A simulation involving MAPS video bandwidth reduction, acoustic channel errors, and error checking

The reliable acoustic transmission of images that have been processed by a video bandwidth reduction technique such as Micro-Adaptive Picture Sequencing (MAPS) necessitates a robust coding scheme. This is due to the fact that errors effect compressed data more seriously than uncompressed data. For this reason image quality is a function of three system variables: image compression, channel noise, and error checking. A real-time simulation has been developed to determine the relationship between the three system variables. The simulator uses two 68000 microcomputers connected by a serial link; one does image compression and noise modeling while the other performs error checking and image reconstruction. The noise model uses 17 characteristics and operating parameters of the acoustic channel to corrupt the image data with single bit random errors. At the receiver the error checking can correct up to 90 percent of the most serious single bit errors.     

海洋多道地震拖缆数据实时传输系统的设计与实现

为满足深拖式高分辨多道地震勘探需求,设计并实现了海洋地震拖缆数据的实时传输系统。系统由数传包与地震采集站连接组成,采用推荐标准485(Recommended Standards 485,RS485)串行总线实现了采集站与数传包的物理连接,利用低电压差分信号(Low-Voltage Differential Signaling,LVDS)、预加重/均衡器、8位/10位(8 bit/10 bit)编码等技术实现了数传包之间的通信链路。设计了无等待反馈重传的差错控制方法,提高系统高效性和可靠性;在现场可编程门阵列(Field Programmable Gate Array,FPGA)内部采用先进先出(First Input First Output,FIFO)构建多优先级任务队列的多级流水线设计,解决了大容量数据并发而产生的数据漏帧问题。在实验室用已知正弦信号对系统进行了对比测试,结果表明系统能够满足海洋多道地震勘探的数据传输需求,对于海洋多道高分辨率地震资料的可靠获取具有重要的意义。     

基于MPI的LAGFD-WAM海浪数值模式并行算法研究

在LAGFD-WAM海浪串行数值模式基础上,利用MPI信息传递机制实现其并行化。通过对模拟区域合理划分,对数据采取分块加载,实现了各个节点的负载平衡;通过对算法的改进实现了粗粒度计算,大幅度减少了通信量,从而提高了程序的执行效率。对串行计算和并行计算的效率比较表明,本文建立的方法能够得到较高的加速比。对全球海浪模式,加速比和CPU数目大致呈线性关系。对高分辨率的区域海浪模式,在128 CPU条件下加速比可以达到91.9。     

非差非组合与组合模型定位性能对比及并行设计

分别采用非差无电离层组合模型与非差非组合模型进行批量静态定位解算,对比两者的定位精度以及ZPD估计精度。设计并实现两种模型的并行解算方法,提高非差模型的计算效率。大网数据实验结果表明,两种模型定位精度基本一致,非差非组合ENU的3个方向平均偏差为(4.2,2.8,6.6)mm,组合模型的平均偏差为(4.0,2.8,6.3)mm,但非差非组合模型的解算更加耗时,约是组合模型计算时间的1.4倍。多核环境下,两种模型的并行解算效率均比传统串行模型得到了提高。结果表明,双核并行和四核并行的计算效率比单核串行计算均分别提高了40%和60%以上。     

烟尘气溶胶对星地量子通信性能的影响

根据烟尘气溶胶的尺寸分布参数和消光系数,分析了烟尘气溶胶粒子数浓度与传输距离对链路衰减的影响。结合幅值阻尼信道对信道容量、信道保真度及信道误码率进行数值仿真。仿真结果表明,当传输距离为3 km,烟尘气溶胶粒子数浓度由2.1×10⁶ m^-3增加到3.2×10⁶ m^-3时,链路衰减由0.30 dB增加到0.46 dB,误码率由0.008 7增加到0.012 2。由此可见,烟尘气溶胶对星地量子通信的各项性能均有影响,且影响程度不一。仿真结果可为烟尘气溶胶影响下的量子信号传输提供参考。     

