WorldWideScience

Sample records for underwater acoustic field

  1. 4th Pacific Rim Underwater Acoustics Conference

    CERN Document Server

    Xu, Wen; Cheng, Qianliu; Zhao, Hangfang

    2016-01-01

    These proceedings are a collection of 16 selected scientific papers and reviews by distinguished international experts that were presented at the 4th Pacific Rim Underwater Acoustics Conference (PRUAC), held in Hangzhou, China in October 2013. The topics discussed at the conference include internal wave observation and prediction; environmental uncertainty and coupling to sound propagation; environmental noise and ocean dynamics; dynamic modeling in acoustic fields; acoustic tomography and ocean parameter estimation; time reversal and matched field processing; underwater acoustic localization and communication as well as measurement instrumentations and platforms. These proceedings provide insights into the latest developments in underwater acoustics, promoting the exchange of ideas for the benefit of future research.

  2. Underwater Acoustic Target Tracking: A Review

    Science.gov (United States)

    Han, Ying; Fan, Liying

    2018-01-01

    Advances in acoustic technology and instrumentation now make it possible to explore marine resources. As a significant component of ocean exploration, underwater acoustic target tracking has aroused wide attention both in military and civil fields. Due to the complexity of the marine environment, numerous techniques have been proposed to obtain better tracking performance. In this paper, we survey over 100 papers ranging from innovative papers to the state-of-the-art in this field to present underwater tracking technologies. Not only the related knowledge of acoustic tracking instrument and tracking progress is clarified in detail, but also a novel taxonomy method is proposed. In this paper, algorithms for underwater acoustic target tracking are classified based on the methods used as: (1) instrument-assisted methods; (2) mode-based methods; (3) tracking optimization methods. These algorithms are compared and analyzed in the aspect of dimensions, numbers, and maneuvering of the tracking target, which is different from other survey papers. Meanwhile, challenges, countermeasures, and lessons learned are illustrated in this paper. PMID:29301318

  3. Digital sonar design in underwater acoustics principles and applications

    CERN Document Server

    Li, Qihu

    2012-01-01

    "Digital Sonar Design in Underwater Acoustics Principles and Applications" provides comprehensive and up-to-date coverage of research on sonar design, including the basic theory and techniques of digital signal processing, basic concept of information theory, ocean acoustics, underwater acoustic signal propagation theory, and underwater signal processing theory. This book discusses the general design procedure and approaches to implementation, the design method, system simulation theory and techniques, sonar tests in the laboratory, lake and sea, and practical validation criteria and methods for digital sonar design. It is intended for researchers in the fields of underwater signal processing and sonar design, and also for navy officers and ocean explorers. Qihu Li is a professor at the Institute of Acoustics, Chinese Academy of Sciences, and an academician of the Chinese Academy of Sciences.

  4. Cooperative OFDM underwater acoustic communications

    CERN Document Server

    Cheng, Xilin; Cheng, Xiang

    2016-01-01

    Following underwater acoustic channel modeling, this book investigates the relationship between coherence time and transmission distances. It considers the power allocation issues of two typical transmission scenarios, namely short-range transmission and medium-long range transmission. For the former scenario, an adaptive system is developed based on instantaneous channel state information. The primary focus is on cooperative dual-hop orthogonal frequency division multiplexing (OFDM). This book includes the decomposed fountain codes designed to enable reliable communications with higher energy efficiency. It covers the Doppler Effect, which improves packet transmission reliability for effective low-complexity mirror-mapping-based intercarrier interference cancellation schemes capable of suppressing the intercarrier interference power level. Designed for professionals and researchers in the field of underwater acoustic communications, this book is also suitable for advanced-level students in electrical enginee...

  5. Classification of underwater targets from autonomous underwater vehicle sampled bistatic acoustic scattered fields.

    Science.gov (United States)

    Fischell, Erin M; Schmidt, Henrik

    2015-12-01

    One of the long term goals of autonomous underwater vehicle (AUV) minehunting is to have multiple inexpensive AUVs in a harbor autonomously classify hazards. Existing acoustic methods for target classification using AUV-based sensing, such as sidescan and synthetic aperture sonar, require an expensive payload on each outfitted vehicle and post-processing and/or image interpretation. A vehicle payload and machine learning classification methodology using bistatic angle dependence of target scattering amplitudes between a fixed acoustic source and target has been developed for onboard, fully autonomous classification with lower cost-per-vehicle. To achieve the high-quality, densely sampled three-dimensional (3D) bistatic scattering data required by this research, vehicle sampling behaviors and an acoustic payload for precision timed data acquisition with a 16 element nose array were demonstrated. 3D bistatic scattered field data were collected by an AUV around spherical and cylindrical targets insonified by a 7-9 kHz fixed source. The collected data were compared to simulated scattering models. Classification and confidence estimation were shown for the sphere versus cylinder case on the resulting real and simulated bistatic amplitude data. The final models were used for classification of simulated targets in real time in the LAMSS MOOS-IvP simulation package [M. Benjamin, H. Schmidt, P. Newman, and J. Leonard, J. Field Rob. 27, 834-875 (2010)].

  6. Underwater unidirectional acoustic transmission through a plate with bilateral asymmetric gratings

    Science.gov (United States)

    Song, Ailing; Chen, Tianning; Wang, Xiaopeng; Xi, Yanhui; Liang, Qingxuan

    2018-04-01

    In this paper, a novel underwater unidirectional acoustic transmission (UAT) device consisting of a plate with bilateral asymmetric gratings is proposed and numerically investigated. The transmission spectra, the acoustic intensity field distributions, and the displacement field distributions are numerically calculated based on the finite element method. The transmission spectra show that the proposed device exhibits different UAT effects in three bands. The acoustic intensity field distributions demonstrate that the proposed device can realize UAT, which agree well with the transmission spectra. The mechanism is discussed by analyzing the displacement field distributions, and the UAT is attributed to the symmetric mode excited in brass plate. Furthermore, the effects of the lattice constant, the upper slit width, and the lower slit width on bands are discussed. Our design provides a good reference for designing underwater UAT devices and has potential applications in some fields, such as medical ultrasonic devices, acoustic barrier, and noise insulation.

  7. Underwater Acoustic Networking Techniques

    CERN Document Server

    Otnes, Roald; Casari, Paolo; Goetz, Michael; Husøy, Thor; Nissen, Ivor; Rimstad, Knut; van Walree, Paul; Zorzi, Michele

    2012-01-01

    This literature study presents an overview of underwater acoustic networking. It provides a background and describes the state of the art of all networking facets that are relevant for underwater applications. This report serves both as an introduction to the subject and as a summary of existing protocols, providing support and inspiration for the development of network architectures.

  8. Game Theory-Based Cooperation for Underwater Acoustic Sensor Networks: Taxonomy, Review, Research Challenges and Directions.

    Science.gov (United States)

    Muhammed, Dalhatu; Anisi, Mohammad Hossein; Zareei, Mahdi; Vargas-Rosales, Cesar; Khan, Anwar

    2018-02-01

    Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal), long propagation delay of acoustic signal, limited bandwidth and loss of connectivity. There are several proposed methods to improve cooperation between the nodes by incorporating information/game theory in the node's cooperation. However, there is a need to classify the existing works and demonstrate their performance in addressing the cooperation issue. In this paper, we have conducted a review to investigate various factors affecting cooperation in underwater acoustic sensor networks. We study various cooperation techniques used for underwater acoustic sensor networks from different perspectives, with a concentration on communication reliability, energy consumption, and security and present a taxonomy for underwater cooperation. Moreover, we further review how the game theory can be applied to make the nodes cooperate with each other. We further analyze different cooperative game methods, where their performance on different metrics is compared. Finally, open issues and future research direction in underwater acoustic sensor networks are highlighted.

  9. Game Theory-Based Cooperation for Underwater Acoustic Sensor Networks: Taxonomy, Review, Research Challenges and Directions

    Directory of Open Access Journals (Sweden)

    Dalhatu Muhammed

    2018-02-01

    Full Text Available Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal, long propagation delay of acoustic signal, limited bandwidth and loss of connectivity. There are several proposed methods to improve cooperation between the nodes by incorporating information/game theory in the node’s cooperation. However, there is a need to classify the existing works and demonstrate their performance in addressing the cooperation issue. In this paper, we have conducted a review to investigate various factors affecting cooperation in underwater acoustic sensor networks. We study various cooperation techniques used for underwater acoustic sensor networks from different perspectives, with a concentration on communication reliability, energy consumption, and security and present a taxonomy for underwater cooperation. Moreover, we further review how the game theory can be applied to make the nodes cooperate with each other. We further analyze different cooperative game methods, where their performance on different metrics is compared. Finally, open issues and future research direction in underwater acoustic sensor networks are highlighted.

  10. Game Theory-Based Cooperation for Underwater Acoustic Sensor Networks: Taxonomy, Review, Research Challenges and Directions

    Science.gov (United States)

    Muhammed, Dalhatu; Anisi, Mohammad Hossein; Vargas-Rosales, Cesar; Khan, Anwar

    2018-01-01

    Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal), long propagation delay of acoustic signal, limited bandwidth and loss of connectivity. There are several proposed methods to improve cooperation between the nodes by incorporating information/game theory in the node’s cooperation. However, there is a need to classify the existing works and demonstrate their performance in addressing the cooperation issue. In this paper, we have conducted a review to investigate various factors affecting cooperation in underwater acoustic sensor networks. We study various cooperation techniques used for underwater acoustic sensor networks from different perspectives, with a concentration on communication reliability, energy consumption, and security and present a taxonomy for underwater cooperation. Moreover, we further review how the game theory can be applied to make the nodes cooperate with each other. We further analyze different cooperative game methods, where their performance on different metrics is compared. Finally, open issues and future research direction in underwater acoustic sensor networks are highlighted. PMID:29389874

  11. OFDM for underwater acoustic communications

    CERN Document Server

    Zhou, Shengli

    2014-01-01

    A blend of introductory material and advanced signal processing and communication techniques, of critical importance to underwater system and network development This book, which is the first to describe the processing techniques central to underwater OFDM, is arranged into four distinct sections: First, it describes the characteristics of underwater acoustic channels, and stresses the difference from wireless radio channels. Then it goes over the basics of OFDM and channel coding. The second part starts with an overview of the OFDM receiver, and develops various modules for the receiver des

  12. Micromachined fiber optic Fabry-Perot underwater acoustic probe

    Science.gov (United States)

    Wang, Fuyin; Shao, Zhengzheng; Hu, Zhengliang; Luo, Hong; Xie, Jiehui; Hu, Yongming

    2014-08-01

    One of the most important branches in the development trend of the traditional fiber optic physical sensor is the miniaturization of sensor structure. Miniature fiber optic sensor can realize point measurement, and then to develop sensor networks to achieve quasi-distributed or distributed sensing as well as line measurement to area monitoring, which will greatly extend the application area of fiber optic sensors. The development of MEMS technology brings a light path to address the problems brought by the procedure of sensor miniaturization. Sensors manufactured by MEMS technology possess the advantages of small volume, light weight, easy fabricated and low cost. In this paper, a fiber optic extrinsic Fabry-Perot interferometric underwater acoustic probe utilizing micromachined diaphragm collaborated with fiber optic technology and MEMS technology has been designed and implemented to actualize underwater acoustic sensing. Diaphragm with central embossment, where the embossment is used to anti-hydrostatic pressure which would largely deflect the diaphragm that induce interferometric fringe fading, has been made by double-sided etching of silicon on insulator. By bonding the acoustic-sensitive diaphragm as well as a cleaved fiber end in ferrule with an outer sleeve, an extrinsic Fabry-Perot interferometer has been constructed. The sensor has been interrogated by quadrature-point control method and tested in field-stable acoustic standing wave tube. Results have been shown that the recovered signal detected by the sensor coincided well with the corresponding transmitted signal and the sensitivity response was flat in frequency range from 10 Hz to 2kHz with the value about -154.6 dB re. 1/μPa. It has been manifest that the designed sensor could be used as an underwater acoustic probe.

  13. Channel coding for underwater acoustic single-carrier CDMA communication system

    Science.gov (United States)

    Liu, Lanjun; Zhang, Yonglei; Zhang, Pengcheng; Zhou, Lin; Niu, Jiong

    2017-01-01

    CDMA is an effective multiple access protocol for underwater acoustic networks, and channel coding can effectively reduce the bit error rate (BER) of the underwater acoustic communication system. For the requirements of underwater acoustic mobile networks based on CDMA, an underwater acoustic single-carrier CDMA communication system (UWA/SCCDMA) based on the direct-sequence spread spectrum is proposed, and its channel coding scheme is studied based on convolution, RA, Turbo and LDPC coding respectively. The implementation steps of the Viterbi algorithm of convolutional coding, BP and minimum sum algorithms of RA coding, Log-MAP and SOVA algorithms of Turbo coding, and sum-product algorithm of LDPC coding are given. An UWA/SCCDMA simulation system based on Matlab is designed. Simulation results show that the UWA/SCCDMA based on RA, Turbo and LDPC coding have good performance such that the communication BER is all less than 10-6 in the underwater acoustic channel with low signal to noise ratio (SNR) from -12 dB to -10dB, which is about 2 orders of magnitude lower than that of the convolutional coding. The system based on Turbo coding with Log-MAP algorithm has the best performance.

  14. The application of standard definitions of sound to the fields of underwater acoustics and acoustical oceanography

    Science.gov (United States)

    Carey, William M.

    2004-05-01

    Recent societal concerns have focused attention on the use of sound as a probe to investigate the oceans and its use in naval sonar applications. The concern is the impact the use of sound may have on marine mammals and fishes. The focus has changed the fields of acoustical oceanography (AO) and underwater acoustics (UW) because of the requirement to communicate between disciplines. Multiple National Research Council publications, Dept. of Navy reports, and several monographs have been written on this subject, and each reveals the importance as well as the misapplication of ASA standards. The ANSI-ASA standards are comprehensive, however not widely applied. The clear definition of standards and recommendations of their use is needed for both scientists and government agencies. Traditionally the U.S. Navy has been responsible for UW standards and calibration; the ANSI-ASA standards have been essential. However, recent changes in the Navy and its laboratory structure may necessitate a more formal recognition of ANSI-ASA standards and perhaps incorporation of UW-AO in the Bureau of Standards. A separate standard for acoustical terminology, reference levels, and notation used in the UW-AO is required. Since the problem is global, a standard should be compatible and cross referenced with the International Standard (CEI/IEC 27-3).

  15. Trade-off Analysis of Underwater Acoustic Sensor Networks

    Science.gov (United States)

    Tuna, G.; Das, R.

    2017-09-01

    In the last couple of decades, Underwater Acoustic Sensor Networks (UASNs) were started to be used for various commercial and non-commercial purposes. However, in underwater environments, there are some specific inherent constraints, such as high bit error rate, variable and large propagation delay, limited bandwidth capacity, and short-range communications, which severely degrade the performance of UASNs and limit the lifetime of underwater sensor nodes as well. Therefore, proving reliability of UASN applications poses a challenge. In this study, we try to balance energy consumption of underwater acoustic sensor networks and minimize end-to-end delay using an efficient node placement strategy. Our simulation results reveal that if the number of hops is reduced, energy consumption can be reduced. However, this increases end-to-end delay. Hence, application-specific requirements must be taken into consideration when determining a strategy for node deployment.

  16. Energy Harvesting Hybrid Acoustic-Optical Underwater Wireless Sensor Networks Localization

    Directory of Open Access Journals (Sweden)

    Nasir Saeed

    2017-12-01

    Full Text Available Underwater wireless technologies demand to transmit at higher data rate for ocean exploration. Currently, large coverage is achieved by acoustic sensor networks with low data rate, high cost, high latency, high power consumption, and negative impact on marine mammals. Meanwhile, optical communication for underwater networks has the advantage of the higher data rate albeit for limited communication distances. Moreover, energy consumption is another major problem for underwater sensor networks, due to limited battery power and difficulty in replacing or recharging the battery of a sensor node. The ultimate solution to this problem is to add energy harvesting capability to the acoustic-optical sensor nodes. Localization of underwater sensor networks is of utmost importance because the data collected from underwater sensor nodes is useful only if the location of the nodes is known. Therefore, a novel localization technique for energy harvesting hybrid acoustic-optical underwater wireless sensor networks (AO-UWSNs is proposed. AO-UWSN employs optical communication for higher data rate at a short transmission distance and employs acoustic communication for low data rate and long transmission distance. A hybrid received signal strength (RSS based localization technique is proposed to localize the nodes in AO-UWSNs. The proposed technique combines the noisy RSS based measurements from acoustic communication and optical communication and estimates the final locations of acoustic-optical sensor nodes. A weighted multiple observations paradigm is proposed for hybrid estimated distances to suppress the noisy observations and give more importance to the accurate observations. Furthermore, the closed form solution for Cramer-Rao lower bound (CRLB is derived for localization accuracy of the proposed technique.

  17. Energy Harvesting Hybrid Acoustic-Optical Underwater Wireless Sensor Networks Localization.

    Science.gov (United States)

    Saeed, Nasir; Celik, Abdulkadir; Al-Naffouri, Tareq Y; Alouini, Mohamed-Slim

    2017-12-26

    Underwater wireless technologies demand to transmit at higher data rate for ocean exploration. Currently, large coverage is achieved by acoustic sensor networks with low data rate, high cost, high latency, high power consumption, and negative impact on marine mammals. Meanwhile, optical communication for underwater networks has the advantage of the higher data rate albeit for limited communication distances. Moreover, energy consumption is another major problem for underwater sensor networks, due to limited battery power and difficulty in replacing or recharging the battery of a sensor node. The ultimate solution to this problem is to add energy harvesting capability to the acoustic-optical sensor nodes. Localization of underwater sensor networks is of utmost importance because the data collected from underwater sensor nodes is useful only if the location of the nodes is known. Therefore, a novel localization technique for energy harvesting hybrid acoustic-optical underwater wireless sensor networks (AO-UWSNs) is proposed. AO-UWSN employs optical communication for higher data rate at a short transmission distance and employs acoustic communication for low data rate and long transmission distance. A hybrid received signal strength (RSS) based localization technique is proposed to localize the nodes in AO-UWSNs. The proposed technique combines the noisy RSS based measurements from acoustic communication and optical communication and estimates the final locations of acoustic-optical sensor nodes. A weighted multiple observations paradigm is proposed for hybrid estimated distances to suppress the noisy observations and give more importance to the accurate observations. Furthermore, the closed form solution for Cramer-Rao lower bound (CRLB) is derived for localization accuracy of the proposed technique.

  18. Energy Harvesting Hybrid Acoustic-Optical Underwater Wireless Sensor Networks Localization

    KAUST Repository

    Saeed, Nasir; Celik, Abdulkadir; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim

    2017-01-01

    Underwater wireless technologies demand to transmit at higher data rate for ocean exploration. Currently, large coverage is achieved by acoustic sensor networks with low data rate, high cost, high latency, high power consumption, and negative impact on marine mammals. Meanwhile, optical communication for underwater networks has the advantage of the higher data rate albeit for limited communication distances. Moreover, energy consumption is another major problem for underwater sensor networks, due to limited battery power and difficulty in replacing or recharging the battery of a sensor node. The ultimate solution to this problem is to add energy harvesting capability to the acoustic-optical sensor nodes. Localization of underwater sensor networks is of utmost importance because the data collected from underwater sensor nodes is useful only if the location of the nodes is known. Therefore, a novel localization technique for energy harvesting hybrid acoustic-optical underwater wireless sensor networks (AO-UWSNs) is proposed. AO-UWSN employs optical communication for higher data rate at a short transmission distance and employs acoustic communication for low data rate and long transmission distance. A hybrid received signal strength (RSS) based localization technique is proposed to localize the nodes in AO-UWSNs. The proposed technique combines the noisy RSS based measurements from acoustic communication and optical communication and estimates the final locations of acoustic-optical sensor nodes. A weighted multiple observations paradigm is proposed for hybrid estimated distances to suppress the noisy observations and give more importance to the accurate observations. Furthermore, the closed form solution for Cramer-Rao lower bound (CRLB) is derived for localization accuracy of the proposed technique.

  19. Energy Harvesting Hybrid Acoustic-Optical Underwater Wireless Sensor Networks Localization

    KAUST Repository

    Saeed, Nasir

    2017-12-26

    Underwater wireless technologies demand to transmit at higher data rate for ocean exploration. Currently, large coverage is achieved by acoustic sensor networks with low data rate, high cost, high latency, high power consumption, and negative impact on marine mammals. Meanwhile, optical communication for underwater networks has the advantage of the higher data rate albeit for limited communication distances. Moreover, energy consumption is another major problem for underwater sensor networks, due to limited battery power and difficulty in replacing or recharging the battery of a sensor node. The ultimate solution to this problem is to add energy harvesting capability to the acoustic-optical sensor nodes. Localization of underwater sensor networks is of utmost importance because the data collected from underwater sensor nodes is useful only if the location of the nodes is known. Therefore, a novel localization technique for energy harvesting hybrid acoustic-optical underwater wireless sensor networks (AO-UWSNs) is proposed. AO-UWSN employs optical communication for higher data rate at a short transmission distance and employs acoustic communication for low data rate and long transmission distance. A hybrid received signal strength (RSS) based localization technique is proposed to localize the nodes in AO-UWSNs. The proposed technique combines the noisy RSS based measurements from acoustic communication and optical communication and estimates the final locations of acoustic-optical sensor nodes. A weighted multiple observations paradigm is proposed for hybrid estimated distances to suppress the noisy observations and give more importance to the accurate observations. Furthermore, the closed form solution for Cramer-Rao lower bound (CRLB) is derived for localization accuracy of the proposed technique.

  20. A Secure Communication Suite for Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Angelica Lo Duca

    2012-11-01

    Full Text Available In this paper we describe a security suite for Underwater Acoustic Sensor Networks comprising both fixed and mobile nodes. The security suite is composed of a secure routing protocol and a set of cryptographic primitives aimed at protecting the confidentiality and the integrity of underwater communication while taking into account the unique characteristics and constraints of the acoustic channel. By means of experiments and simulations based on real data, we show that the suite is suitable for an underwater networking environment as it introduces limited, and sometimes negligible, communication and power consumption overhead.

  1. Cognitive Routing in Software-Defined Underwater Acoustic Networks

    Directory of Open Access Journals (Sweden)

    Huma Ghafoor

    2017-12-01

    Full Text Available There are two different types of primary users (natural acoustic and artificial acoustic, and there is a long propagation delay for acoustic links in underwater cognitive acoustic networks (UCANs. Thus, the selection of a stable route is one of the key design factors for improving overall network stability, thereby reducing end-to-end delay. Software-defined networking (SDN is a novel approach that improves network intelligence. To this end, we propose a novel SDN-based routing protocol for UCANs in order to find a stable route between source and destination. A main controller is placed in a surface buoy that is responsible for the global view of the network, whereas local controllers are placed in different autonomous underwater vehicles (AUVs that are responsible for a localized view of the network. The AUVs have fixed trajectories, and sensor nodes within transmission range of the AUVs serve as gateways to relay the gathered information to the controllers. This is an SDN-based underwater communications scheme whereby two nodes can only communicate when they have a consensus about a common idle channel. To evaluate our proposed scheme, we perform extensive simulations and improve network performance in terms of end-to-end delay, delivery ratio, and overhead.

  2. Passive aquatic listener (PAL): An adoptive underwater acoustic recording system for the marine environment

    International Nuclear Information System (INIS)

    Anagnostou, Marios N.; Nystuen, Jeffrey A.; Anagnostou, Emmanouil N.; Papadopoulos, Anastasios; Lykousis, Vassilios

    2011-01-01

    The ambient sound field in the ocean is a combination of natural and manmade sounds. Consequently, the interpretation of the ambient sound field can be used to quantify these processes. In the frequency range from 1 to 50 kHz, the general character of ocean ambient sound is a slowly changing background that is closely associated with local wind speed, interspersed with shorter time scale events such as rain storms, ships and animal calls. At lower frequencies the underwater ambient sound budget includes geologically generated sound activities including underwater volcanic eruptions, seismic and seepage faults that generate bubbles, etc. that can also potentially be classified and quantified. Acoustic data are collected on hydrophones. Hydrophones are simple, robust sensors that can be deployed on most ocean instrumentation systems including surface or sub-surface moorings, bottom mounted systems, drifters, ARGO floats or autonomous underwater platforms. A dedicated oceanic underwater recorder called a passive acoustic listener (PAL) has been developed. A principal issue is to accurately distinguish different sound sources so that they can be quantified as part of a sound budget, and then quantified if appropriate. Based on ongoing data collected from the Poseidon II network the retrieval potential of multi-parameters from underwater sound, including meteorological (i.e., precipitation and winds) and in general geophysical, anthropogenetic (i.e., ships, submarines, etc.) and biological (whales, etc.) sources is presented.

  3. Passive aquatic listener (PAL): An adoptive underwater acoustic recording system for the marine environment

    Energy Technology Data Exchange (ETDEWEB)

    Anagnostou, Marios N., E-mail: managnostou@ath.hcmr.g [Hellenic Center for Marine Research, Department of Inland Waters, Anavissos (Greece); Nystuen, Jeffrey A. [Hellenic Center for Marine Research, Department of Inland Waters, Anavissos (Greece); Applied Physics Laboratory, University of Washington, Seattle, WA (United States); Anagnostou, Emmanouil N. [Hellenic Center for Marine Research, Department of Inland Waters, Anavissos (Greece); Department of Civil and Environmental Engineering, University of Connecticut, CT (United States); Papadopoulos, Anastasios [Hellenic Center for Marine Research, Department of Inland Waters, Anavissos (Greece); Lykousis, Vassilios [Hellenic Center for Marine Research, Department of Oceanography, Anavissos (Greece)

    2011-01-21

    The ambient sound field in the ocean is a combination of natural and manmade sounds. Consequently, the interpretation of the ambient sound field can be used to quantify these processes. In the frequency range from 1 to 50 kHz, the general character of ocean ambient sound is a slowly changing background that is closely associated with local wind speed, interspersed with shorter time scale events such as rain storms, ships and animal calls. At lower frequencies the underwater ambient sound budget includes geologically generated sound activities including underwater volcanic eruptions, seismic and seepage faults that generate bubbles, etc. that can also potentially be classified and quantified. Acoustic data are collected on hydrophones. Hydrophones are simple, robust sensors that can be deployed on most ocean instrumentation systems including surface or sub-surface moorings, bottom mounted systems, drifters, ARGO floats or autonomous underwater platforms. A dedicated oceanic underwater recorder called a passive acoustic listener (PAL) has been developed. A principal issue is to accurately distinguish different sound sources so that they can be quantified as part of a sound budget, and then quantified if appropriate. Based on ongoing data collected from the Poseidon II network the retrieval potential of multi-parameters from underwater sound, including meteorological (i.e., precipitation and winds) and in general geophysical, anthropogenetic (i.e., ships, submarines, etc.) and biological (whales, etc.) sources is presented.

  4. The Research on Improved Companding Transformation for Reducing PAPR in Underwater Acoustic OFDM Communication System

    Directory of Open Access Journals (Sweden)

    Jinqiu Wu

    2016-01-01

    Full Text Available To solve the problem of the high peak-to-average power ratio (PAPR in Orthogonal Frequency Division Multiplexing (OFDM for the underwater acoustic communication system, the paper offers a method of reducing PAPR which combines the amplitude limiting and the improved nonlinear transformation. Traditional amplitude limiting technique can reduce PAPR in OFDM system effectively, at the cost of reducing the bit error rate (BER. However the companding transformation has far less computation complexity than SLM or PTS technologies and can improve the BER performance compared to the amplitude limiting technique simultaneously. The paper combines these two kinds of techniques, takes full use of advantages of the two method, and puts forward a low-complexity scheme choosing parameters that are more appropriate to the underwater acoustic field, with the result of improved BER performance even in lower SNR. Both simulation and experiment results show that the new method which combines clipping and companding transformation can effectively reduce the PAPR in the underwater acoustic OFDM communication system and improve the BER performance simultaneously.

  5. Task Allocation and Path Planning for Collaborative Autonomous Underwater Vehicles Operating through an Underwater Acoustic Network

    Directory of Open Access Journals (Sweden)

    Yueyue Deng

    2013-01-01

    Full Text Available Dynamic and unstructured multiple cooperative autonomous underwater vehicle (AUV missions are highly complex operations, and task allocation and path planning are made significantly more challenging under realistic underwater acoustic communication constraints. This paper presents a solution for the task allocation and path planning for multiple AUVs under marginal acoustic communication conditions: a location-aided task allocation framework (LAAF algorithm for multitarget task assignment and the grid-based multiobjective optimal programming (GMOOP mathematical model for finding an optimal vehicle command decision given a set of objectives and constraints. Both the LAAF and GMOOP algorithms are well suited in poor acoustic network condition and dynamic environment. Our research is based on an existing mobile ad hoc network underwater acoustic simulator and blind flooding routing protocol. Simulation results demonstrate that the location-aided auction strategy performs significantly better than the well-accepted auction algorithm developed by Bertsekas in terms of task-allocation time and network bandwidth consumption. We also demonstrate that the GMOOP path-planning technique provides an efficient method for executing multiobjective tasks by cooperative agents with limited communication capabilities. This is in contrast to existing multiobjective action selection methods that are limited to networks where constant, reliable communication is assumed to be available.

  6. Acoustic and Vibration Control for an Underwater Structure under Mechanical Excitation

    Directory of Open Access Journals (Sweden)

    Shi-Jian Zhu

    2014-01-01

    Full Text Available Acoustic and vibration control for an underwater structure under mechanical excitation has been investigated by using negative feedback control algorithm. The underwater structure is modeled with cylindrical shells, conical shells, and circular bulkheads, of which the motion equations are built with the variational approach, respectively. Acoustic property is analyzed by the Helmholtz integration formulation with boundary element method. Based on negative feedback control algorithm, a control loop with a coupling use of piezoelectric sensor and actuator is built, and accordingly some numerical examples are carried out on active control of structural vibration and acoustic response. Effects of geometrical and material parameters on acoustic and vibration properties are investigated and discussed.

  7. Multiuser chirp modulation for underwater acoustic channel based on VTRM

    Directory of Open Access Journals (Sweden)

    Fei Yuan

    2017-05-01

    Full Text Available In this paper, an ascheme is proposed for multiuser underwater acoustic communication by using the multi-chirp rate signals. It differs from the well known TDMA (Time Division Multiple Access, FDMA (Frequency Division Multiple Access or CDMA (Code Division Multiple Access, by assigning each users with different chirp-rate carriers instead of the time, frequency or PN code. Multi-chirp rate signals can be separated from each other by FrFT (Fractional Fourier Transform, which can be regarded as the chirp-based decomposing, and superior to the match filter in the underwater acoustic channel. VTRM (Virtual Time Reverse Mirror is applied into the system to alleviate the ISI caused by the multipatch and make the equalization more simple. Results of computer simulations and pool experiments prove that the proposed multiuser underwater acoustic communication based on the multi-chirp rate exhibit well performance. Outfield experments carrie out in Xiamen Port show that using about 10 kHz bandwidth, four users could communicate at the same time with 425 bps with low BER and can match the UAC application.

  8. Acoustically sticky topographic metasurfaces for underwater sound absorption.

    Science.gov (United States)

    Lee, Hunki; Jung, Myungki; Kim, Minsoo; Shin, Ryung; Kang, Shinill; Ohm, Won-Suk; Kim, Yong Tae

    2018-03-01

    A class of metasurfaces for underwater sound absorption, based on a design principle that maximizes thermoviscous loss, is presented. When a sound meets a solid surface, it leaves a footprint in the form of thermoviscous boundary layers in which energy loss takes place. Considered to be a nuisance, this acoustic to vorticity/entropy mode conversion and the subsequent loss are often ignored in the existing designs of acoustic metamaterials and metasurfaces. The metasurface created is made of a series of topographic meta-atoms, i.e., intaglios and reliefs engraved directly on the solid object to be concealed. The metasurface is acoustically sticky in that it rather facilitates the conversion of the incident sound to vorticity and entropy modes, hence the thermoviscous loss, leading to the desired anechoic property. A prototype metasurface machined on a brass object is tested for its anechoicity, and shows a multitude of absorption peaks as large as unity in the 2-5 MHz range. Computations also indicate that a topographic metasurface is robust to hydrostatic pressure variation, a quality much sought-after in underwater applications.

  9. A GPS-free passive acoustic localization scheme for underwater wireless sensor networks

    KAUST Repository

    Mirza, Mohammed; Shakir, Muhammad; Alouini, Mohamed-Slim

    2011-01-01

    Seaweb is an acoustic communication technology that enables communication between sensor nodes. Seaweb interconnects the underwater nodes through digital signal processing (DSP)-based modem by using acoustic links between the neighbouring sensors

  10. NEMO-SMO acoustic array: A deep-sea test of a novel acoustic positioning system for a km3-scale underwater neutrino telescope

    Science.gov (United States)

    Viola, S.; Ardid, M.; Bertin, V.; Enzenhöfer, A.; Keller, P.; Lahmann, R.; Larosa, G.; Llorens, C. D.; NEMO Collaboration; SMO Collaboration

    2013-10-01

    Within the activities of the NEMO project, the installation of a 8-floors tower (NEMO-Phase II) at a depth of 3500 m is foreseen in 2012. The tower will be installed about 80 km off-shore Capo Passero, in Sicily. On board the NEMO tower, an array of 18 acoustic sensors will be installed, permitting acoustic detection of biological sources, studies for acoustic neutrino detection and primarily acoustic positioning of the underwater structures. For the latter purpose, the sensors register acoustic signals emitted by five acoustic beacons anchored on the sea-floor. The data acquisition system of the acoustic sensors is fully integrated with the detector data transport system and is based on an “all data to shore” philosophy. Signals coming from hydrophones are continuously sampled underwater at 192 kHz/24 bit and transmitted to shore through an electro-optical cable for real-time analysis. A novel technology for underwater GPS time-stamping of data has been implemented and tested. The operation of the acoustic array will permit long-term test of sensors and electronics technologies that are proposed for the acoustic positioning system of KM3NeT.

  11. An Environment-Friendly Multipath Routing Protocol for Underwater Acoustic Sensor Network

    Directory of Open Access Journals (Sweden)

    Yun Li

    2017-01-01

    Full Text Available Underwater Acoustic Sensor Network (UASN is a promising technique by facilitating a wide range of aquatic applications. However, routing scheme in UASN is a challenging task because of the characteristics of the nodes mobility, interruption of link, and interference caused by other underwater acoustic systems such as marine mammals. In order to achieve reliable data delivery in UASN, in this work, we present a disjoint multipath disruption-tolerant routing protocol for UASN (ENMR, which incorporates the Hue, Saturation, and Value color space (HSV model to establish routing paths to greedily forward data packets to sink nodes. ENMR applies the mechanism to maintain the network topology. Simulation results show that, compared with the classic underwater routing protocols named PVBF, ENMR can improve packet delivery ratio and reduce network latency while avoiding introducing additional energy consumption.

  12. Optimal Node Placement in Underwater Acoustic Sensor Network

    KAUST Repository

    Felemban, Muhamad

    2011-10-01

    Almost 70% of planet Earth is covered by water. A large percentage of underwater environment is unexplored. In the past two decades, there has been an increase in the interest of exploring and monitoring underwater life among scientists and in industry. Underwater operations are extremely difficult due to the lack of cheap and efficient means. Recently, Wireless Sensor Networks have been introduced in underwater environment applications. However, underwater communication via acoustic waves is subject to several performance limitations, which makes the relevant research issues very different from those on land. In this thesis, we investigate node placement for building an initial Underwater Wireless Sensor Network infrastructure. Firstly, we formulated the problem into a nonlinear mathematic program with objectives of minimizing the total transmission loss under a given number of sensor nodes and targeted volume. We conducted experiments to verify the proposed formulation, which is solved using Matlab optimization tool. We represented each node with a truncated octahedron to fill out the 3D space. The truncated octahedrons are tiled in the 3D space with each node in the center where locations of the nodes are given using 3D coordinates. Results are supported using ns-3 simulator. Results from simulation are consistent with the obtained results from mathematical model with less than 10% error.

  13. Design and Analysis of Underwater Acoustic Networks with Reflected Links

    Science.gov (United States)

    Emokpae, Lloyd

    Underwater acoustic networks (UWANs) have applications in environmental state monitoring, oceanic profile measurements, leak detection in oil fields, distributed surveillance, and navigation. For these applications, sets of nodes are employed to collaboratively monitor an area of interest and track certain events or phenomena. In addition, it is common to find autonomous underwater vehicles (AUVs) acting as mobile sensor nodes that perform search-and-rescue missions, reconnaissance in combat zones, and coastal patrol. These AUVs are to work cooperatively to achieve a desired goal and thus need to be able to, in an ad-hoc manner, establish and sustain communication links in order to ensure some desired level of quality of service. Therefore, each node is required to adapt to environmental changes and be able to overcome broken communication links caused by external noise affecting the communication channel due to node mobility. In addition, since radio waves are quickly absorbed in the water medium, it is common for most underwater applications to rely on acoustic (or sound) rather than radio channels for mid-to-long range communications. However, acoustic channels pose multiple challenging issues, most notably the high transmission delay due to slow signal propagation and the limited channel bandwidth due to high frequency attenuation. Moreover, the inhomogeneous property of the water medium affects the sound speed profile while the signal surface and bottom reflections leads to multipath effects. In this dissertation, we address these networking challenges by developing protocols that take into consideration the underwater physical layer dynamics. We begin by introducing a novel surface-based reflection scheme (SBR), which takes advantage of the multipath effects of the acoustic channel. SBR works by using reflections from the water surface, and bottom, to establish non-line-of-sight (NLOS) communication links. SBR makes it possible to incorporate both line

  14. Microcontroller-based underwater acoustic ECG telemetry system.

    Science.gov (United States)

    Istepanian, R S; Woodward, B

    1997-06-01

    This paper presents a microcontroller-based underwater acoustic telemetry system for digital transmission of the electrocardiogram (ECG). The system is designed for the real time, through-water transmission of data representing any parameter, and it was used initially for transmitting in multiplexed format the heart rate, breathing rate and depth of a diver using self-contained underwater breathing apparatus (SCUBA). Here, it is used to monitor cardiovascular reflexes during diving and swimming. The programmable capability of the system provides an effective solution to the problem of transmitting data in the presence of multipath interference. An important feature of the paper is a comparative performance analysis of two encoding methods, Pulse Code Modulation (PCM) and Pulse Position Modulation (PPM).

  15. Cascading Multi-Hop Reservation and Transmission in Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Jae-Won Lee

    2014-10-01

    Full Text Available The long propagation delay in an underwater acoustic channel makes designing an underwater media access control (MAC protocol more challenging. In particular, handshaking-based MAC protocols widely used in terrestrial radio channels have been known to be inappropriate in underwater acoustic channels, because of the inordinately large latency involved in exchanging control packets. Furthermore, in the case of multi-hop relaying in a hop-by-hop handshaking manner, the end-to-end delay significantly increases. In this paper, we propose a new MAC protocol named cascading multi-hop reservation and transmission (CMRT. In CMRT, intermediate nodes between a source and a destination may start handshaking in advance for the next-hop relaying before handshaking for the previous node is completed. By this concurrent relaying, control packet exchange and data delivery cascade down to the destination. In addition, to improve channel utilization, CMRT adopts a packet-train method where multiple data packets are sent together by handshaking once. Thus, CMRT reduces the time taken for control packet exchange and accordingly increases the throughput. The performance of CMRT is evaluated and compared with that of two conventional MAC protocols (multiple-access collision avoidance for underwater (MACA-U and MACA-U with packet trains (MACA-UPT. The results show that CMRT outperforms other MAC protocols in terms of both throughput and end-to-end delay.

  16. Combined Hybrid DFE and CCK Remodulator for Medium-Range Single-Carrier Underwater Acoustic Communications

    Directory of Open Access Journals (Sweden)

    Xialin Jiang

    2017-01-01

    Full Text Available Advanced modulation and channel equalization techniques are essential for improving the performance of medium-range single-carrier underwater acoustic communications. In this paper, an enhanced detection scheme, hybrid time-frequency domain decision feedback equalizer (DFE combined with complementary code keying (CCK remodulator, is presented. CCK modulation technique provides strong tolerance to intersymbol interference caused by multipath propagation in underwater acoustic channels. The conventional hybrid DFE, using a frequency domain feedforward filter and a time domain feedback filter, provides good performance along with low computational complexity. The error propagation in the feedback filter, caused by feedbacking wrong decisions prior to CCK demodulation, may lead to great performance degradation. In our proposed scheme, with the help of CCK coding gain, more accurate remodulated CCK chips can be used as feedback. The proposed detection scheme is tested by the practical ocean experiments. The experimental results show that the proposed detection scheme ensures robust communications over 10-kilometre underwater acoustic channels with the data rate at 5 Kbits/s in 3 kHz of channel bandwidth.

  17. High-rate wireless data communications: An underwater acoustic communications framework at the physical layer

    Directory of Open Access Journals (Sweden)

    Bessios Anthony G.

    1996-01-01

    Full Text Available A variety of signal processing functions are performed by Underwater Acoustic Systems. These include: 1 detection to determine presence or absence of information signals in the presence of noise, or an attempt to describe which of a predetermined finite set of possible messages { m i , i , ... , M } the signal represents; 2 estimation of some parameter θ ˆ associated with the received signal (i.e. range, depth, bearing angle, etc.; 3 classification and source identification; 4 dynamics tracking; 5 navigation (collision avoidance and terminal guidance; 6 countermeasures; and 7 communications. The focus of this paper is acoustic communications. There is a global current need to develop reliable wireless digital communications for the underwater environment, with sufficient performance and efficiency to substitute for costly wired systems. One possible goal is a wireless system implementation that insures underwater terminal mobility. There is also a vital need to improve the performance of the existing systems in terms of data-rate, noise immunity, operational range, and power consumption, since, in practice, portable high-speed, long range, compact, low-power systems are desired. We concede the difficulties associated with acoustic systems and concentrate on the development of robust data transmission methods anticipating the eventual need for real time or near real time video transmission. An overview of the various detection techniques and the general statistical digital communication problem is given based on a statistical decision theory framework. The theoretical formulation of the underwater acoustic data communications problem includes modeling of the stochastic channel to incorporate a variety of impairments and environmental uncertainties, and proposal of new compensation strategies for an efficient and robust receiver design.

  18. Throughput Analysis on 3-Dimensional Underwater Acoustic Network with One-Hop Mobile Relay

    Science.gov (United States)

    Zhong, Xuefeng; Fan, Jiasheng; Guan, Quansheng; Ji, Fei; Yu, Hua

    2018-01-01

    Underwater acoustic communication network (UACN) has been considered as an essential infrastructure for ocean exploitation. Performance analysis of UACN is important in underwater acoustic network deployment and management. In this paper, we analyze the network throughput of three-dimensional randomly deployed transmitter–receiver pairs. Due to the long delay of acoustic channels, complicated networking protocols with heavy signaling overhead may not be appropriate. In this paper, we consider only one-hop or two-hop transmission, to save the signaling cost. That is, we assume the transmitter sends the data packet to the receiver by one-hop direct transmission, or by two-hop transmission via mobile relays. We derive the closed-form formulation of packet delivery rate with respect to the transmission delay and the number of transmitter–receiver pairs. The correctness of the derivation results are verified by computer simulations. Our analysis indicates how to obtain a precise tradeoff between the delay constraint and the network capacity. PMID:29337911

  19. Throughput Analysis on 3-Dimensional Underwater Acoustic Network with One-Hop Mobile Relay.

    Science.gov (United States)

    Zhong, Xuefeng; Chen, Fangjiong; Fan, Jiasheng; Guan, Quansheng; Ji, Fei; Yu, Hua

    2018-01-16

    Underwater acoustic communication network (UACN) has been considered as an essential infrastructure for ocean exploitation. Performance analysis of UACN is important in underwater acoustic network deployment and management. In this paper, we analyze the network throughput of three-dimensional randomly deployed transmitter-receiver pairs. Due to the long delay of acoustic channels, complicated networking protocols with heavy signaling overhead may not be appropriate. In this paper, we consider only one-hop or two-hop transmission, to save the signaling cost. That is, we assume the transmitter sends the data packet to the receiver by one-hop direct transmission, or by two-hop transmission via mobile relays. We derive the closed-form formulation of packet delivery rate with respect to the transmission delay and the number of transmitter-receiver pairs. The correctness of the derivation results are verified by computer simulations. Our analysis indicates how to obtain a precise tradeoff between the delay constraint and the network capacity.

  20. Investigation on the Effect of Underwater Acoustic Pressure on the Fundamental Mode of Hollow-Core Photonic Bandgap Fibers

    Directory of Open Access Journals (Sweden)

    Adel Abdallah

    2015-01-01

    Full Text Available Recently, microstructured optical fibers have become the subject of extensive research as they can be employed in many civilian and military applications. One of the recent areas of research is to enhance the normalized responsivity (NR to acoustic pressure of the optical fiber hydrophones by replacing the conventional single mode fibers (SMFs with hollow-core photonic bandgap fibers (HC-PBFs. However, this needs further investigation. In order to fully understand the feasibility of using HC-PBFs as acoustic pressure sensors and in underwater communication systems, it is important to study their modal properties in this environment. In this paper, the finite element solver (FES COMSOL Multiphysics is used to study the effect of underwater acoustic pressure on the effective refractive index neff of the fundamental mode and discuss its contribution to NR. Besides, we investigate, for the first time to our knowledge, the effect of underwater acoustic pressure on the effective area Aeff and the numerical aperture (NA of the HC-PBF.

  1. The influence of environmental parameters on the optimal frequency in a shallow underwater acoustic channel

    Science.gov (United States)

    Zarnescu, George

    2015-02-01

    In a shallow underwater acoustic channel the delayed replicas of a transmitted signal are mainly due to the interactions with the sea surface and the bottom layer. If a specific underwater region on the globe is considered, for which the sedimentary layer structure is constant across the transmission distance, then the variability of the amplitude-delay profile is determined by daily and seasonal changes of the sound speed profile (SSP) and by weather changes, such as variations of the wind speed. Such a parameter will influence the attenuation at the surface, the noise level and the profile of the sea surface. The temporal variation of the impulse response in a shallow underwater acoustic channel determines the variability of the optimal transmission frequency. If the ways in which the optimal frequency changes can be predicted, then an adaptive analog transceiver can be easily designed for an underwater acoustic modem or it can be found when a communication link has high throughput. In this article it will be highlighted the way in which the amplitude-delay profile is affected by the sound speed profile, wind speed and channel depth and also will be emphasized the changes of the optimal transmission frequency in a configuration, where the transmitter and receiver are placed on the seafloor and the bathymetry profile will be considered flat, having a given composition.

  2. Model-based processing for underwater acoustic arrays

    CERN Document Server

    Sullivan, Edmund J

    2015-01-01

    This monograph presents a unified approach to model-based processing for underwater acoustic arrays. The use of physical models in passive array processing is not a new idea, but it has been used on a case-by-case basis, and as such, lacks any unifying structure. This work views all such processing methods as estimation procedures, which then can be unified by treating them all as a form of joint estimation based on a Kalman-type recursive processor, which can be recursive either in space or time, depending on the application. This is done for three reasons. First, the Kalman filter provides a natural framework for the inclusion of physical models in a processing scheme. Second, it allows poorly known model parameters to be jointly estimated along with the quantities of interest. This is important, since in certain areas of array processing already in use, such as those based on matched-field processing, the so-called mismatch problem either degrades performance or, indeed, prevents any solution at all. Third...

  3. Deep Learning Methods for Underwater Target Feature Extraction and Recognition

    Directory of Open Access Journals (Sweden)

    Gang Hu

    2018-01-01

    Full Text Available The classification and recognition technology of underwater acoustic signal were always an important research content in the field of underwater acoustic signal processing. Currently, wavelet transform, Hilbert-Huang transform, and Mel frequency cepstral coefficients are used as a method of underwater acoustic signal feature extraction. In this paper, a method for feature extraction and identification of underwater noise data based on CNN and ELM is proposed. An automatic feature extraction method of underwater acoustic signals is proposed using depth convolution network. An underwater target recognition classifier is based on extreme learning machine. Although convolution neural networks can execute both feature extraction and classification, their function mainly relies on a full connection layer, which is trained by gradient descent-based; the generalization ability is limited and suboptimal, so an extreme learning machine (ELM was used in classification stage. Firstly, CNN learns deep and robust features, followed by the removing of the fully connected layers. Then ELM fed with the CNN features is used as the classifier to conduct an excellent classification. Experiments on the actual data set of civil ships obtained 93.04% recognition rate; compared to the traditional Mel frequency cepstral coefficients and Hilbert-Huang feature, recognition rate greatly improved.

  4. An Underwater Acoustic Vector Sensor with High Sensitivity and Broad Band

    Directory of Open Access Journals (Sweden)

    Hu Zhang

    2014-05-01

    Full Text Available Recently, acoustic vector sensor that use accelerators as sensing elements are widely used in underwater acoustic engineering, but the sensitivity of which at low frequency band is usually lower than -220 dB. In this paper, using a piezoelectric trilaminar optimized low frequency sensing element, we designed a high sensitivity internal placed ICP piezoelectric accelerometer as sensing element. Through structure optimization, we made a high sensitivity, broadband, small scale vector sensor. The working band is 10-2000 Hz, sound pressure sensitivity is -185 dB (at 100 Hz, outer diameter is 42 mm, length is 80 mm.

  5. Underwater Acoustic Matched Field Imaging Based on Compressed Sensing

    Directory of Open Access Journals (Sweden)

    Huichen Yan

    2015-10-01

    Full Text Available Matched field processing (MFP is an effective method for underwater target imaging and localizing, but its performance is not guaranteed due to the nonuniqueness and instability problems caused by the underdetermined essence of MFP. By exploiting the sparsity of the targets in an imaging area, this paper proposes a compressive sensing MFP (CS-MFP model from wave propagation theory by using randomly deployed sensors. In addition, the model’s recovery performance is investigated by exploring the lower bounds of the coherence parameter of the CS dictionary. Furthermore, this paper analyzes the robustness of CS-MFP with respect to the displacement of the sensors. Subsequently, a coherence-excluding coherence optimized orthogonal matching pursuit (CCOOMP algorithm is proposed to overcome the high coherent dictionary problem in special cases. Finally, some numerical experiments are provided to demonstrate the effectiveness of the proposed CS-MFP method.

  6. Latency-Optimized and Energy-Efficient MAC Protocol for Underwater Acoustic Sensor Networks: A Cross-Layer Approach

    Directory of Open Access Journals (Sweden)

    Cheng Xiuzhen

    2010-01-01

    Full Text Available Considering the energy constraint for fixed sensor nodes and the unacceptable long propagation delay, especially for latency sensitive applications of underwater acoustic sensor networks, we propose a MAC protocol that is latency-optimized and energy-efficient scheme and combines the physical layer and the MAC layer to shorten transmission delay. On physical layer, we apply convolution coding and interleaver for transmitted information. Moreover, dynamic code rate is exploited at the receiver side to accelerate data reception rate. On MAC layer, unfixed frame length scheme is applied to reduce transmission delay, and to ensure the data successful transmission rate at the same time. Furthermore, we propose a network topology: an underwater acoustic sensor network with mobile agent. Through fully utilizing the supper capabilities on computation and mobility of autonomous underwater vehicles, the energy consumption for fixed sensor nodes can be extremely reduced, so that the lifetime of networks is extended.

  7. Wireless Underwater Monitoring Systems Based on Energy Harvestings

    Directory of Open Access Journals (Sweden)

    Sea-Hee HWANGBO

    2013-01-01

    Full Text Available One of the important research fields for aquatic exploitation and conservation is underwater wireless sensor network. Since limited energy source for underwater nodes and devices is a main open problem, in this paper, we propose wireless underwater monitoring systems powered by energy harvester which resolves the energy constraint. The target system generates renewable energy from energy harvester and shares the energy with underwater sensor nodes. For the realization of the system, key components to be investigated are discriminated as follows: acoustic modem, actuator, smart battery charge controller, energy harvester and wireless power transfer module. By developing acoustic modem, actuator and smart battery charge controller and utilizing off-the-shelf energy harvester and wireless power transfer module, we design and implement a prototype of the system. Also, we verify the feasibility of concept of target system by conducting indoor and outdoor experiments.

  8. Secure Cooperation of Autonomous Mobile Sensors Using an Underwater Acoustic Network

    Directory of Open Access Journals (Sweden)

    Gianluca Dini

    2012-02-01

    Full Text Available Methodologies and algorithms are presented for the secure cooperation of a team of autonomous mobile underwater sensors, connected through an acoustic communication network, within surveillance and patrolling applications. In particular, the work proposes a cooperative algorithm in which the mobile underwater sensors (installed on Autonomous Underwater Vehicles—AUVs respond to simple local rules based on the available information to perform the mission and maintain the communication link with the network (behavioral approach. The algorithm is intrinsically robust: with loss of communication among the vehicles the coverage performance (i.e., the mission goal is degraded but not lost. The ensuing form of graceful degradation provides also a reactive measure against Denial of Service. The cooperative algorithm relies on the fact that the available information from the other sensors, though not necessarily complete, is trustworthy. To ensure trustworthiness, a security suite has been designed, specifically oriented to the underwater scenario, and in particular with the goal of reducing the communication overhead introduced by security in terms of number and size of messages. The paper gives implementation details on the integration between the security suite and the cooperative algorithm and provides statistics on the performance of the system as collected during the UAN project sea trial held in Trondheim, Norway, in May 2011.

  9. A hybrid path-oriented code assignment CDMA-based MAC protocol for underwater acoustic sensor networks.

    Science.gov (United States)

    Chen, Huifang; Fan, Guangyu; Xie, Lei; Cui, Jun-Hong

    2013-11-04

    Due to the characteristics of underwater acoustic channel, media access control (MAC) protocols designed for underwater acoustic sensor networks (UWASNs) are quite different from those for terrestrial wireless sensor networks. Moreover, in a sink-oriented network with event information generation in a sensor field and message forwarding to the sink hop-by-hop, the sensors near the sink have to transmit more packets than those far from the sink, and then a funneling effect occurs, which leads to packet congestion, collisions and losses, especially in UWASNs with long propagation delays. An improved CDMA-based MAC protocol, named path-oriented code assignment (POCA) CDMA MAC (POCA-CDMA-MAC), is proposed for UWASNs in this paper. In the proposed MAC protocol, both the round-robin method and CDMA technology are adopted to make the sink receive packets from multiple paths simultaneously. Since the number of paths for information gathering is much less than that of nodes, the length of the spreading code used in the POCA-CDMA-MAC protocol is shorter greatly than that used in the CDMA-based protocols with transmitter-oriented code assignment (TOCA) or receiver-oriented code assignment (ROCA). Simulation results show that the proposed POCA-CDMA-MAC protocol achieves a higher network throughput and a lower end-to-end delay compared to other CDMA-based MAC protocols.

  10. A Hybrid Path-Oriented Code Assignment CDMA-Based MAC Protocol for Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Huifang Chen

    2013-11-01

    Full Text Available Due to the characteristics of underwater acoustic channel, media access control (MAC protocols designed for underwater acoustic sensor networks (UWASNs are quite different from those for terrestrial wireless sensor networks. Moreover, in a sink-oriented network with event information generation in a sensor field and message forwarding to the sink hop-by-hop, the sensors near the sink have to transmit more packets than those far from the sink, and then a funneling effect occurs, which leads to packet congestion, collisions and losses, especially in UWASNs with long propagation delays. An improved CDMA-based MAC protocol, named path-oriented code assignment (POCA CDMA MAC (POCA-CDMA-MAC, is proposed for UWASNs in this paper. In the proposed MAC protocol, both the round-robin method and CDMA technology are adopted to make the sink receive packets from multiple paths simultaneously. Since the number of paths for information gathering is much less than that of nodes, the length of the spreading code used in the POCA-CDMA-MAC protocol is shorter greatly than that used in the CDMA-based protocols with transmitter-oriented code assignment (TOCA or receiver-oriented code assignment (ROCA. Simulation results show that the proposed POCA-CDMA-MAC protocol achieves a higher network throughput and a lower end-to-end delay compared to other CDMA-based MAC protocols.

  11. Underwater Acoustic Tracer System

    Science.gov (United States)

    2009-03-13

    for controlling and utilizing supercavitating projectile dynamics to produce a distinctive radiated noise signal. (2) Description of the Prior Art...metallic objects which travel relatively closely to a magnetic pickup. For larger, high speed, underwater projectiles, supercavitating underwater vehicles...have been proposed for use. The conditions for supercavitation are known in the art. Supercavitation allows for higher speeds to be sustainable

  12. A Novel Fractional Fourier Transform-Based ASK-OFDM System for Underwater Acoustic Communications

    Directory of Open Access Journals (Sweden)

    Rami Ashri

    2017-12-01

    Full Text Available A key research area in wireless transmission is underwater communications. It has a vital role in applications such as underwater sensor networks (UWSNs and disaster detection. The underwater channel is very unique as compared to other alternatives of transmission channels. It is characterized by path loss, multipath fading, Doppler spread and ambient noise. Thus, the bit error rate (BER is increased to a large extent when compared to its counterpart of cellular communications. Acoustic signals are the current best solution for underwater communications. The use of electromagnetic or optical waves obviously entails a much higher data rate. However, they suffer from high attenuation, absorption or scattering. This paper proposes a novel fractional fast Fourier transform (FrFT—orthogonal frequency division multiplexing (FrFT-OFDM system for underwater acoustic (UWA communication—which employs the amplitude shift keying (ASK modulation technique (FrFT-ASK-OFDM. Specifically, ASK achieves a better bandwidth efficiency as compared to other commonly used modulation techniques, such as quadrature amplitude modulation (QAM and phase shift keying (PSK. In particular, the system proposed in this article can achieve a very promising BER performance, and can reach higher data rates when compared to other systems proposed in the literature. The BER performance of the proposed system is evaluated numerically, and is compared to the corresponding M-ary QAM system in the UWA channel for the same channel conditions. Moreover, the performance of the proposed system is compared to the conventional fast Fourier transform (FFT-OFDM (FFT-OFDM system in the absence and presence of the effect of carrier frequency offset (CFO. Numerical results show that the proposed system outperforms the conventional FFT-based systems for UWA channels, even in channels dominated by CFO. Moreover, the spectral efficiency and data rate of the proposed system are approximately double

  13. The influence of acoustic emissions for underwater data transmission on the behaviour of harbour porpoises (Phocoena phocoena) in a floating pen

    NARCIS (Netherlands)

    Kastelein, R.A.; Verboom, W.C.; Muijsers, M.; Jennings, N.V.; Heul, S. van der

    2005-01-01

    To prevent grounding of ships and collisions between ships in shallow coastal waters, an underwater data collection and communication network is currently under development: Acoustic Communication network for Monitoring of underwater Environment in coastal areas (ACME). Marine mammals might be

  14. Statistical Modeling of Large-Scale Signal Path Loss in Underwater Acoustic Networks

    Directory of Open Access Journals (Sweden)

    Manuel Perez Malumbres

    2013-02-01

    Full Text Available In an underwater acoustic channel, the propagation conditions are known to vary in time, causing the deviation of the received signal strength from the nominal value predicted by a deterministic propagation model. To facilitate a large-scale system design in such conditions (e.g., power allocation, we have developed a statistical propagation model in which the transmission loss is treated as a random variable. By applying repetitive computation to the acoustic field, using ray tracing for a set of varying environmental conditions (surface height, wave activity, small node displacements around nominal locations, etc., an ensemble of transmission losses is compiled and later used to infer the statistical model parameters. A reasonable agreement is found with log-normal distribution, whose mean obeys a log-distance increases, and whose variance appears to be constant for a certain range of inter-node distances in a given deployment location. The statistical model is deemed useful for higher-level system planning, where simulation is needed to assess the performance of candidate network protocols under various resource allocation policies, i.e., to determine the transmit power and bandwidth allocation necessary to achieve a desired level of performance (connectivity, throughput, reliability, etc..

  15. Design and Experimental Validation of a USBL Underwater Acoustic Positioning System

    Directory of Open Access Journals (Sweden)

    Joel Reis

    2016-09-01

    Full Text Available This paper presents the steps for developing a low-cost POrtableNavigation Tool for Underwater Scenarios (PONTUS to be used as a localization device for subsea targets. PONTUS consists of an integrated ultra-short baseline acoustic positioning system aided by an inertial navigation system. Built on a practical design, it can be mounted on an underwater robotic vehicle or be operated by a scuba diver. It also features a graphical user interface that provides information on the tracking of the designated target, in addition to some details on the physical properties inside PONTUS. A full disclosure of the architecture of the tool is first presented, followed by thorough technical descriptions of the hardware components ensemble and the software development process. A series of experiments was carried out to validate the developed prototype, and the results are presented herein, which allow assessing its overall performance.

  16. Design and Experimental Validation of a USBL Underwater Acoustic Positioning System.

    Science.gov (United States)

    Reis, Joel; Morgado, Marco; Batista, Pedro; Oliveira, Paulo; Silvestre, Carlos

    2016-09-14

    This paper presents the steps for developing a low-cost POrtableNavigation Tool for Underwater Scenarios (PONTUS) to be used as a localization device for subsea targets. PONTUS consists of an integrated ultra-short baseline acoustic positioning system aided by an inertial navigation system. Built on a practical design, it can be mounted on an underwater robotic vehicle or be operated by a scuba diver. It also features a graphical user interface that provides information on the tracking of the designated target, in addition to some details on the physical properties inside PONTUS. A full disclosure of the architecture of the tool is first presented, followed by thorough technical descriptions of the hardware components ensemble and the software development process. A series of experiments was carried out to validate the developed prototype, and the results are presented herein, which allow assessing its overall performance.

  17. Multiuser underwater acoustic communication using single-element virtual time reversal mirror

    Institute of Scientific and Technical Information of China (English)

    YIN JingWei; WANG YiLin; WANG Lei; HUI JunYing

    2009-01-01

    Pattern time delay shift coding (PDS) scheme is introduced and combined with spread spectrum tech-nique called SS-PDS for short which is power-saving and competent for long-range underwater acous-tic networks.Single-element virtual time reversal mirror (VTRM) is presented in this paper and validated by the lake trial results.Employing single-element VTRM in multiuser communication system based on SS-PDS can separate different users' information simultaneously at master node as indicated in the simulation results.

