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The increasing global energy demand calls for attention on renewable energy development. Among the available technology, the photovoltaic (PV) panels is a popular solution. Thus, targeted Power Conditioning Systems (PCSs) are drawing increased attention in research. Microconverter is one of the PCS that can support versatile applications in various power line architectures. This work focuses on the comparison of circuit secondary side architectures for LLC converter for microconverter application. As the research foundation, general characteristic of solar energy and PV panel operation are introduced for the understanding of the needs. Previous works are referenced and compared for advantages and limitation. Base on conventional secondary resonant full bridge LLC converter, the two sub-topologies of different secondary rectification network: active, full bridge secondary and active voltage doubler output end LLC converter are presented in detail. The main operating principle is also described in mathematical formula with the corresponding cycle-by-cycle operation to ensure the functional equality before proceeding to performance comparison. Circuit efficiency analysis is conducted on the main power stage and the key components with frequency consideration. The hardware circuit achieved the designed function while the overall hardware efficiency result agrees with analysis. In the implementation, the transformer is costume built for the system pacification. Another part is the parasitic effect analysis. At a high operating frequency and to achieve very high-frequency operation, parasitic effect need to be fully understood and considered as it may have the dominating effect on the system. / Master of Science / With the increasing demand for electric energy in today's world while the traditional natural energy recourses such as coals running towards depletion, renewable energy sources become an important alternative. Among them, solar energy is an option with easy access and convenient utilization. The photovoltaic (PV) panel requires matching Power Conditioning Systems (PCS) for connection and adaptation. Microconverter is one of the PCS that can support versatile applications in various power line architectures. This work focuses on different sub-circuitry for PV application under LLC converter category, which is a popular and effective solution for renewable energy dc-dc power conversion. First, the research background is studied, which lays the ground for the utilization of LLC converter for PV application. Then the topology under study is presented in detail. In this work, the foundation of variation is based on secondary resonant full bridge LLC converter. For verification of functionality, the step-by-step operational breakdown are listed for the two verification proposed of different secondary topology. The efficiency analysis and performance verification are conducted on the given circuitry. Then the analog testing board is built and tested while the result agrees with the analysis. A few additional topics regarding detail of the system is discussed at more length. One is the magnetic component design, which is the key part for stable and efficient system operation; another is the parasitic effect, as at such high frequency and efficiency range, the parasitic effect become significant for the circuit performance.

[EN] The test for determining the resonance frequencies has traditionally been used to investigate the mechanical integrity of concrete cores, to assess the conformity of concrete constituents in different accelerated durability tests, and to ascertain constitutive properties such as the elastic modulus and the damping factor. This nondestructive technique has been quite appealed for evaluation of mechanical properties in all kinds of durability tests. The damage evolution is commonly assessed from the reduction of dynamic modulus which is produced as a result of any cracking process. However, the mechanical behavior of concrete is intrinsically nonlinear and hysteretic. As a result of a hysteretic stress-strain behavior, the elastic modulus is a function of the strain. In dynamic tests, the nonlinearity of the material is manifested by a decrease of the resonance frequencies, which is inversely proportional to the excitation amplitude. This phenomenon is commonly referred as fast dynamic effect. Once the dynamic excitation ceases, the material undergoes a relaxation process whereby the elastic modulus