Дисертації з теми "Guide tube"

Ce mémoire porte sur la modélisation et la simulation non-stationnaires de l'interaction entre le faisceau d'électrons et l'onde électromagnétique dans les tubes à onde progressives (TOP) à hélice. Le TOP étant un instrument sur-dimensionné, les modèles non-stationnaires généraux sur lesquels se basent la plupart des logiciels commerciaux nécessitent de trop grosses ressources de calcul pour pouvoir être utilisés en un temps raisonnable pour des activités de conception industrielle. Il est donc nécessaire de faire appel à des modèles dits 'spécialisés'. Cette thèse porte sur le modèle discret non-stationnaire d'excitation d'un guide d'onde périodique de S. Kuznetsov. Avant nos travaux, il avait été démontré (N. Ryskin et al., 2007) que ce modèle pouvait s'appliquer aux TOP à cavités couplées dans le cadre d'un modèle à une dimension. Néanmoins, il n'existait alors aucune étude venant confirmer ou infirmer son application aux TOP à hélice. Lors de cette thèse, nous avons démontré, via le développement d'un code à une dimension (HelL-1D), que le modèle discret s'applique convenablement aux TOP à hélice. L'utilisation de ce modèle dans un code à deux dimensions (HelL-2D) a, elle aussi, été effectuée. Enfin, nous avons développé une méthode permettant de contrôler quantitativement les réflexions d'onde aux extrémités de la ligne à retard dans le modèle discret. Cette dernière étude constitue une avancée importante vers la simulation pratique des TOP en utilisant le modèle discret.

This thesis deals with the measurement of light tubes efficiency in laboratory conditions during lighting by almost direct light rays. It also deals with the measurement of the spectral reflectance of the reflective materials available on the Czech market. The comparison of the efficiency of different light routes and also the determination of the spectral qualities of different reflective materials are the aims of this thesis. The light tubes were measured by means of the cubic integrator. The light source was moved and manoeuvred by means of the automatic goniophotometer. The light source flow was determined by the method of the zonal flows. The data were calculated in the Matlab programme. The evaluation is both in the graphic and in the numeric forms. The result of the thesis is both the comparison of the reflective materials for light tubes qualities, and the evaluation of efficiency of the assigned light routes. The optimal variant can be then selected during designing of the light tubes route according to the results of the measurements.

L'efficacité croissante dans le domaine des basses fréquences des moyens de détection des cibles sous-marines implique une amélioration des matériaux d'isolement ou de découplage. Cette amélioration passe par la connaissance précise des caractéristiques acoustiques des matériaux employés. Dans ce contexte, l'objet de ce mémoire est la mise au point d'une méthode de caractérisation de ces matériaux utilisable à la pression atmosphérique mais susceptible d'être transposée à quelques dizaines de bars. Pour cela, un tube d'acier rempli d'eau et fermé à chacune de ses extrémités par un transducteur est utilisé. Le transducteur dit récepteur est commandé en tension afin d'établir un système d'ondes progressives. Selon les caractéristiques recherchées, l'échantillon est soit placé au milieu du tube, soit collé sur le pavillon d'un des deux transducteurs. Les paramètres obtenus, dans une gamme de fréquence s'étendant de 500 hz a 3000 hz, sont respectivement les coefficients de réflexion et de transmission ou les coefficients de masquage et d'anechoicite. Le principal matériau étudié dans ce mémoire est le microvon. C'est un matériau viscoélastique utilisé principalement comme matériau de masquage ou comme réflecteur mou. Les mesures du coefficient de masquage de ce matériau sont tout d'abord présentées. Ces mesures sont comparées aux mesures réalisées à la dcn/toulon. Un bon accord est trouvé. Les mesures du coefficient d'anechoicite sont présentées à la suite. Puis l'échantillon est déplacé au milieu du tube pour les mesures des coefficients de réflexion et de transmission. Dans cette position, la mesure de la fonction de transfert de l'échantillon permet de calculer l'ensemble des coefficients décrits dans ce mémoire. En conclusion, plusieurs extensions de la méthode sont envisagées.

La méthode privilégiée d'alimentation des machines à fusion est l'utilisation de glaçons de D et/ou T injectés dans le plasma. Ils sont utilisés actuellement, mais les résultats ne sont pas extrapolables aux futures machines de plus grande taille où le design du système d'injection et la construction de scenarii seront surtout basés sur les simulations. II est donc important de combler les vides dans les modèles existants allant de la fabrication des glaçons au dépôt de matière dans le plasma. Deux manques apparaissent : la modélisation du transport du glaçon dans le tuyau d'injection et la validation du processus d'ablation. Ce travail vise à combler ces vides et comporte 3 parties.- Décrire la physique du dépôt de matière, puis l'état de l'art des principaux résultats et enfin la description des systèmes d'injection de glaçons prévus pour les prochaines machines.- Modéliser le transport du glaçon dans le tuyau d'injection. Les effets pris en compte dans le modèle sont la fragilisation de la glace lors des rebonds, l'augmentation de sa température et son érosion. Le modèle donne notamment le ralentissement et la perte de masse du glaçon au cours du trajet, ainsi que l'énergie élastique stockée lié à son intégrité au sortir du tube.- Contribuer à la validation du code d'ablation HPI2, en comparant ses prédictions aux données mesurées dans les nuages d'ablation. La méthode utilisée est un calcul de jeu de données synthétiques à partir des simulations et en les comparant aux mesures. Cette méthode a permis de valider les hypothèses et approximations du modèle d'ablation susmentionné
The preferred method of fueling fusion device is the use of D and/or T pellets injected into the plasma. They are currently used, but the results cannot be extrapolated to future larger reactors where the design of the injection system and the construction of scenarios will be mainly based on simulations. It is therefore important to fill in the gaps in the existing models from the manufacture of pellets to the deposition of material in the plasma. Two lacks of knowledge appear: the modeling of the pellet transport in the injection pipe and the validation of the ablation process. This work aims to fill these gaps and consists of 3 parts.- Describe the physics of material deposition, then the state of the art of the main results and finally the description of the pellet injection systems planned for the next machines.- Model the transport of the pellet in the injection pipe. The effects taken into account in the model are the weakening of the ice during rebounds, the increase in its temperature and its erosion. The model gives in particular the slowing down and the loss of mass of the pellet during the journey, as well as the stored elastic energy linked to its integrity on leaving the tube.- Contribute to the validation of the HPI2 ablation code, by comparing its predictions to data measured in ablation clouds. The method used is a calculation of synthetic data sets from simulations and comparing them to measurements. This method made it possible to validate the assumptions and approximations of the ablation model

Dans cette thèse est étudié le problème de la propagation des énergies vibratoire et acoustique dans les tuyaux. L'étude commence par la présentation de théories des coques générales en notation tensorielle. Les théories des coques cylindriques de Flügge et de Flügge-Timoshenko sont utilisées pour décrire le comportement vibratoire de la paroi du tuyau. La théorie de Flügge-Timoshenko inclut les effets de cisaillement et d'inertie de rotation. Le fluide à l'intérieur du tuyau est supposé acoustique et son comportement est modélisé par l'équation d'ondes dans le repère cylindrique. Le couplage entre la paroi et le fluide interne est pris en compte. Les ondes élastiques qui se propagent dans la paroi du tuyau et celles acoustiques dans le fluide interne parcourent le tuyau dans le sens axial sous forme d'ondes libres, évanescentes et atténuées. L'énergie nette totale transférée dans le tuyau est constitué de la contribution vibratoire et acoustique. Chaque contribution est due à l'interaction des ondes libres d'une part et à l'interaction des ondes évanescentes d'autre part. L'effet de l'interaction des ondes atténuées n'est pas un transfert d'énergie nette mais une formation d'ondes évanescentes stationnaires. En raison du couplage entre la paroi le fluide interne, le flux total d'énergie nette peut être exprimé en termes de déplacements de la paroi. Ceci permet le développement des techniques expérimentales pour déterminer le flux total par la mesure des grandeurs vibratoires sur la paroi. Les résultats des essais réalisés en laboratoire et sur la tuyauterie d'un compresseur frigorifique sont présentés

