To see the other types of publications on this topic, follow the link: Real-time correction.
Dissertations / Theses on the topic 'Real-time correction'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Real-time correction.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Sancho, Sánchez Irene. "On Adaptive Forward Error Correction for Real Time Traffic." Thesis, KTH, Reglerteknik, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-109478.
Full textAbstract:
Most of the real-time applications use user data protocol (UDP) as their transport protocol. The reason is that UDP does not provide flow control or error recovery and does not require connection management. Consequently it is a fast protocol suitable for applications that only need to transmit little data or for delay sensitive applications. Nevertheless, UDP has a major drawback, if some packets are dropped then there is no way to recover them. Some applications as video or audio could accept lower quality and most of the times the lost of some packets is less critic than the delay introduced by error recovery methods. Since more applications with real-time constraints such as video image and audio are introduced both over the wired Internet and over wireless some improvements should be made in order to obtain better performance. The main contribution of this thesis is to study an intermediate solution providing more reliability to the communication between applications running on top of UDP and at the same time support its fast connection quality using already existing protocols. In order to obtain it, real-time transport protocol (RTP) has been chosen as upper level protocol (to provide ”flowcontrol”) and an adaptive forward error correction (AFEC) technique has been studied (to provide error management). The idea of AFEC is to inject an adaptive amount of redundancy packets in every sent block (or datagram) in order to achieve a desired recovery rate at the receiver without using any retransmission mechanism. The sender dynamically uses feedback information from the receiver to decide the optimal amount of redundancy to introduce in every sent block. This decision task is managed by a control system at the sender side. Using the network simulator, ns-2, the performance of three different controllers using AFEC is evaluated. The results show in various scenarios that the amount of discarded blocks due to the corruption of some of its packets (block loss probability after decoding) decrease considerably when the AFEC mechanism is introduced.
2
Westerlund, Johan. "Forward Error Correction in Real-time Video Streaming Applications." Thesis, Umeå universitet, Institutionen för datavetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-99644.
Full textAbstract:
The Internet is rapidly becoming the dominant platform for video contribution and distribution, but today’s Internet provides a best-effort service without any guarantee of quality. Internet video streaming has to cope with this lack of guarantees. Due to congestion and the heterogeneous infrastructure of the Internet a video transmission will be plagued by packet loss, variability in throughput, and latency. To mitigate some of these these problems f.o.r.w.a.r.d e.r.r.o.r c.o.r.r.e.c.t.i.o.n (F.E.C) can be employed. The aim of this thesis is to present a theoretical introduction to error correcting codes, implement and integrate f.o.r.w.a.r.d e.r.r.o.r c.o.r.r.e.c.t.i.o.n into an existing video streaming application, and test the implementation in both simulated and real-world conditions. Parameters of the F.E.C algorithm will be tweaked and guidelines for parameter selection will be developed
3
Dufau, Michael. "Bias errors in IRLV data and their real time correction." Thesis, Liverpool John Moores University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337786.
Full text
4
Granholm, George Richard 1976. "Near-real time atmospheric density model correction using space catalog data." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/44899.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000.Includes bibliographical references (p. 179-184).
Several theories have been presented in regard to creating a neutral density model that is corrected or calibrated in near-real time using data from space catalogs. These theories are usually limited to a small number of frequently tracked "calibration satellites" about which information such as mass and crosssectional area is known very accurately. This work, however, attempts to validate a methodology by which drag information from all available low-altitude space objects is used to update any given density model on a comprehensive basis. The basic update and prediction algorithms and a technique to estimate true ballistic factors are derived in detail. A full simulation capability is independently verified. The process is initially demonstrated using simulated range, azimuth, and elevation observations so that issues such as required number and types of calibration satellites, density of observations, and susceptibility to atmospheric conditions can be examined. Methods of forecasting the density correction models are also validated under different atmospheric conditions.
by George Richard Granholm.
S.M.
5
Alhamud, Alkathafi Ali. "Implementation of anatomical navigators for real time motion correction in diffusion tensor imaging." Doctoral thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/10052.
Full textAbstract:
Includes bibliographical references.Prospective motion correction methods using an optical system, diffusion-weighted prospective acquisition correction, or a free induction decay navigator have recently been applied to correct for motion in diffusion tensor imaging. These methods have some limitations and drawbacks. This article describes a novel technique using a three-dimensional-echo planar imaging navigator, of which the contrast is independent of the b-value, to perform prospective motion correction in diffusion weighted images, without having to reacquire volumes during which motion occurred, unless motion exceeded some preset thresholds. Water phantom and human brain data were acquired using the standard and navigated diffusion sequences, and the mean and whole brain histogram of the fractional anisotropy and mean diffusivity were analyzed.
6
Brion, Véronique. "Towards real-time diffusion imaging : noise correction and inference of the human brain connectivity." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112058/document.
Full textAbstract:
La plupart des constructeurs de systèmes d'imagerie par résonance magnétique (IRM) proposent un large choix d'applications de post-traitement sur les données IRM reconstruites a posteriori, mais très peu de ces applications peuvent être exécutées en temps réel pendant l'examen. Mises à part certaines solutions dédiées à l'IRM fonctionnelle permettant des expériences relativement simples ainsi que d'autres solutions pour l'IRM interventionnelle produisant des scans anatomiques pendant un acte de chirurgie, aucun outil n'a été développé pour l'IRM pondérée en diffusion (IRMd). Cependant, comme les examens d'IRMd sont extrêmement sensibles à des perturbations du système hardware ou à des perturbations provoquées par le sujet et qui induisent des données corrompues, il peut être intéressant d'investiguer la possibilité de reconstruire les données d'IRMd directement lors de l'examen. Cette thèse est dédiée à ce projet innovant. La contribution majeure de cette thèse a consisté en des solutions de débruitage des données d'IRMd en temps réel. En effet, le signal pondéré en diffusion peut être corrompu par un niveau élevé de bruit qui n'est plus gaussien, mais ricien ou chi non centré. Après avoir réalisé un état de l'art détaillé de la littérature sur le bruit en IRM, nous avons étendu l'estimateur linéaire qui minimise l'erreur quadratique moyenne (LMMSE) et nous l'avons adapté à notre cadre de temps réel réalisé avec un filtre de Kalman. Nous avons comparé les performances de cette solution à celles d'un filtrage gaussien standard, difficile à implémenter car il nécessite une modification de la chaîne de reconstruction pour y être inséré immédiatement après la démodulation du signal acquis dans l'espace de Fourier. Nous avons aussi développé un filtre de Kalman parallèle qui permet d'appréhender toute distribution de bruit et nous avons montré que ses performances étaient comparables à celles de notre méthode précédente utilisant un filtre de Kalman non parallèle. Enfin, nous avons investigué la faisabilité de réaliser une tractographie en temps-réel pour déterminer la connectivité structurelle en direct, pendant l'examen. Nous espérons que ce panel de développements méthodologiques permettra d'améliorer et d'accélérer le diagnostic en cas d'urgence pour vérifier l'état des faisceaux de fibres de la substance blancheMost magnetic resonance imaging (MRI) system manufacturers propose a huge set of software applications to post-process the reconstructed MRI data a posteriori, but few of them can run in real-time during the ongoing scan. To our knowledge, apart from solutions dedicated to functional MRI allowing relatively simple experiments or for interventional MRI to perform anatomical scans during surgery, no tool has been developed in the field of diffusion-weighted MRI (dMRI). However, because dMRI scans are extremely sensitive to lots of hardware or subject-based perturbations inducing corrupted data, it can be interesting to investigate the possibility of processing dMRI data directly during the ongoing scan and this thesis is dedicated to this challenging topic. The major contribution of this thesis aimed at providing solutions to denoise dMRI data in real-time. Indeed, the diffusion-weighted signal may be corrupted by a significant level of noise which is not Gaussian anymore, but Rician or noncentral chi. After making a detailed review of the literature, we extended the linear minimum mean square error (LMMSE) estimator and adapted it to our real-time framework with a Kalman filter. We compared its efficiency to the standard Gaussian filtering, difficult to implement, as it requires a modification of the reconstruction pipeline to insert the filter immediately after the demodulation of the acquired signal in the Fourier space. We also developed a parallel Kalman filter to deal with any noise distribution and we showed that its efficiency was quite comparable to the non parallel Kalman filter approach. Last, we addressed the feasibility of performing tractography in real-time in order to infer the structural connectivity online. We hope that this set of methodological developments will help improving and accelerating a diagnosis in case of emergency to check the integrity of white matter fiber bundles
7
Pagan, Jesus Manuel. "Cable-Suspended Robot System with Real Time Kinematics GPS Position Correction for Algae Harvesting." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1539256829665799.
Full text
8
Patel, Darshan Shyam. "A Real-Time Technique for the Correction of Invasive Blood Pressure Measurements using Counter Pressure." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1205764260.
Full text
9
Hess, Aaron T. "Real-time motion and main magnetic field correction in MR spectroscopy using an EPI volumetric navigator." Doctoral thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11359.
Full textAbstract:
In population groups where subjects do not lie still during Magnetic Resonance Spectroscopy (MRS) scans, real-time volume of interest (VOI), frequency, and main magnetic field (B0) shim correction may be necessary. This work demonstrates firstly that head movement causes significant B0 disruption in both single voxel spectroscopy and spectroscopic imaging.
10
Roujol, Sébastien. "MR-guided thermotherapies of mobile organs : advances in real time correction of motion and MR-thermometry." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14263/document.
