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Gateau, Jérôme. "Imagerie ultrasonore ultrarapide d'évènements de cavitation : application en thérapie par ultrasons et imagerie de détection". Phd thesis, Université Paris-Diderot - Paris VII, 2011. http://pastel.archives-ouvertes.fr/pastel-00863591.
Pełny tekst źródłaGâteau, Jérôme. "Imagerie ultrasonore ultrarapide d'événements de cavitation : application en thérapie par ultrasons et imagerie de détection". Paris 7, 2011. http://www.theses.fr/2011PA077013.
Pełny tekst źródłaThe onset of cavitation activity in an aqueous medium is linked to the formation of gas/vapour-filled cavities of micrometric size. This formation can be acoustically mediated and is then called acoustic bubble nucleation. We focus here in the activation of seed nucléi by short (a few cycles) and high amplitude ultrasonic excitation (order of magnitude MPa). Bubbles are generated during the rarefaction phase of the wave and are transient (they dissolve). The nucleation properties of biological tissues are little known. However, they can be assessed using ultrasound: the formation of a bubble results in the appearance of a new scatterer (which can be detected with a pulse-écho detection), and each cavitation event generates an acoustic emission (detected with passive reception). In n this PhD manuscript, we use ultrafast ultrasound imaging (simultaneous acquisition on an array of transducers with a high frame rate) to detect cavitation events. Two in vitro applications were first validated. On one hand, bubble nucleation was performed through a human skull, and transcranial passive detection of a single cavitation event was used in a time reversal process to optimize adaptive focusing for thermal therapy of brain tissue. On the other hand, the formation and dissolution of bubbles in scattering biological tissues (muscle) were detected with a high sensitivity by combining passive detection and ultrafast active imaging. Finally, in vivo experiments on sheep's brain, and others in vitro on animal blood showed that nucleation in biological tissue is a random phenomenon, and high negative pressure are mandatory to initiate nucleation in vivo (< -12MPa)
Mandroyan, Audrey. "Caractérisation de l'hydrodynamique et de la cavitation dans un réacteur utilisé pour la sonoélectrochimie". Besançon, 2006. http://www.theses.fr/2006BESA2023.
Pełny tekst źródłaPrevious studies have shown positive effects induced by ultrasound during chemical processes. They allow envisaging a large application field for power ultrasound at low frequencies (from 20 to 60 kHz) as well as at high frequencies (from 100 to 1 MHz). In the particular case of industrial electrochemical processes, ultrasound and their effects are difficult to managed, due to numerous phenomena which are caused by the wave propagation in a liquid and especially the acoustic flows and the cavitation in the liquid bulk and at a solid surface. It's is important to note that the distribution of this activity is not homogeneous within the reactor, leading to difficulty in process control. So, the optimisation of sonoelectrochemistry processes needs a good knowledge of both acoustic flow distribution and cavitation, which are essential parameters. The aim of this PhD thesis was to obtain reliable elements for the sonoelectrochemistry systems characterization. This work takes interest in the study of interactions between the hydrodynamic phenomena, the cavitation and the electrochemical reactions, what will allow understanding the mechanisms and their limits. The ultrasonic activity characterization was implemented by several methods, as the calorimetric power measurements, the Fricke’s dosimetry, the mass transfer measurements, the laser tomography, the PIV and chronoamperometry. A systematic study was carried out for all these methods. Thus it has been possible to estimate the reactor geometry influence, the ultrasound beam diameter influence or the frequency influence on the hydrodynamic flows induced by ultrasound and on the cavitation phenomenon at the surface electrode
Polichetti, Maxime. "Traitement d’antenne adaptatif pour l’imagerie ultrasonore passive de la cavitation". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1176/document.
Pełny tekst źródłaThis work focuses on the spatio-temporal monitoring of acoustic cavitation by ultrasonic imaging. This is a complex physical phenomenon used in some ultrasound therapy techniques, corresponding to the formation of gas bubbles that oscillate and implode. Initially, the TD-PAM (Time Domain Passive Acoustic Mapping) method was developed to map cavitation activity from acoustic signals emitted by bubbles, passively recorded by a linear ultrasonic imaging probe. However, the TD-PAM suffers from too low resolution and many reconstruction artifacts. In addition, it is time-consuming because it is formalized in the time domain (TD). To overcome these two limitations, it is proposed to study, compare and develop advanced methods of passive ultrasound imaging. This manuscript is structured around three main contributions: An original adaptive method has been formalised in the time domain, based on the amplitude compression of ultrasonic signals by root pth: TD-pPAM. This approach improves the resolution and contrast of cavitation maps for a computing time equivalent to the TD-PAM. The notion of cross-spectral density matrix has been introduced for cavitation imaging. Four Fourier domain (FD) methods were therefore studied and compared: FD-PAM (non-adaptive), Capon Robuste FD-RCB (adaptive, by optimization), Functional Beamforming FD-FB (adaptive, by non-linear compression) and MUltiple Signal Classification FD-MUSIC (adaptive, by subspaces projection). The performance of these FD methods was studied experimentally in vitro in water tank with a comparison by optical imaging. The proposed adaptive FD methods have demonstrated their potential to improve the spatial and temporal tracking of bubbles. The FD-RCB offers a superior localization to the FD-PAM but suffers from a high algorithmic complexity. The performance of the FD-FB is intermediate to that of the FD-PAM and the FD-RCB, for a calculation complexity equivalent to the FD-PAM. The FD-MUSIC has the potential to highlight weak acoustic sources, but does not keep their relative quantifications
Sivadon, Audrey. "Contributions à l’imagerie passive de la cavitation ultrasonore : formation de voies adaptatives en 3D et extension spatiale de nuages de bulles". Electronic Thesis or Diss., Lyon 1, 2022. http://www.theses.fr/2022LYO10172.
