垂直电偶极子在地-电离层波导中场的球级数解

在非理想导电地面与电离层条件下,我们导出了ELF/SLF垂直电偶极子在球形地-电离层壳体中产生的电磁场的球谐级数表达式,采用一种加速收敛算法,算出了波导中的电磁场分布.根据计算结果,在SLF频段,地面与电离层之间的电磁场可理解为二个"行波"的叠加,且与SLF频段的球面二阶近似算法计算结果吻合很好.在ELF频段,壳体中的电磁场是驻波,其频率变化规律能正确反映出"舒曼"谐振现象.     

并网型风力发电系统的研究

并网发电是大功率风力发电机组高效、大规模利用风能最经济的方式,已成为当今世界风能利用的主要形式。为促进我国的风电事业,概述了并网型风力发电系统的基本工作原理、工作方式和风力发电机的空气动力学特性以及并网型风力发电系统中5种典型的电路拓扑结构及其工作原理、并网技术和控制方法,还比较了不同拓扑结构下风力发电系统的性能和效率,给出了各自的典型应用。最后指出了各种方法的优缺点以及今后的发展方向。结果表明,随着大容量电力电子器件的发展和现代控制技术的引入,并网型风电系统中直驱式永磁同步发电机拓扑结构将会得到更多的应用和发展。并网型大功率风电机组控制系统中,风机模拟系统设计、发电机控制技术、并网技术、桨矩角控制技术和系统监控等关键技术的解决将有助于我国风电产业的国产化和大容量风电系统自主知识产权的建立。     

环锭纺的发展潜力

目前存在3个关键因素导致环锭纺产量无法进一步提高。介绍了一些有利于未来环锭纺技术进一步发展的基本情况。详细分析了环锭纺工序中的能耗问题,这是性能能否提高的基础。环锭纺产量的提高,不仅是技术上是否可行的问题,更重要的是能够获得良好的经济效益。     

基于速度波动的高速凸轮廓线设计

应用最优控制理论,提出以多设计点法来设计既有良好动态特性且抗速度波动力强的凸轮轮廓曲线,并以实例验证了该方法的可行性。     

支承系统的刚度对转子动力特性的影响

转子的动力特性受到很多因素的影响,其中,支承系统的刚度是一个重要因素。通过在有限元分析软件ANSYS中建立某小型燃气轮机支承系统的三维有限元模型,分析了其静刚度和动刚度。以该燃气轮机的压气机转子为例,文中考察了支承系统的刚度对其临界转速和稳态不平衡响应的影响。计算结果表明,与仅考虑轴承的支承刚度相比,同时考虑支承系统刚度的情况下,压气机转子的第一阶临界转速下降了约54%,其第一级叶轮的稳态不平衡位移响应的峰值下降了56.9%。     

Weldability of low-alloy steels in submersion-arc welding at high linear energies

Results of analysis of investigations of welded joints produced in welding low-alloy high-strength 07G2NDMFBT steel at linear energies up to 6 kJ/mm show that the proposed combinations of welding materials and the technology of multi-arc submerged-arc welding result in high hot-cracking resistance and high properties of the weld metal. However, regardless of the high cold-cracking resistance of the steel, in welding at high heat inputs there is a considerable degradation of the structure and the toughness of the metal in the coarse-grained region of the heat-affected zone decreases under the effect of the welding thermal cycle. Consequently, it is concluded that the weldability of this steel is limited and it is therefore necessary to apply restrictions in the practical application of the processes with high heat input.     

Weldability and microstructural variations in weldments of Ti-5Ta-1.8Nb alloy

The successful replacement of the present generation of corrosion-resistant materials (nitric acid-grade stainless steel and Ti) by Ti-5Ta-1.8Nb, which has better corrosion resistance, depends on its weldability characteristics. This article presents the results of a study on the fabrication, qualification, and microstructural characterization of the welds. Welding was carried out using the direct current electrode negative (DCEN) polarity tungsten inert gas (TIG) (manual) welding method with high-purity Ar shielding. Testing was carried out as per the ASME standard (section IX, welding and brazing). Qualification tests found that the weldment met the required properties. The weldment showed heterogeneous microstructures, which are rationalized based on differences in phase transformation mechanisms that are dictated by the thermal cycles experienced by various microscopic regions. The results, described in this article, confirm that the weldability of the developmental Ti-Ta-Nb alloy is excellent. A preliminary evaluation of the corrosion behavior of the welds showed rates comparable to that of the base metal, establishing that this alloy could be considered as an alternative material for use in highly corrosive environments.     

新仪器在水电站截流监测中的应用

根据大渡河瀑布沟电站截流实践,阐述水文新仪器在应用中的基本方法和功能,意在商讨新仪器新技术的推广应用.     

ALPUR除气装置在25 t熔铸生产线中的应用

25 t燃油熔铝炉熔炼的铝合金熔体中氢含量较高,配备ALPUR除气净化装置,通过合理使用,达到了满意的除氢效果,保证了铸锭的内部质量。     

刨煤机的刨运速比选型

本文分析各类刨煤机在不同刨运速比下的运煤能力利用率,讨论刨运速比的最佳选择。