共查询到20条相似文献,搜索用时 31 毫秒
1.
以微弱周期信号激励的非对称双稳系统为模型, 以信噪比增益为指标, 首先针对加性和乘性 α 稳定噪声共同作用的随机共振现象展开了研究, 然后针对单独加性 α 稳定噪声激励的随机共振现象进行了研究, 探究了 α 稳定噪声特征指数 α 和对称参数 β 分别取不同值时, 系统结构参数 a, b, 刻画双稳系统非对称性的偏度 r以及 α 稳定噪声强度放大系数 Q或 D对非对称双稳系统共振输出的作用规律. 研究结果表明, 无论在加性和乘性 α 稳定噪声共同作用下还是在单独加性 α 稳定噪声作用下, 通过调节 a和 b或者 r均可诱导随机共振, 实现微弱信号的检测, 且有多个参数区间与之对应, 这些区间不随 α 或 β 的变化而变化; 在研究噪声诱导的随机共振现象时发现, 调节噪声强度放大系数也可使系统产生随机共振现象, 且达到共振状态时 D的区间也不随 α 或 β 的变化而变化. 这些结论为 α 稳定噪声环境下参数诱导随机共振中系统参数以及噪声诱导随机共振中噪声强度的合理选取提供了依据. 相似文献
2.
Sound pollution is one of the most important urban problems which
endangers mental and physical health of the residents. This study was aimed to
assess the influence of different tree species, including Fraxinus rotundifolia,
Robinia pseudoacacia, Platanus orientalis, Platycladus orientalis, and Pinus
eldarica, in reducing noise pollution in the Abidar Forest Park. A further objective was to identify the contaminated areas of Sanandaj city and to propose suitable noise absorbent tree species in consistent conditions. For each tree stands
the noise measurements were performed during intervals at frequencies of 250,
500 and 1000 Hz, besides an open area with the same topography. With regards
to the second purpose, a total of 50 stations with residential, commercial, residentialcommercial, and green space applications were selected across the city. Equivalent
Continuous Sound Pressure Level (Leq) was determined in five replicates for 30
min. The measurements were performed under stable weather conditions and low
wind velocity at 17:00 (traffic peak) in summer and fall. All of the Leq values were
above the threshold noise level. The highest noise reduction was recorded in summer
(i.e., green season); Platanus and Platycladus species demonstrated the highest and
lowest noise absorption (31.43 dB and 22.28 dB, respectively). Furthermore, a
meaningful difference was observed between Leq values of commercial, residential,
commercial-residential, and green space urban applications, and the central parts of
the city showed noticeable noise pollution. Taken together, due to being exposed to
higher than the acceptable threshold noise level, the residents of Sanandaj will be
endangered to health problems in the near future; thus consideration should be given
to the noise pollution sources. 相似文献
3.
In the presence of 1/ f
β noise, we investigate the logical
stochastic resonance (LSR) in an asymmetric bistable model driven by various
cycling combinations of two logic inputs. The probability of correct logic
outputs is calculated according to true table of logic relationships. Two
major results are presented. Firstly, it is shown that the LSR effect can be
obtained by changing noise strength. Over entire range of noise variance,
white noise can be considered to be better than 1/ f noise or 1/ f
2 noise
to obtain clean logic operation. At a smaller noise level, 1/ f noise can
realize higher output probability than white noise or 1/ f
2 noise. In
the sense, 1/ f noise can be considered to be better than white noise or
1/ f
2. On the other hand, the correct probability can evolves
nonmonotonically as noise exponent β increases, and a kind of SR-like
effect can be obtained as a result of β. At certain intermediate
noise variance, the output probability is able to attain its minimum at
β = 1. It is also shown that actually some finite β sometime can
be better than β = 0 at small range of noise variance. The study might
provide some potential complement to LSR effect in the presence of
1/ f
β noise. 相似文献
4.
