Technological characterization of phosphate ore types from the Salitre Alkaline Complex, MG - Fosfertil Area

São apresentados os resultados de caracterização tecnológica de seis tipos de minério fosfático provenientes do Complexo de Salitre, tendo em vista definir a composição mineralógica das amostras e as características inerentes à apatita e ao minério relevantes para o beneficiamento mineral. Os teores de P2O5 variam de 9 a 25% e a proporção de finos (-0,020 mm) situa-se entre 20 e 34% em massa com perdas associadas de 17 a 22% do total de P2O5 presente. As amostras são compostas, essencialmente, por apatita, oxi-hidróxidos de ferro, ilmenita, argilominerais, carbonatos, quartzo, piroxênio, perovskita, alumino-fosfatos e outros minerais acessórios, variando apenas suas proporções relativas. Verificou-se que a apatita ocorre, predominantemente, liberada já abaixo de 0,21 mm, com superfície límpida a fracamente impregnada por oxi-hidróxidos de ferro; a parcela altamente impregnada (não flotável) varia de 6 a 9%. Do total de fósforo contido nas amostras, mais de 97% ocorre sob a forma de apatita (acima de 0,020 mm) e a recuperação potencial estimada de P2O5 na etapa de flotação é superior a 90% (recuperação global estimada entre 71-76%).The present study was carried out on six different ore types from the Salitre Alkaline Complex aiming to determine their mineralogical composition and the major features that are relevant in the mineral processing. The P2O5 grades vary from 9 to 25%. The slime content (-0,020 mm) varies between 20 and 34% (w/w) and carries 17-22% of the P2O5 content. The samples essentially consist of apatite, iron oxi-hydroxides, ilmenite, clayminerals, carbonate, quartz, pyroxene, perovskite, secondary phosphates and other minor accessory minerals. Below 0.21 mm, apatite essentially occurs in free particles showing a clean surface or a weak coating of iron oxi-hydroxides; the highly covered apatite (not recoverable by flotation) varies from 6 to 9%. In the deslimed fraction (above 0.020 mm) more than 97% of the total phosphor content occurs as apatite; the estimated P2O5 potential recovery in flotation concentration is over 90% (71-76% overall recovery).FOSFERTIL - Fertilizantes Fosfatados S.A

Ready Worker One? High-Res VR for the Home Office

Many employees prefer to work from home, yet struggle to squeeze their office into an already fully-utilized space. Virtual Reality (VR) seemingly offered a solution with its ability to transform even modest physical spaces into spacious, productive virtual offices, but hardware challenges---such as low resolution---have prevented this from becoming a reality. Now that hardware issues are being overcome, we are able to investigate the suitability of VR for daily work. To do so, we (1) studied the physical space that users typically dedicate to home offices and (2) conducted an exploratory study of users working in VR for one week. For (1) we used digital ethnography to study 430 self-published images of software developer workstations in the home, confirming that developers faced myriad space challenges. We used speculative design to re-envision these as VR workstations, eliminating many challenges. For (2) we asked 10 developers to work in their own home using VR for about two hours each day for four workdays, and then interviewed them. We found that working in VR improved focus and made mundane tasks more enjoyable. While some subjects reported issues---annoyances with the fit, weight, and umbilical cord of the headset---the vast majority of these issues seem to be addressable. Together, these studies show VR technology has the potential to address many key problems with home workstations, and, with continued improvements, may become an integral part of creating an effective workstation in the home

Using bone ash as an additive in porcelain sintering

Calcined bovine bone (CBB) is generally used to manufacture high-quality porcelain known as bone china. In these products, the amount of bone ash is about 50%. However, it is known that CBB, in small quantities added to raw materials such as feldspars, can reduce the liquidus temperature and thus promote liquid-phase sintering. The purpose of this study was to evaluate the potential use of bone ash as a sintering promoter of porcelain made by a classical triaxial system. Hard porcelain was prepared with 0, 1, 2, and 5 wt% CBB and sintered at temperatures ranging from 1100 to 1400 °C. For the sample containing 2% CBB, the sintering temperature was reduced by 50 °C relative to 0% CBB, while the sample’s tensile strength was the highest among all samples. Two mechanisms could be observed during porcelain sintering depending on CBB quantities: for 1 and 2% of CBB, the mullite formation determined the final shrinkage without changes on initial sintering temperatures; for 5% the initial sintering temperature was decreased by liquid formation.FAPESPCNPQCAPE

Using bone ash as an additive in porcelain sintering

Calcined bovine bone (CBB) is generally used to manufacture high-quality porcelain known as bone china. In these products, the amount of bone ash is about 50%. However, it is known that CBB, in small quantities added to raw materials such as feldspars, can reduce the liquidus temperature and thus promote liquid-phase sintering. The purpose of this study was to evaluate the potential use of bone ash as a sintering promoter of porcelain made by a classical triaxial system. Hard porcelain was prepared with 0, 1, 2, and 5 wt% CBB and sintered at temperatures ranging from 1100 to 1400 °C. For the sample containing 2% CBB, the sintering temperature was reduced by 50 °C relative to 0% CBB, while the sample’s tensile strength was the highest among all samples. Two mechanisms could be observed during porcelain sintering depending on CBB quantities: for 1 and 2% of CBB, the mullite formation determined the final shrinkage without changes on initial sintering temperatures; for 5% the initial sintering temperature was decreased by liquid formation.FAPESPCNPQCAPE

Cidadania mediada : processos de democratização da política municipal no Brasil

This article discusses the notion that the persistence of &ldquo;traditional&rdquo; political practices weakens Brazil&rsquo;s democracy.Drawing on the cases of three Brazilian municipalities administered by the Workers&rsquo; Party (PT), the author examines the space between &ldquo;traditional&rdquo; and &ldquo;modern&rdquo; and argues that successful democratization does not eradicate practices such as clientelism and patronage, but it tends to incorporate and build on these traditional political elements. Moreover, the article maintains that the democratization of municipal politics is inextricably bound up with the eradication of poverty and the construction of a responsive, state-based social safety net.<br /