基于Alpha稳定分布杂波模型的雷达目标检测方法

针对非高斯相关杂波背景下,移动目标检测(MTD)技术的检测性能严重下降的问题,该文基于Alpha稳定分布杂波模型和本征滤波理论,提出一种非高斯相关杂波背景下的雷达目标检测方法。该方法基于Alpha稳定分布杂波模型,通过幂变换抑制杂波的非高斯特性,以及通过分数低阶相关矩阵白化杂波,在此基础上应用本征滤波实现对目标信号的有效积累,可提高信杂比。仿真实验和实测数据验证表明,该方法在非高斯相关杂波背景下的检测性能明显优于MTD方法的性能。     

非高斯杂波中反辐射导弹的Wald检测方法

Alpha稳定分布是一种有广泛适用范围的非高斯分布模型,本文基于Alpha稳定分布杂波假设,提出了一种反辐射导弹(ARM)的Wald检测方法.当Alpha稳定分布的特征参数α值较小时,基于功率谱或基于共变α谱的频率估计性能将明显下降,为此本文提出基于分数低阶协方差(FLOC)谱方法估计ARM载机信号的多普勒频率,并针对载机信号的强相关性用对消器抑制载机信号,最后导出了标准对称Alpha稳定分布杂波下ARM的Wald检测统计量.仿真结果表明,基于FLOC谱能够准确地估计信号频率,抑制载机信号;基于Alpha稳定分布杂波假设的Wald检测性能与广义似然比检测(GLRT)的渐近性能相当,且明显优于基于高斯分布杂波假设的Wald检测性能.     

非高斯相关杂波背景下雷达目标检测方法研究

在非高斯相关杂波背景下,基于MTD(Moving Target Detection)的雷达目标检测性能严重下降。针对该问题,根据Alpha稳定分布杂波模型、分数低阶统计量理论,以输出信杂比最大为准则,提出了一种适用于非高斯相关杂波背景的雷达目标检测方法。该方法通过分解信号分数低阶协方差矩阵,计算等效杂波分数低阶协方差矩阵特征向量,得到最佳滤波器系数。通过仿真和实测数据,对所提出方法的检测性能进行了验证,并且与基于MTD的检测方法进行了比较,结果表明,在非高斯相关杂波背景下,所提方法的检测性能明显优于传统的MTD。      

高斯混合分布杂波下ARM的Wald检测方法

提出一种在高斯混合分布杂波下检测反辐射导弹(ARM)的Wald检测方法.针对基于期望最大化(EM)算法估计杂波参数时,由于初始化不当使迭代运算落入初值陷阱、导致估计错误的问题,提出基于矩-EM算法估计杂波参数的方法,导出了高斯混合分布杂波下ARM目标的Wald检测统计量.不同参数条件下的仿真表明,矩-EM算法能够更准确地估计杂波参数;基于高斯混合分布杂波假设的Wald检测性能明显优于基于高斯分布杂波假设的Wald检测性能.     

复合高斯杂波中知识辅助的自适应检测算法

研究了在复合高斯杂波中利用先验知识自适应检测目标的问题,证明了基于双参数逆高斯分布纹理的复合高斯模型比传统的K分布、复t分布和单参数逆高斯分布纹理的复合高斯分布模型能够更好地拟合实际杂波。文中选择双参数逆高斯分布作为纹理分量的先验分布、基于广义似然比准则和贝叶斯方法设计得到了一种复合高斯杂波中的自适应检测器。理论分析和数值仿真表明,与自适应匹配滤波器和正则化自适应匹配滤波器相比,该检测器具有更好的检测性能     

一种基于多级维纳滤波的多通道SAR动目标检测算法

该文针对机载多通道SAR-GMTI系统及实测数据,提出一种新的地面慢动目标检测算法。新算法利用多级维纳滤波器实现多通道SAR系统杂波抑制,同时结合对角加载技术和非均匀检测器,进一步改善SAR系统在非均匀环境下的动目标检测性能。实测数据实验结果表明:与常规的自适应检测方法相比,新算法能够明显提高系统对杂波的抑制能力及非均匀环境下系统的动目标检测性能。     

