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1.
柴达木盆地近40年初、终霜冻日变化分析 总被引：1，自引：0，他引：1
本文选取柴达木盆地的都兰、诺木洪、大柴旦、格尔木和德令哈5个代表站，用1961-1999年逐日最低气温资料，分2.0℃、0.0℃、-2.0℃三个温度等级，分析近40年来初、终霜冻日及无霜冻期的变化趋势和年代际变化特征，80年代以后，初霜冻日明显推迟，终霜冻日提前，无霜期明显延长，与60年代相比90年代初霜冻日推迟，终霜冻日提前近半月，无霜期延长20多天。 相似文献
2.
利用柴达木盆地南缘3个气象台(站)1961～2005年霜冻资料,对霜冻及霜期的变化特征进行了分析,结果显示柴达木盆地南缘霜冻分布地域性差异大,年内霜冻主要发生在4月和10月,霜冻年际变化呈明显减少趋势,初霜冻日推迟,终霜冻日提前,无霜期延长. 相似文献
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采用气候统计学方法,对林芝无霜期、初（终）霜日气候特征及其气候变化进行了分析,结果表明：无霜期的绝对变率要比初、终霜日的绝对变率大,短于平均值的年份占41．7％;终霜以推迟0～5d的概率最大,平均每4年一遇。近50年林芝初霜日以1．4d／10a的速度推迟,终霜日以-1．6d／10a的气候倾向率提早,无霜期平均每10年延长3．0d。20世纪60年代初霜提早,无霜期缩短;70年代初（终）霜日变化不大,无霜期接近常年值;80年代无霜期短;90年代和21世纪前8年均表现为终霜结束得早、初霜日无变化、无霜期延长的气候变化特征。 相似文献
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本文利用西宁地区近50年常规地面气象观测资料,运用统计学方法研究霜冻气候特征,采用逐步回归方法建立了霜冻日当天最低气温的预报方程并进行检验,结果表明:(1)近50年西宁地区平均初霜冻日以5d/10a逐渐推后,终霜冻日以5d/10a逐渐提前;(2)西宁地区异常初霜冻偏早年和异常早年以及终霜冻偏晚年和异常晚年出现在上世纪70-80年代;(3)西宁地区的初霜冻日、终霜冻日和无霜期发生了一次显著的气候突变;(4)霜冻日当天最低气温与前一日14时气温的相关关系最好,建立的预报方程预报准确率为42%-64%。 相似文献
5.
利用西藏色季拉山地区东、西坡2个气象站点1961～2010年近50年的逐日最低气温资料,以≤0℃最低气温为霜冻指标,采用气候倾向率、累积距平、信噪比和R／S分析等现代气候统计方法,分析了东、西坡初霜日、终霜日、无霜期和霜冻日气候变化特征。结果表明：（1）近50年东、西坡初霜日以1．3～1．5d／10a的速度稚迟,终霜日平均每10年提早1．5～5．1d,无霜期每10年增加2．8～6．6d,而霜冻日每10年减少5．8～6．4d;东坡的增减幅度要大于西坡。（2）20世纪60至80年代东、西坡初霜来得早、终霜结束得晚、无霜期短、霜冻日多;90年代至21世纪最初的10年,东、西坡均表现为初霜日来得迟、终霜日结束得早、无霜期长、霜冻日少的年代际变化特征。（3）特少霜冻日发生频数为8～10次,主要出现在21世纪初,以西坡较多。（4）东、西坡初霜日、终霜日、无霜期和霜冻日均未出现气候突变现象。（5）东、西坡初霜日Hurst指数小于0．5,说明未来推迟的幅度可能会变小;而终霜日、无霜期和霜冻日的Hurst指数均大于0．5,表明未来东、西坡终霜日仍将趋于提早态势、霜期仍将趋于延长,而霜冻日仍将表现为减少趋势。 相似文献
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7.
气候变暖对山东省农业的影响 总被引：16，自引：3，他引：16
选取山东省资料年代较长的86个地面测站1961年～2004年日平均气温、最高和最低资料，计算历年日平均气温≥0℃、≥10℃积温和<0℃负积温，以及无霜冻终、初日变化，深人研究山东省热量资源对气候变暖的响应及其对农业生产的影响。结果表明：1987年～2004年比1961年～1986年的平均气温明显增高，尤以最低气温增幅最大，这说明最低气温的变化比最高气温的变化更敏感，山东省气候变暖主要来自最低气温升高的贡献；冬季升温幅度大于夏季，日平均气温≥0℃、≥10℃积温增多，无霜冻终日提前、初日推后，无霜冻期天数增多，<0℃负积温绝对值明显减少。山东省20世纪80年代后期气候明显变暖，热量资源增加，对冬季大棚蔬菜等设施农业的生产有利，喜温作物面积扩大，复种指数提高；同时，干旱发生的机率加大，病虫等越冬存活率上升，防止难度加大。气候变暖对山东省农业影响是利弊并存。 相似文献
8.
