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1
Gomes, Umesh Prasad. « Catalyst-assisted and catalyst-free growth of III-V semiconductor nanowires ». Doctoral thesis, Scuola Normale Superiore, 2017. http://hdl.handle.net/11384/85884.
Texte intégralRésumé :
The aim of this thesis is to understand the dynamics of the nucleation and growth of III-V semiconductor nanowires and associated heterostructures grown by chemical beam epitaxy. These nanowires represent well-controlled and high quality materials suitable for both fundamental physics and applications in optical and electronic devices.
The first part of the thesis investigates growth recipes to obtain Au-catalyzed InAs NWs with controlled morphology. Good control of NW length and diameter distributions has been achieved by a systematic study of two different Au deposition techniques: Au thin film deposition and colloidal dispersion.
Triggered by the issues of Au contamination and CMOS compatibility, the second part of the thesis is dedicated to the investigation of the nucleation and growth mechanisms of Au-free InAs NWs on Si (111) substrates. A thorough analysis of the silicon substrate preparation is conducted and an optimized silicon surface for the nucleation of Au-free nanowires is identified. We show that the silicon surface can be modified by in situ and ex situ parameters allowing us to control the density of NWs. Growth conditions were established for growing InAs NWs either by catalyst-free or self-catalyzed mechanisms on Si (111). The catalyst-free growth proceeds in the vapor-solid growth mechanism without the use of any catalyst particle while the self-catalyzed growth proceeds in the vapor-liquid-solid mechanism involving a liquid In droplet. Growth models are proposed in order to interpret the experimental findings.
The third part of the thesis concerns the growth of axial and radial (core-shell) heterostructured NWs. Nanowire heterostructures combining either highly lattice mismatched materials (GaAs and InAs) or almost lattice matched materials (InAs and GaSb) are investigated. GaAs/InAs and InAs/GaAs axial heterostructures are grown by Au-catalyzed method. Here, it is demonstrated that the catalyst composition, rather than other growth parameters, as postulated so far, controls the growth mode and the resulting NW morphology. We have also explored the growth of core-shell InAs/GaSb heterostructures by catalyst-free mechanism. The morphology and structural properties of InAs/GaSb core-shell heterostructures are optimized to fabricate Esaki tunnel diodes exploiting their broken-gap band alignment.
2
Sulistyo, Hary. « Axial and radial heat transport in packed beds ». Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293824.
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Spakovszky, Zoltán S. (Zoltán Sándor) 1972. « Applications of axial and radial compressor dynamic system modeling ». Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8888.
Texte intégralRésumé :
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, February 2001.Includes bibliographical references (p. 255-262).
The presented work is a compilation of four different projects related to axial and centrifugal compression systems. The projects are related by the underlying dynamic system modeling approach that is common in all of them. Two types of models are introduced, suitable for modeling the dynamic behavior of axial and centrifugal compression systems: a compact single semi-actuator disk model, Model I, and a new modular multi semi-actuator disk model, Model II. The first project analyzes aerodynamically induced whirling forces in axial-flow compressors and a new unsteady low order model is introduced to predict the destabilizing whirling forces. The model consists of two parts: compressor Model I with the effect of tip-clearance induced distortion, and an aerodynamically induced force model. The modeling results are compared to experimental data obtained from the GE Aircraft Engines test program on compressor whirl. Previously outstanding whirl-instability issues are resolved, including prediction of the direction and magnitude of rotor whirl-inducing forces; such issues are important in the design of modern axial-flow compressors.
(cont.) Additional insight is gained from the model on the effects of forced rotor whirl. In particular, a non-dimensional parameter is deduced that determines the direction of rotor whirl tendency in both compressors and turbines due to tangential blade loading forces. The second project is a first-of-a-kind feasibility study of an active stall control experiment with a mag- netic bearing servo-actuator in the NASA Glenn high-speed single-stage compressor test facility. Together with CFD and experimental data the tip-clearance sensitive compressor Model I was used in a stochastic estimation and control analysis to determine the required magnetic bearing performance for compressor stall control. A magnetic bearing servo-actuator was designed that fulfilled the performance specifications, setting a milestone in magnetic bearing development for aero-engine applications. Control laws were then developed to stabilize the compressor shaft. In a second control loop, a constant gain controller was imple- mented to stabilize rotating stall. A detailed closed loop simulation at 100% corrected design speed resulted in a 2.3% reduction of stalling mass flow which is comparable to results obtained in the same compressor using unsteady air injection.
(cont.) The third project is the investigation of unsteady impeller-diffuser interaction effects on compressor stability. First, the unsteady blade-row interaction in axial compressors is analyzed using Model II. The results reveal a new signature of pre-stall waves that travel backward, altering the system dynamics when rotor and stator are moderately coupled. The physical mechanism for this behavior is explained from first principles and a coupling criterion is presented. The theory is then applied to centrifugal compressors and in particular to the NASA CC3 high-speed centrifugal compressor, in which experiments are conducted to verify the model predictions. The measurements show the predicted behavior and confirm the existence of backward traveling stall pre-cursors. The fourth project is an experimental demonstration of stability enhancement in the NASA CC3 high-speed centrifugal compressor with air injection. Based ...
by Zoltán Spakovszky.
Ph.D.
4
Renzetti, Andrew John. « Radial and Axial Designs for Magnetic Absorbent Collector in Water ». Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1707371/.
Texte intégralRésumé :
The use of collection systems for magnetic sorbents such as Magnetic Activated Carbon are discussed in order to gauge their efficacy in marine environments. Two collectors were built and tested, one which utilized a radial orientation of magnets and another with axially placed magnets. The two systems underwent a series of test with differing linear velocities and angular velocities. From the results, the axial system outperformed its radial counterpart, being most effective with a relatively high concentration of discs placed in series. The medium concentration, however, proved increasingly effective with higher velocities, meaning an optimization concentration exists for this design. The radial system was tested with high and low concentrations of small and large magnets, respectively. The larger magnets, although providing less concentration points in the alternating array, proved more effective for the collection of MAC. From these tests several new innovations were suggested, including belt tensioners, add on mechanisms, and a hybridized design in order to fully optimize the collection of MAC.
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Kneissler, Andreas. « Multisensor-Strategie zur Optimierung des Anwalzverhaltens beim Radial-Axial-Ringwalzen ». Aachen Shaker, 2008. http://d-nb.info/993898289/04.
