Scuba diving as a recreational activity has increased in popularity over the past few years. It is believed that repeated exposure to the hyperbaric environment may have a long term effect on the auditory system. The research literature has given a lot of attention to acute injury but is very limited relating to the long term implications of scuba diving. Previous research studies did not perform a full audiometric test battery. A comprehensive audiological assessment is critical to determine in which part of the ear a pathology may occur during recreational diving. This study endeavoured to assess and describe the hearing abilities and middle ear functioning of the recreational scuba diver and investigate the possibility that diving, on a recreational level, may have an influence on the auditory system. In order to achieve the aims of this study, a descriptive, correlation research design was selected. The results of the current study indicate that scuba diving on a recreational level does not have a significant effect on the hearing and middle ear functioning of the individual, with the exclusion of static compliance. It appears that the inevitable compression and decompression that the middle ears are exposed to during scuba diving might have a more permanent effect on the elasticity of the tympanic membrane. Finally this study aims to increase the awareness of possible risks concerning the auditory system relating to scuba diving and in so doing, attribute to the prevention, diagnosing and intervention of diving related ear injuries. / Dissertation (M (Communication Pathology))--University of Pretoria, 2007. / Speech-Language Pathology and Audiology / M (Communication Pathology) / unrestricted

In this dissertation we seek to identify ways in which the systems development life cycle (SDLC) can be augmented with improved software engineering practices to measurably address security concerns that have arisen relating to security vulnerability defects in software. By proposing a general model for identifying potential vulnerabilities (weaknesses) and using runtime monitoring for verifying their reachability and exploitability during development and testing reduces security risk in delivered products. We propose a form of contract for our monitoring framework that is used to specify the environmental and system security conditions necessary for the generation of probes that monitor security assertions during runtime to verify suspected vulnerabilities. Our assertion-based security monitoring framework, based on contracts and probes, known as the Contract-Based Security Assertion Monitoring Framework (CB_SAMF) can be employed for verifying and reacting to suspected vulnerabilities in the application and kernel layers of the Linux operating system. Our methodology for integrating CB_SAMF into SDLC during development and testing to verify suspected vulnerabilities reduces the human effort by allowing developers to focus on fixing verified vulnerabilities. Metrics intended for the weighting, prioritizing, establishing confidence, and detectability of potential vulnerability categories are also introduced. These metrics and weighting approaches identify deficiencies in security assurance programs/products and also help focus resources towards a class of suspected vulnerabilities, or a detection method, which may presently be outside of the requirements and priorities of the system. Our empirical evaluation demonstrates the effectiveness of using contracts to verify exploitability of suspected vulnerabilities across five input validation related vulnerability types, combining our contracts with existing static analysis detection mechanisms, and measurably improving security assurance processes/products used in an enhanced SDLC. As a result of this evaluation we introduced two new security assurance test suites, through collaborations with the National Institute of Standards and Technology (NIST), replacing existing test suites. The new and revised test cases provide numerous improvements to consistency, accuracy, and preciseness along with enhanced test case metadata to aid researchers using the Software Assurance Reference Dataset (SARD). / Graduate

This thesis describes possible applications of Prony's method in timing analysis of digital circuits. Such applications include predicting the future shape of the waveform in DTA(Dynamic Timing Analysis) and delay look-up table in STA(Static Timing Analysis). Given some equally spaced output values, the traditional Prony's method can be used to extract poles and residues of a linear system, i.e. to characterize a waveform using an exponential function. In this thesis, not only values but also equally spaced derivatives are tested. Still using same idea of the traditional Prony's method, poles and residues can also be extracted with those values and derivatives. The resultant poles and residues will be used to predict the output waveform in DTA analysis. The benefits brought by the using of derivatives include less simulation steps and less CPU time consuming than the regular constant step simulation. As a matter of fact, the Prony's method can precisely approximate a complicated waveform. Such property can be applied for STA analysis. The Prony's approximation can be used to precisely record an output waveform, which is used as an entry of the look-up table of STA. Since the accuracy of STA analysis relies on the accuracy of the input and output waveform in the look-up table, the accuracy of the Prony's approach is promising.

