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Model-independent determination on H_0 using the latest cosmic chronometer data

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Science China(Physics,Mechanics & Astronomy) 2017年第11期60卷 1-10页

作者： Deng Wang xin He meng Theoretical Physics Division Chern Institute of Mathematics Nankai University Department of Physics Nankai University

We perform the updated constraints on the Hubble constant H_0 by using the model-independent method, Gaussian *** the latest 30 cosmic chronometer measurements, we obtain H_0= 67.38 ± 4.72 km s^(-1)Mpc^(-1), which is consistent with the Planck 2015 and Riess et al. analysis at 1σ confidence level. Different from the results of Busti et al. by only using 19 H(z) measurements, our reconstruction results of H(z) and the derived values of H_0 are insensitive to the concrete choice of covariance functions of Matern family.

关键词： Hubble constant cosmic chronometers model-independent method

Evaluating the biotoxicity of surface water in a grassy lake in North China

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Journal of Environmental Sciences 2021年第4期33卷 316-325页

作者： xin meng Wenqiang Zhang Baoqing Shan State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of the Chinese Academy of Science Beijing 100049China

The biological toxicity of aquatic ecosystems should be considered when assessing the effects of toxicity on the water *** aim of this study was to identify the main pollutants in the Baiyangdian(BYD)and the factors that contribute to biological *** determined various physical and chemical indicators in the surface water of the BYD,including nutrients and heavy metals,and the biological *** also explored the sources of the main pollutants and how the pollutants contributed to toxicity in the lake,using correlation analysis and an index of the biological *** results showed that total nitrogen(TN),ammoniacal nitrogen(NH4^(+)-N),chromium(Cr),and zinc(Zn)were the main pollutants in the BYD surface *** average concentration of Cr was 2.3 times greater than the Class V threshold,and the concentrations at about 65%of the sampling points,mainly those in the southern part of the BYD,exceeded the threshold *** average concentration of Zn was 1.25 times higher than the Class V threshold,with the concentrations of about 35%of the samples greater than the threshold *** integrated toxicity of the surface water to luminescent bacteria ranged from 0.51%to 58%,and averaged 24.07%,which was within the range of moderate *** inhibition rates were high near Diantou(59%)and Duan(51.6%).The pollutant levels in the BYD tend to be related to the population density,with pollution mainly caused by sewage and domestic garbage,with little influence from local *** and TN were strongly correlated,but the biological toxicity was not correlated with any of the individual environmental indicators,which suggests that the toxicity in the surface water of the BYD reflected the combined effects of the environmental factors,rather than a single *** information from this study,about the main pollutants and the relationships between the physical and chemical properties of the surface water in the BYD,can be used to

关键词： Baiyangdian Typical pollutants Biotoxicity Risk assessment

Efficient co-channel interference suppression in MIMO-OFDM systems

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Science China(Information Sciences) 2015年第2期58卷 116-130页

作者： meng xin JIANG Bin GAO XiQi National Mobile Communications Research Laboratory Southeast University

In this paper, we investigate channel frequency response(CFR) matrix and interference-plus-noise covariance matrix(ICM) estimation in multiple-input multiple-output(MIMO) and orthogonal frequency division multiplexing(OFDM) systems to suppress co-channel interference at the receiver side. We employ least square criterion to perform the initial CFR estimation. Then we estimate the autocorrelation function of interference-plus-noise in the time domain, instead of estimating the ICM in the frequency domain *** autocorrelation function estimation has two steps. Firstly, we present the inherent relationship between the expectation of the sample autocorrelation function of the residual(SAFR) and the true autocorrelation function, which is actually a linear transformation. Based on this, we propose a compensating method. This compensation brings significant performance gains when the pilot OFDM symbol number is small. Secondly,since the compensated SAFR cannot be guaranteed to be an autocorrelation sequence(ACS), which will make the obtained ICM loss the positive semidefinite property, we utilize semidefinite programming(SDP) to find an ACS that is the nearest to the compensated SAFR. The SDP is solved in its dual form, which yields a significant reduced complexity. Finally the estimated ICM is reutilized to revise the CFR estimation. The estimated CFR and ICM show excellent interference suppression performances when being applied in an interference rejection combining receiver.