In 2003, Jan Bach completed his monumental Concerto for Tuba and Chamber Orchestra. This concerto requires unique performance techniques and technical skills unlike the majority of available tuba repertoire. In addition to these techniques, the guide explores the influence of popular songs, jazz/rock/funk styles, implied humor, and personal experience through an interview with the composer.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.05.17 – гідравлічні машини та гідропневмоагрегати. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2017. Дисертацію присвячено вирішенню важливої науково-технічної задачі покращення енергетичних характеристик проточної частини низьконапірної осьової гідротурбіни. Виконано огляд науково-технічних джерел щодо методів досліджень гідродинамічних процесів у проточних частинах поворотно-лопатевих гідротурбін. За результатами чисельних досліджень просторової течії в'язкої нестисливої рідини в проточній частині вертикальної поворотно-лопатевої осьової гідротурбіни ПЛ20/3271у Кременчуцької ГЕС отримано детальну інформацію про структуру потоку у всіх елементах проточної частини в широкому діапазоні режимів роботи за допомогою програмного комплексу IPMflow, розробленого в ІПМаш НАН України. Досліджено вплив параметрів потоку на вході в розрахункову область на характеристики проточної частини, встановлено діапазон режимів роботи низьконапірної вертикальної осьової турбіни, при яких забезпечується рівномірний розподіл гідродинамічних величин в окружному напрямку на вході в робоче колесо. Запропоновано підхід до просторового профілювання лопатей робочих коліс осьових гідротурбін, заснований на застосуванні складних навалів в осьовому й окружному напрямках, який дозволяє підвищити ефективність проточної частини. Встановлено закономірності впливу складних осьових і окружних навалів робочих коліс на структуру потоку та інтегральні енергетичні показники, що використовуватимуться при проектуванні та модернізації проточних частин осьових гідротурбін. Розроблено робоче колесо з комбінованим периферійним навалом сучасної високоефективної низьконапірної осьової гідротурбіни ПЛ20/3271у Кременчуцької ГЕС з покращеними енергетичними показниками.
The dissertation for the degree of Candidate of Technical Sciences in the specialty 05.05.17 – hydraulic machines and hydropneumatic units. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2017. The thesis is devoted to solving of important scientific and technical problem of improving the energy characteristics of the flow part of Kaplan turbine. A review of the scientific and technical literatures on the methods of testing of hydrodynamic processes in flow parts of the Kaplan turbines has been carried out. According to the results of numerical investigations of the spatial flow of a viscous incompressible fluid in the flow part of the Kaplan turbine PL 20/3271у of the Kremenchug HPP detailed information on the structure of flow in all elements of the flow part in a wide range of operating modes has been received using software complex IPMflow developed at IPMash NAS of Ukraine. The influence of flow parameters at the inlet to the computational domain on the characteristics of the flow part has been investigated, a range of operation modes of Kaplan turbine that provide uniform distribution of the hydrodynamic values in circular direction at the inlet to the runner has been established. The approach to spatial profiling of the runner blades of Kaplan turbines based on the use of complex offsets in the axial and circular directions, which allows improving the energy characteristics of a flow part has been proposed. The influence of complex axial and circular offsets of the runners on flow structure and integral energy parameters that can be used in the design and modernization of the flow parts of Kaplan turbines have been established. The runner with combined peripheral offset of the modern high-performance Kaplan turbine ПЛ20/3271у Kremenchug HPP with improved energy performance has been developed.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.05.17 – гідравлічні машини та гідропневмоагрегати. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2017. Дисертацію присвячено вирішенню важливої науково-технічної задачі покращення енергетичних характеристик проточної частини низьконапірної осьової гідротурбіни. Виконано огляд науково-технічних джерел щодо методів досліджень гідродинамічних процесів у проточних частинах поворотно-лопатевих гідротурбін. За результатами чисельних досліджень просторової течії в'язкої нестисливої рідини в проточній частині вертикальної поворотно-лопатевої осьової гідротурбіни ПЛ20/3271у Кременчуцької ГЕС отримано детальну інформацію про структуру потоку у всіх елементах проточної частини в широкому діапазоні режимів роботи за допомогою програмного комплексу IPMflow, розробленого в ІПМаш НАН України. Досліджено вплив параметрів потоку на вході в розрахункову область на характеристики проточної частини, встановлено діапазон режимів роботи низьконапірної вертикальної осьової турбіни, при яких забезпечується рівномірний розподіл гідродинамічних величин в окружному напрямку на вході в робоче колесо. Запропоновано підхід до просторового профілювання лопатей робочих коліс осьових гідротурбін, заснований на застосуванні складних навалів в осьовому й окружному напрямках, який дозволяє підвищити ефективність проточної частини. Встановлено закономірності впливу складних осьових і окружних навалів робочих коліс на структуру потоку та інтегральні енергетичні показники, що використовуватимуться при проектуванні та модернізації проточних частин осьових гідротурбін. Розроблено робоче колесо з комбінованим периферійним навалом сучасної високоефективної низьконапірної осьової гідротурбіни ПЛ20/3271у Кременчуцької ГЕС з покращеними енергетичними показниками.
The dissertation for the degree of Candidate of Technical Sciences in the specialty 05.05.17 – hydraulic machines and hydropneumatic units. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2017. The thesis is devoted to solving of important scientific and technical problem of improving the energy characteristics of the flow part of Kaplan turbine. A review of the scientific and technical literatures on the methods of testing of hydrodynamic processes in flow parts of the Kaplan turbines has been carried out. According to the results of numerical investigations of the spatial flow of a viscous incompressible fluid in the flow part of the Kaplan turbine PL 20/3271у of the Kremenchug HPP detailed information on the structure of flow in all elements of the flow part in a wide range of operating modes has been received using software complex IPMflow developed at IPMash NAS of Ukraine. The influence of flow parameters at the inlet to the computational domain on the characteristics of the flow part has been investigated, a range of operation modes of Kaplan turbine that provide uniform distribution of the hydrodynamic values in circular direction at the inlet to the runner has been established. The approach to spatial profiling of the runner blades of Kaplan turbines based on the use of complex offsets in the axial and circular directions, which allows improving the energy characteristics of a flow part has been proposed. The influence of complex axial and circular offsets of the runners on flow structure and integral energy parameters that can be used in the design and modernization of the flow parts of Kaplan turbines have been established. The runner with combined peripheral offset of the modern high-performance Kaplan turbine ПЛ20/3271у Kremenchug HPP with improved energy performance has been developed.

This thesis describes the design and control of snake like concentric tube robots for the purposes of minimally invasive, orthopaedic arthroscopic procedures, although similarities can be drawn in multiple surgical contexts. It analyses multiple aspects of delivering the technology, including different forms of robot hardware, the role of robots in surgery and different control modalities including gesture recognition. A prototype tube robot developed by the Australian Centre for Robotic Vision is tested and end user feedback provided to further refine its development.

This thesis deals with the illuminance space through light guide. It describes it's basic principles, technical features and ways of differentiation between the technologies. The thesis also includes latest methods for evaluation of illumination of space supported by various computer simulations.

Thesis (M.S. in Management) Naval Postgraduate School, December 1995.
Thesis advisor(s): Mark W. Stone, John T. Dillard. "December 1995." Includes bibliographical references. Also available online.

Les tubes gaine et tubes guide réalisés en alliage de zirconium et utilisés dans les réacteurs à eau pressurisée constituent des éléments de structures essentiels de ce type de réacteur. Soumis à de multiples sollicitations (irradiation, corrosion, hydruration…), ils subissent aussi des contraintes mécaniques multiaxées à une température d'environ 320 °C, ce qui induit du fluage thermique. Cette thèse a pour but d'étudier l'influence de trois paramètres sur le comportement en fluage d'alliages de zirconium qui sont fortement anisotropes : le trajet de chargement, l'état métallurgique et la composition chimique. Compte tenu de la géométrie particulière de ces tubes mais surtout de la multiaxialité des chargements en service (pression interne qui augmente, contrainte axiale…), la première partie de la thèse a consisté en la mise au point d'un dispositif de fluage adapté. Celui-ci a été testé et validé en réalisant des essais sur Zircaloy 4 détendu. La suite de l'étude a été menée à une température fixe, 400 °C, en réalisant des essais pour déterminer deux courbes iso-vitesses de fluage (5 10-9 et 3,510-8 s-1) pour chacun des matériaux testés. La comparaison entre les résultats obtenus sur le Zircaloy 4 détendu et recristallisé a permis de déterminer les effets de l'état métallurgique sur le fluage dans cette gamme de vitesses. L'alliage de référence (M5®) nous a permis de montrer, qu'à cette température, pour cette gamme de contraintes, l'ordre des étapes de mise en charge ne semblait pas avoir d'influence sur le comportement en fluage. Les effets de l'oxygène, de l'étain et du fer ont pu être étudiés grâce à 5 autres alliages (M5® haut et bas oxygène, quaternaires Q12, Q32 et Q42). Enfin, à l'aide du logiciel Sidolo, en utilisant d'une part la base expérimentale sur le M5® et d'autre part celle sur le Zircaloy 4 recristallisé, deux modélisations macroscopiques ont été ajustées sur les résultats expérimentaux. La première utilise un critère de Von Mises (isotrope), la seconde un critère de Hill plus adapté pour les matériaux anisotropes. Aucun de ces deux modèles ne parvient à rendre compte de la forte anisotropie du comportement de fluage à 400°C en particulier pour des valeurs de σZZ / σθθ entre 0,5 et 1
Fuel rods and cladding tubes in zirconium are essential structural parts of Pressurized Water Reactors. There are submitted in service to aggressive environment (vapour at ~320°C, 155 bars, and irradiation) and to multiaxial mechanical loadings leading to thermal creep which has to be quantified. The present work aims to determine the effects of 3 parameters on the mechanical behaviour of different zirconium alloys: the loading path, the metallurgical state (stress-relieved, recrystallized) and the chemical composition. The first step to take was to develop a new device adapted to different geometries of tubes, and to validate it by comparing experimental results obtained upon the stress-relieved Zircaloy 4 to bibliographical results. Second, a large database has been constituted on the M5® in order to highlight the effects of an overloading or of cycling on the circumferential stress, and of the loading path (application of the axial then the circumferential stress, or the contrary or proportional loading). Then by comparing the behaviour of the recrystallized and the stress-relieved Zircaloys 4, the effects of the metallurgical state on this hexagonal alloy on the creep behaviour have also been studied. Lastly, the effects of oxygen, stain and iron have been quantified due to 5 other alloys (M5® low and high oxygen, Q12, Q32 and Q42). The last step of this work corresponds to the model of the macroscopic behaviour of 2 alloys (M5® and Zircaloy 4) with isotropic and anisotropic criteria to prove the necessity of developing a new and strong model adapted to highly anisotropic alloys like Zirconium alloys

