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清镇市一次冰雹大风过程的环流及雷达回波分析
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作者 许仍祥 李启芬 +2 位作者 李扬 王君军 陈海凤 《中文科技期刊数据库(全文版)自然科学》 2023年第7期37-42,共6页
利用清镇市的应急加密重要天气报告、MICAPS常规观测资料及贵阳雷达资料,对清镇市一次冰雹大风过程进行分析。结果表明:(1)本次冰雹大风过程是在高空槽、中低层切变线、地面辐合线以及中低层干空气共同作用造成;(2)通常清镇市上游地区... 利用清镇市的应急加密重要天气报告、MICAPS常规观测资料及贵阳雷达资料,对清镇市一次冰雹大风过程进行分析。结果表明:(1)本次冰雹大风过程是在高空槽、中低层切变线、地面辐合线以及中低层干空气共同作用造成;(2)通常清镇市上游地区生成的强风暴在织金东部受背风坡影响而减弱,在接近清镇市西边界的迎风坡时加强发展;当清镇市上游风暴为单体雹云时,不同仰角基本反射率图中的三体散射特征、旁瓣回波特征对于风暴是否有冰雹有很好的指示意义;(3)通过高层基本反射率的增强或减弱更能提前判断风暴的增强减弱;径向速度中负速度区包围正速度区的范围大小及其伸展的高度可指示着风暴的发展或减弱;单体趋势中VIL、降雹概率变化以及基本反射率最大值及其高度变化可反应出雹云增强或减弱,尤其最大反射率超过60dBZ且其高度在湿球0℃层高度以上反复升降,利于冰雹的形成,当其高度持续降低至2km以下时,冰雹可能已降落至地面。(4)此次大风由弓形回波造成,在雷达站50km以内的低仰角径向速度场中可见径向速度大值区,业务中观测到这一现象时即可发布雷雨大风预警。 展开更多
关键词 冰雹 雷雨大风 VIL 基本反射率最大值高度 径向速度
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Study of front bumper process on the basis of hot stamping
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作者 Wang Xiaona Xiong Fei Jin Jianwei 《Engineering Sciences》 EI 2014年第5期33-37,共5页
The fitting method is used for obtaining the constitutive relation of ultra-high strength steel in this paper. At the same time, the forming limit of material is researched under different de/brmation conditions. Thro... The fitting method is used for obtaining the constitutive relation of ultra-high strength steel in this paper. At the same time, the forming limit of material is researched under different de/brmation conditions. Through experiments, the paper obtains stress-strain curve under different deformation temperatures and strain rates. On the basis of experimental data, the constitutive relation model is established which can reflect the de- fomlation capacity of ultra-high strength steel during process of hot stamping. Combining with finite element simulation results of hot stamping by the commercial software AUTOFORM, transfer path of load and matching law of strength, the paper determines the design criteria and forming process requirements of parts manufactured by hot stamping. Through setting different process parameters, such as punch velocity and friction coefficient, and blank shape, the paper finds that process parameters and blank shape have an essential effect on the quality of parts. 展开更多
关键词 ultra-high strength steel hot stamping constitutive relation forming limit
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特高压输电线路设计风速取值的探讨 被引量:27
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作者 廖宗高 张华 陈海波 《电力建设》 2006年第4期28-32,共5页
输电线路杆塔主要荷载为风荷载,设计风速的取值直接影响线路的工程造价和线路的安全运行。文章针对1 000 kV交流特高压及±800 kV直流特高压输电线路的特点,与国际通用标准IEC进行了对比,对设计风速合理取值和风速基本高度进行了探讨。
关键词 特高压 重现期 基本高度 设计风速
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The Extension of the H^k Mean Curvature Flow in Riemannian Manifolds
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作者 Hongbing QIU Yunhua YE Anqiang ZHU 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 2014年第2期191-208,共18页
In this paper,the authors consider a family of smooth immersions Ft : Mn→Nn+1of closed hypersurfaces in Riemannian manifold Nn+1with bounded geometry,moving by the Hkmean curvature flow.The authors show that if the s... In this paper,the authors consider a family of smooth immersions Ft : Mn→Nn+1of closed hypersurfaces in Riemannian manifold Nn+1with bounded geometry,moving by the Hkmean curvature flow.The authors show that if the second fundamental form stays bounded from below,then the Hkmean curvature flow solution with finite total mean curvature on a finite time interval [0,Tmax)can be extended over Tmax.This result generalizes the extension theorems in the paper of Li(see "On an extension of the Hkmean curvature flow,Sci.China Math.,55,2012,99–118"). 展开更多
关键词 Hk mean curvature flow Riemannian manifold Sobolev type inequality Moser iteration
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