System size stochastic resonance in driven finite arrays of coupled bistable elements

The global response to weak time periodic forces of an array of noisy, coupled nonlinear systems might show a nonmonotonic dependence on the number of units in the array. This effect has been termed system size stochastic resonance by other authors. In this paper, we focus on a collective variable of a finite array of one-dimensional globally coupled bistable elements. We analyze the possible nonmonotonic dependence on the system size of its power spectral amplification and its signal-to-noise ratio.     

Bifurcations and loss of orbital stability in nonlinear viscoelastic beam arrays subject to parametric actuation

The collective dynamic response of microbeam arrays is governed by nonlinear effects, which have not yet been fully investigated and understood. This work employs a nonlinear continuum-based model in order to investigate the nonlinear dynamic behavior of an array of N nonlinearly coupled micro-electromechanical beams that are parametrically actuated. Investigations focus on the behavior of small size arrays in the one-to-one internal resonance regime, which is generated for low or zero DC voltages. The dynamic equations of motion of a two-element system are solved analytically using the asymptotic multiple-scales method for the weakly nonlinear system. Analytically obtained results are verified numerically and complemented by a numerical analysis of a three-beam array. The dynamic responses of the two- and three-beam systems reveal coexisting periodic and aperiodic solutions. The stability analysis enables construction of a detailed bifurcation structure, which reveals coexisting stable periodic and aperiodic solutions. For zero DC voltage only quasi-periodic and no evidence for the existence of chaotic solutions are observed. This study of small size microbeam arrays yields design criteria, complements the understanding of nonlinear nearest-neighbor interactions, and sheds light on the fundamental understanding of the collective behavior of finite-size arrays.     

Coupling induced logical stochastic resonance

In this work we will demonstrate the following result: when we have two coupled bistable sub-systems, each driven separately by an external logic input signal, the coupled system yields outputs that can be mapped to specific logic gate operations in a robust manner, in an optimal window of noise. So, though the individual systems receive only one logic input each, due to the interplay of coupling, nonlinearity and noise, they cooperatively respond to give a logic output that is a function of both inputs. Thus the emergent collective response of the system, due to the inherent coupling, in the presence of a noise floor, maps consistently to that of logic outputs of the two inputs, a phenomenon we term coupling induced Logical Stochastic Resonance. Lastly, we demonstrate our idea in proof of principle circuit experiments.     

Output response identification in a multistable system for piezoelectric energy harvesting

In this paper we examine in detail the multiple responses of a novel vibrational energy harvester composed of a vertical bistable beam whose complex non-linear behavior is tuned via magnetic interaction. The beam was excited horizontally by a harmonic inertial force while mechanical vibrational energy is converted to electrical power through a piezoelectric element. The bistable laminate beam coupled to the piezoelectric transducer showed a variety of complex responses in terms of the beam displacement and harvested power output. The range of vibration patterns in this non-linear system included single-well oscillations and snap-through vibrations of periodic and chaotic character. Harvested power was found to be strongly dependent on the vibration pattern with nonlinearities providing a broadband response for energy harvesting. Wavelet analysis of measured voltage, displacement and velocity time histories indicated the presence of a variety of nonlinear periodic and also chaotic phenomena. To measure the complexity of response time series we applied phase portraits and determine stroboscopic points and multiscale entropy. It is demonstrated that by changing parameters such as the magnetic interaction, the characteristics of the bistable laminate harvester, such as the natural frequency, bandwidth, vibration response and peak power can be readily tailored for harvesting applications.     

ZnS…Cu电致发光电压传感器及其温度漂移补偿

利用ZnS…Cu电致发光粉末与环氧树脂胶混合,设计制作了一种梯形电极结构的电压传感单元,实现了电致发光电压传感器输出信号的温度漂移补偿。电致发光电压传感信号通过2根塑料光纤传输到2个硅光电探测器,并选择其开路电压作为传感器的输出信号。在同一外加电压条件下,梯形电极区域内的电场分布是不均匀的,因而不同场点的发光亮度不同。通过测量梯形电极区域内2个不同发光点的发光强度随外加电压的变化,并对两路输出电压传感信号进行数据拟合与计算,可获知被测电压的有效值,并可实现对输出信号温度漂移的补偿。在-40~60℃范围内,采用上述温度漂移补偿方法测量了有效值在0.7~1.5 k V范围内的工频电压,传感器输出信号的非线性误差低于1.6%,验证了该温度漂移补偿方法的有效性。     

Achieving high bit rate logical stochastic resonance in a bistable system by adjusting parameters

The phenomenon of logical stochastic resonance(LSR) in a nonlinear bistable system is demonstrated by numerical simulations and experiments. However, the bit rates of the logical signals are relatively low and not suitable for practical applications. First, we examine the responses of the bistable system with fixed parameters to different bit rate logic input signals, showing that an arbitrary high bit rate LSR in a bistable system cannot be achieved. Then, a normalized transform of the LSR bistable system is introduced through a kind of variable substitution. Based on the transform, it is found that LSR for arbitrary high bit rate logic signals in a bistable system can be achieved by adjusting the parameters of the system,setting bias value and amplifying the amplitudes of logic input signals and noise properly. Finally, the desired OR and AND logic outputs to high bit rate logic inputs in a bistable system are obtained by numerical simulations. The study might provide higher feasibility of LSR in practical engineering applications.     

