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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.
131

Analyse und Modellierung des Reifenübertragungsverhaltens bei transienten und extremen Fahrmanövern: Analysis and modelling of tyre transfer behaviour for transient and extreme driving manoeuvres

Einsle, Stefan 15 December 2010 (has links)
Durch den zunehmenden Einsatz fahrdynamischer Regelsysteme und der Fahrzeugauslegung im Grenzbereich gewinnt die Modellierung des Reifenübertragungsverhaltens bei transienten und extremen Fahrmanövern signifikant an Bedeutung. Die im Rahmen dieser Arbeit neu entwickelten Messverfahren zur Analyse und Charakterisierung des transienten Reifenseitenkraftverhaltens zeigen, dass die bisher gewählten Verzögerungsansätze erster Ordnung, beschrieben durch die Einlauflänge, keine ausreichende Abbildungsgenauigkeit liefern. Folglich wird ein neuer Verzögerungsansatz zweiter Ordnung eingeführt und durch den Parameter Einlaufdämpfung zweckmäßig beschrieben. Weiterhin wird nachgewiesen, dass die allgemein gebräuchliche Schätzung der Einlauflänge aus Schräglaufsteifigkeit und Lateralsteifigkeit vor allem bei hohen Radlasten deutlich zu geringe Werte liefert. Zur Abdeckung eines möglichst breiten Anwendungsbereichs werden die Parametereinflüsse Radlast, Fülldruck, Sturz, Vorspur und Geschwindigkeit messtechnisch ermittelt und im neuen Modellansatz berücksichtigt. Auch für die quasistatische Schräglaufsteifigkeit wird ein neues Bestimmungsverfahren mit entsprechenden Einflussanalysen vorgestellt. Bei extremen Fahrmanövern spielt die Fahrzeugstabilität, welche hochsensitiv auf das Reifenverhalten unter Extrembelastungen reagiert, eine entscheidende Rolle. Auch für diesen Anwendungsfall werden neue Mess‐ und Parametrisierungsverfahren eingeführt. Im Gegensatz zu anderen Arbeiten wird auf den gesamten Entstehungsprozess von Reifenmodelldatensätzen eingegangen. Dieser besteht im Wesentlichen aus Reifenmessung, Signalverarbeitung, Auswahl charakteristischer Kennlinien, methodischer Reifenmodellauswahl, automatischer Parameteridentifikation und qualitativem sowie quantitativem Nachweis der Abbildungsgüte des entstandenen Datensatzes. In diesem Prozess werden Schwachstellen aufgezeigt und durch neue Methoden beseitigt. Die drei Reifenmodelle MF-Tyre, FTire und TM-Easy werden analysiert, parametrisiert und unter transienten und extremen Randbedingungen in Kombination mit MKS-Modellen validiert und getestet. Somit kann die Qualität der erzielten Ergebnisse im Verhältnis zum Parametrisierungsaufwand und der Prozesssicherheit für eine Einsatzempfehlung der verschiedenen Reifenmodelle herangeführt werden. Die Qualität der neuen Reifenmodelldatensätze in Verbindung mit der Radaufhängung wird anhand eines neu entwickelten hochdynamischen Achsprüfstandes durch den Vergleich von Messung und MKS-Simulation validiert. Dazu werden sowohl transiente als auch extreme Manöver mit deren realistischen Belastungssituationen nachgestellt. Auch der Einfluss auf die Gesamtfahrzeugsimulation wird anhand entsprechender Manöver nachgewiesen. Darüber hinaus erfolgt die Herleitung eines linearen Einspurmodells mit transientem Reifenseitenkraftverhalten im Zustandsraum, anhand dessen der dominante Reifeneinfluss auf die Gierreaktion von Fahrzeugen nachgewiesen wird.:1 Einleitung 1.1 Stand der Forschung 1.2 Motivation und Ziele dieser Arbeit 1.3 Aufbau der Arbeit 2 Theoretische Grundlagen 2.1 Reifenkoordinatensysteme 2.2 Reifenprüfstände 2.3 Der Reifen unter Schräglauf 2.4 Grundlagen der Fahrdynamik und Einspurmodell 2.5 Eigenschaften elementarer Übertragungsglieder 2.6 Optimierungsverfahren 2.7 Sensitivitätsanalysen zur Systembetrachtung 2.8 Einbindung von Zwangsbedingungen in Mehrkörpersysteme 3 Transientes Reifenseitenkraftverhalten 