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In this paper, we propose an Error Tolerant Dual-Hydrophone Localization method, i.e., ET-DHL, in underwater sensor networks (USNs). To reduce the impact of the node uncertainty, measurement uncertainty, poor link quality and long latency for underwater localization problem, ET-DHL adds bit-level probability to process the binary sequence. Different from our previous work PCM, each dual-hydrophone...
For the first time, the application of the amplitude dominant component analysis (ADCA) to the segmentation of sonar images is explored. We exploit the saliency of the objects in side scans sonar images for underwater mines recognition. Due to the textural and multicomponent nature of the sonar image, a set of bandpass filters is used to decompose the image into narrowband components which lends itself...
In this article we present an approach to the description of Magnetohydrodynamic Propulsion. Preliminarly, an analytical model which includes an electromagnetic model and a thermal model is presented. Successively, in order to move beyond the analytical model, a 3-D MHD modeling tool and a Runge Kutta method based solver are presented and they are used to investigate an alternative MHD solutions....
In this article the wave energy density of the northern Sicilian coasts is evaluated and is used to evaluate the producibility of a wave nergy converter to be installed in an area in the north west part of Sicily. In particular, the objective of the study is the evaluation of a potential installation in an area between Trapani and Palermo, which are the largest cities in the north west part of Sicily...
Condition monitoring of offshore structures is an indispensable task in the oil and gas industry. Fibre Bragg Grating (FBG) is the key technology used down-hole in order to sense different physical parameters such as strain, vibration, etc. This paper investigates the effect of FBG sensor positions on its reflected signal, in order to optimise the sensor positioning plan in structural health monitoring...
A method is developed and introduced into simulation of waveforms scattered by a spherical shell covered by a visco-elastic layer. Both forward and backward scattered waveforms are investigated. Comparisons of the results and those without the visco-elastic layer show that the forward scattering strength is hardly affected by the visco-elastic layer no matter in a low or a high incident frequency,...
This paper will describe a compact energy generation and storage system to harvest temperature differentials in the ocean. This is a unique power source underwater in the absence of solar and wave energy. The current state-of-the-art autonomous underwater vehicles and sensors are mostly powered by primary battery, and therefore have limited capacity and lifetime. Harvesting the ocean thermal energy...
Multi-targets tracking has shown great prospects in ocean investigations. In this paper, we apply the adaptive background mixture models to extracts the moving target from the image sequences, and propose a new method which is made use of the EKF and SURF-RANSAC to realize multi-targets tracking via multiple underwater cameras. In this method the centroid coordinate homographic mapping and the Speeded...
Computer vision has become the tool of two-dimensional image recognition and analysis, which mainly means extracting image features. But the problem of robustness and real-time property in complex scenarios makes feature extraction become a challenging task. Visual attention is an important psychological adjustment mechanism in the process of human visual information management, under the guidance...
Marine survey is one of the most important methods for oceanic research. During the marine survey process, some collected samples will be distributed in-situ to scientists. In order to effectively manage the sample data, corresponding relations of sample type should be established between the actual distributed sample records and the prior sample applications. This matching result can provide the...
In this paper, an approach is presented to retrieve ionospheric total electron content (TEC) over oceans from Global Navigation Satellite System-Reflectometry (GNSS-R) delay-Doppler map (DDM). Here, an additional ionospheric delay (τI) is considered in the conventional DDM simulation process. Based on this, the least squares (LS) fitting method is employed for TEC retrieval by fitting the simulated...
The characterization of underwater ambient noise using time frequency representations (TFRs) is challenging due to the opulence of the potential information that can be extracted from it. Traditionally Short Term Fourier Transform (STFT) is used to observe underwater ambient noise sources from the signal received by sonar. Short term Fourier Transform is a class of distributions determined by window...
Bearing-time-record (BTR) is widely used in sonar signal processing as an important display formats which may benefit the subsequent processing. The general way to get a BTR display is to parallel the outputs of the beamformer along time axis. This paper proposes a method to generate the BTR display which uses the L1 norm regularization and the total variation (TV) regularization to enhance the point-based...
The past few years have witnessed a significant progress in research of underwater acoustic networks. Some MAC and routing protocols tailored for underwater acoustic networks have been proposed. However, it is difficult and costly to build real underwater network systems as well as conduct field experiments, and most researches are based on theoretical analysis and simulations. To facilitate evaluating...
Recently, underwater acoustic communication system has been received a great interest due to its wide application areas. Since acoustic modem is one of the core technologies for underwater communication systems, there have been many efforts to improve the performance of acoustic modem in terms of data rate, working range, power consumption, size and cost by utilizing state-of-the-art physical layer...
Guide wave is gradually used in non-destructive inspection of submarine pipe in recent years. Interface wave is a type of guide waves. Interface wave has some good characteristics, such as high energy and large displacement at interface. Compared with traditional Lamb wave method, interface wave in pipe structure has less modes in high frequency. Thus, interface wave is more easily analyzed than Lamb...
Underwater speech communication plays an important role in many marine missions, such as oceanographic investigation, environmental monitoring, underwater rescuing and sightseeing. However, the difficulties of underwater acoustic channels such as multipath, time varying and Doppler shifting pose significant challenges to the design of high performance underwater acoustic speech communication. In this...
In underwater wireless optical communications (UWOC), impulse response is essential for performance evaluation and system design. However, most prior works on impulse response modeling for UWOC links utilize curve fitting of Monte Carlo simulation results and require remodeling once the link geometry or system configuration is changed. In this paper, we derive an analytical formula to model the single...
Discarding the phase content of signals from single-channel high-frequency (HF) radar is commonplace among practitioners in the field. From the perspective of complex-valued statistics, this practice implicitly implies that the complex-valued HF data is second-order proper or circular. This paper presents a preliminary investigation into the validity of this assumption using HF surface wave radar...
In this study, we used an improved and more complex productmeter than previously designed for research and education. We performed daytime measurements on photosynthesis of Ulva pertusa on equipment to support one day, in order to examine its potential use as a teaching tool in university (higher education) programs to study environmental maintenance, reproduction, and creation along coastal areas...
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