The combination of X-ray imaging and diffraction techniques provides a unique tool for structural and mechanical analysis of engineering components. A variety of modes can be employed in terms of the spatial resolution (length-scale), time resolution (frequency), and the nature of the physical quantity being interrogated. This thesis describes my contributions towards the development of novel X-ray “rich” imaging experimental techniques and data interpretation. The experimental findings have been validated via comparison with other experimental methods and numerical modelling. The combination of fast acquisition rate and high penetration properties of X-ray beams allows the collection of high-resolution 3-D tomographic data sets at submicron resolution during in situ deformation experiments. Digital Volume Correlation analysis tools developed in this study help understand crack propagation mechanisms in quasi-brittle materials and elasto-plastic deformation in co-sprayed composites. For the cases of crystalline specimens where the knowledge of “live” or residual elastic strain distributions is required, diffraction techniques have been advanced. Diffraction Strain Tomography (DST) allows non-destructive reconstruction of the 2-D (in-plane) variation of the out-of-plane strain component. Another diffraction modality dubbed Laue Orientation Tomography (LOT), a grain mapping approach has been proposed and developed based on the translate-rotate tomographic acquisition strategy. It allows the reconstruction of grain shape and orientation within polycrystalline samples, and provides information about intragranular lattice strain and distortion. The implications of this method have been thoroughly investigated. State-of-the-art engineering characterisation techniques evolve towards scrutinising submicron scale structural features and strain variation using the complementarity of X-ray imaging and diffraction. The first successful feasibility study is reported of in operando stress analysis in an internal combustion engine. Finally, further advancement of ‘rich’ imaging techniques is illustrated via the first successful application of Time-of-Flight Neutron Diffraction Strain (TOF-NDST) tomography for non-destructive reconstruction of the complete strain tensor using an inverse eigenstrain formulation.

Novel semiconductor nanostructures possess a range of notable properties that have the potential to be harnessed in the next generation of optical devices. Electron microscopy is uniquely suited to characterising the complex microstructure, the results of which may be related to the growth conditions and optical properties. This thesis investigates three such novel materials: (1) GaN/InGaN core/shell nanowires, (2) n-GaN/InGaN/p-GaN core/multi-shell microrods and (3) Zn₃N₂ nanoparticles, all of which were grown at Sharp Laboratories of Europe. GaN nanowires were grown by a Ni-catalysed VLS process and were characterised by various techniques before and after InGaN shells were deposited by MOCVD. The majority of the core wires were found to have the expected wurtzite structure and completely defect free – reflected in the strong strain-free photoluminescence peak –with a- and m- axis orientations identified with shadow imaging. A small component, <5%, were found to have the cubic zinc-blende phase and a high density of planar faults running the length of the wires. The deposited shells were highly polycrystalline, partially attributed to a layer of silicon at the core shell interface identified through FIB lift-out of cross section samples, and accordingly the PL was very broad likely due to recombination at defects and grain boundaries. A high throughput method of identifying the core size indirectly via the catalyst particle EDX signal is described which may be used to link the shell microstructure to core size in further studies. An n-GaN/InGaN/p-GaN shell structure was deposited by MOCVD on the side walls of microrods etched from c-axis GaN film on sapphire, which offers the possibility of achieving non-polar junctions without the issues due to non-uniformity found in nanowires. Threading dislocations within the core related to the initial growth on sapphire were shown to be confined to this region, therefore avoiding any harmful effect on the junction microstructure. The shell defect density showed a surprising relationship to core size with the smaller diameter rods having a high density of unusual 'flag' defects in the junction region whereas the larger diameter sample shells appeared largely defect free, suggesting the geometry of the etched core has an impact on the strain in the shell layers. The structure of unusual 'flag' defects in the m-plane junctions was characterised via diffraction contrast TEM, weak beam and atomic resolution ADF STEM and were shown to consist of a basal plane stacking faults meeting a perfect or partial dislocation loop on a pyramidal plane, the latter likely gliding in to resolve residual strain due to the fault formed during growth. Zn₃N₂ has the required bandgap energy to be utilised as a phosphor with the additional advantage over conventional materials of its constituent elements not being toxic or scarce. The first successful synthesis of Zn₃N₂ nanoparticles appropriate to this application was confirmed via SAD, EDX and HRTEM, with software developed to fit experimental polycrystalline diffraction patterns to simulated components suggesting a maximum Zn₃N₂ composition of ~30%. There was an apparent decrease in crystallinity with decreasing particle size evidenced in radial distribution function studies with the smallest particles appearing completely amorphous in 80kV HRTEM images. A rapid change in the particles under the electron beam was observed, characterised by growth of large grains of Zn₃N₂ and ZnO which increased with increasing acceleration voltage suggesting knock-on effects driving the change. PL data was consistent with the bandgap of Zn₃N₂ blue shifted from 1.1eV to around 1.8eV, confirming the potential of the material for application as a phosphor.

