Call number: LD2668 .T4 1984 L386 / Master of Science

published_or_final_version / abstract / Mechanical Engineering / Master / Master of Philosophy

No description available.

The development of grinding technology is a topic that has not received much attention from archaeologists in the American Southwest. Presented here is a technological approach to ground stone analysis capitalizing on the methods of ethnoarchaeology, experimentation, and use-wear analysis. These methods are applied to an existing collection of ground stone artifacts amassed by the University of Arizona field school's excavation of the Point of Pines sites in east-central Arizona. The heart of the technological approach is the recognition that technological behavior is social behavior and as such is culturally distinct. Both puebloan and nonpuebloan ethnographies provide models for understanding how ground stone tools were used by different cultural groups in daily activities and for making inferences about gender-specific behaviors. Culturally distinct behaviors are sustained through technological traditions, defined as the transmitted knowledge and behaviors with which people learn how to do things. A technological approach is applied to the ground stone assemblages from nine Point of Pines sites that date within eight phases, from A.D. 400 to A.D. 1425-1450. The assemblages are compared and assessed in terms of variation that might reflect developments in grinding technology. Developments may have derived from local innovations or from introduced technological traditions. Assemblage variation is evaluated in light of major events in Point of Pines prehistory, particularly the change from pit house villages to pueblo villages and the immigration of Tusayan Anasazi. Point of Pines grinding technology continued relatively unchanged until late in the occupation. Around the mid-1200s, an Anasazi group immigrated to the Point of Pines area and took up residence in the largest Point of Pines pueblo. Foreign technology was introduced but not immediately adopted by the resident Mogollon. Food grinding equipment of two different designs coexisted for about 100 years, until around A.D. 1400 when there is evidence of a change in the social organization of food grinding. It is this change that signals the blending of Mogollon and Anasazi into Western Pueblo.

This research project investigates a new technique to efficiently mix crystalline solid additives with polymers by gentle ball milling with steel balls in the presence of carbon dioxide (C02) at 17 to 30°C and 1300 to 2500 psig. As the ball milling system is agitated, the steel balls transfer mechanical energy to the fluoropolymer and additive thereby converting them to powders. C02 is added into the chamber to expand the polymer and make it amenable to impregnation by the additive. At the end of the mixing process, a free flowing powder is produced consisting of the additive coated with fluoropolymer. The additives were extracted from the powders and intrinsic viscosity measurements were done on the remnant fluoropolymer. Viscosity studies showed that the virgin and post-ball milled fluoropolymers had similar intrinsic viscosities, hence similar molecular weights within experimental error limits. This implies that most of the polymer chains were simply disentangled during the mixing process and not broken. Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) were done on the virgin polymer, the additives and the fabricated powders to determine the loading levels and to ascertain if there were any changes to the physical properties of the polymer. Scanning electron micrographs showed that some of the powder particles had additive particles stuck on the surface, but when these additives were washed off the surface of the powders with a suitable solvent that did not dissolve the polymer, DSC analysis showed the presence of additive incorporated into the polymer matrix.

Master of Science / Department of Grain Science and Industry / Jeffrey A. Gwirtz / Sorghum grain is underutilized in the United States. Most sorghum flour available in the market place is whole grain flour with inferior stability and baking characteristics. The demand exists for high quality stable sorghum flour with low fiber and fat content. However, the current decortication step used for separating the bran from endosperm in sorghum milling is not economically viable and the alternatives techniques, which are based on abrasion and frictions, do poor jobs and tend to increase endosperm loss. The lack of information regarding sorghum dry milling to obtain low fat and low ash white sorghum flour is the rationale for developing a suitable flow. Previous research works in this field made some progress towards the achievement of that goal, but not enough to meet the need for high quality white sorghum flour. The main method (named F20105) developed in this study for processing sorghum (without decortication) consists of the following systems: prebreak, a gradual reduction system with purification, and an impact technology. Also, two short laboratory methods were designed for obtaining white sorghum flour for comparison purposes. These were named F20106 and F20107. The method F20106 was based on the use of Buhler Experimental Mill, a Great Western Gyratory Sieve, and Quadrumat Brabender Sr. Experimental Mill. The method F20107 was based on processing decorticated sorghum in a process which uses a hammer mill, a Great Western Gyratory Sieve and an Alpine Pin Mill. A commercial flour was evaluated along with the flours from the different methods in order to make comparisons among them. The long reduction system (FS20105) which included impact detaching techniques produced white sorghum flour with high extraction rate and good baking properties. An impact dehulling machine and a prebreak roller mill were effective in collecting glumes and cracking the sorghum kernels before first break. The shattering effect of the fragile sorghum bran was avoided by implementing air separation of bran from endosperm before each break. A purification system effectively cleaned and sorted the sorghum grits by size. Sorghum flours with different protein contents were evaluated for their baking quality properties. The protein content of sorghum flour was found strongly positive correlated with the amount of water added to the batter, cell wall thickness, cell diameter and cell volume ([rho]>0.85; P<0.0001), and strongly negative correlated with the number of cells/cm2 and L-value of the bread crust (-0.95>[rho]>-0.91; P<0.0001). It was also correlated with the a-value and b-value of the bread crust ([rho]=0.620, P< 0.014 and [rho]=0.520, P< 0.047, respectively). The diagrams F20105, F20106, and F20107 can be used successfully in their current form or with small adjustments to obtain flour from different sorghum hybrids at the laboratory scale. These diagrams also fill a gap in the currently available milling literature. Additionally they can be scaled up in the sorghum processing industry. The growing gluten-free food product market would potentially provide a rapid return on the necessary investment.

