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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.
31

Construction of Late Cretaceous, Mid-Crustal Sheeted Plutons from the Eastern Transverse Ranges, Southern California

Brown, Kenneth Lee 16 January 2009 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Differential exhumation within the eastern Transverse Ranges of southern California has revealed a tilted crustal section that provides a unique view into the architecture of the Mesozoic arc. At the base of this crustal section is a group of well-exposed sheeted plutons. Well-developed, gentle to moderately dipping magmatic and solid-state fabrics within these plutons are regionally consistent, margin-parallel, discordant to internal sheeting and layering, and are generally parallel to equivalent host rock structures and fabrics. In some plutons, magmatic foliations define regional fold structures, thus recording regional contraction during chamber construction. Collectively, field mapping and fabric analyses within these sheeted plutons show that the observed fabric patterns are better explained by regional deformation rather than internal magma chamber processes. This interpretation is in direct contrast to previous mapping in the region. The host rocks also record complex processes during sheeted pluton emplacement. Deflection of host rock foliations and structures into parallelism with pluton contacts suggest that downward ductile flow played a role in making space for these plutons. However, evidence of regional faulting and shearing is not observed, suggesting that they did not play a significant role. Although there is considerable microstructural variability within each pluton, the observed microstructures are generally consistent with a transition from magmatic to submagmatic/ high-temperature solid-state deformation. Magmatic microstructures are defined by euhedral to subhedral plagioclase, hornblende, and biotite that do not show significant internal crystal-plastic deformation. Evidence for high-temperature solid-state deformation includes high-temperature grain boundary migration in quartz, plagaioclase, potassium feldspar, and hornblende; chessboard extinction in quartz; and ductile bending in plagioclase and hornblende. Microstructural observations also indicate that mafic and intermediate compositions record stronger magmatic fabrics than felsic compositions. Based on the structural and microstructural observations presented in this study, I interpret that these sheeted plutons were emplaced into an active continental arc setting that was undergoing regional contraction. The strong magmatic fabrics and high-temperature solid-state overprinting is likely a consequence of regional deformation during crystallization. The weak fabrics within upper crustal plutons relative to the strong fabrics within the mid-crustal plutons suggest that deformation was largely localized to the more compositionally heterogeneous mid-crustal portions of the arc structure.
32

HIGH RATE DIGITAL CASSETTE RECORDERS

Banks, Simon 11 1900 (has links)
International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Recorders conforming to IRIG Standards have served the data recording community well for many years. Initially, most systems were analog in nature, recording data in either direct or FM modes but as the need for digital recording developed, the IRIG recorder was successfully adapted for this purpose by the addition of formatting and coding sub-systems to form the High Density Digital Recorder (HDDR). Today, user requirements for higher speed, higher capacity and more convenient systems have presented equipment designers with new challenges in terms of the correct choice of technology and system architecture. It is not surprising that system designers should turn for inspiration first to the very high speed transverse and helical products which had been developed for the broadcast industry since these technologies possess many of the attributes necessary for a high rate digital data recorder. It is unfortunate that it has now become a truism that the only logical progression from the longitudinal IRIG system is by means of rotary technology. Recent developments in a technology known as micro-track recording now call this assumption into question. Recording systems based on micro-track technology are available and others are in an advanced state of development, and these offer a costeffective, attractive and low risk alternative to rotary systems for both high rate data capture and tape mass storage applications.
33

Etude expérimentale de la propagation non linéaire dans les guides optiques plans: instabilité serpentine et soliton de Bragg

