共查询到20条相似文献,搜索用时 250 毫秒
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引入正弦平方势,在小振幅近似下,把粒子运动方程化为具有多频激励的Duffing方程.并用Melnikov方法分析了系统的全局分叉与混沌行为.结果表明,当外场为双频激励时,系统将存在不同的次谐和超次谐分叉序列.由于系统的混沌行为与系统参数有关,只需控制材料组分或掺杂浓度,就可望达到避免或控制混沌的目的,为半导体超晶格的制备及其光磁电效应的物理学描述提供了理论分析. 相似文献
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该文提出在参数激励压电俘能器中增设弹性振幅放大器。利用扩展哈密顿原理,建立了系统的动力学方程,通过数值仿真,研究了弹性振幅放大器及其刚度系数对俘能器性能的影响。研究结果表明,当压电梁未发生屈曲,且压电梁的固有频率与弹性振幅放大器固有频率比满足1∶2共振条件时,能够降低参数激励俘能器的激励阈值,并拓宽俘能器的频率带宽。此时的刚度系数称为共振刚度系数ksr。研究表明,当弹性振幅放大器的刚度系数小于ksr时,俘能器的平均输出功率、均方根电压峰值及频率带宽均随着刚度系数的增加而增加;当弹性振幅放大器的刚度系数大于ksr时,随着刚度系数的增加,俘能器的频率带宽增大,均方根电压峰值略减小,而平均输出功率在激励幅值较大时趋于相同。 相似文献
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利用Fourier展开,将应变超晶格中的粒子运动问题转化为多频激励的摆方程问题.用Melnikov方法和Lyapunov方法讨论了系统的稳定性,并对双频激励和单频激励进行了具体分析.结果表明,多频激励系统可通过奇阶次谐分叉进入混沌;当阻尼系数比较大或激励强度比较弱时系统是稳定的. 相似文献
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1.在文献[1]中我们研究了振幅螺旋变化周期Wiggler磁场FEL,表明采用适当的物理参数,其增益比恒定振幅周期Wiggler磁场FEL提高好多倍.为实现这种激光器的需要,本文研究了圆锥形双螺旋线结构的激励电磁场及其解析表达式,并表明振幅螺旋变化周期Wiggler磁场可以用这种双螺旋线结构的反相电流激励下获得.2.我们先分析图1(a)所示的圆锥形顺绕双螺 相似文献
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通过对GSM900M/DCS1800M双频网系统的相关基础知识以及贵阳移动现网网络存在问题的研究,并对双频网整合工程前后的网络参数等进行对比,探讨了移动通信系统双频网整合的优势。 相似文献
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利用磁流变阻尼器特性试验数据,通过曲线拟合等手段建立了双sigmoid力学模型。该模型的参数是控制电流和振动频率、振幅的函数,能准确描述不同激励条件下阻尼力-速度滞回特性。建立了双层隔振系统模型,分析了阻尼比对传递函数的影响。提出了一种模糊半主动振动控制算法。仿真结果表明,该控制算法在宽频范围上能取得很好的隔振效果。 相似文献
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电感非线性RLC电路弹簧耦合系统3次超谐共振研究 总被引:1,自引:0,他引:1
研究电感非线性RLC电路弹簧耦合系统的非线性振动,应用拉格朗日一麦克斯韦方程,建立受简谐激励的具有电感非线性RLC电路弹簧耦合系统的数学模型.根据非线性振动的多尺度法,得到系统满足3次超谐共振条件的一次近似解以及对应的定常解.对其进行数值计算,分析系统参数对幅频响应曲线的影响.当系统3次超谐共振调谐值等于零时,幅频响应曲线的振幅最大.增大电压、极板面积和非线性电感系数,幅频响应曲线的振幅和共振区增大.增大极板间距、电阻和线性电感系数,幅频响应曲线的振幅和共振区减小.系统的固有频率随极板间距的增大而增大,随极板面积和线性电感系数的增大而减小. 相似文献
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利用Melnikov方法讨论了非谐激励系统的混沌行为,并在极限情况κ→0下,把非谐激励转化为谐波激励,而运动方程化为倒置摆方程.倒置摆方程描写了带电粒子在周期弯晶中翻越势垒的横向运动行为.结果表明:系统的稳定性与参数有关,适当调整参数就能保证系统是稳定的;即使保持参数不变,调整系统初始状态也可以使系统完成从无序向有序,或者从有序向无序转换. 相似文献
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This paper describes the results of an amplitude modulation experiment performed on a pulse-preionized transverse-flow transverse-discharge CO2 laser. The amplitude modulation of the laser power was achieved by pulsewidth modulation of the discharge current using a switched-mode power supply. The causes of growth of discharge instability observed during the experiment with long excitation pulses are explained. The power control of the laser using this technique has been studied and this method is compared with the conventional method where the discharge current level is varied to achieve the laser-power control 相似文献
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在磁弹性动力学理论的基础上,应用动力学方法建立电磁场和温度场联合作用下的载流梁的非线性热磁弹性振动方程。应用非线性振动的多尺度法,求得了系统受Lorentz力和温度影响共同作用的3次超谐共振幅频响应方程,并对其进行了数值计算,研究电磁场、温度变化、电流、几何参数等参数对载流梁3次超谐共振响应曲线的影响。结果表明:当温度、磁场强度、长度、横截面积达到特定值时,系统振幅会大幅增加。 相似文献
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A. V. Arsenin A. D. Gladun V. G. Leiman V. L. Semenenko V. I. Ryzhii 《Journal of Communications Technology and Electronics》2011,56(10):1242-1248
A possibility of the parametric instability in the resonance detector of the modulated terahertz radiation is analyzed. The
