2,832 research outputs found
Convergence on Gauss-Seidel iterative methods for linear systems with general H-matrices
It is well known that as a famous type of iterative methods in numerical
linear algebra, Gauss-Seidel iterative methods are convergent for linear
systems with strictly or irreducibly diagonally dominant matrices, invertible
matrices (generalized strictly diagonally dominant matrices) and Hermitian
positive definite matrices. But, the same is not necessarily true for linear
systems with nonstrictly diagonally dominant matrices and general matrices.
This paper firstly proposes some necessary and sufficient conditions for
convergence on Gauss-Seidel iterative methods to establish several new
theoretical results on linear systems with nonstrictly diagonally dominant
matrices and general matrices. Then, the convergence results on
preconditioned Gauss-Seidel (PGS) iterative methods for general matrices
are presented. Finally, some numerical examples are given to demonstrate the
results obtained in this paper
Who are the Devils Wearing Prada in New York City?
Fashion is a perpetual topic in human social life, and the mass has the
penchant to emulate what large city residents and celebrities wear. Undeniably,
New York City is such a bellwether large city with all kinds of fashion
leadership. Consequently, to study what the fashion trends are during this
year, it is very helpful to learn the fashion trends of New York City.
Discovering fashion trends in New York City could boost many applications such
as clothing recommendation and advertising. Does the fashion trend in the New
York Fashion Show actually influence the clothing styles on the public? To
answer this question, we design a novel system that consists of three major
components: (1) constructing a large dataset from the New York Fashion Shows
and New York street chic in order to understand the likely clothing fashion
trends in New York, (2) utilizing a learning-based approach to discover fashion
attributes as the representative characteristics of fashion trends, and (3)
comparing the analysis results from the New York Fashion Shows and street-chic
images to verify whether the fashion shows have actual influence on the people
in New York City. Through the preliminary experiments over a large clothing
dataset, we demonstrate the effectiveness of our proposed system, and obtain
useful insights on fashion trends and fashion influence
Study on the Dual Asymmetric Effect of Monetary Policy Shocks: Empirical Test Based on China’s Stock and Bond Market
The research on dual asymmetric effects of monetary policy shock has important practical significance for laying down capital market regulation monetary policy. This paper uses two-step OLS method to empirically test the dual asymmetric effects of monetary policy shock on stock and bond markets. The test results show that the expansionary and tight monetary policy shocks on the stock and bond markets have dual asymmetric effects; the expansionary and tight monetary policy shocks have dual asymmetric effects during the rise and fall periods. Therefore, when laying down capital market regulation and control policies, government needs to consider the dual asymmetric effects of monetary policy shock, and adopts appropriate monetary policies. Key words: Monetary policy shocks; Dual asymmetric effects; Two-step OLS method; Empirical tes
Stacking sequence determines Raman intensities of observed interlayer shear modes in 2D layered materials - A general bond polarizability model
2D layered materials have recently attracted tremendous interest due to their
fascinating properties and potential applications. The interlayer interactions
are much weaker than the intralayer bonds, allowing the as-synthesized
materials to exhibit different stacking sequences (e.g. ABAB, ABCABC), leading
to different physical properties. Here, we show that regardless of the space
group of the 2D material, the Raman frequencies of the interlayer shear modes
observed under the typical configuration blue shift for AB stacked materials,
and red shift for ABC stacked materials, as the number of layers increases. Our
predictions are made using an intuitive bond polarizability model which shows
that stacking sequence plays a key role in determining which interlayer shear
modes lead to the largest change in polarizability (Raman intensity); the modes
with the largest Raman intensity determining the frequency trends. We present
direct evidence for these conclusions by studying the Raman modes in few layer
graphene, MoS2, MoSe2, WSe2 and Bi2Se3, using both first principles
calculations and Raman spectroscopy. This study sheds light on the influence of
stacking sequence on the Raman intensities of intrinsic interlayer modes in 2D
layered materials in general, and leads to a practical way of identifying the
stacking sequence in these materials.Comment: 30 pages, 8 figure
Molecular geometric deep learning
Geometric deep learning (GDL) has demonstrated huge power and enormous
potential in molecular data analysis. However, a great challenge still remains
for highly efficient molecular representations. Currently, covalent-bond-based
molecular graphs are the de facto standard for representing molecular topology
at the atomic level. Here we demonstrate, for the first time, that molecular
graphs constructed only from non-covalent bonds can achieve similar or even
better results than covalent-bond-based models in molecular property
prediction. This demonstrates the great potential of novel molecular
representations beyond the de facto standard of covalent-bond-based molecular
graphs. Based on the finding, we propose molecular geometric deep learning
(Mol-GDL). The essential idea is to incorporate a more general molecular
representation into GDL models. In our Mol-GDL, molecular topology is modeled
as a series of molecular graphs, each focusing on a different scale of atomic
interactions. In this way, both covalent interactions and non-covalent
interactions are incorporated into the molecular representation on an equal
footing. We systematically test Mol-GDL on fourteen commonly-used benchmark
datasets. The results show that our Mol-GDL can achieve a better performance
than state-of-the-art (SOTA) methods. Source code and data are available at
https://github.com/CS-BIO/Mol-GDL
- …