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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
441

Tvorba mikroklimatu průmyslové haly s vysokými nároky na jeho rovnoměrnost / Creating a microclimate of an industrial building with high demands on its uniformity

Tůmová, Eliška January 2015 (has links)
This diploma thesis deals with the optimization of microclimate of an industrial building. There is required constant temperature with minimal fluctuations during manufacturing process in the building. Due to insufficient cooling power of air-conditioning system was objective to design a solution that ensures stability of internal temperature during production especially in summer and simultaneously should be the solution economically acceptable. Simulation shows original state defined problems. Some new or unusual materials for solar shading are reviewed in the thesis by the experimental measurements and by the comparative method. To each material is assigned shading coefficient according to Czech standards, thereby is achieved universality for calculations of heat gains resulting from solar radiation. By one part of the experiments and their evaluation is determined thickness of the standard single glass glazing. It is also determined proportional transmittance of solar radiation for certain multiwall polycarbonates, which are currently used as fillers of industrial skylights and production hall‘s window openings. From experiments resulting design is subjected to the simulation. Comparison of temperatures is shown for the time before the installation of designed solar shading and after the installation of the solar shading.
442

Syntéza obvodových prvků s fraktální dynamikou / Synthesis of circuit element with fractal dynamics

Domanský, Ondřej January 2016 (has links)
The first aim of this diploma thesis is to clarify problems with circuit elements described by the fractional-order dynamics, show their basic properties and possible applications in circuits with lumped parameters. The second topic is covering the synthesis of two-terminal devices which have different fractional-orders for requested phase shifts. For this kind of devices, the thesis also describes their optimization and approximation in the frequency domain and subsequent implementation in the form of passive ladder structures. The final part of diploma work will be focused on practical realization of universal fractional PID controller and the verification of proper function of this multi-port in various configurations to prove its correct function via real measurement of frequency and time responses.
443

Modeling and control of a SEM-integrated nano-robotic system driven by piezoelectric stick-slip actuators / Modélisation et commande d'un système nano-robotique dédié à des applications sous MEB et actionné par des actionneurs piézoélectriques stick-slip

Oubellil, Raouia 12 December 2016 (has links)
La capacité de réaliser des tâches robotiques dextres à l'échelle nanométrique dans un microscope électronique à balayage (MEB) est un enjeu crucial pour les nanotechnologies. Les systèmes nano-robotiques dédiés à des applications sous MEB ont ainsi émergé dans de nombreux laboratoires de robotique. Ils peuvent être composés d'un ou de plusieurs actionneurs intégrés à des plateformes nano-robotiques avec un ou plusieurs effecteurs. L’actionneur Piézoélectrique Stick-Slip (PSS) est l'un des meilleurs candidats pour actionner les systèmes nano-robotiques dédiés à des applications sous MEB car il est capable d'effectuer un positionnement grossier avec une plage de déplacement millimétrique et un positionnement précis avec une plage de déplacement de quelques micromètres. La modélisation des actionneurs PSS est complexe notamment en raison de leur mode de fonctionnement hybride. La commande est également difficile à cause de plusieurs caractéristiques liées aux actionneurs PSS, soient le frottement, l’hystérésis et les vibrations non-amorties, qui dégradent leur performances en termes de précision et de vitesse. Ce travail porte sur la modélisation et la commande d'un système nano-robotique à 3 axes dédié à des applications sous MEB et actionné par des actionneurs piézoélectriques de type stick-slip. Chaque élément et caractéristique des actionneurs PSS ont été analysés et modélisés afin d’établir par la suite un modèle dynamique complet capable de décrire les deux modes de fonctionnement, à savoir le mode balayage et pas à pas. Pour chacun de ces deux modes, des lois de commande ont ainsi été développées pour les actionneurs PSS. Des stratégies de commande robuste ont été synthétisées pour des objectifs de positionnement rapide et à haute résolution en mode balayage. De telles performances sont fondamentales dans plusieurs tâches micro-/nano-robotique tels que le nano-assemblage rapide et précis et la nano-caractérisation des matériaux. Une commande proportionnelle en fréquence et en amplitude est synthétisée pour effectuer un déplacement millimétrique en mode pas à pas. Ceci est motivé par les applications robotiques pour lesquelles une large plage de déplacement est requise, tels que le scan de grandes surfaces et les phases d’approche d’une sonde d’un échantillon à manipuler. Une stratégie de commutation qui combine les modes balayage et pas à pas, est alors proposée pour remédier au manque de précision en mode pas à pas, lors de passage d’un grand à un petit déplacement. Ce travail a donné lieu à des résultats qui ouvrent de nouvelles perspectives pour l'utilisation des actionneurs PSS dans les systèmes nano-robotiques dédiés à des applications sous MEB. / The capability of doing dexterous robotic tasks at the nanometer scale inside a Scanning Electron Microscope (SEM) is a critical issue for nanotechnologies. SEM-integrated nano-robotic systems have consequently emerged in many robotics laboratories. They can be composed of one or more actuators assembled into nano-robotic platforms with one or several effectors. Piezoelectric Stick-Slip (PSS) actuators is one of the best candidate to actuate SEM-integrated nano-robotic systems because it is able to perform coarse positioning with millimeter displacement range and fine positioning with travel range of few micrometers. Modeling of PSS actuators is complex and difficult mainly because of their hybrid operating mode. Furthermore, control is challenging due to several characteristics related to PSS actuators, namely friction, hysteresis and undamped vibrations, which degrade their performance in terms of precision and speed. This work deals with modeling and control of a 3-axes SEM integrated nano-robotic system driven by piezoelectric stick-slip actuators. Each element and characteristic of PSS actuators are analyzed and modeled to thereafter establish a complete dynamic model able to describe the two functioning modes, namely the scanning and the stepping modes. PSS actuators are then controlled in each of these modes. Robust control strategies are developed to achieve high-resolution and fast positioning in scanning mode. Such performance is fundamental in several micro/nano-robotic tasks such as fast and accurate nano-assembly and nano-material characterization. A frequency/amplitude proportional controller is designed to perform millimeter displacement in stepping mode. This is motivated by robotic tasks where large motion is required, such as large surfaces scan and bringing a probe close to a sample to manipulate. A switched strategy, which combines scanning and stepping motion modes, is then proposed to remedy to the lack of precision in stepping motion, when passing from a large to a small displacement. This work has given rise to results which open new perspectives to the use of PSS actuators in SEM integrated nano-robotic systems.
444

