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Progress in Natural Science:Materials International 2007年第10期17卷 1208-1212页

作者： Wang Jinbo, Qian Weihong and Zhang Xin(Monsoon and Environment Research Group, school of Physics, peking university, beijing 100871, china) Monsoon and Environment Research Group School of Physics Peking University Beijing 100871 China

Using the tropical cyclone (TC) data derived from the Joint Typhoon Warning Center (JTWC) and the sea surface temperature data derived from the Joint Environmental Data Analysis Center (JEDAC) at the Scripps Institute of Oceanography from January 1955 to December 2000, we analyzed the relationship between the TC genesis over the Northwest Pacific (NWP) and the sea surface temperature anomalies (SSTA) over the Pacific basin. A long-term trend indicated that the highest frequency of monthly TC genesis appeared earlier and the annual genesis sum increased gradually during the last half century with some oscillations. No significant synchronous correlation was found between the NWP TC events and the SSTA over the Pacific basin, while the annual sum of TC genesis was closely related with the SSTA averaged from the first three months (January, February and March) of the year in the equatorial western and eastern Pacific and over mid-high latitudes of the North Pacific. The results implied that there are an interannual El Nio SSTA mode in the equatorial western and eastern Pacific and an interdecadal SSTA mode in the northern Pacific, which affected the TC genesis. A regression analysis between the first three-month SSTA and the annual TC sum based on two time scales was conducted. The correlation coefficient between simulated and observed TC sums reached a high value of 0.77.

关键词： tropical cyclone long-term trend sea surface temperature Pacific.

Inclination of Broad Line Region in Narrow Line and Broad Line Seyfert 1 Galaxies

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Chinese Journal of Astronomy and Astrophysics 2002年第6期2卷 487-500页

作者： Tian-Zhi Zhang and Xue-Bing WuDepartment of Astronomy, school of Physics, peking university, beijing 100871 Department of Astronomy School of Physics Peking University Beijing 100871

The sizes of the Broad Line Region (BLR) of some Seyfert 1 galaxies and nearby quasars can be determined by the reverberation mapping method. Combining with the observed FWHM of Hbeta emission line and assuming that the motion of BLR clouds is virialized, the black hole masses of these objects have been estimated. However, this method strongly depends on the poorly-understood geometry and inclination of the BLR. On the other hand, a tight correlation between the black hole mass and the bulge velocity dispersion was recently found for both active and nearby inactive galaxies. This may provide another method, independent of the BLR geometry, for estimating the black hole mass. Using this method for estimating the black hole mass and combining with the measured BLR size and FWHM of Hbeta emission line, we derived the BLR inclination angles for 20 Seyfert 1 galaxies under the assumption that the BLR is disk-like. The derived inclination angles agree well with those derived previously by fitting the UV continuum and Hbeta emission line profiles. Adopting a relation between the FWHMs of [OIII]lambda5007 forbidden line and the stellar velocity dispersion, we also estimated the BLR inclinations for 50 narrow line Seyfert 1 galaxies (NLS1s). We found that the inclinations of broad Line Seyfert 1 galaxies (BLS1s) axe systematically greater than those of NLS1s, which seldom exceed 30degrees. This may be an important factor that leads to the differences between NLS1s and BLS1s if the BLR of NLS1s is really disk-like.

关键词： galaxies : active galaxies : nuclei galaxies : Seyfert

Entropy number and non-linear approximations on multivariate Besov space by manifolds of finite pseudo-dimension

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Progress in Natural Science:Materials International 2006年第3期16卷 260-265页

作者： LONG Jingfan and FANG Gensun (school of mathematical sciences, beijing Normal university, beijing 100875, china Department of Computer Science, Information Technology Institute, beijing 100101, china) school of mathematical sciences Beijing Normal University Beijing 100875 China Department of Computer Science Information Technology Institute Beijing 100101 China

We determine the asymptotic order of entropy number and optimal non -linear approximations of anisotropic periodic Besov class of Bpθr(Td') (1≤p≤∞,1≤0≤∞) by manifolds of finite pseudo-dimension in the metric Lq... 详细信息

关键词： Pseudo-dimension anisotropic Besov class of functions entropy number nonlinear width.

