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Rojiani, Rhonda Hurst. "Caregiving in later life : an attachment explanatory model /." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06062008-170024/.
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Mellencamp, Kagan Alexander. "Depressive Symptoms Trajectories Following Child Death in Later Life: Variation by Race-Ethnicity." Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1563465712524515.
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Hand, Michelle Danäe. "Perceptions of Sexual Violence in Later Life: A Three Paper Dissertation Study." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1589748395072368.
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Reynaud, Amélie. "Modulation noradrénergique et ajustement des processus attentionnels chez le singe." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1227/document.
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L'attention est une fonction au cœur de la cognition qui, à tout moment, nous permet de sélectionner les informations pertinentes à traiter, tout en ignorant les autres. Cette sélection de l’information qui s’opère à la fois dans l'espace et dans le temps résulte de l’intégration des informations sensorielles et d’un contrôle de "haut niveau" en fonction de nos buts. Cette fonction dépend d’un réseau cérébral incluant le système fronto-pariétal et est sous l’influence de différents neuromodulateurs, en particulier la noradrénaline, dont l’action reste encore mal connue. Mon travail de thèse consistait à comprendre le rôle de la noradrénaline sur les processus attentionnels. Mes objectifs étaient d’une part de vérifier notre hypothèse selon laquelle la noradrénaline modulerait les différentes facettes de l’attention (attention spatiale et attention soutenue) et d’autre part d’élucider les mécanismes d’action par lesquelles la noradrénaline exercerait ces effets. Pour répondre à ces questions, nous avons testé l’impact d’une augmentation de la transmission noradrénergique (administration intramusculaire d'atomoxétine) chez le singe, dans des tâches comportementales nécessitant une sélection de l’information visuelle soit dans l’espace (tâche d'attention avec indice et exploration spontanée d'images) soit au cours du temps (tâche de discrimination go/nogo). Nos résultats démontrent que l’atomoxétine facilite les processus attentionnels à la fois dans l’espace et au cours du temps. Dans l’espace, l’atomoxétine module l’orientation de l’attention visuo-spatiale en fonction du contexte, en ajustant le taux d’accumulation sensorielle ou l’impact de la saillance des images sur l’orientation de l’attention. Au cours du temps, l’atomoxétine ajuste la relation entre la sensibilité à discriminer la cible parmi des distracteurs et le biais de réponse des animaux. En résumé, mes résultats démontrent que la noradrénaline influence les deux facettes, spatiale et temporelle de l’attention et suggèrent une action via un ajustement des processus de traitement de l’information sensorielle et un ajustement du contrôle de l’attention au contexte<br>Attention is a function at the heart of cognition that, at any given moment, enables us to select some information for further processing, while setting aside others. This selection of information that operates both in space and time, results from the integration of sensory information and higher-level control according to our goals. This function depends on a cerebral network including the fronto-parietal system. It is also under the influence of different neuromodulators, in particular norepinephrine, the action of which is still poorly understood.The aim of my PhD work was to understand the role of norepinephrine on attentional processes. My objectives were, on the one hand, to test our hypothesis that norepinephrine is capable of acting on the different facets of attention (spatial attention and sustained attention) and, on the other hand, to elucidate the mechanisms of action by which noradrenaline exerts its action. To answer these questions, we tested the impact of an increase in noradrenergic transmission (intramuscular administration of atomoxetine) in monkeys, using behavioral tasks requiring a selection of visual information in space (cued attentional task and spontaneous image exploration) or over time (go/nogo discrimination task). Our results demonstrate that atomoxetine facilitates attentional processes both in space and over time. In space, atomoxetine modulates the orientation of visuospatial attention according to the context, adjusting the rate of sensory accumulation or the impact of image saliency on attention orientation. Over time, atomoxetine adjusts the relationship between the sensitivity to discriminate a target among distractors and the animal’s response bias.In summary, my results demonstrate that norepinephrine influences both the spatial and temporal facets of attention and suggests an action through an adjustment of sensory information processing and an adjustment of attention control to the context
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Fröhlich, Kristina, Alexander Pogoreltsev, and Christoph Jacobi. "The 48 Layer COMMA-LIM Model." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-217766.
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COMMA-LIM (Cologne Model of the Middle Atmosphere - Leipzig Institute for Meteorology) ist ein 3D-mechanistisches Gitterpuktsmodell, welches sich von ca. 0 bis 135 km in logarhitmischen Druckkordinaten z = -H ln(p=p0) erstreckt, wobei H=7 km und p0 den Referenzdruck am unteren Rand bezeichnet. Die vertikale Auflösung von COMMA-LIM wurde auf 48 Schichten erhöht. Zugleich wurde die Beschreibung des Strahlungsprozesses verbessert, zusammen mit den Beiträgen zur Temperaturbilanz durch atmosphärische Wellen und Turbulenz. Weitere Veränderungen betreffen die numerische Realisation der horizontalen Diffusion und des Filterproblems. Die Beschreibung ist unterteilt in den dynamischen Teil und die Strahlungsbeträge. Die jahreszeitlichen Klimatologien werden vorgestellt und diskutiert<br>COMMA-LIM (Cologne Model of the Middle Atmosphere - Leipzig Institute for Meteorology) is a 3D-mechanistic gridpoint model extending up from 0 to 135 km with a logharithmic vertical coordinate z = -H ln(p=p0), where H=7 km and p0 is the reference pressure at lower boundary. The resolution of the 24 layer version has been increased to 48 layers and several improvements are made in the parameterisation of radiative processes, heating/cooling due to atmospheric waves and turbulence, as well as in the numerical realization of the horizontal diffusion and filtering. This description is divided into the section describing the changes in the dynamical part and the modifications in radiation routines. After all, the seasonal climatologies will be shown and discussed to demonstrate what the COMMA-LIM is capable of reproducing
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Ceppe, Jean-Baptiste. "Éléments de dynamique du laser pour l'élaboration d'une source micro-onde miniaturisée sur la base de la double émission monomode d'un laser à mode de galerie." Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1S067/document.
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Ces travaux de thèses portent sur l’étude de la dynamique du laser à mode de galerie dans le but de réaliser une source micro-onde en utilisant un laser à mode de galerie doublement monomode. Nous montrons ici les résultats expérimentaux sur le bruit relatif d’intensité (RIN) d’un laser à mode de galerie en verre ZBLALiP dopé aux ions Er3+. Outre l’aspect performances d’utilisation du laser, le spectre de RIN donne un certain nombre d’informations sur la dynamique du laser (temps de vie des photons, taux de pompage effectif, sources de bruit, ...).Les très forts facteur de qualités de ces résonateurs ainsi que leurs propriétés de confinement spatial amène un couplage non-linéaire etre les photons et les atomes du milieu amplificateur, faisant apparaitre dans le spectre de RIN des harmoniques de la fréquence de relaxation du laser. Le modèle harmonique développé permet d’estimer le volume de mode du mode de galerie en régime laser, quantité difficilement estimable dans ce régime d’émission. D’autre part, les mesures de RIN réalisées sur un verre industriel IOG-1 codopé Yb3+/Er3+ montrent la signature d’un couplage modal, induit par la diffusion Rayleigh, où les deux modes couplés fonctionnent au dessus du seuil laser. La dynamique de ce laser est également étudié et les comportements obtenus sont mis en parallèle avec les études réalisées sur le gyro-Laser à l’état solide<br>This thesis presents the studies of whispering gallery mode laser dynamics in order to realize a micro-wave source using simultaneous oscillations in a unique whispering gallery mode micro-laser. We show experimental results on the relative intensity noise (RIN) of a Whispering Gallery Mode Laser in ZBLALiP glass doped with Er3+ ions. Besides the pure laser specifications, the RIN spectrum gives informations about the dynamics inside the cavity, such as photon lifetime, effective pumping rate and noise sources. Moreover, we have shown that a single-mode emission comes with the presence of multiple harmonics of the relaxation frequency. The theoretical model taking account the non-linear coupling between photons and atoms allows us to determine the mode volume of the whispering gallery mode in laser regime, which is quite difficult to evaluate in this regime. On the other hand, we have studied the laser dynamics in an industrial IOG-1 glass codoped with Yb3+/Er3+ ions where the signature of a modal coupling, induced by Rayleigh scattering, lies in the RIN spectrum. In this particular case, the two coupled modes operate above threshold. The observed behavior is compared with thoses of a solid state gyro-laser
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Chen, Jie. "Modelling of Laser Welding of Aluminium using COMSOL Multiphysics." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284448.
