Dissertations / Theses on the topic 'Fibre Hydrophone'

In this thesis, my main focus was to establish a novel composite-cavity fibre laser (CCFL) and to apply it in sensing, particularly in the hydrophone application. The CCFL that I have proposed is formed by writing three wavelength matched fibre Bragg gratings directly into a continuous length of doped fibre. I have also examined the relative advantages and disadvantages of interferometric and intensity-based hydrophone systems, and have established a hydrophone system that can be switched between the two modes of operation, by making use of digital signal processing. I have established a theoretical model to study the lasing and spectral characteristics of the CCFL. My analysis showed that whilst the CCFL have significantly different phase and threshold conditions from the common semiconductor diode lasers with external cavity, the CCFL also have mode-limiting properties that are often sought after. Through simulations, I was able to identify that a non-uniform straining scheme, that is, when one of the sub-cavities of the CCFL is restrained from strain, can improve the sensitivity with respect to existing single cavity fibre lasers, in both the frequency and intensity domains. My simulations also showed that the sensitivity of such a straining scheme can be optimised by tuning the reflectivity of the gratings, sub-cavity lengths, doping concentration and pump power. I have fabricated multiple CCFLs using the in-house grating writing facilities, and have experimentally assessed their power and spectral related lasing characteristics. Whilst having a significantly longer total cavity length compared to typical fibre lasers, the CCFLs demonstrated stable single longitudinal mode operation and narrow linewidth in the order for a few tens of kHz. Asymmetric output power and frequency as a result of unequal sub-cavity lengths were also examined. Finally, I conducted sensing experiments by applying the CCFLs in strain monitoring and intensity-based hydrophone. My results showed that the non-uniform straining scheme had significantly improved the intensity response of the CCFL, and that the acoustic pressure and frequency can be determined by directly sampling and applying Fourier transform to the output intensity of the fibre laser.

This thesis is composed of two distinct parts. The first part of this work addresses the problem of critical ignition behind a decaying shock wave in the context of cellular detonations. Low-pressure (4.1 kPa) shock tube experiments were performed in a thin rectangular channel using the highly-unstable mixture of CH4 + 2O2 and the weakly-unstable mixture of 2H2 + O2 + 7Ar, with Schlieren visualization of the flow field. The dynamics of the lead shock in a detonation cell was reconstructed from measurements of the lead shock position and curvature. The post-shock state and the expansion rate along the path of a Lagrangian particle crossing the lead shock at any given point in the cell cycle were evaluated with the shock jump and shock change equations. The chemical evolution behind the shock was then integrated using a detailed chemistry model. Quenching of the post-shock reaction zone was found within the first half of the detonation cell for both mixtures, with quenching occurring earlier in the highly unstable mixture. Simplified models derived from 1-step and 2-step chemistry models very accurately predict the quenching of the post-shock reactions and the evolution of the ignition delay through the cell. The second part describes the assembly and characterization of a fibre-optic probe hydrophone (FOPH) for the measurement of shock waves associated with blast-induced neuro-trauma. Compared to traditional polyvinylidene difluoride (PVDF) hydrophones, the assembled FOPH has a higher bandwidth and smaller active diameter, which are comparable to the characteristic time and thickness of shock waves associated with blast-induced neuro-trauma. However, the sensitivity of FOPHs are substantially lower than traditional hydrophones. We assemble a FOPH and provide detailed calculations and measurements of its sensitivity (0.66 mV/MPa) , noise floor, and spatial resolution. The 150 MHz bandwidth, limited by the photodetector, is sufficient for resolving shock waves with over-pressures of up to 174 kPa with 3 measurement points. Experimental measurements of the system noise gives a floor of 260 Pa/√Hz . A detailed noise analysis finds that the system is limited by photodetector noise (215 Pa/√Hz), which is 4x the fundamental shot noise limit, closely followed by a laser noise of 150 Pa/√Hz. We conclude that the system noise floor is insufficient for resolved measurements of the post-shock pressure in the range associated with blast-induced neuro-trauma. From our noise analysis, we quantify the sensitivity enhancement required for resolving this regime, and we conclude that sensitivity-enhancing fibre-coatings could provide a sufficient increase in sensitivity.

This thesis documents the development of a novel fibre optic hydrophone, for the characterisation of medical ultrasound transducers and the measurement of ultrasound induced temperature rises. The transduction mechanism of the hydrophone is based on the detection of acoustically and thermally induced changes in the optical thickness of a Fabry-Perot interferometer deposited at the tip of a single mode optical fibre. The interferometer comprises a layer of Parylene-C sandwiched between two thin gold mirrors. The design of the sensor was optimised using a numerical model of the interferometer transfer function. Through the use of vacuum deposition techniques, a fabrication procedure has been developed which enables batch production of the sensors. A self contained sensor interrogation system has also been developed. The system uses a rapidly tuneable laser developed originally for the telecoms industry to interrogate the sensor and make acoustic and thermal measurement, Control of the system is achieved via a PC using software written in Labview 8.0.