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Golz, Jan. « Prozesssynchrone Simulation der Temperaturverteilung in radial-axial gewalzten Ringen mit Rechteckquerschnitt ». Aachen Shaker, 2008. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=017047408&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Kraus, Peter. « Optimierung eines Axial-Radial-ND-Abströmgehäuses hinsichtlich des Wirkungsgrades sowie der Stossoszillation ». [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965520471.
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Kneißler, Andreas [Verfasser]. « Multisensor-Strategie zur Optimierung des Anwalzverhaltens beim Radial-Axial-Ringwalzen / Andreas Kneißler ». Aachen : Shaker, 2009. http://d-nb.info/1126378577/34.
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Fleischer, Erik [Verfasser]. « Entwurf, Modellierung und nichtlineare Regelung eines integrierten Radial-Axial-Magnetlagers / Erik Fleischer ». Aachen : Shaker, 2018. http://d-nb.info/1161299262/34.
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Müller, Lasse. « Adjoint-Based Optimization of Turbomachinery With Applications to Axial and Radial Turbines ». Doctoral thesis, Universite Libre de Bruxelles, 2019. https://dipot.ulb.ac.be/dspace/bitstream/2013/280380/5/contratLM.pdf.
Texte intégralRésumé :
Numerical optimization methods have made significant progress over the last decades and play an important role in modern industrial design processes. In most cases, gradient-free algorithms are used, which only require the value of the objective function in each optimization step. These methods are robust and can be integrated into a standard design process at low implementation effort. However, in aerodynamic design problems using high-fidelity Computational Fluid Dynamics (CFD), the computational cost is high, especially when a large number of design parameters are used. Gradient-based methods, on the other hand, are particularly suited for problems involving large design spaces and generally converge to a local optimum in a few design cycles. However, the computational efficiency of these methods is mainly determined by the gradient calculation.This thesis presents the development of an efficient gradient-based optimization framework for the aerodynamic design of turbomachinery applications. In particular, the adjoint approach is used to evaluate the gradients of the objective function with respect to all design parameters at low computational cost. The present work covers the various components of the optimization framework, including the solution of the flow governing equations, adjoint-based sensitivity analysis, geometry parameterization, and mesh generation. A substantial part of the thesis describes the implementation and validation of those components. The flow solver is a Reynolds-Averaged Navier-Stokes code applicable to multiblock structured grids. The spatial discretization is realized with a Roe-type upwind scheme with a MUSCL extrapolation for second order spatial accuracy. Viscous fluxes are centrally discretized, and for the turbulence closure problem the Spalart-Allmaras and the Shear-Stress Transport (SST) models are used. The code uses an implicit multistage Runge-Kutta time-stepping scheme, accelerated by local time-stepping and geometric multigrid. The corresponding discrete adjoint solver uses the same time marching scheme as the flow solver and features similar performance characteristics in terms of runtime and memory footprint. The adjoint solver has been implemented primarily by hand with selective use of algorithmic differentiation (AD) to simplify the development. The geometry parameterization is based on B-Spline representations which has two main advantages: (a) the simple integration of geometric constraints for structural requirements, and (b) the connection to Computer-Aided Design (CAD) software for manufacturing. The whole optimization framework is driven by a Sequential Quadratic Programming (SQP) algorithm. The proposed framework has been successfully applied to optimize axial and radial turbines on multiple operating points subject to aerodynamic and geometric constraints. The different studies show the effectiveness of the developed method in terms of improved performances and computational cost. In particular, a comparative study shows that the proposed method is able to find optimized blade shapes at a computational time which is about one order of magnitude lower compared to a gradient-free optimization algorithm.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Kraus, Peter. « Optimierung eines Axial-Radial-ND-Abströmgehäuses hinsichtlich des Wirkungsgrades sowie der Stoßoszillation ». [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10252242.
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Scharfe, Michelle Kristin. « Electron cross field transport modeling in radial-axial hybrid hall thruster simulations / ». May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Golz, Jan [Verfasser]. « Prozesssynchrone Simulation der Temperaturverteilung in radial-axial gewalzten Ringen mit Rechteckquerschnitt / Jan Golz ». Aachen : Shaker, 2008. http://d-nb.info/1161304347/34.
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Birkenheier, David Andrew. « Non-uniform radial meanline method for off-design performance estimation of multistage axial compressors ». Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119062.
Texte intégralRésumé :
Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 111-112).
The increasing use of renewable energy sources necessitates power-generating gas turbines capable of frequently and rapidly starting up to supplement the energy supply when renewable sources alone cannot meet demand [1], [21. This makes the off-design performance of such gas turbines more important as they spend more of their operational life off the design point. Currently off-design performance cannot be estimated with high fidelity until late in the gas turbine compressor design process at which point the design is largely fixed and only limited changes can be made. This thesis presents a Non-Uniform Radial Meanline method for multistage axial compressor off-design performance estimation, capturing the transfer of radial flow non-uniformity and its impact on compressor blade row performance. This method enables the high-fidelity characterization of blade row performance and the stage matching of multistage compressors with non-uniformity effects included. A new representation of non-uniform radial flow profiles using orthonormal basis functions was developed to provide a compact representation suitable for inclusion in a one-dimensional performance estimation method. The link between radial flow non-uniformity and compressor blade row performance was characterized using three-dimensional embedded stage calculations. An initial implementation of the Non-Uniform Radial Meanline method was demonstrated for different compressor inlet non-uniformities. The computations show that the new approach provides an effective means of incorporating radial flow non-uniformity into a one-dimensional compressor performance estimation method.
by David Andrew Birkenheier.
S.M.
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Sairam, Kedharnath. « The Influence of Radial Area Variation on Wind Turbines to the Axial Induction Factor ». University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367942736.
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Ji, Min. « Fully three-dimensional and viscous semi-inverse method for axial/radial turbomachine blade design ». Related electronic resource : Current Research at SU : database of SU dissertations, recent titles available full text, 2008. http://wwwlib.umi.com/cr/syr/main.
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Michl, Dennis. « Untersuchung des flexiblen axialen Profilierens von nahtlosen Ringen auf Radial-Axial-Ringwalzwerken in Stahl / ». Aachen : Shaker, 2009. http://d-nb.info/997891572/04.
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Jabeen, Fauzia. « III-V semiconducting nanowires by molecular beam epitaxy ». Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3097.