  18. A GPS-free passive acoustic localization scheme for underwater wireless sensor networks

    KAUST Repository

    Mirza, Mohammed

    2011-10-01

    Seaweb is an acoustic communication technology that enables communication between sensor nodes. Seaweb interconnects the underwater nodes through digital signal processing (DSP)-based modem by using acoustic links between the neighbouring sensors. In this paper, we design and investigate a global positioning system (GPS)-free passive localization protocol using seaweb technology. This protocol uses the range data and planar trigonometry to estimate the positions of the discovered nodes. We take into consideration the small displacement of sensor nodes due to watch circles and placement of sensor nodes on non-uniform underwater surface, for precise localization. Once the nodes are localized, we divide the whole network .eld into circular levels that minimizes the traf.c complexity and thereby increases the lifetime of the sensor network .eld. We then form the mesh network inside each of the circular levels that increases the reliability. The algorithm is designed in such a way that it overcomes the ambiguous nodes errata and re.ected paths and makes the algorithm more robust. The synthetic network geometries are so designed which can evaluate the algorithm in the presence of perfect or imperfect ranges or in case of incomplete data. A comparative study is made with the existing algorithms which proves our newly proposed algorithm to be more effective. © 2011 IEEE.

  19. Separating underwater ambient noise from flow noise recorded on stereo acoustic tags attached to marine mammals

    NARCIS (Netherlands)

    Benda-Beckmann, A.M. von; Wensveen, P.J.; Samarra, F.I.P.; Beerens, S.P.; Miller, P.J.O.

    2016-01-01

    Sound-recording acoustic tags attached to marine animals are commonly used in behavioural studies. Measuring ambient noise is of interest to efforts to understand responses of marine mammals to anthropogenic underwater sound, or to assess their communication space. Noise of water flowing around the

  20. Acoustical Imaging

    CERN Document Server

    Litniewski, Jerzy; Kujawska, Tamara; 31st International Symposium on Acoustical Imaging

    2012-01-01

    The International Symposium on Acoustical Imaging is a unique forum for advanced research, covering new technologies, developments, methods and theories in all areas of acoustics. This interdisciplinary Symposium has been taking place continuously since 1968. In the course of the years the proceedings volumes in the Acoustical Imaging Series have become a reference for cutting-edge research in the field. In 2011 the 31st International Symposium on Acoustical Imaging was held in Warsaw, Poland, April 10-13. Offering both a broad perspective on the state-of-the-art as well as  in-depth research contributions by the specialists in the field, this Volume 31 in the Series contains an excellent collection of papers in six major categories: Biological and Medical Imaging Physics and Mathematics of Acoustical Imaging Acoustic Microscopy Transducers and Arrays Nondestructive Evaluation and Industrial Applications Underwater Imaging

  1. Underwater electric field detection system based on weakly electric fish

    Science.gov (United States)

    Xue, Wei; Wang, Tianyu; Wang, Qi

    2018-04-01

    Weakly electric fish sense their surroundings in complete darkness by their active electric field detection system. However, due to the insufficient detection capacity of the electric field, the detection distance is not enough, and the detection accuracy is not high. In this paper, a method of underwater detection based on rotating current field theory is proposed to improve the performance of underwater electric field detection system. First of all, we built underwater detection system based on the theory of the spin current field mathematical model with the help of the results of previous researchers. Then we completed the principle prototype and finished the metal objects in the water environment detection experiments, laid the foundation for the further experiments.

  2. Warfare Ecology on an Underwater Demolition Range: Acoustic Observations of Marine Life and Shallow Water Detonations in Hawai`i

    Science.gov (United States)

    Shannon, Lee H.

    Most studies investigating the effects of military-associated anthropogenic noise concentrate on deep sea or open ocean propagation of sonar and its effect on marine mammals. In littoral waters, U.S. military special operations units regularly conduct shallow water explosives training, yet relatively little attention has been given to the potential impact on nearshore marine ecosystems from these underwater detonations. This dissertation research focused on the Pu'uloa Underwater Detonation Range off the coast of O`ahu, and examined multiple aspects of the surrounding marine ecosystem and the effects of detonations using acoustic monitoring techniques. The soundscape of a nearshore reef ecosystem adjacent to the UNDET range was characterized through analysis of passive acoustic recordings collected over the span of 6 years. Snapping shrimp were the predominant source of noise, and a diel pattern was present, with increased sound energy during the night hours. Results revealed a difference of up to 7dB between two Ecological Acoustic Recorder locations 2.5km apart along the 60ft isobath. Passive acoustic recording files were searched visually and aurally for odontocete whistles. Whistles were detected in only 0.6% of files analyzed, indicating this area is not frequently transited by coastal odontocete emitting social sounds. The study also opportunistically captured a humpback whale singing during a detonation event, during which the animal showed no obvious alteration of its singing behavior. Four separate underwater detonation events were recorded using a surface deployed F-42C transducer, and the resulting analysis showed no measurable drop in the biologically produced acoustic energy in reaction to the explosive events. Coral reef fishes were recorded visually and acoustically during detonation events at a known distance and bearing from a known explosive sound source. Individual fish behavioral responses to the explosion varied, and a sharp uptick in fish

  3. A Review of the Emerging Field of Underwater Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Emily Chua

    2016-11-01

    Full Text Available Mass spectrometers are versatile sensor systems, owing to their high sensitivity and ability to simultaneously measure multiple chemical species. Over the last two decades, traditional laboratory-based membrane inlet mass spectrometers have been adapted for underwater use. Underwater mass spectrometry has drastically improved our capability to monitor a broad suite of gaseous compounds (e.g., dissolved atmospheric gases, light hydrocarbons, and volatile organic compounds in the aquatic environment. Here we provide an overview of the progress made in the field of underwater mass spectrometry since its inception in the 1990s to the present. In particular, we discuss the approaches undertaken by various research groups in developing in situ mass spectrometers. We also provide examples to illustrate how underwater mass spectrometers have been used in the field. Finally, we present future trends in the field of in situ mass spectrometry. Most of these efforts are aimed at improving the quality and spatial and temporal scales of chemical measurements in the ocean. By providing up-to-date information on underwater mass spectrometry, this review offers guidance for researchers interested in adapting this technology as well as goals for future progress in the field.

  4. Select Internet Resources on Acoustics

    Directory of Open Access Journals (Sweden)

    Angela R. Davis

    2016-12-01

    Full Text Available Merriam-Webster (2016 defines acoustics as, “a science that deals with the production, control, transmission, reception, and effects of sounds.” According to Rossing (2014, the study of acoustics began in ancient Greece with Pythagoras’ study of vibrating strings on musical instruments. Since those early beginnings, famous scientists including Rayleigh, Alexander Graham Bell, and Thomas Edison, have helped expand the field of acoustics to include architectural, physical, engineering, structural, underwater, physiological and psychological, musical acoustics, and speech. Acoustics is a highly interdisciplinary field and researchers may need resources from physics, medicine, and engineering to understand all aspects of their research.

  5. An Ultra-Lightweight Encryption Scheme in Underwater Acoustic Networks

    Directory of Open Access Journals (Sweden)

    Chunyan Peng

    2016-01-01

    Full Text Available We tackle a fundamental security problem in underwater acoustic networks (UANs. The S-box in the existing block encryption algorithm is more energy consuming and unsuitable for resources-constrained UANs. In this paper, instead of S-box, we present a lightweight, 8-round iteration block cipher algorithm for UANs communication based on chaotic theory and increase the key space by changing the number of iteration round. We further propose secure network architecture of UANs. By analysis, our algorithm can resist brute-force searches and adversarial attacks. Simulation results show that, compared with traditional AES-128 and PRESENT algorithms, our cryptographic algorithm can make a good trade-off between security and overhead, has better energy efficiency, and applies to UANs.

  6. Energy-Efficient Channel Coding Strategy for Underwater Acoustic Networks

    Directory of Open Access Journals (Sweden)

    Grasielli Barreto

    2017-03-01

    Full Text Available Underwater acoustic networks (UAN allow for efficiently exploiting and monitoring the sub-aquatic environment. These networks are characterized by long propagation delays, error-prone channels and half-duplex communication. In this paper, we address the problem of energy-efficient communication through the use of optimized channel coding parameters. We consider a two-layer encoding scheme employing forward error correction (FEC codes and fountain codes (FC for UAN scenarios without feedback channels. We model and evaluate the energy consumption of different channel coding schemes for a K-distributed multipath channel. The parameters of the FEC encoding layer are optimized by selecting the optimal error correction capability and the code block size. The results show the best parameter choice as a function of the link distance and received signal-to-noise ratio.

  7. An acoustically controlled tetherless underwater vehicle for installation and maintenance of neutrino detectors in the deep ocean

    International Nuclear Information System (INIS)

    Ballou, Philip J.

    1997-01-01

    The task of installing and servicing high energy neutrino detectors in the deep ocean from a surface support vessel is problematic using conventional tethered systems. An array of multiple detector strings rising 500 m from the ocean floor, and forming a grid with 50 m spacing between the strings, presents a substantial entanglement hazard for equipment cables deployed from the surface. Such tasks may be accomplished with fewer risks using a tetherless underwater remotely operated vehicle that has a local acoustic telemetry link to send control commands and sensor data between the vehicle and a stationary hydrophone suspended above or just outside the perimeter of the work site. The Phase I effort involves the development of an underwater acoustic telemetry link for vehicle control and sensor feedback, the evaluation of video compression methods for real-time acoustic transmission of video through the water, and the defining of local control routines on board the vehicle to allow it to perform certain basic maneuvering tasks autonomously, or to initiate a self-rescue if the acoustic control link should be lost. In Phase II, a prototype tetherless vehicle system will be designed and constructed to demonstrate the ability to install cable interconnections within a detector array at 4 km depth. The same control technology could be used with a larger more powerful vehicle to maneuver the detector strings into desired positions as they are being lowered to the ocean floor

  8. Reciprocity relationships in vector acoustics and their application to vector field calculations.

    Science.gov (United States)

    Deal, Thomas J; Smith, Kevin B

    2017-08-01

    The reciprocity equation commonly stated in underwater acoustics relates pressure fields and monopole sources. It is often used to predict the pressure measured by a hydrophone for multiple source locations by placing a source at the hydrophone location and calculating the field everywhere for that source. A similar equation that governs the orthogonal components of the particle velocity field is needed to enable this computational method to be used for acoustic vector sensors. This paper derives a general reciprocity equation that accounts for both monopole and dipole sources. This vector-scalar reciprocity equation can be used to calculate individual components of the received vector field by altering the source type used in the propagation calculation. This enables a propagation model to calculate the received vector field components for an arbitrary number of source locations with a single model run for each vector field component instead of requiring one model run for each source location. Application of the vector-scalar reciprocity principle is demonstrated with analytic solutions for a range-independent environment and with numerical solutions for a range-dependent environment using a parabolic equation model.

  9. Near-field/far-field array manifold of an acoustic vector-sensor near a reflecting boundary.

    Science.gov (United States)

    Wu, Yue Ivan; Lau, Siu-Kit; Wong, Kainam Thomas

    2016-06-01

    The acoustic vector-sensor (a.k.a. the vector hydrophone) is a practical and versatile sound-measurement device, with applications in-room, open-air, or underwater. It consists of three identical uni-axial velocity-sensors in orthogonal orientations, plus a pressure-sensor-all in spatial collocation. Its far-field array manifold [Nehorai and Paldi (1994). IEEE Trans. Signal Process. 42, 2481-2491; Hawkes and Nehorai (2000). IEEE Trans. Signal Process. 48, 2981-2993] has been introduced into the technical field of signal processing about 2 decades ago, and many direction-finding algorithms have since been developed for this acoustic vector-sensor. The above array manifold is subsequently generalized for outside the far field in Wu, Wong, and Lau [(2010). IEEE Trans. Signal Process. 58, 3946-3951], but only if no reflection-boundary is to lie near the acoustic vector-sensor. As for the near-boundary array manifold for the general case of an emitter in the geometric near field, the far field, or anywhere in between-this paper derives and presents that array manifold in terms of signal-processing mathematics. Also derived here is the corresponding Cramér-Rao bound for azimuth-elevation-distance localization of an incident emitter, with the reflected wave shown to play a critical role on account of its constructive or destructive summation with the line-of-sight wave. The implications on source localization are explored, especially with respect to measurement model mismatch in maximum-likelihood direction finding and with regard to the spatial resolution between coexisting emitters.

  10. Comparing autonomous underwater vehicle (AUV) and vessel-based tracking performance for locating acoustically tagged fish

    OpenAIRE

    Eiler, John H.; Grothues, Thomas M.; Dobarro, Joseph A.; Masuda, Michele M.

    2013-01-01

    Autonomous underwater vehicles (AUV’s) are increasingly used to collect physical, chemical, and biological information in the marine environment. Recent efforts include merging AUV technology with acoustic telemetry to provide information on the distribution and movements of marine fish. We compared surface vessel and AUV tracking capabilities under rigorous conditions in coastal waters near Juneau, Alaska. Tracking surveys were conducted with a REMUS 100 AUV equipped with an integrated acous...

  11. A Support Vector Learning-Based Particle Filter Scheme for Target Localization in Communication-Constrained Underwater Acoustic Sensor Networks.

    Science.gov (United States)

    Li, Xinbin; Zhang, Chenglin; Yan, Lei; Han, Song; Guan, Xinping

    2017-12-21

    Target localization, which aims to estimate the location of an unknown target, is one of the key issues in applications of underwater acoustic sensor networks (UASNs). However, the constrained property of an underwater environment, such as restricted communication capacity of sensor nodes and sensing noises, makes target localization a challenging problem. This paper relies on fractional sensor nodes to formulate a support vector learning-based particle filter algorithm for the localization problem in communication-constrained underwater acoustic sensor networks. A node-selection strategy is exploited to pick fractional sensor nodes with short-distance pattern to participate in the sensing process at each time frame. Subsequently, we propose a least-square support vector regression (LSSVR)-based observation function, through which an iterative regression strategy is used to deal with the distorted data caused by sensing noises, to improve the observation accuracy. At the same time, we integrate the observation to formulate the likelihood function, which effectively update the weights of particles. Thus, the particle effectiveness is enhanced to avoid "particle degeneracy" problem and improve localization accuracy. In order to validate the performance of the proposed localization algorithm, two different noise scenarios are investigated. The simulation results show that the proposed localization algorithm can efficiently improve the localization accuracy. In addition, the node-selection strategy can effectively select the subset of sensor nodes to improve the communication efficiency of the sensor network.

  12. Underwater Gliders by Dr. Kevin Smith [video

    OpenAIRE

    Naval Postgraduate School Physics

    2015-01-01

    NPS Physics NPS Physics Research Projects Underwater glider research is currently underway in the physics department at the naval postgraduate in Monterey Ca. Dr. Kevin Smith is a specialist in underwater acoustics and sonar systems. He and his team are currently focused on autonomous underwater gliders and developing systems capable of detecting parameters in the ocean and listening for various sources of sound.

  13. Low complexity adaptive equalizers for underwater acoustic communications

    Science.gov (United States)

    Soflaei, Masoumeh; Azmi, Paeiz

    2014-08-01

    Interference signals due to scattering from surface and reflecting from bottom is one of the most important problems of reliable communications in shallow water channels. To solve this problem, one of the best suggested ways is to use adaptive equalizers. Convergence rate and misadjustment error in adaptive algorithms play important roles in adaptive equalizer performance. In this paper, affine projection algorithm (APA), selective regressor APA(SR-APA), family of selective partial update (SPU) algorithms, family of set-membership (SM) algorithms and selective partial update selective regressor APA (SPU-SR-APA) are compared with conventional algorithms such as the least mean square (LMS) in underwater acoustic communications. We apply experimental data from the Strait of Hormuz for demonstrating the efficiency of the proposed methods over shallow water channel. We observe that the values of the steady-state mean square error (MSE) of SR-APA, SPU-APA, SPU-normalized least mean square (SPU-NLMS), SPU-SR-APA, SM-APA and SM-NLMS algorithms decrease in comparison with the LMS algorithm. Also these algorithms have better convergence rates than LMS type algorithm.

  14. Acoustic field modulation in regenerators

    Science.gov (United States)

    Hu, J. Y.; Wang, W.; Luo, E. C.; Chen, Y. Y.

    2016-12-01

    The regenerator is a key component that transfers energy between heat and work. The conversion efficiency is significantly influenced by the acoustic field in the regenerator. Much effort has been spent to quantitatively determine this influence, but few comprehensive experimental verifications have been performed because of difficulties in modulating and measuring the acoustic field. In this paper, a method requiring two compressors is introduced and theoretically investigated that achieves acoustic field modulation in the regenerator. One compressor outputs the acoustic power for the regenerator; the other acts as a phase shifter. A RC load dissipates the acoustic power out of both the regenerator and the latter compressor. The acoustic field can be modulated by adjusting the current in the two compressors and opening the RC load. The acoustic field is measured with pressure sensors instead of flow-field imaging equipment, thereby greatly simplifying the experiment.

  15. Optimal Node Placement in Underwater Wireless Sensor Networks

    KAUST Repository

    Felamban, M.; Shihada, Basem; Jamshaid, K.

    2013-01-01

    Wireless Sensor Networks (WSN) are expected to play a vital role in the exploration and monitoring of underwater areas which are not easily reachable by humans. However, underwater communication via acoustic waves is subject to several performance

  16. Localization with a mobile beacon in underwater acoustic sensor networks.

    Science.gov (United States)

    Lee, Sangho; Kim, Kiseon

    2012-01-01

    Localization is one of the most important issues associated with underwater acoustic sensor networks, especially when sensor nodes are randomly deployed. Given that it is difficult to deploy beacon nodes at predetermined locations, localization schemes with a mobile beacon on the sea surface or along the planned path are inherently convenient, accurate, and energy-efficient. In this paper, we propose a new range-free Localization with a Mobile Beacon (LoMoB). The mobile beacon periodically broadcasts a beacon message containing its location. Sensor nodes are individually localized by passively receiving the beacon messages without inter-node communications. For location estimation, a set of potential locations are obtained as candidates for a node's location and then the node's location is determined through the weighted mean of all the potential locations with the weights computed based on residuals.

  17. Localization with a Mobile Beacon in Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Sangho Lee

    2012-04-01

    Full Text Available Localization is one of the most important issues associated with underwater acoustic sensor networks, especially when sensor nodes are randomly deployed. Given that it is difficult to deploy beacon nodes at predetermined locations, localization schemes with a mobile beacon on the sea surface or along the planned path are inherently convenient, accurate, and energy-efficient. In this paper, we propose a new range-free Localization with a Mobile Beacon (LoMoB. The mobile beacon periodically broadcasts a beacon message containing its location. Sensor nodes are individually localized by passively receiving the beacon messages without inter-node communications. For location estimation, a set of potential locations are obtained as candidates for a node’s location and then the node’s location is determined through the weighted mean of all the potential locations with the weights computed based on residuals.

  18. Underwater acoustic positioning system for the SMO and KM3NeT - Italia projects

    Energy Technology Data Exchange (ETDEWEB)

    Viola, S.; Barbagallo, G.; Cacopardo, G.; Calí, C.; Cocimano, R.; Coniglione, R.; Costa, M.; Cuttone, G.; D' Amato, C.; D' Amato, V.; D' Amico, A.; De Luca, V.; Del Tevere, F.; Distefano, C.; Ferrera, F.; Gmerk, A.; Grasso, R.; Imbesi, M.; Larosa, G.; Lattuada, D. [INFN - Laboratori Nazionali del Sud, via Santa Sofia 62, 95125 Catania (Italy); and others

    2014-11-18

    In the underwater neutrino telescopes, the positions of the Cherenkov light sensors and their movements must be known with an accuracy of few tens of centimetres. In this work, the activities of the SMO and KM3NeT-Italia teams for the development of an acoustic positioning system for KM3NeT-Italia project are presented. The KM3NeT-Italia project foresees the construction, within two years, of 8 towers in the view of the several km{sup 3}-scale neutrino telescope KM3NeT.

  19. Underwater acoustic positioning system for the SMO and KM3NeT - Italia projects

    International Nuclear Information System (INIS)

    Viola, S.; Barbagallo, G.; Cacopardo, G.; Calí, C.; Cocimano, R.; Coniglione, R.; Costa, M.; Cuttone, G.; D'Amato, C.; D'Amato, V.; D'Amico, A.; De Luca, V.; Del Tevere, F.; Distefano, C.; Ferrera, F.; Gmerk, A.; Grasso, R.; Imbesi, M.; Larosa, G.; Lattuada, D.

    2014-01-01

    In the underwater neutrino telescopes, the positions of the Cherenkov light sensors and their movements must be known with an accuracy of few tens of centimetres. In this work, the activities of the SMO and KM3NeT-Italia teams for the development of an acoustic positioning system for KM3NeT-Italia project are presented. The KM3NeT-Italia project foresees the construction, within two years, of 8 towers in the view of the several km 3 -scale neutrino telescope KM3NeT

  20. High-Frequency Seafloor Acoustics

    CERN Document Server

    Jackson, Darrell R

    2007-01-01

    High-Frequency Seafloor Acoustics is the first book in a new series sponsored by the Office of Naval Research on the latest research in underwater acoustics. This exciting new title provides ready access to experimental data, theory, and models relevant to high-frequency seafloor acoustics and will be of interest to sonar engineers and researchers working in underwater acoustics. The physical characteristics of the seafloor affecting acoustic propagation and scattering are covered, including physical and geoacoustic properties and surface roughness. Current theories for acoustic propagation in sediments are presented along with corresponding models for reflection, scattering, and seafloor penetration. The main text is backed up by an extensive bibliography and technical appendices.

  1. Communication and cooperation in underwater acoustic networks

    Science.gov (United States)

    Yerramalli, Srinivas

    In this thesis, we present a study of several problems related to underwater point to point communications and network formation. We explore techniques to improve the achievable data rate on a point to point link using better physical layer techniques and then study sensor cooperation which improves the throughput and reliability in an underwater network. Robust point-to-point communications in underwater networks has become increasingly critical in several military and civilian applications related to underwater communications. We present several physical layer signaling and detection techniques tailored to the underwater channel model to improve the reliability of data detection. First, a simplified underwater channel model in which the time scale distortion on each path is assumed to be the same (single scale channel model in contrast to a more general multi scale model). A novel technique, which exploits the nature of OFDM signaling and the time scale distortion, called Partial FFT Demodulation is derived. It is observed that this new technique has some unique interference suppression properties and performs better than traditional equalizers in several scenarios of interest. Next, we consider the multi scale model for the underwater channel and assume that single scale processing is performed at the receiver. We then derive optimized front end pre-processing techniques to reduce the interference caused during single scale processing of signals transmitted on a multi-scale channel. We then propose an improvised channel estimation technique using dictionary optimization methods for compressive sensing and show that significant performance gains can be obtained using this technique. In the next part of this thesis, we consider the problem of sensor node cooperation among rational nodes whose objective is to improve their individual data rates. We first consider the problem of transmitter cooperation in a multiple access channel and investigate the stability of

  2. The Control Packet Collision Avoidance Algorithm for the Underwater Multichannel MAC Protocols via Time-Frequency Masking

    Directory of Open Access Journals (Sweden)

    Yang Yu

    2016-01-01

    Full Text Available Establishing high-speed and reliable underwater acoustic networks among multiunmanned underwater vehicles (UUVs is basic to realize cooperative and intelligent control among different UUVs. Nevertheless, different from terrestrial network, the propagation speed of the underwater acoustic network is 1500 m/s, which makes the design of the underwater acoustic network MAC protocols a big challenge. In accordance with multichannel MAC protocols, data packets and control packets are transferred through different channels, which lowers the adverse effect of acoustic network and gradually becomes the popular issues of underwater acoustic networks MAC protocol research. In this paper, we proposed a control packet collision avoidance algorithm utilizing time-frequency masking to deal with the control packets collision in the control channel. This algorithm is based on the scarcity of the noncoherent underwater acoustic communication signals, which regards collision avoiding as separation of the mixtures of communication signals from different nodes. We first measure the W-Disjoint Orthogonality of the MFSK signals and the simulation result demonstrates that there exists time-frequency mask which can separate the source signals from the mixture of the communication signals. Then we present a pairwise hydrophones separation system based on deep networks and the location information of the nodes. Consequently, the time-frequency mask can be estimated.

  3. 3D Photo Mosaicing of Tagiri Shallow Vent Field by an Autonomous Underwater Vehicle

    Science.gov (United States)

    Maki, Toshihiro; Kondo, Hayato; Ura, Tamaki; Sakamaki, Takashi; Mizushima, Hayato; Yanagisawa, Masao

    Although underwater visual observation is an ideal method for detailed survey of seafloors, it is currently a costly process that requires the use of Remotely Operated Vehicles (ROVs) or Human Occupied Vehicles (HOVs), and can cover only a limited area. This paper proposes an innovative method to navigate an autonomous underwater vehicle (AUV) to create both 2D and 3D photo mosaics of seafloors with high positioning accuracy without using any vision-based matching. The vehicle finds vertical pole-like acoustic reflectors to use as positioning landmarks using a profiling sonar based on a SLAM (Simultaneous Localization And Mapping) technique. These reflectors can be either artificial or natural objects, and so the method can be applied to shallow vent fields where conventional acoustic positioning is difficult, since bubble plumes can also be used as landmarks as well as artificial reflectors. Path-planning is performed in real-time based on the positions and types of landmarks so as to navigate safely and stably using landmarks of different types (artificial reflector or bubble plume) found at arbitrary times and locations. Terrain tracker switches control reference between depth and altitude from the seafloor based on a local map of hazardous area created in real-time using onboard perceptual sensors, in order to follow rugged terrains at an altitude of 1 to 2 meters, as this range is ideal for visual observation. The method was implemented in the AUV Tri-Dog 1 and experiments were carried out at Tagiri vent field, Kagoshima Bay in Japan. The AUV succeeded in fully autonomous observation for more than 160 minutes to create a photo mosaic with an area larger than 600 square meters, which revealed the spatial distribution of detailed features such as tube-worm colonies, bubble plumes and bacteria mats. A fine bathymetry of the same area was also created using a light-section ranging system mounted on the vehicle. Finally a 3 D representation of the environment was

  4. Cymbal and BB underwater transducers and arrays

    Energy Technology Data Exchange (ETDEWEB)

    Newnham, R.E.; Zhang, J.; Alkoy, S.; Meyer, R.; Hughes, W.J.; Hladky-Hennion, A.C.; Cochran, J.; Markley, D. [Materials Research Laboratory, Penn State University, University Park, PA 16802 (United States)

    2002-09-01

    The cymbal is a miniaturized class V flextensional transducer that was developed for use as a shallow water sound projector and receiver. Single elements are characterized by high Q, low efficiency, and medium power output capability. Its low cost and thin profile allow the transducer to be assembled into large flexible arrays. Efforts were made to model both single elements and arrays using the ATILA code and the integral equation formulation (EQI).Millimeter size microprobe hydrophones (BBs) have been designed and fabricated from miniature piezoelectric hollow ceramic spheres for underwater applications such as mapping acoustic fields of projectors, and flow noise sensors for complex underwater structures. Green spheres are prepared from soft lead zirconate titanate powders using a coaxial nozzle slurry process. A compact hydrophone with a radially-poled sphere is investigated using inside and outside electrodes. Characterization of these hydrophones is done through measurement of hydrostatic piezoelectric charge coefficients, free field voltage sensitivities and directivity beam patterns. (orig.)

  5. Supersonic acoustic intensity with statistically optimized near-field acoustic holography

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Jacobsen, Finn

    2011-01-01

    The concept of supersonic acoustic intensity was introduced some years ago for estimating the fraction of the flow of energy radiated by a source that propagates to the far field. It differs from the usual (active) intensity by excluding the near-field energy resulting from evanescent waves...... to the information provided by the near-field acoustic holography technique. This study proposes a version of the supersonic acoustic intensity applied to statistically optimized near-field acoustic holography (SONAH). The theory, numerical results and an experimental study are presented. The possibility of using...

  6. Maximization of the Supportable Number of Sensors in QoS-Aware Cluster-Based Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Thi-Tham Nguyen

    2014-03-01

    Full Text Available This paper proposes a practical low-complexity MAC (medium access control scheme for quality of service (QoS-aware and cluster-based underwater acoustic sensor networks (UASN, in which the provision of differentiated QoS is required. In such a network, underwater sensors (U-sensor in a cluster are divided into several classes, each of which has a different QoS requirement. The major problem considered in this paper is the maximization of the number of nodes that a cluster can accommodate while still providing the required QoS for each class in terms of the PDR (packet delivery ratio. In order to address the problem, we first estimate the packet delivery probability (PDP and use it to formulate an optimization problem to determine the optimal value of the maximum packet retransmissions for each QoS class. The custom greedy and interior-point algorithms are used to find the optimal solutions, which are verified by extensive simulations. The simulation results show that, by solving the proposed optimization problem, the supportable number of underwater sensor nodes can be maximized while satisfying the QoS requirements for each class.

  7. Room Acoustical Fields

    CERN Document Server

    Mechel, Fridolin

    2013-01-01

    This book presents the theory of room acoustical fields and revises the Mirror Source Methods for practical computational use, emphasizing the wave character of acoustical fields.  The presented higher methods include the concepts of “Mirror Point Sources” and “Corner sources which allow for an excellent approximation of complex room geometries and even equipped rooms. In contrast to classical description, this book extends the theory of sound fields describing them by their complex sound pressure and the particle velocity. This approach enables accurate descriptions of interference and absorption phenomena.

  8. Acoustical Imaging

    CERN Document Server

    Akiyama, Iwaki

    2009-01-01

    The 29th International Symposium on Acoustical Imaging was held in Shonan Village, Kanagawa, Japan, April 15-18, 2007. This interdisciplinary Symposium has been taking place every two years since 1968 and forms a unique forum for advanced research, covering new technologies, developments, methods and theories in all areas of acoustics. In the course of the years the volumes in the Acoustical Imaging Series have developed and become well-known and appreciated reference works. Offering both a broad perspective on the state-of-the-art in the field as well as an in-depth look at its leading edge research, this Volume 29 in the Series contains again an excellent collection of seventy papers presented in nine major categories: Strain Imaging Biological and Medical Applications Acoustic Microscopy Non-Destructive Evaluation and Industrial Applications Components and Systems Geophysics and Underwater Imaging Physics and Mathematics Medical Image Analysis FDTD method and Other Numerical Simulations Audience Researcher...

  9. Scattering of Acoustic Waves from Ocean Boundaries

    Science.gov (United States)

    2015-09-30

    at the Target and Reverberation Experiment 2013 (TREX13),” in Proc. IEEE/OES Acoustics in Underwater Geosciences Symposium, Rio de Janeiro , Brazil...a Sandy Seabed at the Target and Reverberation Experiment 2013 (TREX13),” in Proc. IEEE/OES Acoustics in Underwater Geosciences Symposium, Rio de ... Janeiro , Brazil, July 2015. PRESENTATIONS Presenter: Isakson, M.J., Chotiros, N.P., Piper, J.N. and McNeese, A. “Acoustic Scattering from a Sandy Seabed

  10. Analytical research of vibration and far-field acoustic radiation of cylindrical shell immersed at finite depth

    Directory of Open Access Journals (Sweden)

    GUO Wenjie

    2017-08-01

    Full Text Available Aiming at the current lack of analytical research concerning the cylindrical shell-flow field coupling vibration and sound radiation system under the influence of a free surface, this paper proposes an analytical method which solves the vibration response and far-field acoustic radiation of a finite cylindrical shell immersed at a finite depth. Based on the image method and Graf addition theorem, the analytical expression of the fluid velocity potential can be obtained, then combined with the energy functional of the variation method to deduce the shell-liquid coupling vibration equation, which can in turn solve the forced vibration response. The research shows that, compared with an infinite fluid, a free surface can increase at the same order of resonance frequency; but as the depth of immersion gradually increases, the mean square vibration velocity tends to become the same as that in an infinite fluid. Compared with numerical results from Nastran software, this shows that the present method is accurate and reliable, and has such advantages as a simple method and a small amount of calculation. The far-field radiated pressure can be obtained by the vibration response using the Fourier transformation and stationary phase method. The results indicate that the directivity and volatility of the far-field acoustic pressure of a cylindrical shell is similar to that of an acoustical dipole due to the free surface. However, the far-field acoustic pressure is very different from the vibration characteristics, and will not tend to an infinite fluid as the submerging depth increases. Compared with the numerical method, the method in this paper is simpler and has a higher computational efficiency. It enables the far-field acoustic radiation of an underwater cylindrical shell to be predicted quickly under the influence of external incentives and the free surface, providing guiding significance for acoustic research into the half space structure vibration

  11. Atlantic Herring Acoustic Surveys

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC Advanced Sampling Technologies Research Group conducts annual fisheries acoustic surveys using state-of-the-art acoustic, midwater trawling, and underwater...

  12. Use of acoustic field in gas cleaning

    International Nuclear Information System (INIS)

    Boulaud, D.; Madelaine, G.; Malherbe, C.

    1985-01-01

    The use of acoustic field in gas cleaning can be done in two ways: the first is the conditioning of an aerosol by acoustic agglomeration before filtration by conventional methods (cyclones, granular beds, etc.), the second is the collection efficiency improvement of granular bed filters exposed to an acoustic field. In a first part, experimental results are given on the acoustic agglomeration of a polydisperse aerosol of mass concentration between 0.5 and 1 g/m 3 . An important effect of wall precipitation of particles is described and deposition velocity due to the presence of an acoustic field are measured as a function of particle diameter, sound pressure level and acoustic frequency. A dimensionless relationship between the deposition velocity and particle relaxation time is established for these results. At the end of this part energetic criteria for the use of acoustic agglomeration in a gas cleaning train is given. In a second part, experimental results are given to the influence of acoustic field on the collection efficiency of monodispersed aerosols ranging from 0.1 to 1 μm. For these both uses of acoustic field in industrial gas cleaning the different alternatives for the acoustic field generation are discussed

  13. New Methods for Estimating Water Current Velocity Fields from Autonomous Underwater Vehicles

    Science.gov (United States)

    Kinsey, J. C.; Medagoda, L.

    2016-02-01

    Water current velocities are a crucial component of understanding oceanographic processes and underwater robots, such as autonomous underwater vehicles (AUVs), provide a mobile platform for obtaining these observations. Estimating water current velocities requires both measurements of the water velocity, often obtained with an Acoustic Doppler Current Profiler (ADCP), as well as estimates of the vehicle velocity. Presently, vehicle velocities are supplied on the sea surface with velocity from GPS, or near the seafloor where Doppler Velocity Log (DVL) in bottom-lock is available; however, this capability is unavailable in the mid-water column where DVL bottom-lock and GPS are unavailable. Here we present a method which calculates vehicle velocities using consecutive ADCP measurements in the mid-water using an extended Kalman filter (EKF). The correlation of the spatially changing water current states, along with mass transport and shear constraints on the water current field, is formulated using least square constraints. Results from the Sentry AUV from a mid-water surveying mission at Deepwater Horizon and a small-scale hydrothermal vent flux estimation mission suggest the method is suitable for real-time use. DVL data is denied to simulate mid-water missions and the results compared to ground truth water velocity measurements estimated using DVL velocities. Results show quantifiable uncertainties in the water current velocities, along with similar performance, for the DVL and no-DVL case in the mid-water. This method has the potential to provide geo-referenced water velocity measurements from mobile ocean robots in the absence of GPS and DVL as well as estimate the uncertainty associated with the measurements.

  14. A Relative-Localization Algorithm Using Incomplete Pairwise Distance Measurements for Underwater Applications

    Directory of Open Access Journals (Sweden)

    Kae Y. Foo

    2010-01-01

    Full Text Available The task of localizing underwater assets involves the relative localization of each unit using only pairwise distance measurements, usually obtained from time-of-arrival or time-delay-of-arrival measurements. In the fluctuating underwater environment, a complete set of pair-wise distance measurements can often be difficult to acquire, thus hindering a straightforward closed-form solution in deriving the assets' relative coordinates. An iterative multidimensional scaling approach is presented based upon a weighted-majorization algorithm that tolerates missing or inaccurate distance measurements. Substantial modifications are proposed to optimize the algorithm, while the effects of refractive propagation paths are considered. A parametric study of the algorithm based upon simulation results is shown. An acoustic field-trial was then carried out, presenting field measurements to highlight the practical implementation of this algorithm.

  15. GSR-TDMA: A Geometric Spatial Reuse-Time Division Multiple Access MAC Protocol for Multihop Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Changho Yun

    2016-01-01

    Full Text Available The nonnegligible propagation delay of acoustic signals causes spatiotemporal uncertainty that occasionally enables simultaneous, collision-free packet transmission among underwater nodes (UNs. These transmissions can be handled by efficiently managing the channel access of the UNs in the data-link layer. To this end, Geometric Spatial Reuse-TDMA (GSR-TDMA, a new TDMA-based MAC protocol, is designed for use in centralized, multihop underwater acoustic sensor networks (UASNs, and in this case all UNs are periodically scheduled after determining a geometric map according to the information on their location. The scheduling strategy increases the number of UNs that send packets coincidentally via two subscheduling configurations (i.e., interhop and intrahop scheduling. Extensive simulations are used to investigate the reception success rate (RSR and the multihop delay (MHD of GSR-TDMA, and the results are compared to those of previous approaches, including C-MAC and HSR-TDMA. GSR-TDMA outperforms C-MAC; the RSR of GSR-TDMA is 15% higher than that of C-MAC, and the MHD of GSR-TDMA is 30% lower than that of C-MAC at the most. In addition, GSR-TDMA provides even better performance improvements over HSR-TDMA; the RSR of GSR-TDMA is 50% higher than that of HSR-TDMA, and the MHD of GSR-TDMA is an order of 102 lower than that of HSR-TDMA at the most.

  16. High-Resolution Seafloor Mapping at A Deep-Sea Methane Seep Field with an Autonomous Underwater Vehicle

    Science.gov (United States)

    Skarke, A. D.

    2017-12-01

    A growing body of research indicates that points of seafloor gas emission, known as cold-seeps, are a common feature along many continental margins. Results from recent exploration efforts show that benthic environments at cold-seeps are characterized by extensive authigenic carbonate crusts and complex chemosynthetic communities. The seafloor morphology and geophysical properties of these locations are heterogeneous and relatively complex due to the three-dimensional structure created by carbonate buildups and dense bivalve beds. Seeps are often found clustered and the spatial extent of associated seafloor crusts and beds can reach multiple square kilometers. Here, the results of a 1.25 km2 autonomous underwater vehicle (AUV) survey of a deep-sea methane seep field with 13 vents, at a nominal depth of 1400 m, located near Veatch Canyon on the US Atlantic margin are presented. Multibeam sonar, sidescan sonar, and a sub bottom profiler on the AUV were used to make high-resolution observations of seafloor bathymetry (resolution 1m2) as well as water column, seafloor, and subsurface acoustic backscatter intensity. Additionally, a downward oriented camera was used to collect seafloor imagery coincident with acoustic observations at select locations. Acoustic results indicated the location of discrete gas plumes as well as a continuous area of elevated seafloor roughness and backscatter intensity consistent with the presence of large scale authigenic rock outcrops and extensive mussel beds, which were visually confirmed with camera imagery. Additionally, a linear area of particularly elevated seafloor roughness and acoustic backscatter intensity that lies sub-parallel to an adjacent ridge was interpreted to be controlled by underlying geologic processes such as soft sediment faulting. Automated analysis of camera imagery and coincident acoustic backscatter and bathymetry data as well as derivative metrics (e.g. slope and rugosity) was used to segment and classify bed

  17. Impacts of Underwater Noise on Marine Vertebrates: Project Introduction and First Results.

    Science.gov (United States)

    Liebschner, Alexander; Seibel, Henrike; Teilmann, Jonas; Wittekind, Dietrich; Parmentier, Eric; Dähne, Michael; Dietz, Rune; Driver, Jörg; van Elk, Cornelis; Everaarts, Eligius; Findeisen, Henning; Kristensen, Jacob; Lehnert, Kristina; Lucke, Klaus; Merck, Thomas; Müller, Sabine; Pawliczka, Iwona; Ronnenberg, Katrin; Rosenberger, Tanja; Ruser, Andreas; Tougaard, Jakob; Schuster, Max; Sundermeyer, Janne; Sveegaard, Signe; Siebert, Ursula

    2016-01-01

    The project conducts application-oriented research on impacts of underwater noise on marine vertebrates in the North and Baltic Seas. In distinct subprojects, the hearing sensitivity of harbor porpoises and gray seals as well as the acoustic tolerance limit of harbor porpoises to impulsive noise from pile driving and stress reactions caused by anthropogenic noise is investigated. Animals are equipped with DTAGs capable of recording the actual surrounding noise field of free-swimming harbor porpoises and seals. Acoustic noise mapping including porpoise detectors in the Natura 2000 sites of the North and Baltic Seas will help to fully understand current noise impacts.

  18. Time-Efficient High-Rate Data Flooding in One-Dimensional Acoustic Underwater Sensor Networks

    Directory of Open Access Journals (Sweden)

    Jae Kyun Kwon

    2015-10-01

    Full Text Available Because underwater communication environments have poor characteristics, such as severe attenuation, large propagation delays and narrow bandwidths, data is normally transmitted at low rates through acoustic waves. On the other hand, as high traffic has recently been required in diverse areas, high rate transmission has become necessary. In this paper, transmission/reception timing schemes that maximize the time axis use efficiency to improve the resource efficiency for high rate transmission are proposed. The excellence of the proposed scheme is identified by examining the power distributions by node, rate bounds, power levels depending on the rates and number of nodes, and network split gains through mathematical analysis and numerical results. In addition, the simulation results show that the proposed scheme outperforms the existing packet train method.

  19. Advanced Active Acoustics Lab (AAAL)

    Data.gov (United States)

    Federal Laboratory Consortium — The Advanced Active Acoustics Lab (AAAL) is a state-of-the-art Undersea Warfare (USW) acoustic data analysis facility capable of both active and passive underwater...

  20. An acoustic system for autonomous navigation and tracking of marine fauna

    KAUST Repository

    De la Torre, Pedro; Salama, Khaled N.; Berumen, Michael L.

    2014-01-01

    A marine acoustic system for underwater target tracking is described. This system is part of the Integrated Satellite and Acoustic Telemetry (iSAT) project to study marine fauna. It is a microcontroller-based underwater projector and receiver. A

  1. Adaptive Equalizer Based on Second-Order Cone Programming in Underwater Acoustic Communication

    Directory of Open Access Journals (Sweden)

    Yang CHEN

    2014-01-01

    Full Text Available An improved adaptive equalizer based on the principle of minimum mean square error (MMSE is proposed. This optimization problem which is shown to be convex, is transformed to second-order cone (SOC and solved using the interior point method instead of conventional iterative methods such as least mean squares (LMS or recursive least squares (RLS. To validate its performance a single-carrier system for underwater acoustic communication with digital phase-locked loop and the adaptive fractional spaced equalizers was designed and a lake trial was carried out. According to the results, comparing with traditional equalizers based on LMS and RLS algorithms, the equalizer proposed needs no iterative process and gets rid of the contradiction between convergent rate and precision. Therefore it overcomes the difficulty of parameters setting. Furthermore, the algorithm needs much less training codes to achieve the same equalization performance and improves the communication efficiency.

  2. ?Underwater acoustic channel properties ?in the Gulf of Naples and their effects ?on digital data transmission

    Directory of Open Access Journals (Sweden)

    G. Iannaccone

    2007-06-01

    Full Text Available ?In this paper we studied the physical properties of the Gulf of Naples (Southern Italy for its use as a commu- nication channel for the acoustic transmission of digital data acquired by seismic instruments on the seafloor to a moored buoy. The acoustic link will be assured by high frequency acoustic modems operating with a central frequency of 100 kHz and a band pass of 10 kHz. The main operational requirements of data transmission con- cern the near horizontal acoustic link, the maximum depth of the sea being about 300 m and the planned hori- zontal distance between seismic instruments and buoy 2 km. This study constructs the signal-to-noise ratio maps to understand the limits beyond which the clarity of the transmission is no longer considered reliable. Using ray- theory, we compute the amplitudes of a transmitted signal at a grid of 21×12 receivers to calculate the transmis- sion loss at each receiver. The signal-to-noise ratio is finally computed for each receiver knowing also the trans- mitter source level and the acoustic noise level in the Gulf of Naples. The results show that the multipath effects predominate over the effects produced by the sound velocity gradient in the sea in the summer period. In the case of omnidirectional transmitters with a Source Level (SL of 165 dB and a baud rate of 2.4 kbit/s, the results al- so show that distances of 1400-1600 m can be reached throughout the year for transmitter-receiver connections below 50 m depth in the underwater acoustic channel.

  3. Underwater acoustic channel properties in the Gulf of Naples and their effects on digital data transmission

    Directory of Open Access Journals (Sweden)

    G. Iannaccone

    2007-06-01

    Full Text Available In this paper we studied the physical properties of the Gulf of Naples (Southern Italy for its use as a communication channel for the acoustic transmission of digital data acquired by seismic instruments on the seafloor to a moored buoy. The acoustic link will be assured by high frequency acoustic modems operating with a central frequency of 100 kHz and a band pass of 10 kHz. Since the maximum depth of the sea is about 300 m and the planned horizontal distance between the seismic instruments and the buoy is 2 km, the acoustic data transmission shall be near horizontal. In this study the signal-to-noise ratio is plotted against depth and distance from the source, thus defining the limit after which the transmitted information becomes unreliable. Using ray-theory, we compute the amplitudes of a transmitted signal at a grid of 21×12 receivers to calculate the transmission loss at each receiver. The signal-to-noise ratio is finally computed for each receiver knowing also the transmitter source level and the acoustic noise level in the Gulf of Naples. The results show that the multipath effects predominate over the effects produced by the sound velocity gradient in the sea in the summer period. In the case of omnidirectional transmitters with a Source Level (SL of 165 dB and a bit rate of 2.4 kbit/s, the results also show that distances of 1400-1600 m can be reached throughout the year for transmitter-receiver connections below 50 m depth in the underwater acoustic channel.

  4. A Glider-Assisted Link Disruption Restoration Mechanism in Underwater Acoustic Sensor Networks.

    Science.gov (United States)

    Jin, Zhigang; Wang, Ning; Su, Yishan; Yang, Qiuling

    2018-02-07

    Underwater acoustic sensor networks (UASNs) have become a hot research topic. In UASNs, nodes can be affected by ocean currents and external forces, which could result in sudden link disruption. Therefore, designing a flexible and efficient link disruption restoration mechanism to ensure the network connectivity is a challenge. In the paper, we propose a glider-assisted restoration mechanism which includes link disruption recognition and related link restoring mechanism. In the link disruption recognition mechanism, the cluster heads collect the link disruption information and then schedule gliders acting as relay nodes to restore the disrupted link. Considering the glider's sawtooth motion, we design a relay location optimization algorithm with a consideration of both the glider's trajectory and acoustic channel attenuation model. The utility function is established by minimizing the channel attenuation and the optimal location of glider is solved by a multiplier method. The glider-assisted restoration mechanism can greatly improve the packet delivery rate and reduce the communication energy consumption and it is more general for the restoration of different link disruption scenarios. The simulation results show that glider-assisted restoration mechanism can improve the delivery rate of data packets by 15-33% compared with cooperative opportunistic routing (OVAR), the hop-by-hop vector-based forwarding (HH-VBF) and the vector based forward (VBF) methods, and reduce communication energy consumption by 20-58% for a typical network's setting.

  5. MIMO Underwater Acoustic Communications in Ports and Shallow Waters at Very High Frequency

    Directory of Open Access Journals (Sweden)

    Gaultier Real

    2013-10-01

    Full Text Available Hermes is a Single-Input Single-Output (SISO underwater acoustic modem that achieves very high-bit rate digital communications in ports and shallow waters. Here, the authors study the capability of Hermes to support Multiple-Input-Multiple-Output (MIMO technology. A least-square channel estimation algorithm is used to evaluate multiple MIMO channel impulse responses at the receiver end. A deconvolution routine is used to separate the messages coming from different sources. This paper covers the performance of both the channel estimation and the MIMO deconvolution processes using either simulated data or field data. The MIMO equalization performance is measured by comparing three relative root mean-squared errors (RMSE, obtained by calculations between the source signal (a pseudo-noise sequence and the corresponding received MIMO signal at various stages of the deconvolution process; prior to any interference removal, at the output of the Linear Equalization (LE process and at the output of an interference cancellation process with complete a priori knowledge of the transmitted signal. Using the simulated data, the RMSE using LE is −20.5 dB (where 0 dB corresponds to 100% of relative error while the lower bound value is −33.4 dB. Using experimental data, the LE performance is −3.3 dB and the lower bound RMSE value is −27 dB.

  6. Signal processing for passive detection and classification of underwater acoustic signals

    Science.gov (United States)

    Chung, Kil Woo

    2011-12-01

    This dissertation examines signal processing for passive detection, classification and tracking of underwater acoustic signals for improving port security and the security of coastal and offshore operations. First, we consider the problem of passive acoustic detection of a diver in a shallow water environment. A frequency-domain multi-band matched-filter approach to swimmer detection is presented. The idea is to break the frequency contents of the hydrophone signals into multiple narrow frequency bands, followed by time averaged (about half of a second) energy calculation over each band. Then, spectra composed of such energy samples over the chosen frequency bands are correlated to form a decision variable. The frequency bands with highest Signal/Noise ratio are used for detection. The performance of the proposed approach is demonstrated for experimental data collected for a diver in the Hudson River. We also propose a new referenceless frequency-domain multi-band detector which, unlike other reference-based detectors, does not require a diver specific signature. Instead, our detector matches to a general feature of the diver spectrum in the high frequency range: the spectrum is roughly periodic in time and approximately flat when the diver exhales. The performance of the proposed approach is demonstrated by using experimental data collected from the Hudson River. Moreover, we present detection, classification and tracking of small vessel signals. Hydroacoustic sensors can be applied for the detection of noise generated by vessels, and this noise can be used for vessel detection, classification and tracking. This dissertation presents recent improvements aimed at the measurement and separation of ship DEMON (Detection of Envelope Modulation on Noise) acoustic signatures in busy harbor conditions. Ship signature measurements were conducted in the Hudson River and NY Harbor. The DEMON spectra demonstrated much better temporal stability compared with the full ship

  7. Evanescent Acoustic Wave Scattering by Targets and Diffraction by Ripples Graduate Traineeship Award in Ocean Acoustics

    National Research Council Canada - National Science Library

    Osterhoudt, Curtis F; Marston, Philip L

    2007-01-01

    .... The purpose of his research was to improve the understanding of the way that acoustic evanescent waves interact with targets buried in sediments in situations encountered in underwater acoustics...

  8. On the Performance of the Underwater Acoustic Sensor Networks

    Science.gov (United States)

    2015-05-01

    performance of UWSN. 5.1 Hardware and Software Details 5.1.1 Equipment Our experimental model consisted of an indoor swimming pool , two pairs...UWSN has many constraints mainly due to limited capacity, propagation loss, as well as power limitation since in underwater environment solar energy ...since in underwater environment solar energy cannot be used to recharge batteries. In our approach, we estimate the number of operating receivers

  9. An Acoustic OFDM System with Symbol-by-Symbol Doppler Compensation for Underwater Communication.

    Science.gov (United States)

    MinhHai, Tran; Rie, Saotome; Suzuki, Taisaku; Wada, Tomohisa

    2016-01-01

    We propose an acoustic OFDM system for underwater communication, specifically for vertical link communications such as between a robot in the sea bottom and a mother ship in the surface. The main contributions are (1) estimation of time varying Doppler shift using continual pilots in conjunction with monitoring the drift of Power Delay Profile and (2) symbol-by-symbol Doppler compensation in frequency domain by an ICI matrix representing nonuniform Doppler. In addition, we compare our proposal against a resampling method. Simulation and experimental results confirm that our system outperforms the resampling method when the velocity changes roughly over OFDM symbols. Overall, experimental results taken in Shizuoka, Japan, show our system using 16QAM, and 64QAM achieved a data throughput of 7.5 Kbit/sec with a transmitter moving at maximum 2 m/s, in a complicated trajectory, over 30 m vertically.

  10. Underwater noise due to precipitation

    DEFF Research Database (Denmark)

    Crum, Lawrence A.; Pumphrey, Hugh C.; Prosperetti, Andrea

    1989-01-01

    In 1959, G. Franz published a thorough investigation of the underwater sound produced by liquid drop impacts [G. Franz, J. Acoust. Soc. Am. 31, 1080 (1959)]. He discovered that, under certain conditions, a gas bubble was entrained by the impacting droplet, and the subsequent oscillation of this b...

  11. Underwater Optical Wireless Communications, Networking, and Localization: A Survey

    KAUST Repository

    Saeed, Nasir; Celik, Abdulkadir; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim

    2018-01-01

    Underwater wireless communications can be carried out through acoustic, radio frequency (RF), and optical waves. Compared to its bandwidth limited acoustic and RF counterparts, underwater optical wireless communications (UOWCs) can support higher data rates at low latency levels. However, severe aquatic channel conditions (e.g., absorption, scattering, turbulence, etc.) pose great challenges for UOWCs and significantly reduce the attainable communication ranges, which necessitates efficient networking and localization solutions. Therefore, we provide a comprehensive survey on the challenges, advances, and prospects of underwater optical wireless networks (UOWNs) from a layer by layer perspective which includes: 1) Potential network architectures; 2) Physical layer issues including propagation characteristics, channel modeling, and modulation techniques 3) Data link layer problems covering link configurations, link budgets, performance metrics, and multiple access schemes; 4) Network layer topics containing relaying techniques and potential routing algorithms; 5) Transport layer subjects such as connectivity, reliability, flow and congestion control; 6) Application layer goals and state-of-the-art UOWN applications, and 7) Localization and its impacts on UOWN layers. Finally, we outline the open research challenges and point out the future directions for underwater optical wireless communications, networking, and localization research.

  12. Underwater Optical Wireless Communications, Networking, and Localization: A Survey

    KAUST Repository

    Saeed, Nasir

    2018-02-28

    Underwater wireless communications can be carried out through acoustic, radio frequency (RF), and optical waves. Compared to its bandwidth limited acoustic and RF counterparts, underwater optical wireless communications (UOWCs) can support higher data rates at low latency levels. However, severe aquatic channel conditions (e.g., absorption, scattering, turbulence, etc.) pose great challenges for UOWCs and significantly reduce the attainable communication ranges, which necessitates efficient networking and localization solutions. Therefore, we provide a comprehensive survey on the challenges, advances, and prospects of underwater optical wireless networks (UOWNs) from a layer by layer perspective which includes: 1) Potential network architectures; 2) Physical layer issues including propagation characteristics, channel modeling, and modulation techniques 3) Data link layer problems covering link configurations, link budgets, performance metrics, and multiple access schemes; 4) Network layer topics containing relaying techniques and potential routing algorithms; 5) Transport layer subjects such as connectivity, reliability, flow and congestion control; 6) Application layer goals and state-of-the-art UOWN applications, and 7) Localization and its impacts on UOWN layers. Finally, we outline the open research challenges and point out the future directions for underwater optical wireless communications, networking, and localization research.

  13. A Survey of Routing Issues and Associated Protocols in Underwater Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Muhammad Khalid

    2017-01-01

    Full Text Available Underwater wireless sensor networks are a newly emerging wireless technology in which small size sensors with limited energy and limited memory and bandwidth are deployed in deep sea water and various monitoring operations like tactical surveillance, environmental monitoring, and data collection are performed through these tiny sensors. Underwater wireless sensor networks are used for the exploration of underwater resources, oceanographic data collection, flood or disaster prevention, tactical surveillance systems, and unmanned underwater vehicles. Sensor nodes consist of a small memory, a central processing unit, and an antenna. Underwater networks are much different from terrestrial sensor networks as radio waves cannot be used in underwater wireless sensor networks. Acoustic channels are used for communication in deep sea water. Acoustic signals have many limitations, such as limited bandwidth, higher end-to-end delay, network path loss, higher propagation delay, and dynamic topology. Usually, these limitations result in higher energy consumption with a smaller number of packets delivered. The main aim nowadays is to operate sensor nodes having a smaller battery for a longer time in the network. This survey has discussed the state-of-the-art localization based and localization-free routing protocols. Routing associated issues in the area of underwater wireless sensor networks have also been discussed.

  14. Optical measurement of acoustic radiation pressure of the near-field acoustic levitation through transparent object

    OpenAIRE

    Nakamura, Satoshi; Furusawa, Toshiaki; Sasao, Yasuhiro; Katsura, Kogure; Naoki, Kondo

    2013-01-01

    It is known that macroscopic objects can be levitated for few to several hundred micrometers by near-field acoustic field and this phenomenon is called near-field acoustic levitation (NFAL). Although there are various experiments conducted to measure integrated acoustic pressure on the object surface, up to now there was no direct method to measure pressure distribution. In this study we measured the acoustic radiation pressure of the near-field acoustic levitation via pressure-sensitive paint.

  15. A Glider-Assisted Link Disruption Restoration Mechanism in Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Zhigang Jin

    2018-02-01

    Full Text Available Underwater acoustic sensor networks (UASNs have become a hot research topic. In UASNs, nodes can be affected by ocean currents and external forces, which could result in sudden link disruption. Therefore, designing a flexible and efficient link disruption restoration mechanism to ensure the network connectivity is a challenge. In the paper, we propose a glider-assisted restoration mechanism which includes link disruption recognition and related link restoring mechanism. In the link disruption recognition mechanism, the cluster heads collect the link disruption information and then schedule gliders acting as relay nodes to restore the disrupted link. Considering the glider’s sawtooth motion, we design a relay location optimization algorithm with a consideration of both the glider’s trajectory and acoustic channel attenuation model. The utility function is established by minimizing the channel attenuation and the optimal location of glider is solved by a multiplier method. The glider-assisted restoration mechanism can greatly improve the packet delivery rate and reduce the communication energy consumption and it is more general for the restoration of different link disruption scenarios. The simulation results show that glider-assisted restoration mechanism can improve the delivery rate of data packets by 15–33% compared with cooperative opportunistic routing (OVAR, the hop-by-hop vector-based forwarding (HH-VBF and the vector based forward (VBF methods, and reduce communication energy consumption by 20–58% for a typical network’s setting.

  16. Underwater Multi-Vehicle Trajectory Alignment and Mapping Using Acoustic and Optical Constraints

    Directory of Open Access Journals (Sweden)

    Ricard Campos

    2016-03-01

    Full Text Available Multi-robot formations are an important advance in recent robotic developments, as they allow a group of robots to merge their capacities and perform surveys in a more convenient way. With the aim of keeping the costs and acoustic communications to a minimum, cooperative navigation of multiple underwater vehicles is usually performed at the control level. In order to maintain the desired formation, individual robots just react to simple control directives extracted from range measurements or ultra-short baseline (USBL systems. Thus, the robots are unaware of their global positioning, which presents a problem for the further processing of the collected data. The aim of this paper is two-fold. First, we present a global alignment method to correct the dead reckoning trajectories of multiple vehicles to resemble the paths followed during the mission using the acoustic messages passed between vehicles. Second, we focus on the optical mapping application of these types of formations and extend the optimization framework to allow for multi-vehicle geo-referenced optical 3D mapping using monocular cameras. The inclusion of optical constraints is not performed using the common bundle adjustment techniques, but in a form improving the computational efficiency of the resulting optimization problem and presenting a generic process to fuse optical reconstructions with navigation data. We show the performance of the proposed method on real datasets collected within the Morph EU-FP7 project.

  17. Theoretical Model of Acoustic Wave Propagation in Shallow Water

    Directory of Open Access Journals (Sweden)

    Kozaczka Eugeniusz

    2017-06-01

    Full Text Available The work is devoted to the propagation of low frequency waves in a shallow sea. As a source of acoustic waves, underwater disturbances generated by ships were adopted. A specific feature of the propagation of acoustic waves in shallow water is the proximity of boundaries of the limiting media characterised by different impedance properties, which affects the acoustic field coming from a source situated in the water layer “deformed” by different phenomena. The acoustic field distribution in the real shallow sea is affected not only by multiple reflections, but also by stochastic changes in the free surface shape, and statistical changes in the seabed shape and impedance. The paper discusses fundamental problems of modal sound propagation in the water layer over different types of bottom sediments. The basic task in this case was to determine the acoustic pressure level as a function of distance and depth. The results of the conducted investigation can be useful in indirect determination of the type of bottom.

  18. An Acoustic OFDM System with Symbol-by-Symbol Doppler Compensation for Underwater Communication

    Directory of Open Access Journals (Sweden)

    Tran MinhHai

    2016-01-01

    Full Text Available We propose an acoustic OFDM system for underwater communication, specifically for vertical link communications such as between a robot in the sea bottom and a mother ship in the surface. The main contributions are (1 estimation of time varying Doppler shift using continual pilots in conjunction with monitoring the drift of Power Delay Profile and (2 symbol-by-symbol Doppler compensation in frequency domain by an ICI matrix representing nonuniform Doppler. In addition, we compare our proposal against a resampling method. Simulation and experimental results confirm that our system outperforms the resampling method when the velocity changes roughly over OFDM symbols. Overall, experimental results taken in Shizuoka, Japan, show our system using 16QAM, and 64QAM achieved a data throughput of 7.5 Kbit/sec with a transmitter moving at maximum 2 m/s, in a complicated trajectory, over 30 m vertically.

  19. An Acoustic OFDM System with Symbol-by-Symbol Doppler Compensation for Underwater Communication

    Science.gov (United States)

    MinhHai, Tran; Rie, Saotome; Suzuki, Taisaku; Wada, Tomohisa

    2016-01-01

    We propose an acoustic OFDM system for underwater communication, specifically for vertical link communications such as between a robot in the sea bottom and a mother ship in the surface. The main contributions are (1) estimation of time varying Doppler shift using continual pilots in conjunction with monitoring the drift of Power Delay Profile and (2) symbol-by-symbol Doppler compensation in frequency domain by an ICI matrix representing nonuniform Doppler. In addition, we compare our proposal against a resampling method. Simulation and experimental results confirm that our system outperforms the resampling method when the velocity changes roughly over OFDM symbols. Overall, experimental results taken in Shizuoka, Japan, show our system using 16QAM, and 64QAM achieved a data throughput of 7.5 Kbit/sec with a transmitter moving at maximum 2 m/s, in a complicated trajectory, over 30 m vertically. PMID:27057558

  20. WODA Technical Guidance on Underwater Sound from Dredging.

    Science.gov (United States)

    Thomsen, Frank; Borsani, Fabrizio; Clarke, Douglas; de Jong, Christ; de Wit, Pim; Goethals, Fredrik; Holtkamp, Martine; Martin, Elena San; Spadaro, Philip; van Raalte, Gerard; Victor, George Yesu Vedha; Jensen, Anders

    2016-01-01

    The World Organization of Dredging Associations (WODA) has identified underwater sound as an environmental issue that needs further consideration. A WODA Expert Group on Underwater Sound (WEGUS) prepared a guidance paper in 2013 on dredging sound, including a summary of potential impacts on aquatic biota and advice on underwater sound monitoring procedures. The paper follows a risk-based approach and provides guidance for standardization of acoustic terminology and methods for data collection and analysis. Furthermore, the literature on dredging-related sounds and the effects of dredging sounds on marine life is surveyed and guidance on the management of dredging-related sound risks is provided.