is restored to that at rest. This phenomenon is termed as slow dynamics. These phenomena (fast and slow dynamics) find their origin in the internal friction of the material. Therefore, in cement-based materials, the presence of microcracks and interfaces between its constituents plays an important role in the material nonlinearity. In the context of the assessment of concrete durability, the damage evolution is based on the increase of hysteresis, as a result of any cracking process. In this thesis three different nondestructive techniques are investigated, which use impacts for exciting the resonant frequencies. The first technique consists in determining the resonance frequencies over a range of impact forces. The technique is termed Nonlinear Impact Resonant Acoustic Spectroscopy (NIRAS). It consists in ascertaining the downward resonant frequency shift that the material undergoes upon increasing excitation amplitude. The second technique consists in investigating the nonlinear behavior by analyzing the signal corresponding to a single impact. This is, to determine the instantaneous frequency, amplitude and attenuation variations corresponding to a single impact event. This technique is termed as Nonlinear Resonant Acoustic Single Impact Spectroscopy (NSIRAS). Two techniques are proposed to extract the nonlinear behavior by analyzing the instantaneous frequency variations and attenuation over the signal ring down. The first technique consists in discretizing the frequency variation with time through a Short-Time Fourier Transform (STFT) based analysis. The second technique consists of a least-squares fit of the vibration signals to a model that considers the frequency and attenuation variations over time. The third technique used in this thesis can be used for on-site evaluation of structures. The technique is based on the Dynamic Acousto- Elastic Test (DAET). The variations of elastic modulus as derived through NIRAS and NSIRAS techniques provide an average behavior and do not allow derivation of the elastic modulus variations over one vibration cycle. Currently, DAET technique is the only one capable to investigate the entire range of nonlinear phenomena in the material. Moreover, unlike other DAET approaches, this study uses a continuous wave source as probe. The use of a continuous wave allows investigation of the relative variations of the elastic modulus, as produced by an impact. Moreover, the experimental configuration allows one-sided inspection. / [ES] El ensayo de determinación de las frecuencias de resonancia ha sido tradicionalmente empleado para determinar la integridad mecánica de testigos de hormigón, en la evaluación de la conformidad de mezclas de hormigón en diversos ensayos de durabilidad, y en la terminación de propiedades constitutivas como son el módulo elástico y el factor de amortiguamiento. Esta técnica no destructiva ha sido ampliamente apelada para la evaluación de las propiedades mecánicas en todo tipo de ensayos de durabilidad. La evolución del daño es comúnmente evaluada a partir de la reducción del módulo dinámico, producido como resultado de cualquier proceso de fisuración. Sin embargo, el comportamiento mecánico del hormigón es intrínsecamente no lineal y presenta histéresis. Como resultado de un comportamiento tensión-deformación con histéresis, el módulo elástico depende de la deformación. En ensayos dinámicos, la no linealidad del material se manifiesta por una disminución de las frecuencias de resonancia, la cual es inversamente proporcional a la amplitud de excitación. Este fenómeno es normalmente denominado como dinámica rápida. Una vez la excitación cesa, el material experimenta un proceso de relajación por el cual, el módulo elástico es restaurado a aquel en situación de reposo. Este fenómeno es denominado como dinámica lenta. Estos fenómenos ¿dinámicas rápida y lenta¿ encuentran su origen en la fricción interna del material. Por tanto, en materiales basados en cemento, la presencia de microfisuras y las interfaces entre sus constituyentes juegan un rol importante en la no linealidad mecánica del material. En el contexto de evaluación de la durabilidad del hormigón, la evolución del daño está basada en el incremento de histéresis, como resultado de cualquier proceso de fisuración. En esta tesis se investigan tres técnicas diferentes las cuales utilizan el impacto como medio de excitación de las frecuencias de resonancia. La primera técnica consiste en determinar las frecuencias de resonancia a diferentes energías de impacto. La