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修改了现行教学用网络数据处理系统中的幅频特性描述和求解阻尼系数的方法,采用非线性拟合,不仅能直观描述蜗卷弹簧性能的差异,同时可以从拟合曲线中方便地求解实验的阻尼系数。这是一种实时的数据处理方式,研究结果可成为仪器生产单位数据处理软件的开发方案,为实验室教师机上显示各组仪器的特性曲线和求解阻尼系数提供了一种更直接的方式。 相似文献
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本文修改了现行教学用网络数据处理系统中的幅频特性描述和求解阻尼系数的方法,采用非线性拟合,不仅能直观描述蜗卷弹簧性能的差异,同时可以从拟合曲线中方便地求解实验的阻尼系数.这是一种实时的数据处理方式,研究结果可成为仪器生产单位数据处理软件的开发方案,为实验室教师机上显示各组仪器的特性曲线和求解阻尼系数提供了一种更直接的方式. 相似文献
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非本征光纤法布里-珀罗(F-P)传感器已被用于液-固复合绝缘局部放电检测,但存在液体黏滞阻尼和附加质量影响传感器固有频率和灵敏度的问题。采用有限元方法计算传感膜片在油和空气介质中受迫振动幅频响应,并分析不同温度下传感器幅频特性和灵敏度。提出F-P传感器的液体隔离结构,消除介质对其参数的影响。制备FP传感器并构建实验系统,测试不同温度下两种结构传感器的幅频特性。实验结果表明:液体绝缘油中,F-P传感器因黏滞阻尼和附加质量导致固有频率下降约0.58,幅频曲线带宽变大,响应幅值降低;液体介质温度升高,传感器固有频率增加,幅频曲线带宽变小,响应幅值增加,灵敏度变大;液体隔离结构的F-P传感器不受介质黏滞阻尼和附加质量影响。 相似文献
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使用Matlab/Simulink软件,建立了小球在空气阻力下反复弹跳的实验模型,讨论了小球在不同空气阻尼系数下的位移和速度,加深了学生对质点落体运动以及碰撞问题的认识。 相似文献
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应用法拉第电磁感应定律推导出非磁性旋转导体盘的转动衰减方程;定义并测量了导体盘的摩擦阻尼系数和电磁阻尼系数;分析研究了电磁阻尼系数与励磁电流平方间的关系. 相似文献
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为探究地铁车辆阻尼环扩张状态对阻尼环车轮声振特性影响,在半消声室内进行阻尼环车轮自由状态下的声振特性实验研究,结合有限元仿真对实验结果进行分析。研究表明,环-轮组合振动固有频率与原车轮相比变化不大,但阻尼环使车轮的模态阻尼比显著增加,有效抑制了车轮各模态的振动幅值。改变阻尼环扩张状态,阻尼环降噪效果发生非线性变化,幅值在5.6 dB(A)之内。阻尼环扩张状态可通过调节非闭合阻尼环两端扩张装置来改变。阻尼环处于非最大扩张状态W_3时,可获得最佳降噪效果。 相似文献
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Vertically forced surface wave in weakly viscous fluids bounded in a circular cylindrical vessel 总被引:1,自引:0,他引:1 下载免费PDF全文
Two-time scale perturbation expansions were developed in weakly viscous fluids to investigate surface wave motions by linearizing the Navier-Stokes equation in a circular cylindrical vessel which is subject to a vertical oscillation. The fluid field was divided into an outer potential flow region and an inner boundary layer region. A linear amplitude equation of slowly varying complex amplitude, which incorporates a damping term and external excitation, was derived for the weakly viscid fluids. The condition for the appearance of stable surface waves was obtained and the critical curve was determined. In addition, an analytical expression for the damping coefficient was determined and the relationship between damping and other related parameters (such as viscosity, forced amplitude, forced frequency and the depth of fluid, etc.) was presented. Finally, the influence both of the surface tension and the weak viscosity on the mode formation was described by comparing theoretical and experimental results. The results show that when the forcing frequency is low, the viscosity of the fluid is prominent for the mode selection. However, when the forcing frequency is high, the surface tension of the fluid is prominent. 相似文献
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Tarnopolsky AZ Fletcher NH Lai JC 《The Journal of the Acoustical Society of America》2000,108(1):400-406
