日地共转扰动似稳结构及其反相和漂移规律的最新证据

日地共转扰动似稳结构及其反相现象在第２１及２２周再次显现，从而证实了上述发现是一种在长达世记的时间尺度内存在的普遍规律。包括１９９１－１９９２年内的百年地磁扰动资料还说明偶数太阳周的共转似稳结构扰动峰有逆太阳自转而线性性漂移的趋向。对即将来临的极小年前可能出现的共转扰动作了试验性的预测。     

某型涡轮螺桨发动机转子偏磨故障分析

 某型涡轮螺桨发动机曾发生过多起转子偏磨故障,工厂对此作过许多分析,本文在其基础上再对该项故障的原因和机理结合实际地作了进一步的比较、分析和论证,提出了排故措施。效果显著。     

Waveform-based spaceborne GNSS-R wind speed observation: Demonstration and analysis using UK TechDemoSat-1 data

This paper explores two types of mathematical functions to fit single- and full-frequency waveform of spaceborne Global Navigation Satellite System-Reflectometry (GNSS-R), respectively. The metrics of the waveforms, such as the noise floor, peak magnitude, mid-point position of the leading edge, leading edge slope and trailing edge slope, can be derived from the parameters of the proposed models. Because the quality of the UK TDS-1 data is not at the level required by remote sensing mission, the waveforms buried in noise or from ice/land are removed by defining peak-to-mean ratio, cosine similarity of the waveform before wind speed are retrieved. The single-parameter retrieval models are developed by comparing the peak magnitude, leading edge slope and trailing edge slope derived from the parameters of the proposed models with in situ wind speed from the ASCAT scatterometer. To improve the retrieval accuracy, three types of multi-parameter observations based on the principle component analysis (PCA), minimum variance (MV) estimator and Back Propagation (BP) network are implemented. The results indicate that compared to the best results of the single-parameter observation, the approaches based on the principle component analysis and minimum variance could not significantly improve retrieval accuracy, however, the BP networks obtain improvement with the RMSE of 2.55 m/s and 2.53 m/s for single- and full-frequency waveform, respectively.     

基于变速积分的高速电机磁悬浮控制系统设计

针对磁悬浮高速电机的磁轴承-转子系统,设计了基于MCU+FPGA的数字控制系统。为实现转子系统的高转速下稳定控制,在建立了磁轴承-转子闭环控制系统模型的基础上,针对常规PID控制系统的超调振荡问题和PD控制系统的转子位移静差问题,利用变速积分的思想设计了改进的PID控制器。实验表明,在消除了系统静差的同时明显减小了系统的超调量和调节时间,说明设计的控制系统具有很好的动态特性和稳态精度。     

Equilibrium positions on stationary orbits and planetary principal inertia axis orientations for the Solar System

We present a qualitative analysis in a phase space to determine the longitudinal equilibrium positions on the planetary stationary orbits by applying an analytical model that considers linear gravitational perturbations. We discuss how these longitudes are related with the orientation of the planetary principal inertia axes with respect to their Prime Meridians, and then we use this determination to derive their positions with respect to the International Celestial Reference Frame. Finally, a numerical analysis of the non-linear effects of the gravitational fields on the equilibrium point locations is developed and their correlation with gravity field anomalies shown.     

多点静压落差法在风洞稳速压控制系统中的分析与应用

先介绍了两种测量风洞稳速压控制系统风速反馈值的常用方式-单点风速测量法和多点静压落差法,并对其特点和应用场合进行了分析;然后对多点静压落差法进行数学建模,给出了静压落差与风洞试验段中心点风速的关系;最后用一个工程实例说明此方法在实际风洞设计中的应用。     

远程星际航行补篇

通过一系列变量置换推导出不同喷气速度和不同加速度条件下,计算恒星际飞船加速段的时间和距离的普遍公式及多级火箭加速情况下加速段的时间和距离的公式。最后以天狼星作为航行目标、计算了用5级和10级火箭加速飞行的时间和距离。结果表明,当火箭的级数很多,且各级加速度相等时,其飞行时间与距离非常接近匀加速飞行的情况。     

基于BP神经网络的GNSS-R海面风速反演

针对GNSS-R进行海面风速反演过程中时频域相关物理量较多，数据耦合性强等问题，提出了基于反向传播（BP）神经网络反演海面风速的方法。建立反演过程中相关观测量与风速的对应关系，选取多观测量作为输入，对输入数据进行处理，设置神经元与激励函数，使用BP神经网络自适应调整拟合参数，将风速作为神经网络输出端的特征量提取。反演结果，风速≤ 20 m/s时，反演均方根误差RMSE=1.21 m/s，风速>20 m/s时反演均方根误差RMSE=2.54 m/s，反演结果优于使用时延相关曲线前沿斜率（LES）和时延多普勒相关功率均值（DDMA）方法得到的反演结果，且迭代次数较少，复杂度较低，证明该方法可以应用于GNSS-R海面风速反演。     

Planetary protection on international waters: An onboard protocol for capsule retrieval and biosafety control in sample return mission

Planetary protection has been recognized as one of the most important issues in sample return missions that may host certain living forms and biotic signatures in a returned sample. This paper proposes an initiative of sample capsule retrieval and onboard biosafety protocol in international waters for future biological and organic constituent missions to bring samples from possible habitable bodies in the solar system. We suggest the advantages of international waters being outside of national jurisdiction and active regions of human and traffic affairs on the condition that we accept the Outer Space Treaty. The scheme of onboard biological quarantine definitely reduces the potential risk of back-contamination of extraterrestrial materials to the Earth.     

小积液情况下卧式转子的稳定性实验研究

盘腔积液现象在舰用燃气轮机工作过程中时有发生，汽化的滑油和水蒸气凝结形成积液。转子带动腔内的积液旋转，引发振动失稳，严重时会对发动机结构造成致命性破坏。为此，本文开展燃气轮机压气机盘腔积液的模拟实验研究，以双盘双支承的卧式柔性转子系统作为研究对象，重点关注小积液量的特点，对积液转子的动力学稳定性进行了研究。观测到转子的失稳现象，开展了不同积液体积、不同积液类型（水、植物油和滑油）等因素的影响规律研究，揭示了小积液的卧式转子动力学特征。研究结果表明：①对于积液失稳振动，存在失稳边界积液量，当积液量大于该边界值时，失稳将会发生。②失稳边界转速及恢复转速均高于临界转速。当转速高于失稳边界转速时，失稳将会发生。转速进一步增加，高于恢复转速时，失稳现象可能消失。③失稳时的振动特征为：出现幅值突增，次谐波成分也随之增加；基频和次谐波发生调制，表现出拍振特征。④随着积液体积的增加，失稳边界转速先减小后增加。⑤随着积液粘度系数增大，失稳边界转速和边界积液量均增大。