Dissertations / Theses on the topic 'TCAD ANALYSIS'
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Bäcker, Alexandra. "A TCAD analysis of long-wavelength vertical-cavity surface-emitting lasers." Konstanz Hartung-Gorre, 2009. http://d-nb.info/995591296/04.
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Brunton, Jason A. "TCAD analysis of heating and maximum current density in carbon nanofiber interconnects." Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5495.
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Approved for public release; distribution is unlimited.As devices shrink, the current density through interconnects increases proportionally making new materials a necessity for industry growth. Carbon nanofiber (CNF) and carbon nanotube's (CNT) potential for high current density make them a possible replacement for metal contacts. Learning the limitations of CNFs and CNTs is important if they are to be used in next-generation electronics. As current density increases, heat is generated throughout the CNF structure. This heating eventually leads to breakdown as the temperature reaches the bonding energy of the Carbon-Carbon (C-C) bond, the bond between two carbon atoms. The resultant reaction is the vaporization of the carbon, eliminating electromigration problems common with metal interconnects. The physics of breakdown of CNFs is poorly understood. The CNF interconnects' heating under a voltage sweep between two electrodes is modeled in this thesis. A working model was created with Silvaco ATLAS using experimental data provided by Santa Clara University (SCU). An analytical solution was found for the heat generation occurring within the device. The simulation does not show the breakdown occurring; instead, it accurately predicts the temperature and electrical characteristics of the device. This model will aid in the analysis of CNFs' reliability and potential future integration into the next generation electronics.
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Mazzoli, Andrea. "TCAD analysis of hot-carrier-stress degradation in p-channel LDMOS power devices." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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Nowadays, there is an increasing need to develop, reliable and low-cost power devices able to withstand high voltage drops and currents during the off-state and on-state operation, respectively. A useful strategy is represented by the integration on-chip of power devices with CMOS logic and analog technologies. This kind of solution is named BCD (BIPOLAR-CMOS-DMOS) technology.
One of the fundamental power device on which the BCD technology is based is the LDMOS (Laterally-Diffused Metal-Oxide Semiconductor) transistor. The study and understanding of the degradation mechanisms affecting their long-term reliability is of great interest because of the stringent requirements in terms of safety, robustness, etc., basing on the field of application of the circuit in which the devices are integrated.
This work, in collaboration with STMicroelectronics, focuses on the optimization of the p-channel LDMOS transistors and aims at studying and understanding how the Hot Carrier Stress (HCS) degradation impacts their performance for long working times. The behavior of the device is simulated through the Sentaurus TCAD where a HCS degradation model is employed to understand which are the dominant effects of the hot particles within the semiconductor, applying stress conditions aimed at accelerating the degradation mechanisms causing the drift of key parameters.
In this work the focus is on the on-resistance, since it results to be the main parameter affected by degradation. The goal is to understand exactly which is the main cause of such variation in order to be able to allow a technology improvement. The simulations have been calibrated against experimental data.
The on-resistance curve are correctly calibrated under certain stress conditions. The goal of the thesis activity has been achieved with accurate results, bringing to a more detailed description of a p-channel LDMOS power device through the development of a first version of the predictive simulation tool.
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Couso, Fontanillo Carlos. "Analysis of impact of nanoscale defects on variability in mos structures." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/650408.
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En los últimos años, la información y su análisis se han convertido en la piedra angular del crecimiento de nuestra sociedad, permitiendo la economía compartida, la globalización de productos y conocimientos, etc. Grandes compañías como Amazon, Facebook, Google... que son conscientes del potencial de estos recursos, están desarrollando infraestructuras con el fin de extraer toda la información posible sobre nuestro entorno (Internet de las cosas) o sobre nosotros mismos (redes sociales, teléfonos inteligentes ...), procesar esta información (Big Data Centers) y transmitirla rápidamente y entre cualquier parte del mundo. Sin embargo, la construcción de esta infraestructura requiere cada vez mejores dispositivos electrónicos, que no pueden desarrollarse utilizando las técnicas de escalado convencionales, porque las dimensiones de los dispositivos han alcanzado el rango atómico. Entre las diferentes fuentes de variabilidad, las trampas de interfaz (IT), las distribuciones de dopantes aleatorios (RDD) y la rugosidad de borde de línea (LER) se han identificado como las más destacadas. En consecuencia, la comunidad científica está explorando nuevas soluciones mediante sofisticadas técnicas experimentales o software de simulación, con el fin de superar los problemas de escalado. En este contexto, esta tesis estructurada en 7 capítulos, intentará contribuir a resolver este problema, analizando el impacto de las trampas de la interfaz y los defectos en la variabilidad de dispositivos.
Para presentar al lector los conceptos fundamentales aplicados en esta tesis, en el capítulo 1 se explica la teoría del transporte de carga a través de una unión Schottky y el transistor de efecto de campo semiconductor de metal-óxido (MOSFET). Además, también se presentan el concepto de variabilidad y diferentes fuentes de variabilidad.
En el segundo capítulo, se describen en detalle las técnicas de caracterización avanzada, como la microscopía de fuerza atómica conductiva (CAFM) para obtener información a nanoescala. Después de eso, se explica el simulador TCAD de dispositivos ATLAS y sus limitaciones, el cual es usado en esta tesis.
El tercer capítulo está dedicado a describir el impacto de los defectos (threading dislocations) en la conducción a través de un contacto Schottky. Aquí, diferentes mecanismos de conducción que están asociados a la conducción a través de áreas con TD y sin TD son analizados demostrando que el área con alta densidad de TD muestra mayor corriente de fuga.
En el capítulo cuatro, las técnicas de caracterización explicadas en el capítulo 2 se utilizan para obtener información a nanoescala. Para introducir esta información al simulador TCAD, se desarrollaron dos herramientas de software que son explicadas. Finalmente, la variabilidad de dispositivos MOSFET se estudia teniendo en cuenta los datos experimentales a nanoescala.
En el capítulo cinco, se analiza la influencia de las trampas de interfaz en la variabilidad del dispositivo. En primer lugar, se estudia el impacto de las cargas fijas discretas de la interfaz en dispositivos MOSFET de tecnología de 65 nm con diferentes dimensiones (variabilidad tiempo-cero), donde una desviación de la ley de Pelgrom se prueba mediante datos experimentales y de simulación TCAD. A continuación, el comportamiento dinámico de las trampas se analiza mediante las simulaciones transitorias TCAD, con el fin de estimar sus parámetros físicos de trampas a partir de parámetros empíricos.
El último capítulo de resultados está dedicado a estudiar el compromiso entre el rendimiento y el consumo de potencia en (Silicon On Insulator) SOI MOSFET cuando se opera en un voltaje cercano al umbral. Además, también se analiza el impacto de las trampas de interfaz en el rendimiento y el consumo de potencia del dispositivo.
Finalmente, en el último capítulo, se destacan las conclusiones más relevantes de esta tesis.Over the last years, the information and its analysis have become in the corner stone of growth of our society allowing the sharing economy, globalization of products and knowledge, block-chain technology etc. Huge companies such as: Amazon, Facebook, Google... which were aware of the potential of these resources, are developing vast infrastructures in order to extract as much information as possible about our environment (Internet of Things) or ourselves (social media, smart-phones...), process this information (Big Data Centers) and transmit it quickly all over the world. However, this challenge requires electronic devices with higher performance and low power consumption, which cannot be developed using the conventional scaling techniques because the dimensions of devices have reached the atomic range. In this range of dimensions, the impact of the discrete of matter and charge increases inevitably the variability of devices. Among different variability sources, Interface traps (IT), Random Dopant Distributions (RDD), Line Edge Roughness (LER) and Poly Gate Granularity (PGG) have been identified as the most prominent ones. Consequently, the scientific community is exploring new solutions such as, alternative device materials and/or structures, in order to overcome the different issues owing to the scaling. In this context, this thesis, which is structure in 7 chapters, will try to contribute to solve this problem, analyzing the impact of interface traps and defects on device variability. In order to introduce to the reader, in chapter 1 the charge transport theory through a semiconductor and metal junction (Schottky contact) and the Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) device are explained. Besides, the concept of variability and different sources of variability are also presented. In the second chapter, advanced characterization techniques, such as, Conductive Atomic Force Microscopy (CAFM) and Kelvin Prove Force Microscopy (KPFM) used to obtain nanoscale information are described in detail. After that, the TCAD device simulator called ATLAS is explained. Here, the models and their limitations to simulate the electronic devices are discussed. Third chapter is devoted to describe the impact of threading dislocation (TD) defects on the conduction through a schottky contact formed by a III-V semiconductor material (InGaAs) and a metal. Here, different conduction mechanisms, Poole Frenkel (PF) and Thermionic Emission (TE), have been associated to the conduction through areas with TD and without TD, respectively, proving that III-V materials with high density of TD showing higher leakage current. In chapter four, the development of a simulator called (NAnoscale MAp Simulator (NAMAS)) to generate automatically topography and density charge maps from inputs obtained from CAFM measurements (topography and current maps) of a given sample is explained. From the generated maps, the impact of the oxide thickness and the charge density fluctuations on MOSFET variability is studied. In chapter five, the impact of interface traps in the gate oxide on device variability is analyzed. Firstly, the impact of interface discrete fixed charges on 65 nm technology MOSFET devices with different dimensions is studied (time-zero variability), where a deviation of Pelgrom's law is proved by experimental and TCAD simulation data. Next, the dynamic behavior of traps is analyzed by TCAD transient simulation in order to estimate their physical parameters of traps from empiric parameters. Chapter six is devoted to study the performance and power consumption trade-off in Ultra-thin Body and Buried Oxide Fully Depleted Silicon on Insulator (UTBB FDSOI) MOSFET when it is operated in near-threshold voltage. Besides, the impact of traps in gate oxide / channel and in buried oxide / channel interfaces on the performance and power consumption of device is also analyzed. Finally, the more relevant conclusions are highlighted.
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Ramirez-garcia, Eloy. "Analyse expérimentale et modélisation du bruit haute fréquence des transistors bipolaires à hétérojonctions SiGe et InGaAs/InP pour les applications très hautes fréquences." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112082/document.