Analyses multi-échelles du comportement et la durée de vie d’aciers inoxydables 304L sous sollicitations cycliques avec pré-écrouissage / Multi-scale analysis of behavior and fatigue life of 304L stainless under cyclic loading with pre-hardening

Belattar, Adel 11 February 2013 (has links)
Le travail s’intéresse aux effets d’un pré-écrouissage cyclique axial ou en torsion sur le comportement cyclique et la durée de vie en fatigue sous sollicitation axiale à température ambiante d’un acier inoxydable austénitique 304L. Les essais cycliques séquentiels à amplitude de déformation croissante ou décroissante montrent que la courbe cyclique du 304L est non-unique. Cette caractéristique est liée à la persistance de l’état microstructural généré pendant les cycles d’amplitude de déformation maximale de la première séquence. En augmentant le nombre des séquences, l’acier 304L montre une tendance vers une courbe cyclique asymptotique, l’écrouissage semble se stabiliser. Des essais de fatigue sous chargement axial ont été réalisés sur des éprouvettes vierges ou pré-écrouies en traction-compression ou en torsion. Les durées de vie ont été sensiblement réduites pour les éprouvettes pré-écrouies. Ce phénomène est lié à la formation de structures de dislocations denses héritées de la phase de pré-écrouissage. Cependant, l’augmentation de l’amplitude de déformation en fatigue réduit l’effet du pré-écrouissage. / This study investigates the effects of loading history on the cyclic stress-strain curve and fatigue behavior of 304L stainless steel at room temperature. Tension-compression tests were performed ont the same specimen under controlled strain, using several loading sequences of increasing or decreasing amplitude. The results showed that fatigue life is significantly reduced by the previous loading history. A previously developed method for determining the effect of prehardening was evaluated. Microstructural analyses were also performed; the microstructures after preloading and their evolution during the fatigue cycles were characterized by TEM. The results of these analyses improve our understanding of the macroscopic properties of 304L stainless steel and can help us identify the causes of failure and lifetime reduction.
445

Essais cliniques de recherche de dose en oncologie : d'un schéma d'essai permettant l'inclusion continue à l’utilisation des données longitudinales de toxicité / Dose-finding clinical trials in oncology : from continuous enrolment, to the integration of repeated toxicity measurements

