连锁类的几个不变性质

给出了连锁类的几个不变性质,得到：在ＣＭ局部环中,广义ＣＭ性是连锁类的不变性质;强广义ＣＭ性是偶连锁类的不变性质;在正则局部环中,余维数ｋ≤３可光滑性是连锁类的不变性质。     

CH with no Ostaszewski spaces

There are models of CH without Ostaszeswki spaces. If is locally compact and sub-Ostaszewski, there is a forcing which does not add reals and which forces `` is not sub-Ostaszewski'.

     

On the Anti-forcing Number of Benzenoids

The anti-forcing number is introduced as the smallest number of edges that have to be removed that any benzenoid remains with a single Kekulé structure. Similarly, the anti- Kekulé number is discussed as the smallest number of edges that have to be removed that any benzenoid remains connected but without any Kekulé structure. These concepts have been exemplified on damaged benzenoid parallelograms.     

An Event Dimension for Modeling Damping Due to Time-Varying Forcing Frequency

This article presents an original method for evaluating thedissipative effect in SDOF systems due to the transient phenomenongenerated by time-varying forcing frequencies. The main contributionlies in the use of an event dimension, as additional dimension, andEinstein's method for highlighting and proving the existence of adamping term in the equation of the motion. The variational problem ofthe metric of a pseudo-Riemannian space gives the geodesic equations andthe equation of the motion. The application is concerned with aspring-pendulum system and the associated experimental investigationpermits validating the method proposed. The influence of the variationof the forcing frequency is highlighted using two different load cases:it is shown that the damping depends on the forcing frequency variation.     

带强迫项的二阶泛函微分方程解的振动性和渐近性

该文建立了偏差变元依赖于状态的二阶强迫泛函微分方程解的若干振动和渐近性质 ,所得结果推广和改进了文献中的有关结果     

Borel on the Questions Versus Borel on the Answers

We consider morphisms (also called Galois-Tukey connections) between binary relations that are used in the theory of cardinal characteristics. In [8] we have shown that there are pairs of relations with no Borel morphism connecting them. The reason was a strong impact of the first of the two functions that constitute a morphism, the so-called function on the questions. In this work we investigate whether the second half, the function on the answers' side, has a similarly strong impact. The main question is: Does the nonexistence of a Borel morphism imply the non-existence of a morphism that is only Borel on the answers' side? We give sufficient conditions for an affirmative answer. The results are applied to the unsplitting relations where it has been open whether there is a morphism that is Borel on the answers' side.     

Bifurcations and Dynamics of Spiral Waves

(N) . In this article, it is shown that the dynamics near meandering spiral waves or other patterns is determined by a finite-dimensional vector field that has a certain skew-product structure over the group SESE(N) . This generalizes our earlier work on center-manifold theory near rigidly rotating spiral waves to meandering spirals. In particular, for meandering spirals, it is much more sophisticated to extract the aforementioned skew-product structure since spatio-temporal rather than only spatial symmetries have to be accounted for. Another difficulty is that the action of the Euclidean symmetry group on the underlying function space is not differentiable, and in fact may be discontinuous. Using this center-manifold reduction, Hopf bifurcations and periodic forcing of spiral waves are then investigated. The results explain the transitions to patterns with two or more temporal frequencies that have been observed in various experiments and numerical simulations. Received December 8, 1997; accepted May 19, 1996     

入流激励下可压缩剪切层中Kelvin-Helmholtz涡的响应特性

通过直接数值求解Navier-Stokes方程,研究了入流激励下可压缩剪切层中Kelvin-Helmholtz(KH)涡结构的响应特性,结果清晰地展示了KH涡的独特演化方式.基于流动可视化数据,采用两点相关性分析获得了流场拟序结构的空间尺寸和结构角分布.通过分析不同激励频率下涡结构的动态特性,揭示了入流激励下可压缩剪切层中KH涡结构的独特演化机理.研究结果表明,低频入流激励(f=5 k Hz)下KH涡尺寸在远场区域达到饱和后呈现锁频状态,KH涡量厚度稳定在12-14 mm之间;与自由剪切层涡结构通过配对合并的方式实现生长的机理不同,低频入流激励下剪切层的发展是通过中间涡核顺时针吞噬KH不稳定波诱导的一串外围小涡结构来实现生长.此外,针对高频激励(f=20 k Hz)下的剪切层流动,研究了涡结构特性和入流激励参数之间的定量关系,发现均匀分布涡结构的尺寸近似等于对流速度与入流激励频率之比.     

A notion of selective ultrafilter corresponding to topological Ramsey spaces

We introduce the relation of almost‐reduction in an arbitrary topological Ramsey space ? as a generalization of the relation of almost‐inclusion on ?^[∞]. This leads us to a type of ultrafilter ?? ? ? which corresponds to the well‐known notion of selective ultrafilter on ?. The relationship turns out to be rather exact in the sense that it permits us to lift several well‐known facts about selective ultrafilters on ? and the Ellentuck space ?^[∞] to the ultrafilter ?? and the Ramsey space ?. For example, we prove that the open coloring axiom holds on L (?)[??], extending therefore the result from [3] which gives the same conclusion for the Ramsey space ?^[∞]. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Partition reals and the consistency of t > add(R)

We show that it is consistent with ZFC that the additivity number add(R) of the ideal of meager sets of the real line is strictly greater than the tower number t of the reals. MSC: 03E35, 54D20.