DESIGN OF MODULATION AND COMPRESSION CODING IN UNDERWATER ACOUSTIC IMAGE TRANSMISSION     

程恩  余丽敏  林耿超 《中国海洋湖沼学报》2002,20(3):202-207

This paper describes the design of modulation, compression coding and transmission control in underwater acoustic color image transmission system. This design adapts a special system of modulation and transmission control based on a DSP(Digital Signal Processing) chip, to cope with the complex underwater acoustic channel. The hardware block diagram and software flow chart are presented.  相似文献   

A Free Boundary Problem Related to the Location of Volcanic Gas Sources     

Jesús?Ildefonso DíazEmail author  Giorgio?Talenti 《Pure and Applied Geophysics》2004,161(7):1509-1517

A mathematical model of general gas emitting systems is derived, and a sample of relevant mathematical results is offered. The present paper indicates that shallow subsurface gas sources in typical volcanic areas can be located if appropriate physico-chemical measurements are made on the Earths surface and put to use.  相似文献   

基于流固耦合理论水下隧道冻结壁厚度优化研究     

郑立夫  高永涛  周喻  田书广 《岩土力学》2020,41(3):1029-1038

水下隧道对冻结壁厚度设计有特殊要求，针对珠机城际轨道交通项目下穿马骝洲水道段联络通道冻结壁设计改进问题，基于流固耦合分析理论，利用有限差分数值计算方法对水下隧道冻结壁稳定性进行研究，通过对不同厚度冻结壁响应情况的对比研究，实现对于冻结壁厚度的优化设计。研究表明：相较无渗流模型，流固耦合模型冻结壁应力分布规律相同，但整体量值增大明显，水的作用不可忽略；水的存在使冻结壁受力趋于“均匀”，应力集中现象缓解，但高剪应力区范围扩大，使其剪切破坏风险加大，且冻结壁受力形式有从受压向受拉改变的趋势，对结构稳定不利；冻结壁在流固耦合作用下变形加剧，且随厚度减小而愈发显著，模型厚度达到2.0 m以上时变形基本稳定；流固耦合模型塑性区多集中于两侧拱脚区域， 3.0 m和2.5 m模型整体完好，2.0 m模型两侧拱脚出现相向发展塑性区，1.5 m模型塑性区厚度接近贯穿，1.0 m冻结壁拱脚已形成明显贯穿破坏；综合选定2.5 m为冻结壁改进厚度，成果直接应用于4#联络通道冻结法施工，经现场监测表明该优化方案有效、可行，对类似工程冻结壁厚度设计具有重要的推广应用价值。  相似文献   

Underwater Target Detection Based on Reinforcement Learning and Ant Colony Optimization     

WANG Xinhua  ZHU Yungang  LI Dayu  ZHANG Guang 《中国海洋大学学报(英文版)》2022,21(2):323-330

Underwater optical imaging produces images with high resolution and abundant information and hence has outstanding advantages in short-distance underwater target detection.However,low-light and high-noise scenarios pose great challenges in un-derwater image and video analyses.To improve the accuracy and anti-noise performance of underwater target image edge detection,an underwater target edge detection method based on ant colony optimization and reinforcement learning is proposed in this paper.First,the reinforcement learning concept is integrated into artificial ants’movements,and a variable radius sensing strategy is pro-posed to calculate the transition probability of each pixel.These methods aim to avoid undetection and misdetection of some pixels in image edges.Second,a double-population ant colony strategy is proposed,where the search process takes into account global search and local search abilities.Experimental results show that the algorithm can effectively extract the contour information of underwater targets and keep the image texture well and also has ideal anti-interference performance.  相似文献   

大黄鱼的声刺激行为研究     

刘贞文  许肖梅  黄二辉  杨燕明 《台湾海峡》2014,(1):105-110

为了解水下强噪声对大黄鱼的影响,结合行为学方法开展了3个年龄的大黄鱼声刺激实验．结果发现：3个年龄的大黄鱼在水中声压约10Pa时均能对声波发生条件反应,但是,它们的声波敏感频率和直接致死的声压阈值差异较大;1个月幼苗和8个月小鱼的声波敏感频率分别为800Hz和600Hz,直接致死的声压阈值约为40Pa和4kPa．13个月大鱼的声波敏感频率也在600Hz,但当声压达到4kPa时,鱼群受惊吓明显,且未能直接致死．另外,这些曾经暴露在强声波中的各年龄段的大黄鱼在随后48h里较多出现相继死亡的现象．表明这些长时间暴露在水下噪声中的大黄鱼可能会因累积效应引起行为模式改变和间接致死等慢性危害．  相似文献   

