273 research outputs found
SFD: Single Shot Scale-invariant Face Detector
This paper presents a real-time face detector, named Single Shot
Scale-invariant Face Detector (SFD), which performs superiorly on various
scales of faces with a single deep neural network, especially for small faces.
Specifically, we try to solve the common problem that anchor-based detectors
deteriorate dramatically as the objects become smaller. We make contributions
in the following three aspects: 1) proposing a scale-equitable face detection
framework to handle different scales of faces well. We tile anchors on a wide
range of layers to ensure that all scales of faces have enough features for
detection. Besides, we design anchor scales based on the effective receptive
field and a proposed equal proportion interval principle; 2) improving the
recall rate of small faces by a scale compensation anchor matching strategy; 3)
reducing the false positive rate of small faces via a max-out background label.
As a consequence, our method achieves state-of-the-art detection performance on
all the common face detection benchmarks, including the AFW, PASCAL face, FDDB
and WIDER FACE datasets, and can run at 36 FPS on a Nvidia Titan X (Pascal) for
VGA-resolution images.Comment: Accepted by ICCV 2017 + its supplementary materials; Updated the
latest results on WIDER FAC
Highly parallelizable electronic transport calculations in periodic Rhodium and Copper nanostructures
We extend the highly-parallelizable open-source electronic transport code
TRANSEC to perform real-space atomic-scale electronic transport calculations
with periodic boundary conditions in the lateral dimensions. We demonstrate the
use of TRANSEC in periodic Cu and Rh bulk structures and in large periodic Rh
point contacts, in preparation to perform calculations of reflection
probability across Rh grain boundaries
AT2018dyk Revisited: a Tidal Disruption Event Candidate with Prominent Infrared Echo and Delayed X-ray Emission in a LINER Galaxy
The multiwavelength data of nuclear transient AT2018dyk, initially discovered
as a changing-look low-ionization nuclear emission-line region (LINER) galaxy,
has been revisited by us and found being in agreement with a tidal disruption
event (TDE) scenario. The optical light curve of AT2018dyk declines as a
power-law form approximately with index -5/3 yet its X-ray emission lags behind
the optical peak by days, both of which are typical characteristics
for TDEs. The X-ray spectra are softer than normal active galactic nuclei
(AGNs) although they show a slight trend of hardening. Interestingly, its
rising time scale belongs to the longest among TDEs while it is nicely
consistent with the theoretical prediction from its relatively large
supermassive black hole (SMBH) mass (). Moreover, a
prominent infrared echo with peak luminosity
has been also detected in
AT2018dyk, implying an unusually dusty subparsec nuclear environment in
contrast with other TDEs. In our sample, LINERs share similar covering factors
with AGNs, which indicates the existence of the dusty torus in these objects.
Our work suggests that the nature of nuclear transients in LINERs needs to be
carefully identified and their infrared echoes offer us a unique opportunity
for exploring the environment of SMBHs at low accretion rate, which has been so
far poorly explored but is crucial for understanding the SMBH activity.Comment: 9 pages, 6figures, 1 table. Accepted for publication in MNRA
Hydraulic Fracturing Mechanism in Reservoirs with a Linear Inclusion Fissure
Hydraulic fracturing technology is widely used in most oil-water wells to improve production. However, the mechanism of fracturing in a reservoir with inclusion fissures is still unclear. In this study, a theoretical model was developed to determine the stress distribution during hydraulic fracturing. The line inclusion fissure was regarded as a thin bar and the stress around the artificial fracture, which is affected by a single line inclusion, was determined using the Eshelby equivalent inclusion theory. Stress intensity factors at the tip of both the artificial fracture and the inclusion were achieved, and initiation of the fracture was predicted. Furthermore, to validate the theoretical model, re-fracturing experiments were performed on a large-scale tri-axial system. The results showed that the defects reduce the intensity of the rock, which introduces the possibility that more complex fractures emerge in the reservoir. The results also showed that the fracture direction is governed by far-field stress. The obtained conclusions are helpful to better understand the mechanism of hydraulic fracturing in reservoirs
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Parameter Optimization for Preparing Carbon Fiber/Epoxy Composites by Selective Laser Sintering
Carbon fiber (CF) reinforced thermosetting resin composites offer a wide range
of high performance features including excellent strength, modulus and thermal
resistance and light weight. Consequently, they are increasingly demanded by
aerospace and automotive industries due to the tighter requirements of the transport
vehicles for lightweight as well as higher payloads. Although thermoplastics and their
composites have been widely used in additive manufacturing (AM), to date it is
difficult to manufacture carbon fibers reinforced thermosetting composite parts via
AM technologies. Therefore, this study developed a novel method based on selective
laser sintering (SLS) to fabricate high-performance carbon fiber/epoxy resin
composites. The response surface method was employed to study the processing
parameters affecting the quality of final parts, and an optimized processing condition
was obtained.Mechanical Engineerin
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