9,172 research outputs found
TPA: Fast, Scalable, and Accurate Method for Approximate Random Walk with Restart on Billion Scale Graphs
Given a large graph, how can we determine similarity between nodes in a fast
and accurate way? Random walk with restart (RWR) is a popular measure for this
purpose and has been exploited in numerous data mining applications including
ranking, anomaly detection, link prediction, and community detection. However,
previous methods for computing exact RWR require prohibitive storage sizes and
computational costs, and alternative methods which avoid such costs by
computing approximate RWR have limited accuracy. In this paper, we propose TPA,
a fast, scalable, and highly accurate method for computing approximate RWR on
large graphs. TPA exploits two important properties in RWR: 1) nodes close to a
seed node are likely to be revisited in following steps due to block-wise
structure of many real-world graphs, and 2) RWR scores of nodes which reside
far from the seed node are proportional to their PageRank scores. Based on
these two properties, TPA divides approximate RWR problem into two subproblems
called neighbor approximation and stranger approximation. In the neighbor
approximation, TPA estimates RWR scores of nodes close to the seed based on
scores of few early steps from the seed. In the stranger approximation, TPA
estimates RWR scores for nodes far from the seed using their PageRank. The
stranger and neighbor approximations are conducted in the preprocessing phase
and the online phase, respectively. Through extensive experiments, we show that
TPA requires up to 3.5x less time with up to 40x less memory space than other
state-of-the-art methods for the preprocessing phase. In the online phase, TPA
computes approximate RWR up to 30x faster than existing methods while
maintaining high accuracy.Comment: 12pages, 10 figure
Fast and Accurate Random Walk with Restart on Dynamic Graphs with Guarantees
Given a time-evolving graph, how can we track similarity between nodes in a
fast and accurate way, with theoretical guarantees on the convergence and the
error? Random Walk with Restart (RWR) is a popular measure to estimate the
similarity between nodes and has been exploited in numerous applications. Many
real-world graphs are dynamic with frequent insertion/deletion of edges; thus,
tracking RWR scores on dynamic graphs in an efficient way has aroused much
interest among data mining researchers. Recently, dynamic RWR models based on
the propagation of scores across a given graph have been proposed, and have
succeeded in outperforming previous other approaches to compute RWR
dynamically. However, those models fail to guarantee exactness and convergence
time for updating RWR in a generalized form. In this paper, we propose OSP, a
fast and accurate algorithm for computing dynamic RWR with insertion/deletion
of nodes/edges in a directed/undirected graph. When the graph is updated, OSP
first calculates offset scores around the modified edges, propagates the offset
scores across the updated graph, and then merges them with the current RWR
scores to get updated RWR scores. We prove the exactness of OSP and introduce
OSP-T, a version of OSP which regulates a trade-off between accuracy and
computation time by using error tolerance {\epsilon}. Given restart probability
c, OSP-T guarantees to return RWR scores with O ({\epsilon} /c ) error in O
(log ({\epsilon}/2)/log(1-c)) iterations. Through extensive experiments, we
show that OSP tracks RWR exactly up to 4605x faster than existing static RWR
method on dynamic graphs, and OSP-T requires up to 15x less time with 730x
lower L1 norm error and 3.3x lower rank error than other state-of-the-art
dynamic RWR methods.Comment: 10 pages, 8 figure
EACOF: A Framework for Providing Energy Transparency to enable Energy-Aware Software Development
Making energy consumption data accessible to software developers is an
essential step towards energy efficient software engineering. The presence of
various different, bespoke and incompatible, methods of instrumentation to
obtain energy readings is currently limiting the widespread use of energy data
in software development. This paper presents EACOF, a modular Energy-Aware
Computing Framework that provides a layer of abstraction between sources of
energy data and the applications that exploit them. EACOF replaces platform
specific instrumentation through two APIs - one accepts input to the framework
while the other provides access to application software. This allows developers
to profile their code for energy consumption in an easy and portable manner
using simple API calls. We outline the design of our framework and provide
details of the API functionality. In a use case, where we investigate the
