31 research outputs found

    Impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field

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    We report on the observation and experimental studies of impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field. The terahertz electroluminescence is observed in a wide range of doping levels (at noncompensated donor density from 4.5×10[sup 16] to 3.4×10[sup 18] cm[sup −3]). Spectra of terahertz luminescence and photoconductivity are studied by means of Fourier transform spectrometry. Distinctive features of the spectra can be assigned to intracenter electron transitions between excited and ground states of silicon and oxygen donors and to hot electron transitions to the donor states.Peer reviewe

    Asymptotically d-optimal test of a change-point detection

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    The paper considers the problem of a change-point detection for a sequence of random variables. We construct a d-optimal test guaranteeing the d-risk. The asymptotics of this test is obtained. Translated by M. V. Khatuntseva from Russian journal.2 page(s

    Asymptotically d-optimal test of a posteriori change-point detection

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    We consider the problem of a posteriori change-point detection for a sequence of independent identically distributed random variables. We propose to use d-risks instead of error of the first type and error of the second type. We construct an asymptotically optimal test minimizing one d-risk and guaranteeing another. Translated by M. V. Khatuntseva from Russian journal.5 page(s

    A Multiple optimal stopping rule for sums of independent random variables

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    We consider multiple optimal stopping rules for a finite (with horizon N) sequence of independent random variables. We are interested in finding a stopping rule which maximises the expected sum of k, 1 < k < N, observations. The optimal stopping rule and the value of the game are obtained. This result can be applied in the house-selling problem and in behavioural ecology problems.11 page(s

    Analysis of ontogenetic spectra of populations of plants and lichens via ordinal regression

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    Ontogenetic spectra of plants and lichens tend to vary across the populations. This means that if several subsamples within a sample (or a population) were collected, then the subsamples would not be homogeneous. Consequently, the statistical analysis of the aggregated data would not be correct, which could potentially lead to false biological conclusions. In order to take into account the heterogeneity of the subsamples, we propose to use ordinal regression, which is a type of generalized linear regression. In this paper, we study the populations of cowberry Vaccinium vitis-idaea L. and epiphytic lichens Hypogymnia physodes (L.) Nyl. and Pseudevernia furfuracea (L.) Zopf. We obtain estimates for the proportions of between-sample variability in the total variability of the ontogenetic spectra of the populations.10 page(s

    Correlation structure of bilateral traits

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    4 page(s
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