Dissertations / Theses on the topic 'Decorrelating'
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XU, BIN. "A Blind Space-Time Decorrelating RAKE Receiver in a DS-CDMA System in Multipath Channels." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1078193785.
Full textWang, Yongjian, and Tingxian Zhou. "THE RESEARCH OF A NEW MULTIUSER DETECTION SCHEME COMBINING DECORRELATING DETECTOR AND PARTIAL PARALLEL INTERFERENCE CANCELLER." International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/604934.
Full textThe decorrelating detector can afford good data estimates because it does not need to know many parameters of the received signal. However, it shows great performance deprivation when the background noise is high. On the other hand, partial parallel interference canceller(PPIC) has the potential to combat the near-far problem and have much lower computation complexity. But its performance depends on the initial data estimate. An improved PPIC scheme is proposed in this paper to combat the near-far problem. It utilizes the advantages of the two detectors by combining them. The focus of this paper is on the BER performance and the near-far resistance capability of the proposed scheme. Computer simulations demonstrate that the proposed detector has good BER performance and near-far resistance capability.
LI, XIANGTAO. "PERFORMANCE ANALYSIS OF DECORRELATING DETECTORS FOR DUAL-RATE SYNCHRONOUS DS/CDMA SYSTEMS OVER FREQUENCY-SELECTIVE RAYLEIGH FADING CHANNELS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1028644891.
Full textJones, Haley M., and Haley Jones@anu edu au. "On multipath spatial diversity in wireless multiuser communications." The Australian National University. Research School of Information Sciences and Engineering, 2001. http://thesis.anu.edu.au./public/adt-ANU20050202.152811.
Full textMöhringer, Sandra [Verfasser]. "Decorrelation of Gravimetric Data / Sandra Möhringer." München : Verlag Dr. Hut, 2014. http://d-nb.info/1052375421/34.
Full textAmrani, Naoufal. "Spectral decorrelation for coding remote sensing data." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/402237.
Full textToday remote sensing is essential for many applications addressed to Earth Observation. The potential capability of remote sensing in providing valuable information enables a better understanding of Earth characteristics and human activities. Recent advances in satellite sensors allow recovering large areas, producing images with unprecedented spatial, spectral and temporal resolution. This amount of data implies a need for efficient compression techniques to improve the capabilities of storage and transmissions. Most of these techniques are dominated by transforms or prediction methods. This thesis aims at deeply analyzing the state-of-the-art techniques and at providing efficient solutions that improve the compression of remote sensing data. In order to understand the non-linear independence and data compaction of hyperspectral images, we investigate the improvement of Principal Component Analysis (PCA) that provides optimal independence for Gaussian sources. We analyse the lossless coding efficiency of Principal Polynomial Analysis (PPA), which generalizes PCA by removing non-linear relations among components using polynomial regression. We show that principal components are not able to predict each other through polynomial regression, resulting in no improvement of PCA at the cost of higher complexity and larger amount of side information. This analysis allows us to understand better the concept of prediction in the transform domain for compression purposes. Therefore, rather than using expensive sophisticated transforms like PCA, we focus on theoretically suboptimal but simpler transforms like Discrete Wavelet Transform (DWT). Meanwhile, we adopt predictive techniques to exploit any remaining statistical dependence. Thus, we introduce a novel scheme, called Regression Wavelet Analysis (RWA), to increase the coefficient independence in remote sensing images. The algorithm employs multivariate regression to exploit the relationships among wavelet-transformed components. The proposed RWA has many important advantages, like the low complexity and no dynamic range expansion. Nevertheless, the most important advantage consists of its performance for lossless coding. Extensive experimental results over a wide range of sensors, such as AVIRIS, IASI and Hyperion, indicate that RWA outperforms the most prominent transforms like PCA and wavelets, and also the best recent coding standard, CCSDS-123. We extend the benefits of RWA to progressive lossy-to-lossless. We show that RWA can attain a rate-distortion performance superior to those obtained with the state-of-the-art techniques. To this end, we propose a Prediction Weighting Scheme that captures the prediction significance of each transformed components. The reason of using a weighting strategy is that coefficients with similar magnitude can have extremely different impact on the reconstruction quality. For a deeper analysis, we also investigate the bias in the least squares parameters, when coding with low bitrates. We show that the RWA parameters are unbiased for lossy coding, where the regression models are used not with the original transformed components, but with the recovered ones, which lack some information due to the lossy reconstruction. We show that hyperspectral images with large size in the spectral dimension can be coded via RWA without side information and at a lower computational cost. Finally, we introduce a very low-complexity version of RWA algorithm. Here, the prediction is based on only some few components, while the performance is maintained. When the complexity of RWA is taken to an extremely low level, a careful model selection is necessary. Contrary to expensive selection procedures, we propose a simple and efficient strategy called \textit{neighbor selection} for using small regression models. On a set of well-known and representative hyperspectral images, these small models maintain the excellent coding performance of RWA, while reducing the computational cost by about 90\%.
Subramanian, Swetha. "Thermal Ablation Monitoring Using Ultrasound Echo Decorrelation Imaging." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1428068754.
Full textTullis, Iain David Charles. "The laser torquemeter and implications of speckle decorrelation on torque measurement." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/12168.
Full textWells, Susan K. "Temporal and spatial decorrelation scales of the Yellow Sea thermal fields." Thesis, Monterey, California. Naval Postgraduate School, 1994. http://hdl.handle.net/10945/28595.
Full textHistorically, studies on decorrelation scales have been conducted in the deep ocean waters. As the Navy shifts its interest toward the less understood shallow water regions, decorrelation scales need to be computed in order to use formerly deep water models such as the Optimum Thermal Interpolation System (OTIS) for shallow water regions such as the Yellow Sea. A data set containing over 35,000 temperature profiles from 1929 to 1991 was obtained from the Naval Oceanographic Office's MOODS data set. The winter and summer seasons provide realistic results. Winter has the smallest decorrelation scales of all the seasons, approximately 15 days and 165 km. Summer shows that there are different decorrelation scales between the surface and at depth. The surface has scales of 12.3 days and 251 km while at depth the scales are approximately 16.5 days and 163 km. An observational sampling network design is suggested for future sampling of the region. Spring and fall provide mixed results which may be due to the irregularities in time and space of the data set or to the very complex forcing mechanisms found in the region. Overall, this study gives a ground work for better refinement of decorrelation scales and thus, the ability to assess the conversion of deep water models to shallow water regions
Fosnight, Tyler R. "Echo Decorrelation Imaging of In Vivo HIFU and Bulk Ultrasound Ablation." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447691239.
Full textWells, Susan K. "Temporal and spatial decorrelation scales of the Yellow Sea thermal field[s] /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA288617.
Full textThesis advisor(s): Peter Chu, Steven D. Haeger. "September 1994." Bibliography: p. 45-47. Also available online.
Nessel, James Aaron. "Estimation of Atmospheric Phase Scintillation Via Decorrelation of Water Vapor Radiometer Signals." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1447701180.
Full textAbbass, Mohamed A. M. S. "Real-time Control of Ultrasound Thermal Ablation using Echo Decorrelation Imaging Feedback." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535468911083998.
Full textSiemes, Christian [Verfasser]. "Digital filtering algorithms for decorrelation within large least squares problems / Christian Siemes." Bonn : Universitäts- und Landesbibliothek Bonn, 2020. http://d-nb.info/1205462678/34.
Full textLee, Kenneth Ka Chun. "Hybrid transform, spatial decorrelation and unified coding system for image and video compression /." access abstract and table of contents access full-text, 2004. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-cs-b21471381a.pdf.
Full text"Submitted to Department of Computer Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references (leaves 145-158)
Gribben, Christopher. "Investigations into the perception of vertical interchannel decorrelation in 3D surround sound reproduction." Thesis, University of Huddersfield, 2018. http://eprints.hud.ac.uk/id/eprint/34689/.
Full textGiarra, Matthew Nicholson. "The Signal in the Noise: Understanding and Mitigating Decorrelation in Particle Image Velocimetry." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/84520.
Full textPh. D.
Juntti, M. (Markku). "Multiuser demodulation for DS-CDMA systems in fading channels." Doctoral thesis, University of Oulu, 1997. http://urn.fi/urn:isbn:9514247558.
Full textTrinh, Tuan Phong. "Random and periodic operators in dimension 1 : Decorrelation estimates in spectal statistics and resonances." Thesis, Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCD005/document.
Full textThis thesis consists of two parts : te random and periodic operators in dimension 1. In this part, we prove the decorrelation estimate for a 1D lattice Hamiltonian with off-diagonal disorder. Consequently, we deduce the asymptotic independance of the local level statistics near distinct positive energies in the localized regime. Finally, we revisit a known result on the decorrelation estimate for the 1D discret Anderson model. The second part on my thesis adresses questions on resonances for a 1D Schrödinger operators with truncated periodic potential [...]
Blackburn, Brecken June. "DEVELOPMENT OF PHASE DECORRELATION OPTICAL COHERENCE TOMOGRAPHY FOR ASSESSMENT OF THE OCULAR LENS AND CORNEA." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1629288561842747.
Full textFERREL, CAROLE. "Production et controle des mouvements de pointage de cible : adaptation a une decorrelation vision-proprioception." Grenoble 2, 1998. http://www.theses.fr/1998GRE29049.
Full textSeveral studies on motor control suggest that amplitude and direction parameters involve different processes. In remote operation, operators carry out various visual-motor tasks while viewing their hands by means of video feedback. This situation usually entails a discrepancy between the information provided by visual and proprioceptive systems. Among numerous studies that analyzed the adaptation of the perceptual-motor system to visual spatial distortions, many focused on perceptual-motor adaptation to directional distortions. The present study concerns the adaptation of motor system to the distortion of distance when the production of movement is visually controlled through a video display. The subjects had to perform a pointing movement with information provided by video screen. By changing the zoom of the camera, the amplitude of the movement perceived on the screen was different from the actual movement. Results showed that the movement adapted more quickly to the distortions of distance than to directional distortions. However, adaptation did not transfer to other situations since it was specific to the target and scale. Adaptation occurred at task level, i. E. , was based on information relating to the displacement of the hand. Most of subjects tended to use mainly the information provided by the visual system. The spatial cues (e. G. Reference frame, known objects) facilitated this adaptation. In conclusion, adaptation to distance distortion depends on two processes. The first one leads to a local visual-motor adaptation. The second one, which is necessary for the transfer of adaptation, is slower and involves a general remapping of the whole grasping space
Blackburn, Brecken J. "DEVELOPMENT OF PHASE DECORRELATION OPTICAL COHERNECE TOMOGRAPHY FOR ASSESSMET OF THE OCULAR LENS AND CORNEA." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1623927892578937.
Full textBlick, Christian [Verfasser]. "Multiscale Potential Methods in Geothermal Research: Decorrelation Reflected Post-Processing and Locally Based Inversion / Christian Blick." München : Verlag Dr. Hut, 2015. http://d-nb.info/1080754636/34.
Full textThéry, Clément. "Model-based covariable decorrelation in linear regression (CorReg) : application to missing data and to steel industry." Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10060/document.
Full textThis thesis was motivated by correlation issues in real datasets, in particular industrial datasets. The main idea stands in explicit modeling of the correlations between covariates by a structure of sub-regressions, that simply is a system of linear regressions between the covariates. It points out redundant covariates that can be deleted in a pre-selection step to improve matrix conditioning without significant loss of information and with strong explicative potential because this pre-selection is explained by the structure of sub-regressions, itself easy to interpret. An algorithm to find the sub-regressions structure inherent to the dataset is provided, based on a full generative model and using Monte-Carlo Markov Chain (MCMC) method. This pre-treatment does not depend on a response variable and thus can be used in a more general way with any correlated datasets. In a second part, a plug-in estimator is defined to get back the redundant covariates sequentially. Then all the covariates are used but the sequential approach acts as a protection against correlations. Finally, the generative model defined here allows, as a perspective, to manage missing values both during the MCMC and then for imputation. Then we are able to use classical methods that are not compatible with missing datasets. Once again, linear regression is used to illustrate the benefits of this method but it remains a pre-treatment that can be used in other contexts, like clustering and so on. The R package CorReg implements the methods created during this thesis
Riley, Graeme Alexander. "Optimised mammogram displays for improved breast cancer detection." Thesis, University of Plymouth, 2016. http://hdl.handle.net/10026.1/5150.
Full textWung, Jason. "A system approach to multi-channel acoustic echo cancellation and residual echo suppression for robust hands-free teleconferencing." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53384.
Full textTu, Yifeng. "Multiple Reference Active Noise Control." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36790.
Full textMaster of Science
Vaišnoraitė, Lina. "Diskrečiosios Daubechies 9/7 transformacijos su daline blokų dekoreliacija savybių tyrimas." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110831_144958-96904.
Full textMany kernels (“mother” wavelets) can be used for the discrete wavelet transform DWT, like those of Daubechies, Morlet, discrete Le Gall transform (DLGT) or the discrete Haar transform (HT). Cohen-Daubechies-Feauveau (CDF 9/7) wavelet are the historically first family of biorthogonal wavelets, which was made popular by Ingrid Daubechies. These are not the same as the orthogonal Daubechies wavelets, and also not very similar in shape and properties. However their construction idea is the same. The JPEG 2000 compression standard uses the biorthogonal CDF 5/3 wavelet (also called the LeGall 5/3 wavelet) for lossless compression and a CDF 9/7 wavelet for lossy compression. In this paper, two distinct DWT (CDF 9/7 and CDF 9/7 with decorrelation) as well as their computational algorithms are discussed, analyzed and compared. Comparison criteria are chosen to be one – dimensional hyperbolic filters and smoothness level of the digital signal under processing.
Bellil, Hédi. "Methodes et systemes de decorrelation de temperature et de pression pour capteurs a fibres optiques monomodes a effet intrinseque." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13155.
Full textHorowitz, Eduardo. "Estudo sobre a extração de políticas de firewall e uma proposta de metodologia." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/12075.
Full textAs the number of threats in the Internet grows, firewalls have become a very important defense mechanism. However, configuring a firewall is not an easy task and is prone to errors. Several investigations have been made towards solving these issue. However, most of them have focused on working directly at the configuration level and have a number of limitations. This work investigates methods to extract higher level policies from low level firewall rules. Aiming at extracting real policies from firewall rules, we analyse the firewall decorrelation problem and previously proposed algoritmhs to solve it. In addition, a new type of graph is presented aiming at better visualising and analysing rules’ correlation. We also investigate the merging of decorrelated rules, with the goal of defining more abstract rules. Two algorithms are then presented and a new methodology for the extraction of firewall policies is proposed. This methodology is twofold. The first part consists of the use a new type of decorrelation: the hierachical decorrelation, which is introduced along with a new way of hierarchically merging decorrelated rules. The second part is a new model for blacklist or whitelist firewall rules, separating them from the other rules in the policy extraction. We also present alternatives for accomplishing this separation. Finally, we conclpude and point out directions for future work.
Nagle, Anna S. "Biomechanical Measurements of the Human Female Levator Ani Muscle Ex Vivo and In Vivo." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439561849.
Full textBonnici, Julien. "Décorrélation verticale d'un tourbillon soumis à un champ de cisaillement dans un fluide fortement stratifié." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX024/document.
Full textThis thesis investigates, theoretically and numerically, the vertical decorrelation of an initially vertical vortex by an ambient sinusoidal shear flow in a stratified fluid. It has been conjectured that such process should trigger the shear instability and, as such, contribute to the generation of small scales in strongly stratified turbulence. This type of turbulence is encountered in the atmosphere and the oceans in an intermediate range of scaleswhere Coriolis effects are negligible.The first part analyses the evolutions of the total energy and enstrophy of the vortex in Direct Numerical Simulations (DNS) as functions of the control parameters. This study reveals that the dynamics differs from freely decaying flows: because of the presence of the ambient shear flow, the balance between stretching and dissipation terms in the global enstrophy budget implies that the maximum enstrophy of the vortex scales as $Re^{2/3}$, where $Re$ is the Reynolds number, instead of simply $Re$. However, such simplified balance does not account for the observed effect of the stratification.In order to overcome this difficulty, the local dynamics of the vortex has been investigated by means of two asymptotic analyses, presented in the second part. A short-time analysis first proves that the initial response of the vortex is non-hydrostatic regardless of the stratification. A long-wavelength analysis provides governing equations for the evolution of the angular velocity of the vortex and the deformations of its axis. Internal waves are excited at the start-up of the motion, explaining the initial non-hydrostatic regime. The vortex is mostly advected in the direction of the shear flow but also perpendicularly owing to the self-induced motion. Its angular velocity decays because of dynamic and viscous effects. The former effect is due to the squeezing of the isopycnals in the vortex core which implies a decrease of the vertical vorticity to conserve potential vorticity.In a third part, the DNS show that the shear instability is only triggered if the Froude number is moderate and the wavelength of the shear small enough. The numerical results are compared to the asymptotic predictions. In particular, the evolutions of the vertical shear of horizontal velocity and of the vertical buoyancy gradient for small Froude number are comprehensively and finely captured by the long-wavelength asymptotic predictions. The minimum value of the asymptotic Richardson number almost never goes below the critical threshold $1/4$ necessary for the development of the shear instability. The saturation of the vertical shear is due to the decay of the vortex in the regions of high ambient shear. These results suggest that the shear instability is not easilytriggered by decorrelation processes in strongly stratified flows in contradiction with previous conjectures
Tomlinson, Lee. "Azimuthal decorrelation between leptons in the Drell-Yan process as a probe of infrared QCD : phenomenology, predictions and measurement of a novel collider observable using perturbative resummation techniques." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/azimuthal-decorrelation-between-leptons-in-the-drellyan-process-as-a-probe-of-infrared-qcd-phenomenology-predictions-and-measurement-of-a-novel-collider-observable-using-perturbative-resummation-techniques(b355d586-6438-4cd2-a0fc-753ae1af8752).html.
Full textRibokas, Jonas. "Diskrečiojo Le Gall spektro apskaičiavimo dvimačio vaizdo fragmentams algoritmų analizė." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110902_093308-24497.
Full textIn this paper the main attention is dedicated to discrete Le Gall transformation (DLGT), the family of discrete wavelets transformations, which usage in the image compression is quite popular. Image compression is very important when it comes to low bandwidth network and computer channels. To deal with this problem the discrete Le Gall wavelets are brought up and focused on the image fragment DLGT spectrum. For calculation of this spectrum the new fast procedure is suggested and realized. In comparative analysis the fast procedure is proved to work more than 50 times faster than applying DLGT direct to image fragment. In the beginning of this paper the main concepts of wavelets and their transformations are analyzed. An importance of these properties is illustrated by examples and applications in practice. One of the most important properties is localization in space. Even though DLGT does not fully meet this property decorrelation technique, introduced in paper, benefits in solving localization problem. Moreover, DLGT algorithms are proposed for one-dimensional and 2-dimensional images. According to these algorithms the new program was created, which is dedicated for image analysis. Finally, in the end of paper the instructions of program are presented.
Oksar, Yesim. "Target Tracking With Correlated Measurement Noise." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608198/index.pdf.
Full textSun, Yurong. "Ultrasound characterization of structure and density of coral as a model for trabecular bone." Link to electronic version, 2000. http://www.wpi.edu/Pubs/ETD/Available/etd-0808100-001812/.
Full textKeywords: angular decorrelation function; impulse response; BUA; BMD; ultrasound; coral; trabecular bone; osteoporosis. Includes bibliographical references (p. 189-191).
Degrazia, Franco Caldas. "Derivação de escalas de tempo lagrangeanas dependentes da distância da fonte : uma aplicação na dispersão de contaminantes na camada limite planetária neutra e estável." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/148024.
Full textThere exists a variety of pollution of dispersion models and in general, Gaussian models are used worldwide by environmental agencies in regulatory applications. The CALPUFF model is one of them. In this study, the in uence of decorrelation time scales in the CALPUFF modeling system under neutral conditions is evaluated. To do this a new parameterization of decorrelation time scales is proposed. A spectral distribution of an Eulerian velocity pro le and a formulation of the evolution of the Lagrangian decorrela- tion timescales are used as the forcing mechanisms (shear-dominated boundary layer) for the turbulent dispersion. The model performance was established by comparing ground- level concentrations with Over-Land Alongwind Dispersion experimental results. Line source emissions was evaluated using the CALPUFF model with different forms of the initialization. A second model was also tested, normally used to study and predict the environmental impact and validate turbulent parameterizations. Is the stochastic La- grangian dispersion model LAMBDA (Ferrero and Anfossi, 1998). Also in this study the model LAMBDA and CALPUFF results emphasized the ability of the new derivation of decorrelation time scales to represent the unknown stochastic behavior.
