Sandwich panels using fibre-reinforced composite skins and low-density cores are being increasingly used in the aerospace industry due to their superior specific strength and stiffness, and increased design flexibility over traditional metallic and composite structures. However, it is well-known that sandwich panels are highly vulnerable to the effects of impact damage, with even low-energy impacts potentially causing very severe reductions in the in-plane compressive strength of these structures. The objective of this project was to produce a faithful and reliable numerical model for the simulation of the compression-after-impact strength of composite sandwich panels. An in-depth literature review revealed that delamination within the skins of a sandwich panel is a damage mechanism that has gone almost entirely neglected in previous efforts at modelling this problem, despite the proven significance of this mechanism in the failure of impact damaged sandwich panels in compression. Consequently, the use of the cohesive zone model for delamination initiation and propagation is the key unique feature of this model, with Hashin s criteria being used for intra-laminar damage formation, and a simple plasticity response capturing core crushing. An experimental study is performed to produce a thorough dataset for model validation, featuring differing levels of damage induced via quasi-static indentation, and novel asymmetric panels with skins of unequal thickness (the thinner skin being on the unimpacted side). The experimental study revealed that the use of a thinner distal (undamaged) skin could improve the strength of mildly damaged sandwich panels over undamaged sandwich panels using the same asymmetric configuration. It is believed that this effect is due to the movement of the neutral plane of the sandwich panel caused by the reduction in the stability of the damaged skin through stiffness reduction and geometric imperfections. This removes the eccentricity of the compressive loading that exists in the undamaged asymmetric panels, which has mismatched axial stiffness between the indented skin and the thinner distal skin, and thus a noticeably lower ultimate strength than the undamaged symmetric panels. The sandwich model is developed using pre-existing experimental and material data, and trialled for a variety of different skin lay-ups, core thicknesses and indenter sizes. The numerical model generally agreed well with the ultimate stress found in the experiments for these different configurations, but is quite poor at estimating the magnitude of the damage induced by the indentation. When used to model the experimental study, the model gave generally good, conservative estimates for the residual compressive strength of both the symmetric and asymmetric panels. The tendency of the asymmetric panels to become stronger with mild damage was not captured by the model per se, with the numerical results instead showing an insensitivity to damage in the asymmetric panels, which was not shared by the symmetric panels. However, the numerical model did exhibit erroneous strain-stress responses for both panel configurations, particularly for the undamaged and mildly damaged cases. Investigations revealed that this erroneous behaviour was caused by inconsistency in the material data, which had been collected partially via experimentation and partly from literature sources. Overall, the model developed here represents a promising advancement over previous efforts, but further development is required to provide accurate damage states.

Human surrogates are representations of living humans, commonly adopted to better understand human response to impacts. Though surrogates have been widely used in automotive, defence and medical industries with varying levels of biofidelity, their primary application in the sporting goods industry has been through primitive rigid anvils used in assessing personal protective equipment (PPE) effectiveness. In sports, absence from competition is an important severity measure and soft tissue injuries such as contusions and lacerations are serious concerns. Consequently, impact surrogates for the sporting goods industry need a more subtle description of the relevant soft tissues to assess impact severity and mitigation accurately to indicate the likelihood of injury. The fundamental aim for this research study was to establish a method to enable the development of superior, complementary, increasingly complex synthetic and computational impact surrogates for improved assessment of sports personal protective equipment. With a particular focus on the thigh segment, research was conducted to evaluate incremental increases in surrogate complexity. Throughout this study, empirical assessment of synthetic surrogates and computational evaluation using finite element (FE) models were employed to further knowledge on design features influencing soft tissue surrogates in a cost and time efficient manner. To develop a more representative human impact surrogate, the tissue structures considered, geometries and materials were identified as key components influencing the mechanical response of surrogates. As a design tool, FE models were used to evaluate the changes in impact response elicited with different soft tissue layer configurations. The study showed the importance of skin, adipose, muscle and bone tissue structures and indicated up to 15.4% difference in maximum soft tissue displacement caused by failure to represent the skin layer. FE models were further used in this capacity in a shape evaluation study from which it was determined that a full-scale anatomically contoured thigh was necessary to show the full diversity of impact response phenomena exhibited. This was particularly pertinent in PPE evaluations where simple surrogate shapes significantly underestimated the magnitudes of displacements exhibited (up to 155% difference) when rigid shell PPE was simulated under impact conditions. Synthetic PDMS silicone simulants were then fabricated for each of the organic soft tissues to match their dynamic responses. The developed simulants exhibited a superior representation of the tissues when compared to previous single material soft tissue simulant, Silastic 3483, which showed 324%, 11,140% and -15.8% greater differences than the PDMS when compared to previously reported target organic tissue datasets for relaxed muscle, skin and adipose tissues respectively. The impact response of these PDMS surrogates were compared in FE models with previously used single material simulants in representative knee and cricket ball sports impact events. The models were each validated through experimental tests and the PDMS simulants were shown to exhibit significantly closer responses to organic tissue predictions across all impact conditions and evaluation metrics considered. An anatomically contoured synthetic thigh surrogate was fabricated using the PDMS soft tissue simulants through a novel multi-stage moulding process. The surrogate was experimentally tested under representative sports impact conditions and showed a good comparison with FE model predictions with a maximum difference in impactor displacements and peak accelerations of +6.86% and +12.5% respectively at velocities between 2 - 4 m.s-1. The value of increased biofidelity in the anatomical synthetic and virtual surrogate thighs has been proven through the incremental adoption of important surrogate elements (tissue structures, material and geometries). The predictive capabilities of each surrogate have been demonstrated through their parallel developments and staged comparisons with idealised organic tissue responses. This increase in biofidelity is introduced at modestly higher cost compared to Silastic 3483, but, given the benefits of a more representative human impact response for PPE evaluations, this is shown to be worthwhile.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