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Le développement des technologies de communication et de l’information nécessite des composants semi-conducteurs ultrarapides et à faible niveau de bruit. Les transistors bipolaires à hétérojonction (TBH) sont des dispositifs qui visent des applications à hautes fréquences et qui peuvent satisfaire ces conditions. L’objet de cette thèse est l’étude expérimentale et la modélisation du bruit haute fréquence des TBH Si/SiGe:C (technologie STMicroelectronics) et InP/InGaAs (III-V Lab Alcatel-Thales).Accompagné d’un état de l’art des performances dynamiques des différentes technologies de TBH, le chapitre I rappelle brièvement le fonctionnement et la caractérisation des TBH en régime statique et dynamique. La première partie du chapitre II donne la description des deux types de TBH, avec l’analyse des performances dynamiques et statiques en fonction des variations technologiques de ceux-ci (composition de la base du TBH SiGe:C, réduction des dimensions latérales du TBH InGaAs). Avec l’aide d’une modélisation hydrodynamique, la seconde partie montre l’avantage d’une composition en germanium de 15-25% dans la base du TBH SiGe pour atteindre les meilleurs performances dynamiques. Le chapitre III synthétise des analyses statiques et dynamiques réalisées à basse température permettant de déterminer le poids relatif des temps de transit et des temps de charge dans la limitation des performances des TBH. L’analyse expérimentale et la modélisation analytique du bruit haute fréquence des deux types de TBH sont présentées en chapitre IV. La modélisation permet de mettre en évidence l’influence de la défocalisation du courant, de l’auto-échauffement, de la nature de l’hétérojonction base-émetteur sur le bruit haute fréquence. Une estimation des performances en bruit à basse température des deux types de TBH est obtenues avec les modèles électriquesIn order to fulfil the roadmap for the development of telecommunication and information technologies (TIC), low noise level and very fast semiconductor devices are required. Heterojunction bipolar transistor has demonstrated excellent high frequency performances and becomes a candidate to address TIC roadmap. This work deals with experimental analysis and high frequency noise modelling of Si/SiGe:C HBT (STMicroelectronics tech.) and InP/InGaAs HBT (III-V Lab Alcatel-Thales).Chapter I introduces the basic concepts of HBTs operation and the characterization at high-frequency. This chapter summarizes the high frequency performances of many state-of-the-art HBT technologies. The first part of chapter II describes the two HBT sets, with paying attention on the impact of the base composition (SiGe:C) or the lateral reduction of the device (InGaAs) on static and dynamic performances. Based on TCAD modelling, the second part shows that a 15-25% germanium composition profile in the base is able to reach highest dynamic performances. Chapter III summarizes the static and dynamic results at low temperature, giving a separation of the intrinsic transit times and charging times involved into the performance limitation. Chapter IV presents noise measurements and the derivation of high frequency noise analytical models. These models highlight the impact of the current crowding and the self-heating effects, and the influence of the base-emitter heterojunction on the high frequency noise. According to these models the high frequency noise performances are estimated at low temperature for both HBT technologies
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El, Boubkari Kamal. "Impact de la modélisation physique bidimensionnelle multicellulaire du composant semi-conducteur de puissance sur l'évaluation de la fiabilité des assemblages appliqués au véhicule propre." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00856596.
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A bord des véhicules électriques (VE) et Hybrides (VEH), les fonctions de tractions sont assurées par des convertisseurs électroniques de puissances. Ces derniers sont constitués de module de puissance (IGBTs ou MOSFETs). Au cours de leur fonctionnement, ces modules sont parfois soumis à de fortes contraintes électriques et thermiques qui amènent à une défaillance ou même à une destruction. Le premier objectif sera de réaliser un banc expérimentale permettant d'étudier le vieillissement des modules IGBTs en régîmes extrêmes de fonctionnement (mode de court-circuit). Ainsi, nous évaluerons les différents indicateurs de vieillissements permettant de prédire la défaillance du composant. Il sera question aussi de suivre le vieillissement ou une dégradation initié sur les composants IGBTs par thermographie infrarouge. Le second objectif sera de modéliser et simuler par éléments finis différentes structures d'IGBTs, afin de valider les modèles en fonctionnement statique et dynamique. L'avantage de l'approche multicellulaire par rapport à l'approche unicellulaire sera mis en avant.
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Baccar, El Boubkari Fedia. "Évaluation des mécanismes de défaillance et de la fiabilité d’une nouvelle terminaison haute tension : approche expérimentale et modélisation associée." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0266/document.
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Ces travaux s’intègrent dans le projet de recherche SUPERSWITCH dans lequel des solutions alternatives à l’IGBT, utilisées dans les convertisseurs de puissance dans la gamme des tenues en tension 600-1200 V, sont envisagées. Les nouvelles structures du transistor MOS basées sur le principe de Super-Jonction tel que le transistor DT-SJMOSFET et sa terminaison originale, la « Deep Trench Termination » se propose comme alternative aux IGBT. Dans ce contexte, cette thèse se focalise sur la caractérisation de la robustesse de la terminaison DT2 adapté à une diode plane. Après avoir effectué un état de l’art sur les composants de puissances à semi-conducteur unidirectionnels en tension, les terminaisons des composants de puissance et la fiabilité des modules de puissance, un véhicule de test a été conçu en vue de réaliser les différents essais de vieillissement accéléré et suivi électrique. La fiabilité de la terminaison DT2 a été évaluée par des essais expérimentaux et des simulations numériques, dont une méthodologie innovante a été proposée. Au final de nouvelles structures ont été proposées pour limiter les problèmes de délaminage et de charges aux interfaces mis en avant dans notre étudeThis work is a part of the research project SUPERSWITCH in which alternatives solutions to the IGBT, are investigated. This solution was used IGBT in power converters in the 600-1200 V breakdown voltage range. The new MOSFET structures based on the super-junction, such as the DT-SJMOSFET and its "Deep Trench Termination", is proposed as an alternative to IGBT. In this context, this thesis focuses on the robustness characterization of the DT2 termination adapted to a planar diode. After a state of the art on unidirectional voltage power components, the power components termination, and power modules reliability, a test vehicle has been designed in order to carry out different accelerated ageing tests and electrical monitoring. The reliability of DT2 termination was evaluated by experimental tests and numerical simulations. An innovative modeling methodology has been proposed. Finally, new structures have been proposed to limit the delamination failure mechanisms and interface charges problems highlighted in this thesis
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Tang, Jun. "Causal models for analysis of TCAS-induced collisions." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/309134.
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Una sèrie de col·lisions aèries que van succeir durant un període d’uns 30 anys (1956-1986) van ser un dels principals motius pels quals l’Administració Federal d’Aviació (FAA) va prendre la decisió de desenvolupar i implementar un sistema de prevenció de col·lisions eficaç que actués com a últim recurs, quan es produís una fallada del servei de separació d’aeronaus per part del controlador de trànsit aeri (ATC). El Sistema d’Alerta de Trànsit i Anticol·lisió (TCAS) va ser desenvolupat per a aquest objectiu a partir d’una anàlisi completa de dades de vol. Com a resultat, la influència de TCAS en la seguretat del vol ha estat eficaç, beneficiosa i significativa en la reducció de la probabilitat de col·lisions.
Els projectes Single European Sky ATM Research (SESAR) i Next Generation Air Transportation System (NextGen) pretenen millorar l’eficiència en la gestió del tràfic aeri (ATM) al mateix temps que es pretén reduir l’actual capacitat latent en el costat aire mitjançant la incorporació de noves tecnologies i procediments. En conseqüència, serà necessari investigar l’impacte en seguretat en augmentar la capacitat de l’espai aeri mitjançant una anàlisi exhaustiva i una avaluació efectiva del vol. En aquesta tesi, es proposen diversos models causals de colisions entre aeronaus per millorar el rendiment del TCAS tenint en compte el potencial efecte sobre el trànsit colindant, considerant escenaris futurs amb un nombre elevat de trajectòries.
Els diferents models han estat especificats com a sistemes a esdeveniments discrets mitjançant el formalisme de Xarxes de Petri Acolorides. Mitjançant l’anàlisi de l’espai d’estat d’un volum d’espai aeri amb diverses aeronaus, els models desenvolupats avaluen els efectes dels diferents RAs generats pel TCAS sobre el tràfic col·lindant. Els models han estat validats utilitzant InCAS i ofereixen una perspectiva global de les dinàmiques que es generen, i una millor comprensió de les potencials col·lisions induïdes per a una millor valoració del risc de col·lisió.
Com a resultat, els escenaris amb tràfic col·lindant que podrien iniciar col·lisions induïdes han estat identificats i caracteritzats. L’anàlisi quantitativa del factor de risc de col·lisions induïdes per TCAS ha estat realitzat per avaluar l’impacte de la demora del pilot per respondre als avisos TCAS durant el vol en escenaris d’alta densitat. Mitjançant l’ús de models estocàstics per representar la resposta del pilot s’han analitzat els diferents estats assolibles amb l’objectiu de generar resolucions cooperatives. En conseqüència, el rendiment de TCAS es podria millorar de forma innovadora sense necessitat d’introduir canvis rellevants en la lògica.
Els models causals de col·lisions proposats poden ser utilitzats com a eines auxiliars en l’anàlisi d’escenaris de tràfic dens, i augmentar la capacitat de l’espai aeri, gestionant de manera eficient i segura un major nombre de vols. El present treball contribueix a continuar les investigacions en l’anàlisi de la seguretat dels conceptes ATM actuals i avançats, incloent les futures extensions de TCAS.Una serie de colisiones en el aire que ocurrieron durante un período de unos 30 años (1956-1986) fueron uno de los principales motivos por los que la Administración Federal de Aviación (FAA) tomó la decisión de desarrollar e implementar un sistema de prevención de colisiones eficaz que actuara como último recurso, cuando se produjese un fallo del servicio de separación de aeronaves por parte del controlador de tránsito aéreo (ATC). El Sistema de Alerta de Tráfico y Anticolisión (TCAS) fue desarrollado para este objetivo a partir de un análisis completo de datos de vuelo. Como resultado La influencia de TCAS en la seguridad del vuelo ha sido eficaz, beneficiosa y significativa en la reducción de la probabilidad de colisiones. Los proyectos Single European Sky ATM Research (SESAR) y Next Generation Air Transportation System (NextGen) pretenden mejorar la eficiencia en la gestión del tráfico aéreo (ATM) al mismo tiempo que se pretende reducir la actual capacidad latente en el lado aire mediante la incorporación de nuevas tecnologías y procedimientos,. En consecuencia, va a ser necesario investigar el impacto en seguridad al aumentar la capacidad del espacio aéreo mediante un análisis exhaustivo y una evaluación efectiva del vuelo. En esta tesis, se proponen varios modelos causales de encuentro entre aeronaves para mejorar el rendimiento del TCAS teniendo en cuenta el potencial efecto sobre el tráfico colindante, considerando escenarios futuros con un número elevado de trayectorias. Los diferentes modelos han sido especificados como sistemas a eventos discretos mediante el formalismo de Redes de Petri Coloreadas. Mediante el análisis del espacio de estado de un volumen de espacio aéreo con varias aeronaves, los modelos desarrollados evalúan los efectos de los distintos RAs generados por TCAS sobre el tráfico colindante. Los modelos han sido validados utilizando InCAS y ofrecen una perspectiva global de las dinámicas que se generan, y una mejor comprensión de las potenciales colisiones inducidas para una mejor valoración del riesgo de colisión. Como resultado, los escenarios con tráfico colindante que podrían iniciar colisiones inducidas han sido identificados y caracterizados. El análisis cuantitativo del factor de riesgo de colisiones inducidas por TCAS ha sido realizado para evaluar el impacto de la demora del piloto para responder a los avisos TCAS durante el vuelo en escenarios de alta densidad. Mediante el uso de modelos estocásticos para representar la respuesta del piloto se han analizado los diferentes estados alcanzables con el objetivo de generar resoluciones cooperativas. En consecuencia, el rendimiento de TCAS se podría mejorar de forma innovadora sin necesidad de introducir cambios relevantes en la lógica. Los modelos de encuentros causales propuestos pueden ser utilizados como herramientas auxiliares en el análisis de escenarios de tráfico denso, y aumentar la capacidad del espacio aéreo, gestionando de manera eficiente y segura un mayor número de vuelos. El presente trabajo contribuye a continuar las investigaciones en el análisis de la seguridad de los conceptos ATM actuales y avanzados, incluyendo las futuras extensiones de TCAS.
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Billingsley, Thomas B. (Thomas Boyd). "Safety analysis of TCAS on Global Hawk using airspace encounter models." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35294.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 66).
