1,458 research outputs found

    Color Behavior Of BL Lacertae Object OJ 287 During Optical Outburst

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    This paper aims to study the color behavior of the BL Lac object OJ 287 during optical outburst. According to the revisit of the data from the OJ-94 monitoring project and the analysis the data obtained with the 60/90 cm Schmidt Telescope of NAOC, we found a bluer-when-brighter chromatism in this object. The amplitude of variation tends to decrease with the decrease of frequency. These results are consistent with the shock-in-jet model. We made some simulations and confirmed that both amplitude difference and time delay between variations at different wavelengths can result in the phenomenon of bluer-when-brighter. Our observations confirmed that OJ 287 underwent a double-peaked outburst after about 12 years from 1996, which provides further evidence for the binary black hole model in this object.Comment: 25 pages, 13 figure

    Dual-Refinement: Joint Label and Feature Refinement for Unsupervised Domain Adaptive Person Re-Identification

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    Unsupervised domain adaptive (UDA) person re-identification (re-ID) is a challenging task due to the missing of labels for the target domain data. To handle this problem, some recent works adopt clustering algorithms to off-line generate pseudo labels, which can then be used as the supervision signal for on-line feature learning in the target domain. However, the off-line generated labels often contain lots of noise that significantly hinders the discriminability of the on-line learned features, and thus limits the final UDA re-ID performance. To this end, we propose a novel approach, called Dual-Refinement, that jointly refines pseudo labels at the off-line clustering phase and features at the on-line training phase, to alternatively boost the label purity and feature discriminability in the target domain for more reliable re-ID. Specifically, at the off-line phase, a new hierarchical clustering scheme is proposed, which selects representative prototypes for every coarse cluster. Thus, labels can be effectively refined by using the inherent hierarchical information of person images. Besides, at the on-line phase, we propose an instant memory spread-out (IM-spread-out) regularization, that takes advantage of the proposed instant memory bank to store sample features of the entire dataset and enable spread-out feature learning over the entire training data instantly. Our Dual-Refinement method reduces the influence of noisy labels and refines the learned features within the alternative training process. Experiments demonstrate that our method outperforms the state-of-the-art methods by a large margin.Comment: 14 pages, 5 figure

    pTp_{T} dispersion of inclusive jets in high-energy nuclear collisions

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    In this paper, we investigate the medium modifications of pTp_{T} dispersion(pTDp_{T}D) of inclusive jets with small radius (R=0.2R=0.2) in Pb+Pb collisions at s=2.76\sqrt{s}=2.76~TeV. The partonic spectrum in the initial hard scattering of elementary collisions are obtained by an event generator POWHEG+PYTHIA, which matches the next-to-leading (NLO) matrix elements with parton showering, and energy loss of fast parton traversing in hot/dense QCD medium is calculated by Monte Carlo simulation within Higher-Twist formalism of jet quenching in heavy-ion collisions. We present the model calculations of normalized pTDp_{T}D distributions for inclusive jets in p+p and Pb+Pb collisions at s=2.76\sqrt{s}=2.76~TeV, which give nice descriptions of ALICE measurements. It is shown that the pTDp_{T}D distributions of inclusive jets in Pb+Pb are shifted to higher pTDp_{T}D region relative to that in p+p. Thus the nuclear modification factor of pTDp_{T}D distributions for inclusive jets is smaller than unity at small pTDp_{T}D region, while larger than one at large pTDp_{T}D region. This behaviour results from more uneven pTp_T of jet constituents as well as the fraction alteration of gluon/quark initiated jets in heavy-ion collisions. The difference of pTDp_{T}D distributions between groomed and ungroomed jets in Pb+Pb collisions are also discussed

    Differential responses of two rubber tree clones to chilling stress

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    Chilling stress is one of the most important environmental factors that limit the growth, distribution and yield of rubber tree in China. The effects of chilling stress on the grated plants of two rubber trees clones, GT1 and Wenchang217, were studied by physiological methods in controlled light chamber in order to explore the physiological mechanism of cold tolerance in rubber tree. Our results show a significant change in the tested physiological parameters after chilling treatment between two rubber clones. In comparison with the case of rubber tree clone GT1, the level of malondialdehyde (MDA) increased while superoxide dismutase, especially peroxidase and catalase decreased significantly in the seedlings of rubber tree clone Wenchang217 in response to chilling stress. As the cold tolerance ability of rubber tree clone GT1 is stronger than that of rubber tree clone Wenchang217, activation of oxidative quenching enzyme system should be one of the important factors that determine the cold tolerance of rubber tree.Keywords: Chilling stress, cold tolerance, Hevea brasiliensis Muell. Arg., physiological parameter, seedlin
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