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Atkinson, Juan Pablo. "Cost model for bipolar plate manufacture." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71625.
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Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: This thesis gives a cost model for the manufacture of bipolar plates in South Africa. The methods for the manufacture considered are machining, using a micro-milling machine, and compression moulding. The focus of this thesis is on compression moulding. Details of the work done towards developing and validating the models are described, and then the cost models are discussed in detail. The results of the analysis done using the cost model is given with attention paid to the effect of changing design parameters, such as channel size and flow field area, and of the cost of production for both methods over various production volumes. The thesis concludes that compression moulding becomes the better option for production volumes greater than 324 bipolar plates, with a cost that eventually reaches close to R140 per plate for high enough production volumes (over 5000). The cost to produce 1000 plates using compression moulding is estimated at R294 per plate. An increase of the channel size gives a small reduction in the total cost, while the increase in cost with an increase in flow field area is large.
AFRIKAANSE OPSOMMING: Hierdie tesis gee 'n koste-model vir die vervaardiging van bipolêre plate in Suid- Afrika. Die vervaardigingsmetodes wat oorweeg word, is masjinering deur 'n mikro-freesmasjien en persvorming. Die fokus van hierdie tesis is op persvorming. Die besonderhede van die ontwikkeling en validering van die modelle word beskryf, en daarna word die modelle in besonderhede beskryf. Die resultate van 'n analise wat met die koste-model gedoen is, word daarna gegee, met die oorweging van die verandering van ontwerp-parameters soos die vloeikanaalgrootte en vloeiveld-area, en van die koste van vervaardiging vir beide metodes vir verskeie produksievolumes. Die tesis kom tot die slotsom dat persvorming die voorkeurproses is vir produksievolumes groter as 324 bipolêre plate, met 'n koste wat tot naastenby R140 per plaat daal vir hoë produksievolumes (meer as 5000). Die koste om 1000 plate met persvorming te maak, word op R294 per plaat beraam. 'n Toename in kanaalgrootte gee 'n klein vermindering in die totale koste, terwyl die toename in koste groot is wanneer die vloeiveld-area toeneem.
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Hanemayer, Vincent C. (Vincent Cornelius) Carleton University Dissertation Engineering Civil. "Dilatometer tests using a model plate." Ottawa, 1989.
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Burlachenko, Sofiia. "Model Ball & Plate: simulace a návrh řízení." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-399283.
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This thesis deals with the identification and regulation of the "Ball & Plate" model. The thesis contains a description of the existing real model and the relevant mathematical and simulation model. The root hodograph method and the state space method are used to calculate the controller, especially the feedback controller with integrator. The final part of the work is devoted to the 3D model construction using Simulink and SimScape, which describes and visualizes the behavior of the real model and enables simulation experiments to be performed quickly and easily.
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Jayasuriya, Wadu M. L. "Dynamic analysis of circular plate on elastic foundation using modified Vlasov model." Ohio : Ohio University, 1992. http://www.ohiolink.edu/etd/view.cgi?ohiou1172686917.
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Schütz, Felina. "Surface heat flow and lithospheric thermal structure of the northwestern Arabian Plate." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/6962/.
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The surface heat flow (qs) is paramount for modeling the thermal structure of the lithosphere. Changes in the qs over a distinct lithospheric unit are normally directly reflecting changes in the crustal composition and therewith the radiogenic heat budget (e.g., Rudnick et al., 1998; Förster and Förster, 2000; Mareschal and Jaupart, 2004; Perry et al., 2006; Hasterok and Chapman, 2011, and references therein) or, less usual, changes in the mantle heat flow (e.g., Pollack and Chapman, 1977). Knowledge of this physical property is therefore of great interest for both academic research and the energy industry.
The present study focuses on the qs of central and southern Israel as part of the Sinai Microplate (SM). Having formed during Oligocene to Miocene rifting and break-up of the African and Arabian plates, the SM is characterized by a young and complex tectonic history. Resulting from the time thermal diffusion needs to pass through the lithosphere, on the order of several tens-of-millions of years (e.g., Fowler, 1990); qs-values of the area reflect conditions of pre-Oligocene times. The thermal structure of the lithosphere beneath the SM in general, and south-central Israel in particular, has remained poorly understood.
To address this problem, the two parameters needed for the qs determination were investigated. Temperature measurements were made at ten pre-existing oil and water exploration wells, and the thermal conductivity of 240 drill core and outcrop samples was measured in the lab. The thermal conductivity is the sensitive parameter in this determination. Lab measurements were performed on both, dry and water-saturated samples, which is labor- and time-consuming. Another possibility is the measurement of thermal conductivity in dry state and the conversion to a saturated value by using mean model approaches. The availability of a voluminous and diverse dataset of thermal conductivity values in this study allowed (1) in connection with the temperature gradient to calculate new reliable qs values and to use them to model the thermal pattern of the crust in south-central Israel, prior to young tectonic events, and (2) in connection with comparable datasets, controlling the quality of different mean model approaches for indirect determination of bulk thermal conductivity (BTC) of rocks.
The reliability of numerically derived BTC values appears to vary between different mean models, and is also strongly dependent upon sample lithology. Yet, correction algorithms may significantly reduce the mismatch between measured and calculated conductivity values based on the different mean models. Furthermore, the dataset allowed the derivation of lithotype-specific conversion equations to calculate the water-saturated BTC directly from data of dry-measured BTC and porosity (e.g., well log derived porosity) with no use of any mean model and thus provide a suitable tool for fast analysis of large datasets.
The results of the study indicate that the qs in the study area is significantly higher than previously assumed. The new presented qs values range between 50 and 62 mW m⁻². A weak trend of decreasing heat flow can be identified from the east to the west (55-50 mW m⁻²), and an increase from the Dead Sea Basin to the south (55-62 mW m⁻²). The observed range can be explained by variation in the composition (heat production) of the upper crust, accompanied by more systematic spatial changes in its thickness.
The new qs data then can be used, in conjunction with petrophysical data and information on the structure and composition of the lithosphere, to adjust a model of the pre-Oligocene thermal state of the crust in south-central Israel. The 2-D steady-state temperature model was calculated along an E-W traverse based on the DESIRE seismic profile (Mechie et al., 2009). The model comprises the entire lithosphere down to the lithosphere–asthenosphere boundary (LAB) involving the most recent knowledge of the lithosphere in pre-Oligocene time, i.e., prior to the onset of rifting and plume-related lithospheric thermal perturbations. The adjustment of modeled and measured qs allows conclusions about the pre-Oligocene LAB-depth. After the best fitting the most likely depth is 150 km which is consistent with estimations made in comparable regions of the Arabian Shield. It therefore comprises the first ever modelled pre-Oligocene LAB depth, and provides important clues on the thermal state of lithosphere before rifting. This, in turn, is vital for a better understanding of the (thermo)-dynamic processes associated with lithosphere extension and continental break-up.Der Oberflächenwärmefluss (qs) ist maßgeblich für die Modellierung der thermischen Struktur der Lithosphäre. Änderungen im qs, innerhalb eines speziellen lithosphärischen Abschnitts, reflektieren direkt Änderungen in der krustalen Zusammensetzung und damit der radiogenen Wärmeproduktion (e.g., Rudnick et al., 1998; Förster und Förster, 2000; Mareschal und Jaupart, 2004; Perry et al., 2006; Hasterok und Chapman, 2011) oder aber, weniger häufig, Änderungen im Mantelwärmefluss (e.g., Pollack und Chapman, 1977). Die Kenntnis dieses physikalischen Parameters ist daher von großem Interesse, sowohl für die Forschung als auch für die Energiewirtschaft. Die vorliegende Studie befasst sich mit dem qs von Süd- und Zentralisrael als Teil der Sinai Mikroplatte (SM), welche während des Riftings und Auseinanderbrechens der Afrikanischen und Arabischen Platte im Oligozän entstand und durch diese, sehr junge und komplexe tektonische Geschichte, geprägt ist. Die thermische Diffusion benötigt einige Zehner-Millionen Jahre (e.g., Fowler, 1990) um die Lithosphäre zu durchlaufen, qs-Werte der Region reflektieren daher prä-oligozäne Bedingungen. Die thermische Struktur der Lithosphäre in Süd- und Zentralisrael, ist bis heute nur sehr wenig verstanden. Um dieses Problem anzugehen wurden die Parameter die für die qs-Bestimmung benötigt werden, eingehend untersucht. An zehn ehemaligen Wasser- und Erdölexplorationsbohrungen wurden neue Temperaturmessungen durchgeführt, und die Wärmeleitfähigkeit von 240 Bohrkern- und Aufschlussproben wurde im Labor gemessen. Die Wärmeleitfähigkeit ist in der qs-Bestimmung der sensitive Parameter. Die Labormessungen wurden sowohl an trockenen sowie an wasser-gesättigten Proben durchgeführt, was personal-und zeitaufwendig ist. Eine andere Möglichkeit ist die Messung der Wärmeleitfähigkeit im trockenen Zustand und das Konvertieren zu einem saturierten Wert unter der Verwendung von Mischungsgesetzen. Das Vorhandensein eines umfangreichen und sehr diversen Wärmeleitfähigkeit-Datensatzes ermöglicht (1) in Verbindung mit dem Temperaturgradienten die Berechnung von neuen