Call number: LD2668 .T4 1957 U57 / Master of Science

Master of Science / Department of Grain Science and Industry / Greg Aldrich / Novel ingredients fuel growth in the pet food market. Sorghum grain is a promising ingredient source. It grows in semi-arid regions and the pericarp is rich in phenolic compounds that are well-known antioxidants. The objectives were to determine the impact of milling sorghum on yield and composition of the various fractions, their impact on diet extrusion, and nutrient utilization when fed to dogs. Sorghum milling yields were 68.3% flour, 27.2% mill-feed, and 1.25% germ. Four nutritionally similar dog diets were extruded containing whole sorghum (WSD), sorghum flour (FLD), sorghum mill-feed (MFD), or a control diet (CON) with an equal proportion of corn, wheat and rice. The MFD had the highest (P < 0.05) bulk density and was 1.37-fold heavier than FLD. The FLD had a sectional expansion index (SEI) of 1.92 and 1.35-fold more than MFD and WSD. The FLD and MFD had the hardest kibbles (P < 0.05). Twelve Beagle dogs were fed the experimental diets in a 4 period replicated Latin square design with 9 d adaptation and 5 d total fecal collection (TFC). Fecal output was also estimated using acid insoluble ash (AIA), Cr₂O₃ and TiO₂. Plasma antioxidant activity was measured by oxygen radical absorbance capacity (ORAC) method. Fecal scores were highest (P < 0.05) for MFD treatment and lowest for CON, with FLD and WSD similar to both extremes. Dogs fed the MFD had the largest quantity (P < 0.05) of feces excreted and FLD the least. Dogs fed the FLD had highest (P < 0.05) overall nutrient digestibility values; whereas, MFD had the lowest values. TiO₂ estimates of fecal output correlated best to all other markers. The MFD had more than 2-fold (P < 0.05) the antioxidant value by ORAC versus the other treatments (20,482 vs average 8,923 μM Trolox Equivalent/L). This study suggests that sorghum flour would benefit easy-to-digest foods and the sorghum mill-feed could benefit foods needing indigestible fiber and antioxidants. Titanium dioxide may be a better marker for fecal output than Cr₂O₃ or TFC. Future work should determine the optimal mill-feed level to provide health benefits without affecting nutrient digestibility.

Optimisation of the control of an autogenous grinding circuit requires a better understanding of system dynamics than exists at present. To this end extensive operating data were acquired on an industrial semi-autogenous milling circuit and a model was developed to explain the circuit responses to changes in input variables. This model represents the trends in the data fairly accurately and showed that: • When an excess o f slurry was present in Me load (i.e. more than the volume of the voids) a pool of slurry forms st the toe of the load. • The complexity of the power dependence on the variables describing the mill load defied dynamic modelling with toe limited knowledge avail- • The key parameters determining grinding efficiency vary constantly as the grinding environment is disturbed indicating a need for adaptive con- • The flow through the mili is adequately modelled by a single well mixed Itwasalso clear that maximisation of the power with respect to themass alone was insufficient, and that control of the feed dilution water rate is essential. Mill discharge slurry theology was studied eo gain an insight into conditions in the load. An energy balance using temperature measurements around th t mill discharge sump provided a very reliable estimate of the mill discharge density. This estimate was not successfully used for control although this potential should be exploited. Attempts to commission an on-line measurement of discharge slurry viscosity failed. Several theories and ideas were tested in a production environment subject to a multiplicity of disturbances and conclusive qualitative results were obtained. An improved understanding of milling circuit dynamics and a rationalisation of where controi can be improved has resulted from this work.

Student Number : 9806611F - PhD thesis - School of Chemical and Metallurgical Engineering - Faculty of Engineering and the Built Environment / Modelling of comminution in tumbling mills is usually done using the selection and breakage function models. While this has been a success for ball milling it has not been the case with Autogenous and Semi- Autogenous mills where performance is easily affected by slight variations in operations. A numerical model, Discrete Element Method (DEM) a much more detailed model for the nonlinear behaviour of mill loads is proposed as a possible solution to this problem. The Discrete Element Method algorithm is a numerical technique for solving problems that involve a large number of interacting bodies. The dissipative forces (normal, tangential or frictional) at points of contact are modelled using a springslider- dashpot and the dynamics of the particles are modelled by applying Newton’s laws of motion. A record of information about contact events occurring during simulation is stored in the output files and can be thereafter applied for a wide range of purposes. The contact events and their corresponding energy levels derived from the simulation are applied to determine the particle failure rate in a mill. The probability of particle failure does however also depend on the inherent fracture properties of a material; hence particle fracture tests on the ore samples were conducted using the JK drop-weight impact test machine. Using this tool, data that related the probability of breakage to the energy input and the number of impact attempts were obtained and a model describing this relationship was derived. Using the energy spectra that resulted from the simulations of milling and the Breakage probability model, an attempt was made to predict the experimental results of a mill operating under a wide range of conditions. Good prediction was achieved after a careful choice of model parameters. A systematic approach of establishing the most suitable parameters is recommended for future work. These parameters would also compensate for conditions beyond the limits of the model such as particles being too small to simulate or having a complex shape. The predictions were based on two size fractions as a way of making this task more manageable. It is apparent that this work can be extended to do a full SAG and AG mill simulation.