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1
Hu, Di. "Fully Distributed Multi-parameter Sensors Based on Acoustic Fiber Bragg Gratings." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/85112.
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A fully distributed multi-parameter acoustic sensing technology is proposed. Current fully distributed sensing techniques are exclusively based on intrinsic scatterings in optical fibers. They demonstrate long sensing span, but their limited applicable parameters (temperature and strain) and costly interrogation systems have prevented their widespread applications.
A novel concept of acoustic fiber Bragg grating (AFBG) is conceived with inspiration from optical fiber Bragg grating (FBG). This AFBG structure exploits periodic spatial perturbations on an elongated waveguide to sense variations in the spectrum of an acoustic wave. It achieves ten times higher sensitivity than the traditional time-of-flight measurement system using acoustic pulses. A fast interrogation method is developed to avoid frequency scan, reducing both the system response time (from 3min to <1ms) and total cost.
Since acoustic wave propagates with low attenuation along varieties of solid materials (metal, silica, sapphire, etc.), AFBG can be fabricated on a number of waveguides and to sense multiple parameters. Sub-millimeter metal wire and optical fiber based AFBGs have been demonstrated experimentally for effective temperature (25~700 degC) and corrosion sensing. A hollow borosilicate tube is demonstrated for simultaneous temperature (25~200 degC) and pressure (15~75 psi) sensing using two types of acoustic modes. Furthermore, a continuous 0.6 m AFBG is employed for distributed temperature sensing up to 500 degC and to accurately locate the 0.18 m long heated section.
Sensing parameters, sensitivity and range of an AFBG can be tuned to fit a specific application by selecting acoustic waveguides with different materials and/or geometries. Therefore, AFBG is a fully distributed sensing technology with tremendous potentiality.Ph. D.
2
dos, Santos Maia Correa Julia. "Distributed Acoustic Sensing for Seismic Imaging and Reservoir Monitoring Applied to CO2 Geosequestration." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/75668.
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The thesis is focused on the evaluation of distributed acoustic sensing (DAS) technique applied to seismic imaging and monitoring of CO2 geosequestration. It utilises the data acquired at the CO2CRC Otway site (Victoria) and the National Geosequestration Laboratory (Western Australia) to explore capabilities of the sensing technique, optimise data acquisition and processing, and compare it to other seismic sensors. Surface and downhole acquisition geometries and a range of fibre optic cables and deployment techniques were considered.
3
Marcon, Leonardo. "Development of high performance distributed acoustic sensors based on Rayleigh backscattering." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3423194.
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Distributed optical fiber sensing is a thriving research field that is finding practical applications in a variety of different fields including processes at extreme temperatures, security and civil engineering. The monitoring of dynamic perturbations, usually defined in the literature as distributed acoustic sensing (DAS), can be realized with excellent performance exploiting Rayleigh backscattering both in time and frequency domain. Devices implementing Rayleigh-based DAS are already commercially available.
In this thesis the results of my three-year research are presented, reporting the development of high performance distributed acoustic sensors based on Rayleigh backscattering, and their applications. The research has focused on improving the spatial resolution of the chirped-pulse phase-sensitive optical time-domain reflectometer and on developing a novel algorithm to realize real distributed acoustic sensing with high spatial resolution and high acoustic bandwidth for the optical frequency-domain reflectometer (OFDR). Finally the early results of a measurement campaign performed in collaboration with the European Organization for Nuclear Research (CERN), where distributed optical fiber sensors were used to monitor superconducting lines and magnets, are presented and discussed.
4
Ciervo, Christopher M. "Establishing Hydraulic Connectivity in Bedrock by Measuring the Hydromechanical Response of Fractures with Distributed Acoustic Sensing (DAS)." Thesis, California State University, Long Beach, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10840951.
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Fiber optic Distributed Acoustic Sensing (DAS) is based on the principles of Coherent Rayleigh Optical Time Domain Reflectometry, where light pulses are fired through an optical fiber, and photon backscatter is measured with an optical sensor. Strain in the fiber causes changes in the amplitude and phase of backscattered light. Using light’s two-way travel time, the optical sensor measures strain at distributed points along the length of fiber. In this work, DAS was adapted to establish hydraulic connectivity in bedrock by measuring hydromechanical strain in an observation well, as periodic well tests were conducted at mHz frequencies at an interrogation well ~30 m away. A lognormal relationship with a strong degree of interdependence was found between measured displacements and pressure amplitudes. This behavior is consistent with the semi-logarithmic closure law of fractured rock. The nanometer scale displacements reported here, however, suggest closure occurring as in-contact asperities deform, rather than opposing fracture surfaces coming into contact.
5
Wild, Graham. "Distributed optical fibre smart sensors for acoustic sensing in the structural health monitoring of robust aerospace vehicles." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2010. https://ro.ecu.edu.au/theses/1873.
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The use of distributed optical fibre smart sensors for the detection of acoustic signals in the Structural Health Monitoring (SHM) of robust aerospace vehicles has been demonstrated. Current distributed optical fibre sensors are multiplexed along a single fibre. Inherent problems exist with a multiplexed architecture. Two significant issues are; the possibility of fibre breakage, and the possibility of failure of the single transmitter, the single receiver, or the single processor. In a ‘smart’ architecture, the intelligence, as well as the sensors, is distributed. Hence, if destructive damage occurs, then the SHM system can continue to operate in all other locations on the vehicle, making the system robust.
Work on the optical fibre sensors was limited to acoustic signals. This included acoustic emissions, acousto-ultrasonics, acoustic transmissions and other dynamic strain signals. Fibre Bragg Gratings (FBGs) were chosen as the optical fibre sensor for the detection of the acoustic signals. FBGs offer significant advantages over other types of optical fibre sensors. The most significant of these is the ease of multiplexing and their versatility, i.e. the ability of FBGs to detect a significant number of measurands. In the work on optical fibre sensing, we showed the implementation of an innovative detection system. This Transmit Reflect Detection System (TRDS) made use of both the transmitted and reflected signals from the FBG. The TRDS is an improvement on conventional power detection where either the transmitted or reflected component is used. The TRDS was used to successfully detect all types of dynamic and static signals, the most significant being the acoustic emission from a lead pencil break test.
The use of the FBG sensor as a receiver for acoustic communications was also shown. Acoustic communications have been proposed for use in the SHM of robust aerospace vehicles with the use of autonomous agents, e.g. inspection or repair robots. The FBG receivers were compared with PZT receivers. When communicating through aluminium, the FBG performance was not as good as the PZT receiver, specifically due to the properties of the FBG which limit the frequency response. However, in Carbon Fibre Composites (CFC), the FBG outperformed the PZT due to the properties of the CFC. We also note that when contained within the thermal packaging the FBG had a very interesting frequency response, likely due to the suspended beam nature of the structure. This type of packaging could be used to tune the response of the FBG sensor.
The work on the distributed optical fibre smart sensors showed the implementation of a Smart Transducer Interface Module (STIM), which used the TRDS with a Digital Signal Processor (DSP). The output of the TRDS was differentially amplified with a high speed amplifier, and the output was passed to the ADC onboard the DSP. The DSP was also used to toggle on and off output, including closed loop actuation, and controlling a 1550nm laser, which would represent the source used in the implemented system. The use of STIM to form a distributed optical fibre sensor network was also shown in principle.
6
Wang, Yunjing. "Fiber-Optic Sensors for Fully-Distributed Physical, Chemical and Biological Measurement." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19222.
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Distributed sensing is highly desirable in a wide range of civil, industrial and military applications. The current technologies for distributed sensing are mainly based on the detection of optical signals resulted from different elastic or non-elastic light-matter interactions including Rayleigh, Raman and Brillouin scattering. However, they can measure temperature or strain only to date. Therefore, there is a need for technologies that can further expand measurement parameters even to chemical and biological stimuli to fulfill different application needs. This dissertation presents a fully-distributed fiber-optic sensing technique based on a traveling long-period grating (T-LPG) in a single-mode fiber. The T-LPG is generated by pulsed acoustic waves that propagate along the fiber. When there are changes in the fiber surrounding medium or in the fiber surface coating, induced by various physical, chemical or biological stimuli, the optical transmission spectrum of the T-LPG may shift. Therefore, by measuring the T-LPG resonance wavelength at different locations along the fiber, distributed measurement can be realized for a number of parameters beyond temperature and strain.
Based on this platform, fully-distributed temperature measurement in a 2.5m fiber was demonstrated. Then by coating the fiber with functional coatings, fully-distributed biological and chemical sensing was also demonstrated. In the biological sensing experiment, immunoglobulin G (IgG) was immobilized onto the fiber surface, and the experimental results show that only specific antigen-antibody binding can introduce a measurable shift in the transmission optical spectrum of the T-LPG when it passes through the pretreated fiber segment. In the hydrogen sensing experiment, the fiber was coated with a platinum (Pt) catalyst layer, which is heated by the thermal energy released from Pt-assisted combustion of H2 and O2, and the resulted temperature change gives rise to a measurable T-LPG wavelength shift when the T-LPG passes through. Hydrogen concentration from 1% to 3.8% was detected in the experiment. This technique may also permit measurement of other quantities by changing the functional coating on the fiber; therefore it is expected to be capable of other fully-distributed sensing applications.
Ph. D.
7
Schilke, Sven. "Importance du couplage des capteurs distribués à fibre optique dans le cadre des VSP." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM042/document.