Il a été montré que la cavitation acoustique pouvait se révéler utile dans l'administration de médicaments pour de nombreuses applications biologiques et médicales. Cette thèse commence par une présentation de la cavitation ultrasonore et des mécanismes d'action mis en jeu pour la délivrance de médicaments. A la fin de ce cette synthèse, un dispositif à deux transducteurs ultrasonores disposés de manière confocale est présenté pour résoudre certains des problèmes actuels dans le domaine. Il est ensuite mis en oeuvre dans différentes études de faisabilité. La thèse est organisée en 5 chapitres : 1. L'utilisation de la cavitation acoustique dans un contexte biomédical est présentée ici dans une revue générale. Ce chapitre comprend l'état de l'art pour la génération de cavitation, les techniques expérimentales qui sont actuellement mises en oeuvre pour la mesure de la cavitation, et les approches cliniques et précliniques pour l'utilisation de la cavitation in vivo pour différents types de tissu biologique. 2. Le dispositif ultrasonore utilisé pour toutes les études de cette thèse est ensuite décrit. Il est caractérisé acoustiquement et comparé avec un simple transducteur dans le but de démontrer son efficacité pour la génération de la cavitation. Cette comparaison est d'abord faite par une quantification chimique du niveau de cavitation. A puissance constante, le dispositif à deux transducteurs confocaux est bien plus efficace pour générer de la cavitation. Les causes de cette observation, notamment la réduction de la propagation non-linéaire et la stabilisation du nuage des bulles par les forces Bjerknes, sont ensuite étudiées par des mesures acoustiques, des simulations de pression en régime linéaire et un suivi par une caméra ultra rapide des nuages de bulles induits. 3. Le prototype confocal est utilisé in vivo sur des tumeurs sous cutanées en conjonction avec des liposomes. Dans un premier temps, des essais sous IRM démontrent la possibilité de larguer le contenu des liposomes localement par la cavitation inertielle délivrée par le dispositif. Une seconde étude avec une formulation liposomale de doxorubicine a permis de démontrer l'amélioration de la réponse thérapeutique de la chimiothérapie après application de la cavitation inertielle.. 4. Une étude de faisabilité de l'interférence de l'ARN (RNAi) sur un petit nombre d'animaux est réalisée avec le dispositif confocal et des molécules de siRNA encapsulées dans des liposomes Les expériences sont conduites in vivo avec une xénogreffe de tumeur de sein humain. Après une phase de réglage des paramètres ultrasonores pour limiter la toxicité du traitement, on observe une inhibition significative du gène ciblé. 5. Une deuxième étude de faisabilité est réalisée pour étudier la potentialisation de la chimiothérapie avec l'évérolimus dans un modèle de chondrosarcome de rat. Les traitements ultrasonores et les chimiothérapies sont répétés. Sur un petit nombre d'animaux, on montre l'innocuité du traitement ultrasonore, et l'efficacité en conjonction avec l'agent anti tumoraux, évérolimus
Acoustic cavitation has been shown to be a useful tool in drug delivery for many different biological tissues and indications, and this thesis aims to contribute to the knowledge of cavitation from a drug delivery perspective. This thesis seeks to synthesize the current knowledge and practice concerning acoustic cavitation in a biomedical context, and to present a high intensity confocal ultrasound (US) prototype to address some of the current problems in the field and to give a proof of concept for the therapeutic efficacy of such a prototype. The thesis is organized in 5 chapters: 1. The use of acoustic cavitation in a biomedical context is presented here in a general review. This review comprises the state of the art for cavitation generation, experimental techniques currently being implemented for the measurement of cavitation, and the clinical and preclinical approaches to the use of cavitation in vivo on a tissue by tissue basis. 2. The high intensity confocal US prototype used for all studies in this thesis is presented here. It is characterized in terms of the advantages it gives for the generation of cavitation. Enhancement of cavitation is first demonstrated chemometrically with a fluorescent dosimeter compared to a single transducer at the ultrasonic focus. The mechanisms for cavitation enhancement are then investigated with acoustic measurements, linear pressure simulations, and high speed camera data. 3. The confocal US prototype in used in conjunction with a liposomal formulation of doxorubicin is performed in which a therapeutic enhancement of tumor inhibition is presented. The mechanism of this enhancement is investigated with liposomally encapsulated lanthanide contrast agents and magnetic resonance imaging. 4. A small scale proof of concept for the use of RNA interference using the confocal prototype, and liposomally encapsulated siRNA molecules. The experiments are performed In vivo with a xenograft of human breast tumor. This study also includes data for the safety of the US exposure on a mouse treated one time. 5. Another small scale proof of concept of the use of the confocal device on potentiating chemotherapy with the drug everolimus in a rat chondrosarcoma model. The studies presented here also investigate the use of multiple US exposures on the same tumor in a combined drug / US treatment regimen

Dual purpose fiber optic microbend loss sensors have been developed for measurement of underwater acoustic wave amplitudes and for detection of the direction of wave propagation. Cylindrical sensing elements with external threads have fibers wound around them. Axial slots, cut along the length of the cylinder and deeper than the threads, provide the microbends. Three different construction schemes for cylindrical sensing elements are built. The dual purpose hydrophones are characterized for frequencies ranging from 15 kHz to 75 kHz. Based on the results, an improved design that uses the wavelength dependence of microbend loss in a single mode fiber is proposed.
Master of Science

