湿地生态过程研究进展   总被引：62，自引：2，他引：62  

何池全  赵魁义  余国营  赵志春  王国平 《地球科学进展》2000,15(2):165-171

湿地生态过程的研究是湿地研究的核心内容,是研究其物理过程、化学过程和生物过程及其相互关系以及这些过程与湿地功能的关系。介绍湿地生态过程的概念,并对湿地生态过程的三个方面即有机物的生产过程(生物过程)、营养物质循环(化学过程)和能量流动及其水文过程(物理过程)的研究进展进行了述评,并对生物过程、化学过程和物理过程的研究方法进行了剖析,同时对生态过程的研究前景进行了简要分析。  相似文献   

Numerical modelling of seismic slope failure using MPM     

《Computers and Geotechnics》2016

The Finite Element Method (FEM) is widely used in the simulation of geotechnical applications. Owing to the limitations of FEM to model problems involving large deformations, many efforts have been made to develop methods free of mesh entanglement. One of these methods is the Material Point Method (MPM) which models the material as Lagrangian particles capable of moving through a background computational mesh in Eulerian manner. Although MPM represents the continuum by material points, solution is performed on the computational mesh. Thus, imposing boundary conditions is not aligned with the material representation. In this paper, a non-zero kinematic condition is introduced where an additional set of particles is incorporated to track the moving boundary. This approach is then applied to simulate the seismic motion resulting in failure of slopes. To validate this simulation procedure, two geotechnical applications are modelled using MPM. The first is to reproduce a shaking table experiment where the results of another numerical method are available. After validating the present numerical scheme for relatively large deformation problem, it is applied to simulate progression of a large-scale landslide during the Chi-Chi earthquake of Taiwan in which excessive material deformation and transportation is taking place.  相似文献   

An Introduction to Observations Relevant to Astrophysical Jets and Nebulae     

P. Hartigan 《Astrophysics and Space Science》2007,307(1-3):3-6

This article reviews the basic physics and jargon associated with astronomical observations of nebulae, with an emphasis on processes relevant to shock waves in astrophysical jets.  相似文献   

华北克拉通北缘三叠纪金矿床地质特征、物质来源与控制因素SCIEI北大核心CSCD     

白阳  张连昌  朱明田  黄柯  周伶俐 《岩石学报》2022,38(4):993-1024

三叠纪是华北克拉通重要的成矿期,三叠纪金矿主要分布在华北克拉通北缘,构成一条近东西向延伸、长约1500km的金成矿带,其中包括乌拉山-大青山、张家口、冀东-辽西、青城子及夹皮沟等多个金矿集中区。华北克拉通北缘三叠纪金矿带的赋矿围岩主要为新太古代-中元古代变质岩系和中生代花岗岩类,金矿床以石英脉型矿化为主,伴随蚀变岩型矿化;中、西段金矿集中区矿化组合表现为金或金钼矿化,东段则以金多金属矿化为主。同位素年代学资料表明,该带金矿主要形成于晚三叠世(240~220Ma);流体包裹体特征表明,成矿流体具中温、低盐度、低密度特征,属于H_(2)O-NaCl-CO_(2)±CH_(4)体系,相分离作用可能是石英脉型金矿金沉淀的主要机制;氢-氧同位素组成进一步表明,成矿流体早期为岩浆水或变质水,后期混入了大气降水。矿石碳、硫、铅、氦-氩同位素及金矿集中区内成矿相关岩体的钕、铪同位素组成表明,华北克拉通北缘三叠纪金矿床的成矿流体和成矿物质均与壳-幔混合作用有关,其中,幔源物质及流体的贡献与区域三叠纪岩浆活动有关,壳源组分的贡献主要来自前寒武纪变质围岩。金矿床形成的构造背景整体上与中亚造山带造山后伸展作用有关:晚三叠世,华北北缘受中亚造山带碰撞后伸展作用的影响,发生岩石圈首次减薄事件,同时发育多条深大断裂及碱性花岗岩-碱性岩的侵入活动,为大规模区域金矿的形成提供了优越条件。金矿带的东段可能同时受扬子克拉通与华北板块碰撞作用的影响,是造成其与中、西段金矿集中区成矿特征有一定差异的主因。  相似文献   

