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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
261

Variações florísticas e estruturais em jaboticabais na floresta estacional no planalto sul-brasileiro

Grasel, Daniel January 2016 (has links)
Nós investigamos as relações entre a diversidade e a estrutura do componente arbóreo com as variáveis ambientais, em quatro posições microtopográficas (MPs), ao longo de um gradiente formado entre zonas úmidas depressionais florestadas e terras firmes em jaboticabais (FDWs) no Planalto Sul-Brasileiro. A riqueza específica e a diversidade foram similares nas terras firmes e menores nas zonas úmidas, enquanto que os parâmetros estruturais diferiram pouco entre as MPs. Uma análise de espécies indicadoras mostrou que poucas espécies são indicadoras das terras firmes, revelando que a distribuição das espécies foi relativamente uniforme em comparação às zonas úmidas. Os mesmos padrões foram revelados por uma análise de correspondência canônica (CCA), que mostrou que os alagamentos foram os principais determinantes da zonação de espécies arbóreas. Aparentemente, Plinia peruviana (Poir.) Govaerts (Myrtaceae) é a única espécie com distribuição praticamente restrita às MPs estudadas, mas os jaboticabais podem ter uma importância desproporcionalmente maior na preservação de espécies que são pouco abundantes em outras florestas na região. A ocorrência exclusiva de solos distróficos nas áreas de estudo, em uma região onde solos eutróficos predominam, indicam que as terras firmes estudadas representam zonas transicionais entre as zonas úmidas e a matriz florestal. Como estudo pioneiro em zonas úmidas depressionais florestadas no Planalto Sul-Brasileiro, nossos resultados sugerem que ao menos toda a área correspondente às depressões topográficas deve ser protegida, até que estudos complementares proponham zonas de amortecimento apropriadas, com base em critérios biológicos. Jaboticabais são ecossistemas únicos cuja restauração, manejo e preservação são cruciais para manter ambientes espacialmente heterogêneos e, consequentemente, a riqueza específica e as funções e serviços ecossistêmicos. / We investigated the relationships between tree component diversity and structure with environmental variables of four microtopographic positions (MPs) along a wetland-upland gradient in forested depressional wetlands (FDWs) on the South Brazilian Plateau. Species richness and diversity were quite similar in the uplands and lowest in the wetlands, while structural parameters differed little among MPs. An indicator species analysis showed that few species were indicators of the upland sites, suggesting that species distribution was relatively uniform in comparison to the wetlands. The same patterns were revealed by a canonical correspondence analysis (CCA) that showed flooding to be the main factor driving tree species zonation. Apparently, Plinia peruviana (Poir.) Govaerts (Myrtaceae) is the only tree species with practically restricted distribution to the studied ecosystems, although FDWs and their surrounding uplands can have a disproportionately higher importance in the preservation of species that are under-represented in other regional forests. The occurrence of exclusively dystrophic soils in the study areas, in a region where eutrophic soils predominate, indicates that the studied uplands represent transitional zones between the FDWs and the forest matrix. As a pioneer study in FDWs on the South Brazilian Plateau, our findings suggest that the whole area of the topographic depressions should be protected at least until complementary studies propose proper buffer zones based on biological criteria. FDWs are unique ecosystems whose restoration, management and preservation are crucial to maintain spatial environmental heterogeneity and consequently species richness and ecosystem functions and services.
262

Generalização da técnica de correlação canônica para aplicações em interface cérebro-máquina /