This thesis presents a research project in the field of oxygen system fire safety relating to the heterogeneous burning of iron in normal gravity and reduced gravity. Fires involving metallic components in oxygen systems often occur, with devastating and costly results, motivating continued research to improve the safety of these devices through a better understanding of the burning phenomena. Metallic materials typically burn in the liquid phase, referred to as heterogeneous burning. A review of the literature indicates that there is a need to improve the overall understanding of heterogeneous burning and better understand the factors that influence metal flammability in normal gravity and reduced gravity. Melting rates for metals burning in reduced gravity have been shown to be higher than those observed under similar conditions in normal gravity, indicating that there is a need for further insight into heterogeneous burning, especially in regard to the rate-limiting mechanism. The objective of the current research is to determine the cause of the higher melting rates observed for metals burning in reduced gravity to (a) identify the rate-limiting mechanism during heterogeneous burning and thus contribute to an improved fundamental understanding of the system, and (b) contribute to improved oxygen system fire safety for both ground-based and space-based applications. In support of the work, a 2-s duration ground-based drop tower reduced-gravity facility was commissioned and a reduced-gravity metals combustion test system was designed, constructed, commissioned and utilised. These experimental systems were used to conduct tests involving burning 3.2-mm diameter cylindrical iron rods in high-pressure oxygen in normal gravity and reduced gravity. Experimental results demonstrate that at the onset of reduced gravity, the burning liquid droplet rapidly attains a spherical shape and engulfs the solid rod, and that this is associated with a rapid increase in the observed melting rate. This link between the geometry of the solid/liquid interface and melting rate during heterogeneous burning is of particular interest in the current research. Heat transfer analysis was performed and shows that a proportional relationship exists between the surface area of the solid/liquid interface and the observed melting rate. This is confirmed through detailed microanalysis of quenched samples that shows excellent agreement between the proportional change in interfacial surface area and the observed melting rate. Thus, it is concluded that the increased melting rates observed for metals burning in reduced gravity are due to altered interfacial geometry, which increases the contact area for heat transfer between the liquid and solid phases. This leads to the conclusion that heat transfer across the solid/liquid interface is the rate-limiting mechanism for melting and burning, limited by the interfacial surface area. This is a fundamental result that applies in normal gravity and reduced gravity and clarifies that oxygen availability, as postulated in the literature, is not rate limiting. It is also established that, except for geometric changes at the solid/liquid interface, the heterogeneous burning phenomenon is the same at each gravity level. A conceptual framework for understanding and discussing the many factors that influence heterogeneous burning is proposed, which is relevant to the study of burning metals and to oxygen system fire safety in both normal-gravity and reduced-gravity applications.

This master thesis deals with analysis of battery mass using x-ray spectral microanalysis. For the measurement two scanning electron microscopes equipped with energy dispersive x-ray spectroscopes were used. Appropriate examples were prepaired by standard method. Then elemental analysis was performed with changing conditions of measurement. Two programs were used for spectrums evaluation and in the end the size of errors was observed for every conditions.

