Impact of lubricant traction coefficient on cage's dynamic characteristics in high-speed angular contact ball bearing

In this paper, the formulas of elasto-hydrodynamic traction coefficients of three Chinese aviation lubricating oils, 4109, 4106 and 4050, were obtained by a great number of elasto-hydrodynamic traction tests. The nonlinear dynamics differential equations of high-speed angular contact ball bearing were built on the basis of dynamic theory of rolling bearings and solved by Gear Stiff (GSTIFF) integer algorithm with variable step. The impact of lubricant traction coeffi-cient on cage's dynamic characteristics in high-speed angular contact ball bearing was investigated, and Poincare map was used to analyze the impact of three types of aviation lubricating oils on the dynamic response of cage's mass center. And then, the period of dynamic response of cage's mass center and the slip ratio of cage were used to assess the stability of cage under various working con-ditions. The results of this paper provide the theoretical basis for the selection and application of aviation lubricating oil.     

Statistical study of electrostatic solitary waves associated with reconnection: Geotail observations

The role of waves in the dynamics of the magnetotail has long been a topic of interest in magnetospheric physics. The characteristics of Electrostatic Solitary Waves (ESWs) associated with reconnection have been studied statistically in the magnetotail by surveying the large amounts data obtained from Waveform Capture (WFC) which is an important component of Plasma Wave Instrument (PWI) on the Geotail spacecraft. About 150 reconnection events with WFC data available are selected, and approximately 10 thousands of ESW waveforms are picked up by hands for statistical study. The ESWs are observed near diffusion region and near the plasma sheet boundary layer (PSBL). Two kinds of waveforms of ESWs are observed: bi-polar and tri-polar pulses. It is found that the pulse width of the ESWs is in the order of 1–5 ms and the peak-to-peak amplitude is in the order of 0.1–5 mV/m. The amplitudes of ESWs are larger in the near-earth tail region than that in deep tail region. ESWs have been observed with or without guide magnetic field 〈By〉. The characteristics of ESWs in different reconnection region and under different strength of guild magnetic field, their possible generation mechanism will be discussed.     

微系统自唤醒技术的研究与发展

微系统技术集信息获取、处理、交换、执行以及供能等功能于一体,已广泛应用于物联网终端,而物联网终端电池续航能力限制了其在各类场景中的应用能力.将自唤醒技术——一种能量管理策略——应用于物联网终端微系统,可实现微系统低功耗休眠与唤醒状态的自动切换.对微系统的自唤醒技术进行归纳与分析,根据微系统休眠时功耗特点的不同,将自唤醒...     

辐条式高速转子轴向挠性振动特性

惯性执行机构高速转子轴向挠性振动所诱发的干扰会对高精度、高稳定度的航天器造成不利的影响。为了使这种影响尽可能地降到最低,需要研究高速转子的挠性振动模型。在转子发生轴向挠性振动的过程中,可以将转子的辐条看作是一端固定、一端有集中质量的悬臂梁。文章通过这种方法建立了辐条式转子的轴向挠性振动模型并对转子的轴向挠性振动特性进行了分析。结果表明,当外加激励的频率等于转子的固有频率时,将诱发转子产生大幅的轴向挠性振动。此外,满载精度要求较高的情况下,可以通过能量法建立转子的轴向挠性振动模型,从而提高模型的精度。     

一种易于硬件实现的CCSDS图像数据压缩算法

文章提出了一种易于硬件实现的CCSDS图像数据无损压缩算法。图像数据经过小波变换后,统计规律不尽相同。为了有效进行数据压缩,该标准针对不同的统计规律,采用不同的熵编码。针对不同的图像,讨论了直流系数（DC）量化编码和块交流系数比特深度编码中的参数k、熵编码中长度为3比特码字的编码方式参数choicel和choice3以及长度为4比特码字的编码方式参数choice2和choice4等参数的最优化选择。仿真结果表明,该算法有较低复杂度,易于硬件实现,而且能够有效优化。使输出码率最短。     

Time delay of ionospheric TEC storms to geomagnetic storms and pre-storm disturbance events in East Asia