Planes, Thomas. "Imagerie de chargements locaux en régime de diffusion multiple." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00937217.
Full textWada, Ted S. "System approach to robust acoustic echo cancellation through semi-blind source separation based on independent component analysis." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44851.
Full textKeller, Stefanie. "Life-history, ecology and fisheries of cephalopods in the western Mediterranean." Doctoral thesis, Universitat de les Illes Balears, 2017. http://hdl.handle.net/10803/401646.
Full textLos cefalópodos constituyen un grupo faunístico importante en los ecosistemas marinos, representando elementos clave en la estructura y dinámica de las redes tróficas. Además, son un importante recurso pesquero y su contribución a los desembarcos pesqueros mundiales se ha incrementado significativamente en las últimas décadas. En el Mar Mediterráneo existen varios estudios locales sobre la abundancia y distribución de cefalópodos, pero pocos integran escalas temporales largas y áreas extensas. Esta tesis combina estudios sobre la estructura de la comunidad, la diversidad y la abundancia de cefalópodos a gran escala espacio-temporal (Parte I) con estudios a escala local alrededor de las Islas Baleares (Parte II). En primer lugar, se realizó un análisis de la comunidad de cefalópodos a escala de todo el Mediterráneo para describir el estado actual y determinar posibles diferencias entre las sub-cuencas occidental y oriental (Capítulo 2). El objetivo fue comparar la estructura de las comunidades faunísticas entre estas dos sub-cuencas y analizar la influencia de gradientes ambientales a gran escala sobre la composición específica. Aunque no se observaron diferencias significativas en la composición específica, las contribuciones relativas de las diferentes especies variaron entre ambas cuencas. Debido a su corto ciclo vital y estrategia reproductiva semélpara, los cefalópodos son muy sensibles a los cambios ambientales, adaptándose a ellos con relativa rapidez. Se esperaba, por tanto, que factores ambientales como la temperatura superficial del mar (SST) y el contenido de clorofila a (Chl a) fueran factores importantes en la estructuración de las comunidades de cefalópodos. Si bien su importancia difirió entre las dos sub-cuencas, se confirmó que la profundidad era el factor estructural más importante en dichas comunidades. Se analizaron también cambios en la diversidad específica de las comunidades de cefalópodos a escala de todo el Mediterráneo durante los últimos 20 años (Capítulo 3). Los resultados no mostraron ninguna tendencia temporal ni espacial (latitud, longitud) clara y homogénea en la diversidad. Las únicas tendencias temporales observadas variaron entre diferentes sub-regiones, siendo la posición geográfica, profundidad, SST y productividad los principales factores determinantes de estas tendencias. Para confirmar la importancia de la variabilidad ambiental a nivel específico, se analizó la influencia de la SST y la producción primaria en la estructura espacial y la dinámica poblacional de dos especies de cefalópodos de importancia comercial (Capítulo 4). Aunque Octopus vulgaris e Illex coindetii exhiben diferentes estrategias vitales y viven en diferentes hábitats, las tendencias temporales a largo plazo en su abundancia y el comportamiento sincrónico de sus poblaciones fueron similares, observándose sub-poblaciones temporalmente persistentes a lo largo de todo el Mediterráneo. En consonancia con los capítulos anteriores, la SST y Chla resultaron ser factores significativos en la definición de patrones de distribución y fluctuaciones interanuales de la abundancia. La segunda parte de la tesis estaba motivada por la situación actual de los cefalópodos en el Mar Mediterráneo, donde no existen medidas de evaluación y gestión específica para este grupo y algunas de sus poblaciones se encuentran sobreexplotadas. Para contribuir al conocimiento de la situación actual en el Mar Balear, se analizó la pesquería, ciclo vital y dinámica poblacional de la sepia utilizando series temporales intra-anuales (Capítulo 5). El análisis de diferentes factores ambientales reveló que la SST y la variabilidad climática local influían significativamente en las fluctuaciones de abundancia de la especie. En un trabajo posterior (Capítulo 6) se aplicaron técnicas de evaluación de stocks a las pesquerías de sepia y calamar de las Islas Baleares utilizando datos procedentes de la EU Data Collection Framework (DCF). Hasta donde sabemos, este trabajo constituye la primera aplicación de los Lesly-Delury Depletion Methods a stocks de cefalópodos del Mediterráneo. Los resultados demostraron que el esquema actual de muestreo de la DCF es inadecuado para la evaluación de cefalópodos y se proponen posibles modificaciones.
