La dispersion de particules par une onde de souffle ou de choc induit la formation de structures régulières qui prennent la forme de jets de particules. Jusqu'à présent, les expériences n'ont été réalisées qu'en trois dimensions rendant difficile l'exploitation des données. Dans cette étude, une onde de souffle, générée à l'extrémité d'un tube à choc, débouche au centre d'un anneau de particules solides initialement confiné dans une cellule de Hele-Shaw. Pour la première fois, à partir d'une expérience de laboratoire, la formation de jets de particules est observée dans une configuration quasi bi-dimensionnelle et pour de faibles niveaux de pression. Grâce à un système de visualisation ultra-rapide, il a été mis en évidence que la sélection du nombre de jets de particules est un processus instationnaire. Nous avons observé que les jets de particules sont initialement formés à l'intérieur de l'anneau et sont ensuite expulsés à l'extérieur du front de particules en expansion. L'influence de nombreux paramètres, tels que la densité et le diamètre des particules, la surpression générée et la géométrie de l'anneau, ont été étudiées. La synthèse des résultats expérimentaux obtenus a permis d'établir certaines relations empiriques reliant le nombre de jets aux propriétés initiales. De plus, la formation de fines perturbations sur le front externe de la couche de particules a été observée. Ce phénomène est quant à lui indépendant des jets principaux et dépend seulement de la nature des particules. / The dispersion of particles by a blast or a shock wave induces the formation of coherent structures which take the form of particle jets. All the experiments conducted so far have been performed in three-dimensional geometry. In the present study, a blast wave, issuing from the discharge of a planar shock wave at the exit of a conventional shock tube, is generated in the center of a granular medium ring initially confined inside a Hele-Shaw cell. With the present experimental set-up, under impulsive acceleration, a solid particle jet formation is clearly obtained and observed in a quasi-two-dimensional configuration, for the first time. From fast flow visualizations, we highlighted that the selection of the number of jets is unsteady. We noticed, in all instances, that the jets are initially generated inside the particle ring and thereafter expelled outward. This point has not been observed in three-dimensional experiments. The influence of many parameters such as density and diameter of particles, the generated pressure and the geometry of the ring, has been studied. Empirical relationships were deduced from the experimental curves. Moreover, we observed in detail the formation of very thin perturbations created around the external surface of the dispersed particle layer. This phenomenon is independent of the main jet formation and solely depends on the nature of particles.

Le schéma d'allumage par choc pour la fusion par confinement inertiel utilise une impulsion laser intense à la fin d'une phase d'assemblage de combustible. Les paramètres clefs de ce schéma sont la génération d'une haute pression d'ablation, l'amplification de la pression du choc généré par un facteur supérieur à cent et le couplage du choc avec le point chaud de la cible. Dans cette thèse, de nouveaux modèles semi-analytiques sont développés afin de décrire le choc d'allumage depuis sa génération jusqu'à l'allumage du combustible. Tout d'abord, un choc sphérique convergent dans le coeur pré-chauffé de la cible est décrit. Le modèle est obtenu par perturbation de la solution auto-semblable de Guderley en tenant compte du nombre de Mach du choc élevé mais fini. La correction d'ordre un tient compte de l'effet de la force du choc. Un critère d'allumage analytique est exprimé en fonction de la densité surfacique du point chaud et de la pression du choc d'allumage. Le seuil d'allumage est plus élevé pour un nombre de