4,945 research outputs found
Implementation of non-uniform FFT based Ewald summation in Dissipative Particle Dynamic method
The ENUF method, i.e., Ewald summation based on the Non-Uniform FFT technique
(NFFT), is implemented in Dissipative Particle Dynamics (DPD) simulation scheme
to fast and accurately calculate the electrostatic interactions at mesoscopic
level. In a simple model electrolyte system, the suitable ENUF-DPD parameters,
including the convergence parameter , the NFFT approximation parameter
, and the cut-offs for real and reciprocal space contributions, are
carefully determined. With these optimized parameters, the ENUF-DPD method
shows excellent efficiency and scales as . The ENUF-DPD
method is further validated by investigating the effects of charge fraction of
polyelectrolyte, ionic strength and counterion valency of added salts on
polyelectrolyte conformations. The simulations in this paper, together with a
separately published work of dendrimer-membrane complexes, show that the
ENUF-DPD method is very robust and can be used to study charged complex systems
at mesoscopic level
Heat flow of extrinsic biharmonic maps from a four dimensional manifold with boundary
Let be a four dimensional compact Riemannian manifold with boundary
and be a compact Riemannian manifold without boundary. We show the
existence of a unique, global weak solution of the heat flow of extrinsic
biharmonic maps from to under the Dirichlet boundary condition, which
is regular with the exception of at most finitely many time slices. We also
discuss the behavior of solution near the singular times. As an immediate
application, we prove the existence of a smooth extrinsic biharmonic map from
to under any Dirichlet boundary condition.Comment: 26 pages, Journal of Elliptic and Parabolic Equations, to appea
Microstructures and Dynamics of Tetraalkylphosphonium Chloride Ionic Liquids
Atomistic simulations have been performed to investigate the effect of
aliphatic chain length in tetraalkylphosphonium cations on liquid morphologies,
microscopic ionic structures and dynamical properties of tetraalkylphosphonium
chloride ionic liquids. The liquid morphologies are characterized by
sponge-like interpenetrating polar and apolar networks in ionic liquids
consisting of tetraalkylphosphonium cations with short aliphatic chains. The
lengthening aliphatic chains in tetraalkylphosphonium cations leads to polar
domains consisting of chloride anions and central polar groups in cations being
partially or totally segregated in ionic liquid matrices due to a progressive
expansion of apolar domains in between. Prominent polarity alternation peaks
and adjacency correlation peaks are observed at low and high range in total
X-ray scattering structural functions, respectively, and their peak positions
gradually shift to lower q values with lengthening aliphatic chains in
tetraalkylphosphonium cations. The charge alternation peaks registered in
intermediate q range exhibit complicated tendencies due to the complete
cancellations of peaks and anti-peaks in partial structural functions for ionic
subcomponents. The particular microstructures and liquid morphologies in
tetraalkylphosphonium chloride ionic liquids intrinsically contribute to
distinct dynamics characterized by translational diffusion coefficients, van
Hove correlation functions, and non-Gaussian parameters for ionic species in
heterogeneous ionic environment. The increase of aliphatic chain length in
tetraalkylphosphonium cations leads to concomitant shift of van Hove
correlation functions and non-Gaussian parameters to larger radial distances
and longer timescales, respectively, indicating the enhanced translational
dynamical heterogeneities of tetraalkylphosphonium cations and the
corresponding chloride anions.Comment: 28 pages, 11 figure
Phase controlled single-photon nonreciprocal transmission in a one-dimensional waveguide
We study the controllable single-photon scattering via a one-dimensional
waveguide which is coupled to a two-level emitter and a single-mode cavity
simultaneously. The emitter and the cavity are also coupled to each other and
form a three-level system with cyclic transitions within the zero- and
single-excitation subspaces. As a result, the phase of emitter-cavity coupling
strength serves as a sensitive control parameter. When the emitter and cavity
locate at the same point of the waveguide, we demonstrate the Rabi splitting
and quasidark-state--induced perfect transmission for the incident photons.
More interestingly, when they locate at different points of the waveguide, a
controllable nonreciprocal transmission can be realized and the non-reciprocity
is robust to the weak coupling between the system and environment. Furthermore,
we demonstrate that our theoretical model is experimentally feasible with
currently available technologies.Comment: 11 pages, 8 figures,Accepted by Phys. Rev.
