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Laser-assisted photothermal imprinting of nanocomposite
We report on a laser-assisted photothermal imprinting method for directly patterning carbon
nanofiber-reinforced polyethylene nanocomposite. A single laser pulse from a solid state
Nd:YAG laser (10 ns pulse, 532 nm and 355 nm wavelengths) is used to melt/soften a thin skin
layer of the polymer nanocomposite. Meanwhile, a fused quartz mold with micro-sized surface
relief structures is pressed against the surface of the composite. Successful pattern transfer is
realized upon releasing the quartz mold. Although polyethylene is transparent to the laser beam,
the carbon nanofibers in the high density polyethylene (HDPE) matrix absorb the laser energy
and convert it into heat. Numerical heat conduction simulation shows the HDPE matrix is
partially melted or softened, allowing for easier imprinting of the relief pattern of the quartz
mold.Mechanical Engineerin
The substructure and halo population of the Double Cluster and Persei
In order to study the stellar population and possible substructures in the
outskirts of Double Cluster and Persei, we investigate using the
GAIA DR2 data a sky area of about 7.5 degrees in radius around the Double
Cluster cores. We identify member stars using various criteria, including their
kinematics (viz, proper motion), individual parallaxes, as well as photometric
properties. A total of 2186 member stars in the parameter space were identified
as members. Based on the spatial distribution of the member stars, we find an
extended halo structure of and Persei, about 6 - 8 times larger than
their core radii. We report the discovery of filamentary substructures
extending to about 200 pc away from the Double Cluster. The tangential
velocities of these distant substructures suggest that they are more likely to
be the remnants of primordial structures, instead of a tidally disrupted stream
from the cluster cores. Moreover, the internal kinematic analysis indicates
that halo stars seems to be experiencing a dynamic stretching in the RA
direction, while the impact of the core components is relatively negligible.
This work also suggests that the physical scale and internal motions of young
massive star clusters may be more complex than previously thought.Comment: 9 pagges, 9 figures, Accecpted to A&
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