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Rehren, Felix Gabriel. "Axial algebras." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5948/.
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Axial algebras are nonassociative algebras controlled by fusion rules for idempotents. We have three main results. Firstly, we give a classification of axial algebras with fusion rules of Jordan type, with parameter alpha, in terms of 3-transposition groups. When alpha is 1/2, we also classify the related Jordan algebras. Secondly, we develop a structure theory for Matsuo algebras, especially using large associative subalgebras, and apply it to the special case of the Dynkin diagram of type A\(_n\), which has relations to vertex operator algebras. Thirdly, we generalize dihedral axial algebras of Ising type, with parameters alpha and beta, coming from the Monster sporadic simple group. This also helps determine the role that the parameters play in the larger theory, where indeed the Griess algebra turns out to be a special point.
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Zhang, Lu. "Analytical and experimental studies of instability of an axial compression." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC046/document.
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Cette thèse présente l’étude analytique et expérimentale d’un système de compression axial constitue d’un compresseur, d’un plenum et d’une vanne de régulation du débit. Fondée sur le modèle de Moore-Greitzer, une approche analytique est utilisée par la suite pour interpréter les données expérimentales. Les analyses linéaires et non linéaires sont présentées, ainsi que les résultats obtenus par intégration numérique des équations du modèle non linéaire complet. Un modèle théorique simple pour les modes acoustiques observes est aussi présente. Dans les expériences, les mesures de pression ont été réalisées pour différents taux de rotation et différents vannages. Ceci a permis la détermination de l’augmentation de pression au travers du compresseur et du débit en utilisant un Venturi, ceux qui fournissent la courbe de fonctionnement du compresseur. Les fluctuations de pression sont mesurées par quatre microphones places en amont du compresseur. Nous n’avons pas observé de pompage, mais un décrochage tournant s’est produit quand le système était suffisamment vanne. Avant ceci, des fluctuations correspondant aux modes acoustiques de la conduite ont été trouvées. Au début du décrochage, une cellule de décrochage tournante d’amplitude croissante a été observée. Cependant, la cellule a rapidement éclaté, remplacée par des fluctuations aléatoires. Ainsi, pour le système de compression considéré, la situation de décrochage est mieux décrite comme étant aléatoire plutôt que rotative. Le traitement du signal (spectres en fréquence ainsi que les autocorrélations et corrélations croisées) a permis d’analyser les fluctuations de pression des modes acoustiques et du décrochage développé. Les modes acoustiques montrent des pics spectraux proches des valeurs prédites par la théorie. En présence de décrochage, le spectre est à large bande, et contient un pic de fréquence basse (∼20 Hz) suivi d’une queue s’étendant jusqu’à 1 kHz, bien au-dessus de la fréquence de rotation du rotor (∼150 Hz). Il apparait une gamme fréquentielle située entre le pic à basse fréquence et la chute à haute fréquence, dans laquelle le spectre évolue en loi de puissance. Les autocorrélations et corrélations croisées entre les différents microphones montrent des oscillations à ∼20 Hz. En appliquant un filtre passe-bas aux données, les fonctions de corrélations croisées des signaux filtres des différents microphones suggèrent l’existence d’une cellule rotative qui effectue une rotation complète en ∼0.05 s. Ceci pourrait expliquer le pic spectral a ∼20 Hz et les oscillations des fonctions de corrélation. De ce fait, les fluctuations de pression apparaissent comme contenant une forte composante aléatoire à haute fréquence, et une cellule rotative. La décorrelation du signal filtre quand la séparation en temps augmente indique que la cellule elle-même a un caractère aléatoire, plutôt qu’une forme et une vitesse rotative fixes comme dans une cellule de décrochage classiqueThis thesis presents an analytical and experimental study of an axial compression system consisting of a compressor, plenum and throttle. The analysis is based on the Moore-Greitzer model, the results being later employed to interpret the experimental ones. Linear and weakly nonlinear analyses are presented, as are some results obtained by numerical integration of the fully nonlinear model equations. A simple theoretical model of the experimentally observed acoustic modes is also presented. In the experiments, pressure measurements were carried out for different rotation rates and throttle settings. This allowed the determination of the pressure rise across the compressor and the flow rate using a Venturi, yielding the compressor characteristic function. Pressure fluctuations were measured using four microphones placed upstream of the compressor. We did not observe surge, but rotating stall occurred when the system was sufficiently throttled. Prior to stall, fluctuations corresponding to acoustic duct modes were found. At stall onset, a rotating stall cell of growing amplitude was observed. However, the cell rapidly broke down and gave way to random fluctuations. Thus, for the given compression system, developed stall is perhaps better described as random, rather than rotating. Signal processing (frequency spectra, as well as auto- and cross-correlations) was used to analyse the pressure fluctuations of the acoustic modes and developed stall. The acoustic modes give spectral peaks located close to the expected theoretical values. In the presence of stall, the spectrum is broadband, having a low frequency (∼20 Hz) peak followed by a tail which extends up to ∼1 kHz, well above the rotation frequency (∼150 Hz) of the rotor. There appears to be a frequency range between the low-frequency peak and the high-frequency fall-off in which the spectrum approximates a power law. The autocorrelations and cross-correlations between different microphones show ∼20 Hz oscillations. Low pass filtering the data, the cross-correlation functions of the filtered signals of different microphones suggest a rotating cell which takes ∼0.05 s for a complete rotation. This could explain the ∼20 Hz spectral peak and oscillations of the correlation functions. Thus, the pressure fluctuations appear to consist of a strong high-frequency, random component and a rotating cell. Decorrelation of the filtered signal as separation time increases indicates that, rather than maintaining form and rotational velocity like a classical stall cell, the cell itself exhibits randomness
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Almenara, Díaz Carlos. "Tomografía Axial Computarizada." Bachelor's thesis, Universidad Ricardo Palma. Programa Cybertesis PERÚ, 2007. http://cybertesis.urp.edu.pe/urp/2007/almenara_c/html/index-frames.html.
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Houghton, Timothy Oliver. "Axial compressor stability enhancement." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/252194.
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Aircraft jet engines must operate in a stable manner at all times. One source of instability is compressor stall. Stall problems can be reduced by machining cavities into the compressor casing adjacent to the rotor blades. This ?casing treatment? is the focus of the present work. Two treatment configurations are tested: circumferential grooves cut into the casing above the rotor blades, and axial slots cut into the casing adjacent to the rotor blade leading edges. The performance of a single casing groove is measured at different axial locations over the blade tips. For the first time, it is shown that there are two locations where compressor stability is maximised; near the leading edge and near mid-chord. The interaction between the groove and the compressor flow field is then studied. It is found that when located near the leading edge, the groove has a strong interaction with the near-casing flow and tip leakage vortex, but when located near mid-chord, the interaction is more subtle and less damaging to efficiency. Since the groove works well in both locations, it is concluded that manipulating the tip leakage vortex is not critical for improving compressor stability. Different groove numbers and cross-sections are then tested. For multiple grooves, the effi- ciency reduction is the sum of the constituent grooves, while the stall margin improvement is less than this sum. A simple square-section groove is found difficult to improve on, although in certain circumstances, a new ?intermittent groove? geometry is beneficial. The performance of axial slots is then investigated. Different slot shapes are tested and the results added to previous work to suggest an optimum slot geometry. A computational flow study shows that large variations in blade loading occur as the blades pass the slots, which could cause noise and vibration. It is found that while the flow inside the slot is principally a quasi-steady recirculation, the interaction between the slots and blades is highly unsteady, and this unsteadiness should not be neglected in design. In general, it is found that casing treatments that generate large stability improvements cause large efficiency losses. It is shown for the first time that the performance of casing grooves can be seriously reduced by changes in the stall inception mechanism. Maximum performance is achieved when the treated compressor stalls with a spike inception. Models from the literature are tested, but do not predict the stall inception mechanism well, which makes predicting the performance of casing grooves in a given compressor hard. Finally, it is shown that designing the blades and casing treatment as a unit may improve compressor performance.