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This thesis presents a modelling approach of laser welding process of aluminium alloy from the thermo-mechanical point of view to evaluate the occurrence of hot cracking based on simulation results and relevant criteria. The model was created stepwise in COMSOL Multiphysics, starting with the thermal model where heat conduction of solid and liquid phase was computed. Then the CFD model was created by involving the driving forces of liquid motion in the weld pool, i.e. natural convection and Marangoni effect. Lastly, the temperature profile calculated by the CFD model was loaded into the mechanical model for computation of thermal stress and strain. The mechanical results were required in criteria for measuring the susceptibility of hot cracking. The main findings include that Marangoni effect plays a dominant role in generating the fluid flow and convective heat flux in the weld pool, thus enhancing the heat dissipation and lowering temperature in the workpiece. By contrast, such temperature reduction caused by the air convection, radiation and natural convection is negligible. The welding track further from the clamped side experiences smaller transversal residual stress, but it does not necessarily suggest higher susceptibility to hot cracking according to the applied criteria. It can be concluded judging from current results that these first models of laser welding process work satisfactorily. There is still a work to do to obtain the full maturity of this model due to its limitation and some assumptions made for simplicity.<br>Denna avhandling presenterar en modelleringsmetod för lasersvetsningsprocessen av aluminiumlegering ur termomekanisk synvinkel för att utvärdera förekomsten av het sprickbildning baserat på simuleringsresultat och relevanta kriterier. Modellen skapades stegvis i COMSOL Multiphysics, med början med den termiska modellen där värmeledning av fast och flytande fas beräknades. Sedan skapades CFD-modellen genom att involvera drivkrafterna för flytande rörelse i svetsbassängen, dvs. naturlig konvektion och Marangoni-effekt. Slutligen laddades temperaturprofilen beräknad av CFD-modellen in i den mekaniska modellen för beräkning av termisk stress och töjning. De mekaniska resultaten krävdes i kriterier för att mäta känsligheten för het sprickbildning. De viktigaste resultaten inkluderar att Marangoni-effekten spelar en dominerande roll när det gäller att generera vätskeflödet och konvektivt värmeflöde i svetsbassängen, vilket förbättrar värmeavledningen och sänker temperaturen i arbetsstycket. Däremot är sådan temperaturreduktion orsakad av luftkonvektion, strålning och naturlig konvektion försumbar. Svetsbanan längre från den fastspända sidan upplever mindre tvärgående restspänning, men det föreslår inte nödvändigtvis högre känslighet för hetsprickning enligt de tillämpade kriterierna. Man kan dra slutsatsen utifrån aktuella resultat att dessa första modeller av lasersvetsningsprocesser fungerar tillfredsställande. Det finns fortfarande ett arbete att göra för att få full mognad för denna modell på grund av dess begränsning och vissa antaganden för enkelhetens skull.
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Raabe, Armin, Klaus Arnold, and Astrid Ziemann. "Akustische Tomographie im Bereich der Atmosphärischen Grenzschicht." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-213017.
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Atmosphärenmodelle, die mit Hilfe numerischer Methoden nach einer Lösung der thermohydrodynamischen Gleichungen unter bestimmten Randbedingungen über einer vorgegebenen Unterlage (Landschaft) suchen, prognostizieren Volumenmittel entsprechender Größen. Zur Validierung der Modelle benötigte experimentell erfaßte meteorologische Größen repräsentieren meist Punktwerte. Im folgenden werden theoretische Ansätze und eine experimentelle Meßmethode vorgestellt, die es ermöglichen, volumengemittelte Werte meteorologischer Größen bereitzustellen und somit zu numerischen Atmosphärenmodellen weitgehend konsistente Daten zu liefern. Die Verfahren verwenden die horizontale Ausbreitung von Schallwellen in der Atmosphärischen Grenzschicht. Die Ableitung volumenbezogener Größen erfolgt über die Invertierung von Schallparameterwerten (akustische Tomographie)<br>Atmospheric models, which searching by means of numerical methods after a solution of the thermodynamic equations under determined border conditions over a given underground (landscape), forecast volume averaged values of corresponding parameters. The experimental registrated values for meteorolgical parameters used for the validation of models represent usually point values. In following chapters theoretical estimations and an experimental measuring method are presented which volume averaged values of meteorolgical parameters provide and so rather firm data for numerical atmospheric models deliver. The proceedings use horizontal spreading of acoustic waves in the Atmospheric Boundary Layer. Derivation of volume averaged parameters results from the invertation of acoustic parameter values (acoustic tomography)
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Fröhlich, Kristina, Alexander Pogoreltsev, and Christoph Jacobi. "The 48 Layer COMMA-LIM Model: model description, new aspects, and climatology." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 30 = Meteorologische Arbeiten aus Leipzig ; 8 (2003), S. 157-185, 2003. https://ul.qucosa.de/id/qucosa%3A15247.
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COMMA-LIM (Cologne Model of the Middle Atmosphere - Leipzig Institute for Meteorology) ist ein 3D-mechanistisches Gitterpuktsmodell, welches sich von ca. 0 bis 135 km in logarhitmischen Druckkordinaten z = -H ln(p=p0) erstreckt, wobei H=7 km und p0 den Referenzdruck am unteren Rand bezeichnet. Die vertikale Auflösung von COMMA-LIM wurde auf 48 Schichten erhöht. Zugleich wurde die Beschreibung
des Strahlungsprozesses verbessert, zusammen mit den Beiträgen zur Temperaturbilanz durch atmosphärische Wellen und Turbulenz. Weitere Veränderungen betreffen die numerische Realisation der horizontalen Diffusion und des Filterproblems. Die Beschreibung ist unterteilt in den dynamischen Teil und die Strahlungsbeträge. Die jahreszeitlichen Klimatologien werden vorgestellt und diskutiert.<br>COMMA-LIM (Cologne Model of the Middle Atmosphere - Leipzig Institute for Meteorology) is a 3D-mechanistic gridpoint model extending up from 0 to 135 km with a logharithmic vertical coordinate z = -H ln(p=p0), where H=7 km and p0 is the reference pressure at lower boundary. The resolution of the 24 layer version has been increased to 48 layers and several improvements are made in the parameterisation of radiative processes, heating/cooling due to atmospheric waves and turbulence, as well as in the numerical realization of the horizontal diffusion and filtering. This description is divided into the section describing the changes in the dynamical part and the modifications in radiation routines. After all, the seasonal climatologies will be shown and discussed to demonstrate what the COMMA-LIM is capable of reproducing.
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MACRINI, JOSE LEONARDO RIBEIRO. "FORECAST LOAD MODEL USING NEURAL NETWORK: LAYER BY LAYER IMPROVEMENT." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2000. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7251@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>Nesta dissertação é desenvolvido um modelo de previsão de
energia elétrica de curto prazo (previsão mensal) para o
sistema elétrico no Brasil, em especial para as
concessionárias dos sistemas interligados, através de um
modelo de Redes Neurais que emprega um algoritmo de
otimização camada a camada.
O objetivo principal deste trabalho consiste em demonstrar
que bons resultados preditivos podem ser alcançados com a
utilização desse algoritmo para séries de energia elétrica
e que esse método poderia fazer parte dos métodos de
previsão que compõem o Sistema de Previsão de Carga
(PREVCAR) do Operador Nacional do Sistema (ONS) a saber:
modelo de Holt & Winters, modelo de Box & Jenkins, modelo
de redes Neurais (backpropagation) e modelo de Lógica
Fuzzy.<br>It is developed in this essay a short forecast electric
energy model (monthly forecast) to the electric system in
Brazil, particularly to interconnected systems utilities,
through a neural network model, which employs a layer by
layer improvement algorithm.
The aim of this proposition consists in demonstrating that
good forecast results can be reached with the use this
algorithm to electric energy series and that this method
could be part of the forecast methods, wich compose the
Load Forecasting System (PREVCAR) of National System model
(backpropagation) and Fuzzy logic model.
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DeSilva, Sirilath. "Transient axisymmetric model for laser drilling." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/289927.
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A transient axisymmetric model is developed to study the laser drilling phenomenon. Governing equations are the transient axisymmetric 3-D heat conduction equation for the solid substrate and for the liquid molten part, the thin layer model (TLM) equations are utilized. Boundary element method (BEM) is used for the region encompassing the moving boundary and finite difference method (FDM) is utilized for the remainder. BEM and FDM are coupled using flux and temperature at their interface. TLM is obtained using simplified free surface, mass, momentum and energy equations in body intrinsic coordinates. They are simplified by integrating across the layer using profiles for velocity and temperature thus obtaining a 1-D transient hyperbolic system. This is solved by a space-time flux conservation method. The TLM is coupled to the BEM-FDM by the common interface matching conditions. The constitutive equations governing laser interaction with material are used at the liquid-vapor interface.
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Kwon, Ky-Sang. "Multi-layer syntactical model transformation for model based systems engineering." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42835.
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This dissertation develops a new model transformation approach that supports engineering model integration, which is essential to support contemporary interdisciplinary system design processes. We extend traditional model transformation, which has been primarily used for software engineering, to enable model-based systems engineering (MBSE) so that the model transformation can handle more general engineering models.
