goods experiments. A systematic
feature of such experiments is that, with repetition, people contribute less to public goods. A typical explanation is that
people “learn to play Nash” or something approaching it. To justify such an
explanation, an individual learning model is tested on average or aggregate data. In this paper we will examine this idea
by analysing average and individual behaviour in a series of public goods experiments. We analyse data from a series of games
of contributions to public goods and as is
usual, we test a learning model on the average data. We then look at individual data, examine the changes that this produces
and see if some general model such as the EWA (Expected Weighted Attraction) with varying parameters can account for individual
behaviour. We find that once we
disaggregate data such models have poor explanatory power. Groups do not learn as supposed, their behaviour differs markedly
from one group to another, and the behaviour of the individuals who make up the groups also varies within groups. The decline
in aggregate contributions cannot be
explained by resorting to a uniform model of individual behaviour. However, the Nash equilibrium of such a game is a total
payment for all the individuals and there is some convergence of the group in this respect. Yet the individual contributions
do not converge. How the individuals
“self-organsise” to coordinate, even in this limited way remains to be explained. 相似文献
7.
A. Namazi N. Eissfeldt P. Wagner A. Schadschneider 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):559-570
The Krauss-model is a stochastic model for traffic flow which is continuous in space. For periodic boundary conditions it
is well understood and known to display a non-unique flow-density relation (fundamental diagram) for certain densities. In
many applications, however, the behaviour under open boundary conditions plays a crucial role. In contrast to all models investigated
so far, the high flow states of the Krauss-model are not metastable, but also stable. Nevertheless we find that the current
in open systems obeys an extremal principle introduced for the case of simpler discrete models. The phase diagram of the open
system will be completely determined by the fundamental diagram of the periodic system through this principle. In order to
allow the investigation of the whole state space of the Krauss-model, appropriate strategies for the injection of cars into
the system are needed. Two methods solving this problem are discussed and the boundary-induced phase transitions for both
methods are studied. We also suggest a supplementary rule for the extremal principle to account for cases where not all the
possible bulk states are generated by the chosen boundary conditions.
Received 16 September 2002 / Received in final form 4 November 2002 Published online 31 December 2002 相似文献
8.
M.V. Altaisky 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(4):613-617
Most of dynamic systems which exhibit chaotic behavior are also known to posses self-similarity and manifest strong fluctuations
of all possible scales. The meaning of this terms is not always same. In present note we make an attempt to formulate the
problem in the framework of functional analysis. The statistical hydrodynamics is taken as a vivid physical example. The links
to wavelet analysis are presented.
Received 22 August 1997 相似文献
9.
T. Dudok de Wit 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(3):513-516
An expression is proposed for determining the error made by neglecting finite sample effects in entropy estimates. It is based
on the Ansatz that the ranked distribution of probabilities tends to follow a Zipf scaling.
Received 17 August 1998 and Received in final form 8 February 1999 相似文献
10.
E.G. Campari G. Levi 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(1):159-166
We present results relative to a simple cellular automata model without periodic boundary conditions for an highway with on-ramps.
Simulations performed with this model reproduce experimental phenomena observed in traffic such as free flow, synchronized
flow, congested flow, lane inversion, forward and backward propagating waves. On-ramps play the important role of nucleation
points for the dynamic features of traffic.
Received 4 February 2000 and Received in final form 5 May 2000 相似文献
11.
K. Konishi H. Kokame K. Hirata 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(4):715-722
The jam phenomenon in traffic flow wastes not only considerable traffic-transportation time but also great amounts of fuel
due to many accelerate-decelerate actions. From traffic-economic and traffic-pollution viewpoints, the suppression of traffic
jam is an important issue we have to solve. The present paper shows that -norm, which has been used in the field of control theory, can reveal the traffic jam phenomenon in an optimal velocity traffic
model under an open boundary condition. Furthermore, we suppress the traffic jam in the model by the decentralized delayed-feedback
control method. Some numerical simulations are shown to verify our theoretical results.
Received 27 October 1999 相似文献
12.
Iddo Eliazar 《Physica A》2010,389(4):659-666
Consider a finite sequence of independent-though not, necessarily, identically distributed-real-valued random scores. If the scores are absolutely continuous random variables, the sequence possesses a unique maximum (minimum). We say that “maximal (minimal) independence” holds if the value and the identity of the sequence’s unique maximal (minimal) score are independent random variables. In this research we study the class of statistics for which maximal (minimal) independence holds, and: (i) establish explicit characterizations of this class; (ii) connect this class with the class of Lévy processes; (iii) unveil the underlying spatial Poissonian structure of this class. 相似文献
13.
