改进嵌套稀疏圆阵下基于OGSBL的DOA估计方法

针对现有基于嵌套稀疏圆阵DOA估计方法计算复杂度高、超参数无法快速选取问题,提出了一种基于改进嵌套稀疏圆阵的离格稀疏贝叶斯学习(OGSBL)方法.该方法首先将改进嵌套稀疏圆阵接收信号的协方差矩阵进行向量化处理,然后构造扩展的观测矩阵,进而结合离格模型与稀疏贝叶斯学习算法实现欠定的DOA估计.仿真实验结果表明,所提算法降...     

超宽带系统中基于稀疏恢复的TOA和DOA联合估计方法

针对稀疏表示框架下进行超宽带系统中到达时间(Time of Arrival, TOA)和波达方向(Direction of Arrival, DOA)联合估计的问题,提出了一种基于稀疏恢复的TOA和DOA联合估计方法。采用l范数作为稀疏约束条件,并利用联合正交匹配追踪算法获取TOA估计值,解决了TOA配对问题,最后根据两副天线的时延差与DOA之间的关系获得信号的DOA估计。所提算法考虑了离网格信号参数估计问题,并通过联合稀疏恢复进行补偿。仿真结果表明,所提算法的参数估计性能优于传统的压缩感知算法、传播算子算法、矩阵束算法以及借助旋转不变性的信号参数估计技术(Estimating Signal Parameters via Rotational Invariance Techniques, ESPRIT)算法,同时计算复杂度更低。     

基于具有时序结构的稀疏贝叶斯学习的水声目标 DOA 估计研究

现有的基于CS-MMV（Compressed Sensing-Multiple Measurement Vectors）模型的DOA估计一般都假定信号源为独立同分布（ i．i．d）,算法建立在信号的空间结构上进行分析,而当处理具有时序结构的源信号时表现出性能和鲁棒性差的问题,为此该文提出一种具有时序结构的稀疏贝叶斯学习的DOA算法,该方法通过建立一阶自回归过程（ AR）来描述具有时序结构的水声信号,将信号源的时间结构特性充分应用到DOA估计模型中,然后采用针对多测量矢量的稀疏贝叶斯学习（ Muti-vectors Sparse Bayesian Learning ）算法重构信号空间谱,建立多重测量向量中恢复未知稀疏源的信号的CS（ Compressed Sensing ）模型,最终完成DOA估计．仿真结果表明该方法相对于传统的算法具有更高的空间分辨率和估计精度的特点,且抗干扰能力强．     

四阶累积量稀疏表示的DOA估计方法

针对现有稀疏重构DOA估计算法不能抑制噪声项以及在高斯色噪声背景下不再适用的问题,本文提出了基于四阶累积量稀疏重构的DOA估计方法。首先,利用接收数据的四阶累积量构建了稀疏表示模型,该模型抑制了噪声项;其次对四阶累计量矩阵进行奇异值分解,化简了稀疏表示模型,通过奇异值分解,不仅减小了数据规模,而且进一步抑制了噪声。对于稀疏表示模型的求解,先利用信号子空间与噪声子空间的正交特性选取权值矢量,然后利用加权l1范数法对模型求解实现DOA估计。理论分析和仿真实验表明本文算法在高斯白噪声和色噪声背景下均适用;能够处理非相干和相干信号,且在低信噪比条件下,对相干信号有更高的估计精度;较之同类的稀疏重构算法,本文算法具有较低的算法复杂度和更高的角度分辨力。      

有源欺骗干扰环境下的DOA估计

针对有源欺骗干扰环境下基于小样本的DOA估计问题,该文提出自适应极化滤波(APF)联合块稀疏贝叶斯学习(BSBL)算法的DOA估计方法。首先,通过APF抑制干扰能量,提高信干比。然后,建立有源欺骗干扰环境下的稀疏贝叶斯模型,基于相邻快拍相关性,利用BSBL算法进行DOA估计。仿真和实测数据处理结果表明,所提方法降低了干扰对BSBL算法的影响,且与APF联合子空间类算法或最大似然算法(ML)相比,具有更高的空间分辨率和DOA估计精度。     

