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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
651

BEHAVIOUR OF BURIED PIPELINES SUBJECT TO NORMAL FAULTING

SAIYAR, MASOUMEH 01 February 2011 (has links)
Thesis (Ph.D, Civil Engineering) -- Queen's University, 2011-01-31 20:52:11.162 / One of the most severe hazards for buried pipelines, which are sometimes referred to as lifelines due to their essential role in delivering vital resources, is the hazard due to Permanent Ground Deformation (PGD). Earthquake induced PGD can be caused by surface faulting, landslides and seismic settlement. In this thesis, the behaviour of buried pipelines subject to normal faulting has been experimentally investigated through a series of centrifuge tests performed on both continuous and jointed pipelines. Both pipe and soil displacements were measured using image analysis. Signal processing techniques were then developed to filter this data so as to enable the calculation of curvature and other aspects of the response from the observed pipe deformations. First, a series of centrifuge tests was conducted on continuous pipelines of varying materials, representing a wide range of pipe stiffness relative to the soil and investigating the effect of pipe stiffness relative to the soil on soil-pipe interaction. The experimentally derived p-y curves at different locations along the pipe were compared to the recommended soil-pipe interaction models in the relevant guidelines. These p-y curves showed that the central shearing region was not captured well with independent soil springs. The response of the pipelines predicted by the ALA (2001) guideline, however, was shown to match the experimental data within 50%. Two new simplified design approaches were then developed. The first features calculations based on simplified pressure distributions. The second featured peak curvature normalized using a characteristic length, ipipe, the distance from peak to zero moment. A series of centrifuge tests using brittle pipes was also performed. The pipes were buried at three different depths, and the post-failure fracture angle of the pipe was measured to be used as an input for design of liners. Based on the experimental data, a computationally efficient approach was developed to estimate the initial fracture angle which occurs immediately after the pipe breaks. The last series of centrifuge tests was conducted on jointed pipelines with five different joint stiffnesses to investigate the flexural behaviour of jointed pipelines under normal faulting. Based on the observed pipe response, a simplified kinematic model was proposed to estimate the maximum joint rotation for a given geometry, pipe segment length, and the magnitude of the imposed ground displacement. / Ph.D
652

Desenvolupament, implementació i aplicació de nova metodologia pel càlcul de la contribució vibracional a les propietats elèctriques: contribucions de relaxació nuclear i curvatura

Luis Luis, Josep Maria 28 June 1999 (has links)
The vibrational contribution to nonlinear optics (NLO) properties is the mean goal of study of this Thesis. The vibrational contribution can be split in the nuclear relaxation contribution and the curvature contribution. Nuclear relaxation contribution is caused by the changes in the equilibrium geometry induced by the electric field, while the perturbation on the potential energy surface curvature generates the curvature contribution. The general results of the present Thesis are: the development of new methodology to the calculation of the vibrational contribution, the implementation of the new developed methodology in order to facilitate the routine calculation of the NLO properties, the systematic investigation of the importance of vibrational contribution for several chemical systems / El principal objecte d’estudi d’aquesta tesi doctoral és la contribució vibracional a les propietats òptiques no lineals. La contribució vibracional es pot dividir en la contribució de relaxació nuclear i la contribució de curvatura. La contribució de relaxació nuclear és deguda als canvis en la geometria d’equilibri induïts pel camp elèctric incident, i la contribució de curvatura de la superfície de l’energia potencial induïda pel camp òptic genera la contribució de curvatura. En la primera secció de la tesi s’ha desenvolupat una metodologia per calcular les contribucions de relaxació nuclear i de curvatura a les propietats elèctriques. En la segona secció es presenten un conjunt de programes codificats en FORTRAN90 que permeten el càlcul analític i numèric de les hiperpolaritats vibracionals estàtiques i dinàmiques. En la tercera secció s’estudia l’efecte de les funcions de base i la correlació electrònica en el càlcul de les propietats òptiques no lineals
653

