1,478 research outputs found
User Cooperation in Wireless Powered Communication Networks
This paper studies user cooperation in the emerging wireless powered
communication network (WPCN) for throughput optimization. For the purpose of
exposition, we consider a two-user WPCN, in which one hybrid access point
(H-AP) broadcasts wireless energy to two distributed users in the downlink (DL)
and the users transmit their independent information using their individually
harvested energy to the H-AP in the uplink (UL) through
time-division-multiple-access (TDMA). We propose user cooperation in the WPCN
where the user which is nearer to the H-AP and has a better channel for DL
energy harvesting and UL information transmission uses part of its allocated UL
time and DL harvested energy to help to relay the far user's information to the
H-AP, in order to achieve more balanced throughput optimization. We maximize
the weighted sum-rate (WSR) of the two users by jointly optimizing the time and
power allocations in the network for both wireless energy transfer in the DL
and wireless information transmission and relaying in the UL. Simulation
results show that the proposed user cooperation scheme can effectively improve
the achievable throughput in the WPCN with desired user fairness.Comment: 7 figure
Fracture Detection in Pediatric Wrist Trauma X-ray Images Using YOLOv8 Algorithm
Hospital emergency departments frequently receive lots of bone fracture
cases, with pediatric wrist trauma fracture accounting for the majority of
them. Before pediatric surgeons perform surgery, they need to ask patients how
the fracture occurred and analyze the fracture situation by interpreting X-ray
images. The interpretation of X-ray images often requires a combination of
techniques from radiologists and surgeons, which requires time-consuming
specialized training. With the rise of deep learning in the field of computer
vision, network models applying for fracture detection has become an important
research topic. In this paper, YOLOv8 algorithm is used to train models on the
GRAZPEDWRI-DX dataset, which includes X-ray images from 6,091 pediatric
patients with wrist trauma. The experimental results show that YOLOv8 algorithm
models have different advantages for different model sizes, with YOLOv8l model
achieving the highest mean average precision (mAP 50) of 63.6\%, and YOLOv8n
model achieving the inference time of 67.4ms per X-ray image on one single CPU
with low computing power. In this way, we create "Fracture Detection Using
YOLOv8 App" to assist surgeons in interpreting X-ray images without the help of
radiologists. Our implementation code is released at
https://github.com/RuiyangJu/Bone_Fracture_Detection_YOLOv8
Spatial distribution and sampling of Corythucha ciliata (Hemiptera: Tingidae) in London plane trees
Taylor’s power law and Iwao’s patchiness regression were used to describe the dispersion patterns for overwintering and wandering stages of Corythucha ciliata on the London plane trees, Platanus x acerifolia (Ait.) Willd. Both Taylor’s and Iwao’s tests fit the distribution data for the overwintering stage. The overwintering adults were spatially aggregated. In the wandering stage, Taylor’s power law consistently fit the data, whereas the fit of Iwao’s patchiness regression was erratic. Both Iwao’s and Taylor’s indices indicated a clumped distribution pattern for eggs, nymphs, and wandering adults. Trunk was identified as the best sampling target for the overwintering stage whereas twig was the best for the wandering stage. In order to determine the sample size for evaluating whether the population has reached the control threshold, the sampling of 35 and 7 trunks for the overwintering stage and 32 and 8 twigs per tree for the wandering stage would provide 0.5- and 0.25-precision levels, respectively
Rapid Changes of Photospheric Magnetic Field after Tether-Cutting Reconnection and Magnetic Implosion
The rapid, irreversible change of the photospheric magnetic field has been
recognized as an important element of the solar flare process. This Letter
reports such a rapid change of magnetic fields during the 2011 February 13 M6.6
flare in NOAA AR 11158 that we found from the vector magnetograms of the
Helioseismic and Magnetic Imager with 12-min cadence. High-resolution
magnetograms of Hinode that are available at ~-5.5, -1.5, 1.5, and 4 hrs
relative to the flare maximum are used to reconstruct three-dimensional coronal
magnetic field under the nonlinear force-free field (NLFFF) assumption. UV and
hard X-ray images are also used to illuminate the magnetic field evolution and
energy release. The rapid change is mainly detected by HMI in a compact region
lying in the center of the magnetic sigmoid, where the mean horizontal field
strength exhibited a significant increase by 28%. The region lies between the
initial strong UV and hard X-ray sources in the chromosphere, which are
cospatial with the central feet of the sigmoid according to the NLFFF model.
The NLFFF model further shows that strong coronal currents are concentrated
immediately above the region, and that more intriguingly, the coronal current
system underwent an apparent downward collapse after the sigmoid eruption.
These results are discussed in favor of both the tether-cutting reconnection
producing the flare and the ensuing implosion of the coronal field resulting
from the energy release.Comment: 7 pages, 5 figures, accepted to the Astrophysical Journal Letter
Cathodoluminescence and Cross-sectional Transmission Electron Microscopy Studies for Deformation Behaviors of GaN Thin Films Under Berkovich Nanoindentation
In this study, details of Berkovich nanoindentation-induced mechanical deformation mechanisms of metal-organic chemical-vapor deposition-derived GaN thin films have been systematic investigated with the aid of the cathodoluminescence (CL) and the cross-sectional transmission electron microscopy (XTEM) techniques. The multiple “pop-in” events were observed in the load-displacement (P–h) curve and appeared to occur randomly by increasing the indentation load. These instabilities are attributed to the dislocation nucleation and propagation. The CL images of nanoindentation show very well-defined rosette structures with the hexagonal system and, clearly display the distribution of deformation-induced extended defects/dislocations which affect CL emission. By using focused ion beam milling to accurately position the cross-section of an indented area, XTEM results demonstrate that the major plastic deformation is taking place through the propagation of dislocations. The present observations are in support to the massive dislocations activities occurring underneath the indenter during the loading cycle. No evidence of either phase transformation or formation of micro-cracking was observed by means of scanning electron microscopy and XTEM observations. We also discuss how these features correlate with Berkovich nanoindentation produced defects/dislocations structures
Imbalanced Classification in Medical Imaging via Regrouping
We propose performing imbalanced classification by regrouping majority
classes into small classes so that we turn the problem into balanced multiclass
classification. This new idea is dramatically different from popular loss
reweighting and class resampling methods. Our preliminary result on imbalanced
medical image classification shows that this natural idea can substantially
boost the classification performance as measured by average precision
(approximately area-under-the-precision-recall-curve, or AUPRC), which is more
appropriate for evaluating imbalanced classification than other metrics such as
balanced accuracy
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