Current Issue : January - March Volume : 2016 Issue Number : 1 Articles : 6 Articles
Remote sensing technique using underwater acoustics are one of the most cost-effective methods of resource detection and mapping, particularly in the coastal zone. We measured the acoustic backscatter using single beam echosounder from water column target and sea bottom. The increasing of fish size is followed by target strength value. For sea bottom, the highest acoustic backscattering was sand followed by silt and clay. This was caused by the acoustic impedance difference and also the presence of the organisms in sediment. By this study, classification and characterization of underwater target such as fish and seabed using acoustic technology was possible....
A novel activity recognition method is proposed based on acoustic information acquired from microphones in an unobtrusive\nand privacy-preserving manner. Behavior detection mechanisms may be useful in context-aware domains in everyday life, but\nthey may be inaccurate, and privacy violation is a concern. For example, vision-based behavior detection using cameras is difficult\nto apply in a private space such as a home, and inaccuracies in identifying user behaviors reduce acceptance of the technology.\nIn addition, activity recognition using wearable sensors is very uncomfortable and costly to apply for commercial purposes. In\nthis study, an acoustic information-based behavior detection algorithm is proposed for use in private spaces. This system classifies\nhuman activities using acoustic information. It combines strategies of elimination and similarity and establishes new rules. The\nperformance of the proposed algorithm was compared with that of commonly used classification algorithms such as case-based\nreasoning, k-nearest neighbors, support vector machine, and multiple regression....
This paper presents another application of an images group model for a special enclosure geometry and source orientation. A\nprevious work outlined the concept via application to a special tight-fitting enclosure. Application of the concept to a fan plenum\nrequires different mathematical descriptions for the image groups. This paper describes the sound reverberation inside a sound\nenclosure with mostly open sides where the primary noise sources are the air inlets and exhausts of axial type fans located at the\ntop of the enclosure, the sound transmission through the air inlet openings, and the radiation to wayside positions. The main\nreverberation between the floor and ceiling is determined with an image based mathematical model. The model considers how\nthe main reverberant part image group is amplified by its images from two parallel bulkheads and any side wall frame members.\nThe method of images approach allows the hard surfaces of an untreated plenum to be represented by perfectly reflecting surfaces\nwith zero sound absorption coefficients, thus not requiring any estimate or measurement for these surfaces.Numerical results show\nexcellent comparison to experimental results for an actual plenum.The image model is also shown to be significantly more accurate\nthan the standard large room diffuse field reverberant model....
Carbon nanotubes have attracted interest as contrast agents for biomedical imaging because they strongly absorb electromagnetic\nradiation in the optical and microwave regions. This study applies thermoacoustic (TA) imaging and spectroscopy to measure the\nfrequency-dependent absorption profile of single-walled carbon nanotubes (SWNT) in the ranges of 2.7ââ?¬â??3.1GHz and 7ââ?¬â??9GHz\nusing two tunable microwave sources. Between 7 and 9GHz, the peak TA signal for solutions containing semiconducting and\nmetallic SWNTs increased monotonically with a slope of 1.75AU/GHz (R2 = 0.95) and 2.8AU/GHz (R2 = 0.93), respectively, relative\nto a water baseline. However, after compensating for the background signal from water, it was revealed that the TA signal from\nmetallic SWNTs increased exponentially within this frequency band. Results suggest that TA imaging and spectroscopy could be a\npowerful tool for quantifying the absorption properties of SWNTs and optimizing their performance as contrast agents for imaging\nor heat sources for thermal therapy....
We study the performances of several computationally efficient and simple techniques for estimating direction of arrival (DOA)\nof an underwater acoustic source using a single acoustic vector sensor (AVS) in shallow water. Underwater AVS is a compact\ndevice, which consists of one hydrophone and three accelerometers in a packaged form, measuring scalar pressure and three dimensional\nacceleration simultaneously at a single position. A very controlled experimental setup is prepared to test how\nwell-known techniques, namely, arctan-based, intensity-based, time domain beamforming, and frequency domain beamforming\nmethods, perform in estimating DOA of a source in different circumstances. Experimental results reveal that for almost all cases\nbeamforming techniques perform best. Moreover, arctan-based method, which is the simplest of all, provides satisfactory results\nfor practical purposes....
Underwater Acoustic Sensor Networks (UASNs) have drawn great attention for their potential value in ocean monitoring and\noffshore exploration. In order to make the underwater application possible, the unique characteristics of underwater acoustic\nchannels and continuous node movement inspired the emergence of routing protocols for underwater environment. In this paper,\nwe introduce and compare four prominent routing protocols proposed for UASNs, namely, H2-DAB, GEDAR, E-PULRP, and\nPER. Performances of the routing protocols are evaluated in terms of the average number of control packets, end-to-end delay,\ndata delivery ratio, and total energy consumption. The impact of water currents on the routing algorithms is also analyzed in our\nsimulation. Experimental results demonstrate that E-PULRP provides high data delivery ratio at the cost of end-to-end delay. H2-\nDAB has better real-time performance for minimal delay transmission. GEDAR efficiently addresses the problem of void region\nwithout introducing extra energy. PER requires the most control packets in the process of routing establishment. Our work aims\nto provide useful insights to select appropriate routing protocols to fulfil different application requirements in UASNs....
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