Dissertations / Theses on the topic 'Y-junctions'

The accurate measurement of multiphase flows of oil/water/gas is a critical element of oil exploration and production. Thus, over the last three decades; the development and deployment of in-line multiphase flow metering systems has been a major focus worldwide. Accurate measurement of multiphase flow in the oil and gas industry is difficult because there is a wide range of flow regimes and multiphase meters do not generally perform well under the intermittent slug flow conditions which commonly occur in oil production. This thesis investigates the use of Doppler and cross-correlation ultrasonic measurements made in different high gas void fraction flow, partially separated liquid and gas flows, and homogeneous flow and raw slug flow, to assess the accuracy of measurement in these regimes. This approach has been tested on water/air flows in a 50mm diameter pipe facility. The system employs a partial gas/liquid separation and homogenisation using a T-Y junction configuration. A combination of ultrasonic measurement techniques was used to measure flow velocities and conductivity rings to measure the gas fraction. In the partially separated regime, ultrasonic cross-correlation and conductivity rings are used to measure the liquid flow-rate. In the homogeneous flow, a clamp-on ultrasonic Doppler meter is used to measure the homogeneous velocity and combined with conductivity ring measurements to provide measurement of the liquid and gas flow-rates. The slug flow regime measurements employ the raw Doppler shift data from the ultrasonic Doppler flowmeter, together with the slug flow closure equation and combined with gas fraction obtained by conductivity rings, to determine the liquid and gas flow-rates. Measurements were made with liquid velocities from 1.0m/s to 2.0m/s with gas void fractions up to 60%. Using these techniques the accuracies of the liquid flow-rate measurement in the partially separated, homogeneous and slug regimes were 10%, 10% and 15% respectively. The accuracy of the gas flow-rate in both the homogeneous and raw slug regimes was 10%. The method offers the possibility of further improvement in the accuracy by combining measurement from different regimes.

The accurate measurement of multiphase flows of oil/water/gas is a critical element of oil exploration and production. Thus, over the last three decades; the development and deployment of in-line multiphase flow metering systems has been a major focus worldwide. Accurate measurement of multiphase flow in the oil and gas industry is difficult because there is a wide range of flow regimes and multiphase meters do not generally perform well under the intermittent slug flow conditions which commonly occur in oil production. This thesis investigates the use of Doppler and cross-correlation ultrasonic measurements made in different high gas void fraction flow, partially separated liquid and gas flows, and homogeneous flow and raw slug flow, to assess the accuracy of measurement in these regimes. This approach has been tested on water/air flows in a 50mm diameter pipe facility. The system employs a partial gas/liquid separation and homogenisation using a T-Y junction configuration. A combination of ultrasonic measurement techniques was used to measure flow velocities and conductivity rings to measure the gas fraction. In the partially separated regime, ultrasonic cross-correlation and conductivity rings are used to measure the liquid flow-rate. In the homogeneous flow, a clamp-on ultrasonic Doppler meter is used to measure the homogeneous velocity and combined with conductivity ring measurements to provide measurement of the liquid and gas flow-rates. The slug flow regime measurements employ the raw Doppler shift data from the ultrasonic Doppler flowmeter, together with the slug flow closure equation and combined with gas fraction obtained by conductivity rings, to determine the liquid and gas flow-rates. Measurements were made with liquid velocities from 1.0m/s to 2.0m/s with gas void fractions up to 60%. Using these techniques the accuracies of the liquid flow-rate measurement in the partially separated, homogeneous and slug regimes were 10%, 10% and 15% respectively. The accuracy of the gas flow-rate in both the homogeneous and raw slug regimes was 10%. The method offers the possibility of further improvement in the accuracy by combining measurement from different regimes.