非均匀非高斯杂波的协方差矩阵估计

在雷达目标检测中,杂波的协方差矩阵估计利用了待检测单元附近的杂波数据。本文考虑一种非均匀环境中,非高斯杂波下的杂波协方差矩阵估计问题,即假定待检测单元与参考单元的杂波协方差矩阵之间满足某种统计关系,并假定杂波数据满足复合高斯统计分布模型。在这种场景下,常规的杂波协方差矩阵估计方法会导致信号检测性能的下降。采用共轭先验分布作为非均匀非高斯场景的统计分布模型,利用贝叶斯方法,本文给出了基于Gibbs抽样的杂波协方差最小均方误差估计方法。计算机仿真结果表明,与常规的杂波协方差矩阵估计方法相比较,本文所给出的杂波协方差矩阵的估计算法能够在参考数据较少,累积脉冲个数较少时,非均匀场景中获得较好的检测性能。本文还分析了先验分布模型参数误差对检测性能的影响。      

直接数据域的自适应匹配滤波方法

 研究机载预警雷达非平稳杂波抑制问题. 在获得单个距离门回波数据的最小均方谱分布基础上,利用最小二乘方法和clearing技术拟合杂波谱分布特性并重构无空时孔径损失的杂波子空间,采用自适应匹配滤波方法检测运动目标. 能有效解决传统直接数据域方法存在的空时孔径损失和传统统计空时自适应处理（STAP）方法在非平稳杂波环境存在的性能严重下降,仿真结果表明本文方法能获得良好的动目标检测性能.     

基于WPT-FRFT的微弱动目标检测及性能分析

针对杂波背景的微弱动目标检测问题,提出了一种应用小波包变换的分数阶Fourier域动目标检测算法。算法采用最小Shannon熵标准确定最优小波树,利用阈值删除技术,对杂波背景的参数精确估计,从而对不同频段信号进行滤波。建立了FRFT域的动目标检测模型,采用似然比准则设计检测器,抑制杂波后的信号在FRFT域形成检测统计量,门限比较后判断信号的有无。仿真得出了在高斯杂波和实测海杂波背景下的检测性能曲线,性能接近匹配滤波器,结果表明算法能够在低信杂比环境下有效检测出动目标信号。     

基于改进FRACTA算法的多通道SAR动目标检测技术

该文针对实际非均匀杂波环境对多通道SAR/GMTI动目标检测性能的影响,提出了一种改进型FRACTA算法。该算法将STAP中的FRACTA算法引入多通道SAR系统中,并进行改进,提高了其在多通道SAR系统中的检测性能和运算速度。实测数据处理结果表明,与传统的检测方案相比,该文算法能够在非均匀环境中明显地提高检测性能,是一种非均匀环境中鲁棒的多通道SAR动目标检测算法。     

Interfacial reaction and shear strength of SnAgCu-xNi/Ni solder joints during aging at 150 °C

The interfacial microstructure and shear strength of Sn3.8Ag0.7Cu-xNi (SAC-xNi, x = 0.5, 1, and 2) composite solders on Ni/Au finished Cu pads were investigated in detail after aging at 150 °C for up to 1000 h. The interfacial characteristics of composite solder joints were affected significantly by the weight percentages of added Ni micro-particles and aging time. After aging for 200 h, the solder joints of SAC, SAC-0.5Ni and -1Ni presented duplex intermetallic compound (IMC) layers regardless of the initial interfacial structure on as-reflowed joints, whose upper and lower IMC layers were comprised of (CuNi)₆Sn₅ and (NiCu)₃Sn₄, respectively. Only a single (NiCu)₃Sn₄ IMC layer was ever observed at the SAC-2Ni/Ni interface on whole aging process. Based on the compositional analysis, the amount of Ni within the IMC regions increased as the proportion of Ni addition increased. The IMC (NiCu)₃Sn₄ layer thickness on the interface of SAC and SAC-0.5Ni grew more slowly when compared to that of SAC-1Ni and -2Ni, while for the (CuNi)₆Sn₅ layer the reverse is true. Except the IMCs sizes are increased with increased aging time, the interfacial IMCs tended to transfer their morphologies to polyhedra. In all composite joints testing, the shear strengths were approximately equal to non-composite joints. The fracturing observed during shear testing of composite joints occurred in the bulk solder, indicating that the SAC-xNi/Ni solder joints had a desirable joint reliability.     

