2,428 research outputs found
5-(HyÂdroxyÂmethÂyl)furan-2-carbÂoxyÂlic acid
In the title compound, C6H6O4, the furan ring is nearly coplanar with the carboxyl group, the maximum atomic deviation being 0.0248 (9) Å. The crystal packing is stabilized by classical O—H⋯O and weak C—H⋯O hydrogen bonding
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
A study of photoluminescence properties and performance improvement of Cd-doped ZnO quantum dots prepared by the sol–gel method
In the present work, ZnO quantum dots (QDs) have been prepared by the sol–gel method, and the performance of the QDs has been improved. The effect of Cd concentration on the structural and luminescent properties of the QDs, as well as the effect of the mass ratio of trioctylphosphine oxide (TOPO)/octadecylamine (ODA), has been investigated. The ZnO and Cd-doped ZnO QDs have hexagonal wurtzite structures and are 3 to 6 nm in diameter. When the Cd content was increased, the QD particle size was reduced; this effect was confirmed in the corresponding ultraviolet–visible spectra. The fluorescence intensity was simultaneously enhanced significantly. Both the UV and fluorescence spectra were blue-shifted. The luminous intensity was further enhanced when the QDs were modified with TOPO/ODA. Fourier transform infrared and X-ray diffraction techniques proved that the polymer successfully coated the surfaces of the QDs. A TOPO/ODA mass ratio of 1:2 was determined to result in the best optical performance among the different ratios examined. The results showed that the described synthetic method is appropriate for the preparation of doped QDs with high-fluorescence quantum efficiency
A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz
A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz is carried out
using the Shanghai Tian Ma 65 m Radio Telescope (TMRT-65m) with a sensitivity
of < 7 mK. Thirty-five spectral lines of 12 different molecules and radicals
are detected in total. Except for SiS, the detected molecules are all
carbon-chain molecules, including HC3N, HC5N, HC7N, HC9N, C6H, C6H-, C8H, SiC2,
SiC4, c-C3H2 and l-C5H. The presence of rich carbon-bearing molecules is
consistent with the identity of IRC +10216 as a carbon-rich AGB star. The
excitation temperatures and column densities of the observed species are
derived by assuming a local thermodynamic equilibrium and homogeneous
conditions.Comment: This is the authors' version of the manuscript; 16 pages, 5 figures,
6 tables; Accepted for publication in A&A 8/17/201
UAV-assisted Semantic Communication with Hybrid Action Reinforcement Learning
In this paper, we aim to explore the use of uplink semantic communications
with the assistance of UAV in order to improve data collection effiicency for
metaverse users in remote areas. To reduce the time for uplink data collection
while balancing the trade-off between reconstruction quality and computational
energy cost, we propose a hybrid action reinforcement learning (RL) framework
to make decisions on semantic model scale, channel allocation, transmission
power, and UAV trajectory. The variables are classified into discrete type and
continuous type, which are optimized by two different RL agents to generate the
combined action. Simulation results indicate that the proposed hybrid action
reinforcement learning framework can effectively improve the efficiency of
uplink semantic data collection under different parameter settings and
outperforms the benchmark scenarios.Comment: This paper appears in IEEE Global Communications Conference
(GLOBECOM) 202
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