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El síndrome de Sjögren (SS) es una enfermedad inflamatoria, autoinmune, crónica de etiología desconocida, que compromete esencialmente a las glándulas salivales y lagrimales, generando xeroftalmia (sequedad ocular) y xerostomía (sequedad bucal). Las glándulas salivales de los pacientes con este síndrome presentan cambios importantes en la estructura, organización y funcionalidad del parénquima glandular y de la matriz extracelular. En células acinares, pérdida de polaridad celular, pérdida de microvellosidades apicales, dilatación de lúmenes, redistribución de aquaporina 5 y presencia de colágenos de la matriz extracelular en el lumen de los acinos, son indicadores que la organización del polo apical y la polaridad de estas células está alterada. Un estudio mediante microarreglos de cDNA reveló que las glándulas salivales de pacientes SS presentan una sobreexpresión del mRNA de claudina-4, mientras que los niveles de mRNA de ocludina (ocln), ZO-1, claudinas (cldn)-1, -3, -5, -10, -18 y -23 fueron similares a los controles. En los epitelios en general, y en los acinos en particular, una de las estructuras que participan en la regulación de la organización del polo apical y mantención de la polaridad celular son las Uniones Estrechas (UE) o tight junctions. Estos complejos de unión localizados en la porción más apical de las células epiteliales participan en la difusión de iones, a través de la vía paracelular. Sus funciones más relevantes son: 1) formar la primera barrera que evita el transporte paracelular de solutos y 2) restringir la difusión lateral de proteínas de membrana plasmática, y así mantiene la asimetría entre dominio apical y basolateral. En esta memoria, se abordó el estudio de algunas proteínas de membrana plasmática que son componentes de la Unión Estrecha, claudina-1 -3, -4, ocludina y una proteína citoplasmática, ZO-1. Estos antecedentes y otros, permiten postular la siguiente hipótesis de trabajo: “La pérdida de polaridad de células acinares de glándulas salivales de pacientes con síndrome de Sjögren, y la desorganización de su polo apical, están asociadas a los cambios en expresión génica y de niveles de proteínas de las Uniones Estrechas. Estos cambios en expresión están acompañados de una localización alterada de las proteínas constituyentes de la UE”. Para evaluar esta hipótesis, se determinaron los niveles de mRNA de claudina-4 y de proteínas de claudina-1, -3, -4, ocludina y ZO-1 en glándulas salivales labiales (GSL) de pacientes con síndrome de Sjögren y se compararon con los resultados obtenidos en individuos controles. Además, mediante inmunohistoquímica/inmunofluorescencia, se analizó la localización de claudina-3, -4, ocludina y ZO-1. Los niveles relativos de mRNA para claudina-4 no mostraron diferencias significativas entre pacientes y controles (p=0,052). Los niveles relativos de proteínas de claudina-3, ocludina sin fosforilar y ocludina total, no mostraron diferencias significativas entre el grupo total de pacientes y el grupo control (p=0,052, p=0,06 y p=0,089, respectivamente), sin embargo, al separar el grupo de pacientes de ocludina total en dos subgrupos, de acuerdo a su nivel de expresión, se encontró que sólo el grupo con niveles bajos de ocludina total mostraron diferencias significativas respecto al grupo control (p=0,0008). Los niveles de proteína de claudina-1 y -4 fueron significativamente mayores en pacientes SS, respecto a controles (p=0,023 y p=0,04, respectivamente). Sin embargo, los niveles proteicos relativos de ocludina fosforilada y ZO-1, fueron significativamente menores en pacientes SS que en controles (p=0,034 y p=0,033, respectivamente). En pacientes SS, la localización subcelular de las proteínas que forman las UE, mostraron una marca intensa para claudina-3 y -4, en la superficie apical de acinos y ductos de GSL, y a diferencia de los controles, también se observó marca en la superficie basolateral de acinos. Mientras que ocludina y ZO-1 mostró una disminución marcada, sin modificar su localización en el polo apical de las células acinares y ductales. Estos resultados apoyan la hipótesis, que acinos provenientes de GSL de pacientes SS presentan cambios en los niveles de algunas proteínas de UE y en su localización, los cuales explicarían las alteraciones en las UE. Más aún, estos resultados podrían explicar, en parte, la pérdida de organización detectada en el polo apical de los acinos, y podrían correlacionarse con la hipofuncionalidad secretora observada en pacientes SS
Sjögren`s syndrome (SS) is a chronic autoimmune, inflammatory disease of unknown etiology that essentially compromises lachrymal and salivary glands, producing xeroftalmia (ocular dryness) and xerostomía (oral dryness). The salivary glands of SS patients present important changes in the structure, organization and functionality of the glandular parenchyma and extracellular matrix. In acinar cells, the loss of cell polarity, loss of apical microvilli, luminal dilatation, redistribution of aquaporin 5 and presence of collagens from extracellular matrix in acinar lumen, are indicators of alterations in the apical pole. A cDNA microarray analysis revealed that the salivary glands from SS patients present an overexpression of claudin-4, while the levels of gene expression of occludin, ZO-1, claudin -1, -3, -5, -10, -18 and -23 were similar to the levels found in samples from control individuals. In epithelia and acini in particularly, one of the structures that participate in the regulation of the organization of the apical pole and maintenance of cell polarity are the tight junctions (TJ). These union complexes are located in the apical zone of the epithelial cells participating in the diffusion of ions through the paracellular space. TJ most prominent functions are: 1) to form the first barrier that avoids the paracellular transportation of solutes and 2) to restrict the lateral diffusion of plasma membrane proteins, and thus maintain the asymmetry between the apical and basolateral compartments. In this thesis, the study of TJ components such as the plasma membrane proteins, claudin-1 -3, -4, occludin, and a cytoplasmic protein, ZO-1 was undertaken. We thus postulated the following working hypothesis: "The loss of cell polarity in salivary glands of SS patients and the disorganization of their apical pole, are associated with changes in gene expression and protein levels of TJ. These changes in expression are associated with localization changes of proteins that are part the TJ". To evaluate this hypothesis, the mRNA levels of claudin-4 and protein levels of claudin-1, -3, -4, occludin and ZO-1 in GSL were determined in salivary glands from SS patients and compared with those of control individuals. Using immunohistochemistry/immunofluorescene, the localization of claudin-3, -4, occludin and ZO-1 was also analyzed. The relative mRNA levels of claudin-4 did not show significant differences between patients and controls (p=0.052). The relative protein levels of claudin-3, non phosphorylated occludin and total occludin, did not show significant differences between patients and the control group (p=0.052, p=0.06 and p=0.089, respectively), nevertheless, when the patients group were divided in two sub-groups, according to their level of expression of total occludin, only the group with low levels of total occludin showed differences with the control group (p=0.0008). The protein levels of claudin 1, and-4 were significantly higher in SS patients with respect to controls (p=0.023 and p=0.04, respectively). However, the relative protein levels of phosphorylated occludin and ZO-1, were significantly lower in SS patients compared to controls (p=0.034 and p=0.033, respectively). In SS patients, the subcellular localization of the TJ proteins, showed an intense signal for claudin-3 and -4, in the apical surface of acini and ducts, and in contrast to the control group, it was also detected in the basolateral surface of acini. On the other hand, ocludin and ZO-1 showed a decreased signal and maintaining their localization in the apical pole of acinar and ductal cells. These results support the hypothesis, that acini from LSG of SS patients present changes in some TJ proteins levels and in their localization correlating with alterations in TJ. Moreover, the latter could explain in part, the loss of organization detected in the acini apical pole, which would correlate with the secretory hypofunctionality observed in SS patients

This thesis comprises detailed experimental and theoretical investigations of the transport properties of one-dimensional nanostructures. Most of the work is dedicated to the exploration of the fascinating effects occurring in single wall carbon nanotubes (SWCNT). These particular nanostructures gained an overwhelming interest in the past two decades due to its outstanding electronic and mechanical features. We have investigated the properties of a novel family of carbon nanostructures, named here as Y-shaped rings. The studies show that they present very interesting quantum interference effects. A high structural stability under tensile strain and elevated temperatures is observed. Within the semi-classical potential adopted, the critical strain values of structure rupture lie in the same range of their pristine SWCNT counterparts. This is directly verified by the first observations of these ring-like structures in a transmission electron microscopy. A merging process of asymmetric into symmetric rings is investigated in-situ under electron beam irradiation at high temperatures. The electronic properties of these systems are theoretically studied using Monte Carlo simulations and environment dependent tight-binding calculations. From our results, we address the possibility of double-slit like interference processes of counter-propagating electron waves in the ring-like structures. The nature of well defined, sharp peaks in the density of states are determined as the discrete eigenenergies of the central loop part. Furthermore, the formation and dispersion of standing waves inside the ring is shown to originate from the quantum-dot like confinement of each branch between the leads. The obtained dispersion relation is shown to be the same occurring in purely one-dimensional quantum dots of similar geometries. Furthermore, Fabry-Perot-like interferences are observed. We established at the IFW a bottom-up processing route to fabricate nanotube based electronic devices. The SWCNTs are grown by chemical vapor deposition and we present a detailed study of the different approaches to obtain individual nanotubes suitable for a successful integration into electronic devices. Wet-chemistry and ultra-thin films as well as ferritin were employed as catalyst particles in the growth of SWCNT samples. By adjusting the optimized process parameters, we can control the obtained yield from thick nanotube forests down to just a couple of free-standing individual SWCNTs. The nanotubes are localized, contacted by standard e-beam lithography and characterized at ambient- as well as liquid helium temperatures. We usually obtain quite transparent contacts and the devices exhibit metallic or a mixed metallic/semiconducting behavior. The well-known memory effect upon gate voltage sweeping as well as single electron tunneling in the Coulomb blockade regime are addressed.

