超波束(HBF)用于波束锐化

介绍了一种波束锐化技术,即超波束形成技术（Hyper Beamforming,HBF）,可以在减小波束宽度的同时抑制旁瓣,提高目标检测性能及方位估计能力。该方法结合常规空间加权可以进一步降低旁瓣,从而可以利用较小规模的基阵尺寸,实现大基阵的检测性能。文中给出了恒定束宽HBF实现所需系数,并将该方法应用于CW及FM信号处理,给出了预期的仿真结果。     

MSB-CAATI算法在多波束测深系统中的应用

计算到达角瞬态成像技术(CAATI)是多角测深侧扫声纳(MSBSS)采用的高分辨方位、幅度联合估计技术。本文将CAATI技术扩展到多波束测深声纳(MBBS),提出了一种新的多子阵波束域CAATI(MSB-CAATI)算法。仿真实验证明了该算法与CAATI技术相比具有更高的估计精度和更低的分辨力门限。海试数据的处理验证了MSB-CAATI能很好地应用到多波束测深系统中,使其兼备了FT(傅氏变换)和CAATI各自的优点,能在整个条带宽度内同时获得高分辨力的海底地形和地貌信息,且不易受到低信噪比和复杂地形环境的影响。     

多波束测深声纳技术研究新进展

多波束测深声纳已成为国内外海洋科学研究、海底资源开发、海洋工程建设等海洋活动中最主要的海洋调查勘测仪器之一。以多波束测深声纳为对象,详细介绍了国内外多波束测深声纳产品的发展情况,重点阐述了代表当前多波束测深声纳发展趋势的超宽覆盖、高分辨、高精度、多功能一体化探测等核心技术的研究进展,最后结合实际的海底地形地貌探测需求,给出了多波束测深声纳技术未来发展的展望。     

海洋工程勘察中多波束测深的应用

随着电子技术、计算机技术．特别是高精度GPS定位技术的完善,多波束技术也得到了迅速发展,并广泛应用于海洋工程勘察中,多波束测深系统的优势也越来越明显。本文首先阐述了多波束测深的工作原理,其次,分析了影响海洋工程勘察中多波束测深精度的因素。同时,就多波束测深在海洋工程勘察中的应用进行了深入的探讨,具有一定的参考价值。     

基于多波束测深声呐的海底气体泄漏实时报警系统

随着人们对海底油气资源的开发,在海底铺设的管道越来越多,海底管道泄漏风险日益增加,亟需高效、实时的检测方法。文章利用自主式水下航行器(Autonomous Underwater Vehicle, AUV)平台,搭载多波束测深声呐与基于VxWorks的嵌入式处理单元,设计了一套水下气体泄漏自动检测系统,将多波束测深声呐采集的水体图像数据传送给嵌入式处理单元,采用模板匹配方法对图像数据进行处理,完成对海底管道气体泄漏点的实时检测。湖试和海试都验证了该系统方案的有效性与先进性。     

基于空间平滑的多波束测深声呐相干分布源方位估计

在多波束测深声呐的工作环境中,若海底反向散射信号不满足点源假设,方位估计精度将严重下降,而基于分布源模型的方位估计算法可以适应这种环境。目前,大多数分布源算法要求分布源之间不相干,有人提出采用Toeplitz方法估计相干分布源,但该方法精度不高并且忽略了角度扩展参数。为解决多波束测深声呐相干分布源的方位估计问题,提出了基于空间平滑的广义MUSIC方法,公式推导证明了算法的有效性,通过计算机仿真给出算法方位估计的精度以及不同信噪比条件下的性能,最后采用多波束测深系统的实验数据对算法进行了验证。     

幅度-相位联合检测法在多波束测深系统中的应用

幅度蛳相位联合检测法是传统多波束测深系统海底检测法的发展方向,它充分利用了幅度和相位信息,能大大扩展测量范围,提高测量精度。文章对该方法的具体应用进行了研究,在确定信号粗略到达时间时采用了一种自动跟踪门方法,同时针对相位检测法实时处理数据运算量大的特点,提出了一种数据压缩与动态滑动平均相结合的数据预处理方法,该方法大大减小了运算量,其有效性通过方差分析进行了验证。数据处理结果表明,采用了自动跟踪门和数据预处理相结合的幅度蛳相位联合检测方法可明显扩展多波束测深系统的条带宽度。     

改进的超波束形成算法探讨及性能研究

为进一步提高超波束形成(Hyper Beam Forming,HBF)算法的性能,在传统的HBF基础上提出一种改进的HBF(Improved Hyper Beam Forming,Im-HBF)算法。将基于半阵指向性函数高阶运算修正到基于全阵指向性函数的高阶运算。仿真结果表明,Im-HBF算法具有更窄的主瓣,并且对端射来波信号栅瓣抑制能力更强,进一步提高了对目标的检测能力。同时,Im-HBF算法对指数n具有更为广泛的适用性,当指数n2时也能获得优于常规波束形成(Conventional Beam forming,CBF)的波束性能。     

