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排序方式: 共有369条查询结果,搜索用时 15 毫秒
31.
Let 𝕂 be a field, and let R = 𝕂[x 1,…, x n ] be the polynomial ring over 𝕂 in n indeterminates x 1,…, x n . Let G be a graph with vertex-set {x 1,…, x n }, and let J be the cover ideal of G in R. For a given positive integer k, we denote the kth symbolic power and the kth bracket power of J by J (k) and J [k], respectively. In this paper, we give necessary and sufficient conditions for R/J k , R/J (k), and R/J [k] to be Cohen–Macaulay. We also study the limit behavior of the depths of these rings. 相似文献
32.
利用扰动法导得了非线性强迫Boussinesq方程,利用数值解讨论了地形和外源等局地强迫激发的非线性长波扰动的一般性状和时间演变特征,并对移动性孤波与地形的相互作用进行了分析研究。 相似文献
33.
Ilijas Farah Boban Velickovic 《Proceedings of the American Mathematical Society》2007,135(7):2283-2290
We show that the product of any two nonatomic Maharam algebras adds a Cohen real. As a corollary of this and a result of Shelah (1994) we obtain that the product of any two nonatomic ccc Souslin forcing notions adds a Cohen real.
34.
参数激励与强迫激励联合作用下非线性振动系统的余维2退化分叉 总被引:4,自引:0,他引:4
在本文里我们首先研究了具有Z_2-对称性的范式理论和退化向量场的普适开折理论。然后利用上述理论研究了参数激励与强迫激励联合作用下非线性振动系统的余维2退化分叉,从而解决了当解具有两个零特征值时解的稳定性问题。最后利用Melnikov方法求出了参数平面上的同宿分叉曲线,讨论了全局分叉的存在性。 相似文献
35.
We continue [21] and study partition numbers of partial orderings which are related to (ω)/fin. In particular, we investigate Pf, be the suborder of ((ω)/fin)ω containing only filtered elements, the Mathias partial order M, and (ω), (ω)ω the lattice of (infinite) partitions of ω, respectively. We show that Solomon's inequality holds for M and that it consistently fails for Pf. We show that the partition number of (ω) is C. We also show that consistently the distributivity number of (ω)ω is smaller than the distributivity number of (ω)/fin. We also investigate partitions of a Polish space into closed sets. We show that such a partition either is countable or has size at least D, where D is the dominating number. We also show that the existence of a dominating family of size 1 does not imply that a Polish space can be partitioned into 1 many closed sets. 相似文献
36.
Ralf - Dieter Schindler 《Mathematical Logic Quarterly》1997,43(1):22-28
We show that weakly compact cardinals are the smallest large cardinals k where k+ < k+ is impossible provided 0# does not exist. We also show that if k+Kc < k+ for some k being weakly compact (where Kc is the countably complete core model below one strong cardinal), then there is a transitive set M with M ? ZFC + “there is a strong cardinal”. 相似文献
37.
本文应用Normal Form理论和退化向量场的普适开折理论研究了参数激励与强迫激励联合作用下非线性振动系统的余维2退化分叉,用Melnikov方法讨论了全局分叉的存在性. 相似文献
38.
Transient and steady state dynamic response of a class of slider-crank mechanisms is investigated. Specifically, the class
of mechanisms examined involves rigid members but compliant supporting bearings. Moreover, the mechanisms are subjected to
non-ideal forcing. Namely, both the driving and the resisting loads are expressed as a function of the angular coordinate
describing the crank rotation. First, an appropriate set of equations of motion is derived by applying Lagrange's equations.
These equations are strongly nonlinear due to the large rigid body rotation of the crank and the connecting rod, as well as
due to the nonlinearities associated with the bearing action and the form of the driving and the resisting loads. Consequently,
the dynamics of the resulting dynamical system is examined by solving the equations of motion numerically. More specifically,
transient response is captured by direct integration, while determination of complete branches of steady state response is
achieved by applying appropriate numerical methodologies. Initially, mechanisms whose crankshaft is supported by bearings
with rolling elements and linear stiffness characteristics are examined. Then, numerical results are presented for rolling
element bearings with nonlinear stiffness characteristics. Finally, the study is focused on mechanisms supported by hydrodynamic
bearings. In all cases, the attention is focused on investigating the influence of the system parameters on its dynamics.
Moreover, models with constant crank angular velocity are first analysed, since they provide valuable insight into some aspects
of the system dynamics. Eventually, the emphasis is shifted to the general case of non-ideal forcing, originating from the
dependence of the driving and the resisting moments on the crankshaft motion. 相似文献
39.
Hans Schoutens 《代数通讯》2017,45(1):262-274
We prove Hochster’s small maximal Cohen–Macaulay conjecture for three-dimensional complete F-pure rings. We deduce this from a more general criterion, and show that only a weakening of the notion of F-purity is needed, to wit, being weakly F-split. We conjecture that any complete ring is weakly F-split. 相似文献
40.