深水多波束测深系统脉冲压缩实时算法

线性调频信号是大时宽带宽积信号,通过脉冲压缩可提高探测距离和分辨率,已在深水多波束测深系统中得到广泛应用。针对深水多波束测深系统中脉冲压缩运算量大的问题,提出了一种基于分组的脉冲压缩实时算法。该算法对需要进行脉冲压缩的波束进行分组,每个节拍只计算一组波束,可大幅减少深水多波束测深系统脉冲压缩的运算时间,节省了处理器资源。该算法已成功应用于某深水多波束测深系统,经多次海试证明,工作稳定可靠。     

A Bayesian approach to seafloor classification using multi-beam echo-sounder backscatter data

Seafloor classification using acoustic remote sensing techniques is an attractive approach due to its high-coverage capabilities and limited costs. The multi-beam echo-sounder (MBES) system provides high-resolution bathymetry and backscatter information with 100% coverage. In this paper, we present a seafloor classification method that employs the MBES backscatter data. The method uses the averaged backscatter data per beam. It, therefore, is independent on the quality of the MBES calibration. Also, its performance is insensitive to seafloor type variation along the MBES swathe and corrections for the angular dependence of the backscatter are not needed. The method accounts for the ping-to-ping variability of the backscatter intensity. It estimates both the number of seafloor types present in the survey area and the probability density function for the backscatter strength at a certain angle for each of the seafloor types. Application of the method to MBES backscatter data acquired in a well-known test area in the North Sea shows very good agreement with available ground truth. The method’s discriminatory performance for this area is demonstrated to be comparable to that of taking samples of the sediment. All seafloor types known to be present in the area are resolved for. Application of the method to the Stanton bank data set shows clearly separable areas that differ in seafloor composition.     

A study of multi-beam DICANNE system

I.IntroductionTheprob1cmofsuppressingstrongpointinterferencesourceisavcryimportantthesisinsonardesign.Fortheana1ogsonar,thesolutionofthisprob1emisquitedifficu1t.Untilthedevelopmentofdigitalsonar,thereissomerescarchreportsaboutsuppressingstrongpointin-terferencesource.Theear1ierworkin1969,dedicatcdbyV.C.Anderson,istheconccptofDICANNE(DigitalInterfcrcnceCance1lingAdaptiveNu1lNetworkEquipment)['l.Thisisadoublecompensatormulti-bcamsystcm.Oneisusedtoformintcrfercncebeamandanothcrisusedtofor…     

Analytical and experimental studies on nonlinear characteristics of an L-shape beam structure

This paper focuses on theoretical and experimental investigations of planar nonlinear vibrations and chaotic dynamics of an L-shape beam structure subjected to fundamental harmonic excitation,which is composed of two beams with right-angled L-shape.The ordinary differential governing equation of motion for the L-shape beam structure with two-degree-of-freedom is firstly derived by applying the substructure synthesis method and the Lagrangian equation.Then,the method of multiple scales is utilized to obtain a four-dimensional averaged equation of the L-shape beam structure.Numerical simulations,based on the mathematical model,are presented to analyze the nonlinear responses and chaotic dynamics of the L-shape beam structure.The bifurcation diagram,phase portrait,amplitude spectrum and Poincare map are plotted to illustrate the periodic and chaotic motions of the L-shape beam structure.The existence of the Shilnikov type multi-pulse chaotic motion is also observed from the numerical results.Furthermore, experimental investigations of the L-shape beam structure are performed,and there is a qualitative agreement between the numerical and experimental results.It is also shown that out-of-plane motion may appear intuitively.     

