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1
Kodati, Parasar. "Biomimetic micro underwater vehicle with ostraciiform locomotion system design, analysis and experiments /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 139 p, 2006. http://proquest.umi.com/pqdweb?did=1203586131&sid=7&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Повний текст джерела
2
Farren, Maureen A. "Some experiments with underwater acoustic returns from cylinders relative to object identification for AUV operation/." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23398.
Повний текст джерелаАнотація:
Approved for public release; distribution is unlimitedUnderwater Vehicles, Sonar Sound Analyzers, Underwater Navigation, Acoustics, Anechoic Chambers, Cylindrical Bodies, Data Storage Systems, Delay, Electroacoustic Transducers, Estimates, Experimental Data, Geometric Forms, Identification, Images, Position Location, Propagation, Sonar, Surface Properties, Target Strength, Theses, Time Intervals, Underwater, Underwater Equipment
3
Phaneuf, Matthew D. "Experiments with the REMUS AUV." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FPhaneuf.pdf.
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4
Tucker, Simon. "An ecological approach to the classification of transient underwater acoustic events : perceptual experiments and auditory models." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401126.
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5
Connor, Russya. "The poetics of gravity: Performance experiments from the natural environment to the stage." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2014. https://ro.ecu.edu.au/theses/1561.
Повний текст джерелаАнотація:
Gravity understood scientifically is normally accepted as a dictate, however when encountered creatively, the possibilities for playing with and learning from gravity in natural environments are plentiful.
This practice-led research explores gravity in both artistic and functional contexts. Two nature-specific sports (ocean diving and rock-climbing) and then later, aerial silk work, acted as springboards for explorations of creative expression derived from the states of submersion and suspension. To ‘really feel’ gravity, I decided to explore its effects and impressions, physically and emotionally, in environments that draw attention to its presence. Attempts were made to capture gravity in a series of poetic and performative artefacts, performed in their respective environments; the research culminated in a final performance, Sea Inside in a classical theatre setting. The management of gravity is fundamental in all movement, thus, understanding gravity’s psychophysiological aspects can extend the parameters of performance. Locating physicality underwater and in the air provokes a deep sense of falling and sinking into being and allows both body and mind to access a stiller place of being. Discoveries in natural environment laboratories led to an appreciation of embodied inner verticality and new perceptions about aptitudes for states of flow and “being-in-the-world” (Heidegger, 1976). Submitting to and tuning into kinaesthetic experiences through relations with gravity generated feelings of being enwrapped in the environment, and cultivated a rapport with the myriad landscapes; that are geographical, psychological or metaphorical of Landschaft.
Embodied outdoor experimentation led to the realisation of the significance of applying an ecological lens to investigate my affinity to gravity. I explored when the performer’s body learns to incorporate unconventional experiences like being underwater or up in the air, finding therein emergent opportunities for artistic expression. These possibilities have the potential to impact conventions of training/awareness and thus translation to performance/articulation.
This thesis contextualises the larger project that is my relationship with gravity which includes the often imperceptible poetic aspects of our environment. Additionally this research wrestles with the tension of theatre and ecology but makes no attempt to solve this problem, rather touches on how the arts, in particular performance modes, may contribute to a dialogue on ecological awareness.
6
Becker, Kyle M. "Geoacoustic inversion in laterally varying shallow-water experiments using high-resolution wavenumber estimation." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/29056.
Повний текст джерелаАнотація:
Thesis (Ph. D. in Applied Ocean Sciences)--Joint Program in Applied Ocean Physics and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), February 2002.Includes bibliographical references (leaves 161-170).
Sound propagation in shallow water is highly dependent on the interaction of the sound field with the bottom. In order to fully understand this problem, it is necessary to obtain reliable estimates of bottom geoacoustic properties that can be used in acoustic propagation codes. In this thesis, perturbative inversion methods and exact inverse methods are discussed as a means for inferring geoacoustic properties of the bottom. For each of these methods, the input data to the inversion is the horizontal wavenumber spectrum of a point-source acoustic field. The main thrust of the thesis work concerns extracting horizontal wavenumber content for fully three-dimensionally varying waveguide environments. In this context, a high-resolution autoregressive (AR) spectral estimator was applied to determine wavenumber content for short aperture data. As part of this work, the AR estimator was examined for its ability to detect discrete wavenumbers in the presence of noise and also to resolve closely spaced wavenumbers for short aperture data. As part of a geoacoustic inversion workshop, the estimator was applied to extract horizontal wavenumber content for synthetic pressure field data with range-varying geoacoustic properties in the sediment. The resulting wavenumber content was used as input data to a perturbative inverse algorithm to determine the sound speed profile in the sediment. It was shown using the high-resolution wavenumber estimator that both the shape and location of the range-variability in the sediment could be determined.
(cont.) The estimator was also applied to determine wavenumbers for synthetic data where the water column sound speed contained temporal variations due to the presence of internal waves. It was shown that reliable estimates of horizontal wavenumbers could be obtained that are consistent with the boundary conditions of the waveguide. The Modal Mapping Experiment (MOMAX), an experimental method for measuring the full spatial variability of a propagating sound field and its corresponding modal content in two-dimensions, is also discussed. The AR estimator is applied to extract modal content from the real data and interpreted with respect to source/receiver motion and geometry. For a moving source, it is shown that the wavenumber content is Doppler shifted. A method is then described that allows the direct measure of modal group velocities from Doppler shifted wavenumber spectra. Finally, numerical studies are presented addressing the practical issues associated with using MOMAX type data in the exact inversion method of Gelfand-Levitan.
by Kyle M. Becker.
Ph.D.
7
Louédec, Morgan. "Guaranteed ellipsoidal numerical method for the stability analysis of the formation control of a group of underwater robots." Electronic Thesis or Diss., Brest, École nationale supérieure de techniques avancées Bretagne, 2024. http://www.theses.fr/2024ENTA0007.
Повний текст джерелаАнотація:
Pour développer les activités marines humaines, des groupes de robots sous-marins peuvent automatiser certaines tâches. Ces robots étant difficiles à localiser en raison de contraintes sous-marines, ils doivent se déplacer en formation pour être fiables. Bien que plusieurs contrôleurs théoriques aient été proposés pour faire face à ces contraintes, ils doivent encore s’adapter à des contraintes plus complexes et être testés sur des systèmes réels. Comme pour tout système autonome, la stabilité de la formation doit être vérifiée par une preuve mathématique. Cependant, la complexité de ces systèmes non linéaires rend la méthode de Lyapunov conventionnelle difficile à utiliser. Ainsi, l’objectif principal de cette thèse est de développer des méthodes numériques garanties, basées sur l’arithmétique des intervalles, qui peuvent assister la preuve de stabilité. Basée sur la propagation garantie ellipsoïdale, une première méthode est conçue pour les systèmes à temps discret afin de calculer un domaine d’attraction ellipsoïdal. Cette méthode est ensuite étendue aux systèmes à temps continu, puis aux systèmes hybrides synchrones, qui sont des modélisations plus réalistes. En outre, la propagation ellipsoïdale est étendue pour prendre en compte les applications singulières et les ellipsoïdes dégénérées. Enfin, des test de formation en situation réelle viennent illustrer la stabilitéIn the development of human marine activity, groups of underwater robots can automate certain tasks. Since these robots are difficult to localise because of the underwater constrains, they must move in formation to be reliable. While various theoretical controllers have been proposed to challenge these constrains, they still need to consider more complex constrains and to be tested on real systems. As for every autonomous system, the stability of the formation must be verified by a mathematical proof. However, the complexity of these nonlinear systems makes conventional Lyapunov method difficult to use. Thus, this thesis’ main objective is to develop guaranteed numerical methods, based on interval arithmetic, that can assist the stability proof. Based on ellipsoidal guaranteed propagation, a first method is designed for discrete time systems to compute an ellipsoidal domain of attraction. This method is then extended to continuous-time systems and then to synchronous hybrid systems which are more realistic modellings. In addition, the ellipsoidal propagation is extended to consider singular mappings and degenerate ellipsoids. Finally, some real world underwater formation control was achieved to illustrate the stability
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Real, Gaultier. "An ultrasonic testbench for reproducing the degradation of sonar performance in fluctuating ocean." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4753/document.
Повний текст джерелаАнотація:
Le milieu océanique est sujet à de nombreuses sources de fluctuations. Les plus importantes sont les ondes internes, très fréquentes et entrainant des fluctuations de la distribution spatiale du champ de célérité du son. En raison de la longue période de ces phénomènes comparée au temps de propagation des ondes acoustiques pour des applications sonar, le processus peut être considéré figé dans le temps pour chaque réalisation stochastique du milieu. Le développement de bancs d’essais permettant de reproduire les effets de la turbulence atmosphérique a permis des avancées considérables dans le domaine de l’optique adaptative. Nous voyons donc un fort intérêt dans la possibilité de reproduire les effets des ondes internes sur la propagation du son en environnement contrôlé. Un protocole expérimental dans une cuve d’eau est proposé: une onde ultrasonore est transmise à travers une lentille acoustique aléatoirement rugueuse, ce qui produit des distorsions du front d’onde reçu. Les fluctuations des signaux reçus sont contrôlées en modifiant les paramètres statistiques de rugosité de la lentille. Ces paramètres sont reliés à l’analyse dimensionnelle permettant de classifier les configurations étudiées selon des régimes de fluctuations et de prédire les moments statistiques du champ acoustique jusqu’à l’ordre quatre. Une excellente correspondance est observée entre notre protocole expérimental et des résultats théoriques et numériques.La dégradation des performances des techniques de détection classiques appliquées à nos données expérimentales souligne le besoin de techniques correctives. Un état de l’art des techniques existantes dans divers domaines est proposéThe ocean medium is subject to many sources of fluctuations. The most critical ones were found to be internal waves, occurring frequently and inducing fluctuations of the spatial distribution of the sound speed field. Because of the fairly long period of this phenomenon as compared to the propagation time of acoustic waves for sonar applications, the process can be considered frozen in time for each stochastic realization of the medium. The development of testbenches allowing to reproduce the effect of atmospheric turbulence on optic waves propagation under laboratory conditions lead to considerable advancements in the field of adaptive optics. We therefore see a vivid interest in being able to reproduce the effects of internal waves on sound propagation in controlled environments. An experimental protocol in a water tank is proposed: an ultrasonic wave is transmitted through a randomly rough acoustic lens, producing distortions of the received wavefront. The induced signal fluctuations are controlled by tuning the statistical parameters of the roughness of the lens. Especially, they are linked to dimensional parameters allowing to classify the configurations into regimes of fluctuations and to predict the statistical moment of the acoustic pressure up to the fourth order. A remarkable relevance of our experimental scheme is found when compared to theoretical and simulation results. The degradation of classical signal processing techniques when applied to our acquired data highlights the need for corrective detection techniques. A review of the existing techniques in other domains is proposed
9
Smith, Donald F. "Acoustic modeling of the Monterey Bay tomography experiment." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA242658.
