Teses / dissertações sobre o tema "Propagative regime"
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Lalloz, Samy. "De la diffusion à la propagation d'ondes en magnétohydrodynamique bas-Rm : études théorique et expérimentale". Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALI020.
Texto completo da fonteThe thesis aims to clarify the conditions for Alfvén waves to propagate in a closed liquid metal domain. A first part of the research work presented is dedicated to a linear study of Alfvén waves in the low-Rm approximation and under the inertia-less limit. The second part is the experimental investigation of an electrically-induced oscillating flow subjected to an axial, static and uniform magnetic field and confined between two electrically insulating and no-slip horizontal walls.The theoretical study is itself split into two sub-parts. The first one aims to discuss the dispersion relation which contains the Alfvén wave dynamics. It presents the consequences of (mechanical and magnetic) gradients perpendicular to the imposed magnetic field. As such transverse gradients tend to impede the wave propagation. In the second sub-part an axisymmetric vortex confined between to electrically insulated and no-slip horizontal walls is magnetically forced at a given frequency. This forcing is radially dependent so as to study the impact of transverse gradients on the flow dynamics. A semi-analytical investigation of the flow dynamics is again carried out in the low-Rm approximation and under the inertia-less limit. This investigation is performed by varying the forcing frequency and the magnetic field intensity. This brings to emphasize two very distinct regimes for the oscillating vortex:- an oscillating-diffusive regime governed by the competition between pseudo-diffusive effects of the Lorentz force and the unsteady term of the momentum- a truly propagative regime, obtained for higher forcing frequencies, found definitelygoverned by Alfvén waves.The study also highlights how the propagative regime can be affected by transverse gradients. In addition to over-damping the waves, transverse gradients are found to modify the natural frequencies for which wave resonance peaks result from the superimposition of incident and reflected waves in the container.Beside this theoretical work, a setup has been designed in order to experimentally investigate the dynamics of oscillating flows under a strong magnetic field (up to 10T). A flow was forced in a cuboid vessel 15 cm x 15 cm x 10 cm by means of AC currents injected through a cartesian grid of four electrodes located at the bottom plate. Using instrumentation based on the measurement of local electric potential differences at the top and bottom horizontal (Hartmann) plates, we validate model's prediction. More precisely, a propagative dynamics in the presence of transverse gradients is recovered. The oscillating-diffusive regime is also recovered from experiments performed at small enough forcing frequency.In addition to results obtained at the forcing frequency, a first insight of signals obtained at other frequencies is shown. Frequency peaks obtained, eg the harmonics of the forcing frequency, are demonstrated not to be explained by a linear approach. We suggest that Alfvén wave non-linear interactions are a good candidate to explain these peaks. A preliminary study further shows that peaks at the first harmonic are likely to be Alfvén waves
ELALOUFI, Rachid. "Propagation du rayonnement en milieu diffusant. Etude de la transition entre le regime balistique et le regime diffusif et des fluctuations temporelles d'intensite". Phd thesis, Ecole Centrale Paris, 2003. http://tel.archives-ouvertes.fr/tel-00003084.
Texto completo da fontetravers un milieu diffusant. La propagation peut être décrite
par l'équation de transfert radiatif en régime dynamique
(ETR). Nous proposons une méthode de résolution en
géometrie plane. Elle consiste à appliquer la méthode
des ordonnées discrètes dans le domaine fréquentiel de
l'ETR. Nous calculons ainsi le flux d'énergie directionnel
transmis et rétrodiffuse en fonction du temps et de l'angle.
Dans la seconde partie, nous étudions la validité de
l'approximation de la diffusion. Cependant, l'expression théorique
du coefficient D en milieu absorbant varie selon l'approche
adoptée. Une nouvelle approche fondée sur l'analyse du mode
fondamental de l'ETR est développée. Sans faire aucune
hypothèse concernant le niveau d'absorption, nous obtenons une
nouvelle définition et interprétation de D.