We identify two issues that arise when applying the traditional model transformation to general engineering modeling domains. The first is instance data integration: the traditional model transformation theory does not deal with instance data, which is essential for executing engineering models in engineering tools. The second is syntactical inconsistency: various engineering tools represent engineering models in a proprietary syntax. However, the traditional model transformation cannot handle this syntactic diversity.
In order to address these two issues, we propose a new multi-layer syntactical model transformation approach. For the instance integration issue, this approach generates model transformation rules for instance data from the result of a model transformation that is developed for user model integration, which is the normal purpose of traditional model transformation. For the syntactical inconsistency issue, we introduce the concept of the complete meta-model for defining how to represent a model syntactically as well as semantically. Our approach addresses the syntactical inconsistency issue by generating necessary complete meta-models using a special type of model transformation.
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Hantel, Michael [Verfasser]. "Ein vertikal-integriertes Modell der Passatschicht : A vertically integrated model of the trade layer / Michael Hantel." Bonn : Universitäts- und Landesbibliothek Bonn, 2019. http://d-nb.info/118841626X/34.
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Sandin, Joakim. "Analysis Methods for Structures with Visco-Elastic Damping Treatment." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13250.
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During aircraft development, the impact of vibrations is examined and how this affects the aircraft structure under different conditions. Those vibrations can damage electronic equipment that are installed within the fuselage and can even lead to material fatigue within the structure. To reduce vibrations there are two approaches that are preferred to use, installing vibration insulators attached between the structure and the electrical component or change the design of the structure to a stiffer one. Those methods are easiest to implement in an early stage of the development but in later stages, when vibration problems usually are detected, it is too difficult and expensive to do major changes of the structure and there is lack of space to implement vibration insulators. A third method is then to apply passive damping in form of damper mats to surfaces on structures where critical vibrations occurs. The effects on the structural behavior when damper mats are applied to a certain structure are studied in this thesis work. The purpose is to get deeper knowledge about how damper mats can be used to reduce vibrations in aircraft structures. The type of damper mat that is studied is known as Constrained Layer Damping, CLD, which is a sandwich of a visco-elastic material layer and a stiffer constraining material layer. Modelling and simulation methods that are based on commercial FE-software have been developed. The analysis method is based on doing a modal analysis with structural damping taken into account. This makes it possible to predict the overall global damping at each structural mode. The models for damper mats have in this project been verified with experimental testing using typical damper mats. The methodology can be used to predict the behavior of damped structures in order to obtain an effective and lightweight passive damping solution.<br>Under utvecklingen av flygplan undersöks hur vibrationer påverkar flygplansstrukturen under olika förutsättningar. Dessa vibrationer kan skada elektronisk utrustning som är monterad i flygplanskroppen och kan även göra så att materialutmattning uppstår i flygplansstrukturen. För att motverka vibrationer finns det två metoder som är att föredra, antingen att montera vibrationsisolatorer mellan de elektroniska utrustningarna och strukturen eller att ändra designen på strukturer till en styvare. Dessa metoder är enkla att implementera i ett tidigt steg i utvecklingsprocessen men i senare steg, då vibrationsproblem ofta upptäcks, så är det för komplicerat och för dyrt att göra större ändringar på strukturen och så är det ont om plats för att kunna installera vibrations isolatorer. En tredje metod är istället att implementera passiv dämpning i form av dämpningsmattor på ytor av strukturen där kritiska vibrationer uppstår. Effekterna av det strukturella uppförandet när dämpningsmattor är applicerade på en viss struktur har studerats i det här examensarbetet. Syftet är att få en fördjupad kunskap om hur dämpningsmattor kan användas för att reducera vibrationer i flygplan strukturer. Den typ av dämpningsmatta som har studerats är känd som Constrained Layer Damping, CLD, vilken är en sandwich av ett visko-elastiskt lager samt ett styvare lager. Modellerings och simuleringsmetoder som är baserade på kommersiella FE-mjukvaror har utvecklats. Analysmetoderna är baserade på att utföra modalanalys tillsammans med strukturell dämpning. Detta möjliggör att förutse den övergripande dämpningen vid varje strukturell mod. Modellerna för dämpningsmattorna har i det här projektet verifierats med experimental testning av typiska dämpningsmattor. Metodiken kan användas till att prediktera beteendet av dämpade strukturer för att uppnå en effektiv och lättviktig passiv dämpningslösning.
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Yu, Yi. "Physical layer model design for wireless networks." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1785.
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Kurskoy, Yu S., O. S. Hnatenko, Yu P. Machekhin, and M. V. Neofitnyy. "Topological Model of Laser Emission Parameters Research." Thesis, CAOL, 2019. http://openarchive.nure.ua/handle/document/15100.
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The research paper presents a model for studying both the parameters and dynamics of laser light as a nonlinear dynamic system. The model provides for the measurement of the values of physical quantities by non-linear metrology methods and the analysis of the research findings with topological tools. The model is based on the assumption of interval values of the measured values and the possibility of changing the stationary dynamics into the random one. The model contains an experiment scheme and a procedure for evaluating measurement results. The peculiarity of the model lies in its systemic approach and suitability for measuring and researching stationary and chaotic modes. The model provides for the measurement of the emission parameter values intervals in various modes, of their stability values and time series prediction. Classification of the system dynamics is performed using the fractal dimension. The model can be used both to ensure the stability of the laser light parameters, and to obtain and control random emission.
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Raghavan, Satyanarayanan. "Laser-based hybrid process for machining hardened steels." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47550.
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Cost-effective machining of hardened steel (>60 HRC) components such as a large wind turbine bearing poses a significant challenge. This thesis investigates a new laser tempering based hybrid turning approach to machine hardened AISI 52100 steel parts more efficiently and cost effectively. The approach consists of a two step process involving laser tempering of the hardened workpiece surface followed by conventional machining at higher material removal rates using lower cost ceramic tooling to efficiently cut the laser tempered material.
The specific objectives of this work are to: (a) study the characteristics of laser tempering of hyper-eutectoid 52100 hardened steel, (b) model the laser tempering process to determine the resulting hardness, and (c) conduct machining experiments to evaluate the performance of the laser tempering based hybrid turning process in terms of forces, tools wear and surface finish.
First, the microstructure alterations and phase content in the surface and subsurface layers are analyzed using metallography and x-ray diffraction (XRD) respectively. Laser tempering produces distinct regions consisting of - a tempered white layer and a dark layer- in the heat affected subsurface region of the workpiece. The depth of the tempered region is dependent on the laser scanning conditions. Larger overlap of laser scans and smaller scan speeds produce a thicker tempered region. Furthermore, the tempered region is composed of ferrite and martensite and weak traces of retained austenite (~ 1 %).
Second, a laser tempering model consisting of a three dimensional analytical model to predict the temperature field generated by laser scanning of 52100 hardened steel and a phase change based hardness model to predict the hardness of the tempered region are developed. The thermal model is used to evaluate the temperature field
induced in the subsurface region due to the thermal cycles produced by the laser scanning step. The computed temperature histories are then fed to the phase change model to predict the surface and subsurface hardness. The laser tempering model is used to select the laser scanning conditions that yield the desired hardness reduction at the maximum depth. This model is verified through laser scanning experiments wherein the hardness changes are compared with model predictions. The model is shown to yield predictions that are within 20 % of the measured hardness of the tempered region.
Using the laser scanning parameters determined from the laser tempering model, cutting experiments using Cubic Boron Nitride (CBN) tools and low cost alumina ceramic tools are conducted to compare the performance of laser tempering based hybrid turning with the conventional hard turning process. The machining experiments demonstrate the possibility of higher material removal rates, lower cutting forces, improved tool wear behavior, and consequently improved tool life in the laser tempering based process. In addition, the laser tempered based hybrid turning process produce is shown to yield lower peak-to-valley surface roughness height than the conventional hard turning process. Furthermore, it is found that lower cost ceramic tools can be used in place of CBN tools without compromising the material removal rate.
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Vogl, Stefanie. "Tropical Cyclone Boundary-Layer Models." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-102740.
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Buzo, Amir. "Intelligent Data Layer: : An approach to generating data layer from normalized database model." Thesis, Linnéuniversitetet, Institutionen för datavetenskap, fysik och matematik, DFM, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-22170.
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Model View Controller (MVC) software architecture is widely spread and commonly used in application’s development. Therefore generation of data layer for the database model is able to reduce cost and time. After research on current Object Relational Mapping (ORM) tools, it was discovered that there are generating tools like Data Access Object (DAO) and Hibernate, however their usage causes problems like inefficiency and slow performance due to many connections with database and set up time. Most of these tools are trying to solve specific problems rather than generating a data layer which is an important component and the bottom layer of database centred applications. The proposed solution to the problem is an engineering approach where we have designed a tool named Generated Intelligent Data Layer (GIDL). GIDL tool generates small models which create the main data layer of the system according to the Database Model. The goal of this tool is to enable and allow software developers to work only with object without deep knowledge in SQL. The problem of transaction and commit is solved by the tool. Also filter objects are constructed for filtering the database. GIDL tool reduced the number of connections and also have a cache where to store object lists and modify them. The tool is compared under the same environment with Hibernate and showed a better performance in terms of time evaluations for the same functions. GIDL tool is beneficial for software developers, because it generates the entire data layer.
