36,032 research outputs found
Outward Influence and Cascade Size Estimation in Billion-scale Networks
Estimating cascade size and nodes' influence is a fundamental task in social,
technological, and biological networks. Yet this task is extremely challenging
due to the sheer size and the structural heterogeneity of networks. We
investigate a new influence measure, termed outward influence (OI), defined as
the (expected) number of nodes that a subset of nodes will activate,
excluding the nodes in S. Thus, OI equals, the de facto standard measure,
influence spread of S minus |S|. OI is not only more informative for nodes with
small influence, but also, critical in designing new effective sampling and
statistical estimation methods.
Based on OI, we propose SIEA/SOIEA, novel methods to estimate influence
spread/outward influence at scale and with rigorous theoretical guarantees. The
proposed methods are built on two novel components 1) IICP an important
sampling method for outward influence, and 2) RSA, a robust mean estimation
method that minimize the number of samples through analyzing variance and range
of random variables. Compared to the state-of-the art for influence estimation,
SIEA is times faster in theory and up to several orders of
magnitude faster in practice. For the first time, influence of nodes in the
networks of billions of edges can be estimated with high accuracy within a few
minutes. Our comprehensive experiments on real-world networks also give
evidence against the popular practice of using a fixed number, e.g. 10K or 20K,
of samples to compute the "ground truth" for influence spread.Comment: 16 pages, SIGMETRICS 201
Importance Sketching of Influence Dynamics in Billion-scale Networks
The blooming availability of traces for social, biological, and communication
networks opens up unprecedented opportunities in analyzing diffusion processes
in networks. However, the sheer sizes of the nowadays networks raise serious
challenges in computational efficiency and scalability.
In this paper, we propose a new hyper-graph sketching framework for inflence
dynamics in networks. The central of our sketching framework, called SKIS, is
an efficient importance sampling algorithm that returns only non-singular
reverse cascades in the network. Comparing to previously developed sketches
like RIS and SKIM, our sketch significantly enhances estimation quality while
substantially reducing processing time and memory-footprint. Further, we
present general strategies of using SKIS to enhance existing algorithms for
influence estimation and influence maximization which are motivated by
practical applications like viral marketing. Using SKIS, we design high-quality
influence oracle for seed sets with average estimation error up to 10x times
smaller than those using RIS and 6x times smaller than SKIM. In addition, our
influence maximization using SKIS substantially improves the quality of
solutions for greedy algorithms. It achieves up to 10x times speed-up and 4x
memory reduction for the fastest RIS-based DSSA algorithm, while maintaining
the same theoretical guarantees.Comment: 12 pages, to appear in ICDM 2017 as a regular pape
Interacting partially directed self avoiding walk. From phase transition to the geometry of the collapsed phase
In this paper, we investigate a model for a dimensional
self-interacting and partially directed self-avoiding walk, usually referred to
by the acronym IPDSAW. The interaction intensity and the free energy of the
system are denoted by and , respectively. The IPDSAW is known to
undergo a collapse transition at . We provide the precise asymptotic
of the free energy close to criticality, that is we show that
where is computed
explicitly and interpreted in terms of an associated continuous model. We also
establish some path properties of the random walk inside the collapsed phase
. We prove that the geometric conformation adopted by the
polymer is made of a succession of long vertical stretches that attract each
other to form a unique macroscopic bead, we identify the horizontal extension
of the random walk inside the collapsed phase and we establish the convergence
of the rescaled envelope of the macroscopic bead towards a deterministic Wulff
shape.Comment: Accepted for publication in the Annals of Probabilit
Isogeometric analysis for functionally graded microplates based on modified couple stress theory
Analysis of static bending, free vibration and buckling behaviours of
functionally graded microplates is investigated in this study. The main idea is
to use the isogeometric analysis in associated with novel four-variable refined
plate theory and quasi-3D theory. More importantly, the modified couple stress
theory with only one material length scale parameter is employed to effectively
capture the size-dependent effects within the microplates. Meanwhile, the
quasi-3D theory which is constructed from a novel seventh-order shear
deformation refined plate theory with four unknowns is able to consider both
shear deformations and thickness stretching effect without requiring shear
correction factors. The NURBS-based isogeometric analysis is integrated to
exactly describe the geometry and approximately calculate the unknown fields
with higher-order derivative and continuity requirements. The convergence and
verification show the validity and efficiency of this proposed computational
approach in comparison with those existing in the literature. It is further
applied to study the static bending, free vibration and buckling responses of
rectangular and circular functionally graded microplates with various types of
boundary conditions. A number of investigations are also conducted to
illustrate the effects of the material length scale, material index, and
length-to-thickness ratios on the responses of the microplates.Comment: 57 pages, 14 figures, 18 table
Relationship Between Obesity and Periodontal Status in Vietnamese Patients
