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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.
151

Design and Analysis of a Composite Monocoque for Structural Performance : a Comprehensive Approach

Kamble, Meghana P. 08 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Lately numerous studies have been performed to design composite monocoques with high strength and low weight for various student level racing contests. The objective of this paper is to develop an insightful methodology to design and de veloped a light-weight composite monocoque. The monocoque is designed to pass the mandatory static load tests laid down by the International Automobile Feder ation (FIA)Formula 3. These Formula 3 tests are considered the baseline of the desired structural integrity of the composite monocoque. The presented design tech nique emphasises on a monocoque developed for Sports Car Club of America (SCCA) races. The three standard load tests performed on the monocoque are Survival Cell Side test, Fuel Tank test and Side Intrusion test. A sandwich layup of bi-directional woven carbon/epoxy prepreg and aluminium honeycomb is optimized for minimum weight while predicting the unknown properties of layup and ensuring the mono coque doesnt experience failure. The approach intends to achieve minimum weight with high torsional rigidity and is capable of being used for the design and analysis of any kind of formula type composite monocoque.
152

Numerical Insights Into the Effect of Spacing on Axial Resistance of Auger Cast Piles

Correa Prada, Edgar Camilo 01 January 2023 (has links) (PDF)
The present thesis evaluates numerically and experimentally if the axial capacity of Auger Cast Piles (ACPs) constructed in interbedded layers of granular soil and Limestone should be reduced as a function of pile spacing. The numerical component of this thesis includes a series of parametric studies that consider different sets of normalized spacings, stiffness ratios, relative densities, unconfined compressive strengths, and installation effects for multiple subsurface conditions. The experimental program designed herein involves the construction of multiple components for a laboratory testing program of small-scale physical models that will validate the results of the numerical models in terms of capacities, efficiency ratios and normalized spacings.
153

Identificación y priorización de factores críticos para implantar buenas prácticas agrícolas en productores de café y frutas en el departamento del Huila en Colombia

Gutiérrez Guzmán, Nelson 15 December 2008 (has links)
El presente trabajo comprende dos grandes secciones; en la primera sección se realiza la identificación los factores críticos para implantar un programa de BPA en productores de café y frutas en el departamento del Huila en Colombia, utilizando un análisis de componentes principales (ACP) sobre los resultados de la aplicación de dos instrumentos de evaluación con estructura definida: el instrumento Starbucks C.A.F.E. practices - pequeños caficultores para el caso de los productores de café y el instrumento EUREPGAP V2.1 Oct.2004 - Checklist/Listado de verificación para frutas y Hortalizas, aplicado a los productores de fruta. La segunda parte del estudio fue considerada como la solución de un problema complejo para establecer el orden de prioridades de los factores identificados en el apartado anterior, sobre la implantación del protocolo de buenas practicas agrícolas, se resolvió mediante la utilización de una técnica de decisión multicriterio, utilizando específicamente un proceso de análisis jerárquico (AHP); así mismo, se definió el orden mas adecuado para la implementación de las alternativas de solución que permitirán superar las barreras impuestas por los factores críticos. / Gutiérrez Guzmán, N. (2008). Identificación y priorización de factores críticos para implantar buenas prácticas agrícolas en productores de café y frutas en el departamento del Huila en Colombia [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/3790
154

La sécurité du système bancaire africain : contribution à la modernisation de la régulation bancaire dans la CEMAC / The security of the african banking system : contribution to the modernization of banking regulation in the CEMAC

