Baigiamajame magistro darbe atliekamas sklandytuvo atakos ir slydimo kampo matavimo metodų tyrimas. Pirmoje darbo dalyje apžvelgiami atakos kampo matuokliai: virvutė, pritvirtinta ant stiklinio gaubto, atakos – slydimo kampo matuoklis su vėjarodžiu ir Pitoto vamzdelio tipo daviklis. Davikliai palyginami, aprašomi jų privalumai ir trūkumai lyginant su kitais davikliais. Antroje dalyje aprašomi alfa ir beta kampų matavimo metodai: matavimas vamzdelio tipo davikliu ir metodas, kai nenaudojami specialūs atakos, slydimo kampo davikliai. Toliau apžvelgiami veiksniai, turintys įtakos matavimo tikslumui. Pateikiamos kelių vamzdelio tipo daviklių kalibravimo kreivės. Paskutinėje dalyje programa Matlab kuriamas matematinis-dinaminis sklandytuvo modelis. Modeliu, pagal nustatytas sąlygas, skaičiuojami atakos ir slydimo kampai, analizuojami grafikai. / The thesis made the glider’s attack and slip angle measurement methods for the investigation. The first part gives an overview of measuring devices of angle of attack and slip angle: The side string, attached to the side of the canopy, vane mounted AOA sensor, Pitot-tube type sensor. The sensors are compared, describes their advantages and disadvantages compared with other sensors. The second part describes the alpha and beta angle measurement methods: measurement with the tube-type sensor, and the method without using the specific attack, slip angle sensors. The following gives an overview of factors affecting the measurement accuracy. Several tube-type sensor calibration curves are presented. The last part of thesis presents development of mathematical – dynamic model of the glider using Matlab software. The model calculates the angle of attack and slip using set conditions of flight.

The high-radiation environment in space can lead to anomalies in normal satellite operation. A major cause of concern to spacecraft-designers is the single event upset (SEU). SEUs can result in deviations from expected component behavior and are capable of causing irreversible damage to hardware. In particular, Field Programmable Gate Arrays (FPGAs) are known to be highly susceptible to SEUs. Radiation-hardened versions of such devices are associated with an increase in power consumption and cost in addition to being technologically inferior when compared to contemporary commercial-off-the-shelf (COTS) parts. This thesis consequently aims at exploring the option of using COTS FPGAs in satellite payloads. A framework is developed, allowing the SEU susceptibility of such a device to be studied. SEU testing is carried out in a software-simulated fault environment using a set of Java classes called JBits. A radiation detector module, to measure the radiation backdrop of the device, is also envisioned as part of the final design implementation.

Le phloème est un tissu complexe composé de plusieurs types cellulaires, dont les cellules compagnes et les tubes criblés. Il permet le transport et l'allocation à longue distance de nombreux métabolites et de macromolécules. Il existe dans les tubes criblés des structures très spécifiques dont la fonction est inconnue. Par exemple le rôle des protéines phloémiennes PP2 (Phloem Protein 2) qui ont été de longue date décrite dans les tubes criblés, reste à définir. Les protéines PP2 présentent une activité de lectine et d'interaction avec des protéines de sève phloémienne, suggérant un rôle dans le transport de macromolécules dans le phloème.Nous avons étudié la fonction de deux membres de la famille, PP2-A1 et PP2-A2, chez l'espèce modèle Arabidopsis thaliana. Plusieurs approches ont été mises en œuvre pour étudier ces protéines ; une approche cytologique, la recherche de partenaire protéiques et la création de lignées dérégulées pour l'expression des gènes PP2. L'étude de la localisation de PP2-A1 avec des étiquettes fluorescentes dérivées de la GFP a été réalisée par microscopie confocale, dans les cellules compagnes et dans les tubes criblés ; elle a montré que cette protéine présente une localisation nucléo- cytoplasmique dans les cellules compagnes tandis qu'elle forme des agrégats fixés dans les tubes criblés. Ceci suggère que PP2-A1 est ancrée dans les tubes criblés, à la membrane plasmique ou à certains organites. Des résultats similaires ont été obtenus pour PP2-A2. Sur la base de cette première étude, nous permettant d'identifier in vivo avec précision les cellules compagnes et les tubes criblés, et en utilisant plusieurs marqueurs subcellulaires fluorescents de référence, nous avons réalisé une cartographie subcellulaire fine des cellules compagnes et des tubes criblés in vivo. Cette approche a permis de décrire in vivo l'organisation subcellulaire de ces cellules. Elle a révélé la présence de nombreux organites présents à la périphérie des tubes criblés et de nature énigmatique, suggérant une activité importante dans ces cellules, en accord avec des données récentes de protéome des tubes criblés. L'étude de lignées surexprimant des versions étiquetées de PP2-A1 et PP2-A2 nous a permis de mettre en évidence un phénotype altéré avec des plantes qui présentent un retard de floraison et une biomasse plus importante. Ces observations suggèrent que PP2-A1 et PP2-A2 pourraient avoir un rôle dans la signalisation à longue distance. Ces travaux, qui illustrent la complexité des cellules du phloème, apportent ainsi des éléments nouveaux sur les voies de signalisation à longue distance utilisées par les végétaux pour coordonner leur croissance et leur développement.