The success of modelling partially magnetised linear 3-port junction circulator, which is non-uniformly biased, depends chiefly on the precise representation of the strength of the intrinsic magnetic field in the axial direction across the ferrite material placed at the centre of the junction. The inadequateness of using conventional Polder tensor, which is established with the assumption that the ferrite material is saturated by a constant uniform magnetic field, in modelling partially and non-uniformly magnetised 3-port ferrite junction circulators is presented. It is proposed that the combination of static and microwave finite element (FE) solver overcomes the limit of Polder tensor in modelling partially and non-uniformly magnetised ferrite junction circulator. The proposed combination method requires the generation of the steady magnetic field in a magnetostatic solver, where the magnetic state of the ferrite material is determined, and the information of the static magnetic field of ferrite junction is transferred to the microwave solver for use in the microwave permeability tensor of the partially magnetised ferrite junction. Using the coupling method, the reflection coefficient responses of the 3-port ferrite junction circulator are determined in the low field loss region which coincides with the partially magnetised region and accompanies a few undesirable problems in communication systems, such as the reduction of bandwidth, and intermodulation product interference. The determined reflection coefficient is used to obtain the split frequencies which are important in designing and analysing the performance of a 3-port ferrite circulator in partially magnetised region. The main modelling factors considered are the effects from the number of mesh, the type of the magnetic field, the biasing configurations and the value of the dielectric constant. In each case, various split frequencies are obtained and, by considering all factors step by step, optimal modelling conditions are decided. The modelling results are compared with the experiment and show good agreement.

El edema macular diabético (DME) es una de las primeras causas de disminución de la agudeza visual en pacientes con retinopatía diabética (DR). La rotura de la barrera hematorretiniana (BHR) debido a la disrupción de las tight junctions (TJ) es el principal factor causante del DME. Además, el incremento de las citoquinas proinflamatorias como la IL-1β juega un papel importante en la patogénesis del DME y la retinopatía diabética proliferativa (PDR). Mientras que la alteración de las proteínas implicadas en la disrupción de las TJ de la BHR interna ha sido ampliamente estudiada, existe poca información sobre este proceso en la BHR externa. En el estudio FIELD sobre DR, el tratamiento con fenofibrato redujo en un 30% la necesidad de tratamiento con láser en pacientes diabéticos. Además, en el estudio ACCORD-Eye se observó una reducción del 40% en la progresión de la DR en el grupo de pacientes diabéticos a los que se les administró fenofibrato. Sin embargo, los mecanismos a través de los cuales el fenofibrato ejerce sus efectos beneficiosos en pacientes con DR se desconocen. En base a lo explicado anteriormente, los objetivos de esta tesis han sido: 1. Estudiar el efecto de la hiperglicemia sobre la funcionalidad de la BHR externa y la expresión de las proteínas de TJ en una línea celular humana de RPE (ARPE-19). 2. Estudiar el efecto protector del ácido fenofíbrico (el metabolito activo del fenofibrato) sobre la funcionalidad y la expresión de las proteínas de TJ en células ARPE-19 cultivadas bajo diferentes concentraciones de glucosa, con o sin IL-1β. Además se evaluó la implicación de la vía de la AMPK en la hiperpermeabilidad inducida por la IL-1β y el efecto del ácido fenofíbrico sobre la activación de la AMPK. En nuestro primer trabajo observamos una disminución de la permeabilidad y un aumento de los niveles de claudina-1 en condiciones de hiperglicemia. Sin embargo, después de bloquear la expresión de claudina-1 no se detectaron cambios en la resistencia transepitelial (TER) ni en la permeabilidad. Estos resultados sugieren que la sobreexpresión de claudina-1 inducida por la hiperglicemia no está relacionada con los mecanismos a través de los cuales la glucosa aumenta la función oclusiva de las TJ en las células ARPE-19. Se demuestra que es la combinación de los diferentes factores presentes en el medio diabético, y no la hiperglicemia por sí sola, los que producen una alteración de la funcionalidad de la BHR externa y la disrupción de las TJ. En el segundo trabajo utilizamos una combinación de IL-1β + hiperglicemia con el fin de simular en las células ARPE-19 la lesión producida por el medio diabético. El tratamiento con ácido fenofíbrico redujo (a 25 μmol/l) o previno (a 100 μmol/l) de manera dosis dependiente, el aumento de permeabilidad y la desorganización de las TJ inducida por la IL-1β + 25 mmol/l D-Glucosa, hecho que se asoció a una mayor preservación de la función de sellado de las células del RPE. Este efecto no está relacionado con cambios en la expresión de las proteínas de TJ y sugiere que para el correcto funcionamiento de la BHR externa es más importante una adecuada distribución y estructura de las TJ que un aumento en el contenido neto de éstas. Además, demostramos que el efecto protector del ácido fenofíbrico se debe a su capacidad para suprimir la activación de la AMPK inducida por la IL-1β, previniendo así la hiperpermeabilidad inducida por el medio diabético. Nuestros resultados contribuyen significativamente a aumentar el conocimiento sobre los mecanismos de acción a través de los cuales el fenofibrato ejerce sus efectos beneficiosos en el desarrollo y la progresión del DME.
Diabetic macular edema (DME) is one of the primary causes of poor visual acuity in patients with diabetic retinopathy (DR). The breakdown of the blood-retinal barrier (BRB) due to the disruption of tight junctions (TJ) is the main factor accounting for DME. In addition, the increase of proinflammatory cytokines such as IL-1β plays a key role in the pathogenesis of DME and proliferative diabetic retinopathy (PDR). While extensive work has been carried out to identify the factors involved in the disruption of TJ of the inner BRB, the mechanisms implicated in the outer BRB regulation have been poorly explored. In the FIELD study on DR, treatment with fenofibrate reduced the need for laser treatment for DME and PDR by 30% in diabetic patients. In addition, the ACCORD Eye Study showed a 40% reduction in DR progression in the group of patients receiving fenofibrate. However, the mechanisms by which fenofibrate exerts its beneficial effects in DR remain to be elucidated. With all this background, the main points of this thesis were: 1. To study the effects of high glucose concentration on the outer BRB function and the expression of TJ proteins in a human RPE cell line (ARPE-19). 2. To study the effect of fenofibric acid (the active metabolite of fenofibrate) on the barrier function and the levels of TJ proteins in ARPE-19 cells cultured under different glucose concentrations with and without IL-1β. In addition, we evaluated the role of AMPK in mediating the hyperpermeability induced by IL-1β and the effect of fenofibric acid on AMPK activation. Our first study showed a reduction of permeability and an increment of claudin-1 levels under hyperglycemic conditions. However, after blocking claudin-1 expression no changes in transepithelial electrical resistance (TER) and permeability were observed. These results suggest that the overexpression of claudin-1 induced by high glucose concentration is not involved in the mechanisms by which glucose increases the TJ sealing function in ARPE-19 cells. In addition, our findings demonstrate that hyperglycemia per se is not the only cause responsible for the breakdown of the outer BRB in patients with DR. It is the combination of different factors present in the diabetic milieu with hyperglycemia, the one responsible for the impairment of the outer BRB and TJ disruption. In our second study we used a combination of IL-1β + hyperglycemia to mimic the diabetic milieu and induce the breakdown of ARPE-19 monolayer. Treatment with fenofibric acid was able to reduce (at 25 μmol/l) or prevent (at 100 μmol/l) in a dose-dependent manner, the increment of permeability and the disorganization of TJ induced by IL-1β + 25 mmol/l D-Glucose, which was associated with the preservation of the sealing function of RPE cells. This effect was unrelated to changes in the content of TJ proteins, suggesting that an ordered distribution, rather than a crude assortment, of TJ proteins is essential for the efficient functioning of the outer BRB barrier. In addition, we demonstrated that the protective effect of fenofibric acid was mainly mediated by its ability to lower AMPK activation induced by IL-1β, which prevented the hypermermeability induced by the diabetic milieu. These findings contribute significantly to increasing our knowledge about the mechanisms involved in the beneficial effects of fenofibrate on the development and progression of DME.