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Nguyen, Nhung Phuong. "Axial ligand mutant H229A /." unrestricted, 2007. http://etd.gsu.edu/theses/available/etd-08082008-134926/.
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Thesis (honors)--Georgia State University, 2007.Title from file title page. Under the direction of Dabney White Dixon. Electronic text (88 p. : col. ill.) : digital, PDF file. Description based on contents viewed Sept. 30, 2008. Includes bibliographical references (p. 46-47).
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Nguyen, Nhung Phuong. "Axial Ligand Mutant: H229A." Digital Archive @ GSU, 2008. http://digitalarchive.gsu.edu/honors_theses/1.
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Many pathogenic bacteria use their iron acquisition mechanisms to live inside hosts. Streptococcus pyogenes is a pathogenic bacterium that uses streptococcal iron acquisition ABC transporter to obtain heme. SiaA (HtsA, spy1795), a lipoprotein located on the cell surface, serves as a heme binding protein. To understand the iron-uptake mechanism, histidine 229, one of the two proposed axial ligands in SiaA, was mutated to alanine. SiaA H229A was expressed in E. coli, lysed by French Press, and purified by fast protein liquid chromatography (FPLC). SDS-PAGE indicated that pure protein was isolated. Nickel affinity FPLC gave purer H229A when 0.5 M imidazole was added to the binding buffer. Overall, histidine 229 is likely to be an axial ligand in wild type SiaA, as shown by the fact the mutant readily lost heme as evidenced by UV-vis spectra.
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Li, Yan Sheng. "Mixing in axial compressors." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334235.
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Grimshaw, Samuel David. "Bleed in axial compressors." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707970.
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Spíndola, Flausino Lucas Neves. "Bifurcação de pontos axiumbílicos e ciclos axiais de superfícies imersas em R4." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/45/45132/tde-25012016-153923/.
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O objetivo deste trabalho é descrever a estrutura das linhas axiais principais e médias de imersões de superfícies em R4 na vizinhança de pontos axiumbílicos. Pontos axiumbílicos são aqueles nos quais a elipse de curvatura se degenera em um círculo. Estudamos a perturbação dos ciclos axiais principais, e obtemos resultados sobre a genericidade dos ciclos axiais principais hiperbólicos e semi-hiperbólicos.The aim of this work is to describe the structure of principal and mean axial lines of immersions of surfaces into R4, close to axiumbilic points. Axiumbilic points are those which the ellipse of curvature denegerate in a circle. We study the perturbation of principal axial cycles, and we obtain results about genericity of hyperbolic and semi-hyperbolic principal axial cycles.
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McDougall, Neil Malcolm. "Stall inception in axial compressors." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237803.
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余志偉 and Chi-wai Yu. "An axial field inductor alternator." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1986. http://hub.hku.hk/bib/B31208022.
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Gamache, Robert Normand. "Axial compressor reversed flow performance." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15214.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO.
Includes bibliographical references.
by Robert Normand Gamache.
Ph.D.
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Khalsa, Amrit Singh. "Endwall blockage in axial compressors." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10826.
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Yu, Chi-wai. "An axial field inductor alternator /." [Hong Kong : University of Hong Kong], 1986. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12333670.
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Dafni, Theopisti. "A search for solar axions with the MICROMEGAS detector in CAST." Phd thesis, [S.l. : s.n.], 2005. http://elib.tu-darmstadt.de/diss/000577.
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Barros, Cainã Bemfica de. "Fatigue and cyclic plasticity of 304L stainless steel under axial, torsional and proportional axial-torsional loading." reponame:Repositório Institucional da UnB, 2018. http://repositorio.unb.br/handle/10482/31953.
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Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2018.Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2018-05-07T18:41:32Z No. of bitstreams: 1 2018_CainãBemficadeBarros.pdf: 12251436 bytes, checksum: 876fa05cf00aed82da7e296be39eec5e (MD5)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq).
Os objetivos deste trabalho são investigar o comportamento tensão-deformação cíclico e a fadiga multiaxial do aço inoxidável 304L por meio de ensaios axiais, torsionais e axiais-torsionais proporcionais totalmente alternados controlados por deformação à temperatura ambiente e avaliar os modelos de fadiga do tipo plano crítico propostos por Smith, Watson e Topper (1970), e Fatemi e Socie (1988) em relação à previsão de vida à fadiga e à orientação das trincas macroscópicas. Corpos de prova tubulares com paredes finas usinados após o tratamento térmico de normalização foram submetidos a amplitudes de deformação equivalente de von Mises tais que 0,20% ≤ Δ/2 ≤ 1,00%. Devido à dependência da taxa de carregamento do comportamento tensão deformação do aço inoxidável 304L, todos os ensaios foram realizados com frequências (0,30-2,00 Hz) tais que a taxa de deformação equivalente de von Mises fosse igual a 10-2 s-1. Observou-se que o endurecimento secundário nos ensaios proporcionais só ocorreu para amplitudes de deformação equivalente Δ/2 ≥ 0,80% enquanto todos os ensaios axiais-torsionais apresentaram endurecimento secundário. Baseado na comparação entre os estados de tensão, concluiu-se que há falha por fadiga antes que o endurecimento secundário se torne significativo para os ensaios proporcionais cuja Δ/2 ≤ 0,60%. Observou-se um comportamento do tipo Masing para uma faixa de deformação axial Δ/2 ≤ 0,40% e torsional Δ/2 ≤ 0,61% para ensaios axiais, torsionais e proporcionais. A deformação equivalente de von Mises não pode ser usada como parâmetro limite para o comportamento Masing já que o ensaio proporcional cuja Δ/2 = 0,50% apresenta comportamento semelhante àquele de ensaios cuja Δ/2 ≤0,50%, o que não ocorre para o ensaio axial de mesma amplitude de deformação equivalente. Observou-se não proporcionalidade nos espaços das tensões desviadoras e das deformações plásticas para os ensaios proporcionais no espaço das deformações totais. No entanto, não se observou um aumento na amplitude de tensão destes ensaios quando comparados a ensaios axiais e torsionais, o que sugere que o endurecimento não proporcional está associado à não proporcionalidade no espaço das deformações totais. Não houve influência significativa do endurecimento secundário na análise de fadiga, já que não houve diferença significativa entre as estimativas de vida realizadas com constantes materiais obtidas de diferentes ciclos de referência para os dois modelos. Os modelos investigados previram a vida à fadiga com boa acurária, mas falharam em prever a orientação das trincas para todas as três histórias de deformação.
