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排序方式: 共有528条查询结果,搜索用时 15 毫秒
1.
This study aims to evaluate the tribological behaviour of 3Y-TZP/Ta (20 vol%) ceramic-metal composites and 3Y-TZP monolithic ceramic prepared by spark plasma sintering (SPS) against ultrahigh molecular weight polyethylene (UHMWPE). According to the results of pin (UHMWPE)-on-flat wear test under dry conditions, the UHMWPE – 3Y-TZP/Ta system exhibited lower volume loss and friction coefficient than the UHMWPE – monolithic ceramic combination due to the presence of an autolubricating layer that provides sufficient lubrication for reducing the friction. Owing to the lubrication of the liquid media, under wet conditions obtained using simulated body fluid (SBF), similar behaviour is observed in both cases. Additionally, the ceramic and biocomposite materials were subjected to a low temperature degradation (LTD) process (often referred to as “ageing”) to evaluate the changes in the tribological behaviour after this treatment. In this particular case, the wear properties of the UHMWPE-biocomposite system were found to be less influenced by ageing in contrast to the case of the UHMWPE-zirconia monolithic material. In addition to their exceptional mechanical performance, 3Y-TZP/Ta composites also showed high resistance to low temperature degradation and good tribological properties, making them promising candidates for biomedical applications, especially for orthopaedic implants. 相似文献
2.
Al-10Mg型固溶合金自然时效稳定性研究 总被引:3,自引:0,他引:3
测定了ZL30 5合金自然时效 33年的力学性能变化 ,观察了晶界的析出相 ,研究了组织和性能的关系 ,从而确定了ZL30 5合金具有长期自然时效稳定性。 相似文献
3.
报道了硝酸老化处理方法对MgCr_2O_4—Bi_2O_3陶瓷湿敏元件的结构和性能的影响。实验结果表明,硝酸老化处理不仅是一种可行的造孔方法,而且对元件的力学和电学性能有重要影响。用浓度适宜的硝酸处理后,会得到性能较好的元件。 相似文献
4.
Maria Casapu Jan-Dierk Grunwaldt Marek Maciejewski Meike Wittrock Ulrich Gbel Alfons Baiker 《Applied catalysis. B, Environmental》2006,63(3-4):232-242
The formation and stability of BaAl2O4 and BaCeO3 in Pt-Ba/Al2O3 and Pt-Ba/CeO2 based NOx storage-reduction (NSR) catalysts has been investigated using kinetic measurements, X-ray diffraction, thermal analysis and X-ray absorption spectroscopy. In as-prepared state, the Ba-component in the NSR catalysts was made up of amorphous BaO and BaCO3. The formation of BaAl2O4 started above 850 °C, whereas the formation of BaCeO3 was already observed at 800 °C and was faster than that of BaAl2O4. The stability of BaAl2O4 and BaCeO3 in various liquid and gaseous atmospheres was different. BaAl2O4 was rapidly hydrated at room temperature in the presence of water and transformed to Ba(NO3)2 and γ-alumina in the presence of HNO3, whereas BaCeO3 was decomposed to much lower extent under these conditions. Interestingly, BaCeO3 was transformed to Ba(NO3)2/CeO2 in the presence of NO2/H2O at 300–500 °C. Also, the presence of CO2 led to decomposition of barium cerate, which has important consequences for the catalyst ageing under NOx-storage conditions and can be exploited for regeneration of thermally aged NSR-catalysts. 相似文献
5.
6.
Cu-Ni-Si-Cr合金的时效析出与再结晶 总被引:1,自引:2,他引:1
研究了Cu-Ni-Si-Cr合金在时效过程中,析出与再结晶的交互作用及其对合金性能的影响。研究结果表明,形变使合金时效析出相更加细小、弥散,析出对再结晶的形核和长大过程产生阻碍作用。在再结晶的形成和长大过程中,析出相在晶界前沿快速粗化或重新溶解,并在再结晶区域中重新析出,导致更加弥散的析出相分布。 相似文献
7.
This paper explores how research teams in Intel’s Digital Health Group are using ethnography to identify ‘designable moments’—spaces,
times, objects, issues and practices which suggest opportunities for appropriate interventions. It argues that technology
innovation should aim to incorporate the views, experiences and practices of users from the start of the design process to
support independent living and develop culturally sensitive enhancements that contribute towards wellbeing and a life of quality
for local older populations. 相似文献
8.
Among healthcare workers, shiftwork (mostly if nightwork is also included), ageing and work-related stress may be factors leading to impaired health. Such risk factors may also operate in interaction, resulting in an even increased harm for health. The present study aims at evaluating these relationships in a sample of 1842 hospital workers in Northern Italy. Subjects were mainly women, 33.1% were aged > or = 45 yr, and they were almost evenly distributed between dayworkers and rotating shiftworkers (nights included). Shiftwork was associated with poor sleep, while it was protective against gastrointestinal disorders, poor work ability and job dissatisfaction. Work stress was the risk factor with the highest relevance for poor health. Ageing was associated with lower physical health. Few significant interactions were observed. Shiftwork with nights and high work stress significantly interacted in increasing the risk for poor sleep. The "healthy worker effect" may have played a strong role in study findings. 相似文献
9.
Two general trends, the tightening of time constraints and the ageing of the working population, are likely to raise sensitive problems implying adjustment of both work and workers' characteristics. The statistical studies presented in this paper, referring to a French inter-professional survey conducted on health and work after fifty (11 213 employees), aim at verifying this assumption. The analyses presented are divided in four sub-questions: have part of employees over fifty been removed from time pressure situations? Is time pressure difficult to deal with for older workers (from their point of view)? Does intense time pressure imply increased prevalence of certain health disorders among senior employees? Does pressure increase the desire to end one's professional life early? The results show that intense time pressure raises serious problems for most of the employees in their fifties who are exposed to them. 80% consider this constraint to be “difficult”. They systematically show more frequent rates for most types of physical or psychological health disorders. “Sheltering from the job”, which implies being shifted from work “under pressure” to a job “without pressure”, is not uncommon but only solves a minority of situations. Lastly, the option of earlier retirement is not particularly developed in age group in its fifties working “under pressure”. 相似文献
10.
The aim of this study was to examine the response of the autonomic nervous system in younger (mean age 31 yrs, n=14) and older (mean age 54 yrs, n=14) healthy female teachers during work periods of perceived high and low stress. In the younger participants, heart rate, cortisol excretion rate and psychosomatic symptoms were significantly higher during the high work stress period. The older participants experienced no decrease in their heart rate and cortisol excretion during the low stress period and they exhibited no significant decrease in blood pressure after the work in the evening during both periods. It may be concluded that the recovery from the stress in the older teachers was insufficient particularly in view of their elevated diastolic blood pressure during the low work stress period. Ergonomic and individually tailored measures in terms of work time control, specific relaxation techniques, and a part-time retirement may improve the stress management of older teachers. 相似文献