Modeling tensorial conductivity of particle suspension networks

Significant microstructural anisotropy is known to develop during shearing flow of attractive particle suspensions. These suspensions, and their capacity to form conductive networks, play a key role in flow-battery technology, among other applications. Herein, we present and test an analytical model for the tensorial conductivity of attractive particle suspensions. The model utilizes the mean fabric of the network to characterize the structure, and the relationship to the conductivity is inspired by a lattice argument. We test the accuracy of our model against a large number of computer-generated suspension networks, based on multiple in-house generation protocols, giving rise to particle networks that emulate the physical system. The model is shown to adequately capture the tensorial conductivity, both in terms of its invariants and its mean directionality

Coupled dynamics of flow, microstructure, and conductivity in sheared suspensions

We propose a model for the evolution of the conductivity tensor for a flowing suspension of electrically conductive particles. We use discrete particle numerical simulations together with a continuum physical framework to construct an evolution law for the suspension microsutructure during flow. This model is then coupled with a relationship between the microstructure and the electrical conductivity tensor. The parameters of the joint model are fit experimentally using rheo- electrical conductivity measurements of carbon black suspensions under flow over a range of shear rates. The model is applied to the case of steady shearing as well as time-varying conductivity of unsteady flow experiments. We find that the model prediction agrees closely with the measured experimental data in all cases.Comment: 5 pages, 4 figure

What Works and What Doesn’t When Teaching Large Classes?

What we want to do is talk in this 20 Minute Mentor, share some ideas about what you can do actually during the semester. Once it’s begun, you’re over the shock of having been assigned a large classroom, if it was a surprise, and you’re actually into the semester. Kenneth L. Alford, Ph.D., is an Associate Professor of Church History and Doctrine at Brigham Young University. After serving almost 30 years on active duty in the U.S. Army, he retired as a Colonel in 2008. While on active duty, Ken served in numerous personnel, automation, acquisition, and education assignments, including eight years teaching computer science and information technology at the United States Military Academy at West Point, New York and four years as Professor and Department Chair of the Strategic Leadership Department at the National Defense University in Washington, DC. Tyler J. Griffin, Ph.D., is an assistant professor at Brigham Young University. With degrees in Electrical Engineering and Instructional Technology, combined with 18 years of professional teaching experience, Tyler has three major focal points in his work: (1) Best practices for teaching & learning (2) Best uses of technology to increase the scope and scale of learning, and (3) best practices for teacher development/inservice.https://knowledge.e.southern.edu/onlineseminars/1031/thumbnail.jp

Fitness and Enjoyment Outcomes of a Physical Education Fitness Conditioning Curriculum

Project: Health-related fitness and enjoyment outcomes were analyzed on a physical education program that adopted an exclusive fitness conditioning physical education curriculum. Means: Freshmen enrolled in physical education (n = 228; Mean age = 14.12 years ± .91; Females = 117 (51%); Males = 111 (49%)) completed pre and post FitnessGram curl-ups, push-ups, and the PACER, height and weight measurements, a modified Physical Activity Enjoyment Scale (PACES), and two open-ended questions (likes and dislikes of PE). Pre and post assessments were analyzed using Paired t-tests, one-way ANOVAs, and qualitative categorizing. Outcome: Significant fitness improvements for females occurred in the push-ups (F(1, 105) = - 5.286, p \u3c .000), curl-ups (F(1,107) = -4.171, p \u3c .000), and the PACER (F(1, 89) = -6.680, p \u3c .000) and for males in push-ups (F(1, 98) = -2.939, p \u3c .004) and the PACER ((F(1, 80), -6.196, p \u3c .000). Males reported significantly higher PACES enjoyment scores (F(1, 184) = 19.843, p \u3c . 000) compared to females. Four categories were formed that encompassed open-ended responses: teacher, social/friends, content/curriculum, and affect. Reflection: Although this fitness conditioning program enhanced health-related fitness levels, and many students perceived value and benefits of participating in such a program, males clearly enjoyed their physical education experience more than females

Science of entropy-stabilized ultra-high temperature thin films: Synthesis, validation and properties

The authors report on using multi-cathode magnetron sputtering to fabricate 5-component refractory carbides that are stabilized by configurational entropy to form a robust and high-temperature class of high temperature materials. Magnetron sputtering is an appealing fabrication method as one can prepare layers with high density and the compositional flexibility afforded by five independent metallic sources. Thin layers that comprise mixed carbides of the following elements: W, Mo, Ti, Hf, Zr, Ta, V, and Nb, will be discussed. In all cases sputtering is performed reactively in a gas atmosphere including Ar as the inert sputter gas and propane as the carbon source. Sputter depositions can be conducted between room temperature and 800 °C. The relationship between sputtering parameters including power, pressure, rate, gas mixture, and film properties including density, thermal conductivity, lattice constant, and phase evolution will be discussed. Please click Additional Files below to see the full abstract

Cross-correlation image analysis for real-time particle tracking

Accurately measuring translations between images is essential in many fields, including biology, medicine, geography, and physics. Existing methods, including the popular FFT-based cross-correlation, are not suitable for real-time analysis, which is especially vital in feedback control systems. To fill this gap, we introduce a new algorithm which approaches shot-noise limited displacement detection and a GPU-based implementation for real-time image analysis.Comment: 4 pages, 3 figures, submitted to Optics Letter

Unexpected role of communities colonizing dead coral substrate in the calcification of coral reefs

Global and local anthropogenic stressors such as climate change, acidification, overfishing, and pollution are expected to shift the benthic community composition of coral reefs from dominance by calcifying organisms to dominance by non-calcifying algae. These changes could reduce the ability of coral reef ecosystems to maintain positive net calcium carbonate accretion. However, relationships between community composition and calcification rates remain unclear. We performed field experiments to quantify the metabolic rates of the two most dominant coral reef substrate types, live coral and dead coral substrate colonized by a mixed algal assemblage, using a novel underwater respirometer. Our results revealed that calcification rates in the daytime were similar for the live coral and dead coral substrate communities. However, in the dark, while live corals continued to calcify at slower rates, the dead coral substrate communities exhibited carbonate dissolution. Daytime net photosynthesis of the dead coral substrate communities was up to five times as much as for live corals, which we hypothesize may have created favorable conditions for the precipitation of carbonate minerals. We conclude that: (1) calcification from dead coral substrate communities can contribute to coral reef community calcification during the day, and (2) dead coral substrate communities can also contribute to carbonate mineral dissolution at night, decreasing ecosystem calcification over a diel cycle. This provides evidence that reefs could shift from slow, long-term accretion of calcium carbonate to a state where large daily cycling of calcium carbonate occurs, but with little or no long-term accumulation of the carbonate minerals needed to sustain the reef against erosional forces