Ultrasonic imaging uses higher ultrasound frequencies and power levels to achieve better spacial resolution and image quality. Potential hazard for patients have to be evaluated on the basis of relevant acoustic parameters. Measurements of the acoustic pressure with piezoelectric hydrophones is only reliable up to 40 MHz because of minimum sensor size. This work improves a pizooptical measurement method for acoustic pressure. Acoustic pressure changes the refractive index of water. This is determined by measuring laser power, reflected at a fiber/water interface. To improve calibration uncertainty for that kind of measurement to the level of piezoelectric hydrophones (11% - 14%) was the primary goal. Therefore a piezooptic fiber hydrophone with single mode fiber and single mode light source (laser diode) is developed. The active area of the used single mode fiber type has a diameter of 5 µm. Since the fiber influences sound field propagation due to reflection and diffraction, sensitivity of the device is frequency dependent. These effects are compensated by mathmatic modelling. By calculaing the exact curve progression of the factor of reflection depending on the refractive index gradient at the fiber/water interface, calibration uncertainty is improved from 18% to below 11%. Results are validated by intercomparison with several calibarted piezoelectric hydrophones. Measurements are carried out on different ultrasound imagaing systems.

This thesis reports the advancement of two forms of Fabry-Pérot fibre optic hydrophone for the characterisation of high intensity and high pressure ultrasound fields. The first form of fibre optic hydrophone was realised using a multi-layered hard dielectric Fabry-Pérot interferometer deposited at the tip of an optical fibre. The acoustic transduction mechanism is based on the detection of acoustically induced changes in the optical thickness of the spacer layer. Several hydrophone designs were realised and an extensive investigation into the acoustic performance of the hydrophones was conducted. Each hydrophone design is anticipated to be capable of characterising acoustic fields of high pressure, with working ranges of ~90MPa. In addition, the hydrophones were shown to be able to withstand acoustic fields with intensities up to 1833W.cm-2. The frequency response of the hydrophones was measured using substitution calibration and the features of the response were investigated using a finite difference model (AFiDS). The directional response was also measured, and the hydrophones were found to be most sensitive to acoustic fields of non-normal incidence. The sensors were shown to not be subject to self-heating when interrogated by light of optical power below 3.78mW and to have a noise equivalent pressure of 30.9kPa (at 3.5MHz over a 20MHz noise bandwidth). A 3MHz frequency component was observed during the acoustic characterisation and after extensive experimentation the transduction mechanism was found to be optically sensitive and not due to the Fabry-Pérot interferometer. A second form of Fabry-Pérot fibre optic hydrophone was introduced and has previously been reported to not be able to operate at temperatures in excess of 70°C. The cause for this limitation was investigated and found to be due to the annealing of the Parylene-C spacer within the Fabry-Pérot interferometer when elevated to temperatures exceeding 56°C. The effects of annealing on the interferometer transfer function, and acoustic response were investigated. Annealing was found to produce an irreversible shift in the reflectance minimum of the interferometer transfer function, as well as a change in the frequency response of the sensor, with the features moving to higher frequencies.

Les fibres naturelles telles que le coton et le lin sont utilisées depuis longtemps dans l'industrie textile. De plus, elles prennent de plus en plus d'importance dans l'industrie des composites comme substituants des fibres de verre, de carbone ou d'aramide. Cependant, les fibres naturelles doivent être modifiées pour surmonter certains inconvénients tels que l'inflammabilité, l'hydrophilie et l'oléophilie. Dans ce travail, les retardateurs de flamme (RF) phosphorés et fluoro-phosphorés sont greffés par bombardement électronique et par modification chimique sur des tissus de lin afin d’améliorer leur comportement au feu, l’hydrophobicité et l’oléophobie. L'effet de la composition chimique sur le greffage a été également évalué en utilisant des fibres de miscanthus comparativement aux tissus de lin. La réactivité de la double liaison C = C des monomères phosphorés est étudiée pour contrôler l’efficacité de greffage de différents RF. Les étapes du radiogreffage sont étudiées et contrôlées. L'efficacité de greffage a été évaluée par fluorescence X et analyse par rayons X à dispersion d'énergie (EDS) / microscopie électronique à balayage (SEM). La résonance magnétique nucléaire du proton est utilisée pour analyser l'effet de l'irradiation sur les différents monomères. Le comportement au feu des tissus modifiés est étudié en utilisant l’analyse thermogravimétrique, la microcalorimétrie de combustion, cône calorimètre et un test au feu préliminaire. Des tissus ignifuges et oléophobes ont été développés avec succès
Many natural fibers have been used for a long time in textile industry as cotton and flax. Moreover, natural fibers are getting more importance in composites industry as a substitute for glass, carbon, or aramid fibers. However, they must be modified to overcome some disadvantages such as flammability, hydrophilicity and oleophilicity. In this work, phosphorus and fluoro-phosphorus flame retardants were grafted by e-beam radiation and chemical modification on flax fabrics to improve their flame retardancy, hydrophobicity and oleophobicity. The effect of chemical composition on grafting were also evaluated using miscanthus fibers in comparison to flax fabrics. The reactivity of the double bond C=C of the P-monomers was studied to control the grafting yield of various FRs. Radiation grafting steps were studied and controlled carefully. Grafting efficiency was assessed by X-ray fluorescence and Energy Dispersive X-Ray Analysis (EDX) / Scanning Electron Microscopy (SEM). Proton nuclear magnetic resonance was used to analyze the effect of irradiation on different monomers. Fire behavior of the modified fabrics was studied using thermogravimetric analysis, pyrolysis combustion flow calorimetry, cone calorimetry and a preliminary fire test. Flame retardant and oleophobic fabrics were successfully developed

