Orthogonal Variance Structures in Lake Water Quality Data and Their Use for Geo-chemical Classification of Dimictic, Glacial/Boreal Lakes     

Tomas K. E. Thierfelder 《Aquatic Geochemistry》2000,6(1):47-64

The accumulating volumes of data collected within environmental monitoring programs facilitate the use of exploratory statistical methods of data analysis as a supplement to traditional methods of characterizing lake water quality. When principal component analysis and multidimensional scaling are applied to a matrix containing approximately 24000 samples of lake water quality variables pH, alkalinity, conductivity, hardness, color, Secchi depth and total phosphorus concentration, it is found that the total matrix variance can be approximately reproduced in an orthogonal two-dimensional base with transformations of hardness and color as best principal component representatives. This base is suggested as an empirical lake classification standard where the variance structure of subset lake populations (such as single lakes) can be referenced to the water quality standard of the generic population. Since the principal axes of the base exclusively contain inorganic and organic related variables respectively, the combined inorganic/organic characteristics of the lake can be expressed with the hardness and color variables alone. With the data matrix being large enough to produce high significance levels, and with variable ranges wide enough to represent a majority of dimictic, glacial/boreal lakes, the analysis results should be valid in many lakes throughout the world.  相似文献   

黄河流域上游降水时空结构特征   总被引：23，自引：2，他引：21  

杨志峰  李春晖 《地理科学进展》2004,23(2):27-33

黄河兰州以上区域水资源量占黄河流域水资源的一半以上,研究黄河上游兰州以上区域降水时空结构变化具有重要意义。本文利用黄河兰州以上19个降水站点1959~1998年系列数据,采用EOF技术分析了黄河上游降水的时空结构特征与变化。结果表明：黄河上游兰州以上区域降水存在四种典型降水类型,即“全部一致型”、“南北型”、“东西型”和“相间复杂型”。但第一特征向量为主导,其时间变化系数与年降水量基本一致,说明黄河流域兰州以上降水主要受青藏高原大尺度气候影响,具有降水偏多（少）一致性特征。从时间尺度上降水有减少的趋势;并伴随3、6、和11年的周期变化,而且在1986和1991年发生突变。  相似文献   

GPS地壳形变监测网应变解算方法与程序设计   总被引：7，自引：2，他引：5  

孟国杰  申旭辉  伍吉仓  沈云中  张秋文 《大地测量与地球动力学》2006,26(2):70-74

分析了在平面直角坐标系和大地坐标系内解算应变的方法及其特点,并以Matlab为开发平台,研制出一套在平面直角坐标系和大地坐标系中解算应变的程序GPSstrain。利用GPS监测网测站位移(速率),该程序能够解算剪切应变(γ1、γ2)、面应变、块体旋转、主应变及其方向、最大剪切应变及其方向,同时也可解算出这些应变分量的误差。另外该程序还具有高斯投影解算功能,根据各测站坐标能够自动形成所有的Delaunay三角形,并以图形方式显示。最后以实际算例给出了该解算程序的部分结果,并进行了初步的分析和讨论。  相似文献   

A study of the seismic response of the city of Benevento (Southern Italy) through a combined analysis of seismological and geological data   总被引：1，自引：0，他引：1  

G. Di Giulio  L. Improta  G. Calderoni  A. Rovelli 《Engineering Geology》2008,97(3-4):146-170

A previous analysis [Improta, L., G. Di Giulio, and A. Rovelli (2005). Variations of local seismic response in Benevento (Southern Italy) using earthquakes and ambient noise recordings, J. Seism. 9, 191–210.] of small magnitude earthquakes recorded at 12 sites within the city of Benevento has stressed the significant role played by near-surface geology in causing variability of the ground motion. In this paper, we extend the study of the seismic response from 12 sites to the entire urban area. Based on inferences from the comparison at the 12 sites between earthquake and ambient vibration results, we have collected ambient noise at about 100 sites within the city, intensifying measurements across the main shallow geological variations. We use borehole data to interpret ambient noise H/V spectral ratios in terms of near-surface geology comparing H/V curves to theoretical transfer functions of 1D models along five well-constrained profiles.

