检索结果-南通市图书馆

Homotopy type of smooth weighted complete intersections

在线全文

学校读者我要写书评

暂无评论

Science china mathematics 2010年第6期53卷 1583-1594页

作者： wang JianBo1,& wang YuYu2 1department of mathematics,Tianjin {4.,Tianjin 300072,china 2College of Mathematical Science,Tianjin normal {4.,Tianjin 300387,china 1. department of mathematics Tianjin University Tianjin 300072 China2. College of Mathematical Science Tianjin Normal University Tianjin 300387 China

If the total degree d has no prime divisors less than(n+3)/2,then we prove that the homotopy type of complex odd dimensional smooth weighted complete intersection Xn(d;w) is determined by the dimension n,the total degree d,the Euler characteristic and the Kervaire invariant,provided that the weights w =(ω0,...,ωn+r) is pairwise relatively prime.

关键词： weighted projective space weighted complete intersection homotopy type connected sum

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 Mathematical Sciences, Capital normal university, Beijing 10004., china 2 {4. of mathematics, Zaozhuang university, Zaozhuang 277160, china 1. School of Mathematical Sciences Capital Normal University Beijing 100048 China2. Department of Mathematics Zaozhuang University Zaozhuang 277160 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 < ∞, and the Fourier partial summation operators and the Valle-Poussin operators are the asymptotically optimal linear operators and are as good as optimal nonlinear operators in the L q space for 1≤q < ∞.

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

Bloch constant of holomorphic mappings on the unit polydisk of C^n

在线全文

学校读者我要写书评

暂无评论

Science china mathematics 2008年第4期51卷 652-659页

作者： wang JianFei~(1+) LIU TaiShun~2 1 College of mathematics and Physics Information Engineering Zhejiang normal university Jinhua 321004.{4. 2 department of mathematics Huzhou Teachers College Huzhou 313000 {4. College of mathematics and Physics Information Engineering Zhejiang Normal University Jinhua China department of mathematics Huzhou Teachers College Huzhou China

In this paper,we give a definition of Bloch mappings defined in the unit polydisk D^n, which generalizes the concept of Bloch functions defined in the unit disk *** is known that Bloch theorem fails unless we have some restrictive assumption on holomorphic mappings in several complex *** shall establish the corresponding distortion theorems for subfamiliesβ(K)andβ_(loc)(K) of Bloch mappings defined in the polydisk D^n,which extend the distortion theorems of Liu and Minda to higher *** an application,we obtain lower and upper bounds of Bloch constants for various subfamilies of Bloeh mappings defined in D^*** particular,our results reduce to the classical results of Ahlfors and Landau when n=1.

关键词： Bloch constant Bloch mapping univalent ball critical point Julia lemma locally biholomorphic mapping Landau constant

CONVERGENCE IN THE CHEMOSTAT MODELWITH DELAYED RESPONSE IN GROWTH

在线全文

学校读者我要写书评

暂无评论

Systems Science and Mathematical Sciences 1999年第1期12卷 23-32页

作者： wang Wendi (department of mathematics, Southwest normal {4., Chongqing 4.0715, china)MA Zhien (department of mathematics, Xi’an Jiaotong {4., Xi’an 71004., china) 西南师范大学数学系重庆西安交通大学数学系陕西西安

The asymptotic behavior of solutions of a model for competition between two microorganisms in the chemostat is studied. The model incorporates time delays that allow for cellular components of each competing species to be structured to include unassimilated or stored nutrient and allow uptake functions to be nonmonotone. By introducing two auxiliary functions and using fluctuation lemma, it is shown that at most one competitor survives, and the substrate and the surviving competitor (if one exists), approach limiting values. Our results indicate this kind of time delays do not influence the competitive outcome except for a critical case. The main results of S. F. Ellermeyer[1] are improved on and extended.

关键词： Chemostat competition time delays global dynamics.

Modified Chaplygin gas as an interacting holographic dark energy model

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第4期53卷 598-606页

作者： WU YaBo, YANG WeiQiang, wang Cong & wang Lei department of Physics, Liaoning normal {4., Dalian 116029, china 1. department of Physics Liaoning Normal University Dalian 116029 China

The modified Chaplygin gas (MCG) as an interacting model of holographic dark energy in which dark energy and dark matter are coupled together is investigated in this paper. Concretely, by studying the evolutions of related cosmological quantities such as density parameter Ω, equation of state w, deceleration parameter q and transition redshift zT, we find the evolution of the universe is from deceleration to acceleration, their present values are consistent with the latest observations, and the equation of state of holographic dark energy can cross the phantom divide w = -1. Furthermore, we put emphasis upon the geometrical diagnostics for our model, i.e., the statefinder and Om diagnostics. By illustrating the evolutionary trajectories in r - s, r - q, w -w and Om planes, we find that the holographic constant c and the coupling constant b play very important roles in the holographic dark energy (HDE) model. In addition, we also plot the LCDM horizontal lines in Om diagrams, and show the discrimination between the HDE and LCDM models.