CASTRO, Luan Veira de. Transporte balístico em dispositivos de grafeno nanoestruturados. 2015. 83 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2015.
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In this dissertation, we studied the electronic properties of a graphene nanoestructure under influence of external fields. We considered the application of an uniform transversal electric field and an uniform perpendicular magnetic field. Using a nearest-neighbor Tigh-binding model, we investigated how those fields change the band structure and the local density of states (LDOS) of the system. Then, we studied the transport properties of nanostructures. We assumed ballistic transport due to the long mean free path of graphene. Through a numerical model that it consists in solving the Tight-binding Hamiltonian in real space and the combination of the boundary conditions between the central region and the reservoir, we calculated the transmission coefficients for two specifics systems: First, for a graphene ribbon under the influence of a transversal electric field in a region of finite length; Next, for a three terminal ballistic junction (JBTT) of graphene under the influence of a transversal electric field in the region immediately before the junction.
Nesta dissertação, estudamos as propriedades eletrônicas de nanoestruturas de grafeno submetidas a campos externos. Consideramos a aplicação de um campo elétrico uniforme transversal e um campo magnético uniforme perpendicular à estrutura. Utilizando um modelo Tight-binding com hopping de primeiros vizinhos, vimos como esses campos modificam a estrutura de bandas e a densidade local de estados (LDOS) do sistema. Em seguida, estudamos as propriedades de transporte das nanoestruturas. Consideramos transporte balístico devido ao longo livre caminho médio do grafeno. Através de um modelo numérico que consiste em resolver o Hamiltoniano Tight-binding no espa ̧co real e combinar condições de contorno entre a região central e os reservatórios, calculamos os coeficientes de transporte para dois sistemas específicos: Primeiro, para uma nanofita de grafeno submetida a um campo elétrico transversal em uma região de extensão finita. Em seguida, para uma junção balística de três terminais (JBTT) de grafeno submetida a um campo elétrico transversal na região imediatamente adjacente à junção.

Los modelos de la actividad eléctrica cardiaca son esquemas teóricos de los fenómenos electro fisiológicos basados en formulaciones matemáticas y forman parte de los esfuerzos encaminados a facilitar su comprensión y la predicción de su comportamiento en distintas situaciones normales y patológicas. La modelización matemática y de estructuras anatómicas virtuales, unida a la simulación por ordenador contribuyen a analizar y comprender con mayor detalle el origen de las reentradas que dan lugar a las arritmias auriculares de origen eléctrico, ya que la complejidad inherente a este fenómeno hace muy difícil su estudio utilizando solamente la vía experimental. Este trabajo está basado en el desarrollo de dos modelos tridimensionales de aurícula humana, un modelo de dimensiones fisiológicas y otro con dilatación en la aurícula izquierda (remodelado estructural). A ambos modelos se les incorporó una orientación realista de las fibras y conducción anisotrópica. El remodelado eléctrico y el remodelado de gap junctions, ocasionados por episodios de fibrilación auricular crónica fueron simulados. De esta forma, el estudio contempla cuatro diferentes modelos: 1) un modelo en condiciones fisiológicas, con características anatómicas y eléctricas normales 2) un modelo de características anatómicas normales, pero en condiciones de remodelado eléctrico; 3) un modelo con dilatación y en condiciones de remodelado eléctrico; y 4) un modelo con dilatación y en condiciones de remodelado eléctrico y de gap-junctions. Los modelos reprodujeron la propagación del potencial de acción en situaciones fisiológicas y patológicas. Mediante simulación, se estudió el efecto del remodelado eléctrico, del remodelado estructural (dilatación) y del remodelado gap-junctions en la vulnerabilidad a reentradas. En general, los resultados muestran como el remodelado eléctrico favorece la generación de reentradas.
Ruiz Villa, CA. (2010). Estudio de la vulnerabilidad a reentradas a través de modelos matemáticos y simulación de la aurícula humana [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/9104
Palancia

