Tesis: "Patch methods"

1

Elmezughi, Abdurrezagh y s3089087@student rmit edu au. "Investigation of Methods for Integrating Broadband Microstrip Patch Antennas". RMIT University. Electrical and Computer Engineering, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20090305.093332.

Texto completo

Resumen

The use of the microstrip antenna has grown rapidly for the last two decades, because of the increasing demand for a low profile antenna with small size, low cost, and high performance over a large spectrum of frequencies. However, despite the advantages microstrip antennas provide, a number of technical challenges remain to be solved for microstrip antennas to reach their full potential, particularly if they are to be interfaced with monolithic circuits. The objective of this thesis is to examine novel methods for integrating and constructing broadband microstrip antennas, particularly at high microwave and millimeter wave frequencies where dimensions get very small and fabrication tolerances are critical. The first stage of the thesis investigates techniques to reduce the spurious feed radiation and surface wave generation from edge-fed patch antennas. A technique to reduce the spurious radiation from the edge-fed patch antenna by using a dielectric filled cavity behind the radiating element is explored. From this, a single element edge-fed cavity backed patch antenna was developed. Measured results showed low levels of cross polarization, making it suitable for dual or circular polarization applications. A 2 x 2 edge-fed cavity backed patch antenna array was also developed, which benefited greatly from this new technique due to the extensive feed network required. Furthermore, investigation into edge-fed cavity backed patches on high dielectric materials was also conducted. The measured impedance bandwidth of this edge-fed cavity backed patch is three times greater than the conventional edge-fed patch, and the gain increases to 5.1 dBi compared to 3.6 dBi. Further bandwidth enhancement of the single element edge-fed cavity backed antenna on high dielectric material was achieved by applying the hi-lo substrate structure. The hi-lo substrate structure produced an increase in the bandwidth to 26% from the 1.7% of the single element edge-fed cavity backed patch, while maintaining pattern integrity and radiation efficiency. Next, the development of a flip-chip bonding technique was investigated to enhance the fabrication accuracy and robustness of multilayer antennas on high dielectric materials. This technique was proven through simulation and experiment to provide good impedance and radiation performance via the high accuracy placement of the superstrate layer. The single element flip-chip patch antenna uses a high dielectric constant material for both the base and the patch superstrate, whereas the stacked flip-chip patch again uses a high and low permittivity material combination to achieve efficient wideband performance. Due to the high permittivity feed material, these antennas display the attributes required for integration with MMICs. The measured 10 dB return loss bandwidth of the single element was 4% with a gain of 4.6 dBi, whereas the stacked flip-chip patch showed very broadband performance, with a bandwidth of 23% with a gain of 8.5 dBi. The high accuracy placement and rigid attachment of the upper superstrat e layer via the flip-chip bonding technique also enables these antennas to be scaled up to millimeter-wave operational frequencies. The final section of this thesis is focused on developing a fabrication technique to enable the creation of a low permittivity layer at a nominated thickness.

Los estilos APA, Harvard, Vancouver, ISO, etc.

2

Zhou, Jianwei. "Geometric continuity and rectangular patch methods for surface modelling". Thesis, Brunel University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292978.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

3

Apte, Anuja D. "Simulation of patch antennas on arbitrary dielectric substrates". Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0509103-122816.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

4

Mullins, Andrew. "Sequential MCMC Methods For The Bayesian Inference of Patch-Based Surface Geometry". Thesis, University of Warwick, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491522.

Texto completo

Resumen

This thesis is about video-based rendering, or free-viewpoint video as it sometimes known. The video-based rendering problem can be summarized as follows: after using a set of video cameras to record a dynamic scene from several different points of view, is it possible to play back that scene, but from an arbitrary point of view? First, current work in this area is reviewed and appraised. Then, this thesis makes the argument that for a general studio set-up, only two current approaches provide a realistic solution to this problem: voxel-based approaches, and polygon mesh-based approaches. That is, approaches which construct an explicit model of scene geometry to aid renderings of that scene. vVhen constructing these models of scene geometry, voxels provide a very general representation, whilst the smoothness constraint inherent in a polygon mesh provides a certain degree of robustness. This thesis makes the case for a new representation of scene geometry based on piecewise planar elements, which provides an excellent compromise between the voxel and polygon meshbased approaches. In order for such an approach to make sense, two things are necessary: some method of estimating planar elements which accurately reflect the scene geometry; and some way to produce renderings from this representation. The former is the topic of this thesis, and the problem can be broken down into three sub-problems: how to construct a suitable prior on the surface geometry; how to estimate the surface geometry given this prior; and how this surface geometry can be updated over time to reflect movement within the scene. At each stage a rigorous, Bayesian approach is taken to these problems

Los estilos APA, Harvard, Vancouver, ISO, etc.

5

Zou, Zhihui. "Isogeometric Shell Analysis: Multi-patch Coupling and Overcoming Locking". BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8142.

Texto completo

Resumen

The fundamental advantages of applying Isogeometric Analysis (IGA) to shell analysis have been extensively demonstrated across a wide range of problems and formulations. However, a phenomenon called numerical locking is still a major challenge in IGA shell analysis, which can lead to dramatically deteriorated analysis accuracy. Additionally, for complex thin-walled structures, a simple and robust coupling technique is desired to sew together models composed of multiple patches. This dissertation focuses on addressing these challenges of IGA shell analysis. First, an isogeometric dual mortar method is developed for multi-patch coupling. This method is based on Be ?zier extraction and projection and can be employed during the creation and editing of geometry through properly modified extraction operators. It is applicable to any spline space which has a representation in Be ?zier form. The error in the method can be adaptively controlled, in some cases recovering optimal higher-order rates of convergence, by leveraging the exact refineability of the proposed dual spline basis without introducing any additional degrees-of-freedom into the linear system. This method can be used not only for shell elements but also for heat transfer and solid elements, etc. Next, a mixed formulation for IGA shell analysis is proposed that addresses both shear and membrane locking and improves the quality of computed stresses. The starting point of the formulation is the modified Hellinger-Reissner variational principle with independent displacement, membrane, and shear strains as the unknown fields. To overcome locking, the strain variables are interpolated with lower-order spline bases while the variations of the strain variables are interpolated with the proposed dual spline bases. As a result, the strain variables can be condensed out of the system with only a slight increase in the bandwidth of the resulting linear system and the condensed approach preserves the accuracy of the non-condensed mixed approach but with fewer degrees-of-freedom. Finally, as an alternative, new quadrature rules are developed to release membrane and shear locking. These quadrature rules asymptotically only require one point for Reissner-Mindlin (RM) shell elements and two points for Kirchhoff-Love (KL) shell elements in B-spline and NURBS-based isogeometric shell analysis, independent of the polynomial order p of the elements. The quadrature points are Greville abscissae and the quadrature weights are calculated by solving a linear moment fitting problem in each parametric direction. These quadrature rules are free of spurious zero-energy modes and any spurious finite-energy modes in membrane stiffness can be easily stabilized by using a higher-order Greville rule.