Pełny tekst źródłaPassive imaging relies on beamforming algorithms that require large aperture probes to provide good axial resolutions; however, in 3D passive imaging, the matrix probes currently marketed do not meet this constraint. Moreover, these probes have a large number of elements, which makes their use particularly unwieldy. This thesis work focuses on the study and improvement of passive cavitation imaging by addressing two aspects in particular: (i) the practical and efficient implementation of 3D passive imaging, (ii) the problem of imaging large sources such as cavitation clouds. We have combined the application of sparse methods (to reduce the number of active elements of the probe used) and the transposition from 2D to 3D of adaptive algorithms in the frequency domain. This formalism uses the robust estimation of the inter-spectral density matrix (CSM) and allowed us to implement simply and efficiently different algorithms: Delay-And-Sum (DAS), Robust-Capon-Beamformer and Pisarenko. The efficiency of these algorithms in 3D has been tested in terms of width to half height, contrast and position error, on a point source in simulations and on a point reflector in experiments. Finally, in order to address the reality of cavitation clouds, we have investigated the behavior of these reconstruction methods in the case of extended sources. Our 2D simulations show the evolution of the reconstructed images as a function of the cavitation cloud characteristics. This work provides a concrete solution for a simple implementation of 3D passive imaging as well as answers to the expectations on the localization and characterization of a cavitation cloud
Yon, Jérôme. "Jet Diesel haute presssion en champ proche et lointain : Etude par imagerie". Phd thesis, Université de Rouen, 2003. http://tel.archives-ouvertes.fr/tel-00005366.
Pełny tekst źródłaCornu, Corentin. "Caractérisation et régulation des régimes de cavitation ultrasonore pour la sonoporation cellulaire". Electronic Thesis or Diss., Lyon, 2018. http://www.theses.fr/2018LYSE1121.
Pełny tekst źródłaIn the aim of limiting the destructive behavior of collapsing cavitation bubbles, an exclusively stable cavitation state is targeted for sensitive therapeutics applications like blood-brain barrier opening. Ensuring a stable cavitation regime is complex because of (i) the coexistence of stably oscillating bubbles and collapsing bubbles in the same bubble cloud, and (ii) the stochastic behavior of the phenomenon during time. Therefore, it is necessary to control spatially and temporally the cavitation activity, by discriminating the stable from the inertial regime. Firstly, the theoretical study of the dynamics of a monodisperse and homogeneous cloud shows a modification of the stable cavitation threshold as a function of the bubble density: the subharmonics emission threshold is lowered and the resonance frequency is shifted. The study leads also to the expression of a particular microbubbles density leading to optimized subharmonics emission. Secondly, a real-time control strategy based on a feedback loop process on subharmonics emission is designed. The use of this strategy allows discriminating the two cavitation states during time, and ensures a better reproducibility, time-stability and an acoustic energy gain. The control device is used for cells sonoporation in-vitro. In a first study, the sonoporation by inertial cavitation control is performed in a stationary ultrasonic field configuration. This leads to high sonoporation efficiency coupled to the possibility of counterbalancing the use of supplementary nuclei (encapsulated microbubbles). In a second one, the stable cavitation control applied in a focused ultrasound configuration field pinpoints the possibility of sonoporating cells without inertial cavitation, and then to limit cell lysis
Ceccato, Paul. "Microplasma de cavitation en milieu fluide condensé : application à la purification de l'eau". Phd thesis, Ecole Polytechnique X, 2009. http://pastel.archives-ouvertes.fr/pastel-00005680.
Pełny tekst źródłaYon, Jérôme. "Jet diesel haute pression en champ proche et lointain : étude par imagerie". Rouen, 2003. http://www.theses.fr/2003ROUES038.
Pełny tekst źródłaThe aim of the experimental study presented in this thesis is to improve the understanding of the atomization processes involved in a high injection pressure Diesel jet (up to 100 MPa, direct injection). The real Diesel jet structure and the processes involved are not yet fully understood. The great variety of models found in the literature confirms this state of affairs. This lack of knowledge is due to the difficulty of analyzing the Diesel jet caused by its optical density and the size of its characteristic scales of time ("1 ms) and space ("100 æm). During the work carried out for this thesis, new diagnostics based on image processing have been developed in order to analyze the phenomena occurring in the nozzle near field (first millimeters of the jet) and in the far field (spray formed at a long distance from the nozzle). Using several tomographic configurations with an unfocused imaging system, coupled with a shadowgraph imaging setup it was possible to observe, in the near field, cylindrical cavitation pockets located near the jet interface and to drawn a new model of the Diesel jet's internal structure. An entropic calculation applied to three-state-pictures (continuous liquid phase, dispersed liquid phase and gaseous phase) allows us to observe the evolution of a surface linked to the primary atomization. The morphological statistical analysis of the continuous liquid phase interface also enables us to describe the ligament detachment of the dense liquid jet as a function of the injection time and pressure
Ahyi, Ayayi Claude. "Développement dun système d'imagerie ultra-rapide : application aux études de rayonnement et de diffusion acoustique". Lille 1, 1997. http://www.theses.fr/1997LIL10116.