La troisième partie est consacrée à l'étude de la
transition entre le regime balistique et le regime
diffusif. Nous montrons que les reflexions internes jouent un
rôle important pour les systèmes à faible épaisseur
optique. Nous montrons ainsi que le régime diffusif est atteint
aux temps longs, pour des systèmes de taille 8L ou L est la
longueur de transport.
Enfin, dans la derniere partie, nous modélisons la
corrélation temporelle du signal diffuse. Deux théories
(QELS et DWS) permettent de modéliser respectivement le signal en
diffusion simple et en régime diffusif. Nous avons
développe un modèle décrivant les deux régimes
ainsi que le régime intermédiaire. Le modèle est fondé
sur une approche de type marche au hasard et sur la résolution de
l'équation de transfert radiatif dynamique. Ce modèle a permis
de décrire des expériences récentes de mesures de
fluctuations temporelles de champs et d'intensite dans le
régime de diffusion multiple intermédiaire.
JAKOBER, FRANCOIS. "Etude de la propagation d'impulsions laser ultra-intenses dans un plasma sous-dense en regime faiblement relativiste". Paris 11, 1996. http://www.theses.fr/1996PA112222.
Texto completo da fonteCONSTANTOPOULOS, CONSTANTIN. "Etude theorique, numerique et experimentale de la propagation d'ondes acoustiques dans des empilements metalliques desordonnes en regime lineaire et non lineaire". Paris 6, 1998. http://www.theses.fr/1998PA066447.
Texto completo da fonteRogers, Susan Owen. "Population Biology of the Tan Riffleshell (Epioblasma florentina walkeri) and the Effects of Substratum and Light on Juvenile Propagation". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/36143.
Texto completo da fonteThe tan riffleshell population in Indian Creek was estimated to be 1078 adults (95% CI= 760 - 1853), using Schumacher's modification of Schnabel's maximum likelihood estimator. The sex ratio and size distribution of males and females were approximately equal. Specimen ages, determined from thin-sections of shells, showed that mussels aged by external annuli on shells likely underestimates the true ages of individuals.
Appropriate culture conditions for this species were examined using juveniles of the wavyrayed lampmussel (Lampsilis fasciola) as a surrogate. In the first experiment, juvenile growth and survival was compared between four substratum types (fine sediment, < 120μm; fine sand, 500 μm-800 μm; coarse sand, 1000 μm-1400 μm; and mixed sediment, < 1400 μm) and two light treatments in open versus covered recirculating troughs (2.8 m). Juveniles in fine sediment substratum and covered troughs fared poorest, with 7% survival and growth to only 0.86 mm in length after 16 wk. Juveniles in mixed sediment and open troughs fared best, with 26% survival and growth to 1.09 mm after 16 wk. Additionally, juveniles in fine sand in covered troughs had significantly higher survival (23.1%) than juveniles in fine sediment (p = 0.04), and juveniles in fine sand survived consistently better between light treatments than in the other substrata. There were no significant differences among the other treatments.
A second experiment was performed to determine whether juveniles were responding directly to the presence of light or whether only the increased autochthonous production improved growth and survival. One-half of each of three 2.8 m troughs were covered with 50% shade cloth, while the other sides were left open to ambient light. Additionally, the best and worst sediments from the first experiment (fine sand and fine sediment) were used again to verify the results from the previous experiment. In this case, juveniles in both sides of the troughs grew equally well, but juveniles in the open sides had significantly poorer survival (open mean: 1.78%, sd = 5.01; covered mean: 7.4%, sd = 5.01) (p = 0.046). Fine sediment yielded significantly higher growth of juveniles than fine sand (p = 0.009), with shell lengths of 2.63 mm (sd = 0.075) in fine sediment and 1.94 mm (sd = 0.102) in fine sand. The differences in survival and growth between the two experiments were attributed to differential numbers of chironomids and platyhelminths, which are predators of young juveniles. Additionally, the fine sediment was more tightly packed in the first experiment than in the second, which may have restricted movement and subsequently reduced survival. Light alone likely did not affect juvenile survival and growth; rather, it was seemingly the greater abundance of aufwuchs available as food. This hypothesis was corroborated by a juvenile behavior experiment, which showed that juveniles did not act differently when in tanks not exposed to light versus those open to ambient light.
