极限函数

To discriminate the existence of indeterminate form s double limit to binary function is a relatively difficult question.

判定二元函数f的未定式二重极限的存在性是一个比较困难的问题。

PartⅡ,Applying the developed and extended direct algebraic methods that presented in recent years and based on the 2+1 dimensional variable separation solutions,abundant Jacobi elliptic function doubly periodic waves and periodic propagating wave patterns for many 2+1 dimensional nonlinear wave models are obtained,and in long wave limit solitary waves are derived as well.

第二部分，本文拓展和推广(来源：a2AB7aC论文网www.abclunwen.com)了新近发展的几种典型的直接代数方法和基于分离变量解的间接方法，获得多个2+1维非线性波动模型丰富的雅克比椭圆函数双周期波解和周期传播波模式，并得到长波极限情形下存在的非线性孤立波。

The sufficient condition for the inexistence of limit cycle is found using the method of Dulac function.

运用Dulac函数法，得到了系统不存在极限环的充分条件。

It is proved that there is no limit cycle around the positive equilibra by constructing Dulac function, thus global asymptotic stability of the positive equilibria is proved in the first quadrant.

分析了该系统的平衡点性态，利用Dulac函数证明了系统在正平衡点外围不存在极限环，从而证明了正平衡点在第一象限内是全局渐近稳定的。

A predator model with refuge and toxicity is studied. By constructing a suitable Dulac function, it is shown that there is no limit cycle in the first quadrant, thus the globally stability of the equilibrium is proved. Further more, the paper analyzes the influence of refuge, toxicity and harvesting. It is amazing that ① if the death rate of predator is big or the harvesting effort is big, the existence of the predator is unrelated with refuge; if the death rate of predator and the harvesting effort are small, and the refuge is small enough, the population of both species is increased as the increase of refuge;② if d2=0, the increase of d1 has no influence on the prey population, while the population of predator is decreased.

研究一类有避难所、毒素作用和外界捕获影响的捕食系统，通过构造恰当的Dulac函数，证明系统在第一象限没有极限环，从而证明了平衡点的全局稳定性；分析了避难所、毒素、捕获作用对该系统最终种群数量的影响，发现：①当捕食者的死亡率大或其被捕获得多时，两种群的绝灭与避难所的存在无关；当捕食者的死亡率小、被捕获得多且避难所足够小时，随着食饵避难所的增加，捕食者种群数量也随之增加；②当毒素d2=0时，毒素d1的增加对食饵种群最终数量没有影响，而使捕食者种群数量下降。

When the value of critical threshold larger than 1, the disease and insect pests equilibrium point is locally asymptotically stable An appropriate Dulac function should be choosed and Bendixson-Dulac creterion is used to prove that the limit cycle in this model does not exist. It explains that the disease and insect pests equilibrium point is globally asymptotically stable.

选取适当的Dulac函数，利用Bendixson-Dulac判别法证明了极限环的不存在性，说明局部渐近稳定的病虫害平衡点也全局渐近稳定。

In the paper,according to homogeneous balance principle and F-expantion method,some double-periodic exact solutions of a fifth-order KdV-like equation with variable coefficients are obtained in form of Jacobi elliptic function .

利用齐次平衡原则和F-展开法，求出了一个五阶变系数KdV-like方程的一些用Jacobi 椭圆函数表示的双周期解。并且在极限的情况下，得到了该方程的孤立波解和三角函数表示的周期波解

In long wave limit, these elliptic function wave patterns may degenerate into single valued localized excitations dromion and multi-lumps.

椭圆函数传播波之间的相互作用是非弹性的，而在长波极限下相应相干孤子激发Dromion，Lumps之间的相互作用可以是弹性的，也可以是非弹性的。

Technical analysis; AR-ARCH model; covariance inequality; Strong law of large numbers; Glivenko-Cantelli Lemma ; empirical distribution function; central limit theorem; dependence coefficients

基础科学，数学，概率论、数理统计技术分析； AR-ARCH模型；协方差不等式；强大数定律； Glivenko-Cantelli引理；经验分布函数；中心极限定理；相依系数

The advantages of this method are as follows:①It is available even the ultimate state function is unknown.

该方法的优点是：①可用于极限状态函数未知的情况。

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。