técnica es denominada en inglés: Nonlinear Impact Resonant Acoustic Spectroscopy (NIRAS). Ésta consiste en relacionar el detrimento que el material experimenta en sus frecuencias de resonancia, con el aumento de la amplitud de la excitación. La segunda técnica consiste en investigar el comportamiento no lineal mediante el análisis de la señal correspondiente a un solo impacto. Ésta consiste en determinar las propiedades instantáneas de frecuencia, atenuación y amplitud. Esta técnica se denomina, en inglés, Nonlinear Single Impact Resonant Acoustic Spectroscopy (NSIRAS). Se proponen dos técnicas de extracción del comportamiento no lineal mediante el análisis de las variaciones instantáneas de frecuencia y atenuación. La primera técnica consiste en la discretización de la variación de la frecuencia con el tiempo, mediante un análisis basado en Short-Time Fourier Transform (STFT). La segunda técnica consiste en un ajuste por mínimos cuadrados de las señales de vibración a un modelo que considera las variaciones de frecuencia y atenuación con el tiempo. La tercera técnica empleada en esta tesis puede ser empleada para la evaluación de estructuras in situ. La técnica se trata de un ensayo acusto-elástico en régimen dinámico. En inglés Dynamic Acousto-Elastic Test (DAET). Las variaciones del módulo elástico obtenidas mediante los métodos NIRAS y NSIRAS proporcionan un comportamiento promedio y no permiten derivar las variaciones del módulo elástico en un solo ciclo de vibración. Actualmente, la técnica DAET es la única que permite investigar todo el rango de fenómenos no lineales en el material. Por otra parte, a diferencia de otras técnicas DAET, en este estudio se emplea como contraste una onda continua. El uso de una onda continua permite investigar las variaciones relativas del módulo elástico, para una señal transito / [CA] L'assaig de determinació de les freqüències de ressonància ha sigut tradicionalment empleat per a determinar la integritat mecànica de testimonis de formigó, en l'avaluació de la conformitat de mescles de formigó en diversos assajos de durabilitat, i en la terminació de propietats constitutives com són el mòdul elàstic i el factor d'amortiment. Esta tècnica no destructiva ha sigut àmpliament apel·lada per a l'avaluació de les propietats mecàniques en tot tipus d'assajos de durabilitat. L'evolució del dany és comunament avaluada a partir de la reducció del mòdul dinàmic, produït com resultat de qualsevol procés de fisuración. No obstant això, el comportament mecànic del formigó és intrínsecament no lineal i presenta histèresi. Com resultat d'un comportament tensió-deformació amb histèresi, el mòdul elàstic depén de la deformació. En assajos dinàmics, la no linealitat del material es manifesta per una disminució de les freqüències de ressonància, la qual és inversament proporcional a l'amplitud d'excitació. Este fenomen és normalment denominat com a dinàmica ràpida. Una vegada l'excitació cessa, el material experimenta un procés de relaxació pel qual, el mòdul elàstic és restaurat a aquell en situació de repòs. Este fenomen és denominat com a dinàmica lenta. Estos fenòmens --dinámicas ràpida i lenta troben el seu origen en la fricció interna del material. Per tant, en materials basats en ciment, la presència de microfissures i les interfícies entre els seus constituents juguen un rol important en la no linealitat mecànica del material. En el context d'avaluació de la durabilitat del formigó, l'evolució del dany està basada en l'increment d'histèresi, com resultat de qualsevol procés de fisuración. En esta tesi s'investiguen tres tècniques diferents les quals utilitzen l'impacte com a mitjà d'excitació de les freqüències de ressonància. La primera tècnica consistix a determinar les freqüències de ressonància a diferents energies d'impacte. La tècnica és denominada en anglés: Nonlinear Impact Resonant Acoustic Spectroscopy (NIRAS). Esta consistix a relacionar el detriment que el material experimenta en les seues freqüències de ressonància, amb l'augment de l'amplitud de l'excitació. La segona tècnica consistix a investigar el comportament no lineal per mitjà de l'anàlisi del senyal corresponent a un sol impacte. Esta consistix a determinar les propietats instantànies de freqüència, atenuació i amplitud. Esta tècnica es denomina, en anglés, Nonlinear Single Impact Resonant Acoustic Spectroscopy (NSIRAS). Es proposen dos tècniques d'extracció del comportament no lineal per mitjà de l'anàlisi de les variacions instantànies de freqüència i atenuació. La