Els cefalòpodes constitueixen un grup faunístic important als ecosistemes marins, essent elements clau a les xarxes tròfiques. A més, són importants recursos pesquers i la seva contribució als desembarcs pesquers mundials s’ha incrementat en les últimes dècades. representant al voltant del 30% de la captura desembarcada a nivell mundial. Al Mar Mediterrani existeixen varis estudis locals sobre l’abundància i distribució de cefalòpodes, però pocs integren escales temporals llargues i àrees extenses. Aquesta tesi combina estudis sobre la composició de la comunitat, la diversitat i l’abundància de cefalòpodes a gran escala espaciotemporal (Part I) amb estudis a escala local al voltant de les Illes Balears (Part II). En primer lloc, es va realitzar un anàlisi de les comunitats de cefalòpodes a escala de tot el Mediterrani per descriure l’estat actual i determinar possibles diferències entre les sub-conques occidental i oriental (Capítol 2). L’objectiu fou comparar l’estructura de les comunitats faunístiques entre sub-conques i analitzar la influència de gradients ambientals a gran escala sobre la composició específica. Tot i que no s’observaren diferències significatives en la composició específica, les contribucions relatives de les diferents espècies variaren entre sub-conques. Degut al seu cicle vital curt i estratègia reproductiva semèlpara els cefalòpodes són molt sensibles als canvis ambientals, adaptant-se a ells amb relativa rapidesa. S’esperava, per tant, que factors ambientals com la temperatura superficial del mar (SST) i el contingut de clorofil·la a (Chla) fossin factors importants en l’estructuració de les comunitats de cefalòpodes. Si bé la seva importància va diferir entres les dues sub-conques, es va confirmar que la profunditat era el factor estructural més important en aquestes comunitats. S’analitzaren també canvies en la diversitat específica de les comunitats de cefalòpodes a escala de tot el Mediterrani durant els últims 20 anys (Capítol 3). Els resultats no mostraren cap tendència temporal ni espacial (latitud, longitud) clara i homogènia en la diversitat. Les úniques tendències temporals observades variaren entre diferents sub-regions, essent la posició geogràfica, profunditat, SST i productivitat els principals factors determinants d’aquestes tendències. Per tal de confirmar la importància de la variabilitat ambiental a nivell específic, es va investigar la influència de la SST i la producció primària en l’estructuració espacial i la dinàmica poblacional de dues espècies de cefalòpodes d’importància comercial (Capítol 4). Tot i que Octopus vulgaris i Illex coindetii tenen característiques vitals diferents i viuen en hàbitats diferents, les tendències temporals a llarg plaç en la seva l’abundància i el comportament sincrònic de les seves poblacions va ser similar, observant-se sub-poblacions temporalment persistents al llarg del Mediterrani. En consonància amb els capítols anteriors, la SST i Chla resultaren ser factors significatius en la definició de patrons de distribució i fluctuacions interanuals de l’abundància. La segona part de la tesi estava motivada per la situació actual dels cefalòpodes al Mar Mediterrani, on no existeixen mesures d’avaluació i gestió específica per aquest grup i algunes de les seves poblacions es troben sobre-explotades. Per contribuir al coneixement de la situació actual al Mar Balear, es va analitzar la pesqueria, cicle vital i dinàmica poblacional de la sípia utilitzant sèries temporals intra-anuals (Capítol 5). L’anàlisi de diferents factors ambientals va revelar que la SST i la variabilitat climàtica local influïen significativament en les fluctuacions d’abundància de l’espècie. En un treball posterior (Capítol 6) s’aplicaren tècniques d’avaluació d’stocks a les pesqueries de sípia i calamar de les Illes Balears utilitzant dades procedents de la EU Data Collection Framework (DCF). Fins on sabem, aquest treball constitueix la primera aplicació dels Lesly-Delury Depletion Methods a stocks de cefalòpodes del Mediterrani. Els resultats demostraren que l’esquema actual de mostratge de la DCF és inadequat per a l’avaluació de cefalòpodes i es proposen possibles modificacions.
Cobb, Matthew. "Recoverable resources calculation using non-linear methods: a comparative study." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2016. https://ro.ecu.edu.au/theses/1809.
Full textBoudjenouia, Fouad. "Restauration d’images avec critères orientés qualité." Thesis, Orléans, 2017. http://www.theses.fr/2017ORLE2031/document.
Full textThis thesis concerns the blind restoration of images (formulated as an ill-posed and illconditioned inverse problem), considering a SIMO system. Thus, a blind system identification technique in which the order of the channel is unknown (overestimated) is introduced. Firstly, a simplified version at reduced cost SCR of the cross relation (CR) method is introduced. Secondly, a robust version R-SCR based on the search for a sparse solution minimizing the CR cost function is proposed. Image restoration is then achieved by a new approach (inspired from 1D signal decoding techniques and extended here to the case of 2D images) based on an efficient tree search (Stack algorithm). Several improvements to the ‘Stack’ method have been introduced in order to reduce its complexity and to improve the restoration quality when the images are noisy. This is done using a regularization technique and an all-at-once optimization approach based on the gradient descent which refines the estimated image and improves the algorithm’s convergence towards the optimal solution. Then, image quality measurements are used as cost functions (integrated in the global criterion), in order to study their potential for improving restoration performance. In the context where the image of interest is corrupted by other interfering images, its restoration requires the use of blind sources separation techniques. In this sense, a comparative study of some separation techniques based on the property of second-order decorrelation and sparsity is performed
Chang, Yung-Shun, and 張詠順. "Linear Decorrelating Detector for Asynchronous CDMA Systems." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/40326955007562100392.