南海海底地磁日变站布放选址方法          下载免费PDF全文

邵关  穆敬 《海洋测绘》2014,(1):47-49

南海海底地形以复杂著称,适合布放沉底自容式观测仪器的海区不多.通过对南海海底地形、水深、通航条件及作业时间的科学合理分析,为南海海域海底日变站布防选址提供了有效方法并取得良好的实际效果,确保了南海水下地磁日变观测的安全性.  相似文献   

Deep-water riser fatigue monitoring systems based on acoustic telemetry     

Baojun Li  Haiyan Wang  Xiaohong Shen  Yongsheng Yan  Fuzhou Yang  Fei Hua 《中国海洋大学学报(英文版)》2014,13(6):951-956

Marine risers play a key role in the deep and ultra-deep water oil and gas production. The vortex-induced vibration (VIV) of marine risers constitutes an important problem in deep water oil exploration and production. VIV will result in high rates of structural failure of marine riser due to fatigue damage accumulation and diminishes the riser fatigue life. In-service monitoring or full scale testing is essential to improve our understanding of VIV response and enhance our ability to predict fatigue damage. One marine riser fatigue acoustic telemetry scheme is proposed and an engineering prototype machine has been developed to monitor deep and ultra-deep water risers’ fatigue and failure that can diminish the riser fatigue life and lead to economic losses and eco-catastrophe. Many breakthroughs and innovation have been achieved in the process of developing an engineering prototype machine. Sea trials were done on the 6th generation deep-water drilling platform HYSY-981 in the South China Sea. The inclination monitoring results show that the marine riser fatigue acoustic telemetry scheme is feasible and reliable and the engineering prototype machine meets the design criterion and can match the requirements of deep and ultra-deep water riser fatigue monitoring. The rich experience and field data gained in the sea trial which provide much technical support for optimization in the engineering prototype machine in the future.  相似文献   

GPSRTK与数字测深集成技术在航道疏浚中的应用     

余锐 《测绘信息与工程》2014,(5):47-49

针对目前航道疏浚、兴建港口等水下测量任务众多,以某航道疏浚工程为例,阐述RTK与数字测深仪集成技术在水下地形测量中的应用,介绍断面法计算疏浚工程量的方法,并得出一定的技术结论,对类似的工程项目具有借鉴意义。  相似文献   

GIS支持下的机场三维净空管理系统的研究与开发     

徐茂林  张贺  郭兆鹏 《测绘与空间地理信息》2014,(12)

通过研究《民用机场飞行区技术标准》(MH,50001-2013)对进近面、过渡面、内水平面、锥形面、内进近面、内过渡面、复飞面和起飞爬升面组成的障碍物限制面定义的基础上,基于GIS技术,开发了机场三维净空管理系统.该系统可以按照相应的标准自动生成单跑道或双跑道障碍物限制面,辅助进行净空管理,极大地减少机场选址或者机场净空管理中障碍物评定的工作量,具有可视化、数字化、智能化的优点,在民航领域高速发展的今天具有广阔的应用前景.  相似文献   

主动声纳探测效能评估的HMG法     

李胜全  李宏武  高飞  潘长明  孙磊 《海洋测绘》2015,35(3):67-70

海洋水声环境时空变化显著,评估其对主动声纳探测效能的影响具有重要的理论意义和应用价值。提出HMG方法用以评估水声环境效应对主动声纳探测的影响。采用UMPE(The university of miami parabolic equation)、CANARY、JACKSON模型模拟特定海洋环境下的传播损失、环境噪声、混响分布,将模拟结果融入主动声纳检测概率模型,计算检测概率。评估结果发现近场检测概率较高,远场可检测的区域与声能汇聚区一致。  相似文献