Space Shuttle UHF communications performance evaluation

Computational investigations and experimental measurements were performed to evaluate the Space Shuttle UHF communication system performance for payload bay antenna at the proposed new location. To insure adequate communication coverage at relocated new location, the link margin for the Extravehicular Activity (EVA) astronauts and between Space Shuttle Orbiter and International Space Station (SSO-ISS) during rendezvous were analyzed. The multipath effects from the vehicle structures surrounding the antenna were investigated. The Radio Frequency (RF) electromagnetic radiation to the Orbiter Docking System (ODS) pyrotechnics was also analyzed to ensure the EMC/EMI compliances.     

Implementation of a novel matrix converter PMSM drive

This paper proposes a neural-network current-regulated switching strategy and an intelligent controller for a matrix converter permanent magnet synchronous motor (PMSM) drive system. By using this new switching strategy, the current harmonics of the system are effectively reduced. In addition, by using the intelligent controller, position control of the drive system can be achieved and an adjustable speed range from 1 r/min to 1500 r/min can be obtained. All the current-loop, speed-loop, and position-loop control algorithms are implemented by a 32-bit TMS320C40 digital signal processor. Several experimental results are shown to validate the theoretical analysis     

Power anomaly effects and costs in low-voltage mobile power systems

Electric power anomalies or disturbances can disrupt the normal operation of equipment, accelerate aging, or even cause outright failures thus resulting in increased costs of maintenance and reduced system reliability. Past research on the effects caused by power anomalies has been mostly focused on industrial, commercial, or residential systems, or on power distribution equipment. A literature survey reveals that there is no comprehensive review related to low-voltage (LV) power systems and utilization equipment applicable to military combat vehicles, such as aircraft and ships. This paper summarizes the results of a new literature survey that focused on the causes, effects, and mitigation methods for power anomalies typical of LV mobile power systems. Electric power anomaly cost data collected from the literature are also presented, from which the costs of anomalies to the national defense are estimated using some simple rationales.     

侧链含硝基氮杂基团的聚醚粘合剂的性能及应用──新型硝基粘合剂研究Ⅲ

对新型的侧链含硝基氨杂基因的富能聚醚粘合剂──端羟基２─甲硝胺基乙基缩水甘油醚均聚醚（ＮＰＥ—Ａ）和端羟基共聚醚（ＮＰＥ—Ｂ）的性能进行了研究。结果表明，ＮＰＥ的热稳定性和化学稳定性良好，优于普通碳氢聚醚粘合剂（ＨＣＰＥ）和新型氟碳聚醚粘合剂（ＦＣＰＥ）；其固化后的力学性能良好。简要地叙述了以ＮＰＥ—Ｂ为粘合剂的固体火箭推进剂的配方和性能。     

基于多相正交序列移位序列的CDMA通信系统

介绍多相正交序列的构造方法,对多相正交序列的自相关和互相关特性进行分析。提出采用多相正交序 列的移位序列作为扩频序列的通信方式,并给出接收端序列同步的实现方法。这种方式能解决低相数多相正交序列互 相关特性不理想,而高相数多相正交序列难以搜索的困难。     

Kevlar/Nomex蜂窝夹层结构表面粘贴镀铜箔聚酰亚胺薄膜的工艺研究

文章对Kevlar面板Nomex蜂窝夹层结构表面粘贴镀铜箔聚酰亚胺薄膜的工艺进行了研究,分析了工艺特点、工艺流程、工艺难点,以及针对工艺难点所采取的工艺措施,最后根据产品的研制情况给出结论。     

正—反激组合式变换器与单端式变换器的比较

以５０Ｗ变换器为例，分别从磁性元件的大小，功率管上的电应力、磁恢复问题，输出纹波及输出特性等方面，详细分析比较了组合式变换器与单端式变换器的优缺点，并给出了具体数据，提出了正－反激组合式变换器具有电压应力低，磁性元件小，体积小，重量轻，输出纹波小及可靠性高的结论。     

一种外挂物连投的微机控制系统

本文扼要阐述了飞行器外挂物连投试验中用微机控制的测控自动化系统的原理、性能、软硬件设计和程序流程图。     

摩托车空气动力学研究进展

世界摩托车工业已得到很大的发展。随着近几年来中国摩托车产量的迅速上升,加速摩托车的研究是目前摩托车发展的一种趋势。这种研究无论是对提高产品的性能,还是节能降耗部具有重要的意义。摩托车的气动特性是其设计的重要依据。目前德国,日本等国已经利用道路试验、风洞模拟进行这种研究,并促进了产品的开发,但国内的这种研究还有待进一步完善。     

Time-Optimal Control of a Bounded Phase-Coordinate Process II: High-Order Systems with Multiple Control Inputs

This paper considers the problem arising from the design of an autopilot for a large booster. The motion-controlling actuators of the booster have both position and rate limits. The problem is formulated as a bounded phase-coordinate problem and analyzed by the ``backing out of the target' procedure. A method of constructing the optimal control is presented. An example of an oscillatory system with two control inputs is given, and the optimal control is expressed as an explicit time function.