保温条件下过共晶Al-Si合金半固态浆料的组织演变

研究了保温时间和保温温度对电磁搅拌ZL117合金半固态浆料稳定性的影响.试验结果表明：半固态浆料中初生Si的颗粒直径随着保温时间的延长而逐渐增大,但在前15 min内增长速度比较缓慢,15 min后增长较快;随着保温温度的升高而缓慢增大;初生Si的形状系数随着保温时间的延长而变得越来越大,但也在前15 min内变化较为缓慢,15 min后变大速度突然加快;初生Si的形状系数在620 ℃下保温时最小,在610～620 ℃之间随着保温温度的升高而缓慢变小;在620～650 ℃之间随着保温温度的升高而逐渐增加.     

Dual–primal proximal point algorithms for extended convex programming

This paper presents a class of dual–primal proximal point algorithms (PPAs) for extended convex programming with linear constraints. By choosing appropriate proximal regularization matrices, the application of the general PPA to the equivalent variational inequality of the extended convex programming with linear constraints can result in easy proximal subproblems. In theory, the sequence generated by the general PPA may fail to converge since the proximal regularization matrix is asymmetric sometimes. So we construct descent directions derived from the solution obtained by the general PPA. Different step lengths and descent directions are chosen with the negligible additional computational load. The global convergence of the new algorithms is proved easily based on the fact that the sequences generated are Fejér monotone. Furthermore, we provide a simple proof for the O(1/t) convergence rate of these algorithms.     

Ehrenfeucht-Fraïssé games in finite set theory

In this article, with Ehrenfeucht-Fraïssé games we prove that Δ₁≠Δ₀ on BFR, which implies Δ≠Δ₀ on BFR, and thus solve an open problem raised by Albert Atserias in his dissertation (Δ₀,Δ₁,Δ are fragments of first order logic and BFR is a class of finite sets which in essence is equivalent to a class of finite pure arithmetic structures with built-in BIT predicate).     

网上书店的设计思路

本文从理论构建一个电子商务应用系统——网上书店,按照软件工程的要求,对系统进行需求分析,提出一个网上购书系统的构建思路,首先对系统功能要求及系统运行要求;其次对系统总体设计、软件结构设计、系统数据库的选择与设计;最后为软件测试。