银川平原水资源开发与绿洲的稳定性

目的探讨银川平原水资源开发与绿洲稳定性之间的内在联系。方法应用自然地理方法分析银川平原水文条件、水资源赋存及黄河水资源利用状况。从绿洲水热平衡指标、黄河水量的波动性和递减趋势、银川平原荒漠化和水环境污染等层面分析银川平原绿洲的稳定性。结果银川平原人工灌排渠沟系统已成为地表水系的重要组成部分,地下水与地表水转化关系密切,形成黄河水-渠系(灌溉)水-潜水的整体循环系统。水热平衡分析结果表明,银川平原绿洲生态系统呈退化趋势,在黄河来水量波动大和递减趋势下,不宜大面积扩大引黄灌溉面积,应重视银川平原地域系统生态的整体平衡,注重与周边各大地域系统的关联耦合作用,并有效治理工业废水、城镇污水对水环境的污染。结论在多种不利因素的耦合作用下,银川平原生态环境有进一步恶化的趋势,形成生态环境易受损机理。银川平原绿洲的稳定性取决于该地域系统的人类活动与水环境的整体平衡。     

新疆玛纳斯河流域水资源分布规律及基生态意义

水作为绿洲环境及其经济建设的主要限制因素,直接决定着绿洲建设的规模、方向和水平。分析和研究对水资源形成及其分布规律和生态意义,对整个流域的发展规划和战略布置都具有深远的理论和现实意义。玛纳斯河流域作为新疆干旱区典型的内陆河、上、中、下游及山地、绿洲、荒漠的生态建设和保护均取决于对该流域水资源的集约高效利用。     

塔克拉玛干沙漠西北边缘植被特征与生态保护策略

塔克拉玛千沙漠西北地区属于暖温带干旱荒漠气候，植物区系包括中亚成分、古地中海成分等，分布着荒漠生态系统、自然绿洲生态系统和自然水域生态系统，在过境河流两岸分布着草垫带—森林带—固定沙包带—流沙带，植被类型有草甸植被、森林植被、灌木植被、沙生植被和盐生植被。水分状况是导致区域植被变化的主要因素，人类活动也在影响植物群落演替变迁。本通过实地调查．分析了区域生态系统、植被群落类型及其结构特征和植被动态演替，分析了各种植被类型的生态与生产功能。并对合理利用水资源、保护绿洲、荒漠过渡带值被、优化荒漠边缘带生态系统、促进绿洲可持续发展提出对策建议。     

基于RSEI的玛纳斯河流域自然生态环境变化评价

生态环境是人类生存发展的物质基础,生态环境质量深刻影响着全球变化及区域可持续发展。为了分析玛纳斯河流域的生态环境质量现状及变化特征,本文以1993、2006和2016年的Landset TM/ETM影像为数据源,借助RSEI指数,对玛纳斯河流域的生态环境质量进行监测和动态评价。结果表明:(1)绿度、湿度、热度和干度是生态系统的重要组成部分,在此基础上建立的RSEI指数可较好的反映玛纳斯河流域生态环境质量状况及其时空分异;(2)1993、2006和2016年RSEI指数均值分别为0.31、0.38和0.45,对RSEI指数进行分级处理后,发现流域生态环境质量"差"等级居于主导地位,"优"等级等级急剧增加,流域内生态环境质量向好的方向发展;(3)流域山地-绿洲-荒漠生态系统(MODS)内部生态环境较为稳定,流域内生态环境质量变好的区域远大于变差的区域,生态质量变差的区域主要集中于南部山区林地、水域、城市周边和部分耕地,生态质量变好的区域主要分布在绿洲内部及边缘。     

张掖绿洲水资源的持续利用

绿洲的发展规模基本上取决于水资源的开发规模、利用程度和管理水平．根据张掖绿洲水资源时空分布的不平衡及开发利用中存在的问题，提出必须从保护、持续的角度对水资源加以开发利用，这对建立节水高效的绿洲生态系统和整个绿洲的持续发展都有意义．     