Pełny tekst źródłaCornu, Corentin. "Caractérisation et régulation des régimes de cavitation ultrasonore pour la sonoporation cellulaire". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1121/document.
Pełny tekst źródłaIn the aim of limiting the destructive behavior of collapsing cavitation bubbles, an exclusively stable cavitation state is targeted for sensitive therapeutics applications like blood-brain barrier opening. Ensuring a stable cavitation regime is complex because of (i) the coexistence of stably oscillating bubbles and collapsing bubbles in the same bubble cloud, and (ii) the stochastic behavior of the phenomenon during time. Therefore, it is necessary to control spatially and temporally the cavitation activity, by discriminating the stable from the inertial regime. Firstly, the theoretical study of the dynamics of a monodisperse and homogeneous cloud shows a modification of the stable cavitation threshold as a function of the bubble density: the subharmonics emission threshold is lowered and the resonance frequency is shifted. The study leads also to the expression of a particular microbubbles density leading to optimized subharmonics emission. Secondly, a real-time control strategy based on a feedback loop process on subharmonics emission is designed. The use of this strategy allows discriminating the two cavitation states during time, and ensures a better reproducibility, time-stability and an acoustic energy gain. The control device is used for cells sonoporation in-vitro. In a first study, the sonoporation by inertial cavitation control is performed in a stationary ultrasonic field configuration. This leads to high sonoporation efficiency coupled to the possibility of counterbalancing the use of supplementary nuclei (encapsulated microbubbles). In a second one, the stable cavitation control applied in a focused ultrasound configuration field pinpoints the possibility of sonoporating cells without inertial cavitation, and then to limit cell lysis
Selles, Nathan. "Cavitation et rupture du Polyamide 6 sous état de contrainte multiaxial en traction monotone, fluage et fatigue. Dialogue entre imagerie 3D et modélisation par éléments finis". Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM038/document.
Pełny tekst źródłaMany industrial structures subjected to quasi-static (creep) or cyclic (fatigue) long-term loadings are made of semi-crystalline polymers. Such is the case, for instance, of pressure vessels and pipes. It is therefore considered critical to study the issues related to their durability in order to be able to anticipate and control their end of life. Furthermore, they generally have complex designs and are subjected to multiaxial stress states.The material which has been studied was a semi-crystalline Polyamide 6. Its structure consisted of amorphous and the crystalline phases and a spherolitic microstructure.As a first step, the links between the mechanical behaviour at the global scale of the specimens and the underlying micro-mechanisms of deformation that lead to failure have been established experimentally for monotonic and creep loadings that show similar results and then for fatigue loadings. The influence of the multiaxiality of the stress state has been studied using circumferentially notched round bars with different notch root radii and Compact Tensile specimens. The cavitation phenomena were characterized using synchrotron radiation tomography and laminography techniques that enabled the observation and quantification of the spatial distributions of the voids and the anisotropy of the cavities. An analysis of the fracture surfaces has shown that the initiation of ductile failure resulted from void growth and coalescence mechanismsA poro-visco-plastic model with two mechanisms (that allow the behaviours of the amorphous and crystalline phases to be distinguished) has been used. Thanks to this model, the global behaviour (loading curves) under steady strain rates and steady loads but also the spatial distributions of the void volume fraction could be reproduced numerically. In addition finite element calculations have permitted the spatial distributions of the stress field to be studied and the influence of the stress state on the cavitation state to be investigated. The temporal evolutions during the deformation of the hydrostatic pressure have been linked to the spatial distributions of void volume fraction. The void anisotropy (and thus the void morphology and shape factors) has been related to the evolutions of the components of the Cauchy stress tensor. Finally, the definition of a rupture criterion based on a critical value of the void volume fraction has enabled crack propagation under steady strain rate and steady load to be simulated
Shen, Huanhuan. "Interferometric out-of-focus imaging and digital holography for the characterization of droplets or bubbles : theory, optical design, characterization of a flow, synchronized experiments". Rouen, 2014. http://www.theses.fr/2014ROUES015.
Pełny tekst źródłaAn original simulator of Interferometric Laser Imaging for Droplet Sizing (ILIDS), allowing predicting the image patterns obtained by any imaging system, is developed. The formalism of the simulator relies on the generalized Huygens-Fresnel integral. The initial field scattered by the droplet is simplified by two glare points. An original ILIDS system is designed due to the simulator. The advantage of this configuration is that the three dimensional locations and sizes of droplets can be obtained simultaneously. The cylindrical ILIDS configuration includes a supplemental cylindrical lens rotated in a proper angle with respect to the axis of imaging system. The anamorphic configuration allows to change the orientation of the fringes and the form of the out-of-focus image with respect to the axial location of the particle. Three experiments are successively conducted: water droplets in air, bubbles in water at cubic aquarium and bubbles in glycerin at cylindrical channel. The comparisons of the simulations and experiments show good consistence. The precisions of the axial location and diameter obtained by cylindrical ILIDS technique are evaluated experimentally. The axial locations obtained by cylindrical ILIDS configuration are validated by comparing them with calibrated values, while the diameters are validated due a synchronized experiment coupling Digital In-Line Holography technique and cylindrical ILIDS technique
Asquier, Nicolas. "Etude des moyens de caractérisation de l’ouverture de la barrière hémato-encéphalique induite par un dispositif ultrasonore implantable". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1330/document.