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Les capteurs distribués à fibre optique (aussi nommés DAS) sont une nouvelle technologie d'acquisition sismique qui utilise des câbles traditionnels à fibre optique pour fournir une mesure de la déformation le long du câble. Ce système d'acquisition est largement utilisé dans les profils sismiques verticaux (PSV). Le couplage est un facteur clé qui a une grande influence sur la qualité des données. Alors que, pour les acquisitions PSV, les géophones sont attachés à la paroi du puits, le câble de fibre optique est soit cimenté derrière le tubage, soit attaché avec des pinces rigides au tubage ou simplement descendu dans le puits. Cette dernière stratégie de déploiement donne généralement le plus petit rapport signal sur bruit, mais est considérée comme la plus rentable en particulier pour les installations dans des puits existants. Cette thèse porte sur la problématique du couplage du DAS quand le câble est simplement descendu dans le puits. Nous développons des modèles numériques pour analyser les données réelles. L'interprétation de ces résultats nous permet de conclure qu'un contact immédiat du câble avec la paroi du puits avec une force de contact calculée est nécessaire pour fournir des bonnes conditions de couplage. Sur la base de ces résultats, nous proposons des solutions pour optimiser davantage les acquisitions avec le système DAS. Nous modifions numériquement la force de contact et les propriétés élastiques du câble DAS et démontrons comment ces modifications peuvent améliorer mais aussi détériorer la qualité des données. Enfin, nous proposons un algorithme de détection du couplage qui permet d'assurer l'acquisition de données réelles avec un rapport signal / bruit élevéDistributed Acoustic Sensing (DAS) is a new technology of seismic acquisition that relies on traditional fibre-optic cables to provide inline strain measurement. This acquisition system is largely used in vertical seismic profiling (VSP) surveys. Coupling is a key factor influencing data quality. While geophones and accelerometers are clamped to the borehole wall during VSP surveys, the fibre cable is either clamped and then cemented behind the casing, or attached with rigid clamps to the tubing, or loosely lowered into the borehole. The latter deployment strategy, also called wireline deployment, usually acquires the lowest level of signal but is regarded as the most cost-effective in particular for existing well installations. This PhD thesis addresses the problematic of coupling of DAS using wireline deployment. We develop numerical models that are used to analyse real data. The interpretation of these results allows us concluding that an immediate contact of the cable with the borehole wall with a computed contact force is required to provide good coupling conditions. Based on those findings, we propose solutions to further optimise DAS acquisitions. We numerically modify the contact force and the elastic properties of the DAS cable and show how these modifications can improve but also deteriorate data quality. Finally, we propose a coupling detection algorithm that is applied to real datasets and allows ensuring the acquisition of data with a high signal-to-noise ratio
8
Huynh, Camille. "Real-time seismic monitoring using DAS fiber-optic instrumentation and machine learning : towards autonomous classification of natural and anthropogenic events." Electronic Thesis or Diss., Strasbourg, 2025. http://www.theses.fr/2025STRAH001.
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Ces dernières années, une nouvelle technologie basée sur l'utilisation de fibres optiques est apparue pour surveiller les événements acoustiques naturels ou anthropogéniques : la détection acoustique distribuée (Distributed Acoustic Sensing - DAS). Cette technologie innovante permet de mesurer les vibrations sismiques à très haute résolution spatiale sur des distances allant de quelques dizaines de mètres à plusieurs centaines de kilomètres. Bien que ces données soient plus volumineuses et plus complexes à traiter que celles des sismomètres traditionnels, elles offrent des perspectives prometteuses, notamment pour l'analyse des champs d'ondes générés par les tremblements de terre, la détection des glissements de terrain, la surveillance de divers événements anthropogéniques (tels que les déplacements de piétons, les mouvements de véhicules, ou les signaux sismiques provenant des activités humaines), les événements de faible amplitude ou très localisés, et la localisation précise de l'origine de ces événements sismiques. L'objectif de cette thèse est de développer et de tester des chaînes d'analyse de données automatisées en utilisant des approches basées sur l'IA pour détecter, classer et analyser les données DAS à fibre optique en temps quasi réel. L'objectif est axé sur la surveillance locale et régionale de zones spécifiques afin de permettre la détection et l'identification en temps réel d'événements naturels tels que les tremblements de terre et les glissements de terrainIn recent years, alongside traditional seismometer-based approaches, a new technology based on the use of optical fibers has emerged for monitoring natural or anthropogenic acoustic events: Distributed Acoustic Sensing (DAS). This innovative technology enables the measurement of seismic vibrations at very high spatial resolution over distances ranging from tens of meters to several hundred kilometers. Although these data are larger and more complex to process than those from traditional seismometers, they offer promising perspectives, particularly for analyzing the wavefields generated by earthquakes, detecting landslides, monitoring various anthropogenic events (such as pedestrian movements, vehicle movements, or seismic signals from human activities), low-amplitude or highly localized events, and precisely locating the origin of these seismic events. The goal of this thesis is to develop and test automated data analysis chains using AI-based approaches to detect, classify and analyze near-real-time fiber-optics DAS data. The objective is focused on local and regional monitoring of specific areas to enable the real-time detection and identification of natural events such as earthquakes and landslides
9
Schilke, Sven. "Importance du couplage des capteurs distribués à fibre optique dans le cadre des VSP." Electronic Thesis or Diss., Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM042.
Full textAbstract:
Les capteurs distribués à fibre optique (aussi nommés DAS) sont une nouvelle technologie d'acquisition sismique qui utilise des câbles traditionnels à fibre optique pour fournir une mesure de la déformation le long du câble. Ce système d'acquisition est largement utilisé dans les profils sismiques verticaux (PSV). Le couplage est un facteur clé qui a une grande influence sur la qualité des données. Alors que, pour les acquisitions PSV, les géophones sont attachés à la paroi du puits, le câble de fibre optique est soit cimenté derrière le tubage, soit attaché avec des pinces rigides au tubage ou simplement descendu dans le puits. Cette dernière stratégie de déploiement donne généralement le plus petit rapport signal sur bruit, mais est considérée comme la plus rentable en particulier pour les installations dans des puits existants. Cette thèse porte sur la problématique du couplage du DAS quand le câble est simplement descendu dans le puits. Nous développons des modèles numériques pour analyser les données réelles. L'interprétation de ces résultats nous permet de conclure qu'un contact immédiat du câble avec la paroi du puits avec une force de contact calculée est nécessaire pour fournir des bonnes conditions de couplage. Sur la base de ces résultats, nous proposons des solutions pour optimiser davantage les acquisitions avec le système DAS. Nous modifions numériquement la force de contact et les propriétés élastiques du câble DAS et démontrons comment ces modifications peuvent améliorer mais aussi détériorer la qualité des données. Enfin, nous proposons un algorithme de détection du couplage qui permet d'assurer l'acquisition de données réelles avec un rapport signal / bruit élevéDistributed Acoustic Sensing (DAS) is a new technology of seismic acquisition that relies on traditional fibre-optic cables to provide inline strain measurement. This acquisition system is largely used in vertical seismic profiling (VSP) surveys. Coupling is a key factor influencing data quality. While geophones and accelerometers are clamped to the borehole wall during VSP surveys, the fibre cable is either clamped and then cemented behind the casing, or attached with rigid clamps to the tubing, or loosely lowered into the borehole. The latter deployment strategy, also called wireline deployment, usually acquires the lowest level of signal but is regarded as the most cost-effective in particular for existing well installations. This PhD thesis addresses the problematic of coupling of DAS using wireline deployment. We develop numerical models that are used to analyse real data. The interpretation of these results allows us concluding that an immediate contact of the cable with the borehole wall with a computed contact force is required to provide good coupling conditions. Based on those findings, we propose solutions to further optimise DAS acquisitions. We numerically modify the contact force and the elastic properties of the DAS cable and show how these modifications can improve but also deteriorate data quality. Finally, we propose a coupling detection algorithm that is applied to real datasets and allows ensuring the acquisition of data with a high signal-to-noise ratio
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Becerril, Carlos Ernesto. "Développement de la mesure acoustique distribuée (DAS) à basse fréquence pour la détection des tsunamis." Electronic Thesis or Diss., Université Côte d'Azur, 2024. http://www.theses.fr/2024COAZ5078.
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À ce jour, aucun système efficace d'alerte rapide aux tsunamis (TEWS pour ses initiales en anglais) n'a encore été mis en place à l'échelle mondiale. Cette situation reflète un défi proverbial dans le domaine des géosciences : Instrumenter les fonds marins du monde entier et mener des observations à long terme avec une couverture spatiale et temporelle suffisante. Un paradigme sous la forme d'une nouvelle technologie photonique a été proposé pour une surveillance véritablement multi-échelle, tout en maintenant des coûts relativement bas. La détection acoustique distribuée (DAS) utilise les fibres optiques elles-mêmes pour mesurer la distribution spatiale des propriétés environnementales en chaque point de la fibre optique. En exploitant les plus d'un million de kilomètres de fibres optiques posées sur les continents et les océans, la communauté scientifique disposerait d'un réseau mondial permanent de surveillance composé de capteurs à composante unique, très sensibles et densément espacés, capables de fournir des données en temps réel et en continu. Bien qu'il ait été démontré que le DAS est capable d'enregistrer des phénomènes océanographiques de longue période tels que les marées et les ondes de gravité, et que des observations empiriques de sensibilité aux variations de pression du fond marin aient été rapportées, le mécanisme de détection de la pression dans le DAS reste à décrire quantitativement. Dans ce contexte, cette thèse vise à fournir une preuve de concept d'une architecture DAS spécifique (détection sensible à la phase utilisant des impulsions laser chirpées) adaptée aux applications TEWS. Pour atteindre cet objectif, ce travail a évalué la sensibilité requise et examine les performances de l'instrument DAS pour s'assurer de la détection des vagues de tsunami. Un modèle dérivé des déformations (strain) du fond marin potentiellement induites par les vagues de tsunami est présenté et montre que la compliance du sol marin et l'effet de Poisson sur le câble sont les principaux mécanismes par lesquels le DAS est censé enregistrer le passage des vagues de tsunami. L'analyse du modèle dérivé est étayée par des simulations physiques tridimensionnelles entièrement couplées de la rupture sismique, des ondes sismo-acoustiques et de la propagation des ondes de tsunami. En outre, comme pour la plupart des instruments, la sensibilité aux basses fréquences est principalement entravée par le bruit de 1/f de l'instrument. Ce travail identifie plusieurs améliorations dans le matériel opto-électronique afin de réduire le bruit de l'instrument et d'augmenter la sensibilité aux signaux à basse fréquence pertinents pour les signaux de tsunami, en particulier dans le régime de 1 à 10 mHz. L'analyse théorique et les simulations numériques présentées dans ce travail montrent qu'il est réellement possible de détecter les vagues de tsunami à l'aide de câbles à fibres optiquesTo date, an effective Tsunami Early-Warning System (TEWS) at a global scale is not yet in place. This reflects a proverbial challenge in geosciences: To instrument the world's ocean floors and conduct long-term observations with sufficient spatial and temporal coverage. A paradigm in the form of a novel photonic technology has been proposed for truly multi-scale monitoring, whilst keeping costs relatively low. Distributed Acoustic Sensing (DAS) uses optical fibers themselves to measure the spatial distribution of environmental properties along every point of the optic fiber. By leveraging the more than one million kilometers of optical fiber laid across the continents and oceans, the scientific community stands to gain permanent, global monitoring network of densely-spaced, highly sensitive single-component sensors, capable of providing continuous real-time data. Although it's been shown that DAS is capable of recording long-period oceanographic phenomena such as tides and gravity waves waves, and empirical observations of sensitivity to seafloor pressure variations; the pressure detection mechanism in DAS remains to be quantitatively described.Within this context, this thesis aims to provide a proof-of-concept of a specific DAS architecture (phase-sensitive detection employing chirped laser pulses) suitable for TEWS applications. Towards this objective, this work assessed the sensitivity required, and considers DAS instrument performance to ascertain detection of tsunami waves. A derived model of the expected seafloor strains potentially induced by tsunami waves is presented and finds seafloor compliance and the Poisson effect on the cable as the primary mechanisms through which DAS is anticipated to record the passage of tsunami waves. The analysis of the derived model is supported by fully coupled 3-D physics-based simulations of earthquake rupture, seismo-acoustic waves and tsunami wave propagation. Furthermore, as most instrumentation, the sensitivity at low frequencies is primarily hindered by 1/f instrument noise. This work identifies several enhancements in the opto-electronic hardware towards reducing instrument noise, and increase of sensitivity to low-frequency signals relevant to tsunami signals, specifically in the 1-10 mHz regime. The theoretical analysis and numerical simulations presented in this work point to the real possibility of detecting tsunami waves using fiber optic cables
11
Clement, Pierre. "Solutions aux limites des interrogateurs B-OTDR pour la surveillance d'infrastructures : augmentation de la portée de mesure et décorrélation des paramètres de température et de déformation." Electronic Thesis or Diss., Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAT042.
