检索结果-南通市图书馆

Intrinsic ultracontractivity on Riemannian manifolds with infinite volume measures

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2010年第4期53卷 895-904页

作者： wang fengyu 1,2.1 school of mathematical sciences,{2. normal University,beijing 100875,china 2.Department of Mathematics,Swansea University,Singleton Park,Swansea SA2.8PP,UK school of mathematical {2. Beijing Normal University Beijing China Department of Mathematics Swansea University Swansea UK

By establishing the intrinsic super-Poincar'e inequality,some explicit conditions are presented for diffusion semigroups on a non-compact complete Riemannian manifold to be intrinsically *** conditions,as well as the ... 详细信息

关键词： intrinsic ultracontractivity intrinsic super-Poincar’e inequality Riemannian manifold diffusion semigroup

Development and application of ergodicity model with FRCM and FLAR for hydrological process

在线全文

学校读者我要写书评

暂无评论

Science china(Technological sciences) 2009年第2期52卷 379-386页

作者： wang HongRui1, FENG QiLei2. LIN Xin3 & ZENG WenYi4 1 College of Water Science, Key Laboratory for Water and Sediment sciences of the Ministry of Education, {2. normal University, beijing 100875, china 2.school of Science, {2. Institute of Education, {2. 100011, china 3 school of mathematical sciences, {2. normal University, beijing 100875, china 4 College of Information Science and Technology, {2. normal University, beijing 100875, china College of Water Science Key Laboratory for Water and Sediment Sciences of the Ministry of Education Beijing Normal University Beijing China school of Science Beijing Institute of Education Beijing China school of mathematical {2. Beijing Normal University Beijing China College of Information Science and Technology Beijing Normal University Beijing China

In this paper, a new ergodic property analysis model of hydrological process is proposed based on fuzzy-rough c-means clustering (FRCM), autocorrelogram, and fuzzy least absolute regression (FLAR). A precipitation time series (1951―2.04) from Shanghai Hydrology Station is then analyzed with the model. The results show that the precipitation time series of April, May, June, and September has er-godic property. We conclude that in the long run, the precipitation of April, May, June, and September will not keep decreasing; it will converge to its mean value in some period.

关键词： hydrological process ergodic autocorrelogram fuzzy-rough c-means clustering fuzzy least absolute regression

Quenched moderate deviations principle for random walk in random environment

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2010年第8期53卷 1947-1956页

作者： HONG WenMing 1 & wang HuaMing 1,2.1 Key Laboratory of Mathematics and Complex Systems of Ministry of Education & {2. of mathematical sciences,beijing normal University,beijing 100875,china 2.Department of Basic Courses,Business College,beijing Union University,beijing 10002.,china Key Laboratory of Mathematics and Complex Systems of Ministry of Education & school of mathematical {2. Beijing Normal University Beijing China Department of Basic Courses Business College Beijing Union University Beijing China

We derive a quenched moderate deviations principle for the one-dimensional nearest random walk in random environment,where the environment is assumed to be stationary and *** approach is based on hitting time decompos... 详细信息

关键词： random walk in random environment moderate deviations principle hitting time

Problems in wavelet analysis of hydrologic series and some suggestions on improvement

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2007年第1期17卷 80-86页

作者： wang Hongrui, YE Letian, LIU Changming, YANG Chi and LIU Peng ( College of Water sciences, {2. normal University, beijing 100875, china Key Laboratory for Water and Sediment sciences, Ministry of Education, beijing 100875, china school of mathematical sciences, Peking University, {2. 100089, china College of Engineering sciences, University of Region, Canada) College of Water sciences Beijing Normal University Beijing 100875 China Key Laboratory for Water and Sediment sciences Beijing 100875 China school of mathematical {2. Peking University Beijing 100089 China College of Engineering sciences University of Region Canada

Applying the wavelet theory and methods to investigate the hydrologic processes such as precipitation and runoff is a hot field. However, several aspects in research are usually ignored: the effect of admissible condition of wavelet functions and the disturbance of noises for the detection of periods, the effect of the length of a hydrologic time-series on the final result, and the choice between the anomaly and the original time series for wavelet analysis. In this paper, these issues are fully discussed. Precipitation data from Lanzhou Precipitation Station are taken for case study. The result indicates that in the wavelet analysis of hydrologic series, denoise methods should be used to eliminate the influence of noises. The MexHat wavelet function satisfies the admissible condition, which ensures that the periodic properties of hydrologic processes can be well represented by using the MexHat wavelet for decomposition. The affected range of hydro-logic series which should be discarded before analysis is given. It is also suggested that the anomaly series should be used to highlight the actual undulation of the hydrologic series.

