双目标相干源窄带信号波达方向估计算法

利用水下目标发出的窄带信号,能够实现目标方向的精确估计。针对均匀线列阵接收水下目标窄带信号的特点,提出一种相干源波达方向(Direction of Arrival,DOA)估计的快速算法。通过精确估计目标信号对应的空间频率,直接计算出单目标或双目标信号的波达方向。对该算法进行了理论推导,通过仿真对算法进行验证,并对影响DOA估计精度的因素进行了分析。仿真结果表明,该算法具有较高的估计精度,不受信号时间长度的影响,算法计算量小,便于实时处理,具有较好的工程应用前景。     

目标地震动信号的特征提取及识别研究

地面目标的地震动信号是目标识别的关键,本文研究了机动目标地震动特性,总结出目标的地震动信号的特征提取规律,并将神经网络方法用于目标的地震动信号的分类识别中。给出了识别结构及改进的BP算法,并将改进的BP算法用于实际目标的地震动信号的分类识别,得到令人满意的结果。     

基于子带锐化互相关处理的目标方位估计方法

将双接收器信号分频段处理的思想引入被动测向估计中,提出了一种子带锐化互相关算法。该算法利用高斯函数替代各频段信号互相关函数来实现尖锐化,再进行加权处理,以解决互谱相关算法在多目标或存在干扰情况下的目标方位估计效果不理想问题。仿真和海试数据处理表明,对具有频谱分布差异性的带限信号来说,算法在多目标、强干扰情况下仍可很好地估计目标方位,并且可以同时得到目标的频率信息,根据信号频带的不同还可以分辨相同方位角入射的不同目标。     

基于多目标粒子群算法的稀疏分解参数优化

针对振动信号稀疏分解过程中存在的复杂参数设置问题,提出利用多目标粒子群算法进行稀疏分解参数优化,以实现振动信号的有效压缩。根据多目标粒子群理论,建立稀疏分解参数优化模型,确定粒子群优化目标函数、待优化参数,分析参数设置与目标函数之间的泛函关系。设计仿真实验,研究数据压缩指标之间的约束关系,指导多目标粒子群算法参数优化,改善数据压缩效果。应用实测数据,验证多目标粒子群算法的参数优化能力,实验结果表明:多目标粒子群算法能够优化振动信号稀疏分解参数,取得良好的振动信号数据压缩效果。     

频谱相似性目标识别算法

地面运动目标识别的难点是对不同类型车辆目标的识别。介绍了一种地面运动目标的信号识别方法——频谱相似性,详细地叙述了频谱相似性算法的原理,从理论上证明了算法的正确性。通过对实际采集轮式和履带车辆行驶时所发出的声信号作为样本进行训练,再对测试声信号采用频谱相似性算法进行识别,实验结果证明了该算法的可行性。与复杂声信号识别算法相比,该算法具有计算量小、易于移植到DSP等小型信号处理器件上的优点。     

基于稀疏信号功率迭代补偿的矢量传感器阵列DOA估计

针对现有稀疏信号功率迭代算法对方位相近目标分辨概率与估计精度较低问题,提出了一种稀疏信号功率迭代补偿的矢量传感器阵列波达方向(Direction of Arrival, DOA)估计方法。基于稀疏信号补偿原理和加权协方差矩阵拟合准则,构建了关于稀疏信号功率与补偿权重的目标函数。推导了稀疏信号功率迭代更新表达式的闭式解。通过对稀疏信号功率进行谱峰搜索获得DOA估计值。理论分析表明,所提算法通过对离散网格点上的信号功率进行补偿提高了方位相近目标的分辨率概率与估计精度。仿真结果表明,相较于经典子空间算法与现有稀疏功率迭代算法,所提算法对方位相近目标具有较高的分辨概率与估计精度。     

基于盲分离技术的双目标辨识与定位方法研究

研究了利用盲分离技术对水下目标辐射噪声信号进行辨识和定位，指出了在水声信号盲分离过程中。自然梯度算法具有不稳定收敛的不足，通过构建新的非线性函数和学习因子等。提出了自然梯度算法的改进方法，经实船信号的盲分离实验表明．该算法在稳定性方面有改进。在对目标信号盲分离的同时。估计了目标信号到达基阵的时延，完成了双目标的辨识与定位。     

基于频率着色的稀疏贝叶斯宽带波达角估计方法

为了提升稀疏贝叶斯(Sparse Bayesian Learning, SBL)算法在干扰环境下对目标信号的检测能力,提出将频率着色技术(Frequency Coloring, FC)推广至SBL算法中。在SBL-FC算法中,首先将阵列接收信号通过傅里叶变换转换至各个子带,在各子带内利用SBL算法进行波达角估计,输出功率谱。不同于常规的SBL算法仅将各子带的功率谱进行简单地叠加,算法考虑干扰和目标频谱结构的差异性,对各子带进行不同的着色,使得干扰和目标轨迹在方位时间历程图上对应于不同的颜色,从而使得目标轨迹更易被提取。数值仿真和实验数据分析表明,利用目标和干扰频谱结构的差异性可有效提升SBL算法在干扰环境下对目标信号的检测能力。     

一种基于相关积分的互谱WVD目标方位估计方法

针对水下高速运动目标的被动跟踪问题,将魏格纳-威尔分布(Wigner-Ville Distribution,WVD)算法与互谱法相结合,构建了一种矢量信号处理框架下的目标方位估计方法——基于相关积分的互谱WVD算法。该算法利用了矢量水听器声压通道与振速通道信号的相关特性,首先通过计算两者的互相关函数来提取目标信号的特征信息,然后通过短时积分与傅里叶变换将互相关函数从时域转换到频域,最后在频域提取信号的特征参量,并进行方位估计。仿真研究表明,当目标处于远距离且低速运动时,所提算法的方位估计性能与互谱声强法基本一致;而当目标处于近距离且高速运动时,算法的方位估计性能大大优于互谱声强法。     

一种新的相位编码信号多普勒补偿算法研究

相位编码信号是一种多普勒频率敏感信号,而且码长越大,对多普勒频率越敏感,严重影响了雷达对高径向速度目标和远距离目标探测的能力。该文在分析伪码序列与多普勒容限关系的基础上,提出一种新的伪码调相准连续波雷达的多普勒补偿算法。该算法将回波信号取平方后送到动目标检测(MTD)滤波器中,通过提取回波信号中的多普勒频率信息,进行多普勒补偿。从仿真结果可以看出,该算法能够有效地降低多普勒频率对脉冲压缩结果的影响,验证了方法的可行性。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

卧式金属罐容量的测量结果不确定度

本文根据多年的实践检定经验 ,参照JJF1 0 59- 1 999《测量不确定度评定与表示》以及《测量不确定度表达 1 0讲》 ,对卧式金属罐容量的测量结果不确定度进行了评定。     

盐酸浓度不确定度的评估

通过对盐酸浓度标定的过程分析，找出影响结果的各个分量，进行不确定度的评定，按照计量技术规范给出标准的表示法。     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.