Brogin, João Angelo Ferres. January 2018 (has links)
Orientador: Douglas Domingues Bueno / Resumo: A busca por uma melhor compreensão das regiões do cérebro e suas funções nas ações humanas tem sido uma tarefa árdua, porém muito útil, principalmente para aplicações da engenharia de interface cérebro-máquina (ICM), bem como para o auxílio a diagnósticos médicos a partir de sinais obtidos dos pacientes em avaliação. No contexto do presente trabalho, destacam-se os trabalhos de interface cérebro-máquina (ICM) pela abrangência no envolvimento de técnicas, métodos e ferramentas comumente estudadas nos cursos de engenharia. Em particular, análises envolvendo técnicas de processamento de sinais de eletroencefalograma (EEG) têm se mostrado de significativa importância para o desenvolvimento dessa área. Uma abordagem amplamente utilizada nesse contexto é a ICM usando Potenciais Visuais Evocados de Estados Estacionários (SSVEP, do inglês Steady-State Visual Evoked Potentials), que, de forma geral, são sinais caracterizados pela resposta evocada do cérebro a estímulos visuais modulados em uma frequência específica. Assim, este trabalho tem o objetivo de propor uma generalização do coeficiente de correlação, conceito-base da análise de correlação canônica (CCA), técnica que tem se mostrado robusta e eficiente no reconhecimento de padrões, especialmente no caso dos SSVEP, e detalhar seu comportamento em função dos parâmetros relevantes para se estabelecer melhores práticas de uso em aplicações de ICM, incluindo fatores fisiológicos, técnicos e operacionais. / Abstract: The search for a better understanding of the brain's anatomy and its functions on human actions has been a harsh yet very useful task, especially for brain-computer interface engineering applications, as well as for medical diagnosis using signals from patients. In the context of this work, brain-computer interface (BCI) applications are highlighted due to their compreehensiveness related to techniques, methods and tools commonly studied in engineering. In particular, analyses involving eletroencephalogram (EEG) signals processing have proven to be of great significance for developing this field of study. A widely used approach is Steady State Visual Evoked Potentials (SSVEP) based BCI, which, in general, are signals characterized by the brain’s evoked response to visual stimuli modulated at a certain frequency. This work aims thus to propose a generalization of the correlation coefficient, which entails Canonical Correlation Analysis (CCA), a technique that has presented robustness and efficiency for pattern recognition, especially in SSVEP-based BCIs, and describe its behavior under relevant varying parameters to stablish better use practices in BCI applications, comprising physiological, technical and operational factors. / Mestre
263

Diversity, use and resiliance of woody species in a multiple land use equatorial African savanna, central Uganda