Ngomo Obiang, Renaud Fernand 14 May 2014 (has links)
La recrudescence des crises bancaires et financières place la problématique de la sécurité financière au centre des grands enjeux des politiques de régulation économique. En effet, la crise dite des Subprimes et les crises budgétaires y consécutives, puis la crise chypriote avec le sentiment de défiance du public qui en a résulté, amènent à penser que seule la sécurité financière permet de sauvegarder l’industrie financière malgré elle. Cet enjeu, plus pragmatique du reste, semble davantage trouver un écho en droit, contrairement à celui de stabilité financière qui apparait plutôt subjective, voire incantatoire.En Afrique centrale, comme dans les systèmes juridiques de tradition romano-latine, la question de la sécurité financière procède d’abord du statut juridique des déposants bancaires, de leur place dans l’ordre légal de désintéressement des créanciers, en cas défaillance. Mais la question de la sécurité d’un système bancaire intéresse aussi les établissements de crédit eux-mêmes, non simplement en raison de la nature risquée de leurs activités de transformation, mais surtout en raison de l’existence d’un risque systémique exacerbé par l’ingénierie financière. La question de la sécurité se pose dès lors non simplement en terme de protection des acteurs pris individuellement, mais davantage en terme de préservation voire de sauvegarde de l’outil économique qu’est le système bancaire et/ou financier. / The resurgence of banking and financial crises up the issue of financial security at the center of major policy issues of economic regulation. Indeed, the so-called subprime crisis and subsequent fiscal crises there, and the Cyprus crisis with a sense of public defiance that resulted, one may suggest that financial security will save the financial industry in spite of herself. This issue, more pragmatic moreover, seems to resonate more in law, unlike that of financial stability that appears rather subjective or incantatory. In Central Africa, as in the legal systems of Roman- Latin tradition, the question of financial security shall first the legal status of bank depositors, their place in the legal order of payment of creditors in the event of failure. But the question of the security of the banking system as interest credit institutions themselves, not simply because of the risky nature of their processing activities, but mainly because of the existence of systemic risk exacerbated by financial engineering. The question of safety arises therefore not simply in terms of protection of individual players , but more in terms of preservation or backup tool called economic banking and / or financial .
155

Terahertz imaging and spectroscopy : application to defense and security / Imagerie et spectroscopie térahertz : application aux problématiques de défense et de sécurité

Bou Sleiman, Joyce 02 June 2016 (has links)
Le but de ce travail est de quantifier le potentiel et les capacités de la technologie térahertz à contrôler des colis afin de détecter les menaces telles que les armes et les explosifs, sans avoir besoin d'ouvrir le colis.Dans cette étude, nous présentons la spectroscopie térahertz résolue en temps et l'imagerie multi-spectrale pour la détection des explosifs. Deux types d’explosifs, ainsi que leurs mélanges binaires sont analysés. En raison de la complexité de l'extraction des informations face à tels échantillons, trois outils de chimiométrie sont utilisés: l’analyse en composantes principales (ACP), l'analyse des moindres carrés partiels (PLS) et l'analyse des moindres carrés partiels discriminante (PLS-DA). Les méthodes sont appliquées sur des données spectrales térahertz et sur des images spectrales pour : (i) décrire un ensemble de données inconnues et identifier des similitudes entre les échantillons par l'ACP ; (ii) créer des classes, ensuite classer les échantillons inconnus par PLS-DA ; (iii) créer un modèle capable de prédire les concentrations d’un explosif, à l'état pur ou dans des mélanges, par PLS.Dans la deuxième partie de ce travail, nous présentons l'imagerie par les ondes millimétriques pour la détection d'armes dans les colis. Trois techniques d'imagerie différentes sont étudiées : l'imagerie passive, l’imagerie active par des ondes continues (CW) et l’imagerie active par modulation de fréquence (FMCW). Les performances, les avantages et les limitations de chacune de ces techniques, pour l’inspection de colis, sont présentés. En outre, la technique de reconstruction tomographique est appliquée à chacune de ces trois techniques, pour visualiser en 3D et inspecter les colis en volume. Dans cet ordre, un algorithme de tomographie spécial est développé en prenant en considération la propagation gaussienne de l'onde. / The aim of this work is to demonstrate the potential and capabilities of terahertz technology for parcels screening and inspection to detect threats such as weapons and explosives, without the need to open the parcel.In this study, we first present terahertz time-domain spectroscopy and spectral imaging for explosives detection. Two types of explosives as well as their binary mixture is analyzed. Due to the complexity of extracting information when facing such mixtures of samples, three chemometric tools are used: principal component analysis (PCA), partial least square analysis (PLS) and partial least squares-discriminant analysis (PLS-DA). The analyses are applied to terahertz spectral data and to spectral-images in order to: (i) describe a set of unknown data and identify similarities between samples by PCA; (ii) create a classification model and predict the belonging of unknown samples to each of the classes, by PLS-DA; (iii) create a model able to quantify and predict the explosive concentrations in a pure state or in mixtures, by PLS.The second part of this work focuses on millimeter wave imaging for weapon detection in parcels. Three different imaging techniques are studied: passive imaging, continuous wave (CW) active imaging and frequency modulated continuous wave (FMCW) active imaging. The performances, the advantages and the limitations of each of the three techniques, for parcel inspection, are exhibited. Moreover, computed tomography is applied to each of the three techniques to visualize data in 3D and inspect parcels in volume. Thus, a special tomography algorithm is developed by taking in consideration the Gaussian propagation of the wave.
156