The U.S. Air Force's RQ-4 Global Hawk unmanned aerial vehicle (UAV) is a high altitude, long endurance aircraft used for surveillance and reconnaissance. Because of the potential for close proximity to manned aircraft in civil airspace, collision avoidance is a major concern, and the Air Force is seeking to equip Global Hawk with the Traffic Alert and Collision Avoidance System (TCAS) to reduce the probability of mid-air collision. Currently, Global Hawk is equipped with a Mode S transponder and uses chase aircraft, ground observers and/or ground radar contact to comply with the collision avoidance requirement. In order to evaluate TCAS effectiveness, a fast-time simulation tool has been developed at MIT Lincoln Laboratory that computes the mean probability of a near mid-air collision for a large number of close encounters between two aircraft. Airspace encounter models enable sets of encounters to be simulated that are statistically representative of the aircraft encounters that actually occur in the airspace. The TCAS logic is implemented in the simulation tool and the aircraft responses during the encounters, with and without TCAS, are simulated in parallel.
(cont.) By observing measured vertical miss distance at the closest point of approach between the two aircraft, it is possible to quantify the reduction in collision risk provided by TCAS, termed the risk ratio. Global Hawk's flight characteristics differ from a conventional aircraft. Its mission profile through civil airspace includes slow, steep climbs and descents, and shallower turns than a conventional aircraft. Its vertical acceleration and climb rate limits can hinder its response to a TCAS resolution advisory (RA). Communication latency also may occur. For this thesis, encounter models were developed that reflect Global Hawk's flight characteristics. The new encounter models were then implemented in the simulation tool, and millions of encounters between Global Hawk and a conventional aircraft were simulated. These encounters were compared against encounters between two conventional aircraft to observe how Global Hawk's flight characteristics changed the effectiveness of TCAS. Assuming a standard pilot response to TCAS RAs, TCAS provided a significant safety improvement to Global Hawk over a Mode S transponder alone, yielding risk ratios in the range of 0.003 to 0.079.
(cont.) Global Hawk's flight characteristics generally caused a decrease in TCAS effectiveness from the original encounter models. Encounters were also simulated where Global Hawk's response to TCAS RAs was delayed by increasing amounts to simulate communication latency. A delay of approximately 15 seconds was tolerable before TCAS provided less safety than a Mode S transponder alone.
by Thomas B. Billingsley.
S.M.
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Williams, Thomas C. R. "Metabolic Flux Analysis of the TCA Cycle in Arabidopsis." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515020.
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Puebla-Osorio, Nahum. "Transcriptional analysis of chicken immune cells following exposure to 2,3,7,8,-tetrachlorodibenzo-p-dioxin (TCDD)." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3165.
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In the present investigation, microarray analysis was used to identify potential TCDD gene targets. Three microarray experiments were performed to study the effect of TCDD in an established chicken B-cell line (DT40), in a chicken macrophage cell line (HD11), and in the bursa of Fabricius from embryos exposed in ovo at 6 days of incubation. From the DT40 microarray analyses, clones with sequence similarity to the apoptotic genes caspase 8 and caspase 9, and the transcription factor NFΜB, among others, were identified. Real-time quantitative polymerase chain reaction (RT-PCR) revealed that TCDD elicits aryl hydrocarbon receptor (AhR)-mediated apoptosis in the avian DT40 pre-B-cell line through activation of caspases 9 and 3 (see chapter III). During the course of the HD11 microarray analyses, a consistent down-regulation of the matrix metalloprotease MMP-2 was observed. This finding was the basis for the hypothesis that TCDD has an effect on the gene expression of the MMP-2 and MMP-9 in macrophages. Then, gene expression analysis and functional zymography showed that TCDD impairs the MMP-2 and MMP-9 response to LPS stimulation in HD11 chicken macrophages (see chapter V). The microarray analyses of the embryonic bursa of Fabricius provided the basis to further study of the effect of TCDD in the chicken embryo. The shifted genes were classified according to their function. The down-regulated genes included: precursor of matrix metalloprotease-inhibitor, histone acyl-transferase 1, homeobox protein CUX-2, Death Associated Protein Kinase, and UDPglucosyl transferase, among others. The up-regulated genes included: phosphoinositidespecific phospholipase, acyl Co-A oxidase, and protein effector of Cdc42, among others.
Together, these microarray analyses produced a database of genes of interest that will provide sufficient hypotheses to inspire multiple investigations aimed at confirming and refining the gene expression alterations as a consequence of TCDD exposure.
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Melges, Gustavo Cabrera. "Análise quantitativa automática da vasculatura pulmonar em TCAR de pacientes com hipertensão pulmonar." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/17/17158/tde-17042018-144837/.
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A hipertensão pulmonar (HP) é uma doença caracterizada por elevação da pressão da artéria pulmonar e um aumento da resistência vascular pulmonar levando à disfunção do ventrículo direito, sendo complicação importante de doenças como a doença pulmonar obstrutiva crônica (DPOC), doença pulmonar intersticial (DPI), colagenoses e vasculites. A tomografia computadoriza de alta resolução (TCAR) é um dos principais métodos de diagnóstico e acompanhamento destas doenças. Neste estudo objetivamos a analise quantitativa dos exames de TCAR do tórax em pacientes com doenças parenquimatosas difusas e hipertensão pulmonar diagnosticada por cateterismo direito. Foram analisados retrospectivamente os prontuários eletrônicos e os exames de TCAR de 29 pacientes com HP, em comparação com um grupo controle. Foram excluídos os casos de hipertensão arterial pulmonar primária e tromboembolismo crônico, cuja investigação é feita prioritariamente com exame de angiotomografia. A análise quantitativa foi realizada utilizando programa completamente automático e algumas medidas manuais também foram realizadas. O pacientes com HP, quando comparados ao controle, apresentaram redução do volume pulmonar, aumento da atenuação média do parênquima, aumento na medida do volume vascular pulmonar, aumento da densidade vascular pulmonar e na relação do volume vascular nos lobos superiores em relação aos lobos inferiores. O programa automático foi capaz de identificar as alterações da vasculatura, mesmo em se tratando de exames não contrastados e em meio a alterações arquiteturais do parênquima pulmonar. Estes achados provavelmente representam a redistribuição da trama vascular pulmonar, relacionada ao aumento da resistência vascular pulmonar. A análise quantitativa automática, realizada em exames de TCAR já utilizados na rotina clínica, pode representar nova ferramenta não invasiva capaz de identificar sinais de HP em pacientes com fator de risco, como DPOC, DPI, colagenoses, em que a HP representa complicação importante e de diagnóstico muitas vezes difícilPulmonary hypertension (PH) is a disease characterized by elevation in the mean pressure of the pulmonary artery and an increase in the pulmonary vascular resistance leading to right heart dysfunction, being an important complication of multiple diseases such as chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD), collagen diseases and vasculitis. The high resolution computed tomography (HRCT) is one of the main diagnostic methods and is also important in the follow up of these patients. In this study we aim the quantitative analysis of the thoracic HRCT exams in patients with diffuse parenchymal lung disease and pulmonary hypertension diagnosed by right heart catheterism. We analised retrospectively the clinical records and HRCT exams of 29 patients with PH, comparing to a control group. Were excluded from the study patients with primary pulmonary arterial hypertension (PAH) and chronic thromboembolism pulmonary hypertension (CTEPH), which investigations usually include pulmonary angiotomography. The quantitative analysis was made utilizing a completely automatic software and some manual measures were also noted. Patients with PH, when comparing to control group, presented significant pulmonary volume reduction, elevated mean parenchymal attenuation, elevated measures of the pulmonary vascular volume, increase in the pulmonary vascular density and also an elevation in the relation between vascular volume in the upper pulmonary lobes and the lower lobes. The automatic software was able to identify the vascular alterations, even in non contrast enhanced exams and amidst architectural distortions in the lung parenchyma. These findings probably represent the redistribution of the pulmonary vascular bed, related to the pulmonary vascular resistance increase. .The quantitative automatic analysis, made in HRCT exams, used in clinical practice, can represent a new non invasive tool, able to identify PH signs in risc patients, such as COPD, ILD and collagen diseases, in which PH represents an important complication with, many times, difficult diagnosis.
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Al, Maleh Rawan. "Genetic analysis of the TCA cycle enzyme 2-oxoglutarate dehydrogenase in Sinorhizobium meliloti." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106341.
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Genetic characterization of the mdh-sucCDAB operon, encoding enzymes of the TCA cycle, was performed. Isolation of a sucA knock-out mutant was attempted through homologous recombination with plasmids carrying a mutated fragment of the sucA gene. Several strains were screened for the expected phenotype of a 2-OGD mutant. Carbon-source utilization phenotype of the tested strains did not reveal highly dissimilar growth patterns in comparison to wild-type levels. PCR amplification of these strains did not yield the expected band size of a mutant copy of the gene. Furthermore, Southern blot analysis of the putative mutants was inconclusive in confirming their identity. Therefore, a sucA mutant was not successfully isolated. Expression of TCA cycle genes was examined under different growth conditions through qRT-PCR analysis. The sucA gene did not reveal any increase in transcript levels relative to sucD, under all tested conditions. This indicated the possible absence of a promoter independently controlling its expression. Other TCA cycle genes were differentially expressed in mdh and sucB mutants in comparison to wild type. Expression patterns did not appear to vary greatly across the tested carbon sources. Comparison of expression of TCA cycle genes in mutants, relative to wild type, revealed significant induction of sucB with arabinose in its respective knock-out mutant. Examination of transcript levels in bacteroids would elucidate the gene expression patterns observed in symbiotic conditions. In addition, further investigation of the nature of a sucA mutation will be required, to determine the possibility of a lethal phenotype.La caractérisation génétique de l'opéron mdh-sucCDAB qui encode des enzymes du cycle des acides tricarboxylique, a été effectuée. Isolement d'un mutant de sucA a été tentée par recombinaison homologue avec des plasmides portant une insertion dans le gène. Plusieurs souches ont été criblées pour le phénotype attendu d'un mutant de la déshydrogénase de 2-oxoglutarate. Le phénotype d'utilisation de carbone des souches testées n'ont pas révélé de modèles de croissance très dissemblables par rapport au phénotype sauvage. L'amplification par PCR de ces souches n'a pas donné la taille de la bande attendue d'une copie mutant du gène. L'analyse par Southern blot des mutants putatifs n'a pas été concluante pour confirmer leur identité. Par conséquent, l'isolement d'un mutant de sucA a échoué. L'expression des gènes du cycle des acides tricarboxylique a été examinée avec des conditions différentes grâce à qRT-PCR. L'inspection d'expression génétique de sucA n'a pas révélé une augmentation par rapport à la transcription de sucD. Cela indique une possibilité de l'absence d'un promoteur indépendant contrôlant son expression. D'autres gènes du cycle des acides tricarboxyliques sont exprimés différentiellement par les mutants de mdh et de sucB, en comparaison au type sauvage. Les profils d'expression ne semblent pas varier considérablement selon les sources de carbone testées. Comparaison de l'expression de ses gènes a révélé induction significative de sucB avec l'arabinose dans se mutant respectif. L'observation de transcription dans les bactéroïdes serait élucider l'expression dans des conditions symbiotique. Une enquête plus approfondie d'une mutation de sucA sera nécessaire, afin de déterminer la possibilité d'un phénotype résultant mortelle.
