Made available in DSpace on 2016-12-08T17:19:36Z (GMT). No. of bitstreams: 1 0 Capa - 1 Introducao.pdf: 288577 bytes, checksum: 440b6dcfb8697dcbdfbfecd21ba397c1 (MD5) Previous issue date: 2010-07-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work is part of a research project at UDESC, which aims to understand and compare the process of fracture of ADI with dual matrix structure, such as sites of plastic deformation concentration and crack nucleation, and paths of crack propagation. The fracture mechanisms of two types of duals ADI with different ausferrite volume fraction were compared to those of conventional ADI. Intercritical austenitising temperatures chosen were 790°C and 820°C, and resulted in dual ADI with 17% and 85% of ausferrite respectively. The full ADI, which was austenitised at 900°C, was used to serve as reference material. The three materials were austempered at 360°C for 2h. Results showed that in dual ADI with predominantly ferrite, the nucleation of cracks occurred along the interface graphite/matrix. Increasing the ausferrite volume fraction, the nucleation of cracks tended to occur along the inclusions and intercellular boundaries. Moreover, in dual ADI, the crack propagation and concentration of plastic deformation occurred preferentially in the ferrite. With respect to the fracture´s analysis, all materials showed that the quantities of fracture ductile/fragile were equivalent. The fractures had an aspect predominantly ductile, being formed mostly by dimples with some regions of quasi-cleavage. / Este trabalho faz parte de uma linha de pesquisa executada na UDESC, que visa entender e comparar o processo de fratura dos ADI duais, tais como, locais de concentração de deformação plástica e de nucleação de trincas, e caminhos de propagação de trinca. Os mecanismos de fratura de dois tipos de ADI duais com diferente fração volumétrica de ausferrita foram comparados com o ADI pleno. As temperaturas de austenitização intercrítica escolhidas foram 790°C e 820°C, e resultaram em ADI duais com 17 e 85% de ausferrita respectivamente. O ADI pleno, no qual foi austenitizado a 900°C, foi utilizado para servir de material de referência. Os três materiais foram austemperados a 360°C por 2h. Verificou-se que para o ADI dual com predominância de ferrita, a nucleação da trinca ocorreu junto à interface grafita/matriz. Conforme aumentou a fração volumétrica de ausferrita na matriz, a nucleação da trinca tendeu a ocorrer junto à inclusão intercelular e em contornos de célula. Além disso, nos ADI duais, a propagação da trinca e a concentração de deformação plástica ocorreu preferencialmente na ferrita. Vale ressaltar que os três materiais apresentaram quantidades de fratura dúctil/frágil equivalentes. As fraturas tinham uma característica predominantemente dúctil, sendo formadas na maioria por alvéolos com algumas regiões de quase-clivagem.

Made available in DSpace on 2014-12-17T14:08:55Z (GMT). No. of bitstreams: 1 NataliaMMA_DISSERT.pdf: 1277437 bytes, checksum: 8ffa9b24fa37a0e3b017eb0e4b89299d (MD5) Previous issue date: 2013-09-02 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / An economical solution for cementing oil wells is the use of pre-prepared dry mixtures containing cement and additives. The mixtures may be formulated, prepared and transported to the well where is added water to be pumped.Using this method, becomes dispensable to prepare the cement mixes containing additives in the cementing operation, reducing the possibility of error. In this way, the aim of this work is to study formulations of cement slurries containing solid additives for primary cementing of oil wells onshore for typical depths of 400, 800 and 1,200 meters. The formulations are comprised of Special Class Portland cement, mineral additions and solids chemical additives.The formulated mixtures have density of 1.67 g / cm ? (14.0 lb / gal). Their optimization were made through the analysis of the rheological parameters, fluid loss results, free water, thickening time, stability test and mechanical properties.The results showed that mixtures are in conformity the specifications for cementing oil wells onshore studied depths / Uma solu??o econ?mica para a cimenta??o de po?os de petr?leo ? o emprego de pr?- misturas secas contendo cimento e aditivos s?lidos. As misturas podem ser formuladas, preparadas e transportadas para o po?o onde ser? adicionada ?gua para bombeio. Com essa metodologia, torna-se dispens?vel a prepara??o das misturas de cimento com aditivos no ato da opera??o de cimenta??o, reduzindo a possibilidade de erro. Desta forma, o objetivo desse trabalho ? estudar formula??es de pastas de cimento contendo aditivos s?lidos para a cimenta??o prim?ria de po?os de petr?leo onshore para profundidades t?picas de 400m, 800m e 1.200 metros. As formula??es s?o constitu?das de cimento Portland Classe Especial, adi??es minerais e aditivos qu?micos s?lidos. As misturas formuladas possuem massa espec?fica de 1,67 g/cm? (14,0 lb/gal). Sua otimiza??o foi feita a partir da an?lise de resultados de reologia, comportamento de perda de fluido para a forma??o, forma??o de ?gua livre ambiente, tempo de espessamento, estabilidade da mistura e comportamento mec?nico. Os resultados mostraram que as misturas se adequam ?s especifica??es para a cimenta??o de po?os de petr?leo onshore nas profundidades estudadas