Master of Science
L'HERMITE, DANIEL. "Comparaisons des descriptions cinetique et coherente pour la modelisation de la propagation de l'impulsion laser en milieu optiquement epais et en regime semi-coherent". Paris 11, 1999. http://www.theses.fr/1999PA112259.
Texto completo da fonteBennett, Valerie P. "A microscale study of small crack propagation in multiaxial fatigue". Diss., Atlanta, Ga. : Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/23957.
Texto completo da fonteAlmehmadi, Fares Saleh S. "Secure Chaotic Transmission of Digital and Analog Signals Under Profiled Beam Propagation in Acousto-Optic Bragg Cells with Feedback". University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1426781250.
Texto completo da fonteTombul, Serdar. "A numerical study of the validity regimes of weak fluctuation theory for ocean acoustic propagation through random internal wave sound speed fields". Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion.exe/07Mar%5FTombul.pdf.
Texto completo da fonteThesis Advisor(s): John Colosi. "March 2007." Includes bibliographical references (p. 81-82 ). Also available in print.
Mai, Phuong Thao. "The potential role of copper binding sites in prion propagation". Doctoral thesis, SISSA, 2014. http://hdl.handle.net/20.500.11767/3905.
Texto completo da fonteSibel, Jean-Christophe. "Region-based approximation to solve inference in loopy factor graphs : decoding LDPC codes by the Generalized Belief Propagation". Phd thesis, Université de Cergy Pontoise, 2013. http://tel.archives-ouvertes.fr/tel-00905668.
Texto completo da fonteMassala, Gaston. "Propagation et propriétés électriques des streamers positifs à grande distance dans l'huile minérale sous très haute tension impulsionnelle". Grenoble INPG, 1997. http://www.theses.fr/1997INPG0112.
Texto completo da fonteThe aim of this work is to study the propagation of the "streamers" and their electrical properties in mineral oil at long distances under pulsed voltage (up to 480 kV) under various voltage conditions (from the minimum propagation voltage to the high overvoltages), inter-electrode distance (2. 5 to 35 cm), electrode geometry (plane-to-plane, semi-uniform, planar sphere) of solid insulators. This work makes a contribution on the characterization of the breakdown phenomena and the mechanisms involved in the positive streamers. For voltages below the breakdown voltage, stopping, transition to breakdown and conductivity of the streamers are described. In particular, it has been shown that the streamer is conductive only during a total re-ignition of its main branch. In the presence of overvoltages, the existence of an acceleration voltage correlated with the appearance of the fast streamers is highlighted. Three different propagation modes are identified and characterized: 2nd mode (2 to 4 km / s), 3rd mode (10 to 20 km / s) and 4th mode (> 100 km / s). A correlation between the shape, speed and load of the streamers was highlighted and the voltage drop in the streamer was determined. Calculations of the charge and field on the plane electrode carried out by the Load Simulation Method (CSM), considering different macroscopic models in the presence of a voltage drop, have led to the conclusion that the streamers are comparable to objects conductors of simple shape (cylinder or sphere). A qualitative correlation between the macroscopic field at the end of the streamers calculated by CSM, and the speed was obtained. E there exists a critical field = 400 kV / cm, beyond which the streamers are always fast (> 10 km / s). This work proposes two complementary mechanisms allowing to explain the constancy of the speed of the positive streamers in the mineral oil: the effect of the voltage drop and / or the electrostatic effect due to the branching of the streamers. It has been shown that the overall shape of the streamers determines the field at their end and hence the propagation modes. This has been verified by studying the influence of electrode geometry (shielding effect), insulating solids (positional effect) and the nature of the liquid (additive effect)
Oliveira, Aline Mystica Silva de. "Cultivo in vitro e perfis de isoenzimas antioxidativas em espécies de bromélias". Universidade Federal de Juiz de Fora (UFJF), 2016. https://repositorio.ufjf.br/jspui/handle/ufjf/3059.
