影响广播中波转播站防雷系统作用的几个关键技术

电台中波转播站多建于城市近郊区,由于天线高耸落雷几率高,因而易受雷击干扰。针对建站时原已通过防雷验收的转播站设施在投入使用后依然频遭雷击受损的状况,分析了其防雷系统的内在布设技术问题,认为广播中波转播站原有防雷系统的一些关键技术缺漏是遭雷击受损的主要原因,并从转播站的实际情况出发,提出了转播站防雷设计的几个关键技术问题的解决方法：接地网逐级分流、屏蔽馈线再加设外屏蔽环群技术以及不同的线路、不同系统保护的配合方法等,从而形成广播转播站完整的防雷保护系统框架。     

当前国内酸雨研究进展

回顾了我国在酸雨研究方面所获得的成果,包括酸雨的时空分布特征、影响因素、生态影响模拟以及控制对策等4个方面的内容。大量的研究表明,近些年来酸雨污染的范围有所增加、程度有所加重。酸雨的形成是多种自然和人为因素共同作用的结果,与特定的气象条件、天气类型和大气环流等有密切的关系。针对酸雨污染有所加重的趋势,必须采取有效的控制对策。     

2007年淮河强降水时期低频环流特征

利用NCEP/NCAR再分析资料以及中国气象台站降水资料,研究了2007年夏季淮河流域强降水的低频振荡及其环流特征。结果表明,2007年夏季淮河流域强降水低频振荡的主要周期是10 25天。淮河流域降水强弱与对应低频周期存在联系,降水主要发生在低频周期的正位相时期,而在负位相时期结束或明显减弱。降水的低频变化一方面与副热带高压和南亚高压的低频变化有关,另一方面还受到中高纬度冷空气低频变化的影响。在低频周期的峰值位相,对流层高层出现的低频反气旋使南亚高压偏东,脊线偏北,并有利于西太平洋副热带高压向更西、更北的方向发展,整个对流层垂直方向上有低频的上升运动。中高纬地区出现大片正位势涡度,冷空气的低频活动显著偏强,南下侵入到中国淮河流域的冷空气较多,形成有利于淮河流域强降水的环流场。相反,在低频周期的谷值位相,对流层高层出现的低频气旋使南亚高压偏西,脊线偏南,不利于西太平洋副热带高压向更西、更北的方向发展,整个对流层垂直方向上有低频的下沉运动。高纬度冷空气的低频活动偏弱,南下侵入到中国淮河流域的冷空气也较少,最终形成不利于淮河流域强降水的环流场。     

2007年淮河流域暴雨期间大气环流特征分析

利用NCAR/NCEP再分析资料及国家气象信息中心30年气候平均降水资料,通过动力诊断与分析手段研究了2007年6—7月发生在我国淮河流域的暴雨。结果表明,淮河流域的环流垂直结构和降水有着非常好的对应关系。暴雨期间,鄂霍茨克海阻高与乌拉尔山阻高这种双阻高形势对于淮河流域的持续降水提供了很好的条件;南亚高压高层(200 hPa)基本为正散度区,低层(850 hPa)为负散度区,上下层强烈的抽吸结构对暴雨的发生也是非常有利的条件,同时,在淮河暴雨期问,南亚高压(200 hPa)与500 hPa西太平洋副热带高压有着相向而行的移动路径;位涡对于分析冷空气的活动,有着比较清晰的意义,暴雨发生前,有明显的正位涡异常从高纬度向低纬度伸展。大气非绝热加热分析结果显示,视热源和视水汽汇两者的高值中心与相应时段暴雨中心位置一致。     

重庆10 kV高压输电线路雷击火灾事故分析

针对2007年7月12日重庆华浩冶炼有限公司粉末厂火灾事故,用力学性能分析和剩余磁场测试相结合的方法对该厂火灾发生处的10 kV高压输电线路进行鉴定,并结合雷电天气分析,得出该火灾事故是由雷击10 kV高压输电线路造成。该方法为在没有安装录波器和闪电计数器的情况下,判断输电线路故障是否由于雷击引起提供参考。     

地面气象观测中多普勒雷达回波资料的利用

多普勒天气雷达实时回波通常被广泛应用于短时、临近天气预报、人工增雨(雪)等方面的业务中,事实上,掌握天气雷达回波的演变情况,对做好地面气象观测也是一个很好的辅助工具。通过对2009年4月4日一次强降水过程的多普勒天气雷达云团速度和强度特征分析,结果发现:强降水形成、加强、维持与消散的各个阶段在路径、速度和强度上有明显的体现。     

浅谈长跨度桥梁的雷电防护

介绍了现代化建设中长跨度桥梁直击雷和感应雷防护工程的设计技术和施工要素,重点说明了电源部分和信号部分防感应雷的实施方案,并提出了相应的施工要点和要求。     

2010年4月桂东北一次暖区暴雨天气分析

对2010年4月桂东北一次暖区暴雨天气分析,分析,发现本次过程是由高原南侧的低值系统东移,与副高西北侧西南急流之间形成强烈辐合上升运动造成的;中高纬度稳定的纬向环流和稳定少动的副高为过程提供了很好的环境;高原南侧的低值系统可能与高原的地形摩擦作用有关。     

Formation blockage risk analysis of geothermal water reinjection:Rock property analysis,pumping and reinjection tests,and long-term reinjection prediction

The blockage induced by particle migration and deposition is one of the main reasons for the decrease of reinjection capacity in the porous geothermal reservoir with a low and medium temperature.In this paper,a new drilled geothermal well in Xining basin China is taken as an example to investigate the formation blockage risk due to the movable clay and sand particles in pores.The physical properties of the reservoir rocks were analyzed,a series of pumping and reinjection tests were conducted,and the longterm reinjection performance of the well was predicted by numerical simulation based on the test fitting.The results show that the geothermal reservoir rocks are argillaceous and weakly cemented sandstones with a content of movable clay and sand particles up to 0.18–23.42 wt.%.The well presented a high productivity of 935–2186 m3?d-1 at a pressure difference of 0.7–1.62 MPa in the pumping tests associated with a large amount of clay and sand particles produced out,while in the reinjection test,only a low injectivity of 240–480 m3?d-1 was observed at an injection pressure of 0.2–0.6 MPa with the clay and sand particles near the wellbore move into deep.According to the prediction,under conditions of a blockage risk,the injectivity of the well will start to decline after 100 days of injection,and in the third year,it will decrease by 59.00%–77.09%.The influence of invasion of pretreated suspended particles and scale particles can be neglected.Under conditions of a high blockage risk,the injectivity of the well will decrease significantly in the first 20–30 days,with a decline of 75.39%–78.96%.Generally,the higher the injection pressure or rate,the greater the decrease in injectivity of the well caused by particle blockage.Pump lifting is an effective measure to remove the well blockage which can be used regularly.     

The Important Role Played by Atmospheric Angular Momentum in the Non-linear Prediction of the Variations in the Length of Day

The variation in the length of day has complicated time-varying characteristics and the traditional method for linear time series analysis is always difficult to obtain good effect of prediction. If the non-linear artificial neural network technique is adopted to predict the variation in the length of day, the topological structure of the network model is determined by the least square error method. By taking into account the close relation between the variation in the length of day and the general circulation of atmosphere, the axial sequence of atmospheric angular momentum is introduced into the forecasting model of neural network. The results show that the forecast accuracy is significantly improved by taking advantage of the combination of the length of day and the atmospheric angular momentum sequence in comparison with the individual adoption of the data of the length of day.