线性抽样及分形理论在景观异质性研究中的应用   总被引：3，自引：1，他引：2  

武鹏飞  周德民  宫辉力 《地理研究》2013,32(8):1391-1401

景观异质性是景观生态学研究的核心,对景观格局、动态和功能具有决定作用。将线性抽样与分形理论相结合的方法应用于景观空间异质性的表达中,相比于传统方法,可以定量表达景观类型在空间序列中的组合规律,而该组合规律可以作为指标来测度景观空间异质性的高低。景观类型在空间序列中的组合越复杂,则景观的空间异质性越高。该方法以景观类型空间序列的线形图像为基础,利用分形理论计算线形图像的分维,以分维数值的大小来表达景观空间异质性的高低。但样线的布设方法、分维计算方法以及景观分类系统的不同都会对分维数值产生影响。以妫水河流域为试验区,对该方法的适用性进行验证,结果表明,该方法可以有效表达景观空间异质性的高低。  相似文献   

水利工程震害中土工结构低应力破坏实例分析     

杨玉生  温彦锋  刘小生  赵剑明  刘启旺 《岩土力学》2012,33(9):2729-2735

实际工程活动与低应力下土石料工程性质密切相关。总结了与低应力条件相关的工程活动,在总结分析以往地震中堤防和坝体滑坡案例的基础上,指出滑坡深度通常小于7 m,其上覆有效应力大多小于100 kPa。在对106组地震液化数据资料分析的基础上,指出地基液化大多发生在上覆有效应力低于100 kPa的低应力条件下。在目前的研究中,通常只关注中、高应力条件下土石料的工程性质。在应用中低应力区的土石料计算参数取值通常与中、高应力条件下获得的强度和变形参数一致,而高、低应力条件下土石料的强度和变形特性是不同的,这种计算参数取值方法的适用性存在疑虑。因此,研究低应力条件下土石料的工程性质,探讨数值计算中低应力条件下土石料计算参数的取值方法,具有重要的工程意义和科学价值。  相似文献   

南水北调水源北京西郊回灌的水岩相互作用模拟          下载免费PDF全文

郑凡东  刘立才  杨牧骑  张春义  杨勇 《水文地质工程地质》2012,39(6):22-28

南水北调水进京后余裕水可能回灌至地下储存,以涵养严重亏损的地下水资源。为研究地下回灌后的水岩相互作用,为南水北调水的合理利用提供技术参考,本次试验利用丹江口水库水和北京西郊地下水、西郊砂样开展了两地原水七种配比下的模拟含水层试验。结果表明:当含水层中丹江口水库水占比较高时,可能发生程度较高的阳离子交换吸附和钾长石的溶解;各含水层发生硝化反应,且丹江水占比越高,硝化反应越显著;各含水层发生显著的碳酸平衡作用,白云石和方解石在饱和状态下持续溶解并趋于稳定,表明南水北调水回灌将引起地下水硬度的升高。  相似文献   

Paramagnetic lattice defects in quartz for applications to ESR dating     

《Quaternary Geochronology》2015

Quartz is one of the minerals useful for ESR dating with many applications. Although the study has quite a long history since 1980's, ESR dating of quartz is still in a developing stage. After the basis in physics for the ESR signals in quartz is described, the current status of ESR dating of quartz is summarized for applications to fault gouge, tephra and sediment. Both basic studies for mechanisms and practical applications with independent age controls are still necessary to establish the protocols.  相似文献   

Mesomegaloprepidae,a remarkable new damselfly family (Odonata: Zygoptera) from mid-Cretaceous Burmese amber     

《Cretaceous Research》2017

Mesomegaloprepus magnificus gen. et sp. nov. (Odonata: Zygoptera) is described from more than 14 specimens in eight pieces of mid-Cretaceous (earliest Cenomanian, ca. 99 Ma) amber from Myanmar. Possible phylogenetic affinities with the Neotropical Latibasaliidae, Thaumatoneuridae, and Pseudostigmatinae are discussed, and a relationship with Pseudostigmatinae considered as possible, but because of conflicting evidence separate family status as Mesomegaloprepidae fam. nov. is tentatively preferred. The remarkable degree of homoplastic conflict in the wing venational similarities indicates that these represent relatively weak evidence for phylogenetic relationships. The palaeoecology, including sexual dimorphism in wing colouration, of the new taxon is discussed, and the large number of inclusions explained with possible breeding behaviour in association with water-filled tree holes (phytotelmata) of the amber tree, similar to extant Pseudostigmatinae. The position of all alleged fossil Thaumatoneuridae are discussed and revised: Eothaumatoneura ptychoptera Pongracz, 1935 from the Eocene Geiseltal locality is restored in Thaumatoneuridae. Cretaceous Euarchistigma and Paleogene Eodysagrion are tentatively retained as subfamilies Euarchistigmatinae and Eodysagrioninae in Thaumatoneuridae. Paleogene Dysagrioninae and Petrolestinae are removed from Thaumatoneuridae and attributed to a restored family Dysagrionidae, and Paleocene Latibasaliidae is transferred from Amphipterygoidea to Epallagoidea.  相似文献   

