Flapping wings are important in many biological and bioinspired systems. Here, we investigate the fluid mechanics of flapping wings that possess a single flexible hinge allowing passive wing pitch rotation under load. We perform experiments on an insect-scale (${\approx}1$ cm wing span) robotic flapper and compare the results with a quasi-steady dynamical model and a coupled fluid–structure computational fluid dynamics model. In experiments we measure the time varying kinematics, lift force and two-dimensional velocity fields of the induced flow from particle image velocimetry. We find that increasing hinge stiffness leads to advanced wing pitching, which is beneficial towards lift force production. The classical quasi-steady model gives an accurate prediction of passive wing pitching if the relative phase difference between the wing stroke and the pitch kinematics,${\it\delta}$, is small. However, the quasi-steady model cannot account for the effect of${\it\delta}$on leading edge vortex (LEV) growth and lift generation. We further explore the relationships between LEV, lift force, drag force and wing kinematics through experiments and numerical simulations. We show that the wing kinematics and flapping efficiency depend on the stiffness of a passive compliant hinge. Our dual approach of running at-scale experiments and numerical simulations gives useful guidelines for choosing wing hinge stiffnesses that lead to efficient flapping.
IMPORTANCE Aberrant depressor anguli oris (DAO) activity may arise after recovery from acute facial paralysis and restrict movement of the oral commissure.OBJECTIVE To quantify the degree to which DAO inhibition affects smile dynamics and perceived emotional state. DESIGN, SETTING, AND PARTICIPANTSIn this prospective, pretest-posttest study performed at an academic tertiary referral hospital, patients with unilateral postparalysis facial palsy were studied from January 16 through April 30, 2016. INTERVENTIONS Local anesthetic injection into the ipsilateral DAO.MAIN OUTCOMES AND MEASURES Healthy-and paretic-side commissure displacements from the midline lower vermillion border referenced to the horizontal plane were calculated from random-ordered photographs of full-effort smile before and after injection, and random-ordered hemifacial photographs of the paretic side were assessed as expressing positive, negative, or indiscernible emotion.RESULTS Twenty patients were identified as having unilateral postparalysis facial palsy with marked synkinesis of the ipsilateral DAO. Patient mean age was 46 years (range, 24-67 years), with a male to female ratio of 1:3. Mean paretic-side commissure displacement increased from 27.45 mm at 21.65°above the horizontal plane to 29.35 mm at 23.58°after DAO weakening (mean difference, 1.90 mm; 95% CI, 1.26-2.54 mm; and 1.93°; 95% CI, 0.34°-3.51°; P < .001 and P = .20, respectively). Symmetry of excursion between sides improved by 2.00 mm (95% CI, 1.16-2.83 mm; P < .001) and 2.71°(95% CI, 1.38°-4.03°; P < .001). At baseline, observers assessed 7 of 20 paretic hemifaces (35%) as expressing positive emotion; this proportion increased to 13 of 20 (65%) after DAO weakening (P = .03). CONCLUSIONS AND RELEVANCEIpsilateral DAO weakening results in significant improvements in smile dynamics and perceived expression of positive emotion on the paretic hemiface in postparalysis facial palsy. A trial of DAO weakening should be offered to patients with this disfiguring complication of Bell palsy and similar facial nerve insults.LEVEL OF EVIDENCE 3.
Articulation based on flexure hinges is increasingly popular in microrobotics because of the absence of Coulomb friction, ease of manufacturability, fluid motion, durability, and large angular ranges. However, the inherent flexibility of these hinges makes modeling very complex and specific to the particular engineering applications for which they were developed. In this paper we describe the development and testing of a simplified, versatile method for modeling the stress on a flexure hinge under multi-axis loads in order to maximize hinge lifespan. We also discuss other stress concentration reducing features and design rules that can be applied to more general flexure hinge designs to further extend hinge lifespan.The authors are with the Harvard
Objectives/Hypothesis: Studies across multiple specialties of medical students, residents, and attending physicians demonstrate increased retention, breadth of knowledge, and literature awareness when podcasts are used as an adjunctive educational tool. This Contemporary Review aims to 1) quantify podcast availability and episode frequency for medical learners across a broad range of specialties, and 2) compare these metrics between otolaryngology-specific podcasts with those of other specialties.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.