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91.
A new notion of independence relation is given and associated to it, the class of flat theories, a subclass of strong stable theories including the superstable ones is introduced. More precisely, after introducing this independence relation, flat theories are defined as an appropriate version of superstability. It is shown that in a flat theory every type has finite weight and therefore flat theories are strong. Furthermore, it is shown that under reasonable conditions any type is non-orthogonal to a regular one. Concerning groups in flat theories, it is shown that type-definable groups behave like superstable ones, since they satisfy the same chain condition on definable subgroups and also admit a normal series of definable subgroup with semi-regular quotients. 相似文献
92.
The objective of this study is to understand the flow structures of weak and strong spherical blast waves either propagating
in a free field or interacting with a flat plate. A 5th-order weighted essentially non-oscillatory scheme with a 4th-order
Runge-Kutta method is employed to solve the compressible Euler/Navier-Stokes equations in a finite volume approach. The real-gas
effects are taken into account when high temperature occurs. A shock-tube problem with the real-gas effect is first tested
in order to verify the solver accuracy. Moreover, unsteady shock waves moving over a stationary wedge with various wedge angles,
resulting in different types of shock wave reflections, are also tested. It is found that the computed results agreed well
with the existing data. Second, the propagation of a weak spherical blast wave, created by rupture of a high-pressure isothermal
sphere, in a free field is studied. It is found that there are three minor shock waves moving behind the main shock. Third,
the problem of a strong blast wave interacting with a flat plate is investigated. The flow structures associated with single
and double Mach reflections are reported in detail. It is found that there are at least three local high-pressure regions
near the flat plate.
Received 27 July 2000 / Accepted 25 January 2002 – Published online 17 June 2002 相似文献
93.
94.
Alexander Bendikov Wojciech Cygan Bartosz Trojan 《Stochastic Processes and their Applications》2017,127(10):3268-3290
We consider a random walk which is obtained from the simple random walk by a discrete time version of Bochner’s subordination. We prove that under certain conditions on the subordinator appropriately scaled random walk converges in the Skorohod space to the symmetric -stable process . We also prove asymptotic formula for the transition function of similar to the Pólya’s asymptotic formula for . 相似文献
95.
We establish lower bounds on the matching number of graphs of given odd regularity d and odd girth g, which are sharp for many values of d and g. For d=g=5, we characterize all extremal graphs. 相似文献
96.
97.
We continue the classification, begun in [11], [14] and [12], of quadratic Artin-Schelter regular algebras of global dimension 4 which map onto a twisted homogeneous coordinate ring of a quadric hypersurfcice in P3. In this paper, we consider those cases where the quadric has rank 3. We also give sufficient conditions for the point scheme of any quadratic regular algebra of global dimension 4 to be the graph of an automorphism. 相似文献
98.
After motivating the question, we prove various results about the set of associated primes of Matlis duals of top local cohomology modules. In some cases, we can calculate this set. An easy application of this theory is the well-known fact that Krull dimension can be expressed by the vanishing of local cohomology modules. 相似文献
99.
In this article we introduce a certain family of graded modules associated to a given module. These modules provide a natural extension of the notion of the associated graded ring of an ideal. We will investigate their properties. In particular, we will try to extend Ree' theorem on the associated graded ring of an ideal generated by a regular sequence to this context. 相似文献
100.
Motivated by studying fuzzy congruences in groups, semigroups, and ordered semigroups, and as a continuation of N. Kuroki and Y. Tan's works in regular semigroups in terms of fuzzy subsets, in this article we introduce the notions of a fuzzy good congruence relation, a fuzzy cancellative congruence relation on abundant semigroups, and give some properties, and characterizations of fuzzy good congruences on such semigroups. Furthermore, we characterize fuzzy good congruences of left semiperfect abundant semigroups, and get sufficient and necessary conditions for an abundant semigroup to be left semiperfect. 相似文献