A limited number of studies have been conducted in the literature in order to investigate the behaviour of high-strength fibre-reinforced concrete (HSFRC) structural components subjected to blast loads. This study summarizes the results of a research program investigating the potential of using steel fibres to improve the blast performance of high-strength reinforced concrete beams. As part of the experimental investigation twenty beams were tested, including nine beams tested under static four-point bending, and eleven beams tested under dynamic blast loads using a shock-tube. Parameters considered in the study include the effect of concrete strength, steel fibres, fibre content, fibre type, longitudinal reinforcement ratio, and presence of shear reinforcement. All beams in the study have identical dimensions, with a cross-section of 125 x 250 mm and length of 2440 mm. To manufacture the specimens, two beams were cast with normal-strength self-consolidate concrete (SCC), with a specified strength of 50 MPa, while the remaining beams were cast with either plain or fibre-reinforced high-strength concrete having a compressive strength which varied between 95-110 MPa. The steel fibre content in the HSFRC beams varied between 0.5 and 1.0%, by volume of concrete. To investigate the effect of reinforcement ratio (ρ), the beams were reinforced with 2-#4 (American size) bars, 2-15M bars or 2-20M bars (ρ = 1.02%, 1.59%, and 2.41%, respectively). The majority of the plain concrete beams had transverse reinforcement which consisted of 6 mm stirrups arranged at a spacing of 100 mm in the shear spans, while most of the HSFRC beams were built without stirrups. The results indicate that all the parameters in this study (reinforcement ratio, presence of stirrups, concrete strength, steel fibres, fibre content and fibre type) affected the static and blast response of the beams, however, the results demonstrate that steel fibres have a more remarkable effect when compared to the other parameters. The provision of fibres is found to improve the blast performance of the HSC beams by increasing shear capacity, reducing maximum and residual mid-span displacements, reducing blast fragments and increasing damage tolerance.

Ce travail de thèse a pour objet d’étudier le comportement mécanique en statique, en fatigue, en vibration linéaire et non linéaire et d’évaluer et suivre les mécanismes endommagement par émission acoustique des matériaux composites stratifiés et sandwichs. Deux grandes familles de matériaux composites ont été considérées dans ce travail: a) descomposites stratifiés constitués de fibres de carbone, fibres hybrides (verre/carbone) et fibres de verre avec différentes séquences d’empilement associées à une résine époxyde, b) des matériaux sandwichs constitués de peaux en stratifiés à fibres de verre/résine époxyde et d'une âme en mousse PVC de différentes densités. La mise en oeuvre de l’ensemble de ces matériaux est réalisée au laboratoire (LAUM).Les composites stratifiés ont été caractérisés en sollicitations de traction et de flambement en statique et en fatigue. Au cours de ces essais, les signaux d’émission acoustique sont collectés dans les différents matériaux. Les mécanismes d’endommagement de chaque matériau sont identifiés, caractérisés et suivis en utilisant une analyse multivariable(méthode de coalescence floue) des signaux collectés. L’analyse des résultats obtenus a permis de mettre en évidence l’effet du type de renfort, la séquence d’empilement et de l’épaisseur des couches à 90° sur le comportement mécanique et sur la dynamique de chaque mécanisme d’endommagement jusqu’à la rupture des différents stratifiés. Une analyseexpérimentale du comportement dynamique des composites stratifiés de différents renforts fibreux et différentes orientations des plis a été menée dans le cas de vibration en flexion. La réponse à une excitation par pot vibrant a été établie et les fréquences de résonance et les amortissements ont été déduits et comparés dans différents composites.Ensuite, une étude détaillée est menée pour caractériser le comportement mécanique en statique et en fatigue cyclique des matériaux sandwichs avec une âme de différentes densités.Les essais ont été conduits en flexion 4-points sur des poutres de ces matériaux. L’analyse des résultats et l’observation des signaux d’EA obtenus dans ces structures ont permis de définir les principales signatures acoustiques des différents modes d’endommagement prépondérants dans les peaux et dans l’âme du matériau sandwich. Une étude de comportement vibratoire linéaire des composites sandwichs aux états sains a été menée en flexion.Enfin, une étude du comportement mécanique en statique, en fatigue cyclique, en vibration linéaire et non linéaire des matériaux sandwichs endommagés par des fissures de type cisaillement dans l’âme a été menée. Les caractéristiques statiques sont déterminées en fonction de la densité de fissuration. En fatigue, la rigidité, l’énergie dissipée, l’amortissement et la durée de vie sont évalués à partir des données expérimentales en fonction de la densité defissures et du nombre de cycles. Ensuite, une étude expérimentale du comportement vibratoire linéaire et non-linéaire des composites sandwichs endommagés a été menée. Elle a permis de mesurer les fréquences propres et les amortissements de ces matériaux autour de chaque pic de résonance en fonction de la densité de fissuration. Enfin, la méthode de vibration non linéaire a été appliquée pour caractériser le comportement des matériaux sandwichsendommagés par fissuration. Les paramètres non linéaires relatifs au décalage fréquentiel et à l’amortissement sont mesurés en faisant varier l’amplitude d’excitation et sont comparés aux paramètres linéaires. / The present study investigates the mechanical behavior under static, fatigue, linear and non linear vibration and assesses damage by the acoustic emission method of laminated composite materials (tensile and buckling) and of sandwich composite materials (4 points bending).