西藏丁青县1961—2015年气温变化特征分析 总被引：1，自引：0，他引：1
文章采用丁青县1961~2015年气温资料,运用气候倾向率、M-K趋势检验和突变分析、Morlet小波变换等方法对丁青县气温年、季变化特征进行分析,结果表明:丁青县平均气温、最高气温和最低气温均呈显著的上升趋势,气候倾向率分别为0.246℃/10a、0.242℃/10a和0.275℃/10a,升温率小于青藏高原地区,高于全国平均升温率。无论是平均气温、最高气温还是最低气温,四季均表现为增温趋势,以冬季增温幅度最大。平均气温、最高气温和最低气温的升高均为突变现象,突变点分别在1995年、2002年和1994年左右。气温变化存在明显的周期,且无论较长周期还是较短周期的变化都处于偏暖期,且在未来一定时期内呈向较暖趋势发展的走向。 相似文献
9.
近50年来雅鲁藏布江流域气温变化特征 总被引：1，自引：0，他引：1
利用1961～2010年西藏雅鲁藏布江流域6个气象站逐月平均气温、最高气温、最低气温等资料,采用气候趋势、气候倾向率、滑动平均和M-K法等现代气候诊断方法,分析近50年来雅鲁藏布江流域气温的年、季和年代际变化。结果表明:雅江流域近50年来平均气温、最高气温、最低气温均呈现显著的升温趋势,增温幅度分别为0.35℃/10a、0.31℃/10a和0.45℃/10a。最低气温的增温幅度大于平均气温和最高气温。各气温呈明显的逐年代上升趋势,20世纪90年代以来增温速度极大,尤其是21世纪初增温更加显著。 相似文献
10.
中国西北地区初霜冻的气候变化特征 总被引：7，自引：0，他引：7
利用中国西北地区135个测站,1961年-2009年历年逐日地面最低气温和NCEP/NCAR资料,采用线性趋势分析、Mann-Kendall、子波分析、功率谱分析和合成分析等方法,分析了近49a中国西北区初霜冻的气候变化特征.结果表明:①中国西北地区初霜冻开始最迟的地方在陇南-陕南,平均出现在11月上旬,其次是南疆盆地出现在10月中下旬;初霜冻开始最早的地方在青海高原,一般开始在8月下旬,其余的地方初霜冻开始在9月中下旬-10月上旬.初霜冻开始期的稳定性较差,特别是北疆、高原北部和南部;②西北地区初霜冻平均以1.8d/10a的速率推迟,1986年有明显的突变现象,近49a来初霜冻有显著的2～3a周期;③西北地区有85％的站点以(2～4)d/10a的速率推迟,通过各年代际的变化来看,1980年代以来有50％以上的站偏迟,特别是近10a,有接近90％的站偏迟;④从环流特征量分析,影响西北地区初霜冻的环流特征量主要有副高正相关和极涡负相关;10月500 hPa高度场合成分析表明,初霜冻偏迟年,东亚大槽浅,西太副高偏西偏强,亚洲中北部盛行纬向环流,中国西北区处于新疆脊控制之下,不利于出现降温天气;初霜冻偏早年,乌山脊强,东亚槽深,西太副高偏东偏弱,亚洲中北部盛行径向环流,西北地区上空不断有来自鸟山脊前的冷空气,易形成强降温天气. 相似文献
11.
《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
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)
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
14.
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
15.
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
17.
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
18.
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
19.
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
20.
Prof. SUN Changpu from the CAS Institute of Theoretical Physics coworkers from University of Basel in Switzerland have worked out a way - at least in theory - to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams is similar to the famous Stern-Gerlach effect whereby a beam of atoms passing through a magnetic field is split in two according to the atoms' spin states 《中国科学院院刊(英文版)》2008,22(1):23-23
Prof. SUN Changpu from the CAS Institute of Theoretical Physics and coworkers from University of Basel in Switzerland have worked out a way --at least in theory --to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams and is similar to the famous Stern-Gerlach effect, whereby a beam of atoms passing through a magnetic field is split in two according to the atoms＇ spin states （Phys. Rev. Lett. 99 130403）. 相似文献