Diagnóstico hiperespectral da relação textural entre horizontes de solo: construindo índices / Hyperspectral diagnostic of textural ratio between soil horizons: building indices

Souza, Arnaldo Barros e 20 January 2016 (has links)
A adoção de medidas afinadas à conservação do solo não é apenas uma necessidade, há muito passou a ser estratégico desenvolver técnicas que preencham as lacunas de informação e maximizem o uso adequado do solo. A diferenciação textural entre horizontes de solos é um dos principais aspectos a ser considerado quando do planejamento do uso do solo, pois se relaciona estreitamente com fatores como o enraizamento, a percolação e disponibilidade de água e a susceptibilidade dos solos à erosão. Diante disso, objetivou-se desenvolver Índices Espectroscópicos de Relação Textural (IERT) que estabeleçam quantitativamente o grau de diferenciação textural em perfis de solos via espectroscopia VisNIR-SWIR (350-2.500 nm) e MidIR (4000 - 400 cm-1). Foram utilizados dados espectrais de 150 perfis de solos descritos morfologicamente pertencentes a nove municípios das regiões Sudeste e Centro-Oeste do Brasil. Três modelos espectrais, VisNIR-SWIR, MidIR e VisNIR-SWIR-MidIR foram associados aos teores analíticos de matéria orgânica dos horizontes A e B, totalizando nove modelos, afim de se verificar o potencial daqueles puramente espectrais. Todos os modelos foram estudados por análises de funções discriminantes (CP-AFD) e regressão por mínimos quadrados (PLSR). A construção dos IERT\'s, num total de 15, cinco para cada modelo espectral, considerou a diferença de reflectância em bandas específicas ou associações entre elas, as quais foram selecionadas com base no estudo qualitativo e quantitativo das curvas espectrais. De modo geral, a diferenciação entre horizontes é ditada pelas regiões espectrais associadas principalmente aos óxidos de Fe, minerais de argila e quartzo. É possível determinar o grau de diferenciação textural entre horizontes de perfis de solos com excelente acurácia através de dados espectrais com taxa de acerto global de até 100 %, R2 de 0,76 a 0,82 e RPD de 2,02 a 2,35 nos modelos puramente espectrais, com destaque à região MidIR. O uso de IERT\'s produz bons a excelentes resultados, com R2 de 0,71 a 0,80 e RDP de 1,84 a 2,21 para os melhores índices de cada região espectral. O uso de índices espectrais reduz a dependência de métodos estatísticos avançados e dá suporte ao desenvolvimento de equipamentos óticos que trabalhem em regiões espectrais específicas, reduzindo custos e maximizando a aplicabilidade da técnica. Estudos abrangentes e exaustivos são indispensáveis antes que novos métodos como este se estabeleçam, particularmente em ciência do solo, na qual o objeto de estudo é, por natureza, complexo e intrigante. / The adoption of measures related to soil conservation is not only a necessity, long it has become strategic to develop techniques that meet the information deficits and maximize the appropriate use of land. The textural differentiation between soil horizons is one of the main aspects to be considered dealing with land use planning as it closely relates to factors such as rooting, percolation and water availability and the susceptibility of soils to erosion. Therefore, it was aimed to develop Spectral Textural Ratio Indices (STRI) that quantitatively establish the degree of textural differentiation in soil profiles through VisNIR-SWIR (350-2500 nm) and MidIR (4000- 400 cm-1) spectroscopy. Spectral data of 150 soil profiles morphologically described belonging to nine municipalities in the Southeast and Midwest of Brazil were used. Three spectral models, VisNIR-SWIR, MidIR and VisNIR-SWIR-MidIR were associated with analytical organic matter content of the A and B horizons, comprising nine models in order to verify the potential of those purely spectral. All models were studied by discriminant functions analysis (CP-DFA) and Partial Least Square Regression (PLSR). The construction of the STRIs, a total of 15, five for each spectral model, considered the reflectance difference in specific bands or associations between them, which were selected based on the qualitative and quantitative study of spectral curves. In general, the differentiation between horizons is dictated primarily by spectral regions associated with iron oxides, clay minerals and quartz. It is possible to determine the degree of textural differentiation between soil profile horizons with great accuracy through spectral data with overall accuracy rate of up to 100%, R2 from 0.76 to 0.82 and RPD from 2.02 to 2.35 in the purely spectral models, with emphasis on MidIR region. The use of STRIs produces good to excellent results, with R2 ranging from 0.71 to 0.80 and RPD ranging from 1.84 to 2.21 for the best rates of each spectral region. The use of spectral indices reduces reliance on advanced statistical methods and supports the development of optical devices that work in specific spectral regions, reducing costs and maximizing the applicability of the technique. Large and exhaustive studies are imperatives before new methods like this are established, particularly in soil science, in which the object of study is by nature complex and intriguing.
157

