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1.
吞吐型湖泊最小生态需水研究 总被引：19，自引：0，他引：19
湖泊最小生态需水是协调社会经济用水和湖泊生态用水关系的核心.本文研究了湖泊最小生态需水的理论和计算方法.根据水文循环原理,吞吐型湖泊生态需水由入湖生态需水、湖区生态需水和出湖生态需水3部分组成.湖区最小生态需水分为湖泊最低生态水位、湖区最小生态耗水两个方面.入湖最小生态需水是为了满足湖区和出湖最小生态需水而必须对湖泊补充的水分.湖区最小生态需水是为了维持湖泊最低生态水位而必须保留和消耗的水分.出湖最小生态需水不仅要满足湖泊自身水量更新的需求,而且要满足下游河道的生态需水.根据河流连续体原理,用湖泊出口河道的最小生态需水作为湖泊出湖最小生态需水.提出湖泊最小生态需水计算模型.湖泊最小生态需水的各个部分均有其不同的生态作用,其中某个部分的变化都会对湖泊生态系统产生影响. 相似文献
2.
生态需水的研究对象包括河流、湖泊、湿地、森林、绿洲等众多涉水生态系统.由于河流与人类活动的关系最为密切,影响深远,生态需水的研究也一直主要集中在河流方面.随着我国河流生态需水研究的不断深入,河流生态需水成为水利工程建设项目中环境影响评价所必须考虑的重要内容.因此,如何确定和评价河流生态需水,也就成为各级有关政府部门和众多学者关心的热点问题. 相似文献
3.
泾河流域草地生态需水量的估算与分析 总被引：7，自引：2，他引：7
本文在总结分析草地生态需水的内涵、影响草地生态需水的因素并汇总草地生态需水定额有关研究成果的基础上,通过泾河流域各县温度与降水资料的修正,确定了三类草地覆盖度的生态需水定额.利用1:10万土地类型图提取了三类草地面积,估算了泾河流域的草地生态需水量.研究表明,泾河流域现有草地生态需水量共计569 706×104m3,其中中覆盖度草地需水量占绝对优势,为434 674×104m3,占流域草地总需水量的76.3%;其次是低覆盖度草地,需水量为78 326×104m3,占13.8%;高覆盖度草地的需水量最少,为56 706×104m3,占9.9%.从不同地区情况来看,环县等5县的草地需水量较大,镇原县等19县的草地需水量次之,两者分别占流域草地总需水量的近一半,而咸阳市市辖区等7县草地需水量所占分额最少,仅2.9%.这主要与各地的草地类型、草地面积等有关. 相似文献
4.
重要生态功能区生态安全评价方法初探 总被引：2，自引：0，他引：2
重要生态功能区是保障国家和地区生态安全的重要区域,目前尚无针对重要生态功能区的生态安全评价方法研究。本文依托沙漠化防治区建立基于PSR框架的评价指标,以及基于RS与GIS技术的空间评价方法,旨在探索建立一套适用于重要生态功能区生态安全空间评价的可行的评价模式。重要生态功能区生态安全评价的关键是准确衡量区域主要生态服务功能的强弱,指标选择以反映区域主要生态服务功能和人类活动影响为原则。以沙漠化防治区为例,植被生长、土地覆被类型、土壤理化性质和土壤侵蚀等情况是衡量防风固沙功能强弱的重要因素,而指标的动态变化才能反映人类活动对生态环境的影响,选择能够表征植被生长、植被退化演变、土壤粒径和土壤侵蚀的四类因子作为主要评价因子,应用不同年份的变化值进行评价,使评价结果具有空间性、动态性及可操作性,为区域生态环境保护和管理提供基础。 相似文献
5.
重要生态功能区生态安全评价方法初探——以沙漠化防治区为例 总被引：1，自引：0，他引：1
重要生态功能区是保障国家和地区生态安全的重要区域,目前尚无针对重要生态功能区的生态安全评价方法研究。本文依托沙漠化防治区建立基于PSR框架的评价指标,以及基于RS与GIS技术的空间评价方法,旨在探索建立一套适用于重要生态功能区生态安全空间评价的可行的评价模式。重要生态功能区生态安全评价的关键是准确衡量区域主要生态服务功能的强弱,指标选择以反映区域主要生态服务功能和人类活动影响为原则。以沙漠化防治区为例,植被生长、土地覆被类型、土壤理化性质和土壤侵蚀等情况是衡量防风固沙功能强弱的重要因素,而指标的动态变化才能反映人类活动对生态环境的影响,选择能够表征植被生长、植被退化演变、土壤粒径和土壤侵蚀的四类因子作为主要评价因子,应用不同年份的变化值进行评价,使评价结果具有空间性、动态性及可操作性,为区域生态环境保护和管理提供基础。 相似文献
6.