Doussau de Bazignan, Adélaïde 31 March 2014 (has links)
L’objectif des essais de phase I en oncologie est d’identifier la dose maximale tolérée (DMT). Le schéma « 3+3 » nécessite d’interrompre les inclusions en attendant l’évaluation d’une cohorte de trois patients pour définir la dose à attribuer aux patients suivants. Les investigateurs d’oncologie pédiatrique ont proposé l’adaptation Rolling 6 pour éviter cette suspension temporaire des inclusions. Dans une étude de simulation, nous avons montré qu’un schéma adaptatif avec attribution des doses basées sur un modèle statistique permettait de pallier ce problème, et identifiait plus fréquemment la DMT. Néanmoins ces trois schémas restent limités pour identifier la DMT, notamment du fait que le critère de jugement est un critère binaire, la survenue de toxicité dose-limitante sur un cycle de traitement. Nous avons proposé un nouveau schéma adaptatif utilisant les données ordinales répétées de toxicité sur l’ensemble des cycles de traitement. La dose à identifier est celle associée au taux de toxicité grave maximal par cycle que l’on juge tolérable. Le grade maximal de toxicité par cycle de traitement, en 3 catégories (grave / modéré / nul), a été modélisé par le modèle mixte à cotes proportionnelles. Le modèle est performant à la fois pour détecter un effet cumulé dans le temps et améliore l’identification de la dose cible, sans risque majoré de toxicité, et sans rallonger la durée des essais. Nous avons aussi étudié l’intérêt de ce modèle ordinal par rapport à un modèle logistique mixte plus parcimonieux. Ces modèles pour données longitudinales devraient être plus souvent utilisés pour l’analyse des essais de phase I étant donné leur pertinence et la faisabilité de leur implémentation. / Phase I dose-finding trials aim at identifying the maximum tolerated dose (MTD). The “3+3” design requires an interruption of enrolment while the evaluation of the previous three patients is pending. In pediatric oncology, investigators proposed the Rolling 6 design to allow for a more continuous enrollment. In a simulation study, we showed that an adaptive dose-finding design, with dose allocation guided by a statistical model not only minimizes accrual suspension as with the rolling 6, and but also led to identify more frequently the MTD. However, the performance of these designs in terms of correct identification of the MTD is limited by the binomial variability of the main outcome: the occurrence of dose-limiting toxicity over the first cycle of treatment. We have then proposed a new adaptive design using repeated ordinal data of toxicities experienced during all the cycles of treatment. We aim at identifying the dose associated with a specified tolerable probability of severe toxicity per cycle. The outcome was expressed as the worst toxicity experienced, in three categories (severe / moderate / no toxicity), repeated at each treatment cycle. It was modeled through a proportional odds mixed model. This model enables to seek for cumulated toxicity with time, and to increase the ability to identify the targeted dose, with no increased risk of toxicity, and without delaying study completion. We also compared this ordinal model to a more parsimonious logistic mixed model.Because of their applicability and efficiency, those models for longitudinal data should be more often used in phase I dose-finding trials.
446

Gender and Mortality after Radical Cystectomy: Competing Risk Analysis

Heberling, Ulrike, Koch, Rainer, Hübler, Matthias, Baretton, Gustavo B., Hakenberg, Oliver W., Froehner, Michael, Wirth, Manfred P. 26 May 2020 (has links)
Background: Data on the impact of gender on mortality after radical cystectomy is conflicting. We investigated a large single center sample with long-term follow-up in order to determine the relationship between gender and outcome. Patients and Methods: A total of 1,184 consecutive patients who underwent radical cystectomy for high risk superficial or muscle-invasive urothelial or undifferentiated bladder cancer between 1993 and 2015 were stratified by gender. Demographic data was compared using Mann-Whitney U test, chi-square test, or Fisher exact test. Cox proportional hazard models were used for the analysis of competing risks and logit models were used for the prediction of the receipt of adjuvant cisplatin-based chemotherapy. Results: Female patients were older, healthier, less frequently current smokers and had more extravesical tumors. In the multivariate analyses, female gender was an independent predictor of (lower) non-bladder cancer (competing) mortality (hazards ratio [HR] 0.68, 95% CI 0.49–0.95, p = 0.0248) but no predictor of bladder cancer-specific mortality (HR in the full model 1.20, 95% CI 0.94–1.54, p = 0.15). Gender was no predictor of the receipt of adjuvant cisplatin-based chemotherapy. Conclusions: Female gender was associated with an increased risk of extravesical disease but was no independent predictor of bladder cancer-specific mortality. Anatomical differences might be a plausible explanation for these observations.
447