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Yao, Hanxun. "A local correlation-based transition model for Spalart-Allmaras turbulence model." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17382.
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The Spalart Allmaras (S-A) Reynolds-Averaged Navier-Stokes (RANS) model has had considerable success in application to a wide range of turbulent flow problems. However, as turbulent kinetic energy k is not available in the S-A model, the application of sub-models of additional physical phenomena may not be possible. These phenomena could include turbulent transition models, which require a freestream turbulent intensity, or combustion closures which require a turbulent time scale, or broadband noise prediction based on k. This thesis composes of three main parts. In the first part, a comprehensive study of γ-〖Re〗_θ transition model is presented. In the second part, a local correlation-based γ-〖Re〗_θ transition model is coupled with the Spalart-Allmaras turbulence model (SA-γ-〖Re〗_θ model) in a structured parallelized Navier-Stokes solver, Flamenco and in the OpenFOAM package. The detailed and complete summary of the modified governing equations and a suite of validation and verification tests are given. The results obtained prove the validity of the SA-γ-〖Re〗_θ model. In the third part, a novel turbulence model, denoted the S-A-K model, is developed coupling the Spalart-Allmaras model with a transport equation for kinetic energy k, enabling coupling with the SA model with γ-〖Re〗_θ model (SAK-γ-〖Re〗_θ). The closure strategy of S-A-K model is proposed and validated against four standard benchmark cases. Good results are obtained using the S-A-K model compared to the results from the classical S-A turbulence model and the k-ω Shear Stress Transport Turbulence Model (k-ωSST) model, and experimental data.
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Arnqvist, Johan. "Mean Wind and Turbulence Conditions in the Boundary Layer above Forests." Doctoral thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-237764.
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As wind turbines have grown, new installation areas become possible. Placing wind turbines in forested landscapes introduce uncertainties to the wind resource estimation. Even though close-to-canopy processes have been studied intensively during the last thirty years, the focus has mostly been on exchange processes and the height span of the studies has been below the rotor of a modern wind turbine. This thesis contains analysis of new measurements from a 138 m high tower in a forested landscape. The previous knowledge of near-canopy processes is extended to the region above the roughness sublayer. It is shown that above the roughness sublayer, the surface layer behaves as over low vegetation, and Monin-Obukhov similarity is shown to hold for several variables. However, in stable stratification, effects that could be linked to the boundary layer depth are shown to be present in the measurements. These include wind turning with height, the behaviour of the turbulence length scale and the curvature of the wind profile. Two new analytical models are presented in the thesis. One is a flux-profile expression in the roughness sublayer, which allows for analytical integration of the wind gradient. The model suggests that the roughness-sublayer effect depends on stratification and that the aerodynamic roughness length changes with stability. A decrease of roughness length in stable stratification is confirmed with a new method to determine the roughness length using measurements from the 138 m tower. The other model determines the spectral tensor in stable stratification using analytical solution to the rapid distortion equations for stratified shear flow, with homogeneous stratification and shear. By using a formulation for the integration time of the distortions of an isotropic spectrum, a model is derived which provides the cross spectra of velocity and temperature at any two given points in space. Finally the existence of waves in the wind over forests is investigated and it is concluded that the Kelvin-Helmholtz instability can create waves which are coherent in time and exist over the entire height span of wind turbine rotors. Linear wave theory is shown to be able to explain certain features of the waves.<br>Vindforsk III, Wind power in forests<br>Vindforsk IV, Forest wind
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Reuter, Sabrina [Verfasser]. "Model Calculations for Characterisation and Implementation of Vertical Thin-Layer Structures with Distributed Cavity Mode for Filter and Laser Applications / Sabrina Reuter." Kassel : Universitätsbibliothek Kassel, 2018. http://d-nb.info/115869279X/34.
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Wang, Hongwei. "Boundary Layer Characteristics on a Tiltrotor Blade Model." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33630.
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Boundary layer characteristics at the trailing edge of a tiltrotor blade model were measured using a flattened pitot probe and a single hot wire. The blade was mounted in Virginia Tech Stability Wind tunnel stationary on a turntable on the wind tunnelâ s upper wall with the tip pointing down. The measurement point was located at 1 mm behind the trailing edge to make it possible to measure the flow near the blade surface and measure the boundary layer on both sides of the trailing edge in a same run. Mean velocity profiles were measured for a variety of Reynolds numbers and angles of attack. Turbulence intensity and spectral measurements were performed using a single hot wire at the highest Reynolds number. Conclusion was reached that both of the flattened pitot probe and single hot wire are good for boundary layer thickness measurements. Displacement thickness, which is important in trailing edge noise prediction, was calculated from the profile data and fit using an algebra expression against the tip angle of attack. Once the relationship between tip angle of attack and local effective angle of attack is obtained by lifting line theory, the results can be used in the trailing edge noise prediction code.<br>Master of Science
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Strack, Beata. "Multi-column multi-layer computational model of neocortex." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3279.
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We present a multi-layer multi-column computational model of neocortex that is built based on the activity and connections of known neuronal cell types and includes activity-dependent short term plasticity. This model, a network of spiking neurons, is validated by showing that it exhibits activity close to biology in terms of several characteristics: (1) proper laminar flow of activity; (2) columnar organization with focality of inputs; (3) low-threshold-spiking (LTS) and fast-spiking (FS) neurons function as observed in normal cortical circuits; and (4) different stages of epileptiform activity can be obtained with either increasing the level of inhibitory blockade, or simulation of NMDA receptor enhancement. The aim of this research is to provide insight into the fundamental properties of vertical and horizontal inhibition in neocortex and their influence on epileptiform activity. The developed model was used to test novel ideas about modulation of inhibitory neuronal types in a developmentally malformed cortex. The novelty of the proposed research includes: (1) design and implementation of a multi-layer multi-column model of the cortex with multiple neuronal types and short-time plasticity, (2) modification of the Izhikevich neuron model in order to model biological maximum firing rate property, (3) generating local field potential (LFP) and EEG signals without modeling multiple neuronal compartments, (4) modeling several known conditions to validate that the cortex model matches the biology in several aspects,(5) modeling different abnormalities in malformed cortex to test existing and to generate novel hypotheses.
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Zhao, Zhuang. "Pulse generation from mode locked VECSELS AT 1.55 um." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112204/document.
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Dans un premier temps, nous avons optimisé des structures laser VECSEL dans le but de maximiser la puissance émise par une gestion thermique adéquate. Les structures conçues et fabriquées contiennent une zone active à base d’InP pour l’émission à 1.55 µm. Un miroir hybride métal- semiconducteur à base d’un miroir de Bragg GaAs/AlAs est intégré à la zone active. La structure semiconductrice est intégrée avec différents substrats hôtes de bonne conductivité thermique sur la base de simulations numériques, et les performances des dispositifs fabriqués sont évaluées expérimentalement sous pompage optique Les VECSELs intégrés sur substrat diamant CVD présentent les puissances de sortie les plus élevées, et sont de bons candidats pour l’émission de puissance (> 500 mW) à 1.55 µm et pour les expériences de blocage de modes. D’un autre côté nous montrons que l’intégration d’un substrat de cuivre par voie électrochimique représente une approche flexible et faible-coût, pour atteindre une puissance de sortie de plusieurs dizaines de mW jusqu’à ~ 200 mW.Dans un second temps, nous avons développé des SESAMs à 1.55 µm. La région active est formée de puits quantiques InGaAsN/GaAs, couplés par effet tunnel à des plans GaAsN à recombinaison rapide. Des temps caractéristiques de recouvrement de l’absorption de quelques picosecondes à la dizaine de picoseconde sont ainsi mesurés.La résonance de la microcavité SESAM est ajustée de manière contrôlée grâce à des couches de phase spécifques épitaxiées en surface de la structure. La gravure sélective couche par couche des couches de phase permet d’accorder la profondeur de modulation et la dispersion de vitesse de groupe (GDD) de la structure SESAM.Finalement nous avons assemblé les structures SESAM et VECSEL dans une cavité à quatre miroirs pour obtenir un fonctionnement laser en régime de blocage de modes passif. Nous observons que la durée de l’impulsion de blocage de modes peut être réduite de plusieurs picosecondes (~ 10 ps), jusqu’à moins de la picoseconde (0.9 ps) en accordant la GDD de la structurre SESAM<br>In a first step, we have developed and implemented VECSEL structures, aiming at maximizing the laser output power through a proper thermal management. The fabricated VECSEL chips contain an InP-based active region for emission at 1.55 µm. A hybrid metal-GaAs/AlAs Bragg mirror is used to achieve efficient dissipation of the heat generated in the active region. The semiconductor structure is integrated to various host substrates and the VECSEL performances are investigated numerically and experimentally. VECSELs with CVD diamond substrates have the best overall performance and are promising for large output power (> 500 mW), while electroplated copper substrate is demonstrated to be a flexible and cost-effective approach for thermal management in 1.55 µm OP-VECSEL in order to achieve output power of several tens of mW to ~ 200 mW. The second part of the work is devoted to the development of SESAM structures at 1.55 µm. The structures include an active region consisting of InGaAsN / GaAs quantum wells surrounding by GaAsN planes, allowing to achieve absorption relaxation time of few picoseconds. The SESAM microcavity resonance was adjusted via a selective etching of phase layers specifically designed to control the magnitude of both the modulation depth and the intra cavity group delay dispersion of the device.Finally, assembling VECSEL and SESAM chips in a cavity, we observe experimentally that the mode-locked pulse duration could be reduced from several picoseconds to less than one picosecond when the resonance and group delay dispersion of the SESAM microcavity are tuned
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Bruno, Olimpia. "Turbulence models in the atmospheric boundary layer under convective conditions." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6579/.