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2007/2008This thesis is devoted to the study of the growth of III-V nanowires (NWs) by catalyst assisted and catalyst free molecular beam epitaxy (MBE). The nanostructures have been routinely characterized by scanning electron microscopy (SEM) and, to a minor extent by transmission electron microscopy (TEM). X-ray photoemission spectroscopy (XPS), scanning photoemission microscopy (SPEM), extended X-ray absrorption fi ne structure analysis (EXAFS), photoluminescence (PL) and trans- port measurements have given an important contribution on specifi c topics. The first section of this thesis reports on GaAs, InAs, and InGaAs NWs growth by Au assisted MBE. A substrate treatment is proposed that improves uniformity in the NWS morphology. Thanks to a careful statistical analysis of the NWs shape and dimensions as a function of growth temperature and duration, evidence is found of radial growth of the NWs taking place together with the axial growth at the tip. This eff ect is interpreted in term of temperature dependent diff usion length of the cations on the NWs lateral surface. The control of the NWs radial growth allowed to grow core shell InGaAs/GaAs NWs, displaying superior optical quality. A new procedure is proposed to protect NWs surface from air exposure. This procedure allowed to perform ex-situ SPEM studies of electronic properties of the NWs. The second part of this thesis is devoted to Au-free NWs growth. GaAs and InAs NWs were successfully grown for the first time using Mn as catalyst. Incorporation of Mn in the NW is studied using EXAFS technique. It is shown that Mn atoms are incorporated in the body of GaAs NWs. Use of low growth temperature is suggested in order to improve the Mn incorporation inside GaAs NWs and obtain NWs with magnetic properties. Finally, growth of GaAs and InAs NWs on cleaved Si subtrate is demonstrated without the use of any outside metal catalyst. Two kinds of nanowires have been obtained. The experimental findings suggest that the two types of nanowires grow after di fferent growth processes.
Questa tesi e' dedicata allo studio della crescita di nanofili di semiconduttori III- V tramite epitassia da fasci molecolari (MBE) assistita da catalizzatore e senza l'uso di catalizzatori. Le nanostrutture sono state caratterizzate sistematicamente tramite microscopia elettronica a scansione (SEM), e in maniera minore microscopia elettronica in trasmissione (TEM). Altre tecniche come la spettroscopia di fotoemissione da raggi x (XPS), la microscopia da fotoemissione in scansione (SPEM), la spettroscopia di assorbimento x (in particolare la extended X-ray absorpition fine structure analysis (EXAFS)) la fotoluminescenza (PL), e il trasporto elettrico hanno dato importanti contributi su problematiche specifiche. La prima parte di questa tesi riguarda la crescita di nanofili di GaAs, InAs e InGaAs tramite MBE assistita da oro. Viene proposto un trattamento del substrato che migliora nettamente l'omogeneita' morfologica dei nanofili. Grazie ad un'attenta analisi statistica della forma e delle dimensioni dei nanofili in funzione della temperatura e del tempo di crescita e' stata dimostrata la crescita radiale dei nanofili, che avviene insieme alla crescita assiale che ha luogo alla punta del nanofilo. Le osservazioni sperimentali sono state interpretate in termini di dipendenza dalla temperatura della lunghezza di diffusione dei cationi sulle super ci laterali dei nanofili. Il controllo della crescita radiale ha permesso di crescere nanofili di InGaAs/GaAs core shell, costituiti cioe' da una anima centrale di InGaAs (core) e uno strato esterno di GaAs (shell) , che hanno dimostrato eccellente qualita' ottica. Viene quindi proposta una nuova procedura per proteggere la super ficie dei nanofili durante l'esposizione all'aria. Grazie a questa e' stato possibile realizzare ex-situ uno studio SPEM delle proprieta' elettroniche dei nanofili. La seconda parte della tesi riguarda la crescita di nanofili senza l'uso di oro. Viene per la prima volta dimostrata la possibilita' di crescere nanofili di GaAs e InAs usando il manganese come catalizzatore. L'incorporazione del Mn come impurezza nei nanofili e' stata studiata tramite EXAFS. Le misure hanno dimostrato che atomi di Mn sono effettivamente incorporate nel corpo dei nano fili. La crescita delle nanostrutture a temperatura piu' bassa potrebbe migliorare qualitativamente l'incorporazione del Mn e permettere la crescita di nanofili con proprieta' magnetiche. Viene in fine dimostrata la crescita di nanofili di GaAs e di InAs senza l'utilizzo di materiali diversi da quelli costituenti il semiconduttore. Tale risultato e' ottenuto su superfici sfaldate di silicio. Sono state osservate nanostrutture di due tipi, che sulla base dei dati sperimentali sembrano essere dovuti a due diversi meccanismi di crescita.
XXI Ciclo
1977
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Swetnam, Thomas W., Marna Ares Thompson et Elaine Kennedy Sutherland. « Using Dendrochronology To Measure Radial Growth of Defoliated Trees ». U.S. Department of Agriculture, Forest Service, Cooperative State Research Service, 1985. http://hdl.handle.net/10150/304642.
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Zygmont, Martin. « Reverzační turbokompresor ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229815.
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The diploma thesis consists of a theoretical part, which deals with the description of reversing turbocharger and its components. The following part is devoted to calculating the radial-axial compressor and turbine. It also performs a calculation of gear box and characteristics of the turbine.
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Singh, Gursharanjit. « The study of the interactions between a low pressure steam turbine and axial-radial diffuser ». Thesis, Queen Mary, University of London, 2015. http://qmro.qmul.ac.uk/xmlui/handle/123456789/15029.
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Specific power output from a Low Pressure (LP) steam turbine can be enhanced by increasing the stage efficiency or raising its pressure ratio; both methods are interlinked and must be dealt with together. The latter is achieved by connecting to the exhaust diffuser; space and cost constraints often insist the use of an axial-radial diffuser with high levels of diffusion. The present study aims to investigate the interaction between the last-stage blade and the axial-radial diffuser, which can influence the diffuser performance and thus the total work output from the stage. This work is carried out using CFD simulations of a generic last stage low pressure (LP) turbine and axial-radial exhaust diffuser attached to it. In order to determine the validity of the computational method, the CFD predictions are first compared with data obtained from an experimental test facility. A computational study is then performed for different design configurations of the diffuser and rotor casing shapes. The study focuses on typical flow features such as effects of rotor tip leakage flows and subsequent changes in the rotor-diffuser interactions. The results suggest that the rotor casing shape and diffuser configurations influences the rotor work extraction capability and yields significant improvements in the static pressure recovery.
22
Michael, Paul W., et Shreya Mettakadapa. « Bulk Modulus and Traction Effects in an Axial Piston Pump and a Radial Piston Motor ». Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200173.