Le coton est la fibre textile végétale la plus utilisée mais elle est souvent remplacée par des fibres synthétiques pour des utilisations extérieures du fait de son caractère hydrophile. Nous avons ainsi développé des procédés d'hydrophobation de fibres cellulosiques (fibres, fils et tissus de coton en particulier) par des réactions d'acylation à l'aide de dérivés d'acides gras directement issus des huiles végétales. Puisque la structure cristalline de la cellulose conditionne la réactivité de ses groupements hydroxyles, nous avons utilisé deux types de prétraitement des fibres cellulosiques afin d'y faciliter la pénétration des réactifs gras : l'échange de solvants et, pour la première fois, l'émulsion. Dans un premier temps, nous avons réalisé l'estérification et la transestérification de la cellulose à l'aide respectivement de l'acide octanoi͏̈que et du laurate de méthyle dans un réacteur classique en utilisant un sel d'acide gras. Les esters cellulosiques obtenus après 6 heures de réaction à 195°C ont des degrés de substitution (DS) de 0,28 et 0,13 respectivement. Dans un deuxième temps, nous avons utilisé les micro-ondes comme nouvelles sources d'énergie pour réaliser ces deux réactions. Les esters obtenus ont des DS respectivement de 0,14 et 0,10 après seulement 5 minutes de réaction à 195°C. La diminution considérable de la durée de réaction s'accompagne d'une dégradation moindre des fibres cellulosiques. Ces techniques ont été ensuite généralisées à des réactifs gras de masse moléculaire plus importante entraînant une diminution du DS. Des analyses physiques et mécaniques nous ont permis d'expliquer l'influence du prétraitement, de la nature des réactifs et des conditions expérimentales sur les propriétés de fibres, fils et tissus de coton. Les méthodes d'acylation mises au point permettent ainsi de conférer aux substrats cellulosiques un caractère hydrophobe marqué.

La connaissance précise au fil du temps des propriétés physiques du milieu de culture d’un végétal est importante pour une gestion efficace de l'irrigation et de la fertilisation. Ce travail est consacré a l’évaluation des évolutions hydriques (rétention en eau), structurales (retrait/gonflement) et superficielles (mouillabilité) des matériaux organiques utilisés comme supports de culture pendant plusieurs cycles de dessiccation et ré-humectation. Un effort de développement expérimental important a porté sur la mise au point de méthodes permettant de mesurer simultanément et en continuité les variations de déformation volumique (retrait/gonflement) du massif et de ses propriétés de rétention en eau. Trois matériaux, tourbe blonde de sphaigne, tourbe noire et fibre de coco ont été testés avec des contraintes hydriques atteignant -32 kPa. Les courbes obtenues montrent une évolution importante du volume du massif au cours du cycle de dessiccation et ré-humectation, les 2"’ et 3' Cycle sont répétitifs et superposables. L’intensité de la dessiccation appliquée a un effet important sur les propriétés de rétention en ré-humectation dans le cas des tourbes blondes de sphaigne ; il est peu perceptible pour la tourbe noire et la fibre de coco. Tous les matériaux testés montrent un caractère biporal très marqué avec une première porosité inter-grain ou inter-fibre se vidant autour de -lkPa et une porosité intra-grain plus variable en fonction des matériaux, de -15kPa pour la tourbe blonde a -40kPa pour la tourbe noire. Le caractère hydrophobe des matériaux au cours de la dessiccation a été évalué avec deux méthodes : ascension capillaire et goutte posée. Une approche méthodologique a permis de mettre en correspondance ces deux approches et d’expliquer leurs différences. Pour tous les matériaux, la mouillabilité varie surtout en fonction de l’humidité de matériau. Le retour a un caractère hydrophile avec la ré-humectation est variable et fonction des matériaux, rapide et réversible dans le cas de la fibre de coco, il est plus lent dans le cas des tourbes. Si les phénomènes dits « de bouteilles d’encre » restent probablement prépondérants pour expliquer l’hystérèse des propriétés de rétention dans les états les plus humides, l’utilisation d’un modelé biporal de type van Genuchten et introduisant un angle de contact en ré-humectation a permis de montrer que dans les dessiccations les plus poussées, l ' hydrophobie peut expliquer la plus grande partie des phénomènes d’hystérèse
The precise knowledge over time of physical properties of a plant roots environment is important for the effective management of irrigation and fertilization. This work is devoted to the assessment of the variations in water retention, shrinkage/swelling and wettability of organic materials used as growing media during several drying and resetting cycles. An important effort is done to develop the methods used to measure simultaneously and continuously the changes in volumetric deformation of the massif (shrinkage/swelling) and its water retention properties. Three materials, sphagnum peat, black peat and coco coir were tested with suction up to -32 kPa. The curves obtained show an important evolution during the first drying and rewetting cycle, however the second and third cycle is repetitive and superimposed. The drying intensity has the impact on the irreversibility of water retention measured on peat, however it is not very perceptible with black peat and coco coir. All materials tested showed a double porosities character with a porosity inter-fiber or inter-grain emptied around -1 kPa and another porosity intra-grain with the air entry pressure variable depending on materials, -15 kPa for blond peat and -40 kPa for black peat. The water repellency of material during the drying was assessed with two methods: sessile drop and capillary rising methods. This methodological approach allows finding out their correspondence and difference. The variation of wettability depends mainly on the humidity of material. If the effect of “ink bottle” is probably crucial in explaining the hysteresis of water retention properties in the most wet states, using a bimodal model of van Genuchten introduced a contact angle in resetting has shown the water repellency can explain the hysteresis in the case of more intense drying suction

