激光脉冲编码抗有源干扰效果研究

激光脉冲编码是激光制导武器的抗干扰措施之一。角度欺骗式干扰和高重频干扰是目前半主动激光制导武器的主要有源干扰来源。为研究不同激光脉冲编码方式对激光半主动制导武器抗这两种干扰性能的影响,本文针对敌方激光告警机的识别算法与我方导引头的解码过程,提出自相关函数与归一化互相关函数评价方法,并对目前主要编码方式进行仿真,仿真结果表明:激光脉冲编码的抗角度欺骗式干扰能力受编码序列周期性与脉冲间隔随机性的影响；抗高重频激光干扰能力受编码序列脉冲间隔随机性的影响；LFSR状态码的抗角度欺骗式干扰与抗高重频干扰效果均优于其他编码方式。     

土性参数的互相关性对加筋土挡墙可靠度的影响

分析3对土性参数的互相关性,即土的粘聚力和内摩擦角、填土与筋材的摩擦系数和填土内摩擦角、填土与地基的摩擦系数和填土内摩擦角之间的互相关性对一加筋土挡墙不同破坏模式可靠指标的影响。考虑土性参数的负相关会提高可靠指标;考虑土性参数的正相关,可能降低也可能提高可靠指标。忽略填土与基底的摩擦系数和填土内摩擦角之间的互相关性,则加筋土挡墙的抗滑验算偏于危险;忽略除此以外的其他参数之间的互相关性,则偏于安全。加筋土挡墙在其他破坏模式满足要求的前提下,不会发生倾覆破坏。土性参数互相关性是土的固有特性,对岩土工程的可靠度有一定影响,可根据工程的重要性决定是否需要在可靠度分析中加以考虑。     

基于激光诱导荧光的环状流液膜流速测量与分析

在对传统方法测量和分析液膜特性的基础上,采用激光诱导荧光方法和互相关测量技术,对竖直管道中的液膜流速进行光学测量和分析。基于高速摄影获取气液环状流中液膜图像,采用数字图像处理技术对液膜流动图像进行处理,得到液膜厚度在空间上的分布函数变化曲线,对间隔固定帧频的液膜图像进行互相关处理,进而采用抛物线拟合,有效提高了互相关极值的测量精度。实验结果表明,本文方法非接触、适用面广,可以有效检测环状流中液膜"破断"现象,并准确测量液膜流速参数。     

基于ANMF和非线性映射距离扩展目标检测

针对距离扩展目标的检测问题,提出一种自适应归一化匹配滤波（ANMF）、非线性映射和高阶互相关积累（HOCC）相结合的目标检测方法。首先将距离像按慢时间进行脉冲维划分,得到若干脉冲子区间,再对每个脉冲子区间进行自适应归一化匹配滤波,然后利用非线性函数对滤波的输出进行非线性映射处理,最后将非线性映射的输出进行高阶互相关积累,从而获得检测统计量。仿真实验结果表明,在检测概率为80％时,所述方法比传统 ANMF 方法所需的信杂比低1 dB 左右,性能较为优越。     

Application results of a prototype ultrasonic liquid film sensor to a 7 MPa steam–water two-phase flow experiment

A prototype ultrasonic liquid film sensor was applied to a high-temperature steam–water two-phase flow experiment. The liquid film sensor was vertically installed in a loop which was connected to HUSTLE, a multi-purpose steam source test facility. The hydraulic diameter of the measurement section was 9.4 mm. The output waveforms of the sensor were acquired with a digital oscilloscope. The fluid temperature and system pressure were kept at 288 °C and 7.2 MPa, respectively, during the experiment. The pulse-echo method was used to calculate the liquid film thickness. The cross-correlation calculation was utilized to determine the time difference between the pulse reflected at the sensor surface and the pulse reflected at the liquid film surface. The time-averaged liquid film thicknesses were less than 0.055 mm in the annular flow condition. The increase of the time-averaged thickness was small with the change of the gas momentum flux. The film thicknesses measured with the sensor were compared with the past experimental results; the former were smaller than one-fourth of the thickness estimated as the mean film thickness. The comparison results suggested that the continuous liquid sublayer thickness was measured with the liquid film sensor.     

Six Sigma experience as a stochastic process

This study empirically investigates the states of Six Sigma from a stochastic point of view. By the means of an advanced survey, 97 respondents are asked to rate the effect of Six Sigma on different performance categories, the cost of implementing Six Sigma, the level of enthusiasm and expectations from Six Sigma over 20 years. The autocorrelation and cross-correlation functions of these processes are analyzed to investigate the stages of Six Sigma. Consequently, new concepts namely steady state of Six Sigma and Six Sigma experience functions are introduced which shed light on the life cycle of Six Sigma within the companies.     

The global avalanche characteristics of two Boolean functions and algebraic immunity

The global avalanche characteristics criterion of two Boolean functions was introduced by Zhou et al. [On the global avalanche characteristics criterion of two Boolean functions and the higher order nonlinearity, Inform. Sci. 180(2) (2010), pp. 256–265] to measure the cryptographic behaviour in a global characteristic. The two indicators σ _{f, g} and Δ _{f, g} of Boolean functions f and g were presented. In this paper, a new upper bound on σ _{f, g} is derived, and a technique on constructing Boolean functions to attain the lower bound on the sum-of-squares indicator is described by using the disjoint spectra method. Some new upper bounds on Δ _{f, g} and σ _{f, g} are deduced for two special Boolean functions. Two relationships between σ _{f, g} and algebraic immunity of the two Boolean functions are obtained. Finally, some links among different cryptographic indicators are shown.     

飞秒激光脉冲序列互相关的数值模型与分析

为研究飞秒激光超短脉冲序列在空气中传输的时间相干特性,根据飞秒脉冲序列的传播理论和空气折射率Ciddor公式,建立了飞秒激光脉冲序列间脉冲在空气中传播的互相关数值模型。根据该模型可以得到不同光谱分布、不同光程差和不同大气条件下的飞秒脉冲序列间脉冲的互相关图形。数值模拟结果表明随着脉冲间光程差的增大,由于色散的原因,互相关图形加宽和啁啾,并且峰能量减小;然而当光程差不变,仅改变大气条件时,互相关图形仅仅作线性移动,没有任何额外线性加宽或啁啾。飞秒光学频率梳具有非常高的时间相干性,并且飞秒脉冲间的互相关图形只取决于激光器光源的光谱分布。     

基于循环相关的时延估计方法研究

该文研究了低频通信中的时延估计问题。考虑在低频信道大气噪声干扰的条件下,对接收信号进行削波处理后,采用循环相关法进行多径时延估计。经过削波处理,该方法能准确地估计出低频通信的时延,并且其性能优于广义相关法。该文最后的计算机仿真结果验证了文中的结论。     

泄漏管道波速预测理论及其应用

基于泄漏管道声振特性的互相关检测和定位方法,根据管道声振基本理论并结合管道泄漏的实际情况,提出了泄漏管道中波速预测理论,并对不同PVC塑料管道进行了泄漏检测和定位试验.试验结果表明,波速预测理论是正确可行的,且有效提高了互相关检测法的定位精度,将漏点定位的相对误差减小到5％以下.