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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.
281

Solutions de localisation des systèmes mobiles de cartographie en environnements structurés

Narayana, Keerthi 24 May 2011 (has links) (PDF)
La localisation automatique est une fonctionnalité importante des systèmes de cartographie mobiles (Mobile Mapping Systems, MMS). La présente thèse présente des solutions complémentaires aux méthodes de localisation utilisées actuellement dans un système MMS terrestre, qui utilise des récepteurs GPS et des centrales à inertie (Inertial Measurement Units, IMU). Un post-traitement, par lissage des données, permet d'améliorer les cartes 3D générées par un MMS. Cette approche est cependant insuffisante pour corriger les erreurs à variations lentes des capteurs. La présente thèse propose une technique de localisation alternative, fondée sur des scanners 2D à lasers. La méthode présentée ici, d'odométrie par laser, utilise des repères plans, qui sont fréquents dans les environnements créés par l'Homme : ces repères fixes permettent de déterminer le déplacement opéré par la plateforme mobile. Contrairement à la technique du SLAM (Simultaneous Localization and Mapping), utilisée pour la navigation des robots à l'intérieur d'un bâtiment, la transformation 3D est calculée sans avoir recours à une carte préétablie, mais en exploitant des propriétés invariantes des caractéristiques extraites de l'environnement. Nous proposons une approche par "division pour régner" (divide and conquer, D&C) qui simplifie les tâches d'association des repères (data association, DA) et de reconstruction du mouvement.
282

Devaluing the <em>mitqal</em> : Inherent Trading Fees in the Metrics of Birka

Schultzén, Joakim January 2009 (has links)
<p>Abstract: Previous research on the Viking Age trade centre of Birka has suggested the parallel use of two harmonising standard weight units, differing in mass by five percent. As an explanation to this phenomenon, this paper puts forward a hypothesis of a trading fee, embedded in the weights. This is corroborated through a hypothetical deductive study; including a reassertion of earlier results by means of a new method for archaeometrological analysis, using a 3D scanner and Computer-Aided Design. Further, the role of silver, as a preferred unit of payment in Birka, is supported through a spatial analysis of the distribution of Islamic coins and Oriental beads in the provinces of Middle Sweden. Plausible manufacturing sites for the cylindrical lead weights, adhering to the Birka mitqal, are discussed as a possible way of falsifying the hypothesis. The results suggest that a trading fee was extracted, using the Birka mitqal for imports and the Islamic mitqal for exports. The metrological analysis was also expanded to weights from Sigtuna, which proved the Birka mitqal, as well the dual metrics system, continued to be in use there until, at least, the first half of the 11<sup>th</sup> century. Finally, a short study on the origins of the Scandinavian/Islamic weight system suggests that the direct influence for the system primarily can be attributed the Volga-Bulgarians.</p>
283

Novel methods for 3-D semi-automatic mapping of fracture geometry at exposed rock faces

Feng, Quanhong January 2001 (has links)
To analyse the influence of fractures on hydraulic andmechanical behaviour of fractured rock masses, it is essentialto characterise fracture geometry at exposed rock faces. Thisthesis describes three semi-automatic methods for measuring andquantifying geometrical parameters of fractures, and aims tooffer a novel approach to the traditional mapping methods. Three techniques, i.e. geodetic total station, close-rangephotogrammetry and 3-D laser scanner, are used in this studyfor measurement of fracture geometry. The advantages of thesetechniques compared with the traditional method are: i)fracture geometry is quantified semi-automatically in threedimensions; ii) fracture measurements are obtained withoutphysically touching the rock face; iii) the accuracy offracture measurements is improved comparing with thetraditional method; iv) both quantitative and spatial analysisof fracture geometry is possible; v) it offers a way todigitally record the rock surface in three dimensions and invisual format as a database for other applications. The common approach for fracture mapping by using the noveltechniques comprises three main steps: i) capturing 3-Dco-ordinates of target points; ii) quantifying geometricalparameters of fractures from the recorded co-ordinates; iii)documenting the results of fracture mapping. The details ofcapturing 3-D co-ordinates of target points are introduced. Anew algorithm is developed for computing orientation offracture planes. A multiple approach for documenting thefracture mapping results is presented. Application of thesetechniques for measuring and quantifying the geometricalparameters of fractures, such as orientation, trace length andsurface roughness, are demonstrated. The presented methods can greatly improve the quality offracture measurements and avoid the drawbacks inherent intraditional methods. However, it can not replace the humancapacity to filter out and interpret the large amount ofgeometrical information displayed on the rock faces. Themethods may offer an assistance to engineers or geologists inobtaining as much information as possible about the geometryand orientation of rock fractures for rock engineeringapplications. <b>Keywords:</b>3-D laser scanner, close-range photogrammetry,engineering geology, fracture geometry, fracture mapping, rockengineering, rock faces, rock mechanics, three-dimension, totalstation.
284