离散Hopfield神经网络的稳定性

研究离散Ｈｏｐｆｉｅｌｄ神经网络的串行稳定性和并行稳定性，分别提出了条件较弱的串行稳定性和并行稳定性的新判据．     

Performance of sequential decoding of convolutional codes overfully fading ocean acoustic channels

Sequential decoding of long-constraint convolutional codes is shown to be a feasible technique for digital data telemetry over realistic marine acoustic channels. A computational bound for sequential decoding over a fading dispersive channel is derived for hardlimiting and quantizing decoders. The results indicate that a minimum of 8 dB of bit SNR (signal-to-noise ratio) is required for sequential decoder operation. Simulations indicate that 14-dB bit SNR results in simple and feasible implementations. Diversity methods for coded transmissions over Rayleigh fading channels are examined. The optimal diversity level for minimum error probability of uncoded systems and the diversity level of minimizing the sequential decoder computational load are derived and shown to be different, with the latter requiring a higher order of diversity. Performance differences between fixed-diversity and optimal-diversity systems are presented     

黄河口外沉积物氧化还原环境的表征

为了评价黄河口外石油开发区沉积物的氧化还原特征,本文根据2002年9月航次所取得的黄河口外41个柱状沉积物样品,研究了该区沉积物氧化还原特征参数Fe^3 ,Fe^2 ,Fe^3 ／Fe^2 及Eh,Es和有机碳、氧化还原度(ROD)等的分布特征,以及这些参数之间的相关关系。研究表明,Fe^3 ,Fe^2 ,Fe^3 ／Fe^2 及Eh,Es和有机碳、氧化还原度(ROD)等在表层沉积物中各站之间的差别不大。Fe^3 和Fe^2 在0～40cm深度范围内变化比较复杂。40cm以后变的相对比较稳定。而Eh和Es有随深度减小的趋势,ROD在整个研究区都小于1,有机碳的含量高于整个渤海的平均值。综合所有氧化还原特征参数的特征,可确认该区沉积物的氧化还原环境为还原性,该还原性特征主要是由有机碳控制的,而活性铁的贡献不明显。     

声波定向随钻对接钻井技术及其运用

常规的钻井导向技术测量是钻头的空间方位,误差与钻井深度成正比,不能满足随钻井眼直接对接要求.与常规钻井导向技术不同,声波定向随钻对接钻井技术是在靶点测量安装在钻挺的声波发生器的声波时差确定钻头与靶点的相对方向.钻头与靶点越近,测量精度越高,对接时误差小于1 cm.对接钻井技术省事、省时、省钱,在对接钻井、防碰钻井、重叠钻井、平行钻井等各种特殊钻井领域有广泛地运用价值.     

一种用于认知无线电资源分配的并行免疫遗传算法

提出了用于认知无线电自适应调制和资源分配的并行免疫遗传算法,并对该算法、简单遗传算法和静态调制分配算法进行了仿真.仿真结果显示,该算法具有很强的全局搜索能力和较快的收敛速度,在误码率和功率受限条件下,该算法比简单遗传算法和静态调制方式的性能更好,同时明显降低了计算复杂度.     

A Remotely Operated Serial Sampler for Collecting Gas-Tight Fluid Samples

This paper describes the design, construction and preliminary test results for a gas-tight serial sampler intended to be deployed at seafloor for long-term operation to take time-series fluid samples from deep-sea environments such as cold seeps, water column and hydrothermal vents. The serial sampler is a modular system that is based on independent and identical sampling modules, which are designed to collect six 160 ml gas-tight fluid samples maintained at high pressure to a depth of 4000 meters. With two working modes, the sampler can be deployed either with seafloor cabled observatory for remote control or as a stand-alone device for autonomous operation. A prototype of the instrument has been constructed and tested on the MARS cabled observatory for two months. The laboratory and field tests proved the success of the design and construction of the serial sampler, and indicated the potential for future ocean sciences.     

