共查询到20条相似文献，搜索用时 31 毫秒
1.
深入分析了现有的三次样条拟合方法，指出ldquo;拟合过冲rdquo;现象产生的原因，并提出新的三次样条拟合方法和正弦函数拟合方法. 这两种新拟合方法都具有消除ldquo;过冲rdquo;现象，拟合函数连续、一阶导数连续、计算简便、计算量小、易于操作等优点. 同时，指明了ldquo;端点飞翼rdquo;现象产生的原因，并提出一种处理资料曲线的端点问题的技巧. 该技巧能够在不改变资料曲线的条件下消除ldquo;端点飞翼rdquo;现象. 拟合新方法和新技巧能结合运用，得到完全没有ldquo;拟合过冲rdquo;和ldquo;端点飞翼rdquo;的拟合曲线，为时序曲线固有模态函数分解提供了可靠的技术基础. 相似文献
2.
Based on the existing continuous borehole strain observation, the multiquadric function fitting method was used to deal with time series data. The impact of difference kernel function parameters was discussed to obtain a valuable fitting result, from which the physical connotation of the original data and its possible applications were analyzed. Meanwhile, a brief comparison was made between the results of multiquadric function fitting and polynomial fitting. 相似文献
3.
结构动力分析是工程设计中的重要组成部分，传统结构动力分析不能全面反映结构动力的初值特征，而Gurtin变分原理被认为是目前唯一能全面反映结构动力初值特征的变分原理。本文应用以位移为参变量的Gurtin变分原理，采用复合样条有限元的方法，即在时间域及空间域的y方向采用三次B样条函数，而在空间域的x方向采用多项式逼近广义位移，从而建立了精度较高的计算板动力初值问题的样条有限元模型。数值计算结果表明，本文所建立的方法能有效地求解板的动力初值问题，且计算精度高。 相似文献
4.
地震信号中的随机噪声是一种干扰波,严重降低了地震信号的信噪比,并影响着资料的后续处理和分析.本文根据地震信号中有效信号和随机噪声的差异,结合分数阶B样条小波变换与高斯尺度混合模型提出了一种地震信号随机噪声压制方法.首先利用分数阶B样条小波变换将含噪地震信号映射到最优分数阶小波时频域内,然后对各小波子带系数分别建立高斯尺度混合模型,由贝叶斯方法估计出源地震信号小波系数,最后使用分数阶B样条小波逆变换重构得到降噪后的地震信号.利用本文方法对合成地震记录和实际地震信号进行降噪处理,实验结果表明本文方法能够有效地压制地震信号中的随机噪声,并且较好地保留了有效信号. 相似文献
5.
A method is described for assessing the strength of evidence for differences in the trends in chemical concentrations in stream water between catchments. A smoothing spline technique is used to model changes in water quality as a result of changes in flow rates, seasonal effects and an underlying trend. The method involves fitting the model twice, once with the underlying trends constrained to be identical for each river and once with the trends unconstrained. Statistical properties are assessed by simulation methods that allow for the autocorrelation in the residuals from the unconstrained fit. The method is applied to data from two streams in the Balquhidder catchments in the Highlands of Scotland and to data from the Dee, Don and Ythan rivers in the north‐east of Scotland. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
6.