Scattering of charged particles is accompanied by the emission of soft photons. Handel's theory of 1/ f noise, based on the infrared quasi-divergent coupling of the system to the electromagnetic field, indicates that the current associated with a beam of scattered particles will exhibit 1/ f noise. His derivation is valid in a vacuum. Here we extend his results and obtain the fluctuation spectrum for the fluctuations in cross-section and for the scattering rates w kk′ in k-space, using the Born approximation. Next we consider mobility fluctuations due to these scattering rates, employing the relaxation time solutions of the Boltzmann transport equation, valid in non-degenerate semiconductors. Explicit results are obtained for the mobility-fluctuation noise caused by ionized impurity scattering, acoustic phonon scattering, optical phonon scattering, polar optical phonon scattering, and intervalley scattering. We derive Hooge's law, and the Hooge parameters for the above-mentioned processes are obtained in detail. This is then applied to n-type silicon and n-type gallium arsenide; the overall Hooge parameter, which is a weighted average of the partial α-parameters, is computed as a function of temperature and compared with experiment. For silicon, good agreement is obtained with available data. As a byproduct we also find the mobilities as function of temperature for these materials. Excellent agreement with the well-known experimental data is observed. We still note that this is the first theoretical derivation of Hooge's law and that the magnitude of the noise is obtained in detail without adjustable parameters. We believe that quantum 1/ f noise gives the limiting value of 1/ f noise that can be observed. 相似文献
5.
In this paper, we investigated the procedure of noise assessment in the study of nocturnal noise exposure during sleep in the home situation. The use of two different timeframes (fixed from 11 PM to 07 AM versus personal “Time in Bed” period) was explored as well as the relation between indoor and outdoor noise levels and between the actual and estimated noise levels. Noise recordings were performed inside and outside the bedroom of 24 subjects living in high density road traffic noise areas in the Brussels’ Capital Region during seven consecutive days. Indoor and outdoor noise indicators LAeq, LAmax and individual noise events were analysed. Subjects completed a daily sleep log in which the Time in Bed period was assessed. The results indicate that, for outdoor noise assessment, the use of an average LAeq might not be sufficient to reflect well the noise levels during the sleep period. For indoor measurements, significant differences were found in the comparison between both timeframes ( LAeq: T = 16; p < .001). Considering the relation between indoor and outdoor measurements, low correlations ( r = .49; p < .001) were found even when the location of the bedroom as a mediating factor was accounted for (street side; r = .52; p < .001). Therefore, from our study, caution is needed when relying on outdoor noise measurements for the evaluation of sleep disturbances. Furthermore, one needs to be aware of the weak correspondence between indoor and outdoor noise levels in the discussion of what a harmonized noise indicator for the evaluation of noise exposure and sleep disturbances should consist of. 相似文献
6.
The accurate interpretation of in vivomagnetic resonance spectroscopy (MRS) spectra requires a complete understanding of the associated noise-induced errors. In this paper, we address the effect of complex correlated noise patterns on the measurement of a set of peakparameters. This is examined initially at the level of a single spectral analysis followed by addressing the noise-induced errors associated with determining the signalparameters from the peakparameters. We describe a relatively simple method for calculating these errors for any correlated noise pattern in terms of the noise standard deviation and correlation length. The results are presented in such a way that an estimate of the errors may be made from a single MRS spectrum. We also explore how, under certain circumstances, the lineshape of the signal may be determined. We then apply these results to reexamine a set of in vivo31P MRS spectra obtained from rat brain prior to and following moderate fluid percussion injury. The approach outlined in this paper will demonstrate how meaningful results may be obtained from spectra where the signal-to-noise ratio (SNR) is quite small and where knowledge of the precise shape of the signal and the detail of the noise pattern is unknown. In essence, we show how to determine the expected errors in the spectral parameters from an estimate of the SNR from a single spectrum, thereby allowing a more discriminative interpretation of the data. 相似文献
7.
Liquid 4He presents an important physical system for the experimental study of noise-induced dynamical transitions. At temperatures below T in the He II phase, the flow of heat in the liquid helium is limited by a kind of superfluid turbulence. The steady-state properties of this turbulence are adequately described by a dense tangle of quantized vortex lines in the superfluid component of the He II. The turbulence undergoes a continuous transition as the heat current is increased. At this transition the intrinsic fluctuations in the dissipation and the relaxation time both become large [D. Griswold, C. P. Lorenson, and J. T. Tough, Phys. Rev. B
35:3149 (1987)]. These observations are consistent with a model of the transition as an imperfect pitchfork bifurcation [M. Schumaker and W. Horsthemke, Phys. Rev. A
36:354 (1987)]. External noise can be easily added to the driving heat current. Small-amplitude noise simply causes the system to fluctuate about the deterministic steady states. Large-amplitude noise causes dramatic changes. The stochastic steady states of the turbulence show noise-induced bistability [D. Grisowld and J. T. Tough, Phys. Rev. A
36:1360 (1987)]. Comparison with the imperfect pitchfork model is difficult because the noise is colored, quadratic, and large. Nevertheless, an approximate result obtained by Schumaker and Horsthemke is in good qualitative agreement with the data.This paper will appear in a forthcoming issue of the Journal of Statistical Physics. 相似文献
8.