Different scenarios of the financial situation can take place before the company's bankruptcy. There may be long-term trends in the deteriorating financial situation that indicate the impending corporate bankruptcy, or the bankruptcy may occur unexpectedly, even though the company was ranked among prosperous business units. If the economic situation of the company followed the second scenario, when insolvency was quite predictable, static model, i.e. the model which does not take into account the dynamics of changes in the financial indicators, is a good option to capture the probability of bankruptcy. However, the situation becomes different when the financial indicators fail to show a positive trend throughout some years before the insolvency. In this case, the predictive accuracy of the static model could be increased by a dynamic model by taking into account the fact that the development of the financial indicators in the past periods may affect the company's financial health for the period under consideration.

Mechanical conditioning has been shown to promote tissue formation in a wide variety of tissue engineering efforts. However the underlying mechanisms by which external mechanical stimuli regulate cells and tissues are not known. This is particularly relevant in the area of heart valve tissue engineering owing to the intense hemodynamic environments that surround native valves. Some studies suggest that oscillatory shear stress (OSS) caused by time-varying flow environments, play a critical role in engineered tissue formation derived from bone marrow derived stem cells (BMSCs). There is strong evidence to support this hypothesis in tissue engineering studies of bone. From observing native heart valve dynamics, OSS can be created by means of pulsatility or by cyclic specimen geometry changes. However, quantification of the individual or combined effects of these variables for the maximization of OSS environments in vitro is to date, not known. Accordingly, in this study we examined and quantified the role that i) physiologically relevant scales of pulsatility and ii) changes in geometry as a function of specimen flexure, have in creating OSS conditions for dynamic culture of tissue. A u-shaped custom made bioreactor capable of producing flow stretch and flexure was used. Computational Fluid Dynamic (CFD) simulations were performed through Ansys CFX (Ansys, Pittsburgh, PA) for both steady and pulsatile flow. We have shown that OSS can be maximized by inducing pulsatile flow over straight scaffolds. We believe that OSS promotes BMSCs tissue formation.

Orientador: Fernando Galembeck / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T09:01:49Z (GMT). No. of bitstreams: 1 Balestrin_LiaBeraldodaSilveira_M.pdf: 4255591 bytes, checksum: c4d0f9d5952dc35354bfb9f0d111643b (MD5) Previous issue date: 2015 / Resumo: Quando dois materiais isolantes são atritados, ocorre a triboeletrização de suas superfícies, isto é, a formação de cargas estáticas, distribuídas em padrões fractais. Uma das hipóteses para explicar a eletrização de isolantes é a ocorrência de reações mecanoquímicas seguidas da transferência mútua de massa. Esta dissertação apresenta mapas de potencial elétrico de superfícies atritadas, que também foram examinadas por microscopia eletrônica de varredura (SEI, BEI) e microanálise EDX. Os resultados verificam a hipótese mecanoquímica associada à transferência de fragmentos poliméricos iônicos, sendo as reações iniciadas pela quebra de cadeias seguida da formação de várias espécies de alta energia e produtos de oxidação. Microanálises também detectaram a fixação de N2 nestas superfícies, evidenciando a participação da atmosfera e a formação de triboplasma. As imagens BEI revelam uma distribuição fractal de composição química consistente com a distribuição de fragmentos limitada por difusão, mas superior à dimensão fractal de distribuição de cargas. Esta diferença é atribuída à supressão de cargas devido a microdescargas elétricas desencadeadas por gradientes superiores à rigidez dielétrica do sólido ou do ar. As microdescargas diminuem os gradientes elétricos, mas, ao mesmo tempo, geram novas espécies muito reativas, aumentando a heterogeneidade química das superfícies. Essa dissertação descreve também alguns experimentos acerca da eletrização produzida por simples contato, obtendo-se padrões bem definidos com tempo de contato de 1 h, porém não revelam a transferência de fragmentos poliméricos mutuamente, sugerindo que o cisalhamento desempenhe um papel importante na transferência de fragmentos poliméricos eletrizados. Em um menor grau de aprofundamento, esta dissertação contempla outras consequências de cargas estáticas, como alterações no coeficiente de atrito / Abstract: Triboelectrification occurs when two insulators are rubbed, i.e. static charges are formed on the surface with a fractal distribution pattern. One of the hypotheses raised by the literature indicates that the electrification is accompanied by mutual mass transfer. This dissertation presents electric potential maps of rubbed surfaces, which were also examined by scanning electron microscopy (SEI, BEI) and EDX microanalysis. The results verify the hypothesis that the electrification is due to mechanochemical reactions associated with transfer of charged polymeric fragments. The reaction is initiated by breaking the chains, generating reactive species and oxidation products. Microanalysis also detected N2 fixation on these surfaces, evidencing the contribution of the atmosphere and the formation of triboplasma. The BEI images show a fractal distribution of chemical composition consistent with a fragment distribution limited by diffusion, but higher than the fractal dimension of the charge distribution. This difference is attributed to the suppression of charges due to electrical micro discharge triggered by gradients higher than the dielectric strength of solid or air. The micro discharges decrease electrical gradients, but at the same time, generates very reactive species further increasing the chemical heterogeneity of surfaces. This dissertation also describes some experiments about the electrification produced by single contact, resulting in well-defined patterns with a contact time of 1 h, but do not show the mutual transfer of polymeric fragments, suggesting that the shearing plays an important role in transferring electrified fragments. This work also includes other consequences of static charges, such as changes in the friction coefficient / Mestrado / Físico-Química / Mestra em Química

