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This thesis studies the reliability issues of encapsulated cholesteric LCD, and analyzes the defective pixel. Adjusting fabrication process parameters, we change the thickness of the buffer layer and absorption layer to explore the influence of different boundaries to CLC. It is found that the buffer layer can provide a good protection. When the buffer layer is getting thicker, the less the defective pixels appear, and the absorption layer cannot induce defect. The reflection band of the ITRI¡¦s encapsulated CLCs blue shifts to UV band and then become defective pixel. When CLCs exposed to the atmosphere with large area, the reflected color will be shifted. The shift of reflection band is due to CLC¡¦s inherent properties. Different kind of CLC has different properties, and we found the reflection band of ITRI¡¦s CLC is blue shift and the nematic E48 with chiral dopant R811 is red. Mixing different features of CLCs with appropriate proportion can reduce the color shift. In conclusion, mixing different characteristics CLCs with appropriate proportion and providing good protection to encapsulated CLC, we can reduce CLC¡¦s color shift and restrain the defective pixel.

Master of Agribusiness / Department of Agricultural Economics / Ted C. Schroeder / The CNH Wichita Product Center has had a chronic leak problem with the Skid Steer Loaders. The objective of this project was to analyze the manufacturing plant leak data and make improvements to correct the issue. The objective is twofold: 1) to make process or design improvements on current products produced in the plant and 2) to make recommendations for future designs to prevent such leak issues from reoccurring. The manufacturing data had to be transformed into usable form and then it was analyzed mostly by utilizing Pareto Charts. The highest six problem leak points were chosen from the manufacturing data. Process changes were implemented on these particular leak joints and the results were analyzed using two proportions hypothesis tests. The process changes reduced the leak rate by an average percent reduction of 86 percent. The process changes implemented will also be applied to other similar joints, and results documented in the future. The future design recommendations made from the analyzed data included the increased use of o-ring face seal connections at certain locations and where possible, reducing the number of joints per machine.

The displacement damage induced by primary recoils of fusion neutrons in tungsten and alloys has been studied with self-ion irradiations, followed by damage characterization with electron microscopy. Tungsten and alloys (≤ 5 wt.% Re, Ta, V) were implanted with 2 MeV W+ ions over a dose range of 3.3×1017 - 2.5×1019 W+m-2 at temperatures ranging from 300 to 750°C. Dislocation loops of b = ½<111> (> 60%) and b = <100> were identified, and that ½<111> loops were found more thermally stable. Among loops that were large enough for nature determination, at least 50% were found to be of interstitial type, with larger fractions in high-temperature and high-dose conditions. The diameter of loops did not exceed 20 nm, with the majority being ≤ 5 nm. The loop number density varied between 1022 and 1023 m-3. The effects of ion dose, irradiation temperature, composition and grain orientation on damage microstructure were investigated. In-situ irradiations (150 keV W+ ions) were carried out as a complement to the bulk implantations. Qualitative trends in loop size, geometry and nature with irradiation dose and temperature were similar to bulk irradiated specimens. Also, the dynamics of defects and their effects on the damage evolution were explored. In-situ annealing of irradiated thin foils was performed to investigate the thermal stability of radiation damage in tungsten. The majority of microstructure transformations were completed within 15 min of annealing. However, extended durations did favour the increase of loop size and the fraction of ½<111> loops.

An experimental technique based on the immobilisation of dislocations by segregation of impurity atoms to the dislocation core (dislocation locking) has been developed and used to investigate the critical conditions for slip occurrence in Czochralski-grown and nitrogen-doped floating-zone-grown silicon crystals. The accumulation of nitrogen and oxygen impurities along a dislocation and the resulting dislocation locking effect has been investigated in silicon samples subjected to different annealing conditions. In particular, the stress needed to unlock the dislocations after their decoration by impurities has been measured as a function of annealing duration and temperature. The approach used in this study has allowed the determination of new diffusivity data for oxygen and nitrogen in silicon in the technologically important range of temperatures 350-850°C. No other data covering such wide temperature range are available in the literature. In addition to transport properties, the binding energy of an impurity atom to a dislocation in silicon has been deduced from the experimental data in the case of oxygen and nitrogen impurities. A discussion in terms of the impurity species responsible for transport (monomers or dimers) and dislocation locking is also presented. The role of oxide precipitates in the generation of glide dislocation loops and the parameters affecting the occurrence of slip have been investigated in silicon samples containing precipitates of different sizes and different morphologies. The fundamental parameters deduced in this work have been used to develop a numerical model to investigate the effect of different heat treatments on the mechanical properties of silicon wafers containing a controlled distribution of impurities. This model has then been used to simulate real wafer processing conditions during device fabrication to show how they may be modified to increase dislocation locking. It is hoped that these results will have relevance to how wafers are processed in order to minimise or eliminate dislocation multiplication and consequent warpage.

