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1.
Cyclicity of a kind of degenerate polycycles through three singular points   总被引:1,自引:0,他引:1  
This paper deals with the cyclicity of a kind of degenerate planar polycycles through a saddle-node P0 and two hyperbolic saddles P1 and P2, where the hyperbolicity ratio of the saddle P1 (which connects the saddle-node with hh-connection) is equal to 1 and that of the other saddle P2 is irrational. It is assumed that the connections between P0 to P2 and P0 to P1 keep unbroken. Then the cyclicity of this kind of polycycle is no more than m 3 if the saddle P1 is of order m and the hyperbolicity ratio of P2 is bigger than m. Furthermore, the cyclicity of this polycycle is no more than 7 if the saddle P1 is of order 2 and the hyperbolicity ratio of P2 is located in the interval (1,2).  相似文献   

2.
评估借款人信用是P2P网贷公司控制风险的重要步骤,对于网贷公司的正常运行有着极其重要的意义。论文参考商业银行信用指标体系并根据P2P网贷自身特点,建立了P2P网贷借款人的信用评估指标体系。根据建立的指标体系构建相应的BP神经网络模型,并利用一步正切法进行优化。然后选取具有代表性的P2P网贷平台的相关数据,对该模型进行训练和仿真,证明了该模型对P2P网贷平台的风险控制起到一定的作用。  相似文献   

3.
We discuss bijections that relate families of chains in lattices associated to an order P and families of interval orders defined on the ground set of P. Two bijections of this type have been known:(1) The bijection between maximal chains in the antichain lattice A(P) and the linear extensions of P.(2) The bijection between maximal chains in the lattice of maximal antichains AM(P) and minimal interval extensions of P.We discuss two approaches to associate interval orders with chains in A(P). This leads to new bijections generalizing Bijections 1 and 2. As a consequence, we characterize the chains corresponding to weak-order extensions and minimal weak-order extensions of P.Seeking for a way of representing interval reductions of P by chains we came upon the separation lattice S(P). Chains in this lattice encode an interesting subclass of interval reductions of P. Let SM(P) be the lattice of maximal separations in the separation lattice. Restricted to maximal separations, the above bijection specializes to a bijection which nicely complements 1 and 2.(3) A bijection between maximal chains in the lattice of maximal separations SM(P) and minimal interval reductions of P.  相似文献   

4.
《Quaestiones Mathematicae》2013,36(2):197-217
Abstract

A module P is called F-filtered-projective if for any epimorphism β: B → C and any homomorphism Y: P → C factoring through F, there exists a homomorphism α P → B such that β α = y. We collect for a given module P all such modules F into a class F(P) and all exact sequences relative to which P has the projective property, into a class E(P). Starting with & class P of modules P, we construct the classes F(p) and E(p) as the Intersections of the classes F(P) and E(P) respectively as P runs through P. Relative properties of these classes are investigated and in the special case where P is the class of finitely presented modules, we find a new characterization of flat modules which enables us to introduce the concept of semiflatness which in turn is utilized in a characterization of IF, QF and QF-3 rings.  相似文献   

5.
For any ordered set P, the join dense completions of P form a complete lattice K(P) with least element O(P), the lattice of order ideals of P, and greatest element M(P), the Dedekind–MacNeille completion P. The lattice K(P) is isomorphic to an ideal of the lattice of all closure operators on the lattice O(P). Thus it inherits some local structural properties which hold in the lattice of closure operators on any complete lattice. In particular, if K(P) is finite, then it is an upper semimodular lattice and an upper bounded homomorphic image of a free lattice, and hence meet semidistributive.  相似文献   

6.
快速造P(n,k)大表的左肩法则和斜线法则   总被引:10,自引:0,他引:10  
伍启期 《数学学报》2001,44(5):891-898
设P(n,k)为整数n分为k部的无序分拆的个数,每个分部≥1,它为大师欧拉所建立(1707-1783).它是组合图论和数论里最重要的数据之一.然而,它却十分难于计数和造表.本文,由公式P(n,k)=P(n-1,k-1)+P(n-k,k)定义了P(n,k)的左肩数和锐角数,并由此得到求P(n,k)的左肩法则(第一法则).还根据本文作者[5]的一些重要定理得到求 P(n,k)的斜线法则(第二法则).使用这些法则得到造P(n,k)大表的有趣原理.为方便计,我们仅用第一法则设计了计算机程序,用此程序即可快速造出任意大的P(n,k)表.  相似文献   

7.
设u是Hilbert空间上的σ-弱闭算子空间,称u具有性质(P),如果u中秩-算子生成的子空间在u中是σ-弱稠密的,称u具有扩张性质(P),如果u以及包含u的每个σ-弱闭子空间都具有性质(P),本文研究了性质(P)和扩张性质(P),给出了它们的等从描述。  相似文献   

8.
强P-正则半群上的最小正则*-半群同余   总被引:2,自引:2,他引:0  
主要研究了强P-正则半群S(P)上的最小正则*-半群同余.利用S(P)的正则*-断面S°得到S(P)上最小正则*-半群同余的简单形式γP.由于S(P)/γP同构于S°,实质上S°是S(P)的最大正则*-半群同态象,且S(P)的正则*-断面不唯一,但从同意义上看正则*-断面唯一.  相似文献   

9.
由环的P-性质所确定的根   总被引:1,自引:0,他引:1  
王尧  杨军 《数学研究》1999,32(3):305-309
定义了环的P根P、弱拟P根Pw 和拟P根PQ,证明它们均为Am itsurKurosh 根且P= Pw 为特殊根,给出了P半单环的结构定理和P根的模刻划  相似文献   

10.
张荣华 《数学进展》2001,30(3):203-217
在本文中,我们刻画弱P-正则半群上的最大幂等分离同余,并且证明了有超C-集的弱P-正则半群S[P]是拟P-正则当且仅当它同构于WB(p)[P^*]和某个弱正则^*-半群T的织积,其中B是S[P]的半带,最后,我们获得,在一般情况下,WB(p)[P]的弱P-正则半群但不是P-正则半群的条件。  相似文献   

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