共查询到13条相似文献，搜索用时 62 毫秒
1.
基于GIS的贵州高原复杂地形下积温的精细空间分布 总被引：3，自引：1，他引：2
积温是研究作物生长发育对热量的要求和评价热量资源的一种指标。本文在前人研究的基础上,对原有的模型进行了一些改进,考虑了坡度、坡向和地形相互遮蔽作用对复杂地形下太阳总辐射的影响,基于数字高程模型(DEM)数据,研制了以海拔高度、复杂地形下太阳总辐射为参数的复杂地形下积温的分布式模型,在模型中还考虑了散射辐射的各向异性及坡地反射辐射对复杂地形下太阳总辐射的影响。应用100m×100m分辨率的DEM数据及气象站常规观测气象资料,计算了贵州高原复杂地形下100m×100m分辨率的≥0℃、≥10℃、≥15℃积温。结果表明:①局地地形因子如坡度、坡向、地形遮蔽等对积温的影响显著,使得复杂地形下积温的精细空间分布具有明显的地域分布特征,纬向分布特征不明显。地形对复杂地形下积温的影响是不容忽视的;②同一纬度,由于地形差异,积温的空间分布明显不同。阳坡、海拔较低处的积温偏高,阴坡、海拔较高处的积温偏低;③在缺乏复杂地形下坡面考察资料的情况下,建立以常规气象站观测资料为主的物理经验统计模型是实现细网格热量资源计算的可行途径。 相似文献
2.
本文在陕北岔巴沟流域,依据不同的时间尺度,挑选了1964年及1966年中能覆盖整个岔巴沟流域的9场降雨（次降雨尺度）,包括着9次降雨的6个月份（月尺度）以及1964、1965、1966和1967连续4年（年尺度）的侵蚀产沙数据。分别在峁坡、全坡面、毛沟、支沟、干沟等不同空间尺度下,考虑次暴雨、月、年等不同时间尺度的侵蚀产沙情况。分析结果表明：坡面尺度与支沟、干沟尺度的侵蚀产沙方式有所不同,后者年际产沙模数变幅比较小（年际间产沙模数差异系数为0．42）;在同一时间尺度下,产沙模数的大小,由时间不同造成的差异大于由空间不同造成的差异。在小的时间尺度,产沙模数大小变化比较随机;在大的时间尺度,产沙模数呈现一定尺度效应。相同面积区域不同时间的产沙模数差异系数分别为：不同次暴雨之间最大（1．05）,不同月份之间次之（0．835）,而不同年份之间最小（0．76）。本文将侵蚀产沙的能量分为质与量两个方面,分别讨论了坡面尺度与流域尺度能量变化与侵蚀产沙的关系。 相似文献
3.
青藏高原是世界上总辐射量最高的地区,也是全球超太阳常数的极值区域之一。此处形成了一个"嵌入"对流层中部大气的巨大的热源,可以伸展到自由大气,其超越了世界上任何超级城市群落所产生的中空热岛效应,对全球与区域大气环流系统变化的动力"驱动"产生了难以估计的效应。与地形热力过程季节变化密切相关的亚洲夏季风是世界上范围最广和强度最强的季风;从冬季到早春季节转换过程中,由于太阳辐射的影响造成青藏高原大地形感热的"快速响应"及其相对高值动态移动,在盛夏梅雨及其云降水带前沿线恰好停滞于中国"三阶梯"地形分布山地—平原过渡区。此现象表明,青藏高原可能扮演着夏季风过程陆地—海洋—大气相互作用的关键角色。中国区域低云量与总云量极值区均与青藏高原大江大河的源头(长江、澜沧江、雅鲁藏布江等)、中东部湖泊群与冰川集中区空间分布几乎吻合,这表明"亚洲水塔"形成的关键因素与"世界屋脊"特有的云降水结构不可分割。研究表明,青藏高原大气热源对局地与下游区域云降水过程水汽输送流型等均有显著影响。长江流域降水与全国低云量存在一个明显沿长江流域的带状高相关结构,充分表明长江流域降水与上游"亚洲水塔""热驱动"以及对流系统具有重要相关关系。从跨赤道经向环流的视角可发现,夏季南、北半球跨赤道气流低层强偏南、高层强偏北气流出现在东亚地区和北美区域两大地形对应的赤道区,这2个跨赤道极值区恰与青藏高原、落基山高原位置相对应。青藏高原纬向与经向环流圈结构与区域-全球大气环流相关机制,印证了"世界屋脊"隆起大地形的"热驱动"及其对流活动在全球能量、水分循环的作用。青藏高原特殊水汽三维结构分布和跨半球的纬向和经向大气垂直环流图表明青藏高原对全球尺度大气环流变化的贡献显著。文章进一步以东亚、全球水循环的视角,提出了青藏高原作为全球性大气"水塔"的观念,认为在高原地区一个水塔的"供水"和"蓄水"循环体系,特别是高原地表冰川、积雪和湖泊作为"蓄水池"系统,使得所有的河流可作为"输水管道",将"水塔"的水向周边区域输送出去,高层大气也提供向外输送的渠道。青藏高原特殊的跨半球大气水分循环可构建"世界水塔"与其周边地区独特的水文功能概念,综合描绘了青藏高原"世界水塔"及其地球上一个完整的行星尺度陆地—海洋—大气水分循环物理图像。 相似文献
4.
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
5.
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
6.
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
7.
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
8.
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
9.
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
10.
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
11.
《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
12.
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
13.
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