本文讨论了光纤四波混频零色散波长的随机涨落,运用随机微分方程(SDE)推导出平均参量增益、相位转换效率及增益带宽的理论表达式.理论与实验有很好的一致性.进一步分析了这一效应对相位敏感放大器的噪音系数可能产生的限制. 相似文献
9.
We have experimentally and theoretically investigated the equivalent magnetic noise in a magnetoelectric Metglas/ 0.7Pb(Mg 1/3Nb 2/3)O 3‐0.3PbTiO 3 laminate sensor unit by considering the constituent noise sources of dielectric loss ( NDE) and DC leakage resistance ( NR). In the low frequency range ( f = 1 Hz), theory predicts that NR dominates the noise charge (1.6 times larger than NDE), with a 1 Hz noise of 9.1\;{\rm pt}/\sqrt {\rm Hz}. The experimental equivalent magnetic noise was 10.8\;{\rm pt}/\sqrt {\rm Hz}. This observed value is slightly higher than the predicted one, which might be due to an oversimplification of the theoretical model in terms of electrical charge amplifier and external vibration noise sources. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
讨论色噪声驱动的单模激光系统在噪声间关联程度受时间周期调制情况下的随机共振.用线性化近似的方法计算了光强功率谱及信噪比.具体讨论色噪声情况下信噪比 R受噪声强度 D, Q,时间周期调制频率 Ωλ以及噪声自关联时间 τ1, τ2和噪声间关联程度 λ的影响.发现信噪比随噪声强度的变化呈单峰共振,信噪比随时间周期调制频率的变化呈周期性共振,而信噪比随
关键词:
色噪声
时间周期调制
噪声间关联程度
周期性随机共振 相似文献
11.
We investigate the effects of the non-Gaussian colored noise on a calcium oscillation system using stochastic simulation methods. It is found that the reciprocal coefficient of variance R has a maximum (R max ) with increasing noise intensity Q. The non-Gaussian noise parameter q has an important effect on the system. For some values of q (e.g., q = 0.9, q = 1.0), R has a maximum with increasing correlation time τ. Non-Gaussian noise induced spikes are more regular than Gaussian noise induced spikes when q is small and Q has large values. The R has a maximum with increasing q. Therefore, non-Gaussian noise could play more effective roles in the calcium oscillation system. 相似文献
12.
We analyze the role of the delay time τ
d
and the fraction ε of recycled noise on the enhancement of the mean first-passage time (MFPT) in a metastable system with recycled noise, generated
by the superposition of a primary Gaussian noise source with a second component of constant delay. The results indicate that
MFPT as a function of the noise intensity D shows either a non-monotonic behavior with a maximum or a divergent behavior, which is the identifying characteristic of
the noise enhanced stability (NES) phenomenon. The increasing of τ
d
or ε strengthens the NES effect for ε > 0. However, for ε < 0, there is a critical value of τ
d
, below which we observe an increase of MFPT whose maximum goes to infinity, and above which the divergent behavior tends
to disappear and MFPT versus D shows a transition from one peak to two peaks and eventually one peak as τ
d
or | ε| increases. Moreover, we also discuss the effect of different initial conditions. These observations illustrate that the
noise recycling may be used as an effective scheme for controlling the NES effect. 相似文献
13.
针对半导体器件中普遍存在的1/f噪声提出了一种结合了提升小波变换和维纳滤波器的处理方法.首先利用重新加权迭代最小二乘法拟合1/f噪声的功率谱曲线得到噪声参数的估计,从而选择恰当的小波.其次,对包含了1/f噪声的信号进行提升小波变换.考虑到小波变换对1/f噪声的白化作用,利用维纳滤波器对每一层小波系数进行处理.设计了最优全通滤波器以校正维纳滤波器的相频特性,使得小波系数经滤波后相位不变.最后利用提升小波逆变换获得被1/f噪声淹没的信号.利用实验检验了提出方法的有效性,实验数据采自用于微创外科手术机器人的力传感器.结果表明提出的方法能够有效抑制1/f噪声,并使传感器的分辨力提高了25%.