Sasol Limited experiences extremely high particulate fouling rates inside shell-and-tube heat exchangers that utilize process cooling water. The water and foulants are obtained from various natural and process sources and have irregular fluid properties. The fouling eventually obstructs flow on the shell side of the heat exchanger to such an extent that the tube bundles have to be replaced every nine months. Sasol requested that certain aspects of this issue be addressed. To better understand the problem, the effects of various tube and baffle configurations on the sedimentation rate in a shell-and-tube heat exchanger were numerically investigated. Single-segmental, double-segmental and disc-and-doughnut baffle configurations, in combination with square and rotated triangular tube configurations, were simulated by using the CFD software package, STAR-CCM+. In total, six configurations were investigated. The solution methodology was divided into two parts. Firstly, steady-state solutions of the six configurations were used to identify the best performing model in terms of large areas with high velocity flow. The results identified both single-segmental baffle configurations to have the best performance. Secondly, transient multiphase simulations were conducted to investigate the sedimentation characteristics of the two single-segmental baffle configurations. It was established that the current state of available technology cannot adequately solve the detailed simulations in a reasonable amount of time and results could only be obtained for a time period of a few seconds. By simulating the flow fields for various geometries in steady-state conditions, many of the observations and findings of literature were verified. The single-segmental baffle configurations have higher pressure drops than double-segmental and disc-and-doughnut configurations. In similar fashion, the rotated triangular tube configuration has a higher pressure drop than the square arrangement. The single-segmental configurations have on average higher flow velocities and reduced cross-flow mass flow fractions. It was concluded from this study that the single-segmental baffle with rotated triangular tube configuration had the best steady-state performance. Some results were extracted from the transient multiphase simulations. The transient multiphase flow simulation of the single-segmental baffle configurations showed larger concentrations of stagnant sediment for the rotated triangular tube configuration versus larger concentrations of suspended/flowing sediment in the square tube configuration. This result was offset by the observation that the downstream movement of sediment was quicker for the rotated triangular tube configuration. No definitive results could be obtained, but from the available results, it can be concluded that the configuration currently implemented at Sasol is best suited to handle sedimentation. This needs to be verified in future studies by using advanced computational resources and experimental results. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

