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A sample of active galactic nuclei with strong soft X-ray variabilities

Science China(Physics,Mechanics & Astronomy) 2015年第4期58卷 101-108页

作者： BI Da LIU Teng wang junxian CAS Key Laboratory for Research in Galaxies and Cosmology Department of AstronomyUniversity of Science and Technology of China

Large-amplitude X-ray variation is a special feature of AGN, reflecting possible extreme change in the central engine or the ab- sorption along the line of sight. Till now there are only a few relevant studies on individual sources or rather small samples. In this work we aim to perform a systematic study of AGNs with strong soft X-ray variations at timescale of 〉 10 years. To build the sample, we compare the soft X-ray fluxes of AGNs measured in ROSAT All-Sky Survey （RASS） during 1990-1991 with those measured by XMM-Newton during 2000-2009. This investigation bings forth to a sample of 13 AGNs, which appeared bright in RASS era, and went into low states （flux dropped by a factor of 〉 10） when they were caught by XMM-Newton. Most of the 13 sources are type I Seyfert galaxies. 5 of them are noticed to have strong X-ray vai＇iation for the first time. We study the nature of their variations through performing XMM-Newton spectral analyses and by collecting reports from the existing literature. We find the sample could be divided into three categories according to the possible causes of the strong X-ray variations. The variations in MRK 0478 and 1H 0419-557 are consistent with strong light-bending effect, i.e., the observed X-ray flux drops significantly as the X-ray emitting corona gets much closer to the central black hole. The variations in ESO 140-G043 and NGC 7158 are caused by absorption changes along the line of sight. For one special case MRK 0335, the variation can be explained by either light-bending or absorption variation. In the rest 8 sources （- 60%）, the strong soft X-ray variations are likely to exist due to intrinsic changes in the activities of the corona, although in some of them without high quality X-ray spectra we are unable to rule out alternative models. This sample provides good targets for future monitoring campaigns with more extensive studies.

关键词： soft X-ray active galactic nuclei variation

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On the nature of X-ray “unobscured” Seyfert 2 galaxies

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Science China(Physics,Mechanics & Astronomy) 2012年第12期55卷 2482-2491页

作者： TAN Ying wang junxian ZHANG Kai CAS Key Laboratory for Research in Galaxies and Cosmology Department of AstronomyUniversity of Science and Technology of ChinaHefei 230026China

We present a systematic study to reveal the effect of host galaxy contamination to the identification of X-ray "unobscured" Seyfert 2 *** compiled a sample of 14 X-ray "unobscured" Seyfert 2 galaxies and 29 X-ray obscured Seyfert 2s,with infrared [Ne II] and [O IV] emission line flux *** this work we classify Seyfert 2s as "unobscured" or obscured in X-ray simply based on X-ray spectral *** find that our X-ay "unobscured" Seyfert 2s have statistically higher [Ne II]/[O IV] line ratios,compared with obscured *** the [Ne II]/[O IV] line ratio reflects the relative strength of star formation activity comparing with the SMBH accretion,the observed differences in [Ne II]/[O IV] line ratios clearly indicate relatively stronger X-ray contamination from star formation in the host galaxies in X-ray "unobscured" Seyfert *** we could attribute the X-ray "unobscured" appearance to host galaxy contamination for most(if not all) of our X-ray "unobscured" Seyfert *** analysis indicates that "unobscured" Seyfert 2s have intrinsically lower AGN luminosity but similar star formation rates,compared with obscured *** is also consistent with previous studies showing most X-ray "unobscured" Seyfert 2s are at lower luminosities,and relatively stronger contaminations from the host galaxies are thus *** we develop a screening criterion to distinguish potential pure Seyfert 2s from X-ray "unobscured" appearances which could be caused by strong host galaxy contamination.

关键词： active galactic nuclei X-rays absorption star formation

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Weighing super-massive black holes with narrow Fe Kα line

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Science China(Physics,Mechanics & Astronomy) 2011年第7期54卷 1354-1358页

作者： JIANG Peng wang junxian SHU XinWen CAS Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Hefei 230026 China

It has been suggested that the narrow cores of the Fe Ka emission lines in Active Galactic Nuclei （AGNs） are likely produced in the torus, the inner radius of which can be measured by observing the lag time between the V and K band flux variations. In this paper, we compare the virial products of the infrared time lags, and the narrow Fe Ka widths for 10 type 1 AGNs, with the black hole masses from other techniques. We found the narrow Fe Ka line width is in average 2.6＋0.9-0.4 times broader than expected, assuming an isotropic velocity distribution of the torus at the distance measured by the infrared lags. We propose the thick disk model of the torus may explain the observed larger line width. Another possibility is the contamination by emission from the broad line region or the outer accretion disk. Alternatively, the narrow iron line might originate from the inner most part of the obscuring torus within the sublimation radius, while the infrared emission may be from the outer cooler part. We note the correlations between the black hole masses based on this new technique and those based on other known techniques are statistically insignificant. We argue that this could be attributed to the small sample size and the very large uncertainties in the measurements of iron K line widths. The next generation of X-ray observatories could help verify the origin of the narrow iron Ka line and the reliability of this new technique.

关键词： black hole physics galaxies: active galaxies: nuclei galaxies: Seyfert X-rays: galaxies infrared: galaxies

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Quantitative geochemical reconstruction of Eocene paleoenvironment in Fushun Basin,northeast China

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Acta Geochimica 2024年第3期43卷 571-587页

作者： Yuanji Li Pingchang Sun Qiang Zhang junxian wang Department of Safety Engineering Heilongjiang University of Science and TechnologyHarbin 150022China National Professional Center Lab of Safety Basic Research for Hydrocarbon Gas Pipeline Transportation Network Harbin 150022China College of Earth Sciences Jilin UniversityChangchun 130061JilinChina Beijing Research Institute of Uranium Geology Beijing 100029China

The quantitative estimation of key parameters of paleotemperature and paleoprecipitation is crucial for paleoclimate *** data from mod-ern sediments are highly consistent with climate data,and their relationship can provide an important reference for the quantitative reconstruction of the *** this study,detailed inorganic geochemical analysis was carried out using high-precision sampling of the Paleogene(LFD-1 well)Guchengzi,Jijuntun and Xiloutian Formations in the Fushun Basin located in the mid-latitudes of the Northern *** Eocene Guchengzi Formation(54.51–47.8 Ma)and Jijuntun Formation(47.8–41.2 Ma)in the Fushun Basin were found to have been deposited under a humid *** lower(41.2–40.1 Ma)and upper(40.1–37.8 Ma)parts of the Xiloutian Formation were character-ized by semiarid and semihumid–semiarid climates,respec-tively,which is very similar to the paleoclimatic information reflected by organic carbon *** Eocene Thermal Maximum 2(ETM2,~53.7 Ma),Early Eocene Climatic Optimum(EECO,~53.1–46.5 Ma),Eocene Thermal Maxi-mum 3(ETM 3,~52.8 Ma),and Middle Eocene Climatic Optimum(MECO,~40.7–40.1 Ma)events significantly enhanced chemical weathering during these *** rapid increase in pCO_(2)concentration leads to an increase in temperature,precipitation,and surface runoff,exhibiting strong chemical *** mean annual temperature(MATa)and mean annual precipitation(MAPa,MAPb,and MAPc)were estimated using parameters,such as the corrosion index without potassium(CIA-K),CaO/Al_(2)O_(3),and(Na_(2)O+K_(2)O)/Al_(2)O_(3).Comparing MAPa,MAPb,and MAPc with the MAP estimated using pollen data,MAPa and MAPb were found to be more sensitive to the climate during high precipitation periods(precipitation>1000 mm,Guchengzi Formation),and the recovered average precipi-tation was similar to *** contrast,MAPc was more sensitive to the climate during low precipitation periods(precipitation<1000 mm,Jijuntun,and Xilouti

关键词： Eocene Fushun Basin Major element Paleoclimate Geochemical reconstruction

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Multi-objective optimization of a high speed on/off valve for dynamic performance improvement and volume minimization

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Chinese Journal of Aeronautics 2024年第10期37卷 435-444页

作者： Qi ZHONG junxian wang Enguang XU Cheng YU Yanbiao LI College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310023China Key Laboratory of Special Purpose Equipment and Advanced Processing Technology Ministry of Education and Zhejiang ProvinceZhejiang University of TechnologyHangzhou 310023China

Hydraulic circuits with high speed on/off valve(HSV)for servo control have become commonplace in ***,the individual valve that is not volume-optimized results in a large total size of hydraulic control system,diminishing the *** address this issue,the high-precision equivalent reluctance model of the HSV is established by employing an equivalent magnetic circuit,on which the dynamic characteristic of the HSV,as well as the effects of structural parameters on switching behaviour,are *** on this model,multi-objective optimization is adopted to design an HSV with faster dynamic performance and smaller volume,NSGA-II genetic algorithm is applied to obtain the Pareto front of the desired *** assess the impact before and after optimization,an HSV based on the optimized structure is manufactured and *** experimental results show that the optimized HSV reduces 47.1%of its solenoid volume while improving opening and closing dynamic performance by 14.8%and 43.0%respectively,increasing maximum switching frequency by 6.2%,and expanding flow linear control area by 6.7%.These results validate the optimized structure and indicate that the optimization method provided in the paper is beneficial for developing superior HSV.

关键词： High speed on/off valve Dynamic response Volume Multiobjective optimization NSGA-II genetic algorithm

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New clues to jet launching: The inner disks in radio loud quasars may be more stable

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Science China(Physics,Mechanics & Astronomy) 2019年第6期62卷 108-121页

作者： ZhenYi Cai YuHan Sun junxian wang FeiFan Zhu WeiMin Gu Feng Yuan CAS Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China School of Astronomy and Space Science University of Science and Technology of China Department of Astronomy and Astrophysics 537 Davey Lab The Pennsylvania State University Department of Astronomy Xiamen University SHAO-XMU Joint Center for Astrophysics Xiamen University Shanghai Astronomical Observatory Chinese Academy of Sciences

Jet launching in radio loud(RL) quasars is one of the fundamental problems in astrophysics. Exploring the differences in the inner accretion disk properties between RL and radio quiet(RQ) quasars might yield helpful clues to this puzzle. We previously discovered that the shorter term UV/optical variations of quasars are bluer than the longer term ones, i.e., the so-called timescaledependent color variation. This is consistent with the scheme that the faster variations come from the inner and hotter disk regions,thus providing a useful tool to map the accretion disk which is otherwise unresolvable. In this work we compare the UV/optical variations of RL quasars in SDSS Stripe 82 to those of several RQ samples, including those matched in redshift-luminosity-black hole mass and/or color-magnitude. We find that while both RL and RQ populations appear bluer when they brighten, RL quasars potentially show a weaker/flatter dependence on timescale in their color variation. We further find that while both RL and RQ populations on average show similar variation amplitudes at long timescales, fast variations of RL sources appear weaker/smaller(at timescales of ～25-300 d in the observer's frame), and the difference is more prominent in the g-band than in the *** disk simulations can qualitatively reproduce these observed differences if the inner accretion disk of RL quasars fluctuates less based on simple toy models. Though the implications are likely model dependent, the discovery points to an interesting diagram that magnetic fields in RL quasars may be prospectively stronger and play a key role in both jet launching and the stabilization of the inner accretion disk.

关键词： accretion and accretion disks quasars galactic jets

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An Iterative Two-Grid Method of A Finite Element PML Approximation for the Two Dimensional Maxwell Problem

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Advances in Applied Mathematics and Mechanics 2012年第2期4卷 175-189页

作者： Chunmei Liu Shi Shu Yunqing Huang Liuqiang Zhong junxian wang Hunan Key Laboratory for Computation&Simulation in Science and Engineering and Key Laboratory of Intelligent Computing&Information Processing of Ministry of Education Xiangtan UniversityHunan 411105China School of Mathematical Sciences South China Normal UniversityGuangzhou 510631China

In this paper,we propose an iterative two-grid method for the edge finite element discretizations(a saddle-point system)of Perfectly Matched Layer(PML)equations to the Maxwell scattering problem in two ***,we use a fine space to solve a discrete saddle-point system of H(grad)variational problems,denoted by auxiliary system ***,we use a coarse space to solve the original saddle-point ***,we use a fine space again to solve a discrete H(curl)-elliptic variational problems,denoted by auxiliary system ***,we develop a regularization diagonal block preconditioner for auxiliary system 1 and use H-X preconditioner for auxiliary system *** we essentially transform the original problem in a fine space to a corresponding(but much smaller)problem on a coarse space,due to the fact that the above two preconditioners are efficient and *** with some existing iterative methods for solving saddle-point systems,such as PMinres,numerical experiments show the competitive performance of our iterative two-grid method.

关键词： Maxwell scattering edge finite element PML iterative two-grid method

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The transition from galaxy-wide gas inflow to outflow in quasar host galaxies

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Science China(Physics,Mechanics & Astronomy) 2024年第12期67卷 183-196页

作者： Zhicheng He Zhifu Chen Guilin Liu Tinggui wang Luis CHo junxian wang Weihao Bian Zheng Cai Guobin Mou Qiusheng Gu Zhiwen wang CAS Key Laboratory for Research in Galaxies and Cosmology Department of AstronomyUniversity of Science and Technology of ChinaHefei230026China Department of Physics Guangxi Minzu UniversityNanning530006China Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing100871China School of Physics Nanjing Normal UniversityNanjing210046China Department of Astronomy Tsinghua UniversityBeijing100084China School of Astronomy and Space Science Nanjing UniversityNanjing210093China

Galactic-scale outflows driven by active galactic nuclei(AGNs) represent a commonly invoked feedback mechanism within galaxy evolution ***,the interactions among interstellar gas on galactic scales,the propagation of AGN outflows,and the fundamental parameters of AGNs during their evolutionary processes remain poorly ***,powerful nuclear outflows are typically associated with the early stages of AGN activity,which are characterized by high accretion rates and weak narrow emission *** our analysis of a sample of quasars hosting Mg ii narrow absorption lines(NALs) obtained from the Sloan Digital Sky Survey,we identify a previously unobserved phenomenon wherein galaxy-scale inflow transitions to outflow dominance,concurrent with a notable increase in the strength of the narrow [O Ⅲ] line,achieving a confidence level of 6.7σ.This indicates that while nuclear outflows diminish,galaxy-wide outflows intensify as AGNs *** findings suggest that early-stage outflows interact with the interstellar medium on a galactic scale,thereby facilitating a gradual transition to galaxy-wide *** provides observational support for the hypothetical multi-stage propagation of AGN outflows that globally regulates galaxy evolution.

关键词： active galactic nuclei quasar galaxy winds galaxy evolution feedback

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A transformer generative adversarial network for multi-track music generation

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CAAI Transactions on Intelligence Technology 2022年第3期7卷 369-380页

作者： Cong Jin Tao wang Xiaobing Li Chu Jie Jiessie Tie Yun Tie Shan Liu Ming Yan Yongzhi Li junxian wang Shenze Huang School of Information and Communication Engineering Communication University of ChinaBeijingChina School of Information and Engineering Zhengzhou UniversityZhengzhouChina Central Conservatory of Music BeijingChina Department of computer Science University of TorontoTorontoCanada School of Data Science and Media Intelligence Communication University of ChinaBeijingChina School of Light Industry and Engineering South China University of TechnologyGuangzhouChina School of Animation and Digital Arts Communication University of ChinaBeijingChina

This study proposes a new generation network based on transformers and guided by the music theory to produce high-quality music *** this study,the decoding block of the transformer is used to learn the internal information of single-track music,and cross-track transformers are used to learn the information amongst the tracks of different musical instruments.A reward network based on the music theory is proposed,which optimizes the global and local loss objective functions while training and discriminating the network so that the reward network can provide a reliable adjustment method for the generation of the *** method of combining the reward network and cross entropy loss is used to guide the training of the generator and produce high-quality music *** with other multi-track music generation models,the experimental results verify the validity of the model.

关键词： artificial intelligence deep learning multimedia

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How to Choose Classroom Language in TEFL

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International English Education Research 2014年第9期 7-9页

作者： Liu Chong wang junxian wang Shenshen Cangzhou Vocational College of Technology Hebei Cangzhou 061001

In recent years, the choice of the classroom language has been developed. It has been proposed that English as a TL should be used exclusively in order to facilitate the learners＇ progress in English language acquisition. However it is unrealistic and undesirable to expect a generalist elementary school teacher to teach exclusively in English considering some settings which are shown in this paper. The paper concludes that both English and mother tongue can be used as CL.

关键词： classroom language TEFL English language acquisition mother tongue

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