k=2t·3时不存在以(Fn-k,Fn,Fn)为边长的Fibonacci三角形

Fibonacci三角形是边长为Fibonacci数、面积为整数的三角形.利用平方剩余的方法得到:当k=2'·3时,不存在边长为(Fn-k,Fn,Fn)的Fibonacci三角形(k＜2).     

尾数恰含k个零的正Fibonacci数

根据正Fibonacci数Fn的标准分解式中,因子2和因子5的指数的性质,利用初等数论的知识,讨论了尾数恰含k个零的正Fibonacci数Fn的下标n的特征,并证明了:对于任意大的正整数k,都存在着尾数恰含k个零的正Fibonacci数.     

正Fibonacci数的标准分解式中因子2的指数

Fibonacci数列 {Fn}定义如下 :F0 =0 ,F1 =1,Fn + 1 =Fn +Fn -1 (n =1,2 ,… ) ,我们把 {Fn}中每一项Fn 叫做一个Fibonacci数 ,当n≥ 1时 ,称Fn 为正Fibonacci数 .关于正Fibonacci数的奇偶性及其中偶Fibonacci数中因子 2的指数 ,笔者在文 [1]中已有部分结果 (见下文中引理 1) ,即正Fibonacci数Fn 的奇偶性 ,由其下标n是否含因子 3来确定 ,且当n是一个奇数的 3倍时 ,Fn 的标准分解式中 ,因子 2的指数确定为1.本文所做的工作 ,是利用同余的知识 ,对于n是一个正偶数的 3倍时 ,Fn 的标准分解式中因子 2的指数给出一个准确的结果 .定理 1…     

利用Fibonacci数列解题

Fibonacci数列本身就有很大的魅力 ,吸引着许多数学爱好者去学习和研究 .这里我们将视角定位在如何利用该数列去解决一些数学竞赛中的问题 .Fibonacci数列是指由下面的递推式定义的数列 {Fn}:F0 =F1 =1,Fn + 2 =Fn+ 1 +Fn ,n =0 ,1,2 ,…可以利用特征方程的方法求出其通项公式 ,也可以用数学归纳法证出其许许多多的性质 .但在这里我们更多的是用到其本身 ,而不是它的性质 .例 1(第 5 2届波兰数学竞赛试题 )　考虑数列 {xn}:x1 =a ,x2 =b ,xn + 2 =xn + 1 +xn,n =1,2 ,… ,这里a ,b∈R .对任意c∈R ,如果存在k ,l∈N ,k≠l ,使得xk =xl=…     

Fibonacci数列的模数列的周期性

对于Fibonacci数列{Fn}以及给定的正整数m,由Fn关于模m的最小非负剩余an,构成一个新的数列{an},称为Fibonacci数列的模数列.本文利用初等数论的知识和数学归纳法,证明了Fibonacci数列的模数列是周期数列,并且是纯周期数列.     

正Fibonacci数的标准分解式中因子5的指数

根据Fibonacci数列的定义,利用初等数论的知识和数学归纳法,讨论了正Fibonacci数Fn的标准分解式中因子5的指数与下标n的关系,得到下列结论:正Fibonacci数Fn的标准分解式中因子5的指数,与下标n的标准分解式中因子5的指数一致.     

Fibonacci数的一组整除特征

Fibonacci数列 {Fn}定义如下 :F0 =0 ,F1=1 ,Fn +1=Fn+Fn - 1(n =1 ,2 ,… ,) ,我们把{Fn}中每一项Fn 叫做一个Fibonacci数 .本文将讨论Fibonacci数Fn 被某些整数整除的特征 .在其证明过程中所用到的关于整除、最大公约数、最小公倍数以及同余的一些简单性质 ,恕不一一列作引理 .此外 ,证明过程中还用到下列数据 :F0 =0 ,F1=1 ,F3=2 ,F4 =3,F5=5,F9=34,F10 =55,F15=6 1 0 ,F16 =987,F2 7=1 96 41 8,F2 8=31 781 1 ,等等 ,这些数据 ,都不难利用Fibonacci数列的定义直接计算得到 .以下的引理是后面定理的证明过程所必须的 .引理 1 […     

一个问题的解决

本文将解决文[1]末提出的如下问题： 问题1 求函数y-^n∑i=1Fi｜x-Fi｜的最小值，其中x∈R,{Fn}n≥0为Fibonacci数列，它由F0=0,F1=1,Fn＋2=Fn＋1＋Fn（n∈N）确定。     