Los estilos APA, Harvard, Vancouver, ISO, etc.

6

Ocampo, Blandon Cristian Felipe. "Patch-Based image fusion for computational photography". Electronic Thesis or Diss., Paris, ENST, 2018. http://www.theses.fr/2018ENST0020.

Texto completo

Resumen

Dans de nombreuses situations, la dynamique des capteurs ou la profondeur de champ des appareils photographiques conventionnels sont insuffisantes pour capturer fidèlement des scènes naturelles. Une méthode classique pour contourner ces limitations est de fusionner des images acquises avec des paramètres de prise de vue variables. Ces méthodes nécessitent que les images soient parfaitement alignées et que les scènes soient statiques, faute de quoi des artefacts (fantômes) ou des structures irrégulières apparaissent lors de la fusion. Le but de cette thèse est de développer des techniques permettant de traiter directement des images dynamiques et non-alignées, en exploitant des mesures de similarité locales par patchs entre images.Dans la première partie de cette thèse, nous présentons une méthode pour la fusion d'images de scènes dynamiques capturées avec des temps d'exposition variables. Notre méthode repose sur l'utilisation jointe d'une normalisation de contraste, de combinaisons non-locales de patchs et de régularisations. Ceci permet de produire de manière efficace des images contrastées et bien exposées, même dans des cas difficiles (objets en mouvement, scènes non planes, déformations optiques, etc.).Dans la deuxième partie de la thèse nous proposons, toujours dans des cas dynamiques, une méthode de fusion d'images acquises avec des mises au point variables. Le cœur de notre méthode repose sur une comparaison de patchs entre images ayant des niveaux de flou variables.Nos méthodes ont été évaluées sur des bases de données classiques et sur d'autres, nouvelles, crées pour les besoins de ce travail. Les expériences montrent la robustesse des méthodes aux distortions géométriques, aux variations d'illumination et au flou. Ces méthodes se comparent favorablement à des méthodes de l'état de l'art, à un coût algorithmique moindre. En marge de ces travaux, nous analysons également la capacité de l'algorithme PatchMatch à reconstruire des images en présence de flou et de changements d'illumination, et nous proposons différentes stratégies pour améliorer ces reconstructions
The most common computational techniques to deal with the limited high dynamic range and reduced depth of field of conventional cameras are based on the fusion of images acquired with different settings. These approaches require aligned images and motionless scenes, otherwise ghost artifacts and irregular structures can arise after the fusion. The goal of this thesis is to develop patch-based techniques in order to deal with motion and misalignment for image fusion, particularly in the case of variable illumination and blur.In the first part of this work, we present a methodology for the fusion of bracketed exposure images for dynamic scenes. Our method combines a carefully crafted contrast normalization, a fast non-local combination of patches and different regularization steps. This yields an efficient way of producing contrasted and well-exposed images from hand-held captures of dynamic scenes, even in difficult cases (moving objects, non planar scenes, optical deformations, etc.).In a second part, we propose a multifocus image fusion method that also deals with hand-held acquisition conditions and moving objects. At the core of our methodology, we propose a patch-based algorithm that corrects local geometric deformations by relying on both color and gradient orientations.Our methods were evaluated on common and new datasets created for the purpose of this work. From the experiments we conclude that our methods are consistently more robust than alternative methods to geometric distortions and illumination variations or blur. As a byproduct of our study, we also analyze the capacity of the PatchMatch algorithm to reconstruct images in the presence of blur and illumination changes, and propose different strategies to improve such reconstructions

Los estilos APA, Harvard, Vancouver, ISO, etc.

7

Pan, Youguang. "Bond strength of concrete patch repairs : an evaluation of test methods and the influence of workmanship and environment". Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/7059.

Texto completo

Resumen

Experiments were carried out to study the effect of workmanship and environmental conditions on bond strength for concrete patch repairs. Four repair materials, sand/cement mortar, acrylic modified cementitious mortar, SBR modified cementitious mortar, and flowing concrete, were tested with mainly three test methods (core pull-off test, patch compressive test, and patch flexural test). At the beginning of this project, slant shear tests were also carried out. In the study of the effect of workmanship, the following parameters were included: surface roughness, surface cleanliness, surface soundness, moisture condition, application method, bond coat mistiming, repair material mistiming, and curing methods. In the study of the effect of environmental conditions, four parameters were considered: high temperature curing followed by drying shrinkage, high temperature curing followed by thermal cycling, low temperature curing, and low temperature curing followed by freeze/thaw cycling. A rougher surface produces a higher bond strength, but the increase depends on individual repair material. Sand/cement mortar favours a rough surface, but polymer modified mortars are not very sensitive to surface roughness. Environmental conditions affect the bond strength development, but the effect varies with each repair material. Test results suggest that low temperature curing should be avoided for polymer modified cementitious mortars. In addition to the experimental study, theoretical analyses were carried out to evaluate the available bond test methods. The evaluation was concentrated on answering the following questions: (1) What kind of factors will influence conductinga bond test? (2) What are the response of each factor involved to a specific test method? (3) What kind of influences are crucial in ensuring the full development of the bond strength? (4) Which factors are important to achieve a durable repair? and (5) What kind of a test can be used to monitor the quality of these crucial factors? In total, about 800 tests were conducted (500 core pull-off tests, 90 patch compressive tests, 100 patch flexural tests, and 80 slant shear tests).

Los estilos APA, Harvard, Vancouver, ISO, etc.

8

Bertolino, Mattias. "Extended analysis of a pseudo-spectral approach to the vortex patch problem". Thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-354422.

Texto completo

Resumen

A prestudy indicated superior accuracy and convergence properties of apseudo-spectral method compared to a spline-based method implemented byCòrdoba et al. in 2005 when solving the α-patches problem. In this thesis wefurther investigate the numerical properties of the pseudo-spectral method and makeit more robust by implementing the Nonequispaced Fast Fourier Transform. Wepresent a more detailed overview and analysis of the pseudo-spectral method and theα-patches problem in general and conclude that the pseudo-spectral method issuperior in regards to accuracy in periodic settings.

Los estilos APA, Harvard, Vancouver, ISO, etc.

9

Brunet, Antoine Pierre. "Modélisation multi-échelle de l’effet d’un générateur solaire sur la charge électrostatique d’un satellite". Thesis, Toulouse, ISAE, 2017. http://www.theses.fr/2017ESAE0042/document.

