自适应信号分解方法在主动声呐信号处理中的应用研究

利用基于“Matching Pursuit”算法的自适应信号分解方法,探讨了主动声呐信号处理中多目标回波的检测及参数估计问题。该方法既能实现多目标分辨,又能提取出更多的目标特征信息,所以能够充分发挥宽带信号的优势。再者,不仅对更广泛类型的发射信号具有普适性,而且分解结果能为下一段接收数据的选取提供参考信忠。因而,同已有的信号处理方法相比,该方法具有明显的优越性,是一种比较好的信号分析方法。仿真实验证明了该方法的有效性。     

Java语言及其虚拟机技术探讨

随着Internet的迅猛发展，Internet编程语言Java愈来愈成为计算机行业的焦点。本文在简述了Java的主要特点后，重点对Java最关键的技术──虚拟机进行了深入的探讨。     

多棒高功率固体激光器动态模匹配研究

采用光学矩阵分析了多元热透镜谐振腔内模式的动态匹配特征,给出了平平腔参数调整的关系式,实验结果与理论分析相符,并在两棒连续Nd:YAG系统上得到0W～530W功率范围的稳定输出.     

基于Hausdorff距离的图像匹配技术

文中给出一种新的点匹配方法，这种方法对从传感器图像中抽取的点与从参考图像抽取的图像点进行匹配。点匹配算法要求挫个点集之间得到仿射变换，这种变换使得一个点集到另一个点集的距离最小。     

Epitaxial TiN based contacts for silicon devices

We have grown high quality epitaxial TiN/Si(100) and Cu/TiN/Si(100) heterostructures by pulsed laser deposition. The epitaxial TiN films have the same low (15 μΩ-cm) resistivity as TiSi₂ (C-54) phase with excellent diffusion barrier properties. In addition, Schottky barrier height of TiN was close to that of TiSi₂ (0.6-0.7 eV). Auger and Raman spectroscopy revealed that the films were stoichiometric TiN and free from oxygen impurities. The x-ray diffraction and transmission electron microscope (TEM) results showed that the TiN films deposited at 600°C were single crystal in nature with epitaxial relationship TiN|| Si. The Rutherford baskscattering channeling yield for TiN films was found to be in the range of 10–13%. The epitaxy of Cu on TiN was found to be cube-on-cube, i.e., Cull<100>TiN||Si. The Cu/TiN and TiN/Si interfaces were found to be quite sharp without any indication of interfacial reaction. The growth mechanism of copper on TiN was found to be three-dimensional. We discuss domain matching epitaxy as a mechanism of growth in these large lattice mismatch systems, where three lattice constants of Si(5.43?) match with four of TiN(4.24?) and seven units of Cu(3.62?) match with six of the TiN. Thus, for next generation of device complementary metal oxide semiconductor structures, Cu/TiN/Si(100) contacts hold considerable promise, particularly since Cu is a low resistivity metal (1.6 μΩ-cm) and is considerably more resistant to electromigration than Al. The implications of these results in the fabrication of advanced microelectronic devices are discussed.     

用于射频系统的10 MS/s 10位SAR A/D转换器

设计了一种用于射频系统的低功耗、中速中精度差分输入逐次逼近型(SAR)A/D转换器。采样完成后采用下极板对接的逻辑算法,10位SAR A/D转换器只需9位DAC即可满足其精度要求。DAC阵列采用分段电容结构,节省了芯片面积。比较器采用前置运算放大器加锁存器的结构,达到了同时兼顾速度和精度的要求。该A/D转换器芯片采用GSMC 0.13 μm 1P7M CMOS工艺制造,其核心电路尺寸为500 μm×360 μm,采用1.2 V的单电源供电。测试结果表明,当采样频率为10 MS/s,输入信号频率为2 MHz时,该SAR A/D转换器达到8.45位的有效精度,总功耗为2.17 mW;当采样频率为5 MS/s,输入信号频率为1 MHz时,该SAR A/D转换器达到8.75位的有效精度,总功耗为2.07 mW。     

比较法测试不同颜色匹配函数的性能

为了测试不同颜色匹配函数的预测性能,基于灰色、棕色、紫色和蓝色4个目标色,共制作了16对近同色异谱色样对(围绕每个目标色分别制作了4个待比较色),组织14名年龄不同的色觉正常观察者基于心理物理实验方法中的比较法,开展了色差大小比较实验。结果表明,实验组织的老年观察者的锥细胞响应较年轻观察者有所下降,CIE1931的预测性能优于CIE1964。不同颜色区域,各颜色匹配函数的表现各异,在进行某些颜色(如灰色,紫色和蓝色)区域的色度值表征和色差评估时,即便观察视场角大于4°,CIE1931的计算性能仍然优于CIE1964。现有CIE2006匹配函数考虑到晶状体光谱透光率和中央凹的锥细胞光谱响应,下一步可继续强化中央凹锥细胞光谱响应,优化其计算性能。     

偶氮聚合物薄膜的全光极化研究

报告了分散红共聚物膜HMMM-DR1,HMMM-DR19和偶氮侧链聚合物膜PCN6和PCN2的合成和制备, 并以HMMM-DR1和PCN6为代表比较研究了这两种具有不同吸收性质材料的全光极化特性,研究了他们的实时极化和弛豫过程,对他们的全光极化性质作了最基本的表征.研究了倍频光吸收对薄膜光极化效率的影响,讨论了偶氮聚合物材料光诱导二阶非线性极化率的效率和倍频光透射率之间的折衷关系,这对实用化的全光器件的研制是至关重要的.实验确证了在PCN6薄膜中实现了准相位匹配.对厚膜中光诱导二阶非线性极化率的弛豫抑制效应作出解释.     

Accurate, high-order representation of complex three-dimensional surfaces via Fourier continuation analysis

We present a new method for construction of high-order parametrizations of surfaces: starting from point clouds, the method we propose can be used to produce full surface parametrizations (by sets of local charts, each one representing a large surface patch – which, typically, contains thousands of the points in the original point-cloud) for complex surfaces of scientific and engineering relevance. The proposed approach accurately renders both smooth and non-smooth portions of a surface: it yields super-algebraically convergent Fourier series approximations to a given surface up to and including all points of geometric singularity, such as corners, edges, conical points, etc. In view of their C^∞ smoothness (except at true geometric singularities) and their properties of high-order approximation, the surfaces produced by this method are suitable for use in conjunction with high-order numerical methods for boundary value problems in domains with complex boundaries, including PDE solvers, integral equation solvers, etc. Our approach is based on a very simple concept: use of Fourier analysis to continue smooth portions of a piecewise smooth function into new functions which, defined on larger domains, are both smooth and periodic. The “continuation functions” arising from a function f converge super-algebraically to f in its domain of definition as discretizations are refined. We demonstrate the capabilities of the proposed approach for a number of surfaces of engineering relevance.