This thesis investigates the challenges and opportunities of recycling PA6-GF30, a glass-filled polyamide, to address the pressing environmental concerns surrounding polymer waste. Through a collaboration between Thule Group and Jönköping University, it aims to understand how the properties of recycled materials evolve over time and reprocessing cycles, proposing practical methods for their utilization in sustainable manufacturing practices. Thule Group's commitment to reducing emissions entails transitioning to sustainable materials, particularly through increased use of recycled engineering materials like PA6-GF30, to lower the carbon footprint of products, emphasizing the importance of maintaining product quality and safety while exploring the effects of recycled materials on mechanical properties. Through producing and testing post-industrial and post-consumer samples added to virgin PA6-GF30 with varying ratios, comparison with the commercially available polymers was conducted. In total, 15 different mixtures of pellets of different quantity and quality of recycled composites were investigated with tensile test and impact test, moreover the fibers of some batches were filtrated from the matrix and the fiber aspect ratio was examined with the help of an optical microscope. Results illustrated that recycled polymers generally showed more mechanical property degradation as the ratio of recycled polymers were increased. Furthermore, adding the same amount of post-consumer regrinds as opposed to post-industrial was more detrimental to the overall mechanical performance. Post-industrial composite regrinds performed 11,3% worse in UTS, meanwhile post-consumer regrinds dropped by 25,5% in the same characteristic when the samples made of 100% recycled materials were compared to the virgin composite.  The reason behind this phenomenon was investigated and supported by microscopy. One of them is the natural aging of the material that operates through chain scission, that slowly makes that polymer stiffer and weaker. The other and more dominant reason is the damage taken by the fibers, that create numerous stress concentration sites at fiber ends, within the structure, ultimately damaging the fiber-matrix interface.

Modelling solid-fluid multiphase flows are crucial to many applications such as fluidized beds, pyrolysis and gasification, catalytic cracking etc. Accurate modelling of the fluid-particle forces is essential for lab-scale and industry-scale simulations. Fluid-particle system solutions can be obtained using various techniques including the macro-scale TFM (Two fluid model), the meso-scale CFD-DEM (CFD - Discrete Element Method) and the micro-scale PRS (Particle Resolved Simulation method). As the simulation scale decreases, accuracy increases but with an exponential increase in computational time. Since fluid forces have a large impact on the dynamics of the system, this study trains deep learning models using micro-scale PRS data to predict drag forces on ellipsoidal particle suspensions to be applied to meso-scale and macro-scale models. Two different deep learning methodologies are employed, multi-layer perceptrons (MLP) and 3D convolutional neural networks (CNNs). The former trains on the mean characteristics of the suspension including the Reynolds number of the mean flow, the solid fraction of the suspension, particle shape or aspect ratio and inclination to the mean flow direction, while the latter trains on the 3D spatial characterization of the immediate neighborhood of each particle in addition to the data provided to the MLP. The trained models are analyzed and compared on their ability to predict three different drag force values, the suspension mean drag which is the mean drag for all the particles in a given suspension, the mean orientation drag which is the mean drag of all particles at specific orientations to the mean flow, and finally the individual particle drag. Additionally, the trained models are also compared on their ability to test on data sets that are excluded/hidden during the training phase. For instance, the deep learning models are trained on drag force data at only a few values of Reynolds numbers and tested on an unseen value of Reynolds numbers. The ability of the trained models to perform extrapolations over Reynolds number, solid fraction, and particle shape to predict drag forces is presented. The results show that the CNN performs significantly better compared to the MLP in terms of predicting both suspensions mean drag force and also mean orientation drag force, except a particular case of extrapolation where the MLP does better. With regards to predicting drag force on individual particles in the suspension the CNN performs very well when extrapolated to unseen cases and experiments