Prospects of using a permanent magnetic end effector to despin and detumble an uncooperative target

Space debris, such as defunct satellites and upper stages of rockets, becomes an uncooperative target after losing its attitude control and communication ability. In addition, tumbling motion can occur due to environmental perturbations and residual angular momentum prior to the object’s end-of-mission. To minimize the collision risk during docking and capturing of the tumbling target, a non-contact method based on the eddy current effect is put forward to transmit the control torque to the tumbling target. The main idea is to induce a controllable torque on the conducting surface of the tumbling target using a rotational magnetic field generated by a Halbach rotor. The radial and axial Halbach rotors are used to damp the spinning and nutation motions of the target, respectively. The normal and tangential force are evaluated concerning the relative pose between the chaser and the target. A simplified dynamic model of the nutation damping and despinning processes is developed and the influences of the asymmetrical principal moments of inertia and transverse angular velocity are discussed. The numerical simulation results show that the designed Halbach rotor stabilized the target attitude within an acceptable time. The electromagnetic nutation damping and despinning method provides new solutions for the development of on-orbit capture technology.     

Relationship of the diffuse aurora and SAR arc dynamics to substorms and storms

Investigation results of a diffuse aurora (DA) and stable auroral red (SAR) arc dynamics based on spectrophotometric observations at the Yakutsk meridian (199°E geomagnetic longitude) are presented. The relationship of an equatorward extension of DA in the 557.7 nm emission to a substorm growth phase during the magnetospheric convection intensification after the turn of IMF B_Z to the south is shown. The formation of SAR arc during the substorm expansion phase is investigated. The association of SAR arc dynamics with the development of asymmetric ring current (substorm injection) during the main phase of a storm is analyzed. It is shown how the pulsating precipitations of energetic ring current particles develop in the outer plasmasphere based on photometric observations.     

电源自动测试系统述评

综述了电源自动测试系统的测试原理、测试方法和测试依据，分析了电源自动测试系统的特点、现状和发展趋势。     

大功率LED混光照明恒流驱动电路的设计

在分析了大功率LED混光照明中LED光源特性的基础上,提出了三色LED恒流驱动电路的设计方案。驱动电路分别采用升压和降压拓扑结构,利用具有PWM实时调光功能的RT8452作为驱动控制芯片,通过改变外接PWM占空比即可调节LED亮度。实验证明,此驱动电路工作可靠,效率高,实现简单。     

A solar wind driven model of geosynchronous plasma moments

We describe a tabular specification model of the density and temperature of ions and electrons at geosynchronous orbit as a function of magnetic local time and solar wind parameters. This model can be used to provide boundary conditions for numerical ring current models. Unlike previous specification models of geosynchronous plasma moments, this model is parameterized by upstream solar wind conditions. We find that solar wind parameters are a better predictor of geosynchronous ion density than magnetospheric indices, and as upstream parameters they are often more appropriate as model inputs since they causally precede the model outputs. Of the upstream parameters that were tested, the best predictors of geosynchronous conditions were the solar wind flow pressure and the magnitude and Z-component of the interplanetary magnetic field.     

某刹车装置的活塞组件衬套裂纹机理探究

某刹车装置耐久性试验中,活塞组件的衬套出现疲劳裂纹,经分析是由于汽缸座和刹车壳体外翘,活塞在与刹车盘间的摩擦力作用下对衬套外端产生交变挤压所致,试验验证结果成立,证明产品刚性影响构件的疲劳寿命。     

高温下直流电位法测量裂纹长度的应用

介绍了直流电位法测量疲劳裂纹长度方法的基本原理、实现方法、及所需配置的仪器,并对有关影响因素作了分析.该测量系统主要用于在高温下测量各种材料在恒幅载荷下的疲劳裂纹扩展和门槛值试验中的疲劳裂纹长度,可以提高测量疲劳裂纹长度的自动化水平.     

Modeling of the Magnetospheric Response to the Dynamic Solar Wind

We discuss quasi-static and dynamic models of the magnetotail response to perturbations imposed by the solar wind, focusing particularly on the formation of thin current sheets, their structure and breakup.     

钛合金导管的涡流检测

通过对大批量的钛合金管材进行涡流检测,从涡流检测原理以及影响因素等方面分析了缺陷信号、噪声信号的产生以及差异,通过多次调试试验得到了各种规格管材的检测参数,其中对检测结果影响比较大的频率、增益进行了多次对比试验,得到了最佳参数范围,为管材的可靠性判断提供了依据.     

基于直流换向方法的电阻测量技术

随着现代制造业的飞速发展,电子元器件的体积将变得越来越小,于是测试功率受到了很大的限制,都需要降低测试电流,这就对系统测试小电压信号时的噪声抑制能力提出了极大的挑战,本文在经典偏置补偿测量电阻方法的基础上,介绍了基于直流电流换向方法的电阻测量技术,并对这两种方法进行了比较,得出基于直流电流换向方法在抑制噪声能力上的优越性。