Rosenbrock实时积分方法的精度和稳定性分析及其在结构动力学上的应用

Rosenbrock法以其在稳定性和精度方面的优势得到了广泛的应用,但Rosenbrock法大多局限于一阶微分方程的求解,在结构动力学上的应用相对较少。本文针对其在结构动力学问题上的应用,对2级Rosenbrock实时积分方法的精度和稳定性进行了系统地分析。结果表明:该方法对于满足Lipschitz条件的非线性问题,能保持二阶精度;在求解线性无阻尼问题以及带有摆非线性问题时,该方法具有能量衰减的特性;与平均加速度法相比,该方法在求解Bouc-Wen模型的非线性问题时表现出更好的稳定性。本文为采用Rosenbrock法解决复杂的结构动力学问题提供了更有利的理论依据。     

地震动瞬时谱估计的UnscentedKalman滤波方法

用时变ARMA模型描述地震动时程,提出了采用Unscented Kalman滤波技术实现地震动瞬时谱估计的思路．算例分析表明,Unscented Kalman滤波方法较Kalman滤波方法适用范围广,具有较高的时间和频率分辨率,能够更好地跟踪地震动的局部特性,适合处理非线性模型或有突变特性的模型的辨识问题．不同阶数ARMA模型的估计结果还表明,以往被忽略的ARMA模型的理论频率分辨力对地震动瞬时谱估计精度有重要影响,应作为一个参考指标在ARMA模型的判阶中加以考虑．     

A coaxial HOM coupler for a superconducting RF cavity and its low-power measurement results

A resonant buildup of beam-induced fields in a superconducting radio frequency (RF) cavity may make a beam unstable or a superconducting RF cavity quench. Higher-order mode (HOM) couplers are used for damping higher-order modes to avoid such a resonant buildup. A coaxial HOM coupler based on the TTF (TESLA Test Facility) HOM coupler has been designed for the superconducting RF cavities at the Proton Engineering Frontier Project (PEFP) in order to overcome notch frequency shift and feed-through tip melting issues. In order to confirm the HOM coupler design and finalize its structural dimensions, two prototype HOM couplers have been fabricated and tested. Low-power testing and measurement of the HOM couplers has shown that the HOM coupler has good filter properties and can fully meet the damping requirements of the PEFP low-beta superconducting RF linac.     

Instantaneous spectrum estimation of earthquake ground motions based on unscented Kalman filter method

Representing earthquake ground motion as time varying ARMA model,the instantaneous spectrum can only be determined by the time varying coefficients of the corresponding ARMA model.In this paper,unscented Kalman filter is applied to es- timate the time varying coefficients.The comparison between the estimation results of unscented Kalman filter and Kalman filter methods shows that unscented Kalman fil- ter can more precisely represent the distribution of the spectral peaks in time-frequency plane than Kalman filter,and its time and frequency resolution is finer which ensures its better ability to track the local properties of earthquake ground motions nd to identify the systems with nonlinearity or abruptness.Moreover,the estimation results of ARMA models with different orders indicate that the theoretical frequency resolving power of ARMA model which was usually ignored in former studies has great effect on the estima- tion precision of instantaneous spectrum and it should be taken as one of the key factors in order selection of ARMA model.