De nos jours, les systèmes de télécommunications deviennent de plus en plus complexes et sophistiqués. Les perfonnances électriques des transistors hyperfréquences qui les constituent, doivent être améliorées en terme de fréquence, de puissance, de rendement et de linéarité. Dans le cas des transistors de puissance la caractérisation non linéaire est une étape indispensable afin de mieux comprendre et appréhender les effets limitatifs et d'optimiser leur conception. Dans ce cadre, l'objectif de cette thèse a été de mettre en œuvre un analyseur de réseaux non linéaire, de valider les mesures provenant de cet équipement et de développer des outils de mesures et d'analyse dans le domaine temporel afin de mieux appréhender les effets limitatifs des transistors à effet de champ aux fréquences micro-ondes. Dans un premier temps, nous avons montré l'importance de la caractérisation non linéaire hyperfréquence lors de la conception de circuits actifs. Nous avons effectué ensuite une étude bibliographique des principaux systèmes de caractérisation non linéaires existants et qui ont été précurseurs dans ce domaine. Dans le deuxième chapitre, nous avons décrit le principe de fonctionnement de l'analyseur de réseaux vectoriel non linéaire et sa mise en œuvre. Ensuite, afin d'évaluer les perfonnances de cet équipement, nous avons comparé les mesures provenant de ce dernier à celles effectuées par d'autres laboratoires de recherche sur un même composant de référence. Le troisième chapitre décrit le fonctionnement de l'analyseur de réseaux non linéaire à charge active développé au laboratoire. Une étude de l'incertitude de mesure en fonction de la charge sera présentée. Enfin, afin de valider expérimentalement notre banc, nous avons confronté les mesures effectuées avec ce dernier à des résultats de simulations électriques sur un composant de référence. La suite de ce travail a été consacrée à l'étude expérimentale dans le domaine temporel aux fréquences micro-ondes des effets limitatifs de l'ionisation par impact dans les transistors à effet de champ à hétérojonction de la filière GaAs. Nous avons présenté la technique et les résultats expérimentaux des mesures en régime grand signal effectuées avec le LSNA. Un modèle électrique non linéaire permettant de rendre compte des effets de l'ionisation a été décrit et discuté. La dernière partie est consacrée à une étude expérimentale de passivation et de prétraitement de surface effectuée sur des transistors HEMT à hétérostructure Al0.81In0.19/GaN. Nous avons montré l'avantage d'utiliser l'analyseur de réseaux non linéaire à charge active pour regarder l'influence de la passivation et du prétraitement de surface sur les perfonnances en puissance. Ensuite, nous avons discuté sur la localisation des pièges et de leur dynamique. / The goal of this PhD work has been to implement a non linear network analyzer (LSNA), to validate measurements, to develop measurements and analysis tools in time domain in order to understand limiting effects on field effect transistors at microwave frequencies. First, we show the importance of the non linear characterization for the design of active circuits. Second, we de scribe the Large Signal Network Analyzer setup and its implementation. After that, in order to evaluate the performance of this equipment, we have compared measurements provided by equipment and by those coming from other laboratories on the same reference device. ln the next part, we describe the setup of an active load pull large signal network analyzer developed in our laboratory. Then, in order to validate our setup, we compare non linear measurements obtained under in load pull conditions with data coming from simulation performed on a reference device. The following of this work is devoted to an experimental study in time domain, using LSNA, on the lirniting effects of impact ionization inside GaAs HEMT devices. We present sorne experimental results and mainly measurements under large signal conditions in time domain. A non linear electrical model allows us to account for the impact ionization effects on the time domain waveforms. The next part is devoted to a specific study of passivation and surface pretreatrnent carried out on A 10. 81InO.19N/GaN HEMT device. We show the advantages to use the active load pull large signal network analyzer for studying the influence of passivation and surface pretreatrnent on the power performance. To fmish, we discuss on the traps localization and dynamic

