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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.
11

Návrh metod na hodnocení kapacit letištních subsystémů / Design of assessment methods for airport subsystem capacity

Londa, Jaroslav January 2013 (has links)
This thesis discusses the capacity of airport subsystems and describes various assessment methods of capacity including factors that affect it. The first part contains theoretical analysis of assessment methods for airport subsystems especially runway and terminal. The practical part deals with experimentation using the simulation software Visual Simmod. The objective of these experiments is to evaluate the effect of certain factors to runway operations and observe the change of aircraft delay over the capacity. In the end all simulation results are analyzed and shown in graphs.
12

Validation of the physical effect implementation in a simulation model for the cylinder block/valve plate contact supported by experimental investigations

Wegner, Stephan, Löschner, Fabian, Gels, Stefan, Murrenhoff, Hubertus January 2016 (has links)
Overall losses in swash plate type axial piston machines are mainly defined by three tribological interfaces. These are swash plate/slipper, piston/cylinder and cylinder block/valve plate. Within a research project, funded by the German Research Foundation, a combined approach of experimental research and simulation is chosen to acquire further knowledge on the cylinder block/valve plate contact. The experimental investigations focus on the friction torque within the contact and the measurement of the cylinder block movement in all six degrees of freedom. Simultaneously a simulation model is created focusing on the main physical effects. By considering the results of the experimental investigations significant physical effects for the simulation model are assessed. Within this paper a first comparison between experimental results and the simulation is presented, showing that for a qualitative match the implemented effects (mainly the fluid film, solid body movement, solid body contact, surface deformation) are sufficient to model the general behaviour of theinvestigated pump.
13

Identifikace tekutin rychlostního typu vhodných k modelování geomateriálů / Identification of rate type fluids suitable for modeling geomaterials

Tůma, Karel January 2014 (has links)
In the present thesis we study and compare different viscoelastic rate-type fluid models capable of describing response of geomaterials such as asphalt. Using new thermodynamic approach proposed by Rajagopal and Srinivasa (2000) we derive several classes of non-linear viscoelastic models that generalize standard Oldroyd-B and Burgers models. We show that the new models achieve better results in fitting experimental data with asphalt than the previously considered models (Oldroyd-B, Burgers, Rajagopal and Srinivasa (2000)). In particular they are able to capture the behavior of asphalt observed recently in experiments (torque overshoot and two relaxation mechanisms), which is not possible to describe by the other models. Using both the standard and the newly derived models we compute full simulations of viscoelastic flow with the finite element method in fixed domains and incorporating the Arbitrary Lagrangian-Eulerian description also in deforming domains. For example, we study rolling of asphalt or creation of ruts in the road with the real material parameters obtained by fitting the experiments. Powered by TCPDF (www.tcpdf.org)
14

Синтез системы показателей целевой архитектуры управления данными для сетевого формата организации электронных продаж : магистерская диссертация / Synthesis of the system of indicators of the target architecture of data management for the network format of the organization of electronic sales

Воронов, Д. Е., Voronov, D. E. January 2022 (has links)
Данная работа посвящена прогнозированию эффекта от внедрения цифрового сервиса в деятельность компании «М.Видео». Актуальность темы обусловлена неэффективностью форм организации бизнес-процессов в сервисном центре компании «М.Видео». Разработанная в среде имитационного моделирования Powersim модель позволяет спрогнозировать и обосновать эффективность внедрения дополнительного функционала в приложение для обслуживания клиентов на основе анализа изменения количества клиентов. / This work is devoted to predicting the effect of introducing a digital service into the activities of the M.Video company. The relevance of the topic is due to the inefficiency of the forms of organization of business processes in the service center of the M.Video company. The model developed in the Powersim simulation environment allows predicting and justifying the effectiveness of introducing additional functionality into a customer service application based on an analysis of changes in the number of customers.
15

Etude multi-échelle de la convection océanique profonde en mer Méditerranée : de l'observation à la modélisation climatique / Multi-sale study of ocean deep convection in the Mediterranean sea : from observations to climate modelling

