传感器测量衰减下的水下目标纯方位跟踪算法

为解决多传感器水下目标纯方位跟踪中的传感器测量衰减问题,建立水下目标静态多传感器纯方位跟踪模型,将传感器测量衰减建模为统计特性已知的随机变量,基于融合中心接收到的各水声传感器的原始测量值,设计了一种集中式状态估计器结构,利用最小方差方法推导出最优的集中式目标状态估计增益。通过算例仿真可以得出,所提出的算法能够在水声传感器不做机动的前提下跟踪目标,弥补了单个水声传感器观测性不足的缺点,对比传统的集中式Kalman估计器,具有更高的精度,能够有效解决传感器测量衰减问题。     

目标信号和海上环境噪声的测量及分析

本文主要论述对海上目标信号和海洋环境噪声的测量及其结果的分析。着重分析了目标信号及环境噪声的声级、信噪比、相关性和目标检测作用距离,为短基线系统被动定位系统的设计提供依据。     

水下拖曳测量装置的前置浮球防护法

阐述了保护绳法和拖带浮球法在防止水下拖曳测量装置意外丢失中的应用，在总结经验的基础上，提出了一种新的经济实用且简便易行的防护方法——前置浮球防护法。     

浅水有界水域水下目标辐射噪声测量修正方法

由于适合水下目标辐射噪声测量的理想水域较少,因此测量试验大多在浅水有界水域开展,测量结果难免会受到试验现场界面反射波影响,导致测量的宽带声压级及各频率声压谱级产生偏差。利用虚源法对浅水有界水域下的声场模型进行了数值仿真,重点分析了导致传播损失异常的各项因素,然后基于脉冲声技术提出了一种水下目标浅水有界水域辐射噪声测量结果的修正方法,并进行了外场辐射噪声测量和传播损失异常值标定验证试验,最后对试验数据的测量结果进行了修正。     

基于方位/多径时延的水下目标运动参数估计

讨论了基于方位角、俯仰角及多径时延 TMA 的水下目标运动参数估计方法。采用声基阵测量水下运动目标相对于观测平台的方位角、俯仰角,并测量水下目标的一次水面反射相对于直达波的多径时延差, 根据水下目标方位角、俯仰角与多径时延差的变化,通过目标运动分析(TMA)方法预测目标的航迹、航速及航向,为攻击水下目标提供决策信息。计算机仿真验证了方法的可行性。     

非量测相机制约迭代检校法及水下测量应用

传统的非量测相机检校方法大多依赖于高精度的室内或室外控制场,并对检校环境有较严格的要求。故提出了一种完全抛开控制点的新的相机检校方法,即线面角制约的相机迭代检校法。将该方法分别应用于陆地和水下环境,并与有控制点的相机迭代检校法进行对比分析,试验结果表明新方法的检校精度均小于1个像素,在陆地环境下,新方法的检校精度优于有控制点的相机迭代检校法。同时利用新方法进行了水下三维重建和量测,量测精度达到亚毫米级。试验结果表明新方法具有较好的灵活性和适应性,在多个环境下具有实际应用的价值。     

聚类分析方法识别水下目标

水下目标的固有振动频率与其本身的材料参数密切相关。如能从测得的目标共振频率反演目标材料参数，结合某些先验知识，便可对目标的某些物理属性作出判断，实现或有助于实现水下目标识别。Ｂａｔａｒｄ等人研究了柱形目标中声速与其固有振动频率间的关系。本文分析并简化了这种关系，然后应用模态识别中的动态聚类方法，由目标共振频率反演目标材料参数，所得结果与实际材料参数符合较好。     

高空飞行器被动段运行轨迹精确预测方法研究

高空飞行器被动段运动学状态方程是典型的非线性常微分方程,难以给出其解析解。为了精确预测飞行器被动段运行轨迹,目前常用的解决方法是给出其数值解。在建立飞行器运动学状态方程基础上,提出采用四阶龙格库塔法求解这一常微分方程组,给出了初值的选取方法。采用仿真试验对提出方法的可行性和有效性进行了验证,结论表明:龙格库塔法可以有效计算出飞行器运动学状态方程数值解,能够高精度地预测出飞行器的运行轨迹。     

一种水下磁场测量基阵的设计

针对水下被测磁场目标,根据磁场测量的要求,分析计算了测量单元的布置方式和基阵的受力,设计了一种用于布放该磁场测量系统的基阵结构。 通过海上试验验证,该基阵入水姿态平稳,着底姿态良好,满足测试要求,为水下装备磁场指标评估提供依据和方法。     

一种新型水下声学浮标在目标探测中的应用

针对海上目标探测问题, 将矢量水听器和Argo浮标相结合, 可构建一种具有水中目标探测能力的新型水下声学浮标平台。该浮标平台可多次上浮和下潜, 具有在位时间长、隐蔽性能高、成本低等特点, 单台水下声学浮标即可实现海上目标探测, 利用多台水下声学浮标可快速形成大面积区域覆盖能力。为进一步验证水下声学浮标对海上目标探测性能, 2019年8月在南海海区开展了多台水下声学浮标海上试验, 数据处理结果表明: 南海夏季典型声速剖面下, 水下声学浮标对船长42m航速8.4kn的水面航船目标最远探测距离可达13.8km, 目标估计方位均方根误差最优可达5°, 在水面航船距离最近的1.9km处, 目标估计方位标准差可达2°。     

Measurement of water column primary production using photosynthesis-irradiance relations for surface phytoplankton,the vertical chlorophyll profile,and underwater light intensity

A method has been developed to measure water column integrated primary production (PP_int) in the water column using photosynthesis-irradiance relations for surface phytoplankton, the vertical profile of chlorophyll a concentration, and the underwater light intensity. Good correlation has been found for the results calculated with this method and light dependences in situ. The advantages of this method are the independence of PP_int calculation from CTD profiling and water sampling, and thus optimization (reduction) of the station working time.     

