用多元分析法研究泥蚶(Tegillarca granosa)氨基酸地区差异   总被引：2，自引：0，他引：2  

潘沙芳  李太武  苏秀榕 《海洋与湖沼》2006,37(6):536-540

采用贝克曼System6300氨基酸分析仪检测了7个地区泥蚶群体的氨基酸种类及含量,并利用多元分析法对这些群体的氨基酸含量差异进行了比较研究。聚类分析结果表明,7个泥蚶群体中,乐清和韩国群体间的氨基酸含量差异最小,汕头群体与其他6个群体间的氨基酸差异程度最大。通过软件分析,构建3个能反映氨基酸信息的综合性指标——主成分1、主成分2和主成分3,三者的贡献率分别为50.138%、23.332%和15.619%,累计贡献率高达89.089%。  相似文献   

一种基于Helmert方差分量估计的Vondrak滤波方法     

郭固良  曾凡河  周晓卫 《现代测绘》2008,31(1):11-12,22

从基于Helmert方差分量估计的Vondrak滤波方法(简称HVF法)的基本假设入手,介绍了HVF方法,该方法能够在未知拟合函数的情况下,通过自动选择合理的平滑因子控制数据平滑的程度,对时序数据序列进行合理平滑,最大限度的削弱数据序列中的随机误差,将信号与噪声合理分离.  相似文献   

泰山顶部近地层风的方差与谱分析   总被引：2，自引：0，他引：2       下载免费PDF全文

王秀梅  王海英冯磊  丁善文赵勇 《应用气象学报》2003,14(6):739-744

风在速度与方向上的不稳定性可引发结构振动并可导致损坏。山顶风较少受局地作用影响, 流场较稳定，作为典型风况对山顶风湍流脉动情形进行的观测和分析，对于研究建筑结构风载振动情形有着重要意义。在不同风况下对泰山气象站近地层风的风速和风向进行了同时、逐秒测记，所得样本经检验符合正态分布。计算表明，风向样本方差显著大于风速样本方差。绘制了各风速、风向样本自、互谱密度曲线图。谱图显示诸样本具有红噪声序列特征，不同样本自、互谱密度曲线具有相近形状，而以风速自谱曲线吻合程度最好，谱密度曲线在周期为4秒及2秒处有峰值。此后的研究应结合记录仪器的改进增加采样频率，对周期为2秒以下谱曲线作进一步分析。  相似文献   

The separation of the influence of nutrients and climate on the varve time-series of baldeggersee, Switzerland   总被引：7，自引：2，他引：7  

A. F. Lotter  H. J. B. Birks 《Aquatic Sciences - Research Across Boundaries》1997,59(4):362-375

The varve data-set from a freeze-core taken in the deepest part of Baldeggersee was subjected to different multivariate statistical analyses in order to estimate the amount of variance in the varve thickness measures explicable by past climate and by the trophic state of the lake. A comparison of two different time-periods (1902 to1992 versus 1920 to 1980) revealed that the lake restoration programme since 1982 has had a significant impact on the formation of the seasonal layers. Results of the partitioning of the variance in the varve thickness measures showed that about two thirds of the variance are unexplained by a climate and trophic state model and that trophic state explains 6%, whereas climate accounts for about 28% of the variance before the effect of lake restoration had a strong impact on the varves. Among the climate parameters the amount of annual precipitation is a strong predictor for explaining the thickness of both dark layer and total couplet thickness, whereas summer precipitation is important for the thickness of the light layer.  相似文献   

统一方差分量估计公式     

李广云 《测绘学院学报》1993,(3)

本文提出了一种适用于协方差阵奇异或非奇异、设计阵列满秩或降秩时的方差分量估计方法;其公式推导简单,形式统一,不需解线性方程组,同时可保证迭代计算方差分量的非负要求。作为特例还和Helmert法及MINQUE法作了比较。最后讨论了用真误差进行方差分量估计的计算公式,并给出了一个测距误差分析的实例。  相似文献   

我国太阳辐射量区域性变化特征研究^*   总被引：7，自引：1，他引：7  

查良松 《地理研究》1996,15(2):21-27

对我国近35年来到达地面的太阳辐射量观测资料进行方差分析和统计检验,结果表明:从70年代开始,我国太阳直接辐射和总辐射量普遍减少,变化趋势分别为-246MJ/m2·10a和-16.8MJ/m2·10a,减少量最大中心在长江流域。太阳散射辐射量在东北、华北以及南方地区增加,在长江流域和西北地区减少。此外,用太阳辐射量倾向率的形式归纳出我国四种典型的区域性太阳辐射量季节变化特征。  相似文献   