Waldman, Robin 16 December 2016 (has links)
La Méditerranée Nord-Occidentale, ou bassin Liguro-Provençal, est l'un des rares sièges de la convection océanique profonde. Ce phénomène localisé et intermittent est l'un des principaux modes d'interaction de l'océan profond avec le système climatique. Il est d'une importance primordiale pour la redistribution verticale de chaleur, de dioxyde de carbone et d'éléments biogéochimiques par l'océan, et donc pour le climat et la biologie marine. Le travail de thèse s'inscrit dans le cadre du programme HyMeX, il vise à caractériser le phénomène de convection dans le bassin Liguro-Provençal à partir du cas d'étude de l'année 2012-2013 et à comprendre le rôle de la dynamique de méso-échelle et de la variabilité intrinsèque océanique qui en résulte sur la convection. Le travail de thèse a tout d'abord porté sur la caractérisation du phénomène de convection océanique profonde à partir des observations du cas d'étude 2012-2013. On a estimé le taux de convection hivernale et de restratification printanière et une Expérience de Simulation d'un Système d'Observations (OSSE) a été développée pour estimer l'erreur d'observation associée. On conclut à la validité des observations du réseau MOOSE pour estimer les taux de convection et de restratification sur la période 2012-2013. On caractérise la période comme exceptionnellement convective avec un taux de convection hivernal de 2.3±0.5Sv (1Sv=106m³/s) et on estime pour la première fois un taux de restratification printanière de 0.8±0.4Sv. Deux approches numériques novatrices ont été développées au cours de la thèse pour caractériser le rôle de la méso-échelle et de la variabilité intrinsèque océanique sur le phénomène de convection. On a implémenté l'outil de raffinement de maille AGRIF en Méditerranée Nord-Occidentale dans le modèle régional NEMOMED12 pour documenter l'impact de la méso-échelle sur la convection océanique profonde et sur la circulation thermohaline Méditerranéenne. On a de plus réalisé des simulations d'ensemble à état initial perturbé pour documenter l'impact de la variabilité intrinsèque océanique sur la convection. Après avoir extensivement évalué le réalisme de la convection dans le modèle numérique NEMOMED12 grâce aux données de 2012-2013, on étudie avec ce modèle l'impact de la variabilité intrinsèque océanique sur ce phénomène. Sur le cas d'étude comme sur la période historique 1979-2013, la variabilité intrinsèque océanique module largement la géographie du patch convectif, en particulier dans le domaine hauturier. Aux échelles climatiques, la variabilité intrinsèque module largement la variabilité interannuelle du taux de convection. En moyenne climatologique, elle module aussi la géographie de la convection, mais elle impacte marginalement son intensité et les propriétés climatiques des eaux profondes. Enfin, on étudie avec l'outil AGRIF l'impact de la dynamique de méso-échelle sur la convection profonde et sur la circulation thermohaline. Sur le cas d'étude de 2012-2013, la méso-échelle augmente le réalisme de la convection. On montre qu'elle augmente la variabilité intrinsèque de la convection. Sur cette période comme sur la période historique, elle diminue l'intensité moyenne de la convection et réduit les transformations des eaux profondes. On relie principalement son impact sur la convection à une modification de la circulation stationnaire marquée par un repositionnement et une intensification des courants de bord, et la présence d'un méandre stationnaire du Front Baléare. Par ailleurs, sur la période historique, les échanges avec le bassin Algérien sont intensifiés par la méso-échelle, ce qui modifie les propriétés climatiques des masses d'eau. On montre enfin que la signature de la méso-échelle en surface est susceptible d'impacter les échanges air-mer et donc le climat côtier voire régional Méditerranéen. / The northwestern Mediterranean sea, also named the Liguro-Provençal basin, is one of the few places where ocean deep convection occurs. This localized and intermittent phenomenon is one of the main modes of interaction between the deep ocean and the climate system. It is of paramount importance for the vertical redistribution of heat, carbon dioxyde and biogeochemical elements, and therefore for climate and marine biology. The PhD has been carried out in the framework of HyMeX programme, it aims at characterizing the ocean deep convection phenomenon in the Liguro-Provençal basin from the year 2012-2013 case study and at understanding the role of mesoscale dynamics and of the resulting intrinsic ocean variability on deep convection. The PhD work has first focused on characterizing the ocean deep convection phenomenon from observations collected during the 2012-2013 case study. We estimated the winter deep convection and spring restratification rates and an Observing System Simulation Experiment (OSSE) was developed to estimate the associated observation error. We conclude on the validity of MOOSE network observations to estimate the deep convection and restratification rates in the period 2012-2013. We characterize the period as exceptionally convective with a winter deep water formation rate of 2.3±0.5Sv (1Sv=106m³/s) and we estimate for the first time a spring deep water restratification rate of 0.8±0.4Sv. Two novel numerical approaches were developped during the PhD to characterize the roles of mesoscale dynamics and of intrinsic variability in the deep convection phenomenon. We implemented AGRIF grid refinement tool in the northwestern Mediterranean Sea within NEMOMED12 regional model to document the impact of mesoscale on deep convection and on the Mediterranean thermohaline circulation. In addition, we carried out perturbed initial state ensemble simulations to characterize the impact of ocean intrinsic variability on convection. After extensively evaluating the realism of deep convection in NEMOMED12 numerical model thanks to the 2012-2013 observations, we study with this model the impact of intrinsic variability on deep convection. During the case study as well as in the 1979-2013 historical period, intrinsic ocean variability largely modulates the mixed patch geography, particularly in the open-sea domain. At climatic timescales, intrinsic variability modulates largely the deep convection rate interannual variability. On average over the historical period, it also modulates the mixed patch geography, but it impacts marginally its magnitude and the properties of the deep water formed. Finally, we study with AGRIF tool the impact of mesoscale dynamics on deep convection and on the thermohaline circulation. In the 2012-2013 case study, mesoscale improves the realism of the simulated convection. We show that it increases the deep convection intrinsic variability. In this period as well as during the 1979-2013 historical period, it decreases the mean deep convection rate and it reduces deep water transformations. We mainly relate its impact on convection to the modifincation of the stationary circulation characterized by a relocation and an intensification of boundary currents and the presence of a stationary Balearic Front meander. Also, in the historical period, exchanges with the Algerian basin are increased, which modifies water mass climatological properties. Finally, the surface signature of mesoscale is likely to alter air-sea interactions and the coastal to regional Mediterranean climate.
16

