<p>3D fractals can be visualized as 3D objects with complex structure and has unlimited details. This thesis will be about methods to render 3D fractals effectively and efficiently, both to explore it in real-time and to create beautiful high resolution images with high details. The methods discussed is direct volume rendering with ray-casting and cut plane rendering to explore the fractal and an approach that uses super sampling to create high resolution images. Stereoscopic rendering is discussed and how it enhance the visual perception of the fractal</p>

Poles are used as an important constituent of transmission, distribution and communication structures / highway and street lighting systems and other various structural applications. Concrete is the main production material of the pole industry. Concrete is preferred to steel and wood due not only to environmental and economic reasons but also because of its high durability to environmental effects and relatively less frequent maintenance requirements. Centrifugal casting is the most preferred way of manufacturing concrete poles. However, misapplication of the method may lead to a significant reduction in strength and durability of the poles. Segregation of concrete mixture is a frequent problem of centrifugal casting. The segregated concrete within the pole cross-section possesses different physical properties. In particular, the shrinkage tendency of the inner concrete, where the cement paste is accumulated, becomes significantly larger. Differential shrinkage of hardened concrete across the pole section gives rise to the development of internal tensile stresses, which, in turn, results in longitudinal cracking along the poles. There is a vast literature on experimental studies of parameters affecting differential shrinkage of centrifugally cast poles. This research aims to computationally investigate the differential shrinkage-induced internal stress development and cracking of concrete poles. To this end, two and three-dimensional mathematical models of the poles are constructed and finite element analyses of these models are carried out for different scenarios. The computationally obtained results that favorably agree with the existing experimental data open the possibility to improve the centrifugal manufacturing technique by using computational tools.

Aluminum alloys are having more attention due to their high specific stiffness and processing advantages. 7075 aluminum alloy is a wrought composition aluminum alloy in the Al-Zn-Mg-Cu series. Due to the significant addition of these alloying elements, 7075 has higher strength compared to all other aluminum alloys and effective precipitation hardenability characteristic. On the other hand, aluminum alloys have some drawbacks, which hinder the widespread application of them. One of the most commonly encountered defects in aluminum alloys is the hydrogen porosity. Additionally, in case of 7075, another problem is the lack of fluidity. Magnesium addition is thought to be effective in compensating this deficiency. Accordingly, in this study, die cast 7075 aluminum alloy samples with hydrogen porosity and additional magnesium content were investigated. The aim was to determine the relationship between hydrogen content and hydrogen porosity, and the effects of hydrogen porosity, additional magnesium and T6 heat treatment on ultimate tensile and flexural strength properties of pressure die cast 7075 aluminum alloy. 7075 aluminum alloy returns were supplied from a local pressure die casting company. After spectral analysis, pressure die casting was conducted at two stages. In the first stage, 7075 aluminum alloy with an increase in magnesium concentration was melted and secondly 7075 aluminum alloy was cast directly without any alloying addition. While making those castings, hydrogen content was measured continuously before each casting operation. As a final operation T6 heat treatment is carried out for certain samples. Finally, in order to accomplish our aim, mechanical and microstructural examination tests were conducted.

Large Area Maskless Photopolymerization (LAMP) is a technology being developed to fabricate integrally-cored ceramic molds for the investment casting of turbine airfoils. In LAMP, ultraviolet (UV) light in the form of bitmap images is projected from a spatial light modulator (SLM) onto a photocurable ceramic material system (PCMS). Exposed and unexposed regions are determined through black and white portions of the bitmaps, respectively. UV light induces photopolymerization and the formation of an insoluble solidified network. Three-dimensional structures are built layer-by-layer through sequential application and curing of PCMS layers of 100 micron thickness. To date, ceramic molds fabricated using LAMP have been successfully implemented in investment casting of single-crystal turbine airfoils without internal cooling schemes. Two particularly important challenges for the fabrication of airfoil molds with internal cooling passages are: (a) fabrication of unsupported structures in the mold geometry and; (b) mitigation of internal stresses that arise during layer-by-layer build-up due to volumetric shrinkage during photopolymerization. Unsupported geometries arise in nearly every cored airfoil mold and often in a location where support structures cannot be easily removed after fabrication. Internal stresses generated by volumetric shrinkage can lead to cracking during binder burnout (BBO), sintering and casting. This thesis aims to simultaneously address these challenges through the investigation of grayscale exposure to control the degree of monomer conversion during photopolymerization of single and multiple layers. The effective intensity of the UV light incident on the monomer system can be reduced by selectively turning off pixels within the nominally "white" or "on" regions of the projected bitmaps, effectively producing an exposure with a lower light intensity. In an effort to reduce internal stresses in the mold, the grayscale exposure can be tuned to create regions of uncured or partially cured monomer within the mold geometry to reduce the connectivity between cured regions and thus reduce the net effect of volumetric shrinkage. Grayscale exposure can also be used to generate support structures with a low degree of polymerization to create a gel state beneath and surrounding the unsupported segments of the mold, which can be washed away after completion of mold fabrication. In order to successfully utilize grayscale techniques in LAMP, the cure depth must be predicted. This is accomplished through cure depth measurements at different exposure times to develop a "working curve." In addition, the degree of monomer conversion and its relation to cure depths resulting from grayscale exposure must be understood. Measurements of the degree of conversion are obtained through Fourier Transform Infrared spectroscopy (FTIR). Empirical models are developed and compared to theoretical predictions. Also, the scattering length pixelation model is introduced as a technique to predict the light intensity distribution within the PCMS for exposure patterns at multiple length scales. Results from these grayscale investigations are then applied to LAMP and the effectiveness of grayscale to fabricate unsupported geometries and internal stresses from volumetric shrinkage is discussed.

