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Alizadehyazdi, Vahid. "Stability of Discrete Time Transfer Matrix Method (DT-TMM)." Thesis, Southern Illinois University at Edwardsville, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10128867.
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Large dynamic systems and flexible structures like long robot links with many degree of freedoms are always challenging issues for engineers to model and control. These structures can be modeled with some methods like modal superposition and numerical integration.
Transfer Matrix Method (TMM) is another method that can be used to model large systems with a huge number of subsystems and flexible structures.By using Transfer matrix method, the size of matrix reduces. Having smaller matrix sizes helps us to have less computation and fast answer. Also, this method is very flexible, because it is possible for us to add or eliminate one subsystem easily. Transfer matrix method like other methods has its drawbacks. TMM is limited to linear systems and can not be used for non-linear ones. Moreover, this method just gives frequency-domain output and can not perform time-domain simulation.
By combining TMM and numerical integration methods, we have a new method which is called Discrete Time Transfer Matrix Method (DT-TMM). DT-TMM can model non-linear systems too. Time-domain output is another advantage of this method. Two approaches considered in this research to combine TMM and numerical integration. First approach is describing acceleration and velocity based on the displacement. Another approach is using acceleration to calculate the velocity and displacement. Also, different methods of numerical integration like Fox-Euler, Houbolt, Park Stiffly Stable, Newmark Beta and Wilson studied in this research.
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Li, Han. "Transfer Matrix Approach to Propagation of Angular Plane Wave Spectra Through Metamaterial Multilayer Structures." University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1324508726.
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Frithiof, Fredrik. "A framework for designing a modular muffler system by global optimization." Thesis, KTH, Optimeringslära och systemteori, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-169650.
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When creating a muffler to be installed on a noise generating machine, the design parameters as well as the placements of sound attenuating elements has to be optimized in order to minimize the sound coming out of the equipage. This is exemplified in a small project task for students of a basic course in optimization at KTH. The task is however flawed, since both the way in which the optimization problem is formed is overly simplistic and the algorithm used to solve the problem, fmincon, does not cope well with the mathematical complexity of the model, meaning it gets stuck in a local optimum that is not a global optimum. This thesis is about investigating how to solve both of these problems. The model is modified to combine several frequencies and adjusting them to the sensitivity to different frequencies in the human ear. By doing this, the objective is changed from the previous way of maximizing Dynamic Insertion Loss Dilfor a specific frequency to minimize the total perceived sound level LA. The model is based on the modular design of TMM from four-pole theory. This divides the muffler into separate parts, with the sound attenuating elements being mathematically defined only by what T matrix it has. The element types to choose from are the Expansion Chamber, the Quarter Wave Resonator and the Helmholtz Resonator. The global optimization methods to choose from are Global Search, MultiStart, Genetic Algorithm, Pattern Search and Simulated Annealing. By combining the different types of sound attenuating elements in every way and solving each case with every global optimization method, the best combination to implement to the model is chosen. The choice is two Quarter Wave Resonators being solved by MultiStart, which provides satisfactory results. Further analysis is done to ensure the robustness of chosen implementation, which does not reveal any significant flaws. The purpose of this thesis is fulfilled.När man skapar en ljuddämpare som ska installeras på en ljud-genererande maskin bör designparametrarna samt placeringarna av ljuddämpande element optimeras för att minimera ljudet som kommer ut ur ekipaget. Detta exemplifieras i en liten projektuppgift för studenter till en grundkurs i optimering på KTH. Uppgiften är dock bristfällig, eftersom både det sätt som optimeringsproblemet är utformat är alltför förenklat och den algoritm som används för att lösa problemet, fmincon, inte klarar av modellens matematiska komplexitet bra, vilket menas med att den fastnar i ett lokalt optimum som inte är ett globalt optimum. Detta examensarbete handlar om att undersöka hur man kan lösa båda dessa problem. Modellen är modifierad för att kombinera flera frekvenser och anpassa dem till känsligheten för olika frekvenser i det mänskliga örat. Genom att göra detta är målet ändrat från det tidigare sättet att maximera den dynamiska insatsisoleringen DIL för en specifik frekvens till att minimera den totala upplevda ljudnivån LA. Modellen bygger på den modulära designen av TMM från 4-polsteori. Detta delar upp ljuddämparen i separata delar, med ljuddämpande element som matematiskt endast definieras av vilken T matris de har. De elementtyper att välja mellan är expansionskammare, kvartsvågsresonator och Helmholtzresonator. De globala optimeringsmetoder att välja mellan är Global Search, MultiStart, Genetic Algorithm, Pattern Search och Simulated Annealing. Genom att kombinera de olika typerna av ljuddämpande element på alla sätt och lösa varje fall med varje global optimeringsmetod, blir den bästa kombinationen vald och implementerad i modellen. Valet är två kvartsvågsresonatorer som löses genom MultiStart, vilket ger tillfredsställande resultat. Ytterligare analyser görs för att säkerställa robustheten av den valda implementationen, som inte avslöjar några väsentliga brister. Syftet med detta examensarbete är uppfyllt.
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Helán, Radek. "Modelování a optimalizace komplexních vláknových difrakčních struktur." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-233450.
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The thesis discusses the fiber Bragg gratings simulations, analysis and design. In the present time, there are several methods to simulate fiber gratings response based on the stated parameters that define their dimensions and material features. However, this work deals with a different issue, that is the synthesis of the input parameters for demanded spectral responses. The main aim of the work is to achieve a synthesis method that would help to discover parameters describing advanced grating structure, based on the required spectral reflectivity. The basic demand for the parameter synthesis is an achievement of the real values in terms of the consequent production of the suggested structure. The described synthesis method considers advanced fiber grating structure as a structure of several uniform grating sections. The input parameters are estimated in steps, using the well-known direct methods in order to obtain grating responses and feedback to establish the parameters changes. The principle methods involve establishment of initial input parameter values and necessary subsequent algorithm leading to optimize the required spectral response. The initial values are calculated by a simplified model based on the coupled theory equations that are handled for the periodic disturbances in cylindrical waveguide. The following optimization uses the multiple thin film stack and transfer matrix methods. The properties of grating structure spectral reflectivity are step by step calculated while using these direct methods. Input parameters are established in the next several steps. Establishment of input parameters is done subsequently, based on the demanded and calculated output spectral reflectivity properties. Optimizing process is limited by possibilities of the grating manufacture technology. It is possible to assemble arbitrary fiber grating structure taking in term the demanded spectral response. Nevertheless, the calculated input parameters are real for the following manufacture. This method could be used to design optical band stop filter, high-pass and low-pass filters or filters for special applications.
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Ramanathan, Sathish Kumar. "Linear Acoustic Modelling and Testing of Exhaust Mufflers." Thesis, KTH, Aeronautical and Vehicle Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4340.
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Intake and Exhaust system noise makes a huge contribution to the interior and exterior noise of automobiles. There are a number of linear acoustic tools developed by institutions and industries to predict the acoustic properties of intake and exhaust systems. The present project discusses and validates, through measurements, the proper modelling of these systems using BOOST-SID and discusses the ideas to properly convert a geometrical model of an exhaust muffler to an acoustic model. The various elements and their properties are also discussed.
When it comes to Acoustic properties there are several parameters that describe the performance of a muffler, the Transmission Loss (TL) can be useful to check the validity of a mathematical model but when we want to predict the actual acoustic behavior of a component after it is installed in a system and subjected to operating conditions then we have to determine other properties like Attenuation, Insertion loss etc,.
Zero flow and Mean flow (M=0.12) measurements of these properties were carried out for mufflers ranging from simple expansion chambers to complex geometry using two approaches 1) Two Load technique 2) Two Source location technique. For both these cases, the measured transmission losses were compared to those obtained from BOOST-SID models.