Radiale Diffusoren in Warmwasserspeichern: Einfluss des Beladesystems auf Strömungsverhalten und Schichtungsqualität

Findeisen, Fabian 19 April 2018 (has links)
Radiale Diffusoren beeinflussen signifikant die Qualität der thermischen Schichtung in Warmwasserspeichern. Um die Effizienz der Energiespeicherung zu verbessern, ist das Verständnis des komplexen Strömungsverhaltens notwendig. Diese Arbeit liefert Grundlagen zur Beschreibung der auftretenden Effekte und stellt ein geeignetes CFD-Simulationsmodell vor. Als Untersuchungsobjekt dient eine neuartige Speicherkonstruktion, wobei der Radialdiffusor direkt an einer schwimmenden Decke montiert ist. Vorteile dieser Anordnung werden aufgezeigt, die auftretenden Strömungseffekte beschrieben sowie der Einfluss verschiedener Beladergeometrien auf die thermische Schichtung untersucht. Für das Entladen bis 98 °C bei Atmosphärendruck wurde ein strömungsoptimierter Freiformdiffusor entwickelt, um Kavitation beim Ansaugen zu vermeiden. Die Untersuchungen zeigen außerdem, dass bei der Beladung über dem Umfang des Radialdiffusors ein stark asymmetrisches und einseitig gerichtetes Ausströmen auftreten kann. Gegenmaßnahmen in Form von Leit- und Lochblechen stellen ein nahezu symmetrisches Ausströmen wieder her und verbessern damit die Schichtungsqualität. Neben umfangreichen numerischen Studien mit RANS und LES fanden zahlreiche Experimente im Labor und an einem 100 m³-Speicher statt. / Radial diffusers have a significant influence on the quality of thermal stratification in hot water storage tanks. In order to improve the efficiency of energy storage, it is necessary to understand the complex flow behaviour. This thesis provides a basis for describing the effects and introduces a CFD simulation model. An innovative storage tank construction is used as the object of investigation, whereby the radial diffuser is mounted directly to a floating ceiling. Advantages of this arrangement are shown, flow effects are described and the influence of different loader geometries on the thermal stratification is investigated. For discharging up to 98 °C at atmospheric pressure, a flow-optimized free-form diffuser was developed to avoid cavitation inside the loading device. The tests also show that a highly asymmetrical and unidirectional flow over the circumference of the radial diffuser can occur during loading. Thanks to countermeasures like baffles and perforated plates, an almost symmetrical outflow can be restored and the stratification quality improved. In addition to numerical studies with RANS and LES, numerous experiments in the laboratory and at a 100m3 store were performed.
17

Experimentell-numerische Vorgehensweise zur Entwicklung von Probekörper-Setups für die Charakterisierung technischer Elastomere