L'étude porte sur les pertes acoustiques non linéaires localisées à la sortie d'un tube cylindrique. Trois aspects sont envisagés: tout d'abord la mise en évidence du phénomène par la mesure de l'impédance terminale du tube, puis la modélisation physique du phénomène et enfin l'application aux instruments de musique à vent. Le travail comprend trois parties qui traitent des trois aspects envisagés. Dans une première partie, des mesures de l'impédance terminale réalisées à l'aide d'une méthode à deux microphones montrent que les pertes à la sortie du tube - partie réelle de l'impédance terminale dans le cadre de l'approximation du premier harmonique - augmentent avec l'amplitude de la vitesse acoustique. Les résultats montrent que l'importance de ces pertes dépend fortement du rayon de courbure des bords intérieurs à la sortie de tube. En outre, pour les faibles rayons de courbure, deux régimes sont mis en évidence. L'existence de ces deux régimes est confirmée par des observations utilisant la vélocimétrie par imagerie de particules (PIV) réalisées en collaboration avec l'Université d'Edimbourg : dans les deux cas un anneau tourbillonnaire est formé à la sortie du tube mais dans le cas du premier régime (faibles vitesses acoustiques) l'anneau reste accroché aux bords du tube alors que dans le cas du second régime (fortes vitesses acoustiques) il est expulsé. La seconde partie concerne la modélisation du phénomène dans le but de mieux comprendre les mécanismes physiques mis en jeu. La théorie du bruit tourbillonnaire ("vortex sound theory") est appliquée afin d'estimer directement les pertes à la sortie du tube. Trois calculs utilisant cette théorie sont menés: le premier, analytique, sur la base d'un unique anneau tourbillonnaire fixe ou mobile, le second à partir des mesures par PIV et le troisième par la méthode numérique dite des réseaux de Boltzmann. Les trois calculs conduisent à des résultats similaires qui démontrent que les pertes non linéaires trouvent leur origine dans la formation d'anneaux tourbillonnaires en sortie de tube. Ces résultats sont confrontés avec succès aux résultats issus des mesures d'impédance. La troisième partie analyse les conséquences que peuvent avoir les pertes non linéaires dans le fonctionnement d'un instrument de musique à trous latéraux. Il est montré expérimentalement et à l'aide de simulations numériques que la dynamique de jeu d'un instrument à vent dépend directement des pertes dans l'instrument et que cette dynamique peut être étendue lorsque les pertes à la sortie sont minimisées par exemple en chanfreinant les bords des trous latéraux
The study deals with localised non-linear acoustic losses at the open end of a tube. Three aspects are considered : firstly, a description of the phenomenon by the measurement of the terminal Impedance of the tube, secondly, the physical modeling of the phenomenon and finally the application to woodwind instruments. In a first part,measurements of the terminal impedance using a two microphone method show that losses at the open end of the tube - real part of the terminalion impedance in the first harmonic approximation - increase with the acoustical velocity amplitude. Results show that the losses highly depend on the radius of curvature of the tube's inner edges. Moreover, for low values of the radius of curvature, two behaviours are observed. Particle image velocimetry (PIV) visualisations carried out at the University of Edinburgh confirm these two behaviours : in both cases, a vortex ring is created at the open end but it stays in the vicinity of the exit for low acoustical velocities whereas it is expelled for higher acoustical velocities. The second part deals with the physical modeling of the phenomena. The application of the vortex-sound theory allows a direct estimation of the losses at the open end. Three calculations using this theory are carried out. The first calculation is analylical and is based on a discrete vortex ring which can be either fixed or mobile; the second one cornes from PIV visualisations; and the third one is numerical, using the lattice Boltzmann method. The three calculations lead to similar results : non-linear losses find their origin in the formation of vortex rings at the end of the tube. These results are succesfully compared to impedance measurements. The third part analyses the influence of non-linear losses on the behaviour of a side-holed wind instrument. Experiments and simulations show that the playing range of a wind instrument depends on the losses in the instrument and that the playing range can be extended by reducing the non-linear losses at the open end

Eddy current testing is the non-destructive test method of choice for the inspection of condenser tubes. However, unplanned shutdowns of power stations, due to unexpected condenser tube failures, still occur despite rigorous eddy current inspection programs. In addition to the improvement required in the reliability of inspections, there is also a need to shorten the duration of inspections.

Nerve injury is a serious clinical problem that has a direct impact on the quality of life. Nerve tissue engineering (NTE) is one of the most promising methods in human health care to restore the function of damaged neural tissues. The current state of the art involves the construction of a tissue engineered, nano or micropatterned 3-D nerve tube that has fibers or channels in the inside. The scope of this study is to construct a 3-D, biodegradable nerve tube which consists of an aligned, electrospun mat seeded with stem cells that is wrapped in a porous micropatterned film which contains support cells. In two separate approaches human mesenchymal stem cells (MSCs) and mouse neural stem cells (NSCs) were used. In the design with the MSCs, the micropatterned exterior part of the nerve tube contained undifferentiated MSCs as support cells and this was wrapped around the fibers seeded with MSCs which were induced to neural differentiation. In the other case, NSCs differentiated into astrocytes were used as support cells seeded on the micropatterned film and the mat was loaded with undifferentiated NSCs. Differentiation into neural cells and astrocytes were shown with immunocytochemistry and RT-PCR. The neuron-like MSCs and NSCs were shown to express neural marker &
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-Tubulin III whereas astrocytes expressed glial fibrillary acidic protein (GFAP), an astrocyte marker. RT-PCR showed that early neural markers, nestin and Nurr 1, were expressed at passage 4 by undifferentiated MSCs and by MSCs induced to neural differentiation, while these markers were not expressed in undifferentiated MSCs at passages 2 and 3. The cells aligned along the axis of the micropattern of the film and along the axis of the fiber on the fibrous mat. This behavior was also maintained after construct formation. MTS and confocal microscopy revealed that the cells were viable and homogeneously distributed over the two parts of the scaffold. This indicates that the construct has a potential to be tested in vivo for nerve tissue engineering purposes.

Cette thèse a pour objectif d’instrumenter un contenant familier dans le domaine du biomédical et de la chimie (un tube à essai) avec des éléments piézoélectriques à ondes longitudinales (L) et d’implémenter, en les optimisant, diverses méthodes ultrasonores pour mesurer les viscosités rapidement, sans changer de banc de mesure et cela de quelques Hz à plusieurs dizaines de mégahertz au voisinage de la température ambiante. Grâce au système mis en place il est possible en quelques minutes de déterminer le comportement rhéologique du liquide, étudié en mesurant sa viscosité de cisaillement. Par ailleurs, la gamme de viscosité atteinte est extrêmement large puisque les mesures sont possibles de quelques dizaines de mPa.s à plusieurs centaines de Pa.s. Enfin, au-delà de résultats quantitatifs en terme de viscosité, le banc de mesure peut être aussi utilisé pour suivre de façon qualitative des cinétiques de réaction (polymérisation par exemple)
The main goal of this thesis is to set specific piezoelectric elements emitting longitudinal waves (L) on a well-known container in the field of biomedical and chemistry (a test tube) and to implement with some optimizations various ultrasonic methods to measure viscosities quickly, without changing the measurement bench. The measurement has to be done from a few Hz to several tens of megahertz around room temperature. Up to now it is possible to determine in a few minutes the rheological behavior of the liquid studied thanks to the evaluation of its shear viscosity. Furthermore, the viscosity range reached is extremely wide: the measurements are possible from a few tens of mPa.s to several hundred Pa.s. Finally, beyond quantitative results in terms of viscosity, the measurement bench can also be used to qualitatively monitor reactions (polymerization for example)

Luigi Nono's work Post-Prae-Ludium No.1 "per Donau" represents a model for the emerging genre of electroacoustic tuba music. It is important to preserve this electroacoustic work because of its value to the tuba literature. Not only is it one of the first electroacoustic works for the tuba, but it also was composed by a man who is highly regarded in the field of music composition. Its preservation will be difficult because of the rapid advancement in technology. Within the last three decades of existence, the technology has evolved three times. An examination of the performance practice in Post-Prae-Ludium was undertaken to understand the demand on the performer required to play this work. This study will look at both non-traditional performance practices, as well as an inherent problem of how the advancement of technology can actually threaten the survival of a work dependent upon a specific version of electronic technology. Nono worked in collaboration with Giancarlo Schiaffini to compose a work for tuba and live electronics. Correspondence with Schiaffini has provided his thoughts on the collaboration of Post-Prae-Ludium with Nono and given a better understanding of how to perform the work. Technology will change, and these current adaptations of Post-Prae-Ludium may not be valid in one or two decades. However, with the description and instruction given by Nono and Schiaffini, in addition to recordings made of Post-Prae-Ludium, there is a record from which to reproduce this work. This study provides a source allowing performers to reproduce this work, thereby preserving it for future performers.