and performs reasonably well when extrapolating to unseen Reynolds numbers and solid fractions. / M.S. / Multiphase solid-fluid flows are ubiquitous in various industries like pharmaceuticals (tablet coating), agriculture (grain drying, grain conveying), mining (oar roasting, mineral conveying), energy (gasification). Accurate and time-efficient computational simulations are crucial in developing and designing systems dealing with multiphase flows. Particle drag force calculations are very important in modeling solid-fluid multiphase flows. Current simulation methods used in the industry such as two-fluid models (TFM) and CFD-Discrete Element Methods (CFD-DEM) suffer from uncertain drag force modeling because these simulations do not resolve the flow field around a particle. Particle Resolved Simulations (PRS) on the other hand completely resolve the fluid flow around a particle and predict very accurate drag force values. This requires a very fine mesh simulation, thus making PRS simulations many orders more computationally expensive compared to the CFD-DEM simulations. This work aims at using deep learning or artificial intelligence-based methods to improve the drag calculation accuracy of the CFD-DEM simulations by learning from the data generated by PRS simulations. Two different deep learning models have been used, the Multi-Layer Perceptrons(MLP) and Convolutional Neural Networks(CNN). The deep learning models are trained to predict the drag forces given a particle's aspect ratio, the solid fraction of the suspension it is present in, and the Reynolds number of the mean flow field in the suspension. Along with the former information the CNN, owing their ability to learn spatial data better is additionally provided with a 3D image of particles' immediate neighborhood. The trained models are analyzed on their ability to predict drag forces at three different fidelities, the suspension mean drag force, the orientation mean drag, and the individual particle drag. Additionally, the trained models are compared on their abilities to predict unseen datasets. For instance, the models would be trained on particles of an aspect ratio of 10 and 5 and tested on their ability to predict drags of particles of aspect ratio 2.5. The results show that the CNN performs significantly better compared to the MLP in terms of predicting both suspension mean drag force and also mean orientation drag force, except a particular case of extrapolation where the MLP does better. With regards to predicting drag force on individual particles in the suspension, the CNN performs very well when extrapolated to unseen cases and experiments and performs reasonably well when extrapolating to unseen Reynolds numbers and solid fractions.

No description available.

The aim of this investigation was to review literature for the most suitable aeroelastic tailoring analysis tools for long slender composite structures, and integrate them into an aeroelastic tailoring process. The JS1C Revelation is a high performance sailplane made from modern composites, mostly carbon fibre. This has the advantage of being more rigid than traditional engineering materials, thereby reducing the effects of the twisting deflections on these long slender structures due to aerodynamic loads. The implementing of aeroelastic tailoring can create bend-twist couples for performance improvements. Composites enable the use of aeroelastic tailoring to improve gliding performance. Flaperon 3 of the JS1C 21 m was used as the design problem for aeroelastic tailoring. Aeroelastic tailoring was done by analysing the flaperon structure at the different layup angles to determine the correct design point to tailor the structure to improve aerodynamic performance at thermalling and cruise, but mostly cruise since it accounts for 70% of the flight time. The composite structure analysis tool has the objective to get results during concept design. This directed the line of research of analysis tools to a solution method of two dimensional cross-section mesh properties projected onto a one dimensional beam. The literature of Hodges had good verification and published data on the analysis tools. The analysis tools comprised of three programs that were not very user friendly. Thus the author compiled a Matlab program as a user interface tool to run the three programs together. The aeroelastic tailoring process systematically works through the known design variables and objectives, which are given as inputs to the analysis tool. The analysis tool plots the coupling data versus layup angle. From this the best layup angles for a sought-after bend-twist couple is used to aeroelastically tailor the wing. The composite structure analysis tool’s accuracy was verified by analysing cantilever beam deflections and