The results of experiments on the threshold behavior and large-amplitude oscillation of "outward-swinging door" vibrating flap valves in an air environment are reported and compared with the predictions of a simple nonlinear theory that parametrizes aerodynamic effects by means of a simple damping coefficient together with a contraction coefficient for the flow. The agreement is acceptably good for the threshold blowing pressure for valve oscillation, the large-signal vibration amplitude, the pressure jump in the transition from threshold to large-signal behavior, and the variation in vibration frequency, all as functions of reservoir volume. The calculated pressure waveform in the reservoir has the observed phase and magnitude but fails to reproduce finer details. It is concluded that the simple theory provides an adequate account of the behavior of such valves. There are just two parameters in the theory, describing jet contraction and aerodynamic damping, respectively. Since these may depend significantly upon the detailed geometry, valves with different shapes may behave in quantitatively different ways. 相似文献
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较之于线性噪声, 非线性噪声更广泛地存在于实际系统中, 但其研究远不能满足实际情况的需要. 针对作为非线性阻尼涨落噪声基本构成成分的二次阻尼涨落噪声, 本文考虑了周期信号与之共同作用下的线性谐振子, 关注这类具有基本意义的阻尼涨落噪声的非线性对系统共振行为的影响. 利用Shapiro-Loginov公式和Laplace变换推导了系统稳态响应振幅的解析表达式, 并分析了稳态响应振幅的共振行为, 且以数值仿真验证了理论分析的有效性. 研究发现: 系统稳态响应振幅关于非线性阻尼涨落噪声系数具有非单调依赖关系, 特别是非线性阻尼涨落噪声比线性阻尼涨落噪声更有助于增强系统对外部周期信号的响应程度; 而且, 非线性阻尼涨落噪声比线性阻尼涨落噪声使得稳态响应振幅关于噪声强度具有更为丰富的共振行为; 同时, 二次阻尼涨落噪声使得稳态响应振幅关于系统频率出现真正的共振现象; 而在这些现象和性质中, 非线性噪声项的非线性性质对共振行为起着关键的作用. 显然, 以二次阻尼涨落作为基本形式引入的非线性阻尼涨落噪声, 可以有助于提高微弱周期信号检测的灵敏度和实现对周期信号的频率估计. 相似文献
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Renaud Garrel Ronald Scherer Richard Nicollas Antoine Giovanni Maurice Ouaknine 《Journal of voice》2008,22(4):385-398
Well-known multimass models of vocal folds are useful to describe main behavior observed in human voicing but their principle of functioning, based on harmonic oscillation, may appear complex. This work is designed to show that a simple one-mass model ruled by laws of relaxation oscillation can also depict main behavior of glottis dynamic. Theory of relaxation oscillation is detailed. A relaxation oscillation model is assessed through a numerical simulation using conventional values for tissue characteristics and subglottal pressure. As expected, raising the mass decreases the fundamental frequency and increases the amplitude of vocal fold vibration: for a mass ranging from 0.01 to 0.4 g, F0 decreased from 297.5 to 42.5 Hz and vibrational amplitude increased from 1.26 to 3.25 mm (for stiffness k=10Nm(-1), damping r=0.015 N s m(-1), and subglottal pressure=1 kPa). Stiffness value has the opposite effect. The subglottal pressure controls the fundamental frequency with a rate ranging from 20 to 50 Hz/kPa. The vibrational amplitude is also controlled linearly by subglottal pressure from 0.22 to 0.26 mm/kPa. The range of phonation threshold pressure (PTP) is close to the values currently proposed, that is, 0.1 to 1 kPa and varies with the fundamental frequency. The relaxation oscillator is a simple and useful tool for modeling vocal fold vibration. 相似文献
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研究了含两类分数阶微分项的线性单自由度振子, 通过平均法得到了系统的近似解析解. 在近似解中, 两类分数阶微分项的系数和阶次均以等效线性阻尼和等效线性刚度的形式影响着系统的动力学特性, 这一点和现有文献中大多数直接将分数阶微分项归类为阻尼进行处理是完全不同的. 对近似解析解和数值解进行了比较, 二者符合精度很高, 证明了该结果的准确性. 然后分析了两类分数阶微分项的系数和阶次对系统响应特性的影响, 发现两类分数阶微分项的系数和阶次都既可以影响系统的共振振幅, 又可以影响系统的共振频率. 最后研究了第二类分数阶微分项对共振频率的影响, 指出了在振动控制工程中如何通过选取合适的第二类分数阶微分项的系数达到满意的控制效果. 相似文献