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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.
221

Point Cloud-Based Analysis and Modelling of Urban Environments and Transportation Corridors

Yun-Jou Lin (5929979) 03 January 2019 (has links)
3D point cloud processing has been a critical task due to the increasing demand of a variety of applications such as urban planning and management, as-built mapping of industrial sites, infrastructure monitoring, and road safety inspection. Point clouds are mainly acquired from two sources, laser scanning and optical imaging systems. However, the original point clouds usually do not provide explicit semantic information, and the collected data needs to undergo a sequence of processing steps to derive and extract the required information. Moreover, according to application requirements, the outcomes from the point cloud processing could be different. This dissertation presents two tiers of data processing. The first tier proposes an adaptive data processing framework to deal with multi-source and multi-platform point clouds. The second tier introduces two point clouds processing strategies targeting applications mainly from urban environments and transportation corridors.<div><br></div><div>For the first tier of data processing, the internal characteristics (e.g., noise level and local point density) of data should be considered first since point clouds might come from a variety of sources/platforms. The acquired point clouds may have a large number of points. Data processing (e.g., segmentation) of such large datasets is time-consuming. Hence, to attain high computational efficiency, this dissertation presents a down-sampling approach while considering the internal characteristics of data and maintaining the nature of the local surface. Moreover, point cloud segmentation is one of the essential steps in the initial data processing chain to derive the semantic information and model point clouds. Therefore, a multi-class simultaneous segmentation procedure is proposed to partition point cloud into planar, linear/cylindrical, and rough features. Since segmentation outcomes could suffer from some artifacts, a series of quality control procedures are introduced to evaluate and improve the quality of the results.<br></div><div><br></div><div>For the second tier of data processing, this dissertation focuses on two applications for high human activity areas, urban environments and transportation corridors. For urban environments, a new framework is introduced to generate digital building models with accurate right-angle, multi-orientation, and curved boundary from building hypotheses which are derived from the proposed segmentation approach. For transportation corridors, this dissertation presents an approach to derive accurate lane width estimates using point clouds acquired from a calibrated mobile mapping system. In summary, this dissertation provides two tiers of data processing. The first tier of data processing, adaptive down-sampling and segmentation, can be utilized for all kinds of point clouds. The second tier of data processing aims at digital building model generation and lane width estimation applications.<br></div>
222

Associação do red blood cell distribution width (RDW) com readmissão e mortalidade de pacientes críticos na unidade de terapia intensiva

Tonietto, Tiago Antônio January 2016 (has links)
Introdução: O Red blood cell distribution width (RDW) é um preditor de mortalidade em pacientes criticamente enfermos. A associação do RDW na alta da UTI com o risco de readmissão à UTI não é conhecida. Nós fizemos este estudo com o objetivo de investigar a associação entre a presença de anisocitose na alta da UTI e o risco de readmissão à UTI ou óbito inesperado na enfermaria. Métodos: Estudo de coorte retrospectivo que incluiu 813 pacientes com alta da UTI para a enfermaria em um hospital terciário de Porto Alegre, Brasil. A variável de interesse foi o RDW coletado no momento da alta da UTI. Anisocitose foi definida como RDW > 16%. Desfechos de interesse foram readmissão à UTI, óbito inesperado na enfermaria e óbito hospitalar. Hazard ratios (HR) foram estimadas usando o Modelo de Riscos proporcionais de Cox. Variáveis com P < 0.1 na análise univariada foram incluídas na análise multivariada para ajuste. Resultados: Anisocitose na alta da UTI está independentemente associada com readmissão à UTI ou óbito inesperado na enfermaria (HR: 1,682; IC 95% 1,219 – 2,322; P = 0,002). Outras variáveis associadas com este desfecho foram: idade, escore Sequential Organ Failure Assessment (SOFA) na alta da UTI e traqueostomia. Resultados significativos semelhantes foram obtidos após exclusão dos óbitos inesperados na enfermaria (HR: 2,031; IC 95% 1,428 – 2,889; P< 0,001) e para óbito hospitalar (HR: 1,716; IC 95% 1,141 – 2,580; P = 0,01). Conclusões: Anisocitose no momento da alta da UTI está independentemente associada com readmissão à UTI e óbito hospitalar. / Introduction: Red blood cell distribution width (RDW) is a predictor of mortality in critically ill patients. The relationship between the RDW at ICU discharge and the risk of ICU readmission is unknown. The purpose of this study was to investigate the association between the presence of anisocytosis at ICU discharge and the risk of ICU readmission or unexpected death in the ward. Methods: This retrospective cohort study included 813 patients discharged alive from the ICU to the ward in a tertiary hospital in Porto Alegre, Brazil. The target variable was the RDW collected at the time of ICU discharge. Anisocytosis was defined as an RDW > 16%. Outcomes of interest included readmission to the ICU, unexpected death in the ward and in-hospital death. Hazard ratios (HR) were estimated using the Cox proportional hazards model. Variables with a value of P < 0.1 in the univariate analysis were included in the multivariate analysis for adjustment. Results: Anisocytosis at ICU discharge was independently associated with readmission to the ICU or unexpected death in the ward (HR: 1.682; 95% CI 1.219-2.322; P = 0.002). Other variables associated with this outcome included age, Sequential Organ Failure Assessment (SOFA) score at ICU discharge and tracheostomy. Similar significant results were obtained after the exclusion of unexpected deaths in the ward (HR 2.031; CI 1.428 – 2.889; P < 0.001) and for in-hospital deaths (HR 1.716; 95% CI 1.141-2.580; P = 0.01). Conclusions: Anisocytosis at ICU discharge is independently associated with ICU readmission and in-hospital death.
223

