Dynamical analysis,circuit realization,and application in pseudorandom number generators of a fractional-order laser chaotic system

A new five-dimensional fractional-order laser chaotic system (FOLCS) is constructed by incorporating complex variables and fractional calculus into a Lorentz-Haken-type laser system. Dynamical behavior of the system, circuit realization and application in pseudorandom number generators are studied. Many types of multi-stable states are discovered in the system. Interestingly, there are two types of state transition phenomena in the system, one is the chaotic state degenerates to a periodical state, and the other is the intermittent chaotic oscillation. In addition, the complexity of the system when two parameters change simultaneously is measured by the spectral entropy algorithm. Moreover, a digital circuit is design and the chaotic oscillation behaviors of the system are verified on this circuit. Finally, a pseudo-random sequence generator is designed using the FOLCS, and the statistical characteristics of the generated pseudo-random sequence are tested with the NIST-800-22. This study enriches the research on the dynamics and applications of FOLCS.     

Application of wake oscillators to two-dimensional vortex-induced vibrations of circular cylinders in oscillatory flows

A nonlinear time-domain simulation model for predicting two-dimensional vortex-induced vibration (VIV) of a flexibly mounted circular cylinder in planar and oscillatory flow is presented. This model is based on the utilization of van der Pol wake oscillators, being unconventional since wake oscillators have typically been applied to steady flow VIV predictions. The time-varying relative flow–cylinder velocities and accelerations are accounted for in deriving the coupled hydrodynamic lift, drag and inertia forces leading to the cylinder cross-flow and in-line oscillations. The system fluid–structure interaction equations explicitly contain the time-dependent and hybrid trigonometric terms. Depending on the Keulegan–Carpenter number (KC) incorporating the flow maximum velocity and excitation frequency, the model calibration is performed, entailing a set of empirical coefficients and expressions as a function of KC and mass ratio. Parametric investigations in cases of varying KC, reduced flow velocity, cylinder-to-flow frequency ratio and mass ratio are carried out, capturing some qualitative features of oscillatory flow VIV and exploring the effects of system parameters on response prediction characteristics. The model dependence of hydrodynamic coefficients on the Reynolds number is studied. Discrepancies and limitations versus advantages of the present model with different feasible solution scenarios are illuminated to inform the implementation of wake oscillators as a computationally efficient prediction model for VIV in oscillatory flows.     

Effects of van der Waals force on nonlinear vibration of electromechanical integrated electrostatic harmonic actuator

An electromechanical integrated electrostatic harmonic actuator is promising for the miniaturization of electromechanical devices. As the dimensions of the actuator decrease, the effects of the van der Waals force become obvious. In this study, by considering the nonlinearity of electrostatic and van der Waals forces, nonlinear vibration equations of the flexible ring of an electrostatic harmonic actuator are deduced. Using these equations, the nonlinear free vibration and nonlinear forced response of the actuator are investigated. The effects of the van der Waals force on the nonlinear vibration of the flexible ring are analyzed. Results show that these effects of the van der Waals force are relatively obvious under some conditions and should be considered.     

某型电动飞机螺旋桨振动特性实验研究

某型电动飞机采用螺旋桨产生拉力,为了防止螺旋桨工作时共振,利用ES-2-150振动实验系统进行了两叶木质螺旋桨和碳纤维螺旋桨的振动特性实验,采用谐振搜索与驻留方法测量出木质螺旋桨的第一阶固有频率为36.07Hz,碳纤维螺旋桨的第一阶固有频率为73.58Hz。螺旋桨爬升状态转频为39Hz,这与木质螺旋桨的第一阶固有频率非常接近,导致木质螺旋桨在爬升状态出现比较严重的振动故障。因此,某型电动飞机最终选择两叶碳纤维螺旋桨作为其拉力产生装置。     

双稳态结构中的1/2次谐波共振及其对隔振特性的影响

以典型的双稳态系统——屈曲梁结构为例,基于等效模型,结合解析、数值和实验手段,研究了双稳态结构中的1/2次谐波共振特性、演化过程、参数调节规律及其对隔振特性的影响.研究发现,当非线性刚度系数或激励幅值增加到一定程度时,系统会在一定带宽下产生显著的1/2次谐波共振;随着激励幅值增加,阻尼系统的1/2次谐波遵循“产生-增强-衰退-消失”的过程,该过程对峰值频率和峰值传递率有重要影响;适当提高非线性强度能有效改善双稳态结构隔振特性.针对双稳态屈曲梁结构开展的实验验证了1/2次谐波特性和隔振特性变化规律.     

托卡马克工程试验混合堆等离子体性能的等值线图分析

本文简要叙述托卡马克工程试验混合堆等离子体概念设计的物理基础,对等离子体性能进行了等值线图(Plasma Operation Contour)分析。根据工程试验混合堆的要求,得出一组等离子体参数。     

微振动光电检测与数据采集系统的设计

提出了一种新的光学非接触式测量方法测量了物体的微振动振幅。用激光作为光源,以四象限硅光电池[1]作为光电探测器,借助三角测量原理,投射在振动源表面的激光反射光束在光电探测器上产生平面位移,将位移信号放大,通过A/D模块采集电压数值,并通过串口通信机制在PC终端实时显示。实验结果表明,该方法原理正确,灵敏度高,便于实现连续、快速、自动化检测,在工业在线检测方面具有良好的应用前景。     

Simulation of the nonlinear vibration of a string using the Cellular Automata based on the reflection rule

In this study, the nonlinear dynamic responses of a string are simulated using the Cellular Automata method based on the reflection rule. In the case of nonlinear systems, the velocity of wave propagation is not constant and depends on the amplitude. A new treatment of the dynamic time step is proposed for the Cellular Automata method considering the effect of the propagation velocity. As numerical examples, first, the dynamic responses of a string with linear characteristic are simulated using the Cellular Automata method. A typical resonance curve can be obtained. Second, the dynamic responses of a string with nonlinear characteristic are simulated using the proposed method. Some characteristic types of vibration can be obtained. It is concluded that the linear and nonlinear dynamic responses of a string may be obtained by simulation using the Cellular Automata method.     

微光像增强器图像传递信噪比的测试研究

图像传递信噪比是微光像增强器的重要特性参数．能够全面定量地表征像增强器在探测弱辐射图像时的综合性能，对于确定像增强器的图像探测灵敏闽具有重要意义。针对其测试原理．采用高灵敏度低噪声CCD器件作为像管输出图像的探测接收器．并引入数字图像处理技术。利用设计的测试系统实现了典型目标图像传递信噪比的自动测试．多次实验结果表明．陔测试系统具有测试过程自动快速及测试数据准确稳定的优点．相同测试条件下的不确定度优于±3%。     

Statistical Inference with Fractional Brownian Motion

We give a test between two complex hypothesis; namely we test whether a fractional Brownian motion (fBm) has a linear trend against a certain non-linear trend. We study some related questions, like goodness-of-fit test and volatility estimation in these models.