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A modified stochastic model for LS+AR hybrid method and its application in polar motion short-term prediction

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Geodesy and Geodynamics 2024年第1期15卷 100-105页

作者： fei ye Yunbin Yuan State Key Laboratory of Geodesy and Earth's Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430077China BeiDou High-precision Satellite Navigation and Location Service Hunan Engineering Research Center Hunan Institute of Geomatics Sciences and TechnologyChangsha 410007China Hunan Continuously Operating Reference Stations(HNCORS)Data Center Hunan Institute of Geomatics Sciences and TechnologyChangsha 410007China

Short-term(up to 30 days)predictions of Earth Rotation Parameters(ERPs)such as Polar Motion(PM:PMX and PMY)play an essential role in real-time applications related to high-precision reference frame ***,least squares(LS)+auto-regressive(AR)hybrid method is one of the main techniques of PM ***,the weighted LS+AR hybrid method performs well for PM short-term ***,the corresponding covariance information of LS fitting residuals deserves further exploration in the AR *** this study,we have derived a modified stochastic model for the LS+AR hybrid method,namely the weighted LS+weighted AR hybrid *** using the PM data products of IERS EOP 14 C04,the numerical results indicate that for PM short-term forecasting,the proposed weighted LS+weighted AR hybrid method shows an advantage over both the LS+AR hybrid method and the weighted LS+AR hybrid *** to the mean absolute errors(MAEs)of PMX/PMY sho rt-term prediction of the LS+AR hybrid method and the weighted LS+AR hybrid method,the weighted LS+weighted AR hybrid method shows average improvements of 6.61%/12.08%and 0.24%/11.65%,***,for the slopes of the linear regression lines fitted to the errors of each method,the growth of the prediction error of the proposed method is slower than that of the other two methods.

关键词： Stochastic model LS+AR Short-term prediction The earth rotation parameter(ERP) Observation model

Improved LS+MAR hybrid method to UT1-UTC ultra-short-term prediction by using first-order-difference UT1-UTC

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Geodesy and Geodynamics 2024年第4期15卷 379-385页

作者： fei ye Yunbin Yuan BeiDou High-precision Satellite Navigation and Location Service Hunan Engineering Research Center Hunan Institute of Geomatics Sciences and TechnologyChangsha410007China State Key Laboratory of Geodesy and Earth's Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan430077China HNCORS Data Center Hunan Institute of Geomatics Sciences and TechnologyChangsha 410007China

Accurate ultra-short-term prediction of the Earth rotation parameters(ERP)holds paramount impor-tance for real-time applications,particularly in reference frame *** them,diurnal rota-tion(UT1-UTC)which cannot be directly estimated through Global Navigation Satellite System(GNSS)techniques,significantly affects the rapid and ultra-rapid orbit determination of GNsS ***-ently,the traditional LS(least squares)+AR(autoregressive)and LS+MAR(multivariate autoregressive)hybrid methods stand as primary approaches for UT1-UTC ultra-short-term predictions(1-10 days).The LS+MAR hybrid method relies on the UT1-UTC and LOD(length of day)***,the correlation between LOD and first-order-difference UT1-UTC is stronger than that between LOD and *** light of this,and with the aid of the first-order-difference UT1-UTC,we propose an enhanced LS+MAR hybrid method to UT1-UTC ultra-short-term *** using the UT1-UTC and LOD data series of the IERS(International Earth Rotation and Reference Systems Service)EOP 14 C04 product,we conducted a thorough analysis and evaluation of the improved method's prediction performance compared to the traditional LS+AR and LS+MAR hybrid *** to the numerical results over more than 210 days,they demonstrate that,when considering the correlation information between the LoD and the first-order-difference UT1-UTC,the mean absolute errors(MAEs)of the improved LS+MAR hybrid method range from 21 to 934μs in 1-10 days *** comparison to the traditional LS+AR hybrid method,the MAEs show a reduction of 7-53μs in 1-10 days predictions,with corresponding improvement percentages ranging from 1 to 28%.Similarly,when compared to the traditional LS+MAR hybrid method,the MAEs have a reduction of 5-42μs in 1-10 days predictions,with corresponding improvement percentages ranging from 4-20%.Additionally,when aided by GNSS-derived LOD data series,the MAEs of improved LS+MAR hybrid method experience further