Повний текст джерелаАнотація:
Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, December 1990.Thesis Advisor(s): MIller, James H. ; Chiu, Ching-Sang. "December 1990." Description based on title screen as viewed on April 2, 2010. DTIC Identifier(s): Sound transmission, underwater sound, sea water, bathymetry, ray tracing, mathematical models, HARPO computer program, underwater acoustics, wave propagation, Monterey Bay (California), bays, California, shallow water, acoustic tomography, three dimensional, continental shelves, acoustic velocity, theses. Author(s) subject terms: Acoustic tomography, acoustic modeling, eigenrays, Monterey Bay. Includes bibliographical references (p. 57-58). Also available in print.
10
Morin, Russell Walter. "A Novel Localization System for Experimental Autonomous Underwater Vehicles." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-theses/233.
Повний текст джерелаАнотація:
Localization is a classic and complex problem in the field of mobile robotics. It becomes particularly challenging in an aqueous environment because currents within the water can move the robot. A novel localization module and corresponding localization algorithm for experimental autonomous underwater vehicles is presented. Unlike other available positioning systems which require fixed hardware beacons, this custom built module relies only on information available from sensors on-board the vehicle and knowledge of its bounded domain. This allows the user to save valuable time which would otherwise be devoted to the setup and calibration of a beacon or sensor network. The module uses three orthogonal ultrasonic transducers to measure distances to the tank boundaries. Using the measured tri-axial orientation of the vehicle, the algorithm analytically determines the robot's position within the domain in absolute coordinates. Certain vehicle states do not allow the position to be completely resolved by the algorithm alone. In this case, state estimation is used to estimate the robot position until its state is no longer indeterminate. The modular design of this system makes it ideal for application on underwater vehicles which operate in a bounded environment for research purposes. An experimental version of the module was constructed and tested in the WPI swimming pool and showed successful localization under normal conditions.
11
Abrahamson, Scott. "Automated psycho-acoustic experimental station." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/19566.
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Hartfield, Grant I. "Link-layer and network-layer performance of an undersea acoustic network at Fleet Battle Experiment-India." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FHartfield.pdf.
Повний текст джерелаАнотація:
Thesis (M.S. in Information Systems and Operations)--Naval Postgraduate School, June 2003.Thesis advisor(s): Joseph A. Rice, Dan C. Boger. Includes bibliographical references (p. 35). Also available online.
13
Petrich, Jan. "Improved Guidance, Navigation, and Control for Autonomous Underwater Vehicles: Theory and Experiment." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/27222.
Повний текст джерелаАнотація:
This dissertation addresses attitude control and inertial navigation of autonomous underwater vehicles (AUVs). We present theoretical justification for using simplified models, derive system identification algorithms, and verify our results through extensive field trials. Although this research focuses on small AUVs with limited instrumentation, the results are useful for underwater vehicles of any size.
For attitude control of aircraft systems, second-order equivalent pitch-axis models are common and extensively studied. However, similar analysis has not been performed for the pitch-axis motion of underwater vehicles. In this dissertation, we study the utility and the limitations of second-order approximate models for AUVs. We seek to improve the flight performance and shorten the time required to re-design a control algorithm when the shape, mass-distribution, and/or net buoyancy of an AUV/payload configuration changes.
In comparison to commonly implemented AUV attitude controllers, which neglect roll motion and address pitch and yaw dynamics separately, we derive a novel linear time-varying model that explicitly displays the coupling between pitch and yaw motion due to nonzero roll angle and/or roll rate. The model facilitates an Hâ control design approach that explicitly addresses robustness against those coupling terms and significantly reduces the effect of pitch and yaw coupling.
To improve AUV navigation, we investigate algorithms for calibrating a triaxial gyroscope using angular orientation measurements and formally define AUV trajectories that are persistently exciting and for which the calibration coefficients are uniformly observable. To improve AUV guidance, we propose a near real-time ocean current identification method that estimates a non-uniform flow-field using only sparse flow measurements.Ph. D.
14
McCarter, Brian Raymond. "Experimental Evaluation of Viscous Hydrodynamic Force Models for Autonomous Underwater Vehicles." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/50445.
Повний текст джерелаАнотація:
A comparison of viscous hydrodynamic force models is presented, with application on an autonomous underwater vehicle (AUV). The models considered here are \emph{quasi-steady}, meaning that force is expressed as a function of instantaneous vehicle state. This is in contrast to physical reality, where the force applied to a rigid body moving through a viscous fluid is history-dependent. As a result, the comparison of models is restricted to how well they are able to recreate a force history, rather than how closely they represent the underlying physics. Of the models under consideration, no single model performs significantly better than the others, but several perform worse.
Each viscous hydrodynamic force model presented here is expressed as a linear combination of basis functions, which are nonlinear functions of body-relative velocity. The greater dynamical model is presented in a rigid-body framework with six degrees of freedom, with terms which account for inviscid fluid flow, restoring forces due to gravity, and control forces due to actuator motion. The models are selected from several that have been proposed in the literature, which include empirically-derived and physics-based models. Some models assume that the relationship between force and velocity is fundamentally linear or quadratic in nature, or make assumptions about coupled motion. The models are compared by their relative complexities, and also by their ability to reproduce data sets generated from field experiments. The complete dynamical equations are presented for each model, including coefficients suitable for use with the Virginia Tech 690 AUV.Master of Science
15
McCall, George Samuel II. "An experimental apparatus for measuring underwater acoustic scattering from complex finite cylindrical shells." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17667.
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16
Calderon, Antonino M. "An experimental driving mechanism for a rigid oscillating foil propeller." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ62374.pdf.
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17
Sfakiotakis, Michael. "Development and evaluation of an experimental undulating-fin device using the parallel bellows actuator." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/522.
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Anastasiadis, Kosmas. "The development of an experimental system for insertion loss measurements using a truncated, transient parametric array operating in a wide bore tube." Thesis, University of Bath, 1990. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278264.
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Kapodistrias, Georgios. "A theoretical and experimental study on multiple scattering from bubbles, with emphasis on scattering from a bubble located close to the air-sea interface /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/7150.
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20
Heinemann, Michael Gerhard. "Experimental studies of applications of time-reversal acoustics to non-coherent underwater communications." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/.
Повний текст джерелаАнотація:
Thesis (M.S. in Engineering Acoustics and M.S. in Applied Physics) Naval Postgraduate School, March 2000.Thesis advisor(s): Larraza, Andrès ; Smith, Kevin B. "March 2000." Includes bibliographical references (p. 59-60). Also available online.
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Gray, Michael Dean. "An experimental investigation of the anomalous behavior of underwater acoustic volume displacement sensors." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16796.
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Meinecke, Torsten Volker. "Experimental study of underwater laser cutting of steel with a view on subsea decommissioning." Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=196283.
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23
Ferris, Emma Grace. "A computational and experimental study of the underwater implosion of single and multiple metallic spherical shells." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/111762.
Повний текст джерелаАнотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 103-104).
Analysis of the implosion of pressure vessels in a deep-water environment is an important research area for the ocean engineering community. The majority of previous implosion research focused on the implosion of metallic cylinders, while the implosion behavior of volumes of different geometries and materials is less well researched. The behavior of pressure pulses resulting from the implosion of multiple pressure vessels is also less well researched. This thesis addresses these questions by investigating the implosion behavior of single and multiple spherical shells. Over the course of this research, I designed and predicted the collapse depth of metallic spherical volumes using shell buckling theory, then used a computational tool to model several implosion scenarios of both single and multiple sphere configurations. I then conducted implosion tests of single and multiple spherical shell configurations. The results from the initial computational models were compared with results of experimental tests and used to develop updated computational models that more accurately represented the true geometry of the test articles. Based on the analysis of the results of initial computational models and the experimental results, and the correlation between the updated computational models and experimental results, I identified ways to more accurately model scenarios involving implosions of spherical shells. In addition, I analyzed the behavior of a sympathetic implosion event involving two spherical shells and compared the result of the sympathetic implosion event to that of a single equivalent volume. This thesis concludes with guidance for future modeling and experimental testing efforts.
by Emma Grace Ferris.
S.M.
24
Ferris, Emma Grace. "A computational and experimental study of the underwater implosion of single and multiple metallic spherical shells." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111762.
Повний текст джерелаАнотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 103-104).