The goals of this work are to investigate the cyclic stress-strain behaviour and the multiaxial fatigue of the 304L stainless steel through fully reversed strain-controlled axial, torsional and proportional axial-torsional experiments at room temperature and to evaluate the critical plane fatigue models proposed by Smith, Watson and Topper (1970), and Fatemi and Socie (1988) regarding the fatigue life and the macroscopic fatigue crack orientation. Thin-walled tubular specimens machined after a normalization heat treatment were submitted equivalent von Mises strain amplitudes such that 0:20% "eq=2 1:00%. Due to the rate-dependent cyclic stressstrain behaviour of the 304L stainless steel, all experiments were performed with frequencies (0.30{2.00 Hz) such that the equivalent von Mises strain rate was equal to 102 s1. It was observed that the secondary hardening upon proportional loads occurred only for "eq=2 0:80%, whilst it occurred for all axial and torsional experiments. Based upon the comparison between stress states, it was concluded that fatigue failure occurs before the secondary hardening becomes important for proportional experiments whose "eq=2 0:60%. A Masing-type behaviour was observed for a range of axial strain "=2 0:40% and torsional strain sur=2 0:61% for axial, torsional and proportional experiments. The equivalent von Mises strain amplitude cannot be used as a threshold since the proportional experiment whose "eq=2 = 0:50% exhibits a behaviour similar to experiments whose "eq=2 < 0:50%, which does not occur for the axial experiment with the same equivalent strain amplitude. non-proportionality upon deviatoric stress and plastic strain spaces was observed for proportional experiments upon total strain space. Nonetheless, an increase in stress amplitude was not observed for those experiments when compared to axial and torsional ones, which suggests that non-proportional hardening is related to non-proportionality upon the total strain space. There was no signi cant inuence of secondary hardening upon fatigue analysis since there was no signi cant di erence between life predictions generated from material constants obtained from di erent reference cycles for both models. The investigated models predicted accurately fatigue life, but failed to predict crack orientation for all the three strain histories.
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Lombardi, Daniele. "The DFSZ axion: analysis and generalization." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16397/.
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Lo scopo di questo progetto è quello di prendere in esame alcune estensioni del modello standard capaci di incorporare al loro interno l'assione QCD.
Nel primo capitolo vengono analizzate da zero le motivazioni per l'introduzione del concetto di assione. Il problema della violazione CP nelle interazioni forti è introdotto a partire dalla non banale struttura topologica del gruppo di simmetria di colore in QCD.
Nel secondo capitolo viene studiato un particolare modello di assione, ossia quello DFSZ. Vengono quindi sviluppati il suo contenuto di campi di e il suo spettro di massa. In particolare, viene considerata una versione leggermente differente di modello DFSZ, dove il termine quartico misto del potenziale di Higgs è sostituito da un contributo cubico.
Una piccola frazione di questo lavoro è inoltre dedicata a riassumere il problema dei domain walls. Grande importanza è data alla costruzione di modelli teorici che possano mettere al sicuro la teoria da una catastrofe cosmologica per mezzo di una oculata scelta dell'attribuzione delle cariche di Peccei-Quinn.
Per concludere, gli accoppiamenti degli assioni con i fermioni sono presi in esame. Grande attenzione viene rivolta alla generalizzazione del modello richiedendo la simultanea soppressione degli accoppiamenti assionici a protoni, neutroni ed elettroni. Una applicazione importante di questa impostazione è la capacità di indebolire diversi vincoli astrofisici, permettendo di raggiungere la cosiddetta finestra di massa pesante per l'assione. Viene argomentato come una condizione necessaria perchè questo avvenga sia l'introduzione di una assegnazione di cariche di Peccei-Quinn non universale per i quark e i leptoni del modello standard. A seguire, viene identificata una classe minimale di questi assioni DFSZ, dove le proprietà di nucleofobia ed elettrofobia possono essere implementate.
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Frauendorf, Stefan, and V. V. Pashkevich. "General Axial Shapes of Sodium Clusters." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-32476.
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Carrasco, Bustamante Ludwing Alberto. "Comportamiento axial de arriostres de acero." Universidad Nacional de Ingeniería. Programa Cybertesis PERÚ, 2011. http://cybertesis.uni.edu.pe/uni/2011/carrasco_bl/html/index-frames.html.
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La presente tesis utiliza los resultados experimentales de Black, Weger y Popov y los métodos analíticos de Michio Shibata, Takeshi Nakamura, Minoru Wakahayashi y Kangning U, con la finalidad de crear una herramienta de cómputo que permita calcular y comparar el comportamiento histerético de un arriostre de acero. Los resultados experimentales de Black, Weger y Popov utilizados para la comparación de curvas histeréticas, fueron obtenidos para un arriostre de acero de sección circular hueca, con extremos fijo y articulado y expuesto a carga axial cíclica incremental. Por medio de un macro implementada en VBA del Excel, se creó el código basado en la teoría de Shibata. Nakamura. Wakabayashi y Kangning Li. Para verificar los resultados obtenidos con la macro del Excel, se realizó el análisis estático con carga cíclica del mismo arriostre usando el programa Canny 2009This thesis uses experimental results of Black, Weger and Popov and anlytical methods of Michio Shihata, Takeshi Nakamura, Minoru Wakabayashi and Li Kangning. in order to create a computational tool to calculate and compare the hyslerelic hehavior of a steel brace. The experimental resufts of Black, Weger and Popov uscd for the comparison of hysteresis curves, were obtained for a steel brace with circular hollow section, with fixed pin ends and subjected to incremental cyclic axial loading. Through a VBA macro in excel implemented, created the code based un the theory of Shibata, Nakamura, Wakabayashi and Li Kangning. To verify the results obtained by the excel macro; a static analysis of the cyclic oading using the program bracing Canny 2009 was performed
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Seitz, Peter Alexander. "Casing treatment for axial flow compressors." Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/251677.
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Storer, John Andrew. "Tip clearance flow in axial compressors." Thesis, University of Cambridge, 1991. https://www.repository.cam.ac.uk/handle/1810/251503.
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Moulatsiotis, Photis. "Constraints on three families axion models." Thesis, University of Sussex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285114.
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Wiklund, Pär-Eric. "Suction dynamics of axial piston pumps /." Stockholm, 1998. http://www.lib.kth.se/abs98/wikl0511.pdf.
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Beevers, A. "Transition Modelling for Axial Compressor Flows." Thesis, Cranfield University, 2008. http://hdl.handle.net/1826/3479.
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Abstract
The application of Menter's transition model (Menter et al. (2004a), here-after known as the ץ - θ model) available in the CFX CFD code, for use within an axial compressor design group was studied. Simulations of a range of turbomachinery applicable test cases were undertaken, including a range of transitional flat plates and a 2D compressor cascade. Results were com¬pared to experimental data and the results of simulations performed with standard turbulence models.
The ץ - θ model significantly improved the prediction of the boundary layer development, compared to the turbulence models. Comparisons with ex¬perimental data were also good. Features such as mid-chord transitional separation bubbles were predicted with the ץ - θ model, but not with the turbulence models. The ץ - θ model offered no consistent improved accuracy over the κ - ω SST turbulence model when predicting leading edge separa¬tion bubbles. The more accurate simulation of the boundary layer enables a closer prediction of viscous losses.
