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341.
342.
Introduction The velocity field of surface plate motion can be split into a poloidal and a toroidal parts.At the Earth′s surface,the toroidal component is manifested by the existence of transform faults,and the poloidal component by the presence of convergence and divergence,i.e.spreading and subduc-tion zones.They have coupled each other and completely depicted the characteristics of plate tec-tonic motions.The mechanism of poloidal field has been studied fairly clearly which is related to … 相似文献
343.
Alkaline lavas were erupted as phonolites and trachytes around Karaburhan (Sivrihisar–Eskisehir, NW Anatolia) within the Izmir–Ankara–Erzincan suture zone. These volcanic rocks were emplaced as domes, close and parallel to the ophiolite thrust line. According to 40Ar/39Ar geochronological analyses of sanidine crystals from the phonolites, the age of the alkaline volcanics is 25 Ma (Late Oligocene–Early Miocene).The flow-textured phonolites are porphyritic and consist mainly of sanidine, clinopyroxene, and feldspathoid crystals. The clinopyroxenes show compositional zoning, with aegirine (Na0.82–0.96Fe+30.68–0.83) rims and aegirine–augite cores (containing calcium, magnesium, and Fe+2). Some aegirine–augites are replaced with sodium-, calcium-, and magnesium-rich amphibole (hastingsite). Feldspathoid (hauyne) crystals enriched with elemental Na and Ca have been almost completely altered to zeolite and carbonate minerals. The fine-grained trachytes with a trachytic texture consist of feldspar (oligoclase and sanidine) phenocrystals and clinopyroxene microphenocrystals within a groundmass made up largely of alkali feldspar microlites.Although there are some differences in their element patterns, the phonolites and trachytes exhibit enrichment in LILEs (Sr, K, Rb, Ba, Th) and LREEs (La, Ce, Pr, Nd) and negative anomalies in Nb and Ta. These geochemical characteristics indicate a lithospheric mantle enriched by fluids extracted from the subduction component. In addition, the high 87Sr/86Sr (0.706358–0.708052) and low 143Nd/144Nd (0.512546–0.512646) isotope concentrations of the alkaline lavas reflect a mantle source that has undergone metasomatism by subduction-derived fluids. Petrogenetic modeling indicates that the alkaline lavas generated from the subduction-modified lithospheric mantle have undergone assimilation, fractional crystallization, and crustal contamination, acquiring high Pb, Ba, Rb, and Sr contents and Pb isotopic compositions during their ascent through the thickened crust in an extensional setting. 相似文献
344.
NUMERICAL STUDY ON THE ROLE OF VORTICAL AND DIVERGENT COMPONENTS OF WIND STRESS IN ENSO CYCLE 下载免费PDF全文
The 1960-1991 monthly mean FSU (Florida State University)wind stress data aredecomposed into a vortical and a divergent component with each of which to force the model oceanin the context of a two-layer tropical Pacific model.Evidence suggests that for the seasonalvariation the ocean forcing does not produce a realistic cold tongue using either of the componentsand the tongue will not be effectively improved in its intensity and pattern even if the componentsare doubled or halved:the utilization of climatic mean wind stress(no decomposition is done of thewind stress)that contains its seasonal variation will lead to a realistic SST distribution on which isimposed,separately,the interannual anomalies of each of the components so as to get the SSTApattern:under the action of the interannual anomaly of the vortical(divergent)component therearises qnite intense SSTA oscillation marked by noticeable ENSO periods(feeble SSTA withhigher oscillation frequency for obscure ENSO periods),thereby illustrating that the roles of thetwo components differ from each other in the genesis of SST variation on a seasonal and aninterannual basis such that a realistic cold tongue pattern follows under the joint effects on themodel ocean of the two components of wind stress while rational E1 Nino/La Nina phenomenaresult under the forcing of an anomalous wind stress vortical component.Moreover,the divergentcomponent is innegligible in generating a mean climatic condition of the ocean sector but of lessimportance compared to the vortical component in ENSO development. 相似文献
345.
