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1
Mikula, Léopold. « Contribution à la Modélisation des pertes dans les matériaux magnétiques de dispositifs électromécaniques : Extension vectorielle du Modèle LS et intégration en résolution éléments finis ». Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALT052.
Texte intégralRésumé :
Afin de parvenir a augmenter les performances des machines tournantes, les logiciels de conception doivent être affinés pour fournir de meilleurs estimations des pertes générées. L'objectif dans cette étude est donc l'amélioration des modèles de matériaux magnétiques doux en 2D . Des approches dites 'a priori' et 'a posteriori' (Preisach, loss surface) seront évaluées et comparées en s'appuyant sur l'expérimentation et la simulation. Le modèle Loss surface a été vectorisé afin de permettre la prise en des phénomène dit d'hystérésis dynamique en résolution élément finisIn order to increase the performance of rotating machines, design software must be refined to provide better estimates of the losses generated. The aim of this study is therefore to improve 2D soft magnetic material models. So-called 'a priori' and 'a posteriori' approaches (Preisach, loss surface) will be evaluated and compared, based on experimentation and simulation. The loss surface model has been vectorized to take into account dynamic hysteresis phenomena in finite element resolution
2
Conrad, Joël. « Modélisation d'un transformateur de courant à charge variable ». Grenoble INPG, 1997. http://www.theses.fr/1997INPG0171.
Texte intégralRésumé :
Les transformateurs de courant débitent généralement dans une charge de faible impédance. Si cette condition n'est pas remplie, l'induction dans le tore et le courant magnétisant ne sont plus négligeables. Ce mémoire traite ce cas de figure avec en plus des courants éventuellement non sinusordaux et avec une composante contin!le. Un modèle analytique s'étoffe au fur et à mesure afin de tenir compte de ces spécificités. - D'abord nous analysons le comportement de la chaîne de mesure avec des courants sinusoidaux, nous développons un modèle analytique non linéaire de l'impédance magnétisante et évaluons l'importance des flux de fuite. Ensuite nous étendons ce modèle d'impédance magnétisante aux types de courants cités. Notre modèle, analytique, est alors robuste en fréquence. Enfin nous enrichissons notre modèle en tenant compte de la non-linéarité des matériaux. N est alors valable quelque soient les conditions de fonctionnement Une étude sur la caractérisation des matériaux magnétiques soumis à une excitation dissymétrique clôt ce mémoireCurrent transformers are generally connected to small impedance. If it is not the case, the flux density and the magnetizing current are not negligIble. This report deals with this case. More over the current may he non sinusoidal and its mean value May he different than zero. To take account these specificity an anaIytical model is developed. In a first time the hehavior of the assembly (current transformer and its load) with sinusoidal currents is studied. An non linear, analytical, model is developed. The importance of the leakage flux is evaluated In a second time the model is extended to any type of current' s wave form. The frequency' s variations of the magnetic characteristic are taken into account In a third time the non linearity of the magnetic material is modelised At this time the hehavior of the transformer submitted to any type of current May he computed. This report is closed by a study of magnetic characterization using a non symmetrical current
3
Adedoyin, Ayodeji Adeoye. « Analysis of aftereffect phenomena and noise spectral properties of magnetic hysteretic systems using phenomenological models of hysteresis ». Tallahassee, Florida : Florida State University, 2009. http://etd.lib.fsu.edu/theses/available/etd-09212009-165524/.
Texte intégralRésumé :
Thesis (Ph. D.)--Florida State University, 2009.Advisor: Petru Andrei, Florida State University, College of Engineering, Dept. of Electrical and Computer Engineering. Title and description from dissertation home page (viewed on May 6, 2010). Document formatted into pages; contains xxi, 120 pages. Includes bibliographical references.
4
Cortial, Fabienne. « Modélisation de l'hystérésis et des dispositifs d'enregistrement magnétique ». Grenoble INPG, 1996. http://www.theses.fr/1996INPG0136.
Texte intégralRésumé :
L'amélioration des têtes pour l'enregistrement magnétique numérique passe par la simulation des procédés d'écriture et de lecture des milieux d'enregistrement. Il apparaît donc indispensable de rechercher un modèle d'hystérésis représentant au mieux le comportement de ces milieux (bandes et disques) : tel est l'objectif de cette thèse. Deux modèles scalaires originaux ont été développés. Ils permettent de représenter analytiquement le cycle majeur en utilisant plus de données expérimentales que les modèles existants et de calculer des cycles mineurs fermés à partir du cycle majeur et des deux derniers points de rebroussement constituant l'histoire. Ces modèles ont été implantés dans un logiciel éléments finis. Ils ont conduit à une simulation de l'écriture et de la lecture d'une tête clavaire couches minces sur un disque dur mince très satisfaisante. L'hypothèse du comportement magnétique scalaire est valide pour ces disques mais ne l'est plus pour les bandes parascolaires (métal et ferrite de baruym) et de métal évaporé (ME) actuellement utilisées : un modèle vectoriel d'hystérésis est alors nécessaire. Après une étude bibliographique approfondie des modèles vectoriels existants, nous avons choisi le modèle le plus performant pour les bandes pelliculaires qui est le modèle 3D Preisach/stoner-Worhlfarth. Nous l'avons amélioré pour modéliser correctement les bandes ME. Par ailleurs, les mesures sont rélarisées sur un VSM vectoriel. L'intérêt de la caractérisation est double. Elle permet d'abord de déterminer les sept paramètres du modèle à partir des courbes, qui se réduisent au cycle majeur longitudinal, à la courbe M longitudinale et à l'aimantation rémanente du cycle transverse. La comparaison des mesures aux courbes calculées permet ensuite de valider le modèle. Nous avons, de plus, participé à la construction d'un tel appareil, doté d'un nouveau système de bobines de détection
5
Fuad, Mohammad Naser Mohammad. « On the consistency of hysteresis models ». Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/353622.
Texte intégralRésumé :
Hysteresis is a nonlinear behavior encountered in a wide variety of processes including biology, optics, electronics, ferroelectricity, magnetism, mechanics, structures, among other areas. One of the main features of hysteresis processes is the property of consistency formalized in [52]. The class of operators that are considered in [52] consists of the causal ones, with the additional condition that a constant input leads to a constant output. For this class of systems, consistency has been defined formally. This property is useful in system modeling and identification as it limits the search for the system's parameters to those regions where consistency holds.
The thesis applies the concepts introduced in [52] to some hysteresis models, namely LuGre model and Duhem model. The aim of the thesis is to derive necessary conditions and sufficient one for consistency (or/and strong consistency) to hold.
For the LuGre model, the consistency and the strong consistency are studied under minimal conditions in Chapter 2. As a by-product of this study, explicit expressions are derived for the hysteresis. Such expression may be useful for identification purposes as shown in [53].
A classification of the possible Duhem models in terms of their consistency is carried out in Chapter 3. This study shows that a parameter’s should be one for the Duhem model to be compatible with a hysteresis behavior.La histéresis es un fenómeno nolineal encontrado en varios procesos como biología, óptica, electrónica, ferroelectricidad, magnetismo, mecánica, estructuras, así como en otras áreas. Una de las características de los sistemas con histéresis es la propiedad de consistencia formalizada en [52]. La clase de operadores considerados en [52] consiste en aquellos que son causales, con la condición adicional que a una entrada constante corresponda una salida constante. Para esta clase d sistemas, la consitencia ha sido definida formalmente. Esta propiedad es útil en modelado e identificación dado que limita la búsqueda de parámetros a aquellas regiones donde la consistencia es válida. * Esta tesis aplica los conceptos introducidos en [52] a algunos modelos de histéresis, más precisamente al modelo de LuGre y al modelo de Duhem. El objetivo de esta tesis es encontrar condiciones necesarias y condiciones suficientes para que se satisfaga la consistencia (o/y la consitencia fuerte). * Para el modelo de LuGre, la consistencia "fuerte" se estudia en el capítulo 2 bajo condiciones mínimas. Como resultado de este estudio, se hallan fórmulas explícitas del lazo de histéresis. Tales fórmulas podrían ser de utilidad para tareas de identificación como se demuestra en [53]. * El capítulo 3 de la tesis presenta una clasificación de los modelos de Duhem posibles en términos de su consistencia. Este estudio muestra que hay un parámetro que tiene que valer uno para que el modelo sea compatible con un comportamiento histerético
6
Phelps, Brian F. « An inclusive model of ferromagnetic hysteresis ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0006/NQ42968.pdf.
Texte intégral
7
Joseph, Daniel Scott. « Parameter Identification for the Preisach Model of Hysteresis ». Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/27295.