2D and 3D unsteady simulations of a low-speed axial compressor stator blade boundary layer, subject to impinging rotor wakes, were conducted. The pur¬pose was to determine the performance of the ץ - θ model in this environment,
as there is no available literature for this. For both simulations, the model gave a good qualitative agreement to experimental data in the prediction of passing rotor wake effects on the suction surface. The effects on the pressure surface transition region due to wake passing were poorly predicted.
All models were simulated on low and high-speed axial compressor stages. Results showed no improvement over the turbulence models of the ץ - θ model to predict blade exit parameters. The ץ - θ model does not present a significant enough improvement in the prediction of the flow to warrant its regular use in the design of axial compressor blading. However, it presents a useful tool in the development of high lift compressor blading.
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Piscopo, Giovanni. "Preliminary aerothermal design of axial compressors." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/7909.
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The research work disclosed in this publication is partially funded by the
Strategic Educational Pathways Scholarship Scheme (Malta). The
scholarship is part-financed by the European Union – European Social
Fund under Programme II – Cohesion Policy 2007-2013.This dissertation documents a compressor preliminary design study conducted by the author in fulfilment of his MSc thesis requirements. The compressor is intended for a new development engine within the 20Klbf thrust category, planned to be used on a short-haul aircraft, namely the ERJ-190. A market research suggests that there exists a definite opportunity for a commercially profitable engine within this thrust class. Furthermore, the proposed new engine is projected to outperform current production engines on critical issues such as fuel efficiency and operability. By and large, the objectives of this work have been achieved and a compressor design and layout is suggested, which matched or exceeded all the initial requirements. The quality of the results from this study are thought to be of sufficient detail to allow a further, more detailed development study to resolve some subtle pending issues. It is expected that, some compressor stages may have to be altered slightly during detailed design to augment their performance and ease of manufacture and assembly. Throughout this study, the importance of the compressor design figure of merits, pertaining to a short haul engine, has been outlined and their interaction on the design process is well documented. Furthermore, some rather unorthodox objectives such as compressor performance retention and reliability have been discussed. The author approached these subjects in an innovative way due to the limited non-proprietary knowledge available on these issues, especially considering their implications within preliminary design. Furthermore, the author developed and tested a new preliminary turbomachinery design code, named Turbodev, which can be used as an aid in future compressor design endeveours. Turbodev can handle most types of compressor layouts and generates an overall aerodynamic assessment of the turbomachinery performance. In conclusion; this documentation and the associated literature review aim to provide the reader with an overview of the work done and yield a better understanding of the decisions that face any design bureau when developing a new or modified engine component.
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Paone, Matthew Paul. "Rotary-axial spindles for precision machining." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/18715.
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This thesis presents the design, analysis, fabrication, instrumentation, and control of a new type of machine tool spindle. Its primary contributions include the design and experimental demonstration of: two rotary-axial spindle prototypes, MIMO current control for a 1 kW linear power amplifier, sensorless rotary motion feedback, a novel method for increasing ADC resolution, and loop-shaping motion control systems.
Some machining operations, such as face grinding, require rotational and feed motion to remove material. Conventional machine tools accomplish this by attaching a spindle which has thrust and journal support to a feed drive which also has thrust and lateral support systems. In modern machine design, the trend is towards increasing the stiffness of each individual element. However, the inherent serial duplication of support presents a fundamental limitation to stiffness and precision.
The rotary-axial spindle architecture alleviates this problem by discarding the feed drive and spindle thrust bearing, replacing them both with a high force electromagnetic actuator. This provides millimeter range stroke for the spindle shaft, resulting in a single inertial element capable of both rotary and axial motion. This topology has several advantages. It allows kHz range bandwidth and hundreds of N/μm dynamic stiffness, improves acceleration, reduces structural bending moments, and eliminates thermal effects of fluid thrust bearings.
Two prototypes are developed to demonstrate this technology. The first is a small scale rotary-axial spindle. Driven by a four-channel 1 kW linear power amplifier with decoupled current loops, the magnetic thrust bearing can handle 600 N peak axial loads over a 1 mm stroke. A novel method for increasing ADC resolution achieves sub-5 nm RMS positioning noise. Loop shaping compensation of the position loop results in 100 N/μm minimum dynamic stiffness and 2.6 kHz closed loop bandwidth. To control the spindle speed, a sensorless rotary motion feedback algorithm was developed. It produces results equivalent to a 1000 line rotary encoder. The second prototype is a full size machine tool. It demonstrated 6 kN continuous axial load capacity, 340 N/μm minimum dynamic stiffness, 800 Hz bandwidth, and 7 nm RMS positioning noise over a 1.5 mm stroke.
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Bagshaw, David Andrew. "Passage shaping in axial flow turbines." Thesis, Durham University, 2009. http://etheses.dur.ac.uk/2065/.
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This thesis describes the novel combination of reverse compound lean, leading edge extension and non-axisymmetric endwall profiling in a highly loaded turbine geometry, for the reduction of secondary flow and loss. The thesis describes each geometrical modification in turn (in addition to their combination) and details their development from concept to experimentally measured performance. The designs are assessed using 3D Navier Stokes modelling. The best performing designs were manufactured and tested experimentally using pneumatic probes, flow visualisation and static pressure tappings. The key sections of the thesis include: • A review of previous non-axisymmetric profiled endwalls, with a view to understanding their performance in a full 3D passage design • The assessment of reverse compound lean in a highly loaded turbine cascade • The design development and subsequent testing of a 3D turbine passage design for minimising pressure loss associated with and kinetic energy in secondary flows. In summary, Passage Shaping works by using reverse compound lean to draw the secondary flows in to the endwall, where a combination of leading edge extension and non-axisymmetric endwall profiling work on the secondary flows to reduce their intensity. The key changes in the downstream flowfield, as a result of the passage shaping designs, are a reduction in loss (both profile and secondary) and a reduction in secondary flow, resulting in a more uniform exit yaw angle
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Fernandes, J. X. "Axial-flow compressor stall and stability." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598988.
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The research described in this dissertation is a computational study aimed at investigating blade row stability and stall inception in a high-speed compressor. Three-dimensional, steady and unsteady Navier-Stokes flow solvers were used to identify and understand the differences in the off-design low mass flow performance and stalling inception mechanism of a high-speed rotor blade row when it operates in isolation and as part of a single-stage (rotor-stator) build. The main conclusion from steady flow analysis is that when the rotor operates in the presence of a downstream stator, it is able to maintain stable axisymmetric performance down to a lower mass flow compared to when it operates in isolation. The rotor’s stability is extended when operating in the stage environment primarily because the stator acts to redistribution the radial pressure variation imposed at the rotor exit, thereby unloading the sensitive tip region. Unsteady flow analysis of the isolated rotor reveals that stall inception is associated with reversed flow at the tip region of a single rotor blade spilling forward of the leading edge. This results in the development of a spike-type disturbance that grows rapidly into a single finite stall cell. The reversed flow at the rotor tip and the resulting increase in tip-clearance related blockage that are both associated with the initial development of the spike disturbance are attributable to modal perturbations promoting localised flow separation at the rotor tip and to spanwise migration of fluid within the suction surface boundary layer. When the rotor operates as part of a stage, a qualitatively different type of stall inception mechanism is observed. Unsteady flow analysis reveals a one-dimensional breakdown of the rotor tip-clearance flow, with the flow observed to ‘surge’ upstream in an axisymmetric stalling pattern. Unlike the development of traditional rotating stall, no evidence of modal or spike-type disturbances are detected prior to the onset of stall and no stall cell structure is formed.