尺度不变范数比正则的稀疏DOA估计

波达方向估计(Direction Of Arrival,DOA)通过使用传感器阵列来识别声源方位,而传统的DOA估计方法忽略了声源在空间分布的稀疏性,目前的凸稀疏DOA估计方法和非凸稀疏DOA估计方法所使用的惩罚函数未考虑稀疏度量l₀范数的重要特性——尺度不变性,因此无法精确描述声源的空域稀疏结构,难以获得较高的DOA估计精度.为此,本文首先使用具有尺度不变性的范数比函数来逼近l₀范数,刻画声源空域稀疏结构;接着,针对范数比函数的非凸特性,采用光滑化的思想,构建了平滑的近似函数;然后,构建了基于光滑l_p比l_q范数的稀疏DOA估计模型,开发了基于光滑l_p比l_q范数的稀疏DOA估计算法(Smoothed l_p-Over-l_q regularized Sparse DOA Estimation algorithm,SPOQ-SDOA).大量仿真分析表明,与流行的多快拍DOA估计算法相比,本文提出的算法在不同信噪比和快拍...     

基于稀疏贝叶斯学习的空间紧邻信号DOA估计算法

离格(off-grid)波达方向(DOA)估计解决的是实际DOA和假设网格点的失配问题.对于空间紧邻信号的DOA,稀疏的网格点会导致精度和分辨率的下降,密集的网格点虽然可以提高估计精度却显著增加计算负担.针对此问题,该文提出基于稀疏贝叶斯学习(SBL)的空间紧邻信号DOA估计算法,主要包括3个步骤.首先,通过最大化阵列输出的边缘似然函数,推导了信号在拉普拉斯先验下的新不动点迭代方法,进行超参数的预估计,相比其他经典SBL算法提高了收敛速度;其次,利用新网格插值方法优化网格点集,并二次估计噪声方差和信号功率以分辨空间紧邻信号的DOA;最后,推导了似然函数关于角度的最大化公式以改进离格DOA搜索.仿真表明该算法比其他经典SBL类算法对空间紧邻信号的DOA具有更高的精度和分辨率,同时有计算效率的提升.     

基于两步加权L1范数约束的高分辨率波达方向和功率估计

该文提出一种基于两步加权L1范数约束的波达方向(DOA)和功率联合估计新算法。该算法首先对阵列协方差矩阵元素进行求和平均运算获得统计性能更优的向量观测模型,进而在相应的过完备基下获得观测模型的稀疏表示。利用MUSIC谱函数和初始估计结果作为权值构建两步加权L1范数约束稀疏重构方法,重构获得多信源的DOA和功率估计。通过2分布函数选择了合理的正则化参数。计算机仿真结果显示,与同类其它方法相比,该文所提算法具有更高的分辨率和估计精度。     

一种新的基于压缩感知理论的稀疏信号重构算法

针对基于l1范数优化的稀疏信号重构算法需要的观测样本数较多,本文以lp范数最小化为目标,结合传统的罚函数(PF)优化思想,给出了基于PF的lp范数迭代重构算法,需要的观测样本数大大低于基于l1范数的优化计算需求,并通过数值实验表明该算法对稀疏信号具有较优的重构效果.     

参数自适应调整的稀疏贝叶斯重构算法

稀疏表示模型中的正则化参数由未知的噪声和稀疏度共同决定,该参数的设置直接影响稀疏重构性能的好坏。然而目前稀疏表示问题优化求解算法或依靠主观、或依靠相关先验信息、或经过实验设置该参数,均无法自适应地设置调整该参数。针对这一问题,该文提出一种无需先验信息的参数自动调整的稀疏贝叶斯学习算法。首先对模型中各参数进行概率建模,然后在贝叶斯学习的框架下将参数设置及稀疏求解问题转化为一系列混合L1范数与加权L2范数之和的凸优化问题,最终通过迭代优化得到参数设置和问题求解。由理论推导和仿真实验可知,已知理想参数时,该算法与其它非自动设置参数的迭代重加权算法性能相当,甚至更优;在理想参数未知时,该算法的重构性能要明显优于其它算法。     

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.