3.1 Reifenverhalten nach SCHLIPPE\\DIETRICH 3.2 Reifenverhalten nach BÖHM 3.3 Reifenverhalten nach PACEJKA 3.4 Reifenverhalten nach RILL 3.5 Gegenüberstellung des transienten Reifenseitenkraftverhaltens 4 Reifenmodellierung 4.1 Einteilung der Reifenmodelle 4.2 Magic Formula Tyre: MF‐Tyre 4.3 Flexible Ring Tire Model: FTire 4.4 Tyre Model Easy: TM‐Easy 4.5 Handlungsempfehlungen für die Auswahl von Reifenmodellen 5 Messungen am Reifenprüfstand 5.1 Signalverarbeitung von Reifenmessdaten 5.2 Neue Reifenmessprozeduren 5.3 Statische Reifensteifigkeiten 5.4 Reifenverhalten beim Lenken im Stand 5.5 Schräglaufsteifigkeit 5.6 Übertragbare Seitenkraft – Reibbeiwert 5.7 Transientes Seitenkraftverhalten 5.8 Ergebnisse der Messungen am Reifenprüfstand 6 Parameteridentifikation von Reifenmodellen 6.1 Der virtuelle Reifenprüfstand (vRPS) 6.2 Abbildungsgüte kommerziell parametrisierter Reifendatensätze 6.3 Automatischer Gütereport von Reifenmodelldatensätzen 6.4 Parameteridentifikation von MF‐Tyre Datensätzen 6.5 Parameteridentifikation von FTire Datensätzen 6.6 Parameteridentifikation von TM‐Easy Datensätzen 6.7 Extrapolationsfähigkeit der Reifenmodelle 6.8 Übertragbarkeit der Reifenmodelldatensätze auf reale Straßen 6.9 Neue Ansätze zur Parametrisierung von Reifenmodellen 7 Eine neue transiente Zusatzkomponente 7.1 Vergleich verschiedener Übertragungsglieder im Frequenzbereich 7.2 Einbindung in MKS‐Modelle 7.3 Übertragungsmodul als nichtholonome Zwangsbedingung 7.4 Einbindung einer transienten Zusatzseitenkraft 7.5 Schlussfolgerungen zu Zusatzübertragungskomponenten 8 Reifenverhalten am neuen hochdynamischen Achsprüfstand 8.1 Der Aufbau des neuen Achsprüfstandes am IAD 8.2 Das MKS‐Modell des virtuellen Achsprüfstands 8.3 Vergleich der Spurstangenkräfte beim Lenken im Stand 8.4 Einfluss des transienten Reifenverhaltens am Achsprüfstand 8.5 Sinuslenken am Achsprüfstand 8.6 Extremmanöver am Beispiel Fishhook 8.7 Schlussfolgerungen aus den Achsprüfstandsuntersuchungen 9 Gesamtfahrzeugsimulation 9.1 Einspurmodell mit transientem Reifenverhalten 9.2 Mehrkörperfahrzeugmodell mit transientem Reifenverhalten 9.3 Fahrmanöver mit optimierten Reifenmodelldatensätzen 9.4 Beschreibung von Reifenkennwerten mit statistischen Methoden 9.5 Schlussfolgerungen aus der Gesamtfahrzeugsimulationen 10 Zusammenfassung und Ausblick / Due to the growing influence of vehicle dynamic control systems and suspension dimensioning in stability regions, transient and extreme tyre transfer behaviour gains importance significantly. Two new measurement procedures are introduced to analyze and characterize this tyre behaviour. The results show that the commonly used estimation of the relaxation length by the quotient of cornering and lateral stiffness yields far too small values and that the first order transfer model is insufficient to describe the transient tyre lateral force behaviour. Consequently, a new second order approach is introduced and described by the new parameter relaxation damping. The performed parameter study regarding wheel load, inflation pressure, camber angle, toe angle and driving velocity covers a wide application range of tyres. Moreover, the quasi‐static cornering stiffness is measured and evaluated in an extended range with reduced temperature and wear influences. Extreme manoeuvres are utilized to examine the stability of vehicles, which is dominated by the tyre transfer behaviour under extreme conditions. A new measurement and parameter identification procedure for those conditions is portrayed, as well. This thesis depicts the entire process to obtain a tyre model dataset, namely tyre measurements, signal processing, selection of characteristic curves, methodical selection of a tyre model, automatic parameter identification and qualitative