Introduction Data mining (SHAO and YU, 2003) is a new kind of technique developed with database and artificial intelligence in recent years, which processes the data in the database to abstract the im- plied and pre-unknown, but potentially useful information and knowledge from large amounts of incomplete, noisy, blurring and stochastic data. For data mining, data purging is an important link beforehand that includes eliminating noise, making up lost domain, and deleting ineffective data, as… 相似文献
346.
Spatial character of the gaseous and particulate state compound correlation of urban atmospheric pollution in winter and summer 总被引:1,自引:0,他引:1
XU Xiangde SHI Xiaohui XIE Lian DING Guoan MIAO Qiuju MA Jianzhong ZHENG Xiangdong 《中国科学D辑(英文版)》2005,48(Z2)
The spatial/temporal variation information of atmospheric dynamic-chemical processes at observation site points of the "canopy" boundary of Beijing urban building ensemble and over urban area "surface", as well as the seasonal correlation structure of the gaseous and particulate states of urban atmospheric pollution (UAP) and its seasonal conversion feature at observation points are investigated, using the comprehensive observation data of the Beijing City Air Pollution Observation Experiment (BECAPEX) in winter and summer 2003 with a "point-surface" combined research approach. By using "one dimension spatial empirical orthogonal function (EOF)" principal component analysis (PCA) mode, the seasonal change of gaseous and particulate states of atmospheric aerosols and the association feature of pollutant species under the background of the complicated structure of urban boundary layer (UBL) are analyzed. The comprehensive analyses of the principal components of particle concentrations,gaseous pollutant species, and meteorological conditions reveal the seasonal changes of the complex constituent and structure features of the gaseous and particulate states of UAP to further trace the impact feature of urban aerosol pollution surface sources and the seasonal difference of the component structure of UAP. Research results suggest that in the temporal evolution of the gaseous and particulate states of winter/summer UAP, NOx, CO, and SO2 showed an "in-phase" evolution feature, however, O3 showed an "inverse-phase" relation with other species,all possessing distinctive dependent feature. On the whole, summer concentrations of gaseous pollutants CO, SO2, and NOx were obviously lower than winter ones, especially, the reduction in CO concentration was most distinctive, and ones in SO2 and NOx were next. However, the summer O3 concentration was more than twice winter one. Winter/summer differences in PM10and PM2.5 particle concentrations were relatively not obvious, which indicates that responses of PM10 and PM2.5 particle concentrations to the difference of winter/summer heating period emission sources are far less distinctive than those of NOx, SO2, and CO. The correlation feature of winter/summer gaseous and particulate states depicts that both PM10 and PM2.5 particles were significantly correlated with NOx, and their correlations with NOx are more significant than those with other pollutants. Through PCA, it is found that there was a distinctive difference in the principal component combination structure of winter/summer PM10 and PM2.5 particles: SO2 and NOx dominated in the principal component of winter PM10 and PM2.5 particles; while CO and NOx played the major role in the principal component of summer PM10 and PM2.5 particles. For winter/summer PM10 and PM2.5 particles, there might exist the gaseous and particulate states correlation structures of different "combinations" of such dependent pollutant species. Research results also uncover that the interaction processes of gaseous and particulate states were also related with the vertical structure of UBL, that is to say, the low value layer of UBL O3 concentration was associated with the collocation of atmospheric vertical structures of the low level inversion,inverse humidity, and small wind, which depicts summer boundary layer atmospheric character, i.e.the compound impact of the dependent factor "combination" of wind, temperature, and humidity elements and their collocation structure on the variations of different gaseous pollutant concentrations. Such a depth structure of the extremely low value of O3 concentration in the UBL accords with its "inverse-phase" relation with other gaseous pollutant species. The PCA of meteorological factors associated with PM10 and PM2.5 concentrations also reveals the sensitivity of PM10 and PM2.5 concentration to the combinatory feature of local meteorological conditions. 相似文献
347.