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A família Bromeliaceae apresenta distribuição essencialmente neotropical, contando com 52 gêneros que abrangem 3.320 espécies. Das espécies de bromélias, 34% são exclusivas da Mata Atlântica, sendo que Portea petropolitana e Billbergia horrida se enquadram nessa categoria. O acelerado processo de destruição dos ecossistemas, somado ao extrativismo predatório, tem levado a reduções drásticas nas populações. Apesar de sua importância ecológica, medicinal e ornamental, a realização de pesquisas fisiológicas com bromélias ainda é rara. A cultura de tecidos apresenta-se como uma alternativa bastante atrativa para a conservação de espécies ameaçadas, possibilitando a obenção de taxas elevadas de multiplicação a partir de diferentes explantes. Visando promover a conservação in vitro de plantas de Billbergia horrida, Portea petropolitana e Tillandsia polystachia assim como a multiplicação em larga escala, este estudo teve por objetivos o estabelecimento de protocolos eficientes de multiplicação utilizando diferentes reguladores de crescimento (BAP, CIN, TDZ e GA3) buscando identificar as concentrações ideais dos mesmos para o cultivo de cada uma das espécies. O tratamento que promoveu as maiores taxas de multiplicação in vitro de P. petropolitana foi o suplementado com BAP a 7,5 μM. As maiores taxas de enraizamento foram observadas no tratamento suplementado com 5 μM de GA3. Para B. horrida o tratamento que promoveu as maiores taxas de propagação in vitro foi o suplementado com BAP a 2,5 μM. Plântulas com maior número de raízes foram obtidas em resposta à suplementação do meio de cultura com GA3 a 2,5 μM. O tratamento que promoveu a melhor taxa de propagação in vitro de T. polystachia foi o suplementado com BAP a 2,5 μM. Um maior número de raízes foi obtido em resposta ao GA3 a 10 μM. Plântulas das três espécies foram eficientemente aclimatizadas ex vitro. Devido à presença do O2 na atmosfera terrestre, a formação de espécies reativas de oxigênio (EROs) é um processo inevitável em eventos metabólicos essenciais como a fotossíntese e a respiração. Os sistemas de defesa que promovem a eliminação das EROs envolvem mecanismos enzimáticos e não enzimáticos. Embora alguns estudos tenham investigado a separação funcional existente ao longo das folhas de bromélias epífitas com tanque, alguns deles inclusive envolvendo enzimas essenciais ao metabolismo vegetal, pesquisas relacionando os sistemas enzimáticos e isoenzimáticos antioxidativos nas diferentes regiões das folhas de bromélias inexistem até o momento. No presente estudo, em plantas mantidas em condições de campo, foram avaliadas as atividades enzimáticas brutas e os perfis isoenzimáticos das enzimas catalase (CAT), peroxidase (POD) e superóxido dismutase (SOD) em diferentes regiões das folhas (apical, mediana e basal) de Portea Petropolitana e Billbergia horrida, assim como em diferentes estratos de altura de um forófito (inferior, mediano e superior) em Tillandsia polystachia. Padrões específicos de expressão das isoenzimas SOD e POD foram observados nas diferentes porções das folhas de P. petropolitana. A atividade da CAT não foi detectada em nenhuma das porções das folhas das três espécies. O maior número de isoformas da SOD e a maior intensidade da isoforma da POD, observados na região apical das folhas de P. petropolitana, estão, aparentemente, relacionados à atividade metabólica mais intensa resultante da maior atividade fotossintética e do nível de maturidade dessa porção da folha. Esses resultados foram corroborados pelas maiores atividades dessas enzimas também observadas na porção apical das folhas por meio de métodos espectrofotométricos. A região apical da folha é o principal sítio de assimilação fotossintética e de biossíntese de parede celular e lignina nas bromélias, envolvendo processos metabólicos normalmente relacionados à geração de EROs. Nos estudos de eletroforese realizados com B. horrida um mesmo padrão de isoformas da SOD foi observado em todas as regiões foliares avaliadas. Todavia, para a POD, diferentes padrões de intensidade na expressão isoenzimática foram detectados nas diferentes partes da folha. A maior intensidade das isoformas da POD observada na região apical das folhas também parece estar relacionada à maior maturidade fisiológica