Kanzenbach, Lars 12 December 2019 (has links)
Für die Materialcharakterisierung und Parameteridentifikation von technischen Elastomeren werden homogene Probekörper benötigt. Eine besonders wichtige Beanspruchungsart ist dabei der einachsige Zug/Druck. Für Versuche dieser Art findet die Standard-Hantel Anwendung, die für kombinierte Zug-/Druckversuche geeignet ist. Allerdings lässt sich hier schon bei geringen Druckbelastungen ein inhomogener Messbereich detektieren. Ein Ziel dieser Arbeit besteht in der Entwicklung eines neuen und verbesserten Probekörpers, der für hochpräzise Zug-/Druckversuche geeignet ist. Im Gegensatz zur Standard-Hantel wird der für Messungen zugänglich gemachte homogene Messbereich deutlich verbessert. Darüber hinaus soll der Bereich der maximal erreichbaren Stauchung signifikant erhöht werden. Der Probekörper selbst weist dabei eine verhältnismäßig einfache Hantelgeometrie mit verlängertem Mittelteil auf. Durch ein spezielles Design der Halterungsgeometrie kann sowohl ein homogenes Verzerrungsfeld erreicht als auch eine hohe Knickstabilität gewährleistet werden. Die Grundidee besteht dabei darin, dass der Probekörper mit zunehmender Stauchung immer weiter mit der Halterungsgeometrie in Kontakt tritt und dadurch seine knickgefährdete Länge reduziert wird. Mit Hilfe eines speziellen Halterungsalgorithmus kann eine neue, verbesserte Halterungsgeometrie berechnet werden. Mit dem entwickelten Probekörper-Setup (bestehend aus Hantel- und Halterungsgeometrie) lassen sich dann eine Vielzahl phänomenologischer Eigenschaften von technischen Elastomeren wie Payne- Effekt, Mullins-Effekt, Erholungs- und Relaxationsverhalten vorzugsweise bei extremen Stauchungen (bis zu 70 %) untersuchen. Ein weiteres Ziel dieser Arbeit besteht in der Entwicklung eines Scherprobekörpers zur Realisierung präziser Schermessungen. Das Design soll dabei auf einem flächigen Probekörper (Elastomermatte) beruhen, um Alterungsuntersuchungen, Untersuchungen mit faserverstärkten Materialien und Versuche mit Vorreckungen realisieren zu können. Im Gegensatz zu herkömmlichen Scherprobekörpern soll dabei auf eine stoffschlüssige Verbindung mittels Kleben oder Anvulkanisieren aufgrund von Materialirritationen oder Schrumpf verzichtet werden. Im Rahmen dieser Arbeit wurde diesbezüglich ein spezielles Fixierdesign mit Stiften entwickelt, welches zur Ausbildung nahezu homogener Scherdeformationen führt. Damit lassen sich eine Vielzahl wichtiger Eigenschaften bei einer annähernd homogenen Scherdeformation untersuchen. / Homogeneous test specimens are required for material characterization and model parameter identification. An important kind of loading is uniaxial tension/compression. For this, a standard dumbbell is available for combined tension-compression tests. But even for small compressive strains the standard dumbbell leads to an inhomogeneous stress state in the measuring zone. One aim of this work is the development of a new test specimen, which is suitable for high-precision tension/compression tests. In comparison to the standard dumbbell the homogeneity in the measuring zone is significantly improved. Furthermore, the range of maximal compression is increased substantially. The test specimen itself consists of a slender dumbbell structure. By a special design of the mounting geometry, homogeneous stress and strain fields as well as a high stability can be achieved. For an increasing compression, the test specimen comes into contact with the mounting geometry and the critical length is reduced. By means of dynamic analysis, the mounting geometry was calculated and optimized. This method is a powerful tool for developing new mounting geometries, by taking into account both the stability and the homogeneity characteristic. With the developed specimen-setup (consisting of dumbbell and mounting geometry), the phenomenological characteristics of rubber like Payne effect, Mullins effect, recovery and relaxation behavior can be investigated up to a compressive strain of 70 %. Another aim of this work is the development of a shear specimen, which enables precision shear measurements for large shear values. The design is based on a planar test specimen (rubber mat) in order to enable ageing tests, tests with fibre-reinforced materials and tests with pre-stretching. In contrast to other shear specimens, a material-locking connection by gluing or vulcanizing sould be avoided in consequence of material irritation or shrinkage. For this, a special fixing design was developed, which enables a uniform initiation of shear deformation for different rubber thicknesses. Finally, the new shear specimen enables the investigation of typical rubber properties.

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