检索结果-南通市图书馆

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

在线全文

学校读者我要写书评

暂无评论

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,{3. Department of Physics Institute of Theoretical Physics Beijing Normal University Beijing 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) = (0.3., 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

Estimate of Exponential Convergence Rate in Total Variation by Spectral Gap

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 1998年第1期14卷 9-16页

作者： Chen Mufa Department of Mathematics, beijing normal University, beijing 100875,{3. 北京师范大学数学系北京

This note is devoted to study the exponential convergence rate in the total variation for reversible Markov processes by comparing it with the spectral gap. It is proved that in a quite general setup, with a suitable restriction on the initial distributions, the rate is bounded from below by the spectral gap. Furthemore, in the compact case or for birth-death processes or half-line diffosions, the rate is shown to be equal to the spectral gap.

关键词： Total variation Spectral gap Markov processes

Convergence rates for reversible Markov chains without the assumption of nonnegative definite matrices

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 1979-1988页

作者： MAO Yong-Hua school of Mathematical Sciences,beijing normal University,Laboratory of Mathematics and Complex Systems,Ministry of Education,beijing 100875,china school of Mathematical Sciences Beijing Normal University Laboratory of Mathematics and Complex Systems Ministry of Education Beijing China

Explicit convergence rates in geometric and strong ergodicity for denumerable discrete time Markov chains with general reversible transition matrices are obtained in terms of the geometric moments or uniform moments of the hitting times to a fixed *** way by Lyapunov's drift conditions is also used to derive these convergence *** a typical example,the discrete time birth-death process(random walk) is studied and the explicit criteria for geometric ergodicity are presented.

关键词： Markov chain spectral theory convergence rate geometric ergodicity strong ergodicity Lyapunov’s condition

Estimation of Spectral Gap for Markov Chains

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 1996年第4期12卷 337-360页

作者： Chen Mufa Department of Mathematics beijing normal University beijing, {3. china Department of Mathematics Beijing Normal University Beijing China

The study of the convergent rate (spectra gap) in the L^2-sense is motivated from several different fields: probability statistics, mathematical physics, computer science and so on and it is now an artive research topic. Based on a new approach (the coupling technique) introduced in [7] for the estimate of the convergent rate and as a continuation of [4],[5],[7-9],[23. and [24], this paper studies the estimate of the rate for time-continuous Markov chains. Two variational formulas for the rate are presented here for the first time for birth-death processes. For diffusions, similar results are presented in an accompany paper [10]. The new formulas enable us to recover or improve the main known results. The connection between the sharp estimate and the corresponding eigenfunction is explored and illustrated by various examples. A previous result on optimal Markovian couplings is also extended in the paper.

关键词： Markov chains Spectral gap Couplings

Efficient estimation for additive hazards regression with bivariate current status data

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2012年第4期55卷 763-774页

作者： TONG XingWei 1,,HU Tao 2 & SUN JianGuo 3.4 1 school of Mathematical Sciences,beijing normal University,beijing 100875,china 2 school of Mathematical Sciences,Capital normal University,beijing 100048,china 3.school of Mathematics,Jilin University,Changchun 13.012.china 4 Department of Statistics,University of Missouri,Columbia,MO 65211,USA school of Mathematical Sciences Beijing Normal University Beijing China school of Mathematical Sciences Capital Normal University Beijing China school of Mathematics Jilin University Changchun China Department of Statistics University of Missouri Columbia USA

This paper discusses efficient estimation for the additive hazards regression model when only bivariate current status data are available. Current status data occur in many fields including demographical studies and tumorigenicity experiments （Keiding, 1991; Sun, 2006） and several approaches have been proposed for the additive hazards model with univariate current status data （Linet M., 1998; Martinussen and Scheike, 2002）. For bivariate data, in addition to facing the same problems as those with univariate data, one needs to deal with the association or correlation between two related failure time variables of interest. For this, we employ the copula model and an efficient estimation procedure is developed for inference. Simulation studies are performed to evaluate the proposed estimates and suggest that the approach works well in practical situations. An illustrative example is provided.

关键词： bivariate current status data copula model counting processes efficient estimation joint survivalfunction

Self-talk of Reflection Hologram During its construction

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Lasers 1996年第4期B5卷 334-340页

作者： LIU Dahe ZHOU Jing(Department of Physics, beijing normal University,beijing{3., china) beijing normal Univ Beijing China

Ｓｅｌｆ－ｔａｌｋｏｆＲｅｆｌｅｃｔｉｏｎＨｏｌｏｇｒａｍＤｕｒｉｎｇｉｔｓｃｏｎｓｔｒｕｃｔｉｏｎ￥ＬＩＵＤａｈｅ；ＺＨＯＵＪｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓ，ＢｅｉｊｉｎｇＮｏｒｍａｌＵｎｉｖｅｒｓ... 详细信息

Ｓｅｌｆ－ｔａｌｋｏｆＲｅｆｌｅｃｔｉｏｎＨｏｌｏｇｒａｍＤｕｒｉｎｇｉｔｓｃｏｎｓｔｒｕｃｔｉｏｎ￥ＬＩＵＤａｈｅ；ＺＨＯＵＪｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓ，ＢｅｉｊｉｎｇＮｏｒｍａｌＵｎｉｖｅｒｓｉｔｙ，Ｂｅｉｊｉｎｇ１００８７５...