comparing the results with hand calculations and SolidWorks Simulation FEM results. The analysis tool’s accuracy was further verified by comparing the aerodynamic torsional load’s twist deflections with thin walled tube theory. The analysis tool was validated by applying a torsional load at the tip of a JS1C production Flaperon 3 in an experimental setup and then comparing this result with the Flaperon 3 modelled in the analysis tool. These comparisons also ensured that the model’s composite material properties and the meshing of the flaperon cross-sectional properties were correct. This aeroelastic tailoring was validated with the advantage of then being used to improve the aerodynamic performance of the JS1C Revelation 21 m tip’s flaperon. This improvement could be made by making use of a tailored bend-twist couple to reduce the effect of the aerodynamic load’s twist deflections. A test sample of the JS1C 21 m flaperon 3 was used to validate aeroelastic tailoring. The test sample was designed to be 1 m in length and have all the specified tailoring coupling characteristics that could improve the aerodynamic performance of the JS1C 21 m flaperon 3. The test sample was manufactured according to Jonker Sailplanes manufacturing standards and experimentally set up with the same applied deflections as in the analysis tool. The calculated bend-twist values and the experimental setup results were similar with a negligible difference, assuming small displacements and an aspect ratio greater than 13; this confirmed that the PreVABS/VABS/GEBT composite structure analysis tool could be used in aeroelastic tailoring to predict and design the bend-twist couple needed to improve the aerodynamic performance of the JS1C 21 m. While the twist behaviour of Flaperon 3 was improved by the tailored bend-twist couple, it was still necessary to add pre-twist as well, to fully address the effects of twisting by aerodynamic forces. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

The aim of this investigation was to review literature for the most suitable aeroelastic tailoring analysis tools for long slender composite structures, and integrate them into an aeroelastic tailoring process. The JS1C Revelation is a high performance sailplane made from modern composites, mostly carbon fibre. This has the advantage of being more rigid than traditional engineering materials, thereby reducing the effects of the twisting deflections on these long slender structures due to aerodynamic loads. The implementing of aeroelastic tailoring can create bend-twist couples for performance improvements. Composites enable the use of aeroelastic tailoring to improve gliding performance. Flaperon 3 of the JS1C 21 m was used as the design problem for aeroelastic tailoring. Aeroelastic tailoring was done by analysing the flaperon structure at the different layup angles to determine the correct design point to tailor the structure to improve aerodynamic performance at thermalling and cruise, but mostly cruise since it accounts for 70% of the flight time. The composite structure analysis tool has the objective to get results during concept design. This directed the line of research of analysis tools to a solution method of two dimensional cross-section mesh properties projected onto a one dimensional beam. The literature of Hodges had good verification and published data on the analysis tools. The analysis tools comprised of three programs that were not very user friendly. Thus the author compiled a Matlab program as a user interface tool to run the three programs together. The aeroelastic tailoring process systematically works through the known design variables and objectives, which are given as inputs to the analysis tool. The analysis tool plots the coupling data versus layup angle. From this the best layup angles for a sought-after bend-twist couple is used to aeroelastically tailor the wing. The composite structure analysis tool’s accuracy was verified by analysing cantilever beam deflections and comparing the results with hand calculations and SolidWorks Simulation FEM results. The analysis tool’s accuracy was further verified by comparing the aerodynamic torsional load’s twist deflections with thin walled tube theory. The analysis tool was validated by applying a torsional load at the tip of a JS1C production Flaperon 3 in an experimental setup and then comparing this result with the Flaperon 3 modelled in the analysis tool. These comparisons also ensured that the model’s composite material properties and the meshing of the flaperon cross-sectional properties were correct. This aeroelastic tailoring was validated with the advantage of then being used to improve the aerodynamic performance of the JS1C Revelation 21 m tip’s flaperon. This improvement could be made by