249 research outputs found
Orientation-dependent adhesion strength of a rigid cylinder in non-slipping contact with a transversely isotropic half-space
Recently, Chen and Gao [Chen, S., Gao, H., 2007. Bio-inspired mechanics of reversible adhesion: orientation-dependent adhesion strength for non-slipping adhesive contact with transversely isotropic elastic materials. J. Mech. Phys. solids 55, 1001â1015] studied the problem of a rigid cylinder in non-slipping adhesive contact with a transversely isotropic solid subjected to an inclined pulling force. An implicit assumption made in their study was that the contact region remains symmetric with respect to the center of the cylinder. This assumption is, however, not self-consistent because the resulting energy release rates at two contact edges, which are supposed to be identical, actually differ from each other. Here we revisit the original problem of Chen and Gao and derive the correct solution by removing this problematic assumption. The corrected solution provides a proper insight into the concept of orientation-dependent adhesion strength in anisotropic elastic solids
Flame-like Ellerman Bombs and Their Connection to Solar UV Bursts
Ellerman bombs (EBs) are small-scale intense brightenings in H wing
images, which are generally believed to be signatures of magnetic reconnection
events around the temperature minimum region of the solar atmosphere. They have
a flame-like morphology when observed near the solar limb. Recent observations
from the Interface Region Imaging Spectrograph (IRIS) reveal another type of
small-scale reconnection events, termed UV bursts, in the lower atmosphere.
Though previous observations have shown a clear coincidence of some UV bursts
and EBs, the exact relationship between these two phenomena is still under
debate. We investigate the spatial and temporal relationship between flame-like
EBs and UV bursts using joint near-limb observations between the 1.6--meter
Goode Solar Telescope (GST) and IRIS. In total 161 EBs have been identified
from the GST observations, and 20 of them reveal signatures of UV bursts in the
IRIS images. Interestingly, we find that these UV bursts have a tendency to
appear at the upper parts of their associated flame-like EBs. The intensity
variations of most EB-related UV bursts and their corresponding EBs match well.
Our results suggest that these UV bursts and EBs are likely formed at different
heights during a common reconnection process.Comment: 5 figures; accepted by ApJ
A numerical investigation of 3D structural behaviour for steel-composite structures under various travelling fire scenarios
202309 bcvcVersion of RecordRGCPublishe
Modeling and dynamic analysis of spiral bevel gear coupled system of intermediate and tail gearboxes in a helicopter.
The coupled dynamic model of the intermediate and tail gearboxesâ spiral bevel gear-oblique tail shaft-laminated membrane coupling was established by employing the hybrid modeling method of finite element and lumped mass. Among them, the dynamic equation of the shaft was constructed by Timoshenko beam; spiral bevel gears were derived theoretically by the lumped-mass method, where the effects of time-varying meshing stiffness, transmission error, external imbalance excitation and the like were considered simultaneously; laminated membrane coupling was simplified to a lumped parameter model, in which the stiffness was obtained by the finite element simulation and experiment. On this basis, the laminated membrane coupling and effects of several important parameters, including the unbalance value, tail rotor excitation, oblique tail shaftâs length and transmission error amplitude, on the systemâs dynamic characteristics were discussed. The results showed that the influences of laminated membrane coupling and transmission error amplitude on the coupled systemâs vibration response were prominent, which should be taken into consideration in the dynamic model. Due to the bending-torsional coupled effect, the lateral vibration caused by gear eccentricity would enlarge the oblique tail shaftâs torsional vibration; similarly, the tail rotorâs torsional excitation also varies the lateral vibration of the oblique tail shaft. The coupled effect between the eccentricity of gear pairs mainly hit the torsional vibration. Also, as the oblique tail shaftâs length increased, the torsional vibration of the oblique tail shaft tended to diminish while the axis orbit became larger. The research provides theoretical support for the design of the helicopter tail transmission system
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