El modelado se ha convertido en los últimos años en una herramienta esencial en el diseño de motores de combustión interna alternativos, ya que permite reducir considerablemente el tiempo y los costes de desarrollo. Las metodologías de diseño clásicas se basan en la fabricación de prototipos y la realización de pruebas de ensayo y error. Actualmente, la mayoría de estas pruebas han sido sustituidas por cálculos numéricos, de modo que sólo las opciones de diseño más prometedoras se prueban en realidad en banco motor. Durante años, los códigos unidimensionales de dinámica de gases en el dominio del tiempo han sido suficientes para modelar tanto las prestaciones y el consumo del motor como el ruido de admisión y escape. Sin embargo, para un nivel más exigente de diseño, una representación 1D puede no ser suficiente para describir con precisión el flujo en ciertos elementos. Esto es especialmente importante en el caso de silenciadores, donde la hipótesis unidimensional sólo se puede aplicar a geometrías simples. En el caso de las uniones de conductos es la existencia de estructuras tridimensionales de flujo complejas lo que establece el límite de la aplicabilidad de una descripción simple cero-dimensional. En vista de estas limitaciones, la primera opción sería el uso de un modelo de dinámica de fluidos computacional (CFD); sin embargo, su aplicación conllevaría un tiempo de cálculo excesivo. Una posible solución de compromiso viene dada por los modelos cuasi-3D, basados en esquemas tridimensionales, pero con ciertas simplificaciones capaces de reducir significativamente el tiempo de cálculo sin afectar excesivamente a la precisión. Tales soluciones se han convertido en estándar en los códigos comerciales y se han aplicado con éxito a los silenciadores, tanto para excitaciones acústicas en el régimen lineal como en condiciones reales de motor, típicamente no lineales. Esta tesis tiene como objetivo el desarrollo de un nuevo método numérico cuasi-3D en una malla escalonada, basado en la simplificación de la ecuación de la cantidad de movimiento, para ser incluido en un código unidimensional existente. Tal método, sin embargo, no está libre de inconvenientes. En particular, se ve afectado por la aparición de oscilaciones no físicas, especialmente en gradientes de presión significativos. De la revisión bibliográfica se determina que este comportamiento es típico en esquemas de segundo orden y se puede ver acentuado por las simplificaciones adoptadas. Tras estudiar las posibles soluciones aplicables a este problema, se desarrollan tres limitadores de flujo diferentes, basados en las metodologías MDT, FCT y TVD. Una vez definido el método numérico y asegurada su estabilidad, es necesario desarrollar las condiciones de contorno adecuadas que permitan su utilización. Con este objetivo, se desarrollan las condiciones de pulso de presión de entrada y de extremo anecoico, los cuales permiten simular un banco de impulso. No hay que olvidar, sin embargo, que el objetivo final es la conexión con un código unidimensional, por lo que hay que comprobar que el método numérico cuasi-3D creado es compatible con los unidimensionales existentes, mostrando algunos resultados preliminares. Finalmente, con el método ya completamente operativo, se procede a su validación en las aplicaciones para las que ha sido diseñado principalmente, las cuales son, modelado de silenciadores y uniones de conductos. Para el caso de los silenciadores, se modelan dispositivos de complejidad creciente, pasando por geometrías de sección constante hasta sistemas con geometrías reales. Los resultados obtenidos se validan con otras herramientas tanto lineales como no lineales. En el caso de las uniones de conductos, el objetivo principal es el de establecer el potencial del nuevo método numérico frente a los tradicionales unidimensionales, por lo que los resultados de ambos se comparan con datos experiment
Engine modelling has become an essential tool in the design of internal combustion engines, allowing considerable reductions in development time and cost. Classical design methodologies are based on prototype manufacturing and trial-and-error tests, but currently, most of those tests have been replaced by numerical computations, so that only the most promising design options are actually tested on engine bench. For years, one-dimensional gas dynamics codes in the time domain have offered sufficiently good solutions for modelling both engine performance and intake and exhaust noise. However, for a more demanding level of design, a 1D representation may not be sufficient to describe accurately the flow in certain elements. This is especially important in the case of silencers. In the case of duct junctions, the existence of complex 3D flow structures is what sets the applicability limit for a simple zero-dimensional description. In view of these limitations, the first option would typically be the use of a computational fluid dynamics (CFD) model; however, the application of such a model to a complete intake or exhaust system entails an excessive computational time. A possible compromise solution is given by quasi-3D models, based on three-dimensional schemes, but with certain simplifications able to significantly reduce the calculation time without excessively affecting the accuracy. Such solutions have become standard in commercial codes and have been successfully applied to silencers with perforated tubes and absorbing material, both in the linear acoustic regime and in real engine conditions, typically non-linear. The objective of this thesis is the development a new quasi-3D numerical method in a staggered-grid, based on the simplification of the momentum equation, to be included in an existing one-dimensional code. Such method however, is not hassle free. In particular, it is affected by the appearance of non-physical oscillations, specially near significant pressure gradients. From the literature review it is determined that this behaviour is typical among second-order schemes and it can be aggravated by the simplifications adopted. After researching the possible solutions to face this problem, three different flux limiters are developed, based on the MDT, FCT and TVD methodologies. In the case of the two latter methods, its effectiveness is well established for finite differences schemes, thus defining a clear improving line for quasi-3D models. Once the numerical method is defined and its stability assured, proper boundary conditions that allow its use must be developed. With this objective, a pressure pulse inlet and an anechoic termination boundary condition are developed, which allow the simulation of an impulse test rig. It should not be forgotten, however, that the ultimate objective is the connection with a one-dimensional code, therefore the compatibility of the quasi-3D numerical method created with the existing one-dimensional methods has to be tested, showing some preliminary results. Eventually, with a fully operative method, the validation process for the applications which it has been mainly developed for, takes place, namely, mufflers and duct junctions modelling. In the case of mufflers, increasingly complex devices are modelled, from constant section geometries to real geometry systems. The results obtained are validated with both linear and non-linear tools. In the case of duct junctions, the main objective is to establish the potential of the new numerical method against the traditional one-dimensional schemes, consequently, results from both approaches are compared to experimental measures, obtaining promising results.
El modelatge s'ha convertit en els últims anys en una eina essencial en el disseny de motors de combustió interna alternatius, ja que permet reduir considerablement el temps i els costos de desenvolupament. Les metodologies de disseny clàssiques es basen en la fabricació de prototips i la realització de proves d'assaig i error. Actualment, la majoria d'aquestes proves han sigut substituïdes per càlculs numèrics, de manera que només les opcions de disseny més prometedores es proven en realitat en banc motor. Durant anys, els codis unidimensionals de dinàmica de gasos en el domini del temps han sigut suficients per a modelar tant les prestacions i el consum del motor com el soroll d'admissió i escapament. No obstant això, per a un nivell més exigent de disseny, una representació 1D pot no ser prou per a descriure amb precisió el flux en certs elements. Açò és especialment important en el cas de silenciadors, on la hipòtesi unidimensional només es pot aplicar a geometries simples. En el cas de les unions de conductes és l'existència d'estructures tridimensionals de flux complexes el que establix el límit de l'aplicabilitat d'una descripció simple zero-dimensional. En vista d'estes limitacions, la primera opció seria típicament l'ús d'un model de dinàmica de fluids computacional (CFD); no obstant això, l'aplicació comporta un temps de càlcul excessiu. Una possible solució de compromís ve donada pels models quasi-3D, basats en esquemes tridimensionals, però amb certes simplificacions capaços de reduir significativament el temps de càlcul sense afectar excessivament la precisió. Tals solucions s'han convertit en estàndard en codis comercials i s'han aplicat amb èxit als silenciadors, tant per a excitacions acústiques en el règim lineal com en condicions reals de motor, típicament no lineals. Aquesta tesi té com a objectiu el desenvolupament d'un nou mètode numèric quasi-3D en una malla escalonada, basat en la simplificació de l'equació de la quantitat de moviment, per a ser inclòs en un codi unidimensional existent. Tal mètode, però, no està lliure d'inconvenients. En particular, es veu afectat per l'aparició d'oscil·lacions no físiques, especialment en gradients de pressió significatius. De la revisió bibliogràfica es determina que aquest comportament és típic en esquemes de segon ordre i es pot veure accentuat per les simplificacions adoptades. Després d'estudiar les possibles solucions aplicables a aquest problema, es desenvolupen tres limitadors de flux diferents, basats en les metodologies MDT, FCT i TVD. En el cas dels dos últims mètodes, la seua efectivitat està ben establida per als esquemes de diferències finites, la qual cosa definix una clara via de millora per als models quasi-3D. Una vegada definit el mètode numèric i assegurada la seua estabilitat, és necessari desenvolupar les condicions de contorn adequades que permeten la seua utilització. Amb aquest objectiu, es desenvolupen les condicions de pols de pressió d'entrada i d'extrem anecoic, els quals permeten simular un banc d'impuls. No cal oblidar que l'objectiu final és la connexió amb un codi unidimensional, per la qual cosa cal comprovar que el mètode numèric cuasi-3D creat és compatible amb els unidimensionals existents, mostrant alguns resultats preliminars. Finalment, es procedix a la seua validació en les aplicacions per a les que ha sigut dissenyat principalment, les quals són, modelatge de silenciadors i unions de conductes. Per al cas dels silenciadors, es modelen dispositius de complexitat creixent, passant per geometries de secció constant fins a sistemes amb geometries reals. Els resultats obtinguts es validen amb altres eines tant lineals com no lineals. En el cas de les unions de conductes, l'objectiu principal és el d'establir el potencial del nou mètode numèric front als unidimensionals tradicionals, per la qual cosa els resultats d'ambdós es comparen amb dades experim
Hernández Marco, M. (2018). A non-linear quasi-3D model for air management modelling in engines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/103683
TESIS