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Sung, Wang-Kyung. "High-frequency tri-axial resonant gyroscopes." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52936.
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This dissertation reports on the design and implementation of a high-frequency, tri-axial capacitive resonant gyroscopes integrated on a single chip. The components that construct tri-axial rotation sensing consist of a yaw, a pitch and a roll device. The yaw-rate gyroscope has a wide bandwidth and a large full-scale range, and operates at a mode-matched condition with DC polarization voltage of 10V without frequency tuning requirement. The large bandwidth of 3kHz and expected full-scale range over 30,000˚/sec make the device exhibit fast rate response for rapid motion sensing application. For the pitch-and-roll rate sensing, an in-plane drive-mode and two orthogonal out-of-plane sense-modes are employed. The rotation-rate sensing from lateral axes is performed by mode-matching the in-plane drive-mode with out-of-plane sense-modes to detect Coriolis-force induced deflection of the resonant mass. To compensate process variations and thickness deviations in the employed silicon-on-insulator (SOI) substrates, large electrostatic frequency tunings of both the drive and sense modes are realized. A revised high aspect ratio combined polysilicon and silicon (HARPSS) process is developed to resolve the Coriolis response that exists toward out-of-plane direction while drive-mode exists on in-plane, and tune individual frequencies with minimal interference to unintended modes. To conclude and overcome the performance limitation, design optimization of high-frequency tri-axial gyroscopes is suggested. Q-factor enhancement through reduction of thermoelastic damping (TED) and optimizations of physical dimensions are suggested for the yaw disk gyroscope. For the pitch-and-roll gyroscope, scaling property of physical dimension and its subsequent performance enhancement are analyzed.
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Gentles, Andrew James. "Nonperturbative propagators in axial gauge QCD." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243921.
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Hall, David Kenneth. "Performance limits of axial turbomachine stages." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/63042.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 111-114).
This thesis assesses the limits of stage efficiency for axial compressor and turbine stages. A stage model is developed, consisting of a specified geometry and a surface velocity distribution with turbulent boundary layers. The assumptions and parameterization of the stage geometry allow for calculation of the magnitude of various loss sources in terms of eight input parameters. By (1) considering only the losses which cannot be eliminated (such as viscous dissipation within the boundary layer on wetted surface area), (2) selecting stage design variables for minimum loss, and (3) assessing performance in the incompressible limit, an upper bound on stage efficiency can be determined as a function of four stage design parameters. Under the given conditions, the maximum stage efficiencies are found to be 95.5% and 97.2% for compressor and turbine stages, respectively. The results of the stage analysis are evaluated in the context of gas turbine generator and turbofan cycles for different levels of material and cooling technology. If the cycle temperature and pressure ratios are selected for minimum fuel consumption, even small increases in component efficiency can lead to substantial increases in overall engine efficiency. For example, if the efficiency of components is increased from 90% to 95% and the design is optimized, the specific fuel consumption of a gas turbine generator and turbofan engine are reduced by 17% and 19%, respectively. The stage level and cycle analyses carried out imply that component efficiency improvements leading to an appreciable increase in cycle thermal efficiency still remain to be realized.
by David Kenneth Hall.
S.M.
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Young, Anna Mollie. "Tip-clearance effects in axial compressors." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610603.
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Gill, Andrew. "Four quadrant axial flow compressor performance." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20075.
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Thesis (PhD)--Stellenbosch University, 2012.ENGLISH ABSTRACT: The aims of this thesis are to identify all possible modes of operaton for a multi-stage axial flow compressor; then to characterise the performance, attempt to numerically model operation, and determine the main flow field features for each mode. Four quadrant axial flow compressor operation occurs when the direction of flow through the compressor or the sign of the pressure difference across the compressor reverses, or any combination of these. Depending on the direction of rotation of the compressor, six modes of operation are possible in the four quadrants of the performance map. The rotor rotates in the design direction for three modes, and in the opposite direction for the other three. The stationary-rotor pressure characteristic is S-shaped and passes through the second and fourth quadrants. A three-stage axial flow compressor operating in the incompressible flow regime was used for the experimental investigation. Flow through the compressor was reversed or augmented by means of an auxiliary axial flow fan. Compressor performance was measured by means of static pressure tappings, a turbine anemometer calibrated to measure forward and reversed volumetric flow and a load cell for torque measurement. The inter-blade row flow fields were measured with pneumatic probes and 50 μm cylindrical hot film probes. Three dimensional single blade-passage Navier-Stokes simulations were performed using the Numeca FineTurbo package. Steady state simulations used a mixing plane approach. A nonlinear harmonic approximation was used for time-unsteady simulations. Unstalled first quadrant operation was unremarkable, and good agreement was obtained between experimental and numerical data. A single stall cell was detected experimentally during stalled operation, which was not modelled numerically. In the fourth quadrant for positive rotation, (windmilling), the compressor acts as an inefficient turbine. Flow separates from the pressure surface of the blade, rendering the steady-state mixing plane approach unsuitable. The performance characteristic curves for second quadrant for positive rotation, are discontinuous with those of first quadrant operation. The temperature rise in the working fluid is significantly higher than at design point. Periodic flow structures occurring across two blade passages were detected at all flow coefficients investigated, invalidating numerical modelling assumptions. Better agreement was obtained between experimental and numerical data from a case found in literature. If the compressor operates as a compressor in reverse (third quadrant operation), significant separation occurs on the pressure surface of all blades, and flow conditions resemble severe first quadrant stall. Separation becomes less severe at larger flow rates, allowing numerical simulation, though this is sensitive to the initial flow field. In the the part of the second quadrant, where the compressor rotates in reverse, it operates as a turbine. The blade angles and the direction of curvature match the flow angles and turning well, leading to high turbine efficiencies. Numerical simulations yielded good agreement with measured results, but were again sensitive to the initial flow field. Fourth quadrant operation with negative rotation occurs when flow is forced through the compressor in the design direction. Large separation bubbles are attached to the pressure surfaces of rotor and stator blades, so virtually all throughflow occurs near the hub and casing
