112 research outputs found
Transient Stability Analysis of Droop-Controlled Grid-Connected Converters With Inertia Emulating Low-Pass Filters
Transient Stability of Voltage-Source Converters With Grid-Forming Control:A Design-Oriented Study
Ultrafast spectroscopy of propagating coherent acoustic phonons in GaN/InGaN heterostructures
We show that large amplitude, coherent acoustic phonon wavepackets can be
generated and detected in InGaN/GaN epilayers and heterostructures
in femtosecond pump-probe differential reflectivity experiments. The amplitude
of the coherent phonon increases with increasing Indium fraction and unlike
other coherent phonon oscillations, both \textit{amplitude} and \textit{period}
are strong functions of the laser probe energy. The amplitude of the
oscillation is substantially and almost instantaneously reduced when the
wavepacket reaches a GaN-sapphire interface below the surface indicating that
the phonon wavepackets are useful for imaging below the surface. A theoretical
model is proposed which fits the experiments well and helps to deduce the
strength of the phonon wavepackets. Our model shows that localized coherent
phonon wavepackets are generated by the femtosecond pump laser in the epilayer
near the surface. The wavepackets then propagate through a GaN layer changing
the local index of refraction, primarily through the Franz-Keldysh effect, and
as a result, modulate the reflectivity of the probe beam. Our model correctly
predicts the experimental dependence on probe-wavelength as well as epilayer
thickness.Comment: 11 pages, 14 figure
Pose-Free Neural Radiance Fields via Implicit Pose Regularization
Pose-free neural radiance fields (NeRF) aim to train NeRF with unposed
multi-view images and it has achieved very impressive success in recent years.
Most existing works share the pipeline of training a coarse pose estimator with
rendered images at first, followed by a joint optimization of estimated poses
and neural radiance field. However, as the pose estimator is trained with only
rendered images, the pose estimation is usually biased or inaccurate for real
images due to the domain gap between real images and rendered images, leading
to poor robustness for the pose estimation of real images and further local
minima in joint optimization. We design IR-NeRF, an innovative pose-free NeRF
that introduces implicit pose regularization to refine pose estimator with
unposed real images and improve the robustness of the pose estimation for real
images. With a collection of 2D images of a specific scene, IR-NeRF constructs
a scene codebook that stores scene features and captures the scene-specific
pose distribution implicitly as priors. Thus, the robustness of pose estimation
can be promoted with the scene priors according to the rationale that a 2D real
image can be well reconstructed from the scene codebook only when its estimated
pose lies within the pose distribution. Extensive experiments show that IR-NeRF
achieves superior novel view synthesis and outperforms the state-of-the-art
consistently across multiple synthetic and real datasets.Comment: Accepted by ICCV202
Leadless pacemaker implantation and azygos continuation in the inferior vena cava:a case description
Pivotal Role of Dogs in Rabies Transmission, China
The number of dog-mediated rabies cases in China has increased exponentially; the number of human deaths has been high, primarily in poor, rural communities. We review the incidence of rabies in China based on data from 1950 and 2004, obtained mainly from epidemiologic bulletins published by the Chinese Ministry of Health
Ferret badger rabies origin and its revisited importance as potential source of rabies transmission in Southeast China
<p>Abstract</p> <p>Background</p> <p>The frequent occurrence of ferret badger-associated human rabies cases in southeast China highlights the lack of laboratory-based surveillance and urges revisiting the potential importance of this animal in rabies transmission. To determine if the ferret badgers actually contribute to human and dog rabies cases, and the possible origin of the ferret badger-associated rabies in the region, an active rabies survey was conducted to determine the frequency of rabies infection and seroprevalence in dogs and ferret badgers.</p> <p>Methods</p> <p>A retrospective survey on rabies epidemics was performed in Zhejiang, Jiangxi and Anhui provinces in southeast China. The brain tissues from ferret badgers and dogs were assayed by fluorescent antibody test. Rabies virus was isolated and sequenced for phylogenetic analysis. The sera from ferret badgers and dogs were titrated using rabies virus neutralizing antibodies (VNA) test.</p> <p>Results</p> <p>The ferret badgers presented a higher percentage of rabies seroconversion than dogs did in the endemic region, reaching a maximum of 95% in the collected samples. Nine ferret badger-associated rabies viruses were isolated, sequenced, and were phylogenetically clustered as a separate group. Nucleotide sequence revealed 99.4-99.8% homology within the ferret badger isolates, and 83-89% homology to the dog isolates in the nucleoprotein and glycoprotein genes in the same rabies endemic regions.</p> <p>Conclusions</p> <p>Our data suggest ferret badger-associated rabies has likely formed as an independent enzootic originating from dogs during the long-term rabies infestation in southeast China. The eventual role of FB rabies in public health remains unclear. However, management of ferret badger bites, rabies awareness and control in the related regions should be an immediate need.</p
Investigation on temperature distribution under the coupling action of transverse position and fire sealing of linear fire in tunnel
Funding Information: The work was supported by the National Key Research and Development Program of China (No. 2016YFC0802900 ). Publisher Copyright: © 2021 The Author(s). Copyright: Copyright 2021 Elsevier B.V., All rights reserved.By sealing the portal at one end of tunnel and changing the transverse location of linear fire source in tunnel, the hot smoke layer, longitudinal temperature distribution and maximum temperature of linear fire source were investigated. It is found that the flame will bend under the influence of curved ceiling and hot smoke layer will be thicker when the linear fire source approaches to the side wall. The variation law of heat release rate is analyzed by considering the limiting effect of side wall and thermal feedback. By modifying the previous formula of effective ceiling height, an empirical formula for predicting longitudinal temperature distribution of linear fire sources with different aspect ratios is proposed, and the ventilation coefficient is obtained to characterized the temperature under sealing and without sealing. Moreover, the accuracy of predicted temperature under sealing is verified by using the ventilation coefficient. Based on dimensional analysis, it's concluded that the maximum temperature mainly depends on the heat release rate, and an empirical formula is proposed to predict the maximum temperature rise of linear fire sources with different aspect ratios in several transverse positions. The error of predicted values and actual values is within 13%.Peer reviewe
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