关键词:
半导体器件
f噪声')" href="#">1/f噪声
提升小波变换
维纳滤波 相似文献
14.
We consider wide ballistic microcontacts with electron-electron scattering in the leads and calculate electric noise and nonlinear
conductance in them. Due to a restricted geometry the collisions of electrons result in a shot noise even though they conserve
the total momentum of electrons. We obtain the noise and the conductivity for arbitrary relations between voltage V and temperature T. The positive inelastic correction to the Sharvin conductance is proportional to T at low voltages eV ≪ T, and to | V| at high voltages. At low voltages the noise is defined by the Nyquist relation and at high voltages the noise is related
with the inelastic correction to the current by the Schottky formula S
in = 2 eI
in. 相似文献
15.
The correlation coefficient vs. prediction time profile has been widely used to distinguish chaos from noise. The correlation coefficient remains initially
high, gradually decreasing as prediction time increases for chaos and remains low for all prediction time for noise. We here
show that for some chaotic series with dominant embedded cyclical component(s), when modelled through a newly developed scheme
of periodic decomposition, will yield high correlation coefficient even for long prediction time intervals, thus leading to
a wrong assessment of inherent chaoticity. But if this profile of correlation coefficient vs. prediction horizon is compared with the profile obtained from the surrogate series, correct interpretations about the underlying
dynamics are very much likely.
Received 8 March 1999 相似文献
16.
We calculate the frequency-dependent shot noise in the edge states of a two-dimensional topological insulator coupled to a magnetic impurity with spin S = 1/2 of arbitrary anisotropy. If the anisotropy is absent, the noise is purely thermal at low frequencies, but tends to the Poisson noise of the full current I at high frequencies. If the interaction only flips the impurity spin but conserves those of electrons, the noise at high voltages eV ≫ T is frequency-independent. Both the noise and the backscattering current Ibs saturate at voltageindependent values. Finally, if the Hamiltonian contains all types of non-spin-conserving scattering, the noise at high voltages becomes frequency-dependent again. At low frequencies, its ratio to 2eIbs is larger than 1 and may reach 2 in the limit Ibs→0. At high frequencies, it tends to 1. 相似文献
17.
Summary The proposed K
a
band link on the Cassini orbiter can be used for very accurate Doppler tracking. A two-way K
a
band coherent link, near opposition, or more complex schemes involving the X-band link also, can virtually eliminate the noise due to interplanetary plasma, giving an accuracy Δ f/f better than 10 −15 for time scales of (10 3÷10 4) s. To achieve this accuracy, the other error sources, mainly the tropospheric delay and the clock stability, must be accurately
controlled. This sensitivity will allow for the first time for a search for gravitational waves of reasonable amplitude.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
18.
We investigate the noise-induced transport of Brownian particle in a deterministic spatial symmetrical periodic potential
driven by colored cross correlation between a multiplicative white noise and an additive white noise. We derive the general
formula of the stationary current. Based on numerical computation, we found that directed motion of the Brownian particles
can be induced by the correlation time τ of cross correlation between the multiplicative noise and the additive noise and the current reversal and the direction of
the current is controlled by the τ. 相似文献
19.
研究了金属氧化物半导体(MOS)器件在高、中、低三种栅压应力下的热载流子退化效应及其1/ fγ噪声特性.基于Si/SiO 2界面缺陷氧化层陷阱和界面陷阱的形成理论,结合MOS器件1/ f噪声产生机制,并用双声子发射模型模拟了栅氧化层缺陷波函数与器件沟道自由载流子波函数及其相互作用产生能级跃迁、交换载流子的具体过程.建立了热载流子效应、材料缺陷与电参量、噪声之间的统一物理模型.还提出了用噪声参数 Sf
关键词:
金属氧化物半导体场效应管
热载流子
fγ噪声')" href="#">1/fγ噪声 相似文献
20.
We investigate that the average fidelity of the standard quantum teleportation communication protocol when the quantum channel is affected by different local collective noise environments frequently encountered in real quantum communication protocol. We show that the quantum teleportation efficiency can be enhanced when the noise is unavoidable by choose the fit Bell state as the quantum channel, especially we can get perfect quantum teleportation efficiency under the local collective Pauli σy noise environment. Our work can shed some light on the application of practical standard quantum teleportation communication protocol. 相似文献
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