台风载荷作用下输电塔线体系时程分析及补强措施

为研究±800 kV输电线路所使用的横担较长的铁塔在受到台风载荷作用时的时程响应分析,通过建立三塔两线有限元模型,基于风速不随高度变化的Von Karman谱,利用谐波叠加法生成了基准风速为50 m/s的风速时程,应用模拟的台风载荷进行时长为50 s的时程分析,共分析了风载荷45°、60°、90°作用下塔线体系的三种情况。仿真结果显示,在45°和60°风作用下,铁塔中部、塔头和塔身连接的平口处应力超过屈服强度,导、地线挂线板处所受应力也超限,铁塔在90°风作用时,塔身腰部主材和塔腿主材应力也超过屈服强度。要预防台风对铁塔的破坏,应该从上述三个部位对铁塔进行补强,在塔腿及塔腰之间增加水平材是一种有效的加固措施。     

三塔单索部分斜拉桥模型试验研究

以福州市浦上大桥三塔单索部分斜拉桥主桥为原型,设计制作1∶40缩尺有机玻璃模型,开展三塔单索部分斜拉桥全桥有机玻璃模型试验和有限元结构分析,研究全桥弹性阶段结构受力性能.重点测试模型主梁变形、纵横向应力、桥墩和桥塔截面应力和支承反力,并模拟斜拉索换索状态,测试换索时结构受力性能变化情况.研究结果表明:三塔单索部分斜拉桥具有独特的受力特性,由于斜拉索的弹性支承能够承担部分活载作用,使主梁截面高度减小,结构轻巧优美、整体受力合理;但在换索时主梁应力明显增大,且变形增加约20%.     

On the T-ramified, S-split p-class field towers over an extension of degree prime to p

Let K be a number field, p a prime, and let be the T-ramified, S-split p-class field tower of K, i.e., the maximal pro-p-extension of K unramified outside T and totally split on S, where T and S are disjoint finite sets of places of K. Using a theorem of Tate on nilpotent quotient groups, we give (Theorem 2 in Section 3) an elementary characterisation of the finite extensions L/K, with a normal closure of degree prime to p, such that the analogous p-class field tower of L is equal to the compositum . This N.S.C. only depends on classes and units of L. Some applications and examples are given.     

Towers of derivation for Lie rings and some results on complete Lie rings

The well-known tower theorem of groups (resp. Lie algebras) shows that the tower of automorphism groups (resp. derivation algebras) of a finite group (resp. a finite dimensional Lie algebra) with trivial center terminates after finitely many steps. We generalize these results for Lie rings, and present some necessary and sufficient conditions for Lie rings to be complete.     

TOWERS OF DERIVATION FOR LIE RINGS AND SOME RESULTS ON COMPLETE LIE RINGS

The well-known tower theorem of groups （resp. Lie algebras） shows that the tower of automorphism groups （resp. derivation algebras） of a finite group （resp. a finite dimensional Lie algebra） with trivial center terminates after finitely many steps. We generalize these results for Lie rings, and present some necessary and sufficient conditions for Lie rings to be complete.     

逆流冷却塔的热工性能评定及预测

作者通过对运行塔测试数据的观察和理论分析,认为除气水比外,进水温度和湿球温度的影响不容忽视,并归纳为水的温态比的影响,从而建立塔的热工特性方程。由此可求得运行塔在设计工况下所具有的交换数,与该工况所需交换数相比较即可评定塔的热工性能。也可用来预测各运行工况下塔的排热量。由于仅考虑气水比影响的塔(填料)热工特性方程的求解值偏大,作者建议在试验塔测试台上整理热工特性方程时,应考虑水温态比的影响,使藉此设计的塔具有足够的填料容积,保证有良好的热工性能。     

刍立塔双锥形中波天线的结构可行性分析

从结构分析上探讨自立塔双锥形中波天线的可行性。根据容许应力设计理论,对天线撑杆的风荷载和承载能力进行结构计算,并对天线撑杆进行内力分析。该种天线形式的结构可行性较差,需天线电气设计改变天线形式。     

基于远距离无线电和窄带物联网的杆塔姿态监测系统

针对现有高压输电杆塔姿态监测系统存在监测方式单一、监测精度低、无法实时监测和提前预警等缺点的问题,提出了一种基于远距离无线电和窄带物联网的杆塔姿态监测系统。系统采用STM32F103C8T6嵌入式单片机搭配微机电系统(micro-electro-mechanical system, MEMS)陀螺仪倾角传感器实时采集杆塔姿态数据,使用远距离无线电(long range radio, LoRa)局域网通信技术完成杆塔监测区域内多节点的数据交互与汇总,并通过窄带物联网专网将汇总后的数据上报至OneNET云平台以实现在线监测杆塔倾斜状态。同时为提高倾角传感器的测量精度及稳定性,针对零偏不稳定性、速率斜坡和角度随机游走白噪声建立随机漂移误差模型,通过引入Softmax函数完成自适应调节反馈功能,动态调整测量噪声协方差矩阵和过程噪声协方差矩阵来优化卡尔曼滤波算法,以提升在角速率变化较快的情况下卡尔曼滤波器的跟踪性能。杆塔姿态监测系统经过测试,具有输出数据精度高、功耗低的优点,工作稳定可靠,能够实时监测高压输电杆塔的姿态和完成预警等功能,对预防高压输电杆塔倾斜、倒塌,维持电力系统的安全运行有一定的...     

On towers of function fields of Artin-Schreier type

In this article we derive strong conditions on the defining equations of asymptotically good Artin-Schreier towers. We will show that at most three kinds of defining equations can give rise to a recursively defined good tower, if we restrict ourselves to prime degrees. ¹A. Garcia and H. Stichtenoth did part of thiswork during their stay at Sabanci University, Istanbul, Turkey (Sept. 2002). ²A. Garcia was partially supported by PRONEX # 662408/1996-3 (CNPq-Brazil).     

Some lower bounds on Shelah rank in the free group

We give some lower bounds on the Shelah rank of varieties in the free group whose coordinate groups are hyperbolic towers.