Full textAbstract:
L'ablation des tissus par hyperthermie locale guidée par IRM est une technique prometteuse pour le traitement du cancer et des arythmies cardiaques. L'IRM permet d'extraire en temps réel des informations anatomiques et thermiques des tissus. Cette thèse a pour objectif d'améliorer et d'étendre la méthodologie existante pour des interventions sur des organes mobiles comme le rein, le foie et le coeur. La première partie a été consacrée à l'introduction de l'imagerie rapide (jusqu'à 10-15 Hz) pour le guidage de l'intervention par IRM en temps réel. L'utilisation de cartes graphiques (GPGPU) a permis une accélération des calculs afin de satisfaire la contrainte de temps réel. Une précision, de l'ordre de 1°C dans les organes abdominaux et de 2-3°C dans le coeur, a été obtenue. Basé sur ces avancées, de nouveaux développements méthodologiques ont été proposés dans une seconde partie de cette thèse. L'estimation du mouvement basée sur une approche variationnelle a été améliorée pour gérer la présence de structures non persistantes et de fortes variations d'intensité dans les images. Un critère pour évaluer la qualité du mouvement estimé a été proposé et utilisé pour auto-calibrer notre algorithme d'estimation du mouvement. La méthode de correction des artefacts de thermométrie liés au mouvement, jusqu'ici restreinte aux mouvements périodiques, a été étendue à la gestion de mouvements spontanés. Enfin, un nouveau filtre temporel a été développé pour la réduction du bruit sur les cartographies de température. La procédure interventionnelle apparaît maintenant suffisamment mature pour le traitement des organes abdominaux et pour le transfert vers la clinique. Concernant le traitement des arythmies cardiaques, les méthodes ont été évaluées sur des sujets sains et dans le ventricule gauche. Par conséquent, la faisabilité de l'intervention dans les oreillettes mais aussi en présence d'arythmie devra être abordéeMR-guided thermal ablation is a promising technique for the treatment of cancer and atrial fibrillation. MRI provides both anatomical and temperature information. The objective of this thesis is to extend and improve existing techniques for such interventions in mobile organs such as the kidney, the liver and the heart. A first part of this work focuses on the use of fast MRI (up to 10-15 Hz) for guiding the intervention in real time. This study demonstrated the potential of GPGPU programming as a solution to guarantee the real time condition for both MR-reconstruction and MR-thermometry. A precision in the range of 1°C and 2-3°C was obtained in abdominal organs and in the heart, respectively. Based on these advances, new methodological developments have been carried out in a second part of this thesis. New variational approaches have proposed to address the problem of motion estimation in presence of structures appearing transient and high intensity variations in images. A novel quality criterion to assess the motion estimation is proposed and used to autocalibrate our motion estimation algorithm. The correction of motion related magnetic susceptibility variation was extended to treat the special case of spontaneous motion. Finally, a novel temporal filter is proposed to reduce the noise of MR-thermometry measurements while controlling the bias introduced by the filtering process. As a conclusion, all main obstacles for MR-guided HIFU-ablation of abdominal organs have been addressed in in-vivo and ex-vivo studies, therefore clinical studies will now be realized. However, although promising results have been obtained for MR-guided RF-ablation in the heart, its feasibility in the atrium and in presence of arrhythmia still remains to be investigated
11
Liu, Kai. "Real-time 3-D Reconstruction by Means of Structured Light Illumination." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/81.
Full textAbstract:
Structured light illumination (SLI) is the process of projecting a series of light striped patterns such that, when viewed at an angle, a digital camera can reconstruct a 3-D model of a target object's surface. But by relying on a series of time multiplexed patterns, SLI is not typically associated with video applications. For this purpose of acquiring 3-D video, a common SLI technique is to drive the projector/camera pair at very high frame rates such that any object's motion is small over the pattern set. But at these high frame rates, the speed at which the incoming video can be processed becomes an issue. So much so that many video-based SLI systems record camera frames to memory and then apply off-line processing. In order to overcome this processing bottleneck and produce 3-D point clouds in real-time, we present a lookup-table (LUT) based solution that in our experiments, using a 640 by 480 video stream, can generate intermediate phase data at 1063.8 frames per second and full 3-D coordinate point clouds at 228.3 frames per second. These achievements are 25 and 10 times faster than previously reported studies. At the same time, a novel dual-frequency pattern is developed which combines a high-frequency sinusoid component with a unit-frequency sinusoid component, where the high-frequency component is used to generate robust phase information and the unit-frequency component is used to reduce phase unwrapping ambiguities. Finally, we developed a gamma model for SLI, which can correct the non-linear distortion caused by the optical devices. For three-step phase measuring profilometry (PMP), analysis of the root mean squared error of the corrected phase showed a 60х reduction in phase error when the gamma calibration is performed versus 33х reduction without calibration.
12
Kaczorowski, Andrzej. "Adaptive aberration correction for holographic projectors." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/270322.
Full textAbstract:
This work builds up on the greatest minds of Cambridge Holography: Adrian Cable, Edward Buckley, Jonathan Freeman, and Christoph Bay. Cable and Buckley, developed an OSPR algorithm which was the first to provide high-quality real-time hologram generation using general-purpose hardware while Freeman designed a method to correct arbitrary aberrations. As ingenious as the method was, the calculations were extensively lengthy. Addressing this issue, a variant of OSPR suited for correcting spatially-varying aberration is presented. The algorithm combines the approaches of Cable, Buckley and Freeman to provide real-time hologram generation while incorporating various corrections (aberration, distortion, and pixel shape envelope). A high-performance implementation on a mid-range GPU achieved hologram generation up to 12 fps. Following topic studied is an adaptive optical correction. This work attempts to construct a set of methods, forming an automated testbed for holographic projectors. Each model, after exiting the production line is placed on such testbed, having all of its imperfections characterized. Once calibrated, each model is able to display highest-quality image throughout its life-span. An application of this work to industry was carried in collaboration with Dr Phillip Hands (University of Edinburgh) and LumeJET. Three demonstrators are constructed intending for a cost-effective system for holographic lithography. They are characterized using the developed testbed. Using the supersampled Adaptive OSPR algorithm, the diffraction limit was surpassed 2.75 times allowing to increase the patterning area. This combines approaches of Cable, Buckley, Freeman and Bay to achieve a wide field-of-view and high pixel-count replay field using off-the-shelf components. This thesis is finished describing the work on 3D holography carried with Penteract28. It is shown that the 2D hologram in the presence of spatially-varying aberrations is mathematically equivalent to a 3D hologram. The same implementation of the algorithm can be used to provide real-time 3D hologram generation.
13
Bisplinghoff, Andreas [Verfasser]. "Design of Efficient and Robust Forward Error Correction for Real-Time Application in Coherent Optical Communication Systems / Andreas Bisplinghoff." Aachen : Shaker, 2016. http://d-nb.info/1101184965/34.
Full text
14
Marques, Haroldo Antonio [UNESP]. "PPP em tempo real com estimativa das correções dos relógios dos satélites no contexto de rede GNSS." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/100256.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:30:31Z (GMT). No. of bitstreams: 0
Previous issue date: 2012-04-26Bitstream added on 2014-06-13T20:40:33Z : No. of bitstreams: 1
marques_ha_dr_prud.pdf: 2254240 bytes, checksum: 4a444b57aeb7b0a9588734345c28c149 (MD5)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dentre os diversos métodos possíveis de posicionamento GNSS, encontra-se atualmente em evidência aqueles que proporcionam posicionamento em tempo real (ou próximo do tempo real) com acurácia ao nível centimétrico ou decimétrico. Nesse caso, destaca-se o PPP em tempo real, o qual requer a disponibilização de órbitas precisas em tempo real, bem como as correções ou erros dos relógios dos satélites. Atualmente, é possível utilizar as efemérides preditas denominadas IGU, as quais são disponibilizadas pelo IGS, porém, as correções dos relógios dos satélites contidas nessas efemérides não apresentam acurácia suficiente (3 ns @ 0,9 m) para obtenção de resultados com qualidade centimétrica no PPP. Logo, é necessário pesquisar e desenvolver metodologias adequadas para estimar as correções dos relógios dos satélites com melhor qualidade para aplicação no PPP em tempo real. A estimativa das correções dos relógios dos satélites pode ser realizada com base numa rede de estações GNSS de referência. Nesta tese, a metodologia adotada para estimar estas correções consiste em realizar o ajustamento dos dados no modo PPP para uma rede de estações GNSS. Dessa forma, todos os efeitos sistemáticos envolvidos com os sinais dos satélites GNSS devem ser modelados adequadamente para cada estação da rede, realizando-se assim a estratégia denominada de PPP em rede. Uma vez estimadas as correções dos relógios dos satélites em tempo real, estas devem ser enviadas ao usuário, o qual as utilizará para aplicação...
Among several possible methods of GNSS positioning, it is currently in evidence those that provide real time positioning (or near real time) with accuracy near to decimeter or centimeter level. In this case, we highlight the real time PPP method, which requires the availability of real time precise orbits and corrections or errors of the satellites clocks. Currently, it is possible to use the predicted IGU ephemerides which are made available by the IGS centers. However, the satellites clocks corrections available in the IGU do not present enough accuracy (3 ns @ 0.9 m) to accomplish real time PPP with the level of centimeter accuracy. Therefore, it is necessary to research and develop appropriate methodologies for estimating the satellite clock corrections in real time with better quality for real time PPP aplication. The estimation of satellite clock corrections can be performed based on a GNSS network of reference. In this PhD thesis, the methodology used to estimate these corrections is based on the adjustment of data in the PPP mode for stations of a GNSS network. Thus, all systematic effects involved with the GNSS satellite signals must... (Complete abstract click electronic access below)
15
Maier, Joscha [Verfasser], and Peter [Akademischer Betreuer] Bachert. "Artifact Correction and Real-Time Scatter Estimation for X-Ray Computed Tomography in Industrial Metrology / Joscha Maier ; Betreuer: Peter Bachert." Heidelberg : Universitätsbibliothek Heidelberg, 2019. http://d-nb.info/1191760596/34.
