Browsing by Subject "texture"
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Item Development and Testing of a BI-2212 Textured Powder Conductor(2014-03-10) Damborsky, KyleSuperconducting wires based on the high field superconductor Bi_(2)Sr_(2)Ca_(1)Cu_(2)O_(8)+x are an enabling technology for the development of very high field (>18 T) magnets. While these conductors have the potential to serve as the conductors for magnets operating in excess of 45 T, the achieved current carrying capacity of these materials is too low for economical implementation in high field operation. This is in part due to low density of the superconductors within the cores, the presence of current occluding non-superconducting phases, and a non-optimum alignment of the superconducting particles that form the conductor. The body of work reported in this dissertation aims to develop methods to align (texture) the superconducting particles within the conductors, to enhance the density of the superconducting filaments, to examine a heat treatment that does not form parasitic phases, and to demonstrate that long lengths of superconducting wire can be fabricated with these properties. Three general experimental thrusts are carried out within the work. First, methods for texturing Bi-2212 loose powders were developed and the products of these developments were characterized via x-ray diffraction and microscopy to qualify the degree of imparted texture. The second thrust focused on the development of a monocore wire based on a high density textured Bi-2212 precursor. Multiple wires were extruded and drawn through traditional processes and the products were characterized microscopically to ascertain the quality of the products. The third and final thrust was the development of a non-melt heat treatment that was shown to grow grains of Bi-2212 powder and densify composites. Measurements of the transport critical currents for the heat treated conductors were carried out in boiling liquid helium and background magnetic fields of up to 5 T. These results were correlated to microstructural observations. Ultimately, it was found that the connections between grains in the sintered conductors were insufficient to allow robust transport current and only 1% of the predicted transport currents were reached through the sintering study.Item Effect of Texture on Formability and Mechanical Anisotropy of a Severe Plastically Deformed Magnesium Alloy(2012-02-14) Modarres Razavi, SoniaMagnesium and its alloys have been considered as alternatives to aluminum alloys and steels for structural applications in automotive and aerospace applications due to their superior specific strength and light-weight. However, they have hexagonal-close packed (hcp) structure, and thus have a small number of deformation systems resulting in low ductility and formability near room temperature, anisotropic thermo-mechanical response and strong deformation textures. The aim of this work is to investigate experimentally the effect of crystallographic texture generated during severe plastic deformation (SPD), on the subsequent formability and mechanical flow anisotropy in AZ31B Mg alloy. The proper control of grain size and texture through SPD is expected to result in better low temperature formability and better control of mechanical flow anisotropy. AZ31B Mg alloy has been successfully processed using equal channel angular extrusion (ECAE) following different processing routes, multiple passes, and different processing temperatures, in order to obtain samples with a wide variety of grain sizes, ranging from ~370 nm up to few microns, and crystallographic textures. Low temperature processing of the AZ31B Mg alloy was successful after initial high temperature processing. Smaller grain sizes were achieved using the temperature step-down method leading to incremental reduction in grain size at each ECAE pass. The temperature step-down method was utilized to develop hybrid ECAE routes to obtain specific crystallographic textures. Optimized hybrid ECAE routes were developed which resulted in a high strength/high ductility material with the average grain size of ~370 nm. The ECAE processed alloy showed a high tensile yield strength of ~380 MPa that has never been reported so far in AZ31 ingot metallurgy Mg alloys. The influence of grain size on the critical stress for the activation of individual deformation mechanisms was also investigated by systematically controlling the texture and grain size, and assuming the activation of mainly a single deformation mechanism through the careful selection of the loading direction on the processed samples. It was revealed that the Hall-Petch slope for the basal slip was much smaller than those of prismatic slip and tensile twinning.Item Effects of barley flour and beta-glucans in corn tortillas(Texas A&M University, 2004-09-30) Silva, LauraThe effects of b-glucan on corn tortilla texture were evaluated. Barley flour (9.7% b-glucan) was substituted at 2.5, 5 and 10% for dry masa flour in corn tortillas. Texture was evaluated after 4 hr and up to 7 d storage at 4?C. Substitution of 2.5-10% barley flour significantly improved tortilla texture. Combined effects of barley flour (0-2.5%), maltogenic amylase (0-1650MAU) and carboxymethylcellulose (0-0.5%) were evaluated using surface response methodology. Barley flour increased rollability, pliability, energy dissipated and reduced rupture force and final stiffness. Overall, maltogenic amylase decreased rupture force and Young's modulus but decreased rupture distance, rollability and pliability at levels above 825 MAU. CMC improved rollability, pliability, and rupture distance. The best response was found using barley flour and CMC with 825 MAU, where rollability, pliability, rupture distance and energy dissipated increased while rupture force, Young's modulus and final stiffness decreased. A 70% barley b-glucan concentrate combined with amylase (550 MAU) or CMC (0-0.5%) was evaluated in corn tortillas. Amylase combined with b-glucan did not improve texture. Tortillas with b-glucan and CMC had significantly improved pliability, rollability, final stiffness and energy dissipated. Texture measurements analysis showed that depending on the