Texte intégralRésumé :
Hysteresis, defined as a rate independent memory
effect, is a phenomenon that occurs in many
physical systems. The effect is sometimes
desired, sometimes a nuisance, sometimes cata-
strophic, but in every case we must understand
hysteresis if we are to better understand the
system itself.
This work introduces a method of parameter
identification for the Preisach model of hyster-
esis. This identification method is explored
in both the setting of non-singular measures
and the setting of singular measures.Ph. D.
8
Chevalier, Thierry. « Modélisation et mesure des pertes de fer dans les machines électriques : application à la machine asynchrone ». Phd thesis, Grenoble INPG, 1999. http://www.theses.fr/1999INPG0172.
Texte intégralRésumé :
L'énergie dissipée dans les machines électrique se situe, pour une grande partie, dans les tôles électriques utilisées pour la composition de leur circuit magnétique. Une analyse complète du comportement dynamique des ces tôles est menée, elle met en évidence sa sensibilité à la vitesse de variation de l'induction. Cette analyse conduit, grâce à une séparation des aspects statiques et dynamiques, à la définition d'un modèle d'hystérésis dynamique qui permet une représentation précise des tôles électriques. Le modèle d'hystérésis est ensuite combiné à une méthode d'analyse numérique par éléments finis pour évaluer localement la puissance dissipée par le circuit magnétique de la machine. La méthode est validée dans le cas de machines asynchrones de faible puissance. Une analyse complémentaire dans ce cas précis permet de déterminer d'autres phénomènes dissipatifs responsables de pertes supplémentaires. Ils ont pour origine soit des propriétés intrinsèques des matériaux, comme l'anisotropie, soit des opérations du processus de fabrication, comme les courts-circuits en surface du rotor. La prise en compte de l'ensemble de ces phénomènes a conduit à un modèle qui permet de prédire avec précision le rendement des machines électriques
9
Lahey, Timothy. « Modelling Hysteresis in the Bending of Fabrics ». Thesis, University of Waterloo, 2002. http://hdl.handle.net/10012/941.
Texte intégralRésumé :
This thesis presents a model of fabric bending hysteresis. The hysteresis model is designed to reproduce the fabric bending measurements taken by the Kawabata Evaluation System (KES) and the model parameters can be derived directly from these property measurements. The advantage to using this technique is that it provides the ability to simulate a continuum of property curves. Results of the model and its components are compared and constrasted with experimental results for fabrics composed of different weaves and yarn types. An attempt to incorporate the bending model as part of a fabric drape simulation is also made.
10
Foliente, Greg C. « Hysteresis modeling of wood joints and structural systems ». Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09292009-020259/.
Texte intégral
11
Xie, Xiaoyue S. B. Massachusetts Institute of Technology. « Modified Maxwell Model for hysteresis compensation of piezoelectric stack actuators ». Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98747.
Texte intégralRésumé :
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (page 29).
This thesis presents new observations of the hysteresis behavior of piezoelectric stack actuators and proposes an Input-Range Dependent Maxwell Model for more accurate hysteresis compensation. Experimental studies show that the assumptions of the classical Maxwell model do not fully hold: the actuator behaves differently in the initiation stage compared to the later cycles, and the parameters of the Maxwell model are dependent on the input history. Two most prominent factors are the input range of the most recent half loop and the local extremum input at the beginning of the current half loop. To accommodate for these variations, two types of modified Maxwell model are presented: the Input-Range Dependent Maxwell Model and the Local-Extremum Dependent Maxwell Model. We further propose parameter estimation schemes for each modified model. In both models, one set of parameters is obtained for the initiation stage and another set for later cycles, and the first Maxwell spring constant is related to the input history - input range or local extremum, respectively. Further studies suggested that the linear dependence of the first spring constant on the input range is much stronger than on the local extremum. Simulations with the identified Input-Range Dependent Maxwell Model gave a maximum percentage error of 2.71%, as compared with a percentage error of 8.29% using the classical Maxwell model. This suggests that the model can accurately predict the response of a piezoelectric stack actuator and is promising for hysteresis compensation in nano-positioning applications.
by Xiaoyue Xie.
S.B.
12
Mohd, Mustafah Anas. « Proposed framework of building nonlinear models : a study using the Bouc-Wen hysteretic model ». Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/15459/.
Texte intégralRésumé :
Nonlinear models are useful tools in current engineering practice for benefits such as cost savings and improved safety features, especially for testing, designing and maintenance of engineering services. Such models have been widely used for understanding the physics of systems and structures, predictions of abnormalities, predictions of specific scenarios to enable control and for planning of production. Having the correct fit-for-purpose model is very important for the model to be utilised in any of the functions as required, which enables accurate understanding and predictions of the real system to be modelled. The work presented in this thesis is concerned with proposing a framework for building a fit-for-purpose nonlinear model using the Bouc-Wen model of hysteresis as an example nonlinear model to be identified. The proposed framework is presented with steps suggested for the understanding of the requirements and purpose of building a nonlinear model. This is the main idea of the thesis where sufficient initial understanding of a problem will lead to experimental design to be able to provide the right sets of data to fit the purpose of the model to be built. Using a variant of the Differential Evolution algorithm, the inputs of data sets for identification or parameter estimation were investigated. The investigation compared the input magnitudes, input types and noise levels to show that the result of identification can be misleading without a real understanding of the model requirements. This shows the importance of the specification of model requirements suggested in the framework. A measure of Improvement Ratio is also suggested to improve confidence of nonlinear parameter estimation by way of evaluation against linear parameter estimates. Finally, a Volterra series approximation method for nonlinear polynomial models is used to estimate the parameters of the Bouc-Wen hysteretic model. It is shown that only linear parameters can be identified accurately in the presence of noise. Another key finding relates the nonlinear parameters to parameters of a nonlinear polynomial model to show some physical resemblance to the nonlinear polynomial damping and stiffness term, further work is required to truly understand this.
13
Chevalier, Thierry. « Modélisation et mesure des pertes de fer dans les machines électriques : application à la machine asynchrone ». Phd thesis, Grenoble INPG, 1999. http://tel.archives-ouvertes.fr/tel-00764023.
Texte intégralRésumé :
Les conséquences importantes sur l'environnement d'une consommation grandissante d'énergie rendent indispensable une maîtrise du rendement des dispositifs électriques. Il est nécessaire pour améliorer les performances de ces dispositifs de posséder non seulement d'une connaissance fine des phénomènes dissipatifs mais aussi d'outils permettant une simulation- efficace. Parmi tous ces dispositifs, les machines électriques représentent une part très importante. L'énergie dissipée s'y situe, pour une grande partie, dans les tôles électriques utilisées pour la composition de leur circuit magnétique. Une analyse complète du comportement dynamique des ces tôles est menée, elle met en évidence sa sensibilité à la vitesse de variation de l'induction. Cette analyse conduit, grâce à une séparation des aspects statiques et dynamiques, à la définition d'un modèle d'hystérésis dynamique qui permet une représentation précise des tôles électriques. Le modèle d'hystérésis est ensuite combiné à une méthode d'analyse numérique par éléments finis pour évaluer localement la puissance dissipée par le circuit magnétique de la machine. La méthode est validée dans le cas de machines asynchrones de faible puissance. Une analyse complémentaire dans ce cas précis permet de déterminer d'autres phénomènes dissipatifs responsables de pertes supplémentaires. Ils ont pour origine soit des propriétés intrinsèques des matériaux, comme l'anisotropie, soit des opérations du processus de fabrication, comme les courts-circuits en surface du rotor. La prise en compte de l'ensemble de ces phénomènes a conduit à un modèle qui permet de prédire avec précision le rendement des machines électriques.
14
Schubert, Sven. « Stochastic and temperature-related aspects of the Preisach model of hysteresis ». Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-70798.