Full text
16
Nilsson, Linus. "Quality and real-time performance assessment of color-correction methods : A comparison between histogram-based prefiltering and global color transfer." Thesis, Mittuniversitetet, Avdelningen för informationssystem och -teknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-33877.
Full textAbstract:
In the field of computer vision and more specifically multi-camera systems color correction is an important topic of discussion. The need for color-tone similarity among multiple images that are used to construct a single scene is self-evident. The strength and weaknesses of color- correction methods can be assessed by using metrics to measure structural and color-tone similarity and timing the methods. Color transfer has a better structural similarity than histogram-based prefiltering and a worse color-tone similarity. The color transfer method is faster than the histogram-based prefiltering. Color transfer is a better method if the focus is a structural similar image after correction, if better color-tone similarity at the cost of structural similarity is acceptable histogram-based prefiltering is a better choice. Color transfer is a faster method and is easier to run with a parallel computing approach then histogram-based prefiltering. Color transfer might therefore be a better pick for real-time applications. There is however more room to optimize an implementation of histogram-based prefiltering utilizing parallel computing.
17
MARTINS, LILIAN ALVES. "METROLOGICAL ANALYSIS ON THE ECONOMICAL IMPACT OF REAL TIME FLUID PROPERTY CORRECTION IN NATURAL GAS FLOW MEASUREMENT ON THE TRANSPORTATION PIPELINES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7847@1.
Full textAbstract:
A presente dissertação de mestrado faz uma análise
metrológica focada na
medição da vazão e totalização do volume de gás natural
através de placa de
orifício. O trabalho considera no cômputo da vazão a
determinação das
propriedades físico-químicas do combustível e a
utilização
desses parâmetros na
medição de volume de gás natural. O trabalho também
considera aspectos
relativos à aquisição eletrônica de outras variáveis
como
pressão, temperatura e
pressão diferencial, comumente amostradas em uma estação
de medição de
vazão de gás natural por placa de orifício. Não
obstante,
o estudo reflete uma
permanente preocupação da Petrobras em garantir a
confiabilidade de suas
medições e encontra sua motivação em mostrar que
metrologia constitui-se, de
fato, em importante insumo para avaliação de impacto
técnico e econômico. O
estudo considera três alternativas para aplicação da
composição química do gás
natural no cálculo da vazão de gás natural em cada um
dos
pontos de
transferência de custódia da malha de gasodutos da
Petrobras. Cada uma das
soluções técnicas está associada a investimentos em
instalação, operação e
manutenção de complexos equipamentos, criando inusitadas
oportunidades para
análise da confiabilidade metrológica capazes de
produzir
impacto econômico,
cabendo aqui lembrar que incertezas e erros associados
ao
processo de
medição não necessariamente são reduzidos com o aumento
dos investimentos
em tecnologia e instrumentação. O estudo dessas questões
torna-se ainda mais
atraente quando se considera que a malha de gasodutos da
Petrobras
distribuem cerca de 35 dos 45 milhões de m3 de gás
natural
consumidos
diariamente no Brasil. Cabe ainda salientar a relevância
deste estudo no âmbito
das melhorias estruturais propostas, uma vez que a
presente dissertação mostra
que é possível garantir controle metrológico a um custo
justificado, agregando
benefícios que não se limitam à malha de gasodutos
existente.This study presents a metrological analysis focused on the natural gas flow and volume measurement by orifice plate measurement systems. It takes into account the determination of chemical and physical properties and the application of these parameters in the flow and volume measurement. The study also considers aspects related to the electronic sampling of other process information such as pressure, temperature and differential pressure. Nevertheless, it demonstrates that metrology is, in fact, an important input of economical and technical analysis and shows a permanent concern of Petrobras: to guarantee measurement reliability. The dissertation presents three alternatives to the application of the natural gas composition in the computation of flow and volume measurement. When measuring natural gas flow and volume at the custody transfer points, the invoicing process begins to take place. Therefore, each one of the alternatives is associated to benefits, such as reduction of uncertainty, and costs and investments in equipments. It`s worthy to mention that it creates interesting opportunities to develop metrological analysis capable of generate economical impact. This study is even more attractive when referring to a 50 million cubic meters scenario, the Brazilian daily natural gas volume consumption. The relevance of this study is to show that is possible guarantee metrological control to a justified cost.
18
Roy, Sayan. "A Phase Correction Technique Based on Spatial Movements of Antennas in Real-Time (S.M.A.R.T.) for Designing Self-Adapting Conformal Array Antennas." Diss., North Dakota State University, 2017. https://hdl.handle.net/10365/26683.
Full textAbstract:
This research presents a real-time adaptive phase correction technique for flexible phased array antennas on conformal surfaces of variable shapes. Previously reported pattern correctional methods for flexible phased array antennas require prior knowledge on the possible non-planar shapes in which the array may adapt for conformal applications. For the first time, this initial requirement of shape curvature knowledge is no longer needed and the instantaneous information on the relative location of array elements is used here for developing a geometrical model based on a set of B\'ezier curves. Specifically, by using an array of inclinometer sensors and an adaptive phase-correctional algorithm, it has been shown that the proposed geometrical model can successfully predict different conformal orientations of a 1?by?4 antenna array in real-time without the requirement of knowing the shape-changing characteristics of the surface the array is attached upon. Moreover, the phase correction technique is validated by determining the field patterns and broadside gain of the 1?by?4 antenna array on four different conformal surfaces with multiple points of curvatures. Throughout this work, measurements are shown to agree with the analytical solutions and full-wave simulations.Doctoral Dissertation Fellowship by the Graduate School, North Dakota State University
19
Simegn, Gizeaddis Lamesgin. "Double volumetric navigators for real-time simultaneous shim and motion measurement and correction in Glycogen Chemical Exchange Saturation Transfer (GlycoCEST) MRI." Doctoral thesis, Faculty of Health Sciences, 2018. http://hdl.handle.net/11427/30039.
Full textAbstract:
Glycogen is the primary glucose storage mechanism in in living systems and plays a central role in systemic glucose homeostasis. The study of muscle glycogen concentrations in vivo still largely relies on tissue sampling methods via needle biopsy. However, muscle biopsies are invasive and limit the frequency of measurements and the number of sites that can be assessed. Non-invasive methods for quantifying glycogen in vivo are therefore desirable in order to understand the pathophysiology of common diseases with dysregulated glycogen metabolism such as obesity, insulin resistance, and diabetes, as well as glycogen metabolism in sports physiology. Chemical Exchange Saturation Transfer (CEST) MRI has emerged as a non-invasive contrast enhancement technique that enables detection of molecules, like glycogen, whose concentrations are too low to impact the contrast of standard MR imaging. CEST imaging is performed by selectively saturating hydrogen nuclei of the metabolites that are in chemical exchange with those of water molecules and detecting a reduction in MRI signal in the water pool resulting from continuous chemical exchange. However, CEST signal can easily be compromised by artifacts. Since CEST is based on chemical shift, it is very sensitive to field inhomogeneity which may arise from poor initial shimming, subject respiration, heating of shim iron, mechanical vibrations or subject motion. This is a particular problem for molecules that resonate close to water, such as - OH protons in glycogen, where small variations in chemical shift cause misinterpretation of CEST data. The purpose of this thesis was to optimize the CEST MRI sequence for glycogen detection and implement a real-time simultaneous motion and shim correction and measurement method. First, analytical solution of the Bloch-McConnell equations was used to find optimal continuous wave RF pulse parameters for glycogen detection, and results were validated on a phantom with varying glycogen concentrations and in vivo on human calf muscle. Next, the CEST sequence was modified with double volumetric navigators (DvNavs) to measure pose changes and update field of view and zero- and first-order shim parameters. Finally, the impact of B0 field fluctuations on the scan-rescan reproducibility of CEST was evaluated in vivo in 9 volunteers across 10 different scans. Simulation results showed an optimal RF saturation power of 1.5µT and duration of 1s for glycoCEST. These parameters were validated experimentally in vivo and the ability to detect varying glycogen concentrations was demonstrated in a phantom. Phantom data showed that the DvNav-CEST sequence accurately estimates system frequency and linear shim gradient changes due to motion and corrects resulting image distortions. In addition, DvNav-CEST was shown to yield improved CEST quantification in vivo in the presence of motion and motion-induced field inhomogeneity. B0 field fluctuations were found to lower the reproducibility of CEST measures: the mean coefficient of variation (CoV) for repeated scans was 83.70 ± 70.79 % without shim correction. However, the DvNav-CEST sequence was able to measure and correct B0 variations, reducing the CoV to 2.6 ± 1.37 %. The study confirms the possibility of detecting glycogen using CEST MRI at 3 T and shows the potential of the real-time shim and motion navigated CEST sequence for producing repeatable results in vivo by reducing the effect of B0 field fluctuations.
