大口径钢筋混凝土管管道安装施工方法

随着改革开放的飞速发展,我国的国民经济水平不断提高。市政排水工程也有了突飞猛进的发展,小直径的排水管道已经不能满足的人口日益增多的大中城市排水的需要,所以应运而生的大口径钢筋混凝土管道很适合市政     

Switching between antenna subset selection and quasi-orthogonal space-time block code in presence of correlation

We address the problem of adaptive modulation and coding scheme (AMCS) for a multi-input multioutput (MIMO) system in presence of time-varying transmitting correlation. Antenna subset selection and quasiorthogonal space-time block code (QOSTBC) have different error performances with different signal-to-noise ratios (SNRs) and in different spatial correlation scenarios. The error performance can be improved by selecting an appropriate transmission scheme to adapt to various channel conditions. The maximum distance criterion is the simplest and very effective algorithm for the antenna subset selection without needs of complex calculation and channel state information at transmitter (CSIT). The minimum error performance criteria and the simplified linear decision strategy are developed for constant transmission rate traffic to select the optimal transmission scheme. It can dramatically decrease algorithm complexity for obtaining error probability according to the known quantities comparing with using instant CSIT. Simulation results show that, remarkable performances including low SNR and weak spatial correlation at the expense of simple calculation and almost no bandwidth loss by adopting AMCS can be achieved. The proposed AMCS improves robustness of slowly varying spatial correlated channels.     

大口径管道水平定向钻穿越大型河流施工风险控制研究

长距离大口径管道水平定向钻穿越大型河流施工,由于其地质条件复杂、回拖阻力大等因素,施工风险大。本文以南水北调中线工程水平定向钻穿越潮白新河段为例,通过分析水平定向钻施工过程中周边环境、地质不均、施工工艺、设备故障、钻具、导向控制等风险,并提出相应控制措施。实践表明：选取具有交流定向钻地磁控向系统的水平定向钻钻机,根据不同地层选用不同配比、不同性能的泥浆,管道发送形式选用发送沟注水与猫背方式,管道回拖采用钢管内穿PE管注水等控制措施,使钻进轨迹满足设计要求,防止塌孔、缩径、回拖过程中管道防腐层破坏以及焊口的断裂等风险发生,相关经验值得借鉴。     

时域有限差分法在天线辐射可视化中的应用研究

针对常见的舰载单极套筒天线,利用时域有限差分法（FDTD）对仿真空间进行了Yee网格划分,并建立了该天线的数理模型。在工作频率为30MHz时,对天线进行了可视化仿真,通过对天线表面电流的幅度与相位进行分析,验证了模型的正确性以及计算的精确性;同时,利用天线辐射相位分布图直观地分析了天线的辐射过程。仿真结果表明,针对舰载单极套筒天线的FDTD建模方法对舰载天线的辐射分析与工程设计具有一定的指导意义。     

An L-strip fed stacked patch antenna for maritime satellite communications

A practical antenna has been designed and developed for INMARSAT mobile satellite communications. The design uses low cost materials such as foam and copper foil to create a stacked microstrip antenna array. Several techniques were adopted to enhance the impedance bandwidth and axial ratio bandwidth. The final design parameters were optimized by EM simulation. Finally, the L-strip fed six-element stacked microstrip antenna array was constructed and tested. Simulated and measured results show that in the whole INMARSAT work band, the VSWR of the antenna is less than 1.6, its antenna gain is higher than 15dB and wide-angle axial ratio （AR） 3dB is more than 21°. The antenna has been successfully used with a HNS 9201 terminal.     

关于大口径舰炮技术发展的思考

本文围绕大口径舰炮技术发展,针对某自行火炮炮塔移植上舰现象,从使用方式、使用环境、设计特点对二者的差异进行分析,深入剖析了自行火炮炮塔上舰的制约因素、改进工作量和技术风险,认为大口径舰炮技术发展绝不能简单地从陆军火炮"拿来"移植,而应当从信息化条件下的作战使用需求出发,科学规划、协调发展,提出了"信息化牵引、一体化规划,简约化发展、模块化设计"的技术发展建议。     

微波超天线技术的研究与发展北大核心CSCD

天线技术的发展一直局限于其基本的物理特性。人造结构(即超构材料)的发展具备了独特的电特性,对现有天线设计的性能改善和引入新的功能带来了机会。首先简要介绍超构材料和超构表面的概念。以微波超透镜为例,详细介绍超构表面以及超构表面天线的设计。接着,简要概述微波超天线技术(即基于超构材料和超构表面的天线)的最新研究进展。最后,对微波超天线研究与开发的前景和重点课题进行展望。     

水面舰艇避雷针对天线性能影响仿真评估

采用矩量法仿真分析水面舰艇避雷针对桅顶天线性能影响,评估设备受避雷针的影响程度,以确保桅顶设备与避雷针一体化安装设计的情况下能够正常工作。