Modelagem farmacocinética-farmacodinâmica da morfina administrada através de bomba controlada pelo paciente no pós-operatório de revascularização do miocárdio / Morphine pharmacokinetic-pharmacodynamic modeling administered by patient controlled analgesia (PCA) pump in the postoperative period of myocardial revascularization surgery

Santos, Verônica Jorge 17 March 2008 (has links)
Introdução: A administração de morfina através de bomba de infusão controlada pelo paciente (ACP) no tratamento da dor pós-cirurgica e traumática tem-se mostrado promissora e faz parte da rotina terapêutica de muitos hospitais. No entanto, doses altas ou repetidas deste opióide estão associadas a efeitos adversos dose dependentes, dentre eles, a depressão respiratória. No caso de pacientes submetidos a cirurgias de tórax, além da analgesia pós-operatória, devem também ser considerados como parâmetros relevantes a anestesia regional (intratecal) no intra-operatório, a qual pode contribuir para melhora da função pulmonar pós-operatória e extubação precoce no pós-operatório e a circulação extracorpórea (CEC), potencial fator de alteração na cinética de fármacos. Objetivos: Investigar a influência da morfina intratecal e da circulação extracorpórea (CEC) sobre o consumo de morfina ACP, área sob a curva e escores de dor no período pós-operatório, bem como propor modelo farmacocinético-farmacodinâmico (PK-PD) para correlação dessas variáveis. Adicionalmente, foi desenvolvido método analítico para quantificação da morfina plasmática. Métodos: 59 pacientes submetidos à cirurgia eletiva de revascularização com CEC e sem CEC, na presença ou não de morfina intratecal intra-operatória foram distribuídos em grupos com base na combinação das intervenções acima mencionadas. No período pós-operatório, todos os pacientes receberam bolus IV de 1mg de morfina, e então o dispositivo ACP foi instalado na unidade de terapia intensiva, através de cateter venoso após a extubação orotraqueal. A morfina ACP foi liberada através de livre demanda solicitada pelo paciente (bolus de 1 mg), lock-out de 5 min até 36 horas do pós-operatório. Coletaram-se amostras seriadas de sangue de cateter venoso no período (3,6,12,18,24,36 horas) e a morfina plasmática foi determinada através da cromatografia líquida - espectrometria de massas (LC-MS/MS ESI+) após a purificação das amostras de plasma. A intensidade da dor foi monitorada no mesmo período pela escala análoga visual (EAV). A modelagem PK-PD foi investigada pelo GraphPad Prism 5.0. Resultados: O consumo de morfina e a intensidade da dor diferiram entre os grupos. O modelo do EMAX e a curva de histerese foram propostos pela modelagem PK-PD. Conclusões: O método analítico mostrou-se adequado na determinação da morfina plasmática. O consumo de morfina os escores de dor EAV no pós-operatório diferiram pela comparação dos grupos de pacientes investigados. Menores doses de morfina ACP foram requeridas pelos pacientes que receberam morfina intratecal intra-operatória. Demonstrou-se através do modelo do EMAX correlação não linear entre os parâmetros consumo de morfina e AUC0-36, e curva de histerese foi obtida quando se plotou consumo de morfina versus escore de dor. / Introduction: Morphine