During solid surface impact, a falling drop's energy is transformed into oscillations of its liquid/gas interface. We consider drop deposition during oblique impact in the capillary-ballistic regime characterized by high Reynolds number and moderate Weber number. We treat this as an inverse problem showing that post-impact observations of the frequency spectrum and modal partition of energy allow one to determine a drop's pre-impact characteristics and wetting properties. Our analysis is useful for quantifying contact-line dissipation during inertial spreading and can be used as a diagnostic technique for determining substrate wetting properties.
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Winding down the Chicxulub impact: The transition between impact and normal marine sedimentation near ground zero
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Abstract Porosity and its distribution in impact craters has an important effect on the petrophysical properties of impactites: seismic wave speeds and reflectivity, rock permeability, strength, and density. These properties are important for the identification of potential craters and the understanding of the process and consequences of cratering. The Chicxulub impact structure, recently drilled by the joint International Ocean Discovery Program and International Continental scientific Drilling Program Expedition 364, provides a unique opportunity to compare direct observations of impactites with geophysical observations and models. Here, we combine small‐scale petrographic and petrophysical measurements with larger‐scale geophysical measurements and numerical simulations of the Chicxulub impact structure. Our aim is to assess the cause of unusually high porosities within the Chicxulub peak ring and the capability of numerical impact simulations to predict the gravity signature and the distribution and texture of porosity within craters. We show that high porosities within the Chicxulub peak ring are primarily caused by shock‐induced microfracturing. These fractures have preferred orientations, which can be predicted by considering the orientations of principal stresses during shock, and subsequent deformation during peak ring formation. Our results demonstrate that numerical impact simulations, implementing the Dynamic Collapse Model of peak ring formation, can accurately predict the distribution and orientation of impact‐induced microfractures in large craters, which plays an important role in the geophysical signature of impact structures.
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Background: Service-learning has historically been seen as a high-impact practice that empowers undergraduates to develop essential learning outcomes. Most service-learning discussed within the literature occurs as a required element of a credit-bearing academic course. Purpose: This study explored what happens when service-learning is reimagined to be disconnected from a specific course and credit hours, and available via application to all undergraduates regardless of the liberal arts/science major or year in the college. Methodology/Approach: HyperRESEARCH was used to identify themes and categories from 45 sets of weekly reflections submitted by 36 participants engaged in reimagined service-learning projects across five semesters. Findings/Conclusions: Key findings reveal that not only do undergraduates develop essential learning outcomes as delineated in the existing literature, but in many cases, their understandings, and abilities to execute these skills, are deepened when service-learning is reimagined. Findings also reveal that undergraduates may experience service-learning differently depending upon year in college. Implications: Results from this study suggest that practitioners should investigate ways to reimagine service-learning, with specific emphasis placed on the differential ways college students at various stages in their undergraduate career experience, and learn from, service-learning.
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.margeo.2020.106368
