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Browsing by Author "Tan, Li"

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    A Computational Iteration Method to Analyze Mechanics of Timing Belt Systems with Non-Circular Pulleys
    Tan, Li (Virginia Tech, 2018-09-10)
    Timing belt systems, usually consisting of a toothed belt and multiple pulleys, are used in many mechanical devices, especially in the internal combustion engine to synchronize the rotation of the crankshafts and the camshafts. When the system operates, the belt teeth will be transmitted by the pulley teeth meshed with them. Timing belt drives can make sure that the engine' s valves open and close properly due to their precise transmission ratio. In this thesis, a quasi-static computational model is developed to calculate the belt load distributions and the torques around pulleys for different timing belt systems. The simplest system is a two-pulley system with one oval pulley and one circular pulley. This computational model is then extended to a two-pulley system with one special-shaped pulley and finally generalized to determine the load conditions for a multi-pulley system with multiple special-shaped pulleys. Belt tooth deflections, tooth loads, belt tension distributions, friction forces, and the effect of friction hysteresis have been taken into consideration. Results of these quantities are solved by a nested numerical iteration method. Periodic torques generated by the varied radius of noncircular pulley are calculated by this computational model to cancel the undesired external cyclic torque, which will increase the life of timing belts.
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    The correlation between undergraduate student diversity and the representation of women of color faculty in engineering
    Main, Joyce B.; Tan, Li; Cox, Monica F.; McGee, Ebony O.; Katz, Andrew (2020-10-21)
    Background Despite the critical role of faculty diversity in the persistence and academic experiences of undergraduate students as well as in the development of engineering innovations, women of color (WoC) faculty are still underrepresented in engineering programs across the United States. Purpose/Hypothesis This study identifies whether the demographic composition of undergraduate engineering students is correlated with the representation of WoC faculty. It also highlights the institutional- and departmental-level factors that contribute to the race-gender diversification of the engineering professoriate. Design/Method Informed by organizational demography as the theoretical framework, the methods include linear and logit regression analyses. Data come from the American Society for Engineering Education, the Integrated Postsecondary Education Data System, and the American Community Survey, and include engineering departmental-level observations across 345 institutions over 12 years. Results Engineering departments that award more bachelor's degrees to women African American/Black undergraduate students are more likely to employ relatively more African American/Black women faculty. This positive relationship is also found among Asian Americans and Hispanics/Latinas. Conclusions Research findings demonstrate the relationship between engineering undergraduate composition, as well as other departmental- and institutional-level factors, and the prevalence of WoC faculty. The findings highlight important areas for stakeholders and academic administrators to consider when developing strategies and programs to diversify the composition of engineering faculty.