Kalema, Vettes Neckemiah 17 March 2011 (has links)
Savanna woodlands are vitally important in providing ecological services (e.g. erosion protection, micro-climate) and economic services (e.g. timber, food, fodder non-wood products, and wild-life habitats) that sustain local livelihoods and national economies. Increasing demands and the need for sustainable savanna woodland resource management requires that the ecological, economic, social and cultural values of these resources be explored and brought to the attention of decision makers and the general public. The identification and better understanding of the structure and dynamics of woodland community types, patterns of species distribution and quantitative properties of their diversity is important to the conservation and sustainable management of these woodlands. This study seeks to contribute to a better understanding of Nakasongola woodland community types, species diversity patterns and environment correlates, natural regeneration processes (i.e. sprouting and seedling establishment) and identifying livelihood strategies adopted by households, woody species utilised, and the contribution of charcoal production to household livelihoods. Data on vegetation and environmental variables were collected using 75 rectangular 20 x 50 m (0.1 ha) plots. Data on land use and land cover changes, and relevant associated socio-economic parameters were collected through the analysis of multi-temporal satellite imagery and field observations, as well as interviews of local households and key informants. The basic major livelihood activities for the rural households in this savanna dryland are charcoal production, subsistence crop cultivation and livestock grazing. However, it, sometimes, includes various combinations of activities, i.e. charcoal production and subsistence crop cultivation for both food and cash, and livestock keeping for income generation through selling the livestock products such as milk and, sometimes, the whole animal. At least 24 woody species, including fruit trees (Mangifera indica and Artocarpus heterophyllus), are frequently harvested, including 16 species that are considered the most utilized for charcoal production. Charcoal production, being the major source of income to the rural households, contributes on average US$ 259 ± 46 (S.E.) per household annually. There were significant differences in charcoal production (Kruskal-Wallis; H = 31.42, p < 0.0001), producer sale prices per bag of charcoal (H = 35.62, p < 0.0001), and annual incomes from charcoal production (H = 32.44, p < 0.0001) per households across the 8 sub-counties. Most of the youth (≤ 20 years old) derive their livelihoods from charcoal production, a small amount of trade, offering labour services, livestock keeping, fishing, bee keeping and earth brick making. Charcoal production, livestock keeping and hunting are carried out particularly by men, whereas, crop cultivation, and collection of fire wood, medicinal plants and fruits are carried out, mainly, by women. However, men are also engaged in cultivation only during the rainy seasons. There have been significant land cover changes in the area during the period 1984 to 2001, resulting in a 64% decrease in dense woodland cover, and an 80% increase in areas under cultivation/settlements. These changes are attributed to significant spatial expansion in agriculture increased commercialisation of charcoal production, grazing and human population growth. A total of 44,195 (5,893 plants/ha) woody plants representing 99 species in 67 genera and 31 families were recorded. The most species rich families were Mimosaceae (13), Rubiaceae (9), Moraceae (7), Euphorbiaceae (7), Anacardiaceae (6), Combretaceae (5) and Verbenaceae (5). Density of woody species differed significantly (F2, 72 = 6.3, P < 0.003) among land uses, being higher under charcoal production (7,131 ± 755 plants/ha) and cultivation (6,612 ± 665) areas and significantly lower under grazing lands (4,152 ± 525). Community species composition differed significantly (Global RANOSIM = 0.14, p = 0.001) among land use types. All measures of beta-diversity (spatial “turnover” in species composition) showed consistently higher beta-diversity in the grazing land use (βW = 3.1; βT = 3.1), followed by cultivation (βW = 2.8; βT = 3.0) and charcoal production (βW = 2.7; βT = 2.8), suggesting a more heterogeneous spatial distribution of species in the grazing lands. This suggests that variations in the composition and diversity of woody species are to a great extent influenced by land use type and anthropogenic disturbances in this region. Basal area of woody species differed significantly (F2, 72 = 12.0, P < 0.0001) among land uses, being highest under cultivation and charcoal production and significantly lower under grazing. Woody plant density differed (F2,72 = 6.3, P = 0.003) across landuses, being highest under charcoal production and cultivation and significantly lower under grazing. The species that contributed most to both basal area and density across all the land uses were Combretum collinum and Combretum molle. However, different species contributed the next most i.e. Piliostigma thonningii for grazing; Albizia zygia and Harrisonia abyssinica for cultivation and Vepris nobilis for charcoal production areas. For both basal area and abundance of all woody species, the total variance in species-environmental factor relations (for the combined first four canonical axes) was higher than 50%, suggesting a relatively strong influence of the measured environment variables on species composition and distributions. The CCA points to a significant influence of soil Ca2+ and Mg2+ in association with grazing on gradients in the composition and structure of woody species in the savanna woodland of Nakasongola. Resprouting was generally common among the woody species. A total of 2,595 stumps, representing 74 species in 31 families were recorded from all plots. Of these, 98.3% resprouted and were identified to species level. Density of both stumps and total resprout differed significantly (p < 0.05) among the land uses, being higher in charcoal production areas than in grazing and cultivation land uses. For the overall pooled data, resprouts per stump differed significantly among land uses (F2, 456 = 7.75, p = 0.0005), being highest in charcoal production (mean ± S.E.; 14 ± 1) and cultivation (13 ± 1) land uses and lowest under grazing areas (10 ± 1). Generally, the mean number of resprouts per stump increased with increasing stump basal diameter (BD), being highest for BD size class > 41 cm. In relation to stump height, the highest mean resprouts/stump was found on stumps with heights ranging from 0.31- 0.40 m. Based on pooled species data, regression analyses showed weakly significant negative relationships between BD of leading resprouts and number of resprouts/stump (r2 = 0.123, p < 0.0001) and between height of leading resprouts and number of resprouts/stump (r2 = 0.068, p < 0.0001). Density of seedlings of woody species differed significantly among land use types (ANOVA; F2, 72 =5.9, p = 0.004), being highest for cultivation (3,162 ± 440 individuals ha-1), followed by charcoal production (2,416 ± 295 ha-1) and lowest for grazing (1,629 ± 205 ha-1). Composition of seedlings differed significantly among land use types (Global RANOSIM = 0.119, p = 0.001). The distributions and densities of some seedlings were explained by gradients in environmental variables, with edaphic factors (i.e. Ca2+, Mg2+, K+ and organic matter) and charcoal production being the most important. The first two axes of the Canonical Correspondence Analysis (CCA) explained 41.9% of the variance in species – environmental relations and were a reflection of edaphic and charcoal production land use gradients. All of the 16 highly utilized species were well represented in both the juvenile and adult classes, with gradually declining number of individuals with increasing stem size-class. This indicates that most of these species have high regeneration potential. Juvenile:adult tree ratios >1 and negative DSCD slopes indicate good recruitment and probably successful regeneration for these species. The study revealed land cover changes mainly in the dense and medium dense woodlands, reflected by the increase in open woodland, grasslands and cultivation/settlements. These trends threaten the livelihoods of local communities who are entirely dependent on these natural resources. Sustainable management will require the establishment of suitable integrated community-based institutions and management practices, with support from all key stakeholders (i.e. National Forest Authority (NFA)) and local communities. Maintenance of savanna woodland resources and other ecosystem services essential for human well-being will require an effective legal framework to prevent over-exploitation and give incentives for the protection of the fragile savanna woodland vegetation. An appropriate savanna woodland management policy will be required to guide changes in land use that accommodate the requirements of land users, aided by targeted conservation efforts to all woody plants and particularly for the highly utilized species for charcoal production as well as the multipurpose species. In addition, there is urgent need to build local capacity for improved harvesting and utilization of these tree species. This can be achieved through equipping local users with up to date information as well as observing the existing skills.
264