Made available in DSpace on 2014-12-17T15:04:56Z (GMT). No. of bitstreams: 1 JoaoBRS_DISSERT.pdf: 3574050 bytes, checksum: 936d245cdf0bbc662d39401341e467f4 (MD5) Previous issue date: 2011-10-20 / The present dissertation performs a study about abacus part on the continuous education of Elementary School s Mathematic teachers on what concerns the basic operations of addition and subtraction with (re)unification by using the manipulative and/or informatical abacus. Therefore, the research intends to answer the following question: How does a teacher reframe the pedagogical practice while teaching the Decimal Numeral System and the conventional operations of addition and subtraction with (re)unification through manipulative and informatical abacus? In order to do so, we rely ourselves on the Guy Brousseau s Theory of Didactic Situations (TDS) from 1996 that affirms the necessity to trace a way in accordance with the teaching situations that lead the student s learning; and on the work of Pierre L?vy (1993), in which the poles of communication oral, written and virtual create three ways of communication through which the learning process happens. The methodology of this paper was based on the Strategic Research-Action of Franco (2005). The didactic sequence was elaborated in accordance with TDS and used the manipulative and informatical abacus as didactic resource. With the application of the didactic sequence, it was verified that the continued formation of Elementary School s teachers concerning the operations of addition and subtraction on the initial years/levels is pertinent once it has been observed some difficulties of the teachers concerning this mathematical subject. Besides, the analysis of the didactic sequence has allowed one to realize that teachers had some difficulties concerning the numeric representation with order zero, the resolution of operations of addition and subtraction using the manipulative and informatical abacus and the realization of (re)unification on the subtraction with meaning. These observations has been discussed with the teachers and, after that, it has been done some didactic-methodological routings of the operations of addition and subtraction with re(unification) that contributes with the teaching and learning process. / A presente disserta??o realiza um estudo sobre o papel do ?baco na forma??o continuada dos professores de Matem?tica do Ensino Fundamental, acerca das opera??es de adi??o e subtra??o com (re) agrupamento por meio do uso do ?baco manipulativo e/ou inform?tico. Assim, a pesquisa pretende responder a seguinte quest?o: Como o professor ressignifica a sua pr?tica pedag?gica ao ensinar o Sistema de Numera??o Decimal e as opera??es convencionais de adi??o e subtra??o com (re) agrupamento por meio do ?baco manipulativo e inform?tico? Para isso, baseamo-nos na Teoria das Situa??es Did?ticas (TSD) de Guy Brousseau (1996) que afirma ser necess?rio tra?ar um caminho de acordo com as situa??es de ensino que conduza a aprendizagem dos estudantes e, no trabalho de Pierre L?vy (1993), no qual os polos da comunica??o: oral, escrito e virtual, possibilitam as tr?s maneiras de comunica??o pelas quais ocorre a aprendizagem. A metodologia do trabalho apoiou-se na Pesquisa-a??o Estrat?gica de Franco (2005). A sequ?ncia did?tica foi elaborada de acordo com a TSD e, o ?baco manipulativo e inform?tico foi usado como ferramenta did?tica. Com a aplica??o da sequ?ncia did?tica foi verificado que a forma??o continuada de professores do Ensino Fundamental, nas s?ries/anos iniciais a respeito das opera??es de adi??o e subtra??o com (re) agrupamento ? pertinente, visto que foram observadas algumas dificuldades dos professores sobre esse conte?do matem?tico. Al?m disso, a an?lise da sequ?ncia did?tica permitiu perceber que as professoras tinham dificuldade: na representa??o num?rica com a ordem zero, na resolu??o das opera??es de adi??o e subtra??o utilizando o ?baco manipulativo e/ou inform?tico e na realiza??o do (re) agrupamento na subtra??o com significado. Tais observa??es foram discutidas com as professoras, ap?s a discuss?o, foram realizados encaminhamentos did?tico-metodol?gicos das opera??es de adi??o e subtra??o com (re) agrupamento que contribuem com o processo de ensino e aprendizagem.

