Efficient Triangle Counting in Large Graphs via Degree-based Vertex Partitioning

The number of triangles is a computationally expensive graph statistic which is frequently used in complex network analysis (e.g., transitivity ratio), in various random graph models (e.g., exponential random graph model) and in important real world applications such as spam detection, uncovering of the hidden thematic structure of the Web and link recommendation. Counting triangles in graphs with millions and billions of edges requires algorithms which run fast, use small amount of space, provide accurate estimates of the number of triangles and preferably are parallelizable. In this paper we present an efficient triangle counting algorithm which can be adapted to the semistreaming model. The key idea of our algorithm is to combine the sampling algorithm of Tsourakakis et al. and the partitioning of the set of vertices into a high degree and a low degree subset respectively as in the Alon, Yuster and Zwick work treating each set appropriately. We obtain a running time $O \left(m + \frac{m^{3/2} \Delta \log{n}}{t \epsilon^2} \right)$ and an $\epsilon$ approximation (multiplicative error), where $n$ is the number of vertices, $m$ the number of edges and $\Delta$ the maximum number of triangles an edge is contained. Furthermore, we show how this algorithm can be adapted to the semistreaming model with space usage $O\left(m^{1/2}\log{n} + \frac{m^{3/2} \Delta \log{n}}{t \epsilon^2} \right)$ and a constant number of passes (three) over the graph stream. We apply our methods in various networks with several millions of edges and we obtain excellent results. Finally, we propose a random projection based method for triangle counting and provide a sufficient condition to obtain an estimate with low variance.Comment: 1) 12 pages 2) To appear in the 7th Workshop on Algorithms and Models for the Web Graph (WAW 2010

Comparison of inclusive and photon-tagged jet suppression in 5.02 TeV Pb+Pb collisions with ATLAS

Parton energy loss in the quark–gluon plasma (QGP) is studied with a measurement of photon-tagged jet production in 1.7 nb−1 of Pb+Pb data and 260 pb−1 of pp data, both at √sNN = 5.02 TeV, with the ATLAS detector. The process pp → γ +jet+X and its analogue in Pb+Pb collisions is measured in events containing an isolated photon with transverse momentum (pT) above 50 GeV and reported as a function of jet pT. This selection results in a sample of jets with a steeply falling pT distribution that are mostly initiated by the showering of quarks. The pp and Pb+Pb measurements are used to report the nuclear modification factor, RAA, and the fractional energy loss, Sloss, for photon-tagged jets. In addition, the results are compared with the analogous ones for inclusive jets, which have a significantly smaller quark-initiated fraction. The RAA and Sloss values are found to be significantly different between those for photon-tagged jets and inclusive jets, demonstrating that energy loss in the QGP is sensitive to the colour-charge of the initiating parton. The results are also compared with a variety of theoretical models of colour-charge-dependent energy loss

Exact k-Wise Intersection Theorems

ISSN:0911-0119ISSN:1435-591

Finite and infinite arithmetic progressions in sumsets

We prove that if A is a subset of at least cn1/2 elements of {1, . . . , n}, where c is a sufficiently large constant, then the collection of subset sums of A contains an arithmetic progression of length n. As an application, we confirm a long standing conjecture of Erd¿os and Folkman on complete sequences

Harmonic and modal frequency discrimination in time domain operational modal analysis

An algorithm of operational modal analysis in time domain is presented for the discrimination between structural modes, harmonic excitations and spurious modes. A classification factor is developed and based on the construction of the damped signal- to- noise ratio which separates the physical modes from the numerical ones. The harmonic excitations are then recognized at very high power indexes and zero damping. Furthermore, after the modal discrimination, the harmonic spectrum and the estimated frequency response function can be derived. The method can be updated in the time domain either by a short time sliding window or a recursive technique to provide the modal monitoring in both stationary and non-stationary process. An industrial application on a hydro-electrical generator is discussed to identify the machine frequencies under operational working conditions

Surface Saturation with Carbon Using Plasma Arc and Graphite Coating

This study presents the development of a novel equipment for carburizing, by means of a plasma arc and a graphite paste based on liquid glass. After processing by this method, the microstructure and microhardness of the hardened layer were studied. The assay revealed that during a brief plasma exposure, the surface layer was saturated with carbon to a concentration level, which corresponds to white cast iron. The microstructures and characteristics of the metal surface post plasma cementation were also studied. The main parameters of the cemented layer were determined: the depth of the cemented layer was 150-200 µm, microhardness was up to 1000 HV0.2

Modal parameters of the human hand-arm using finite element and operational modal analysis

This study presents a finite element (FE) model of the human hand-arm system to derive natural frequencies and mode shapes. The FE model is calibrated by considering modal parameters obtained from experimental vibration analyzed by using operational modal analysis (OMA) and transmissibility. Modal and harmonic analyses of the FE model are performed for two boundary conditions. The first one considers fixed shoulder condition while the second one introduces the trunk in order to permit motion of the shoulder. The results show that the natural frequencies of the second model that permits shoulder motion are comparable with those determined from measurements. Especially, the natural frequency about 12 Hz, which is corresponding to the frequency of maximum weight in ISO-5349-1 (2001), is not present in the model with fixed shoulder condition, while it appears in the second model. The results of the present study suggest that improved finite element models of the human hand-arm system may reveal hand-arm injury mechanism, the understanding of which may assist in deriving appropriate frequency weightings for the assessment of different components of the hand-arm vibration syndrome

Suspected tuberculosis case detection and referral in private pharmacies in Viet Nam

SETTINGS: Private pharmacies in Hanoi, Viet Nam. OBJECTIVES: To explore the response of health care providers (HCPs) in private pharmacies to suspected tuberculosis (TB) patients. METHODS: A simulated patient method combined with an interview in 128 randomly selected private pharmacies and 10 private pharmacies near TB hospitals. RESULTS: In the simulated patient method and interview, respectively 59 (46%) and 70 (55%) of HCPs referred the TB suspect to general health care. Only 11 (9%) referred the simulated patient to a TB care facility. Fifty-two (42%) of the HCPs identified suspected TB from a fictitious case described on paper; 34 (27%) were aware that free treatment was provided under the National Tuberculosis Programme (NTP). Knowledge about free NTP treatment predicted a higher rate of direct referrals to TB facilities (OR 5.80, 95%CI 1.88-19.62) and greater ability to identify suspected TB from a fictitious case on paper (OR 5.14, 95%CI 2.36-11.73). Pharmacies with Good Pharmacy Practice (GPP) certification were less likely to refer simulated patients to TB facilities than non-GPP pharmacies (OR 0.10, 95%CI </=0.01-0.79). CONCLUSIONS: Nearly half of HCPs in private pharmacies do not refer TB suspects, possibly contributing to delays in diagnosis and treatment. Knowledge about free NTP treatment predicted better performance of HCPs

Stablecoins versus traditional cryptocurrencies in response to interbank rates

This study investigates the impacts of the United States (US) federal funds rate and Chinese interbank rate on the behaviors of stablecoins and traditional cryptocurrencies. We employ GARCH, EGARCH and Fixed Effects models for the daily sample of the top five stablecoins and the top five traditional cryptocurrencies in terms of market capitalization from December 2018 to December 2019. Our results show that a higher federal funds rate and Chinese interbank rate compress the prices and price volatility of stablecoins. In contrast, higher rates from both countries increase the prices and price volatility of traditional cryptocurrencies. Both rates also increase the trading value of both types of coins. The federal funds rate tends to have stronger impacts compared to the Chinese interbank rate on both types of coins, except for the price response of traditional cryptocurrencies