and quantitative evaluation of the final dataset. The tyre models MF‐Tyre, FTire, and TM‐Easy are analysed, parameterized and validated under transient and extreme conditions. A comparison of the results in relation to the complexity of the parameter identification and the process stability leads to global recommendations of applications for different tyre models. The quality of the created tyre model datasets in combination with a vehicle suspension is assessed by a comparison of measurements from the newly developed highly dynamical suspension test rig and equivalent multi‐body simulations. That is, transient and extreme manoeuvres are performed and analysed. Additionally, a linear single‐track model with transient tyre behaviour is been derived, that shows the dominant tyre influence on the vehicle’s yaw behaviour. Finally, the influence of the created tyre model datasets and the additional lateral transfer behaviour on full‐vehicle simulations is verified.:1 Einleitung 1.1 Stand der Forschung 1.2 Motivation und Ziele dieser Arbeit 1.3 Aufbau der Arbeit 2 Theoretische Grundlagen 2.1 Reifenkoordinatensysteme 2.2 Reifenprüfstände 2.3 Der Reifen unter Schräglauf 2.4 Grundlagen der Fahrdynamik und Einspurmodell 2.5 Eigenschaften elementarer Übertragungsglieder 2.6 Optimierungsverfahren 2.7 Sensitivitätsanalysen zur Systembetrachtung 2.8 Einbindung von Zwangsbedingungen in Mehrkörpersysteme 3 Transientes Reifenseitenkraftverhalten 3.1 Reifenverhalten nach SCHLIPPE\\DIETRICH 3.2 Reifenverhalten nach BÖHM 3.3 Reifenverhalten nach PACEJKA 3.4 Reifenverhalten nach RILL 3.5 Gegenüberstellung des transienten Reifenseitenkraftverhaltens 4 Reifenmodellierung 4.1 Einteilung der Reifenmodelle 4.2 Magic Formula Tyre: MF‐Tyre 4.3 Flexible Ring Tire Model: FTire 4.4 Tyre Model Easy: TM‐Easy 4.5 Handlungsempfehlungen für die Auswahl von Reifenmodellen 5 Messungen am Reifenprüfstand 5.1 Signalverarbeitung von Reifenmessdaten 5.2 Neue Reifenmessprozeduren 5.3 Statische Reifensteifigkeiten 5.4 Reifenverhalten beim Lenken im Stand 5.5 Schräglaufsteifigkeit 5.6 Übertragbare Seitenkraft – Reibbeiwert 5.7 Transientes Seitenkraftverhalten 5.8 Ergebnisse der Messungen am Reifenprüfstand 6 Parameteridentifikation von Reifenmodellen 6.1 Der virtuelle Reifenprüfstand (vRPS) 6.2 Abbildungsgüte kommerziell parametrisierter Reifendatensätze 6.3 Automatischer Gütereport von Reifenmodelldatensätzen 6.4 Parameteridentifikation von MF‐Tyre Datensätzen 6.5 Parameteridentifikation von FTire Datensätzen 6.6 Parameteridentifikation von TM‐Easy Datensätzen 6.7 Extrapolationsfähigkeit der Reifenmodelle 6.8 Übertragbarkeit der Reifenmodelldatensätze auf reale Straßen 6.9 Neue Ansätze zur Parametrisierung von Reifenmodellen 7 Eine neue transiente Zusatzkomponente 7.1 Vergleich verschiedener Übertragungsglieder im Frequenzbereich 7.2 Einbindung in MKS‐Modelle 7.3 Übertragungsmodul als nichtholonome Zwangsbedingung 7.4 Einbindung einer transienten Zusatzseitenkraft 7.5 Schlussfolgerungen zu Zusatzübertragungskomponenten 8 Reifenverhalten am neuen hochdynamischen Achsprüfstand 8.1 Der Aufbau des neuen Achsprüfstandes am IAD 8.2 Das MKS‐Modell des virtuellen Achsprüfstands 8.3 Vergleich der Spurstangenkräfte beim Lenken im Stand 8.4 Einfluss des transienten Reifenverhaltens am Achsprüfstand 8.5 Sinuslenken am Achsprüfstand 8.6 Extremmanöver am Beispiel Fishhook 8.7 Schlussfolgerungen aus den Achsprüfstandsuntersuchungen 9 Gesamtfahrzeugsimulation 9.1 Einspurmodell mit transientem Reifenverhalten 9.2 Mehrkörperfahrzeugmodell mit transientem Reifenverhalten 9.3 Fahrmanöver mit optimierten Reifenmodelldatensätzen 9.4 Beschreibung von Reifenkennwerten mit statistischen Methoden 9.5 Schlussfolgerungen aus der Gesamtfahrzeugsimulationen 10 Zusammenfassung und Ausblick
132