多注毫米波行波管收集极的热设计

 为解决多注毫米波行波管收集极的散热问题,保障行波管工作可靠性与稳定性,利用 ANSYS 有限元软件模拟分析了收集极的传热特性,针对性地调整和优化了收集极相关参数与结构。研究结果表明：接触热阻是造成收集极具有较高温升的一个重要因素,由接触热阻所造成的温升约占收集极内外温度差的1/3;并不是第二电极与磁环接触宽度越宽所对应的收集极散热能力就越强,而是在一定工作条件下其散热能力存在极限值;对于绝缘陶瓷材料,应根据绝缘陶瓷的温度特性以及行波管的功率大小来进行选择;翼片式散热器是一种符合设计要求的理想散热结构。     

高峰值功率多注速调管的初步研究

 高峰值功率速调管因其作为高功率微波源而受到各国的重视。采用单电子注方案的高峰值功率速调管存在许多难以克服的问题,如工作电压很高,输出效率偏低,系统体积偏大等。对高峰值功率多注速调管进行了初步的研究,重点研究了S波段50 MW多注速调管的电子光学系统和高频互作用系统。研究表明,在与单注速调管相同的功率电平下,多注速调管的工作电压明显降低,输出效率明显提高,同时,这种管型也存在结构复杂、电子注聚焦和消除非工作模式困难等技术问题。     

TM610高次模圆柱谐振腔的模拟研究

 根据电磁场理论设计了S波段TM610高次模圆柱谐振腔。运用HFSS，ISFELD3D， CST-MS及MAFIA软件计算了该谐振腔中TM₆₁₀及其附近模式的电磁场分布、谐振频率及模式间隔。计算表明：TM₆₁₀模式的电磁场集中在漂移管头周围的区域，谐振腔中心处无电磁场分布。根据TM₆₁₀模式的特点，采取了在腔中心放置铁氧体微波吸收材料的方法来抑制杂模。HFSS模拟表明：腔内吸收材料可消除TM₅₁₀模式外大部分杂模的影响。采用了在主谐振腔外加耦合吸收腔的方法来抑制TM₅₁₀模式，该吸收腔基模TM₀₁₀的谐振频率等于TM₅₁₀的谐振频率。模拟表明：TM₅₁₀模式的大部分能量可以被吸收腔内的铁氧体材料衰减掉，Q值从15 604下降到571。     

Entangled orbital angular momentum states of multi-Laguerre Gaussian Schell beams pumping in a Zernike tilt corrected turbulence

Based on the paraxial approximation of the beams propagation in communication system, the square approximation of the wave structure function, the Zernike polynomial expansion of the non-Kolmogorov atmospheric turbulence-aberration and the assumption of the signal photon propagation in slant Zernike tilt corrected turbulence-channel, we analyze the effect of the multi-beam on entangled orbital angular momentum states. The joint detection probability of orbital angular momentum state entangled photons is modeled. Our work shows that the correction of the Zernike tilt aberration by adaptive optics is a method to improve the joint detection probability of orbital angular momentum state entangled photons. The crosstalk probability of the entangled orbital angular momentum states decreases as increasing of the degree of the spatial coherence of the partially coherent source and the beamlet number of the multil-Laguerre Gaussian Schell model beams.     

基于TDLAS检测西林瓶内氧气浓度的多光束干涉抑制方法

应用可调谐半导体激光吸收光谱(TDLAS)技术开放单光路短光程检测西林瓶内氧气浓度，因玻璃瓶壁造成入射光多次反射和透射，形成多光束干涉，严重影响信号波形和检测精度。本文提出了一种改变激光入射角度来抑制瓶壁光学干扰的方法，理论分析了入射角度对透射光强分布的影响，详细推导了使两相干光束叠加部分在接收端探测范围之外的入射角度计算公式，并根据现场参数得到理论最佳入射角度。对氧气浓度1%的样瓶进行多次测量，将二次谐波信号峰值的平均值作为信号，峰值的标准差作为噪声，以信噪比(signal to noise radio, SNR)最大作为系统入射角角度的优化指标，实验获得系统的实际最佳入射角度。与决定系数较高的入射角度进行浓度预测对比，交互验证后的最小二乘拟合结果显示：相关系数分别为0.995 9和0.988 9，前者相比后者提高了0.7%，预测的均方根误差(root mean square errors of prediction, RMSEP)分别是0.003 1和0.005 3，前者相比后者降低了41.5%，说明本文方法所确定的最佳入射角，能有效抑制玻璃瓶壁引起的多光束干涉影响，改善系统检测精度。