AFRIKAANSE OPSOMMING: Die doelwitte van hierdie tesis is om al die moontlike werkmodusse vir ’n bestaande multi-stadium aksiaalvloei kompressor uit te ken; om dan die gedrag te gekarakteriseer, ’n poging aan te wend om die werking numeries te modelleer, en die belangrikste vloeiveldkenmerke vir elke modus te bepaal. Vier-kwadrant aksiaalvloei kompressor werking vind plaas as die rigting van die vloei deur die kompressor, of die teken van die drukverskil oor die kompressor omkeer, of enige kombinasie daarvan. Afhangende van die rigting van rotasie van die kompressor is ses operasionele modusse moontlik in die vier kwadrante van die kompressorkaart. Die rotor draai in die ontwerprigting vir drie van die modes, en in die teenoorgestelde rigting vir die ander drie. Die stilstaande-rotor drukkarakteristiek is S-vormig gaan deur die tweede en vierde kwadrante. ’n Drie-stadium onsamedrukbare vloei aksiaalvloei kompressor is vir die eksperimentele ondersoek gebruik. Vloei deur die kompressor is omgekeer of aangehelp deur middel van ’n aksiaalvloei hulpwaaier. Kompressor werking is gemeet deur middel van statiese druk meetpunte in die omhulsel, ’n turbine anemometer wat gekalibreer is om vorentoe en omgekeerde volumetriese vloei te meet, en ’n lassel vir wringmoment meting. Interlemryvloeivelde is opgemeet met pneumatiese sensors en 50-μm silindriese warm film sensors. Drie-dimensionele Navier-Stokes simulasies is uitgevoer vir ’n enkele lem van elke lemry, met behulp van die Numeca FineTurbo sagtewarepakket. ’n Mengvlakbenadering is gebruik vir bestendige toestand simulasies, terwyl ’n nie-linere harmoniese benadering gebruik is vir die tyd-afhanklike simulasies. Ongestaakte eerste kwadrant werking was alledaags, en goeie ooreenkoms is gevind tussen die eksperimentele en numeriese data. ’n Enkele staak-sel is eksperimenteel ontdek tydens gestaakte werking. Gestaakte werking is nie numeries gemodelleer nie. In die vierde kwadrant vir positiewe rotasie, (”windmeulwerking”), werk die kompressor as ’n ondoeltreffende turbine. Vloei-wegbrekinging op die lem drukoppervlaktes maak die bestendige toestand mengvlakbenadering ongeskik. In die kenlyne vir tweede kwadrant positiewe rotasie, is daar ’n diskontinu¨ıteit in die prestasie karakteristiekkrommes vir die eerste en tweede kwadrant werking. Die temperatuurstyging in die werk- vloeistof is beduidend ho¨er as as by die ontwerppunt. Periodiese vloeistrukture wat oor twee lemme plaasvind is gevind by alle vloei ko¨effisi¨ente wat ondersoek is, en dit maak die numeriese modellering aannames ongeldig. Beter ooreenkoms tussen die eksperimentele en numeriese data iss verkry met ’n geval wat uit die literatuur gevind is. Indien die kompressor werk as ’n kompressor in omgekeerde (derde kwadrant weking), vind beduidende wegbreking op die drukoppervlak van al die lemme plaas, wat lyk soos ernstige gestaakte eerste kwadrant werking. Die vloeiskeiding raak minder ernstig by ’n groter vloeitempo, wat numeriese nabootsing toelaat, maar die nabootsings is sensitief vir die aanvanklike vloeiveld. In die tweede kwadrant, by omgekeerde rotasie, werk die kompressor as ’n turbine. Die lemhoeke en die rigting van lemkromming stem ooreen met die vloeihoeke en verwringing, wat lei tot ho¨er turbine doeltreffendheid. Numeriese nabootsings stem goed ooreen met gemete resultate, maar is weereens sensitief vir die keuse van die aanvanklike vloeiveld. Vierde kwadrant werking met negatiewe rotasie vind plaas wanneer die lug gedwing word om deur die kompressor in die ontwerprigting te vloei. Groot skeidingborrels sit vas aan die drukoppervlaktes van alle lemme, sodat meeste deurvloei naby die naaf en die omhulsel plaas vind.
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Doherty, K. "Axial postural deformities in Parkinson's disease." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1419081/.
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Studies have been performed to detail the phenomenology, investigate the skeletal changes and explore the spinal biomechanics underlying the main axial deformities – Pisa syndrome and camptocormia in Parkinson’s disease. Results demonstrate that the clinical picture of these deformities varies greatly but that certain particular features allow distinction from other neurological, muscular and bony aetiologies. The tone of the axial muscles, the level at which spinal flexion occurs, the patient’s ability and method to try to overcome the chronically abnormal posture, and the flexibility or fixity of the trunk provide clinical pointers to the likely underlying cause. The scoliotic curve in a patient with Pisa syndrome was C-shaped, involved a large element of collapse and occurred without evidence of a secondary upper compensatory curvature (S-shaped curve). On supine imaging patients with camptocormia were severely mechanically disadvantaged as a result of their alordotic lumbar spines in relation to pelvic angulation. This lumbar alordosis may reflect the effects of Parkinson’s disease on the axial musculature, particularly in those with axial akinetic rigid predominant PD. Radiological examination also demonstrated that Pisa syndrome was different from de novo degenerative scoliosis and camptocormia not typical of adult onset degenerative kyphosis. Fixed bony changes were rare but the severity of these postural deformities and their consequent effects (e.g. knee flexion contractures, gluteal muscle atrophy) are likely to render conservative interventions unsuccessful unless instigated very early in the evolution of the abnormal posture.
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Day, Francesca. "Astrophysical signatures of axion-like particles." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:215f6432-6dbb-4a16-80d8-3ad0bc76ec2d.
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The Standard Model of particle physics has enjoyed unprecedented success in predicting experimental results. However, evidence from astrophysical observations points to the existence of a dark sector of particles that interact only very weakly with the Standard Model. In this work, we search for dark sector signatures in X-ray telescope data. Much of this work concerns a class of hypothetical particles, the axion-like particle (ALP). ALPs are a theoretically well-motivated extension of the Standard Model. If ALPs exist, they may lead to intriguing astrophysical signatures: in the presence of a background magnetic field, ALPs and photons can interconvert. We could detect ALPs by searching for photon to ALP conversion. For example, photons produced by point sources in or behind galaxy clusters may convert to ALPs in the cluster's magnetic field. This could lead to observable spectral anomalies. Using this strategy, we place world leading bounds on the ALP-photon coupling. One potential signal of dark matter is an anomalous line in the spectra of galaxies and galaxy clusters. In 2014, an anomalous line was found at an energy of 3.5 keV. The nature and cause of this line is still under discussion. We analyse a scenario in which the 3.5 keV line arises from dark matter decay to ALPs, which interconvert with 3.5 keV photons in astrophysical magnetic fields. We further report an anomalous deficit at 3.5 keV in the spectrum of the Active Galactic Nucleus at the centre of the Perseus galaxy cluster. This motivates the study of a new model in which both features are caused by âfluorescent dark matterâ which resonantly interacts with 3.5 keV photons. We analyse observations of Perseus at 3.5 keV to date, and show that they are well explained by this model. Further theoretical and experimental work is needed to discover or exclude fundamental physics effects in X-ray spectra.
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Wantz, Olivier. "The instanton liquid and the axion." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/225235.