关键词： wavelet analysis hydrologic process admissible condition noise period.

Coexistence of unbounded solutions and periodic solutions of Liénard equations with asymmetric nonlinearities at resonance

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china Mathematics 2007年第8期50卷 1205-1216页

作者： Zai-hong wang school of {2. sciences,Capital normal University,beijing 100037,china school of mathematical {2. Capital Normal University Beijing China

In this paper, we deal with the existence of unbounded orbits of the mapping $$\left\{ \begin{gathered} \theta _1 = \theta + 2.\pi + \frac{1}{\rho }\mu (\theta ) + o(\rho ^{ - 1} ), \hfill \\ \rho _1 = \rho + c - \mu ... 详细信息

In this paper, we deal with the existence of unbounded orbits of the mapping $$\left\{ \begin{gathered} \theta _1 = \theta + 2.\pi + \frac2.{\rho }\mu (\theta ) + o(\rho ^{ - 1} ), \hfill \\ \rho _1 = \rho + c - \mu '(\theta ) + o(1), \rho \to \infty \hfill \\ \end{gathered} \right.$$ , where n is a positive integer, c is a constant and μ(θ) is a 2.-periodic function. We prove that if c > 0 and μ(θ) ≠ 0, θ, ∈ [0, 2.], then every orbit of the given mapping goes to infinity in the future for ρ large enough; if c 2.], then every orbit of the given mapping goes to infinity in the past for ρ large enough. By using this result, we prove that the equation x″+f(x)x′+ax +?bx ?+?(x)=p(t) has unbounded solutions provided that a, b satisfy $1/\sqrt a + 1/\sqrt b = 2.n$ and ?(x) satisfies some limit conditions. At the same time, we obtain the existence of 2.-periodic solutions of this equation.

关键词： Liénard equations unbounded solutions periodic solutions 34C11 34C2.

Characterization for commutators of n-dimensional fractional Hardy operators

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2007年第10期50卷 1418-1426页

作者： Zun-wei FU~(1,2. Zong-guang LIU~3 Shan-zhen LU~(1+) Hong-bin wang~3 ~1 school of {2. sciences,beijing normal University,beijing 100875,china ~2.Department of Mathematics,Linyi normal University,Linyi 2.6005,china ~3 Department of Mathematics,china University of Mining and Technology (beijing),beijing 100083,china school of mathematical {2. Beijing Normal University Beijing China Department of Mathematics Linyi Normal University Linyi China Department of Mathematics China University of Mining and Technology (Beijing) Beijing China

In this paper,it was proved that the commutator H_(β,b)generated by an n-dimensional fractional Hardy operator and a locally integrable function b is bounded from L^(p1)(R^n)to L^(p2.(R^n)if and only if b is a CMO(R^n)function,where 1/p1-1/p2.β/n,11<∞,0≤β<***, the characterization of H_(β,b)on the homogenous Herz space K_q^(α,p)(R^n)was obtained.

关键词： n-dimensional fractional Hardy operator, commutator, C(M)O function, homogeneous Herz space

Approximation of functions on the Sobolev space with a Gaussian measure

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2010年第2期53卷 373-384页

作者： wang HePing 1, ZHANG YanWei 2.& ZHAI XueBo 1 1 school of {2. sciences, Capital normal University, beijing 100048, china 2.Department of Mathematics, Zaozhuang University, Zaozhuang 2.7160, china school of mathematical {2. Capital Normal University Beijing China Department of Mathematics Zaozhuang University Zaozhuang China

We discuss the best approximation of periodic functions by trigonometric polynomials and the approximation by Fourier partial summation operators, Valle-Poussin operators, Ces`aro operators, Abel opera-tors, and Jackson operators, respectively, on the Sobolev space with a Gaussian measure and obtain the average error estimations. We show that, in the average case setting, the trigonometric polynomial subspaces are the asymptotically optimal subspaces in the L q space for 1≤q 1≤q < ∞.