The efficiency of the conventional, explicit finite difference time domain (FDTD)method is constrained by the upper limit on the temporal discretization, imposed by the Courant–Friedrich–Lewy (CFL) stability condition. Therefore, there is a growing interest in overcoming this limitation by employing unconditionally stable FDTD methods for which time-step and space-step can be independently chosen. Unconditionally stable Crank Nicolson method has not been widely used in time domain electromagnetics despite its high accuracy and low anisotropy. There has been no work on the Crank Nicolson FDTD (CN–FDTD) method for frequency dependent medium. In this thesis a new three-dimensional frequency dependent CN–FDTD (FD–CN–FDTD) method is proposed. Frequency dependency of single–pole Debye materials is incorporated into the CN–FDTD method by means of an auxiliary differential formulation. In order to provide a convenient and straightforward algorithm, Mur’s first-order absorbing boundary conditions are used in the FD–CN–FDTD method. Numerical tests validate and confirm that the FD–CN–FDTD method is unconditionally stable beyond the CFL limit. The proposed method yields a sparse system of linear equations which can be solved by direct or iterative methods, but numerical experiments demonstrate that for large problems of practical importance iterative solvers are to be used. The FD–CN–FDTD sparse matrix is diagonally dominant when the time-stepis near the CFL limit but the diagonal dominance of the matrix deteriorates with the increase of the time-step, making the solution time longer. Selection of the matrix solver to handle the FD–CN–FDTD sparse system is crucial to fully harness the advantages of using larger time-step, because the computational costs associated with the solver must be kept as low as possible. Two best–known iterative solvers, Bi-Conjugate Gradient Stabilised (BiCGStab) and Generalised Minimal Residual (GMRES), are extensively studied in terms of the number of iteration requirements for convergence, CPU time and memory requirements. BiCGStab outperforms GMRES in every aspect. Many of these findings do not match with the existing literature on frequency–independent CN–FDTD method and the possible reasons for this are pointed out. The proposed method is coded in Fortran and major implementation techniques of the serial code as well as its parallel implementation in Open Multi-Processing (OpenMP) are presented. As an application, a simulation model of the human body is developed in the FD–CN–FDTD method and numerical simulation of the electromagnetic wave propagation inside the human head is shown. Finally, this thesis presents a new method modifying the frequency dependent alternating direction implicit FDTD (FD–ADI–FDTD) method. Although the ADI–FDTD method provides a computationally affordable approximation of the CN–FDTD method, it exhibits a loss of accuracy with respect to the CN-FDTD method which may become severe for some practical applications. The modified FD–ADI–FDTD method can improve the accuracy of the normal FD–ADI–FDTD method without significantly increasing the computational costs.