Conception et implémentation d'un convertisseur temps numérique dans un ASIC en technologie CMOS 0,18 ?m, appliqué à la tomographie d'émission par positrons

Abidi, Mouadh January 2012 (has links)
L'imagerie moléculaire est un domaine permettant d'observer et d'analyser in vivo le fonctionnement cellulaire et tissulaire. Elle permet une meilleure compréhension des bioprocessus et par ricochet, le diagnostic, le traitement et le suivi de plusieurs maladies telles que les maladies neurologiques, cardiovasculaires ou les tumeurs cancéreuses. Le LabPET[indice supérieurTM] II, un scanner d'imagerie médicale TEP en développement au sein du Groupe de Recherche en Appareillage Médical de Sherbrooke (GRAMS), vise à atteindre une résolution spatiale submillimétrique. Ceci demande une densité de détecteurs de l'ordre de 37 000, répartis sur un anneau de 15 cm de diamètre par 12 cm de longueur axiale. Le but ultime est de pouvoir jumeler la tomodensitométrie (TDM) durant la même séance, et de combiner ainsi les informations métaboliques et les informations anatomiques tout en assurant une réduction par un facteur 1,5 à 5 la dose de rayon X par rapport aux doses actuelles en TDM. Ce défi est réparti sur plusieurs axes, parmi lesquels se trouve la chaîne de détection frontale analogique. Un circuit intégré (ASIC) a été développé pour atteindre les performances attendues en TEP et initier des travaux en TDM par comptage de photons individuels. La conception se base sur l'approche de mesures au-dessus d'un seuil (Time Over Threshold (TOT)). Ce choix impose un soin particulier au niveau de l'extraction de l'information temporelle des événements détectés. Ainsi, un convertisseur temps numérique a été conçu à partir d'une boucle à verrouillage de délai (DLL). Le convertisseur comporte deux composantes dont un compteur grossier synchronisé sur l'horloge de référence de 100 MHz (10 ns) et un autre compteur d'une résolution de 312.5 ps.
133

Geometric Model for Tracker-Target Look Angles and Line of Sight Distance

Laird, Daniel T. 10 1900 (has links)
ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NV / To determine the tracking abilities of a Telemetry (TM) antenna control unit (ACU) requires 'truth data' to analyze the accuracy of measured, or observed tracking angles. This requires we know the actual angle, i.e., that we know where the target is above the earth. The positional truth is generated from target time-space position information (TSPI), which implicitly places the target's global positioning system (GPS) as the source of observational accuracy. In this paper we present a model to generate local look-angles (LA) and line-of-sight (LoS) distance with respect to (w.r.t.) target global GPS. We ignore inertial navigation system (INS) data in generating relative position at time T; thus we model the target as a global point in time relative to the local tracker's global fixed position in time. This is the first of three companion papers on tracking This is the first of three companion papers on tracking analyses employing Statistically Defensible Test & Evaluation (SDT&E) methods.
134

Application Of ¹⁴C Wiggle-Matching To Support Dendrochronological Analysis In Japan

Nakamura, T., Okuno, M., Kimura, K., Mitsutani, T., Moriwaki, H., Ishizuka, Y., Kim, K. H., Jing, B. L., Minami, M., Takada, H., Oda, H. 06 1900 (has links)
¹⁴C wiggle-matching was applied to two wood samples closely related to geological and archaeological events with associated dendrochronological dates, to demonstrate the accuracy of ¹⁴C dating with accelerator mass spectrometry (AMS). Wiggle-matching on charred wood with bark, excavated from a pyroclastic mud-flow deposited by the huge 10th Century eruption of the Baitoushan Volcano, revealed the eruption age as cal A.D. 935 +8/-5 with 95% confidence. This date is consistent with the eruption age of A.D. 912 to A.D. 972 estimated by dendrochronology on two wooden boards that had clear stratigraphical connections to the B-Tm tephra deposit in Japan, an ash fall layer formed by the eruption of the Baitoushan Volcano. The date is also consistent with an A.D. 937–938 date estimated by the analysis of varved sediments from Lake Ogawarako in Aomori prefecture. The other wooden board collected from the Mawaki archaeological site in Ishikawa prefecture was wiggle-matched as 783 +13/-11 cal B.C. with 95% confidence, which is consistent with the dates of 830 cal B.C. to 759 cal B.C. obtained for seven wooden poles from the same wooden structures as the wooden board. These results are highly encouraging for obtaining accurate dates on wood when dendrochronology cannot be used.
135

Spatial Analysis of Post-Hurricane Katrina Thermal Pattern and Intensity in Greater New Orleans: Implications for Urban Heat Island Research

Lief, Aram P 16 May 2014 (has links)
In 2005, Hurricane Katrina’s diverse impacts on the Greater New Orleans area included damaged and destroyed trees, and other despoiled vegetation, which also increased the exposure of artificial and bare surfaces, known factors that contribute to the climatic phenomenon known as the urban heat island (UHI). This is an investigation of UHI in the aftermath of Hurricane Katrina, which entails the analysis of pre and post-hurricane Katrina thermal imagery of the study area, including changes to surface heat patterns and vegetative cover. Imagery from Landsat TM was used to show changes to the pattern and intensity of the UHI effect, caused by an extreme weather event. Using remote sensing visualization methods, field data, and local knowledge, the author found there was a measurable change in the pattern and intensity of the New Orleans UHI effect, as well as concomitant changes to vegetative land cover. This finding may be relevant for urban planners and citizens, especially in the context of recovery from a large-scale disaster of a coastal city, regarding future weather events, and other natural and human impacts.
136

Modelagem hidro-bioquímica de reatores anaeróbios: aplicação da dinâmica de fluidos computacional e da dinâmica de sistemas / Hydro-biochemical modeling of anaerobic reactors: application of computational fluid dynamics and systems dynamic