Study of the structure of unstable nuclei through the reaction experiments

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Science china(Physics,Mechanics & Astronomy) 2011年第S1期54卷 1-5页

作者： CAO ZhongXin & YE YanLin State Key Laboratory of Nuclear Physics and Technology, school of Physics, peking university, beijing 100871, china peking university State Key Laboratory of Nuclear Physics and Technology School of Physics Beijing China (GRID:grid.11135.37) (ISNI:***)

Along with the development of the radioactive nuclear beam facility, the study of the structure of unstable nuclei has progressed rapidly over the last few decades. Due to the weakly binding property, the structure information of the unstable nuclei comes primarily from the scattering or reaction experiments. Therefore it would be very important to understand clearly the reaction mechanism involved in the experiment. We outlined here the major reaction mechanisms which are adequate to the study of unstable nuclei, with the focus on the new phenomena and methods in comparison with those with traditional stable nucleus beam. Especially emphasized are the breakup and knockout reactions, developed as accurate tools for spectroscopy investigation into the nuclear structure with low intensity secondary beam. Couplings of the breakup channel to the elastic scattering and the fusion and transfer reactions are also reviewed.

关键词： binaries: unstable nuclei nuclear structure breakup reaction knockout reaction fusion reaction transfer reaction

Nonlinear autoregressive models with heavy-tailed innovation

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Science china mathematics 2005年第3期48卷 333-340页

作者： JIN Yang & AN Hongzhi school of Statistics, Renmin university of china, beijing 100872, china Academy of mathematics and Systems Science, Chinese Academy of sciences, beijing 100080, china Sch. of Statistics Renmin Univ. of China Beijing 100872 China Acad. of mathematics and Syst. Sci. Chinese Acad. of Sci. Beijing 100080 China

In this paper, we discuss the relationship between the stationary marginal tail probability and the innovation's tail probability of nonlinear autoregressive models. We show that under certain conditions that ensure the stationarity and ergodicity, one dimension stationary marginal distribution has the heavy-tailed probability property with the same index as that of the innovation's tail probability.

关键词： nonlinear autoregressive model, innovation, tail probability.

Can the inner gap sparking take place in millisecond pulsars?

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Chinese Journal of Astronomy and Astrophysics 2003年第5期3卷 443-452页

作者： Hong-Guang Wang, Guo-Jun qiao and Ren-Xin XuDepartment of Astronomy, peking university, beijing 100871 Department of Astronomy Peking University Beijing 100871

The inner vacuum gap model has become the foundation stone of most theorieson pulsar radio emission. The fundamental picture of this model is the sparking, which wasconjectured to be induced by magnetic absorption of background gamma photons. However, a questionis, can the sparking be triggered in the millisecond pulsars (MSPs) with magnetic fields (B) onlyabout 10~8 G? We investigate this problem by including the pair production above the inner *** the assumption that the magnetic field is dipolar, our results show the background gamma-rayemission can not be the key factor that triggers the sparking, at least not in MSPs with B ～ 10~8G, if the temperature in the polar cap region is only so high as is observed (< 4 x 10~6K). Someother mechanisms are required.

关键词： pulsar: general gamma rays magnetic fields

Finite time extinction of super-Brownian motions with deterministic catalyst

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Science china mathematics 2003年第4期46卷 538-551页

作者：任艳霞王永进 LMAM School of Mathematical Sciences Peking University Beijing 100871China school of mathematics Nankai UniversityTianjin 300071 China

In this paper we consider a super-Brownian motion X with branching mechanism k(x)z α, where k(x) > 0 is a bounded H?lder continuous function on ?d and ${}_{{}_x \in \mathbb{R}^d }k(x) = 0$ . We prove that ifk(x)?‖x‖?l (0?l<∞) for sufficiently large x, then X has compact support property, and for dimension d = 1, ifk(x)?exp(=?l‖x‖)(0?l<∞) for sufficiently large x, then X also has compact support property. The maximal order of k(x) for finite time extinction is different between d = 1, d = 2 and d ≥ 3: it isO(‖x‖?(α+1)) in one dimension,O(‖x‖?2(log ‖x‖))?(α+1)) in two dimensions, andO(‖x‖2) in higher dimensions. These growth orders also turn out to be the maximum order for the nonexistence of a positive solution for 1/2Δu=k(x)u α.

关键词： super-Brownian motion, compact support property, finite time extinction, positive solutions to nonlinear pde's.