关键词： reflection hologram hologram grating self-talk

Principle and application of three-band gradient difference vegetation index

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 Earth Sciences 2005年第2期48卷 241-249页

作者： TANG Shihao, ZHU Qijiang, WANG Jindi, ZHOU Yuyu & ZHAO Feng Research Center for Remote Sensing and GIS, Department of geography, beijing normal University,{3., china National Satellite Meteorological Center, china Meteorological Administration, beijing 100081, china Research Center for Remote Sensing and GIS Department of Geography Beijing Normal University Beijing China National Satellite Meteorological Center China Meteorological Administration Beijing China

Vegetation index is a simple, effective and experiential measurement of terrestrial vegetation activity, and plays a very important role in qualitative and quantitative remote sensing. Aiming at shortages of current vegetation indices, and starting from the analysis of vegetation spectral characteristics, we put forward a new vegetation index, the three-band gradient difference vegetation index (TGDVI), and established algorithms to inverse crown cover fraction and leaf area index (LAI) from it. Theoretical analysis and model simulation show that TGDVI has high saturation point and the ability to remove the influence of background to some degree, and the explicit functional relation with crown cover fraction and LAI can be established. Moreover, study shows that TGDVI also has the ability to partly remove the influence of thin cloud. Experiment in the Shunyi District, beijing, china shows that reasonable result can be reached using the vegetation index to retrieve LAI. We also theoretically analyzed the reason why the normalized difference vegetation index (NDVI) owns the low saturation point, and show that it is determined by the definition of NDVI and the characteristic of vegetation spectra, and is unavoidable to some degree. Meanwhile, through model simulation, we also indicate that the relationship between simple ratio vegetation index (SR) and LAI closes to a piecewise linear one instead of a linear one, which is mainly caused by the influence of background and different change rates of reflectance in red and infrared bands with LAI increasing.

关键词： vegetation index, remote sensing, LAI, crown cover fraction, remote sensing inversion.

Effect of Bcl-2 and caspase-3.on calcium distribution in apoptosis of HL-60 cells

在线全文

学校读者我要写书评

暂无评论

Cell Research 2000年第3期10卷 213-220页

作者： ZHANG MIN, HONG QING ZHANG, SHAO BAI XUE (Department of Biology, beijing normal University, beijing 100875,{3.) Department of Biology Beijing Normal University Beijing China

Apoptosis manifests in two major execution programs downstream of the death signal: the caspase pathway and organelle dysfunction. An important antiapoptosis factor, Bcl-2 protein, contributes in caspase pathway of apoptosis. Calcium, an important intracellular signal element in cells, is also observed to have changes during apoptosis, which maybe affected by Bcl-2 protein. We have previously reported that in Harringtonine (HT) induced apoptosis of HL-60 cells, there’s a change of intracellular calcium distribution, moving from cytoplast especially Golgi’s apparatus to nucleus and accumulating there with the highest concentration. We report here that caspase-3.becomes activated in HT-induced apoptosis of HL-60 cells, which can be inhibited by overexpression of Bcl-2 protein. No sign of apoptosis or intracellular calcium movement from Golgi’s apparatus to nucleus in HL-60 cells overexpressing Bcl-2 or treated with Ac-DEVD-CHO, a specific inhibitor of caspase-3. The results indicate that activated caspase-3.can promote the movement of intracellular calcium from Golgi’s apparatus to nucleus, and the process is inhibited by Ac-DEVD-CHO (inhibitor of caspase-3., and that Bcl-2 can inhibit the movement and accumulation of intracellular calcium in nucleus through its inhibition on caspase3. Calcium relocalization in apoptosis seems to be irreversible, which is different from the intracellular calcium changes caused by growth factor.

关键词： Apoptosis calcium caspase-3 bcl-2 laser scanning confocal microscopy (LSCM).

Superprocesses arising from interactive stochastic flows

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 2006年第4期49卷 451-476页

作者： YAN Guojun & LI Zhanbing Medical school, Shantou University, Shantou 515063. china Department of Mathematics, Bejing normal University,{3., china Medical school Shantou University Shantou China Department of Mathematics Bejing Normal University Beijing China

In this paper, we give a unified construction for superprocesses with dependent spatial motion constructed by Dawson, Li, Wang and superprocesses of stochastic flows constructed by Ma and Xiang. Furthermore, we also g... 详细信息

关键词： superprocess, interactive stochastic flows, martingale problem, dual processes.