dessa região, resultado corroborado pela atividade enzimática mais intensa observada para essa enzima na análise espectrofotométrica realizada com materiais provenientes da região apical da folha. Durante a senescência foliar, as PODs, juntamente com outras enzimas, estão envolvidas na biossíntese de parede celular e de lignina, através de mecanismos que envolvem a produção e o acúmulo de EROs. Em T. polystachia, um mesmo padrão de isoenzimas da SOD foi observado nos diferentes estratos do forófito. Nessa espécie, a atividade da POD não foi observada nas análises de eletroforese, embora tenha sido detectada por espectrofotometria, especialmente nas posições medianas e mais elevados do forófito. Na análise espectrofotométrica, as atividades das CATs e das SODs mostraram padrões de expressão similares, com valores mais elevados encontrados nas posições mais baixas e mais elevadas do forófito. Esses resultados revelaram a ocorrência de variação na atividade enzimática em plantas de T. polystachia em resposta à posição (altura) no forófito. O teor de proteínas também seguiu o mesmo padrão em resposta ao estrato de localização das plantas no forófito. Os resultados encontrados no presente estudo permitem concluir que, para as três espécies estudadas, o BAP foi o regulador de crescimento que promoveu as maiores taxas de multiplicação in vitro, sendo o GA3 o regulador de crescimento que possibilitou a obtenção de plântulas enraizadas e prontas para a fase de aclimatização. As três espécies de bromélias estudadas foram eficientemente aclimatizadas após três meses de cultivo in vitro. O perfil de expressão das isoenzimas da SOD e da POD variou conforme as regiões das folhas em P. petropolitana. Em B. horrida, a SOD exibiu o mesmo padrão de isoformas em todas as regiões foliares, embora diferentes padrões de intensidade na expressão isoenzimática da POD tenham sido detectados. Em T. polystachia, a SOD exibiu o mesmo perfil de isoenzimas nos diferentes estratos do forófito. Esses resultados são os primeiros relatos sobre a variação espacial da atividade enzimática antioxidativa e da expressão isoenzimática em folhas de espécies de bromélias.
Bromeliaceae has essentially neotropical distribution, with 52 genera covering 3,320 species. The bromeliad species, 34% are unique to the Atlantic Forest, Portea petropolitana and Billbergia horrida fall into this category. The accelerated process of destruction of ecosystems, coupled with the predatory extraction has led to drastic reductions in populations. Although its ecological importance, medicinal and ornamental, conducting physiological studies with bromeliads is still rare. Tissue culture is presented as a very attractive alternative for the conservation of endangered species, allowing obenção of high multiplication rates from different explants. To promote in vitro conservation Billbergia horrida, Portea petropolitana and Tillandsia polystachia plants as multiplication on a large scale, this study aimed to establish efficient multiplication protocols using different growth regulators (BAP, KIN, TDZ and GA3 ) seeking to identify the optimal concentrations there of for the cultivation of individual species. The treatment produced the greatest in vitro multiplication rates of P. petropolitana was supplemented with BAP at 7.5 uM. The highest rooting rates were observed in the treatment supplemented with 5 uM of GA3. To B. horrida treatment which produced the greatest of in vitro propagation rates was supplemented with 2.5 uM BAP. Seedlings with larger roots were obtained in response to the supplementation of culture medium with GA3 at 2.5 uM. The treatment promoted the best in vitro propagation rate T. polystachia was supplemented with 2.5 uM BAP. A higher number of roots was obtained in response to GA3 10 uM. Seedlings of the three species were efficiently acclimatized ex vitro. Due to the presence of O2 in the atmosphere, the formation of reactive oxygen species (ROS) is an inevitable process in essential metabolic events such as photosynthesis and respiration. Defense systems that promote the elimination of ROS involving enzymatic and non-enzymatic mechanisms. Although some studies have investigated the existing functional compartmentalization along the leaves of epiphytic bromeliad tank, including some involving enzymes