20
Saleh, Muhammad G. "Real-time motion and magnetic field correction for GABA editing using EPI volumetric navigated MEGA-SPECIAL sequence: Reproducibility and Gender effects." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22734.
Full textAbstract:
γ-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter and is of great interest to the magnetic resonance spectroscopy (MRS) community due to its role in several neurological diseases and disorders. Since GABA acquisition without macromolecule contamination requires long scan times and strongly depends on magnetic field (B0) stability, it is highly susceptible to motion and B0 inhomogeneity. In this work, a pair of three-dimensional (3D) echo planar imaging (EPI) volumetric navigators (vNav) with different echo times, were inserted in MEGA-SPECIAL to perform prospective correction for changes in the subject's head position and orientation, as well as changes in B0. The navigators do not increase acquisition time and have negligible effect on the GABA signal. The motion estimates are obtained by registering the first of the pairs of successive vNav volume images to the first volume image. The 3D field maps are calculated through complex division of the pair of vNav contrasts and are used for estimating zero- and first-order shim changes in the volume of interest (VOI). The efficacy of the vNav MEGA-SPECIAL sequence was demonstrated in-vitro and in vivo. Without motion and shim correction, spectral distortions and increases in spectral fitting error, linewidth and GABA concentration relative to creatine were observed in the presence of motion. The navigated sequence yielded high spectral quality despite significant subject motion. Using the volumetric navigated MEGA-SPECIAL sequence, the reproducibility of GABA measurements over a 40 minute period was investigated in two regions, the anterior cingulate (ACC) and medial parietal (PAR) cortices, and compared for different analysis packages, namely LCModel, jMRUI and GANNET. LCModel analysis yielded the most reproducible results, followed by jMRUI and GANNET. GABA levels in ACC were unchanged over time, while GABA levels in PAR were significantly lower for the second measurement. In ACC, GABA levels did not differ between males and females. In contrast, males had higher GABA levels in PAR. This gender difference was, however, only present in the first acquisition. Only in males did GABA levels in PAR decrease over time. These results demonstrate that gender differences are regional, and that GABA levels may fluctuate differently in different regions and sexes.
21
Marques, Haroldo Antonio. "PPP em tempo real com estimativa das correções dos relógios dos satélites no contexto de rede GNSS /." Presidente Prudente : [s.n.], 2012. http://hdl.handle.net/11449/100256.
Full textAbstract:
Orientador: João Francisco Galera MonicoCoorientador: Milton Hirokazu Shimabukuro
Coorientador: : Marcio de Oliveira Aquino
Banca: Celso Braga de Mendonça
Banca: Hélio Koiti Kuga
Banca: Silvio Jacks dos Anjos Garnés
Resumo: Dentre os diversos métodos possíveis de posicionamento GNSS, encontra-se atualmente em evidência aqueles que proporcionam posicionamento em tempo real (ou próximo do tempo real) com acurácia ao nível centimétrico ou decimétrico. Nesse caso, destaca-se o PPP em tempo real, o qual requer a disponibilização de órbitas precisas em tempo real, bem como as correções ou erros dos relógios dos satélites. Atualmente, é possível utilizar as efemérides preditas denominadas IGU, as quais são disponibilizadas pelo IGS, porém, as correções dos relógios dos satélites contidas nessas efemérides não apresentam acurácia suficiente (3 ns @ 0,9 m) para obtenção de resultados com qualidade centimétrica no PPP. Logo, é necessário pesquisar e desenvolver metodologias adequadas para estimar as correções dos relógios dos satélites com melhor qualidade para aplicação no PPP em tempo real. A estimativa das correções dos relógios dos satélites pode ser realizada com base numa rede de estações GNSS de referência. Nesta tese, a metodologia adotada para estimar estas correções consiste em realizar o ajustamento dos dados no modo PPP para uma rede de estações GNSS. Dessa forma, todos os efeitos sistemáticos envolvidos com os sinais dos satélites GNSS devem ser modelados adequadamente para cada estação da rede, realizando-se assim a estratégia denominada de PPP em rede. Uma vez estimadas as correções dos relógios dos satélites em tempo real, estas devem ser enviadas ao usuário, o qual as utilizará para aplicação... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Among several possible methods of GNSS positioning, it is currently in evidence those that provide real time positioning (or near real time) with accuracy near to decimeter or centimeter level. In this case, we highlight the real time PPP method, which requires the availability of real time precise orbits and corrections or errors of the satellites clocks. Currently, it is possible to use the predicted IGU ephemerides which are made available by the IGS centers. However, the satellites clocks corrections available in the IGU do not present enough accuracy (3 ns @ 0.9 m) to accomplish real time PPP with the level of centimeter accuracy. Therefore, it is necessary to research and develop appropriate methodologies for estimating the satellite clock corrections in real time with better quality for real time PPP aplication. The estimation of satellite clock corrections can be performed based on a GNSS network of reference. In this PhD thesis, the methodology used to estimate these corrections is based on the adjustment of data in the PPP mode for stations of a GNSS network. Thus, all systematic effects involved with the GNSS satellite signals must... (Complete abstract click electronic access below)
Doutor
22
Ržonca, Michal. "On-line korekce dráhy robotu na základě dat ze snímače vzdálenosti." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443251.
Full textAbstract:
The main aim of this master’s thesis is to provide online path correction of 6 – axis robot leaded by an external distance measuring sensor interface. First part is describing the actual state and required options of some robot manufacturers. Next part justifies selection and is describing the real robotic cell. Third part is focused on programming of path correction of Kuka KR16 based on generated signal and also based on signal from distance sensor interface. There is also described the communication between PLC and robot and how to display data from robot to HMI. Last part is focused on data analysis and is describing some problems discovered by application of path correction.
23
Sharp, Kirk, and Lorraine Masi Thompson. "Adaptation of a Loral ADS 100 as a Remote Ocean Buoy Maintenance System." International Foundation for Telemetering, 1989. http://hdl.handle.net/10150/614641.
Full textAbstract:
International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, CaliforniaThe Naval Ocean Research and Development Activity (NORDA) has adapted the Loral Instrumentation Advanced Decommutation system (ADS 100) as a portable maintenance system for one of its remotely deployable buoy systems. This particular buoy system sends up to 128 channels of amplified sensor data to a centralized A/D for formatting and storage on a high density digital recorder. The resulting tapes contain serial PCM data in a format consistent with IRIG Standard 106-87. Predictable and correctable perturbations exist within the data due to the quadrature multiplexed telemetry system. The ADS 100 corrects for the perturbations of the telemetry system and provides the user with diagnostic tools to examine the stored data stream and determine the operational status of the buoy system prior to deployment.
24
Roy, Tirthankar, Aleix Serrat-Capdevila, Hoshin Gupta, and Juan Valdes. "A platform for probabilistic Multimodel and Multiproduct Streamflow Forecasting." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/623110.
Full textAbstract:
We develop and test a probabilistic real-time streamflow-forecasting platform, Multimodel and Multiproduct Streamflow Forecasting (MMSF), that uses information provided by a suite of hydrologic models and satellite precipitation products (SPPs). The SPPs are bias-corrected before being used as inputs to the hydrologic models, and model calibration is carried out independently for each of the model-product combinations (MPCs). Forecasts generated from the calibrated models are further bias-corrected to compensate for the deficiencies within the models, and then probabilistically merged using a variety of model averaging techniques. Use of bias-corrected SPPs in streamflow forecasting applications can overcome several issues associated with sparsely gauged basins and enable robust forecasting capabilities. Bias correction of streamflow significantly improves the forecasts in terms of accuracy and precision for all different cases considered. Results show that the merging of individual forecasts from different MPCs provides additional improvements. All the merging techniques applied in this study produce similar results, however, the Inverse Weighted Averaging (IVA) proves to be slightly superior in most cases. We demonstrate the implementation of the MMSF platform for real-time streamflow monitoring and forecasting in the Mara River basin of Africa (Kenya & Tanzania) in order to provide improved monitoring and forecasting tools to inform water management decisions.
25
Carré, Maxime. "Interprétation d'images acquises en situation de faible éclairement ou d'éclairement variable." Thesis, Saint-Etienne, 2013. http://www.theses.fr/2013STET4012.
Full textAbstract:
La qualité d’une prise de vue est un point incontournable dans la résolution des problèmes d’imagerie. Un capteur non adapté, un éclairage non contrôlé, ou des conditions variables de la scène observée peuvent être à l’origine de problèmes très difficiles à surmonter. Nous présentons différentes méthodes de traitement d’image permettant de prendre en compte au mieux ces conditions de prise de vue instables. Les approches que nous proposons sont définies dans le cadre du modèle LIP (Logarithmic Image Processing). Dans une première partie, nous nous intéressons à des notions de contraste : le contraste LIP additif et un nouveau contraste LIP multiplicatif, ainsi qu’à leurs métriques associées. De nouveaux outils de traitement basés sur ces notions sont ensuite définis : seuillage, détecteur de contours, reconnaissance de modèle. L’utilisation de ces notions de contraste confère à ces algorithmes la capacité des contrastes LIP à s’adapter à différents types d’images mal conditionnées. Nous proposons ensuite de nouvelles techniques de correction de dynamique d’images en exploitant les opérations LIP. Différentes corrections globales et locales sont présentées ainsi que leurs applications directes : correction de dérive d’éclairement pour du contrôle industriel ou amélioration d’image pour de la visualisation. Nous obtenons notamment une méthode de correction locale dont les résultats se rapprochent de ceux de certaines techniques de tone mapping. En comparaison, notre technique s’avère simple, rapide (temps réel à 30 images par seconde) et réaliste car basée sur une interprétation physique de la problématiqueThe quality of image acquisitions is crucial in the resolution of imaging problems. Troubles during acquisiton can lead to unstability for image processing algorithms. We propose different methods (thresholding techniques, contour detection, pattern matching) based on new metrics and contrasts in the LIP context. The LIP (Logarithmic Image Processing) model is recognized as an efficient framework to process images acquired in transmitted light and to take into account the human visual system. LIP operations are also useful to simulate varitations of image parameters in situation of reflected light. Finally, we propose new methods of global and local dynamic enhancement in the LIP framework like a real time and realistic local dynamic correction that brings results close to those obtained by certain tone mapping methods
26
Buschmann, Tilo. "The Systematic Design and Application of Robust DNA Barcodes." Doctoral thesis, Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-209812.
