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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.
1

Understanding diagrams based on symbolic and spatial mapping

Fathulla, Kamaran A. January 2007 (has links)
Diagrams have been used for over a millennium to communicate rich meaning for diverse purposes. Three major and persistent problems concerning our understanding of diagrams have been identified and must be addressed: 1. The variety of diagram types 2. Handling changes while retaining well formedness 3. Semantically mixed diagrams. A variety of both scientific and philosophical approaches to understanding diagrams is examined, and all are found unable to meet these challenges in full.
2

An investigation into a GIS based approach for modelling hillslope soil erosion in England and Wales

Brazier, Richard Edward January 2000 (has links)
No description available.
3

Application of pharmacokinetic models to projection data in positron emission tomography

Maguire, Ralph Paul January 1999 (has links)
In positron emission tomography (PET), coincidence detection of annihilation photons enables the measurement of Radon transforms of the instantaneous activity concentration of labelled tracers in the human body. Using reconstruction algorithms, spatial maps of the activity distribution can be created and analysed to reveal the pharmacokinetics of the labelled tracer. This thesis considers the possibility of applying pharmacokinetic modelling to the count rate data measured by the detectors, rather than reconstructed images, A new concept is proposed - parameter projections - Radon transforms of the spatial distribution of the parameters of the model, which simplifies the problem considerably. Using this idea, a general linear least squares GLLS framework is developed and applied to the one and two tissue-compartment models for [O-15]water and [F-18]FDG. Simulation models are developed from first principles to demonstrate the accuracy of the GLLS approach to parameter estimation. This requires the validation of the whole body distribution of each of the tracers, using pharmacokinetic techniques, leading to novel compartment based whole body models for [O-15]water and [F-18]FDG. A simplified Monte-Carlo framework for error estimation of the tissue models is developed, based on system parameters. It is also shown that the variances of maps of the spatial variance of the parameters of the model - parametric images - can be calculated in projection space. It is clearly demonstrated that the precision of the variance estimates is higher than that obtained from estimates based on reconstructed images. Using the methods, it is shown how statistical parametric maps of the difference between two neuronal activation conditions can be calculated from projection data. The methods developed allow faster results analysis, avoiding lengthy reconstruction of large data sets, and allow access to robust statistical techniques for activation analysis through use of the known, Poisson distributed nature, of the measured projection data.
4

Enhancing Structure-Function Correlations in Glaucoma with Customised Spatial Mapping

Ganeshrao, S.B., Turpin, A., Denniss, Jonathan, McKendrick, A.M. 08 1900 (has links)
no / Purpose To determine whether the structure–function relationship in glaucoma can be strengthened by using more precise structural and functional measurements combined with individualized structure–function maps and custom sector selection on the optic nerve head (ONH). Design Cross-sectional study. Participants One eye of each of 23 participants with glaucoma. Methods Participants were tested twice. Visual fields were collected on a high-resolution 3° × 3° grid (164 locations) using a Zippy Estimation by Sequential Testing test procedure with uniform prior probability to improve the accuracy and precision of scotoma characterization relative to standard methods. Retinal nerve fiber layer (RNFL) thickness was measured using spectral-domain optical coherence tomography (OCT; 4 scans, 2 per visit) with manual removal of blood vessels. Individualized maps, based on biometric data, were used. To customize the areas of the ONH and visual field to correlate, we chose a 30° sector centered on the largest defect shown by OCT and chose visual field locations using the individualized maps. Baseline structure–function correlations were calculated between 24-2 locations (n = 52) of the first tested visual field and RNFL thickness from 1 OCT scan, using the sectors of the Garway-Heath map. We added additional data (averaged visual field and OCT, additional 106 visual field locations and OCT without blood vessels, individualized map, and customized sector) and recomputed the correlations. Main Outcome Measures Spearman correlation between structure and function. Results The highest baseline correlation was 0.52 (95% confidence interval [CI], 0.13–0.78) in the superior temporal ONH sector. Improved measurements increased the correlation marginally to 0.58 (95% CI, 0.21–0.81). Applying the individualized map to the large, predefined ONH sectors did not improve the correlation; however, using the individualized map with the single 30° ONH sector resulted in a large increase in correlation to 0.77 (95% CI, 0.47–0.92). Conclusions Using more precise visual field and OCT measurements did not improve structure–function correlation in our cohort, but customizing the ONH sector and its associated visual field points substantially improved correlation. We suggest using customized ONH sectors mapped to individually relevant visual field locations to unmask localized structural and functional loss.
5

