290 research outputs found
CHARACTERIZATION OF THE INITIAL SPRAY FROM A JET IN CROSSFLOW
An experimental study on the initial spray from a liquid jet in air crossflow was conducted using Shadowgraphy and Particle Image Velocimetry (PIV) techniques. Momentum ratio and gas Weber number were varied to study their effects on the column trajectory, spray trajectory, breakup locations and spray characteristics after column breakup. Correlations for column trajectory, spray trajectory, breakup locations in terms of momentum ratio and gas Weber number were obtained using linear regression of the experimental data. Two breakup modes were recognized in the test (Column breakup and Bag breakup), a breakup mode regime map was provided including effects of momentum ratio and gas Weber number. Drop characteristics in the spray were also investigated
Intense keV isolated attosecond pulse generation by orthogonally polarized multicycle midinfrared two-color laser field
We theoretically investigate the generation of intense keV attosecond pulses
in an orthogonally polarized multicycle midinfrared two-color laser field. It
is demonstrated that multiple continuum-like humps, which have a spectral width
of about twenty orders of harmonics and an intensity of about one order higher
than adjacent normal harmonic peaks, are generated under proper two-color
delays, owing to the reduction of the number of electron-ion recollisions and
suppression of inter-half-cycle interference effect of multiple electron
trajectories when the long wavelength midinfrared driving field is used. Using
the semiclassical trajectory model, we have revealed the two-dimensional
manipulation of the electron-ion recollision process, which agrees well with
the time frequency analysis. By filtering these humps, intense isolated
attosecond pulses are directly generated without any phase compensation. Our
proposal provides a simple technique to generate intense isolated attosecond
pulses with various central photon energies covering the multi-keV spectral
regime by using multicycle driving pulses with high pump energy in experiment.Comment: 11 pages,5 figures, research articl
Trends and variability of daily temperature extremes during 1960–2012 in the Yangtze River Basin, China
Fine-Grained Access Control Systems Suitable for Resource-Constrained Users in Cloud Computing
For the sake of practicability of cloud computing, fine-grained data access is frequently required in the sense that users with different attributes should be granted different levels of access privileges. However, most of existing access control solutions are not suitable for resource-constrained users because of large computation costs, which linearly increase with the complexity of access policies. In this paper, we present an access control system based on ciphertext-policy attribute-based encryption. The proposed access control system enjoys constant computation cost and is proven secure in the random oracle model under the decision Bilinear Diffie-Hellman Exponent assumption. Our access control system supports AND-gate access policies with multiple values and wildcards, and it can efficiently support direct user revocation. Performance comparisons indicate that the proposed solution is suitable for resource-constrained environment
MixEdit: Revisiting Data Augmentation and Beyond for Grammatical Error Correction
Data Augmentation through generating pseudo data has been proven effective in
mitigating the challenge of data scarcity in the field of Grammatical Error
Correction (GEC). Various augmentation strategies have been widely explored,
most of which are motivated by two heuristics, i.e., increasing the
distribution similarity and diversity of pseudo data. However, the underlying
mechanism responsible for the effectiveness of these strategies remains poorly
understood. In this paper, we aim to clarify how data augmentation improves GEC
models. To this end, we introduce two interpretable and computationally
efficient measures: Affinity and Diversity. Our findings indicate that an
excellent GEC data augmentation strategy characterized by high Affinity and
appropriate Diversity can better improve the performance of GEC models. Based
on this observation, we propose MixEdit, a data augmentation approach that
strategically and dynamically augments realistic data, without requiring extra
monolingual corpora. To verify the correctness of our findings and the
effectiveness of the proposed MixEdit, we conduct experiments on mainstream
English and Chinese GEC datasets. The results show that MixEdit substantially
improves GEC models and is complementary to traditional data augmentation
methods.Comment: Accepted to Findings of EMNLP 202
Privacy-preserving communication and power injection over vehicle networks and 5G smart grid slice
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