administration using patient controlled analgesia (PCA) for treatment of post surgical and traumatic pain has been a current practice in many hospitals. However, large or repeated doses of this opioid are associated to dose dependent adverse events, including, respiratory depression. Considering patients submitted to thoracic surgery, in addition to the postoperatory analgesia, two other relevant parameters must be considered: regional anesthesia (intrathecal) in the intra-operatory period, which should contribute to the respiratory function improvement and decrease in the extubation time; and the cardiopulmonary bypass (OPCAB), that potentially alters the drugs\' kinetics. Objectives: To investigate the influence of intrathecal morphine administration and cardiopulmonary bypass (OPCAB) in the morphine PCA drug requirements, area under the curve of morphine plasma concentration versus time and pain scores in the postoperative period, and to choose a pharmacokinetic-pharmacodynamic model to correlate these variables. In addition, an analytical method was developed to quantify morphine in plasma. Methods: 59 patients submitted to elective coronary artery bypass grafting (CABG) with (CPB) and without cardiopulmonary bypass (OPCAB), with and without intrathecal morphine in the intra-operative period were distributed by the combination of the above mentioned interventions. In the postoperative period, all the patients were given an IV bolus of 1mg of morphine, and then PCA device was installed in the intensive care unit by a venous catheter after the orotracheal extubation. Morphine PCA was delivered on demand (boluses of 1 mg), lock-out of 5 min until 36 hours of the postoperative period. A serial of blood samples were collected from venous catheter of patients at the postoperative period (3,6,12,18,24,36 hrs) and morphine plasma concentrations were determined by Liquid Chromatography-Mass Spectrometry ((LC-MS/MS ESI+)) after the purification of plasma samples. Pain scores were monitored during the same period by a visual analogue scale, VAS or 1-2-3 pain scale. PK-PD modeling was investigated by applying the GraphPad Prism 5.0. Results: Drug dose requirements and analgesia were significant different in patients of groups investigated. EMAX model and the hysteresis curve were proposed by PK-PD modeling to correlate drug requirements and AUC 0-36 or VAS. Conclusions: LC-MS/MS (ESI+) method was adequate for drug measurements in plasma. Morphine dose requirements and analgesia were different by comparison of groups. Lower doses of morphine by PCA were required for the groups that have received intrathecal morphine intraoperatively. It was demonstrated a non linear correlation between parameters by EMAX model when drug requirements and AUC0-36 were plotted, and the hysteresis curve was obtained when analgesia dose requirements was plotted against pain score.
158

Modelagem farmacocinética-farmacodinâmica da morfina administrada através de bomba controlada pelo paciente no pós-operatório de revascularização do miocárdio / Morphine pharmacokinetic-pharmacodynamic modeling administered by patient controlled analgesia (PCA) pump in the postoperative period of myocardial revascularization surgery

