A quasi-elastic regime for vibrated granular gases

Using simple scaling arguments and two-dimensional numerical simulations of a granular gas excited by vibrating one of the container boundaries, we study a double limit of small $1-r$ and large $L$, where $r$ is the restitution coefficient and $L$ the size of the container. We show that if the particle density $n_0$ and $(1-r^2)(n_0 Ld)$ where $d$ is the particle diameter, are kept constant and small enough, the granular temperature, i.e. the mean value of the kinetic energy per particle, $/N$, tends to a constant whereas the mean dissipated power per particle, $/N$, decreases like $1/\sqrt{N}$ when $N$ increases, provided that $(1-r^2)(n_0 Ld)^2 < 1$. The relative fluctuations of $E$, $D$ and the power injected by the moving boundary, $I$, have simple properties in that regime. In addition, the granular temperature can be determined from the fluctuations of the power $I(t)$ injected by the moving boundary.

Retrofitting housing with lightweight green roof technology in Sydney, Australia, and Rio de Janeiro, Brazil

© 2015 by the authors. The built environment contributes around half of total greenhouse gas emissions and with 87% of residential buildings that we will have by 2050 already built, it is vital to adopt sustainable retrofitting practices. The question is: what are the viable solutions? One answer may be green roof retrofitting. The environmental benefits include reduced operational carbon emissions, reduced urban heat island effect, increased bio-diversity, housing temperature attenuation and reduced stormwater run-off. The economic benefits are the reduced maintenance costs and lower running costs. The social gain is the creation of spaces where people have access to green areas. However, the barriers to retrofitting include the perceptions of structural adequacy, the risk of water damage, high installation and maintenance costs, as well as access and security issues. Many Australian and Brazilian residential buildings have metal sheet roofs, a lightweight material with poor thermal performance. During the summer, temperatures in Sydney and Rio de Janeiro reach 45 degrees Celsius, and in both cities, rainfall patterns are changing, with more intense downpours. Furthermore, many residential buildings are leased, and currently, tenants are restricted by the modifications that they can perform to reduce running costs and carbon emissions. This research reports on an experiment on two small-scale metal roofs in Sydney and Rio de Janeiro to assess the thermal performance of portable small-scale modules. The findings are that considerable variation in temperature was found in both countries, indicating that green roof retrofitting could lower the cooling energy demand considerably

Evaluating the Thermal Performance of Retrofitted Lightweight Green Roofs and Walls in Sydney and Rio de Janeiro

© 2017 The Authors. With increasing densification in urban settlements, environmental issues are a challenge in the sustainable development of all cities globally. Considering that the built environment releases almost half of the total greenhouse gas emissions, an effective solution to mitigating the impacts of increasing temperatures can be the improved performance of existing buildings. Furthermore 87% of the buildings we will have in 2050 are already built. Retrofitting roofs and walls with a living vegetated system such as green roofs and walls could be an upgrade option, increasing sustainable construction. The benefits are improved thermal performance but also improved air quality, stormwater attenuation, increased bio-diversity and lower heating and / or cooling energy consumption. No empirical data exists for Sydney and Rio de Janeiro and the question is; what is the extent of thermal improvement with retrofitted green walls and roof in timber framed and blockwork structures? This study analyses both effects and benefits of the green roofs and walls through an experiment in two countries: one in Sydney, Australia; a timber framed construction, and another one in Rio de Janeiro, Brazil; with blockwork construction. This difference in the material choice was made according to the most common type of construction for housing in each country. In each site, the walls and the roof of one of the prototypes were covered with plants and compared to the performance of an unplanted but otherwise identical prototype. The thermal performance was analysed by observing the temperature variation simultaneously in a non-vegetated and vegetated structure. The initial findings show that the combination of green roof and green walls have a relevant role in temperature attenuation. These results indicate, that this lightweight retrofit green technology could not only represent an important advance on sustainable development, but can that it also lead to more comfortable internal conditions for humans living in dense urban environments

Efeitos da fertirrigação com chorume bovino sobre características físicas e químicas de solos.