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In this work a modelization of the turbulence in the atmospheric boundary
layer, under convective condition, is made. For this aim, the equations that
describe the atmospheric motion are expressed through Reynolds averages
and, then, they need closures.
This work consists in modifying the TKE-l closure used in the BOLAM
(Bologna Limited Area Model) forecast model. In particular, the single
column model extracted from BOLAM is used, which is modified to obtain
other three different closure schemes: a non-local term is added to the flux-
gradient relations used to close the second order moments present in the
evolution equation of the turbulent kinetic energy, so that the flux-gradient
relations become more suitable for simulating an unstable boundary layer.
Furthermore, a comparison among the results obtained from the single
column model, the ones obtained from the three new schemes and the
observations provided by the known case in literature ”GABLS2” is made.
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Dontsova, Dariya. "Titania based photocatalytically active layer-by-layer coatings on model surfaces and textile materials." Strasbourg, 2011. http://www.theses.fr/2011STRA6203.
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Les propriétés photocatalytiques de catalyseurs commerciaux et synthétiques ont été étudiées pour la décomposition sous flux d'un composé odorant modèle, le sulfure d'hydrogène (H2S), sous irradiation UV-A et visible. Un modèle simplifié qualitatif pour la visualisation de la désactivation du catalyseur est proposé. En outre, les catalyseurs ont été incorporés dans des films multicouches en utilisant différents polyélectrolytes. Ces films ont été caractérisés par ellipsométrie, AFM, spectroscopie UV-visible et SEM sur des surfaces modèles. Ces films sont homogènes et transparents, et leur porosité permet un transport de masse quasiment libre des composés volatiles dans le film. Afin de tester l'activité photocatalytique des films LbL contenant des catalyseurs, ces films ont été assemblés sur des réacteurs tubulaires en verre (avec un diamètre de 2,7 cm et une longueur de 40 cm) et soumis à un flux de H2S sous irradiation UV-A. L'activité des films s’est montrée proportionnelle au nombre de couches de catalyseur constitutif du film et dépendante de la nature chimique du polyélectrolyte constitutif du film. Après optimisation de la structure du film par rapport à la composante catalytique et au composant polyélectrolyte, les films les plus efficaces ont été déposés sur des textiles en coton et leur activité photocatalytique a été mesurée pour la décomposition en flux de H2S sous irradiation à la lumière visible. De plus, les applications potentielles de ces textiles revêtus par LbL pour l'élimination d'autres polluants intérieurs communs ont été illustrées par la décomposition d’acétaldéhyde, de méthyl éthyl cétone et d’ammoniac gazeux sous irradiation à la lumière visible<br>The photocatalytic properties of commercially available and synthesized catalysts were studied for on-stream decomposition of a model odorous compound hydrogen sulphide (H2S) under UV-A and visible light irradiation. A simplified qualitative model for visualization of the catalyst deactivation is proposed. Further, catalysts were incorporated into multilayer films using different polyelectrolytes. Such films were characterized by ellipsometry, AFM, UV-visible spectroscopy and SEM on model surfaces. These films are homogeneous and transparent, and their porosity allow for almost free mass transport of the volatile compounds within the film. In order to test the photocatalytic activity of LbL films containing catalysts, such films were assembled on tubular glass reactors (with the diameter of 2. 7 cm and the length of 40 cm) and subjected to H2S flow under UV-A irradiation. The activity of films was found to be proportional to the number of film constituent layers of catalyst and dependent on the chemical nature of the film constituent polyelectrolyte. After the film structure was optimized with respect to catalytic component and polyelectrolyte component, the most efficient films were deposited on cotton textiles, and their photocatalytic activity was measured for on-stream decomposition of H2S under visible light irradiation. Further, the potential applications of such LbL-coated textiles for the removal of other common indoor pollutants were exemplified by decomposition of acetaldehyde, methyl ethyl ketone and ammonia gas under visible light irradiation
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Dunne, R. A. "Multi-layer perceptron models for classification." Thesis, Dunne, R.A. (2003) Multi-layer perceptron models for classification. PhD thesis, Murdoch University, 2003. https://researchrepository.murdoch.edu.au/id/eprint/50257/.
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This thesis concerns the Multi-layer Perceptron (MLP) model, one of a variety of neural network models that have come into wide prominence since the mid 1980s for the classification of individuals into pre-defined classes based on a vector of individual measurements.
Each discipline in which the MLP model has had influence, including computing, electrical engineering and psychology, has recast the model into its own language and imbued it with its own concerns. This divergence of terminologies has made the literature somewhat impenetrable but has also led to an appreciation of other disciplines' priorities and interests.
The major aim of the thesis has been to bring the MLP model within the framework of statistics. We have two aims here: one is to make the MLP model more intelligible to statisticians; and the other is to bring the insights of statistics to the MLP model. A statistical modeling approach can make valuable contributions, ranging from small but important clarifications, such as clearing up the confusion in the MLP literature between the model and the methodology for fitting the model, to much larger insights such as determining the robustness of the model in the event of outlying or atypical data.
We provide a treatment of the relationship of the MLP classifier to more familiar statistical models and of the various fitting and model selection methodologies currently used for MLP models. A description of the influence curves of the MLP is provided, leading to both an understanding of how the MLP model relates to logistic regression (and to robust versions of logistic regression) and to a proposal for a robust MLP model.
Practical problems associated with the fitting of MLP models, from the effects of scaling of the input data to the effects of various penalty terms, are also considered. The MLP model has a variable architecture with the major source of variation being the number of hidden layer processing units. A direct method is given for determining this in multi-class problems where the pairwise decision boundary is linear in the feature space.
Finally, in applications such as remote sensing each vector of measurements or pixel contains contextual information about the neighboring pixels. The MLP model is modified to incorporate this contextual information into the classification procedure.
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Sun, Congcong. "Multi-layer model predictive control of complex water systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/326739.
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This thesis is devoted to design a multi-layer MPC controller applied to the complex water network taking into account that the different layers with different time scales and control objectives have their own controller. A two-layer temporal hierarchy coordinating scheme has been applied to coordinate the MPC controllers for the supply and transportation layers. An integrated real-time simulation-optimization approach which contributes to consider the effect of more complex dynamics, better represented by the simulation model, has been developed for regional water networks. The use of the combined approach of optimization and simulation coordination between simulator and optimizer allows to test the proposed multi-layer MPC in a feedback scheme using a realistic simulator of the regional network.