Kerr效应对二项式腔场谱量子干涉的影响

研究了含Kerr介质高Q腔内单个二能级原子与双模二项式光场发生双光子共振相互作用系统的腔场谱,给出了Kerr效应与量子干涉项ΔS(ω)关系的数值计算结果,讨论了Kerr效应对二项式腔场谱量子干涉的影响.结果表明:若初始时刻原子处于激发态而双模光场处于二项式态,随Kerr效应的增强,致使量子干涉项引起谱线强度的改变量呈现出"不规则的周期性衰减振荡"特性,震荡幅度与两模光场的频差密切相关.在Kerr系数χ＜g(g为光场与原子的耦合常数)时,Kerr效应对干涉项的影响比     

Intensity Measurement of Backscattered Light from Underwater Targets Using Femtosecond Pulse Laser

In this paper, we experimentally perform the measurement of the backscattered light intensity from the underwater targets with different size. We develop a simple system, which can easily measure the intensity of the backscattered light, after the laser is scattered at the target underwater. We find that, the signal period is related to the particle size, and the stability of the intensity (standard deviation) varies linearly with changing the particle size. After the calibration, our system can be used to precisely determine the particle size of arbitrary targets. Our method could open a new opportunity for the future underwater detection using femtosecond pulse laser.     

Depth-trim mapping control of underwater vehicle with fins

Underwater vehicle plays an important role in ocean engineering.Depth control by fin is one of the difficulties for underwater vehicle in motion control.Depth control is indirect due to the freedom coupling between trim and axial motion.It includes the method of dynamic analysis and lift-resistance-coefficient experiment and theory algorithm.By considering the current speed and depth deviation,comprehensive interpretation is used in object-planning instruction.Expected depth is transformed into expected trim.Dynamic output fluctuation can be avoided,which is caused by linear mapping of deviation.It is steady and accurate for the motion of controlled underwater vehicles.The feasibility and efficiency of the control method are testified in the pool and natural area for experiments.     

面向典型海洋现象观测的水下滑翔机应用综述

水下滑翔机是一种浮力驱动的无人水下自治观探测平台, 具有持续性、鲁棒性、自主性等特点, 是构建海洋观测技术体系重要的水下航行器之一。文章从水下滑翔机发展历程、运行方式和专用传感器展开, 基于国内外海洋学文献综述研究, 重点对水下滑翔机在典型海洋现象观测应用方面进行总结。水下滑翔机的运行稳定性、长时续, 观测高分辨率、低成本的特点, 满足了对海洋中尺度涡、内波、湍流、环流/边界流和锋面的长时间、精细化立体观测要求; 鲁棒性、自主性的特点使其能够适应台风过境、地震、原油泄漏前后等紧急恶劣海洋状况的监测; 运行平稳、低噪声的特点使其成为声学监测与探测的良好平台。对比分析国内外的水下滑翔机(组网)应用状况可以发现, 国内水下滑翔机在传感器、数据处理和组网技术方面都需要进一步完善。最后总结并展望了国内外水下滑翔机面向海洋现象观测的应用。     

Measurement of directional spectrum of wind waves using an array of wave detectors

A method is proposed to estimate the true directional spectrum of wind waves by making use of more than four wave detectors. The true spectrum of wind waves whose wave lengths lie between about 1.1 and 2.6 times the largest span between the wave gauges can be recovered with an error less than 0.5 %. An additional wave gauge with fixed maximum span extends its effectivity to shorter wave lengths, but does not effect the upper limit of wave length.The method is based on the fact that the spectrum estimated byBarber (1961) is connected with true directional spectrum by the Fredholm integral equation of the first kind if the wave component satisfies the dispersion relation. Solving the equation by using the Fourier series method, we can get true spectrum.     

Measurement of shipwreck-derived waterborne trace metals using DGT samplers

ABSTRACT

A contemporary approach to the assessment of metal pollutants in aquatic environments has been to measure contaminant concentrations in biological indicator species (mussels, oysters). However, for environments in which such indicator species do not occur naturally and cannot be deployed, alternative approaches for monitoring trace-metal pollution are required. Three years after the 2011 grounding of the MV Rena, diffusive gradients in thin films (DGT) samplers were deployed at Otaiti (the offshore reef where the Rena grounded) to assess levels of waterborne trace-metal contamination. Although the probability of detecting waterborne contaminants within a dynamic open ocean reef environment would seem low, due to mixing and dilution, our analyses confirmed the presence of copper (≤0.43 vs ≤0.27?nmol?kg^?1), iron (≤6.3 vs ≤4.2?nmol?kg^?1), aluminium (≤8.9 vs ≤1.3?nmol?kg^?1), zinc (≤2.8 vs ≤2.0?nmol?kg^?1) and manganese (≤0.11 vs ≤0.09?nmol?kg^?1) at elevated concentrations in the Rena debris field relative to reference sites. The results demonstrate the utility of DGTs as a tool for measuring waterborne contaminants and suggest further research is required to characterise the contaminant plume and determine what effect it might have on the recovery of Otaiti's impacted biological communities.