相控参量阵波束合成设计

针对矩形和圆环形换能器阵列,完成了宽带参量阵信号的波束合成仿真与结果比较分析.仿真结果表明,同等阵元个数N=9、相似阵列边界半径rm=49 mm条件下,矩形阵列差频波波束主瓣-3 dB指向角约为6.3°(圆环阵列约为7.4°),旁瓣几乎被完全抑制(圆环阵列约为主瓣峰值的10％),矩形阵列更利于提高主瓣指向性和抑制旁瓣幅度.针对矩形阵列,该文仿真分析了采用阵元信号延时方法实现参量阵信号波束偏转时的各波束特征,仿真结果显示,偏转后波束存在主瓣峰值点幅值削弱、主瓣峰值点未对准预定方向、主瓣宽度增大等问题.分析表明,以上问题可通过增加阵元数目及增大阵列尺寸进行修正.     

基于多特征动态融合模型的海陆分割算法

海陆分割是遥感图像中进行海上目标检测、监视的关键技术.传统的基于灰度的海陆分割算法没有充分利用图像中的梯度、纹理等灰度变化及空间分布信息;而基于梯度或纹理的海陆分割算法又没有考虑到图像本身灰度特性.由此提出基于多特征动态融合模型的海陆分割算法,该算法通过动态融合模型提取多种图像特征,生成综合特征图,并对综合特征图进行分...     

一种新的IP网络视频通信丢包错误纠正方案

分组丢失是IP交换网络常见的现象。该文针对下一代网络多媒体通信,提出了一套IP网络抗分组丢失的方案。包括纠删编码、打包和发送以及接收端错误掩盖。与常见的纠删编码相比,该文提出的[9,5,3]码具有构造简单,编解码时间短,纠删能力高的优点。打包和发送方案根据[9,5,3]码的纠删性能对视频数据打包,并以一定顺序发送,提高了纠删码抗突发错误的能力。采用新的视频编码方案H.264所提供的抗误码工具灵活的宏块次序(FMO),对纠删失效的视频数据在解码端进行错误掩盖。     

基于贪心算法的小型楼宇太阳能系统优化设计

针对小型楼宇太阳能系统的设计问题,根据量纲和谐原理,对全年发电总量最大,单位发电量费用小的双目标进行量纲统一化,转化为寿命期内经济效益最大的单目标,将一个看似无法解决的复杂双目标问题转化为单目标规划问题,从而大幅降低了问题复杂度。该模型首先根据不同型号电池和逆变器的各项参数,确定电池型号及数量与逆变器型号间的最优组合方式,并计算最优组合方式下单位面积产生的经济效益,以此对电池性能排序。然后根据电池性能的优劣顺序及限制条件,利用贪心算法得到小屋外表电池铺设方案。最终,评价了所建立的模型,并对问题作了进一步推广。     

主流大数据处理开源架构的分析及对比评测

结合电信增值业务领域中对大数据处理的实际需求,对现有主流的分布式大数据处理架构(Hive、Impala、Spark)的核心进行分析与实测,比较它们在大数据处理过程中的优劣及适用的场景,从而为大数据分析所面临的架构适用性选型提供参考.     

硅基结构混合等离子激元波导模式特性的数值研究

首先建立了一种由相同宽度的金属带,SiO2间隔层与Si介质脊构成的导体-夹层-硅基结构(Conductor-Gap-Silicon,CGS)的混合等离子激元波导模型,分析了间隔层的厚度以及波导宽度对模式传输特性的影响,提出了模场面积为0.08 m2与430 m传输距离的设计方案.在此基础上,通过增加数值模型中介质脊的宽度而形成硅基板CGS波导结构.数值分析结果表明:硅基板CGS波导可将模式有效折射率增至2.8,同时传输长度能够延长到1.74 mm.并且模场面积可以进一步压缩到0.025 m2.此外,硅基板CGS波导制作更加简便,并可采用现有COMS制作技术完成,进而具有较大的实用前景.     

