应用于JPEG2000的离散小波变换并行VLSI结构

针对离散小波变换硬件资源占用率高的问题,提出了一种应用于JPEG2000的离散小波变换并行VLSI结构;引入了基于时间差的(9,7)小波并行滤波技术,使行和列滤波器同时进行滤波;采用2×2转置模块,实现了几个寄存器代替大量的中间转置存储空间。实验结果表明,该结构在关键路径的约束条件下,有效降低了硬件复杂性,大大提高了硬件资源利用率,几乎达到100%。该结构已通过VHDL 布局布线后仿真验证,并可作为单独的IP核应用于正在开发的VDR雷达图像采集卡中。     

Femtosecond nonlinear optical characterisation of silicon wafers: the role of symmetry

Femtosecond second-harmonic generation from the surface of as-grown 6 in silicon wafers is used as a tool for in situ characterisation of Czochralski-grown crystals. Exploiting the symmetry sensitivity of surface SHG, we used a particular two-pulse arrangement, similar to a conventional pump-probe set-up, to obtain non-destructive, in situ information about the location of three commonly known different areas of crystal quality: a central zone of vacancy-rich and an outer zone of interstitial-rich crystal which are separated by a ring of stacking faults. Finally, the applicability of the technique for on-line analysis and control during the growth of different types of gate dielectrics is discussed.     

基于层次诊断的水下结构振动噪声源分离量化

从声学的角度看,潜艇具有振动噪声源数目众多、相互之间耦合严重以及传递路径复杂的特点。层次诊断通过建立递阶层次结构对振动噪声源分离量化问题进行分解,从而形成了自上而下的支配关系,然后借助于标度通过两两比较建立判断矩阵,从而得到各振动噪声源对评价点的贡献量。根据声学中的分贝数相加原理,对层次分析法中的标度进行调整使其具有物理意义,从而使层次诊断结果是具有实际物理意义的测度。将潜艇层次诊断过程分为两个环节,分别为从艇内设备到壳体以及从壳体到水声场,并采用加权平均方法和D-S证据理论对这两个环节的计算结果进行融合。仿真计算和舱段试验验证了层次诊断应用到舱段模型振动噪声源分离量化问题中的可行性。     

基于小波—循环谱的新型识别技术

在通信系统中经常遇到的许多非平稳信号都具有循环平稳特性,可以用循环谱的方法来识别.但当信号本身的频谱结构比较复杂、噪声成分过大或噪声本身也具有循环平稳特性时,解调效果就不是很理想.针对循环谱识别信号的这一局限性,文中在介绍循环谱原理和识别特性的基础上,研究了几种典型通信信号的谱相关性,并提出了基于小波包与循环谱的识别技术,即先采用小波包进行软阈值消噪,再结合各自不同的循环谱特性进行识别.通过大量实验仿真表明,该方法具有很好的噪声抑制能力,能达到较好的识别效果.     

Design of a fiber-optic quasi-distributed strain sensors ring network based on a white-light interferometric multiplexing technique

A fiber-optic quasi-distributed strain sensors ring network has been designed based on a Mach-Zehnder optical paths interrogator. The optical paths matching for each sensor are discussed, and the optical power budgetary analysis is performed. The relation between the number of sensors and the intensity of the signals of the ring network is given for evaluation of the multiplexing capacity. Experimentally, a seven-sensor array ring network was realized under the condition of light source power 35 microW at 1310 nm, and the distribution strain test was also demonstrated.     

基于IAPES的分布式SAR高分辨成像

分布式SAR成像通常采用FFT估计信号频率参数,但其估计精度差且旁瓣高,在多目标的情况下会产生严重的相互干扰,降低成像质量。对此提出一种分布式SAR干涉幅度相位估计融合成像方法。该方法通过构造全局自适应FIR滤波器对分布式SAR信号进行分维滤波,同时应用干涉技术估计相位差完成相位校正,进而估计出带宽展宽的融合信号频谱,提高成像分辨率。而且IAPES频率估计精度高并能抑制旁瓣,从而精确估计目标的散射强度,达到改善成像质量的目的。实验仿真验证了该方法的有效性。     

Analysis of cooling effectiveness for heat flux based on reference enthalpy

In order to quickly and accurately compute the wall temperature distribution along the combustor axial line, a method to compute the temperature field of combustion chamber with active regeneratively cooling was presented. On the condition of nonstationary wall temperature, the one-dimensional cooling model based on reference enthalpy was established, and the distribution of the wall heat flux and the wall temperature along the combustor axial line were obtained at different mach numbers by using the heat transfer empirical equation. For the existing two types of cooling system structure, the cooling effectiveness of which was investigated through the presented method. And the satisfactory results obtained show the validity of the method.     

添加铝箔对DP590双相钢/AZ31B镁合金激光熔化焊接头显微组织和温度场的影响（英文）

对DP590双相钢和AZ31B镁合金进行钢上/镁下搭接和钢/镁层间添加铝箔的激光熔化焊试验,采用COMSOL有限元软件对钢/镁熔化焊温度场进行数值模拟。结果表明:添加铝箔可实现钢/镁有效连接,无明显气孔、裂纹和热影响区软化等缺陷,接头结合强度提高;添加铝箔可调控钢/镁层间热量传递,钢/镁熔池分上、下两部分,其相互接触但不发生混合,界面为铁和铝反应生成的AlFe、Al₂Fe和AlFe₃化合物组成的过渡层,促进上、下熔池冶金结合。因此,添加铝箔激光熔化焊是实现钢/镁异种金属连接的有效方法。