基于生态足迹的1990-2010年石河子绿洲动态变化

利用生态足迹分析方法,从能值理论角度对石河子绿洲1990-2010年的生态足迹和生态承载力进行计算和动态分析研究。结果表明:该地区人均生态足迹从1990年的2.1309hm2增至2010年4.2368hm2,增加了98.83%;人均生态承载力、人均生态足迹赤字呈逐年上升的趋势,从1990年的0.7725hm2增加至2010年的2.7190hm2。说明石河子绿洲目前已超出了自然生态系统的生态承载力范围,生态足迹与生态承载力之间的矛盾加剧,现有的发展模式是不可持续的,生态系统处于不安全状态。最后提出了解决这一问题的有关对策。     

基于生态足迹的喀什绿洲水资源承载力研究

水资源承载力是绿洲可持续发展的基础,生态足迹模型作为分析自然资源消费量的有效方法被广泛运用。本研究运用生态足迹模型对喀什绿洲2004-2014年水资源承载力及利用效率进行研究,为喀什绿洲水资源良性循环利用提供参考依据。研究表明,喀什绿洲水资源生态足年纪变化幅度较小,10年来几乎没有明显增加,水资源承载力有一定波动,也成为水资源盈亏的主要影响因素,单位GDP水资源生态足迹呈明显下降趋势,说明水资源经济效率越来越高。目前的经济发展、城市化与水资源关系相对和谐,但是未来的产业升级及城市化中潜在的水资源危机必需在发展规划中予以重视。     

黑河尾闾东居延海适宜水面面积研究

东居延海维持一定的水面面积是黑河"97"分水方案实施成功的重要标志,调水以来,黑河尾闾东居延海已实现连续13年不干涸,湖周生态环境得到了很大的改善,但在枯水年份,进入东居延海的水量有限,东居延海有可能干涸。如何在枯水年份既能保证东居延海一定的水面面积,维持东居延海基本生态功能,又能不挤占额济纳绿洲植被生态用水,实现绿洲生态用水效益的最大化是值得研究的科学问题。文中通过分析东居延海生态服务功能,计算东居延海不同水面面积情况下生态价值,构建黑河下游额济纳绿洲水资源配置模型,模拟不同来水条件下绿洲水资源配置和东居延海可入湖水量,从额济纳绿洲整体生态环境出发,提出既能实现东居延海基本生态功能,又能维持东居延海长期不干涸的适宜水面面积。通过研究得到:①东居延海生态价值随着水面面积的增加而增加,在水面面积0～18km~2变化过程中,生态价值增加显著,大于18km~2后,生态价值增加趋势明显变缓,单位面积水面面积增加所产生的生态价值不显著;②根据额济纳绿洲各生态分区的生态用水需求,通过水资源合理配置,无论黄藏寺水库是否建成运行,东居延海在连续枯水年会再次出现干涸,且最长干涸时间会达到6个月;③在东居延海维持18km~2水面面积,湖深为6m时,既能保持东居延海长年不干涸,维持基本的生态功能,,又能使绿洲生态缺水量最小,实现了水资源生态效益的最大化。     

虚拟水战略与民勤绿洲可持续发展问题研究

虚拟水是近年来水资源管理领域中出现的新概念,虚拟水战略是缺水区域通过贸易的方式从富水区购进水资源密集型产品(尤指粮食)来获得本区水资源安全的一种构想.位于甘肃石羊河下游的民勤绿洲极度缺水,"三生"用水矛盾尖锐,生态经济系统难以为继.本文分析了民勤绿洲生态经济系统可持续发展的水资源约束条件;探讨了虚拟水战略实施的可行性及预期效益;构建了可持续发展的水资源保障框架体系.     

民勤荒漠绿洲植被的生态服务功能价值化研究

以"中国生态系统生态服务价值当量因子表"为基础,通过生物量等因子的校正,评价民勤荒漠绿洲植被的生态服务功能价值及其变化,并分析其变化原因.结果表明:1983,1993和2003年民勤绿洲植被的生态服务功能价值分别为2.22×109,3.02×109,5.22×109元/a.1983～2003年植被的生态服务功能价值增长1.35倍.民勤绿洲生态系统服务功能主要由林地植被和草地植被生态提供,影响最大的是土壤形成与保护和生物多样性维持功能.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the