426 research outputs found
Dependence of electronic and optical properties on a high-frequency field for carbon nanotubes
We study theoretically the electronic structure, transport and optical
properties for a zigzag single-wall carbon nanotube connected to two normal
conductor leads under the irradiation of an external electromagnetic field at
low temperatures, with particular emphasis on the features of high-frequency
response. Using the standard nonequilibrium Green's function techniques, we
examine the time-averaged density of states, the conductivity, the dielectric
function and the electron energy loss spectra for the system with photon
polarization parallel with the tunneling current direction, respectively.
Through some numerical examples, it is shown that the density of states is
strongly dependent on the incident electron energy, the strength and frequency
of the applied field. For higher electron energies in comparison with
lead-nanotube coupling energy, the system conductance decreases with increasing
the field strength and increases with increasing the field frequency
respectively, and shows some oscillation structures. Moreover, the optical
functions for the system have also a rich structure with the variation of field
frequency. It may demonstrate that this transport dependence on the external
field parameters can be used to give the energy spectra information of carbon
nanotubes and to detect the high-frequency microwave irradiation.Comment: 6 Revtex pages, 4 figures. to be appeared in JA
How to Train Your Agent to Read and Write
Reading and writing research papers is one of the most privileged abilities
that a qualified researcher should master. However, it is difficult for new
researchers (\eg{students}) to fully {grasp} this ability. It would be
fascinating if we could train an intelligent agent to help people read and
summarize papers, and perhaps even discover and exploit the potential knowledge
clues to write novel papers. Although there have been existing works focusing
on summarizing (\emph{i.e.}, reading) the knowledge in a given text or
generating (\emph{i.e.}, writing) a text based on the given knowledge, the
ability of simultaneously reading and writing is still under development.
Typically, this requires an agent to fully understand the knowledge from the
given text materials and generate correct and fluent novel paragraphs, which is
very challenging in practice. In this paper, we propose a Deep ReAder-Writer
(DRAW) network, which consists of a \textit{Reader} that can extract knowledge
graphs (KGs) from input paragraphs and discover potential knowledge, a
graph-to-text \textit{Writer} that generates a novel paragraph, and a
\textit{Reviewer} that reviews the generated paragraph from three different
aspects. Extensive experiments show that our DRAW network outperforms
considered baselines and several state-of-the-art methods on AGENDA and
M-AGENDA datasets. Our code and supplementary are released at
https://github.com/menggehe/DRAW
Deep Learning-Based Modeling of 5G Core Control Plane for 5G Network Digital Twin
Digital twin is a key enabler to facilitate the development and
implementation of new technologies in 5G and beyond networks. However, the
complex structure and diverse functions of the current 5G core network,
especially the control plane, lead to difficulties in building the core network
of the digital twin. In this paper, we propose two novel data-driven
architectures for modeling the 5G control plane and implement corresponding
deep learning models, namely 5GC-Seq2Seq and 5GC-former, based on the Vanilla
Seq2Seq model and Transformer decoder respectively. To train and test models,
we also present a solution that allows the signaling messages to be
interconverted with vectors, which can be utilized in dataset construction. The
experiments are based on 5G core network signaling data collected by the
Spirent C50 network tester, including various procedures related to
registration, handover, PDU sessions, etc. Our results show that 5GC-Seq2Seq
achieves over 99.98% F1-score (A metric to measure the accuracy of positive
samples) with a relatively simple structure, while 5GC-former attains higher
than 99.998% F1-score by establishing a more complex and highly parallel model,
indicating that the method proposed in this paper reproduces the major
functions of the core network control plane in 5G digital twin with high
accuracy
SpOctA: A 3D Sparse Convolution Accelerator with Octree-Encoding-Based Map Search and Inherent Sparsity-Aware Processing
Point-cloud-based 3D perception has attracted great attention in various
applications including robotics, autonomous driving and AR/VR. In particular,
the 3D sparse convolution (SpConv) network has emerged as one of the most
popular backbones due to its excellent performance. However, it poses severe
challenges to real-time perception on general-purpose platforms, such as
lengthy map search latency, high computation cost, and enormous memory
footprint. In this paper, we propose SpOctA, a SpConv accelerator that enables
high-speed and energy-efficient point cloud processing. SpOctA parallelizes the
map search by utilizing algorithm-architecture co-optimization based on octree
encoding, thereby achieving 8.8-21.2x search speedup. It also attenuates the
heavy computational workload by exploiting inherent sparsity of each voxel,
which eliminates computation redundancy and saves 44.4-79.1% processing
latency. To optimize on-chip memory management, a SpConv-oriented non-uniform
caching strategy is introduced to reduce external memory access energy by 57.6%
on average. Implemented on a 40nm technology and extensively evaluated on
representative benchmarks, SpOctA rivals the state-of-the-art SpConv
accelerators by 1.1-6.9x speedup with 1.5-3.1x energy efficiency improvement.Comment: Accepted to ICCAD 202
Galactic Phylogenetics
Phylogenetics is a widely used concept in evolutionary biology. It is the
reconstruction of evolutionary history by building trees that represent
branching patterns and sequences. These trees represent shared history, and it
is our intention for this approach to be employed in the analysis of Galactic
history. In Galactic archaeology the shared environment is the interstellar
medium in which stars form and provides the basis for tree-building as a
methodological tool.
Using elemental abundances of solar-type stars as a proxy for DNA, we built
in Jofre et al 2017 such an evolutionary tree to study the chemical evolution
of the solar neighbourhood. In this proceeding we summarise these results and
discuss future prospects.Comment: Contribution to IAU Symposium No. 334: Rediscovering our Galax
Utility of cone-beam CT imaging for the determination of feeding vessels during arterial embolization for massive hemoptysis
PURPOSE:We aimed to evaluate the role of cone-beam computed tomography (CT) performed as an adjunct to angiography for the determination of feeding vessels responsible for bleeding during arterial embolization for massive hemoptysis.METHODS:In this retrospective study, 23 patients with massive hemoptysis who underwent cone-beam CT evaluation prior to arterial embolization from December 2014 to December 2017 were included. During the angiographic session, two interventional radiologists selected the possible feeding vessels that were likely to supply the bleeding target lesions. Contrast-enhanced cone-beam CT was performed at the indefinite feeding arteries as an adjunct to angiography to determine whether the artery was a real feeding vessel, based on whether the target lesion was detected in the perfused territory of the study artery on images.RESULTS:Selective cone-beam CT was successfully performed in 21 patients, at 26 possible feeding vessels that were detected by selective angiography. Cone-beam CT determined the feeding vessel in 24 arteries (92.3%) in 19 patients (90.5%). As a result of cone-beam CT findings, 16 of 24 study arteries were judged as definitively not feeding vessels (66.7%) and the remaining 8 study arteries were judged as definitively feeding vessels (33.3%). In 2 of 26 study arteries, cone-beam CT could not determine the feeding vessel (7.7%).CONCLUSION:Cone-beam CT performed as an adjunctive technique to angiography is sufficient to provide adequate information for confident determination of the feeding vessel, which is essential for the operators to perform accurate embolization during arterial embolization for massive hemoptysis
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