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Cette thèse porte sur l’étude des systèmes de mesure répartie de la rétrodiffusion Brillouin dans une fibre optique, que l’on nomme B-OTDR et qui sont sensibles à la température et à la déformation de la fibre. Les solutions d'interrogateurs actuelles permettent l'instrumentation de grandes infrastructures. Cependant, il existe des limites, inhérentes au phénomène physique utilisé, qui ne permettent pas d'adresser certaines applications spécifiques. Ces limites portent sur la distance de mesure maximale accessible par ces interrogateurs mais également sur la décorrélation de la mesure des paramètres de température et de déformation. Nous avons donc cherché, au cours de cette thèse, à adresser des solutions à ces problématiques. Un nouveau système de ré-amplification optique, basé sur les technologies EDFA, a été mis au point. Associé à un système B-OTDR, cette solution nous a permis de réaliser une mesure distribuée de température sur 150 km de fibre avec une répétabilité de 1,5 °C. Cette avancée propose, à notre connaissance, les meilleurs résultats obtenus avec un tel système et nous permet d’envisager son déploiement pour la surveillance d’infrastructures du transport de l’énergie sur de longues distances. Nous avons dans un second temps conçu un nouvel interrogateur, utilisant la rétrodiffusion Brillouin, et permettant la décorrélation des mesures de température et de déformation sur une seule et unique fibre optique. Ce nouvel interrogateur, caractérisé et breveté durant cette thèse, a permis de réaliser une mesure indépendante de température et de déformation sur un câble spécifique inséré dans un puits de forage. Les résultats de ces mesures ont montré à la fois des variations de température et de déformation sur le câble, donnant des informations précieuses à l’opérateur du puits. Le nouvel interrogateur mis au point, permet une séparation de ces deux paramètres avec une répétabilité inférieure à 1 °C et 20 μm/m pour une distance de l’ordre du kilomètre. Pour des distances de l’ordre de la dizaine de kilomètres, la répétabilité de mesure est de 3 °C et 75 μm/m. Ce résultat fait l'état de l'art dans la séparation température/déformation par B-OTDR. Enfin, les différents travaux réalisés pour répondre à ces deux problématiques ont abouti au développement d’un prototype d’interrogateur qui laisse envisager une mesure simultanée de la température, de la déformation, des vibrations acoustiques et de la pression hydrostatique. Ce prototype conduit à des perspectives intéressantes pour une solution complète de surveillance d’infrastructuresThis thesis deals with distributed optical fiber sensors, especially Brillouin sensors called B-OTDR that are sensitive both to temperature and strain. Some actual limitations due to the scattering phenomenon avoid deployment of this technology for some specific applications. These limitations are about the maximum length measured by the sensor but also the double sensitivity to strain and temperature. From our current B-OTDR sensor, we propose solutions to address these issues.A new re-amplification module using EDFA has been developed and characterized associated to a B-OTDR system. A 150 km distributed temperature measurement with 1,5 °C repeatability has been reached. This record performance let us consider a deployment for very long infrastructure monitoring for the energy transport. In another hand, we developed a new sensing device using Brillouin scattering and able to separate temperature and strain. This patented device has been characterized and used on a specific cable inserted in a well drilling. Results have shown a combination of strain and temperature variations on the cable that give very useful information to the well operator. We have reached a temperature repeatability of 1 °C and a strain repeatability of 20 μm/m for 1 km fiber. At 10 km, temperature repeatability has been evaluated to be 3 °C and strain to 75 μm/m. These results are to the state of art for temperature/strain separation using B-OTDR.These works have led to a new distributed measurement prototype that could address simultaneously temperature, strain, acoustic vibrations, and pressure sensing. Some interesting perspectives could result from these works to address a complete infrastructure monitoring using fiber optic sensing
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Coelho, Emanuel F. "Acoustic Sensing of Ocean Turbulence." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/38241.
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Approved for public release, distribution is unlimitedThe need for direct turbulence measurements in the upper ocean arise from widespread requirements to correctly parameterize momentum and scalar fluxes across the air/ocean interface. Until recently these observations were limited by a lack of instrumentation capable of measuring the fine-structure velocity field down to dissipation scales. The recently developed CDV package allows simultaneous sub-centimeter resolution measurements of temperature, conductivity, pressure, shear and the 3 component velocity field. As part of the development of this system a Monte-Carlo simulation was used to analyze the performance of several spectral estimators of the mean acoustic Doppler shifts, from which the velocity components are derived. The selected algorithms were implemented on a Digital Signal Processor allowing real-time estimation of the velocity, shear and scalar quantities. To verify the performance of the CDV package, it was deployed off Wharf 2 in Monterey for 24 hours while simultaneously recording meteorological data. Reynold's stresses, buoyancy fluxes and fine scale stratification were characterized and the surface gravity waves field identified.
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Khacef, Yacine. "Surveillance avancée du trafic routier par détection acoustique distribuée et apprentissage profond." Electronic Thesis or Diss., Université Côte d'Azur, 2024. http://www.theses.fr/2024COAZ5070.
Full textAbstract:
La gestion du trafic urbain est un enjeu crucial pour les villes du monde entier, en raison de l'augmentation continue du nombre de véhicules. Les méthodes classiques, telles que les caméras et les boucles de détection, s'avèrent souvent inadaptées à cause de leurs coûts élevés, de la faible résolution des capteurs, et des enjeux de protection de la vie privée. Récemment, la technologie de détection acoustique distribuée (DAS) a émergé comme une solution innovante pour la surveillance du trafic. En convertissant des câbles de fibre optique en un réseau de capteurs de vibration, la technologie DAS capte les déformations générées par les véhicules avec une haute résolution spatio-temporelle, offrant ainsi une alternative rentable et respectueuse de la vie privée. Dans cette thèse, nous développons plusieurs modèles et méthodes pour une surveillance complète du trafic à l'aide de la technologie DAS, en nous concentrant sur quatre axes : la détection des véhicules, l'estimation de la vitesse, le comptage et la classification. Nous introduisons d'abord un modèle d'alignement des données DAS auto-supervisé, permettant d'extraire des informations cruciales sur le trafic grâce à l'alignement temporel des données recueillies en divers points de mesure. Ce modèle intègre un module d'apprentissage profond et un bloc de déformation temporelle non uniforme, capable de gérer des conditions de circulation complexes et d'aligner les données DAS avec précision. Nous proposons ensuite une méthode pour la détection des véhicules et l'estimation de leur vitesse, basé sur le modèle d'alignement. La détection est formulée selon le cadre du test de rapport de vraisemblance généralisé (GLRT), permettant de localiser et de détecter les véhicules de manière fiable. L'estimation de la vitesse est réalisée sur les véhicules détectés, et nos résultats sont validés avec des capteurs dédiés. Notre méthode affiche une précision supérieure, avec une erreur inférieure à kmph{3}, surpassant de 80% les méthodes traditionnelles d'alignement temporel telles que la déformation temporelle dynamique (DTW), tout en étant 16 fois plus rapide, ce qui permet une application en temps réel. Nous développons également de nouvelles méthodes de comptage et de classification des véhicules en exploitant la technologie DAS. Une première solution, basée uniquement sur la détection des véhicules, est efficace pour le comptage des camions mais montre des limites pour le comptage des voitures en trafic dense. Pour y remédier, nous proposons un modèle d'apprentissage profond supervisé pour le comptage, entraîné sur une section spécifique de la route, utilisant les résultats du comptage de la première méthode et des étiquettes à faible résolution temporelle. Une technique de transfert de caractéristiques permet d'étendre ce modèle à d'autres segments routiers, démontrant ainsi son adaptabilité. En conclusion, cette thèse propose une solution robuste et scalable pour la surveillance du trafic à l'aide de la technologie DAS, assurant à la fois une haute précision et une exécution en temps réel. Cette approche ouvre la voie à l'extraction de diverses informations critiques, telles que la détection d'accidents, et peut être étendue à d'autres modes de transport, comme les tramways ou les trains, illustrant ainsi son large potentiel d'applicationUrban traffic management poses a significant challenge for cities worldwide, intensified by the growing number of vehicles on road infrastructures. Traditional methods, such as cameras and loop detectors, are often suboptimal due to their high deployment and maintenance costs, limited sensing resolution, and privacy concerns. Recently, Distributed Acoustic Sensing (DAS) technology has emerged as a promising solution for traffic monitoring. By transforming standard fiber-optic telecommunication cables into an array of vibration sensors, DAS captures vehicle-induced subsurface deformation with high spatio-temporal resolution, providing a cost-effective and privacy-preserving alternative.In this thesis, we propose several models and frameworks for comprehensive traffic monitoring using DAS technology, focusing on four key aspects: vehicle detection, speed estimation, counting, and classification. First, we introduce a self-supervised DAS data alignment model that temporally aligns the recorded DAS data across multiple measurement points, enabling the extraction of the traffic information. Our model integrates a deep learning module with a non-uniform time warping block, making it capable of handling challenging traffic conditions and accurately aligning DAS data.Next, we present a vehicle detection and speed estimation framework built on the alignment model. Vehicle detection is formulated within the Generalized Likelihood Ratio Test (GLRT) framework, allowing for reliable detection and localization of vehicles. Speed estimation is achieved over the detected vehicles using the warps from the alignment model, and the results are validated against dedicated sensors. Our method achieves a mean error of less than kmph{3}, outperforming traditional time series alignment methods like Dynamic Time Warping (DTW) by nearly 80%. Furthermore, our model's computing time is 16 times faster than DTW, enabling real-time performance.Lastly, we introduce new vehicle counting and classification methods that leverage the DAS technology. We present a first solution, based solely on vehicle detection results, which is effective for truck counting but shows limitations in cars counting under high-traffic conditions. To address these limitations, we develop a second approach for vehicle counting using a supervised deep learning model trained on a specific road section, using the vehicle counting results of the first method and low-time-resolution labels from dedicated sensors. Through an optimal transport-based feature mapping technique, we extend the model to other road segments, demonstrating its scalability and adaptability. Using the first truck counting method along with the deep learning-based vehicle counting model results in a comprehensive vehicle counting and classification solution.Overall, this thesis presents a robust and scalable framework for road traffic monitoring using DAS technology, delivering both high accuracy and real-time performance. The framework paves the way for extracting a wide range of other crucial traffic information, such as accident detection. Moreover, this approach can be generalized to various road configurations and extended to other transportation modes, such as tramways and trains, demonstrating its broader applicability
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Malkireddy, Sivakesava Reddy. "Spectrum Sensing of acoustic OFDM signals." Thesis, Linköpings universitet, Kommunikationssystem, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-86811.
