7,335 research outputs found

    Correct ordering in the Zipf-Poisson ensemble

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    We consider a Zipf--Poisson ensemble in which X_i\sim\poi(Ni^{-\alpha}) for α>1\alpha>1 and N>0N>0 and integers i≄1i\ge 1. As N→∞N\to\infty the first nâ€Č(N)n'(N) random variables have their proper order X1>X2>...>Xnâ€ČX_1>X_2>...>X_{n'} relative to each other, with probability tending to 1 for nâ€Čn' up to (AN/log⁥(N))1/(α+2)(AN/\log(N))^{1/(\alpha+2)} for an explicit constant A(α)≄3/4A(\alpha)\ge 3/4. The rate N1/(α+2)N^{1/(\alpha+2)} cannot be achieved. The ordering of the first nâ€Č(N)n'(N) entities does not preclude Xm>Xnâ€ČX_m>X_{n'} for some interloping m>nâ€Čm>n'. The first n"n" random variables are correctly ordered exclusive of any interlopers, with probability tending to 1 if n"≀(BN/log⁥(N))1/(α+2)n"\le (BN/\log(N))^{1/(\alpha+2)} for B<AB<A. For a Zipf--Poisson model of the British National Corpus, which has a total word count of 100,000,000100{,}000{,}000, our result estimates that the 72 words with the highest counts are properly ordered

    Empirical stationary correlations for semi-supervised learning on graphs

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    In semi-supervised learning on graphs, response variables observed at one node are used to estimate missing values at other nodes. The methods exploit correlations between nearby nodes in the graph. In this paper we prove that many such proposals are equivalent to kriging predictors based on a fixed covariance matrix driven by the link structure of the graph. We then propose a data-driven estimator of the correlation structure that exploits patterns among the observed response values. By incorporating even a small fraction of observed covariation into the predictions, we are able to obtain much improved prediction on two graph data sets.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS293 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Phylogenetic revision of Atherinopsinae (Teleostei, Atherinopsidae), with comments on the systematics of the South American freshwater fish genus Basilichthys Girard

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    http://deepblue.lib.umich.edu/bitstream/2027.42/56429/1/MP185.pd

    Ablation debris control by means of closed thick film filtered water immersion

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    The performance of laser ablation generated debris control by means of open immersion techniques have been shown to be limited by flow surface ripple effects on the beam and the action of ablation plume pressure loss by splashing of the immersion fluid. To eradicate these issues a closed technique has been developed which ensured a controlled geometry for both the optical interfaces of the flowing liquid film. This had the action of preventing splashing, ensuring repeatable machining conditions and allowed for control of liquid flow velocity. To investigate the performance benefits of this closed immersion technique bisphenol A polycarbonate samples have been machined using filtered water at a number of flow velocities. The results demonstrate the efficacy of the closed immersion technique: a 93% decrease in debris is produced when machining under closed filtered water immersion; the average debris particle size becomes larger, with an equal proportion of small and medium sized debris being produced when laser machining under closed flowing filtered water immersion; large debris is shown to be displaced further by a given flow velocity than smaller debris, showing that the action of flow turbulence in the duct has more impact on smaller debris. Low flow velocities were found to be less effective at controlling the positional trend of deposition of laser ablation generated debris than high flow velocities; but, use of excessive flow velocities resulted in turbulence motivated deposition. This work is of interest to the laser micromachining community and may aide in the manufacture of 2.5D laser etched patterns covering large area wafers and could be applied to a range of wavelengths and laser types
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