primera tècnica consistix en la discretización de la variació de la freqüència amb el temps, per mitjà d'una anàlisi basat en Short-Time Fourier Transform (STFT). La segona tècnica consistix en un ajust per mínims quadrats dels senyals de vibració a un model que considera les variacions de freqüència i atenuació amb el temps. La tercera tècnica empleada en esta tesi pot ser empleada per a l'avaluació d'estructures in situ. La tècnica es tracta d'un assaig acusto-elástico en règim dinàmic. En anglés Dynamic Acousto-Elastic Test (DAET). Les variacions del mòdul elàstic obtingudes per mitjà dels mètodes NIRAS i NSIRAS proporcionen un comportament mitjà i no permeten derivar les variacions del mòdul elàstic en un sol cicle de vibració. Actualment, la tècnica DAET és l'única que permet investigar tot el rang de fenòmens no lineals en el material. D'altra banda, a diferència d'altres tècniques DAET, en este estudi s'empra com contrast una ona contínua. L'ús d'una ona contínua permet investigar les variacions relatives del mòdul elàstic, per a un senyal transitori. A més, permet la inspecció d'elements per mitjà de l'accés per una sola cara. / Eiras Fernández, JN. (2016). Studies on nonlinear mechanical wave behavior to characterize cement based materials and its durability [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/71439 / Premios Extraordinarios de tesis doctorales

Ce travail présente l’optimisation d’un système de spectroscopie Raman résolue en temps dédiée aux très hautes températures. Ce dispositif répond au besoin sans cesse croissant d’étudier en temps réels les transformations de phases et des cinétiques de réactions dans des environnements extrêmes. Ce dispositif a été validé dans des conditions d’usages sur des oxydes (Gd₂O3, Y₂O3, ZrO₂ , ZrSiO4 et CeO₂) et des nitrures (h-BN). Le potentiel du système a permis de lever les principaux verrous technologiques et instrumentaux qui limitent l’utilisation de la spectroscopie Raman à haute température. Les trois principaux faits marquants qui illustrent le caractère innovant de ce travail sont les suivants : Le premier correspond au nouveau record mondial d’analyse Raman à haute température à travers l’acquisition du mode E₂g de h-BN jusqu’à 2700°C. La comparaison des performances des deux voies Pockels et ICCD montrent que la voie Pockels est plus performante que l’ICCD, mais plus délicate de mise en oeuvre. Le second fait marquant concerne les autres applications du Raman résolu en temps, comme pour séparer la contribution de la diffusion Raman et de la luminescence. La dernière application quant à elle présente l’étude de la dépendance temporelle comparée des diffusions Raman résonnante et non résonante. Le Raman résonnant se déclenche systématiquement avant le non résonnant. Plus généralement, l’intérêt des méthodes Raman résolues en temps ouvre de nouveaux champs d’application dans la caractérisation de matériaux en condition extrêmes, éventuellement in situ : aéronautique, réfractaire ; sidérurgie, nucléaire, etc… / This work presents the optimization of a time-resolved Raman spectroscopy device dedicated to very high temperatures. This device meets the ever-increasing need to study in real time phase transformations and reaction kinetics in extreme environments. This device has been validated under working conditions on oxides (Gd₂O3, Y₂O3, ZrO₂ , ZrSiO4 et CeO₂) and nitrides (h-BN). The potentialities of the device have enabled the main technological and instrumental locks that limit the use of high temperature Raman spectroscopy to be removed. The three main highlights illustrating the innovative nature of this work are as follows. The first corresponds to the new world record for high temperature Raman analysis through the acquisition of the E₂g mode of h-BN up to 2700°C.A comparison of the performance of the two Pockels and ICCD channels shows that the Pockels channel is more efficient than the ICCD, but more difficult to implement. The second important fact concerns the other applications of time-resolved Raman, as to separate the contribution of Raman scattering and luminescence. The last application presents the study of the comparative time dependence of resonant and non-resonant Raman scattering. The resonant Raman is triggered systematically before the non-resonant. More generally, the interest of time-resolved Raman methods opens new fields of application in the characterization of materials in extreme conditions, possibly in situ: aeronautics, refractories, steel industry, nuclear, etc....