Analysis of the implosion of pressure vessels in a deep-water environment is an important research area for the ocean engineering community. The majority of previous implosion research focused on the implosion of metallic cylinders, while the implosion behavior of volumes of different geometries and materials is less well researched. The behavior of pressure pulses resulting from the implosion of multiple pressure vessels is also less well researched. This thesis addresses these questions by investigating the implosion behavior of single and multiple spherical shells. Over the course of this research, I designed and predicted the collapse depth of metallic spherical volumes using shell buckling theory, then used a computational tool to model several implosion scenarios of both single and multiple sphere configurations. I then conducted implosion tests of single and multiple spherical shell configurations. The results from the initial computational models were compared with results of experimental tests and used to develop updated computational models that more accurately represented the true geometry of the test articles. Based on the analysis of the results of initial computational models and the experimental results, and the correlation between the updated computational models and experimental results, I identified ways to more accurately model scenarios involving implosions of spherical shells. In addition, I analyzed the behavior of a sympathetic implosion event involving two spherical shells and compared the result of the sympathetic implosion event to that of a single equivalent volume. This thesis concludes with guidance for future modeling and experimental testing efforts.
by Emma Grace Ferris.
S.M.
25
Leonhardt, Bradley J. "Mission planning and mission control software for the Phoenix Autonomous Underwater Vehicle (AUV) : implementation and experimental study." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA307305.
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Avachat, Siddharth. "Experimental and numerical analyses of dynamic deformation and failure in marine structures subjected to underwater impulsive loads." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44904.
Повний текст джерелаАнотація:
The need to protect marine structures from the high-intensity impulsive loads created by underwater explosions has stimulated renewed interest in the mechanical response of sandwich structures. The objective of this combined numerical and experimental study is to analyze the dynamic response of composite sandwich structures and develop material-structure-property relations and design criteria for improving the blast-resistance of marine structures. Configurations analyzed include polymer foam core structures with planar geometries. A novel experimental facility to generate high-intensity underwater impulsive loads and carry out in-situ measurements of dynamic deformations in marine structures is developed. Experiments are supported by fully dynamic finite-element simulations which account for the effects of fluid-structure interaction, and the constitutive and damage response of E-glass/polyester composites and PVC foams.
Results indicate that the core-density has a significant influence on dynamic deformations and failure modes. Polymeric foams experience considerable rate-effects and exhibit extensive shear cracking and collapse under high-magnitude multi-axial underwater impulsive loads. In structures with identical masses, low-density foam cores consistently outperform high-density foam cores, undergoing lesser deflections and transmitting smaller impulses. Calculations reveal a significant difference between the response of air-backed and water-backed structures. Water-backed structures undergo much greater damage and consequently need to absorb a much larger amount of energy than air-backed structures. The impulses transmitted through water-backed structures have significant implications for structural design. The thickness of the facesheets is varied under the conditions of constant material properties and core dimensions. The results reveal an optimal thickness of the facesheets which maximizes energy absorption in the core and minimizes the overall deflection of the structure.
27
Bender, Asher. "Autonomous Exploration of Large-Scale Natural Environments." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/9450.
Повний текст джерелаАнотація:
This thesis addresses issues which arise when using robotic platforms to explore large-scale, natural environments. Two main problems are identified: the volume of data collected by autonomous platforms and the complexity of planning surveys in large environments. Autonomous platforms are able to rapidly accumulate large data sets. The volume of data that must be processed is often too large for human experts to analyse exhaustively in a practical amount of time or in a cost-effective manner. This burden can create a bottleneck in the process of converting observations into scientifically relevant data. Although autonomous platforms can collect precisely navigated, high-resolution data, they are typically limited by finite battery capacities, data storage and computational resources. Deployments are also limited by project budgets and time frames. These constraints make it impractical to sample large environments exhaustively. To use the limited resources effectively, trajectories which maximise the amount of information gathered from the environment must be designed. This thesis addresses these problems. Three primary contributions are presented: a new classifier designed to accept probabilistic training targets rather than discrete training targets; a semi-autonomous pipeline for creating models of the environment; and an offline method for autonomously planning surveys. These contributions allow large data sets to be processed with minimal human intervention and promote efficient allocation of resources. In this thesis environmental models are established by learning the correlation between data extracted from a digital elevation model (DEM) of the seafloor and habitat categories derived from in-situ images. The DEM of the seafloor is collected using ship-borne multibeam sonar and the in-situ images are collected using an autonomous underwater vehicle (AUV). While the thesis specifically focuses on mapping and exploring marine habitats with an AUV, the research applies equally to other applications such as aerial and terrestrial environmental monitoring and planetary exploration.
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Bahrke, Fredric G. "On-line identification of the speed, steering and diving response parameters of an autonomous underwater vehicle from experimental data." Thesis, Monterey, Calif. : Naval Postgraduate School, 1992. http://handle.dtic.mil/100.2/ADA252703.
Повний текст джерелаАнотація:
Thesis (M.S. in Mechanical Engineering and Mechanical Engineer)--Naval Postgraduate School, March 1992.Thesis Advisor: Healey, Anthony J. "March 1992." Includes bibliographical references (p. 157-159). Also available in print.
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Potter, Ian J. "A systematic experimental and analytical investigation of the autonomous underwater vehicle design process with particular regard to power system integration." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0020/NQ47924.pdf.
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30
Durham, Richard W. "Experimental investigation of the effects of underwater exposure on the damping characteristics of bolted structural connections for plates and shells." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23223.
Повний текст джерелаАнотація:
Recent studies have indicated that use of the bolted structural connection and the introduction of a viscoelastic material at the joint build-up can reduce the vibration response of a structure. Many potential applications utilizing this type of vibration reduction must operate in an underwater environment. A test structure consisting of two concentric circular shells connected by four vanes and assembled with bolts was tested to determine the effects of underwater exposure on the damping properties of a bolted structure. The effects of underwater exposure on system damping were examined for various structural bolt torques and for the application of a viscoelastic layer at the joint interfaces. With increasing underwater exposure time, the modal frequencies, damping and response amplitude remained constant. The changes in the frequency response of the structure with underwater exposure resulted from the effects of increased viscous fluid layer damping at the joint interfaces. As water replaced the air at the joint interfaces, with continued underwater exposure, the effects of viscous fluid layer damping increased
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Prado, Alex de Almeida. "Metodologia experimental para obtenção dos parâmetros hidrodinâmicos do VSNT JAHU II, baseado em processamento digital de imagens." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-26032009-170419/.
Повний текст джерелаАнотація:
Atualmente está aumentando a necessidade de utilização de veículos submersíveis não tripulados nos meios aquáticos, tanto para observação científica, como também para monitoramento de obras de engenharia. As posições destes veículos são controladas, em geral, manualmente o que torna essas operações tarefas longas e cansativas aos seus pilotos. Uma alternativa que simplifica estas operações é a utilização, quando necessário, de um sistema automático de posição para aliviar o piloto de funções básicas. Para o desenvolvimento de um sistema de posicionamento automático eficiente é necessário um modelo matemático para a dinâmica do veículo, que envolve o conhecimento dos parâmetros hidrodinâmicos que caracterizam o comportamento do veículo, principalmente em casos onde o veículo possua formas geométricas complexas, sendo assim torna-se compulsório a realização de métodos experimentais para a determinação dos coeficientes hidrodinâmicos do modelo. Na Faculdade de Tecnologia de Jahu vem se desenvolvendo desde 1999 a segunda versão de um veículo submersível não tripulado para utilização em ambiente fluvial denominado VSNT JAÚ II. Este trabalho propõe a utilização de métodos experimentais para a obtenção de alguns dos coeficientes hidrodinâmicos do veículo, no qual são considerados massa adicional e amortecimento viscoso que serão estimados através de ensaios de decaimento livre, utilizando um modelo em escala reduzida e técnicas de processamento digital de imagem. Para estimativa dos coeficientes de massa adicional e amortecimento viscoso o método proposto é baseado método dos mínimos quadrados e separa os movimentos do veículo em dois planos, vertical e horizontal, considerando termos de acoplamento nos movimentos nesses planos.Unmanned underwater vehicles they have been used continually by the planet in spite of the difficulties of your operation, both for scientific observation, but also for monitoring of engineering works. The positions of these vehicles are controlled, in general, which makes manually they work long and tiring to their pilots. An alternative that simplifies this operation is the use of an automatic system of position to relieve the pilot of basic functions. For the development of an efficient of automatic positioning system it is necessary a mathematical model of the vehicle, it is necessary the knowledge of the hydrodynamic parameters that characterize the behavior of the vehicle. Those parameters are difficult to obtain through theoretical procedures, in cases where the vehicle possesses complex forms, and then experimental methods are used. In Faculdade de Tecnologia de Jahu it comes the developing since 1999 the second version of an unmanned underwater vehicle for use in fluvial environments denominated VSNT JAÚ II. This work proposes the use of an experimental method for the obtaining of some of the hydrodynamic coefficients of the Vehicle, based on rehearsals of free decay, using a model in reduced scale and techniques of digital image processing. The proposed procedure separates the movements of the vehicle in two plans, vertical and horizontal, considering joining terms in the movements in those plans.
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Tashmukhambetov, Arslan. "Experimental Design, Data Analysis, and Modeling for Characterizing the Three-Dimensional Acoustic Field of a Seismic Airgun Array." ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/1084.