Real-Time Object Removal in Augmented Reality

Dahl, Tyler 01 June 2018 (has links)
Diminished reality, as a sub-topic of augmented reality where digital information is overlaid on an environment, is the perceived removal of an object from an environment. Previous approaches to diminished reality used digital replacement techniques, inpainting, and multi-view homographies. However, few used a virtual representation of the real environment, limiting their domains to planar environments. This thesis provides a framework to achieve real-time diminished reality on an augmented reality headset. Using state-of-the-art hardware, we combine a virtual representation of the real environment with inpainting to remove existing objects from complex environments. Our work is found to be competitive with previous results, with a similar qualitative outcome under the limitations of available technology. Additionally, by implementing new texturing algorithms, a more detailed representation of the real environment is achieved.
6

Quantification et spatialisation de la contamination en éléments traces métalliques du système fluvio-estuarien girondin / Quantification and spatial distribution of trace element contamination in the Gironde fluvio- estuarine system

Larrose, Aurélie 08 July 2011 (has links)
L’estuaire de la Gironde est affecté par une pollution polymétallique historique provenant de son bassin versant (affluent du Lot). L’analyse de 320 échantillons de sédiments couvrant l’ensemble de la surface estuarienne nous a permis d’établir les premières cartographies à haute résolution spatiale de la contamination métallique des sédiments de surface. Elles révèlent des zones d’accumulation préférentielle des ETM au niveau de la zone des îles en amont de l’estuaire et du chenal nord en aval de l’estuaire. Le facteur de contrôle dominant cette répartition est la granularité des sédiments.L’estimation des stocks métalliques potentiellement re-mobilisables, des facteurs d’enrichissement et de la toxicité potentielle du cocktail des ETM prioritaires nous ont permis d’évaluer un risque de toxicité faible à moyen des ETM vis-à-vis du biota. La contamination en ETM des bassins versants affluents de l’estuaire de la Gironde inclus dans le périmètre du SAGE Estuaire a été appréhendée en couplant sous SIG les caractéristiques typologiques de 57 bassins versants et la géochimie des sédiments prélevés à l’exutoire de ces bassins.Les anomalies les plus importantes concernent les bassins proches de l’agglomération bordelaise et correspondent au cortège des « traceurs urbains » : Ag, Cd, Cu, Hg, Sb et Zn, ainsi que Cu pour les bassins viticoles. L’étude des variations temporelles et spatiales des concentrations en ETM sur les chenaux drainant deux bassins versants agricoles montre des apports ponctuels ou chroniques en Ag,As, Cu et U attribués aux activités anthropiques. Les zones de marais jouent un rôle important dans la spéciation des ETM en lien avec les transformations de la matière organique (e.g. As). Des expérimentations de laboratoire ont permis de caractériser les processus affectant les ETM issus des sols agricoles lors de leur transfert et de leur transport dans les systèmes aquatiques. Les phénomènes de relargage à long terme de Cu soulignent le rôle important des colloïdes organiques dans la mobilité et la biodisponibilité potentielle de cet élément. / The Gironde estuarine system is impacted by historic polymetallic pollution due to mining and smelting activities in the upper watershed. Based on a high spatial resolution sampling strategy, wepropose the first maps of trace element (TE) contamination in the surface sediment at the estuarine scale. The highest TE concentrations occurred in the North Channel in the downstream estuary and inthe island zone in the upper estuary. Estimation of potentially releasable TE fraction, of enrichment factors and a comparison between measured TE concentrations and sediment quality guidelines allow us to class a major part of the estuary as a low to medium priority zone in terms of potential toxicityfor aquatic organisms.The TE contamination in the intra-estuarine watersheds included in a project of water quality management of the Gironde estuary (SAGE), was assessed for 57 watersheds by coupling into GIS,typological characteristics of the watersheds and geochemical analyses of stream sediments. Highest anomalies were found for urban watersheds for which urban tracers were identified as Ag, Cd, Cu, Hg,Sb and Zn, and for vineyard watersheds with Cu. A study of temporal and spatial variations of TEconcentrations in two small agricultural watersheds lead us to identify inputs from point and diffusive sources, especially for Ag, As, Cu and U related to anthropogenic activities. Marsh areas also play an important role in TE reactivity mainly due to organic matter transformations. In laboratory experiments simulating the transportation of TE from agricultural soils to aquatic systems and the maturing process of soil particles in the stream help us to identify processes responsible for TE release in the environment. Long term release of copper was mainly attributed to organic colloid transformation which implies an increase in the mobility, and consequently, the potential bioavailability/toxicity of Cu for aquatic organisms.
7

GEOGRAFISK KARTERING AV RÖRLIGT FRILUFTSLIV : MÖJLIGHETER ATT BIDRA TILL EN VÄGLEDNING / Geographical mapping of outdoor recreation : Opportunities to contribute to a guidance