Pełny tekst źródłaThe blood-brain barrier (BBB) is a natural protection of the central nervous system. However, it limits the delivery of many drugs to the brain tissues. It can be temporarily disrupted by ultrasound exposure combined with intravenous injection of microbubbles. In this manuscript, BBB disruption with an implantable unfocused ultrasound device is studied. An automatic method for quantifying the volume of BBB disruption using MR images from a phase 1/2a clinical study in patients with reccurent glioblastoma was assessed and validated. A correlation between the probability of disruption and the local acoustic pressure was found. Microbubbles cavitation activity was studied in vitro to better understand its effect on BBB disruption. The uncertainty on the amplitudes of cavitation signals recorded with a passive single-element detector (PCD) through the skull was quantified. A position-based correction of the PCD signal was assessed and validated. The effect of the volume of a cavitation cloud in the unfocused ultrasound field on the signal amplitude recorded by the PCD during the clinical treatment was discussed. Two methods for localizing and discriminating cavitation sources in a transcranial context were evaluated by simulations and in vitro
Ali, Muhammad. "Etude d'un nouveau dispositif de bioimpression par laser". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0070/document.
Pełny tekst źródłaLaser-based approaches are among the pioneering works in cell printing. These techniques are being extensively focussed for two or three-dimensional structures of any size in transferring pattern materials including deposition of 3D biological constructs. In this context, Laser-Assisted Bioprinting (LAB), based on Laser-Induced Forward Transfer (LIFT) has emerged as a nozzleless method to surmount the drawbacks (e.g. clogging) of inkjet printing technologies. LAB is a laser direct-write technique that offers printing micropatterns with high spatial resolution from a wide range of solid or liquid materials, such as dielectrics, biomaterials and living cells. The technique enables controlled transfer of droplets onto a receiving substrate. A typical LAB setup comprises three key components: (i) a pulsed laser source, (ii) a ribbon coated with the material to be transferred and (iii) a receiving substrate. The ribbon integrates three layers: (i) a quartz disk support transparent to laser wavelength, (ii) a thin (1–100 nm) absorbing layer (like Ti or Au), and (iii) a bioink layer (few tens of microns) incorporating the material to print. The receiving substrate is faced to the bioink and placed at 100 μm to 1 mm distance from the ribbon. Rapid thermal expansion of metallic layer (on absorbing laser pulse) propels a small volume (~pL) of the ink towards a receiving substrate. Such a metallic interlayer eliminates direct interaction between the laser beam and the bioink. Volume of deposited material depends linearly on the laser pulse energy, and that a minimum threshold energy is required for microdroplet ejection. The thickness of the absorbing layer, viscosity and thickness of the bioink, different optical parameters such as the focus spot and the laser fluence are the controlling parameters to obtain a microscopic resolution and to limit the shock inflicted on the ejected cells. In our research works, we considered experimental approach to study the physical mechanism involved in the LAB using a time-resolved imaging method in order to gain a better insight into the dynamics of the transfer process and to use the technique for printing biomaterials. First we designed and implemented a novel configuration of LAB for upward printing. Then we characterized different ejection regimes to define suitable conditions for bioprinting. We further explored jetting window to study the influence of laser energy on jet dynamics. Ejection dynamics has been investigated by temporal evolution of the liquid jet for their potential use in cell printing. In addition parametric studies like effect of viscosity and printing distance on the morphology of the printed drops were conducted to explore jetting “window”. This configuration allows debris-free printing of fragile bioinks with extremely smooth and uniform edges at larger separation distance (ranging from 3 to 10mm). Material criteria required for realization of the cell printing are discussed and supported by experimental observations obtained by TRI investigation of cell printing from donors with different cell concentrations. These results provide key insights into optimization and better control of transfer mechanism of LAB. Finally, in the light of these studies, a comprehensive mechanism is proposed for printing micro-drops by LAB
Asquier, Nicolas. "Etude des moyens de caractérisation de l’ouverture de la barrière hémato-encéphalique induite par un dispositif ultrasonore implantable". Electronic Thesis or Diss., Lyon, 2019. https://n2t.net/ark:/47881/m6rn376t.
Pełny tekst źródłaThe blood-brain barrier (BBB) is a natural protection of the central nervous system. However, it limits the delivery of many drugs to the brain tissues. It can be temporarily disrupted by ultrasound exposure combined with intravenous injection of microbubbles. In this manuscript, BBB disruption with an implantable unfocused ultrasound device is studied. An automatic method for quantifying the volume of BBB disruption using MR images from a phase 1/2a clinical study in patients with reccurent glioblastoma was assessed and validated. A correlation between the probability of disruption and the local acoustic pressure was found. Microbubbles cavitation activity was studied in vitro to better understand its effect on BBB disruption. The uncertainty on the amplitudes of cavitation signals recorded with a passive single-element detector (PCD) through the skull was quantified. A position-based correction of the PCD signal was assessed and validated. The effect of the volume of a cavitation cloud in the unfocused ultrasound field on the signal amplitude recorded by the PCD during the clinical treatment was discussed. Two methods for localizing and discriminating cavitation sources in a transcranial context were evaluated by simulations and in vitro
Boulos, Paul. "Ultrasound imaging of the ultrasound thrombolysis". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1251/document.
