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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.
11

THE CARBON AND SULFUR SPECIATION OF DIESEL EMISSIONS FROM A NON-ROAD GENERATOR

LIU, ZIFEI 27 September 2005 (has links)
No description available.
12

Continuous DPM Monitoring in Underground Mine Environments: Demonstration of Potential Options in the Laboratory and Field

Barrett, Chelsea A. 26 March 2018 (has links)
Diesel particulate matter (DPM) is the solid portion of diesel exhaust. DPM occurs primarily in the submicron range, and poses a number of respiratory and other health hazards including cardiovascular and pulmonary disease. Underground miners typically have the highest DPM exposures compared to other occupations. This is because many mines are characterized by confined work spaces and large diesel equipment fleets. Exposures can be a particularly high hazard in large opening mines where ventilation can be challenging. As such, DPM monitoring is critical to protecting miner health and informing a range of engineering decisions. DPM is primarily composed of two components, elemental carbon (EC) and organic carbon (OC), which are often summed to report total carbon (TC). The ratio of EC to OC, and presence of a number of other minor constituents such as sorbed metals, can vary with many factors such as engine operating conditions, maintenance, fuel types and additives, and the level and type of exhaust after-treatments used. Given its complexity, DPM cannot be measured directly, and either TC or EC are generally used as a surrogate. Currently, the Mining Safety and Health Administration (MSHA) limits personal exposures of underground metal/non-metal miners to 160 µg TC/m3 on an 8-hr time weighted average basis. Compliance is demonstrated by collecting full-shift personal filter samples, which are later analyzed using the NIOSH 5040 Standard Method. For engineering purposes, area samples can also be collected and analyzed. The typical lag time between sample collection and reporting of results is on the order of weeks, and this presents a real problem for identifying and remediating conditions that led to overexposures or high DPM in area samples. The handheld FLIR Airtec monitor was developed to provide real-time DPM data and allow immediate decision making. The monitor works on a laser extinction principle to measure EC, the black component of DPM, as mass accumulates on a filter. The Airtec has proven useful for personal monitoring and short-term DPM surveying. However, capabilities are needed for continuous, long-term monitoring. Continuous DPM monitoring would be highly valuable for applications such as design and operation of ventilation on demand systems, or engineering studies of new ventilation, exhaust treatment or other DPM controls. The work presented in this thesis considers three continuous monitors, two of which are already commercially available: Magee Scientific's AE33 black carbon (BC) Aethalometer and Sunset Laboratory's Semi-Continuous OCEC Field Analyzer. The third monitor, called the Airwatch, is still in development. The AE33 and Airwatch effectively operate on the same principle as the Airtec, but include a self-advancing filter tape to allow autonomous operation over relatively long periods of time. The OCEC field monitor is essentially a field version of the laboratory analyzer used for traditional 5040 Method analysis. The AE33 has been briefly demonstrated in mine environments in a couple of other studies, but further testing is needed. The current prototype of the Airwatch and the OCEC field monitor have never been mine-tested. Two separate studies are reported here. The first is a field study in an underground stone mine that tested the Airwatch prototype and AE33 head-to-head under relatively high DPM conditions. Results demonstrated that both instruments could track general trends, but that further work was needed to identify and resolve issues associated with use of both instruments in high-DPM environments – and with basic design elements of the Airwatch. Additionally, the need to calibrate the monitors' output data to the standard measure of EC (i.e., 5040 Method EC) was made clear. In the second study, laboratory testing was conducted under very controlled conditions to meet this need, and another round of field testing was also done. The second study also included the OCEC field monitor. The laboratory tests yielded data to allow interpretation of the AE33 and Airwatch results with respect to 5040 EC. These tests also shed light on the current range EC concentrations over which these monitors can provide reliable data – which is indeed a primary range of interest for mines. As expected, the OCEC field monitor was shown to produce lab-grade results across a wide range of concentrations. The field testing in the second study demonstrated that all three monitors could operate autonomously in a mine environment over extended periods of time (i.e., weeks to months). Overall, it can be concluded that the AE33 and OCEC field monitor represent off-the-shelf options for DPM monitoring in mines, and the Airwatch might be another option if fully developed in the future. Selection of a particular monitoring tool should include careful consideration of specific factors including data quality needs, conditions in the intended monitoring location(s), and general user friendliness of the monitor. / Master of Science
13

