358 research outputs found
Optimal Active Social Network De-anonymization Using Information Thresholds
In this paper, de-anonymizing internet users by actively querying their group
memberships in social networks is considered. In this problem, an anonymous
victim visits the attacker's website, and the attacker uses the victim's
browser history to query her social media activity for the purpose of
de-anonymization using the minimum number of queries. A stochastic model of the
problem is considered where the attacker has partial prior knowledge of the
group membership graph and receives noisy responses to its real-time queries.
The victim's identity is assumed to be chosen randomly based on a given
distribution which models the users' risk of visiting the malicious website. A
de-anonymization algorithm is proposed which operates based on information
thresholds and its performance both in the finite and asymptotically large
social network regimes is analyzed. Furthermore, a converse result is provided
which proves the optimality of the proposed attack strategy
Seeded Graph Matching: Efficient Algorithms and Theoretical Guarantees
In this paper, a new information theoretic framework for graph matching is
introduced. Using this framework, the graph isomorphism and seeded graph
matching problems are studied. The maximum degree algorithm for graph
isomorphism is analyzed and sufficient conditions for successful matching are
rederived using type analysis. Furthermore, a new seeded matching algorithm
with polynomial time complexity is introduced. The algorithm uses `typicality
matching' and techniques from point-to-point communications for reliable
matching. Assuming an Erdos-Renyi model on the correlated graph pair, it is
shown that successful matching is guaranteed when the number of seeds grows
logarithmically with the number of vertices in the graphs. The logarithmic
coefficient is shown to be inversely proportional to the mutual information
between the edge variables in the two graphs
Mixing of a passive scalar in isotropic and sheared homogeneous turbulence
In order to calculate the velocity and scalar fields, the three dimensional, time-dependent equations of motion and the diffusion equation were solved numerically. The following cases were treated: isotropic, homogeneous turbulence with decay of a passive scalar; and homogeneous turbulent shear flow with a passive scalar whose mean varies linearly in the spanwise direction. The solutions were obtained at relatively low Reynolds numbers so that all of the turbulent scales could be resolved without modeling. Turbulent statistics such as integral length scales, Taylor microscales, Kolmogorov length scale, one- and two-point correlations of velocity-velocity and velocity-scalar, turbulent Prandtl/Schmidt number, r.m.s. values of velocities, the scalar quantity and pressure, skewness, decay rates, and decay exponents were calculated. The results are compared with the available expermental results, and good agreement is obtained
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Modeling of micro flows using perturbation method
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.A new method for modeling micro flows is presented in this research. The basis of this method is the development of governing continuum equations on fluid dynamics using perturbation expansion of the velocity, pressure, density and temperature fields in dependence of Knudsen number. In the present work, we use three-term perturbation expansions and reach three order of equations O(1), O(Kn), O(Kn2). Required
boundary conditions (BC) for solving each order of these equations are obtained by substitution of the perturbation expansions into the general boundary conditions for the velocity slip and temperature jump. This set of equations is discretized in two-dimensional state on a staggered grid using the finite volume method. A three-part computer program has been produced for solving the set of discretized equations. Each part of this code, solve one order of the equations with the SIMPLE algorithm. Incompressible slip micro Poiseuille and micro Couette flows are solved either analytically or numerically using the perturbation method (PM). Good agreement is found between analytical and numerical results in the low Knudsen numbers, whereas numerical results deviate from analytical results by increasing the Knudsen number. The
results of perturbation method are also compared with the results obtained from different slip models
Fatty acid composition of oilseed rapeseed genotypes as affected by vermicompost application and different thermal regimes
ArticleVegetable oils with a high relative amount of unsaturated fatty acids are of great
significance for human health. Hence, in a 2-year factorial split plot experiment, the effects of
different sowing date (optimum (October 17) and late (October 27)), vermicompost (0 and
20 ton ha-1
) and genotypes (BAL104, DIE710.08, BAL102, FJL330, FJL290 and Okapi) on the
fatty acid composition of rapeseed were evaluated. Rapeseed genotypes and the combination of
sowing date and vermicompost application were randomized to sub and main-plots, respectively.
The present results revealed that yield, oil percentage and fatty acids composition is affected by
sowing dates along with genotypes. However, the unsaturated fatty acid, eicosanoic acid was not
affected by interaction sowing date and genotype. Vermicomposting increased the yield, oil
percentage, oleic, linoleic and linolenic acids and decrease erucic unsaturated fatty acid. The
FJL290 and BAL102 genotypes produced the highest values of grain yield (5,853 and
5,763 kg ha−1, respectively), oil percentage (43.98% and 43.85%, respectively), linoleic % acid
(20.51 and 20.37% respectively), oleic % acid (65.23 and 64.93% respectively) and linolenic %
acid (7.20 and 7.09% respectively) in comparison to the other genotypes, when they were sown
at the optimum sowing date. The FJL290 and BAL102 also accelerated their growth period at the
late sowing date. Consequently, oleic, linoleic and linolenic acids had the highest direct and
indirect effect influence on grain oil percentage indicating their importance as selection criteria
to improve yield and oil quality of rapeseed. Concluding the combination of sowing date,
vermicompost and FJL290 and BAL102 lines may be the most favourable cropping strategy for
rapeseed production in Iran
Diffusion basis spectrum imaging for identifying pathologies in MS subtypes
Diffusion basis spectrum imaging (DBSI) combines discrete anisotropic diffusion tensors and the spectrum of isotropic diffusion tensors to model the underlying multiple sclerosis (MS) pathologies. We used clinical MS subtypes as a surrogate of underlying pathologies to assess DBSI as a biomarker of pathology in 55 individuals with MS. Restricted isotropic fraction (reflecting cellularity) and fiber fraction (representing apparent axonal density) were the most important DBSI metrics to classify MS using brain white matter lesions. These DBSI metrics outperformed lesion volume. When analyzing the normal-appearing corpus callosum, the most significant DBSI metrics were fiber fraction, radial diffusivity (reflecting myelination), and nonrestricted isotropic fraction (representing edema). This study provides preliminary evidence supporting the ability of DBSI as a potential noninvasive biomarker of MS neuropathology
CNS aspergillosis in a patient with Crohn’s disease on immunosuppressants: a case report
Fungal infections of the central nervous system are an uncommon cause of rapid decline in consciousness. We describe the case of central nervous system aspergillosis in a patient on immunosupressants whose clinical course highlights the need for an aggressive approach to diagnosis
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