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This paper describes an investigation into the effects of fluid bulk modulus and traction coefficient properties on piston pump flow losses and radial pison motor torque losses through experimentation, modelling and simulation. Synthetic ester, high bulk modulus, multi-grade, and single grade mineral oils were evaluated. The high bulk modulus fluid exhibited 20% lower pump case and compensator flow losses than a conventional mineral oil of the same viscosity grade. Low traction coefficient fluids reduced the lowspeed torque losses of the radial piston motor by 50%. Physical models for pump case flow and motor torque losses were derived from the experimental data. Field data was collected from a hydraulically propelled agricultural machine. This data was used to model fluid performance in the machine. The simulation results predict that at an operating temperature of 80⁰C, optimizing the bulk modulus and traction coefficients of the fluid could reduce flow losses by 18% and torque losses by 5%. These findings demonstrate the potential of combining comprehensive fluid analysis with modeling and simulation to optimize fluids for the efficient transmission of power.
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Michl, Dennis [Verfasser]. « Untersuchung des flexiblen axialen Profilierens von nahtlosen Ringen auf Radial-Axial-Ringwalzwerken in Stahl / Dennis Michl ». Aachen : Shaker, 2009. http://d-nb.info/1159836329/34.
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Yilmaz, Kurtulus. « Comparison Of Axial Flux And Radial Flux Brushless Dc Motor Topologies For Control Moment Gyroscope Wheel Applications ». Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610565/index.pdf.
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In this thesis axial flux and radial flux brushless dc motors will be studied as a drive motor for the control of moment gyroscope wheel. Design equations for axial flux and radial flux brushless dc motor topologies will be reviewed. Based on these equations radial and axial flux motors with different number of poles will be designed that meet control moment gyroscope wheel application requirements. The results will be evaluated in terms of efficiency, torque/mass and torque/volume, and suitability for the control moment gyroscope application.
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Lagao, Patrick [Verfasser]. « Einsatzpotenziale des Data Mining bei der Klassifikation komplexer Fertigungsprozesse am Beispiel des Radial-Axial Ringwalzens / Patrick Lagao ». Aachen : Shaker, 2004. http://d-nb.info/1172616353/34.
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Akiki, Paul. « Conception multi-physique de machines électriques à flux radial et axial pour des applications à entraînement direct ». Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLC055/document.
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Les travaux présentés dans cette thèse portent sur la modélisation et l’optimisation de machines électriques pour des applications à entraînement direct. Ils s’inscrivent dans un contexte de réduction de l’utilisation des aimants en terres rares et d’amélioration du rendement énergétique. Un état de l’art des machines électriques est réalisé et l’accent est mis sur les machines à flux radial et axial pour les applications à fort couple et basse vitesse. Une classification est établie visant à identifier les structures intéressantes et innovantes. L’étude de la machine radiale est d’abord réalisée. Une étude comparative de différentes machines issues de l’étude bibliographique est effectuée. Cette étude a permis de choisir une structure originale à bobinage concentré sur dents et aimants en multi-V. Dans le but de calculer les performances du moteur avec un temps de calcul réduit, une modélisation analytique multi-physique de la structure est réalisée. Un premier dimensionnement de la machine a conduit à la définition d’un prototype qui a servi à la validation expérimentale du modèle multi-physique. Une approche de conception par optimisation multi-objectifs est adoptée pour obtenir les machines optimales répondant à un cahier des charges industriel. La suite de l’étude concerne une machine à flux axial à structure innovante. Il s’agit d’une machine à double rotor et simple stator avec plusieurs barrières de flux par pôle. Une étude par éléments finis est d’abord réalisée afin de valider le passage d’un modèle tridimensionnel à modèle bidimensionnel. L’analyse des pertes fer a permis de choisir les matériaux utilisés au stator et aux rotors. L’étape suivante consiste à établir un modèle analytique multiphysique de la machine à flux axial et de l’optimiser selon le même cahier des charges que celui de la machine radiale. Finalement, une comparaison entre les deux structures radiale et axiale est effectuée pour évaluer les avantages en termes de densité de coupleThe work presented in this thesis deals with the modeling and optimization of electrical machines for direct drive applications. The objective is to reduce the use of rare earth permanent magnets along with the improvement of the motor’s efficiency. A state of the art of electrical machines is realized. It focused on radial and axial flow structures for high torque and low speed applications. A classification is established to identify interesting and innovative structures. Firstly, the radial machine is studied. The choice of the structure is made after a finite element comparison of different machines resulting from the literature. This led to an original structure with concentrated winding and multi-V shape barriers. Then, a multi-physics analytical modeling of the structure is detailed in order to calculate the performances with a reduced calculation time. A preliminary design led to the definition of a prototype which was used to experimentally validate the multi-physics model. An optimization design approach is adopted to obtain optimal machines meeting industrial specifications. Secondly, a novel axial flux structure is studied. It is a machine with double rotor and single stator with several barriers per pole. A finite element study is carried out in order to validate the transition from a three dimensional to a two-dimensional model. The analysis of iron losses made it possible to choose the materials used in the stator and the rotors. Then, the development of a multi-physics analytical model for the axial machine is proposed. It is used to optimize the structure according to the same specifications defined for the radial machine. Finally, a comparison between the radial and axial structures is performed in order to evaluate the advantages in terms of torque density
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Fekedulegn, Desta. « Spatial and temporal analysis of radial growth in an Appalachian watershed ». Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2140.
Texte intégralRésumé :
Thesis (Ph. D.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains ix, 270 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 260-270).
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Despain, Del Westover. « Radial Growth Relationships in Utah Juniper (Juniperus Osteosperma) and Pinyon Pine (Pinus Edulis) ». Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184705.
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The assumption that each latewood ring in trees represents one year of growth was tested for Utah juniper (Juniperus osteosperma) and pinyon pine (Pinus edulis). Ring characteristics and growth rates were evaluated for 72 years of growth following scars of consistent date on all trees sampled. Errors in age and growth rate estimates based on ring counts were evaluated. Potential variation among observers was accounted for. Average error in ring counts was lowest when rings were counted on the fastest-growing portions of each cross-section. Errors for more than 40% of the junipers exceeded 10 percent with about half of the trees with more rings and half with less rings than actual years. Pinyons rarely had more rings than years and only 5% of the trees were missing more than 10% of the 72 annual rings. Percentage errors in growth rate estimates based on ring counts were similar to ring count errors for both species. Assigning junipers to age classes based on ring counts also can lead to error in assumed ages of trees. Assuming that ring count error for each tree for the 72 year period studied approximates potential error over the life of each tree, more than half of junipers older than 250 years would be assigned to the wrong age class when using 50 year age classes. Number of rings in junipers was highly correlated with growth rate. Competition from surrounding trees explained as much as 53% and 40% of the variation in growth rates of junipers and pinyons respectively. Relating growth rates and ring counts to ordinations of stand, site and soil characteristics indicated that trees with relatively fast growth rates or trees with the most rings tended to occur on gentle, north to northeast aspects with relatively better- developed soils. However, stand competition often had an overriding influence on growth. Presence of Koelaria pyramidata in the understory was generally an indicator of relatively favorable growing conditions for junipers. Results suggest the need for more caution in the use of ring counts for estimating ages or growth rates of Utah junipers and pinyons than has generally been used in the past, especially when drawing conclusions about specific individuals.