Amplified signal response in scale-free networks by collaborative signaling

Many natural and artificial two-states signaling devices are connected forming networks. The information-processing potential of these systems is usually related to the response to weak external signals. Here, using a network of overdamped bistable elements, we study the effect of a heterogeneous complex topology on the signal response. The analysis of the problem in random scale-free networks, reveals that heterogeneity plays a crucial role in amplifying external signals. We have contrasted numerical simulations with analytical calculations in simplified topologies.     

Stochastic resonance characteristic analysis of new potential function under Levy noise and bearing fault detection

Based on the output saturation of classcial bistable stochastic resonance (CBSR), a new type of piecewise nonlinear bistable stochastic resonance (PNBSR) system is constructed. The mean signal-to-noise ratio gain is regarded as an index to measure the stochastic resonance phenomenon. The laws for the resonant output of piecewise nonlinear bistable system governed by l, c, a, b and D of Levy noise are explored under different characteristic index α and symmetry parameter β of Levy noise. The results show that the output of PNBSR system has increased 4?dB by comparing with the output signal-to-noise ratio of CBSR system. And the stochastic resonance phenomenon can be induced by adjusting the piecewise nonlinear system's parameters under any α or β of Levy noise. The interval of the parameters of system which induces good stochastic resonance is roughly the same. And the output signal waveform of resonance is very similar to the input signal waveform, which has some reference value for the signal recovery. Moreover, we can find the good stochastic resonance interval of the system parameters do not change with D of Levy noise under the different noise intensity D of Levy noise. On the basis of this, adjusting the intensity amplification factor D of Levy noise, which induces good stochastic resonance, and the interval does not change with α or β. At last, the piecewise nonlinear bistable system is applied to detect bearing fault signals, which achieves better performance compared with the classical bistable system.     

Signal detection for frequency-shift keying via short-time stochastic resonance

A series of short-time stochastic resonance (SR) phenomena, realized in a bistable receiver, can be utilized to detect a train of information represented by signals that adopt frequency-shift keying (FSK). It is demonstrated that the values of noise intensity at resonance regions are close for adjacent periodic signals with an appropriate frequency separation. This establishes the possibility of decoding subthreshold or slightly suprathreshold M-ary FSK signals in bistable receivers. Furthermore, the mechanism of FSK signal detection via short-time SR effects is elucidated in terms of the receiver response speed. This phenomenon provides a possible mechanism for information processing in a bistable device operating in nonstationary noisy environments, where even the inputs appear over a short timescale or have a frequency shift.     

Coherence resonance and stochastic resonance in directionally coupled rings

In coupled systems, symmetry plays an important role for the collective dynamics. We investigate the dynamical response to noise with and without weak periodic modulation for two classes of ring systems. Each ring system consists of unidirectionally coupled bistable elements but in one class, the number of elements is even while in the other class the number is odd. Consequently, the rings without forcing show at a certain coupling strength, either ordering (similar to anti-ferromagnetic chains) or auto-oscillations. Analysing the bifurcations and fixed points of the two ring classes enables us to explain the dynamical response measured to noise and weak modulation. Moreover, by analysing a simplified model, we demonstrate that the response is universal for systems having a directional component in their stochastic dynamics in phase space around the origin.     

A reliable high average power dye laser

A flashlamp-pumped dye laser with an average output power of 6.6 W at 100 Hz repetition rate is described, which utilizes thyristors as switching elements instead of the normally used spark gaps. Using a simmering-mode operation of the flashlamps, no high voltage sparks are required to initiate the discharge even at low capacitor voltages. In this way the amplitude and time jitter of the laser output pulse are decreased and the life and reliability of the laser considerably increased.     

Adaptive fuzzy nonlinear inversion-based control for uncertain chaotic systems

<正>This paper presents a robust output feedback control method for uncertain chaotic systems,which comprises a nonlinear inversion-based controller with a fuzzy robust compensator.The proposed controller eliminates the unknown nonlinear function by using a fuzzy system,whose inputs are not the state variables but feedback error signals.The underlying stability analysis as well as parameter update law design are carried out by using the Lyapunov-based technique.The proposed method indicates that the nonlinear inversion-based control approach can also be applied to uncertain chaotic systems.Theoretical results are illustrated through two simulation examples.     

Automation of CO2 laser output power measurement as a function of the absorber gas pressure in a cell located inside or outside the laser cavity

The automation of CO₂ laser output power measurement is discussed in this paper as a function of the absorber gas pressure in a cell located inside or outside the laser cavity. A manually tunable laser was used which can be operated in one of about 44 different laser lines aligned by the user and registered respectively by the acquisition program for further analysis.The voltages representing the absorber gas pressure and the output power were very small (a few hundred μV), therefore a proper voltage amplification circuit was designed to amplify the analog outputs of both the pressure meter and the laser output power meter. These amplified signals were then applied directly to a PCI-9112 ADLINK data acquisition card using a personal computer (PC).A suitable controlling program using LabVIEW graphical programming language was written to measure the pressure and laser power signals, draw the relationship between them and save the results for later processing and analysis; such as, gas absorbance coefficient α, mean absorption cross section σ calculations that can be applied in many areas such as molecular spectroscopy and environmental pollution studies.     

