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Effects of sample density on the assimilation performance of an explicit four-dimensional variational data assimilation method

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Science China Earth Sciences 2009年第11期52卷 1849-1856页

作者： TIAN XiangJun xie zhengHui ICCES/LASE Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

The concepts of sample sphere radius and sample density are proposed in this paper to help illustrate that different vector transformations result in diverse sample density with the same sample ensemble, which finally affects their assimilation performance. Several numerical experiments using a onedimensional (1-D) soil water equation and synthetic observations are conducted to evaluate this new theory in land data assimilation.

关键词： POD/SVD-E4DVAr data assimilation sample density

Integral closure of a quartic extension

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Science China Mathematics 2015年第3期58卷 553-564页

作者： TAN ShengLi xie DaJun Department of Mathematics and Shanghai Key Laboratory of PMMP East China Normal University

Let r be a Noetherian unique factorization domain such that 2 and 3 are units,and let A=r[α]be a quartic extension over r by adding a rootαof an irreducible quartic polynomial p(z)=z4+az2+bz+c over *** will compute explicitly the integral closure of A in its fraction field,which is based on a proper factorization of the coefficients and the algebraic invariants of p(z).In fact,we get the factorization by resolving the singularities of a plane curve defined by z4+a(x)z2+b(x)z+c(x)=*** integral closure is expressed as a syzygy module and the syzygy equations are given *** compute also the ramifications of the integral closure over r.

关键词： algebraic invariants quartic extension integral closure discriminant syzygy

A preliminary study on spatial unmasking of virtual separated sources

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Science China(Physics,Mechanics & Astronomy) 2008年第10期51卷 1565-1572页

作者： xie zhiWen JIN Jing School of Physics South China University of TechnologyGuangzhou 510640China

An experimental method with headphone virtual reproduction is proposed and a series of experiments to study forward masking effect when the masker and the masked signal are spatially separated in azimuth are conducted. Then, the masking thresholds are compared with those when the masker and the masked signal source are at the same place. The results show that, although both the thresholds of 0° and ±30° sound images increase with the sound pressure level (SPL) of the masker, spatial unmasking may be really observed. The maximum unmasking is as large as 15 dB. This spatial unmasking effect is mainly attributed to better-ear contribution.

关键词： spatial unmasking virtual separated sources forward masking

On Constacyclic Codes over zp1p2…pt

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Chinese Annals of Mathematics,Series B 2019年第4期40卷 555-566页

作者： Derong xie Qunying LIAO College of Mathematical Science Sichuan Normal University

Let t ≥ 2 be an integer, and let p1, ···, ptbe distinct primes. By using algebraic properties, the present paper gives a sufficient and necessary condition for the existence of non-trivial self-orthogonal cyclic codes over the ring zp1p2···ptand the corresponding explicit enumerating formula. And it proves that there does not exist any self-dual cyclic code over zp1p2···pt.

关键词： Ideal Isomorphism Constacyclic code Self-orthogonal code Self-orthogonal cyclic code

An explicit four-dimensional variational data assimilation method based on the proper orthogonal decomposition: Theoretics and evaluation

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Science China Earth Sciences 2009年第2期52卷 279-286页

作者： TIAN XiangJun xie zhengHui Institute of Atmospheric Physics Chinese Academy of SciencesBeijing 100029China

The proper orthogonal decomposition (POD) method is used to construct a set of basis functions for spanning the ensemble of data in a certain least squares optimal sense. Compared with the singular value decomposition (SVD), the POD basis functions can capture more energy in the forecast ensemble space and can represent its spatial structure and temporal evolution more effectively. After the analysis variables are expressed by a truncated expansion of the POD basis vectors in the ensemble space, the control variables appear explicitly in the cost function, so that the adjoint model, which is used to de-rive the gradient of the cost function with respect to the control variables, is no longer needed. The application of this new technique significantly simplifies the data assimilation process. Several as-similation experiments show that this POD-based explicit four-dimensional variational data assimila-tion method performs much better than the usual ensemble Kalman filter method on both enhancing the assimilation precision and reducing the computation cost. It is also better than the SVD-based ex-plicit four-dimensional assimilation method, especially when the forecast model is not perfect and the forecast error comes from both the noise of the initial filed and the uncertainty of the forecast model.