Texte intégralRésumé :
Ziel der vorliegenden Arbeit ist es, das Preisach-Modell bezüglich stochastischer äußerer Felder und temperaturbezogener Aspekte zu untersuchen. Das phänomenologische Preisach-Modell wird oft erfolgreich angewendet, um Systeme mit Hysterese zu beschreiben. Im ersten Teil der Arbeit wird die Antwort des Preisach-Modells auf stochastische äußere Felder untersucht. Hier liegt das Augenmerk hauptsächlich auf der Autokorrelation; sie dient dazu den Einfluss des hysteretischen Gedächtnisses zu quantifizieren. Mit analytischen Methoden wird gezeigt, dass sich ein Langzeitgedächtnis, sichtbar in der Autokorrelation der Systemantwort, entwickeln kann, selbst wenn das treibende Feld unkorreliert ist. Im Anschluss werden diese Resultate, m.H. von Simulationen, auf äußere Felder ausgeweitet, die selbst Korrelationen aufweisen können. Der zweite Teil der Arbeit befasst sich mit dem Einfluss einer endlichen Temperatur auf das Preisach-Modell. Es werden unterschiedliche Methoden besprochen, wie das Nichtgleichgewichtsmodell in seiner mikromagnetischen Interpretation mit Temperatur als Gleichgewichtseigenschaft verknüpft werden kann. Eine Formulierung wird genutzt, um die Magnetisierung von Nickelnanopartikeln in einer Fullerenmatrix zu simulieren und mit Experimenten zu vergleichen. Des Weiteren wird die Relaxationsdynamik des Gedächtnisses des Preisach-Modells bei endlichen Temperaturen untersuchtThe aim of this thesis is to investigate the Preisach model in regard to stochastically driving and temperature-related aspects. The Preisach model is a phenomenological model for systems with hysteresis which is often successfully applied. Hysteresis is a widespread phenomenon which is observed in nature and the key feature of certain technological applications. Further, it contributes to phenomena of interest in social science and economics as well. Prominent examples are the magnetization of ferromagnetic materials in an external magnetic field or the adsorption-desorption hysteresis observed in porous media. Hysteresis involves the development of a hysteresis memory, and multistability in the interrelations between external driving fields and system response. In the first part, we mainly investigate the response of Preisach hysteresis models driven by stochastic input processes with regard to autocorrelation functions to quantify the influence of the system’s memory. Using rigorous methods, it is shown that the development of a hysteresis memory is reflected in the possibility of long-time tails in the autocorrelation functions, even for uncorrelated driving fields. In the case of uncorrelated driving, these long-time tails in the autocorrelations of the system’s response are determined only by the tails of the involved densities. They will be observed if there are broad Preisach densities assigning a high weight to elementary loops of large width and narrow input densities such that rare extreme events of the input time series contribute significantly to the output for a long period of time. Afterwards, these results are extended by simulations to driving fields which themselves show correlations. It is shown that the autocorrelation of the output does not decay faster than the autocorrelation of the input process. Further, there is a possibility that long-term memory in the hysteretic response is more pronounced in the case of uncorrelated driving than in the case of correlated driving. The behavior of the output probability distribution at the saturation values is quite universal. It is not affected by the presence of correlations and allows conclusions whether the input density is much more narrow than the Preisach density or not. Moreover, the existence of effective Preisach densities is shown which define equivalence classes of systems of input and Preisach densities which lead to realizations of the same output variable. The asymptotic behavior of an effective Preisach density determines the asymptotic correlation decay of the system’s response in the case of uncorrelated driving. In the second part, temperature-related effects are considered. It is reviewed how the non-equilibrium Preisach model in its micromagnetic picture can be related to temperature within the framework of extended irreversible thermodynamics. The irreversible response of a ferromagnetic material, namely, Nickel nanoparticles in a fullerene matrix, is simulated. The model includes superparamagnetism where ferromagnetism breaks down at temperatures lower than the Curie temperature and the results are compared to experimental data. Furthermore, we adapt known results for the thermal relaxation of the system’s memory in the form of a front propagation in the Preisach plane derived basically from solving a master equation and by the use of a contradictory assumption. A closer look is taken at short time scales which dissolves the contradiction and shows that the known results apply, taking into account the fact that the dividing line propagation starts with an additional delay time depending on the front coordinates in the Preisach plane. Additionally, it is outlined how thermal relaxation behavior in the Preisach model of hysteresis can be studied using a Fokker-Planck equation. The latter is solved analytically in the non-hysteretic limit using eigenfunction methods. The results indicate a change in the relaxation behavior, especially on short time scales
15
Stakvik, Jon Åge. « Identification, Inversion and Implementaion of the Preisach Hysteresis Model in Nanopositioning ». Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-25744.
Texte intégralRésumé :
Atomic force microscopes offer the possibility for imaging a sample topography with accuracy in the nanometer scale. This kind of performance is impossible without actuators enabling a certain accuracy. A frequently used actuator in such nanopositioning applications is the piezoelectric actuator which, although precise, exhibit the unwanted phenomenon of hysteresis. Hysteresis is recognized as the main nonlinearity in the piezoelectric actuator, and introduces severe control issues for accurate positioning.To compensate for hysteresis an accurate model of the nonlinearity has to be identified. A discrete and a piecewise-continuous model, based on the Preisach operator, is identified with a constraint least squares method. An algorithm for computing the output of the continuous model is proposed and outlined together with a solution for the discrete model. The general approach for control of hysteresis is to create a right inverse of the identified model. Since the Preisach operator does not have an analytical inverse, this is done numerically by a closest match algorithm. These algorithms are described based on previous literature.In order to achieve a well designed model for the Preisach operator, the input function has to be thoughtfully designed. It is pointed out that to achieve a persistently excited input signal, the number of reversals has to be sufficient compared to the discretization level of the implemented Preisach operator. Additionally, effects from systematic errors in the signal loop, such as negative phase due to low pass filtering, time delay, creep and actuator dynamics, has to be minimized. It was shown that negative phase in the signal loop can invalidate the identified models.Both the discrete and continuous model was shown to describe the hysteresis nonlinearity. To reduce the step-size of each discrete value, a higher discretization level can be applied to the discrete model. The inverse models were simulated to verify the inversion algorithms, followed by results from testing the inverse signal. The inverted signal based on the discrete method showed need for interpolation between the discrete levels, while the continuous inverse exhibit higher frequency components that causing vibrations due to resonance dynamics. An input signal consisting of the same amount of reversals as the discretization level was shown to give a valid identified model. Furthermore, increasing the number of reversals was shown to continue improving the accuracy. The effect of negative phase, from low pass filtering and time delay, was tested, and changes in the distribution of the Preisach weights were shown. Such effects can cause significant errors in identification of hysteresis models, especially if the reference frequency is subject to changes.
16
Keane, Michael K. « Hysteresis phenomena of ferromagnetic bodies using the nonlocal exchange energy model ». Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06062008-171642/.
Texte intégral
17
Meurer, Thomas. « Wave propagation in hysteretic media ». Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19090.
Texte intégral
18
Hutton, Richard Shane. « Modeling the United States Unemployment Rate with the Preisach Model of Hysteresis ». Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/32595.
Texte intégralRésumé :
A system with hysteresis is one that exhibits path dependent but rate independent memory. Hysteresis can be observed physically through the magnetization of a ferromagnetic material. In order to mathematically describe systems with hysteresis, we use the Preisach model. A discussion of the Preisach model is given as well as a method for computing the hysteretic transformation of an input variable. The focus of this paper is hysteresis in economics, namely, unemployment. We consider essential time series techniques for analyzing time series data, i.e. unit root testing for stationarity. However, we point out problems in modeling hysteresis with these techniques and argue that unit root tests cannot capture the selective memory of a system with hysteresis. For that, hysteresis in economic time series data is modeled using the Preisach model. We test the explanatory power of the previous unemployment rate on the current unemployment rate using both a hysteretic and non-hysteretic model. We find that the non-hysteretic model is better at explaining current unemployment rates, which suggests hysteresis is not present in the United States unemployment rate.Master of Science
19
Wilde, Timothy Philip. « An Energy Based Model for the Compressive Behavior of Goose Down ». Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4899.
Texte intégralRésumé :
Very little work has been done to study and understand the internal mechanisms that provide goose down with its resiliency under repeated compression. We have employed low magnification optical microscopy to identify some of these important mechanisms. Microscopy showed that a small tertiary structure exists on most goose down fibers and creates an important point of contact when two fibers interact. This tertiary contact mechanism has been coupled with fiber orientation and incorporated into a unique strain-energy function. The principal stresses for an initial compression cycle can be determined from this strain-energy function according to the hyperelastic constitutive theory. Irreversible deformation and hysteresis necessitate another means to determine the stresses during unloading and reloading. For these stages, the framework used by Beatty et al. (2002) for an ideal Mullins material will be utilized in conjunction with a shift in the stress-free state to determine the principal stresses. The proposed model is then evaluated for uniaxial compression and shown to capture the general behavior of goose down in compression including the irreversible deformation and hysteresis.
20
Garcia, Danilo César Cascaldi. « Hysteresis nas exportações manufaturadas brasileiras : um modelo de cointegração com transição suavizada ». Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/96/96131/tde-05052009-161857/.