In the investigation of correlated electron systems which are characterized by strong spin-orbit coupling, one of the central challenges is the description of the complex interplay of different microscopic energy scales and the elucidation of its influence on the formation of exotic electronic phases like complex ordering phenomena and superconductivity. In the present thesis, exemplary three case studies of iridium-based compounds are presented, in which the effects of such an interplay have been investigated employing state-of-the-art synchrotron-based techniques. The particular focus is set on experimental possibilities to influence this equilibrium utilizing external parameters. In the first study, magnetic excitations are investigated in iridate double perovskites, which exhibit a nonmagnetic ground state. Upon increasing the influence of kinetic contributions, the potential condensation of these excitations is predicted to drive a novel kind of magnetic transitions, called ’excitonic magnetism’. A comprehensive investigation of the dynamics of these excitations via resonant inelastic x-ray scattering allows for an estimation of the relevant energy scales. These results indeed reveal that the influence of kinetic contributions is too small to drive such a transition under ambient conditions. Therefore the influence of excitonic magnetism on the macroscopic properties of the investigated compounds can be excluded. In the second case, the development of a new experimental setup is presented, facilitating the investigation of complex ordering phenomena at low temperatures as a function of pressure via resonant elastic x-ray scattering. This setup has been developed and implemented as part of this work in strong collaboration with the staff of the beamline P09 at the synchrotron PETRAIII (DESY). The functionality of this setup has been illustrated by measurements of the resonant magnetic x-ray scattering in the spin-orbit coupled Mott-insulator Sr 2IrO4. Since the magnetic ground state and magnetic order in iridates result from a complex interplay of different microscopic energy scales, these systems are particularly susceptible to external influences like hydrostatic pressure. In the third case, structural phase transitions are investigated in the iridium-based dichalcogenide IrTe2. Despite the macroscopic itinerant properties of IrTe2, the phase transitions are characterized by the formation of strongly localized states. These transitions have been investigated in the course of this work using single crystal x-ray diffraction experiments as a function of hydrostatic pressure and temperature. The presented experimental data show that these strongly localized states are stabilized with increasing pressure, which is observed as an increased density of Ir-Ir dimer bonds.

Gegenstand dieser Dissertation ist die Etablierung des Elastizitätsmoduls als Parameter, der qualitative Aussagen über den Schädigungszustand des Baustoffs Straßenbeton ermöglicht. Zu diesem Zweck erfolgte eine systematische Ermüdung von labormaßstäblichen Betonprobekörpern bei zeitgleicher Messung des Elastizitätsmoduls mit Hilfe von unterschiedlichen Verfahren. Im ersten Schritt wurde ein Versuchsprogramm entwickelt, mit dem Probekörper mittels des Spaltzug-Schwellversuchs gezielt in einen definierten Ermüdungszustand versetzt werden können. Hierfür wurde der Parameter des Grenz-Elastizitätsmoduls definiert, welcher, wenn er unterschritten wird, zum Pausieren des Versuchs führt. In diesen systematisch eingehaltenen Lastpausen erfolgten begleitende Untersuchungen der Ultraschalllaufzeit und der Eigenfrequenz zur Bestimmung des Elastizitätsmoduls der Probekörper während des Ermüdungsvorganges. Es zeigt sich zwischen den Ergebnissen aller untersuchten Verfahren eine sehr gute Synchronität hinsichtlich des qualitativen ermüdungsbedingten Verlaufs des Elastizitätsmoduls. Die vier angewandten Verfahren, die sich voneinander unabhängiger physikalischer Phänomene bedienen, ermöglichen neben einer qualitativen Aussage über die Schädigung des Materials die Bestimmung von Absolutwerten des Elastizitätsmoduls. Je nach verwendetem Verfahren weichen die absoluten Elastizitätsmoduln leicht voneinander ab. Der Elastizitätsmodul bestätigt sich als geeigneter Parameter zur Beschreibung der Degradation des Baustoffs Straßenbeton im Zuge des Ermüdungsprozesses. Im