Verônica Jorge Santos 17 March 2008 (has links)
Introdução: A administração de morfina através de bomba de infusão controlada pelo paciente (ACP) no tratamento da dor pós-cirurgica e traumática tem-se mostrado promissora e faz parte da rotina terapêutica de muitos hospitais. No entanto, doses altas ou repetidas deste opióide estão associadas a efeitos adversos dose dependentes, dentre eles, a depressão respiratória. No caso de pacientes submetidos a cirurgias de tórax, além da analgesia pós-operatória, devem também ser considerados como parâmetros relevantes a anestesia regional (intratecal) no intra-operatório, a qual pode contribuir para melhora da função pulmonar pós-operatória e extubação precoce no pós-operatório e a circulação extracorpórea (CEC), potencial fator de alteração na cinética de fármacos. Objetivos: Investigar a influência da morfina intratecal e da circulação extracorpórea (CEC) sobre o consumo de morfina ACP, área sob a curva e escores de dor no período pós-operatório, bem como propor modelo farmacocinético-farmacodinâmico (PK-PD) para correlação dessas variáveis. Adicionalmente, foi desenvolvido método analítico para quantificação da morfina plasmática. Métodos: 59 pacientes submetidos à cirurgia eletiva de revascularização com CEC e sem CEC, na presença ou não de morfina intratecal intra-operatória foram distribuídos em grupos com base na combinação das intervenções acima mencionadas. No período pós-operatório, todos os pacientes receberam bolus IV de 1mg de morfina, e então o dispositivo ACP foi instalado na unidade de terapia intensiva, através de cateter venoso após a extubação orotraqueal. A morfina ACP foi liberada através de livre demanda solicitada pelo paciente (bolus de 1 mg), lock-out de 5 min até 36 horas do pós-operatório. Coletaram-se amostras seriadas de sangue de cateter venoso no período (3,6,12,18,24,36 horas) e a morfina plasmática foi determinada através da cromatografia líquida - espectrometria de massas (LC-MS/MS ESI+) após a purificação das amostras de plasma. A intensidade da dor foi monitorada no mesmo período pela escala análoga visual (EAV). A modelagem PK-PD foi investigada pelo GraphPad Prism 5.0. Resultados: O consumo de morfina e a intensidade da dor diferiram entre os grupos. O modelo do EMAX e a curva de histerese foram propostos pela modelagem PK-PD. Conclusões: O método analítico mostrou-se adequado na determinação da morfina plasmática. O consumo de morfina os escores de dor EAV no pós-operatório diferiram pela comparação dos grupos de pacientes investigados. Menores doses de morfina ACP foram requeridas pelos pacientes que receberam morfina intratecal intra-operatória. Demonstrou-se através do modelo do EMAX correlação não linear entre os parâmetros consumo de morfina e AUC0-36, e curva de histerese foi obtida quando se plotou consumo de morfina versus escore de dor. / Introduction: Morphine administration using patient controlled analgesia (PCA) for treatment of post surgical and traumatic pain has been a current practice in many hospitals. However, large or repeated doses of this opioid are associated to dose dependent adverse events, including, respiratory depression. Considering patients submitted to thoracic surgery, in addition to the postoperatory analgesia, two other relevant parameters must be considered: regional anesthesia (intrathecal) in the intra-operatory period, which should contribute to the respiratory function improvement and decrease in the extubation time; and the cardiopulmonary bypass (OPCAB), that potentially alters the drugs\' kinetics. Objectives: To investigate the influence of intrathecal morphine administration and cardiopulmonary bypass (OPCAB) in the morphine PCA drug requirements, area under the curve of morphine plasma concentration versus time and pain scores in the postoperative period, and to choose a pharmacokinetic-pharmacodynamic model to correlate these variables. In addition, an analytical method was developed to quantify morphine in plasma. Methods: 59 patients submitted to elective coronary artery bypass grafting (CABG) with (CPB) and without cardiopulmonary bypass (OPCAB), with and without intrathecal morphine in the intra-operative period were distributed by the combination of the above mentioned interventions. In the postoperative period, all the patients were given an IV bolus of 1mg of morphine, and then PCA device was installed in the intensive care unit by a venous catheter after the orotracheal extubation. Morphine PCA was delivered on demand (boluses of 1 mg), lock-out of 5 min until 36 hours of the postoperative period. A serial of blood samples were collected from venous catheter of patients at the postoperative period (3,6,12,18,24,36 hrs) and morphine plasma concentrations were determined by Liquid Chromatography-Mass Spectrometry ((LC-MS/MS ESI+)) after the purification of plasma samples. Pain scores were monitored during the same period by a visual analogue scale, VAS or 1-2-3 pain scale. PK-PD modeling was investigated by applying the GraphPad Prism 5.0. Results: Drug dose requirements and analgesia were significant different in patients of groups investigated. EMAX model and the hysteresis curve were proposed by PK-PD modeling to correlate drug requirements and AUC 0-36 or VAS. Conclusions: LC-MS/MS (ESI+) method was adequate for drug measurements in plasma. Morphine dose requirements and analgesia were different by comparison of groups. Lower doses of morphine by PCA were required for the groups that have received intrathecal morphine intraoperatively. It was demonstrated a non linear correlation between parameters by EMAX model when drug requirements and AUC0-36 were plotted, and the hysteresis curve was obtained when analgesia dose requirements was plotted against pain score.
159