Повний текст джерелаАнотація:
In June 2003, the Littoral Acoustic Demonstration Center conducted an acoustic characterization experiment for a standard seismic exploration array. Two moorings with Environmental Acoustic Recording Systems (EARS) were deployed in the northern part of the Gulf of Mexico to measure ambient noise and collect shot information. A 21-element seismic airgun array was towed along five parallel linear tracks with horizontal closest approach points to the EARS buoy position of 63, 500, 1000, 2000, and 5000 m. Calibrated acoustic pressure measurements collected during the experiment were analyzed to obtain zero-to-peak sound pressures, sound exposure levels, and pressure levels in 1/3-octave frequency bands. In addition, the experimental data were modeled by using a modified underwater acoustic propagation model to fill in missing data measurements. The resulting modeling procedure showed good agreement between measured and modeled data in absolute pressure amplitudes and frequency interference patterns for frequencies up to 1000 Hz. The analysis is important for investigating the potential impact on marine mammals and fish and predicting the exposure levels for newly planned seismic surveys in other geographic areas. Based on results of the experiment conducted and data analysis performed, a new experimental design was proposed to maximize the amount of collected data using the available equipment while minimizing the time needed for the source ship. The design used three patches, one with 3º angular spacing between the lines at a reference depth. Embedded is a smaller patch with 1º spacing and within that a still smaller patch with one half degree spacing. This arrangement gives a reasonably uniform distribution of shots versus solid angle with a large variety of emission and azimuthal angles for different ranges. Due to the uncertainty of positioning systems, the angular space is divided into solid angle bins. Simulations predicted more than 200 shots per bin for emission angles greater than 13 degrees. Statistical analysis of collected data will be performed on the proposed bin basis. An experiment based on the proposed design was conducted in Fall 2007. The data measurements collected during the experiment are currently being analyzed and will be reported in the near future.
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Korakas, Alexios. "Approche numérique et expérimentale de la propagation sonore en environnements océaniques tridimensionnels : application aux problèmes inverses." Phd thesis, Ecole Centrale de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00514915.
Повний текст джерелаАнотація:
On s'intéresse dans ce travail à l'aspect tridimensionnel (3D) de la propagation sonore en milieux océaniques petits fonds dans le cadre des problèmes inverses. Les problèmes inverses en acoustique sous-marine se basent sur la modélisation bidimensionnelle (2D) de la propagation, ignorant ainsi les effets de réfraction horizontale, qualifiés d'effets 3D. Toutefois, la propagation acoustique en environnements petits fonds, tels le plateau continental, peut être affectée par des effets 3D, leur prise en compte nécessitant l'utilisation de modèles pleinement 3D. Une inversion basée sur un modèle 3D devient inabordable pour plus de deux paramètres à la fois en raison de temps CPU particulièrement élevés. L'objectif de ce travail est d'examiner l'importance des effets 3D sur la performance et la fiabilité des procédures d'inversion habituellement utilisées dans les problèmes de l'acoustique sous-marine. Pour cela, on se place dans un guide d'onde océanique à géométrie inclinée. Des expérimentations à échelle réduite sont menées afin d'identifier et d'interpréter les effets 3D. Une procédure d'inversion par champs d'onde adaptés, formulée dans un cadre Bayesien et basée sur la recherche exhaustive dans l'espace des paramètres, est élaborée. L'inversion s'effectue en comparant des données basse fréquence du champ acoustique, recueillies le long d'antennes linéaires verticales ou horizontales, aux répliques générées par des modèles d'équation parabolique 2D et 3D. Les paramètres importants sont identifiés au moyen d'une étude de sensibilité de la fonction de coût. Dans une étape préliminaire, la performance de l'inversion est étudiée, sur données synthétiques bruitées, dans un cas simple permettant l'utilisation de modèles 2D. Une stratégied'inversion en sous-espaces résultant en une réduction importante des temps CPU pour l'inversion, est examinée. L'inversion est ensuite abordée en présence d'un fond incliné. La possibilité et les limites d'une inversion basée sur un modèle 2D sont explorées. Cette approche, mise en œuvre sur données synthétiques, met en évidence la pertinence de l'utilisation de modèles 2D en champ relativement proche. Une inversion basée sur un modèle 3D n'étant alors nécessaire que pour la pente, des temps CPU raisonnables sont ainsi réalisés. En revanche, en champ lointain, nous sommes confrontés à un risque potentiel d'estimation erronée et le recours à une modélisation 3D devient nécessaire.
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LEITE, Fabiana Soares. "Simulating Gas Blowout In Tropical Shallow Waters." Universidade Federal de Pernambuco, 2012. https://repositorio.ufpe.br/handle/123456789/12186.
Повний текст джерелаАнотація:
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FACEPE
A exploração de óleo e gás vem apresentando um rápido crescimento em regiões de baixa latitude, mesmo assim pouquíssimos experimentos e modelagens envolvendo vazamento de gás têm sido publicados pela comunidade científica. Este estudo foi desenvolvido de modo a aumentar o conhecimento a respeito do comportamento da pluma de gás durante um vazamento acidental em águas rasas. Os métodos usados e os resultados obtidos são apresentados neste estudo, assim como um modelo para simular o transporte e a dispersão de uma pluma de gás liberada em águas rasas. Primeiramente, experimentos de campo foram realizados através da simulação de um vazamento de gás natural a aproximadamente 30 m de profundidade na costa nordeste do Brasil. Quatro cenários distintos, com variadas condições de forçantes geofísicas, foram associados a diferentes fluxos de gás (de 3000 a 9000 L.h-1) e períodos sazonais (verão e inverno). Num segundo estágio, a análise de dispersão da pluma de gás foi realizada com os dados obtidos in situ. O modelo usou um volume de controle lagrangiano para discretização e simulou a evolução da pluma de gás associando a termodinâmica e o impacto desta na hidrodinâmica da pluma de gás. De acordo com os dados coletados, o transporte predominante da corrente ocorreu para sulsudoeste (nordeste) durante o verão (inverno). A diferença no diâmetro da pluma ocorreu principalmente na camada mais próxima à superfície. A pluma de gás deslocou-se para sul-sudoeste no verão e para nordestenorte durante o inverno. Os fluxos de gás liberados no assoalho oceânico pareceram não afetar a hidrodinâmica local. O movimento da pluma foi sempre influenciado pelas forçantes de maré e meteorológica, nesta ordem. Os resultados de modelagem indicaram que, à medida que a pluma sobe na coluna de água, a mesma é deslocada horizontalmente na direção da corrente predominante. A situação extrema estabeleceu um raio crítico (máximo deslocamento horizontal) da fonte de gás de 35,2 m. A comparação entre os dados medidos e os calculados mostrou que o modelo representou satisfatoriamente as principais características da liberação de gás, tais como o deslocamento, o diâmetro e o tempo de ascensão da pluma. Apesar das plumas apresentarem a largura média da mesma ordem de magnitude entre as medições e os cálculos, melhorias podem aumentar o desempenho do modelo durante o desenvolvimento inicial das plumas. Dados importantes e únicos foram coletados durante os vazamentos de gás, os quais contribuíram para a caracterização do comportamento de diferentes fluxos em diferentes períodos. Os experimentos forneceram uma base de dados para um modelo computacional que foi capaz de reproduzir o transporte e a dispersão de uma pluma de gás no ambiente marinho. O modelo foi capaz de prever o transporte e destino do gás liberado no ambiente. O mesmo pode, portanto, ser usado como uma ferramenta para planos de contingência de vazamentos acidentais de gás no oceano.
Underwater oil and gas exploration has been growing fast in low latitude regions, even though very few experimental data acquisition and modeling involving gas release in tropical and shallow waters have been published by the scientific community. This study was developed to increase the knowledge concerning the gas behavior during a subsurface blowout in shallow waters. The methods used and the results obtained from this study are presented, as well as a model to simulate the transport and dispersion of a subsurface gas plume released from shallow waters. At first, field experiments were carried out by simulating a subsurface blowout with natural gas at approximately 30 m depth in the Northeast Brazilian coast. Four distinct scenarios with varied conditions of geophysical forcing were associated with different fluxes (from 3000 to 9000 L.h-1) and seasonal periods (summer and winter). As a second stage, the analysis of the gas plume dispersion was accomplished with the data obtained from the above campaigns. The model used a Lagrangian control volume for discretization and simulated the gas plume evolution, associating thermodynamics and the impact of the thermodynamics on the hydrodynamics of the gas plume. The predominant transport occurred toward the south-southwest (northeast) during the summer (winter) period. The difference in the plume width occurred mainly in the upper surface layer. The gas plume displaced toward the south-southwest (northeast-north) during the summer (winter) period. The gas flow releases seemed not to affect the local hydrodynamics. The plume movement was always influenced by the tidal and meteorological forcings, in that order. The simulation results indicated that, as the gas plume rose in the water column, the same plume was horizontally displaced toward current predominant direction. The extreme situation provided a critical radius (maximum horizontal displacement) from the gas release source of 35.2 m. The comparison between the measured and the calculated data showed that the model satisfactorily represented the main features of the gas release, such as the displacement, diameter and ascending time of the plume. Although the mean plume widths have the same order of magnitude between the measurements and the calculations, improvements may enhance the model’s performance during the earlier plume development. Important and unique data were collected during these subsurface releases, which contributed to the characterization of the behavior of different blowouts in different seasons. The experiments provided a baseline for a computational model capable of reproducing gas plume transport and dispersion in the marine environment. The model was able to predict the gas release transport and fate in the environment. Thus it can be used as a tool for contingency planning of an accidental underwater gas release.
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Capdevila, Lanzaco Pol. "Life history, population dynamics and conservation of underwater Mediterranean forests: insights from the long-lived alga Cystoseira zosteroides = Història de vida, ecologia de poblacions i conservació dels boscos submergits del Mediterrani: el cas de l'alga longeva Cystoseira zosteroides." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/456298.