La demande annuelle de coton augmente en raison de la croissance démographique mondiale et de l’évolution des comportements d’achat des consommateurs. D'autres options de fibres naturelles telles que la laine, le lin et la soie, entre autres, sont produites dans des proportions très maigres. Le polyester (poly (téréphtalate d’éthylène) (PET) présente des qualités qui pourraient répondre à cette préoccupation pour les vêtements. Malheureusement, les consommateurs hésitent à porter des vêtements 100% polyester, principalement en raison d’un confort sensoriel inférieur, du toucher et parfois de leur apparence. Cette étude visait à améliorer le tissu en PET caractéristiques afin de réduire l'écart entre la perception humaine et la performance hydrophile du coton par rapport au PET Pour déterminer la disparité existant entre le coton et les tissus tissés en PET, une étude multisensorielle a été réalisée à l'aide d'un panel de 12 juges formés sur 11 descripteurs sensoriels. Des algorithmes de Monte Carlo, des algorithmes génétiques et la technique de Borda Count (BK) ont été utilisés pour la fusion de rangs .L'analyse en composantes principales (PCA) et la classification hiérarchique par agglomération (AHC) ont été utilisées pour créer des profils sensoriels. Tissus en PET et en coton (p = 0,05). Il a été déduit que l’aspect visuel et esthétique peut être utilisé pour distinguer le PET du tissus de coton. Pour remplacer le coton par du PET via cette approche sensorielle, la modification de la rigidité des tissus en polyester a été judicieusement réalisée à l'aide de NaOH et d'un adoucissant en silicium, avec une pré-oxydation au plasma atmosphérique. Les tissus en PET traités avec NaOH et l’adoucissant en silicone ont été perçus comme étant doux, lisses, moins nets et moins raides par rapport à certains tissus en coton et en PET non traité. Le profilage des tissus indique que les tissus en PET conventionnels peuvent être distingués des tissus en coton conventionnels en utilisant une évaluation à la fois subjective et objective. Il est également avancé que la perception sensorielle humaine sur textile ne peut être directement représentée par des mesures instrumentales. La dernière partie de l’étude compare le potentiel hydrophile et l’efficacité de deux monomères vinyliques: le poly- (éthylène glycol) diacrylate (PEGDA) et le chlorure de [2- (méthacryloyloxy) éthyl] triméthylammonium (METAC) radicalement photo-greffé sur la surface de Tissu en PET. Une étude de surface utilisant la spectroscopie photoélectronique à rayons X (XPS) et la spectroscopie à dispersion d'énergie (EDS) a confirmé le greffage. Les tests d'humidité indiquent que PEGDA et METAC induisent un mouillage complet du PET à des concentrations de 0,1 à 5% (V: V). Les mesures colorimétriques (K/S et CIELAB/CH) et la stabilité de la couleur sur les tissus teints en PET suggèrent que les deux monomères améliorent considérablement l'efficacité de la teinture du PET. Il est suggéré que PEGDA et METAC génèrent des groupes hydrophiles sur le PET; les macroradicaux sont sous la forme de structures vinyliques qui forment des greffes à chaîne courte et démontrent une fonction hydrophile. Les résultats de cette recherche peuvent jouer un rôle directeur pratique dans la conception des tissus, la conception des propriétés sensorielles et contribuer au développement de tissus en polyester de type coton
There is increasing annual demand for cotton due to world population growth and changes in consumers’ purchasing behavior. Other natural fiber options such as wool, linen and silk among others, are produced in very meager proportions. Polyester (poly(ethylene terephthalate) (PET) has qualities that could address this concern for apparel. Unfortunately, consumers are reluctant to wear 100% polyester clothing mainly due to inferior sensory comfort, touch and sometimes appearance. This study sought to improve PET fabric characteristics in order to decrease the gap between human perception and hydrophilic performance of cotton vs. PET. To determine the disparity between cotton and PET woven fabrics, a multisensory study was undertaken using a panel of 12 trained judges against 11 sensory descriptors. Cross-entropy Monte Carlo algorithms, Genetic algorithms, and the Borda Count (BK) technique were used for rank fusion. Principle component analysis (PCA) and agglomerative hierarchical clustering (AHC) were used to create sensory profiles. The descriptor crisp accounted for the highest variability between PET and cotton fabrics (p˂0.05). It was deduced that visual and aesthetics can be used to distinguish between PET and cotton fabrics. To replace cotton with PET via this sensory approach, the modification of stiffness of polyester fabrics was judiciously carried out using NaOH and a silicon softener, with atmospheric air plasma pre-oxidation. PET fabrics treated with NaOH and the silicon softener were perceived soft, smooth, less crisp, and less stiff compared to some cotton and untreated PET fabrics. The profiling of fabrics indicates that conventional PET fabrics can be distinguished from conventional cotton fabrics using both subjective and objective evaluation. It is also argued that textile human sensory perception cannot be directly represented by instrumental measurements. The final part of the study compares the hydrophilic potential and efficacy of two vinyl monomers: Poly-(ethylene glycol) diacrylate (PEGDA) and [2-(methacryloyloxy) ethyl]-trimethylammonium chloride (METAC) radically photo-grafted on the surface of PET fabric. Surface study using X-ray photoelectron spectroscopy (XPS) and Energy Dispersive Spectroscopy (EDS) confirmed the grafting. Moisture tests indicate that PEGDA and METAC induce complete wetting of PET at concentrations 0.1-5% (V:V). Colorimetric measurements (K/S and CIELAB/CH) and colorfastness on dyed PET fabrics suggest that both monomers greatly improve the dyeing efficiency of PET. It is suggested that PEGDA and METAC generate hydrophilic groups on PET; the macroradicals are in a form of vinyl structures which form short chain grafts and demonstrate hydrophilic function. The results of this research can play a practical guiding role in the design of fabrics, sensory property design and contribute to the development of cotton-like polyester fabrics