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The ultimate goal of this thesis is to improve our understanding of the cosmology of axions. Axions couple to QCDinstantons and these non-perturbative effects are modeled within the framework of the interacting instanton liquid model (IILM). The thesis describes the significant advances made within the IILM in order to study the quark-gluon plasma in realistic parameter regimes. In particular, a determination of the temperature-dependent axion mass in the IILM lays the foundation for a critical reevaluation and update of present cosmological axion constraints. We develop grand canonical Monte Carlo routines to study topological fluctuations in the quark-gluon plasma. The model is calibrated against the topological susceptibility at zero temperature, in the chiral regime of physical quark masses. A numerical framework to derive interactions among the pseudo-particles is developed that is in principle exact, and is used to cure a pathology in the presently available finite temperature interactions. The IILM reduces field theory to a molecular dynamics description, and we show that, quite generically, the dynamics for non-trivial backgrounds in the presence of light quarks is reminiscent of a strongly associating fluid. To deal with the well-known difficulty in simulating ionic fluids, we develop advanced algorithms based on Biased Monte Carlo techniques. We study the IILM at finite temperature in the quenched and unquenched sector, with due diligence to a consistent thermodynamic limit. Of particular interest is chiral symmetry breaking and the temperature dependence of the topological susceptibility, and we study in detail the effects of instanton--anti-instanton pairs. Our determination of the topological susceptibility provides, for the first time, a well-motivated axion mass for all temperatures. The misalignment mechanism for axion production is studied in detail, solving the evolution equations exactly in a radiation dominated FRW universe with the full temperature dependence of the effective degrees of freedom taken into account. Improved constraints in the classic and anthropic axion window are derived. We generalise the latter to large angle fine-tuning by including in the isocurvature contribution to the cosmic microwave background radiation the full anharmonic axion potential effects. Finally, we reexamine bounds from axion string radiation in the thermal scenario to complete a comprehensive update of all cosmological axion constraints.
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Frauendorf, Stefan, and V. V. Pashkevich. "General Axial Shapes of Sodium Clusters." Forschungszentrum Rossendorf, 1994. https://hzdr.qucosa.de/id/qucosa%3A22074.
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Smith, Robert. "Axial Spondyloarthropathies in the Western Cape." Master's thesis, Faculty of Health Sciences, 2019. http://hdl.handle.net/11427/31120.
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Impaired Health-Related Quality of Life and Work Productivity amongst South African patients with Axial Spondyloarthritis. Background: No studies have investigated health-related quality of life (HRQoL) or work productivity in patients with axial spondyloarthritides (axSpA) living in sub-Saharan Africa. Methods: This cross-sectional study of adults with axSpA collated demographic particulars and patient questionnaires: Bath Ankylosing Spondylitis Disease Activity Index (BASDAI); Bath Ankylosing Spondylitis Functional Index (BASFI); Bath Ankylosing Spondylitis Global Score (BASG); Medical Short Form (SF)-36; and Work Productivity and Activity Impairment Questionnaire: Specific Health Problem (WPAI:SHP). Results: Of 36 patients, the mean (SD) age was 40.3 (13.3) years and mean (SD) diagnostic delay was 8.7 (8.4) years. Most patients were male (80.6%) and of mixed racial ancestry (69.4%). Most (66.7%) patients were smokers and only 5 (13.9%) patients received tumor necrosis factor inhibitor (TNFi) therapy. The mean (SD) BASDAI was 5.3 (2.1), and 72.2% had a BASDAI ≥ 4. Patients with a high BASDAI (i.e. BASDAI ≥ 4) had higher BASG scores (p=0.003), higher WPAI:SHP activity impairment scores (p=0.003), and poorer SF-36 scores, particularly in the role-physical, bodily pain, and social functioning domains (p=0.0001, 0.001 and 0.02 respectively). Activity impairment according to the WPAI:SPH was 57.4%, with the BASDAI and activity impairment correlating closely (p=0.006). The SF-36 scores were low in physical (particularly role-physical, bodily pain, and general health) and mental (notably vitality and role emotional) domains. 6 Conclusion: This study describes a cohort of South African patients with axSpA who have poor prognostic features including diagnostic delay and cigarette smoking. Active disease, impaired function, poor physical- and mental HRQoL, and work disability are unmet needs.
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FU, YONGQIANG. "Aerodynamics and Combustion of Axial Swirlers." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204551619.
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Figueiredo, de Medeiros Lucas. "Linhas de continuidade no Sistema Axial." Universidade Federal de Pernambuco, 2004. https://repositorio.ufpe.br/handle/123456789/3580.
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Previous issue date: 2004A representação axial do ambiente construído tem sido reavaliada por especialistas nos últimos anos. Alguns argumentam que o seu conceito original o menor conjunto das mais longas linhas de acessibilidade e visibilidade contém um grau de subjetividade que pode gerar distorções ou diferentes modelos para um mesmo objeto descrito. Outros aceitam essa imprecisão demonstrando que a robustez desse sistema descritivo passa por cima de pequenas distorções, mas tentam refiná-lo ao introduzir novas técnicas para descrever sistemas espaciais. Esta dissertação apresenta uma contribuição a esse recente debate ao propor uma nova técnica descritiva, denominada linha de continuidade, que vai além da representação axial. Uma linha de continuidade agrega várias linhas axiais para representar um caminho urbano em sua máxima extensão, respeitando uma sinuosidade máxima pré-definida. Ela se baseia em dois argumentos principais: primeiro, que a noção de continuidade já está presente no sistema axial; segundo, que as linhas de continuidade reforçam a relação entre as medidas configuracionais e a geometria oculta dos mapas axiais. São elaboradas regras objetivas para criar linhas de conectividade num mapa axial comum e apresentadas novas variáveis associadas ao sistema. Um conjunto significativo de mapas axiais, diverso em tamanho e propriedades configuracionais, foi usado para testar a técnica e os resultados obtidos demonstraram sua consistência. O efeito de centralidade em mapas de integração foi reduzido, expressando mais claramente o caráter distribuído da acessibilidade e destacando a importância de caminhos curvos ou sinuosos. Finalmente, a hipótese de que a nova técnica descritiva aprimora o sistema axial foi testada
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Contreras, Jesse Alberto. "Axial Temperature Gradients in Gas Chromatography." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2645.
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The easiest and most effective way to influence the separation process in gas chromatography (GC) is achieved by controlling the temperature of the chromatographic column. In conventional GC, the temperature along the length of the column is constant at any given time, T(t). In my research, I investigated the effects of temperature gradients on GC separations as a function of time and position, T(t,x), along the column. This separation mode is called thermal gradient GC (TGGC). The research reported in this dissertation highlights the fundamental principles of axial temperature gradients and the separation potential of the TGGC technique. These goals were achieved through the development of mathematical models and instrumentation that allowed study of the effects of axial temperature gradients. The use of mathematical models and computer simulation facilitated evaluation of different gradient profiles and separation strategies prior to development of the instrumentation, providing theoretical proof of concept. Three instruments capable of generating axial temperature gradients, based on convective cooling and resistive heating, were developed and evaluated. Unique axial temperature gradients, such as nonlinear and moving sawtooth temperature gradients with custom profiles were generated and evaluated. The results showed that moving sawtooth temperature gradients allowed continuous analysis and were well-suited for comprehensive GCxGC separations. The use of custom temperature profiles allowed unique control over the separation power of the system, improving separations, as well as selectively increasing the peak capacity and signal-to-noise. A direct comparison of TGGC with conventional GC methods showed that TGGC produces equivalent separations to temperature programmed GC. This technology holds great promise for performing smart separations in which the column volume is most efficiently utilized and optimum separations can be quickly achieved. Moreover, precise control of the elution of compounds can be used to greatly reduce method development time in GC. This feature can be automated using feedback to develop efficient separations with minimum user intervention. This technology is of special interest in micro-GC systems, which allows relatively easy incorporation of resistive heating elements in the micro-column design.
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Arévalo, Salaet Marta. "El papel del HLA-B27 en la Espondiloartritis Axial." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/671576.
