模拟海洋环境下新型水润滑尾轴承材料摩擦性能

利用高密度聚乙烯与不同浓度愈创树脂混合制备系列新型水润滑尾轴承材料,在CBZ-1摩擦磨损试验机上考察其在模拟海洋环境下的摩擦性能,对比分析不同配比材料摩擦因数和磨损量以及磨损表面形貌的变化情况。结果表明,在高密度聚乙烯中加入适量的愈创树脂可很好地改善材料的自润滑性能,且随着愈创树脂含量的增加,材料的摩擦因数和磨损率先减小后增加,这是因为愈创树脂在摩擦过程中会因受热软化分泌出一定量的油脂,有助于摩擦副表面水膜的形成,从而提高材料的摩擦磨损性能;适量愈创树脂的加入可以有效降低材料的表面粗糙度,改善摩擦副的表面性能,从而提高材料的工作稳定性。

光温条件对新热带干旱树种种子萌发和苗木建成的影响

A study was conducted to examine the germination requirements of Cedrela odorata, Guaiacum sanctum and Calycophyllum candidissimum seeds, and the effect of light intensity on survival and growth of C. odorata and G. sanctum seedlings planted on open, partially-open and beneath the canopy of a dry forest in Nicaragua. The results show that germination of C. candidissimum seeds was signifi- cantly higher in light than darkness at constant temperatures ranging from 20-35℃. Both C. odorata and G. sanctum seeds germinated in light and darkness to a varying extent, and the optimal germination temperature was around 20-25℃. Alternating temperature regimes did not improve germination. Survival of G. sanctum seedlings was 70% beneath the canopy and 80% in the open, and its relative growth rate in collar diameter was 1.88 mm/month in the open and 1.42 mm/month in the understory. Survival was generally poor for C. odorata, particularly in the understory. We concluded that light is an absolute requirement for the germination of C. candidissimum seeds while germination of C. odorata and G. sanctum seeds are more sensitive to temperature. Owing to its high survival rate on open site, G. sanctum could serve as a candidate species for reforestation of degraded sites.

航海贸易与“中国根”——菝葜类中草药在欧洲的传播和重定义

俗称“中国根”的一类中草药在16世纪介绍到欧洲,市场需求维持约二百年。为了认识这些草药的来源植物、外销原因及在欧洲古典医学中的应用,本文从记载有中国根的4种16世纪欧洲古籍的成书背景和刊行源流出发,介绍了它们在传布药物知识方面的有效作用;结合同时期引入欧洲的其他治疗梅毒的植物药的情况以及当时的疾病流行背景和医学实践,分析了中国根进入和逐渐退出欧洲药材市场的原因;基于欧洲古籍出现的中国根图像、中国本草记载和中国国内中医学、生物学的有关研究成果,讨论了“中国根”来源植物的种属;根据欧洲医生对中国根用法的多处具体描述和同时期中国医籍的记载,对比了16世纪的中西医生对同一疾病和同一类药物认识上的相通点与相异之处,解释此种医治新发疾病的外来新药物是如何在盖仑医学体液论的旧有理论框架中得到定义。结论认为:中国根是菝葜族若干植物和其他一些外观形态及药理作用相似的药用植物的统称;它们因梅毒的流行而进入欧洲药材市场,其间最主要的原因当是该类药物发汗利尿的显著作用,但另一因素也同等重要,即东半球的产地和低廉售价使得它们成为葡萄牙商人的理想选择。它们在欧洲取代了售价昂贵的愈创木,承袭了前者在盖仑医学体系中的使用方式。尽管医学理论迥然不同,中西医生为中国根找到的用途大致相似。中国根进入和退出欧洲药材市场更多是由商业利益而非医学考虑决定的。它在欧洲医生手中得到采用和重新定义的过程,代表了药物及其知识的流通在航海贸易时代出现的全新方式。

Seed germination and seedling establishment of Neotropical dry forest species in response to temperature and light conditions

A study was conducted to examine the germination requirements of Cedrela odorata, Guaiacum sanctum and Calycophyllum candidissimum seeds, and the effect of light intensity on survival and growth of C.odorata and G.sanctum seedlings planted on open, partially-open and beneath the canopy of a dry forest in Nicaragua.The results show that germination of C.candidissimum seeds was significantly higher in light than darkness at constant temperatures ranging from 20-35oC.Both C.odorata and G.sanctum seeds germinated in light and darkness to a varying extent, and the optimal germination temperature was around 20-25oC.Alternating temperature regimes did not improve germination.Survival of G.sanctum seedlings was 70% beneath the canopy and 80% in the open, and its relative growth rate in collar diameter was 1.88 mm/month in the open and 1.42 mm/month in the understory.Survival was generally poor for C.odorata, particularly in the understory.We concluded that light is an absolute requirement for the germination of C.candidissimum seeds while germination of C.odorata and G.sanctum seeds are more sensitive to temperature.Owing to its high survival rate on open site, G.sanctum could serve as a candidate species for reforestation of degraded sites.

新型愈创树脂-高密度聚乙烯水润滑尾轴承材料的制备及性能研究

尾轴承是船舶推进系统的重要组成部分,尾轴承材料对轴承的性能起着决定性作用。本文设计并制备了不同配比的愈创树脂-高密度聚乙烯复合材料,对合成的新复合材料和普通高密度聚乙烯材料进行力学性能测试,并比较添加了不同含量的愈创树脂对复合材料的性能影响。在CBZ-1船舶轴系摩擦磨损试验机上对4种材料进行摩擦试验,考察在渐变转速下复合材料的摩擦系数和磨损率。通过分析试验数据,确定了材料混合最佳配比。试验结果表明B型(0.5%愈创树脂)复合材料在力学性能和摩擦性能方面综合性能最好,该研究为该类材料未来在水润滑尾轴承方面的应用提供试验依据。