Full textAbstract:
OFDM is a fast growing technology in the area of wireless communication due to its numerous advantages and applications. The current and future technologies in the area of wireless communications like WiMAX, WiFi, LTE, MBWA and DVB-T uses the OFDM signals. The OFDM technology is applicable to the radio communication as well as the acoustic communication. Though the licensed spectrum is intended to be used only by the spectrum owners, Cognitive radio is a concept of reusing this licensed spectrum in an unlicensed manner. Cognitive radio is motivated by the measurements of spectrum utilization . Cognitive radio must be able to detect very weak primary users signal and to keep the interference level at a maximum acceptable level. Hence spectrum sensing is an essential part of the cognitive radio. Spectrum is a scarce resource and spectrum sensing is the process of identifying the unused spectrum, without causing any harm to the existing primary user’s signal. The unused spectrum is referred to as spectrum hole or white space and this spectrum hole could be reused by the cognitive radio. This thesis work focuses on implementing primary acoustic transmitter to transmit the OFDM signals from a computer through loudspeaker and receive the signals through a microphone. Then by applying different detection methods on the received OFDM signal for detection of the spectrum hole, the performance of these detection methods is compared here. The commonly used detection methods are power spectrum estimation, energy detection and second–order statistics (GLRT approach, Autocorrelation Function (ACF) detection and cyclostationary feature detection ). The detector based on GLRT approach exploits the structure of the OFDM signal by using the second order statistics of the received data. The thesis mainly focuses on GLRT approach and ACF detectors and compare their performance.
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Pickering, Benjamin. "Changepoint detection for acoustic sensing signals." Thesis, Lancaster University, 2016. http://eprints.lancs.ac.uk/81171/.
Full textAbstract:
This thesis considers the application of changepoint detection methodology for the analysis of acoustic sensing signals. In the first part, we propose a detection procedure for changes in the second-order structure of a univariate time series. This utilises a penalised likelihood based on Whittle’s approximation and allows for a non-linear penalty function. This procedure is subsequently used to detect changes in acoustic sensing data which correspond to external disturbances of the measuring cable. The second part shifts focus to multivariate time series, and considers the detection of changes which occur in only a subset of the variables. We introduce the concept of changepoint vectors which we use to model such changes. A dynamic programming scheme is proposed which obtains the optimal configuration of changepoint vectors for a given multivariate series. Consideration of pruning techniques suggests that these are not practically viable for this setting. We therefore introduce approximations which vastly improve computational speed with negligible detrimental impact on accuracy. This approximated procedure is applied to multivariate acoustic sensing data.
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Jacquemai, Ivo. "Acoustic wireless sensing for environmental monitoring." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2011. https://ro.ecu.edu.au/theses/395.
Full textAbstract:
The European House Borer (EHB) is a timber pest which attacks dead timber. This pest can cause large scale damage to wooden structures and has already spread throughout many parts of the world. The larvae usually remains undetected for many years while it busily inflicts irrevocable and substantial harm to the timber. Since the pest was first discovered in Western Australia in 2004 the Government has endeavoured to extinguish its existence. In this research, an electronic sensor has been developed in order to detect the presence of EHB larvae in timber. Only an accurate detection can allow for selective treatment, which is required in order to eliminate the pest. In the past no reliable detection methods were available. However, with the developed acoustic sensing device, non-destructive and reliable detection of EHB is now possible. The developed handheld device is capable of analysing the acoustic emissions from a timber structure which allows for determining whether or not EHB is present in its vicinity. Depending on the level of the infestation, the detection can take as little as a few seconds. The tests, which have been carried out on infested timber beams in a secured laboratory, show a reliable detection of the larvae over a distance of several metres. The research discusses the challenges encountered throughout the development of the acoustic sensor and the limitations of the technology. Also presented are other potential applications for the device and areas which require further research in order to improve the efficiency of the sensor.
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Sundman, Dennis. "Greedy Algorithms for Distributed Compressed Sensing." Doctoral thesis, KTH, Kommunikationsteori, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-144907.
Full textAbstract:
Compressed sensing (CS) is a recently invented sub-sampling technique that utilizes sparsity in full signals. Most natural signals possess this sparsity property. From a sub-sampled vector, some CS reconstruction algorithm is used to recover the full signal. One class of reconstruction algorithms is formed by the greedy pursuit, or simply greedy, algorithms, which is popular due to low complexity and good performance. Meanwhile, in sensor networks, sensor nodes monitor natural data for estimation or detection. One application of sensor networking is in cognitive radio networks, where sensor nodes want to estimate a power spectral density. The data measured by different sensors in such networks are typically correlated. Another type are multiple processor networks of computational nodes that cooperate to solve problems too difficult for the nodes to solve individually. In this thesis, we mainly consider greedy algorithms for distributed CS. To this end, we begin with a review of current knowledge in the field. Here, we also introduce signal models to model correlation and network models for simulation of network. We proceed by considering two applications; power spectrum density estimation and distributed reconstruction algorithms for multiple processor networks. Then, we delve deeper into the greedy algorithms with the objective to improve reconstruction performance; this naturally comes at the expense of increased computational complexity. The main objective of the thesis is to design greedy algorithms for distributed CS that exploit data correlation in sensor networks to improve performance. We develop several such algorithms, where a key element is to use intuitive democratic voting principles. Finally, we show the merit of such voting principles by probabilistic analysis based on a new input/output system model of greedy algorithms in CS. By comparing the new single sensor algorithms to well known greedy pursuit algorithms already present in the literature, we see that the goal of improved performance is achieved. We compare complexity using big-O analysis where the increased complexity is characterized. Using simulations we verify the performance and confirm complexity claims. The complexity of distributed algorithms is typically harder to analyze since it depends on the specific problem and network topology. However, when analysis is not possible, we provide extensive simulation results. No distributed algorithms based on the signal-models used in this thesis were so far available in the literature. Therefore, we compare our algorithms to standard single-sensor algorithms, and our results can then easily be used as benchmarks for future research. Compared to the stand-alone case, the new distributed algorithms provide significant performance gains. Throughout the thesis, we strive to present the work in a smooth flow of algorithm design, simulation results and analysis.Compressed sensing (CS) är en nyutvecklad teknik som utnyttjar gleshet i stora undersamplade signaler. Många intressanta signaler besitter dessa glesa egenskaper. Utifrån en undersamplad vektor återskapar CS-algoritmer hela den sökta signalen. En klass av rekonstruktionsalgoritmer är de så kallade giriga algoritmerna, som blivit populära tack vare låg komplexitet och god prestanda. CS kan användas i vissa typer av nätverk för att detektera eller estimera stora signaler. En typ av nätverk där detta kan göras är i sensornätverk för kognitiv radio, där man använder sensorer för att estimera effektspektrum. Datan som samplas av de olika sensorerna i sådana nätverk är typiskt korrelerad. En annan typ av nätverk är multiprocessornätverk bestående av distribuerade beräkningsnoder, där noderna genom samarbete kan lösa svårare problem än de kan göra ensamma. Avhandlingen kommer främst att behandla giriga algoritmer för distribuerade CS-problem. Vi börjar med en överblick av nuvarande kunskap inom området. Här introducerar vi signalmodeller för korrelation och nätverksmodeller som används för simulering i nätverk. Vi fortsätter med att studera två tillämpningar; estimering av effektspektrum och en distribuerad återskapningsalgoritm för multiprocessornätverk. Därefter tar vi ett djupare steg i studien av giriga algoritmer, där vi utvecklar nya algoritmer med förbättrad prestanda, detta till priset av ökad beräkningskomplexitet. Huvudmålet med avhandlingen är giriga algoritmer för distribuerad CS, där algoritmerna utnyttjar datakorrelationen i sensornätverk. Vi utvecklar flera sådana algoritmer, där en huvudingrediens är att använda demokratiska röstningsalgoritmer. Vi analyserar sedan denna typ av röstningsalgoritmer genom att introducera en ingång/utgångs modell. Analysen visar att algoritmerna ger bra resultat. Genom att jämföra algoritmer för enskilda sensorer med redan befintliga algoritmer i litteraturen ser vi att målet med ökad prestanda uppnås. Vi karaktäriserar också komplexiteten. Genom simulationer verifierar vi både prestandan och komplexiteten. Att analysera komplexitet hos distribuerade algoritmer är generellt svårare eftersom den beror på specifik signalrealisation, nätverkstopologi och andra parametrar. I de fall där vi inte kan göra analys presenterar vi istället genomgående simuleringsresultat. Vi jämför våra algoritmer med de vanligaste algoritmerna för enskilda sensorsystem, och våra resultat kan därför enkelt användas som referens för framtida forskning. Jämfört med prestandan för enskilda sensorer visar de nya distribuerade algoritmerna markant förbättring.
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Kelly, Devin WW. "A Practical Distributed Spectrum Sensing System." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-theses/378.
Full textAbstract:
As the demand for wireless communication systems grows, the need for spectrum grows accordingly. However, a large portion of the usable spectrum has already been exclusively licensed to various entities. This exclusive allocation method encourages spectrum to be left unused if the licensee has no need for that spectrum. In order to better utilize spectrum and formulate new approaches for greater spectrum use efficiency, it is imperative to possess a thorough understanding about how wireless spectrum behaves over time, frequency, and space. In this thesis, a practical, scalable, and low-cost wideband distributed spectrum sensing system is designed, implemented, and tested. The proposed system is made up of a collection of nodes that use general purpose, off-the-shelf computer hardware as well as a collection of inexpensive software-defined radio (SDR) equipment in order to collect and analyze spectrum data that varies across time, frequency, and space. The spectrum data the proposed system collects is the power present at a given frequency. The tools needed to analyze the gathered data are also created, including a periodogram and spectrogram function, which visualize average spectrum use over a period of time and as spectrum use varies with time, respectively. The proposed system also facilitates the testing of a spatio-spectrum characterization method using real data. This method has only been simulated up to this point. The characterization technique allows for spatially varying spectrum measurements to be visualized using heat maps.
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McGonigle, Chris. "Mapping benthic habitat using acoustic remote sensing." Thesis, University of Ulster, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551582.
