共查询到20条相似文献，搜索用时 35 毫秒
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A mathematical model is proposed to investigate electromagnetic fields induced by the motion of conductive sea water in the wake of a moving body. An exact solution is obtained for the induced field. The results show that undersea mobile vehicles can generate measurable fields. The frequency-domain solution and its unique properties are also derived 相似文献
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Tasman Sea guyots are former volcanic islands that have subsided an average of 166 fathoms since the Middle or Late Tertiary. These guyots have heights up to 2333 fathoms above the surrounding sea floor; their flat-topped platforms are at depths ranging from 50 to 500 fathoms below present sea level. Reef formations are found along the edges and on the tops of the guyots. Volcanic rocks dredged from these truncated undersea mountains are alkaline olivine basalts with large augite, olivine and plagioclase phenocrysts in a glassy matrix. Limestones dredged from the guyots are either hard, light brown, massive foraminiferal limestones or grey, porous limestones composed mainly of skeletal material. Using foraminiferal evidence we assign an age for the limestone accumulation of Late Pliocene or Early Pleistocene. Phosphorite is also present and is thought to be formed from the replacement of carbonate ions in calcareous material by phosphate ions. There is some evidence of direct precipitation of phosphatic material as coatings on many of the basalt samples. 相似文献
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The necessity and the preliminary tentative plan for the construction of the undersea tunnel across Taiwan Strait are expounded in this atricle. The strait undersea tunnels, which have been built and investigated in the world, and their engineering characteristics and construction methods have been introduced herein briefly. Taiwan has been a part of China since ancient times and the people between the mainland and Taiwan are kindred compatriots in the extended family of the Chinese multinational country. For a long time, the people between southeast of China and Taiwan have had frequent communication in economy and culture. With the progress of times and the need of development, it has been put forward to build a safe and reliable undersea tunnel that is not affected by the environment across Taiwan Strait, and one which is also a magnificent project for the China in the long-term. Whether by using a bridge or an undersea tunnel or both across the strait is a problem worthy of further research. According to such conditions as the weather of Taiwan Strait, depth of water, undersea terrain, possibility of engineering and hydrological geology under the sea, as well as the possibility of Taiwan Strait as a main shipping passage from south to north of China and the experience of existing passage across strait in the world, the primary analysis shows that the scheme of an undersea tunnel should be considered. Therefore the concept of the undersea tunnel engineering across Taiwan Strait is introduced in detail here. 相似文献
6.
《Ocean Engineering》2006,33(11-12):1413-1430
This paper presents the design of an adaptive input–output feedback linearizing dorsal fin control system for the yaw plane control of low-speed bio-robotic autonomous underwater vehicles (BAUVs). The control forces are generated by cambering two dorsal fins mounted in the vertical plane on either side of the vehicle. The BAUV model includes nonlinear hydrodynamics, and it is assumed that its hydrodynamic coefficients as well as the physical parameters are not known. For the purpose of design, a linear combination of the yaw angle tracking error and its derivative and integral is chosen as the controlled output variable. An adaptive input–output feedback linearizing control law is derived for the trajectory control of the yaw angle. Unlike indirect adaptive control, here the controller gains are directly tuned. The stability of the zero dynamics is examined. Simulation results are presented for tracking exponential and sinusoidal yaw angle trajectories and for turning maneuvers, and it is shown that the adaptive control system accomplishes precise yaw angle control of the BAUV using dorsal fins in spite of the nonlinearity and large uncertainties in the system parameters. 相似文献
7.
In this paper,the dynamic response of undersea -+towed systems is numerically simulated.Atwo body towed system is especially considered in detail.The factors influencing the heave oftowed-bodies,such as the weight of the towed-body(in sea water),the length and the weight(in sea water)per unit length of the cable between towed-bodies and towing ship,are investigated in detail.Calculationsshow that the two-body towed system can greatly increases the stability of the towed system. 相似文献
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The necessity and the preliminary tentative plan for the construction of the undersea tunnel across Taiwan Strait are expounded in this atricle. The strait undersea tunnels, which have been built and investigated in the world, and their engineering characteristics and construction methods have been introduced herein briefly.?Taiwan has been a part of China since ancient times and the people between the mainland and Taiwan are kindred compatriots in the extended family of the Chinese multinational country. For a long time, the people between southeast of China and Taiwan have had frequent communication in economy and culture. With the progress of times and the need of development, it has been put forward to build a safe and reliable undersea tunnel that is not affected by the environment across Taiwan Strait, and one which is also a magnificent project for the China in the long-term.?Whether by using a bridge or an undersea tunnel or both across the strait is a problem worthy of further research. According to such conditions as the weather of Taiwan Strait, depth of water, undersea terrain, possibility of engineering and hydrological geology under the sea, as well as the possibility of Taiwan Strait as a main shipping passage from south to north of China and the experience of existing passage across strait in the world, the primary analysis shows that the scheme of an undersea tunnel should be considered. Therefore the concept of the undersea tunnel engineering across Taiwan Strait is introduced in detail here. 相似文献
9.