Identificação de patologias na laringe com base na Discriminative Paraconsistent Machine (DPM) / Identification of pathology in larynx based on Discriminative Paraconsistent Machine

Barbon Júnior, Sylvio 14 October 2011 (has links)
Este trabalho de doutorado apresenta duas inovações: a Discriminative Paraconsistent Machine (DPM), que consiste em um novo classificador elaborado com base na lógica paraconsistente anotada (LPA) e a aplicação da DPM para a identificação de patologias na laringe, por meio de exames nos sinais de voz de um locutor. Não há relatos na literatura sobre o uso da LPA para construção de um classificador e sobre suas aplicações para a finalidade proposta. Os resultados obtidos são motivadores, indicando um avanço na área. / This PhD thesis presents two novelties: the Discriminative Paraconsistent Machine (DPM), which is a new classifier built on the basis of the annotated paraconsistent logic (APL), and the applications of DPM to identify larynx pathologies, by inspecting a voice signal. There is neither a comment on literature about the use of APL to built a classifier nor about its applications for the proposed application. The results obtained create motivation, showing a clear progress in the field.
14

Identificação de patologias na laringe com base na Discriminative Paraconsistent Machine (DPM) / Identification of pathology in larynx based on Discriminative Paraconsistent Machine

Sylvio Barbon Júnior 14 October 2011 (has links)
Este trabalho de doutorado apresenta duas inovações: a Discriminative Paraconsistent Machine (DPM), que consiste em um novo classificador elaborado com base na lógica paraconsistente anotada (LPA) e a aplicação da DPM para a identificação de patologias na laringe, por meio de exames nos sinais de voz de um locutor. Não há relatos na literatura sobre o uso da LPA para construção de um classificador e sobre suas aplicações para a finalidade proposta. Os resultados obtidos são motivadores, indicando um avanço na área. / This PhD thesis presents two novelties: the Discriminative Paraconsistent Machine (DPM), which is a new classifier built on the basis of the annotated paraconsistent logic (APL), and the applications of DPM to identify larynx pathologies, by inspecting a voice signal. There is neither a comment on literature about the use of APL to built a classifier nor about its applications for the proposed application. The results obtained create motivation, showing a clear progress in the field.
15

Identificação de padrões de sinais acústicos com base em classificação paraconsistente / Identification of acoustic signal patterns based on paraconsistent classification

Paulo, Katia Cristina Silva 20 September 2016 (has links)
Com o uso de um conceito ainda não explorado para fins de classificação de dados, baseado em Lógica Paraconsistente Anotada (LPA), este trabalho visa à construção de um sistema inteligente para classificação de gêneros musicais (Music Genre Classification - MGC). Este tema, de caráter emergente na literatura, tem recebido atenção crescente da comunidade científica, tendo em vista a sua grande aplicabilidade, destacando-se o potencial de comercialização de dados multimídia pela Internet, assim como a automatização de inúmeras tarefas de data mining que envolvem sinais musicais. Utilizando uma base de dados composta por amostras de músicas representativas de cada gênero musical, tais como jazz, bolero, bossa nova, forró, salsa e sertanejo, assim como de um classificador discriminativo paraconsistente, uma abordagem supervisionada é proposta para solucionar o problema. O primeiro módulo do sistema realiza a extração de características dos diversos segmentos das músicas com base na análise tempo-frequência associada com as bandas críticas do ouvido humano. Por outro lado, o segundo módulo utiliza o classificador proposto, que deve permitir a manipulação de sinais com características contraditórias de uma maneira mais semelhante àquela realizada pelo cérebro humano. Os resultados, quando comparados com as abordagens pré-existentes para MGC, demonstram a viabilidade do uso da LPA para tal fim. Além disso, caracteriza-se neste trabalho, uma contribuição original ao estado-da-arte no tema, que consiste justamente no uso da LPA para MGC, procedimento para o qual inexiste descrição na literatura até este momento. / By using a new concept, which is based on Paraconsistent Logic (LPA) and has not yet been applied for classification, this work aims at constructing an intelligent system for Music Genre Classification (MGC). This topic, that is emergent in the literature, has received an increasing attention from the scientific community due to its applicability, emphazising both a commercial potential to commercialize multimedia content on the Internet and data mining tasks involving music signals. By adopting a database formed by samples of songs, which represent different styles of music, such as jazz, bolero, bossa nova, forró, salsa and sertanejo, and a discriminative paraconsistent classifier, a supervised procedure is used to solve the problem. The system is divided in two modules. The first extracts features from the music files, based on the concepts of time-frequency analysis and crictical bands of the human ear. On the other hand, the second implements the proposed classifier, which allows an efficient treatment of contradictions in such a way that is more similar to the human brain. The results obtained, when compared with existing approaches used to MGC, demonstrate how LPA is suitable for this purpose. Additionally, this is the original contribution to the state-of-the-art: the use of LPA for MGC, an inexistent approach up to date.
16