Organic solar cells (OSC) are interesting as low cost alternative to conventional solar cells. Unsubstituted Metal-phthalocyanines (Pc) are excellent electron donating molecules for heterojunction OSC. Usually organic solar cells with Pcs are produced by vapor deposition, although solution based deposition (like spin casting) is cheaper and offers more possibilities to control the structure of the film. With solution based deposition several parameters (like temperature, solvent and etc.) affect the self-organized structure formation via nucleation and growth. The reason why vapor deposition is typically used is the poor solubility of the metal-phthalocyanines in most common solvents. Furthermore the process of nucleation and growth of Pc aggregates from solution is not well understood. For preparation of Pc films from solution, it is necessary to find the appropriate solvents, assess the solution deposition techniques, such as dip coating, and spin casting. It is necessary to understand the nucleation and growth process for aggregation/precipitation and to use this knowledge to produce nanostructures appropriate for OSC. This is important because the nanostructure of the films determines their performance. In this thesis, optical absorption and the stability of 8 different unsubstituted metal Pc’s were studied quantitatively in 28 different solvents. Among the several solution based deposited thin films produced based on this study, copper phthalocyanine (CuPc) dissolved in trifluoroacetic acid (TFA) is chosen as a model system for an in-depth study. CuPc has sufficient solubility and stability in TFA and upon solution processing forms appropriate structures for OSCs. CuPc molecules aggregate into layers of nanoribbons with a thickness of ~ 1 nm and an adjustable width and length. The morphology and the number of deposited layers in the thin films are controlled by different parameters, like temperature and solution concentration. Material properties of CuPc deposited from TFA are studied in detail via x-ray diffraction, UV-Vis and FT-IR spectroscopy. Atomic force microscopy was used to study the morphology of the dried film. The mechanism of the formation of CuPc nanoribbons from spin casted CuPc/TFA solution in ambient temperature is investigated and explained. The parameters (e.g. solution concentration profile) governing nucleation and growth are calculated based on the spin casting theory of a binary mixture of a nonvolatile solute and evaporative solvent. Based on this and intermolecular interactions between CuPc and substrate a nucleation and growth model is developed explaining the aggregation of CuPc in a supersaturated TFA solution. Finally, a solution processed thin film of CuPc is applied as a donor layer in a functioning bilayer heterojunction OSC and the influence of the structure on OSC performance is studied. / In den vergangenen Jahren wurden kosteneffiziente nasschemische Beschichtungsverfahren für die Herstellung organischer Dünnfilme für verschiedene opto-elektronische Anwendungen entdeckt und weiterentwickelt. Unter anderem wurden Phthalocyanin-Moleküle in photoaktiven Schichten für die Herstellung von Solarzellen intensiv erforscht. Aufgrund der kleinen bzw. unbekannten Löslichkeit wurden Phthalocyanin-Schichten durch Aufdampfverfahren im Vakuum hergestellt. Des Weiteren wurde die Löslichkeit durch chemische Synthese erhöht, was aber die Eigenschaften von Pc beeinträchtigte. In dieser Arbeit wurde die Löslichkeit, optische Absorption und Stabilität von 8 verschiedenen unsubstituierten Metall-Phthalocyaninen in 28 verschiedenen Lösungsmitteln quantitativ gemessen. Wegen ausreichender Löslichkeit, Stabilität und Anwendbarkeit in organischen Solarzellen wurde Kupferphthalocyanin (CuPc) in Trifluoressigsäure (TFA) für weitere Untersuchungen ausgewählt. Durch die Rotationsbeschichtung von CuPc aus TFA Lösung wurde ein dünner Film aus der verdampfenden Lösung auf dem Substrat platziert. Nach dem Verdampfen des Lösungsmittels, die Nanobändern aus CuPc bedecken das Substrat. Die Nanobänder haben eine Dicke von etwa ~ 1 nm (typische Dimension eines CuPc-Molekül) und variierender Breite und Länge, je nach Menge des Materials. Solche Nanobändern können durch Rotationsbeschichtung oder auch durch andere Nassbeschichtungsverfahren, wie Tauchbeschichtung, erzeugt werden. Ähnliche Fibrillen-Strukturen entstehen durch Nassbeschichtung von anderen Metall-Phthalocyaninen, wie Eisen- und Magnesium-Phthalocyanin, aus TFA-Lösung sowie auf anderen Substraten, wie Glas oder Indium Zinnoxid. Materialeigenschaften von aufgebrachten CuPc aus TFA Lösung und CuPc in der Lösung wurden ausführlich mit Röntgenbeugung, Spektroskopie- und Mikroskopie Methoden untersucht. Es wird gezeigt, dass die Nanobänder nicht in der Lösung, sondern durch Verdampfen des Lösungsmittels und der Übersättigung der Lösung entstehen. Die Rasterkraftmikroskopie wurde dazu verwendet, um die Morphologie des getrockneten Films bei unterschiedlicher Konzentration zu studieren. Der Mechanismus der Entstehung der Nanobändern wurde im Detail studiert. Gemäß der Keimbildung und Wachstumstheorie wurde die Entstehung der CuPc Nanobänder aus einer übersättigt Lösung diskutiert. Die Form der Nanobändern wurde unter Berücksichtigung der Wechselwirkung zwischen den Molekülen und dem Substrat diskutiert. Die nassverarbeitete CuPc-Dünnschicht wurde als Donorschicht in organischen Doppelschicht Solarzellen mit C60-Molekül, als Akzeptor eingesetzt. Die Effizienz der Energieumwandlung einer solchen Zelle wurde entsprechend den Schichtdicken der CuPc Schicht untersucht.