Dans ce projet de doctorat, des membranes microporeuses (fibres creuses) et hautement hydrophobes à base de polyéthylène basse densité (LDPE) pour utilisation dans la capture du CO2 dans des contacteurs gaz-liquide à membrane (GLMC), ont été fabriquées en utilisant une nouvelle méthode simple, sans solvant ou diluants, autant écologique qu’économique, et qui ne nécessite aucun post-traitement mécanique ou thermique. Pour produire des fibres creuses et contrôler leur porosité, on combine deux techniques, l’extrusion et le lavage de sel. Un mélange de LDPE et de particules de NaCl de différentes concentrations en sel conduit à la production des fibres (par extrusion) qui sont ensuite immergées dans l’eau pour éliminer le sel emprisonné dans le polymère et obtenir autant une structure microporeuse qu’une surface rugueuse hautement hydrophobe. La nouvelle méthode constitue une alternative très prometteuse aux méthodes actuellement utilisées pour la fabrication des membranes hydrophobes, principalement basées sur un processus d'inversion de phase qui implique des solvants toxiques et coûteux. Les membranes fabriquées ont été caractérisées en termes de morphologie, densité, porosité et distribution de taille des pores, hydrophobicité, pression de percée et propriétés mécaniques. Comme le phénomène de mouillage des membranes en contact avec les solutions absorbantes est la cause principale de la réduction de l’efficacité des GLMC à long terme, une étude approfondie sur la compatibilité membrane/liquide absorbant a été réalisée. La stabilité morphologique, chimique et thermique des membranes en contact avec différentes solutions aqueuses d'alcanolamines à base de monoéthanolamine (MEA) et 2-amino-2-hydroxyméthyl-1,3-propanediol (AHPD), ainsi que des mélanges MEA/PZ (pipérazine) et AHPD/PZ, a été investiguée en détail.
In this work, highly hydrophobic low density polyethylene (LDPE) hollow fiber membranes aiming to be used for CO2 capture in gas-liquid membrane contactors (GLMC) were fabricated using a simple, novel method, without solvent or diluents, economic and environmentally friendly, which does not require any mechanical or thermal post-treatments. In order to produce hollow fibers and control their porosity, the process combines melt extrusion and template-leaching techniques. A mixture of LDPE and NaCl particles first produce blends with different salt contents. A microporous structure and a rough highly hydrophobic surface can then be produced by leaching the salt particles from the hollow fiber matrix via immersion in water. The new method represents a very promising alternative to conventional membrane fabrication approaches which are mainly based on phase inversion process that involves toxic and expensive solvents. The fabricated membranes were characterized in terms of morphology, density, porosity and pore size distribution, hydrophobicity, breakthrough pressure and mechanical properties. Since the phenomenon of membrane wetting by liquid absorbents is the major cause of the reduction of long-term efficiency of GLMC, a comprehensive study on the compatibility between membrane and absorbent liquid was performed. Morphological, chemical and thermal stability of LDPE membranes in contact with different aqueous alkanolamine solutions including monoethanolamine (MEA) and 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD), as well as blends of MEA/PZ (piperazine) and AHPD/PZ, was investigated in detail.