Texto completo

Resumen

L’estimation de la charge d’un satellite et du risque de décharge nécessite dans certains cas la prise en compte dans les modèles numériques d’échelles spatiales très différentes. En particulier, les interconnecteurs présents à la surface des générateurs solaires d’un satellite sont susceptibles de modifier son équilibre électrostatique lors de missions spatiales rencontrant un environnement plasma dense. Une modélisation classique de cet effet nécessiterait le maillage d’éléments à des échelles submillimétriques,sur un satellite de plusieurs dizaines de mètres d’envergure, ce qui rendrait la simulation extrêmement onéreuse en temps de calcul. De plus, ces interconnecteurs sont parfois fortement chargés positivement par rapport à l’environnement, ce qui empêche l’application du modèle de Maxwell-Boltzmann classiquement utilisé pour les populations d’électrons. Dans une première partie, nous avons développé une méthode itérative de type Patch adaptée à la résolution du problème non-linéaire de Poisson-Boltzmann pour la simulation du plasma spatial. Cette méthode numérique multigrille permet la simulation de l’impact d’éléments de petite taille à la surface d’un satellite complet. Dans une seconde partie, nous avons développé un schéma correctif permettant d’utiliser le modèle de Maxwell-Boltzmann pour la population d’électrons, malgré la présence de surfaces satellites chargées positivement, en y ajoutant un terme de correction calculé à l’aide de la méthode Particle-in-Cell. Nous avons montré que ce schéma permet, tout en limitant le coût en calculs, de déterminer avec précision les courants collectés par les surfaces du satellites, qu’elles soient chargées négativement ou positivement
The numerical simulation of spacecraft charging can require to resolve widely different geometrical scales. In particular, solar array interconnects on the surface of solar panels have a major impact ona satellite electrostatic equilibrium. A classical model of this effect would require a mesh refined tosub-millimetre scales, on a spacecraft spanning several dozen metres, which would make the simulation computationally expensive. Moreover, the solar array interconnects can have a large positive potentialrelative to the space plasma, preventing the use of the classical Maxwell-Boltzmann model for theelectrons in the plasma. In a first part, we have developed an iterative patch method to solve thenonlinear Poisson-Boltzmann equation used in plasma simulations. This multigrid numerical scheme allows to resolve the impact of small-scale components on the surface of a complete spacecraft. In asecond part, we have developed a corrective scheme for the Maxwell-Boltzmann model to account for the presence of charged surfaces in the simulation. We have shown that this simple model is able to precisely compute the currents collected by the spacecraft surfaces

Los estilos APA, Harvard, Vancouver, ISO, etc.

10

Bin-Melha, Mohammed S. "Design and implementation of band rejected antennas using adaptive surface meshing and genetic algorithms methods. Simulation and measurement of microstrip antennas with the ability of harmonic rejection for wireless and mobile applications including the antenna design optimisation using genetic algorithms". Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/6358.

Texto completo

Resumen

With the advances in wireless communication systems, antennas with different shapes and design have achieved great demand and are desirable for many uses such as personal communication systems, and other applications involving wireless communication. This has resulted in different shapes and types of antenna design in order to achieve different antenna characteristic. One attractive approach to the design of antennas is to suppress or attenuate harmonic contents due to the non-linear operation of the Radio Frequency (RF) front end. The objectives of this work were to investigate, design and implement antennas for harmonic suppression with the aid of a genetic algorithm (GA). Several microstrip patch antennas were designed to operate at frequencies 1.0, 1.8 and 2.4 GHz respectively. The microstrip patch antenna with stub tuned microstrip lines was also employed at 1.0 and 1.8 GHz to meet the design objectives. A new sensing patch technique is introduced and applied in order to find the accepted power at harmonic frequencies. The evaluation of the measured power accepted at the antenna feed port was done using an electromagnetic (EM) simulator, Ansoft Designer, in terms of current distribution. A two sensors method is presented on one antenna prototype to estimate the accepted power at three frequencies. The computational method is based on an integral equation solver using adaptive surface meshing driven by a genetic algorithm. Several examples are demonstrated, including design of coaxially-fed, air-dielectric patch antennas implanted with shorting and folded walls. The characteristics of the antennas in terms of the impedance responses and far field radiation patterns are discussed. The results in terms of the radiation performance are addressed, and compared to measurements. The presented results of these antennas show a good impedance matching at the fundamental frequency with good suppression achieved at the second and third harmonic frequencies.
Home government

Los estilos APA, Harvard, Vancouver, ISO, etc.

11

Binmelha, Mohammed Saeed. "Design and implementation of band rejected antennas using adaptive surface meshing and genetic algorithms methods : simulation and measurement of microstrip antennas with the ability of harmonic rejection for wireless and mobile applications including the antenna design optimisation using genetic algorithms". Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/6358.

Texto completo

Resumen

With the advances in wireless communication systems, antennas with different shapes and design have achieved great demand and are desirable for many uses such as personal communication systems, and other applications involving wireless communication. This has resulted in different shapes and types of antenna design in order to achieve different antenna characteristic. One attractive approach to the design of antennas is to suppress or attenuate harmonic contents due to the non-linear operation of the Radio Frequency (RF) front end. The objectives of this work were to investigate, design and implement antennas for harmonic suppression with the aid of a genetic algorithm (GA). Several microstrip patch antennas were designed to operate at frequencies 1.0, 1.8 and 2.4 GHz respectively. The microstrip patch antenna with stub tuned microstrip lines was also employed at 1.0 and 1.8 GHz to meet the design objectives. A new sensing patch technique is introduced and applied in order to find the accepted power at harmonic frequencies. The evaluation of the measured power accepted at the antenna feed port was done using an electromagnetic (EM) simulator, Ansoft Designer, in terms of current distribution. A two sensors method is presented on one antenna prototype to estimate the accepted power at three frequencies. The computational method is based on an integral equation solver using adaptive surface meshing driven by a genetic algorithm. Several examples are demonstrated, including design of coaxially-fed, air-dielectric patch antennas implanted with shorting and folded walls. The characteristics of the antennas in terms of the impedance responses and far field radiation patterns are discussed. The results in terms of the radiation performance are addressed, and compared to measurements. The presented results of these antennas show a good impedance matching at the fundamental frequency with good suppression achieved at the second and third harmonic frequencies.

Los estilos APA, Harvard, Vancouver, ISO, etc.

12

Oliver, Parera Maria. "Scene understanding from image and video : segmentation, depth configuration". Doctoral thesis, Universitat Pompeu Fabra, 2018. http://hdl.handle.net/10803/663870.

Texto completo

Resumen

In this thesis we aim at analyzing images and videos at the object level, with the goal of decomposing the scene into complete objects that move and interact among themselves. The thesis is divided in three parts. First, we propose a segmentation method to decompose the scene into shapes. Then, we propose a probabilistic method, which works with shapes or objects at two diﬀerent depths, to infer which objects are in front of the others, while completing the ones which are partially occluded. Finally, we propose two video related inpainting method. On one hand, we propose a binary video inpainting method that relies on the optical ﬂow of the video in order to complete the shapes across time taking into account their motion. On the other hand, we propose a method for optical ﬂow that takes into account the informational from the frames.
Aquesta tesi té per objectiu analitzar imatges i vídeos a nivell d’objectes, amb l’objectiu de descompondre l’escena en objectes complets que es mouen i interaccionen entre ells. La tesi està dividida en tres parts. En primer lloc, proposem un mètode de segmentació per descompondre l’escena en les formes que la componen. A continuació, proposem un mètode probabilístic, que considera les formes o objectes en dues profunditats de l’escena diferents, i infereix quins objectes estan davant dels altres, completant també els objectes parcialment ocults. Finalment, proposem dos mètodes relacionats amb el vídeo inpainting. Per una banda, proposem un mètode per vídeo inpainting binari que utilitza el ﬂux òptic del vídeo per completar les formes al llarg del temps, tenint en compte el seu moviment. Per l’altra banda, proposem un mètode per inpainting de ﬂux òptic que té en compte la informació provinent dels frames.

