基于异常反射型超表面的天线反射面设计

在实际应用中有许多场合需要对电磁波的传播进行人工调控, 传统的光学器件或者人工电磁介质都是采用三维结构, 但传统的三维结构介质很难与其他器件或设备进行集成.利用相位非连续人工电磁表面则可以在传播路径的介质分界面上引入相位突变, 进而实现人工调控电磁波.文章在此基础上在微波波段利用构造分界面相位梯度提出了一种异常反射型超表面的设计, 用作天线反射面可将圆极化波高效地转化为交叉极化波, 为微波段的电磁波人工调控提供了新的手段.根据广义反射定律及斜入射时相位突变修正设计的天线反射面, 在X波段可以实现对入射电磁波的人工调控, 并通过仿真分析验证了该设计方法的准确性, 为人工电磁表面作为天线反射面提供了一种设计思路.     

疫情下高职“计算机信息技术”课程的教学探讨

新冠疫情的突如其来改变了人们很多原先的生活节奏,学校里的师生同样面临此困境。文章以高职教学中的基础课“计算机信息技术”为例,指出了线上教学时所面临的一些问题,并给出了一些解决的方法,论述了笔者在线上教学中所实施的教学步骤,力争做到线上线下教学效果的同质等效。     

群集技术在广州电视台综合信息平台中的运用

本文主要介绍了群集技术的概念以及在广州电视台综合信息平台中的实际运用，并介绍了每一个群集具体的实施过程和在实际运用中产生的功能和优点。     

小灵通:趋势、思考与建议

在中国,以PHS为基础的小灵通在多种因素的共同作用下获得了飞速发展。然而．小灵通自身的技术缺陷与3G时代的到来,使其进一步发展充满较大的不确定性,通过分析小灵通的发展趋势．对小灵通现象进行了深入思考,并对其未来发展提出了可行建议。     

基于邻域平均和正交分解的双通道SAR图像域慢动目标检测方法

慢动目标检测是利用合成孔径雷达(Synthetic Aperture Radar, SAR)实现空间对地观测应用的一个主要方面,具有广泛的应用背景和重要的学术价值。为了构建检测率高、实用性强的双通道SAR地面慢动目标检测过程,本文提出了一种基于邻域平均和协方差矩阵正交分解的检测算法。该算法在对特征值分解量进行修正的基础上,通过获取采样协方差矩阵与杂波协方差矩阵正交的分量,以此构造出有效的动目标检测量,结合采样协方差矩阵的邻域平均处理,实现慢动目标的精确检测。相比常规的DPCA(Displaced Phase Center Antenna)技术,该算法具有杂波抑制能力强、旁瓣抑制能力好、检测门限设定简单、检测率高、虚警率低等特点,仿真结果证明了该算法的有效性。     

DVB-S接收系统中包同步机制的分析与实现

本文对DVB-S接收系统中包同步搜索机制的进行了深入细致的研究，分析了相关参数对搜索性能的影响，并给出一种高效且节省资源的实现结构。     

Enhanced On–Off Ratio Photodetectors Based on Lead‐Free Cs3Bi2I9 Single Crystal Thin Films

Hybrid organic–inorganic lead halide perovskite single crystal thin film (SCTF) recently has attracted enormous interest in the field of optoelectronic devices, since it efficiently resolves the trade‐off between thickness and carrier diffusion length. However, the toxicity of lead element and the instability induced by organic component still hinder its future developments. In this work, lead‐free all‐inorganic Cs₃Bi₂I₉ SCTF with a high orientation along (00h) has been in situ grown on indium tin oxide (ITO) glass via a space‐limited solvent evaporation crystallization method. The trap density of Cs₃Bi₂I₉ SCTF (5.7 × 10¹² cm^?3) is 263 folds lower than that of the polycrystalline thin film (PCTF) counterpart, together with a 5‐order‐of‐magnitude higher carrier mobility. These superior charge transfer properties enable a photoresponse on–off ratio as high as 11 000, which far surpasses that of the PCTF device by 460 folds, comparable to the lead halide perovskite. Furthermore, the Cs₃Bi₂I₉ SCTF photodetector exhibits outstanding stability even without any encapsulation, whose initial performance is well maintained after aging 1000 h in humid air of 50% RH or continuous on–off light illumination for 20 h. This work will pave the way to produce new families of high‐performance, stable, and nontoxic perovskite SCTF for future optoelectronic applications.     

一种针对AVS去块滤波的高性能结构

在AVS视频解码器设计中,环路去块滤波成为实时处理的瓶颈之一。该文提出了一种实用的环路滤波结构,处理一个宏块只需要164个周期。使用新颖的滤波顺序,待滤波数据缓冲从1616宏块大小降低为168半宏块大小。使用数据重用策略, 滤波中间数据的存储空间大大减小。实验表明,使用0.18m CMOS工艺,在50MHz下综合,该文提出的设计只需要9.2k门。工作在50MHz频率下,该文提出的设计能够支持高清视频解码的实时滤波处理。     

基于证据理论的雷达辐射源特征权重提取

为了更加准确、合理地提取雷达辐射源载频、重复频率、脉宽等特征参数的权重,文章提出一种新算法,根据侦测数据的可信度、识别库参数的自身特征分别给出基本概率赋值,再从决策层给出不同融合系数结合D—s证据理论来提取特征权重。最后举例说明了该算法的演算过程。     

Thermal-Electromagnetic Analysis for 14 kA Fast Discharge of a Model Coil

A model coil for 40-T hybrid magnet superconducting outsert magnet has been constructed and tested at the High Magnetic Field Laboratory, Chinese Academy of Sciences. The model coil was wound with Nb₃Sn cable-in-conduit conductor (CICC) cabled in a 316LN jacket cooled with supercritical helium. The model coil alone can produce about 4 T maximum magnetic field with an operating current of 14 kA. The model coil, in combination with 7.57-T NbTi background coil, can produce 11.5 T central field at 14 kA. During the test campaigns, a fast discharge was triggered by a dump resistor of 3.6 mΩ to evaluate the thermal-electromagnetic behavior of the model coil. In order to avoid a quench of the background coil, no current was exerted on the background coil through a power supply during the fast discharge of the model coil. The test results show that the central magnetic field is not scaled proportionally to the current decay of the model coil. The circuit model gives excellent results compared with the measured ones for the central magnetic field evolution as a function of time in this paper. For the thermal-hydraulic behavior during the fast discharge, the maximum temperature at the inlet simulated by the 1-D Gandalf code gives excellent agreement results compared with the measured ones with the conductor coupling time constant of 63 ms.