As the title implies, the chief goal of the present work is the improvement of the barrier effects of textile fabrics in the medical sector, in particular, in the operating room, which would be an effective safeguard against the causative pathogens allowing the health workers to work in and around hostile atmospheres and to accomplish useful tasks. To overcome the inherent drawbacks of surgical gown from classical fibers of both natural and synthetic origins, polyester micro filament fabric, down to 0.62 dtex per filament, was used to substitute them. Two major pathways have been chosen to render the surface hydrophobic: - Wet-chemical treatment - Plasma modification For the maximum efficiency of a specific wet-chemical, the following application formulations were found to be best effective: pH =4-5 Drying temperature and time=100°C / 90s Pick-up = 80% Curing temperature and time= 160°C / 120s A range of physical and chemical parameters have been found exerting significant influence on the extent of modification of the material: - Wetting agent - Amount of fluorine content in the chemical - Subsequent heat treatment of the finished material after washing - Ironing of the fabric For the plasma enhanced surface fluorination the following plasma gases were used: - Saturated fluorine compounds: CF4 and C2F6 - Reducing agent: H2 and C2H4 The exposure of the substrate to a pure C2F6 discharge resulted in higher hydrophobicity than the substrates exposed to CF4 plasma. Stepwise increased mixture of H2 or C2H4 to a proportionally decreased amount of C2F6 plasma showed a gradual decrease in contact angle and a substantial increase in sliding angle values. In addition to the treatments with gas mixtures a two-step technique, i.e., treatment with C2H4 prior to C2F6 plasma, was applied that appeared to be very promising in modifying the surface characteristics. Both, the contact angles and the sliding angles remaining almost constant on a very high level with increasing amount of C2H4 in the feed composition. An essentially vital concern of the work was the characterization of the treatment effect comprising both physical and chemical aspects. By washing the materials for 20 times no significant impairment of hydrophobic character has been noticed in case of fluorocarbon finishing agents as well as by the surface treated with C2H4 followed by C2F6 plasma (i.e., a two-step technique), wherein a complete loss of hydrophobic effect washing the silicone-treated materials for 10 times was observed. In breathability aspect, the plasma modification was found to be the best-suited technique with zero reduction of air permeability in comparison to wet-chemical finishing. The barrier test as a measure of dye absorption was conducted using protein solution, synthetic and human blood and the efficiency were verified by colorimetric technique. In contrast to pure plasma treatments, modification of the fabric with plasma in two-step treatment as well as with wet-finishing method using fluorocarbon compounds were completely impervious to artificial and real blood. The most striking feature was the zero uptake of the protein solution by all treated surfaces.

碩士
逢甲大學
電機工程學系
106
This thesis proposed a shape-curved hydrophone based on fiber Bragg gratings to detect acoustic waves in water. In comparison with the previous design, the shape-curved design can sense a larger angle and then receive more directions of signals. The sensing principle is based on the acoustic wave to push and to vibrate the thin film and then to stretch the fiber Bragg gratings. The sensing grating wavelength will be shifted forth and back to create different overlaps with the matching grating wavelength to cause the reflected light intensity variation. Then, the detected light signal is converted into a voltage-frequency electrical signal and displayed on oscilloscope for further analysis. In addition, fiber etching technology is used to reduce the fiber diameter for increasing the sensor sensitivity. Moreover, we also investigate the effect of different directions of acoustic source and curvatures of polymer structure on the frequency response. By means of the frequency response curves, the shaped-curved hydrophone has stable efficiency with the ability of sensing angle of 60°. The shape-curved hydrophone can accurately detect the acoustic wave under the water by a simple design. Because of fiber hydrophone has excellent characteristics like light weight and easier to maintained than conventional electrical types, it belongs to be a novel research.

碩士
逢甲大學
電機工程學系
103
The hydrophone based on fiber Bragg gratings is proposed in this research in which the main sensing elements include two fiber Bragg gratings with the similar bandwidth, reflectivity and central wavelengths. One of the two FBGs is packaged in the special packaged-structure and one end of the other FBG is connected to a 3dB coupler and the other end is linked to an InGaAs switchable gain detector. By means of opto-electronic energy transferring, the oscilloscope will show the voltage variation. The mechanism of the FBG hydrophone is that the acoustic waves with the frequency and intensity from the source in the water. The acoustic waves will push the water regular and then to vibrate the silicone diaphragm on the acrylic plate. Diaphragm vibration will cause the wavelength shift of FBG which is fixed on the silicone diaphragm. By using the InGaAs switchable gain detector, the optical signal will be converted into the electric signal to show this signal variation on the oscilloscope. From the voltage variation¸ we can know the acoustic frequency and the distance between the source and the hydrophone.

碩士
國立中山大學
電機工程學系研究所
91
In this paper, the fesibility of using a Fiber Bragg Grating (FBG) as a sensing scheme to detect the underwater acoustic signals is analyzed. When a FBG is disturbed by an underwater sound, the wavelength of the FBG is changed. Therefore, the central spectrum of the reflected light is shifted according to the wavelength change of the FBG. This spectrum can be detected by an imbalanced two-arm interferometer. Its transfer function will be studied. Also, the polarization induced signal fading of those two-arm interferometers will be studied.

碩士
逢甲大學
電機工程學系
107
This thesis proposes a novel structure based on a fiber Bragg grating hydrophone. The sensor is based on the Bragg fiber grating by using the Spherical cap’s principle to design the structure of the sensor. The architecture is mainly composed of two circular areas in which one side is use for receiving sound source and the other side is the sensing end with the fiber grating. Because the receiving area becomes larger than the sensing area, and the sensing end will receive the lager sound pressure for increasing the sensitivity of the sensor. The operating principle is that the receiving end receives the sound wave from the sound source. The sound wave passes through the medium to the other end with a sensing element. The sensing element is mainly composed of a silicon thin film to coat a Bragg fiber grating. When the acoustic wave pushes the thin film to cause the fiber Bragg grating wavelength shift. The grating wavelength will be shifted to the longer wavelength side. Therefore, the reflected wavelength will leave away from the matching grating to cause the light power change which is converted to the voltage signal by using a photodetector. The result displays on the oscilloscope. This research investigates the acoustic frequency response by changing matching position, the internal pressure, the elastic coefficient of the thin film, the thickness of the thin film. The results show that the receiving surface area, the internal pressure, the elastic coefficient of the thin film, number of the pulse all will affect the sensing result. This novel hydrophone has a good response for sensing sound wave.

