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101.
Guangzhi Tu 《中国科学D辑(英文版)》1998,41(1):1-13
The new plants documented here, including a representative of the trimerophytesPsilophyton primitiuum sp. nov., a questionable rhyniophyte or trimerophyteHedeia sinica sp. nov., a prelycopodBragwanathia sp. and two species of zosterophyllophytes,Zosterophyllum australianum Lang and Cookson 1930 and2. sp. 1, from the Posongchong Formation of southeastern Yunnan, China, add to the known floral diversity of the Early Devonian
of this region. Two sections of the Posongchong Formation, Changputang section of Wenshan district and Gegu section of Mengzi
district also are introduced. After comparing the plants with those of the coeval flora of Australia and considering the data
of recent paleocontinental reconstructions, the authors suggest that there is a northeastern Gondwana phytogeographic unit
during the early Devonian comprising Australia, South China Block and perhaps Shan-Thai Block. The similarity of the floral
component between Australia and South China is discussed. Because both Australia and South China also have dominant or endemic
taxa, each might be recognized as a subunit, separately characterized byHedeia for Australia andEophyllophyton for South China.
Project supported by the National Natural Science Foundation of China (Grant Nos. 49372075 and 49742004) 相似文献
102.
103.
THREEKINDSOFTIMEDISTRIBUTIONFUNCTIONSOFREMARKABLEEARTHQUAKESINSEISMICSEQUENCESDiaoShouzhongWangHongweiChaoHongtaiHuaAijun(Sei... 相似文献
104.
本文把湖泊营养化系统看作一个灰色系统,应用灰色聚类法进行营养化评价,并通过实例和层次决策法,Fuzzy-Greey决策法的评价结果进行分析与比较。 相似文献
105.
We consider how the Alfven fluctuation varies as it passes through a slow MHD shock, assuming the fluctuation to originate on the Sun and such slow shocks are present between 2 and 6 solar radii. The results are 1) low latitude region in the vicinity of the neutral sheet is where the fluctuation can propagate with no or little distortion; 2) high latitude region far from the neutral sheet is a region of small distortion only for low Alfven-Mach numbers (about 0.3 or lower); 3) the observation of the Alfven fluctuations in space is consistent with, and lends support to their originating in the Sun and the existence of slow shock around the Sun. 相似文献
106.
This paper presents a boundary element method (BEM) procedure for a linear elastic fracture mechanics analysis in two‐dimensional anisotropic bimaterials. In this formulation, a displacement integral equation is only collocated on the uncracked boundary, and a traction integral equation is only collocated on one side of the crack surface. A fundamental solution (Green's function) for anisotropic bimaterials is also derived and implemented into the boundary integral formulation so that except for the interfacial crack part, the discretization along the interface can be avoided. A special crack‐tip element is introduced to capture the exact crack‐tip behavior. A computer program using FORTRAN has been developed to effectively calculate the stress intensity factors of an anisotropic bimaterial. This BEM program has been verified to have a good accuracy with previous studies. In addition, a central cracked bimaterial Brazilian specimen constituting cement and gypsum is prepared to conduct the Brazilian test under diametral loading. The result shows that the numerical analysis can predict relatively well the direction of crack initiation and the path of crack propagation. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
107.
Microdiamond and graphite occur in quartzofeldspathic rocks (saidenbachites) of the central Erzgebirge in Saxony. Zircon from such rocks contains not only relatively high but also variable amounts of early formed graphite and later crystallized diamond, however no carbonate. Six purified zircon concentrates were analysed by mass spectrometry for δ13C(PDB) values which were between −24 and −33‰. The carbon inclusions resulted in C contents of the concentrates as high as 0.5 wt%. It is hypothesized that the observed δ13C signature results from organic material in the sedimentary protoliths of the saidenbachites probably deposited not earlier than Mid‐Devonian. This material was transformed to graphite during early metamorphism and subsequently to diamond after an anatectic event at great depths (>150 km). During these processes, the δ13C signature of the carbon did not (significantly) change. 相似文献
108.
高密度采集福建前湖湾海岸剖面133个泥沙样品做粒度分析,其频率曲线显示多种粒度分布特征,预示多种沉积环境的变化。采集研究剖面周边海滩、河口浅滩、河口、滨海沼泽和海岸沙丘等已知环境的样品作为目标样本。将目标样本沉积参数平均粒径(Mz)、标准偏差(σ)、峰态(Kg)设为判别参数,利用Excel计算海岸剖面样品与目标样本参数的距离,筛选最小距离样品,归为已知目标样本的同类。据此,分析了海岸剖面蕴含的6个沉积环境变化阶段。利用剖面底部淤泥测年14C=(328 15±170)a BP,和剖面上部泥炭测年14C=(24 130±100)a BP,了解这一变化发生的年代。自(32 815±170)a BP以来,前湖湾经历了河口浅滩-河口、沙丘-河口-滨海沼泽-海滩-沙丘等海岸环境演变过程。 相似文献
109.
A retrieval algorithm of arctic sea ice concentration (SIC) based on the brightness temperature data of “HY-2” scanning microwave radiometer has been constructed. The tie points of the brightness tempe... 相似文献
110.