关键词： POD data assimilation 4DVAr explicit method

Electronic Properties of BaTiO3 （110） Polar Terminations

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Chemical research in Chinese Universities 2014年第5期30卷 794-799页

作者： xie Ying YU Haitao Key Laboratory of Functional Inorganic Material Chemistry Ministry of EducationSchool of Chemistry and Materials Science Heilongjiang University Harbin 150080 P. R. China

The band structures, electron, density differences, and surface energies of five different BaTiO3 （110） ter- minations were investigated by first-principles calculations. According to the calculated results of electron density differences, the bonding characteristics of these considered terminations were discussed. The computational results indicate that the BaTiO-terminated surface is metallic, while the 02-, O-, Ba- and TiO-terminated surfaces are all in- sulative. Furthermore, the computed surface energies suggest that for the considered terminations, the polarity com- pensation achieved through surface reconstruction or surface defect is more effective than by change in surface elec- tronic structure. The defected or reconstructed terminations predominate over cleavage and construction of BaTiO3 crystal along （110） direction.

关键词： BaTiO3 (110) Polar surface Polar termination Polarity compensation

Thermal currents obtained and mutually switched by a modified Haldane model in graphene

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Communications in Theoretical Physics 2022年第3期74卷 119-129页

作者： Xiao-Long Lü Hang xie College of Science Guangxi University of Science and TechnologyLiuzhou 545006China College of Physics Chongqing UniversityChongqing 400000China Chongqing Key Laboratory for Strongly-Coupled Physics Chongqing UniversityChongqing 400000China

By using the transfer matrix method,we discover three types of current,such as the 100%spinvalley polarized current,pure spin-valley current and pure charge current,in a two-terminal graphene *** types of current can be obtained and mutually switched by modulating the parameters of the modified Haldane model(MHM).In our work,these types of current are driven by the thermal *** with this method of increasing the one-lead temperature(with a fixed temperature difference),the thermal currents can be more effectively strengthened by increasing the temperature difference(with a fixed one-lead temperature).In order to rapidly turn off these currents,we choose to enhance the intensity of the off-resonant circularly polarized light instead of canceling the temperature *** results indicate that the graphene system with the MHM has promising applications in the spin and valley caloritronics.

关键词： graphene modified Haldane model thermal currents

Possibility of Searching for Accreting White Dwarfs with the Chinese Space Station Telescope

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research in Astronomy and Astrophysics 2022年第5期22卷 21-27页

作者： Wei xie Hai-Liang Chen Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of the Chinese Academy of Sciences Beijing 100049China

Accreting WDs are very important for the studies of binary evolution,binary population synthesis and accretion *** far,there are a lot of accreting WD binaries with low accretion rates,such as cataclysmic variables,detected by different ***,few accreting WD binaries with high accretion rates have been *** this paper,we studied the spectrum properties of accreting WD binaries and investigated whether accreting WD binaries with high accretion rates can be detected by the Chinese Space Station Telescope(CSST).We found that some accreting WD binaries with high accretion rates can be distinguishable from other types of stars with(NUV-y,u-y),(NUV-r,u-g),(NUV-i,u-g),(NUV-z,u-g)and(NUV-y,u-g)color-color ***,some accreting WD binaries with high accretion rates can be detected by the CSST.

关键词： white dwarf stars whitedwarfs-binarystars close binarystars-low massstars low-massstar

A Note on 3-Divisibility of Class Number of Quadratic Field

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Chinese Annals of Mathematics,Series B 2022年第2期43卷 307-318页

作者： Jianfeng xie Kuok Fai CHAO Wu Wen-Tsun Key Laboratory of Mathematics School of Mathematical SciencesUniversity of Science and Technology of ChinaHefei 230026China Lui Che Woo College University of MacaoMacaoChina

In this paper,the authors show that there exists infinitely many family of pairs of quadratic fields Q(√D)and Q((√D+n)(1/2))with D,n∈z whose class numbers are both divisible by 3.

关键词： Quadratic field Class number Hilbert class field