Multi-layer model for the web graph

This paper studies stochastic graph models of the WebGraph. We present a new model that describes the WebGraph as an ensemble of different regions generated by independent stochastic processes (in the spirit of a recent paper by Dill et al. [VLDB 2001]). Models such as the Copying Model [17] and Evolving Networks Model [3] are simulated and compared on several relevant measures such as degree and clique distribution

Four methods to distinguish between fractal dimensions in time series through recurrence quantification analysis

Fractal properties in time series of human behavior and physiology are quite ubiquitous, and several methods to capture such properties have been proposed in the past decades. Fractal properties are marked by similarities in statistical characteristics over time and space, and it has been suggested that such properties can be well-captured through recurrence quantification analysis. However, no methods to capture fractal fluctuations by means of recurrence-based methods have been developed yet. The present paper takes this suggestion as a point of departure to propose and test several approaches to quantifying fractal fluctuations in synthetic and empirical time-series data using recurrence-based analysis. We show that such measures can be extracted based on recurrence plots, and contrast the different approaches in terms of their accuracy and range of applicability

ADS-B/MLAT surveillance system from high altitude platform systems

In this work the potential usage of ADS-Band Wide Area Multilateration(WAM)Surveillance with High Altitude Platform Systems(HAPS)is considered.The paper investigates the possible configuration ofthesystem,thelinkbudget,thege-ometryandthelimitationduetotherandomaccesstothechannelbytheModeSSignals(capacity).ThesurveillanceperformanceoftheproposedarchitectureinaWideAreaMultilaterationcontextisevaluatedbybothsimulationandstatisticalanalysis(CramerRaoLowerBound)

Large eddy simulations of a utility-scale horizontal axis wind turbine including unsteady aerodynamics and fluid-structure interaction modelling

Growing horizontal axis wind turbines are increasingly exposed to significant sources of unsteadiness, such as tower shadowing, yawed or waked conditions and environmental effects. Due to increased dimensions, the use of steady tabulated airfoil coefficients to determine the airloads along long blades can be questioned in those numerical fluid models that do not have the sufficient resolution to solve explicitly and dynamically the flow close to the blade. Various models exist to describe unsteady aerodynamics (UA). However, they have been mainly implemented in engineering models, which lack the complete capability of describing the unsteady and multiscale nature of wind energy. To improve the description of the blades' aerodynamic response, a 2D unsteady aerodynamics model is used in this work to estimate the airloads of the actuator line model in our fluid–structure interaction (FSI) solver, based on 3D large eddy simulation. At each section along the actuator lines, a semi-empirical Beddoes-Leishman model includes the effects of noncirculatory terms, unsteady trailing edge separation, and dynamic stall in the dynamic evaluation of the airfoils' aerodynamic coefficients. The aeroelastic response of a utility-scale wind turbine under uniform, laminar and turbulent, sheared inflows is examined with one- and two-way FSI coupling between the blades' structural dynamics and local airloads, with and without the enhanced aerodynamics' description. The results show that the external half of the blade is dominated by aeroelastic effects, whereas the internal one is dominated by significant UA phenomena, which was possible to represent only thanks to the additional model implemented

Numerical tests of AdS/CFT at strong coupling

We study various correlation functions (two and three point functions) in a large $N$ matrix model of six commuting matrices with a numerical Monte Carlo algorithm. This is equivalent to a model of a gas of particles in six dimensions with a confining quadratic potential and logarithmic repulsions at finite temperature, where we are measuring the leading order non-gaussianities in the thermal fluctuations. This is a simplified model of the low energy dynamics of N=4 SYM at strong coupling. We find strong evidence that the simplified matrix model matches with the dual gravitational description of three point functions in the AdS/CFT correspondence.Comment: 23 pages, 7 figures, revtex. v2: minor correction

Unidimensional and Multidimensional Methods for Recurrence Quantification Analysis with crqa

Recurrence quantification analysis is a widely used method for characterizing patterns in time series. This article presents a comprehensive survey for conducting a wide range of recurrence based analyses to quantify the dynamical structure of single and multivariate time series and capture coupling properties underlying leader-follower relationships. The basics of recurrence quantification analysis (RQA) and all its variants are formally introduced step-by-step from the simplest auto recurrence to the most advanced multivariate case. Importantly, we show how such RQA methods can be deployed under a single computational framework in R using a substantially renewed version of our crqa 2.0 package. This package includes implementations of several recent advances in recurrence based analysis, among them applications to multivariate data and improved entropy calculations for categorical data. We show concrete applications of our package to example data, together with a detailed description of its functions and some guidelines on their usage

Budget Feasible Mechanisms on Matroids

Motivated by many practical applications, in this paper we study budget feasible mechanisms with the goal of procuring an independent set of a matroid. More specifically, we are given a matroid M= (E, I). Each element of the ground set E is controlled by a selfish agent and the cost of the element is private information of the agent itself. A budget limited buyer has additive valuations over the elements of E. The goal is to design an incentive compatible budget feasible mechanism which procures an independent set of the matroid of largest possible value. We also consider the more general case of the pair M= (E, I) satisfying only the hereditary property. This includes matroids as well as matroid intersection. We show that, given a polynomial time deterministic algorithm that returns an α-approximation to the problem of finding a maximum-value independent set in M, there exists an individually rational, truthful and budget feasible mechanism which is (3 α+ 1) -approximated and runs in polynomial time, thus yielding also a 4-approximation for the special case of matroids

Predatory ability of generalist predators on eggs, young nymphs and adults of the invasive Halyomorpha halys in southern Europe

Halyomorpha halys (Stål, 1855) is an invasive pest causing serious damage to agricultural crops in Europe and the USA. Very little is known about H. halys predators in Europe. This survey evaluated the potential of generalist predators/omnivorous species by means of predation bioassays in tri-dimensional arenas, where the predator had to locate H. halys prey items on the leaves of a bean plant. Eleven species of different taxa were tested and the prey items consisted in fresh eggmasses, 1st and 2nd instar nymphs. One species was also tested against adults. Some predators were species commercially available as biocontrol agents against plant pests, other predators were wild, captured in habitats shared with H. halys. All tested specimens were starved 24 h before starting the experiment. The survivorship of control prey items in predator-excluding cages was compared to that of predator treatment groups to determine the effect of predator presence. According to the results, the generalist species showed a quite low acceptance of H. halys prey items, since only two species caused 80% mortality on at least one item (Eupholidoptera chabrieri and Rhynocoris iracundus) and mortality due the other species never exceed 60%. Among commercially available species only Adalia bipunctata adults and Chrysoperla carnea larvae were effective, predating the eggs and 1st instar nymphs, respectively. Among the field collected specimens, the orthopteran E. chabrieri and the predatory hemipterans R. iracundus, Nagusta goedelii and Himacerus mirmicoides showed efficacy against 1st instar nymphs, E. chabrieri and R. iracundus showed efficacy against 2nd instar nymphs, whereas only E. chabrieri and N. goedelii predated the eggs. R. iracundus was also tested on the adults and successfully predated them. By identifying some of the species that can exploit H. halys as a suitable prey in southern Europe, the present investigation provides an important contribution for conservation biological control of this pest