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针对传统无损检测方法对自升式海洋平台检测工作量大、费时费力等问题,提出了一种金属磁记忆(MMM)与交流电磁场(ACFM)联合检测的新方法。在简介MMM和ACFM检测机理之后,将其应用到自升式海洋平台关键部位的无损检测中。分别以齿条座板与桩腿之间的T型焊缝和桩腿环焊缝为例,首先通过MMM快速全面扫描待检测表面,基于磁场分布及梯度值确定应力集中部位;在此基础上,利用ACFM方法重点对应力集中部位进行裂纹缺陷的定量化检测,结果表明MMM对应力集中或微观缺陷非常敏感,而ACFM方法可精确给出裂纹缺陷的深度信息,为平台结构的安全可靠运行和维修方案制定提供了方法参考和理论依据。 相似文献
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各类抛弃式探头下沉运动的数值计算研究都需要对探头表面和整个计算域进行网格划分的前处理过程,选择不同的网格划分方法和划分精度,会影响数值计算速度和计算精度,最终生成的网格质量决定了计算结果的收敛性和准确性。针对抛弃式探头的复杂结构,对比了两种网格划分方法、三种网格划分精度,完成探头计算区域的网格划分,采用k-ε湍流模型,进行抛弃式探头下沉运动的数值计算,并将计算结果与水箱和水库实验结果进行对比,验证了混合网格划分方法和普通精度网格对抛弃式探头下沉运动数值计算的适用性,研究结果对类似较为复杂结构的水下运动体的数值计算前处理过程具有一定的参考和借鉴意义。 相似文献
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针对水下目标图像探测一直是困扰海洋界的1个难题，进行了水下探测的线扫描系统的设计和相关试验。从实验结果来看，线扫描系统可以很好地描述水下物体的三维外形细节，对于水下目标探测、识别十分有效。 相似文献
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1 .IntroductionWiththe advent of underwater vehicle technology in the offshore industry, major survey and in-spectiontasks can be done at lower cost withfaster execution.Pipe inspection is of major interest inthat respect because thousands of meters of pi… 相似文献
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Currently, most submerged bodies use the long-baseline acoustic position system (LBL) to identify the navigation position for submerging. A precise navigation position is always the target pursued by underwater technology. The conventional long-baseline acoustic position systems normally use Kalman filter correction to handle the problem of positional errors. This article proposes a new modification, which is based on the periodically measured actual navigation distance, and associated with the three-dimensional geometrical relations between the transponder on the seabed and the navigation distance. This new modification employs the iterative approximation to modify the errors of the measured navigation position from the conventional long-baseline acoustic position system. In order to verify the availability of the modified model by the essay, the study uses the navigation position for an underwater surveying submerged body as the study object. After the numerical simulation analysis, the result shows that the modification was presented by the article can only use very few iterations to precisely modify the errors of the measured navigation position from the conventional long-baseline acoustic position system, which is highly applicable for positioning in long-term and long-distance submersion. Moreover, the modification method proposed by the paper can also help submersion positioning for the underwater vehicle, as well as the military submerged body. 相似文献
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随着武器装备的逐渐智能化和信息化，武器系统的水下预置已经成为了未来水下无人作战体系中的重要研究内容之一。以封锁作战为背景，用水下预置反舰导弹构建多层防御阵线封锁战略航道，对敌实施打击。利用排队论相关理论研究了水下预置反舰导弹对来袭舰船编队总的命中概率并建立了其线形部署优化模型。通过仿真算例验证了模型的有效性，分析了影响优化结果的其他因素，结果表明：该模型能够准确找出在总命中概率最大时最佳的部署层数和各层部署数量，可为水下预置反舰导弹的部署决策提供一定科学参考。 相似文献
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为实现长期、连续、定点、低成本的上层海洋垂直剖面要素的准实时观测,提出了一种以STM32单片机(microcontroller unit,MCU)为主控器、采用国产温盐深传感器(conductivity temperature depth,CTD)和声学多普勒剖面流速仪(acoustic doppler current profilers,ADCP)等仪器进行剖面观测、搭载铱星通信模块或其他通信设备、适用于近海和远海的低功耗水下升降式准实时通信潜标控制系统设计方案。介绍了潜标的结构组成、控制系统硬件和软件设计,以及服务器接收软件的设计;实现了基于无线双向通信的数据补发机制和对潜标的远程控制;提出了一种适用于霍尔无刷直流电机(hall brushless direct current motor,HBLDCM)的堵转保护方法。近海和远海试验表明,该型潜标可以实现海洋垂直剖面的连续观测和数据的准实时传输,验证了潜标控制系统设计方案的可行性与稳定性。 相似文献
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Cho-Chung Liang 《Marine Geodesy》1999,22(1):19-30