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Vedera, Kevin G. « An Experimental Methodology for Evaluating Power Losses of Rolling Element Bearings Subjected to Combined Radial and Axial Loads ». The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1522933829712819.
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Gao, Lushuang, Chunyu Zhang, Xiuhai Zhao et Klaus Gadow. « Gender-Related Climate Response Of Radial Growth In Dioecious Fraxinus Mandshurica Trees ». Tree-Ring Society, 2010. http://hdl.handle.net/10150/622620.
Texte intégralRésumé :
This paper presents an analysis of tree-ring growth patterns of male and female Fraxinus
mandshurica trees from 1931 to 2007. The specific object was to study the response of radial growth to climate variables separately for male and female trees. The results show that the growth patterns in the two genders were similar during the mid-1950s to 1970s but different in the periods 1931–1940s and 1980–2007. In the period 1980–2007, the mean sensitivity and mean widths of the tree rings were significantly different between the genders (p < 0.05). The climate-growth response in female and male trees was also different. Female trees are sensitive to precipitation in November of the previous year, whereas male trees respond to mean temperature in November of the previous year. The results confirm that climatic sensitivity in male and female trees of dioecious species is different, yet this difference is not stable through time.
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Walker, David Matthew. « Radial growth response of eastern hemlock to infestation of hemlock woolly adelgid ». Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/31920.
Texte intégralRésumé :
Hemlock woolly adelgid (Adelges tsugae Annand) is causing defoliation and mortality of eastern hemlock (Tsuga canadensis (L.) Carrière) in the eastern United States. The objectives of this study were to quantify changes in tree-ring width and wood anatomy for trees that survived adelgid infestation, and to contrast dendroclimatic relationships across a latitudinal gradient. Six sites spanning the current range of hemlock woolly adelgid (HWA) infestation were selected. At each site, 23 infested eastern hemlocks were cored and two trees were felled at the Virginia site
and thin-sectioned using a sliding microtome for analysis of wood anatomy. Tree cores were cross-dated and ring widths were measured. For each site, t-tests were used to determine if there
was a difference in radial growth pre- and post-HWA arrival. To compare differences in pre- and post-HWA cell properties, t-tests were used. For dendroclimatic analysis, Pearson correlation
coefficients were calculated between radial growth and monthly climate variables. Three sites showed significant suppression in radial growth after HWA arrival and latewood produced post-
HWA arrival had significantly smaller cells with reduced cell-wall thickness than latewood produced before HWA arrival. This indicates that HWA can reduce a treeâ s photosynthate production. The relationship between hemlock growth and climate also varied with latitude and site, with trees growing further south or on shallower soils being more sensitive to moisture levels. This sensitivity to drought can also partially explain the variation in hemlock response to adelgid feeding, as trees affected by moisture stress tend to be more sensitive to insect attack.Master of Science
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Klinka, Karel, Bernhard E. Splechtna, Jaroslav Dobry et Christine Chourmouzis. « Climate - radial growth relationships in some major tree species of British Columbia ». Forest Sciences Department, University of British Columbia, 1998. http://hdl.handle.net/2429/671.
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This study examines the influence of climate on tree-ring properties of several major tree species: Pacific silver fir (Abies amabilis (Dougl. ex Loud.) Forbes), subalpine fir (Abies lasiocarpa (Hook.) Nutt.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and lodgepole pine (Pinus contorta var. latifolia Dougl. ex Loud.). Our three objectives were to determine how (1) tree-ring properties change along an elevation gradient, (2) short-term climatic influences are correlated with tree-ring properties, and (3) long-term climatic influence on tree-ring properties.
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Марцинковський, Володимир Альбінович, Владимир Альбинович Марцинковский, Volodymyr Albinovych Martsynkovskyi, Вячеслав Ігорович Вороненко, Вячеслав Игоревич Вороненко et Viacheslav Ihorovych Voronenko. « Радіально-осьові коливання ротора з гідроп`ятою ». Thesis, Вид-во СумДУ, 2010. http://essuir.sumdu.edu.ua/handle/123456789/5915.
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Rosa, Vitor da Silva. « Análise da transferência de calor por convecção em tanques com impulsores mecânicos equipados com chicanas verticais tubulares ». reponame:Repositório Institucional da UFABC, 2014.
Trouver le texte intégralRésumé :
Orientadora: Profa. Dra. Juliana Tófano de Campos Leite ToneliDissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Energia, 2014.
Os tanques com impulsores mecânicos são empregados nas indústrias químicas, petroquímicas, alimentícia, farmacêutica e mineral, como reatores químicos, diluidores, decantadores, misturadores e trocadores de calor. A transmissão de calor em tanques com agitação é realizada através das jaquetas, serpentinas helicoidais, serpentinas em espiral e chicanas tubulares verticais, sendo que existe uma carência de dados na literatura sobre a utilização das chicanas tubulares, em projetos em escala industrial. O presente estudo teve por objetivo principal comparar a transferência de calor e o consumo energético em tanques com impulsores mecânicos, axial e radial, equipados com chicanas tubulares verticais. Como objetivos específicos, o presente estudo visou determinar correlações semi-empíricas para o coeficiente convectivo no escoamento externo, em relação aos impulsores mecânicos utilizados em função dos parâmetros de similaridade Reynolds e Prandtl, e avaliar o efeito do impulsor mecânico sobre a potência consumida e a transmissão de calor. A unidade experimental consistiu, basicamente, de um tanque de acrílico com um volume útil de 50 litros, um impulsor mecânico axial, um impulsor radial tipo turbina, um motor elétrico de 2,5 hp e uma chicana tubular com 4 bancos de tubos de cobre. Os fluidos frios utilizados foram água e solução de sacarose com concentrações de 20% e 50% em massa. O fluido quente utilizado foi água à temperatura constante de 60°C e vazão de 1,2 LPM. Os ensaios foram realizados alternando as rotações na faixa de 90 a 330 RPM e a temperatura de entrada do fluido frio no intervalo de 28°C a 45°C. A potência consumida por ambos os impulsores mecânicos foi determinada a partir da técnica da medição do torque gerado no motor elétrico. O modelo obtido para a previsão do coeficiente externo de convecção, com o impulsor axial apresentou, um desvio médio de 21% e o modelo para o impulsor radial, um desvio médio de 25%. A partir dos modelos obtidos, verificou-se que o impulsor radial incrementa a transmissão de calor em 43% quando comparado com o impulsor axial. A rotação ideal para a maior transmissão de calor, durante o aquecimento das soluções, com o menor consumo de energia foi de 300 rpm. A partir das curvas simultâneas do número de potência e do número de Nusselt, conclui-se que o impulsor axial é o mais indicado para o aquecimento tendo em vista o seu baixo consumo de potência em relação ao impulsor radial.
