基于频率选择和高仰角天线的通信盲区解决方案

针对工作实践中遇到的短波通信盲区问题,分析了盲区产生的原因,提出了两种解决盲区问题的途径,并阐述了可行性,并给出了在工程应用中通过选用较低频率和高仰角天线来解决短波通信盲区问题的具体方法,从而有效解决了模拟系统短波通信的盲区问题。     

LTE室分高倒流小区解决方案的研究

LTE室分高倒流直接影响室内4G用户的感知，同时较大程度拉低LTE网络驻留率指标。由于室内无线环境的封闭性，室分小区之间的覆盖独立性，仅仅通过参数调整的手段达到降低高倒流的效果非常不明显，因此本文针对目前影响室内用户感知的高倒流问题，从高倒流小区的标准出发，对室分高倒流小区的发现手段，产生原因及解决方案进行详尽地阐述，并针对各类型的高倒流情形提出解决方法，最终提供读者发现、分析及解决室分高倒流小区的有效方案，从而作为研究方法提供给LTE室内小区高倒流问题解决的指导意见     

Development of a highly sensitive high‐performance thin‐layer chromatography method for the screening and simultaneous determination of sofosbuvir,daclatasvir, and ledipasvir in their pure forms and their different pharmaceutical formulations

The combination of sofosbuvir and daclatasvir or sofosbuvir and ledipasvir is now widely used as an ideal treatment for hepatitis C virus infection. For this purpose, a simple, sensitive, accurate, economic, and precise high‐performance thin‐layer chromatography was developed and validated for the determination of sofosbuvir, daclatasvir, and ledipasvir in their pure form as well as their different pharmaceutical products. The method used Merck high‐performance thin‐layer chromatography aluminum plates precoated with silica gel 60 F254 as a stationary phase and mobile phase consisting of methylene chloride/methanol/ethyl acetate/ammonia (25%) (6:1:4:1, v/v/v/v). This system was found to give compact symmetric peaks of sofosbuvir, daclatasvir, and ledipasvir with retardation factors of 0.27 ± 0.01, 0.50 ± 0.007, and 0.68 ± 0.008, respectively. The densitometric scanner was set at 275 nm using a deuterium lamp. The calibration curves were linear over the range of 100–3000 ng/spot for sofosbuvir, and daclatasvir, and range of 50–3000 ng/spot for ledipasvir. The detection limits were 22.5, 31.90, and 15.80 for sofosbuvir, daclatasvir, and ledipasvir. The quantitation limits were 67.50, 95.60, and 47.50 for sofosbuvir, daclatasvir, and ledipasvir. The proposed method was validated according to International Conference on Harmonization (ICH) guidelines and the results were acceptable.     

不同变质程度煤的高分辨率透射电镜分析

利用高分辨率透射电子显微镜(HRTEM)分析了三种不同变质程度煤样的结构特征。基于傅里叶-反傅里叶变换方法,并结合Matlab、Arcgis和Auto CAD软件,通过图像分析技术,获得了HRTEM照片的晶格条纹参数。结果表明,三种煤样的晶格条纹呈现不同特征,按条纹长度分别归属于1×1-8×8共计八个类型。以3×3为临界点,在1×1和2×2中,ML-8中芳香层片的比例高于DP-4和XM-3;在3×3-8×8中,ML-8中芳香层片的比例低于DP-4和XM-3。对比HRTEM和XRD参数d002发现,随着镜质组反射率的增加d002都呈现递减趋势。     

Simulation of viscoelastic fluids in a 2D abrupt contraction by spectral element method

This study presents the vortex structure and numerical instability increase occurring when the level of elasticity is enhanced in inertial flows in planar contraction configuration for finitely extensible nonlinear elastic model by Peterlin (FENE‐P) fluid 1 . The re‐entrant corner effect on corner vortices is also considered. The calculations are performed using extended matrix logarithm formulation described in a previous paper: A. Jafari et al. A new extended matrix logarithm formulation for the simulation of viscoelastic fluids by spectral elements. Computer & Fluids 2010; 39 (9):1425–1438. In that reference, the proposed algorithm has been tested for simple geometry such as Poiseuille flow. In this study, we are interested in the capability of this algorithm for more complex geometry. This formulation helps to reach higher values of the Weissenberg number when compared with the classical one. Copyright © 2015 John Wiley & Sons, Ltd.     

High-voltage portable pulsed power supply fed by low voltage source

This article proposes a new structure of voltage multiplier for portable pulsed power applications. In this configuration, which is based on capacitor-diode voltage multiplier, the capacitors are charged by low AC input voltage and discharge through the load in series during pulse generation mode. The proposed topology is achieved by integrating of solid-state switches with conventional voltage multiplier, which can increase the low input voltage step by step and generate high-voltage high-frequency pulsed power across the load. After some discussion, simulations and experimental results are provided to verify the effectiveness of the proposed topology.     

利用高压热处理技术提高Bi-2223/Ag高温超导带材临界电流

提高临界电流密度(Jc)对促进Bi-2223/Ag高温超导带材的应用有着重要意义.在常压热处理条件下所制备的带材中存在大量的裂纹、孔洞和第二相颗粒等,这些因素都会对带材的超导连接性能产生破坏作用.我们成功建立了一套可用氧气氛的热等静压设备,工作气压和温度可同时达到15MPa和850°C.通过引入裂纹愈合热处理过程,我们成功对带材进行了高压热处理,所得样品中第二相颗粒和裂纹数量大幅度降低,77K、自场下的临界电流相比常压热处理样品提高了20%左右.     

Surface modification of pure titanium by pulsed electron beam

The microstructure, hardness and corrosion resistance of commercially pure Ti treated by low energy high current pulsed electron beam (LEHCPEB) have been investigated. The thin near-surface melted layer rapidly solidified into β and subsequently transformed into ultrafine α′ martensite. This has led to a drastic improvement of the corrosion properties and a significant increase (more than 60%) in hardness of the top surface.