Texte intégralRésumé :
A literatura é extensa no que se refere a estimações de modelos de oferta e demanda para exportações, mas poucos consideram que a resposta em exportações a variações na taxa de câmbio possa ser lenta e assimétrica. Dixit (1989) afirma que a firma que deseja passar a atuar no mercado externo ou deixar tal mercado deve incorrer em custos irrecuperáveis. Além disso, políticas de wait and see fazem com que estas não mudem seu estado (atuantes ou não) imediatamente quando variações significativas na taxa de câmbio acontecem. Tais fatores criam o fenômeno da hysteresis econômica, caracterizado pela forte não-linearidade de uma variável, gerando assimetria dependendo do estado e da magnitude do choque em tal. Assim, propõe-se neste trabalho uma forma alternativa de se captar tal efeito, via modelo de cointegração com transição suavizada, desenvolvido em Saikkonen e Choi (2004). Os resultados encontrados apontam para a evidência do efeito histerético, apresentando tal modelagem não-linear para quatro dos dezesseis setores industriais estudados do Brasil.The literature is large on what refers to estimation of export supply and demand models, but just a few consider that the response on exports to variations on the exchange rate can be slow and asymmetric. Dixit (1989) says that the firm who wishes to operate on the foreign market or leave it must incur on sunk costs. Besides, wait-and-see policies makes the firm to remain it state unaltered (operating or not) immediately when significant variations on the exchange rate happens. This factor creates the phenomena called economic hysteresis, representing a strong non-linearity of a variable, generating asymmetries depending on the state and magnitude of the shock on the variable. Thus, its proposed on this work an alternative form to capture this effect, by smooth transition cointegration model, developed on Saikkonen and Choi (2004). The results indicate to the evidence of the hysteretic effect, presenting non-linear modeling for four of sixteen industrial sectors studied of Brazil.
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CHINNI, Federico. « Hysteretic magnetic behavior of AuCo nanocomposite systems ». Doctoral thesis, Università degli studi di Ferrara, 2018. http://hdl.handle.net/11392/2487888.
Texte intégralRésumé :
Nowadays, the search for innovative nanocomposite systems consisting of at least two different magnetic phases is attracting remarkable attention. Indeed, the intimate mixing of the different phases at the nano scale level may give rise to new materials showing unique properties. In particular, a fine tuning of their overall magnetic anisotropy may be obtained and, accordingly, of their magnetic hysteretic properties.
In this framework, this thesis is dedicated to an in-depth study of the magnetic properties of AuCo nanostructures in form of both continuous films and Nano Holes Array (NHA) systems. The studied structures have been grown by magnetron sputtering co-deposition technique; method, which working far from the thermodynamic equilibrium, allows the alloying of Au and Co and the production of a bimetallic compound can be achieved to a good extent. Our samples mainly consist of a structurally disordered ferromagnetic alloy in which segregated Co nanoparticles are dispersed and the two phases are finely intermixed. The aim of this research is mainly focused on the magnetism of these AuCo nanocomposite structures in function of both the concentration ratio between the two metals and the thickness. In addition, the study highlights how the nanostructuring process affects the overall magnetic behavior. The magnetic properties of the studied AuCo nanostructures have been investigated from both an experimental point of view and a micromagnetic point of view.
Our magnetic analyses emphasize that the investigated systems must be treated as fully-fledged composite structures and the obtained results enlarge the knowledge on nanocomposite materials in the prespective to control their overall magnetic anisotropy and, hence, the magnetization reversal process.Oggigiorno, la ricerca di sistemi nanocompositi costituiti da almeno due fasi magnetiche sta suscitando una sempre maggiore attenzione. In effetti, l’intima miscelazione di due o più fasi magnetiche a livello nanometrico può dare origine a materiali che mostrano proprietà uniche. In particolare, è possibile raggiungere un accurato controllo della anisotropia complessiva del sistema e, di conseguenza, delle sue caratteristiche isteretiche. In questo contesto, questa tesi è dedicata ad un approfondito studio delle proprietà magnetiche di nano- strutture oro-cobalto (AuCo) sia in forma di film continui che di matrici periodiche nanostrutturate (Nano Holes Arrays). Le strutture in esame sono state cresciute grazie alla tecnica del co-sputtering; metodo che, lavorando lontano dalla condizione di equilibrio termodinamico, consente di ottenere una lega di Au e Co e la produzione di un composto bimetallico può essere raggiunta in buona misura. I campioni prodotti consistono principalmente di una lega ferromagnetica strutturalmente disordinata in cui sono disperse nanoparticelle di Co e le due fasi sono finemente mescolate. Lo scopo di questa ricerca è principalmente focalizzato sull’evoluzione delle proprietà magnetiche sia in funzione del rapporto di concentrazione tra i due metalli che dello spessore. Inoltre, lo studio evidenzia come il processo di nanostrutturazione influisca sul comportamento magnetico generale. La caratterizzione magnetica è stata condotta sia da un punto di vista sperimentale che da un punto di vista micromagnetico. I nostri studi sottolineano come i sistemi investigati debbano essere considerati struttute magnetiche nanocomposite a tutti gli effetti ed i risultati ottenuti ampliano la conoscenza su questa tipologia di mate- riali nella prospettiva di controllare la loro anisotropia magnetica e, quindi, il processo di inversione della magnetizzazione.
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Zhang, Bin. « Model for coupled ferroelectric hysteresis using time fractional operators : Application to innovative energy harvesting ». Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0065/document.
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Les systèmes de récupération d’énergies basées sur les vibrations mécaniques environnantes suscitent l’intérêt depuis de nombreuses années. Augmenter l’efficacité de la conversion d'énergie est primordial, mais celle-ci pour être bien maitrisée, passe par la mise au point de modèles précis et notamment par la prise en compte des lois régissant les matériaux piézoélectriques. En effet, ces matériaux sont à la base des couplages mécano/électriques et il est capital de comprendre comment ils fonctionnent quelque soit l'excitation externe. Un modèle précis du matériau ferroélectrique est indispensable pour établir des critères de conception des prototypes et leur optimisation. Dans cette thèse, un modèle précis, temporel, large bande tenant compte de l’ensemble des non-linéarités d’une céramique piézoélectrique a été développé. L’utilisation d’opérateurs fractionnaires a permis d’augmenter fortement la bande de fréquence de validité du modèle. Le modèle permet notamment de prévoir l’évolution de la polarisation diélectrique ainsi que le déplacement mécanique de l’échantillon testé et ceci quelque soit le type de stimulation (contrainte mécanique pure, champ électrique et même excitation hybride électriques/mécaniques). La dérivé fractionnaire a dans un premier temps été utilisée pour l’hystérésis sous excitation électrique pour décrire le comportement dynamique de la polarisation diélectrique. En effet, au delà d’un seuil de fréquence, lorsque l’état du matériau n’est plus quasi-statique, une contribution dynamique apparaît. Cette contribution joue un rôle primordial lorsque les niveaux de fréquence et d’amplitude sont élevés. La même étude a ensuite été menée sous contrainte mécanique, et le même opérateur fractionnaire a été utilisé avec succès. Nous avons entre autre constaté que sur un même échantillon les paramètres de simulation établis sous champ électrique étaient conservés sous contrainte mécanique. Ensuite, un modèle inverse permettant d’imposer la forme d’onde de la polarisation ou du déplacement a été proposé. Pour une polarisation ou un déplacement donné, le modèle inverse permet de déterminer avec précision l’effort mécanique à appliquer sur la céramique piézo-électrique. Ces modèles sont nécessaires pour optimiser une forme d’onde de contrainte mécanique ou électrique et obtenir un rendement supérieur des systèmes récupérateurs d’énergie. En effet, une nouvelle technique couplée champ électrique/contrainte mécanique de récupération d’énergie est présentée à la fin de la thèse, technique qui nous a permis de valider l’utilisation du modèle. L’utilisation du modèle permet d’optimiser la mise au point d’un prototype mais également d’obtenir la valeur exacte du rendement de la méthode en rendant compte notamment des pertes diélectriques. Dans la thèse, le modèle sous ses différentes variantes est décrit de manière exhaustiveEnergy harvesting based on mechanical vibration has been a long time research topic for the last few decades. In addition to enhancing the energy conversion amount, another objective is to master and give a precise model with consideration of the disciplines of piezoelectric material behavior. A precise model for the ferroelectric material is mighty needed in the energy harvesting process, so as to give an instruction to the prototype designing and modelling optimizing. In this thesis, a model working on wide bandwidth considering the nonlinearity of the piezoceramic has been developed. The employment of the fractional derivative has broadened the usage of this model on expanded bandwidth. The model permit to predict the evolution of the dielectric polarization as well as the mechanical displacement, which has been tested on different samples under different kinds of stimulation (pure mechanical, pure electrical and hybrid of electrical and mechanical excitations). This fractional derivative factor has been first developed under electrical excitations to describe the dynamic behavior. In the development of this model to mechanical field, the fractional derivative factor was found available as well under the mechanical excitation in the same value. In the following study, an inverse of mechanical model has been developed as well. In the end, we stimulate the piezoceramic using both electrical and mechanical excitation to augment the energy harvesting amount which could become a promising method in energy harvesting field. Every model has been exhaustively demonstrated and specific measuring benches have been established to validate these models. Experiments results and simulations in different kinds of excitations (amplitudes, frequencies) for every kind of the above models have been compared. Good approximation has been acquired indicating the model has a good accuracy in describing the material property and dynamic behavior
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Liu, Min. « A Three-Dimensional Hyper-Viscoelasticity Constitutive Model for the Dynamic Response of Rubber ». University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1185546966.
