镁合金压铸件在汽车行业中的巨大应用潜力

国外镁合金压铸件在２０００年前将以２０％～２５％的速度增长,尤其在汽车行业需求量大。文中讲述镁合金压铸件特点和国外汽车行业对镁合金压铸件的需求情况。论述我国应抓住机遇,开发研制镁合金压铸件,迅速占领国内市场,并向国外发展的有利条件。     

一个具有高可用性的动态容错VoD系统

提出了一个在VoD系统中具有高可用性的动态容错算法。针对分布式应用的特点,能对控制节点实现服务器切换的容错,数据服务节点负载均衡分配和故障节点提供服务的恢复。同时按照文章一致性保证机制可以实现媒体服务故障恢复对客户端的透明。通过对系统可用性分析和仿真试验表明,该算法可以有救地提高系统的可用性。     

散列索引多分支Trie树快速路由查找算法

路由器的主要任务是转发IP分组,实现高速分组转发的关键是快速的路由查找算法。我们针对IPv4地址,首先建立前缀长度为8、16和24的3张hash表,在此基础上,再分别针对不同长度的前缀建立最多只涉及其余8比特的多分支Trie树。在这种结构中进行IP路由查找,其存储器访问次数最多为7次,而且还具有易于更新、易于扩展等特点。     

数据仓库的存储优化设计

随着数据仓库逐渐成为企业决策支持的重要技术手段,对数据仓库的存储能力与性能的优化问题日益成为人们重视与关注的焦点之一。该文在数据仓库的模型结构以及数据分析过程中所采用的一些算法进行分析的基础上,对数据仓库与OLAP的数据存储方式以及优化的方法进行了深入的讨论,并在此基础上提出了一个通过数据分割技术存储细节数据,利用分层的方式来存储聚合数据,通过提高系统的并行处理能力来改善数据仓库系查询访问的效率的存储设计优化方案。     

TA2拉压力学性能不对称性及应变速率敏感性

本文研究了不同应变速率下工业纯钛TA2室温拉伸和压缩力学行为,结果发现TA2具有明显的拉压屈服不对称性和拉压应变硬化不对称性;随着应变速率的增加,拉压不对称性有明显增加。采用电子背散射衍射（EBSD）技术分析了拉伸和压缩时TA2微观变形机制及微观组织演化规律,结果表明,TA2压缩时以孪晶变形机制为主,拉伸时以位错滑移为主;TA2微观变形行为的载荷敏感性导致了宏观力学性能的不对称性。     

钢筋锈蚀破坏和修补技术

混凝土中钢筋锈蚀是导致结构物破坏的主要因素。本文介绍钢筋锈蚀的危害性、经济损失和修补技术等。试验表明，ＦＣ—０１型和ＲＰ—Ｗ型防腐砂浆是较好的修补材料。     

5株低产乙醇的非酿酒酵母筛选及其酿造特性

为获得葡萄酒中低产乙醇的非酿酒酵母(non-Saccharomyces)菌株,首先采用纯种发酵方式对分离自湖南、辽宁和新疆的38株本土非酿酒酵母进行产乙醇能力的评价.初步筛选到5株乙醇体积分数、乙醇产率和潜在乙醇体积分数均低于酿酒酵母(S.cerevisiae)EC1118的菌株,包括红酵母(Rhodotorula m...     

Effects of mediums on fermentation behaviour and aroma composition in pure and mixed culture of Saccharomyces cerevisiae with Torulaspora delbrueckii

The nutrient status and composition in mediums have a significant effect on yeast metabolism and phenotypic characteristics in wine fermentation. In this study, the effects of three frequently used mediums, including synthetic grape juice (SGJ), grape juice without grape pericarp and seeds (GJ) and grape must with grape pericarp and seeds (GMPS), on yeast fermentation behaviour and aroma compounds produced by pure and mixed culture of Saccharomyces cerevisiae T73 with Torulaspora delbrueckii TD20 were investigated after alcoholic fermentation. The results showed that high fermentation activities and cell population were always found in GJ medium irrespective of inoculated approach. More esters and higher alcohols were produced in GMPS medium fermented by pure S. cerevisiae, while SGJ medium had increased levels of fatty acids. Consistent with previous literatures, the mixed fermentation of T. delbrueckii and S. cerevisiae produced more acetate esters and fatty acids than the pure culture of S. cerevisiae, while this enological trait was only found in SGJ and GJ, not in GMPS. Our results highlighted that more attention should be paid to the fermentation medium when evaluating the enological and aromatic properties of selected yeasts used in industrial winemaking. In this regard, the combined use of GJ and GMPS medium might be a suitable choice.     

单向短纤维增强复合材料应力传递模型及其细观力学分析

建立了含单纤维和基体的双圆柱复合材料细观力学模型,采用基体剪应力的Lame形式推导了纤维轴向应力和纤维基体间界面剪应力计算方程。分析了纤维/基体模量比、纤维长径比和纤维体积分数等细观结构参数对纤维轴向应力和界面剪应力分布的影响,并对结果进行了验证。     

Interfacial fatigue damage behavior of fiber reinforced rubber—A combined experimental and cohesive zone model approach

The interfacial damage behavior of short fiber reinforced rubber sealing composites (SRRC) under fatigue load is researched in this article, where an experimental and cohesive zone model approach are employed. The fiber mass fractions of samples are 2%, 5%, and 10%, respectively. The curves of the fatigue strain (ε _n) varying with the fatigue cycle number (n) were obtained by the fatigue test. The damage patterns of SRRC with different fiber mass fractions were confirmed by scanning electron microscope. A finite element model (FEM) was established to predict interfacial fatigue damage, where the cohesive element was imbedded in the interface between fiber and matrix. The results show that the ε _n-n curves of SRRC predicted by FEM agree well with experimental data when fiber mass fractions are high. The samples with 5% fiber mass fraction are optimal to restrain the origination of the interfacial abhesion, and a possible damage path of SRRC is obtained.