关键词： UT1-UTCultra-short-termprediction Rapidandultra-rapidproducts LS+AR and LS+MAR Correlation First-order-differenceUT1-UTC

General relative error criterion and M-estimation

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Frontiers of Mathematics in China 2013年第3期8卷 695-715页

作者： Ying YANG fei ye Department of Mathematical Sciences Tsinghua University Beijing 100084 China

Relative error rather than the error itself is of the main interest in many practical applications. Criteria based on minimizing the sum of absolute relative errors （MRE） and the sum of squared relative errors （RLS） were proposed in the different areas. Motivated by K. Chen et al.＇s recent work [J. Amer. Statist. Assoc., 2010, 105： 1104-1112] on the least absolute relative error （LARE） estimation for the accelerated failure time （AFT） model, in this paper, we establish the connection between relative error estimators and the M-estimation in the linear model. This connection allows us to deduce the asymptotic properties of many relative error estimators （e.g., LARE） by the well-developed M-estimation theories. On the other hand, the asymptotic properties of some important estimators （e.g., MRE and RLS） cannot be established directly. In this paper, we propose a general relative error criterion （GREC） for estimating the unknown parameter in the AFT model. Then we develop the approaches to deal with the asymptotic normalities for M-estimators with differentiable loss functions on R or R／{0} in the linear model. The simulation studies are conducted to evaluate the performance of the proposed estimates for the different scenarios. Illustration with a real data example is also provided.

关键词： Relative error accelerated failure time model M-estimation asymptotic normality general loss function

Carbon nanotubes-Nafion composites as Pt-Ru catalyst support for methanol electro-oxidation in acid media

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Journal of Natural Gas Chemistry 2009年第2期18卷 199-204页

作者： Shengzhou Chen fei ye Weiming Lin School of Chemistry and Chemical Engineering Guangzhou University Guangzhou 510006 Guangdong China School of Chemical and Energy Engineering South China University of Technology Guangzhou 510640 Guangdong China

Carbon nanotubes-Nafion （CNTs-Nation） composites were prepared by impregnated CNTs with Nation in ethanol solution and characterized by FT-IR. Pt-Ru catalysts supported on CNTs-Nafion composites were synthesized by microwave-assisted polyol process. The physical and electrochemical properties of the catalysts were characterized by X-ray diffraction （XRD）, transmission electron microscope （TEM）, CO stripping voltammetry, cyclic voltammetry （CV） and chronoamperometry （CA）. The results showed that the Nation incorporation in CNTs-Nation composites did not significantly alter the oxygen-containing groups on the CNTs surface. The Pt-Ru catalyst supported on CNTs-Nafion composites with 2 wt% Naton showed good dispersion and the best CO oxidation and methanol electro-oxidation activities.

关键词： carbon nanotubes-Nafion composites Pt-Ru catalysts methanol electro-oxidation

Convenient Synthesis of Two Novel Oxazolidines and Primary Research on their Biological Activities

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Chinese Chemical Letters 2006年第7期17卷 891-894页

作者： Ying Jiao LI fei ye College of Science Northeast Agricultural University Harbin 150030

Two novel N-dichloroacetyl oxazolidines were synthesized with a simple, mild and convenient method in good yields. The compounds were Characterized by IR, 1^H NMR and elemental analysis. The preliminary biological tes... 详细信息

关键词： Herbicide safener oxazolidines biological activity.

