高功率大模场光纤激光器高阶模抑制技术的研究进展

大模场光纤可以降低纤芯功率密度及提高非线性效应的阈值,是进一步提高光纤激光器功率的重要技术途径,但随着纤芯的增大,光纤中将产生多横模运转,降低光束质量。对国内外大模场光纤激光器中的高阶模抑制技术的研究进展进行详细的介绍。对大模场光纤激光器模式控制的发展前景进行了展望。     

千瓦级3倍衍射极限的高功率热容激光器

开展了热容激光器光束质量控制研究,进行了耦合系统的优化设计,采用了透镜压缩结合波导匀化的设计思想,使抽运均匀性提高到90%的水平;进一步建立了有源非稳腔的理论分析模型,针对热容激光器的抽运条件开展了非稳腔的优化设计,实验结果表明实现了2.7倍衍射极限的千瓦级热容激光输出.     

激光冲击强化区的残余应力测试分析

用高重复率钕玻璃激光器,对QT700-2进行了激光冲击强化处理,利用X-350A残余应力测试仪对QT700-2激光冲击强化区残余应力进行了测试,结果显示经激光冲击处理后试件表面具有较高的残余压应力,可达-200Mpa以上;分析了表面残余应力及沿层深方向残余应力的分布情况。对激光冲击强化处理技术的实际工程应用具有指导性意义。     

基于提取双选紧密特征的RGB-D显著性检测网络

针对现有算法对不同来源特征之间的交互选择关注度欠缺以及对跨模态特征提取不充分的问题,提出了一种基于提取双选紧密特征的RGB-D显著性检测网络。首先,为了筛选出能够同时增强RGB图像显著区域和深度图像显著区域的特征,引入双向选择模块(bi-directional selection module, BSM);为了解决跨模态特征提取不充分,导致算法计算冗余且精度低的问题,引入紧密提取模块(dense extraction module, DEM);最后,通过特征聚合模块(feature aggregation module, FAM)对密集特征进行级联融合,并将循环残差优化模块(recurrent residual refinement aggregation module, RAM)配合深度监督实现粗显著图的持续优化,最终得到精确的显著图。在4个广泛使用的数据集上进行的综合实验表明,本文提出的算法在4个关键指标方面优于7种现有方法。     

Two-dimensional DOA estimation for acoustic vector-sensor array using a successive MUSIC

This paper discusses the problem of two-dimensional (2D) direction of arrival (DOA) estimation for acoustic vector-sensor array, and derives a successive multiple signal classification (MUSIC) algorithm therein. The proposed algorithm obtains initial estimations of the azimuth and elevation angles obtained from the signal subspace, and uses successively one-dimensional local searches to achieve the joint estimation of 2D-DOA. The proposed algorithm, which requires the one-dimension local searches, can avoid the high computational cost within 2D-MUSIC algorithm. The proposed algorithm can obtain automatically-paired 2D-DOA estimation for acoustic vector-sensor array, and it has better DOA estimation performance than propagator method, estimation of signal parameters via rotational invariance technique algorithm and trilinear decomposition algorithm. Meanwhile, it has very close angle estimation to 2D-MUSIC algorithm. Furthermore, it is suitable for non-uniform linear arrays, works well for the sources with the same azimuth angle, and imposes less constraint on the sensor spacing, which does not have to be restricted within half-wavelength. We have also derived the mean-square error of DOA estimation of the proposed algorithm and the Cramer-Rao bound of DOA estimation. Simulation results verify the usefulness of the proposed algorithm.     

Reduced-Dimensional ESPRIT for Direction Finding in Monostatic MIMO Radar with Double Parallel Uniform Linear Arrays

In this paper, the issue of two-dimensional direction of arrival estimation in monostatic multiple-input–multiple-output (MIMO) radar with double parallel uniform linear arrays is studied, and an algorithm based on estimation of signal parameters via rotational invariance techniques (ESPRIT) is proposed. Through a series of reduced-dimensional transformations, the proposed algorithm has very low complexity due to the low dimension. Meanwhile, the estimation performance of the proposed algorithm is slightly improved compared to the conventional ESPRIT, especially in low signal-to-noise ratio. Furthermore, the algorithm can estimate azimuth and elevation angles without additional pair matching in monostatic MIMO radar. Error analysis of the angle estimation and Cramér–Rao bound are derived. Simulation results verify the usefulness of our algorithm.     

基于Sagnac型的双光路平衡探测光纤声传感器

为解决传统声电传声器易腐蚀、易受电磁干扰等问题,提出了一种用光纤提取声音的声光换能器结构。该传感器以Sagnac干涉仪为原型,利用声压作用于感应光纤产生的光弹效应实现光波相位的调制,采用3 × 3耦合器构建双光路平衡探测系统,通过干涉实现语音信号的解调,将光电转换后得到的幅值相等的两路信号进行差分处理,消除共模干扰信号和降低光源噪声。实验测试表明,系统性能稳定,波形失真小,在300~3 400 Hz范围内实现声音信号的提取与还原。     

DOA estimation for sparse nested MIMO radar with velocity receive sensor array

Direction of arrival (DOA) estimation for sparse nested MIMO radar with velocity receive sensor array is studied, and an algorithm based on extended unitary root multiple signal classification (MUSIC) is proposed. The nested MIMO radar utilizes sparse transmit array and velocity receive array with nested inter-element distances, which can make the final virtual array to be a long and sparse velocity sensor array. After exploiting unitary transformation to transform the data into real-valued one, an extended root MUSIC based method is developed to decompose the angle estimation into high-resolution but ambiguous and low-resolution but unambiguous DOA estimations, which are automatically paired. Thereafter, the ambiguous estimation is used to recover all possible DOAs, and the unambiguous DOA estimation is used as a reference to resolve the estimation ambiguity problem. Compared to conventional methods, the proposed algorithm requires no peak search, maintains larger aperture and achieves better DOA estimation performance. The simulation results verify the effectiveness of our approach.     

大口径主镜支撑液压缸用弹性膜片优化设计

在大口径望远镜主镜液压支撑形式中,液压缸需要一种简单可靠、不需要润滑维护的精密导向机构,而且可以输出较大行程范围(毫米级)。设计了一种柔性金属膜片机构用于液压缸的径向定位导向。建立了金属膜片机构有限元模型,采用几何非线性算法,研究分析了不同拓扑结构对金属膜片柔度的影响,通过不同拓扑结构金属膜片的性能分析对比可知,V 型膜片能够很好地克服应力刚化,保证柔度的稳定性;以柔度为优化目标,对金属膜片V 型的位置尺寸和形状尺寸进行了优化设计,金属膜片在导向方向上的柔度提高了14.2%;搭建了柔性金属膜片机构柔度测试平台,验证了仿真计算结果。结合实验和仿真结果可知:V 型柔性金属膜片具有良好的定位导向性能,对用于液压支撑的液压缸和主动光学的微位移促动器的导向机构的设计具有指导意义。     

基于SCA的软件无线电平台研究

本文在全面深刻理解SCA规范的基础上提出了一个具体方案来实现符合SCA规范的软件无线电系统。本技术方案包括系统的软硬件体系结构，基于SCA规范的通信波形的开发以及系统中频板的研制等，其中系统中频板的研制主要介绍PCI接口电路的设计，Vxworks实时操作系统下驱动程序的编写等。