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Optical observations of the broad-lined type Ic supernova SN 2012ap

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Research in Astronomy and Astrophysics 2015年第2期15卷 225-236页

作者： Zheng Liu Xu-Lin Zhao Fang Huang Xiao-Feng Wang tian-meng zhang Jun-Cheng Chen Tong-Jie zhang Astronomy Department Beijing Normal University Physics Department and Tsinghua Center for Astrophysics Tsinghua University National Astronomical Observatories Chinese Academy of Sciences Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Center for High Energy Physics Peking University

Abstract The optical observations of the type Ic supernova （SN lc） SN 2012ap in NGC 1729 are presented. A comparison with other SNe Ic indicates that SN 2012ap is highly reddened （with E（B - V）host-0.8 mag） and may represent one of the most luminous SNe Ic ever observed, with an absolute V-band peak magnitude of - 19.3±0.5 mag after extinction correction. The near-maximum-light spectrum shows wide spectral features that are typical of broad-lined SNe Ic. One interesting feature in the spectrum is the appearance of some narrow absorption features that can be at- tributed to the diffuse interstellar bands, consistent with the large reddening inferred from the photometric method. Based on the light curves and the spectral data, we esti- mate that SN 2012ap produced a 56Ni mass of - 0.3 -b 0.1M in the explosion, with an ejecta mass of 2.4^＋0.7 -0.7M and a kinetic energy of EK=1.1^＋0.4 -0.4×10^52 erg. The properties of its progenitor are also briefly discussed.

关键词： supernovae: general supernovae: individual: SN 2012ap

Multicolor photometry of the nearby galaxy cluster A119

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Research in Astronomy and Astrophysics 2012年第10期12卷 1381-1401页

作者： Jin-Tao tian Qi-Rong Yuan Xu Zhou Zhao-Ji Jiang Jun Ma Jiang-Hua Wu Zhen-Yu Wu tian-meng zhang Hu Zou National Astronomical Observatories Chinese Academy of Sciences Beiiing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academyof Sciences Beijing 100012 China Department of Physics Nanjing Normal University Nanjing 210046 China Department of Astronomy Beijing Normal University Beijing 100875 China

This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 （z = 0.0442） with the Beijing-Arizona-Taiwan-Connecticut system of 15 intermediate bands. Within the BATC field of view of 58＇× 58＇, there are 368 galaxies with known spectroscopic redshifts, including 238 member galaxies （called sample I）. Based on the spectral energy distributions of 1376 galaxies brighter than iBATC ---- 19.5, the photometric redshift technique and the color-magnitude relation of early-type galaxies are applied to select faint member galaxies. As a result, 117 faint galaxies were selected as new member galaxies. Combined with sample I, an enlarged sample （called sample II） of 355 member galaxies is obtained. Spatial distribution and localized velocity structure for two samples demonstrate that A119 is a dynami- cally complex cluster with at least three prominent substructures in the central region within 1 Mpc. A large velocity dispersion for the central clump indicates a merging along the line of sight. No significant evidence for morphology or luminosity segrega- tions is found in either sample. With the PEGASE evolutionary synthesis model, the environmental effect on the properties of star formation is confirmed. Faint galaxies in the low-density region tend to have longer time scales of star formation, smaller mean stellar ages, and lower metallicities in their interstellar medium, which is in agreement with the context of the hierarchical cosmological scenario.

关键词： galaxies: clusters: individual (A119)- galaxies: distances and redshifts-- galaxies: evolution-- galaxies: kinematics and dynamics-- methods: data analysis

Kinematics and stellar population properties of the Andromeda galaxy by using the spectroscopic observations of the Guoshoujing Telescope

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Research in Astronomy and Astrophysics 2011年第9期11卷 1093-1110页

作者： Hu ZOU Yan-Bin Yang tian-meng zhang Jun Ma Xu Zhou Ali Luo Hao-Tong zhang Zhong-Rui Bai Yong-Heng Zhao National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

The Andromeda galaxy was observed by the Guoshoujing Telescope （formerly named the Large Sky Area Multi-Object Fiber Spectroscopic Telescope -- LAMOST）, during the 2009 commissioning phase. Due to the absence of standard stars for flux calibration, we use the photometric data of 15 intermediate bands in the Beijing-Arizona-Taipei-Connecticut （BATC） survey to calibrate the spectra. In to- tal, 59 spectra located in the bulge and disk of the galaxy are obtained. Kinematic and stellar population properties of the stellar content are derived with these spectra. We obtain the global velocity field and calculate corresponding rotation velocities out to about 7 kpc along the major axis. These rotation velocity measurements comple- ment those of the gas content, such as the H I and CO. The radial velocity dispersion shows that the stars in the bulge are more dynamically thermal and the disk is more rotationally-supported. The age distribution shows that the bulge was formed about 12 Gyr ago, the disk is relatively younger and the ages of some regions along the spi- ral arms can reach as young as about 1 Gyr. These young stellar populations have a relatively richer abundance and larger reddening. The overall average metallicity of the galaxy approximates the solar metallicity and a very weak abundance gradient is gained. The reddening map gives a picture of a dust-free bulge and a distinct dusty ring in the disk.

