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黄淮海平原治理和农业发展与地下水开发有密切的关系。浅层地下水具有较好的补给条件和可更新能力,从综合治理角度出发,调节控制浅层地下水位,既有利于减少潜水蒸发损失,又有利于防涝、治理盐碱和防渍。开采利用浅层地下水也是对降水、地表水和地下水进行调节的先决条件。本文根据黄淮海平原许多地区试验与调查资料,对井灌效益进行了分析,同时提出了提高井灌效益的若干措施。 相似文献
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华北平原深层地下水的更新与资源属性 总被引：6，自引：0，他引：6
学术界对于华北平原深层地下水的资源属性存在争议,这直接关系到地下水的合理开发利用以及管理方式和开发战略的制定。本文从地下水资源属性的定义、内涵,地下水补给以及开发后含水层系统的响应等方面来讨论深层地下水的更新性。含氚的现代地下水分布在山前平原,其稳定同位素组成接近当地降水加权平均值,说明当地降水补给占有相当的比重,氚含量与深度的关系反映了150 m深度以上地下水是可更新的,其更新强度约为3%/a。中东部承压含水层地下水的放射性碳-14年龄为10 ka B.P至大于35ka B.P,其稳定同位素δ18O和δD值比现代地下水要低得多,反映了末次冰期补给水的特征。根据水均衡方法估算的河北平原承压含水层1985年～1995 年间的平均更新强度为 0.09%/a,1990年～2000年间的平均补给强度为0.12%/a,说明大规模开采地下水诱发了一定程度的侧向补给,但是其更新强度仍然小于一般意义上的可更新含水层系统的更新强度0.2%/a。尽管这部分承压地下水并不是严格意义上的“不可更新地下水资源”,但因其更新相对比较缓慢,可以看作“不可更新地下水资源”,应该按不可更新地下水资源来规划开发与管理。 相似文献
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黄河下游悬河段地下水资源计算及开发潜力分析 总被引：9，自引：2，他引：9
黄河水资源是沿黄地区经济和社会发展的重要制约因素.由于黄河在其下游河段(花园口-人海口)河床淤积而形成地上悬河,黄河水侧渗补给已成为该地区地下水的重要补给源.黄河下游悬河段地下水系统面积为29 313km2,赋存着潜水、微承压水(浅层含水层系统)和承压水(深层含水层系统).含水层垂直向上概化为3层:浅层潜水和微承压含水层组、深层承压含水层组及两含水层之间20m～30m厚的弱透水层.计算域边界除梁山一长清一带、徒骇河上游及郑州西南侧为补给边界,其余均为排泄边界.在建立水文地质概念模型的基础上,构建三维地下水流模拟模型,应用FEFLOW有限元软件求解.运用识别和验证后的模型计算了不同保证率年份地下水补给量和可开采资源量.研究区50%和75%降水保证率年份地下水补给资源量分别为62.51×108 m3和54.88×108 m3,可开采资源量为44.82×108 m3和39.20×108m3.将研究区分成18个子区进行地下水开采潜力评价,其中12个区尚有开采潜力,1个区采补基本平衡,5个区开采潜力不足. 相似文献
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现代黄河三角洲浅层地下水对降水的响应 总被引：1，自引：0，他引：1
对地下水动态的研究是地下水资源评价和合理开发利用的基础.本文通过在黄河三角洲代表性区域黄河农场地区的典型地貌单元上安装的自计水位计,获得自2004年5月到2005年5月30分钟一次的浅层地下水水位和水温动态资料,和其中一个观测孔地下水电导率动态.结合同时期日降水量资料,阐明一个完整水文年内浅层地下水对降水入渗补给的响应过程和特点,讨论了浅层地下水动态形成的机理.主要结论有:①沉积物之间岩性的差别导致浅层地下水动态类型的差别.泛滥平原相沉积物中地下水的动态类型为渗入-蒸发型,而河流相沉积物中地下水的动态类型为渗入-径流-蒸发型.降水是引起浅层地下水水位上升的主要因素;②浅层地下水温度变化主要受大气温度年内周期变化的驱动.然而雨季日降水量大于10mm时地下水温度平均升高约0.3℃;③进入雨季后累积降水量超过300mm是地下水EC值对降水响应的闲值,雨季降水对浅层地下水有暂时的淡化作用. 相似文献
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地下水对煤矿开采有较大的影响作用,为了安全、高效、正常地开采,现总结羊场湾矿地下水情况,认为可划分为孔隙潜水、裂隙孔隙潜水和裂隙层间承压水三种类型。区内基岩地下水的补给来源,主要仍然是大气降水或通过第四系间接补给,地下水沿着岩层层面及裂隙通过沟谷及地下深处裂隙带由南往北偏西运动排泄。羊场湾煤矿一号井可划分五个含水岩组。 相似文献
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姚凤山 《内蒙古科技与经济》2002,(1):37-38
呼和浩特市区的地理位置处于呼和浩特盆地北部大青山冲洪积扇的中上游.该盆地西南方向开口,是由北部的大青山和东南部的蛮汗山组成的一个簸箕形盆地.本地区多年平均降水量远小于多年平均蒸发量,这种趋势近几年越来越明显,是典型的北方干旱型气候.呼和浩特有兰种形式的地下水:①浅层潜水;②潜水--承压水交替带水;③深层承压水.虽然盆地中有丰富的地下水资源,但由于侧向补给量有限,人为过量开采和不合理利用,出现了含水层的疏干现象,且疏干的面积越来越大.如果不认真采取科学的对策,保护好我们赖以生存的水资源,呼和浩特市的城市发展必将受到水源的制约. 相似文献
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大青山南坡呼和浩特段是土默川平原地下水含水层的径流区和补给区,同时该区域也是国家北方重要的生态屏障,该区域地质环境的优劣,对呼和浩特地区的地下水资源和生态环境将产生重大的影响.通过对大青山南坡呼和浩特段的地质环境及地质灾害进行调查,为地质环境及地质灾害的治理提供依据. 相似文献
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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
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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
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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
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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
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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
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Milton Mueller 《The Information Society》2001,17(3):151-163
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP. 相似文献
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Prof. Raymond C.K. Chen a neuropsychologist with the CAS Institute of Psychology has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology. 相似文献
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《中国科学院院刊(英文版)》2014,(3)
<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence 相似文献
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Chinese Scientists Use Earth Observation Technologies to Study and Protect Wild Camels 总被引：1，自引：0，他引：1
《中国科学院院刊(英文版)》2014,(3):267-268
<正>Chinese scientists plan to apply Earth Observation technologies to protect the critically endangered wild camels(Camelus ferus).With the help of remote sensing,satellite positioning,geographical information system and wireless sensors networks,they will be able to access the distribution and population of the wild camels and protect their habitats.The project will be carried out by the International Research Center for Wild Camel Conservation,which was jointly established earlier this year by the Institute of Remote Sensing and Digital Earth(RADI)of the Chinese 相似文献
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WANG Sijia 《中国科学院院刊(英文版)》2014,(2):192-194
<正>The Paul Gerson Unna Research Group on Dermatogenomics was founded in October 2012 at the Partner Institute for Computational Biology.The ultimate goal of the group is to understand the biology of skin and skin appendages. 相似文献