Full text國立臺灣大學
電信工程學研究所
89
In a code division multiple access (CDMA) system, as the number of active users increases, multiple access interference (MAI) will degrade the system performance severely. Therefore, the CDMA system is an inference limited multiple access system, and the capacity is dominant by MAI, i.e., soft capacity. Multiuser detection (MUD) is investigated to suppress MAI, improve the performance and then increase the capacity of CDMA systems. Typically, for an asynchronous CDMA system, the first step of MUD is to transform the asynchronous system into an equivalent synchronous system. Furthermore, if the signals are transmitted in a multipath environment, the signal in each path is treated as a different user’s signal. Then, at the receiver, the multipath signals belonging to the same user will be combined to attain a better decision, i.e., RAKE receiver. The disadvantages of this method are the large complexity and long detection delay as the number of users and paths increase. In this thesis, we’ll propose a linear decorrelating detector (LDD), one type of MUD that can reduce the detection delay to be less than one bit duration. Furthermore, by exploiting an adaptive algorithm, we can reduce the complexity of the proposed scheme to the simplest as same as the complexity of the LDD used in synchronous CDMA systems and maintain the performance.
Fang, Chieh-cheng, and 方玠程. "Relay-Assisted Decorrelating Multiuser Detection for Asynchronous Cooperative Uplink Networks." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/70615300571039163933.
Full text國立中山大學
通訊工程研究所
98
In this thesis, we consider the uplink of a cooperative code division multiple access (CDMA) network, where users cooperate by relaying each other’s messages to the base station. The sources adopt CDMA to share the informations offered by relays. In general, spreading waveforms of sources are not orthogonal to each others due to pratical design issues of CDMA network. Therefore, the source signals will suffer from multiple access interference (MAI) at the relays and destination. The MAI results in the increase of bit error rate increased, and diminishes the cooperative network diveristy gains. In order to mitigate MAI, the decorrelating multiuser detection and zero-forcing precoder have been commonly adopted. But, the decorrelating multiuser detection causes noise enhancement, while the zero-forcing precoder causes power expansion. In this thesis, we adopt relay-assisted decorrelating multiuser detector (RAD-MUD) to mitigate MAI as proposed in [1].In this scheme, the relays perform half of decorrelating operation and the destination performs the other half. In this way, neither noise enhancement nor power expansion will occur. However, in the reference [1], the authers assume the transmission is synchronous between sources and relays. The assumption is unrealistic, because it is difficult to achieve synchronization between all sources and relays due to various propagation delays. In this thesis, we extend the research in [1] and relax restriction of synchronization between all sources and relays. Besides, we also adopt cooperative strategies such as transmit beamforming or selective relaying to enhance system performance. Compared with other’s multiuser detection schemes, we show that the proposed schemes can effectively reduce the bit error rate.
Tsai, Chung-Ming, and 蔡忠明. "The Decorrelating Ambiguity Resolution for GPS Positioning with Dual Reference Stations." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/30665435189458522710.
Full text國立中央大學
土木工程研究所
90
Phase Ambiguity plays an important role in GPS positioning using phase Data. There are two major ways to deal with the ambiguity resolution, vie to solve for and to eliminate. In order to solve for high correlation between ambiguities and geometry parameters, the decorrelation method is used, and then to fix the integer ambiguities. Dual reference GPS positioning is then going on after the ambiguities fixed. In the dual reference GPS positioning, there is redundant information, i.e. ambiguity constraint. By adding ambiguity constraint into the dual reference GPS positioning model, the theoretical parameter accuracy can be improved. After parameter decorrelating ,the correct integer ambiguities can be solved and single epoch positioning can then be carried on. While doing single epoch positioning, there are different appearances in the models by adding ionosphere effecting parameter or introducing variance and covariance component estimation. Base on the analysis between the models, the results coming form the dual reference positioning shows its superior to the single reference positioning.
Chou, Tai-Wei, and 周代偉. "Quasi-Decorrelating Detector (QDD) - A Study on New Algorithm for CMDA Multiuser Detection." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/93288597461615562407.
Full text國立中興大學
電機工程學系
90
We propose a multi-user detection scheme for downlink channel and uplink link channel, including multi-path effect. The Quasi-Decorrelating detector (QDD) is a linear detector but the decorrelating algorithm is performed without inverse matrix transform, as an effort to overcome the problem associated with the DD. The QDD can be implemented by multi-stage feed-forward filters, the number os which can be made scalable to trade MAI suppression for noise enhancement reduction according to varying channel conditions. On the contrary, the DD has a rigid structure and is unable to adapt to changing operation environment. For downlink channel, we considering the multi-path and fading effect, and we assume that there are 12 kinds of channels to simulation. To improve the system performance, two different types of RAKE receiver structures, equal gain combining RAKE and maximum ratio combining RAKE, are also considered for CDMA systems to mitigate multi-path fading effects of mobile channels. For uplink channel, the assumption are the same with downlink channel, the different is just the users are asynchronous each other.
Jiang, TyauJiun, and 江條均. "Improvements of the Decorrelating Detector Using Overlapping Window and Decision Feedback in DS-CDMA." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/44074437605466493687.