Espalhamento e absorção de campos bosônicos por buracos negros estáticos e análogos / Scattering and absorption of bosonic fields by static blach holes and analogues

Oliveira, Ednilton Santos de 11 December 2009 (has links)
Nesta tese apresentamos a análise da absorção e do espalhamento de partículas não massivas de spins 0 e 1 por buracos negros de Schwarzschild, assim como a absorção e espalhamento por análogos acústicos destes buracos negros. Apresentamos também a análise da absorção e do espalhamento do campo escalar não massivo por buracos negros de Reissner-Nordström. A presente pesquisa se baseia no método de decomposição em ondas parciais. Devido a estes espaços-tempos serem estáticos e esfericamente simétricos, as partes temporal e angular das soluções das equações de campo se reduzem a funções conhecidas. O mesmo não acontece com a parte radial, o que nos leva a abordar o problema, principalmente, por meio de métodos numéricos. Cálculos analíticos também são realizados, geralmente para podermos verificar a precisão dos resultados numéricos. Os principais resultados analíticos mostrados aqui são a seção de choque de absorção em baixas e altas frequências e a seção de choque diferencial de espalhamento para ângulos próximos a 180 (efeito glória). Mostramos, de forma analítica, que as principais características das seções de choque de absorção e diferencial de espalhamento estão diretamente relacionadas à existência da órbita instável de partículas não massivas. Os nossos resultados numéricos estão em excelente concordância com os resultados obtidos por meio de cálculos analíticos. Com relação ao espaço-tempo de Reissner-Nordström, mostramos qual o comportamento das seções de choque com a variação da intensidade de carga do buraco negro. No caso de buracos negros descarregados, fazemos comparações das seções de choque obtidas para partículas de diferentes spins. / We present an analysis of the absorption and scattering of massless particles of spin 0 and 1 by Schwarzschild black holes, and the absorption and scattering by analogues of these black holes. We present also the analysis of the massless scalar field absorption and scattering by Reissner-Nordström black holes. This research is based on the partial wave methods. Since these spacetimes are static and spherically symmetric, the time and angular dependence of the field equation solutions can be written in terms of well known functions. The same does not happen with the radial part of the field equation solutions, so that we apply numerical methods to solve the absorption and scattering problem. Analytical computations are also performed and we use them to verify the precision of our numerical computations. The main analytical results obtained here are the low- and high-frequency absorption cross sections and the dierential scattering cross section for angles near 180 (the glory eect). We use our analytical results to show that the main cross sections properties are related to the existence of an unstable orbit for massless particles. We compare our numerical results with semiclassical approximations from a geodesic analysis, and find excellent agreement. In the Reissner-Nordström spacetime case, we show how the cross sections behave as we vary the black hole charge. For uncharged black holes, we compare cross sections for particles with dierent spins.
265