zweiten Schritt wurden der Einfluss längerer Lastpausen sowie die Verminderung der Betonfestigkeit im Zuge der Materialermüdung tiefergehend untersucht. Es wurde festgestellt, dass längere Lastpausen in der zyklischen Belastung einen signifikanten Einfluss auf den ermüdungsbedingten Verlauf des Elastizitätsmoduls haben können. Weiterhin legen die Untersuchungen nahe, dass es im Zuge einer starken Ermüdung zu einer zum Teil signifikanten Verminderung der Festigkeit kommt. Als Resultat der Untersuchungen konnten sowohl ein Verfahren zur Bestimmung charakteristischer Verläufe für die Verminderung des Elastizitätsmoduls als auch ein Verfahren zur Abschätzung der materialspezifischen Verminderung der Festigkeit im Zuge der Ermüdung entwickelt werden. Diese Verfahren könnten zukünftig den Regelwerken der RSO Beton und der RDO Beton zugeführt werden, um die ermüdungsbedingte zeitliche Entwicklung des Elastizitätsmoduls und der Festigkeit in den durch die Regelwerke festgeschriebenen Prognose- und Dimensionierungsprozessen zu berücksichtigen. Durch die Einbeziehung zeitlich veränderlicher Werte im Prognoseverfahren, welches als Grundlage für die RSO Beton dienen soll, wird in dieser Dissertation exemplarisch gezeigt, dass die Berücksichtigung der Auswirkungen der Betonermüdung auf diese für die Prognose und die Dimensionierung von Betonfahrbahnbefestigungen sehr relevanten Parameter zur signifikanten Erhöhung der Ausfallrate gegenüber der Verwendung konstanter Werte führen kann. / The subject of this doctoral dissertation is the establishment of the elastic modulus as a parameter that enables qualitative statements about the state of damage of the concrete pavement building material. For this purpose, a systematic fatigue of laboratory-scale concrete specimens was carried out with simultaneous measurement of the elastic modulus by means of different methods. In the first step, a test program was developed for the targeted and systematic fatigue of concrete specimens by means of the cyclic indirect tensile test. For this purpose, a limit value for the elastic modulus was defined. When the elastic modulus fell below the limit, the test was paused to perform accompanying investigations of the ultrasonic transit time and the natural frequency in order to determine the change of the elastic modulus of the specimens during the fatigue process. There is a very good synchronicity between the results of all investigated methods for the qualitative determination of the elastic modulus. The four methods applied, which make use of physical phenomena that are independent of each other, allow, in addition to a qualitative statement about the damage to the material, the determination of absolute values of the elastic modulus. Although there are slight differences between the methods for the determination of the elastic modulus, it is confirmed as a suitable parameter for describing the degradation of the concrete pavement building material in the course of the fatigue process. In the second step, the influence of longer loading pauses and the reduction of concrete strength due to material fatigue were investigated in more detail. It was found that longer loading pauses during cyclic loading can have a significant influence on the fatigue-related course of the elastic modulus. Furthermore, the investigations suggest that in the course of severe fatigue there is a sometimes significant reduction in strength. As a result of the investigations, both a method for determining characteristic curves for the reduction of the elastic modulus and a method for estimating the material-specific reduction of strength in the course of fatigue could be developed. In the future, these methods could be implemented into the RSO Beton and RDO Beton regulations in order to take into account the fatigue-related temporal development of the elastic modulus and the strength in the forecasting and dimensioning processes specified by the regulations. By including time-varying values in the forecasting procedure, which is to serve as the basis for the RSO Beton, this doctoral dissertation exemplifies that the consideration of the effects of concrete fatigue on these very relevant parameters for the forecasting and dimensioning of concrete pavements, can lead to the significant increase of the failure rate compared to the use of constant values.