Rocha, Vinícius Carvalho 26 January 2017 (has links)
Modelos matemáticos são representações ou interpretações simplificadas da realidade ou uma representação de um fragmento de um sistema. As simulações destes fenômenos auxiliam na tomada de decisão da parte interessada, ou seja, aqueles que trabalham em uma área. A modelagem de um sistema de processos anaeróbios, como o tratamento de um efluente em reatores UASB (Upflow Anaerobic Sludge Blanket), auxilia os gestores destes sistemas na operação e no controle de estabilidade. O modelo ADM1 (Anaerobic Digestion Model Nº 1), criado pela IWA em 2002, simula o comportamento da digestão anaeróbia. Entretanto, este modelo não considera a hidrodinâmica do sistema como fator relevante no desempenho do processo. O estudo do comportamento do escoamento de efluente no interior de um reator é possível através de ensaios de hidrodinâmica. Estes são conduzidos, majoritariamente, por meio de experimentos laboratoriais que se utilizam de traçadores que, por sua vez, podem resultar em custos elevados. A Dinâmica de Fluidos Computacional (DFC) é uma área na mecânica dos fluidos que utiliza análises numéricas e algoritmos para solucionar e analisar problemas relacionados com escoamento de fluidos. Os softwares de DFC que resolvem estes algoritmos podem ser utilizados na simulação dos ensaios de hidrodinâmica. Foi utilizado nesta tese o pacote de DFC Ansys®, em que o software CFXTM foi o escolhido para realizar as simulações de escoamento. Um dos objetivos desta tese foi a validação desta simulação por meio de ensaios de laboratório e ensaios virtuais em um reator UASB em escala de bancada (1,5 L). Resultou-se, dessa comparação, em dados estatisticamente similares (teste U de Mann-Whitney), proporcionando validação do método. Após esta validação, simulou-se o mesmo tipo de ensaio para um reator UASB em formato de \"Y\" (escala piloto; 119,3 L). Foram simuladas três condições operacionais, em que se variou a vazão de alimentação, sendo esta função da carga orgânica volumétrica aplicada ao lodo (COV). As COV foram 7,5, 12,5 e 17,5 kgDQO m-3d-1. Obteve-se N-CSTR (número de reatores de mistura completa em série) igual a 11, 10 e 10 unidades para cada condição, respectivamente. A ferramenta de Dinâmica de Sistemas utiliza-se de uma abordagem de entendimento de modelos complexos e, por meio de ciclos de retroalimentação (feedback) e estoques e fluxos (stocks and flows), demonstra que modelos aparentemente simples podem ser muito complexos. Existem vários softwares de Dinâmica de Sistemas e neles podem ser implementados os mais variados modelos. Utilizando o software Vensim PLE®, modelou-se a digestão anaeróbia do ácido acético por meio de equações baseadas no modelo de cinética enzimática de Monod e no modelo de digestão anaeróbia ADM1. Considerou-se as taxas de consumo de substrato e crescimento de biomassa bacteriana, a inibição causada pelo pH e a quantidade de alcalinizante necessária para atingir o pH desejado deste meio. De forma complementar, integrou-se um modelo de cálculo de alcalinidade do meio e, desta forma, foi possível determinar as concentrações de cada espécie que confere alcalinidade ao meio, considerando o equilíbrio do carbonato. Denominou-se esta modelação (DFC e dinâmica de sistemas) de Modelo Hidro-bioquímico do processamento anaeróbio. Os resultados obtidos por Del Nery et al. (2016) corroboraram com os obtidos nesta tese. / Mathematical models are representations and simplified interpretations of reality or a representation of a system fragment. The modeling of anaerobic processes, such as wastewater treatment in UASB (Upflow Anaerobic Sludge Blanket) reactors, helps managers in the operation of these systems and stability control. The Anaerobic Digestion Model No. 1 (ADM1), created by IWA in 2002, simulates the behavior of anaerobic digestion. However, this model does not consider the system hydrodynamics as a relevant factor in the performance of the process. The effluent flow behavior studies on the reactor inside is possible by hydrodynamic tests. These are conducted through laboratory experiments that uses tracers and this can result in high costs in the conduct of the tests. The Computational Fluid Dynamics (CFD) is an area in fluid mechanics that uses numerical analysis and algorithms to solve and analyze problems related to fluid flow. CFD software can be used to simulate the hydrodynamics assays. It was used in this thesis Ansys® workbench, wherein the CFXTM software was chosen to perform CFD flow simulations. One objective of this thesis was to validate the CFD simulation through laboratory and virtual testing in a UASB bench scale (1.5 liters). In this comparison, it resulted in similar data statistically (Mann-Whitney U test). After validation of the hydrodynamic test, was simulated the same type of assay for an UASB reactor \"Y\" shaped (pilot scale; = 82.27 liters working volume). The test result was N-CSTR (number of complete mixing reactors in series) equal to 4 units, considering a 103.9 liters per day of feed flow (hydraulic retention time of 19 hours). The system dynamics tool makes use of understanding approach of complex models and, through feedback loops and stocks and flows, shows that seemingly simple models can be very complex. There are several system dynamics software and most varied models can be implemented. Using Vensim PLE® software, it was developed an acetate anaerobic digestion model (in this case acetic acid) via equations based on the Monod and ADM1 model. It was considered for the hydro-biochemical modeling, substrate consumption and growth of bacterial biomass rates, the pH inhibition and the amount of alkalizing necessary to achieve the desired pH of the medium. Complementarily, integrated into a calculation alkalinity model of the medium and thus it was possible to determine the concentrations of each species imparts environment alkalinity, considering the carbonate balance.
137