stage of storage, objective and subjective methods correlate differently. Subjective and objective measurements of texture were not correlated at 4 hr storage. At the end of storage, pliability had significant correlations with stress relaxation measurements, but rollability had higher correlation coefficients with extensibility measurements. Pliability had higher R2 and lower coefficients of variation compared to rollability. Sensory evaluation was conducted using reheated 14-day-old tortillas of control, 825 MAU with 0.25% CMC, 0.12% b-glucans, 0.18% b-glucan with 0.375% CMC, and 0.24% b-glucan with 0.25% CMC. All tortillas had similar appearance, flexibility, gumminess, flavor and overall quality. Softness and chewiness of treatments with 0.12% b-glucan or 0.24% b-glucan with 0.25% CMC were similar to control. Other tortillas were significantly tougher and chewier. b-glucan may be the active ingredient in barley flour that modifies firming of corn tortillas during storage. Barley flour is inexpensive and effectively improves texture of corn tortillas.Item Improvement of Low Quality Meat Utilizing Functional Ingredients(2011-08-08) Booren, Betsy LynAlternative methods to reduce the variation caused by pale, soft, and exudative (PSE) and dark, firm, and dry (DFD) conditions in meat tissues need to be examined. The objective of this dissertation was to determine if functional ingredients, like hydrocolloids and bicarbonates, improved the quality of PSE and DFD meat. This was accomplished by examining the rheological characteristics of meat model systems and products after enhancement with hydrocolloids and bicarbonates ingredient solutions. These results will be used to formulate and manufacture either enhanced beef steaks, beef roasts, or frankfurters to test the efficacy of use to improve the quality of DFD or PSE meat. The flow behavior, steady-shear viscosity, and dynamic testing of hydrocolloid solutions were determined. Torsion Analysis (TA) and Texture Profile Analysis (TPA) were performed on PSE muscle tissue gel samples and frankfurters. Raw and cooked CIE color space values, pH, and sensory evaluation determination were made on meat gel samples, beef steaks, roast beef, and frankfurters. Hydroxypropyl methylcellulose (1.0%HPMC), methylcellulose (1.0%SGMC), and konjac flour (0.125%KF) were found to be Newtonian in behavior. The dynamic moduli of these ingredients were resistant to changes in ionic strength and were tested for viability in a meat model system. Potassium bicarbonate (KHCO) was a viable substitute for sodium bicarbonate. The synergistic effect of combining KHCO with hydrocolloids, salt and sodium phosphate (SP) improved the color, pH, and textural properties of PSE ground pork and frankfurters, but did not effect sensory characteristics. Acetic acid (AA), KF, and xanthan gum (XG) were added to beef steaks and bottom rounds to reduce the meat quality variation caused by high pH and animal age. The addition of AA and hydrocolloid treatments improved the color and pH of high pH muscles and did not appreciable affect shelf-life flavor of cooked roast beef. Solutions of AA, KF and XG were viable enhancement treatments for use in high pH beef bottom rounds to produce a fully cooked roast beef product.Item Mapping textures on 3d terrains: a hybrid cellular automata approach(Texas A&M University, 2007-04-25) Sinvhal, SwapnilIt is a time consuming task to generate textures for large 3D terrain surfaces in computer games, flight simulations and computer animations. This work explores the use of cellular automata in the automatic generation of textures for large surfaces. I propose a method for generating textures for 3D terrains using various approaches - in particular, a hybrid approach that integrates the concepts of cellular automata, probabilistic distribution according to height and Wang tiles. I also look at other hybrid combinations using cellular automata to generate textures for 3D terrains. Work for this thesis includes development of a tool called "Texullar" that allows users to generate textures for 3D terrain surfaces by configuring various input parameters and choosing cellular automata rules. I evaluate the effectiveness of the approach by conducting a user survey to compare the results obtained by using different inputs and analyzing the results. The findings show that incorporating concepts of cellular automata in texture generation for terrains can lead to better results than random generation of textures. The analysis also reveals that incorporating height information along with cellular automata yields better results than using cellular automata alone. Results from the user survey indicate that a hybrid approach incorporating height information along with cellular automata and Wang tiles is better than incorporating height information along with cellular automata in the context of texture generation for 3D meshes. The survey did not yield enough evidence to suggest whether the use of Wang tiles in combination with cellular automata and probabilistic distribution according to height results in a higher mean score than the use of only cellular automata and probabilistic distribution. However, this outcome could have been influenced by the fact that the survey respondents did not have information about the parameters used to generate the final image - such as probabilistic distributions, the population configurations and rules of the cellular automata.Item Relative advantage of touch over vision in the exploration of texture(Texas A&M University, 2008-10-10) Bai, Yoon HoTexture segmentation is an effortless process in scene analysis, yet its mechanisms have not been sufficiently understood. Several theories and algorithms exist for texture discrimination based on vision. These models diverge from one another in algorithmic approaches to address texture imagery using spatial elements and their statistics. Even though there are differences among these approaches, they all begin from the assumption that texture segmentation is a visual task. However, considering that texture is basically a surface property, this assumption can at times be misleading. An interesting possibility is that since surface properties are