Cette these presente une etude de realisation et de caracterisation de jonctions josephson fabriquees a partir de joints de grains artificiels induits dans le film d'ybco. Deux procedes differents ont ete etudies: la fabrication du joint de grains par bi-epitaxie et le depot d'une couche supraconductrice sur substrat bi-cristallin. Le but du travail a ete de developper un procede de fabrication reproductible et d'etudier les proprietes des dispositifs obtenus. Les couches minces ont ete fabriquees par ablation laser pulse. Les dispositifs ont ete obtenus en gravant des lignes de differentes largeurs traversant le joint. Pour les echantillons realises par bi-epitaxie nous avons obtenus a travers un empilement de couches tampons adapte, le joint de grains dans l'ybco sur substrat de saphir ainsi que sur srtio3. Les mesures electriques ont mis en evidence que, pour ce type de joint, le courant josephson est trop faible et que la distribution de courant dans la jonction est inhomogene. Les limitations principales de cette technique sont liees aux contraintes imposes par l'angle de desorientation et par les defauts de fabrication. Pour les jonctions fabriquees sur bi-cristaux, les mesures en champ magnetique ont montre qu'un controle soigne de l'etat de la surface est necessaire pour avoir une barriere homogene. Ce resultat permet le controle de la jonction en regime flux flow. Les resultats preliminaires obtenus sur les transistors a flux de vortex josephson ont mis en evidence que ce type de dispositifs peut etre comme element amplificateur dans un circuit electronique supraconducteur

博士
國立臺灣大學
物理學研究所
107
High dielectric constant and low dielectric loss are of great importance for the energy saving and efficient power delivery. This thesis aims to investigate fundamental frequency dependent dielectric properties and high-k dielectric constant in the double perovskites related oxides. Throughout this thesis, we have observed the role of the oxygen stoichiometry and polarization on the dielectric properties of the double perovskites oxides, allowing a great understanding of the synthesis condition and polarization mechanisms. In the first section of the thesis, we explore the dielectric properties of the double perovskites Ba2LnRuO6 samples sintered at different cooling rates, using the impedance techniques in order to resolve the electrical heterogeneities components contributing to the dielectric constant. We observe a significant polarization dependence on the microstructure due to the grain/grain boundary effect at high and low temperatures.. The second section of this thesis investigates the dielectric materials Ba2LnMoO6 sintered at different atmospheres, one is in the Ar/H2 and the other is in the O2. We observe that Ba2LnMoO6 sintered in Ar/H2 shows a high dielectric constant while the Ba2LnMoO6 sintered in O2 exhibits a low dielectric constant. This allow us to tune the oxygen stoichiometry and obtain the more intrinsic dielectric properties for Ba2LnMoO6. The final part of the thesis is to investigate 2- and 4- terminal spin transfer torque systems using non-equilibrium Green function method. For coherent cases, We find that the lateral geometry (4-terminal) renders enhanced anti-damping torques compared with the conventional one (2-terminal) in a certain parameter region. For incoherent cases, we discover that the dephasing can enhance the anti-damping torque. The results show that enhancement of the anti-damping torques declines when the scattering region is longer. For the four-terminal MTJ of larger scattering length, the dephasing can expedite the anti-damping torque.