Identificação de padrões de sinais acústicos com base em classificação paraconsistente / Identification of acoustic signal patterns based on paraconsistent classification

Katia Cristina Silva Paulo 20 September 2016 (has links)
Com o uso de um conceito ainda não explorado para fins de classificação de dados, baseado em Lógica Paraconsistente Anotada (LPA), este trabalho visa à construção de um sistema inteligente para classificação de gêneros musicais (Music Genre Classification - MGC). Este tema, de caráter emergente na literatura, tem recebido atenção crescente da comunidade científica, tendo em vista a sua grande aplicabilidade, destacando-se o potencial de comercialização de dados multimídia pela Internet, assim como a automatização de inúmeras tarefas de data mining que envolvem sinais musicais. Utilizando uma base de dados composta por amostras de músicas representativas de cada gênero musical, tais como jazz, bolero, bossa nova, forró, salsa e sertanejo, assim como de um classificador discriminativo paraconsistente, uma abordagem supervisionada é proposta para solucionar o problema. O primeiro módulo do sistema realiza a extração de características dos diversos segmentos das músicas com base na análise tempo-frequência associada com as bandas críticas do ouvido humano. Por outro lado, o segundo módulo utiliza o classificador proposto, que deve permitir a manipulação de sinais com características contraditórias de uma maneira mais semelhante àquela realizada pelo cérebro humano. Os resultados, quando comparados com as abordagens pré-existentes para MGC, demonstram a viabilidade do uso da LPA para tal fim. Além disso, caracteriza-se neste trabalho, uma contribuição original ao estado-da-arte no tema, que consiste justamente no uso da LPA para MGC, procedimento para o qual inexiste descrição na literatura até este momento. / By using a new concept, which is based on Paraconsistent Logic (LPA) and has not yet been applied for classification, this work aims at constructing an intelligent system for Music Genre Classification (MGC). This topic, that is emergent in the literature, has received an increasing attention from the scientific community due to its applicability, emphazising both a commercial potential to commercialize multimedia content on the Internet and data mining tasks involving music signals. By adopting a database formed by samples of songs, which represent different styles of music, such as jazz, bolero, bossa nova, forró, salsa and sertanejo, and a discriminative paraconsistent classifier, a supervised procedure is used to solve the problem. The system is divided in two modules. The first extracts features from the music files, based on the concepts of time-frequency analysis and crictical bands of the human ear. On the other hand, the second implements the proposed classifier, which allows an efficient treatment of contradictions in such a way that is more similar to the human brain. The results obtained, when compared with existing approaches used to MGC, demonstrate how LPA is suitable for this purpose. Additionally, this is the original contribution to the state-of-the-art: the use of LPA for MGC, an inexistent approach up to date.
17