The measured acoustic properties compared well with the simulated model for almost all the cases.
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Kameshki, Esmat Saleh. "Stability of steel frames by the transfer matrix method." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315349.
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Wang, Peiji. "On Saint-Venant's principle and the state transfer matrix method." Thesis, University of Southampton, 1998. https://eprints.soton.ac.uk/45937/.
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Three exact solutions are considered, within the context of the linear mathematical theory of elasticity, pertaining to the decay of self-equilibrated end loading for a class of geometries based upon polar coordinates. For a curved plane beam, an eigen-equation is derived, whose roots determine the rates of decay and degenerate to the Papkovitch-Fadle solution for the plane strain strip when the beam centre-line radius of curvature approaches infinity; this shows that the decay rates are largely insensitive to the beam curvature except for very small inner radius. For the plane and anti-plane elastic wedge, subjected to self-equilibrated loading on the inner or outer arcs, radial variation of stress is affected by a combination of free-edge stress interference and the convergent or divergent geometry. When the load is applied to the inner arc, the two effects act in concert in which case decay is assured; when the load is applied to the outer arc, the two effects act in opposition, and Saint-Venant’s principle (S.V.P) ceases to be applicable for wedge angles 2α > π for symmetric loading and anti-plane deformation, and 2α > 257º for asymmetric loading. It is concluded that the crack tip stress singularity, which is at the heart of Linear Elastic Fracture Mechanics, is attributable to the failure of S.V.P. for just one particular eigenmode for the wedge angle 2α = 2 π. A Finite Element-Transfer Matrix Method is developed for determination of decay rates of self-equilibrated end loading for frameworks and continuum prismatic beam of arbitrary cross-section. Nodal displacements and forces on either side of a repeating cell are considered as state variables and are related by a cell transfer matrix. Assuming consecutive state vectors to be related by a constant multiple λ leads directly to an eigenvalue problem; the decay factors, λ, are the eigenvalues of the symplectic transfer matrix. Eigenvalues occurs as reciprocal pairs (that is, if λi is an eigenvalue then so is 1/ λi) according to whether decay is from left to right or vice-versa. The multiple eigenvalues λi = 1/ λi = 1 are associated with the rigid body eigenvectors and their related principal vectors which describe the force transmission modes. The matrix of eigen-and principal vectors then forms a similarity matrix which transforms the original transfer matrix into Jordan canonical form. Both bi-orthogonality and symplectic adjoint orthogonality properties of the eigenvectors allow modal decomposition of an arbitrary end load. As a by-product of the method, it is possible to determine exact ‘continuum’ beam properties of the framework, which is useful in preliminary design work. The method is applied to the important case of a beam of rectangular cross-section for a wide range of aspect ratios. The Transfer Matrix Method is modified to become the Force or Displacement Transfer Matrix Method, which has the advantage of reducing in size the original transfer matrix by one half, and overcomes numerical ill-conditioning. Accuracies of all the developed methods are found to be very good when compared with available exact solutions.
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Fletcher, Daniel Alden. "Internal cooling of turbine blades : the matrix cooling method." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360259.
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Cuesta, Juan D. "Modeling helicopter blade dynamics using a modified Myklestad-Prohl transfer matrix method." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA289891.
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Komandur, Deepak K. "Load Identification using Matrix Inversion Method (MIM) for Transfer Path Analysis (TPA)." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563872419648032.
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Atintilo, I. A. "Non-linear analysis of r/c coupled shearwalls by the transfer matrix method." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381247.
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Shah, Samir Harshadrai. "Computer aided analyses of symmetrically loaded thin cylindrical shell using transfer matrix method." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-10022008-063134/.
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Zhebel, Elena. "A multigrid method with matrix-dependent transfer operators for 3D diffusion problems with jump coefficients." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2009. http://nbn-resolving.de/urn:nbn:de:bsz:105-682918.
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Gegeben sei ein lineares Gleichungssystem $Au = f$ mit Koeffizientenmatrix $A$, welche eine spezielle block-tridiagonale Struktur besitzt. Solche lineare Gleichungssysteme entstehen bei der Diskretisierung dreidimensionaler elliptischer Randwertprobleme mit 7- oder 27-Punkte-Stern. In geophysikalischen Anwedungen, insbesondere bei Aufgaben aus der Geoelektrik, haben die Randwertprobleme unstetige Koeffizienten und sind meistens auf nicht-uniformen Gittern diskretisiert. Klassische geometrische Mehrgitterverfahren konvergieren um so langsamer, je stärker die Koeffizientensprünge ausfallen. Außerdem kann die Konvergenz durch die Variation der Gitterabstände beeinträchtigt werden. Zur Lösung wird ein matrix-abhängiges Mehrgitterverfahren vorgestellt. Als Glätter wird eine unvollständige Block LU-Zerlegung verwendet. Die Gittertransferoperationen werden anhand der Einträge der Matrix $A$ ermittelt. Das resultierende Verfahren erweist sich als sehr robust, insbesondere wenn es als Vorkonditionierung für das Verfahren der konjugierten Gradienten eingesetzt wird.
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Nippa, David W. "A modal transfer matrix method for analysis of Bragg and long-period optical fiber gratings /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488205318508366.
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Linacre, Jacob Thomas. "A top quark mass measurement using a matrix element method." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:c716f985-1913-46fb-a11b-1ef973ba4e6f.
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A measurement of the mass of the top quark is presented, using top-antitop pair (t-tbar) candidate events for the lepton+jets decay channel. The measurement makes use of Tevatron proton-antiproton collision data at centre-of-mass energy 1.96 TeV, collected at the CDF detector. The top quark mass is measured by employing an unbinned maximum likelihood method where the event probability density functions are calculated using signal (t-tbar) and background (W+jets) matrix elements, as well as a set of parameterised jet-to-parton mapping functions. The likelihood function is maximised with respect to the top quark mass, the fraction of signal events, and a correction to the jet energy scale (JES) of the calorimeter jets. The simultaneous measurement of the JES correction (ΔJES) provides an in situ jet energy calibration based on the known mass of the hadronically decaying W boson. Using 578 lepton+jets candidate events corresponding to 3.2 inverse femtobarns of integrated luminosity, the top quark mass is measured to be 172.4 ± 1.4(stat+ΔJES) ± 1.3(syst) GeV/c², one of the most precise single measurements to date.
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Majette, Mark W. "Modal state variable control of a linear distributed mechanical system modeled with the transfer matrix method." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/15917.
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O'Leary, Beth Andrews. "Analysis of high-speed rotating systems using Timoshenko beam theory in conjunction with the transfer matrix method /." Online version of thesis, 1989. http://hdl.handle.net/1850/10608.
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Cinkraut, Jakub. "Transfer Path Analysis of a Passenger Car." Thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-180435.
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Even though there are no regulations on the interior noise level of passenger cars, it is a significant quality aspect both for customers and for car manufacturers. The reduction of many other car noise sources pushed tyre road noise to the forefront.What is more, well known phenomenon of the tyre acoustic cavity resonance (TCR), appearing around 225 Hz, makes the interior noise noticeably worse. Some techniques to mitigate this phenomenon right at the source are discussed in this thesis, however, these has not been adopted by the tyre nor car manufacturers yet.Therefore, there is a desire to minimise at least the transmission of the acoustic or vibration energy from the tyre to the compartment. This is where methods like TPA (Transfer Path Analysis) come into play.In this thesis, two different approaches to TPA are used to investigate transmission of the TCR energy.First, the coherence based road decomposition method is used to determine whether the TCR energy is transmitted by a structure-borne or an air-borne mechanism. The same method serves to identify if the TCR noise comes mainly from the front or the rear suspension.Second, the impedance matrix method was used to determine critical structure-borne transfer paths yielding clear results indicating two critical mounts at the rear suspension which dominate the transfer of vibro-acoustic energy. Subsequent physical modification of the critical mount was tested to verify the results of the transmission study.Moreover, deflection shape analysis of the tyre, rim, front and rear suspension was performed to identify possible amplification effects of the TCR phenomenon.
