59,097 research outputs found
Monotone iterative schemes for positive solutions of a fractional differential system with integral boundary conditions on an infinite interval
In this paper, using the monotone iterative technique and the Banach
contraction mapping principle, we study a class of fractional differential
system with integral boundary on an infinite interval. Some explicit monotone
iterative schemes for approximating the extreme positive solutions and the
unique positive solution are constructed
A CDG-FE method for the two-dimensional Green-Naghdi model with the enhanced dispersive property
In this work, we investigate numerical solutions of the two-dimensional
shallow water wave using a fully nonlinear Green-Naghdi model with an improved
dispersive effect. For the purpose of numerics, the Green-Naghdi model is
rewritten into a formulation coupling a pseudo-conservative system and a set of
pseudo-elliptic equations. Since the pseudo-conservative system is no longer
hyperbolic and its Riemann problem can only be approximately solved, we
consider the utilization of the central discontinuous Galerkin method which
possesses an important feature of needlessness of Riemann solvers. Meanwhile,
the stationary elliptic part will be solved using the finite element method.
Both the well-balanced and the positivity-preserving features which are highly
desirable in the simulation of the shallow water wave will be embedded into the
proposed numerical scheme. The accuracy and efficiency of the numerical model
and method will be illustrated through numerical tests.Comment: 27 pages, 35 figure
Hand Action Detection from Ego-centric Depth Sequences with Error-correcting Hough Transform
Detecting hand actions from ego-centric depth sequences is a practically
challenging problem, owing mostly to the complex and dexterous nature of hand
articulations as well as non-stationary camera motion. We address this problem
via a Hough transform based approach coupled with a discriminatively learned
error-correcting component to tackle the well known issue of incorrect votes
from the Hough transform. In this framework, local parts vote collectively for
the start end positions of each action over time. We also construct an
in-house annotated dataset of 300 long videos, containing 3,177 single-action
subsequences over 16 action classes collected from 26 individuals. Our system
is empirically evaluated on this real-life dataset for both the action
recognition and detection tasks, and is shown to produce satisfactory results.
To facilitate reproduction, the new dataset and our implementation are also
provided online
Structure/property relationship of semi-crystalline polymer during tensile deformation: A molecular dynamics approach
A coarse-grained molecular dynamics model of linear polyethylene-like polymer
chain system was built to investigate the responds of structure and mechanical
properties during uniaxial deformation. The influence of chain length,
temperature, and strain rate were studied. The molecular dynamic tests showed
that yielding may governed by different mechanisms at temperatures above and
below Tg. Melt-recrystallization was observed at higher temperature, and
destruction of crystal structures was observed at lower temperatures beyond
yield point. While the higher temperature and lower strain rate have similar
effects on mechanical properties. The correlated influences of time and
temperature in the microscopic structures are more complicated. The evolution
of microscopic characteristics such as the orientation parameter, the bond
length, and the content of trans-trans conformation were calculated from the
simulation. The results showed that the temperature have double effects on
polymer chains. Higher temperature on one hand makes the chains more flexible,
while on the other hand shortens the relaxation time of polymers. It is the
interaction of these two aspects that determine the orientation parameter.
During deformation, the trans conformation has experienced a rising process
after the first drop process. And these microscopic structure parameters
exhibit critical transaction, which are closely related to the yield point. A
hypothetical model was thus proposed to describe the micro-structure and
property relations based the investigations of this study.Comment: 30 pages, 16 figure
Improving Secrecy with Nearly Collinear Main and Wiretap Channels via a Cooperative Jamming Relay
In physical layer security (PHY-security), the frequently observed high
correlation between the main and wiretap channels can cause a significant loss
of secrecy. This paper investigates a slow fading scenario, where a transmitter
(Alice) sends a confidential message to a legitimate receiver (Bob) while a
passive eavesdropper (Eve) attempts to decode the message from its received
signal. It is assumed that Alice is equipped with multiple antennas while Bob
and Eve each have a single antenna (i.e., a MISOSE system). In a MISOSE system,
high correlation results in nearly collinear main and wiretap channel vectors,
which help Eve to see and intercept confidential information. Unfortunately,
the signal processing techniques at Alice, such as beamforming and artificial
noise (AN), are helpless, especially in the extreme case of completely
collinear main and wiretap channel vectors. On this background, we first
investigate the achievable secrecy outage probability via beamforming and AN at
Alice with the optimal power allocation between the information-bearing signal
and AN. Then, an ingenious model, in which a cooperative jamming relay (Relay)
is introduced, is proposed to effectively mitigate the adverse effects of high
correlation. Based on the proposed model, the power allocation between the
information-bearing signal at Alice and the AN at Relay is also studied to
maximize secrecy. Finally, to validate our proposed schemes, numerical
simulations are conducted, and the results show that a significant performance
gain with respect to secrecy is achieved
Exploring the Mass Segregation Effect of X-ray Sources in Globular Clusters: The Case of 47 Tucanae
Using archival {\it Chandra} observations with a total exposure of 510 ks, we
present an updated catalog of point sources for Globular Cluster 47 Tucanae.