SEGUIMIENTO DE PERSONAS APLICANDO RESTRICCIONES CINEMÁTICAS BASADAS EN MODELOS DE CUERPOS RÍGIDOS ARTICULADOS

Martínez Bertí, Enrique 01 September 2017 (has links)
The present thesis deals with the study of vision techniques for the detection of human pose based on the analysis of a single image, as well as the tracking of these poses along a sequence of images. It is proposed to model the human pose by four kinematic chains that model the four articulated extremities. These kinematic chains and head remain attached to the body. The four kinematic chains are composed by three keypoints. Therefore, the model initially has a total of $14$ parts. In this thesis it is proposed to modify the technique called Deformable Parts Model (DPM), adding the depth channel. Initially, the DPM model was defined over three RGB channel images. While in this thesis it is proposed to work on images of four RGBD channels, so the proposed extension is called 4D-DPM. The experiments performed with 4D-DPM demonstrate an improvement in the accuracy of pose detection with respect to the initial DPM model, at the cost of increasing its computational cost when treating an additional channel. On the other hand, it is defined to reduce the previous computational cost by simplifying the model that defines the human pose. The idea is to reduce the number of variables to be detected with the 4D-DPM model, so that the suppressed variables can be calculated from the detected variables using inverse kinematics models based on dual quaternions. In addition, it is proposed to use a particle filter models to continue improving the accuracy of detection of human poses along a sequence of images. Considering the problem of detection and monitoring of human body pose along a video sequence, this thesis proposes the use of the following method. 1. Camara calibration. RGBD image processing. Subtraction of the image background with the MSER method. 2. 4D-DPM: method used to detect the keypoints (variables of the pose model) within an image. 3. Particle filters: this type of filter is designed to track the keypoints over time and correct the data obtained by the sensor. 4. Inverse kinematic modeling: the control of kinematic chains is performed with the help of dual cuaternions in order to obtain the complete pose model of the human body. The overall contribution of this thesis is the proposal of the previous method that, combining the previous methods, is able to improve the accuracy in the detection and the follow up of the human body pose in a video sequence, also reducing its computational cost . This is possible due to the combination of the 4D-DPM method with the use of inverse kinematics techniques. The original DPM method should detect $14$ point of interest on an RGB image to estimate the human pose. However, the proposed method, where a point of interest for each limb is removed, must detect $10$ point of interest on an RGBD image. Subsequently, the eliminated $4$ point of interest are calculated by using inverse kinematics methods from the calculated $10$ point of interest. To solve the problem of inverse kinematics a dual quaternions methods is proposed for each of the $4$ kinematic chains that model the extremities of the skeleton of the human body. The particle filter is applied over the time sequence of the 10 points of interest of the posture model detected through the 4D-DPM method. To design these particle filters it is proposed to add the following restrictions to weight the particles generated: 1. Restrictions on joint limits. 2. Softness restrictions. 3. Collision detection. 4. Projection of poly-spheres / La presente tesis trata sobre el estudio de técnicas de visión para la detección de la postura del esqueleto del cuerpo humano basada en el análisis de una sola imagen, además del seguimiento de estas posturas a lo largo de una secuencia de imágenes. Se propone modelar la postura del esqueleto cuerpo humano mediante cuatro cadenas cinemáticas que modelan las cuatro extremidades articuladas. Estas cadenas cinemáticas y la cabeza permanecen unidas al cuerpo. Las cuatro cadenas cinemáticas se componen de tres puntos de interés. Por lo tanto, el modelo inicialmente dispone de un total de 14 puntos de interés. En esta tesis se propone modificar la técnica denominada Deformable Parts Model (DPM), añadiendo el canal de profundidad denominado ``Depth''. Inicialmente el modelo DPM se definió sobre imágenes de tres canales RGB. Mientras que en esta tesis se propone trabajar sobre imágenes de cuatro canales RGBD, por ello a la ampliación propuesta se le denomina 4D-DPM. Por otra parte, se propone reducir el coste computacional anterior simplificando el modelo que define la postura del cuerpo humano. La idea es reducir el número de variables a detectar con el modelo 4D-DPM, de tal manera que las variables suprimidas se puedan calcular a partir de las variables detectadas, utilizando modelos de cinemática inversa basados en cuaterniones duales. Los experimentos realizados demuestran que la combinación de estas dos técnicas permite, reduciendo el coste computacional del método original DPM, mejorar la precisión de la detección de postura debido a la información extra del canal de profundidad. Adicionalmente, se propone utilizar modelos de filtros de partículas para continuar mejorando la precisión de la detección de las posturas humanas a lo largo de una secuencia de imágenes. Atendiendo al problema de detección y seguimiento de las postura del esqueleto del cuerpo humano a lo largo de una secuencia de vídeo, esta tesis propone el uso del siguiente método. 1. Calibración de cámaras. Procesamiento de imágenes RGBD. Sustracción del fondo de la imagen con el método MSER. 2. 