Approaches to Mobile Robot Localization in Indoor Environments

Jensfelt, Patric January 2001 (has links)
QC 20100621
285

Devaluing the mitqal : Inherent Trading Fees in the Metrics of Birka

Schultzén, Joakim January 2009 (has links)
Abstract: Previous research on the Viking Age trade centre of Birka has suggested the parallel use of two harmonising standard weight units, differing in mass by five percent. As an explanation to this phenomenon, this paper puts forward a hypothesis of a trading fee, embedded in the weights. This is corroborated through a hypothetical deductive study; including a reassertion of earlier results by means of a new method for archaeometrological analysis, using a 3D scanner and Computer-Aided Design. Further, the role of silver, as a preferred unit of payment in Birka, is supported through a spatial analysis of the distribution of Islamic coins and Oriental beads in the provinces of Middle Sweden. Plausible manufacturing sites for the cylindrical lead weights, adhering to the Birka mitqal, are discussed as a possible way of falsifying the hypothesis. The results suggest that a trading fee was extracted, using the Birka mitqal for imports and the Islamic mitqal for exports. The metrological analysis was also expanded to weights from Sigtuna, which proved the Birka mitqal, as well the dual metrics system, continued to be in use there until, at least, the first half of the 11th century. Finally, a short study on the origins of the Scandinavian/Islamic weight system suggests that the direct influence for the system primarily can be attributed the Volga-Bulgarians.
286

Computer vision techniques for early detection of skin cancer

Quintana Plana, Josep 14 June 2012 (has links)
This thesis investigates the problem of developing new computer vision techniques for early detection of skin cancer. The first part of this work presents a novel methodology to correct color reproduction in dermatological images when different cameras and/or dermoscopes are used. Next, the problem of automatic full body mapping is addressed by proposing a mosaicing method based on an on-the-shelf digital compact camera and a set of markers. This method increases the possibilities of total body photography by taking the low-resolution images of a whole body exploration and automatically combining them into a high-resolution photomosaic. The third contribution of this work consists of the development of a full body scanner for acquiring cutaneous images. On one hand, the scanner reduces the long time-consuming examinations done in dermoscopy explorations, and on the other hand, it increases the resolution of total body photography systems. / En aquesta tesi s'investiga el desenvolupament de noves tècniques de visió per computador per a la detecció del càncer de pell. La primera part del treball presenta una nova metodologia per a la correcció del color en imatges dermatològiques quan s'utilitzen diferents càmeres i/o els dermatoscops. A continuació és proposa una solució al problema del registre automàtic d'imatges de cos complert amb la proposta d’un mètode de mosaicing basat en l'ús de càmeres compactes i un conjunt de markers. Incrementant les possibilitats de la fotografia de cos complert mitjançant la combinació automàtica d’imatges de baixa resuloció per a l'obtenció d'un fotomosaic d’alta resolució. La tercera contribució d'aquest treball consisteix en el desenvolupament d'un escàner de cos complert per a l'adquisició d'imatges cutànies. D'una banda l'escàner redueix el llarg temps necessari per a les exploracions dermatoscòpiques, i de l'altre, incrementa la resolució de la fotografia de cos complet.
287