  1. Behavioural Response Thresholds in New Zealand Crab Megalopae to Ambient Underwater Sound

    Science.gov (United States)

    Stanley, Jenni A.; Radford, Craig A.; Jeffs, Andrew G.

    2011-01-01

    A small number of studies have demonstrated that settlement stage decapod crustaceans are able to detect and exhibit swimming, settlement and metamorphosis responses to ambient underwater sound emanating from coastal reefs. However, the intensity of the acoustic cue required to initiate the settlement and metamorphosis response, and therefore the potential range over which this acoustic cue may operate, is not known. The current study determined the behavioural response thresholds of four species of New Zealand brachyuran crab megalopae by exposing them to different intensity levels of broadcast reef sound recorded from their preferred settlement habitat and from an unfavourable settlement habitat. Megalopae of the rocky-reef crab, Leptograpsus variegatus, exhibited the lowest behavioural response threshold (highest sensitivity), with a significant reduction in time to metamorphosis (TTM) when exposed to underwater reef sound with an intensity of 90 dB re 1 µPa and greater (100, 126 and 135 dB re 1 µPa). Megalopae of the mud crab, Austrohelice crassa, which settle in soft sediment habitats, exhibited no response to any of the underwater reef sound levels. All reef associated species exposed to sound levels from an unfavourable settlement habitat showed no significant change in TTM, even at intensities that were similar to their preferred reef sound for which reductions in TTM were observed. These results indicated that megalopae were able to discern and respond selectively to habitat-specific acoustic cues. The settlement and metamorphosis behavioural response thresholds to levels of underwater reef sound determined in the current study of four species of crabs, enables preliminary estimation of the spatial range at which an acoustic settlement cue may be operating, from 5 m to 40 km depending on the species. Overall, these results indicate that underwater sound is likely to play a major role in influencing the spatial patterns of settlement of coastal crab

  2. Delay Tolerance in Underwater Wireless Communications: A Routing Perspective

    Directory of Open Access Journals (Sweden)

    Safdar Hussain Bouk

    2016-01-01

    Full Text Available Similar to terrestrial networks, underwater wireless networks (UWNs also aid several critical tasks including coastal surveillance, underwater pollution detection, and other maritime applications. Currently, once underwater sensor nodes are deployed at different levels of the sea, it is nearly impossible or very expensive to reconfigure the hardware, for example, battery. Taking this issue into account, considerable amount of research has been carried out to ensure minimum energy costs and reliable communication between underwater nodes and base stations. As a result, several different network protocols were proposed for UWN, including MAC, PHY, transport, and routing. Recently, a new paradigm was introduced claiming that the intermittent nature of acoustic channel and signal resulted in designing delay tolerant routing schemes for the UWN, known as an underwater delay tolerant network. In this paper, we provide a comprehensive survey of underwater routing protocols with emphasis on the limitations, challenges, and future open issues in the context of delay tolerant network routing.

  3. A Data Link Layer in Support of Swarming of Autonomous Underwater Vehicles

    Science.gov (United States)

    Jabba Molinares, Daladier

    2009-01-01

    Communication underwater is challenging because of the inherent characteristics of the media. First, common radio frequency (RF) signals utilized in wireless communications cannot be used under water. RF signals are attenuated in such as way that RF communication underwater is restricted to very few meters. As a result, acoustic-based…

  4. Underwater navigation using diffusion-based trajectory observers

    DEFF Research Database (Denmark)

    Jouffroy, Jerome; Opderbecke, Jan

    2007-01-01

    This paper addresses the issue of estimating underwater vehicle trajectories using gyro-Doppler (body-fixed velocities) and acoustic positioning signals (earth-fixed positions). The approach consists of diffusion-based observers processing a whole trajectory segment at a time, allowing the consid...

  5. Evaluation of an Efficient Approach for Target Tracking from Acoustic Imagery for the Perception System of an Autonomous Underwater Vehicle

    Directory of Open Access Journals (Sweden)

    Sebastián A. Villar

    2014-02-01

    Full Text Available This article describes the core algorithms of the perception system to be included within an autonomous underwater vehicle (AUV. This perception system is based on the acoustic data acquired from side scan sonar (SSS. These data should be processed in an efficient time, so that the perception system is able to detect and recognize a predefined target. This detection and recognition outcome is therefore an important piece of knowledge for the AUVs dynamic mission planner (DMP. Effectively, the DMP should propose different trajectories, navigation depths and other parameters that will change the robot's behaviour according to the perception system output. Hence, the time in which to make a decision is critical in order to assure safe robot operation and to acquire good quality data; consequently, the efficiency of the on-line image processing from acoustic data is a key issue. Current techniques for acoustic data processing are time and computationally intensive. Hence, it was decided to process data coming from a SSS using a technique that is used for radars, due to its efficiency and its amenability to on-line processing. The engineering problem to solve in this case was underwater pipeline tracking for routine inspections in the off-shore industry. Then, an automatic oil pipeline detection system was developed borrowing techniques from the processing of radar measurements. The radar technique is known as Cell Average – Constant False Alarm Rate (CA – CFAR. With a slight variation of the algorithms underlying this radar technique, which consisted of the previous accumulation of partial sums, a great improvement in computing time and effort was achieved. Finally, a comparison with previous approaches over images acquired with a SSS from a vessel in the Salvador de Bahia bay in Brazil showed the feasibility of using this on-board technique for AUV perception.

  6. Blind source separation based on time-frequency morphological characteristics for rigid acoustic scattering by underwater objects

    Science.gov (United States)

    Yang, Yang; Li, Xiukun

    2016-06-01

    Separation of the components of rigid acoustic scattering by underwater objects is essential in obtaining the structural characteristics of such objects. To overcome the problem of rigid structures appearing to have the same spectral structure in the time domain, time-frequency Blind Source Separation (BSS) can be used in combination with image morphology to separate the rigid scattering components of different objects. Based on a highlight model, the separation of the rigid scattering structure of objects with time-frequency distribution is deduced. Using a morphological filter, different characteristics in a Wigner-Ville Distribution (WVD) observed for single auto term and cross terms can be simplified to remove any cross-term interference. By selecting time and frequency points of the auto terms signal, the accuracy of BSS can be improved. An experimental simulation has been used, with changes in the pulse width of the transmitted signal, the relative amplitude and the time delay parameter, in order to analyzing the feasibility of this new method. Simulation results show that the new method is not only able to separate rigid scattering components, but can also separate the components when elastic scattering and rigid scattering exist at the same time. Experimental results confirm that the new method can be used in separating the rigid scattering structure of underwater objects.

  7. The Theseus Autonomous Underwater Vehicle: A Canadian Success Story

    Science.gov (United States)

    1997-04-01

    P502414.PDF [Page: 1 of 9] P502414.PDF [Page: 2 of 9] P502414.PDF [Page: 3 of 9] The Theseus Autonomous Underwater Vehicle A Canadian Success Story...autonomous underwater vehicle, named Theseus , for laying optical fiber cables in ice- covered waters. In trials and missions conducted in 1996, this...stations. An acoustic telemetry system enables communication with Theseus from surface stations, and an optical telemetry system is used for system

  8. Deep sea AUV navigation using multiple acoustic beacons

    Science.gov (United States)

    Ji, Da-xiong; Song, Wei; Zhao, Hong-yu; Liu, Jian

    2016-04-01

    Navigation is a critical requirement for the operation of Autonomous Underwater Vehicles (AUVs). To estimate the vehicle position, we present an algorithm using an extended Kalman filter (EKF) to integrate dead-reckoning position with acoustic ranges from multiple beacons pre-deployed in the operating environment. Owing to high latency, variable sound speed multipath transmissions and unreliability in acoustic measurements, outlier recognition techniques are proposed as well. The navigation algorithm has been tested by the recorded data of deep sea AUV during field operations in a variety of environments. Our results show the improved performance over prior techniques based on position computation.

  9. L2-LBMT: A Layered Load Balance Routing Protocol for underwater multimedia data transmission

    Science.gov (United States)

    Lv, Ze; Tang, Ruichun; Tao, Ye; Sun, Xin; Xu, Xiaowei

    2017-12-01

    Providing highly efficient underwater transmission of mass multimedia data is challenging due to the particularities of the underwater environment. Although there are many schemes proposed to optimize the underwater acoustic network communication protocols, from physical layer, data link layer, network layer to transport layer, the existing routing protocols for underwater wireless sensor network (UWSN) still cannot well deal with the problems in transmitting multimedia data because of the difficulties involved in high energy consumption, low transmission reliability or high transmission delay. It prevents us from applying underwater multimedia data to real-time monitoring of marine environment in practical application, especially in emergency search, rescue operation and military field. Therefore, the inefficient transmission of marine multimedia data has become a serious problem that needs to be solved urgently. In this paper, A Layered Load Balance Routing Protocol (L2-LBMT) is proposed for underwater multimedia data transmission. In L2-LBMT, we use layered and load-balance Ad Hoc Network to transmit data, and adopt segmented data reliable transfer (SDRT) protocol to improve the data transport reliability. And a 3-node variant of tornado (3-VT) code is also combined with the Ad Hoc Network to transmit little emergency data more quickly. The simulation results show that the proposed protocol can balance energy consumption of each node, effectively prolong the network lifetime and reduce transmission delay of marine multimedia data.

  10. Underwater target positioning with a single acoustic sensor

    Digital Repository Service at National Institute of Oceanography (India)

    David, M-S; Pascoal, A.M.; Joaquin, A.

    The availability of reliable underwater positioning systems to localize one or more vehicles simultaneously based on information received on-board a support ship or an autonomous surface vessel is key to the operation of some classes of AUVs...

  11. Aerosol behaviour in an acoustic field

    International Nuclear Information System (INIS)

    Malherbe, C.

    1985-01-01

    The average size of an aerosol submitted to acoustic waves is increased. This results from coagulation of the finest particles on the largest ones. The mechanisms responsible for acoustic agglomeration are mentioned. An experimental apparatus was developed in order to control the evolution of aerosol distribution in an acoustic field. Important deposition on the walls of the agglomeration chamber was observed as a consequence of the acoustically induced turbulent flow. Finally, a dimensionless relationship was established between deposition rates and particle diameters as a function of experimental parameters (aeraulic and acoustic conditions, etc...) [fr

  12. Ray and wave chaos in underwater acoustic waveguides

    International Nuclear Information System (INIS)

    Virovlyansky, Anatolii L; Makarov, Denis V; Prants, Sergei V

    2012-01-01

    In the 1990s, the study of the chaotic behavior of ray trajectories in inhomogeneous waveguides emerged as a new field in ocean acoustics. It turned out that at ranges on the order of or larger than 1000 km ray chaos is well developed and should be taken into account when describing long-range sound propagation in the ocean. The theoretical analysis of ray chaos and of its finite-wavelength manifestation, wave chaos, is to a large extent based on well-known methods and ideas from the theory of dynamical and quantum chaos. Concrete examples are used to review the results obtained in this field over the last two decades. (reviews of topical problems)

  13. Impacts of underwater noise on marine vertebrates

    NARCIS (Netherlands)

    Liebschner, Alexander; Seibel, Henrike; Teilmann, Jonas; Wittekind, Dietrich; Parmentier, Eric; Dähne, Michael; Dietz, Rune; Driver, Jörg; Elk, van Cornelis; Everaarts, Eligius; Findeisen, Henning; Kristensen, Jacob; Lehnert, Kristina; Lucke, Klaus; Merck, Thomas; Müller, Sabine; Pawliczka, Iwona; Ronnenberg, Katrin; Rosenberger, Tanja; Ruser, Andreas; Tougaard, Jakob; Schuster, Max; Sundermeyer, Janne; Sveegaard, Signe; Siebert, Ursula

    2016-01-01

    The project conducts application-oriented research on impacts of underwater noise on marine vertebrates in the North and Baltic Seas. In distinct subprojects, the hearing sensitivity of harbor porpoises and gray seals as well as the acoustic tolerance limit of harbor porpoises to impulsive noise

  14. Silent Localization of Underwater Sensors Using Magnetometers

    Directory of Open Access Journals (Sweden)

    Jonas Callmer

    2010-01-01

    Full Text Available Sensor localization is a central problem for sensor networks. If the sensor positions are uncertain, the target tracking ability of the sensor network is reduced. Sensor localization in underwater environments is traditionally addressed using acoustic range measurements involving known anchor or surface nodes. We explore the usage of triaxial magnetometers and a friendly vessel with known magnetic dipole to silently localize the sensors. The ferromagnetic field created by the dipole is measured by the magnetometers and is used to localize the sensors. The trajectory of the vessel and the sensor positions are estimated simultaneously using an Extended Kalman Filter (EKF. Simulations show that the sensors can be accurately positioned using magnetometers.

  15. Acoustic Communications Measurement Systems (ACOMMS)

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Design and develop adaptive signal processing techniques to improve underwater acoustic communications and networking. Phase coherent and incoherent signal...

  16. Measurement and Modeling of Narrowband Channels for Ultrasonic Underwater Communications

    Directory of Open Access Journals (Sweden)

    Francisco J. Cañete

    2016-02-01

    Full Text Available Underwater acoustic sensor networks are a promising technology that allow real-time data collection in seas and oceans for a wide variety of applications. Smaller size and weight sensors can be achieved with working frequencies shifted from audio to the ultrasonic band. At these frequencies, the fading phenomena has a significant presence in the channel behavior, and the design of a reliable communication link between the network sensors will require a precise characterization of it. Fading in underwater channels has been previously measured and modeled in the audio band. However, there have been few attempts to study it at ultrasonic frequencies. In this paper, a campaign of measurements of ultrasonic underwater acoustic channels in Mediterranean shallow waters conducted by the authors is presented. These measurements are used to determine the parameters of the so-called κ-μ shadowed distribution, a fading model with a direct connection to the underlying physical mechanisms. The model is then used to evaluate the capacity of the measured channels with a closed-form expression.

  17. Autonomous Acoustic Receiver System

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Collects underwater acoustic data and oceanographic data. Data are recorded onboard an ocean buoy and can be telemetered to a remote ship or shore station...

  18. Acoustic radiation force on a multilayered sphere in a Gaussian standing field

    Science.gov (United States)

    Wang, Haibin; Liu, Xiaozhou; Gao, Sha; Cui, Jun; Liu, Jiehui; He, Aijun; Zhang, Gutian

    2018-03-01

    We develop a model for calculating the radiation force on spherically symmetric multilayered particles based on the acoustic scattering approach. An expression is derived for the radiation force on a multilayered sphere centered on the axis of a Gaussian standing wave propagating in an ideal fluid. The effects of the sound absorption of the materials and sound wave on acoustic radiation force of a multilayered sphere immersed in water are analyzed, with particular emphasis on the shell thickness of every layer, and the width of the Gaussian beam. The results reveal that the existence of particle trapping behavior depends on the choice of the non-dimensional frequency ka, as well as the shell thickness of each layer. This study provides a theoretical basis for the development of acoustical tweezers in a Gaussian standing wave, which may benefit the improvement and development of acoustic control technology, such as trapping, sorting, and assembling a cell, and drug delivery applications. Project supported by National Key R&D Program (Grant No. 2016YFF0203000), the National Natural Science Foundation of China (Grant Nos. 11774167 and 61571222), the Fundamental Research Funds for the Central Universities of China (Grant No. 020414380001), the Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, Chinese Academy of Sciences (Grant No. SSHJ-KFKT-1701), and the AQSIQ Technology R&D Program of China (Grant No. 2017QK125).

  19. Dynamics of levitated objects in acoustic vortex fields.

    Science.gov (United States)

    Hong, Z Y; Yin, J F; Zhai, W; Yan, N; Wang, W L; Zhang, J; Drinkwater, Bruce W

    2017-08-02

    Acoustic levitation in gaseous media provides a tool to process solid and liquid materials without the presence of surfaces such as container walls and hence has been used widely in chemical analysis, high-temperature processing, drop dynamics and bioreactors. To date high-density objects can only be acoustically levitated in simple standing-wave fields. Here we demonstrate the ability of a small number of peripherally placed sources to generate acoustic vortex fields and stably levitate a wide range of liquid and solid objects. The forces exerted by these acoustic vortex fields on a levitated water droplet are observed to cause a controllable deformation of the droplet and/or oscillation along the vortex axis. Orbital angular momentum transfer is also shown to rotate a levitated object rapidly and the rate of rotation can be controlled by the source amplitude. We expect this research can increase the diversity of acoustic levitation and expand the application of acoustic vortices.

  20. Patch near-field acoustic holography: The influence of acoustic contributions from outside the source

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Jacobsen, Finn; Zhang, Yong-Bin

    2009-01-01

    It is a requirement of conventional Near-field Acoustic Holography that the measurement area covers the entire surface of the source. In the case of Patch Near-field Acoustic Holography (patch NAH), the measurement area can be reduced to cover only a specific area of the source which...... is of particular interest (known as the “patch” or “source patch”). The area of the source beyond this patch is not of interest in the analysis. However, its acoustic output may nevertheless contribute to the total sound field in the measurement plane, and influence the reconstruction of the field close...... to the patch. The purpose of this paper is to investigate how the acoustic radiation from outside the patch area influences the reconstruction of the sound field close to the source. The reconstruction is based on simulated measurements of sound pressure and particle velocity. The methods used in this paper...

  1. An Alignment Method for the Integration of Underwater 3D Data Captured by a Stereovision System and an Acoustic Camera

    Directory of Open Access Journals (Sweden)

    Antonio Lagudi

    2016-04-01

    Full Text Available The integration of underwater 3D data captured by acoustic and optical systems is a promising technique in various applications such as mapping or vehicle navigation. It allows for compensating the drawbacks of the low resolution of acoustic sensors and the limitations of optical sensors in bad visibility conditions. Aligning these data is a challenging problem, as it is hard to make a point-to-point correspondence. This paper presents a multi-sensor registration for the automatic integration of 3D data acquired from a stereovision system and a 3D acoustic camera in close-range acquisition. An appropriate rig has been used in the laboratory tests to determine the relative position between the two sensor frames. The experimental results show that our alignment approach, based on the acquisition of a rig in several poses, can be adopted to estimate the rigid transformation between the two heterogeneous sensors. A first estimation of the unknown geometric transformation is obtained by a registration of the two 3D point clouds, but it ends up to be strongly affected by noise and data dispersion. A robust and optimal estimation is obtained by a statistical processing of the transformations computed for each pose. The effectiveness of the method has been demonstrated in this first experimentation of the proposed 3D opto-acoustic camera.

  2. Equation Chapter 1 Section 1Cross Layer Design for Localization in Large-Scale Underwater Sensor Networks

    Directory of Open Access Journals (Sweden)

    Yuanfeng ZHANG

    2014-02-01

    Full Text Available There are many technical challenges for designing large-scale underwater sensor networks, especially the sensor node localization. Although many papers studied for large-scale sensor node localization, previous studies mainly study the location algorithm without the cross layer design for localization. In this paper, by utilizing the network hierarchical structure of underwater sensor networks, we propose a new large-scale underwater acoustic localization scheme based on cross layer design. In this scheme, localization is performed in a hierarchical way, and the whole localization process focused on the physical layer, data link layer and application layer. We increase the pipeline parameters which matched the acoustic channel, added in MAC protocol to increase the authenticity of the large-scale underwater sensor networks, and made analysis of different location algorithm. We conduct extensive simulations, and our results show that MAC layer protocol and the localization algorithm all would affect the result of localization which can balance the trade-off between localization accuracy, localization coverage, and communication cost.

  3. EDOVE: Energy and Depth Variance-Based Opportunistic Void Avoidance Scheme for Underwater Acoustic Sensor Networks.

    Science.gov (United States)

    Bouk, Safdar Hussain; Ahmed, Syed Hassan; Park, Kyung-Joon; Eun, Yongsoon

    2017-09-26

    Underwater Acoustic Sensor Network (UASN) comes with intrinsic constraints because it is deployed in the aquatic environment and uses the acoustic signals to communicate. The examples of those constraints are long propagation delay, very limited bandwidth, high energy cost for transmission, very high signal attenuation, costly deployment and battery replacement, and so forth. Therefore, the routing schemes for UASN must take into account those characteristics to achieve energy fairness, avoid energy holes, and improve the network lifetime. The depth based forwarding schemes in literature use node's depth information to forward data towards the sink. They minimize the data packet duplication by employing the holding time strategy. However, to avoid void holes in the network, they use two hop node proximity information. In this paper, we propose the Energy and Depth variance-based Opportunistic Void avoidance (EDOVE) scheme to gain energy balancing and void avoidance in the network. EDOVE considers not only the depth parameter, but also the normalized residual energy of the one-hop nodes and the normalized depth variance of the second hop neighbors. Hence, it avoids the void regions as well as balances the network energy and increases the network lifetime. The simulation results show that the EDOVE gains more than 15 % packet delivery ratio, propagates 50 % less copies of data packet, consumes less energy, and has more lifetime than the state of the art forwarding schemes.

  4. Estimating the Total Heat Flux from the ASHES Hydrothermal Vent Field Using the Sentry Autonomous Underwater Vehicle

    Science.gov (United States)

    Crone, T. J.; Kinsey, J. C.; Mittelstaedt, E. L.

    2017-12-01

    Hydrothermal venting at mid-ocean ridges influences ocean chemistry, the thermal and chemical structure of the oceanic crust, and the evolution of unique and diverse autolithotrophically-supported ecosystems. Axially-hosted hydrothermal systems are responsible for 20-25% of the total heat flux out of Earth's interior, and likely play a large role in local as well as global biogeochemical cycles. Despite the importance of these systems, only a few studies have attempted to constrain the volume and heat flux of an entire hydrothermal vent field. In July of 2014 we used the Sentry autonomous underwater vehicle (AUV) to survey the water column over the ASHES hydrothermal vent field which is located within the caldera of Axial Seamount, an active submarine volcano located on the Juan de Fuca Ridge. To estimate the total heat and mass flux from this vent field, we equipped Sentry with a Nortek acoustic Doppler velocimeter (ADV), an inertial measurement unit (IMU), two acoustic Doppler current profilers (ADCPs), and two SBE3 temperature probes, allowing us to obtain precise measurements of fluid temperature and water velocity. The survey was designed using a control volume approach in which Sentry was pre-programmed to survey a 150-m-square centered over the vent field flying a grid pattern with 5-m track line spacing followed by a survey of the perimeter. This pattern was repeated multiple times during several 10-h dives at different altitudes, including 10, 20, 40, and 60 m above the seafloor, and during one 40-h survey at an altitude of 10 m. During the 40-h survey, the pattern was repeated nine times allowing us to obtain observations over several tidal cycles. Water velocity data obtained with Sentry were corrected for platform motion and then combined with the temperature measurements to estimate heat flux. The analysis of these data will likely provide the most accurate and highest resolution heat and mass flux estimates at a seafloor hydrothermal field to date.

  5. Diversity of acoustic streaming in a rectangular acoustofluidic field.

    Science.gov (United States)

    Tang, Qiang; Hu, Junhui

    2015-04-01

    Diversity of acoustic streaming field in a 2D rectangular chamber with a traveling wave and using water as the acoustic medium is numerically investigated by the finite element method. It is found that the working frequency, the vibration excitation source length, and the distance and phase difference between two separated symmetric vibration excitation sources can cause the diversity in the acoustic streaming pattern. It is also found that a small object in the acoustic field results in an additional eddy, and affects the eddy size in the acoustic streaming field. In addition, the computation results show that with an increase of the acoustic medium's temperature, the speed of the main acoustic streaming decreases first and then increases, and the angular velocity of the corner eddies increases monotonously, which can be clearly explained by the change of the acoustic dissipation factor and shearing viscosity of the acoustic medium with temperature. Commercialized FEM software COMSOL Multiphysics is used to implement the computation tasks, which makes our method very easy to use. And the computation method is partially verified by an established analytical solution. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Study of aerosol behaviour in an acoustic field

    International Nuclear Information System (INIS)

    Malherbe, C.

    1988-01-01

    The average size of an aerosol submitted to acoustic waves is increased. This results from coagulation of the finer particles on the larger ones. An experimental apparatus was developed in order to control the evolution of aerosol distribution in an acoustic field. Important deposition on the walls of the agglomeration chamber was observed as a consequence of the acoustically induced turbulent flow. Consequently, we experimentally evaluated the turbulent properties of the system. A granular bed submitted to an acoustic field and set downstream an agglomerator constitutes an almost absolute filter for an usually penetrating aerosol [fr

  7. The near-field acoustic levitation of high-mass rotors

    International Nuclear Information System (INIS)

    Hong, Z. Y.; Lü, P.; Geng, D. L.; Zhai, W.; Yan, N.; Wei, B.

    2014-01-01

    Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope

  8. The near-field acoustic levitation of high-mass rotors

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Z. Y.; Lü, P.; Geng, D. L.; Zhai, W.; Yan, N.; Wei, B., E-mail: bbwei@nwpu.edu.cn [Department of Applied Physics, Northwestern Polytechnical University, Xi' an 710072 (China)

    2014-10-15

    Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope.

  9. The near-field acoustic levitation of high-mass rotors.

    Science.gov (United States)

    Hong, Z Y; Lü, P; Geng, D L; Zhai, W; Yan, N; Wei, B

    2014-10-01

    Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope.

  10. EARLY DETECTION OF NEAR-FIELD TSUNAMIS USING UNDERWATER SENSOR NETWORKS

    Directory of Open Access Journals (Sweden)

    L. E. Freitag

    2012-01-01

    Full Text Available We propose a novel approach for near-field tsunami detection, specifically for the area near the city of Padang, Indonesia. Padang is located on the western shore of Sumatra, directly across from the Mentawai segment of the Sunda Trench, where accumulated strain has not been released since the great earthquake of 1797. Consequently, the risk of a major tsunamigenic earthquake on this segment is high. Currently, no ocean-bottom pressure sensors are deployed in the Mentawai basin to provide a definitive tsunami warning for Padang. Timely warnings are essential to initiate evacuation procedures and minimize loss of human life. Our approach augments existing technology with a network of underwater sensors to detect tsunamis generated by an earthquake or landslide fast enough to provide at least 15 minutes of warning. Data from the underwater sensor network would feed into existing decision support systems that accept input from land and sea-based sensors and provide warning information to city and regional authorities.

  11. Carbon Nanotube Underwater Acoustic Thermophone

    Science.gov (United States)

    2016-09-23

    nanotubes (unless encapsulated or housed) are quite fragile and are susceptible to disintegration especially if the nanotubes are touched or moved too...The acoustic impedance (defined as the product of material density and sound speed) of the top shell 12 should match the Attorney Docket No. 300009

  12. Acoustic communication for Maya Autonomous Underwater Vehicle - performance evaluation of acoustic modem

    Digital Repository Service at National Institute of Oceanography (India)

    Afzulpurkar, S.; Maurya, P.; Navelkar, G.S.; Desa, E.S.; Mascarenhas, A.A.M.Q.; Dabholkar, N.A.; Madhan, R.; Prabhudesai, S.P.

    traffic. This necessitates monitoring the AUV status and data quality through an acoustic link which needs to perform reliably under such conditions, at long range. To address these situations partially, acoustic communication capability is planned...

  13. Polar Cooperative Navigation Algorithm for Multi-Unmanned Underwater Vehicles Considering Communication Delays

    Directory of Open Access Journals (Sweden)

    Zheping Yan

    2018-03-01

    Full Text Available To solve the navigation accuracy problems of multi-Unmanned Underwater Vehicles (multi-UUVs in the polar region, a polar cooperative navigation algorithm for multi-UUVs considering communication delays is proposed in this paper. UUVs are important pieces of equipment in ocean engineering for marine development. For UUVs to complete missions, precise navigation is necessary. It is difficult for UUVs to establish true headings because of the rapid convergence of Earth meridians and the severe polar environment. Based on the polar grid navigation algorithm, UUV navigation in the polar region can be accomplished with the Strapdown Inertial Navigation System (SINS in the grid frame. To save costs, a leader-follower type of system is introduced in this paper. The leader UUV helps the follower UUVs to achieve high navigation accuracy. Follower UUVs correct their own states based on the information sent by the leader UUV and the relative position measured by ultra-short baseline (USBL acoustic positioning. The underwater acoustic communication delay is quantized by the model. In this paper, considering underwater acoustic communication delay, the conventional adaptive Kalman filter (AKF is modified to adapt to polar cooperative navigation. The results demonstrate that the polar cooperative navigation algorithm for multi-UUVs that considers communication delays can effectively navigate the sailing of multi-UUVs in the polar region.

  14. An acoustic system for autonomous navigation and tracking of marine fauna

    KAUST Repository

    De la Torre, Pedro

    2014-08-01

    A marine acoustic system for underwater target tracking is described. This system is part of the Integrated Satellite and Acoustic Telemetry (iSAT) project to study marine fauna. It is a microcontroller-based underwater projector and receiver. A narrow-band, passive sonar detection architecture is described from signal generation, through transduction, reception, signal processing and up to tone extraction. Its circuit and operation principles are described. Finally, a comparison between the current energy detection method versus an alternative matched filter approach is included.

  15. Technical data report : marine acoustics modelling study

    Energy Technology Data Exchange (ETDEWEB)

    Chorney, N.; Warner, G.; Austin, M. [Jasco Applied Sciences, Victoria, BC (Canada)

    2010-07-01

    This study was conducted to predict the ensonification produced by vessel traffic transiting to and from the Enbridge Northern Gateway Project's marine terminal located near Kitimat, British Columbia (BC). An underwater acoustic propagation model was used to model frequency bands from 20 Hz to 5 kHz at a standard depth of 20 metres. The model included bathymetric grids of the modelling area; underwater sound speed as a function of depth; and geo-acoustic profiles based on the stratified composition of the seafloor. The obtained 1/3 octave band levels were then used to determine broadband received sound levels for 4 scenarios along various transit routes: the Langara and Triple Island in Dixon Entrance; the Browning Entrance in Hecate Strait, and Cape St. James in the Queen Charlotte Basin. The scenarios consisted of a tanker transiting at 16 knots, and an accompanying tug boat. Underwater sound level maps for each scenario were presented. 14 refs., 5 tabs., 16 figs.

  16. Passive Mode Carbon Nanotube Underwater Acoustic Transducer

    Science.gov (United States)

    2016-09-20

    Acoustical transducer arrays can reflect a sound signal in reverse to the sender which can be used for echo location devices. [0008] In Jiang...States Patent No. 8,494,187) a sound wave generator is disclosed which includes a carbon nanotube structure and an insulating reinforcement structure... acoustic device that includes an electrode layer and a sound wave generator. The sound wave generator is disposed on a surface of the electrode

  17. Hearing in the Juvenile Green Sea Turtle (Chelonia mydas: A Comparison of Underwater and Aerial Hearing Using Auditory Evoked Potentials.

    Directory of Open Access Journals (Sweden)

    Wendy E D Piniak

    Full Text Available Sea turtles spend much of their life in aquatic environments, but critical portions of their life cycle, such as nesting and hatching, occur in terrestrial environments, suggesting that it may be important for them to detect sounds in both air and water. In this study we compared underwater and aerial hearing sensitivities in five juvenile green sea turtles (Chelonia mydas by measuring auditory evoked potential responses to tone pip stimuli. Green sea turtles detected acoustic stimuli in both media, responding to underwater stimuli between 50 and 1600 Hz and aerial stimuli between 50 and 800 Hz, with maximum sensitivity between 200 and 400 Hz underwater and 300 and 400 Hz in air. When underwater and aerial hearing sensitivities were compared in terms of pressure, green sea turtle aerial sound pressure thresholds were lower than underwater thresholds, however they detected a wider range of frequencies underwater. When thresholds were compared in terms of sound intensity, green sea turtle sound intensity level thresholds were 2-39 dB lower underwater particularly at frequencies below 400 Hz. Acoustic stimuli may provide important environmental cues for sea turtles. Further research is needed to determine how sea turtles behaviorally and physiologically respond to sounds in their environment.

  18. International Conference on Underwater Environment

    CERN Document Server

    Jaulin, Luc; Creuze, Vincent; Debese, Nathalie; Quidu, Isabelle; Clement, Benoît; Billon-Coat, Annick

    2016-01-01

    This volume constitutes the results of the International Conference on Underwater Environment, MOQESM’14, held at “Le Quartz” Conference Center in Brest, France, on October 14-15, 2014, within the framework of the 9th Sea Tech Week, International Marine Science and Technology Event. The objective of MOQESM'14 was to bring together researchers from both academia and industry, interested in marine robotics and hydrography with application to the coastal environment mapping and underwater infrastructures surveys. The common thread of the conference is the combination of technical control, perception, and localization, typically used in robotics, with the methods of mapping and bathymetry. The papers presented in this book focus on two main topics. Firstly, coastal and infrastructure mapping is addressed, focusing not only on hydrographic systems, but also on positioning systems, bathymetry, and remote sensing. The proposed methods rely on acoustic sensors such as side scan sonars, multibeam echo sounders, ...

  19. A scalable global positioning system-free localization scheme for underwater wireless sensor networks

    KAUST Repository

    Mohammed, A.M.

    2013-05-07

    Seaweb is an acoustic communication technology that enables communication between sensor nodes. Seaweb technology utilizes the commercially available telesonar modems that has developed link and network layer firmware to provide a robust undersea communication capability. Seaweb interconnects the underwater nodes through digital signal processing-based modem by using acoustic links between the neighboring sensors. In this paper, we design and investigate a global positioning system-free passive localization protocol by integrating the innovations of levelling and localization with the Seaweb technology. This protocol uses the range data and planar trigonometry principles to estimate the positions of the underwater sensor nodes. Moreover, for precise localization, we consider more realistic conditions namely, (a) small displacement of sensor nodes due to watch circles and (b) deployment of sensor nodes over non-uniform water surface. Once the nodes are localized, we divide the whole network field into circular levels and sectors to minimize the traffic complexity and thereby increases the lifetime of the sensor nodes in the network field. We then form the mesh network inside each of the sectors that increases the reliability. The algorithm is designed in such a way that it overcomes the ambiguous nodes errata and reflected paths and therefore makes the algorithm more robust. The synthetic network geometries are so designed which can evaluate the algorithm in the presence of perfect or imperfect ranges or in case of incomplete data. A comparative study is made with the existing algorithms which proves the efficiency of our newly proposed algorithm. 2013 Mohammed et al.

  20. Underwater Broadband Source Localization Based on Modal Filtering and Features Extraction

    Directory of Open Access Journals (Sweden)

    Dominique Fattaccioli

    2010-01-01

    Full Text Available Passive source localization is a crucial issue in underwater acoustics. In this paper, we focus on shallow water environment (0 to 400 m and broadband Ultra-Low Frequency acoustic sources (1 to 100 Hz. In this configuration and at a long range, the acoustic propagation can be described by normal mode theory. The propagating signal breaks up into a series of depth-dependent modes. These modes carry information about the source position. Mode excitation factors and mode phases analysis allow, respectively, localization in depth and distance. We propose two different approaches to achieve the localization: multidimensional approach (using a horizontal array of hydrophones based on frequency-wavenumber transform (F-K method and monodimensional approach (using a single hydrophone based on adapted spectral representation (FTa method. For both approaches, we propose first complete tools for modal filtering, and then depth and distance estimators. We show that adding mode sign and source spectrum informations improves considerably the localization performance in depth. The reference acoustic field needed for depth localization is simulated with the new realistic propagation modelMoctesuma. The feasibility of both approaches, F-K and FTa, are validated on data simulated in shallow water for different configurations. The performance of localization, in depth and distance, is very satisfactory.

  1. Underwater Broadband Source Localization Based on Modal Filtering and Features Extraction

    Directory of Open Access Journals (Sweden)

    Cristol Xavier

    2010-01-01

    Full Text Available Passive source localization is a crucial issue in underwater acoustics. In this paper, we focus on shallow water environment (0 to 400 m and broadband Ultra-Low Frequency acoustic sources (1 to 100 Hz. In this configuration and at a long range, the acoustic propagation can be described by normal mode theory. The propagating signal breaks up into a series of depth-dependent modes. These modes carry information about the source position. Mode excitation factors and mode phases analysis allow, respectively, localization in depth and distance. We propose two different approaches to achieve the localization: multidimensional approach (using a horizontal array of hydrophones based on frequency-wavenumber transform ( method and monodimensional approach (using a single hydrophone based on adapted spectral representation ( method. For both approaches, we propose first complete tools for modal filtering, and then depth and distance estimators. We show that adding mode sign and source spectrum informations improves considerably the localization performance in depth. The reference acoustic field needed for depth localization is simulated with the new realistic propagation modelMoctesuma. The feasibility of both approaches, and , are validated on data simulated in shallow water for different configurations. The performance of localization, in depth and distance, is very satisfactory.

  2. Optimal Node Placement in Underwater Wireless Sensor Networks

    KAUST Repository

    Felamban, M.

    2013-03-25

    Wireless Sensor Networks (WSN) are expected to play a vital role in the exploration and monitoring of underwater areas which are not easily reachable by humans. However, underwater communication via acoustic waves is subject to several performance limitations that are very different from those used for terresstrial networks. In this paper, we investigate node placement for building an initial underwater WSN infrastructure. We formulate this problem as a nonlinear mathematical program with the objective of minimizing the total transmission loss under a given number of sensor nodes and targeted coverage volume. The obtained solution is the location of each node represented via a truncated octahedron to fill out the 3D space. Experiments are conducted to verify the proposed formulation, which is solved using Matlab optimization tool. Simulation is also conducted using an ns-3 simulator, and the simulation results are consistent with the obtained results from mathematical model with less than 10% error.

  3. Determination of the viscous acoustic field for liquid drop positioning/forcing in an acoustic levitation chamber in microgravity

    Science.gov (United States)

    Lyell, Margaret J.

    1992-01-01

    The development of acoustic levitation systems has provided a technology with which to undertake droplet studies as well as do containerless processing experiments in a microgravity environment. Acoustic levitation chambers utilize radiation pressure forces to position/manipulate the drop. Oscillations can be induced via frequency modulation of the acoustic wave, with the modulated acoustic radiation vector acting as the driving force. To account for tangential as well as radial forcing, it is necessary that the viscous effects be included in the acoustic field. The method of composite expansions is employed in the determination of the acoustic field with viscous effects.

  4. Full-field peak pressure prediction of shock waves from underwater explosion of cylindrical charges

    NARCIS (Netherlands)

    Liu, Lei; Guo, Rui; Gao, Ke; Zeng, Ming Chao

    2017-01-01

    Cylindrical charge is a main form in most application of explosives. By employing numerical calculation and an indirect mapping method, the relation between peak pressures from underwater explosion of cylindrical and spherical charges is investigated, and further a model to predict full-field peak

  5. Prevention of Pressure Oscillations in Modeling a Cavitating Acoustic Fluid

    Directory of Open Access Journals (Sweden)

    B. Klenow

    2010-01-01

    Full Text Available Cavitation effects play an important role in the UNDEX loading of a structure. For far-field UNDEX, the structural loading is affected by the formation of local and bulk cavitation regions, and the pressure pulses resulting from the closure of the cavitation regions. A common approach to numerically modeling cavitation in far-field underwater explosions is Cavitating Acoustic Finite Elements (CAFE and more recently Cavitating Acoustic Spectral Elements (CASE. Treatment of cavitation in this manner causes spurious pressure oscillations which must be treated by a numerical damping scheme. The focus of this paper is to investigate the severity of these oscillations on the structural response and a possible improvement to CAFE, based on the original Boris and Book Flux-Corrected Transport algorithm on structured meshes [6], to limit oscillations without the energy loss associated with the current damping schemes.

  6. Compression of a Deep Competitive Network Based on Mutual Information for Underwater Acoustic Targets Recognition

    Directory of Open Access Journals (Sweden)

    Sheng Shen

    2018-04-01

    Full Text Available The accuracy of underwater acoustic targets recognition via limited ship radiated noise can be improved by a deep neural network trained with a large number of unlabeled samples. However, redundant features learned by deep neural network have negative effects on recognition accuracy and efficiency. A compressed deep competitive network is proposed to learn and extract features from ship radiated noise. The core idea of the algorithm includes: (1 Competitive learning: By integrating competitive learning into the restricted Boltzmann machine learning algorithm, the hidden units could share the weights in each predefined group; (2 Network pruning: The pruning based on mutual information is deployed to remove the redundant parameters and further compress the network. Experiments based on real ship radiated noise show that the network can increase recognition accuracy with fewer informative features. The compressed deep competitive network can achieve a classification accuracy of 89.1 % , which is 5.3 % higher than deep competitive network and 13.1 % higher than the state-of-the-art signal processing feature extraction methods.

  7. Shallow Water Acoustics Studies

    Science.gov (United States)

    2017-11-19

    LE O CEAN RAPHIC I TITUTI Appli d Oc:ean Physics and E11gi1i,ering Depar1111,11t vember 9, 2017 Dr. Robert Headrick ffice of Naval Resear h, ode...UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT Applied Ocean Physics and Engineering Department...2015). [3] J.F. Lynch and A.E. Newhall, "Shallow water acoustics", book chapter in "Practical Underwater Acoustics," L. Bjorno, T. Neighbors, and D

  8. Coordinated Formation Control of Multiple Autonomous Underwater Vehicles for Pipeline Inspection

    Directory of Open Access Journals (Sweden)

    Xianbo Xiang

    2010-02-01

    Full Text Available This paper addresses the control problem of inspecting underwater pipeline on the seabed, with coordinated multiple autonomous underwater vehicles in a formation. Based on the leader-follower strategy, the dedicated nonlinear path following controller is rigorously built on Lyapunov-based design, driving a fleet of vehicles onto assigned parallel paths elevated and offset from the underwater pipeline, while keeping a triangle formation to capture complete 3D images for inspection. Due to the spatial-temporal decoupling characteristics of individual path following controller, the velocities of the followers can be adapted in the coordinated control level, only relying on the information of generalized along-path length from the leader, in order to build the desired formation. Thus, the communication variable broadcast from the leader is kept to a minimum, which is feasible under the severely constraints of acoustic communication bandwidth. Simulation results illustrate the efficiency of coordinated formation controller proposed for underwater pipeline inspection.

  9. Asymmetric Propagation Delay-Aware TDMA MAC Protocol for Mobile Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    A-Ra Cho

    2018-06-01

    Full Text Available The propagation delay in mobile underwater acoustic sensor network (MUASN is asymmetric because of its low sound propagation speed, and this asymmetry grows with the increase in packet travel time, which damages the collision avoidance mechanism of the spatial reuse medium access control (MAC protocols for MUASN. We propose an asymmetric propagation delay-aware time division multiple access (APD-TDMA for a MUASN in which periodic data packet transmission is required for a sink node (SN. Collisions at the SN are avoided by deferring data packet transmission after reception of a beacon packet from the SN, and data packets are arrived at the SN in a packet-train manner. The time-offset, which is the time for a node to wait before the transmission of a data packet after reception of a beacon packet, is determined by estimating the propagation delay over two consecutive cycles such that the idle interval at the SN is minimized, and this time-offset is announced by the beacon packet. Simulation results demonstrate that the APD-TDMA improves the channel access delay and the channel utilization by approximately 20% and 30%, respectively, compared with those of the block time bounded TDMA under the given network conditions.

  10. Acoustic Communications and Navigation for Mobile Under-Ice Sensors

    Science.gov (United States)

    2017-02-04

    contact below the ice. 15. SUBJECT TERMS Arctic Ocean , Undersea Workstations & Vehicles, Signal Processing, Navigation , Underwater Acoustics 16...Partan, Peter Koski, and Sandipa Singh, "Long Range Acoustic Communications and Navigation in the Arctic", Proc. IEEE/MTS Oceans Conf., Washington, DC...Oct. 2015. Freitag, L., P. Koski, A. Morozov, S. Singh, J. Partan, "Acoustic Communications and Navigation Under Arctic Ice", OCEANS , 2012

  11. DE-Sync: A Doppler-Enhanced Time Synchronization for Mobile Underwater Sensor Networks.

    Science.gov (United States)

    Zhou, Feng; Wang, Qi; Nie, DongHu; Qiao, Gang

    2018-05-25

    Time synchronization is the foundation of cooperative work among nodes of underwater sensor networks; it takes a critical role in the research and application of underwater sensor networks. Although numerous time synchronization protocols have been proposed for terrestrial wireless sensor networks, they cannot be directly applied to underwater sensor networks. This is because most of them typically assume that the propagation delay among sensor nodes is negligible, which is not the case in underwater sensor networks. Time synchronization is mainly affected by a long propagation delay among sensor nodes due to the low propagation speed of acoustic signals. Furthermore, sensor nodes in underwater tend to experience some degree of mobility due to wind or ocean current, or some other nodes are on self-propelled vehicles, such as autonomous underwater vehicles (AUVs). In this paper, we propose a Doppler-enhanced time synchronization scheme for mobile underwater sensor networks, called DE-Sync. Our new scheme considers the effect of the clock skew during the process of estimating the Doppler scale factor and directly substitutes the Doppler scale factor into linear regression to achieve the estimation of the clock skew and offset. Simulation results show that DE-Sync outperforms existing time synchronization protocols in both accuracy and energy efficiency.

  12. Non-contact transportation using near-field acoustic levitation

    Science.gov (United States)

    Ueha; Hashimoto; Koike

    2000-03-01

    Near-field acoustic levitation, where planar objects 10 kg in weight can levitate stably near the vibrating plate, is successfully applied both to non-contact transportation of objects and to a non-contact ultrasonic motor. Transporting apparatuses and an ultrasonic motor have been fabricated and their characteristics measured. The theory of near-field acoustic levitation both for a piston-like sound source and a flexural vibration source is also briefly described.

  13. Transducers and arrays for underwater sound

    CERN Document Server

    Butler, John L

    2016-01-01

    This improved and updated second edition covers the theory, development, and design of electro-acoustic transducers for underwater applications. This highly regarded text discusses the basics of piezoelectric and magnetostrictive transducers that are currently being used as well as promising new designs. It presents the basic acoustics as well as the specific acoustics data needed in transducer design and evaluation. A broad range of designs of projectors and hydrophones are described in detail along with methods of modeling, evaluation, and measurement. Analysis of projector and hydrophone transducer arrays, including the effects of mutual radiation impedance and numerical models for elements and arrays, are also covered. The book includes new advances in transducer design and transducer materials and has been completely reorganized to be suitable for use as a textbook, as well as a reference or handbook. The new edition contains updates to the first edition, end-of-chapter exercises, and solutions to select...

  14. Induced clustering of Escherichia coli by acoustic fields.

    Science.gov (United States)

    Gutiérrez-Ramos, Salomé; Hoyos, Mauricio; Ruiz-Suárez, J C

    2018-03-16

    Brownian or self-propelled particles in aqueous suspensions can be trapped by acoustic fields generated by piezoelectric transducers usually at frequencies in the megahertz. The obtained confinement allows the study of rich collective behaviours like clustering or spreading dynamics in microgravity-like conditions. The acoustic field induces the levitation of self-propelled particles and provides secondary lateral forces to capture them at nodal planes. Here, we give a step forward in the field of confined active matter, reporting levitation experiments of bacterial suspensions of Escherichia coli. Clustering of living bacteria is monitored as a function of time, where different behaviours are clearly distinguished. Upon the removal of the acoustic signal, bacteria rapidly spread, impelled by their own swimming. Nevertheless, long periods of confinement result in irreversible bacteria entanglements that could act as seeds for levitating bacterial aggregates.

  15. Aspect-dependent radiated noise analysis of an underway autonomous underwater vehicle.

    Science.gov (United States)

    Gebbie, John; Siderius, Martin; Allen, John S

    2012-11-01

    This paper presents an analysis of the acoustic emissions emitted by an underway REMUS-100 autonomous underwater vehicle (AUV) that were obtained near Honolulu Harbor, HI using a fixed, bottom-mounted horizontal line array (HLA). Spectral analysis, beamforming, and cross-correlation facilitate identification of independent sources of noise originating from the AUV. Fusion of navigational records from the AUV with acoustic data from the HLA allows for an aspect-dependent presentation of calculated source levels of the strongest propulsion tone.

  16. AFSC/ABL: Autonomous underwater vehicle for tracking acoustically-tagged fish 2010

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Autonomous underwater vehicles (AUVs) are increasingly being used to collect physical, chemical, and biological information in the marine environment. Recent efforts...

  17. ECS: Efficient Communication Scheduling for Underwater Sensor Networks

    Directory of Open Access Journals (Sweden)

    Lu Hong

    2011-03-01

    Full Text Available TDMA protocols have attracted a lot of attention for underwater acoustic sensor networks (UWSNs, because of the unique characteristics of acoustic signal propagation such as great energy consumption in transmission, long propagation delay and long communication range. Previous TDMA protocols all allocated transmission time to nodes based on discrete time slots. This paper proposes an efficient continuous time scheduling TDMA protocol (ECS for UWSNs, including the continuous time based and sender oriented conflict analysis model, the transmission moment allocation algorithm and the distributed topology maintenance algorithm. Simulation results confirm that ECS improves network throughput by 20% on average, compared to existing MAC protocols.

  18. Field-Deployable Acoustic Digital Systems for Noise Measurement

    Science.gov (United States)

    Shams, Qamar A.; Wright, Kenneth D.; Lunsford, Charles B.; Smith, Charlie D.

    2000-01-01

    Langley Research Center (LaRC) has for years been a leader in field acoustic array measurement technique. Two field-deployable digital measurement systems have been developed to support acoustic research programs at LaRC. For several years, LaRC has used the Digital Acoustic Measurement System (DAMS) for measuring the acoustic noise levels from rotorcraft and tiltrotor aircraft. Recently, a second system called Remote Acquisition and Storage System (RASS) was developed and deployed for the first time in the field along with DAMS system for the Community Noise Flight Test using the NASA LaRC-757 aircraft during April, 2000. The test was performed at Airborne Airport in Wilmington, OH to validate predicted noise reduction benefits from alternative operational procedures. The test matrix was composed of various combinations of altitude, cutback power, and aircraft weight. The DAMS digitizes the acoustic inputs at the microphone site and can be located up to 2000 feet from the van which houses the acquisition, storage and analysis equipment. Digitized data from up to 10 microphones is recorded on a Jaz disk and is analyzed post-test by microcomputer system. The RASS digitizes and stores acoustic inputs at the microphone site that can be located up to three miles from the base station and can compose a 3 mile by 3 mile array of microphones. 16-bit digitized data from the microphones is stored on removable Jaz disk and is transferred through a high speed array to a very large high speed permanent storage device. Up to 30 microphones can be utilized in the array. System control and monitoring is accomplished via Radio Frequency (RF) link. This paper will present a detailed description of both systems, along with acoustic data analysis from both systems.

  19. Some far-field acoustics characteristics of the XV-15 tilt-rotor aircraft

    Science.gov (United States)

    Golub, Robert A.; Conner, David A.; Becker, Lawrence E.; Rutledge, C. Kendall; Smith, Rita A.

    1990-01-01

    Far-field acoustics tests have been conducted on an instrumented XV-15 tilt-rotor aircraft. The purpose of these acoustic measurements was to create an encompassing, high confidence (90 percent), and accurate (-1.4/ +1/8 dB theoretical confidence interval) far-field acoustics data base to validate ROTONET and other current rotorcraft noise prediction computer codes. This paper describes the flight techniques used, with emphasis on the care taken to obtain high-quality far-field acoustic data. The quality and extensiveness of the data base collected are shown by presentation of ground acoustic contours for level flyovers for the airplane flight mode and for several forward velocities and nacelle tilts for the transition mode and helicopter flight mode. Acoustic pressure time-histories and fully analyzed ensemble averaged far-field data results (spectra) are shown for each of the ground contour cases.

  20. Active control of passive acoustic fields: passive synthetic aperture/Doppler beamforming with data from an autonomous vehicle.

    Science.gov (United States)

    D'Spain, Gerald L; Terrill, Eric; Chadwell, C David; Smith, Jerome A; Lynch, Stephen D

    2006-12-01

    The maneuverability of autonomous underwater vehicles (AUVs) equipped with hull-mounted arrays provides the opportunity to actively modify received acoustic fields to optimize extraction of information. This paper uses ocean acoustic data collected by an AUV-mounted two-dimensional hydrophone array, with overall dimension one-tenth wavelength at 200-500 Hz, to demonstrate aspects of this control through vehicle motion. Source localization is performed using Doppler shifts measured at a set of receiver velocities by both single elements and a physical array. Results show that a source in the presence of a 10-dB higher-level interferer having exactly the same frequency content (as measured by a stationary receiver) is properly localized and that white-noise-constrained adaptive beamforming applied to the physical aperture data in combination with Doppler beamforming provides greater spatial resolution than physical-aperture-alone beamforming and significantly lower sidelobes than single element Doppler beamforming. A new broadband beamformer that adjusts for variations in vehicle velocity on a sample by sample basis is demonstrated with data collected during a high-acceleration maneuver. The importance of including the cost of energy expenditure in determining optimal vehicle motion is demonstrated through simulation, further illustrating how the vehicle characteristics are an integral part of the signal/array processing structure.

  1. Long-term measurements of acoustic background noise in very deep sea

    International Nuclear Information System (INIS)

    Riccobene, G.

    2009-01-01

    The NEMO (NEutrino Mediterranean Observatory) Collaboration installed, 25 km E offshore the port of Catania (Sicily) at 2000 m depth, an underwater laboratory to perform long-term tests of prototypes and new technologies for an underwater high energy neutrino km 3 -scale detector in the Mediterranean Sea. In this framework the Collaboration deployed and successfully operated for about two years, starting from January 2005, an experimental apparatus for on-line monitoring of deep-sea noise. The station was equipped with four hydrophones and it is operational in the range 30 Hz-43 kHz. This interval of frequencies matches the range suitable for the proposed acoustic detection technique of high energy neutrinos. Hydrophone signals were digitized underwater at 96 kHz sampling frequency and 24 bits resolution. The stored data library, consisting of more than 2000 h of recordings, is a unique tool to model underwater acoustic noise at large depth, to characterize its variations as a function of environmental parameters, biological sources and human activities (ship traffic, etc.), and to determine the presence of cetaceans in the area.

  2. Annotated Bibliography of Underwater Acoustic Research, 1942-1945.

    Science.gov (United States)

    1983-11-02

    easily be produced in underwater-telephony adapter was quantities by existing facilities at sea-tested on USS LIONFISH . The New the Submarine Base...including 7500 lacquering, waxing, making and yd, with the LIONFISH operating fitting pointers, and maintenance, underway at periscope deptn and the Two...R61 1-452 D24/R62i -462 * USS PERCH (SS-313) USS JORDAN (DE204) D24/R736-564 P42 /R75 9-584 D16/R1388-i 152 D24/R780-603 054 /R992-783 USS LIONFISH (SS

  3. Assessing the Underwater Acoustics of the World's Largest Vibration Hammer (OCTA-KONG) and Its Potential Effects on the Indo-Pacific Humpbacked Dolphin (Sousa chinensis)

    Science.gov (United States)

    Wang, Zhitao; Wu, Yuping; Duan, Guoqin; Cao, Hanjiang; Liu, Jianchang; Wang, Kexiong; Wang, Ding

    2014-01-01

    Anthropogenic noise in aquatic environments is a worldwide concern due to its potential adverse effects on the environment and aquatic life. The Hongkong-Zhuhai-Macao Bridge is currently under construction in the Pearl River Estuary, a hot spot for the Indo-Pacific humpbacked dolphin (Sousa chinensis) in China. The OCTA-KONG, the world's largest vibration hammer, is being used during this construction project to drive or extract steel shell piles 22 m in diameter. This activity poses a substantial threat to marine mammals, and an environmental assessment is critically needed. The underwater acoustic properties of the OCTA-KONG were analyzed, and the potential impacts of the underwater acoustic energy on Sousa, including auditory masking and physiological impacts, were assessed. The fundamental frequency of the OCTA-KONG vibration ranged from 15 Hz to 16 Hz, and the noise increments were below 20 kHz, with a dominant frequency and energy below 10 kHz. The resulting sounds are most likely detectable by Sousa over distances of up to 3.5 km from the source. Although Sousa clicks do not appear to be adversely affected, Sousa whistles are susceptible to auditory masking, which may negatively impact this species' social life. Therefore, a safety zone with a radius of 500 m is proposed. Although the zero-to-peak source level (SL) of the OCTA-KONG was lower than the physiological damage level, the maximum root-mean-square SL exceeded the cetacean safety exposure level on several occasions. Moreover, the majority of the unweighted cumulative source sound exposure levels (SSELs) and the cetacean auditory weighted cumulative SSELs exceeded the acoustic threshold levels for the onset of temporary threshold shift, a type of potentially recoverable auditory damage resulting from prolonged sound exposure. These findings may aid in the identification and design of appropriate mitigation methods, such as the use of air bubble curtains, “soft start” and “power down

  4. Assessing the underwater acoustics of the world's largest vibration hammer (OCTA-KONG and its potential effects on the Indo-Pacific humpbacked dolphin (Sousa chinensis.

    Directory of Open Access Journals (Sweden)

    Zhitao Wang

    Full Text Available Anthropogenic noise in aquatic environments is a worldwide concern due to its potential adverse effects on the environment and aquatic life. The Hongkong-Zhuhai-Macao Bridge is currently under construction in the Pearl River Estuary, a hot spot for the Indo-Pacific humpbacked dolphin (Sousa chinensis in China. The OCTA-KONG, the world's largest vibration hammer, is being used during this construction project to drive or extract steel shell piles 22 m in diameter. This activity poses a substantial threat to marine mammals, and an environmental assessment is critically needed. The underwater acoustic properties of the OCTA-KONG were analyzed, and the potential impacts of the underwater acoustic energy on Sousa, including auditory masking and physiological impacts, were assessed. The fundamental frequency of the OCTA-KONG vibration ranged from 15 Hz to 16 Hz, and the noise increments were below 20 kHz, with a dominant frequency and energy below 10 kHz. The resulting sounds are most likely detectable by Sousa over distances of up to 3.5 km from the source. Although Sousa clicks do not appear to be adversely affected, Sousa whistles are susceptible to auditory masking, which may negatively impact this species' social life. Therefore, a safety zone with a radius of 500 m is proposed. Although the zero-to-peak source level (SL of the OCTA-KONG was lower than the physiological damage level, the maximum root-mean-square SL exceeded the cetacean safety exposure level on several occasions. Moreover, the majority of the unweighted cumulative source sound exposure levels (SSELs and the cetacean auditory weighted cumulative SSELs exceeded the acoustic threshold levels for the onset of temporary threshold shift, a type of potentially recoverable auditory damage resulting from prolonged sound exposure. These findings may aid in the identification and design of appropriate mitigation methods, such as the use of air bubble curtains, "soft start" and "power down

  5. Novel acoustic technology for studying free-ranging shark social behaviour by recording individuals' interactions.

    Directory of Open Access Journals (Sweden)

    Tristan L Guttridge

    Full Text Available Group behaviours are widespread among fish but comparatively little is known about the interactions between free-ranging individuals and how these might change across different spatio-temporal scales. This is largely due to the difficulty of observing wild fish groups directly underwater over long enough time periods to quantify group structure and individual associations. Here we describe the use of a novel technology, an animal-borne acoustic proximity receiver that records close-spatial associations between free-ranging fish by detection of acoustic signals emitted from transmitters on other individuals. Validation trials, held within enclosures in the natural environment, on juvenile lemon sharks Negaprion brevirostris fitted with external receivers and transmitters, showed receivers logged interactions between individuals regularly when sharks were within 4 m ( approximately 4 body lengths of each other, but rarely when at 10 m distance. A field trial lasting 17 days with 5 juvenile lemon sharks implanted with proximity receivers showed one receiver successfully recorded association data, demonstrating this shark associated with 9 other juvenile lemon sharks on 128 occasions. This study describes the use of acoustic underwater proximity receivers to quantify interactions among wild sharks, setting the scene for new advances in understanding the social behaviours of marine animals.

  6. Research on the Combination of Underwater Acoustic Countermeasure Equipments Against Torpedo

    Directory of Open Access Journals (Sweden)

    Meng Jie

    2016-01-01

    Full Text Available Today the use of acoustic countermeasure equipment has become the main means in submarine defense torpedo operation. Combination of acoustic countermeasure equipments are used during the operation so that we can amplify the countermeasure effect. Based on the subject of the acoustic countermeasure equipments’ combined use, this paper analyses the interference between these soft kill countermeasure equipments including gas curtain, acoustic decoy and acoustic interferometer, summarizes the advantages and disadvantages of the different combined use of acoustic countermeasure equipments.

  7. Directional Acoustic Wave Manipulation by a Porpoise via Multiphase Forehead Structure

    Science.gov (United States)

    Zhang, Yu; Song, Zhongchang; Wang, Xianyan; Cao, Wenwu; Au, Whitlow W. L.

    2017-12-01

    Porpoises are small-toothed whales, and they can produce directional acoustic waves to detect and track prey with high resolution and a wide field of view. Their sound-source sizes are rather small in comparison with the wavelength so that beam control should be difficult according to textbook sonar theories. Here, we demonstrate that the multiphase material structure in a porpoise's forehead is the key to manipulating the directional acoustic field. Computed tomography (CT) derives the multiphase (bone-air-tissue) complex, tissue experiments obtain the density and sound-velocity multiphase gradient distributions, and acoustic fields and beam formation are numerically simulated. The results suggest the control of wave propagations and sound-beam formations is realized by cooperation of the whole forehead's tissues and structures. The melon size significantly impacts the side lobes of the beam and slightly influences the main beams, while the orientation of the vestibular sac mainly adjusts the main beams. By compressing the forehead complex, the sound beam can be expanded for near view. The porpoise's biosonar allows effective wave manipulations for its omnidirectional sound source, which can help the future development of miniaturized biomimetic projectors in underwater sonar, medical ultrasonography, and other ultrasonic imaging applications.