关键词： methods: data analysis -- techniques: spectroscopic -- galaxies: indi- vidual (M31) -- galaxies: stellar content

Late-time photometry of two nearby type II-P supernovae: 2004dj and 2004et

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Research in Astronomy and Astrophysics 2009年第7期9卷 783-790页

作者： tian-meng zhang Xiao-Feng Wang Xu Zhou Jun Ma Zhao-Ji Jiang Jiang-Hua Wu Zhen-Yu Wu Stephane Basa NationalAstronomicalObservatories Chinese Academy of Sciences Beijing 100012 China Observatoire Astronomique de Marseille-Provence 38 rue Fric Joliot-Curie 13388 Marseille Cedex 13 France Physics Department and Tsinghua Center for Astrophysics （THCA） Tsinghua University Beijing 100084 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Department of Astronomy University of California Berkeley CA 94720-3411 USA

We present late-time photometry for two bright type II-P supernovae （SNe） 2004dj and 2004et, extending over 400 d after the explosion, which are measured with a set of intermediate-band filters that have the advantage of tracing the strength variations of some spectral features. Although these two SNe II-P exhibit similar photometric evolution at earlier times, they diverge during the nebular phase. SN 2004dj shows a slow late-time decline rate with - 0.7 ±0.1 mag （100d）^-1 during the period ranging from t ≈ 200 - 300 d after the explosion, while SN 2004et shows a much faster decline rate at a comparable phase, e.g., 1.3 ± 0.1 mag （100d）^-1. The steeper decay rate seen in SN 2004et is likely due to dust formation in the explosion ejecta. Based on intermediate-band photometry, we derived the evolution of the feature lines [e.g., Hα] of SNe 2004dj and 2004et which are similar in flux at comparable phases but perhaps with significantly different decay rates. The origin of the observed variations in the continuum and the feature lines is briefly discussed.

关键词： supernovae general - supernovae: individual (SN 2004dj SN 2004et) -techniques: photometric

Multi-distortion suppression for neutron radiographic images based on generative adversarial network

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Nuclear Science and Techniques 2024年第4期35卷 176-188页

作者： Cheng-Bo meng Wang-Wei Zhu Zhen zhang Zi-Tong Wang Chen-Yi Zhao Shuang Qiao tian zhang School of Physics Northeast Normal UniversityChangchun 130024China

Neutron radiography is a crucial nondestructive testing technology widely used in the aerospace,military,and nuclear ***,because of the physical limitations of neutron sources and collimators,the resulting neutron radiographic images inevitably exhibit multiple distortions,including noise,geometric unsharpness,and white ***,these distortions are particularly significant in compact neutron radiography systems with low neutron ***,in this study,we devised a multi-distortion suppression network that employs a modified generative adversarial network to improve the quality of degraded neutron radiographic *** neutron radiographic image datasets with various types and levels of distortion were built for the first time as multi-distortion suppression ***,the coordinate attention mechanism was incorporated into the backbone network to augment the capability of the proposed network to learn the abstract relationship between ideally clear and degraded *** experiments were performed;the results show that the proposed method can effectively suppress multiple distortions in real neutron radiographic images and achieve state-of-theart perceptual visual quality,thus demonstrating its application potential in neutron radiography.

关键词： Neutron radiography Multi-distortion suppression Generative adversarial network Coordinate attention mechanism

Prediction of ball-on-plate friction and wear by ANN with data-driven optimization

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Friction 2024年第6期12卷 1235-1249页

作者： Alexander KOVALEV Yu tian Yonggang meng State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China

For training artificial neural network(ANN),big data either generated by machine or measured from experiments are used as input to"learn"the unspecified functions defining the *** experimental data are fed directly into the optimizer allowing training to be performed according to a predefined loss *** predict sliding friction and wear at mixed lubrication conditions,in this study a specific ANN structure was so designed that deep learning algorithms and data-driven optimization models can be *** ball-on-plate friction and wear data were analyzed using the specific training procedure to optimize the weights and biases incorporated into the neural layers of the ANN,and only two independent experimental data sets were used during the ANN optimization *** the training procedure,the ANN is capable to predict the contact and hydrodynamic pressure by adapting the output data according to the tribological condition implemented in the optimization algorithm.