by Han Dejun.
Thesis (Ph.D.)--Chinese University of Hong Kong, 1996.
Includes bibliographical references (leaves [117]-[129]).
Abstract --- p.ii
Acknowledgment --- p.iv
Table of Contents --- p.v
Chapter 1. --- Introduction --- p.1-1
Chapter 1.1 --- The Current Situation of Space-division Optical Switches --- p.1-1
Chapter 1.1.1 --- Digital Optical switches (DOS) --- p.1-2
Chapter 1.1.2 --- Twin-guide amplifier (TGA) --- p.1-3
Chapter 1.1.3 --- Direction coupler with amplifiers --- p.1-4
Chapter 1.1.4 --- Total internal reflection type switch with amplifier --- p.1-5
Chapter 1.1.5 --- Semiconductor optical amplifier gate switches --- p.1-6
Chapter 1.2 --- Existing Problems --- p.1-9
Chapter 1.3 --- New Proposals --- p.1-10
Chapter 1.3.1 --- New features --- p.1-11
Chapter 1.3.2 --- New technology for OEIC --- p.1-13
Chapter 1.3.3 --- Expected improvement in performance --- p.1-14
Chapter 1.4 --- Organization of thesis --- p.1-17
Chapter 2. --- Band Lineup And Optical Gain Calculation --- p.2-1
Chapter 2.1 --- Introduction --- p.2-1
Chapter 2.2 --- Band Lineup for InGaAsP MQW Structures --- p.2-3
Chapter 2.2.1 --- Derivation According to Ishikawa et al.'s Scheme --- p.2-3
Chapter 2.2.2 --- Derivation According to Krijn's scheme --- p.2-5
Chapter 2.2.3 --- Improved band lineup calculation scheme --- p.2-7
Chapter 2.3 --- Gain and Spontaneous Emission Rate Expressions --- p.2-13
Chapter 2.3.1 --- Optical gain expressions --- p.2-13
Chapter 2.3.2 --- Spontaneous Emission Rate Expressions --- p.2-16
Chapter 2.3.3 --- Polarization characteristics --- p.2-17
Chapter 2.4 --- Optical Absorption and Its Polarization Sensitivity --- p.2-18
Chapter 2.4.1 --- Absorption in an intermixed QW Structure --- p.2-18
Chapter 2.4.2 --- Electro-optical Absorption --- p.2-19
Chapter 3. --- Design of the Optical Switches --- p.3-1
Chapter 3.1 --- Design of Material Layer Structure --- p.3-2
Chapter 3.2 --- Design of Device Geometrical Structure --- p.3-7
Chapter 3.3 --- Optical Gain in Polarization Insensitive Gain Medium-- An Example --- p.3-8
Chapter 3.4 --- Optical Absorption in Polarization Insensitive Gain Medium-- An Example --- p.3-15
Chapter 4. --- Fabrication Technology --- p.4-1
Chapter 4.1 --- Passive Waveguide Formation --- p.4-2
Chapter 4.1.1 --- Impurity-free vacancies diffusion technology --- p.4-3
Chapter 4.1.2 --- High energy ion implantation enhanced intermixing technology --- p.4-4
Chapter 4.1.3 --- Elevated temperature O+ HE-IIEI of MQWs --- p.4-6
Chapter 4.2 --- Oxygen Implant Isolation --- p.4-6
Chapter 4.3 --- Self Aligned Ridged Waveguide Technology --- p.4-7
Chapter 4.4 --- Reduction of Effective Facet Reflectivity --- p.4-11
Chapter 4.5 --- Fabrication Process Flow --- p.4-12
Chapter 4.5.1 --- Layer structure of the material --- p.4-12
Chapter 4.5.2 --- Fabrication process flow for the Y-junction optical switches --- p.4-14
Chapter 4.6 --- Schematic Structure of the Fabricated Switches --- p.4-19
Chapter 5. --- Experimental Results --- p.5-1
Chapter 5.1 --- High Energy Ion Implantation Enhanced Intermixing of Quantum Wells --- p.5-2
Chapter 5.1.1 --- High energy ion implantation --- p.5-2
Chapter 5.1.2 --- Rapid thermal annealing --- p.5-4
Chapter 5.2 --- Photoluminescence --- p.5-6
Chapter 5.3 --- Electroluminescence --- p.5-9
Chapter 5.4 --- Current-Voltage characteristics --- p.5-12
Chapter 5.5 --- Guided-Wave Optoelectronic Measurement --- p.5-14
Chapter 5.5.1 --- Setup of the measurement --- p.5-14
Chapter 5.5.2 --- Measurement of absorption loss for the blue-shifted QW structure --- p.5-16
Chapter 5.5.3 --- Optical losses measurement by Fabry-Perot interference method --- p.5-18
Chapter 5.5.4 --- Electroabsorption peak shift in IIEI wafer --- p.5-21
Chapter 5.6 --- Oxygen Implant Isolation --- p.5-21
Chapter 5.7 --- Characteristics of Optical Switches --- p.5-23
Chapter 5.7.1 --- Current-voltage characteristics --- p.5-23
Chapter 5.7.2 --- Optical mode and transmission characteristics --- p.5-24
Chapter 5.7.3 --- Switch characteristics --- p.5-29
Chapter 5.7.4 --- Discussion --- p.5-32
Chapter 6. --- Conclusion and Future Studies --- p.6-1
Chapter 6.1 --- Conclusion --- p.6-1
Chapter 6.1.1 --- The major contributions to the Y-JOS --- p.6-1
Chapter 6.1.2 --- The major contribution to the bandgap engineering for InGaAs(p)/InP heterostructure --- p.6-3
Chapter 6.1.3 --- The major contributions to the HE-IIEI technology --- p.6-4
Chapter 6.2 --- Topics for Future Studies --- p.6-5
Chapter 6.2.1 --- Band lineup and optical gain calculation --- p.6-5
Chapter 6.2.2 --- Optimization of HE-IIEI technology --- p.6-6
Chapter 6.2.3 --- Optimization of the Fabrication of Y-JOS --- p.6-7
Reference --- p.R1
Appendix A Characteristics Of Strained Quantum Wells --- p.A1
Appendix B Effective Index Change Induced by Quantum Well Intermixing --- p.A3
Appendix C Abbreviation --- p.A13
Appendix D List of Publications --- p.A14

碩士
龍華科技大學
電機工程系碩士班
103
This paper presents a high-transmission Y-junction photonic crystal power splitter. The designed Y-junction power splitter has the characteristics of high-transmission efficiency by moving,adding or deleting the dielectric rods at the fort part of the junction.The results show that comparing with conventional photonic crystal Y-junction power splitter, this paper's design can significantly reduce the reflectivity and increase the transmission efficiency.

The need for mass scale testing in areas such as microbiology and chemistry requires faster processing times, multiplexing capability, and reduced reagent requirements. To achieve this, the volumes processed must be reduced. This work intends to produce a microfluidic chip capable of producing increasingly smaller droplets that serve as testing vessels, by taking advantage of the dynamics of two immiscible fluids. The purpose of the present chip is to be used in the future in a digital Polymerised Chain Reaction (dPCR) for DNA amplification and detection. The microfluidic device was first simulated using COMSOL Multiphysics to understand the different behaviours of the droplet generator junctions. Glass sealed devices were produced using soft-lithography, composed of two different parts, a glass substrate and a top PDMS slab fabricated by photolithography of a SU-8 mould on a Si wafer that was used to mould the PDMS. Devices were tested with two immiscible fluids, which were injected at a constant flow rate into two inlets that lead to the junction were the droplets were formed. We were able to obtain droplets as small as 1 nL in devices with a channel size of 50 μm. We concluded that reducing the entry section to the main channel until the junction point, will decrease droplet size keeping the same size of the channels after the junction. Faster droplet generation rate was also obtained, using side channels width smaller (50 μm) than the main channel (100 μm).

