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  1. Experiments were carried out to observe the flow inside counterflow atomizers over a range of operating conditions and fluid properties. Liquids used were water and propylene glycol, while the gas was either air or helium. Liquid flow rates ranged from 10 ml/min to 40 ml/min, with gas liquid ratio (GLR) ranging from 0.1 to 0.6. The primary experiments used the 7-BM line of the Advanced Photon Source in Argonne National Laboratories with a 2.6 mm atomizer produced from (Poly)Ethyl-Ether-Ketone (PEEK). The X-Ray beam was operated in phase contrast mode, leading to interference patterns near the gas-liquid interface and enabling a qualitative understanding of the flow structure. Complementary optical work applied laser shadowgraphy to a 1 mm orifice atomizer constructed with quartz capillary tubing. A diffuse pulsed Nd:YAG laser backlight captured instantaneous gas-liquid interface positions in the internal flow. With both techniques, two distinct flow behaviors are observed corresponding to low and high GLR values. At low GLR, the inertia of the injected gas is insufficient to penetrate the liquid downflow. The gas stream entering the mixing chamber in the upstream direction is immediately deflected by the denser liquid and enters the discharge tube around a central liquid jet, which ismore »sheared and accelerated by the surrounding gas, leading to breakup. A distinct frequency of jet breakup is observed inside the discharge tube, with the liquid jet oscillating and fragmenting against the walls. The situation at high GLR is quite different, however, as the incoming gas stream asymmetrically penetrates upstream into the mixing chamber, taking the form of a high-speed jet confined along one wall, and displaying a flapping instability as it encounters the liquid flowing downstream. This flapping causes violent mixing, resulting in a highly disturbed interface, along with the generation of liquid ligaments and gas bubbles. This two-phase mixture enters the discharge tube with no liquid jet formation evident for this case. The transition between these two regimes is explored by changing the liquid viscosity and gas molar mass, and weak sensitivity to fluid properties is observed. Further, quantitative image analysis techniques applied to the low and high GLR cases allow extraction of the frequencies of the liquid jet in the discharge tube at low GLR, as well as the flapping mode at high GLR.« less
    Free, publicly-accessible full text available May 25, 2023
  2. Scholarly literature on the concept of entrepreneurial ecosystems has increased sharply over the past five years. The surge in interest has also heightened the demand for robust empirical measures that capture the complexity of dynamic relationships among ecosystem constituents. We offer a framework for measurement that places collaborative relationships among entrepreneurs, firms, government agencies, and research institutions at the center of the ecosystem concept. We further emphasize the four roles of the federal government as a catalyst, coordinator, certifier, and customer in shaping these relationships. Despite the central importance of these firm-government interactions, there is surprisingly little research on suitable methodologies and appropriate data for systematically and reliably incorporating them into measures of ecosystem health. Our study aims to address this gap in the literature by first developing a conceptual framework for measuring entrepreneurial ecosystems and then describing an array of accompanying databases that provide rich and detailed information on firms and their relationships with government organizations, accelerators, and research institutions. A major advantage of our approach is that all the underlying databases are drawn from non-confidential, publicly available sources that are transparently disclosed and regularly updated. This greatly expands the potential community of scholars, managers, and policymakers that maymore »independently use these databases to test theories, make decisions, and formulate policies related to innovation and entrepreneurship.« less
  3. A coastal eddy is modelled as a barotropic vortex propagating along a coastal shelf. If the vortex speed matches the phase speed of any coastal trapped shelf wave modes, a shelf wave wake is generated leading to a ux of energy from the vortex into the wave eld. Using a simply shelf geometry, we determine analytic expressions for the wave wake and the leading order ux of wave energy. By considering the balance of energy between the vortex and wave eld, this energy ux is then used to make analytic predictions for the evolution of the vortex speed and radius under the assumption that the vortex structure remains self similar. These predictions are examined in the asymptotic limit of small rotation rate and shelf slope and tested against numerical simulations. If the vortex speed does not match the phase speed of any shelf wave, steady vortex solutions are expected to exist. We present a numerical approach for nding these nonlinear solutions and examine the parameter dependence of their structure.
  4. Johnson, E. & Arnold, J. E. (2021). Does SES affect pronoun comprehension and prediction in implicit causality scenarios? Technical Report #4. UNC Language Processing Lab, Department of Psychology & Neuroscience, University of North Carolina – Chapel Hill, Chapel Hill, North Carolina. This paper examines whether individuals’ pronoun resolution varies with respect to their socioeconomic status (SES). It uses the data from the Johnson and Arnold (2021) paper to determine whether the author recognition task (ART) effect that was found could instead be explained by participants’ SES. Both socioeconomic status and the author recognition task have been shown to correlate with measures of reading skill, so as a secondary analysis, SES was included as a possible predictor of individual differences.
  5. Intelligent tutoring systems have proven very effective at teaching hard skills such as math and science, but less research has examined how to teach “soft” skills such as negotiation. In this paper, we introduce an effective approach to teaching negotiation tactics. Prior work showed that students can improve through practice with intelligent negotiation agents. We extend this work by proposing general methods of assessment and feedback that could be applied to a variety of such agents. We evaluate these techniques through a human subject study. Our study demonstrates that personalized feedback improves students’ use of several foundational tactics.