Diagnóstico hiperespectral da relação textural entre horizontes de solo: construindo índices / Hyperspectral diagnostic of textural ratio between soil horizons: building indices

Arnaldo Barros e Souza 20 January 2016 (has links)
A adoção de medidas afinadas à conservação do solo não é apenas uma necessidade, há muito passou a ser estratégico desenvolver técnicas que preencham as lacunas de informação e maximizem o uso adequado do solo. A diferenciação textural entre horizontes de solos é um dos principais aspectos a ser considerado quando do planejamento do uso do solo, pois se relaciona estreitamente com fatores como o enraizamento, a percolação e disponibilidade de água e a susceptibilidade dos solos à erosão. Diante disso, objetivou-se desenvolver Índices Espectroscópicos de Relação Textural (IERT) que estabeleçam quantitativamente o grau de diferenciação textural em perfis de solos via espectroscopia VisNIR-SWIR (350-2.500 nm) e MidIR (4000 - 400 cm-1). Foram utilizados dados espectrais de 150 perfis de solos descritos morfologicamente pertencentes a nove municípios das regiões Sudeste e Centro-Oeste do Brasil. Três modelos espectrais, VisNIR-SWIR, MidIR e VisNIR-SWIR-MidIR foram associados aos teores analíticos de matéria orgânica dos horizontes A e B, totalizando nove modelos, afim de se verificar o potencial daqueles puramente espectrais. Todos os modelos foram estudados por análises de funções discriminantes (CP-AFD) e regressão por mínimos quadrados (PLSR). A construção dos IERT\'s, num total de 15, cinco para cada modelo espectral, considerou a diferença de reflectância em bandas específicas ou associações entre elas, as quais foram selecionadas com base no estudo qualitativo e quantitativo das curvas espectrais. De modo geral, a diferenciação entre horizontes é ditada pelas regiões espectrais associadas principalmente aos óxidos de Fe, minerais de argila e quartzo. É possível determinar o grau de diferenciação textural entre horizontes de perfis de solos com excelente acurácia através de dados espectrais com taxa de acerto global de até 100 %, R2 de 0,76 a 0,82 e RPD de 2,02 a 2,35 nos modelos puramente espectrais, com destaque à região MidIR. O uso de IERT\'s produz bons a excelentes resultados, com R2 de 0,71 a 0,80 e RDP de 1,84 a 2,21 para os melhores índices de cada região espectral. O uso de índices espectrais reduz a dependência de métodos estatísticos avançados e dá suporte ao desenvolvimento de equipamentos óticos que trabalhem em regiões espectrais específicas, reduzindo custos e maximizando a aplicabilidade da técnica. Estudos abrangentes e exaustivos são indispensáveis antes que novos métodos como este se estabeleçam, particularmente em ciência do solo, na qual o objeto de estudo é, por natureza, complexo e intrigante. / The adoption of measures related to soil conservation is not only a necessity, long it has become strategic to develop techniques that meet the information deficits and maximize the appropriate use of land. The textural differentiation between soil horizons is one of the main aspects to be considered dealing with land use planning as it closely relates to factors such as rooting, percolation and water availability and the susceptibility of soils to erosion. Therefore, it was aimed to develop Spectral Textural Ratio Indices (STRI) that quantitatively establish the degree of textural differentiation in soil profiles through VisNIR-SWIR (350-2500 nm) and MidIR (4000- 400 cm-1) spectroscopy. Spectral data of 150 soil profiles morphologically described belonging to nine municipalities in the Southeast and Midwest of Brazil were used. Three spectral models, VisNIR-SWIR, MidIR and VisNIR-SWIR-MidIR were associated with analytical organic matter content of the A and B horizons, comprising nine models in order to verify the potential of those purely spectral. All models were studied by discriminant functions analysis (CP-DFA) and Partial Least Square Regression (PLSR). The construction of the STRIs, a total of 15, five for each spectral model, considered the reflectance difference in specific bands or associations between them, which were selected based on the qualitative and quantitative study of spectral curves. In general, the differentiation between horizons is dictated primarily by spectral regions associated with iron oxides, clay minerals and quartz. It is possible to determine the degree of textural differentiation between soil profile horizons with great accuracy through spectral data with overall accuracy rate of up to 100%, R2 from 0.76 to 0.82 and RPD from 2.02 to 2.35 in the purely spectral models, with emphasis on MidIR region. The use of STRIs produces good to excellent results, with R2 ranging from 0.71 to 0.80 and RPD ranging from 1.84 to 2.21 for the best rates of each spectral region. The use of spectral indices reduces reliance on advanced statistical methods and supports the development of optical devices that work in specific spectral regions, reducing costs and maximizing the applicability of the technique. Large and exhaustive studies are imperatives before new methods like this are established, particularly in soil science, in which the object of study is by nature complex and intriguing.
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Modèles statistiques d'apparence non gaussiens. Application à la création d'un atlas probabiliste de perfusion cérébrale en imagerie médicale