Die Arbeit beschäftigt sich mit der Erweiterung der für dicke Proben schon mit Erfolg eingesetzten Werkstoffanalytischen Methode Elektronenstrahl-Mikroanalyse (ESMA) mittels Peak/Untergrund-Verhältnissen auf die Analyse von dünnen Schichten (unter 1 μm) zur qualitative und quantitativen Elementanalyse sowie zur Ermittlung von Schichtdicken. Weiterhin wird auf der Basis von einer ESMA-Methode für zwei dünne Schichten auf einem Substrat wird ein Modell zur Ermittlung des Phasenwachstumskoeffizienten für eine intermetallische Phase die sich bei der Diffusion zwischen einer dünnen Schicht und einem Substrat bildet, mittels ESMA-Messungen bei gleichzeitiger Erwärmung der Probe dargestellt. / The paper deals with the application of the materials analysis method EPMA by peak-to-background ratios, which is currently being used for the analysis of thick samples successfully, to thin layers (less than 1 μm) for the quantitative element analysis as well as for thickness prediction. In addition a model has been established on the Basis of an EPMA method for two films on a substrate for deriving the phase growth coefficient of an inter-metallic phase which grows during the diffusion between a thin layer and a substrate from EPMA measurements while simultaneously heating the sample.

The Davle Volcanic Complex (DVC) situated in the Teplá-Barrandian unit (TBU) of the Bohemian Massif, is considered as a Neoproterozoic-Cambrian magmatic arc that developed on the northern active margin of Gondwana supercontinent during Cadomian accretionary orogeny. This study combines data obtained from fieldwork, petrography, rock-forming mineral microanalysis, major and trace element analysis, Sr-Nd-Pb isotopic systematics and U-Pb zircon geochronology in order to reveal the petrogenesis and evolution of the DVC. At least three-stage metamorphism including Cadomian seafloor alteration, Variscan regional metamorphism as well as contact metamorphism related to the emplacement of the Central Bohemian Plutonic Complex affected the DVC. The studied rocks follow calc-alkaline trend whereas tholeiitic trend previously reported is rather related to younger magmatic events. The northern part of the DVC is dominated by felsic subvolcanic (plagiogranite), volcanic (dacite- rhyolite) and pyroclastic (dacitic-rhyolitic tuffs and breccias) rocks with a few outcrops of basaltic andesite-andesite pillow lavas documenting the subaqueous activity of the DVC. These rocks are Na-rich, but K-poor, the plagiogranite contains albite most likely primary in origin, and exhibit highly radiogenic εNd values (~ +6 to +11),...

[ES] Esta tesis presenta un nuevo modelo llamado "Modelo dinámico de interacción social y multitud urbana (DUCSIM)", que tiene como objetivo calcular la densidad de multitudes y descifrar las redes sociales en entornos oportunistas. Con la creciente similitud de los dispositivos electrónicos conectados a Internet y la influencia generalizada de las redes sociales en línea, se ha creado un enorme rastro digital. Las huellas digitales basadas en la movilidad humana y el mayor uso de sistemas de comunicación inalámbrica como 3G, 4G y 5G forman una rica base de datos que puede analiarse. Estas huellas digitales ofrecen una forma única de modelar los patrones de multitud dentro de diferentes contextos, como asambleas espontáneas en espacios públicos y escenarios planificados, como en el caso de los megaeventos. El estudio se centra en el desafío de las reuniones multitudinarias oportunistas, donde las personas se congregan por diferentes motivos sin planificación; manifiestan sus movimientos de forma dinámica e inesperada. El análisis del comportamiento humano en las ciudades modernas y desarrolladas requiere que estas reuniones se produzcan en centros comerciales, cruces de carreteras y flash mobs. El análisis macroscópico de la densidad de multitudes basado en datos de las torres de telefonía móvil sirve como primera etapa para delinear el marco DUCSIM. Se adopta el método Median-of-Median (M-o-M) para mayor solidez, ya que este análisis implica umbrales de conteo bruto de multitudes diario y semanal. Las densidades de multitud se clasifican en cuartiles para mostrar distintos grados de distribución de la multitud. A través del análisis macroscópico, el marco avanza hacia el análisis de movilidad acumulativa de multitudes. La dinámica del movimiento de multitudes se mide cambiando las señales de las torres de telefonía movil y formulando un mapa de densidad de multitudes para pronosticar sus movimientos posteriores. Examina el microanálisis del movimiento individual y las relaciones interpersonales a menor escala. Incluye asignar personas a torres de telefonía móvil y formar