1,849 research outputs found
YouTube AV 50K: An Annotated Corpus for Comments in Autonomous Vehicles
With one billion monthly viewers, and millions of users discussing and
sharing opinions, comments below YouTube videos are rich sources of data for
opinion mining and sentiment analysis. We introduce the YouTube AV 50K dataset,
a freely-available collections of more than 50,000 YouTube comments and
metadata below autonomous vehicle (AV)-related videos. We describe its creation
process, its content and data format, and discuss its possible usages.
Especially, we do a case study of the first self-driving car fatality to
evaluate the dataset, and show how we can use this dataset to better understand
public attitudes toward self-driving cars and public reactions to the accident.
Future developments of the dataset are also discussed.Comment: in Proceedings of the Thirteenth International Joint Symposium on
Artificial Intelligence and Natural Language Processing (iSAI-NLP 2018
Strong enhancement of chlorophyll a concentration by a weak typhoon
Recent studies demonstrate that chlorophyll a (chl a) concentrations in the
surface ocean can be significantly enhanced due to typhoons. The present study
investigated chl a concentrations in the middle of the South China Sea (SCS)
from 1997-2007. Only the Category1 (minimal) Typhoon Hagibis (2007) had a
notable effect on the chl a concentrations. Typhoon Hagibis had a strong
upwelling potential due to its location near the equator, and the forcing time
of the typhoon (>82 h) was much longer than the geostrophic adjustment time
(~63 h). The higher upwelling velocity and the longer forcing time increased
the depth of the mixed-layer, which consequently induced a strong phytoplankton
bloom that accounted for about 30% of the total annual chl a concentration in
the middle of the SCS. The implication is that the forcing time of a typhoon
should be long enough to establish a strong upwelling and consequently for the
induction of significant upper ocean responses.Comment: Typhoon-Ocean Environment interaction
Optical Monitoring of the Seyfert Galaxy NGC 4151 and Possible Periodicities in the Historical Light Curve
We report B, V, and R band CCD photometry of the Seyfert galaxy NGC 4151
obtained with the 1.0-m telescope at Weihai Observatory of Shandong University
and the 1.56-m telescope at Shanghai Astronomical Observatory from 2005
December to 2013 February. Combining all available data from literature, we
have constructed a historical light curve from 1910 to 2013 to study the
periodicity of the source using three different methods (the Jurkevich method,
the Lomb-Scargle periodogram method and the Discrete Correlation Function
method). We find possible periods of P_1=4\pm0.1, P_2=7.5\pm0.3 and
P_3=15.9\pm0.3 yr.Comment: 8 pages, 5 figures, Accepted by Research in Astronomy and
Astrophysic
Iron(III) bromide catalyzed bromination of 2-tert-butylpyrene and corresponding position-dependent aryl-functionalized pyrene derivatives
The present work probes the bromination mechanism of 2-tert-butylpyrene (1), which regioselectively affords mono-, di-, tri- and tetra-bromopyrenes, by theoretical calculation and detailed experimental methods. The bromine atom may be directed to the K-region (positions 5- and 9-) instead of the more reactive 6- and 8-positions in the presence of iron powder. In this process, FeBr₃ plays a significant role to release steric hindrance or lower the activation energy of the rearrangement. The intermediate bromopyrene derivatives were isolated and confirmed by ¹H NMR spectrometry, mass spectroscopy and elemental analysis. Further evidence on substitution position originated from a series of aryl substituted pyrene derivatives, which were obtained from the corresponding bromopyrenes on reaction with 4-methoxy-phenylboronic acid by a Suzuki–Miyaura cross-coupling reaction. All position-dependent aryl-functionalized pyrene derivatives are characterized by single X-ray diffraction, ¹H/¹³C NMR, FT-IR and MS, and offered straightforward evidence to support our conclusion. Furthermore, the photophysical properties of a series of compounds were confirmed by fluorescence and absorption, as well as by fluorescence lifetime measurements
Stability studies of ZnO and AlN thin film acoustic wave devices in acid and alkali harsh environments
Surface acoustic wave (SAW) devices based on piezoelectric thin-films such as ZnO and AlN are widely used in sensing, microfluidics and lab-on-a-chip applications. However, for many of these applications, the SAW devices will inevitably be used in acid or alkali harsh environments, which may cause their early failures. In this work, we investigated the behavior and degradation mechanisms of thin film based SAW devices in acid and alkali harsh environments. Results show that under the acid and alkali attacks, chemical reaction and corrosion of ZnO devices are very fast (usually within 45 s). During the corrosion, the crystalline orientation of the ZnO film is not changed, but its grain defects are significantly increased and the grain sizes are decreased. The velocity of ZnO-based SAW devices is decreased due to the formation of porous structures induced by the chemical reactions. Whereas an AlN thin-film based SAW device does not perform well in acid–alkali conditions, it might be able to maintain a normal performance without obvious degradation for more than ten hours in acid or alkali solutions. This work could provide guidance for the applications of both ZnO or AlN-based SAW devices in acid/alkali harsh environments
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