zuverlässigen qs-Werten sowie deren Verwendung zur Modellierung der thermischen Struktur der prä-oligozänen Kruste in Israel und (2) in Verbindung mit vergleichbaren Datensätzen, die vorhandenen Mischungsgesetzte zur indirekten Bestimmung der saturierten Gesamtwärmeleitfähigkeit (BTC) qualitativ zu überprüfen. Die Zuverlässigkeit numerisch bestimmter BTC-Werte variiert für die verschiedenen Mischungsgesetze und ist darüber hinaus stark von der Lithologie der Proben abhängig. Mittels spezifischer Korrekturgleichungen können Abweichungen zwischen gemessenen und berechneten Werten jedoch erheblich reduziert werden. Die Datenanzahl und die statistische Analyse ermöglichte darüber hinaus die Ableitung von lithotypspezifischen Konvertierungsgleichungen, um die saturierte BTC anhand von trocken gemessenen BTC- und Porositätswerten (z.B. aus Logs) zu berechnen. Dieser Ansatz führt, für alle Lithotypen, zu einer guten Reproduzierbarkeit gemessener Werte und ist daher eine nützliche Alternative, wann immer große Probenmengen behandelt werden. Die Ergebnisse dieser Studie zeigen, dass der qs im Untersuchungsgebiet signifikant höher ist, als bisher angenommen. Die qs-Werte, die in dieser Studie für Israel bestimmt wurden, schwanken zwischen 50 und 62 mW m⁻². Ein schwacher Trend abnehmender Werte von Ost nach West (55-50 mW m⁻²), und ein leichter Trend ansteigender Werte vom Toten Meer nach Süden (55-62 mW m⁻²) können identifiziert werden. Diese beobachteten Schwankungen lassen sich mit Variationen in der krustalen Zusammensetzung (Wärmeproduktion) erklären, einhergehend mit regionalen Änderungen der Krustenmächtigkeit. Die neuen qs-Daten können dann, im Zusammenhang mit petrophysikalischen Daten und Informationen über die Struktur und Zusammensetzung der Lithosphäre, verwendet werden um ein Model des prä-oligozänen thermischen Zustandes der Kruste Zentral- und Südisraels abzugleichen. Das stationäre 2-D Temperatur-Modell wurde entlang einer E-W Traverse, basierend auf dem seismischen DESIRE-Profil (Mechie et al., 2009), berechnet. Es reicht bis zur Lithosphären–Asthenosphären Grenze (LAB) und bezieht sich auf das aktuellste Wissen über die prä-oligozäne Lithosphäre, also vor dem Einsetzen von Rifting und plumebedingten thermischen Störungen. Durch den Abgleich zwischen gemessenen und modellierten qs-Werten ist es möglich auf die prä-oligozäne LAB-Tiefe zurückzuschließen. Als wahrscheinlichste Tiefe ergeben sich 150 km, was konsistent ist mit LAB-Tiefen Abschätzungen aus vergleichbaren stabilen Regionen des Arabischen Schildes. Dies liefert wichtige Anhaltspunkte über den thermischen Zustand der Lithosphäre vor dem Einsetzen von Rifting in der Region und ist wiederum entscheidend für ein besseres Verständnis der dynamischen Prozesse in Assoziation mit Extension der Lithosphäre und dem kontinentalem Auseinanderbrechen.
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Afhami, Shahab. "Strip model for capacity of flat plate-column connections." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq22943.pdf.
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Kuppa, Subrahmanyam. "End plate gap effects on a half-wing model." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/44054.
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Differences in the aerodynamic performance data obtained at different test facilities were observed for the Wortmann FX-63-l37 airfoil. Earlier investigations found that the size of the hysteresis loop was affected by the tunnel environment and that single strut mounting of a three dimensional wing model interfered negligibly with the wing. Theoretical and experimental evaluations of a half wing model mounted with an end plate gap were done. Vortex panel method was used in the theoretical evaluation. The results from this indicated an effect of reduced aspect ratio with increase in end plate gap size.
Tests were conducted in the VPI Stability Tunnel at low Reynolds numbers for different gap sizes including sealed gap. Results from the experiments showed that even very small gaps produce substantial changes in zero lift angle of attack (αu) and the change in αu, was reduced as Reynolds number increased. Sealed gap test results did not show such a behavior. Flow visualization of the flow through the gap showed a significant flow through the gap even at very low Reynolds number and small gap size.
Master of Science
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Milde, Lucy(Lucy E. ). "Model of reflectance of thermophotovoltaic cell and cold plate." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127903.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 22-23).
The reflectivity of a gold-plated cold plate, and mounted multi-junction photovoltaic cells, is studied in the context of a thermal energy grid storage system. The emitter is modeled as a black body emitter. Improving the efficiency of the system requires high reflectance below the bandgap energy of the cells, and high absorption above the bandgap. The matrix transfer method is used to predict the total reflectance of the cell, and to study the effect of changing the thickness of the most significant layer. Decreasing the thickness of this layer can lead to a higher reflectance below the bandgap, but more data is needed to fully integrate the effect of doping concentration (using the Drude model) into these reflectance calculations.
by Lucy Milde.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Bardin, Sébastien. "Vers un Model Checking avec accélération plate des systèmes hétérogènes." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2005. http://tel.archives-ouvertes.fr/tel-00131834.
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Cette thèse s'inscrit dans le cadre de la vérification formelle de systèmes informatiques. Plus exactement nous nous intéressons au calcul de l'ensemble d'accessibilité d'automates étendus par des variables à domaines infinis. Bien que cet ensemble ne soit pas récursif en général, des techniques à base d'accélération permettent de le calculer en pratique. Cependant ces méthodes sont encore mal connues. Nous nous intéressons à l'étude de l'accélération, des points de vue théorique, algorithmique et implantation logicielle.
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Prasad, Suryanarayana A. N. "Two-port electroacoustic model of a piezoelectric composite circular plate." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE0000594.
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Kohli, Karan. "Structural Dynamics Model Calibration and Validation of a Rectangular Steel Plate Structure." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396454705.
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Baldwin, Metzger Kirsten Anne. "Experimental Verification of a New Single Plate Shear Connection Design Model." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/32576.
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Single plate shear connections are designed to have sufficient strength to resist the shear force and moment transferred from the beam. The connections must also provide sufficient ductility to allow the beam end to rotate freely. In the United States the current recommended design method is found in the AISC 13th Edition Steel Construction Manual (2005b). The limited experimental work which led to the current method necessitated additional single plate shear connection investigations.
This paper summarizes the results and analysis of eight full scale single plate shear connections tested at Virginia Polytechnic Institute and State University. The test setup consisted of a test beam attached to a test column with a single plate shear connection at one end and supported by a roller at the other end. The single plate was welded to the column flange and bolted to the beam web. Load was applied to the test beam at third points until failure of the connection or test beam.
The current design method used in the United States was examined with respect to the connection tests performed. In particular, the ultimate shear strength and the rotational capacity were investigated. Suggestions are made regarding changes to the method and further research.Master of Science
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Chantalakhana, Chak. "Model-based control of plate vibrations using active constrained layer damping." Thesis, University of Sheffield, 2000. http://etheses.whiterose.ac.uk/14796/.
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In this thesis, the author presents a numerical and experimental study of the application of active constrained layer damping to a clamped-clamped plate. Piezoelectric actuators with modal controllers are used to improve the performance of vibration suppression from the passive constrained layer damping treatment. Surface damping treatments are often effective at suppressing higher frequency vibrations in thin-walled structures such as beams, plates and shells. However, the effective suppression of lower frequency modes usually requires the additional of an active vibration control scheme to augment the passive treatment. Advances in the technologies associated with so-called smart materials are dramatically reducing the cost, weight and complexity of active structural control and make it feasible to consider active schemes in an increasing number of applications. Specifically, a passive constrained layer damping treatment is enhanced with an active scheme employing a piezoceramic (PZT) patch as the actuator. Starting with an established finite element formulation it is shown how model updating and model reduction are required to produce a low-order state-space model which can be used as the basis for active control. The effectiveness of the formulation is then demonstrated in a numerical study. Finally, in the description of the experimental study it is shown how modes in the frequency range from 0 to 600 Hz are effectively suppressed: the two lowest modes (bending and torsional) through active control, the higher modes (around ten in number) by the passive constrained damping layer. The study'S original contribution lies in the experimental demonstration that given a sufficiently accurate model of the plate and passive constrained damping layer, together with a suitable active feedback control algorithm, spillover effects are not significant even when using a single sensor and single actuator. The experimental traces show, in some instances, minor effects due to spillover. However, it can be concluded that the presence of the passive layer introduces sufficient damping into the residual modes to avoid any major problems when using only the minimum amount of active control hardware.
