共查询到20条相似文献，搜索用时 31 毫秒
1.
Clifford R. Stanley 《Mathematical Geosciences》1990,22(8):933-956
Recent publications have demonstrated that the composition of a system can be described by the angles which define the vector resulting from the projection of the composition onto the unit hypersphere. Although published trigonometric relationships allow determination of the angles in any number of dimensions, no general hyperdimensional recursive formulae exist for the calculation of these quantities and their variances and covariances. A general methodology for calculating the angles which describe the compositions of systems in any number of dimensions is presented. These angles can be used to calculate statistics (central moments and resultant vectors) describing the central tendency and dispersion among rock compositions, as well as to quantify the angular differences between compositions. Equations that relate the variances and covariances of these angular variables to the variances and covariances of the actual component proportion variables are presented, allowing projection of these measurements from one reference frame to another (cartesian to spherical and vice versa). 相似文献
2.
评述“前陆盆地”名词在中国中西部含油气盆地中的引用——反思中国石油构造学的发展 总被引：22，自引：5，他引：17
“前陆盆地”一词,在中国中西部含油气盆地研究中被许多学者广泛引用,在空间上有“泛前陆盆地化”,在地史演化中有“扩大化”,名词术语引用上有“复杂化”的倾向,因而引起同行的关注。本文从文献中追踪前陆盆地原命名者的涵义和沿革,正确理解国外学者提出前陆盆地的特及模式,再根据中国的实际地质特征与国外典型前陆盆地对比,结果发现我国中西部前陆盆地的特殊在于大国外所称的前陆盆地的共同性。因而认为在中国中西部直接引用“前陆盆地”一词不当。建议采用“陆内俯冲型前陆盆地”（Intracontinental subduction foreland basin）一(间称－C型前陆盆地）,以示有中国地质特色的前陆盆地,为今后建立油气成藏模式和指导油气勘探理论依据。最后,还讨论了中国石油学发展中,值得反思的3个问题。 相似文献
3.
Clifford R. Stanley 《Mathematical Geology》1990,22(8):933-956
Recent publications have demonstrated that the composition of a system can be described by the angles which define the vector resulting from the projection of the composition onto the unit hypersphere. Although published trigonometric relationships allow determination of the angles in any number of dimensions, no general hyperdimensional recursive formulae exist for the calculation of these quantities and their variances and covariances. A general methodology for calculating the angles which describe the compositions of systems in any number of dimensions is presented. These angles can be used to calculate statistics (central moments and resultant vectors) describing the central tendency and dispersion among rock compositions, as well as to quantify the angular differences between compositions. Equations that relate the variances and covariances of these angular variables to the variances and covariances of the actual component proportion variables are presented, allowing projection of these measurements from one reference frame to another (cartesian to spherical and vice versa). 相似文献
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青藏高原地区云水时空变化特征及其与降水的联系 总被引：4，自引：1，他引：3
利用1984-2009年ISCCP的云量、云光学厚度(COT)、云水路径(CWP)资料,分析了青藏高原云水的分布特征、变化趋势,及其与夏秋季降水、冬春季降雪的联系.结果表明:青藏高原地区大气中的云水有着显著的季节变化与水平分布差异;青藏高原春夏季总云量、高云云量高于秋冬季,CWP、COT与总云量的分布特征具有较好的一致性.高原云量高值区位于喀喇昆仑山与高原东南部;可可西里地区由于羌塘高压的下沉作用为云量低值区.青藏高原总云量在1984-2009年间呈现减少趋势;而CWP在高原总体以增加为主,但在各区域上的变化不一致,高原东部CWP增加而西部出现较弱的减小,这与来自孟加拉湾的水汽输送增加有关.青藏高原中东部地区夏秋季降水受云量减少影响较小而与CWP的增加相一致呈增长趋势;该地区冬春季降雪略有减少,与总云量的年际变化具有正相关. 相似文献
6.
A previously described method of combining measurements of numerous pebble cross-sections in three orthogonal planes into a single average ellipsoid was found to be in need of improvement. The method of reconciling redundancies and of distributing the errors can be left unchanged. The original measurements of principal half-axes, however, rather than being normalized as the ratios of larger half-axes divided by the smaller, should be normalized so that they produce ellipses of standard area. The coefficients of ellipses so normalized will produce distributions with a pronounced central tendency even in those cases that produce markedly skewed distributions of coefficients for ellipses normalized by the former method. Equations of the previous paper that must be amended are given in their new form. 相似文献
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为了揭示循环扰动和高温影响下砂岩的岩爆机制,开展了循环扰动和高温作用下砂岩单轴压缩试验和CT扫描试验,研究了不同条件下砂岩的力学特性、岩爆倾向性及破坏特征,探讨了岩爆倾向性与破坏特征的关系。研究结果表明：循环扰动和高温对砂岩的力学性能及岩爆倾向性影响效果显著;无循环扰动砂岩的单轴抗压强度、弹性模量及岩爆倾向性随温度的升高呈先增加后降低的趋势,200℃为该类砂岩的阈值温度,受循环扰动砂岩的力学特性及岩爆倾向性随温度的上升而降低;而砂岩的力学特性及岩爆倾向性随循环应力幅值增加而下降;随着循环应力幅值和温度的增加,砂岩破坏模式由劈裂破坏向剪切破坏转变,同时砂岩的岩爆倾向性与裂隙三维分形维数呈良好的负相关关系;此外,高温对砂岩的力学性能、岩爆倾向性及破坏程度影响效果强于循环扰动。研究结果可为高温工程岩爆防治提供理论依据和工程参考价值。 相似文献
9.
