Two-parameter stochastic resonance in a model of electrochemical oxidation of formic acid on Pt

Stochastic resonance (SR) is shown in a two-parameter system, a model of electrochemical oxidation of formic acid on Pt. The driving current and the saturation coverage for carbon monoxide are two control parameters in this model. Modulation of an excitable focal stable state close to a Hopf bifurcation by a weak periodic signal in one parameter and noise in the other parameter is found to give rise to SR. The results indicate that the noise can enlarge a weak periodic signal and lead the system to be ordered. The scenario and novel aspects of SR in this system are discussed.     

Periodic and random perturbation of catalytic oxidation of CO

When a controllable input is modulated by noise and signal, the response of a nonlinear system may exhibit a synchronized effect, which is referred to as stochastic resonance(SR). With the help of noise, the detection of weak signal may become possible and its signal-to-noise ratio can be increased. A model to describe catalytic oxidation of CO on single crystal was adopted, and its stability was studied by linear analysis method. Through computer simulation, the responses under periodic and random perturbation were analyzed. Stochastic resonance behavior was found in a narrow bistable region, or near the oscillatory region. The results shows more characteristics than those of 1-dimensional system does.     

Influences of a periodic signal on a noisy synthetic gene network

The effects of noise and a periodic signal on a synthetic gene network have been investigated. By tuning the distance of a parameter from the Hopf bifurcation point, both implicit internal signal stochastic resonance and explicit internal signal stochastic resonance can be induced by noise. Furthermore, a switch process can also be elicited. When a periodic signal is coupled to the gene network, two interesting phenomena occur with the modulation of the frequency of the signal: the effect of noise amplifyin...     

A method based on stochastic resonance for the detection of weak analytical signal

An effective method for detection of weak analytical signals with strong noise background is proposed based on the theory of stochastic resonance (SR). Compared with the conventional SR-based algorithms, the proposed algorithm is simplified by changing only one parameter to realize the weak signal detection. Simulation studies revealed that the method performs well in detection of analytical signals in very high level of noise background and is suitable for detecting signals with the different noise level by changing the parameter. Applications of the method to experimental weak signals of X-ray diffraction and Raman spectrum are also investigated. It is found that reliable results can be obtained.     

化学体系随机共振现象的理论研究

化学体系中随机共振现象的特性、机理、本质和应用的研究是非常重要的前沿课题。综述中国科学技术大学非线性化学实验室,在化学体系随机共振现象的理论研究中,所取得的主要成果,并阐述化学体系随机共振现象研究中所提出来的若干重要问题：非均相化学体系中随机共振;化学体系中内信号随机共振;化学体系中多重随机共振;化学体系中随机共振的调制;化学体系中色噪声作用下的随机共振;化学体系中时空随机共振;耦合化学体系中随机共振;化学体系中双参量随机共振。     

非恒温CO表面催化氧化体系双随机共振

当考虑化学反应热、热传导和热辐射的影响时, Pt(110)/CO+O2表面催化氧化体系温度出现时空变化. 以衬底温度为控制参数, 通过计算机模拟, 研究了衬底温度噪声对该非恒温表面反应体系振荡动力学行为的影响. 研究发现, 温度噪声可以诱导体系双随机共振现象, 而且增大衬底温度可以使体系共振行为由双随机共振变为单随机共振. 这表明体系可以利用温度噪声加强其反应振荡, 并对其具有双重选择性, 人们可以通过改变衬底温度大小来控制体系的共振行为.     

随机扰动和周期信号对基因调控系统的影响

采用数值模拟方法,研究了生物信息学中人类遗传因子——基因的转录调控系统.研究表明:噪音对该系统的影响作用,体系可以出现内随机共振现象和噪音诱导的"开-关"过程;当周期信号加到系统上时,信号振幅和频率的改变能够使细胞信号产生更为丰富的动力学行为,如周期共振现象.     

