Effects of the radial force on the static contact properties and sealing performance of a radial lip seal

The radial force is a critical factor to determine the sealing performance of radial lip seals.The effects of radial force produced by garter spring and interference on the static contact properties and sealing performance of a radial lip seal are investigated by numerical simulations and experiments.Finite-element analysis and mixed elastohydrodynamic lubrication simulation are used.Radial force,contact width,temperature in the sealing zone,the reverse pumping rate and friction torque are measured.A critical value of interference for a cost-effectively designed radial lip seal is found.Spring force is required to compensate the decrease of the radial force because of the interference and used as a possible way to obtain intelligent control of sealing performance.The quantitative results gotten in this study could provide guide for the seal design and improvement.     

神经网络控制算法在工控软件Lookout中的应用

提出基于MATLAB平台设计的神经网络控制算法,通过使用COM Builder将MATLAB开发的神经算法程序做成COM组件,直接由Visual Basic(VB)调用,并在VB中编制成ActiveX控件,然后在Lookout中调用,实现实时控制.     

基于耦合场分析的电磁振动料斗的动态设计

对电磁振动料斗进行参数化有限元建模,运用有限元分析软件ANSYS对该模型进行动态分析,计算出振动料斗的固有频率和振型、电磁铁吸力、谐响应振幅等,通过电磁场和机械结构的顺序耦合分析,得到最佳的料斗参数。实际应用效果表明,有效缩短了电磁振动料斗的设计和调试周期。     

Concept of the solar ring mission: An overview

The concept of the Solar Ring mission was gradually formed from L5/L4 mission concept, and the proposal of its pre-phase study was funded by the National Natural Science Foundation of China in November 2018 and then by the Strategic Priority Program of Chinese Academy of Sciences in space sciences in May 2019. Solar Ring mission will be the first attempt to routinely monitor and study the Sun and inner heliosphere from a full 360-degree perspective in the ecliptic plane. The current preliminary design of the Solar Ring mission is to deploy six spacecraft, grouped in three pairs, on a sub-AU orbit around the Sun. The two spacecraft in each group are separated by about 30° and every two groups by about 120°. This configuration with necessary science payloads will allow us to establish three unprecedented capabilities: (1) determine the photospheric vector magnetic field with unambiguity, (2) provide 360-degree maps of the Sun and the inner heliosphere routinely, and (3) resolve the solar wind structures at multiple scales and multiple longitudes. With these capabilities, the Solar Ring mission aims to address the origin of solar cycle, the origin of solar eruptions, the origin of solar wind structures and the origin of severe space weather events. The successful accomplishment of the mission will advance our understanding of the star and the space environment that hold our life and enhance our capability of expanding the next new territory of human.

     

离子注入机中行星传动扫描靶的设计

将行星传动机构应用于离子注入机中,使得受注物体受注均匀,明显提高了产品的表面质量。     

改进滑模模型参考自适应的PMSM无传感控制

针对MRAS（模型参考自适应）观测器对PMSM（永磁同步电机）参数变化和外部干扰敏感的缺点,设计了一种用于PMSM无传感控制的软开关滑模模型参考自适应观测器。该观测器将滑模控制与MRAS相结合,并构造了边界层可变的正弦饱和函数,以抑制由于滑模控制引起的系统抖动,增强系统鲁棒性。同时引入sigmoid函数,以提高滑模软切换速度控制器的稳定性。实验仿真结果表明,软开关滑模模型参考自适应控制不仅可以实现边界层内的快速收敛、弱化抖动,而且跟踪能力强。     

Effects of proton radiation on field limiting ring edge terminations in 4H–SiC junction barrier Schottky diodes

In this study, the effects of high-energy proton radiation on the effectiveness of edge terminations using field limiting rings(FLRs) in 4 H–SiC junction barrier Schottky(JBS) diodes were examined in detail. The devices were irradiated using 5-MeV protons at fluences ranging from 5×10~(12) cm~(-2) to 5×10~(14) cm~(-2). Further, the reverse breakdown performances of the investigated devices were measured both before and after irradiation. Proton irradiation initially decreased the breakdown voltage(BV);subsequently, the BV was increased as the proton fluence increased. At a fluence of 5×10~(13) cm~(-2), the BV was reduced by approximately 18%, whereas it was reduced by approximately 5% at a higher proton fluence of 5×10~(14) cm~(-2). The related degradation mechanism that was associated with this phenomenon was also investigated using the numerical simulations of the current-voltage(I-V) and capacitance-voltage(C-V) characteristics of the device. The main contribution to the radiation-induced changes in BV originates from the variations of charge distribution at the SiO_2/4 H–SiC interface and the reduction of the net carrier density in the drift region. Both the aforementioned variations affect the spread of the electric field in the FLR edge termination regions.     

Unsupervised droplet identification during the pulsed laser enhanced GMAW process

Pulsed laser-enhanced gas metal arc welding (GMAW) is an innovative arc welding process developed recently at the University of Kentucky. It uses the recoil pressure force generated by a pulsed laser to provide an additional force to reduce the needed electromagnetic detaching force (which is produced by the current) to assure the detachment of the droplet and the arc stability. The reduction in the current needed to detach droplets and maintain the arc stability improves the controllability of the most widely used arc welding process—GMAW—and its application range. To accurately control the detachment of the droplets, the force generated by the pulsed laser needs to be computed. Since this force is proportional to the distance from the center of the droplet to the welding wire, the problem can thus be changed to compute the distance between the droplet and the wire. To compute this distance, image processing method is the most effective way. Hence, different well-known image processing algorithms are implemented to address this problem and their performances are evaluated in this paper. Considering the robustness, processing speed, and automation, none of the evaluated image processing methods produce an acceptable result. To solve this specific problem, a novel image processing method is proposed. It is unsupervised and fast. Experimental results indicate that this proposed method can also achieve adequate computation accuracy.     

黄酮类化合物抗肿瘤活性的构效关系研究

应用分子力学MM 和半经验量子化学AM1法对18种黄酮类化合物进行了几何优化,并计算了各化合物的电子结构,根据其电子结构,结合它们在体外抑制60-Cellline人体肿瘤细胞的活性数据(IC50)进行讨论,得出了黄酮类化合物抗肿瘤活性的定量构效关系。结果表明：B环和C环对黄酮类化合物抗肿瘤活性影响大;且B环负电性越高,活性越强,而C环正电性越高,活性越强。     

毫米波LFMCW雷达加速运动目标回波检测与加速度-速度估计

在毫米波线性调频连续波（LFMCW）雷达中,目标加速度存在使回波多普勒信号受到二次项调制,造成多普勒频谱畸变,从而导致目标检测性能下降和参数估计精度损失．采用最大似然模型进行加速运动目标检测和加速度-速度估计,提出了适合在一般高斯噪声环境中（包括色噪声）该模型的速度-加速度联合估计快速算法．另外也推导出了一般高斯环境下Chirp信号参数估计的CRB界,为一般高斯环境下Chirp信号参数的方差提供了实际下界．