POSITIVE PERIODIC SOLUTION FOR A CLASS OF DIFFERENTIAL EQUATION WITH STATE-DEPENDENT DELAYS

By utilizing the Krasnoselskii's fixed point theorem in cones we obtain some sufficient conditions which guarantee the existence of positive periodic solution for a class of differential equations with state-dependent delays. The results in the papers [1,2] have been improved.     

Beam quality changes of Gaussian Schell-model beams propagating through axicons

Beam quality changes of Gaussian Schell-model (GSM) beams propagating through axicons are investigated in detail. The expressions showing beam quality changes of GSM beams are derived in terms of Wigner distribution function. It is shown that, when a GSM beam passes through a divergent or convergent axicon, the beam quality factor (M2 factor) becomes larger. The increment of the M2 factor is dependent on the incident beam size, wave number, refractive index of the axicon material and the angle of the axicon; but it is independent of the coherence of the beam. The explanation for the increment of the M2 factor is also given.     

实物期权定价与风险对冲方法研究

实物期权定价面临的一个主要问题是其基本资产不可交易问题，在这种情况下，通常的解决办法是在市场中寻找一个与该基本资产最为相关的可交易资产，利用可交易资产的价格信息来对特定实物期权进行定价和风险对冲．利用随机动态规划法，本文得到基本资产不可交易时实物期权的最优风险对冲策略，在一定条件下还可以得到近似定价．     

活性染料废水脱色正交试验设计与分析

使用正交试验设计方法设计出试验方案,对总体数据用方差分析等方法对选择方案进行期望评估,从而避免了常规试验中由于随机误差导致的判断失误,达到了试验效率非常高的效果.     

金属切削变形与显微高速摄影分析

运用显微高速摄影技术分析了切削过程中金属显微组织塑性变形规律。结果指出,切削中金属晶粒变形具有不均匀性和多晶体变形协调性,以晶粒为单元发生了波浪式起伏立体型变化,但受到晶界的制约。     

Multi-symplectic scheme for the coupled Schrdinger-Boussinesq equations

In this paper, a multi-symplectic Hamiltonian formulation is presented for the coupled Schrdinger-Boussinesq equations (CSBE). Then, a multi-symplectic scheme of the CSBE is derived. The discrete conservation laws of the Langmuir plasmon number and total perturbed number density are also proved. Numerical experiments show that the multi-symplectic scheme simulates the solitary waves for a long time, and preserves the conservation laws well.     

高阶抛物型方程的一族高精度恒稳差分格式

A family of three-layer implicit difference Schemes of high accuracy with two parameters for solving high order parabolic equationδu/δt=(-1)^m 1δ^2mu/δx^2m(where m is positive integers) are constructed. In the special case α=1/2, β=0, We obtain a two-layer difference scheme. These schemes are proved to be absolutely stable for arbiratily chosen non-negative parameters, And the order of the truncation error is O((△t)^2 (△x)^6). They are shown by numerical examples to be effective, and practice consistant with theoretical analysis.     

诺贝尔化学奖

介绍诺贝尔奖的由来、评选和颁奖仪式,总结了历年诺贝尔化学奖获奖名单。     

两个锰的18-氮杂金属冠醚-6配合物的合成、晶体结构和磁性质研究

以负三价、五啮的N-乙酰水杨酰肼(ashz^3-)作为配体,合成了二个大环六核氮杂金属冠醚[Mn^Ⅲ₆(ashz)₆(MeOH)₆]·6MeOH (1)和[Mn^Ⅲ₆(ashz)₆(DMF)₆]·3DMF (2)。晶体学数据是:配合物1,三方晶系,空间群R3,a=b=24.806(2),c=11.260(1)?,Z=3,μ=1.007mm^-1,R=0.0572,wR=0.1142;配合物2,三方晶系,空间群R3,a=b=26.629(3),c=23.298(4)?,Z=6,μ=0.856mm^-1,R=0.0671,wR=0.1661。这两个配合物属18-氮杂金属冠醚-6结构类型,冠醚分子具有晶体学C_3i对称性。配体ashz^3-通过它的肼基的N-N桥连金属原子,从而形成有中央空穴的六核锰的大环配合物。变温磁化率(4～275K)研究表明,配合物1中金属离子间存在着反铁磁性耦合。     

Photocatalytic intercalated material based on HLaNb<Subscript>2</Subscript>O<Subscript>7</Subscript> as host and Cd<Subscript>0.8</Subscript>Zn<Subscript>0.2</Subscript>S as guest

A novel photocatalytic material (Pt,Cd0.8Zn0.2S)/HLaNb2O7 was fabricated by successive intercalation and exchange reactions. The (Pt,Cd0.8Zn0.2S)/HLaNb2O7 possessed a gallery height less than 0.5 nm and showed a broad absorption with wavelength over 370-500 nm. Using (Pt,Cd0.8Zn0.2S)/HLaNb2O7 as catalyst, the photocatalytic H2 evolution was more than 160 cm3·h-1·g-1 in the presence of Na2S as a sacrificial agent under irradiation with wavelength more than 290 nm from a 100-W mercury lamp. Furthermore, the catalyst showed photocatalytic activity even under visible light irradiation.