The protection of plasma facing components from heat and particle overloads is paramount to ensure the operability and desired lifetime of magnetic fusion devices. The possibility of using external 3D magnetic perturbations to improve the steady-state heat exhaust in diverted tokamaks has been studied in this thesis. This approach involves producing a controlled stochastic region in the plasma edge without significantly affecting the core of the plasma. Using field line tracing and 3D advection-diffusion heat transport models, the resulting magnetic and heat flux footprints on the divertor have been analyzed. An optimized configuration has been obtained, which reveals the potential of this approach for considerably reducing the peak heat load on the divertor. / Att skydda plasmakomponenter mot höga värmeflöden och snabba partiklar är av största vikt föratt säkerställa funktionsduglighet och önskad livslängd för en magnetisk fusionsreaktor. Möjlighetenatt använda externa 3D-magnetiska störningar för förbättrad statisk värmeavledningeni tokamaker med magnetiska avledare har studerats i denna avhandling. Tillvägagångssättetinnebär att man producerar en kontrollerad stokastisk region i plasmakanten utan att väsentligtpåverka plasmakärnan. Med hjälp av fältlinjespårning och 3D-modellering av värmetransportsom en advektions-diffusionsprocess har de resulterande magnetiska fotspåren och värmeflödetpå avledaren analyserats. En optimerad konfiguration har erhållits, vilket visar potentialen i dettatillvägagångssätt för att avsevärt minska den maximala värmebelastningen på avledaren.

This thesis addresses the investigation of doubly excited 2l´nl states in helium atoms and double core excitations in solid lithium compounds. Measurements on He are made in field free environments and under the influence of electric and magnetic fields, using synchrotron based inelastic photon scattering. Cross sections for scattering to singly excited final states are directly determined and compared to theoretical results and are found to be in excellent agreement. Radiative and spin-orbit effects are quantified and are shown to play an important role in the overall characterization of highly excited He states below the N =2 threshold. A dramatic electric field dependence is also observed in the flourecence yield already for relatively weak fields. This signal increase, induced by electric as well as magnetic fields, is interpreted in terms of mixing with states of higher fluorescence branching ratios. Double core excitations at the lithium site in solid lithium compounds are investigated using resonant inelastic x-ray scattering (RIXS). The lithium halides LiF, LiCl, LiBr and LiI are studied as well as the molecular compounds Li2O, Li2CO3 and LiBF4. States with one, as well as both, of the excited electrons localized at the site of the bare lithium nucleus are identified, and transitions which involve additional band excitations are observed. A strong influence of the chemical surrounding is found, and it is discussed in terms of the ionic character of the chemical bond.

In order to develop more economical and ecologically friendly transformers it is necessary to know the losses throughout the product development process. There are several losses related to transformers, but in this particular case the focus will be on the resistive loss of the transformer. In order to measure this loss first the resonant frequency of the transformer is determined. Since at resonance the secondary side of the transformer is considered to be purely resistive. The aim of this paper is to design and build a closed loop measurement system that is able to perform this task.

This thesis studies a new class of high gain planar resonant cavity antennas based on metamaterial surfaces. High-gain planar antennas are becoming increasing popular due to their significant advantages (e.g. low profile, small weight and low cost). Metamaterial surfaces have emerged over the last few years as artificial structures that provide properties and functionalities not readily available from existing materials. This project addresses novel applications of innovative metamaterial surfaces on the design of high-gain planar antennas. A ray analysis is initially employed in order to describe the beamfonning action of planar resonant cavity antennas. The phase equations of resonance predict the possibility of low-profile/subwavelength resonant cavity antennas and tilted beams. The reduction of the resonant cavity profile can be obtained by virtue of novel metamaterial ground planes. Furthermore, the EBG property of metamaterial ground planes would suppress the surface waves and obtain lower backlobes. By suppressing the TEM mode in a resonant cavity, a novel aperture-type EBG Partially Reflective Surface (PRS) is utilized to get low sidelobes in both planes (E-plane and H-plane) in a relatively finite structure. The periodicity optimization of PRS to obtain a higher maximum directivity is also investigated. Also it is shown that antennas with unique tilted beams are achieved without complex feeding mechanism. Rectangular patch antennas and dipole antennas are employed as excitations of resonant cavity antennas throughout the project. Three commercial electromagnetic simulation packages (Flomerics Microstripes ™ ver6.S, Ansoft HFSSTM ver9.2 and Designer ™ ver2.0) are utilized during the rigorous numerical computation. Related measurements are presented to validate the analysis and simulations.