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The stationarity and invertibility of a class of nonlinear ARMA models

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Science china Mathematics 2011年第3期54卷 469-478页

作者： CHEN DanQing1,2 & WANG HaiBin2 1department of Mathematics and physics, Fujian university of Technology, Fuzhou 350108, china 2 School of Mathematical Sciences, Xiamen university, Xiamen 361005, china 1. department of Mathematics and physics Fujian University of Technology Fuzhou 350108 China2. School of Mathematical Sciences Xiamen University Xiamen 361005 China

We investigate some probabilistic properties of a new class of nonlinear time series models. A sufficient condition for the existence of a unique causal, strictly and weakly stationary solution is derived. To understand the proposed models better, we further discuss the moment structure and obtain some Yule-Walker difference equations for the second and third order cumulants, which can also be used for identification purpose. A sufficient condition for invertibility is also provided.

关键词： auto-covariance invertibility stationarity time series Yule-Walker difference equation

An improved network layer protocol based on mobile IPv6

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Journal of Central South university 2001年第4期8卷 263-267页

作者： WANG Jian xin 1,HUANG Guo sheng 2,CHEN Song qiao 1,CHEN Jian er 1 (1.College of Information Science and Engineering, Central South university, Changsha 410083, china 2.department of physics and Electronic Engineering, Jishou university, Jisho 1. College of Information Science and Engineering Central South University 410083 Changsha China 2. department of physics and Electronic Engineering Jishou University 416000 Jishou China

The mobile IPv6 proposed by the IETF aims at providing mobility support on the next generation Internet. First, the authors described the basic principle of mobile IPv6 in brief and analyzed the advantages and disadvantages of it, presented a new idea of allocating a specific address space for mobile node (MN) and developed a new extension header and two ICMP message types for mobile IPv6. Lastly the authors proposed an optimization strategy for mobile IPv6 based on these extensions of protocol, which has the following advantages: 1) It is more convenient to manage the MNs because MN can be judged from its IP address; 2) When the correspondent node (CN) is not actively communicating with a MN, the MN and its home agent (HA) need not send Binding Update to the CN, and the CN need not send Binding Request to the MN. Only when the CN really wants to send a packet to the MN, will the CN voluntarily send a MN Discovery Request message to acquire the MN′s care of address. In this way,the transmission of Binding Update and Binding Request is greatly reduced, consequently the network overhead is also decreased; 3) While sending packets, the CN simply uses a MN Home Address Extension Header without using IPinIP encapsulation and routing header, which can reduce the redundant information in the packet and the message delay; 4) All the packets sent by the CN can be directly routed to the MN and the triangle routing can be completely avoided. By using these protocol extensions, the overhead of the network is greatly reduced and the network quality of services (QoS) is improved.

关键词： mobile IP home agent mobile node care of address binding

Applications of URANS on predicting unsteady turbulent separated flows

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Acta Mechanica Sinica 2009年第3期25卷 319-324页

作者： Jinglei Xu Huiyang Ma department of physics, Graduate university of the Chinese Academy of Sciences, 100049 Beijing, china department of physics Graduate University of the Chinese Academy of Sciences 100049 Beijing China

Accurate prediction of unsteady separated turbulent flows remains one of the toughest tasks and a practi cal challenge for turbulence modeling. In this paper, a 2D flow past a circular cylinder at Reynolds number 3,900 is numerically investigated by using the technique of unsteady RANS （URANS）. Some typical linear and nonlinear eddy viscosity turbulence models （LEVM and NLEVM） and a quadratic explicit algebraic stress model （EASM） are evaluated. Numerical results have shown that a high-performance cubic NLEVM, such as CLS, are superior to the others in simulating turbulent separated flows with unsteady vortex shedding.

关键词： URANS Nonlinear eddy viscosity turbulencemodel ,Separated flows Circular cylinder

Entanglement Involved in Pair Coherent State Studied via Wigner Function Formalism

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Communications in Theoretical physics 2009年第12期52卷 1071-1075页

作者： HU Li-Yun~(1,2)and FAN Hong-Yi~21 College of physics and Communication Electronics, Jiangxi Normal university, Nanchang 330022, china2.department of physics, Shanghai Jiao Tong university, Shanghai 200030, china College of physics and Communication Electronics Jiangxi Normal University Nanchang 330022 China department of physics Shanghai Jiao Tong University Shanghai 200030 China

We calculate Wigner function,tomogram of the pair coherent state by using its Schmidt decompositionin the coherent state *** turns out that the Wigner function can be seen as the quantum entanglement(QE)between two two-variable Hermite polynomials(TVHP)and the tomogram is further simplified as QE of twosingle-variable Hermite *** Husimi function of pair coherent state is also calculated.

关键词： pair coherent state Wigner function Tomogram Husimi function

Constraints of f(R) gravity in Palatini approach with observational Hubble data

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Science china(physics,Mechanics & Astronomy) 2011年第8期54卷 1378-1383页

作者： ZHAI ZhongXu & LIU WenBiao department of physics, Institute of Theoretical physics, Beijing Normal university, Beijing 100875, china 1. department of physics Institute of Theoretical Physics Beijing Normal University Beijing 100875 China

We use the newly released observational H(z) data (OHD), the Cosmic Microwave Background (CMB) shift parameter, and the Baryon Acoustic Oscillation (BAO) measurements data to constrain cosmological parameters of f(R) gravity in Palatini formalism in which the f(R) form is defined as f(R) = R β/Rn. Under the assumption of a spatially flat FRW universe, we get the best fitting results of the free parameters (Ωm0, n). In the calculation, we marginalize the likelihood function over H0 by integrating the probability density P ∝ e-χ2/2 to obtain the best fitting results and the confidence regions in the Ωm0-n plane. The constraints results of (Ωm0, n) = (0.33, 0.41) by OHD only and (Ωm0, n) = (0.23, 0.08) by the combination of OHD+CMB+BAO both indicate that the universe goes through three last phases, i.e., radiation dominated, matter-dominated, and late time accelerated expansion without introduction of dark energy.