A second species of the genus Cretoleptochromus Cai & Huang (Coleoptera: Staphylinidae: Scydmaeninae) from mid-Cretaceous Burmese amber     

《Cretaceous Research》2017

A second species of the extinct scydmaenine genus Cretoleptochromus Cai & Huang, C. burmiticus sp. nov., is described and figured based on three exquisitely preserved specimens embedded in mid-Cretaceous Burmese amber. The new taxon possesses an extremely elongate body form and strongly extended legs and antennae that provide reliable means for species diagnosis and a ready separation from the only known congener, the type species C. archaicus Cai & Huang, also reported from Burmese amber. The morphology of C. burmiticus also suggests that this species was probably an active diurnal predator living in open environments.  相似文献   

A new species of Glaesoconis Meinander (Neuroptera: Coniopterygidae) from the Santonian Taimyr amber     

《Cretaceous Research》2017

Glaesoconis popovi sp. nov. (Neuroptera: Coniopterygidae) is described from Upper Cretaceous (Santonian) Taimyr amber of northern Siberia (Yantardakh locality). The new species may be distinguished from others in the genus by much smaller eyes and the shape of the terminal segment of the maxillary palpus. The generic affinity of Glaesoconis baliopteryx Engel, 2004 from the mid-Cretaceous Burmese amber needs confirmation.  相似文献   

First fossil Coloninae from Upper Cretaceous Burmese amber (Coleoptera: Staphylinoidea: Leiodidae)     

《Cretaceous Research》2017

Fossil leiodids are sparse, and they are confined to the Cenozoic. Here we describe and illustrate the first definitive Mesozoic leiodid, Colonellus burmiticus sp. nov., based on two well-preserved adults from the Upper Cretaceous Burmese amber. The fossil is firmly placed in the extant Coloninae based on multiple synapomorphies, such as antennae with normal-sized antennomere 8 and abdominal intersegmental membranes with “brick-wall” pattern. It can be further assigned to the extant genus Colonellus (subgenus Pentacolonellus) by its five-segmented antennal club. The discovery suggests that Colonellus is an ancient group, originating no later than the mid-Cretaceous.  相似文献   

Electrodysagrion lini gen. et sp. nov., the oldest Dysagrionini (Odonata: Zygoptera: Dysagrionidae) from mid-Cretaceous Burmese amber     

《Cretaceous Research》2017

The dysagrionid damselflies are relatively diverse in Burmese amber, with two genera already recorded. A new dysagrionid damselfly, Electrodysagrion lini Zheng, Nel and Wang, gen. et sp. nov., corresponding to the oldest record of the tribe Dysagrionini, is described herein. It has the unique ‘sieblosiid-dysagrionine’ type of discoidal cell. It differs from other genera of Dysagrionini in having no antenodal crossveins distal of Ax2, Arc aligned with Ax2, and only one row of cells in the cubito-anal area below the nodus. This find puts the origin of Dysagrionini back to at least the mid-Cretaceous.  相似文献   

复式河道滩槽交互区水沙运动机理          下载免费PDF全文

吉祖稳  胡春宏 《水科学进展》2017,28(3):321-328

滩槽复式河道是冲积河流中最为常见的一种形态,也是河流动力学研究最为重要的内容之一。以复式河道概化试验数据和水沙运动的区域性特征为依据,在提出滩槽复式断面主槽平衡区、滩槽交互区、滩地平衡区以及边壁区4个分区的基础上,将水流流态最为复杂的滩槽交互区进一步划分为对数流速区（内区）和非对数流速区（外区）,通过引入描写动植物生长过程的S型曲线,提出了内外区分界线的确定方法。以滩槽交互区横向分布公式为基础,通过线性假定和积分变换,给出了滩槽交互区内断面平均流速和含沙量的计算公式,并对不同分区内的流速和含沙量的差异性进行了比较分析。  相似文献