Vik, Torbjorn 21 September 2004 (has links) (PDF)
La tomoscintigraphie par émission mono-photonique (TEMP) est une méthode d'imagerie fonctionnelle 3D qui apporte des informations sur le débit sanguin cérébral (également appelé perfusion cérébrale). Cette méthode d'imagerie, par la détection visuelle d'anomalies de perfusion caractérisées par des zones hypo- ou hyper-intenses, est utilisée pour le diagnostic chez des patients atteints d'accidents vasculaires cérébraux, de démence, d'épilepsie ou d'autres pathologies cérébrales. La détection d'anomalies focalisées observées chez les patients ayant une attaque cérébrale est relativement aisée, alors que les anomalies diffuses, observées en début de démence, lors d'un accident entraînant une oxygénation insuffisante du cerveau ou suite à une exposition à une substance toxique, sont plus difficilement observables. Dans ces cas, une analyse quantitative des images, utilisant un atlas et des outils statistiques s'appuyant sur une base d'images de cas normaux, peut apporter une aide précieuse au diagnostic. Le travail présenté dans cette thèse est centré sur la problématique de la construction et de l'évaluation d'un atlas probabiliste de perfusion cérébrale à partir des images TEMP de sujets dits normaux. Les objectifs d'un tel atlas sont doubles : (1) création d'une cartographie statistique de la perfusion cérébrale d'une population normale, décrite de manière compacte, et (2) identification des différences de perfusion cérébrale qui sont statistiquement significatives entre une image TEMP d'un individu et l'atlas probabiliste. L'utilisation d'un atlas devrait avoir un impact important sur les applications cliniques où l'analyse qualitative d'images TEMP est pratique courante. Afin d'atteindre ces objectifs, trois points ont été abordés : le développement de modèles statistiques qui décrivent de façon fidèle la perfusion cérébrale, les outils de traitement d'images utilisés pour rendre les cerveaux "comparables", et enfin, l'évaluation expérimentale de l'atlas.

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