5,172 research outputs found

    Characterizing Some Gaia Alerts with LAMOST and SDSS

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    Gaia is regularly producing Alerts on objects where photometric variability has been detected. The physical nature of these objects has often to be determined with the complementary observations from ground-based facilities. We have compared the list of Gaia Alerts (until 20181101) with archival LAMOST and SDSS spectroscopic data. The date of the ground-based observation rarely corresponds to the date of the Alert, but this allows at least the identification of the source if it is persistent, or the host galaxy if the object was only transient like a supernova. A list of Gaia Nuclear Transients from Kostrzewa-Rutkowska et al. (2018) has been included in this search also. We found 26 Gaia Alerts with spectra in LAMOST+SDSS labelled as stars (12 with multi-epoch spectra). A majority of them are CVs. Similarly 206 Gaia Alerts have associated spectra labelled as galaxies (49 with multi-epoch spectra). Those spectra were generally obtained on a date different from the Alert date, are mostly emission-line galaxies, leading to the suspicion that most of the Alerts were due to a SN. As for the GNT list, we found 55 associated spectra labelled as galaxies (13 with multi-epoch spectra). In two galaxies, Gaia17aal and GNTJ170213+2543, was the date of the spectroscopic observation close enough to the Alert date: we find a trace of the SN itself in their LAMOST spectrum, both classified here as a type Ia SN. The GNT sample has a higher proportion of AGNs, suggesting that some of the detected variations are also due to the AGN itself. Similar for Quasars, we found 30 Gaia Alerts but 68 GNT cases have single epoch quasar spectra, while 12 plus 23 have multi-epoch spectra. For ten out of these 35, their multi-epoch spectra show appearance or disappearance of the broad Balmer lines and also variations in the continuum, qualifying them as "Changing Look Quasars".Comment: Accepted for publication in APSS, 14 pages, 8 figures, 2 table

    Atomic Entanglement vs Photonic Visibility for Quantum Criticality of Hybrid System

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    To characterize the novel quantum phase transition for a hybrid system consisting of an array of coupled cavities and two-level atoms doped in each cavity, we study the atomic entanglement and photonic visibility in comparison with the quantum fluctuation of total excitations. Analytical and numerical simulation results show the happen of quantum critical phenomenon similar to the Mott insulator to superfluid transition. Here, the contour lines respectively representing the atomic entanglement, photonic visibility and excitation variance in the phase diagram are consistent in the vicinity of the non-analytic locus of atomic concurrences.Comment: 4 pages, 2 figure

    High temperature plastic deformation constitutive model of Mg-Zn-Zr-Y alloy

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    In order to accurately predict the flow stress of Mg-Zn-Zr-Y alloy at high temperature, the hot compression test of Mg-Zn-Zr-Y alloy was carried out on Gleeble-1500 thermal / mechanical simulator. The deformation temperature was 523 K, 573 K, 623 K, and the strain rate was 0,01 ~ 1 s-1. By obtaining the true stress-strain curve, the strain compensation factor Z parameter was introduced into the Arrhenius equation to establish a more accurate strain coupling constitutive model. The results show that the theoretical value of the peak stress calculated by the constitutive model is in good agreement with the experimental results, and the average relative error is 5,67 %, which verifies the feasibility of the model

    High temperature plastic deformation constitutive model of Mg-Zn-Zr-Y alloy

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    In order to accurately predict the flow stress of Mg-Zn-Zr-Y alloy at high temperature, the hot compression test of Mg-Zn-Zr-Y alloy was carried out on Gleeble-1500 thermal / mechanical simulator. The deformation temperature was 523 K, 573 K, 623 K, and the strain rate was 0,01 ~ 1 s-1. By obtaining the true stress-strain curve, the strain compensation factor Z parameter was introduced into the Arrhenius equation to establish a more accurate strain coupling constitutive model. The results show that the theoretical value of the peak stress calculated by the constitutive model is in good agreement with the experimental results, and the average relative error is 5,67 %, which verifies the feasibility of the model

    2209 duplex stainless steel high temperature plastic deformation intrinsic modeling

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    The high temperature compression experiments of 2209 duplex stainless steel were carried out by using Gleeble3800 thermal simulator, the rate was 0,01~10 s–1, and the deformation temperature was 950~1 100°C. The strain rate and deformation temperature were analyzed and the effect of strain rate and deformation temperature were analyzed. The high-temperature rheological behavior of 2209 duplex stainless steel was investigated, and the effects of strain rate and deformation temperature on the two-phase relationship of 2209 duplex stainless steel were analyzed, the strain rate compensation factor Z was introduced, and the Arrhenius eigenmodel equation was established. The results show that the theoretical value of peak stress calculated numerically by this constitutive model fits well with the experimental results, and the correlation is 97,3 %, which verifies the feasibility of the model

    2209 duplex stainless steel high temperature plastic deformation intrinsic modeling

    Get PDF
    The high temperature compression experiments of 2209 duplex stainless steel were carried out by using Gleeble3800 thermal simulator, the rate was 0,01~10 s–1, and the deformation temperature was 950~1 100°C. The strain rate and deformation temperature were analyzed and the effect of strain rate and deformation temperature were analyzed. The high-temperature rheological behavior of 2209 duplex stainless steel was investigated, and the effects of strain rate and deformation temperature on the two-phase relationship of 2209 duplex stainless steel were analyzed, the strain rate compensation factor Z was introduced, and the Arrhenius eigenmodel equation was established. The results show that the theoretical value of peak stress calculated numerically by this constitutive model fits well with the experimental results, and the correlation is 97,3 %, which verifies the feasibility of the model
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