Browsing by Subject "Cutting"
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Item Effect of sanitizer treatments on Salmonella enterica serotype Poona on the surface of cantaloupe and cell transfer to the internal tissue during cutting practices(Texas A&M University, 2005-02-17) Vadlamudi, SasiIn recent years, due to the increasing number of produce-related outbreaks, greater attention has been given to interventions that remove human pathogens on fresh produce. Survival of Salmonella Poona on the surface and stem scar portions of inoculated cantaloupe, effect of chlorine or lactic acid or ozone on the survival of bacteria, transfer of pathogen from the rind to the fresh-cut tissue during cutting and growth and survival of Salmonella Poona on the fresh-cut tissues during 15 days of refrigerated storage were investigated. Preliminary studies were conducted to confirm that the rifampicin-resistant strain used in the study was indistinguishable from the parent strain of Salmonella Poona. Growth curve, heat tolerance and lactic acid resistance studies were performed, all of which showed no differences in behavior between the organisms. Cantaloupes were immersed in an inoculum containing rifampicicn-resistant strain of Salmonella Poona (107 CFU/ml) for 3 min and then dried for 12 h. The inoculated melons were washed with chlorine (200 ppm) for 3 min or lactic acid (2%) for 2 min or ozone (30 ppm) for 5 min and fresh cut tissues were prepared by peeling the rind and cutting into pieces or cutting the melon and removing the rind. Results obtained indicate that the levels of Salmonella Poona recovered were higher when the sample was obtained from the scar portion than the surface. Surface treatment with tap water or chlorine did not reduce Salmonella Poona. However treatment with lactic acid or ozone reduced the levels by 2.5 and 2.3 log10 CFU/cm2 respectively on the surface. Fresh-cut tissue prepared from melons sanitized with lactic acid resulted in less transfer during cutting and reached below detectable limits after 9 days of refrigerated storage. Cutting melons after peeling the rind was found effective in reducing the transfer of Salmonella Poona into the tissue in comparison with cutting of melons and removing the rind later. Thus these data suggest that treatment with lactic acid and ozone may be effective in reducing Salmonella from the surface of the cantaloupe where as lactic acid was effective in reducing the transfer from the surface to the flesh.Item Interior sensation and exterior forces : cutting away(2014-05) Salazar, Samantha Parker; Mutchler, LeslieIn my work, traditional printmaking techniques are pushed to their limits as a foundation for cut-paper installations and sculptures. The work reflects on notions of interiority and exteriority in relation to the body and nature, drawing from my experiences in meditation to create a two and three-dimensional visual play primarily using paper. Because of their illustrative looseness, the biomorphic structures convey a variety of sensations, shapes, and movements that are related to the interior of the body and exterior forces in nature. In this report, I plan to discuss topics of process, materiality, sensation, objecthood and phenomenology within the context of my work and as these topics relate to other artists such as: Lee Bontecou, Francis Bacon, Oskar Fischinger, Richard Serra, and Judy Pfaff. I also plan to indicate a contemporary and art historical context for the work, placing my pieces within a specific canon of visual culture.Item Thermal-mechanical modeling of laser ablation hybrid machining(Texas Tech University, 2001-05) Matin, KaiserHard, brittle and wear-resistant materials like (ceramics pose a problem when being machined using conventional machining processes. Machining ceramics even with a diamond cutting tool is very difficult and costly. Near net-shape processes, like laser evaporation, produce micro-cracks that require extra finishing. Thus it is anticipated that ceramic machining will have to continue to be explored with new-sprung techniques before ceramic materials become commonplace. This numerical investigation results from the numerical simulations of the thermal and mechanical modeling of simultaneous material removal from hard-to-machine materials using both laser ablation and conventional tool cutting utilizing the finite element method. The model is formulated using a two dimensional, planar, computational domain. The process acronymed, LAHM (Laser Ablation Hybrid Machining), uses laser energy for two purposes. The first purpose is to remove the material by ablation. The second purpose is to heat the unremoved material that lies below the ablated material in order to "soften" it. The softened material is then simultaneously removed by conventional machining processes. The complete solution determines the temperature distribution and stress contours within the material and tracks the moving boundary that occurs due to material ablation. The temperature distribution is used to determine the distance below the phase change surface where sufficient "softening" has occurred, so that a cutting tool may be used to remove additional material. The model used for tracking the ablative surface does not assume an isothermal melt phase (e.g., Stefan problem) tor laser ablation. Both surface absorption and volume absorption of laser energy as a function of depth have been considered in the models. LAHM, from the thermal and mechanical point of view, is a (complex machining process involving large deformations at high strain rates, thermal effects of the laser, removal of materials and contact between workplace and tool. The theoretical formulation associated with LAHM for solving the thermal-mechanical problem using the finite element method is presented. The thermal formulation is incorporated in the user defined subroutines called by ABAQUS/Standard. The mechanical portion is modeled using ABAQUS/Explicit’s general capabilities of modeling interactions involving contact and separation. The results obtained from the FEA simulations showed that the cutting force decreases considerably in both the LAHM Surface Absorption (LAHM-SA) and LAHM volume absorption (LAHM-VA) models relative to the LAM model. It is observed that the HAZ can be expanded or narrowed depending on the laser speed and power. The cutting force is minimal at the last extent of the HAZ (heat affected zone). In both the models the laser ablates material thus reducing material stiffness as well as relaxing the thermal stress. The stress values obtained showed compressive yield stresses just below the ablated surface and chip. The failure occurs by conventional cutting where tensile stress exceeds the tensile strength of the material at that temperature. In this hybrid machining process, the advantages of both the conventional and laser machining processes were realized.