基于全球一体化的中原城市群城市竞争力研究 总被引:5,自引:0,他引:5
全球化背景下,城市群主导世界经济的趋势不可阻挡,关于城市群的研究随之也越来越受到人们的重视。近几年,中原城市群悄悄崛起,但只是一个雏形,还存在很多问题。为了更好的促进中原城市群的发育,特别是加强城市群内部各城市发挥特长、合理分工、优势互补,进而提升中原地区区域经济的发展水平,文章选用了九大类44项城市竞争力指标,建立了城市竞争力的指标体系,从定量的角度对中原城市群的城市竞争力进行了排序、对比、分析,其城市竞争力排名依次是郑州、济源、洛阳、焦作、漯河、新乡、许昌、平顶山及开封。得到的结论如下:(1)首位城市竞争力强,但还没有发挥核心城市的作用。(2)工业型的城市经济实力竞争力强。(3)农业型城市的经济竞争力较弱。(4)产业竞争力和资金实力是影响城市综合竞争力的主要因子。(5)个别城市的单项指标存在异常点,显现出其优劣势。最后根据分析结果,笔者提出了四点优化对策,为城市群中的城市定位、产业分工、资源优化配置及相应区域互动政策的制定提供决策依据。 相似文献
348.
利用2011年10月至2017年12月黄河源区鄂陵湖野外观测数据,对比分析多雪年与少雪年土壤冻结与消融时间、土壤温湿度、地表能量分量的变化特征。结果表明:多雪年地表反照率偏高,净辐射偏低,地表感热输送偏低,土壤由热“源”转为热“汇”的时间晚于少雪年。积雪可减少土壤吸收辐射能量,减少地表感热通量,在土壤完全冻结期与消融期增大地表潜热通量,在完全冻结期,减少土壤向大气的热输送,在消融期,减少大气向土壤的热输送。积雪在冻结期有降温作用,使得多雪年土壤较早发生冻结,且同一时期土壤温度偏低;在完全冻结期有保温作用,使得土壤温度偏高;在消融期有保温(“凉”)作用,使得消融较晚,且同一时期土壤温度偏低。在整个积雪年内,多雪年浅层土壤湿度高于少雪年,积雪对浅层土壤有保湿作用。积雪使土壤开始冻结时间有所提前,开始消融的时间有所滞后,可延长该年土壤完全冻结持续天数。 相似文献
349.
以祁连山排露沟流域青海云杉林为研究对象,研究了海拔梯度上土壤肥力因子的分布特征及变化规律,并运用主成分分析法对青海云杉林土壤肥力状况进行了评价。结果表明:(1)研究区土壤呈碱性,pH值均大于8.0;高海拔地区(3 300 m)含水量达到过饱和状态,各土层含水量均大于100%;随海拔升高,全氮含量呈增大趋势,全钾含量呈减小趋势,而全磷含量呈先减小后增大趋势;不同海拔梯度速效磷含量差异不显著(P>0.05),海拔3 300 m处速效钾含量显著高于其他海拔段(P<0.05)。(2) 不同海拔梯度下土壤有机质、全氮、全磷、全钾、速效磷和速效钾含量都有明显的“表聚效应”,其中3 300 m处0~10 cm土层有机质含量高达325.93 g·kg-1,是本海拔段其他土层的1.6~1.8倍,是同土层其他海拔段的1.3~2.0倍。(3) 土壤肥力因子间关系密切,土壤含水量与有机质、全氮呈极显著正相关关系,与土壤容重、pH和全钾呈极显著负相关关系,土壤养分含量之间存在不同程度的显著正相关关系。(4) 不同海拔梯度土壤肥力质量为:3 300 m>3 200 m>3
100 m>3 000 m>2 900 m。 相似文献
350.
DAVID LEE DUEWER 《地理学报(英文版)》1990,(4)
The Free-Wilson paradigm is an established and powerful tool for quantitatively relating activity withchemical structure.Current implementations of the paradigm,however,are flawed both conceptually andin execution.As part of an attempt to more fully realize the promise of the paradigm,it was necessaryto examine these limitations in detail.This report introduces a robust,theory-founded Free-Wilson implementation:stepwise principalcomponents regression analysis(SPCRA).SPCRA is computationally superior to previousimplementations but does not in itself correct their conceptual flaws.The development of SPCRA did,however,facilitate derivation of a simple and chemically significantinterpretation of the Free-Wilson structure-activity model.A number of statistical aspects of this modelcommonly misused in previous applications are discussed at length.These discussions provide criticalbackground for the development of an alternative implementation of the Free-Wilson paradigm. 相似文献