Microstructure,mechanical properties and wear resistance of an Al–Mg–Si alloy produced by equal channel angular pressing

Microstructure, mechanical properties and wear resistance in an ultrafine-grained Al–Mg–Si alloy fabricated utilizing a combination of equal channel angular pressing (ECAP) and dynamic aging were investigated in this paper. The results indicated that the grain size of the ECAP alloy was significantly refined, i.e., to ~239 nm after three ECAP passes. Meanwhile, the yield and tensile strength of the ECAPed material reached 340 MPa and 445 MPa, respectively, while maintaining a significant uniform elongation of 14%. Wear resistance results demonstrated that the wear rate, wear depth and width of the ECAPed material decreased in comparison with the solution-treated (SST) and peak-aged (T6) conditions under a load range of 5–25 N. The adhesive wear that occurs in the undeformed specimens at 10 N does not appear in the ECAPed specimen at the same load, indicating that the ECAPed specimen delay the appearance of more serious wear mechanisms under certain loads. The cooperative interaction of high density nano-scale β" precipitates and dislocations resulted in a combination of super-high strength and good work hardening ability which suppressed the extension of cracks between the friction layer and the plastic deformation zone. As a consequence, the combination of ECAP and dynamic aging brings a significant improvement for antifriction performance of the 6061 aluminum alloy.     

激光快速成型TC4合金显微组织及力学性能

采用金相显微镜、扫描电镜、电子拉伸机等，研究了激光快速成型TC4合金沉积态在平行沉积方向和垂直沉积方向的组织和力学性能.结果表明:激光快速成型TC4合金沉积态宏观组织沿沉积方向生长的粗大β柱状晶呈明暗相间的条带状结构，具备典型的魏氏组织特征;垂直沉积方向的强度比平行沉积方向的强度高，但塑性低;合金断口为韧窝状断口，垂直沉积方向的断口韧窝尺寸比平行沉积方向的小.     

四-对羟基苯基卟啉的自组装及光电特性

利用X射线光电子能谱(XPS)测试5,10,15,20-四-(对羟基苯基)卟啉单体和5,10,15,20-四-(对羟基苯基)卟啉自组装二聚体,并通过化学模拟得到卟啉自组装二聚体分子的最优构象.结果表明:两种卟啉化合物中氧原子的类型不同;在单体卟啉中未检测到瞬态表面光电压信号,卟啉自组装二聚体表现出较好的瞬态表面光伏特性;卟啉自组装二聚体的光限幅性质优于卟啉1单体.     

国内外高校特殊教育专业课程设置的比较研究

对俄罗斯等世界一些主要国家和地区高等院校特殊教育专业的课程设置进行了介绍，并对这些院校特教专业的课程设置和内容进行了分类，论述了各类特教专业课程设置的特点，在此基础上对各类型课程设置进行了比较，分析了他们的异同，最后，对各类型课程设置提出了意见和值得借鉴的地方。     

钛酸铋的热力学理论

利用点群４／ｍｍｍ的对称性给出了应力作用下的钛酸铋的弹性吉布斯自由能的表达式，并导出了自发应变，介电性质和压电性质。     

40Cr大轴断裂分析

对冶金矿山某产品的40Cr材料制作的大轴热处理后发生断裂现象，进行了理化检验及综合分析，找出了造成大轴断裂原因－首先是由于存在淬火应力，而未得到及时回火，其次是原材料中存在严重的冶金缺陷。     

关于世行贷款基础教育项目实施效果的调查

世界银行贷款第四个贫困地区基础教育发展项目 ,自 1997年在我国西部贫困地区启动以来 ,取得了实实在在的成效。本文以云南省宣威市“贫四项目”实施效果为对象 ,进行了实事求是的调查与分析     

铝合金加工用刀具的使用研究（三）

当前我国各机械加工生产厂家引进国外进口设备及生产线较多，实现引进设备及生产线上刀具的国产化以降低生产成本，成为当前国内整个机械加工领域亟待解决的问题。     

Science Letters： A synthetic Toll-like receptor 2 ligand decreases allergic immune responses in a mouse rhinitis model sensitized to mite allergen

It has been proposed that activation of Toll-like receptors （TLRs） plays crucial roles in the polarization of adaptive immune responses. A synthetic Toll-like receptor 2 （TLR2） ligand, Pam3CSK4, has been reported to modulate the balance of Th1/Th2 responses. We evaluated the modulation effect of Pam3CSK4 on allergic immune response in a mouse rhinitis model sensitized to house dust mite allergen （HDM）. Mice were sensitized and challenged with Dermatophagoidesfarinae allergen （Der f）, and then the allergic mice were treated by Pam3CSK4. Nasal allergic symptoms and eosinophils were scored. Der f-specific cytokine responses were examined in the splenocytes and bronchoalveolar lavage fluid （BALF）. Serum level of total IgE was also detected. After establishing a mouse allergic rhinitis model with HDM, we have showed that Pam3CSK4 treatment not only ameliorated the nasal allergic symptoms remarkably but also decreased the eosinophils and total inflammation cells in BALF significantly. Analysis of cytokine profile found that IFN-7 released from either BALF or stimulated splenocytes increased markedly in Pam3CSK4-treated mice, while IL-13 decreased significantly. Moreover, serum level of total IgE was significantly lower in Pam3CSK4-treated mice than in the untreated. Thus, in an allergic rhinitis mouse model developed with HDM, Pam3CSK4 was shown to exhibit an antiallergic effect, indicating its potential application in allergic diseases.     

4G移动通信系统及其关键技术

提出了3G通信系统的局限性,概述了4G通信系统的特点和关键技术,对4G系统网络结构作了简单介绍。