4D-DPM: método utilizado para detectar los puntos de interés (variables del modelo de postura) dentro de una imagen. 3. Filtros de partículas: se diseña este tipo de filtros para realizar el seguimiento de los puntos de interés a lo largo del tiempo y corregir los datos obtenidos por el sensor. 4. Modelado cinemático inverso: se realiza el control de cadenas cinemáticas con la ayuda de cuaterniones duales con el fin de obtener el modelo completo de la postura del esqueleto del cuerpo humano. La contribución global de esta tesis es la propuesta del método anterior que, combinando los métodos anteriores, es capaz de mejorar la precisión en la detección y el seguimiento de la postura del esqueleto del cuerpo humano en una secuencia de vídeo, reduciendo además su coste computacional. El método original DPM debe detectar 14 puntos de interés sobre una imagen RGB para estimar la postura de un cuerpo humano. Sin embargo, el método propuesto debe detectar 10 puntos de interés sobre una imagen RGBD. Posteriormente, los 4 puntos de interés eliminados se calculan mediante la utilización de métodos de cinemática inversa a partir de los 10 puntos de interés calculados. Para resolver el problema de la cinemática inversa se propone utilizar cuaterniones duales para cada una de las 4 cadenas cinemáticas que modelan las extremidades del esqueleto del cuerpo humano. El filtro de partículas se aplica sobre la secuencia temporal de los 10 puntos de interés del modelo de postura detectados a través del método 4D-DPM. Para diseñar estos filtros de partículas se propone añadir las siguientes restricciones, explicadas en la memoria, para ponderar las partículas generadas: 1. Restricciones en los límites de articulaciones. 2. Restricciones de suavidad. 3. Detección de colisiones. 4. Proyección de las poli-esferas. / La present tesi tracta sobre l'estudi de tècniques de visió per a la detecció de la postura de l'esquelet del cos humà basada en l'anàlisi d'una sola imatge, a més del seguiment d'estes postures al llarg d'una seqüència d'imatges. Es proposa modelar la postura de l'esquelet del cos humà per mitjà de quatre cadenes cinemàtiques que modelen les quatre extremitats articulades. Estes cadenes cinemàtiques i el cap romanen unides al cos. Les quatre cadenes cinemàtiques es componen de tres punts d'interés. Per tant, el model inicialment disposa d'un total de $14$ punts d'interés. En esta tesi es proposa modificar la tècnica denominada Deformable Parts Model (DPM) , afegint el canal de profunditat denominat ``Depth''. Inicialment el model DPM es va definir sobre imatges de tres canals RGB. Mentres que en esta tesi es proposa treballar sobre imatges de quatre canals RGBD, per això a l'ampliació proposada se la denomina 4D-DPM. D'altra banda, es proposa reduir el cost computacional anterior simplificant el model que definix la postura del cos humà. La idea és reduir el nombre de variables a detectar amb el model 4D-DPM, de tal manera que les variables suprimides es puguen calcular a partir de les variables detectades, utilitzant models de cinemàtica inversa basats en quaternions duals. Els experiments realitzats demostren que la combinació d'estes dos tècniques permet, reduint el cost computacional del mètode original DPM, millorar la precisió de la detecció de la postura degut a la informació extra del canal de profunditat. Addicionalment, es proposa utilitzar models de filtres de partícules per a continuar millorant la precisió de la detecció de les postures humanes al llarg d'una seqüència d'imatges. Atenent al problema de detecció i seguiment de les postura de l'esquelet del cos humà al llarg d'una seqüència de vídeo, esta tesi proposa l'ús del següent mètode. 1. Calibratge de càmeres. Processament d'imatges RGBD. Sostracció del fons de la imatge amb el mètode MSER. 2. 4D-DPM: mètode utilitzat per a detectar els punts d'interés (variables del model de postura) dins d'una imatge. 3. Filtres de partícules: es dissenya este tipus de filtres per a realitzar el seguiment dels punts d'interés al llarg del temps i corregir les dades obtingudes pel sensor. 4. Modelatge cinemàtic invers: es realitza el control de cadenes cinemàtiques amb l'ajuda de quaternions duals a fi d'obtindre el model complet de l'esquelet del cos humà. La contribució global d'esta tesi és la proposta del mètode anterior que, combinant els mètodes anteriors, és capaç de millorar la precisió en la detecció i el seguiment de la postura de l'esquelet del cos humà en una seqüència de vídeo, reduint a més el seu cost computacional. Açò és possible a causa de la combinació del mètode 4D-DPM amb la utilització de tècniques de cinemàtica inversa. El mètode original DPM ha de detectar 14 punts d'interés sobre una imatge RGB per a estimar la postura d'un cos humà. No obstant això, el mètode proposat ha de detectar 10 punts d'interés sobre una imatge RGBD. Posteriorment, els 4 punts d'interés eliminats es calculen per mitjà de la utilització de mètodes de cinemàtica inversa a partir dels 10 punts d'interés calculats. Per a resoldre el problema de la cinemàtica inversa es proposa utilitzar quaternions duals per a cada una de les 4 cadenes cinemàtiques que modelen les extremitats de l'esquelet del cos humà. El filtre de partícules s'aplica sobre la seqüència temporal dels 10 punts d'interés del model de postura detectats a través del mètode 4D-DPM. Per a dissenyar estos filtres de partícules es proposa afegir les següents restriccions per a ponderar les partícules generades: 1. Restriccions en els límits d'articulacions. 2. Restriccions de suavitat. 3. Detecció de col·lisions. 4. Projecció de les poli-esferes. / Martínez Bertí, E. (2017). SEGUIMIENTO DE PERSONAS APLICANDO RESTRICCIONES CINEMÁTICAS BASADAS EN MODELOS DE CUERPOS RÍGIDOS ARTICULADOS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86159 / TESIS
18