Our study covers an area of arcmin (i.e., with
R\lesssim7.5\arcmin) with 537 X-ray sources. We show that the surface density
distribution of X-ray sources in 47 Tuc is highly peaked in cluster center,
rapidly decreases at intermediate radii, and finally rises again at larger
radii, with two distribution dips at R\sim 100\arcsec and R\sim 170\arcsec
for the faint () and bright
() groups of X-ray sources,
separately. These distribution features are similar to those of Blue Straggler
Stars (BSS), where the distribution dip is located at R\sim 200\arcsec
\citep{ferraro2004}. By fitting the radial distribution of each group of
sources with a "generalized King model", we estimated an average mass of
, and
for the BSS, bright and faint X-ray sources, respectively. These results are
consistent with the mass segregation effect of heavy objects in GCs, where more
massive objects drop to the cluster center faster and their distribution dip
propagates outward further. Besides, the peculiar distribution profiles of
X-ray sources and BSS are also consistent with the mass segregation model of
binaries in GCs, which suggests that in addition to the dynamical formation
channel, primordial binaries are also a significant contributor to the X-ray
source population in GCs.Comment: 19 pages, 7 figures 3 tables, accepted for publication in Ap
Cyclone intensity estimate with context-aware cyclegan
Deep learning approaches to cyclone intensity estimationhave recently shown
promising results. However, sufferingfrom the extreme scarcity of cyclone data
on specific in-tensity, most existing deep learning methods fail to
achievesatisfactory performance on cyclone intensity estimation,especially on
classes with few instances. To avoid the degra-dation of recognition
performance caused by scarce samples,we propose a context-aware CycleGAN which
learns the la-tent evolution features from adjacent cyclone intensity
andsynthesizes CNN features of classes lacking samples fromunpaired source
classes. Specifically, our approach synthe-sizes features conditioned on the
learned evolution features,while the extra information is not required.
Experimentalresults of several evaluation methods show the effectivenessof our
approach, even can predicting unseen classes.Comment: 5 page
Semantic Adversarial Network for Zero-Shot Sketch-Based Image Retrieval
Zero-shot sketch-based image retrieval (ZS-SBIR) is a specific cross-modal
retrieval task for retrieving natural images with free-hand sketches under
zero-shot scenario. Previous works mostly focus on modeling the correspondence
between images and sketches or synthesizing image features with sketch
features. However, both of them ignore the large intra-class variance of
sketches, thus resulting in unsatisfactory retrieval performance. In this
paper, we propose a novel end-to-end semantic adversarial approach for ZS-SBIR.
Specifically, we devise a semantic adversarial module to maximize the
consistency between learned semantic features and category-level word vectors.
Moreover, to preserve the discriminability of synthesized features within each
training category, a triplet loss is employed for the generative module.
Additionally, the proposed model is trained in an end-to-end strategy to
exploit better semantic features suitable for ZS-SBIR. Extensive experiments
conducted on two large-scale popular datasets demonstrate that our proposed
approach remarkably outperforms state-of-the-art approaches by more than 12\%
on Sketchy dataset and about 3\% on TU-Berlin dataset in the retrieval.Comment: There is a big problem with the paper and I hope it can be retracte
Drawing cone spherical metrics via Strebel differentials
Cone spherical metrics are conformal metrics with constant curvature one and
finitely many conical singularities on compact Riemann surfaces. By using
Strebel differentials as a bridge, we construct a new class of cone spherical
metrics on compact Riemann surfaces by drawing on the surfaces some class of
connected metric ribbon graphs.Comment: 25 pages, 8 figures. Version 2: minor typo corrections; revised
according to referee's comments. We substantially revised the proof of the
second theorem to make its exposition easier to understand. We added a new
section, where we discuss on the Riemann sphere the consistence of metrics
generated by Strebel differentials with the two angle conditions by
Mondello-Panov and Eremenko, respectivel
Gevrey regularity with weight for incompressible Euler equation in the half plane
In this work we prove the weighted Gevrey regularity of solutions to the
incompressible Euler equation with initial data decaying polynomially at
infinity. This is motivated by the well-posedness problem of vertical boundary
layer equation for fast rotating fluid. The method presented here is based on
the basic weighted - estimate, and the main difficulty arises from the
estimate on the pressure term due to the appearance of weight function
- …