New methods of characterizing spatio-temporal patterns in laboratory experiments

Kurtuldu, Huseyin 25 August 2010 (has links)
Complex patterns arise in many extended nonlinear nonequilibrium systems in physics, chemistry and biology. Information extraction from these complex patterns is a challenge and has been a main subject of research for many years. We study patterns in Rayleigh-Benard convection (RBC) acquired from our laboratory experiments to develop new characterization techniques for complex spatio-temporal patterns. Computational homology, a new topological characterization technique, is applied to the experimental data to investigate dynamics by quantifying convective patterns in a unique way. The homology analysis is used to detect symmetry breakings between hot and cold flows as a function of thermal driving in experiments, where other conventional techniques, e.g., curvature and wave-number distribution, failed to reveal this asymmetry. Furthermore, quantitative information is acquired from the outputs of homology to identify different spatio-temporal states. We use this information to obtain a reduced dynamical description of spatio-temporal chaos to investigate extensivity and physical boundary effects in RBC. The results from homological analysis are also compared to other dimensionality reduction techniques such as Karhunen-Loeve decomposition and Fourier analysis.
654

Jet and coat of adaptive sustainable thin films

Singhal, Shrawan 13 November 2013 (has links)
Deposition of nanoscale thickness films is ubiquitous in micro- and nano-scale device manufacturing. Current techniques such as spin-coating and chemical vapor deposition are designed to create only uniform thin films, and can be wasteful in material consumption. They lack the ability to adaptively prescribe desired film thickness profiles. This dissertation presents a novel inkjet-based zero-waste polymer deposition process referred to as Jet and Coat of Adaptive Sustainable Thin Films or J-CAST. The core of this process is built on an experimentally validated multi-scale fluid evolution model, based on extensions of lubrication theory. This model involves a nano-scale fluid film sandwiched between two flat plates: a compliant superstrate and a rigid substrate, with spatial topography on both surfaces. Accounting for the flexural elasticity of the compliant superstrate, and describing the temporal evolution of the fluid film in the presence of different boundary conditions reveals that instead of seeking process equilibrium, non-equilibrium transients should be exploited to guide film deposition. This forms the first core concept behind the process. This concept also enables robust full-wafer processes for creation of uniform films as well as nanoscale films with prescribed variation of thickness at mm-scale spatial wavelengths. The use of inkjets enables zero-waste adaptive material deposition with the preferred drop volumes and locations obtained from an inverse optimization formulation. This forms the second core concept behind the process. The optimization is based on the prescribed film thickness profile and typically involves >100,000 integer parameters. Using simplifying approximations for the same, three specific applications have been discussed - gradient surfaces in combinatorial materials science and research, elliptical profiles with ~10km radius of curvature for X-ray nanoscopy applications and polishing of starting wafer surfaces for mitigation of existing nanotopography. In addition, the potential of extending the demonstrated process to high throughput roll-roll systems has also been mentioned by modifying the model to incorporate the compliance of the substrate along with that of the superstrate. / text
655