Mach faible. Il est montré que la pression minimale du choc, lorsqu'il entre dans le coeur de la cible, est de 20Gbar. La dynamique du choc dans la coquille en implosion est ensuite analysée. Le choc se propage dans un milieu non inertiel avec un fort gradient de pression et une augmentation temporelle générale de la pression. La pression du choc est amplifiée plus encore durant la collision avec une onde de choc divergente provenant de la phase d'assemblage. Les modèles analytiques développés permettent une description de la pression et de la force du choc dans une simulation typique de l'allumage par choc. Il est démontré que, dans le cas d'une cible HiPER, une pression initiale du choc de l'ordre de 300 Mbar dans la zone d'ablation est nécessaire. Il est proposé une analyse des expériences sur la génération de chocs forts avec l'installation laser OMEGA. Il est montré qu'une pression du choc proche de 300Mbar est atteinte près de la zone d'ablation avec une intensité laser absorbée de l'ordre de 2 X 10(15) W.cm-2 et une longueur d'onde de 351 nm. Cette valeur de la pression est deux fois plus importante que la valeur attendue en considérant une absorption collisionnelle de l'énergie laser. Cette importante différence est expliquée par la contribution d'électrons supra-thermiques générés durant l'interaction laser/plasma dans la couronne. Les modèles analytiques proposés permettent une optimisation de l'allumage par choc lorsque les paramètres de la phase d'assemblage, sont pris en compte. Les diverses approches analytiques, numériques et expérimentales sont cohérentes entre-elles. / The shock ignition concept in inertial confinement fusion uses an intense power spike at the end of an assembly laser pulse. the key feature of shock ignition are the generation of a high ablation pressure, the shock pressure amplification by at least a factor of a hundred in the cold fuel shell and the shock coupling to the hot-spot. in this theses, new semi-analytical hydrodynamic models are developed to describe the ignitor shock from its generation up to the moment of fuel ignition. A model is developed to describe a spherical concerging shock wave in a pre-heated hotspot. The self-similar solution developed by Guderley is perturbed over the shock Mach number Ms >>1. The first order correction accounts for the effects of the shock strength. An analytical ignition criterion is defined in terms of the shock strength ans th hot-spot areal density. The ignition threshold is higher when the initial Mach number of the shock is lower. A minimal shock pressure of 20 Gbar is needed when it enters the hot-spot. The shock dynamics in the imploding shell is the analyzed. The shock is propagating into a non inertial medium with a high radial pressure gradient and an averall pressure increase with time. The collision with a returning shock coming from the assembly phase enhances further the ignitor shock pressure. The analytica theory allows to des cribe the shock pressure and strength evolution in a typical shock ignition implosion. It is demonstrated that, in the case of the HiPER target design, a generation shock pressure near the ablation zone on the order of 300-400 Mbar is needed. An analysis of experiments on the strong shock generation performed on the OMEGA laser facility is presented. It is sown that a shock presssure close to 300 Mbar near the ablation zone has been reached with an absorbed laser intensity up to 2 x 10(15) W:cm-2 and a laser wavelength of 351 nm. This value is two times higher than the one expected from collisional laser absorption only. That significant pressure enhancement is explained by contribution of hot-electrons generated by non-linear laser/plasma interaction in the corona. The proposed analytical models allow to optimize the shock ignition scheme, including the inuence of the implosion parameters. Analytical, numerical and experimental results are mutualy consistent.

