摘要:

Dynamic positioning (DP) is an operation method whereby the position of a surface vessel is maintained in close proximity to a required position in the horizontal plane through the controlled application of forces and moments generated by purposely installed thrusters. When estimating thrust, this kind of conventional control system often uses many acceleration sensors, velocity sensors, environment sensors, and filters. Usually, these sensors have measured electrical errors. To reduce the number of sensors used and to decrease the measurement errors, this article presents an effective control system for estimating thrust and moment commands, which is based on energy and impulsemomentum principles. Donha and Brinati's example is followed to verify the feasibility of the present control system, which performs semisubmersible platform positioning using an LQG controller, and the results are feasible and economical. A simulated coring vessel marine positioning in southern Taiwan is presented, which can estimate the counterthrust and moment commands, and the complex environmental forces and moments are described. The results can provide a valuable control system for dynamically positioned vessels.

ISSN:0149-0419    

DOI:10.1080/014904199273353

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor

摘要:

This article describes the design, operation, and field testing of the depthimeter. The depthimeter merges heave and acoustically derived vessel depth to form estimates of instantaneous vessel depth and instantaneous sea surface height, both relative to mean sea level. Results from sea trials held in December 1997 demonstrate successful operation of the system.

ISSN:0149-0419    

DOI:10.1080/014904199273362

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor

摘要:

Monthly mesoscale eddy kinetic energy (EKE) per unit mass has been computed for four years, 1993-1996, from TOPEX altimeter data in the Indian Ocean. It ranges from 50 cm2/s2to 2,700 cm2/s2(about 4,000 cm2/s2near the Somali region in a few months). In the Arabian Sea and the Bay of Bengal, regions of high energies associated with various current systems under the influence of monsoonal winds have been delineated. Monthly variation of EKE near the Somali region has been studied. In this region the maximum EKE per unit mass has been observed during August every year, with variations in magnitude from year to year. The mesoscale eddy kinetic energy computed from TOPEX altimeter-derived SSH during 1993-1996 is highest near the Somali region during the SW monsoon, due to formation of mesoscale eddies and also because of upwelling. In the Bay of Bengal, high eddy kinetic energy is seen toward the western side during nonmonsoonal months due to the western boundary current. In the South Indian Ocean, it is high at a few places in some of the months. A large part of the Indian Ocean exhibits low eddy kinetic energy (less than 300 cm2/s2) year-round.

ISSN:0149-0419    

DOI:10.1080/014904199273371

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor

摘要:

In recent years shallow-water mapping systems have been developing rapidly for various applications of coastal, nearshore, and other shallow-water regions. Some systems can operate in only 0.5 m deep water, while the operating range of some systems is over 600 m depth. This article reviews the characteristics of nine shallow-water mapping systems developed by seven manufacturers. The design and the data collection methods of these systems are different from each other, and each has its advantage. Most of these systems have been tested in the real environment and are in use for various purposes around the world.

ISSN:0149-0419    

DOI:10.1080/014904199273380

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor

摘要:

We describe software for an IBM compatible personal computer (PC) that we have developed and used to collect and analyze backscatter data from a multi-wavelength Mie-Rayleigh scanning lidar system. Both one and two-dimensional distributions of optical scattering coefficients are calculated from the lidar return signals and displayed in real time. Although we are using the software for analyzing marine aerosols, the modular nature of the software and data acquisition drivers make it straightforward to adapt the software to different systems, such as differential absorption lidar (DIAL) and oceanic lidars. We show examples of both horizontal and vertical Mie-Rayleigh lidar scans collected at the Makai Pier and Bellows Beach on the northeast side of the island of Oahu.

ISSN:0149-0419    

DOI:10.1080/014904199273399

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor

ISSN:0149-0419    

DOI:10.1080/014904199273407

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor

ISSN:0149-0419    

DOI:10.1080/014904199273416

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor