Approved for public release, distribution is unlimited / This thesis investigates the simulation performance of multiple-input multiple-output (MIMO) systems utilizing Alamoutibased space-time block coding (STBC) technique. The MIMO communication systems using STBC technique employing both single- carrier modulation and orthogonal frequency division multiplexing (OFDM) are simulated in Matlab. The physical layer part of the IEEE 802.16a standard is used in constructing the simulated OFDM schemes. Stanford University Interim (SUI) channel models are selected for the wireless channel in the simulation process. The performance results of the simulated MIMO systems are compared to those of conventional single antenna systems. / Lieutenant Junior Grade, Turkish Navy

La fixation symbiotique d'azote par l'ajonc d'Europe (Ulex europaeus) représente une source importante d'azote dans la forêt cultivée de pins maritimes des 'Landes de Gascogne'. Cette thèse a pour objectif la création d'un modèle conceptuel de dynamique de population de l'ajonc dans la région en vue de la prédiction du flux d'azote associé. Pour cela plusieurs étapes du cycle de vie de l'espèce ont été étudiées: la production et la prédation des graines, puis le recrutement de nouveaux individus depuis le stock de graines du sol. Nos résultats suggèrent que le maintien de cette espèce héliophile à l'ombre de la canopée des pins est facilité par la diminution de l'allocation de ressources à la reproduction, lui permettant de maintenir sa croissance, et par la diminution de la prédation des graines. Par ailleurs, le recrutement de nouveaux ajoncs semble influencé par des facteurs écologiques identifiables (e.g. humidité du sol). Mais ces facteurs sont fortement variables dans l'espace et dans le temps, et aucun micro habitat n'apparait comme plus favorable à la régénération de l'espèce. Ces résultats sont intégrés à un modèle conceptuel, représentant les différentes étapes du cycle de vie de l'espèce, et l'impact des opérations sylvicoles sur ces étapes. Les connaissances issues de cette thèse pourraient aussi bénéficier à d'autres problématiques liées à l'espèce (e.g. c'est une espèce invasive dans de nombreuses régions du monde) et à la compréhension de l'écologie de la régénération des espèces ligneuses. En effet, l'allocation des ressources à la reproduction pourrait être plastique et permettre une réponse adaptative à un environnement changeant; et la variabilité spatiotemporelle de la régénération des ligneux pourrait reposer sur l'existence de niches écologiques de régénération définies dans l'espace écologique. / Symbiotic nitrogen fixation by European gorse (Ulex europaeus) is a major source of nitrogen in the 'Landes de Gascogne' cultivated forest of maritime pine. This thesis aims to build a conceptual model of the population dynamic of gorse in the region, with a view to predict the associated flux of nitrogen. To achieve this, several steps of the life cycle of the species were studied: production and predation of seeds, and the recruitment of new plants from the seedbank.The results suggest that the maintenance of this light demanding species in the shade of the canopy of pines is improved by the decrease of reproductive allocation, which enable to maintain its growth, and by the decrease of the predation of seeds. The recruitment of new gorse plants seems controlled by identifiable ecological factors (e.g. soil moisture), however these factors are highly variable in space and time, and no specific micro-habitat appears to be more favourable for the species regeneration.These results are integrated into a conceptual model based on the different steps of the life cycle of the species, and taking into consideration the influence of forestry practices on these steps. Furthermore, the production of knowledge could benefit other subjects related to the species (e.g gorse is a noxious weed in many region in the world) and the understanding of the ecology of woody plants' regeneration. Allocation of resources to reproduction may be plastic and enable an adaptative response to a changing environment; and spatiotemporal variability of the regeneration of woody plants may rely on the existence of ecological regeneration niches defined in the ecological space.

<p>Combustion instability, a complex phenomenon observed in combustion chambers is due to the coupling between heat release and other unsteady flow processes. Combustion instability has long been a topic of interest to rocket scientists and has been extensively investigated experimentally and computationally. However, to date, there is no computational tool that can accurately predict the combustion instabilities in full-size combustors because of the amount of computational power required to perform a high-fidelity simulation of a multi-element chamber. Hence, the focus is shifted to reduced fidelity computational tools which may accurately predict the instability by using the information available from the high-fidelity simulations or experiments of single or few-element combustors. One way of developing reduced fidelity computational tools involves using a reduced fidelity solver together with the flame transfer functions that carry important information about the flame behavior from a high-fidelity simulation or experiment to a reduced fidelity simulation.</p> <p> </p> <p>To date, research has been focused mainly on premixed flames and using acoustic solvers together with the global flame transfer functions that were obtained by integrating over a region. However, in the case of rockets, the flame is non-premixed and distributed in space and time. Further, the mixing of propellants is impacted by the level of flow fluctuations and can lead to non-uniform mean properties and hence, there is a need for reduced fidelity solver that can capture the gas dynamics, nonlinearities and steep-fronted waves accurately. Nonlinear Euler equations have all the required capabilities and are at the bottom of the list in terms of the computational cost among the solvers that can solve for mean flow and allow multi-dimensional modeling of combustion instabilities. Hence, in the current work, nonlinear Euler solver together with the spatially distributed local flame transfer functions that capture the coupling between flame, acoustics, and hydrodynamics is explored.</p> <p> </p> <p>In this thesis, the approach to extract flame transfer functions from high-fidelity simulations and their integration with nonlinear Euler solver is presented. The dynamic mode decomposition (DMD) was used to extract spatially distributed flame transfer function (FTF) from high fidelity simulation of a single element non-premixed flame. Once extracted, the FTF was integrated with nonlinear Euler equations as a fluctuating source term of the energy equation. The time-averaged species destruction rates from the high-fidelity simulation were used as the mean source terms of the species equations. Following a variable gain approach, the local species destruction rates were modified to account for local cell constituents and maintain correct mean conditions at every time step of the nonlinear Euler simulation. The proposed reduced fidelity model was verified using a Rijke tube test case and to further assess the capabilities of the proposed model it was applied to a single element model rocket combustor, the Continuously Variable Resonance Combustor (CVRC), that exhibited self-excited combustion instabilities that are on the order of 10% of the mean pressure. The results showed that the proposed model could reproduce the unsteady behavior of the CVRC predicted by the high-fidelity simulation reasonably well. The effects of control parameters such as the number of modes included in the FTF, the number of sampling points used in the Fourier transform of the unsteady heat release, and mesh size are also studied. The reduced fidelity model could reproduce the limit cycle amplitude within a few percent of the mean pressure. The successful constraints on the model include good spatial resolution and FTF with all modes up to at least one dominant frequency higher than the frequencies of interest. Furthermore, the reduced fidelity model reproduced consistent mode shapes and linear growth rates that reasonably matched the experimental observations, although the apparent ability to match growth rates needs to be better understood. However, the presence of significant heat release near a pressure node of a higher harmonic mode was found to be an issue. This issue was rectified by expanding the pressure node of the higher frequency mode. Analysis of two-dimensional effects and coupling between the local pressure and heat release fluctuations showed that it may be necessary to use two dimensional spatially distributed local FTFs for accurate prediction of combustion instabilities in high energy devices such as rocket combustors. Hybrid RANS/LES-FTF simulation of the CVRC revealed that it might be necessary to use Flame Describing Function (FDF) to capture the growth of pressure fluctuations to limit cycle when Navier-Stokes solver is used.</p> <p> </p> <p>The main objectives of this thesis are:</p> <p>1. Extraction of spatially distributed local flame transfer function from the high fidelity simulation using dynamic mode decomposition and its integration with nonlinear Euler solver</p> <p>2. Verification of the proposed approach and its application to the Continuously Variable Resonance Combustor (CVRC).</p> <p>3. Sensitivity analysis of the reduced fidelity model to control parameters such as the number of modes included in the FTF, the number of sampling points used in the Fourier transform of the unsteady heat release, and mesh size.</p> <p> </p> <p>The goal of this thesis is to contribute towards a reduced fidelity computational tool which can accurately predict the combustion instabilities in practical systems using flame transfer functions, by providing a path way for reduced fidelity multi-element simulation, and by defining the limitations associated with using flame transfer functions and nonlinear Euler equations for non-premixed flames.</p> <p> </p><br>

Depuis deux décennies, la révolution technologique est avant tout numérique entrainant une forte croissance de la quantité de données à stocker. Le rythme de cette croissance est trop importante pour les solutions de stockage matérielles, provoquant une augmentation du coût de l'octet. Il est donc nécessaire d'apporter une amélioration des solutions de stockage ce qui passera par une augmentation de la taille des réseaux et par la diminution des copies de sauvegarde dans les centres de stockage de données. L'objet de cette thèse est d'étudier l'utilisation des codes en graphe dans les réseaux de stockage de donnée. Nous proposons un nouvel algorithme combinant construction de codes en graphe et allocation des noeuds de ce code sur le réseau. Cet algorithme permet d'atteindre les hautes performances des codes MDS en termes de rapport entre le nombre de disques de parité et le nombre de défaillances simultanées pouvant être corrigées sans pertes (noté R). Il bénéficie également des propriétés de faible complexité des codes en graphe pour l'encodage et la reconstruction des données. De plus, nous présentons une étude des codes LDPC Spatiallement-Couplés permettant d'anticiper le comportement de leur décodage pour les applications de stockage de données.Il est généralement nécessaire de faire des compromis entre différents paramètres lors du choix du code correcteur d'effacement. Afin que ce choix se fasse avec un maximum de connaissances, nous avons réalisé deux études théoriques comparatives pour compléter l'état de l'art. La première étude s'intéresse à la complexité de la mise à jour des données dans un réseau dynamique établi et déterminons si les codes linéaires utilisés ont une complexité de mise à jour optimale. Dans notre seconde étude, nous nous sommes intéressés à l'impact sur la charge du réseau de la modification des paramètres du code correcteur utilisé. Cette opération peut être réalisée lors d'un changement du statut du fichier (passage d'un caractère hot à cold par exemple) ou lors de la modification de la taille du réseau. L'ensemble de ces études, associé au nouvel algorithme de construction et d'allocation des codes en graphe, pourrait mener à la construction de réseaux de stockage dynamiques, flexibles avec des algorithmes d'encodage et de décodage peu complexes. / For two decades, the numerical revolution has been amplified. The spread of digital solutions associated with the improvement of the quality of these products tends to create a growth of the amount of data stored. The cost per Byte reveals that the evolution of hardware storage solutions cannot follow this expansion. Therefore, data storage solutions need deep improvement. This is feasible by increasing the storage network size and by reducing data duplication in the data center. In this thesis, we introduce a new algorithm that combines sparse graph code construction and node allocation. This algorithm may achieve the highest performance of MDS codes in terms of the ratio R between the number of parity disks and the number of failures that can be simultaneously reconstructed. In addition, encoding and decoding with sparse graph codes helps lower the complexity. By this algorithm, we allow to generalize coding in the data center, in order to reduce the amount of copies of original data. We also study Spatially-Coupled LDPC (SC-LDPC) codes which are known to have optimal asymptotic performance over the binary erasure channel, to anticipate the behavior of these codes decoding for distributed storage applications. It is usually necessary to compromise between different parameters for a distributed storage system. To complete the state of the art, we include two theoretical studies. The first study deals with the computation complexity of data update and we determine whether linear code used for data storage are update efficient or not. In the second study, we examine the impact on the network load when the code parameters are changed. This can be done when the file status changes (from a hot status to a cold status for example) or when the size of the network is modified by adding disks. All these studies, combined with the new algorithm for sparse graph codes, could lead to the construction of new flexible and dynamical networks with low encoding and decoding complexities.

Non-overflow flow-through rockfill structures are river engineering elements used to attenuate and delay inflow hydrographs. They represent expedient places to deposit rather enormous quantities of waste rock at mountainous mine sites. Their application has become so common that matters of safety regarding their design have been laid out in Section 8.5 of the Canadian Dam Safety Guidelines (CDA 2007). The research described herein was directed at investigating the different aspects of the hydraulics of these flow-through rockfill structures. In order to assess the potential for an unraveling failure of flow-through rockfill dams, a systematic study of the hydraulic design of these structures was conducted and the non-linear nature of flow through these structures was dealt with using a p-LaPlacian-like partial differential equation. Subsequently, factors of safety against this type of failure are presented for a range of downstream slopes, thus showing the unsafe combinations of embankment slope and particle diameter. Three different index gradients within the toe of such structures were investigated. In this regard, the gradient most suitable for independently computing the height of the point of first flow emergence on the downstream face is examined and a method for independently computing the variation in hydraulic head within that vertical (which allows for the toe of the structure to be isolated) is presented. An additional gradient that allows for the independent estimation of the default tailwater depth is proposed. In order to provide better tools to assess the behavior of these embankments at the toe, laboratory and analytical studies were undertaken. In this regard, the hydraulics associated with the zone of the downstream toe were studied. The depth variation of the seepage-face was computationally modeled, and two approaches for solving the spatially varied flow (SVF) condition problem within the toe region undertaken. The results show that a dual linear variation in depth can be used to good accuracy, without inducing any unrealistic exit gradients in the zone of primary concern with respect to unraveling. It is hoped that these techniques and computational tools provided herein will aid in facilitating the design and assessment of these flow-through rockfill structures.

[Truncated abstract] Ecologists are increasingly interested in quantifying local interacting processes and their impacts on spatial vegetation patterns. In arid and semiarid ecosystems, theoretical models (often spatially explicit) of dynamical system behaviour have been used to provide insight into changes in vegetation patterning and productivity triggered by ecological events, such as fire and episodic rainfall. The incorporation of aerial imagery of vegetation patterning into current theoretical model remains a challenge, as few theoretical models may be inferred directly from ecological data, let alone imagery. However, if conclusions drawn from theoretical models were well supported by image data then these models could serve as a basis for improved prediction of complex ecosystem behaviour. The objective of this thesis is therefore to innovate methods for inferring theoretical models of vegetation dynamics from imagery. ... These results demonstrate how an ad hoc inference procedure returns biologically meaningful parameter estimates for a germ-grain model of T. triandra vegetation patterning, with VLSA photography as data. Various aspects of the modelling and inference procedures are discussed in the concluding chapter, including possible future extensions and alternative applications for germ-grain models. I conclude that the state-and-transition model provides an effective exploration of an ecosystem?s dynamics, and complements spatially explicit models designed to test specific ecological mechanisms. Significantly, both types of models may now be inferred from image data through the methodologies I have developed, and can provide an empirical basis to theoretical models of complex vegetation dynamics used in understanding and managing arid (and other) ecological systems.

