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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.
21

Handling of Rolling Shutter Effects in Monocular Semi-Dense SLAM Algorithms

Tallund, Lukas January 2016 (has links)
Since most people now have a high-performing computing device with an attached camera in their pocket, in the form of a smartphone, robotics and computer vision researchers are thrilled about the possibility this creates. Such devices have previously been used in robotics to create 3D maps of environments and objects by feeding the camera data to a 3D reconstruction algorithm. The big downside with smartphones is that their cameras use a different sensor than what is usually used in robotics, namely a rolling shutter camera.These cameras are cheaper to produce but are not as well suited for general 3D reconstruction algorithms as the global shutter cameras typically used in robotics research. One recent, accurate and performance effective 3D reconstruction method which could be used on a mobile device, if tweaked, is LSD-SLAM. This thesis uses the LSD-SLAM method developed for global shutter cameras and incorporates additional methods developed allow the usage of rolling shutter data.The developed method is evaluated by calculating numbers of failed 3D reconstructions before a successful one is obtained when using rolling shutter data.The result is a method which improves this metric with about 70\% compared to the unedited LSD-SLAM method.
22

Processing and sintering of carbonate hydroxyapatite

Barralet, Jake Edward January 1995 (has links)
Since the early 1970's there have been a number of investigations into the preparation of dense sintered hydroxyapatite for medical applications. However, there have been few studies reporting the production of sintered carbonate apatite, which resembles more closely the composition of human bone mineral. This work has studied the precipitation, processing and sintering of carbonate apatites. Crystallisation variables such as temperature and bicarbonate ion concentration have been investigated in order to determine some effects on the size, morphology and composition of carbonate apatite precipitates. By employing the correct conditions, nanoscale precipitates have been produced that have enabled the use of a colloidal filtration route in processing. The effect of sintering atmosphere, green density, and carbonate content were investigated isochronally over a range of temperatures. Isothermal experiments demonstrated the evolution of microstructure and changes in density with time. Results from this study indicated that translucent 99.9% relative density carbonated hydroxyapatite could be produced by sintering in an atmosphere of carbon dioxide and water. Water was found to enhance densification in carbon dioxide furnace atmospheres. The temperature at which maximum densification occurred decreased with carbonate content. Bloating was found to be related to carbonate content as larger expansions were observed in higher carbonate content materials. The partial pressure of water did not effect the composition of the carbonate apatite, whereas the green composition did, contrary to the findings of other workers.
23

Suivi de caméra image en temps réel base et cartographie de l'environnement / Real-time image-based RGB-D camera motion tracking and environment mapping

Tykkälä, Tommi 04 September 2013 (has links)
Dans ce travail, méthodes d'estimation basées sur des images, également connu sous le nom de méthodes directes, sont étudiées qui permettent d'éviter l'extraction de caractéristiques et l'appariement complètement. L'objectif est de produire pose 3D précis et des estimations de la structure. Les fonctions de coût présenté minimiser l'erreur du capteur, car les mesures ne sont pas transformés ou modifiés. Dans la caméra photométrique estimation de la pose, rotation 3D et les paramètres de traduction sont estimées en minimisant une séquence de fonctions de coûts à base d'image, qui sont des non-linéaires en raison de la perspective projection et la distorsion de l'objectif. Dans l'image la structure basée sur le raffinement, d'autre part, de la structure 3D est affinée en utilisant un certain nombre de vues supplémentaires et un coût basé sur l'image métrique. Les principaux domaines d'application dans ce travail sont des reconstitutions d'intérieur, la robotique et la réalité augmentée. L'objectif global du projet est d'améliorer l'image des méthodes d'estimation fondées, et pour produire des méthodes de calcul efficaces qui peuvent être accueillis dans des applications réelles. Les principales questions pour ce travail sont : Qu'est-ce qu'une formulation efficace pour une image 3D basé estimation de la pose et de la structure tâche de raffinement ? Comment organiser calcul afin de permettre une mise en œuvre efficace en temps réel ? Quelles sont les considérations pratiques utilisant l'image des méthodes d'estimation basées sur des applications telles que la réalité augmentée et la reconstruction 3D ? / In this work, image based estimation methods, also known as direct methods, are studied which avoid feature extraction and matching completely. Cost functions use raw pixels as measurements and the goal is to produce precise 3D pose and structure estimates. The cost functions presented minimize the sensor error, because measurements are not transformed or modified. In photometric camera pose estimation, 3D rotation and translation parameters are estimated by minimizing a sequence of image based cost functions, which are non-linear due to perspective projection and lens distortion. In image based structure refinement, on the other hand, 3D structure is refined using a number of additional views and an image based cost metric. Image based estimation methods are usable whenever the Lambertian illumination assumption holds, where 3D points have constant color despite viewing angle. The main application domains in this work are indoor 3D reconstructions, robotics and augmented reality. The overall project goal is to improve image based estimation methods, and to produce computationally efficient methods which can be accomodated into real applications. The main questions for this work are : What is an efficient formulation for an image based 3D pose estimation and structure refinement task ? How to organize computation to enable an efficient real-time implementation ? What are the practical considerations of using image based estimation methods in applications such as augmented reality and 3D reconstruction ?
24