H. B. Zhu H. X. Ge L. Y. Dong S. Q. Dai 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(1):103-108
Based on the Nagel-Schreckenberg (NaSch)
model of traffic flow, a modified cellular automaton (CA) traffic
model with the density-dependent randomization (abbreviated as the
DDR model) is proposed to simulate traffic flow. The fundamental
diagram obtained by simulation shows the ability of this modified
NaSch model to capture the essential features of traffic flow,
e.g., synchronized flow, metastable state, hysteresis and phase
separation at higher densities. Comparisons are made between this
DDR model and the NaSch model, also between this DDR model and the
VDR model. And the underlying mechanism is analyzed. All these
results indicate that the presented model is reasonable and more
realistic. 相似文献
14.
T. Neumann 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(1):133-138
Cellular automata models play an important role in traffic modeling. For some variants of the Nagel-Schreckenberg model, the
effects of traffic light boundary conditions are considered. Based on previous results, the exact density profiles can be
derived easily for deterministic dynamics. Additionally, the exact average outflow per traffic light cycle is presented not
only in the deterministic case, but also for an important semi-stochastic variant with slow-to-start behaviour. Thereby, the
models are strongly related to the well-known totally asymmetric simple exclusion process (TASEP) which can be regarded as
a generic model for many driven particle systems. 相似文献
15.
E. Katzav 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):137-140
In the paper the role of long range interactions on the
growth of a volume conserving surface is studied using the Nonlocal
Conserved Kardar-Parisi-Zhang (NCKPZ) equation. It is shown that
previous theoretical predictions are inconsistent with an exact
one-dimensional result. This serves as a motivation for construction
of a Self-Consistent Expansion (SCE) that recovers the exact
one-dimensional result, and gives the scaling exponents in higher
dimensions as well. A possible application of this result to
colloidal systems is discussed. 相似文献
16.
T. Neumann P. Wagner 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):255-264
A simple cellular automaton to model traffic flow is used to analyze the impact of traffic lights on travel times. The model
is investigated on a stretch of road with open boundaries, where the inflow is driven stochastically, but the outflow is controlled
by a traffic light with periodically changing outflow rates. Especially in the transition regime from free flow to oversaturated
flow, the detailed space-time structure can be used to derive analytical lower and upper boundaries for the travel time function.
The analytical results have been verified by a simulation study. The function displays a strong non-trivial dependency on
the length of the system, which is at odds with a well-known formula derived almost 50 years ago by Webster. Such a model
is interesting both from a theoretical point of view and for applications. 相似文献
17.
18.
M. A. Fuentes H. S. Wio 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(2):249-253
With the aim of studying stochastic resonance (SR) in a
double-well potential when the noise source has a spectral density
of the form f-κ (with varying κ), we have extended
a procedure introduced by Kaulakys et al. (Phys. Rev. E 70,
020101 (2004)). In order to achieve an analytical understanding of
the results, we have obtained an effective Markovian approximation
that allows us to make a systematic study of the effect of such
noise on the SR phenomenon. A comparison of the numerical and
analytical results shows an excellent qualitative agreement
indicating that the effective Markovian approximation is able to
correctly describe the general trends. 相似文献
19.
I. Lubashevsky P. Wagner R. Mahnke 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(2):243-247
This paper introduces a car following model where the driving scheme takes into account the deficiencies of human decision
making in a general way. Additionally, it improves certain shortcomings of most of the models currently in use: it is stochastic
but has a continuous acceleration. This is achieved at the cost of formulating the model in terms of the time derivative of
the acceleration, making it non-Newtonian. However, the recipe for construction of bounded rational driver models proposed
in this paper seems to be very general and can be applied to most, if not all of the traditional car-following models.
Received 18 November 2002 / Received in final form 6 February 2003 Published online 1st April 2003
RID="a"
ID="a"e-mail: ialub@fpl.gpi.ru
RID="b"
ID="b"e-mail: peter.wagner@dlr.de
RID="c"
ID="c"e-mail: reinhard.mahnke@physik.uni-rostock.de 相似文献
20.
S. Roux J.F. Muzy A. Arneodo 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(2):301-322
Swirling turbulent flows display intermittent pressure drops associated with intense vorticity filaments. Using the wavelet
transform modulus maxima representation of pressure fluctuations, we propose a method of characterizing these pressure drop
events from their time-scale properties. This method allows us to discriminate fluctuations induced by just formed (young)
as well as by burst (old) filaments from background pressure fluctuations. The statistical characteristics of these filaments
(core size, waiting time) are analyzed in details and compared with previously reported experimental and numerical findings.
Their intermittent occurrence is found to be governed by a pure Poisson's law, the hallmark of independent events. Then we
apply the wavelet transform modulus maxima (WTMM) method to the background pressure fluctuations. This study reveals that,
once removed all the filaments, the “multifractal” nature of pressure fluctuations still persists. This is a clear indication
that the statistical contribution of the filaments is not important enough to account for the intermittency phenomenon in
turbulents flows.
Received 27 July 1998 and Received in final form 23 November 1998 相似文献