Estudo tribológico de biolubrificantes com adição de nanopartículas de óxidos (zinco e cobre)

Currently, vegetable oils have been studied for bio-lubricants base that fits the new environmental standards. Since, in a world full of finite natural resources, mineral oils bring consequences to the environment due to its low biodegradability and toxicity, also it is important to consider that synthetic oils have a high cost The aim of this work is to obtain a biolubricant additived with oxide nanoparticles (ZnO and CuO) for better resistance to friction and wear, which is not toxic to the environment and have better adherence under boundary lubrication. The methodology consisted in the synthesis of bio-lubricants (soybean and sunflower base) by epoxidation reaction. Then, some physical-chemical analysis in bio-lubricants are made to characterize theses lubricants, such as, density, acidity, iodine value, viscosity, viscosity index. Later, the lubricants were additive with nanoparticles. The tribological performance was evaluated by the equipment HFRR (High Frequency Reciprocating Rig) consisting of a wear test ball-plan type. The characterization of wear analysis was performed by SEM / EDS. The results show that bio-lubricants may be synthesized by reaction of epoxidation with good conversion. Tribological point of view, the epoxidized oils are more effective than lubricant additived with the oxide nanoparticles, they had lower coefficients of friction and better rate of film formation in the study. However, because they are environmentally friendly, bio-lubricants gain the relevant importance in tribological field

Dádiva e internet: os artífices dos tutoriais de software livre

The research proposes a reflection on tutorial videos from Youtube, seen as a form of gift in modern society. Our reflection parts form a perspective of mutual exchange, which avoids the patterns of trade with current economic purposes. We present these video producers as craftsmen of cyberculture due to the skill and competence which they transmit their knowledge. The research is consisted by the observation of video tutorials on YouTube over the Linux operating system and its distributions. Analyzing the interactions between video producers, users and the website. The analysis is based on the classic Mauss (2003) and his reinterpretations of Caille (1998, 2001, 2002, 2006), Godbout (1992, 1998) assisted by Aime Cossetta (2010) and Sennett (2009) to help understand the idea of the craftsmen. The Internet as an open territory in expansion ables us to understand that the relationship in this medium also constitutes the reciprocal links pointed out by Mauss in the early twentieth century. The circulation of intangible property, in this case the knowledge beyond the establishment of social links, promotes a collaborative extent to produce the common in cyberspace.