Повний текст джерелаАнотація:
Life history theory and population ecology have been especially neglectful of marine species, with most ecological principles developed from studies based on terrestrial species. This is especially true for macroalgae species, for which population dynamics and life history studies are still scarce. Given their fundamental role as habitat-forming species and primary producers in temperate seas worldwide, understanding the dynamics of macroalgae populations is fundamental, not only for their own conservation but also for their associated biodiversity and marine coastal ecosystems functioning.
Therefore, the present dissertation aims to unravel some of the processes and mechanisms that shape the population dynamics of the deep-water, long-lived and habitat-forming macroalga, Cystoseira zosteroides. With this information, we aim to bolster our ability to predict the future of this species in a globally impacted world, as well as to develop management tools to improve their conservation status. Overall, we aim to improve our current comprehension about the population dynamics and life history of macroalgae.
The results obtained from our monitored populations show that C. zosteroides have slow population dynamics. By using comparative analyses, we observed contrasting life history strategies among macroalgae species. While other intertidal fucoid and kelp populations highly depend on reproductive processes and the growth of organisms, natural and undisturbed C. zosteroides populations are maintained by the high survival and long lifespan of adult individuals. We also demonstrated that the dispersal ability of brown macroalgae is very limited compared to other taxa, with kelps showing higher dispersal potential than fucoids.
Our findings showed that disturbances highly influence C. zosteroides population dynamics. After an extreme storm and the impact of a ghost fishing net, their populations displayed a high increase in recruitment rates, suggesting a negative density-dependence effect of adults on early stages. We observed that in recruitment plates located inside well-developed adult canopies post-settlement survival is lower than outside the adult canopy. This evidence that adult C. zosteroides individuals establish a ceiling for the development of recruits. Thus, density-dependence plays a key role regulating C. zosteroides population dynamics, triggering their recovery after major disturbances. In contrast to natural populations, after major mortality events, their recovery and dynamics highly depend on the reproductive process. This is particularly worrying given the limited effective dispersal of this species.
Finally, despite the high ability of C. zosteroides to compensate morality pulses through density-dependence, their recovery can take decades, rendering their populations more vulnerable. Although isolated mortality events can be compensated, our demographic simulations showed that the combined effect of physical disturbances, compromise the viability of C. zosteroides populations. Furthermore, we demonstrated that warming has a high impact on early life stages of this species. Decreased early survival and settlement rates due to rising temperatures delay the recovery ability of C. zosteroides and increase the vulnerability of their populations.
Overall, our findings do not only contribute to better comprehend macroalgae population dynamics, but also provide new insights for their effective management. With this dissertation we evidence the key role of population ecology and life history into understanding the dynamics of species, stressing how these disciplines may help us to better comprehend the future of coastal marine ecosystems.La teoria sobre les històries de vida i l’ecologia de poblacions desenvolupen principis ecològics basats principalment en estudis realitzats en espècies terrestres, sovint sense tenir en compte les espècies marines. A través d’aquesta tesi preteníem descriure alguns dels processos i mecanismes que configuren la dinàmica poblacional de Cystoseira zosteroides, una macroalga longeva i formadora d’hàbitat, que habita en aigües profundes del Mediterrani Nord- Occidental. En un context més ampli, també es pretén augmentar la nostra comprensió actual sobre la dinàmica poblacional i la història de vida de les macroalgues. Els resultats obtinguts mostren que C. zosteroides presenta una dinàmica poblacional molt lenta. Mentre que altres poblacions de Fucals i de Kelps d’hàbitats de poca profunditat depenen principalment de processos reproductius i del creixement dels organismes, les poblacions naturals i no pertorbades de C. zosteroides es mantenen gràcies a l’elevada supervivència i la llarga esperança de vida dels individus adults. També demostrem que la capacitat de dispersió de les macroalgues brunes és molt limitada en comparació amb altres taxons, tot i que els Kelps presenten un major potencial de dispersió que les Fucals. Els nostres resultats també demostren que la denso-dependència juga un paper clau regulant la dinàmica poblacional de C. zosteroides, ja que pot impulsar la seva recuperació després de grans pertorbacions. A diferència de les poblacions no alterades, després de grans esdeveniments de mortalitat, la recuperació i dinàmica de les poblacions de C. zosteroides depèn molt dels processos reproductius. Això és especialment preocupant donada la limitada dispersió efectiva d’aquesta espècie. No obstant, tot i que els esdeveniments de mortalitat aïllats es poden compensar amb polsos de reclutament, les nostres simulacions demogràfiques demostren que l’efecte combinat dels pertorbacions físiques, com les tempestes i les xarxes de pesca abandonades, comprometen la viabilitat de les poblacions de C. zosteroides. A més, hem demostrat que l’escalfament té un gran impacte en les primeres etapes de vida d’aquesta espècie, fet que retarda la capacitat de recuperació de C. zosteroides i augmenta la seva vulnerabilitat a altres pertorbacions. En general, els nostres resultats no només contribueixen a comprendre millor la dinàmica poblacional de les macroalgues, sinó que també proporcionen noves idees per a la seva gestió eficaç. Amb aquesta tesi, es demostra el paper clau de l’ecologia de poblacions i la història de la vida en la comprensió de la dinàmica de les espècies i destaca com aquestes disciplines poden ajudar-nos a entendre millor el futur dels ecosistemes marins costaners.
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Ducos, Salomé. "Restauration de population du denti Dentex dentex et du corb Sciaena umbra en Méditerranée : évaluation des performances individuelles, suivi individuel et populationnel des juvéniles." Electronic Thesis or Diss., Corte, 2023. http://hal-univ-corse.archives-ouvertes.fr/view_by_stamp.php?&action_todo=view&id.
Повний текст джерелаАнотація:
Le denti, Dentex dentex, et le corb, Sciaena umbra, sont deux espèces de poissons Téléostéens vivants le long des côtes méditerranéennes. Il s’agit de deux espèces emblématiques d’intérêt écologique, économique et patrimonial dans cette région, où ils sont malheureusement considérés comme menacés d’extinction par l’UICN. Au coeur de la mer Méditerranée, la plateforme corse de recherche et de production aquacole STELLA MARE maîtrise actuellement la reproduction et l’élevage de larves et juvéniles de denti et de corb. Suite à l’acquisition de ce savoir-faire zootechnique, ce projet de thèse s’inscrit dans une volonté de tester la faisabilité d’utiliser les juvéniles de D. dentex et de S. umbra, produits au sein de cette plateforme, à des fins de restauration active de populations autour de la Corse. Dans ce but, divers aspects ont été considérés. Dans un premier temps, des réponses comportementales et des performances individuelles ont été étudiées, en lien avec les conditions d’élevage et la taille des individus testés, chez des juvéniles d’élevage de denti et de corb. Ces tests expérimentaux en bassins ont permis de mettre en évidence un important effet de la taille i) sur les comportements et performances de nage, sur les comportements d’audace et d’exploration, sur les performances de fuite et sur les performances de prédation de S. umbra, ainsi que ii) sur la sensibilité à la manipulation et sur les performances de nage de D. dentex. De plus, un entraînement au nourrissage sur proies vivantes durant six jours a permis l’amélioration des performances de prédation de juvéniles des deux espèces. Dans un second temps, des actions expérimentales de relâchés de juvéniles de denti et de corb ont été effectuées in situ afin d’étudier la survie, la dispersion et les comportements de ces individus dans le milieu naturel, par le biais i) de suivis en plongée (UVC) et ii) d’un suivi par télémétrie acoustique. Il a été signalé que les juvéniles doivent être consciencieusement sélectionnés avant les relâchés afin d’éviter de potentielles anomalies morpho-anatomiques, en particulier pour le denti. Ces études ont permis d’atteindre, chez ces deux espèces, un très bon taux de survie (> 99 %) suite au transport, à la manipulation et l’acclimatation dans le milieu, avant le relâché. Le suivi par télémétrie acoustique a mis en évidence que les juvéniles de ces deux espèces semblent être capables d’amorcer leur acclimatation dans le milieu naturel mais se dispersent assez rapidement loin de la zone de relâché. Les juvéniles de corb semblent largement se dissimuler dans l’herbier de posidonie, et les juvéniles de denti n’ont que très peu été ré-observés lors des suivis en plongée. Dans un troisième temps, la diversité génétique des lots de juvéniles d’élevage a été étudiée chez ces deux espèces afin de la comparer avec celle retrouvée dans les populations sauvages. Cette étude a mis en évidence que les lots de géniteurs étudiés présentent une diversité génétique représentative de celle retrouvée in situ. Cependant, les lots de juvéniles présentent une différentiation génétique notable d’avec les populations sauvages du fait de la contribution majoritaire de seulement quelques individus, parmi l’ensemble des géniteurs, à la production de juvéniles. Ces travaux ont permis l’acquisition de nouvelles connaissances sur l’utilisation potentielle de juvéniles de D. dentex et S. umbra d’élevage à des fins de restauration active de populations. Cette thèse correspond ainsi à une approche pluridisciplinaire constituant la base d’un travail expérimental préalable à toute action de repeuplementThe common dentex, Dentex dentex, and the brown meagre, Sciaena umbra, are two teleost fish inhabiting Mediterranean coastal waters. Dentex dentex and S. umbra are emblematic species of ecological, economic and cultural interest in the Mediterranean Sea, where they are under threat of extinction and redlisted by the IUCN. Located in the heart of the Mediterranean Sea, the Corsican platform STELLA MARE is a centre of scientific research and aquaculture production that has succeeded in captive breeding D. dentex and S. umbra and rearing their hatchery-produced juveniles. Following these aquaculture innovations, this project aimed to investigate the feasibility of using hatchery-reared D. dentex and S. umbra juveniles for restocking efforts in Corsican waters. First, behavioural responses and performance of hatchery-reared D. dentex and S. umbra juveniles were studied, linked to their rearing conditions and body size. These experiments highlighted a significant effect of body size i) on swimming behaviour, swimming performance, exploratory behaviour, boldness, escape performance and feeding performance of S. umbra juveniles, and ii) on handling sensitivity and swimming performance of D. dentex juveniles. Moreover, six days of feeding training led to higher feeding performance on live prey for hatchery-reared D. dentex and S. umbra juveniles. Second, experimental releases of D. dentex and S. umbra juveniles were performed in the wild to estimate post-release survival, dispersion and behaviours. These outcomes were investigated through i) underwater visual census (UVC) surveys and ii) an acoustic telemetry survey. These studies highlighted a high survival rate (> 99%) following transportation, handling and in situ acclimation for the two species. The acoustic telemetry survey highlighted that both species seemed to start acclimating to the natural environment and quickly dispersed away from the release site. Sciaena umbra juveniles seem to mostly hide in Posidonia oceanica meadows, and D. dentex juveniles were rarely observed during the UVC surveys. Finally, the genetic diversity of hatchery stocks was studied and compared to the genetic diversity of wild populations. This study highlighted that broodstocks’ genetic diversity was fairly representative of wild populations. However, significant genetic differentiation was observed between wild and juvenile samples as well as between juvenile and broodstock samples in both species. This seemed to be due i) to a very small effective number of breeders in S. umbra, and ii) to the presence of a few dominant reproductive breeders producing the majority of juveniles in D. dentex. In conclusion, the combination of these results provides new knowledge on the potential use of hatchery-reared D. dentex and S. umbra juveniles for restocking purposes. This project employs a multi-disciplinary approach and acts as a pilot study, providing a foundation for future potential restocking efforts
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Lu, Yu-Lun, and 呂宇倫. "Sub-scaled underwater experiments of Rayleigh surface wave on elastic solid." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/30992896902986388353.