Fibonacci数列与三道不等式的指数推广

著名的斐波那契 (Fibonacci)数列具有以下一个重要性质 :设 F1 =F2 =1 ,Fn 2 =Fn 1 Fn,n≥ 1 ,则Fn 3 =2 Fn 1 Fn.文 [1 ] [2 ] [3] [4]曾先后涉及到三道不等式 ,笔者发现其字母指数恰按斐波那契数列呈现 .请看 :问题 1　 (第 2 6届 USAMO赛题 )证明对所有正实数 a、b、c     

广义Fibonacci立方体的网络容错性质分析

主要研究广义Fibonacci立方体的容错直径和宽直径,证明了n维Fibonacci立方体网络的k-1容错直径和k宽直径都是n-1,其中k=[n/3].     

带有免疫和传染年龄的传染病模型

建立了带有免疫和传染年龄的传染病模型,这种传染病带有病原体Ⅰ或Ⅱ,病原体Ⅰ可发展为病原体Ⅱ,得到了无病平衡态全局稳定和局部稳定的条件.当病原体Ⅰ不发展为病原体Ⅱ时,得到了病原体Ⅰ类平衡态的稳定性依赖于病原体Ⅱ类的基本再生指数.     

Modelling and simulation of micro-well formation

Physico-chemical processes on the micro-scale require new modelling concepts because some effects become dominating that are negligible for macroscopic systems. This is illustrated by a new method for the production of micro-wells based on the placement of a small drop of toluene on a plate of polystyrene. After droplet evaporation, a micro-well is left. A mathematical model has been developed to understand the elementary processes of the micro-well formation. The model accounts for: (1) growth of the drop on the substrate, (2) evaporation process of the solvent, (3) dissolution of the substrate, (4) flow rate in the evaporating drop caused by the pinning effect, including the vertical velocity profile, and (5) increase in the concentration of dissolved material followed by precipitation. In the modelling and simulation process, it could be shown that the method of drop production also has a significant influence on the shape of the micro-wells.     

A perturbed risk model with dependence between premium rates and claim sizes

This paper considers a dependent risk model with diffusion for the surplus of an insurer, in which a current premium rate will be adjusted after a claim occurs and the adjusted rate is determined by the amount of the claim. At the same time, the diffusion is changed correspondingly. Using Rouché’s theorem, we first derive the closed-form solution for the Laplace transform of the survival probability in the dependent risk model. Then, using the Laplace transform, we derive a defective renewal equation satisfied by the survival probability. For the exponential claim sizes, we present the explicit recursion expression for the survival probability, by which we can exactly solve the survival probability step-by-step. We also illustrate the influence of the model parameters in the dependent risk model on the survival probability by numerical examples.     

Multi‐dimensional Lotka–Volterra systems for carcinogenesis mutations

In the paper we consider three classes of models describing carcinogenesis mutations. Every considered model is described by the system of (n+1) equations, and in each class three models are studied: the first is expressed as a system of ordinary differential equations (ODEs), the second—as a system of reaction–diffusion equations (RDEs) with the same kinetics as the first one and with the Neumann boundary conditions, while the third is also described by the system of RDEs but with the Dirichlet boundary conditions. The models are formulated on the basis of the Lotka–Volterra systems (food chains and competition systems) and in the case of RDEs the linear diffusion is considered. The differences between studied classes of models are expressed by the kinetic functions, namely by the form of kinetic function for the last variable, which reflects the dynamics of malignant cells (that is the last stage of mutations). In the first class the models are described by the typical food chain with favourable unbounded environment for the last stage, in the second one—the last equation expresses competition between the pre‐malignant and malignant cells and the environment is also unbounded, while for the third one—it is expressed by predation term but the environment is unfavourable. The properties of the systems in each class are studied and compared. It occurs that the behaviour of solutions to the systems of ODEs and RDEs with the Neumann boundary conditions is similar in each class; i.e. it does not depend on diffusion coefficients, but strongly depends on the class of models. On the other hand, in the case of the Dirichlet boundary conditions this behaviour is related to the magnitude of diffusion coefficients. For sufficiently large diffusion coefficients it is similar independently of the class of models, i.e. the trivial solution that is unstable for zero diffusion gains stability. Copyright © 2009 John Wiley & Sons, Ltd.     