An Approach to 3D Building Model Reconstruction from Airborne Laser Scanner Data Using Parameter Space Analysis and Fusion of Primitives / Eine Methode zur Rekonstruktion von 3D Gebäudemodellen aus Flugzeuglaserscannerdaten unter der Verwendung von Parameterräumen und der Fusion von Primitiven

Hofmann, Alexandra 05 August 2005 (has links) (PDF)
Within this work an approach was developed, which utilises airborne laser scanner data in order to generate 3D building models. These 3D building models may be used for technical and environmental planning. The approach has to follow certain requirements such as working automatically and robust and being flexible in use but still practicable. The approach starts with small point clouds containing one building at the time extracted from laser scanner data set by applying a pre-segmentation scheme. The laser scanner point cloud of each building is analysed separately. A 2.5D-Delaunay triangle mesh structure (TIN) is calculated into the laser scanner point cloud. For each triangle the orientation parameters in space (orientation, slope and perpendicular distance to the barycentre of the laser scanner point cloud) are determined and mapped into a parameter space. As buildings are composed of planar features, primitives, triangles representing these features should group in parameter space. A cluster analysis technique is utilised to find and outline these groups/clusters. The clusters found in parameter space represent plane objects in object space. Grouping adjacent triangles in object space - which represent points in parameter space - enables the interpolation of planes in the ALS points that form the triangles. In each cluster point group a plane in object space is interpolated. All planes derived from the data set are intersected with their appropriate neighbours. From this, a roof topology is established, which describes the shape of the roof. This ensures that each plane has knowledge on its direct adjacent neighbours. Walls are added to the intersected roof planes and the virtual 3D building model is presented in a file written in VRML (Virtual Reality Macro Language). Besides developing the 3D building model reconstruction scheme, this research focuses on the geometric reconstruction and the derivation of attributes of 3D building models. The developed method was tested on different data sets obtained from different laser scanner systems. This study will also show, which potential and limits the developed method has when applied to these different data sets. / In der vorliegenden Arbeit wird eine neue Methode zur automatischen Rekonstruktion von 3D Gebäudemodellen aus Flugzeuglaserscannerdaten vorgestellt. Diese 3D Gebäudemodelle können in technischer und landschaftsplanerischer Hinsicht genutzt werden. Bezüglich der zu entwickelnden Methode wurden Regelungen und Bedingungen erstellt, die eine voll automatische und robuste Arbeitsweise sowie eine flexible und praktikable Nutzung gewährleisten sollten. Die entwickelte Methode verwendet Punktwolken, welche mittels einer Vorsegmentierung aus dem gesamten Laserscannerdatensatz extrahiert wurden und jeweils nur ein Gebäude beinhalten. Diese Laserscannerdatenpunktwolken werden separat analysiert. Eine 2,5D-Delaunay-Dreiecksvermaschung (TIN) wird in jede Punktwolke gerechnet. Für jedes Dreieck dieser Vermaschung werden die Lageparameter im Raum (Ausrichtung, Neigungsgrad und senkrechter Abstand der Ebene des Dreiecks zum Schwerpunkt der Punktwolke) bestimmt und in einen Parameterraum aufgetragen. Im Parameterraum bilden diejenigen Dreiecke Gruppen, welche sich im Objektraum auf ebenen Flächen befinden. Mit der Annahme, dass sich ein Gebäude aus ebenen Flächen zusammensetzt, dient die Identifizierung von Clustern im Parameterraum der Detektierung dieser Flächen. Um diese Gruppen/Cluster aufzufinden wurde eine Clusteranalysetechnik genutzt. Über die detektierten Cluster können jene Laserscannerpunkte im Objektraum bestimmt werden, die eine Dachfläche formen. In die Laserscannerpunkte der somit gefundenen Dachflächen werden Ebenen interpoliert. Alle abgeleiteten Ebenen gehen in den entwickelten Rekonstruktionsalgorithmus ein, der eine Topologie zwischen den einzelnen Ebenen aufbaut. Anhand dieser Topologie erhalten die Ebenen ?Kenntnis? über ihre jeweiligen Nachbarn und können miteinander verschnitten werden. Der fertigen Dachgestalt werden Wände zugefügt und das komplette 3D Gebäudemodell wird mittels VRML (Virtual Reality Macro Language) visualisiert. Diese Studie bezieht sich neben der Entwicklung eines Schemas zu automatischen Gebäuderekonstruktion auch auf die Ableitung von Attributen der 3D Gebäudemodellen. Die entwickelte Methode wurde an verschiedenen Flugzeuglaserscannerdatensätzen getestet. Es wird gezeigt, welche Potentiale und Grenzen die entwickelte Methode bei der Bearbeitung dieser verschiedenen Laserscannerdatensätze hat.
288

