强电磁场真空击穿中的电子束轰击初步研究

当前,抑制强电磁场真空击穿的方法主要是结构改进和工艺处理,对于提高材料耐电子轰击性能来抑制击穿的研究相对较少。文章主要结合Monte-Carlo方法和Bethe能量损失规律,研究了兆电子伏级能量的电子垂直入射金属靶材的能量损失规律。研究表明,材料原子序数和原子密度越小,电子在材料中的有效射程越长,单位体积内沉积的平均能量越低,从而越有利于材料耐受电子束轰击。在此基础上,通过试验比较了铜、不锈钢和钛三种材料耐电子束轰击的性能,在相同的电子束能量下,铜由于密度最高而最容易受到电子束轰击破坏,密度最低的钛材料具有最好的耐电子束轰击性能。进一步的高功率微波（HighPowerMicrowave）试验证实,相对于不锈钢材料,在2.8GW输出微波功率水平下,使用耐电子轰击性能更优的钛材料能够将输出微波脉宽由18ns增加到27ns,由强电磁场真空击穿引起的脉冲缩短明显得到有效抑制。     

气相沉积技术的现状与发展

本文阐述了气相沉积技术的发展和应用,概括了此技术在我国的现状,分析并展望其未来的发展,还注意到了研究领域中的动向和趋势。     

A real-time ionospheric model based on GNSS Precise Point Positioning

This paper proposes a method of real-time monitoring and modeling the ionospheric Total Electron Content (TEC) by Precise Point Positioning (PPP). Firstly, the ionospheric TEC and receiver’s Differential Code Biases (DCB) are estimated with the undifferenced raw observation in real-time, then the ionospheric TEC model is established based on the Single Layer Model (SLM) assumption and the recovered ionospheric TEC. In this study, phase observations with high precision are directly used instead of phase smoothed code observations. In addition, the DCB estimation is separated from the establishment of the ionospheric model which will limit the impacts of the SLM assumption impacts. The ionospheric model is established at every epoch for real time application. The method is validated with three different GNSS networks on a local, regional, and global basis. The results show that the method is feasible and effective, the real-time ionosphere and DCB results are very consistent with the IGS final products, with a bias of 1–2 TECU and 0.4 ns respectively.     

Ionospheric TEC prediction using hybrid method based on ensemble empirical mode decomposition (EEMD) and long short-term memory (LSTM) deep learning model over India

Total electron data (TEC) from GPS nowadays can be used as a tool for understanding the space weather phenomena. The development of prediction model for TEC is quiet crucial and challenging due to the dynamic behavior of the ionosphere, since it depends on different factors such as seasonal, diurnal and spatial variations, solar geomagnetic conditions etc. In this paper, an attempt is made for predicting the GPS derived TEC values for different GNSS stations over India using a hybrid method based on Ensemble empirical mode decomposition (EEMD) and Long Short-Term Memory (LSTM) deep learning method. The daily TEC time series data from the IISc Bangalore (Latitude 13.021, Longitude 77.570), Lucknow (Latitude 26.912, Longitude 80.956) and Hyderabad (Latitude 17.417, Longitude 78.551) stations over India during the period 2008 to 2015 of solar cycle 23 and 24 is used for analysis. The assessment of model performance for testing predicted output compared with LSTM and EMD-LSTM models, and their comparison results show that the hybrid EEMD-LSTM model presents better than the other models.     

