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排序方式: 共有696条查询结果,搜索用时 31 毫秒
1.
土−水特征曲线是非饱和土持水性能和水气运移规律的重要表征,由于其测试过程繁杂、影响因素众多,很难通过系列试验和数学模型全面表达。为探索土的类型和物理状态对土−水特征曲线的影响,以国内外大量试验数据为基础,以反映其形态的3个特征值(进气值、减湿率、残余含水率)为对象,采用数据分析统计方法揭示不同赋存条件对特征值的作用规律,采用机器学习方法探究影响因素的敏感性。研究结果表明:土体的物质组成(颗粒级配、粒径尺度、塑性指数)及赋存状态(密实程度、饱和含水率、干湿循环作用、环境温度)是影响其持水性能的常见分析指标,各影响因素对3个特征值的影响特征既有巨大差异也有相互联系,敏感性成果表明代表黏粒含量的塑性指数和反映密实程度的干密度是影响土体持水性能的最主导因素,给出的特征值分布范围考虑了两个主导因素的影响,具有较强的代表性和借鉴意义。 相似文献
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Composition and origin of organic matter in surface sediments of Lake Sarbsko: A highly eutrophic and shallow coastal lake (northern Poland) 总被引:1,自引:0,他引:1
Micha? Woszczyk Achim Bechtel Reinhard Gratzer Maciej J. Kotarba Miko?aj Kokociński Jens Fiebig Roman Cie?liński 《Organic Geochemistry》2011,42(9):1025-1038
We present an organic geochemical study of surface sediments of Lake Sarbsko, a shallow coastal lake on the middle Polish Baltic coast. The aim was to provide evidence concerning the origin of the organic matter (OM) and its compositional diversity in surface deposits of this very productive, highly dynamic water body. The content and composition of the OM in the bottom sediments were investigated at 11 sampling stations throughout the lake basin. OM sources were assigned on the basis of bulk indicators [total organic carbon (TOC), total nitrogen (TN), δ13CTOC and δ15N and extractable OM yield], biomarker composition of extractable OM and compound-specific C isotope signatures. The source characterization of autochthonous compounds was verified via phytoplankton analysis. The distribution of gaseous hydrocarbons in the sediments, as well as temporal changes in lake water pH, the concentration of DIC (dissolved inorganic carbon) and δ13CDIC were used to trace OM decomposition.The sedimentary OM is composed mainly of well preserved phytoplankton compounds and shows minor spatial variability in composition. However, the presence of CH4 and CO2 in the bottom deposits provides evidence for microbial degradation of sedimentary OM. The transformation of organic compounds in surface, bottom and pore waters via oxidative processes influences carbonate equilibrium in the lake and seasonally favours precipitation or dissolution of CaCO3.The data enhance our understanding of the relationships between the composition of sedimentary OM and environmental conditions within coastal ecosystems and shed light on the reliability of OM proxies for environmental reconstruction of coastal lakes. 相似文献
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The Late Cretaceous (Santonian) continental vertebrate locality of Iharkút, western Hungary has provided numerous azhdarchid pterosaur remains including the recently described, Bakonydraco galaczi. Since the first report of these fossils, additional remains have been discovered that improve considerably our knowledge of some aspects of the anatomy of azhdarchid pterosaurs. New cranial material described here indicates an edentulous, non-crested premaxillary rostrum in Bakonydraco similar to that of Quetzalcoatlus and reveals that this rostrum was considerably thinner and more lightly built than the relatively massive, pointed mandibular symphysis. In addition, the contact surface of the upper and lower jaws of Bakonydraco at least in the symphyseal region was more similar to Tapejara wellnhoferi than to other azdarchids: the contact is irregular and the premaxilla does not fit closely the rostral part of the mandible. Among the postcranial material the atlas-axis complex possessing lateral pneumatic foramina is of great importance because it further supports the notion of interspecific variability of vertebral pneumaticity among pterosaurs. 相似文献
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五河-凤阳地区具有较好的成矿地质条件,目前已知该地区有多种金铅锌多金属矿床类型,但对于该地区的成矿模式的探讨,迄今为止没有一个统一的成矿模式可以较好地解释该地区已知的多种不同类型的成矿模型。本文依托安徽省基金项目,对该地区的成矿模式进行了探讨。 相似文献
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本文使用2009~2012年新疆冬季43场暴雪天气过程中ECWMF和T639L60(2.5*2.5)数值预报产品预报场资料,通过天气学检验方法,对新疆主要影响系统,即西西伯利亚低槽、乌拉尔山大槽、北方横槽、中亚低值系统和其对应的高空500hPa形势、海平面气压做72小时内的滚动预报场与相对应实况场的检验。检验结果表明:两家模式对于高空500hPa形势场预报都比较好,尤其是48h之内,ECWMF的准确率略高于T639;海平面气压场两家模式的预报准确率均低于500hPa形势场,T639要优于ECWMF,尤其是48h之内,一般海平面气压中心强度的预报值较实况会有偏小3~5hPa的误差,以上结论可较好地指导预报业务。 相似文献
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介绍了三态内容寻址存储器的硬件组成,分析了三态内容寻址存储器的工作原理,结合March算法的理论设计了三态内容寻址存储器故障诊断的方法,并介绍了故障检测的流程,在VxWorks的操作系统下以Tornado为开发平台实现了三态内容寻址存储器的故障诊断功能,最后给出了实验结果。实际应用表明结果可靠性能高能满足用户的需求。 相似文献
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Coastal lakes have a specific hydrological regime determined by the influence of sea and inland water and the local hydrographic conditions. There are several problems concerning the protection and assessment of water quality of these bodies. The most important features differentiating coastal lakes from other lakes are: high salinity, a wide range of seasonal and short-term water quality changes, and specific aquatic ecosystems adapted to these conditions. These matters have not been sufficiently taken into account in the existing classifications and typologies of lakes in Poland. The problem has not been solved by the establishment of the adequate reference conditions and new guidelines for the classification of water status (which are being prepared according to the Common Strategy for the Implementation of the Water Framework Directive) regarding inland surface waters (rivers and lakes) and marine waters (coastal and transitional). An important issue is to define criteria which would help to distinguish all those hydrographic objects and to establish water quality standards for them. 相似文献