A necessary and sufficient condition for the existence of an exponential attractor

We give a necessary and sufficient condition for the existence of an exponential attractor. The condition is formulated in the context of metric spaces. It also captures the quantitative properties of the attractor, i.e., the dimension and the rate of attraction. As an application, we show that the evolution operator for the wave equation with nonlinear damping has an exponential attractor.     

ON NEWMAN-TYPE RATIONAL INTERPOLATION TO ｜x｜ AT THE CHEBYSHEV NODES OF THE SECOND KIND

Recently Brutman and Passow considered Newman-type rational interpolation to ｜x｜ induced by arbitrary set of symmetric nodes in [-1,1] and gave the general estimation of the approximation error.By their methods one could establish the exact order of approximation for some special nodes. In the present paper we consider the special case where the interpolation nodes are the zeros of the Chebyshev polynomial of the second kind and prove that in this case the exact order of approximation is O（1/n｜nn）     

面向远海岛屿的救助基地选址优化模型及其算法

为解决在远海海域选择岛屿建设救助基地的方案优化问题,建立了基于GIS和智能算法的双目标优化模型,采用自适应拉伸的拥挤距离计算公式,设计了自适应精英保留策略对算法进行改进,通过剖析决策者选择最优方案的基本原则,得到了性价比最高的优化方案。最后,以我国南海南沙群岛选择岛屿建设救助基地的方案优化为例进行分析,得到了较好结果。为验证文中改进算法的有效性,选取多个不同规模的方案进行分析比较,结果显示本文提出的算法在优化结果及解的分布性等方面均更优。本文研究为我国海上岛屿救助基地选址和在资源有限的情况下如何科学配置救助船队提供了分析方法。     

基于韧性度的低轨卫星通信网络抗毁性度量及优化

低轨卫星通信网络的抗毁性是描述网络安全可靠的有效工具,在网络体系结构设计和路由策略等领域得到了广泛的应用。根据低轨卫星通信网络中卫星在轨道平面内移动,需要不断进行切换的特点,从建立抗毁性测度模型以及网络抗毁性优化两个角度来评估和提高网络抗毁性,提出一种基于韧性度的低轨卫星通信网络抗毁性度量方法。通过对移动模型以及切换模型的结构分析,对每种结构以一定概率出现的低轨卫星通信网络,应用韧性度函数,求得网络在某个时刻及某一段时间段内的抗毁性,并针对切换模型的不足之处进行优化,用赋权韧性度来体现优化的效果,得到了优化后的网络抗毁性。以铱星系统为应用实例进行仿真,结果表明:任意时刻网络的抗毁性跟拓扑结构的韧性度值有关,并且是一种线性关系,即随着韧性度的增加,其抗毁性也增加。通过对铱星通信系统切换模型的优化,网络的抗毁性与平均抗毁性都得到了提升,说明本文所构建模型的有效性和实用性。     

Computing a closest bifurcation instability in multidimensional parameter space

Summary Engineering and physical systems are often modeled as nonlinear differential equations with a vector λ of parameters and operated at a stable equilibrium. However, as the parameters λ vary from some nominal value λ₀, the stability of the equilibrium can be lost in a saddle-node or Hopf bifurcation. The spatial relation in parameter space of λ₀ to the critical set of parameters at which the stable equilibrium bifurcates determines the robustness of the system stability to parameter variations and is important in applications. We propose computing a parameter vector λ_* at which the stable equilibrium bifurcates which is locally closest in parameter space to the nominal parameters λ₀. Iterative and direct methods for computing these locally closest bifurcations are described. The methods are extensions of standard, one-parameter methods of computing bifurcations and are based on formulas for the normal vector to hypersurfaces of the bifurcation set. Conditions on the hypersurface curvature are given to ensure the local convergence of the iterative method and the regularity of solutions of the direct method. Formulas are derived for the curvature of the saddle node bifurcation set. The methods are extended to transcritical and pitchfork bifurcations and parametrized maps, and the sensitivity to λ₀ of the distance to a closest bifurcation is derived. The application of the methods is illustrated by computing the proximity to the closest voltage collapse instability of a simple electric power system.     

On the Index of Differential Operators on Manifolds with Conical Singularities

The paper contains the proof of the index formula for manifolds with conical points. For operators subject to an additional condition of spectral symmetry, the index is expressed as the sum of multiplicities of spectral points of the conormal symbol (indicial family) and the integral from the Atiyah–Singer form over the smooth part of the manifold. The obtained formula is illustrated by the example of the Euler operator on a two-dimensional manifold with conical singular point.