The second part of this thesis is focused on the design of a control scheme which uses the combination of linear MPC with a constraint satisfaction problem (CSP) to optimize the non-linear operational control of DWNs. The network aggregation method (NAM) is used to simplify a complex water network into an equivalent conceptual one for the bidirectional network before the use of CSP. The proposed approach is simulated using Epanet to represent the real DWN. Non-linear MPC is used for validation using a generic operational tool for controlling water networks named PLIO. A two-layer scheduling scheme for pump stations in a water distribution network has also been designed in the second part of this thesis. The tuning parameters of such algorithm are the lower layer control sampling period and the number of parallel pumps in the pump station.<br>Aquesta tesi està dedicada a dissenyar un controlador MPC multicapa que s'aplica a una complexa xarxa regional emprant com a principal idea el fet de què les diferents capes treballen amb diferents escales de temps i objectius de control s'aconseguiran amb el seu propi controlador. Un esquema jeràrquic de coordinació temporal de dues capes s'ha aplicat per a coordinar als controladors MPC per a les xarxes de captació i transport. Un enfocament integrat de simulació-optimizació que contribueix a asegurar que l'efecte de les dinàmiques complexes, millor representades pel model de simulació s'hagin tingut en compte, s'ha propostat per la gestió operacional temps real de les xarxes regionals. La segona part d'aquesta tesi es centra en el disseny d'un esquema de control que utilitza la combinació del control MPC lineal amb una problema de satisfacció de restriccions (CSP) per optimitzar el control operacional no-lineal de les xarxes d'aigua potable. El mètode d'agregació de xarxes (NAM) s'utilitza per simplificar una xarxa d'aigua complexa en una xarxa conceptual bidireccional equivalent abans d'utilitzar el CSP. L'enfocament proposat es simula utilitzant Epanet per representar el comportament hidràulic de la xarxa d'aigua potable. Finalment, el MPC no lineal s'utilitza per a la validació fent ús de l'eina PLIO per a la seva implementació. I també, un esquema de planificació de dues capes per a estacions de bombament en una aigua xarxa de distribució ha estat proposat en la segona part d'aquesta tesi. Els paràmetres d'ajust d'aquest algorisme són el período de mostreig de control de la capa inferior i el número de bombes en paral·lel en la estació de bombament.
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Hone, David M. "Time and space resolution and mixed layer model accuracy." Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/9080.
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The oceanic turbulent boundary layer is a critical region to understand for oceanic and atmospheric prediction. This thesis answers two fundamental questions: (1) what is the response of the ocean mixed layer system to transient forcing at the air sea surface? (2) what is the necessary time and space resolution in an ocean mixed layer model to resolve important transient responses? Beginning with replication of de Szoeke and Rhines' work, additional physical processes were added to include more realistic viscous dissipation and anisotropy in the three-dimensional turbulent kinetic energy (TKE) budget. These refinements resulted in modification of de Szoeke and Rhines' findings. Firstly, TKE unsteadiness is important for a minimum of 10 to the 5th power seconds. Secondly, viscous dissipation should not be approximated as simply proportional to shear production. Thirdly, entrainment shear production remains significant for a minimum of one pendulum-day. The required temporal model resolution is dependent on the phenomena to be studied. This study focused on the diurnal, synoptic, and annual cycles, which the one-hour time step of the Naval Postgraduate School model adequately resolves. The study of spatial resolution showed unexpectedly that model skill was comparable for 1 m, 10 m and even 20 m vertical grid spacing
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Ryder, Gerard Joseph. "A numerical model of the selective laser sintering process." Thesis, University of Leeds, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271961.
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Adams, David C. (David Christopher). "A delay-constrained cross-layer model using network coding." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91099.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.<br>27<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 79-81).<br>Traditionally, most packet-switched networks have only one wireless hop: the link between the end users and their access point. However, there is increasing interest in using wireless links to reach the edge of the network. Having more than one wireless link is a game changer. Network layer architecture is predicated on the assumption that the lower layers are reliable, but this comes at a high cost in terms of data rate on a band-limited, lossy wireless channel. This cost is tolerable over one underutilized link, but when the network demands high-capacity wireless links, it may be time to rethink the way the packet-switched network interacts with its underlying infrastructure. The aim of this thesis is to provide a general model that can be used to frame a wide variety of cross-layer coding problems. We do not explicitly consider the channel code, medium access, or modulation; instead, we leverage the maturity of these fields to observe the general effect they produce on higher layers. We focus our model on applications where delay is constrained, which forces us to consider coding results in the regime where code length is non-asymptotically large. In trying to extend our analysis to multi-hop flows, we develop an analytical tool that can be useful in wider applications. This tool simplifies certain network flows to a distribution on the amount of information available to the destination; it is a step towards characterizing network information flows in the non-asymptotic regime. Finally, we will use the model to design encoding schemes, given practically-motivated constraints.<br>by David C. Adams.<br>S.M.
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Abu, Hussain Nurulakmar. "FE modelling and model updating of laser weld joints." Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540067.
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Assembled structures are typically constructed by structural elements that are connected together by structural joints. For example, thousands of spot weld joints are used in a typical automotive structure in order to provide connections between layers of thin metal sheets used to form the structure. The spot weld joints also significantly contribute to the vehicles structural stiffness and dynamic characteristics; hence it is very important to have an acceptable FE model of the joints in order to evaluate the dynamic behaviour of such structures. It appears that most of the studies regarding spot weld joints have concentrated on spot welds made by the more conventional Resistance Spot Welding, while to the author's best knowledge, there is no reported works on modelling the dynamic behaviour of structures with laser welds, which is the main objective of this thesis. Existing elements available in commercial FE software are researched and a suitable element is chosen to represent the laser weld joints for its dynamic predictions. A set of laser spot welded structures are manufactured and FE model representing the structures is developed systematically, starting from modelling and updating the substructures to the development of the FE model of the welded structures. Experimental modal analysis is conducted in order to obtain the modal parameters from the test structures, which are then employed in validating and improving the correlation between the developed FE models and their experimental counterparts. Variability that exists in the test structures is also investigated and non-deterministic (or stochastic) model updating is carried out by using the perturbation method. Parameter selection for the stochastic model updating is studied first using two sets of very different structures: the first set consists of nominally identical (simple) flat plates, while the second set comprises of (more complicated) formed structures. The stochastic updating procedure is conducted with different combinations of parameters, and it is found that geometrical features (such as thickness) alone cannot converge the predicted outputs to the measured counterparts, hence material properties (for instance, Young's modulus and shear modulus) must be included in the updating process. Then, the stochastic model updating is also conducted on the welded structures, using two approaches of parameter weighting matrix assignments. Results from one of the approaches demonstrate good correlation between the predicted mean natural frequencies and their measured data, but poor correlation is obtained between the predicted and measured covariances of the outputs. In another approach, different parameter weighting matrices are assigned to the means and covariances updating equations. Results from this approach are in very good agreement with the experimental data and excellent correlation between the predicted and measured covariances of the outputs is achieved. Finally, the developed deterministic FE model of the welded structures is used in damage identification exercise, consisting of two parts: (I) identification of defects, and (2) identification of real damage in the welded structure. In the first part, a defective structure is selected from the set of nominally identical structures and FE model updating procedure is performed in order to quantify the defects in the defective structure. In this exercise, only the natural frequencies are employed in the identification procedure and the identified defects are found to be reasonable and in agreement with the findings from visual inspection conducted prior to the identification work. In identifying real damage in the welded structure, the identification procedure is conducted based on the natural frequencies and the mode shapes information of the damaged structure. The damage is characterised by the reductions in the Young's modulus of the weld patches to indicate the loss of material/stiffness at the damage region. Based on the updating results, it can be concluded that the identification procedure has successfully identified, localised and quantified the damage. The identification procedure also brings the predicted natural frequencies closer to their measured counterparts, with a very good correlation is achieved between the numerical and experimental modes.
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Хоменко, Олексій Віталійович, Алексей Витальевич Хоменко, Oleksii Vitaliiovych Khomenko, B. N. J. Persson, М. А. Khomenko, and S. V. Rudenko. "Synergetic model of frictional softening of ice surface layer." Thesis, Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна Національної академії наук України, 2015. http://essuir.sumdu.edu.ua/handle/123456789/41630.
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Chu, Feng. "Validation of a Lagrangian model for laser-induced fluorescence." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6077.
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Extensive information can be obtained on wave-particle interactions and wave fields by direct measurement of perturbed ion distribution functions using laser-induced fluorescence (LIF). For practical purposes, LIF is frequently performed on metastable states that are produced from neutral gas particles and ions in other electronic states. If the laser intensity is increased to obtain a better LIF signal, then optical pumping can produce systematic effects depending on the collision rates which control metastable population and lifetime. We numerically simulate the ion velocity distribution measurement and wave-detection process using a Lagrangian model for the LIF signal. The simulations show that optical pumping broadening affects the ion velocity distribution function (IVDF) $f_0(v)$ and its first-order perturbation $f_1(v,t)$ when laser intensity is increased above a certain level. The results also suggest that ion temperature measurements are only accurate when the metastable ions can live longer than the ion-ion collision mean free time. For the purposes of wave detection, the wave period has to be significantly shorter than the lifetime of metastable ions for a direct interpretation. Experiments are carried out to study the optical pumping broadening and metastable lifetime effects, and the results are compared with the simulation in order to validate the Lagrangian model for LIF. It is more generally true that metastable ions may be viewed as test-particles. As long as an appropriate model is available, LIF can be extended to a range of environments.
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Kim, Jae Hong. "Wide-Band and Scalable Equivalent Circuit Model for Multiple Quantum Well Laser Diodes." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7129.
