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941.
ZHUPeijun ZHENGYongguang WANGHongqing TAOZuyu 《科学通报(英文版)》2005,50(8):800-808
Spiral rainband is a prominent structure of tropical cyclone. Though its forming mechanism, vortex Rossby wave theory, has been widely accepted in recent years,its internal structural features are still not well known. The spiral rainband in the severe tropical storm Kammuri (2002),which caused heavy rainfall in southeast China, is simulated using the mesoscale model MM5 (V3). Results show that the simulated spiral rainband propagates azimuthally at a speed close to that of vortex Rossby wave in theory, and is accompanied with energy dispersion in the radial direction. The structural features of simulated spiral rainband are analyzed with the high-resolution model output including the full physical process. Positive vorticity, ascending motion, horizontal momentum and so on are highly concentrated in the spiral rainband. The convergent moisture of spiral rainband comes mostly from the planetary boundary layer under 1 km.Airflow from the outside of spiral rainband is convective instability, which can provide instability energy for convection development. However, the atmospheric stratification in the inside of spiral rainband is neutral, implying that the instability energy has been released. There is a mesoscale strong wind band just near the spiral rainband in the outer side with a maximum wind speed exceeding 30 m/s, which results from the pressure force acceleration when the air flows into the spiral rainband along the gradient of pressure. 相似文献
942.
如何推进知识管理战略是现在众多工程项目类企业面临的重点和难点问题。从企业项目团队遇到重要问题的解决流程出发,分析了其中的知识活动,总结出知识流的特征,指出项目团队中不同成员知识共享及使用方面的不足,从而得到工程项目类知识管理改进的现实依据。 相似文献
943.
Cl-对N80油套管钢钝化膜半导体性能的影响 总被引:1,自引:0,他引:1
利用电化学阻抗谱技术研究了N80油套管钢在0.05mol/L NaHCO3溶液中所成钝化膜的电化学性能,借助于莫特-肖特基曲线分析了成膜电位、测试频率以及Cl^-浓度对钝化膜半导体性能的影响.结果表明:钝化膜呈n型半导体特征;随着成膜电位的增加,膜的容抗和施主密度减小;随着Cl^-浓度的增加,膜的容抗和施主密度增加,膜的点蚀现象加剧.X射线光电子光谱(XPS)分析结果表明,钝化膜主要由Fe的氧化物Fe2O3和FeO组成. 相似文献
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947.
QI Guoqin DONG Wei ZHENG Liang ZHAO Lingxia GAO Feng YUE Leping ZHANG Yunxiang 《科学通报(英文版)》2006,51(6):704-712
When, where and from which hominoid the human originated has been one of the key subjects in the study of human natural history. It is therefore very important to learn the chronological, geographical and taxonomic distribution of all hominoids. Yunnan Pr… 相似文献
948.
A New Algorithm for On-Line Handwriting Signature Verification Based on Evolutionary Computation 总被引:6,自引:0,他引:6
ZHENG Jianbin ZHU Guangxi 《武汉大学学报:自然科学英文版》2006,11(3):596-600
The paper proposes an on-line signature verification algorithm, through which test sample and template signatures can be optimizedly matched, based on evolutionary computation (EC). Firstly, the similarity of signature curve segment is defined, and shift and scale transforms are also introduced due to the randoness of on-line signature. Secondly, this paper puts forward signature verification matching algorithm after establishment of the mathematical model. Thirdly, the concrete realization of the algorithm based on EC is discussed as well. In addition, the influence of shift and scale on the matching result is fully considered in the algorithm. Finally, a computation example is given, and the matching results between the test sample curve and the template signature curve are analyzed in detail, The preliminary experiments reveal that the type of signature verification problem can be solved by EC. 相似文献
949.
ZHANG Hua YUAN Zheng WEN Qiaoyan 《武汉大学学报:自然科学英文版》2006,11(6):1915-1918
Zhou et al give an attack on Ham's modified authenticated multi-key agreement protocol, and give a protocol that can prevent the unknown key-share attack. The paper points out that the protocol is vulnerable to a concatenation attack. This paper proposes an improved authenticated multi-key agreement protocol which shows how to make Harn's protocol more secure by modifying the signature and verification. And this protocol can escape the concatenation attack. 相似文献
950.
预时效对高强铝锂合金2A97组织和性能的影响 总被引:1,自引:0,他引:1
以高强Al-Cu-Li-X铝锂合金2A97为研究对象,采用拉伸试验、TEM和SEM等手段测试分析了带有预时效双级时效合金组织和性能.结果表明:淬火后的双级时效和淬火变形后的双级时效,由于在终时效前增加预时效,使合金塑性提高,但强度略有下降.淬火变形后预时效过程形成的位错环和变形导致的位错有相同的作用,增加基体T1(Al2CuLi)相数量,使T1分布更均匀,淬火变形后双级时效获得T1,θ′和δ′的混合组织,同时预时效减小晶界T1尺寸.淬火后预时效导致的空位团和位错环增加基体δ′和T1形核,但数量有限,预时效有利于促进溶质原子团簇形成,增加δ′(Al3Li)和θ″(Al2Cu)析出相形核,并有利于... 相似文献