The molecular hydrogen explorer H2EX     

《Experimental Astronomy》2009,23(1):277-302

The Molecular Hydrogen Explorer, H2EX, was proposed in response to the ESA 2015 - 2025 Cosmic Vision Call as a medium class space mission with NASA and CSA participations. The mission, conceived to understand the formation of galaxies, stars and planets from molecular hydrogen, is designed to observe the first rotational lines of the H₂ molecule (28.2, 17.0, 12.3 and 9.7 μm) over a wide field, and at high spectral resolution. H2EX can provide an inventory of warm (≥ 100 K) molecular gas in a broad variety of objects, including nearby young star clusters, galactic molecular clouds, active galactic nuclei, local and distant galaxies. The rich array of molecular, atomic and ionic lines, as well as solid state features available in the 8 to 29 μm spectral range brings additional science dimensions to H2EX. We present the optical and mechanical design of the H2EX payload based on an innovative Imaging Fourier Transform Spectrometer fed by a 1.2 m telescope. The 20’×20’ field of view is imaged on two 1024×1024 Si:As detectors. The maximum resolution of 0.032 cm^− 1 (full width at half maximum) means a velocity resolution of 10 km s^− 1 for the 0 – 0 S(3) line at 9.7 μm. This instrument offers the large field of view necessary to survey extended emission in the Galaxy and local Universe galaxies as well as to perform unbiased extragalactic and circumstellar disks surveys. The high spectral resolution makes H2EX uniquely suited to study the dynamics of H₂ in all these environments. The mission plan is made of seven wide-field spectro-imaging legacy programs, from the cosmic web to galactic young star clusters, within a nominal two years mission. The payload has been designed to re-use the Planck platform and passive cooling design.

J. P. Maillard (Corresponding author)Email:

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云南江城岩脚铅锌矿控矿因素     

董诗位  田宗春  刘相琴 《云南地质》2010,29(4):424-428

矿床位于江城中新生代拗陷盆地,铅锌矿赋存于F1断层两侧景星组下段一、三、五岩段中,分砂岩型和角砾岩型。存在三种矿物组合,受盆地演化、构造、岩性控制明显。  相似文献   

江苏科技信息网之天文数据库     

李民 《紫金山天文台台刊》1999,18(1):87-89

中国科学院紫金山天文台受江苏省科工委、江苏省科技信息中心委托研制的天文数据库,是省科技信息网的重要组成部分。该信息网包括工业、农业、土壤、地理等较为全面的科技信息,将于年底全面开通。天文数据库已于十月中旬上网。它包括了阴阳历对照、行星特殊天象、太阳、恒星、人造地球卫星等方面的内容。用ＦｏｘＰｒｏ５ ．０ 建立的天文数据库管理系统,包括了成百个数据库表,数据量５ 兆左右,记录约为５ 万余条。天体力学部和天体物理部等有关部门,在提供数据方面,给予了大力支持,在此一并表示感谢。  相似文献   

生态足迹评介及国际研究前沿   总被引：68，自引：1，他引：67  

龙爱华  张志强  苏志勇 《地球科学进展》2004,19(6):971-981

生态足迹评价方法是评估可持续发展的一个全球可比的、可测度的直观且综合的指标,有明显的政策含义,是迄今提出的评估可持续发展的众多指标中最受生态经济学界关注、推崇和广泛应用的一个指标。评介了生态足迹方法模型的优缺点,综述了国际上生态足迹研究的最新进展及研究前沿,指出了国内围绕生态足迹研究应该尽快开展的工作：①生态足迹方法模型的改进及应用研究;②丰富生态足迹方法模型携带的信息量和政策内涵;③社会经济系统新陈代谢以及人类对初级生产力的占用研究;④消费模式与全球资源和环境的压力的关系;⑤物质流核算帐户研究和生态包袱分析研究。  相似文献   

Conditions for instabilities in collapsible solids including volume implosion and compaction banding     

Ronaldo I. Borja 《Acta Geotechnica》2006,1(2):107-122

We review conditions for material instabilities in porous solids induced by a bifurcation of solution into non-unique strain rate fields. Bifurcation modes considered include jumps in the strain rate tensor of ranks one and higher representing deformation band and diffuse instability modes, respectively. Eigenmodes (e-modes) are extracted for each type of instability to fully characterize various frameworks of deformation in collapsible solids. For diffuse instability these e-modes are determined from a homogeneous system of linear equations emanating from the condition of zero jump in the stress rate tensor, which in turn demands that the tangent constitutive tensor be singular for the existence of nontrivial solutions. For isotropic materials we describe two types of singularity of the constitutive tensor: (a) singularity of the constitutive matrix in principal axes, and (b) singularity of spin. Accordingly, we derive the e-modes for each type of singularity. We utilize the singularity of the constitutive matrix in principal axes as a precursor to volume implosion in collapsible solids such as loose sands undergoing liquefaction instability and high-porosity rocks undergoing cataclastic flow. Finally, we compare conditions and e-modes for volume implosion and compaction banding, two similar failure modes ubiquitous in granular soils and rocks.Supported by U.S. Department of Energy, Grant DE-FG02-03ER15454, and U.S. National Science Foundation, Grants CMS-0201317 and CMS-0324674.  相似文献   

利用IRC进行国际天文遥在观测     

季凯帆  曹文达  宋谦 《天文研究与技术》1998,(2)

１９９７年３月６日至３月７日,我们利用ＩＮＴＥＲＮＥＴＲＥＬＡＹＣＨＡＴ（ＩＲＣ）进行了首次国际天文联合遥在观测试验,并获得了成功。本次试验由分布在全球７个不同地点的工作组联合进行,包括中国、美国、加拿大和英国。这一试验的成功为天文观测开创了一个新型的途径,也是对通过Ｉｎｔｅｒ－ｎｅｔ进行更紧密的国际合作的一种尝试。  相似文献