Повний текст джерелаАнотація:
碩士國立中山大學
機械工程學系研究所
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This thesis studies the target identified by analyzed scattering signal which is from active sonar impinged under water. In general, the specular reflected waves and corner waves provide the information of target profile in scattering signal. The resonance scattering waves and surface waves submit the material properties of target by analysis signal. The Rayleigh wave is a candidate for target identified in surface wave analysis. Since then, the theorem focuses on Rayleigh wave propagation on solid sphere and cylinder in this thesis. To analyze the problem of scattering wave, if the normal mode methed is applied to solve it, the character of reflected surface wave can not appear on the solution. So the Sommerfeld-Watson transform(SWT) method is used to solve it. This method can convege the infinite partial-wave series rapidly and the physical property of acoustic wave can be elucidated easily. In experiment, the reduced scale experiment is setup for Rayleigh wave measurement using ultrasonic wave. For Rayleigh wave discussion, the individual profile, sizes and material of target is applied respectively in this experiment. The beam pattern is also measured in the Rayleigh wave filed. The result appears the target identified by analytical Rayleigh wave obviously.
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Ambrósio, Joana Ester Vaz. "JWL parameters optimization for isentropic THOR prediction and confined underwater blasting generators experiments." Master's thesis, 2013. http://hdl.handle.net/10316/38857.
Повний текст джерелаАнотація:
Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra.As operações de detonação submarinas têm sido, durante as últimas décadas, alvo de pesquisa e desenvolvimento das operações de detonação marítimas, incluindo testes de torpedo, bem como, em testes em piscinas para a medição de energia de detonação de explosivos industriais. O estudo dos geradores de demolição por carga submersa (WBWG) tiveram por base nestes conceitos. Com o presente trabalho pretendo apresentar o estudo do comportamento de WBWG, com base em dois tipos de recipientes de plástico com água (25 litros e 1000 litros), contendo no seu interior exactamente no centro um detonador dentro de uma carga explosiva cilíndrica. As cargas explosivas usadas foram uma emulsão de nitrato de amónio com fuel oil (ANFO) e cordão detonante (12 g/m) de pentrite (PETN). Muito resumidamente uma revisão bibliográfica foi realizada. As propriedades de detonação dos explosivos foram previstas utilizando um programa termoquímico, designado por THOR. Para a expansão dos produtos de detonação dos explosivos foi aplicado uma equação de estado JWL. Foi realizado uma revisão aos conceitos fundamentais desta equação e os seus coeficientes foram determinados e optimizados correlacionando as previsões do THOR e a equação de estado (EOS) JWL para a mínima diferença através de uma função quadrática auxiliar. Por forma a calcular os coeficientes de JWL um novo método foi usado. Este baseia-se na evolução das curvas adiabáticas e isentrópicas obtidas pelo THOR, utilizando uma função do Microsoft Excel ® Solver, assumindo algumas suposições para o coeficiente Grüneisen (a partir do exponencial da curva adiabática; do exponencial da curva isentrópica para um volume adimensional limite; do exponencial da curva isentrópica para todos os valores da expansão, e por último; deduzido por Handley, 2011). Os melhores resultados obtidos foram pela utilização do coeficiente Grüneisen do exponencial da curva isentrópica para todos os valores da expansão, onde para a emulsão de ANFO e para PETN. As dimensões e o design da configuração de “WBWG” experimental foram apresentadas, juntamente com a descrição de uma experiência de detonação tipo utilizando 3 g de PETN (detonador No.8 mais 2.4 g de cordão detonante de PETN). Foi realizada uma simulação a 2D e 3D de “WBWG” usando o programa Autodyn para um contentor de metro cúbico cheio de água (1000 litros) para ambos os explosivos. Os resultados obtidos mostram a possibilidade de ter este tipo de cargas explosivas sem a destruição do “WBWG” contentor. Uma vez que, os níveis de pressão na água, perto das paredes plásticas, sob a maior carga admissível, ronda os 6 MPa. Foi sempre possível observar a deformação elástica das paredes do contentor, as reflecções do choque subaquático, alterando a sua forma cúbica original para uma espiral transiente. Adicionalmente os procedimentos executados para o THOR, para o Microsoft Excel ® Solver e para a interface do programa de simulação Autodyn “material input data” foram apresentados.
Underwater blasting operations have been, during last decades, subject of research and development of maritime blasting operations, including torpedo studies. Aquarium tests, for the measurement of blasting energy of industrial explosives, are based in studies of confined underwater blast wave generators (WBWG). The current work present the study of the behavior of WBWG, based in two different water plastic containers (25 litres and 1000 litres), having in the center a detonator inside a cylindrical explosive charge. The explosive charges used were ammonium nitrate with fuel oil (ANFO) emulsion and pentaerythritol tetranitrate (PETN) detonating cords (12 g/m). Summarily the theoretical background was review. The explosives detonation properties were predicted using a thermochemical computer code, named THOR. For the expansion of the detonation products of the explosives was applied JWL EoS. JWL fundamentals were review and his parameters were determined and optimized correlating THOR predictions and JWL EoS to a minimum difference with an auxiliary quadratic function. In order to calculate the JWL coefficients, a new numerical method was used. It was based in the evolution of adiabate and isentrope curves, obtained by THOR code, using a function of the Microsoft Excel ® Solver, assuming a few assumptions for Grüneisen coefficient (from the exponential of the adiabatic curve; from the exponential of the isentrope curve at a limit adimensional volume; from the exponential of the total expansion of isentrope curve and, at last; deducted from Handley, 2011). The best results were obtained using the Grüneisen coefficient from the exponential of the total expansion of isentrope curve, which were for ANFO emulsion and for PETN. The dimensions and design configurations of the experimental WBWG were presented and also a blast type experiment for 3 g of PETN (detonator No. 8 plus 2.4 g charge of PETN detonation cord) was described. Autodyn 2D and 3D simulations of WBWG were performed using a cubic meter water container (1000 litres) for both explosive. The obtained results show the possibility of having these explosive charges without destruction of WBWG containers. Since water pressure levels, close to plastic walls, under maximum admissible charges, are closed to 6 MPa. It was always observed the elastic deformation of containers wall, under the water shock reflections, changing from its original cubic shape to a transient spherical one. Additionally the execution procedures of THOR code, Microsoft Excel ® Solver and the interface of Autodyn simulations material input data was presented.
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Huang, Wei Nan, and 黃為南. "Computation and experimental study on the underwater trajectory." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/15231745151502772641.
Повний текст джерела
40
Han-Chieh, Wu, and 吳漢傑. "Experimental Study on the Underwater Rain-Drop Noise." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/43696474984500475983.
Повний текст джерелаАнотація:
碩士國立成功大學
水利及海洋工程學系
87
ABSTRACT The underwater sound and the bubble formation caused by rain drops were studied experimentally in the present paper. A CCD camera was set up to photograph the drop impact and the process of bubble formation. Underwater noise was received with a hydrophone connected to a charge amplifier and a FFT analyzer for capturing the main characteristics. The experimental results showed that two types of bubbles are generated as a single rain drop strikes the free surface. The first one is the formation of a single bubble, radiating sound of frequencies ranging from 3 to 5 kHz. This type of bubble has been accepted by many researchers as the main source of rain drop noise. The second one is that as the rain drop impacts the free surface, a downward jet is formed which develops into a vortex ring. Several bubbles are generated along this ring. The latter bubbles are smaller than the former one, hence radiating sounds of higher frequencies, ranging from 8 to 20 kHz, with a peak sound pressure level at about 14 kHz. The first mode of bubble generation happens to rain drops of lower impact velocities. However, as the impact velocities increase, both modes of bubble generation are possible. These two different types of bubbles and the radiated sounds can be used to explain the double peak pressure of the real rain drop noise, one locates at 3-5kHz, the other one at about 14 kHz. Finally, the sound spectra of different rain rates were also studied in this paper.