有机发光二极管中ADN掺杂ErQ的1.54μm电致发光

自行设计了基于8-羟基喹啉铒(ErQ)为发射层(EMLs)和二硝酰胺铵(ADN)为蓝光主体材料的近红外有机发光二级管.器件的基本结构为(p-Si/NPB/EML/Bphen/Bphen:Cs2CO3/Sm/Au),设计并比较了三套不同发射层结构(ErQ/ADN为双层结构器件,(ErQ/ADN)×3为多层结构器件,ErQ:ADN为掺杂结构器件)的器件.三组器件在一定的偏压下,均可发出1.54μm的光,对应三价铒离子4I13/2→4I15/2的跃迁.其中,ADN:ErQ(1∶1)掺杂结构的近红外电致发光强度是ADN/ErQ双层结构中的三倍.此外,不同掺杂浓度的ADN:ErQ复合膜做了以下表征:吸收谱、光致发光谱和荧光寿命谱.实验结果证实了在近红外电致发光过程中存在从ADN主体分子到ErQ发射分子的高效率的能量转移.     

BNBST无铅压电陶瓷的制备工艺研究

设计了（Bi0.55Na0.5）1-X（BaaSrb）xTiO3（BNBST[100x-100a／100b]）无铅压电陶瓷新体系。该体系压电陶瓷具有工艺特性及压电响应好，压电常数高的特点，且有实际应用前景的新型压电陶瓷材料体系。采用传统的陶瓷工艺制备了（Bi0.55Na0.5）1-X（BaaSrb）xTiO3无铅压电陶瓷，研究了制备工艺参数对其物化结构性能的影响。生料的热重-差热（TGA-DTA）分析表明，粉料合成过程中，先是SrTiO3、BaTiO3的形成，然后是（Bi0．5Na0．5）Tio，的形成，同时三者形成固溶体；密度测试表明，陶瓷的体积密度随烧结温度的升高而增大，可较易获得理论密度94％的陶瓷；X-射线能谱分析（EDAX）研究表明，陶瓷的Bi、Na的挥发随着烧结温度的升高而加剧。研究结果表明，要制备性能优良的无铅压电陶瓷，需要精确控制制备工艺。     

Emerging interconnects: a state-of-the-art review and emerging solutions

Aluminium was a primary material for interconnection in integrated circuits (ICs) since their inception. Later, copper was introduced as interconnect material which has better metallic conductivity and resistance to electromigration. As the aggressive technology scaling continues, the copper resistivity increased because of size effects, which causes increase in delay, power dissipation and electromigration. The need to reduce the resistor-capacitor??????? delay, dynamic power utilisation and the crosstalk commotion is as of now the fundamental main impetus behind the presentation of new materials. The purpose of this paper is to do a survey of interconnect material used in IC from introduction of ICs to till date. This paper studies and reviews new materials available for interconnect application which are optical interconnects, carbon nanotube (CNT), graphene nanoribbons (GNRs) and silicon nanowires which are alternatives to copper. While doing a survey of interconnect material, it is found that multiwalled CNTs, multilayer GNR and mixed CNT bundles are promising candidates and are ultimate choice that can strongly address the problems faced by copper but on integration basis copper would last for coming years.     

钠离子对poly(dT).poly(dA).poly(dT)三螺旋DNA分子呼吸模式的影响

利用分子结构的螺旋对称性,建立了一个包括钠离子的三链DNA分子poly(dT)*poly(dA)*poly(dT)的晶格动力学模型,计算了poly(dT)*poly(dA)*poly(dT)的氢键呼吸模式.结果发现钠离子的加入明显地淬灭了位于较低频率的几个最为强烈的Hoogensteen氢键呼吸模式,而对Watson-Crick氢键呼吸模式影响不明显,这说明钠离子能提高poly(dT)*poly(dA)*poly(dT)三螺旋结构的稳定性.该计算结果很好地解释了poly(dT)*poly(dA)*poly(dT)的热融化实验.     