Acoustical characteristics are used to classify the structural and operational conditions in underground pipes with advanced signal classification methods.

This thesis is concerned with the development and study of a pattern recognition system for siphon and sewer condition/defect analysis based on acoustic characteristics. Pattern recognition has been studied and used widely in many fields including: identification and authentication; medical diagnosis and musical modelling. Audio based classification and research has been mainly focusing on speech recognition and music retrieval, but few applications have attempted to use acoustic characteristics for underground pipe condition classification. Traditional CCTV inspection methods are relatively expensive and subjective so remote techniques have been developed to overcome this concern and increase the inspection efficiency. The acoustic environment provides a rich source of information about the internal conditions of a pipe. This thesis reports on a classification system based on measuring the direct and reflected acoustic signals and describing the energy spectrum for each condition/pipe defect. A K-nearest neighbour classifier (KNN) and Support vector machines (SVMs) classifier have been adopted to train the classification system to identify sediment and pipe surface defects by comparing the measured acoustic signals with a database containing a range of typical conditions. Laboratory generated data and field collected data were used to train the proposed system and evaluate its ability. The overall accuracy of the system recognizing blockage and structural aspects in each of the series of experiments varies between 70% and 95%.

Designing materials for fusion applications is a very challenging problem, requiring detailed understanding of the behaviour of materials under the kinds of extreme conditions expected in a fusion environment. During the lifetime of fusion-reactor components, materials will be subjected to high levels of neutron irradiation, but must still perform effectively at high operating temperatures and under significant loading conditions. Body-centred cubic (bcc) transition metals are some of the most promising candidates for structural materials in fusion because of their relatively high density, which allows for effective neutron-shielding with the minimum volume and mass of material. In this work we perform atomistic simulations on two of the most important of these, Fe and W. In this thesis we describe atomic-scale simulations of defects found in bcc systems. In part I we consider the vacancy and interstitial loop defects that are produced and accumulated as a result of irradiation-induced displacement cascades. We show that vacancy dislocation loops have a critical size below which they are highly unstable relative to planar void defects, and thus offer an explanation as to why they are so rarely seen in TEM observations of irradiated bcc metals. Additionally, we compare the diffusion rates of these vacancy loops to their interstitial counterparts and find that, while interstitial loops are more mobile, the difference in mobility is not as significant as might have been expected. In part II we study screw dislocations, which, as the rate limiting carriers of plastic deformation, are significantly responsible for the strength of materials. We present results from large-scale finite temperature molecular dynamics simulations of screw dislocations under stress and observe the thermally-activated kink-pair formation regime at low stress, which appears to be superseded by a frictional regime at higher stresses. The mobility functions fitted to the results are vital components in simulations of dislocation networks and other large-scale phenomena. Lastly, we develop a multi-string Frenkel-Kontorova model that allows us to study the core structure of screw dislocations. Subtle changes in the form of the interaction laws used in this model demonstrate the difference between the non-degenerate and degenerate core structures. We provide simple criteria to guarantee the correct structure when developing interatomic potentials for bcc metals.