Los estilos APA, Harvard, Vancouver, ISO, etc.

13

Akkasli, Cem. "Methods for Path loss Prediction". Thesis, Växjö University, School of Mathematics and Systems Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-6127.

Texto completo

Resumen

Large scale path loss modeling plays a fundamental role in designing both fixed and mobile radio systems. Predicting the radio coverage area of a system is not done in a standard manner. Wireless systems are expensive systems. Therefore, before setting up a system one has to choose a proper method depending on the channel environment, frequency band and the desired radio coverage range. Path loss prediction plays a crucial role in link budget analysis and in the cell coverage prediction of mobile radio systems. Especially in urban areas, increasing numbers of subscribers brings forth the need for more base stations and channels. To obtain high efficiency from the frequency reuse concept in modern cellular systems one has to eliminate the interference at the cell boundaries. Determining the cell size properly is done by using an accurate path loss prediction method. Starting from the radio propagation phenomena and basic path loss models this thesis aims at describing various accurate path loss prediction methods used both in rural and urban environments. The Walfisch-Bertoni and Hata models, which are both used for UHF propagation in urban areas, were chosen for a detailed comparison. The comparison shows that the Walfisch-Bertoni model, which involves more parameters, agrees with the Hata model for the overall path loss.

Los estilos APA, Harvard, Vancouver, ISO, etc.

14

De, bortoli Valentin. "Statistiques non locales dans les images : modélisation, estimation et échantillonnage". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASN020.

Texto completo

Resumen

Dans cette thèse, on étudie d'un point de vueprobabiliste deux statistiques non locales dans les images : laredondance spatiale et les moments de certaines couches de réseauxde neurones convolutionnels. Plus particulièrement, on s'intéresse àl'estimation et à la détection de la redondance spatiale dans lesimages naturelles et à l'échantillonnage de modèles d'images souscontraintes de moments de sorties de réseaux deneurones.On commence par proposer une définition de la redondance spatialedans les images naturelles. Celle-ci repose sur une analyseGestaltiste de la notion de similarité ainsi que sur un cadrestatistique pour le test d'hypothèses via la méthode acontrario. On développe un algorithme pour identifier cetteredondance dans les images naturelles. Celui-ci permet d'identifierles patchs similaires dans une image. On utilise cette informationpour proposer de nouveaux algorithmes de traitement d'image(débruitage, analyse de périodicité).Le reste de cette thèse est consacré à la modélisation et àl'échantillonnage d'images sous contraintes non locales. Les modèlesd'images considérés sont obtenus via le principe de maximumd'entropie. On peut alors déterminer la distribution cible sur lesimages via une procédure de minimisation. On aborde ce problème enutilisant des outils issus de l'optimisationstochastique.Plus précisément, on propose et analyse un nouvel algorithme pourl'optimisation stochastique : l'algorithme SOUL (StochasticOptimization with Unadjusted Langevin). Dans cette méthodologie, legradient est estimé par une méthode de Monte Carlo par chaîne deMarkov (ici l'algorithme de Langevin non ajusté). Les performancesde cet algorithme repose sur les propriétés de convergenceergodiques des noyaux de Markov associés aux chaînes de Markovutilisées. On s'intéresse donc aux propriétés de convergencegéométrique de certaines classes de modèles fonctionnelsautorégressifs. On caractérise précisément la dépendance des taux deconvergence de ces modèles vis à vis des constantes du modèle(dimension, régularité,convexité...).Enfin, on applique l'algorithme SOUL au problème de synthèse detexture par maximum d'entropie. On étudie les liens qu'entretientcette approche avec d'autres modèles de maximisation d'entropie(modèles macrocanoniques, modèles microcanoniques). En utilisant desstatistiques de moments de sorties de réseaux de neuronesconvolutionnels on obtient des résultats visuels comparables à ceux del'état de l'art
In this thesis we study two non-localstatistics in images from a probabilistic point of view: spatialredundancy and convolutional neural network features. Moreprecisely, we are interested in the estimation and detection ofspatial redundancy in naturalimages. We also aim at sampling images with neural network constraints.We start by giving a definition of spatial redundancy in naturalimages. This definition relies on two concepts: a Gestalt analysisof the notion of similarity in images, and a hypothesis testingframework (the a contrario method). We propose an algorithm toidentify this redundancy in natural images. Using this methodologywe can detect similar patches in images and, with this information,we propose new algorithms for diverse image processing tasks(denoising, periodicity analysis).The rest of this thesis deals with sampling images with non-localconstraints. The image models we consider are obtained via themaximum entropy principle. The target distribution is then obtainedby minimizing an energy functional. We use tools from stochasticoptimization to tackle thisproblem.More precisely, we propose and analyze a new algorithm: the SOUL(Stochastic Optimization with Unadjusted Langevin) algorithm. Inthis methodology, the gradient is estimated using Monte Carlo MarkovChains methods. In the case of the SOUL algorithm we use an unadjustedLangevin algorithm. The efficiency of the SOUL algorithm is relatedto the ergodic properties of the underlying Markov chains. Thereforewe are interested in the convergence properties of certain class offunctional autoregressive models. We characterize precisely thedependency of the convergence rates of these models with respect totheir parameters (dimension, smoothness,convexity).Finally, we apply the SOUL algorithm to the problem ofexamplar-based texture synthesis with a maximum entropy approach. Wedraw links between our model and other entropy maximizationprocedures (macrocanonical models, microcanonical models). Usingconvolutional neural network constraints we obtain state-of-the artvisual results

Los estilos APA, Harvard, Vancouver, ISO, etc.

15

Sturdy, Yvette Katherine. "Molecular simulation with path integral methods". Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436950.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

16

Krykova, Inna. "Evaluating of path-dependent securities with low discrepancy methods". Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0113104-140925.

Texto completo

Resumen

Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: variance-reduction techniques; Quasi- Monte Carlo; path-dependent securities; low-discrepancy methods. Includes bibliographical references (p. 64-65).

Los estilos APA, Harvard, Vancouver, ISO, etc.

17

Markland, Thomas E. "Development and Applications of Path Integral Methods". Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504433.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

18

Yiğit, Konuralp. "Path planning methods for Autonomous Underwater Vehicles". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67807.