Full textAbstract:
Backscatter imagery from multibeam echosounders (MBES) is increasingly used for benthic habitat mapping. This research explores MBES backscatter classification using QTC-Multiview on data from Stanton Banks (UK) and Cashes Ledge (USA). Image-processing algorithms are used to extract values from samples of backscatter data, which are reduced by principal components analysis and are objectively clustered. This process is initially evaluated using 2005 data from Stanton Banks and compared with ground-truth data to determine their biological validity. Low-levels of agreement are observed between acoustic class and ground- truth data «35%); video is determined to be the most spatially appropriate method for comparison. Subsequently, the area was resurveyed in 2006 using the same MBES with different operational parameters, acquiring low- and high-density data coverage. Percentage agreement between classifications was 78%, determined to be due to operational parameters as opposed to environmental change. Agreement with ground truth data improved from 71 % to 77% with increased data density. In 2008, a 2 km2 area was resurveyed at two different orientations and vessel speeds within the same 24 hr period. Classification revealed 53% similarity at 4 rns-1 and 49% at 2 rns-1 from opposing orientations. The same orientations surveyed at different speeds were between 68% (k=0.583) and 53% (k=0.384) similar. These results suggest that both orientation and speed are significant considerations in image-based classification. Finally, the significance of water-column biomass in backscatter classification was examined at Cashes Ledge using MBES data from kelp beds. Two approaches were examined for detecting the presence of macrophytes; image-based and manual picking. Comparison with video data revealed comparable success, with both methods most successful at predicting Laminaria sp. (77.3%-82.6% correct) in shallow water «30m). This research demonstrates the significance of MBES backscatter and image-based classification as potential tools for the emergent discipline of benthic habitat mapping.
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Kloser, Rudolf J. "Seabed biotope characterisation based on acoustic sensing." Thesis, Curtin University, 2007. http://hdl.handle.net/20.500.11937/524.
Full textAbstract:
The background to this thesis is Australia’s Oceans Policy, which aims to develop an integrated and ecosystem-based approach to planning and management. An important part of this approach is the identification of natural regions in regional marine planning, for example by establishing marine protected areas for biodiversity conservation. These natural regions will need to be identified on a range of scales for different planning and management actions. The scale of the investigation reported in this thesis is applicable to spatial management at 1 km to 10 km scale and monitoring impacts at the 10s of m to 1 km biotope scale. Seabed biotopes represent a combination of seabed physical attributes and related organisms. To map seabed biotopes in deep water, remote sensing using a combination of acoustic, optical and physical sensors is investigated. The hypothesis tested in this thesis is that acoustic bathymetry and backscatter data from a Simrad EM1002 multi-beam sonar (MBS) can be used to infer (act as a surrogate of) seabed biotopes. To establish a link between the acoustic data and seabed biotopes the acoustic metrics are compared to the physical attributes of the seabed in terms of its substrate and geomorphology at the 10s m to 1 km scale using optical and physical sensors. At this scale the relationship between the dominant faunal functional groups and both the physical attributes of the seabed and the acoustic data is also tested. These tests use data collected from 14 regions and 2 biomes to the south of Australia during a voyage in 2000. Based on 62 reference sites of acoustic, video and physical samples, a significant relationship between ecological seabed terrain types and acoustic backscatter and bathymetry was observed.These ecological terrain types of soft-smooth, soft-rough, hard-smooth and hard-rough were chosen as they were the most relevant to the biota in their ability to attach on or burrow into the seabed. A seabed scattering model supported this empirical relationship and the overall shape of backscatter to incidence angle relationship for soft and hard seabed types. The correlation between acoustic data (backscatter mean and standard deviation) and the visual and physical samples was most consistent between soft-smooth and hard-rough terrain types for a large range of incidence angles (16o to 70o). Using phenomenological backscatter features segmented into 10 common incidence angle bins from -70o to 70o the length resolution of the data decreased to 0.55 times depth. The decreased resolution was offset by improved near normal incidence (0o to 30o) seabed type discrimination with cross validation error reducing from 32% to 4%. A significant relationship was also established between the acoustic data and the dominant functional groups of fauna. Faunal functional groups were based on the ecological function, feeding mode and substrate preference, with 8 out of the 10 groups predicted with 70% correctness by the four acoustically derived ecological terrain types. Restricting the terrain classification to simple soft and hard using the acoustic backscatter data improved the prediction of three faunal functional groups to greater than 80%. Combining the acoustic bathymetry and backscatter data an example region, Everard Canyon, was interpreted at a range of spatial scales and the ability to predict the preferred habitat of a stalked crinoid demonstrated.Seabed terrain of soft and hard was predicted from the acoustic backscatter data referenced to a common seabed incidence angle of 40o. This method of analysis was selected due to its combined properties of high spatial resolution, consistent between terrain discrimination at the widest range of incidence angles and consistent data quality checking at varying ranges. Based in part on the research reported in this thesis a mid-depth Simrad EM300 multibeam sonar was purchased for use in Australian waters. A sampling strategy is outlined to map all offshore waters with priority within the 100 m to 1500 m depths.
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Kloser, Rudolf J. "Seabed biotope characterisation based on acoustic sensing." Curtin University of Technology, Faculty of Science and Engineering, Department of Imaging and Applied Physics, 2007. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=18566.
Full textAbstract:
The background to this thesis is Australia’s Oceans Policy, which aims to develop an integrated and ecosystem-based approach to planning and management. An important part of this approach is the identification of natural regions in regional marine planning, for example by establishing marine protected areas for biodiversity conservation. These natural regions will need to be identified on a range of scales for different planning and management actions. The scale of the investigation reported in this thesis is applicable to spatial management at 1 km to 10 km scale and monitoring impacts at the 10s of m to 1 km biotope scale. Seabed biotopes represent a combination of seabed physical attributes and related organisms. To map seabed biotopes in deep water, remote sensing using a combination of acoustic, optical and physical sensors is investigated. The hypothesis tested in this thesis is that acoustic bathymetry and backscatter data from a Simrad EM1002 multi-beam sonar (MBS) can be used to infer (act as a surrogate of) seabed biotopes. To establish a link between the acoustic data and seabed biotopes the acoustic metrics are compared to the physical attributes of the seabed in terms of its substrate and geomorphology at the 10s m to 1 km scale using optical and physical sensors. At this scale the relationship between the dominant faunal functional groups and both the physical attributes of the seabed and the acoustic data is also tested. These tests use data collected from 14 regions and 2 biomes to the south of Australia during a voyage in 2000. Based on 62 reference sites of acoustic, video and physical samples, a significant relationship between ecological seabed terrain types and acoustic backscatter and bathymetry was observed.These ecological terrain types of soft-smooth, soft-rough, hard-smooth and hard-rough were chosen as they were the most relevant to the biota in their ability to attach on or burrow into the seabed. A seabed scattering model supported this empirical relationship and the overall shape of backscatter to incidence angle relationship for soft and hard seabed types. The correlation between acoustic data (backscatter mean and standard deviation) and the visual and physical samples was most consistent between soft-smooth and hard-rough terrain types for a large range of incidence angles (16o to 70o). Using phenomenological backscatter features segmented into 10 common incidence angle bins from -70o to 70o the length resolution of the data decreased to 0.55 times depth. The decreased resolution was offset by improved near normal incidence (0o to 30o) seabed type discrimination with cross validation error reducing from 32% to 4%. A significant relationship was also established between the acoustic data and the dominant functional groups of fauna. Faunal functional groups were based on the ecological function, feeding mode and substrate preference, with 8 out of the 10 groups predicted with 70% correctness by the four acoustically derived ecological terrain types. Restricting the terrain classification to simple soft and hard using the acoustic backscatter data improved the prediction of three faunal functional groups to greater than 80%. Combining the acoustic bathymetry and backscatter data an example region, Everard Canyon, was interpreted at a range of spatial scales and the ability to predict the preferred habitat of a stalked crinoid demonstrated.
Seabed terrain of soft and hard was predicted from the acoustic backscatter data referenced to a common seabed incidence angle of 40o. This method of analysis was selected due to its combined properties of high spatial resolution, consistent between terrain discrimination at the widest range of incidence angles and consistent data quality checking at varying ranges. Based in part on the research reported in this thesis a mid-depth Simrad EM300 multibeam sonar was purchased for use in Australian waters. A sampling strategy is outlined to map all offshore waters with priority within the 100 m to 1500 m depths.
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Bohner, Christopher George 1972. "A distributed approach to underwater acoustic communications." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/91806.
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Thesis (S.M.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, the Woods Hole Oceanographic Institution), 2003.Includes bibliographical references (p. 118-120).
by Christopher George Bohner.
S.M.
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Khalid, Muhammad Arslan. "Engineering surface acoustic wave sensing and diagnostic devices." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/30999/.
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Globally, over 50% of deaths occur due to the top 10 global diseases which include cardiovascular disease, cancer and infectious diseases. Low and middle-income countries (LMICs) are disproportionately affected. 80% of all deaths due to non-communicable diseases occur in low and middle income countries and with numbers on the rise. In these disadvantaged and vulnerable populations, diseases are often detected late. The treatment required is therefore increasingly extensive and expensive. Early detection, treatment and monitoring coupled with life-style changes can reduce mortality and morbidity. Many laboratory and clinical diagnostic tests have been developed. However, in order to provide healthcare in resource poor areas near the patient side (point-of-care), portable and low-cost bioanalytical assays are required. Lab-on-a-chip technology has emerged as a contender for point-of-care testing and monitoring but due to the complexity of the systems, there has been limited success in miniaturisation of fully integrated assays. This thesis takes a new approach to make use of existing and readily available mobile technologies to engineer on-chip, integrated, portable and low-cost microfluidic platforms using surface acoustic waves (SAW). The ability of SAW to manipulate fluids has been used to develop therapeutic and sensing devices. In the first application, SAW acoustic streaming was used to mechanically ‘clot’ or ‘solidify’ a droplet of human whole blood containing anti-coagulants in as quickly as 6 seconds. To analyse this mechanical process of a change in state, in small sample volumes, a new method which used light deflection from the surface perturbations was developed which could potentially replace clinical thromboelastography. The higher order acoustic streaming is known to be significantly influenced by a fluid’s viscosity. In a second application, as a proof of concept, it was demonstrated that the drop vibration due to SAW streaming together with the light deflection method can be used to study the relative viscosity response in samples. Furthermore, to aid the development of an integrated digital microfluidics, such as a blood monitoring device, a low cost (~$65) smart-phone based SAW platform prototype has been built using additive manufacturing technologies. Many lab-on-chip devices rely on optical detection such as microscopes. SAW already have shown promise in fluid manipulation and can eliminate the need for external pumps in sample processing. However, optical detection remains a challenge to create truly point-of-care devices. In this thesis, integration of SAW with portable lens-free microscopy that offers a large field of view (FOV) (~30 mm2) is demonstrated. Furthermore, a new method has been proposed for label-free visualisation of waves in fluids and to study their rheological response by analysing the wave relaxation process. This method can potentially be developed into a high-throughput viscosity sensor for disease diagnostics. Finally, by coupling SAW in transmissive superstrates (a low-cost disposable chip), acoustically tuneable nanolenses were created which allowed the detection of sub-micron particles in liquids without super-resolution techniques. As an application of this technique, detection of herpes simplex virus (type I) has been shown. In summary, this thesis presents the potential of SAW through its integration with mobile platforms such as a smartphone or lens-free microscope to engineer label-free, low-cost and high-throughput sensing and testing devices.
