基于生态竞争方程的企业竞争动态演化研究

从生态学视角来研究企业竞争的动态演化已成为一个研究热点,针对现有研究文献中只讨论二维系统的不足,以三个企业之间的竞争为例,构造了企业间竞争的三维模型,运用微分方程稳定性理论分析其稳定性,并由此揭示出企业间竞争的动力学机制.数值仿真结果表明,该三维模型能有效地模拟企业间竞争的动态演化规律.     

洪水作用下土石坝系统结构图仿真与渗流稳定性分析

为了研究土石坝在洪水作用下的渗流稳定性,依托实际水库工程,以土石坝的坝体为主体,重点考虑洪水、水库、泄洪洞模型输入输出的约束关系,建立了该土石坝洪水过程的结构图仿真模型,并计算得到了在典型洪水过程中水库水位变化曲线;在此基础上采用有限元法,考虑非饱和区的影响,对土石坝非稳定渗流场进行了模拟;利用暂态渗流场计算结果,运用Morgenstern-Price法计算分析了土石坝上、下游坝坡的稳定性。结果表明:上、下游坝坡的稳定系数变化趋势与库水位一致,即坝坡稳定系数随库水位的上升而增大,随库水位的下降而减小。库水位变化的结构图仿真、渗流计算、稳定系数计算构建了较为完整的解决方案,为洪水作用下的土石坝渗流稳定性分析提供了新的手段。     

Linear stability of a fluid channel with a porous layer in the center简

We perform a Poiseuille flow in a channel linear stability analysis of a inserted with one porous layer in the centre, and focus mainly on the effect of porous filling ratio. The spectral collocation technique is adopted to solve the coupled linear stability problem. We investigate the effect of permeability, σ, with fixed porous filling ratio ψ = 1/3 and then the effect of change in porous filling ratio. As shown in the paper, with increasing σ, almost each eigenvalue on the upper left branch has two subbranches at ψ = 1/3. The channel flow with one porous layer inserted at its middle （ψ = 1/3） is more stable than the structure of two porous layers at upper and bottom walls with the same parameters. By decreasing the filling ratio ψ, the modes on the upper left branch are almost in pairs and move in opposite directions, especially one of the two unstable modes moves back to a stable mode, while the other becomes more instable. It is concluded that there are at most two unstable modes with decreasing filling ratio ψ. By analyzing the relation between ψ and the maximum imaginary part of the streamwise phase speed, Cimax, we find that increasing Re has a destabilizing effect and the effect is more obvious for small Re, where ψ a remarkable drop in Cimax can be observed. The most unstable mode is more sensitive at small filling ratio ψ, and decreasing ψ can not always increase the linear stability. There is a maximum value of Cimax which appears at a small porous filling ratio when Re is larger than 2 000. And the value of filling ratio 0 corresponding to the maximum value of Cimax in the most unstable state is increased with in- creasing Re. There is a critical value of porous filling ratio （= 0.24） for Re = 500; the structure will become stable as ψ grows to surpass the threshold of 0.24; When porous filling ratio ψ increases from 0.4 to 0.6, there is hardly any changes in the values of Cimax. We have also observed that the critical Reynolds number is especially sensitive for small ψ where the fastest drop is observed, and there may be a wide range in which the porous filling ratio has less effect on the stability （ψ ranges from 0.2 to 0.6 at σ = 0.002）. At larger permeability, σ, the critical Reynolds number tends to converge no matter what the value of porous filling ratio is.     

二维扩散方程的单点子域精细积分法

建立了二维扩散方程的单点子域精细积分法,并通过稳定性分析,表明了单点子域精细积分法相对于差分法的优越性。     

X-90型荧光光谱仪在无机定性分析中的应用探讨

目前用于金、银、铂饰品检测的 X- 90荧光光谱仪 ,具有检测方法简便、快捷、准确、成本低、无损伤等优点 ,也可利用此仪器的特点 ,扩展测定范围。1　理论依据每一种物质都有其特定的原子结构。样品被某种激发源 (本机为2 4 1Am放射性同位素 )所发射的初级射线激发而自发地发射出其所含元素特征的荧光X射线。每个元素的特征荧光 X射线都具有特定的能量 ,探测这些特征荧光 X射线并识别其能量 ,就能识别出该被测样品中含有哪些主要元素。2　操作步骤按操作规程 ,打开仪器 ,以银、铜块校准峰位 (即谱峰尖顶所对应横座标的位置 ) ;将被测物放入…     

品味定性分析在物理解题中的妙用——一道选择压轴题的定性与定量求解

高考物理在考查知识的同时,注重考查能力,其中包括(定性与定量)分析综合能力和应用数学处理物理问题的能力.上海市宝山区2013届高三第一学期期末调研与江苏省扬州中学2013届高三第二学期质量检测卷选择题的压轴题则提供了很好的示范.在这里和大家一起赏析这道压轴题.【题目】如图1所示,在光滑的水平地面上有一     

STABILITY ANALYSIS OF NONLINEAR GALERKIN ＆ GALERKIN METHODS FOR NONLINEAR EVOLUTION EQUATIONS

Abstract. Ogr object in this artlcle is to describe tbe Galerkln scheme and nonlin-eax Galerkin scheme for the approximation of nonlinear evolution equations, and tostudy the stability of these schemes. Spatial discretizatlon can be pedormed by eitherGalerkln spectral method or nonlinear Galerldn spectral method; time discretizatlort isdone hy Euler sin.heine wklch is explicit or implicit in the nonlinear terms. According tothe stability analysis of the above schemes, the stability of nonllneex Galerkln methodis better than that of Galexkln method.     

Stability Analysis of Some Nonlinear Feedback Control Methods for Beam Halo-ChaosSuppression

Control of beam halo-chaos has been a very challenging subject for research in recent years, in which some nonlinear feedback methods have been developed for suppression of beam halo-chaos in high-current proton linear accelerators. However, stability analysis of such successful nonlinear feedback control methods has not yet been rigorously carried out, which remains an important open topic in the field. In this letter, we present a rigorous mathematical analysis of several nonlinear feedback control methods that are applied to control beam halo-chaos with great success on simulations.     

N种群周期系数非线性关系捕食—竞争系统的定性分析

本文应用比较定理，Ｂｒｏｕｗｅｒ不动点定理和Ｖ函数方法，讨论了Ｎ种群周期系数非线性关系捕食－竞争系统的正解的有界性，正周期解的存在性，正周期解的全局吸引性及唯一性。