L'interaction d'une impulsion laser intense et de courte durée avec un plasma permet de produire une onde de plasma de grande amplitude dans son sillage, auquel est associé un champ électrique longitudinal. Celui-ci peut être utilisé pour accélérer des électrons relativistes injectés dans l'onde jusqu'à de grandes énergies - de l'ordre du GeV - sur de courtes distances - quelques centimètres - au regard des distances dans les accélérateurs conventionnels. Le contrôle des caractéristiques du faisceau d'électrons lors du processus d'accélération est fondamental pour réaliser un étage d'accélération laser-plasma utilisable. Le travail de thèse a porté sur la création et la caractérisation d'une onde de plasma en régime faiblement non linéaire sur une longueur de plusieurs centimètres. Des tubes capillaires sont utilisés pour guider le faisceau laser sur ces distances tout en maintenant une intensité susante (~ 1E17 W/cm²). Le faisceau laser guidé ionise le gaz contenu dans le tube et crée l'onde de plasma. Un diagnostic optique reposant sur la modification du spectre de l'impulsion laser a été utilisé pour déterminer l'amplitude de l'onde de plasma le long du tube. Sa dépendance en fonction de la pression de remplissage du gaz, de la longueur du capillaire et de l'énergie laser, a été étudiée. Les résultats expérimentaux comparés aux résultats analytiques et de modélisation sont en excellent accord, et montrent que le champ électrique associé à l'onde de plasma est compris entre 1 et 10 GV/m sur une longueur allant jusqu'à 8 cm. Ce travail a permis de montrer la possibilité de créer de façon contrôlée une onde de plasma en régime faiblement non linéaire.

L'étude porte sur les pertes acoustiques non-linéaires localisées à la sortie d'un tube cylindrique. Trois aspects sont envisagés : tout d'abord la mise en évidence du phénomène par la mesure de l'impédance terminale du tube, puis la modélisation physique du phénomène et enfin l'application aux instruments de musique à vent. Le travail comprend trois parties qui traitent des trois aspects envisagés.

Dans une première partie, des mesures de l'impédance terminale réalisées à l'aide d'une méthode à deux microphones montrent que les pertes à la sortie du tube - partie réelle de l'impédance terminale dans le cadre de l'approximation du premier harmonique - augmentent avec l'amplitude de la vitesse acoustique. Les résultats montrent que l'importance de ces pertes dépend fortement du rayon de courbure des bords intérieurs à la sortie de tube. En outre, pour les faibles rayons de courbure, deux régimes sont mis en évidence. L'existence de ces deux régimes est confirmée par des observations utilisant la vélocimétrie par imagerie de particules (PIV) réalisées en collaboration avec l'Université d'Edimbourg : dans les deux cas un anneau tourbillonnaire est formé à la sortie du tube mais dans le cas du premier régime (faibles vitesses acoustiques) l'anneau reste accroché aux bords du tube alors que dans le cas du second régime (fortes vitesses acoustiques) il est expulsé.

La seconde partie concerne la modélisation du phénomène dans le but de mieux comprendre les mécanismes physiques mis en jeu. La théorie du bruit tourbillonnaire (``vortex sound theory'') est appliquée afin d'estimer directement les pertes à la sortie du tube. Trois calculs utilisant cette théorie sont menés : le premier, analytique, sur la base d'un unique anneau tourbillonnaire fixe ou mobile, le second à partir des mesures par PIV et le troisième par la méthode numérique dite des réseaux de Boltzmann. Les trois calculs conduisent à des résultats similaires qui démontrent que les pertes non linéaires trouvent leur origine dans la formation d'anneaux tourbillonnaires en sortie de tube. Ces résultats sont confrontés avec succès aux résultats issus des mesures d'impédance.

La troisième partie analyse les conséquences que peuvent avoir les pertes non linéaires dans le fonctionnement d'un instrument de musique à trous latéraux. Il est montré expérimentalement et à l'aide de simulations numériques que la dynamique de jeu d'un instrument à vent dépend directement des pertes dans l'instrument et que cette dynamique peut être étendue lorsque les pertes à la sortie sont minimisées par exemple en chanfreinant les bords des trous latéraux.

An examination of the musical style, compositional techniques and performance practice issues of American composer Thom Ritter George with special attention paid to his Quintet No. 4 written in 1986. The document also includes a short history of brass instruments in chamber music, history of the brass quintet in America, discussion of the role of the trumpet in the quintet, overview of the composers contributions to music and brass quintet in America, discussion of the role of the trumpet in the quintet, overview of the composers contributions to music and brass quintet, and background information on the composer.

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Este trabalho desenvolveu um novo método para a detecção de contornos em imagens digitais que apresentam objetos de interesse muito próximos e que contêm complexidades associadas ao fundo da imagem como variação abrupta de intensidade e oscilação de iluminação. O método desenvolvido utiliza lógicafuzzy e desvio padrão da declividade (Desvio padrão da declividade fuzzy - FuzDec) para o processamento de imagens e detecção de contorno. A detecção de contornos é uma tarefa importante para estimar características de escoamento bifásico através da segmentação da imagem das bolhas para obtenção de parâmetros como a fração de vazio e diâmetro de bolhas. FuzDec foi aplicado em imagens de instabilidades de circulação natural adquiridas experimentalmente. A aquisição das imagens foi feita utilizando o Circuito de Circulação Natural (CCN) do Instituto de Pesquisas Energéticas e Nucleares (IPEN). Este circuito é completamente constituído de tubos de vidro, o que permite a visualização e imageamento do escoamento monofásico e bifásico nos ciclos de circulação natural sob baixa pressão.Os resultados mostraram que o detector proposto conseguiu melhorar a identificação do contorno eficientemente em comparação aos detectores de contorno clássicos, sem a necessidade de fazer uso de algoritmos de suavização e sem intervenção humana.
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IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Cette thèse de doctorat intitulée “Micro structuration de Réseaux Résonants complexes” étudie les dispositifs de détection optique, qui impliquent diverses techniques de photolithographie et outils de micro/nanotechnologie pour leur fabrication. Ces dispositifs, dans leur forme classique, consistent en un réseau de diffraction formé de lignes microscopiques gravées périodiquement sur une surface photosensible, qui est déposée sur une couche diélectrique, le guide d'onde. Les deux couches sont supportées sur un substrat. Pour activer les fonctions de détection, le réseau de diffraction doit être extrêmement sélectif, c'est-à-dire qu'il doit avoir la capacité de rejeter toutes les composantes spectrales reçues, en sélectionnant qu’une seule longueur d'onde pour la coupler au guide d'onde. Après le découplage, une réflexion dite résonante liée à sa très grande amplitude et sélectivité spectrale et angulaire se produit. Différents types de composants en fonction de l'application envisagée peuvent être réalisés sur différents types de substrats, matériaux ou géométries (plan, cylindrique). L'un des projets de cette thèse consiste à concevoir des WRG (Waveguide Resonant Gratings) sur les parois intérieures d'un tube pour coupler les modes TE et TM à l’intérieur du guide d’onde. La fabrication est réalisée par un masque de phase radial spécialement conçu, tandis que la fonction optique est mise en évidence en utilisant un miroir conique, capable de réfléchir la lumière de manière isotrope pour l'excitation des modes. De plus, des matériaux innovants peuvent être utilisés pour leur intégration dans des structures résonantes planaires. L'un des matériaux à l'étude est le dioxyde de vanadium (VO2), qui subit respectivement des transitions de phase de premier ordre (isolant vers métal) à basses et hautes températures. La fabrication d'un composé aussi délicat est complétée par deux méthodes de synthèse différentes, le dépôt par laser pulsé et la pulvérisation cathodique magnétron. La capacité d'induire une résonance en déclenchant thermiquement le dispositif est destinée aux applications de sécurité laser afin d'éviter l’endommagement lors d'une surchauffe
This PhD thesis entitled “Micro patterning of complex Waveguide Resonant Gratings (WRG)” studies the optical sensing devices, which involve various photolithography techniques and nanotechnology tools with clean room processes for their fabrication. These devices, in their classic form, consist of a diffraction grating formed by microscopic lines engraved periodically on a photosensitive surface, which is deposited on a dielectric layer, the waveguide. Both layers are supported on a substrate. To enable sensing functions, the diffraction grating must be extremely selective, i.e. it must have the ability to reject all the received spectral components, while selecting only one wavelength to couple it into the waveguide. After the out coupling, a reflection with a very large amplitude and great finesse occurs. Different types of components depending on the intended application can be produced on different types of substrates, materials or geometries (plane, cylindrical).One of the projects of this thesis engineers WRG on the interior walls of a tube to couple TE and TM modes into the waveguide. The fabrication is achieved by a specially designed radial phase mask, whereas the optical function is highlighted by the use of a conical mirror, able to reflect light isotropically for mode excitation. In addition, innovative materials can be used for their integration into flat WRG. One of the materials under study is the Vanadium Dioxide (VO2), which undergoes first-order phase transitions (Insulator to Metal) at low and high temperatures respectively. The fabrication of such a delicate compound is completed by two different synthesis methods, the Pulsed Laser Deposition and Magnetron Sputtering. The ability to induce resonance by thermally triggering the device is intended for laser safety applications to avoid damage during overheating