博士
國立彰化師範大學
電機工程學系
107
This dissertation mainly proposes a symmetrical/asymmetrical Y-junction coupler with arc-bend branch structures to be used as a beam combiner and splitter so that the light generated by the sun or artificial light sources can be effectively combined and introduced into the room and then be appropriately split into all corners as auxiliary lighting. For the operation of this curved Y-junction coupler, this dissertation uses a ray-tracing theory to investigate the propagation characteristics of the beam in a curved optical waveguide. It is found that the alteration of the beam direction in a curved optical waveguide is equivalent to the reflection formed by a concave mirror. This simple concept is, therefore, used to derive an optimal arc structure for designing a symmetric/asymmetric Y-junction coupler with high coupling efficiency and concentrated beam-energy for general distributed lighting systems. In order to further investigate the beam combination/split efficiency generated by the Y-junction coupler and the beam intensity distribution at its exit, this dissertation uses an optical software to introduce the practical light source rays into the Y-junction coupler and perform ray tracing. So, the output-beam energy and distribution at the exit can be investigated, and the beam combination/split efficiency of the coupler and the outgoing beam angle can be calculated. The optical simulation results show that the Y-junction coupler has a coupling efficiency over 88%, whether used as a beam splitter or a combiner, and an energy-concentrated outgoing beam (i.e., a small beam angle). Therefore, it is advantageous for the outgoing beam to be transmitted in the subsequent optical waveguide, which greatly reduces the large fresnel loss caused by a large beam angle. In addition, under the same coupling conditions, i.e., the fixed branch length and the same cross angle of branches, the curved Y-junction coupler of this dissertation, as compared with the traditional linear Y-junction coupler, can have a smaller and smooth taper angle in the two-branch overlapping area and thus has higher splitting or combining efficiency. Meanwhile, the optical simulation results show that these two Y-junction couplers with different structures will have a larger difference in coupling efficiency between each other when the cross angle of branches becomes larger (over 20%). In addition to the use of a single arc-bend branch structure to construct the Y-junction coupler, this paper further uses two arc structures of the same (or different) size to form a S-shaped structure in series for constructing various multi-junction couplers with S-shaped branch structures, which can be applied to a more complex distributed lighting system.

碩士
國立彰化師範大學
電機工程學系
107
The thesis mainly applies a multi-step index (MSI) fiber and arc-branch structure to the design and research of a Y-junction coupler in a distributed illumination system. Generally, an optical fiber illumination system usually needs to combine multiple light-source beams into one beam or divide one beam into multiple beams, and the used beam combining or splitting elements are usually the Y-junction coupler. In previous researches, most of couplers were designed and fabricated with a single material of step-index (SI) fibers; however, the efficiency of the couplers is declined due to the susceptibility of a taper region formed by multi-branch stacks. Therefore, this thesis uses a MSI plastic optical fiber (POF), which is similar to a graded-index (GRIN) fiber having property of self-focus, to design the Y-junction coupler and improve the light loss caused by the taper region so that the coupling efficiency can be increased, the output beam-angle becomes more convergent, and the size of the coupler is greatly reduced. Optical simulation results show that the combining and splitting efficiencies of the MSI-POF Y-junction coupler designed in this thesis can reach 74 and 85%, respectively, and corresponding minimum output half-beam angles can be respectively reduced to 67 and 45% of the original half source-beam angle. As compared with a high efficient SI-POF Y-junction coupler, the MSI-POF Y-junction coupler has good coupling efficiency even at a smaller bending radius, and the associated convergence angle is less than that of the SI-POF coupler even up to 78% that the volume of the coupler can be greatly reduced.

碩士
國立高雄大學
電機工程學系碩士班
101
In this thesis a ridge waveguide ring laser with double ring cavities and Y-junction couplers had been fabricated on a MOCVD grown AlGaInP/InGaP multiple quantum well substrate. It is found that a single mode output spectrum which related to the 8 figure shape cavity formed by two circular ring cavities is dominated at threshold current density at 1.4 kA/cm2.As the injection current increased up higher until the threshold of the lasing from the solitons cavity was reached, a multi-modes output spectrum due to Fabery-Perot resonance was observed. Model based on the principle of emission rate equilibrium of the laser cavity with two ring cavities and the combination of a soliton cavity has been developed to explain the results of the output characteristics of laser devices fabricated. In addition, lasing modes from each circular ring emission was difficult to existed due to higher threshold current than the figure 8 cavity which overlapping these two ring cavities and had longer cavity length path.

碩士
國立高雄大學
電機工程學系碩士班
99
In this thesis we demonstrate a ridge waveguide circular ring laser device, with two Y-junction output couplers ,and the development of the device process . We have studied the spectrum and L-I characteristics of both two outputs at Y-junction terminals.and found that the output spectrum at the Y-junction couplers are hybrid of single mode and multi-modes , and the outputs at two terminals have almost same characteristics.By destroying the optical property of the waveguide ,we found that the single mode output is refered to the emission from the circular ring resonator ,and the multi-modes output is refered to the U-shaped resonator .In addition,a simple model of the single ring + U-shaped resonator is suggested to verify the results in this experiment.The result and references of this experiments will help to develop the opto-electronics integrated system in the future.

碩士
龍華科技大學
電機工程系碩士班
101
This thesis is focused on the design and analysis of polarization splitter in two-dimensional compound-type photonic crystal. The plane wave expansion method and the finite-difference time-domain method are employed to calculate photonic bandgap and to simulate wave propagation, respectively. Firstly, Three line-defect waveguides which can guide only the transverse electric (TE) wave, only the transverse magnetic (TM) wave, and both the TE and TM waves are designed in a compound-type lattice with a complete photonic bandgap. Secondly, an asymmetric Y-junction polarization splitter is designed based on the three line-defect waveguides. Transmission efficiencies of the polarization splitter can be improved by modifying the radius of the air holes. According to simulation results, transmission efficiencies larger than 85% and 95% can be obtained for TM and TE waves, respectively.

碩士
國立高雄大學
電機工程學系碩士班
100
In this thesis a semiconductor ridge waveguide circular ring laser with two Y-junction couplers had been fabricated. We observed both self-focusing of two beams propagating through the non-waveguide region and self-competing of two lines waveguide. We found a semiconductor circular ridge waveguide ring laser with multiple outputs by etching depth of 0.8μm has more opportunity to generate soltion than etching depth of 1.1μm. We have studied the characteristic of two output terminals at Y-junction and at soliton emission . In ideal case when a semiconductor circular ridge waveguide by etching depth of 1.1μm the output spectrum of two output terminals is single mode, and both outputs have almost the same L-I characteristics. As well as when a semiconductor circular ridge waveguide by etching depth of 0.8μm the two line waveguide competing brought almost all output power would focus on one line waveguide, and the output spectrum of the line is also single mode. So we can generate the soliton emission by controlling etching depth of ridge waveguide.