Acoustic plane-wave scattering from a rough interface over an inhomogeneous transition fluid layer     

Jin-Yuan Liu  Chen-Fen Huang 《Ocean Engineering》2001,28(6)

Acoustic scattering of a plane wave incident upon a rough surface over a transition fluid layer within which both the density and sound speed vary with depth is considered. A theory based upon a boundary perturbation method has been applied to a typical seabed environment to study the power spectral density representing the energy distribution of the scattered field over the space. The effects of frequency and roughness properties, including the roughness height, spatial correlation, and power spectrum, on the power spectral density have been investigated. The results demonstrate that the power spectral density of the scattered field depends upon all the aforementioned parameters, particularly the correlation length and the power spectrum of the rough surface, a conclusion in distinct contrast to the results for the coherent field obtained in an earlier study. It was found that the constituents of the rough surface such as the correlation length and wavenumber spectrum dominate the angular distribution of the scattered energy. These results indicate that it is crucial to employ a suitable topological model in the study of rough seabed scattering.  相似文献   

Monitoring moored instrument motion by optimal estimation     

Fabienne Gaillard  Thierry Terre 《Ocean Engineering》2006,33(1):1-22

Many oceanographic applications require the positioning of the underwater sensor at measurement times. We consider here the case of subsurface moored tomographic instruments, where the distance between source and receiver must be known within a few meters. For that purpose, a long baseline array is deployed: this system includes a navigator, attached to the mooring element and an array of three transponders set on the ocean bottom. To process the navigation data collected with such system, we have developed a method based on optimal estimation. The triangulation problem is not a basic spherical constraints one and the specificity of deep underwater positioning, related to the variability of the ocean sound speed profile are pointed out. Correcting terms are proposed and introduced into the system. Simultaneous inversion of all data, defining an overconstrained problem allows to estimate biases and errors. The algorithm is applied here to a dataset collected in the Azores-Canary basin during CAMBIOS experiment.  相似文献   

Evaluation of the effects of the communication cable on the dynamics of an underwater flight vehicle   总被引：2，自引：0，他引：2  

Z. Feng  R. Allen 《Ocean Engineering》2004,31(8-9):1019-1035

This paper presents a numerical scheme to evaluate the effects of the communication cable attached to an underwater flight vehicle. Both simulation and model validation results show that the numerical scheme is effective and provides a means for developing a feed-forward controller to compensate for the cable effects when developing an autopilot for the tethered vehicle. Moreover, the numerical scheme can also be applied to predict the effects of the ROVs umbilical during its deployment.  相似文献   

自治水下机器人在深海采矿系统湖试中的应用     

李一平  燕奎臣 《海洋工程》2006,24(2):67-71

以大洋采矿前期的湖试为例,介绍了AUV在矿产资源调查和深海采矿中的应用。在深海采矿系统作业前期,利用AUV调查湖底的地形地貌、结核的分布与覆盖率,确定集矿机作业地点的大地坐标。在深海采矿系统作业后期,利用AUV调查集矿机在湖底的行走轨迹和压陷深度,估算回采率。  相似文献   

浮游生物图像现场拍摄     

于连生  宋家驹  唐宏寰 《海洋技术学报》2006,25(1):47-49

利用“水下全自动数字显微成像仪”拍摄了水中的浮游生物图像,介绍了仪器性能和拍摄结果,并对仪器用于赤潮预测预报的可能性作了探讨。  相似文献   

Pseudo long base line navigation algorithm for underwater vehicles with inertial sensors and two acoustic range measurements     

Pan-Mook Lee  Bong-Huan Jun 《Ocean Engineering》2007,34(3-4):416-425

This paper presents an integrated navigational algorithm for unmanned underwater vehicles (UUV) using two acoustic range transducers and strap-down inertial measurement unit (SD-IMU). A range measurement model is derived for a UUV having one acoustic transducer and cruising around two reference transponders at sea floor or surface. The proposed algorithm, called pseudo long base line (PLBL), estimates the position of the vehicle integrating the SD-IMU signals corrected with the two range measurements. Extended Kalman filter was applied to propagate error covariance, to update measurement errors and to correct state equation whenever the external measurements are available. Simulations were conducted to illustrate the effectiveness of the PLBL using the 6-d.o.f. nonlinear numerical model of a UUV at current flow, excluding bottom-fixed DVL. This paper also shows the error convergence of the vehicle's initial position by the additional range measurements without velocity information.  相似文献   

水声数据通信系统研究   总被引：4，自引：0，他引：4  

程恩  许俊  黄联芬  许茹 《海洋科学》2002,26(1):1-5

提出一种基于并行传输体制的水声数据通信系统设计方案,发射端采用纠错能力很强的级联码和MFSK调制,分集技术采用抑制载波的双边带调制方式,接收端对接收信号利用快速频谱分析进行解调,并进行硬判决Viterbi译码和BM迭代译码。实验表明,该水声数据通信系统的传输波特率为200bits/s。误码率达到10^-5～10^-6以下。  相似文献   

A conceptual design of an underwater missile launcher     

Carl T.F. Ross   《Ocean Engineering》2005,32(1):1281-99

The paper presents a conceptual design of an underwater missile launcher, which will be more difficult to detect by the enemy than conventional surface missile launchers which are currently being used.The paper suggests that the material of construction should be a composite and not a metal, as use of the latter for a large deep diving underwater vessel will result in such a structure sinking like a stone, due to the fact that it will have no reserve buoyancy. The paper also shows that composites have better sound absorption characteristics, thereby making the underwater structure difficult to detect through sonar equipment. It is proposed that this launcher should operate up to a depth of 5000 m, as at this depth, some 60% of the oceans' bottoms can be reached.The author shows that current technology can be used to construct and operate such a vessel.  相似文献   

厦门沪救码头附近海底滑坡特征及机理     

许文锋 《工程地质学报》2008,16(3):319-326

根据多种勘察手段的识别,查明厦门沪救码头附近海底地形等值线明显扭曲;码头南侧外块石与淤泥互为翻转;滑体后方淤泥可见到蜂窝状孔隙;北码头一带不连续分布有新近沉积的灰黄色淤泥且沿海岸;另外地震映像也出现绕射波相对严重等现象。本文结合地形、地层、海洋水动力条件等因素,对滑动机理进行综合分析;在不考虑海浪、地震作用下,对水下坡体采用极限平衡理论方法、后壁岸坡选择圆弧条分法进行不同的稳定性评价。研究得出:该海底滑坡形成是自然地质、人为活动和重力、海洋动力共同作用以及地层因素的综合结果。  相似文献   

China's state-led working model on protection of underwater cultural heritage: Practice,challenges, and possible solutions     

《Marine Policy》2016

China is one of the most significant country with regard to underwater cultural heritage (UCH). One prominent feature of the Chinese regime on UCH protection is that the government has played a dominant and leading role. This paper first surveys this State-led working model and typical cases and then points out this model's major problems, including lack of staff and funds, the threat of looting and destruction, and the pressure from neighboring countries. Possible solutions consistent with the basic principles of the UNESCO Convention on the Protection of the Underwater Cultural Heritage are explored. It is argued that China shall strengthen preservation in situ as the first option. Considering the limitations of preservation in situ, an appropriate approach to excavation is also required, and a two-tier system of excavation is proposed. Under the proposed system, all sites of UCH should be protected; however, the government should concentrate its resources on the most significant UCH sites. For other sites, commercial involvement may be introduced in rescue excavation. Economic income from deposition and exhibition may provide the main incentive to salvage corporations. Nevertheless, the sale of artifacts recovered should be strictly forbidden.  相似文献