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Richards, Russell Joseph. « Comparison of Linear, Nonlinear, Hysteretic, and Probabilistic MR Damper Models ». Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31447.
Texte intégralRésumé :
Magnetorheolgical (MR) fluid dampers have the capability of changing their effective damping force depending on the current input to the damper. A number of factors in the construction of the damper, as well as the properties of the fluid and the electromagnet, create a dynamic response of the damper that cannot be fully described with a static model dependent on current and velocity. This study will compare different techniques for modeling the force response of the damper in the current-velocity space.
To ensure that all the dynamic response characteristics of the damper are captured in data collection, random input signals were used for velocity and current inputs. By providing a normally distributed random signal for velocity to a shock dynamometer and a uniformly distributed random signal for current to a Lord rheonetic seat damper, the force response could be measured.
The data from this test is analyzed as a two dimensional signal, a three dimensional force plot in the current velocity plane, and as a probability density function. Four models are created to fit the data. The first is a linear model dependent solely on current. The second is a nonlinear model dependent on both current and velocity. The third model takes the nonlinear model and includes a filter that affects the force response of the model with time. Each of these three approaches are compared based on the total error in the force response and the models? ability to match the PDF of the data. Finally, a fourth model is created for the damper that improves the nonlinear model by making one parameter a probability parameter defined by a PDF calculated from the data. However, because it is a probability model, the error cannot be found through comparison to the data.Master of Science
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Köthe, Alexandra [Verfasser], et Anna [Akademischer Betreuer] Marciniak-Czochra. « Hysteresis-driven pattern formation in Reaction-diffusion-Ode models / Alexandra Köthe ; Betreuer : Anna Marciniak-Czochra ». Heidelberg : Universitätsbibliothek Heidelberg, 2013. http://d-nb.info/1177809214/34.
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MEHRPARVAR, MAHSHID. « Control Systems for Experimental Magnetic Materials Characterization Using Dynamic Preisach Models ». Thesis, KTH, Elektrisk energiomvandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160704.
Texte intégralRésumé :
The eciency of electrical machines is of major concern due to their widespread usage and the globally increasing awareness of energy consumption issues. Iron losses have a signicant impact on the total and thus researchers and manufacturers of electrical machines are developing dierent strategies in order to reduce them. The iron losses are highly dependent on the magnetic material that is used and thus it is necessary to identify its relevant characteristics. In this work, the development of a control system for inducing a pure sinusoidal magnetic ux density in the magnetic material is described. This is necessary in order to perform characterisation of the magnetic material. The main diculty is the highly non-linear and hysteretic relationship between the magnetic eld strength and the magnetic ux density. In order to mitigate the eect of the hysteresis, a mathematical inverse model was used in the control system. To nd a suitable model, an extensive study of literature was performed and discussed in this work. The Preisach model and its dynamic extension was chosen as the most suitable approach. A detailed description of both theory and implementation details is provided in this work. Furthermore, the model is validated by comparing simulation against measurement data for two dierent materials. In the last part of this work, the inverse model is combined with a controller to form a feedback control system. Two dierent control schemes are investigated: a simpler PI controller and a more elaborate disturbance observer (DOB) based control scheme. The DOB is used to observe the hysteresis inversion error and the observation is used to correct for the error. The controller's ability to produce a pure sinusoidal magnetic ux density was assessed by simulations with dierent magnetic materials at varying frequencies.Verkningsgraden for elmotorer ar av okande intresse pa grund av deras omfattande anvandning och vaxande oro for globala energiforbrukningsfragor. Jarnforluster har ett stort inytande i de totala forlusterna och ar darfor ett viktigt omrade for forskare och tillverkare av elektriska motorer. Jarnforlusterna beror till stor del av det magnetiska materialet som anvands i konstruktion av elmotorer och det ar darfor nodvandigt att identiera materialets egenskaper. I det har arbetet beskrivs utvecklingen av ett reglersystem for att inducera en ren sinusformat magnetisk odestathet i ett magnetiskt material. Detta ar nodvandigt for att kunna bestamma det magnetiska materialets egenskaper under kontrollerade forhallanden. Huvudsvarigheten ar det icke-linjara sambandet mellan magnetiska faltstyrkan och odest atheten. Sambandet formar en hysteres och for att eliminera dess inytande anvandes en matematisk invers model. For att hitta en lamplig model genomfordes en literaturstudie och Preisach modellen och dess dynamiska utokning valdes. I detta arbete nns en detaljerad beskrivning av bade teorin bakom modellen och dess implementering. Modellen utvarderades genom att jamfora matvarden med simulationsresultat for olika magnetiska material. I sista delen av detta arbete kombineras inversmodellen med ett reglerssystem for att kunna uppna en sinusformat odestathet i det magnetiska materialet. Tva olika regleralgoritmer utvarderas, en enklare PI-regulator och en regulator som inkluderar en sa kallat "Disturbance Observer" (DOB). DOB:n anvandes for att observera felet som uppstar vid invertering av hysteresen och for att korrigera felet. De bada regulatorernas formaga attaterskapa en ren sinusformat magnetisk odestathet testas genom att genomfora simulationer for olika magnetiska material vid varierande frekvenser.
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Dehghannayyeri, Atefeh. « Developing a Fluid Flow Model for Mobile Video Transmission in the Presence of Play-Out Hysteresis ». Thesis, Blekinge Tekniska Högskola, Institutionen för kommunikationssystem, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13510.
Texte intégralRésumé :
This work focuses on improving video transmission quality over a mobile link. More specifically, the impact of buffering and link outages on the freeze probability of transmitted videos is studied. It introduces a new fluid flow model that provides an approximation of the freeze probability in the presence of play-out hysteresis. The proposed model is used to study the impact of two streaming buffer sizes over different possible combinations of outage parameters (data channel on/off times). The outcome of this thesis shows that outage parameters play a dominant role in freezing of streaming video content, and that an increase in these parameters cannot be easily compensated for by an increase in the size of the receiving buffer. Generally, in most cases when there is a variation in outage parameters, an increased buffer size has a negative impact on the freeze probability. To lower the probability of freeze during video playback over a weak mobile link, it is better to sacrifice resolution just to keep the video content playing. Similarly, shifting focus from off to on times brings better results than increasing buffer size.
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Oduro, Bismark. « Mathematical Models of Triatomine (Re)infestation ». Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1458563770.
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Sheta, Hussam. « Simulation von Mehrphasenvorgängen in porösen Medien unter Einbeziehung von Hysterese-Effekten ». [S.l. : s.n.], 1999. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB12168134.
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Perry, Logan Andrew. « Sensitivity Study on Modification of Vertical Distribution of Strength and Stiffness in Wood Shear Wall Building Models ». Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/96023.
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This thesis presents a numerical study of the influence of varying story strength on the seismic performance of multi-story wood-frame shear wall buildings. In the prior FEMA P695 studies of these buildings, the non-simulated collapse limit-state was exceeded primarily in the first story. This observation raised interest in quantifying the influence of varying strength from story to story on seismic response.
In this study, four distributions of strength are used as bounding cases. The Parabolic strength distribution (1) results from the ELF vertical force distribution method in ASCE 7 that assigns forces to each level based on weight and story height. The Triangular strength distribution (2) results from an assumed vertical force distribution that assigns lateral forces based on the seismic weight at each level. The Constant strength distribution (3) results from an assumed vertical force distribution that assigns a concentrated lateral force at the uppermost level based on the total seismic weight of all levels. The Baseline distribution (4) reflects a realistic vertical strength distribution resulting from the ELF vertical force distribution method.