关键词： machine learning deep learning artificial neural network mixed lubrication

In memoriam:Shizhu Wen(1932-2023)

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Friction 2024年第7期12卷 1341-1346页

作者： Jianbin LUO Yonggang meng Yu tian State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China

Professor Shizhu Wen,the winner of the 2015 Tribology Gold Medal,passed away due to illness on November 3,2023,at the age of *** was a professor of Tsinghua University,an academician of the Chinese Academy of Sciences,and the Honorary President of the Chinese Tribology Institute(CTI)from 1997 to *** Wen was born in 1932 in Jiangxi Province of China and graduated from Tsinghua University in 1955,where he was awarded the Outstanding Graduate Gold Medal and then remained as an assistant professor at the *** Wen was promoted to full professor in *** had undertaken tribology research at the Imperial College London in 1979 and *** 1985,he presided over the establishment of the State Key Laboratory of Tribology(SKLT)of Tsinghua University and served as the first director of the SKLT.

关键词： sided professor zhu

The photometric system of the Tsinghua-NAOC 80-cm telescope at NAOC Xinglong Observatory

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Research in Astronomy and Astrophysics 2012年第11期12卷 1585-1596页

作者： Fang Huang Jun-Zheng Li Xiao-Feng Wang Ren-Cheng Shang tian-meng zhang Jing-Yao Hu Yu-Lei Qiu Xiao-Jun Jiang Astronomy Department Beijing Normal University Beijing 100875 China Physics Department and Tsinghua Center for Astrophysics Tsinghua University Beijing100084 China National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academyof Sciences Beijing 100012 China

The Tsinghua-NAOC （National Astronomical Observatories of China） Telescope （hereafter, TNT） is an 80-cm Cassegrain reflecting telescope located at the Xinglong Observatory of NAOC, with the main scientific goals of monitoring various transients in the universe such as supernovae, gamma-ray bursts, novae, variable stars, and active galactic nuclei. We present a systematic test and analysis of the photometric performance of this telescope. Based on the calibration observations taken on 12 pho- tometric nights, spanning the period from 2004 to 2012, we derived an accurate trans- formation equation between the instrumental ubvri magnitudes and standard Johnson UBV and Cousins RI magnitudes. In particular, the color terms and the extinction coefficients of different passbands are well determined. With these data, we also ob- tained the limiting magnitudes and the photometric precision of TNT. It is worthwhile to point out that the sky background at the Xinglong Observatory became gradually worse over the period from 2005 to 2012 （e.g., -21.4 mag vs. ,-20.1 mag in the V band）.

关键词： instrumentation detectors -- site testing -- telescopes

Spin effect on redox acceleration and regioselectivity in Fe-catalyzed alkyne hydrosilylation

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National Science Review 2024年第2期11卷 155-167页

作者： Peng He meng-Yang Hu Jin-Hong Li tian-zhang Qiao Yi-Lin Lu Shou-Fei Zhu Frontiers Science Center for New Organic Matter State Key Laboratory and Institute of Elemento-Organic Chemistry Nankai University

Iron catalysts are ideal transition metal catalysts because of the Earths abundant, cheap, biocompatible features of iron salts. Iron catalysts often have unique open-shell structures that easily undergo spin crossover in chemical transformations, a feature rarely found in noble metal catalysts. Unfortunately, little is known currently about how the open-shell structure and spin crossover affect the reactivity and selectivity of iron catalysts, which makes the development of iron catalysts a low efficient trial-and-error program. In this paper, a combination of experiments and theoretical calculations revealed that the iron-catalyzed hydrosilylation of alkynes is typical spin-crossover catalysis. Deep insight into the electronic structures of a set of well-defined open-shell active formal Fe(0) catalysts revealed that the spin-delocalization between the iron center and the 1,10-phenanthroline ligand effectively regulates the iron center's spin and oxidation state to meet the opposite electrostatic requirements of oxidative addition and reductive elimination, respectively,and the spin crossover is essential for this electron transfer process. The triplet transition state was essential for achieving high regioselectivity through tuning the nonbonding interactions. These findings provide an important reference for understanding the effect of catalyst spin state on reaction. It is inspiring for the development of iron catalysts and other Earth-abundant metal catalysts, especially from the point of view of ligand development.

关键词： spin effect spin-delocalization spin crossover iron-catalysis alkyne hydrosilylation