The underwater position of the beacon determined using the conventional mode of the short-baseline acoustic positioning system (SBL system) is usually incorrect due to the inaccuracy of underwater-measured sound speed, which is affected by the environment. This article presents a corrected mode of SBL system to offer a precise solution for the underwater beacon position. The corrected mode using the formulation of Euclidean geometry converges quickly and efficiently, obtaining the precise position of the beacon. Finally, a simulation of coring missions of a vessel is presented to verify the accuracy of the corrected mode of the SBL system. 相似文献
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一种水下激光成像的新方法 总被引：1，自引：0，他引：1
在我国沿海近岸,急需通过激光同步扫描方法建立1套浑水观测系统,解决水下视觉问题。本文研究了激光在水下的传输特性,结合散射光的分布特性,确定同步扫描的光学结构设计,通过对获得的系统各类信号特性的分析,设计合适的成像系统;并从理论和水池试验两方面分别论证了这种系统消除散射影响的有效性;论述了这种系统在浑水中的宽视角场和全景深的优良特性。 相似文献
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海水液压作业工具系统的研制 总被引：2，自引：0，他引：2
介绍了一种以海水液压驱动的水下作业工具，分析了该系统的组成、工作原理、研制难点及解决方案。该工具系统能工作于300m以浅的海域，完成水下钢缆切断、船体和水下结构物表面的清刷、打磨等工作。 相似文献
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Signal detection is a critical stage in the implementation of any effective communications system. The underwater acoustic environment, particularly in the presence of underwater vehicles, presents significant challenges to reliable detection without excessive false alarms. While there is often sufficient signal-to-noise ratio with respect to stationary broad-band background noise to permit reliable operation, the presence of strong event-like interference signals such as narrow-band signals and impulsive broad-band signals complicates the detection problem significantly. Frequency-hopped signals interleaved with quiescent bands are proposed as the basis of a robust detection system. These signals also make robust detection possible in a multi-access communications system. Two new detection algorithms that exploit the particular structure of these frequency-hopped signals are developed and their performance is analyzed. This analysis uses a modification of the doubly noncentral F-distribution that has not been used previously for such analysis. This distribution makes possible the direct calculation of probabilities of detection and false-alarm under interference and signal scenarios that cannot be analyzed using the better known noncentral F-distribution. With this analysis, the two developed detectors are shown to offer superior performance to that of either the CFAR detector or the binary data sequence detector. Experimental data confirms the theoretically derived results 相似文献
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研究自主水下航行器系统的软变结构控制策略问题。首先分析软变结构控制系统的结构特征,利用双曲正切函数,给出控制受限情形的软变结构控制策略。其次利用Lyapunov稳定性理论,讨论自主水下航行器软变结构控制系统的稳定性,然后构造了基于双曲正切函数的软变结构控制器,给出自主水下航行器软变结构控制的具体算法。基于双曲正切函数的自主水下航行器软变结构控制系统调节精度高,响应速度快,有效地削弱了系统抖振。最后通过一个仿真实验,比较了自主水下航行器垂直深度通道的4种控制策略对系统性能的影响,从而验证了研究方法的有效性。 相似文献
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A detection model of underwater topography with a series of SAR images acquired at different time 总被引：1，自引：1，他引：0
underwater topography is one of oceanic features detected by Synthetic Aperture Radar. Underwater topography SAR imaging mechanism shows that tidal current is the important factor for underwater topography SAR imaging. Thus under the same wind field condition, SAR images for the same area acquired at different time include different information of the underwater topography. To utilize synchronously SAR images acquired at different time for the underwater topography SAR detection and improve the precision of detection, based on the detection model of underwater topography with single SAR image and the periodicity of tidal current, a detection