Modelagem hidro-bioquímica de reatores anaeróbios: aplicação da dinâmica de fluidos computacional e da dinâmica de sistemas / Hydro-biochemical modeling of anaerobic reactors: application of computational fluid dynamics and systems dynamic

Vinícius Carvalho Rocha 26 January 2017 (has links)
Modelos matemáticos são representações ou interpretações simplificadas da realidade ou uma representação de um fragmento de um sistema. As simulações destes fenômenos auxiliam na tomada de decisão da parte interessada, ou seja, aqueles que trabalham em uma área. A modelagem de um sistema de processos anaeróbios, como o tratamento de um efluente em reatores UASB (Upflow Anaerobic Sludge Blanket), auxilia os gestores destes sistemas na operação e no controle de estabilidade. O modelo ADM1 (Anaerobic Digestion Model Nº 1), criado pela IWA em 2002, simula o comportamento da digestão anaeróbia. Entretanto, este modelo não considera a hidrodinâmica do sistema como fator relevante no desempenho do processo. O estudo do comportamento do escoamento de efluente no interior de um reator é possível através de ensaios de hidrodinâmica. Estes são conduzidos, majoritariamente, por meio de experimentos laboratoriais que se utilizam de traçadores que, por sua vez, podem resultar em custos elevados. A Dinâmica de Fluidos Computacional (DFC) é uma área na mecânica dos fluidos que utiliza análises numéricas e algoritmos para solucionar e analisar problemas relacionados com escoamento de fluidos. Os softwares de DFC que resolvem estes algoritmos podem ser utilizados na simulação dos ensaios de hidrodinâmica. Foi utilizado nesta tese o pacote de DFC Ansys®, em que o software CFXTM foi o escolhido para realizar as simulações de escoamento. Um dos objetivos desta tese foi a validação desta simulação por meio de ensaios de laboratório e ensaios virtuais em um reator UASB em escala de bancada (1,5 L). Resultou-se, dessa comparação, em dados estatisticamente similares (teste U de Mann-Whitney), proporcionando validação do método. Após esta validação, simulou-se o mesmo tipo de ensaio para um reator UASB em formato de \"Y\" (escala piloto; 119,3 L). Foram simuladas três condições operacionais, em que se variou a vazão de alimentação, sendo esta função da carga orgânica volumétrica aplicada ao lodo (COV). As COV foram 7,5, 12,5 e 17,5 kgDQO m-3d-1. Obteve-se N-CSTR (número de reatores de mistura completa em série) igual a 11, 10 e 10 unidades para cada condição, respectivamente. A ferramenta de Dinâmica de Sistemas utiliza-se de uma abordagem de entendimento de modelos complexos e, por meio de ciclos de retroalimentação (feedback) e estoques e fluxos (stocks and flows), demonstra que modelos aparentemente simples podem ser muito complexos. Existem vários softwares de Dinâmica de Sistemas e neles podem ser implementados os mais variados modelos. Utilizando o software Vensim PLE®, modelou-se a digestão anaeróbia do ácido acético por meio de equações baseadas no modelo de cinética enzimática de Monod e no modelo de digestão anaeróbia ADM1. Considerou-se as taxas de consumo de substrato e crescimento de biomassa bacteriana, a inibição causada pelo pH e a quantidade de alcalinizante necessária para atingir o pH desejado deste meio. De forma complementar, integrou-se um modelo de cálculo de alcalinidade do meio e, desta forma, foi possível determinar as concentrações de cada espécie que confere alcalinidade ao meio, considerando o equilíbrio do carbonato. Denominou-se esta modelação (DFC e dinâmica de sistemas) de Modelo Hidro-bioquímico do processamento anaeróbio. Os resultados obtidos por Del Nery et al. (2016) corroboraram com os obtidos nesta tese. / Mathematical models are representations and simplified interpretations of reality or a representation of a system fragment. The modeling of anaerobic processes, such as wastewater treatment in UASB (Upflow Anaerobic Sludge Blanket) reactors, helps managers in the operation of these systems and stability control. The Anaerobic Digestion Model No. 1 (ADM1), created by IWA in 2002, simulates the behavior of anaerobic digestion. However, this model does not consider the system hydrodynamics as a relevant factor in the performance of the process. The effluent flow behavior studies on the reactor inside is possible by hydrodynamic tests. These are conducted through laboratory experiments that uses tracers and this can result in high costs in the conduct of the tests. The Computational Fluid Dynamics (CFD) is an area in fluid mechanics that uses numerical analysis and algorithms to solve and analyze problems related to fluid flow. CFD software can be used to simulate the hydrodynamics assays. It was used in this thesis Ansys® workbench, wherein the CFXTM software was chosen to perform CFD flow simulations. One objective of this thesis was to validate the CFD simulation through laboratory and virtual testing in a UASB bench scale (1.5 liters). In this comparison, it resulted in similar data statistically (Mann-Whitney U test). After validation of the hydrodynamic test, was simulated the same type of assay for an UASB reactor \"Y\" shaped (pilot scale; = 82.27 liters working volume). The test result was N-CSTR (number of complete mixing reactors in series) equal to 4 units, considering a 103.9 liters per day of feed flow (hydraulic retention time of 19 hours). The system dynamics tool makes use of understanding approach of complex models and, through feedback loops and stocks and flows, shows that seemingly simple models can be very complex. There are several system dynamics software and most varied models can be implemented. Using Vensim PLE® software, it was developed an acetate anaerobic digestion model (in this case acetic acid) via equations based on the Monod and ADM1 model. It was considered for the hydro-biochemical modeling, substrate consumption and growth of bacterial biomass rates, the pH inhibition and the amount of alkalizing necessary to achieve the desired pH of the medium. Complementarily, integrated into a calculation alkalinity model of the medium and thus it was possible to determine the concentrations of each species imparts environment alkalinity, considering the carbonate balance.
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Evolutions microstructurales et mécaniques de l’AS7G03 modifié au strontium au cours de l’étape de forge du procédé COBAPRESSTM / Microstructural and mechanical evolutions of the AS7G03 modified with strontium during the forging step of the COBAPRESSTM