现代深水多波束测深系统简介

对目前国外深水多波束测深系统的发展状况进行了介绍,以目前世界上最流行的深水多波束测深系统EM120为代表,介绍了其技术特点和性能指标。并且阐述了深水多波束测深系统的发展趋势;     

多波束系统在水下探测中的应用

由于单波束在水下探测的局限性,因此为实现大范围,全覆盖和高精度的探测,本文对多波束系统在水下探测中的应用进行研究。在介绍多波束系统的构成与测量的基础上,结合水下探测项目,通过多波束系统波束脚印归位、数据检测、数据改正和数据结构统一,对精度进行评估。通过分析成果精度得出,应用多波束系统的成果精度更满足实际需求,有一定的先进性和实用性。     

Reduction of residual stress and deformation in electron beam welding by using multiple beam technique

The electron beam could be controlled by magnetic field for fast deflection, in which way multi-beam could be produced by deflection technique. The multi-beams run simultaneously for material processing with different heat input and positions. Therefore, it is possible to adjust the thermal effects and optimize the process. In this paper, the generation of multi-beams in electron beam welding (EBW) was investigated, and the processes of EBW with multi-beams were also investigated by both the numerical simulation methods, i.e., finite element analysis (FEA), and the experiments. The result shows that the residual stress of EBW could be minimized by using the multiple beam technique, and at the same time the welding deformation could also be reduced with the optimized parameters.     

应用chirp声呐探测海冰的试验研究

应用声呐技术可以实现在水下连续监测海冰的厚度和速度等参数,为海洋研究和工程提供重要的数据.采用chirp 信号的声呐能有效探测冰水界面,试验表明声呐测距的精度优于1cm,能够满足探测渤海海冰的指标要求.     

基于波束域MUSIC方法的高分辨方位估计

现代声纳系统普遍采用水听器基阵和一定的信号处理来提高对目标的检测和定位能力，而基阵的波束形成则在其中起着核心作用。文中研究了窄带波束域高分辨方位估计技术，分析了波束域MUSIC方位估计的构造过程和具体实现方法。仿真计算表明，基于波束域MUSIC的方位估计算法是一种分辨空间小角域内多个目标的有效方法。     

Note on polarization of electron beam

Based on the classical theory of electrodynamics, we show the feasibility of using superconductors to realize transversal and longitudinal polarizations of electron beams. The results can in principle be used with beams of positron and/or other particles with magnetic moments without major modifications. We briefly discuss applications of polarized electron beams in physical sciences and technology.     

Implementation of intra-cavity beam shaping technique to enhance pump efficiency

In this work we propose an implementation of a new intra-cavity beam shaping technique to vary the intensity distribution of the fundamental mode in a resonator cavity while maintaining a constant intensity distribution at the output. This method can be useful for fitting a transversal intensity profile of the required mode with a pump beam profile in the region of the active medium to increase mode discrimination.     

Tunneling control of cavity linewidth narrowing via quantum interference in triangular quantum dot molecules

A scheme for tunneling control of cavity linewidth narrowing by quantum interference in triangular-type triple quantum dots (TQDs) is proposed. In such system, quantum interference induced by tunneling between the TQDs can result in the appearance of two transparency windows and a steep dispersion. Furthermore, when the sample is embedded in a ring cavity, an ultranarrow transmission peak is obtained within the narrowed transparency windows. And by varying the tunneling, the linewidth and the position of the ultranarrow transmission peak can be engineered. Because no coupling laser is required, the scheme proposed here is more convenient for future experiments and applications in optics, and may be useful in designing novel optoelectronic devices.     

Influence of laser array performance on spectrally combined beam

Abstract

Incoherent spectral beam combining (SBC) of multiple laser beams is accomplished along the emitters’ arraying direction. Considering that the output beams from a laser array (LA) usually have deflection angles, positional displacements and divergence angles even after being collimated, a propagation model of SBC systems based on multilayer dielectric gratings has been built up. On the basis, properties of the spectrally combined beam affected by parameters of the LA have been discussed in detail. Simulation results show that with the increase in the deflection angle, both the power and the beam quality of the combined beam degrade dramatically. The positional displacement has little impact on the intensity distribution and the beam quality of combined beam but change the wavelength composition of the combined beam. The divergence angle strongly affects the intensity distribution and the beam quality of the combined beam. Additionally, the effect of the deflection angle on the output beam quality is more obvious and may shift the beam spot when comparing with that of the divergence angle.