AnÃlise NumÃrica do Acoplador Duplo NÃo-Linear Baseado em Fibras de Cristais FotÃnicos (NLDC-PCF) Operando com PAM e PWM para ObtenÃÃo de Portas LÃgicas / Numerical Analysis of Nonlinear Dual Core Coupler Based on Photonic Crystal Fibers (PCF-NLDC) Operating with PAM and PWM for Obtaining Logic Gates

Marcos Benedito Caldas Costa 01 January 2013 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Neste trabalho, apresentamos uma anÃlise numÃrica para a obtenÃÃo de portas lÃgicas totalmente Ãptica baseada em um acoplador direcional nÃo-linear simÃtrico (NLDC) em fibras de cristal fotÃnico (PCF). O projeto mais comumente usado para o NLDC-PCF à uma fibra holey, utilizada neste trabalho, em que a seÃÃo transversal à uma matriz periÃdica de buracos de ar que se prolonga por todo o comprimento da fibra, operando com dois pulsos de luz ultracurtos na forma de sÃlitons, de duraÃÃo mÃnima de 100fs (femtosegundos). Investigamos dois formatos de modulaÃÃo por pulsos, a modulaÃÃo por amplitude de pulso (PAM) na modalidade de chaveamento de mudanÃa de amplitude (ASK) e a modulaÃÃo por largura de pulso (PWM) para obter portas lÃgicas no NLDC-PCF duplo simÃtrico. Avaliamos o efeito resultante de um incremento no parÃmetro codificaÃÃo PAM (&#949;) e PWM (w), considerando a dispersÃo de segunda ordem (&#946;2), a dispersÃo de terceira ordem (&#946;3) e efeitos nÃo-lineares, tais como: SPM (Self Phase Modulation), SS (Self-Steepening) e IRS (lntrapulse Raman Scattering) em uma configuraÃÃo sem perdas. Os nossos resultados indicam que à possÃvel obter operaÃÃes lÃgicas utilizando um controle de fase entre os pulsos de entrada. / We present a numerical analysis for obtaining all-optical logic gates based on a nonlinear directional coupler symmetric (NLDC) based on photonic crystal fibers (PCF). The most commonly used to project the NLDC-PCF is a holey fiber, used here in cross section which is a periodic array of air holes extending through the length of the fiber, using two ultrashort light pulses in form of solitons, the minimum duration of 100fs (femtoseconds). We investigated two forms of modulation pulse, pulse amplitude modulation (PAM) in the form of amplitude shift keying (ASK) modulation and pulse width modulation (PWM) for logic gate NLDC-PCF symmetrical double. We evaluated the effect resulting from an increase in the offset parameter encoding PAM (&#949;) and PWM (w), considering the second order dispersion (&#946;2), the third order dispersion (&#946;3) and non-linear modulation effects SPM (Self Phase Modulation), SS (Self-Steepening) and IRS (lntrapulse Raman Scattering) in a configuration without loss. Our results indicate that logical operations can be obtained using a phase control between the input pulses.
224