关键词： MIMO-OFDM channel estimation co-channel interference interference-plus-noise covariance ma-trix moving average autocorrelation sequence semidefinite programming interference rejection combining

Effect of hydrogen donating ability of benzofuranone on the antioxidant activity

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Chinese Science Bulletin 2010年第1期55卷 27-31页

作者： meng xin xin Zhong State Key Laboratory of Chemical Engineering and Product Engineering Department School of Chemical Engineering East China University of Science and Technology Shanghai 200237 China

The rate constants for the hydrogen donation of three 3-aryl-benzofuranone compounds with tert-butoxyl radicals have been cal-culated through laser flash photolysis (LFP) technique, which were used to evaluate the hydrogen donating abilities of those 3-aryl-benzofuranone compounds. The antioxidant activities of those 3-aryl-benzofuranone compounds in polypropylene (PP) have been studied using the oxidation induction time (OIT) of PP stabilized by those 3-aryl-benzofuranone compounds too. It has been found that the methyl group on the 2'-position can prevent the hydrogen donation of 3-aryl-benzofuranone with tert-butoxyl radicals and weakens the antioxidant activity of 3-aryl-benzofuranone in the oxidation of PP, i.e., the greater is the hydrogen do-nating ability of 3-aryl-benzofuranone with radicals, the better is the antioxidant activity of 3-aryl-benzofuranone in the oxidation of PP in the presence of oxygen.

关键词：苯并呋喃酮抗氧化活性能力氢氧化诱导时间抗氧化作用化合物聚丙烯

Traversable braneworld wormholes supported by astrophysical observations

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Frontiers of physics 2018年第1期13卷 109-118页

作者： Deng Wang xin-He meng Theoretical Physics Division Chern Institute of Mathematics Nankai University Tianjin 300071 China Department of Physics Nankai University Tianjin 300071 China

In this study, we investigate the characteristics and properties of a traversable wormhole constrained by the current astrophysical observations in the framework of modified theories of gravity （MOG）. As a concrete case, we study traversable wormhole space-time configurations in the Dvali-Gabadadze- Porrati （DGP） braneworld scenario, which are supported by the effects of the gravity leakage of extra dimensions. We find that the wormhole space-time structure will open in terms of the 2o confidence level when we utilize the joint constraints supernovae （SNe） Ia ＋ observational Hubble parameter data （OHD）＋ Planck ＋ gravitational wave （GW） and z 〈 0.2874. Furthermore, we obtain several model-independent conclusions, such as （i） the exotic matter threading the wormholes can be divided into four classes during the evolutionary processes of the universe based on various energy conditions; （ii） we can offer a strict restriction to the local wormhole space-time structure by using the current astrophysical observations; and （iii） we can clearly identify a physical gravitational resource for the wormholes supported by astrophysical observations, namely the dark energy components of the universe or equivalent space-time curvature effects from MOG. Moreover, we find that the strong energy condition is always violated at low redshifts.

关键词： braneworld model traversable wormholes astrophysical observations

Stellar population analysis on the stacked spectra of double-peaked emission-line galaxies

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Research in Astronomy and Astrophysics 2019年第9期19卷 37-54页

作者： meng-xin Wang A-Li Luo National Astronomical Observatories Chinese Academy of SciencesBeijing100101China University of Chinese Academy of Sciences Beijing100049China Department of Physics and Astronomy University of DelawareNewarkDE19716USA

Double-peaked emission-line galaxies have long been perceived as objects related to merging galaxies or other phenomena with disturbed dynamical activities, such as outflows and disk rotation. In order to find the connection between the unique activities happening in these objects and their stellar population physics, we study the stellar populations of the stacked spectra drawn from double-peaked emission-line galaxies in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) Data Release 4(DR4) and the Sloan Digital Sky Survey(SDSS) Data Release 7(DR7) databases. We group the selected double-peaked emission-line objects into 10 different types of pairs based on the Baldwin-Phillips-Terlevich(BPT) diagnosis for each pair of blueshifted and redshifted components, and then stack the spectra of each group for analysis. The software STARLIGHT is employed to fit each stacked spectrum, and the contributions of stars at different ages and metallicities are quantified for subsequent comparative study and analysis. To highlight the commonality and uniqueness in these double-peaked emitting objects, we compare the population synthesis results of the stacked spectra of double-peaked emission-line galaxies with those of their counterpart reference samples displaying single-peaked emission features. The reference samples are also selected from the LAMOST DR4 and SDSS DR7 databases. From the comparison results,we confirm the strong correlations between stellar populations and their spectral classes, and find that the double-peaked emitting phenomenon is more likely to occur in an ‘older’ stellar environment and the subgroups hosting different BPT components will show an obvious heterogeneous star formation history.

