Hopf bifurcation near a double singular point

The nonlinear equation f(x,λ,) = 0, f:X × R²→X, where X is a Banach space and f satisfies a Z₂-symmetry relation is considered. Interest centres on a certain type of double singular point, where the solution x is symmetric and f_x has a double zero eigenvalue, with one eigenvector symmetric and one antisymmetric.

We show that under certain nondegeneracy conditions, which are stated both algebraically and geometrically, there exists a path of Hopf bifurcations or imaginary Hopf bifurcations passing through the double singular point, and for which x is not symmetric except at the double singular point. An easy geometrical test is found to decide which type of phenomenon occurs. A biproduct of the analysis is that explicit expressions are obtained for quantities which help to provide a reliable numerical method to compute these paths. A pseudo-spectral method was used to obtain numerical results for the Brusselator equations to illustrate the theory.     

矩形薄板的屈曲状态*

本文根据薄板的广义变分原理,用有限元法对单向受压矩形板的屈曲状态进行了讨论,并用延续算法获得了在不同边界条件下的屈曲状态.     

BIFURCATION SOLUTION BRANCHES AND ITS NUMERICAL ANALYSIS OF A SEMI-LINEAR ELLIPTIC PROBLEM

1　IntroductionConsider the parameter dependent equationu"+ (λ+ s(μ) ) f( u) -μsinx =0　 in ( 0 ,π)u( 0 ) =u(π) =0 ( 1 .1 )whereλ,μ∈R are parameters and f:R→R and S:R→R are smooth odd functions anda) f′( 0 ) =1 ,　　 b) f ( 0 )≠ 0 ,　　 c) s( 0 ) =0 ,　　 d) s′( 0 ) =1 . ( 1 .2 )Let S:u( x)→ u(π-x) ,Γ ={ S,I} ,then ( 1 .1 ) isΓ -equivariant.The equality ( 1 .2 a) isjust a normalization of f at x=0 .Otherwise,one may reseek the parameter x to ensure( 1 .2 a) .To simplify an…     

Multiplicity results for a class of fourth order semipositone m-point boundary value problems

Using bifurcation techniques, we investigate the existence of multiple solutions for a class of fourth order semipositone m-point boundary value problems. Our results improve those in the literature.     

Asymptotic bifurcation points, and global bifurcation of nonlinear operators and its applications

Using the cone theory and lattice structure, we discuss the existence of asymptotic bifurcation points and the global bifurcation of nonlinear operators which are not assumed to be cone mappings and may not be Frechet differentiable at points at infinity. As an application, the structure of the set of solutions of the superlinear Sturm-Liouville problems is investigated.     

简单高阶奇异性的数值模拟

本文对高阶奇异性的分歧数值计算问题进行了研究，构造了计算简单高阶分歧点的扩充系统，并数值模拟了相应的实际问题。     

一类典型分歧问题的初等识别方法

给出了一类典型分歧问题的初等识别方法．     

N阶分歧问题解的数值分析

本文构造了Ｎ阶分歧问题解分支扩充系统的有限维逼近形式最其解的存在性,并给出了解的误差估计。     

Dynamics of a population in two patches with dispersal

A two-dimensional discrete system of a species in two patches proposed by Newman et al. is studied. It is shown that the unique interior steady state is globally asymptotically stable if the active population has a Beverton–Holt type growth rate. If the population is also subject to Allee effects, then the system has two interior steady states whenever the density-independent growth rate is large. In addition, the model has period-two solutions if the symmetric dispersal exceeds a critical threshold. For small dispersal, populations may either go extinct or eventually stabilize. However, populations are oscillating over time if dispersal is beyond the critical value and the initial populations are large.     

8-形同宿轨道附近的同宿轨分支性质

In this paper we investigate the homoclinic bifurcation properties near an eight-figure homoclinic orbit of co-dimension two of a planar dynamical system. The corresponding local bifurcation diagram is also illustrated by numerical computation.     

