极限环

A methodology of noise-like key generation is presented. Chaotic process of tentmap function is used as a deterministic generation of noise-like key, image storage and retrieval are completed in a algebraic form. A mathematics model of noise-like chaotic coding memory is constructed, meanwhile the basic mechanism of circulant convolution and circulant correlation in image information storage and retrieval are demonstrated.

在详细阐明数字序列和字母序列的1-D映射函数设计方法的基础上，利用构造出的1-D映射的稳定周期环和不稳定极限环完成了存储和联想记忆功能，为了识别有关的输入信息，提出了映射函数直接控制的方法；在此基础上，提出了一种1-D映射型混沌神经网络模型，该网络本身不当作一个"黑箱"处理，网络的参数值由网络中实现的映射函数来确定，该网络模型具有联想记忆、容错性、模式识别和奇异滤波等一系列智能信息处理的基本功能。

In chapter 3, the stability and bifurcation of the equator of a cubic system are investigated.

在第三章中，我们研究一类三次系统的赤道环的稳定性和极限环分支问题。

We study cuspidal loop bifurcation、 Homoclinic or double Homoclinic bifurcation、 Hopf bifurcation and obtain the necessary conditions to generate limit cycles by using the coefficients of the expansion of the first Melnikov function.

利用一阶Melnikov函数的展开式的系数研究了尖点环分支、同宿分支、双同宿分支和Hopf分支，并给出了产生极限环的充分条件。

For the infective subsystem, we obtain the existent condition of the subsystem equilibrium point and the uniqueness of the positive equilibrium point by the no infectious subsystem's conclusion and the image analysis. The partial stability of the subsystem equilibrium points is discussed by analyzing eigenvalue. The condition that the system has no limit cycle is obtained by the Dulac function.

对染病子系统，利用无病子系统所得结论及图像分析法，得到了系统平衡点的存在条件，正平衡点的存在唯一性；利用特征根方法判断了系统平衡点的局部稳定性；利用Dulac函数得到了系统不存在极限环的条件；利用极限方程理论得到了系统疾病消除平衡点和地方病平衡点的全局稳定性。

The third chapter discusses and proves Il"yashenko"s Theorem, that is, if every vertex on the polycycle of an analytic vector field in the real plane is hyperbolic, then limit cycles cannot accumulate on this polycycle.

第三章详细讨论和证明了Il'yashenko定理，即平面解析向量场的多边环上每一顶均为双曲奇点，则此多边环附近不能结集无限多个极限环。

In the second chapter, we consider a kind of Kolmogorov system. The sufficient condition for nonexistence of the closed orbit and existence of the unique and stable limit cycle are obtained by using divergence integral, Poincare-Bendixson theorem and Zhang Zhifenunique theorem.

第二章讨论了一类Kolmogorov系统，利用发散量积分、环域定理和张芷芬唯一性定理，得到了该系统无闭轨的充分条件和存在唯一极限环的条件。

A pilot vehicle system mathematical model containing nonlinear control elements of the flight control system is established by the describing function method; the limit cycle of PVS is determined; the relation between the limit cycle and pilot induced oscillation and the influence of nonlinear control elements on PIO are explored.

采用描述函数法建立了含有非线性控制系统的人机系统数学模型，确定了系统的极限特性，探讨了极限环与驾驶员诱发振荡之间关系和操纵系统非线性因素对PIO影响等。

In the paper we consider a wide class of slow-fa.st second order systems and give sufficient conditions for the existence of a singular limit cycle related to a homoclinic orbit.

本文研究一类正二阶快-慢系统中奇性同宿轨道和极限环，并且给出了此系统存在奇性同宿轨道和极限环的充分条件。

The theoretical analysis are verified by numerical simulations.Chapter 3 mainly considers a class of predator-prey model with sublinear functional response function. We deduce some sufficient conditions ensuring stability of equilibrium, nonexistence , existence as well as uniqueness of the limit cycle around the positive equilibrium.

第3章研究了一类食饵为线性密度制约，功能反应函数为次线性函数的食饵-捕食者模型，完整地对模型的平衡点的全局稳定性和极限环的存在惟一性进行了定性分析，得到了该系统不存在闭轨线，正平衡点全局稳定和存在惟一稳定的极限环的充分条件。

When these parameters surpass a certain value, the system cannot appear the limitcycle. Through the various parameters\' changing, it demonstrates the forming process of the dissipative structure. Thus it show the dissipative structure\'s characteristic of the trophodynamics predation model and point out the ecological significance of the various parameters in the model.On the fourth chapter, the spruce aphides and its predator model is a predator model.

第四章，以两个捕食者作用于同一食饵的竞争关系模型为例，应用微分方程定性理论，对捕食模型中存在极限环的情况进行了讨论，用MATLAB在相平面上模拟出系统的极限环，此时该体系状态的发展呈现周期振荡趋势，从而揭示出营养动力学为基础的捕食模型耗散结构特征。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。