Continuous Restricted Radial Motion of a Gas under the Action of a Piston

The possibility of continuous conjugation of the straightline radial motion of a gas sphere toward the center and away from the center with the motion where the gas in the entire sphere stops simultaneously is shown. The motion is described by an invariant submodel of rank 1. Time reflections allow one to construct a solution that describes a periodic continuous restricted motion of the gas sphere under the action of a piston.     

混凝土高拱坝孔口三维非线性分析

采用有限元方法中的子模型技术,对混凝土高拱坝的1^#底孔进行了三维非线性分析,研究了孔口在坝体自重、库水压力和温度作用下混凝土开裂和裂缝发展情况,以及配筋对孔口开裂的影响。研究表明,采用子模型法不仅大大降低了网格剖面的难度,而且减少了三维非线性分析的计算时间。     

Kripke submodels and universal sentences

We define two notions for intuitionistic predicate logic: that of a submodel of a Kripke model, and that of a universal sentence. We then prove a corresponding preservation theorem. If a Kripke model is viewed as a functor from a small category to the category of all classical models with (homo)morphisms between them, then we define a submodel of a Kripke model to be a restriction of the original Kripke model to a subcategory of its domain, where every node in the subcategory is mapped to a classical submodel of the corresponding classical model in the range of the original Kripke model. We call a sentence universal if it is built inductively from atoms (including ? and ⊥) using ∧, ∨, ?, and →, with the restriction that antecedents of → must be atomic. We prove that an intuitionistic theory is axiomatized by universal sentences if and only if it is preserved under Kripke submodels. We also prove the following analogue of a classical model‐consistency theorem: The universal fragment of a theory Γ is contained in the universal fragment of a theory Δ if and only if every rooted Kripke model of Δ is strongly equivalent to a submodel of a rooted Kripke model of Γ. Our notions of Kripke submodel and universal sentence are natural in the sense that in the presence of the rule of excluded middle, they collapse to the classical notions of submodel and universal sentence. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Strong zero-dimensionality of hyperspaces

For a space X, X² denotes the collection of all non-empty closed sets of X with the Vietoris topology, and K(X) denotes the collection of all non-empty compact sets of X with the subspace topology of X². The following are known:

•

ω² is not normal, where ω denotes the discrete space of countably infinite cardinality.

•

For every non-zero ordinal γ with the usual order topology, K(γ) is normal iff whenever cf γ is uncountable.

In this paper, we will prove:

(1)

ω² is strongly zero-dimensional.

(2)

K(γ) is strongly zero-dimensional, for every non-zero ordinal γ.

In (2), we use the technique of elementary submodels.     

Erratum to “Normality and countable paracompactness of hyperspaces of ordinals” [Topology Appl. 154 (2007) 358-362]

We correct the proof of Theorem 8 in “Normality and countable paracompactness of hyperspaces of ordinals” [Topology Appl. 154 (2007) 358-362].     

L(Q)逻辑的一种保持性定理

对广义逻辑Ｌ（Ｑ）的一种保持性定理给予了证明。     

L (Q)格值模型的初等子模型

将带广义量词Q的一阶逻辑的二值弱模型推广到取值于完备弱可补格上,对有限的线性序弱可补格,讨论了关于L(Q)模型的初等子模型的一些性质,如强升和强降L－S－T定理,初等图像在初等扩充下的保持性等。     

超媒体系统组织层子模型的研究和设计

超媒体技术是管理多媒体信息的有效方法和手段，它以网络方式进行信息的存储和检索。系统中组织层设计的优劣涉及到整个超媒体系统的成功与否。作者运用面向对象的方法对其组织层的关键元素──链和节点进行了分析，并讨论了各自的设计方法。     

超深水水下分离器承压性能数值分析与试验研究

以中国自主设计制造的2 000 m超深水水下分离器为研究对象,基于图算法和一致缺陷模态法分析分离器样机极限承载能力;建立包含嵌入式接管子模型的水下分离器精细数值模型,研究马鞍形焊缝应力分布规律;设计高压舱试验验证水下分离器样机的物理承压能力,并对比分析高压舱试验数据和数值计算结果。研究表明:水下分离器样机失稳模式为塑性失稳,下放工况应该主要评估其结构强度;接管马鞍形焊缝的鞍点和冠点以及N1接管焊缝的角度φ为45°和135°位置为应力特征点;试验样机在高压舱试验过程中整体应力水平处于线弹性变形阶段,能够满足2 000 m水深的承压强度要求,模拟结果和试验结果吻合较好。     

Preservation theorems for Kripke models

There are several ways for defining the notion submodel for Kripke models of intuitionistic first‐order logic. In our approach a Kripke model A is a submodel of a Kripke model B if they have the same frame and for each two corresponding worlds A^α and B^α of them, A^α is a subset of B^α and forcing of atomic formulas with parameters in the smaller one, in A and B, are the same. In this case, B is called an extension of A. We characterize theories that are preserved under taking submodels and also those that are preserved under taking extensions as universal and existential theories, respectively. We also study the notion elementary submodel defined in the same style and give some results concerning this notion. In particular, we prove that the relation between each two corresponding worlds of finite Kripke models A ≤ B is elementary extension (in the classical sense) (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)