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Chin, Liu Tsai, and 劉財欽. "The Experimental Analysis And Research Of Underwater Breathing Regulators." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/03059783351467743176.
Повний текст джерелаАнотація:
碩士國防大學理工學院
機械工程碩士班
100
An underwater breathing regulator is composed of a first-stage device and a second-stage device. The main function of the breathing regulator is to devide the air from the air-tank and reduce the high pressure to the pressure of the surrounding environment. It also supplies sufficient air for divers to use the regulator in the diving equipment. Previous studies were focused on the simulation of environmental factors and the flow analysis to explore the performance of the breathing regulator. This study setup the experimental equipments and the procedures for the performance of the regulators. Different types of the first-stages are used in this study. The results showed that the pressure curves during breathing are different for different regulators.
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Ma, Chun-shen, and 馬俊生. "The Analysis for a Moving Miniature Underwater Vehicle by the Experimental Approach." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/80258939626921963598.
Повний текст джерелаАнотація:
碩士義守大學
機械與自動化工程學系碩士班
93
The study of a miniature underwater vehicle is relevant to how to miniaturize it effectively. If the miniaturized vehicle can successfully complete its mission, it means that materials and power consumption of the vehicle can be saved substantially. Moreover, it can be operated effectively in a limited space due to its small size. For a start, the operating properties of a miniature underwater vehicle is analyzed. This work aims to employ the drag and propulsive force estimation method for moving miniature underwater vehicles via the experimental approach. After the vehicle model is trimmed to be neutral buoyancy in the tank, the drag can be obtained by the experimental method, which is proposed in this paper. Two ways are employed in the drag experiment; one is the drag measurement method of one-side towed body and the other is the drag measurement method of two-side towed body. From the measured data and visualizations of the moving vehicle, the cost effectiveness and accuracy for the experiment are discussed. Thereafter, a feasible method has been chosen to conduct the parametric study. In regard to the propulsion of the miniature vehicle, the model for the propulsive force is obtained by the experimental method, which is chosen among several proposed ones. Finally, results from both drag and propulsion are analyzed to study the design of miniature vehicles.
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Rout, Raja. "Design and Experimental Realization of Adaptive Control Schemes for an Autonomous Underwater Vehicle." Thesis, 2016. http://ethesis.nitrkl.ac.in/8470/1/2016_MTR_RRout_512EE104_Design.pdf.
Повний текст джерелаАнотація:
Research on Autonomous Underwater Vehicle(AUV) has attracted increased attention of control engineering community in the recent years due to its many interesting applications such as in Defense organisations for underwater mine detection, region surveillance, oceanography studies, oil/gas industries for inspection of underwater pipelines and other marine related industries. However, for the realization of these applications, effective motion control algorithms need to be developed. These motion control algorithms require mathematical representation of AUV which comprises of hydrodynamic damping, Coriolis terms, mass and inertia terms etc. To obtain dynamics of an AUV, different analytical and empirical methods are reported in the literature such as tow tank test, Computational Fluid Dynamics (CFD) analysis and on-line system identification. Among these methods, tow-tank test and CFD analysis provide white-box identified model of the AUV dynamics. Thus, the control design using these methods are found to be ineffective in situation of change in payloads of an AUV or parametric variations in AUV dynamics. On the other hand, control design using on-line identification, the dynamics of AUV can be obtained at every sampling time and thus the aforesaid parametric variations in AUV dynamics can be handled effectively. In this thesis, adaptive control strategies are developed using the parameters of AUV obtained through on-line system identification. The proposed algorithms are verified first through simulation and then through experimentation on the prototype AUV. Among various motion control algorithms, waypoint tracking has more practical significance for oceanographic surveys and many other applications. In order to implement, waypoint motion control schemes, Line-of-Sight (LoS) guidance law can be used which is computationally less expensive. In this thesis, adaptive control schemes are developed to implement LoS guidance for an AUV for practical realization of the control algorithm.
Further, in order to realize the proposed control algorithms, a prototype AUV is developed in the laboratory. The developed AUV is a torpedo-shaped in order to experience low drag force, underactuated AUV with a single thruster for forward motion and control planes for angular motion. Firstly, the AUV structure such as nose profile, tail profile, hull section and control planes are designed and developed. Secondly, the hardware configuration of the AUV such as sensors, actuators, computational unit, communication module etc. are appropriately selected. Finally, a software framework called Robot Operating System (ROS) is used for seamless integration of various sensors, actuators with the computational unit. ROS is a software platform which provides right platform for the implementation of the control algorithms using the sensor data to achieve autonomous capability of the AUV. In order to develop adaptive control strategies, the unknown dynamics of the AUV is identified using polynomial-based Nonlinear Autoregressive Moving Average eXogenous (NARMAX) model structure. The parameters of this NARMAX model structure are identified online using Recursive Extended Least Square (RELS) method. Then an adaptive controller is developed for realization of the LoS guidance law for an AUV. Using the kinematic equation and the desired path parameters, a Lyapunov based backstepping controller is designed to obtain the reference velocities for the dynamics. Subsequently, a self-tuning PID controller is designed for the AUV to track these reference velocities. Using an inverse optimal control technique, the gains of the selftuning PID controller are tuned on-line. Although, this algorithm is computationally less expensive but there lie issues such as actuator constraints and state constraints which need to be resolved in view of practical realization of the control law. It is also observed that the proposed NARMAX structure of the AUV consists of redundant regressor terms. To alleviate the aforesaid limitations of the Inverse optimal self-tuning control scheme, a constrained adaptive control scheme is proposed that employs a minimum representation of the NARMAX structure (MR-NARMAX) for capturing AUV dynamics. The regressors of the MR-NARMAX structure are identified using Forward Regressor Orthogonal Least Square algorithm. Further, the parameters of this MRNARMAX model structure of the AUV are identified at every sampling time using RELS algorithm. Using the desired path parameters and the identified dynamics, an error objective function is defined which is to be minimized. The minimization problem where the objective function with the state and actuator constraints is formulated as a convex optimization problem. This optimization problem is solved using quadratic programming technique. The proposed MR-NARMAX based adaptive control is verified in the simulation and then on the prototype AUV. From the obtained results it is observed that this algorithm provides successful tracking of the desired heading. But, the proposed control algorithm is computational expensive, as an optimization problem is to be solved at each sampling instant. In order to reduce the computational time, an explicit model predictive control strategy is developed using the concept of multi-parametric programming. A Lyapunov based backstepping controller is designed to generate desired yaw velocity in order to steer the AUV towards the desired path. This explicit model predictive controller is designed using the identified NARMAX model for tracking the desired yaw velocity. The proposed explicit MPC algorithm is implemented first in simulation and then in the prototype AUV. From the simulation and experimental results, it is found that this controller has less computation time and also it considers both the state and actuator constraints whilst exhibiting good tracking performance.
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De, Candia SM. "Experimental and numerical investigations into the underwater explosion induced whipping response of submerged platforms." Thesis, 2019. https://eprints.utas.edu.au/31703/1/De_Candia_whole_thesis.pdf.
Повний текст джерелаАнотація:
This thesis reports the findings of an experimental and numerical investigation into the whipping response of a submerged platform, due to loading from near-field, non-contact underwater explosion (UNDEX) events.
The experimental investigation examined the whipping response of a generic submerged platform subjected to UNDEX. Eight scenarios were investigated, using different explosive charge sizes, longitudinal, and transverse stand-off locations, to explore the effects of these variables on the platform’s whipping response, and to provide validation data for the numerical investigation. It was found that UNDEX stand-off locations near the anti-node of the first bending mode shape induced the most severe whipping responses, while stand-offs near the node of the first bending mode shape had greatly reduced whipping responses.
A numerical model was developed and validated against the experimental results, using incident pressure and strain measurements. Three numerical studies were conducted with the validated numerical model, investigating the effects of additional stand-off distances at the previously explored longitudinal stand-off locations, the whipping response from an intermediate charge size, and the effects of the UNDEX bubble loading on the whipping response by using a shock-only loading model.
From these studies, the following novel contributions were made:
The stand-off distance was found to only affect the whipping severity while the charge size and stand-off location determined the modal contributions of the whipping response.
A comparison of the peak whipping response to the bubble pressure impulse suggests that three distinct forms of whipping could be induced, and these can be determined by the proximity of the UNDEX stand-off location to the nodes and anti-nodes of the platform’s first bending mode shape. These were classified as critical, resilient, and general whipping responses.
The critical whipping response occurred when the UNDEX stand-off location was near the anti-node of the first bending mode shape. This was characterised by a dominant response of the first bending mode and minimal contribution from other bending modes in the overall response. The severity of this response increased nonlinearly as the bubble impulse increased and when the bubble pulsation frequency was similar to the first bending mode frequency. This is the most severe form of UNDEX induced whipping.
The resilient whipping response occurred when the UNDEX stand-off location was near the node of the first bending mode shape. This was characterised by minimal contribution of the first bending mode compared to others in the overall response. From these scenarios, the bubble loading had minimal effect on the whipping response. This was confirmed from good correlation in comparisons of the strain responses from experimental measurements and the results from the numerical shock-only loading study. This is the least severe form of UNDEX induced whipping and the most desirable outcome from an unavoidable UNDEX threat.
The general whipping response occurred when the UNDEX stand-off location was between the nodes and anti-nodes of the first bending mode shape. This was characterised by similar contributions of multiple bending mode responses in the overall response. The severity from this response increased linearly for increases in the bubble impulse. It is suggested this is the most likely form of UNDEX induced whipping to occur, based on the large number of variables involved with UNDEX loading and platform response scenarios.