碩士
逢甲大學
電機工程學系
102
The content of this research is composed of two different types of fiber sensors including the wind-velocity meter and the hydrophone in which the key sensing elements are two different center-wavelength fiber-Bragg gratings with the same bandwidth and reflectivity. The wind-velocity meter is based on two fiber-Bragg gratings which are glued axially on the surface of stainless steel with the separation of 90 degrees. By using the optical sensing interrogator, the two FBGs wavelength shifts are monitored for obtaining the velocity and direction of wind. The mechanism of the wind-velocity meter is that testing the wind forces the sphere of the sensor to cause the bending of the stainless steel with FBGs. The bending will cause the FBGs’ central wavelength to be shifted. The hydrophone is based on a fiber-Bragg grating to be packaged in the special packaged-structure with a silicone diaphragm design. The acoustic wave pushes the water regularly and vibrates the silicone diaphragm to result in the fiber grating to be strained and pressured. One end of the other FBG is connected to a 3dB coupler and the other end is linked to an InGaAs switchable gain detector and oscilloscope. Diaphragm vibration will cause the wavelength shift of the FBG and the variation of the reflection optical power will be monitored by an oscilloscope. From these data, the acoustic frequency and the distance between the source and the sensor will be obtained. By means of improving the sensor’s performance in the future, the fiber wind-velocity meter and the fiber hydrophone are separately expected to apply in the practical wind measurement and in the low-frequency sonar detection.

M.Ing.
A study was done on optical fibre hydrophones. Integrated optic hydrophone components as well as optical fibre components were investigated. An optical fibre coupler was successfully manufactured with an etch process. The coupling ratio can be varied mechanically or by means of refraction index variation. Experimental procedures and results will be shown. Bending losses excited in an optical fibre coil were investigated as a function of different coil diameters. The results were extrapolated to determine the amount of losses arising in a hydrophone coil.

碩士
大同大學
光電工程研究所
92
ABSTRACT The characteristics and principles of the evanescent field for the side-polished single mode fiber are discussed, and the details of the various processes of fabricating the side-polished fibers are also described in this thesis. Furthermore, two kinds of the long period fiber grating (LPFG) micro-vibration sensors are presented. For increasing the sensitivity of the sensor, we polish the fiber into the evanescent region, and then fabricating a long period grating with rectangular groove structure on the side-polished surface by virtue of the ICP-RIE dry etching technique. This steep grating structure not only increases the sensitivity of the sensor, but also makes the sensing frequency up to the degree of MHz. In order to simplify the processes of the fabrication, we use the techniques of photolithography and thermal vaporization for the side-polished fiber to make up the thin film LPFG structure on the polished surface for acoustic wave sensing in the water. Several fabrication methods have been tested for the assessment of the sensitivity and stability analysis; two frequencies of the acoustic wave (520 Hz acoustic wave and 42K Hz ultrasonic wave) have been used in the experiment. The fiber grating sensors we proposed in this thesis posses several advantages, such as small size, easy fabrication, and low cost, as well as very good performances have been demonstrated and discussed for the hydrophone applications in the water. Several measurements are carried out, and the experimental results have very good frequency response from low to high frequency region.

碩士
國立中山大學
電機工程學系研究所
92
Because the acoustic wave is capable of propagating at a long-distance in water, the hydrophone plays a key role in the underwater acoustic sensing all the time. The hydrophone based on fiber optic interferometry has an extremely high sensitivity and large dynamic range. In addition, the electrically passive, immunity to electromagnetic interference, and multiplexing properties of fiber optic sensor offer great advantages over traditional piezoelectric hydrophone. Due to the complete path-balance between the two counterpropagating waves, a Sagnac interferometric configuration can employ a low-coherent light source to reduce the cost. This configuration can easily route optical paths and replace sensor heads to compare with each other. But, the sensitivity varying with frequency and the polarization-induced signal fading problem make it unsuitable for applications in need of detecting correct amplitude of signals. The Michelson interferometric configuration with Farady rotator mirror (FRM) has a constant sensitivity and solves the polarization-induced signal fading problem. But, this configuration uses a high-coherent light source and expensive FRMs, and be difficult to route. In this paper, we use the polarization-insensitive Michelson fiber optic sensor to adjust the demodulation circuits we design. In this paper, we establish the interferometric hydrophones. The fiber optic coil of the sensor head is embedded with the special materials in order to acoustic impedance matching and waterproofing. We employ phase generated carrier demodulation technology to get the acoustic signal of interest from the output of the interferometer. In our experiment, the dual Sagnac configuration has a dynamic range of 23 dB and a sensitivity of -226 dB re V/1uPa, the Michelson configuration with FRMs has a dynamic range of 25 dB and a sensitivity of -204 dB re V/1uPa.