This study aims to investigate periodontal status, and the relationship between obesity and periodontal status in patients who first visited the Institute of Traditional Medicine, Ho Chi Minh City, Vietnam. 118 patients aged 18 or older, including 56 obese subjects (BMI≥27.5, mean age: 33.8, males: 11, females: 45) and 62 non-obese subjects (BMI<27.5, mean age: 34.3, males: 4, females: 58) were enrolled for a period of 5 months from February 2014 to June 2014. The information on socio-demographic characteristics and dental habits were collected by questionnaire. Periodontal status (PLI, GI, BOP, PD, CAL) was examined and the anthropometric index was measured. There was significantly higher prevalence of periodontitis (39.3%) in the obese group than the non-obese group (16.4%). Means of GI, BOP, PD, and CAL in obese subjects were significantly higher than those in non-obese subjects. Significantly higher percentages of subjects who had lower education, visited dental offices, scaled and polished their teeth regularly were in the non-obese group than in the obese group. Multiple logistic regression analysis revealed that age (OR=3.10), routine of dental visit (OR=3.34) and obesity (OR=2.79) were risk factors significantly related to periodontitis. Periodontal status in obese subjects was poorer than non-obese subjects. Obesity might be the risk factor for periodontitis in Vietnamese patients
Collective excitations in the inner crust of neutron stars : supergiant resonances
We investigate the nuclear collective excitations of Wigner-Seitz cells
containing nuclear clusters immersed in a gas of neutrons. This baryonic
non-uniform system is specific to the structure of inner crust matter of
neutron stars. The collective excitations are studied in the framework of a
spherical Hartree-Fock-Bogoliubov + Quasiparticle Random Phase Approximation,
formulated in coordinate representation. The calculations are done for two
representative Wigner-Seitz cells with baryonic density equal to 0.02 fm
and 0.08 fm. It is shown that the excitations with low multipolarities
are concentrated almost entirely in one strongly collective mode which exhausts
a very large fraction of the energy-weighted sum rule. Since these collective
modes are located at very low energies compared to the giant resonances in
standard nuclei, they may affect significantly the specific heat of baryonic
inner crust matter of neutron stars.Comment: 6 pages, 4 figure
Influence of complex configurations on properties of pygmy dipole resonance in neutron-rich Ca isotopes
Starting from the quasiparticle random phase approximation based on the
Skyrme interaction SLy5, we study the effects of phonon-phonon coupling~(PPC)
on the low-energy electric dipole response in Ca. Using the same set
of parameters we describe available experimental data for Ca and
give prediction for Ca. The inclusion of the PPC results in the
formation of low-energy states. There is an impact of the PPC effect on
low-energy ~strength of Ca. The PPC effect on the electric
dipole polarizability is discussed. We predict a strong increase of the summed
~strength below 10MeV, with increasing neutron number from Ca till
Ca.Comment: 11 pages, 10 figure
Structure of low-lying quadrupole states in nuclei near 132Sn
The properties of the low-lying 2^+ states in the even-even nuclei around
132Sn are studied within the quasiparticle random phase approximation. Starting
from a Skyrme interaction in the particle-hole channel and a density-dependent
zero-range interaction in the particle-particle channel, we use the finite rank
separable approach in our investigation. It is found that the fourth 2^+ state
in 132Te could be a good candidate for a mixed-symmetry state.Comment: 6 pages, 2 figures, proceedings of International Conference on
Nuclear Structure and Related Topics (NSRT09), June 2009, JINR, Dubna, Russi
Coordinated NanoSIMS and TEM Analysis of a Large 26Mg-Rich AGB Silicate from the Meteorite Hills 00426 CR2 Chondrite
Silicates are one of the most abundant presolar phases around evolved stars, in the inter-stellar medium (ISM), and in our Solar System. These grains afford the opportunity for O, Si, Mg, Fe, and Ca isotopic analyses to constrain stellar nucleosynthetic and mixing processes, and Galactic chemical evolution (GCE). While Mg and Fe isotopic studies have been successfully conducted on presolar silicates, isotopic analyses beyond O and Si are often hampered by the small grain sizes (average ~250 nm). This also makes coordinated mineral and chemical characterization challenging. These studies provide insight into the dust condensation conditions as well as subsequent alteration in the ISM and/or the Solar System. TEM studies of presolar silicates have shown that they are much more mineralogically and chemically diverse than other presolar phases [1 and references therein]. Large (>500nm) presolar silicate grains are rare, but they allow for detailed isotopic, mineral, and chemical characterization. We identified a large presolar silicate grain in the MET 00426 CR2 chondrite and report the O, Si, Mg, and Fe isotopic compositions and TEM study of this grain
Comparison of single-phase matrix converter and H-bridge converter for radio frequency induction heating
This paper compares the newly developed single-phase matrix converter and the more conventional H- bridge converter for radio frequency induction heating. Both the converters exhibit unity power factor, very low total harmonic distortion at the utility supply interface, good controllability under soft switching condition for a wide range of power, and high efficiencies, whilst still having simple structures. A novel switching control pattern has been proposed for the matrix converter in order to maintain the comparable performance to the H-bridge converter. Simulation and experimental results for both converters are presented. Comparisons between two converters have confirmed the excellent performance of the proposed matrix converter
- …