Mass flow in a circumbinary disk with a gap around supermassive binary black holes

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Research in Astronomy and Astrophysics 2013年第12期13卷 1455-1462页

作者： Ning-Yu Tang ye-fei Yuan Key Laboratory for Research in Galaxies and Cosmology Chinese Academy of Sciences Department of Astronomy University of Science and Technology of China

We study the interaction between supermassive binary black holes in an elliptical orbit and their surrounding disk with a gap. The gap in the disk is a low density region formed due to the tidal effects of the less massive black hole. The binary we have investigated has a sub-parsec separation and is coplanar with the disk. We find that the maximum variation of the surface density in the gap reaches 50% during an orbital period. However, in other regions of the disk, the density variation is much less than 1%. Furthermore, we calculate the corresponding variation of spectral energy distribution within a period, but little variation is found. The reason for these results is that the viscosity timescale of the disk at the binary radius is much longer than the orbital period of the binary.

关键词： binaries: close -- accretion disks -- methods: numerical

The study of proto-magnetar winds

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Research in Astronomy and Astrophysics 2010年第3期10卷 244-252页

作者： Yan-Jun Chen ye-fei Yuan Department of Physics and Electronic Science Changsha University of Science and Technology Changsha Hunan 410114 Center for Astrophysics University of Science and Technology of China Hefei 230026 China

The velocity profiles and properties of proto-magnetar winds are investigated. It is found that the corotation of wind matter with magnetic field lines significantly affects r-process nucleosynthesis and could lead to... 详细信息

关键词： stars: neutron -- stars: winds outflows -- supernovae: general -- stars magnetic fields -- nuclear reactions nucleosynthesis abundances

SIMULATION OF SOLUTE TRANSPORT IN A PARALLEL SINGLE FRACTURE WITH LBM/MMP MIXED METHOD

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Journal of Hydrodynamics 2008年第3期20卷 365-372页

作者： TAN ye-fei ZHOU Zhi-fang College of Civil Engineering Hohai University NanJing 210098 China

This article deals with the solute transport in a single fracture with the combination of the Lattice Boltzmann Method （LBM） and Modified Moment Propagation （MMP） method, and this mixed method is proved to have several advantages over the LBM and Moment Propagation （MP） mixed method which leads to negative concentrations under some conditions in computation. The disadvantage of LBM/MP has been overcome to a certain extent. Also, this work presents an LBM solution of modeling single fractures with uniformly or randomly distributed grains, which can provide a new path of applying the LBM in solute transport simulation in fractures.

关键词： Lattice Boltzmann Method (LBM) Modified Moment Propagation (MMP) method LBM/MMP mixed method single fracture solute transport rough fracture

Screening Effect in Isotropic Gaussian Processes

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Acta Mathematica Sinica,English Series 2020年第5期36卷 512-534页

作者： Jing Yu BAO fei ye Ying YANG Department of Mathematical Sciences Tsinghua UniversityBeijing 100062.P.R.China School of Statistics Capital University of Economics and BusinessBeijing 100026P.R.China

The screening effect is the phenomenon that optimal linear prediction of a spatial process on an unobserved location mostly depends on nearby *** is,the optimal predictor based on just nearby observations yields a good approximation of which based on the whole large ***,the approximation does not always perform well since the screening effect may not hold in all *** determine when the screening effect holds is an important issue in spatial *** paper provides some sufficient conditions for ensuring an asymptotic screening effect in Rd based on the spectral density of the underlying isotropic Gaussian process and the geometries of nearby *** results apply to isotropic processes with an arbitrary degree of *** we are predicting at origin,the conditions are(1)the spectral density is nearly a constant in balls of finite radius far from the origin,(2)the positions of nearby observations do not fall on a curve with non-zero intercept whose degree is less or equal to the order of mean square differentiability of the *** conditions are easy to verify in *** rates of the asymptotic screening effect are also *** rates depend on the rate of decrease of the spectral *** studies on the screening effect for finite samples are also provided.

关键词： Spatial statistics spectral analysis kriging screening effect