Irradiation damage structures induced in pure Fe and Fe-Cr (up to 14%Cr) alloys by 2 MeV Fe+ ion irradiations in the temperature range 300-460°C were investigated by transmission electron microscopy. Specimens were irradiated in bulk to doses of 1.5 x 1019 Fe+/m2 (about 2.5 displacements per atom: dpa) and 4.5 x 1019 Fe+/m2 (about 7 dpa). In most cases, damage took the form of dislocation loops with diameters from 2-100nm; the loops were distributed uniformly within all the samples. At higher irradiation temperatures (400°C, 460°C), complex microstructures such as finger loops (50nm in width and 1 micron in length) and perpendicular <100> loop clusters, were observed in both pure Fe and Fe-Cr samples. Loop sizes and densities were seen to change as a function of irradiation temperature and dose. Loop sizes were seen to increase as the increase of irradiation temperatures and doses, while loop densities only increased with increasing doses and decreased as increasing temperatures. Loops with both types of Burgers vectors (<100> and ½<111>) were observed in all the samples. The proportion of <100> loops was higher in Fe than that in Fe-Cr alloys at the same irradiation condition, which has can be attributed to the high mobility of ½<111> loops in Fe, so that a large proportion of them will escape to the (001) foil surface. A transition in loop Burgers vectors as a consequence of increasing temperature was observed. In Fe, the proportion of <100> loops increased with increasing irradiation temperature from 40% at 300°C to 60% at 460°C. A similar trend was found in the Fe-Cr alloys, but due to the higher proportion of ½<111> loops in these alloys, the increase of <100> loops was not that obvious, being from 30% at 300°C to 45% at 460°C(Fe-11Cr). The effects of irradiation dose rate on the formation of dislocation loops by 2 MeV Fe+ ions were also investigated. These irradiations were carried out at 300°C with two different implantation dose rates: 6 x 10-4 dpa/s and 3 x 10-5 dpa/s. The implantation dose for both implantations was 0.38 x 1019 Fe+/m2 (0.5 dpa). Both the average loop size and loop densities for the Fe-Cr specimens subjected to the high dose rate irradiation were higher than that in the low dose rate irradiations. Take Fe-14Cr as an example, that the loop densities in high dose rate irradiation increased about 90% compared to that in low dose rate, and the average loop size in high dose rate irradiation was 30% larger than that in low dose rate irradiation. The ‘inside-outside contrast’ method was applied to determine the loop nature in all the samples. It was found that all the large loops (>5nm) are of interstitial type. Any vacancies are believed to exist in the form of small dislocation loops (<5nm) or sub-microscopic voids.

The primary aim of this research was to develop and improve the experimental method and data interpretation for strain measurements using diffraction methods to gain a better understanding of micromechanical deformation and anisotropy of lattice strain response. Substantial part of the research was devoted to the development of the laboratory high energy X-ray diffractometer (HEXameter) for bulk residual strain evaluation. White beam energy dispersive X-ray diffraction was chosen as the principal diffraction mode due to its extreme efficiency in utilising X-ray flux and its ability to capture large segments of diffraction patterns. The specimens that have been examined were real engineering components, mechanically deformed specimens and thermally treated specimens, ranging from dynamic in-situ measurements to ex-situ materials engineering. For the real engineering components, a wedge coupon from the trailing edge of a Ti64 wide fan blade and a turbine combustion casing were examined. Among the mechanically deformed specimens that have been measured were shot-peened steel plates, elasto-plastically bent bars of Mg alloy and cold expanded Al disks. Amongst the thermally deformed specimens, laser-formed steel plates, thermal spray coatings, a manual inert gas weld of Al plates, a friction stir weld of Al plates and Ni tubes and a quenched Ni superalloy cylinder used for strain tomography were studied. In-situ loading experiments have also been carried out, such as experiments on pointwise mapping of grain orientation and strain using the 3DXRD microscope at the ESRF and in-situ loading experiments on titanium alloy, rheo-diecast and high pressure diecast Mg alloy, IN718 Ni-base superalloy and Al2024 aluminium alloy. Experimental results from X-Ray diffraction and strain tomography were used to achieve a better understanding of the material properties. Some results were compared with polycrystal Finite Element model predictions. Amongst the most prominent research achievements are the development on the HEXameter laboratory instrument, including: (i) the development of special collimation systems for the detectors and the source tube; (ii) the development of a twin-detector setup (that allows for simultaneous determination of strain in two mutually orthogonal directions); (iii) improved alignment procedures for better performance; and (iv) the adaptation of instrumentation for efficient scanning of both large and small components, that included choosing and adapting translation devices, programming of the translation system and designing sample mounting procedures. In this research several approaches to data treatment were investigated. Quantitative phase analysis, single peak fitting (using custom Matlab routines and GSAS) and full pattern fitting (with individual pattern data refined by GSAS and batch refinement done by invoking GSAS via a Matlab routine) were applied. Different Matlab routines were written for specific experimental setups; and various analysis methods were selected and used for refinement depending on the requirements of the measurement results interpretation. 16 papers were published, ensuring that the results of this thesis are readily available to other researchers in the field.