Trends in biorobotic autonomous undersea vehicles 总被引：1，自引：0，他引：1
The emergence of biorobotic autonomous undersea vehicle (AUV) as a focus for discipline-integrated research in the context of underwater propulsion and maneuvering is considered within the confines of the Biorobotics Program in the Office of Naval Research. The significant advances in three disciplines, namely the biology-inspired high-lift unsteady hydrodynamics, artificial muscle technology and neuroscience-based control, are discussed in an effort to integrate them into viable products. The understanding of the mechanisms of delayed stall, molecular design of artificial muscles and the neural approaches to the actuation of control surfaces is reviewed in the context of devices based on the pectoral fins of fish, while remaining focused on their integrated implementation in biorobotic AUVs. A mechanistic understanding of the balance between cruising and maneuvering in swimming animals and undersea vehicles is given. All aquatic platforms, in both nature and engineering, except during short duration burst speeds that are observed in a few species, appear to lie within the condition where their natural period of oscillation equals the time taken by them to travel the distance of their own lengths. Progress in the development of small underwater experimental biorobotic vehicles is considered where the three aforementioned disciplines are integrated into one novel maneuvering device or propulsor. The potential in maneuvering and silencing is discussed. 相似文献
10.
This paper describes a complete set of methods for arranging acoustic images of the sea floor by projecting and interpolating data gathered with a novel front-scan sonar system, developed in the context of the EC-COSMOS project. Traditional sonar imaging systems for sea-floor analysis generate acoustic images during the motion of a ship; on the contrary, the front-scan sonar system not only provides information unreachable by traditional devices (blind region), but also does not need the ship motion to compose a whole image of the sea floor. Two different projection methods have been devised: a simpler analytical solution and a more precise ray-tracing approach. The development of an analytical solution is possible under the classical assumptions about a flat sea floor and a constant sound velocity profile; when these hypotheses are not realistic or a more precise image is required, a numerical solution obtained by a ray-tracing approach can be applied, which is based on some ad hoc solutions worked out for the front-scan sonar system. To move from the projection results to an image defined over a dense matrix of pixels, an interpolation stage is needed. To this end, an algorithm based on the generation of virtual-beam signals (only where necessary) has been tested and compared with more-traditional techniques. The potentials of the proposed projection and interpolation methods have been evaluated and some comparisons have been made, using real data gathered with the COSMOS sonar prototype during trials at sea. 相似文献
11.
A newly developed towed transient electromagnetic (TEM) system is capable of measuring the electrical conductivity of the
uppermost 5–10 m of sediments on the sea floor. The profiles of conductivity may be interpreted to give the porosity and likely
texture of the bottom sediments. Recent tests of the system have demonstrated that data may be collected continuously in a
surveying mode. Results from Knight Inlet, British Columbia, are in good agreement with sea floor samples from the area.
Applications for the system include the rapid identification of sediment types for dredging operations, geotechnical surveys,
or reconnaissance mapping of Quaternary geology. 相似文献
12.
Haruzo Eda 《Ocean Engineering》1980,7(3):379-397
Equations of yaw, sway, roll and rudder motions are formulated to represent realistic maneuvering behavior of high-speed ships such as destroyers. Important coupling terms between yaw, sway, roll and rudder were included on the basis of recent captive model test results of a high-speed ship. A series of computer runs was made by using equations of yaw, sway, roll and rudder motions. Results indicate substantial coupling effects between yaw, roll, and rudder, which introduce changes in maneuvering characteristics and reduce course stability in high-speed operation. These effects together with relatively small GM (which is typical for certain high-speed ships) produce large rolling motions in a seaway as frequently observed in actual operations. Results of digital simulations and captive model tests clearly indicate the major contributing factors to such excessive rolling motions at sea. 相似文献
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《Oceanic Engineering, IEEE Journal of》1994,19(2):175-182
Navigation of an underwater minefield by a remotely operated vehicle (ROV) or an autonomous undersea vehicle (AUV) requires the detection, localization, and avoidance of obstacles. The sizes of obstacles to be avoided range from the diameter of cables up to the size of other vehicles. A classical solution to this problem is the use of an obstacle avoidance sonar, but due to the high degree of sophistication of modern-day mines and unfriendly vehicles, it is desirable to avoid signal energies that might be detectable. The use of spread-spectrum signal structures is one possible way to avoid this difficulty while retaining the capability of despreading the energy at the receiver. This paper presents the development of a beamforming system that uses a frequency-decomposition FFT beamformer and a spread-spectrum signal structure for low-probability-of-detection navigation 相似文献
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Large Area 3-D Reconstructions From Underwater Optical Surveys 总被引：1，自引：0，他引：1
《Oceanic Engineering, IEEE Journal of》2009,34(2):150-169
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Biologically inspired maneuvering of autonomous undersea vehicles (AUVs) in the dive plane using pectoral-like oscillating fins is considered. Computational fluid dynamics are used to parameterize the forces generated by a mechanical flapping foil, which attempts to mimic the pectoral fin of a fish. Since the oscillating fins produce periodic force and moment of a variety of wave shapes, the essential characteristics of these signals are captured in their Fourier expansions. Maneuvering of the biorobotic AUV in the dive plane is accomplished by periodically altering the bias angle of the oscillating fin. Based on a discrete-time AUV model, an inverse control system for the dive-plane control is derived. It is shown that, in the closed-loop system, the inverse control system accomplishes accurate tracking of the prescribed time-varying depth trajectories and the segments of the intersample depth trajectory remain close to the discrete-time reference trajectory. The results show that the fins located away from the center of mass toward the nose of the vehicle provide better maneuverability. 相似文献
16.