Computergestützte Entwurfsmethoden auf gekrümmten Oberflächen

Kühnert, Tom 27 August 2015 (has links) (PDF)
Im Fokus dieser Arbeit steht die Entwicklung und Realisierung einer Nutzerschnittstelle für die computergestützte Bearbeitung von Oberflächen dreidimensionaler Designobjekte, die durch herkömmliche CAD-Systeme nur unzureichend unterstützt werden können. Es werden Methoden und Algorithmen erarbeitet, um die Interaktion des Benutzers direkt auf Basis der für das Design relevanten 3D Objektoberflächen zu ermöglichen. Den Ausgangspunkt bildet das Proxy-Konzept des Forschungsfeldes zur Mensch-Maschine-Interaktion, in welchem physische Stellvertreterobjekte zur Manipulation virtueller Objekte genutzt werden. Im ersten Teil der Arbeit wird dieses Konzept um eine auf die Oberfläche des bearbeiteten Objektes bezogene Interaktion und Designfunktionalität erweitert. Dazu wird das Konzept eines CAD-Proxys entwickelt und verschiedene Umsetzungen und Anwendungen erläutert. Dabei werden die CAD-Proxys in drei Typen unterschieden. Der exakte CAD-Proxy ermöglicht es, ein virtuelles Objekt mit einem formgleichen, physischen Gegenstück zu bearbeiten. Beim abstrakten CAD-Proxy wird gezeigt, wie auch ein anders geformtes Gegenstück zum Einsatz kommen kann. Der augmentierte CAD-Proxy erlaubt die Anzeige des Designs direkt auf dem physischen Gegenstück. Nutzerstudien belegen, dass die CAD-Proxys zur Erstellung eines Designs auf einer Oberfläche deutlich besser geeignet sind als eine klassische Nutzerschnittstelle. Dies gilt insbesondere für anspruchsvolle Designaufgaben, etwa im künstlerischen Design. Im zweiten Teil der Arbeit wird die Verarbeitung von Linienzügen im Gestaltungsprozess eingeführt, welche das Konzept der aktiven Konturen auf Oberflächen erweitern. Diese Linienzüge werden auf die Form der Oberfläche bezogen verarbeitet und beachten gleichzeitig wichtige Merkmale, wie bspw. die Kanten des Objektes. Es wird ein neues Verfahren vorgestellt, mit dem aktive Konturen auch auf schlecht vernetzten Oberflächen eingesetzt werden können und gleichzeitig Formen flexibler repräsentieren können als bisherige Ansätze. Für den Bezug der Designlinien zur Oberfläche wird eine neue Datenstruktur eingeführt, die ein geometrisches Nachbarschaftsproblem löst. Es wird gezeigt, dass diese Struktur auf den getesteten Objekten mindestens um Faktor 14 schneller ist als alternative Ansätze und auch direkt auf andere Problemstellungen anwendbar ist. Der dritte Teil enthält die Betrachtungen zum Formverständnis der Designobjekte, welche für die Designlinien und die Modellierung der Designobjekte benötigt werden. Dabei kommt die Krümmungsberechnung als etabliertes Werkzeug derartiger Analysen zum Einsatz. Hier wird eine neue Betrachtung erarbeitet, die den Einfluss unterschiedlicher Faktoren auf die Genauigkeit der Krümmungsschätzung und auf die Eignung verschiedener Schätzungsverfahren erstmals umfassend untersucht. Durch die Kombination existierender Verfahren kann das Verfahren der Shape Operator Approximation entwickelt werden, welches Eigenschaften wie Schätzungsgenauigkeit, Performanz und eine einfache Formulierung bekannter Verfahren vereint.
656

Index Theory and Positive Scalar Curvature / Index-Theorie und positive Skalarkrümmung

Pape, Daniel 23 September 2011 (has links)
No description available.
657

Vektorinių sluoksniuočių tęsinių sietys / Linear connection of extension of vector bundle

Čiburaitė, Irena 23 June 2006 (has links)
The vector bundles with the basic structure space with affine connection. It is shown that in the present bundles the linear inducts the affine connection, and the curvature of the objects of the present connection is traced. Having defined the concept of the first differential extension of the vector bundles, an indication is made that the linear connection of vector bundles inducts the elongated linear connection of space and linear co-connection, expression form of the linear co-connection components and their interrelation. There are derived commutative formulas of the inducted connection and forms of its components of curvature objects.
658

Evolution and Regularity Results for Epitaxially Strained Thin Films and Material Voids

Piovano, Paulo 01 June 2012 (has links)
In this dissertation we study free boundary problems that model the evolution of interfaces in the presence of elasticity, such as thin film profiles and material void boundaries. These problems are characterized by the competition between the elastic bulk energy and the anisotropic surface energy. First, we consider the evolution equation with curvature regularization that models the motion of a two-dimensional thin film by evaporation-condensation on a rigid substrate. The film is strained due to the mismatch between the crystalline lattices of the two materials and anisotropy is taken into account. We present the results contained in [62] where the author establishes short time existence, uniqueness and regularity of the solution using De Giorgi’s minimizing movements to exploit the L2 -gradient flow structure of the equation. This seems to be the first analytical result for the evaporation-condensation case in the presence of elasticity. Second, we consider the relaxed energy introduced in [20] that depends on admissible pairs (E, u) of sets E and functions u defined only outside of E. For dimension three this energy appears in the study of the material voids in solids, where the pairs (E, u) are interpreted as the admissible configurations that consist of void regions E in the space and of displacements u of the atoms of the crystal. We provide the precise mathematical framework that guarantees the existence of minimal energy pairs (E, u). Then, we establish that for every minimal configuration (E, u), the function u is C 1,γ loc -regular outside an essentially closed subset of E. No hypothesis of starshapedness is assumed on the voids and all the results that are contained in [18] hold true for every dimension d ≥ 2.
659

The derivation and quasinormal mode spectrum of acoustic anti-de sitter black hole analogues