impact of data bit width on the energy consumption of various sorting
algorithms, we demonstrate that the data obtained using EACOF provides
interesting, sometimes counter-intuitive, insights. All the code is available
online under an open source license. http://github.com/eaco
Controlling internal barrier in low loss BaTiO3 supercapacitors
Supercapacitor behavior has been reported in a number of oxides including reduced BaTiO3 ferroelectric ceramics. These so-called giant properties are however not easily controlled. We show here that the continuous coating of individual BaTiO3 grains by a silica shell in combination with spark plasma sintering is a way to process bulk composites having supercapacitor features with low dielectric losses and temperature stability. The silica shell acts both as an oxidation barrier during the processing and as a dielectric barrier in the final composite
Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
We investigate anew the distribution of absolute carbon abundance, (C) (C), for carbon-enhanced metal-poor (CEMP) stars in the halo of
the Milky Way, based on high-resolution spectroscopic data for a total sample
of 305 CEMP stars. The sample includes 147 CEMP- (and CEMP-r/s) stars, 127
CEMP-no stars, and 31 CEMP stars that are unclassified, based on the currently
employed [Ba/Fe] criterion. We confirm previous claims that the distribution of
(C) for CEMP stars is (at least) bimodal, with newly determined peaks
centered on (C) (the high-C region) and (C) (the low-C
region). A very high fraction of CEMP- (and CEMP-r/s) stars belong to the
high-C region, while the great majority of CEMP-no stars reside in the low-C
region. However, there exists complexity in the morphology of the (C)-[Fe/H]
space for the CEMP-no stars, a first indication that more than one class of
first-generation stellar progenitors may be required to account for their
observed abundances. The two groups of CEMP-no stars we identify exhibit
clearly different locations in the (Na)-(C) and (Mg)-(C) spaces,
also suggesting multiple progenitors. The clear distinction in (C) between
the CEMP- (and CEMP-) stars and the CEMP-no stars appears to be $as\
successfullikely\ more\ astrophysically\ fundamental$, for the
separation of these sub-classes as the previously recommended criterion based
on [Ba/Fe] (and [Ba/Eu]) abundance ratios. This result opens the window for its
application to present and future large-scale low- and medium-resolution
spectroscopic surveys.Comment: 26pages, 7 figures, and 3 Tables ; Accepted for publication in ApJ;
added more data and corrected minor inconsistencies existed in the compiled
data of the previous studie
Trapping a Free-propagating Single-photon into an Atomic Ensemble as a Quantum Stationary Light Pulse
Efficient photon-photon interaction is one of the key elements for realizing
quantum information processing. The interaction, however, must often be
mediated through an atomic medium due to the bosonic nature of photons, and the
interaction time, which is critically linked to the efficiency, depends on the
properties of the atom-photon interaction. While the electromagnetically
induced transparency effect does offer the possibility of photonic quantum
memory, it does not enhance the interaction time as it fully maps the photonic
state to an atomic state. The stationary light pulse (SLP) effect, on the
contrary, traps the photonic state inside an atomic medium with zero group
velocity, opening up the possibility of the enhanced interaction time. In this
work, we report the first experimental demonstration of trapping a
free-propagating single-photon into a cold atomic ensemble via the quantum SLP
(QSLP) process. We conclusively show that the quantum properties of the
single-photon state are preserved well during the QSLP process. Our work paves
the way to new approaches for efficient photon-photon interactions, exotic
photonic states, and many-body simulations in photonic systems
Rice genetic marker database: An identification of single nucleotide polymorphism (SNP) and quantitative trait loci (QTL) markers
The National Academy of Agricultural Science (NAAS) has developed a web-based genetic marker system to provide information about SNP and QTL markers in rice. The SNP marker database provides 7,227 SNP markers including location information on chromosomes by using genetic map. It allows users to access a detailed characterization table of 12,829 potential SNPs in 3,356 genes. The QTL marker database provides 175 QTL markers information with 942 polymorphic markers on each of the12 chromosomes in rice. Users are assisted in tracing any new structures of the chromosomes and gene positional functions through comparisons using specific SNP and QTL markers
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