基于虚拟仪器技术的海洋移动气象观测系统

介绍一种自主研发的、基于Labview虚拟仪器技术的海洋移动气象观测系统,它可广泛用于各种舰船、海洋移动平台上,能够有效地去除安装平台的移动给风参数测量造成的影响,从而给出真风速、真风向、温度、湿度、气压、安装平台移动轨迹、速度等参数,并能够实时地显示相关参数的随时间的变化趋势,为海洋气象的研究及预报工作提供真实有效的原始数据分析资料。     

双通道实时数据采集处理系统的设计与实现

本文提出了一种基于 TMS32 0 C31串行接口的双通道实时数据采集处理系统的设计与实现方案 ,该设计以 TMS32 0 C31和 TL C32 0 AD5 0 C为核心器件 ,具有两个独立的 A/D,D/A通道 ,能够实现 32位浮点计算和 16位数据采集与回放。应用该系统进行归一化最小均方误差 (Normal-ized L east Mean Square,NLMS)算法实时自适应噪声抵消实验 ,实验结果表明 ,该系统能够实现实时的自适应噪声抵消 ,可广泛应用于实时语音信号处理等领域。     

Direct estimation of motion from sea floor images for automaticstation-keeping of submersible platforms

Maintaining a fixed position near the sea floor is a critical capability during the deployment of remotely operated or intelligent (autonomous) undersea vehicles in a variety of missions, including inspection and repair of undersea structures, data collection, and surveillance. We present an automatic optical station-keeping system for application to submersible vehicles in deep waters by exploiting the information in sea floor images. Readily measurable spatio-temporal image gradients are used to detect and compute the vehicle's translational and yaw motions using a direct motion vision technique. The vision system has been implemented on a Windows-NT Pentium platform, and the estimated positions and yaw angles are communicated via a serial link to the control system, running on a PC-386. Accurate station-keeping is demonstrated in experiments with a three-thruster floating vehicle in a 6-ft×12-ft×6-ft water tank     

水声通信中基于小波变换的图像编码研究

提出了一种高误比特率传输条件下的图像编码方法，它适用于水声信道的图像传输。针对水下图像的特点，选取合适的小波基和变换参数对图像进行离散小波变换；依据小波系数的能量分布特性，对不同的子带采用不同的量化和定长编码，编码率为0．8比特／像素。水声通信试验表明，在传输误比特率达到10^-2时，仍能得到可接受的图像质量。     

Investigating the seasonal vertical structure of phytoplankton in shelf seas

A 1-dimensional (vertical) physical-biological coupled model is presented. The model is designed for investigations into the link between the vertical turbulent structure of a coastal or shelf sea water column, and the primary production. The physical model employs a turbulence closure scheme to provide the link between local vertical stability (driven by seasonal solar heating) and the vertical turbulent mixing (driven by tidal currents and surface wind stress). The biological component of the model is a simple cell quota, threshold limitation model, with either 1 or 2 taxa/species of phytoplankton growing in response to light and dissolved inorganic nitrogen. The user has control over all model physical and biological driving parameters. Graphical screen output, suitable for basic visualisation and teaching purposes, is generated as the model operates, and more detailed data are written to files for later analysis.In order to demonstrate the model's use in simple hypothesis investigation, an example of the model operation is illustrated. This focuses on the effect that the springs-neaps tidal cycle has on the production within the summer sub-surface biomass maximum, illustrating the fortnightly input of new nitrogen into the thermocline and the subsequent new production.     

Biochemical composition and size distribution of organic matter at the Pacific and Atlantic time-series stations

