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In this paper, the advantages, state-of-the-art, and current challenges in the field of adaptive composite marine propulsors and turbines are reviewed. Adaptive composites are used in numerous marine technologies, including propulsive devices and control surfaces for marine vessels, offshore platforms, unmanned surface and underwater vehicles, and renewable energy harvesting devices. In the past, most marine propulsors and turbines have been designed as rigid bodies, simplifying the design and analysis process; however, this can lead to significant performance decay when operating in off-design conditions or in spatially or temporally varying flows. With recent advances in computational modeling, materials research, and manufacturing, it is possible to take advantage of the flexibility and anisotropic properties of composites to enable passive morphing capabilities to delay cavitation and improve overall energy efficiency, agility, and dynamic stability. Moreover, active materials can be embedded inside composites to enable energy harvesting, in situ health and condition monitoring, mitigation and control of flow-induced vibrations, and further enhancements of system performance. However, care is needed in the design and testing of adaptive composite marine propulsors and turbines to account for the inherent load-dependent deformations and to avoid potential material failures and hydroelastic instabilities (resonance, parametric excitations, divergence, flutter, buffeting, etc.). Here, we provide a summary of recent progress in the modeling, design, and optimization of adaptive composite marine propulsors and turbines, followed by a discussion of current challenges and future research directions.

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On March 8, 2022 this report was posted as an MMWR Early Release on the MMWR website (https://www.cdc.gov/mmwr).Masks are effective at limiting transmission of SARS-CoV-2, the virus that causes COVID-19 (1), but the impact of policies requiring masks in school settings has not been widely evaluated (2-4). During fall 2021, some school districts in Arkansas implemented policies requiring masks for students in kindergarten through grade 12 (K-12). To identify any association between mask policies and COVID-19 incidence, weekly school-associated COVID-19 incidence in school districts with full or partial mask requirements was compared with incidence in districts without mask requirements during August 23-October 16, 2021. Three analyses were performed: 1) incidence rate ratios (IRRs) were calculated comparing districts with full mask requirements (universal mask requirement for all students and staff members) or partial mask requirements (e.g., masks required in certain settings, among certain populations, or if specific criteria could not be met) with school districts with no mask requirement; 2) ratios of observed-to-expected numbers of cases, by district were calculated; and 3) incidence in districts that switched from no mask requirement to any mask requirement were compared before and after implementation of the mask policy. Mean weekly district-level attack rates were 92-359 per 100,000 persons in the community* and 137-745 per 100,000 among students and staff members; mean student and staff member vaccination coverage ranged from 13.5% to 18.6%. Multivariable adjusted IRRs, which included adjustment for vaccination coverage, indicated that districts with full mask requirements had 23% lower COVID-19 incidence among students and staff members compared with school districts with no mask requirements. Observed-to-expected ratios for full and partial mask policies were lower than ratios for districts with no mask policy but * Community attack rates were based on the weekly number of cases in the school district, minus the weekly number of cases among staff members or students during the same period. Denominators were calculated based on the population for each school district, minus the district student and staff member 2021-22 enrollment.