Pełny tekst źródłaUltrasound therapy techniques emerged very recently with the discovery of high intensity focused ultrasound (HIFU) technology. Extracorporeal ultrasound thrombolysis is one of these promising innovative low-invasive treatment based on the mechanical destruction of thrombus caused by acoustic cavitation mechanisms. Yet, it is a poorly controlled phenomenon and therefore raises problems of reproducibility that could damage vessel walls. Thus, better control of cavitation activity during the ultrasonic treatment and especially its localization during the therapy is an essential approach to consider the development of a therapeutic device. A prototype has already been designed and improved with a real-time feedback loop in order to control the cavitation power activity. However, to monitor the treatment in real-time, an ultrasound imaging system needs to be incorporated into the therapeutic device. It should be able to first spot the blood clot, to position the focal point of the therapy transducer, control the proper destruction of the thrombus, and evaluate in real-time the cavitation activity. Present work focusses mainly on the development of passive ultrasound techniques used to reconstruct cavitation activity maps. Different beamforming algorithms were investigated and validated through point source simulations, in vitro experiments on a wire, and cavitation experiments in a water tank. It was demonstrated that an accurate beamforming algorithm for focal cavitation point localization is the passive acoustic mapping weighted with the phase coherence factor (PAM-PCF). Additionally, in vivo testing on an animal model of acute limb ischemia was assessed. Finally, some optimizations of the previous developed imaging system were carried out as 3D imaging, real-time implementation, and hybrid imaging combining active anatomical imaging with passive cavitation mapping
Mauger, Cyril. "Cavitation dans un micro-canal modèle d'injecteur diesel : méthodes de visualisation et influence de l'état de surface". Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00747628.
Pełny tekst źródłaZhang, Guangjian. "Etude expérimentale de la structure et de la dynamique des écoulements cavitants". Thesis, Paris, HESAM, 2020. http://www.theses.fr/2020HESAE050.
Pełny tekst źródłaCavitation is a complex phenomenon involving mass transfer between liquid and vapour phase at nearly constanttemperature. Advances in the understanding of the physical processes of cavitating flows are challenging, mainlydue to the lack of quantitative experimental data on the two-phase structures and dynamics inside the opaquecavitation areas. In this thesis, partial cavitation developed in small convergent-divergent (Venturi) channels wasstudied experimentally in detail for a better knowledge of the physical mechanisms governing the cavitationinstabilities. This was achieved by using an ultra-fast synchrotron X-ray imaging technique aided withconventional high speed photography and Particle Image Velocimetry. The main contributions of the presentstudy can be summarized as follows: (1) detailed description of the two-phase flow structures in quasi-stablesheet cavitation, which is characterized by a low-speed re-entrant flow existing continuously underneath thecavity; (2) analysis of the complex effect of cavitation on turbulent velocity fluctuations; (3) identification ofthree distinct mechanisms responsible for the transition of sheet-to-cloud cavitation, with a discussion of thedifferences between them; (4) analysis of the scale effect on cavitation in the studied Venturi flows
Souquet, Agnès. "Etude des processus physiques mis en jeu lors de la microimpression d'éléments biologiques assistée par laser". Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14232/document.
Pełny tekst źródłaOver this decade, cell printing strategy has emerged as one of the promising approaches to organize cells in two and three dimensional engineered tissues. In parallel with ink-jet printing and bioplotting, Laser Assisted Bioprinting (LAB) using Laser-Induced Forward Transfer (LIFT) has emerged as an alternative method in the assembly and micropatterning of biomaterials and cells. LAB is a laser direct-write technique that offers the possibility of printing micropatterns with high spatial resolution from a wide range of solid or liquid materials, such as dielectrics, biomolecules and living cells in solution. In our research works, we considered an experimental and numerical approach to study the physical mechanisms involved in the biological elements microprinting laser assisted.First we defined the rheological parameters of bioinks and the transfer conditions (composition, thickness and viscosity of the bioink and laser energy). Then we led a statistical analysis of the volume of the transfer droplets for four viscosities of bioink, five thicknesses of bioink and five laser energies. Then we designed and implemented a system for time resolved imaging to study the effects of viscosity on the dynamics of the ejection. Thus we have differentiated three ejection regimes in function of the laser energy released in the absorbing layer, the visocsity and the thickness of the bioink. In parallel, a numerical model was developed to understand and predict the dynamics of the ejection parameters according to multiple choice and thickness of the absorbing layer, thickness of the layer bioencre, energy deposited. Finally, with regard to these studies, we propose a mechanism for ejecting droplets involved in the process of laser-assisted microprinting
Peterson, Ashley Thomas. "Cavitation prediction". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612813.
Pełny tekst źródłaJohansen, Kristoffer. "Stable-inertial cavitation". Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/30796/.
Pełny tekst źródłaOdeyemi, Babatunde O. "Hydrodynamic cavitation : effects of cavitation on inactivation of Escherichia coli (E.coli)". Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/11009.
Pełny tekst źródłaKrahl, Dominik, Jürgen Weber i Maik Fuchs. "Visualization of cavitation and investigation of cavitation erosion in a valve". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-199616.
Pełny tekst źródłaRobin, Justine. "Development of a 3D time reversal cavity for pulsed cavitational ultrasound : application to non-invasive cardiac therapy". Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC273/document.