Understand Scene Categories by Objects: A Semantic Regularized Scene Classifier Using Convolutional Neural Networks
Scene classification is a fundamental perception task for environmental
understanding in today's robotics. In this paper, we have attempted to exploit
the use of popular machine learning technique of deep learning to enhance scene
understanding, particularly in robotics applications. As scene images have
larger diversity than the iconic object images, it is more challenging for deep
learning methods to automatically learn features from scene images with less
samples. Inspired by human scene understanding based on object knowledge, we
address the problem of scene classification by encouraging deep neural networks
to incorporate object-level information. This is implemented with a
regularization of semantic segmentation. With only 5 thousand training images,
as opposed to 2.5 million images, we show the proposed deep architecture
achieves superior scene classification results to the state-of-the-art on a
publicly available SUN RGB-D dataset. In addition, performance of semantic
segmentation, the regularizer, also reaches a new record with refinement
derived from predicted scene labels. Finally, we apply our SUN RGB-D dataset
trained model to a mobile robot captured images to classify scenes in our
university demonstrating the generalization ability of the proposed algorithm
Place classification with a graph regularized deep neural network model
Place classification is a fundamental ability that a robot should possess to
carry out effective human-robot interactions. It is a nontrivial classification
problem which has attracted many research. In recent years, there is a high
exploitation of Artificial Intelligent algorithms in robotics applications.
Inspired by the recent successes of deep learning methods, we propose an
end-to-end learning approach for the place classification problem. With the
deep architectures, this methodology automatically discovers features and
contributes in general to higher classification accuracies. The pipeline of our
approach is composed of three parts. Firstly, we construct multiple layers of
laser range data to represent the environment information in different levels
of granularity. Secondly, each layer of data is fed into a deep neural network
model for classification, where a graph regularization is imposed to the deep
architecture for keeping local consistency between adjacent samples. Finally,
the predicted labels obtained from all the layers are fused based on confidence
trees to maximize the overall confidence. Experimental results validate the
effective- ness of our end-to-end place classification framework in which both
the multi-layer structure and the graph regularization promote the
classification performance. Furthermore, results show that the features
automatically learned from the raw input range data can achieve competitive
results to the features constructed based on statistical and geometrical
information
Energy Conditions and Stability in generalized gravity with arbitrary coupling between matter and geometry
The energy conditions and the Dolgov-Kawasaki criterion in generalized
gravity with arbitrary coupling between matter and geometry are derived in this
paper, which are quite general and can degenerate to the well-known energy
conditions in GR and gravity with non-minimal coupling and non-coupling
as special cases. In order to get some insight on the meaning of these energy
conditions and the Dolgov- Kawasaki criterion, we apply them to a class of
models in the FRW cosmology and give some corresponding results.Comment: 12 pages. arXiv admin note: substantial text overlap with
arXiv:1203.5593, arXiv:1212.465
Some New Symmetric Relations and the Prediction of Left and Right Handed Neutrino Masses using Koide's Relation
Masses of the three generations of charged leptons are known to completely
satisfy the Koide's mass relation. But the question remains if such a relation
exists for neutrinos? In this paper, by considering SeeSaw mechanism as the
mechanism generating tiny neutrino masses, we show how neutrinos satisfy the
Koide's mass relation, on the basis of which we systematically give exact
values of not only left but also right handed neutrino masses
Phoenix Cloud: Consolidating Different Computing Loads on Shared Cluster System for Large Organization
Different departments of a large organization often run dedicated cluster
systems for different computing loads, like HPC (high performance computing)
jobs or Web service applications. In this paper, we have designed and
implemented a cloud management system software Phoenix Cloud to consolidate
heterogeneous workloads from different departments affiliated to the same
organization on the shared cluster system. We have also proposed cooperative
resource provisioning and management policies for a large organization and its
affiliated departments, running HPC jobs and Web service applications, to share
the consolidated cluster system. The experiments show that in comparison with
the case that each department operates its dedicated cluster system, Phoenix
Cloud significantly decreases the scale of the required cluster system for a
large organization, improves the benefit of the scientific computing
department, and at the same time provisions enough resources to the other
department running Web services with varying loads.Comment: 5 page, 8 figures, The First Workshop of Cloud Computing and its
Application, The modified version. The original version is on the web site of
http://www.cca08.org/, which is dated from August 13, 200
Study on Estimating Quantum Discord by Neural Network with Prior Knowledge
Machine learning has achieved success in many areas because of its powerful
fitting ability, so we hope it can help us to solve some significant physical
quantitative problems, such as quantum correlation. In this research we will
use neural networks to predict the value of quantum discord. Quantum discord is
a measure of quantum correlation which is defined as the difference between
quantum mutual information and classical correlation for a bipartite system.
Since the definition contains an optimization term, it makes analytically
solving hard. For some special cases and small systems, such as two-qubit
systems and some X-states, the explicit solutions have been calculated.
However, for general cases, we still know very little. Therefore, we study the
feasibility of estimating quantum discord by machine learning method on
two-qubit systems. In order to get an interpretable and high performance model,
we modify the ordinary neural network by introducing some prior knowledge which
come from the analysis about quantum discord. Our results show that prior
knowledge actually improve the performance of neural network
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