聚对苯撑苯并双(口恶)唑发光及其器件制备

采用光谱技术,研究了聚对苯撑苯并双(口恶)唑(PBO)溶液的光敏发光特性,并用相对法估算出溶液发光效率在50%范围.结合光谱技术、半导体电学和电化学等研究手段,具体研究了以PBO为发光层的单层电致发光器件,研究结果显示,电致发光与薄膜的光致发光有具有相同的发光中心,峰值位于510 nm左右.同时发现,由于存制备过程中不同处理条件使得不同厚度薄膜残留的掺杂物质浓度不同,从而引起薄膜的导电性的不同.使得器件的阈值场强随PBO厚度的减小而逐渐增加.     

人小肠粘膜免疫酶的定位研究—光镜和电镜免疫组织化学染色法

本文对免疫酶组织化学的样品制备程序和染色方法做了详细的阐述。用直接法、间接法和ABC法,对人小肠免疫酶的定位,进行了光镜和电镜的观察,染色阳性反应显著,获得了满意的效果。并对染色技巧做了分析和探讨。     

Arsenic deposition as a precursor layer on silicon (211) and (311) surfaces

We investigate the properties of arsenic (As) covered Si(211) and Si(311) surfaces by analyzing data from x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) images. We then create a model using total surface energy calculations. It was found that both Si(211) and Si(311) had 0.68±0.08 surface As coverage. Si(211) had 0.28±0.04 Te coverage and Si(311) had 0.24±0.04 Te coverage. The Si(211) surface replaces the terrace and trench Si atoms with As for a lower surface energy, while the Si edge atoms form dimers. The Si(311) surface replaces all terrace atoms and adsorbs an As dimer every other edge site. These configurations imply an improvement in the mean migration path from the bare silicon surface by allowing the impinging atoms for the next epitaxial layer, tellurium (Te), to bind at every other pair of edge atoms, and not the step terrace sites. This would ensure a nonpolar, B-face growth.     

Joint estimation of TOA and DOA in IR-UWB system using a successive propagator method

Impulse radio ultra-wideband (IR-UWB) ranging and positioning require accurate estimation of time-of-arrival (TOA) and direction-of-arrival (DOA). With receiver of two antennas, both of the TOA and DOA parameters can be estimated via two-dimensional (2D) propagator method (PM), in which the 2D spectral peak searching, however, renders much higher computational complexity. This paper proposes a successive PM algorithm for joint TOA and DOA estimation in IR-UWB system to avoid 2D spectral peak searching. The proposed algorithm firstly gets the initial TOA estimates in the two antennas from the propagation matrix, then utilises successively one-dimensional (1D) local searches to achieve the estimation of TOAs in the two antennas, and finally obtains the DOA estimates via the difference in the TOAs between the two antennas. The proposed algorithm, which only requires 1D local searches, can avoid the high computational cost in 2D-PM algorithm. Furthermore, the proposed algorithm can obtain automatically paired parameters and has better joint TOA and DOA estimation performance than conventional PM algorithm, estimation of signal parameters via rotational invariance techniques algorithm and matrix pencil algorithm. Meanwhile, it has very close parameter estimation to that of 2D-PM algorithm. We have also derived the mean square error of TOA and DOA estimation of the proposed algorithm and the Cramer-Rao bound of TOA and DOA estimation in this paper. The simulation results verify the usefulness of the proposed algorithm.     

系统级封装新型埋入式电源滤波结构的研究

在高密度小尺寸的系统级封装(SiP)中,对供电系统的完整性要求越来越高,多芯片共用一个电源网路所产生的电压抖动除了会影响到芯片的正常工作,还会通过供电网路干扰到临近电路和其他敏感电路,导致芯片误动作,以及信号完整性和其他电磁干扰问题.这种电压抖动所占频带相当宽,几百MHz到几个GHz的中频电源噪声普通方法很难去除.结合埋入式电容和电源分割方法的特点,提出一种新型高性能埋入式电源低通滤波结构直接替代电源/地平面.研究表明,在0.65～4GHz的频带内隔离深度可达-40～75 dB,电源阻抗均在0.25ohm以下,实现了宽频高隔离度的高性能滤波作用.分别用电磁场和广义传输线两种仿真器模拟,高频等效电路模型分析这种低通滤波器的工作原理以及结构对隔离性能的影响,并进行了实验验证.