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Scott, L. H., Pamela H. Scott, and Donald W. Good. "Third and Fourth Grade TCAP Scores and the Universal Breakfast Program in Unicoi County." Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/etsu-works/287.
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Gorouhi, Hadi. "Novel fatigue analysis of old metallic bridges through the theory of critical distances (TCD)." Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/845859/.
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Majority of the railway bridges built in the UK and around the world before the middle of 20th century are of riveted type made of wrought iron or old mild steel. Many of these bridges are approaching their useful design life. Despite their old age, many are still in operation. In-service fatigue cracking and failure in the riveted double-angle connections in such bridges, especially in the rivets and outstanding leg of the angles, had been reported in the past. These connections are one of the most fatigue-prone details found in riveted railway bridges. Fatigue assessment of riveted details is generally based on a global life assessment, such as the S-N approach. The S-N approach involves the challenge of selecting an appropriate detail classification on an S-N basis as well as defining a nominal stress, free from stress raiser effects. By contrast, local stress methods, such as the Theory of Critical Distances (TCD), which directly considers the effect of stress raisers and loading conditions through finite element analysis, may provide a more favourable option for fatigue evaluation since it avoids the need for S-N classification and nominal stress calculation. In this thesis, the fatigue life prediction capability of the TCD and the S-N methods when applied to riveted bridge details was investigated through finite element analysis of simple and complex riveted details focusing on stringer-to-floor-beam connections. The fatigue life predictions of both the TCD and the traditional S-N methods were compared with the experimental data. Thus, a database of static and fatigue tests available in the literature on structural wrought iron and mild steel riveted details and connections was created. The choice of the suitable modelling techniques for the finite element analysis of the riveted details was verified using a benchmark study on a riveted single lap joint. The critical length vs. number of cycles to failure relationship, L vs. Nf, necessary for fatigue analysis based on the TCD was calibrated for structural wrought-iron material obtained from a real bridge. Fatigue assessment of the investigated riveted details was performed based on both the TCD and the S-N methods to quantify the differences. The results of this study showed that the TCD was successful in predicting fatigue life with the predictions falling within the constant amplitude scatter bands of the experimental data. In the single lap joint, the TCD method accurately estimated the average rivet clamping force values developed in the rivets of the specimens experimentally investigated. In the butt joints, the results of the TCD method was found to conformed well with the experimental research in the literature by predicting higher rivet clamping forces in the specimens with longer grip length. The novel formalisations of the TCD effectively predicted the fatigue life of full-scale riveted built-up girders with the results in the medium- and high-cycle always falling inside the CA scatter bands of the experimental data. The accuracy of the TCD method in estimating the rivet clamping forces present in the rivets of the investigated girders was found to be very high. The TCD was highly accurate when used to estimate the fatigue life of different components of the stringer-to-floor-beam connection subjected to four-point bending with the predictions falling in the scatter of the available experimental data. The hotspot locations identified by the TCD method were consistent with the results of the experimental study. By contrast, the predictions of the S-N method were very nonconservative in the case of the stringer-to-floor-beam connections (up to a factor of 2900). In general, the S-N method predictions were found to be sensitive to the choice of the detail classification. In the case of the stringer-to-floor-beam connection, Modified Class B resulted in the most nonconservative results (up to a factor of 10) when compared with the results of the other S-N classifications. The findings of this thesis may provide the bridge owners and authorities with a safe and effective alternative method in determining the remaining fatigue life of such bridge details.
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HEDMAN, MOLLY, and GRETA KNUTSSON. "Adaptation to ClimateChange : Climate Scenario Analysis in the Swedish Banking Sector." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300073.
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Climate change presents financial risks for banks and must therefore be treated accordingly. To assess and manage these risks, banks are expected to apply scenarioanalysis and adopt the TCFD’s recommendations on climate-related risk disclosures. This study analyzes how climate scenario analysis is implemented and reported in the Swedish banking sector. Empirical data has been collected through interviews with six banks, as well as through public annual and sustainability reports. The results of the study indicate that banks are in a learning phase characterized by uncertainty and lack of data, resulting in careful considerations in making strategic decisions based on the scenario analysis and when disclosing climate related information. Thus, banks do not disclose their scenario analysis as transparently as the TCFD suggests, thereby affecting the comparability within the sector. Further improvements related to more accessible and granular data are needed. In addition, many banks consider this to be a governmental issue where regulations are beneficial for establishing standardized models and common practices, which in turn could increase transparency and comparability.Klimatförändringar medför finansiella risker som banker behöver beakta. För att bedöma och hantera dem bör banker genomföra scenarioanalyser samt följa de rekommendationer som TCFD gett ut gällande klimatrelaterad rapportering. Denna studie ger en nulägesanalys av hur scenarioanalys implementeras och rapporteras inom den svenska banksektorn. Studien bygger på empirisk data från intervjuer med sex banker, samt från publika års- och hållbarhetsredovisningar. Resultatet av studien visar att bankerna är i en lärandefas präglad av osäkerhet, där bland annat datatillgänglighet är ett stort problem. Bristfälligheterna medför att bankerna är försiktiga med att fatta strategiska beslut utifrån scenarioanalyserna samt med vad de rapporterar publikt, vilket påverkar transparensen och jämförbarheten inom sektorn. Dessutom anser många banker att detta är en samhällsfråga där regleringar kan bidra till ökad standardisering av data och modeller samt etablering av gemensamma standarder, vilket även kan ha en positiv inverkan på rapporteringen och således öka transparensen och jämförbarheten inom sektorn.
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Makley, Meghan Katherine. "NMR analyses show TCDD elicits differences in hepatic metabolism in female C57BL/6 mice and Sprague-Dawley rats." Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1230048333.
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Saugnon, Damien. "Contribution aux analyses de fiabilité des transistors HEMTs GaN : exploitation conjointe du modèle physique TCAD et des stress dynamiques HF pour l'analyse des mécanismes de dégradation." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30164/document.
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Dans la course aux développements des technologies, une révolution a été induite par l'apparition des technologies Nitrures depuis deux décennies. Ces technologies à grande bande interdite proposent en effet une combinaison unique tendant à améliorer les performances en puissance, en intégration et en bilan énergétique pour des applications hautes fréquences (bande L à bande Ka en production industrielle). Ces technologies mobilisent fortement les milieux académiques et industriels afin de proposer des améliorations notamment sur les aspects de fiabilité. Les larges efforts consentis par des consortiums industriels et académiques ont permis de mieux identifier, comprendre et maîtriser certains aspects majeurs limitant la fiabilité des composants, et ainsi favoriser la qualification de certaines filières. Cependant, la corrélation et l'analyse physique fine des mécanismes de dégradation suscite encore de nombreux questionnements, et il est indispensable de renforcer ces études par une approche d'analyse multi-outils. Nous proposons dans ce travail de thèse une stratégie d'analyse selon deux aspects majeurs. Le premier concerne la mise en œuvre d'un banc de stress qui autorise le suivi de nombreux marqueurs électriques statiques et dynamiques, sans modifier les conditions de connectiques des dispositifs sous test. Le second consiste à mettre en œuvre un modèle physique TCAD le plus représentatif de la technologie étudiée afin de calibrer le composant à différentes périodes du stress.Le premier chapitre est consacré à la présentation des principaux tests de fiabilité des HEMTs GaN, et des défauts électriques et/ou structuraux recensés dans la littérature ; il y est ainsi fait état de techniques dites non-invasives (c.-à-d. respectant l'intégrité fonctionnelle du composant sous test), et de techniques destructives (c.-à-d. n'autorisant pas de reprise de mesure). Le second chapitre présente le banc de stress à haute fréquence et thermique développé pour les besoins de cette étude ; l'adjonction d'un analyseur de réseau vectoriel commutant sur les quatre voies de tests permet de disposer de données dynamiques fréquentielles, afin d'interpréter les variations du modèle électrique petit-signal des modules sous test à différentes périodes du stress. [...]In the race to technologies development, disruptive wide bandgap GaN devices propose challenging performances for high power and high frequency applications. These technologies strongly mobilize academic and industrial partners in order to improve both the performances and the reliability aspects. Extensive efforts have made it possible to better identify, understand and control first order degradation mechanisms limiting the lifetime of the devices; however, the correlation (and fine physical analysis) of different degradation mechanisms still raises many questions, and it is essential to strengthen these studies by mean of multi-tool analysis approach. In this thesis, we propose a twofold analysis strategy. The first aspect concerns the implementation of a stress bench that allows the monitoring of numerous static and dynamic electrical markers, without removing the devices under test from their environment (in order to have a consistent data set during the period of the strain application). The second aspect consists in implementing a physical TCAD model of the technology under study, in order to calibrate the component before stress, and to tune the model at different periods of stress (still considering stress-dependent parameters potentially affecting the device). The first chapter is devoted to the presentation of the main reliability tests of GaN HEMTs, and of the electrical and/or structural defects identified in the literature; it thus refers to so-called non-invasive techniques (i.e. respecting the functional integrity of the component under test), and destructive techniques (i.e. not allowing additive electrical measurement). The second chapter presents the high frequency and thermal stress bench dedicated to this study; the addition of a vector network analyzer switching between the four test channels provides dynamic frequency data, in order to interpret the variations of the small signal electrical model of the devices under test at different stress periods.[...]
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Brown, Janie. "A Comparative Analysis of TCAP Reading-Language Arts Scores between Students Who Used Accelerated Reader and Students Who Used Sustained Silent Reading." Digital Commons @ East Tennessee State University, 2008. https://dc.etsu.edu/etd/1904.
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The purpose of this study was to determine if a difference existed between TCAP scores of students who used the Accelerated Reader (AR) program and students who used Sustained Silent Reading strategy (SSR) as measured by the Tennessee Comprehensive Assessment Program (TCAP). The variables of grade level (6th, 7th, and 8th), gender, and socioeconomic status (free- or reduced- price meals program) were considered. The population consisted of 108 6th graders who attended a Cocke County school or a McMinn County school in Tennessee. Data were obtained from the TCAP for 3 consecutive years beginning in 2004-2005 for students who completed the tests all 3 years. A t test for independent samples and analysis of variance (ANOVA) were used to determine if there was a difference on associations and interactions between variables.
The researcher's investigation of the reading achievement of students who used Accelerated Reader and those who used Sustained Silent Reading should assist educators in planning for supplemental reading instruction. The information gathered from this research might be beneficial to other school systems when determining which method of reading instruction to use to increase students' reading achievement.
The findings indicated the students who used the Accelerated Reader program had an increase in reading-language arts scale scores for 3 consecutive years. The findings of this study also revealed that gender had no significance on student achievement for 6th graders. The findings did indicate a significant interaction between gender and type of program used during 7th and 8th grades. Females who used the Accelerated Reader program outscored males who used the program. The findings of this study also determined that socioeconomic status had no association with TCAP scores during the 6th, 7th, or 8th grades.
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Snyder, Andrew David. "A FUNCTIONAL ANALYSIS OF THE 3’ REGULATORY REGION OF THE IMMUNOGLOBULIN HEAVY CHAIN GENE." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1472469664.
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Levisson, Renée. "Implementation of a straightforward derivatizationmethod for the simultaneous analysis of short chainfatty acids and tricarboxylic acid cycle metabolitesby LC-qToF-MS." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-93417.