gráficos de interacción social que infieren y actualizan las relaciones sociales. La parte más importante de DUCSIM radica en su capacidad de aprender y adaptarse dinámicamente para crear un modelo de representación novedoso que se adapte al patrón recién detectado. Esta flexibilidad ayuda a garantizar la relevancia del marco, que debe actualizarse continuamente. El modelado predictivo personalizado se combina con datos históricos que engloban la tesis. El marco utiliza densidades de multitudes anteriores y datos de movimiento para descubrir tendencias y predecir dinámicas de multitudes futuras, mejorando así la eficiencia de la planificación urbana, la respuesta a emergencias o las ciudades inteligentes. El marco DUCSIM proporciona un método integral, flexible y de previsión para comprender y controlar los fenómenos de aglomeración urbana. Una forma moderna de análisis de datos que involucra varias fuentes de datos, respaldada por matemáticas rigurosas, hace que este método sea único para los estudios urbanos. Además, da impulso al ámbito académico y proporciona recomendaciones prácticas sobre la aplicación de esta metodología en la gestión y planificación de las ciudades modernas. / [CA] Aquesta tesi presenta un nou model anomenat "Dynamic Urban Crowd and Social Interaction Model (DUCSIM)", que té com a objectiu calcular la densitat de multituds i desxifrar xarxes socials en entorns oportunistes. Amb la creixent comú d'aparells electrònics enllaçats a Internet i la influència generalitzada de les xarxes socials en línia, s'ha creat un enorme rastre digital. Les traces digitals basades en la mobilitat humana i l'augment de l'ús de sistemes de comunicació sense fils com 3G, 4G i 5G formen una base de dades rica per ser analitzada. Aquestes traces digitals ofereixen una manera única de modelar els patrons de multituds en diferents contextos, com ara assemblees espontànies en espais públics i escenaris planificats, com en el cas dels megaesdeveniments. L'estudi se centra en el repte de les reunions multitudinàries oportunistes, on la gent es congrega per diferents motius sense planificació; manifesten els seus moviments de manera dinàmica i inesperada. L'anàlisi del comportament humà a les ciutats modernes i desenvolupades requereix que aquestes reunions es produeixin en centres comercials, cruïlles de carreteres i flash mobs. L'anàlisi macroscòpic de la densitat de multituds basada en dades de les torres de telefonía mòbil serveix com a primera etapa per descriure el marc DUCSIM. El mètode M-o-M s'adopta per a la robustesa, ja que aquesta anàlisi implica umbrals de recompte de multituds diaris i setmanals. Les densitats de multitud es classifiquen en quartils per mostrar diferents graus de distribució de multitud. Mitjançant l'anàlisi macroscòpic, el marc avança cap a l'anàlisi de la mobilitat acumulat de multituds. La dinàmica del moviment de la multitud es mesura canviant els senyals de les torres de telefonía mòbil i formulant un mapa de densitat de la multitud per preveure els seus moviments posteriors. Examina el microanàlisi del moviment individual i les relacions interpersonals a menor escala. Inclou assignar persones a torres de telefonía mòbil i formar gràfics d'interacció social que dedueixin i actualitzin les relacions socials. La part més important de DUCSIM està en la seua capacitat per aprendre i adaptar-se de manera dinàmica per crear un model de representació nou que s'adapte al patró recentment detectat. Aquesta flexibilitat ajuda a garantir la rellevància del marc, que s'ha d'actualitzar contínuament. El modelatge predictiu personalitzat es combina amb les dades històriques que engloben la tesi. El marc utilitza dades de moviment i densitats de multitud anteriors per descobrir tendències i predir les properes dinàmiques de multituds, millorant així l'eficiència de la planificació urbana, la resposta d'emergència o les ciutats intel·ligents. El marc DUCSIM proporciona un mètode complet, flexible i de previsió per entendre i controlar els fenòmens d'aglomeracions urbanes. Una forma moderna d'anàlisi de dades que inclou diverses fonts de dades, amb el suport de matemàtiques rigoroses, fa que aquest mètode sigui únic per als estudis urbans. A més, dóna un impuls a l'àmbit acadèmic i ofereix recomanacions pràctiques sobre l'aplicació d'aquesta metodologia en la gestió i planificació de la ciutat moderna. / [EN] This thesis presents a new framework called the "Dynamic Urban Crowd and Social Interaction Model (DUCSIM)," which is aimed at calculating crowd density and deciphering social networks in opportunistic environments. With the growing commonality of internet-linked electronic gadgets and the widespread influence of