The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Marine ranching is a new concept of modern fishery, which has extremely significance to the development of modern ocean economy. Various technologies are required to ensure the efficiency of marine ranching. Among those, the technology of ocean resource assessment, especially fish resource, plays an indispensible and key role. This paper introduces an effective and precise method to assess the fishery...
Like other dolphins, Sousa Chinensis produces click signals to echolocate in underwater. Research on the source level (SL) of click signal transmitted by Sousa Chinensis is beneficial to understand the survival and behavior of such animals. In the shallow sea where the Sousa Chinensis lives, the underwater environment is so complex that causes the click signals propagation to the receiving hydrophone...
Studying low frequency sound transmission through water-air interface can help understand airplane-generated sound for acoustic remote sensing and effects of airborne sources on marine life. In this paper ray theory and wave theory are utilized to evaluate the acoustic transparency. Ray theory is first used to calculate the energy of the plane and spherical wave that transmits from water to air. Wave...
This paper describes a development of a broad band underwater acoustic transducer for Doppler Velocity Log(DVL). The transducer uses thickness vibration mode of a disk type piezoelectric(PZT) ceramic. Three types of transducers, each having different configuration of acoustic impedance matching layer and backing are composed. Transmitting voltage response(TVR), receiving voltage sensitivity(RVS) and...
Wave force plays an important role in the deepwater pile stick-up analysis. Especially when the pile top is near sea surface, with the addition of wave dynamic response, wave force will increase significantly. Based on the characteristics of the deepwater pile, main attention in this paper is focused on the important influence of wave dynamic response on the deepwater pile stick-up analysis and an...
An experiment was performed to shoot airgun and receive the seismic signal with long-term seafloor seismic observatories (DONET seafloor and IODP borehole observatory) above the seismogenic zone in the Nankai Trough. The purpose of the experiment is to assess possibility to detect temporal change in seismic velocity structure which might change due to the stress accumulation in and around the subducting...
A reciprocal acoustic transmission experiment was conducted in Bachimen Harbor, Keelung on December 4, 2009. Sound pulses were transmitted reciprocally between two Coastal Acoustic Tomography Systems (CATs) placed on the North bank and separated by 490 m. The received pulse responses show two dominant ray groups. Using horizontal ray simulation from the BELLHOP ray tracing program, the two arrival...
According to shallow water, vast area, sailing inconvenience, the crest of Dongsha Atoll have less complete survey for a long time. However, the investigation is not conducive to the traditional surveys, but just very suitable for satellite images of large area investigation. This study used multispectral optical satellite images cooperated with in situ ground truth data, to investigate bottom and...
This work introduces a low-cost energy measurement method and proposes a simple linear model to estimate the vehicle energy consumption when navigating a given trajectory. Experimental results on Nessie VII AUV show that the developed system can be used to measure the energy used during the vehicle's operations with a good confidence level. Moreover the proposed estimation model can be trained using...
A small-size autonomous underwater vehicle (AUV) for underwater environmental sampling is developed. Example applications include bottom mapping using a sidescan sonar, and thermocline tracking using the conductivity-temperature-depth sensor. The AUV has a modular mechanical, electronic and software design which allows for a simple integration of payload sensors selected for different applications...
Compared with autonomous underwater gliders (AUGs) with fixed wings, gliders with controllable wings have variable hydrodynamics coefficients to achieve better flight performance. In this paper, relations between flight performance and shapes of wings are analyzed. A combined mechanism which contains two sub-mechanisms is presented. It can achieve three kinds of shape changing motions including wings...
This paper investigates the fault diagnosis and fault tolerant control problems for the actuators of marine vehicles through the processes of detection, isolation, and tolerant control. Two categories of observers contribute to detect the predefined fault influence parameters that represent the fault situations by relying on the singular value decomposition for the control matrix. The parameter changing...
In this paper, the consistent fish tracking strategies have been present for the underwater surveillance system with multiple static cameras in the overlapping field of views (FOV). The discriminative appearance model has been first introduced to distinguish the swimming fish and the background by the superpixel. The centroid coordinate homographic mapping and the Speeded Up Robust Features (SURF)...
Detecting underwater objects is an important application in marine applications. Most of the techniques are based on the amplitude related techniques, whereby the amplitude of the received echo is used to detect objects within specified bounds. Amplitude techniques however are prone to interference and attenuation, thus limiting the capabilities of such systems. Hence, the aim of this paper is to...
This paper presents the dynamic features of gravity waves based on coherent radar observations. We demonstrate that it is practical to detect wave breaking events via the sea surface backscattering intensity and Doppler velocity. Both parameters are acquired from coherent X-band radars operating at grazing incidence. Our measurements show a range dependency of the Doppler velocity which results from...
Underwater network technologies are of growing interest for applications in marine research, oceanography, marine commercial operations, offshore oil industry and defense. Long propagation delays and low bit rates of underwater acoustic networks is the nature of underwater acoustic channels. This necessitates a research of underwater network protocols that show benefits in success probability and...
The sonic layer depth (SLD) is the acoustical equivalent of the mixed layer depth (MLD), although they are defined differently. The SLD characterizes the potential of the upper ocean to trap acoustic energy in a surface duct while the MLD characterizes upper ocean mixing. The SLD and MLD often coincide because sound speed increases with depth down to the MLD, where (typically) a decrease in temperature...
A set of information acquisition and monitoring system of subsea observatory network was designed. A kind of monitoring system transmitting IP packets by optical network based on event-triggered and timing-driven was proposed. A sort of overall framework of the monitoring and control system was put forward, which is composed of the shore station control center layer, the optical transmission backbone...
Linear frequency-modulated continuous wave (LFMCW) is applied in continuous active sonar (CAS). Methods for echo detection and direct path interference (DPI) suppression are studied and evaluated by simulation and sea trial data. To detect the LFMCW echo, the received signal is first demodulated by the transmitting signal, resulting in a de-chirped signal, which is similar as in LFMCW radar. However,...
In this paper, techniques for retrieving wind direction and speed from shipborne X-band nautical radar images are presented. First, by analyzing the radar backscatter intensity histogram and zero-pixel percentage, each individual image is designed to go through a data quality control process. With this processing, the rain cases and all-black images can be recognized. Then, a harmonic function that...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.