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Rhazi, Dilal. "Prédiction par la méthode des matrices de transfert de la réponse vibroacoustique des structures complexes multimatériaux sous excitation mécanique et source ponctuelle." Mémoire, Université de Sherbrooke, 2007. http://savoirs.usherbrooke.ca/handle/11143/1409.
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In the field of aeronautics (Aircraft, helicopters, space launchers...), as in the field of the automobile, reducing the harmful effects of acoustics constitutes a major concern at the international level and justifies the call for further research. With these challenges in mind, the manufacturers have expressed the need for simple models immediately available as early as the stage of preliminary drafts. This Master's Thesis presents the study and the validation of three different approaches to meet this industrial need. The first approach is based on the propagation of waves in the structure; the second approach uses the technique of SEA by calculating the equivalent damping; and the last approach uses the modal technique.In the three approaches, the transfer matrix method has been used to study the succession of layers. Applying these approaches to some aircraft structures confirm their relevance in relation to more exact and costly methods, such as the finite elements method.
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Huawei, Ren. "Transfer Path Analysis of Wind Noise on a Passenger Car." Thesis, KTH, Farkost och flyg, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-261091.
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Over the last years, due to the development of quieter engines and drivetrains, the importance of addressing the vehicle wind noise problem has significantly increased.In this thesis work, several existing Transfer Path Analysis methods have been applied on an experimental database acquired during a wind tunnel test on a passenger car with the objective of analyzing the distribution of the wind noise sources and their contribution to the target microphones located inside the vehicle. A major challenge for the Transfer Path Analysis (TPA) consists of the high complexity of the aerodynamic sources exciting the structure. Moreover, the existence of multiple incoherent source phenomena, and the presence of distributed coherent source regions of different correlation scales make the analysis very complex.The thesis work provides a solid and comprehensive analysis of the results obtained by different methods. The outcomes can be potentially useful for optimizing the vehicle NVH performance in future practical cases.Under de senaste åren har vikten av att arbeta med vägfordons problem med aerodynamisk ljudgenerering ökat avsevärt på grund av utvecklingen av tystare motorer och drivlinor. I det här projektet har flera existerande metoder för Transfer Path Analysis (TPA) tillämpats på en databas med experimentella data som samlats in vid vindtunneltest på en personbil, med målet att analysera fördelningen av källorna orsakade av vindbruset och deras påverkan på ljudnivån vid de uppsatta målmikrofonerna inuti fordonet. En stor utmaning för TPA är den höga komplexiteten hos de aerodynamiska källorna som exciterar strukturen. Vidare gör förekomsten av flera okorrelerade källor, och närvaron av distribuerade koherenta källregioner med olika korrelationsskalor, analysen mycket komplex. Arbetet presenterar en solid och omfattande analys av resultat som erhållits med olika metoder. Resultaten är potentiellt användbara för att optimera fordonets NVH-prestanda i praktiktiken i framtiden.
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He, Shujian. "A TRANSFER MATRIX APPROACH TO DETERMINE THE LOW FREQUENCY INSERTION LOSS OF ENCLOSURES INCLUDING APPLICATIONS." UKnowledge, 2017. https://uknowledge.uky.edu/me_etds/104.
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Partial enclosures are commonly used to reduce machinery noise. However, it is well known in industry that enclosures sometimes amplify the sound at low frequencies due to strong acoustic resonances compromising the performance. These noise issues are preventable if predicted prior to prototyping and production. Though boundary and finite element approaches can be used to accurately predict partial enclosure insertion loss, modifications to the model require time for remeshing and solving. In this work, partial enclosure performance at low frequencies is simulated using a plane wave transfer matrix approach. Models can be constructed and the effect of design modifications can be predicted rapidly. Results are compared to finite element analysis and measurement with good agreement. The approach is then used to design and place resonators into a sample enclosure. Improvements in enclosure performance are predicted using plane wave simulation, compared with acoustic finite element analysis, and then validated via measurement.
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Gnawali, Rudra. "Berreman Approach to Optical Propagation Through Anisotropic Metamaterials." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1541108034610795.
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Krauss, Ryan Walter. "An Improved Technique for Modeling and Control of Flexible Structures." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11519.
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Control design for flexible robots is a challenging problem. Part of the difficulty comes from a lack of controls-focused modeling tools. Practical flexible robots have several aspects that make them difficult to model: continuous elements, complicated actuators, multiple feedback loops, non-collocated sensors and actuators, and the ability to take on arbitrary three-dimensional poses. Even if existing techniques for modeling flexible structures could model the closed-loop response of a hydraulically-actuated flexible robot with a vibration suppression controller, how would such a model be used for control design?
This work presents the development of a modeling approach that meets the needs of a controls engineer. The approach is based on the transfer matrix method (TMM). The TMM has been expanded in several ways to enable it to accurately model practical flexible robots. Quantitative agreement is shown between model and experiment for the interaction of a hydraulic actuator and a flexible structure as well as for the closed-loop response of a system with vibration suppression.
Once the ability to model the closed-loop response of the system has been demonstrated, this work focuses on using the model for control design. Control design is facilitated by symbolic implementation of the TMM, which allows closed-form expressions for the closed-loop response of the system to be found without discretization. These closed-form expressions will be transcendental transfer functions for systems with continuous elements. These transfer functions can then be used in various optimization approaches for designing the closed-loop system response.
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Pretorius, Morné. "Comprehensive active magnetic bearing modelling taking rotor dynamics into account / M. Pretorius." Thesis, North-West University, 2008. http://hdl.handle.net/10394/2647.
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The McTronX Research Group at the North-West University is conducting research in the field of Active Magnetic Bearings (AMBs) with the aim of establishing a knowledge base for future industry consultation. AMBs are environmentally friendly and are a necessity in the pebble bed modular reactor (PBMR), a South-African initiated project, which is predicted to be the means of supplying Africa and many other countries with modular energy in the future. Aside from the PBMR, there are numerous other AMB industrial applications.
The aim of this project is to develop a comprehensive AMB model that considers the effect that rotor dynamics has on an AMB system. This model is used to analyse a double radial AMB, capable of suspending a rigid- and flexible rotor, to explain previously noticed phenomena. Two modelling methods are focussed on namely the System Matrix Method and Transfer Matrix Method (TMM) both of which are implemented in MATLAB®.
The rigid rotor model is firstly implemented as a point mass in state-space form followed by use of the TMM to analyse its bending modes. The stability and critical speeds of the system are analysed due to a change in the supports' properties along with rotor gyroscopy and its effect on the system.
During analysis of the flexible rotor the TMM was used via a similar approach as was followed with the rigid rotor.
The results indicate that the system is experiencing lower than expected damping due to the model that is used within the control loop. The previously assumed rotor model in the control loop is not sufficient to describe its complex behaviour. This causes the unexpected damping characteristics.
This project suggests future work to be conducted in expanding the frequency domain model of the rotor within the control loop to account for its physical shape.Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2009.
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Li, Ming. "The study of electromagnetic wave propagation in photonic crystals via planewave based transfer (scattering) matrix method with active gain material applications." [Ames, Iowa : Iowa State University], 2007.
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weathers, jeffrey wayne. "COMBINING THE MATRIX TRANSFORM METHOD WITH THREE-DIMENSIONAL FINITE ELEMENT MODELING TO ESTIMATE THE INTERFACIAL HEAT TRANSFER COEFFICIENT CORRESPONDING TO VARIOUS MOLD COATINGS." MSSTATE, 2005. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04072005-143359/.