Computational modelling of monocyte deposition in abdominal aortic aneurysms

Hardman, David January 2011 (has links)
Abdominal aortic aneurysm (AAA) disease involves a dilation of the aorta below the renal arteries. If the aneurysm becomes sufficiently dilated and tissue strength is less than vascular pressure, rupture of the aorta occurs entailing a high mortality rate. Despite improvements in surgical technique, the mortality rate for emergency repair remains high and so an accurate predictor of rupture risk is required. Inflammation and the associated recruitment of monocytes into the aortic wall are critical in the pathology of AAA disease, stimulating the degradation and remodeling of the vessel wall. Areas with high concentrations of macrophages may experience an increase in tissue degradation and therefore an increased risk of rupture. Determining the magnitude and distribution of monocyte recruitment can help us understand the pathology of AAA disease and add spatial accuracy to the existing rupture risk prediction models. In this study finite element computational fluid dynamics simulations of AAA haemodynamics are seeded with monocytes to elucidate patterns of cell deposition and probability of recruitment. Haemodynamics are first simulated in simplified AAA geometries of varying diameters with a patient averaged flow waveform inlet boundary condition. This allows a comparison with previous experimental investigations as well as determining trends in monocyte adhesion with aneurysm progression. Previous experimental investigations show a transition to turbulent flow occurring during the deceleration phase of the cardiac cycle. There has thus far been no investigation into the accuracy of turbulence models in simulating AAA haemodynamics and so simulations are compared using RNG κ − ε, κ − ω and LES turbulence models. The RNG κ − ε model is insufficient to model secondary flows in AAA and LES models are sensitive to inlet turbulence intensity. The probability of monocyte adhesion and recruitment depends on cell residence time and local wall shear stress. A near wall particle residence time (NWPRT)model is created incorporating a wall shear stress-limiter based on in vitro experimental data. Simulated haemodynamics show qualitative agreement with experimental results. Peaks of maximum NWPRT move downstream in successively larger geometries, correlating with vortex behaviour. Average NWPRT rises sharply in models above a critical maximum diameter. These techniques are then applied to patient-specific AAAs. Geometries are created from CT slices and velocity boundary conditions taken from Phase Contrast-MRI (PC-MRI) data for 3 patients. There is no gold standard for inlet boundary conditions and so simulations using 3 velocity components, 1 velocity component and parabolic flow profiles at the inlet are compared with each other and with PC-MRI data at the AAA midsection. The general trends in flow and wall shear stress are similar between simulations with 3 and 1 components of inlet velocity despite differences in the nature and complexity of secondary flow. Applying parabolic velocity profiles, however, can cause significant deviations in haemodynamics. Axial velocities show average to good correlation with PC-MRI data though the lower magnitude radial velocities produce high levels of noise in the raw data making comparisons difficult. Patient specific NWPRT models show monocyte infiltration is most likely at or around the iliac bifurcation.
19