迭代微分方程解的存在性及分支

本文讨论迭代微分方程ｘ（ｔ）＝ｆ（ｘ（ｔ），ｘ（ｘ（ｔ）））的解的性态，并在ｆ（ｘ（ｔ），ｘ（ｘ（ｔ）））＝（ｘ＾２（ｔ）－μ）ｘ（ｘ（ｔ））时研究解的分支问题，更正了现有文献中的错误，结出了正确，完整的结果。     

简单高阶分歧点的正则化

构造了计算简单高阶分歧点的扩充系统．     

A kind of bifurcation of limit cycle from a nilpotent critical point

In this paper, an interesting and new bifurcation phenomenon that limit cycles could be bifurcated from nilpotent node (focus) by changing its stability is investigated. It is different from lowing its multiplicity in order to get limit cycles. We prove that $n^2+n-1$ limit cycles could be bifurcated by this way for $2n+1$ degree systems. Moreover, this upper bound could be reached. At last, we give two examples to show that $N(3)=1$ and $N(5)=5$ respectively. Here, $N(n)$ denotes the number of small-amplitude limit cycles around a nilpotent node (focus) with $n$ being the degree of polynomials in the vector field.     

一类非线性方程分歧点的存在性

讨论多参数非线性方程F（λ，x）=0的分歧问题，给出了（λ0，0）是F（λ，x）=0的分歧点的一个充分条件．     

Box dimension of Neimark–Sacker bifurcation

In this article we show how a change of a box dimension of orbits of two-dimensional discrete dynamical systems is connected to their bifurcations in a non-hyperbolic fixed point. This connection is already shown in the case of one-dimensional discrete dynamical systems and Hopf bifurcation for continuous systems. Namely, at the bifurcation point the box dimension changes from zero to a certain positive value which is connected to the appropriate bifurcation. We study a two-dimensional discrete dynamical system with only one multiplier on the unit circle, and show a result for the box dimension of an orbit on the centre manifold. We also consider a planar discrete system undergoing a Neimark–Sacker bifurcation. It is shown that box dimension depends on the order of non-degeneracy at the non-hyperbolic fixed point and on the angle–displacement map. As it was expected, we prove that the box dimension is different in the rational and irrational case.     

包含极值点和分枝点的解曲线跟踪算法的摄动解法

本文提出了采用摄动格式求解非线性方程组的解曲线跟踪算法的计算格式.文中着重讨论了解曲线上非正则点的搜索,以及从这些非正则点——转向点或分枝点——继续跟踪超临界平衡路径的计算方法.文中把这一算法应用于弹性薄壳的屈曲分析。通过柱壳和环壳的算例得到它们的整个屈曲过程的平衡路径和变形形态.     

简单高阶对称破坏分歧点的研究

In this paper,the bifurcation problem g(x, λ) = 0 with symmetry con-dition is studied. An extended system is introduced for computing the simple high order symmetry-breaking bifurcation point. Numerical example is given. Key words Bifurcation problem, Symmetry-breaking bifurcation point, High order Singularities     

Global dynamics,forbidden set,and transcritical bifurcation of a one-dimensional discrete-time laser model

We study the dynamical properties about fixed points, the existence of prime period and periodic points, and transcritical bifurcation of a one-dimensional laser model in ${\mathbb{R}}^{+}$. For the special case, we explore the global dynamics about fixed points, boundedness of positive solution, construction of invariant rectangle, existence of prime period-2 solution, construction of forbidden set, the existence of a prime period and periodic points, and transcritical bifurcation of the discrete-time laser model. Finally, theoretical results are illustrated using numerical simulations.     

Singular Points in Electromechanical Systems and Their Determination

An approach to determine turning points in electromechanical systems is presented and applied to the determination of pull-in parameters. The pull-in phenomenon is an inherent instability in devices using electrostatic actuation where an electrostatic force works against an elastic restoring force. The paper presents a relation between multi-valued characteristics describing MEMS devices and weakly singular tracking problems. The technique of augmented systems that characterize turning points is applied to the analytical and numerical determination of pull-in parameters. The method is discussed using a computer algebra system and a VHDL-AMS simulation engine.     

COMPUTATION OF HOPF BRANCHES BIFURCATING FROM A HOPF/PITCHFORK POINT FOR PROBLEMS WITH Z_2-SYMMETRY

1.IntroductionThispaperisdevotedtothecalculatiollofT,ranchesofHopfpointswhichemallatefromacertaillsingularPointofatwopar:lmeterII()nlinearsystemwhereXisarealHillersspac(},Aabifllrcationparallleter,oranadditionalcontrolparameter,alldgisasnlootllmapping.\Nreassllllle(HI)gisA--synlnletric:thereexistsalillearoperators:X-Xsatisfying(I:identicaloperatorillX)Itiswellknottrnthat(1.2)irldllcestilesplittillgl)Th.firstauthorhasbeedsupportedbyar(>searchgralltoftileV'Olkswagen-StiftungWesaythatxiss…