Associative CAD References in the Neutral Parametric Canonical Form

Staves, Daniel Robert 01 March 2016 (has links)
Due to the multiplicity of computer-aided engineering applications present in industry today, interoperability between programs has become increasingly important. A survey conducted among top engineering companies found that 82% of respondents reported using 3 or more CAD formats during the design process. A 1999 study by the National Institute for Standards and Technology (NIST) estimated that inadequate interoperability between the OEM and its suppliers cost the US automotive industry over $1 billion per year, with the majority spent fixing data after translations. The Neutral Parametric Canonical Form (NPCF) prototype standard developed by the NSF Center for e-Design, BYU Site offers a solution to the translation problem by storing feature data in a CAD-neutral format to offer higher-fidelity parametric transfer between CAD systems. This research has focused on expanding the definitions of the NPCF to enforce data integrity and to support associativity between features to preserved design intent through the neutralization process. The NPCF data structure schema was defined to support associativity while maintaining data integrity. Neutral definitions of new features was added including multiple types of coordinate systems, planes and axes. Previously defined neutral features were expanded to support new functionality and the software architecture was redefined to support new CAD systems. Complex models have successfully been created and exchanged by multiple people in real-time to validated the approach of preserving associativity and support for a new CAD system, PTC Creo, was added.
266

Images et imaginaires scolaires de la littérature française du XVI°siècle : constitution, modélisation et transmission d'un corpus canonique de la Renaissance (1880-2011) / Academic images of the XVIth century literature : creating a canonical figure of the French Renaissance literature in literary history (1890-2011)

Broussin, Marjorie 01 July 2019 (has links)
De l’Histoire de la littérature française de Gustave Lanson, dont la première édition date de 1894, aux manuels de littérature pour les classes de lycée publiés en 2011, une même représentation de la Renaissance et de sa littérature parcourt les ouvrages scolaires et peint la période sous les traits d’un « beau XVIe siècle », moment de réveil des arts, des lettres et des sciences. Or, si cette image s’impose comme une évidence, à travers les mécanismes itératifs de la transmission, elle s’avère en réalité une construction dont l’évolution historique souligne la dimension fictionnelle de la notion même de siècle littéraire.Liée aux mécanismes propres à l’histoire littéraire, qui découpe et met en récit la littérature selon des visées institutionnelles, l’image scolaire de la littérature du XVIe siècle s’avère en effet l’aboutissement de phénomènes parallèles de sélection, de modélisation et de hiérarchisation des auteurs et des textes. La mise en œuvre de ces différents mécanismes se traduit d’une part par la constitution et la diffusion d’un corpus canonique de la littérature du XVIe siècle dans les ouvrages scolaires, et d’autre par la création dans le discours scolaire de figures classiques pour les écrivains et poètes du siècle. La conjonction de ces processus détermine dès lors un ensemble canonique hiérarchisé et un discours unifié, une doxa, qui servent defondement à la représentation scolaire du siècle. Ce sont ces deux aspects constitutifs de l’image canonique de la littérature du XVIe siècle, la constitution du canon d’une part, la pérennité du discours scolaire d’autre part, qui sont analysés ici au moyen d’un large corpus d’ouvrages scolaires, étalé sur plus d’un siècle. Ce faisant, seront mis au jour les phénomènes de stabilisation et d’évolution de la doxa et du canon, en regard des mutations historiques et institutionnelles.La représentation canonique du siècle, de même que le canon des auteurs et des œuvres, se construit en effet en lien avec les impératifs institutionnels liés à la transmission de la littérature. Déterminant pourquoi et comment doit être transmise la littérature nationale, ces impératifs soulignent que les règles de sélection et de hiérarchisation des œuvres dans le canon sont édictées en fonction de visées politiques, sociales et idéologiques. L’étude de l’image scolaire de la littérature du XVIe siècle suppose dès lors d’interroger les valeurs et les représentations qui informent le discours des manuels et déterminent les formes prises par les représentations canoniques du siècle, afin de dégager les enjeux de l’imaginaire scolaire qui sous-tend cettevision. / From Michelet’s definition of the Renaissance and its literary productions in 1855 to the actual discourse of high school textbooks, this dissertation reveals the process by which a canonical representation of 16th century French Literature, as well as a canonical form of this literature, are built and shared. The study is based on a wide range of school textbooks, from Gustave Lanson’s Histoire de la littérature française to textbooks published in 2011, as well as literary anthologies from the first half of the 20th century and the famous Lagarde et Michard published from the 1940’s until the 1980’s.The form in which 16th century authors and their work are represented in these textbooks and anthologies indicates that several mechanisms contributed to bringing out the idea of a « literary century » which was organized by an institutional selection of texts on one hand, and, on the other hand, by the circulation of a doxa about both the writers and their writing. Therefore, as this discussion underlines the construction of classical representations for each of the most represented authors, it also establishes that these figures tend to create an overarching canonical representation of the century, as well as a canonical corpus for this time period. This canonical representation and its corpus take shape as a hierarchical construction, within which each author and literary work are given a specific place. This place thus determines the ranking of the writers in the canonical space, which cannot easily be changed, as the canon turns out to be quite identical throughout the length of the study. On the contrary, the institutional representations seem to evolve during the 20th century, and so the « 16th century » of Lanson proves to be quite different in its discursive form than the one of the current textbooks.Moreover, the canonical « idea » of a 16th century in French Literature is linked to the development of French literary history and its institutional goals. Thus, this idea has to be put in perspective with the ideological values which are meant to be transmitted by the national school curricula, from the end of the 19th century to the beginning of the 21st. This reveals that the notion of a « literary century » is essentially a historical construction, a narrative that ought to be questioned in order to understand its presuppositions and the values that inform its construction.
267