[pt] A disposição de rejeitos tem sido uma preocupação muito importante nas empresas de mineração de todo o mundo, tendo como principal motivo a proteção do meio ambiente. Diariamente geram-se grandes quantidades de rejeitos nas plantas de beneficiamento de minérios, sendo necessário dispor de estruturas de armazenamento adequadas (barragem de rejeito) que, dependendo da produção industrial, devem ser alteadas para aumentar a capacidade de armazenamento destas estruturas. Três métodos de alteamento de barragens podem ser utilizados: o método à montante, o método à jusante e o método da linha de centro. O método à montante, discutido nesta dissertação, começa com a construção de um dique de partida. Terminada esta etapa, os rejeitos são depositados à montante, formando uma praia que adensará com o tempo, aumentando gradualmente a resistência ao cisalhamento do rejeito e servindo de fundação para futuros diques de alteamento. Este procedimento continua sucessivamente, até atingir a cota prevista de projeto. É um método de construção simples e de baixo custo, mas sua principal desvantagem é que velocidades de alteamento excessivas podem induzir a liquefação estática, causa principal do colapso de várias barragens de rejeito construídas no mundo. Neste trabalho é investigado o potencial de liquefação de uma barragem de rejeito de cobre, situada no Peru, com auxílio do método empírico de Olson, baseado em correlações com resultados de ensaios de campo SPT, e do método de elementos finitos, com utilização do modelo constitutivo elastoplástico UBCSand para previsão de liquefação. / [en] The disposal of tailings has been a very important concern in mining companies around the world, with the main objective to protect the environment. Large quantities of tailings are generated daily in the ore processing plants, being necessary the availability of specific storage structures (tailings dam) which, depending on the industrial production, must be successively raised in their lifetime to provide higher storage capacity. Three methods of dam raising can be used: the upstream method, the downstream method and the centerline method. The upstream method, discussed in this thesis, begins with the construction of a starting dyke. After this step, the tailings are deposited upstream, forming a beach which will consolidate over time, gradually increasing the shear resistance of the waste and serving as a foundation for future raising dikes. This procedure continues until the final dam elevation is reached. This method is of simple construction and low cost, but its main disadvantage is that the raising speeds can be excessive and they may induce static liquefaction, a major cause of failure of tailing dams around the world. This dissertation investigates the liquefaction potential of a copper tailing dam, situated in Peru, making use of the empirical method proposed by Olson, based on correlations with data from SPT field tests, and the finite element method, considering the elastoplastic constitutive model UBCSand.