EThe tanks with mechanical impellers are employed in chemical, petrochemical, food, pharmaceutical and mineral industries, as chemical reactors, thinners, decanters, mixers and heat exchangers. The heat transmission in tanks with agitation is performed through the jackets, helical coils, coils in spiral and vertical tubular baffles, considering that there is a lack of data in the literature on the use of tubular baffles, in industrial scale projects. The present study aimed to compare the main heat transfer and energy consumption in tanks with mechanical axial and radial impellers equipped with tubular vertical baffles. As specific objectives, this study aimed to determine correlations for convective coefficient in the external flow in relation to mechanical impellers used in function of Reynolds and Prandtl similarity parameters, and evaluate the mechanical effect on power consumption and heat transmission. The experimental unit consisted primarily of an acrylic tank with a useful volume of 50 liters, an axial mechanical and turbine type radial impeller, a 2.5 hp electric motor and a tubular chicanery with 4 banks of copper tubes. The cold fluids applied were water, and sucrose solution with concentrations of 20% and 50% by mass. The hot fluid applied was water at constant temperature of 60° C and a 1.2 LPM flow. The tests were carried out in the range of rotations by 90 to 330 RPM and the cold fluid inlet temperature in the range from 28° C to 45° C. The power consumed by both mechanical impellers was determined through the thechnique of measurement of the torque generated at electric motor. The model obtained for external coefficient prediction of convection with the axial impeller presented an average deviation of 21% and the template for the radial impeller, a standard deviation of 25%. From the models obtained, it was found that the radial impeller increases the transmission of heat in 43% when compared with the axial impeller. The ideal rotation for greater heat transfer during heating of the solutions with the lowest energy consumption amounted to 300 rpm. From the number of concurrent power curves and Nusselt number, it is concluded that the axial impeller is the most indicated for heating in view of its low power consumption compared to radial impeller.
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Nault, Jason Ray. « Radial distribution of thujaplicins and thujic acid in old growth and second growth western redcedar (Thuja plicata donn) ». Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26011.
Texte intégralRésumé :
Radial cross sections of seven old growth cedars and ten second growth cedars taken at breast height were cut into increments averaging about 60 years growth for old growth trees and 10 years growth for second growth trees. These increments were extracted with ethanol:benzene (1:2). The extractives were analyzed for thujaplicin content by colorimetry of their ferric chelates, as well as by a new method utilizing capillary gas chromatography (GC) of their methylated derivatives. A statistical analysis of the two methods gave an r² value of 0.81 and a slope of 0.99. Thujic acid contents were also determined by the new GC method.
Distribution of thujaplicins and thujic acid generally increased from pith to outside heartwood, then decreased in the sapwood. Maximum thujaplicin contents were also related to the tree age.Forestry, Faculty of
Graduate
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Gardiner, Brooke Bridget Anne. « Molecular changes defining the transition from radial to vertical growth phase in melanoma / ». [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19280.pdf.
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Boone, Rachel, Jacques Tardis et Richard Westwood. « Radial Growth of Oak and Aspen Near a Coal-Fired Station, Manitoba, Canada ». Tree-Ring Society, 2004. http://hdl.handle.net/10150/262615.
Texte intégralRésumé :
Eighteen stands of bur oak (Quercus macrocarpa Michx.) and trembling aspen (Populus tremuloides Michx.) were sampled and analyzed using dendrochronological methods to study the potential effects on tree growth of emissions from a 132 MW coal-fired generating station. Sixteen stands were sampled within a 16-km radius of the station, and two control stands were sampled outside of the range of influence, at distances . 40 km. All stands showed similar radial growth patterns from 1960-2001, regardless of distance from or direction relative to the generating station, and a number of stands, including the controls, had below average growth after 1970. Both species were significantly affected by climatic factors, showing decreased radial growth with increasing June temperature. The species differed in their growth responses to spring precipitation and temperature in the previous October. One bur oak site displayed marked radial growth decline beginning in the mid-1970s, strongly pronounced following 1977. This decline does not appear to be related to emissions from the station, but is suspected to be a result of poor site conditions (shallow soil developed over calcareous till), confounded by a change in drainage (a road was built adjacent to the stand in 1977, perpendicular to the direction of drainage). The below average growth seen in 1970-2001 across most stands is likely attributable to stand dynamics and age effects.
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Guevara, Mauricio, et Boris Flyash. « SOFT RECOVERY RECORDING SYSTEM FOR INTERIOR AND EXTERIOR BALLISTICS CHARACTERIZATION ». International Foundation for Telemetering, 2007. http://hdl.handle.net/10150/604266.
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ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, NevadaThe US ARMY, ARDEC; in cooperation with AMCOM AMRDEC, Missile Guidance and Engineering Directorates; the Office of Naval Research; Naval Surface Fire Support; and the Naval Surface Weapon Center, requires multiphase development of a common, low-cost, high G survivable, high accuracy, Micro Electro-Mechanical Systems (MEMS) Inertial Measurement Unit (IMU) and Common, Deeply Integrated, Guidance and Navigation Unit (DI-GNU) for DoD gun launched guided munition and missile applications. The challenge for the Precision Munition Instrumentation Division (PMID) was to develop a Telemetry System to record the interior and exterior ballistics of a M831 TP-T projectile, which will be used as a carrier for soft recovery testing of IMUs and GNUs. This valuable data that would help The Government and contractors develop and validate multiple MEMS IMU design efforts, culminating with live fire verification performance test of pre-production in the Army’s 155-mm Soft Recovery Vehicle (SRVs) and missiles airframes.
