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81.
Journal of Crop Science and Biotechnology - We examined the effects of drought stress on flowering time, grain yield, and agronomic traits using 10 upland-adapted rice genotypes, i.e. eight... 相似文献
82.
进入新世纪以来,管理科学在我国取得了蓬勃的发展,逐渐形成了庞杂的学科知识体系,与此同时,管理学也涌现了一大批管理科学专家,并在各自的领域中作出了卓越的贡献。利用中国期刊全文数据库(CNKI)2000~2009年的20种管理科学重要期刊文献为数据,从文献计量的角度对我国管理科学十年来的发展进行分析,通过可视化分析工具CiteSpace展示了企业与事业单位管理、管理基础与方法、宏观管理与政策研究三个主要的学科领域的代表人物和研究热点。 相似文献
83.
是我国最早的数量经济学博士(1952年,芝加哥大学经济学院),学界对其介绍却并不多。本文根据他的相关论著、史料和档案,并与近几年论述中国经济学史和管理学史的大量文献进行比较,发现他早在1944年就用数理经济学方法,对区位(区域)经济奠基者韦伯(Alfred Weber)的理论做了部分修正。他在芝加哥大学经济学院读博期间写的毕业论文得到了两位获诺贝尔经济学奖大师的指导,经过严谨的分析与论证,对萨缪尔森的理论提出了自己独特的见解。1953年,他还主持国际计量经济学会会长雅各布·马尔沙克委托的研究项目。回国后即与钱学森、许国志、刘源张等为中国运筹学的引进和发展作出了最早的贡献。 相似文献
84.
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86.
针对局部均值分解(Local Mean Decomposition,LMD)中乘积函数(Product Function,PF)分量的瞬时频率计算问题,引入了一种新的信号瞬时频率计算方法.该方法基于分段波形,先将信号分成若干个全波段(full wave),然后以一组递增的反正弦函数定义每个全波段的瞬时相位,进而得到信号的瞬时频率.由该方法得到的瞬时频率理论上是正的、稳定的并且能够确保信号局部特征信息的完整.应用该方法计算了仿真信号和实际齿轮故障振动信号的瞬时频率,并与其他方法求得的瞬时频率进行了对比.结果表明,本文方法非常适合求取信号的瞬时频率. 相似文献
87.
Xichang Tan Myounghee Kang Jiangping Tao Xinhui Li Daoming Huang 《Fisheries Science》2011,77(6):891-901
Hydroacoustic surveys were conducted to understand the relationship between fish density, spatial distribution, and behavior
upstream and downstream of the Changzhou Dam on the Pearl River, China, and the condition (open/closed) of the spillways.
When the spillways were open on 24 June 2010, numerous fish were observed to be densely distributed in the forebay upstream
of the dam, with an average fish density was 0.22 fish m−3. When the spillways were closed on 25 June 2010, the fish upstream of the dam dispersed, and the average fish density decreased
to 0.007 fish m−3. Prior to operating the spillways on 24 May 2010, the average fish density downstream of the dam was 0.28 fish m−3; in comparison, on 26 June, immediately following closure of the spillways, the average fish density downstream of the dam
was 0.08 fish m−3. Fish were more active on June 24 than on 25 June: they swam faster and their positions in the water column varied greatly.
On 26 June, fish did not to swim as freely in the water column as those measured on 24 May. Based on these observations, we
conclude that a large number of fish are able to swim to the upstream side of the dam while the spillways are open. 相似文献
88.
89.
Determination of comprehensive quality index for tomato and its response to different irrigation treatments 总被引:5,自引:0,他引:5
Feng WangShaozhong Kang Taisheng DuFusheng Li Rangjian Qiu 《Agricultural Water Management》2011,98(8):1228-1238
In order to investigate better irrigation scheduling with the compromise between yield and quality of greenhouse-grown tomato under limit water supply, two experiments of different irrigation treatments were conducted in the arid region of northwest China during spring to summer in 2008 (2008 season) and winter in 2008 to summer in 2009 (2008-2009 season). After measuring single quality attributes, the analysis hierarchy process (AHP) and technique for order preference by similarity to an ideal solution (TOPSIS) were used to determine the weight of single quality attributes and comprehensive quality index, respectively. The results show that the rank of comprehensive quality index had good fitness to that of single quality attributes, indicating that the comprehensive quality index was reliable. Compared to full irrigation, applying 1/3 or 2/3 of full irrigation amount at the seedling stage had slight improvement of comprehensive quality and limit water saving. Applying 1/3 or 2/3 of full irrigation amount at the fruit maturation and harvesting stage decreased the yield by 23.0-40.9%, but had the best comprehensive quality. However, applying 1/3 of full irrigation amount at the flowering and fruit development stage significantly reduced crop water consumption and had obvious improvement of comprehensive quality, but did not decrease the yield significantly and water use efficiency in the 2008 season. And applying 2/3 of full irrigation amount at the flowering and fruit development stage significantly decreased crop water consumption and slightly improved the comprehensive quality, but did not decrease the yield significantly in the 2008-2009 season. Considering the water saving amount, yield and comprehensive quality, applying 1/3 or 2/3 of full irrigation amount at the flowering and fruit development stage and no water stress in other growth stages appears to be a better irrigation scheduling with the compromise between yield and quality of greenhouse-grown tomato, which can be recommended for the spring to summer and winter to summer seasons in the arid region of northwest China. 相似文献
90.
Impacts of climate variability on reference evapotranspiration over 58 years in the Haihe river basin of north China 总被引:3,自引:0,他引:3
Physically, evaporative demand is driven by net radiation (Rn), vapour pressure (ea), wind speed (u2), and air temperature (Ta), each of which changes over time. By analyzing temporal variations in reference evapotranspiration (ET0), improved understanding of the impacts of climate change on hydrological processes can be obtained. In this study, variations in ET0 over 58 years (1950-2007) at 34 stations in the Haihe river basin of China were analyzed. ET0 was calculated by the FAO Penman-Monteith formula. Calculation of Kendall rank coefficient was done by analyzing the annual and seasonal trends in ET0 derived from its dependent climate variables. Inverse distance weighting (IDW) was used to analyze the spatial variation in annual and seasonal ET0, and in each climate variable. An attribution analysis was performed to quantify the contribution of each input variable to ET0 variation. The results showed that ET0 gradually decreased in the whole basin over the 58 years at a rate of −1.0 mm yr−2, at the same time, Rn, u2 and precipitation also decreased. Changes in ET0 were attributed to the variations in net radiation (−0.9 mm yr−2), vapour pressure (−0.5 mm yr−2), wind speed (−1.3 mm yr−2) and air temperature (1.7 mm yr−2). Looking at all data on a month by month basis, we found that Ta had a positive effect on dET0/dt (the derivative of reference evapotranspiration to time) and Rn and u2 had negative effects on dET0/dt. While changes in air temperature were found to produce a large increase in dET0/dt, changes in other key variables each reduced rates, resulting in an overall negative trend in dET0/dt. 相似文献