Dans l'industrie aéronautique, les traitements acoustiques placés en ras de paroi du réacteur commencent à atteindre leur limite en terme d'efficacité, notamment aux fréquences de passage de pâles (BPF) qui sont le résultat de l'Interaction entre les pales de la soufflante et les redresseurs Ainsi, des raies dans le spectre du bruit émis par le réacteur sont présentes durant toutes les phases de vol. En complément des matériaux absorbants, les tubes de Herschel-Quincke (HQ) offrent une alternative pour atténuer les raies émergentes aux BPF. Ces tubes sont placés en périphérie du conduit principal et déphasent les ondes acoustiques du conduit principal avec celles qui se propagent dans les tubes HQ afin d'atténuer le bruit transmis. Un modèle mixte analytique-numérique a été développé pour le calcul de la matrice de diffusion d'une couronne de tubes HQ intégrée à un conduit cylindrique traité de longueur finie. La technique développé permet de prendre en compte la forme exacte des tubes H Q que l'on met en périphérie du conduit principal ainsi que la possibilité d'avoir une vitesse acoustique non uniforme aux interfaces tube HQ-conduit principal. Le modèle permet une étude paramétrique sur les tubes HQ afin de cibler les fréquences à atténuer et et offre également un gain de temps par rapport à un modèle éléments finis
In aeronautic industry, the efficiency of acoustic liners in bypass and inter-stage regions of the turbofan engine is reached the limit, especially at the Blade Passage Frequencies (BPF), due to the interaction between the fan blades and the struts. Then, pure tones are produced in the noise spectrum for all flight phases, in addition of acoustic liners, Herschel-Quincke (HQ) tubes provide an alternative to improve the attenuation at the BPF. These tubes are placed in the periphery of the main duct and produce phase differences between acoustic waves in the main duct and in the HO tubes in order to attenuate the transmitted acoustic power. A mixed numerical-analytical model was developed for the fast computation of the scattering matrix of a ring of HO tubes integrated in a finite length line wall circular duct. This technic takes into account the exact shape of HO tube and the possibility of a non uniform acoustic velocity at the interfaces between the main duct and the HO tube. This model also allows a study of HQ tube parameters with a time swing compared to a standard element method. Finally, the mixed model has no frequency limit

Ce travail porte sur la modélisation physique des tubes acoustiques pour la simulation numérique en temps-réel. Le but principal est la synthèse sonore d'instruments à vent, avec un modèle réaliste, une méthode modulaire et une implémentation numérique faible coût. Le modèle acoustique de "Webster-Lokshin", utilisé ici, est un modèle à 1 dimension prenant en compte à la fois la "courbure" du profil et les "pertes visco-thermiques" à la paroi. Pour ce modèle acoustique, une structure de simulation compatible avec l'approche des "Guides d'Ondes" est obtenue : un tube y est représenté par un système bouclé, avec retards, faisant intervenir plusieurs sous-systèmes sans retard interne. Une difficulté est la présence de sous-systèmes de dimension infinie qui se comportent comme des sommes infinies de systèmes du premier ou du second ordre. Dans un premier temps, ils sont approximés par des systèmes de dimension finie, puis leur "représentation d'état" à temps discret est obtenue. Enfin, en utilisant des outils standard de l'automatique, ces représentations nous permettent de faciliter la connexion d'éléments acoustiques et de réduire les coûts de calcul de la simulation numérique. Dans ce travail, l'étude de la stabilité et de la passivité est faite. Pour des cas paticuliers de tubes, un problème survient : même si les relations entrées/sorties du tube sont stables, certains sous-systèmes internes possèdent une infinité de singularités à l'origine d'instabilités internes. Nous présentons une explication de ce phénomène et ceci nous amène à proposer une nouvelle décomposition en sous-systèmes pour lever ce problème.

Borehole sonic measurements are an important tool to characterize formation and completion properties of hydrocarbon or water reservoirs. Such measurements can provide direct information about rock physical parameters such as permeability or elastic moduli. These properties are obtained from guided waves propagating along boreholes. The so called tube wave or Stoneley wave is a symmetric mode which compresses the fluid column leading to a piston like motion. If the medium around the borehole wall is permeable, the radial expansion of the fluid column will result in fluid flow across the borehole wall. This results in a sensitivity of the tube wave signature to the permeability of the surrounding formation which manifests itself in a characteristic dispersion and attenuation of the tube wave. Information about the permeability of the surrounding formation provides essential knowledge for reservoir characterization.In addition to the traditional method of using tube wave signatures for formation permeability estimations, the same approach may be used for production monitoring. In sand reservoirs a complicated borehole completion is installed during the production phase for the purpose of controlling sand production. In such a setup highly permeable layers such as a sand screen or a gravel pack are used to prevent sand production.The problem with such completions is that they are very expensive to install and susceptible to plugging or corrosion. No permanent surveillance tool exists to date which allows diagnosis of problems in sand-screened deepwater completions. However, the recently proposed Real-Time Completion Monitoring (RTCM) uses the signature of tube waves to identify permeability changes: the increase of the tube wave velocity can indicate a decrease of permeability and vice versa. Therefore, RTCM has potential to identify problems in sand-screened deepwater completions.In order to understand the acoustic response of such deepwater completions, the dispersion and attenuation of tube waves in this complicated setup needs to be studied. To this end I have developed a modelling algorithm based on a spectral method. The developed algorithm computes the dispersion and attenuation of borehole modes propagating in a cylindrically layered structure with an arbitrary number of fluid, elastic and poroelastic layers. The numerical algorithm discretizes the medium along the radial axis using Chebyshev interpolation points derived from Chebyshev polynomials. The differential operators are discretized using spectral differentiation matrices. Thus, for any number of layers, the corresponding equations can be expressed as a generalized algebraic eigenvalue problem. For a given frequency, the eigenvalues correspond to the wavenumbers of different modes. The eigenvectors, computed along with the eigenvalues, correspond to the displacement potentials. They can be used to obtain the variation of displacement and stress components along the radius of the structure.In this thesis the spectral method was first developed for structures with an arbitrary number of fluid and elastic layers. Subsequently, the algorithm was extended for poroelasticity. The results produced by the modelling program are benchmarked against analytical solutions. Such analytical solutions are known for elastic and poroelastic cylinders as well as fluid filled tubes. The tube wave dispersion in a fluid-filled borehole surrounded by an elastic or poroelastic formation obtained with the spectral method was compared to the analytical low-frequency solution.I obtained the dispersion of the two tube waves propagating in a four layer completion model: fluid – permeable sand-screen – fluid – elastic casing. Varying the permeability of the sand-screen layer allowed me to account for the effect of fluid flow across this layer. Being able to obtain the acoustic response can help to identify broken fluid communication which increases the tube wave velocity. A corroded sand-screen has an extremely attenuated tube wave signature.Furthermore, I have implemented the more complex model of a borehole surrounded by an altered zone in the algorithm. Due to drilling damage the altered zone is an area of reduced permeability. In order to account for the effect of the altered zone on the tube wave signature, up to ten layers were used with stepwise increase of permeability from the borehole towards the formation. Overall, the spectral method proved to be a valuable algorithm to model wave propagation in cylindrical structures.Using borehole modes to evaluate the physical properties of the formation or completions is an important application. However, in borehole seismic modelling, such as crosshole or VSP, it is also important to account for the effect of boreholes and the associated modes. Since the borehole radius is a thousand times smaller then the investigated volume it would require a prohibitively small grid size to explicitly model the borehole. However, it is possible to effectively represent a borehole as a superposition of point sources. This mimics the presence of borehole modes. In order to implement this technique for poroelasticity, it is necessary to model source signatures in poroelastic media. To this end I have analyzed the radiation characteristics and moment tensor solutions for various source types. Together with the spectral method these point source representations can be used to model the effect of boreholes. This will pave the way for more efficient poroelastic seismic modelling in various fluid-filled boreholes and completions.