essential to plant metabolism, research relating the enzyme systems and antioxidative isozyme in different regions of the bromeliad leaves do not exist yet. In this study, in plants grown under field conditions, gross enzymatic activities and enzyme profiles of catalase enzymes were evaluated (CAT), peroxidase (POD) and superoxide dismutase (SOD) in different regions of the leaves (apical, median and basal ) of Portea petropolitana and Billbergia horrida, and in different strata of height of a host tree (lower, middle and higher) in Tillandsia polystachia specific patterns of expression of SOD isoenzymes and POD were observed in different portions of the sheets P. petropolitana. The CAT activity was not detected in any of the portions of the sheets of the three species. The largest number of isoforms of SOD and the greater intensity of isoform of POD, observed in the apical region of P. petropolitana leaves are apparently related to more intense metabolic activity resulting from higher photosynthetic activity and the level of maturity of this portion of the leaf. These results were supported by higher activity of these enzymes also observed in the apical portion of the leaves through spectrophotometric methods. The apical region of the leaf is the primary photosynthetic assimilation site and cell wall biosynthesis and lignin in bromeliads, involving metabolic processes typically related to the generation of ROS. In electrophoresis studies with B. horrida the same pattern of SOD isoforms was observed in all evaluated foliar regions. However, for the POD different intensity patterns in the isozyme expression were detected in different parts of the sheet. The greatest intensity of POD isoforms observed in the apical region of the leaves also seems to be related to increased physiological maturity of the region, a result confirmed by more intense enzymatic activity observed for this enzyme in the spectrophotometric analysis with materials from the apical region of the sheet. During senescence, the pods along with other enzymes, are involved in cell wall biosynthesis and lignin, through mechanisms that envovem the production and accumulation of ROS. In T. polystachia, the same pattern of SOD isoenzymes was observed in different strata of the host tree. In this species, the POD activity was not observed in the electrophoresis analysis, although it has been detected by spectrophotometry, especially in middle positions and higher phorophyte. In the spectrophotometric analysis, the activities of CAT and SODs showed similar patterns of expression, with highest values observed in lower positions and higher phorophyte. These results revealed the occurrence of variation in the enzymatic activity in T. polystachia plants in response to the position (height) in phorophyte. The protein content also followed the same pattern in response to the stratum location of the plants in phorophyte. The results of this study allow us to conclude that, for the three species studied, the BAP was the growth regulator which promoted the highest in vitro multiplication rates, and the GA3 growth regulator which enabled obtaining rooted and ready seedlings for the acclimatization phase. The three species of bromeliads studied were efficiently acclimatized after three months of in vitro culture. The expression profile of the isoenzymes of SOD and POD varied as the regions of the leaves of P. petropolitana. In B. horrida, SOD exhibited the same pattern of isoforms in all foliar regions, although different intensity patterns in the isozyme expression of POD were detected. In T. polystachia, SOD showed the same profile of isozymes in different strata of the host tree. These results are the first reports of the spatial variation of antioxidative enzyme activity and isoenzyme expression in leaves of bromeliads species.
Ayachi, Mohamed. "Determination de la temperature dans la mesosphere a partir de la mesure de la vitesse de phase des ondes longues sur un trajet grande distance". Caen, 1988. http://www.theses.fr/1988CAEN2021.
Texto completo da fonteMethenni, Hajer. "Modélisation mathématique et méthode numérique pour la simulation du contrôle santé intégré par ultrasons de plaques composites stratifiées". Electronic Thesis or Diss., Institut polytechnique de Paris, 2021. http://www.theses.fr/2021IPPAE002.