detector represents a system of capacitively coupled plasma and mechanical resonators. A layer of 2D electron gas with a relatively
high electron mobility and a cylindrical gate electrode that is fixed at the ends serve as the first and second resonators,
respectively. The method of coupled oscillations is used to obtain the dependence of the minimum threshold pump power of the
plasma circuit that corresponds to the excitation of the parametric instability on the main geometrical and electric parameters
of the system. 相似文献
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《Mechatronics》2006,16(8):451-459
This paper proposes a new electromagnetic force model and its parameter identification method. As a case study, the parameters of the proposed model for an experimental electromagnetic bearing system are obtained using extended Kalman filter (EKF). The experimental setup includes a symmetric rigid rotor which is disturbed by the electromagnet of a magnetic bearing. Experimental results show that the system response to harmonic excitation includes super-harmonic terms which are not shown by the well-known conventional electromagnetic force model. This shortcoming necessitates an investigation to propose a more realistic electromagnetic force model. Based on the observations of the system response, a novel parametric model is presented in the form of a nonlinear Mathieu–Duffing equation with unknown coefficients. Then in the operating frequency range, a random input is synthesized and applied to the experimental system as a persistent excitation and the response of the system is recorded. In order to estimate the states and parameters of the model, the EKF method has been applied to the recorded input–output data. To validate the identification results the outputs of estimated and experimental models are compared in time and frequency domains. The results show a notable improvement in modeling of magnetic force. The proposed model and the method for identifying its parameters are applicable for all magnetic fields. 相似文献
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Yang Jing Wen Xiang Lin Yang 《Journal of Infrared, Millimeter and Terahertz Waves》1998,19(7):963-975
The modified quantum nonlinear Schrodinger equation of ultra-short pulse propagating in fiber is derived using dispersion relation and the Hamiltonian of the transmission system. The derived equation is solved with linearization approximation, and modulation instability is analyzed. The equation is also solved with Hartree approximation. The results indicate that pulse power, loss and self-steeping effect change the critical frequency, the maximum gain and the gain spectrum range, but the third order dispersion has no effect on modulation instability. The expectation value of optical field is average of a set of modified classical solitons, and higher order terms change the amplitude, pulse position and phase of soliton. 相似文献
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超声红外锁相热像检测法是超声波激励与红外锁相热像检测技术相结合的一种红外无损检测方法。采用超声红外锁相热像检测法实现对金属板材构件接触界面类缺陷的检测,分析超声波激励构件缺陷的选择性加热过程。通过有限元仿真模型对热流在金属板材内部的热传导过程进行研究并分析超声激励参数对检测结果的影响;利用所建立的超声红外锁相检测系统对预制金属板材构件接触界面类缺陷中的裂纹缺陷进行检测实验,验证有限元模型的有效性。研究结果表明,加载中心位置远离缺陷时,裂纹缺陷幅值降低,相位不变;超声激励振幅(即初始静压)增加,缺陷处的幅值升高,相位基本保持不变;超声调制频率增加,缺陷处幅值降低,相位升高。通过对比仿真结果与实验结果发现,所建立的仿真模型能够较好地预测检测过程中的热流传递,并且能够用于超声红外锁相热像技术检测金属板材接触界面类缺陷检测结果的预测,为超声红外锁相热像技术激励参数的选择提供了指导。 相似文献