Sasol Limited experiences extremely high particulate fouling rates inside shell-and-tube heat exchangers that utilize process cooling water. The water and foulants are obtained from various natural and process sources and have irregular fluid properties. The fouling eventually obstructs flow on the shell side of the heat exchanger to such an extent that the tube bundles have to be replaced every nine months. Sasol requested that certain aspects of this issue be addressed. To better understand the problem, the effects of various tube and baffle configurations on the sedimentation rate in a shell-and-tube heat exchanger were numerically investigated. Single-segmental, double-segmental and disc-and-doughnut baffle configurations, in combination with square and rotated triangular tube configurations, were simulated by using the CFD software package, STAR-CCM+. In total, six configurations were investigated. The solution methodology was divided into two parts. Firstly, steady-state solutions of the six configurations were used to identify the best performing model in terms of large areas with high velocity flow. The results identified both single-segmental baffle configurations to have the best performance. Secondly, transient multiphase simulations were conducted to investigate the sedimentation characteristics of the two single-segmental baffle configurations. It was established that the current state of available technology cannot adequately solve the detailed simulations in a reasonable amount of time and results could only be obtained for a time period of a few seconds. By simulating the flow fields for various geometries in steady-state conditions, many of the observations and findings of literature were verified. The single-segmental baffle configurations have higher pressure drops than double-segmental and disc-and-doughnut configurations. In similar fashion, the rotated triangular tube configuration has a higher pressure drop than the square arrangement. The single-segmental configurations have on average higher flow velocities and reduced cross-flow mass flow fractions. It was concluded from this study that the single-segmental baffle with rotated triangular tube configuration had the best steady-state performance. Some results were extracted from the transient multiphase simulations. The transient multiphase flow simulation of the single-segmental baffle configurations showed larger concentrations of stagnant sediment for the rotated triangular tube configuration versus larger concentrations of suspended/flowing sediment in the square tube configuration. This result was offset by the observation that the downstream movement of sediment was quicker for the rotated triangular tube configuration. No definitive results could be obtained, but from the available results, it can be concluded that the configuration currently implemented at Sasol is best suited to handle sedimentation. This needs to be verified in future studies by using advanced computational resources and experimental results. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

Cette thèse étudie le transfert de chaleur par rayonnement observé dans les conditions d'écoulement raréfié, en régime hypersonique qui seraient rencontrés au cours d'une mission d'aérocapture dans l'atmosphère de Titan. Des estimations précises du rayonnement hors-équilibre dans des écoulements à grande vitesse tels que ceux autour des corps de re-entrée, sont indispensables pour la conception de systèmes de protection thermique plus efficace. Parce que la masse du système de protection thermique est une fraction importante de la masse totale du véhicule, il ya un grand intérêt dans la conception de systèmes plus légers et plus efficaces. Les expériences en vol sont coûteuses et contraignantes, c'est pourquoi l'essai en laboratoire dans des installations capables de produire des écoulements hypersoniques est nécessaire. Malheureusement, les échelles de longueur généralement impliquées dans les expériences en vol sont trop grandes pour être testées dans des installations expérimentales et donc des modèles réduits de véhicules 'aeroshells' sont généralement testés. Les tubes d'expansion de l'université de Queensland - X1, X2 et X3 - ont été largement utilisés pour la modélisation à l'échelle réduite des écoulements hypersoniques (Morgan 2001). Pour les installations d'essais au sol telle que la soufflerie X2, une mise à l'échelle binaire est utilisée pour tester des modèles à échelle réduite de véhicules de vol, ce qui constitue le paramètre le plus important à respecter afin de reproduire un vol à haute vitesse. La mise à l'échelle binaire, appelé aussi 'mise à l'échelle 'ƒÏL', exige que le produit de la densité et de la longueur caractéristique du véhicule soit conservé entre le vol et les conditions expérimentales. Toutefois, il a été montré par Capra (2007) que le transfert de chaleur par rayonnement ne suit pas cette même loi de mise à l'échelle, et la similitude n'est pas crée pour les cas en vol où le transfert de chaleur par rayonnement et par convection sont fortement couplés. Cela peut entraîner d'importantes erreurs dans les estimations des propriétés d'écoulement associée et l'estimation du transfert de chaleur due au rayonnement. L'installation X2 a été modifiée en 2006 pour permettre l'expérimentation à basse pression en mode tube à choc non-réfléchi. L'utilisation d'un tube à choc non-réfléchi a permis la mesure du transfert de chaleur par rayonnement à la densité réelle en vol et supprimé les problèmes d'échelle liés à la mesure des rayonnements sur les véhicules en modèle réduit, au moins pour une partie de l'écoulement. Des mesures ont été effectuées dans la région immédiatement située derrière le choc et le long de la ligne médiane de l'écoulement de base, où le choc reste plan. Les écoulements externes, tels que ceux entourant une capsule de re-enntrée, n'ont pas été reproduits. La limite de basse pression d'exploitation était d'environ 10 Pa, limitée par la croissance de la couche limite sur les murs