Current analysis methodologies are able to identify the resilient whipping response but some methods that focus on the shock response of a platform may not identify the critical and general whipping responses. This was demonstrated by comparison of the experimental measurements to a numerical shock-only loading models for the most severe UNDEX scenarios, where shock-only loading and response assumptions under-predicted the whipping response by 39 % and 54 % for the critical and general whipping responses respectively.
The relative increase in the severity of the whipping response from a reduction in the stand-off distance was consistent for all similar forms of whipping. This suggests that the whipping severity from many different stand-off distances can be approximated through analysis of only a few scenarios at different stand-off locations on a specific naval platform. It is suggested that this knowledge may allow a rapid assessment tool to be developed that could determine a platform’s survivability from a wide variety of UNDEX scenarios.
The trends from each form of whipping severity compared to bubble pressure impulse were examined with limited extrapolation. This suggested that four whipping response analysis regimes exist: far-field elastic, near-field and non-contact elastic, non-contact plastic, and contact damage. Exact limits of these regimes were not identified, and all are promising areas for further investigation.
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Itoh, Yoshito, Yasuo Kitane, and Xiao Chen. "EXPERIMENTAL STUDY ON STRENGTH AND DUCTILITY OF UNDERWATER FILLET WELDS IN REPAIRING OFFSHORE STEEL STRUCTURES." 2009. http://hdl.handle.net/2237/18874.
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46
周育緯. "Experimental Study and Simulation on the Application of Ground Penetrating Radar in Underwater Topographic Survey." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/362dsp.
Повний текст джерела
47
Yen-TsenLin and 林彥岑. "Experimental Study on the Reduction of Underwater Ship Propeller Noises by Using Bubble Screen Techniques." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/z4w49h.
Повний текст джерелаАнотація:
博士國立成功大學
水利及海洋工程學系
104
Experimental Study on the Reduction of Underwater Ship Propeller Noises by Using Bubble Screen Techniques Yen-Tsen Lin Ching-Jer Huang Department of Hydraulic and Ocean Engineering National Cheng Kung University SUMMARY The purpose of this experimental study is to design an optimal bubble screen for reducing the underwater propeller noises of surface vessels.The experiments were carried out in a towing tank. A propeller was installed in a ship model to simulate the noises produced by a surface vessel and hydrophones were used to monitor the radiated sounds. The bubble screen is generated by passing the compressed air through a long bubble emitter belt. By measuring the attenuated sounds behind the bubble screen, the optimal bubble size and air volume fraction for reducing the radiated sounds can be fixed. Furthermore, the calibration experiments of the bubble screen were implemented in a water tank to estimate the bubble populations and gas void fraction while the bubble emitter belt with different orifice sizes was pumped into variable air pressures and flow rates. KEY WORDS: optimal bubble screen, propeller, surface vessel, towing tank, bubble emitter belt, attenuated sounds. INTRODUCTION The sound speed in the bubbly flow differs significantly from the standard sound velocity in the sea water and the speed is frequency dependent. Propeller noise is produced by a purely hydrodynamic mechanism such as cavitation at the tips of the blades or cavitation on the blades themselves, or by mechanical vibration of the blades. Usually flow noise, propeller noise and mechanical noise will be concealed. Propeller noises are commonly reduced by using the variable pitch, skew, and the appropriate number of propeller blades. The spontaneous noises generated by the ship propeller are the main signal source of reconnaissance. The noises generated by the propeller are mostly in the low frequency range （less than 500 Hz）. Accordingly, the low-frequency sound generated by the propeller becomes an important clue for the underwater vehicle to search for the sea surface vessels. It has been known for a long time that the speed of sound propagating in the water is affected by the presence of the gas bubbles. The propagation of sound through bubbly liquid has been thoroughly investigated both theoretically and experimentally. It was revealed that when the frequency of the incident sound coincides with the resonant frequency of the bubble in the bubbly flow, a small amount of sound will penetrate through the bubbly flow. Figure 1.3 shows that two air emitter belts were installed to reduce the noise of the ship. FR 253 air emitter belt is fitted to the ship’s propeller, while FR177 belt is fitted to the external hull in the vicinity of the propulsion plant. Air bubbles are employed to mask potential target, or to provide alternate targets. For the best use of the air emitter belt, the effect of belt control parameters, such as the air pressure, flow rate, and the size of orifice on the bubble size and air-volume fraction of the bubbly flow must be tested. Furthermore, by applying the air bubble screen technique for the reduction of the self-noises of the surface vessels, effect of bubble size and volume fraction on the reduction of noises produced by a propeller installed to a ship under way must also investigated. Based on the above-mentioned experimental studies, this work aims to design an optimal bubble screen for reducing the underwater propeller noises of surface vessels. MATERIALS AND METHODS In this study, the experiments are divided into three main parts. In the first part of the experiments, surface ships use air bubbles with a bubble curtain to weaken the main and auxiliary mechanical noise through the hull of radiative transfer to the sound of water, shelter air curtain with the cast bubble screen control mechanism and influence factors include: flow, pressure and gas screen with a pore size such as the three main control parameters. In this study, experiment to experiment according to different control parameters in order to find out the relationship between the bubble screen and associated control parameters in the water tank of Laboratory for fiber-optic sensing and underwater acoustics at the Department of Hydraulic and Ocean Engineering, National Cheng Kung University（NCKU） , Taiwan. In the second part of the experiments, underwater noises generated by the propellers shown in Fig.3.13 and Fig.4.2 were measured. Effects of the bubble screen on the reduction of sound transmission were then studied by deploying a bubble curtain at the rear side of the propeller. These experiments were carried out in the towing tank of the Department of Systems and Naval Mechatronic Engineering, NCKU. In the third part of the experiments, the ship model is equipped with two air bubble emitting belts. The underwater noises generated by the installed propeller in a moving ship hull with or without the emission of air bubble will be measured and compared. Effect of the air flow rate and bubble size on the reduction of sound transmission through the bubbly flow will be systematically investigated. RESULT AND DISCUSSION The effect of different air flows for high-speed propeller, by the bubble curtain noise reduction. As shown in Figure 4.20. The black line represents the location of underwater ambient noise for the experimental flume（not including the propeller and bubble）. The Green line represents the sound spectrum of the propeller in shallow water（0.15 m depth）, and high speed（rpm = 488）. The main radiation of propeller is approximated to 0.6 ~ 6 KHz. The blue and red lines, represents the sound spectrum of the propeller noise through the bubble curtain by 1.0 and 20.0（L / min）of air flow. In fact, the bubble screen generates a noise reduction effect of roughly 10 dB in the frequency range of 0.6 ~ 1.1 KHz. CONCLUSION （1） By the research results, the use of the principle of the bubble screen to reduce or change the propeller noise is concrete and feasible. （2） The range of radiated noise frequency for four-leaf propeller between 600 to 6000 Hz. Bubble screen generated by Bubble stone can attenuate low-frequency radiation of propeller noise between 600 to 1100 Hz and attenuate cavitation noise about 700 Hz significantly, the result was match its natural resonance theory bubble frequency of the incident sound wave frequency equal happen. （3） Bubble curtain control parameters include: flow, pressure and gas screen with pore sizes. Its impact factors are the volume fraction of bubbles (bubble cover ratio), the bubble curtain width (thickness). （4） Gas volume fraction in bubble curtain is proportional to the gas flow. When the greater the volume fraction , the incident sound waves more difficult to penetrate. （5） The relationship between bubble size and pore size is enlarged 8-13 times. （6） Pore size is the direct effect factor for the bubble size of bubble screen, it’s the most critical parameter of the reducing noise frequency. （7） CO2 really helps reduce the life cycle of the bubble, bubble and reduce ship stern flow generating interaction time.
48
Yu-FangHuang and 黃郁芳. "An experimental study on underwater sounds producedby a freely falling sphere impacting on water surface." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/09218940110678629915.
Повний текст джерела
49
陳洵民. "Study of Underwater Acoustic Transmission Experiment and Acoustic Mode Coupling Effect in Kao-pin Canyon off Southwestern Taiwan." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/91291136942390028437.
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50
Morgan, Ira James. "An experimental investigation and design of a digital telemetry acoustic receiving array." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-08-4257.
Повний текст джерелаАнотація:
Acoustic Receiving Line Arrays are critical tools for measuring the acoustic properties of any oceanographic region. Vertical, horizontal, and combinations of the two array configurations allow us to measure acoustic propagation, bottom characteristics through inversion, and ambient noise. These properties are vitally important for effective implementation of any passive or active detection system in both shallow and deep water environments. Measurement systems must be designed with flexibility since the exact array design that yields the best signal processing results is not known prior to a survey. Flexibility, in this case, refers to large numbers of hydrophones, higher sample rates for greater bandwidth, and longer recording time to facilitate experimentation at each survey site. Repeated deployment and recovery of such a system demands a battery powered autonomous design that can be deployed and recovered from available research vessels at sea. Conventional deep ocean analog array cable designs, while power efficient, become physically challenging in size and weight when the sensor count exceeds 100 and array lengths remain in the 100s of meters. The purpose of this thesis is to detail the design, development, and testing of a pressure tolerant full ocean depth rated prototype acoustic line array with digital telemetry of all hydrophone data from the sensors to the recording system. The design is to support up to 300 hydrophones each with a maximum sample rate of 4 kHz and a per sensor power requirement of ¾ of a watt. Lower sensor counts will allow higher sample rates to be used based on available telemetry bandwidth. A single element of a line array was built and tested at the University of Texas at Austin Applied Research Laboratories and it was used to demonstrate real-time telemetry and recording of acoustic hydrophone data.text