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Prasad, Abhinav. "Bulk-acoustic micromechanical resonator platforms for interfacial sensing." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708654.
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Clark, Robert L. Jr. "Advanced sensing techniques for active structural acoustic control." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/37880.
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This study presents a basis for the analytical and experimental procedures as well as design techniques required in achieving adaptive structures for active structural acoustic control (ASAC). Test structures studied in this work included a baffled simply supported beam and a baffled simply supported plate which were subjected to a harmonic input disturbance created physically with a shaker and modelled by a point force input. Structural acoustic control was achieved with piezoelectric actuators bonded to the surface of the test structure. The primary focus of this work was devoted to studying alternative sensing techniques in feed forward control applications. Specifically, shaped distributed structural sensors constructed from polyvinylidene fluoride (PVDF), distributed acoustic near-field sensors constructed from PVDF, and accelerometers were explored as alternatives to microphones which are typically implemented as error sensors in the cost function of the control approach. The chosen control algorithm in this study was the feed forward filtered-x version of the adaptive LMS algorithm. A much lower level of system modelling is required with this method of control in comparison to state feedback control methods. As a result, much of the structural acoustic coupling (i.e. system modelling) must be incorporated into the sensor design.Ph. D.
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Clark, Robert L. "Advanced sensing techniques for active structural acoustic control /." This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-05222007-091351/.
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Sternlicht, Daniel D. "High frequency acoustic remote sensing of seafloor characteristics /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p9935453.
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Feced, Ricardo. "Nonlinear techniques for distributed optical fibre sensing." Thesis, King's College London (University of London), 1998. https://kclpure.kcl.ac.uk/portal/en/theses/nonlinear-techniques-for-distributed-optical-fibre-sensing(48661ada-da47-4da7-b6db-fc995f840603).html.
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Dhliwayo, Jabulani. "Stimulated Brillouin scattering for distributed temperature sensing." Thesis, University of Kent, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242858.
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Frazier, Janay Amber Wright. "High-Definition Raman-based Distributed Temperature Sensing." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/95934.
Full textAbstract:
Distributed Temperature Sensing (DTS) has been used in a variety of different applications. Its ability to detect temperature fluctuations along fiber optic lines that stretch for several kilometers has made it a popular topic in various fields of science, engineering, and technology. From pre-fire detection to ecological monitoring, DTS has taken a vital role in scientific research. DTS uses the principle of backscattering by three different spectral components, e.g., Rayleigh scattering, Brillouin scattering, and Raman scattering. Although there have been various improvements to DTS, its slow response time and poor spatial resolution have been hard to overcome. Its repetition rate is low because the pulse must travel the distance of the fiber optic line and return to the detector to record the temperature change along the fiber. A spatial resolution of 7.4 cm with a response time as low as 1 second and a temperature resolution of the 0.196 ℃ is achieved from the current Raman-based DTS system. This research proves that high-spatial resolution can be obtained with the use of a Silicon Avalanche Photodetector with a 1 GHz bandwidth.MS
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Hahn, Matthew J. "Undersea navigation via a distributed acoustic communications network." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FHahn%5FMatthew.pdf.
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Ali, Andreas Mantik. "Distributed acoustic localization and tracking design and analysis." Diss., Restricted to subscribing institutions, 2010. http://proquest.umi.com/pqdweb?did=2023768071&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Jain, Ankita Deepak. "Instantaneous continental-shelf scale sensing of cod with Ocean Acoustic Waveguide Remote Sensing (OAWRS)." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100125.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 259-278).
Reported declines in the population of Atlantic cod have a potential to affect long-term ecological balance and the sustainability of the cod fishery along the US northeast coast. These assessments have led to severe fishing cuts over the past few years, have consequently threatened the centuries-old Atlantic cod fishery along the New England coast and put the livelihood of thousands of fishermen at risk. Amidst this fisheries crisis, calls by elected officials, environmental groups and fishing consortiums were made for an Ocean Acoustic Waveguide Remote Sensing (OAWRS) survey of the Gulf of Maine cod stock. Typically, cod stock assessments incorporate data collected from conventional acoustic and trawl line transect surveys that highly undersample the marine environment in space and time and lead to ambiguities in population estimates. The combination of conventional methods and OAWRS techniques, however, has been demonstrated to provide rapid and accurate fish stock assessments over ecosystem-scale areas for other species. In this thesis, the feasibility of accurately surveying cod stocks with OAWRS is theoretically assessed. These theoretical predictions are then experimentally verified by successfully sensing cod with OAWRS over ecosystem scales in the Nordic Seas. Following direct requests by Massachusetts state officials to determine if OAWRS could be used to detect and survey the reported waning cod populations in coastal New England waters, we obtained measurements of typical aggregation densities and occupancy depths of spawning cod in Ipswich Bay from conventional echosounder surveys conducted in Spring 2011. Cod length distributions were also measured from which we estimated the swimbladder resonance frequencies of local cod via a harmonic oscillator model that includes the effects of damping, the cod's swim bladder air volume at a given neutral buoyancy depth as well as changes to this volume for deviations from neutral buoyancy depth. The optimal frequency for OAWRS detection typically corresponds to that where the resonance peak is found. We showed that our theoretical estimates of cod swimbladder resonance matched very well with independent measurements of caged cod resonance from decades old Norwegian data. Using parabolic equation modeling of ocean waveguide propagation, the scattered level of typical spawning cod aggregations was estimated and compared with that from seafloor scattering, which is a typical limiting factor in long range active sensing. Seafloor scattering was estimated via a Rayleigh-Born approach we developed, where the magnitude squared of seafloor scattering amplitude was empirically determined from thousands of measurements made during major OAWRS experiments along the US Northeast coast. It was found that near cod swimbladder resonance (roughly 150-600 Hz), determined from the New England length and depth distribution data, OAWRS was capable of robustly detecting spawning cod aggregations from many tens of kilometers in range with high signal-to- noise ratios (SNRs) greater than 20 dB for typical spawning cod configurations in New England waters. Above the resonance frequency peak, it is possible to detect cod for typical shoaling densities because cod scattering reaches a plateau due to geometric scattering that is above the seafloor scattering trend for typical OAWRS frequencies. Well below the resonance peak, scattering from cod is expected to fall off rapidly and faster than seafloor scattering, and so provides important information about resonance behavior but can be difficult to probe given the very low frequencies involved. This theoretical feasibility study emphasized the need for a low frequency source that spans cod swimbladder resonance and helped demonstrate the potential for use of OAWRS for cod assessments over ecosystem scales. To confirm our theoretical predictions on the OAWRS detection of cod and other keystone fish species, we designed, prepared and conducted a major oceanographic experiment in the Nordic Seas in the Arctic in the winter (February-March) of 2014 using three major research vessels, the US RV Knorr, the Norwegian RV Johan Hjort and the Norwegian FV Artus. The Nordic Seas 2014 experiment was conducted in difficult gale and hurricane force weather conditions along most of Norway's western and northern coast. MIT's OAWRS Source, obtained through a NSF-Sloan MRI grant, spanned the 800-1600 Hz range, and the receiver was ONR's Five Octave Receiver Array (FORA). Unlike the declining trend of cod population in New England waters, cod population in the Nordic Seas has been thriving for many years and is currently at its healthiest recorded state. The experiment period was chosen such that it coincided with the peak spawning period of cod along the coastal Lofoten region in Norway where they congregate in high densities, as well as other keystone species that migrate from the ice-edge to spawn in some of the world's largest mass migrations. In planning, we determined likely spawning grounds for cod, and other keystone species such as capelin, herring, and haddock using historic survey data collected along the Norwegian coast. With our calibrated model of fish swimbladder resonance and historic length distribution data from Norway, swimbladder resonance frequencies and target strengths of these fish species were estimated. We also determined optimal OAWRS ship tracks for remote detection of these species above seafloor scattering using waveguide propagation modeling. While the OAWRS frequencies were greater than those expected for cod swimbladder resonance, cod shoals over ten kilometers in length were robustly detected and successfully imaged from tens of kilometer ranges during the experiment. This produced the first instantaneous images of a vast cod shoal. It also confirmed our predictions that OAWRS can be used to remotely sense and survey cod populations. Our theoretical predictions suggest that the use of lower OAWRS frequencies near cod swimbladder resonance would lead to greater dynamic range in population density estimates. The Nordic Seas experiment provided the first look revealing the entire horizontal morphology of vast cod, capelin, haddock and Norwegian herring shoals. This was done with instantaneous OAWRS imaging. The presence of multiple shoaling fish species during the Nordic Seas experiment provided us with a unique opportunity to study general shoaling behavior across species over ecosystem scales with OAWRS. For example, many pelagic and demersal fish species are known to undergo distant migrations for feeding, spawning and overwintering year after year. This suggests that migrating populations have an ability to efficiently sense their environment. By combining OAWRS estimates of fish scattering strength and population density obtained from simultaneous depth echo-sounding along line transects, areal population densities over entire shoals were determined. This enabled estimation of total shoal population, shoal aspect ratio, and shoal migration speed via cross correlation of population density over time. It was shown that across several species, as shoal population increased (tens of thousands to hundreds of millions of individuals), shoal aspect ratio also increased (roughly from one to ten). Single-celled organisms with higher aspect ratios have been shown to more efficiently and accurately detect chemical gradients at microscopic scales. The high-aspect ratio or elongated morphology of a large migrating fish shoal is consistent with the entire shoal serving the function of a biological antenna for efficient spatial and temporal sensing of mesoscale processes in the environment. We also studied the evolution of air resonance power efficiency in the violin and its ancestors. We collected historical data, including samples from roughly 500 classical Cremonese violins from the renowned workshops of Amati, Stradivari and Guarneri, to establish historic time series of key design traits. We determined the primary physical mechanisms governing radiated air resonance power in the violin and its ancestors and used this knowledge to explain the evolutionary trends we discovered.
by Ankita Deepak Jain.
Ph. D.
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Srinivasan, krishnan. "Nanomaterial sensing layer based surface acoustic wave hydrogen sensors." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001325.
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Schuler, Leo Pius. "Wireless identification and sensing using surface acoustic wave devices." Thesis, University of Canterbury. Electrical Engineering, 2003. http://hdl.handle.net/10092/1081.