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En la tesi que presento s'avaluen les implicacions de la presencia de l'HLA-B27 en el fenotip i les comorbilitats de pacients amb Espondiloartritis AxialEn la tesis que presento se evalúan las implicaciones de la presencia del HLA-B27 en el fenotipo y las comorbilidades de pacientes con Espondiloartritis Axial
The present thesis assesses the implications of the presence of HLA-B27 in phenotype and comorbidities in Axial Spondyloarthritis patients
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Abchir, Zineb. "Contribution à l'étude du comportement des pieux soumis à des sollicitations axiales monotones et cycliques." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1079/document.
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Les fondations profondes sont largement utilisées et peuvent subir différent types de sollicitations axiales. Ces dernières peuvent avoir un caractère monotone ou cyclique. Le développement de méthodes de calcul pour prévoir le comportement des pieux sous ces deux types de chargements en termes de tassement et d’évolution de capacité portante, est d’une grande utilité pour l’ingénierie géotechnique. Le travail de cette thèse est une contribution à une meilleure prévision du comportement des pieux sous charges axiales monotones et cycliques. La thèse comporte deux parties principales. La première partie traite la problématique de la prévision du tassement d’un pieu sous charge axiale monotone. Un intérêt particulier est porté aux tassements car le dimensionnement d’un pieu requiert une estimation adéquate à la fois de la capacité portante et du déplacement en tête de pieu. La méthode utilisée dans cette partie est celle des courbes de transfert. L’étude commence tout d’abord par une analyse statistique du modèle habituellement utilisé pour le calcul de tassement nommé Frank et Zhao. Ensuite, deux nouveaux modèles de calcul de tassement sont proposés et analysés. Une analyse comparative entre les trois modèles de calcul de déplacement d’un pieu est réalisée dans cette étude. L’objectif de cette analyse est d’estimer la dispersion des modèles de calcul en comparant les tassements calculés aux tassements mesurés et répertoriés dans la base de données de l’IFSTTAR. La seconde partie s’intéresse à la problématique des chargements cycliques. En effet, plusieurs types de structures sont sollicités cycliquement et peuvent subir des désordres du fait de l’accumulation de déplacements en tête des fondations. L’objectif de cette partie de la thèse est de proposer un modèle permettant de rendre compte principalement de l’évolution de la capacité portante du pieu au cours des cycles, et aussi de proposer une estimation des déplacements. Le modèle développé se base sur la méthode des courbes de transfert, et est associé à deux procédures de dégradation du frottement axial limite. Il est tout d’abord présenté et ensuite appliqué à un exemple théorique. Afin de valider ce modèle, ses résultats sont comparés aux résultats d’essais de pieux en vraie grandeurDifferent types of loads can be applied to deep foundations which are widely used nowadays. Piles can be subjected to monotonic or cyclic loads. Thus, geotechnical engineering needs the development of calculation methods to predict the behavior of piles under these types of loads in terms of displacements and bearing capacity. The study presented in this thesis aims to ameliorate the prediction of the behavior of piles under axial monotonic and cyclic loads. This thesis is divided into two parts. The issue of the first part is the prediction of the settlement of a pile submitted to monotonic and axial load. This part focuses on the estimation of settlements because a correct design of a pile requires a correct estimation of bearing capacity as well as displacements. The approach used in this part is the load transfer method. The study starts by a statistical analysis of the t-z model of Frank and Zhao which is generally used for the calculation of pile settlements. Two new t-z models of settlement calculation are presented and analyzed later. Moreover, a comparative analysis between the three t-z models is presented in this study. The aim of this analysis is to estimate the dispersion of the models using the comparison between calculated settlements and measured settlements listed in IFSTTAR’s database. The second part of the thesis deals with the issue of cyclic loads. Indeed, different structures can be subjected to cyclic loads and disorders can be noted due to the accumulation of displacements at the top of the pile. The aim of this part is to propose a calculation model allowing essentially the estimation the evolution of bearing capacity during cycles. It permits also the estimation of displacements. The model developed in this part is based on load transfer approach, and is associated to two calculation methods of degradation of shaft friction. This model is firstly presented, and then it is applied to a theoretical case. In order to validate this model, its numerical results are compared to experimental results of full scale pile tests
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Bloch, Gregory S. "A wide-range axial-flow compressor stage performance model." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08182009-040326/.
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Russler, Patrick M. "An investigation of the surge behavior of a high-speed ten-stage axial flow compressor." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09192009-040554/.
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Bice, Jonathon Ray. "Experimental investigation of a meso-scale axial flow pump." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Shepherd, Paul. "The performance in fire of restrained columns in steel-framed construction." Thesis, University of Sheffield, 1999. http://etheses.whiterose.ac.uk/2996/.
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The University of Sheffield has a non-linear finite element analysis program called VULCAN which has been developed in-house over a number of years and has been thoroughly validated. A parametric study has been conducted using this software, which assesses the influence of such factors as load, geometric imperfection, material properties, temperature profile and axial and rotational restraint on the behaviour, of isolated steel columns in fire. This study is then extended to investigate the behaviour of steel columns as part of a larger multi-storey frame, in which axial restraint to thermal expansion of the heated column is provided by the floors above. A method of modelling these effects in VULCAN using a linear spring element to provide axial restraint has been developed and validated. An experimental partner project has been carried out at the University of Ulster, in which steel columns were furnace-tested with various levels of load, slenderness and axial restraint. These tests have been paralleled with analyses using VULCAN and a good correlation with test results has been shown. The VULCAN program was then used to examine the effects of parameters outside the range of the physical constraints imposed by the test facility. A numerical model, capable of assessing the level of axial restraint imparted on a column by a general multi-storey framed structure has been developed, which has a number of levels of complexity, each giving a higher degree of accuracy. Once the level of restraint for a structure has been assessed, the parametric studies and test data can be applied, and conclusions drawn about the behaviour of the frame. The applicability of different mathematical solution procedures to the analysis of these columns, which exhibit snap-through and snap-back behaviour, has been conducted. The arc-length method has been identified as applicable in such cases and a skeleton version of the procedure introduced into the VULCAN program. The program structure of VULCAN has been improved and the format for data input and output has been developed to allow flexibility. A graphical file-viewer program has also been created. Details of these changes are shown in appendices.
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Porreca, Luca. "Aerothermal optimization of partially shrouded axial turbines /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17138.
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Climente, Plasencia Juan Ignacio. "Integración del Hamiltoniano K·P en Simetria Axial." Doctoral thesis, Universitat Jaume I, 2005. http://hdl.handle.net/10803/10545.
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Aquesta tesi mostra un mètode eficient per integrar numèricament una hamiltoniana k·p per heteroestructures semiconductores zero-dimensionals (punts quàntics). S'ofereixen nombrosos exemples d'aplicació en punts quàntics col·loidals sota camps magnètics, anells quàntics, punts quàntics auto-organitzats sota strain i punts quàntics amb ions magnètics. Especial èmfasi es fa en l'efecte d'acoblament entre bandes de forats lleugers i pesants.
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Zaki, Mina Adel. "Physics based modeling of axial compressor stall." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31683.
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Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2010.Committee Chair: Dr. Lakshmi N. Sankar; Committee Member: Dr. Alex Stein; Committee Member: Dr. J.V. R. Prasad; Committee Member: Dr. Richard Gaeta; Committee Member: Dr. Suresh Menon. Part of the SMARTech Electronic Thesis and Dissertation Collection.