Ba(Zr0.1Ce0.7Y0.2)O3-£_ (BZCY) shows high proton conductivity as well as high chemical stability over a wide range of solid oxide fuel cell (SOFC) operating conditions. Sm0.5Sr0.5CoO3-£_ (SSC) cathode deposited by electrostatic spray deposition (ESD) on SOFC half cell obtained via tape-casting shows porous and reticular microstructure, and the SOFC single cell consists of substrate/ BZCY+NiO/ BZCY/ SSC. The electrolyte thickness decrease from 22 £gm, 20 £gm, 17.6 £gm to 15.1 £gm after sintering as the content of carbon pore former in the corresponding anode functional layer increased from 0.0 wt.%, 5.0 wt.%, 10.0 wt.% to 15.0 wt.%, and the maximum power density of corresponding cells at 700¢J varies from 476.89 mW/cm2, 713.34 mW/cm2, 862.50 mW/cm2 to 706.89 mW/cm2, respectively.

In the last decade, computational power, memory bandwidth and programmability capabilities of graphics processing units (GPU) have rapidly evolved. Therefore, many researches have been performed to use GPUs in advanced graphics rendering. Because of its high degree of parallelism, ray tracing has been one of the rst algorithms studied on GPUs. However, the rendering of large scenes with ray tracing can easily exceed the GPU&#039 / s memory capacity. The algorithm proposed in this work uses a data parallel approach where the scene is partitioned and assigned to CPU-GPU couples in a cluster to overcome this problem. Our algorithm focuses on ray casting which is a special case of ray tracing mainly used in visualization of volumetric data. CPUs are pretty ecient in ow control and branching while GPUs are very fast performing intense oating point operations. Using these facts, the GPUs in the cluster are assigned the task of performing ray casting while the CPUs are responsible for traversing the rays. In the end, we were able to visualize large scenes successfully by utilizing CPU-GPU couples eectively and observed that the performance is highly dependent on the viewing angle as a result of load imbalance.