online social networks, an enormous digital trail has been created. The digital traces based on human mobility and the increased usage of wireless communication systems such as 3G, 4G, and 5G form a rich database to be analyzed. These digital traces offer a unique way of modelling the crowd patterns within different contexts, like spontaneous assemblies in public spaces and planned scenarios, as in the case of mega-events. The study focuses on the challenge of opportunistic crowd gatherings, where people congregate for different reasons without planning; they manifest their motions dynamically and unexpectedly. The analysis of human behaviour in modern, developed cities requires that these gatherings occur in malls, road junctions, and flash mobs. Macroscopic crowd density analysis based on data from MOBILE towers serves as the first stage in outlining the DUCSIM framework. The Median-of-Median (M-o-M) method is adopted for robustness as this analysis involves daily and weekly raw crowd count thresholds. Crowd densities are ranked in quartiles to show varying degrees of crowd distribution. Through the macroscopic analysis, the framework progresses to cumulative crowd mobility analysis. Crowd movement dynamics are measured by changing signals from MOBILE towers and formulating a crowd's density map to forecast its subsequent motions. It examines the micro-analysis of individual movement and interpersonal relations on a smaller scale. It includes assigning people to MOBILE towers and forming social interaction graphs that infer and update social relationships. The most important part of DUCSIM lies in its ability to dynamically learn and adapt to create a novel representation model to suit the newly detected pattern. This flexibility helps to ensure the relevancy of the framework, which must be continually updated. Custom predictive modelling combines with historical data that encompasses the thesis. The framework uses previous crowd densities and movement data to discover trends and predict upcoming crowd dynamics, thus improving urban planning efficiency, emergency response, or smart cities. The DUCSIM framework provides a comprehensive, flexible and forecasting method of understanding and controlling urban crowd phenomena. A modern form of data analysis involving several data sources, supported by rigorous mathematics, makes this method unique for urban studies. Moreover, it gives impetus to the academic sphere and provides practical recommendations concerning the application of this methodology within modern city management and planning. / Addepalli, L. (2024). An Architecture for Crowd Density Estimation in Heterogenous Opportunistic Environment [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/204747

This thesis describes the design, manufacture and characterisation of thick vacuum plasma sprayed tungsten (W) coatings on steel substrates. Fusion is a potentially clean, sustainable, energy source in which nuclear energy is generated via the release of internal energy from nuclei. In order to fuse nuclei the Coulomb barrier must be breached - requiring extreme temperatures or pressures – akin to creating a ‘star in a box’. Tungsten is a promising candidate material for future fusion reactors due to a high sputtering threshold and melting temperature. However, the large coefficient of thermal expansion mismatch with reactor structural steels such as the low activation steel Eurofer’97 is a major manufacturing and in-service problem. A vacuum plasma spraying approach for the manufacture of tungsten and tungsten/steel graded coatings has been developed successfully. The use of graded coatings and highly textured 3D interface surfi-sculpt substrates has been investigated to allow the deposition of thick plasma sprayed tungsten coatings on steel substrates. Finite element models have been developed to understand the residual stresses that develop in W/steel systems and made use of experimental measurements of coating thermal history during manufacture and elastic moduli measured by nano-indentation. For both the graded and surfi-sculpt coating, the models have been used to understand the mechanism of residual stress redistribution and relief in comparison with simple W on steel coatings, particularly by consideration of stored strain energy. In the case of surfi-sculpt W coatings, the patterned substrate gave rise to regular stress concentrating features, and allowed 2mm thick W coatings to be produced reproducibly without delamination. Preliminary through thickness residual stress measurements were compared to model predictions and provided tentative evidence of significant W coating stress relief by regulated coating segmentation.