Texto completo

Resumen

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 75-81).
From naval operations to ocean science missions, the importance of autonomous vehicles is increasing with the advances in underwater robotics technology. Due to the dynamic and intermittent underwater environment and the physical limitations of autonomous underwater vehicles, feasible and optimal path planning is crucial for autonomous underwater operations. The objective of this thesis is to develop and demonstrate an efficient underwater path planning algorithm based on the level set method. Specifically, the goal is to compute the paths of autonomous vehicles which minimize travel time in the presence of ocean currents. The approach is to either utilize or avoid any type of ocean flows, while allowing for currents that are much larger than the nominal vehicle speed and for three-dimensional currents which vary with time. Existing path planning methods for the fields of ocean science and robotics are first reviewed, and the advantages and disadvantages of each are discussed. The underpinnings of the level set and fast marching methods are then reviewed, including their new extension and application to underwater path planning. Finally, a new feasible and optimal time-dependent underwater path planning algorithm is derived and presented. In order to demonstrate the capabilities of the algorithm, a set of idealized test-cases of increasing complexity are first presented and discussed. A real three-dimensional path planning example, involving strong current conditions, is also illustrated. This example utilizes four-dimensional ocean flows from a realistic ocean prediction system which simulate the ocean response to the passage of a tropical storm in the Middle Atlantic Bight region.
by Konuralp Yiğit.
S.M.

Los estilos APA, Harvard, Vancouver, ISO, etc.

19

Ramanata, Peeroon Pete. "Optimal Vehicle Path Generator Using Optimization Methods". Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36615.

Texto completo

Resumen

This research explores the idea of developing an optimal path generator that can be used in conjunction with a feedback steering controller to automate track testing experiment. This study specifically concentrates on applying optimization concepts to generate paths that meet two separate objective functions; minimum time and maximum tire forces.

A three-degree-of freedom vehicle model is used to approximate the handling dynamics of the vehicle. Inputs into the vehicle model are steering angle and longitudinal force at the tire. These two variables approximate two requirements that are essential in operating a vehicle. The Third order Runge-Kutta integration routine is used to integrate vehicle dynamics equations of motion. The Optimization Toolbox of Matlab is used to evaluate the optimization algorithm. The vehicle is constrained with a series of conditions, includes, a travel within the boundaries of the track, traction force limitations at the tire, vehicle speed, and steering.

The simulation results show that the optimization applied to vehicle dynamics can be useful in designing an automated track testing system. The optimal path generator can be used to develop meaningful test paths on existing test tracks. This study can be used to generate an accelerated tire wear test path, perform parametric study of suspension geometry design using vehicle dynamics handling test data, and to increase repeatability in generating track testing results.

Vita removed at author's request. GMc 3/13/2013
Master of Science

Los estilos APA, Harvard, Vancouver, ISO, etc.

20

Beddiaf, Salah. "Continuous steepest descent path for traversing non-convex regions". Thesis, University of Hertfordshire, 2016. http://hdl.handle.net/2299/17175.

Texto completo

Resumen

In this thesis, we investigate methods of finding a local minimum for unconstrained problems of non-convex functions with n variables, by following the solution curve of a system of ordinary differential equations. The motivation for this was the fact that existing methods (e.g. those based on Newton methods with line search) sometimes terminate at a non-stationary point when applied to functions f(x) that do not a have positive-definite Hessian (i.e. ∇²f → 0) for all x. Even when methods terminate at a stationary point it could be a saddle or maximum rather than a minimum. The only method which makes intuitive sense in non-convex region is the trust region approach where we seek a step which minimises a quadratic model subject to a restriction on the two-norm of the step size. This gives a well-defined search direction but at the expense of a costly evaluation. The algorithms derived in this thesis are gradient based methods which require systems of equations to be solved at each step but which do not use a line search in the usual sense. Progress along the Continuous Steepest Descent Path (CSDP) is governed both by the decrease in the function value and measures of accuracy of a local quadratic model. Numerical results on specially constructed test problems and a number of standard test problems from CUTEr [38] show that the approaches we have considered are more promising when compared with routines in the optimization tool box of MATLAB [46], namely the trust region method and the quasi-Newton method. In particular, they perform well in comparison with the, superficially similar, gradient-flow method proposed by Behrman [7].

Los estilos APA, Harvard, Vancouver, ISO, etc.

21

Xu, Song. "Non-interior path-following methods for complementarity problems /". Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/5793.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

22

Giraud, Remi. "Algorithmes de correspondance et superpixels pour l’analyse et le traitement d’images". Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0771/document.

Texto completo

Resumen

Cette thèse s’intéresse à diverses composantes du traitement et de l’analyse d’images par méthodes non locales. Ces méthodes sont basées sur la redondance d’information présente dans d’autres images, et utilisent des algorithmes de recherche de correspondance, généralement basés sur l’utilisation patchs, pour extraire et transférer de l’information depuis ces images d’exemples. Ces approches, largement utilisées par la communauté de vision par ordinateur, sont souvent limitées par le temps de calcul de l’algorithme de recherche, appliqué à chaque pixel, et par la nécessité d’effectuer un prétraitement ou un apprentissage pour utiliser de grandes bases de données.Pour pallier ces limites, nous proposons plusieurs méthodes générales, sans apprentissage,rapides, et qui peuvent être facilement adaptées à diverses applications de traitement et d’analyse d’images naturelles ou médicales. Nous introduisons un algorithme de recherche de correspondances permettant d’extraire rapidement des patchs d’une grande bibliothèque d’images 3D, que nous appliquons à la segmentation d’images médicales. Pour utiliser de façon similaire aux patchs,des présegmentations en superpixels réduisant le nombre d’éléments de l’image,nous présentons une nouvelle structure de voisinage de superpixels. Ce nouveau descripteur permet d’utiliser efficacement les superpixels dans des approches non locales. Nous proposons également une méthode de décomposition régulière et précise en superpixels. Nous montrons comment évaluer cette régularité de façon robuste, et que celle-ci est nécessaire pour obtenir de bonnes performances de recherche de correspondances basées sur les superpixels
This thesis focuses on several aspects of image analysis and processing with non local methods. These methods are based on the redundancy of information that occurs in other images, and use matching algorithms, that are usually patch-based, to extract and transfer information from the example data. These approaches are widely used by the computer vision community, and are generally limited by the computational time of the matching algorithm, applied at the pixel scale, and by the necessity to perform preprocessing or learning steps to use large databases. To address these issues, we propose several general methods, without learning, fast, and that can be easily applied to different image analysis and processing applications on natural and medical images. We introduce a matching algorithm that enables to quickly extract patches from a large library of 3D images, that we apply to medical image segmentation. To use a presegmentation into superpixels that reduces the number of image elements, in a way that is similar to patches, we present a new superpixel neighborhood structure. This novel descriptor enables to efficiently use superpixels in non local approaches. We also introduce an accurate and regular superpixel decomposition method. We show how to evaluate this regularity in a robust manner, and that this property is necessary to obtain good superpixel-based matching performances

Los estilos APA, Harvard, Vancouver, ISO, etc.