The N4,5 - OO Auger and “N3” N4,5O2,3 Coster-Kronig spectra of xenon induced by electron impact

The N_4,5OO Auger electron spectrum in the kinetic energy region (14–37) eV has been measured with high resolution at electron incident energies between 71 eV and 2019 eV. The Auger and satellite lines are assigned by comparison with previous literature data. Several states which correspond to the resonant Auger transitions from the 4d_{3/2, 5/2} 6p states are observed. The PCI effects on the N₅-O_2,3O_2,3(¹S₀) Auger peak when the incident electron energy approaches to the N₅ edge (67.55 eV) is investigated and it is found that the dependence of the energy shift on the excess energy, E_exc, is well represented by the function E_exc^β with β = (-1.40 ± 0.05). The ^“N₃^” N_4,5O_2,3 Coster-Kronig spectrum is measured at various electron incident energies. The assignments of the features are made in comparison with a similar spectrum from synchrotron radiation measured by Kivimäki et al. [J. Electron Spectrosc. Relat. Phenom. 1999, 101–103, 43–47]. The Auger spectrum in the kinetic energy regions (68–78) eV and (90–138) eV is observed for the first time in an electron impact experiment and a comparison is made with the photoionization experiment by Hikosaka et al. [Phys. Rev. A 2007, 76, 032708].     

A novel method of utilizing static mixer to obtain mixing homogeneity of multi-species powders in laser metal deposition

Real-time mixing of multi-species powder challenges Laser Metal Deposition (LMD) of Functionally Graded Materials (FGMs). The current work proposes a novel method of using a static mixer to realize rapid, uniform multi-species powder mixing. Firstly, copper powder and 316L stainless steel powder are selected to complete the powder mixing observation experiment with Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS). Secondly, computational fluid dynamics and particle mixing simulation models are used to analyze the flow field and particle motion characteristics in the static mixer. Finally, LMD experiment and metallographic observation are carried out with 316L stainless steel powder and WC powder to verify the feasibility of the static mixer. This study provides a theoretical and practical basis for powder mixing in laser processing with a static mixer. The conclusions can also be applied to other processing fields requiring real-time and uniform mixing of multi-species powders.     

热障涂层的研究进展

主要介绍了热障涂层在现阶段的研究和应用，以及它们的组成和性能。讨论了热障涂层现有的三种涂层制备工艺和寿命预测模型，并对等离子喷涂和电子束物理气相沉积作了详细的对比，同时指出了热障涂层未来的研究方向。     

基于环境试验的某发动机舰面清洗时机影响分析

提出了一种基于环境试验的发动机舰面清洗时机研究方法。首先，通过海洋大气暴露试验，模拟某发动机部件典型材料在北方某海域服役的实际情况，并获取其盐沉积量与点蚀的变化规律，初步分析了这2个关键因素对于确定发动机舰面清洗时机的影响；然后，通过对比分析南方某海域与北方某海域的环境差异，综合给出某发动机在不同海域服役时舰面清洗时机的初步建议。     

利用低轨道卫星间微波信号探测反演温湿廓线

通过同时测量微波信号的折射和吸收信息，低地球轨道卫星间（LEO-LEO）微波掩星探测技术能够独立反演温度和水汽廓线。通过仿真手段，首先，正演模拟了微波信号穿过大气层后由折射和吸收效应分别导致的相位延迟和振幅衰减，在此基础上，对温度、水汽和云中液态水反演廓线进行了个例分析，然后，统计分析了温度和水汽在不同纬度带的反演性能，以及云对反演精度的影响。结果表明：温度在约35 km以上存在明显正偏差，高纬度的最大，中纬度次之，低纬度最小。水汽反演误差在约4 km以下明显增大，低纬度的最大，中纬度次之，高纬度最小。有云存在时，需要去除云的吸收作用，否则温度和水汽会出现明显的正偏差。上述研究为进一步发展LEO-LEO掩星探测计划提供了理论参考依据。     

Parylene C薄膜微波电路的应用可行性研究

针对三防材料在微波电路中多余物防控方面的可行性、可靠性问题,提出在产品表面用真空化学气相沉积法镀Parylene C薄膜,结果表明该膜层可有效控制直径d小于1 mm的可动多余物,提高微波产品PIND(颗粒碰撞粒子检测)测试的合格率.同时与焊接、胶粘、互联、清洗等配装工艺有良好的适配性,且满足可靠性要求.该薄膜较高的绝缘...