  8. Synthetical optimization of hydraulic radius and acoustic field for thermoacoustic cooler

    International Nuclear Information System (INIS)

    Kang Huifang; Li Qing; Zhou Gang

    2009-01-01

    It is well known that the acoustic field and the hydraulic radius of the regenerator play key roles in thermoacoustic processes. The optimization of hydraulic radius strongly depends on the acoustic field in the regenerator. This paper investigates the synthetical optimization of hydraulic radius and acoustic field which is characterized by the ratio of the traveling wave component to the standing wave component. In this paper, we discussed the heat flux, cooling power, temperature gradient and coefficient of performance of thermoacoustic cooler with different combinations of hydraulic radiuses and acoustic fields. The calculation results show that, in the cooler's regenerator, due to the acoustic wave, the heat is transferred towards the pressure antinodes in the pure standing wave, while the heat is transferred in the opposite direction of the wave propagation in the pure traveling wave. The better working condition for the regenerator appears in the traveling wave phase region of the like-standing wave, where the directions of the heat transfer by traveling wave component and standing wave component are the same. Otherwise, the small hydraulic radius is not a good choice for acoustic field with excessively high ratio of traveling wave, and the small hydraulic radius is only needed by the traveling wave phase region of like-standing wave.

  9. HARDWARE REALIZATION OF CANNY EDGE DETECTION ALGORITHM FOR UNDERWATER IMAGE SEGMENTATION USING FIELD PROGRAMMABLE GATE ARRAYS

    Directory of Open Access Journals (Sweden)

    ALEX RAJ S. M.

    2017-09-01

    Full Text Available Underwater images raise new challenges in the field of digital image processing technology in recent years because of its widespread applications. There are many tangled matters to be considered in processing of images collected from water medium due to the adverse effects imposed by the environment itself. Image segmentation is preferred as basal stage of many digital image processing techniques which distinguish multiple segments in an image and reveal the hidden crucial information required for a peculiar application. There are so many general purpose algorithms and techniques that have been developed for image segmentation. Discontinuity based segmentation are most promising approach for image segmentation, in which Canny Edge detection based segmentation is more preferred for its high level of noise immunity and ability to tackle underwater environment. Since dealing with real time underwater image segmentation algorithm, which is computationally complex enough, an efficient hardware implementation is to be considered. The FPGA based realization of the referred segmentation algorithm is presented in this paper.

  10. Forecast of Remote Underwater Sensing Technology.

    Science.gov (United States)

    1980-07-01

    Ndgrt o oth NIA ye ’ Suite 709NrtFaothMAO5i Arligton VA 2202Attn: Dave Ho0soci, Chief Enginee~r Attn : Jay W. -arford, Manlager, (617) 563-59)17 (703...0,1305 Attn: Dr. A. Zielinski , Asst. Professor Attn: C. R. B. Lister Faculty of Engineering and (20t) 325-5497 Applied Science (709) 753-1200 Lockheed...157. Zielinski , A.; Barbour, L.; "Swept Carrier Acoustic Underwater Communica- tions," IEEE/MTS Oceans 󈨒, Washington, DC, Sept. 6-8, 1978. 158

  11. New developments in near-field acoustic holography

    NARCIS (Netherlands)

    Roozen, N.B.; Geerlings, A.C.; Verhaar, B.T.; Vliegenthart, T.

    2007-01-01

    In the field of noise-control engineering, information about the individual strength, andlocation, of the most dominant sources is of vital importance. This information allows theacoustic engineer to take effective measures in his effort to reduce the emitted acoustic noiselevels. Near-field

  12. Real-time temperature field measurement based on acoustic tomography

    International Nuclear Information System (INIS)

    Bao, Yong; Jia, Jiabin; Polydorides, Nick

    2017-01-01

    Acoustic tomography can be used to measure the temperature field from the time-of-flight (TOF). In order to capture real-time temperature field changes and accurately yield quantitative temperature images, two improvements to the conventional acoustic tomography system are studied: simultaneous acoustic transmission and TOF collection along multiple ray paths, and an offline iteration reconstruction algorithm. During system operation, all the acoustic transceivers send modulated and filtered wideband Kasami sequences simultaneously to facilitate fast and accurate TOF measurements using cross-correlation detection. For image reconstruction, the iteration process is separated and executed offline beforehand to shorten computation time for online temperature field reconstruction. The feasibility and effectiveness of the developed methods are validated in the simulation study. The simulation results demonstrate that the proposed method can reduce the processing time per frame from 160 ms to 20 ms, while the reconstruction error remains less than 5%. Hence, the proposed method has great potential in the measurement of rapid temperature change with good temporal and spatial resolution. (paper)

  13. Acoustic Tweezing and Patterning of Concentration Fields in Microfluidics

    DEFF Research Database (Denmark)

    Karlsen, Jonas Tobias; Bruus, Henrik

    2017-01-01

    that weakly perturb the fluid density and speed of sound is presented and applied to study manipulation of concentration fields in rectangular-channel acoustic eigenmodes and in Bessel-function acoustic vortices. In the first example, methods to obtain horizontal and vertical multilayer stratification...

  14. Female harbor seal (Phoca vitulina) behavioral response to playbacks of underwater male acoustic advertisement displays.

    Science.gov (United States)

    Matthews, Leanna P; Blades, Brittany; Parks, Susan E

    2018-01-01

    During the breeding season, male harbor seals ( Phoca vitulina ) make underwater acoustic displays using vocalizations known as roars. These roars have been shown to function in territory establishment in some breeding areas and have been hypothesized to be important for female choice, but the function of these sounds remains unresolved. This study consisted of a series of playback experiments in which captive female harbor seals were exposed to recordings of male roars to determine if females respond to recordings of male vocalizations and whether or not they respond differently to roars from categories with different acoustic characteristics. The categories included roars with characteristics of dominant males (longest duration, lowest frequency), subordinate males (shortest duration, highest frequency), combinations of call parameters from dominant and subordinate males (long duration, high frequency and short duration, low frequency), and control playbacks of water noise and water noise with tonal signals in the same frequency range as male signals. Results indicate that overall females have a significantly higher level of response to playbacks that imitate male vocalizations when compared to control playbacks of water noise. Specifically, there was a higher level of response to playbacks representing dominant male vocalization when compared to the control playbacks. For most individuals, there was a greater response to playbacks representing dominant male vocalizations compared to playbacks representing subordinate male vocalizations; however, there was no statistical difference between those two playback types. Additionally, there was no difference between the playbacks of call parameter combinations and the controls. Investigating female preference for male harbor seal vocalizations is a critical step in understanding the harbor seal mating system and further studies expanding on this captive study will help shed light on this important issue.

  15. Validation of Underwater Sensor Package Using Feature Based SLAM

    Directory of Open Access Journals (Sweden)

    Christopher Cain

    2016-03-01

    Full Text Available Robotic vehicles working in new, unexplored environments must be able to locate themselves in the environment while constructing a picture of the objects in the environment that could act as obstacles that would prevent the vehicles from completing their desired tasks. In enclosed environments, underwater range sensors based off of acoustics suffer performance issues due to reflections. Additionally, their relatively high cost make them less than ideal for usage on low cost vehicles designed to be used underwater. In this paper we propose a sensor package composed of a downward facing camera, which is used to perform feature tracking based visual odometry, and a custom vision-based two dimensional rangefinder that can be used on low cost underwater unmanned vehicles. In order to examine the performance of this sensor package in a SLAM framework, experimental tests are performed using an unmanned ground vehicle and two feature based SLAM algorithms, the extended Kalman filter based approach and the Rao-Blackwellized, particle filter based approach, to validate the sensor package.

  16. Validation of Underwater Sensor Package Using Feature Based SLAM

    Science.gov (United States)

    Cain, Christopher; Leonessa, Alexander

    2016-01-01

    Robotic vehicles working in new, unexplored environments must be able to locate themselves in the environment while constructing a picture of the objects in the environment that could act as obstacles that would prevent the vehicles from completing their desired tasks. In enclosed environments, underwater range sensors based off of acoustics suffer performance issues due to reflections. Additionally, their relatively high cost make them less than ideal for usage on low cost vehicles designed to be used underwater. In this paper we propose a sensor package composed of a downward facing camera, which is used to perform feature tracking based visual odometry, and a custom vision-based two dimensional rangefinder that can be used on low cost underwater unmanned vehicles. In order to examine the performance of this sensor package in a SLAM framework, experimental tests are performed using an unmanned ground vehicle and two feature based SLAM algorithms, the extended Kalman filter based approach and the Rao-Blackwellized, particle filter based approach, to validate the sensor package. PMID:26999142

  17. SIMULATION AND ANALYSIS OF GREEDY ROUTING PROTOCOL IN VIEW OF ENERGY CONSUMPTION AND NETWORK LIFETIME IN THREE DIMENSIONAL UNDERWATER WIRELESS SENSOR NETWORK

    Directory of Open Access Journals (Sweden)

    SHEENA KOHLI

    2017-11-01

    Full Text Available Underwater Wireless Sensor Network (UWSN comprises of a number of miniature sized sensing devices deployed in the sea or ocean, connected by dint of acoustic links to each other. The sensors trap the ambient conditions and transmit the data from one end to another. For transmission of data in any medium, routing protocols play a crucial role. Moreover, being battery limited, an unavoidable parameter to be considered in operation and analysis of protocols is the network energy and the network lifetime. The paper discusses the greedy routing protocol for underwater wireless sensor networks. The simulation of this routing protocol also takes into consideration the characteristics of acoustic communication like attenuation, transmission loss, signal to noise ratio, noise, propagation delay. The results from these observations may be used to construct an accurate underwater communication model.

  18. A new electronic control system for unmanned underwater vehicles

    OpenAIRE

    Molina Molina, J.C.; Guerrero González, A.; Gilabert, J.

    2015-01-01

    In this paper a new electronic control system for unmanned underwater vehicles is presented. This control system is characterized by a distribution in control over two network of type CANBus and Ethernet. This new electronic control system integrates functionalities of AUVs, as the automatic execution of preprogrammed trajectories. The control system also integrates an acoustic positioning system based on USBL. The information of relative positioning is sent through specific...

  19. Stability analysis of hybrid-driven underwater glider

    Science.gov (United States)

    Niu, Wen-dong; Wang, Shu-xin; Wang, Yan-hui; Song, Yang; Zhu, Ya-qiang

    2017-10-01

    Hybrid-driven underwater glider is a new type of unmanned underwater vehicle, which combines the advantages of autonomous underwater vehicles and traditional underwater gliders. The autonomous underwater vehicles have good maneuverability and can travel with a high speed, while the traditional underwater gliders are highlighted by low power consumption, long voyage, long endurance and good stealth characteristics. The hybrid-driven underwater gliders can realize variable motion profiles by their own buoyancy-driven and propeller propulsion systems. Stability of the mechanical system determines the performance of the system. In this paper, the Petrel-II hybrid-driven underwater glider developed by Tianjin University is selected as the research object and the stability of hybrid-driven underwater glider unitedly controlled by buoyancy and propeller has been targeted and evidenced. The dimensionless equations of the hybrid-driven underwater glider are obtained when the propeller is working. Then, the steady speed and steady glide path angle under steady-state motion have also been achieved. The steady-state operating conditions can be calculated when the hybrid-driven underwater glider reaches the desired steady-state motion. And the steadystate operating conditions are relatively conservative at the lower bound of the velocity range compared with the range of the velocity derived from the method of the composite Lyapunov function. By calculating the hydrodynamic coefficients of the Petrel-II hybrid-driven underwater glider, the simulation analysis has been conducted. In addition, the results of the field trials conducted in the South China Sea and the Danjiangkou Reservoir of China have been presented to illustrate the validity of the analysis and simulation, and to show the feasibility of the method of the composite Lyapunov function which verifies the stability of the Petrel-II hybrid-driven underwater glider.

  20. DUMAND-II (deep underwater muon and neutrino detector) progress report

    Science.gov (United States)

    Young, Kenneth K.

    1995-07-01

    The DUMAND II detector will search for astronomical sources of high energy neutrinos. Successful deployment of the basic infrastructure, including the shore cable, the underwater junction box, and an environmental module was accomplished in December, 1993. One optical module string was also deployed and operated, logging data for about 10 hours. The underwater cable was connected to the shore station where we were able to successfully exercise system controls and log further environmental data. After this time, water leaking into the electronics control module for the deployed string disabled the string electrical system. The acquired data are consistent with the expected rate of downgoing muons, and our ability to reconstruct muons was demonstrated. The measured acoustical backgrounds are consistent with expectation, which should allow acoustical detection of nearby PeV particle cascades. The disabled string has been recovered and is undergoing repairs ashore. We have identified the source of the water leak and implemented additional testing and QC procedures to ensure no repetition in our next deployment. We will be ready to deploy three strings and begin continuous data taking in late 1994 or early 1995.

  1. An algebraic perspective to single-transponder underwater navigation

    DEFF Research Database (Denmark)

    Jouffroy, Jerome; Reger, Johann

    This paper studies the position estimation of an underwater vehicle using a single acoustic transponder. The chosen estimation approach is based on nonlinear differential algebraic methods which allow to express very simply conditions for observability. These are then used in combination with an ...... with an integrator-based time-derivative estimation technique to design an algebraic estimator, which, contrary to asymptotic observers, does not require sometimes tedious convergence verification. Simple simulation results are presented to illustrate the approach....

  2. Ultrasound acoustic wave energy transfer and harvesting

    Science.gov (United States)

    Shahab, Shima; Leadenham, Stephen; Guillot, François; Sabra, Karim; Erturk, Alper

    2014-04-01

    This paper investigates low-power electricity generation from ultrasound acoustic wave energy transfer combined with piezoelectric energy harvesting for wireless applications ranging from medical implants to naval sensor systems. The focus is placed on an underwater system that consists of a pulsating source for spherical wave generation and a harvester connected to an external resistive load for quantifying the electrical power output. An analytical electro-acoustic model is developed to relate the source strength to the electrical power output of the harvester located at a specific distance from the source. The model couples the energy harvester dynamics (piezoelectric device and electrical load) with the source strength through the acoustic-structure interaction at the harvester-fluid interface. Case studies are given for a detailed understanding of the coupled system dynamics under various conditions. Specifically the relationship between the electrical power output and system parameters, such as the distance of the harvester from the source, dimensions of the harvester, level of source strength, and electrical load resistance are explored. Sensitivity of the electrical power output to the excitation frequency in the neighborhood of the harvester's underwater resonance frequency is also reported.

  3. A Survey on Underwater Wireless Sensor Networks: Progresses, Applications, and Challenges

    Directory of Open Access Journals (Sweden)

    Premalatha J.

    2016-01-01

    Full Text Available The endangered underwater species always drew the attention of the scientific society since their disappearance would cause irreplaceable loss. Asia is home to some of the most diverse habitats in the earth, but it is estimated that more than one in four species are endangered. In Underwater, a lot of factors are putting marine life under immense pressure. Extreme population pressure is leading to pollution, over-fishing and the devastation of crucial habitats. Consequently, the numbers of almost all fish are declining and many are already endangered. To help these species to survive, their habitat should be strictly protected. This can be achieved by strictly monitoring them. During this course, several parameters, constraints about the species and its environments are focused. Now, advances in sensor technology facilitate the monitoring of species and their habitat with less expenditure. Indeed, the increasing sophistication of underwater wireless sensors offers chances that enable new challenges in a lot of areas, like surveillance one. This paper endorses the use of sensors for monitoring underwater species endangered in their habitat. This paper further examines the key approaches and challenges in the design and implementation of underwater wireless sensor networks. We summarize major applications and the main phenomena related to acoustic propagation, and discuss how they affect the design and operation of communication systems and networking protocols at various layers.

  4. Electrolocation-based underwater obstacle avoidance using wide-field integration methods

    International Nuclear Information System (INIS)

    Dimble, Kedar D; Faddy, James M; Humbert, J Sean

    2014-01-01

    Weakly electric fish are capable of efficiently performing obstacle avoidance in dark and navigationally challenging aquatic environments using electrosensory information. This sensory modality enables extraction of relevant proximity information about surrounding obstacles by interpretation of perturbations induced to the fish’s self-generated electric field. In this paper, reflexive obstacle avoidance is demonstrated by extracting relative proximity information using spatial decompositions of the perturbation signal, also called an electric image. Electrostatics equations were formulated for mathematically expressing electric images due to a straight tunnel to the electric field generated with a planar electro-sensor model. These equations were further used to design a wide-field integration based static output feedback controller. The controller was implemented in quasi-static simulations for environments with complicated geometries modelled using finite element methods to demonstrate sense and avoid behaviours. The simulation results were confirmed by performing experiments using a computer operated gantry system in environments lined with either conductive or non-conductive objects acting as global stimuli to the field of the electro-sensor. The proposed approach is computationally inexpensive and readily implementable, making underwater autonomous navigation in real-time feasible. (paper)

  5. Underwater hearing sensivity of a male and female Steller sea lion (Eumetopias jubatus)

    NARCIS (Netherlands)

    Kastelein, R.A.; Schie, van R.; Verboom, W.C.; Haan, de D.

    2005-01-01

    The unmasked underwater hearing sensitivities of an 8-year-old male and a 7-year-old female Steller sea lion were measured in a pool, by using behavioral psychophysics. The animals were trained with positive reinforcement to respond when they detected an acoustic signal and not to respond when they

  6. Zebra mussel control using acoustic energy

    International Nuclear Information System (INIS)

    Tiller, G.W.; Gaucher, T.A.; Menezes, J.K.; Dolat, S.W.

    1992-01-01

    A practical and economical device or method that reduces zebra mussel colonization without detrimental side effects is highly desirable. An ideal method is one that could be installed near, on, or in existing raw water intakes and conduits. It must have a known effect that is limited to a defined area, should have maximum effects on a targeted species, and preferably have a low life cycle cost than the current alternative methods of control and maintenance. Underwater sound could be such a desirable solution, if found to be an effective control measure for zebra mussels. Although sound most often applies specifically to acoustic energy that is audible to humans, 20 Hertz (Hz) to 20 kiloHertz (kHz), in this report we will use the terms sound and acoustic to include acoustic energy between 100 Hz and 100 MegaHertz (MHz). This research on zebra mussel biofouling is designed to effect the early developmental stages in the life cycle of Dreissena polymorpha (Pallas). Vulnerable stages in the development of D. polymorpha that might yield to site-specific acoustic deterrence measures include the free-swimming larval veliger stage, the postveliger pre-attachment demersal stage, and the immediate post-attachment stage. The proposed applications include surface treatment to prevent, reduce or eliminate colonization on underwater structures, and the stream treatment to reduce or eliminate (destroy) mussel larvae entrained in a moving volume of water

  7. An Underwater Image Enhancement Algorithm for Environment Recognition and Robot Navigation

    Directory of Open Access Journals (Sweden)

    Kun Xie

    2018-03-01

    Full Text Available There are many tasks that require clear and easily recognizable images in the field of underwater robotics and marine science, such as underwater target detection and identification of robot navigation and obstacle avoidance. However, water turbidity makes the underwater image quality too low to recognize. This paper proposes the use of the dark channel prior model for underwater environment recognition, in which underwater reflection models are used to obtain enhanced images. The proposed approach achieves very good performance and multi-scene robustness by combining the dark channel prior model with the underwater diffuse model. The experimental results are given to show the effectiveness of the dark channel prior model in underwater scenarios.

  8. Signal Processing of Underwater Acoustic Waves

    Science.gov (United States)

    1969-11-01

    for the interest they have shown in the work and for many helpful discussions. The book was supported by Naval Ship Systems Corn- mand tinder ...inclination of the ray. The relationship is such that for the maximum values of dnldz just quoted radius of 0ectromapnetic ray 2,0 radius of acoustic... relationship for the angles, in, of the geometric ray, and carry out the limiting process as h -- 0. Show that when the velocity func- tion c(z) is

  9. Spatiotemporal dynamics of underwater conical shock wave focusing

    Czech Academy of Sciences Publication Activity Database

    Hoffer, Petr; Lukeš, Petr; Akiyama, H.; Hosseini, H.

    2017-01-01

    Roč. 27, č. 4 (2017), s. 685-690 ISSN 0938-1287 Grant - others:Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100431203 Program:M Institutional support: RVO:61389021 Keywords : Underwater shock wave focusing * multichannel * electrohydraulic discharge * conical shock wave reflection * medical application Subject RIV: BI - Acoustics OBOR OECD: Applied mechanics Impact factor: 1.107, year: 2016 https://link.springer.com/article/10.1007/s00193-016-0703-7

  10. Acoustic inversion with self noise of an autonomous underwater vehicle to measure sound speed in marine sediments

    NARCIS (Netherlands)

    van Leijen, A.V.; Rothkranz, L.J.M.; Groen, F.C.A.

    2009-01-01

    This work reports on an experiment from the Maritime Rapid Environmental Assessment sea trials in 2007, where autonomous underwater vehicles were deployed for environmental assessment. Even though these underwater vehicles are very quiet platforms, this work investigates the potential of vehicle

  11. Underwater Sound Propagation from Marine Pile Driving.

    Science.gov (United States)

    Reyff, James A

    2016-01-01

    Pile driving occurs in a variety of nearshore environments that typically have very shallow-water depths. The propagation of pile-driving sound in water is complex, where sound is directly radiated from the pile as well as through the ground substrate. Piles driven in the ground near water bodies can produce considerable underwater sound energy. This paper presents examples of sound propagation through shallow-water environments. Some of these examples illustrate the substantial variation in sound amplitude over time that can be critical to understand when computing an acoustic-based safety zone for aquatic species.

  12. A field guide to valuable underwater aquatic plants of the Great Lakes

    Science.gov (United States)

    Schloesser, Donald W.

    1986-01-01

    Underwater plants are a valuable part of the Great Lakes ecosystem, providing food and shelter for aquatic animals. Aquatic plants also help stabilize sediments, thereby reducing shoreline erosion. Annual fall die-offs of underwater plants provide food and shelter for overwintering small aquatic animals such as insects, snails, and freshwater shrimp.

  13. Axisymmetric scattering of an acoustical Bessel beam by a rigid fixed spheroid.

    Science.gov (United States)

    Mitri, Farid G

    2015-10-01

    Based on the partial-wave series expansion (PWSE) method in spherical coordinates, a formal analytical solution for the acoustic scattering of a zeroth-order Bessel acoustic beam centered on a rigid fixed (oblate or prolate) spheroid is provided. The unknown scattering coefficients of the spheroid are determined by solving a system of linear equations derived for the Neumann boundary condition. Numerical results for the modulus of the backscattered pressure (θ = π) in the near field and the backscattering form function in the far field for both prolate and oblate spheroids are presented and discussed, with particular emphasis on the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid), the half-cone angle of the Bessel beam, and the dimensionless frequency. The plots display periodic oscillations (versus the dimensionless frequency) because of the interference of specularly reflected waves in the backscattering direction with circumferential Franz' waves circumnavigating the surface of the spheroid in the surrounding fluid. Moreover, the 3-D directivity patterns illustrate the near- and far-field axisymmetric scattering. Investigations in underwater acoustics, particle levitation, scattering, and the detection of submerged elongated objects and other related applications utilizing Bessel waves would benefit from the results of the present study.

  14. Investigation into the Effect of Acoustic Radiation Force and Acoustic Streaming on Particle Patterning in Acoustic Standing Wave Fields

    Directory of Open Access Journals (Sweden)

    Shilei Liu

    2017-07-01

    Full Text Available Acoustic standing waves have been widely used in trapping, patterning, and manipulating particles, whereas one barrier remains: the lack of understanding of force conditions on particles which mainly include acoustic radiation force (ARF and acoustic streaming (AS. In this paper, force conditions on micrometer size polystyrene microspheres in acoustic standing wave fields were investigated. The COMSOL® Mutiphysics particle tracing module was used to numerically simulate force conditions on various particles as a function of time. The velocity of particle movement was experimentally measured using particle imaging velocimetry (PIV. Through experimental and numerical simulation, the functions of ARF and AS in trapping and patterning were analyzed. It is shown that ARF is dominant in trapping and patterning large particles while the impact of AS increases rapidly with decreasing particle size. The combination of using both ARF and AS for medium size particles can obtain different patterns with only using ARF. Findings of the present study will aid the design of acoustic-driven microfluidic devices to increase the diversity of particle patterning.

  15. Investigation into the Effect of Acoustic Radiation Force and Acoustic Streaming on Particle Patterning in Acoustic Standing Wave Fields

    Science.gov (United States)

    Yang, Yanye; Ni, Zhengyang; Guo, Xiasheng; Luo, Linjiao; Tu, Juan; Zhang, Dong

    2017-01-01

    Acoustic standing waves have been widely used in trapping, patterning, and manipulating particles, whereas one barrier remains: the lack of understanding of force conditions on particles which mainly include acoustic radiation force (ARF) and acoustic streaming (AS). In this paper, force conditions on micrometer size polystyrene microspheres in acoustic standing wave fields were investigated. The COMSOL® Mutiphysics particle tracing module was used to numerically simulate force conditions on various particles as a function of time. The velocity of particle movement was experimentally measured using particle imaging velocimetry (PIV). Through experimental and numerical simulation, the functions of ARF and AS in trapping and patterning were analyzed. It is shown that ARF is dominant in trapping and patterning large particles while the impact of AS increases rapidly with decreasing particle size. The combination of using both ARF and AS for medium size particles can obtain different patterns with only using ARF. Findings of the present study will aid the design of acoustic-driven microfluidic devices to increase the diversity of particle patterning. PMID:28753955

  16. Acoustic MIMO communications in a very shallow water channel

    Science.gov (United States)

    Zhou, Yuehai; Cao, Xiuling; Tong, Feng

    2015-12-01

    Underwater acoustic channels pose significant difficulty for the development of high speed communication due to highly limited band-width as well as hostile multipath interference. Enlightened by rapid progress of multiple input multiple output (MIMO) technologies in wireless communication scenarios, MIMO systems offer a potential solution by enabling multiple spatially parallel communication channels to improve communication performance as well as capacity. For MIMO acoustic communications, deep sea channels offer substantial spatial diversity among multiple channels that can be exploited to address simultaneous multipath and co-channel interference. At the same time, there are increasing requirements for high speed underwater communication in very shallow water area (for example, a depth less than 10 m). In this paper, a space-time multichannel adaptive receiver consisting of multiple decision feedback equalizers (DFE) is adopted as the receiver for a very shallow water MIMO acoustic communication system. The performance of multichannel DFE receivers with relatively small number of receiving elements are analyzed and compared with that of the multichannel time reversal receiver to evaluate the impact of limited spatial diversity on multi-channel equalization and time reversal processing. The results of sea trials in a very shallow water channel are presented to demonstrate the feasibility of very shallow water MIMO acoustic communication.

  17. SBMAC: Smart Blocking MAC Mechanism for Variable UW-ASN (Underwater Acoustic Sensor Network Environment

    Directory of Open Access Journals (Sweden)

    Soo-Hyun Park

    2010-01-01

    Full Text Available In this paper, several MAC scheduling methods applicable to an underwater environment are proposed. Besides, a new marine communication system model was proposed to improve the reliability of the proposed SBMAC method. The scheme minimizes transmission of control frames except for data transmission and various transmission methods and ACK methods can be used together. Simulation models are set indices and analysis of the underwater environment is established to conduct reliable simulations. Consequently, the performance improvement of the proposed method is verified with respect to delay time, data transmission rate, memory utilization, energy efficiency, etc.

  18. Research on the Influence of an Acoustic Field on Particle Cohesion in Liquid

    Directory of Open Access Journals (Sweden)

    Ramūnas Vilkišius

    2012-12-01

    Full Text Available Iron is one of the most common natural elements. When iron concentration in water is more than 0,3 mg/l, it causes the formation of rust drain tag or changes the colour of the fabric during washing. Thus, the use of the acoustic field to improve water quality is a very relevant topic. Acoustic oscillations are currently widely used in various industrial sectors, including water treatment, metallurgy, chemical and food industry, equipment manufacturing and medicine. When materials are affected by acoustic fields, physical-chemical processes begin. Acoustic fields cause material dispersion, emulsification, coagulation and degassing (gas removal as well as influence the crystallization and melting processes. Acoustic vibrations may also cause various chemical transformations such as oxidation, polymerization processes and depolymerisation. The utilization of acoustics to enhance water oxidation and precipitation of coarse impurities further extends the scope of the use of this physical method.Article in Lithuanian

  19. Research on the Influence of an Acoustic Field on Particle Cohesion in Liquid

    Directory of Open Access Journals (Sweden)

    Ramūnas Vilkišius

    2013-02-01

    Full Text Available Iron is one of the most common natural elements. When iron concentration in water is more than 0,3 mg/l, it causes the formation of rust drain tag or changes the colour of the fabric during washing. Thus, the use of the acoustic field to improve water quality is a very relevant topic. Acoustic oscillations are currently widely used in various industrial sectors, including water treatment, metallurgy, chemical and food industry, equipment manufacturing and medicine. When materials are affected by acoustic fields, physical-chemical processes begin. Acoustic fields cause material dispersion, emulsification, coagulation and degassing (gas removal as well as influence the crystallization and melting processes. Acoustic vibrations may also cause various chemical transformations such as oxidation, polymerization processes and depolymerisation. The utilization of acoustics to enhance water oxidation and precipitation of coarse impurities further extends the scope of the use of this physical method.Article in Lithuanian

  20. Underwater Electromagnetic Sensor Networks—Part I: Link Characterization

    Directory of Open Access Journals (Sweden)

    Gara Quintana-Díaz

    2017-01-01

    Full Text Available Underwater Wireless Sensor Networks (UWSNs using electromagnetic (EM technology in marine shallow waters are examined, not just for environmental monitoring but for further interesting applications. Particularly, the use of EM waves is reconsidered in shallow waters due to the benefits offered in this context, where acoustic and optical technologies have serious disadvantages. Sea water scenario is a harsh environment for radiocommunications, and there is no standard model for the underwater EM channel. The high conductivity of sea water, the effect of seabed and the surface make the behaviour of the channel hard to predict. This justifies the need of link characterization as the first step to approach the development of EM underwater sensor networks. To obtain a reliable link model, measurements and simulations are required. The measuring setup for this purpose is explained and described, as well as the procedures used. Several antennas have been designed and tested in low frequency bands. Agreement between attenuation measurements and simulations at different distances was analysed and made possible the validation of simulation setups and the design of different communications layers of the system. This leads to the second step of this work, where data and routing protocols for the sensor network are examined.

  1. Integrated Optimization of Long-Range Underwater Signal Detection, Feature Extraction, and Classification for Nuclear Treaty Monitoring

    NARCIS (Netherlands)

    Tuma, M.; Rorbech, V.; Prior, M.; Igel, C.

    2016-01-01

    We designed and jointly optimized an integrated signal processing chain for detection and classification of long-range passive-acoustic underwater signals recorded by the global geophysical monitoring network of the Comprehensive Nuclear-Test-Ban Treaty Organization. Starting at the level of raw

  2. Upwelling regime off the Cabo Frio region in Brazil and impact on acoustic propagation.

    Science.gov (United States)

    Calado, Leandro; Camargo Rodríguez, Orlando; Codato, Gabriel; Contrera Xavier, Fabio

    2018-03-01

    This work introduces a description of the complex upwelling regime off the Cabo Frio region in Brazil and shows that ocean modeling, based on the feature-oriented regional modeling system (FORMS) technique, can produce reliable predictions of sound speed fields for the corresponding shallow water environment. This work also shows, through the development of simulations, that the upwelling regime can be responsible for the creation of shadow coastal zones, in which the detection probability is too low for an acoustic source to be detected. The development of the FORMS technique and its validation with real data, for the particular region of coastal upwelling off Cabo Frio, reveals the possibility of a sustainable and reliable forecast system for the corresponding (variable in space and time) underwater acoustic environment.

  3. Underwater hearing sensitivity of a male and a female Steller sea lion (Eumetopias jubatus)

    NARCIS (Netherlands)

    Kastelein, R.A.; Schie, R. van; Verboom, W.C.; Haan, D. de

    2005-01-01

    The unmasked underwater hearing sensitivities of an 8-year-old male and a 7-year-old female Steller sea lion were measured in a pool, by using behavioral psychophysics. The animals were trained with positive reinforcement to respond when they detected an acoustic signal and not to respond when they

  4. Compact, Isolating Elastomeric Suspension for Vehicle Acoustic Vector Sensor

    Science.gov (United States)

    2007-09-30

    well as underwater acoustics. His Master’s thesis, funded by NUSC, was a study of near-body acoustic signal behavior entitled “Some Characteristics of ...in non-polymer based composites, including cermets . He has formulated a very wide range of materials for an equally wide range of applications, and...with a moving vehicle of an instrument responsive to particle accelerations in the surrounding medium. The overall goal of this project is to develop

  5. Investigation of air-assisted sprays submitted to high frequency transverse acoustic fields: Droplet clustering

    Science.gov (United States)

    Ficuciello, A.; Blaisot, J. B.; Richard, C.; Baillot, F.

    2017-06-01

    An experimental investigation of the effects of a high amplitude transverse acoustic field on coaxial jets is presented in this paper. Water and air are used as working fluids at ambient pressure. The coaxial injectors are placed on the top of a semi-open resonant cavity where the acoustic pressure fluctuations of the standing wave can reach a maximum peak-to-peak amplitude of 12 kPa at the forcing frequency of 1 kHz. Several test conditions are considered in order to quantify the influence of injection conditions, acoustic field amplitude, and injector position with respect to the standing wave acoustic field. A high speed back-light visualization technique is used to characterize the jet response. Image processing is used to obtain valuable information about the jet behavior. It is shown that the acoustic field drastically affects the atomization process for all atomization regimes. The position of the injector in the acoustic field determines the jet response, and a droplet-clustering phenomenon is highlighted in multi-point injection conditions and quantified by determining discrete droplet location distributions. A theoretical model based on nonlinear acoustics related to the spatial distribution of the radiation pressure exerted on an object explains the behavior observed.

  6. First description of underwater acoustic diversity in three temperate ponds

    Directory of Open Access Journals (Sweden)

    Camille Desjonquères

    2015-11-01

    Full Text Available The past decade has produced an increased ecological interest in sonic environments, or soundscapes. However, despite this rise in interest and technological improvements that allow for long-term acoustic surveys in various environments, some habitats’ soundscapes remain to be explored. Ponds, and more generally freshwater habitats, are one of these acoustically unexplored environments. Here we undertook the first long term acoustic monitoring of three temperate ponds in France. By aural and visual inspection of a selection of recordings, we identified 48 different sound types, and according to the rarefaction curves we calculated, more sound types are likely present in one of the three ponds. The richness of sound types varied significantly across ponds. Surprisingly, there was no pond-to-pond daily consistency of sound type richness variation; each pond had its own daily patterns of activity. We also explored the possibility of using six acoustic diversity indices to conduct rapid biodiversity assessments in temperate ponds. We found that all indices were sensitive to the background noise as estimated through correlations with the signal-to-noise ratio (SNR. However, we determined that the AR index could be a good candidate to measure acoustic diversities using partial correlations with the SNR as a control variable. Yet, research is still required to automatically compute the SNR in order to apply this index on a large data set of recordings. The results showed that these three temperate ponds host a high level of acoustic diversity in which the soundscapes were variable not only between but also within the ponds. The sources producing this diversity of sounds and the drivers of difference in daily song type richness variation both require further investigation. Such research would yield insights into the biodiversity and ecology of temperate ponds.

  7. Near-field acoustic imaging based on Laplacian sparsity

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Daudet, Laurent

    2016-01-01

    We present a sound source identification method for near-field acoustic imaging of extended sources. The methodology is based on a wave superposition method (or equivalent source method) that promotes solutions with sparse higher order spatial derivatives. Instead of promoting direct sparsity......, and the validity of the wave extrapolation used for the reconstruction is examined. It is shown that this methodology can overcome conventional limits of spatial sampling, and is therefore valid for wide-band acoustic imaging of extended sources....

  8. Underwater robots

    CERN Document Server

    Antonelli, Gianluca

    2014-01-01

    This book, now at the third edition, addresses the main control aspects in underwater manipulation tasks. The mathematical model with significant impact on the control strategy is discussed. The problem of controlling a 6-degrees-of-freedoms autonomous underwater vehicle is deeply investigated and a survey of fault detection/tolerant strategies for unmanned underwater vehicles is provided. Inverse kinematics, dynamic and interaction control for underwater vehicle-manipulator systems are then discussed. The code used to generate most of the numerical simulations is made available and briefly discussed.       

  9. Customization of the acoustic field produced by a piezoelectric array through interelement delays

    Science.gov (United States)

    Chitnis, Parag V.; Barbone, Paul E.; Cleveland, Robin O.

    2008-01-01

    A method for producing a prescribed acoustic pressure field from a piezoelectric array was investigated. The array consisted of 170 elements placed on the inner surface of a 15 cm radius spherical cap. Each element was independently driven by using individual pulsers each capable of generating 1.2 kV. Acoustic field customization was achieved by independently controlling the time when each element was excited. The set of time delays necessary to produce a particular acoustic field was determined by using an optimization scheme. The acoustic field at the focal plane was simulated by using the angular spectrum method, and the optimization searched for the time delays that minimized the least squared difference between the magnitudes of the simulated and desired pressure fields. The acoustic field was shaped in two different ways: the −6 dB focal width was increased to different desired widths and the ring-shaped pressure distributions of various prescribed diameters were produced. For both cases, the set of delays resulting from the respective optimization schemes were confirmed to yield the desired pressure distributions by using simulations and measurements. The simulations, however, predicted peak positive pressures roughly half those obtained from the measurements, which was attributed to the exclusion of nonlinearity in the simulations. PMID:18537369

  10. Acoustic Characterization of a Stationary Field Synchronous Motor

    National Research Council Canada - National Science Library

    Woodward, E

    2001-01-01

    .... We investigate the gross acoustic signature of a notional stationary field synchronous motor utilized as a marine propulsion motor in a naval combatant using the following methodology: (1) model the forces...

  11. Multi-carrier Communications over Time-varying Acoustic Channels

    Science.gov (United States)

    Aval, Yashar M.

    Acoustic communication is an enabling technology for many autonomous undersea systems, such as those used for ocean monitoring, offshore oil and gas industry, aquaculture, or port security. There are three main challenges in achieving reliable high-rate underwater communication: the bandwidth of acoustic channels is extremely limited, the propagation delays are long, and the Doppler distortions are more pronounced than those found in wireless radio channels. In this dissertation we focus on assessing the fundamental limitations of acoustic communication, and designing efficient signal processing methods that cam overcome these limitations. We address the fundamental question of acoustic channel capacity (achievable rate) for single-input-multi-output (SIMO) acoustic channels using a per-path Rician fading model, and focusing on two scenarios: narrowband channels where the channel statistics can be approximated as frequency- independent, and wideband channels where the nominal path loss is frequency-dependent. In each scenario, we compare several candidate power allocation techniques, and show that assigning uniform power across all frequencies for the first scenario, and assigning uniform power across a selected frequency-band for the second scenario, are the best practical choices in most cases, because the long propagation delay renders the feedback information outdated for power allocation based on the estimated channel response. We quantify our results using the channel information extracted form the 2010 Mobile Acoustic Communications Experiment (MACE'10). Next, we focus on achieving reliable high-rate communication over underwater acoustic channels. Specifically, we investigate orthogonal frequency division multiplexing (OFDM) as the state-of-the-art technique for dealing with frequency-selective multipath channels, and propose a class of methods that compensate for the time-variation of the underwater acoustic channel. These methods are based on multiple

  12. Analyzing panel acoustic contributions toward the sound field inside the passenger compartment of a full-size automobile.

    Science.gov (United States)

    Wu, Sean F; Moondra, Manmohan; Beniwal, Ravi

    2015-04-01

    The Helmholtz equation least squares (HELS)-based nearfield acoustical holography (NAH) is utilized to analyze panel acoustic contributions toward the acoustic field inside the interior region of an automobile. Specifically, the acoustic power flows from individual panels are reconstructed, and relative contributions to sound pressure level and spectrum at any point of interest are calculated. Results demonstrate that by correlating the acoustic power flows from individual panels to the field acoustic pressure, one can correctly locate the panel allowing the most acoustic energy transmission into the vehicle interior. The panel on which the surface acoustic pressure amplitude is the highest should not be used as indicative of the panel responsible for the sound field in the vehicle passenger compartment. Another significant advantage of this HELS-based NAH is that measurements of the input data only need to be taken once by using a conformal array of microphones in the near field, and ranking of panel acoustic contributions to any field point can be readily performed. The transfer functions between individual panels of any vibrating structure to the acoustic pressure anywhere in space are calculated not measured, thus significantly reducing the time and effort involved in panel acoustic contributions analyses.

  13. Event localization in underwater wireless sensor networks using Monitoring Courses

    KAUST Repository

    Debont, Matthew John Robert

    2012-08-01

    We propose m-courses (Monitoring Courses), a novel solution to localize events in an underwater wireless sensor network. These networks consists of surface gateways and relay nodes. GPS can localize the position of surface gateways which can then distribute their locations through the network using acoustic modems. Relay nodes are deployed to remain static, but these untethered nodes may drift due to water currents, resulting in disruption of communication links. We develop a novel underwater alarm system using a cyclic graph model. In the event of link failure, a series of alarm packets are broadcast in the network. These alarms are then captured by the underwater m-courses, which can also be used to assure network connectivity and identify node failures. M-courses also allow the network to localize events and identify network issues locally before forwarding results upwards to a Surface Gateway node. This reduces communication overhead and allows for efficient management of nodes in a mobile network. Our results show that m-course routing reduces the number of sends required to report an event to a Surface Gateway by up to 80% when compared to a naïve routing implementation.

  14. 3D DOCUMENTATION OF ARCHEOLOGICAL REMAINS IN THE UNDERWATER PARK OF BAIAE

    Directory of Open Access Journals (Sweden)

    F. Bruno

    2015-04-01

    Full Text Available This paper presents some experimentations, which have been conducted in the submerged archeological Park of Baiae, aimed to identify the problems related to the underwater 3D documentation process. The first test has been addressed to verify if a dense stereo mapping technique, usually employed in terrestrial and aerial applications, might be employed in critical underwater conditions by assessing the influence of different factors on the results. In the second test, the accuracy of the 3D model obtained through this technique has been evaluated. The third test deals with the geo-localization of the 3D models, conducted by merging the optical and acoustic data, through a multi-resolution bathymetric map of the site as a reference.

  15. Detection and localisation of very high energy particles in underwater acoustic; Detection et localisation de particules de tres hautes energies en acoustique sous-marine

    Energy Technology Data Exchange (ETDEWEB)

    Juennard, N

    2007-12-15

    The theme of this thesis is included in the Antares international project whose object is to build a neutrino telescope located in a deep water environment in the Mediterranean sea. In deep water sea, a neutrino can interact with a water molecule. The collision generates a luminous flash and an acoustic wave. The goal of this work is to study this acoustic sound wave and develop a system able to detect the corresponding wave front and to estimate the initial direction of the particle. We first focus on the acoustic sound wave. Two different models are studied, and works made recently have led to a mathematical expression of both signal and wave front. Then, several detection methods are studied, from the most classical to the more recent ones. The experimental comparison in semi-real situation leads to the choice of a detection method: the Extended stochastic matched filter. Position and direction of the neutrino are now estimated with a Gauss-Newton inspired algorithm. This estimator is based on a wave front propagation model and on the time detection information given by the telescope hydro-phones. Performances of the system are then estimated. An antenna structure is then proposed and a global simulation finalizes this thesis. In this simulation, detection and estimation are based on the results found in the previous sections. Underwater sea noise is real and the results of the simulation valid our works. (author)

  16. Environmental effects on underwater optical transmission

    Science.gov (United States)

    Chu, Peter C.; Breshears, Brian F.; Cullen, Alexander J.; Hammerer, Ross F.; Martinez, Ramon P.; Phung, Thai Q.; Margolina, Tetyana; Fan, Chenwu

    2017-05-01

    Optical communication/detection systems have potential to get around some limitations of current acoustic communications and detection systems especially increased fleet and port security in noisy littoral waters. Identification of environmental effects on underwater optical transmission is the key to the success of using optics for underwater communication and detection. This paper is to answer the question "What are the transfer and correlation functions that relate measurements of hydrographic to optical parameters?" Hydrographic and optical data have been collected from the Naval Oceanographic Office survey ships with the High Intake Defined Excitation (HIDEX) photometer and sea gliders with optical back scattering sensor in various Navy interested areas such as the Arabian Gulf, Gulf of Oman, east Asian marginal seas, and Adriatic Sea. The data include temperature, salinity, bioluminescence, chlorophyll-a fluorescence, transmissivity at two different wavelengths (TRed at 670 nm, TBlue at 490 nm), and back scattering coefficient (bRed at 700 nm, bBlue at 470 nm). Transfer and correlation functions between the hydrographic and optical parameters are obtained. Bioluminescence and fluorescence maxima, transmissivity minimum with their corresponding depths, red and blue laser beam peak attenuation coefficients are identified from the optical profiles. Evident correlations are found between the ocean mixed layer depth and the blue and red laser beam peak attenuation coefficients, bioluminescence and fluorescence maxima in the Adriatic Sea, Arabian Gulf, Gulf of Oman, and Philippine Sea. Based on the observational data, an effective algorithm is recommended for solving the radiative transfer equation (RTE) for predicting underwater laser radiance.

  17. Theory of the Auger effect in an intense acoustic noise field

    International Nuclear Information System (INIS)

    Doan Nhat Quang.

    1995-10-01

    A study is given of the effect on Auger processes produced by an intense acoustic noise flux affecting charge carriers via deformation-potential interaction. The calculation of Auger coefficients is carried out within a semiclassical approach to the acoustic noise field and non-degenerate carrier statistics. Simple analytic expressions are then obtained, which expose an exponential dependence of the Auger coefficients on flux intensity. The Auger recombination is found, in analogy with the case of piezoelectric noise field, to be strongly enhanced as compared to that in no-noise conditions by up to several orders of magnitude at high flux intensity, short acoustic wavelength, small carrier concentration and low temperature. (author). 29 refs, 4 figs, 1 tab

  18. The near-field acoustic levitation for spheres by transducer with concave spherical radiating surface

    International Nuclear Information System (INIS)

    Liu, Jian Fang; Sun, Xu Guang; Jiao, Xiao Yang; Chen, Hong Xia; Hua, Shun Ming; Zhang, Hong Chun

    2013-01-01

    To levitate ICF target spheres in the near-field acoustic levitation, a transducer with concave spherical radiating surface and a nearfield acoustic levitation system is established. The concave spherical radiating surface of the transducer is designed by the finite element parametric method. Then the levitation height and levitation perturbation of spheres with different mass and diameters in the near-field acoustic levitation system are tested and discussed in the driving voltage at 400V, 500V and 600V, respectively, when the levitation system is under the resonant frequency. Finally, based on the experimental results, the height formula of the near-field acoustic levitation for spheres is deduced by introducing a coupling coefficient.

  19. The near-field acoustic levitation for spheres by transducer with concave spherical radiating surface

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jian Fang; Sun, Xu Guang; Jiao, Xiao Yang; Chen, Hong Xia [Jilin University, Changchun (China); Hua, Shun Ming [Zhejiang University, Ningbo (China); Zhang, Hong Chun [Aviation University of AirForce, Changchun (China)

    2013-02-15

    To levitate ICF target spheres in the near-field acoustic levitation, a transducer with concave spherical radiating surface and a nearfield acoustic levitation system is established. The concave spherical radiating surface of the transducer is designed by the finite element parametric method. Then the levitation height and levitation perturbation of spheres with different mass and diameters in the near-field acoustic levitation system are tested and discussed in the driving voltage at 400V, 500V and 600V, respectively, when the levitation system is under the resonant frequency. Finally, based on the experimental results, the height formula of the near-field acoustic levitation for spheres is deduced by introducing a coupling coefficient.

  20. Prediction and near-field observation of skull-guided acoustic waves.

    Science.gov (United States)

    Estrada, Héctor; Rebling, Johannes; Razansky, Daniel

    2017-06-21

    Ultrasound waves propagating in water or soft biological tissue are strongly reflected when encountering the skull, which limits the use of ultrasound-based techniques in transcranial imaging and therapeutic applications. Current knowledge on the acoustic properties of the cranial bone is restricted to far-field observations, leaving its near-field unexplored. We report on the existence of skull-guided acoustic waves, which was herein confirmed by near-field measurements of optoacoustically-induced responses in ex-vivo murine skulls immersed in water. Dispersion of the guided waves was found to reasonably agree with the prediction of a multilayered flat plate model. We observed a skull-guided wave propagation over a lateral distance of at least 3 mm, with a half-decay length in the direction perpendicular to the skull ranging from 35 to 300 μm at 6 and 0.5 MHz, respectively. Propagation losses are mostly attributed to the heterogenous acoustic properties of the skull. It is generally anticipated that our findings may facilitate and broaden the application of ultrasound-mediated techniques in brain diagnostics and therapy.

  1. Prediction and near-field observation of skull-guided acoustic waves

    Science.gov (United States)

    Estrada, Héctor; Rebling, Johannes; Razansky, Daniel

    2017-06-01

    Ultrasound waves propagating in water or soft biological tissue are strongly reflected when encountering the skull, which limits the use of ultrasound-based techniques in transcranial imaging and therapeutic applications. Current knowledge on the acoustic properties of the cranial bone is restricted to far-field observations, leaving its near-field unexplored. We report on the existence of skull-guided acoustic waves, which was herein confirmed by near-field measurements of optoacoustically-induced responses in ex-vivo murine skulls immersed in water. Dispersion of the guided waves was found to reasonably agree with the prediction of a multilayered flat plate model. We observed a skull-guided wave propagation over a lateral distance of at least 3 mm, with a half-decay length in the direction perpendicular to the skull ranging from 35 to 300 μm at 6 and 0.5 MHz, respectively. Propagation losses are mostly attributed to the heterogenous acoustic properties of the skull. It is generally anticipated that our findings may facilitate and broaden the application of ultrasound-mediated techniques in brain diagnostics and therapy.

  2. Vapor Bubbles in Flow and Acoustic Fields

    NARCIS (Netherlands)

    Prosperetti, Andrea; Hao, Yue; Sadhal, S.S

    2002-01-01

    A review of several aspects of the interaction of bubbles with acoustic and flow fields is presented. The focus of the paper is on bubbles in hot liquids, in which the bubble contains mostly vapor, with little or no permanent gas. The topics covered include the effect of translation on condensation

  3. Characterization of the acoustic field generated by a horn shaped ultrasonic transducer

    Science.gov (United States)

    Hu, B.; Lerch, J. E.; Chavan, A. H.; Weber, J. K. R.; Tamalonis, A.; Suthar, K. J.; DiChiara, A. D.

    2017-09-01

    A horn shaped Langevin ultrasonic transducer used in a single axis levitator was characterized to better understand the role of the acoustic profile in establishing stable traps. The method of characterization included acoustic beam profiling performed by raster scanning an ultrasonic microphone as well as finite element analysis of the horn and its interface with the surrounding air volume. The results of the model are in good agreement with measurements and demonstrate the validity of the approach for both near and far field analyses. Our results show that this style of transducer produces a strong acoustic beam with a total divergence angle of 10°, a near-field point close to the transducer surface and a virtual sound source. These are desirable characteristics for a sound source used for acoustic trapping experiments.

  4. Characterization of the acoustic field generated by a horn shaped ultrasonic transducer

    Energy Technology Data Exchange (ETDEWEB)

    Hu, B.; Lerch, J. E.; Chavan, A. H.; Weber, J. K. R.; Tamalonis, A.; Suthar, K. J.; DiChiara, A. D.

    2017-09-04

    A horn shaped Langevin ultrasonic transducer used in a single axis levitator was characterized to better understand the role of the acoustic profile in establishing stable traps. The method of characterization included acoustic beam profiling performed by raster scanning an ultrasonic microphone as well as finite element analysis of the horn and its interface with the surrounding air volume. The results of the model are in good agreement with measurements and demonstrate the validity of the approach for both near and far field analyses. Our results show that this style of transducer produces a strong acoustic beam with a total divergence angle of 10 degree, a near-field point close to the transducer surface and a virtual sound source. These are desirable characteristics for a sound source used for acoustic trapping experiments

  5. Practical spreading laws: The snakes and ladders of shallow water acoustics

    NARCIS (Netherlands)

    Ainslie, M.A.; Dahl, P.H.; Jong, C.A.F. de; Laws, R.M.

    2014-01-01

    Geometrical spreading laws are widely used in underwater acoustics because they provide - if chosen carefully - an accuracy that is sufficient for many applications (source characterisation, impact assessment, sound mapping, regulation) for negligible computation time. The simplest and most widely

  6. Adaptive acoustic energy delivery to near and far fields using foldable, tessellated star transducers

    Science.gov (United States)

    Zou, Chengzhe; Harne, Ryan L.

    2017-05-01

    Methods of guiding acoustic energy arbitrarily through space have long relied on digital controls to meet performance needs. Yet, more recent attention to adaptive structures with unique spatial configurations has motivated mechanical signal processing (MSP) concepts that may not be subjected to the same functional and performance limitations as digital acoustic beamforming counterparts. The periodicity of repeatable structural reconfiguration enabled by origami-inspired tessellated architectures turns attention to foldable platforms as frameworks for MSP development. This research harnesses principles of MSP to study a tessellated, star-shaped acoustic transducer constituent that provides on-demand control of acoustic energy guiding via folding-induced shape reconfiguration. An analytical framework is established to probe the roles of mechanical and acoustic geometry on the far field directivity and near field focusing of sound energy. Following validation by experiments and verification by simulations, parametric studies are undertaken to uncover relations between constituent topology and acoustic energy delivery to arbitrary points in the free field. The adaptations enabled by folding of the star-shaped transducer reveal capability for restricting sound energy to angular regions in the far field while also introducing means to modulate sound energy by three orders-of-magnitude to locations near to the transducer surface. In addition, the modeling philosophy devised here provides a valuable approach to solve general sound radiation problems for foldable, tessellated acoustic transducer constituents of arbitrary geometry.

  7. Estimating sub-surface dispersed oil concentration using acoustic backscatter response.

    Science.gov (United States)

    Fuller, Christopher B; Bonner, James S; Islam, Mohammad S; Page, Cheryl; Ojo, Temitope; Kirkey, William

    2013-05-15

    The recent Deepwater Horizon disaster resulted in a dispersed oil plume at an approximate depth of 1000 m. Several methods were used to characterize this plume with respect to concentration and spatial extent including surface supported sampling and autonomous underwater vehicles with in situ instrument payloads. Additionally, echo sounders were used to track the plume location, demonstrating the potential for remote detection using acoustic backscatter (ABS). This study evaluated use of an Acoustic Doppler Current Profiler (ADCP) to quantitatively detect oil-droplet suspensions from the ABS response in a controlled laboratory setting. Results from this study showed log-linear ABS responses to oil-droplet volume concentration. However, the inability to reproduce ABS response factors suggests the difficultly in developing meaningful calibration factors for quantitative field analysis. Evaluation of theoretical ABS intensity derived from the particle size distribution provided insight regarding method sensitivity in the presence of interfering ambient particles. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Near field acoustic holography with microphones mounted on a rigid sphere

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Moreno, Guillermo; Fernandez Grande, Efren

    2008-01-01

    Spherical near field acoustic holography (spherical NAH) is a technique that makes it pos-sible to reconstruct the sound field inside and just outside an acoustically transparent spherical surface on which the sound pressure is measured with an array of microphones with negligible scattering...... is only valid if it can be assumed that the sphere has a negligible in-fluence on the incident sound field, and this is not necessarily a good assumption when the sphere is very close to a radiating surface. This paper describes the modified spherical NAH theory and examines the matter through simulations...

  9. Spherical near field acoustic holography with microphones on a rigid sphere

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Hald, Jørgen; Fernandez Grande, Efren

    2008-01-01

    Spherical near field acoustic holography (SNAH) is a recently developed technique that makes it possible to reconstruct the sound field inside and just outside an acoustically transparent spherical surface on which the sound pressure is measured with an array of microphones with negligible...... with an array of microphones flush-mounted on a rigid sphere. However, this approach is only valid if it can be assumed that the sphere has a negligible influence on the incident sound field, in other words if multiple scattering can be ignored, and this is not necessarily a good assumption when the sphere...

  10. Use of acoustic vortices in acoustic levitation

    DEFF Research Database (Denmark)

    Cutanda Henriquez, Vicente; Santillan, Arturo Orozco; Juhl, Peter Møller

    2009-01-01

    Acoustic fields are known to exert forces on the surfaces of objects. These forces are noticeable if the sound pressure is sufficiently high. Two phenomena where acoustic forces are relevant are: i) acoustic levitation, where strong standing waves can hold small objects at certain positions......, counterbalancing their weight, and ii) acoustic vortices, spinning sound fields that can impinge angular momentum and cause rotation of objects. In this contribution, both force-creating sound fields are studied by means of numerical simulations. The Boundary Element Method is employed to this end. The simulation...... of acoustical vortices uses an efficient numerical implementation based on the superposition of two orthogonal sound fields with a delay of 90° between them. It is shown that acoustic levitation and the use of acoustic vortices can be combined to manipulate objects in an efficient and controlled manner without...

  11. Highly Localized Acoustic Streaming and Size-Selective Submicrometer Particle Concentration Using High Frequency Microscale Focused Acoustic Fields.

    Science.gov (United States)

    Collins, David J; Ma, Zhichao; Ai, Ye

    2016-05-17

    Concentration and separation of particles and biological specimens are fundamental functions of micro/nanofluidic systems. Acoustic streaming is an effective and biocompatible way to create rapid microscale fluid motion and induce particle capture, though the >100 MHz frequencies required to directly generate acoustic body forces on the microscale have traditionally been difficult to generate and localize in a way that is amenable to efficient generation of streaming. Moreover, acoustic, hydrodynamic, and electrical forces as typically applied have difficulty manipulating specimens in the submicrometer regime. In this work, we introduce highly focused traveling surface acoustic waves (SAW) at high frequencies between 193 and 636 MHz for efficient and highly localized production of acoustic streaming vortices on microfluidic length scales. Concentration occurs via a novel mechanism, whereby the combined acoustic radiation and streaming field results in size-selective aggregation in fluid streamlines in the vicinity of a high-amplitude acoustic beam, as opposed to previous acoustic radiation induced particle concentration where objects typically migrate toward minimum pressure locations. Though the acoustic streaming is induced by a traveling wave, we are able to manipulate particles an order of magnitude smaller than possible using the traveling wave force alone. We experimentally and theoretically examine the range of particle sizes that can be captured in fluid streamlines using this technique, with rapid particle concentration demonstrated down to 300 nm diameters. We also demonstrate that locations of trapping and concentration are size-dependent, which is attributed to the combined effects of the acoustic streaming and acoustic forces.

  12. Droplet Vaporization In A Levitating Acoustic Field

    Science.gov (United States)

    Ruff, G. A.; Liu, S.; Ciobanescu, I.

    2003-01-01

    Combustion experiments using arrays of droplets seek to provide a link between single droplet combustion phenomena and the behavior of complex spray combustion systems. Both single droplet and droplet array studies have been conducted in microgravity to better isolate the droplet interaction phenomena and eliminate or reduce the effects of buoyancy-induced convection. In most experiments involving droplet arrays, the droplets are supported on fibers to keep them stationary and close together before the combustion event. The presence of the fiber, however, disturbs the combustion process by introducing a source of heat transfer and asymmetry into the configuration. As the number of drops in a droplet array increases, supporting the drops on fibers becomes less practical because of the cumulative effect of the fibers on the combustion process. To eliminate the effect of the fiber, several researchers have conducted microgravity experiments using unsupported droplets. Jackson and Avedisian investigated single, unsupported drops while Nomura et al. studied droplet clouds formed by a condensation technique. The overall objective of this research is to extend the study of unsupported drops by investigating the combustion of well-characterized drop clusters in a microgravity environment. Direct experimental observations and measurements of the combustion of droplet clusters would provide unique experimental data for the verification and improvement of spray combustion models. In this work, the formation of drop clusters is precisely controlled using an acoustic levitation system so that dilute, as well as dense clusters can be created and stabilized before combustion in microgravity is begun. While the low-gravity test facility is being completed, tests have been conducted in 1-g to characterize the effect of the acoustic field on the vaporization of single and multiple droplets. This is important because in the combustion experiment, the droplets will be formed and

  13. Restoration and Enhancement of Underwater Images Based on Bright Channel Prior

    Directory of Open Access Journals (Sweden)

    Yakun Gao

    2016-01-01

    Full Text Available This paper proposed a new method of underwater images restoration and enhancement which was inspired by the dark channel prior in image dehazing field. Firstly, we proposed the bright channel prior of underwater environment. By estimating and rectifying the bright channel image, estimating the atmospheric light, and estimating and refining the transmittance image, eventually underwater images were restored. Secondly, in order to rectify the color distortion, the restoration images were equalized by using the deduced histogram equalization. The experiment results showed that the proposed method could enhance the quality of underwater images effectively.

  14. Acoustic wave simulation using an overset grid for the global monitoring system

    Science.gov (United States)

    Kushida, N.; Le Bras, R.

    2017-12-01

    The International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) has been monitoring hydro-acoustic and infrasound waves over the globe. Because of the complex natures of the oceans and the atmosphere, computer simulation can play an important role in understanding the observed signals. In this regard, methods which depend on partial differential equations and require minimum modelling, are preferable. So far, to our best knowledge, acoustic wave propagation simulations based on partial differential equations on such a large scale have not been performed (pp 147 - 161 of ref [1], [2]). The main difficulties in building such simulation codes are: (1) considering the inhomogeneity of medium including background flows, (2) high aspect ratio of computational domain, (3) stability during long time integration. To overcome these difficulties, we employ a two-dimensional finite different (FDM) scheme on spherical coordinates with the Yin-Yang overset grid[3] solving the governing equation of acoustic waves introduces by Ostashev et. al.[4]. The comparison with real recording examples in hydro-acoustic will be presented at the conference. [1] Paul C. Etter: Underwater Acoustic Modeling and Simulation, Fourth Edition, CRC Press, 2013. [2] LIAN WANG et. al.: REVIEW OF UNDERWATER ACOUSTIC PROPAGATION MODELS, NPL Report AC 12, 2014. [3] A. Kageyama and T. Sato: "Yin-Yang grid": An overset grid in spherical geometry, Geochem. Geophys. Geosyst., 5, Q09005, 2004. [4] Vladimir E. Ostashev et. al: Equations for finite-difference, time-domain simulation of sound propagation in moving inhomogeneous media and numerical implementation, Acoustical Society of America. DOI: 10.1121/1.1841531, 2005.