Full textAbstract:
High-throughput sequencing technologies are improving in quality, capacity, and costs, providing versatile applications in DNA and RNA research. For small genomes or fraction of larger genomes, DNA samples can be mixed and loaded together on the same sequencing track. This so-called multiplexing approach relies on a specific DNA tag, index, or barcode that is attached to the sequencing or amplification primer and hence accompanies every read. After sequencing, each sample read is identified on the basis of the respective barcode sequence.
Alterations of DNA barcodes during synthesis, primer ligation, DNA amplification, or sequencing may lead to incorrect sample identification unless the error is revealed and corrected. This can be accomplished by implementing error correcting algorithms and codes. This barcoding strategy increases the total number of correctly identified samples, thus improving overall sequencing efficiency. Two popular sets of error-correcting codes are Hamming codes and codes based on the Levenshtein distance.
Levenshtein-based codes operate only on words of known length. Since a DNA sequence with an embedded barcode is essentially one continuous long word, application of the classical Levenshtein algorithm is problematic. In this thesis we demonstrate the decreased error correction capability of Levenshtein-based codes in a DNA context and suggest an adaptation of Levenshtein-based codes that is proven of efficiently correcting nucleotide errors in DNA sequences. In our adaptation, we take any DNA context into account and impose more strict rules for the selection of barcode sets. In simulations we show the superior error correction capability of the new method compared to traditional Levenshtein and Hamming based codes in the presence of multiple errors.
We present an adaptation of Levenshtein-based codes to DNA contexts capable of guaranteed correction of a pre-defined number of insertion, deletion, and substitution mutations. Our improved method is additionally capable of correcting on average more random mutations than traditional Levenshtein-based or Hamming codes. As part of this work we prepared software for the flexible generation of DNA codes based on our new approach. To adapt codes to specific experimental conditions, the user can customize sequence filtering, the number of correctable mutations and barcode length for highest performance.
However, not every platform is susceptible to a large number of both indel and substitution errors. The Illumina “Sequencing by Synthesis” platform shows a very large number of substitution errors as well as a very specific shift of the read that results in inserted and deleted bases at the 5’-end and the 3’-end (which we call phaseshifts). We argue in this scenario that the application of Sequence-Levenshtein-based codes is not efficient because it aims for a category of errors that barely occurs on this platform, which reduces the code size needlessly. As a solution, we propose the “Phaseshift distance” that exclusively supports the correction of substitutions and phaseshifts. Additionally, we enable the correction of arbitrary combinations of substitution and phaseshift errors. Thus, we address the lopsided number of substitutions compared to phaseshifts on the Illumina platform.
To compare codes based on the Phaseshift distance to Hamming Codes as well as codes based on the Sequence-Levenshtein distance, we simulated an experimental scenario based on the error pattern we identified on the Illumina platform. Furthermore, we generated a large number of different sets of DNA barcodes using the Phaseshift distance and compared codes of different lengths and error correction capabilities. We found that codes based on the Phaseshift distance can correct a number of errors comparable to codes based on the Sequence-Levenshtein distance while offering the number of DNA barcodes comparable to Hamming codes. Thus, codes based on the Phaseshift distance show a higher efficiency in the targeted scenario. In some cases (e.g., with PacBio SMRT in Continuous Long Read mode), the position of the barcode and DNA context is not well defined. Many reads start inside the genomic insert so that adjacent primers might be missed. The matter is further complicated by coincidental similarities between barcode sequences and reference DNA. Therefore, a robust strategy is required in order to detect barcoded reads and avoid a large number of false positives or negatives.
For mass inference problems such as this one, false discovery rate (FDR) methods are powerful and balanced solutions. Since existing FDR methods cannot be applied to this particular problem, we present an adapted FDR method that is suitable for the detection of barcoded reads as well as suggest possible improvements.
27
Scholz, Jason B. "Real-time performance estimation and optimizaton of digital communication links /." Title page, contents and abstract only, 1992. http://web4.library.adelaide.edu.au/theses/09PH/09phs368.pdf.
Full text
28
Chen, Huifeng. "Correcting the effect of thermal ageing for Real-Time power device Temperature Estimators." Thesis, University of Newcastle Upon Tyne, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519582.
Full text
29
Oksenhendler, Vincent. "Développement d'un système opto-électronique de vision 3-D pour l'établissement en temps réel de cartes de distances." Rouen, 1997. http://www.theses.fr/1997ROUES047.
Full textAbstract:
Dans ce mémoire, est présenté un capteur de vision 3-D dont l'objectif est de permettre l'assistance à la conduite de véhicule. Cela entraîne un certain nombre de contraintes telles que la fiabilité, la rapidité et l'auto-adaptabilité. Ainsi, le capteur que nous avons développé est fondé sur la stéréovision passive et la mise en correspondance de contours verticaux. L'utilisation d'une configuration spécifique des caméras nous permet de limiter l'espace de recherche des primitives stéréocorrespondantes aux lignes images de même numéro. La réalisation d'un tel capteur nous a amené à développer tout particulièrement 3 parties de ce dernier. La première partie concerne la réalisation d'un détecteur de contour monodimensionnel rapide, auto-adaptatif, de résolution sub-pixel et qui est fonde sur le seuillage des déclivités étendues. Les résultats obtenus sur des scènes réelles et synthétiques montrent que celui-ci peut être utilise afin de réaliser un capteur de précision. La seconde partie est constituée par un processus de correction et d'étiquetage des contours 3-D obtenus à la suite de la mise en correspondance. Ce traitement exploite la continuité de la disparité le long des contours permettant ainsi de rectifier la majorité des points 3-D issus de mauvais appariements. La dernière partie porte sur l'implémentation parallèle du processus de stéréovision sur 3 DSP tms320c31 hébergés dans un système de traitement d'imaging technology 150/40.
30
Randrianjanahary, Liantsoa Finaritra. "Cosmology with HI intensity mapping: effect of higher order corrections." University of the Western Cape, 2020. http://hdl.handle.net/11394/7248.
Full textAbstract:
Masters of ScienceOne of the main challenges of cosmology is to unveil the nature of dark energy and dark matter. They can be constrained with baryonic acoustic oscillations (BAO) and redshift space distortions, amongst others. Both have characteristic signatures in the dark matter power spectrum. Biased tracers of dark matter, such as neutral hydrogen, are used to quantify the underlying dark matter density field. It is generally assumed that on large scales the bias of the tracer is linear. However, there is a coupling between small and large scales of the biased tracer which gives rise to a significant non-linear contribution on linear scales in the power spectrum of the biased tracer. The Hydrogen Intensity and Real-time eXperiment (HIRAX) will map the brightness temperature of neutral hydrogen (HI) over BAO scales thanks to the intensity mapping technique. We forecasted cosmological parameters for HIRAX taking into account non-linear corrections to the HI power spectrum and compared them to the linear case. We used methods based on Fisher matrices. We found values for the bias to error ratio of the cosmological parameters as high as 1 or 7, depending on the noise level. We also investigated the change in peaks location on the baryonic acoustic oscillations signal. The value of the shift goes up to Δk = 10-2h/Mpc with a reduction of amplitude of the BAO features from 16:33% to 0:33%, depending on the scales.
31
Zinoune, Clément. "Autonomous integrity monitoring of navigation maps on board intelligent vehicles." Thesis, Compiègne, 2014. http://www.theses.fr/2014COMP1972/document.
