纳米TiO_2光催化降解次甲基蓝的影响因素研究

以TiCl4为原料,采用水解沉淀法,并在空气气氛下于不同温度煅烧2h,制备得到纳米TiO2。采用XRD、TEM及UV-Vis对样品进行表征。在卤钨灯照射下,研究了不同煅烧温度、不同pH值以及H2O2的加入等因素对TiO2光催化降解次甲基蓝的影响。结果表明:以水解沉淀法制备的纳米TiO2,随煅烧温度的提高,在600℃开始向金红石相转变,1000℃时全部转变为金红石相,并且TiO2粒子长大,吸收带边向长波方向移动。锐钛矿相与金红石相共存的纳米TiO2比纯锐钛矿相和金红石相有更优异的光催化活性,在卤钨灯下照射90min,对次甲基蓝的降解率达到97%。     

Low-complexity transmit antenna selection algorithm formassive MIMO

Massive multiple input multiple output (MIMO) systems can increase capacity and reliability greatly. However,extremely high hardware costs and computational complexity lead to the demand for reasonable antenna selection.Aiming at the problem that the traditional antenna selection algorithm based on maximizing sum capacity has largecomplexity and worse bit error rate (BER) performance, a two-step selection algorithm is proposed, which selectsa part of the antennas based on the norm-based antenna selection (NBS) firstly, and then selects the antenna basedon maximizing capacity via convex optimization. The simulation results show that the improved algorithm has betterBER performance than the traditional algorithms. At the same time, it reduces computational complexity greatly.     

电子束诱导沉积钴微米线及其铁磁性

通过电子束诱导沉积的方法制备了钴(Co)微米线,并利用扫描电子显微镜(SEM)、原子力/磁力显微镜(AFM/MFM)以及物性测量系统(PPMS)等手段对Co微米线的沉积尺寸、微结构、铁磁性和电学性质进行了测试和分析。研究结果表明:Co微米线轮廓清晰、均匀性好。在不同的沉积条件下,微米线的实际长度与设定长度基本一致;实际宽度数据呈类梯形分布,半高宽是设定值的2~10倍;实际厚度低于设定厚度的60%。沉积电流对Co微米线的铁磁特性有重要影响。当沉积电流大于0.5 nA时,样品呈现出良好的铁磁特性。另外,电学性能测试结果显示Co微米线呈现绝缘特性。成功制备了室温铁磁绝缘Co微米线,这将有助于深入开展微纳尺度的结构与器件的研究和应用。     

Primary User Emulation Detection Algorithm Based on Distributed Sensor Networks

In this paper, we propose a novel primary user emulation (PUE) detection approach which employs a distributed sensor network, where each sensor node operates as an independent PUE detector. Distributed nodes collaborate in order to obtain the final detection results for the whole network. A voting algorithm is used to improve the performance of energy detection, while the classification is conducted by the nearest node in order to improve the efficiency of the detector. As a result of voting, if a potential primary user exists, then the features of the unknown user is compared with entries from the database in order to obtain a solid detection match. An artificial neural network (ANN) is used for the classification of an unknown user. To assess the accuracy of the detection result, we implement a reliability check at the output of ANN. The proposed algorithm is validated via computer simulations as well as by experimental hardware implementations using the Universal Software Radio Peripheral (USRP) software-defined radio (SDR) platform. The experiment results show that the distributed network detector detects the PUE 180–200%, depending on the number of primary users, faster than single node detector.     

面向图像复原的广义岭估计模式法波前重构

为了提高自适应光学图像的复原效果,提出了一种面向图像复原的广义岭估计Zernike模式波前重构算法。首先,按照用时间换精度的思路,把广义岭估计引入自适应光学波前重构算法中。改善最小二乘估计的奇异性,抑制波前测量误差的放大。然后,引入迭代计算提高方程的解算精度,进一步提高点扩散函数(PSF)重建质量。最后,利用广义岭估计重建的PSF对降质图像进行复原实验验证PSF的重建质量。实验结果证明,广义岭估计PSF的复原效果比最小二乘估计PSF高约15%,更接近成像系统的光学衍射极,同时复原计算迭代次数也减少了35%。新算法重构的PSF在图像复原中有更好的图像重建效果。     

任意波长间隔的光纤光栅梳状滤波器设计与实现

采样啁啾光纤光栅理论是实现超高信道数梳状滤波器的理想方案,但是一个啁啾模板只能实现特定波长间隔的光梳状滤波器。提出一种利用光纤布拉格光栅(FBG)直流相移实现任意波长间隔梳状滤波器方法。该方法只需一个啁啾模板与亚微米精度的位移台,在灵活性、简单性和制作成本方面有明显优势。仿真和实验表明FBG直流折射率调制可以引入任意的相位偏移。利用该方法实现了波长间隔为100,50,40GHz的梳状滤波器。最后分析了直流相移光栅长度与相位误差对滤波器边带抑制度的影响。     

CDMA2000覆盖公路隧道的工程实例分析

简要介绍了公路隧道的孔径尺寸、电信运营商所需的电源、站点、管沟资源及隧道覆盖工程费用构成;详细论述了无线覆盖建设方案中的共建共享、公路隧道无线传播特点及信号源、天馈系统、天线、站点选择等有关问题,并通过多个具体实例对典型覆盖工程分别进行了测试验证。     

单站雷达系统的极化匹配系数

在通讯系统中天线的极化匹配系数这一概念的基础上,根据雷达目标应用中的最优极化状态的分析,提出了单站雷达系统中天线的共极化匹配系数,交叉极化匹配系数和自适应极化匹配系数的新概念,并给出了便于计算的表达式。     

对影响内引线键合可靠性的因素的分析与对策

简述了半导体器件内引线键合的机制及如何检测内引线的键合质量, 分析了影响内引线键合质量的因素, 重点分析了半导体器件最常见的失效模式——键合点脱落的因素, 并提出改进键合质量的几点措施     

基于SVM的语音情感识别研究

随着计算机技术的发展,人们对和谐人机交互的要求不断提高,这就要求计算机能理解说话人的情感信息,即能进行语音情感识别。本文提出了一种基于支持向量机（SVM）的语音情感识别方法,主要对人类的6种基本情感：高兴、惊奇、愤怒、悲伤、恐惧、平静进行研究。首先对自建语音情感数据库的情感语句提取特征,然后运用序列前向选择（SFS）算...