524 research outputs found
Shadow of a Schwarzschild black hole surrounded by a Bach-Weyl ring
We have studied the shadows of a Schwarzschild black hole surrounded by a
Bach-Weyl ring through the backward ray-tracing method. The presence of
Bach-Weyl ring leads to that the photon dynamical system is non-integrable and
then chaos would appear in the photon motion, which affects sharply the black
hole shadow. The size and shape the black hole shadow depend on the black hole
parameter, the Bach-Weyl ring mass and the Weyl radius between black hole and
ring. Some self-similar fractal structures also appear in the black hole
shadow, which originates from the chaotic lensing. We also study the change of
the image of Bach-Weyl ring with the ring mass and the Weyl radius. Finally, we
analyze the invariant manifolds of Lyapunov orbits near the fixed points and
discuss further the formation of the shadow of a Schwarzschild black hole with
Bach-Weyl ring.Comment: 16 pages,8 figures, the version published in EPJ
Chaos in the motion of a test scalar particle coupling to Einstein tensor in Schwarzschild-Melvin black hole spacetime
We present firstly the equation of motion for a test scalar particle coupling
to Einstein tensor in the Schwarzschild-Melvin black hole spacetime through the
short-wave approximation. Through analysing Poincar\'{e} sections, the power
spectrum, the fast Lyapunov exponent indicator and the bifurcation diagram, we
investigate the effects of coupling parameter on the chaotic behavior of the
particles. With the increase of the coupling strength, we find that the motion
of coupled particle for the chosen parameters becomes more regular and order
for the negative couple constant. While, for the positive one, the motion of
coupled particles first undergoes a series of transitions between chaotic
motion and regular motion and then falls into horizon or escapes to spatial
infinite. Our results show that the coupling brings about richer effects for
the motion of the particles.Comment: 18 pages, 9 figures. The title is changed, some content and
references are modified. Accepted by EPJC for publication;arXiv admin note:
text overlap with arXiv:1604.0278
Learning Local Metrics and Influential Regions for Classification
The performance of distance-based classifiers heavily depends on the
underlying distance metric, so it is valuable to learn a suitable metric from
the data. To address the problem of multimodality, it is desirable to learn
local metrics. In this short paper, we define a new intuitive distance with
local metrics and influential regions, and subsequently propose a novel local
metric learning method for distance-based classification. Our key intuition is
to partition the metric space into influential regions and a background region,
and then regulate the effectiveness of each local metric to be within the
related influential regions. We learn local metrics and influential regions to
reduce the empirical hinge loss, and regularize the parameters on the basis of
a resultant learning bound. Encouraging experimental results are obtained from
various public and popular data sets
A Value Chain Based Analysis of Electronic Commerce’s Transformation of China’s Pharmaceutical Industry
In this paper we explore the impact of electronic commerce on the industry structure and market power allocation of China’s pharmaceutical industry. Firstly, we describe the overall characteristics of the pharmaceutical Industry in general. Secondly, we develop a value chain based framework of analysis for China’s pharmaceutical industry. We divide the pharmaceutical industry value chain into three tiers: the initial market, the middle market and the end market. Based on these works, we analyze the profound impacts of Electronic Commerce on the transformation of China’s pharmaceutical Industry, with particular emphasis on the evolution of market structure and the re-allocation of market power due to the introduction of E-Commerce procedures
Dynamic Face Video Segmentation via Reinforcement Learning
For real-time semantic video segmentation, most recent works utilised a
dynamic framework with a key scheduler to make online key/non-key decisions.
Some works used a fixed key scheduling policy, while others proposed adaptive
key scheduling methods based on heuristic strategies, both of which may lead to
suboptimal global performance. To overcome this limitation, we model the online
key decision process in dynamic video segmentation as a deep reinforcement
learning problem and learn an efficient and effective scheduling policy from
expert information about decision history and from the process of maximising
global return. Moreover, we study the application of dynamic video segmentation
on face videos, a field that has not been investigated before. By evaluating on
the 300VW dataset, we show that the performance of our reinforcement key
scheduler outperforms that of various baselines in terms of both effective key
selections and running speed. Further results on the Cityscapes dataset
demonstrate that our proposed method can also generalise to other scenarios. To
the best of our knowledge, this is the first work to use reinforcement learning
for online key-frame decision in dynamic video segmentation, and also the first
work on its application on face videos.Comment: CVPR 2020. 300VW with segmentation labels is available at:
https://github.com/mapleandfire/300VW-Mas
Effect of gravitational wave on shadow of a Schwarzschild black hole
We have studied the shadows of a Schwarzschild black hole under a special
polar gravitational perturbation, which is a particular solution of Einstein
equations expanded up to first order. It is shown that the black hole shadow
changes periodically with time and the change of shadow depends on the Legendre
polynomial order parameter l and the frequency sigma of gravitational wave. For
the odd order of Legendre polynomial, the center of shadow oscillates along the
direction which is vertical to equatorial plane. For even l, the center of
shadow does not move, but the shadow alternately stretches and squeezes with
time along the vertical direction. Moreover, the presence of the gravitational
wave leads to the self-similar fractal structures appeared in the boundary of
the black hole shadow. We also find that this special gravitational wave has a
greater influence on the vertical direction of black hole shadow.Comment: 19 pages, 13 figure
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