1,273 research outputs found
Exploring differences in injury severity between occupant groups involved in fatal rear-end crashes: A correlated random parameter logit model with mean heterogeneity
Rear-end crashes are one of the most common crash types. Passenger cars
involved in rear-end crashes frequently produce severe outcomes. However, no
study investigated the differences in the injury severity of occupant groups
when cars are involved as following and leading vehicles in rear-end crashes.
Therefore, the focus of this investigation is to compare the key factors
affecting the injury severity between the front- and rear-car occupant groups
in rear-end crashes. First, data is extracted from the Fatality Analysis
Reporting System (FARS) for two types of rear-end crashes from 2017 to 2019,
including passenger cars as rear-end and rear-ended vehicles. Significant
injury severity difference between front- and rear-car occupant groups is found
by conducting likelihood ratio test. Moreover, the front- and rear-car occupant
groups are modelled by the correlated random parameter logit model with
heterogeneity in means (CRPLHM) and the random parameter logit model with
heterogeneity in means (RPLHM), respectively. From the modeling, the
significant factors are occupant positions, driver age, overturn, vehicle type,
etc. For instance, the driving and front-right positions significantly increase
the probability of severe injury when struck by another vehicle. Large
truck-strike-car tends to cause severe outcomes compared to car-strike-large
truck. This study provides an insightful knowledge of mechanism of occupant
injury severity in rear-end crashes, and propose some effective countermeasures
to mitigate the crash severity, such as implementing stricter seat belt laws,
improving the coverage of the streetlights, strengthening car driver's
emergency response ability
Investigating the spatial heterogeneity of factors influencing speeding-related crash severities using correlated random parameter order models with heterogeneity-in-means
Speeding has been acknowledged as a critical determinant in increasing the
risk of crashes and their resulting injury severities. This paper demonstrates
that severe speeding-related crashes within the state of Pennsylvania have a
spatial clustering trend, where four crash datasets are extracted from four
hotspot districts. Two log-likelihood ratio (LR) tests were conducted to
determine whether speeding-related crashes classified by hotspot districts
should be modeled separately. The results suggest that separate modeling is
necessary. To capture the unobserved heterogeneity, four correlated random
parameter order models with heterogeneity in means are employed to explore the
factors contributing to crash severity involving at least one vehicle speeding.
Overall, the findings exhibit that some indicators are observed to be spatial
instability, including hit pedestrian crashes, head-on crashes, speed limits,
work zones, light conditions (dark), rural areas, older drivers, running stop
signs, and running red lights. Moreover, drunk driving, exceeding the speed
limit, and being unbelted present relative spatial stability in four district
models. This paper provides insights into preventing speeding-related crashes
and potentially facilitating the development of corresponding crash injury
mitigation policies
EUCLIA - Exploring the UV/optical continuum lag in active galactic nuclei. I. a model without light echoing
The tight inter-band correlation and the lag-wavelength relation among
UV/optical continua of active galactic nuclei have been firmly established.
They are usually understood within the widespread reprocessing scenario,
however, the implied inter-band lags are generally too small. Furthermore, it
is challenged by new evidences, such as the X-ray reprocessing yields too much
high frequency UV/optical variations as well as it fails to reproduce the
observed timescale-dependent color variations among {\it Swift} lightcurves of
NGC 5548. In a different manner, we demonstrate that an upgraded inhomogeneous
accretion disk model, whose local {\it independent} temperature fluctuations
are subject to a speculated {\it common} large-scale temperature fluctuation,
can intrinsically generate the tight inter-band correlation and lag across
UV/optical, and be in nice agreement with several observational properties of
NGC 5548, including the timescale-dependent color variation. The emergent lag
is a result of the {\it differential regression capability} of local
temperature fluctuations when responding to the large-scale fluctuation. An
average speed of propagations as large as of the speed of light
may be required by this common fluctuation. Several potential physical
mechanisms for such propagations are discussed. Our interesting
phenomenological scenario may shed new light on comprehending the UV/optical
continuum variations of active galactic nuclei.Comment: 18 pages, 8 figures. ApJ accepted. Further comments are very welcome
Cross Aggregation Transformer for Image Restoration
Recently, Transformer architecture has been introduced into image restoration
to replace convolution neural network (CNN) with surprising results.