Snöbohm, Johanna January 2019 (has links)
Biologisk mångfald och produktionen av ekosystemtjänster minskar och framtida klimatförändringar förväntas påskynda den processen. Genom att kartlägga ekosystemtjänster och de nyttor de ger till människor kan det hjälpa till att belysa naturens värde och skapa incitament för att skydda och bevara dem. Möjligheten till rörligt friluftsliv, en viktig ekosystemtjänst i Sverige, har ett samhälleligt värde då det bidrar till människors hälsa och välbefinnande. Denna studie syftar till att bidra till en vägledning för att rumsligt kartlägga ekosystemtjänster i Sverige med fokus på rörligt friluftsliv. Resultatet visar att kartläggningarna delas upp i kartering av naturområden och av de människor som använder dem. Dessa benämns ofta som tillgång och efterfrågan. En koppling ses mellan valet av metoder och dataunderlag i förhållande till vilket syfte och fokusområde kartläggningarna har. Ett mönster går att urskilja i återkommande aktiviteter i kartläggningarna, vilket resulterar i ett förslag på vägledande flödesdiagram över turordningen av aktiviteterna. / Biodiversity and thus the delivery of ecosystem services are declining, and future climate change is expected to accelerate the process. By mapping ecosystem services and the benefits they provide to humans, one can shed light on the value of nature, and help create incentives in protecting and preserving it. The opportunity for outdoor recreation, an important ecosystem service in Sweden, has a social value as it contributes to human health and wellbeing. This study aims at to contributing to a guide for spatially mapping ecosystem services in Sweden, with a focus on outdoor recreation. The result shows that outdoor recreation mappings can be about mapping either natural areas or the people who use them. These are often referred to as supply and demand. A connection is seen between the choice of methods and data, in relation to the aim and focus of the studies. A pattern is revealed in recurring activities in the mappings, resulting in a suggested flow chart for the sequence of activities when mapping outdoor recreation.
8

Understanding Formation and Evolution of Dune Fields by Spatial Mapping and Analysis: Upper Muskegon River Valley, Michigan

O'Malley, Paul W. 09 August 2019 (has links)
No description available.
9

Spatial Mapping in virtuellen Umgebungen / Spatial mapping in virtual environments: The effects of stereoscopy and natural mappping on user experience

Pietschmann, Daniel 22 August 2014 (has links) (PDF)
Die vorliegende Arbeit untersucht die Auswirkung von reichhaltigen, natürlichen Eingabe- und Ausgabeinformationen in virtuellen Umgebungen in Form von Natural Mapping und Stereoskopie. Dabei steht insbesondere die Kombination der Ein- und Ausgabemodalitäten mit dem damit verbundenen Interaktionsgegenstand im Fokus. Auf Basis von mentalen Modellen werden Transferprozesse von Wissen und Fertigkeiten bezüglich realer Handlungen auf virtuelle Handlungen angenommen. Diese resultieren in einer potenziell höheren User Experience und Performance bei der Interaktion. Spatial Mapping wird als Konzept der räumlichen Übereinstimmung von Wahrnehmungsräumen der Ein- und Ausgabeinformationen eingeführt und damit als holistische Erweiterung von Natural Mapping verstanden. Spatial Mapping bezeichnet in der vorliegenden Arbeit den Grad der Verknüpfung der physikalischen und virtuellen Umgebung, sodass Nutzer im Idealfall eine isomorphe Abbildung der beiden Wahrnehmungsräume erfahren und notwendige Transformationsprozesse für die Verarbeitung der virtuellen Umgebung minimiert werden können. Im Resultat stehen mehr kognitive Ressourcen für andere Inhalte zur Verfügung. Auf Basis des Spatial-Mapping-Ansatzes wurde ein Pfadmodell konstruiert, das experimentell überprüft wurde. In zwei Experimenten wurden Effekte von Natural Mapping und Stereoskopie in Szenarien mit hohem Spatial Mapping untersucht. Das erste Experiment nutzte dafür ein kommerzielles Computerspiel, bei dem Spatial Mapping für die Interaktion nicht handlungsrelevant war. Beim zweiten Experiment kam ein Virtual-Reality-Simulator zum Einsatz, bei dessen Aufgabenstellung Nutzer vom hohen Spatial Mapping deutlich profitieren konnten. Meist wird Stereoskopie auf existierende mediale Inhalte angewendet, ohne die Inhalte entsprechend darauf anzupassen. Diese Vorgehensweise lässt sich sowohl bei kommerziellen Computerspielen als auch in der Filmindustrie beobachten. Die Experimente zeigen, dass Stereoskopie keinen Einfluss auf UX und Performance hat, wenn das verfügbare Spatial Mapping für den Interaktionsgegenstand nicht handlungsrelevant ist. Die Arbeit diskutiert den Einsatz von Stereoskopie und Natural Mapping in Abhängigkeit des verwendeten Interaktionsgegenstandes und liefert damit einen Erklärungsansatz, der Eingabe- und Ausgabemodalitäten kombiniert betrachtet.
10