关键词： average width best approximation approximation by linear operators Sobolev space Gaussian measure

Morphology and valence state evolution of Cu:Unraveling the impact on nitric oxide electroreduction

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2024年第4期91卷 276-286页

作者： Ting Sun fengyu Gao Ya wang Honghong Yi Qingjun Yu Shunzheng Zhao Xiaolong Tang school of Energy and Environmental Engineering University of Science and Technology BeijingBeijing 100083China

Ammonia(NH3)serves as a critical component in the fertilizer industry and fume gas ***,the conventional NH3production process,namely the Haber-Bosch process,leads to considerable energy consumption and waste gas *** address this,electrocatalytic nitric oxide reduction reaction(NORR)has emerged as a promising strategy to bridge NH3consumption to NH3production,harnessing renewable electricity for a sustainable ***(Cu)stands out as a prominent electrocatalyst for NO reduction,given its exceptional NH3yield and ***,a crucial aspect that remains insufficiently explored is the effects of morphology and valence states of Cu on the NORR *** this investigation,we synthesized CuO nanowires(CuO-NF)and Cu nanocubes(Cu-NF)as cathodes through an in situ growth ***,CuO-NF exhibited an impressive NH3yield of 0.50±0.02.mg cm^(-2.h^(-1)at-0.6 V *** hydrogen electrode(RHE)with faradaic efficiency of2.,68%±1,35%,surpassing that of Cu-NF(0.17±0.01 mg cm^(-2.h^(-1),16.18%±1.40%).Throughout the electroreduction process,secondary cubes were generated on the CuO-NF surface,preserving their nanosheet cluster morphology,sustained by an abundant supply of subsurface oxygen(s-O)even after an extended duration of 10 h,until s-O depletion ***,Cu-NF exhibited inadequate s-O content,leading to rapid crystal collapse within the same *** distinctive current-potential relationship,akin to a volcano-type curve,was attributed to distinct NO hydrogenation *** Tafel analysis revealed the exchange current density(i0)and standard heterogeneous rate constant(k0)for CuO-NF,yielding 3.44×10^(-6)A cm^(-2.and 3.77×10^(-6)cm^(-2.s^(-1)when NORR was driven by *** findings revealed the potential of CuO-NF for NO reduction and provided insights into the intricate interplay between crystal morphology,valence states,and electrochemical performance.

关键词： NORR Ammonia Synthesis Copper Morphology Valence States Mechanism

Suitability evaluation for land reclamation in mining area:A case study of Gaoqiao bauxite mine

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 2011年第S3期21卷 506-515页

作者： wang Shi-dong1, 2. LIU Chang-hua2. ZHANG He-bing2.1. College of Resources Science and Technology, {2. normal University, beijing 100875, china 2. school of Surveying and Land Information Engineering, Henan Polytechnic University, Jiaozuo 454000, china College of Resources Science and Technology Beijing Normal University Beijing 100875 China school of Surveying and Land Information Engineering Henan Polytechnic University Jiaozuo 454000 China

Suitability evaluation plays an important role in land reclamation because the choice of evaluation methods affects the accuracy and objectivity of the suitability evaluation results. Furthermore, it influences the decision-making related to land reclamation. An improved method, which is called limit comprehensive conditions method, was developed after different suitability evaluation methods were studied. Based on this method, the reclaimed land of the Gaoqiao bauxite mining area was evaluated. The Gaoqiao mining area was divided into seven evaluation units that were evaluated respectively by selecting evaluation factors and establishing grade standards. The results show that the proposed method is more applicable and easier to handle. Moreover, its evaluation results are more scientific compared with the traditional evaluation methods. The improved method can be beneficial to the rapid monitoring and the effective management of reclaimed land in the opencast mine area.

关键词： mining area land reclamation suitability evaluation Gaoqiao bauxite mine