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Bourret, Pierre. "Modèle à Composant pour Plate-forme Autonomique." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENM083/document.
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Ces dernières décennies, les environnements informatiques sont devenus de plus en plus complexes, parsemés de dispositifs miniatures et sophistiqués gérant la mobilité et communiquant sans fil. L'informatique ubiquitaire, telle qu'imaginée par Mark Weiser en 1991, favorise l'intégration transparente de ces environnements avec le monde réel pour offrir de nouveaux types d'applications. La conception de programmes pour environnements ubiquitaires soulève cependant de nombreux défis, en particulier le problème de rendre une application auto-adaptable dans un contexte en constante évolution. Parallèlement, alors que la taille et la complexité de systèmes plus classiques ont explosé, IBM a proposé le concept d'informatique autonomique afin de réduire le fardeau de l'administration de systèmes imposants et largement disséminés. Cette thèse se base sur une approche où les applications sont conçues sous la forme de composants utilisant et fournissant des services. Un modèle de développement fondé sur une architecture de référence pour la conception d'applications ubiquitaires est proposée, fortement inspiré des recherches dans le domaine de l'informatique autonomique. Dans ce modèle, les applications sont prises en charge par une hiérarchie de gestionnaires autonomiques, qui appuient leurs décisions sur une représentation centrale du système. La mise en œuvre de cette contribution requiert de rendre la couche d'exécution sous-jacente plus réflexive, en vue de supporter de nouveaux types d'adaptations à l'exécution. Nous proposons également un modèle qui décrit le système à l'exécution et reflète sa dynamique de manière uniforme, suivant les principes du style d'architecture REST. Les applications reposant sur ce cette couche d'exécution réflexive et représentées par ce modèle sont qualifiées d'Autonomic-Ready. L'implantation de nos propositions ont été intégrées dans le modèle à composant orienté service Apache Felix iPOJO. Le modèle de représentation du système, nommé Everest, est publié en tant que sous-projet d'OW2 Chameleon. Ces propositions ont été évaluées et validées par la conception et l'exécution d'une application ubiquitaire sur iCASA, un environnement de développement et de simulationIn the last decades, computing environments have been getting more and more complex, filled with miniaturized and sophisticated devices that can handle mobility and wireless communications. Ubiquitous computing, as envisioned by Mark Weiser in 1991, promote the seamless integration of those computing environments with the real world in order to offer new kinds of applications. However, writing software for ubiquitous environments raises numerous challenges, mainly the problem of how to make an application adapt itself in an ever changing context. From another perspective, as classical softwares were growing in size and complexity, IBM proposed the concept of autonomic computing to help to contain the burden of administering massive and numerous systems. This PhD thesis is based on an approach where applications are designed in terms of components using and providing services. A development model based on a reference architecture for the conception of ubiquitous applications is proposed, greatly inspired by researches in the autonomic computing field. In this model, the application is managed by a hierarchy of autonomic managers, that base their decisions on a central representation of the system. The fulfilment of this contribution requires to make the underlying middleware more reflexive, in order to support new kinds of runtime adaptations. We also provide a model that depicts the running system and its dynamics in a uniform way, based on REST principles. Applications relying on this reflexive middleware and represented by this model are what we called Autonomic-Ready. Implementations of our proposals have been integrated in the Apache Felix iPOJO service-oriented component model. The system representation, named Everest, is provided as a OW2 Chameleon subproject. Validation is based on the iCASA pervasive environment development and simulation environment
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Keating, Pierre B. "The inversion of time-domain airborne electromagnetic data using the plate model /." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75772.
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Airborne electromagnetic methods were developed in the early 1950's, mostly by Canadian mining exploration companies as a means of economically and successfully searching large areas for conductive massive sulfide mineralisations. As new technologies developed they have become more and more sophisticated. They can detect conductors at depths in excess of 200 m and are routinely used for overburden mapping. The data is digitally recorded and processed. One of the most successful methods is the time domain airborne INPUT$ sp1$ system, for numerous mineral deposits were found by this system in the Canadian Shield.Present interpretation techniques are based on the use of nomograms (i.e. families of pre-computed characteristic responses) and the method is easily amenable to digital processing as it is easy to program and economic to use. For high accuracy interpretation however it is necessary to develop quantitative interpretation techniques that can make full use of all the data available. Inverse theory has been used with great success in all branches of geophysics, but to date in mining exploration it has been used for the interpretation of airborne E.M. data using only the one layer earth model. Use of inverse theory for the plate model has been limited by the high cost of numerically solving the forward problem.
In this thesis we show how to use inverse theory to interpret time domain E.M. data with the rectangular thin plate model by introducing some economies. It is then possible to estimate parameter errors, the correlation matrix and to assess the validity of the model. This is extended to the joint inversion of magnetic and aeromagnetic data a case that often arises in mining problems. It is finally shown that under some assumptions the late time channels can be used to interpret time domain E.M. data in the presence of conductive overburden. ftn$ sp1$Registered trademark of Barringer Research Ltd.
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Brodersen, Scott D. "Dynamic modelling and measurement of a structural model with thin plate elements." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ26987.pdf.
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Petty, David M. "An elasto-viscoplastic finite element model of hot rolling of steel plate." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386760.
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Brodersen, Scott D. (Scott David) Carleton University Dissertation Engineering Civil and Environmental. "Dynamic modelling and measurement of a structural model with thin plate elements." Ottawa, 1997.
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Jacobs, Frederick Julius. "The effect of innovative screw angled mini-plates on biomechanical stability of mono-cortical fixation an in vitro model /." Thesis, Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-10012009-130238/.
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Filipowicz, Dean. "A Biomechanical Comparison of 3.5 Locking Compression Plate Fixation to 3.5 Limited Contact Dynamic Compression Plate Fixation in a Canine Cadaveric Distal Humeral Metaphyseal Gap Model." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/33558.
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Objective- To compare the biomechanical properties of 3.5 locking compression plate (LCP) fixation to 3.5 limited contact dynamic compression plate (LC-DCP) fixation in a canine cadaveric, distal humeral metaphyseal gap model in static axial compression and cyclic axial compression and torsion.
Study Design- Biomechanical in vitro study.
Sample Population- 30 paired humeri from adult, medium to large breed dogs.
Methods- Testing was performed monotonically to failure in axial compression on ten pairs of humeri, cyclically in axial compression for 10,000 cycles on ten pairs and cyclically in torsion for 500 cycles on the last ten pairs.
Results- Humeral constructs stabilized with LCPs were significantly stiffer than those plated with LC-DCPs when loaded in axial compression (P=0.0004). When cyclically loaded in axial compression over 10,000 cycles, the LC-DCP constructs were significantly stiffer than those constructs stabilized with LCPs (P=0.0029). Constructs plated with LC-DCPs were significantly more resistant to torsion over 500 cycles than those plated with LCPs (P<0.0001), though no difference was detected during the first 280 cycles.
Conclusions- The increased stiffness of LCP constructs in monotonic loading compared to constructs stabilized with non-locking plates may be attributed to the stability afforded by the plate-screw interface of locking plates. The LCP constructs demonstrated less stiffness in dynamic testing in this model, likely due to plate-bone offset secondary to non-anatomic contouring and occasional incomplete seating of the locking screws when using the torque-limiting screw driver.
Clinical Relevance- LCPs yield less stiff fixation under dynamic loading than conventional LC-DCPs when applied to severely comminuted, metaphyseal fractures. Improving anatomical contouring of the plate and insuring complete screw insertion into the locking plate hole may improve stiffness when using LCPs in comminuted fractures.Master of Science
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García-Martínez, José Antonio. "Fundamental model for the prediction of distillation sieve tray efficiency : hydrocarbon and aqueous systems /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Khanal, Santosh. "Backcalculation of Plate Loading Tests using PLAXIS 2D and the Hardening Soil Model." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23328.