Full textAbstract:
Les véhicules dits intelligents actuellement développés par la plupart des constructeurs automobiles, ainsi que les véhicules autonomes nécessitent des informations sur le contexte dans lequel ils évoluent. Certaines de ces informations (par exemple la courbure de la route, la forme des intersections, les limitations de vitesses) sont fournies en temps réel par le système de navigation qui exploite les données de cartes routières numériques. Des défauts résultant de l’évolution du réseau routier ou d’imprécisions lors de la collecte de données peuvent être contenus dans ces cartes numériques et entraîner le dysfonctionnement des systèmes d’aide à la conduite. Les recherches menées dans cette thèse visent à rendre le véhicule capable d’évaluer, de manière autonome et en temps réel, l’intégrité des informations fournies par son système de navigation. Les véhicules de série sont désormais équipés d’un grand nombre de capteurs qui transmettent leurs mesures sur le réseau central interne du véhicule. Ces données sont donc facilement accessibles mais de faible précision. Le défi de cette thèse réside donc dans l’évaluation de l’intégrité des informations cartographiques malgré un faible degré de redondance et l’absence de données fiables. On s’adresse à deux types de défauts cartographiques : les défauts structurels et les défauts géométriques. Les défauts structurels concernent les connections entre les routes (intersections). Un cas particulier de défaut structurel est traité : la détection de ronds-points qui n’apparaissent pas dans la carte numérique. Ce défaut est essentiel car il est fréquent (surtout en Europe) et perturbe le fonctionnement des aides à la conduite. Les ronds-points sont détectés à partir de la forme typique de la trajectoire du véhicule lorsqu’il les traverse, puis sont mémorisés pour avertir les aides à la conduite aux prochains passages du véhicule sur la zone. Les imprécisions de représentation du tracé des routes dans la carte numérique sont quant à elles désignées comme défauts géométriques. Un formalisme mathématique est développé pour détecter ces défauts en comparant l’estimation de la position du véhicule d’après la carte à une autre estimation indépendante de la carte. Cette seconde estimation pouvant elle aussi être affectée par un défaut, les anciens trajetsdu véhicule sur la même zone sont utilisés. Un test statistique est finalement utilisé pour améliorer la méthode de détection de défauts géométriques dans des conditions de mesures bruitées. Toutes les méthodes développées dans le cadre de cette thèse sont évaluées à l’aide de données réellesSeveral Intelligent Vehicles capabilities from Advanced Driving Assistance Systems (ADAS) to Autonomous Driving functions depend on a priori information provided by navigation maps. Whilst these were intended for driver guidance as they store road network information, today they are even used in applications that control vehicle motion. In general, the vehicle position is projected onto the map to relate with links in the stored road network. However, maps might contain faults, leading to navigation and situation understanding errors. Therefore, the integrity of the map-matched estimates must be monitored to avoid failures that can lead to hazardous situations. The main focus of this research is the real-time autonomous evaluation of faults in navigation maps used in intelligent vehicles. Current passenger vehicles are equipped with proprioceptive sensors that allow estimating accurately the vehicle state over short periods of time rather than long trajectories. They include receiver for Global Navigation Satellite System (GNSS) and are also increasingly equipped with exteroceptive sensors like radar or smart camera systems. The challenge resides on evaluating the integrity of the navigation maps using vehicle on board sensors. Two types of map faults are considered: Structural Faults, addressing connectivity (e.g., intersections). Geometric Faults, addressing geographic location and road geometry (i.e. shape). Initially, a particular structural navigation map fault is addressed: the detection of roundabouts absent in the navigation map. This structural fault is problematic for ADAS and Autonomous Driving. The roundabouts are detected by classifying the shape of the vehicle trajectory. This is stored for use in ADAS and Autonomous Driving functions on future vehicle trips on the same area. Next, the geometry of the map is addressed. The main difficulties to do the autonomous integrity monitoring are the lack of reliable information and the low level of redundancy. This thesis introduces a mathematical framework based on the use of repeated vehicle trips to assess the integrity of map information. A sequential test is then developed to make it robust to noisy sensor data. The mathematical framework is demonstrated theoretically including the derivation of definitions and associated properties. Experiments using data acquired in real traffic conditions illustrate the performance of the proposed approaches
32
Pham, Nga D. "Weapons control re-entry simulation enhancement." Master's thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-02022010-020315/.
Full text
33
Marano, Susan Aileen. "Smarticles: A Method for Identifying and Correcting Instability and Error Caused by Explicit Integration Techniques in Physically Based Simulations." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1304.
Full textAbstract:
Using an explicit integration method in physically based animations has many advantages including conceptual and computational simplicity, however, it re- quires small time steps to ensure low numerical instability. Simulations with large numbers of individually interacting components such as cloth, hair, and fluid models, are limited by the sections of particles most susceptible to error. This results in the need for smaller time steps than required for the majority of the system. These sections can be diverse and dynamic, quickly changing in size and location based on forces in the system. Identifying and handling these trou- blesome sections could allow for a larger time step to be selected, while preventing a breakdown in the simulation.
This thesis presents Smarticles (smart particles), a method of individually de- tecting particles exhibiting signs of instability and stabilizing them with minimal adverse effects to visual accuracy. As a result, higher levels of error introduced from large time steps can be tolerated with minimal overhead. Two separate approaches to Smarticles were implemented. They attempt to find oscillating particles by analyzing a particle’s (1) past behavior and (2) behavior with re- spect to its neighbors along a strand. Both versions of Smarticles attempt to correct unstable particles using velocity dampening. Smarticles was applied to a two dimensional hair simulation modeled as a continuum using smooth particle hydrodynamic. Hair strands are formed by linking particles together using one of two methods: position based dynamics or mass-spring forces.
Both versions of Smarticles, as well as a control of normal particles, were directly compared and evaluated based on stability and visual fluidity. Hair particles were exposed to various forms of external forces under increasing time step lengths. Testing showed that both versions of Smarticles working together allowed an average increase of 18.62% in the time step length for hair linked with position based dynamics. In addition, Smarticles was able to significantly reduce visible instability at even larger time steps. While these results suggest Smarticles is successful, the method used to correct particle instability may jeopardize other important aspects of the simulation. A more accurate correction method would likely need to be developed to make Smarticles an advantageous method.
34
Zachariáš, Michal. "Návrh a Aplikace Dvourozměrných Vizuálních Markerů pro Speciální Účely." Doctoral thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2016. http://www.nusl.cz/ntk/nusl-412574.
Full textAbstract:
Současné vizuální markerové systémy mají jednu zásadní nevýhodu oproti tzv. markerless přístupům - pohyb kamery je omezen na oblast pokrytou markery. V každém snímku musí být marker dostatečně velký, aby jej bylo možné identifikovat a vypočítat pozici a rotaci kamery. Zároveň musí být dostatečně malý, aby se celý (nebo alespoň jeho podstatná část) vešel do záběru kamery. Avšak tyto požadavky jsou protichůdné. Tato práce nabízí řešení tohoto problému za pomoci konceptu Marker Fields. Jde o strukturu, jejíž přítomnost je možné v obraze kamery snadno detekovat a identifikovat část, na kterou se kamera právě dívá, a to na základě jakékoli (malé) podoblasti s definovanou velikostí. Aby bylo možné podoblasti identifikovat zblízka i zdálky, nejsou od sebe odděleny, ale do velké míry se překrývají. V této práci jsou vysvětleny různé implementace konceptu marker fields, spolu s jejich zamýšleným použitím a výhodami a nevýhodami. Jako důkaz použitelnosti marker fields v reálném světě, se druhá největší část této práce věnuje popisu jejich reálných aplikací.
35
Vestin, Albin, and Gustav Strandberg. "Evaluation of Target Tracking Using Multiple Sensors and Non-Causal Algorithms." Thesis, Linköpings universitet, Reglerteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-160020.
Full textAbstract:
Today, the main research field for the automotive industry is to find solutions for active safety. In order to perceive the surrounding environment, tracking nearby traffic objects plays an important role. Validation of the tracking performance is often done in staged traffic scenarios, where additional sensors, mounted on the vehicles, are used to obtain their true positions and velocities. The difficulty of evaluating the tracking performance complicates its development. An alternative approach studied in this thesis, is to record sequences and use non-causal algorithms, such as smoothing, instead of filtering to estimate the true target states. With this method, validation data for online, causal, target tracking algorithms can be obtained for all traffic scenarios without the need of extra sensors. We investigate how non-causal algorithms affects the target tracking performance using multiple sensors and dynamic models of different complexity. This is done to evaluate real-time methods against estimates obtained from non-causal filtering. Two different measurement units, a monocular camera and a LIDAR sensor, and two dynamic models are evaluated and compared using both causal and non-causal methods. The system is tested in two single object scenarios where ground truth is available and in three multi object scenarios without ground truth. Results from the two single object scenarios shows that tracking using only a monocular camera performs poorly since it is unable to measure the distance to objects. Here, a complementary LIDAR sensor improves the tracking performance significantly. The dynamic models are shown to have a small impact on the tracking performance, while the non-causal application gives a distinct improvement when tracking objects at large distances. Since the sequence can be reversed, the non-causal estimates are propagated from more certain states when the target is closer to the ego vehicle. For multiple object tracking, we find that correct associations between measurements and tracks are crucial for improving the tracking performance with non-causal algorithms.
36
Dai, Ping-Ping. "A real-time error correction system for boring." 1992. http://catalog.hathitrust.org/api/volumes/oclc/28123285.html.
Full textAbstract:
Thesis (Ph. D.)--University of Wisconsin--Madison, 1992.Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 119-121).
37
Huang, Yu-Chen, and 黃育成. "Online Real-time Multimedia Correction System for English Writing." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/78583545237779610723.
Full textAbstract:
碩士國立暨南國際大學
資訊工程學系
96
In recent years, although many kinds of online English compositions correcting systems have been constructed, most of them do not provide live lecture function. To solve this problem, we design a system in which students can immediately watch the compositions correcting process and directly propose their own questions for obtaining teachers’ instruction while they are confused in writing. Our system also provides a broadcast model in which one teacher can deliver a live lecture for several students at the same time. It not only provides students with a live lecture function but also provides a review function. By this review function, students can review the whole correcting process after the live lecture. Our system provides a platform which can synchronize the voice and correction events. Because this system is a real-time network application, we have to face the challenge in network bandwidth.
38
ZeYuan and 袁舴. "Real-time Error Correction for Hourly Rainfall Ensemble Forecasting." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/87588595661855293860.