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Short-chain fatty acids (SCFAs) and the tricarboxylic acid (TCA) cycle metabolites aresmall hydrophilic compounds that play crucial roles in biological species ranging fromenergy metabolism, immune homeostasis to cellular signalling. There is a need for reliableand precise quantification of these metabolites in biological matrices as they can providecrucial information of metabolic status and potentially be used as diagnostic biomarkersfor different pathological and physiological conditions. However, their retention andseparation in traditional reversed-phase system, without chemical derivatization, is oftenproblematic due to their volatile and hydrophilic characteristics. The aim of this studywas to implement a facile and effective derivatization method for the simultaneousquantitation of SCFAs and TCA cycle metabolites by LC-qToF-MS in negative ion mode. Inthis work, 3-nitrophenylhydrazine (3-NPH) was employed for preanalyticalderivatization to convert the compounds to their respective 3-nitrophenylhydrazones.Analytical standards and faecal samples were used to assess the linearity, matrix effect,accuracy, extraction efficiency, precision, retention-time shift and short-term stability.The compounds were successfully separated within 6 minutes on a reverse-phase C18column. All the compounds showed good linearity (R2≥ 0.97) in both solvent-only andfaecal samples. The matrix effect was minimal and did not affect the compoundsquantitation. The extraction efficiency ranged from 80% to 110% (CV≤9.7%, n = 6). Theaccuracy of quantitation was determined to be between 82.8% to 113.8% (CV≤9.0%, n =6). The intra-day (CV%) demonstrated good precision for all analytes, the inter-day (%)were more variable due to the derivatives’ chemical instability. However, most of thederivatives were chemical stable up to 5 days in the autosampler (10°C). The method wasalso applied to explore the levels of these metabolites in human faecal samples and mousebrain samples.
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Guyonneau, David. "Contribution à la détermination de surfaces conjuguées pour la transmission de puissance." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4134.
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Les travaux présentés à travers ce manuscrit s'inscrivent dans un contexte de recherches exploratoires sur l'optimisation des surfaces engrenantes. Après une étude approfondie de l'emploi des engrenages dans un environnement aéronautique, l'élaboration d'une nouvelle méthodologie de génération de profils de denture est proposée. Les travaux s'attachent à caractériser le comportement mécanique spécifique d'un montage d'engrenages dans les Boites de Transmission de Puissances (BTP) d'hélicoptère.Un outil informatique a été créé dans le module VBA (Visual Basic Application) d'Excel. Il permet de créer automatiquement des profils de denture conjugués et optimisés. Il a l'avantage de définir analytiquement plusieurs grandeurs physiques. L'outil a ainsi pour objectif de proposer des profils de denture optimisés selon plusieurs critères. Les « objectifs » retenus sont le rendement et la contrainte équivalente de Hertz au contact suivant le critère de Von Mises.Les travaux s'articulent autour de trois axes : - la reconstruction de profils conjugués de denture par une approche novatrice basée sur le « contact », - la construction de critères physiques (glissement, pression, contrainte, …), - la recherche de profils de denture optimaux en utilisant la simulation de Monte Carlo.Enfin, la perspective de rendre générique cette méthode afin qu'elle puisse générer n'importe quels types d'engrenage est envisagée en fin de manuscritThe work described in the present manuscript is part of exploratory researches dealing with gears meshing surfaces optimization. After a short study of gears used in an aeronautical environment, the development of an innovative tool for tooth profile design is defined. Then, the specific behavior of a gear mesh within a helicopter main gearbox (MGB) is evaluated.A VBA software has been coded under MS Excel to generate conjugated and optimized gear tooth profiles. It advantageously defines and uses several physical parameters with their analytical formulation. The software provides at the user optimized tooth profiles according to a couple of criteria. The two “objective” functions evaluated are the efficiency and the Hertz equivalent stress within the contact using the Von Mises criterion.The work has been focused on three aspects:- The design of conjugated tooth profiles by contact sharing,- The definition of the relevant physical parameters,- The optimization of tooth profiles using Monte Carlo SimulationEventually, a generic method to design gear profiles, taking into account any physical parameters related to a gear mesh, could be expected as a future of this thesis work
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Caprarulo, V. "ANIMAL NUTRITION: NEW STRATEGIES FOR NUTRITIONAL OPTIMIZATION." Doctoral thesis, Università degli Studi di Milano, 2017. http://hdl.handle.net/2434/489607.
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This dissertation focuses on the impact of nutrition to modulate and optimize milk production, blood metabolites and liver metabolism. Specifically, the main aim was to elucidate the effects of rumen protected choline (RPC) supplementation to lactating dairy cows on production, metabolic health and hepatic gene expression, for which two different studies were performed.
The first study, a meta-analysis of the effect of RPC supplementation on milk yield (MY), nonesterified fatty acids (NEFA) and β-hydroxybutyrate (BHBA) in lactating dairy cows was performed in order to obtain an overall view of the effect of rumen protected choline. Rumen protected choline supplementation has been reported to have a positive effect on milk yield and metabolic health in lactating dairy cows. In light of this, a meta-analysis has been performed in order to elucidate the effect of choline chloride supplemented as RPC on both milk yield and selected blood metabolites. For this purpose, 21 peer-reviewed articles published from 1985 to 2016 were selected. This systematic review was carried out to evaluate the effects of RPC supplementation on MY, NEFA, and BHBA. Results obtained showed positive effects of RPC supplementation on MY in lactating dairy cows. The studies selected for this meta- analysis supplemented choline chloride in a range from 6.25 to 50g/d and milk production increase averaged 2.14±1.86 kg/d. Meta-regression on the dose- response relationship between dietary RPC and MY was significant. When NEFA and BHBA were evaluated, no overall effect was detected. Moderator analysis revealed that all outcomes, MY, NEFA and BHBA, were not significantly affected by the mode of choline supplementation (blended vs. topdressed).
In the second study, the mechanism beyond the metabolic changes due to RPC was investigated, with emphasis on hepatic gluconeogenesis, lipid oxidation and transport that occur during the transition period; particularly, the interaction of RPC and dietary energy concentration was tested and the expression of selected hepatic genes was analyzed. Hepatic gluconeogenic and oxidation genes were studied during the transition from late pregnancy to early lactation dependent upon RPC supplementation during the periparturient period, and prepartum energy intake. Controlling prepartum energy intake or supplementing RPC during the periparturient period, are two strategies to optimize hepatic metabolic function. At -48 days relative to calving (DRTC), multiparous Holstein cows were assigned to either a controlled (1.40 Mcal of NEL/kg DM; CE) or high (1.63 Mcal NEL/kg DM; HE) energy prepartum diet with or without RPC (top-dressed daily from -21 to +21 DRTC). Postpartum diets only differed in addition vs absence of RPC. Liver tissue biopsy samples were collected at -14, +7, +14, and +21 DRTC for RNA isolation and cDNA generation (n=16/treatment). Six genes involved in gluconeogenesis, lipid oxidation and lipid transportation were selected. Results obtained indicate that an increase in the expression of pyruvate carboxylase mRNA was reduced in cows receiving RPC after calving, which suggests that RPC had improved energy status and carbohydrate metabolism in the liver and reduced the need for pyruvate carboxylase. RPC supplementation decreased PCK1 in HE+RPC probably due to higher oxidation of increased circulating NEFA that translated to increased oxidative capacity of the TCA cycle. Moreover, this change can help to maintain the oxaloacetate pool. No effect of RPC supplementation was observed with regard to CPT1A, which is involved in fatty acid transportation. On the other hand, PPARA and MTTP were affected by RPC treatment, indicating that RPC supplementation may have modulated FA transport and oxidation.
In light of the two studies performed, RPC can improve milk production through lactation. Additionally, RPC supplementation may support and increase hepatic oxidative capacity.
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Mahamat, Chabakata. "Analyse et commandes des convertisseurs multi-niveaux pour un générateur photovoltaïque connecté au réseau électrique." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLN024/document.
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Ces travaux de thèse préparés au laboratoire SATIE, s’inscrivent dans la promotion de l’énergie solaire photovoltaïque (PV). Dans ces travaux, nous nous intéressons particulièrement au dimensionnement et au contrôle-commande du système PV connecté au réseau dans un contexte d’utilisation au Tchad où l’on doit tenir compte des problématiques du coût, du rendement, de fiabilité du système et de la qualité de l’énergie. Le réseau considéré est un réseau basse tension BT (220 V) avec une fréquence égale à 50 Hz mais susceptible de varier, auquel on injecte une puissance de 5,2 kW. Une méthode de dimensionnement des éléments passifs du filtre, a été préposée en premier lieu. Dans le but de réduire le coût de fabrication et le volume du filtre passif, une technique de fragmentation en plusieurs petites inductances en série a été adoptée. Cette technique optimise le volume et le coût du système PV classique. Ensuite, nous avons proposé une nouvelle architecture du système PV connecté au réseau utilisant un onduleur multi-niveaux. L’adaptation de cet onduleur à structure innovante a permis de réduire le coût de fabrication du filtre passif d’environ 40 % par rapport au système classique optimisé, tout en augmentant le rendement. Enfin, une commande PQ découplée, utilisant une boucle à verrouillage de phase PLL pour synchronisation, a été conçue et appliquée aux deux systèmes PV. Elle est bien adaptée au système avec onduleur multi-niveauxThis PhD work, prepared at SATIE laboratory, is part of the promotion of solar photovoltaic (PV) energy. In this work, we are particularly interested in design and control of the grid-connected PV system in a context of use in Chad where cost, reliability, efficiency, and energy quality issues of the system should be taken into account. The considered grid is a low voltage grid (220 V) with a frequency equal to fifty hertz (50 Hz) but likely to vary, in which a power of five point two ( 5.2 kW) is injected. A design method of the filter passive to reduce the filter elements is proposed firstly. In order to reduce manufacturing cost and volume of the passive filter, we apply a technique consisting of dividing each inductance value and making it in several small inductances in series. This technique optimizes the conventional PV system. Then, we proposed a new grid-connected PV system architecture using a multi-level inverter. The adaptation of this innovative structure has reduced the manufacturing cost of passive filter by nearly 40 % compared to the classical optimized system. Finally, a decoupled PQ control, using a phase locked loop for sysnchronization, has been designed and applied for both systems. It is well adapted to the system with multilevel inverter
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Viberg, Victor. "Quantifying metabolic fluxes using mathematical modeling." Thesis, Linköpings universitet, Institutionen för medicinsk teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-149588.