Orientador: William Dias Belangero / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-28T23:43:39Z (GMT). No. of bitstreams: 1 Faria_LidiaDornelasde_M.pdf: 3066212 bytes, checksum: 6cb5506682740e2fcb2de4b1694998a3 (MD5) Previous issue date: 2015 / Resumo: A Terapia por ondas de choque (TOC) é uma alternativa não invasiva utilizada como método de indução a formação óssea que consiste em pulsos sonoros de alta energia transmitidas de modo focal a um tecido específico. Artigos demonstram aumento de vascularização, que ativação de proteínas como BMP (bone morphogenic protein) e Erk (extracellular signal-regulated kinase) induzindo diferenciação osteogênica após sua utilização no tecido ósseo. O presente estudo visou avaliar os níveis das proteínas Erk e Akt (akutely transforming), envolvidas na cascata protéica responsiva a deformação celular gerada por estímulo mecânico e consequente transformação em estímulo bioquímico induzindo a osteogênese. Os animais selecionados para o estudo foram anestesiados e divididos em dois diferentes grupos, onde no dia 1, o primeiro grupo foi submetido a TOC em sessão única de 500 impulsos gerados por aparelho eletrohidráulico a 0,12mJ/mm²na tíbia intacta e o segundo não recebeu TOC. Na sequência, os animais foram divididos em 3 subgrupos para cada tempo de segmento de 7, 14 e 21 dias A determinação dos níveis das proteínas propostas foi realizada por meio de immunoblotting. A fosforilação das proteínas Erk e Akt dos tecidos ósseos das tíbias extraídas dos ratos aumentou nos grupos submetidos a TOC após 7, 14 e se manteve elevado até o 21° dia quando comparado ao controle / Abstract: Extracorporeal shock wave therapy (ESWT) is a non-invasive alternative used as a method for inducing bone formation that consists of high-energy acoustic pulses transmitted in a focal way to a specific tissue. Studies show increase in vascularization which activate proteins such as BMP and Erk inducing osteogenic differentiation after its use in the bone tissue. The present study aimed at evaluating the levels of Erk and AKT proteins involved in the protein cascade responsive to cell deformation in biochemical stimulus inducing osteogenesis. The animals selected for the study were under anesthesia and divided in two different groups where on day 1 the first group was submitted to ESWT in one 500 pulse-session generated by an electrohydraulic device at 0,12mJ/mm² in intact tibia and fibula and the second did not receive ESWT. Then the animals were divided into 3 sub-groups, one for each segment times of 7, 14 and 21 days. Immunoblotting analysis was performed to determine the levels of the proposed proteins. The Erk and Akt protein phosphorylation of the bone tissues of extracted tibia from the animals increased in the groups submitted to ESWT and kept elevated until the 21st day when compared to the control group / Mestrado / Fisiopatologia Cirúrgica / Mestra em Ciências

A doença arterial coronariana crônica apresenta alta prevalência e morbidade na população, manifestando-se como uma síndrome clínica caracterizada por sintomas álgicos tipicamente desencadeados ou agravados pelo esforço físico - a angina. Define-se a angina como refratária na presença de isquemia miocárdica documentada não passível de tratamento por meio de revascularização e não controlada a despeito do tratamento farmacológico máximo tolerado. O uso de terapia com ondas de choque extracorpóreas no tratamento da isquemia miocárdica tem sido proposto como uma alternativa promissora para o alívio dos sintomas anginosos e melhora da carga isquêmica por meio da promoção de vasodilatação e neoangiogênese. No presente estudo, avaliamos o efeito da terapia guiada com ondas de choque na reserva de fluxo miocárdico, obtida pela ecocardiografia de perfusão miocárdica em tempo real (EPMTR), em pacientes com angina refratária. Determinamos, também, as implicações da terapia com ondas de choque nas variáveis clínicas por meio da avaliação da classe funcional de angina pelo escore da Canadian Cardiovascular Society (CCS), capacidade funcional pelo escore de insuficiência cardíaca da New York Heart Association (NYHA) e qualidade de vida pelo Seattle Angina Questionnaire (SAQ), assim como nas variáveis ecocardiográficas. Foram estudados 15 pacientes com angina refratária procedentes do Ambulatório de Angina Refratária do Instituto do Coração (InCor, HC-FMUSP), os quais foram submetidos a 9 sessões de terapia com ondas de choque, ao longo de 9 semanas, e acompanhados por um período de 6 meses após a conclusão do tratamento. A dinâmica das microbolhas no miocárdio foi quantificada pela EPMTR utilizando programas computacionais específicos, tanto em repouso como durante o estresse pelo dipiridamol (0,84 mg/Kg). A reserva de volume miocárdico normatizada (Anor), a reserva de velocidade de repreenchimento de microbolhas no miocárdio (?) e a reserva de fluxo miocárdico (Anor x ?) foram obtidas pela relação entre os parâmetros de fluxo durante a hiperemia e o repouso, antes e 6 meses após o tratamento com ondas de choque. Nos 15 pacientes incluídos no estudo, avaliamos 32 segmentos com isquemia miocárdica submetidos à terapia, 31 segmentos com isquemia miocárdica não submetidos à terapia e 60 segmentos não isquêmicos. Os pesquisadores que realizaram as quantificações da EPMTR não tinham conhecimento dos dados clínicos no momento da análise de perfusão. A média etária da amostra foi de 61,5 (± 12,8) anos com predomínio do sexo masculino (67%), sendo que 93% deles apresentavam doença multiarterial. Após 6 meses da conclusão da terapia com ondas de choque, foi observada uma melhora da classe de angina (CCS) de 3,20 ± 0,56 para 1,93 ± 0,70 (p = 0,0001) e de insuficiência cardíaca (NYHA) de 2,8 ± 0,56 para 2,33 ± 0,81 (p = 0,048), resultados que foram concordantes com os achados do SAQ, o qual evidenciou melhora significativa da pontuação em todas as categorias (análise global com incremento da pontuação média de 42,33 ± 13,0 para 71,16 ± 14,3; p = 0,0001). Houve uma variação da fração de ejeção do ventrículo esquerdo de 50,30 ± 13,1% para 53,20 ± 10,6% (p = 0,049) na ausência de alterações no diâmetro diastólico final (de 53,80 ± 6,61 mm para 53,53 ± 7,05 mm; p = 0,81), no volume diastólico final (de 134,67 ± 34,33 mL para 146,13 ± 59,45 mL; p = 0,29) ou na função diastólica. A análise da perfusão miocárdica pela EPMTR evidenciou um aumento significativo da reserva de fluxo miocárdico (Anor x ?) de 1,33 ± 0,22 para 1,74 ± 0,29 (p = 0,0001) e também da reserva Anor de 1,02 ± 0,21 para 1,24 ± 0,33 (p = 0,004) nos segmentos isquêmicos submetidos à terapia com ondas de choque, mas não da reserva beta (de 1,33 ± 0,24 para 1,47 ± 0,35; p = 0,055). Não houve alterações significativas na perfusão miocárdica nos segmentos isquêmicos não tratados ou nos segmentos não isquêmicos. A análise global demonstrou uma melhora na reserva de fluxo miocárdico (de 1,78 ± 0,54 para 1,89 ± 0,49; p = 0,017) e na reserva beta (de 1,63 ± 0,43 para 1,70 ± 0,40; p = 0,039). Não foram registrados eventos cardiovasculares maiores durante o período de acompanhamento. Concluímos que a EPMTR foi capaz de identificar melhora da reserva de fluxo miocárdico nos segmentos submetidos à terapia com ondas de choque, possivelmente devido à neoproliferação vascular. Os resultados sugerem que a terapia com ondas de choque em pacientes com angina refratária é segura e tem o potencial de melhorar a isquemia miocárdica nos segmentos isquêmicos tratados, com impacto nos sintomas e na qualidade de vida / Chronic coronary artery disease shows high prevalence and morbidity levels in general population. In the clinical scenario, it is usually characterized by pain symptoms typically triggered or aggravated by physical effort - the angina. Refractory angina is defined as a documented and uncontrolled myocardial ischemia, untreatable by revascularization, despite maximum tolerated drug therapy. The use of extracorporeal cardiac shock wave therapy to treat myocardial ischemia has been suggested as a promising alternative to relieve angina symptoms and improve the ischemic load by promoting vasodilation and neoangiogenic phenomena. In the present study, we evaluated the effect of guided shock wave therapy on myocardial flow reserve, determined by real-time myocardial perfusion echocardiography (RTMPE), in patients with refractory angina. We also evaluated the implications of shock wave therapy in clinical variables by assessing the Canadian Cardiovascular Society (CCS) grading of angina pectoris, New York Heart Association (NYHA) functional classification and quality of life by the Seattle Angina Questionnaire (SAQ), as well as echocardiographic variables. Fifteen patients with refractory angina, from the refractory angina outpatient clinic of the Instituto do Coração (InCor, HC-FMUSP), were studied. Each patient underwent 9 shock wave therapy sessions over the course of 9 weeks and was followed for 6 months once the treatment was concluded. Using specific software, myocardial microbubble dynamics was quantified by RTMPE at rest as well as in stress by dipyridamole (0.84 mg/Kg). Normalized myocardial blood (Anor) reserve, myocardium microbubbles replenishment rate (?) reserve and myocardial flow reserve (Anor x ?) were obtained by the ratio of flow parameters during hyperemia and rest, before and 6 months after treatment. In the 15 patients included in the study, we evaluated 32 segments with myocardial ischemia