The aim of the present study was to investigate the effects of different levels of Saffil alumina fiber addition, magnesium content in aluminum alloy matrix and casting temperature on the mechanical behavior, microstructure and physical properties of short fiber reinforced aluminum matrix composites. The main alloying element silicon was kept constant at 10 wt%. Magnesium contents were selected as 0.3 wt% and 1 wt%. Saffil alumina fiber preforms varied from 10 to 30 vol%. The casting temperatures were fixed at 750 &deg / C and 800 &deg / C. Micro porosity was present at the fiber-fiber interactions. Closed porosity of the composites increased when fiber vol% increased, however, variation in casting temperature and magnesium content in matrix did not have influence on porosity. Hardness of the composites was enhanced with increasing fiber vol%, magnesium content in matrix and decreasing casting temperature. Alignment of fibers within the composite had an influence on hardness / when fibers were aligned perpendicular to the surface, composites exhibited higher hardness. The highest hardness values obtained from surfaces parallel and vertical to fiber orientation were 155.6 Brinell hardness and 180.2 Brinell hardness for AlSi10Mg1 matrix 30 vol% alumina fiber reinforced composite cast at 800 &deg / C and at 750 &deg / C, respectively. 30 vol% Saffil alumina fiber reinforced AlSi10Mg0.3 matrix composite cast at 750 &deg / C showed the highest flexural strength which is 548 MPa. Critical fiber content was found as 20 vol% for all composites.

In this study, the aim is to investigate the stiffness, longitudinal tensile strength and circumferential tensile strength of short fiber reinforced polyester composite pipes produced by centrifugal casting production method. To achieve this aim, theoretical calculation of modulus of elasticity of pipes was done and then test program was carried out on pipe samples produced with three different resin types which were orthophthalic, isophthalic and vinyl ester resin and three different fiber types which were E glass fiber, ECR glass fiber and basalt fiber. The tests were performed according to ISO (International Organization for Standardization) standards. When resin type and fiber type effect on the fiber reinforced polyester pipe samples were evaluated, calculated elastic modulus values were in accordance with the test results. According to the experimental test data, which were used to evaluate the effect of resin type on fiber reinforced polyester pipe properties, there is not a significant difference was observed in the stiffness, longitudinal and circumferential tensile strength test results of pipes having different resin types. In other words, there was not a significant effect of resin type on the stiffness, longitudinal tensile strength and circumferential tensile strength of short fiber reinforced pipes produced by centrifugal casting method. According to the experimental test data, which were used to evaluate the effect of fiber type on the properties of fiber reinforced polyester pipe, basalt fiber reinforced pipe samples showed higher mechanical performance over E glass fiber and ECR glass fiber reinforced pipes. However, the test results of basalt reinforced polyester pipe were not as good as the individual properties of basalt fiber. Finally, by comparing the basalt fiber reinforced pipe samples having almost the same stiffness and tensile test results as E glass fiber reinforced pipe samples, the gain in fiber and resin amount were investigated. Basalt fiber reinforced pipes were slightly lighter and thinner than E glass fiber reinforced pipes. However, the decrease in the amount of the fiber and resin in basalt reinforced pipe did not result in an overall cost reduction.

Before beginning the experimental work of this study, a magnesium high pressure die casting facility is set up to manufacture magnesium cast parts for defence industry. In this thesis two components are cold chamber high pressure die casted using magnesium alloy AZ91 as raw material, and one component was manufactured using both aluminium alloy A.413, and magnesium alloy AZ91. Mechanical properties of high pressure die casting parts depend on various parameters such as, thickness of the cast part, position of the cast part in the cavity, molten metal temperature, die temperature, piston speeds, and injection pressure. The aim of this study is to investigate the effects of section thickness of the cast part, position of the cast part in the die cavity, piston speeds, and molten metal temperature on mechanical properties of magnesium die cast parts. Tensile properties of products from Al A.413 and Mg AZ91 alloys are also compared. Casting analysis software is used to simulate filling and temperature evolution of three different casting components. Piston speeds are first calculated from equations in the literature and then verified by using the software. Specimens for microstructural investigation, and mechanical tests are machined directly from the mass produced parts. Optical microscopy, and scanning electron microscopy investigations are carried out for grain size and porosity determination. Tensile tests are conducted for yield strength, ultimate tensile strength, and % elongation values. The results of casting analysis software simulations, grains size investigations, porosity investigations, and tensile tests are correlated to each other. Optimum piston speeds, optimum molten metal temperatures are observed, effect of grain size and porosity concentrations on the effect of mechanical properties are compared. Weight of cast parts produced from Mg AZ91 are 35 % lower than that of Al A.413 parts. However, ultimate tensile strength of the cast parts produced from Mg AZ91 are found to be similar to the aluminium parts.