The comprehension of the viscoelastic behaviour of metals is of high interest as these materials are subjected to dynamic loads in most of their structural applications, and also because it enables a deeper understanding of several technologically essential properties, like mechanical damping and yielding. Thus, research on this field is needed not only because it may lead to new potential applications of metals, but also because predictability of the fatigue response may be greatly enhanced. Indeed, fatigue is the consequence of microstructural effects induced in a material under dynamic loading, while the viscoelastic behaviour is also intimately linked to the microstructure. Accordingly, the characterization of the viscoelastic response of a material offers an alternative method for analysing its microstructure and ultimately its fatigue behaviour. This research is aimed at the identification, characterization and modelling of the effects of temperature, excitation frequency and microstructure/phase transformations (when present) on the viscoelastic behaviour of aluminium alloys AA 7075-T6 and AA 2024-T3, and of pure aluminium in the H24 temper. The identification of the mechanical relaxation processes taking place and the relation between the viscoelastic response of AA 7075-T6 and AA 2024-T3 and the fatigue behaviour will be attempted for all these materials. Finally, we intend to investigate possible influences of the dynamic loading frequency on fatigue, and especially the existence of a threshold frequency marking the transition from a static-like response of the material to the advent of fatigue problems. AA 7075-T6 and AA 2024-T3 were selected for this study because these alloys are key representatives of their important families and are highly suitable to a number of industrial applications in the aerospace sector and transport industry. Pure aluminium was selected because of the inherent interest of this metal, for comparison purposes and for discussing the phenomena observed for the alloys. To accomplish the objectives, the viscoelastic response of the materials was measured experimentally with a Dynamic- Mechanical Analyser (DMA). The results were combined with Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC). An analytical model was proposed which fits the storage modulus up to 300 ºC. The model takes into account the effect of temperature, the excitation frequency and the concentration of some precipitates for the alloys. This allows us to test models proposed for the reaction rates of the associated microstructural transformations, to determine their kinetic parameters and to characterize their influence on the viscoelastic behaviour, showing that the DMA is a good tool for studying the material microstructure, phase transformation kinetics and the influence of transformations on the viscoelastic properties of materials. The Time-Temperature Superposition (TTS) principle has been successfully applied to the DMA data, providing master curves for the storage and loss moduli. Also, it is proposed that the decrease of yield and fatigue strength with temperature observed in some aluminium alloys may be due to the internal friction increase with temperature. Finally, the existence of a threshold frequency is suggested, below which materials subjected to dynamic loading exhibit a static-like, elastic response, such that creep mechanisms dominate and deterioration due to fatigue may be neglected. A procedure to estimate this transition frequency is proposed. / La comprensión del comportamiento visco-elástico de los metales es de gran interés ya que estos están sometidos a cargas dinámicas en la mayoría de sus aplicaciones estructurales, y también porque posibilita un conocimiento más profundo de varias propiedades esenciales tecnológicamente, como el amortiguamiento mecánico y el límite elástico. Así, la investigación en este campo es necesaria no sólo porque puede conducir hacia nuevas aplicaciones potenciales de los metales, sino también porque la capacidad de predecir el comportamiento en fatiga de los mismos puede verse ampliamente mejorada. De hecho, la fatiga de los metales es consecuencia de efectos microestructurales inducidos en el material bajo cargas dinámicas, y el comportamiento visco-elástico está también íntimamente relacionado con la microestructura. Así, la caracterización de la respuesta visco-elástica de un material ofrece un método alternativo para analizar su microestructura y, en último término, su respuesta en fatiga. Este trabajo tiene por objetivos la identificación, caracterización y modelización de los efectos de la temperatura, la frecuencia de excitación y la microestructura/transformaciones de fase en el comportamiento visco-elástico de las aleaciones de aluminio AA 7075-T6 y AA 2024-T3, y de aluminio puro en estado H24. Se aborda también la identificación de los procesos de relajación mecánicos que tienen lugar en estos materiales y la identificación de la relación entre el comportamiento visco-elástico de AA 7075-T6 y 2024-T3 y su respuesta en fatiga. Finalmente, se intentará investigar posibles influencias de la frecuencia de la carga dinámica en la fatiga, y en especial la existencia de una frecuencia umbral que marque la transición desde una respuesta cuasi-estática del material hacia la aparición de problemas de fatiga. AA 7075-T6 y AA 2024-T3 fueron seleccionadas porque son representantes clave de sus importantes familias de aleaciones, y son altamente adecuadas para un gran número de aplicaciones en los sectores aeroespacial y del transporte. El aluminio puro fue seleccionado para este estudio por su interés inherente, y para realizar comparaciones y discutir algunos de los fenómenos observados en las aleaciones. Para cumplir los objetivos, el comportamiento visco-elástico de los materiales fue medido experimentalmente con un Dynamic-Mechanical Analyser (DMA). Los resultados se combinaron con microscopía electrónica y calorimetría. Se propuso un modelo analítico que ajusta la componente real del módulo elástico dinámico (el storage modulus) hasta 300 ºC. El modelo toma en consideración los efectos de la temperatura, la frecuencia de la carga dinámica y la concentración de ciertos precipitados para el caso de las aleaciones. Esto permitió testear modelos propuestos para las velocidades de reacción de las transformaciones microestructurales asociadas, determinar sus parámetros cinéticos y caracterizar su influencia en el comportamiento visco-elástico, demostrando que el DMA es una buena herramienta para estudiar la microestructura del material, la cinética de las transformaciones de fase y la influencia de las transformaciones en las propiedades visco-elásticas de los materiales. El principio de superposición de tiempo y temperatura ha sido aplicado con éxito, proporcionando curvas maestras para las componentes del módulo elástico dinámico. Asimismo, se sugiere que el descenso en el límite elástico y la resistencia a fatiga con la temperatura observado en algunas aleaciones de aluminio puede ser debido al incremento de la fricción interna con la temperatura. Finalmente, se propone la existencia de una frecuencia umbral, por debajo de la cual los materiales sometidos a cargas dinámicas exhiben una respuesta cuasi-estática y elástica, de tal modo que mecanismos de termofluencia son dominantes y el deterioro del material debido a fatiga puede ser despreciado. Se propone un procedimiento para estimar esta frecuencia de transición.

