46,304 research outputs found
Some Recent Progress on the Studies of Supernova Remnants
We briefly reviewed some recent progress on the studies of supernova remnants
(SNRs), including the radio SNRs (the structure, polarization, spectrum etc.),
observational characteristics of X-ray emission, pulsar wind nebulae (PWNe),
association properties between SNR and PSR, interaction of SNR and interstellar
medium (ISM), cosmos ray and the SNRs in external galaxies, etc..
Correspondingly to the continue improvement of space and spectrum resolution of
the on-ground and in-space astronomical equipments at wavelengthes as radio,
optical, X-ray and so on, we know about SNRs more and deeper.Comment: 10 pages, no figur
Generalized BBV Models for Weighted Complex Networks
We will introduce two evolving models that characterize weighted complex
networks. Though the microscopic dynamics are different, these models are found
to bear a similar mathematical framework, and hence exhibit some common
behaviors, for example, the power-law distributions and evolution of degree,
weight and strength. We also study the nontrivial clustering coefficient C and
tunable degree assortativity coefficient r, depending on specific parameters.
Most results are supported by present empirical evidences, and may provide us
with a better description of the hierarchies and organizational architecture of
weighted networks. Our models have been inspired by the weighted network model
proposed by Alain Barrat et al. (BBV for short), and can be considered as a
meaningful development of their original work.Comment: 9 pages, 11 figures, submitted to PR
Arithmetic Coding Based Multi-Composition Codes for Bit-Level Distribution Matching
A distribution matcher (DM) encodes a binary input data sequence into a
sequence of symbols (codeword) with desired target probability distribution.
The set of the output codewords constitutes a codebook (or code) of a DM.
Constant-composition DM (CCDM) uses arithmetic coding to efficiently encode
data into codewords from a constant-composition (CC) codebook. The CC
constraint limits the size of the codebook, and hence the coding rate of the
CCDM. The performance of CCDM degrades with decreasing output length. To
improve the performance for short transmission blocks we present a class of
multi-composition (MC) codes and an efficient arithmetic coding scheme for
encoding and decoding. The resulting multi-composition DM (MCDM) is able to
encode more data into distribution matched codewords than the CCDM and achieves
lower KL divergence, especially for short block messages
A Physarum-inspired model for the probit-based stochastic user equilibrium problem
Stochastic user equilibrium is an important issue in the traffic assignment
problems, tradition models for the stochastic user equilibrium problem are
designed as mathematical programming problems. In this article, a
Physarum-inspired model for the probit-based stochastic user equilibrium
problem is proposed. There are two main contributions of our work. On the one
hand, the origin Physarum model is modified to find the shortest path in
traffic direction networks with the properties of two-way traffic
characteristic. On the other hand, the modified Physarum-inspired model could
get the equilibrium flows when traveller's perceived transportation cost
complies with normal distribution. The proposed method is constituted with a
two-step procedure. First, the modified Physarum model is applied to get the
auxiliary flows. Second, the auxiliary flows are averaged to obtain the
equilibrium flows. Numerical examples are conducted to illustrate the
performance of the proposed method, which is compared with the Method of
Successive Average method.Comment: 24 pages,5 figure
Simulating the Chiral Magnetic Wave in a Box System
The chiral magnetic wave from the interplay between the chiral magnetic
effect and the chiral separation effect is simulated in a box system with the
periodic boundary condition based on the chiral kinetic equations of motion.
Simulation results are compared with available limits from theoretical
derivations, and effects of the temperature, the magnetic field, and the
specific shear viscosity on the key properties of the chiral magnetic wave are
discussed. Our study serves as a baseline for further simulations of chiral
anomalies in relativistic heavy-ion collisions.Comment: 7 pages, 5 figure
Further Results on the Distinctness of Decimations of l-sequences
Let be an \textit{l}-sequence generated by a
feedback-with-carry shift register with connection integer , where is an odd prime and . Goresky and Klapper conjectured that when , all decimations of are cyclically
distinct. When and , they showed that the set of distinct
decimations is large and, in some cases, all deciamtions are distinct. In this
article, we further show that when and, all decimations
of are also cyclically distinct.Comment: submitted to IEEE-I
Simulating chiral anomalies with spin dynamics
Considering that the chiral kinetic equations of motion (CEOM) can be derived
from the spin kinetic equations of motion (SEOM) for massless particles with
approximations, we simulate the chiral anomalies by using the latter in a box
system with the periodic boundary condition under a uniform external magnetic
field. We found that the chiral magnetic effect is weaker while the damping of
the chiral magnetic wave is stronger from the SEOM compared with that from the
CEOM. In addition, effects induced by chiral anomalies from the SEOM are less
sensitive to the decay of the magnetic field than from the CEOM due to the spin
relaxation process.Comment: 6 pages, 6 figure
Self-assembly and glass-formation in a lattice model of telechelic polymer melts: Influence of stiffness of the sticky bonds
The lattice cluster theory (LCT) for strongly interacting, self-assembling
telechelic polymers provides a theoretical tool that enables establishing the
connections between important microscopic molecular details of self-assembling
polymers and their bulk thermodynamics. The original LCT for self-assembly of
telechelic polymers considers a model of fully flexible linear chains [J.
Dudowicz and K. F. Freed, J. Chem. Phys. \textbf{136}, 064902 (2012)], while
our recent work introduces a significant improvement to the LCT by including a
description of chain semiflexibility for the bonds within each individual
telecheic chain [W.-S. Xu and K. F. Freed, J. Chem. Phys. \textbf{143}, 024901
(2015)], but the physically associative (or called "sticky") bonds between the
ends of the telechelics are left as fully flexible. Motivated by the ubiquitous
presence of steric constraints on the association of real telechelic polymers
that impart an additional degree of bond stiffness (or rigidity), the present
paper further extends the LCT to permit the sticky bonds to be semiflexible but
to have a stiffness differing from that within each telechelic chain. An
analytical expression for the Helmholtz free energy is provided for this model
of linear telechelic polymer melts, and illustrative calculations demonstrate
the significant influence of the stiffness of the sticky bonds on the
self-assembly and thermodynamics of telechelic polymers. A brief discussion is
also provided for the impact of self-assembly on glass-formation by combining
the LCT description for this extended model of telechelic polymers with the
Adam-Gibbs relation between the structural relaxation time and the
configurational entropy.Comment: 13 pages, 14 figures, to be published in The Journal of Chemical
Physic
Feasibility study on the least square method for fitting non-Gaussian noise data
This study is to investigate the feasibility of least square method in
fitting non-Gaussian noise data. We add different levels of the two typical
non-Gaussian noises, L\'evy and stretched Gaussian noises, to exact value of
the selected functions including linear equations, polynomial and exponential
equations, and the maximum absolute and the mean square errors are calculated
for the different cases. L\'evy and stretched Gaussian distributions have many
applications in fractional and fractal calculus. It is observed that the
non-Gaussian noises are less accurately fitted than the Gaussian noise, but the
stretched Gaussian cases appear to perform better than the L\'evy noise cases.
It is stressed that the least-squares method is inapplicable to the
non-Gaussian noise cases when the noise level is larger than 5%
On Lin-Ni's conjecture in dimensions four and six
We give negative answers to Lin-Ni's conjecture for any four and six
dimensional domains. No condition on the symmetry, geometry nor topology of the
domain is needed.Comment: 28 page
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