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1.
This article addresses the problem of parametric time-domain identification and dynamic analysis for time-varying (TV) mechanical structures under unobservable random excitation. The methods presented are based on time-dependent autoregressive moving average (TARMA) models, and are classified according to the mathematical structure imposed on the TV parameter evolution as unstructured parameter evolution, stochastic parameter evolution, and deterministic parameter evolution. The features and relative merits of each class are outlined. A representative method from each is then assessed through its application to the identification and dynamic analysis of a laboratory TV structure consisting of a beam with a mass moving on it. The results are mutually compared and contrasted to those obtained through “frozen-configuration” (multiple experiment) baseline identification.  相似文献
2.
光子多普勒速度测量系统的数据处理方法   总被引:1,自引:0,他引:1  
光子多普勒速度测量(Photonic Doppler Velocimetry,PDV)系统是一种新型的激光测速系统,可广泛用于冲击波、爆轰波以及其他短时高速运动的测量。数据处理是PDV测速技术重要的组成部分,旨在从含有大量噪声的测量数据中获得靶面等运动体的速度信息。在分析PDV系统测速原理的基础上,讨论了激光冲击强化实验PDV数据中噪声的来源和特点,解释了条纹法的去噪原理,并针对小波变换的去噪问题,提出了一些新的处理方法。分别采用条纹法,短时傅里叶变换和小波变换法对激光冲击强化实验中的PDV数据进行了处理,从误差、处理的实时性和通用性等角度对三种方法进行了比较,并说明了小波变换法特别适合激光冲击强化实验PDV测速数据的处理。  相似文献
3.
类GPS超声定位系统中自主导引小车动态定位算法   总被引:1,自引:0,他引:1       下载免费PDF全文
针对自主导引小车(AGV)常规超声波局部定位系统的缺陷,提出了类GPS超声定位系统并阐述了其工作原理。研究了小车动态情况下与定位基站的距离估计问题,在获得AGV与定位基站的观测距离后可通过Gauss-Newton迭代定位算法获得小车空间位置的粗估计值。仿真结果表明,将上述获得的粗估计值序列经过卡尔曼滤波器进一步处理后,可提高AGV动态定位精度和速度的估计精度。  相似文献
4.
马再如  隋展  冯国英  孙年春  王屹山  张彬  陈建国 《物理学报》2012,61(7):74206-074206
在时间--频率域中,啁啾脉冲被淹没在放大自发辐射等噪声中,且其瞬时频率线性分布,基于此,提出采用光谱扫描滤波的办法来提升高功率飞秒激光系统的信噪比,并以法布里--珀罗干涉仪作为光谱扫描滤波器,对该法提升信噪比的效果进行了详细的理论分析.采用短时傅里叶变换方法,研究了光谱扫描滤波器对自发辐射放大(ASE)的滤波效果,数值分析表明,在时间抖动为-2 ps到2 ps之间、光谱扫描滤波器的通带宽度为0.4 nm条件下,该法能将飞秒激光系统的信噪比提升2个量级,而啁啾信号光以超过90%的透光率通过光谱扫描滤波器;级联光谱扫描滤波方式能进一步提升飞秒激光信噪比.  相似文献
5.
传统谱峭度方法通常采用基于短时傅里叶变换(Short Time Fourier Transform,STFT)的峭度图方法来实现。针对STFT不能保证对瞬态脉冲这种高度非平稳信号最优的分解效果的缺点,提出一种基于经验模式分解(Empirical Mode Decomposition ,EMD)的谱峭度方法。该方法首先利用EMD和Hilbert变换得到信号的时频分布,然后将信号的时频分布按照不同层数分成若干频段,通过计算各频段的峭度值得到相应的峭度图,再根据峭度最大原则选择滤波频段进行带通滤波,最后对滤波信号采用包络分析确定故障信息。实验结果表明:相比传统基于STFT的谱峭度方法,本文方法更能准确的获得轴承加速度信号的故障特征频率信息。  相似文献
6.
White-light scanning interferometry (WLSI) is a powerful tool for investigating the profile of a test object that contains sharp steps. Due to the light source used in WLSI system, it is able to overcome phase ambiguity problem, which is often encountered in monochromatic interferometry. In this paper, a new algorithm based on least-square estimation using short-time Fourier transform (STFT) is proposed to measure the profile of a test object. STFT is used to extract the peak position of the coherence envelope of a white-light interference signal and retrieve the corresponding phase values simultaneously at first. A complex phasor (CP) method is introduced to further reduce the phase noise. Then, the phase values at several positions around are utilized to achieve a more accurate peak position based on least-square line fitting. Both simulated and experimental results show that the proposed algorithm is able to accurately measure the profile of a test object.  相似文献
7.
We show a representation of the spaces of Gabor transforms using the general decomposition method of Vasilevski. This provides an interesting characterization of a class of Gabor-Toeplitz operators and enables to obtain their representation formulae, Wick calculus and the commutativity of the algebra of such operators particularly simply.  相似文献
8.
Conventionally, the Fourier transform is applied for sound intensity analysis of stationary signals, but this method can be applied for analyzing non-stationary transient signals. Instead of the Fourier transform analysis, instantaneous spectrum analysis methods such as the Wigner-Ville distribution and the wavelet transform are proposed. By using the mathematical example as a transient signal, advantages and disadvantages of these methods including the short-time Fourier transform are compared. From calculation results, it is considered that the STFT method is the most suitable for the accurate measurement of sound intensity levels, but the WT method is also recommended from its higher resolution of transient signals.  相似文献
9.
以傅里叶变换极限脉冲作参考脉冲,利用单次测量分析法对复杂的皮秒脉冲进行测量,用窗口傅里叶变换代替傅里叶变换对干涉条纹进行时间-频率分析,直接提取出复杂脉冲的啁啾特性或光谱成分,将光谱图中的功率密度S(ω,t)沿ω轴求和重建脉冲的时域包络.分别用该方法和传统频域干涉测量法测量一个线性啁啾脉冲和一个复杂脉冲.结果表明,该方法可实现复杂整形脉冲的实时测量,且时间分辨率为70 fs.  相似文献
10.
马再如  隋展  周桂勇  孙年春  王屹山  王向林  张彬  张蓉竹 《物理学报》2013,62(15):154202-154202
光谱调制所形成的预脉冲和后沿脉冲的时频谱图将等间距、 平行地分布于啁啾主脉冲时频谱图的两侧, 基于光谱调制啁啾光脉冲的这种时频谱特点, 采用扫描滤波方式来提升其对比度. 数值模拟分析了扫描滤波过程中时间抖动、 扫描率差异和通带宽度等因素对扫描滤波效果的影响, 结论表明, 在扫描轨迹与信号光频率相同的情况下, 控制通带宽度, 相干信噪比提升率接近0.41F2倍, 而啁啾信号光以超过90%的透光率通过光谱扫描滤波器. 关键词: 超快激光技术 相干信噪比 光谱扫描滤波 短时傅里叶变换法  相似文献
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