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941.
Ambient noise data measured in an experiment conducted in shallow water near a sea-route were analyzed. It was observed that,
at low frequency, the horizontal correlation has an obvious difference from that predicted by the classical ambient noise
model. The theoretical analyses show that this phenomenon is caused by wind noise together with the discrete shipping noise
nearby. An ambient noise model was proposed to include the effects caused by both the noise sources. Data measured at different
times verify that the proposed model can be used to forecast the ambient noise field in shallow water near the sea-route.
Supported by the National Natural Science Foundation of China (Grant No. 10734100), the Knowledge Innovation Program of the
Chinese Academy of Sciences (Grant No. KZCX1-YW-12-2), the National Basic Research Program of China (Grant No. 2007CB209603),
and the Open Foundation of China National Petroleum Corporation Key Laboratory (Grant No. GPKL0804) 相似文献
942.
Studies on some superheavy nuclei are performed. The α decay energies are calculated by an improved local binding energy formula, and the α decay half-lives are calculated by the Viola-Seaborg formula. Good agreements between theoretical and experimental results are reached. 相似文献
943.
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
944.
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
945.
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
946.
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
947.
Q. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(3):387-392
The effects of the non-rotating wave approximation (non-RWA) on the
spontaneous emission of a V-type three-level atom are studied, where the
excited states are coupled to a common ground state by a weak laser field
and the upper-level doublet is driven by a strong microwave field. When the
non-RWA is applied to the interaction of the atom with the microwave field,
for some values of the parameters involved, the spontaneous emission
spectrum is comprised of a central peak and a series of sidebands with a
constant spacing of the microwave frequency, and the central peak and/or
sidebands can be split into two components. The physical interpretation of
the spectral characteristics is given in light of the dressed states. 相似文献
948.
通过数值模拟方法, 研究了在具有稳定次阈值振荡特性的二维映射神经元体系中, 噪声对体系非线性动力学的调控作用. 通过计算发现了噪声诱导的动作电位和随机共振现象. 另外,还研究了体系的控制参数及输入信号的频率对体系动力学的影响, 发现了该体系中频率依赖的随机共振现象.
关键词:
二维映射神经元模型
次阈值振荡
高斯白噪声
随机共振 相似文献
949.
建立了自发噪声谱测量系统来研究稀磁半导体(Ga,Mn)As的电学噪声性质.通过测量(Ga,Mn)As材料的自发噪声谱,发现(Ga,Mn)As的自发涨落会随温度升高而逐渐增大,同时,外加磁场会降低(Ga,Mn)As的自发涨落,这来源于外加磁场导致的(Ga,Mn)As磁畴部分有序化.此外,不同频率的噪声随温度的变化规律有很大差异:当频率低于30 kHz的时候,噪声谱和温度的变化关系和热噪声很相似,但数值上明显大于热噪声的值;当频率在30 kHz左右的时候,噪声大小和温度成线性关系;当频率大于30 kHz以后,在相变点附近噪声大小和温度的关系出现了明显的转折,高频高温噪声的大小和热噪声的理论值非常接近.这些结果有助于深入理解(Ga,Mn)As磁性起源的物理机制.
关键词:
自旋电子学
稀磁半导体
自发涨落谱 相似文献
950.
以正硅酸乙酯作为前驱体,利用碱催化方式制备了SiO2溶胶,采用提拉法在K9基片上镀制SiO2单层薄膜,分别用热处理、紫外辐射处理、氨水加六甲基二硅胺烷气氛处理和酸碱复合膜4种后处理法对膜层进行处理,采用分光光度计、红外光谱、扫描探针显微镜、静滴接触角测量仪、椭偏仪等分析了薄膜的特性,通过真空环境加速污染实验对处理前后的膜层进行抗污染能力对比,结果表明:在碱性SiO2膜层上加镀一层酸性SiO2膜的复合膜层整体透过率仍保持在99%以上,疏水角达到128°,膜层真空抗污染能力大大加强。 相似文献