  15. Effect of inhomogeneous temperature fields on acoustic streaming structures in resonators.

    Science.gov (United States)

    Červenka, Milan; Bednařík, Michal

    2017-06-01

    Acoustic streaming in 2D rectangular resonant channels filled with a fluid with a spatial temperature distribution is studied within this work. An inertial force is assumed for driving the acoustic field; the temperature inhomogeneity is introduced by resonator walls with prescribed temperature distribution. The method of successive approximations is employed to derive linear equations for calculation of primary acoustic and time-averaged secondary fields including the streaming velocity. The model equations have a standard form which allows their numerical integration using a universal solver; in this case, COMSOL Multiphysics was employed. The numerical results show that fluid temperature variations in the direction perpendicular to the resonator axis influence strongly the streaming field if the ratio of the channel width and the viscous boundary layer thickness is big enough; the streaming in the Rayleigh vortices can be supported as well as opposed, which can ultimately lead to the appearance of additional vortices.

  16. Simulated performance of an acoustic modem using phase-modulated signals in a time-varying, shallow-water environment

    DEFF Research Database (Denmark)

    Bjerrum-Niese, Christian; Jensen, Leif Bjørnø

    1996-01-01

    and dynamic multipath channel. Multipath arrivals at the receiver cause phase distortion and fading of the signal envelope. Yet, for extreme ratios of range to depth, the delays of multipath arrivals decrease, and the channel impulse response coherently contributes energy to the signal at short delays......Underwater acoustic modems using coherent modulation, such as phase-shift keying, have proven to efficiently exploit the bandlimited underwater acoustical communication channel. However, the performance of an acoustic modem, given as maximum range and data and error rate, is limited in the complex...... relative to the first arrival, while longer delays give rise to intersymbol interference. Following this, the signal-to-multipath ratio (SMR) is introduced. It is claimed that the SMR determines the performance rather than the signal-to-noise ratio (SNR). Using a ray model including temporal variations...

  17. Hoeren unter Wasser: Absolute Reizschwellen und Richtungswahrnehnumg (Underwater Hearing: Absolute Thresholds and Sound Localization),

    Science.gov (United States)

    The article deals first with the theoretical foundations of underwater hearing, and the effects of the acoustical characteristics of water on hearing...lead to the conclusion that, in water , man can locate the direction of sound at low and at very high tonal frequencies of the audio range, but this ability is probably vanishing in the middle range of frequencies. (Author)

  18. Acoustic radiosity for computation of sound fields in diffuse environments

    Science.gov (United States)

    Muehleisen, Ralph T.; Beamer, C. Walter

    2002-05-01

    The use of image and ray tracing methods (and variations thereof) for the computation of sound fields in rooms is relatively well developed. In their regime of validity, both methods work well for prediction in rooms with small amounts of diffraction and mostly specular reflection at the walls. While extensions to the method to include diffuse reflections and diffraction have been made, they are limited at best. In the fields of illumination and computer graphics the ray tracing and image methods are joined by another method called luminous radiative transfer or radiosity. In radiosity, an energy balance between surfaces is computed assuming diffuse reflection at the reflective surfaces. Because the interaction between surfaces is constant, much of the computation required for sound field prediction with multiple or moving source and receiver positions can be reduced. In acoustics the radiosity method has had little attention because of the problems of diffraction and specular reflection. The utility of radiosity in acoustics and an approach to a useful development of the method for acoustics will be presented. The method looks especially useful for sound level prediction in industrial and office environments. [Work supported by NSF.

  19. Sound field simulation and acoustic animation in urban squares

    Science.gov (United States)

    Kang, Jian; Meng, Yan

    2005-04-01

    Urban squares are important components of cities, and the acoustic environment is important for their usability. While models and formulae for predicting the sound field in urban squares are important for their soundscape design and improvement, acoustic animation tools would be of great importance for designers as well as for public participation process, given that below a certain sound level, the soundscape evaluation depends mainly on the type of sounds rather than the loudness. This paper first briefly introduces acoustic simulation models developed for urban squares, as well as empirical formulae derived from a series of simulation. It then presents an acoustic animation tool currently being developed. In urban squares there are multiple dynamic sound sources, so that the computation time becomes a main concern. Nevertheless, the requirements for acoustic animation in urban squares are relatively low compared to auditoria. As a result, it is important to simplify the simulation process and algorithms. Based on a series of subjective tests in a virtual reality environment with various simulation parameters, a fast simulation method with acceptable accuracy has been explored. [Work supported by the European Commission.

  20. Underwater inspection training in intense radiation field

    International Nuclear Information System (INIS)

    Taniguchi, Ryoichi

    2017-01-01

    Osaka Prefecture University has a large dose cobalt 60 gamma ray source of about 2 PBq, and is engaged in technological training and human resource development. It is assumed that the decommissioning underwater operation of Fukushima Daiichi Nuclear Power Station would be the focus. The university aims at acquisition of the basic of underwater inspection work under radiation environment that is useful for the above purpose, radiation measurement under water, basic training in image measurement, and aims as well to evaluate the damage of imaging equipment due to radiation, and master practical knowledge for the use of inspection equipment under a large dose. In particular, it is valuable to train in the observation of Cherenkov light emitted from a large dose cobalt radiation source in water using a high sensitivity camera. The measurement of radiation dose distribution in water had difficulty in remote measurement due to water shielding effect. Although it took much time before, the method using high sensitivity camera is easy to sequentially perform two-dimensional measurement, and its utility value is large. Its effect on the dose distribution measurement of irregularly shaped sources is great. The contents of training includes the following: radiation source imaging in water, use of a laser rangefinder in water, dose distribution measurement in water and Cherenkov light measurement, judgment of equipment damage due to irradiation, weak radiation measurement, and measurement and decontamination of surface contamination. (A.O.)

  1. Underwater video enhancement using multi-camera super-resolution

    Science.gov (United States)

    Quevedo, E.; Delory, E.; Callicó, G. M.; Tobajas, F.; Sarmiento, R.

    2017-12-01

    Image spatial resolution is critical in several fields such as medicine, communications or satellite, and underwater applications. While a large variety of techniques for image restoration and enhancement has been proposed in the literature, this paper focuses on a novel Super-Resolution fusion algorithm based on a Multi-Camera environment that permits to enhance the quality of underwater video sequences without significantly increasing computation. In order to compare the quality enhancement, two objective quality metrics have been used: PSNR (Peak Signal-to-Noise Ratio) and the SSIM (Structural SIMilarity) index. Results have shown that the proposed method enhances the objective quality of several underwater sequences, avoiding the appearance of undesirable artifacts, with respect to basic fusion Super-Resolution algorithms.

  2. Properties of sound attenuation around a two-dimensional underwater vehicle with a large cavitation number

    International Nuclear Information System (INIS)

    Ye Peng-Cheng; Pan Guang

    2015-01-01

    Due to the high speed of underwater vehicles, cavitation is generated inevitably along with the sound attenuation when the sound signal traverses through the cavity region around the underwater vehicle. The linear wave propagation is studied to obtain the influence of bubbly liquid on the acoustic wave propagation in the cavity region. The sound attenuation coefficient and the sound speed formula of the bubbly liquid are presented. Based on the sound attenuation coefficients with various vapor volume fractions, the attenuation of sound intensity is calculated under large cavitation number conditions. The result shows that the sound intensity attenuation is fairly small in a certain condition. Consequently, the intensity attenuation can be neglected in engineering. (paper)

  3. Investigation of acoustic field near to elastic thin plate using integral method

    Directory of Open Access Journals (Sweden)

    В.І. Токарев

    2004-01-01

    Full Text Available  Investigation of acoustic field near to elastic thin plate using  integral method The influence of boundary conditions on sound wave propagation, radiation and transmission through thin elastic plate is investigated. Necessary for that numerical model was found using the Helmholtz equation and equation of oscilated plate by means of integral formulation of the solution for acoustic fields near to elastic thin plate and for bending waves of small amplitudes.

  4. Swarm Underwater Acoustic 3D Localization: Kalman vs Monte Carlo

    Directory of Open Access Journals (Sweden)

    Sergio Taraglio

    2015-07-01

    Full Text Available Two three-dimensional localization algorithms for a swarm of underwater vehicles are presented. The first is grounded on an extended Kalman filter (EKF scheme used to fuse some proprioceptive data such as the vessel's speed and some exteroceptive measurements such as the time of flight (TOF sonar distance of the companion vessels. The second is a Monte Carlo particle filter localization processing the same sensory data suite. The results of several simulations using the two approaches are presented, with comparison. The case of a supporting surface vessel is also considered. An analysis of the robustness of the two approaches against some system parameters is given.

  5. Effect of non-uniform mean flow field on acoustic propagation problems in computational aeroacoustics

    DEFF Research Database (Denmark)

    Si, Haiqing; Shen, Wen Zhong; Zhu, Wei Jun

    2013-01-01

    Acoustic propagation in the presence of a non-uniform mean flow is studied numerically by using two different acoustic propagating models, which solve linearized Euler equations (LEE) and acoustic perturbation equations (APE). As noise induced by turbulent flows often propagates from near field t...

  6. NEAR- AND FAR-FIELD RESPONSE TO COMPACT ACOUSTIC SOURCES IN STRATIFIED CONVECTION ZONES

    International Nuclear Information System (INIS)

    Cally, Paul S.

    2013-01-01

    The role of the acoustic continuum associated with compact sources in the Sun's interior wave field is explored for a simple polytropic model. The continuum produces a near-field acoustic structure—the so-called acoustic jacket—that cannot be represented by a superposition of discrete normal modes. Particular attention is paid to monochromatic point sources of various frequency and depth, and to the surface velocity power that results, both in the discrete f- and p-mode spectrum and in the continuum. It is shown that a major effect of the continuum is to heal the surface wave field produced by compact sources, and therefore to hide them from view. It is found that the continuous spectrum is not a significant contributor to observable inter-ridge seismic power.

  7. Introducing passive matched field acoustic tomography

    International Nuclear Information System (INIS)

    Gasparini, O.; Camporeale, C.; Crise, A.

    1997-01-01

    In acoustic tomography sea-basin environmental parameters such as temperature profiles and current-velocities are derived, when ray propagation models are adopted, by the travel time estimates relative to the identifiable ray paths. The transmitted signals are either single frequency, or impulsive, or intermittent and deterministic. When the wavelength is comparable with the scale lengths present in the propagation scenario, Matched Field Tomography (MFT) is used, entailing the consideration of waveguide modes instead of rays. A new concept in tomography is introduced in the paper, that employs passively the noise emitted by ships of opportunity (cargoes, ferries) as source signals. The passive technique is acoustic-pollution-free, and if a basin is selected in which a regular ship traffic occurs data can be received on a regular schedule, with no transmission cost. A novel array pre-processor for passive tomography is introduced, such that the signal structure at the pre-processor output in nearly the same as that obtainable in the case of single-frequency source signals

  8. The Intensity, Directionality, and Statistics of Underwater Noise From Melting Icebergs

    Science.gov (United States)

    Glowacki, Oskar; Deane, Grant B.; Moskalik, Mateusz

    2018-05-01

    Freshwater fluxes from melting icebergs and glaciers are important contributors to both sea level rise and anomalies of seawater salinity in polar regions. However, the hazards encountered close to icebergs and glaciers make it difficult to quantify their melt rates directly, motivating the development of cryoacoustics as a remote sensing technique. Recent studies have shown a qualitative link between ice melting and the accompanying underwater noise, but the properties of this signal remain poorly understood. Here we examine the intensity, directionality, and temporal statistics of the underwater noise radiated by melting icebergs in Hornsund Fjord, Svalbard, using a three-element acoustic array. We present the first estimate of noise energy per unit area associated with iceberg melt and demonstrate its qualitative dependence on exposure to surface current. Finally, we show that the analysis of noise directionality and statistics makes it possible to distinguish iceberg melt from the glacier terminus melt.

  9. Remote sensing of deep hermatypic coral reefs in Puerto Rico and the U.S. Virgin Islands using the Seabed autonomous underwater vehicle

    Science.gov (United States)

    Armstrong, Roy A.; Singh, Hanumant

    2006-09-01

    Optical imaging of coral reefs and other benthic communities present below one attenuation depth, the limit of effective airborne and satellite remote sensing, requires the use of in situ platforms such as autonomous underwater vehicles (AUVs). The Seabed AUV, which was designed for high-resolution underwater optical and acoustic imaging, was used to characterize several deep insular shelf reefs of Puerto Rico and the US Virgin Islands using digital imagery. The digital photo transects obtained by the Seabed AUV provided quantitative data on living coral, sponge, gorgonian, and macroalgal cover as well as coral species richness and diversity. Rugosity, an index of structural complexity, was derived from the pencil-beam acoustic data. The AUV benthic assessments could provide the required information for selecting unique areas of high coral cover, biodiversity and structural complexity for habitat protection and ecosystem-based management. Data from Seabed sensors and related imaging technologies are being used to conduct multi-beam sonar surveys, 3-D image reconstruction from a single camera, photo mosaicking, image based navigation, and multi-sensor fusion of acoustic and optical data.

  10. Investigation of the Propagation Characteristics of Underwater Shock Waves in Underwater Drilling Blasting

    Directory of Open Access Journals (Sweden)

    Xin Liu

    2018-01-01

    Full Text Available During the first-stage project of the main channel of Ningbo-Zhoushan Port’s Shipu Harbor, underwater shock waves were monitored. By analyzing a typical measured pressure time history curve, the characteristics of underwater shock waves in an engineering context were obtained. We obtained a traditional exponential attenuation formula for underwater shock waves based on the measured data, simplified the model of underwater drilling blasting based on engineering practice, deduced a revised formula for underwater shock wave peak overpressure on the basis of dimensional analysis, established a linear fitting model, and obtained the undetermined coefficients of the revised formula using a linear regression analysis. In addition, the accuracies of the two formulas used to predict underwater shock wave peak overpressure and the significance order of influence and influence mechanism of factors included in the revised formula on the underwater shock wave peak overpressure were discussed.

  11. Theoretical and experimental examination of near-field acoustic levitation.

    Science.gov (United States)

    Nomura, Hideyuki; Kamakura, Tomoo; Matsuda, Kazuhisa

    2002-04-01

    A planar object can be levitated stably close to a piston sound source by making use of acoustic radiation pressure. This phenomenon is called near-field acoustic levitation [Y. Hashimoto et al., J. Acoust. Soc. Am. 100, 2057-2061 (1996)]. In the present article, the levitation distance is predicted theoretically by numerically solving basic equations in a compressible viscous fluid subject to the appropriate initial and boundary conditions. Additionally, experiments are carried out using a 19.5-kHz piston source with a 40-mm aperture and various aluminum disks of different sizes. The measured levitation distance agrees well with the theory, which is different from a conventional theory, and the levitation distance is not inversely proportional to the square root of the surface density of the levitated disk in a strict sense.

  12. An OFDM Receiver with Frequency Domain Diversity Combined Impulsive Noise Canceller for Underwater Network

    Science.gov (United States)

    Saotome, Rie; Hai, Tran Minh; Matsuda, Yasuto; Suzuki, Taisaku; Wada, Tomohisa

    2015-01-01

    In order to explore marine natural resources using remote robotic sensor or to enable rapid information exchange between ROV (remotely operated vehicles), AUV (autonomous underwater vehicle), divers, and ships, ultrasonic underwater communication systems are used. However, if the communication system is applied to rich living creature marine environment such as shallow sea, it suffers from generated Impulsive Noise so-called Shrimp Noise, which is randomly generated in time domain and seriously degrades communication performance in underwater acoustic network. With the purpose of supporting high performance underwater communication, a robust digital communication method for Impulsive Noise environments is necessary. In this paper, we propose OFDM ultrasonic communication system with diversity receiver. The main feature of the receiver is a newly proposed Frequency Domain Diversity Combined Impulsive Noise Canceller. The OFDM receiver utilizes 20–28 KHz ultrasonic channel and subcarrier spacing of 46.875 Hz (MODE3) and 93.750 Hz (MODE2) OFDM modulations. In addition, the paper shows Impulsive Noise distribution data measured at a fishing port in Okinawa and at a barge in Shizuoka prefectures and then proposed diversity OFDM transceivers architecture and experimental results are described. By the proposed Impulsive Noise Canceller, frame bit error rate has been decreased by 20–30%. PMID:26351656

  13. An OFDM Receiver with Frequency Domain Diversity Combined Impulsive Noise Canceller for Underwater Network.

    Science.gov (United States)

    Saotome, Rie; Hai, Tran Minh; Matsuda, Yasuto; Suzuki, Taisaku; Wada, Tomohisa

    2015-01-01

    In order to explore marine natural resources using remote robotic sensor or to enable rapid information exchange between ROV (remotely operated vehicles), AUV (autonomous underwater vehicle), divers, and ships, ultrasonic underwater communication systems are used. However, if the communication system is applied to rich living creature marine environment such as shallow sea, it suffers from generated Impulsive Noise so-called Shrimp Noise, which is randomly generated in time domain and seriously degrades communication performance in underwater acoustic network. With the purpose of supporting high performance underwater communication, a robust digital communication method for Impulsive Noise environments is necessary. In this paper, we propose OFDM ultrasonic communication system with diversity receiver. The main feature of the receiver is a newly proposed Frequency Domain Diversity Combined Impulsive Noise Canceller. The OFDM receiver utilizes 20-28 KHz ultrasonic channel and subcarrier spacing of 46.875 Hz (MODE3) and 93.750 Hz (MODE2) OFDM modulations. In addition, the paper shows Impulsive Noise distribution data measured at a fishing port in Okinawa and at a barge in Shizuoka prefectures and then proposed diversity OFDM transceivers architecture and experimental results are described. By the proposed Impulsive Noise Canceller, frame bit error rate has been decreased by 20-30%.

  14. An OFDM Receiver with Frequency Domain Diversity Combined Impulsive Noise Canceller for Underwater Network

    Directory of Open Access Journals (Sweden)

    Rie Saotome

    2015-01-01

    Full Text Available In order to explore marine natural resources using remote robotic sensor or to enable rapid information exchange between ROV (remotely operated vehicles, AUV (autonomous underwater vehicle, divers, and ships, ultrasonic underwater communication systems are used. However, if the communication system is applied to rich living creature marine environment such as shallow sea, it suffers from generated Impulsive Noise so-called Shrimp Noise, which is randomly generated in time domain and seriously degrades communication performance in underwater acoustic network. With the purpose of supporting high performance underwater communication, a robust digital communication method for Impulsive Noise environments is necessary. In this paper, we propose OFDM ultrasonic communication system with diversity receiver. The main feature of the receiver is a newly proposed Frequency Domain Diversity Combined Impulsive Noise Canceller. The OFDM receiver utilizes 20–28 KHz ultrasonic channel and subcarrier spacing of 46.875 Hz (MODE3 and 93.750 Hz (MODE2 OFDM modulations. In addition, the paper shows Impulsive Noise distribution data measured at a fishing port in Okinawa and at a barge in Shizuoka prefectures and then proposed diversity OFDM transceivers architecture and experimental results are described. By the proposed Impulsive Noise Canceller, frame bit error rate has been decreased by 20–30%.

  15. Near field acoustic holography with microphones on a rigid sphere

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Moreno-Pescador, Guillermo; Fernandez Grande, Efren

    2011-01-01

    Spherical near field acoustic holography (spherical NAH) is a technique that makes it possible to reconstruct the sound field inside and just outside a spherical surface on which the sound pressure is measured with an array of microphones. This is potentially very useful for source identification...

  16. NEAR- AND FAR-FIELD RESPONSE TO COMPACT ACOUSTIC SOURCES IN STRATIFIED CONVECTION ZONES

    Energy Technology Data Exchange (ETDEWEB)

    Cally, Paul S., E-mail: paul.cally@monash.edu [Monash Centre for Astrophysics and School of Mathematical Sciences, Monash University, Clayton, Victoria 3800 (Australia)

    2013-05-01

    The role of the acoustic continuum associated with compact sources in the Sun's interior wave field is explored for a simple polytropic model. The continuum produces a near-field acoustic structure-the so-called acoustic jacket-that cannot be represented by a superposition of discrete normal modes. Particular attention is paid to monochromatic point sources of various frequency and depth, and to the surface velocity power that results, both in the discrete f- and p-mode spectrum and in the continuum. It is shown that a major effect of the continuum is to heal the surface wave field produced by compact sources, and therefore to hide them from view. It is found that the continuous spectrum is not a significant contributor to observable inter-ridge seismic power.

  17. Comparison of PAM Systems for Acoustic Monitoring and Further Risk Mitigation Application.

    Science.gov (United States)

    Ludwig, Stefan; Kreimeyer, Roman; Knoll, Michaela

    2016-01-01

    We present results of the SIRENA 2011 research cruises conducted by the NATO Undersea Research Centre (NURC) and joined by the Research Department for Underwater Acoustics and Geophysics (FWG), Bundeswehr Technical Centre (WTD 71) and the Universities of Kiel and Pavia. The cruises were carried out in the Ligurian Sea. The main aim of the FWG was to test and evaluate the newly developed towed hydrophone array as a passive acoustic monitoring (PAM) tool for risk mitigation applications. The system was compared with the PAM equipment used by the other participating institutions. Recorded sounds were used to improve an automatic acoustic classifier for marine mammals, and validated acoustic detections by observers were compared with the results of the classifier.

  18. Efficient Underwater RSS Value to Distance Inversion Using the Lambert Function

    Directory of Open Access Journals (Sweden)

    Majid Hosseini

    2014-01-01

    Full Text Available There are many applications for using wireless sensor networks (WSN in ocean science; however, identifying the exact location of a sensor by itself (localization is still a challenging problem, where global positioning system (GPS devices are not applicable underwater. Precise distance measurement between two sensors is a tool of localization and received signal strength (RSS, reflecting transmission loss (TL phenomena, is widely used in terrestrial WSNs for that matter. Underwater acoustic sensor networks have not been used (UASN, due to the complexity of the TL function. In this paper, we addressed these problems by expressing underwater TL via the Lambert W function, for accurate distance inversion by the Halley method, and compared this to Newton-Raphson inversion. Mathematical proof, MATLAB simulation, and real device implementation demonstrate the accuracy and efficiency of the proposed equation in distance calculation, with fewer iterations, computation stability for short and long distances, and remarkably short processing time. Then, the sensitivities of Lambert W function and Newton-Raphson inversion to alteration in TL were examined. The simulation results showed that Lambert W function is more stable to errors than Newton-Raphson inversion. Finally, with a likelihood method, it was shown that RSS is a practical tool for distance measurement in UASN.

  19. Modeling of Acoustic Field for a Parametric Focusing Source Using the Spheroidal Beam Equation

    Directory of Open Access Journals (Sweden)

    Yu Lili

    2015-09-01

    Full Text Available A theoretical model of acoustic field for a parametric focusing source on concave spherical surface is proposed. In this model, the source boundary conditions of the Spheroidal Beam Equation (SBE for difference frequency wave excitation were studied. Propagation curves and beam patterns for difference frequency component of the acoustic field are compared with those obtained for Khokhlov-Zabolotskaya-Kuznetsov (KZK model. The results demonstrate that the focused parametric model of SBE is good valid for a large aperture angle in the strongly focused acoustic field. It is also investigated that high directivity and good focal ability with the decreasing of downshift ratio and the increasing of half-aperture angle for the focused parametric model of SBE.

  20. Underwater inverse LIBS (iLIBS) for marine archaeology

    Science.gov (United States)

    Asmus, J.; Magde, M.; Elford, J.; Magde, D.; Parfenov, V.

    2013-05-01

    In recent years there have been enormous advances in nautical archaeology through developments in SONAR technologies as well as in manned and robotic submersible vehicles. The number of sunken vessel discoveries has escalated in many of the seas of the world in response to the widespread application of these and other new tools. Customarily, surviving artifacts within the debris field of a wreck are collected and then moved to laboratories, centers, or institutions for analyses and possible conservation. Frequently, the conservation phase involves chemical treatments to stabilize an artefact to standard temperature, pressure, and humidity instead of an undersea environment. Many of the artefacts encountered at an underwater site are now characterized and restored in-situ in accordance with modern trends in art conservation. Two examples of this trend are exemplified by the resting place of the wreck of the Titanic in the Atlantic and the Cancun Underwater Park in the Caribbean Sea. These two debris fields have been turned into museums for diving visitors. Several research groups have investigated the possibility of adapting the well-established analytical tool Laser Induced Breakdown Spectroscopy (LIBS) to in-situ elemental analyses of underwater cultural, historic, and archaeological artefacts where discovered, rather than as a phase of a salvage operation. As the underwater laser ablation associated with LIBS generates a "snowplough" shockwave within the aqueous matrix, the atomic emission spectrum is usually severely attenuated in escaping from the target. Consequently, probative experiments to date generally invoke a submerged air chamber or air jet to isolate water from the interaction zone as well as employ more complex double-pulse lasers. These measures impose severe logistical constraints on the examination of widely dispersed underwater artefacts. In order to overcome this constraint we report on water-immersion LIBS experiments performed with oblique

  1. Experimental Measurements of Temporal Dispersion for Underwater Laser Communications and Imaging

    Science.gov (United States)

    Cochenour, Brandon Michael

    The challenge in implementing optical sensors underwater lies in the high variability of the ocean environment where propagation of light in the ocean is complicated by absorption and scattering. Most underwater optical sensors operate in the blue/green portion of the electromagnetic spectrum where seawater exhibits an absorption minimum. Mitigating scattering however is a greater challenge. In particular, scattering causes both spatial distortion (beam spreading) and temporal dispersion (pulse spreading or distortion). Each of type of dispersion decreases sensor performance (operating range, image resolution, data bandwidth, etc.). While spatial dispersion has received a great deal of attention in previous decades, technological limitations of sensor hardware have made experimental measurements of temporal dispersion underwater difficult until now. The main contribution of this thesis are experimental measurements of temporal dispersion of optical beams in turbid water, made with a high sensitivity/high dynamic range experimental technique. Measurements are performed as a function of water clarity (0-20 attenuation lengths), transmitter/receiver alignment (0-30 degrees, half angle), receiver field of view (1-7 degrees, full angle), and transmitter beam divergence (collimated and diffuse). Special attention is paid to the interdependency between spatial and temporal dispersion. This work provides severable notable contributions: 1. While experimental characterization of spatial dispersion has received significant attention underwater, there has been a lack of measurements characterizing temporal dispersion underwater. This work provides the most comprehensive set of experimental measurements to date regarding the temporal dispersion of optical beams underwater. 2. An experimental analysis of the influence of scattering phase function on temporal dispersion. Coarse estimates of the scattering phase function are used to determine the ranges (or attenuation lengths

  2. Optimum LED wavelength for underwater optical wireless communication at turbid water

    Science.gov (United States)

    Rosenkrantz, Etai; Arnon, Shlomi

    2014-10-01

    Underwater optical wireless communication is an emerging technology, which can provide high data rate. High data rate communication is required for applications such as underwater imaging, networks of sensors and swarms of underwater vehicles. These applications pursue an affordable light source, which can be obtained by light emitting diodes (LED). LEDs offer solutions characterized by low cost, high efficiency, reliability and compactness based on off-the-shelf components such as blue and green light emitting diodes. In this paper we present our recent theoretical and experimental results in this field.

  3. The magnetized electron-acoustic instability driven by a warm, field-aligned electron beam

    International Nuclear Information System (INIS)

    Sooklal, A.; Mace, R.L.

    2004-01-01

    The electron-acoustic instability in a magnetized plasma having three electron components, one of which is a field-aligned beam of intermediate temperature, is investigated. When the plasma frequency of the cool electrons exceeds the electron gyrofrequency, the electron-acoustic instability 'bifurcates' at sufficiently large propagation angles with respect to the magnetic field to yield an obliquely propagating, low-frequency electron-acoustic instability and a higher frequency cyclotron-sound instability. Each of these instabilities retains certain wave features of its progenitor, the quasiparallel electron-acoustic instability, but displays also new magnetic qualities through its dependence on the electron gyrofrequency. The obliquely propagating electron-acoustic instability requires a lower threshold beam speed for its excitation than does the cyclotron-sound instability, and for low to intermediate beam speeds has the higher maximum growth rate. When the plasma is sufficiently strongly magnetized that the plasma frequency of the cool electrons is less than the electron gyrofrequency, the only instability in the electron-acoustic frequency range is the strongly magnetized electron-acoustic instability. Its growth rate and real frequency exhibit a monotonic decrease with wave propagation angle and it grows at small to intermediate wave numbers where its parallel phase speed is approximately constant. The relevance of the results to the interpretation of cusp auroral hiss and auroral broadband electrostatic noise is briefly discussed

  4. SERDP/Office of Naval Research Workshop on Acoustic Detection and Classification of UXO in the Underwater Environment

    Science.gov (United States)

    2013-09-01

    and range in diameter from 20 mm to 155 mm or greater. Shallow water mines can be small and are often squat cylinders; offshore mines are larger and...characterized acoustic responses from both free -field, proud and buried UXO. Most, if not all, the sediments were fine to medium sand. Data were

  5. Cross-field dust acoustic instability in a dusty negative ion plasma

    International Nuclear Information System (INIS)

    Rosenberg, M

    2010-01-01

    A cross-field dust acoustic instability in a dusty negative ion plasma in a magnetic field is studied using kinetic theory. The instability is driven by the ExB drifts of the ions. It is assumed that the negative ions are much heavier than the positive ions, and that the dust is negatively charged. The case where the positive ions and electrons are magnetized, the negative ions are marginally unmagnetized, and the dust is unmagnetized is considered. The focus is on a situation where Doppler resonances near harmonics of the positive ion gyrofrequency can affect the spectrum of unstable dust acoustic waves. Application to possible laboratory experimental parameters is discussed.

  6. A bio-inspired electrocommunication system for small underwater robots.

    Science.gov (United States)

    Wang, Wei; Liu, Jindong; Xie, Guangming; Wen, Li; Zhang, Jianwei

    2017-03-29

    Weakly electric fishes (Gymnotid and Mormyrid) use an electric field to communicate efficiently (termed electrocommunication) in the turbid waters of confined spaces where other communication modalities fail. Inspired by this biological phenomenon, we design an artificial electrocommunication system for small underwater robots and explore the capabilities of such an underwater robotic communication system. An analytical model for electrocommunication is derived to predict the effect of the key parameters such as electrode distance and emitter current of the system on the communication performance. According to this model, a low-dissipation, and small-sized electrocommunication system is proposed and integrated into a small robotic fish. We characterize the communication performance of the robot in still water, flowing water, water with obstacles and natural water conditions. The results show that underwater robots are able to communicate electrically at a speed of around 1 k baud within about 3 m with a low power consumption (less than 1 W). In addition, we demonstrate that two leader-follower robots successfully achieve motion synchronization through electrocommunication in the three-dimensional underwater space, indicating that this bio-inspired electrocommunication system is a promising setup for the interaction of small underwater robots.

  7. Analysis of underwater decoupling properties of a locally resonant acoustic metamaterial coating

    International Nuclear Information System (INIS)

    Huang Ling-Zhi; Xiao Yong; Wen Ji-Hong; Yang Hai-Bin; Wen Xi-Sen

    2016-01-01

    This paper presents a semi-analytical solution for the vibration and sound radiation of a semi-infinite plate covered by a decoupling layer consisting of locally resonant acoustic metamaterial. Formulations are derived based on a combination use of effective medium theory and the theory of elasticity for the decoupling material. Theoretical results show good agreements between the method developed in this paper and the conventional finite element method (FEM), but the method of this paper is more efficient than FEM. Numerical results also show that system with acoustic metamaterial decoupling layer exhibits significant noise reduction performance at the local resonance frequency of the acoustic metamaterial, and such performance can be ascribed to the vibration suppression of the base plate. It is demonstrated that the effective density of acoustic metamaterial decoupling layer has a great influence on the mechanical impedance of the system. Furthermore, the resonance frequency of locally resonant structure can be effectively predicted by a simple model, and it can be significantly affected by the material properties of the locally resonant structure. (paper)

  8. Impacts of an underwater high voltage DC power cable on fish migration movements in the San Francisco Bay.

    Science.gov (United States)

    Wyman, M. T.; Kavet, R.; Klimley, A. P.

    2016-02-01

    There is an increasingly strong interest on a global scale in offshore renewable energy production and transportation. However, there is concern that the electromagnetic fields (EMF) produced by these underwater cables may alter the behavior and physiology of marine species. Despite this concern, few studies have investigated these effects in free-living species. In 2009, a 85 km long high-voltage DC (HVDC) power cable was placed within the San Francisco Bay, running parallel, then perpendicular to, the migration route of anadromous species moving from the inland river system to the oceans. In this study, we assess the impacts of this HVDC cable on the migration behaviors of EMF-sensitive fish, including juvenile salmonids (Chinook salmon, Oncorhynchus tshawytscha, and steelhead trout, Oncorhynchus mykiss) and adult green sturgeon, Acipenser medirostris. Acoustic telemetry techniques were used to track fish migration movements through the San Francisco Bay both before and after the cable was activated; individuals implanted with acoustic transmitters were detected on cross-channel hydrophone arrays at key locations in the system. Magnetic fields were surveyed and mapped at these locations using a transverse gradiometer, and models of the cable's magnetic field were developed that closely matched the empirically measured values. Here, we present our analyses on the relationships between migration-related behavioral metrics (e.g., percent of successful migrations, duration of migration, time spent near vs. far from cable location, etc.) and environmental parameters, such as cable activation and load level, local magnetic field levels, depth, and currents.

  9. The Blind Identification of Multi-Inputs and Multi-Outputs Shallow-Water Acoustic Channel

    International Nuclear Information System (INIS)

    Li, R Y; Zhou, J H; Wang, L

    2006-01-01

    Blind channel identification/estimation is very important for object detection, trace, localization in the ocean acoustics. Time domain blind identification algorithm requiring exact length of the channel being identification. Due to the characteristics of the shallow-water channel, the length of channel impulse response sequence is uncertain, Hence a frequency domain method for the blind MIMO (Multiple-Input Multiple-Output) underwater identification based on higher order statistics (HOS) is used to estimate the original acoustic channel from received signals on hydrophones only, with the low signal to noise ratio (SNR). The simulation results in the acoustic environment proved this work is effective and efficient for blind identification of the shallow-water acoustic channel

  10. Experimental Results for Direction of Arrival Estimation with a Single Acoustic Vector Sensor in Shallow Water

    Directory of Open Access Journals (Sweden)

    Alper Bereketli

    2015-01-01

    Full Text Available We study the performances of several computationally efficient and simple techniques for estimating direction of arrival (DOA of an underwater acoustic source using a single acoustic vector sensor (AVS in shallow water. Underwater AVS is a compact device, which consists of one hydrophone and three accelerometers in a packaged form, measuring scalar pressure and three-dimensional acceleration simultaneously at a single position. A very controlled experimental setup is prepared to test how well-known techniques, namely, arctan-based, intensity-based, time domain beamforming, and frequency domain beamforming methods, perform in estimating DOA of a source in different circumstances. Experimental results reveal that for almost all cases beamforming techniques perform best. Moreover, arctan-based method, which is the simplest of all, provides satisfactory results for practical purposes.

  11. On the Impacts and Benefits of Implementing Full-Duplex Communications Links in an Underwater Acoustic Network

    National Research Council Canada - National Science Library

    Gibson, J; Larraza, A; Rice, J; Smith, K; Xie, G

    2002-01-01

    .... These networks may provide command and control for autonomous underwater vehicles, forward reporting by arrays of sensor grids, ad hoc communications links to covert forces, or positive control...

  12. Modified electron acoustic field and energy applied to observation data

    Energy Technology Data Exchange (ETDEWEB)

    Abdelwahed, H. G., E-mail: hgomaa-eg@yahoo.com, E-mail: hgomaa-eg@mans.edu.eg [College of Science and Humanitarian Studies, Physics Department, Prince Sattam Bin Abdul Aziz University, Alkharj 11942 (Saudi Arabia); Theoretical Physics Research Group, Physics Department, Faculty of Science, Mansoura University, Mansoura 35516 (Egypt); El-Shewy, E. K. [Theoretical Physics Research Group, Physics Department, Faculty of Science, Mansoura University, Mansoura 35516 (Egypt)

    2016-08-15

    Improved electrostatic acoustic field and energy have been debated in vortex trapped hot electrons and fluid of cold electrons with pressure term plasmas. The perturbed higher-order modified-Korteweg-de Vries equation (PhomKdV) has been worked out. The effect of trapping and electron temperatures on the electro-field and energy properties in auroral plasmas has been inspected.

  13. A 20 MW podded ship underwater electromagnetic signature - the alternative electric field; Signature electromagnetique sous-marine d'un paquebot de 20 MW a pods - le champ electrique alternatif

    Energy Technology Data Exchange (ETDEWEB)

    Lucas, B.; Henocq, H.; Rannou, C. [Delegation Generale pour l' Armement, DET/GESMA, 75 - Paris (France); Albert, Th.; Harpin, D. [ALSTOM Marine (France); Bourguet, S.; Guerin, P. [Institut de Recherche en Electrotechnique et Electronique de Nantes Atlantique, 44 (France)

    2006-03-15

    Today, electric podded propulsion is used for many ships, cruise liners and Navy vessels.This propulsion uses high currents in extremely low frequencies (ELFE); currents flow through electrical network, equipment and pods. These alternative currents could generate important underwater electromagnetic field. GESMA has to quantify the level of this field and its impact on the signature of this kind of ship. Then, GESMA carried out electromagnetic measurements using a multi-sensors underwater and autonomous facility named AMI. It was placed on the route of a 20 MW podded ship, at one hundred meters depth from the surface. Especially, AMI observed an alternative radiated electric field... (authors)

  14. 12th Anglo-French Physical Acoustics Conference (AFPAC2013)

    Science.gov (United States)

    2014-04-01

    The Anglo-French Physical Acoustics Conference (AFPAC) had its 12th annual meeting in Villa Clythia, Fréjus, France, from 16th to 18th January 2013. This series of meetings is a collaboration between the Physical Acoustics Group (PAG) of the Institute of Physics and the Groupe d'Acoustique Physique, Sous-marine et UltraSonore (GAPSUS) of the Société Française d'Acoustique. This year, attendees got the opportunity to see the French Riviera with its Mediterranean vegetation covered by a nice thick snow layer. The participants heard 34 excellent oral presentations and saw 3 posters covering an exciting and diverse range of subjects and of frequencies, from ultrasonic wave propagation in chocolate to metamaterials applied to seismic waves for protecting buildings. Among them, invited talks were given by Pr F A Duck ( Enhanced healing by ultrasound: clinical effects and mechanisms), Pr. J-C Valiére, who actually gave two invited talks ( 1. Measurement of audible acoustic particle velocity using laser: Principles, signal processing and applications, 2. Acoustic pots in ancient and medieval buildings: Literary analysis of ancient texts and comparison with recent observations in French churches), Dr P Huthwaite ( Ultrasonic imaging through the resolution of inverse problems), Dr X Lurton ( Underwater acoustic systems on oceanographic research vessels: principles and applications), Dr S Guenneau ( From platonics to seismic metamaterials). For the fifth consecutive year AFPAC is followed by the publication of its proceedings with 12 peer-reviewed papers which cover the most recent research developments in the field of Physical Acoustics in the UK and France. Alain Lhémery (CEA, France) and Nader Saffari (UCL, United Kingdom) French Riviera 12th AFPAC — Villa Clythia, Fréjus (French Riviera), the 17th of January 2013

  15. Design of underwater work systems

    International Nuclear Information System (INIS)

    Lovelace, R.B.

    1980-01-01

    In the near future, underwater vehicles will replace divers as the principal means for inspection and maintenance work. These vehicles will provide a maneuverable work platform for an underwater viewing system and manipulator/tool package. Some of the problems faced by the underwater designer, and some areas to consider in the design of an integrated underwater work system, are considered

  16. Sound field reproduction as an equivalent acoustical scattering problem.

    Science.gov (United States)

    Fazi, Filippo Maria; Nelson, Philip A

    2013-11-01

    Given a continuous distribution of acoustic sources, the determination of the source strength that ensures the synthesis of a desired sound field is shown to be identical to the solution of an equivalent acoustic scattering problem. The paper begins with the presentation of the general theory that underpins sound field reproduction with secondary sources continuously arranged on the boundary of the reproduction region. The process of reproduction by a continuous source distribution is modeled by means of an integral operator (the single layer potential). It is then shown how the solution of the sound reproduction problem corresponds to that of an equivalent scattering problem. Analytical solutions are computed for two specific instances of this problem, involving, respectively, the use of a secondary source distribution in spherical and planar geometries. The results are shown to be the same as those obtained with analyses based on High Order Ambisonics and Wave Field Synthesis, respectively, thus bringing to light a fundamental analogy between these two methods of sound reproduction. Finally, it is shown how the physical optics (Kirchhoff) approximation enables the derivation of a high-frequency simplification for the problem under consideration, this in turn being related to the secondary source selection criterion reported in the literature on Wave Field Synthesis.

  17. Design of acoustic logging signal source of imitation based on field programmable gate array

    Science.gov (United States)

    Zhang, K.; Ju, X. D.; Lu, J. Q.; Men, B. Y.

    2014-08-01

    An acoustic logging signal source of imitation is designed and realized, based on the Field Programmable Gate Array (FPGA), to improve the efficiency of examining and repairing acoustic logging tools during research and field application, and to inspect and verify acoustic receiving circuits and corresponding algorithms. The design of this signal source contains hardware design and software design,and the hardware design uses an FPGA as the control core. Four signals are made first by reading the Random Access Memory (RAM) data which are inside the FPGA, then dealing with the data by digital to analog conversion, amplification, smoothing and so on. Software design uses VHDL, a kind of hardware description language, to program the FPGA. Experiments illustrate that the ratio of signal to noise for the signal source is high, the waveforms are stable, and also its functions of amplitude adjustment, frequency adjustment and delay adjustment are in accord with the characteristics of real acoustic logging waveforms. These adjustments can be used to imitate influences on sonic logging received waveforms caused by many kinds of factors such as spacing and span of acoustic tools, sonic speeds of different layers and fluids, and acoustic attenuations of different cementation planes.

  18. Influence of electrical boundary conditions on profiles of acoustic field and electric potential of shear-horizontal acoustic waves in potassium niobate plates.

    Science.gov (United States)

    Kuznetsova, I E; Nedospasov, I A; Kolesov, V V; Qian, Z; Wang, B; Zhu, F

    2018-05-01

    The profiles of an acoustic field and electric potential of the forward and backward shear-horizontal (SH) acoustic waves of a higher order propagating in X-Y potassium niobate plate have been theoretically investigated. It has been shown that by changing electrical boundary conditions on a surface of piezoelectric plates, it is possible to change the distributions of an acoustic field and electric potential of the forward and backward acoustic waves. The dependencies of the distribution of a mechanical displacement and electrical potential over the plate thickness for electrically open and electrically shorted plates have been plotted. The influence of a layer with arbitrary conductivity placed on a one or on the both plate surfaces on the profiles under study, phase and group velocities of the forward and backward acoustic waves in X-Y potassium niobate has been also investigated. The obtained results can be useful for development of the method for control of a particle or electrical charge movement inside the piezoelectric plates, as well a sensor for definition of the thin film conductivity. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. Multireceiver Acoustic Communications in Time-Varying Environments

    Science.gov (United States)

    2014-06-01

    Conf. on Computer Science and Information Technology (ICCSIT), Chengdu, China , 2010, pp. 606–609, vol. 9. [8] P. Bouvet and A. Loussert, “Capacity...analysis of underwater acoustic MIMO communications,”OCEANS, Sydney, NSW, 2010, pp. 1–8. [9] Wines lab (2013). Wireless networks and embedded... China , 2012, pp. 2059–2063. [17] S. Katwal, R. Nath and G. Murmu, “A simple Kalman channel equalizer using adaptive algorithms for time-variant channel

  20. Motion analysis and trials of the deep sea hybrid underwater glider Petrel-II

    Science.gov (United States)

    Liu, Fang; Wang, Yan-hui; Wu, Zhi-liang; Wang, Shu-xin

    2017-03-01

    A hybrid underwater glider Petrel-II has been developed and field tested. It is equipped with an active buoyancy unit and a compact propeller unit. Its working modes have been expanded to buoyancy driven gliding and propeller driven level-flight, which can make the glider work in strong currents, as well as many other complicated ocean environments. Its maximal gliding speed reaches 1 knot and the propelling speed is up to 3 knots. In this paper, a 3D dynamic model of Petrel-II is derived using linear momentum and angular momentum equations. According to the dynamic model, the spiral motion in the underwater space is simulated for the gliding mode. Similarly the cycle motion on water surface and the depth-keeping motion underwater are simulated for the level-flight mode. These simulations are important to the performance analysis and parameter optimization for the Petrel-II underwater glider. The simulation results show a good agreement with field trials.

  1. Calculation of acoustic field based on laser-measured vibration velocities on ultrasonic transducer surface

    Science.gov (United States)

    Hu, Liang; Zhao, Nannan; Gao, Zhijian; Mao, Kai; Chen, Wenyu; Fu, Xin

    2018-05-01

    Determination of the distribution of a generated acoustic field is valuable for studying ultrasonic transducers, including providing the guidance for transducer design and the basis for analyzing their performance, etc. A method calculating the acoustic field based on laser-measured vibration velocities on the ultrasonic transducer surface is proposed in this paper. Without knowing the inner structure of the transducer, the acoustic field outside it can be calculated by solving the governing partial differential equation (PDE) of the field based on the specified boundary conditions (BCs). In our study, the BC on the transducer surface, i.e. the distribution of the vibration velocity on the surface, is accurately determined by laser scanning measurement of discrete points and follows a data fitting computation. In addition, to ensure the calculation accuracy for the whole field even in an inhomogeneous medium, a finite element method is used to solve the governing PDE based on the mixed BCs, including the discretely measured velocity data and other specified BCs. The method is firstly validated on numerical piezoelectric transducer models. The acoustic pressure distributions generated by a transducer operating in an homogeneous and inhomogeneous medium, respectively, are both calculated by the proposed method and compared with the results from other existing methods. Then, the method is further experimentally validated with two actual ultrasonic transducers used for flow measurement in our lab. The amplitude change of the output voltage signal from the receiver transducer due to changing the relative position of the two transducers is calculated by the proposed method and compared with the experimental data. This method can also provide the basis for complex multi-physical coupling computations where the effect of the acoustic field should be taken into account.

  2. A Comparison of Acoustic Field Measurement by a Microphone and by an Optical Interferometric Probe

    Directory of Open Access Journals (Sweden)

    R. Bálek

    2002-01-01

    Full Text Available The objective of this work is to show that our optical method for measuring acoustic pressure is in some way superior to measurement using a microphone. Measurement of the integral acoustic pressure in the air by a laser interferometric probe is compared with measurement using a microphone. We determined the particular harmonic components in the acoustic field in the case of relatively high acoustic power in the ultrasonic frequency range.

  3. Dynamics of a spherical particle in an acoustic field: A multiscale approach

    International Nuclear Information System (INIS)

    Xie, Jin-Han; Vanneste, Jacques

    2014-01-01

    A rigid spherical particle in an acoustic wave field oscillates at the wave period but has also a mean motion on a longer time scale. The dynamics of this mean motion is crucial for numerous applications of acoustic microfluidics, including particle manipulation and flow visualisation. It is controlled by four physical effects: acoustic (radiation) pressure, streaming, inertia, and viscous drag. In this paper, we carry out a systematic multiscale analysis of the problem in order to assess the relative importance of these effects depending on the parameters of the system that include wave amplitude, wavelength, sound speed, sphere radius, and viscosity. We identify two distinguished regimes characterised by a balance among three of the four effects, and we derive the equations that govern the mean particle motion in each regime. This recovers and organises classical results by King [“On the acoustic radiation pressure on spheres,” Proc. R. Soc. A 147, 212–240 (1934)], Gor'kov [“On the forces acting on a small particle in an acoustical field in an ideal fluid,” Sov. Phys. 6, 773–775 (1962)], and Doinikov [“Acoustic radiation pressure on a rigid sphere in a viscous fluid,” Proc. R. Soc. London A 447, 447–466 (1994)], clarifies the range of validity of these results, and reveals a new nonlinear dynamical regime. In this regime, the mean motion of the particle remains intimately coupled to that of the surrounding fluid, and while viscosity affects the fluid motion, it plays no part in the acoustic pressure. Simplified equations, valid when only two physical effects control the particle motion, are also derived. They are used to obtain sufficient conditions for the particle to behave as a passive tracer of the Lagrangian-mean fluid motion

  4. The Influence of Acoustic Field Induced by HRT on Oscillation Behavior of a Single Droplet

    Directory of Open Access Journals (Sweden)

    Can Ruan

    2017-01-01

    Full Text Available This paper presents an experimental and theoretical study on the effects of an acoustic field induced by Hartmann Resonance Tube (HRT on droplet deformation behavior. The characteristics of the acoustic field generated by HRT are investigated. Results show that the acoustic frequency decreases with the increase of the resonator length, the sound pressure level (SPL increases with the increase of nozzle pressure ratio (NPR, and it is also noted that increasing resonator length can cause SPL to decrease, which has rarely been reported in published literature. Further theoretical analysis reveals that the resonance frequency of a droplet has several modes, and when the acoustic frequency equals the droplet’s frequency, heightened droplet responses are observed with the maximum amplitude of the shape oscillation. The experimental results for different resonator cavity lengths, nozzle pressure ratios and droplet diameters confirm the non-linear nature of this problem, and this conclusion is in good agreement with theoretical analysis. Measurements by high speed camera have shown that the introduction of an acoustic field can greatly enhance droplet oscillation, which means with the use of an ultrasonic atomizer based on HRT, the quality of atomization and combustion can be highly improved.

  5. Taiwan's underwater cultural heritage documentation management

    Science.gov (United States)

    Tung, Y.-Y.

    2015-09-01

    Taiwan is an important trading and maritime channels for many countries since ancient time. Numerous relics lie underwater due to weather, wars, and other factors. In the year of 2006, Bureau of Cultural Heritage (BOCH) entrusted the Underwater Archaeological Team of Academia Sinica to execute the underwater archaeological investigation projects. Currently, we verified 78 underwater targets, with 78 site of those had been recognized as shipwrecks sites. Up to date, there is a collection of 638 underwater objects from different underwater archaeological sites. Those artefacts are distributed to different institutions and museums. As very diverse management methods/systems are applied for every individual institution, underwater cultural heritage data such as survey, excavation report, research, etc. are poorly organized and disseminated for use. For better communication regarding to Taiwan's underwater cultural heritage in every level, a universal format of documentation should be established. By comparing the existing checklist used in Taiwan with guidelines that are followed in other countries, a more intact and appropriate underwater cultural heritage condition documentation system can be established and adapted in Taiwan.

  6. HULU SUNGAI PERAK BED SEDIMENT MAPPING USING UNDERWATER ACOUSTIC SONAR

    Directory of Open Access Journals (Sweden)

    N. Arriafdi

    2016-09-01

    Full Text Available Development in acoustic survey techniques in particular side scan sonar have revolutionized the way we are able to image, map and understand the riverbed environment. It is now cost effective to image large areas of the riverbed using these techniques and the backscatter image created from surveys provides base line data from which thematic maps of the riverbed environment including maps of morphological geology, can be derived when interpreted in conjunction with in situ sampling data. This article focuses on investigation characteristics of sediments and correlation of side scan backscatter image with signal strength. The interpretation of acoustic backscatter rely on experienced interpretation by eye of grey scale images produced from the data. A 990F Starfish Side Scan Sonar was used to collect and develop a series of sonar images along 6 km of Hulu Sungai Perak. Background sediments could be delineated accurately and the image textures could be linked to the actual river floor appearance through grab sampling. A major difference was found in the acoustic returns from the two research area studies: the upstream area shows much rougher textures. This is due to an actual differences in riverbed roughness, caused by a difference in bottom currents and sediment dynamics in the two areas. The highest backscatter correlates with coarsest and roughness sediment. Result suggest that image based backscatter classification shows considerable promise for interpretation of side scan sonar data for the production of geological maps.

  7. Development of underwater laser cutting technology

    International Nuclear Information System (INIS)

    Sato, Seiichi; Inaba, Takanori; Inose, Koutarou; Matsumoto, Naoyuki; Sakakibara, Yuji

    2015-01-01

    In is desirable to use remote underwater device for the decommissioning work of highly radioactive components such as the nuclear internals from a view point of reducing the ranitidine exposure to the worker. Underwater laser cutting technology has advantages. First advantage in underwater laser cutting technology is that low reaction force during cutting, namely, remote operability is superior. Second point is that underwater laser cutting generates a little amount of secondary waste, because cutting kerf size is very small. Third point is that underwater laser cutting has low risk of the process delay, because device trouble is hard to happen. While underwater laser cutting has many advantages, the careful consideration in the safe treatment of the offgas which underwater laser cutting generates is necessary. This paper describes outline of underwater laser cutting technology developed by IHI Corporation (IHI) and that this technology is effective in various dismantling works in water. (author)

  8. Electrostatic images for underwater anisotropic conductive half spaces

    International Nuclear Information System (INIS)

    Flykt, M.; Lindell, I.; Eloranta, E.

    1998-01-01

    A static image principle makes it possible to derive analytical solutions to some basic geometries for DC fields. The underwater environment is especially difficult both from the theoretical and practical point of view. However, there are increasing demands that also the underwater geological formations should be studied in detail. The traditional image of a point source lies at the mirror point of the original. When anisotropic media is involved, however, the image location can change and the image source may be a continues, sector-like distribution. In this paper some theoretical considerations are carried out in the case where the lower half space can have a very general anisotropy in terms of electrical conductivity, while the upper half space is assumed isotropic. The reflection potential field is calculated for different values of electrical conductivity. (orig.)

  9. Blind equalization for underwater communications

    NARCIS (Netherlands)

    Blom, K.C.H.

    2014-01-01

    Underwater wireless (sensor) networks would vastly improve man's ability to explore and exploit remote aquatic environments. Despite underwater sensor and vehicle technology being relatively mature, underwater communications is still a major challenge. The most challenging characteristics of the

  10. Event Localization in Underwater Wireless Sensor Networks using Monitoring Courses

    KAUST Repository

    Debont, Matthew

    2011-11-01

    In this thesis we consider different methods to localize events in a multi-hop wireless sensor network operating underwater using acoustic modems. The network consists of surface gateway nodes and relay nodes. Localization of surface gateways can be achieved through GPS, but we cannot rely on this technology for localizing underwater nodes. Surface Gateway nodes can distribute their locations through the network using the incoming signals by the acoustic modems from the relay nodes. Relay nodes are deployed to remain static but due to water currents, floating, and the untethered nature of the nodes, they often suffer from frequent drifting which can result in a deployed network suffering link failures. In this work, we developed a novel concept of an underwater alarming system, which adapts a cyclic graph model. In the event of link failure, a series of alarm packets are broadcasted in the network. These alarms are then captured through a novel concept of underwater Monitoring Courses (M-Courses), which can also be used to assure network connectivity and identify node faults. M-Courses also allow the network to localize events and identify network issues at a local level before forwarding any results upwards to a Surface Gateway nodes. This reduces the amount of communication overhead needed and allowing for distributed management of nodes in a network which may be constantly moving. We show that the proposed algorithms can reduce the number of send operations needed for an event to be localized in a network. We have found that M-Course routing reduces the number of sends required to report an event to a Surface Gateway by up to 80% in some cases when compared to a naive routing implementation. But this is achieved by increasing the time for an event to reach a Surface Gateway. These effects are both due to the buffering effect of M-Course routing, which allows us to efficiently deal with multiple events in an local area and we find that the performance of M

  11. Underwater Acoustic Measurements to Estimate Wind and Rainfall in the Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Sara Pensieri

    2015-01-01

    Full Text Available Oceanic ambient noise measurements can be analyzed to obtain qualitative and quantitative information about wind and rainfall phenomena over the ocean filling the existing gap of reliable meteorological observations at sea. The Ligurian Sea Acoustic Experiment was designed to collect long-term synergistic observations from a passive acoustic recorder and surface sensors (i.e., buoy mounted rain gauge and anemometer and weather radar to support error analysis of rainfall rate and wind speed quantification techniques developed in past studies. The study period included combination of high and low wind and rainfall episodes and two storm events that caused two floods in the vicinity of La Spezia and in the city of Genoa in 2011. The availability of high resolution in situ meteorological data allows improving data processing technique to detect and especially to provide effective estimates of wind and rainfall at sea. Results show a very good correspondence between estimates provided by passive acoustic recorder algorithm and in situ observations for both rainfall and wind phenomena and demonstrate the potential of using measurements provided by passive acoustic instruments in open sea for early warning of approaching coastal storms, which for the Mediterranean coastal areas constitutes one of the main causes of recurrent floods.

  12. Underwater Acoustic Wireless Sensor Networks: Advances and Future Trends in Physical, MAC and Routing Layers

    NARCIS (Netherlands)

    Climent, S.; Sanchez, A.; Capella, J.V.; Meratnia, Nirvana; Serrano, J.J.

    2014-01-01

    This survey aims to provide a comprehensive overview of the current research on underwater wireless sensor networks, focusing on the lower layers of the communication stack, and envisions future trends and challenges. It analyzes the current state-of-the-art on the physical, medium access control

  13. Polymer coating of glass microballoons levitated in a focused acoustic field

    International Nuclear Information System (INIS)

    Young, A.T.; Lee, M.C.; Feng, I.A.; Elleman, D.D.; Wang, T.G.

    1981-01-01

    Inertial confinement fusion (ICF) glass microballoons (GMBs) levitated in a focusing radiator acoustic device can be coated with liquid materials by deploying the liquid into the levitation field with a stepped-horn atomizer. The GMB can be forced to the center of the coating liquid with a strong acoustically generated centering force. Water solutions of organic polymers, uv-curable liquid organic monomers, and paraffin waxes have been used to prepare solid coatings on the surface of GMBs using this technique

  14. Design of acoustic logging signal source of imitation based on field programmable gate array

    International Nuclear Information System (INIS)

    Zhang, K; Ju, X D; Lu, J Q; Men, B Y

    2014-01-01

    An acoustic logging signal source of imitation is designed and realized, based on the Field Programmable Gate Array (FPGA), to improve the efficiency of examining and repairing acoustic logging tools during research and field application, and to inspect and verify acoustic receiving circuits and corresponding algorithms. The design of this signal source contains hardware design and software design,and the hardware design uses an FPGA as the control core. Four signals are made first by reading the Random Access Memory (RAM) data which are inside the FPGA, then dealing with the data by digital to analog conversion, amplification, smoothing and so on. Software design uses VHDL, a kind of hardware description language, to program the FPGA. Experiments illustrate that the ratio of signal to noise for the signal source is high, the waveforms are stable, and also its functions of amplitude adjustment, frequency adjustment and delay adjustment are in accord with the characteristics of real acoustic logging waveforms. These adjustments can be used to imitate influences on sonic logging received waveforms caused by many kinds of factors such as spacing and span of acoustic tools, sonic speeds of different layers and fluids, and acoustic attenuations of different cementation planes. (paper)

  15. The use of a sparse planar array sensor for measurement of the acoustic properties of panel materials at simulated ocean conditions

    OpenAIRE

    Beamiss, Graham A.; Robinson, Stephen P.; Wang, Lian S.; Hayman, Gary; Humphrey, Victor F.; Smith, John D.; Martin, M. J.

    2015-01-01

    Characterisation of the acoustic properties of materials for underwater acoustics is often carried out by measuring the transmitted and/or reflected pressure signals after insonification of a test panel by an incident acoustic wave. For this method to be reliable, the incident and transmitted (or reflected) signals arriving at the hydrophone receiver should be well separated in time (enabling windowing techniques to be applied), and the diffracted signals from the panel edge should not contam...

  16. Schlieren imaging of the standing wave field in an ultrasonic acoustic levitator

    Science.gov (United States)

    Rendon, Pablo Luis; Boullosa, Ricardo R.; Echeverria, Carlos; Porta, David

    2015-11-01

    We consider a model of a single axis acoustic levitator consisting of two cylinders immersed in air and directed along the same axis. The first cylinder has a flat termination and functions as a sound emitter, and the second cylinder, which is simply a refector, has the side facing the first cylinder cut out by a spherical surface. By making the first cylinder vibrate at ultrasonic frequencies a standing wave is produced in the air between the cylinders which makes it possible, by means of the acoustic radiation pressure, to levitate one or several small objects of different shapes, such as spheres or disks. We use schlieren imaging to observe the acoustic field resulting from the levitation of one or several objects, and compare these results to previous numerical approximations of the field obtained using a finite element method. The authors acknowledge financial support from DGAPA-UNAM through project PAPIIT IN109214.

  17. Advances in the ROBLINKS project on long-range shallow-water robust acoustic communciation links

    NARCIS (Netherlands)

    Gijzen, M.B. van; Walree, P.A. van; Cano, D.; Passerieux, J-M.; Waldhorst, A.; Weber, R.

    2000-01-01

    Within the ROBLINKS project waveforms and algorithms have been developed to establish robust underwater acoustic communication links with high data rates in shallow water. To evaluate the signalling schemes, a wide range of experiments has been performed during a sea trial that has been held in May

  18. Recovering an elastic obstacle containing embedded objects by the acoustic far-field measurements

    Science.gov (United States)

    Qu, Fenglong; Yang, Jiaqing; Zhang, Bo

    2018-01-01

    Consider the inverse scattering problem of time-harmonic acoustic waves by a 3D bounded elastic obstacle which may contain embedded impenetrable obstacles inside. We propose a novel and simple technique to show that the elastic obstacle can be uniquely recovered by the acoustic far-field pattern at a fixed frequency, disregarding its contents. Our method is based on constructing a well-posed modified interior transmission problem on a small domain and makes use of an a priori estimate for both the acoustic and elastic wave fields in the usual H 1-norm. In the case when there is no obstacle embedded inside the elastic body, our method gives a much simpler proof for the uniqueness result obtained previously in the literature (Natroshvili et al 2000 Rend. Mat. Serie VII 20 57-92 Monk and Selgas 2009 Inverse Problems Imaging 3 173-98).