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Wireless Surface Acoustic Wave (SAW) devices were fabricated and tested using planar Lithium Niobate (LiNbO₃) as substrate. The working frequencies were in the 180 MHz and 360 MHz range. Using a network analyser, the devices were interrogated with a wireless range of more than 2 metres. Trials with Electron Beam Lithography (EBL) to fabricate SAW devices working in the 2450 MHz with a calculated feature size of 350 nm are discussed. Charging problems became evident as LiNbO₃ is a strong piezoelectric and pyroelectric material. Various attempts were undertaken to neutralise the charging problems. Further investigation revealed that sputtered Zinc Oxide (ZnO) is a suitable material for attaching SAW devices on irregularly shaped material. DC sputtering was used and several parameters have been optimised to achieve the desired piezoelectric effect. ZnO was sputtered using a magnetron sputtering system with a 75 mm Zn target and a DC sputter power of 250 Watts. Several trials were performed and an optimised material has been prepared under the following conditions: 9 sccm of Oxygen and 6 sccm of Argon were introduced during the process which resulted in a process pressure of 1.2x10⁻² mbar. The coatings have been characterised using Rutherford Backscattering, X-ray diffraction, SEM imaging, and Atomic force microscopy. SAW devices were fabricated and tested on 600 nm thick sputtered ZnO on a Si substrate with a working frequency of 430 MHz. The phase velocity has been calculated as 4300m/s. Non-planar samples have been coated with 500 nm of sputtered ZnO and SAW structures have been fabricated on using EBL. The design frequency is 2450 MHz, with a calculated feature size of 1 µm. The surface roughness however prevented a successful lift-off. AFM imaging confirmed a surface roughness in the order of 20 nm. Ways to improve manufacturability on these samples have been identified.
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Schuler, Leo P. "Wireless identification and sensing using surface acoustic wave devices." Thesis, University of Canterbury. Engineering, 2003. http://hdl.handle.net/10092/8565.
Full textAbstract:
Wireless Surface Acoustic Wave (SAW) devices were fabricated and tested using planar Lithium Niobate (LiNbO₃) as substrate. The working frequencies were in the 180 MHz and 360 MHz range. Using a network analyser, the devices were interrogated with a wireless range of more than 2 metres. Trials with Electron Beam Lithography (EBL) to fabricate SAW devices working in the 2450 MHz with a calculated feature size of 350 nm are discussed. Charging problems became evident as LiNbO₃ is a strong piezoelectric and pyroelectric material. Various attempts were undertaken to neutralise the charging problems.
Further investigation revealed that sputtered Zinc Oxide (ZnO) is a suitable material for attaching SAW devices on irregularly shaped material. DC sputtering was used and several parameters have been optimised to achieve the desired piezoelectric effect.
ZnO was sputtered using a magnetron sputtering system with a 75 mm Zn target and a DC sputter power of 250 Watts. Several trials were performed and an optimised material has been prepared under the following conditions: 9 sccm of Oxygen and 6 seem of Argon were introduced during the process which resulted in a process pressure of 1.2x10⁻² mbar. The coatings have been characterised using Rutherford Backscattering, X-ray diffraction, SEM imaging, and Atomic force microscopy. SAW devices were fabricated and tested on 600 nm thick sputtered ZnO on a Si substrate with a working frequency of 430 MHz. The phase velocity has been calculated as 4300m/s.
Non-planar samples have been coated with 500 nm of sputtered ZnO and SAW structures have been fabricated on using BBL. The design frequency is 2450 MHz, with a calculated feature size of 1 μm. The surface roughness however prevented a successful lift-off. AFM imaging confirmed a surface roughness in the order of 20 nm. Ways to improve manufacturability on these samples have been identified.
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Radzicki, Vincent, and Koki Matsuura. "Passive Acoustic Sensing for the Assessment of Knee Conditions." International Foundation for Telemetering, 2015. http://hdl.handle.net/10150/596462.
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ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NVEarly detection and diagnosis of knee related health disease is critical in mitigating the long term health risks of such ailments. Passive acoustic sensing is an under-utilized monitoring system that can be used in the assessment and potential diagnosis of knee health that has many potential benefits when compared to current medical technology. Developing accurate acoustic models and procedures for analyzing acoustic sensor data in these applications is of great importance. This paper presents the design and development of passive acoustic sensing system for characterizing knees along with data analysis techniques towards this end.
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Maillard, Julien. "Advanced Time Domain Sensing For Active Structural Acoustic Control." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30335.
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Active control of sound radiation from vibrating structures has been an area of much research in the past decade. In Active Structural Acoustic Control (ASAC), the minimization of sound radiation is achieved by modifying the response of the structure through structural inputs rather than by exciting the acoustic medium (Active Noise Control, ANC). The ASAC technique often produces global far-field sound attenuation with relatively few actuators as compared to ANC. The structural control inputs of ASAC systems are usually constructed adaptively in the time domain based on a number of error signals to be minimized. One of the primary concerns in active control of sound is then to provide the controller with appropriate ``error'' information. Early investigations have implemented far-field microphones, thereby providing the controller with actual radiated pressure information. Most structure-borne sound control approaches now tend to eliminate the use of microphones by developing sensors that are integrated in the structure. This study presents a new sensing technique implementing such an approach. A structural acoustic sensor is developed for estimating radiation information from vibrating structures. This technique referred to as Discrete Structural Acoustic Sensing (DSAS) provides time domain estimates of the radiated sound pressure at prescribed locations in the far field over a broad frequency range. The structural acoustic sensor consists of a set of accelerometers mounted on the radiating structure and arrays of digital filters that process the measured acceleration signals in real time. The impulse response of each filter is constructed from the appropriate radiation Green's function for the source area associated with each accelerometer.
Validation of the sensing technique is performed on two different systems: a baffled rectangular plate and a baffled finite cylinder. For both systems, the sensor is first analyzed in terms of prediction accuracy by comparing estimated and actual sound pressure radiated in the far field. The analysis is carried out on a numerical model of the plate and cylinder as well as on the real structures through experimental testing. The sensor is then implemented in a broadband radiation control system. The plate and cylinder are excited by broadband disturbance inputs over a frequency range encompassing several of the first flexural resonances of the structure. Single-sided piezo-electric actuators provide the structural control inputs while the sensor estimates are used as error signals. The controller is based on the filtered-x version of the adaptive LMS algorithm. Results from both analytical and experimental investigations are again presented for the two systems. Additional control results based on error microphones allow a comparison of the two sensing approaches in terms of control performance.
The major outcome of this study is the ability of the structural acoustic sensor to effectively replace error microphones in broadband radiation control systems. In particular, both analytical and experimental results show the level of sound attenuation achieved when implementing Discrete Structural Acoustic Sensing rivaled that achieved with far-field error microphones. Finally, the approach presents a significant alternative over other existing structural sensing techniques as it requires very little system modeling.Ph. D.
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Ferreira, Ricardo Xavier da Graça. "Acoustic optical modulation in optical fibre for sensing applications." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11646.
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Mestrado em Engenharia FísicaO presente trabalho teve como objetivo desenvolver um sensor de fibra óptica intrínseco para viscosidade com base no efeito acústoótico aplicado em redes de Bragg. Foram utilizadas fibras de silica e poliméricas para medições com baseadas no espectro e no tempo de resposta da rede quanto sujeitas ao efeito acústo-ótico. O resultado é um viscosímetro multi-paramétrico com um distinto potencial futuro. Com base no conhecimento adquirido, é proposto um novo design e mecanismo de detecção.
The present work aimed to develop an intrinsic optical fibre sensor for viscosity based on the acousto-optic effect applied into fibre Bragg grating. Polymer and silica optical fibres were employed for measurements based on the spectra and the grating response times when subjected to the acousto-optic effect. The results is a multi-parameter viscometer with a distinctive future potential. Based on the knowledge acquired, a new design and sensing mechanism is advanced.
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Srinivasan, Krishnan. "Nanomaterial Sensing Layer Based Surface Acoustic Wave Hydrogen Sensors." Scholar Commons, 2005. https://scholarcommons.usf.edu/etd/873.
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This thesis addresses the design and use of suitable nanomaterials and surface acoustic wave sensors for hydrogen detection and sensing.
Nanotechnology is aimed at design and synthesis of novel nanoscale materials. These materials could find uses in the design of optical, biomedical and electronic devices. One such example of a nanoscale biological system is a virus. Viruses have been given a lot of attention for assembly of nanoelectronic materials. The tobacco mosaic virus (TMV) used in this research represents an inexpensive and renewable biotemplate that can be easily functionalized for the synthesis of nanomaterials. Strains of this virus have been previously coated with metals, silica or semiconductor materials with potential applications in the assembly of nanostructures and nanoelectronic circuits. Carbon nanotubes are another set of well-characterized nanoscale materials which have been widely investigated to put their physical and chemical properties to use in design of transistors, gas sensors, hydrogen storage cells, etc. Palladium is a well-known material for detection of hydrogen. The processes of absorption and desorption are known to be reversible and are known to produce changes in density, elastic properties and conductivity of the film. Despite these advantages, palladium films are known to suffer from problems of peeling and cracking in hydrogen sensor applications. They are also required to be cycled for a few times with hydrogen before they give reproducible responses.
The work presented in this thesis, takes concepts from previous hydrogen sensing techniques and applies them to two nanoengineered particles (Pd coated TMV and Pd coated SWNTs) as SAW resonator sensing materials. Possible sensing enhancements to be gained by using these nanomaterial sensing layers are investigated. SAW resonators were coated with these two different nano-structured sensing layers (Pd-TMV and Pd-SWNT) which produced differently useful hydrogen sensor responses. The Pd-TMV coated resonator responded to hydrogen with nearly constant increases in frequency as compared to the Pd-SWNT coated device, which responded with concentration-dependent decreases in frequency of greater magnitude upon hydrogen exposure. The former behavior is more associated with acousto-electric phenomena in SAW devices and the later with mass loading. The 99% response times were 30-40 seconds for the Pd-TMV sensing layer and approximately 150 seconds for the Pd-SWNT layer. Both the films showed high robustness and reversibility at room temperature. When the Pd film was exposed to hydrogen it was observed that it produced decreases in frequency to hydrogen challenges, conforming to mass loading effect. It was also observed that the Pd film started degrading with repeated exposure to hydrogen, with shifts after each exposure going smaller and smaller.
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Hole, Erik Lillebø. "Optical Fiber sensing of acoustic waves using overlapping FBGs." Thesis, Mittuniversitetet, Institutionen för elektronikkonstruktion, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-37779.