Los juegos serios colaborativos tienen un impacto positivo en el comportamiento y el aprendizaje, pero siguen desarrollándose para plataformas tecnológicas tradicionales como videoconsolas y ordenadores de sobremesa o portátiles, los cuales han sido identificados como sub-óptimos para niños en diversos estudios. En su lugar, el uso de dispositivos móviles como tabletas y teléfonos inteligentes presenta diversas ventajas: son económicamente asequibles, están ampliamente distribuidos, y pueden ser transportados, lo cual permite la actividad física y poder iniciar un juego sin necesitar que los usuarios se trasladen a una localización fija, especialmente dedicada para tal fin. Además, combinar varios de estos dispositivos y coordinar la interacción entre ellos en lo que se denomina Entorno Multi-Pantalla (EMP) proporciona beneficios adicionales para la colaboración tales como una mayor escalabilidad, conciencia del espacio de trabajo, paralelismo y fluidez de las interacciones. La interacción en estos entornos multi-tableta es por tanto un aspecto crítico. Los dispositivos móviles están diseñados para ser interactuados mediante el toque de los dedos principalmente, lo cual es muy sencillo y directo, pero está normalmente limitado a la pequeña dimensión de las pantallas, lo que puede conllevar la oclusión de la pantalla y la infrautilización del espacio periférico. Por esta razón, esta tesis se centra en la exploración de otro mecanismo de interacción que puede complementar al táctil: interacciones tangibles alrededor del dispositivo. Las interacciones tangibles están basadas en la manipulación de objetos físicos, lo que presenta un valor adicional en la educación de los niños puesto que resuena con los manipulativos educativos tradicionales y permite la exploración del mundo físico. Por otra parte, la explotación del espacio que envuelve a las pantallas tiene diversos beneficios adicionales para actividades educativas colaborativas: reducida oclusión de la pantalla (lo cual puede incrementar la conciencia del espacio de trabajo), el uso de objetos tangibles como contenedores de información digital que puede ser transportada de forma continua entre dispositivos, y la identificación de un determinado estudiante a través de la codificación de su ID en un operador tangible (lo cual facilita el seguimiento de sus acciones y progreso durante el juego). Esta tesis describe dos enfoques distintos para construir juegos educativos colaborativos en EMPs utilizando interacciones tangibles alrededor de los dispositivos. Una, denominada MarkAirs, es una solución óptica aérea que no necesita ningún hardware adicional aparte de las tabletas excepto diversas tarjetas de cartón impresas. La otra, Tangibot, introduce un robot tangiblemente controlado y otro atrezo físico en el entorno, y se basa en tecnología RFID. Ambas interacciones son respectivamente evaluadas, y se observa que MarkAirs es usable y poco exigente tanto para adultos como para niños, y que se pueden realizar con éxito gestos de grano fino encima de las tabletas con ella. Además, al aplicarse en juegos colaborativos, puede ayudar a reducir la oclusión de las pantallas y la interferencia entre las distintas acciones de los usuarios, lo cual es un problema que puede surgir en este tipo de escenarios cuando solamente se dispone de interacciones táctiles. Se evalúa un juego educativo colaborativo con MarkAirs con niños de educación primaria, y se concluye que este mecanismo es capaz de crear experiencias de aprendizaje colaborativo y de presentar un valor añadido en términos de experiencia de usuario, aunque no en eficiencia. Con respecto a Tangibot, se muestra que controlar colaborativamente un robot móvil mediante unas palas tangibles con cierta precisión es factible para niños a partir de los tres años de edad, e incluso para personas mayores con un deterioro cognitivo leve. Además, proporciona una experiencia divertida / Collaborative serious games have a positive impact on behavior and learning, but the majority are still being developed for traditional technological platforms, e.g., video consoles and desktop/laptop computers, which have been deemed suboptimal for children by several studies. Instead, the use of handheld devices such as tablets and smartphones presents several advantages: they are affordable, very widespread, and