关键词： galaxies:evolution galaxies:stellar content

Comprehensive analysis of nitrogen distributions and ammonia nitrogen release fluxes in the sediments of Baiyangdian Lake, China

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Journal of Environmental Sciences 2019年第2期31卷 319-328页

作者： Yaoyao Zhu xin Jin Wenzhong Tang xin meng Baoqing Shan State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental SciencesChinese Academy of Sciences University of Chinese Academy of Sciences

The condition of Baiyangdian Lake(BYDL) will improve as the Xiongan New Area evolves and fulfills its role of easing overcrowding and supporting economic growth. Water and sediment samples from BYDL were analyzed to provide information on nitrogen(N) contamination in BYDL. The mean ammonium N(NH_4^+-N), nitrate N, and total N concentrations in the water samples were 0.36, 0.12, and 2.22 mg/L, respectively, and the ranges were 0.003–8.38, 0.06–0.30,and 1.25–10.34 mg/L, respectively. The N concentrations in water gradually increased from the north to the south of BYDL. Sediment at 90% of the sampling sites was in or above the moderately contaminated class(1000–2000 mg/kg) defined in US Environmental Protection Agency total N pollution standards. Positive NH_4^+-N fluxes were found for 28 of the 34 sediment core samples, so the potential for NH_4^+-N being released from sediment was relatively high. The NH_4^+-N fluxes were 5.35–48.76 mg/m^2/day, and the mean and maximum fluxes were 8.71 and 48.76 mg/m^2/day, respectively. Benthic organisms will be affected more by NH_4^+-N and NH_3·H_2O in the surface sediment pore water(mean concentrations 4.93 and 0.13 mg/L, respectively) than by the other forms of N.

关键词： Nitrogen Ammonia nitrogen Baiyangdian Lake Flux Sediment

Comparative Experimental and Numerical Study of Wave Loads on A Monopile Structure Using Different Turbulence Models

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China Ocean Engineering 2021年第4期35卷 554-565页

作者： ZENG xin-meng SHI Wei Constantine MICHAILIDES WANG Kai LI xin DeepWater Engineering Research Centre Dalian University of TechnologyDalian 116024China State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China Civil Engineering and Geomatics Cyprus University of TechnologyLimassol 2026Cyprus School of Marine Engineering and Technology Sun Yat-Sen UniversityZhuhai 51900China

This study numerically and experimentally investigates the effects of wave loads on a monopile-type offshore wind turbine placed on a 1:25 slope at different water depths as well as the effect of choosing different turbulence models on the efficiency of the numerical *** numerical model adopts a two-phase flow by solving Unsteady Reynolds-Averaged Navier−Stokes(URANS)equations using the Volume Of Fluid(VOF)method and three differentk-􀀀ωturbulence *** environmental conditions from the East China Sea are *** wave run-up and the wave loads applied on the monopile are investigated and compared with relevant experimental data as well as with mathematical predictions based on relevant *** numerical model is well validated against the experimental data at model *** use of different turbulence models results in different predictions on the wave height but less differences on the wave *** baseline k-􀀀ωturbulence model and Shear-Stress Transport(SST)k-􀀀ωturbulence model exhibit better performance on the prediction of hydrodynamic load,at a model-scale water depth of 0.42 m,while the laminar model provides better results for large water *** SST turbulence model performs better in predicting wave run-up for water depth 0.42 m,while the laminar model and standard k-􀀀ωmodel perform better at water depth 0.52 m and 0.62 m,respectively.

关键词： hydrodynamic loads turbulence models Morison equation wave run-up numerical wave tank monopile structure

Lamellar Spacing Selection in Regular Eutectic Solidification at Low Velocity

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Journal of Materials Science & Technology 2007年第6期23卷 851-854页

作者： Guanghui meng xin LIN Weidong HUANG State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi＇an 710072 China

Based on the Jackson and Hunt＇s analysis, the selection of lamellar spacing in regular eutectics was reexamined at low velocity. The isothermal assumption was released and the effective interface undercooling was determined by the weighted average of the eutectic phases. It is found that the lamellar spacing minimized the effective interface undercooling depends only on the intrinsic characteristics of a given system at a fixed velocity. In addition, the selection of lamellar spacing is related to the relationship between the average interracial undercoolings of the eutectic phases and the lamellar spacing. The selected lamellar spacing obviously deviated from that predicted by the Jackson and Hunt＇s analysis if the variation of the average interracial undercoolings of the solid phases with the lamellar spacing was markedly different at a constant growth rate.

关键词： Solidification Eutectic Lamellar spacing Undercooling