H. J. MEYERHOFF 《Geophysical Prospecting》1968,16(4):491-510
It was found in Part I of this paper that approximating the sharp cut-off frequency characteristic best in a mean square sense by an impulse response of finite length M produced a characteristic whose slope on a linear frequency scale was proportional to the length of impulse response, but whose maximum overshoot of ±9% was independent of this length (Gibbs' phenomenon). Weighting functions, based on frequency tapering or arbitrarily chosen, were used in Part II to modify the truncated impulse response of the sharp cut-off frequency characteristic, and thereby obtain a trade-off between the value of maximum overshoot and the sharpness of the resulting characteristic. These weighting functions, known as apodising functions, were dependent on the time-bandwidth product Mξ, where 2ξ, corresponded to the tapering range of frequencies. Part III now deals with digital filters where the number 2N–1 of coefficients is directly related to the finite length M of the continuous impulse response. The values of the filter coefficients are taken from the continuous impulse response at the sampling instants, and the resulting characteristic is approximately the same as that derived in Part II for the continuous finite length impulse response. Corresponding to known types of frequency tapering, we now specify a filter characteristic which is undefined in the tapering range, and determine the filter coefficients according to a mean square criterion over the rest of the frequency spectrum. The resulting characteristic is dependent on the time bandwidth product Mξ= (N–1/2)ξ up to a maximum value of 2, beyond which undesirable effects occur. This optimum partially specified characteristic is an improvement on the previous digital filters in terms of the trade-off ratio for values of maximum overshoot less than 1%. Similar to the previous optimum characteristic is the optimum partially specified weighted digital filter, where greater “emphasis is placed on reducing the value of maximum overshoot than of maximum undershoot”. Such characteristics are capable of providing better trade-off ratios than the other filters for maximum overshoots greater than 1/2%. However these filters have critical maximum numbers 2.NC–1 of coefficients, beyond which the resulting characteristics have unsuitable shapes. This type of characteristic differs from the others in not being a biassed odd function about its cut-off frequency. 相似文献
7.
8.
利用中国大陆以及蒙古、 缅甸、 印度、 尼泊尔和喜马拉雅等周边地区多年的GPS观测资料, 基于连续介质假设, 采用双三次样条函数模拟方法, 给出中国大陆整体水平位移速度, 拟合精度优于3 mm/a, 获得了中国大陆的水平应变率场, 并分析了中国大陆现今构造变形、 水平应变率场的空间分布特征. 结果表明: 对大范围、 密集的GPS速度场的连续变形分析, 既能揭示中国大陆现今构造变形的总体特征, 又能显示局部地区现今的构造活动特征. 总体上, 中国大陆构造的水平变形强度和变形速度在南北地震带产生突变, 呈西强东弱、 南强北弱态势. 而昆仑山地块中部、 鲜水河断裂带和云南中部地区, 其应变速率最大, 速度变化最快; 阿尔金断裂带现今处于其构造活动的平静期, 中天山东部地区具有拉张环境. 相似文献
9.
利用2001年昆仑山口西MS8.1地震现场观测所提供的地表破裂同震位移数据,使用简单滑移弱化破裂模型,估算了发震主断层上的破裂传播速度. 该模型中考虑了断层破裂时动摩擦过程中应力上调和下调机制对地震波辐射能量分配的影响. 对比Bouchon和Valleacute;e有关昆仑山口西地震主断层破裂传播速度超过剪切波速度,甚至达到P波速度的结果, 采用动摩擦应力下调时的滑移弱化模型 (分数应力降模型),结果表明,伴随较高的地震波辐射效率,主断层的平均破裂传播速度等于或小于瑞利波速度,这与许力生和陈运泰的体波反演结果,以及陈学忠震源应力场估算的结果是一致的. 最后,联系到由地表破裂现象所反映出的断层力学特征,如与视应力相关的分数应力降 (动摩擦应力下调), 基于滑移弱化模型, 讨论了可能的震源破裂机制. 相似文献
10.
采用代数重建技术重建三维物体,提出了一种基于splatting原理的ART权值计算方法,以增强重建图像的空间分辨率.该算法基于三维锥束扫描方式,采用双三次样条局部基函数作为插值核,并利用其足印函数对物体进行插值来计算像素的权值.与常量插值相比,这种方法对物体的灰度值有更精确的近似,在相同的实验条件下可重建出分辨率高的物体.给出了适用于三维锥束重建的splatting算法的具体实现,并对实验数据进行了实物重建及误差分析. 相似文献
11.