Babb, James Patrick 08 March 2013 (has links)
Dumb holes (also known as acoustic black holes) are fluid flows which include an "acoustic horizon:" a surface, analogous to a gravitational horizon, beyond which sound may pass but never classically return. Soundwaves in these flows will therefore experience "effective geometries" which are identical to black hole spacetimes up to a conformal factor. By adjusting the parameters of the fluid flow, it is possible to create an effective geometry which is conformal to the Anti-de Sitter black hole spacetime- a geometry which has recieved a great deal of attention in recent years due to its conjectured holographic duality to Conformal Field Theories. While we would not expect an acoustic analogue of the AdS-CFT correspondence to exist, this dumb hole provides a means, at least in principle, of experimentally testing the theoretical properties of the AdS spacetime. In particular, I have calculated the quasinormal mode spectrum of this acoustic geometry. / Graduate / 0986 / 0753 / jpbabb@yahoo.ca
660

Local variation in bending stiffness in structural timber of Norway spruce : for the purpose of strength grading

Hu, Min January 2014 (has links)
Most strength grading machines on the European market use an averagemodulus of elasticity (MOE), estimated on a relatively large distance along awood member, as the indicating property (IP) to bending strength. Theaccuracy of such grading machines in terms of coefficient of determination israther low at R2 ≈ 0.5. This research is motivated by a desire to increase theaccuracy of the strength grading in the industry today. The aim of the presentstudy is to contribute knowledge of local variation in bending stiffness/MOEwith high resolution and thus locate weak sections due to stiffness reducingfeatures (the most important is knots) for structural timber.The present study introduces three methods that involve structural dynamics,classical beam theory and optical measurement to assess local wood stiffness.Specifically: The dynamic method, in which a wood member is treated as an ordinaryphysical structure and the local stiffness is studied by exploring itsdynamic properties. In Method II, a bending MOE profile is established based on local fibre angle information. The local fibre orientation is detected through highresolution laser scanning based on the tracheid effect.  For Method III, a bending MOE profile is established using surfacestrain information under four-point bending. A high resolution strainfield is obtained using the digital image correlation (DIC) technique. From the present study, the two latter methods are more favourable inevaluating the local stiffness within a piece of structural timber. Moreover, thestudy reveals that the established bending MOE profiles using the two lattermethods, i.e. based on information of the local fibre angle and surface strain,agree reasonably well. However, for some patterns of knot clusters, the localbending MOE, calculated on the basis of fibre angles, is significantly higherthan the local bending MOE estimated on the basis of surface strain. / De flesta av de utrustningar för hållfasthetssortering som utnyttjas på deneuropeiska marknaden använder ett medelvärde på elasticitetsmodulen(MOE), beräknat på en relativt stor längd av en sågad planka, som indikativparameter (IP). Sådan hållfasthetssortering ger en noggrannhet i termer avförklaringsgrad på R2 ≈ 0.5, vilket är ganska lågt. Arbetet i denna studiemotiveras av en önskan att öka noggrannheten i hållfasthetssorteringen. Syftetmed denna studie är att bidra med kunskap om lokala variationer iböjstyvhet/MOE med hög upplösning och att lokalisera veka snitt (där kvistarär den viktigaste försvagande faktorn) för konstruktionsvirke.Den aktuella studien introducerar tre metoder som omfattar strukturdynamik,klassisk balkteori och optisk mätning vid bedömningen av lokal styvhet imaterialet. Specifikt:  Metod I, där den lokala böjstyvheten studerades genom de dynamiskaegenskaperna såsom egenfrekvens och modform.  Metod II, där en MOE profil beräknas på basis av information om lokalafibervinklar på ett virkesstyckes ytor. Den lokala fiberorienteringen mätsmed högupplöst laserskanning baserad på den så kallade trakeideffekten.  Metod III, där en MOE-profil fastställdes med hjälp avtöjningsinformation för en hel flatsida av en planka belastad med konstantböjmoment. Det högupplösta töjningsfältet erhölls med hjälp av teknikför Digital Image Correlation (DIC). Studien visar att de två sistnämnda metoderna är mycket lämpade för attutvärdera den lokala styvheten i ett virkesstycke. Dessutom visar studien att deMOE-profiler som togs fram med hjälp av de två sistnämnda metoderna,vilka baseras på information om lokala fibervinklar och töjningsfältet på ytan,stämde överens för större delen av virkesstycket. För visa kvistgrupper kan dock den lokala böjstyvheten högre med metoden baserad på fibervinklar.

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