Tese de doutoramento em Materiais e Processamento Avançados (AdvaMTech), apresentada ao Departamento de Engenharia Mecânica da Faculdade de Ciências e Tecnologia da Universidade de Coimbra
The main goal of this PhD work was the development and evaluation of novel nerve guide conduits based on biocompatible and biodegradable polymers for regenerative medicine, namely peripheral nerve regeneration. The injury of the peripheral nerves are a quite common, especially in the young male population due to accidental traumatic events. The degree of injury may vary, being the most severe cases associated with permanent disability. Since the last century, new strategies to improve peripheral nerve regeneration after injury have been studied. The first technique proposed and still nowadays showing the best results is the use of nerve autograph. Nevertheless, this technique is associated to some disadvantages, which include the need of two surgeries and site morbidity. In this sense, nerve guide conduits, which consist in hollow tubes that are sutured to both nerve ends have been proposed as alternative. These conduits should guide the newly formed axons to the opposite nerve stump while providing a suitable environment for the enhancement of axon regeneration. Among several materials tested for the preparation of these devices, polymers have presented the most promising results. However, a device, which could reproduce results comparable to nerve autograph with suitable degradation ratio in vivo remains to be developed. In an attempt to overcome these limitations, the present work involved the use of the polysaccharide dextran as core material in the preparation of nerve guide conduits. The choice of this polymer relies on its well stablished biocompatibility and biodegradability. In addition, dextran is frequently reported for biomedical applications, being approved by the US Food and Drug Administration (FDA). The initial work undertaken aimed to modify the chemical structure of dextran by the incorporation of double bonds in its chains, for further crosslinking. In this sense, dextrans with different molecular weights were modified with two different monomers, Glycidyl methacrylate (GMA) and 2-Isocyanatoethyl methacrylate (IEMA). Circular transparent membranes were prepared by ultraviolet (UV)-photocrosslinking and the physico-chemical characteristics of the resulting products were evaluated. After the washing and drying stages, the final membranes presented a fragile structure. For this reason, a poly (ε-caprolactone) (PCL) macromonomer modified with IEMA was added to the membrane formulations. As a result, the flexibility of the membranes increased considerably. Additionally, the incorporation of PCL_IEMA did not affect the thermal-mechanical properties. On the other hand, the swelling capacity and in vitro degradation ratio decreased. The work continued with the evaluation of the cytotoxicity of the most promising membranes, using human dental pulp stem cells (hDPSCs). The intracellular concentration of the calcium ion was also measured after the cell viability test. All membranes were considered suitable substrates for cell adhesion and proliferation based on their morphology and healthy calcium ion concentration, suggesting the absence of any apoptosis process. Considering the promising results obtained, the next step focused on the evaluation of the extension of immune response due to implantation of the membranes in rats dorsum. After 15 days of implantation, membranes prepared with dextran modified with GMA and PCL derivative caused an immune response that was classified as “non-irritant”, by the scoring system of the standard ISO 10-998-6. After the relevant results obtained for the prepared materials in a membrane shape, the next step of the work was to achieve the tube conformation. In this regard, molds composed by a quartz tube with an internal 316L stainless steel rod, and with different dimensions were prepared. In order to tailor the final dimensions of the prepared tubes, shrinkage studies were conducted. The formulation, which presented the final dimensions more similar to the commercial product Neurolac®, was then chosen for the further characterization. The structures revealed to be very compact, showing no porosity. For this reason, in order to enhance permeability, D-mannitol was added to the formulations, as porogenic agent, to create voids in the structure of the tubes. The obtained pores presented a mean size in the range between 10-20μm. Posteriorly, the physico-chemical properties of the normal tube and porous tube were evaluated. With the incorporation of D-mannitol, the swelling capacity of the tubes decreased, which may be related to a lower crosslinking density. Moreover, for the porous structure, the in vitro degradation ratio increased, as expected, since the contact surface area also increases. Furthermore, after six months under in vitro hydrolytic tests, both tube structures were able to maintain their structural integrity. The mechanical properties of the tubes were evaluated by performing tensile tests, which revealed that both tubes have the ability to support tension and elongation forces slightly higher than the ones reported for the rat sciatic nerve. It is noteworthy to state that the tubes also were able to resist to preliminary suture tests without visible fragmentation. Finally, nerve guide conduits were tested in the rat sciatic nerve after a neurotmesis injury, for 20 weeks. The functional evaluation results showed that the recovery percentage of motor function is similar for both tubes. In what concerns the sensorial function, the rat group, which received the porous tube revealed higher percentage of recovery. In this sense, porosity seems to induce a positive effect on nerve regeneration. To sum up, this PhD work allowed the validation of dextran as core material for the preparation of nerve guide conduits for peripheral nerve regeneration. The obtained materials present a set of characteristics and properties, which may be relevant for the regeneration process. Furthermore, the fine-tuning of these properties can be easily achieved by changing the formulations used to prepare the tubes.
O principal objetivo deste trabalho de doutoramento consistiu no desenvolvimento e avaliação de novos tubos guia preparados a partir polímeros biocompatíveis e biodegradáveis, com aplicação em medicina regenerativa, nomeadamente regeneração de nervos do sistema nervoso periférico. As lesões de nervo periférico são bastante comuns, sendo que as principais causas de incidência desta patologia estão associadas à população jovem masculina, por ocorrência de eventos traumáticos acidentais. A severidade destas lesões varia bastante, no entanto, nos casos mais graves, pode mesmo resultar em incapacidade nervosa permanente. Por este motivo, ao longo do último século têm sido estudadas novas formas de melhorar a regeneração de nervo periférico após uma lesão. A utilização da técnica do autoenxerto revelou ser apresenta resultados mais satisfatórios, provando melhorar a qualidade do nervo regenerado. Contudo, esta técnica implica o recurso a duas cirurgias. Na perspetiva de evitar esta desvantagem, surge o conceito de tubo guia que consiste num tubo oco cuja principal função é fornecer um meio adequado à regeneração do novo nervo guiando o seu crescimento até à extremidade oposta. Nos últimos anos vários materiais têm sido utilizados na preparação destes dispositivos, sendo os materiais poliméricos aqueles que melhores resultados produziram. Porém, ainda não foi desenvolvida uma solução comparável à técnica de autoenxerto com um tempo de degradação in vivo que acompanhe o crescimento do nervo. No sentido de dar resposta a estas limitações, este trabalho envolve a utilização do polissacarídeo dextrano para a preparação de tubos guia. Este polímero foi escolhido como material base devido à sua biocompatibilidade e biodegradabilidade. Com efeito, o dextrano é recorrentemente reportado para aplicações biomédicas, sendo aprovado pela “US Food and Drug Administration” (FDA). Numa fase inicial do trabalho pretendeu-se modificar a estrutura química do dextrano, através da incorporação de ligações duplas nas suas cadeias, para posterior reticulação. Assim, dextrano de pesos moleculares diferentes foi modificado com dois monómeros diferentes, metacrilato de glicidilo (GMA) e metacrilato de 2-isocianoetilo (IEMA). Seguidamente, membranas circulares transparentes foram preparadas através da reticulação das cadeias dos materiais preparados, por radiação ultravioleta (UV). As suas características físico-químicas foram posteriormente avaliadas. Devido à fragilidade demonstrada por estas membranas, foi adicionado às formulações iniciais um macro monómero de base poli (ε-caprolactona) (PCL) modificado com IEMA. Como resultado, as membranas preparadas com dextrano modificado juntamente com o co monómero revelaram maior flexibilidade comparativamente às membranas previamente preparadas. Com a incorporação deste macro monómero verificou-se uma diminuição na capacidade de inchaço e da velocidade de degradação in vitro, não prejudicando, contudo, as propriedades térmo-mecânicas das membranas. O trabalho prosseguiu com a avaliação da citotoxicidade das membranas que apresentaram propriedades mais apropriadas para a aplicação em questão, com recurso a células da polpa dentária humana (hDPSC). A concentração do ião cálcio intracelular foi medida para atestar a viabilidade celular das células aderidas às membranas. Todas as membranas mostraram ser substratos apropriados para a adesão e proliferação celular, sugerindo a ausência de início do processo apoptótico. Seguidamente foi avaliada a extensão da reação imunológica provocada pela implantação subcutânea destas membranas no dorso de ratos. Neste caso, as membranas preparadas com dextrano modificado com GMA, e com a adição de PCL modificado com IEMA provocaram uma resposta imunológica, ao fim de 15 dias, que foi classificada de “não irritante”, através do sistema de pontuação proposto pela norma ISO 10-998-6. Face aos resultados relevantes, a etapa seguinte do trabalho consistiu na preparação de um tubo, utilizando as melhoras formulações de membranas. Neste sentido, foi preparado um molde de quartzo com uma vara de aço inoxidável 316L por forma a criar tubos ocos. Os moldes foram preparados com vista à obtenção de dimensões finais semelhantes às do produto comercial Neurolac®. Foram conduzidos estudos para avaliar o encolhimento das estruturas tubulares, permitindo assim a escolha da formulação mais adequada. Através de microscopia electrónica de varrimento (SEM) foi possível avaliação a superfície dos tubos, que se revelou ser bastante compacta. Neste sentido, foi adicionado D-Mannitol como agente porogénico, de modo que aumentar a permeabilidade dos tubos, por meio de indução de porosidade. Com recurso a esta técnica foi possível obter porosidade com tamanho médio compreendido entre 10-20µm. Posteriormente foi feito um estudo comparativo das propriedades físico-químicas do tubo sem porosidade e com porosidade. Com a introdução do D-mannitol, a capacidade de inchamento dos tubos diminuiu, o que pode denotar uma estrutura com menor densidade de reticulação. No entanto, com a porosidade, a velocidade de degradação dos tubos aumentou, como seria de esperar, visto que a superfície de contacto com o meio também é superior. Contudo, ao fim de seis meses, em solução de PBS os dois tubos mantiveram a sua integridade estrutural. As propriedades mecânicas destes tubos foram também avaliadas através de ensaios de tração uniaxial. Estes testes revelaram que os tubos têm capacidade de resistir a forças de tensão e elongação ligeiramente superiores às do nervo ciático de rato. De notar que estes tubos revelaram ser resistentes a testes preliminares de perfuração com sutura, sem fragmentação visível. Finalmente, os tubos guia foram testados em nervos ciáticos de ratos, após uma lesão de neurotmese induzida. Ao longo de 20 semanas os resultados da avaliação funcional do nervo lesionado mostram que em termos de função motora, a recuperação é semelhante para o tubo não poroso e para o tubo poroso. No que concerne a função sensorial, o grupo de ratos que recebeu o tubo poroso mostrou maior índice de recuperação. Assim, a porosidade aparenta ter um efeito positivo na regeneração do nervo. Este trabalho permitiu validar o dextrano como material base para a preparação de tubos-guia para a regeneração de nervo periférico. Os materiais obtidos apresentam um conjunto de características e propriedades relevantes para o processo regenerativo. Com efeito, estas podem ainda ser facilmente adaptadas através da alteração das formulações utilizadas para preparar os tubos.
Fundação para a Ciência e Tecnologia (FCT) - bolsa de doutoramento PD/BD/52626/2014