With co-seismic surface rupture slip displacements provided by the field observation for the 2001 MS8.1 West Kunlun Mountain Pass earthquake, this paper estimates the rupture speed on the main faulting segment with a long straight fault trace on the surface based on a simple slip-weakening rupture model, in which the frictional overshoot or undershoot are involved in consideration of energy partition during the earthquake faulting. In contrast to the study of Bouchon and Vallée, in which the rupture propagation along the main fault could exceed the local shear-wave speed, perhaps reach the P-wave speed on a certain section of fault, our results show that, under a slip-weakening assumption combined with a frictional undershoot (partial stress drop model), average rupture speed should be equal to or less than the Rayleigh wave speed with a high seismic radiation efficiency, which is consistent with the result derived by waveform inversion and the result estimated from source stress field. Associated with the surface rupture mechanism, such as partial stress drop (frictional undershoot) associated with the apparent stress, an alternative rupture mechanism based on the slip-weakening model has also been discussed. 相似文献
12.
13.
Double-column bridge piers are prone to local damage during earthquakes, leading to the destruction of bridges. To improve the earthquake resistance of double-column bridge piers, a novel swing column device (SCD), consisting of a magnetorheological (MR) damper, a current controller, and a swing column, was designed for the present work. To verify the seismic energy dissipation ability of the SCD, a lumped mass model for a double-column bridge pier with the SCD was established according to the low-order modeling method proposed by Steo. Furthermore, the motion equation of the double-column bridge pier with the SCD was established based on the D’Alembert principle and solved with the use of computational programming. It was found that the displacement response of the double-column bridge pier was effectively controlled by the SCD. However, due to rough current selection and a time delay, there is a significant overshoot of the bridge acceleration using SCD. Hence, to solve the overshoot phenomenon, a current controller was designed based on fuzzy logic theory. It was found that the SCD design based on fuzzy control provided an ideal shock absorption effect, while reducing the displacement and acceleration of the bridge pier by 36.43%–40.63% and 30.06%–33.6%, respectively.
相似文献14.
Summary A method of approximation, minimizing the number of knots and satisfying the smoothing and fitting properties of the cubic spline approximation, is suggested. Two modifications of the method are presented. The first approach is specified to provide an adequate simple approximation to the digitalized smooth curve (such as the velocity-depth function in seismology), while the second is more general and may be used to approximate geophysical measurements, which may include errors. 相似文献
15.
在气枪源探测过程中,由于各种干扰因素的影响,导致部分有效信号缺失或受随机干扰严重,为了重构出连续完整的数据,依据气枪源信号在傅里叶变换域中具有稀疏性的特点,构建了一种基于压缩感知(Compressive Sensing,简称CS)的缺失信号重建方法。首先进行数值模拟,并将该方法与传统的插值方法处理效果进行对比,对重建效果进行均方根误差及信噪比(SNR)分析,结果显示:压缩感知方法重建前后信号的波形吻合度高、振幅一致性更强、同相轴清晰且连续性相同,对噪声压制较好。综上表明:该方法重建效果优于传统的三次样条插值方法。将该方法应用于实际资料,结果显示受干扰的有效信号能够得到很好的恢复重建。 相似文献
16.
2005年11月26日九江——瑞昌MＳ5.7地震发生前,震中及其周围地区的地磁基本场测量和相应的ldquo;2005.0中国地磁基本场曲面样条模型rdquo;显示,震中周围100 km范围内存在显著的ldquo;2005.0九江——瑞昌地磁基本场水平分量异常rdquo;. 而该异常在ldquo;1970.0中国地磁基本场曲面样条模型rdquo;中并不存在. 2005年12月在震中及其周围地区的21个测点上进行了地磁重复测量, 并建立了ldquo;局部修订2005.0中国地磁基本场曲面样条模型rdquo;. 该模型显示,震后ldquo;2005.0九江——瑞昌地磁基本场水平分量异常rdquo;明显减弱. 因此认为,ldquo;2005.0九江——瑞昌地磁基本场水平分量异常rdquo;是地震地磁前兆异常现象. 相似文献
17.