Improvement of signal-to-noise ratio by stochastic resonance in sigmoid function threshold systems, demonstrated using a CMOS inverter

Stochastic resonance (SR) has become a well-known phenomenon that can enhance weak periodic signals with the help of noise. SR is an interesting phenomenon when applied to signal processing. Although it has been proven that SR does not always improve the signal-to-noise ratio (SNR), in a strongly nonlinear system such as simple threshold system, SR does in fact improve SNR for noisy pulsed signals at appropriate noise strength. However, even in such cases, when noise is weak, the SNR is degraded. Since the noise strength cannot be known in advance, it is difficult to apply SR to real signal processing. In this paper, we focused on the shape of the threshold at which SR did not degrade the SNR when noise was weak. To achieve output change when noise was weak, we numerically analyzed a sigmoid function threshold system. When the slope around the threshold was appropriate, SNR did not degrade when noise was weak and instead was improved at suitable noise strength. We also demonstrated SNR improvement for noisy pulsed voltages using a CMOS inverter, a very common threshold device. The input-output property of a CMOS inverter resembles the sigmoid function. By inputting the noisy signal voltage to a CMOS inverter, we measured the input and output voltages and analyzed the SNRs. The results showed that SNR was effectively improved over a wide range of noise strengths.     

激光二极管触发光导开关实验研究

介绍了利用大功率半导体激光二极管触发3 mm间隙GaAs光导开关、产生非线性电脉冲输出的实验,激光二极管输出功率为70 W,上升前沿约20 ns,脉冲半高宽（FWHM）约40 ns。随着开关两端偏置场强增加,输出电压也线性增加,当偏置场强超过一定阈值,增至约2.53 kV/mm时,经过一个较小的电压峰值和时间延迟后,输出电压急剧增加,产生雪崩现象。实验结果表明:GaAs开关非线性输出的产生与载流子聚集和碰撞电离有关,偏置电场的提高增加了开关芯片中载流子聚集数量,加剧了碰撞离化程度,从而使开关从线性模式进入雪崩模式。     

耦合双稳系统的随机共振控制

两个双稳系统经非线性耦合而成为多稳态系统,该耦合系统与单一双稳系统相比具有较高的理论研究和实际应用价值.解析地分析了耦合系统在含噪弱周期信号作用下的响应特性,给出了耦合系数和双稳系统参数对随机共振的影响,表明耦合系统的随机共振是在带状的双势阱作用下产生的,还构建了反馈耦合控制原理框图.这为在双稳类系统中人为地产生随机共振或使共振效应更加强烈即随机共振的控制及其应用提供了可靠的理论依据.数值仿真结果与理论分析完全符合. 关键词： 耦合双稳系统 随机共振 控制     

Collective phase sensitivity

The collective phase response to a macroscopic external perturbation of a population of interacting nonlinear elements exhibiting collective oscillations is formulated for the case of globally coupled oscillators. The macroscopic phase sensitivity is derived from the microscopic phase sensitivity of the constituent oscillators by a two-step phase reduction. We apply this result to quantify the stability of the macroscopic common-noise-induced synchronization of two uncoupled populations of oscillators undergoing coherent collective oscillations.     

XOR gate response in a mesoscopic ring with embedded quantum dots

We address XOR gate response in a mesoscopic ring threaded by a magnetic flux . The ring, composed of identical quantum dots, is symmetrically attached to two semi-infinite one-dimensional metallic electrodes and two gate voltages, viz, V_a and V_b, are applied, respectively, in each arm of the ring which are treated as the two inputs of the XOR gate. The calculations are based on the tight-binding model and the Green’s function method, which numerically compute the conductance–energy and current–voltage characteristics as functions of the ring-electrodes coupling strengths, magnetic flux and gate voltages. Quite interestingly it is observed that, for =₀/2 (₀=ch/e, the elementary flux-quantum) a high output current (1) (in the logical sense) appears if one, and only one, of the inputs to the gate is high (1), while if both inputs are low (0) or both are high (1), a low output current (0) appears. It clearly demonstrates the XOR behavior and this aspect may be utilized in designing the electronic logic gate.     

State observer for stochastic resonance in bistable system

We investigate numerically stochastic resonance variation in bistable system. Putting signals with different intensities into a bistable system, or adjusting system structural parameters for an input, will produce different motion trajectories. These trajectories contain both chaos and non-chaos parts. We classify these states according to the state of resonance and chaos, and propose a state observer. In this way, bistable system becomes an observable nonlinear system. State observer can provide us with a new perspective that is not available through conventional observation methods. These investigations contribute to nonlinear system optimization, and can also be applied to other interesting noise-induced phenomena.