Texto completo da fonteThis thesis is embedded in the context of « Structural Health Monitoring ». This method of non-destructive testing aiming at monitoring in-situ an engineered structure is increasingly used in numerous industrial fields, e.g. the aeronautics industry. It is based upon elastic guided waves propagating over large distances. The interactions between incident wave fields and structural defects are gathered through a network of receiving sensors. The dispersive nature of guided waves, combined with the inherent anisotropy of some industrial materials, such as composites, makes the interpretation of the output signals difficult. The goal of this thesis is to provide meaningful numerical tools enhancing the understanding and analysis of propagation and interaction phenomena, appearing during the control experiment. The thesis lies between the physical and mathematical modelling of elastic waves and the construction of relevant numerical schemes, altogether in an innovating industrial context involving complex geometries and materials
Cheron, Elie. "Guides d'ondes et transport dans les milieux désordonnés : effets de la symétrie et de la localisation". Thesis, Le Mans, 2019. http://www.theses.fr/2019LEMA1017.
Texto completo da fonteThis thesis focuses on the wave propagation in disordered waveguides. First, we introduce the basic tools and concepts in order to present the different transport regimes and phenomena related to coherent effects (such as universal conductance fluctuations, enhanced backscattering or Anderson's localization). Beside the remarkable phenomena associated to diffuse transport, the coherent effects are also noticeable when the spatial distribution of the scatterers displays symmetries. The second part is dedicated to the observation of a significant and broadband enhancement in transmission through opaque barriers. The sensitivity of this phenomenon to symmetry defects is discussed in Chapter 4. Limitations due to absorption, which are always present in an experimental context, and localization are also inspected. The fourth chapter focuses on one of the signatures of the localization regime: the propagation within these insulating media is insensitive to the source. We present some special cases in which this property is broken. Finally, several preliminary studies related to other propagation phenomena in complex media are discussed as perspectives for this work
PILLAI, Vinoshene. "Intravital two photon clcium imaging of glioblastoma mouse models". Doctoral thesis, Scuola Normale Superiore, 2021. http://hdl.handle.net/11384/109211.
Texto completo da fonteWang, Jieyu. "Ultrashort Pulse Propagation in the Linear Regime". Thesis, 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7362.
Texto completo da fonteAbraham, Nimmy Mariam. "Studies on Propagating and Non-Propagating Cracks in Concrete Under Fatigue Loading in the Short Crack Regime". Thesis, 2013. http://etd.iisc.ac.in/handle/2005/3464.
Texto completo da fonteAbraham, Nimmy Mariam. "Studies on Propagating and Non-Propagating Cracks in Concrete Under Fatigue Loading in the Short Crack Regime". Thesis, 2013. http://etd.iisc.ernet.in/2005/3464.
Texto completo da fonteYan, Yan. "The propagation of light in the linear and nonlinear regimes in multicore photonic crystal fibers". 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3358116.
Texto completo da fontePinos, THOMAS. "Combustion Wave Propagation Regimes in a Channel equipped with an Array of Cross-flow Cylindrical Obstacles". Thesis, 2013. http://hdl.handle.net/1974/8116.
Texto completo da fonteThesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-07-18 21:13:40.436
Ruben, Perez Mora. "Study of the fatigue strength in the gigacycle regime of metallic alloys used in aeronautics and off-shore industries". Phd thesis, 2010. http://pastel.archives-ouvertes.fr/pastel-00671657.
Texto completo da fonteFernandes, Beatriz Carolina Vasco Gonçalves Costa. "Fatigue crack propagation study on the Portuguese Air Force Epsilon TB-30 aircraft". Master's thesis, 2021. http://hdl.handle.net/10400.6/11935.
