Effect of equal channel angular pressing on aging treatment of Al-7075 alloy

The effect of aging treatment on microstructure and mechanical properties of equal channel angular pressed Al-7075 alloy was examined.Commercial Al-7075 alloy in the solid solution heat-treated condition was processed by equal channel angular pressing through route BCat both the room temperature and 120 1C. Only three passes of equal channel angular pressing was possible due to the low ductility of the alloy at both temperatures. Followed by equal channel angular pressing, the specimens have been aged at 120 1C for different aging times. Mechanical properties were measured by Vickers microhardness and tensile tests and microstructural observations were undertaken using transmission electron microscopy, X-ray diffractometer as well as optical microscopy. Microstructural investigations showed that ultrafine-grained materials with grain size in the range of 200–350 nm and 300–500 nm could be obtained after three passes of equal channel angular pressing at room temperature and 120 1C, respectively. Equal channel angular pressing of solid solution heat-treated Al-7075 alloy accelerates precipitation rate and subsequently leads to a significant decrease in aging time to attain maximum mechanical properties. Furthermore, it is possible to achieve maximum mechanical properties during equal channel angular pressing at 120 1C as a result of dynamic aging and formation of small η′ phase.     

舱底液压蝶阀密封优选与应用

本文针对舱底液压蝶阀容易泄漏、洗舱更换阀门作业困难等难题,在阐述液压蝶阀工作的液压原理和密封件的受力机理基础上,通过对故障液压蝶阀执行机构的拆检,分析执行机构密封失效的原因,提出选用聚四氟乙烯加石墨和青铜密等材质做密封件的方法,以提高密封材料的耐高温、耐腐蚀和抗老化性能,从而延长液压蝶阀维修周期.通过油田现场的应用证明,该新型密封件在耐腐蚀和抗老化方面都比原有密封圈有较大幅度提高.     

浅谈电梯老龄化问题——兼论电梯维修保养的重要性

本文首先介绍了电梯目前"老龄化"的现状,对电梯目前所存在的问题进行分析,特别是电梯的维修保养所存在的问题,并提出了相应的解决问题的方法。     

Multifractal analysis of resting state fMRI series in default mode network: age and gender effects

Age-related changes of resting state in default mode network （DMN） may provide new clues to the developing mechanism of normal brain as well as early diagnosis and therapy of some neuropsychiatric disorders. The application of multifractal theory to functional magnetic resonance imaging （fMRI） signals has recently raised increasing attention. We aim to explore the multifractal characteristics underlying the resting state functional magnetic resonance imaging （rs-fMRI） series extracted from DMN, and two issues are mainly discussed： （1） whether there exist multifractals in rs-fMRI series; （2） whether it is possible to distinguish between the different ages or genders by means of multifractal characteristics. Results demon- strated the existence of multifractals in rs-fMRI series in DMN. In addition, slight differences between young subjects and middle-aged or elderly subjects can be successfully detected by △asα, a modified measure we proposed. Furthermore, it is revealed that the rs-fMRI series from young subjects possess smaller averaged scale index and weaker long range correlation, while those from middle-aged or elderly people present increasing averaged scale index andstronger long range correlation. Whereas no significant statistical differences has been found between male and female group. Our results, therefore, highlight the potential useful- ness of multifractal analysis in fMRI series of a certain brain region, and provide important insights into healthy aging in DMN.     

一种准晶强化钢热处理过程中的组织和性能

超高强马氏体时效钢是集良好的加工性能和超高强使用性能的新材料。热处理对马氏体时效钢性能有着至关重要的影响。本文通过试验研究热处理工艺对典型超高强马氏体时效钢00Cr12Ni9Mo4Cu2组织性能的影响。发现：     

Impaired insulin release in aging rats: Metabolic and ionic events

We investigated the effect of aging on glucose uptake, glucose-induced O₂ consumption, glucose-induced⁴⁵Ca movements, and calmodulin content to elucidate age-related impairment of glucose-induced insulin release in pancreatic islets of Wistar rats. Intact pancreatic islets from old (24-month-old) rats showed impaired glucose-induced insulin release; glucose uptake and O₂ consumption were lower in old than in young (2-month-old) or adult (12-month-old) rats. Moreover,⁴⁵Ca uptake and calmodulin content were decreased in pancreatic islets from older rats, which explained the impairment in glucose-induced insulin release in aging. No major differences between the 3 age groups in glucose-induced⁴⁵Ca efflux in pancreatic islets were observed.     

时效处理对Sn57Bi0.5Ag/Cu钎焊接头组织及性能的影响

研究了Sn57Bi0.5Ag/Cu钎焊接头在70℃、100℃时效过程中的显微组织和剪切强度的变化。结果表明:在钎料和Cu基体的界面间存在金属间化合物,随时效时间的延长,界面金属间化合物层的厚度增厚,接头区的组织出现了粗化;脆性的金属间化合物是钎焊接头的薄弱环节,接头剪切强度随时效时间的增加和界面化合物的增厚而下降;在时效时间达1000min以后,容易在金属间化合物层内观察到空洞。     

山东省人口老龄化问题及对策分析

依据先期预测结果和世界权威部门提供的有关数据，从人口老龄化程度、速度、总量等3个方面指标及其与经济发展的变动关系角度分析了山东省目前和未来可能出现的人口老龄化问题，认为强化社会养老职能是应对未来老龄化问题的必然选择，并就完善社会养老体系提出了几点对策建议．     

时效工艺对Cu-Ag-Zr合金电磨损性能的影响

对Cu-0．1Ag-0．18Zr合金时效后的电导率、显微硬度以及电滑动磨损性能进行了研究。结果表明：该合金940℃固溶1h后，在560℃时效可获得较高的电导率，在480℃时效可获得较高的显微硬度。时效前冷变形能大大加快第二相的析出过程，使合金综合性能显著提高。该合金经940℃固溶再经60％变形后，在480℃时效1h，其电导率和显微硬度分别可达85．6％IACS和HV131．2，而固溶后直接时效为81．3％IACS和HV116．1。在载流条件下，合金的磨损量随加载电流的增加而增大；磨损机制是以电蚀为主的电蚀、犁削和磨粒磨损。     

偏铌酸铅压电陶瓷材料老化问题的探讨

对偏铌酸铅压电陶瓷的老化性能作了一些探讨,实验表明,掺杂改性后的偏铌酸铅显微结构发生了变化,晶界处有杂质分凝使得该材料老化性能好。