电氧化甲酸反应体系的随机共振调制

采用甲酸电氧化的反应模型对随机共振的调制进行了研究。反应模型中有驱动电流和CO的饱和覆盖率两个控制参量。当弱信号和噪声同时作用于驱动电流时,固定信号强度,体系输出的脉冲间隔分布可以在合适的噪声强度时最有序,表明出现了随机共振现象。对CO的饱和覆盖率施加周期性信号的作用可以对随机共振行为进行调制,调制的结果取决于调制信号的周期及初相位。     

The Gray-Scott model under the influence of noise: reentrant spatiotemporal intermittency in a reaction-diffusion system

We investigate the influence of noise on the spatiotemporal behavior of the Gray-Scott model, a prototype for a simple reaction-diffusion system. In the parameter regime studied it is characterized deterministically by a stable fixed point. As the noise increases a regular periodic pattern is replaced first by an irregularly oscillating periodic pattern and then by spatiotemporal intermittency. With further increasing noise strength the spatiotemporal intermittency is first replaced by a low amplitude noisy regime followed by spatiotemporal intermittency (STI) embedded into a noisy background. At sufficiently high noise intensity high amplitude noise prevails. We point out that the transition from spatiotemporal intermittency to low amplitude noise can be traced back to the fact that the spatially homogeneous state is a global attractor. As the noise strength grows further the "noisy" fixed point starts to communicate with STI leading to noise-induced spatiotemporal intermittency as an excitable state. At high enough noise strength high amplitude noise is left over wiping out all details of the underlying deterministic dynamical system.     

Internal signal stochastic resonance of a synthetic gene network

Noise is generally regarded as a disadvantageous factor, which would smear weak signals; therefore, people always try to reduce its influence. However, recent studies show that, for a nonlinear system, under certain circumstances, noise can enhance system…     

Enhancement of spike coherence by the departure from Gaussian noise in a Hodgkin-Huxley neuron

Experimental study has shown that non-Gaussian noise exists in sensory systems like neurons. The departure from Gaussian behavior is a characteristic parameter of non-Gaussian noise. In this paper, we have numerically studied the effect of a particular kind of non-Gaussian colored noise (NGN), especially its departure q from Gaussian noise (q = 1), on the spiking activity in a deterministic Hodgkin-Huxley (HH) neuron driven by sub-threshold periodic stimulus. Simulation results show that the departure q can affect the spiking activity induced by noise intensity D. For smaller q values, the minimum in the variation coefficient (CV) as a function of noise intensity (D) becomes smaller, showing that D-induced stochastic resonance (SR) becomes strengthened. Meanwhile, depending on the value of D, q can either enhance or reduce the spiking regularity. Interestingly, CV changes non-monotonously with varying q and passes through a minimum at an intermediate q, representing the presence of “departure-induced SR”. This result shows that appropriate departures of the NGN can enhance the spike coherence in the HH neuron. Since the departure of the NGN determines the probability distribution and hence may denote the type of the noise, “departure-induced SR” shows that different types of noise can enhance the spike coherence, and hence may improve the timing precision of sub-threshold signal encoding in the HH neuron. Supported by the Science Foundation of Ludong University (L20072805)     

内噪声作用下的随机共振算法对弱信号的检测

基于随机共振理论提出了一种简便、有效地检测弱信号的方法。在内噪声协同作用下，通过调节输入噪声信号的大小能较好地提高系统输出信号的信噪比，从而实现检测背景噪声很强的弱信号的目的。应用于模拟信号和实验信号的结果证明了方法是可行的。     

Signal transduction in a coupled hormone system: selective explicit internal signal stochastic resonance and its control

Cooperative interactions of signal transduction and environmental noise are investigated with a coupled hormone system, in which selective explicit internal signal stochastic resonance (EISSR) is observed. More specifically, the large peak of a period-2 oscillation (i.e., a strong signal) is greatly amplified by the environmental noise while the small peak (i.e., a weak signal) does not exhibit cooperative interactions with noise. The EISSR phenomenon could be controlled by adjusting the frequency or amplitude of an external signal and a critical amplitude for external signal is found. Significantly, the maximal signal-to-noise ratio increases almost linearly with the increment of control parameter, despite that the magnitude of the large peak is decreased. In addition, the noise does not alter the fundamental frequencies of the strong signal and the weak signal, which implicates that the system can keep its intrinsic oscillatory state and resist the effect of environmental fluctuations.     

基于周期调节的随机共振算法对化学弱信号的检测研究

提出了一种新的随机共振算法,通过对系统的周期进行调节以实现系统的共振.讨论了实现共振的系统参数,并对模拟信号和拉曼光谱实验信号进行了处理.结果表明,该方法不仅可方便地用于弱化学信号的处理,克服检出信号的滞后现象,而且对不同噪声水平的信号均有良好的适用性.     