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The objective of this thesis was to investigate if an optical fiber sensing method with the use of two overlapping fiber Bragg gratings to measure Lamb wave $S_0$ modes in a steel plate, and how it would compare to traditional PZT transducers. A solution was proposed where the use of an optical fiber sensing system was built and took advantage of the strain dependence of a fiber Bragg grating mounted to a steel plate. Together with an overlapping reference fiber Bragg grating, the system can translate strain to light intensity. A method of controlling the Bragg wavelength of the reference fiber Bragg grating to optimize the overlap between the two fiber Bragg gratings, enabling the system to compensate for drift in the sensing fiber Bragg grating. Testing of the system was performed and yielded promising results, being able to measure the Lamb wave signal from the steel plate. The system showed some sensitivity limitations and signal to noise ratio, as well as the software created to compensate for the drift. With the improvement proposed for further work with the system in terms of improving the system's sensitivity, signal to noise ratio and drift control should make the system able to perform at levels as traditional PZT transducers.
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Wimmer, Jason D. "Acoustic sensing: Roles and applications in monitoring avian biodiversity." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/84852/9/Jason_Wimmer_Thesis.pdf.
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This thesis examined the use of acoustic sensors for monitoring avian biodiversity. Acoustic sensors have the potential to significantly increase the spatial and temporal scale of ecological observations, however acoustic recordings of the environment can be opaque and complex. This thesis developed methods for analysing large volumes of acoustic data to maximise the detection of bird species, and compared the results of acoustic sensor biodiversity surveys with traditional bird survey techniques.
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Read, Tom Oliver Trevett. "Applications of distributed temperature sensing in subsurface hydrology." Thesis, University of East Anglia, 2016. https://ueaeprints.uea.ac.uk/59401/.
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In the study of dynamic subsurface processes there is a need to monitor temperature and groundwater fluxes efficiently in both time and space. Distributed Temperature Sensing has recently become more accessible to researchers in Earth Sciences, and allows temperatures to be measured simultaneously, at small intervals, and over large distances along fibre optic cables. The capability of DTS in conjunction with heat injection to detect groundwater fluxes, is assessed in this thesis using a combination of numerical modelling, laboratory tests, and field trials at the Ploemeur research site in Brittany, France. In particular, three methodological approaches are developed: thermal dilution tests, point heating, and the hybrid cable method. A numerical model was developed to assess the sensitivity range of thermal dilution tests to groundwater flow. Thermal dilution tests undertaken at Ploemeur showed lithological contrasts, and allowed the apparent thermal conductivity to be estimated in-situ, but failed to detect previously identified transmissive fractures. The use of DTS to monitor in-well vertical flow is then investigated. This is first using a simple experiment deploying point heating (T-POT), which tracks a parcel of heated water vertically through the borehole. The method allowed for the relatively quick estimation of velocities in the well. The use of heated fibre optics is then trialled, and through a field test was shown to be sensitive to in-well vertical flow. However, the data suffered from a number of artefacts related to the cable installation. To address this, a hybrid cable system was deployed in a flume to determine the sensitivity relationship with flow angle and electrical power input. Additionally, a numerical model was developed, which suggested a lower limit for velocity estimation due to thermal buoyancy. With the emergence of Distributed Acoustic Sensing, fibre optics may become an increasingly practicable and complete solution for monitoring subsurface processes.
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Li, Xiaowei. "A weighted ℓ₁-minimization for distributed compressive sensing." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54836.
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Distributed Compressive Sensing (DCS) studies the recovery of jointly sparse signals. Compared to separate recovery, the joint recovery algorithms in DCS are usually more effective as they make use of the joint sparsity. In this thesis, we study a weighted ℓ₁-minimization algorithm for the joint sparsity model JSM-1 proposed by Baron et al. Our analysis gives a sufficient null space property for the joint sparse recovery. Furthermore, this property can be extended to stable and robust settings. We also presents some numerical experiments for this algorithm.Science, Faculty of
Mathematics, Department of
Graduate
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Mohamad, Hisham. "Distributed optical fibre strain sensing of geotechnical structures." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612416.
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Liu, Bo. "Sapphire Fiber-based Distributed High-temperature Sensing System." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/82741.
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From the monitoring of deep ocean conditions to the imaging and exploration of the vast universe, optical sensors are playing a unique, critical role in all areas of scientific research. Optical fiber sensors, in particular, are not only widely used in daily life such as for medical inspection, structural health monitoring, and environmental surveillance, but also in high-tech, high-security applications such as missile guidance or monitoring of aircraft engines and structures. Measurements of physical parameters are required in harsh environments including high pressure, high temperature, highly electromagnetically-active and corrosive conditions. A typical example is fossil fuel-based power plants. Unfortunately, current optical fiber sensors for high-temperature monitoring can work only for single point measurement, as traditional fully-distributed temperature sensing techniques are restricted for temperatures below 800°C due to the limitation of the fragile character of silica fiber under high temperature.
In this research, a first-of-its-kind technology was developed which pushed the limits of fully distributed temperature sensing (DTS) in harsh environments by exploring the feasibility of DTS in optical sapphire waveguides. An all sapphire fiber-based Raman DTS system was demonstrated in a 3-meters long sapphire fiber up to a temperature of 1400°C with a spatial resolution of 16.4cm and a standard deviation of a few degrees Celsius.
In this dissertation, the design, fabrication, and testing of the sapphire fiber-based Raman DTS system are discussed in detail. The plan and direction for future work are also suggested with an aim for commercialization.Ph. D.
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Xu, Yong Tai Yu-Chong. "Flexible MEMS skin technology for distributed fluidic sensing /." Diss., Pasadena, Calif. : California Institute of Technology, 2002. http://resolver.caltech.edu/CaltechETD:etd-12302004-144248.
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Chakraborty, Rupayan. "Acoustic event detection and localization using distributed microphone arrays." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/134364.
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Automatic acoustic scene analysis is a complex task that involves several functionalities: detection (time), localization (space), separation, recognition, etc. This thesis focuses on both acoustic event detection (AED) and acoustic source localization (ASL), when several sources may be simultaneously present in a room. In particular, the experimentation work is carried out with a meeting-room scenario. Unlike previous works that either employed models of all possible sound combinations or additionally used video signals, in this thesis, the time overlapping sound problem is tackled by exploiting the signal diversity that results from the usage of multiple microphone array beamformers.
The core of this thesis work is a rather computationally efficient approach that consists of three processing stages. In the first, a set of (null) steering beamformers is used to carry out diverse partial signal separations, by using multiple arbitrarily located linear microphone arrays, each of them composed of a small number of microphones. In the second stage, each of the beamformer output goes through a classification step, which uses models for all the targeted sound classes (HMM-GMM, in the experiments). Then, in a third stage, the classifier scores, either being intra- or inter-array, are combined using a probabilistic criterion (like MAP) or a machine learning fusion technique (fuzzy integral (FI), in the experiments).
The above-mentioned processing scheme is applied in this thesis to a set of complexity-increasing problems, which are defined by the assumptions made regarding identities (plus time endpoints) and/or positions of sounds. In fact, the thesis report starts with the problem of unambiguously mapping the identities to the positions, continues with AED (positions assumed) and ASL (identities assumed), and ends with the integration of AED and ASL in a single system, which does not need any assumption about identities or positions.
The evaluation experiments are carried out in a meeting-room scenario, where two sources are temporally overlapped; one of them is always speech and the other is an acoustic event from a pre-defined set. Two different databases are used, one that is produced by merging signals actually recorded in the UPC¿s department smart-room, and the other consists of overlapping sound signals directly recorded in the same room and in a rather spontaneous way. From the experimental results with a single array, it can be observed that the proposed detection system performs better than either the model based system or a blind source separation based system. Moreover, the product rule based combination and the FI based fusion of the scores resulting from the multiple arrays improve the accuracies further. On the other hand, the posterior position assignment is performed with a very small error rate.
Regarding ASL and assuming an accurate AED system output, the 1-source localization performance of the proposed system is slightly better than that of the widely-used SRP-PHAT system, working in an event-based mode, and it even performs significantly better than the latter one in the more complex 2-source scenario. Finally, though the joint system suffers from a slight degradation in terms of classification accuracy with respect to the case where the source positions are known, it shows the advantage of carrying out the two tasks, recognition and localization, with a single system, and it allows the inclusion of information about the prior probabilities of the source positions. It is worth noticing also that, although the acoustic scenario used for experimentation is rather limited, the approach and its formalism were developed for a general case, where the number and identities of sources are not constrained.
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Egger, Sean Robert. "A Turbo Approach to Distributed Acoustic Detection and Estimation." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/35866.
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Networked, multi-sensor array systems have proven to be advantageous in the
sensor world. A large amount of research has been conducted with these systems, with a
main interest in data fusion. Intelligently processing the large amounts of data collected
by these systems is required in order to fully utilize the benefits of a multi-sensor array
system. A robust but flexible simulation environment would provide a platform for
accurately comparing current and future data fusion theories.
This thesis proposes a simulator model for testing fusion theories for these acoustic
multi-sensor networks. An iterative, lossless data fusion algorithm was presented as the
model for simulation development. The arrangement and orientation of objects in the
simulation environment, as well as most other system parameters are defined by the user
before the simulation runs. The sensor data, including noise, is generated at the
appropriate time delay and propagation loss before being processed by a delay and sum
beamformer and a matched filter. The resulting range-Doppler maps are modified to
probability density functions, and translated to a single point of reference. The data is
then combined into a single world model.
An iterative process is used to filter out false targets and amplify true target
detections. Data is fused from each multi-sensor array and from each simulation run.
Target amplitudes are gained if they are present in all combined world models, and are
otherwise reduced. This thesis presents the results of the fusion algorithm used, including
multiple iterations, to prove the algorithms effectiveness.Master of Science
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Wang, Jing. "Distributed Pressure and Temperature Sensing Based on Stimulated Brillouin Scattering." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/78066.
Full textAbstract:
Brillouin scattering has been verified to be an effective mechanism in temperature and strain sensing. This kind of sensors can be applied to civil structural monitoring of pipelines, railroads, and other industries for disaster prevention. This thesis first presents a novel fiber sensing scheme for long-span fully-distributed pressure measurement based on Brillouin scattering in a side-hole fiber. After that, it demonstrates that Brillouin frequency keeps linear relation with temperature up to 1000°C; Brillouin scattering is a promising mechanism in high temperature distributed sensing.
A side-hole fiber has two longitudinal air holes in the fiber cladding. When a pressure is applied on the fiber, the two principal axes of the fiber birefringence yield different Brillouin frequency shifts in the Brillouin scattering. The differential Brillouin scattering continuously along the fiber thus permits distributed pressure measurement. Our sensor system was designed to analyze the Brillouin scattering in the two principal axes of a side-hole fiber in time domain. The developed system was tested under pressure from 0 to 10,000 psi for 100m and 600m side-hole fibers, respectively. Experimental results show fibers with side holes of different sizes possess different pressure sensitivities. The highest sensitivity of the measured pressure induced differential Brillouin frequency shift is 0.0012MHz/psi. The demonstrated spatial resolution is 2m, which maybe further improved by using shorter light pulses.Master of Science