Bostad till salu : En analys av tid-till-försäljning på Uppsalas bostadsmarknad

Eriksson, Fabian, Ajdert, Alexander January 2022 (has links)
Denna uppsats har undersökt tid-till-försäljning på Uppsala kommuns bostadsmarknad för lägenheter under året 2021. För att analysera tid-till-försäljning har metoder från överlevnadsanalys använts. Överlevnadsfunktionen och den kumulativa hasardfunktionen har skattats med Kaplan-Meier-skattningen och Nelson-Aalen-skattningen. Därutöver har tre modeller skattats; en Cox proportionell hasardmodell och två 'Accelerated Failure Time'-modeller varav en var en Weibullmodell och en var en Loglogistiskmodell. Resultaten indikerar att tid-till-försäljning har en hög hasard efter två veckor på marknaden varefter en avtagande hasard. Resultaten indikerar att kovariat har en statistisk signifikant effekt på tid-till-försäljning. Grafiska tester indikerar att antagandet om proportionalitet för Cox proportionella hasardmodell och antagandet om den underliggande hasardfunktionen för Weibullmodellen är orimliga. Antagandet om den underliggande hasardfunktionen för loglogistiskamodellen verkar rimlig. Goodness-of-fit indikerar att Weibullmodellen och loglogistiskamodellen var mer välanpassade till datamaterialet än Cox proportionella hasardmodell. / This bachelor's thesis has investigated time-to-sale on the Uppsala municipality property market for apartments during 2021. Analysis has been performed utilising methods from survival analysis. Both the survival function and cumulative hazard function were estimated using the Kaplan-Meier estimate and the Nelson-Aalen estimate respectively. Furthermore, three models were estimated; a Cox Proportional Hazards model as well as two Accelerated Failure Time models of which one was a Weibullmodell and the other was a loglogistic model. The results indicate that time-to-sale has a high hazard after two weeks on the market followed by a decreasing hazard. The results also indicate that covariates have a statistically significant effect on time-to-sale. Graphical tests indicate that the assumption of proportionality for the Cox Proportional Hazards model and the assumption of the underlying hazard function for the Weibullmodell are unreasonable. The assumed hazardfunction of the loglogistic model was found to be reasonable. Goodness of fit indicates that the Weibull model and loglogistic model were a better fit to the data than the Cox proportional Hazardsmodel.
448

Multi-input multi-output proportional integral derivative controller tuning based on improved particle swarm optimization

Nkwanyana, Thamsanqa Bongani 07 1900 (has links)
The PID controller is regarded as a dependable and reliable controller for process industry systems. Many researchers have devoted time and attention to PID controller tuning and they all agree that PID controllers are very important for control systems. A PID equation is very sensitive; its parameters must always be varied following the specific application to increase performance, such as by increasing the system’s responsiveness. PID controllers still have many problems despite their importance for control systems in industries. The problem of big overshoot on the conventional gain tuning is one of the serious problems. Researchers use the PSO algorithm to try and overcome those problems. The tuning of the MIMO PID controller based on the PSO algorithm shows many disadvantages such as high-quality control with a short settle time, steady-state error, and periodical step response. The traditional PSO algorithm is very sensitive and it sometimes affects the quality of good PID controller tuning. This research has proposed a new equation for improving the PSO algorithm. The proposed algorithm is the combination of linearly decreasing inertia weight and chaotic inertia weight, after which a control factor was introduced as an exponential factor. This was very useful for simulations as it is adjustable. The Matlab simulation results of the experiments show that the simulations as it is adjustable. The Matlab simulation results of the experiments show that the new proposed equation converges faster and it gives the best fitness compared to linear inertia weight and oscillating inertia weight and other old equations. The MIMO PID controller system that consists of four plants was tuned based on the new proposed equation for the PSO algorithm (LCPSO). The optimized results show the best rise time, settling time, time delays, and steady-state compared to the systems that are tuned using the old equations. The exploration was directed at considering the impact of using the PSO calculation as an instrument for MIMO PID tuning. The results obtained in the examination reveal that the PSO tuning output improved reactions and can be applied to various system models in the measure control industry. The results for the MIMO PID controller tuned using PSO were assessed using integral square error (ISE), integral absolute error (IAE), and the integral of time expanded by absolute error (ITAE). The five well-known benchmark functions were also used to endorse the feasibility of the improved PSO and excellent results in terms of convergence and best fitness were attained. / Electrical and Mining Engineering / M. Tech. (Electrical Engineering)
449

Multiaxial Fatigue Analysis under Complex Non-proportional Loading Conditions

Sharifimehr, Shahriar January 2018 (has links)
No description available.
450

Targeting the Minority: A New Theory of Diversionary Violence

Arnold, Nathaniel M. 03 June 2020 (has links)
No description available.

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