Pełny tekst źródłaThe objective of this thesis was to explore new applications for cardiac histotripsy, and to develop the tools making it possible non-invasively. Cardiac ultrasound therapy indeed still remains limited due to the tremendous challenge of treating a constantly and rapidly moving organ, well protected behind the ribcage.We first showed in vivo, on a large animal model, that histotripsy could be used non-invasively to cut mitral chordae, and to treat calcified aortic stenosis in a beating heart. Cavitation on the valve leaflets can indeed locally and remotely act on the calcifications, and globally soften the valve. Simultaneously, we developed a therapeutic device allowing completely non-invasive cardiac shock-wave therapy based on the time reversal cavity concept. In particular, this device allows the emission of high intensity ultrasound pulses, and provides 3D electronical steering of the therapy focal spot in a large volume. After a thorough optimisation process, this device was capable of creating well controlled mechanical lesions over a 2 000 cm3 region of interest. To tackle the challenge of ultrasound propagation through the rib cage, we developed an adaptive focusing method (DORT method through a time reversal cavity), and implemented it in a 2D prototype of the device. With this method, we not only could build an adaptive ultrasonic wavefront propagating preferentially through the intercostal spaces, but due to time reversal cavities properties, we could also increase the peak pressure obtained on target.Finally, we pushed our work on adaptive focusing further, and considered the case of transcranial imaging. For this application, we chose to use the time reversal of speckle noise technique, to correct the aberrations induced by the skull. In numerical simulations, we were able to derive the phase and amplitude modulations induced by the bones, and could improve the contrast and resolution of a B-mode image
Jin, Yong-Hua. "Optical investigations of cavitation". Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/27390.
Pełny tekst źródłaWatson, Peter. "Cavitation in human joints". Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304536.
Pełny tekst źródłaHou, Hang-sheng. "Cavitation instability in solids". Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13697.
Pełny tekst źródłaGerold, Bjoern. "Cavitation in focused ultrasound". Thesis, University of Dundee, 2013. https://discovery.dundee.ac.uk/en/studentTheses/f41bf6b9-ae59-4a41-ba29-d5873821418b.
Pełny tekst źródłaWilms, Jeffrey. "Flow visualization of cavitation". Thesis, Kansas State University, 2013. http://hdl.handle.net/2097/32158.
Pełny tekst źródłaDepartment of Mechanical and Nuclear Engineering
Mohammad Hosni
A typical refrigeration loop is composed of an evaporator, compressor, condenser, and an expansion valve. There are many possible refrigerants that can be used, but the physical properties of water make it ineffective in the traditional refrigeration loop. But if water could be used it would have many advantages as it is abundant, cheap, and is safe for the environment. This research focuses on a different kind of refrigeration loop using water. This new refrigeration loop utilizes water flowing through a nozzle, initiating cavitation. Cavitation is generally defined as creating vapor from liquid, not through adding heat, but by decreasing the pressure. In a converging/ diverging nozzle, as the cross sectional area is constricted, the velocity of the flow will increase, decreasing the pressure. Therefore, by flowing water through the nozzle it will cavitate. Transforming liquid into gas requires a certain amount of energy, defined as the latent heat. When a liquid is turned to vapor by an increase in the temperature, the latent heat is provided by the heat transfer to the system. As no energy is being added to the nozzle to cause the cavitation, the energy transfer to create the vapor comes from the remaining liquid, effectively causing a temperature drop. This research focused on the flow visualization of water cavitating as it travelled through a converging/ diverging nozzle. Under different flow conditions and different nozzle geometries, the cavitation manifested itself in different formations. When gasses were entrained in the water they formed bubbles, which acted as nucleation sites as they moved through the nozzle. This was called travelling bubble cavitation. In venturi nozzles the cavitation nucleated off of the wall, forming attached wall cavitation. When water flowed out of an orifice, a turbulent mixture of liquid and vapor, orifice jet, was formed which caused vapor to form around it. This was known as shear cavitation. When the water was rotated prior to the throat of an orifice, the orifice jet expanded radially and formed swirl cavitation. In addition to studying how the cavitation was formed, the void fraction and velocity were measured for attached wall cavitation.
Letchford, Nicholas. "Cavitation in lubricating films". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:17a49106-bb6d-443c-be6b-50398bbd4590.
Pełny tekst źródłaZuo, Zhigang. "Experimental and Numerical study of Laser-induced Cavitation Bubbles on Warwick Cavitation Rig". Thesis, University of Warwick, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488496.
Pełny tekst źródłaGoudot, Guillaume. "Applications innovantes des ultrasons en pathologie vasculaire : utilisation de l'imagerie ultrarapide dans l'analyse de la rigidité artérielle et des ultrasons pulsés en thérapie Arterial stiffening assessed by ultrafast ultrasound imaging gives new insight into arterial phenotype of vascular Ehlers–Danlos mouse models Aortic wall elastic properties in case of bicuspid aortic valve Segmental aortic stiffness in bicuspid aortic valve patients compared to first-degree relatives Wall shear stress measurement by ultrafast vector flow imaging for atherosclerotic carotid stenosis Pulsed cavitational therapy using high-frequency ultrasound for the treatment of deep vein thrombosis in an in vitro model of human blood clot". Thesis, Sorbonne Paris Cité, 2018. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=2215&f=13951.
Pełny tekst źródłaHerbert, Éric. "Cavitation acoustique dans l'eau pure". Phd thesis, Université Paris-Diderot - Paris VII, 2006. http://tel.archives-ouvertes.fr/tel-00139435.
Pełny tekst źródłaEwunkem, Asoumu Emmanuel. "Cavitation erosion of engineering materials". Thesis, City University London, 1993. http://openaccess.city.ac.uk/8358/.
Pełny tekst źródłaPennathur, Sumita 1978. "Micro-scale turbopump blade cavitation". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8719.
Pełny tekst źródłaIncludes bibliographical references (p. 195-196).