Instrument calibration of ocean bottom seismographs 总被引：1，自引：0，他引：1
To increase the accuracy of measuring sea floor motion with ocean bottom seismometers, we calibrate the seismometer system on the ocean floor. Data from the sea floor calibration, augmented with electronic and land calibration data, enables us to find the OBS transfer function to an accuracy of 0.5% in the frequency range of 0.1 to 32 Hz. We are able to distinguish between temperature, instrument and OBS ground coupling effects, all of which alter the transfer function. This paper reviews our method of calibration and discusses the effects of temperature and some of the instrument design features on the vertical seismometer transfer function. 相似文献
17.
GAO Xiang DING Kang REN Yu-gang FU Wen-tao DING Zhong-jun ZHAO Sheng-y LIU Bao-hua 《海洋工程》2017,31(5):618-623
China''s 7000 m manned submersible JIAOLONG carried out an exploration cruise at the Mariana Trench from June to July 2016. The submersible completed nine manned dives on the north and south area of the Mariana Trench from the depth of 5500 to 6700 m, to investigate the geological, biological and chemical characteristics in the hadal area. During the cruise, JIAOLONG deployed a gas-tight serial sampler to collect the water near the sea bottom regularly. Five days later, the sub located the sampler in another dive and retrieved it successfully from the same location, which is the first time that scientists and engineers finished the high accuracy in-situ deployment and retrieval using a manned submersible with Ultra-Short Base Line (USBL) positioning system at the depth more than 6600 m. In this task, we used not only the USBL system of the manned submersible but also a compound strategy, including five position marks, the sea floor terrain, the depth contour, and the heading of the sub. This paper introduces the compound strategy of the target deployment and retrieval with the practical diving experience of JIAOLONG, and provides a promising technique for other underwater vehicles such as manned submersible or Remote Operated Vehicle (ROV) under similar conditions. 相似文献
18.
李粹中 《海洋地质与第四纪地质》1992,12(4):75-86
海底扩张中心的热液矿化作用是国际地球科学研究中最为活跃的领域之一。本文介绍了:1.热液多金属矿床调查的历史沿革;2.九十年代热液多金属矿床的海上调查方法;3.海底热液矿床的赋存条件;4.海底热液矿化作用过程;5.高强度热液活动与地质构造事件;6.热液矿体形状和流体动力学。作者认为,在我国开展太平洋多金属结核资源调查的同时,应对热液矿床的研究给予足够的重视。 相似文献
19.
Jan Petrich 《Ocean Engineering》2011,38(1):197-204
Attitude control systems for autonomous underwater vehicles are often implemented with separate controllers for pitch motion in the vertical plane and yaw motion in the horizontal plane. We propose a novel time-varying model for a streamlined autonomous underwater vehicle that explicitly displays the coupling between yaw and pitch motion due to nonzero roll angle and/or roll rate. The model facilitates the use of a multi-input multi-output H∞ control design that is robust to yaw-pitch coupling. The efficacy of our approach is demonstrated with field trials. 相似文献
20.
Félix Avedik Vincent Renard Didier Buisine Jean-Yves Cornic 《Marine Geophysical Researches》1978,3(4):357-379
This paper describes a pop-up ocean bottom seismograph designed primarily for refraction surveys both on the continental shelf and in deep sea. Its development is the extension of our system based on seismic detectors located on the sea floor with radio transmission of seismic signals and used for seismic refraction studies on the continental shelf. The seismic detectors (vertical geophone or hydrophone and two orthogonally mounted horizontal geophones) are located outside of the pressure vessel on the main frame. Optionally, the seismic sensors may be decoupled from the main frame assembly. This decoupling is performed by a mobile arm positioning the separate three component sensor package on the sea floor.Contribution No. 455 of the Département Scientifique, Centre Océanologique de Bretagne. 相似文献