Detection of explosives has always been a challenging issue all over the world. Different analytical techniques and instrumentation methods have been explored to obtain a 100% fail proof detector. Some technologies have matured and have been deployed in the field already. However, active research is still being pursued to make the ultimate explosive detection device. The present thesis broadly addresses the development of Raman spectroscopy based techniques for the detection of explosives. Although Raman spectroscopy has technologically developed and has become a regular tool for chemical identification, its use in the field of detection of explosives has been limited. Two aspects of detection were addressed in this thesis. The first part consists of the detection of minute quantities or traces of explosives using a Raman based method. In order to approach this problem, surface enhanced Raman spectroscopy (SERS), an offshoot of Raman spectroscopy was explored. Chapters 2-4 deal with developing efficient SERS substrates. In this endeavour, the first and the most obvious choice as SERS substrates were silver (Ag) nanoparticles (NPs). However, we were exploring methods that could be simple one-pot synthesis methods, cost-effective and without employing strong reducing agents (green). Therefore, Ag NPs were synthesized using biosynthetic route. These nanoparticles were used to study their SERS efficiency. Sub-nano molar concentration of dye as well explosive like trinitrotoluene (TNT) and hexanitrohexaazaisowurtzitane (CL-20) could be obtained for both the clove reduced as well as pepper Ag nanoparticles. Hence Ag NPs are very efficient SERS substrates. In the second part of the work on SERS, bimetallic nanoparticles with core-shell (Agcore-Aushell) architecture were synthesized, characterized and tested for SERS activity. After successful synthesis and characterization of the bimetallic nanoparticles, these were tested for their SERS activities using a dye molecule and an explosive molecule. SERS spectra could be obtained for the bimetallic nanoparticles. It was observed that the sensitivity of these NPs were almost at par with the mono-metallic Ag NPs. In order to bring SERS from laboratory to field, a more practical approach was to prepare solid SERS substrates or SERS substrates on solid platform. In the next chapter, we ventured into the most abundant material which forms the backbone of the organic world, carbon. Various carbonaceous materials ranging from chemically synthesized graphene, graphene oxide, multi-walled carbon nanotube (MWCNT), graphite and activated charcoal were explored as potential substrates for surface enhanced Raman spectroscopic applications. The analytes chosen for this particular study were some fluorescent molecules such as rhodamine B (RB), rhodamine 6G (R6G), crystal violet (CV), Nile blue A (NBA) and a non-fluorescent molecule acetaminophen, commonly known as paracetamol. Enhanced Raman signals were observed for the fluorescent molecules, especially for the molecules whose absorbance maxima are near the excitation wavelength of the laser (514.5 nm). The most interesting outcome of this work was obtaining enhanced Raman signals of nanomolar concentration of R6G on activated charcoal. However, for the non-fluorescent molecule, paracetamol, Raman spectra could not be observed beyond -5 10M concentration for all the carbon substrates including chemically synthesized graphene and MWCNT. This study was crucial in our quest for an ideal SERS substrate. Our observations let us to conclude that chemically synthesized graphene was not the only candidate for the preparation of SERS substrates. Since carbon materials efficiently adsorb and also provide a separate channel for energy decay (fluorescence quenching), even activated charcoal could be employed as a SERS platform. However, carbon alone could not provide an effective solution for the preparation of SERS substrates. Therefore, combining the plasmonic effect of the metal nanoparticles with the efficient adsorption and fluorescence quenching of carbon materials would be ideal. In the next part of the carbon studies, graphene-Ag composites which were either prepared by in situ reduction process or physically mixed were studied for SERS activity. An ideal SERS substrate should possess the following properties: (i) Support plasmon, thereby provide SERS enhancement (ii) Easy to fabricate or synthesize (large scale/bulk) (iii) Ensure high reproducibility and sensitivity (iv) Low false alarm from matrix chemicals (v) Cost effective (vi) Solid substrate (in the form of chip, pellet, slide etc.) Hence, as a final study, carbon silver based composites were explored. R6G was chosen as an analyte again and SERS experiments were conducted. Raman signals at low concentration could be obtained for the carbon-Ag composites as well. In addition, feasibility experiments were also conducted for an explosive molecule, FOX-7. From these preliminary experiments we observed that carbon-metal NP composites can be efficient, cost-effective SERS substrates that will overcome the current issue. The previous chapters dealt with the trace detection of explosives. The next part of the thesis deals with the development of the Raman