Automotive embedded systems used much in the main body control system. Also because the system needs to meet functional requirement, environment requirement, timing requirement, interface requirement and Failure Mode and Effects Analysis (FMEA) so it is necessary to have an automotive embedded systems modeling methodology. Therefore, this study proposes an automotive embedded systems modeling methodology which combines MDA and UML, and detailed description of the model diagram used by each modeling phase and the diagram modeling method and steps. System development team can be clearly implemented in accordance with the methods and steps for automotive embedded system modeling. The methodology also can be used as the communication standard of the system development team. Systems modeling during system modular can promote module reuse rate in order to enhance the efficiency of system development. The methodology of this study is based on design science research methods, usability evaluation of the modeling methodology is implemented for the modeling of demand for Parking aid control unit, the PIM modeling and code conversion. With prove the availability of this modeling methodology. From the results of the assessment system development team can be based on the methodology of modeling methods and procedures to express the results in line with the needs and systems analysis and design of automotive embedded systems and convert the system operating platform and code.

This study has three main objectives. First, it provides a theoretical framework that challenges the mainstream approaches to allow for a new reading of the Cyprus Question. Second, it identifies continuities, transformations and tendencies within different historical periods by analyzing the positions of the various actors and the international conjecture in order to offer a correct reading of all previous settlement proposals and indicate the basis on which perceptions and policies were constructed and why the latter failed repeatedly to resolve the Cyprus issue. Continuities are those factors that created the continuum of the crisis and were concretely reflected in the successive failures of different peace talks, plans and initiatives / examining these means analyzing the hegemonic projects of the various actors involved. Examining transformations means looking specifically at how and why these hegemonic projects changed. Examining tendencies means pointing out the latest developments such as accumulated sovereignty, shared sovereignty as protectorate, Taiwan Model, return to 1960, integration through class strategy and independent TRNC and exploring the logical consequences of developments. Third, this study focuses on the European Union&rsquo / s hegemonic projects related to Cyprus &ndash / how they emerged, the relationship between these projects and the domestic and international political conjectures, their aspects of continuity and reasons for transformation and their successes and failures. This thesis argues that all the previous plans and initiatives by international and local actors, latest being the EU-initiated Annan Plan, led not only to failure, but transformed the Cyprus Question from one paradigm to another.

