涂敷介质目标的表面反射系数及其雷达散射截面

在金属目标表面涂敷吸波材料可以有效地抑制雷达散射截面．增强雷达目标的隐身性能,而在求解这种目标的雷达散射截面过程中一个重要的问题是计算介质表面的反射系数．给出了一种求解反射系数的通用公式,并且以金属平板为例分别计算其在涂敷三层和五层介质时的反射系数．以及有涂敷五层介质时金属球的雷达散射截面．     

复杂目标的太赫兹波近场RCS快速计算

在太赫兹频段,散射目标大部分处于近场区域,远场计算方法已经不再适用,为此该文推导了近场雷达散射截面(RCS)的计算公式。针对太赫兹频段近场条件下,物理光学法(PO)由于面元数量巨大引起的遮挡判断耗时过长,以及图形电磁学(GRECO)以像素为计算单位计算误差过大的问题,该文提出一种以面元为计算单位,以像素为遮挡判断单位的复杂目标太赫兹波近场RCS的快速计算方法,该方法在保证计算精度的基础上,大大降低了遮挡判断的计算复杂度和时间。最后,以标准目标体平板、球体以及复杂目标体卫星在不同距离下的雷达散射截面的计算为例,验证了该方法的有效性和准确性。     

不同吸波涂层对三维复杂目标的RCS影响的分析

利用有限元-快速多极子算法(FEM-FMM)分析了三维复杂目标涂有不同吸波涂层的雷达散射截面(RCS).以圆锥体为例,详细计算分析了涂敷有耗各向同性、正单轴各向异性、负单轴各向异性和纳米吸波材料4种典型吸波材料对目标电磁散射特性的影响,并首次讨论了每种吸波材料随不同涂层厚度对RCS的影响,得到了最佳隐身效果的吸波材料和涂层厚度的组合.结果表明,涂敷最佳吸波材料目标的后向RCS比目标没有吸波涂层时可以降低16.6dB.     

高低频混合方法估算角反射器阵RCS

结合高频算法处理复杂目标雷达散射截面(RCS)的思路,提出了利用HFSS仿真软件得到的数据计算复杂目标RCS,给出了计算式,并运用Matlab验证计算公式的适用性。     

部分涂敷目标的RCS仿真计算

涂敷雷达吸波材料(RAM)是目前最为常用的一种减缩雷达散射截面(RCS)的方法,可以在全角度下减小雷达目标的RCS值.采用非均匀有理B样条(NURBS)参数曲面模拟目标外形,运用物理光学法计算电大尺寸部分涂敷目标的RCS.结果显示,在目标一定的部位上而不是在所有部件上涂敷吸波材料,在一定的观察点上仍然能起到减小RCS的作用,既满足了角度范围的需要又节省了RAM的使用费用.     

一种超宽带雷达散射截面减缩的超表面设计

提出一种具有超宽带雷达散射截面(RCS)减缩特性的超表面(MS)。该MS结构由聚四氟乙烯(Polytef)介质层、空气层和金属地板组成,同时在Polytef介质层的两侧刻蚀金属图案。为了拓展RCS,减缩带宽,设计两种几何结构相似但是工作在不同频段的宽带双频单元,两种单元的有效相位差区域得到极大拓展。采用经典的棋盘方式进行布阵,实现了超宽频带的RCS减缩。仿真和实验结果表明,与等尺寸金属平板相比,该MS在3.0～20.0 GHz的频带范围,后向RCS均有减缩,其中在5.3～17.7 GHz(107.8%)的范围,后向RCS减缩基本都在10 dB以上,证实了MS的超宽带RCS减缩特性。     

磁化等离子体的并行三维JEC-FDTD算法及其应用

 给出了三维磁化等离子体的电流密度卷积－时域有限差分(JEC-FDTD)算法的迭代公式,指出该算法与一般FDTD算法实现并行时的不同:增加了电流密度的迭代,以及并行计算时在子域交界面上增加了一些数据的交换.并实现了基于MPI (Message Passing Interface)的并行JEC-FDTD算法.然后用计算涂覆等离子体的金属球的雷达散射截面(RCS)的算例验证了并行程序的可靠性,并测试了并行程序在某集群上的并行效率.最后计算了涂敷磁化等离子体的全尺寸飞机的单站RCS.结果表明并行JEC-FDTD算法是可靠的,而且并行效率高,能计算各向异性磁化等离子体的电大尺寸目标的散射.     

半空间电大均匀介质目标散射分析方法

研究了半空间电大尺寸均匀介质目标散射的高频求解方法.考虑电大均匀介质目标散射特性,将半空间并矢格林函数引入物理光学近似中,结合图形电磁学(GRECO)和射线追踪方法,分别对半空间复杂目标的消隐和多重散射进行考虑,快速有效地计算了半空间电大均匀介质目标的雷达散射截面(RCS),数值结果证明了该方法的准确性.     

基于并行MLFMA的SAR舰船目标RCS计算

为提高合成孔径雷达（SAR）图像仿真效果,针对SAR图像中舰船目标雷达散射截面（RCS）计算的精度和效率问题,在利用几何建模方法构建三维舰船模型的基础上,采用并行多层快速多极子算法（MLFMA）计算了舰船目标RCS并分析了该算法的并行加速比。仿真实验表明,并行MLFMA算法适用于高频范围内较大尺寸舰船目标RCS的计算,比物理光学法（PO）和物理光学与矩量混合算法（PO—MOM）具有更高的计算精度且并行方案能明显提高求解目标RCS的效率。     

复杂目标电磁散射混合算法

分析了复杂目标高频散射雷达截面(RCS)计算理论,提出了一种有效的混合算法.改进了等效电磁流方法(IMEC),推导了几何光学/物理光学区域投影算法(GO/PO).IMEC能有效地消除反射边界和阴影边界的奇异性,GO/PO法用于计算多重散射.通过AutoCAD软件,使用三角面元法构建目标三维模型.目标的高频雷达散射截面通过几何光学、物理光学、改进的等效电磁流和几何光学/物理光学区域投影等混合方法计算获得.同时,计算了某型号导弹的RCS,理论值同测量结果基本一致,说明该方法能满足复杂目标电磁散射分析的需要.     

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.