spectroscopic methods for non-invasive detection of concealed objects. Chapters 4 and 5 primarily focus on explosives detection. Spatially offset Raman spectroscopy (SORS) instrumentation was developed in the laboratory for non-invasive detection solid and liquid explosives. Several experiments were carried out to detect concealed materials inside high density polyethylene (HDPE) containers, coloured glass bottles, envelopes etc. with this technique, Raman signals of materials could be retrieved even within 4 mm thick outer-layer. SORS imaging experiments were also performed on bilayered compounds, tablets etc. However, while performing the SORS experiments, it was observed that due to the restriction in geometry imposed by the method, the signals from the inner-layers could be obtained only up to a certain depth. This posed a serious limitation of SORS for practical scenarios, where the thickness of the outer layer may be tens of mm. In such situation, SORS may not be an effective method. We then performed Raman experiments using a transmission geometry using a series of samples. The transmission Raman (TR) experiments yielded better SNR for the inner (concealed) material as compared to the outer material. Although transmission Raman experiments yielded better signal but these experiments were again geometry dependent, hence, less flexible and TR experiments did not provide information about the position of the underlying materials. In order to obtain complete information, it was necessary to understand photon migration in a multiple scattering medium. It is known that a photon in a multiple scattering medium may be approximated to undergo a random-walk. Statistically, the photon that undergoes multiple scattering in a medium loses its sense of origin (direction), hence, there is a finite probability to observe the exiting photon in any direction. Rayleigh and NIR based imaging modalities have been conducted using this model. Diffuse optical tomographic (DOT) measurements also deal with measuring the photons that have exited the sample after undergoing multiple scattering in a turbid medium. If it was possible to collect the Rayleigh photons or the diffuse photons in DOT experiments, in principle, Raman photons could also be collected from several directions. It was then proposed that if Rayleigh scattered photons can exit at 4π solid angle from a sample, then it can be assumed that some Rayleigh photons may convert to Raman photons, which in turn, shall have a finite probability to exit the sample from all the sides (4π solid angles). This idea of collecting Raman photons has never been discussed before! Thus, as expected based on the above principles, we were able to record Raman scattered photons at all angles and on all sides. This new technique has been termed as ‘Universal Multiple Angle Raman Spectroscopy (UMARS)’. Monte Carlo simulation studies were also performed to understand the distribution of photons in a multiple scattering medium. Simulation studies also revealed that Raman photons exited from all sides of the medium at varying percentages. Hence, several fiber optic probes were designed for illumination and collection to perform the UMARS experiments for samples concealed at depths beyond 20 mm. UMARS was not only applied successfully for the detection of concealed explosives, but also for biologically relevant samples as well. In fact a pharmaceutical tablet as thick as 7 mm was also tested with UMARS and signals could be successfully obtained. Since the UMARS signals were obtained from all possible angles, imaging experiments were also conducted to obtain sample specific information. Frequency-specific images of bilayer materials could be obtained. In the case where one material was concealed within another, the reconstruction of the frequency-specific intensities in a contour plot revealed the position of the concealed layer. One of the most challenging and exciting studies that was conducted was to use UMARS to obtain shapes of hidden materials. Several shapes such as dumbbell, ellipsoid etc were fabricated (made of glass) and were filled with a test chemical, trans-stilbene (TS). This shape was placed inside an outer material like ammonium nitrate (AN) that was taken in a glass beaker. The diameter of the beaker was varied from 25 mm to 60 mm. A series of UMARS measurement was carried out with 10 collection fiber optic probes. The spatial resolution (vertical) was varied from 200 μm to 1 mm. Series of UMARS images were obtained which were then processed and the intensity of the individual fibers were averaged (CCD row pixels) based on the image of the individual fiber on the CCD. The frequency specific intensity of the materials was utilized to reconstruct 2D or a 3D shape. The shapes of the objects could be clearly discerned using UMARS imaging. This marks a major step for the development of UMARS as a 3D imaging modality. UMARS experiments conducted so far have affirmed our belief that this technology can be used as an effective technique for screening solid and liquid samples at airports, railway stations and other entry points. 