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The interfacial heat transfer coefficient is an important variable regarding the subject of metal castings. The error associated with the experimental temperature data must be dealt with appropriately so that they do not significantly affect the resulting interfacial heat transfer coefficient. The systematic and random errors are addressed using a combination of three-dimensional finite element modeling and the matrix transform method, respectively. Experimentally obtained A356 permanent mold casting data was used to estimate the interfacial heat transfer coefficient corresponding to common industrial mold coatings.
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Zhai, Pengwang. "A fourth-order symplectic finite-difference time-domain (FDTD) method for light scattering and a 3D Monte Carlo code for radiative transfer in scattering systems." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1839.
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Nagesh, Mahesh. "Rotordynamic Design Analysis of a Squeeze Film Damper Test Rig." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin14915608677634.
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Hussain, Mallik Mohd Raihan. "Effective Nonlinear Susceptibilities of Metal-Insulator and Metal-Insulator-Metal Nanolayered Structures." University of Dayton / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1591207594352716.
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Li, Han. "Analysis and Applications of Novel Optical Single - and Multi - Layer Structures." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1450393885.
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Kukačka, Radek. "Výpočet průhybu hřídele elektrického stroje zahrnující vliv magnetického tahu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231063.
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This Master thesis desires the design of methodology for calculating shaft deflection and critical speed of electric machines. There are two methods used. The first one is transfer matrix method, which is represented by a simple programme for shaft creation and calculating needed results built in the Matlab software. The second one is finite element method, which is presented in the Ansys Workbench software.
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Vrána, Jiří. "Využití dynamického tlumiče v hydrodynamice." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401519.
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The master thesis deals with the possibility of using dynamic damper in hydrodynamics. Specifically, the assessment of the impact of dynamic damper on the dynamic stability of the fluid system when the system exhibited unstable behaviour prior to damper installation due to self-excited vibration. In the thesis is presented the algorithm for the calculation of pressure and flow pulsations based on the transfer matrix method, the transition matrices for different damper designs variants are derived. Using the algorithm, the effect of a damper placed in a stable and unstable fluid system is solved. The output of this work is software for solution of pressure and flow pulsations in the system with serially arranged hydrodynamic elements created in the MATLAB program.
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AL-Ghezi, Hammid. "Optical Propagation in Anisotropic Metamaterials: Application to Analysis and Design of Metallo-Dielectric Filters." University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1628263495632462.
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Alimonti, Luca. "Développement d'une méthode hybride éléments finis-matrice de transfert pour la prédiction de la réponse vibroacoustique de structures avec traitements acoustiques." Thèse, Université de Sherbrooke, 2014. http://hdl.handle.net/11143/5988.
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Résumé : Les véhicules aériens et terrestres sont constitués de systèmes bâtis complexes. La structure principale est généralement composée de panneaux légers renforcés par des éléments rigides. Cette solution de conception est répandue parce qu’elle allie la force et un faible poids. Cependant, on sait qu’elle offre des résultats vibroacoustiques médiocres, c’est à dire que l’effet des perturbations externes qui touchent le système peut générer un niveau de bruit excessif à l’intérieur de la cabine des passagers. C’est une préoccupation majeure chez les fabricants, parce que ce niveau de bruit nuit sensiblement au confort ressenti par les clients et peut causer de la fatigue chez les conducteurs et les pilotes. Pour cette raison, les composants passifs constitués de matériaux dissipatifs assemblés en mode multicouche sont généralement intégrés à la structure. Ces assemblées bordées intègrent surtout des matériaux poroélastiques, qui sont plutôt répandus, grâce à l’agencement intéressant de bonnes propriétés d’isolation sonore et de faible poids.
L’intégration en amont des traitements de contrôle du bruit au processus de conception
est la clé de succès d’un produit. Pour ce faire, des outils pratiques numériques en mesure de capter le comportement dynamique des systèmes vibroacoustiques impliquant les structures, les cavités et les matériaux d’insonorisation sont requis. D’une part, la modélisation de ces systèmes couplés en utilisant des procédés à base d’éléments finis peut être, bien que précis, irréalisable pour des applications pratiques. D’autre part, les approches analytiques telles que la méthode de matrice de transfert sont souvent préférées grâce à leur facilité d’utilisation, même si elles manquent de précision en raison des hypothèses rigoureuses inhérentes au cadre analytique. Dans ce contexte, les procédures de structuration hybrides sont récemment devenues très populaires. En effet, les différentes techniques de modélisation sont généralement recherchées pour décrire les systèmes vibroacoustiques complexes arbitraires sur la plus large gamme de fréquences possible.
L’objectif du projet proposé est de mettre au point un cadre hybride offrant une mé-
thodologie simple pour tenir compte des traitements de contrôle du bruit dans l’analyse
vibroacoustique par éléments finis. A savoir, le modèle de calcul qui en découle conserve la souplesse et la précision de la méthode des éléments finis en bénéficiant de la simplicité et de l’efficacité de la méthode de matrice de transfert pour obtenir une réduction de la charge de calcul pour la modélisation de composants acoustiques passifs. La performance de la méthode pour prédire la réponse vibroacoustique de structures planes homogènes avec des traitements acoustiques attachées est évaluée. Les résultats démontrent que la méthode hybride proposée est très prometteuse, parce qu’elle permet une réduction de l’effort de calcul tout en conservant suffisamment de précision par rapport à l’analyse complète par éléments finis. En outre, la méthode de matrice de transfert proposée de modélisation des traitements de contrôle des bruits est générale, comme on peut l’appliquer dans d’autres cadres outre l’application de l’élément fini considéré dans ce travail. // Abstract : Aerial and terrestrial vehicles consist of complex built-up systems. The main structure is typically made of light panels strengthened by stiffer components. Such design solution is widely used as it combines strength and low weight. However, it is known to give poor vibroacoustic performances, i.e. the effect of external disturbances acting on the system may generate an excessive noise level inside the passengers cabin. This is a main concern for the manufacturers, as it significantly affects the comfort experienced by the costumers and may fatigue drivers and pilots. For this reason, passive components consisting of dissipative materials assembled in a multilayer fashion are typically integrated within the structure. These lined assemblies mainly involve poroelastic materials, which are commonly used thanks to the appealing combination of good noise insulation properties and low weight.
The early integration of noise control treatments in the design process is the key to a successful product. For this purpose, practical numerical tools able to capture the dynamic behavior of vibroacoustic systems involving structures, cavities and noise proofing materials are demanded. On the one hand, modeling such coupled systems using finite element based methods can be, albeit accurate, time consuming for practical applications. On the other hand, analytical approaches such as the transfer matrix method are often preferred thanks to their ease of use, although they suffer from a lack of accuracy due to the stringent assumptions inherent within the analytical framework. In this context, hybrid substructuring procedures have recently become quite popular. Indeed, different modeling techniques are typically sought to describe arbitrarily complex vibroacoustic systems over the widest possible frequency range.
The aim of this thesis is to devise a hybrid framework providing a simple methodology to
account for noise control treatments in vibroacoustic finite element analysis. Namely, the
resulting computational model retains the flexibility and accuracy of the finite element
method while taking advantage from the simplicity and efficiency of the transfer matrix
method to obtain a reduction of the computational burden in the modeling of passive
acoustic components. The performance of the method in predicting the vibroacoustic
response of flat structures with attached homogeneous acoustic treatments is assessed.
The results prove that the proposed hybrid methodology is very promising, as it allows for a reduction of the computational effort while preserving enough accuracy with respect to full finite element analysis. Furthermore, the proposed transfer matrix based methodology for noise control treatments modeling is general, as it can be used in alternative frameworks besides the finite element application considered in this work.