mobile---which enables physical activity and being able to engage in a game without requiring users to gather around a fixed, dedicated, location. Plus, combining several of these devices and coordinating interactions across them in what is called a Multi-Display Environment (MDE) brings on additional benefits to collaboration like higher scalability, awareness, parallelism, and fluidity of the interaction. How to interact with these multi-tablet environments is therefore a critical issue. Mobile devices are designed to be interacted mainly via touch, which is very straightforward but usually limited to the small area of the displays, which can lead to the occlusion of the screen and the underuse of the peripheral space. For this reason, this thesis focuses on the exploration of another interaction mechanism that can complement touch: tangible around-device interactions. Tangible interactions are based on the manipulation of physical objects, which have an added value in childhood education as they resonate with traditional learning manipulatives and enable the exploration of the physical world. On the other hand, the exploitation of the space surrounding the displays has several potential benefits for collaborative-learning activities: reduced on-screen occlusion (which may increase workspace awareness), the use of tangible objects as containers of digital information that can be seamlessly moved across devices, and the identification of a given student through the encoding of their ID in a tangible manipulator (which facilitates the tracking of their actions and progress throughout the game). This thesis describes two different approaches to build collaborative-learning games for MDEs using tangible around-device interactions. One, called MarkAirs, is a mid-air optical solution relying on no additional hardware besides the tablets except for several cardboard printed cards. The other, Tangibot, introduces a tangible-mediated robot and other physical props in the environment and is based on RFID technology. Both interactions are respectively evaluated, and it is observed that MarkAirs is usable and undemanding both for adults and for children, and that fine-grained gestures above the tablets can be successfully conducted with it. Also, when applied to collaborative games, it can help reduce screen occlusion and interference among the different users' actions, which is a problem that may arise in such settings when only touch interactions are available. A collaborative learning game with MarkAirs is evaluated with primary school children, revealing this mechanism as capable of creating collaborative learning experiences and presenting an added value in user experience, although not in performance. With respect to Tangibot, we show how collaboratively controlling a mobile robot with tangible paddles and achieving certain precision with it is feasible for children from 3 years of age, and even for elderly people with mild cognitive impairment. Furthermore, it provides a fun experience for children and maintains them in a constant state of flow. / Els jocs seriosos col·laboratius tenen un impacte positiu en el comportament i l'aprenentatge, però continuen sent desenvolupats per a plataformes tecnològiques tradicionals com videoconsoles i ordinadors de sobretaula o portàtils, els quals han sigut identificats com sub-òptims per a xiquets en diversos estudis. D'altra banda, l'ús de dispositius mòbils com ara tabletes i telèfons intel·ligents presenta diversos avantatges: són econòmicament assequibles, estan àmpliament distribuïts i poden ser transportats, la qual cosa permet l'activitat física i poder iniciar un joc sense necessitat de què els usuaris es traslladen a una localització fixa i especialment dedicada per a eixa finalitat. A més, combinar diversos d'estos dispositius i coordinar la interacció entre ells en el que es denomina Entorn Multi-Pantalla (EMP) proporciona beneficis addicionals per a la col·laboració tals com una major escalabilitat, consciència de l'espai de treball, paral·lelisme i fluïdesa de les interaccions. La interacció amb estos entorns multi-tableta és per tant crítica. Els dispositius mòbils estan dissenyats per a ser interactuats mitjançant tocs de dit principalment, mecanisme molt senzill i directe, però està normalment limitat a la reduïda dimensió de les