Tennessee Per-pupil Expenditures in Special Education and Academic Achievement

Davidson, Melanie C 01 August 2015 (has links)
Federal legislation known as the No Child Left Behind act has required states to close achievement gaps. The purpose of this study was to investigate the relationships between special education spending by districts in the state of Tennessee and standardized achievement for students with disabilities. Secondary data were obtained from the Tennessee Department of Education’s website (www.tn.gov/education). Data from each local education association were collected for the years of 2010-2014 in the areas of special education spending, special education population, and TCAP proficiency percentages in reading and math grades 3-8. Data from each local education association were collected for the years of 2011-2014 for gap size percentages between students with and without disabilities for reading and math grades 3-8 and the percentage of economically disadvantaged students. The researcher performed 6 Pearson correlation coefficient tests for this analysis. The findings showed a positive correlation between spending and performance on standardized assessments in the areas of reading and mathematics for students with disabilities. The analysis indicated that per pupil expenditures in special education has not had a statistically significant impact on reducing the gap size between students with and without disabilities. However, the percentage of economically disadvantaged students in a local education association inversely impacted the gap size. Those local education agencies with a higher population of economically disadvantaged students were more likely to have smaller gap sizes between students with and without disabilities in reading and mathematics on standardized testing.
225

<em>η'</em> Decay to π<sup>+</sup>π<sup>-</sup>π<sup>+</sup>π<sup>−</sup>

Jafari, Ehsan 01 January 2018 (has links)
With the use of chiral theory of mesons [1], [2] we evaluate the decay rate of η′ → π+π−π+π−. Our theoretical study of this problem is different from the previous theo- retical study [3] and our predicted result is in a good agreement with the experiment. In this chiral theory we evaluate Feynman diagrams up to one loop and the decay rate is calculated with the use of triangle and box diagrams. The ρ0 meson includes in both type of diagrams as a resonance state. Divergent integrals in the loop calculations are regularized with the use of n-dimensional ’t Hooft-Veltman regularization technique. At the last step to obtain the decay rate, the phase space integral has been calculated.
226

Controlling a Brushless DC Motor in a Shift-by-Wire System / Styrning av en borstlös DC-motor i ett Shift-by-Wire-system

Wiberg, Johan January 2003 (has links)
<p>Shift-by-Wire is about replacing the mechanical link between the automatic transmission and the shift lever with an electromechanical system. This will make new safety functions possible and assist the driver in other ways. </p><p>To do this, an actuator with a brushless DC motor is built into the transmission. It controls the position of the shift valve, which decides the driving position. </p><p>This thesis concerns the controlling of the brushless DC motor. This is done by programming a shift control unit with a Motorola HC12 microcontroller. The performance of the motor is then tested and evaluated.</p>
227

Tooth-anchored vs. bone-anchored maxillary expansion: a randomized controlled trial comparing dental and skeletal effects

Cote, Brent 11 1900 (has links)
Aim:To investigate the differences, if any, between tooth-anchored maxillary expansion (TME) and bone-anchored maxillary expansion (BME) in terms of the produced longitudinal dentoskeletal changes -and the stability of these changes- in adolescents with maxillary constriction. Methods:Sixty two suitable subjects were randomly assigned to one of three groups: (1) TME group; (2) BME group; (3) Control group. Lateral cephalograms, posteroanterior cephalograms, and dental casts were obtained at baseline and at three post-expansion time points. Records from all time points were analyzed. Results:There were no clinically significant differences between the TME and BME groups at any data collection time point. Both showed initial increases in dentoskeletal widths and dental tipping which were subsequently largely lost to relapse in the absence of retention. Conclusion:There are no clinically significant differences in the dentoskeletal changes -or the stability of these changes- produced by TME and BME in adolescents with maxillary constriction.
228

New leading/trailing edge modulation strategies for two-stage AC/DC PFC adapters to reduce DC-link capacitor ripple current