韶关市近50年强降水频数统计及周期分析     

李丽 《广东气象》2003,(3):21-23

利用韶关市近50年降水资料,对逐日降水量R24（20～20时）≥50．0mm的强降水次数进行统计分析,结果表明韶关暴雨及以上强降水主要集中在多水期的3～7月,其中5、6月份为最多,这与韶关的自然季节降水特点是相吻合的;从50年代至90年代,各年代大暴雨和暴雨分别呈现出偏少．正常-正常-偏少-偏多和偏多～正常-偏少～偏少～偏多的演变趋势;R24≥50．0mm的强降水总次数及历年5、6月份R24≥50．0mm的强降水次数存在周期变化。  相似文献   

Negative water vapour skewness and dry tongues in the convective boundary layer: observations and large-eddy simulation budget analysis     

F. Couvreux  F. Guichard  V. Masson  J.-L. Redelsperger 《Boundary-Layer Meteorology》2007,123(2):269-294

This study focuses on the intrusion of dry air into the convective boundary layer (CBL) originating from the top of the CBL. Aircraft in-situ measurements from the IHOP_2002 field campaign indicate a prevalence of negative skewness of the water vapour distribution within the growing daytime CBL over land. This negative skewness is interpreted according to large-eddy simulations (LES) as the result of descending dry downdrafts originating from above the mixed layer. LES are used to determine the statistical properties of these intrusions: their size and thermodynamical characteristics. A conditional sampling analysis demonstrates their significance in the retrieval of moisture variances and fluxes. The rapid CBL growth explains why greater negative skewness is observed during the growing phase: the large amounts of dry air that are quickly incorporated into the CBL prevent a full homogenisation by turbulent mixing. The boundary-layer warming in this phase also plays a role in the acquisition of negative buoyancy for these dry tongues, and thus possibly explains their kinematics in the lower CBL. Budget analysis helps to identify the processes responsible for the negative skewness. This budget study underlines the main role of turbulent transport, which distributes the skewness produced at the top or the bottom of the CBL into the interior of the CBL. The dry tongues contribute significantly to this turbulent transport.  相似文献   

基于主成分分析和决策级融合的高光谱图像分类方法研究     

李晓敏  张杰  马毅  任广波 《海洋科学》2015,39(2):25-34

为了评价主成分分析方法和决策级数据融合方法对高光谱图像地物分类结果的影响,作者利用各分类器和主成分分量的优势,提出了两组地物分类结果的决策级融合策略,利用8种常用监督分类方法对高光谱原始图像和PCA变换后不同分量组合图分类得到的结果进行决策级融合,并应用覆盖黄河入海口新老河道交界处的CHRIS/PROBA高光谱图像开展实验研究。结果表明:直接采用每类地物分类精度最高的、空穴和缝隙采用总体分类精度最高的融合策略,在综合考虑生产者精度和用户精度的情形下,仅使用最大似然法、支持向量机和人工神经网络3种分类方法,按照分类精度从高到低的顺序进行的融合分类效果最好,总体分类精度为87.82%。与8种监督分类方法中效果最好的最大似然法相比,精度提高了2.7个百分点,同时明显减少了错分现象,尤其是对于分布面积较小的翅碱蓬和柽柳,滩涂被误分为翅碱蓬、芦苇被误分为柽柳的现象大大降低。  相似文献   

THE QUALITY OF MEAN AND VARIANCE ESTIMATES FOR NORMAL AND LOGNORMAL DATA WHEN THE UNDERLYING DISTRIBUTION IS MISSPECIFIED     

《地理学报(英文版)》1991,(3)

Theoretical and simulation results are employed to evaluate mean and variance estimaies for normal datawhen a lognormal distribution is assumed and for lognormal data when a normal distribution is assumed.Misspecifying the distribution leads to the use of suboptimal estimation methods.However,the resultsshow that the suboptimal methods still produce estimators of good quality(low bias and variance)relativeto the minimum variance unbiased estimators for each distribution,at least when practical efficiency isconsidered.  相似文献