An improved evaluation of the neutron background in the PandaX-Ⅱ experiment

In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.     

On the solutions of the time-delayed Burgers equation

The time-delayed Burgers equation is introduced and the improved tanh-function method is used to construct exact multiple-soliton and triangular periodic solutions. For an understanding of the nature of the exact solutions that contained the time-delay parameter, we calculated the numerical solutions of this equation by using the Adomian decomposition method and the variational iteration method (IVM) to the boundary value problem.     

On social percolation and small world network

The social percolation model is generalized to include the propagation of two mutually exclusive competing effects on a one-dimensional ring and a two-dimensional square lattice. It is shown that the result depends significantly on which effect propagates first i.e. it is a non-commutative phenomenon. Then the propagation of one effect is studied on a small network. It generalizes the work of Moore and Newman of a disease spread to the case where the susceptibility of the population is random. Three variants of the Domany-Kinzel model are given. One of them (delayed) does not have a chaotic region for some value of the delay weight. Received 24 February 2000     

Percolation on Inhomogeneous Bethe Lattice and Forest Fire Models

The inhomogeneous Bethe lattice (IBL) is definedand studied. It is used to study the random neighbor forforest fire model, and we show that it is more realisticthan the Bethe lattice, and gives large probability for the subcritical case.     

A Numerical Calculation for Electron Impact Excitation of Copper

The scattering of electrons by atomic copper has been studied using Born approximation and the concept of the generalized oscillator strength (GOS). Differential and total cross-sections for the excitation of the 3d¹⁰ 4p² P state are calculated at incident energies of 100 eV and are compared with other available experimental and theoretical data. The agreement between our calculation for the differential cross-section and the available experimental results is fairly good at the forward angles, while the agreement at large angles is poor. The calculated total cross-sections are compared with the experimental data and those predicted by several theories. It is found that our calculation for the total cross-sections are in a good agreement with the close coupling calculation of Msezane and Henry (1986a, Physical Review A 33, 1631) for incident energies greater than 20 eV. The integrated cross-section measurements of Ismail and Teubner (1995, Journal of Physics B: Atomic, Molecular and Optical Physics 28, 4164) are in good agreement with the present calculation.     

关于中值定理中值点的渐近性质

在［１］中，ＢｅｒｎａｒｄＪａｃｏｂｓｏｎ研究了Ｒｉｅｍａｎｎ积分第一中值定理的中值点的渐近性质·本文讨论Ｒｉｅｍａｎｎ积分第二中值定理和微分中值定理的中值点的渐近性质．     

Dynamics and percolation in the immune system

The immune system is studied as a dynamical system. A lattice model for the immune system's memory without percolation is given. An upper limit for the probability of the existence of the memory state is derived. It agrees with the numerical results.     

基于3S的塔里木河中游景观格局变化特征分析

景观格局变化研究,是目前景观生态学的研究热点.本文把生态环境脆弱与人类活动的影响比较强烈的塔里木河中游选为研究靶区,利用遥感的手段获取试验区1973、1992和2000年景观格局的基础数据,在3S技术和景观生态学方法支持下,对塔里木河中游近30年土地利用和景观结构的时空变化特征进行了研究,对该地区的开发利用和生态环境保护提供科学依据.     

A Semigroup Approach to Queueing Systems

We prove asymptotic stability of the solutions of equations describing a simple queueing system consisting of two machines separated by a finite storage buffer. Following an approach by G. Gupur, we apply the theory of C₀-semigroups and spectral theory of positive operators.     

Percolation and Julia sets

The types of Julia sets for the renormalization group (RG) transformation for percolation on the hierarchial model are derived. The RG transformation for the concentration for two-dimensional triangular lattice site percolation problems and two-dimensional square lattice bond percolation problems are generalized to the complex plane. Julia sets for both cases are found.