most immediately accessible to touch, texture perception may be more intimately associated with texture than with vision (it is known that tactile input can affect vision). Coincidentally, the basic organization of the touch (somatosensory) system bears some analogy to that of the visual system. In particular, recent neurophysiological findings showed that receptive fields for touch resemble that of vision, albeit with some subtle differences. The main novelty and contribution of this thesis is in the use of tactile receptive field responses for texture segmentation. Furthermore, we showed that touch-based representation is superior to its vision-based counterpart when used in texture boundary detection. Tactile representations were also found to be more discriminable (LDA and ANOVA). We expect our results to help better understand the nature of texture perception and build more powerful texture processing algorithms. The results suggest that touch has an advantage over vision in texture processing. Findings in this study are expected to shed new light on the role of tactile perception of texture and its interaction with vision, and help develop more powerful, biologically inspired texture segmentation algorithms.Item The effect of enzymes and hydrocolloids on the texture of tortillas from fresh nixtamalized masa and nixtamalized corn flour(Texas A&M University, 2004-09-30) Gutierrez de Velasco, Arturo CarlosThe texture of tortillas was improved by the addition of maltogenic amylase and carboxymethylcellulose (CMC) and guar gum to fresh masa from ground nixtamal (FNM) and nixtamalized corn flour (NCF) masa. Differences in the performance of additives in tortillas held under refrigeration or ambient storage were documented. For NCF tortillas, significant improvements were obtained in objective and subjective texture measurements by two treatments. Tortilla texture was improved by a treatment with a high enzyme level (170 mg/kg of maltogenic ?-amylase, 0.14% CMC, 0.85% guar) as measured by objective tests and by a treatment with low enzyme level (60 mg/kg of maltogenic ?-amylase, 0.43% CMC, 0.57% guar) as measured by subjective tests. The addition of maltogenic ?-amylase (70 mg/kg) and CMC (0.35%) to FNM tortillas at levels similar to the low enzyme NCF treatment but with lower guar level (0.12%) improved tortilla texture. The maltogenic ?-amylase softened tortillas by trimming the starch structure. This allowed the guar to interfere with amylopectin re-crystallization inside gelatinized starch granules. The CMC created a more flexible intergranular matrix that helped maintain the disrupted tortilla structure. Guar was ineffective in refrigerated tortillas, whereas, maltodextrins effectively improved refrigerated tortillas. The sequence of partial starch hydrolysis, warm holding condition, and time for guar to associate with starch and CMC was necessary to improve tortilla texture. Thus, different additives may be required for cold versus room temperature storage. Sugars increased in enzyme-treated tortillas during storage. This suggests that maltogenic ?-amylase was only partially inactivated during baking of corn tortillas. Tortillas with more enzyme had lower and later pasting viscosity as measured by a Rapid Viscoanalyzer. Tortillas prepared from FNM also had lower and later pasting viscosity compared to NCF tortillas. Pasting viscosity of tortillas revealed intrinsic starch polymer characteristics and interactions. Results of this study provide commercially applicable information about desired levels for the extent of starch hydrolysis, the type and amount of gums and starches, and product microstructure to delay staling of corn tortillas.Item The effect of strain and path change on the mechanical properties and microstructural evolution of ultrafine grained interstitial free steel during equal channel angular extrusion (ECAE)(Texas A&M University, 2007-04-25) Sutter, Steven GeorgeThe objectives of this study were to examine the effect of strain and path change on the microstructural evolution of ultrafine grained interstitial free (IF) steel during equal channel angular extrusion (ECAE); to determine the mechanical properties; to observe the resulting texture; and to perform optical and electron microscopy of the resulting material. The effects of different routes of extrusion (A, B, C, C' and E), heat treatment and plastic strains from 1.15 to 18.4 were examined. Monotonous tensile testing was used to determine mechanical behavior of processed materials. X-ray diffraction and TEM analyses were performed to evaluate the effect of processing on texture and grain morphology. Hardness measurements were performed to determine recrystallization behavior of the processed material. Optical microscopy was conducted on heat treated samples to determine their grain size and refinement. Monotonous tensile testing of processed materials showed that there was significant strengthening after the first extrusion. Further processing resulted in increasing values of yield strength and ultimate tensile strength, with ductility at failure varying depending upon which processing route was used. The best tensile strength results were obtained after processing Routes 8C' and 16E, due to the significant grain refinement these routes produced. X-ray diffraction revealed increases in strength of preferred texture along the directions [111] and [001], perpendicular to the transverse plane, for all specimens that were processed using ECAE. TEM observations showed a consistent refinement of grain size as the amount of processing increased, especially within Routes C' and E. Hardness measurements of heat treated specimens showed that the onset of recrystallization occurred at approximately the same temperature of recrystallization as that of pure iron, 450????C. The recrystallization curves for all samples showed that grain growth begins at a temperature of around 700????C. The low carbon content of IF steel made optical microscopy challenging. The grain size of annealed materials becomes finer and more uniform, ranging between 60 and 90 ????m2, at high strain levels under Routes C' and E, due to the many potential nucleation sites developed in highly worked material.