pantalles, cosa que pot ocasionar l'oclusió de la pantalla i la infrautilització de l'espai perifèric. Per aquesta raó, la present tesi se centra en l'exploració d'un altre mecanisme d'interacció que pot complementar al tàctil: interaccions tangible al voltant dels dispositius. Les interaccions tangibles estan basades en la manipulació d'objectes físics, cosa que presenta un valor addicional en l'educació dels xiquets ja que ressona amb els manipulatius tradicionals i permet l'exploració del món físic. D'altra banda, l'explotació de l'espai que envolta a les pantalles té diversos beneficis addicionals per a activitats educatives col·laboratives: reduïda oclusió de la pantalla (la qual cosa pot incrementar la consciència de l'espai de treball), l'ús d'objectes tangibles com a contenidors d'informació digital que pot ser transportada de forma continua entre dispositius, i la identificació d'un estudiant determinat a través de la codificació de la seua identitat en un operador tangible (cosa que facilita el seguiment de les seues accions i progrés durant el joc). Aquesta tesi descriu dos enfocaments distints per a construir jocs educatius col·laboratius en EMPs utilitzant interaccions tangibles al voltant dels dispositius. Una, denominada MarkAirs, és una solució òptica aèria que no precisa de cap maquinari addicional a banda de les tabletes, exceptuant diverses targetes de cartró impreses. L'altra, Tangibot, introdueix un robot controlat tangiblement i attrezzo físic addicional en l'entorn, i es basa en tecnologia RFID. Ambdues interaccions són avaluades respectivament, i s'observa que MarkAirs és usable i poc exigent tant per a adults com per a xiquets, i que es poden realitzar gestos de granularitat fina dalt de les tabletes amb ella. A més a més, en aplicar-se a jocs col·laboratius, pot ajudar a reduir l'oclusió de les pantalles i la interferència entre les distintes accions dels usuaris, problema que pot aparèixer en este tipus d'escenaris quan solament es disposa d'interaccions tàctils. S'avalua un joc educatiu col·laboratiu amb MarkAirs amb xiquets d'educació primària, i es conclou que aquest mecanisme és capaç de crear experiències d'aprenentatge col·laboratiu i de presentar un valor afegit en termes d'experiència d'usuari, tot i que no en eficiència. Respecte a Tangibot, es mostra que controlar conjuntament un robot mòbil mitjançant unes pales tangibles amb certa precisió és factible per a xiquets a partir de tres anys i inclús per a persones majors amb un lleu deteriorament cognitiu. A més, proporciona una experiència divertida per als xiquets i els manté en un estat constant de flow. / García Sanjuan, F. (2018). CREAME: CReation of Educative Affordable Multi-surface Environments [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/101942 / TESIS

The numerical treatment of linear-quadratic regulator problems for parabolic partial differential equations (PDEs) on infinite time horizons requires the solution of large scale algebraic Riccati equations (ARE). The Newton-ADI iteration is an efficient numerical method for this task. It includes the solution of a Lyapunov equation by the alternating directions implicit (ADI) algorithm in each iteration step. On finite time intervals the solution of a large scale differential Riccati equation is required. This can be solved by a backward differentiation formula (BDF) method, which needs to solve an ARE in each time step. Here, we study the selection of shift parameters for the ADI method. This leads to a rational min-max-problem which has been considered by many authors. Since knowledge about the complete complex spectrum is crucial for computing the optimal solution, this is infeasible for the large scale systems arising from finite element discretization of PDEs. Therefore several alternatives for computing suboptimal parameters are discussed and compared for numerical examples.

The numerical solution of Stein (aka discrete Lyapunov) equations is the primary step in Newton's method for the solution of discrete-time algebraic Riccati equations (DARE). Here we present a low-rank Smith method as well as a low-rank alternating-direction-implicit-iteration to compute low-rank approximations to solutions of Stein equations arising in this context. Numerical results are given to verify the efficiency and accuracy of the proposed algorithms.