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Nascimento, Denise Andrade do. "Comportamento termodinâmico de cadeias de dímeros." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/8656.
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In this Thesis we propose to describe the thermodynamical properties of dimer chains in a one-dimensional lattice rstly considering q-states of chain orientation in the lattice and secondly by a three states model where the chain orientation is associated with a energy " > 0 or " = 0. For this reason we describe our system by a microcanonical ensemble to get the canonical partition function and through this function obtain the Helmholtz free energy, the entropy, internal energy and pressure. We solved also the problem by adopting the grand canonical ensemble using the transfer matrix method and we get in the thermodynamical limit the equivalence between both ensembles. However the analysis of the thermodynamic properties for systems with nite size is quite relevant since for these nite systems can be found a inequivalence of ensembles. Thereby we performed a detailed study of the Statistical Mechanics for nite particles systems verifying the equivalence o ensembles.
O presente trabalho tem por finalidade descrever as propriedades termodinâmicas de cadeias de dímeros em uma rede unidimensional, inicialmente considerando q-estados de orientações das cadeias na rede, e posteriormente um modelo de 3 estados, onde orientação da cadeia está associada a uma energia " > 0 ou " = 0. Para isso, consideramos o problema de um ponto de vista combinatório, no ensemble microcanônico, de maneira a obter sua função de partição canônica e através dela encontrarmos as grandezas termodinâmicas de interesse, tais como a energia livre de Helmholtz, entropia, energia interna, pressão, por exemplo. Posteriormente, resolvemos o problema no ensemble grande canôncio usando a técnica de matriz de transferência, obtendo assim, no limite termodinâmico a equivalência entre os ensembles. Entretanto, têm-se tornado cada vez mais importante e frequente, o estudo termodinâmico de sistemas “pequenos", onde nestes casos pode haver a inequivalência entre as grandezas físicas obtidas nos ensembles. Desse modo, realizamos um estudo detalhado do que acontece ao aplicarmos ferramentas da mecânica estatística a sistemas com poucas partículas, verificando se os diferentes ensembles estatísticos estudados neste trabalho ainda levam aos mesmos resultados.
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Đerđ, Varju. "Teorijska i eksperimentalna analiza dinamičkog ponašanja jezgra visokih zgrada." Phd thesis, Univerzitet u Novom Sadu, Građevinski fakultet u Subotici, 2016. https://www.cris.uns.ac.rs/record.jsf?recordId=104682&source=NDLTD&language=en.
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U ovoj disertaciji, izvršena su teorijska i eksperimentalna istraživanja dinamičkog onašanja jezgra visokih zgrada. Model je zasnovan na Vlasovoj teoriji tankozidnih nosača, kao i na metodi prenosnih matrica. Jezgro se tretira kao tankozidni nosač otvorenog poprečnog preseka, koji je na dnu uklješten u temeljnu ploču, dok je na vrhu slobodan. Duž ose smicanja, jezgro je podeljeno na čvorove u nivoima spratova u kojima su redukovane mase. Poseban naglasak je stavljen na analizu uticaja poprečnih greda, međuspratnih ploča, kao i načinu oslanjanja međuspratnih ploča po spoljašnjoj konturi na dinamičke karakteristike jezgra. Razvijeni numerički postupak je primenjen na armiranobetonskom jezgru petnaestospratne zgrade, koja je analizirana ranijeu radovima mnogih autora. U tu svrhu korišćen je računarski program TWBEIG, napisan primenom Visual Fortran programskog jezika. Analize su urađene i MKE, a dobijeni rezultati su upoređeni. Vrednosti sopstvenih frekvencija pokazuju dobro slaganje.Ovaj rad daje detalje i o eksperimentalnoj studiji u kojoj se primenjuje pleksiglas model u cilju pružanja eksperimentalnih podataka zaproveru tačnosti i pouzdanosti numeričkih rezultata. Dobijeni rezultati su takođe upoređeni sa rezultatima dobijenim TWBEIG računarskim programom, kao i MKE.Predstavljeni numerički metod nudi solidnu osnovu za formiranje jednostavnog modela proračuna, a ipak obezbeđuje odgovarajući nivo preciznosti. Predloženi postupak može biti korišćen i u fazi prethodne analize zgrade, kao i u fazi konačnog projektovanja.In this dissertation, a theoretical and experimental study of the dynamic behaviourof the tall buildings core was carried out. The model is based on the Vlasov'stheory of thin-walled beams and the transfer matrixmethod. The core is treated asa thin wall-walled, open cross section cantilever beam. Along the shear axis thecore is divided into nodes, in the level of the floors, in which the masses arereduced. Special emphasis was given to the analysis of the influence, of lintelbeams, floor slabs, as well as the type of restraints along the outer edge of thefloor slabs, on the dynamic characteristics of the core.The developed numerical procedure was applied to the fifteen-storey reinforcedconcrete core tall building, analyzed previously inthe papers of many authors. Forthis purpose, the computer program TWBEIG was used, written using VisualFortran programming language. The analyses were also performed with FEM andsubsequently the results were compared. The values of natural frequencies showsignificant agreement. This paper presents details about the experimental study which applies the plexiglas model in order to provide experimental data to verify the accuracy and reliability of the numerical results. The results are also compared with the results obtained with the TWBEIG computer program, as well as with FEM. The values of frequencies show reasonable agreement.The proposed numerical method offers a solid base for the creation of a simplecalculation model, yet provides the appropriate level of precision. It can be eitherused for preliminary analysis or for the final design.
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Guzej, Michal. "Rotující odtržení v prostoru odstředivého kompresoru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230025.
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This thesis deals with a procedure for determining the complete processing of aerodynamic flow instabilities (rotating stall and surge) in a centrifugal compressor. At small flows the performance of a compressor system is limited by the surge line, which is caused by flow instabilities. Numerical solution is obtained using the method of transfer matrix. This system is simulated through several models with local resistances that represent the dissipation of pressure energy. Pulses are excitated in these models by the pressure jump placed before the centrifugal compressor. From the frequency-amplitude characteristics for the selected range of frequencies and flow the impedance characteristic of the compressor system is determined. We are looking for problematic frequencies in this characteristic that cause flow instabilities in the compressor system.
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Gonçalves, Evandro Assis Costa. "Análise de dispositivos com materiais magnetoópticos para aplicações em sistemas de comunicações ópticas." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-05062017-163122/.
