基于DRFM的合成孔径雷达干扰技术研究

本文首先对SAR成像原理进行简要介绍，在分析对SAR干扰的重要性和干扰的难点所在的基础上，提出了利用DRFM对SAR的点目标和分布式目标进行干扰，并在理论推导的基础上进行了仿真实验。仿真结果证明该方法能有效破坏SAR的成像效果。     

High-performance 94-GHz single balanced mixer using 70-nm MHEMTs and surface micromachined technology

We reported 94-GHz, low conversion loss, and high isolation single balanced active gate mixer based on 70-nm gate length InGaAs/InAlAs metamorphic high-electron mobility transistors (MHEMTs). This mixer showed that the conversion loss and isolation characteristics were 2.5/spl sim/3.5 dB and under -29 dB in the range of 92.95/spl sim/94.5 GHz, respectively. The low conversion loss of the mixer is mainly attributed to the high-performance of the MHEMTs exhibiting a maximum drain current density of 607 mA/mm, an extrinsic transconductance of 1015 mS/mm, a current gain cutoff frequency (f/sub t/) of 330 GHz, and a maximum oscillation frequency (f/sub max/) of 425 GHz. High isolation characteristics are due to hybrid ring coupler which adopted dielectric-supported air-gapped microstrip line structure using surface micromachined technology. To our knowledge, these results are the best performance demonstrated from 94 GHz single balanced mixer utilizing GaAs-based HEMTs in terms of conversion loss as well as isolation characteristics.     

电导调制型功率器件用穿通结构的基区优化理论

通过对临界击穿电场近似得出的穿通限制击穿电压的分析 ,提出了电导调制型功率器件用穿通结构的基区优化设计解析理论 :对于电导调制功率器件用的各种穿通结构 ,只要其耐压基区的厚度选择为同衬底浓度突变结击穿时的耗尽层宽度的最佳分割长度 ,即穿通因数 F等于4,就可使外延基区的厚度为最小 .同时 ,该耐压基区的击穿电压为最大 .运用该理论的结果 ,得出了此类应用的基区优化设计公式 ,并将计算结果与一些文献的设计值进行了比较 ,纠正了先前计算的不准确性 .     

高斜率效率隧道结叠层激光器的研制

隧道结叠层激光器技术具有广泛的应用空间,如高斜率效率、高功率密度、多波长激光器等。采用LP-MOCVD系统生长隧道结材料,CCl4作为p型掺杂源,SiH4作为n型掺杂源,并采用δ掺杂技术,使得n+-GaAs的掺杂浓度大于1×1019/cm3,隧道结的面电阻率小于2×10-4Ω.cm2。设计生长了双叠层、三叠层材料,该材料制作的900nm双叠层激光器在200ns脉宽、20A工作电流下输出功率35W,斜率效率1.8W/A,是单层材料的1.8倍,隧穿结引入的压降约为0.15V;860nm三叠层激光器的斜率效率大于2.7W/A,是单层材料的2.7倍。     

折射式扫描系统设计及应用

分析异形微孔激光加工的现状,开展了折射式扫描系统的设计和应用研究。利用振镜电机快速改变折射式光学元件组相对激光束光轴的角度,从而精确控制激光聚焦光斑在加工面上的微小位移值。这种加工方式既保留了振镜扫描定位速度快,加工轨迹控制简便,可以实现各种异形孔加工的优势;又通过折射式光学元件组将传统反射式振镜扫描系统的几十毫米的加工范围精确缩微至几百微米,这种百倍级的光学缩微系统大幅度降低了高速振镜电机的角度分辨率、热漂移、零点漂移带来的影响,从而保证了激光加工的高精度定位和重复性。     

双目立体视频最小可辨失真模型及其在质量评价中的应用

该文针对目前最小可辨失真(JND)模型只能应用于评价单视点视频的问题,探索一种以双眼亮度关系为基本出发点的双目立体视频的JND模型。首先根据立体视频特性引入双眼亮度关系模型,然后考虑了背景亮度掩盖、纹理掩盖、帧间掩盖、空间时间对比灵敏度、眼睛运动等因素,提出了双目JND模型,最后将该双目JND模型应用到立体视频质量评价方法中。实验结果表明该文提出的质量评价方法符合人类的视觉感知特性,更接近于主观测试结果。     

基于移动网数据的城市交通分析研究

传统的智慧交通数据采集方式,包括交通调查、定点监测、摄像机摄像等,技术成熟且精度较高,然而其缺点也非常明显,采集范围小、成本高、施工周期长。而电信行业的大数据具有实时性强、数据量大、覆盖人群广、成本低廉、信息丰富等特点,可为城际交通和市内交通提供丰富的数据支持。基于移动网用户侧计费账单、计费详单以及XDR数据,给出了典型交通应用场景下的分析方法及应用案例。     

A Systematic Approach to Achieving High Performance Hybrid Lighting Phosphors with Excellent Thermal‐ and Photostability

The authors have designed and synthesized a family of high‐performance inorganic–organic hybrid phosphor materials composed of extended and robust networks of one, two, and three dimensions. Following a bottom‐up solution‐based synthetic approach, these structures are constructed by connecting highly emissive Cu₄I₄ cubic clusters via carefully selected ligands that form strong Cu? N bonds. They emit intensive yellow‐orange light with high luminescence quantum efficiency, coupled with large Stokes shift, which greatly reduces self‐absorption. They also demonstrate exceptionally high framework‐ and photostability, comparable to those of commercial phosphors. The high stabilities are the result of significantly enhanced Cu? N bonds, as confirmed by the density functional theory (DFT) binding energy and electron density calculations. Possible emission mechanisms are analyzed based on the results of theoretical calculations and optical experiments. Two‐component white phosphors obtained by blending blue and yellow emitters reach an internal quantum yield as high as 82% and correlated color temperature as low as 2534 K. The performance level of this subfamily exceeds all other types of Cu–I based hybrid systems. The combined advantages make them excellent candidates as alternative rare‐earth element‐free phosphors for possible use in energy‐efficient lighting devices.     

一种新的视点间预测结构

多视点视频编码除应具有较高的编码效率外,还应该包括后向兼容性、时间随机访问和视点可分级性等,这些都主要取决于所采用的预测结构。目前所提供的多视点视频编码(Joint Multi-view Video Coding, JMVC)采用固定的视点间预测结构,难以适应复杂情况的多视点视频编码。该文综合考虑编码效率和用户随机访问等因素,根据多视点视频相关性分析自适应调整视点间预测结构,以获得较好的编码综合性能。试验结果表明,与JMVC相比,该文的方法在提高编码效率的同时,有较好的随机访问性能。     

基于IPv6的资产管理系统概要设计与实现

IPv6具备海量的地址空间,地址生成随机性强,对IPv6网络空间中的资产进行管理将面临许多新的挑战。本文吸取了业界IPv6存活地址快速发现理论的核心思想,结合现网网络特点,设计开发出基于IPv6的资产管理系统,用于辅助对IPv6资产进行管理。