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Castilho, Guilherme José de 1983. « Determinação experimental das distribuições radial e axial de concentração de solidos em uma seção riser utilizando sonda de fibras opticas ». [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266221.
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Orientador: Marco Aurelio CremascoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-09T06:13:25Z (GMT). No. of bitstreams: 1 Castilho_GuilhermeJosede_M.pdf: 55720465 bytes, checksum: ff5e31cd4371ec0283beb9eec7df3f35 (MD5) Previous issue date: 2007
Resumo: Regimes gás-sólido têm inúmeras aplicações industriais, sendo empregados, por exemplo, em sistemas de transporte pneumático das partículas e em leito fluidizado. Nas últimas duas décadas notou-se a aplicação crescente do leito fluidizado circulante, principalmente para facilidades de geração de energia, como caldeira e reações catalíticas. No processo de craqueamento catalítico fluidizado (FCC), dentre os vários equipamentos que compõem uma unidade conversora, é no riser onde praticamente ocorrem todas as reações de craqueamento. Medidas de grandezas como concentração de sólidos são fundamentais para a compreensão da fluidodinâmica nestes reatores e é pré-requisito para o projeto técnico bem sucedido de sistemas de transporte pneumático. Dentre as várias técnicas utilizadas para medidas de grandezas básicas em sistemas particulados, a sonda de fibra óptica é relativamente simples, de alta precisão e utilizada em várias situações que envolvem o sistema fluido-partícula. Nesta Dissertação, a oncentração volumétrica dos sólidos é medida por meio de uma sonda de fibra óptica. A concentração volumétrica dos sólidos é tomada radialmente e em diversas posições axiais ao longo do riser sob diferentes condições de operação, na Unidade Multipropósito do Laboratório de Processos em Meios Porosos da Faculdade de Engenharia Química da Universidade Estadual de Campinas. Resultados mostram que a concentração volumétrica de sólidos é maior na parede em comparação ao centro do riser, para todas posições axiais, exceto para o ponto mais alto do reator, onde há a influência da região de saída do escoamento. Sobre a distribuição axial de de concentração, verificou-se que o escoamento é mais concentrado na parte inferior do equipamento e tende a ficar menos concentrado ao longo do reator. Através dos espectros de sinais obtidos pela sonda, pôde-se analisar as flutuações através da distribuição de probabilidade dos sinais e da distribuição do desvio padrão do sinal médio. Distribuições de probabilidade permitem identificar a presença de clusters em determinados pontos radiais, revelando que para as condições de mais concentradas, as flutuações são as maiores. As distribuições de desvio padrão apresentam picos, onde sugere maior interação entre as partículas
Abstract: Gas-solid systems have innumerable industrial applications, being used, for example, in the pneumatic conveying of particles and in fluidized bed. In the last two decades it was noticed increasing application of the circulating fluidized bed, mainly for easinesses of energy generation, as boilers and catalytic reactions. In the process of fluidized catalytic cracking (FCC), amongst some equipment that composes a converting unit, it is in riser where the cracking reactions practically occur at all. Measures as solid concentration are basic for the understanding of the fluidodynamic in these reactors and are prerequisite for the successful design of pneumatic transport systems. Amongst the several techniques used for measures in particulates systems, the optical-fiber probe is relatively simple, of high precision and used in some situations that involve fluid-particle system. In this Dissertation, the volumetric concentration of solids is measured by means of an optical-fiber probe. The volumetric concentration of solids is taken radially and in diverse axial positions throughout riser under different operation conditions, in the Multipurpose Unit of the Laboratory of Processes in Porous Means of the College of Chemical Engineering of the State University of Campinas. Results show that the volumetric solid concentration is bigger in the wall in comparison to the center of the riser, for all axial positions, except forthe highest point of the reactor, where it has the influence of the exit region of the flow. On the axial distribution of concentration, it was verified that the flow is more concentrated in the inferior part of the equipment. Through the electrical signs specters gotten by the probe, it could be analyzed the fluctuations through the distribution of probability of the signals and the distribution of the standard deviation of the average signal. The distribution of probability allows identifying the presence of clusters in determined radial points, disclosing that for the most concentrated conditions, the fluctuations are the greater. The distributions of the standard deviation present peaks, where it suggests greater interaction between particles
Mestrado
Engenharia de Processos
Mestre em Engenharia Química
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Biondi, Franco 1960. « Influence of Gambel oak on radial growth of southwestern ponderosa pine : a dendrochronological study ». Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/191955.
Texte intégralRésumé :
Gambel oak influence on diameter increment of young-growth ponderosa pines was evaluated by intensively sampling three pine-oak stands on the Beaver Creek Watershed in north-central Arizona. Sampled stands had homogeneous climate, topography, soil parent material, vegetation structure and soil type. Increment cores were collected from five dominant pines on 34 randomly selected study plots. As revealed by dendrochronological techniques, radial growth of sampled pines had fluctuated around a relatively constant level during the last 50 years (1936-85). Differences in this level among stands were related to differences in competition, oak presence, pine age and site index. Pine diameter growth increased with increasing Gambel oak presence and with decreasing intraspecific competition.
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Homsher, Ryan B. « Growth and Reproduction of Oaks in Southeastern Ohio ». Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1331395406.
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Naidoo, Robin. « The effects of gypsy moth defoliation and climatic conditions on radial growth of deciduous trees ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0015/MQ37153.pdf.
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Kanoti, Allison M. « Relationship between Balsam woolly adelgid Damage, Radial Growth, Climate and Stand Characteristics in Eastern Maine ». Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/KanotiAM2006.pdf.
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Kasson, Matthew T. « Relationships between Climate, Disease, Radial Growth Response, and Mortality of American Beech in Northern Maine ». Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/KassonMT2007.pdf.
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Tarelkin, Yegor. « Radial Patterns of Wood Features Reveal Site-Specific Tree Growth Dynamics in the Congo Basin ». Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/273503.