  19. Modeling of Focused Acoustic Field of a Concave Multi-annular Phased Array Using Spheroidal Beam Equation

    International Nuclear Information System (INIS)

    Yu Lili; Shou Wende; Hui Chun

    2012-01-01

    A theoretical model of focused acoustic field for a multi-annular phased array on concave spherical surface is proposed. In this model, the source boundary conditions of the spheroidal beam equation (SBE) for multi-annular phased elements are studied. Acoustic field calculated by the dynamic focusing model of SBE is compared with numerical results of the O'Neil and Khokhlov-Zabolotskaya-Kuznetsov (KZK) model, respectively. Axial dynamic focusing and the harmonic effects are presented. The results demonstrate that the dynamic focusing model of SBE is good valid for a concave multi-annular phased array with a large aperture angle in the linear or nonlinear field. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  20. Springer Handbook of Acoustics

    CERN Document Server

    Rossing, Thomas D

    2007-01-01

    Acoustics, the science of sound, has developed into a broad interdisciplinary field encompassing the academic disciplines of physics, engineering, psychology, speech, audiology, music, architecture, physiology, neuroscience, and others. The Springer Handbook of Acoustics is an unparalleled modern handbook reflecting this richly interdisciplinary nature edited by one of the acknowledged masters in the field, Thomas Rossing. Researchers and students benefit from the comprehensive contents spanning: animal acoustics including infrasound and ultrasound, environmental noise control, music and human speech and singing, physiological and psychological acoustics, architectural acoustics, physical and engineering acoustics, signal processing, medical acoustics, and ocean acoustics. This handbook reviews the most important areas of acoustics, with emphasis on current research. The authors of the various chapters are all experts in their fields. Each chapter is richly illustrated with figures and tables. The latest rese...

  1. Underwater wireless communication system

    International Nuclear Information System (INIS)

    Goh, J H; Shaw, A; Al-Shamma'a, A I

    2009-01-01

    Underwater communication has a range of applications including remotely operated vehicle (ROV) and autonomous underwater vehicle (AUV) communication and docking in the offshore industry. Current underwater transmission techniques is primarily utilise sound waves for large distance at lower frequencies and the velocity of sound in water is approximately 1500m/s the resultant communications have problems with multi-path propagation and low bandwidth problems. The use of electromagnetic (EM) techniques underwater has largely been overlooked because of the attenuation due to the conductivity of seawater. However, for short range applications, the higher frequencies and much higher velocity can prove advantageous. This paper will outline a project which will utilise recent investigations that demonstrate EM wave propagation up to the MHz frequency range is possible in seawater.

  2. Underwater Scene Composition

    Science.gov (United States)

    Kim, Nanyoung

    2009-01-01

    In this article, the author describes an underwater scene composition for elementary-education majors. This project deals with watercolor with crayon or oil-pastel resist (medium); the beauty of nature represented by fish in the underwater scene (theme); texture and pattern (design elements); drawing simple forms (drawing skill); and composition…

  3. Acoustic scattering of a Bessel vortex beam by a rigid fixed spheroid

    Science.gov (United States)

    Mitri, F. G.

    2015-12-01

    Partial-wave series representation of the acoustic scattering field of high-order Bessel vortex beams by rigid oblate and prolate spheroids using the modal matching method is developed. The method, which is applicable to slightly elongated objects at low-to-moderate frequencies, requires solving a system of linear equations which depends on the partial-wave index n and the order of the Bessel vortex beam m using truncated partial-wave series expansions (PWSEs), and satisfying the Neumann boundary condition for a rigid immovable surface in the least-squares sense. This original semi-analytical approach developed for Bessel vortex beams is demonstrated for finite oblate and prolate spheroids, where the mathematical functions describing the spheroidal geometry are written in a form involving single angular (polar) integrals that are numerically computed. The transverse (θ = π / 2) and 3D scattering directivity patterns are evaluated in the far-field for both prolate and oblate spheroids, with particular emphasis on the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid) not exceeding 3:1, the half-cone angle β and order m of the Bessel vortex beam, as well as the dimensionless size parameter kr0. Periodic oscillations in the magnitude plots of the far-field scattering form function are observed, which result from the interference of the reflected waves with the circumferential (Franz') waves circumnavigating the surface of the spheroid in the surrounding fluid. Moreover, the 3D directivity patterns illustrate the far-field scattering from the spheroid, that vanishes in the forward (θ = 0) and backward (θ = π) directions. Particular applications in underwater acoustics and scattering, acoustic levitation and the detection of submerged elongated objects using Bessel vortex waves to name a few, would benefit from the results of the present investigation.

  4. Resources for Underwater Robotics Education

    Science.gov (United States)

    Wallace, Michael L.; Freitas, William M.

    2016-01-01

    4-H clubs can build and program underwater robots from raw materials. An annotated resource list for engaging youth in building underwater remotely operated vehicles (ROVs) is provided. This article is a companion piece to the Research in Brief article "Building Teen Futures with Underwater Robotics" in this issue of the "Journal of…

  5. Impact of Vessel Noise on Oyster Toadfish (Opsanus tau) Behavior and Implications for Underwater Noise Management

    Science.gov (United States)

    Krahforst, Cecilia S.

    Underwater noise and its impacts on marine life are growing management concerns. This dissertation considers both the ecological and social concerns of underwater noise, using the oyster toadfish (Opsanus tau) as a model species. Oyster toadfish call for mates using a boatwhistle sound, but increased ambient noise levels from vessels or other anthropogenic activities are likely to influence the ability of males to find mates. If increased ambient noise levels reduce fish fitness then underwater noise can impact socially valued ecosystem services (e.g. fisheries). The following ecological objectives of the impacts of underwater noise on oyster toadfish were investigated: (1) to determine how noise influences male calling behavior; (2) to assess how areas of high vessel activity ("noisy") and low vessel activity ("quiet") influence habitat utilization (fish standard length and occupancy rate); and (3) to discover if fitness (number of clutches and number of embryos per clutch) is lower in "noisy" compared with "quiet" sites. Field experiments were executed in "noisy" and "quiet" areas. Recorded calls by males in response to playback sounds (vessel, predator, and snapping shrimp sounds) and egg deposition by females ("noisy" vs. "quiet" sites) demonstrated that oyster toadfish are impacted by underwater noise. First, males decreased their call rates and called louder in response to increased ambient noise levels. Second, oyster toadfish selected nesting sites in areas with little or no inboard motorboat activity. Third, male oyster toadfish at "noisy" sites either had no egg clutches on their shelters or the number of embryos per clutch was significantly lower than in the "quiet" areas. Underwater noise and disturbance from vessels are influencing the fitness of the oyster toadfish. The social significance of the growing concerns regarding underwater noise was investigated by identifying dominant themes found within two types of texts: four recent underwater noise

  6. Panel acoustic contribution analysis.

    Science.gov (United States)

    Wu, Sean F; Natarajan, Logesh Kumar

    2013-02-01

    Formulations are derived to analyze the relative panel acoustic contributions of a vibrating structure. The essence of this analysis is to correlate the acoustic power flow from each panel to the radiated acoustic pressure at any field point. The acoustic power is obtained by integrating the normal component of the surface acoustic intensity, which is the product of the surface acoustic pressure and normal surface velocity reconstructed by using the Helmholtz equation least squares based nearfield acoustical holography, over each panel. The significance of this methodology is that it enables one to analyze and rank relative acoustic contributions of individual panels of a complex vibrating structure to acoustic radiation anywhere in the field based on a single set of the acoustic pressures measured in the near field. Moreover, this approach is valid for both interior and exterior regions. Examples of using this method to analyze and rank the relative acoustic contributions of a scaled vehicle cabin are demonstrated.

  7. A model of the enhancement of coal combustion using high intensity acoustic fields

    International Nuclear Information System (INIS)

    Yavuzkurt, S.; Ha, M.Y.; Koopmann, G.H.; Scaroni, A.

    1989-01-01

    In this paper a model for the enhancement of coal combustion in the presence of high intensity acoustics is developed. A high intensity acoustic field induces an oscillating velocity over pulverized coal particles otherwise entrained in the main gas stream, resulting in increased heat and mass transfer. The augmented heat and mass transfer coefficients, expressed as space- and time-averaged Nusselt and Sherwood numbers for the oscillating flow, were implemented in an existing computer code (PCGC-2) capable of predicting various aspects of pulverized coal combustion and gasification. Increases in the Nusselt and Sherwood numbers of about 45, 60 and 82.5% at sound pressure levels of 160, 165, and 170 dB for 100 μm coal particles were obtained due to increases in the acoustic slop velocity associated with the increased sound pressure levels. The main effect of the acoustic field was observed during the char combustion phase in a diffusionally controlled situation. A decrease in the char burnout length (time) of 15.7% at 160 dB and 30.2% at 170 dB was obtained compared to the case with no sound for the 100 μm coal particles

  8. A new technique for robot vision in autonomous underwater vehicles using the color shift in underwater imaging

    Science.gov (United States)

    2017-06-01

    FOR ROBOT VISION IN AUTONOMOUS UNDERWATER VEHICLES USING THE COLOR SHIFT IN UNDERWATER IMAGING by Jake A. Jones June 2017 Thesis Advisor...techniques to determine the distances from each pixel to the camera. 14. SUBJECT TERMS unmanned undersea vehicles (UUVs), autonomous ... AUTONOMOUS UNDERWATER VEHICLES USING THE COLOR SHIFT IN UNDERWATER IMAGING Jake A. Jones Lieutenant Commander, United States Navy B.S

  9. Geometric and Optic Characterization of a Hemispherical Dome Port for Underwater Photogrammetry

    Directory of Open Access Journals (Sweden)

    Fabio Menna

    2016-01-01

    Full Text Available The popularity of automatic photogrammetric techniques has promoted many experiments in underwater scenarios leading to quite impressive visual results, even by non-experts. Despite these achievements, a deep understanding of camera and lens behaviors as well as optical phenomena involved in underwater operations is fundamental to better plan field campaigns and anticipate the achievable results. The paper presents a geometric investigation of a consumer grade underwater camera housing, manufactured by NiMAR and equipped with a 7′′ dome port. After a review of flat and dome ports, the work analyzes, using simulations and real experiments, the main optical phenomena involved when operating a camera underwater. Specific aspects which deal with photogrammetric acquisitions are considered with some tests in laboratory and in a swimming pool. Results and considerations are shown and commented.

  10. On measurement of acoustic pulse arrival angles using a vertical array

    Science.gov (United States)

    Makarov, D. V.

    2017-11-01

    We consider a recently developed method to analyze the angular structure of pulsed acoustic fields in an underwater sound channel. The method is based on the Husimi transform that allows us to approximately link a wave field with the corresponding ray arrivals. The advantage of the method lies in the possibility of its practical realization by a vertical hydrophone array crossing only a small part of the oceanic depth. The main aim of the present work is to find the optimal parameter values of the array that ensure good angular accuracy and sufficient reliability of the algorithm to calculate the arrival angles. Broadband pulses with central frequencies of 80 and 240 Hz are considered. It is shown that an array with a length of several hundred meters allows measuring the angular spectrum with an accuracy of up to 1 degree. The angular resolution is lowered with an increase of the sound wavelength due to the fundamental limitations imposed by the uncertainty relation.

  11. Acoustic emission and magnification of atomic lines resolution for laser breakdown of salt water in ultrasound field

    International Nuclear Information System (INIS)

    Bulanov, Alexey V.; Nagorny, Ivan G.

    2015-01-01

    Researches of the acoustic effects accompanying optical breakdown in a water, generated by the focused laser radiation with power ultrasound have been carried out. Experiments were performed by using 532 nm pulses from Brilliant B Nd:YAG laser. Acoustic radiation was produced by acoustic focusing systems in the form hemisphere and ring by various resonance frequencies of 10.7 kHz and 60 kHz. The experimental results are obtained, that show the sharply strengthens effects of acoustic emission from a breakdown zone by the joint influence of a laser and ultrasonic irradiation. Essentially various thresholds of breakdown and character of acoustic emission in fresh and sea water are found out. The experimental result is established, testifying that acoustic emission of optical breakdown of sea water at presence and at absence of ultrasound essentially exceeds acoustic emission in fresh water. Atomic lines of some chemical elements like a Sodium, Magnesium and so on were investigated for laser breakdown of water with ultrasound field. The effect of magnification of this lines resolution for salt water in ultrasound field was obtained

  12. Theory and numerical calculation of the acoustic field exerted by eddy-current forces

    Energy Technology Data Exchange (ETDEWEB)

    Kawashima, K.

    1976-01-01

    The equations for calculating the acoustic field produced within a nonmagnetic metal by interaction of eddy currents with a static magnetic field were obtained on the assumptions (1) an ultrasonic wave is generated by the electromagentic force through classical and macroscopic phenomena; (2) the electric, magnetic, and elastic properties of the metal are linear, isotropic, and homogeneous throughout the metal, which occupies semi-infinite space; (3) the whole system is axially symmetric; and (4) eddy currents and elastic waves show a steady-state sinusoidal variation. The acoustic field produced by a specific electromagnetic ultrasonic transducer with axial symmetry was calculated numerically, and the results showed a well-defined ultrasonic wave beam, which was narrower than had been expected from the size of the transducer. (auth)

  13. Underwater Communications for Video Surveillance Systems at 2.4 GHz

    Directory of Open Access Journals (Sweden)

    Sandra Sendra

    2016-10-01

    Full Text Available Video surveillance is needed to control many activities performed in underwater environments. The use of wired media can be a problem since the material specially designed for underwater environments is very expensive. In order to transmit the images and videos wirelessly under water, three main technologies can be used: acoustic waves, which do not provide high bandwidth, optical signals, although the effect of light dispersion in water severely penalizes the transmitted signals and therefore, despite offering high transfer rates, the maximum distance is very small, and electromagnetic (EM waves, which can provide enough bandwidth for video delivery. In the cases where the distance between transmitter and receiver is short, the use of EM waves would be an interesting option since they provide high enough data transfer rates to transmit videos with high resolution. This paper presents a practical study of the behavior of EM waves at 2.4 GHz in freshwater underwater environments. First, we discuss the minimum requirements of a network to allow video delivery. From these results, we measure the maximum distance between nodes and the round trip time (RTT value depending on several parameters such as data transfer rate, signal modulations, working frequency, and water temperature. The results are statistically analyzed to determine their relation. Finally, the EM waves’ behavior is modeled by a set of equations. The results show that there are some combinations of working frequency, modulation, transfer rate and temperature that offer better results than others. Our work shows that short communication distances with high data transfer rates is feasible.

  14. Field tests of acoustic telemetry for a portable coastal observatory

    Science.gov (United States)

    Martini, M.; Butman, B.; Ware, J.; Frye, D.

    2006-01-01

    Long-term field tests of a low-cost acoustic telemetry system were carried out at two sites in Massachusetts Bay. At each site, an acoustic Doppler current profiler mounted on a bottom tripod was fitted with an acoustic modem to transmit data to a surface buoy; electronics mounted on the buoy relayed these data to shore via radio modem. The mooring at one site (24 m water depth) was custom-designed for the telemetry application, with a custom designed small buoy, a flexible electro-mechanical buoy to mooring joint using a molded chain connection to the buoy, quick-release electro-mechanical couplings, and dual hydrophones suspended 7 m above the bottom. The surface buoy at the second site (33 m water depth) was a U.S. Coast Guard (USCG) channel buoy fitted with telemetry electronics and clamps to hold the hydrophones. The telemetry was tested in several configurations for a period of about four years. The custom-designed buoy and mooring provided nearly error-free data transmission through the acoustic link under a variety of oceanographic conditions for 261 days at the 24 m site. The electro mechanical joint, cables and couplings required minimal servicing and were very reliable, lasting 862 days deployed before needing repairs. The acoustic communication results from the USCG buoy were poor, apparently due to the hard cobble bottom, noise from the all-steel buoy, and failure of the hydrophone assembly. Access to the USCG buoy at sea required ideal weather. ??2006 IEEE.

  15. Energy Consumption Research of Mobile Data Collection Protocol for Underwater Nodes Using an USV

    Directory of Open Access Journals (Sweden)

    Zhichao Lv

    2018-04-01

    Full Text Available The Unmanned Surface Vehicle (USV integrated with an acoustic modem is a novel mobile vehicle for data collection, which has an advantage in terms of mobility, efficiency, and collection cost. In the scenario of data collection, the USV is controlled autonomously along the planning trajectory and the data of underwater nodes are dynamically collected. In order to improve the efficiency of data collection and extend the life of the underwater nodes, a mobile data collection protocol for underwater nodes using the USV was proposed. In the protocol, the stop-and-wait ARQ transmission mechanism is adopted, where the duty cycle is designed considering the ratio between the sleep mode and the detection mode, and the transmission ratio is defined by the duty cycle, wake-up signal cycles, and USV’s speed. According to protocol, the evaluation index for energy consumption is constructed based on the duty cycle and the transmission ratio. The energy consumption of the protocol is simulated and analyzed using the mobile communication experiment data of USV, taking into consideration USV’s speed, data sequence length, and duty cycle. Optimized protocol parameters are identified, which in turn denotes the proposed protocol’s feasibility and effectiveness.

  16. Performance analysis of passive time reversal communication technique for multipath interference in shallow sea acoustic channel

    Science.gov (United States)

    Kida, Yukihiro; Shimura, Takuya; Deguchi, Mitsuyasu; Watanabe, Yoshitaka; Ochi, Hiroshi; Meguro, Koji

    2017-07-01

    In this study, the performance of passive time reversal (PTR) communication techniques in multipath rich underwater acoustic environments is investigated. It is recognized empirically and qualitatively that a large number of multipath arrivals could generally raise the demodulation result of PTR. However, the relationship between multipath and the demodulation result is hardly evaluated quantitatively. In this study, the efficiency of the PTR acoustic communication techniques for multipath interference cancelation was investigated quantitatively by applying a PTR-DFE (decision feed-back filter) scheme to a synthetic dataset of a horizontal underwater acoustic channel. Mainly, in this study, we focused on the relationship between the signal-to-interference ratio (SIR) of datasets and the output signal-to-noise ratio (OSNR) of demodulation results by a parametric study approach. As a result, a proportional relation between SIR and OSNR is confirmed in low-SNR datasets. It was also found that PTR has a performance limitation, that is OSNR converges to a typical value depending on the number of receivers. In conclusion, results indicate that PTR could utilize the multipath efficiently and also withstand the negative effects of multipath interference at a given limitation.

  17. Ontogenetic investigation of underwater hearing capabilities in loggerhead sea turtles (Caretta caretta) using a dual testing approach.

    Science.gov (United States)

    Lavender, Ashley L; Bartol, Soraya M; Bartol, Ian K

    2014-07-15

    Sea turtles reside in different acoustic environments with each life history stage and may have different hearing capacity throughout ontogeny. For this study, two independent yet complementary techniques for hearing assessment, i.e. behavioral and electrophysiological audiometry, were employed to (1) measure hearing in post-hatchling and juvenile loggerhead sea turtles Caretta caretta (19-62 cm straight carapace length) to determine whether these migratory turtles exhibit an ontogenetic shift in underwater auditory detection and (2) evaluate whether hearing frequency range and threshold sensitivity are consistent in behavioral and electrophysiological tests. Behavioral trials first required training turtles to respond to known frequencies, a multi-stage, time-intensive process, and then recording their behavior when they were presented with sound stimuli from an underwater speaker using a two-response forced-choice paradigm. Electrophysiological experiments involved submerging restrained, fully conscious turtles just below the air-water interface and recording auditory evoked potentials (AEPs) when sound stimuli were presented using an underwater speaker. No significant differences in behavior-derived auditory thresholds or AEP-derived auditory thresholds were detected between post-hatchling and juvenile sea turtles. While hearing frequency range (50-1000/1100 Hz) and highest sensitivity (100-400 Hz) were consistent in audiograms pooled by size class for both behavior and AEP experiments, both post-hatchlings and juveniles had significantly higher AEP-derived than behavior-derived auditory thresholds, indicating that behavioral assessment is a more sensitive testing approach. The results from this study suggest that post-hatchling and juvenile loggerhead sea turtles are low-frequency specialists, exhibiting little differences in threshold sensitivity and frequency bandwidth despite residence in acoustically distinct environments throughout ontogeny. © 2014

  18. Measurement of incident sound power using near field acoustic holography

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Tiana Roig, Elisabet

    2009-01-01

    ; and it has always been regarded as impossible to measure the sound power that is incident on a wall directly. This paper examines a new method of determining this quantity from sound pressure measurements at positions on the wall using ‘statistically optimised near field acoustic holography’ (SONAH...

  19. A modeling approach to predict acoustic nonlinear field generated by a transmitter with an aluminum lens.

    Science.gov (United States)

    Fan, Tingbo; Liu, Zhenbo; Chen, Tao; Li, Faqi; Zhang, Dong

    2011-09-01

    In this work, the authors propose a modeling approach to compute the nonlinear acoustic field generated by a flat piston transmitter with an attached aluminum lens. In this approach, the geometrical parameters (radius and focal length) of a virtual source are initially determined by Snell's refraction law and then adjusted based on the Rayleigh integral result in the linear case. Then, this virtual source is used with the nonlinear spheroidal beam equation (SBE) model to predict the nonlinear acoustic field in the focal region. To examine the validity of this approach, the calculated nonlinear result is compared with those from the Westervelt and (Khokhlov-Zabolotskaya-Kuznetsov) KZK equations for a focal intensity of 7 kW/cm(2). Results indicate that this approach could accurately describe the nonlinear acoustic field in the focal region with less computation time. The proposed modeling approach is shown to accurately describe the nonlinear acoustic field in the focal region. Compared with the Westervelt equation, the computation time of this approach is significantly reduced. It might also be applicable for the widely used concave focused transmitter with a large aperture angle.

  20. Underwater Noise Pollution at the Strait of Istanbul (Bosphorus

    Directory of Open Access Journals (Sweden)

    Cem Gazioğlu

    2016-12-01

    Full Text Available Underwater noise pollution (UNP has become a major concern in marine habitats, which is intense anthropogenic noise in the marine (aquatic environment. It is caused by ship traffic, oceanographic experiments, and use of explosives in geophysical research, underwater construction, active sonars and seismic survey techniques. Oceans are much nosier than 1960s. Narrow and shallow channel noisy aquatic environments where noise levels reach the highest value is not surprising. The Strait of Istanbul (SoI; Bosphorus is one of the most important maritime passages (app. 50 000 vessel/year or 140 vessel/day which is situated between the Black Sea and the Aegean Sea are also biologically extremely important gateway not only it provides access to a channel. Many of the varieties of fish migration hunting value are realized through the TSS. Local maritime traffic is another important acoustic sources which are more than 3 000 elements (Kesgin and Vardar, 2001 of everyday local traffic in SoI, which are causing noise in the 2 and 10 kHz range. Large vessels create signals both in bands below 1 kHz (main engine, electrical instruments cavitation noise creates higher frequency bands. Almost all elements of marine traffic in SoI located therefore encountered UND in all bands.

  1. Acoustic emission in a superconductor (Nb-Ti) during magnetic field and current sweep

    International Nuclear Information System (INIS)

    Nomura, Harehiko

    1980-01-01

    Though superconducting magnets are indispensable in the fields of nuclear fusion, MHD power generation, high energy technology, and the trains using magnetic levitation, the safety of the magnets used for those fields is required to be fully investigated because their accumulating energy reaches up to several GJ. For this purpose, the improvement of monitoring techniques is extremely important to grasp exactly the magnetization of such large energy magnets. Although the detection of the terminal voltage of the magnets has been mainly used so far, the purpose has not yet been fulfilled because various phenomena appear in the form of noises in the terminal voltage. The authors have found the monitoring method using acoustic emission in a system completely independent from voltage observation. From this viewpoint, the experiments have been performed aiming at the generation of acoustic emission in conjunction with magnetization out of the fine structure of super-conductors, taking notice of the emitted sound frequency ranging over several hundred kHz. The results and investigation revealed that the superconductor itself emitted ultrasonic sound. It was found that the observation of this acoustic power intensity was able to monitor not only the magnetization of superconductors but also its current sweep. Since the motion of the magnetic flux is converted into the signal of acoustic field, this measuring method is less affected by noise disturbance from electromagnetic systems, and is expected to be useful for the researches on analyzing superconductor characteristics. (Wakatsuki, Y.)

  2. Distributed acoustic sensing technique and its field trial in SAGD well

    Science.gov (United States)

    Han, Li; He, Xiangge; Pan, Yong; Liu, Fei; Yi, Duo; Hu, Chengjun; Zhang, Min; Gu, Lijuan

    2017-10-01

    Steam assisted gravity drainage (SAGD) is a very promising way for the development of heavy oil, extra heavy oil and tight oil reservoirs. Proper monitoring of the SAGD operations is essential to avoid operational issues and improve efficiency. Among all the monitoring techniques, micro-seismic monitoring and related interpretation method can give useful information about the steam chamber development and has been extensively studied. Distributed acoustic sensor (DAS) based on Rayleigh backscattering is a newly developed technique that can measure acoustic signal at all points along the sensing fiber. In this paper, we demonstrate a DAS system based on dual-pulse heterodyne demodulation technique and did field trial in SAGD well located in Xinjiang Oilfield, China. The field trail results validated the performance of the DAS system and indicated its applicability in steam-chamber monitoring and hydraulic monitoring.

  3. Underwater Acoustic Modem Configured for Use in a Local Area Network

    National Research Council Canada - National Science Library

    Rice, J

    1998-01-01

    The U.S. Navy Telesonar RDT&E effort is developing a low cost, non-coherent acoustic modem capable of data transmission under adverse channel conditions at data rates up to 2400 bits per second (bps...

  4. Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic Testing

    Science.gov (United States)

    Kolaini, Ali R.; O'Connell, Michael R.; Tsoi, Wan B.

    2009-01-01

    Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in

  5. On the slow dynamics of near-field acoustically levitated objects under High excitation frequencies

    Science.gov (United States)

    Ilssar, Dotan; Bucher, Izhak

    2015-10-01

    This paper introduces a simplified analytical model describing the governing dynamics of near-field acoustically levitated objects. The simplification converts the equation of motion coupled with the partial differential equation of a compressible fluid, into a compact, second order ordinary differential equation, where the local stiffness and damping are transparent. The simplified model allows one to more easily analyse and design near-field acoustic levitation based systems, and it also helps to devise closed-loop controller algorithms for such systems. Near-field acoustic levitation employs fast ultrasonic vibrations of a driving surface and exploits the viscosity and the compressibility of a gaseous medium to achieve average, load carrying pressure. It is demonstrated that the slow dynamics dominates the transient behaviour, while the time-scale associated with the fast, ultrasonic excitation has a small presence in the oscillations of the levitated object. Indeed, the present paper formulates the slow dynamics under an ultrasonic excitation without the need to explicitly consider the latter. The simplified model is compared with a numerical scheme based on Reynolds equation and with experiments, both showing reasonably good results.

  6. Development of a tentacle propulsion technique for underwater application

    International Nuclear Information System (INIS)

    Alamgir, T; Rashid, M M; Khan, M R

    2013-01-01

    As robotic technology matures and more platforms are fielded in unstructured real-world situations, the more new areas of applications are being thought for robotic deployment. After successes in industrial robots, researchers are now trying to explore new robots with biological features of different biological creatures like, snake, bird, and spider for their stunning advantages. Underwater exploration using robots is a new avenue. Research on the tentacle robot for underwater application is a new field of research besides the other research in this arena. There are few researches on this topic are explored and mostly are on biological robot. Besides those researches this paper aims to propose and demonstrate another technique to build a tentacle for propulsion purposes. Therefore, in this paper will discuss more on mathematical development for the propulsion technique and its software verification technique in considering the environmental constrains

  7. Interior near-field acoustical holography in flight.

    Science.gov (United States)

    Williams, E G; Houston, B H; Herdic, P C; Raveendra, S T; Gardner, B

    2000-10-01

    In this paper boundary element methods (BEM) are mated with near-field acoustical holography (NAH) in order to determine the normal velocity over a large area of a fuselage of a turboprop airplane from a measurement of the pressure (hologram) on a concentric surface in the interior of the aircraft. This work represents the first time NAH has been applied in situ, in-flight. The normal fuselage velocity was successfully reconstructed at the blade passage frequency (BPF) of the propeller and its first two harmonics. This reconstructed velocity reveals structure-borne and airborne sound-transmission paths from the engine to the interior space.

  8. Modelling, Design and Robust Control of a Remotely Operated Underwater Vehicle

    Directory of Open Access Journals (Sweden)

    Luis Govinda García-Valdovinos

    2014-01-01

    Full Text Available Underwater remotely operated vehicles (ROVs play an important role in a number of shallow and deep-water missions for marine science, oil and gas extraction, exploration and salvage. In these applications, the motions of the ROV are guided either by a human pilot on a surface support vessel through an umbilical cord providing power and telemetry, or by an automatic pilot. In the case of automatic control, ROV state feedback is provided by acoustic and inertial sensors and this state information, along with a controller strategy, is used to perform several tasks such as station-keeping and auto-immersion/heading, among others. In this paper, the modelling, design and control of the Kaxan ROV is presented: i The complete six degrees of freedom, non linear hydrodynamic model with its parameters, ii the Kaxan hardware/software architecture, iii numerical simulations in Matlab/Simulink platform of a model-free second order sliding mode control along with ocean currents as disturbances and thruster dynamics, iv a virtual environment to visualize the motion of the Kaxan ROV and v experimental results of a one degree of freedom underwater system.

  9. Temporal coherence of the acoustic field forward propagated through a continental shelf with random internal waves.

    Science.gov (United States)

    Gong, Zheng; Chen, Tianrun; Ratilal, Purnima; Makris, Nicholas C

    2013-11-01

    An analytical model derived from normal mode theory for the accumulated effects of range-dependent multiple forward scattering is applied to estimate the temporal coherence of the acoustic field forward propagated through a continental-shelf waveguide containing random three-dimensional internal waves. The modeled coherence time scale of narrow band low-frequency acoustic field fluctuations after propagating through a continental-shelf waveguide is shown to decay with a power-law of range to the -1/2 beyond roughly 1 km, decrease with increasing internal wave energy, to be consistent with measured acoustic coherence time scales. The model should provide a useful prediction of the acoustic coherence time scale as a function of internal wave energy in continental-shelf environments. The acoustic coherence time scale is an important parameter in remote sensing applications because it determines (i) the time window within which standard coherent processing such as matched filtering may be conducted, and (ii) the number of statistically independent fluctuations in a given measurement period that determines the variance reduction possible by stationary averaging.

  10. ROV Based Underwater Blurred Image Restoration

    Institute of Scientific and Technical Information of China (English)

    LIU Zhishen; DING Tianfu; WANG Gang

    2003-01-01

    In this paper, we present a method of ROV based image processing to restore underwater blurry images from the theory of light and image transmission in the sea. Computer is used to simulate the maximum detection range of the ROV under different water body conditions. The receiving irradiance of the video camera at different detection ranges is also calculated. The ROV's detection performance under different water body conditions is given by simulation. We restore the underwater blurry images using the Wiener filter based on the simulation. The Wiener filter is shown to be a simple useful method for underwater image restoration in the ROV underwater experiments. We also present examples of restored images of an underwater standard target taken by the video camera in these experiments.

  11. Thin Fresnel zone plate lenses for focusing underwater sound

    International Nuclear Information System (INIS)

    Calvo, David C.; Thangawng, Abel L.; Nicholas, Michael; Layman, Christopher N.

    2015-01-01

    A Fresnel zone plate (FZP) lens of the Soret type creates a focus by constructive interference of waves diffracted through open annular zones in an opaque screen. For underwater sound below MHz frequencies, a large FZP that blocks sound using high-impedance, dense materials would have practical disadvantages. We experimentally and numerically investigate an alternative approach of creating a FZP with thin (0.4λ) acoustically opaque zones made of soft silicone rubber foam attached to a thin (0.1λ) transparent rubber substrate. An ultra-thin (0.0068λ) FZP that achieves higher gain is also proposed and simulated which uses low-volume fraction, bubble-like resonant air ring cavities to construct opaque zones. Laboratory measurements at 200 kHz indicate that the rubber foam can be accurately modeled as a lossy fluid with an acoustic impedance approximately 1/10 that of water. Measured focal gains up to 20 dB agree with theoretical predictions for normal and oblique incidence. The measured focal radius of 0.68λ (peak-to-null) agrees with the Rayleigh diffraction limit prediction of 0.61 λ/NA (NA = 0.88) for a low-aberration lens

  12. Diving with microparticles in acoustic fields

    DEFF Research Database (Denmark)

    2012-01-01

    Sound can move particles. A good example of this phenomenon is the Chladni plate, in which an acoustic wave is induced in a metallic plate and particles migrate to the nodes of the acoustic wave. For several years, acoustophoresis has been used to manipulate microparticles in microscopic scales...

  13. Effect of temperature on Acoustic Evaluation of standing trees and logs: Part 2: Field Investigation

    Science.gov (United States)

    Shan Gao; Xiping Wang; Lihai Wang; R. Bruce Allison

    2013-01-01

    The objectives of this study were to investigate the effect of seasonal temperature changes on acoustic velocity measured on standing trees and green logs and to develop models for compensating temperature differences because acoustic measurements are performed in different climates and seasons. Field testing was conducted on 20 red pine (Pinus resinosa...

  14. Underwater 3D filming

    Directory of Open Access Journals (Sweden)

    Roberto Rinaldi

    2014-12-01

    Full Text Available After an experimental phase of many years, 3D filming is now effective and successful. Improvements are still possible, but the film industry achieved memorable success on 3D movie’s box offices due to the overall quality of its products. Special environments such as space (“Gravity” and the underwater realm look perfect to be reproduced in 3D. “Filming in space” was possible in “Gravity” using special effects and computer graphic. The underwater realm is still difficult to be handled. Underwater filming in 3D was not that easy and effective as filming in 2D, since not long ago. After almost 3 years of research, a French, Austrian and Italian team realized a perfect tool to film underwater, in 3D, without any constrains. This allows filmmakers to bring the audience deep inside an environment where they most probably will never have the chance to be.

  15. Pressure vessel made by free forming using underwater explosion

    Directory of Open Access Journals (Sweden)

    H Iyama

    2016-03-01

    Full Text Available Explosive forming is one particular forming technique, in which, mostcommonly, water is used as the pressure transmission medium. In recentyears, we have done the development of the method which obtains anecessary form of the metal by the control of underwater shock wave actson the metal plate, without a metal die. On the other hand, the pressurevessel is required in various fields, but we think that the free forming usingthe underwater shock wave is advantageous in the production of pressurevessel of a simple spherical, ellipse, parabola shape. In this paper, we willintroduce an experiment and several numerical simulations that we carriedout for this technical development.

  16. CUDA based Level Set Method for 3D Reconstruction of Fishes from Large Acoustic Data

    DEFF Research Database (Denmark)

    Sharma, Ojaswa; Anton, François

    2009-01-01

    Acoustic images present views of underwater dynamics, even in high depths. With multi-beam echo sounders (SONARs), it is possible to capture series of 2D high resolution acoustic images. 3D reconstruction of the water column and subsequent estimation of fish abundance and fish species identificat...... of suppressing threshold and show its convergence as the evolution proceeds. We also present a GPU based streaming computation of the method using NVIDIA's CUDA framework to handle large volume data-sets. Our implementation is optimised for memory usage to handle large volumes....

  17. Acoustic field generated by flight of rocket at the Earth surface

    International Nuclear Information System (INIS)

    Drobzheva, Ya.V.; Krasnov, V.M.; Maslov, A.N.

    2006-01-01

    In this paper we present a model, which describes the propagation of acoustic impulses produced by explosion of carrier rocket at the active part of trajectory, down through the atmosphere. Calculations of acoustic field parameters on the earth surface were made for altitudes of rocket flight from 2.8 to 92.3 km and yield of explosions from 0.001 to 0.5 t tnt. It was shown the infrasound accompaniment of rocket flight with the goal to register the explosion it is possible only for an altitude about 70 km. For this case, test set should be situated at the distance not exceeding 120 km from the starting place. (author)

  18. Underwater welding of steel

    International Nuclear Information System (INIS)

    Ibarra, S.; Olson, D.L.

    1992-01-01

    A fundamental basis to understand the behavior of wet underwater welding of steel is introduced. Both the pyrometallurgical and physical metallurgy concepts are discussed. Modifications of welding consumables and practice are suggested. This chapter promotes further contributions of meatllurgical research to improve and promote wet underwater welding. (orig.)

  19. Principles of Sonar Performance Modeling

    NARCIS (Netherlands)

    Ainslie, M.A.

    2010-01-01

    Sonar performance modelling (SPM) is concerned with the prediction of quantitative measures of sonar performance, such as probability of detection. It is a multidisciplinary subject, requiring knowledge and expertise in the disparate fields of underwater acoustics, acoustical oceanography, sonar

  20. Colour reconstruction of underwater images

    OpenAIRE

    Hoth, Julian; Kowalczyk, Wojciech

    2017-01-01

    Objects look very different in the underwater environment compared to their appearance in sunlight. Images with correct colouring simplify the detection of underwater objects and may allow the use of visual SLAM algorithms developed for land-based robots underwater. Hence, image processing is required. Current algorithms focus on the colour reconstruction of scenery at diving depth where different colours can still be distinguished. At greater depth this is not the case. In this study it is i...

  1. Quantum imaging for underwater arctic navigation

    Science.gov (United States)

    Lanzagorta, Marco

    2017-05-01

    The precise navigation of underwater vehicles is a difficult task due to the challenges imposed by the variable oceanic environment. It is particularly difficult if the underwater vehicle is trying to navigate under the Arctic ice shelf. Indeed, in this scenario traditional navigation devices such as GPS, compasses and gyrocompasses are unavailable or unreliable. In addition, the shape and thickness of the ice shelf is variable throughout the year. Current Arctic underwater navigation systems include sonar arrays to detect the proximity to the ice. However, these systems are undesirable in a wartime environment, as the sound gives away the position of the underwater vehicle. In this paper we briefly describe the theoretical design of a quantum imaging system that could allow the safe and stealthy navigation of underwater Arctic vehicles.

  2. Numerical Calculation and Measurement of Nonlinear Acoustic Fields in Ultrasound Diagnosis

    Science.gov (United States)

    Kawagishi, Tetsuya; Saito, Shigemi; Mine, Yoshitaka

    2002-05-01

    In order to develop a tool for designing on the ultrasonic probe and its peripheral devices for tissue-harmonic-imaging systems, a study is carried out to compare the calculation and observation results of nonlinear acoustic fields for a diagnostic ultrasound system. The pulsed ultrasound with a center frequency of 2.5 MHz is emanated from a weakly focusing sector probe with a 6.5 mm aperture radius and a 50 mm focal length into an agar phantom with an attenuation coefficient of about 0.6 dB/cm/MHz or 1.2 dB/cm/MHz. The nonlinear acoustic field is measured using a needle-type hydrophone. The calculation is based on the Khokhlov-Zabolotskaya-Kuznetsov(KZK) equation which is modified so that the frequency dependence of the attenuation coefficient is the same as that in biological tissue. This equation is numerically solved with the implicit backward method employing the iterative method. The measured and calculated amplitude spectra show good agreement with each other.

  3. Experimental Study on the Measurement of Water Bottom Vibration Induced by Underwater Drilling Blasting

    Directory of Open Access Journals (Sweden)

    Gu Wenbin

    2015-01-01

    Full Text Available Due to the lack of proper instrumentations and the difficulties in underwater measurements, the studies about water bottom vibration induced by underwater drilling blasting are seldom reported. In order to investigate the propagation and attenuation laws of blasting induced water bottom vibration, a water bottom vibration monitor was developed with consideration of the difficulties in underwater measurements. By means of this equipment, the actual water bottom vibration induced by underwater drilling blasting was measured in a field experiment. It shows that the water bottom vibration monitor could collect vibration signals quite effectively in underwater environments. The followed signal analysis shows that the characteristics of water bottom vibration and land ground vibration induced by the same underwater drilling blasting are quite different due to the different geological environments. The amplitude and frequency band of water bottom vibration both exceed those of land ground vibration. Water bottom vibration is mainly in low-frequency band that induced by blasting impact directly acts on rock. Besides the low-frequency component, land vibration contains another higher frequency band component that induced by followed water hammer wave acts on bank slope.

  4. The Environmental Cost of Marine Sound Sources

    NARCIS (Netherlands)

    Ainslie, M.A.; Dekeling, R.P.A.

    2011-01-01

    Cumulative acoustic exposure is used as an indicator for the risk of negative impact to animals as a consequence of exposure to underwater sound. The free-field energy of a single source, defined as the total acoustic energy that would exist in the source’s free field, is shown to be closely related

  5. Evaluation of a Loudspeaker-Based Virtual Acoustic Environment for Investigating sound-field auditory steady-state responses

    DEFF Research Database (Denmark)

    Zapata-Rodriguez, Valentina; Marbjerg, Gerd Høy; Brunskog, Jonas

    2017-01-01

    Measuring sound-field auditory steady-state responses (ASSR) is a promising new objective clinical procedure for hearing aid fitting validation, particularly for infants who cannot respond to behavioral tests. In practice, room acoustics of non-anechoic test rooms can heavily influence the audito...... tool PARISM (Phased Acoustical Radiosity and Image Source Method) and validated through measurements. This study discusses the limitations of the system and the potential improvements needed for a more realistic sound-field ASSR simulation....

  6. Autonomous Underwater Gliders

    OpenAIRE

    Wood,; Stephen,

    2009-01-01

    Autonomous Underwater Vehicles are only now being marketed as robust commercial vehicles for many industries, and of these vehicles underwater gliders are becoming the new tool for oceanographers. Satellites have provided scientists and marine specialists with measurements of the sea surface such as temperature since the late 1970s, and data via subsurface oceanographic moorings since the 1950's. As stated by David Smeed of the National Oceanography Centre, Southampton, England, that "gliders...

  7. Online monitoring of the two-dimensional temperature field in a boiler furnace based on acoustic computed tomography

    International Nuclear Information System (INIS)

    Zhang, Shiping; Shen, Guoqing; An, Liansuo; Niu, Yuguang

    2015-01-01

    Online monitoring of the temperature field is crucial to optimally adjust combustion within a boiler. In this paper, acoustic computed tomography (CT) technology was used to obtain the temperature profile of a furnace cross-section. The physical principles behind acoustic CT, acoustic signals and time delay estimation were studied. Then, the technique was applied to a domestic 600-MW coal-fired boiler. Acoustic CT technology was used to monitor the temperature field of the cross-section in the boiler furnace, and the temperature profile was reconstructed through ART iteration. The linear sweeping frequency signal was adopted as the sound source signal, whose sweeping frequency ranged from 500 to 3000 Hz with a sweeping cycle of 0.1 s. The generalized cross-correlation techniques with PHAT and ML were used as the time delay estimation method when the boiler was in different states. Its actual operation indicated that the monitored images accurately represented the combustion state of the boiler, and the acoustic CT system was determined to be accurate and reliable. - Highlights: • An online monitoring approach to monitor temperature field in a boiler furnace. • The paper provides acoustic CT technology to obtain the temperature profile of a furnace cross-section. • The temperature profile was reconstructed through ART iteration. • The technique is applied to a domestic 600-MW coal-fired boiler. • The monitored images accurately represent the combustion state of the boiler

  8. Underwater Inherent Optical Properties Estimation Using a Depth Aided Deep Neural Network

    Directory of Open Access Journals (Sweden)

    Zhibin Yu

    2017-01-01

    Full Text Available Underwater inherent optical properties (IOPs are the fundamental clues to many research fields such as marine optics, marine biology, and underwater vision. Currently, beam transmissometers and optical sensors are considered as the ideal IOPs measuring methods. But these methods are inflexible and expensive to be deployed. To overcome this problem, we aim to develop a novel measuring method using only a single underwater image with the help of deep artificial neural network. The power of artificial neural network has been proved in image processing and computer vision fields with deep learning technology. However, image-based IOPs estimation is a quite different and challenging task. Unlike the traditional applications such as image classification or localization, IOP estimation looks at the transparency of the water between the camera and the target objects to estimate multiple optical properties simultaneously. In this paper, we propose a novel Depth Aided (DA deep neural network structure for IOPs estimation based on a single RGB image that is even noisy. The imaging depth information is considered as an aided input to help our model make better decision.

  9. Underwater Inherent Optical Properties Estimation Using a Depth Aided Deep Neural Network.

    Science.gov (United States)

    Yu, Zhibin; Wang, Yubo; Zheng, Bing; Zheng, Haiyong; Wang, Nan; Gu, Zhaorui

    2017-01-01

    Underwater inherent optical properties (IOPs) are the fundamental clues to many research fields such as marine optics, marine biology, and underwater vision. Currently, beam transmissometers and optical sensors are considered as the ideal IOPs measuring methods. But these methods are inflexible and expensive to be deployed. To overcome this problem, we aim to develop a novel measuring method using only a single underwater image with the help of deep artificial neural network. The power of artificial neural network has been proved in image processing and computer vision fields with deep learning technology. However, image-based IOPs estimation is a quite different and challenging task. Unlike the traditional applications such as image classification or localization, IOP estimation looks at the transparency of the water between the camera and the target objects to estimate multiple optical properties simultaneously. In this paper, we propose a novel Depth Aided (DA) deep neural network structure for IOPs estimation based on a single RGB image that is even noisy. The imaging depth information is considered as an aided input to help our model make better decision.

  10. Underwater welding using remote controlled robots. Development of remote underwater welding technology with a high power YAG laser

    International Nuclear Information System (INIS)

    Miwa, Yasuhiro; Sato, Syuuichi; Kojima, Toshio; Owaki, Katsura; Hirose, Naoya

    2002-01-01

    As components in nuclear power plant have been periodically carried out their inspection and repair to keep their integrity, on radioactive liquid wastes storage facility, because of difficulty on their inspection by human beings, some are remained without inspection, and even when capable of inspection, conversion from human works to remote operations is desired from a viewpoint of their operation efficiency upgrading. For response to these needs, some developments on a technology capable of carrying out inspection of their inside at underwater environment and repairing welding with YAG laser by means of remote operation, have been performed. Remote underwater inspection and repair technology is a combination technology of already applied underwater mobile technique (underwater inspection robot) with underwater YAG laser welding technique which is recently at actual using level. Therefore, this technology is composed of an inspection robot and a repair welding robot. And, testing results using the underwater inspection robot and welding test results using the underwater repair welding robot, were enough preferable to obtain forecasting applicable to actual apparatuses. This technology is especially effective for inspection and repair of inside of nuclear fuel cycle apparatuses and relatively high dose apparatuses, and can be thought to be applicable also to large capacity tanks, tanks dealing with harmful matters, underwater structures, and so on, in general industries. (G.K.)

  11. iSAT: The Integrated Satellite and Acoustic Telemetry system for tracking marine megafauna

    KAUST Repository

    De La Torre, Pedro R.

    2014-05-01

    In this dissertation an innovative technology to study whale sharks, Rhincodon typus is presented. The Integrated Satellite and Acoustic Telemetry project (iSAT) combines underwater acoustic telemetry, autonomous navigation and radio frequency communications into a standalone system. The whale shark, a resident of the Saudi Arabian Red Sea, is the target of the study. The technology presented is designed to help close current gaps in the knowledge of whale shark biology; these are gaps that prohibit the design of optimal conservation strategies. Unfortunately, the various existing tracking technologies each have limitations and are unable to solve all the unanswered questions. Whale shark populations are increasingly threatened by anthropogenic activities such as targeted and indirect fishing pressure, creating an urgent need for better management practices. This dissertation addresses the current state-of-the-art of relevant technologies, including autonomous surface vehicles (ASVs), sensors for research in the ocean and remote monitoring of wild fauna (biotelemetry). iSAT contains components of all of these technologies, but the primary achievement of this dissertation is the development of iSAT’s Acoustic Tracking System (ATS). Underwater, the most efficient way of transmitting energy through long distances is sound. An electronic tag is attached to an animal and works as its acoustic identifier. iSAT’s hydrophone array detects the presence and direction of the acoustic signal generated by the tag. The expected performance, range, and capacity to tell the direction to the tag are explained and compared to the actual measured values. The first operational iSAT ATS is demonstrated. This work represents significant advancement towards a fully autonomous iSAT system. Developments on the power electronics, navigation, renewable energy harvesting, and other modules are included in this research. With the recent integration of digital acquisition systems, i

  12. Underwater sound and vibrations due to oil & gas activities

    NARCIS (Netherlands)

    Beek, P.J.G. van; Binnerts, B.; Nennie, E.D.; Benda-Beckmann, A.M. von

    2014-01-01

    In the oil & gas industry there is a trend towards more subsea activities. To improve gas recovery from existing and new fields at greater depths, the produced gas will be compressed, processed and transported via subsea templates and underwater networks (pipelines, flexible risers, etc.). Besides

  13. A highly versatile autonomous underwater vehicle with biomechanical propulsion

    NARCIS (Netherlands)

    Simons, D.G.; Bergers, M.M.C.; Henrion, S.; Hulzenga, J.I.J.; Jutte, R.W.; Pas, W.M.G.; Van Schravendijk, M.; Vercruyssen, T.G.A.; Wilken, A.P.

    2009-01-01

    An autonomous underwater vehicle with a biomechanical propulsion system is a possible answer to the demand for small, silent sensor platforms in many fields. The design of Galatea, a bio-mimetic AUV, involves four aspects: hydrodynamic shape, the propulsion, the motion control systems and payload.

  14. Suppression of sound radiation to far field of near-field acoustic communication system using evanescent sound field

    Science.gov (United States)

    Fujii, Ayaka; Wakatsuki, Naoto; Mizutani, Koichi

    2016-01-01

    A method of suppressing sound radiation to the far field of a near-field acoustic communication system using an evanescent sound field is proposed. The amplitude of the evanescent sound field generated from an infinite vibrating plate attenuates exponentially with increasing a distance from the surface of the vibrating plate. However, a discontinuity of the sound field exists at the edge of the finite vibrating plate in practice, which broadens the wavenumber spectrum. A sound wave radiates over the evanescent sound field because of broadening of the wavenumber spectrum. Therefore, we calculated the optimum distribution of the particle velocity on the vibrating plate to reduce the broadening of the wavenumber spectrum. We focused on a window function that is utilized in the field of signal analysis for reducing the broadening of the frequency spectrum. The optimization calculation is necessary for the design of window function suitable for suppressing sound radiation and securing a spatial area for data communication. In addition, a wide frequency bandwidth is required to increase the data transmission speed. Therefore, we investigated a suitable method for calculating the sound pressure level at the far field to confirm the variation of the distribution of sound pressure level determined on the basis of the window shape and frequency. The distribution of the sound pressure level at a finite distance was in good agreement with that obtained at an infinite far field under the condition generating the evanescent sound field. Consequently, the window function was optimized by the method used to calculate the distribution of the sound pressure level at an infinite far field using the wavenumber spectrum on the vibrating plate. According to the result of comparing the distributions of the sound pressure level in the cases with and without the window function, it was confirmed that the area whose sound pressure level was reduced from the maximum level to -50 dB was

  15. A study on practical use of underwater abrasive water jet cutting

    Science.gov (United States)

    Yamaguchi, Hitoshi; Demura, Kenji

    1993-09-01

    The practicality of underwater abrasive water jet cutting technology was studied in experiments. A study of abrasives in slurried form showed that optimum polymer concentration can be selected to suit underwater conditions. For the long-distance transport of slurry from the ocean surface to the ocean floor, a direct supply system by hose proved to be practical. This system takes advantage of the insolubility of the slurry in water due to a difference in specific gravity. For cutting thick steel plate at great ocean depths, a simulation with a pressurized container revealed the requirements for actual cutting. Confirmation of remote cutting operations will become the most important technology in field applications. Underwater sound vibration characteristics were found to change significantly in direct response to modifications in cutting conditions. This will be important basic data to develop an effective sensoring method.

  16. A Novel Detection Method for Underwater Moving Targets by Measuring Their ELF Emissions with Inductive Sensors

    Directory of Open Access Journals (Sweden)

    Jinhong Wang

    2017-07-01

    Full Text Available In this article, we propose a novel detection method for underwater moving targets by detecting their extremely low frequency (ELF emissions with inductive sensors. The ELF field source of the targets is modeled by a horizontal electric dipole at distances more than several times of the targets’ length. The formulas for the fields produced in air are derived with a three-layer model (air, seawater and seafloor and are evaluated with a complementary numerical integration technique. A proof of concept measurement is presented. The ELF emissions from a surface ship were detected by inductive electronic and magnetic sensors as the ship was leaving a harbor. ELF signals are of substantial strength and have typical characteristic of harmonic line spectrum, and the fundamental frequency has a direct relationship with the ship’s speed. Due to the high sensitivity and low noise level of our sensors, it is capable of resolving weak ELF signals at long distance. In our experiment, a detection distance of 1300 m from the surface ship above the sea surface was realized, which shows that this method would be an appealing complement to the usual acoustic detection and magnetic anomaly detection capability.

  17. Coupled acoustic-gravity field for dynamic evaluation of ion exchange with a single resin bead.

    Science.gov (United States)

    Kanazaki, Takahiro; Hirawa, Shungo; Harada, Makoto; Okada, Tetsuo

    2010-06-01

    A coupled acoustic-gravity field is efficient for entrapping a particle at the position determined by its acoustic properties rather than its size. This field has been applied to the dynamic observation of ion-exchange reactions occurring in a single resin bead. The replacement of counterions in an ion-exchange resin induces changes in its acoustic properties, such as density and compressibility. Therefore, we can visually trace the advancement of an ion-exchange reaction as a time change in the levitation position of a resin bead entrapped in the field. Cation-exchange reactions occurring in resin beads with diameters of 40-120 microm are typically completed within 100-200 s. Ion-exchange equilibrium or kinetics is often evaluated with off-line chemical analyses, which require a batch amount of ion exchangers. Measurements with a single resin particle allow us to evaluate ion-exchange dynamics and kinetics of ions including those that are difficult to measure by usual off-line analyses. The diffusion properties of ions in resins have been successfully evaluated from the time change in the levitation positions of resin beads.

  18. Communication Acoustics

    DEFF Research Database (Denmark)

    Blauert, Jens

    Communication Acoustics deals with the fundamentals of those areas of acoustics which are related to modern communication technologies. Due to the advent of digital signal processing and recording in acoustics, these areas have enjoyed an enormous upswing during the last 4 decades. The book...... the book a source of valuable information for those who want to improve or refresh their knowledge in the field of communication acoustics - and to work their way deeper into it. Due to its interdisciplinary character Communication Acoustics is bound to attract readers from many different areas, such as......: acoustics, cognitive science, speech science, and communication technology....

  19. Angular Spectrum Method for the Focused Acoustic Field of a Linear Transducer

    Science.gov (United States)

    Belgroune, D.; de Belleval, J. F.; Djelouah, H.

    Applications involving non-destructive testing or acoustical imaging are more and more sophisticated. In this context, a model based on the angular spectrum approach is tackled in view to calculate the focused impulse field radiated by a linear transducer through a plane fluid-solid interface. It is well known that electronic focusing, based on a cylindrical delay law, like for the classical cases (lenses, curved transducer), leads to an inaccurate focusing in the solid due to geometric aberrations errors affecting refraction. Generally, there is a significant difference between the acoustic focal distance and the geometrical focal due to refraction. In our work, an optimized delay law, based on the Fermat's principle is established, particularly at an oblique incidence where the geometrical considerations, relatively simple in normal incidence, become quickly laborious. Numerical simulations of impulse field are judiciously carried out. Subsequently, the input parameters are optimally selected in order to achieve good computation accuracy and a high focusing. The overall results, involving compression and shear waves, have highlighted the focusing improvement in the solid when compared to the currently available approaches. Indeed, the acoustic focal distance is very close to geometrical focal distance and then, allows better control of the refracted angular beam profile (refraction angle, focusing depth and focal size).

  20. Diversity-based acoustic communication with a glider in deep water.

    Science.gov (United States)

    Song, H C; Howe, Bruce M; Brown, Michael G; Andrew, Rex K

    2014-03-01

    The primary use of underwater gliders is to collect oceanographic data within the water column and periodically relay the data at the surface via a satellite connection. In summer 2006, a Seaglider equipped with an acoustic recording system received transmissions from a broadband acoustic source centered at 75 Hz deployed on the bottom off Kauai, Hawaii, while moving away from the source at ranges up to ∼200 km in deep water and diving up to 1000-m depth. The transmitted signal was an m-sequence that can be treated as a binary-phase shift-keying communication signal. In this letter multiple receptions are exploited (i.e., diversity combining) to demonstrate the feasibility of using the glider as a mobile communication gateway.

  1. Acoustically Induced Streaming Flows near a Model Cod Otolith and their Potential Implications for Fish Hearing

    Energy Technology Data Exchange (ETDEWEB)

    Kotas, Charlotte W [ORNL; Rogers, Peter [Georgia Institute of Technology; Yoda, Minami [Georgia Institute of Technology

    2011-01-01

    The ears of fishes are remarkable sensors for the small acoustic disturbances associated with underwater sound. For example, each ear of the Atlantic cod (Gadus morhua) has three dense bony bodies (otoliths) surrounded by fluid and tissue, and detects sounds at frequencies from 30 to 500 Hz. Atlantic cod have also been shown to localize sounds. However, how their ears perform these functions is not fully understood. Steady streaming, or time-independent, flows near a 350% scale model Atlantic cod otolith immersed in a viscous fluid were studied to determine if these fluid flows contain acoustically relevant information that could be detected by the ear s sensory hair cells. The otolith was oscillated sinusoidally at various orientations at frequencies of 8 24 Hz, corresponding to an actual frequency range of 280 830 Hz. Phaselocked particle pathline visualizations of the resulting flows give velocity, vorticity, and rate of strain fields over a single plane of this mainly two-dimensional flow. Although the streaming flows contain acoustically relevant information, the displacements due to these flows are likely too small to explain Atlantic cod hearing abilities near threshold. The results, however, may suggest a possible mechanism for detection of ultrasound in some fish species.

  2. Simulation of an Underwater Acoustic Communication Channel Characterized by Wind-Generated Surface Waves and Bubbles

    NARCIS (Netherlands)

    Dol, H.S.; Colin, M.E.G.D.; Ainslie, M.A.; Walree, P.A. van; Janmaat, J.

    2012-01-01

    Sea surface scattering by wind-generated waves and bubbles is regarded to be the main non-platform related cause of the time variability of shallow acoustic communication channels. Simulations for predicting the quality of acoustic communication links in such channels thus require adequate modeling

  3. Calculation of the radiation force on a cylinder in a standing wave acoustic field

    Energy Technology Data Exchange (ETDEWEB)

    Haydock, David [Unilever R and D Colworth, Sharnbrook, Bedford MK44 1LQ (United Kingdom); Department of Physics, Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom)

    2005-04-15

    We present a new calculation of the radiation force on a cylinder in a standing wave acoustic field. We use the formula to calculate the force on a cylinder which is free to move in the field and one which is fixed in space.

  4. Calculation of the radiation force on a cylinder in a standing wave acoustic field

    International Nuclear Information System (INIS)

    Haydock, David

    2005-01-01

    We present a new calculation of the radiation force on a cylinder in a standing wave acoustic field. We use the formula to calculate the force on a cylinder which is free to move in the field and one which is fixed in space

  5. Research on the underwater target imaging based on the streak tube laser lidar

    Science.gov (United States)

    Cui, Zihao; Tian, Zhaoshuo; Zhang, Yanchao; Bi, Zongjie; Yang, Gang; Gu, Erdan

    2018-03-01

    A high frame rate streak tube imaging lidar (STIL) for real-time 3D imaging of underwater targets is presented in this paper. The system uses 532nm pulse laser as the light source, the maximum repetition rate is 120Hz, and the pulse width is 8ns. LabVIEW platform is used in the system, the system control, synchronous image acquisition, 3D data processing and display are realized through PC. 3D imaging experiment of underwater target is carried out in a flume with attenuation coefficient of 0.2, and the images of different depth and different material targets are obtained, the imaging frame rate is 100Hz, and the maximum detection depth is 31m. For an underwater target with a distance of 22m, the high resolution 3D image real-time acquisition is realized with range resolution of 1cm and space resolution of 0.3cm, the spatial relationship of the targets can be clearly identified by the image. The experimental results show that STIL has a good application prospect in underwater terrain detection, underwater search and rescue, and other fields.

  6. Coupled Research in Ocean Acoustics and Signal Processing for the Next Generation of Underwater Acoustic Communication Systems

    Science.gov (United States)

    2016-08-05

    the analysis of data collected during the VHF acoustics test con - ducted in a wave tank at the Scripps Institution of Oceanography in October 2015...a first look at the statistics, the Scintillation Index (traditional narrowband def - inition) was calculated as a function of arrival delay and wind

  7. NW-MILO Acoustic Data Collection

    Energy Technology Data Exchange (ETDEWEB)

    Matzner, Shari; Myers, Joshua R.; Maxwell, Adam R.; Jones, Mark E.

    2010-02-17

    There is an enduring requirement to improve our ability to detect potential threats and discriminate these from the legitimate commercial and recreational activity ongoing in the nearshore/littoral portion of the maritime domain. The Northwest Maritime Information and Littoral Operations (NW-MILO) Program at PNNL’s Coastal Security Institute in Sequim, Washington is establishing a methodology to detect and classify these threats - in part through developing a better understanding of acoustic signatures in a near-shore environment. The purpose of the acoustic data collection described here is to investigate the acoustic signatures of small vessels. The data is being recorded continuously, 24 hours a day, along with radar track data and imagery. The recording began in August 2008, and to date the data contains tens of thousands of signals from small vessels recorded in a variety of environmental conditions. The quantity and variety of this data collection, with the supporting imagery and radar track data, makes it particularly useful for the development of robust acoustic signature models and advanced algorithms for signal classification and information extraction. The underwater acoustic sensing system is part of a multi-modal sensing system that is operating near the mouth of Sequim Bay. Sequim Bay opens onto the Straight of Juan de Fuca, which contains part of the border between the U.S. and Canada. Table 1 lists the specific components used for the NW-MILO system. The acoustic sensor is a hydrophone permanently deployed at a mean depth of about 3 meters. In addition to a hydrophone, the other sensors in the system are a marine radar, an electro-optical (EO) camera and an infra-red (IR) camera. The radar is integrated with a vessel tracking system (VTS) that provides position, speed and heading information. The data from all the sensors is recorded and saved to a central server. The data has been validated in terms of its usability for characterizing the

  8. Modeling of Focused Acoustic Field of a Concave Multi-annular Phased Array Using Spheroidal Beam Equation

    Science.gov (United States)

    Yu, Li-Li; Shou, Wen-De; Hui, Chun

    2012-02-01

    A theoretical model of focused acoustic field for a multi-annular phased array on concave spherical surface is proposed. In this model, the source boundary conditions of the spheroidal beam equation (SBE) for multi-annular phased elements are studied. Acoustic field calculated by the dynamic focusing model of SBE is compared with numerical results of the O'Neil and Khokhlov—Zabolotskaya—Kuznetsov (KZK) model, respectively. Axial dynamic focusing and the harmonic effects are presented. The results demonstrate that the dynamic focusing model of SBE is good valid for a concave multi-annular phased array with a large aperture angle in the linear or nonlinear field.

