环

In the fifth section, we obtain some sufficient conditions under which a class of a planar quintic system has at most two limit cycles by transforming it into Abel equation.

第五章讨论了一类可化为Abel方程的五次多项式系统的极限环的个数，得到此类平面五次多项式系统至多存在两个极限环的充分条件。

The numerical algorithm based on theories of projecting and Laguerre,such as homology,circular points and ω of absolute conic is established,an iterative elimination method is applied to boost the nonlinear problem solving.

通过调和射影及Laguerre定理的推论求解出平面圆环点的共轭虚像，利用平行六面体照片存在的三对圆环点的虚像，构造对无穷远平面绝对二次曲线的像ω的约束，使用辗转相除法求解非线性问题。

By applying the tools such as modulus of curves and rings, together with Rohde s theorem, it proves that a homeomorphism is a bi Lipschitz map if and only if it satisfies a logarithmically absolute value inequality of rings.

运用曲线族的模和环模等工具，结合 Rohde定理，证明同胚为双 Lipschitz映射的充要条件是：它适合环的对数绝对值不等式；还得到了同胚为拟共形映射的一个充分条件。

The preparation method comprises monomer synthesis and polymer synthesis. The polymer synthesis is that cyclopentadienyl sodium monomer is added into metallic cobalt complex-triphenyl phosphorus cobalt chloride under strict oxygen-free and water-free conditions, and then double inner alkyne or outer alkyne conjugate monomer is added in, and after reaction, the precipitation, filtering, abstersion and vacuum-drying are carried out, the large molecules polymer containing cyclopentadienyl cobaltocenium organometallic cobalt is obtained.

制备方法，包括单体合成和聚合物的合成，聚合物的合成是在严格无氧无水条件下，在金属钴配合物三-三苯基磷氯化钴，加入环戊二烯钠单体，随后加入双内炔或双外炔共轭单体，反应后沉淀，过滤，洗涤，真空干燥，得到含环戊二烯茂钴有机金属钴的大分子聚合物。

Objective To study the relationship between the depth of abutment undercut and the retention of gold alloy clasp.

目的 研究金合金卡环固位力与卡环臂进入基牙倒凹深度间的关系。

The total yield of the product was 28%. Bridged imine acetamide was used to produce a new type of antibiotic derivatives from macrolid via removing cladinose sugar from macrolid and joining 6 and 11 position on macrolid ring.

桥红霉素亚胺用于生产新型抗生素类药物——桥红霉素，它是在红霉素内酯环结构上脱掉cladinosesugar，并将红霉素内酯环上6，11位相连，成为全新的红霉素衍生物。

This dissertation deals with the synthetic method of benzotellurazoles containing various substituents in benzene nuclei: introducing tellurium atom to the acetanilide derivatives in ortho-position by direct or indirect ways, then reduced and cyclized to give substituted benzotellurazoles directly or indirectly.

本文系统研究了含各类取代基的苯并碲唑杂环的合成方法，即向原料中用四氯化碲以直接或间接定位的方法引入碲，再经过直接或间接还原关环法制备苯并碲唑。

For finding the way of systems stability,the two step closed supply chain with risk-neutral agents is studied in this paper,supply chain revenue sharing control model is analyzed,and the conclusion that it can make supply chain systems stability and improves performance of the supply chain is given.

为探索使系统达到稳定的方法，以供应链参与主体均为风险中性的两阶闭环供应链系统为背景，研究了收益共享控制模型对闭环供应链协调性和稳定性的影响，证明了收益共享控制能够使产品再制造闭环供应链稳定，提升供应链的绩效。

Conditions of integral chain can be closed.

基于函数S粗集和F粗积分，本文研究粗积分的动态特征，定义粗积分链和粗积分环的概念，给出上积分链，下积分链定理，粗积分链定理，以及积分链的存在性定理，讨论了积分链的可闭条件，得到积分环定理，粗积分环定理。

From the viewpoint of supply chain,the basic request of continuous development is transferring from the single and open circle of "resources-produce-consume-abandon" to the closed and feedback supply chain of "resources-produce-consume-recycle".

从供应链的角度，可持续发展的基本要求就是由&资源—生产—消费—废弃&的单向开环供应链到&资源—生产—消费-再生资源&闭环反馈式供应链的转化，基于废旧产品再制造的闭环供应链问题近几年引起学者的广泛重视。

Do you know, i need you to come back

你知道吗，我需要你回来

Yang yinshu、Wang xiangsheng、Li decang,The first discovery of haemaphysalis conicinna.

1〕 杨银书，王祥生，李德昌。安徽省首次发现嗜群血蜱。