Modeling Endogenous Treatment Eects with Heterogeneity: A Bayesian Nonparametric Approach

Hu, Xuequn 01 January 2011 (has links)
This dissertation explores the estimation of endogenous treatment effects in the presence of heterogeneous responses. A Bayesian Nonparametric approach is taken to model the heterogeneity in treatment effects. Specifically, I adopt the Dirichlet Process Mixture (DPM) model to capture the heterogeneity and show that DPM often outperforms Finite Mixture Model (FMM) in providing more flexible function forms and thus better model fit. Rather than fixing the number of components in a mixture model, DPM allows the data and prior knowledge to determine the number of components in the data, thus providing an automatic mechanism for model selection. Two DPM models are presented in this dissertation. The first DPM model is based on a two-equation selection model. A Dirichlet Process (DP) prior is specified on some or all the parameters of the structural equation, and marginal likelihoods are calculated to select the best DPM model. This model is used to study the incentive and selection effects of having prescription drug coverage on total drug expenditures among Medicare beneficiaries. The second DPM model utilizes a three-equation Roy-type framework to model the observed heterogeneity that arises due to the treatment status, while the unobserved heterogeneity is handled by separate DPM models for the treated and untreated outcomes. This Roy-type DPM model is applied to a data set consisting of 33,081 independent individuals from the Medical Expenditure Panel Survey (MEPS), and the treatment effects of having private medical insurance on the outpatient expenditures are estimated. Key Words: Treatment Effects, Endogeneity, Heterogeneity, Finite Mixture Model, Dirichlet Process Prior, Dirichlet Process Mixture, Roy-type Modeling, Importance Sampling, Bridge Sampling
20

Water uptake of aerosols with a focus on seeded aerosols and instrumentation techniques

Meyer, Nicholas Karl January 2008 (has links)
This thesis focuses on the volatile and hygroscopic properties of mixed aerosol species. In particular, the influence organic species of varying solubility have upon seed aerosols. Aerosol studies were conducted at the Paul Scherrer Institut Laboratory for Atmospheric Chemistry (PSI-LAC, Villigen, Switzerland) and at the Queensland University of Technology International Laboratory for Air Quality and Health (QUT-ILAQH, Brisbane, Australia). The primary measurement tool employed in this program was the Volatilisation and Hygroscopicity Tandem Differential Mobility Analyser (VHTDMA - Johnson et al. 2004). This system was initially developed at QUT within the ILAQH and was completely re-developed as part of this project (see Section 1.4 for a description of this process). The new VHTDMA was deployed to the PSI-LAC where an analysis of the volatile and hygroscopic properties of ammonium sulphate seeds coated with organic species formed from the photo-oxidation of á-pinene was conducted. This investigation was driven by a desire to understand the influence of atmospherically prevalent organics upon water uptake by material with cloud forming capabilities. Of particular note from this campaign were observed influences of partially soluble organic coatings upon inorganic ammonium sulphate seeds above and below their deliquescence relative humidity (DRH). Above the DRH of the seed increasing the volume fraction of the organic component was shown to reduce the water uptake of the mixed particle. Below the DRH the organic was shown to activate the water uptake of the seed. This was the first time this effect had been observed for á-pinene derived SOA. In contrast with the simulated aerosols generated at the PSI-LAC a case study of the volatile and hygroscopic properties of diesel emissions was undertaken. During this stage of the project ternary nucleation was shown, for the first time, to be one of the processes involved in formation of diesel particulate matter. Furthermore, these particles were shown to be coated with a volatile hydrophobic material which prevented the water uptake of the highly hygroscopic material below. This result was a first and indicated that previous studies into the hygroscopicity of diesel emission had erroneously reported the particles to be hydrophobic. Both of these results contradict the previously upheld Zdanovksii-Stokes-Robinson (ZSR) additive rule for water uptake by mixed species. This is an important contribution as it adds to the weight of evidence that limits the validity of this rule.

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