Vacuum microwave tubes, such as klystron, traveling-wave tube, gyrotron are high efficiency devices, where the RF interaction structure facilitates efficient energy transfer from the kinetic energy of the high energy electron beam to the electromagnetic wave. Traveling-wave Tube is the most versatile microwave power amplifier widely used for terrestrial communication, radar and aerospace applications. The waveguide based slow-wave structures like Millman, Karp, inter digital, grated waveguide, ring-plane, ring-bar, millitron and folded-waveguide structure gathered importance for application in millimeter-wave traveling-wave tubes. Among these millimeter-wave interaction structures, the folded-waveguide slow-wave structure became the most popular due to its robust structure, high power capability, low RF loss, simpler coupling, reasonably wide bandwidth and ease of fabrication for millimeter-wave to terahertz frequencies. Hence this thesis aims to analyse the folded-waveguide slow-wave structure for broad-banding and efficiency enhancement. The existing approaches for the analysis of cold circuit parameters (dispersion and interaction impedance characteristics) of folded-waveguide slow-wave structure are reinvestigated and found that these have limitation, as the effects of E-plane bend and beam-hole discontinuities are ignored in the parametric analysis. A cascaded matrix equivalent circuit model includes the effect of E-plane and beam-hole discontinuities for the analysis, but reported only for the serpentine folded-waveguide slow-wave structure. The cold test measurement technique was reported only for the dispersion characteristics. Hence the measurement technique has to be extended for the measurement of interaction impedance. The author proposes to orient the present doctoral work to (i) extend the proposed cascaded transmission matrix equivalent model for the analysis of rectangular folded-waveguide slow-wave structure, (ii) develop a non-resonant perturbation technique for the measurement of interaction impedance characteristics of the folded-waveguide slow-wave structure and also to (iii) establish new analysis models for the folded-waveguide slow-wave structure. The effect of E-plane bend and beam-hole discontinuities on the RF characteristics have been considered and simple, yet accurate closed form expressions for the computation of dispersion and interaction impedance characteristics have been established by three different approaches namely: transmission line equivalent circuit model, conformal mapping equivalent circuit model and quasi-TEM approach. The analysis results are benchmarked against 3-D electromagnetic modeling. The non-resonant perturbation theory is developed for the interaction impedance measurement. Typical Ka-band structures are fabricated by wire-EDM process and cold test measurements are carried out to benchmark the analysis approaches. The equivalent circuit models based on lumped circuit model are simpler than the cascaded matrix equivalent circuit model and can give closed form expressions for the prediction of dispersion and interaction impedance characteristics. The quasi-TEM approach can be extended for the complicated structure like ridge-loaded FWG-SWS. Broad-banding of the conventional folded-waveguide slow-wave structure is attempted by ridge-loading on the broad wall of the structure. The ridge-loaded folded-waveguide slow-wave structure is analyzed by parametric approach, cascaded transmission matrix equivalent circuit model and quasi-TEM approach and validated against numerical simulation. The analysis is extended for exploring the efficacy of the ridge-loading on broad-banding of the traveling-wave tube. Finally efficiency enhancement of the folded-waveguide slow-wave structure is attempted by introducing grating on the broad wall of the structure. The analysis is carried out by numerical simulation for exploring the efficacy of the grating on efficiency enhancement of the traveling-wave tube.

Vacuum microwave tubes, such as klystron, traveling-wave tube, gyrotron are high efficiency devices, where the RF interaction structure facilitates efficient energy transfer from the kinetic energy of the high energy electron beam to the electromagnetic wave. Traveling-wave Tube is the most versatile microwave power amplifier widely used for terrestrial communication, radar and aerospace applications. The waveguide based slow-wave structures like Millman, Karp, inter digital, grated waveguide, ring-plane, ring-bar, millitron and folded-waveguide structure gathered importance for application in millimeter-wave traveling-wave tubes. Among these millimeter-wave interaction structures, the folded-waveguide slow-wave structure became the most popular due to its robust structure, high power capability, low RF loss, simpler coupling, reasonably wide bandwidth and ease of fabrication for millimeter-wave to terahertz frequencies. Hence this thesis aims to analyse the folded-waveguide slow-wave structure for broad-banding and efficiency enhancement. The existing approaches for the analysis of cold circuit parameters (dispersion and interaction impedance characteristics) of folded-waveguide slow-wave structure are reinvestigated and found that these have limitation, as the effects of E-plane bend and beam-hole discontinuities are ignored in the parametric analysis. A cascaded matrix equivalent circuit model includes the effect of E-plane and beam-hole discontinuities for the analysis, but reported only for the serpentine folded-waveguide slow-wave structure. The cold test measurement technique was reported only for the dispersion characteristics. Hence the measurement technique has to be extended for the measurement of interaction impedance. The author proposes to orient the present doctoral work to (i) extend the proposed cascaded transmission matrix equivalent model for the analysis of rectangular folded-waveguide slow-wave structure, (ii) develop a non-resonant perturbation technique for the measurement of interaction impedance characteristics of the folded-waveguide slow-wave structure and also to (iii) establish new analysis models for the folded-waveguide slow-wave structure. The effect of E-plane bend and beam-hole discontinuities on the RF characteristics have been considered and simple, yet accurate closed form expressions for the computation of dispersion and interaction impedance characteristics have been established by three different approaches namely: transmission line equivalent circuit model, conformal mapping equivalent circuit model and quasi-TEM approach. The analysis results are benchmarked against 3-D electromagnetic modeling. The non-resonant perturbation theory is developed for the interaction impedance measurement. Typical Ka-band structures are fabricated by wire-EDM process and cold test measurements are carried out to benchmark the analysis approaches. The equivalent circuit models based on lumped circuit model are simpler than the cascaded matrix equivalent circuit model and can give closed form expressions for the prediction of dispersion and interaction impedance characteristics. The quasi-TEM approach can be extended for the complicated structure like ridge-loaded FWG-SWS. Broad-banding of the conventional folded-waveguide slow-wave structure is attempted by ridge-loading on the broad wall of the structure. The ridge-loaded folded-waveguide slow-wave structure is analyzed by parametric approach, cascaded transmission matrix equivalent circuit model and quasi-TEM approach and validated against numerical simulation. The analysis is extended for exploring the efficacy of the ridge-loading on broad-banding of the traveling-wave tube. Finally efficiency enhancement of the folded-waveguide slow-wave structure is attempted by introducing grating on the broad wall of the structure. The analysis is carried out by numerical simulation for exploring the efficacy of the grating on efficiency enhancement of the traveling-wave tube.

