@article{talley_zimmer_bolotnov_2017, title={Coalescence Prevention Algorithm for Level Set Method}, volume={139}, ISSN={["1528-901X"]}, DOI={10.1115/1.4036246}, abstractNote={An algorithm to prevent or delay bubble coalescence for the level set (LS) method is presented. This novel algorithm uses the LS method field to detect when bubbles are in close proximity, indicating a potential coalescence event, and applies a repellent force to simulate the unresolved liquid drainage force. The model is introduced by locally modifying the surface tension force near the liquid film drainage area. The algorithm can also simulate the liquid drainage time of the thin film by controlling the length of time the increased surface tension has been applied. Thus, a new method of modeling bubble coalescence has been developed. Several test cases were designed to demonstrate the capabilities of the algorithm. The simulations, including a mesh study, confirmed the abilities to identify and prevent coalescence as well as implement the time tracking portion, with an additional 10–25% computational cost. Ongoing tests aim to verify the algorithm's functionality for simulations with different flow conditions, a ranging number of bubbles, and both structured and unstructured computational mesh types. Specifically, a bubble rising toward a free surface provides a test of performance and demonstrates the ability to consistently prevent coalescence. In addition, a two bubble case and a seven bubble case provide a more complex demonstration of how the algorithm performs for larger simulations. These cases are compared to much more expensive simulations capable of resolving the liquid film drainage (through very high local mesh resolution) to investigate how the algorithm replicates the liquid film drainage process.}, number={8}, journal={JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME}, author={Talley, Matthew L. and Zimmer, Matthew D. and Bolotnov, Igor A.}, year={2017}, month={Aug} }
 @article{talley_shannon_chen_verboncoeur_2017, title={IEDF distortion and resolution considerations for RFEA operation at high voltages}, volume={26}, ISSN={1361-6595}, url={http://dx.doi.org/10.1088/1361-6595/aa9465}, DOI={10.1088/1361-6595/aa9465}, abstractNote={Retarding field energy analyzers (RFEA) have been used extensively to measure the ion flux energy distribution function of plasmas. For consistency, the ion flux energy distribution function is referred to as the ion energy distribution function (IEDf) even though it more accurately represents the one-dimensional ion velocity distribution function. In the past, these devices have operated at voltages less than 1 kV. Higher operating voltages (>2 kV) are currently desired. For an RFEA to operate at these voltages, design changes are necessary that impact the energy resolution and cause space charge build-up. To investigate the effect the design changes have for a high voltage RFEA, electromagnetic simulations and particle-in-cell (PIC) simulations were used to analyze the electric field between the grids, the potential drop in the grid holes, and space charge build-up between the grids. Non-unique optimized dimensions for the RFEA increased the electric field uniformity. The optimization minimizes the electric field from distorting the IV curve or adversely affecting the energy resolution. It was found that a larger grid gap distance and smaller grid hole diameter decreases the potential drop in the grid holes improving energy resolution. IV curves from the PIC simulation were used to obtain space charge distorted IEDfs. The point at which space charge distorts the IV curve is dependent on the grid gap distance and incoming flux. Space charge build-up was found to only affect low energy ions which manifested by cutting off the low energy portion of the IEDf. To fix space charge distortions, the flux into the probe can be limited or it may be possible to account for the distortion when calculating the IEDf.}, number={12}, journal={Plasma Sources Science and Technology}, publisher={IOP Publishing}, author={Talley, M L and Shannon, S and Chen, L and Verboncoeur, J P}, year={2017}, month={Nov}, pages={125001} }
 @article{hechavarria_terjesen_ingram_renko_justo_elam_2017, title={Taking care of business: the impact of culture and gender on entrepreneurs' blended value creation goals}, volume={48}, ISSN={["1573-0913"]}, DOI={10.1007/s11187-016-9747-4}, number={1}, journal={SMALL BUSINESS ECONOMICS}, author={Hechavarria, Diana M. and Terjesen, Siri A. and Ingram, Amy E. and Renko, Maija and Justo, Rachida and Elam, Amanda}, year={2017}, month={Jan}, pages={225–257} }