making use of a tailored bend-twist couple to reduce the effect of the aerodynamic load’s twist deflections. A test sample of the JS1C 21 m flaperon 3 was used to validate aeroelastic tailoring. The test sample was designed to be 1 m in length and have all the specified tailoring coupling characteristics that could improve the aerodynamic performance of the JS1C 21 m flaperon 3. The test sample was manufactured according to Jonker Sailplanes manufacturing standards and experimentally set up with the same applied deflections as in the analysis tool. The calculated bend-twist values and the experimental setup results were similar with a negligible difference, assuming small displacements and an aspect ratio greater than 13; this confirmed that the PreVABS/VABS/GEBT composite structure analysis tool could be used in aeroelastic tailoring to predict and design the bend-twist couple needed to improve the aerodynamic performance of the JS1C 21 m. While the twist behaviour of Flaperon 3 was improved by the tailored bend-twist couple, it was still necessary to add pre-twist as well, to fully address the effects of twisting by aerodynamic forces. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

A near-field technique known as evanescent interferometric lithography allows for high resolution imaging. However its primary limitation is that the image exponentially decays within the photoresist due to physical limits. This thesis aims to overcome this limitation and presents a method to considerably enhance the depth of focus of images created using evanescent interferometric lithography by using a material underlay beneath the photoresist. A key enabler of this is the understanding that evanescent fields couple to surface states and operating within proximity of a resonance, the strength of the coupling allows for considerable energy extraction from the incident beam and redistribution of this energy in a photoresist cavity. This led to the analysis of the Fresnel equations, which suggested that such coupling was in fact the result of an enhanced reflectance that takes place at boundaries of carefully chosen materials. While it is known that metals and lossy dielectrics result in surface plasmon polaritons (SPP) and surface exciton polaritons (SEP) as conventional solutions to the Fresnel reflection equations for the TM polarization of light, there is no such naturally occurring surface state that allows evanescent wave enhancement with the TE polarization of light. Further investigation of the Fresnel reflection equations revealed both for TM and TE that in fact another solution exists that is but unconventional to enhance the reflectivity. This solution requires that one of the media have a negative loss. This is a new type of surface resonance that requires that one of the media be a gain medium; not one in the optical pumped sense but one that would naturally supply energy to a wave to make it grow. This new surface resonance is also a key result of this thesis. Clearly, however this is only a hypothetical solution as a real gain medium would violate the conservation of energy. However, as it is only the reflectance of this gain medium that is useful for evanescent wave enhancement, in fact a multilayered stack consisting of naturally occurring materials is one way to achieve the desired reflectivity. This would of course be only an emulation of the reflectivity aspect of the gain medium. This multilayered stack is then an effective gain medium for the reflectivity purposes when imaging is carried out at a particular NA at a particular wavelength. This proposal is also a key idea of this thesis. At λ = 193 nm, this method was used to propose a feasible design to image high resolution structures, NA = 1.85 at an aspect ratio of ~3.2. To experimentally demonstrate the enhancements, a new type of solid immersion test bed, the solid immersion Lloyd's mirror interference lithography test-bed was constructed. High quality line and space patterns with a half-pitch of 55.5 nm were created using λ = 405 nm, corresponding to a NA of 1.824, that is well in the evanescent regime of light. Image depths of 33-40 nm were seen. Next, the evanescent image was coupled to an effective gain medium made up of a thin layer of hafnium oxide (HfO) upon silicon dioxide (SiO2). This resulted in a considerable depth enhancement, and 105 nm tall structures were imaged. The work in this thesis details the construction of the solid immersion lithography test-bed, describes the implementation of the modeling tools, details the theory and analysis required to achieve the relevant solutions and understanding of the physical mechanism and finally experimentally demonstrates an enhancement that allows evanescent interferometric lithography beyond conventional limits.