A three-component geomagnetic survey was carried out during the period from 2002 to 2004 in China including Jiujiang-Ruichang region. Comparing the ＂2005.0 surface spline model of China geomagnetic field＂ created on the basis of the survey data with the ＂1970.0 surface spline model of China geomagnetic field＂, we can see an obvious abnormity in the geomagnetic horizontal component within a range of about 100 km around the epicenter of the Ms=5.7 Jiujiang-Ruichang earthquake occurred on November 26, 2005. After the earthquake, we carded out a repeated geomagnetic survey at 21 stations in the Jiujiang-Ruichang region and created a corresponding ＂2005.0 partially revised surface spline model of China geomagnetic field＂. By comparing the above three models, analyzing the geomagnetic horizontal component at the profile in the Jiujiang-Ruichang region and quantitatively studying the geomagnetic data of every stations around the Ms=5.7 earthquake, we have obtained the geomagnetic abnormity associated with this earthquake. Then the geomagnetic abnormity and its relation with seismic activity are discussed in this paper. 相似文献
18.
With co-seismic surface rupture slip displacements provided by the field observation for the 2001 MS8.1 West Kunlun Mountain Pass earthquake, this paper estimates the rupture speed on the main faulting segment with a long straight fault trace on the surface based on a simple slip-weakening rupture model, in which the frictional overshoot or undershoot are involved in consideration of energy partition during the earthquake faulting. In contrast to the study of Bouchon and Vallée, in which the rupture propagation along the main fault could exceed the local shear-wave speed, perhaps reach the P-wave speed on a certain section of fault, our results show that, under a slip-weakening assumption combined with a frictional undershoot (partial stress drop model), average rupture speed should be equal to or less than the Rayleigh wave speed with a high seismic radiation efficiency, which is consistent with the result derived by waveform inversion and the result estimated from source stress field. Associated with the surface rupture mechanism, such as partial stress drop (frictional undershoot) associated with the apparent stress, an alternative rupture mechanism based on the slip-weakening model has also been discussed. 相似文献
19.
Bingzhu Wang Stephen S. Gao Kelly H. Liu Edward S. Krebes 《Geophysical Prospecting》2012,60(5):1001-1016
Potential, potential field and potential‐field gradient data are supplemental to each other for resolving sources of interest in both exploration and solid Earth studies. We propose flexible high‐accuracy practical techniques to perform 3D and 2D integral transformations from potential field components to potential and from potential‐field gradient components to potential field components in the space domain using cubic B‐splines. The spline techniques are applicable to either uniform or non‐uniform rectangular grids for the 3D case, and applicable to either regular or irregular grids for the 2D case. The spline‐based indefinite integrations can be computed at any point in the computational domain. In our synthetic 3D gravity and magnetic transformation examples, we show that the spline techniques are substantially more accurate than the Fourier transform techniques, and demonstrate that harmonicity is confirmed substantially better for the spline method than the Fourier transform method and that spline‐based integration and differentiation are invertible. The cost of the increase in accuracy is an increase in computing time. Our real data examples of 3D transformations show that the spline‐based results agree substantially better or better with the observed data than do the Fourier‐based results. The spline techniques would therefore be very useful for data quality control through comparisons of the computed and observed components. If certain desired components of the potential field or gradient data are not measured, they can be obtained using the spline‐based transformations as alternatives to the Fourier transform techniques. 相似文献
20.
The estimation of velocity and depth is an important stage in seismic data processing and interpretation. We present a method for velocity-depth model estimation from unstacked data. This method is formulated as an iterative algorithm producing a model which maximizes some measure of coherency computed along traveltimes generated by tracing rays through the model. In the model the interfaces are represented as cubic splines and it is assumed that the velocity in each layer is constant. The inversion includes the determination of the velocities in all the layers and the location of the spline knots. The process input consists of unstacked seismic data and an initial velocity-depth model. This model is often based on nearby well information and an interpretation of the stacked section. Inversion is performed iteratively layer after layer; during each iteration synthetic travel-time curves are calculated for the interface under consideration. A functional characterizing the main correlation properties of the wavefield is then formed along the synthetic arrival times. It is assumed that the functional reaches a maximum value when the synthetic arrival time curves match the arrival times of the events on the field gathers. The maximum value of the functional is obtained by an effective algorithm of non-linear programming. The present inversion algorithm has the advantages that event picking on the unstacked data is not required and is not based on curve fitting of hyperbolic approximations of the arrival times. The method has been successfully applied to both synthetic and field data. 相似文献