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971.
Using 36 SSR markers and 889 accessions of common wild rice in China, the genetic diversity and the divergence among different geographical populations are investigated. Guangdong Province has the largest number of alleles, which account for 84% of the total alleles detected in the study, followed by Guangxi Province. The Nei's gene diversity indices, from high to low, are in the sequence of Hainan, Guangdong, Guangxi, Fujian, Hunan, Jiangxi, and Yunnan provinces. Two genetic diversity centers of Chinese common wild rice are detected on the basis of geographic analysis, i.e., the region covering Boluo, Zijin, Lufeng, Haifeng, Huidong and Huiyang counties of Guangdong Province and the region covering Yongning, Longan, Laibin and Guigang counties of Guangxi Province. The common wild rice in Yunnan, Hunan, Jiangxi, and Fujian provinces are diverged into respectively independent populations with relatively large genetic distances, whereas, those in Hainan, Guangdong and Guangxi provinces have relatively low genetic divergence. Under the condition of geographic separation, natural selection is considered as one of the primary forces contributing to the divergence of common wild rice in China.  相似文献   
972.
The program structure designing and optimizing tests of GRAPES physics   总被引:7,自引:3,他引:4  
According to the modularization and standardization of program structure in Global/Regional Assimilation and Prediction System (GRAPES), the plug-compatible and transplantable regional meso-scale and global middle-range physics software package is established. The package's component integrality is comparative with the other advanced models physics. A three-level structure of connecting GRAPES physics and dynamic frame has been constructed. The friendly interface is designed for users to plug in their own physics packages. Phenomenon of grid-point storm rainfall in numerical prediction is analyzed with the numerical tests. The scheme of air vertical velocity calculation is improved. Opti- mizing tests of physics schemes are performed with the correlative parameters adjusting. The results show that the false grid-point storm rainfall is removed by precipitation scheme improving. Then the score of precipitation forecast is enhanced.  相似文献   
973.
由于网络化控制系统分析与设计的复杂性,其控制与通信协同设计问题一直没有得到解决.该文讨论了一类离散线性时不变网络化控制系统在服从介质访问约束和传感器-控制器端存在Markov随机延迟的情况下控制与通信协同设计问题,提出了系统均方稳定的条件.采用静态通信序列,使通信序列和控制器可以分别设计,应用V-K迭代算法设计最优周期控制增益.仿真算例验证了系统在所设计的最优控制器下达到均方稳定.  相似文献   
974.
Meiyu in the middle and lower reaches of the Yangtze River since 1736   总被引:7,自引:0,他引:7  
"Yu Xue Fen Cun" records during the Qing Dynasty are used to identify the starting and ending dates of Meiyu at the period of 1736-1911. These results, along with the instrumental meteorological records, are used to reconstruct the series of length and precipitation of Meiyu during 1736-2000 over the middle and lower reaches of the Yangtze River. The characteristics of Meiyu are analyzed since 1736. Moreover, the strength of East Asian Summer Monsoon and locations of rainband are discussed, based on the relationship between the length of Meiyu and the Index of East Asian Summer Monsoon. It is found that the starting and ending dates and the length of Meiyu have significant interannual and interdecadal variations. Apart from 7-8 years, 20-30 years and 40 years cycles for the lengths of Meiyu, the centennial oscillation is also presented. The length of Meiyu, monsoon rainband movement over eastern China, and the strength of East Asian Summer Monsoon (EASM) have a very good correlation, which can be expressed in the following: during the periods of 1736-1770, 1821-1870 and 1921-1970, the EASM was stronger, and the monsoon rainband was located in North China and South China easily, corresponding to the decreased length of Meiyu. Whereas during the periods of 1771-1820, 1871-1920 and 1971-2000, the EASM was weaker and monsoon rainband usually stopped at the middle and lower reaches of the Yangtze River, corresponding to the increased length of Meiyu.  相似文献   
975.
The rate constants for the ozone reactions with n-butyl methyl sulfide (n-BMS, CHaCH2CH2CH2SCH3), sec-butyl methyl sulfide (s-BMS, CH3CH2(CH3)CHSCHa) and tert-butyl methyl sulfide (t-BMS, (CH3)3CSCH3) were measured using our smog chamber under supposedly pseudo-first-order conditions at 30002 K and 760 Torr. The experimental determined rate constants for n-butyl, s-butyl and t-butyl methyl sulfide are (1.23 ± 0.06)×10-19, (5.08 ± 0.19)×10-20 and (2.26 ± 0.14)×10-20 cm3 molecule-1· s-1, respectively. The reactivity-structure relationship of the reactions was discussed and used to illustrate the mechanism of the ozone reaction with thioethers. The results enrich the kinetics data of atmospheric chemistry.  相似文献   
976.
采用1979年—2001年太原市6个县(市、区)气象局的历史资料,分析了降雹的空间分布和年变化、日变化及持续时间。根据当地情况,提出了加强预测预报、植树造林和改良土壤等减轻冰雹灾害的对策。  相似文献   
977.
To implement the computation of AHP (Analytic Hierarchy Process) automatically, make the implementation independence on the platform, and to convenient the service composition and service computation, this study implemented AHP model as a Web service and stored the evaluation information as XML form. This paper introduces the overall demands of AHP evaluation system firstly, and then presents some key technologies to implement AHP evaluation system, including mainly AHP evaluation index architecture based on XML, the class of AHP model, the Web service encapsulation of AHP, the publication and invocation of AHP and the client application. At last, the system is used to analyze the impact factors of online consumption behavior.  相似文献   
978.
“吃+宾”结构是现代汉语中讨论得比较多的问题,本文结合语境理论对其作了综合述评,着重探讨其言内语境;对学者们研究较少的“吃+补”结构着重从语义指向角度分析其言内语境对语义的彰显作用。指出“吃+宾(补)”结构生成发展的深层因素是汉民族的文化、心理、语言习惯。  相似文献   
979.
浅议高校本科生参与教师科研过程机制的探索   总被引:1,自引:0,他引:1  
为适应社会发展对人才素质提出的要求,提高高校大学生的创新精神和研究能力,应加强教学与科研的有机结合,倡导学生,尤其是低年级学生参与教师的科研工作,鼓励把研究性教学贯穿于教学的全过程。  相似文献   
980.
数据流连接操作的执行方式直接影响到查询执行的效率和结果的正确性.在STREAM项目流化方法的基础上,对复杂应用下的数据流滑动窗口连接的准确语义进行了分析和建模,以时间窗口连接的增量维护为例提出了两种改进的基本维护策略,给出了针对元组窗和分组窗的维护方法,讨论了根据参数和环境的不同进行适应性的维护.实验证明了在不同的窗口、流速和选择度下,适应性地选择不同的优化算法会达到最优的处理性能.  相似文献   
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