O aumento das ocorrências de VIM em plataformas flutuantes do tipo \"spar\" e monocoluna serviu de motivação para a investigação dos fundamentos do fenômeno de VIV em cilindros com baixa razão de aspecto e pequena razão de massa. Tal investigação também foi motivada pela necessidade de se preencher lacunas de conhecimento a respeito deste assunto, articularmente por conta da escassa disponibilidade de resultados acerca do VIV em cilindros curtos, bem como pela ausência de modelo fluido que justifique os comportamentos dinâmicos conhecidos. Para o entendimento pretendido, três grupos de experimentos com cilindros dotados de razão de aspecto na faixa 0,1 <= L/D <= 2,0 foram realizados em um canal de água circulante na Escola Politécnica da Universidade de São Paulo, sendo: o primeiro grupo focado nos cilindros curtos estacionários; o segundo nos cilindros curtos de baixa razão de massa, 1,00 <= m* <= 4,36, e dois graus de liberdade; e o grupo final interessado no VIV em cilindros flutuantes, ou seja, razão de massa unitária e seis graus de liberdade. De uma maneira geral, a partir dos resultados aqui obtidos e das comparações com os resultados respectivamente encontrados na literatura, conclui-se que o VIV em cilindros curtos somente acontece se L/D > 0,2. Além de original, a determinação deste valor crítico também identificou outras três regiões com comportamentos fluido-dinâmicos distintos, cada qual marcada por especificidades quanto aos impactos nas amplitudes, frequências e coeficientes de força. Assim sendo, para cilindros com L/D > 2,0 a esteira de von Kármán foi a principal responsável pelas forças sustentação; fato não identificado para os cilindros com 0,5 < L/D < 2,0, onde esta mesma esteira sofreu forte contaminação das estruturas partindo da extremidade livre, principalmente aquelas com vorticidade predominante no plano vertical. Para os cilindros na faixa de 0,2 < L/D <= 0,5, apenas estas últimas estruturas foram responsáveis pelas oscilações de VIV. Finalmente, buscando compreender a origem das forças oscilatórias em cilindros com baixíssima razão de aspecto, \"end-plates\" foram aplicadas e confirmaram que o fenômeno de VIV nestes casos está relacionado à liberação de vórtices junto à extremidade livre, o que indica uma solução interessante para a mitigação do VIM de plataformas. / The increase of VIM occurrences on spar and monocolumn platforms was the motivation to study the vortex-induced vibrations of cylinders with low aspect ratio and small mass ratio under a fundamental perspective. The present work was also motivated by the small number of works in the literature dealing with VIV of cylinders with low aspect ratio, as well as by the scarce concerns about the flow models around this cylinders, which justify the dynamic behaviors observed. Aiming to better understand this problem, three groups of experiments with cylinders of 0.1 <= L/D <= 2.0 were carried out in a recirculating water channel at Escola Politécnica of University of São Paulo, as follow: firstly, the flow around stationary cylinders; secondly, VIV of cylinders with two degrees-of-freedom and 1.00 <= m* <= 4.36. finally, VIV of floating cylinder, thus six degrees-of-freedom. The works concluded that VIV occurs only for cylinders with L/D > 0.2. Besides of being original, this result was also related to the observation of three regions of aspect ratio, each of them with different behaviors of the motion amplitudes, frequency ratios and force coefficients. For cylinders with L/D > 2.0, the von Kármán wake was the mainly responsible for the oscillatory lift forces. On the other hand, the von Kármán wake was contaminated by the effects coming from the free end of cylinders with 0.5 < L/D < 2.0, mainly by the vortex structures with vorticity in the vertical plane. And for cylinders with 0.2 < L/D <=0.5, the vortex structures at the free end were predominant, thus the only one responsible for the oscillatory lift forces. Finally, in order to understand the source for oscillatory lift forces on cylinders with very low aspect ratio, end-plates were applied and confirmed that VIV in these cases is related to the vortex-shedding around the free end, which indicates an interesting solution for VIM mitigation of platforms.