23

Vitten, Harald. "Charakterisierung von Glutamat-Rezeptoren bei Neuronen im auditorischen Hirnstamm der Ratte". [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=961910585.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

24

Schmidt, Darren A. (Darren Arnold) 1975. "An automated method for data path construction". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50044.

Texto completo

Resumen

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.
Includes bibliographical references (leaf 124).
by Darren A. Schmidt.
B.S.
M.Eng.

Los estilos APA, Harvard, Vancouver, ISO, etc.

25

Matthews, James Christopher Gordon. "Patch moment method modelling of wire fed vehicular structures as adaptive antennas". Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412702.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

26

Lauer, Lars. "Netzwerke von Nervenzellen auf strukturierten Oberflächen charakterisiert mit optischen und elektrophysiologischen Methoden". [S.l.] : [s.n.], 2001. http://ArchiMeD.uni-mainz.de/pub/2001/0059/diss.pdf.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

27

Frese, Jan. "Molekulare Interaktion von Lidocain mit dem isolierten tetrodotoxinresistenten Natriumkanal vom Typ NaV1.8 exprimiert in humanen embryonalen Nierenstammzellen HEK293 /". Giessen : VVB Laufersweiler, 2007. http://d-nb.info/988754215/34.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

28

Lepski, Guilherme. "A comparative analysis of human adult mesenchymal and fetal neuronal stem cells with regard to their neurogenic potential". Giessen VVB Laufersweiler, 2009. http://d-nb.info/1000206017/04.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

29

Plotnick, Fredric Leigh Martin Joseph P. "RDM - relationship diagramming method /". Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2934.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

30

Gruhlke, Daniel [Verfasser]. "Convergence of Multilevel MCMC methods on path spaces / Daniel Gruhlke". Bonn : Universitäts- und Landesbibliothek Bonn, 2014. http://d-nb.info/1057915068/34.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

31

Siu, Ernest. "Methods and issues in path provisioning on ring-based networks". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0012/MQ60177.pdf.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

32

Lolla, Sri Venkata Tapovan. "Path planning in time dependent flows using level set methods". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78212.

Texto completo

Resumen

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 167-177).
Autonomous underwater vehicles such as gliders have emerged as valuable scientific platforms due to their increasing uses in several oceanic applications, ranging from security, acoustic surveillance and military reconnaissance to collection of ocean data at specific locations for ocean prediction, monitoring and dynamics investigation. Gliders exhibit high levels of autonomy and are ideal for long range missions. As these gliders become more reliable and affordable, multi-vehicle coordination and sampling missions are expected to become very common in the near future. This endurance of gliders however, comes at an expense of being susceptible to typical coastal ocean currents. Due to the physical limitations of underwater vehicles and the highly dynamic nature of the coastal ocean, path planning to generate safe and fast vehicle trajectories becomes crucial for their successful operation. As a result, our motivation in this thesis is to develop a computationally efficient and rigorous methodology that can predict the time-optimal paths of underwater vehicles navigating in continuous, strong and dynamic ow-fields. The goal is to predict a sequence of steering directions so that vehicles can best utilize or avoid ow currents to minimize their travel time. In this thesis, we fist review existing path planning methods and discuss their advantages and drawbacks. Then, we discuss the theory of level set methods and their utility in solving front tracking problems. Then, we present a rigorous (partial differential equation based) methodology based on the level set method, which can compute time-optimal paths of swarms of underwater vehicles, obviating the need for any heuristic control based approaches. We state and prove a theorem, along with several corollaries, that forms the foundation of our approach for path planning. We show that our algorithm is computationally efficient - the computational cost grows linearly with the number of vehicles and geometrically with spatial directions. We illustrate the working and capabilities of our path planning algorithm by means of a number of applications. First, we validate our approach through simple benchmark applications, and later apply our methodology to more complex, realistic and numerically simulated ow-fields, which include eddies, jets, obstacles and forbidden regions. Finally, we extend our methodology to solve problems of coordinated motion of multiple vehicles in strong dynamic ow-fields. Here, coordination refers to maintenance of specific geometric patterns by the vehicles. The level-set based control scheme that we derive is shown to provide substantial advantages to a local control approach. Specifically, the illustrations show that the resulting coordinated vehicle motions can maintain specific patterns in dynamic flow fields with strong and complex spatial gradients.
by Sri Venkata Tapovan Lolla.
S.M.

Los estilos APA, Harvard, Vancouver, ISO, etc.

33

Ballikaya, Elif. "Analysis Of Slot Coupled Microstrip Patch Antennas". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609094/index.pdf.

Texto completo

Resumen

Method of Moments (MoM)/Green&rsquo
s function formulation is developed for the analysis of electromagnetic radiation from planar rectangular microstrip antennas with different feeding techniques. Investigated structures are microstrip line fed patch antenna, proximity coupled patch antenna and slot coupled patch antenna. For all these structures equivalent problems are defined. Then, integral equations where currents are the unknowns are obtained from boundary conditions and by using spectral domain representation of Green&rsquo
s functions. Finally, MoM is applied to convert these integral equations to a system of linear equations. Currents on the conducting surfaces as well as equivalent magnetic currents on the apertures are modeled as a sum of piecewise sinusoidal subdomain basis functions with unknown coefficients which are calculated by solving the system of linear equations. Based on the formulations provided in this study, a Fortran code is developed. Numerical results calculated by using the code are presented in the form of patch and line currents and input impedances. Presented results are in good agreement with the results given in the literature.

Los estilos APA, Harvard, Vancouver, ISO, etc.

34

Baboulet, Olivier. "Path Exchange Method for Hybrid Life-Cycle Assessment". Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9930.

Texto completo

Resumen

To keep process-specificity while extending system boundaries hybrid techniques were developed allowing the micro structure of the important parts of a system to be revealed at the same time the entire economic system in which the system is embedded to be covered. Despite the substantial improvements bestowed by hybrid techniques some downsides still hold. Tiered hybrid LCA first does not model feedbacks whereas the relationship between the process-based system and the input-output based system is interactive and second it may suffer from double counting incidents as a process may be instigated in both the IO and LCI data. Integrated hybrid LCA overcomes those aforementioned pitfalls but only at a price of high labor and data intensity. This work aims to elaborate a new hybridisation method that avoids previously mentioned drawbacks. This technique is designed to not operate anymore at the matrix level as is the case for current hybridisation techniques but at the structural path level, per se the finest level of detail possible for the disaggregation of the Leontief inverse, and as such an ad hoc basis to carry out an hybrid analysis. It is argued that the method presented here constitutes a culmination amongst hybridization techniques. Its operability and capabilities are demonstrated before an interpretation from an input-output vantage point is carried out on a case-study not to be found in the literature, a comparison across the faculties of a university.

Los estilos APA, Harvard, Vancouver, ISO, etc.

