滇东南地区三次典型冰雹天气特征分析

文章结合滇东南地区的三次降雹天气过程,利用垂直累积液态水含量、冰雹指数、反射率垂直剖面、云顶高度等产品对天气过程冰雹云的回波特征展开分析。分析发现,在冰雹发展阶段速度场出现速度强势辐合,降雹过程中存在非典型钩状回波、“V”形缺口回波、三体散射、悬垂回波、中气旋等典型的降雹回波特征。经检验,各类雷达产品观测不同过程冰雹云的效果存在差异,综合使用雷达产品对准确做好降雹预警有重大意义。

松原市两次强冰雹过程消雹对比及效果评估

利用718天气雷达对2007年7月6日午后出现在松原市境内不同地点的两次强冰雹天气过程进行了跟踪监测,结合松原市冰雹云模式,通过对两块强冰雹云进行消雹与否的比较,以及同一雷达回波消雹前后参数特征的变化分析,对消雹效果进行了评估。结果表明:在冰雹云旺盛发展阶段进行积极的消雹作业能使冰雹云快速消散,减少成核机率,大大减少大冰雹发生概率,经济效益非常可观。

龙岩一次冰雹的雷达回波特征分析

利用模式探空资料和龙岩多普勒天气雷达产品,对2020年4月21日发生在龙岩的冰雹天气过程进行分析。结果表明,此次雹云回波形态先后呈现出椭圆形、“S”形和弓状,具有回波强度强、强回波区面积大、维持时间长的特点,并出现有“V”形缺口、低层弱回波区和其上的强回波悬垂等超级单体特征;速度场出现逆风区、中气旋、低空急流等;风廓线产品中,中层干冷空气的入侵有利于雹云的剧烈发展。

An Effect of Temperature and Notch Geometry on Correlated Toughness of a Stainless Steel

To determine the toughness of materials, Charpy V notch test has been widely used over the world. Originally, the Charpy-V or U tests were used mainly as a quality control tests. In this paper, effects of temperature and notch geometry on variation of toughness/yield stress ratio were investigated. The experimental work has been performed on austenitic stainless steel 316L using Charpy tests and carried out at temperature range from 20 ℃ to 250 ℃ on different dimension of V- and U-notch specimens. Energy of fracture was determined directly from machine tests. Furthermore, Barsoum correlation has been applied to determine toughness/yield stress ratio as function of temperature. In addition, several parameters were investigated namely specimen thickness and notch cut angles. U-notch specimen offers a high resistance comparatively to the V-notch and that toughness depends on temper situation and orientation of notch relative to the rolling direction.