242 research outputs found
Dynamic analysis and optimal control of a novel fractional-order 2I2SR rumor spreading model
In this paper, a novel fractional-order 2I2SR rumor spreading model is investigated. Firstly, the boundedness and uniqueness of solutions are proved. Then the next-generation matrix method is used to calculate the threshold. Furthermore, the stability of rumor-free/spreading equilibrium is discussed based on fractional-order Routh–Hurwitz stability criterion, Lyapunov function method, and invariance principle. Next, the necessary conditions for fractional optimal control are obtained. Finally, some numerical simulations are given to verify the results
Storm-induced changes in pCO2 at the sea surface over the northern South China Sea during Typhoon Wutip
In situ oceanographic measurements were made before and after the passage of Typhoon Wutip in September 2013 over the northern South China Sea. The surface geostrophic circulation over this region inferred from satellite altimetry data features a large‐size anticyclonic eddy, a small‐size cyclonic eddy, and smaller‐size eddies during this period. Significant typhoon‐induced changes occurred in the partial pressure of CO2 at the sea surface (pCO2sea) during Wutip. Before the passage of Wutip, pCO2sea was about 392.92 ± 1.83, 390.31 ± 0.50, and 393.04 ± 4.31 μatm over the cyclonic eddy water, the anticyclonic eddy water, and areas outside two eddies, respectively. The entire study region showed a carbon source (1.31 ± 0.46 mmol CO2 m?2 d?1) before Wutip. In the cyclonic eddy water after Wutip, high sea surface salinity (SSS), low sea surface temperature (SST), and high pCO2sea (413.05 ± 7.56 μatm) made this area to be a carbon source (3.30 ± 0.75 mmol CO2 m?2 d?1). In the anticyclonic eddy water after Wutip, both the SSS and SST were lower, pCO2sea was also lower (383.03 ± 3.72 μatm), and this area became a carbon sink (-0.11 ± 0.55 mmol CO2 m?2 d?1), in comparison with the pretyphoon conditions. The typhoon‐induced air‐sea CO2 flux reached about 0.03 mmol CO2 m?2 d?1. Noticeable spatial variations in pCO2sea were affected mainly by the typhoon‐induced mixing/upwelling and vertical stratifications. This study suggests that the local air‐sea CO2 flux in the study region was affected significantly by oceanographic conditions during the typhoon
Augmenting Sports Videos with VisCommentator
Visualizing data in sports videos is gaining traction in sports analytics,
given its ability to communicate insights and explicate player strategies
engagingly. However, augmenting sports videos with such data visualizations is
challenging, especially for sports analysts, as it requires considerable
expertise in video editing. To ease the creation process, we present a design
space that characterizes augmented sports videos at an element-level (what the
constituents are) and clip-level (how those constituents are organized). We do
so by systematically reviewing 233 examples of augmented sports videos
collected from TV channels, teams, and leagues. The design space guides
selection of data insights and visualizations for various purposes. Informed by
the design space and close collaboration with domain experts, we design
VisCommentator, a fast prototyping tool, to eases the creation of augmented
table tennis videos by leveraging machine learning-based data extractors and
design space-based visualization recommendations. With VisCommentator, sports
analysts can create an augmented video by selecting the data to visualize
instead of manually drawing the graphical marks. Our system can be generalized
to other racket sports (e.g., tennis, badminton) once the underlying datasets
and models are available. A user study with seven domain experts shows high
satisfaction with our system, confirms that the participants can reproduce
augmented sports videos in a short period, and provides insightful implications
into future improvements and opportunities
Palladium-Catalyzed Cascade Carbonylation to α,β-Unsaturated Piperidones via Selective Cleavage of Carbon-Carbon Triple Bonds
A direct and selective synthesis of α,β-unsaturated piperidones by a new palladium-catalyzed cascade carbonylation is described. In the presented protocol, easily available propargylic alcohols react with aliphatic amines to provide a broad variety of interesting heterocycles. Key to the success of this transformation is a remarkable catalytic cleavage of the present carbon–carbon triple bond by using a specific catalyst with 2-diphenylphosphinopyridine as ligand and appropriate reaction conditions. Mechanistic studies and control experiments revealed branched unsaturated acid 11 as crucial intermediate. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH Gmb