Full textAbstract:
Background Cancer is one of the leading causes of death in Sweden. In order to develop better treatments against cancer we need to better understand it. One area of special interest is cancer metabolism and the metabolic fluxes. As these fluxes cannot be directly measured, modeling is required to determine them. Due to the complexity of cell metabolism, some limitations in the metabolism model are required. As the TCA-cycle (TriCarboxylic Acid cycle) is one of the most important parts of cell metabolism, it was chosen as a starting point. The primary goal of this project has been to evaluate the previously constructed TCA-cycle model. The first step of the evaluation was to determine the CI (Confidence Interval) of the model parameters, to determine the parameters’ identifiability. The second step was to validate the model to see if the model could predict data for which the model had not been trained for. The last step of the evaluation was to determine the uncertainty of the model simulation. Method The TCA-cycle model was created using Isotopicaly labeled data and EMUs (ElementaryMetabolic Units) in OpenFlux, an open source toolbox. The CIs of the TCA-cycle model parameters were determined using both OpenFlux’s inbuilt functionality for it as well as using amethod called PL (Profile Likelihood). The model validation was done using a leave one out method. In conjunction with using the leave on out method, a method called PPL (Prediction Profile Likelihood) was used to determine the CIs of the TCA-cycle model simulation. Results and Discussion Using PL to determine CIs had mixed success. The failures of PL are most likely caused by poor choice of settings. However, in the cases in which PL succeeded it gave comparable results to those of OpenFLux. However, the settings in OpenFlux are important, and the wrong settings can severely underestimate the confidence intervals. The confidence intervals from OpenFlux suggests that approximately 30% of the model parameters are identifiable. Results from the validation says that the model is able to predict certain parts of the data for which it has not been trained. The results from the PPL yields a small confidence interval of the simulation. These two results regarding the model simulation suggests that even though the identifiability of the parameters could be better, that the model structure as a whole is sound. Conclusion The majority of the model parameters in the TCA-cycle model are not identifiable, which is something future studies needs to address. However, the model is able to to predict data for which it has not been trained and the model has low simulation uncertainty.
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Bruyère, Jérôme. "Contribution à l'optimisation de la conception des engrenages coniques à denture droite : analyse et synthèse de la géométrie et des tolérances." Phd thesis, Paris, ENSAM, 2006. http://pastel.archives-ouvertes.fr/pastel-00002262.
Full textAbstract:
La maîtrise accrue des matériaux et des procédés de forgeage permet aujourd'hui d'obtenir des engrenages coniques d'une qualité suffisante pour pouvoir les utiliser sans autre procédé de finition. Ce sont les pièces dites «net shape». Grâce à cette évolution technologique, il est nécessaire de d'optimiser la définition géométrique de ces engrenages en tenant compte des possibilités des procédés de forgeage, en particulier. Tout d'abord, la définition de la géométrie nominale des engrenages coniques à denture droite basée sur les propriétés géométriques et cinématiques du profil en développante de cercle sphérique est réétudiée et a abouti à une modélisation paramétrique des surfaces actives en intégrant un bombé longitudinal. Afin de garantir un certain niveau de qualité de l'engrènement, il est nécessaire de limiter les variations inhérentes au procédé de forgeage et aux ressources de fabrication, il s'agit de l'analyse et de la synthèse des tolérances. Cette analyse a nécessité une modélisation géométrique des engrenages incluant les écarts intrinsèques et les écarts de situation. L'analyse de l'impact de ces écarts sur l'erreur cinématique (Tooth Contact Analysis) repose sur la résolution d'un système d'équations non linéaires pour chaque position du pignon et d'un traitement de ces résultats; la difficulté de cette analyse est la grande sensibilité des résultats aux écarts. Cet outil «TCA» est le module principal de l'analyse des tolérances qui est réalisée de façon statistique par simulation de Monte Carlo. L'analyse des tolérances permet de valider une solution d'allocation de celles-ci mais ne permet pas son allocation automatique. Ainsi une approche de synthèse des tolérances a été validée, il s'agit de l'optimisation par algorithme génétique où la fonction objectif est de minimiser le ratio coût des tolérances sur la probabilité de respect des exigences. Cette analyse et cette synthèse ont été menées dans un premier temps sans charge, en considérant l'engrenage comme indéformable. Puis, la prise en compte des déformations est réalisée par la méthode des coefficients d'influences. Le problème de contact et de déformation globale de la denture sont découplés. Les coefficients d'influences de contact sont estimés par la méthode de Boussinesq et Cerruti. Les coefficients d'influence de flexion sont estimés par interpolation et méthode des éléments finis. Ce modèle permet l'analyse de l'engrènement sous charge mais les temps de calculs restent un handicap pour l'analyse des tolérances. Ces modèles de comportement pourront être affinés dans de futurs travaux et être le support de nouveaux modèles de spécification des engrenages, de suivi du processus de fabrication, d'une meilleure connaissance des interactions géométrie-mécanique-matériau, etc.
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Al-Qahtani, Khalid Mohammad. "Developing liquid chromatography-mass spectrometry strategies for investigating energy metabolism with application to isocitrate dehydrogenase mutations in cancer : development and application of methods for qualitative and quantitative analysis of TCA cycle metabolites using liquid chromatography coupled to mass spectrometry." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:354009b1-30a5-43a0-bbf1-5907437ea53a.
Full textAbstract:
Isocitrate dehydrogenases (IDHs) act in the tricarboxylic acid (TCA) cycle to catalyse the conversion of isocitrate to 2-oxoglutarate (2-OG) with concomitant production of NADH and/or NADPH. In humans, mutations causing IDH1 and IDH2 substitutions have been found during DNA sequencing of human glioblastomas. Some cancerassociated IDH mutations promote the reduction of 2-OG to give D-2-hydroxyglutarate (D-2-HG) a chiral, polar dicarboxylic acid. Investigations on the underlying links between 2-HG and cancer require sensitive methods for monitoring IDH1 and IDH2 activities. The reported LC/MS methods for the analysis of TCA cycle metabolites are limited in term of their accuracy and ability to identity isomers. Methods for the direct measurement of levels of TCA cycle and associated metabolites using mass spectrometry based metabolomics are desired. However, for the reported methods, the limits of detection are often prohibitive; they are normally suited for the investigation of known metabolites rather than for the discovery of new compounds. With some exceptions, the existing methods have not been extensively validated, e.g. with respect to limits of detection and quantification as well as precision. The main aim of the research presented in this thesis was to develop methods for TCA cycle metabolite analysis in cells and to apply these methods to investigations on variant IDH enzymes. A range of LC-MS approaches were investigated including: (1) C18 reversed phase chromatography of non-derivatised TCA cycle metabolites, (2) ion paring chromatography, and (3) mixed mode chromatography with either MS, or isotope ratio mass spectrometry detection, gas chromatography of TBDMS derivatised TCA cycle metabolites. Analysis of the elution patterns for these separation techniques enabled estimation of the retention parameters of TCA cycle metabolites and investigations on their metabolism. The most sensitive approach developed employed mixed mode chromatography coupled to isotope ratio mass spectrometry, which was optimised for the analysis of TCA cycle metabolites. This was shown to have a limit of detection two orders of magnitude lower (4μM) than more conventional mass spectrometry techniques. Using 13C-[4C]-Aspartate labelling in cell culture, a quantification protocol was developed which employed a non-labelled internal standard and selectively labelled cell culture. The method was shown to be suitable for both very accurate quantification at low concentration levels and metabolic studies. The analytical methods developed for TCA cycle metabolites analysis were successfully applied to the analysis of 2-OG and D-2-HG metabolism. The stereochemistry of 2-HG in the cell pellets as well as of the citrate/isocitrate isomers was investigated. IDH1R132H was shown to catalyse reduction of 2-OG resulting in D-2-HG. TCA cycle analysis was used in order to investigate 2-OG and 2-HG metabolism related to IDH1R132H. Using the method developed for the analysis of non-derivatised TCA cycle intermediates, the screening of potential substrates of IDH1R132H was carried out. The isotope ratio mass spectrometry protocol was applied to the study of IDH1R132H in cell culture; levels of D-2-HG were quantified. The analytical methods described complement the established metabolomics techniques. The methods developed enable the investigation into the regio- and stereo- chemistry of TCA cycle and associated metabolites and are powerful tools for investigating cancer cell metabolism.
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Ruegg, Evonne Teresa Nicole. "Investigating the porphyrias through analysis of biochemical pathways." Thesis, University of Canterbury. Biochemistry, 2014. http://hdl.handle.net/10092/10257.
Full textAbstract:
ABSTRACT
The porphyrias are a diverse group of metabolic disorders arising from diminished
activity of enzymes in the heme biosynthetic pathway. They can present with acute
neurovisceral symptoms, cutaneous symptoms, or both. The complexity of these
disorders is demonstrated by the fact that some acute porphyria patients with the
underlying genetic defect(s) are latent and asymptomatic while others present with
severe symptoms. This indicates that there is at least one other risk factor required in
addition to the genetic defect for symptom manifestation. A systematic review of the
heme biosynthetic pathway highlighted the involvement of a number of micronutrient
cofactors. An exhaustive review of the medical literature uncovered numerous reports
of micronutrient deficiencies in the porphyrias as well as successful case reports of
treatments with micronutrients. Many micronutrient deficiencies present with
symptoms similar to those in porphyria, in particular vitamin B6. It is hypothesized
that a vitamin B6 deficiency and related micronutrient deficiencies may play a major
role in the pathogenesis of the acute porphyrias. In order to further investigate the
porphyrias, a computational model of the heme biosynthetic pathway was developed
based on kinetic parameters derived from a careful analysis of the literature. This
model demonstrated aspects of normal heme biosynthesis and illustrated some of the
disordered biochemistry of acute intermittent porphyria (AIP). The testing of this
model highlighted the modifications necessary to develop a more comprehensive
model with the potential to investigated hypotheses of the disordered biochemistry of
the porphyrias as well as the discovery of new methods of treatment and symptom
control. It is concluded that vitamin B6 deficiency might be the risk factor necessary
in conjunction with the genetic defect to trigger porphyria symptoms.
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Hall-Ponselè, Andrew M. "Genetic engineering of the primary/secondary metabolic interface in tobacco BY-2 cells." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:be5a3ee3-33c7-455c-b043-409987395f98.
Full textAbstract:
The supply of precursors from primary metabolism is often overlooked when engineering secondary metabolism for increased product yields. This is because precursor supply may be assumed to be non-limiting, and it is considered difficult to engineer primary metabolism, because control of carbon flow (flux) is generally distributed among most enzymes of the pathway. The aim of this thesis was to increase the production of sterols, part of the isoprenoid class of secondary metabolites, in tobacco (Nicotiana tabacum) Bright Yellow 2 (BY-2) cell cultures. This was achieved by genetically engineering increased activity of mitochondrial citrate synthase, an enzyme of the tricarboxylic acid (TCA) cycle that is involved in the provision of cytosolic acetyl coenzyme A, the primary metabolite precursor to sterols. Metabolic flux analysis revealed that citrate synthase exerts significant control over cyclic TCA cycle flux in BY-2 cells and suggested that increasing the activity of downstream enzymes within secondary metabolism could lead to a further redirection of TCA-cycle-derived precursors into sterol biosynthesis. Attempts were made to achieve this by genetically engineering increased activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), a key enzyme of secondary metabolism involved in sterol biosynthesis. Consistent with previous research, transgenic lines had increased sterol levels. However, the high sterol phenotype was unstable, and attempts to co-express HMGR and citrate synthase genes were unsuccessful. The thesis demonstrates that increasing the provision of precursors to secondary metabolites can result in increased yields of those secondary metabolites but suggests that in most cases the activity of enzymes within secondary metabolism has a greater effect on those yields. It also reveals that single enzymes can exert significant control of flux within primary metabolism, although the control exerted by specific enzymes probably changes with the demands placed on metabolism.
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Siao, Pei-Chi, and 蕭珮琪. "TCAD simulation analysis of thin film heterojuction solar cells." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/y2rfer.