submitted to therapy, 31 segments with myocardial ischemia not submitted to therapy and 60 non-ischemic segments. Researchers were blinded to all clinical data at the time of the perfusion analysis. Patients had mean age of 61.5 (± 12.8) years old, were predominantly men (67%), and 93% presented multiarterial disease. Six months after the completion of shock wave therapy, an improvement in CCS grading of angina pectoris was observed from 3.20 ± 0.56 to 1.93 ± 0.70 (p = 0.0001) and in NYHA functional classification (from 2.80 ± 0.56 to 2.33 ± 0.81; p = 0.048), results consistent with those found by SAQ, which evidenced a significant score improvement in all categories (global analysis with average score increased from 42.33 ± 13.0 to 71.16 ± 14.3; p = 0.0001). There was a variation in the left ventricular ejection fraction (from 50.3 ± 13.1% to 53.20 ± 10.6%; p = 0.049) in the absence of changes in end-diastolic diameter (from 53.80 ± 6.61 mm to 53.53 ± 7.05 mm; p = 0.81), the end-diastolic volume (from 134.67 ± 34.33 mL to 146.13 ± 59.45 mL; p = 0.29) or the diastolic function. Myocardial perfusion analysis by RTMPE evidenced a relevant increase in myocardial flow reserve (Anor x ?) from 1.33 ± 0.22 to 1.74 ± 0.29; p = 0.0001, as well as in the Anor reserve from 1.02 ± 0.21 to 1.24 ± 0.33 (p = 0.004) in ischemic segments submitted to shock wave therapy, but not in ? reserve (from 1.33 ± 0.24 to 1.47 ± 0.35; p = 0.055). There was no significant myocardial perfusion alteration in untreated ischemic segments or non-ischemic segments. Global analysis showed an improvement in myocardial flow reserve (from 1.78 ± 0.54 to 1.89 ± 0.49; p = 0.017) and ? reserve (1.63 ± 0.43 to 1.70 ± 0.40; p = 0.039). No major cardiac events were registered during the follow-up period. We concluded that RTMPE was able to identify an increase in myocardial flow reserve in the segments submitted to shock wave therapy, possibly due to vascular neoproliferation. Results suggest that shock wave therapy on patients with refractory angina is safe, with the potential to improve myocardial ischemia on treated ischemic segments, and positively affect symptoms and quality of life

Wood structural elements are more vulnerable to blast loading due to the inherent brittle nature and low density of the material, as demonstrated by recent significant research efforts on the behaviour of timber elements subjected to the effect of blast loading. These studies showed that wood performs poorly under blast loading. A way of improving this performance is to provide additional ductility or energy absorption capabilities to wooden elements. Recently, there was interest in investigating and developing energy-absorbing connections (EAC) to improve timber assemblies’ ductility and energy absorption capabilities. Although some research effort has been made to investigate the use of EACs to enhance the ductility of reinforced concrete or structural steel members, only limited work is available on this topic about timber elements. The current study aims to systematically investigate the use of various shapes of EACs to be used to enhance the post-peak performance of timber assemblies. Preliminary finite element analysis led to selecting nine steel EACs with varying geometries for further experimental investigation. A total of eighteen specimens were tested statically. In comparison, a total of eighteen specimens were tested dynamically in the shock tube facility of the University of Ottawa to simulate the effects of far-field blast explosions. The experimental results showed that decreasing the leg length or increasing the thickness of EACs manufactured with steel angles and reducing the diameter of EACs manufactured with circular HSS caused an increase in yield load and elastic stiffness while reducing the densification displacement. Connections with angles and a centre weld, and connections with 90-degree arcs from circular HSS, were identified as unsuitable for the application of EACs. The experimental program also showed that EACs manufactured from angles offer a well-defined plateau able to absorb a large quantity of energy, making them particularly suitable for blast mitigation. EACs manufactured from multiple circular HSS were shown to achieve multiple load-displacement plateaus and present an interesting option for systems with multiple failure modes occurring at different levels. SDOF analysis and FEA were conducted to predict the experimental behaviour with some success. The importance of the weld type was also highlighted from both the analytical and experimental results. A methodology for developing idealized load-displacement curves from experimental results of EACs was also proposed and evaluated.