基于薄层刚度矩阵方法,研究了瑞利波在3种典型刚度缓变介质中传播特性,并对瑞利波在缓变介质及分层介质中传播特性进行比较。结果显示,无论剖面刚度是缓变还是分层变化,对规则剖面,表面波场基阶模态占主导地位,远场表面波有效相速度与基阶模态相速度接近;对不规则剖面,表面波场中高阶模态影响较大,影响程度及频率范围与剖面刚度变化有关。在缓变介质中,模态相速度高频趋势值高于剖面最小剪切波速介质的瑞利波速,有效相速度趋势值也明显偏离表面介质瑞利波速,这些特性与分层介质不同。研究结果显示,当缓变介质用数量有限的虚构分层来模拟时,表面波频散测试数据与理论值匹配程度及剖面分析精度会受虚构层数量影响。 相似文献
10.
The presence of outliers and the statistical noise that affects the data for reference materials have undesirable effects on the mean and on other indicators of the central value. Five robust indicators of the central value, which are resistant to obvious outliers and less obvious contamination (spurious data), were investigated: the dominant cluster mode, the modian, the Gastwirth median, the trimean, and the trimmed mean. The mean and the median were investigated for purposes of comparison.
The results confirm that the mean is very unreliable, and that the Gastwirth median and the dominant cluster mode are strong indicators of the central value. 相似文献
The results confirm that the mean is very unreliable, and that the Gastwirth median and the dominant cluster mode are strong indicators of the central value. 相似文献
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Times of switches from the normal to the abnormal radiation mode have been recorded in observations of individual pulses of pulsar B0329+54 using the Large Phased Array of the Pushchino Radio Astronomy Observatory at 111.4 MHz. The variations in the amplitudes of the outer components that accompany the switch to the abnormal pulse profile occurred simultaneously in only half the cases. The phase of component IV of the integrated pulse does not vary during mode switches. In half the cases, instantaneous variations of the phases of component I and the central component during mode switches may be preceeded by additional smooth variations of the phases of individual pulses occuring over several minutes. We detected a decrease in the linear polarization of the central component by, on average, 8% in the abnormal mode for the integrated pulse, due to variations in the relative intensities of two orthogonally polarized modes of the pulsar radiation. 相似文献
13.
Xuejing XIE Mingcai YAN Lianzhong LI Huijun SHEN 《Geostandards and Geoanalytical Research》1985,9(1):83-159
A set of eight geochemical standard reference samples of stream sediments was prepared. The original purpose was to use these samples as primary standards for the data quality monitoring of a nation-wide regional geochemical survey program in China. But their use has been soon extended to other fields. Forty-one laboratories in China have joined in a collaborative venture to analyse these samples, using a variety of analytical procedures. Recommended values for over 50 trace and minor elements were derived by a method of repetitive elimination of outliers and calculation of central "tendency" from several central values. 相似文献
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利用高分辨率激光粒度仪MS2000对安固里淖、三台河以及长江等多个地点湖泊和河流沉积物样品细粒部分的粒度多组分分布特征进行了系统、深入研究。总结了其粒度分布特征及组分间差异并讨论了其成因机制。研究认为:1)湖泊沉积物粒度一般由多个组分叠加构成,表现为多组分粒度分布特征,其受控于水动力强度和搬运方式等因素。2)粒度分布最多可有6个组分（中值粒径范围分别为①<1μm,②2～10μm,③10～70μm,④70～>150μm,⑤150～700μm,⑥>700μm）,其中前4个组分属悬浮组分（③组分是流域内风成作用强弱的判别标志）,⑤为跳跃组分,⑥为滚动组分,整体分选性差。3)据粒度分布特征可分为湖滨、过渡和湖心三相,三相间粒度分布特征有明显差异,同时又存在此消彼长的良好过渡关系。湖滨相以④组分为优势组分,该组分含量越高,指示沉积物越靠近湖滨;过渡相④组分含量随距湖心距离靠近而减小,但②组分含量却在逐渐增加;湖心相以②组分占主导优势,该组分含量越高,指示沉积物越靠近湖心。4)湖相沉积物受湖滨拍岸浪和湖心波浪的影响而产生了明显的粒度分异规律。 相似文献
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基于ArcIMS的网络矿产勘探信息系统方案 总被引：2，自引：0，他引：2
随着网络的发展,网络矿产勘探信息系统成为矿产勘探信息系统发展的必然趋势。本文采用当前比较流行的WebGIS软件平台ArcIMS对网络矿产勘探信息系统框架的构建进行了探讨,同时给出了相应的系统数据库设计方案和功能模块设计方法。结果表明,该系统具有良好的实用价值和运行效率。 相似文献
16.