Full textAbstract:
碩士國立中興大學
光電工程研究所
99
This thesis simulated three solar cell structures with TCAD Tool developed by SILVACO, Inc. First, the change of HIT (hetero-junction with an intrinsic thin amorphous layer) solar cells, which combined single crystalline silicon and amorphous silicon, was probed with several variables, including thickness and carrier lifetime of single crystalline silicon, thickness, band gap and doping concentration of p-type amorphous silicon, and thickness and trap density of state of intrinsic amorphous silicon. Second, a-Si/μc-Si tandem solar cells were simulated by adding an interlayer, ITO, between top a-Si and bottom μc-Si component cells to enhanced TRJ effect and build up EQE simulation models. Finally, physical models for a-Si/a-SiGe/a-SiGe multi-junction solar cells were built up with the experiment data from ITRI.
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Rodriguez, Juan Antonio. "ESD circuit synthesis and analysis using TCAD and SPICE." Thesis, 1999. http://hdl.handle.net/1911/19421.
Full textAbstract:
This thesis describes the development of a SPICE sub-circuit model for an avalanche triggered SCR used for ESD protection in integrated circuits. The purpose of this work was to develop a model that accurately predicts the terminal characteristics of the SCR operating under steady state and transient conditions. Process and device simulations (using Technology Computer Aided Design tools, or TCAD tools) were used to gain insight into the dynamics of the complex SCR behavior prior to and during the latchup triggering. Test structures of the SCR, as well as its sub-components, were fabricated for characterization and modeling data collection. The TCAD results gave us access to internal physical quantities at key points along the I--V characteristics, which explicitly indicated the dynamics leading to latchup triggering. These analyses and the test structure characterization were necessary to properly formulate the SPICE model. The SPICE model development approach is presented, as well as methods to validate the model including steady state and fast rise time transient measurements on the actual ESD circuit. This is the first SPICE model presented for an avalanche triggered SCR demonstrating accurate terminal behavior under both steady state and transient triggering conditions. It is intended for use in a design environment for examining ESD circuit behavior at the chip level. The model allows a way to synthesize new circuits in a simulation environment without the need to fabricate test circuits and variations in silicon. Furthermore, the physical insight gained from the models will become more important as process technologies scale into deep submicron feature sizes.
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Yang, Chih-hsiang, and 楊智翔. "Optimization and simulation of high efficiency solar cell by TCAD analysis." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/18941710395092371434.
Full textAbstract:
碩士明道大學
材料科學與工程學系碩士班
99
Photovoltaic industrials have already attracted worldwide attention. Single crystalline solar cells play most important roles due to their high conversion efficiency especially passivated-emitter rear locally diffused (PERL) cells fabricated at university of New South Wales in Australia. In this study lots of parameters that influenced the devices performances were analyzed by Technology Computer Aided Design (TCAD) especially the different materials of back passivation layers (SiO2, Al2O3) and different ratios of rear diffused areas to whole device areas. Some physical models including Shockley-Read-Hall and Auger recombination mechanisms model, concentration dependant lifetimes and low field mobility model that could solve the Poisson, the continuity, and the current density equations were used. We set some parameters of Al2O3 such as energy band gap, refractive index (N), extinction coefficient (K), electron affinity, and dielectric constant replacing those of SiO2 for investigating the variation of performances. It was found that devices with Al2O3 performed better especially in short-circuit current density (Jsc) and fill factor (FF). The characteristic of charge carriers effect for Al2O3 successfully reduced the recombination at the interface of c-Si and metal, and shielded minority carriers back to p-n junction. Furthermore, in order to research the influence of the rear locally diffused ranges on cell’s performance, we tried to vary the ratios of rear diffused areas to whole device areas containing 10%, 8%, 6%, 4%, 2%, 0.5%, respectively. From the result J-V curve, it was obtained that as the ratio decreased, open-circuit voltage (Voc) and Jsc almost maintained a constant, and the FF increased gradually. And the optimum efficiency reached 21.51%. In real process, the sizes of rear locally diffused areas fabricated by laser technology or lithography process technology are restricted to reduce endlessly. Generally the performances of PERL devices get better as the size of areas reduces.
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Yang, Ruei-Lin, and 楊叡霖. "Transient Analysis of Conductivity Modulation for ESD Protection Devices by TCAD." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/79920322116457637434.
Full textAbstract:
碩士逢甲大學
電子工程學系
104
In this paper, we utilize the TCAD tool to simulate the transient responses of various ESD devices, including voltage, current, and differential conductance responses. In addition, we analyze the physic phenomenon during the ESD issue by cross-section chart. The simulation results lead to the correlation among conductivity modulation, V_peak, and overshoot voltage of DUT(Device Under Test) depending on the comparison between I_DUT^ and V_pulse^. Both simulation and measurement show that the V_peak apparently decreases as the maximum of differential conductivity gets larger at the clamping moment. This concept helps designers understand how to design a well clamping ESD device with lower V_peak.
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Du, Yan-Ting, and 杜衍廷. "Analysis of Sub-5 nm Transistors Trend by 3D TCAD Simulation." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/2ec8c9.
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GUPTA, NEHA. "TCAD ANALYSIS AND SIMULATION OF GATE ELECTRODE WORKFUNCTION ENGINEERED (GEWE) SILICON NANOWIRE MOSFET FOR HIGH PERFORMANCE ANALOG AND RF APPLICATIONS." Thesis, 2017. http://dspace.dtu.ac.in:8080/jspui/handle/repository/15802.
Full textAbstract:
Scaling MOSFETs beyond sub-nm gate lengths is extremely
challenging using planar device architecture due to the stringent
criteria required for the transistor switching. The development of
three dimensional devices like Multi-gate MOSFETs, ultra-thin SOI
MOSFETs, FinFETs, Silicon Nanowires, Nanotubes etc. become
important for the further advancement in the integrated chip industry.
The top-down fabricated, gate-all-around architecture with a Si
nanowire channel is a promising candidate among these for future
technology generations. The gate-all-around geometry enhances the
electrostatic control and hence gate length scalability and also
suppress short channel effects effectively. Silicon nanowire MOSFET
in gate all around configuration has proved to be good candidate due
to its ability to suppress short channel effects. In nanoscale MOSFET,
to improve speed and performance of a device, several engineering
schemes have been proposed but the main problem associated is gate
transport efficiency. As dual gate-MOSFET and Split Gate-MOSFET
structures cannot improve both carrier transport efficiency and shortchannel
effect. Gate Electrode Workfunction Engineering structure
opens a new way to improve device performance. To eliminate
polysilicon depletion width effects and polysilicon dopant penetration,
polysilicon gates need to be replaced by metal gates. In 1997, Wei
vi NEHA GUPTA
Long and Ken K. Chin proposed a novel structure the Dual Material
Gate MOSFET, which suppress short channel effects and enhance
carrier velocity. In the DMG-MOSFET, the gate consists of two
contacting materials with different work functions. The metal with
higher work function is close to source and metal with lower work
function is close to drain, and hence threshold voltage VT1>VT2 which
improve the carrier transport efficiency. It is observed the step
potential profile in the channel region because of two metal gates of
different work function, which ensures reduction in short channel
effects without sacrificing other device characteristics, unlike in dual
gate or other gate structures.
In this dissertation, gate metal workfunction engineering
scheme is amalgamated onto SiNW MOSFET and its Hot-Carrier
fidelity and DIBL are studied to scrutinize its efficacy in high power
CMOS applications. It is found that with k = 21(HfO2) as gate oxide,
device performance in terms of hot-carrier reliability further enhanced
due to increased capacitance and thus offer its effectiveness in subnm
range analog applications. Extensive device simulation results
shows that GEWE-SiNW MOSFET exhibit improved RF performance in
terms of high cut-off and maximum oscillator frequency and its
performance further intensified with tuning of device parameters such
as gate length, radius of nanowire, oxide thickness and workfunction
of gate metals. Thus, providing detailed knowledge about the device’s
RF performance at such aggressively scaled dimensions. For
comprehensive RF analysis of GEWE-SiNW MOSFET and its
effectiveness at HF, the small signal behaviour in terms of scattering
parameters is also discussed. This would be useful for evaluating the
microwave performance of the device in terms of forward and reverse
gains. In addition, noise metrics have also been evaluated which
affects the device performance at HF. The RF investigation carried over
is circumscribed to intrinsic components of MOSFET only. However,
NEHA GUPTA vii
at GHz frequency range, the importance of extrinsic component (the
part outside the channel region) dominates to that of its intrinsic
counterpart. Therefore, there is a need for an RF model which should
consider the behaviour of both the intrinsic and the extrinsic
components of a device for achieving accurate and predictive results
in the simulation of designed circuit. Thus, the extrinsic and intrinsic
parameters of GEWE-SiNW MOSFET and numerical modelling of
small signal parameters such as Z and Y parameters are also studied
in this work.
Furthermore, as oxide thickness scales down to 1.5 nm or
below, the leakage current increases up to 1 A/cm2 at 1 V due to
direct tunneling of carriers which, consequently increases the static
power and hence affect the circuit operation. So, high-k films are
proved to be the most promising solution. Though, these films result
in high fringing fields from gate to source/drain regions and thus
degrading the device performance. This constraint can be overcome by
using gate stack architecture consisting of SiO2 layer as a passivation
between high-k films and bulk by keeping the effective oxide thickness
(EOT) constant, high-k dielectrics permit the increase in physical
oxide thickness to prevent gate tunneling and thus improves the
carrier efficiency. Thus, stack gate (SG) is amalgamated onto GEWESiNW
MOSFET to examine its performance in terms of analog and
linearity FOMs. It is observed that SiNW MOSFET modeled with HfO2
as a gate stack over SiO2 interfacial layer, and gate metal
workfunction difference (ΔW) of 4.4 eV can be considered as a
promising potential for low power switching component in ICs and
Linear RF amplifiers. Moreover, a reliability issue of Stacked Gate
(SG)-Gate Electrode Workfunction Engineered (GEWE)-Silicon
Nanowire (SiNW) MOSFET is examined over a wide range of ambient
temperatures (200–600 K). It is observed that at low temperature SGviii
NEHA GUPTA
GEWE-SiNW shows improved Analog/RF performance in terms of
Ion/Ioff, Subthreshold Swing (SS), device efficiency, fT, noise
conductance and noise figure and also unveil highly stable linearity
performance owing to reduced distortions. The results so obtained can
be serving as a worthy design tool for circuits operating at wide range
of temperatures.
Immunity against SCEs, high current driving capability,
optimum high frequency performance and suitability at low
temperature makes GEWE-SiNW MOSFET a promising device for low
power, high performance CMOS applications.
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Lin, Kuan-Chou, and 林冠州. "Performance and Ruggedness Analysis of Superjunction MOSFET under Unclamped Inductive Switching using TCAD Simulation." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/ehmybm.
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KUMAR, AJAY. "TCAD ANALYSIS OF HOT CARRIER RELIABILITY AND THERMAL BEHAVIOUR OF TRANSPARENT GATE RECESSED CHANNEL MOSFET." Thesis, 2014. http://dspace.dtu.ac.in:8080/jspui/handle/repository/15638.
Full textAbstract:
In this thesis, a novel device structure called Transparent Gate Recessed Channel MOSFET
(TGRC-MOSFET) is proposed to alleviate the hot carrier effects for the advanced nanometer
process. TGRC-MOSFET involving a recessed channel and incorporates Indium Tin Oxide
as a transparent gate. TCAD analysis shows that performance of TGRC-MOSFET surpasses
Conventional Recessed Channel (CRC)-MOSFET in terms of high ION/IOFF ratio and better
carrier transport efficiency in compare to Conventional Recessed Channel (CRC) MOSFET.