La prise d’un supplément d’acide folique en période préconceptionnelle réduit le risque d’une anomalie du tube neural (ATN), une malformation du système nerveux. Dans le but d’en réduire la prévalence, la Société des Obstétriciens et Gynécologues du Canada a émis de nouvelles directives cliniques en 2007 qui tenaient compte de différents facteurs de risque pour les ATN et pour qui la dose recommandée variait selon le profil de risque de la femme, allant de 0,4 à 5,0 mg d’acide folique. Jusqu’à présent, peu de données sont disponibles sur les effets de la prise d’une haute dose d’acide folique. Les objectifs de cette étude étaient: 1) d’évaluer la concordance entre la supplémentation en acide folique chez les femmes enceintes et les nouvelles recommandations canadiennes; 2) d’identifier les déterminants d’une utilisation concordante et 3) d’évaluer si la prise de hautes doses d’acide folique en période périconceptionnelle réduisait le risque de malformations congénitales autre que les ATN. Pour répondre à ces objectifs, une étude transversale et une étude écologique ont été effectuées. La première incluait 361 femmes enceintes recrutées aux cliniques d’obstétriques du CHU Sainte-Justine et la deuxième utilisait le Registre Québécois des Grossesses, issu du jumelage de trois banques de données administratives au Québec (RAMQ, Med-Écho et ISQ), où 152 392 couples mère-enfant ont été identifiés. Seul 27% des femmes enceintes ayant participé à l’étude transversale avaient une supplémentation en acide folique, avec ou sans ordonnance, concordante aux lignes directrices canadiennes. La concordance variait selon leur profil de facteurs de risque pour les ATN. Notre étude écologique montre que la prévalence annuelle de l’utilisation de haute dose d’acide folique (avec ordonnance) en période périconceptionnelle a augmenté de 0,17% à 0,80% (p < 0,0001) entre 1998 et 2008 et que la prévalence des malformations congénitales majeures a augmenté de 15% au cours de la même période (3,35% à 3,87%, p<0,0001). Les résultats de nos deux études montrent que l’acide folique n’est pas largement utilisé par les femmes en âge de procréer et ce, peu importe la dose. De nouvelles campagnes de santé publique devront être mises sur pied, afin d’inciter les femmes à consommer de l’acide folique avant et pendant leur grossesse. Également, la prise de haute dose d’acide folique ne semble pas avoir diminué le risque de malformations congénitales, à l’échelle populationnelle.
The use of folic acid during the preconceptionnal period reduces the risk of neural tube defects (NTD), a malformation of the nervous system. In order to reduce it’s prevalence, the Society of Obstetricians and Gynaecologists of Canada proposed new practice clinical guidelines, in 2007, on the use of pre-conceptional vitamin/folic acid supplementation for the prevention of NTDs, with specific recommendations to prevent recurrences and occurrences among women with intermediate to high health risk factors and for whom the dose was different. The objectives of this study were to evaluate the concordance between the new guidelines and folic acid use in real life; 2) to identify predictors associated with a recommended folic acid supplementation, and 3) to evaluate if the use of folic acid could reduce the risk of congenital malformations other than NTDs. A cross-sectional study and an ecological study have been conducted. 361 women were recruited in obstetrics outpatient clinic at the CHU Ste-Justine for the first study and 152,392 pregnancies and babies were identified in the Quebec Pregnancy Registry, which results from the linkage of three administrative health care databases from Quebec (RAMQ, Med-Echo and ISQ) for the second study. Only 27% of the wowen recruited for the first study had periconceptional folic acid supplementation intake that was concordant with guideline. Concordance varied according to their health risk factors profile for NTD. Our ecological study showed that the annual prevalence of periconceptional folic acid use increased from 0.17% to 0.80% (p < 0,0001) from 1998 to 2008 and birth prevalence of major congenital malformations increased by 15% (3.35% to 3.87%, p < 0,0001) during the same period. Our findings highlight the fact that folic acid is not widely used by women of childbearing age, regardless of the dose. There is a need for new public health programs to encourange women to consume folic acid every day before and during pregnancy. Moreover, the use of high dose folic acid does not seem to be correlated with a decline in the prevalence of major congenital malformations, on a populational level.

碩士
國立交通大學
機械工程研究所
86
Filament wound composite pressure vessels are being increasingly used in industry. This has resulted in a critical neeed for reliable and effective nondestructive testing methods for quality assurance and safety assessment. This study presents an analysis of guided wave propagation in laminated composite tubes by using finite element method based on Hamilton's principle. Each lamina of the composite tube is assumed to be transversely isotropic medium with five independent material stiffness components. The phase velocities were determined by numerical computation and compared with measurements. The transient guided waves were excited by a Q-switched Nd;YAG laser and were detected by a broadband conical transducer mounted on the surface of a composite tube. After transformation from local coordinates of eaxh lamina to the global coordinates of the tube, the number of independent material constants is still the same for the ones manufactured with symmetric filament winding at ±a angles .Three of the material constants are directly measured by pulse-echoes of pressure wave and shear wave and shear waves propagating along the thickness of the tube. The remaining two stiffness components are determined by inversion of simplex based on phase velocities of the guided waves.

abstract: Trenchless technologies have emerged as a viable alternative to traditional open trench methods for installing underground pipelines and conduits. Pilot Tube Microtunneling, also referred to as the pilot tube system of microtunneling, guided auger boring, or guided boring method, is a recent addition to the family of trenchless installation methods. Pilot tube microtunneling originated in Japan and Europe, and was introduced to the United States in the year 1995 (Boschert 2007). Since then this methodology has seen increased utilization across North America particularity in municipal markets for the installation of gravity sewers. The primary reason contributing to the growth of pilot tube microtunneling is the technology's capability of installing pipes at high precision in terms of line and grade, in a wide range of ground conditions using relatively inexpensive equipment. The means and methods, applicability, capabilities and limitations of pilot tube microtunneling are well documented in published literature through many project specific case studies. However, there is little information on the macroscopic level regarding the technology and industry as a whole. With the increasing popularity of pilot tube microtunneling, there is an emerging need to address the above issues. This research effort surveyed 22 pilot tube microtunneling contractors across North America to determine the current industry state of practice with the technology. The survey examined various topics including contractor profile and experience; equipment, methods, and pipe materials utilized; and issues pertaining to project planning and construction risks associated with the pilot tube method. The findings of this research are based on a total of 450 projects completed with pilot tube microtunneling between 2006 and 2010. The respondents were diverse in terms of their experience with PTMT, ranging from two to 11 years. A majority of the respondents have traditionally provided services with other trenchless technologies. As revealed by the survey responses, PTMT projects grew by 110% between the years 2006 and 2010. It was found that almost 72% of the 450 PTMT projects completed between 2006 and 2010 by the respondents were for sanitary sewers. Installation in cobbles and boulders was rated as the highest risk by the contractors.
Dissertation/Thesis
M.S. Construction 2011

碩士
國立交通大學
機械工程系
89
The first order shear deformation theory for analysis of guided wave propagation in anisotropic circular cylindrical shells is developed in this thesis to determine the elastic stiffness constants of a filament wound composite tube. The phase velocity and group velocity dispersion curves of circumferential waves, torsional waves, longitudinal waves and flexural waves are numerically calculated. The approximate theory with the best fit of shear deformation correction factors has a very good agreement with the exact solution for isotropic tubes within the framework of elasticity and save a large number of computation time. The best determination of the shear deformation correction factor in circumferential direction approaches to Mindlin’s estimation, but the axial one converges to a slightly larger value. The material in each filament of a composite tube is assumed to be transversely isotropic with its symmetry at the winding angle to the axis. As the winding angle increases, phase velocities of the torsional waves become greater and those of the longitudinal waves are decreasingly less. But changes in wave speeds of the flexural waves depend on each individual mode. Six effective stiffness constants, corresponding to five independent elastic constants and winding angle of the composite tube, are determined using simplex algorithm to search the best fit of the least squares of errors among those predicated and measured phase velocities of and modes. The results indicate that the stiffness components , , and achieve proper convergence in a broad range of initial guess values, but and converge under limited conditions.

碩士
長庚大學
機械工程研究所
93
Zircaloy material often been used in fuel cladding of nuclear power station. When the operation time, it will produce “hydrogen absorbed” in Zircaloy tubes. When reaching the threshold limit value, hydrogen embrittlement will be happened. It will precipitate a layer of ZrH2 on the outer surface of Zircaloy tubes. The hydrogen embrittlement reduces the ductility of Zircaloy tubes. It will influence the structure reliable in nuclear power station. In the past, we detected the hydrogen concentration of Zircaloy tubes by destructive method, for example, hot vacuum extraction method, inert gas fusion method and SEM method. However, these techniques require destructive inspection and cost a lot of money and time, too. Ultrasonic technique can appear the hydrogen concentration of Zircaloy tubes in the dispersion cuves. In the past studies, they ever researched the dispersion relations of uniform distributed hydrogen in Zircaloy tubes. However, It is more complex that precipitating ZrH2 on the outer surface of Zircaloy tubes. It can be seen for two-layered composite material tubes. So, I study the dispersion relations of two-layered tubes in this research, and it is convenient to inspect the hydrogen concentration of Zircaloy tubes. Theory and experiment are separated to research in two stages that is one-layered tubes and two-layered tubes. The theory of one-layered tubes was derived by Gazis. The results are given of a numerical evaluation of a characteristic equation derived by Gazis. The theory of two-layered tubes was derived by Armenakas. The results are given of a numerical evaluation of a characteristic equation derived by him. At the same time, this study also uses non-destructive laser ultrasonic technique to measure the dispersion relations of Zircaloy tubes with precipitating ZrH2. It appears that Theory and experiment conform well, and can use laser ultrasonic technique to measure the dispersion relations of Zircaloy tubes correctly.

Biovilla is a cooperative that intends to boost a culture of regeneration and currently faces many challenges. With newly acquired funding, Biovilla aims to overcome these challenges by expanding its organization and increasing its environmental, social, and financial impact. To guide Biovilla on the path towards organizational sustainability, this project revises the organization’s current growth strategy. The evaluation of the strategy reveals that it will provide Biovilla with sustainable growth. To further improve the strategy, recommendations are provided to fine-tune it. Lastly, an implementation roadmap was developed to ensure a successful execution. Overall, the fine-tuned strategy will improve Biovilla’s environmental, social and financial impact and make the organization a showroom for sustainability.

碩士
長庚大學
機械工程研究所
95
The characterization of hydrogen concentration (HC) in Zircaloy cladding tubes is an important task. At the same HC, material property (strength and ductility) grown worse quickly with radial hydride than circumferential hydride. So that the important task is not only HC but also RH. Guided waves (GW) propagating in tubes have been extensively used to characterize properties of tubes. In previous study, Axially propagating guided waves (AGW) has been reported to characterize HC in Zircaloys. So, This study is focused on circumferentially propagating guided waves (CGW) to inspect direction of hydride. In this study, a NDE technique employing the LUT and a simplex inversion process is reported for the characterization of radial and circumferential hydride. It’s shown that Young’s modulus of radial hydride be higher than circumferential hydride with CGW, but unchanged with AGW.