关键词： f(R) gravity OHD CMB BAO accelerating expansion dark energy

X-ray spectra induced by slow highly charged Ar^(q+) ions in collision with Nb surface

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Science china(physics,Mechanics & Astronomy) 2008年第10期51卷 1463-1469页

作者： YANG ZhiHu1, CUI Ying2, CHEN XiMeng2, SONG ZhangYong1, SHAO JianXiong2, RUAN FangFang1, ZHANG HongQiang2, DU Juan2, LIU YuWen2, GAO ZhiMing2, ZHANG XiaoAn3, ZHU KeXin1, YU DeYang1 & CAI XiaoHong1 1 Institute of Modern physics, Chinese Academy of Sciences, Lanzhou 730000, china 2.department of Modern physics, Lanzhou university, Lanzhou 730000, china 3 department of physics, Xianyang Normal College, Xianyang 712000, china 1. Institute of Modern physics Chinese Academy of Sciences Lanzhou 730000 China 2. department of Modern physics Lanzhou University Lanzhou 730000 China 3. department of physics Xianyang Normal College Xianyang 712000 China

The X-ray spectra of Nb surface induced by Arq+ (q =16,17) ions with the energy range from 10 to 20 keV/q were studied by the optical spectrum technology. The experimental results indicate that the multi-electron excitation occurred as a highly charged Ar16+ ion was neutralized below the metal surface. The K shell electron of Ar16+ was excited and then de-excited cascadly to emit K X-ray. The intensity of the X-ray emitted from K shell of the hollow Ar atom decreased with the increase of projectile kinetic energy. The intensity of the X-ray emitted from L shell of the target atom Nb increased with the increase of projectile kinetic energy. The X-ray yield of Ar17+ is three magnitude orders larger than that of Ar16+.

关键词： highly charged ion hollow atom multi-electron X-ray

Micromagnetic Simulation of Demagnetization Curves for Single-Phase Nanocrystalline Nd-Fe-B Magnet

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Journal of Materials Science & Technology 2000年第2期16卷 107-108页

作者： Hanmin JIN, Sufen ZHAO and Xuefeng WANG (department of physics, Jinn university, Changchun 130012, china) department of physics Jilin University Changchun 130012 China

The demangetization curves for the nanocrystalline Nd-Fe-B magnets of the stoichiometric composition were calculated by using the finite element technique of micromagnetism. The curve, especially iHc become smaller with increase of *** most small iHc from a series of the curves along different field directions is closer to that for N=∞. iHc increases with increase of L, and are close cr some what smaller than that the experimental values should be.

关键词： Simulation Nd Fe

Views on “Principle of limitation of physical quantities and cyclic universe”

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Science china(physics,Mechanics & Astronomy) 2010年第9期53卷 1772-1774页

作者： LI LianGang department of physics,School of Sciences,Tianjin university,Tianjin 300072,china 1. department of physics School of Sciences Tianjin University Tianjin 300072 China

This paper presents an analysis of a paper entitled "Principle of limitation of physical quantities and cyclic universe" and proposes different results for some formulae from that *** addition,this paper shows that the principle of limits coupling may lead to an approximation of current theories(i.e.,quantum theory and relativistic theory),which have interesting correlations with the Plank formula and the special theory of relativity.

关键词： principle of limitation of physical quantities limits coupling formulae Plank formula theory of relativity

A fractal study for nucleate pool boiling heat transfer of nanofluids

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Science china(physics,Mechanics & Astronomy) 2010年第1期53卷 30-37页

作者： XIAO BoQi 1 , JIANG GuoPing 2 & CHEN LingXia 1 1 department of physics and Electromechanical Engineering, Sanming university, Sanming 365004, china 2 Earthquake Engineering Research Test Center, Guangzhou university, Guangzhou 510405, china 1. department of physics and Electromechanical Engineering Sanming University Sanming 365004 China2. Earthquake Engineering Research Test Center Guangzhou University Guangzhou 510405 China

In this paper, a fractal model for nucleate pool boiling heat transfer of nanofluids is developed based on the fractal distribution of nanoparticles and nucleation sites on boiling surfaces. The model shows the dependences of the heat flux on nanoparticle size and the nanoparticle volume fraction of the suspension, the fractal dimension of the nanoparticle and nucleation site, temperature of nanofluids and properties of fluids. The fractal model predictions show that the natural convection stage continues relatively longer in the case of nanofluids. The addition of nanoparticles causes a decrease of the pool nucleate boiling heat transfer. The nucleate pool boiling heat transfer coefficient is decreased by increasing particle concentration. An excellent agreement between the proposed model predictions and experimental data is found. The validity of the fractal model for nucleate pool boiling heat transfer is thus verified.

关键词： nanofluid nucleate pool boiling fractal heat transfer