Nanomaterials have attracted great interest due to the unique physical properties and great potential in the applications of nanoscale devices. Two dimensional atomic crystals, which are atomic thickness, especially graphene, have triggered the gold rush recently due to the fascinating high mobility at room temperature for future electronics. The crystal structure of nanomaterials will have great influence on their physical properties. Thus, this thesis is focused on developing the methods to control the crystal structure of nanomaterials, namely quantum dots as semiconductor, boron nitride (BN) as insulator, graphene as semimetal, with low cost for their applications in photonics, structural support and electronics. In this thesis, firstly, Mn doped ZnSe quantum dots have been synthesized using colloidal synthesis. The shape control of Mn doped ZnSe quantum dots has been achieved from branched to spherical by switching the injection temperature from kinetics to thermodynamics region. Injection rates have been found to have effect on controlling the crystal phase from zinc blende to wurtzite. The structural-property relationship has been investigated. It is found that the spherical wurtzite Mn doped ZnSe quantum dots have the highest quantum yield comparing with other shape or crystal phase of the dots. Then, the Mn doped ZnSe quantum dots were deposited onto the BN sheets, which were micron-sized and fabricated by chemical exfoliation, for high resolution imaging. It is the first demonstration of utilizing ultrathin carbon free 2D atomic crystal as support for high resolution imaging. Phase contrast images reveal moiré interference patterns between nanocrystals and BN substrate that are used to determine the relative orientation of the nanocrystals with respect to the BN sheets and interference lattice planes using a newly developed equation method. Double diffraction is observed and has been analyzed using a vector method. As only a few microns sized 2D atomic crystal, like BN, can be fabricated by the chemical exfoliation. Chemical vapour deposition (CVD) is as used as an alternative to fabricate large area graphene. The mechanism and growth dynamics of graphene domains have been investigated using Cu catalyzed atmospheric pressure CVD. Rectangular few layer graphene domains were synthesized for the first time. It only grows on the Cu grains with (111) orientation due to the interplay between atomic structure of Cu lattice and graphene domains. Hexagonal graphene domains can form on nearly all non-(111) Cu surfaces. The few layer hexagonal single crystal graphene domains were aligned in their crystallographic orientation over millimetre scale. In order to improve the alignment and reduce the layer of graphene domains, a novel method is invented to perform the CVD reaction above the melting point of copper (1090 ºC) and using molybdenum or tungsten to prevent the balling of the copper from dewetting. By controlling the amount of hydrogen during the growth, individual single crystal domains of monolayer over 200 µm are produced determined by electron diffraction mapping. Raman mapping shows the monolayer nature of graphene grown by this method. This graphene exhibits a linear dispersion relationship and no sign of doping. The large scale alignment of monolayer hexagonal graphene domains with epitaxial relationship on Cu is the key to get wafer-sized single crystal monolayer graphene films. This paves the way for industry scale production of 2D single crystal graphene.

No description available.