Master of Science / Department of Agricultural Economics / Ted C. Schroeder / The livestock industry is susceptible to several diseases, of which Foot and Mouth Disease (FMD) is one. FMD is neither a fatal nor zoonotic animal disease, but most animals less than one year of age are killed in about 80% of cases. FMD also causes reductions in yield and milk production. FMD is recognized as an economic disease because any outbreak will lead to a drastic reduction in the export market. This study is centered on livestock production in mid-western United States. The study incorporated the result from an epidemiology model into an equilibrium displacement model; this is used to determine the economic impact of the FMD outbreak on both consumers and producers. Three vaccination-to-die scenarios were simulated. Each scenario had 200 disease spread simulation runs. The economic impact results were presented with normal distribution curves in order to see how the economic impacts were distributed across the 200 runs in each scenario. Scenario 14 with 50 and 80 herds vaccination capacity at 22 and 40 days respectively, coupled with 50 km vaccination zone has the lowest negative impact on both consumer and producers. The diseases lasted for shorter period of time in scenario 14 than scenarios 2 and 12. Scenario 14 also has least number of animals killed. It can be concluded from the equilibrium displacement outcomes that the best mitigation strategy for the control of FMD is to have a large vaccination zone area, and increment in the vaccination capacity will also curb the disease on time.

Flight and drop tests of the Martin 270 (M270) seaplane were conducted in 1955. Theoretical and empirical pressures were determined by use of Wagner’s theory and also by the Code of Federal Regulations (CFR). The pressure results from the experimental tests on the hull were compared with pressures calculated from Wagner’s theory to determine how well the theory correlated with the measured pressures. The experimental pressure data was also compared with the CFR results to determine how the current industry standard of estimating impact loads compares with actual pressures a seaplane is subjected to. Using the structural design and geometry of the M270 the seaplane hull was modeled in Maestro with a coarse mesh finite element model. The pressures from Wagner’s theory and the CFR were applied to the model of the M270 hull. The structural reactions of the drop test section were compared with the reactions determined from Maestro.

No description available.

The main goal of main thesis is to analyze the impact of specific training course, which is focused on project management for employees of the company XY. I will focus on the analysis of one component of evaluating the effectiveness of training. This component examines whether there is a transfer of knowledge, understanding and taught practices in the common business practice. The work includes a theoretical part, which introduce the theory of corporate training, adult education and project management. In the methodological part is the specification of whole research process, including the research hypotheses. The following section summarizes the concrete results of the research.

Magister Administrationis - MAdmin / HIV and TB are major problems in the South African context and the burden of these diseases is proving detrimental to the development of the country. These diseases have been evident in the country for many years and in recent times the infection rates of TB and HIV has been alarming. The World Health Organization (WHO) classified TB as a problem and the world was to actively implement strategies to combat this epidemic. The issue with TB control strategies is the emergence of HIV which has been the largest contributing factor to the increase in the TB burden in South Africa and many countries like it. South Africa has made great strides in the control of HIV in areas such as mother to child transmission, awareness programs, initiation of ARVs and medical male circumcision which have proven to be successful. In contrast, the TB burden does not share the same fate. The number of deaths caused by TB is continuously rising, as well as the number of new Multi-drug resistant TB cases. Furthermore the emergence of Extreme –drug resistant TB is seen as a sign of a failing health system. Policy makers are now faced with fact that the Directly Observed Therapy Short course (DOTS) program for the prevention of TB is inadequate in an area with a high HIV prevalence, which is what South Africa is faced with. The research objectives are therefore to identify if knowledge from South African TB policies are being disseminated to people who suffer from TB, also to measure if a lack of knowledge may have an impact on treatment success. A policy analysis was done of 5 South African TB policies to identify areas of the policies which are patient specific. The TB policies emphasized a patient-centred approach and the researcher used this concept to motivate that patient-specific areas must be known by the patients. The specific areas identified were: TB specific areas, Treatment specific areas, Adherence specific areas and information/education specific areas. Based on the policy analysis a case study was conducted at Brooklyn Chest Hospital to measure implementation of the policies on the ground. The study found that education was adequate in areas around TB diagnosis, treatment length, signs and symptoms, and family education. The participants lacked knowledge in areas such as TB contacts, monitoring of TB disease, education of TB prior to diagnosis and a high prevalence of non-adherence and multiple cases of TB were found among the participants. Also, the Chi-Square test found no statistical significance between the length of admission to hospital and treatment outcome. The result also shows that of the participants studied, over 30% of the study had not adhered to TB treatment after discharge. The study finds that there are significant shortfalls in the knowledge of participants based on South African TB policies, with a high non-adherence rate before and after discharge. The study shows a lack in the implementation of policy directives on education, following a patient-centred approach, which is evident in the lack of knowledge found in the participants in many facets of the TB disease and the processes to control TB.

The main objective of our essay is to analyze the influence of the spouse on the partner’s retirement decision. Drawing on a large sample of older citizens and a combination of a postal survey and register data, we use standard econometric techniques to identify the impact of the spouse’s characteristics on the partner’s decision to retire. The results of our estimations show that cohabiting/married males’ decision to retire was negatively affected by their partners’ health condition. On the other hand, cohabiting/married women were more likely to retire if their partner had already retired.