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As redes ópticas de comunicação têm possibilitado, cada vez mais, o oferecimento de serviços do tipo faixa larga. A rede de comunicação totalmente óptica está se tornando a meta tecnológica mais ambiciosa. Grandes esforços têm sido concentrados no desenvolvimento e aperfeiçoamento de materiais e dispositivos não-recíprocos, como isoladores e circuladores constituem uma importante classe de dispositivos ópticos. Os isoladores são utilizados em sistemas ópticos para prevenir a reflexão de luz em lasers e amplificadores. Os circuladores são empregados em esquemas de derivação de sinais que utilizam multiplexação em comprimento de onda (WDM). O funcionamento destes dispositivos é baseado nas propriedades de materiais magnetoópticos. As metas desta dissertação são apresentar as principais características dos materiais magnetoópticos, explorando as características não-recíprocas dos modos TM. Guias planares e tridimensionais são analisados neste trabalho. Para tanto, são obtidas as expressões das componentes dos campos e as equações características dos modos de interesse em estruturas planares por meio da técnica de matriz de transferência (TMT). A análise de propagação de onda em guias planares com materiais magnetoópticos é feita por meio de simulação numérica empregando o método de propagação de feixe (BPM) baseado em diferenças finitas (FD) e o esquema de Crank-Nicholson (CN) na discretização da solução da equação de onda. A condição de fronteira transparente (TBC) é incorporada ao algoritmo FD-BPM com a finalidade de se evitar reflexões de ondas eletromagnéticas para dentro da janela computacional. O método do índice efetivo é empregado na análise de guias de onda tridimensionais do tipo rib.Optical communication networks have allowed a continuous increase of broadband services offer. The all-optical communication networks are becoming the most ambitious technological goal. Great efforts have been concentrated on the materiaIs and devices development and improvement to make it possible. Nonreciprocal devices, such as isolators and circulators constitute an important class of optical devices. Isolators are used in optical systems to avoid reflection of light in lasers and amplifiers. Circulators are used in signal derivation schemes that use wavelength division multiplexing (WDM). The operation of these devices is based on the properties of magnetooptic materiaIs. The purposes of this dissertation are to present the main features of the magnetooptic materiaIs as well as to analyze the eletromagnetic wave propagation in magnetooptic waveguides, exploring nonreciprocal features of TM modes. Planar and three-dimensional waveguides are analysed in this present study. Therefore expressions of electromagnetic field components and characteristic equations of the modes of interest in planar structures are obtained by using transfer matrix technique (TMT). The wave propagation analysis in planar magnetooptic waveguides is realized by using the finite-difference beam propagation method (FD-BPM) and Crank-Nicholson scheme (CN) applied to wave equation solution discretization. In order to avoid electromagnetic wave reflection into computational window, the transparent boundary condition (TBC) is incorporated to the FD-BPM formalism. The effective index method (EIM) is used in the analysis of three-dimensional rib magnetooptic waveguides.
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Foteinopoulou, Stavroula. "Electromagnetic Wave Propagation in Two-Dimensional Photonic Crystals." Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2003. http://www.osti.gov/servlets/purl/822058-9BqHHS/native/.
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Thesis (Ph.D.); Submitted to Iowa State Univ., Ames, IA (US); 12 Dec 2003.Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 2048" Stavroula Foteinopoulou. 12/12/2003. Report is also available in paper and microfiche from NTIS.
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MEYER, HENDRIK. "Approches numeriques pour des modeles de physique statistique. I. Diagrammes de phase de modeles a spins. Ii. Theorie de matrices aleatoires et integrabilite." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10239.
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Cette these etudie les diagrammes de phase et l'integrabilite de differents modeles de physique statistique classique et quantique. Plusieurs methodes numeriques sont employees ; en particulier, un critere fonctionnel pour decider de l'integrabilite est presente. Le document est organise en deux parties independantes qui sont fortement reliees par les modeles etudies. La premiere partie applique la simulation de monte carlo a des modeles a spins classiques, non integrables, pour confronter des resultats de simulation a des propositions analytiques, obtenues recemment par l'etude des relations d'inverses et du groupe de symetries de ces modeles. Nous determinons ainsi les diagrammes de phase d'un modele de potts chiral a six etats sur reseau carre et du modele de potts standard a trois etats sur reseau triangulaire avec interactions a deux et trois spins. La deuxieme partie etudie l'integrabilite de differents modeles en physique statistique. Par des methodes de la theorie des matrices aleatoires nous analysons les proprietes statistiques du spectre d'un operateur decrivant le modele (le hamiltonien ou une matrice de transfert). En utilisant les symetries connues de celui-ci, on peut operer une decomposition en sous-espaces stables de cet operateur. Nous developpons la methode par l'etude systematique d'une chaine quantique de hubbard avec un terme d'echange. Par la suite, nous l'appliquons pour la premiere fois aux matrices de transfert de modeles classiques (modele d'ising 2d, 3d, modele de potts, modele a huit vertex asymetrique)
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Saleur, Hubert. "Phenomenes critiques bidimensionnels." Paris 6, 1987. http://www.theses.fr/1987PA066613.
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Etude theorique des divers aspects des phenomenes critiques bidimensionnels par des methodes essentiellement analytiques: transformation en modeles de champ libre, exploitation de la symetrie conforme. Determination des valeurs exactes d'exposants critiques, et des expressions des fonctions de partition et des fonctions de correlation. Test d'un certain nombre de resultats par des calculs de matrice de transfert ou des simulations de monte carlo
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Dias, Mariama Rebello de Sousa. "Transport phenomena in quasi-one-dimensional heterostructures." Universidade Federal de São Carlos, 2014. https://repositorio.ufscar.br/handle/ufscar/4973.
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Previous issue date: 2014-02-21Universidade Federal de Sao Carlos
O crescimento e caracterização de sistemas de heteroestruturas semicondutoras quasi-unidimensionais têm atraído grande interesse devido à sua potencial de aplicação tecnológica, como foto-detectores, dispositivos opto-eletrônicos assim como seu para o processamento de informação quântica e aplicações em fotônica. O objetivo desta tese é o estudo das propriedades de transporte eletrônico e de spin em sistemas semicondutores quasi-unidimensionais, especificamente trataremos de nanofios (NWs) homogêneos, NWs acoplados, NWs do tipo plano-geminado (TP), diodos de tunelamento ressonante (ETD) e cadeias de pontos quânticos (QDCS). Escolhemos o método k-p, particularmente o Hamiltoniano de Luttinger, para descrever os efeitos de confinamento e tensão biaxial. Este sugeriu uma modulação do caráter do estado fundamental que, complementada com a dinâmica fônons fornecidas pelas simulações da Dinâmica Molecular (MD), permitiu a descrição da modulação da mobilidade de buracos por emissão ou absorção de fônons. Em relação ao sistema de NWs acoplado,estudamos, através do método da matriz de transferência (TMM), as propriedades de transporte de elétrons e spin sob a interação de spin-órbita (SOI) de Eashba, localizada na região de acoplamento entre fios. Foram consideradas várias configurações de tensões de gate (Vg) aplicadas nos fios. Desse modo, compreendemos a modulação do transporte de spin quando esse é projetado no direção-z através da combinação do SOI e das dimensionalidades do sistema. Da mesma forma, a combinação de SOI e da Vg aplicada deu origem a modulação da polarização, quando o spin medido é projetado na mesma direção em que o SOI de Eashba atua, a direção y. Usando o TMM, exploramos as propriedades de transporte de um DBS e o efeito de uma resistência em série com o intuito de provar a natureza da biestabilidade das curvas características I V bem como o aumento de sua área com temperatura, resultados fornecidos por experimentos. O modelo indicou que aumentando da resistência pela diminuição sa temperatura aumenta a área biestável. A presença de uma hetero-junção adicional ao sistema induz uma densidade de carga nas suas interfaces. De acordo com esta configuração, a queda de tensão total do ETDS muda, podendo ser confirmada experimentalmente. A formação dos peculiares campos de deformação e sua influência sobre a estrutura eletrônicas e propriedades de transporte em superredes de TP foi estudada sistematicamente. Assim, as propriedades de transporte, de ambos os elétrons e buracos, pode ser sintonizada eficientemente, mesmo no caso de elétrons r em sistemas de blenda de zinco, contrastando com a prevista transparência de elétrons r em superredes de semicondutores III-V heteroestruturados. Além disso, constatamos que a probabilidade de transmissão para buracos da banda de valência também poderia ser efetivamente modificada através de uma tensão externa.Por fim, colaboradores sintetizaram com sucesso sistemas de QDCs de InGaAs através da epitaxia de feixe molecular e engenharia de tensão. Um comportamento anisotrópico da condutância com a temperatura foi observado em QDCs com diferentes concentrações de dopagem, medida realizada ao longo e entre os QDCs. O modelo teórico 1D de hoppíng desenvolvido mostrou que a presença de estados OD modela a resposta anisotrópica da condutância neste sistemas.