关键词： modified Chaplygin gas interacting holographic dark energy geometrical diagnostics

A new approach to the synthesis of diacetals(diketals) pentaerythritol catalyzed by SO_3H-functionalized ionic liquids

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2010年第5期21卷 524-528页

作者： Yuan Yuan wang,Yan Nan Xu,Zhi Zhong wang,Li Yi Dai Shanghai Key Laboratory of Green Chemistry and Chemical Process,department of Chemistry, east china normal university,Shanghai 200062,{4. [a] Shanghai Key Laboratory of Green Chemistry Chemical Process Department of Chemistry East China Normal University Shanghai 200062 China

In this article,an efficient,simple and environmentally friendly approach to the synthesis of diacetals(diketals) pentaerythritol using SOH-functionalized ionic liquids(ILs) as catalysts was *** ILs show high catalytic activity and reusability with good to excellent yields of the desired *** method has been used to determine the acidity order of these ionic liquids and the results are consistent with the catalytic activities observed in acetalization *** product yield of 93%was observed on using[PSPy][OTf]as catalyst and it can be reused at least 8 times without obvious activity loss.

关键词： SO3H-functionalized ionic liquids Diacetals(diketals) pentaerythritol Catalyze Hammett method Reusability

Denitrification in Chongming east tidal flat sediment, Yangtze estuary, china

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2006年第10期49卷 1090-1097页

作者： wang Dongqi1,2, CHEN Zhenlou1,3, XU Shiyuan1,2, HU Lingzhen1 & wang Jun1,2 1. College of Resources & Environment, east china normal university, Shanghai 200062, china 2. State Key Laboratory of Estuarine and Coastal Sediment Dynamics and Morphodynamics, east china normal university, Shanghai 200062, china 3. Key Laboratory of Geographical Information Science of Ministry of Education,east china normal university,Shanghai 200062, china 1. College of Resources & Environment East China Normal University Shanghai 200062 China 2. State Key Laboratory of Estuarine and Coastal Sediment Dynamics and Morphodynamics East China Normal University Shanghai 200062 China 3. Key Laboratory of Geographical Information Science of Ministry of Education East China Normal University Shanghai 200062 China

From July 2003 to July 2004. samples were collected on Chongming Island east tidal flat every two months. The research showed that the nitrous oxide (N2O) production rate was very low in the water, Chongming east tidal flat (CM) sediment was the N2O source of the water. Sediment N2O natural production rate was between -0.08 and 1.74.μmolN·m-2·h-1. N2O natural production rate was higher in the summer. The difference of the N2O natural production rate in the different tidal flats, the correlation between the N2O natural production rate and the denitrification rate, and those with the temperature and DO indicate that middle tidal flat sediment denitrification was the main process of the N2O production, while in the low tidal flat sediment, the production of the N2O came from several processes of the nitrogen cycling. Tidal flat sediment denitrification reaction was stronger in summer and winter but relatively lower in the late autumn and early spring. Seasonal change of the sediment denitrification rate was wide, from 1.12 to 33.34.μmolN·m-2·h-1. Temperature, DO and the coactions of them had the prominent effect on the tidal flat sediment denitrification.

关键词： Yangtze estuary, tidal flat sediment, denitrification, nitrous oxide, effect factor.

LARGE TIME BEHAVIOR OF SOLUTIONS TO NEWTONIAN FILTRATION EQUATIONS WITH SOURCES

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Scientia 2010年第3期30卷 968-974页

作者：王路生尹景学王泽佳 department of mathematics Jilin University department of mathematics South China Normal University

This article is concerned with large time behavior of solutions to the Neumann or Dirichlet problem for a class of Newtonian filtration equations ｜x｜λ＋Эt^-Эu=div（｜x｜^k∨u^m）＋｜x｜λ＋ku^p with 0 〈 m 〈 1,p 〉 1,λ≥0, k ∈ R. An interesting phenomenon is that there exist two thresholds k∞ and kl for the exponent k, such that the critical Fujita exponent pc for p exists and is finite if k E （k∞, k1）, otherwise, pc is infinite or does not exist.

关键词： Newtonian filtration equation critical exponent exterior problem Thresh -old

The empirical likelihood goodness-of-fit test for regression model

在线全文

学校读者我要写书评

暂无评论

Science china mathematics 2007年第6期50卷 829-840页

作者： Li-xing ZHU, Yong-song QIN & wang-li XU department of mathematics, Hong Kong Baptist university, Kowloon Tong, Hong Kong, {4. School of Mathematical Sciences, Guangxi normal Uinversity, Guilin 54.004. {4. School of Statistics, Renmin university of {4., Beijing 100875, {4. department of mathematics Hong Kong Baptist University Kowloon Tong Hong Kong China School of Mathematical Sciences Guangxi Normal Uinversity Guilin 541004 China School of Statistics Renmin University of China Beijing 100875 China

Goodness-of-fit test for regression modes has received much attention in literature. In this paper, empirical likelihood (EL) goodness-of-fit tests for regression models including classical parametric and autoregressive (AR) time series models are proposed. Unlike the existing locally smoothing and globally smoothing methodologies, the new method has the advantage that the tests are self-scale invariant and that the asymptotic null distribution is chi-squared. Simulations are carried out to illustrate the methodology.

关键词： regression model AR time series models empirical likelihood asymptotic normality goodness-of-fit 62G05 62G20 62G30