This thesis primarily focused on the development of novel composite tubes by braiding. The objective was to use hierarchical scale technique, i.e., micro, meso and macro scales, with the transfer of information from one scale to another to develop novel braided composite tubes. This research was conducted and reported in three journal papers. The aim of the first paper was to predict plane elastic properties for E-glass/epoxy braided composite structures at different braid orientations, by analytical and finite element techniques. The lenticular shape has been used to describe the geometry of the tow. Modified lenticular geometric model was developed to improve an existing geometric model, in terms of tow parameters, thereafter, plane elastic properties from Chamis micromechanical model for E-glass fibre and epoxy matrix without any knockdown effects were used as benchmark to develop predictive models, namely; Lekhnitskii's methodology and braided unit cell meso-scale finite element model to account for the effects of tow geometry, undulations/crimp, cross-over and braid orientations on the plane elastic properties of E-glass/epoxy composite. The results showed agreement in trend between the predictive models, Chamis micromechanical model, and a similar existing model. However, the plane elastic properties were knocked down in predictive models by 30% in the E11 direction and 32% in the E22 direction, when compared with Chamis micro-mechanical model for largest ±65° braid angle, among the braid angles, considered. The aim of the second paper was to manufacture E-glass/epoxy braided tubes at different braid orientations by vacuum bag infusion technique, conduct internal pressure tests, and determine the hoop and axial moduli of the infused tubes. Lekhnitskii's methodology was also used to develop plane elastic moduli by experiment using microscopy results, and by calculation. The experimental elastic moduli of the infused tubes and the experimental elastic moduli from Lekhnitskii's methodology were used to compare the predictive elastic moduli for E-glass/epoxy braided structures by Chamis micro-mechanical model, and the braided unit cell meso-scale finite element model. The two were from another paper. Results showed a perfect agreement in trend between the experimental results and the predictive results. However, the values of the experimental results were close but lower than the predicted results. Optical microscopy was performed on braided tube cross-section to evaluate the level of crimp or undulation. This was done by the determination of tow centreline crimp angle and aspect ratio. Results show that when compared with the predicted crimp, there was an agreement in trend, although the experimental results were lower than the predicted. Also, the knockdown factor was evaluated and used to quantify the reduction in experimental elastic moduli when compared with the predicted. Results showed that the absences of crimp in the Chamis model caused a tremendous difference between it, other predicted models and the experiment results. The elastic moduli of Chamis were by far higher than all others, including other predictive models. The purpose of the third paper was to manufacture E-glass/epoxy braided tube at ±31°, ±45°, ±55°, ±65° braid orientations using vacuum bagging and resin infusion technique, to design and manufacture a rig for tube internal pressures experiment, to determine the hoop and axial stress performances of the tubes by internal pressure experiment, to compare experimental results with laminate analysis predictions to evaluate the effect of crimp on the internal pressure performance of the braided tubes. To use E-glass braided tow meso-scale unit cell finite element model to predict the tow critical stresses, and the optimum braided tube architecture, using tube hoop and axial failure stresses or strains. The tubes were manufactured and subjected to internal pressure test (2:1), to failure. Failure mode was by weeping and bursting. Hoop stress was twice the axial stress. The highest value of hoop stress was at the ±65° braid angle, higher than the hoop stresses at the ±31°, ±45°, and ±55 ° braid angles by 50%, 39%, and 28% respectively. Hoop stress increased with increase in braid angle. The experimental results were validated by laminate analysis predictions by Chamis micro-mechanical model and Lekhnitskii's methodology, and the trend of the laminate analysis prediction matched that of the experimental results. However, the predicted values were higher than the experimental results by 21%, 14%, 11%, 10% for the ±31°, ±45°, ±55°, ±65° braid angles for the Chamis micro-mechanical model and 5%, 7%, 7%, 5% for the ±31°, ±45°, ±55°, ±65 braid angles respectively for the Lekhnitskii's model, showing the severe effect of crimp in the experimental tube, mostly when compared with Chamis micro-mechanical model. Braided tow unit cell finite element model prediction, showed that tow axial stresses increased with increase in braid angle, while the tow transverse stresses decreased with increase in braid angle. The predictions showed that the tow critical stresses and the tube optimum braided architecture lie between the ±65° and 90° braid angles. The tow critical stresses are the stresses at which the tow decreasing transverse stress and the tow increasing axial stress causes the tube to fail.