3D imaging for biomedical diagnostics will provide molecular information in addition to the location and shape of an object inside a tissue such as calcified masses and bones. In the final part of the thesis, 2D Raman correlation spectroscopic method was applied to understand the dynamics of a system that was subjected to external perturbation. In the field of explosive processing and formulations, large batches are generally prepared. However, it is very difficult to ascertain the molecular or structural changes that occur during the processing of these formulations in situ. Analytical methods to monitor the changes online are limited. Raman spectroscopy can be an effective technique for such measurements. This process however, generates a large number of spectra. In such cases, it becomes cumbersome to handle such large number of data and obtain meaningful information. 2D correlation spectroscopy can be applied under such situations. 2D correlation analysis generates essentially two maps, synchronous and asynchronous. In this study, 2D Raman correlation spectroscopy was applied to ammonium nitrate that was subjected to temperature variations. 2D maps were constructed to obtain information about the structural changes associated with temperature. The synchronous map reveals the overall similarity of the intensity changes. Whereas, the 2D asynchronous maps provide the sequence of changes that occur. Based on the set of well defined rules proposed by Isao Noda, the synchronous and the asynchronous correlation maps were analysed. Hence, generalized 2D correlation spectroscopy can be extended to any kind of perturbation and will prove useful in understanding the structural dynamics. The objective of the thesis was to explore various facets of Raman spectroscopy that would be useful in the field of high energy materials specifically in the detection of explosives. Attempts were made for the development of trace detection of explosives using Raman based technique, SERS. In addition, bulk detection of concealed explosives was performed non-invasively using SORS and UMARS. In the field of high energy materials, these techniques will find immense applications. Raman spectroscopy, as we saw is a very important technique that can be used as a stand-alone method and can also be interfaced with other analytical or imaging modalities. This treatise is an example where the strength of this powerful spectroscopic method has been explored to some extent.

In this thesis we study the key requirements and solutions for the feasibility and application of Ethernet-TCP/IP technology to the networks we termed Highly-Variable Real-Time Networks (HVRN). This particular class of networks poses exceptionally demanding requirements because their physical and logical topologies are both temporally and spatially variable. We devised and introduced specific mechanisms for applying Ethernet-TCP/IP to HVRNs with particular emphasis on effective and reliable modular connectivity. Using a railroad train as a reference, this work analyzes the unique requirements of HVRNs and focuses on the backbone architecture for such a system under Ethernet and TCP/IP. / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

In recent years, Polarimetric Synthetic Aperture Radar (PolSAR) has been one of the most important instruments for earth observation, and is increasingly used in various remote sensing applications. Statistical modelling and scattering analysis are two main ways for PolSAR data interpretation, and have been intensively investigated in the past two decades. Moreover, spatial analysis was applied in the analysis of PolSAR data and found to be beneficial to achieve more accurate interpretation results. This thesis focuses on extracting typical spatial information, i.e., edges and regions by exploring the statistical characteristics of PolSAR data. The existing spatial analysing methods are mainly based on the complex Wishart distribution, which well characterizes the inherent statistical features in homogeneous areas. However, the non-Gaussian models can give better representation of the PolSAR statistics, and therefore have the potential to improve the performance of spatial analysis, especially in heterogeneous areas. In addition, the traditional fixed-shape windows cannot accurately estimate the distribution parameter in some complicated areas, leading to the loss of the refined spatial details. Furthermore, many of the existing methods are not spatially adaptive so that the obtained results are promising in some areas whereas unsatisfactory in other areas. Therefore, this thesis is dedicated to extracting spatial information by applying the non-Gaussian statistical models and spatially adaptive strategies. The specific objectives of the thesis include: (1) to develop reliable edge detection method, (2) to develop spatially adaptive superpixel generation method, and (3) to investigate a new framework of region-based segmentation. Automatic edge detection plays a fundamental role in spatial analysis, whereas the performance of classical PolSAR edge detection methods is limited by the fixed-shape windows. Paper 1 investigates an enhanced edge detection method using the proposed directional span-driven adaptive (DSDA) window. The DSDA window has variable sizes and flexible shapes, and can overcome the limitation of fixed-shape