月球探测器飞越多小天体的拓展任务设计

为充分利用月球探测任务完成后的探测器,提出控制其从环绕月球或地球的轨道出发开展多个小天体飞越探测拓展任务。结合月球探测任务完成后的探测器飞行状态,重点分析了逃逸月球或地球的能量需求,以及小天体飞越探测的其他必要条件,如小天体亮度、星载设备能力约束等。研究了小天体目标确定和转移轨道设计方法,针对小天体目标众多引起的搜索空间和计算量大、多目标序列优化复杂等问题,设计了小天体目标多层择优搜索算法。以嫦娥五号为例,搜索得到了多个可行的小天体飞越探测方案,结果表明在给定约束下可以交会最多5个小天体,包括尺寸较大的小行星12923。研究结论可直接用于嫦娥五号拓展任务,并为后续月球和小天体探测任务提供有益参考和借鉴。     

无人机飞行训练资源配置效率的AHP-Arena综合评价方法

为降低传统层次分析法(analytic hierarchy process,AHP)赋权过程主观片面性影响,提出了一种综合AHP与Arena仿真建模技术的无人机训练资源配置效率评价方法。基于飞行训练流程分析,确定了训练资源配置效率影响因素和效率评价指标,建立了层次型综合评价体系,概括了AHP-Arena综合评价步骤。利用Arena建模软件构建训练流程动态仿真系统并验证有效性,采用单变量数值仿真法、均方差决策法完成了影响因素客观赋权,通过线性加权综合法得出综合评价系数,实现资源配置效率评价与方案优选。实例应用说明了该方法的有效性,同时,该方法可推广至其他类似的训练过程中,亦可为其他多因素、多指标评价决策过程提供借鉴。     

ZCS半桥式DC/DC变流器状态空间法建模及Matlab仿真分析

分析了一种ZCS半桥式DC DC变流器时域工作特性.通过研究其工作各阶段的特性建立了其状态空间模型,采用Matlab语言进行编程仿真,得到其输出电压时域仿真波,与实测吻合,证明了所建状态空间模型的正确性,得到变流器工作的一些有用结论,有助于指导下一步变流器的传导干扰分析和抑制.     

浅谈变声期声乐教学的要求与方法

对于许多高等院校的音乐教育专业来说,培养目标的主要在于培养合格的中小学音乐教师。而这对于即将成为音乐教师的学生来说,如何掌握青少年变声期前后的声音特征,心理特征;并能运用科学的方法,适当的要求来进行教学,具有非常重要的意义。     

进气口位置和进气体积流量对油罐油气惰化置换效率的影响

采用机械通风方式对油罐油气进行处理,具有安全性差、通风时间长和效率低下的缺点;利用燃惰气对油罐油气进行处理,可较好地克服上述缺点。在前期研究的基础上,设计模拟实验台架,以燃惰气为介质,实验研究进气口位置和进气体积流量对燃惰气惰化置换油罐油气的影响。     

Supercritical carbon dioxide as a new working medium for pneumatic launch: A theoretical study

Compared with the conventionally gaseous or liquid working media, the specific internal energy of supercritical carbon dioxide (SCD) is higher at the same temperature and pressure, and the critical temperature of carbon dioxide is close to room temperature, making SCD a potential new working medium for pneumatic launch. To analyze the feasibility of this conception, an analytical model of a pneumatic catapult is established on basis of the conservations of mass and energy. The model consists of a high-pressure chamber and a low-pressure chamber connected by multiple valves, and there is a movable piston in the low-pressure chamber that can push an aircraft to accelerate. The effects of the launch readiness state of SCD in the high-pressure chamber, the initial volume of the low-pressure chamber and the valve control on the movement of the aircraft are analyzed. It is found that there is a restrictive relation between the temperature and pressure of the launch readiness state of SCD, i.e., there is a maximum allowable launch readiness pressure when the launch readiness temperature is fixed. If this restrictive relation is not satisfied, the working medium in the low-pressure chamber will drop to its triple point within a few milliseconds, leading to a launch failure. Owing to this restrictive relation, there is an optimal launch readiness state of SCD with the highest working capacity for any allowable launch readiness temperature. The pressure of the low-pressure chamber will decrease significantly as the initial volume increases, leading to a decreased acceleration of the aircraft. The ac-celeration can be controlled below a critical value by a designed sequential blasting technique of multiple valves. The calculated results show that a 500 kg aircraft can be accelerated from 0 to 58 m/s in 0.9 s with 36 kg of carbon dioxide. This research provides a new technique for the controllable cold launch of an aircraft.     

GBAS中抑制电离层异常的改进自适应Hatch滤波算法

针对单频地基增强系统(Ground Based Augmentation System, GBAS)中电离层异常时Hatch滤波器平滑精度降低问题,系统分析了电离层延时对Hatch滤波器平滑精度的影响,提出一种改进自适应Hatch滤波算法。根据卫星信号计算码载偏离度,并利用二阶线性时不变低通滤波器抑制码载偏离度高频信号,以实现电离层异常实时检测;建立平滑后伪距误差均方根与电离层延时变化率、伪距测量噪声标准差以及平滑时间三者之间的函数模型,并由此确定出Hatch滤波器最优平滑时间。利用GBAS原理样机进行验证实验,结果表明:自适应Hatch滤波算法能够根据卫星信号电离层延时变化率确定滤波器最优平滑时间,且当电离层异常时,自适应Hatch滤波器机载位置误差最大由1.15 m减小为0.43 m,从而验证了所提算法的有效性。