Texto completo da fonteA fadiga é um fenómeno causado por cargas dinâmicas que se caracteriza pela propagação de fissuras e pode culminar na rotura total de um material. No sector aeronáutico militar, particularmente na formação de pilotos, este problema assume especial importância dada a diversidade de missões e manobras que são levadas a cabo. O avião Epsilon TB-30 é utilizado na Força Aérea Portuguesa para instrução básica de pilotagem na Frota 101, na Base Aérea nº11 em Beja. No âmbito da monitorização da integridade estrutural, uma aeronave da frota foi recentemente instrumentada com um sistema que inclui a instalação de um acelerómetro no centro de gravidade da aeronave e cinco extensómetros em locais críticos da aeronave, o que levou à definição dos principais objectivos deste trabalho: o desenvolvimento de uma ferramenta de propagação automática de fenda para um local crítico na estrutura da aeronave, bem como a comparação na propagação de uma fenda quando sujeita a um regime de voo severo e não-severo, voos típicos na operacção da frota Epsilon. A fim de simular a propagação da fenda, este trabalho incluiu um modelo de elementos finitos desenvolvido no software Ansys para a obtenção dos valores do factor de intensidade de tensão para vários tamanhos de fenda. Foi também realizado, com o recurso a Matlab, a modelação da propagação da fenda utilizando as leis de propagação Walker e NASGRO para a obtenção de uma expressão para o factor geométrico, Y. Posteriormente, foi realizada uma análise comparativa do comportamento de crescimento da fenda para diferentes regimes de severidade de voo, leis de propagação e tamanhos iniciais da fenda. Finalmente, foi desenvolvida uma aplicação web que permite simular de forma simples e automática a propagação da fenda para um voo real.
Saracco, Ginette. "Propagation acoustique en régime harmonique & transitoire a travers un milieu inhomogène: Méthodes asymptotiques & Transformation en ondelettes". Phd thesis, 1989. http://tel.archives-ouvertes.fr/tel-00178676.
Texto completo da fonteDans un premier temps, nous avons traité le cas s'une source ponctuelle monochromatique à l'aide de méthodes asymptotiques, de façon à vérifier l'existence physique de cette contribution. Dans le cas du dioptre plan air-eau, nous avons pu séparer expérimentalement la contribution latérale de la contribution géométrique, et mettre en évidence le comportement et les propriétés de celles-ci. Le champ réfracté total fait alors apparaître des zones d'interférences en parfait accord avec l'étude théorique et numérique. La contribution latérale présentant un caractère "dispersif", montre l'intérêt dans le cas du régime transitoire, d'utiliser une méthode de type temps-échelle.
La fonction de Green peut être décomposée de façon naturelle en trois contributions analogues à celles du régime harmonique. La transformée en ondelettes permet alors de calculer de façon exacte ces différentes contributions et d'en étudier leur comportement. L'orginalité des résultats obtenus est la mise en évidence à certaines échelles, de phénomènes transitoires très brefs (échos) qui permettent d'engager une discussion nouvelle de ce type de problème. Une expérimentation combinée à une analyse temps-échelle (ondelettes) a confirmé ces observations.
Par analogie à la formule de reconstitution simple de la transformée en ondelettes inverse, nous avons pu élaborer, pour de grandes distances radiales, une formule de reconstruction de la dépendance temporelle du signal-source (problème inverse) à partir de la mesure de la pression transmise (jouant le rôle de "pseudo-coefficients d'ondelettes") sur les profondeurs.
Enfin, l'application de cette transformation à un problème de rétrodiffusion acoustique par des coques sphériques élastiques (interface fluide/solide) a montré qu'il est possible d'accéder à certaines caractéristiques physiques de la cible.
Vuthaluru, Rupa. "MF radar observations of D-region electron densities at Adelaide / by Rupa Vuthaluru". 2003. http://hdl.handle.net/2440/22029.
Texto completo da fonteIncludes bibliographical references (leaves 177-183)
xxii, 183 leaves : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, School of Chemistry and Physics, Discipline of Physics and Mathematical Physics, 2004
Proulx, Louis-Xavier. "Étude numérique et asymptotique d'une approche couplée pour la simulation de la propagation de feux de forêt avec l'effet du vent en terrain complexe". Thèse, 2016. http://hdl.handle.net/1866/20586.
Texto completo da fonte"Occurrence and Causes of F-region Echoes for the Canadian PolarDARN/SuperDARN Radars". Thesis, 2013. http://hdl.handle.net/10388/ETD-2013-03-949.
Texto completo da fonte