方程Δx_n=r_nx_n(1-x_n)/(1 λx_n)的全局吸引性

考虑非自治差分方程Δxn =rnxn1-xn1 λxn,　n =0 ,1,2 ,…的全局吸引性 .这里 {rn}是正实数列 ,λ >0 .获得了方程每一解趋于 1的充分条件 .     

k-较多规则的理性条件

对于群体决策问题,证明了k-较多规则满足有关文献提出的关于序数型的匿名性、中立性、局部非独裁性及pareto原则等的理性条件,并给出了该规则的几个性质.     

包头市农民工生存状态调查研究

农民工是我国工业化和城镇化进程中产生的独特社会现象，他们对推动我国经济社会发展作出了积极的贡献。但这支劳动大军无论从自身的文化素质、技能水平、生活条件而言，还是从政府及社会的引导、管理、服务而言，都存在着一些亟需解决的问题。因此，他们面临种种生存压力，越来越成为和谐社会中不和谐的音符。     

点阵素单位与复单位中晶面指标的标定

本文就点阵素单位与复单位中晶面指标的标定问题，从点阵周期性的角度出发，作了一些讨论     

Transfer efficiency in ballistic electron emission microscopy taking diffraction of emitted hot electrons into account

We have analyzed the transfer efficiency of ballistic electron emission microscopy (BEEM), taking the finite spot size of the emitted electron beam from scanning probes into account. Three-dimensional diffraction from an aperture at a surface-metal/air interface is introduced to model an effect caused by the finiteness of spot size. As a general trend, the diffraction decreases BEEM transfer efficiency. The diffraction effect increases as the spot size decreases and the air-gap distance increases. In a Au/GaAs sample, BEEM transfer efficiency markedly deteriorates down to 6% of the value derived from a conventional planar tunneling theory when a spot size of 0.2 nm, an air-gap distance of 0.6 nm, and an electron energy of 0.2 eV, measured from the bottom of the GaAs conduction band, are assumed. BEEM transfer efficiency is markedly dependent on the spot size of the emitted hot electron. This result indicates that the BEEM current depends on the spatial resolution of the scanning probe, that is, the condition of the tip apex.     

Denumerable controlled Markov chains with average reward criterion: Sample path optimality

We consider discrete-time nonlinear controlled stochastic systems, modeled by controlled Makov chains with denumerable state space and compact action space. The corresponding stochastic control problem of maximizing average rewards in the long-run is studied. Departing from the most common position which usesexpected values of rewards, we focus on a sample path analysis of the stream of states/rewards. Under a Lyapunov function condition, we show that stationary policies obtained from the average reward optimality equation are not only average reward optimal, but indeed sample path average reward optimal, for almost all sample paths.Research supported by a U.S.-México Collaborative Research Program funded by the National Science Foundation under grant NSF-INT 9201430, and by CONACyT-MEXICO.Partially supported by the MAXTOR Foundation for applied Probability and Statistics, under grant No. 01-01-56/04-93.Research partially supported by the Engineering Foundation under grant RI-A-93-10, and by a grant from the AT&T Foundation.     

条件Erlang分布单参数加法定理的推广

X(γ)和Y(k)服从参数(γ,λ)和(k,μ)的Erlang分布且相互独立。本文利用条件分布知识证明了在X(γ)相似文献   

Unobserved Component models applied to the assessment of wear in railway points: A case study

Railways are experiencing a fundamental transformation. The introduction of high speed networks and the increased traffic levels on suburban routes and freight lines require new technologies for both railway infrastructure and trains, all of which must be subjected to rigorous quality control before and during operation and must be supported with effective maintenance processes during their operating lives. Safety in railway infrastructure provision must be ensured by all the main components operating reliably all the time. From an economic, quality and safety point of view, points are probably one of the most critical infrastructure elements in railway transportation.     

A 3D implementation of ray tracing combined with diffraction on facets: Verification and a potential application

A 3D implementation of a new model of light scattering applicable to dielectric faceted objects is introduced. The model combines standard geometric optics with diffraction on individual facets. It can be applied to any faceted geometry. The model adds no significant computational overheads to classical geometric optics yet provides much improved results. Initial results for long hexagonal columns are compared to SVM and appear favourable. 2D scattering patterns are calculated for a hexagonal column in a fixed orientation and compared to those created by ice analogue crystals in the laboratory with close agreement. The comparison includes the observation of a guided wave propagating along the length of the column. The new model is then applied to a selection of geometries to illustrate how it could be used to aid particle characterization, particularly in the case of cirrus ice.     

More precise determination of thermal lens focal length for end-pumped solid-state lasers

A method of more precise determination of the focal length of equivalent thermal lens (TL) is presented in this paper. The method is based on the diffraction theory of aberrations. By numerically calculating the optical path difference (OPD) distribution and the Strehl ratio, the focal lengths for “top-hat” pumping and Gaussian pumping are obtained and the equations for the focal lengths are presented by curve fitting. Also the equations for average pump radii are presented. The experiment on a fiber-coupled LD pumped Nd:YAG laser is carried out. The experimental results verify the validity of the method.