35

Baumann, Markus. "Newton's Method for Path-Following Problems on Manifolds". Doctoral thesis, kostenfrei, 2008. http://www.opus-bayern.de/uni-wuerzburg/volltexte/2008/2809/.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

36

Lüdders, Dörte Wiebke. "Einfluss des Phosphodiesterase-Typ-5 Inhibitors Sildenafil auf den Ca 2+ -aktivierten K + -Kanal mit großer Leitfähigkeit in humanen Endothelzellen". Giessen : VVB Laufersweiler, 2007. http://geb.uni-giessen.de/geb/volltexte/2007/4536/index.html.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

37

Most, Astrid Kerstin. "Einfluss von Endothelin-1 auf den Ca2+-aktivierten K+-Kanal mit grosser Leitfähigkeit, die Ca2+-Homöostase und die humane Endothelzellproliferation". Giessen VVB Laufersweiler, 2007. http://d-nb.info/989790835/04.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

38

Reinhold, Lars Henning. "Einfluss von SDF 1-[alpha] [1-Alpha] auf den Ca2+-aktivierten K+-Kanal mit grosser Leitfähigkeit und die daraus resultierenden Auswirkungen auf die Proliferation, Migration, NO- und Ca2+-Homöostase humaner Endothelzellen". Giessen VVB Laufersweiler, 2007. http://d-nb.info/991416503/04.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

39

Kücherer, Christian [Verfasser] y Barbara [Akademischer Betreuer] Paech. "Domain-specific Adaptation of Requirements Engineering Methods / Christian Kücherer ; Betreuer: Barbara Paech". Heidelberg : Universitätsbibliothek Heidelberg, 2018. http://d-nb.info/1177149524/34.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

40

Barros, Joyce Moniz Martim. "Models and methods for Traffic Engineering problems with single-path routing". Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/238366.

Texto completo

Resumen

Traffic Engineering (TE) uses methods and models from a variety of mathematical fields, such as statistics and optimization, to improve the performance of telecommunication networks. In this thesis, we study TE problems dealing with networks that impose single-path routing. As the name infers, in this type of routing, the traffic flow of each "commodity" cannot be split in its path between its origin and destination. Given its cheap cost, single-path routing is widely used in today's data centers, where thousands of stored servers perform computations or host Internet services. One common case of single-path routing is the one enforced by the Spanning Tree Protocol (STP) in switched Ethernet networks. The STP requires the network to keep its activated links loop-free, while maintaining the other redundant links ready for back-up, in case of link failure. The Multiple Spanning Tree Protocol (MSTP) extends the STP by installing multiple virtual networks compliant with the STP, over a single physical topology. Therefore, the MSTP is greatly beneficial for network service providers, as it allows for a more efficient use of the existing resources.Network design problems dealing with the MSTP are generally highly combinatorial and very hard to solve. As such, TE literature mainly suggests heuristic methods, which can quickly produce reasonable designs. Notwithstanding, due to a scarce existence of lower bounds to the optimum values of such problems, there is little knowledge about the quality of the solutions provided by these heuristics.In this sense, we propose mathematical programming models and methods that can provide optimal designs for these networks, or at the very least, obtain valid lower bounds. Taking into mind the goal of avoiding congestion in the network, we focus on two problems that deal with the following load-balancing objectives: the minimization of the worst-case link utilization, and the minimization of flow costs given by piecewise linear functions that penalize heavily-loaded links. The study of both these problems yielded relevant by-products: the first is the study of a MSTP network design problem, where we minimize the total load, and the second is the study of a fundamental unsplittable multicommodity flow problem with piecewise linear costs.For all the considered problems, we provide studies of complexity, extensive polyhedral studies to compare the proposed formulations, and a wide array of computational experiments to evaluate the performance of the proposed models and methods.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

Los estilos APA, Harvard, Vancouver, ISO, etc.

41

Omar, Rosli bin. "Path planning for unmanned aerial vehicles using visibility line-based methods". Thesis, University of Leicester, 2012. http://hdl.handle.net/2381/10906.

Texto completo

Resumen

This thesis concerns the development of path planning algorithms for unmanned aerial vehicles (UAVs) to avoid obstacles in two- (2D) and three-dimensional (3D) urban environments based on the visibility graph (VG) method. As VG uses all nodes (vertices) in the environments, it is computationally expensive. The proposed 2D path planning algorithms, on the contrary, select a relatively smaller number of vertices using the so-called base line (BL), thus they are computationally efficient. The computational efficiency of the proposed algorithms is further improved by limiting the BL’s length, which results in an even smaller number of vertices. Simulation results have proven that the proposed 2D path planning algorithms are much faster in comparison with the VG and hence are suitable for real time path planning applications. While vertices can be explicitly defined in 2D environments using VG, it is difficult to determine them in 3D as they are infinite in number at each obstacle’s border edge. This issue is tackled by using the so-called plane rotation approach in the proposed 3D path planning algorithms where the vertices are the intersection points between a plane rotated by certain angles and obstacles edges. In order to ensure that the 3D path planning algorithms are computationally efficient, the proposed 2D path planning algorithms are applied into them. In addition, a software package using Matlab for 2D and 3D path planning has also been developed. The package is designed to be easy to use as well as user-friendly with step-by-step instructions.

Los estilos APA, Harvard, Vancouver, ISO, etc.

42

Javvaji, Pavan Kumar. "STATISTICAL METHODS FOR CRITICAL PATHS SELECTION AND FAULT COVERAGE IN INTEGRATED CIRCUITS". OpenSIUC, 2019. https://opensiuc.lib.siu.edu/dissertations/1664.

Texto completo

Resumen

With advances in technology, modern integrated circuits have higher complexities and reduced transistor sizing. In deep sub-micron, the parameter variation-control is difficult and component delays vary from one manufactured chip to another. Therefore, the delays are not discrete values but are a statistical quantity, and statistical evaluation methods have gained traction. Furthermore, fault injection based gate-level fault coverage is non-scalable and statistical estimation methods are preferred. This dissertation focuses on scalable statistical methods to select critical paths in the presence of process variations, and to improve the defect coverage for complex integrated circuits. In particular, we investigate the sensitization probability of a path by a test pattern under statistical delays. Next, we investigate test pattern generation for improving the sensitization probability of a path, selecting critical paths that yield high defect coverage, and scalable method to estimate fault coverage of complex designs using machine learning techniques.

Los estilos APA, Harvard, Vancouver, ISO, etc.

43

Cherukuri, Chandrasekhar. "Analysis of coaxial fed U-slot patch antennas using finite difference time domain method". FIU Digital Commons, 2002. http://digitalcommons.fiu.edu/etd/2158.

Texto completo

Resumen

The objective of this thesis was to analyze a Coaxial-Fed U-slot Rectangular Patch Antenna using Finite Difference Time Domain (FDTD) method. Important parameters such as S-parameters and Input Impedance of the antenna were simulated using XFDTD software and were analyzed. An important goal of this thesis was to provide design information about the U-slot antenna. For this purpose the effects of antenna layout on the resonant frequency and the bandwidth of the antenna were investigated. First the effect of varying slot width on the S-parameters, Voltage Standing Wave Ratio (VSWR) and Input Impedance were studied. Next the length of the slot was varied and effect of changing this design parameter of the antenna was analyzed. Finally the substrate thickness was varied and its effect on the antenna parameters is studied. This work concluded that by varying antenna dimensions such as slot width, slot length and substrate thickness, higher bandwidth could be achieved with required impedance matching.