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Shallow foundations are extensively used to support structures of all sizes in order to safely transmit the structural load to the ground without exceeding the bearing capacity of the ground and causing excessive settlement. They are typically embedded up to a few meters into the soil profile. While designing foundations, two requirements need to be satisfied: complete failure of the foundation must be avoided with adequate margin of safety (bearing capacity) and relative settlement should be within limits that can be tolerated by superstructure. Foundation is that part of the structure which is in direct contact with soil and involves the footing and the ground influenced by the footing. The master thesis aims to back-calculate the load tests using advanced soil models in PLAXIS 2D in order to gather experience on soil behavior and constitutive models. For this, extensive study of literature with full-scale load tests was carried out. Both tests on clay and sand were the theme interest.To examine the plate-load tests, three case studies were selected. In this report, the load-settlement responses of vertically loaded footings placed on both sands and clay were analysed using the finite element method. The numerical analysis was performed using PLAXIS 2D. The soil profiles and parameters used in the analysis were based on either in situ tests or laboratory tests. The Hardening Soil model was used as a material model to analyse the soil behavior. Finally, the load-settlement curves obtained from finite element analysis were compared with those from plate-load tests and see whether they are well fitted.The first case study was on clay till from Sweden. In this case, the back-calculated results showed that c_ref^' = 11.45 to 14.45 kPa and ɸ = 300. The second case was in saprolitic soil from Portugal. In this case, c_ref^' = 8 to 13 kPa and ɸ = 370 to 380. The third case was on sand from USA. In this case, sand shows some varying behavior in stiffness. The stiffness from laboratory tests and back-calculated vary by a factor of 3 to 8. The angle of friction was from 360 to 390.
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Hill, Misha K. (Misha Kim) 1975. "A model of a fundamental-mode Lorentz force actuated flexural plate wave resonator." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80071.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (leaves 37-38).
by Misha K. Hill.
M.Eng.
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Pirttijärvi, M. (Markku). "Numerical modeling and inversion of geophysical electromagnetic measurements using a thin plate model." Doctoral thesis, University of Oulu, 2003. http://urn.fi/urn:isbn:951427119X.
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Abstract
The thesis deals with numerical methods designed for the modeling and inversion of geophysical electromagnetic (EM) measurements using a conductive thin plate model. The main objectives are to study the EM induction problem in general and to develop practical interpretation tools for mineral prospecting in particular.
The starting point is a linearized inversion method based on the singular value decomposition and a new adaptive damping method. The inversion method is introduced to the interpretation of time-domain EM (TEM) measurements using a thin plate in free-space. The central part of the thesis is a new approximate modeling method, which is based on an integral equation approach and a special lattice model. At first the modeling method is applied to the interpretation of frequency-domain EM (FEM) data using a thin plate in conductive two-layered earth. After this time-domain responses are modeled applying a Fourier-sine transform of broadband FEM computations.
The results demonstrate that the approximate computational method can model the geophysical frequency and time-domain EM responses of a thin conductor in conductive host medium with sufficient accuracy, and that the inversion method can provide reliable estimates for the model parameters. The fast forward computation enables interactive interpretation of FEM data and feasible forward modeling of TEM responses. The misfit function mapping and analysis of the singular value decomposition have provided additional information about the sensitivity, resolution, and the correlation behavior of the thin plate parameters.
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Simões, Eduardo Tenório. "Linear and nonlinear hirarchical plate models and a posteriori kinematical error estimator." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-26072016-151855/.
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This study explores the use of hierarchical models to represent three-dimensional solids in a computationally inexpensive way. First, it is investigated the choice of the finite element spaces and how it affects the convergence in relation to the thickness parameter. It was studied three different models. It was shown that the best lowest order suitable combination of spaces grows in all fields as the model order is enriched. After, it is presented a theory to evaluate the error in the discretization and the kinematical hypothesis. It is shown that the implemented error in discretization technique is capable of capturing the boundary layer in automated way for any model. It is also given a posteriori error procedure for kinematical hypothesis. The method is based on the equilibrium error of higher order models. Good results are shown. In the end, it is presented a geometrical nonlinear hierarchical shell model and its discretization. It is shown that the model succeeds in representing the three-dimensional solution when compared with solid elements in a commercial code.Este estudo explora o uso de modelos hierárquicos para representar sólidos tridimensionais de forma computacionalmente barata. Em primeiro lugar, é explorada a escolha dos espaços de elementos finitos e como isso afeta a convergência em relação ao parâmetro da espessura. Foram estudados três modelos diferentes. Mostrou-se que a menor ordem adequada do espaço de discretização cresce para todos os campos conforme a ordem do modelo é enriquecida . Isso impõe um problema, já que um maior polinômio exige maior custo computacional e modelos de alta ordem só são necessários perto do contorno. Depois, são usados estimadores de erro na discretização e na hipótese cinemática. Mostra-se que o erro implementado na discretização é capaz de capiturar a camada limite de forma automatizada para qualquer modelo. Também é apresentada uma técnica de erro a posteriri na hipótese cinemática com base no erro no equilíbrio de modelos de ordem superior. No final, é apresentado um modelo hierárquico de casca geométricamente não linear e sua discretização. Mostra-se que o modelo consegue representar a solução tridimensional quando comparado com o um software comercial.
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Liu, Youhua. "Efficient Methods for Structural Analysis of Built-Up Wings." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/77972.
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The aerospace industry is increasingly coming to the conclusion that physics-based high-fidelity models need to be used as early as possible in the design of its products. At the preliminary design stage of wing structures, though highly desirable for its high accuracy, a detailed finite element analysis(FEA) is often not feasible due to the prohibitive preparation time for the FE model data and high computation cost caused by large degrees of freedom. In view of this situation, often equivalent beam models are used for the purpose of obtaining global solutions. However, for wings with low aspect ratio, the use of equivalent beam models is questionable, and using an equivalent plate model would be more promising.
An efficient method, Equivalent Plate Analysis or simply EPA, using an equivalent plate model, is developed in the present work for studying the static and free-vibration problems of built-up wing structures composed of skins, spars, and ribs. The model includes the transverse shear effects by treating the built-up wing as a plate following the Reissner-Mindlin theory (FSDT). The Ritz method is used with the Legendre polynomials being employed as the trial functions. Formulations are such that there is no limitation on the wing thickness distribution. This method is evaluated, by comparing the results with those obtained using MSC/NASTRAN, for a set of examples including both static and dynamic problems.
The Equivalent Plate Analysis (EPA) as explained above is also used as a basis for generating other efficient methods for the early design stage of wing structures, such that they can be incorporated with optimization tools into the process of searching for an optimal design. In the search for an optimal design, it is essential to assess the structural responses quickly at any design space point. For such purpose, the FEA or even the above EPA, which establishes the stiffness and mass matrices by integrating contributions spar by spar, rib by rib, are not efficient enough.
One approach is to use the Artificial Neural Network (ANN), or simply called Neural Network (NN) as a means of simulating the structural responses of wings. Upon an investigation of applications of NN in structural engineering, methods of using NN for the present purpose are explored in two directions, i.e. the direct application and the indirect application. The direct method uses FEA or EPA generated results directly as the output. In the indirect method, the wing inner-structure is combined with the skins to form an "equivalent" material. The constitutive matrix, which relates the stress vector to the strain vector, and the density of the equivalent material are obtained by enforcing mass and stiffness matrix equities with regard to the EPA in a least-square sense. Neural networks for these material properties are trained in terms of the design variables of the wing structure. It is shown that this EPA with indirect application of Neural Networks, or simply called an Equivalent Skin Analysis (ESA) of the wing structure, is more efficient than the EPA and still fairly good results can be obtained.
Another approach is to use the sensitivity techniques. Sensitivity techniques are frequently used in structural design practices for searching the optimal solutions near a baseline design. In the present work, the modal response of general trapezoidal wing structures is approximated using shape sensitivities up to the second order, and the use of second order sensitivities proved to be yielding much better results than the case where only first order sensitivities are used. Also different approaches of computing the derivatives are investigated. In a design space with a lot of design points, when sensitivities at each design point are obtained, it is shown that the global variation in the design space can be readily given based on these sensitivities.Ph. D.
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Coleman, Rhima M. "Development of a small animal model to study tissue engineering strategies for growth plate defects." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-07092007-093731/.
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Thesis (Ph. D.)--Bioengineering, Georgia Institute of Technology, 2008.Guldberg, Robert, Committee Chair ; Boyan, Barbara, Committee Member ; O'Keefe, Regis, Committee Member ; Vito, Ray, Committee Member ; Bellankonda, Ravi, Committee Member.
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Genc, Balkan Ziya. "Implementation And Comparison Of Turbulence Models On A Flat Plate Problem Using A Navier-stokes Solver." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1096668/index.pdf.
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For turbulent flow calculations, some of the well-known turbulence models in the literature are applied on a previously developed Navier-Stokes solver designed to handle laminar flows. A finite volume formulation, which is cell-based for inviscid terms and cell-vertex for viscous terms, is used for numerical discretization of the Navier-Stokes equations in conservative form. This formulation is combined with one-step, explicit time marching Lax-Wendroff numerical scheme that is second order accurate in space. To minimize non-physical oscillations resulting from the numerical scheme, second and fourth order artificial smoothing terms are added. To increase the convergence rate of the solver, local time stepping technique is applied.
Before applying turbulence models, Navier-Stokes solver is tested for a case of subsonic, laminar flow over a flat plate. The results are in close agreement with Blasius similarity solutions.
To calculate turbulent flows, Boussinesq eddy-viscosity approach is utilized. The eddy viscosity (also called turbulent viscosity), which arises as a consequence of this approach, is calculated using Cebeci-Smith, Michel et. al., Baldwin-Lomax, Chien&rsquos k-epsilon and Wilcox&rsquo
s k-omega turbulence models. To evaluate the performances of these turbulence models and to compare them with each other, the solver has been tested for a case of subsonic, laminar - transition fixed - turbulent flow over a flat plate. The results are verified by analytical solutions and empirical correlations.
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Wang, Wei. "Simulation of hard projectile impact on friction stir welded plate." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/7213.
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A numerical simulation is conducted using LS-DYNA to simulate hard projectile impact on a friction stir welded (FSW) plate. As the hard projectile has a wide range of velocity, mass and shape, when referring to AMC 25.963(e) of CS-25, ―Fuel Tank Access Cover‖, the hard projectile can be defined as 9.5 mm cubic-shaped steel engine debris with an initial impact velocity of 213.4 m/s (700 ft/s). This preliminary study was to evaluate whether the fuel tank adjacent skin panel joined by FSW would pass the regulation. First, the geometry and Johnson-Cook material model of the FSW joint were developed based on previous experimental research and validated by comparison with the tensile test on the FSW specimen. Then the impact on an Aluminium Alloy 2024 (AA 2024) plate without FSW was modelled. The minimum thickness of a homogeneous AA 2024 plate which could withstand the impact from engine debris is 3 mm. Finally the impact on 3 mm thick AA 2024 FSW plate was simulated. The welding induced residual stress was implemented in the plate model. The impact centre was changed from the nugget zone to the thermo-mechanically affected zone, heat-affected zone and base material zone of the FSW joint. Penetration only occurred in the model with impact centre on the nugget zone. Additional simulation indicated that increasing the thickness of the FSW plate to 3.6 mm could prevent the penetration.
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Ferrari, Alberto. "Analytical model for the prediction of wrinkling of rear pressure bulkheads." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8587/.
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In Airbus GmbH (Hamburg) has been developed a new design of Rear Pressure Bulkhead (RPB) for the A320-family. The new model has been formed with vacuum forming technology. During this process the wrinkling phenomenon occurs. In this thesis is described an analytical model for prediction of wrinkling based on the energetic method of Timoshenko. Large deflection theory has been used for analyze two cases of study: a simply supported circular thin plate stamped by a spherical punch and a simply supported circular thin plate formed with vacuum forming technique. If the edges are free to displace radially, thin plates will develop radial wrinkles near the edge at a central deflection approximately equal to four plate thicknesses w0/ℎ≈4 if they’re stamped by a spherical punch and w0/ℎ≈3 if they’re formed with vacuum forming technique. Initially, there are four symmetrical wrinkles, but the number increases if the central deflection is increased. By using experimental results, the “Snaptrhough” phenomenon is described.
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Kalnický, Jakub. "Deformační a napěťová analýza šroubu a kostní tkáně se zlomeninou zafixovanou pomocí dlahy." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318799.
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In the field of orthopaedics and traumatology, a whole series of problems appear related to fracture fixation by means of various types of plates. Appropriate application of the plate is the difficult task that a doctor needs to deal with in the operating room. Regarding mechanics, the number of screws and their spacing have a major impact on the healing process. If there are too many screws or lack of them, the fracture does not heal properly. This can lead to implant failure. This work deals with stress-strain analysis of screws and bone tissue with a fracture fixed by LCP. It deals with the influence of different geometrical configurations of the screws on the stress, deformation and strain of the system. For this purpose, the computational modelling was used by means of the finite element method. Two computational models have been created, on which different screw arrangement was analysed. The first computational model represents diaphysis of the femur that is at the beginning of the healing process. For the four load models and eleven geometric configurations and number of the screws, a total of 44 computations were performed. The second computational model represents the distal part of the femur. Femoral geometry model was created based on CT (computed tomography) examination, geometric model of the plate was created by 3D scanning. Deformations and stresses were compared in the three geometric configurations of the screws during the healing process.
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Kazemi, Noj. "Circuit analysis of a parallel plate waveguide." Thesis, KTH, Elektroteknisk teori och konstruktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-222617.
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The aim of this work was to model a four-port waveguide as a simple circuit,by first starting with a two-port then a three-port waveguide. Duethat the work was based on Nathan Marcuvitz book Waveguide handbook,an analytical solution for the circuit parameters was desired. In order toobtain an analytical solution three methods were studied; the Variationalmethod, the Integral equation method and the Static method. Out of thesethree methods the latter was chosen, because its strength of simplifying theboundary conditions. The goal to model a four-port and a three-portedwaveguide was too complicated. This led to that the goal was changed totrying to get a higher accuracy on the existing circuit model for a two-portwaveguide, by solving an extension to the circuit parameter. This was donebecause Marcuvitz only treated the first two modes correctly and it was notclear if the circuit model was stable for the higher orders of Taylor series. Inthe end a circuit model for a waveguide with an iris that treats the first 16modes correctly was solved. By looking at the dispersive properties of thecircuit a comparison with simulation software CST Microwave Studio couldbe done, which resulted in that the circuit model gave good results up to2b/ < 1. It was also showed that the accuracy was about the same as thecircuit model found in Waveguide handbook, but it can be mentioned thatthe accuracy is minimally better for the circuit model that was developed inthis work. Something that was discovered in this work is that the restrictionmentioned in Waveguide handbook for the case when the window is centeredis unreliable, it should be 2b/ < 1. It also appeared that the circuit modelremained stable for higher orders of the Taylor series, in this case up to the16:th order.M°alet med detta arbete var att modellera en fyr-portars v°agledare somen simpel elektrisk krets, genom att f¨orst b¨orja med en tv°a-portars sedantre-portars -v°agledare. Detta arbete var baserat p°a Nathan Marcuvitz bokWaveguide handbook, d¨arav s¨oktes det en analytisk l¨osning f¨or kretsparametrarna.F¨or att kunna f°a en analytisk l¨osning, studerades tre metoder;Variationsmetoden, Integralsekvationsmetoden samt den Statiskametoden.Av dessa tre metoder valdes den sistn¨amnda, p°a grund av dess styrka medatt f¨orenkla randvillkoren. M°alet att modellera en fyr-portars samt en treportarsv°agledare var alldeles f¨or komplicerat. Detta ledde till att m°alet¨andrades till att f¨ors¨oka f°a en h¨ogre precision p°a den befintliga kretsmodellenf¨or en tv°a portars v°agledare, genom att l¨osa ut flera termer till kretsparametern.Detta gjordes d°a Marcuvitz endast hanterade de tv°a f¨orstamoderna korrekt, samt att det inte framgick ifall kretsmodellen ¨ar stabil f¨orh¨ogre ordningar av Taylor serier. I slut¨andan l¨ostes en kretsmodel f¨or env°agledare med en iris som hanterar de f¨orsta 16 moderna korrekt. Genomatt kolla p°a de dispersiva egenskaperna f¨or kretsen, kunde en j¨amf¨orelse medsimuleringsprogrammet CST Microwave Studio ske, d¨ar slutsatsen blev attkretsmodellen gav goda resultat upp till 2b/ < 1. Det visade ¨aven sig attprecisionen var ungef¨ar densamma som den kretsmodell som°aterfinns i Waveguidehandbook, men det kan n¨amnas att precisionen ¨ar minimalt b¨attref¨or den kretsmodell som togs fram i detta arbete. En sak som uppt¨acktes underdetta arbete var att restriktionen som n¨amns i Waveguide handbook f¨orfallet n¨ar gapet f¨or irisen ¨ar centrerad st¨ammer inte, den b¨or vara 2b/ < 1.Dessutom visade det sig att kretsmodellen fortfarande var stabil f¨or h¨ogreordningar av Taylorserier, i detta fall upp till den 16:e ordningen.
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Desai, Krishna P. "A Biomechanical Comparison of Locking Compression Plate Constructs with Plugs/Screws in Osteoporotic Bone Model." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1271706065.
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Löfstrand, Grip Rasmus. "A mechanical model of an axial piston machine." Licentiate thesis, KTH, Machine Design (Div.), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10948.
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A mechanical model of an axial piston-type machine with a so-called wobble plate and Z-shaft mechanism is presented. The overall aim is to design and construct an oil-free piston expander demonstrator as a first step to realizing an advanced and compact small-scale steam engine system. The benefits of a small steam engine are negligible NOx emissions (due to continuous, low-temperature combustion), no gearbox needed, fuel flexibility (e.g., can run on biofuel and solar), high part-load efficiency, and low noise. Piston expanders, compared with turbines or clearance-sealed rotary displacement machines, have higher mechanical losses but lower leakage losses, much better part-load efficiency, and for many applications a more favourable (i.e., lower) speed. A piston expander is thus feasible for directly propelling small systems in the vehicular power range. An axial piston machine with minimized contact pressures and sliding velocities, and with properly selected construction materials for steam/water lubrication, should enable completely oil-free operation. An oil-free piston machine also has potential for other applications, for example, as a refrigerant (e.g., CO2) expander in a low-temperature Rankine cycle or as a refrigerant compressor.
An analytical rigid-body kinematics and inverse dynamics model of the machine is presented. The kinematical analysis generates the resulting motion of the integral parts of the machine, fully parameterized. Inverse dynamics is applied when the system motion is completely known, and the method yields required external and internal forces and torques. The analytical model made use of the “Sophia” plug-in developed by Lesser for the simple derivation of rotational matrices relating different coordinate systems and for vector differentiation. Numerical solutions were computed in MATLAB. The results indicate a large load bearing in the conical contact surface between the mechanism’s wobble plate and engine block. The lateral force between piston and cylinder is small compared with that of a comparable machine with a conventional crank mechanism.
This study aims to predict contact loads and sliding velocities in the component interfaces. Such data are needed for bearing and component dimensioning and for selecting materials and coatings. Predicted contact loads together with contact geometries can also be used as input for tribological rig testing. Results from the model have been used to dimension the integral parts, bearings and materials of a physical demonstrator of the super-critical steam expander application as well as in component design and concept studies.
35
Shahzad, Muhammad Khurram [Verfasser], and E. [Akademischer Betreuer] Plate. "A Data Based Flood Forecasting Model for the Mekong River / Muhammad Khurram Shahzad. Betreuer: E. Plate." Karlsruhe : KIT-Bibliothek, 2011. http://d-nb.info/1014279585/34.
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Legerský, Radek. "Deformačně napěťová analýza prasečího femuru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229819.
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This master’s thesis deals with the strain-stress analyses of the pig femoral bone in physiological and pathological condition. Pathological condition is determined by a significant defect in diaphysis of the bone fixed by using direct angular stable locking plate with screws. The thesis describes the creation of computational models with special focus on bone tissues models of material, which are based on analysis of digital images from computed tomography (CT). There are created and analyzed three types of computational models: the first one corresponds to physiological condition of femur, the second one to femur with significant defect and fixation plate and the third one to femur with significant defect, fixation plate and rod. Every model is loaded in three ways: the first of them simulating the experimental conditions of pressure testing of the femur, the second one bone stress in the sagittal plane and the third one stress by using load determined from probational release of the pig hind limb. Strain-stress states are determined by finite element method using Ansys computational system. Gained results of stress and strain are compared with experimental measurements. The thesis presents a basic idea of the mechanical behavior of porcine femur and porcine femur with significant bone defect.
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Delhorme, Maxime. "Thermodynamics and Structure of Plate-Like Particle Dispersions." Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00818964.
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A considerable amount of mineral particles are found to have a plate-like shape. The work in this thesis concerns theoretical investigations, using a Monte Carlo method, of the properties of such particles in aqueous solutions. The objectives were first to create a model that could capture the essential physics of clay suspensions and also to understand the role of thermodynamics in certain chemical processes. For all investigations, the results are related to experimental studies. The acid-base behavior of clays have been studied, using the primitive model, and an excellent agreement between simulated and experimental results was found. The formation of gel phases as a function of the charge anisotropy have also been investigated. Liquid-gel and sol-gel transitions are found to occur for high and moderate charge anisotropy, respectively. These transitions were also found to be size and salt dependent. In absence of charge anisotropy, a liquid-glass transition is reported. The formation of smectic and columnar liquid crystals phases with plate-like particles has been found to be favored by a strong charge anisotropy, in opposition to what was observed for nematic phases. New liquid-crystal phases were also reported. The stability and growth of nanoplatelets is discussed. It was found that the internal Coulombic repulsion could be the cause of the limited growth of C-S-H platelets. The influence of thermodynamics on the agregation mode of such platelets was also investigated
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Muro, Noelle Marie. "Mechanical Comparison of a Type II External Skeletal Fixator and Locking Compression Plate in a Fracture Gap Model." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/86276.
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The purpose of this study was to compare the stiffness of a Type II external skeletal fixator (ESF) to a 3.5 mm locking compression plate (LCP) in axial compression, mediolateral, and craniocaudal bending in a fracture gap model. The hypothesis was that the Type II ESF would demonstrate comparable stiffness to the LCP. A bone simulant consisting of short fiber reinforced epoxy cylinders and a 40 mm fracture gap was used. The LCP construct consisted of a 12 hole 3.5 mm plate with three 3.5 mm bicortical locking screws per fragment. The Type II ESF construct consisted of 3 proximal full fixation pins (Centerface®) per fragment in the mediolateral plane, and 2 carbon fiber connecting rods. Five constructs of each were tested in non-destructive mediolateral and craniocaudal bending, and axial compression. Stiffness was determined from the slope of the elastic portion of force-displacement curves. A one-way ANOVA and a Tukey-Kramer multiple comparisons test were performed, with significance defined as p < 0.05. In mediolateral bending, the stiffness of the Type II ESF (mean ± standard deviation; 1584.2 N/mm ± 202.8 N/mm) was significantly greater than that of the LCP (110.0 N/mm ± 13.4 N/mm). In axial compression, the stiffness of the Type II ESF (679.1 N/mm ± 20.1 N/mm) was significantly greater than that of the LCP (221.2 N/mm ± 19.1 N/mm). There was no significant difference between the constructs in craniocaudal bending. This information can aid in decision-making for fracture fixation, although ideal stiffness for healing remains unknown.Master of Science
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Charlesworth, Peter S. "A full-scale and model study of convective heat transfer from roof mounted flat-plate solar collectors." Thesis, University of Sheffield, 1986. http://etheses.whiterose.ac.uk/5993/.
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This study is concerned with the convective heat transfer, due to the action of the wind, from the upper surface of roof mounted flat plate solar collectors. The ability to predict the quantity of heat transferred from a collector, in this manner, is necessary in order to facilitate the evaluation of the overall efficiency of a collector panel. Previous methods of determining this convection coefficient have generally relied upon extrapolations of small scale wind tunnel results to full-scale values. The validity of these methods is questionable, and it was found that there was a lack of full-scale data relating to the convection coefficient from the upper surface of a flat-plate collector. It was also found that no systematic attempt to relate model results to full scale values had been made. Full-scale experiments have been performed to evaluate the convective heat transfer coefficient, h, from the upper surface of a roof mounted flat plate. The convection coefficient was found to be dependent upon the wind speed as measured above the roof ridge line, V 6R, and to some extent upon the direction of the prevailing wind, G. Relationships between h and V 6R are presented, as are relationships between h and VH (the wind speed measured at the mid-panel height) and h and V 10 (the meteorological 10m wind speed). Small scale wind tunnel experiments were also performed. This was in order to assess the potential of using wind tunnel model results to predict accurately full-scale convective heat losses. These experiments showed some qualitative agreement with the full-scale tests. However, extrapolation of these model results to full-scale values rendered heat transfer coefficients in excess of those found in the full-scale work. Therefore the use of previously derived full-scale results from wind tunnel studies must be treated with caution. It is suggested that the full-scale results, presented here, represent a more satisfactory means of evaluating the convective heat transfer from the upper surface of roof mounted flat plate solar collectors.
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Ogunmodimu, Olumide. "Developing a mechanistic model for flow through a perforated plate with application to screening of particulate materials." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/24456.
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Screening in mineral processing is the practice of separating granulated ore materials into multiple particle size fractions, and is employed in most mineral processing plants. Models of screening performance have been developed previously with the aim of improving process efficiency. Different methods have been used, such as physical modelling, empirical modelling, and mathematical modelling including the discrete element method (DEM). These methods have major limitations in practice, and experimental data to validate the models have been difficult to obtain. Currently, the design and scale-up of screens still relies on rules of thumb and empirical factor methods rather than a fundamentally based understanding of the behaviour of the granular system. To go beyond the current state-of-the-art in screen modelling requires a clear understanding of the particle motion along a dynamic (vibrating) inclined plane. Central to this understanding is the notion that granular systems exhibit a unique rheology that is not observed in fluids; i.e. neither Newtonian nor non-Newtonian. It is thus imperative to fully quantify the granular rheology, which is determined by the depth of the particle bed along the screen, the solids concentration, and the average velocity of the granular avalanche on the screen. The concept of granular rheology is important. Existing empirical models of vibrating screens tend to be extremely dependent on boundary conditions of a particular machine design. The concept of granular rheology is important because, akin to fluid flow, granular flow exhibits different flow regimes depending on the extent of energy input in the system. This work employed DEM to quantify the granular rheology of particles moving along a vibrating inclined screen in order to begin the development of a phenomenological model of screening. The model extends the visco-plastic rheology formation of Pouliquen et al. (2006) to capture the kinetic and turbulent stresses obtained in granular flow on an inclined vibrating screen. In general, DEM was employed to develop a mechanistic model of screening which includes a description of the rheology of granular flow on a vibrating screen. Microscopic properties of granular flow were used in DEM to simulate screening of particulate materials. Granular mixtures of two particle constituents (3 mm and 5 mm) were simulated on an inclined vibrating screen of 3.5 mm apertures. For the base case, frequency and amplitude are 4 Hz and 1 mm, respectively. While microscopic properties were employed for the simulation, the properties extracted from the simulations are macroscopic fields which are consistent with the continuum equations of mass, momentum and energy balance. From the continuum equations, a micro-macro transition method called the coarse-graining approach was employed to obtain the volume fraction and the tangential velocity as a function of the depth of flow along the inclined surface. This approach is suitable for this work because the produced fields satisfy the equations of continuum mechanics; even near the base of the flow. The continuum analysis of the flowing layer reveals a coexistence of flow regimes- (i) quasi-static, (ii) dense (liquid-like), and (iii) inertial. The regimes are consistent with the measured solids concentrations spanning these regimes on inclined vibrating screens. The quasi-static regime is dominated by frictional stress and corresponds to low inertial number (I). Beyond the quasi-static regime, the frictional stress chains break and the collisional-kinetic and turbulent stress begin to dominate. The variation of the effective frictional coefficient with the inertial number (I) characterises the flow. Finally, an effective frictional coefficient model that is based on frictional, collisionalkinetic and turbulent stress was developed. Data analyses for this model were done at a steady flow in the base case where a coexistence of three flow regimes were observed. It was observed that each regime of flow is dominated by corresponding shear stresses. While the quasi-static regime is dominated by frictional stress, the kinetic and the inertial regimes are dominated by kinetic and turbulent shear stresses, respectively. This model was tested by varying the intensity of vibration in the base case and it was observed that at higher frequencies and amplitudes, the quasi-static regime gradually disappeared. Furthermore, the inertial number at which transition occurs to different regimes varies in response to the intensity of vibration. This is an important step in developing a phenomenological model of screening. The model presents a fundamental understanding of the mechanisms governing transport of granular matter on an inclined vibrating screen.
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Kayani, Omer Khaleeq, and Muhammad Sohaib. "Generic Simulation Model Development of Hydraulic Axial Piston Machines." Thesis, Linköpings universitet, Fluida och mekatroniska system, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-76575.
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This master thesis presents a novel methodology for the development of simulation models for hydraulic pumps and motors. In this work, a generic simulation model capable of representing multiple axial piston machines is presented, implemented and validated. Validation of the developed generic simulation model is done by comparing the results from the simulation model with experimental measurements. The development of the generic model is done using AMESim. Today simulation models are an integral part of any development process concerning hydraulic machines. An improved methodology for developing these simulation models will affect both the development cost and time in a positive manner. Traditionally, specific simulation models dedicated to a certain pump or motor are created. This implies that a complete rethinking of the model structure has to be done when modeling a new pump or motor. Therefore when dealing with a large number of pumps and motors, this traditional way of model development could lead to large development time and cost. This thesis work presents a unique way of simulation model development where a single model could represent multiple pumps and motors resulting in lower development time and cost. An automated routine for simulation model creation is developed and implemented. This routine uses the generic simulation model as a template to automatically create simulation models requested by the user. For this purpose a user interface has been created through the use of Visual Basic scripting. This interface communicates with the generic simulation model allowing the user to either change it parametrically or completely transform it into another pump or motor. To determine the level of accuracy offered by the generic simulation model, simulation results are compared with experimental data. Moreover, an optimization routine to automatically fine tune the simulation model is also presented.
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Spinler, Joshua C. "Investigating Crustal Deformation Associated With The North America-Pacific Plate Boundary In Southern California With GPS Geodesy." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/332879.
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The three largest earthquakes in the last 25 years in southern California occurred on faults located adjacent to the southern San Andreas fault, with the M7.3 1992 Landers and M7.1 1999 Hector Mine earthquakes occurring in the eastern California shear zone (ECSZ) in the Mojave Desert, and the M7.2 2010 El Mayor-Cucapah earthquake occurring along the Laguna Salada fault in northern Baja California, Mexico. The locations of these events near to but not along the southern San Andreas fault (SSAF) is unusual in that the last major event on the SSAF occurred more than 300 years ago, with an estimated recurrence interval of 215± 25 years. The focus of this dissertation is to address the present-day deformation field along the North America-Pacific plate boundary in southern California and northern Baja California, through the analysis of GPS data, and elastic block and viscoelastic earthquake models to determine fault slip rates and rheological properties of the lithosphere in the plate boundary zone. We accomplish this in three separate studies. The first study looks at how strain is partitioned northwards along-strike from the southern San Andreas fault near the Salton Sea. We find that estimates for slip-rates on the southern San Andreas decrease from ~23 mm/yr in the south to ~8 mm/yr as the fault passes through San Gorgonio Pass to the northwest, while ~13-18 mm/yr of slip is partitioned onto NW-SE trending faults of the ECSZ where the Landers and Hector Mine earthquakes occurred. This speaks directly to San Andreas earthquake hazards, as a reduction in the slip rate would require greater time between events to build up enough slip deficit in order to generate a large magnitude earthquake. The second study focuses on inferring the rheological structure beneath the Salton Trough region. This is accomplished through analysis of postseismic deformation observed using a set of the GPS data collected before and after the 2010 El Mayor-Cucapah earthquake. By determining the slip-rates on each of the major crustal faults prior to the earthquake, we are able to model the pre-earthquake velocity field for comparison with velocities measured using sites constructed post-earthquake. We then determine how individual site velocities have changed in the 3 years following the earthquake, with implications for the rate at which the lower crust and upper mantle viscously relax through time. We find that the viscosity of the lower crust is at least an order of magnitude higher than that of the uppermost mantle, and hypothesize that this is due to mafic material emplaced at the base of the crust as the spreading center developed beneath the Salton Trough since about 6 Ma. The final study investigates crustal deformation and fault slip rates for faults in the northern Mojave and southern Walker Lane regions of the ECSZ. Previous geodetic studies estimated slip-rates roughly double those inferred via geological dating methods in this region for NW striking strike-slip faults, but significantly smaller than geologic estimates for the Garlock fault. Through construction of a detailed elastic block model, which selects only active fault structures, and applying a new, dense GPS velocity field in this region, we are able to estimate slip-rates for the strike-slip faults in the ECSZ that are much closer to those reported from geology.
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Ortman, Kevin Charles. "Assessing an Orientation Model and Stress Tensor for Semi-Flexible Glass Fibers in Polypropylene Using a Sliding Plate Rheometer: for the Use of Simulating Processes." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77164.
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Great interest exists in adding long fibers into polymeric fluids due to the increase in properties associated with the composite, as compared to the neat resin. These properties, however, are dependent on the fiber orientations generated during processing, such as injection molding. In an effort to optimize industrial processing, optimize mold design, and maximize desired properties of the final part, it is highly desirable to predict long fiber orientation as a function of processing conditions.
The purpose of this research is to use rheology as a fundamental means of understanding the transient orientation behavior of concentrated long glass (> 1mm) fiber suspensions. Specifically, this research explores the method of using rheology as a means of obtaining stress tensor and orientation model parameters needed to accurately predict the transient fiber orientation of long glass fiber reinforced polypropylene, in a well-defined simple shear flow, with the hopes of extending the knowledge gained from these fundamental experiments for the use of simulating processing flows, such as injection molding. Two fiber orientation models were investigated to predict the transient orientation of the long glass fiber systems explored. One model, the Folgar-Tucker model, has been particularly useful for predicting fiber orientation in short glass fiber systems and was used in this paper to assess its performance with long glass fibers. A second orientation model, one that accounts for the semi-flexibility of fibers, was extended to describe non-dilute suspension and coupled with an augmented stress tensor that accounts for fiber bending. Stress tensor and orientation model parameters were determined (in all cases) by best fitting these coupled equations to measured stress data obtained using a sliding plate rheometer. Results showed the semi-flexible orientation model and stress tensor combination, overall, provided improved rheological results as compared to the Folgar-Tucker model when coupled with the stress tensor of Lipscomb (1988). Furthermore, it was found that both stress tensors required empirical modification to accurately fit the measured data. Both orientation models provided encouraging results when predicting the transient fiber orientation in a sliding plate rheometer, for all initial fiber orientations explored. Additionally, both orientation models provided encouraging results when the model parameters, determined from the rheological study, were used for the purpose of predicting fiber orientation in an injection molded center-gated disk.Ph. D.
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Bouldoires, Mumenthaler Céline. "Development and validation of an acute arthritis model in dogs : urate crystal synovitis evaluated by force plate analysis /." [S.l.] : [s.n.], 2002. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Le, Thi Huyen Cham. "Robust variable kinematics plate finite elements for composite structures." Thesis, Paris 10, 2019. http://faraway.parisnanterre.fr/login?url=http://bdr.parisnanterre.fr/theses/intranet/2019/2019PA100053/2019PA100053.pdf.
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Le but de ce travail est de développer deux nouveaux éléments finis quadrilatéraux à quatre et à huit nœuds implantés dans le code commercial de calcul par Eléments Finis (EF) Abaqus pour plaques composites. Les modèles plaques à cinématique variable sont formulés dans le cadre de la formulation unifiée de Carrera (CUF), qui regroupent des descriptions de type: couche équivalente (ESL) et couches discrètes (LW), avec les variables définies par des polynômes jusqu’au 4ème ordre suivant épaisseur z. Les deux formulations variationnelles sont utilisées pour dériver les matrices des éléments finis: le Principe des Déplacements Virtuels (PVD) et le Théorème Variationnel Mixte de Reissner (RMVT). Grâce à la technique de condensation statique, une formulation hybride basée sur le RMVT est introduite. Afin d’éliminer la pathologie de verrouillage en cisaillement transverse, deux approximations compatibles pour le champ de déformations de cisaillement transverse indépendantes en z, notée QC4 et CL8, sont étendues aux éléments plaques à cinématique variable basés sur CUF. De plus, les QC4S et CL8S interpolations sont également introduites pour les contraintes de cisaillement transverse dans les éléments mixtes et les éléments hybrides. Les résultats numériques comparés à ceux disponibles dans la littérature montrent que les FE proposés sont efficaces pour modéliser des éléments finis robustesThe aim of this work is the development of two classes of new four-node and eightnode quadrilateral finite elements implemented into the commercial finite element (FE) code Abaqus for composite plates. Variable kinematics plate models are formulated in the framework of Carrera’s Unified Formulation (CUF), which encompasses Equivalent Single Layer (ESL) as well as Layer-Wise (LW) models, with the variables that are defined by polynomials up to 4th order along the thickness direction z. The two classes refer to two variational formulations that are employed to derive the finite elements matrices, namely the Principle of Virtual Displacement (PVD) and Reissner’s Mixed Variational Theorem (RMVT). Thanks to the static condensation technique, a Hybrid formulation based on the RMVT is derived. For the purpose of eliminating the shear locking pathology, two field compatible approximations for only the z−constant transverse shear strain terms, referred to as QC4 and CL8 interpolations, are extended to all variable kinematics CUF plate elements. Moreover, the QC4S and CL8S interpolations, are also introduced for the transverse shear stress field within RMVT-based and Hybrid mixed-based elements. Numerical results in comparison with those available in literature show that the proposed FEs are efficient for modeling a robust finite elements
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Marques, Julien. "Plate-forme d'aide à l'éco-conception de systèmes multiphysiques : démarche énergétique pour la validation et la réduction de modèles." Phd thesis, Université d'Orléans, 2010. http://tel.archives-ouvertes.fr/tel-00587474.
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De nos jours, les évolutions technologiques imposent aux ingénieurs de modéliser desphénomènes toujours plus multiphysiques et complexes tout au long du processus dedéveloppement d'un système : le cycle en V. Pour cela, il est primordial d'avoir à disposition desoutils adaptés et performants, afin de réduire les temps de mise sur le marché, tout en obtenantdes produits plus matures et plus économes en énergie. Les travaux présentés ici décrivent lamise en place d'une plate-forme de prototypage virtuel et l'intérêt d'intégrer des considérationsénergétiques dans toutes les étapes de la modélisation. Cette approche permet, par exemple, dequantifier l'efficacité d'un système et de ses composants, et donc d'optimiser au plus tôt le coûténergétique d'une solution technique. Nous avons, dans un second temps, souhaité répondre àla problématique du " modèle le plus adapté ". Après analyse des différentes méthodes deréduction de modèles, nous avons décidé de développer la méthode PEMRA permettant depallier les limitations de la méthode MORA, introduite par Louca et al. en 1997. Les variables depuissance et d'énergie introduites précédemment sont utilisées pour calculer deux nouveauxcritères dans le processus de réduction de modèles, permettant de converger vers un modèleréduit plus simple et plus précis qu'avec la méthode MORA. Nous montrons enfin qu'enchoisissant judicieusement le signal d'excitation et un critère dit de précision temporelle adapté, ilest possible, par une approche innovante à la fois énergétique et fréquentielle, de trouver unmodèle réduit mieux adapté aux exigences imposées par l'utilisateur.
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Semeraro, Onofrio. "Active Control and Modal Structures in Transitional Shear Flows." Doctoral thesis, KTH, Stabilitet, Transition, Kontroll, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-117916.
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Flow control of transitional shear flows is investigated by means of numerical simulations. The attenuation of three-dimensional wavepackets of Tollmien-Schlichting (TS) and streaks in the boundary layer is obtained using active control in combination with localised sensors and actuators distributed near the rigid wall. Due to the dimensions of the discretized Navier-Stokes operator, reduced-order models are identified, preserving the dynamics between the inputs and the outputs of the system. Balanced realizations of the system are computed using balanced truncation and system identification. We demonstrate that the energy growth of the perturbations is substantially and efficiently mitigated, using relatively few sensors and actuators. The robustness of the controller is analysed by varying the number of actuators and sensors, the Reynolds number, the pressure gradient and by investigating the nonlinear, transitional case. We show that delay of the transition from laminar to turbulent flow can be achieved despite the fully linear approach. This configuration can be reproduced in experiments, due to the localisation of sensing and actuation devices. The closed-loop system has been investigated for the corresponding twodimensional case by using full-dimensional optimal controllers computed by solving an iterative optimisation based on the Lagrangian approach. This strategy allows to compare the results achieved using open-loop model reduction with model-free controllers. Finally, a parametric analysis of the actuators/ sensors placement is carried-out to deepen the understanding of the inherent dynamics of the closed-loop. The distinction among two different classes of controllers – feedforward and feedback controllers - is highlighted. A second shear flow, a confined turbulent jet, is investigated using particle image velocimetry (PIV) measurements. Proper orthogonal decomposition (POD) modes and Koopman modes via dynamic mode decomposition (DMD) are computed and analysed for understanding the main features of the flow. The frequencies related to the dominating mechanisms are identified; the most energetic structures show temporal periodicity.QC 20130207
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Hueffed, Anna Kathrine. "A SIMPLIFIED MODEL OF HEAT AND MASS TRANSFER BETWEEN AIR AND FALLING-FILM DESICCANT IN A PARALLEL-PLATE ABSORBER." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11092007-150013/.
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A simplified model is developed to predict the heat and mass transfer between air and falling-film liquid desiccant during dehumidification in a parallel-plate absorber. Compared to the second-order partial differential equations that describe fluid motion, first-order, non-coupled, ordinary differential equations are used to estimate the heat and mass transferred and explicit equations are derived from conservation principles to determine the exiting conditions of the absorber for different flow arrangements. The model uses a control volume approach that accounts for the change in desiccant film thickness and property values. The model agreed with a more complicated parallel flow model in literature. Using existing experimental data for a counterflow arrangement the model was validated over the range of input variables at the level of 8% for varying inlet desiccant flow rates and 10% for varying inlet air mass flow rates when an experimentally determined mass transfer coefficient was used in the model.
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Hueffed, Anna Kathrine. "A simplified model of heat and mass transfer between air and falling-film desiccant in a parallel-plate dehumidifier." Master's thesis, Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-11092007-150013.
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Bouzitouna, Salim. "Construction d'applications réparties par réutilisation de modèles dans l'approche MDA : application à la plate-forme EJB." Paris 6, 2006. http://www.theses.fr/2006PA066448.
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L'approche MDA (Model Driven Architecture) définie par l'OMG préconise une séparation entre les aspects métier des applications dans des modèles indépendants des plates-formes appelés PIMs, et ceux liés à l'implémentation dans des modèles dépendants des plates-formes appelés PSMs. Cela faciliterait ainsi la migration des applications vers de nouvelles plates-formes. Cependant, l'approche MDA ne traite qu’un seul aspect de l’évolution de ces applications qui est celui de leurs plates-formes mais non pas celui de l'évolution de leurs métiers, i. E. PIMs. Une manière de traiter ce deuxième aspect de l'évolution est de réutiliser autant que possible les modèles PIMs et PSMs existants. Pour cela, nous proposons une initiative basée sur deux points : 1) l’expression d'opérations de réutilisation (composition, extension et modification) sur les PIMs ; 2) la génération automatique, à partir de cette expression, d'entités de la plate-forme (entités glus) qui appliqueront ces opérations sur les PSMs