Quiver representations and their dense orbits

Lara, Danny 01 May 2019 (has links)
We can view quiver representations of a fixed dimension vector as an algebraic variety over an algebraically closed field $K$. There is an action of the product of general linear groups on each of these varieties where the orbits of the action correspond to isomorphism classes of quiver representation. A $K$-algebra $A$ is said to have the dense orbit property if for each dimension vector, the product of the general linear group acts on each irreducible component of the module variety with a dense orbit. Under certain conditions, a $K$ algebra $A$ is representation finite if and only if it $A$ has the dense orbit property. The implication representation finite implies the dense orbit property is always true. The converse is not true in general, as shown by Chindris, Kinser, and Weyman in \cite{ryan}. Our main theorem of this thesis builds on their work to give a family of representation infinite algebras with the dense orbit property. We also give a conjectured classification of indecomposables with dense orbits. \par In the future, we hope the work presented here can be used to find even more examples of representation infinite algebra with the dense orbit property to then develop deeper theory to classify algebras with the dense orbit property that are representation infinite.
25

A Phase Based Dense Stereo Algorithm Implemented in CUDA

Macomber, Brent David 2011 May 1900 (has links)
Stereo imaging is routinely used in Simultaneous Localization and Mapping (SLAM) systems for the navigation and control of autonomous spacecraft proximity operations, advanced robotics, and robotic mapping and surveying applications. A key step (and generally the most computationally expensive step) in the generation of high fidelity geometric environment models from image data is the solution of the dense stereo correspondence problem. A novel method for solving the stereo correspondence problem to sub-pixel accuracy in the Fourier frequency domain by exploiting the Convolution Theorem is developed. The method is tailored to challenging aerospace applications by incorporation of correction factors for common error sources. Error-checking metrics verify correspondence matches to ensure high quality depth reconstructions are generated. The effect of geometric foreshortening caused by the baseline displacement of the cameras is modeled and corrected, drastically improving correspondence matching on highly off-normal surfaces. A metric for quantifying the strength of correspondence matches is developed and implemented to recognize and reject weak correspondences, and a separate cross-check verification provides a final defense against erroneous matches. The core components of this phase based dense stereo algorithm are implemented and optimized in the Compute Uni ed Device Architecture (CUDA) parallel computation environment onboard an NVIDIA Graphics Processing Unit (GPU). Accurate dense stereo correspondence matching is performed on stereo image pairs at a rate of nearly 10Hz.
26

Application of in-situ bioremediation technology to remediate trichloroethylene-contaminated groundwater