Gerade in Hinblick auf die Kombination aus hervorragender Festigkeit, relativ guter Zähigkeit und Dauerfestigkeit sowie beachtlicher Verschleißbeständigkeit macht bainitisches Gusseisen mit Kugelgrafit und dabei besonders das ADI (Austempered Duktile Iron) durch sein ausferritisches Gefüge seine Vorteile gegenüber Gusseisenwerkstoffen insbesondere Gusseisen mit Kugelgraphit und auch Stahlguss deutlich. Die konventionelle Herstellung von ADI erfolgt über ein Austenitisieren und ein anschließendes Abschrecken und Halten im Salzbad. Die Salzbadbehandlung stellt einen technologisch und ökologisch problematischen Prozess dar. Im Rahmen dieser Arbeit wurde im Labormaßstab eine neue Technologie, die auf dem Einfluss des Nickels auf die Martensitstarttemperatur des Gusseisens und auf seinen zahlreichen positiven Wirkungen basiert, zur alternativen Herstellung von ausferritischem Gusseisen mit Kugelgraphit erforscht. Des Weiteren wurde der Einfluss von erhöhten Nickelzusätzen auf die mechanischen Eigenschaften des nach konventioneller Wärmebehandlung im Salzbad hergestellten bainitischen Gusseisens mit Kugelgraphit untersucht. Als Ergebnis ergibt sich eine deutliche Reduzierung der Ms-Temperatur bis unter 100°C und damit die Möglichkeit einfacher, wirtschaftlicher und ökologischer Fertigung. Jedoch zeigte sich auch ein Einfluss des Nickels auf die erreichbaren Eigenschaften, der ggf. für die Anwendung berücksichtigt werden muss.

This dissertation concerns the model reduction of linear periodic descriptor systems both in continuous and discrete-time case. In this dissertation, mainly the projection based approaches are considered for model order reduction of linear periodic time varying descriptor systems. Krylov based projection method is used for large continuous-time periodic descriptor systems and balancing based projection technique is applied to large sparse discrete-time periodic descriptor systems to generate the reduce systems. For very large dimensional state space systems, both the techniques produce large dimensional solutions. Hence, a recycling technique is used in Krylov based projection methods which helps to compute low rank solutions of the state space systems and also accelerate the computational convergence. The outline of the proposed model order reduction procedure is given with more details. The accuracy and suitability of the proposed method is demonstrated through different examples of different orders. Model reduction techniques based on balance truncation require to solve matrix equations. For periodic time-varying descriptor systems, these matrix equations are projected generalized periodic Lyapunov equations and the solutions are also time-varying. The cyclic lifted representation of the periodic time-varying descriptor systems is considered in this dissertation and the resulting lifted projected Lyapunov equations are solved to achieve the periodic reachability and observability Gramians of the original periodic systems. The main advantage of this solution technique is that the cyclic structures of projected Lyapunov equations can handle the time-varying dimensions as well as the singularity of the period matrix pairs very easily. One can also exploit the theory of time-invariant systems for the control of periodic ones, provided that the results achieved can be easily re-interpreted in the periodic framework. Since the dimension of cyclic lifted system becomes very high for large dimensional periodic systems, one needs to solve the very large scale periodic Lyapunov equations which also generate very large dimensional solutions. Hence iterative techniques, which are the generalization and modification of alternating directions implicit (ADI) method and generalized Smith method, are implemented to obtain low rank Cholesky factors of the solutions of the periodic Lyapunov equations. Also the application of the solvers in balancing-based model reduction of discrete-time periodic descriptor systems is discussed. Numerical results are given to illustrate the effciency and accuracy of the proposed methods.

The thesis is focused on assessment of fatigue behaviour of austempered ductile iron with nodular graphite. Optimal period of transformation was determined based on the best combination of stress and strain characteristics established by tensile test. Cyclic response and low-cycle fatigue life were studied under both stress-control and longitudinal strain-control mode at room temperature. For both modes, shapes of cyclic hardening curves are dependent on stress amplitude. Cyclic deformation curves (CDC) were fitted by power regression function. Results were compared with CDC established by multiple step test in both modes with verification of the influence of cyclic creep (high stress levels, stress-control mode). Experimental data of S-N curves are in agreement with the Manson-Coffin and the Basquin law. Fatigue and cyclic parameters were compared. Fatigue life time in high-cycle fatigue region was determined. Experimental data were fitted by suitable regression functions. Regression parameters and fatigue limit were established by means of each regression function. Experimental data in low- and high-cycle fatigue regions were used to construct S-N curve and to determine relevant parameters. Discontinuity of experimental data was not observed. Low-cycle fatigue behaviour was predicted. Approximation of tolerance bands was realized in high-cycle and both high and low cycle fatigue regions.