Generation of mm- and Sub mm-wave Bessel Beams Using DOE’s Designed by BOR-FDTD Method and MGA

A new way for generating Bessel beams at mm and sub mm-wavelengths is presented in this paper, in which diffractive optical elements (DOE’s) are designed for converting incident Gaussian beams into Bessel beams. In order to reduce the computational burden and therefore improve the design efficiency, two measures are adopted in our design. One is a body-of-revolution finite-difference time-domain (BOR-FDTD) method that uses a two-dimensional (2-D) solution space instead of a full 3-D space and thereby saves tremendous computational resources, and that is utilized to calculate the fields diffracted by the DOE’s. The other is a microgenetic algorithm (MGA) that has been proved to be more effective than the conventional GA, and that is employed for accelerative optimization. The utility of the present design tool, which combines a MGA with a BOR-FDTD method, is demonstrated by three examples. Numerical simulation results indicate that the designed DOE’s can not only flexibly generate zero- or higher- order Bessel beams when compared with axicons, but also have higher diffraction efficiencies when compared with amplitude holograms. An erratum to this article can be found at     

Nitrogen‐Doped Graphene Ribbon Assembled Core–Sheath MnO@Graphene Scrolls as Hierarchically Ordered 3D Porous Electrodes for Fast and Durable Lithium Storage

Graphene scroll is an emerging 1D tubular form of graphitic carbon that has potential applications in electrochemical energy storage. However, it still remains a challenge to composite graphene scrolls with other nanomaterials for building advanced electrode configuration with fast and durable lithium storage properties. Here, a transition‐metal‐oxide‐based hierarchically ordered 3D porous electrode is designed based on assembling 1D core–sheath MnO@N‐doped graphene scrolls with 2D N‐doped graphene ribbons. In the resulting architecture, porous MnO nanowires confined in tubular graphene scrolls are mechanically isolated but electronically well‐connected, while the interwoven graphene ribbons offer continuous conductive paths for electron transfer in all directions. Moreover, the elastic graphene scrolls together with enough internal voids are able to accommodate the volume expansion of the enclosed MnO. Because of these merits, the as‐built electrode manifests ultrahigh rate capability (349 mAh g^?1 at 8.0 A g^?1; 205 mAh g^?1 at 15.0 A g^?1) and robust cycling stability (812 mAh g^?1 remaining after 1000 cycles at 2.0 A g^?1) and is the most efficient MnO‐based anode ever reported for lithium‐ion batteries. This unique multidimensional and hierarchically ordered structure design is believed to hold great potential in generalizable synthesis of graphene scrolls composited with oxide nanowires for mutifuctional energy storage.     

基于超声波传感器的可压缩式垃圾箱检测系统分析

随着我国城市化的快速发展,创造和谐美好的城市环境越来越重要,公共场所垃圾箱容量有限,导致其周围环境既不美观,又容易滋生细菌的问题越来越显现。文章提出的垃圾箱控制系统围绕压缩垃圾的关键技术问题重点展开工程化技术研究。经过实验证明,本系统可以通过微信小程序智能检测垃圾箱中的垃圾容量,进行自动压缩,有效解决垃圾存放超时或放置过量垃圾并无人清理的情况,具有较强的实用性。     

XDSL信号测试专用虚拟频谱仪的设计

功率谱密度是通信信号非常重要的参数，所以在通信的各个阶段都需要对功率谱密度进行测量。在接入网产品的开发中，有多个产品要同时进行开发，因此需要多台频谱分析仪。然而，频谱分析仪属于贵重仪器，配备多台频谱分析仪将导致开发成本增加。虚拟仪器的出现解决了这一问题。这里给出了XDSL接入产品测试专用的虚拟频谱分析仪设计的方法，实践表明，它具有功能齐全价格低廉的优势，作为传统频谱分析仪的替代，虚拟频谱分析仪能够极大的降低仪器的投资。     

南宁市防洪堤防洪效益估算办法

在分析计算南宁市历次致灾洪水水位与淹没范围，淹没范围与经济损失之间的相关关系后，建立以物价增长指数和当地经济增长率为参数的合轴相关图表，若未来再遇致灾洪水，即可从曲线上读得致灾洪水造成的经济损失，供今后统计当年实际防洪效益参考     

一种新颖的晶闸管串联均压的检验方法

为了改善由串联不均压引起的晶闸管失效问题,从晶闸管的选配和测试原理出发,详细分析了通态电流和器件温度等因素对串联选配的影响.提出了一种新颖的晶闸管串联均压的检验方法,并搭建了一个可以在一个周期中实现双电流测试,且温度可控的实验平台.该平台还具有人机互动功能,可以快速实现数据的采集和分析,方便了测试人员的操作,并大大提高了工作效率.经过现场满功率和未开满功率运行测试,均压系数与实验平台测试结果相似,验证了该方法的可靠性.该检验方法已应用于晶闸管中频电源选配中.     

电能计量器具质量监督自动预警系统的建立

本文在大量调研智能电能表业务数据的基础上,基于大数据技术,设计了一套电能计量器具质量监督自动预警系统.系统可根据电能计量器具采集的相关数据生成辅助决策,并以多种方式实时展现决策结果与预警信息,实现对电能计量器具质量监督和管控.本文重点对该系统架构、硬件部署、建设重点进行了研究,对电能计量器具质量提升有着一定意义.     

材料科学中的高分辨电子显微学—发展历史、现状与展望

本文综述了材料科学中的高分辨电子显微学发展历史、现状与展望。重点讨论了在高分辨电子显微学中能直接观察物质中原子排列的直接成像法 ,能区分原子种类的选择成像法、能量过滤选择成像法和 Z-衬度像 ,能研究物质结构变化动态过程的分辨时间高分辨电子显微学 ,能定量地分析物质结构的定量高分辨电子显微学和遥控电子显微术的发展以及其在材料科学中的应用和展望     

BOARD-LEVEL BUILT-IN SELF-REPAIR METHOD OF RAM

This paper describes the method of built-in self-repairing of RAM on board,designs hardware circuit,and logic for the RAM's faults self-repairing system based on FPGA.The key technology is that it util...     

驻极体空气过滤材料消静电实验研究

选取4片不同级别的驻极体空气过滤材料,对滤料消除静电效应前后的计数效率和PM2.5净化效率等性能参数进行了试验研究,消静电方法采用的是异丙醇浸泡法,试验用气溶胶为KCl固态气溶胶。试验结果表明:采用异丙醇浸泡法能够在一定程度上消除驻极体过滤材料本身所带的静电;消除静电效应后滤料对不同粒径颗粒的计数效率均有所下降,特别是颗粒物粒径越小,过滤效率下降的幅度也越大;消静电后滤料对PM2.5的净化效率也有所下降。研究结果揭示了采用驻极体过滤材料制造而成的带静电过滤器在实际使用过程中可能存在的因静电消失后带来的效率下降风险,试验数据也能为将来空气过滤器国家相关标准的修订提供参考建议。