The growth and characterization of semiconductor quasi-one-dimensional heterostructure systems have attracted increasing interest due to their potential technological application, like photo-detectors, optoelectronic devices and their promising features for quantum information processing and photonic applications. The goal of this thesis is the study of electronic and spin transport properties on quasi-one-dimensional semiconductor systems; specifically, homogenous nanowires (NWs), coupled NW s, twin-plane (TP) NWs, resonant tunneling diodes (RTDs), and quantum dot chains (QDCs). The k-p method, in particular the Luttinger Hamiltonian, was chosen to describe the effects of biaxial confinement and strain. This suggested a modulation of the ground state character that, complemented with the phonon dynamics provided by Molecular Dynamics (MD) simulations, allowed the description of the hole mobility modulation by either phonon emission or absorption. Regarding the coupled NW s system, the electron and spin transport properties affected by a Rashba spin-orbit interaction (SOI) at the joined region were unveiled through the Transfer Matrix Method (TMM). Various configurations of gate voltages (Vg), applied on the wire structure, were considered. We were able to understand the modulation of the spin transport projected in the z-direction trough the combination of the SOI and the system dimensionalities. Likewise, the combination of SOI and applied Vg gave rise to a modulation of the polarization, when the measured spin is projected in the same direction where the Rashba SOI acts, the y-direction. The transport properties of a DBS and the effect of a resistance in series was explored within the TMM to prove the nature of a bistability of the I V characteristics and its enhanced area with temperature provided by the experiment. The model indicates that increasing the resistente by decreasing the temperature, the bistable area enhances. The presence of an additional heterojunction induces a sheet charge at its interfaces. Under this configuration, the total voltage drop of the RTD changes and can be confirmed experimentally.The formation of the peculiar strain fields and their influence on the electronic structure and transport properties of a TP superlattice was systematically studied. Hence, the transport properties of both electrons and holes could be effectively tuned even in the case of T-electrons of zincblende systems, contrasting to the predicted transparency of T-electrons in heterolayered III-V semiconductor superlattices. Also, the transmission probability for holes at valence band could also be effectively modified by applying an external stress. Finally, using molecular-beam-epitaxy and skillful strain engineering, systems of In-GaAs QDCs were successfully synthesized by collaborators. The QDCs with different doping concentrations showed an anisotropic behavior of the conductance, measured along and across the QDCs, with temperature. The theoretical ID hopping model developed found that the presence of OD states shapes the anisotropic response of the conductance in this system.
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Guédra, Matthieu. "Etudes semi-analytiques des conditions de déclenchement et de saturation des auto-oscillations dans des moteurs thermoacoustiques de géométries diverses." Phd thesis, Université du Maine, 2012. http://tel.archives-ouvertes.fr/tel-00821108.
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Les moteurs thermoacoustiques sont des oscillateurs autonomes constitués d'un résonateur acoustique partiellement occupé par un matériau poreux (stack) soumis à un important gradient de température grâce à un apport de chaleur externe. Lorsque le gradient de température imposé le long du stack devient supérieur à un certain gradient critique, appelé seuil de déclenchement, l'interaction fluide-parois se traduit par l'amplification d'une onde acoustique auto-entretenue de fort niveau sur le mode le plus instable du résonateur. L'objet des travaux présentés dans ce mémoire est double. D'une part, il est de proposer un formalisme pour la description du fonctionnement de moteurs thermoacoustiques facilement généralisable à l'ensemble de ces systèmes, qu'ils soient à ondes stationnaires ou à ondes progressives. D'autre part, il est de proposer une approche expérimentale pour la caractérisation du noyau thermoacoustique (incluant le stack et la portion de guide inhomogène en température), qui permette de décrire le comportement de systèmes thermoacoustiques sans formuler d'hypothèses sur la forme du champ de température ou la géométrie du stack.Une modélisation analytique des conditions marginales de stabilité et du taux d'amplification de l'onde est tout d'abord proposée, basée sur l'écriture des matrices de transfert des différents éléments qui constituent le moteur. Ces matrices de transfert associées aux conditions aux limites du système étudié conduisent à une équation caractéristique dont la forme dépend de la géométrie de moteur considérée. La solution de cette équation est une pulsation acoustique complexe dont la partie imaginaire correspond au coefficient d'amplification thermoacoustique.La mesure de la matrice de transfert du noyau thermoacoustique constitue la partie expérimentale des travaux exposés. Elle est réalisée pour différentes conditions de chauffage au moyen d'une méthode à quatre microphones. Dans un premier temps, les résultats expérimentaux sont introduits dans le modèle développé précedemment pour prédire le seuil de déclenchement de divers moteurs thermoacoustiques équipés de ce noyau. Les résultats obtenus grâce à cette méthode sont très proches des observations expérimentales, validant ainsi le banc de mesure et le modèle décrivant les conditions de stabilité. Dans un second temps, les données expérimentales sont utilisées pour affiner un modèle analytique décrivant les mécanismes couplés de propagation acoustique et de transport de la chaleur dans le noyau thermoacoustique : ceci permet notamment d'ajuster les valeurs de paramètres acoustiques et thermiques au moyen d'une méthode inverse.Au-delà du seuil de déclenchement, l'amplification et la saturation de l'onde résultent pour une bonne part du transport de chaleur thermoacoustique et de la convection forcée liée à la génération d'un écoulement redressé (vent acoustique), ces deux mécanismes étant généralement responsables d'une dynamique d'évolution complexe de l'amplitude de pression acoustique au cours du régime transitoire. La dernière partie de ces travaux est consacrée à l'introduction de ces deux effets dans le modèle décrit ci-avant, donnant ainsi accès à la description du régime transitoire de l'onde. Une modélisation simplifiée des transports de chaleur associés au vent acoustique de Rayleigh est notamment proposée, qui permet de montrer que cet effet joue vraisemblablement un rôle important dans la dynamique des régimes transitoires observés expérimentalement dans un générateur thermoacoustique quart d'onde.
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Onelli, Olimpia Domitilla. "Complex photonic structures in nature : from order to disorder." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/273768.
Full textAbstract:
Structural colours arise from the interaction of visible light with nano-structured materials. The occurrence of such structures in nature has been known for over a century, but it is only in the last few decades that the study of natural photonic structures has fully matured due to the advances in imagining techniques and computational modelling. Even though a plethora of different colour-producing architectures in a variety of species has been investigated, a few significant questions are still open: how do these structures develop in living organisms? Does disorder play a functional role in biological photonics? If so, is it possible to say that the optical response of natural disordered photonics has been optimised under evolutionary pressure? And, finally, can we exploit the well-adapted photonic design principles that we observe in Nature to fabricate functional materials with optimised scattering response? In my thesis I try to answer the questions above: I microscopically investigate $\textit{in vivo}$ the growth of a cuticular multilayer, one of the most common colour-producing strategies in nature, in the green beetles $\textit{Gastrophysa viridula}$ showing how the interplay between different materials varies during the various life stages of the beetles; I further investigate two types of disordered photonic structures and their biological role, the random array of spherical air inclusions in the eggshells of the honeyguide $\textit{Prodotiscus regulus}$, a species under unique evolutionary pressure to produce blue eggs, and the anisotropic chitinous network of fibres in the white beetle $\textit{Cyphochilus}$, the whitest low-refractive index material; finally, inspired by these natural designs, I fabricate and study light transport in biocompatible highly-scattering materials.
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Xiang, Ziyin. "Enhancing low-frequency induction heating effect of ferromagnetic composites : Toward medical applications." Thesis, Lyon, 2021. http://www.theses.fr/2021LYSEI022.