Mitigation of the blast risk associated with terrorist attacks and accidental explosions threatening critical infrastructure has become a topic of great interest in the civil engineering community, both in Canada and abroad. One method of mitigating blast risk is to retrofit vulnerable structures to resist the impulsive effects of blast loading. A comprehensive re-search program has been undertaken to develop fibre reinforced polymer (FRP) retrofit methodologies for structural and non-structural elements, specifically reinforced concrete slabs and walls, subjected to blast loading. The results of this investigation are equally valid for flexure dominant reinforced concrete beams subject to blast effects. The objective of the research program was to generate a large volume of research data for the development of blast-resistant design guidelines for externally bonded FRP retrofit systems. A combined experimental and analytical investigation was performed to achieve the objectives of the program. The experimental program involved the construction and simulated blast testing of a total of thirteen reinforced concrete wall and slab specimens divided into five companion sets. These specimens were subjected to a total of sixty simulated explosions generated at the University of Ottawa Shock Tube Testing Facility. Companion sets were designed to study one- and two-way bending, as well as the performance of specimens with simply-supported and fully-fixed boundary conditions. The majority of the specimens were retrofitted with externally bonded carbon fibre reinforced polymer (CFRP) sheets to improve overall load-deformation characteristics. Specimens within each companion set were subjected to progressively increasing pressure-impulse combinations to study component behaviour from elastic response up to inelastic component failure. The blast performance of companion as-built and retrofitted specimens was quantified in terms of measured load-deformation characteristics, and observed member behaviour throughout all stages of response. The results show that externally bonded FRP retrofits are an effective retrofit technique to improve the blast resistance of reinforced concrete structures, provided that debonding of the composite from the concrete substrate is prevented. The test results also indicate that FRP retrofitted reinforced concrete structures may survive initial inbound displacements, only to failure by moment reversals during the negative displacement phase. The experimental test data was used to verify analytical techniques to model the behaviour of reinforced concrete walls and slabs subjected to blast loading. The force-deformation characteristics of one-way wall strips were established using inelastic sectional and member analyses. The force-deformation characteristics of two-way slab plates were established using commonly accepted design approximations. The response of all specimens was computed by explicit solution of the single degree of freedom dynamic equation of motion. An equivalent static force procedure was used to analyze the response of CFRP retrofitted specimens which remained elastic after testing. The predicted maximum displacements and time-to-maximum displacements were compared against experimental results. The analysis indicates that the modelling procedures accurately describe the response characteristics of both retrofitted and unretrofitted specimens observed during the experiment.