Porous TiNi alloys (Ti-50.4 at. %Ni and Ti-50.6 at. %Ni) with porosities in the range 21%-81% were prepared successfully applying a new powder metallurgy fabrication route in which magnesium was used as space holder resulting in either single austenite phase or a mixture of austenite and martensite phases dictated by the composition of the starting prealloyed powders but entirely free from secondary brittle intermetallics, oxides, nitrides and carbonitrides. Magnesium vapor do not only prevents secondary phase formation and contamination but also provides higher temperature sintering opportunity preventing liquid phase formation at the eutectic temperature, 1118 &deg / C resulting from Ni enrichment due to oxidation. By two step sintering processing (holding the sample at 1100 &deg / C for 30 minutes and subsequently sintering at temperatures higher than the eutectic temperature, 1118 &deg / C) magnesium may allow sintering probably up to the melting point of TiNi. The processed alloys exhibited interconnected (partially or completely depending on porosity content) open macro-pores spherical in shape and irregular micro-pores in the cell walls resulting from incomplete sintering. It has been found that porosity content of the foams have no influence on the phase transformation temperatures while deformation and oxidation are severely influential. Porous TiNi alloys displayed excellent superelasticity and shape memory behavior. Space holder technique seems to be a promising method for production of porous TiNi alloys. Desired porosity level, pore shape and accordingly mechanical properties were found to be easily adjustable.

Application of optimization techniques for determining the optimal operating policy for reservoirs is a major title in water resources planning and management. Genetic algorithms, ruled by evolution techniques, have become popular for solving optimization problems in diversified fields of science. The main aim of this research was to explore the efficiency and effectiveness of the applicability of genetic algorithm in optimization of multi-reservoirs. A computer code has been constructed for this purpose and verified by means of a reference problem with a known global optimum. Three reservoirs in the Colorado River Storage Project were optimized for maximization of energy production. Besides, a real-time approach utilizing a blend of online and a posteriori data was proposed. The results achieved were compared to the real operational data and genetic algorithms were found to be effective, competitive and can be utilized as an alternative technique to other traditional optimization techniques.

Entanglement is a special correlation of the quantum states of two or more particles. It is also a useful resource enabling us to complete tasks that cannot be done by classical means. As a result, the transformation of entangled states of distant particles by local means arose as an important problem in quantum information theory. In this thesis, we first review some of the studies done on the entanglement transformations. We also develop the necessary and sufficient conditions for the deterministic transformation of W-type states.

There has been a recent interest in the model-based development approach in the modeling and simulation community. The Model-Driven Architecture (MDA) of OMG envisions a fully model-based development process where models are created for capturing not only requirements, but also designs and implementations. Domain-specific metamodels and model transformations constitute the cornerstones of this approach. We have developed transformations from the data part of Field Artillery (FA) domain models to High Level Architecture (HLA) Object Model Template (OMT) models, honoring the MDA philosophy. In the MDA terminology, the former corresponds to the CIM (Computation-Independent Model) or, arguably, PIM (Platform-Independent Model), and the latter corresponds to the PSM (Platform-Specific Model), where the platform is HLA. As a case study for the source metamodel, we have developed a metamodel for the data model part of the (observed) fire techniques of the FA domain. All of the entities in the metamodel are derived from the NATO&rsquo / s Command and Control Information Exchange Data Model (C2IEDM) elements.

Effect of stress-assisted aging on stress induced martensitic transformation in hot-rolled Ni-rich 50.7at. Ni%-Ti alloy has been investigated. Alloys are aged freely and under 20 MPa, 100 MPa, and 200 MPa stress at 400 o C for 90 minutes. Aging procedure affected both stress-induced and thermally induced transformation behavior. Superelasticity behavior is correlated with the multistep transformation in aged Ni-rich NiTi alloys and the aging stress level is found to be effective. Relative to the free aged alloy, the alloy aged under 20 MPa exhibited a slight and the alloy aged under 100 MPa exhibited a considerable reduction, whereas the alloy aged under 200 MPa exhibited an increase in the critical transformation stress. DSC studies have shown that the transformation is multistep for freely aged and aged under 20 MPa alloys, whereas it is single step and two-step for alloys aged under 100 MPa and 200 MPa, respectively, and this has been attributed to the effect of stress on nucleation and growth rates. As a result of the different response mechanisms to the applied stress upon loading during superelasticity testing, the recovered strain amounts varied considerably depending on the aging conditions and the test temperatures.