Amino acids, neutral sugars and amino sugars were analyzed to investigate the chemical composition and diagenetic processing of suspended particulate organic matter (POM, > 100 nm), high-molecular-weight dissolved organic matter (HMW DOM, 1–100 nm) and low-molecular-weight dissolved organic matter (LMW DOM, < 1 nm) at the time-series stations near Bermuda (BATS) and Hawaii (HOT). Differences between BATS and HOT were principally related to location-specific biogeochemical processes and water mass ventilation ages. Concentrations of amino acids, neutral sugar and amino sugars in unfiltered seawater sharply declined with depth at both stations, indicating an upper ocean source and rapid turnover of these components. The size distribution of organic matter was heavily skewed to smaller molecular sizes. Depth comparisons showed that larger size classes of organic matter were more efficiently removed than smaller size classes. Carbon-normalized yields of amino acids, neutral sugars and amino sugars decreased rapidly with depth and molecular size. Together these biochemicals accounted for 55% of organic carbon in surface POM but only 2% of the organic carbon in LMW DOM in deep water. Chemical compositions showed distinct differences between organic matter size classes indicating the extent of diagenetic processing increased with decreasing molecular size. These findings are consistent with the size-reactivity continuum model for organic matter in which bioreactivity decreases with decreasing molecular size and diagenetic processes lead to the formation of smaller components that are resistant to biodegradation. The data also provided evidence for a size-composition continuum. Carbon-normalized yields of amino acids, neutral sugars and amino sugars were sensitive indicators of diagenetic alterations. Diagenetic indicators based on amino acid compositions revealed distinct patterns for the North Pacific and Sargasso Sea possibly indicating the influence of varying sources or diagenetic processing.     

多种群并行进化神经网络的研究及应用

提出一种新的多种群并行遗传算法 (NMPGA) ,并将其作为多层前馈神经网络(MFNNs)的学习算法 ,从而形成一类新的 MFNN模型——多种群并行进化神经网络(MPENNs)。首先 ,对一给定的网络结构 ,随机产生一初始权重的集合 ,这个集合实际上对应着一组具有相同结构但不同权重的神经网络。然后 ,采用 NMPGA对 MFNNs的权重进行进化。最后 ,性能最好的网络被选作目标问题的解。在 NMPGA算法中 ,作者采用浮点数编码来克服传统二进制编码的精度不足问题 ,并设计了专门的杂交算子和变异算子来增强算法性能。实验结果表明 ,MPENNs能成功解决异或问题、三元奇偶问题及成品烟的感官质量评价问题。     

Fault patterns at outer trench walls

Profiles across subduction-related trenches commonly show normal faulting of the outer trench wall. Such faulting is generally parallel or sub-parallel to the trench and is ascribed to tension in the upper part of the oceanic plate as it is bent into the subduction zone. A number of authors have noted that outer trench wall faulting may involve re-activation of the oceanic spreading fabric of the subducting plate, even when the trend of this fabric is noticeably oblique to the extensional stress direction. However, one previous review of outer trench wall fault patterns questioned the occurrence of a consistent link between fault orientation and such controlling factors. This latter study predated the widespread availability of swath bathymetry and longrange sidescan sonar data over trenches. Based only on profile data, it was unable to analyse fault patterns with the accuracy now possible. This paper therefore re-examines the relationship between outer trench wall faulting and the structure of the subduction zone and subducting plate using GLORIA and Seabeam swath mapping data from several locations around the Pacific and Indian Oceans. The principal conclusions is that the trend of outer trench wall faults is almost always controlled by either the subducting slab strike or by the inherited oceanic spreading fabric in the subducting plate. The latter control operates when the spreading fabric is oblique to the subducting slab strike by less than 25–30°; in all other cases the faults are parallel to slab strike (and parallel or sub-parallel to the trench). Where the angle between spreading fabric and slab strike is close to 30°, two fault trends may coexist; evidence from the Aleutian Trench indicates a gradual change from spreading fabric to slab strike control of fault trend as the angle between the two increases from 25 to 30°. The only observed exception to the above rule of fault control comes from the western Aleutian Trench, where outer trench wall faults are oblique to the slab strike, almost perpendicular to the spreading fabric, and parallel to the convergence direction. Re-orientation of the extensional stress direction due to right-lateral shear at this highly oblique plate boundary is the best explanation of this apparently anomalous observation.     

Hydrodynamic loads on subsea robots

Free floating subsea robots are often subjected to complex hydrodynamic loads due to waves/currents and wakes from nearby structures. This makes control extremely difficult. Good hydrodynamics data might counteract this. This paper presents hydrodynamics data for two configurations undergoing various combinations of steady translation and approximately steady rotation. The two configurations are: a spherical body with a single fixed link arm and a two link arm without a body. For both configurations neural networks were found to provide a reasonable fit to the data. We believe that such fits could be used to improve control.