Pressure-induced structural modulations in coesite
Silica phases, SiO2, have attracted significant attention as important phases in the fields of condensed-matter physics, materials science, and (in view of their abundance in the Earth's crust) geoscience. Here, we experimentally and theoretically demonstrate that coesite undergoes structural modulations under high pressure. Coesite transforms to a distorted modulated structure, coesite-II, at 22–25 GPa with modulation wave vector q=0.5b∗. Coesite-II displays further commensurate modulation along the y axis at 36–40 GPa and the long-range ordered crystalline structure collapses beyond ∼40GPa and starts amorphizing. First-principles calculations illuminate the nature of the modulated phase transitions of coesite and elucidate the modulated structures of coesite caused by modulations along the y-axis direction. The structural modulations are demonstrated to result from phonon instability, preceding pressured-induced amorphization. The recovered sample after decompression develops a rim of crystalline coesite structure, but its interior remains low crystalline or partially amorphous. Our results not only clarify that the pressure-induced reversible phase transitions and amorphization in coesite originate from structural modulations along the y-axis direction, but also shed light on the densification mechanism of silica under high pressure
The Immediate Economic Impact of Maternal Deaths on Rural Chinese Households
OBJECTIVE: To identify the immediate economic impact of maternal death on rural Chinese households. METHODS: Results are reported from a study that matched 195 households who had suffered a maternal death to 384 households that experienced a childbirth without maternal death in rural areas of three provinces in China, using quantitative questionnaire to compare differences of direct and indirect costs between two groups. FINDINGS: The direct costs of a maternal death were significantly higher than the costs of a childbirth without a maternal death (US370, p<0.001). More than 40% of the direct costs were attributed to funeral expenses. Hospitalization and emergency care expenses were the largest proportion of non-funeral direct costs and were higher in households with maternal death than the comparison group (US305, p<0.001). To cover most of the high direct costs, 44.1% of affected households utilized compensation from hospitals, and the rest affected households (55.9%) utilized borrowing money or taking loans as major source of money to offset direct costs. The median economic burden of the direct (and non-reimbursed) costs of a maternal death was quite high--37.0% of the household's annual income, which was approximately 4 times as high as the threshold for an expense being considered catastrophic. CONCLUSION: The immediate direct costs of maternal deaths are extremely catastrophic for the rural Chinese households in three provinces studied
Doublade: Unknown Vulnerability Detection in Smart Contracts Via Abstract Signature Matching and Refined Detection Rules
With the prosperity of smart contracts and the blockchain technology, various
security analyzers have been proposed from both the academia and industry to
address the associated risks. Yet, there does not exist a high-quality
benchmark of smart contract vulnerability for security research. In this study,
we propose an approach towards building a high-quality vulnerability benchmark.
Our approach consists of two parts. First, to improve recall, we propose to
search for similar vulnerabilities in an automated way by leveraging the
abstract vulnerability signature (AVS). Second, to remove the false positives
(FPs) due to AVS-based matching, we summarize the detection rules of existing
tools and apply the refined rules by considering various defense mechanisms
(DMs). By integrating AVS-based code matching and the refined detection rules
(RDR), our approach achieves higher precision and recall. On the collected
76,354 contracts, we build a benchmark consisting of 1,219 vulnerabilities
covering five different vulnerability types identified together by our tool
(DOUBLADE) and other three scanners. Additionally, we conduct a comparison
between DOUBLADE and the others, on an additional 17,770 contracts. Results
show that DOUBLADE can yield a better detection accuracy with similar execution
time
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