向海自然保护区湿地生态需水研究 总被引：2，自引：0，他引：2
湿地生态需水是指维持湿地生态系统结构和功能正常所需要消耗的水量,对其进行科学核算可为湿地的科学管理和保护提供重要依据.近年来,受自然和人为因素影响特别是来水量的减少,向海湿地面临严重威胁.本文以1996年和2000年两期Landsat TM遥感影像为数据源,对上个世纪末期向海自然保护区湿地的变化特征进行了剖析;在此基础上,采用水量平衡的原理,对不同水平年向海湿地生态需水进行分析研究.结果表明,保护区湖沼湿地景观面积基本保持在300km2,占保护区总面积的28.7%.在平、枯水年湿地生态需水量分别是3.40×108m3和3.65×108m3,其中4月～8月需水量约占全年需水量的78%.向海湿地位于松嫩平原西部,属半干旱地区,天然降水不能满足湿地的生态需水要求,对流域水资源进行综合管理和调度是解决向海湿地水源问题的根本途径. 相似文献
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8.
基于水分的北方农牧交错带植被生态系统退化机理研究 总被引：2，自引：1，他引：1
水是北方农牧交错带最关键的生态环境因子,水资源与生态环境之间的相互关系和相互影响很大程度上决定了北方农牧交错带的环境状况与环境动态.文章从生态缺水的角度,以内蒙古自治区武川县为例,探讨了生态系统退化机理,为北方农牧交错带的生态恢复与重建提供科学依据.研究结果表明,生态缺水是造成北方农牧交错带植被生态系统退化的主要原因.2006年武川县天然草地、灌木、乔木、农作物生长季平均耗水量分别为150.3mm、193.4mm、213.3mm、158.6mm,最小生态缺水量分分别为93.1mm、38.2mm、251.5mm、96.6mm,植被生态系统继续向退化方向演替.合理调整植物品种结构,配置有限的水资源是当地生态恢复与重建的紧迫任务. 相似文献
9.
本文对月保证率设定法进行改进,不仅考虑了不同保证率年份河流生态需水的差异,而且对不同的生态需水推荐流量等级进行了区分。随后采用改进月保证率设定法研究了青海湖流域的河流生态需水特征,结果表明:布哈河和沙柳河径流量的年际变化幅度较大,但增加或减少趋势不明显,夏季径流量年际波动最为明显,而径流量年内分布均呈单峰变化态型,峰值都出现在7月-8月份;伴随着保证率的降低,河流生态需水量不断增加,而且需水等级越高、增加幅度越大,同时不同保证率年份河流逐月生态需水呈现不同的变化规律;平水年(P=50%)青海湖流域两条主要河流布哈河和沙柳河适宜的生态需水量分别为2.18亿m3、1.36亿m3,枯水年(P=90%)二者分别为1.16亿m3和0.70亿m3。 相似文献
10.
由供水管理转需水管理 实现我国需水的零增长 总被引：2，自引：0，他引：2
水资源是基础性自然资源和战略性经济资源,是国家可持续发展的重要支撑。随着我国经济社会的快速发展,对水资源的需求不断增长,目前的开发利用已达到了空前程度,全国水资源的供需矛盾突出。由于水资源数量的有限性与用水的无序性,以往按需求供水的管理模式已无法支撑人类与自然的和谐可持续发展。本文作者就转变供水管理模式为需水管理的问题进行了分析．并提出通过严格的需水管理,我国至2030年前后可望实现需水零增长。 相似文献
11.
A research group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol-a chemical found in the skins of red grapes in red wine-can improve the sensitivity of mice to the hormone insulin according to a report in the October issue of Cell Metabolism.…… 《中国科学院院刊(英文版)》2008,22(1):14-15
Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said. 相似文献
12.
Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
13.
《中国科学院院刊(英文版)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 相似文献
14.
《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 相似文献
15.
A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
16.
Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
17.
Active biological molecules functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery disease diagnosis therapy new nanodevice construction.…… 《中国科学院院刊(英文版)》2008,22(1):22-22
Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction. 相似文献
18.
Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
19.
Leah A. Lievrouw 《The Information Society》2000,16(2):155-159
This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment. 相似文献
20.
Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献