Perrier, Frédéric 11 July 2013 (has links)
Le procédé COBAPRESSTM est un procédé hybride qui consiste à forger une préforme de fonderie. Nous nous intéressons dans cette thèse à son application pour fabriquer des pièces en alliage d’aluminium AS7G03 modifié au strontium. La première partie de l’étude présente des résultats de simulations obtenues grâce à 2 logiciels de calcul par éléments finis qui sont Simufact et ABAQUS. Nous avons pu voir que la déformation est maximale dans le plan de joint des pièces avec une déformation supérieure à 0,5 pour des vitesses qui peuvent atteindre 10 s-1. Les déformations en peau dues à la rugosité de surface des préformes ont aussi été prises en compte.La deuxième partie expose la microstructure dans les pièces après forge. Ces observations ont été effectuées par microscopie optique ainsi qu’en EBSD. Cette microstructure peut être majoritairement restaurée ou recristallisée pour des paramètres de Zener-Hollomon supérieurs à 1012. La microstructure de peau ainsi que l’effet de la trempe ont aussi été étudiés. Enfin, nous nous sommes intéressés à l’évolution des propriétés mécaniques statiques et cycliques. Nous avons pu voir que l’étape de forge permettait de refermer et souder les retassures de fonderie avec une tenue mécanique suffisante pour résister en fatigue. La Rp0,2, la Rm ainsi que l’allongement à rupture sont augmentés. La microstructure optimale semble être une sous-structure des dendrites qui est la meilleure pour une déformation de 0,5 et une vitesse de 5 s-1 avec une température de préforme de 530°C. Une bonne sous-structuration ainsi qu’une faible rugosité en peau permettent aussi une amélioration de la durée de vie en fatigue après la frappe à chaud. / The COBAPRESSTM is a hybrid process consisting of forging a cast preform. In this thesis, we are interested in its application to make parts with an AS7G03 aluminum alloy modified with strontium. Microstructural evolutions in hot conditions and the mechanical properties resulted from are not well known for this cast alloy and constitute the present work. The first part of the study presents the results obtained by simulation with two finite elements analysis software Simufact and ABAQUS. We could see that the maximal deformation occurs in the parting surface with a deformation closed to 0.5 and a rate which cans reach 10 s-1. Deformation in the skin due to the preform surface roughness is considered. The second part exposes the microstructure in the parts after forging. These observations were made by optical micrography and also by EBSD. This microstructure is predominantly substructured but can be recrystallized for Zener-Hollomon parameters higher than 1012. The typical skin microstructure and the effect of the quenching were also studied.Finally, we studied the evolutions of the static and cyclic mechanical properties. We could see that the forging step allows the welding of the shrinkage porosities with mechanical characteristics good enough to resist fatigue tests. The yield stress, the ultimate tensile stress and the ductility are all improved. The optimal microstructure seems to be a substructure of the dendrites which is the best for a deformation of 0.5 and a rate of 5 s-1 with a preform temperature of 530°C. The good substructuration and the reduced roughness of the skin allow a greater improvement of the fatigue life of the samples after the forging step.
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C-Ply (Trademark) NCF Carbone extra fin : Etude du procédé de fabrication et optimisation du renfort / C-Ply (Trademark) Ultra light CarbonNCF : Study of the manufacturing process and textile reinforcement optimization