Gorza, Simon-Pierre S.-P. 14 January 2005 (has links)
The topic of this thesis is about experimental study of phenomena which are associated with light propagation in nonlinear dielectric media. In the first part of this work, we study experimentally the snake instability of the bright soliton stripe of the (2+1)-dimensional hyperbolic nonlinear Schrödinger equation. The instability is observed, through spectral measurements, on spatially extended femtosecond pulses propagating in a normally dispersive self-defocusing semiconductor planar waveguide. The second part of this thesis is about light propagation in nonlinear periodic media. We experimentally observe a stationary spatial gap (or Bragg) soliton in a periodic semiconductor planar waveguide. Based on the interference pattern of the soliton beam, we measure the power parameter of the soliton which is related to the position of the spatial spectrum in the linear band gap. Cette thèse de doctorat a pour sujet l’étude expérimentale de phénomènes associés à la propagation de la lumière dans les milieux diélectriques non linéaires. La première partie porte sur la démonstration expérimentale de l’instabilité serpentine d’une bande solitonique dans un système décrit par une équation de Schrödinger non linéaire à (2+1)-dimensions. L’instabilité est observée sur base de mesures du spectre spatial ainsi que du profil spatio-fréquentiel d’une impulsion femtoseconde après propagation dans un guide plan semi-conducteur qui présente une dispersion normale et une non-linéarité défocalisante. Le second thème abordé concerne la propagation de la lumière dans les milieux non linéaires périodiques. Les expériences réalisées ont montré l’existence du soliton de Bragg spatial stationnaire sous forme de faisceaux se propageant dans des guides plans semi-conducteurs périodiquement gravés. Sur base du profil de la distribution modale en intensité du faisceau soliton, il a été possible de mesurer le paramètre de puissance du soliton de Bragg qui détermine la position du spectre spatial dans la bande interdite linéaire.
34

Large-eddy simulation of unidirectional turbulent flow over dunes

Omidyeganeh, MOHAMMAD 28 May 2013 (has links)
We performed large eddy simulation of the flow over a series of two- and three-dimensional dune geometries at laboratory scale using the Lagrangian dynamic eddy-viscosity subgrid-scale model. First, we studied the flow over a standard 2D transverse dune geometry, then bedform three-dimensionality was imposed. Finally, we investigated the turbulent flow over barchan dunes. The results are validated by comparison with simulations and experiments for the 2D dune case, while the results of the 3D dunes are validated qualitatively against experiments. The flow over transverse dunes separates at the dune crest, generating a shear layer that plays a crucial role in the transport of momentum and energy, as well as the generation of coherent structures. Spanwise vortices are generated in the separated shear; as they are advected, they undergo lateral instabilities and develop into horseshoe-like structures and finally reach the surface. The ejection that occurs between the legs of the vortex creates the upwelling and downdrafting events on the free surface known as “boils”. The three-dimensional separation of flow at the crestline alters the distribution of wall pressure, which may cause secondary flow across the stream. The mean flow is characterized by a pair of counter-rotating streamwise vortices, with core radii of the order of the flow depth. Staggering the crestlines alters the secondary motion; two pairs of streamwise vortices appear (a strong one, centred about the lobe, and a weaker one, coming from the previous dune, centred around the saddle). The flow over barchan dunes presents significant differences to that over transverse dunes. The flow near the bed, upstream of the dune, diverges from the centerline plane; the flow close to the centerline plane separates at the crest and reattaches on the bed. Away from the centerline plane and along the horns, flow separation occurs intermittently. The flow in the separation bubble is routed towards the horns and leaves the dune at the tips. Barchan dunes induce two counter-rotating streamwise vortices, along each of the horns, which direct high-momentum fluid toward the symmetry plane and low-momentum fluid near the bed away from the centerline. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-05-27 18:58:48.969
35

Laboratory Testing of Precast Bridge Beck Panel Transverse Connections for Use in Accelerated Bridge Construction

Porter, Scott D. 01 May 2009 (has links)
Precast concrete bridge deck panels have been used for decades to accelerate bridge construction. Cracking of the transverse connection between panels is a common problem that can damage deck overlays and cause connection leaking leading to corrosion of lower bridge elements. To better understand the behavior of bridge deck transverse female-to-female connections, shear and moment lab testing were performed at Utah State University for the Utah Department of Transportation. Two existing UDOT connections were tested, a welded stud connection and a post tensioned connection. A variation of the welded connection using rebar was also tested. In addition, two new curved bolt connections were tested as a new method of post tensioning a connection. The manner of connection cracking and associated cracking loads were recorded along with the ultimate connection capacities. The connections were also tested in a low cycle, high amplitude cyclical shear test. Lab testing showed that the welded stud connection had the lowest moment capacity. It also showed that the welded rebar connection had significantly higher strength than the welded stud connection with higher cracking and ultimate loads. Curved bolts were also shown to be a good way to post tension a connection with similar moment capacities as the post tensioned connection. Longer curved bolts were found to perform better than shorter curved bolts.
36