On the basis of geological, geotechnical, and seismic data, we identify three main typologies of seismic response in the city. Each type of response is associated to zones sharing common soil conditions and similar soil classes according to building codes for seismic design. Moreover, we find that the spatial variation of the seismic response in the ancient town area is consistent with the damage pattern produced by a very destructive, well-documented historical earthquake that struck the city in 1688, causing MCS intensity of IX–X in Benevento.

Finally, we use ground motions recorded during the experiment by Improta et al. [Improta, L., G. Di Giulio, and A. Rovelli (2005). Variations of local seismic response in Benevento (Southern Italy) using earthquakes and ambient noise recordings, J. Seism. 9, 191–210.] to generate synthetic seismograms of moderate to strong (Mw 5.7, Molise 2002 and Ms 6.9, 1980 Irpinia) earthquakes. We calibrate the random summation technique by Ordaz et al. [Ordaz, M., J. Arboleda, and S.K. Singh (1995). A scheme of random summation of an Empirical Green's Function to estimate ground motions for future large earthquakes, Bull. Seism. Soc. Am. 85, 1635–1647.] using recordings of these earthquakes available in Benevento. After a satisfactory fit between observed and synthetic seismograms, we compute response spectra at different sites and speculate on effects of the geology class at large level of shaking, including soil nonlinearity. We find that large discrepancies from design spectra prescribed by seismic codes can occur for a wide sector of Benevento, especially for periods < 0.5 s.  相似文献   

神经网络模型预报湖北汛期降水量的应用研究   总被引：18，自引：1，他引：18  

胡江林  张礼平  宇如聪 《气象学报》2001,59(6):776-783

使用人工神经网络方法建立了湖北省汛期 (6～ 8月 )总降水量的短期气候预测模型 ,该神经网络模型的输入是汛期前期 (2～ 4月 )的北半球月平均 5 0 0 h Pa高度场、海平面气压场和太平洋海温场的扩展自然正交展开 (EEOF)的前几个主要模态的时间系数 ,输出了湖北汛期降水场的自然正交展开 (EOF)的前 2个主要模态的时间系数。41 a历史资料的交叉检验表明 :样本试验的预报技巧评分平均为 0 .2 4 6 ,虽然该模型对各年的预报效果仍存在一定的不稳定性 ,但它可为湖北汛期降水的短期气候预测提供一种具有明显统计预报正技巧的预报方法  相似文献   

三峡库区土地持续利用潜力与途径模式   总被引：16，自引：6，他引：16  

刘彦随  冯德显 《地理研究》2001,20(2):139-145

建立了量化评价模型,对三峡库区土地资源持续利用的潜力及其差异性进行了评价与分析。指出库区土地利用总体上处于弱持续发展的阶段,而且地区差异悬殊、面临的障碍因素多。因此,未来库区土地利用优化决策的关键在于遵照因地制宜和分类指导的原则,正确处理生态建设、移民安置和经济协调发展的关系。主要的途径模式包括植树造林、坡地改梯田、优化结构和产业突破等四个方面。  相似文献   

Simulation of structural phase transition in NaNO3 and CaCO3     

Jianjun Liu  C.-G. Duan  M. M. Ossowski  W. N. Mei  R. W. Smith  J. R. Hardy 《Physics and Chemistry of Minerals》2001,28(8):586-590

 The order-disorder phase transitions in NaNO₃ and CaCO₃ are simulated by molecular dynamics. The simulations are based on the potentials calculated from the Gordon–Kim modified electron gas formalism extended to molecular ions. We successfully reproduced the transition temperature T _c and the abnormally large c axis thermal expansion observed in experiment. The phase transitions in NaNO₃ and CaCO₃ were found to be initiated by ±60 and ±180° reorientation of the NO₃ and CO₃ ions about the c axis. The orientations of NO₃ and CO₃ ions are continuous with six preferred calcite-type orientations above the phase-transition temperature. Received: 30 January 2001 / Accepted: 11 May 2001  相似文献   

Hydrogen Incorporation in Crystalline Jadeite: Insight from First Principles Calculations     

