LEO原子氧剥蚀太阳电池阵Ag互连材料的试验研究

暴露在低地球轨道(LEO)上的太阳电池阵,会与大量具有极强氧化性的原子氧发生碰撞,导致太阳电池阵中对氧原子敏感的Ag互连材料受到剥蚀。文章依据原子氧剥蚀Ag材料的机理,选取了约400 km高度轨道上1年时间内原子氧的累积通量作为最高剂量,进行了原子氧剥蚀不同厚度Ag互连材料的地面模拟环境试验。试验表明:Ag在原子氧作用下在宏观上会经历"氧化—剥落"的循环剥蚀过程。根据反应方程简化推导了Ag互连片的剥蚀厚度公式,同时结合试验结果计算出了不同厚度Ag互连材料的厚度损失率。该研究成果可为LEO太阳电池阵原子氧防护设计提供技术支持。     

后缘小翼型智能旋翼桨叶模型设计分析与试验研究

提出了一种基于推挽式双X压电驱动机构的后缘小翼型智能旋翼方案,开展了后缘小翼型智能旋翼模型的设计分析与试验研究.空载试验主要用于验证驱动机构的驱动特性,测试了压电堆和驱动机构的静态输出;为了验证悬停时小翼在铰链力矩作用下驱动机构能否有效驱动后缘小翼,进行了加载试验.试验采用线性霍尔传感嚣对推挽式双X型驱动机构在不同电压和频率驱动下小翼的偏转角度进行了测量.理论分析与试验测试结果基本吻合,压电驱动机构能够有效驱动后缘小翼,该智能旋翼方案是合理和可行的.     

受平行壁限制的燃油喷雾二相流特征

通过试验诊断了燃油喷雾在模拟环形燃烧室火焰筒内、外壁面间的二相流型。其结果显示 ,与不受壁面限制的结果相比 ,其基本流型在下游有明显改变     

退火对P(VDF-HFP)共聚物薄膜结构和介电性能的影响

设法提高电介质材料的介电性能和击穿特性,进而改善PVDF基的电介质脉冲电容器储能性能,对于促进其在军事和民用领域的应用具有重要意义。偏氟乙烯-六氟丙烯共聚物(P(VDF-HFP))是一类综合性能优良的电介质材料。为了进一步提高其介电性能,文章首先通过溶液流延法制得P(VDF-HFP)薄膜,在不同温度和时间下对其进行退火处理,以考察后处理对P(VDF-HFP)晶体结构及介电性能的影响。采用X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)和示差扫描量热分析(DSC)对样品的晶体结构、结晶度和电活性β相含量进行表征,并对薄膜的介电性能进行测试。结果表明,退火处理可有效提高P(VDF-HFP)共聚物的β相含量,在120℃下退火12 h,体系的β相含量可高达92.1%,对应的介电常数可达15.3(100 Hz),较原始薄膜提高45%,同时样品介电损耗可降至0.019。     

软件故障树分析实例研究

软件故障树分析(SFTA)是硬件或系统FTA的扩展,可应用于安全性关键软件的验证和可靠性分析.本文首先阐述了SFTA的原理和应用过程,然后介绍了结合某嵌入式软件进行实际应用的过程以及最小割集的生成,并在此基础上提出了对该软件的改进建议.     

浅析重庆机场雷暴天气条件下的塔台管制指挥

重庆江北机场周围的地形复杂、空域有限,每年的3月至10月份是雷暴天气的频发期。本文以重庆空管分局塔台管制室的实际运行程序为基础,提出了一些在雷暴天气条件下管制指挥建议,在提高运行效率、降低管制运行风险等方面能起到较大作用。     

风洞模型-支撑系统涡激振动测量与分析

以0.55m×0.4m低湍流航空声学风洞某模型及其支撑系统为研究对象,采用基于加速度传感器直接测量支撑系统和热线间接测量模型尾流相结合的方法,测量并分析了风洞模型-支撑系统的涡激振动模态,给出了测量方案和数据处理方法。采用基于加速度传感器的功率谱分析方法,获得了模型-支撑系统的三阶振动频率分别为31.1、120.9和221.4Hz;采用基于加速度传感器的频域滤波和频域积分方法,提高了有效信号的信噪比,获得了模型-支撑系统振动的振型和振动节点位置;采用热线测量模型尾流分离涡脱落频率的方法,获得了模型一阶和二阶振动的尾流涡激频率分别为31.1和124.1 Hz,并从测量尾流速度脉动量获得了模型振幅变化和抖振边界信息。实验结果表明,采用热线测量模型尾流从而分析模型振动的方法,有利于小尺度的模型振动测量,而且相对于加速度传感器装于模型表面的直接测量方法而言,对试验模型的绕流流场干扰较小,为测量风洞试验模型的涡激振动模态提供了一种方法。     

Fractional order tension control for stable and fast tethered satellite retrieval

The retrieval of a tethered satellite system is intrinsically unstable. This paper develops a new control strategy to retrieve the tethered satellite system stably and quickly using the fractional order control theory. The governing equation of the tethered satellite system and classic linear feedback tension control law were first reviewed and examined as a benchmark. Then, a new fractional order tension control law has been to avoid the tethered satellite winds around the main satellite near the end of retrieval by existing integer order tension control laws. The newly proposed control law has been discretized and implemented by the Laplace transform and Tustin operator. Unlike the existing integer order control laws, which are based on the feedback of current state and memoryless, the fractional order control law has the memory of previous states and thus controls the tether retrieval more smoothly while maintaining the retrieving speed. The effectiveness and advantage of the new fractional order tension control law is demonstrated numerically by comparing with its integer order counterpart. The results show that the new control law not only retrieves the subsatellite without winding around the main satellite, but also provides a better control performance with smaller in-plane libration angles.     

An innovative navigation scheme of powered descent phase for Mars pinpoint landing

Pinpoint landing (within 100 m from the target) is essential for future Mars exploration missions. This paper deals with one aspect of the pinpoint landing architecture—the navigation performance improvement during the powered descent phase, and proposes an innovative navigation scheme to obtain the vehicle complete and accurate states. On the basis of dead reckoning relying on the Inertial Measurement Unit, measurements of the Integrated Doppler Radar are adopted to correct the vehicle velocity and altitude. Distance between the vehicle and one Mars Orbiter as well as their line-of-sight relative velocity is measured by a radio sensor, and integrated in the filter to correct the vehicle horizontal position. The innovative navigation system is based on an Extend Kalman Filter. Two observation schemes are developed. One considers measurements of the Integrated Doppler Radar and radio range measurement. Another further considers radio velocity measurement. The performance of the innovative navigation scheme is greatly influenced by the position of the Mars Orbiter with respect to the target. Stochastic analyses are performed to obtain optimal locations of Mars Orbiter. Finally, the innovative navigation scheme performances are assessed through stochastic simulations. Its performance improvements are demonstrated by comparison with the Integrated Doppler Radar only navigation scheme.     

脉压雷达旁瓣匿影工作模式与抗干扰性能分析

旁瓣匿影是脉冲压缩雷达中常用的抗干扰技术。首先基于旁瓣匿影的一般结构,构建了脉压前匿影与脉压后匿影两种工作模式。然后重点针对不同工作模式下的雷达抗干扰性能和检测性能进行了理论分析和仿真研究。结果表明,脉压前匿影比较适合对抗压制性脉冲干扰,而脉压后匿影则更适合对抗欺骗性脉冲干扰。