Sun, Jing 17 September 2007 (has links)
AC/DC adapters mostly employ two-stage topology: Power Factor Correction (PFC) pre-regulation stage followed by an isolated DC/DC converter stage. Low power AC/DC adapters require a small size to be competitive. Among their components, the bulk DC-link capacitor is one of the largest because it should keep the output voltage with low ripple. Also, the size of this capacitor is penalized due to the universal line voltage application. Synchronization through employing leading edge modulation for the first PFC stage and trailing edge modulation for the second DC/DC converter stage can significantly reduce the ripple current and ripple voltage of the DC-link capacitor. Thus, a smaller DC-link capacitance can be used, lowering the cost and size of the AC/DC adapter. Benefits of the synchronous switching scheme were already demonstrated experimentally. However, no mathematical analysis was presented. In this thesis, detailed mathematical analyses in per-unit quantity are given to facilitate the calculation of the DC-link capacitor ripple current reduction with Leading/Trailing Edge Modulation strategies. One of the limitations of leading/trailing edge modulation is that the switching frequencies of the two stages need to be equal to achieve the best reduction of the DC-link capacitor ripple current. The DC-link capacitor ripple current will become larger if the switching frequency of the DC/DC converter is larger than that of the PFC pre-regulator, which blocks us to employ higher frequency for isolated DC/DC converter to reduce its transformer size. This thesis proposed a new Leading/Trailing Edge Modulation strategy to further reduce the DC-link bulk capacitor ripple current when switching frequency of DC/DC converter stage is twice the switching frequency of PFC stage. This proposed pulse width modulation scheme was verified by simulation. Experimental results obtained through digital control based on FPGA are also presented in this thesis.
229

Experimental study and numerical simulations of the spectral properties of XUV lasers pumped by collisional excitation.

Meng, Limin 20 December 2012 (has links) (PDF)
Improving the knowledge of the spectral and temporal properties of plasma-based XUV lasers is an important issue for the ongoing development of these sources towards significantly higher peak power. The spectral properties of the XUV laser line actually control several physical quantities that are important for applications, such as the minimum duration that can be achieved (Fourier-transform limit). The shortest duration experimentally achieved to-date is ~1 picosecond. The demonstrated technique of seeding XUV laser plasmas with a coherent femtosecond pulse of high-order harmonic radiation opens new and promising prospects to reduce the duration to a few 100 fs, provided that the gain bandwidth can be kept large enough.XUV lasers pumped by collisional excitation of Ni-like and Ne-like ions have been developed worldwide in hot plasmas created either by fast electrical discharge, or by various types of high-power lasers. This leads to a variety of XUV laser sources with distinct output properties, but also markedly different plasma parameters (density, temperature) in the amplification zone. Hence different spectral properties are expected. The purpose of our work was then to investigate the spectral behaviour of the different types of existing collisional excitation XUV lasers, and to evaluate their potential to support amplification of pulses with duration below 1 ps in a seeded mode.The spectral characterization of plasma-based XUV lasers is challenging because the extremely narrow bandwidth (typically ∆λ/λ ~10-5) lies beyond the resolution limit of existing spectrometers in this spectral range. In our work the narrow linewidth was resolved using a wavefront-division interferometer specifically designed to measure temporal coherence, from which the spectral linewidth is inferred. We have characterized three types of collisional XUV lasers, developed in three different laboratories: transient pumping in Ni-like Mo, capillary discharge pumping in Ne-like Ar and quasi-steady state pumping in Ne-like Zn. Besides the accurate measurement of the temporal coherence of the laser in each case, we have studied the spectral behaviour when the laser is operated in the saturation regime and (in Ni-like Mo) when it is seeded with high-order harmonic radiation. We have also investigated the temporal behaviour of the Ni-like Mo transient XUV laser, using an ultrafast X-ray streak camera. Our linewidth measurements are compared with detailed numerical calculations including relevant broadening mechanisms as well as radiative transfer effects. The evolution of the spectral profile with amplification and saturation was studied for different plasma parameters, and corresponding Fourier-transform limit duration were evaluated.The shortest temporal coherence (ie the largest bandwidth) is measured for the quasi-steady state pumping XUV laser, which operates at the highest density and ionic temperature.
230