Laser Beam Induced Conductance Modulations as a Potential Microprobe in the Investigation of Defects and Inhomogeneities in Bulk Si and PbS, HgCdTe Quantum Dot Heterostructures

Abhale, Atul Prakash January 2017 (has links) (PDF)
In this thesis, the strength of the LBIC system is enhanced in different aspects that includes its feasibility as a non-destructive characterization tool, the signal analysis and development of analytical solution to have better understanding on the defects and inhomogeneities in the quantum dot based hetero-structures for device applications, finally understanding its limits due to the size of the laser beam and interpretation of artefacts in the signal appearance due to the presence of co-devices. Chapter#1 provides the introduction and literature survey of the LBIC system. It covers the importance and area of application of the LBIC. Chapter#2 various tools and instrumentation are discussed briefly for the systems that are developed in the lab as well as standard tools utilised for the material characterization. A LBIC instrumentation a novel colloidal quantum dots (CQD) thin film deposition system is discussed. In the last part along with the standard characterization systems a software tool (semiconductor device simulator) is discussed, which is used to visualize and understand the LBIC profile that is obtained experimentally. Chapter#3 provides the information of colloidal synthesis of PbS and HgxCd1-xTe quantum dots. Device fabrication process is explained step by step for the following devices. p-n junction silicon diodes, PbS-CQD/Si hetero-structures, ITO/PbS-CQD/Al crossbar structures and HgCdTe-CQD/Si hetero-structures. Chapter#4 deals with the major constraints imposed on the LBIC due to the need of Ohmic contacts. To overcome this major limitation, in this work, the origin of the signal is studied with the remote contact geometry for silicon p-n junction devices. It was observed that the signals can be collected with the capacitively coupled remote contacts, where LBIC was ultimately demonstrated as contactless measurement tool without any compromise on the measurements and thus obtained physical parameters. The effect of finite laser beam size is also described, which was found to have effect on the actual dimensions measured with the LBIC images. LBIC utility is further enhanced with the Si/CQD based hetero-structure devices, which are the potential candidates in the evolving device technology to be utilized in various modular systems such as PDs and LED applications. Chapter#5 discusses the origin and possible mechanisms for lateral photo-voltage which is closely monitored in the PbS-CQD/Si hetero-junction device systems. Interestingly, it is observed that there are two different line profiles for n and p type Si substrates. Different mechanisms that give rise to this kind of profiles were found to be distinct and are related to the band alignment of the CQD/Si hetero-structure. It lead to the revelation of an interesting phenomenon and believed to be universally observed irrespective of the materials involved in the formation of hetero-junction. Simulations and experimental results are quite consistent and in agreement with each other, which confirm the underlying physical mechanism that connects the LBIC anomalies with the band alignment. Chapter#6 deals with the spatial variations in the transverse photocurrent in the PbS-CQD film which is studied as a function of applied bias. Analytical equation is setup for the photocurrent in the CQD film under applied bias with the help of available transport mechanism and equations from the literature. The spatial non-uniformity that exists in the photocurrent proved to be the result of spatial inhomoginities in the physical parameters. By correlating the spatial data to the analytical equation, it is shown that the inhomoginities can be predicted. This approach is important for the devices, where monolithic detectors are fabricated by depositing CQD film on Read-Out-Integrated-Circuit (ROIC), where the manifestation of non-uniformity can be understood and probably fixed. Chapter#7 HgCdTe CQD based devices are studied for the purpose of photo-detector applications in MWIR (3  5 μm) region. HgxCd1-xTe Colloidal quantum dots are technologically important due to their wide absorption range that covers different regions of the atmospheric window. HgxCd1-xTe are successfully synthesised, which covers the absorption edge up to ~6.25 m in the IR region. Absorption and photo-response studies are carried out on HgxCd1-xTe/Si hetero-junctions under incident IR radiation. It is observed that the band gap of the quantum dots can be tuned easily by controlling the growth time as a parameter, thus moulded HgxCd1-xTe CQD/Si hetero-structures were found to have good photo-response. Chapter#8 the summary and the future direction and scope of the work is discussed. This includes the interesting observations during this thesis work which are not reported here in details.

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