Algorithmes de diagonalisation conjointe par similitude pour la décomposition canonique polyadique de tenseurs : applications en séparation de sources / Joint diagonalization by similarity algorithms for the canonical polyadic decomposition of tensors : Applications in blind source separation

André, Rémi 07 September 2018 (has links)
Cette thèse présente de nouveaux algorithmes de diagonalisation conjointe par similitude. Cesalgorithmes permettent, entre autres, de résoudre le problème de décomposition canonique polyadiquede tenseurs. Cette décomposition est particulièrement utilisée dans les problèmes deséparation de sources. L’utilisation de la diagonalisation conjointe par similitude permet de paliercertains problèmes dont les autres types de méthode de décomposition canonique polyadiquesouffrent, tels que le taux de convergence, la sensibilité à la surestimation du nombre de facteurset la sensibilité aux facteurs corrélés. Les algorithmes de diagonalisation conjointe par similitudetraitant des données complexes donnent soit de bons résultats lorsque le niveau de bruit est faible,soit sont plus robustes au bruit mais ont un coût calcul élevé. Nous proposons donc en premierlieu des algorithmes de diagonalisation conjointe par similitude traitant les données réelles etcomplexes de la même manière. Par ailleurs, dans plusieurs applications, les matrices facteursde la décomposition canonique polyadique contiennent des éléments exclusivement non-négatifs.Prendre en compte cette contrainte de non-négativité permet de rendre les algorithmes de décompositioncanonique polyadique plus robustes à la surestimation du nombre de facteurs ou lorsqueces derniers ont un haut degré de corrélation. Nous proposons donc aussi des algorithmes dediagonalisation conjointe par similitude exploitant cette contrainte. Les simulations numériquesproposées montrent que le premier type d’algorithmes développés améliore l’estimation des paramètresinconnus et diminue le coût de calcul. Les simulations numériques montrent aussi queles algorithmes avec contrainte de non-négativité améliorent l’estimation des matrices facteurslorsque leurs colonnes ont un haut degré de corrélation. Enfin, nos résultats sont validés à traversdeux applications de séparation de sources en télécommunications numériques et en spectroscopiede fluorescence. / This thesis introduces new joint eigenvalue decomposition algorithms. These algorithms allowamongst others to solve the canonical polyadic decomposition problem. This decomposition iswidely used for blind source separation. Using the joint eigenvalue decomposition to solve thecanonical polyadic decomposition problem allows to avoid some problems whose the others canonicalpolyadic decomposition algorithms generally suffer, such as the convergence rate, theoverfactoring sensibility and the correlated factors sensibility. The joint eigenvalue decompositionalgorithms dealing with complex data give either good results when the noise power is low, orthey are robust to the noise power but have a high numerical cost. Therefore, we first proposealgorithms equally dealing with real and complex. Moreover, in some applications, factor matricesof the canonical polyadic decomposition contain only nonnegative values. Taking this constraintinto account makes the algorithms more robust to the overfactoring and to the correlated factors.Therefore, we also offer joint eigenvalue decomposition algorithms taking advantage of thisnonnegativity constraint. Suggested numerical simulations show that the first developed algorithmsimprove the estimation accuracy and reduce the numerical cost in the case of complexdata. Our numerical simulations also highlight the fact that our nonnegative joint eigenvaluedecomposition algorithms improve the factor matrices estimation when their columns have ahigh correlation degree. Eventually, we successfully applied our algorithms to two blind sourceseparation problems : one concerning numerical telecommunications and the other concerningfluorescence spectroscopy.
268