Los estilos APA, Harvard, Vancouver, ISO, etc.

44

Lau, Pak Fai. "CNC machining accuracy enhancement by tool path compensation method /". View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?IEEM%202005%20LAU.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

45

Lindefelt, Anna y Anders Nordlund. "A Path Following Method with Obstacle Avoidance for UGVs". Thesis, Linköping University, Department of Electrical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11242.

Texto completo

Resumen

The goal of this thesis is to make an unmanned ground vehicle (UGV) follow a given reference trajectory, without colliding with obstacles in its way. This thesis will especially focus on modeling and controlling the UGV, which is based on the power wheelchair Trax from Permobil.

In order to make the UGV follow a given reference trajectory without colliding, it is crucial to know the position of the UGV at all times. Odometry is used to estimate the position of the UGV relative a starting point. For the odometry to work in a satisfying way, parameters such as wheel radii and wheel base have to be calibrated. Two control signals are used to control the motion of the UGV, one to control the speed and one to control the steering angles of the two front wheels. By modeling the motion of the UGV as a function of the control signals, the motion can be predicted. A path following algorithm is developed in order to make the UGV navigate by maps. The maps are given in advance and do not contain any obstacles. A method to handle obstacles that comes in the way is presented.

Los estilos APA, Harvard, Vancouver, ISO, etc.

46

Yamazato, Takaya, Iwao Sasase y Shinsaku Mori. "A New Viterbi Algorithm with Adaptive Path Reduction Method". IEICE, 1993. http://hdl.handle.net/2237/7839.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

47

Bachmann, Michael. "Path integral methods in quantum statistics, quantum field theory and membrane physics". [S.l.] : [s.n.], 2001. http://www.diss.fu-berlin.de/2001/106/index.html.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

48

Nygaard, Ranveig. "Shortest path methods in representation and compression of signals and image contours". Doctoral thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2000. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1182.

Texto completo

Resumen

Signal compression is an important problem encountered in many applications. Various techniques have been proposed over the years for adressing the problem. The focus of the dissertation is on signal representation and compression by the use of optimization theory, more shortest path methods.

Several new signal compression algorithms are presented. They are based on the coding of line segments which are used to spproximate, and thereby represent, the signal. These segments are fit in a way that is optimal given some constraints on the solution. By formulating the compession problem as a graph theory problem, shortest path methods can be applied in order to yeild optimal compresson with respect to the given constraints.

The approaches focused on in this dissertaion mainly have their origin in ECG comression and is often referred to as time domain compression methods. Coding by time domain methods is based on the idea of extracting a subset of significant signals samples to represent the signal. The key to a successful algoritm is a good rule for determining the most significant samples. Between any two succeeding samples in the extracted smaple set, different functions are applied in reconstruction of the signal. These functions are fitted in a wy that guaratees minimal reconstruction error under the gien constraints. Two main categories of compression schemes are developed:

1. Interpolating methods, in which it is insisted on equality between the original and reconstructed signal at the points of extraction.

2. Non-interpolating methods, where the inerpolatian restriction is released.

Both first and second order polynomials are used in reconstruction of the signal. There is solso developed an approach were multiple error measures are applied within one compression algorithm.

The approach of extracting the most significant smaples are further developed by measuring the samples in terms of the number of bits needed to encode such samples. This way we develop an approach which is optimal in the ratedistortion sense.

Although the approaches developed are applicable to any type of signal, the focus of this dissertaion is on the compression of electrodiogram (ECG) signals and image contours, ECG signal compression has traditionally been

Los estilos APA, Harvard, Vancouver, ISO, etc.

49

Oshaug, Christian A. J. "Lévy Processes and Path Integral Methods with Applications in the Energy Markets". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13730.

Texto completo

Resumen

The objective of this thesis was to explore methods for valuation of derivatives in energy markets. One aim was to determine whether the Normal inverse Gaussian distributions would be better suited for modelling energy prices than normal distributions. Another aim was to develop working implementations of Path Integral methods for valuing derivatives, based on some one-factor model of the underlying spot price. Energy prices are known to display properties like mean-reversion, periodicity, volatility clustering and extreme jumps. Periodicity and trend are modelled as a deterministic function of time, while mean-reversion effects are modelled with auto-regressive dynamics. It is established that the Normal inverse Gaussian distributions are superior to the normal distributions for modelling the residuals of an auto-regressive energy price model. Volatility clustering and spike behaviour are not reproduced with the models considered here. After calibrating a model to fit real energy data, valuation of derivatives is achieved by propagating probability densities forward in time, applying the Path Integral methodology. It is shown how this can be implemented for European options and barrier options, under the assumptions of a deterministic mean function, mean-reversion dynamics and Normal inverse Gaussian distributed residuals. The Path Integral methods developed compares favourably to Monte Carlo simulations in terms of execution time. The derivative values obtained by Path Integrals are sometimes outside of the Monte Carlo confidence intervals, and the relative error may thus be too large for practical applications. Improvements of the implementations, with a view to minimizing errors, can be subject to further research.

Los estilos APA, Harvard, Vancouver, ISO, etc.

50

Rahmani, Mahmood. "Path Inference of Sparse GPS Probes for Urban Networks : Methods and Applications". Licentiate thesis, KTH, Trafik och logistik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104524.

Texto completo

Resumen

The application of GPS probes in traffic management is growing rapidly as the required data collection infrastructure is increasingly in place in urban areas with significant number of mobile sensors moving around covering expansive areas of the road network. Most travelers carry with them at least one device with a built-in GPS receiver. Furthermore, vehicles are becoming more and more location aware. Currently, systems that collect floating car data are designed to transmit the data in a limited form and relatively infrequently due to the cost of data transmission. That means the reported locations of vehicles are far apart in time and space. In order to extract traffic information from the data, it first needs to be matched to the underlying digital road network. Matching such sparse data to the network, especially in dense urban, area is challenging. This thesis introduces a map-matching and path inference algorithm for sparse GPS probes in urban networks. The method is utilized in a case study in Stockholm and showed robustness and high accuracy compared to a number of other methods in the literature. The method is used to process floating car data from 1500 taxis in Stockholm City. The taxi data had been ignored because of its low frequency and minimal information. The proposed method showed that the data can be processed and transformed into information that is suitable for traffic studies. The thesis implemented the main components of an experimental ITS laboratory, called iMobility Lab. It is designed to explore GPS and other emerging traffic and traffic-related data for traffic monitoring and control.

QC 20121107

Los estilos APA, Harvard, Vancouver, ISO, etc.

Tesis sobre el tema "Patch methods"

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros