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Classification study of WISE infrared sources:identification of candidate asymptotic giant branch stars

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Research in Astronomy and Astrophysics 2013年第3期13卷 323-333页

作者： Xun Tu zhong-xiang Wang Key Laboratory for Research in Galaxies and Cosmology and Shanghai Astronomical Observatory Chinese Academy of Sciences Graduate University of Chinese Academy of Sciences

In the Wide-field Infrared Survey Explorer （WISE） all-sky source catalog there are 76 million mid-infrared point sources that were detected in the first three WISE bands and have association with only one 2MASS near-IR source within 3. We search for their identifications in the SIMBAD database and find 3.2 million identified sources. Based on these known sources, we establish three criteria for selecting candidate asymptotic giant branch （AGB） stars in the Galaxy, which are three defined zones in a color-color diagram, Galactic latitude ｜b｜〈 20°, and ＂corrected＂ WISE third-band W3c≤ 11. Applying these criteria to the WISE＋2MASS sources, 1.37 million of them are selected. We analyze the WISE third-band W3 distribution of the selected sources, and further establish that W3〈8 is required in order to exclude a large fraction of normal stars from them. We therefore find 0.47 million candidate AGB stars in our Galaxy from the WISE source catalog. Using W3c, we estimate their distances and derive their Galactic distributions. The candidates are generally distributed around the Galactic center uniformly, with 68% （1-σ） of them within approximately 8 kpc. We discuss the idea that optical spectroscopy can be used to verify the C-rich AGB stars in our candidates, and thus a fraction of them （-10%） will be good targets for the Large Sky Area Multi-Object Fiber Spectroscopic Telescope （LAMOST） survey that is planned to start in fall of 2012.

关键词： stars: AGB and post-AGB -- infrared: stars -- stars: carbon

Exact Confidence Limits for the Parameter of an Exponential Distribution in the Accelerated Life Tests under Type-ⅠCensoring

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Acta Mathematicae Applicatae Sinica 2021年第2期37卷 393-408页

作者： De-qiang ZHENG xiang-zhong FANG School of Mathematical Sciences Peking UniversityBejing 100871China

Life data frequently arise in many reliability studies,such as accelerated life tests *** paper considers the part of life data where failure and censoring observations may *** develop statistical methods and theory for the analysis of these data,a new approach was proposed to obtain the exact lower and upper confidence limits for the mean life of the exponential distribution with Type-I censoring *** is assumed that the acceleration factor is a random variable,and that the distribution of the acceleration factor is known from some empirical information or the meta analysis.A method for constructing the lower and upper confidence limits for the parameter based on an ordering relation among the sample space was *** studies and analyses of two examples suggest that the proposed method performed well.

关键词： mean life confidence limit acceleration factor sample space ordering relation

A maximum a posteriori super resolution algorithm based on multidimensional Lorentzian distribution

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第12期10卷 1705-1713页

作者： Wen CHEN xiang-zhong FANG Yan CHENG Shanghai Key Lab of Digital Media Processing and Transmissions Institute of Image Communication and Information Processing Shanghai Jiao Tong University Shanghai 200240 China College of Information Technology East China University of Political Science and Law Shanghai 201620 China

This paper presents a threshold-free maximum a posteriori (MAP) super resolution (SR) algorithm to reconstruct high resolution (HR) images with sharp edges. The joint distribution of directional edge images is modeled as a multidimensional Lorentzian (MDL) function and regarded as a new image prior. This model makes full use of gradient information to restrict the solution space and yields an edge-preserving SR algorithm. The Lorentzian parameters in the cost function are replaced with a tunable variable, and graduated nonconvexity (GNC) optimization is used to guarantee that the proposed multidimensional Lorentzian SR (MDLSR) algorithm converges to the global minimum. Simulation results show the effectiveness of the MDLSR algorithm as well as its superiority over conventional SR methods.

关键词： Edge preservation Multidimensional Lorentzian distribution (MDL) Super resolution Threshold

Development of an ε-type actuator for enhancing high-speed electro-pneumatic ejector valve performance

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第11期9卷 1552-1559页

作者： zhong xiang Hao LIU Guo-Liang TAO Jun MAN Wei zhong State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

A novel ε-type solenoid actuator is proposed to improve the dynamic response of electro-pneumatic ejector valves by reducing moving mass weight. A finite element analysis (FEA) model has been developed to describe the static and dynamic operations of the valves. Compared with a conventional E-type actuator, the proposed ε-type actuator reduced the moving mass weight by almost 65% without significant loss of solenoid force, and reduced the response time (RT) typically by 20%. Prototype valves were designed and fabricated based on the proposed ε-type actuator model. An experimental setup was also established to investigate the dynamic characteristics of valves. The experimental results of the dynamics of valves agreed well with simulations, indicating the validity of the FEA model.

关键词： ε-type actuator High-speed electro-pneumatic ejector valve Finite element method Dynamic simulation and experiment

Dynamics of neutrino-driven winds:inclusion of accurate weak interaction rates in strong magnetic fields

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Research in Astronomy and Astrophysics 2013年第2期13卷 207-214页

作者： Men-Quan Liu zhong-xiang Wang Shanghai Astronomical Observatory Chinese Academy of Sciences Institute of Theoretical Physics China West Normal University

Solving Newtonian steady-state wind equations while considering the ac- curate weak interaction rates and magnetic fields （MFs） of young neutron stars, we study the dynamics and nucleosynthesis of neutrino-driven winds （NDWs） from proto neutron stars （PNSs）. For a typical 1.4 Mo PNS model, we find that the nucleosyn- thesis products are closely related to the luminosity of neutrinos and anti-neutrinos. The lower the luminosity is, the larger is the effect on the NDWs caused by weak in- teractions and MFs. At a high anti-neutrino luminosity of typically 8 × 1051 erg s-1, neutrinos and anti-neutrinos dominate the processes in an NDW and the MFs hardly change the wind＇s properties. But at a low anti-neutrino luminosity of 1051 erg s-1 at the late stage of an NDW the mass of the product and process of nucleosynthesis are changed significantly in strong MFs. Therefore, in most of the models considered for the NDWs from PNSs, based on our calculations, the influences of MFs and the net weak interactions on the nucleosynthesis are not significant.

关键词： nuclear reactions, nucleosynthesis, abundances -- hydrodynamics --stars neutrons

A new estimation of manganese distribution for local dwarf spheroidal galaxies

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Research in Astronomy and Astrophysics 2016年第9期16卷 137-144页

作者： Men-Quan Liu zhong-xiang Wang School of Physics and Space Science China West Normal University Shanghai Astronomical Observatory Chinese Academy of Sciences

The distribution of abundance for iron-peak elements in dwarf spheroidal galaxies （dSphs） is important for galaxy evolution and supernova （SN） nucleosynthesis. Nowadays, manganese （Mn） is one of the most observed iron-peak elements in local dSphs. Studies of its distributions allow us to derive and understand the evolution history of these dSphs. We improve a phenomenological model by a two-curve model including a new initial condition, that includes detailed calculations of SN explosion rates and yields. We compare the results with the observed Mn distribution data for three dSphs： Fornax, Sculpture and Sextans. We find that the model can describe the observed Fe and Mn distributions well simultaneously for the three dSphs. The results also indicate that the initial conditions should be determined by the low metallicity sam- ples in the beginning time of the galaxies and the previous assumption of metellicity-dependant Mn yield of SNIa is not needed when a wide mass range of core-collapse SNe is included. Our method is applicable to the chemical evolution of other iron-peak elements in dSphs and can be modified to provide more detailed processes for the evolution of dSphs.

关键词： galaxies dwarf-- galaxies individual (Fornax, Sculptor, Sextans) -- galaxies evolution --supernovae general

Searching forγ-ray counterparts to very faint X-ray transient neutron star binaries

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Research in Astronomy and Astrophysics 2018年第9期18卷 47-52页

作者： Ge-Ge Wang zhong-xiang Wang Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China University of Chinese Academy of Sciences Beijing 100049China

Very faint X-ray transients （VFXTs） are a group of X-ray binaries with low luminosities, displaying peak X-ray luminosities during their outbursts of only 1034-1036 erg s^-1. Using γ-ray data obtained with the Large Area Telescope （LAT） onboard the Fermi Gamma-Ray Space Telescope （Fermi）, we investigate their possible nature of containing rotation-powered pulsars, or more specifically being transitional millisecond pulsars （MSPs）. Among more than 40 known VFXTs, we select 12 neutron star systems. We analyze the LAT data for the fields of 12 VFXTs in the energy range 0.2-300GeV, but do not find any counterparts likely detected by Fermi. We obtain luminosity upper limits for the 12 sources. While the distances to the sources are largely uncertain, the upper limits are comparable to the luminosities of two transitional systems, PSR J1023-0038 and XSS J12270-4859. From our study, we conclude that no evidence is found at γ-rays for the suggestion that some VFXTs could contain rotation-powered MSPs （or be transitional MSP systems）.

关键词： stars pulsars - stars binaries - gamma rays stars

Possible modulated γ-ray emission from the transitional millisecond pulsar binary PSR J1023+0038

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Research in Astronomy and Astrophysics 2018年第10期18卷 109-116页

作者： Yi Xing zhong-xiang Wang Jumpei Takata Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences School of Physics Huazhong University of Science and Technology

We report the results from our analysis of Fermi Large Area Telescope （LAT） data for the transitional millisecond pulsar binary PSR J1023＋0038. The time period of the data is nearly 9 yr, and that after the source＇s transition, in June 2013 from the disk-free state to the active state of having an accretion disk, is approximately 4 yr. We identify a high-energy 〉5.5 GeV component in the source＇s spectrum in the active state, and find this component is only significantly detected in half of the orbital phase centered at the descending node （when the pulsar is moving towards the Earth）. Considering the pulsar scenario proposed for multi-frequency emission from the source, in which the pulsar is still active and a cold-relativistic pulsar wind inverse-Compton scatters the photons from the accretion disk, we discuss the origin of the high-energy component. In order to explain the observed spectrum, a power-law distribution of particles, with an index of ~3, in the pulsar wind is required, while the orbital variations are possibly due to changes in power-law index as a function of orbital phase.

关键词： gamma rays stars - binaries eclipsing - stars neutron

Degradation of 2,4-dichlorophenol with a novel TiO_2/Ti-Fe-graphite felt photoelectrocatalytic oxidation process

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Journal of Environmental Sciences 2007年第8期19卷 1020-1024页

作者： ZHAO Bao-xiu LI xiang-zhong WANG Peng School of Municipal and Environmental Engineering Harbin Institute of Technology Harbin 150090 China. Department of Civil and Structural Engineering The Hong Kong Polytechnic of University Hunghom Kowloon Hong Kong China

Degradation of 2,4-dichlorophenol （2,4-DCP） was studied in a novel three-electrode photoelectrocatalytic （PEC） integrative oxidation process, and the factors influencing the degradation rate, such as applied current, flow speed of O2, pH, adscititious voltage and initial 2,4-DCP concentration were investigated and optimized. H2O2 was produced nearby cathode and Fe^2＋ continuously generated from Fe anode in solution when current and O2 were applied, so, main reactions, H2O2-assisted TiO2 PEC oxidation and E-Fenton reaction, occurred during degradation of 2,4-DCP in this integrative system. The degradation ratio of 2,4-DCP was 93% in this integrative oxidation process, while it was only 31% in E-Fenton process and 46% in H2O2-assisted TiO2 PEC process. So, it revealed that the degradation of 2,4-DCP was improved greatly by photoelectrical cooperation effect. By the investigation of pH, it showed that this integrative process could work well in a wide pH range from pH 3 to pH 9.

关键词： 2,4-dicholrophenol TiO2 photoelectrocatalytic hydrogen peroxide E-Fenton