In this paper, the simultaneous effect of North Atlantic Oscillation (NAO) and Southern Oscillation (SO) on monsoon rainfall
over different homogeneous regions/subdivisions of India is studied. The simultaneous effect of both NAO and SO on Indian
summer monsoon rainfall (ISMR) is more important than their individual impact because both the oscillations exist simultaneously
throughout the year. To represent the simultaneous impact of NAO and SO, an index called effective strength index (ESI) has
been defined on the basis of monthly NAO and SO indices. The variation in the tendency of ESI from January through April has
been analyzed and reveals that when this tendency is decreasing, then the ESI value throughout the monsoon season (June–September)
of the year remains negative andvice versa. This study further suggests that during the negative phase of ESI tendency, almost all subdivisions of India show above-normal
rainfall andvice versa. The correlation analysis indicates that the ESI-tendency is showing an inverse and statistically significant relationship
with rainfall over 14 subdivisions of India. Area wise, about 50% of the total area of India shows statistically significant
association. Moreover, the ESI-tendency shows a significant relationship with rainfall over north west India, west central
India, central north east India, peninsular India and India as a whole. Thus, ESI-tendency can be used as a precursor for
the prediction of Indian summer monsoon rainfall on a smaller spatial scale. 相似文献
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This work focuses on the characterization of the central tendency of a sample of compositional data. It provides new results about theoretical properties of means and covariance functions for compositional data, with an axiomatic perspective. Original results that shed new light on geostatistical modeling of compositional data are presented. As a first result, it is shown that the weighted arithmetic mean is the only central tendency characteristic satisfying a small set of axioms, namely continuity, reflexivity, and marginal stability. Moreover, this set of axioms also implies that the weights must be identical for all parts of the composition. This result has deep consequences for spatial multivariate covariance modeling of compositional data. In a geostatistical setting, it is shown as a second result that the proportional model of covariance functions (i.e., the product of a covariance matrix and a single correlation function) is the only model that provides identical kriging weights for all components of the compositional data. As a consequence of these two results, the proportional model of covariance function is the only covariance model compatible with reflexivity and marginal stability. 相似文献
19.
筒型基础防波堤稳定性简化计算方法 总被引：5，自引：0，他引：5
筒型基础防波堤是一种新型港口与海岸工程结构,依靠下部筒体沉入土中维持结构稳定。结合实际工程,建立了筒型基础防波堤稳定性分析的三维弹塑性有限元模型,得出了其失稳模式为绕基础筒底以下某点发生转动失稳。通过对结构进行极限状态受力分析,建立了基于实际转动点的结构稳定性计算方法,对稳定性计算模型和土体作用力计算公式等进行了检验。在此基础上,将转动点移至基础筒底部距结构中心线水平距离为h′的位置,以此作为结构倾覆破坏时的假想支撑点,建立了基于重力式结构稳定性验算模式的筒型基础防波堤稳定性分析的简化方法。通过不同基础尺度下计算结果的分析比较,建议了h′的取值。与有限元计算结果的比较表明,建立的简化计算方法具有较高的精度,可供实际工程参用。 相似文献
20.
Species introductions are among the most dramatic human-induced impacts on aquatic and terrestrial ecosystems around the world.
Stability patterns of an estuarine benthic community were investigated through guild interaction models representing the community
before and after human-mediated species invasions. The study area was Yaquina Bay, a developed estuary on the central Oregon
coast, U.S., where at least 12 species of nonindigenous invertebrates have been inadvertently introduced. Three of the introduced
species (the polychaetes Hobsonia florida and Pseudopolydora kempi and the cumacean Nippoleucon hinumensis) are probably among the 10 most abundant invertebrate species in the intertidal benthic community. To estimate effects and
potential risks of species introductions on the native community we constructed 2 types of community models based on functional-group
interactions, namely, activity guild models and trophic guild models. In both cases we observed that overall feedback has
a strong tendency towards zero in pre-invasion and post-invasion models. We generated 12,000 random models of similar size
and could not detect this tendency. We suggest that the weak or absent overall feedback in this community may be an ecological
property and not an intrinsic property of large systems as such. The reduced response to input from either invertebrate invasions
or removal of native top predators, may to some extent buffer the community from such impacts. Alternative guild models suggested
increased risk of stability decline in the invaded community even after accounting for potential complexity effects on stabllity.
Further species introductions in this intermediately invaded estuary should be avoided. 相似文献