Singery, Vicky 03 February 2016 (has links)
L’industrie aéronautique travaille sur l’amélioration des systèmes propulsifs parl’introduction de composites dans la fabrication des aubes de soufflante afin d’alléger lastructure et ainsi de réduire la consommation en carburant des avions. Ces pièces réaliséesen tissage 3D présentent généralement des irrégularités de surface. Une manière d’optimisercet aspect est d’ajouter un pli additionnel de surface : nos travaux de thèse portent sur ledéveloppement de ce pli sous la forme d’un renfort « Non Crimp Fabric » (NCF) biaxial extrafinen fibre de carbone de module intermédiaire (IM), inférieur à 100 g/m², régulier et ayant unebonne déformabilité. Lors de nos travaux de thèse, nous avons utilisé la méthode des plans d’expériencepour améliorer la technologie d’étalement afin de répondre aux exigences demandées. Nousavons pu définir la configuration optimale d’étalement permettant d’atteindre la cible d’un pliinférieur à 50 g/m² en fibre de carbone IM. Pour réaliser un NCF extra-fin, après étalement,les plis sont assemblés par couture afin d’assurer la tenue du renfort. La combinaison decouture choisie (armure, tension, longueur, jauge …) conditionne l’aspect du NCF et sacapacité à être manipulée et déformée. Nous avons donc optimisé les paramètres de coutureafin d’obtenir les propriétés souhaitées. Après avoir optimisé l’étalement des fibres et l’assemblage des plis, nous avons réalisé et caractérisé les renforts NCF extra-fins pour valider leurs propriétés. Nous sommesfinalement parvenus à mettre au point un renfort NCF en fibre de carbone IM, inférieur à50 g/m² par pli ayant un taux de couverture supérieur à 98 % et une bonne capacité à sedéformer. / Aircraft manufacturers are working on the improvement of their engines bymanufacturing fan blades with advanced composite materials to reduce fuel consumption.However, fan blades are made from 3D woven fabrics which often have surface irregularities.It can be minimized by an additional thin layer on the surface : our thesis work is focused onthe development of a new textile structure based on ultra-thin biaxial “Non Crimp Fabric” (NCF)technology. This spread NCF made from intermediate modulus (IM) carbon fibers must belighter than 100 gsm, regular and deformable.During our thesis work, we used Design of Experiments (DOE) methodology to improvethe spreading technology used by Chomarat to make ultra-light NCF materials and meet theestablished requirements. We were able to reach the ultra-thin ply target of less than 50 gsmper ply. After optimizing the spreading process these thin ply tapes are stitched together tocreate NCF. Stability, visual aspect, handling and deformability are dependent on the stitchingsettings (stitching pattern, tension, length, gauge, etc.). Therefore we optimized the stitchingparameters to get the desired properties.After the spreading and stitching process had been optimized, the NCF weremanufactured and tested to validate the desired properties had been achieved. The testingconfirmed that we were able to develop a new carbon fiber NCF that was less than 50 gsm perply, had a coverage rate of higher than 98 % and had good deformability characteristics.
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Imagerie microonde: influence de la polarimétrie du champ diffracté

Le Brusq, E. 23 October 2003 (has links) (PDF)
Le travail présenté dans ce mémoire de thèse s'intéresse au problème de l'imagerie microonde bidimensionnelle polarimétrique. Il est scindé en deux parties, la première est dédiée aux études expérimentales liées à la détection d'objets enfouis tandis que la seconde présente le développement d'un algorithme d'imagerie quantitative. Ainsi le travail effectué dans la première partie du manuscrit porte sur la réalisation d'antennes ultra-large bande et la détermination de leur comportement lors de mesures polarimétriques sur sites. Dans ce dernier cas, plusieurs tests ont été réalisés et permettent de conclure sur les qualités des capteurs développés. Dans une deuxième phase, un code d'imagerie bidimensionnelle prenant en compte à la fois la polarisation 2D-TM et 2D-TE est présenté. Le développement d'un algorithme de diffraction électromagnétique est tout d'abord exposé. Son association avec un algorithme de problème inverse existant déjà au laboratoire permet alors de générer le code d'imagerie quantitative. Plusieurs configurations de reconstruction d'objet homogène, isotrope ou non, permettent ensuite de mettre en évidence ses capacités.

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