Hamilton-Jacobi Theory and Superintegrable Systems

Armstrong, Craig Keith January 2007 (has links)
Hamilton-Jacobi theory provides a powerful method for extracting the equations of motion out of some given systems in classical mechanics. On occasion it allows some systems to be solved by the method of separation of variables. If a system with n degrees of freedom has 2n - 1 constants of the motion that are polynomial in the momenta, then that system is called superintegrable. Such a system can usually be solved in multiple coordinate systems if the constants of the motion are quadratic in the momenta. All superintegrable two dimensional Hamiltonians of the form H = (p_x)sup2 + (p_y)sup2 + V(x,y), with constants that are quadratic in the momenta were classified by Kalnins et al [5], and the coordinate systems in which they separate were found. We discuss Hamilton-Jacobi theory and its development from a classical viewpoint, as well as superintegrability. We then proceed to use the theory to find equations of motion for some of the superintegrable Hamiltonians from Kalnins et al [5]. We also discuss some of the properties of the Poisson algebra of those systems, and examine the orbits.
269

非線性典型相關分析的應用 / The application of nonlinear canonical correlation analysis

趙瑞韻, Chao, Jui Yun Unknown Date (has links)
隨著典型相關分析應用的日益廣泛,線性典型相關分析並不足以描述兩個主題事務間確實的關連及與其個別相關事務的互動關係,為了更適切地解釋資料數據背後所表達的現象,近來不斷地有關於非線性典型相關分析的理論發表,本文利用1992年Sheng所發表的非線性典型相關分析的理論,將之應用在對臺灣地區民國八十二年的前二十五名最有聲望的企業的資料分析上,並比較應用線性典型相關分析與非線性典型相關分析做資料分析的結果。
270

Spatial pattern and uncertainty of soil carbon and nitrogen in a subtropical savanna landscape in southern Texas

Liu, Feng 15 May 2009 (has links)
Woody invasion into grasslands has been reported world-wide and has affected both the magnitude and spatial heterogeneity of soil carbon (C) and nitrogen (N). Since grasslands cover a large portion of the Earth's land surface, invasion of woody plants could have impacts on regional and global biogeochemistry. To understand large-scale ecological and policy implications of woody invasion, it is critical to understand the spatial pattern and uncertainty of soil C and N and their relationship with vegetation and soil attributes, as well as develop effective approaches to estimate soil C and N over large landscapes and regions. The goal of this study was to improve our understanding of the spatial pattern of soil organic carbon (SOC) and total nitrogen (TN) and their controlling factors in savanna landscapes and develop efficient sampling strategies for evaluating the effects of woody invasion. Specific objectives of this study were to: (1) Quantify the spatial pattern and uncertainty associated with SOC and develop efficient sampling strategies to estimate SOC storage; (2) Assess the influence of soil and vegetation factors on spatial distribution of SOC and TN; and (3) Determine the influence of physical variables related to landscape position and soil on woody vegetation structure. Conditional sequential indicator simulations indicated that woody encroachment into grassland increased both spatial heterogeneity and uncertainty of SOC, which increased errors in estimating SOC storage. Stratified random sampling with higher density in woody patches, plus structured sampling in cluster with strong spatial pattern, substantially increased estimation accuracy. Efficient sampling strategies for estimating SOC storage were developed based on these findings. Direct and spatial correlation and scaling analyses showed that SOC and TN were strongly correlated with litter and root biomass. Invaded woody vegetation has the most impact on spatial distribution of SOC and TN. Canonical correspondence analysis showed that variables related to landscape position were the primary factors determining the spatial distribution of woody species. These new insights will facilitate the estimation of soil C and N pools at landscape and regional scales, and will help evaluate the potential impacts of woody plant encroachment on the biogeochemistry of C and N.

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