ZHANG Xiaoling  FAN Xiaoyu  MENG Dawei  WU Xiuling  LIU Weiping 《《地质学报》英文版》2016,90(3):939-945

Hydrogen incorporation is critical for explaining defect energies, structure parameters and other physical characteristics of minerals and understanding mantle dynamics. This work analyzed the hydrogen complex defects in jadeite by the plane-wave pseudo-potential method based on density functional theory, and optimized the atomic positions and lattice constants in all configurations(different defective systems). Incorporation mechanisms considered for hydrogen(H) in jadeite include:(1) hydrogen incorporating with the O2 site oxygen and coexisting with M2 vacancy;(2) one H atom combined with an Al atom replacing Si in tetrahedron;(3) 4H atoms directly replacing Si in tetrahedron and(4) 3H atoms replacing Al on the M1 site. The four incorporation mechanisms mentioned above form the corresponding V_(Na)-H_i, Al_(Si)-H_i, V_(Si)-4H_i and V_(Al)-3H_i point defects. The molecular dynamics simulation to the ideal, V_(Na)-H_i, Al_(Si)-H_i, V_(Si)-4H_i and V_(Al)-3H_i point defects under the P-T conditions of 900 K, 2 GPa, the V_(Na)-H_i and Al_(Si)-H_i point defects under different pressures at T = 900 K, and Al_(Si)-H_i point defects under different temperatures at P = 3 GPa was performed to examine the preferential mode of hydrogen incorporation in jadeite by means of first-principles calculations. The calculations show that the averaged O–H bond-length in the hydrogen point defects system decreased in the order of Al_(Si)-H_i, V_(Na)-H_i, V_(Si)-4H_i and V_(Al)-3H_i. V_(Na)-H_i complex defects result in a contraction of the jadeite volume and the presence of Al_(Si)-H_i, V_(Si)-4H_i and V_(Al)-3H_i defects could increase the supercell volume, which is the most obvious in the V_(Al)-3H_i defects. The energy of formation of Al_(Si)-H_i and V_(Al)-3H_i complex defects was much lower than that of other defect systems. The V_(Al)-3H_i defects system has the lowest energy and the shortest O–H bond-length, suggesting that this system is the most favorable. The analytical results of vacancy formation energy, O–H bondlength, and the stability of the hydrogen defects in jadeite have suggested that the preferred hydration incorporation mode in jadeite is V_(Al)-3H_i complex defect.  相似文献   

北太平洋SST的时空分布特征及其与黑潮大弯曲和El—Nino的关系     

王志联  徐启春  刘秦玉 《中国海洋大学学报(自然科学版)》1993,(3)

用EOF分析方法对北太平洋及赤道太平洋地区1949～1979年31年海表面温度距平场进行分解,得到几个主要距平海温模态(EOF1～3),分析了EOF1～3的时空分布特征。得到海温距平场的EOF1和EOF2～3模态分别对E1—Nino事件和黑潮大弯曲有很显著的相关性,指出SST第三模态场对黑潮大弯曲的影响具有很好的持续性,持续时间为1～2年。最后讨论了相互的影响过程,为黑潮大弯曲和E1—Nino事件的预报的可能性提供了依据。  相似文献   

Quantitative estimation of petroleum prospect outcome probabilities: an overview of procedures     

John W. Harbaugh 《Marine and Petroleum Geology》1984,1(4):298-312

Estimation of prospect outcome probabilities in numerical form should be a central objective for petroleum geologists. Most numerical estimates of outcome probabilities represent subjective guesses. While the effectiveness of subjective procedures is difficult to gauge, several postmortem analyses suggest that subjective procedures are ineffective. Objective procedures for estimating outcome probabilities should yield much improved estimates. Objective procedures require that geological, geophysical and production data be organized so that geological and geophysical characteristics of prospects interpreted before they were drilled can be compared systematically with outcomes of prospects after they have been drilled. An example application that involves well data and an example application that involves seismic data demonstrate that objective procedures are simple in principle, but require organization of information in a form suitable for computation of frequencies, on which objective estimates of probabilities can be based.  相似文献