Cette thèse développe des outils permettant de prouver qu’un système dynamique est sûr. En supposant qu’une partie de l’espace d’état est dangereuse, un système dynamique est dit sûr lorsque son état n’atteint jamais cette partie dangereuse au cours du temps, quel que soit l’état initial appartenant à un ensemble d’états initiaux admissibles et quel que soit le niveau de perturbation restant dans un domaine admissible. Les outils proposés cherchent à établir des preuves de sûreté pour des systèmes décrits par des modèles dynamiques non-linéaires et des modèles dynamiques hybrides. Prouver qu’un système dynamique est sûr en calculant explicitement l’ensemble des trajectoires possibles du système lorsque le modèle dynamique est non-linéaire et perturbé reste une tâche très difficile. C’est pourquoi cette thèse aborde ce problème à l’aide de fonctions barrières paramétrées. Une barrière, lorsqu’elle existe, permet de partitionner l’espace d’état et d’isoler l’ensemble des trajectoires possibles de l’état du système de la partie dangereuse de l’espace d’état. La fonction paramétrique décrivant la barrière doit satisfaire un certain nombre de contraintes impliquant la dynamique du modèle, l’ensemble des états initiaux possibles, et l’ensemble dangereux. Ces contraintes ne sont pas convexes en général, ce qui complique la recherche de fonctions barrières satisfaisantes. Précédemment, seules des fonctions barrières polynomiales ont été considérées pour des modèles dynamiques polynomiaux. Cette thèse considère des systèmes dynamiques relativement généraux avec des barrières paramétriques quelconques. Les solutions présentées exploitent des outils de satisfaction de contraintes sur des domaines continus et des outils issus de l’analyse par intervalles. Dans un premier temps, cette thèse considère des systèmes dynamiques non-linéaires à temps continu. Le problème de conception d’une barrière paramétrique est formulé comme un problème de satisfaction des contraintes sur des domaines réels avec des variables quantifiées de manière existentielle et universelle. L’algorithme CSC-FPS a été adapté afin de résoudre le problème de synthèse de barrière. Cet algorithme combine une exploration de l’espace des paramètres de la barrière et une phase de vérification des propriétés de la barrière. A l’aide de contracteurs, il est possible de significativement accélérer la recherche de solutions. Dans un second temps, ces résultats sont étendus au cas de systèmes décrits par des modèles dynamiques hybrides. La propriété de sûreté doit être prouvée lors de l’évolution à temps continu du système dynamique, mais aussi pendant les transitions du système. Ceci nécessite l’introduction de contraintes supplémentaires qui lient les fonctions barrières associées à chaque mode à temps continu entre elles. Réaliser la synthèse de toutes les fonctions barrières pour les différents modes simultanément n’est envisageable que pour des systèmes de très petite dimension avec peu de modes. Une approche séquentielle a été proposée. Les contraintes liées aux transitions sont introduites progressivement entre les modes pour lesquels une barrière a déjà été obtenue. Lorsque certaines contraintes de transition ne sont pas satisfaites, une méthode de backtracking doit être mise en œuvre afin de synthétiser des barrières offrant une meilleure prise en compte des contraintes de transition non satisfaites. Ces approches ont été évaluées et comparées avec des techniques de l’état de l’art sur des systèmes décrits par des modèles à temps continu et des modèles hybrides. / This thesis addresses the problem of proving the safety of systems described by non-linear dynamical models and hybrid dynamical models. A system is said to be safe if all trajectories of its state do not reach an unsafe region. Proving the safety of systems by explicitly computing all its trajectories when its dynamic is non-linear or when its behavior is described by an hybrid model with non-linear dynamics remains a challenging task. This thesis considers the barrier function approach to prove the safety of a system. A barrier function, when it exists, partitions the state space and isolates the trajectories of the system starting from any possible initial values of the state and the unsafe part of the state space. The set of constraints, which have to be satisfied by a barrier function are usually non-convex, rendering the search of satisfying barrier functions hard. Previously, only polynomial barrier functions were taken in consideration and for systems with polynomial dynamics. This thesis considers relatively general dynamical systems with generic non-linear barrier functions. The solutions presented are based on template barrier functions, constraint satisfaction problems, and interval analysis. The first part of the thesis focuses on non-linear dynamical systems. The barrier function design problem is formulated as a constraint satisfaction problem that can be solved using tools from interval analysis. This formulation allows one to prove the safety of a non-linear dynamical system by finding the parameters of a template barrier function such that all constraints are satisfied using the FPS-CSC algorithm, which has been adapted and supplemented with contractors to improve its efficiency. The second part of the thesis is dedicated to the design of barrier functions for systems described by hybrid dynamical models. Safety properties have to be proven during the continuous-time evolution of the system, but also during transitions. This leads to additional constraints that have to be satisfied by candidate barrier functions. Solving all the constraints simultaneously to find all the barrier functions is usually computationally intractable. In the proposed approach, the algorithm explores all the locations sequentially. Transition constraints are introduced progressively between the already explored locations. Backtracking to previous location is considered when transition constraints are not satisfied. The efficiency of the proposed approaches has been compared with state-of-the-art solutions.