7,072 research outputs found
Evidence of an Internal Dissipation Origin for the High-energy Prompt Emission of GRB 170214A
The origin of the prompt high-energy (MeV) emission of Gamma-ray Bursts
(GRBs), detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray
Space Telescope, is still under debate, for which both the external shock
origin and internal dissipation origin have been suggested. In the internal
dissipation scenario, the high energy emission is expected to exhibit
significant temporal variability, tracking the keV/MeV fast variable behavior.
Here, we report a detailed analysis on the Fermi data of GRB~170214A, which is
sufficiently bright in the high energy to enable a quantitative analysis of the
correlation between high-energy emission and keV/MeV emission with high
statistics. Our result shows a clear temporal correlation between high-energy
and keV/MeV emission in the whole prompt emission phase as well as in two
decomposed short time intervals. Such correlation behavior is also found in
some other bright LAT GRBs, i.e., GRB 080916C, 090902B and 090926A. For these
GRBs as well as GRB 090510, we also find the rapid temporal variability in the
high-energy emission. We thus conclude that the prompt high-energy emission in
these bright LAT GRBs should be due to internal origin.Comment: 12 pages, 4 figures, Accepted for publication in Ap
Bis{1,2-bis[2-(1H-imidazol-1-yl)ethoxy]ethane-κ2 N 3,N 3′}dichloridocadmium(II) monohydrate
The asymmetric unit of the title compound, [CdCl2(C12H18N4O2)2]·H2O, contains one water molecule and two halves of a [CdCl2(BIEE)2] complex molecule {BIEE is 1,2-bis[2-(1H-imidazol-1-yl)ethoxy]ethane}, with the CdII atoms lying on inversion centres. Each metal atom displays an elongated octahedral coordination geometry provided by two trans-arranged chloride anions and four N atoms from two BIEE ligands. Weak O—H⋯Cl hydrogen-bond interactions contribute to the stability of the crystal packing
Read, Watch, and Move: Reinforcement Learning for Temporally Grounding Natural Language Descriptions in Videos
The task of video grounding, which temporally localizes a natural language
description in a video, plays an important role in understanding videos.
Existing studies have adopted strategies of sliding window over the entire
video or exhaustively ranking all possible clip-sentence pairs in a
pre-segmented video, which inevitably suffer from exhaustively enumerated
candidates. To alleviate this problem, we formulate this task as a problem of
sequential decision making by learning an agent which regulates the temporal
grounding boundaries progressively based on its policy. Specifically, we
propose a reinforcement learning based framework improved by multi-task
learning and it shows steady performance gains by considering additional
supervised boundary information during training. Our proposed framework
achieves state-of-the-art performance on ActivityNet'18 DenseCaption dataset
and Charades-STA dataset while observing only 10 or less clips per video.Comment: AAAI 201
Sub-Band Knowledge Distillation Framework for Speech Enhancement
In single-channel speech enhancement, methods based on full-band spectral
features have been widely studied. However, only a few methods pay attention to
non-full-band spectral features. In this paper, we explore a knowledge
distillation framework based on sub-band spectral mapping for single-channel
speech enhancement. Specifically, we divide the full frequency band into
multiple sub-bands and pre-train an elite-level sub-band enhancement model
(teacher model) for each sub-band. These teacher models are dedicated to
processing their own sub-bands. Next, under the teacher models' guidance, we
train a general sub-band enhancement model (student model) that works for all
sub-bands. Without increasing the number of model parameters and computational
complexity, the student model's performance is further improved. To evaluate
our proposed method, we conducted a large number of experiments on an
open-source data set. The final experimental results show that the guidance
from the elite-level teacher models dramatically improves the student model's
performance, which exceeds the full-band model by employing fewer parameters.Comment: Published in Interspeech 202
2-{2,6-Bis[bis(4-fluorophenyl)methyl]-4-chlorophenylimino} -3-aryliminobutylnickel(II) bromide complexes: Synthesis, characterization, and investigation of their catalytic behavior
The series of 2-{2,6-bis[di(4-fluorophenyl)methyl]-4-chlorophenylimino}-3- aryliminobutane derivatives (L1-L5) and their nickel(II) dibromide complexes (Ni1-Ni5) were synthesized, and all organic compounds were fully characterized by the Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy and by elemental analysis, while the nickel complexes were characterized by FT-IR spectroscopy, elemental analysis, as well as by single-crystal X-ray diffraction for two representative examples, namely Ni1 and Ni4. A distorted tetrahedral geometry was observed for these four-coordinate nickel complexes. Upon the activation with either Methylaluminoxane or modified methylaluminoxane as co-catalyst, all nickel complex precatalysts showed very high activity toward ethylene polymerization with activities of up to 10 7 g(PE)·mol -1 (Ni)·h -1 , and afforded highly branched polyethylene with a bimodal distribution. © 2014 Elsevier B.V
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