Novel methods for 3-D semi-automatic mapping of fracture geometry at exposed rock faces

Feng, Quanhong January 2001 (has links)
<p>To analyse the influence of fractures on hydraulic andmechanical behaviour of fractured rock masses, it is essentialto characterise fracture geometry at exposed rock faces. Thisthesis describes three semi-automatic methods for measuring andquantifying geometrical parameters of fractures, and aims tooffer a novel approach to the traditional mapping methods.</p><p>Three techniques, i.e. geodetic total station, close-rangephotogrammetry and 3-D laser scanner, are used in this studyfor measurement of fracture geometry. The advantages of thesetechniques compared with the traditional method are: i)fracture geometry is quantified semi-automatically in threedimensions; ii) fracture measurements are obtained withoutphysically touching the rock face; iii) the accuracy offracture measurements is improved comparing with thetraditional method; iv) both quantitative and spatial analysisof fracture geometry is possible; v) it offers a way todigitally record the rock surface in three dimensions and invisual format as a database for other applications.</p><p>The common approach for fracture mapping by using the noveltechniques comprises three main steps: i) capturing 3-Dco-ordinates of target points; ii) quantifying geometricalparameters of fractures from the recorded co-ordinates; iii)documenting the results of fracture mapping. The details ofcapturing 3-D co-ordinates of target points are introduced. Anew algorithm is developed for computing orientation offracture planes. A multiple approach for documenting thefracture mapping results is presented. Application of thesetechniques for measuring and quantifying the geometricalparameters of fractures, such as orientation, trace length andsurface roughness, are demonstrated.</p><p>The presented methods can greatly improve the quality offracture measurements and avoid the drawbacks inherent intraditional methods. However, it can not replace the humancapacity to filter out and interpret the large amount ofgeometrical information displayed on the rock faces. Themethods may offer an assistance to engineers or geologists inobtaining as much information as possible about the geometryand orientation of rock fractures for rock engineeringapplications.</p><p><b>Keywords:</b>3-D laser scanner, close-range photogrammetry,engineering geology, fracture geometry, fracture mapping, rockengineering, rock faces, rock mechanics, three-dimension, totalstation.</p>
289

Analyse du comportement mécanique des côtes humaines en dynamique

Charpail, Estelle 27 October 2006 (has links) (PDF)
Dans les accidents automobiles, les blessures au thorax arrivent en deuxième position après celles à la tête pour : la zone la plus souvent lésée et le nombre global de décès et de lésions sérieuses. Les fractures de côtes et les volets costaux sont les blessures les plus fréquentes suivies par les lacérations des poumons, du foie et des artères. Afin de mieux comprendre la réponse du thorax lors d'un crash, des modèles en éléments finis ont été développés. Cependant, ces modèles échouent à reproduire des mécanismes lésionnels détaillés tels que les fractures costales. Améliorer la biofidélité de ces modèles passe par une meilleure connaissance des propriétés mécaniques des côtes. L'objectif de ce travail est donc d'étudier expérimentalement et numériquement le comportement mécanique des côtes humaines en dynamique. Des essais de compression axiale et des tests de calcination ont été réalisés pour caractériser le matériau costal. Des essais de flexion trois points et un nouvel essai permettant de solliciter la côte dans la direction antéropostérieure ont servi à caractériser la structure. Les résultats montrent que le niveau costal influence les propriétés de matériaux en compression et le comportement en sollicitation antéropostérieure. Les simulations numériques ont permis de mettre en évidence l'influence de l'os spongieux dans le comportement mécanique des modèles ainsi que l'importance de la géométrie sur la réponse en effort. Aucune influence de l'âge, ni de la vitesse de sollicitation a été relevée. Il faut noter le nombre de pièces testées est petit par rapport aux variations inter-individuelles.
290