The possibility of a silicon micro-fabricated turbopump for the use in a micro-fabricated bipropellant liquid rocket engine is of interest. Such a pump might have airfoils on the order of 1mm chord and 0.2mm span and operate at a Reynolds number of 6000. Cavitation is a major technical issue in such a pump, but there is little work in the literature at this length scale. This work documents analytical and experimental investigations of cavitation on millimeter long pump blading. Cavitation inception and bubble growth are analyzed on a micro-scale and deviations from macro-scale theory are discussed. The analysis suggests that residence time, surface roughness, surface tension, and passage area constraints are significant factors in cavitation inception and growth. A non-rotating microfabricated cascade has been designed, fabricated, and tested to quantify the behavior of micro-scale cavitation. An experimental rig has been constructed, and 18 micro-cascades have been tested. Visual observations confirm the existence of cavitation, and illustrate the phenomena of hysteresis and time lag. Comparisons of test results with analysis indicate that cavitation inception is adequately modeled by macro-scale theory. Test repeatability is established and the experimental data is found to be in agreement with 3D numerical results. Performance impacts of cavitation on micro-scale bade rows are discussed and several useful correlations are included. No apparent surface damage has been observed in these experiments. The experimental and analytical results are compiled in the form of design criteria for micro-scale turbopumps, and are used to evaluate the performance impacts due to cavitation. It is estimated that for a micro-turbopump operating at the most severe expected cavitating conditions, the performance loss in terms of pressure recovery is not greater than 20%.
by Sumita Pennathur.
S.M.
Kotopoulis, Spiros. "Biomedical ultrasonics, cavitation, and sonoporation". Thesis, University of Hull, 2011. http://hydra.hull.ac.uk/resources/hull:4746.
Pełny tekst źródłaLisle-Taylor, S. C. "Cavitation performance of pumped hydrocarbons". Thesis, Cranfield University, 1997. http://dspace.lib.cranfield.ac.uk/handle/1826/9676.
Pełny tekst źródłaHerbert, Eric. "Cavitation acoustique dans l'eau pure". Paris 7, 2006. http://www.theses.fr/2006PA077185.
Pełny tekst źródłaAny liquid can be superheated or stretched beyond its boiling curve. It will then remain in a metastable state, until a vapor bubble appears : this is the cavitation phenomenon. The study of the metastability limit gives information about the cohesion of the liquid and its equation of state. The case of water is of special interest ; indeed competiting theories predict qualitatively different temperature variations of the stability limit : either monotonic (the cavitation pressure increase with temperature), or with a minimum. We have stretched water with an ultrasonic wave, generated by a hemispherical piezoelectric ceramic, duting a short time and a small volume, far from any wall, which reduces the effect of impurities. We obtain very accurate and reproducible results, allowing u to study in details the statistic of cavitation and to define a cavitation thresold. The ceramic was calibrated using two independent methods : needle hydrophones, and a method based on the variation of the static pressure. Both of them lead to the same result. We find a monotically increasing cavitation pressure, from -26 MPa at 0°C to -16 MPa at 80°C. These values are among the most negative reported, but far away from the values expected theoritically (-120 Mpa), and observed only once (Zheng et al. , 1991, Science 254, 829). We discuss the possible origin of this discrepancy : it can be due either to the presence of impurities in the liquid, whose nature and concentration we discuss, or to an unexpected change in the equation of state of water at large negative pressures
Hankey, S. E. "Cavitation erosion of WC-Co". Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/21135.
Pełny tekst źródłaAn investigation involving the vibratory cavitation erosion of WC-Co alloys was undertaken in order to determine the mechanisms of material removal. Nineteen grades of WC-Co alloys were studied. These alloys had been previously characterised according to microstructural and mechanical properties. Further characterisation by way of Young's modulus and density of the materials was undertaken. An investigation of the i nfluence of various parameters on cavitation erosion established a binder content dependence on erosion. For two grain sizes, erosion was found to increase to a maximum at 12 vo1-% binder content (1.8 μm grain size) and 23 vol-% binder (2.8 μm grain size). The main mode of material removal was found to be cobalt removal followed by WC grain pull-out. In high binder content alloys, cobalt removal was predominant with little loss of WC grains. X-ray diffraction showed that the allotropic phase transformation of the binder under cavitational attack was beneficial to the erosion resistance of these alloys. The erosion of low binder content alloys was controlled by the contiguity of the WC skeleton. Maximum erosion occurred at binder contents which corresponded to the combination of a fragile WC skeleton and a small volume of available cobalt for strain induced transformation.
Lesko, Timothy Michael McKoy Vincent. "Chemical effects of acoustic cavitation /". Diss., Pasadena, Calif. : California Institute of Technology, 2004. http://resolver.caltech.edu/CaltechETD:etd-04262004-184449.
Pełny tekst źródłaHe, Bingrong. "An investigation of cavitation thresholds /". Search for this dissertation online, 2004. http://wwwlib.umi.com/cr/ksu/main.
Pełny tekst źródłaLi, Shengcai. "Cavitation associated low-frequency fluctuation". Thesis, University of Warwick, 1990. http://wrap.warwick.ac.uk/108599/.
Pełny tekst źródłaPineda, Rondon Saira Freda. "Numerical prediction of cavitation erosion". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC031/document.