Full text國立海洋大學
電機工程學系
92
The second generation mobile communication system has shor-tcomings, such as low data rate, poor quality of service(Qos), limited service types -- speech and data only, and low system capacity. But the third generation mobile communication system overcomes the shortcomings above, and direct-sequence code division multiple access (DS-CDMA) is one of the best candi-dates.It has advantages; for example, anti-mulpath, anti-noise, keeping a secret well and high capacity at the cost of band-width. However, multiple access interference (MAI) between the users contributes to the limitation of Qos and capacity. Trad-itionally, the multiuser detection (MUD) scheme is applied to reduce or eliminate the MAI. Although the decorrelating detector can remove the MAI comp-letely, has linear complexity in the number of users, and does not need the knowledge of users' signal energy, but it has noise enhancement, causing poor performance. A new structure that combines the overlapping window with decision feedback to improve the performance of the detector is proposed in the thesis. When removing the correlation between users, we replace the inverse matrix with the algorithm of recursive least square(RLS) in order to reduce the computation complexity of the detector. The overlapping window has the properties that allow the states of data bits undecided in the previous window to be decided in the next window. Decision feedback has the charact- eristic that in the environment of near-far effect, the perform-ance of the weakest SNR user can be improved due to the remove of MAI of the stronger SNR users. Simulation results have shown that the bit-error-rate of the detector using overlapping window and decision feedback is better. Therefore, it can make the communication quality perfect.
Lee, Chih-Chien, and 李志堅. "Blind energy estimation for decorrelating decision-feedback CDMA multiuser detection using learning type stochastic approximations." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/05499243399646261757.
Full text國立交通大學
電信工程研究所
84
This paper investigates the application of linear reinforcement learning stochastic approximation to the blind adaptive energy estimation for a decorrelating decision-feedback (DDF) multiuser detector over synchronous CDMA radio channel in the presence of multiple access interference (MAI) and additive Gaussian noise. The decision feedback incorporated into the structure of linear decorrelating detector is able to significantly improve the weaker users' performance by cancelling the MAI from the stronger users. However, the DDF receiver requires knowledge of the received energies. In this paper, a new novel blind estimation mechanism is proposed to estimate all the users' energies using a stochastic approximation algorithm without training data. In order to increase the convergence speed of the energy estimation, a linear reinforcement learning technique is conducted to accelerate the stochastic approximation algorithms. Results show that our blind adaptation mechanism is able to accurately estimate all the users' energies even the users of DDF detector are not ranked properly. After performing the blind energy estimation and then re-ordering the users in a nonincreasing order, numerical simulations show that the DDF detector for the weakest user performs closely to the maximum likelihood detector, whose complexity grows exponentically with the number of users.
Tsai, Yong-Chun, and 蔡詠淳. "Robust Design of Precoder and Decoder for Relay-Assisted Decorrelating CDMA Systems with Imperfect CSI." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/13952943915255291596.
Full text國立中山大學
通訊工程研究所
100
In this paper, we explore a cooperative code-division-multiple-access(CDMA) network. Users cooperate by forwarding each other’s messages toward the destination. For simplicity, we assume that signal reception at the destination is well-synchronized. Due to practical design issues of CDMA systems, spreading waveforms allocated to users are not perfectly orthogonal in general. This results in multiple-access interference(MAI) at relays and destination. In CDMA uplink networks one common approach is to adopt decorrelating multi-user detection, but it will lead to noise amplification[16,17]. Therefore, we employ relay-assisted decorrelating multiuser detector(RAD-MUD) to mitigate MAI[1] by performing half of decorrelation at the relay and destination respectively. Based on the availability of CSI at relays, we can further adopt cooperative strategies to improve performance, e.g., transmit beamforming and selective relaying. The destination side will use minimum mean-square error(MMSE) detector to demodulate source symbols. In the existing literatures, channel state information(CSI) is assumed to be perfectly known at relay and destination. Actually, CSI is obtained from channel estimation, which usually contains estimation errors. In order to alleviate effects of channel estimation, one goal of this thesis is to design a robust system. Using estimated CSI and statistical property channel estimation errors, we design robust precoder and detector for the relay and destination. It shows that, even with distortion on channel estimations, the system still achieve excellent transmission efficiency. From the simulation results, it shows that the robust design is better than the system without consider channel estimation errors. Finally, we can see that the stable robust design can effectively mitigate effects of imperfect CSI.
Wang, Chun-Han, and 王駿翰. "Design of Multiuser Detector for Time-Hopping UWB M-SIMO Systems Based on Decorrelating-MRC Technigue." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/34414346776806651567.
Full text大葉大學
電信工程學系碩士班
96
In this paper, we propose a two-stage linear multiuser detector (LMD) for Ultra wideband (UWB) Multiple Single-input Multiple-output (M-SIMO) system and multipath fading environment. Time-hopping (TH) and antipodal pulse amplitude modulation (PAM) are employed for the multiple access system. The decorrelating detector is first employed at the front end of each receive antenna to eliminate the multi-user interference (MUI), then a set of maximum-ratio-combiners (MRC) are proceeded to maximize the signal-to-noise power ratio (SNR) for each user. Since the channel information is crucial for the Decorrelating-MRC (D-MRC) receiver, we develop a subspace-based blind M-SIMO channel estimation method. The effect of channel estimation error on system performance is extensively evaluated. It is also verified from the analytical and numerical results that by exploiting both spatial and temporal diversities, the D-MRC outperforms the conventional single-antenna decorrelating detector. Moreover, we demonstrate that both the decorrelating-MRC (D-MRC) receiver and subspace based M-SIMO channel estimators are computationally feasible and near-far resistant.