Alternative Statistical Methods for Analyzing Geological Phenomena: Bridging the Gap Between Scientific Disciplines

Van Gaalen, Joseph Frank 01 January 2011 (has links)
When we consider the nature of the scientific community in conjunction with a sense of typical economic circumstances we find that there are two distinct paths for development. One path involves hypothesis testing and evolution of strategies that are linked with iterations in equipment advances. A second, more complicated scenario, can involve external influences whether economic, political, or otherwise, such as the government closure of NASA's space program in 2011 which will no doubt influence research in associated fields. The following chapters are an account of examples of two statistical techniques and the importance of both on the two relatively unrelated geological fields of coastal geomorphology and ground water hydrology. The first technique applies a multi-dimensional approach to defining groundwater water table response based on precipitation in areas where it can reasonably be assumed to be the only recharge. The second technique applies a high resolution multi-scalar approach to a geologic setting most often restricted to either high resolution locally, or low resolution regionally. This technique uses time-frequency analysis to characterize cuspate patterns in LIDAR data are introduced using examples from the Atlantic coast of Florida, United States. These techniques permit the efficient study of beachface landforms over many kilometers of coastline at multiple spatial scales. From a LIDAR image, a beach-parallel spatial series is generated. Here, this series is the shore-normal position of a specific elevation (contour line). Well-established time-frequency analysis techniques, wavelet transforms, and S-Transforms, are then applied to the spatial series. These methods yield results compatible with traditional methods and show that it is useful for capturing transitions in cuspate shapes. To apply this new method, a land-based LIDAR study allowing for rapid high-resolution surveying is conducted on Melbourne Beach, Florida and Tairua Beach, New Zealand. Comparisons and testing of two different terrestrial scanning stations are evaluated during the course of the field investigation. Significant cusp activity is observed at Melbourne Beach. Morphological observations and sediment analysis are used to study beach cusp morphodynamics at the site. Surveys at Melbourne were run ~500 m alongshore and sediment samples were collected intertidally over a five-day period. Beach cusp location within larger scale beach morphology is shown to directly influence cusp growth as either predominantly erosional or accretional. Sediment characteristics within the beach cusp morphology are reported coincident with cusp evolution. Variations in pthesis size distribution kurtosis are exhibited as the cusps evolve; however, no significant correlation is seen between grain size and position between horn and embayment. During the end of the study, a storm resulted in beach cusp destruction and increased sediment sorting. In the former technique using multi-dimensional studies, a test of a new method for improving forecasting of surficial aquifer system water level changes with rainfall is conducted. The results provide a more rigorous analysis of common predictive techniques and compare them with the results of the tested model. These results show that linear interpretations of response-to-rainfall data require a clarification of how large events distort prediction and how the binning of data can change the interpretation. Analyses show that the binning ground water recharge data as is typically done in daily format may be useful for quick interpretation but only describes how fast the system responds to an event, not the frequency of return of such a response. Without a secure grasp on the nonlinear nature of water table and rainfall data alike, any binning or isolation of specific data carries the potential for aliasing that must be accounted for in an interpretation. The new model is proven capable of supplanting any current linear regression analysis as a more accurate means of prediction through the application of a multivariate technique. Furthermore, results show that in the Florida surficial aquifer system response-to-rainfall ratios exhibit a maxima most often linked with modal stage.

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