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This dissertation presents a wide-band lumped element equivalent circuit model and a building block-based scalable circuit model for multiple quantum well laser diodes. The wide-band multiple-resonance model expresses two important laser diode characteristics such as input reflection and electrical-to-optical transmission together. Additionally, it demonstrates good agreements with the measurement results of the selected commercial discrete laser diodes. The proposed building block-based modeling approach proves its validity using a numerically derived scalable rate equation. Since success in a circuit design depends largely on the availability of accurate device models, the practical application of the proposed models provides improved accuracy, simple implementation and a short design time.
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Walid, Hanna Motaz. "Aanvändning av lantmäteriets nya nationella höjdmodell (laserdata) i skogsmark." Thesis, Högskolan Väst, Avdelningen för data-, elektro- och lantmäteriteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-10352.
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Detta arbete redogör för hur användning av den nya nationella höjdmodellen (NNH) ur/i Lantmäteriet databas kan användas i olika terräng och vilka förutsättningar det finns för identifiering av specifika landskapselement i denna, manuellt och visuellt. Sedan 2009 har Lantmäteriet laserskannat hela landet, både på land och över vatten. Uppdraget är slutfört 2015. Målet med laserskanning är att framställa en rikstäckande höjdmodell med ett medelfel som är bättre än 0.5 m. Idag är all NNH-data tillgänglig som LAS-filer på Lantmäteriets databas. För att kunna utföra ett utvärderingsexperiment valdes ett geografiskt begränsat område: I Skepplanda, Ale kommun i Västra Götalands län. De hjälpmedel som användes var GPS-mottagare, LAS-filer, Ortofoto och applikationsprogram såsom OL-laser och ArcGis. Det främsta syftet med studien var att undersöka hur bearbetning och utvärdering av olika kartmaterial kan utföras, för att sedan kunna bedöma i vilken mån användning av Lantmäteriets NNH-data, i olika typer av terräng, kan vara möjlig t.ex. hur små detaljer kan urskiljas i det. För undersökningen valdes specifika objekt, såsom stenmurar och ett dike. Tre olika kartunderlag framtogs av OL-laserprogrammet: lutningsbilder, intensitetsbilder och terrängskuggningsbilder. Utifrån insamling av inmätta punkter och med hjälp av vektordata kunde materialet utvärderas visuellt. Två kartor valdes, vilka uppfyllde kriterierna för att kunna uppnå studiens syfte. Eftersom kartan med terrängskuggning och lutningsbild ger en tydligare profil av områdets karaktäristiska drag på marknivå, är det möjligt att identifiera små markdetaljer såsom stenmurar och diken. Resultatet varierade från fall till fall, beroende på kartunderlaget. En mur på den ena platsen i en bild kunde t.ex. detekteras, men inte i en annan bild, trots att det finns en mur där. Studien visade att laserpulserna har svårt att tränga igenom tät vegetation, dock kan olika solvinklar och belysningsriktningar ändå framhäva vissa små markdetaljer under en tätskog. Andra faktorer som kan ha påverkat kvalitén på lasermaterialet är flyghöjden, laserskannerns vinkel och under vilken period under året skanningen genomfördes. Ett antagande gjordes, att laserskanning från lägre flyghöjd och mindre öppningsvinkel kan höja kvalitén på laserdata. Med dessa två faktorer kan högre upplösning per kvadratmeter yta uppnås. Ett annat sätt som kan vara aktuellt i en undersökning är att använda OL-laser verktygslåda och tillämpa andra inställningar genom att skapa objekthöjdbilder där höjd färgläggs med olika ekvidansnivå. Genom att prova fram olika inställningar i programmet, där olika lutningshöjd och solvinklar tillämpas kan läsbarheten på kartunderlaget förbättras.<br>This work describes how the use of the new national elevation model (NNH) from the National Land Survey database may be used in a variety of terrain and the conditions they are identification of specific landscape elements, manually and visually. From the start of 2009, the national land Survey laserscannat whole country, both on land and over water. The mission will be completed in 2015. The goal of laser scanning is to produce a nationwide elevation model with a standard error of better than 0.5 m for a 2 m GRID. Today, all NNH data available as LAS files on Lantmäteriet's database. To perform an evaluation experiment was elected a geographically limited area: Skepplanda, Ale Municipality in Västra Götaland. The devices used were GPS receiver, LAS files, Orth imagery and application programs such as OL laser and ArcGIS. The main aim of the study was to investigate the processing and evaluation of different map material can be performed, and then to assess to what extent the use of Lantmäteriets NNH- data in different types of terrain may be possible. For the investigation, the specific items, such as stone walls and a ditch. Three different maps material was developed by the OL laser program: slope images, intensity images and terrain shading images. Based on the collection of measured points and using vector data could material evaluated visually. Two maps were chosen, which met the criteria for being able to achieve the objectives of the study. Since the map with terrain shading and gradient image provides a clearer profile of the area's characteristic features at ground level, it is possible to identify small land features such as stone walls and ditches. Results will vary from case to case, depending on the substrate maps. A wall at one location in an image could e.g. detect, but not in another image, even though it's a wall there. That’s why definitive conclusions could be not established. The study showed that the laser pulses are difficult to penetrate dense vegetation; however different solar angles and lighting directions nonetheless highlight some small land details during a dense forest. Other factor that may have affected the quality of the laser material is the altitude, laser scans angle and during which period of the year the scan was performed. An assumption was made that the laser scans from lower altitude and smaller opening angle can add value to laser data. With these two factors, higher resolution per square meter of surface is achieved. Another way that can be relevant in an investigation is to use the OL laser toolbox and apply different settings to create objects height pictures where height is colored with different evidence level. By trying out different settings in the program, where different slope height and solar angles applied to the readability of the chart surface is improved.
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Berglöf, Patrick, and Love Lind. "Lagereffektivisering : Framtagande av modell." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Industriell organisation och produktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-22435.
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Raabe, Armin, Klaus Arnold, and Astrid Ziemann. "Akustische Tomographie im Bereich der Atmosphärischen Grenzschicht." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 4 = Meteorologische Arbeiten aus Leipzig ; 2 (1996), S. 113-123, 1996. https://ul.qucosa.de/id/qucosa%3A15058.
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Atmosphärenmodelle, die mit Hilfe numerischer Methoden nach einer Lösung der thermohydrodynamischen Gleichungen unter bestimmten Randbedingungen über einer vorgegebenen Unterlage (Landschaft) suchen, prognostizieren Volumenmittel entsprechender Größen. Zur
Validierung der Modelle benötigte experimentell erfaßte meteorologische Größen repräsentieren meist Punktwerte. Im folgenden werden theoretische Ansätze und eine experimentelle Meßmethode vorgestellt, die es ermöglichen, volumengemittelte Werte meteorologischer Größen bereitzustellen und somit zu numerischen Atmosphärenmodellen weitgehend konsistente Daten zu liefern. Die Verfahren verwenden die horizontale Ausbreitung von Schallwellen in der Atmosphärischen Grenzschicht. Die Ableitung volumenbezogener Größen erfolgt über die Invertierung von Schallparameterwerten (akustische Tomographie).<br>Atmospheric models, which searching by means of numerical methods after a solution of the thermodynamic equations under determined border conditions over a given underground (landscape), forecast volume averaged values of corresponding parameters. The experimental registrated values for meteorolgical parameters used for the validation of models represent usually point values. In following chapters theoretical estimations and an experimental measuring method are presented which volume averaged values of meteorolgical parameters provide and so rather firm data for numerical atmospheric models deliver. The proceedings use horizontal spreading of acoustic waves in the Atmospheric Boundary Layer. Derivation of volume averaged parameters results from the invertation of acoustic parameter values (acoustic tomography).
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Stewart, I. J. "A model for transition by attachment line contamination and an examination of cross-flow instability in three-dimensional boundary layers." Thesis, Cranfield University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380625.
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Kuběna, Michael. "Vhodnost modelování skutečného modelu půdy náhradním jednovrstvým nebo dvouvrstvým horizontálním modelem půdy." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-400578.
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The present thesis deals with soil resistivity and especially the suitability of replacing various soil models with a two-layer horizontal model. First, the factors that influence soil resistivity as well as the methodology of its measuring are described, and various soil models are introduced. Then, the Ansys program was used to create several soil models: a vertical model with perpendicular or oblique division, a model with a pronounced inhomogeneity and a three-layer model. In all of these models, a Wenner measurement simulation was performed, followed by a two-layer horizontal replacement model. Then the size of the error that was created by replacing the actual model with a two-layer horizontal model was examined.
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Harris, Brad G. "Analysis of lateral boundary effects on inner domain of COAMPS." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Sep%5FHarris.pdf.
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Thesis (M.S. in Meteorology and Physical Oceanography and M.S. in Applied Mathematics)--Naval Postgraduate School, Sept. 2004.<br>Thesis advisor(s): Douglas K. Miller, Beny Neta. Includes bibliographical references (p. 83). Also available online.