Texte intégralRésumé :
Les forêts tropicales couvrent environ 7% de la surface terrestre et stockent environ 25% du carbone terrestre. Elles jouent un rôle important dans les cycles biogéochimiques et fournissent divers services écosystémiques. Cependant, elles sont menacées par l’activité anthropique et le changement climatique. Il y a un besoin pressant de mieux comprendre les effets du changement climatique sur la croissance des arbres afin de mieux estimer son impact sur la composition des forêts et leur capacité à fournir leurs services.Jusqu’à récemment, les réponses des forêts aux changements climatiques ont été étudiées via des expérimentations en laboratoire ou en rapportant les changements à l’échelle des populations. Cependant, notre connaissance de l’influence des changements climatiques graduels sur la croissance ligneuse reste limitée. L’étude des cernes de croissance a permis la reconstruction du climat passé et l’étude de son influence sur la dynamique de croissance des arbres dans les régions tempérées. Son application dans un contexte tropical reste cependant limitée par l’absence d’une saisonnalité marquée des facteurs limitants la croissance. La distinction des cernes de croissance chez les espèces tropicales est très variable et des études supplémentaires sont nécessaires pour correctement les identifier et les utiliser dans les études dendrochronologiques.Dans cette thèse, nous explorons le potentiel d’utilisation de l’anatomie et de la densité du bois dans l’étude des réponses des arbres aux changements climatiques. Nous évaluons la variabilité anatomique du coeur à l’écorce et la manière dont le climat l’influence. Le travail est subdivisé en trois chapitres, chacun répondant à une question spécifique. Plus particulièrement, nous avons étudié (i) la variabilité de la distinction et de l’anatomie des cernes de croissance dans les tropiques, (ii) la relation entre l’anatomie et la densité du bois ainsi que son potentiel d’utilisation comme un proxy pour estimer variabilité anatomique et (iii) l’influence de la saisonnalité des précipitations sur la rythmicité de la croissance des arbres via leurs profils de densité du bois.En premier lieu, nous avons décrit les traits anatomiques impliqués dans la démarcation des limites des cernes de croissance et évalué leur contribution à la distinction des cernes. Nous avons constaté une grande variabilité intra et interspécifique et mis en avant le fait que les définitions actuelles de la distinction des cernes ne décrivent pas suffisamment la complexité de l’anatomie du bois dans les tropiques. Au lieu de se concentrer sur la détection des cernes, nous proposons d’étudier la variabilité des traits anatomiques depuis le coeur jusqu’à l’écorce dans le but de reconstruire la croissance ligneuse passée et estimer les effets du climat.Ensuite nous avons automatisé les mesures de proportions de parenchyme et de vaisseaux ainsi que le ratio lumen/diamètre total des fibres dans le plan transversal de la moelle à l’écorce. Nous les avons étudiés en parallèle avec des profils à haute résolution de la densité du bois de huit espèces. Nous avons montré que la densité du bois est influencée par l’anatomie des fibres et que la relation entre l’anatomie et la densité du bois dépend de l’espèce. Notre étude suggère qu’il est possible d’utiliser les profils de la densité du bois comme un proxy pour étudier la variabilité de l’anatomie du bois.Finalement, nous avons utilisé les profils de densité afin de comparer les patterns de croissance ligneuse de 13 espèces le long d’un gradient de précipitation. Nous avons utilisé l’analyse en ondelettes afin de dériver trois descripteurs de croissance :la régularité, la périodicité et l’amplitude des variations. Nous avons montré que la saisonnalité de précipitations influence la régularité de la croissance ligneuse et que les variations sont plus abruptes dans les sites avec une saisonnalité plus marquée. Nous avons aussi montré que les espèces décidues et sempervirentes ne réagissent pas de la même façon aux variations des patterns de précipitations.Nous pensons que ces résultats vont favoriser l’émergence d’outils prometteurs pour étudier la croissance des arbres et sa relation avec le climat. L’automatisation des mesures des traits anatomiques et l’utilisation des profils de densité du bois comme proxies vont aider à diminuer le temps de traitement des échantillons et augmenter leur nombre ainsi que la puissance des traitements statistiques. Par la description très fine des signaux cycliques qu’elle permet, l’analyse en ondelettes ouvre de nouvelles perspectives pour la description des profils de variation de la densité du bois et donc l’interprétation de la dynamique de croissance des arbres.Doctorat en Sciences agronomiques et ingénierie biologique
info:eu-repo/semantics/nonPublished
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Kadoshima, Taisuke. « Self-organization of axial polarity, inside-out layer pattern and species-specific progenitor dynamics in human ES cell-derived neocortex ». Kyoto University, 2014. http://hdl.handle.net/2433/188695.
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Wolfe, David R. « Delamination buckling, postbuckling, and growth in axially loaded beam-plates ». Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/80114.
Texte intégralRésumé :
The purpose of this study is to develop a simple one-dimensional model to analyze axially loaded beam-plates containing cracks which extend through the thickness of the beam-plates. Although the material analyzed is isotropic, these cracks will be referred to as delaminations. Buckling, postbuckling, and growth of delaminations in these beam-plates will be analyzed. A finite element method in which all of the terms of the stiffness matrices are obtained by exact integration is employed to determine the linear buckling load and postbuckling solution. The energy release rate is then determined using the postbuckling solution. Curves are provided to show the effect of delamination length and location on buckling loads, energy release rates, and strengths of the beam-plates. The problem of buckling and postbuckling of beams with multiple delaminations is also considered. A method of calculating the energy release rate for beams with multiple delaminations using numerical differentiation is introduced.Master of Science
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Noble, Andrew G. « The Repeatability of Peripheral Axial Length Measurements ». The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1330654198.
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Wilkosz, Benjamin Eduard [Verfasser]. « Aerodynamic Losses in an Aero Engine Centrifugal Compressor with a Close-Coupled Pipe-Diffuser and a Radial-Axial Deswirler / Benjamin Eduard Wilkosz ». München : Verlag Dr. Hut, 2015. http://d-nb.info/1070800406/34.
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Shiwakoti, Rochak. « Design and Analysis of Modular Axial Flux Switched Reluctance Motor ». ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2680.
Texte intégralRésumé :
This thesis presents a new modular structure of the axial flux Switched Reluctance Motor (SRM). The design consists of four stator disks with each adjacent disk rotated 30 degrees apart and four rotor disks connected to a common shaft. The proposed design aims to reduce the unwanted radial force, mitigate the torque ripple, and improve the efficiency. The modular structure distributes the radial force and torque strokes along the axial length of the motor, potentially damping the torque pulsation. In addition, the modular structure would deliver the rating power at a lower current level, reducing the overall ohmic loss. Moreover, if a fault occurs on a motor disk or its control unit, the motor would still operate through other disks, increasing the reliability of the system. To verify the effectiveness of the proposed design, the magneto-static and transient performance of the motor are compared with the conventional single layer structure using 3-D Finite-Element (FE) software tool to see that the proposed motor performs better with lower torque ripple and lower radial force than a conventional single layer structure.