The FEMA P695 methodology, which quantifies seismic performance via adjusted collapse margin ratios, is employed in this study. The analytical models include P-Delta effects and utilize the 10-parameter hysteresis CASHEW model. It is observed that the Parabolic strength distribution allows for dissipation of energy over the height of the building, has less collapse risk than other strength distributions studied, and reduces occurrence of concentrated deformations in a single story from the onset of applied lateral force.MS
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Lauerer, Alexander, Philipp Zeigermann, Jörg Lenzner, Christian Chmelik, Rustem Valiullin et Jörg Kärger. « IR Micro-imaging of mesoporous silicon as a model system for the investigation of hysteresis phenomena ». Diffusion fundamentals 20 (2013) 93, S. 1-2, 2013. https://ul.qucosa.de/id/qucosa%3A13682.
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Lauerer, Alexander, Philipp Zeigermann, Jörg Lenzner, Christian Chmelik, Rustem Valiullin et Jörg Kärger. « IR Micro-imaging of mesoporous silicon as a model system for the investigation of hysteresis phenomena ». Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183825.
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Heine, Christian P. « Simulated Response of Degrading Hysteretic Joints With Slack Behavior ». Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28576.
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A novel, general, numerical model is described that is capable of predicting the load-displacement relationship up to and at failure of multiple-bolt joints in timber of various configurations. The model is not tied to a single input function and bolt holes are permitted to be drilled oversize resulting in a slack system.
The model consists of five parts. A new mathematical hysteresis model describes the stiffness of the individual bolt at each time step increment and accounts for non-linear and slack behavior; a mechanically-based structural stiffness model explains the interaction of one bolt with another bolt within a joint; an analytically-based failure model computes the stresses at each time step and initiates failure if crack length equals fastener spacing; a stochastic routine accounts for material property variation; and a heuristic optimization routine estimates the parameters needed.
The core model is a modified array of differential equations whose solution describes accurate hysteresis shapes for slack systems. Hysteresis parameter identification is carried out by a genetic algorithm routine that searches for the best-fit parameters following evolutionary principles (survival of the fittest). The structural model is a linear spring model. Failure is predicted based on a newly developed 'Displaced-Volume-Method' in conjunction with beam on elastic foundation theory, elastic theory, and a modified Tsai-Wu Failure criterion.
The devised computer model enhances the understanding of the mechanics of multiple-bolt joints in timber, and yields valid predictions of joint response of two-member multiple-bolt joints. This research represents a significant step towards the simulation of structural wood components.Ph. D.
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Ribbenfjärd, David. « A lumped element transformer model including core losses and winding impedances ». Licentiate thesis, KTH, School of Electrical Engineering (EES), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4307.
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In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be tested.
In this thesis a time-domain transformer model is presented. The model includes core losses as magnetic static hysteresis, eddy current and excess eddy current losses. Moreover, the model comprises winding losses including eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a total transformer model. This results in a detailed transformer model.
One important result of the thesis is the possibility to simulate dynamic hysteresis including the eddy current shielding in the magnetic core material. This is achieved by using Cauer circuit combined with analytical expression for static and dynamic hysteresis. Thereby, all magnetic loss components in the material can be simulated accurately. This dynamic hysteresis model is verified through experiments showing very good agreement.
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Dean, Michael C. « The Effect of Implementing a Boundary Element Cohesive Zone Model with Unloading-Reloading Hysteresis on Bulk Material Response ». The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397664062.
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Kozina, Thomas. « Using the mean field model to analyze the influence of texture on the hysteresis behaviour of silicon steels ». Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59284.
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A critical study of the Jiles and Atherton Mean Field Model was done to determine the validity of the model, a tool in describing and understanding the magnetization process in textured silicon steels.Hysteresis loops were generated using an Epstein apparatus in various directions with respect to the rolling direction and for various external magnetic fields. Techniques were then used to obtain the model parameters, namely a$ sp prime,$ $ alpha sp prime,$ and k$ sp prime.$ After creating a new version of the model, M$ sb{ rm s}$ was also obtained from the data hysteresis loops.
The model gives a close description of the influence of texture on hysteresis behaviour and predicts the variation of the parameter k$ sp prime,$ which agrees with our understanding of the role of texture in changing the parameter. We have observed that the highest value of this parameter coincides with the angles at which it is most difficult to magnetize the specimen.
The proposal of the model's creators that the main drawback of the model that the pinning parameter $k sp prime$ is not constant, is not justified by them and not supported by our analysis of experimental data.
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Six, Lancelot. « Vers un modèle de comportements de véhicules lourds en utilisant une méthode incrémentale basée sur la vérification et l'hystérésis : le modèle ArchiPL ». Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066497/document.
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Les phénomènes de congestion sont dangereux, et couteux économiquement. La compréhension de ces phénomènes est un sujet majeur ayant occupé la communauté scientifique depuis la moitié du vingtième siècle. L'approche microscopique, cherchant à reproduire les phénomènes macroscopiques grâce à la modélisation des comportements individuels, a proposé un grand nombre de modèles. Cependant, alors que la littérature a mis en avant l'impact négatif des véhicules lourds, peu se sont intéressés à savoir si les véhicules lourds ont un comportement similaire à celui des véhicules légers. Les principaux modèles considèrent que les comportements sont indifférenciés, à quelques paramètres près. Dans ces travaux, nous proposons de remettre en cause cette hypothèse. Nous proposons une démarche incrémentale, VIM4MAS, au cours de laquelle nous cherchons à identifier les principales différences entre les propriétés du comportement d'un véhicule lourd avec celle d'un véhicule léger. Cette démarche nous permet de construire un modèle de véhicules lourds en se fondant sur un modèle pré-existant de véhicules légers et en n'apportant que les modifications nécessaires. Dans le cadre de cette démarche, nous proposons également une méthode d'analyse des comportements longitudinaux fondée sur l'étude des boucles d'hystérésis. Cette méthode permet d'étudier les capacités d'anticipation des conducteurs, selon une approche boite noire. Le modèle de véhicules lourds produit, ArchiPL, montre d'une part des comportements de meilleure qualité du point de vue individuel, et d'autre part une cohérence avec la littérature existanteCongestion phenomena are a major issue modern societies have to face. Understanding them, their creation, their evolution and their real impact are major questions addressed by the scientific community since the half of the twentieth century. A large number of simulation models have been developed to reproduce and study the traffic dynamics. Among them, microscopic model are designed to reproduce macroscopic phenomena such as congestion by reproducing individual vehicles' behavior. However, despite the negative influence of large vehicles on the flow, very few models took them into account. Those vehicles are usually dealt with as any other vehicle, except for a few parameters. In this thesis, we reconsider this hypothesis and try to identify how the behavior of large vehicles differs from other vehicles' behavior. We propose the VIM4MAS development methodology to help in this process. This method is used to improve a generic vehicle's behavior model and refine it until it can reproduce the most important aspects of the large vehicles' behaviors. To understand and identify key properties of longitudinal behaviors of vehicles, we have developed an analysis methodology based on the study of hysteresis phenomena. This analysis methodology allows to highlight key properties such as anticipation capabilities of drivers. The outcome of this work is the ArchiPL model for large vehicles' behaviors. This models shows an improvement of the behaviour quality at the microscopic level, while being consistent with the literature with respect to emergent phenomena
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Schönborg, Niclas. « Development of loss models for a high-temperature superconducting tape ». Doctoral thesis, KTH, Electrical Systems, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3268.
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In the recent years significant progresses in thedevelopment of high-temperature superconductors have been made.It is realistic to believe that power applications, based onthese conductors, in a few years will become available. To beable to utilise the conductors in an optimum way, theunderstanding of their behaviour under application-likecondition is essential. One important parameter that has to beoptimised is the power loss, which means that mathematicalmodels of these losses have to be developed. In a typicalapplication the superconductor is utilised in a coilconfiguration where the actual magnetic field is considerablehigher than for a straight structure. For power frequencies thelosses are dominated by hysteresis losses and flux flowlosses.
In this thesis, mathematical models of the hysteresis andthe flux flow losses as a function of a transport current, anexternal magnetic field, the temperature and the frequency havebeen developed. The transport current and the magnetic field,which are assumed to be proportional to each other, includeboth an ac and a dc component. The models of the hysteresislosses are based on the critical state theory, and for twoidealised geometries, an infinite slab and a thin strip, newexact closed form equations have been derived. The equationsfor the two idealised geometries are then superimposed tofacilitate the description of a more realistic geometry, i.e. asuperconducting tape with a finite width and thickness. Themodel of the flux flow losses is valid for a tape shapedconductor and is based on both measurements and reasonablephysical assumptions. For the development and the validation ofthe models, a calorimetric measurement set-up has been used.From a limited number of relatively simple measurements, thedeveloped models can be adjusted to a certain superconductor,and the power losses for the actual superconductor can bepredicted in considerable more complicated cases.