Full textAbstract:
Les composites ferromagnétiques, matrices polymères renforcées de particules ferromagnétiques présentent un potentiel intéressant dans de nombreuses applications médicales. Dans cette thèse, nous nous concentrons particulièrement autour du Chauffage par Induction Basse Fréquence (CIBF) de cathéters ferromagnétiques, une méthode alternative pour l'ablation des varices. L'effet CIBF apparaît dès lors que le composite est exposé à un champ magnétique alternatif. Ce phénomène est principalement dû aux courants de Foucault dits "microscopiques" générés par les mouvements des parois des domaines magnétiques. En introduisant le cathéter à travers la varice endommagée et en l'excitant par un champ magnétique basse fréquence, haute amplitude, il est concevable d'atteindre une température suffisamment élevée pour guérir correctement la zone endommagée sans perturber les zones saines environnantes. Par comparaison aux traitements existants, la méthode CIBF est précise, économique et simple. En transférant la chaleur sans conduction, l'encombrement du cathéter est réduit et le procédé semble applicable même pour des veines très sinueuses. Des composites ferromagnétiques de différentes formes et fractions volumiques ont été fabriqués et testés grâce à un dispositif expérimental dédié. Différents paramètres (fréquence, pourcentage de particules…) ont été analysés afin d’établir la combinaison présentant la meilleure réponse thermique. Les propriétés physiques (perméabilité, conductivités électrique et thermique) ont également été caractérisées. Un modèle Comsol® combinant comportement ferromagnétique et thermique a été conçu afin d’améliorer la compréhension des phénomènes. Pour améliorer la conversion, des échantillons anisotropes ont été développés en imposant un champ magnétique statique dans la phase de solidification. Finalement, une imprimante 3D de type extrusion a été utilisée pour imprimer des échantillons de formes proches de celle d’un cathéter. Des spécimens isotropes et anisotropes ont été imprimés. Les réponses CIBF distinctes et marquées entre les différentes directions testées chez les échantillons anisotropes ouvrent la voie à d’autres applications médicales comme le suivi électromagnétique (navigation chirurgicale)Ferromagnetic composites, polymer matrix mixed with ferromagnetic particles show good potential in medical applications. In this thesis, we especially focus on the Low Frequency Induction Heating (LFIH) of ferromagnetic catheters as an alternative process for varicose veins ablation. The LFIH effect appears as soon as the composite is exposed to an alternating magnetic field. This phenomenon is mainly due to the so-called "microscopic" eddy currents generated by the magnetic domain wall motions. By inserting the catheter through a damaged varicose vein, and exciting it with a low frequency, high amplitude magnetic field, it is conceivable to reach a temperature high enough to properly heal the damaged area without injuring the surrounding healthy ones. Compared to the existing treatments, the LFIH method is accurate, cost competitive and simple. By transferring heat in a non-conductive way, the catheter bulkiness is reduced and the method is applicable even in tortuous veins. Ferromagnetic composites with different shapes and particle volume fractions were built and tested in a specific experimental bench. Different parameters (frequency, particle fraction …) were analyzed to reach the best thermal answer. The physical properties (permeability, electrical and thermal conductivities) were also characterized. A Comsol® model combining ferromagnetic behavior and thermal transfer properties was designed to improve the understanding of the phenomena. For a better efficiency, specimens with anisotropic magnetic behaviors were built by curing them under the influence of a static magnetic field. Finally, a commercial extrusion-type 3D printer was used to print samples with catheter shapes. Isotropic and anisotropic specimens were built. Interesting LFIH behavior were observed and for the later ones directional answers potentially interesting in alternative medical applications like the electromagnetic tracking (surgery navigation)
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Hunter, Brandon. "Channel Probing for an Indoor Wireless Communications Channel." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/64.
Full textAbstract:
The statistics of the amplitude, time and angle of arrival of multipaths in an indoor environment are all necessary components of multipath models used to simulate the performance of spatial diversity in receive antenna configurations. The model presented by Saleh and Valenzuela, was added to by Spencer et. al., and included all three of these parameters for a 7 GHz channel. A system was built to measure these multipath parameters at 2.4 GHz for multiple locations in an indoor environment. Another system was built to measure the angle of transmission for a 6 GHz channel. The addition of this parameter allows spatial diversity at the transmitter along with the receiver to be simulated. The process of going from raw measurement data to discrete arrivals and then to clustered arrivals is analyzed. Many possible errors associated with discrete arrival processing are discussed along with possible solutions. Four clustering methods are compared and their relative strengths and weaknesses are pointed out. The effects that errors in the clustering process have on parameter estimation and model performance are also simulated.
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Orliac, Jean-Guillaume. "Analyse et simulation du comportement anisotrope lors de la mise en forme de renforts tissés interlock." Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00823359.
Full textAbstract:
Afin de pouvoir prédire le comportement des renforts de composites 3D interlock au cours d'un procédé de mise en forme, il est nécessaire de connaitre la position des mèches dans le renfort durant la phase de préformage du procédé. Les travaux présentés ici traitent de la simulation du préformage de renforts 3D épais à l'aide d'un élément fini hexaédrique semi-discret spécifique. En utilisant le principe des travaux virtuels, on distingue le travail interne virtuel dû à la tension des mèches des autres travaux virtuels. La raideur due aux tensions de mèches, qui constitue la contribution principale de la rigidité du matériau, est prise en compte à l'aide de barres incluses dans les éléments. Les rigidités dues aux autres sollicitations, comme la compression transverse, les cisaillements ou les frottements inter-mèches, sont décrites par un matériau continu additionnel. La combinaison de ce modèle discret du premier ordre et d'un matériau continu hyperélastique anisotrope dit du second ordre, pour formuler le comportement du matériau va permettre la simulation du préformage des renforts tissés épais. Conjointement aux travaux sur la simulation, des travaux expérimentaux pour l'identification des paramètres matériau de la loi de comportement ont été définis et réalisés. Ces paramètres concernent les deux parties de la formulation du comportement.
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Wen-Chang, Kuo, and 郭文章. "A Modified Transfer Matrix Method To Rotor Dynamics." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/42234160053429857590.
Full textAbstract:
碩士國立臺灣科技大學
機械工程研究所
83
The purpose of this research is to apply a modified transfer matrix (MTM) method for dynamic behavior analysis of rotor system. First, the complicated rotor system is decomposed into three kind of units : shafts, disks and bearing supports. The governing equations of shaft and disk are derived by Hamilton's principle to obtain MTM of shaft and disk. Then, the Newton's second law is applied to construct the MTM of bearing support. The overall transfer matrix of the whole rotor system in the sequence of units are then solved for the natural frequencies, mode shapes and critical speeds. The couplingshear effect of shaft on natural frequencies due to rotation is also discussed. Moreover, the analyses of the unbalance responses of rotor system brought by off-center disks or unbalanced mass and the whirling orbit of unbalance responses are well accomplished.
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Liaw, Jiing-Yun, and 廖景雲. "Flexible robot arm control by transfer matrix method." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/71156965557805944172.
Full textAbstract:
碩士國立成功大學
機械工程研究所
81
The purpose of this study is to apply Transfer Matrix method (TMM) to carry out the dynamic analysis of integrated control and flexible robot arm system and design suitable controller. The presented scheme treats the control reference input signal as part of the state variables of system, and then modifies the transfer matrices by considering the coupling and noncoupling characteristics between the control and mechanical interfaces. So we can model system and design controller at the same time which leads to computational saving but without losing any re- -lationship between control and mechanism. Moverover, the presented method provides a simple way to de- -sign multiform controllers in a simular procedure. And a lot of control laws can be used without any difficulty if they can be involved in polynominal forms. Two different types of fixed-con- -figuration control system designs are studied.
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LIU, XING-LI, and 劉信利. "An improved transfer matrix method for rotor dynamics." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/70023100712266777148.
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