Development of Laser System to Measure Pavement Rutting

Wang, Hongzhi 20 October 2005 (has links)
Asphalt pavement rutting is one of the most common and destructive pavement distresses observed on U.S. roads, particularly in the urban environment at intersections. They are an important indicator of the structural integrity of the pavement as well as having an impact on road user safety. For these reasons, most road agencies regularly monitor the levels of rut depths on their pavement. There are four technologies used for estimating rut depth in automated measurement way: ultrasonics, point lasers, scanning lasers, Optical. This thesis will focus on the development of the laser scanner rut depth measurement system, including the improvement of the hardware design, the software development and data analysis. In order to evaluate the accuracy and correction of the laser scanner system, the researcher used it to measure different pavement in different situations. This research focused on the performance measures, such as correlativity, repeatability. From field experiments and data analysis, the following results had been obtained: 1. Laser scanner showed satisfactory repeatability performances; 2. Laser scanner has good correlations with manual rut data. 3. High power laser scanner in dark asphalt has good correlations with in light pavement. The findings of this research will contribute to the development of laser system in the measurement of pavement rutting.
37

Etudes expérimentales d'avalanches granulaires

Malloggi, Florent G.J. 17 February 2006 (has links) (PDF)
- Les instabilités de dépôts granulaire sont omniprésentes dans la nature, elles présentent un comportement solide et liquide comme en témoigne les avalanches et les écoulements de boue qui sont a l'origine de nombreuses catastrophes humaines et économiques. Malgré son importance pratique, ces phénomènes sont encore loin d'être compris et bien décrit notamment en raison du manque de compréhension de leur rhéologie. Ce manuscrit présente une étude expérimentale d'avalanche se propageant sur une couche granulaire érodable. Dans la première partie, l'équilibre d'une couche granulaire sur un plan incline est étudiée, aussi bien dans l'air que dans l'eau. A partir de ce dépôt granulaire, la méthode de propagation d'avalanche est expliquée dans ces différentes phases. La rhéologie des écoulements stationnaires de sable est déduite et comparée aux résultats communément trouvés. Des mesures expérimentales, dites "méthode de la lame de suie" et "méthodes des feuillets colorées", montrent l'existence d'une couche statique prenant place sous l'écoulement. Dès lors la rhéologie précédemment établie est modifiée permettant ainsi de décrire les avalanches en termes de rhéologie locales. En appliquant cette rhéologie aux cas des ondes solitaires érosives, le profil d'érosion en est extrait. Pour le sable sur la feutrine il ressort que l'onde ne creuse pas la couche jusqu'au fond tandis que pour les ondes de billes la couche est entièrement érodée. Dans la dernière partie la stabilité de ces ondes est étudiée. Au delà d'un seuil les ondes se déstabilisent transversalement. Après une longueur d'onde initiale, un phénomène de coalescence par fusion est observé. Ce dernier est lui-même stoppé par la formation de doigts. Une étude expérimentale de stabilité a montré que c'est une instabilité linéaire à grande longueur d'onde et à nombre d'onde nul. Toutes les longueurs d'onde mesurées aussi bien dans l'air que dans l'eau se regroupent autour d'une même courbe dès lors qu'elles sont adimensionnées par la taille des grains.
38

Relaxométrie à champ variable de tissus humains contenant du fer

Hocq, Aline 25 September 2009 (has links)
Un excès de fer est observé dans les noyaux du cerveau de patients atteints de maladies neurodégénératives ainsi que dans le foie et la rate de patients souffrant d’hémochromatose et de thalassémie. La ferritine est la protéine qui stocke le fer chez l’Homme. Les tissus contenant du fer apparaissent assombris sur les images IRM pondérées T2 à cause d’une relaxation T2 rapide. Cette caractéristique de la ferritine pourrait donc permettre de déterminer le contenu en fer des organes de façon non invasive. L’IRM pourrait alors être utilisée pour détecter certaines maladies et suivre leur évolution. Dans ce travail, les propriétés de relaxation magnétique nucléaire de tissus contenant du fer sont étudiées. Une corrélation potentielle des taux de relaxation avec le contenu en fer de ces tissus est également recherchée. Les mesures relaxométriques sur des échantillons de noyaux gris du cerveau, de substance blanche, de foie et de rate sont réalisées à différents champs magnétiques (entre 0.00023 T et 14.06 T) et à différents temps inter-écho. Le contenu en fer des tissus est déterminé par ICP (Inductively Coupled Plasma). Pour tous les échantillons, 1/T1 diminue avec le champ magnétique. 1/T2 augmente fortement avec le champ magnétique, soit linéairement, soit quadratiquement suivant les échantillons. Le taux de relaxation transverse dépend également du temps inter-écho, à bas et/ou haut champ selon le type de tissu. Un mélange de contributions (diffusion, déphasage, échange,...), certainement dû à la complexité de ces tissus, est nécessaire pour décrire théoriquement leur relaxation. Une corrélation entre les taux de relaxation et la concentration en fer est observée, principalement, à haut champ et pour les noyaux du cerveau. Les coefficients de corrélation que nous obtenons ne sont pas excellents. La quantification précise du contenu en fer d’un tissu par IRM semble donc complexe. Il n’empêche que l’IRM, à haut champ magnétique, reste un outil de choix pour la détection "qualitative" de ferritine dans un organe.
39

Methods for experimental estimation of anelastic material properties

Dalenbring, Mats January 2001 (has links)
No description available.
40

Traffic Load Effects on Bridges, Statistical Analysis of Collected and Monte Carlo Simulated Vehicle Data

Getachew, Abraham January 2003 (has links)
Research in the area of bridge design has been and still isconcentrated on the study of the strength of materials andrelatively few studies have been performed on traffic loads andtheir effects. Traffic loads have usually been assumed to begiven in codes. This is mainly because it is very difficult tomodel traffic loads in an accurate manner because of theirrandomness. In this work, statistical evaluations of traffic loadeffects, obtained from real as well as Monte Carlo (MC)simulated vehicle data, are presented. As the dynamiccontribution of the vehicle load was filtered by the systemused for measuring vehicle weight, no attention was paid in thepresent study to the dynamic effects or the impact factor. Thedynamic contribution of the traffic load models from codes wasdeducted wherever they were compared with the result from theevaluation of the real data. First, the accuracy of thecollected data was investigated. This was done to examine theinfluence of what was most probably unreasonable data on thefinal evaluated results. Subsequently, the MC simulationtechnique, using a limited amount of the collected data, wasused to generate fictitious vehicle data that could representresults from field measurements which would otherwise have tobe recorded under a long period. Afterwards, the characteristictotal traffic loads for bridges with large spans weredetermined by probabilistic analysis. This was done using realas well as simulated data and the two were compared. Theseresults were also compared with the corresponding valuescalculated using the traffic load model from the Swedish bridgedesign code. Furthermore, using traffic data, different load effects onbridges (girder distribution factor of slab-on-girder bridgesand the mid-span deflection as well as the longitudinal stressat critical locations on box-girder bridges) were investigated.The main task was to obtain a more accurate knowledge oftraffic load distributions on bridges as well as their effectsfor infrastructure design. The results showed that the trafficload models from codes gave considerably higher load effectscompared to the current actual traffic load effects. Theseinvestigations were based on the available data for the actualposition of the vehicles on a single bridge and might not coverall possible traffic scenarios. The results showed only how thereal traffic loads, under”normal”conditions andtheir transverse positions relate to the load model accordingto the codes. <b>KEYWORDS:</b>bridge, traffic load, load effect, transversedistribution, characteristic value,weigh in motion, MonteCarlo simulation, Rice’s formula, level crossinghistogram, vehicle queue.

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