Improvement of spectral resolution in the presence of periodic noise and microphonics for hyper-pure germanium detector gamma-ray spectrometry using a new digital filter

The radiation dose of workers and patients resulting from inhaling radon and through the consumption of spring waters was examined in the hospital near the Héviz lake in Hungary. The radiation dose originating from radon was 2.15–3.95 mSv·y⁻¹ concerning workers at the spa. The radiation dose originating from radon in the case of those regularly taking a bath was an average of 0.75 mSv·y⁻¹. Due to the limited duration of treatments a bound effective dose of maximum 100 μSv·y⁻¹ may originate from radon and inhaling radon, while a maximum of 1.4 μSv·y⁻¹ may originate from ingestion of ²²²Rn, ²²⁶Ra, ²³⁴U and ²³⁸U radionuclides.     

Canard explosion and coherent biresonance in the rate oscillation of CO oxidation on platinum surface

The relationship between canard explosion and coherent biresonance is analyzed by numerically investigating a temporal dynamical model of CO oxidation on Pt surface. Canard explosion, manifesting itself by a dramatic change in the amplitude and period of a periodic orbit within a very narrow interval of a control parameter, is the result of multiple time scales in a dynamical system and is common in excitable systems. Coherent biresonance, namely, two peaks on the signal-to-noise ratio (SNR) curve when varying noise intensity, is a novel phenomenon of coherent resonance which is well-known in excitable systems. When the control parameter is varied from a stable fixed point, crossing the supercritical Hopf bifurcation, one of the peaks that corresponds to relatively larger noise intensity, keeps a constant height and position, while the other becomes higher and moves to lower noise level. When we consider the case in which two control parameters are perturbed by independent noise simultaneously, an interesting picture of one valley between two ridges appears on the 3D surface of SNR.     

Simulation of noise characteristic effects on stochastic resonance in Belousov-Zhabotinsky flow reaction

A three-variable model, which was proposed to account for the stochastic resonance (SR) in Belousov-Zhabotinsky (B-Z) reaction in a continuous-flow stirred-tank reactor, is investigated when the control parameter kr, the flow rate, is modulated by noise near supercritical Hopf bifurcation point. Using the computer simulation, noise-induced oscillations are observed, and the signal-to-noise ratio (SNR) goes through a maximum with the increment of noise intensity, which means occurrence of stochastic resonance. in addition, we have also investigated the effects of correlation time of colored noise and the duration time of white noise on the system's dynamics.     

Frequency-selective response of periodically forced coupled FHN models via system size multi-resonance

We consider system of globally coupled FitzHugh-Nagumo (FHN) models; each element is subjected to a subthreshold periodic signal and independent Gaussian white noise. With the variation of the system size, the spike train of the mean field of the system fires according to the period of the subthreshold external signal or to the interior time scale of the FHN model. The influence of the coupling strength is also investigated. It only influences the response of the mean field to external signal. If two external signals are injected to the system simultaneously, the least-common-multiple periods or other common multiples may be selected by different system sizes.     

嘈杂小世界网络中的随机共振现象

以双稳态振荡器耦合而成的具有小世界拓扑结构的网络为研究对象,重点研究了该体系在周期弱信号和乘性高斯白噪声的共同作用下,振荡器之间的耦合强度与网络拓扑结构的无序度对于网络动力学行为的影响．结果显示噪声可以诱导产生随机共振现象,在适中的耦合强度下增加体系拓扑的无序度可以使整个体系的随机共振现象得到加强．另外,研究表明体系中存在着一组最优的耦合强度和拓扑无序度,在它们的协同作用下体系能够最有效地检测到外界的弱信号．     

调制BZ-CSTR反应体系小振荡诱导非平衡相变

以流量为扰动参数,对连续搅拌釜式反应器（ＣＳＴＲ）中的Ｂｅｌｏｕｓｏｖ－Ｚｈａｂｏｔｉｎｄｓｋｙ（ＢＺ）反应体系小振荡进行周期或噪声扰动,改变扰动周期或扰动强度,在某些条件下可以诱导非平衡相变。以ＢＺ反应的四变量Ｍｏｎｔａｎａｔｏｒ模型为基础,对相应流率区进行周期或噪声扰动,计算结果与实验基本定性一致。