This work describes briefly electron microscopy issue and physical model of fluid flow. Then presented diploma thesis will be describing analysis and evaluation of the impact of supersonic flow on the pressure and density in the path of the primary electron beam in the differential pumping chamber. For analysis, evaluation and examination of the issue will be used CAD and CAE (Computer Aided Engineering) programs. At the same time it will be developed a methodology of calculation applicable to supersonic flow in the low pressure system at ANSYS CFX.

This master thesis deals with stress-strain analysis of simplified model of the thin wall transformer case subjected to impact load of electrical blast. Electrical blast is replaced by chemical blast (detonation of high explosive). The problem is solved using computational modeling utilizing the Finite Element Method (FEM) and LS-DYNA solver. After the introduction where detonation and shock wave propagation is explained the analytical approach is presented. This approach serves to results verification. In the next chapter is conducted research of applicable methods from which ALE method is chosen. In preliminary study is performed the mesh size analysis that is focused on finding the size of element which is both computational effective and gives accurate results. Next the infulence of input conditions (shape, location and parametres of high explosive, location of detonation point, boundary conditions) on distribution and time progress of pressure is investigated. Then influence of the opening on upper side of the case on overall pressure redistribution and strain and stress of the case is analysed. The stress-strain analysis of the case´s door which are connected to case by various types of contact models is performed as well as stiffness analysis of these types of contact.

No description available.

No description available.

Modelling the full event of an underwater explosion (UNDEX) is complex and requires advanced modelling methods in order to achieve accurate responses. The process of an UNDEX includes a series of events that has to be considered. When a detonation is initiated, a shock-wave propagates and the rest products from the explosive material creates a gaseous bubble with high pressure which pulsates and impacts the surroundings. Reflections of the initial shock-wave can also appear if it hits the sea floor, water surface or other obstacles. There are different approaches how to numerically model the impact of an UNDEX on a structure, some with analytical approaches without a water domain and others where a water domain has to be modelled. This master’s thesis focuses on two modelling methods that are available in the finite element software LS-DYNA. The simpler method is called Sub-Sea Analysis (SSA) and does not require a water domain, thus it can be beneficial to use in an early design stage, or when only approximated responses are desired. To increase the accuracy, a more complex method called S-ALE can be used. By implementing this method, the full process of an UNDEX can be studied since both the fluid domain and explosive material are meshed. These methods are studied separately together with a combination of them. Another important aspect to be considered is that oscillations of a structure submerged in water differs from the behavior it has in air. Depending on the numerical method used, the impact of the water can be included. Natural frequencies of structures submerged in water are studied, how it changes and how the methods takes this into account. To verify the numerical models, experiments were executed with a cylindrical test object where the distance and weight of charge were altered through out the test series. It was found that multiple aspects affects the results from the experiments, that are not captured in the numerical models. These aspects have for instance to do with reflections, how accurate the test object is modelled and the damping effects of the water. It is concluded that the numerical models are sensitive when small charges and fragile structures are studied. High frequency oscillations were not triggered in the experiment but found for both methods. It should be further investigated if the methods are more accurate for larger charges and stronger structures. Experiments with larger water domain would also be beneficial to reduce effects from reflections, as well as a more accurate model of the cylinder in the simulations.