5,817 research outputs found
Enabling Inter-Repository Access Management between iRODS and Fedora
4th International Conference on Open RepositoriesThis presentation was part of the session : Conference PresentationsDate: 2009-06-04 08:30 AM – 10:00 AMMany digital repositories have been built using different technologies such as Fedora and the integrated Rule-Oriented Data System (iRODS). This paper analyzes both the Fedora and iRODS technologies to understand how to integrate the two systems to enable cross-repository data sharing. The areas considered include the digital object model, services, management of distributed storage, external data resources, and policy enforcement.National Science Foundatio
Two-photon Exchange Corrections to Single Spin Asymmetry of Neutron and He
In a simple hadronic model, the two-photon exchange contributions to the
single spin asymmetries for the nucleon and the He are estimated. The
results show that the elastic contributions of two-photon exchange to the the
single spin asymmetries for the nucleon are rather small while those for the
He are relatively large. Besides the strong angular dependence, the
two-photon contributions to the single spin asymmetry for the He are very
sensitive to the momentum transfer.Comment: 11 pages, 8 figure
Unification of Gravitation, Gauge Field and Dark Energy
This paper is composed of two correlated topics: 1. unification of
gravitation with gauge fields; 2. the coupling between the daor field and other
fields and the origin of dark energy. After introducing the concept of ``daor
field" and discussing the daor geometry, we indicate that the complex daor
field has two kinds of symmetry transformations. Hence the gravitation and
SU(1,3) gauge field are unified under the framework of the complex connection.
We propose a first-order nonlinear coupling equation of the daor field, which
includes the coupling between the daor field and SU(1,3) gauge field and the
coupling between the daor field and the curvature, and from which Einstein's
gravitational equation can be deduced. The cosmological observations imply that
dark energy cannot be zero, and which will dominate the doom of our Universe.
The real part of the daor field self-coupling equation can be regarded as
Einstein's equation endowed with the cosmological constant. It shows that dark
energy originates from the self-coupling of the space-time curvature, and the
energy-momentum tensor is proportional to the square of coupling constant
\lambda. The dark energy density given by our scenario is in agreement with
astronomical observations. Furthermore, the Newtonian gravitational constant G
and the coupling constant \epsilon of gauge field satisfy G=
\lambda^{2}\epsilon^{2}.Comment: 24 pages, revised version; references added; typos correcte
Tensor-polarized structure function in the standard convolution description of the deuteron
Tensor-polarized structure functions of a spin-1 hadron are additional
observables which do not exist for the spin-1/2 nucleon. They could probe novel
aspects of the internal hadron structure. Twist-2 tensor-polarized structure
functions are and , and they are related by the Callan-Gross-like
relation in the Bjorken scaling limit. In this work, we theoretically calculate
in the standard convolution description for the deuteron. Two different
theoretical models, a basic convolution description and a virtual nucleon
approximation, are used for calculating and their results are compared
with the HERMES measurement. We found large differences between our theoretical
results and the data. Although there is still room to improve by considering
higher-twist effects and in the experimental extraction of from the spin
asymmetry , there is a possibility that the large differences require
physics beyond the standard deuteron model for their interpretation. Future
studies could shed light on a new field of hadron physics. In particular,
detailed experimental studies of will start soon at the Thomas Jefferson
National Accelerator Facility. In addition, there are possibilities to
investigate tensor-polarized parton distribution functions and at Fermi
National Accelerator Laboratory and a future electron-ion collider. Therefore,
further theoretical studies are needed for understanding the tensor structure
of the spin-1 deuteron, including a new mechanism to explain the large
differences between the current data and our theoretical results.Comment: 12 pages, 7 eps figures, 3 style files, typos are corrected as
published in Phys. Rev. D 95, 074036 (2017
Standard convolution description of deuteron tensor spin structure
Spin-1 hadrons have additional structure functions not present for spin 1/2
hadrons. These could probe novel aspects of hadron structure and QCD dynamics.
For the deuteron, the tensor structure function inherently mixes quark
and nuclear degrees of freedom. These proceedings discuss two standard
convolution models applied to calculations of the deuteron structure
functions. We find large differences with the existing HERMES data and other
convolution model calculations. This leaves room for non-standard contributions
to in the deuteron. We also discuss the influence of higher twist nuclear
effects in the model calculations and data extraction at kinematics covered in
HERMES and Jefferson Lab.Comment: Proceedings of 25th International Workshop on Deep Inelastic
Scattering and Related Topics, 3-7 April 2017 University of Birmingha
New Geometric Formalism for Gravity Equation in Empty Space
In this paper, a complex daor field which can be regarded as the square root
of space-time metric is proposed to represent gravity. The locally complexified
geometry is set up, and the complex spin connection constructs a bridge between
gravity and SU(1,3) gauge field. Daor field equations in empty space are
acquired, which are one-order differential equations and not conflict with
Einstein's gravity theory.Comment: 20 pages, to appear in Int. J. Mod. Phys.
HFR Code: A Flexible Replication Scheme for Cloud Storage Systems
Fractional repetition (FR) codes are a family of repair-efficient storage
codes that provide exact and uncoded node repair at the minimum bandwidth
regenerating point. The advantageous repair properties are achieved by a
tailor-made two-layer encoding scheme which concatenates an outer
maximum-distance-separable (MDS) code and an inner repetition code. In this
paper, we generalize the application of FR codes and propose heterogeneous
fractional repetition (HFR) code, which is adaptable to the scenario where the
repetition degrees of coded packets are different. We provide explicit code
constructions by utilizing group divisible designs, which allow the design of
HFR codes over a large range of parameters. The constructed codes achieve the
system storage capacity under random access repair and have multiple repair
alternatives for node failures. Further, we take advantage of the systematic
feature of MDS codes and present a novel design framework of HFR codes, in
which storage nodes can be wisely partitioned into clusters such that data
reconstruction time can be reduced when contacting nodes in the same cluster.Comment: Accepted for publication in IET Communications, Jul. 201
Understanding molecular representations in machine learning: The role of uniqueness and target similarity
The predictive accuracy of Machine Learning (ML) models of molecular
properties depends on the choice of the molecular representation. Based on the
postulates of quantum mechanics, we introduce a hierarchy of representations
which meet uniqueness and target similarity criteria. To systematically control
target similarity, we rely on interatomic many body expansions, as implemented
in universal force-fields, including Bonding, Angular, and higher order terms
(BA). Addition of higher order contributions systematically increases
similarity to the true potential energy and predictive accuracy of the
resulting ML models. We report numerical evidence for the performance of BAML
models trained on molecular properties pre-calculated at electron-correlated
and density functional theory level of theory for thousands of small organic
molecules. Properties studied include enthalpies and free energies of
atomization, heatcapacity, zero-point vibrational energies, dipole-moment,
polarizability, HOMO/LUMO energies and gap, ionization potential, electron
affinity, and electronic excitations. After training, BAML predicts energies or
electronic properties of out-of-sample molecules with unprecedented accuracy
and speed
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