Keywords:high-temperature superconductor, hysteresislosses, flux flow losses, critical state model, calorimetricmeasurements
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Chiruta, Daniel-Gabriel. « The analysis of hysteretic behavior in bistable spin transition nanomaterials and its applications towards nanoelectronics devices ». Versailles-St Quentin en Yvelines, 2014. http://www.theses.fr/2014VERS0020.
Texte intégralRésumé :
L’objectif principal de ce travail est d’appliquer des méthodes exactes (matrice de transfert) ou semi-exactes (en utilisant des simulations Monte Carlo avec l’algorithme de l’échantillonnage entropique) à l’étude du comportement des matériaux moléculaires. Nous avons utilisé le modèle type-Ising en tenant compte des interactions à courte et à longue portée afin de simuler la réponse à des effets extérieurs dans des composés à transition de spin de taille macroscopique ainsi que des tailles nanométriques. Grâce à leur bistabilité ces composés à transition de spin sont potentiellement utilisables dans la fabrication de nouveaux dispositifs (capteurs de températures et/ou de pression, stockage de l’information). Notre travail contient deux parties. La première partie, les trois premiers chapitres, est consacrée à l’état de l’art des matériaux à transition de spin (SCO) et à la description de modèles et méthodes proposés pour expliquer le phénomène de transition de spin. La deuxième partie, les 4 derniers chapitres, concerne nos études théoriques sur l’effet de la taille, la forme et l’effet des molécules en surface dans le domaine des matériaux à transition de spin. Cette thèse, dans le domaine de la Sciences des matériaux, traite à travers tous ces chapitres de deux axes. Dans un premier axe nous avons modélisé et simulé le comportement de plusieurs matériaux SCO existant en utilisant le modèle type Ising afin de comprendre le mécanisme de transition de spin. Nous avons également analysé les effets des différents facteurs extérieurs, notamment l’effet des molécules en surface, dans les composés à transition de spin avec différents types de configurations : 1D, 2D et 3D. Ayant trouvé un bon accord entre les résultats numériques et les données expérimentales, nous avons étudié de nouveaux comportements thermiques de ces matériaux à transition spin obtenus expérimentalement : transition incomplète et transition à plusieurs étapesThe main purpose of this thesis is to develop exact methods (i. E. Matrix transfer) or semi-exact methods (using Monte Carlo technique with entropic sampling algorithm) to study the behaviour of molecular materials. Using an Ising like model that takes into account both short-range and long-range interactions in Spin Crossover (SCO materials) the response resulting from the spin state switching phenomenon (from bulk materials down to nanoscale size) was simulated. SCO materials have potential applications in the fabrication of novel devices (i. E. Storing information, sensing, and display). This work contains two main parts divided in seven chapters. The first part, the first three chapters, is devoted to some overview of SCO materials and to the description of several models and methods proposed to explain the Spin Transition (ST) phenomenon while the second part, the last four chapters, is focused on some theoretical studies on size and shape effects as well as the molecules at the surface effect in the SCO area which is a new subject. This thesis, in the field of Computing Materials Science, treats two axes. In the first axe we have modeled and simulated the behaviour of several existing materials using an Ising like model in order to understand the ST mechanism and the effects of different external factors in different SCO compounds in 1D, 2D or 3D structures. From the good agreement between the numerical and the experimental data in the first part, we have studied in the second part different architectures and we have predicted some novel SCO behaviours, obtained recently experimentally, as incomplete or multi-step transition
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Ribbenfjärd, David. « Electromagnetic transformer modelling including the ferromagnetic core ». Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-13080.
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In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be assessed. In this thesis a time-domain transformer model is presented. The model includes core phenomena as magnetic static hysteresis, eddy current and excess losses. Moreover, the model comprises winding phenomena as eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a composite transformer model. This results in a detailed transformer model. One important result of the thesis is the feasibility to simulate dynamic magnetization including the inhomogeneous field distribution due to eddy currents in the magnetic core material. This is achieved by using a Cauer circuit combined with models for static and dynamic magnetization. Thereby, all magnetic loss components in the material can be simulated accurately. This composite dynamic magnetization model is verified through experiments showing very good correspondence with measurements. Furthermore, the composite transformer model is verified through measurements. The model is shown to yield good correspondence with measurements in normal operation and non-normal operations like no-load, inrush current and DC-magnetization.QC20100708
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Six, Lancelot. « Vers un modèle de comportements de véhicules lourds en utilisant une méthode incrémentale basée sur la vérification et l'hystérésis : le modèle ArchiPL ». Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066497.
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Les phénomènes de congestion sont dangereux, et couteux économiquement. La compréhension de ces phénomènes est un sujet majeur ayant occupé la communauté scientifique depuis la moitié du vingtième siècle. L'approche microscopique, cherchant à reproduire les phénomènes macroscopiques grâce à la modélisation des comportements individuels, a proposé un grand nombre de modèles. Cependant, alors que la littérature a mis en avant l'impact négatif des véhicules lourds, peu se sont intéressés à savoir si les véhicules lourds ont un comportement similaire à celui des véhicules légers. Les principaux modèles considèrent que les comportements sont indifférenciés, à quelques paramètres près. Dans ces travaux, nous proposons de remettre en cause cette hypothèse. Nous proposons une démarche incrémentale, VIM4MAS, au cours de laquelle nous cherchons à identifier les principales différences entre les propriétés du comportement d'un véhicule lourd avec celle d'un véhicule léger. Cette démarche nous permet de construire un modèle de véhicules lourds en se fondant sur un modèle pré-existant de véhicules légers et en n'apportant que les modifications nécessaires. Dans le cadre de cette démarche, nous proposons également une méthode d'analyse des comportements longitudinaux fondée sur l'étude des boucles d'hystérésis. Cette méthode permet d'étudier les capacités d'anticipation des conducteurs, selon une approche boite noire. Le modèle de véhicules lourds produit, ArchiPL, montre d'une part des comportements de meilleure qualité du point de vue individuel, et d'autre part une cohérence avec la littérature existanteCongestion phenomena are a major issue modern societies have to face. Understanding them, their creation, their evolution and their real impact are major questions addressed by the scientific community since the half of the twentieth century. A large number of simulation models have been developed to reproduce and study the traffic dynamics. Among them, microscopic model are designed to reproduce macroscopic phenomena such as congestion by reproducing individual vehicles' behavior. However, despite the negative influence of large vehicles on the flow, very few models took them into account. Those vehicles are usually dealt with as any other vehicle, except for a few parameters. In this thesis, we reconsider this hypothesis and try to identify how the behavior of large vehicles differs from other vehicles' behavior. We propose the VIM4MAS development methodology to help in this process. This method is used to improve a generic vehicle's behavior model and refine it until it can reproduce the most important aspects of the large vehicles' behaviors. To understand and identify key properties of longitudinal behaviors of vehicles, we have developed an analysis methodology based on the study of hysteresis phenomena. This analysis methodology allows to highlight key properties such as anticipation capabilities of drivers. The outcome of this work is the ArchiPL model for large vehicles' behaviors. This models shows an improvement of the behaviour quality at the microscopic level, while being consistent with the literature with respect to emergent phenomena
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Wolf, Felix [Verfasser]. « Generalisiertes Preisach-Modell für die Simulation und Kompensation der Hysterese piezokeramischer Aktoren / Felix Wolf ». München : Verlag Dr. Hut, 2014. http://d-nb.info/1063221862/34.
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Araújo, Francisco Adriano de. « Formulação de um modelo de dissipação concentrada para a análise não-linear de estruturas reticuladas planas em concreto armado ». Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-18102007-105937/.
