8,298 research outputs found
Nuclear dipole polarizability from mean-field modeling constrained by chiral effective field theory
We construct a new Skyrme interaction Skm by fitting the equation
of state and nucleon effective masses in asymmetric nuclear matter from chiral
two- and three-body forces as well as the binding energies of finite nuclei.
Employing this interaction to study the electric dipole polarizabilities of
Ca, Ni, Sn, and Pb in the random-phase
approximation, we find that the theoretical predictions are in good agreement
with experimentally measured values without additional fine tuning of the
Skyrme interaction, thus confirming the usefulness of the new Skyrme
interaction in studying the properties of nuclei. We further use this
interaction to study the neutron skin thicknesses of Ca and Pb,
and they are found to be consistent with the experimental data.Comment: Significantly revised, 7 pages, 4 figures. Published version in PL
TILDE-Q: A Transformation Invariant Loss Function for Time-Series Forecasting
Time-series forecasting has caught increasing attention in the AI research
field due to its importance in solving real-world problems across different
domains, such as energy, weather, traffic, and economy. As shown in various
types of data, it has been a must-see issue to deal with drastic changes,
temporal patterns, and shapes in sequential data that previous models are weak
in prediction. This is because most cases in time-series forecasting aim to
minimize norm distances as loss functions, such as mean absolute error
(MAE) or mean square error (MSE). These loss functions are vulnerable to not
only considering temporal dynamics modeling but also capturing the shape of
signals. In addition, these functions often make models misbehave and return
uncorrelated results to the original time-series. To become an effective loss
function, it has to be invariant to the set of distortions between two
time-series data instead of just comparing exact values. In this paper, we
propose a novel loss function, called TILDE-Q (Transformation Invariant Loss
function with Distance EQuilibrium), that not only considers the distortions in
amplitude and phase but also allows models to capture the shape of time-series
sequences. In addition, TILDE-Q supports modeling periodic and non-periodic
temporal dynamics at the same time. We evaluate the effectiveness of TILDE-Q by
conducting extensive experiments with respect to periodic and non-periodic
conditions of data, from naive models to state-of-the-art models. The
experiment results indicate that the models trained with TILDE-Q outperform
those trained with other training metrics (e.g., MSE, dynamic time warping
(DTW), temporal distortion index (TDI), and longest common subsequence (LCSS)).Comment: 9 pages paper, 2 pages references, and 7 pages appendix. Submitted as
conference paper to ICLR 202
Potential and Technological Advancement of Biofuels
This scientific paper examines the feasibility of biofuels as a solution to the world‟s energy crisis. It studies the development of the four different generations of biofuel that have been discerned over the years, determining the pros and cons of each. The paper further investigates the issues concerning each generation, and determines how their successors have solved and improved on those problems. In order to give the reader an unbiased perspective, the paper studies both general advantages and disadvantages that encompasses social, economic and environmental impacts. Research and development on the first two generations of biofuels have matured, and case studies have been used to allude to their current applications. The challenge of making third and fourth generation biofuels economically viable has also been highlighted due to their significant environmental and production benefits over the first two generations. The prospects of third and fourth generation biofuels have also been looked into to determine its outlook in the near future. If these next generation biofuels can garner enough support and become cost-competitive, mankind‟s quest for an alternative, renewable source of energy may finally be completed
SSumM: Sparse Summarization of Massive Graphs
Given a graph G and the desired size k in bits, how can we summarize G within
k bits, while minimizing the information loss?
Large-scale graphs have become omnipresent, posing considerable computational
challenges. Analyzing such large graphs can be fast and easy if they are
compressed sufficiently to fit in main memory or even cache. Graph
summarization, which yields a coarse-grained summary graph with merged nodes,
stands out with several advantages among graph compression techniques. Thus, a
number of algorithms have been developed for obtaining a concise summary graph
with little information loss or equivalently small reconstruction error.
However, the existing methods focus solely on reducing the number of nodes, and
they often yield dense summary graphs, failing to achieve better compression
rates. Moreover, due to their limited scalability, they can be applied only to
moderate-size graphs.
In this work, we propose SSumM, a scalable and effective graph-summarization
algorithm that yields a sparse summary graph. SSumM not only merges nodes
together but also sparsifies the summary graph, and the two strategies are
carefully balanced based on the minimum description length principle. Compared
with state-of-the-art competitors, SSumM is (a) Concise: yields up to 11.2X
smaller summary graphs with similar reconstruction error, (b) Accurate:
achieves up to 4.2X smaller reconstruction error with similarly concise
outputs, and (c) Scalable: summarizes 26X larger graphs while exhibiting linear
scalability. We validate these advantages through extensive experiments on 10
real-world graphs.Comment: to be published in the 26th ACM SIGKDD International Conference on
Knowledge Discovery and Data Mining (KDD '20
Discrepancy in Determination of Chi Parameters by Melting Point Depression Versus Small-Angle Neutron Scattering in Blends of Deuterated Polycarbonate and Isotactic Poly(Methyl Methacrylate)
The discrepancy in the chi interaction parameters of deuterated polycarbonate/isotactic poly(methyl methacrylate) blends as determined by the melting point depression approach and the small-angle scattering technique is reported. We have modified the Flory diluent theory by removing the inherent assumption of complete rejection of the solvent from the crystal solid by taking into consideration the crystal-amorphous, amorphous-crystal, and crystal-crystal interactions. The discrepancy in chi values obtained by the two methods is discussed
To the Edge of M87 and Beyond: Spectroscopy of Intracluster Globular Clusters and Ultra Compact Dwarfs in the Virgo Cluster
We present the results from a wide-field spectroscopic survey of globular
clusters (GCs) in the Virgo Cluster. We obtain spectra for 201 GCs and 55
ultracompact dwarfs (UCDs) using the Hectospec on the Multiple Mirror
Telescope, and derive their radial velocities. We identify 46 genuine
intracluster GCs (IGCs), not associated with any Virgo galaxies, using the 3D
GMM test on the spatial and radial velocity distribution.They are located at
the projected distance 200 kpc R 500 kpc from the center
of M87. The radial velocity distribution of these IGCs shows two peaks, one at
= 1023 km s associated with the Virgo main body, and another
at = 36 km s associated with the infalling structure. The
velocity dispersion of the IGCs in the Virgo main body is 314 km s, which is smoothly connected to the velocity dispersion
profile of M87 GCs, but much lower than that of dwarf galaxies in the same
survey field, 608 km s. The UCDs are more
centrally concentrated on massive galaxies, M87, M86, and M84. The radial
velocity dispersion of the UCD system is much smaller than that of dwarf
galaxies. Our results confirm the large-scale distribution of Virgo IGCs
indicated by previous photometric surveys. The color distribution of the
confirmed IGCs shows a bimodality similar to that of M87 GCs. This indicates
that most IGCs are stripped off from dwarf galaxies and some from massive
galaxies in the Virgo.Comment: 19 pages, 20 figures, 8 tables, accepted for publication in Ap
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