Browsing by Subject "viscosity"

Now showing 1 - 6 of 6

Application of Machine Learning Methods to the Open-Loop Control of a Freeform Fabrication System
(2004) Malone, Evan; Purwin, Oliver
Freeform fabrication of complete functional devices requires the fabrication system to achieve well-controlled deposition of many materials with widely varying material properties. In a research setting, material preparation processes are not highly refined, causing batch property variation, and cost and time may prohibit accurate quantification of the relevant material properties, such as viscosity, elasticity, etc. for each batch. Closed-loop control based on the deposited material road is problematic due to the difficulty in non-contact measurement of the road geometry, so a labor-intensive calibration and open-loop control method is typically used. In the present work, k-Nearest Neighbor and Support Vector Machine (SVM) machine learning algorithms are applied to the problem of generating open-loop control parameters which produce desired deposited material road geometry from a description of a given material and tool configuration comprising a set of qualitative and quantitative attributes. Training data for the algorithms is generated in the course of ordinary use of the SFF system as the results of manual calibration of control parameters. Given the large instance space and the small training data set compiled thus far, the performance is quite promising, although still insufficient to allow complete automation of the calibration process. The SVM-based approach produces tolerable results when tested with materials not in the training data set. When control parameters produced by the learning algorithms are used as a starting point for manual calibration, significant operator time savings and material waste reduction may be achieved.
Cargo Transport by Cytoplasmic Dynein Can Center Embryonic Centrosomes
(PLOS One, 2013-07-01) Longoria, Rafael A.; Shubeita, George
To complete meiosis II in animal cells, the male DNA material needs to meet the female DNA material contained in the female pronucleus at the egg center, but it is not known how the male pronucleus, deposited by the sperm at the periphery of the cell, finds the cell center in large eggs. Pronucleus centering is an active process that appears to involve microtubules and molecular motors. For small and medium-sized cells, the force required to move the centrosome can arise from either microtubule pushing on the cortex, or cortically-attached dynein pulling on microtubules. However, in large cells, such as the fertilized Xenopus laevis embryo, where microtubules are too long to support pushing forces or they do not reach all boundaries before centrosome centering begins, a different force generating mechanism must exist. Here, we present a centrosome positioning model in which the cytosolic drag experienced by cargoes hauled by cytoplasmic dynein on the sperm aster microtubules can move the centrosome towards the cell’s center. We find that small, fast cargoes (diameter ~100 nm, cargo velocity ~2 µm/s) are sufficient to move the centrosome in the geometry of the Xenopus laevis embryo within the experimentally observed length and time scales.
Experimental Characterization of Long-Chain Polymer Drilling Fluids
(2018-05) Johnson, Mitchell David; van Oort, Eric
Sophisticated new drilling technologies such as managed pressure drilling (MPD) and dual gradient drilling (DGD) rely critically on accurate hydraulics modeling. Current fluid measurement and characterization technology performs well under a variety of conditions, but long-chain polymer additives have been shown to introduce significant complexity into the process of predicting frictional pressure losses in drilling operations. Considering the frequent use of long-chain polymer additives as both viscosifiers and friction reducers in drilling, completions and well intervention operations, this work seeks to further investigate the behavior of fluids containing these materials and propose improvements to existing measurement and pressure loss prediction methods. A series of experiments was performed using a fully automated high temperature pipe viscometer to understand the effects of long chain polymer-based additives on fluid behavior in laminar, transitional and turbulent flow. Frictional pressure losses were measured in a cesium formate fluid viscosified with concentrations of xanthan gum up to 2.5 lb/bbl at temperatures ranging from 100 – 230°F. Results were compared with widely used theoretical models for frictional pressure losses, showing significant discrepancy between current theory and empirical results. In light of this discrepancy, a new method for determining frictional pressure losses in turbulent flow was proposed and evaluated. Direct measurement of pressure losses using a flow loop was shown to provide substantially improved pressure prediction in turbulent flow when compared to theoretical correlations commonly used in industry. A field-scale prototype was also developed to apply the pipe viscometer concept, providing the means to conduct future field trials of the technology. The field prototype’s ability to characterize complex drilling fluid behavior in both laminar and turbulent flow shows significant promise for future applications in the drilling fluids domain.
Heat Transfer and Pressure Drop in Heat Exchangers
(University of Texas at Austin, 1938-05-15) University of Texas at Austin
Heat Transfer and Pressure Drop in Heat Exchangers (Revision of Bulletin 3819
(University of Texas at Austin, 1943-06-22) University of Texas at Austin
Rheology and Applications of Particulate Composites in Additive Manufacturing
(University of Texas at Austin, 2019) Xia, Bin; Krueger, Paul S.
To provide different functionalities such as electrical conductivity or magnetic permeability, particulate composites have been utilized widely in additive manufacturing. These types of materials are usually formulated with different functional particles and shear thinning non-Newtonian fluids such as polymer melts and silicone. The materials are viscous non-Newtonian suspensions during formulation and printing, and their rheology is a key factor for the processing. This paper will concentrate on suspensions with micron-sized particles, and discuss the rheology and overall flow behavior in capillaries scaled appropriately for additive manufacturing applications (around 1 mm ID). Micron size glass beads and shear thinning silicone are used to demonstrate the impact of particle volume fraction on the shear thinning behavior. The impact of particle and capillary size on viscosity and jamming conditions will be discussed. Previous models based on Newtonian fluids and in free flowing conditions will also be reviewed and compared.