  9. Acoustic tweezers via sub-time-of-flight regime surface acoustic waves.

    Science.gov (United States)

    Collins, David J; Devendran, Citsabehsan; Ma, Zhichao; Ng, Jia Wei; Neild, Adrian; Ai, Ye

    2016-07-01

    Micrometer-scale acoustic waves are highly useful for refined optomechanical and acoustofluidic manipulation, where these fields are spatially localized along the transducer aperture but not along the acoustic propagation direction. In the case of acoustic tweezers, such a conventional acoustic standing wave results in particle and cell patterning across the entire width of a microfluidic channel, preventing selective trapping. We demonstrate the use of nanosecond-scale pulsed surface acoustic waves (SAWs) with a pulse period that is less than the time of flight between opposing transducers to generate localized time-averaged patterning regions while using conventional electrode structures. These nodal positions can be readily and arbitrarily positioned in two dimensions and within the patterning region itself through the imposition of pulse delays, frequency modulation, and phase shifts. This straightforward concept adds new spatial dimensions to which acoustic fields can be localized in SAW applications in a manner analogous to optical tweezers, including spatially selective acoustic tweezers and optical waveguides.

  10. Oyster larvae settle in response to habitat-associated underwater sounds.

    Science.gov (United States)

    Lillis, Ashlee; Eggleston, David B; Bohnenstiehl, DelWayne R

    2013-01-01

    Following a planktonic dispersal period of days to months, the larvae of benthic marine organisms must locate suitable seafloor habitat in which to settle and metamorphose. For animals that are sessile or sedentary as adults, settlement onto substrates that are adequate for survival and reproduction is particularly critical, yet represents a challenge since patchily distributed settlement sites may be difficult to find along a coast or within an estuary. Recent studies have demonstrated that the underwater soundscape, the distinct sounds that emanate from habitats and contain information about their biological and physical characteristics, may serve as broad-scale environmental cue for marine larvae to find satisfactory settlement sites. Here, we contrast the acoustic characteristics of oyster reef and off-reef soft bottoms, and investigate the effect of habitat-associated estuarine sound on the settlement patterns of an economically and ecologically important reef-building bivalve, the Eastern oyster (Crassostrea virginica). Subtidal oyster reefs in coastal North Carolina, USA show distinct acoustic signatures compared to adjacent off-reef soft bottom habitats, characterized by consistently higher levels of sound in the 1.5-20 kHz range. Manipulative laboratory playback experiments found increased settlement in larval oyster cultures exposed to oyster reef sound compared to unstructured soft bottom sound or no sound treatments. In field experiments, ambient reef sound produced higher levels of oyster settlement in larval cultures than did off-reef sound treatments. The results suggest that oyster larvae have the ability to respond to sounds indicative of optimal settlement sites, and this is the first evidence that habitat-related differences in estuarine sounds influence the settlement of a mollusk. Habitat-specific sound characteristics may represent an important settlement and habitat selection cue for estuarine invertebrates and could play a role in driving

  11. Oyster larvae settle in response to habitat-associated underwater sounds.

    Directory of Open Access Journals (Sweden)

    Ashlee Lillis

    Full Text Available Following a planktonic dispersal period of days to months, the larvae of benthic marine organisms must locate suitable seafloor habitat in which to settle and metamorphose. For animals that are sessile or sedentary as adults, settlement onto substrates that are adequate for survival and reproduction is particularly critical, yet represents a challenge since patchily distributed settlement sites may be difficult to find along a coast or within an estuary. Recent studies have demonstrated that the underwater soundscape, the distinct sounds that emanate from habitats and contain information about their biological and physical characteristics, may serve as broad-scale environmental cue for marine larvae to find satisfactory settlement sites. Here, we contrast the acoustic characteristics of oyster reef and off-reef soft bottoms, and investigate the effect of habitat-associated estuarine sound on the settlement patterns of an economically and ecologically important reef-building bivalve, the Eastern oyster (Crassostrea virginica. Subtidal oyster reefs in coastal North Carolina, USA show distinct acoustic signatures compared to adjacent off-reef soft bottom habitats, characterized by consistently higher levels of sound in the 1.5-20 kHz range. Manipulative laboratory playback experiments found increased settlement in larval oyster cultures exposed to oyster reef sound compared to unstructured soft bottom sound or no sound treatments. In field experiments, ambient reef sound produced higher levels of oyster settlement in larval cultures than did off-reef sound treatments. The results suggest that oyster larvae have the ability to respond to sounds indicative of optimal settlement sites, and this is the first evidence that habitat-related differences in estuarine sounds influence the settlement of a mollusk. Habitat-specific sound characteristics may represent an important settlement and habitat selection cue for estuarine invertebrates and could play a

  12. PIV for the characterization of focused field induced acoustic streaming: seeding particle choice evaluation.

    Science.gov (United States)

    Ben Haj Slama, Rafika; Gilles, Bruno; Ben Chiekh, Maher; Béra, Jean-Christophe

    2017-04-01

    This research evaluates the use of Particle Image Velocimetry (PIV) technique for characterizing acoustic streaming flow generated by High Intensity Focused Ultrasound (HIFU). PIV qualification tests, focusing on the seeding particle size (diameter of 5, 20 and 50μm) were carried out in degassed water subjected to a focused field of 550kHz-frequency with an acoustic pressure amplitude of 5.2, 10.5 and 15.7bar at the focus. This study shows that the ultrasonic field, especially the radiation force, can strongly affect seeding particle behavior. Large particles (50μm-diameter) are repelled from the focal zone and gathered at radiation pressure convergence lines on either side of the focus. The calculation of the acoustic radiation pressure applied on these particles explains the observed phenomenon. PIV measurements do not, therefore, properly characterize the streaming flow in this case. On the contrary, small particles (5μm-diameter) velocity measurements were in good agreement with the Computational Fluid Dynamics (CFD) simulations of the water velocity field. A simple criterion approximating the diameter threshold below which seeding particles are qualified for PIV in presence of focused ultrasound is then proposed. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Patch near field acoustic holography based on particle velocity measurements

    DEFF Research Database (Denmark)

    Zhang, Yong-Bin; Jacobsen, Finn; Bi, Chuan-Xing

    2009-01-01

    Patch near field acoustic holography (PNAH) based on sound pressure measurements makes it possible to reconstruct the source field near a source by measuring the sound pressure at positions on a surface. that is comparable in size to the source region of concern. Particle velocity is an alternative...... examines the use of particle velocity as the input of PNAH. Because the particle velocity decays faster toward the edges of the measurement aperture than the pressure does and because the wave number ratio that enters into the inverse propagator from pressure to velocity amplifies high spatial frequencies...

  14. Human Factors Issues When Operating Underwater Remotely Operated Vehicles and Autonomous Underwater Vehicles

    Science.gov (United States)

    2011-03-01

    etiquette (Parasuraman & Miller, 2004). Through natural and intuitive communication, Johnson et al., (2007) hope that this interface will instill greater...and etiquette in high criticality automated systems. Communications of the ACM, 47(4), 51-55. Parasuraman, R., & Riley, V. (1997). Humans and... protocols for underwater wireless communications. IEEE Communications Magazine, pp. 97-102. Quazi, A. H., & Konrad, W. L. (1982, March 1982). Underwater

  15. Inferring Pre-shock Acoustic Field From Post-shock Pitot Pressure Measurement

    Science.gov (United States)

    Wang, Jian-Xun; Zhang, Chao; Duan, Lian; Xiao, Heng; Virginia Tech Team; Missouri Univ of Sci; Tech Team

    2017-11-01

    Linear interaction analysis (LIA) and iterative ensemble Kalman method are used to convert post-shock Pitot pressure fluctuations to static pressure fluctuations in front of the shock. The LIA is used as the forward model for the transfer function associated with a homogeneous field of acoustic waves passing through a nominally normal shock wave. The iterative ensemble Kalman method is then employed to infer the spectrum of upstream acoustic waves based on the post-shock Pitot pressure measured at a single point. Several test cases with synthetic and real measurement data are used to demonstrate the merits of the proposed inference scheme. The study provides the basis for measuring tunnel freestream noise with intrusive probes in noisy supersonic wind tunnels.

  16. The Fluid-Solid Interaction Dynamics between Underwater Explosion Bubble and Corrugated Sandwich Plate

    Directory of Open Access Journals (Sweden)

    Hao Wang

    2016-01-01

    Full Text Available Lightweight sandwich structures with highly porous 2D cores or 3D (three-dimensional periodic cores can effectively withstand underwater explosion load. In most of the previous studies of sandwich structure antiblast dynamics, the underwater explosion (UNDEX bubble phase was neglected. As the UNDEX bubble load is one of the severest damage sources that may lead to structure large plastic deformation and crevasses failure, the failure mechanisms of sandwich structures might not be accurate if only shock wave is considered. In this paper, detailed 3D finite element (FE numerical models of UNDEX bubble-LCSP (lightweight corrugated sandwich plates interaction are developed by using MSC.Dytran. Upon the validated FE model, the bubble shape, impact pressure, and fluid field velocities for different stand-off distances are studied. Based on numerical results, the failure modes of LCSP and the whole damage process are obtained. It is demonstrated that the UNDEX bubble collapse jet local load plays a more significant role than the UNDEX shock wave load especially in near-field underwater explosion.

  17. Vehicle Based Vector Sensor

    Science.gov (United States)

    2015-09-28

    buoyant underwater vehicle with an interior space in which a length of said underwater vehicle is equal to one tenth of the acoustic wavelength...underwater vehicle with an interior space in which a length of said underwater vehicle is equal to one tenth of the acoustic wavelength; an...unmanned underwater vehicle that can function as an acoustic vector sensor. (2) Description of the Prior Art [0004] It is known that a propagating

  18. Determining spherical lens correction for astronaut training underwater.

    Science.gov (United States)

    Porter, Jason; Gibson, C Robert; Strauss, Samuel

    2011-09-01

    To develop a model that will accurately predict the distance spherical lens correction needed to be worn by National Aeronautics and Space Administration astronauts while training underwater. The replica space suit's helmet contains curved visors that induce refractive power when submersed in water. Anterior surface powers and thicknesses were measured for the helmet's protective and inside visors. The impact of each visor on the helmet's refractive power in water was analyzed using thick lens calculations and Zemax optical design software. Using geometrical optics approximations, a model was developed to determine the optimal distance spherical power needed to be worn underwater based on the helmet's total induced spherical power underwater and the astronaut's manifest spectacle plane correction in air. The validity of the model was tested using data from both eyes of 10 astronauts who trained underwater. The helmet's visors induced a total power of -2.737 D when placed underwater. The required underwater spherical correction (FW) was linearly related to the spectacle plane spherical correction in air (FAir): FW = FAir + 2.356 D. The mean magnitude of the difference between the actual correction worn underwater and the calculated underwater correction was 0.20 ± 0.11 D. The actual and calculated values were highly correlated (r = 0.971) with 70% of eyes having a difference in magnitude of astronauts. The model accurately predicts the actual values worn underwater and can be applied (more generally) to determine a suitable spectacle lens correction to be worn behind other types of masks when submerged underwater.

  19. Determination of the Accommodation Coefficient Using Vapor/gas Bubble Dynamics in an Acoustic Field

    Science.gov (United States)

    Gumerov, Nail A.; Hsiao, Chao-Tsung; Goumilevski, Alexei G.; Allen, Jeff (Technical Monitor)

    2001-01-01

    Nonequilibrium liquid/vapor phase transformations can occur in superheated or subcooled liquids in fast processes such as in evaporation in a vacuum. The rate at which such a phase transformation occurs depends on the "condensation" or "accommodation" coefficient, Beta, which is a property of the interface. Existing measurement techniques for Beta are complex and expensive. The development of a relatively inexpensive and reliable technique for measurement of Beta for a wide range of substances and temperatures is of great practical importance. The dynamics of a bubble in an acoustic field strongly depends on the value of Beta. It is known that near the saturation temperature, small vapor bubbles grow under the action of an acoustic field due to "rectified heat transfer." This finding can be used as the basis for an effective measurement technique of Beta. We developed a theory of vapor bubble behavior in an isotropic acoustic wave and in a plane standing acoustic wave. A numerical code was developed which enables simulation of a variety of experimental situations and accurately takes into account slowly evolving temperature. A parametric study showed that the measurement of Beta can be made over a broad range of frequencies and bubble sizes. We found several interesting regimes and conditions which can be efficiently used for measurements of Beta. Measurements of Beta can be performed in both reduced and normal gravity environments.

  20. Dynamics and Control of Underwater Gliders I: Steady Motions

    OpenAIRE

    Mahmoudian, N.; Geisbert, J.; Woolsey, C.

    2007-01-01

    This paper describes analysis of steady motions for underwater gliders, a type of highly efficient underwater vehicle which uses gravity for propulsion. Underwater gliders are winged underwater vehicles which locomote by modulating their buoyancy and their attitude. Several such vehicles have been developed and have proven their worth as efficient long-distance, long-duration ocean sampling platforms. To date, the primary emphasis in underwater glider development has been on locomotive effici...

  1. PASSIVE ACOUSTIC MONITORING OF ODONTOCETES IN THE VICINITY OF PUULOA UNDERWATER DETONATION TRAINING RANGE, HAWAII RANGE COMPLEX, OAHU

    Science.gov (United States)

    2016-09-25

    Printed on recycled paper Approved for public release; distribution is unlimited. SITE SPECIFIC REPORT SSR-NAVFAC-EXWC-EV-1702 SEPTEMBER 2016...NOAA’s Coral Reef Ecosystem Division. The EAR is an autonomous underwater recorder controlled by a Persistor CF2 microcontroller that may be

  2. Mach-Zehnder interferometric photonic crystal fiber for low acoustic frequency detections

    Energy Technology Data Exchange (ETDEWEB)

    Pawar, Dnyandeo; Rao, Ch. N.; Kale, S. N., E-mail: sangeetakale2004@gmail.com [Department of Applied Physics, Defence Institute of Advanced Technology (DU), Girinagar, Pune 411 025, Maharashtra (India); Choubey, Ravi Kant [Department of Applied Physics, Amity Institute of Applied Sciences, Amity University, Noida 201 313 (India)

    2016-01-25

    Low frequency under-water acoustic signal detections are challenging, especially for marine applications. A Mach-Zehnder interferometric hydrophone is demonstrated using polarization-maintaining photonic-crystal-fiber (PM-PCF), spliced between two single-mode-fibers, operated at 1550 nm source. These data are compared with standard hydrophone, single-mode and multimode fiber. The PM-PCF sensor shows the highest response with a power shift (2.32 dBm) and a wavelength shift (392.8 pm) at 200 Hz. High birefringence values and the effect of the imparted acoustic pressure on this fiber, introducing the difference between the fast and slow axis changes, owing to the phase change in the propagation waves, demonstrate the strain-optic properties of the sensor.

  3. Distributed estimation of sensors position in underwater wireless sensor network

    Science.gov (United States)

    Zandi, Rahman; Kamarei, Mahmoud; Amiri, Hadi

    2016-05-01

    In this paper, a localisation method for determining the position of fixed sensor nodes in an underwater wireless sensor network (UWSN) is introduced. In this simple and range-free scheme, the node localisation is achieved by utilising an autonomous underwater vehicle (AUV) that transverses through the network deployment area, and that periodically emits a message block via four directional acoustic beams. A message block contains the actual known AUV position as well as a directional dependent marker that allows a node to identify the respective transmit beam. The beams form a fixed angle with the AUV body. If a node passively receives message blocks, it could calculate the arithmetic mean of the coordinates existing in each messages sequence, to find coordinates at two different time instants via two different successive beams. The node position can be derived from the two computed positions of the AUV. The major advantage of the proposed localisation algorithm is that it is silent, which leads to energy efficiency for sensor nodes. The proposed method does not require any synchronisation among the nodes owing to being silent. Simulation results, using MATLAB, demonstrated that the proposed method had better performance than other similar AUV-based localisation methods in terms of the rates of well-localised sensor nodes and positional root mean square error.

  4. Hidden acoustic information revealed by intentional nonlinearity

    Science.gov (United States)

    Dowling, David R.

    2017-11-01

    Acoustic waves are omnipresent in modern life and are well described by the linearized equations of fluid dynamics. Once generated, acoustic waves carry and collect information about their source and the environment through which they propagate, respectively, and this information may be retrieved by analyzing recordings of these waves. Because of this, acoustics is the primary means for observation, surveillance, reconnaissance, and remote sensing in otherwise opaque environments, such as the Earth's oceans and crust, and the interior of the human body. For such information-retrieval tasks, acoustic fields are nearly always interrogated within their recorded frequency range or bandwidth. However, this frequency-range restriction is not general; acoustic fields may also carry (hidden) information at frequencies outside their bandwidth. Although such a claim may seem counter intuitive, hidden acoustic-field information can be revealed by re-introducing a marquee trait of fluid dynamics: nonlinearity. In particular, an intentional quadratic nonlinearity - a form of intra-signal heterodyning - can be used to obtain acoustic field information at frequencies outside a recorded acoustic field's bandwidth. This quadratic nonlinearity enables a variety of acoustic remote sensing applications that were long thought to be impossible. In particular, it allows the detrimental effects of sparse recordings and random scattering to be suppressed when the original acoustic field has sufficient bandwidth. In this presentation, the topic is developed heuristically, with a just brief exposition of the relevant mathematics. Hidden acoustic field information is then revealed from simulated and measured acoustic fields in simple and complicated acoustic environments involving frequencies from a few Hertz to more than 100 kHz, and propagation distances from tens of centimeters to hundreds of kilometers. Sponsored by ONR, NAVSEA, and NSF.

  5. Underwater welding and repair technologies applied in PWR environment

    International Nuclear Information System (INIS)

    Scandella, Fabrice; Carpreau, Jean-Michel

    2012-01-01

    The authors describe several welding processes and technologies which have been used for underwater applications and which can be applied when repairing components of a PWR type reactor. They address, describe and discuss wet arc welding processes, the peculiarities of underwater welding, and the use of various processes such as 111, 114 and 135 processes, underwater welding with the hybrid plasma MIG-MAG process, underwater welding with the laser wire process, underwater welding with the FSW, FSP or UWFSW processes, underwater welding with variants of the friction welding process (friction surfacing, taper stitch welding, hydro-pillar processing

  6. Autonomous Navigation for Autonomous Underwater Vehicles Based on Information Filters and Active Sensing

    Directory of Open Access Journals (Sweden)

    Tianhong Yan

    2011-11-01

    Full Text Available This paper addresses an autonomous navigation method for the autonomous underwater vehicle (AUV C-Ranger applying information-filter-based simultaneous localization and mapping (SLAM, and its sea trial experiments in Tuandao Bay (Shangdong Province, P.R. China. Weak links in the information matrix in an extended information filter (EIF can be pruned to achieve an efficient approach-sparse EIF algorithm (SEIF-SLAM. All the basic update formulae can be implemented in constant time irrespective of the size of the map; hence the computational complexity is significantly reduced. The mechanical scanning imaging sonar is chosen as the active sensing device for the underwater vehicle, and a compensation method based on feedback of the AUV pose is presented to overcome distortion of the acoustic images due to the vehicle motion. In order to verify the feasibility of the navigation methods proposed for the C-Ranger, a sea trial was conducted in Tuandao Bay. Experimental results and analysis show that the proposed navigation approach based on SEIF-SLAM improves the accuracy of the navigation compared with conventional method; moreover the algorithm has a low computational cost when compared with EKF-SLAM.

  7. Autonomous navigation for autonomous underwater vehicles based on information filters and active sensing.

    Science.gov (United States)

    He, Bo; Zhang, Hongjin; Li, Chao; Zhang, Shujing; Liang, Yan; Yan, Tianhong

    2011-01-01

    This paper addresses an autonomous navigation method for the autonomous underwater vehicle (AUV) C-Ranger applying information-filter-based simultaneous localization and mapping (SLAM), and its sea trial experiments in Tuandao Bay (Shangdong Province, P.R. China). Weak links in the information matrix in an extended information filter (EIF) can be pruned to achieve an efficient approach-sparse EIF algorithm (SEIF-SLAM). All the basic update formulae can be implemented in constant time irrespective of the size of the map; hence the computational complexity is significantly reduced. The mechanical scanning imaging sonar is chosen as the active sensing device for the underwater vehicle, and a compensation method based on feedback of the AUV pose is presented to overcome distortion of the acoustic images due to the vehicle motion. In order to verify the feasibility of the navigation methods proposed for the C-Ranger, a sea trial was conducted in Tuandao Bay. Experimental results and analysis show that the proposed navigation approach based on SEIF-SLAM improves the accuracy of the navigation compared with conventional method; moreover the algorithm has a low computational cost when compared with EKF-SLAM.

  8. Underwater sound due to a subsea high speed turbo compressor

    NARCIS (Netherlands)

    Binnerts, B.; Benda-Beckmann, A.M. von; Beek, P.J.G. van

    2014-01-01

    In the oil & gas industry there is a trend towards more subsea activities. To improve gas recovery from existing and new fields at greater depths, the produced gas will be compressed, processed and transported via subsea templates and underwater networks (pipelines, flexible risers, etc.). Besides

  9. Stimulated Brillouin scattering phase-locking using a transient acoustic standing wave excited through an optical interference field

    International Nuclear Information System (INIS)

    Ondrej Slezak; Milan Kalal; Hon Jin Kong

    2010-01-01

    Complete text of publication follows. Analytical description of an experimentally verified scheme leading to a phase-locked stimulated Brillouin scattering (SBS), used in a laser beam combination systems, is presented. The essential condition for the phase-locking effect for SBS is the fixation of the starting position and time of the acoustic Brillouin wave. It is shown that the starting position fixation of this acoustic wave may have its origin in a transient acoustic standing wave initiated by an arising optical interference field produced by the back-seeding concave mirror. This interference field leads to a stationary density modulation of the medium. However, the way to the formation of this density modulation leads via the acoustic standing wave. An appropriate solution, in the form of the standing wave, was obtained from solving the acoustic wave-equation using the electrostriction as a driving force. As a consequence of the damping term included in this equation the acoustic standing wave becomes gradually attenuated and contrary to the undamped solution published earlier, thus constitutes a truly transient phenomenon. Using a mathematical formalism similar to that which is used for the SBS description in the case of a random phase, the coupled equations describing the phase-locked SBS were derived. Contrary to the case without the back-seeding mirror, where the wave chosen from the thermal noise background subsequently plays the role of a trigger of the stimulated process, in this case it is replaced by the transient standing wave produced as a consequence of the presence of an optical interference field arisen in the focal region of the back-seeding concave mirror.

  10. Underwater object classification using scattering transform of sonar signals

    Science.gov (United States)

    Saito, Naoki; Weber, David S.

    2017-08-01

    In this paper, we apply the scattering transform (ST)-a nonlinear map based off of a convolutional neural network (CNN)-to classification of underwater objects using sonar signals. The ST formalizes the observation that the filters learned by a CNN have wavelet-like structure. We achieve effective binary classification both on a real dataset of Unexploded Ordinance (UXOs), as well as synthetically generated examples. We also explore the effects on the waveforms with respect to changes in the object domain (e.g., translation, rotation, and acoustic impedance, etc.), and examine the consequences coming from theoretical results for the scattering transform. We show that the scattering transform is capable of excellent classification on both the synthetic and real problems, thanks to having more quasi-invariance properties that are well-suited to translation and rotation of the object.

  11. Estimating uncertainty in subsurface glider position using transmissions from fixed acoustic tomography sources.

    Science.gov (United States)

    Van Uffelen, Lora J; Nosal, Eva-Marie; Howe, Bruce M; Carter, Glenn S; Worcester, Peter F; Dzieciuch, Matthew A; Heaney, Kevin D; Campbell, Richard L; Cross, Patrick S

    2013-10-01

    Four acoustic Seagliders were deployed in the Philippine Sea November 2010 to April 2011 in the vicinity of an acoustic tomography array. The gliders recorded over 2000 broadband transmissions at ranges up to 700 km from moored acoustic sources as they transited between mooring sites. The precision of glider positioning at the time of acoustic reception is important to resolve the fundamental ambiguity between position and sound speed. The Seagliders utilized GPS at the surface and a kinematic model below for positioning. The gliders were typically underwater for about 6.4 h, diving to depths of 1000 m and traveling on average 3.6 km during a dive. Measured acoustic arrival peaks were unambiguously associated with predicted ray arrivals. Statistics of travel-time offsets between received arrivals and acoustic predictions were used to estimate range uncertainty. Range (travel time) uncertainty between the source and the glider position from the kinematic model is estimated to be 639 m (426 ms) rms. Least-squares solutions for glider position estimated from acoustically derived ranges from 5 sources differed by 914 m rms from modeled positions, with estimated uncertainty of 106 m rms in horizontal position. Error analysis included 70 ms rms of uncertainty due to oceanic sound-speed variability.

  12. A comparison of inverse boundary element method and near-field acoustical holography

    DEFF Research Database (Denmark)

    Schuhmacher, Andreas; Hald, Jørgen; Saemann, E.-U.

    1999-01-01

    An inverse boundary element method (IBEM) is used to estimate the surface velocity of a rolling tyre from measurements of the near-field pressure. Subsequently, the sound pressure is calculated over a finite plane surface next to the tyre from the reconstructed velocity field on the tyre surface........ In order to verify the reconstruction process, part of the measurement data is used together with Near-Field Acoustical Holography (NAH). Estimated distributions of sound pressure and particle velocity over a plane surface obtained from the two methods are compared....

  13. Whose Line Sound is it Anyway? Identifying the Vocalizer on Underwater Video by Localizing with a Hydrophone Array

    Directory of Open Access Journals (Sweden)

    Matthias Hoffmann-Kuhnt

    2016-11-01

    Full Text Available A new device that combined high-resolution (1080p wide-angle video and three channels of high-frequency acoustic recordings (at 500 kHz per channel in a portable underwater housing was designed and tested with wild bottlenose and spotted dolphins in the Bahamas. It consisted of three hydrophones, a GoPro camera, a small Fit PC, a set of custom preamplifiers and a high-frequency data acquisition board. Recordings were obtained to identify individual vocalizing animals through time-delay-of-arrival localizing in post-processing. The calculated source positions were then overlaid onto the video – providing the ability to identify the vocalizing animal on the recorded video. The new tool allowed for much clearer analysis of the acoustic behavior of cetaceans than was possible before.

  14. Calibration of acoustic emission transducers

    International Nuclear Information System (INIS)

    Leschek, W.C.

    1976-01-01

    A method is described for calibrating an acoustic emission transducer to be used in a pre-set frequency range. The absolute reception sensitivity of a reference transducer is determined at frequencies selected within the frequency range. The reference transducer and the acoustic emission transducer are put into acoustic communication with the surface of a limited acoustic medium representing an equivalent acoustic load appreciably identical to that of the medium in which the use of the acoustic emission transducer is intended. A blank random acoustic noise is emitted in the acoustic medium in order to establish a diffuse and reverberating sound field, after which the output responses of the reference transducer and of the acoustic emission transducer are obtained with respect to the diffuse and reverberating field, for selected frequencies. The output response of the acoustic emission transducer is compared with that of the reference transducer for the selected frequencies, so as to determine the reception sensitivity of the acoustic emission transducer [fr

  15. Acoustic field characteristics and performance analysis of a looped travelling-wave thermoacoustic refrigerator

    International Nuclear Information System (INIS)

    Jin, T.; Yang, R.; Wang, Y.; Feng, Y.; Tang, K.

    2016-01-01

    Highlights: • Key issues for a highly efficient thermoacoustic conversion are analyzed. • A looped thermoacoustic refrigerator with one engine stage and one refrigerator stage is proposed. • Effective refrigeration powered by heat sources below 250 °C is demonstrated in the simulation. • Impact of cooling/heating temperatures on system performance is analyzed in view of acoustic field. - Abstract: This paper focuses on a looped travelling-wave thermoacoustic refrigerator powered by thermal energy. Based on a simplified model for the regenerator, key issues for a highly efficient thermoacoustic conversion, including both thermal-to-acoustic and heat-pumping processes, are summarized. A looped travelling-wave thermoacoustic refrigerator with one engine stage and one refrigerator stage is proposed, with emphasis on high normalized acoustic impedance, sufficient volumetric velocity and appropriate phase relation close to travelling wave in the regenerators of both engine and refrigerator. Simulation results indicate that for the ambient temperature of 30 °C, the looped travelling-wave thermoacoustic refrigerator can be powered by the heat at 210–250 °C to achieve the refrigeration at −3 °C with the overall coefficient of performance above 0.4 and the relative Carnot coefficient of performance over 13%. The characteristics of the acoustic field inside the loop configuration are analyzed in detail to reveal the operation mechanism of the looped travelling-wave thermoacoustic refrigerator. Additional analyses are conducted on the impact of the cooling and the heating temperatures, which are of great concern to the refrigeration applications and the utilization of low-grade thermal energy.

  16. Human Injury Criteria for Underwater Blasts.

    Directory of Open Access Journals (Sweden)

    Rachel M Lance

    Full Text Available Underwater blasts propagate further and injure more readily than equivalent air blasts. Development of effective personal protection and countermeasures, however, requires knowledge of the currently unknown human tolerance to underwater blast. Current guidelines for prevention of underwater blast injury are not based on any organized injury risk assessment, human data or experimental data. The goal of this study was to derive injury risk assessments for underwater blast using well-characterized human underwater blast exposures in the open literature. The human injury dataset was compiled using 34 case reports on underwater blast exposure to 475 personnel, dating as early as 1916. Using severity ratings, computational reconstructions of the blasts, and survival information from a final set of 262 human exposures, injury risk models were developed for both injury severity and risk of fatality as functions of blast impulse and blast peak overpressure. Based on these human data, we found that the 50% risk of fatality from underwater blast occurred at 302±16 kPa-ms impulse. Conservatively, there is a 20% risk of pulmonary injury at a kilometer from a 20 kg charge. From a clinical point of view, this new injury risk model emphasizes the large distances possible for potential pulmonary and gut injuries in water compared with air. This risk value is the first impulse-based fatality risk calculated from human data. The large-scale inconsistency between the blast exposures in the case reports and the guidelines available in the literature prior to this study further underscored the need for this new guideline derived from the unique dataset of actual injuries in this study.

  17. A line array based near field imaging technique for characterising acoustical properties of elongated targets

    NARCIS (Netherlands)

    Driessen, F.P.G.

    1995-01-01

    With near field imaging techniques the acoustical pressure waves at distances other than the recorded can be calculated. Normally, acquisition on a two dimensional plane is necessary and extrapolation is performed by a Rayleigh integral. A near field single line instead of two dimensional plane

  18. A new theoretical basis for numerical simulations of nonlinear acoustic fields

    Science.gov (United States)

    Wójcik, Janusz

    2000-07-01

    Nonlinear acoustic equations can be considerably simplified. The presented model retains the accuracy of a more complex description of nonlinearity and a uniform description of near and far fields (in contrast to the KZK equation). A method has been presented for obtaining solutions of Kuznetsov's equation from the solutions of the model under consideration. Results of numerical calculations, including comparative ones, are presented.

  19. A COMPARISON BETWEEN ACTIVE AND PASSIVE TECHNIQUES FOR UNDERWATER 3D APPLICATIONS

    Directory of Open Access Journals (Sweden)

    G. Bianco

    2012-09-01

    Full Text Available In the field of 3D scanning, there is an increasing need for more accurate technologies to acquire 3D models of close range objects. Underwater exploration, for example, is very hard to perform due to the hostile conditions and the bad visibility of the environment. Some application fields, like underwater archaeology, require to recover tridimensional data of objects that cannot be moved from their site or touched in order to avoid possible damages. Photogrammetry is widely used for underwater 3D acquisition, because it requires just one or two digital still or video cameras to acquire a sequence of images taken from different viewpoints. Stereo systems composed by a pair of cameras are often employed on underwater robots (i.e. ROVs, Remotely Operated Vehicles and used by scuba divers, in order to survey archaeological sites, reconstruct complex 3D structures in aquatic environment, estimate in situ the length of marine organisms, etc. The stereo 3D reconstruction is based on the triangulation of corresponding points on the two views. This requires to find in both images common points and to match them (correspondence problem, determining a plane that contains the 3D point on the object. Another 3D technique, frequently used in air acquisition, solves this point-matching problem by projecting structured lighting patterns to codify the acquired scene. The corresponding points are identified associating a binary code in both images. In this work we have tested and compared two whole-field 3D imaging techniques (active and passive based on stereo vision, in underwater environment. A 3D system has been designed, composed by a digital projector and two still cameras mounted in waterproof housing, so that it can perform the various acquisitions without changing the configuration of optical devices. The tests were conducted in a water tank in different turbidity conditions, on objects with different surface properties. In order to simulate a typical

  20. Underwater Ranging

    OpenAIRE

    S. P. Gaba

    1984-01-01

    The paper deals with underwater laser ranging system, its principle of operation and maximum depth capability. The sources of external noise and methods to improve signal-to-noise ratio are also discussed.

  1. UNDERWATER COATINGS FOR CONTAMINATION CONTROL

    International Nuclear Information System (INIS)

    Julia L. Tripp; Kip Archibald; Ann Marie Phillips; Joseph Campbell

    2004-01-01

    The Idaho National Laboratory (INL) deactivated several aging nuclear fuel storage basins. Planners for this effort were greatly concerned that radioactive contamination present on the basin walls could become airborne as the sides of the basins became exposed during deactivation and allowed to dry after water removal. One way to control this airborne contamination was to fix the contamination in place while the pool walls were still submerged. There are many underwater coatings available on the market for marine, naval and other applications. A series of tests were run to determine whether the candidate underwater fixatives were easily applied and adhered well to the substrates (pool wall materials) found in INL fuel pools. Lab-scale experiments were conducted by applying fourteen different commercial underwater coatings to four substrate materials representative of the storage basin construction materials, and evaluating their performance. The coupons included bare concrete, epoxy painted concrete, epoxy painted carbon steel, and stainless steel. The evaluation criteria included ease of application, adherence to the four surfaces of interest, no change on water clarity or chemistry, non-hazardous in final applied form and be proven in underwater applications. A proprietary two-part, underwater epoxy owned by S. G. Pinney and Associates was selected from the underwater coatings tested for application to all four pools. Divers scrubbed loose contamination off the basin walls and floors using a ship hull scrubber and vacuumed up the sludge. The divers then applied the coating using a special powered roller with two separate heated hoses that allowed the epoxy to mix at the roller surface was used to eliminate pot time concerns. The walls were successfully coated and water was removed from the pools with no detectable airborne contamination releases

  2. Acoustic spin pumping in magnetoelectric bulk acoustic wave resonator

    Directory of Open Access Journals (Sweden)

    N. I. Polzikova

    2016-05-01

    Full Text Available We present the generation and detection of spin currents by using magnetoelastic resonance excitation in a magnetoelectric composite high overtone bulk acoustic wave (BAW resonator (HBAR formed by a Al-ZnO-Al-GGG-YIG-Pt structure. Transversal BAW drives magnetization oscillations in YIG film at a given resonant magnetic field, and the resonant magneto-elastic coupling establishes the spin-current generation at the Pt/YIG interface. Due to the inverse spin Hall effect (ISHE this BAW-driven spin current is converted to a dc voltage in the Pt layer. The dependence of the measured voltage both on magnetic field and frequency has a resonant character. The voltage is determined by the acoustic power in HBAR and changes its sign upon magnetic field reversal. We compare the experimentally observed amplitudes of the ISHE electrical field achieved by our method and other approaches to spin current generation that use surface acoustic waves and microwave resonators for ferromagnetic resonance excitation, with the theoretically expected values.

  3. Acoustic spin pumping in magnetoelectric bulk acoustic wave resonator

    Energy Technology Data Exchange (ETDEWEB)

    Polzikova, N. I., E-mail: polz@cplire.ru; Alekseev, S. G.; Pyataikin, I. I.; Kotelyanskii, I. M.; Luzanov, V. A.; Orlov, A. P. [Kotel’nikov Institute of Radio Engineering and Electronics of Russian Academy of Sciences, Mokhovaya 11, building 7, Moscow, 125009 (Russian Federation)

    2016-05-15

    We present the generation and detection of spin currents by using magnetoelastic resonance excitation in a magnetoelectric composite high overtone bulk acoustic wave (BAW) resonator (HBAR) formed by a Al-ZnO-Al-GGG-YIG-Pt structure. Transversal BAW drives magnetization oscillations in YIG film at a given resonant magnetic field, and the resonant magneto-elastic coupling establishes the spin-current generation at the Pt/YIG interface. Due to the inverse spin Hall effect (ISHE) this BAW-driven spin current is converted to a dc voltage in the Pt layer. The dependence of the measured voltage both on magnetic field and frequency has a resonant character. The voltage is determined by the acoustic power in HBAR and changes its sign upon magnetic field reversal. We compare the experimentally observed amplitudes of the ISHE electrical field achieved by our method and other approaches to spin current generation that use surface acoustic waves and microwave resonators for ferromagnetic resonance excitation, with the theoretically expected values.

  4. Ion acoustic solitary waves in a dusty plasma obliquely propagating to an external magnetic field

    International Nuclear Information System (INIS)

    Choi, Cheong Rim; Ryu, Chang-Mo; Lee, Nam C.; Lee, D.-Y.

    2005-01-01

    The nonlinear ion acoustic solitary wave in a magnetized dusty plasma, obliquely propagating to the embedding external magnetic field, is revisited. It is found that when the charge density of dust particles is high, the Sagdeev potential needs to be expanded up to δn 4 near n=1. In this case, it is shown that there could exist rarefactive ion acoustic solitary waves as well as the kink-type double layer solutions, in addition to the conventional hump-type ones found in the δn 3 expansion. The amplitude variations of ion acoustic solitary waves in a magnetized dusty plasma are also examined with respect to the change of the dust charge density and the wave directional angle

  5. Springer handbook of acoustics

    CERN Document Server

    2014-01-01

    Acoustics, the science of sound, has developed into a broad interdisciplinary field encompassing the academic disciplines of physics, engineering, psychology, speech, audiology, music, architecture, physiology, neuroscience, and electronics. The Springer Handbook of Acoustics is also in his 2nd edition an unparalleled modern handbook reflecting this richly interdisciplinary nature edited by one of the acknowledged masters in the field, Thomas Rossing. Researchers and students benefit from the comprehensive contents. This new edition of the Handbook features over 11 revised and expanded chapters, new illustrations, and 2 new chapters covering microphone arrays  and acoustic emission.  Updated chapters contain the latest research and applications in, e.g. sound propagation in the atmosphere, nonlinear acoustics in fluids, building and concert hall acoustics, signal processing, psychoacoustics, computer music, animal bioacousics, sound intensity, modal acoustics as well as new chapters on microphone arrays an...

  6. Numerical investigation of symmetry breaking and critical behavior of the acoustic streaming field in high-intensity discharge lamps

    International Nuclear Information System (INIS)

    Baumann, Bernd; Schwieger, Joerg; Wolff, Marcus; Manders, Freddy; Suijker, Jos

    2015-01-01

    For energy efficiency and material cost reduction it is preferred to drive high-intensity discharge lamps at frequencies of approximately 300 kHz. However, operating lamps at these high frequencies bears the risk of stimulating acoustic resonances inside the arc tube, which can result in low frequency light flicker and even lamp destruction. The acoustic streaming effect has been identified as the link between high frequency resonances and low frequency flicker. A highly coupled three-dimensional multiphysics model has been set up to calculate the acoustic streaming velocity field inside the arc tube of high-intensity discharge lamps. It has been found that the velocity field suffers a phase transition to an asymmetrical state at a critical acoustic streaming force. In certain respects the system behaves similar to a ferromagnet near the Curie point. It is discussed how the model allows to investigate the light flicker phenomenon. Concerning computer resources the procedure is considerably less demanding than a direct approach with a transient model. (paper)

  7. The low-frequency sound power measuring technique for an underwater source in a non-anechoic tank

    Science.gov (United States)

    Zhang, Yi-Ming; Tang, Rui; Li, Qi; Shang, Da-Jing

    2018-03-01

    In order to determine the radiated sound power of an underwater source below the Schroeder cut-off frequency in a non-anechoic tank, a low-frequency extension measuring technique is proposed. This technique is based on a unique relationship between the transmission characteristics of the enclosed field and those of the free field, which can be obtained as a correction term based on previous measurements of a known simple source. The radiated sound power of an unknown underwater source in the free field can thereby be obtained accurately from measurements in a non-anechoic tank. To verify the validity of the proposed technique, a mathematical model of the enclosed field is established using normal-mode theory, and the relationship between the transmission characteristics of the enclosed and free fields is obtained. The radiated sound power of an underwater transducer source is tested in a glass tank using the proposed low-frequency extension measuring technique. Compared with the free field, the radiated sound power level of the narrowband spectrum deviation is found to be less than 3 dB, and the 1/3 octave spectrum deviation is found to be less than 1 dB. The proposed testing technique can be used not only to extend the low-frequency applications of non-anechoic tanks, but also for measurement of radiated sound power from complicated sources in non-anechoic tanks.

  8. Computational Ocean Acoustics

    CERN Document Server

    Jensen, Finn B; Porter, Michael B; Schmidt, Henrik

    2011-01-01

    Since the mid-1970s, the computer has played an increasingly pivotal role in the field of ocean acoustics. Faster and less expensive than actual ocean experiments, and capable of accommodating the full complexity of the acoustic problem, numerical models are now standard research tools in ocean laboratories. The progress made in computational ocean acoustics over the last thirty years is summed up in this authoritative and innovatively illustrated new text. Written by some of the field's pioneers, all Fellows of the Acoustical Society of America, Computational Ocean Acoustics presents the latest numerical techniques for solving the wave equation in heterogeneous fluid–solid media. The authors discuss various computational schemes in detail, emphasizing the importance of theoretical foundations that lead directly to numerical implementations for real ocean environments. To further clarify the presentation, the fundamental propagation features of the techniques are illustrated in color. Computational Ocean A...

  9. Underwater Gliders: A Review

    OpenAIRE

    Javaid Muhammad Yasar; Ovinis Mark; Nagarajan T; Hashim Fakhruldin B M

    2014-01-01

    Underwater gliders are a type of underwater vehicle that transverse the oceans by shifting its buoyancy, during which its wings develop a component of the downward motion in the horizontal plane, thus producing a forward force. They are primarily used in oceanography sensing and data collection and play an important role in ocean research and development. Although there have been considerable developments in these gliders since the development of the first glider concept in 1989, to date, no ...

  10. Underwater noise pollution in a coastal tropical environment.

    Science.gov (United States)

    Bittencourt, L; Carvalho, R R; Lailson-Brito, J; Azevedo, A F

    2014-06-15

    Underwater noise pollution has become a major concern in marine habitats. Guanabara Bay, southeastern Brazil, is an impacted area of economic importance with constant vessel traffic. One hundred acoustic recording sessions took place over ten locations. Sound sources operating within 1 km radius of each location were quantified during recordings. The highest mean sound pressure level near the surface was 111.56±9.0 dB re 1 μPa at the frequency band of 187 Hz. Above 15 kHz, the highest mean sound pressure level was 76.21±8.3 dB re 1 μPa at the frequency 15.89 kHz. Noise levels correlated with number of operating vessels and vessel traffic composition influenced noise profiles. Shipping locations had the highest noise levels, while small vessels locations had the lowest noise levels. Guanabara Bay showed noise pollution similar to that of other impacted coastal regions, which is related to shipping and vessel traffic. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Perancangan Prototipe Receiver Beacon Black Box Locator Acoustic 37,5 kHz Pingers

    OpenAIRE

    RUSTAMAJI RUSTAMAJI; PAULINE RAHMIATI; SARAH PERMATASARI

    2016-01-01

    ABSTRAK Ketika suatu pesawat terbang mengalami kecelakaan terjatuh ke dalam air, maka lokasi keberadaannya dapat dideteksi oleh alat yang disebut receiver beacon black box locator acoustic (pingers receiver). Pingers receiver berfungsi untuk menerima sinyal dengan frekuensi 37,5 kHz ± 1 kHz dari pingers transmitter atau Underwater Locator Beacon (ULB) yang berada pada black box pesawat. Dalam penelitian ini dibuat perancangan pingers receiver yang tersusun dari rangkaian Band Pass Filter (BPF...

  12. Underwater Calibration of Dome Port Pressure Housings

    Science.gov (United States)

    Nocerino, E.; Menna, F.; Fassi, F.; Remondino, F.

    2016-03-01

    Underwater photogrammetry using consumer grade photographic equipment can be feasible for different applications, e.g. archaeology, biology, industrial inspections, etc. The use of a camera underwater can be very different from its terrestrial use due to the optical phenomena involved. The presence of the water and camera pressure housing in front of the camera act as additional optical elements. Spherical dome ports are difficult to manufacture and consequently expensive but at the same time they are the most useful for underwater photogrammetry as they keep the main geometric characteristics of the lens unchanged. Nevertheless, the manufacturing and alignment of dome port pressure housing components can be the source of unexpected changes of radial and decentring distortion, source of systematic errors that can influence the final 3D measurements. The paper provides a brief introduction of underwater optical phenomena involved in underwater photography, then presents the main differences between flat and dome ports to finally discuss the effect of manufacturing on 3D measurements in two case studies.

  13. Near-Real-Time Acoustic Monitoring of Beaked Whales and Other Cetaceans Using a Seaglider™

    Science.gov (United States)

    Klinck, Holger; Mellinger, David K.; Klinck, Karolin; Bogue, Neil M.; Luby, James C.; Jump, William A.; Shilling, Geoffrey B.; Litchendorf, Trina; Wood, Angela S.; Schorr, Gregory S.; Baird, Robin W.

    2012-01-01

    In most areas, estimating the presence and distribution of cryptic marine mammal species, such as beaked whales, is extremely difficult using traditional observational techniques such as ship-based visual line transect surveys. Because acoustic methods permit detection of animals underwater, at night, and in poor weather conditions, passive acoustic observation has been used increasingly often over the last decade to study marine mammal distribution, abundance, and movements, as well as for mitigation of potentially harmful anthropogenic effects. However, there is demand for new, cost-effective tools that allow scientists to monitor areas of interest autonomously with high temporal and spatial resolution in near-real time. Here we describe an autonomous underwater vehicle – a glider – equipped with an acoustic sensor and onboard data processing capabilities to passively scan an area for marine mammals in near-real time. The glider was tested extensively off the west coast of the Island of Hawai'i, USA. The instrument covered approximately 390 km during three weeks at sea and collected a total of 194 h of acoustic data. Detections of beaked whales were successfully reported to shore in near-real time. Manual analysis of the recorded data revealed a high number of vocalizations of delphinids and sperm whales. Furthermore, the glider collected vocalizations of unknown origin very similar to those made by known species of beaked whales. The instrument developed here can be used to cost-effectively screen areas of interest for marine mammals for several months at a time. The near-real-time detection and reporting capabilities of the glider can help to protect marine mammals during potentially harmful anthropogenic activities such as seismic exploration for sub-sea fossil fuels or naval sonar exercises. Furthermore, the glider is capable of under-ice operation, allowing investigation of otherwise inaccessible polar environments that are critical habitats for many

  14. Near-real-time acoustic monitoring of beaked whales and other cetaceans using a Seaglider™.

    Directory of Open Access Journals (Sweden)

    Holger Klinck

    Full Text Available In most areas, estimating the presence and distribution of cryptic marine mammal species, such as beaked whales, is extremely difficult using traditional observational techniques such as ship-based visual line transect surveys. Because acoustic methods permit detection of animals underwater, at night, and in poor weather conditions, passive acoustic observation has been used increasingly often over the last decade to study marine mammal distribution, abundance, and movements, as well as for mitigation of potentially harmful anthropogenic effects. However, there is demand for new, cost-effective tools that allow scientists to monitor areas of interest autonomously with high temporal and spatial resolution in near-real time. Here we describe an autonomous underwater vehicle--a glider--equipped with an acoustic sensor and onboard data processing capabilities to passively scan an area for marine mammals in near-real time. The glider was tested extensively off the west coast of the Island of Hawai'i, USA. The instrument covered approximately 390 km during three weeks at sea and collected a total of 194 h of acoustic data. Detections of beaked whales were successfully reported to shore in near-real time. Manual analysis of the recorded data revealed a high number of vocalizations of delphinids and sperm whales. Furthermore, the glider collected vocalizations of unknown origin very similar to those made by known species of beaked whales. The instrument developed here can be used to cost-effectively screen areas of interest for marine mammals for several months at a time. The near-real-time detection and reporting capabilities of the glider can help to protect marine mammals during potentially harmful anthropogenic activities such as seismic exploration for sub-sea fossil fuels or naval sonar exercises. Furthermore, the glider is capable of under-ice operation, allowing investigation of otherwise inaccessible polar environments that are critical

  15. NRL Fact Book

    Science.gov (United States)

    1988-05-01

    interests are centered on signal processing and the physics of underwater acoustic propagation, ambient noise, and reverberation. Mr. Rojas is a member...Airborne underwater acoustics Bottom-limited acoustics Arctic underwater acoustics Propagation Noise Ambient noise measurements and modeling Spectral...Multispectral image correlation Space sensor and mission analysis CROWN" STALK Time, ms (100 ms after impactO Time-history of the . radar backscatter from a

  16. Amélioration des performances du traitement des interférences dans le domaine fréquentiel pour les communications acoustiques sous marines

    OpenAIRE

    YOUCEF , Abdelhakim

    2013-01-01

    Underwater acoustic (UWA) communications allow wireless transmission between the surface and the bottom of a subsea environment based on acoustic waves. The wireless acoustic link reduces the physical infrastructure cost compared to the cable-based underwater communications. However, underwater acoustic channel imposes severe degradations on the transmitted signal. Its propagation characteristics are widely different from those of the radio channel. The multipath propagation caused by multipl...

  17. Measurements of the acoustic field on austenitic welds: a way to higher reliability in ultrasonic tests

    International Nuclear Information System (INIS)

    Kemnitz, P.; Richter, U.; Klueber, H.

    1997-01-01

    In nuclear power plants many of the welds in austenitic tubes have to be inspected by means of ultrasonic techniques. If component-identical test pieces are available, they are used to qualify the ultrasonic test technology. Acoustic field measurements on such test blocks give information whether the beam of the ultrasonic transducer reaches all critical parts of the weld region and which transducer type is best suited. Acoustic fields have been measured at a bimetallic, a V-shaped and a narrow gap weld in test pieces of wall thickness 33, 25 and 17 mm, respectively. Compression wave transducers 45, 60 and 70 and 45 shear wave transducers have been included in the investigation. The results are presented: (1) as acoustic C-scans for one definite probe position, (2) as series of C-scans for the probe moving on a track perpendicular to the weld, (3) as scan along the weld and (4) as effective beam profile. The influence of the scanning electrodynamic probe is also discussed. (orig.)

  18. Development of a highly maneuverable unmanned underwater vehicle on the basis of quad-copter dynamics

    Science.gov (United States)

    Amin, Osman Md; Karim, Md. Arshadul; Saad, Abdullah His

    2017-12-01

    At present, research on unmanned underwater vehicle (UUV) has become a significant & familiar topic for researchers from various engineering fields. UUV is of mainly two types - AUV (Autonomous Underwater vehicle) & ROV (Remotely Operated Vehicle). There exist a significant number of published research papers on UUV, where very few researchers emphasize on the ease of maneuvering and control of UUV. Maneuvering is important for underwater vehicle in avoiding obstacles, installing underwater piping system, searching undersea resources, underwater mine disposal operations, oceanographic surveys etc. A team from Dept. of Naval Architecture & Marine Engineering of MIST has taken a project to design a highly maneuverable unmanned underwater vehicle on the basis of quad-copter dynamics. The main objective of the research is to develop a control system for UUV which would be able to maneuver the vehicle in six DOF (Degrees of Freedom) with great ease. For this purpose we are not only focusing on controllability but also designing an efficient hull with minimal drag force & optimized propeller using CFD technique. Motors were selected on the basis of the simulated thrust generated by propellers in ANSYS Fluent software module. Settings for control parameters to carry out different types of maneuvering such as hovering, spiral, one point rotation about its centroid, gliding, rolling, drifting and zigzag motions were explained in short at the end.

  19. Review of potential impacts to sea turtles from underwater explosive removal of offshore structures

    International Nuclear Information System (INIS)

    Viada, Stephen T.; Hammer, Richard M.; Racca, Roberto; Hannay, David; Thompson, M. John; Balcom, Brian J.; Phillips, Neal W.

    2008-01-01

    The purpose of this study was to collect and synthesize existing information relevant to the explosive removal of offshore structures (EROS) in aquatic environments. Data sources were organized and summarized by topic - explosive removal methods, physics of underwater explosions, sea turtle resources, documented impacts to sea turtles, and mitigation of effects. Information was gathered via electronic database searches and literature source review. Bulk explosive charges are the most commonly used technique in EROS. While the physical principles of underwater detonations and the propagation of pressure and acoustic waves are well understood, there are significant gaps in the application of this knowledge. Impacts to sea turtles from explosive removal operations may range from non-injurious effects (e.g. acoustic annoyance; mild tactile detection or physical discomfort) to varying levels of injury (i.e. non-lethal and lethal injuries). Very little information exists regarding the impacts of underwater explosions on sea turtles. Effects of explosions on turtles often must be inferred from documented effects to other vertebrates with lungs or other gas-containing organs, such as mammals and most fishes. However, a cautious approach should be used when determining impacts to sea turtles based on extrapolations from other vertebrates. The discovery of beached sea turtles and bottlenose dolphins following an explosive platform removal event in 1986 prompted the initiation of formal consultation between the U.S. Department of the Interior, Minerals Management Service (MMS) and the National Marine Fisheries Service (NMFS), authorized through the Endangered Species Act Section 7, to determine a mechanism to minimize potential impacts to listed species. The initial consultation resulted in a requirement for oil and gas companies to obtain a permit (through separate consultations on a case-by-case basis) prior to using explosives in Federal waters. Because many offshore

  20. Hydroelastic behaviour of a structure exposed to an underwater explosion.

    Science.gov (United States)

    Colicchio, G; Greco, M; Brocchini, M; Faltinsen, O M

    2015-01-28

    The hydroelastic interaction between an underwater explosion and an elastic plate is investigated num- erically through a domain-decomposition strategy. The three-dimensional features of the problem require a large computational effort, which is reduced through a weak coupling between a one-dimensional radial blast solver, which resolves the blast evolution far from the boundaries, and a three-dimensional compressible flow solver used where the interactions between the compression wave and the boundaries take place and the flow becomes three-dimensional. The three-dimensional flow solver at the boundaries is directly coupled with a modal structural solver that models the response of the solid boundaries like elastic plates. This enables one to simulate the fluid-structure interaction as a strong coupling, in order to capture hydroelastic effects. The method has been applied to the experimental case of Hung et al. (2005 Int. J. Impact Eng. 31, 151-168 (doi:10.1016/j.ijimpeng.2003.10.039)) with explosion and structure sufficiently far from other boundaries and successfully validated in terms of the evolution of the acceleration induced on the plate. It was also used to investigate the interaction of an underwater explosion with the bottom of a close-by ship modelled as an orthotropic plate. In the application, the acoustic phase of the fluid-structure interaction is examined, highlighting the need of the fluid-structure coupling to capture correctly the possible inception of cavitation. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  1. Underwater microwave ignition of hydrophobic thermite powder enabled by the bubble-marble effect

    International Nuclear Information System (INIS)

    Meir, Yehuda; Jerby, Eli

    2015-01-01

    Highly energetic thermite reactions could be useful for a variety of combustion and material-processing applications, but their usability is yet limited by their hard ignition conditions. Furthermore, in virtue of their zero-oxygen balance, exothermic thermite reactions may also occur underwater. However, this feature is also hard to utilize because of the hydrophobic properties of the thermite powder, and its tendency to agglomerate on the water surface rather than to sink into the water. The recently discovered bubble-marble (BM) effect enables the insertion and confinement of a thermite-powder batch into water by a magnetic field. Here, we present a phenomenon of underwater ignition of a thermite-BM by localized microwaves. The thermite combustion underwater is observed in-situ, and its microwave absorption and optical spectral emission are detected. The vapour pressure generated by the thermite reaction is measured and compared to theory. The combustion products are examined ex-situ by X-ray photo-electron spectroscopy which verifies the thermite reaction. Potential applications of this underwater combustion effect are considered, e.g., for detonation, wet welding, thermal drilling, material processing, thrust generation, and composite-material production, also for other oxygen-free environments

  2. Underwater microwave ignition of hydrophobic thermite powder enabled by the bubble-marble effect

    Energy Technology Data Exchange (ETDEWEB)

    Meir, Yehuda; Jerby, Eli, E-mail: jerby@eng.tau.ac.il [Faculty of Engineering, Tel Aviv University, Ramat Aviv 6997801 (Israel)

    2015-08-03

    Highly energetic thermite reactions could be useful for a variety of combustion and material-processing applications, but their usability is yet limited by their hard ignition conditions. Furthermore, in virtue of their zero-oxygen balance, exothermic thermite reactions may also occur underwater. However, this feature is also hard to utilize because of the hydrophobic properties of the thermite powder, and its tendency to agglomerate on the water surface rather than to sink into the water. The recently discovered bubble-marble (BM) effect enables the insertion and confinement of a thermite-powder batch into water by a magnetic field. Here, we present a phenomenon of underwater ignition of a thermite-BM by localized microwaves. The thermite combustion underwater is observed in-situ, and its microwave absorption and optical spectral emission are detected. The vapour pressure generated by the thermite reaction is measured and compared to theory. The combustion products are examined ex-situ by X-ray photo-electron spectroscopy which verifies the thermite reaction. Potential applications of this underwater combustion effect are considered, e.g., for detonation, wet welding, thermal drilling, material processing, thrust generation, and composite-material production, also for other oxygen-free environments.

  3. Modelling of the underwater disposal of uranium mine tailings in Elliot Lake

    International Nuclear Information System (INIS)

    Halbert, B.E.; Scharer, J.M.; Chakravatti, J.L.; Barnes, E.

    1982-01-01

    Underwater disposal of uranium mine tailings from the Elliot Lake area operations offers potential advantages in controlling radon gas release, emission of airborne particulate matter, and acid production from pyrites in the tailings. In addition, the proximity of the three active properties, one owned by Denison Mines Limited and two by Rio Algom Limited, to a large deep lake has spurred interest in the concept. It has been estimated that the placement of approximately 150 million tonnes of tailings from future planned production would occupy less than 20% of the lake volume. To assess the applicability of the underwater tailings disposal concept, a multi-stage study was developed in conjunction with the regulatory agencies. The most important facet identified for investigation during the first-stage investigations was an assessment of the effects of underwater disposal on water quality in the Serpent River Basin watershed. To simulate the effects of underwater disposal, a computer simulation routine was developed and integrated with a water quality model previously developed for the Basin which predicts levels of total dissolved solids, ammonia, dissolved radium-226 and pH. The underwater disposal model component reflects the effects of direct input of tailings into the hypolimnion, the chemical/biological transformation of dissolved constituents in the water column, the reactions of pyritic tailings deposited on the bottom, and the flux of dissolved constituents from the tailings into the water column. To establish site-specific values for the underwater disposal model, field and laboratory experiments were utilized to evaluate rates of pyrite and ammonia oxidation, and pH-alkalinity relationships. The results of these studies and their use in the water quality model are discussed. In addition, the results of two model run simulations are presented. (author)

  4. Near-field multiple traps of paraxial acoustic vortices with strengthened gradient force generated by sector transducer array

    Science.gov (United States)

    Wang, Qingdong; Li, Yuzhi; Ma, Qingyu; Guo, Gepu; Tu, Juan; Zhang, Dong

    2018-01-01

    In order to improve the capability of particle trapping close to the source plane, theoretical and experimental studies on near-field multiple traps of paraxial acoustic vortices (AVs) with a strengthened acoustic gradient force (AGF) generated by a sector transducer array were conducted. By applying the integration of point source radiation, numerical simulations for the acoustic fields generated by the sector transducer array were conducted and compared with those produced by the circular transducer array. It was proved that strengthened AGFs of near-field multiple AVs with higher peak pressures and smaller vortex radii could be produced by the sector transducer array with a small topological charge. The axial distributions of the equivalent potential gradient indicated that the AGFs of paraxial AVs in the near field were much higher than those in the far field, and the distances at the near-field vortex antinodes were also proved to be the ideal trapping positions with relatively higher AGFs. With the established 8-channel AV generation system, theoretical studies were also verified by the experimental measurements of pressure and phase for AVs with various topological charges. The formation of near-field multiple paraxial AVs was verified by the cross-sectional circular pressure distributions with perfect phase spirals around central pressure nulls, and was also proved by the vortex nodes and antinodes along the center axis. The favorable results demonstrated the feasibility of generating near-field multiple traps of paraxial AVs with strengthened AGF using the sector transducer array, and suggested the potential applications of close-range particle trapping in biomedical engineering.

  5. Tunable coupled surface acoustic cavities

    Science.gov (United States)

    de Lima, M. M.; Santos, P. V.; Kosevich, Yu. A.; Cantarero, A.

    2012-06-01

    We demonstrate the electric tuning of the acoustic field in acoustic microcavities (MCs) defined by a periodic arrangement of metal stripes within a surface acoustic delay line on LiNbO3 substrate. Interferometric measurements show the enhancement of the acoustic field distribution within a single MC, the presence of a "bonding" and "anti-bonding" modes for two strongly coupled MCs, as well as the positive dispersion of the "mini-bands" formed by five coupled MCs. The frequency and amplitude of the resonances can be controlled by the potential applied to the metal stripes.