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Miller, Teresa S. "Turbulent boundary layer models for acoustic analysis." Diss., Wichita State University, 2011. http://hdl.handle.net/10057/3933.
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An analysis of the three types of turbulent boundary layer (TBL) models for acoustic analysis is presented because current preferred models over-predict TBL contributions to aircraft interior noise predictions. The mean square pressure is a measure of the total energy due to the pressure fluctuations beneath a turbulent boundary layer. The single point wall pressure spectrum sorts the energy into frequencies. The normalized wavenumber-frequency spectrum sorts the energy into wavenumbers. The pressure fluctuations beneath a turbulent boundary layer are found by solving the Poisson equation. In this work, the Poisson equation is solved both numerically and analytically using data from an LES/DES simulation. The numerical solution uses the point Gauss-Seidel method and has reasonable results. The analytical solution uses an eigenvalue expansion method that is less successful. The empirical mean square pressure models predict a relatively large spread in the pressure fluctuation values. It is difficult to draw any meaningful conclusions on which mean square pressure model is preferred when compared to data from the Spirit AeroSystems 6x6 duct. The single point wall pressure spectrum models are evaluated and the two more modern models of Smol’yakov and Goody seem to perform the best. These models are also compared to data from the Spirit AeroSystems 6x6 duct. The spectrum at low frequencies rolled off similar to the Goody model. This analysis indicates that the Goody model is the appropriate single point wall pressure spectrum model for aircraft applications. Important features of the normalized wavenumber-frequency spectrum models are presented and can be classified as either separable or non-separable. Separable models in the Corcos normalized wavenumber-frequency spectrum model class tend to over-predict the response for a range of cases. Both the non-separable Chase 1 and Smol’yakov-Tkachenko models appear to match the M.I.T. low noise, low turbulence wind tunnel data throughout the range of comparison. The Smol’yakov-Tkachenko model does not lend itself to straight forward Fourier transforms needed by the acoustic models. But the Chase 1 model can be converted from wavenumber-frequency spectrum to the cross spectrum, so it is the preferred model for aircraft applications. Therefore, the preferred turbulent boundary layer models for aircraft interior noise predictions are the single point wall pressure spectrum model of Goody and the normalized wavenumber-frequency spectrum model of Chase 1.<br>Dissertation (Ph.D.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering
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Wykes, James G. "Numerical models for high power laser diodes." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420361.
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Kummailil, John. "Process models for laser engineered net shaping." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0429104-103828.
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Thesis (Ph. D.)--Worcester Polytechnic Institute.<br>Keywords: rapid prototyping; solid freeform fabrication; LENS; laser engineered net shaping; laser; titanium. Includes bibliographical references (p. 83-85).
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Jakobsen, Per Kristen. "Stability and instability in two laser models." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185255.
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In the first part we study linear stability of travelling wave solutions of a system of equations derived from the Maxwell-Bloch system by adiabatically eliminating the polarization. For the reduced system we find exact conditions for stability and instability. We also find that the adiabatic elimination procedure produces a very badly behaved system in the presence of diffraction. The full Maxwell-Bloch system or the system we get by removing both the polarization and the inversion adiabatically does not have these problems. In the second part we study the stability of index guided laser arrays using an ODE model derived by a coupled mode approach. Stationary solutions to the model equations are found under free running and injection locking conditions and their stability are investigated numerically and analytically for large arrays.
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Gustafsson, Emil. "Tailoring Adhesion and Wetting Properties of Cellulose Fibres and Model Surfaces Using Layer-by-Layer Technology." Doctoral thesis, KTH, Fiberteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155932.
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The versatile layer-by-layer (LbL) technique, for consecutive adsorption of polyelectrolytes and charged nanoparticles onto a substrate, was used to modify cellulose fibres and model surfaces for improved mechanical and wetting properties. In addition to being used to modify cellulose substrates, the LbL technique was also used to create cellulose surfaces suitable for high resolution adhesion measurements. LbL assembly of cellulose nanofibrils and polyethylenimine was used to prepare cellulose model surfaces on polydimethylsiloxane hemispheres which allowed for the first known Johnson-Kendall-Roberts (JKR) adhesion measurements between cellulose and smooth, well-defined model surfaces of cellulose, lignin and glucomannan. The work of adhesion on loading and the adhesion hysteresis were comparable for all three systems which suggest that adhesion between wood constituents is similar. The LbL technique was also used to decrease the hydrophilicity of paper, while improving the dry strength, by coating cellulose fibres with a polylallylamine hydrochloride (PAH) and polyacrylic acid (PAA) LbL film, followed by adsorption of anionic wax particles. Paper sheets made from the modified fibres were highly hydrophobic with a contact angle of 150°, while retaining, and in some cases improving, the tensile index of the paper. It was also observed that PAH/PAA modified sheets without the addition of wax became hydrophobic when heat treated. The mechanism behind the increased hydrophobicity was studied by the interface sensitive technique, vibrational sum frequency spectroscopy, which indicated that the increased hydrophobicity is a result of the reorientation of polymer chains to expose more hydrophobic CH2 and CH groups at the polymer-air interface. Paper sheets prepared from LbL-modified bleached softwood fibres using PAH and the biopolymer hyaluronic acid (HA) exhibited a 6.5% strain at break and a tensile index which was increased 3-fold compared to unmodified fibres. The wet adhesive properties of the PAH/HA system were studied by colloidal probe atomic force microscopy and correlated to film growth and viscoelastic behavior. The presence of background salt was a crucial parameter for achieving high adhesion but time in contact and LbL film thickness also strongly affected the adhesion. Finally, the wet adhesive properties of carboxymethylcellulose (CMC), which had been irreversibly adsorbed to regenerated cellulose, and polyvinylamine (PVAm) were evaluated by means of 90° peel tests. Strong wet adhesion was achieved for dried rewetted samples without any obvious chemical crosslinking, which was attributed to interdigitation and complex formation in PVAm-CMC films. This system also gave significant wet adhesion for non-dried systems at water contents around 45%.<br><p>QC 20141117</p>
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Bennett, Philip Desmond. "Spherically symmetric model atmospheres for late-type giant stars." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30908.
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The ATHENA computer code has been developed to model the extended atmospheres of late-type giant and supergiant stars. The atmospheres are assumed to be static, spherically
symmetric and in radiative and hydrostatic equilibrium. Molecular line blanketing (for now) is handled using the simplifying assumption of mean opacities. The complete linearization method of Auer and Mihalas [7], adapted to spherical geometry, is used to solve the model system. The radiative transfer is solved by using variable Eddington factors to close the system of moment transfer equations, and the entire system of transfer
equations plus constraints is solved efficiently by arrangement into the Rybicki [83] block matrix form. The variable Eddington factors are calculated from the full angle-dependent formal solution of the radiative transfer problem using the impact parameter method of Hummer, Kunasz and Kunasz [47]. We were guided by the work of Mihalas and Hummer [72] in their development of extended models of O stars, but our method differs in the choice of the independent variable. The radius depth scale used by Mihalas and Hummer was found to fail because of the strongly temperature-dependent opacities of late-type atmospheres. Instead, we were able to achieve an exact linearization of the radius. This permitted the use of the numerically well-behaved column mass or optical
depth scales. The resulting formulation is analogous to the plane-parallel complete linearization method and reduces to this method in the compact atmosphere limit.
Models of M giants were calculated for T[formula omitted] = 3000K and 3500K with opacities of the CN, TiO and H₂0 molecules included, and the results were in general agreement with other published spherical models. These models were calculated assuming radiative equilibrium. The importance of convective energy transport was estimated by calculating the convective flux that would result from the temperature structure of the models. The
standard local mixing length theory was used for this purpose. Convection was found to be important only at depths with Ƭ[formula omitted] > 15 for the low gravity models with log g = 0, but significant out to Ƭ[formula omitted] ~ 1 at the most transparent frequencies for the higher gravity models with log g = 2. Thus, the temperature structure of the surface layers and the emergent flux for the log g = 0 models should be accurately modelled but the emergent flux for the log g = 2 models may be in error by up to 5% at the most transparent frequencies.<br>Science, Faculty of<br>Physics and Astronomy, Department of<br>Graduate
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Mrůzek, Tomáš. "3D model vybraného objektu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2021. http://www.nusl.cz/ntk/nusl-444254.
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This diploma thesis describes the implementation of a 3D model of two objects using laser scanning. This paper deals with the accuracy evaluation of several data interpretation. The first two methods are the outputs of the results from the FARO SCENE program and other interpretations are the outputs from the TRIMBLE REAL WORKS program. To assess accuracy and veracity, the exact test field of points previously built in the AdMas complex was used. The result of the project is a georeferenced 3D model of two objects with the surrounding environment.
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Adams, Barry D. O. "Models of fluid microstructure." Thesis, University of Kent, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308827.
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