A Robust,Freestanding MXene‐Sulfur Conductive Paper for Long‐Lifetime Li–S Batteries

Freestanding, robust electrodes with high capacity and long lifetime are of critical importance to the development of advanced lithium–sulfur (Li–S) batteries for next‐generation electronics, whose potential applications are greatly limited by the lithium polysulfide (LiPS) shuttle effect. Solutions to this issue have mostly focused on the design of cathode hosts with a polar, sulfurphilic, conductive network, or the introduction of an extra layer to suppress LiPS shuttling, which either results in complex fabrication procedures or compromises the mechanical flexibility of the device. A robust Ti₃C₂T_x/S conductive paper combining the excellent conductivity, mechanical strength, and unique chemisorption of LiPSs from MXene nanosheets is reported. Importantly, repeated cycling initiates the in situ formation of a thick sulfate complex layer on the MXene surface, which acts as a protective membrane, effectively suppressing the shuttling of LiPSs and improving the utilization of sulfur. Consequently, the Ti₃C₂T_x/S paper exhibits a high capacity and an ultralow capacity decay rate of 0.014% after 1500 cycles, the lowest value reported for Li–S batteries to date. A robust prototype pouch cell and full cell of Ti₃C₂T_x/S paper // lithium foil and prelithiated germanium are also demonstrated. The preliminary results show that Ti₃C₂T_x/S paper holds great promise for future flexible and wearable electronics.     

Large‐Area Silver‐Coated Silicon Nanowire Arrays for Molecular Sensing Using Surface‐Enhanced Raman Spectroscopy

A new and facile method to prepare large‐area silver‐coated silicon nanowire arrays for surface‐enhanced Raman spectroscopy (SERS)‐based sensing is introduced. High‐quality silicon nanowire arrays are prepared by a chemical etching method and used as a template for the generation of SERS‐active silver‐coated silicon nanowire arrays. The morphologies of the silicon nanowire arrays and the type of silver‐plating solution are two key factors determining the magnitude of SERS signal enhancement and the sensitivity of detection; they are investigated in detail for the purpose of optimization. The optimized silver‐coated silicon nanowire arrays exhibit great potential for ultrasensitive molecular sensing in terms of high SERS signal enhancement ability, good stability, and reproducibility. Their further applications in rapidly detecting molecules relating to human health and safety are discussed. A 10 s data acquisition time is capable of achieving a limit of detection of approximately 4 × 10^?6 M calcium dipicolinate (CaDPA), a biomarker for anthrax. This value is 1/15 the infectious dose of spores (6 × 10^?5 M required), revealing that the optimized silver‐coated silicon nanowire arrays as SERS‐based ultrasensitive sensors are extremely suitable for detecting Bacillus anthracis spores.     

Design and Fabrication of a High-Voltage nMOS Device

High-voltage nMOS devices are fabricated successfully and the key technology parameters of the process are optimized by TCAD software.Experiment results show that the device’s breakdown voltage is 114V,the threshold voltage and maximum driven ability are 1.02V and 7.5mA(W/L=50),respectively.Experimental results and simulation ones are compared carefully and a way to improve the breakdown performance is proposed.     

旋转对称目标双基地一维距离像特性分析

双基地雷达成像研究中通常直接采用了单基地散射中心模型,忽略了双基地几何配置引起散射中心位置变化的这一事实。该文研究了旋转对称目标的双基地散射特性,采用几何绕射理论求解了锥体目标底面边缘双基地散射中心的位置,为入射波方向与散射波方向的夹角角平分线与目标对称轴构成的平面与底面边缘的交点,并据此建立了宽带双基地雷达目标回波模型,进而获得双基地1维距离像。最后,通过电磁计算软件获得了锥体目标的双基地1维距离像,计算结果与理论分析相一致,证明了理论分析的正确性。该文揭示的目标双基地散射中心的位置为旋转对称目标的宽带双基地雷达回波模拟、成像、特征提取与识别等应用提供了准确的数学模型。