Pełny tekst źródłaHydraulic turbines can experience cavitation, which is a phenomenon occurring when vapor bubbles collapse in the vicinity of the machine’s surface. This phenomenon can lead to negative consequences, such as erosion, that affect the machine’s performance. The compression of a non-condensable gas bubble in water is simulated with the Smoothed Particle Hydrodynamics method following the Arbitrary Lagrange Euler approach (SPHALE), where a compressible and multiphase model has been developed. The model solves the mass, momentum and energy conservation equations of the Euler system using the Stiffened Gas EOS for water and the ideal gas EOS for the non-condensable gas inside the bubble. Both phases are modeled as compressible and the phase change is not considered. The meshless feature of the SPH-ALE method allows the calculation of multiphase flows where the interface is sharply defined. For cavitation applications, where the Mach number reaches values of 0.5, the distribution of particles must be corrected, which is achieved by the ALE feature. The compressible model was validated through monodimensional configurations, such as shock tube test cases for monophase and multiphase flows. The bubble compression close to the wall has been addressed as the fundamental mechanism producing damage. Its general behavior is characterized by the formation of a water jet and by the collapse of the bubble by itself. The phenomenon is analyzed by considering the major parameters that govern the bubble collapse dynamics, such as the initial distance between the bubble center and the wall (H0), the bubble size (R0), and the collapse driven pressure ratio (pw/pb). It is shown that the intensity of the collapse depends mainly on the pressure ratio between the liquid and the bubble (pw/pb). As well, four indicators, such as the pressure at the wall, the impulse, the water-hammer pressure and the water jet velocity, are used to determine the loading. This analysis gives that the bubble initially located at a distance lower than H0/R0 = 2 presents high potential to cause damage. In order to predict the damage due to the bubble collapse, the solid mechanics is analyzed through fluid-structure interaction simulations. It is obtained that the material reacts to the hydraulic loads by having compression and traction zones, suggesting that a fatigue mechanism drives the damage phenomenon. Additionally, it is found that the highest stresses are located below the material surface, indicating that this zone may reach plastic deformation
Lafond, Maxime. "Confocal Ultrasound for the Potentiation of Chemotherapy by Ultrasonic Cavitation without External Nucleation Agents". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1243/document.
Pełny tekst źródłaCancer is recognized as one of the major health issues of this beginning century. Even if great achievements have been performed, chemotherapies induce systemic toxicity and combinable physical agents are invasive. Ultrasound has shown a great potential as an external physical agent. Applied extracorporeally, it can penetrate in depth in tissue and induce various biological effects, mechanical of thermal. Notably, cavitation, which is the formation and oscillatory motion of bubbles in a media, has effects providing the possibility to enhance the delivery of chemotherapeutic agents. This effect can be induced in biological tissues by using external nucleation agents such as ultrasound contrast agents. However, to avoid diffusion issues, this work focuses on cavitation without external nucleation agents. For this purpose, a particular setup based on two confocal transducers was designed. Simulations showed its advantages for cavitation applications. A developed preclinical device demonstrated the safety of using unseeded inertial cavitation for the potentiation of doxorubicin (DOX) regarding the drug stability, the effect on healthy tissues and the metastatic spreading. Unfortunately, no effect of combining inertial cavitation with DOX in could have been demonstrated in vivo. To investigate stable cavitation phenomenon, a control process was developed. It permitted to evidence in vitro the synergistic interaction between DOX and stable cavitation. Again, preclinical studies were not able to prove this synergy in vivo. To assess the correct tissue exposures to stable cavitation, a localization method was developed and validated
Guilleumas, Montserrat. "Nucleation and cavitation in liquid helium". Doctoral thesis, Universitat de Barcelona, 1995. http://hdl.handle.net/10803/667593.
Pełny tekst źródłaZhou, Zhi-ang. "Gas nucleation and cavitation in flotation". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40477.
Pełny tekst źródłaExperimentally, the existence of gas nuclei in water was demonstrated from coagulation, sedimentation and filtration tests of fine coal (d$ sb{50} approx 5 mu$m) and silica (d$ sb{50} approx 3.5 mu$m) particles. Small bubbles are generated, from the expansion of the pre-existing gas nuclei, by hydrodynamic cavitation induced by flow of liquid through a nozzle at a velocity of 8-15 m/s, depending on nozzle diameter and length. This velocity of bubble initiation is reduced 5-7 m/s when the liquid is gas-supersaturated. Surfactants do not affect the on-set of bubble formation by cavitation, but increase the amount of bubbles formed. The addition of a small amount of hydrophobic particles in gas-supersaturated systems increases the quantity of bubbles generated, while the presence of hydrophilic particles reduces bubble formation.
Dissolved air (or carbon dioxide) flotation of fine silica (d$ sb{50} approx 1.6 mu$m) has shown that recovery increases with the slurry flow velocity, regardless of the saturation pressures applied (102-310 kPA). Releasing the gas-supersaturated slurry into a solution gives a higher recovery than releasing the gas-supersaturated slurry into a slurry. These observations suggest that bubble nucleation is a better mechanism for enhancing particle collection compared with the direct particle-bubble contact.
Flotation results using a newly designed flotation reactor indicate that adding a cavitation tube and a small amount of air in the feed stream increases recovery significantly, and that bubbles formed by hydrodynamic cavitation play a role in improving flotation kinetics, even in the absence of added gas in the stream.
Moule, R. T. "Cavitation erosion in a corrosive environment". Thesis, Coventry University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374256.
Pełny tekst źródłaLloyd, James G. "The cavitation phenomenon in nonlinear elasticity". Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589654.
Pełny tekst źródłaVilleneuve, Randall A. (Randall Alan). "Effects of viscosity on hydrofoil cavitation". Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/17325.
Pełny tekst źródłaIncludes bibliographical references (leaves 118-120).
by Randall A. Villeneuve.
M.S.