It is of great importance for a materials scientist both from fundamental and applicability aspects to have better understanding of solid-state phase transformations and its kinetics responsible for micro-/nano-structure development in alloys and corresponding physical and mechanical properties. Transformation kinetics can be analyzed by various experimental techniques such as thermal analysis, laborious electron microscopy combined with extensive image analysis or by measuring changes in electrical resistivity, specimen volume and relative intensities of diffraction lines caused by the phase transformation. Beyond these conventional techniques, this dissertation provides a novel magnetic monitoring approach to study the isothermal kinetics of phase transformations in multicomponent alloy systems involving measurable changes in overall magnetic moment as the transformation proceeds. This dissertation focuses on understanding the microstructural evolution, macro- and micro-alloying behavior, magnetic properties, thermal characteristics, mechanical properties and kinetics of solid-state transformations, i.e. nanoscale precipitation and nanocrystallization, in nickel aluminides and Fe-based bulk amorphous alloys. Microstructural characterization of alloys was done by X-ray diffraction, scanning electron microscopy and transmission electron microcopy techniques. Magnetic properties were analyzed by vibrating sample magnetometry whereas thermal characteristics were evaluated by differential scanning calorimetry. Mechanical properties of alloys were determined by microhardness measurements and compression tests. The influence of Fe macroalloying and 3d transition metal microalloying on the microstructure and properties of Ni-Al-Fe alloys were studied for as-cast and annealed states and it is shown that desired microstructure and related properties can be obtained by proper selection of the type and concentration of macro- or micro-alloying elements together with an appropriate annealing procedure. Thermomagnetic characterization reveals the nanoscale precipitation of a ferromagnetic second phase with annealing. In conjunction with saturation magnetization dependence on annealing, an optimum temperature is identified where nanoscale precipitates impart the highest extent of precipitation strengthening. The isothermal kinetics of ferromagnetic second phase precipitation reveals invariant Avrami exponents close to unity, indicating that nanoscale precipitation is governed by a diffusion-controlled growth process with decreasing growth rate, which closely resembles continuous precipitation kinetics. Appropriate annealing of the Fe-based bulk amorphous alloy precursor produced by suction casting demonstrated extremely fine microstructures containing uniformly distributed and densely dispersed nanocrystals inside a residual amorphous matrix. In order to have better understanding of nanocrystallization mechanisms, kinetic parameters were determined via isothermal magnetic monitoring and non-isothermal differential scanning calorimetry where excellent agreement was obtained in Avrami exponent and activation energy. Analyzing the local kinetics, the nanocrystalline phase was found to evolve through distinct transformation regimes during annealing which were discussed on the basis of transformation kinetics theory and microscopical investigations on each characteristic transformation regime.

This thesis addresses four topics in the area of applied harmonic analysis. First, we show that the affine densities of separable wavelet frames affect the frame properties. In particular, we describe a new relationship between the affine densities, frame bounds and weighted admissibility constants of the mother wavelets of pairs of separable wavelet frames. This result is also extended to wavelet frame sequences. Second, we consider affine pseudodifferential operators, generalizations of pseudodifferential operators that model wideband wireless communication channels. We find two classes of Banach spaces, characterized by wavelet and ridgelet transforms, so that inclusion of the kernel and symbol in appropriate spaces ensures the operator is Schatten p-class. Third, we examine the Schatten class properties of pseudodifferential operators. Using Gabor frame techniques, we show that if the kernel of a pseudodifferential operator lies in a particular mixed modulation space, then the operator is Schatten p-class. This result improves existing theorems and is sharp in the sense that larger mixed modulation spaces yield operators that are not Schatten class. The implications of this result for the Kohn-Nirenberg symbol of a pseudodifferential operator are also described. Lastly, Fourier integral operators are analyzed with Gabor frame techniques. We show that, given a certain smoothness in the phase function of a Fourier integral operator, the inclusion of the symbol in appropriate mixed modulation spaces is sufficient to guarantee that the operator is Schatten p-class.