论GPS星座组成及若干抗AS方案

本文首先讨论GPS星座组成及美国的用政策，阐述了AS措施及其对GPS测量的影响。然后，对抗AS的若干方案进行介绍，分别对平方法、互相关法、码相关干法及P－W技术（Ashtech法）进行叙述和评论，指出它们的优缺点，评述它们在GPS技术发展过程所起的作用。最后，对GPS星座建成后的形势作了小结，并对当前我国GPS事业的有关问题提出四点建议。     

互相关函数法在声学测温技术中的应用研究

该文介绍了利用声学方法测量烟气温度的基本原理，并对声波飞渡时间的测量进行了计算机模拟分析和实验研究。利用信号处理技术中的互相关函数分析方法，计算声波发射端和接收端两路信号之间的时间延迟。采用计算机模型进行的研究表明，当接收端背景噪声和接收的信号水平相当时，在不作降噪处理的情况下，也能得到比较满意的分析结果。由于稳定周期信号作为测温声源在技术处理上有难度，该文设计了500—2000Hz范围内的扫频声波作为声源，对声波飞渡时间的测量进行了实验研究，结果表明该种声源和信号处理方法可以满足声学测温的技术要求。     

基于小波金字塔和轮廓特征的医学图像配准

提出一种快速而精确的自动医学图像配准算法.先提取图像的轮廓,根据力矩主轴法计算初步配准变换参数的值,实现参考图像和待配准图像的初步配准;然后在此基础上,利用小波分解图像,提取图像的边缘特征点,采用小波金字塔分层搜索的策略在一个相对较小的范围对变换参数进行迭代搜索,最终实现图像的精确配准.不但提高了配准的精度,而且可减少精配准过程中所需的时间,有效地降低了配准过程所需的计算量.由实验结果可以看出,配准结果精确,实现速度快,因此是一种实用的多模态配准算法.     

基于相关法的分布式全相参雷达相干参数估计及相参性能

针对一般结构的分布式全相参雷达,研究了基于相关法的时延差和相位差估计性能以及输出信噪比增益(oSNRg)。首先分别建立多输入多输出(MIMO)模式和全相参(FC)模式下的信号模型。然后重点分析估计相位差时的相位模糊问题,并提出一种有效的解模糊方法。数值实验结果表明：当输入信噪比足够高时,相关法能够获得稳健的相干参数估计,且oSNRg接近理想值。     

On the use of the coefficient of variation to measure spatial and temporal correlation of global solar radiation

In this work we perform a statistical analysis of global solar radiation measured at two sites, Petit Canal and Pointe a Pitre, 38 km distant from, Guadeloupe, French West Indies. We have established a correlation model based on the coefficient of variation assuming a time scale separation. The coefficient of variation is calculated on 10 min interval with data measured at 1 Hz. This analysis highlights the dynamic correlation that can occur between measurements from two different sites with a time step of 1 s. From these results, knowing the coefficient of variation on a site, we have established a new correlation model on this parameter for another site. A diagram linking the standard deviation for the studied sites, for a given coefficient of variation is proposed for correlated and non-correlated cases. Moreover this analysis evidences the existence of a threshold time under which there is no significant correlation. The methodology and the model can be applied to any other sites to establish diagrams of the coefficient of variation.This model can be useful in choosing new sites of PV production in establishing correlation from on site to another.     

基于波场分离的逆时偏移成像条件研究及在准噶尔盆地的应用

与传统深度偏移成像方法相比,基于双程波的逆时偏移方法针对地下陡倾角地区和复杂地下地质条件地区的成像有着无可比拟的优势。逆时偏移方法的实现通常有3个步骤:①在时间域实现震源波场的正向外推;②在时间域实现检波点波场的反向外推;③应用合理的成像条件构建成像结果。在实际应用过程中,通常是采用互相关成像条件来构建成像,然而,互相关成像条件构建的逆时偏移成像结果会产生强振幅的低频噪音,这些噪音会极大地降低资料的信噪比,容易导致浅层构造被噪音掩盖而无法识别,仅采用单纯的带通滤波并不能很好地滤除这种噪音。提供了一种新的基于波场分离理论的逆时偏移成像条件,此方法能有效地消除这些特定的噪音,其核心思路就是将震源及检波点波场分离成它们的单程波传播分量,然后仅在反射点处利用互相关的成像条件构建成像结果,从而实现逆时偏移成像。Marm-ousi模型数据验证了该方法的准确性;同时,采用文中提到的成像条件在准噶尔盆地百口泉地区进行了逆时偏移测试,测试结果充分证明新成像条件对野外资料的适应性。     

具有低相关值的新的修改的二元Jacobi序列

根据修改的二元Jacobi序列的构造方法,利用任意起点的二元Jacobi序列,构造了大量的新的二元序列。并利用kgendre特征函数的求和公式,给出了其中一类序列的自相关值及其它类序列在一定条件下的互相关值。结果表明,这类序列在一定条件下具有非常平坦的相关值分布。     

Feasibility study on optical vortex generation at Shanghai deep ultraviolet free-electron laser

Coherent light with orbital angular momentum （OAM） is of great interest. Recently, OAM light generation by coupling a relativistic electron beam with a Gaussian mode laser pulse at the high harmonics of a helical undulator has been demonstrated experimentally. In this paper, the possibility of delivering coherent OAM light at the 3rd harmonic of the Gaussian mode seed laser is discussed for the Shanghai deep ultraviolet free- electron laser （SDUV-FEL）. Considerations are given on the experiment setup, the expected performance and the possible measurement method.     

Electrical resistance tomography for flow characterization of a gas-liquid-solid three-phase circulating fluidized bed

Electrical resistance tomography (ERT) as an imaging technique was employed in this study for flow characterization, including simultaneous measurements of phase holdups and velocity distribution of individual phases in a gas-liquid-solid circulating fluidized Bed (GLSCFB). Application of ERT in three-phase flow systems is completely new. ERT is a non-invasive technique based on conductivity of the continuous phase, which provides color-coded cross-sectional view of the phases with a frequency of up to 250 Hz. The local conductivity measured by 16 electrodes located at the periphery of the plane inside the ERT measurement section, was then further converted into local phase concentration distribution based on Maxwell's relation. By cross-correlation analysis between the data obtained from both upstream and downstream planes, each consisting of eight electrodes, the phase propagation velocity was determined. Water was used as the continuous and conductive phase, while glass beads and air were non-conductive solid and gas phases, respectively. Qualitative and quantitative radial profiles of the phase holdup and propagation velocities were obtained. Phase holdup was also measured by pressure fluctuation, using online non-invasive pressure transducers and the results were in close agreement with the ERT results.     

Digital Cross-Correlation Detection of Multi-Laser Beams Measuring System for Wind Field Detection

A cross-correlation detection method to process backscatter signals of multi-laser beams measuring(MLBM) is presented,which can be firstly filtered by the digital filter composed of average median filter and finite impulse response(FIR) digital filter.The processing of backscatter signals using single-pulse and three-pulse cross-correlation detection methods is depicted in detail.From calculation results,the multi-pulse cross-correlation detection could effectively improve signal-to-noise ratio(SNR).Finally,both wind velocity and direction are determined by the peak-delay method based on the correlation function which shows high measuring precision and high SNR of the MLBM system with the assistance of the digital cross-correlation detection.