Background: Ventilator associated pneumonia (VAP) is a major cause of morbidity, longer intensive care unit (ICU) stay, increased duration of mechanical ventilation, and increased healthcare cost in critically ill patients. Critically ill patients are at increased risk for malnutrition, which is associated with impaired immune function, impaired ventilator drive and weakened respiratory muscles. Malnutrition has been thought to increase the risk of VAP due to bacterial translocation from the gastrointestinal tract to the lungs. Previous research that has evaluated the effect of enteral nutrition on malnutrition associated with VAP has been inconsistent in part because of the subjectivity of the old definition of VAP. In 2013, the Center for Disease Control and Prevention (CDC) developed a new definition for the diagnosis of VAP, which includes three tiers of a ventilator associated event (VAE); ventilator associated condition, infection-related ventilator-associated complication, or possible or probable VAP). The purpose of this study is to retrospectively examine the relationship between enteral formula, tube-feeding placement site, time of tube feeding initiation and the incidence of VAE using this new CDC definition. Objective: The aim of the study was to retrospectively examine the relationship between enteral formula, tube-feeding placement site, time of tube feeding initiation and the incidence of VAE using this new CDC definition. Participants/setting: The medical records of 162 adult patients admitted to one of the ICUs (Medical ICU, Surgical ICU, Neurological ICU, Burn ICU) at Grady Memorial Hospital (GMH) in Atlanta, GA in 2013 Main outcome measures: Demographic and baseline medical characteristics including the type of enteral formula used (standard, immune-modulating, hydrolyzed, immune-modulating and hydrolyzed, or mixed), enteral tube feeding placement (gastric or small bowel), and timing of enteral nutrition (never fed, fed48 hours after admission) were collected. Statistical analysis: Demographic and baseline medical characteristics were described using frequency statistics and compared by VAE status using the Mann-Whitney U and Kruskal-Wallis tests. The relationship between tube placement, enteral formula, timing of feeding and the diagnosis of a VAE was evaluated using the Chi-square test. Results: In 2013, 81 patients admitted to the ICU at GMH were diagnosed with a VAE. The median age of the study population (n=162) was 50 years (range, 19 to 88 years) and the median BMI was 27.6 kg/m2 (range, 13.2 to 83.2 kg/m2). The majority of the population was African American (53.1%) and male (64.2%). Most patients were fed through a gastric tube (86.4%), were given an immune-modulating enteral formula (32.1%) and were fed after 48 hours of admission (44.4%). After subdividing by ICU location, 12 of 14 patients (86%) in the Medical ICU who were diagnosed with a VAE were either never fed or fed >48 hours after admission vs. 7 of 13 (54%) of patients in the Medical ICU who were not diagnosed with a VAE (p=0.031). No other relationships between the type of feeding initiation, tube placement, and enteral formula were found by VAE status for the population or by ICU location. Conclusion: Adults admitted to the Medical ICU may have a reduced risk of developing a VAE if fed within 48 hours of admission. The type of enteral formula provided and the route of administration was not associated with the diagnosis of VAE. Future prospective studies should include all critical care patients to further evaluate the effect of nutrition on VAE outcome.

The phenomenon dropwise condensation on a horizontal gold coated tube is investigated by both analytical and experimental methods in this study. A computer program is prepared to calculate the dropwise condensation heat transfer rate on the horizontal gold coated tube. An experimental setup was also manufactured to measure the dropwise condensation heat transfer rate. The effects of flow rate, temperature of cooling water and also steam to wall temperature difference have been analytically investigated by using Mathcad computer program. Experiments were carried out at different inlet temperatures of cooling water. Effects of cooling water at different flow rates are also experimentally investigated. Results of the experiments are compared to those of the literature and the analytical results.

Producing axi-symmetrical parts with holes from tubular stock by tube upsetting is a frequently used technique in industry. There are basically four types of tube upsetting process / external, internal, simultaneous internal and external upsetting, and expanding of tube. In general, tubular parts require more than one upsetting stage. In industry, generally trial-error methods, which require lots of time and effort depending on experience, are used for the design of stages. Wrong design causes failures during production. On the other hand, the problems, which are likely to be encountered in manufacturing, can be observed and solved in the design stage by using finite element analysis. In this study, the finite element analyses of external, internal, simultaneous internal and external tube upsetting, and tube expanding processes have been realized. During the analyses, the part and the die geometries at the intermediate stages, which have been designed according to the proposed procedures, have been used. The stress and strain distributions and die filling actions have been observed during the process. The process design and die geometries have been evaluated according to the finite element results. It has been seen that the recommended procedures generally generate acceptable designs. In some cases, it has been noted that minor modifications may be required on the design.