Tseng, Shih-hao 02 September 2009 (has links)
Chlorinated organic compounds are widely used in various industrial processes. Due to their high density and low water solubility, they are mainly utilized as cleaning solvents in dry cleaning operations, as well as semiconductor manufacturers. Many chlorinated organic compounds spilled sites contain residuals, which present in a pure liquid phase (dense non-aqueous phase liquids, DNAPLs). Trichloroethylene (TCE) is the most typical compound as a result. In situ bioremediation has been successfully used for the removal of TCE. This process has several advantages, such as relative simplicity, low cost, and potentially remarkable efficiency in contamination removal than others. By using the in situ bioremediation to remediate TCE contaminated groundwater, it must ensure (1) biodegradability of contaminants, and the presence of a competent biodegrading population of microorganisms, (2) presence of electron acceptors, and (3) environment condition and, nutrient sources. A field study for biodegradation TCE through molasses injection was conducted at the industrial trading estate in Kaohsiung City. The study included electronic products, semiconductor, nicety optical industry and so on. Molasses, nitrate and phosphate were introduced from injection well (BW1-1 and BW2-1) into aerobic and anaerobic groundwater contaminated site. In the aerobic zone, there were four wells being monitored: BW1-1, C029, BW1-2 and BW1-3. After 213 days of biostimulation treatment, TCE concentration detection results showed TCE concentrations in all wells monitored. BW1-1 and C029, there was a sharp decrease from 0.0853 mg/L to below the detection limit and from 0.1340 mg/L to 0.0038 mg/L. BW1-2 and BW1-3 showed a slight decrease from 0.0668 mg/L to 0.0211 mg/L and from 0.0323 mg/L to 0.0161 mg/L. After treatments, TCE concentrations in all wells monitored were dropped to 0.05 mg/L. In anaerobic zone, there were four wells being monitored: BW2-1, SW-4, BW2-2 and BW2-3. After 193 days of biostimulation treatment, TCE concentration detection results showed TCE concentrations in all wells monitored. BW2-1, SW-4, BW2-2 and BW2-3 all had a slight decrease from 0.0399 mg/L to 0.0043 mg/L, from 0.14603 mg/L to 0.0687 mg/L, from 0.1030 mg/L to 0.0365 mg/L and from 0.0492 mg/L to 0.0289 mg/L. According to the results from BIOCHLOR modeling, elevated aqueous concentration of chloroethenes with a classical reduction pathway for TCE leading to an accumulation of vinyl chloride and ethane. All the results revealed that bioremediation technology is one of the more feasible approaches to clean up TCE contaminated groundwater in this field.
27

Isochoric heating of copper to Warm Dense Matter state using protons produced through laser solid-laser interactions

Feldman, Samuel Henry 24 July 2013 (has links)
This thesis examines the equation of state of copper at Warm Dense Matter states, between 1-100 eV and .1-10 times solid density. Protons accelerated off a thin metal foil irradiated with a high intensity laser beam flash heat solid density copper to between 5-10 eV before significant expansion occurs. The measured temperature and expansion are compared against simulations using various equations of states. The production and characterization of the laser system and proton beam used to heat the matter is also presented. / text
28

Evaluation of microbial reductive dechlorination in tetrachloroethene (PCE) Dense Nonaqueous Phase Liquid (DNAPL) source zones

Amos, Benjamin Keith January 2007 (has links)
Thesis (Ph.D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Löffler, Frank E.; Committee Member: Hughes, Joseph B.; Committee Member: Pennell, Kurt D.; Committee Member: Spain, Jim C.; Committee Member: Taillefert, Martial
29

Value and reliability of DNAPL investigation programs /

McGrath, Travis Christopher, January 1998 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 469-477). Available also in a digital version from Dissertation Abstracts.
30

High Productivity Programming of Dense Linear Algebra on Heterogeneous NUMA Architectures

Alomairy, Rabab M. 07 1900 (has links)
High-end multicore systems with GPU-based accelerators are now ubiquitous in the hardware landscape. Besides dealing with the nontrivial heterogeneous environ- ment, end users should often take into consideration the underlying memory architec- ture to decrease the overhead of data motion, especially when running on non-uniform memory access (NUMA) platforms. We propose the OmpSs parallel programming model approach using its Nanos++ dynamic runtime system to solve the two challeng- ing problems aforementioned, through 1) an innovative NUMA node-aware scheduling policy to reduce data movement between NUMA nodes and 2) a nested parallelism feature to concurrently exploit the resources available from the GPU devices as well as the CPU host, without compromising the overall performance. Our approach fea- tures separation of concerns by abstracting the complexity of the hardware from the end users so that high productivity can be achieved. The Cholesky factorization is used as a benchmark representative of dense numerical linear algebra algorithms. Superior performance is also demonstrated on the symmetric matrix inversion based on Cholesky factorization, commonly used in co-variance computations in statistics. Performance on a NUMA system with Kepler-based GPUs exceeds that of existing implementations, while the OmpSs-enabled code remains very similar to its original sequential version.

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