Study of Jet Fires Geometry and Radiative Features

Palacios Rosas, Adriana 11 January 2011 (has links)
Entre els accidents greus que poden ocórrer a les instal·lacions industrials o durant el transport de substàncies perilloses, els dolls de foc presenten un especial interès. Tot i que tenen una distància relativament més curta d'afectació que altres accidents greus, es caracteritzen per originar grans fluxos de calor i, en cas de contacte de la flama amb un equip, originen sovint un efecte domino, desencadenant una subseqüent explosió, incendi o altres esdeveniments amb greus conseqüències.Diversos estudis experimentals i teòrics han estat efectuats; no obstant això, la majoria d'aquests han estat enfocats a dolls de foc a escala de laboratori, flames subsòniques o torxes, les condicions de les quals difereixen significativament d'aquelles trobades en dolls de foc accidentals reals, que normalment assoleixen majors longituds de flama i velocitats de sortida sònica. Aquesta manca d'investigació és la raó per explicar perquè els dolls de foc eren encara molt mal coneguts i la predicció dels seus efectes i conseqüències era encara un problema. Aquesta tesi ha estat elaborada per a obtenir informació nova i útil sobre els dolls de foc, millorant la comprensió de la seva geometría i de les característiques tèrmiques, mitjançant l'anàlisi, l'experimentació i el modelatge matemàtic.Aquest estudi s'ha centrat alhora en dades existents i en noves dades experimentals, implicant Aixa dolls de foc verticals i horitzontals alliberats en absència de vent, implicant diversos combustibles (hidrogen, metà i propà). L'estudi comprèn una àmplia gamma de variables d'operació (velocitats de sortida del combustible, pressions en la canonada i diàmetres d'orifici de sortida). L'estudi experimental ha implicat dolls de foc amb flames de fins a 10.3 m de longitud i 1.5 m d'amplada. El combustible utilitzat ha estat propà, amb velocitats de sortida sònica i subsònica, utilitzant diversos diàmetres d'orifici de sortida. Els dolls de foc han estat filmats amb dues càmeres de vídeo (VHS) i una càmera termográfica d'alta velocitat (IR). Les principals característiques geomètriques de les flames (dimensions i forma) han estat analitzades en funció de la velocitat de sortida del combustible,del flux màssic i del diàmetre d'orifici de sortida. L'anàlisi i tractament d'imatges infraroges i de les mesures obtingudes amb tres sensors de flux de calor situats a diferents distàncies de la sortida del doll de foc han permès l'obtenció de les seves principals característiques de radiació: flux de calor irradiat als voltants (persones i instal·lacions) en funció de la distancia, poder emissiu i emisivitat de les flames. Diverses expressions han estat proposades per estimar les dimensions de la flama en funció de diverses variables (flux màssic, diàmetre d'orifici de sortida i nombres de Froude i Reynolds). Els resultats i expressions obtinguts en aquest estudi contribueixen a una millor comprensió dels dolls de foc, representant un avanç en les metodologies i l'establiment de noves mesures, normes i polítiques de planificació per a la prevenció i/o el control d'aquest tipus d'accident greu amb foc, tant en establiments industrials com en el transport de materials perillosos. / Among the major accidents that can occur in processing plants or in the transportation of hazardous materials, jet fires are of particular interest. Although they have a relatively shorter distance of influence than other major accidents, they are characterized by high heat fluxes and if there is flame impingement they can originate a domino effect, leading to a subsequent explosion, large fire, or other events with severe effects. Several experimental and theoretical studies have been carried out; however, most of those works have been focused on small-scale jet fires, subsonic flames or flares, the conditions of which significantly differ from those found in real accidental jet fires, usually reaching larger flame lengths and sonic exit velocities. This lack of research is the reason to explain why the current knowledge of jet fires was still rather poor and the accurate prediction of their effects and consequences was still a problem. The present thesis has been addressed to produce a significant amount of novel and useful information on jet fires, by improving understanding of jet fire structure, reach and radiative features, through analyses, experiment and mathematical modelling. This study has been focused on both existing and also new experimental jet flame data, comprising all together, turbulent non-premixed jet flames vertically and horizontally released into still air, involving several fuels (hydrogen, methane and propane), over a wide range of operational conditions (jet exit velocities, release pressures and pipe diameters). The experimental study developed in this thesis has concerned relatively large jet fires with flames of up to 10.3 m in length and 1.5 m in width. The fuel was propane, and both sonic and subsonic jet exit velocities were obtained from different outlet diameters. The jet fires were filmed with two videocameras registering visible light (VHS) and a thermographic camera (IR). The main geometrical features of the flames were analyzed as a function of the fuel velocity, mass flow rate and jet outlet diameter: jet flame size and flame shape. The treatment of infrared images and measurements obtained from three heat flow sensors located at different distances from the jet fire outlet also led the main radiative features of jet fires to be obtained: incident thermal radiation heat over a target, surface emissive power and emissivity of the flames.Expressions for estimating jet flame reach as a function of several variables (mass flow rate, orifice exit diameter, Froude and Reynolds numbers) have also been proposed. The results and the expressions obtained in this study contribute to a better understanding of jet fires for accurate risk assessment, allowing the obtention of important advances in risk assessment methodologies and the establishment of new measures, regulations, and risk planning policies for the prevention and/or control of this type of major fire, occurred world-wide in industrial establishments and in the transportation of hazardous materials.

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