Full textAbstract:
碩士國立成功大學
水利及海洋工程學系
104
The main purpose of this study is to correct the errors of weather research and forecasting (WRF) model in precipitation forecasting. The study area is Kaoping River Basin located in southern Taiwan where usually suffers from floods during typhoon season. In this study, the radar precipitation data are regard as the reference (i.e., true values) to eliminate WRF forecasting error. Two methods, random forests (RF) and support vector machines (SVM), are used to correct the discrepancies between the forecasted precipitation data from WRF model and the radar precipitation data. The correction is based on a real-time updating procedure where two error correction models will be updated every 6 hours (i.e., WRF model provides 6-hour forecast in each run). For example, the error correction models applied to correct the 6-hour ahead precipitation forecasts from WRF model which were set up based on the precipitation data (WRF and the radar precipitation data) from the past 6 hours. The results reveal that the error correction models can further improve WRF model rainfall forecasting by using the real-time updating procedure, however, the accuracy of forecasting decreases with lead time increasing. The results also show that either SVM-based model or RF-based model performs well on two performance indexes (i.e., correlation coefficient and root mean squared error) which can improve the accuracy of precipitation forecasting by 5% to 300% when it compares to original WRF model.
39
Ivancevich, Nikolas M. "Phase Aberration Correction for Real-Time 3D Transcranial Ultrasound Imaging." Diss., 2009. http://hdl.handle.net/10161/1243.
Full textAbstract:
Phase correction has the potential to increase the image quality of real-time 3D (RT3D) ultrasound, especially for transcranial ultrasound. Such improvement would increase the diagnostic utility of transcranial ultrasound, leading to improvements in stroke diagnosis, treatment, and monitoring. This work describes the implementation of the multi-lag least-squares cross-correlation and partial array speckle brightness methods for static and moving targets and the investigation of contrast-enhanced (CE) RT3D transcranial ultrasound.
The feasibility of using phase aberration correction with 2D arrays and RT3D ultrasound was investigated. Using the multi-lag cross-correlation method on electronic and physical aberrators, we showed the ability of 3D phase aberration correction to increase anechoic cyst identification, image brightness, contrast-to-noise ratio (CNR), and, in 3D color Doppler experiments, the ability to visualize flow. With a physical aberrator, CNR increased by 13%, while the number of detectable cysts increased from 4.3 to 7.7.
We performed an institutional review board (IRB) approved clinical trial to assess the ability of a novel ultrasound technique, namely RT3D CE transcranial ultrasound. Using micro-bubble contrast agent, we scanned 17 healthy volunteers via a single temporal window and 9 via the sub-occipital window and report our detection rates for the major cerebral vessels. In 82% of subjects, we identified the ipsilateral circle of Willis from the temporal window, and in 65% we imaged the entire circle of Willis. From the sub-occipital window, we detected the entire vertebrobasilar circulation in 22% of subjects, and in 50% the basilar artery.
We then compared the performance of the multi-lag cross-correlation method with partial array reference on static and moving targets for an electronic aberrator. After showing that the multi-lag method performs better, we evaluated its performance with a physical aberrator. Using static targets, the correction resulted in an average contrast increase of 22.2%, compared to 13.2% using moving targets. The CNR increased by 20.5% and 12.8%, respectively. Doppler signal strength and number of Doppler voxels increased, by 5.6% and 14.4%, respectively, for the static method, and 9.3% and 4.9% for moving targets.
We performed two successful in vivo aberration corrections. We used this data and measure the isoplanatic patch size to be an average of 10.1°. The number of Doppler voxels increased by 38.6% and 19.2% for the two corrections. In both volunteers, correction enabled the visualization of a vessel not present in the uncorrected volume. These results are promising, and could potentially have a significant impact on public health.
Lastly, we show preliminary work testing the feasibility of a unique portable dedicated transcranial ultrasound system capable of simultaneous scanning from all three acoustic windows. Such a system would ideally be used in a preclinical setting, such as an ambulance.
Dissertation
40
Klyszejko, Erika Suzanne. "Hydrologic Validation of Real-Time Weather Radar VPR Correction Methods." Thesis, 2006. http://hdl.handle.net/10012/2635.
Full textAbstract:
Weather radar has long been recognized as a potentially powerful tool for hydrological modelling. A single radar station is able to provide detailed precipitation information over entire watersheds. The operational use of radar in water resources applications, however, has been limited. Interpretation of raw radar data requires several rigorous analytical steps and a solid understanding of the technology. In general, hydrologists’ lack of meteorological background and the persistence of systematic errors within the data, has led to a common mistrust of radar-estimated precipitation values.
As part of the Enhanced Nowcasting of Extreme Weather project, researchers at McGill University’s J.S. Marshall Radar Observatory in Montreal have been working to improve real-time quantitative precipitation estimates (QPEs). The aim is to create real-time radar precipitation products for the water resource community that are reliable and properly validated.
The validation of QPEs is traditionally based on how well observed measurements agree with data from a precipitation gauge network. Comparisons between radar and precipitation gauge quantities, however, can be misleading. Data from a precipitation gauge network represents a series of single-point observations taken near ground surface. Radar, however, estimates the average rate of precipitation over a given area (i.e. a 1-km grid cell) based on the intensity of reflected microwaves at altitudes exceeding 1 km. Additionally, both measurement techniques are susceptible to a number of sources of error that further confound efforts to compare the two.
One of the greatest challenges facing radar meteorologists is the variation in the vertical profile of reflectivity (VPR). A radar unit creates a volumetric scan of the atmosphere by emitting microwave beams at several elevation angles. As a beam travels away from the radar, its distance from ground surface increases. Different precipitation types are sampled at a number of heights (i.e. snow above the 0º C elevation and rain below it) that vary with range. The difficulty lies in estimating the intensity of precipitation at the Earth’s surface, based on measurements taken aloft. Scientists at McGill University have incorporated VPR correction techniques into algorithms used to automatically convert raw radar data into quantitative hydrological products.
This thesis evaluates three real-time radar precipitation products from McGill University’s J.S. Marshall Radar Observatory in the context of hydrological modelling. The C0 radar product consists of radar precipitation estimates that are filtered for erroneous data, such as ground clutter and anomalous precipitation. The C2 and C3 radar products use different VPR correction techniques to improve upon the C0 product. The WATFLOOD hydrological model is used to assess the ability of each radar product to estimate precipitation over several watersheds within the McGill radar domain. It is proposed that using a watershed as sample area can reduce the error associated with sampling differences between radar and precipitation gauges and allow for the evaluation of a precipitation product over space and time.
The WATFLOOD model is run continuously over a four-year period, using each radar product as precipitation input. Streamflow hydrographs are generated for 39 gauging stations within the radar domain, which includes parts of eastern Ontario, south-western Quebec and northern New York and Vermont, and compared to observed measurements. Streamflows are also modelled using distributed precipitation gauge data from 44 meteorological stations concentrated around the Montreal region.
Analysis of select streamflow events reveals that despite the non-ideal placement of precipitation gauges throughout the study area, distributed precipitation gauge data are able to reproduce hydrological events with greater accuracy and consistency than any of the provided radar products. Precipitation estimates within the McGill radar domain are found to only be useful in areas within the Doppler range (120-km) where the radar beam is unobstructed by physiographic or man-made features.
Among radar products, the C2 VPR-corrected product performed best during the greatest number of the flood events throughout the study area.
41
"Phase Aberration Correction for Real-Time 3D Transcranial Ultrasound Imaging." Diss., 2009. http://hdl.handle.net/10161/1243.
Full text
42
Lin, Shih-Hao, and 林士浩. "Real time correction and analysis to 6-hour-precipitation forecast." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/3e79wz.
Full textAbstract:
碩士國立臺北科技大學
土木與防災研究所
100
River warning levels often vary according to flood rising rates and riverside disaster response time. These warning levels are initially set to protect the lives and property of citizens living by the riverside and minimize the chances of damage due to external water overflow during flood control periods. However, flood rising rates are frequently subject to change due to physiographical and geomorphological factors in the catchment area, such as rainstorm characteristics as well as erosion and deposition along the river course. In order to increase the disaster response time of riverside regions, water level forecasts using various hydrological and hydrographical methods has become a common measure. In spite of this, currently the time scale of such forecasts depends heavily on rainfall forecasts, therefore in order to lengthen disaster response time, extending the time scale of rainfall forecasts is a critical issue. At present, most hydrological and hydrographical methods utilize Quantitative Precipitation Forecast (QPF) for quantification of rainfall forecasts; these results in turn serve as input for hydrologic calculations. The downside is this method provides a mere three-hour forecast, which does not allow sufficient time for disaster response along riverside areas. In light of this issue, this study combined two rainfall forecast methods, QPF and the Weather Research and Forecasting Model (WRF), thus extending forecast time from three hours to six hours. These results can serve as information for subsequent downstream hydrological and hydrographical methods, and moreover improve disaster response time of riverside areas. In addition, to improve reliability of this combined forecasting approach, this study applied a real-time correction method developed by Dr. Shiang-Jen Wu of the National Center for High Performance Computing. This was done through utilization of the General Adapter module of the FEWS_Taiwan hydrological prediction integrated platform developed by the Water Resources Agency, Ministry of Economic Affairs. Through consistent data exchange techniques embedded in the FEWS_Taiwan platform, real-time correction was performed on preliminary rainfall forecasts of the QPF-WRF combined measure, thus producing highly reliable rainfall forecast results.
43
You, Ren-Zhi, and 游仁植. "A real-time fault identification and correction method of sensor systems." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/31115101389426555763.
