2,599 research outputs found
The collective motion of self-propelled particles affected by the spatial-dependent noise
We study the collective motion of self-propelled particles affected by the
spatial-dependent noise based on the Vicsek rules. Only the particles inside
the special region will affected by noise. The consideration of the
spatial-dependent noise is closer to reality because of the complexity of the
environment. Interestingly, we find that there exists an optimal amplitude of
noise to adjust the average motional direction of the system. Particular
orientation of the noisy region makes the motional direction of the system
parallel to the orientation of the noisy region. The adjustment of the motional
direction of the system also depends on the shape, the proportion and the
spatial distribution of the noisy region. Our findings may inspire the capture
of the key features of collective motion underlying various phenomena.Comment: 12 pages, 6 figures, 39 reference
An optical fiber tip micrograting thermometer
An ~12 µm long Bragg grating was engraved in an ~5 µm diameter optical fiber tip by focused ion beam (FIB) milling. An ~10-dB extinction was achieved at 1570 nm with only 11 indentations. The grating was used for temperature sensing, and it exhibited a temperature sensitivity of ~22 pm/°C
Polarization switch using thick holographic polymer-dispersed liquid crystal grating
Theoretical study of the optical diffraction properties of holographic polymer-dispersed liquid crystal (HPDLC)-based thick volume grating was presented. It is found that the HPDLC grating can selectively diffract the s-polarized light only, p-polarized light only, or both s and p beams by selecting suitable grating parameters. When an electric field is applied, the s- and p-polarized lights exhibit different diffraction behaviors and, thus, the tunable dual-state or three-state polarization switching could be realized
Molecular Lines of 13 Galactic Infrared Bubble Regions
We investigated the physical properties of molecular clouds and star
formation processes around infrared bubbles which are essentially expanding HII
regions. We performed observations of 13 galactic infrared bubble fields
containing 18 bubbles. Five molecular lines, 12CO (J=1-0), 13CO (J=1-0),
C18O(J=1-0), HCN (J=1-0), and HCO+ (J=1-0), were observed, and several publicly
available surveys, GLIMPSE, MIPSGAL, ATLASGAL, BGPS, VGPS, MAGPIS, and NVSS,
were used for comparison. We find that these bubbles are generally connected
with molecular clouds, most of which are giant. Several bubble regions display
velocity gradients and broad shifted profiles, which could be due to the
expansion of bubbles. The masses of molecular clouds within bubbles range from
100 to 19,000 solar mass, and their dynamic ages are about 0.3-3.7 Myr, which
takes into account the internal turbulence pressure of surrounding molecular
clouds. Clumps are found in the vicinity of all 18 bubbles, and molecular
clouds near four of these bubbles with larger angular sizes show shell-like
morphologies, indicating that either collect-and-collapse or radiation-driven
implosion processes may have occurred. Due to the contamination of adjacent
molecular clouds, only six bubble regions are appropriate to search for
outflows, and we find that four of them have outflow activities. Three bubbles
display ultra-compact HII regions at their borders, and one of them is probably
responsible for its outflow. In total, only six bubbles show star formation
activities in the vicinity, and we suggest that star formation processes might
have been triggered.Comment: 55 Pages, 32 figures. Accepted for publication in A
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