  6. Optical aberrations in underwater photogrammetry with flat and hemispherical dome ports

    Science.gov (United States)

    Menna, Fabio; Nocerino, Erica; Remondino, Fabio

    2017-06-01

    The paper analyses differences between dome and flat port housings used for underwater photogrammetry. The underwater environment negatively affects image quality and 3D reconstructions, but this influence on photogrammetric measurements, so far, has not been addressed properly in the literature. In this work, motivations behind the need for systematic underwater calibrations are provided, then experimental tests using a specifically designed photogrammetric modular test object in laboratory and at sea are reported. The experiments are carried out using a Nikon D750 24 Mpx DSLR camera with a 24 mm f2.8 AF/D lens coupled with a NIMAR NI3D750ZM housing, equipped first with a dome and, successively, with a flat port. To quantify the degradation of image quality, MTF measurements are carried out, then the outcomes of self-calibrating bundle adjustment calibrations are shown and commented. Optical phenomena like field curvature as well as chromatic aberration and astigmatism are analysed and their implications on the degradation of image quality is factored in the bundle adjustment through a different weighting of 2D image observations.

  7. Underwater 3D filming

    OpenAIRE

    Rinaldi, Roberto

    2014-01-01

    After an experimental phase of many years, 3D filming is now effective and successful. Improvements are still possible, but the film industry achieved memorable success on 3D movie’s box offices due to the overall quality of its products. Special environments such as space (“Gravity” ) and the underwater realm look perfect to be reproduced in 3D. “Filming in space” was possible in “Gravity” using special effects and computer graphic. The underwater realm is still difficult to be handled. Unde...

  8. Biogeography-based combinatorial strategy for efficient autonomous underwater vehicle motion planning and task-time management

    Science.gov (United States)

    Zadeh, S. M.; Powers, D. M. W.; Sammut, K.; Yazdani, A. M.

    2016-12-01

    Autonomous Underwater Vehicles (AUVs) are capable of spending long periods of time for carrying out various underwater missions and marine tasks. In this paper, a novel conflict-free motion planning framework is introduced to enhance underwater vehicle's mission performance by completing maximum number of highest priority tasks in a limited time through a large scale waypoint cluttered operating field, and ensuring safe deployment during the mission. The proposed combinatorial route-path planner model takes the advantages of the Biogeography-Based Optimization (BBO) algorithm toward satisfying objectives of both higher-lower level motion planners and guarantees maximization of the mission productivity for a single vehicle operation. The performance of the model is investigated under different scenarios including the particular cost constraints in time-varying operating fields. To show the reliability of the proposed model, performance of each motion planner assessed separately and then statistical analysis is undertaken to evaluate the total performance of the entire model. The simulation results indicate the stability of the contributed model and its feasible application for real experiments.

  9. Acoustic detection of UHE neutrinos in the Mediterranean sea: status and perspective

    Directory of Open Access Journals (Sweden)

    Simeone Francesco

    2017-01-01

    Full Text Available In recent years the astro-particle community is involved in the realization of experimental apparatuses for the detection of high energy neutrinos originated in cosmic sources or produced in the interaction of Cosmic Rays with the Cosmic Microwave Background. For neutrino energies in the TeV-PeV range, optical Cherenkov detectors, that have been so far positively exploited by Baikal[1], IceCube[2] and ANTARES[3], are considered optimal. For higher energies, three different experimental techniques are under study: the detection of radio pulses produced by showers induced by a neutrino interaction, the detection of air showers initiated by neutrinos interacting with rocks or deep Earth’s atmosphere and the detection of acoustic waves produced by deposition of energy following the interaction of neutrinos in an acoustically transparent medium. The potential of the acoustic detection technique, first proposed by Askaryan[4], to build very large neutrino detectors is appealing, thanks to the optimal properties of media such as water or ice as sound propagator. Though the studies on this technique are still in an early stage, acoustic positioning systems used to locate the optical modules in underwater Cherenkov neutrino detectors, give the possibility to study the ambient noise and provide important information for the future analysis of acoustic data.

  10. Combined Opto-Acoustical sensor modules for KM3NeT

    International Nuclear Information System (INIS)

    Enzenhöfer, A.

    2013-01-01

    KM3NeT is a future multi-cubic-kilometre water Cherenkov neutrino telescope currently entering a first construction phase. It will be located in the Mediterranean Sea and comprise about 600 vertical structures called detection units. Each of these detection units has a length of several hundred metres and is anchored to the sea bed on one side and held taut by a buoy on the other side. The detection units are thus subject to permanent movement due to sea currents. Modules holding photosensors and additional equipment are equally distributed along the detection units. The relative positions of the photosensors has to be known with an uncertainty below 20 cm in order to achieve the necessary precision for neutrino astronomy. These positions can be determined with an acoustic positioning system: dedicated acoustic emitters located at known positions and acoustic receivers along each detection unit. This article describes the approach to combine an acoustic receiver with the photosensors inside one detection module using a common power supply and data readout. The advantage of this approach lies in a reduction of underwater connectors and module configurations as well as in the compactification of the detection units integrating the auxiliary devices necessary for their successful operation.

  11. IVO develops a new repair technique for underwater sites. Viscous doughlike substance underwater cracks

    Energy Technology Data Exchange (ETDEWEB)

    Klingstedt, G.; Leisio, C. [ed.

    1998-07-01

    A viscous sealant is revolutionizing repair of the stone and concrete masonry of underwater dams, bridges and canals. There is now no need for expensive and time-consuming cofferdams, since a diver can extrude quick-setting mortar into underwater structures needing repair. This technique has worked well in recent years in various parts of Finland even in strongly flowing water. IVO experts are now starting to look more beyond the borders of Finland

  12. Acoustic forcing of a liquid drop

    Science.gov (United States)

    Lyell, M. J.

    1992-01-01

    The development of systems such as acoustic levitation chambers will allow for the positioning and manipulation of material samples (drops) in a microgravity environment. This provides the capability for fundamental studies in droplet dynamics as well as containerless processing work. Such systems use acoustic radiation pressure forces to position or to further manipulate (e.g., oscillate) the sample. The primary objective was to determine the effect of a viscous acoustic field/tangential radiation pressure forcing on drop oscillations. To this end, the viscous acoustic field is determined. Modified (forced) hydrodynamic field equations which result from a consistent perturbation expansion scheme are solved. This is done in the separate cases of an unmodulated and a modulated acoustic field. The effect of the tangential radiation stress on the hydrodynamic field (drop oscillations) is found to manifest as a correction to the velocity field in a sublayer region near the drop/host interface. Moreover, the forcing due to the radiation pressure vector at the interface is modified by inclusion of tangential stresses.

  13. PHYSICAL FIELDS OF CIRCULAR CYLINDRICAL PIEZOCERAMIC RECEIVER IN PRESENCE OF A FLAT ACOUSTIC SOFT SCREEN

    Directory of Open Access Journals (Sweden)

    A. V. Derepa

    2017-01-01

    Full Text Available System in the form of a circular cylindrical piezoceramic transducer near a flat acoustic screen was analyzed. The aim of the work was to solve the problem of receiving plane sound waves by «cylindrical piezoceramic transducer – flat acoustically soft screen» system.Considered system was characterized by a violation of the radial symmetry of the radiation load of the transducer while maintaining the radial symmetry of the electric load. At the same time, the energy perceived by the system under consideration is distributed between all modes of oscillation of the transducer, while the conversion of mechanical energy into electric is realized only at zero mole of oscillations.Special attention was paid to the method of coupled fields in multiply connected domains using the imaging method. The design model of the «transducer–creen» system was formulated taking into account the interaction of acoustic, mechanical and electric fields in the process of energy conversion, the interaction of a cylindrical transducer with a flat screen and the interaction of a converter with elastic media outside and inside it. The physical fields of the system under consideration were determined by following solutions: the wave equation; equations of motion of thin piezoceramic cylindrical shells in displacements; equations of stimulated electrostatics for piezoceramics for given boundary conditions, conditions for coupling fields at interfaces and electrical conditions.A general conclusion was made concerning solving of an infinite system of linear algebraic equations with respect to the unknown coefficients of the expansion of the fields. As an example of the application of the obtained relations, a calculation was made and an analysis of the dependences of the electric fields of the system under consideration for various parameters of its construction on the direction of arrival on the plane wave system was conducted.

  14. The flame structure in round and plane propane microjet combustion in a transverse acoustic field at low Reynolds numbers

    Science.gov (United States)

    Kozlov, V. V.; Grek, G. R.; Katasonov, M. M.; Korobeinichev, O. P.; Litvinenko, Yu. A.; Shmakov, A. G.

    2014-12-01

    The results of experimental studies of the structure and features of flame evolution under propane combustion in round and plane microjet flows at low Reynolds numbers in a transverse acoustic field are discussed in this paper. The specific features of flame evolution under these conditions are shown. Based on the new information obtained on free microjet evolution, new phenomena in flame evolution in a transverse acoustic field with round and plane propane microjet combustion are discovered and explained.

  15. A man-made object detection for underwater TV

    Science.gov (United States)

    Cheng, Binbin; Wang, Wenwu; Chen, Yao

    2018-03-01

    It is a great challenging task to complete an automatic search of objects underwater. Usually the forward looking sonar is used to find the target, and then the initial identification of the target is completed by the side-scan sonar, and finally the confirmation of the target is accomplished by underwater TV. This paper presents an efficient method for automatic extraction of man-made sensitive targets in underwater TV. Firstly, the image of underwater TV is simplified with taking full advantage of the prior knowledge of the target and the background; then template matching technology is used for target detection; finally the target is confirmed by extracting parallel lines on the target contour. The algorithm is formulated for real-time execution on limited-memory commercial-of-the-shelf platforms and is capable of detection objects in underwater TV.

  16. Design of Autonomous Underwater Vehicle

    Directory of Open Access Journals (Sweden)

    Tadahiro Hyakudome

    2011-03-01

    Full Text Available There are concerns about the impact that global warming will have on our environment, and which will inevitably result in expanding deserts and rising water levels. While a lot of underwater vehicles are utilized, AUVs (Autonomous Underwater Vehicle were considered and chosen, as the most suitable tool for conduction survey concerning these global environmental problems. AUVs can comprehensive survey because the vehicle does not have to be connected to the support vessel by tether cable. When such underwater vehicles are made, it is necessary to consider about the following things. 1 Seawater and Water Pressure Environment, 2 Sink, 3 There are no Gas or Battery Charge Stations, 4 Global Positioning System cannot use, 5 Radio waves cannot use. In the paper, outline of above and how deal about it are explained.

  17. Validation of simulations of an underwater acoustic communication channel characterized by wind-generated surface waves and bubbles

    NARCIS (Netherlands)

    Dol, H.S.; Colin, M.E.G.D.; Ainlie, M.A.; Gerdes, F.; Schäfke, A.; Özkan Sertlekc, H.

    2013-01-01

    This paper shows that it is possible to simulate realistic shallow-water acoustic communication channels using available acoustic propagation models. Key factor is the incorporation of realistic time-dependent sea surface conditions, including both waves and bubbles due to wind.

  18. Thermo-mechanic and Microstructural Analysis of an Underwater Welding Joint

    Directory of Open Access Journals (Sweden)

    Pedro Hernández Gutiérrez

    Full Text Available Abstract The aim of this research is to present a comparative analysis between theoretical and experimental thermal fields as well as a microstructural behaviour and residual stresses applying multiple weld beads in the joint of two API 5L X52 pipe sections. The thermal field, microstructural and residual stresses were numerically modelled through the finite element method (FEM and compared to experimentally. The simulation conditions used in the FEM analysis were similar considerations to the underwater welding conditions. The finite element analysis was carried out, first by a non-linear transient thermal analysis for obtaining the global temperature history generated during the underwater welding process. Subsequently, a microstructural behaviour was determined using the temperatures distribution obtained in the pipe material by calculating the structural transformations of the material during the welding process, and finally a stress analysis was developed using the temperatures obtained from the thermal analysis. It was found that this simulation method can be used efficiently to determinate with accuracy the optimum welding parameters of this kind of weld applications.

  19. Underwater-manipulation system for measuring- and cutting tasks in dismantling decommissioned nuclear facilities. Final report

    International Nuclear Information System (INIS)

    Stegemann, D.; Reimche, W.; Hansch, M.; Spitzer, M.

    1995-01-01

    Not only manipulators are necessary for dismantling and inspection of structure parts in decomissioned nuclear facilities, but flexible underwater-vehicles. Free-diving underwater-vehicles for inspection and dismantling tasks are still not developed and tested. Aim of the project is the development of sensors and devices for the position determination and the depth regulation. For inspection tasks an ultrasonic measurement and dosimeter device shall be built up. A measurement device has been developed which evaluates the ultrasonic time of flight from a transmitter at the vehicle to several receivers, installed in the reactor pressure vessel. The depth regulation is based on a pressure sensor and the direct control of the thrusters. The ultrasonic measurements are realized by an adapted ultrasonic card, the γ-dosimetry with an ionization chamber and a pA-amplifier. An acoustic orientation system was built up, which measures very accurately with one transmitter mounted on the vehicle and four receivers. Problem occur by reflection from the walls of the basin. The depth regulation is working faultless. The ultrasonic device is preferably used for distance measurement. The radiation measurement device was tested and mounted in the vehicle. (orig./HP) [de

  20. Open-Lake Experimental Investigation of Azimuth Angle Estimation Using a Single Acoustic Vector Sensor

    Directory of Open Access Journals (Sweden)

    Anbang Zhao

    2018-01-01

    Full Text Available Five well-known azimuth angle estimation methods using a single acoustic vector sensor (AVS are investigated in open-lake experiments. A single AVS can measure both the acoustic pressure and acoustic particle velocity at a signal point in space and output multichannel signals. The azimuth angle of one source can be estimated by using a single AVS in a passive sonar system. Open-lake experiments are carried out to evaluate how these different techniques perform in estimating azimuth angle of a source. The AVS that was applied in these open-lake experiments is a two-dimensional accelerometer structure sensor. It consists of two identical uniaxial velocity sensors in orthogonal orientations, plus a pressure sensor—all in spatial collocation. These experimental results indicate that all these methods can effectively realize the azimuth angle estimation using only one AVS. The results presented in this paper reveal that AVS can be applied in a wider range of application in distributed underwater acoustic systems for passive detection, localization, classification, and so on.

  1. Remote Underwater Characterization System - Innovative Technology Summary Report

    International Nuclear Information System (INIS)

    Willis, Walter David

    1999-01-01

    Characterization and inspection of water-cooled and moderated nuclear reactors and fuel storage pools requires equipment capable of operating underwater. Similarly, the deactivation and decommissioning of older nuclear facilities often requires the facility owner to accurately characterize underwater structures and equipment which may have been sitting idle for years. The underwater characterization equipment is often required to operate at depths exceeding 20 ft (6.1 m) and in relatively confined or congested spaces. The typical baseline approach has been the use of radiation detectors and underwater cameras mounted on long poles, or stationary cameras with pan and tilt features mounted on the sides of the underwater facility. There is a perceived need for an inexpensive, more mobile method of performing close-up inspection and radiation measurements in confined spaces underwater. The Remote Underwater Characterization System (RUCS) is a small, remotely operated submersible vehicle intended to serve multiple purposes in underwater nuclear operations. It is based on the commercially-available ''Scallop'' vehicle, but has been modified by Department of Energy's Robotics Technology Development Program to add auto-depth control, and vehicle orientation and depth monitoring at the operator control panel. The RUCS is designed to provide visual and gamma radiation characterization, even in confined or limited access areas. It was demonstrated in August 1998 at Idaho National Engineering and environmental Laboratory (INEEL) as part of the INEEL Large Scale Demonstration and Deployment Project. During the demonstration it was compared in a ''head-to-head'' fashion with the baseline characterization technology. This paper summarizes the results of the demonstration and lessons learned; comparing and contrasting both technologies in the areas of cost, visual characterization, radiological characterization, and overall operations

  2. 3D photo mosaicing of Tagiri shallow vent field by an autonomous underwater vehicle (3rd report) - Mosaicing method based on navigation data and visual features -

    Science.gov (United States)

    Maki, Toshihiro; Ura, Tamaki; Singh, Hanumant; Sakamaki, Takashi

    Large-area seafloor imaging will bring significant benefits to various fields such as academics, resource survey, marine development, security, and search-and-rescue. The authors have proposed a navigation method of an autonomous underwater vehicle for seafloor imaging, and verified its performance through mapping tubeworm colonies with the area of 3,000 square meters using the AUV Tri-Dog 1 at Tagiri vent field, Kagoshima bay in Japan (Maki et al., 2008, 2009). This paper proposes a post-processing method to build a natural photo mosaic from a number of pictures taken by an underwater platform. The method firstly removes lens distortion, invariances of color and lighting from each image, and then ortho-rectification is performed based on camera pose and seafloor estimated by navigation data. The image alignment is based on both navigation data and visual characteristics, implemented as an expansion of the image based method (Pizarro et al., 2003). Using the two types of information realizes an image alignment that is consistent both globally and locally, as well as making the method applicable to data sets with little visual keys. The method was evaluated using a data set obtained by the AUV Tri-Dog 1 at the vent field in Sep. 2009. A seamless, uniformly illuminated photo mosaic covering the area of around 500 square meters was created from 391 pictures, which covers unique features of the field such as bacteria mats and tubeworm colonies.

  3. Transfer functions of laminar premixed flames subjected to forcing by acoustic waves, AC electric fields, and non-thermal plasma discharges

    KAUST Repository

    Lacoste, Deanna

    2016-06-23

    The responses of laminar methane-air flames to forcing by acoustic waves, AC electric fields, and nanosecond repetitively pulsed (NRP) glow discharges are reported here. The experimental setup consists of an axisymmetric burner with a nozzle made from a quartz tube. Three different flame geometries have been studied: conical, M-shaped and V-shaped flames. A central stainless steel rod is used as a cathode for the electric field and plasma excitations. The acoustic forcing is obtained with a loudspeaker located at the bottom part of the burner. For forcing by AC electric fields, a metallic grid is placed above the rod and connected to an AC power supply. Plasma forcing is obtained by applying high-voltage pulses of 10-ns duration applied at 10 kHz, between the rod and an annular stainless steel ring, placed at the outlet of the quartz tube. The chemiluminescence of CH is used to determine the heat release rate fluctuations. For forcing by acoustic waves and plasma, the geometry of the flame plays a key role in the response of the combustion, while the flame shape does not affect the response of the combustion to electric field forcing. The flame response to acoustic forcing of about 10% of the incoming flow is similar to those obtained in the literature. The flames are found to be responsive to an AC electric field across the whole range of frequencies studied. A forcing mechanism, based on the generation of ionic wind, is proposed. The gain of the transfer function obtained for plasma forcing is found to be up to 5 times higher than for acoustic forcing. A possible mechanism of plasma forcing is introduced.

  4. Transfer functions of laminar premixed flames subjected to forcing by acoustic waves, AC electric fields, and non-thermal plasma discharges

    KAUST Repository

    Lacoste, Deanna; Xiong, Yuan; Moeck, Jonas P.; Chung, Suk-Ho; Roberts, William L.; Cha, Min

    2016-01-01

    The responses of laminar methane-air flames to forcing by acoustic waves, AC electric fields, and nanosecond repetitively pulsed (NRP) glow discharges are reported here. The experimental setup consists of an axisymmetric burner with a nozzle made from a quartz tube. Three different flame geometries have been studied: conical, M-shaped and V-shaped flames. A central stainless steel rod is used as a cathode for the electric field and plasma excitations. The acoustic forcing is obtained with a loudspeaker located at the bottom part of the burner. For forcing by AC electric fields, a metallic grid is placed above the rod and connected to an AC power supply. Plasma forcing is obtained by applying high-voltage pulses of 10-ns duration applied at 10 kHz, between the rod and an annular stainless steel ring, placed at the outlet of the quartz tube. The chemiluminescence of CH is used to determine the heat release rate fluctuations. For forcing by acoustic waves and plasma, the geometry of the flame plays a key role in the response of the combustion, while the flame shape does not affect the response of the combustion to electric field forcing. The flame response to acoustic forcing of about 10% of the incoming flow is similar to those obtained in the literature. The flames are found to be responsive to an AC electric field across the whole range of frequencies studied. A forcing mechanism, based on the generation of ionic wind, is proposed. The gain of the transfer function obtained for plasma forcing is found to be up to 5 times higher than for acoustic forcing. A possible mechanism of plasma forcing is introduced.

  5. Underwater fiber-wireless communication with a passive front end

    Science.gov (United States)

    Xu, Jing; Sun, Bin; Lyu, Weichao; Kong, Meiwei; Sarwar, Rohail; Han, Jun; Zhang, Wei; Deng, Ning

    2017-11-01

    We propose and experimentally demonstrate a novel concept on underwater fiber-wireless (Fi-Wi) communication system with a fully passive wireless front end. A low-cost step-index (SI) plastic optical fiber (POF) together with a passive collimating lens at the front end composes the underwater Fi-Wi architecture. We have achieved a 1.71-Gb/s transmission at a mean BER of 4.97 × 10-3 (1.30 × 10-3 when using power loading) over a 50-m SI-POF and 2-m underwater wireless channel using orthogonal frequency division multiplexing (OFDM). Although the wireless part is very short, it actually plays a crucial role in practical underwater implementation, especially in deep sea. Compared with the wired solution (e.g. using a 52-m POF cable without the UWOC part), the proposed underwater Fi-Wi scheme can save optical wet-mate connectors that are sophisticated, very expensive and difficult to install in deep ocean. By combining high-capacity robust POF with the mobility and ubiquity of underwater wireless optical communication (UWOC), the proposed underwater Fi-Wi technology will find wide application in ocean exploration.

  6. Acquisition and tracking for underwater optical communications

    Science.gov (United States)

    Williams, Andrew J.; Laycock, Leslie L.; Griffith, Michael S.; McCarthy, Andrew G.; Rowe, Duncan P.

    2017-10-01

    There is a growing requirement to transfer large volumes of data between underwater platforms. As seawater is transmissive in the visible band, underwater optical communications is an active area of interest since it offers the potential for power efficient, covert and high bandwidth datalinks at short to medium ranges. Short range systems have been successfully demonstrated using sources with low directionality. To realise higher data rates and/or longer ranges, the use of more efficient directional beams is required; by necessity, these must be sufficiently aligned to achieve the required link margin. For mobile platforms, the acquisition and tracking of each node is therefore critical in order to establish and maintain an optical datalink. This paper describes work undertaken to demonstrate acquisition and tracking in a 3D underwater environment. A range of optical sources, beam steering technologies, and tracking sensors have been assessed for suitability. A novel scanning strategy exploiting variable beam divergence was developed to provide robust acquisition whilst minimising acquisition time. A prototype system was assembled and demonstrated in a large water tank. This utilised custom quadrant detectors based on Silicon PhotoMultiplier (SiPM) arrays for fine tracking, and a Wide Field of View (WFoV) sCMOS camera for link acquisition. Fluidic lenses provided dynamic control of beam divergence, and AC modulation/filtering enabled background rejection. The system successfully demonstrated robust optical acquisition and tracking between two nodes with only nanowatt received optical powers. The acquisition time was shown to be dependent on the initial conditions and the transmitted optical power.

  7. Pulsed TV holography measurement and digital reconstruction of compression acoustic wave fields: application to nondestructive testing of thick metallic samples

    International Nuclear Information System (INIS)

    Trillo, C; Doval, A F; Deán-Ben, X L; López-Vázquez, J C; Fernández, J L; Hernández-Montes, S

    2011-01-01

    This paper describes a technique that numerically reconstructs the complex acoustic amplitude (i.e. the acoustic amplitude and phase) of a compression acoustic wave in the interior volume of a specimen from a set of full-field optical measurements of the instantaneous displacement of the surface. The volume of a thick specimen is probed in transmission mode by short bursts of narrowband compression acoustic waves generated at one of its faces. The temporal evolution of the displacement field induced by the bursts emerging at the opposite surface is measured by pulsed digital holographic interferometry (pulsed TV holography). A spatio-temporal 3D Fourier transform processing of the measured data yields the complex acoustic amplitude at the plane of the surface as a sequence of 2D complex-valued maps. Finally, a numerical implementation of the Rayleigh–Sommerfeld diffraction formula is employed to reconstruct the complex acoustic amplitude at other planes in the interior volume of the specimen. The whole procedure can be regarded as a combination of optical digital holography and acoustical holography methods. The technique was successfully tested on aluminium specimens with and without an internal artificial defect and sample results are presented. In particular, information about the shape and position of the defect was retrieved in the experiment performed on the flawed specimen, which indicates the potential applicability of the technique for the nondestructive testing of materials

  8. Testing of an acoustic smolt deflection system, Blantyre hydroelectric power scheme

    International Nuclear Information System (INIS)

    1996-01-01

    The aim of this study was to test the effectiveness of an underwater acoustic barrier as a means of preventing the entry of salmon (Salmo salar) and sea trout (Salmo trutta) smolts and other fish into the water intake of a hydro-electric power (HEP) station. A secondary objective was to measure the injury rate of fish passed through the turbine, so that the risk to any fish that penetrated the acoustic barrier could also be determined. The test site, which was a 575kW Kaplan plant located at Blantyre on the R. Clyde, Lanarkshire, was selected as being representative of run-of-river sites currently being developed under the Government's NFFO (Non-Fossil Fuel Obligation) and SRO (Scottish Renewables Order) schemes. A further objective was to disseminate information arising from the project to the scientific and HEP community. (author)

  9. Probability-Based Recognition Framework for Underwater Landmarks Using Sonar Images †.

    Science.gov (United States)

    Lee, Yeongjun; Choi, Jinwoo; Ko, Nak Yong; Choi, Hyun-Taek

    2017-08-24

    This paper proposes a probability-based framework for recognizing underwater landmarks using sonar images. Current recognition methods use a single image, which does not provide reliable results because of weaknesses of the sonar image such as unstable acoustic source, many speckle noises, low resolution images, single channel image, and so on. However, using consecutive sonar images, if the status-i.e., the existence and identity (or name)-of an object is continuously evaluated by a stochastic method, the result of the recognition method is available for calculating the uncertainty, and it is more suitable for various applications. Our proposed framework consists of three steps: (1) candidate selection, (2) continuity evaluation, and (3) Bayesian feature estimation. Two probability methods-particle filtering and Bayesian feature estimation-are used to repeatedly estimate the continuity and feature of objects in consecutive images. Thus, the status of the object is repeatedly predicted and updated by a stochastic method. Furthermore, we develop an artificial landmark to increase detectability by an imaging sonar, which we apply to the characteristics of acoustic waves, such as instability and reflection depending on the roughness of the reflector surface. The proposed method is verified by conducting basin experiments, and the results are presented.

  10. A new, simple electrostatic-acoustic hybrid levitator

    Science.gov (United States)

    Lierke, E. G.; Loeb, H.; Gross, D.

    1990-01-01

    Battelle has developed a hybrid levitator by combining the known single-axis acoustic standing wave levitator with a coaxial DC electric field. The resulting Coulomb forces on the charged liquid or solid sample support its weight and, together with the acoustic force, center the sample. Liquid samples with volumes approximately less than 100 micro-liters are deployed from a syringe reservoir into the acoustic pressure node. The sample is charged using a miniature high voltage power supply (approximately less than 20 kV) connected to the syringe needle. As the electric field, generated by a second miniature power supply, is increased, the acoustic intensity is reduced. The combination of both fields allows stable levitation of samples larger than either single technique could position on the ground. Decreasing the acoustic intensity reduces acoustic convection and sample deformation. Neither the electrostatic nor the acoustic field requires sample position sensing or active control. The levitator, now used for static and dynamic fluid physics investigations on the ground, can be easily modified for space operations.

  11. Acoustic Emission Technology and Application

    International Nuclear Information System (INIS)

    Joo, Y. S.; Lim, S. H.; Eom, H. S.; Kim, J. H.; Jung, H. K.

    2003-10-01

    Acoustic emission is the elastic wave that is generated by the rapid release of energy from the localized sources within a material. After the observation of acoustic emission phenomenon in 1950, the research and further investigation had been performed. Acoustic emission examination becomes a rapidly matured nondestructive testing method with demonstrated capabilities for characterizing material behavior and for detecting the defect. It is of interest as a possible passive monitoring technique for detecting, locating and characterizing the defects in component and structure. Acoustic emission technology has recently strengthened the on-line monitoring application for the detection of incipient failures and the assurance of structural integrity. The field of acoustic emission testing is still growing vigorously and presents many challenges. Especially, acoustic emission has been successfully applied in the leak detection of primary pressure boundary of nuclear power plants. In this state-of-art report, the principle, measurement and field applications of acoustic emission technique is reviewed and summarized. Acoustic emission technology will contribute to the assurance of nuclear safety as the on-line monitoring technique of structural integrity of NSSS components and structures

  12. 3D Laser Scanner for Underwater Manipulation.

    Science.gov (United States)

    Palomer, Albert; Ridao, Pere; Youakim, Dina; Ribas, David; Forest, Josep; Petillot, Yvan

    2018-04-04

    Nowadays, research in autonomous underwater manipulation has demonstrated simple applications like picking an object from the sea floor, turning a valve or plugging and unplugging a connector. These are fairly simple tasks compared with those already demonstrated by the mobile robotics community, which include, among others, safe arm motion within areas populated with a priori unknown obstacles or the recognition and location of objects based on their 3D model to grasp them. Kinect-like 3D sensors have contributed significantly to the advance of mobile manipulation providing 3D sensing capabilities in real-time at low cost. Unfortunately, the underwater robotics community is lacking a 3D sensor with similar capabilities to provide rich 3D information of the work space. In this paper, we present a new underwater 3D laser scanner and demonstrate its capabilities for underwater manipulation. In order to use this sensor in conjunction with manipulators, a calibration method to find the relative position between the manipulator and the 3D laser scanner is presented. Then, two different advanced underwater manipulation tasks beyond the state of the art are demonstrated using two different manipulation systems. First, an eight Degrees of Freedom (DoF) fixed-base manipulator system is used to demonstrate arm motion within a work space populated with a priori unknown fixed obstacles. Next, an eight DoF free floating Underwater Vehicle-Manipulator System (UVMS) is used to autonomously grasp an object from the bottom of a water tank.

  13. Preliminary study of the effect of the turbulent flow field around complex surfaces on their acoustic characteristics

    Science.gov (United States)

    Olsen, W. A.; Boldman, D.

    1978-01-01

    Fairly extensive measurements have been conducted of the turbulent flow around various surfaces as a basis for a study of the acoustic characteristics involved. In the experiments the flow from a nozzle was directed upon various two-dimensional surface configurations such as the three-flap model. A turbulent flow field description is given and an estimate of the acoustic characteristics is provided. The developed equations are based upon fundamental theories for simple configurations having simple flows. Qualitative estimates are obtained regarding the radiation pattern and the velocity power law. The effect of geometry and turbulent flow distribution on the acoustic emission from simple configurations are discussed.

  14. Influence of Pulse Shaping Filters on PAPR Performance of Underwater 5G Communication System Technique: GFDM

    Directory of Open Access Journals (Sweden)

    Jinqiu Wu

    2017-01-01

    Full Text Available Generalized frequency division multiplexing (GFDM is a new candidate technique for the fifth generation (5G standard based on multibranch multicarrier filter bank. Unlike OFDM, it enables the frequency and time domain multiuser scheduling and can be implemented digitally. It is the generalization of traditional OFDM with several added advantages like the low PAPR (peak to average power ratio. In this paper, the influence of the pulse shaping filter on PAPR performance of the GFDM system is investigated and the comparison of PAPR in OFDM and GFDM is also demonstrated. The PAPR is restrained by selecting proper parameters and filters to make the underwater acoustic communication more efficient.

  15. Acoustic Shotgun System

    Science.gov (United States)

    2009-09-16

    dispersing a plurality of relatively small, supercavitating projectiles in the water over a wide spatial field at long ranges from an underwater gun...or surface gun. (2) Description of the Prior Art [0004] One major technical challenge related to employing supercavitating projectiles against...accordingly is more limited. [0005] A second problem common to supercavitating projectiles is the configuration of the projectile itself. The primary

  16. Underwater hearing in the great cormorant (Phalacrocorax carbo sinensis)

    DEFF Research Database (Denmark)

    Hansen, Kirstin Anderson; Larsen, Ole Næsbye; Wahlberg, Magnus

    2016-01-01

    The underwater hearing threshold of a great cormorant (Phalacrocroax carbo sinensis) was measured at 2 kHz using psychophysical methods. Previous in-air and underwater testing suggests that cormorants have rather poor in-air hearing compared to other birds of similar size (Johansen, 2016). Prelim......The underwater hearing threshold of a great cormorant (Phalacrocroax carbo sinensis) was measured at 2 kHz using psychophysical methods. Previous in-air and underwater testing suggests that cormorants have rather poor in-air hearing compared to other birds of similar size (Johansen, 2016...

  17. Numerical computation of underwater explosions due to fuel-coolant interactions

    International Nuclear Information System (INIS)

    Lee, J.H.S.; Frost, D.L.; Knystautas, R.; Teodorczyk, A.; Ciccarelli, G.; Thibault, P.; Penrose, J.

    1989-03-01

    If coarse molten material is released into a coolant the possibility exists for a violent steam explosion. A detailed quantitative description of the processes involved in steam explosions is currently beyond the capabilities of the scientific community. However, a conservative estimate of the pressure transients resulting from a steam explosion can be obtained by studying the dynamics of the shock associated with the expansion of a high-pressure vapour bubble. In this study, the hydrodynamic equations governing the shock propagation of an expanding bubble were integrated numerically using the Flux Corrected Transport code. Simpler acoustic models based on experience with underwater explosions were also developed and used to estimate pressure transients and to calculate the peak pressures for benchmark cases. The results were found to be an order of magnitude higher than the corresponding pressures obtained using a complex model developed by Henry. A simplified version of the Henry model was developed by neglecting the complex description of the two-phase flow inside the ruptured tube and the arbitrarily assumed heat transfer and condensation rates. Results from the simplified model were found to be generally similar to, but had higher peak pressures than those obtained using the Henry model. It is concluded that the results produced by simple acoustic models, or by a simplified Henry model, are more conservative than the corresponding results obtained with the original Henry model

  18. Effects of the partially movable control fin with end plate of underwater vehicle

    Directory of Open Access Journals (Sweden)

    Chul-Min Jung

    2017-01-01

    Full Text Available Underwater torpedo has control fin with very low aspect ratio due to launching from limited size of cylindrical torpedo tube. If the aspect ratio of control fin of underwater vehicle is very low three-dimensional flow around control fin largely reduces control forces. In this study, the end plate was applied to reduce the three-dimensional flow effects of partially movable control fin of underwater vehicle. Through numerical simulations the flow field around control fin was examined with and without end plate for different flap angles. The pressure, vorticity, lift and torque on the control fin were analyzed and compared to experiments. The comparison have shown a reasonable agreement between numerical and experimental results and the effect of end plate on a low aspect ratio control fin. When the end plate was attached to the movable control fin, the lift increased and the actuator shaft torque did not significantly change. As this means less consumption of the actuator shaft torque compared to the control fin that has the same control force, the inner actuator capacity can be reduced and energy consumption can be saved. Considering this, it is expected to be effectively applied to the control fin design of underwater vehicles such as torpedoes.

  19. Intelligent Navigation for a Solar Powered Unmanned Underwater Vehicle

    Directory of Open Access Journals (Sweden)

    Francisco García-Córdova

    2013-04-01

    Full Text Available In this paper, an intelligent navigation system for an unmanned underwater vehicle powered by renewable energy and designed for shadow water inspection in missions of a long duration is proposed. The system is composed of an underwater vehicle, which tows a surface vehicle. The surface vehicle is a small boat with photovoltaic panels, a methanol fuel cell and communication equipment, which provides energy and communication to the underwater vehicle. The underwater vehicle has sensors to monitor the underwater environment such as sidescan sonar and a video camera in a flexible configuration and sensors to measure the physical and chemical parameters of water quality on predefined paths for long distances. The underwater vehicle implements a biologically inspired neural architecture for autonomous intelligent navigation. Navigation is carried out by integrating a kinematic adaptive neuro-controller for trajectory tracking and an obstacle avoidance adaptive neuro- controller. The autonomous underwater vehicle is capable of operating during long periods of observation and monitoring. This autonomous vehicle is a good tool for observing large areas of sea, since it operates for long periods of time due to the contribution of renewable energy. It correlates all sensor data for time and geodetic position. This vehicle has been used for monitoring the Mar Menor lagoon.

  20. Multi-relaxation-time lattice Boltzmann modeling of the acoustic field generated by focused transducer

    Science.gov (United States)

    Shan, Feng; Guo, Xiasheng; Tu, Juan; Cheng, Jianchun; Zhang, Dong

    The high-intensity focused ultrasound (HIFU) has become an attractive therapeutic tool for the noninvasive tumor treatment. The ultrasonic transducer is the key component in HIFU treatment to generate the HIFU energy. The dimension of focal region generated by the transducer is closely relevant to the safety of HIFU treatment. Therefore, it is essential to numerically investigate the focal region of the transducer. Although the conventional acoustic wave equations have been used successfully to describe the acoustic field, there still exist some inherent drawbacks. In this work, we presented an axisymmetric isothermal multi-relaxation-time lattice Boltzmann method (MRT-LBM) model with the Bouzidi-Firdaouss-Lallemand (BFL) boundary condition in cylindrical coordinate system. With this model, some preliminary simulations were firstly conducted to determine a reasonable value of the relaxation parameter. Then, the validity of the model was examined by comparing the results obtained with the LBM results with the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation and the Spheroidal beam equation (SBE) for the focused transducers with different aperture angles, respectively. In addition, the influences of the aperture angle on the focal region were investigated. The proposed model in this work will provide significant references for the parameter optimization of the focused transducer for applications in the HIFU treatment or other fields, and provide new insights into the conventional acoustic numerical simulations.

  1. Nonstationary random acoustic and electromagnetic fields as wave diffusion processes

    International Nuclear Information System (INIS)

    Arnaut, L R

    2007-01-01

    We investigate the effects of relatively rapid variations of the boundaries of an overmoded cavity on the stochastic properties of its interior acoustic or electromagnetic field. For quasi-static variations, this field can be represented as an ideal incoherent and statistically homogeneous isotropic random scalar or vector field, respectively. A physical model is constructed showing that the field dynamics can be characterized as a generalized diffusion process. The Langevin-It o-hat and Fokker-Planck equations are derived and their associated statistics and distributions for the complex analytic field, its magnitude and energy density are computed. The energy diffusion parameter is found to be proportional to the square of the ratio of the standard deviation of the source field to the characteristic time constant of the dynamic process, but is independent of the initial energy density, to first order. The energy drift vanishes in the asymptotic limit. The time-energy probability distribution is in general not separable, as a result of nonstationarity. A general solution of the Fokker-Planck equation is obtained in integral form, together with explicit closed-form solutions for several asymptotic cases. The findings extend known results on statistics and distributions of quasi-stationary ideal random fields (pure diffusions), which are retrieved as special cases

  2. Mobile Sinks Assisted Geographic and Opportunistic Routing Based Interference Avoidance for Underwater Wireless Sensor Network.

    Science.gov (United States)

    Ahmed, Farwa; Wadud, Zahid; Javaid, Nadeem; Alrajeh, Nabil; Alabed, Mohamad Souheil; Qasim, Umar

    2018-04-02

    The distinctive features of acoustic communication channel-like high propagation delay, multi-path fading, quick attenuation of acoustic signal, etc. limit the utilization of underwater wireless sensor networks (UWSNs). The immutable selection of forwarder node leads to dramatic death of node resulting in imbalanced energy depletion and void hole creation. To reduce the probability of void occurrence and imbalance energy dissipation, in this paper, we propose mobility assisted geo-opportunistic routing paradigm based on interference avoidance for UWSNs. The network volume is divided into logical small cubes to reduce the interference and to make more informed routing decisions for efficient energy consumption. Additionally, an optimal number of forwarder nodes is elected from each cube based on its proximity with respect to the destination to avoid void occurrence. Moreover, the data packets are recovered from void regions with the help of mobile sinks which also reduce the data traffic on intermediate nodes. Extensive simulations are performed to verify that our proposed work maximizes the network lifetime and packet delivery ratio.

  3. Mobile Sinks Assisted Geographic and Opportunistic Routing Based Interference Avoidance for Underwater Wireless Sensor Network

    Directory of Open Access Journals (Sweden)

    Farwa Ahmed

    2018-04-01

    Full Text Available The distinctive features of acoustic communication channel-like high propagation delay, multi-path fading, quick attenuation of acoustic signal, etc. limit the utilization of underwater wireless sensor networks (UWSNs. The immutable selection of forwarder node leads to dramatic death of node resulting in imbalanced energy depletion and void hole creation. To reduce the probability of void occurrence and imbalance energy dissipation, in this paper, we propose mobility assisted geo-opportunistic routing paradigm based on interference avoidance for UWSNs. The network volume is divided into logical small cubes to reduce the interference and to make more informed routing decisions for efficient energy consumption. Additionally, an optimal number of forwarder nodes is elected from each cube based on its proximity with respect to the destination to avoid void occurrence. Moreover, the data packets are recovered from void regions with the help of mobile sinks which also reduce the data traffic on intermediate nodes. Extensive simulations are performed to verify that our proposed work maximizes the network lifetime and packet delivery ratio.

  4. Underwater passive acoustic localization of Pacific walruses in the northeastern Chukchi Sea.

    Science.gov (United States)

    Rideout, Brendan P; Dosso, Stan E; Hannay, David E

    2013-09-01

    This paper develops and applies a linearized Bayesian localization algorithm based on acoustic arrival times of marine mammal vocalizations at spatially-separated receivers which provides three-dimensional (3D) location estimates with rigorous uncertainty analysis. To properly account for uncertainty in receiver parameters (3D hydrophone locations and synchronization times) and environmental parameters (water depth and sound-speed correction), these quantities are treated as unknowns constrained by prior estimates and prior uncertainties. Unknown scaling factors on both the prior and arrival-time uncertainties are estimated by minimizing Akaike's Bayesian information criterion (a maximum entropy condition). Maximum a posteriori estimates for sound source locations and times, receiver parameters, and environmental parameters are calculated simultaneously using measurements of arrival times for direct and interface-reflected acoustic paths. Posterior uncertainties for all unknowns incorporate both arrival time and prior uncertainties. Monte Carlo simulation results demonstrate that, for the cases considered here, linearization errors are small and the lack of an accurate sound-speed profile does not cause significant biases in the estimated locations. A sequence of Pacific walrus vocalizations, recorded in the Chukchi Sea northwest of Alaska, is localized using this technique, yielding a track estimate and uncertainties with an estimated speed comparable to normal walrus swim speeds.

  5. Imaging of microwave-induced acoustic fields in LiNbO{sub 3} by high-performance Brillouin microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Vincent, B [Lab. Europeen de Recherche Univ.: Saarland-Lorraine, Univ. des Saarlandes, D-66041 Saarbruecken (Germany)]|[Lab. de Physique des Milieux Ionises et Applications, CNRS-UMR 7040, Univ. H. Poincare, Nancy I, F-54506 (France); Krueger, J K [Lab. Europeen de Recherche Univ.: Saarland-Lorraine, Univ. des Saarlandes, D-66041 Saarbruecken (Germany)]|[Fachrichtung 7.2, Experimentalphysik, Univ. des Saarlandes, Bau 38, D-66041 Saarbruecken (Germany); Elmazria, O [Laboratoire Europeen de Recherche Universitaire: Saarland-Lorraine, Universitaet des Saarlandes, D-66041 Saarbruecken (Germany)]|[Laboratoire de Physique des Milieux Ionises et Applications, CNRS-UMR 7040, Universite H. Poincare, Nancy I, F-54506 (France); Bouvot, L [Laboratoire Europeen de Recherche Universitaire: Saarland-Lorraine, Universitaet des Saarlandes, D-66041 Saarbruecken (Germany)]|[Laboratoire de Physique des Milieux Ionises et Applications, CNRS-UMR 7040, Universite H. Poincare, Nancy I, F-54506 (France); Mainka, J [Laboratoire Europeen de Recherche Universitaire: Saarland-Lorraine, Universitaet des Saarlandes, D-66041 Saarbruecken (Germany)]|[Fachrichtung 7.2, Experimentalphysik, Universitaet des Saarlandes, Bau 38, D-66041 Saarbruecken (Germany); Sanctuary, R [Laboratoire Europeen de Recherche Universitaire: Saarland-Lorraine, Universitaet des Saarlandes, D-66041 Saarbruecken (Germany)]|[Laboratoire de Physique des Materiaux, Campus Luxembourg-Limpertsberg, L-1511 Luxembourg (Luxembourg); Rouxel, D [Lab. Europeen de Recherche Univ.: Saarland-Lorraine, Univ. des Saarlandes, D-66041 Saarbruecken (Germany)]|[Lab. de Physique des Milieux Ionises et Applications, CNRS-UMR 7040, Univ. H. Poincare, Nancy I, F-54506 (France); Alnot, P [Lab. Europeen de Recherche Univ.: Saarland-Lorraine, Univ. des Saarlandes, D-66041 Saarbruecken (Germany)]|[Lab. de Physique des Milieux Ionises et Applications, CNRS-UMR 7040, Univ. H. Poincare, Nancy I, F-54506 (France)

    2005-06-21

    High performance Brillouin microscopy (BM) has been used to characterize the spatial distribution of piezoelectrically induced acoustic fields excited at microwave frequencies in a LiNbO{sub 3} single crystal. It is demonstrated that under suitable conditions BM is able to detect microwave-induced bulk as well as surface acoustic waves. Brillouin spectroscopy is able to probe sound wave intensities of induced phonons, which are as small as those of thermal phonons.

  6. Does Attention Play a Role in Dynamic Receptive Field Adaptation to Changing Acoustic Salience in A1?

    OpenAIRE

    Fritz, Jonathan; Elhilali, Mounya; David, Stephen; Shamma, Shihab

    2007-01-01

    Acoustic filter properties of A1 neurons can dynamically adapt to stimulus statistics, classical conditioning, instrumental learning and the changing auditory attentional focus. We have recently developed an experimental paradigm that allows us to view cortical receptive field plasticity on-line as the animal meets different behavioral challenges by attending to salient acoustic cues and changing its cortical filters to enhance performance. We propose that attention is the key trigger that in...

  7. Acoustic characteristics of sand sediment with circular cylindrical pores

    International Nuclear Information System (INIS)

    Roh, Heui-Seol; Lee, Kang-Il; Yoon, Suk-Wang

    2004-01-01

    The acoustic pressure transmission coefficient and the phase velocity are experimentally measured as functions of the frequency and the porosity in sand sediment slabs with circular cylindrical pores filled with water and air. They are also theoretically estimated with the modified Biot-Attenborough (MBA) model, which uses a separate treatment of the viscous and the thermal effects in a non-rigid porous medium with water- and air-filled cylindrical pores. In this study, the fast (first kind) wave and the slow (second kind) wave are not separated in the transmitted signals through a sediment slab without the circular cylindrical pores, but they are separated in the transmitted signals through a sediment slab with pores. Both the phase velocities and the transmission coefficients of the fast wave and the slow wave in the sediment slabs with water- and air-filled cylindrical pores are sensitive to the air and the water porosities. It is proposed that the fast and the slow waves have opposite behaviors for several acoustic characteristics. The generalized tortuosity factor and the dynamic shape factor are introduced from the acoustic characteristics of the fast wave. The experimental results show reasonable agreement with the theoretical results estimated with the MBA model. These results suggest the possibility of predicting the acoustic characteristics of a sediment as functions of arbitrary water and air porosities. This study may also be applicable to understanding acoustic wave propagations in a bubbly liquid sediment for underwater applications and in cancellous bone for the diagnosis of osteoporosis.

  8. Underwater television camera for monitoring inner side of pressure vessel

    International Nuclear Information System (INIS)

    Takayama, Kazuhiko.

    1997-01-01

    An underwater television support device equipped with a rotatable and vertically movable underwater television camera and an underwater television camera controlling device for monitoring images of the inside of the reactor core photographed by the underwater television camera to control the position of the underwater television camera and the underwater light are disposed on an upper lattice plate of a reactor pressure vessel. Both of them are electrically connected with each other by way of a cable to rapidly observe the inside of the reactor core by the underwater television camera. The reproducibility is extremely satisfactory by efficiently concentrating the position of the camera and image information upon inspection and observation. As a result, the steps for periodical inspection can be reduced to shorten the days for the periodical inspection. Since there is no requirement to withdraw fuel assemblies over a wide reactor core region, and the device can be used with the fuel assemblies being left as they are in the reactor, it is suitable for inspection of detectors for nuclear instrumentation. (N.H.)

  9. 3D Laser Scanner for Underwater Manipulation

    Directory of Open Access Journals (Sweden)

    Albert Palomer

    2018-04-01

    Full Text Available Nowadays, research in autonomous underwater manipulation has demonstrated simple applications like picking an object from the sea floor, turning a valve or plugging and unplugging a connector. These are fairly simple tasks compared with those already demonstrated by the mobile robotics community, which include, among others, safe arm motion within areas populated with a priori unknown obstacles or the recognition and location of objects based on their 3D model to grasp them. Kinect-like 3D sensors have contributed significantly to the advance of mobile manipulation providing 3D sensing capabilities in real-time at low cost. Unfortunately, the underwater robotics community is lacking a 3D sensor with similar capabilities to provide rich 3D information of the work space. In this paper, we present a new underwater 3D laser scanner and demonstrate its capabilities for underwater manipulation. In order to use this sensor in conjunction with manipulators, a calibration method to find the relative position between the manipulator and the 3D laser scanner is presented. Then, two different advanced underwater manipulation tasks beyond the state of the art are demonstrated using two different manipulation systems. First, an eight Degrees of Freedom (DoF fixed-base manipulator system is used to demonstrate arm motion within a work space populated with a priori unknown fixed obstacles. Next, an eight DoF free floating Underwater Vehicle-Manipulator System (UVMS is used to autonomously grasp an object from the bottom of a water tank.

  10. Autonomous Underwater Navigation and Optical Mapping in Unknown Natural Environments

    Directory of Open Access Journals (Sweden)

    Juan David Hernández

    2016-07-01

    Full Text Available We present an approach for navigating in unknown environments while, simultaneously, gathering information for inspecting underwater structures using an autonomous underwater vehicle (AUV. To accomplish this, we first use our pipeline for mapping and planning collision-free paths online, which endows an AUV with the capability to autonomously acquire optical data in close proximity. With that information, we then propose a reconstruction pipeline to create a photo-realistic textured 3D model of the inspected area. These 3D models are also of particular interest to other fields of study in marine sciences, since they can serve as base maps for environmental monitoring, thus allowing change detection of biological communities and their environment over time. Finally, we evaluate our approach using the Sparus II, a torpedo-shaped AUV, conducting inspection missions in a challenging, real-world and natural scenario.

  11. Marine mammal tracks from two-hydrophone acoustic recordings made with a glider

    Science.gov (United States)

    Küsel, Elizabeth T.; Munoz, Tessa; Siderius, Martin; Mellinger, David K.; Heimlich, Sara

    2017-04-01

    A multinational oceanographic and acoustic sea experiment was carried out in the summer of 2014 off the western coast of the island of Sardinia, Mediterranean Sea. During this experiment, an underwater glider fitted with two hydrophones was evaluated as a potential tool for marine mammal population density estimation studies. An acoustic recording system was also tested, comprising an inexpensive, off-the-shelf digital recorder installed inside the glider. Detection and classification of sounds produced by whales and dolphins, and sometimes tracking and localization, are inherent components of population density estimation from passive acoustics recordings. In this work we discuss the equipment used as well as analysis of the data obtained, including detection and estimation of bearing angles. A human analyst identified the presence of sperm whale (Physeter macrocephalus) regular clicks as well as dolphin clicks and whistles. Cross-correlating clicks recorded on both data channels allowed for the estimation of the direction (bearing) of clicks, and realization of animal tracks. Insights from this bearing tracking analysis can aid in population density estimation studies by providing further information (bearings), which can improve estimates.

  12. Waveform-preserved unidirectional acoustic transmission based on impedance-matched acoustic metasurface and phononic crystal

    Science.gov (United States)

    Song, Ai-Ling; Chen, Tian-Ning; Wang, Xiao-Peng; Wan, Le-Le

    2016-08-01

    The waveform distortion happens in most of the unidirectional acoustic transmission (UAT) devices proposed before. In this paper, a novel type of waveform-preserved UAT device composed of an impedance-matched acoustic metasurface (AMS) and a phononic crystal (PC) structure is proposed and numerically investigated. The acoustic pressure field distributions and transmittance are calculated by using the finite element method. The subwavelength AMS that can modulate the wavefront of the transmitted wave at will is designed and the band structure of the PC structure is calculated and analyzed. The sound pressure field distributions demonstrate that the unidirectional acoustic transmission can be realized by the proposed UAT device without changing the waveforms of the output waves, which is the distinctive feature compared with the previous UAT devices. The physical mechanism of the unidirectional acoustic transmission is discussed by analyzing the refraction angle changes and partial band gap map. The calculated transmission spectra show that the UAT device is valid within a relatively broad frequency range. The simulation results agree well with the theoretical predictions. The proposed UAT device provides a good reference for designing waveform-preserved UAT devices and has potential applications in many fields, such as medical ultrasound, acoustic rectifiers, and noise insulation.

  13. Acoustical and optical radiation pressure and the development of single beam acoustical tweezers

    International Nuclear Information System (INIS)

    Thomas, Jean-Louis; Marchiano, Régis; Baresch, Diego

    2017-01-01

    Studies on radiation pressure in acoustics and optics have enriched one another and have a long common history. Acoustic radiation pressure is used for metrology, levitation, particle trapping and actuation. However, the dexterity and selectivity of single-beam optical tweezers are still to be matched with acoustical devices. Optical tweezers can trap, move and position micron size particles, biological samples or even atoms with subnanometer accuracy in three dimensions. One limitation of optical tweezers is the weak force that can be applied without thermal damage due to optical absorption. Acoustical tweezers overcome this limitation since the radiation pressure scales as the field intensity divided by the speed of propagation of the wave. However, the feasibility of single beam acoustical tweezers was demonstrated only recently. In this paper, we propose a historical review of the strong similarities but also the specificities of acoustical and optical radiation pressures, from the expression of the force to the development of single-beam acoustical tweezers. - Highlights: • Studies on radiation pressure in acoustics and optics have enriched one another and have a long common history. • Acoustic radiation pressure is used for metrology, levitation, particle trapping and actuation. • However, the dexterity and selectivity of single-beam optical tweezers are still to be matched with acoustical devices. • Optical tweezers can trap, move and positioned micron size particles with subnanometer accuracy in three dimensions. • One limitation of optical tweezers is the weak force that can be applied without thermal damage due to optical absorption. • Acoustical tweezers overcome this limitation since the force scales as the field intensity divided by its propagation speed. • However, the feasibility of single beam acoustical tweezers was demonstrated only recently. • We propose a review of the strong similarities but also the specificities of acoustical

  14. Centralised versus Decentralised Control Reconfiguration for Collaborating Underwater Robots

    DEFF Research Database (Denmark)

    Furno, Lidia; Nielsen, Mikkel Cornelius; Blanke, Mogens

    2015-01-01

    The present paper introduces an approach to fault-tolerant reconfiguration for collaborating underwater robots. Fault-tolerant reconfiguration is obtained using the virtual actuator approach, Steen (2005). The paper investigates properties of a centralised versus a decentralised implementation an...... an underwater drill needs to be transported and positioned by three collaborating robots as part of an underwater autonomous operation....

  15. Equipment and appliances for underwater operations. Pt. 2

    International Nuclear Information System (INIS)

    Krueger, P.

    1976-01-01

    The 6/75 edition of 'mt' reported on the 'ARGE underwater appliances' and the study on 'design development of appliances and equipment for underwater use' in a brief summary. One of these designs, the 'unmanned DSWS underwater appliance' was described in detail. The present article describes three further design developments mentioned in the above study and which are based on unmanned appliances connected to the mother-ship. These designs were developed by Preussag-Meerestechnik. (orig.) [de

  16. Surveying the Underwater Arcaheological Site of Cape Glaros at Pagasetikos Gulf

    Science.gov (United States)

    Diamanti, E.; Spondylis, E.; Vlachaki, F.; Kolyva, E.

    2017-02-01

    The Hellenic Institute of Marine Archaeology (H.I.M.A.)1 has been conducting an underwater archaeological research in the west coast of southern Pagasetikos Gulf, since 2000. Every year the underwater research focuses on specific archaeological targets that have been recovered during previous field campaigns. The current publication elaborates on the comprehensive documentation of the underwater archaeological site at Cape Glaros, during the 2015 field season, under the direction of the archaeologist Elias Spondylis. The 2015 research campaign was conducted within the framework of the ITACA- Innovation Technologies and Applications for Coastal Archaeological sites European Project (FP7/2007-2013, GA No 606805), at two archaeological sites, namely the Cape Glaros and Metohi. It was among the most important challenges of the project to successfully produce the detailed and accurate 3D mapping of the Cape Glaros site that covers an extended area. Four large concentrations of pottery finds and numerous anchors of different typology have been recorded, that can be dated from the late Hellenistic to the Byzantine periods. This challenge was tackled through the simultaneous implementation of three recording methods; photogrammetry, geodesy and conventional architectural mapping. The workflow of the documentation process, including data acquisition, processing and graphic visualization, along with the derived results are presented below. 1The Hellenic Institute of Marine Archaeology (H.I.M.A.) is a private, non-profit organization, founded in 1973, which undertakes maritime archaeological research under the supervision or in collaboration with the Greek Ministry of Culture. It has over 100 members, with diverse academic credentials, all of whom work, mainly, on a voluntary basis. 3D recording of underwater archaeological sites has been applied to numerous projects that have been carried out by the multidisciplinary team of H.I.M.A. in locations of utmost archaeological

  17. Magnetoactive Acoustic Metamaterials.

    Science.gov (United States)

    Yu, Kunhao; Fang, Nicholas X; Huang, Guoliang; Wang, Qiming

    2018-04-11

    Acoustic metamaterials with negative constitutive parameters (modulus and/or mass density) have shown great potential in diverse applications ranging from sonic cloaking, abnormal refraction and superlensing, to noise canceling. In conventional acoustic metamaterials, the negative constitutive parameters are engineered via tailored structures with fixed geometries; therefore, the relationships between constitutive parameters and acoustic frequencies are typically fixed to form a 2D phase space once the structures are fabricated. Here, by means of a model system of magnetoactive lattice structures, stimuli-responsive acoustic metamaterials are demonstrated to be able to extend the 2D phase space to 3D through rapidly and repeatedly switching signs of constitutive parameters with remote magnetic fields. It is shown for the first time that effective modulus can be reversibly switched between positive and negative within controlled frequency regimes through lattice buckling modulated by theoretically predicted magnetic fields. The magnetically triggered negative-modulus and cavity-induced negative density are integrated to achieve flexible switching between single-negative and double-negative. This strategy opens promising avenues for remote, rapid, and reversible modulation of acoustic transportation, refraction, imaging, and focusing in subwavelength regimes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Underwater cladding with laser beam and plasma arc welding

    International Nuclear Information System (INIS)

    White, R.A.; Fusaro, R.; Jones, M.G.; Solomon, H.D.; Milian-Rodriguez, R.R.

    1997-01-01

    Two welding processes, plasma arc (transferred arc) (PTA) and laser beam, were investigated to apply cladding to austenitic stainless steels and Inconel 600. These processes have long been used to apply cladding layers , but the novel feature being reported here is that these cladding layers were applied underwater, with a water pressure equivalent to 24 m (80 ft). Being able to apply the cladding underwater is very important for many applications, including the construction of off-shore oil platforms and the repair of nuclear reactors. In the latter case, being able to weld underwater eliminates the need for draining the reactor and removing the fuel. Welding underwater in reactors presents numerous challenges, but the ability to weld without having to drain the reactor and remove the fuel provides a huge cost savings. Welding underwater in reactors must be done remotely, but because of the radioactive corrosion products and neutron activation of the steels, remote welding would also be required even if the reactor is drained and the fuel removed. In fact, without the shielding of the water, the remote welding required if the reactor is drained might be even more difficult than that required with underwater welds. Furthermore, as shall be shown, the underwater welds that the authors have made were of high quality and exhibit compressive rather than tensile residual stresses

  19. Underwater image mosaicking and visual odometry

    Science.gov (United States)

    Sadjadi, Firooz; Tangirala, Sekhar; Sorber, Scott

    2017-05-01

    This paper summarizes the results of studies in underwater odometery using a video camera for estimating the velocity of an unmanned underwater vehicle (UUV). Underwater vehicles are usually equipped with sonar and Inertial Measurement Unit (IMU) - an integrated sensor package that combines multiple accelerometers and gyros to produce a three dimensional measurement of both specific force and angular rate with respect to an inertial reference frame for navigation. In this study, we investigate the use of odometry information obtainable from a video camera mounted on a UUV to extract vehicle velocity relative to the ocean floor. A key challenge with this process is the seemingly bland (i.e. featureless) nature of video data obtained underwater which could make conventional approaches to image-based motion estimation difficult. To address this problem, we perform image enhancement, followed by frame to frame image transformation, registration and mosaicking/stitching. With this approach the velocity components associated with the moving sensor (vehicle) are readily obtained from (i) the components of the transform matrix at each frame; (ii) information about the height of the vehicle above the seabed; and (iii) the sensor resolution. Preliminary results are presented.

  20. Underwater Gliders: A Review

    Directory of Open Access Journals (Sweden)

    Javaid Muhammad Yasar

    2014-07-01

    Full Text Available Underwater gliders are a type of underwater vehicle that transverse the oceans by shifting its buoyancy, during which its wings develop a component of the downward motion in the horizontal plane, thus producing a forward force. They are primarily used in oceanography sensing and data collection and play an important role in ocean research and development. Although there have been considerable developments in these gliders since the development of the first glider concept in 1989, to date, no review of these gliders have been done. This paper reviews existing underwater gliders, with emphasis on their respective working principles, range and payload capacity. All information on gliders available in the public domain or published in literature from the year 2000-2013 was reviewed. The majority of these gliders have an operational depth of 1000 m and a payload of less than 25 kg. The exception is a blend-body shape glider, which has a payload of approximately 800 kg and an operational depth around about 300 m. However, the commercialization of these gliders has been limited with only three know examples that have been successfully commercialized.