Full textAbstract:
碩士國立交通大學
機械工程系所
96
In a sensing system that was constructed by employing redundant devices (components), the conventional approach for the fault-identification was done through the “voting equations”. However, when the outputs of the devices were contaminated by noise, the conventional fault-finding measure had to set up a threshold values and an observation periods along with voting equations. Due to the setup of an observation period, the conventional approach can not be done in a real-time manner. As a consequence, the real-time fault-correction was not possible. In this thesis, we proposed a novel real-time fault-identification method to solve the problem above. Furthermore, the proposed method can combine with various feedback techniques to achieve real-time fault-correction. The proposed method uses the novel “output equations” along with “voting equations” to describe the relationship between each device output. After that, the real-time fault-identification problem was formulated into a nonlinear state estimation problem. The method of the newly added “output equations” was the key to the success of the proposed real-time fault-identification method. Furthermore, in order to handle the sensor drift (or time-varying fault) problem, we use the “Kalman filter with fading memory” techniques for the state observer. Moreover, we use state feedback techniques for the purpose of the correction of fault, and the corrected device can be kept in the “fault-tolerant of sensor system” to increase the accuracy of system output. We can estimate fault signals successfully by simulation of 3 sensors of the system, and its error standard deviation is about .For drift, its standard deviation of estimation is about .The minimum fault value that estimated is equals to 1/2 times of standard deviation of noise approximately. Besides, the state feedback technique give a fault correction to sensor output which has fault and, thus, a corrected signal is approximate to ideal signal. More facts shows in the thesis.
44
Rotenberg, David. "Real-time Correction By Optical Tracking with Integrated Geometric Distortion Correction for Reducing Motion Artifacts in fMRI." Thesis, 2012. http://hdl.handle.net/1807/32275.
Full textAbstract:
Artifacts caused by head motion are a substantial source of error in fMRI that limits its use in neuroscience research and clinical settings. Real-time scan-plane correction by optical tracking has been shown to correct slice misalignment and non-linear spin-history artifacts, however residual artifacts due to dynamic magnetic field non-uniformity may remain in the data. A recently developed correction technique, PLACE, can correct for absolute geometric distortion using the complex image data from two EPI images, with slightly shifted k-space trajectories. We present a correction approach that integrates PLACE into a real-time scan-plane update system by optical tracking, applied to a tissue-equivalent phantom undergoing complex motion and an fMRI finger tapping experiment with overt head motion to induce dynamic field non-uniformity. Experiments suggest that including volume by volume geometric distortion correction by PLACE can suppress dynamic geometric distortion artifacts in a phantom and in vivo and provide more robust activation maps.
45
Dong, Wei-Chen, and 董威成. "Implementation of a Real-Time Image Correction Processing for Distorted Projection Images." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/7mwm6p.
Full textAbstract:
碩士國立臺北科技大學
機電整合研究所
99
The non-planar screen display is now popularly applied in many applications, such as large surrounding screen display, virtual reality and other immersive visualization environment. Researchers use theories of non-linear image distortion and manual modification to correct the distorted display but the technologies are not matured and require time and manpower. Therefore, this proposed project takes the advantages of computer vision to design a simple routine using the digital image processing methods, such as positioning point, the grain and color information, theory of Bezier and B-Spline to construct and correct the final projection image automatically. This automatic image correction procedure can be done with low-cost equipment and save time with traditional manual modification. Finally, will the aid of computer vision capture the correction vector information with image processing techniques, this developed system can project the corrected image on the non-planar screen without any distortion.
46
Ping-WenHsiao and 蕭秉文. "Dynamic Scalable Sliding Window Forward Error Correction For Real-time Video Streaming." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/19500538398124688334.
Full textAbstract:
碩士國立成功大學
電腦與通信工程研究所
104
The mobile devices have become explosive hits on global markets. The applications of multimedia and video streaming have a significant growth. It have become a crucial part of modern lives to view video streaming and broadcasting as well as other multimedia applications via wireless internet. To provide stable high quality multimedia instantly have therefore become an important issue to be addressed. Data transmission through a lossy channel is in the risk of packets losses or error occurrences. Forward Error Correction (FEC) have been widely used in the area of video streaming and multimedia broadcasting. The quality performance and transmission delay have been a trade-off that troubles researchers for years to find a balance in between. This paper proposed a Dynamic Scalable Sliding Window scheme as a novel FEC to provide higher quality of video streaming with lower delay and more stable quality compared to previous similar approaches. The scheme exploit Decodable Frame Rate (DFR) to estimate the quality expectation and dynamically adjust the FEC coding block. In addition, the sliding window algorithm overlaps one frame each time as the window slides. The simulation results indicates that, with the extra overlapped frame, the overall recovery rate is enhanced and the video fluctuation in real-time transmission is also much improved. The experimental results also shows the scheme provides higher DFR performances than previous related researches and frame-level FEC throughout varies packet loss rate.
47
Yang, Sheng-ming. "Modeling and real time correction of errors in a three-dimensional tactile probe." 1985. http://catalog.hathitrust.org/api/volumes/oclc/12755275.html.
Full textAbstract:
Thesis (M.S.)--University of Wisconsin--Madison, 1985.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 129-130).
48
Yung-TsungWeng and 翁泳聰. "Low-delay Forward Error Correction using Linear Prediction for Real-time Video Streaming." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/51208023834594482096.
Full textAbstract:
博士國立成功大學
電腦與通信工程研究所
104
Real-time video streaming applications typically use an on-line forward error correction (FEC) technique to recover transmission losses with a low delay overhead so that the high perceived visual quality can be ensured. However, transmitting the prioritized video data over variable-rate transmission channels complicates the FEC rate allocation process, and the on-line FEC is difficult to efficiently utilize the available FEC bandwidth without the prior information of video traffic. Generally, the optimal FEC configuration can be computed off-line based on an analytical model. In this paper, a prediction-based FEC scheme is proposed to achieve the real-time FEC allocation by extending the analytical FEC model with the frame size prediction technique. Optimal FEC calculation can be conducted for a series of predicted video frames to lead a frame-by-frame FEC rate allocation, resulting in a significantly reduced data buffering delay. A greedy algorithm is proposed to mitigate the performance effects of frame-size prediction errors by continuously revising the FEC configuration each time a new frame arrives. Moreover, a transmission rate control mechanism is proposed to ensure that each video frames satisfies its presentation deadline. The simulation results show that the proposed prediction-based FEC scheme can minimize the additional FEC processing delay while achieving virtually the same perceived video quality that can be obtained by the off-line FEC model.
49
Li, Yi-Chi, and 李依淇. "GPS Cycle-Slip Correction and Near-Real-Time Positioning Based on Bayesian Inference." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/6476ku.
Full textAbstract:
碩士國立中央大學
土木工程研究所
96
GPS carrier phase observation is more precise than code observation, but it causes the problems of phase ambiguity and cycle-slips. Detecting and correcting cycle-slips is a classical issue and is part of the more general problem of fixing integer variables in GPS phase observations. Furthermore, the key point to reach the target of precision and efficiency while using carrier phase for location is how to obtain quickly accurate integers of ambiguity. The main aims of this research are: (1) correcting cycle-slips at the data preprocessing stage by the Bayesian principle, (2) exploiting a Bayesian near-real-time data processing technique for ambiguity resolution based on the concept that phase ambiguities should be integer unknown parameters, (3) determining the confidence regions of the positioning parameters by using a Monte Carlo method. The experimental results in this paper indicate that the cycle-slips in carrier-phase data can be successfully identified. Furthermore, the accuracy of positioning results can be improved by using Bayesian approach and the confidence regions of positioning solutions can be visualized in near-real-time by using a Monte Carlo method.
50
Karaim, MALEK. "Real-time Cycle-slip Detection and Correction for Land Vehicle Navigation using Inertial Aiding." Thesis, 2013. http://hdl.handle.net/1974/8026.
Full textAbstract:
Processing GPS carrier-phase measurements can provide high positioning accuracy for several navigation applications. However, if not detected, cycle slips in the measured phase can strongly deteriorate the positioning accuracy. Cycle slips frequently occur in areas surrounded by trees, buildings, and other obstacles. The dynamics experienced by the GPS receiver in kinematic mode of navigation also increases the possibility of cycle slips. Detection and correction of these cycle-slips is essential for reliable navigation. One way of detecting and correcting for cycle slips is to use another system to be integrated with GPS. Inertial Navigation Systems (INS), using three-axis accelerometers and three-axis gyroscopes, is integrated with GPS to provide more reliable navigation solution. Moreover, INS was utilized in the past for GPS cycle slip detection and correction. For low cost applications, Micro-Electro-Mechanical-Systems (MEMS) accelerometers and gyroscopes are used inside INS. For land navigation, reduced inertial sensor system (RISS) utilizing two accelerometers, one gyroscope, and the vehicle odometer was suggested. MEMS-based RISS has the advantage of using less number of MEMS-based gyroscopes and accelerometers thus reducing the overall cost and avoiding the complex error characteristics associated with MEMS sensors. In this thesis, we investigate the use of MEMS – based RISS to aid GPS and detect and correct for cycle slips. The Kalman filter was employed in centralized fashion to integrate the measurements from both GPS and RISS. This thesis research also offers a new threshold selection criterion resulting in a more robust cycle slip detection and correction. The proposed method was tested in different scenarios of road tests in land vehicle. Results show accuracy
iii
improvement over the conventional double differenced pseudoranges-based integrated system. Moreover, the adaptive selection criterion of the detection threshold proposed in this thesis improves the detection rate, especially in the case of small-sized cycle slips.Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2013-05-06 18:11:57.076