Texte intégralRésumé :
O trabalho trata da formulação, implementação e aplicação de um modelo para análise não-linear de estruturas reticuladas planas em concreto armado, baseado no conceito simplificado de localização dos processos físicos irreversíveis (dano, plasticidade e histerese) em zonas previamente definidas denominadas rótulas que se localizam nas extremidades de um elemento finito de barra. O modelo proposto tem por objetivo reproduzir os deslocamentos residuais relacionados tanto ao comportamento plástico do concreto danificado quanto ao escoamento do aço, além de possibilitar a reprodução de laços de histerese observados experimentalmente em diagramas momento-rotação, ou equivalentemente força-deslocamento, quando a história de carregamento incluir ciclos de descarregamento e recarregamento. A formulação termodinâmica é desenvolvida fazendo-se referência as variáveis de tensão e deformação generalizadas em razão de sua aplicação no âmbito da teoria clássica de flexão de barras. Neste modelo a não-linearidade do elemento estrutural é totalmente decorrente da dissipação de energia localizada nas rótulas e é representada por três variáveis escalares a elas associadas: a variável adimensional de dano, a rotação plástica e a rotação por escorregamento, que representa o fenômeno físico do escorregamento entre as faces das microfissuras no concreto (encaixe e desencaixe dos agregados). Na fase de aplicações as respostas numéricas obtidas com a utilização do modelo proposto foram avaliadas mediante o confronto com diversos resultados experimentais disponíveis na literatura para estruturas de concreto armado sob solicitações estáticas e dinâmicas. Os resultados obtidos evidenciam o bom funcionamento do modelo no caso das solicitações estáticas, tendo sido obtidos resultados limitadamente satisfatórios no caso das solicitações dinâmicas.This work deals with the formulation, implementation and application of a model for nonlinear analysis of reinforced concrete planed frame structures, based on the simplified concept of localization of the irreversible physical processes (damage, plasticity and hysteresis) in zones previously defined called hinges which are located in the extremities of a bar finite element. The proposed model has as objective to reproduce the residual displacements related to the plastic behavior of the damaged concrete as well as to the steel yielding, moreover making possible the reproduction of hysteresis loops experimentally observed in moment-rotation diagrams, or equivalently force-displacement, when the loading history includes unloading and reloading cycles. The thermodynamic formulation is developed referring to generalized stress and deformation variables due to their application in the scope of the classic theory of bars bending. In this model the nonlinearity of the structural element is totally due to the energy dissipation in the hinges and is represented by three scalar variables associated to them: the non-dimensional damage variable, the plastic rotation and the sliding rotation, which represents the physical phenomenon of sliding between the microcracks faces in the concrete (aggregate interlocking). In the applications phase, the numerical solutions obtained with the use of the proposed model had been evaluated by confrontation with various experimental results available in the literature of reinforced concrete structures under static and dynamic solicitations. The obtained results evidence the good performance of the model in the case of static solicitations, having been obtained limited satisfactory results in the case of dynamic solicitations.
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Calik, Ertugrul Emre. « Development Of A Physical Theory Model For The Simulation Of Hysteretic Behavior Of Steel Braces ». Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608328/index.pdf.
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Bracing members are considered to be effective earthquake-resistant elements as they improve the lateral strength and stiffness of the structural system and contribute to seismic energy dissipation by deforming inelastically during severe earthquake motions. However, the cyclic behavior of such bracing members is quite complex because it is influenced by both buckling and yielding.
This thesis presents simple but an efficient analytical model that can be used to simulate the inelastic cyclic behavior of steel braces. This model achieves realism and efficiency by combining analytical formulations with some semi-empirical formulas developed on the basis of a study of experimental data. A brace is idealized as a pin-pin ended member with a plastic hinge located at mid-length of a brace Input parameters of the model are based on only material properties such as steel yield strength and modulus of elasticity as well as geometric properties including cross-sectional area, moment of inertia, etc. The obtained results are verified by the experimental and available analytical results.
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Roy, Su-Kim Delores. « Development and incorporation of a NAPL residual into the Lenhard-Parker pressure-saturation hysteretic model ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0004/MQ43347.pdf.
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Vaidya, Anirudha. « Load-Displacement Relations for an Edge-Cracked Beam with a Hysteretic Bilinear Cohesive Zone Model ». The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408958644.
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Roy, Sue-Kim Delores Carleton University Dissertation Engineering Civil and Environmental. « Development and incorporation of a NAPL residual into the Lenhard- Parker pressure-saturation hysteretic model ». Ottawa, 1999.
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Cornejo, Daniel Reinaldo. « Aplicação do Modelo de Preisach em Ímãs Nanocristalinos ». Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-30082012-153600/.
Texte intégralRésumé :
Estudamos propriedades magnéticas de ligas nano cristalinas de Sm-F e-Co. As ligas foram preparadas por mecano-síntese e posterior tratamento térmico. Como resultado, obtivemos ímãs nanocristalinos de Sm18 (Fe,Co)82 , com Sm(Fe,Co)7 como fase principal. As ligas apresentaram excelentes propriedades magnéticas: remanências relativas Mn/ Ms ~ 0.6 e coercividades na faixa 5-20 kOe, dependendo do teor de Fe nos materiais. Interações magnéticas nas ligas foram estudadas com base nos gráficos ele Henkel. Interpretamos, nestes gráficos, de maneira consistente a influência elas interações e dos estados desmagnetizados.We studied the magnetic properties of nanocrystalline Sm-Fe-Co alloys. These alloys were prepared by mechanical alloying and subsequent annealing. We obtained nanocrystalline rnagnets of composition Sm18 (Fe, Co )82 , for which the main hard magnetic phase is Sm(Fe, Co)82. The alloys showed excellent magnetic properties: relative remanence Mn/ Ms :2; 0.6 and coercive fields ranging from 5 to 20 k0e, depending upon the amount of Fe present. Henkel plots were used in order to study magnetic interactions in these alloys. The influence of the interactions and the demagnetized state on the Henkel plots was also studied.
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Vadakkeveetil, Sunish. « Analytical Modeling for Sliding Friction of Rubber-Road Contact ». Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/79596.
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Rubber friction is an important aspect to tire engineers, material developers and pavement engineers because of its importance in the estimation of forces generated at the contact, which further helps in optimizing tire and vehicle performances, and to estimate tire wear. It mainly depends on the material properties, contact mechanics and operating condition. There are two major contributions to rubber friction, due to repeated viscoelastic deformation from undulations of surface called hysteresis and due to Vander Waals interaction of the molecules called adhesion. The study focuses on analytical modeling of friction for stationary sliding of rubber block on rough surfaces. Two novel approaches are discussed and compared. Frictional shear stress is obtained from the energy dissipated at the contact interface due to the elastic deformations of rubber block at different length scales. Contact mechanics theories based on continuity approach combined with stochastic processes to estimate the real contact area, mean penetration depth and true stresses at contact depending on operating conditions. Rubber properties are highly temperature dependent. Temperature model developed based on heat diffusion relation is integrated to consider the effects of temperature rise due to frictional heating.
Model results are validated with theoretical results of literature. Simulation results of friction model is obtained for Compound A sliding on rough surface. Material properties are obtained using Dynamic Mechanical Analysis and Time temperature superposition. Influence of the friction models under different conditions are discussed. Model results are validated with experimental data from Dynamic friction tester on a 120-grit surface followed by future works.Master of Science
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Niemoczynski, Bogdan. « Nonlinear Control of Magnetic Signatures ». Master's thesis, Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/360321.
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Electrical EngineeringM.S.E.E.
Magnetic properties of ferrite structures are known to cause fluctuations in Earth's magnetic field around the object. These fluctuations are known as the object's magnetic signature and are unique based on the object's geometry and material. It is a common practice to neutralize magnetic signatures periodically after certain time intervals, however there is a growing interest to develop real time degaussing systems for various applications. Development of real time degaussing system is a challenging problem because of magnetic hysteresis and difficulties in measurement or estimation of near-field flux data. The goal of this research is to develop a real time feedback control system that can be used to minimize magnetic signatures for ferrite structures. Experimental work on controlling the magnetic signature of a cylindrical steel shell structure with a magnetic disturbance provided evidence that the control process substantially increased the interior magnetic flux. This means near field estimation using interior sensor data is likely to be inaccurate. Follow up numerical work for rectangular and cylindrical cross sections investigated variations in shell wall flux density under a variety of ambient excitation and applied disturbances. Results showed magnetic disturbances could corrupt interior sensor data and magnetic shielding due to the shell walls makes the interior very sensitive to noise. The magnetic flux inside the shell wall showed little variation due to inner disturbances and its high base value makes it less susceptible to noise. This research proceeds to describe a nonlinear controller to use the shell wall data as an input. A nonlinear plant model of magnetics is developed using a constant to represent domain rotation lag and a gain function to describe the magnetic hysteresis curve for the shell wall. The model is justified by producing hysteresis curves for multiple materials, matching experimental data using a particle swarm algorithm, and observing frequency effects. The plant model is used in a feedback controller and simulated for different materials as a proof of concept.
Temple University--Theses