一类非线性振子中有界噪声诱发的混沌运动

研究谐和外力与有界噪声激励联合作用下的一类非线性振子的混沌运动。利用Melnikov方法，通过计算扰动系统的Melnikov积分，分析了系统在参数发生变化时的同宿分岔，得出系统产生混沌运动的参数阈值，并讨论了有界噪声激励对系统的混沌运动的影响。最后利用数值方法模拟了系统的安全盆的侵蚀状况，并进一步通过计算系统运动的Lyapunov指数，给出了由噪声诱发的混沌运动与噪声激励下非混沌运动之间的差别。     

达芬-谐波振子的改进解析逼近解

研究达芬-谐波振子的解析逼近解。所谓达芬-谐波振子是指当位移远小于1时，系统可化为三次非线性振子，而当位移远大于1时，该系统则化为线性谐波振子。通过将变形后的控制方程的线性化与谐波平衡法组合起来，我们建立了达芬-谐波振子频率及周期解的改进解板逼近。改进的解析逼近在振幅的全部取值范围内，包括振幅趋于零及无穷的情况，都有令人非常满意的精度。     

利用辛算法求解谐振子薛定谔方程误差分析

通过谐振子实例揭示了利用辛算法求解薛定谔方程所得波函数的相对误差变化的规律性 .通过计算发现任一时刻波函数在各个x格点处的相对误差完全相同 .波函数实数部分和虚数部分的相对误差随着时间的推演均周期性地在正数和负数之间来回变动 ,其周期为 62 8步或说是πs .波函数的实数部分和虚数部分的相对误差之间有类似于不确定关系的特点 .一个相对误差趋向于无穷小时另一个相对误差趋向于无穷大 .两者的乘积为一稳定的小数 .随着时间的推进这一小数的绝对值缓慢增大     

用复合振子模型计算纳米尺度滑动摩擦力的研究

以光滑界面摩擦为研究对象,探讨用复合振子模型计算纳米尺度滑动摩擦力的原理和方法,推导出滑动摩擦力和摩擦因数的计算公式,并用原子力显微镜探针在硅试样和云母试样上做扫描实验进行验证。实验值与理论计算值的对比结果表明,两者所反映的规律基本一致,表明所提出的理论和方法可行。研究表明,滑动摩擦力与接触面积成线性增长关系,并随宏观振子横向刚度的增大而减小,由于可通过改变摩擦表面的几何形貌来改变宏观振子的横向刚度,因此这一结论将为摩擦控制提供一种新途径。     

On a driven nonlinear circuit and chaotic behaviour

Abstract

The chaotic behaviour of the sinusoidally driven nonlinear circuit proposed by Hunt is investigated. The results are compared with those from other driven nonlinear circuits.     

3.705 μm紧凑型光参量振荡器

报道了一种基于工程应用的3.705 μm紧凑型高稳定性光参量振荡器。采用半导体制冷、强制气体对流冷却和热管导热技术相结合的方式,对主振荡功率放大结构的掺Yb光纤泵浦模块泵浦过程中产生的废热进行有效管理,再将经过耦合后的泵浦光注入到使用温控炉精确控温的PPMgLN晶体,在重复频率为55.56 kHz时,获得了功率不稳定度优于1.5%的1.78 W,脉冲宽度120 ns,峰值波长3.705 μm的线偏中红外激光输出,光光转换效率为12.6%。     

New sinusoidal oscillator configurations using operational transresistance amplifier

The objective of this brief is to introduce four new structures of electronically tunable sinusoidal oscillators (SOs) designed using operational transresistance amplifier (OTRA). Each of the proposed SO consists of forward path derived from a generic structure along with one/two OTRA-based resistive gain stages or differentiator in its feedback path. All the proposed SOs enjoy independent tuning of the frequency of oscillation (FO) through resistors without affecting the condition of oscillation (CO). Further, all topologies are found to exhibit low f_o sensitivities at all frequencies with respect to circuit parameters, and the second topology is capable of achieving very low frequencies (VLFs) using less RC component spread and provides linear tuning too. The fourth circuit provides quadrature output. The proposed SOs have been successfully implemented and verified in 180-nm CMOS technology node using ADE (analog design environment) tool Cadence Virtuoso. Both prelayout and postlayout simulation results have been included. To assess the oscillator prefabrication performances, Monte Carlo and process-voltage-temperature (PVT) analyses have been performed. The total harmonic distortion (THD) is observed to be less than 3.5%.     

Microbubble generator excited by fluidic oscillator's third harmonic frequency

Efficient generation of sub-millimetre microbubbles was recently made possible by pulsating the flow of gas supplied into a parallel-exits aerator, using a fluidic oscillator for the purpose. Without moving parts, it can generate oscillation at high frequency, an important factor due to bubble natural frequency rapidly increasing with the desirable decrease of their size. This paper discusses development of an unusual oscillator – a part of an integral oscillator/aerator unit – capable of generating a particularly high driving frequency, in the kilohertz range, in a layout that promotes a strong third harmonic frequency of the basic oscillation.     

一种基于混沌振子的DSSS信号盲检测方法

直接序列扩频通信是一种具有强保密性和抗干扰性的先进通信体制,对DSSS信号的检测具有重要作用。将非线性科学中的混沌理论应用于DSSS信号的盲检测,结合DSSS信号特征研究了一种利用混沌振子进行检测的方法。首先分析了洛伦兹混沌振子检测周期信号的原理和DSSS信号模型,然后构造出了一个基于混沌振子阵列的盲检测系统,可实现对低信噪比条件下对DSSS信号的盲检测。最后,通过计算机仿真结果表明了该方法的有效性,且性能优于过去的一些算法。