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991.
The one-dimensional Brownian motion and the Brownian motion of a spherical particle in an infinite medium are described by
the conventional methods and integral transforms considering the entrainment of surrounding particles of the medium by the
Brownian particle. It is demonstrated that fluctuations of the Brownian particle velocity represent a non-Markovian random
process. A harmonic oscillator in a viscous medium is also considered within the framework of the examined model. It is demonstrated
that for rheological models, random dynamic processes are also non-Markovian in character.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 66–74, February, 2009. 相似文献
992.
993.
B. Spagnolo S. Spezia L. Curcio N. Pizzolato A. Fiasconaro D. Valenti P. Lo Bue E. Peri S. Colazza 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):133-146
We investigate the role of the colored noise in two
biological systems: (i) adults of Nezara viridula (L.)
(Heteroptera: Pentatomidae), and (ii) polymer translocation. In the
first system we analyze, by directionality tests, the response of
N. viridula individuals to subthreshold signals plus noise
in their mating behaviour. The percentage of insects that react to
the subthreshold signal shows a nonmonotonic behaviour,
characterized by the presence of a maximum, as a function of the
noise intensity. This is the signature of the non-dynamical
stochastic resonance phenomenon. By using a “soft” threshold model
we find that the maximum of the input-output cross correlation
occurs in the same range of noise intensity values for which the
behavioural activation of the insects has a maximum. Moreover this
maximum value is lowered and shifted towards higher noise
intensities, compared to the case of white noise. In the second
biological system the noise driven translocation of short polymers
in crowded solutions is analyzed. An improved version of the Rouse
model for a flexible polymer is adopted to mimic the molecular
dynamics by taking into account both the interactions between
adjacent monomers and the effects of a Lennard-Jones potential
between all beads. The polymer dynamics is simulated in a
two-dimensional domain by numerically solving the Langevin equations
of motion in the presence of thermal fluctuations and a colored
noise source. At low temperatures or for strong colored noise
intensities the translocation process of the polymer chain is
delayed. At low noise intensity, as the polymer length increases, we
find a nonmonotonic behaviour for the mean first translocation time
of the polymer centre of inertia. We show how colored noise
influences the motion of short polymers, by inducing two different
regimes of translocation in the dynamics of molecule transport. 相似文献
994.
T. Prager A. B. Neiman L. Schimansky-Geier 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(1):119-126
Stimulation with periodic force is a standard method to
study response properties of a system. Here we examine a special
type of systems which generate a sequence of events with
uncorrelated time intervals. We review analytical tools to calculate
the gain and the signal-to-noise ratio for such systems when
perturbed by sinusoidal signal and then apply these tools to the
stochastic FitzHugh-Nagumo model. 相似文献
995.
Yong Woon Parc Duk-Su Koh Wokyung Sung 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):127-131
Stochastic resonance (SR) is a novel cooperative phenomenon occurring in
nonlinear systems due to coupling of an ambient noise and an external
signal. Biological systems may use SR mechanism to detect the signal
efficiently from an external environment. A number of studies have addressed
the SR in artificial ion channels considering external voltages as noises.
More important than these external noises is the internal, thermal noise
which changes the channel conformations essential for biological functions.
In this work, we consider that the channel gating rates follow a
non-Arrhenius temperature dependence derived from experimental data of a
real biological channel. Using the Monte-Carlo simulations, we find that in
this channel SR occurs near a physiological temperature in a very
distinctive manner compared with that for the Arrhenius gating model. 相似文献
996.
M. Treiber D. Helbing 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(4):607-618
This contribution presents a derivation of the steady-state distribution of velocities and
distances of driven particles on a onedimensional periodic ring, using a Fokker-Planck formalism. We will compare two different
situations: (i) symmetrical interaction forces fulfilling Newton’s law
of “actio = reactio” and (ii) asymmetric, forwardly directed interactions as, for example
in vehicular traffic. Surprisingly, the steady-state velocity and distance distributions
for asymmetric interactions and driving terms agree with the equilibrium distributions of
classical many-particle systems with symmetrical interactions, if the system is large enough.
This analytical result is confirmed by computer simulations and
establishes the possibility of approximating the steady state
statistics in driven many-particle systems by Hamiltonian systems. Our finding is also
useful to understand the various departure time distributions of queueing systems as a possible
effect of interactions among the elements in the respective queue [Physica A 363, 62 (2006)]. 相似文献
997.
文中以有效介质近似理论为基础,考虑了纳米颗粒在基液中强烈的B rown ian运动对强化传热的作用和纳米颗粒的表面吸附液体层、纳米颗粒的粒径和体积分数对纳米悬浮液有效导热系数的影响,建立了预测纳米悬浮液有效导热系数的模型,通过对纳米CuO-去离子水溶液的验证,发现该模型比几种经典模型具有更高的精度,因此具有一定的参考价值。 相似文献
998.
999.
Structural equation and Mei conserved quantity of Mei symmetry for Appell equations in holonomic systems with unilateral constraints are investigated. Appell equations and differential equations of motion for holonomie mechanic systems with unilateral constraints axe established. The definition and the criterion of Mei symmetry for Appell equations in holonomic systems with unilateral constraints under the infinitesimal transformations of groups axe also given. The expressions of the structural equation and Mei conserved quantity of Mei symmetry for Appell equations in holonomic systems with unilateral constraints expressed by Appell functions are obtained. An example is given to illustrate the application of the results. 相似文献
1000.
The chaotic classical single-particle motion in an oblate octupole deformed potential with a nonzero z-component of angular momentum Lz is investigated. The stability analysis of the trajectories shows that with increasing rotation of the system, the unstable negative curvature regions of the effective potential surface decrease, which converts the chaotic motion of the system into a regular one. 相似文献