windows by adaptively selecting homogeneous samples. The spherically invariant random vector (SIRV) product model is adopted to characterize the PolSAR data, and a span ratio is combined with the SIRV distance to highlight the dissimilarity measure. The experimental results demonstrated that the proposed method can detect not only the obvious edges, but also the tiny and inconspicuous edges in heterogeneous areas. Edge detection and region segmentation are two important aspects of spatial analysis. As to the region segmentation, paper 2 presents an adaptive PolSAR superpixel generation method based on the simple linear iterative clustering (SLIC) framework. In the k-means clustering procedure, multiple cues including polarimetric, spatial, and texture information are considered to measure the distance. Since the constant weighting factor which balances the spectral similarity and spatial proximity may cause over- or under-superpixel segmentation in different areas, the proposed method sets the factor adaptively based on the homogeneity analysis. Then, in heterogeneous areas, the spectral similarity is more significant than the spatial constraint, generating superpixels which better preserved local details and refined structures. Paper 3 investigates another PolSAR superpixel generation method, which is achieved from the global optimization aspect, using the entropy rate method. The distance between neighbouring pixels is calculated based on their corresponding DSDA regions. In addition, the SIRV distance and the Wishart distance are combined together. Therefore, the proposed method makes good use of the entropy rate framework, and also incorporates the merits of the SIRV distance and the Wishart distance. The superpixels are generated in a homogeneity-adaptive manner, resulting in smooth representation of the land covers in homogeneous areas, and well preserved details in heterogeneous areas. / <p>QC 20171123</p>

Le Miscanthus x giganteus est une culture pérenne, nouvellement produite en Europe et présentant un intérêt fort pour son usage énergétique. Son implantation présage donc une réorganisation territoriale pérenne. Pour anticiper cette réorganisation, de nombreuses études modélisent les dynamiques spatialement explicites de son insertion. Notre thèse se positionne dans ce courant de recherche. Celle-ci vise à proposer un nouveau cadre de modélisation des processus de décision des agriculteurs, permettant la dissémination horizontale (scaling out) de ces processus issus d’études de cas, vers des territoires élargis. Pour cela, la thèse exploite le modèle du raisonnement à partir de cas. Elle articule (i) une démarche d’acquisition de connaissances sur les processus de décision des agriculteurs relatifs à l’insertion territoriale du miscanthus et (ii) la conception et évaluation d’un prototype ad hoc de raisonnement à partir de cas. La phase d’acquisition des connaissances montre que le processus d’insertion territoriale du miscanthus est complexe : celui-ci est étroitement lié aux contraintes parcellaires du territoire. Ces connaissances nous conduisent alors à discuter du choix des variables biophysiques et humaines intégrées à ce jour dans les modèles spatialement explicites. La phase de conception et d’évaluation du prototype de raisonnement à partir de cas montre que le modèle du raisonnement à partir de cas est particulièrement bien adapté pour modéliser un phénomène contextualisé. Evalués sur nos données d’enquêtes, ces résultats nous conduisent à discuter des modalités d’application du prototype sur d’autres bassins de production de miscanthus / Miscanthus x giganteus is the perennial crop, newly produced in Europe. Even if miscanthus is not so heavily produced nowadays, this crop would be of great interest for energy use. However, the allocation of miscanthus could produce a sustainable reorganization of the landscape. Therefore, many studies aim to model the land use change caused by miscanthus, in order to identify sustainable supply areas: our research belongs to this field. In our research, we propose a new framework for modeling decision-making process of farmers, relying on scaling out. More accurately, we propose to use the case-based reasoning model which solves problems based on an analogical reasoning. Then our research is structured: (i) by a knowledge acquisition step about decision-making process of farmers, based on farm surveys, conducted in the Côte d'Or department (Burgundy region) and (ii) by the design and evaluation of an ad hoc prototype of case-based reasoning. On the one hand, results of knowledge acquisition phase show that miscanthus allocation process is complex, more accurately, that miscanthus allocation process is closely related to land constraints, particularly in terms of logistic and environmental preservation of plots. These results lead us to discuss the selection of biophysical and human variables included to the current spatially explicit models. On the other hand, the design and evaluation phase of our prototype shows that case-based reasoning is particularly well suited to model a contextual phenomenon. These results lead us to discuss the modalities for implementing the prototype in other production areas of miscanthus