On the Relative Gain Array (RGA) with singular and rectangular matrices

This paper identifies a significant deficiency in the literature on the application of the Relative Gain Array (RGA) formalism in the case of singular matrices. Specifically, it is shown that the conventional use of the Moore–Penrose pseudoinverse is inappropriate because it fails to preserve critical properties that can be assumed in the nonsingular case. It is then shown that such properties can be rigorously preserved using an alternative generalized matrix inverse.     

B型套筒角焊缝缺陷相控阵超声检测定量方法

B型套筒修复作为油气管道修复的主要方式之一,在其修复的焊接过程中,该结构的环形角焊缝内部常常出现以气孔、夹渣为代表的孔型缺陷。这类缺陷由于角焊缝特殊的结构,在利用相控阵超声无损检测技术对其检测时,难以对其进行定量分析。通过数值模拟和实验,发现通过相控阵超声扇扫得到缺陷回波信号峰值与孔型缺陷直径呈正相关,为孔型缺陷的定量分析提供了一种可靠的手段。     

基于现场可编程门阵列单探测器复合轴控制技术

为了解决空间激光通信系统中单探测器复合轴结构的粗精解耦难题,通过分析二维关联控制矩阵,得出粗精跟踪解耦的必要条件,提出了一种单探测器复合轴结构的工作方式.在跟踪过程中,相机直接配合子轴执行器完成精跟踪工作,而主轴的跟踪信息由子轴的角度偏转器来提供,同时所有的图像处理算法、位置检测算法、以及粗精伺服控制算法都在现场可编程门阵列中实现,完成了系统的轻小型化设计.实验搭建了测试系统,并对现场可编程门阵列硬件和系统跟踪性能进行测试,结果表明单探测器复合控制系统可以实现跟踪准确度优于3μrad,为工程化奠定了良好的基础.     

Time and direction of arrival detection and filtering for imaging in strongly scattering random media

We study detection and imaging of small reflectors in heavy clutter, using an array of transducers that emits and receives sound waves. Heavy clutter means that multiple scattering of the waves in the heterogeneous host medium is strong and overwhelms the arrivals from the small reflectors. Building on the adaptive time-frequency filter of [Borcea et al, SIIMS 2011;4(3)], we propose a robust method for detecting the direction of arrival of the direct echoes from the small reflectors, and suppressing the unwanted clutter backscatter. This improves the resolution of imaging. We illustrate the performance of the method with realistic numerical simulations in a non-destructive testing setup.     

Photocatalytic performance of ZnO:Fe array films under sunlight irradiation

ZnO:Fe array thin films were prepared by the hydrothermal method using the sol-gel grown film as a seed layer. The samples were characterized by X-ray diffraction (XRD), ultraviolet/visible absorption spectra (UV-vis) and scanning electron microscopy (SEM). The photocatalytic activities of the prepared samples were investigated for the photodegradation of methylene blue (MB) under sunlight irradiation. The results show that the lattice constant a and the cell volume of ZnO:Fe film increase due to the substitution of Fe for Zn. The absorption edge of Fe-doped ZnO displays a red shift with a significant absorption between 600 and 700 nm. The ZnO:Fe array film is composed of disk particles with uniformity and compactness. Doping Fe ions enhances the photodegradation rate of ZnO array film for MB. 1.5% Fe doped ZnO sample exhibits the highest activity under irradiation time of 4 h. Its degradation rate increases about 1.6 times compared to the undoped ZnO.     

利用拖线阵运动特性的阵形估计方法

有效估计阵形是提高机动条件下拖线阵声呐探测性能的关键,流体力学类阵形估计方法稳定性和可靠性欠佳,导致其难以应用于工程实际,该文针对此问题提出一种基于拖线阵运动特性的阵形估计方法。利用稳态振荡响应公式计算拖船回转机动时拖线阵稳态阵形特性,将转向机动过程中阵上各点运动状态划分为若干阶段,进而依据偏微分方程特征线理论计算各阶段的分界时刻,探究阵上相邻两点的沿阵切线方向差变化规律,最后通过计算当前阵上各点的沿阵方向实现阵形估计。计算机仿真和海上实验数据验证表明算法可行且有效,与传统的流体力学类阵形估计方法相比具有更高的稳定性和更好的工程应用前景。     

小快拍高分辨目标方位估计算法 GMUSIC的性能分析*

针对水下运动阵列在运动过程中进行方位估计时存在快拍不足的问题,研究了基于随机矩阵理论的MUSIC改进算法GMUSIC,该方法通过Stieltjes变换建立起统计协方差矩阵真实特征值、特征向量与样本协方差矩阵之间在逼近域中的关联,以修正样本协方差特征分解的结果,进而实现小快拍方位估计。仿真与试验表明:GMUSIC算法可以更好地分辨相邻目标,且需要的快拍数较MUSIC算法要少;在低信噪比情况下,GMUSIC算法方位估计均方根误差远小于MUSIC算法,估计成功概率远大于MUSIC算法。因此,GMUSIC算法适用于解决水声目标的小快拍方位估计问题。     

基于阵列倏逝波荧光传感器的雌二醇免疫检测方法

近年来,环境内分泌干扰物愈来愈受到人们的关注。对其用传统的检测技术分析,过程复杂、耗时长、价格昂贵,因此急需发展灵敏度高、反应迅速快、价格低廉的检测手段。介绍了一种平面波导型阵列倏逝波荧光生物传感器,在对系统光路参数进行模拟优化的基础上,可实现24个传感位点的同步、快速、灵敏检测。基于此阵列倏逝波荧光传感器,运用间接竞争免疫检测模式,优化并建立环境内分泌干扰物雌二醇的标准检测条件。实验结果表明,入射角在61.8°时,系统灵敏度最高。该方法对雌二醇检测线性检测区间为0.08~2.52 μg·L-1,检测限为0.05 μg·L-1,半抑制浓度为0.46 μg·L-1,完成单次样品的检测时间为20 min。利用该传感器对污水处理厂出水进行加标回收测试,回收率在84%~120%之间,相对标准偏差小于15%,表明该方法能够用于实际水体中雌二醇的快速检测。