High aspect ratio silicon etching used for DRAM manufacturing still remains as one of the biggest challenges in semiconductor fabrication, requiring well understood and characterized process fundamentals. In this study, physical and chemical interactions during etching silicon in capacitively coupled plasma discharges were investigated in detail for different HBr/NF3 mixed chemistries for single frequency as well as dual frequency operation and medium discharge pressures inside an industrial MERIE CCP reactor typically used for DRAM fabrication. Utilization of the dual frequency concept for separate control of ion energy and ion flux, as well as the impact on discharge properties and finally on etching at relevant substrate surfaces were studied systematically. The complex nature of multi frequency rf sheaths was both analyzed experimentally by applying mass resolved ion energy analysis, and from simulation of ion energy distributions by using a Hybrid Plasma Sheath Model. Discharge composition and etch processes were investigated by employing standard mass spectrometry, Appearance Potential Mass Spectrometry, Quantum Cascade Laser Absorption Spectroscopy, rf probe measurements, gravimetry and ellipsometry. An etch model is developed to explain limitations of silicon etching in HBr/NF3 discharges to achieve highly aniostropic etching. / Siliziumätzen mit hohen Aspektverhältnissen zur Herstellung von DRAM-Speicherstrukturen stellt nach wie vor eine der größten Herausforderungen in der Halbleiterherstellung dar und erfordert ein grundlegendes Prozessverständnis. Diese Studie beinhaltet eine umfassende und detaillierte Untersuchung physikalischer und chemischer Wechselwirkungen von Siliziumätzprozessen in kapazitiv gekoppelten HBr/NF3-Gasentladungen in einem kommerziellen, typischerweise für die DRAM-Fertigung eingesetzten MERIE CCP Reaktor mit Ein- und Zweifrequenzanregung bei mittleren Entladungsdrücken. Die Anwendung eines Zweifrequenzkonzeptes zur separaten Kontrolle von Ionenenergie und Ionenstromdichte, als auch deren Einfluss auf die Entladungseigenschaften und letztendlich auf das Ätzverhalten auf relevanten Substratoberflächen wurden systematisch untersucht. Die komplexe Natur von mehrfrequenzangeregten HF-Randschichten wurde sowohl experimentell über eine Anwendung von massenaufgelöster Ionenenergieanalyse als auch rechnerisch über Simulationen von Ionenenergieverteilungsfunktionen mit Hilfe eines hybriden Plasmarandschichtmodells analysiert. Gaszusammensetzungen verschiedener Entladungen und Ätzprozesse wurden mit Hilfe von Standard-Massenspektrometrie, Schwellwert-Massenspektrometrie, Quantenkaskaden-Laserabsorptionsspektroskopie, HF-Sondenmessungen, Gravimetrie und Ellipsometrie charakterisiert. Eine neuartige Modellvorstellung zum Siliziumätzen in HBr/NF3-Entladungsgemischen liefert eine plausible Erklärung für die Limitierung der Ätzrate zum Erreichen eines hoch anisotropen Ätzverhaltens.

<p>The purpose of this master thesis was to study different content-aware video retargeting techniques, concentrating on a generalization of seam carving for video. Focus have also been put on the possibility to combine different techniques to achieve better retargeting of both multi-shot video and single-shot video. This also involved significant studies of automatic cut detection and different measures of video content. The work resulted in a prototype application for semi-automatic video retargeting, developed in Matlab. Three different retargeting techniques, seam carving, automated pan & scan and subsampling using bi-cubic interpolation, have been implemented in the prototype. The techniques have been evaluated and compared to each other from a content preservation perspective and a perceived quality perspective.</p> / <p>Syftet med examensarbetet har varit att studera tekniker för ändring av bredd/höjd-förhållandet i videosekvenser, där hänsyn tas till innehållet i bilderna. Fokus har lagts på en generalisering av "seam carving" för video och möjligheterna att kombinera olika tekniker för att nå bättre kvalitet både för videosekvenser som består av endast ett, eller flera, klipp. Detta innefattade således också omfattande studier av automatisk klippdetektering och olika mått av videoinnehåll. Arbetet har resulterat i en prototypapplikation utvecklad i Matlab för halvautomatisk förändring av bildförhållande där hänsyn tas till innehållet i sekvenserna. I prototypen finns tre metoder implementerade, "seam carving", automatiserad "pan & scan" och nedsampling med bi-kubisk interpolering. Dessa metoder har utvärderats och jämförts med varandra från ett innehållsbevarande perspektiv och ett kvalitetsperspektiv.</p>