LIMIT CYCLES AND BIFURCATION CURVES FOR THE QUADRATIC DIFFERENTIAL SYSTEM （Ⅲ）m=0 HAVING THREE ANTI-SADDLES （Ⅱ）

As a continuation of [1], the author studies the limit cycle bifurcation around the focus S1 other than O(0, 0) for the system (1) as δ varies. A conjecture on the non-existence of limit cycles around S1, and another one on the non-coexistence of limit cycles wound both O and S1 are given, together with some numerical examples.     

LIMIT CYCLES AND BIFURCATION CURVES FOR THE QUADRATIC DIFFERENTIAL SYSTEM （III）m=0 HAVING THREE ANTI-SADDLES （I）

For the quadratic system: x=-y δx lx2 ny2, y=x(1 ax-y) under conditions -10 the author draws in the (a, ()) parameter plane the global bifurcationdiagram of trajectories around O(0,0). Notice that when na2 l < 0 the system has one saddleN(0,1/n) and three anti-saddles.     

ON THE NON-EXISTENCE OF LIMIT CYCLES OF CERTAIN QUADRATIC SYSTEMS

§１．Ｆｏｒｔｈｅｓｙｓｔｅｍｘ＝－ｙ＋δｘ＋ｌｘ２＋ｎｙ２＝Ｐ（ｘ，ｙ），ｙ＝ｘ（１＋ａｘ－ｙ）＝Ｑ（ｘ，ｙ），｛（１．１）ｗｅｃａｎｆｉｎｄｉｎ［１］ｔｈｅｆｏｌｏｗｉｎｇ：ＣｏｎｊｅｃｔｕｒｅＩ．Ａｓｓｕｍｅ１ａ＜０，ｎ＞１，ｎ＋ｌ＞０，ｎａ２...     

QUALITIVE THEORY OF THE QUADRATIC DIFFERENTIAL SYSTEMS (I)

Westudyinthispaperqualitativepropertiesofthequadraticdifferentialsystemsfundertheconditions:Inthissectionwewillshowthatunder(4),theanti-saddleFI(xl,yi)of(2)(withxl>0)lyingon1 ax--y=0canbeaweakfocusfortwotimesas6varIes.*ProjectsupportedbytheNationalNatural…     

二次微分系统极限环的分布

在假设文中命题Ａ成立的条件下证明了一般二次微分系统的极限环所有可能的分布为（３,１）,（１,３）,（３,０）,（０,３）,（２,１）,（１,２）,（２,０）,（１,１）,（０,２）,（１,０）,（０,１）和（０,０）。     

ON A CONJECTURE CONCERNING THE NON-EXISTENCE OF LIMIT CYCLES FOR QUADRATIC DIFFERENTIAL SYSTEMS

Aconjecturewasgivenin[l]asfollows:Ifforthesystemoftypeill(i.e.,6/0):wehavewhereW=(n b)(l n)'--a'(6 ZI n),thenthereisnolicestcycle(LC,forabbreviation)aroundO(0,0).Noticethatcondition(2)canbedividedintothefollowingfoursub-cases:i)m=0,a(b ZI)/0,n)a=0,m(l n)/0,iii)W=0,WI/0,tv)m--sa=2a2 n(l Zn)=0,a/0,WI/0.(3)Non-existenceofLCunderi)orn)hasbeenprovedin[2]515,Theorem15.1and15.2;andthatunderWI/0,6=0hasbeenprovedin[2]514.Ifiniii)m(l n)>0then[3]hasprovedthenon-existenceofLCaroundObytheDulacfun…     

一类7次微分自治系统的极限环分支

研究一类平面7次微分系统,通过作两个适当的变换以及焦点量的仔细计算,得出了系统的无穷远点与2个初等焦点能够同时成为广义细焦点的条件,进一步得出在一定条件下该系统能够分支出15个极限环的结论,其中5个大振幅极限环来自无穷远点,10个小振幅极限环来自2个初等焦点.     

一类四次系统极限环的个数与分布

本文研究一类四次系统的极限环,通过计算四次系统鞍点分界线之间的有向距离,计算一阶焦点量 及二阶焦点量,判别同宿轨内外的稳定性,利用分支理论与定性分析技巧发现这类系统有六个极限环, 并给出了它们的分布．     

BOUNDEDNESS OF SOLUTIONS AND EXISTENCEOF LIMIT CYCLES FOR A NONLINEAR SYSTEMOF DIFFERENTIAL EQUATIONS

IntroductionTheautonomousplanarsystemoftheformwasfirststudiedbyLevinsonandSmithintheclassicalpaper[2]astheequivalelltsystellloftheequationofLienardtypeandlateronsomeauthorshavecontributedtotiletheoryofthissystemwithrespecttoqualitativebehaviorofsolutionsll--9].InthepresentpaperwestudyasystemOfaslightlymoregeneraltype,namely,wherethefllnctionsp(y),q(y),g(x)andh(x,y)arecontilluousforallvalueoftheirarguments,and3'resubjecttotheconditionswhichensurethattheexistenceofuniquesolutiontotheinitialvalu…     