This simulation divulges the reduction in hot-carrier-effects metrics like electron velocity,
electron temperature, potential, and electron mobility. All the simulations have been done
using DEVEDIT-3D and ATLAS device simulator. The work proposes the novel design for
reduction in hot carrier and low power switching application.
Ajay Kumar iv
In thermal analysis of a novel design Transparent Gate Recessed Channel MOSFET (TGRCMOSFET)
at 300K. TGRC- MOSFET involves a recessed channel and incorporates Indium
Tin Oxide as a transparent gate. Simulation results show that performance of TGRCMOSFET
surpasses Conventional Recessed Channel (CRC)-MOSFET in terms of heat
capacity, heat conductivity, lattice temperature and total heat power in comparison to CRCMOSFET.
All the simulations have been done using DEVEDIT-3D AND ATLAS device
simulator. Indium tin oxide (ITO or tin-doped indium oxide) is a solid solution of indium
oxide (In2O3) and tin oxide (SnO2). It is transparent and colourless in thin layers. Because of
its two key properties, i.e. electrical conductivity and optical transparency, indium tin oxide is
used as one of the most widely used transparent conducting oxides. Also, the In2O3 phase
itself contributes free electron for electrical conductivity. Furthermore, with the reduction in
transistor size, intrinsic self-heating effects have become unfavourable in low power
applications. As the issue of heat becomes increasingly important in sub-micron MOSFETs,
it becomes increasingly more important to accurately measure and model its thermal
parameters to fully characterize its thermal performance.
High heat capacity of TGRC-MOSFET device is favourable for high power applications as
compared to CRC MOSFET. Furthermore, low thermal conductivity of a device, finding
application as heat insulation. TGRC-MOSFET has lower thermal conductivity as shown in
fig. 3. In addition, there is reduction in hot electron (HE) injection gate current and impact
ionization (II) substrate current in TGRC-MOSFET compared to CRC MOSFET which
improves the device speed performance and hence reduced the power dissipation as it is
evident from results respectively. Since, there is appreciable reduction in electric field at the
drain side in TGRC-MOSFET in comparison to CRC-MOSFET which results in lower
leakage current.
The noise assessment of Novel Transparent Gate Recessed Channel MOSFET has been
investigated based on the simulated result from ATLAS device simulation. TCAD
simulation results show TGRC-MOSFET divulges Conventional Recessed Channel (CRC)-
MOSFET in terms of reduction in noise figure, noise conductance and parasitic capacitances.
It also achieves higher optimum source impedance for high performance applications where
noise immunity is a key factor. Here we accentuate our focus on Transparent Gate
architecture incorporation onto the Conventional Recessed Channel MOSFET for superior
noise performance of scaled MOS devices. Intensive TCAD device simulations have been
performed to probe the internal transport conditions of CRC MOSFET and TGRC-MOSFET,
Ajay Kumar v
and substantial interpretation is given to the internal behaviours observed in all the devices
investigated. TCAD simulation reveals the deterioration in minimum noise figure, noise
conductance and parasitic capacitances. It also achieves higher optimum source impedance.
This work presents a TGRC-MOSFET device which is reliable for RF applications and
CMOS technology for the designing of multi-gigahertz communication circuits.
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PANDEY, RAHUL. "DESIGN AND SIMULATIONS OF SiC BASED REAR CONTACT Si AND SiGe SOLAR CELLS FOR STANDALONE AND TANDEM APPLICATIONS." Thesis, 2017. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16135.
Full textAbstract:
The most abundant renewable source of energy on the earth is solar energy, yet its potential has not been exploited efficiently by solar cells present in the market. Affordability of solar energy can be enhanced, either by increasing the efficiency of a solar cell or by reducing its cost. In this thesis, several approaches for improving solar efficiency with careful design have been proposed using Technology Computer Aided Design (TCAD). These approaches attempt to improve the solar cell current, solar cell voltage, light absorption, surface recombination, and ultraviolet (UV) stability. Finally, the mechanically stacked tandem architecture addresses thermalization and lack of absorption losses for improved efficiency. The initial focus is to minimize the issues associated with thin devices such as low absorption and high surface recombination. These issues have been resolved using novel front surface design which consists of Zirconia (ZrO2) based texturing along with Silicon Carbide (SiC) based front surface passivation. Design principle balances out photonic and electronic effects together and resulted in 15.7% efficient rear contact silicon (Si) solar cell, in the sub10 µm-thick regime. The next focus is to minimize the thermalisation losses. 300 microns and 10 microns thick SiC passivated rear-contact solar cell has been placed in four terminal (mechanically stacked) tandem configuration with 20.9% efficient perovskite top subcell. Realistic TCAD analysis has been done for both top and bottom subcell; which resulted in 27.6% and 22.4% efficient tandem devices under single air mass 1.5 (AM 1.5) irradiance. Further, SiC passivated interdigitated back contact silicon heterojunction solar cell (IBCSiHJ) has also been discussed for bottom subcell application under perovskite top subcell since IBC-SiHJ solar cell uses low-temperature fabrication processes and has excellent photovoltaic (PV) performance. The efforts resulted in 29.5% and 23.7% efficient tandem devices which contain 250 µm and 25 µm thick IBC-SiHJ bottom subcells, respectively.
Si as an active material for most of the PV devices, whose absorption coefficient is small at higher wavelengths; therefore, thick silicon wafers are required to obtain greater efficiencies in both standalone as well as tandem configuration. Thicker silicon wafer eventually increases the module cost, and hence, modification in the bandgap (Eg< 1.1 eV) of the Si is required to increase the absorption of sunlight at higher wavelengths while keeping the thickness low. Therefore, Silicon-Germanium (SiGe) material has been introduced to rear contact solar cell designs and investigation is done for both standalone and tandem configuration. The thickness of SiGe based devices reported in this thesis is 10 microns, which is projected to enhance the efficiencies keeping the thickness low. The device exhibits improved higher wavelength absorption without the need of complex texturing schemes and suggested its potential use as a bottom subcell under tandem configuration. 15.4% power conversion efficiency (PCE) is reflected in convention rear contact SiGe solar cell, whereas in interdigitated back contact SiGe heterojunction solar cell (IBC-SiGeHJ) architecture, 15.5% PCE is achieved in a stand-alone configuration, and in combination with perovskite top subcell, further 25.7% PCE is demonstrated.
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Tawakol, Abdel Maguid. "Performance Analysis of TCAMs in Switches." Thesis, 2012. http://hdl.handle.net/10012/6654.
Full textAbstract:
The Catalyst 6500 is a modern commercial switch, capable of processing millions of packets per second through the utilization of specialized hardware. One of the main hardware components aiding the switch in performing its task is the Ternary Content Addressable Memory (TCAM). TCAMs update themselves with data relevant to routing and switching based on the traffic flowing through the switch. This enables the switch to forward future packets destined to a location that has already been previously discovered - at a very high speed.
The problem is TCAMs have a limited size, and once they reach their capacity, the switch has to rely on software to perform the switching and routing - a much slower process than performing Hardware Switching that utilizes the TCAM. A framework has been developed to analyze the switch’s performance once the TCAM has reached its capacity, as well as measure the penalty associated with a cache miss. This thesis concludes with some recommendations and future work.
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Yu, Yung-Mie, and 于永宓. "Effectiveness and Tolerability of Selective Serotonin Reuptake Inhibitors (SSRIs) versus Tricyclic Antidepressants (TCAs) in Depression Disorders: A Meta-analysis." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/89770298712021720696.
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碩士高雄醫學大學
藥學研究所碩士在職專班
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Background: Tricyclic antidepressants (TCAs) have been considered as one of the pharmacological treatments of depression. However, the newly marketed selective serotonin reuptake inhibitors (SSRIs) are generally though to have better efficacies and fewer side effects clinically than TCAs. Objectives: The purpose of this study was to compare the relative efficacies and tolerability of SSRIs and TCAs using meta-analysis. Methods: We searched the Cochrane Collaboration Depression, Anxiety and Neurosis Controlled Trials Registers, MEDLINE, EMBASE, SDOS, PubMed, and JAMA. The literature search also included American Chemical Society, and New England Journal of Medicine which were from the database. Most of randomized controlled trials were included in this study. Study participants could include both genders and any age range with a primary diagnosis of depression. Data collected from each study included proportion of responders or drop-outs due to side effect and ineffectiveness. A series of meta-analyses of regarding therapy efficacies and side effects were performed using Review Manager v.4.2.6. Heterogeneity of treatment effect was considered. Results and Discussion: Thirty-eight trials were finally selected and contributed data to the meta-analysis of the relative efficacy of SSRIs and TCAs. Analysis of efficacy of drug therapy in depression resulted from 16,186 patients treated with SSRIs; 12,125 patients treated with TCAs. TCAs could be a better choice for patients with severe or major depression (odds ratio 0.89, 95% CI= [0.82, 0.97], p = 0.009). Drug efficacy in dysthymia control significantly favored in SSRIs (odds ratio 1.39, 95% CI= [0.88, 2.22], p = 0.16), although less drop-out rate for SSRIs therapy group was observed than that of TCAs (odds ratio 0.83, 95% CI= [0.77, 0.89], p<0.00001). The total drop-outs due to inefficacy for SSRIs was higher than that of TCAs (odds ratio 1.13, 95% CI= [1.05, 1.21], p = 0.0008). In the aspect of side effects, drop-out rate due to side effects for SSRIs was lower than that of TCAs (odds ratio 0.65, 95% CI= [0.61, 0.70], p<0.00001). Conclusions: Even though there are significant differences in efficacies of drug therapy for patients with major-depression between SSRIs and TCAs that is favor TCAs. SSRIs do appear to show an advantage over TCAs in terms of total drop-outs.
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"A Comparative Analysis of TCAP Reading-Language Arts Scores Between Students Who Used Accelerated Reader and Students Who Used Sustained Silent Reading." East Tennessee State University, 2008. http://etd-submit.etsu.edu/etd/theses/available/etd-0328108-172531/.
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Rico, Marta de Oliveira Pimentel Rosado. "Analysis of tricarboxylic acids in cancer by LC-MS." Master's thesis, 2013. http://hdl.handle.net/10451/29616.
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Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, Universidade de Lisboa, Faculdade de Farmácia, 2014Metabolomics is the comprehensive and quantitative study of metabolites in a biological system. The Tricarboxylic acid (TCA) cycle intermediates, such as citric acid, isocitric acid, alpha-ketoglutaric acid and fumaric acid are important metabolites for the energy production in the cells. In this cycle, the enzyme Isocitrate Dehydrogenase (IDH) converts the isocitrate to alpha-ketoglutarate, but in some types of cancer cells, IDH is mutated and L-hydroxyglutaric acid is formed. In this work, we established a Liquid Chromatography-Electrospray Ionization-Mass Spectrometry (HPLC-ESI-MS) method to identify the TCAs in mutated and non-mutated astrocytes and to compare their levels. A HILIC column was used to separate the compounds and a Quadrupole Time-of-Flight (Q-TOF) was used to analyze their accurate mass and elemental composition. The compounds were identified using databases and fragmentation spectra. All the other metabolites present in these cells, including amino acids, phospholipids and other compounds were also observed and their fold changes between mutated and non-mutated astrocytes were also successfully determined.
University of Eastern Finland (Kuopio).