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A long time series (170 years) of daily flows of the river Warta (Poland) are subject to fractal analysis. A binary variable (renewal stream) illustrating excursions of the process of flow is examined. The raw series is subject to de-seasonalization and normalization. Fractal dimensions of crossings of Warta flows are determined using a novel variant of the box-counting method. Temporal variability of the flow process is studied by determination of fractal dimensions for shifted horizons of 10 or 30 years length. Spectral properties are compared between the time series of flows, and the fractional Brownian motion which describes both the fractal structure of the process and the Hurst phenomenon. The approach may be useful in further studies of non-stationary of the process of flow, analysis of extreme hydrological events and synthetic flow generation. 相似文献
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关系数据库设计中规范化与逆规范化的应用 总被引：7，自引：0，他引：7
讨论了在大型关系数据库优化设计中关系的规范化和逆规范化的应用。通过对数据库所需存储空间和查询响应时间的分析, 讨论了两者的优缺点, 给出了一些具体使用的准则。 相似文献
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Normalizing XRF-scanner data: A cautionary note on the interpretation of high-resolution records from organic-rich lakes 总被引：2，自引：0，他引：2
L. Lwemark H.-F. Chen T.-N. Yang M. Kylander E.-F. Yu Y.-W. Hsu T.-Q. Lee S.-R. Song S. Jarvis 《Journal of Asian Earth Sciences》2011,40(6):429-1256
X-ray fluorescence (XRF) scanning of unlithified, untreated sediment cores is becoming an increasingly common method used to obtain paleoproxy data from lake records. XRF-scanning is fast and delivers high-resolution records of relative variations in the elemental composition of the sediment. However, lake sediments display extreme variations in their organic matter content, which can vary from just a few percent to well over 50%. As XRF scanners are largely insensitive to organic material in the sediment, increasing levels of organic material effectively dilute those components that can be measured, such as the lithogenic material (the closed-sum effect). Consequently, in sediments with large variations in organic material, the measured variations in an element will to a large extent mirror the changes in organic material. It is therefore necessary to normalize the elements in the lithogenic component of the sediment against a conservative element to allow changes in the input of the elements to be addressed. In this study we show that Al, which is the lightest element that can be measured using the Itrax XRF-scanner, can be used to effectively normalize the elements of the lithogenic fraction of the sediment against variations in organic content. We also show that care must be taken when choosing resolution and exposure time to ensure optimal output from the measurements. 相似文献
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Rodolpho Vilhena de Moraes Regina Elaine Santos Cabette Maria Cecília Zanardi Teresinha J. Stuchi Jorge Kennety Formiga 《Celestial Mechanics and Dynamical Astronomy》2009,104(4):337-353
The stability of the rotational motion of artificial satellites is analyzed considering perturbations due to the gravity gradient
torque, using a canonical formulation, and Andoyer’s variables to describe the rotational motion. The stability criteria employed
requires the reduction of the Hamiltonian to a normal form around the stable equilibrium points. These points are determined
through a numerical study of the Hamilton’s equations of motion and linear study of their stability. Subsequently a canonical
linear transformation is used to diagonalize the matrix associated to the linear part of the system resulting in a normalized
quadratic Hamiltonian. A semi-analytic process of normalization based on Lie–Hori algorithm is applied to obtain the Hamiltonian
normalized up to the fourth order. Lyapunov stability of the equilibrium point is performed using Kovalev and Savchenko’s
theorem. This semi-analytical approach was applied considering some data sets of hypothetical satellites, and only a few cases
of stable motion were observed. This work can directly be useful for the satellite maintenance under the attitude stability
requirements scenario. 相似文献
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Compositional data arise naturally in several branches of science,including chemistry,geology,biology,medicine,ecology and manufacturing design.In chemistry,these constrained data seem to occur typicallywhen raw data are normalized or when output is obtained from a constrained estimation procedure,suchas might be used in a source apportionment problem.It is important not only for chemists to be awarethat the usual multivariate statistical techniques are not applicable to constrained data,but also to haveaccess to appropriate techniques as they become available.The currently available methodology is dueprincipally to Aitchison and is based on log-normal models.This paper suggests new parametric andnon-parametric approaches to significantly improve the existing methodology.In the parametric setting,some recent work of Rayens and Srinivasan is extended and a practical regression model is proposed.In the development of the non-parametric approach,minimum distance methods coupled withmultivariate bootstrap techniques are used to obtain point and region estimators. 相似文献
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基于分形维数的原始定义，本文给出一种维数的数值计算方法。若被测量对象在某一标度范围内确具有统计意义上的标度不变性，则该方法能够较好地得到所需精度的维数计算结果并进而反推“无标度区”范围。在假设维数集｛ｂｋ｝服从正态分布的前提下，引入柯氏检验方法对（ｂｋ｝样本分布的一致性进行检验，以此判断｛ｂｋ｝中是否具有“异常值”存在，并由标准化极差检验法对｛ｂｋ｝中“异常值”进行检测并剔除，其目的是在“直观判定”的基础上对维数作进一步的精确计算及对“无标在区”作进一步的精确界定．本文方法的一个显著特点是所有判断及统计检验皆针对最终结果（维数）。人造数据的应用检验亦表明了该方法的客观实用性． 相似文献
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黄河上游某坝基岩体弹性波速的各向异性与归一化研究 总被引：1，自引：0，他引：1
本文以黄河上游某坝基岩体弹性波测试，研究了层状结构岩体波速的各向异性规律，并对其进行了归一化校正。 相似文献
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针对蒙自地区膨胀土,进行了饱和重塑条件下的固结排水(CD)与固结不排水(CU)试验,系统研究了饱和土在不同固结围压3、初始干密度d、初始含水量0、剪切速率、排水条件下的应力应变特性。通过对临界状态试验结果的归一化处理,揭示了不同试验方法对同一土样抗剪强度量测差异的内在统一性,得到了重塑饱和膨胀土在固结排水与不排水条件下p'-q-空间内的破坏线。利用双曲线模型较好地拟合了弱硬化型应力应变曲线,用指数曲线模型拟合了弱软化型应力应变曲线,为模拟边坡在降雨条件下的抗剪强度变化及构筑物土体处于正常水位时的强度状态等工况提供了技术参数与理论支持。 相似文献