Rate of strong consistency of quasi maximum likelihood estimate in generalized linear models

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Science china mathematics 2004年第6期47卷 882-893页

作者： YUE Li & CHEN Xiru school of mathematics and Statistics, Wuhan university, Wuhan 430072, china Graduate school, Chinese Academy of sciences, beijing 100039, china school of mathematics and Statistics Wuhan University Wuhan China Graduate school Chinese Academy of Sciences Beijing China

Under the assumption that in the generalized linear model (GLM) the expectation of the response variable has a correct specification and some other smooth conditions, it is shown that with probability one the quasi-likelihood equation for the GLM has a solution when the sample size n is sufficiently large. The rate of this solution tending to the true value is determined. In an important special case, this rate is the same as specified in the LIL for iid partial sums and thus cannot be improved anymore.

关键词： quasi-likelihood function generalized linear models strong consistency

A BATCH ARRIVAL RETRIAL QUEUE WITH STARTING FAILURES,FEEDBACK AND ADMISSION CONTROL

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Journal of Systems Science and Systems Engineering 2010年第3期19卷 306-320页

作者： Jinting WANG Peng-Feng ZHOU Department of mathematics,school of Science,beijing Jiaotong university,beijing,china Department of mathematics School of Science Beijing Jiaotong University Beijing China

This paper is concerned with the analysis of a feedback M^[X]/G/1 retrial queue with starting failures and general retrial times. In a batch, each individual customer is subject to a control admission policy upon arrival. If the server is idle, one of the customers admitted to the system may start its service and the rest joins the retrial group, whereas all the admitted customers go to the retrial group when the server is unavailable upon arrival. An arriving customer （primary or retrial） must turn-on the server, which takes negligible time. If the server is started successfully （with a certain probability）, the customer gets service immediately. Otherwise, the repair for the server commences immediately and the customer must leave for the orbit and make a retrial at a later time. It is assumed that the customers who find the server unavailable are queued in the orbit in accordance with an FCFS discipline and only the customer at the head of the queue is allowed for access to the server. The Markov chain underlying the considered queueing system is studied and the necessary and sufficient condition for the system to be stable is presented. Explicit formulae for the stationary distribution and some performance measures of the system in steady-state are obtained. Finally, some numerical examples are presented to illustrate the influence of the parameters on several performance characteristics.

关键词： Batch arrival feedback repair retrial queue starting failure

Mobius Isoparametric Hypersurfaces in S^(n+1) with Two Distinct Principal Curvatures

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Acta Mathematica Sinica,English Series 2002年第3期18卷 437-446页

作者： Hai Zhong LI Department of mathematics, Tsinghua university. beijing 100084. P. R. china Hui Li LIU Department of mathematics, Northeastern university. Shenyang 110000. P. R. china Chang Ping WANG Key Laboratory of Pure and Applied mathematics, school of mathematical sciences. peking university, beijing 100871, P. R. china Guo Song ZHAO Department of mathematics, Sichuan university, Chengdu 610064. P. R. china Department of mathematics Tsinghua University Beijing P. R. China Department of mathematics Northeastern University Shenyang P. R. China Key Laboratory of Pure and Applied mathematics School of Mathematical Sciences Peking University Beijing P. R. China Department of mathematics Sichuan University Chengdu P. R. China

A hypersurface x: M→S^(n+1) without umbilic point is called a Mbius isoparametric hypersurface if its Mbius form Φ=-ρ^(-2)∑_i(ei(H)+∑_j(h_(ij)-Hδ_(ij))e_j(logρ))θ_i vanishes and its Mbius shape operator S=ρ^(-1)(S-Hid) has constant eigenvalues. Here {e_i} is a local orthonormal basis for I=dx·dx with dual basis {θ_i}, II=∑_(ij)h_(ij)θ_iθ_J is the second fundamental form, H=1/n∑_i h_(ij), ρ~2=n/(n-1)(‖II‖~2-nH^2) and S is the shape operator of x. It is clear that any conformal image of a (Euclidean) isoparametric hypersurface in S^(n+1) is a Mbius isoparametric hypersurface, but the converse is not true. In this paper we classify all Mbius isoparametric hypersurfaces in S^(n+1) with two distinct principal curvatures up to Mbius transformations. By using a theorem of Thorbergsson [1] we also show that the number of distinct principal curvatures of a compact Mbius isoparametric hypersurface embedded in S^(n+1) can take only the values 2, 3, 4, 6.

关键词： Mobius geometry Isoparametric hypersurface Principal curvature