Considering the high computational complexity of Transformer with global
attention, some methods use the local square window to limit the scope of
self-attention. However, these methods lack direct interaction among different
windows, which limits the establishment of long-range dependencies. To address
the above issue, we propose a new image restoration model, Cross Aggregation
Transformer (CAT). The core of our CAT is the Rectangle-Window Self-Attention
(Rwin-SA), which utilizes horizontal and vertical rectangle window attention in
different heads parallelly to expand the attention area and aggregate the
features cross different windows. We also introduce the Axial-Shift operation
for different window interactions. Furthermore, we propose the Locality
Complementary Module to complement the self-attention mechanism, which
incorporates the inductive bias of CNN (e.g., translation invariance and
locality) into Transformer, enabling global-local coupling. Extensive
experiments demonstrate that our CAT outperforms recent state-of-the-art
methods on several image restoration applications. The code and models are
available at https://github.com/zhengchen1999/CAT.Comment: Accepted to NeurIPS 2022. Code is available at
https://github.com/zhengchen1999/CA
An intrinsic link between long-term UV/optical variations and X-ray loudness in quasars
Observations have shown that UV/optical variation amplitude of quasars depend
on several physi- cal parameters including luminosity, Eddington ratio, and
likely also black hole mass. Identifying new factors which correlate with the
variation is essential to probe the underlying physical processes. Combining
~ten years long quasar light curves from SDSS stripe 82 and X-ray data from
Stripe 82X, we build a sample of X-ray detected quasars to investigate the
relation between UV/optical variation amplitude () and X-ray
loudness. We find that quasars with more intense X-ray radiation (com- pared to
bolometric luminosity) are more variable in UV/optical. Such correlation
remains highly significant after excluding the effect of other parameters
including luminosity, black hole mass, Ed- dington ratio, redshift, rest-frame
wavelength (i.e., through partial correlation analyses). We further find the
intrinsic link between X-ray loudness and UV/optical variation is gradually
more prominent on longer timescales (up to 10 years in the observed frame), but
tends to disappear at timescales < 100 days. This suggests a slow and long-term
underlying physical process. The X-ray reprocessing paradigm, in which
UV/optical variation is produced by a variable central X-ray emission
illuminating the accretion disk, is thus disfavored. The discovery points to an
interesting scheme that both the X-ray corona heating and UV/optical variation
is quasars are closely associated with magnetic disc turbulence, and the
innermost disc turbulence (where corona heating occurs) correlates with the
slow turbulence at larger radii (where UV/optical emission is produced).Comment: 9 pages, 4 figures, 1 table, accepted by Ap
Hierarchical Integration Diffusion Model for Realistic Image Deblurring
Diffusion models (DMs) have recently been introduced in image deblurring and
exhibited promising performance, particularly in terms of details
reconstruction. However, the diffusion model requires a large number of
inference iterations to recover the clean image from pure Gaussian noise, which
consumes massive computational resources. Moreover, the distribution
synthesized by the diffusion model is often misaligned with the target results,
leading to restrictions in distortion-based metrics. To address the above
issues, we propose the Hierarchical Integration Diffusion Model (HI-Diff), for
realistic image deblurring. Specifically, we perform the DM in a highly
compacted latent space to generate the prior feature for the deblurring
process. The deblurring process is implemented by a regression-based method to
obtain better distortion accuracy. Meanwhile, the highly compact latent space
ensures the efficiency of the DM. Furthermore, we design the hierarchical
integration module to fuse the prior into the regression-based model from
multiple scales, enabling better generalization in complex blurry scenarios.
Comprehensive experiments on synthetic and real-world blur datasets demonstrate
that our HI-Diff outperforms state-of-the-art methods. Code and trained models
are available at https://github.com/zhengchen1999/HI-Diff.Comment: Code is available at https://github.com/zhengchen1999/HI-Dif
Research on the ZigBee Network and Equipment Design Based on the CC2530
It is known to us all that embedded systems designed on the 51 chip microcomputer are mature. This research finished to plant the system from 51 chip microcomputer to the CC2530 chip of TI. After analyzing and mastering the ZigBee 2007 PRO protocol stack, a new set of wireless sensor network (WSN) products has been developed. In the system, the coordinator can establish the Mesh network on its own initiative and the child nodes can join the network. The coordinator can be connected to the personal computer or the embedded gateway. The gateway had the Ethernet port and can send the data from the sensors to the cable or wireless network. The operator can issue instructions automatically and manually. The information of the sensor nodes can be returned and displayed on the serial debugging assistant. The equipment has passed the test with different environments in which there are obstacles among the communicating sensors and can be applied in the traffic, environmental monitoring and other fields widely
Linalool inhibits the angiogenic activity of endothelial cells by downregulating intracellular ATP levels and activating TRPM8
Angiogenesis crucially contributes to various diseases, such as cancer and diabetic retinopathy. Hence, anti-angiogenic therapy is considered as a powerful strategy against these diseases. Previous studies reported that the acyclic monoterpene linalool exhibits anticancer, anti-inflammatory and anti-oxidative activity. However, the effects of linalool on angiogenesis still remain elusive. Therefore, we investigated the action of (3R)-(−)-linalool, a main enantiomer of linalool, on the angiogenic activity of human dermal microvascular endothelial cells (HDMECs) by a panel of angiogenesis assays. Non-cytotoxic doses of linalool significantly inhibited HDMEC proliferation, migration, tube formation and spheroid sprouting. Linalool also suppressed the vascular sprouting from rat aortic rings. In addition, Matrigel plugs containing linalool exhibited a significantly reduced microvessel density 7 days after implantation into BALB/c mice. Mechanistic analyses revealed that linalool promotes the phosphorylation of extracellular signal-regulated kinase (ERK), downregulates the intracellular level of adenosine triphosphate (ATP) and activates the transient receptor potential cation channel subfamily M (melastatin) member (TRPM)8 in HDMECs. Inhibition of ERK signaling, supplementation of ATP and blockade of TRPM8 significantly counteracted linalool-suppressed HDMEC spheroid sprouting. Moreover, ATP supplementation completely reversed linalool-induced ERK phosphorylation. In addition, linalool-induced ERK phosphorylation inhibited the expression of bone morphogenetic protein (BMP)-2 and linalool-induced TRPM8 activation caused the inhibition of β1 integrin/focal adhesion kinase (FAK) signaling. These findings indicate an anti-angiogenic effect of linalool, which is mediated by downregulating intracellular ATP levels and activating TRPM8
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