model of underwater topography with a series of SAR images acquired at different time is developed by combing with tide and tidal current numerical simulation. To testify the feasibility of the presented model, Taiwan Shoal located at the south outlet of Taiwan Strait is selected as study area and three SAR images are used in the underwater topography detection. The detection results are compared with the field observation data of water depth carried out by R/V Dongfanghong 2, and the errors of the detection are compared with those of the single SAR image. All comparisons show that the detection model presented in the paper improves the precision of underwater topography SAR detection, and the presented model is feasible. 相似文献
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介绍了基于CORS的网络RTK技术在水下测绘的应用及技术优势,并与常规测绘方法进行了比较分析.通过实例介绍了利用FJCORS进行的水下测绘应用及采用的CORS定位精度检测法,结果表明满足精度要求,验证了其在水下测绘的适用性. 相似文献
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随着对水下目标特性研究的深入和声学探测技术的发展,基于单模态的阵列式信息融合或基于空间信息的分布式信息融合的水下目标识别方法研究已有一定成果,但针对复杂海况导致单一物理场或单一融合层次的系统识别性能提高有限等方面影响的水下目标识别方法研究还有所不足,因此,开展基于多模态深度融合模型的水下目标识别方法研究可利用模态互补,共享信息而提升识别率。文中在国内外研究基础上,深入研究了基于到达时差法和多模态方法组合的检测方法,初步形成了基于水声环境空间中多模态深度融合模型的识别框架,开展了海洋中典型自然与人为事件的信号分析与特征提取,并在此基础上,设计新型基于海底基站的被动识别系统。该系统同步记录和由位置等组成的时间序列标记声、磁和压数据,可实现高精度、高分辨率的识别。本研究可满足未来海洋观测对高性能水下目标探测、定位和跟踪系统的迫切需要,为海洋安全监管、海洋突发事件应急响应等领域提供新的技术手段和科学参考。 相似文献
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Carl T.F. Ross 《Ocean Engineering》2006,33(16):2087-2104
The paper presents a conceptual design of an underwater star wars’ system, which will be more difficult to detect by the enemy than a recently proposed ‘surface’ star wars’ system.The paper suggests that for the proposed structures needed for the underwater star wars’ system, the material of construction should be a composite and not a metal, as use of the latter for large deep diving underwater vessels will result in such structures sinking to the bottom of the ocean like stones, due to the fact that they will have no reserve buoyancy. The paper also shows that composites have better sound absorption characteristics, thereby making the underwater structures difficult to detect through sonar equipment. It is proposed that these underwater structures should operate up to a depth of 7.16 miles (11.52 km), as at this depth, all of the oceans’ bottoms can be reached.The author shows that current technology can be used to construct and operate such vessels, but more progress needs to be made with metal matrix and ceramic composites, so that the hulls of underwater missiles and torpedoes can be constructed in these materials. 相似文献
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An experimental set-up is developed and proved to be effective for laboratory study of an underwater towed system. The experimental technique gives a practical method for monitoring the kinematic and dynamic performance of an underwater towed system in a ship towing tank. Both the theoretical and experimental results in the investigation indicate that the hydrodynamic response of a towed vehicle to the wave induced motion of a towing ship can be significantly reduced by applying a two-part tow method. A comparison of the numerical and experimental results in the investigation demonstrates that the numerical simulation results are close to the experimental data, overall agreement between experimental and theoretical results is satisfactory. The results qualitatively verify the mathematical model of a two-part underwater towed system proposed by Wu and Chwang [Wu, J., Chwang, A.T., 2000. A hydrodynamic model of a two-part underwater towed system. Ocean Engineering 27 (5), 455–472]. 相似文献