Numerical simulation of the unsteady aerodynamic interaction of two plane airfoil cascades

A method for the calculation of unsteady aerodynamic interaction of two plane airfoil cascades that are in relative motion in a subsonic flow of ideal gas is developed. This interaction provides a two-dimensional approximation of the flow in a stage of an axial turbomachine. The method is based on the reduction of the problem to the calculation of the unsteady flow in a single interblade passage of each of the cascades. The calculation uses generalized space-time periodicity relations corresponding to the unsteady process of interest. The calculation is based on the direct numerical integration of the non-stationary gas dynamics equations with the use of the finite difference Godunov-Kolgan-Rodionov scheme of the second approximation order with respect to time and space. The calculation procedure includes the determination of the acoustic fields that are generated by the stage in the incident flow and in the flow behind it. The results of the calculations that illustrate the accuracy of the numerical solution and the capabilities of the method are presented.     

Orders of Indescribable Sets

We extract some properties of Mahlo’s operation and show that some other very natural operations share these properties. The weakly compact sets form a similar hierarchy as the stationary sets. The height of this hierarchy is a large cardinal property connected to saturation properties of the weakly compact ideal.     

所有双理想都是素双理想的半群

设S为一个半群,B是S的一个双理想(即B是S的一个满足条件BSBB的子半群)．如果对S的任意双理想C,D都有CDB蕴涵CB或DB,我们就称B为S的一个素双理想．如果K是一个N-覆盖的纯LR-带,我们就称K为一条拟链．本文证明了半群S的所有双理想都是素双理想的充分必要条件是S是一个幂等元形成拟链的纯整群并半群．     

用MATLAB求解二元理想体系的泡露点问题

通过MATLAB工程计算软件，采用步长法、二分法、迭代法和黄金分割法等多种方法．求解了二元理想体系的泡露点问题．结果表明，几种计算值都能与手算值吻合地很好．相对误差远远小于1％，完全满足工程要求；用MATLAB内部函数Solve计算最为便捷．     

Conic Set-Valued Maps in Vector Optimization

The paper deals with the properties of a conic set-valued function defined on the set of all ideal points of vector programming problems. The results here about the continuity and derivability of this conic set-valued map, can be used to get information about the sensitivity of the problem and the stability of the order associated to every ideal point. Furthermore, it is proved that certain contingent cones are determined by the ideal conic set-valued map.      

半连续格的刻画和映射

本文讨论了半连续格的一些性质,在半连续格中引入半Scott开集族,用半Scott开集族来刻画半连续格,同时定义了半连续格之间的半连续映射,得到闭包算子的像仍是半连续格的条件.最后,研究了半连续格上的半连续映射的全体不动点之集的性质。     

PP-理想

引入了环的PP-理想的概念,证明了PP-理想的一些性质及它与一些环、模、理想的联系,得到了一些有用的结论.     

Artinian level modules and cancellable sequences

In order to use dualization to study Hilbert functions of artinian level algebras we extend the notion of level sequences and cancellable sequences, introduced by Geramita and Lorenzini, to include Hilbert functions of certain artinian modules. As in the case of algebras a level sequence is cancellable, but now by dualization its reverse is also cancellable which gives a new condition on level sequences. We also give a characterization of the cancellable sequences involving Macaulay representations.     

D×D上的Toeplitz型与Hankel型算子

本文给出了空间Ｌ￣ａ，２（Ｄ×Ｄ，）的一个完全正交分解，定义了一系列Ｔｏｅｐｌｉｔｚ型与Ｈａｎｋｅｌ型算子，并且证明了它们的有界性，紧性及其Ｓｃｈａｔｔｅｎ－ｖｏｎＮｅｕｍａｎｎ性质．     

特征为2的素环的Lie理想上中心化自同构

Let R be a prime ring with an automorphism σ≠1, an identity map. Let L be a noncentral Lie ideal of R such that [x^σ,x] E Z for all x ∈ L, where Z is the center of R. Then L is contained in the center of R, unless char(R)=2 and dimc RC = 4.