Using the TEC data at Beijing (39.61°N, 115.89°E)/Yakutsk (62.03°N, 129.68°E) stations of East Asia regions and relevant geomagnetic data from 2010 to 2017, we have studied the time delay of ionospheric storms to geomagnetic storms and compare it with our previous results of Taoyuan (25.02°N, 121.21°E) station (Zhang et al., 2020). The data shows a well-known local time dependence of the time delay, and seasonal dependences are different at these stations. In addition, there is no correlation between the time delay and the magnetic storm intensity /solar activity, except the time delay of negative storms has weakly negative dependence on the solar activity. Comparing with the results of Taoyuan station which is located at EIA region in East Asia, we find that the time delay increases nonlinearly as the latitude decreases due to different ionospheric backgrounds at these places. Moreover, the pre-storm disturbance events are found to have similar statistical characteristics as the pre-storm enhancement in Europe middle latitudes (Bure?ová and La?tovi?ka, 2007). By subtracting the common features of the pre-storm disturbance events, we preliminarily infer that auroral activity might be main driver of the pre-storm disturbance events.     

磁悬浮斜翼节静动态特性

作为直动式电-机械转换器和二维阀本体之间的连接桥梁，反馈放大机构起着位置反馈、运动转换和推力放大的重要作用。但现有二维伺服比例阀的机械式反馈放大机构都存在摩擦磨损等非线性环节，对阀的静态特性影响明显。基于永磁悬浮技术提出一种新型的无接触式磁悬浮斜翼节，其依靠磁斥力将斜翼动子和阀芯悬浮在中位，同时实现位置反馈和运动转换功能，以彻底去除传统机械式反馈放大机构由于接触带来的摩擦磨损等因素对阀控制特性的不利影响。首先基于电磁场理论建立了磁悬浮斜翼节的数学解析模型，讨论了关键结构参数对磁力矩的影响；随后在Maxwell和Adams平台上分别对其静动态特性进行了基于有限元模拟和多体运动学分析的参数优化，在此基础上制作了实验样机，搭建实验台架研究了斜翼节的静动态特性，从而验证了其工程实用性。仿真和实验结果基本相符，3种验证的斜翼节样机中，当外接比例电磁铁推动外动子移动3 mm时，最大磁力矩可达到0.252 N·m，阶跃响应时间约120 ms。参数化设计表明减小工作气隙和增加斜翼节倾角均能提升斜翼节的磁力矩和动态响应，而在气隙中添加磁流体可提升磁力矩，但同时影响阶跃响应。研究工作对于后续磁悬浮斜翼节在二维伺服比例阀上的实际应用具有重要的参考价值。     

原始儒家道德之于历史发展的动力因——兼评陈鹏《原始儒家孝、忠、礼、德观念的变异》

读陈鹏先生《原始儒家孝、忠、礼、德观念的变异》一书,深感作者对原始儒家所重视的个人道德之于历史发展之间的因果关联深为关注,个人道德与文化存续之间并非对立存在,文化的存续是原始儒家道德的应有之义。对于君主而言,君主个人道德甚至成为影响国家兴衰与社会治乱的关键因素。于是,以儒家道德为内涵所形成的传统核心价值观对历史的发展走向产生根深蒂固的复杂影响。     

旋转蛇形通道内换热的非稳态实验

在旋转状态下,研究了涡轮内冷蛇形通道的非稳态换热特性.实验主要针对旋转状态下,通道内流量的变化和系统旋转速度的变化来进行的.结果表明:对于旋转通道的非稳态过程,换热系数的变化呈波动变化过程,且主要发生在实验参数变化的阶段.加速旋转时,角加速度力的作用会加强进气通道前缘面的换热,而降低后缘面的;减速旋转时,情况相反.而且,角加速度力的作用效果容易在旋转开始变化的时刻显现.当旋转速度在2个值之间往复时,换热系数变化呈现滞后环状,旋转速度越高滞后环越大.     

舷外有源干扰评估方法研究

根据舷外有源干扰的特点,选取引导时间、干扰功率、干扰频率对准度、电磁信号环境及干扰机的干扰样式,作为有源干扰效果的五个评价指标,使用模糊综合评估方法实现对舷外有源干扰进行评估,此评估方法综合考虑有源干扰效果的五个评价指标,提高了对舷外有源干扰评估的全面性.