(Ⅲ)m=0类二次系统的极限环问题(Ⅲ)

§1Introduction Continuingthestudyofpapers[1]and[2],weconsideraquadraticsystemofYe's type()systemwithm=0.Withoutlossofgenerality,wemayassumethatb=-1anda<0,thenthesystemtobeconsideredbecomes dx dt=-y+δx+lx2+ny2,dydt=x(1+ax-y).(1)Paper[1]studiedthecases00andn>1,l<0,aswellasthe case01/2forwhichZhanghaveprovedtheuniquenessoflimitcyclesin[7],andpaper[2]discussedthecasen<0,01/2andn>1,l>0,whichwillbediscussedinthispape res…     

一类三次系统极限环的个数与分布

本文研究一类三次系统的极限环,利用分支理论与定性分析技巧发现这类系统有四个极限环,并给出了他们的分布。     

一类三次系统的极限环个数与奇点分支

给出二次系统I的一类相伴系统在奇点O(0,0)的焦点量公式,证明了O至多为2阶细焦点,δlmn=0时系统在O外围至多有一个极限环,从而说明了系统在细焦点外围至多有一个极限环。最后给出了各个奇点的分支情况及几何特征。     

一类Kolmogorov捕食系统的极限环

本文研究Ｋｏｌｍｏｇｒｏｖ的捕食系统ｘ＝ｘ（ａ０＋ａ１ｘ－ａ２ｘ＾２－ψ（ｙ）） ｙ＝ｙ（ｂｘ＾２－ｄ），得到了极限环存在唯一的充要条件，从而推广了前人相关的结果，其中ψ（０）＝０，ψ（ｙ）＞δ＞０，ｙ＞０。     

一个在无穷远点分支出八个极限环的多项式微分系统

本文研究一类高次系统无穷远点的中心条件与极限环分支问题．作者首先推出一个计算系统无穷远点奇点量的线性递推公式，并利用计算机代数系统计算出该系统在无穷远点处的前11个奇点量，从而导出无穷远点成为中心和最高阶细焦点的条件，在此基础上作者首次给出了多项式系统在无穷远点分支出8个极限环的实例。     

ON THE NONEXISTENCE OF THE LIMIT CYCLEFOR QUADRATIC SYSTEM OF TYPE III

1ResultsC()nsid'3rtlloq,,.d,.ti<1sVstemofTypeIll[1]withoutlossofgenerality,wemayassumen>0.TheresultsontilenonexiStenceoflimitcycleforquadraticsystemofTypeillcanbefoundin[2],[3]and[4].Inthispaper,weestablishagainseveralnewcriteriaofdecidingthenonoxistenceoflimitcycle.FOrsimplicity,letN(0)andN(0)denotethenumberoflimitcyclesof(1)aroundthesingularpointsO(0,0)andO(0,1),resl)ccl\ively,weobtail]tilefollowingresults:Theorem1Supposetlsatjn b<0,axldthattilefollowingconditionsaresatisfied,tlsenN(O)…     

一类五次系统赤道环的稳定性与极限环分枝

本文解决了一类五次系统赤道环的稳定性与极限环分枝问题，所得的结论与二次系统的若干结论形 成有趣的对比．     

再论一类二次系统的无界双中心周期环域的POincare分支

本文再一次讨论了具有双曲线与赤道弧为边界的双中心周期环域的二次系统的Poincare分支，并构造出了此系统出现极限环的(0，3)分布或出现一个三重极限环的具体例子．     

LIMIT CYCLES BIFURCATED FROM THE ORIGIN AND EQUATOR FOR A CLASS OF FIFTH SYSTEM

For a class of real fifth system, the first 8 singular point quantities of the origin and the first 6 singular point quantities of the equator are obtained, and at the same time, the two highest-order cases are proved respectively. Moreover, the problems of stability and limit cycle bifurcated from the origin and the equator are studied comparatively, then some better results are obtained.     

二维非线性动力系统的多极限环分叉的参数控制

本文研究了一类具有Z2-等变性质的5次扰动平面Hamilton向量场，利用动力系统的分叉理论和判定函数法，通过控制其参数，得到系统在两组不同的参数条件下分别存在20和23个极限环，以及它们之间相对位置的不同构型.这一结果对机械振动中相应的控制问题有理论指导意义。