O experimento foi conduzido no Departamento de Solos e Engenharia Rural do Centro de Ciências Agrárias da Universidade Federal da Paraíba, Areia-PB com o objetivo de avaliar os efeitos da aplicação de chorume bovino em diferentes proporções em água: 0:1; 1:5; 1:4; 1:3 e 1:2 correspondentes aos percentuais de 0; 17; 20; 25 e 33% de chorume respectivamente, sobre características físicas e químicas de dois solos: um de textura argilosa e outro de textura arenosa. O delineamento experimental foi inteiramente casualizado em esquema fatorial 5 x 2 com três repetições. Para cada tratamento a aplicação da solução foi feita imediatamente após o volume de 5kg de solo terem sidos acondicionados em sacos de polietileno preto com 30cm de altura de 20cm de diâmetro e aos dez e vinte dias após a primeira aplicação. Os efeitos do chorume foram mais expressivos sobre a retenção de água pelo solo, densidade do solo, soma de bases, capacidade de troca catiônica do solo mais argiloso em relação ao solo mais arenoso. A aplicação do chorume não contribuiu no aumento da condutividade elétrica a ponto de tornar os solos salinos

DODAB and DODAC bilayer-like aggregates in the micromolar surfactant concentration domain

In the millimolar concentration domain (typically 1 mM), dioctadecyldimethylammonium bromide and chloride (DODAX, X representing Br- or Cl- counterions) molecules assemble in water as large unilamellar vesicles. Differential scanning calorimetry (DSC) is a suitable technique to obtain the melting temperature (Tm) characteristic of surfactant bilayers, while fluorescence spectroscopy detects formation of surfactant aggregates, like bilayers. These two techniques were combined to investigate the assemble of DODAX molecules at micromolar concentrations, from 10 to 100 micromolar. At 1 mM surfactant, Tm ~ 45 ºC and 49 oC, respectively for DODAB and DODAC. DSC and fluorescence of Nile Red were used to show the formation of DODAX aggregates, at the surfactant concentration as low as 10 micromolar, whose Tm decreases monotonically with increasing DODAX concentration to attain the value for the ordinary vesicles. The data indicate that these aggregates are organized as bilayer-like structures.Fundação para a Ciência e a Tecnologia (FCT

A fluidized granular medium as an instance of the Fluctuation Theorem

We study the statistics of the power flux into a collection of inelastic beads maintained in a fluidized steady-state by external mechanical driving. The power shows large fluctuations, including frequent large negative fluctuations, about its average value. The relative probabilities of positive and negative fluctuations in the power flux are in close accord with the Fluctuation Theorem of Gallavotti and Cohen, even at time scales shorter than those required by the theorem. We also compare an effective temperature that emerges from this analysis to the kinetic granular temperature.Comment: 4 pages, 5 figures, submited to Physical Review Letters; Revised versio

Caracterização físico-química de jenipapo.

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Tratamento hidrotérmico e aplicação de cera de carnaúba sobre a qualidade da manga Tommy Atkins.

O trabalho teve como objetivo estudar os efeitos do tratamento hidrotérmico isolado e também aliado à aplicação de cera de carnaúba sobre as qualidades comerciais de frutos de manga da variedade Tommy Atkins. Os frutos de manga foram analisados antes do tratamento hidrotérmico, aos 6 dias e aos 12 dias após o tratamento. Foram avaliados os seguintes parâmetros: dados médios de Sólidos Solúveis Total, dados médios de Perda de Peso dos frutos, dados médios da Acidez Total Titulável, da Firmeza dos frutos e Aparência Externa e Interna dos frutos. Constatou-se que o tratamento hidrotérmico feito isolado acelerou significativamente a perda de peso e a degradação da aparência e qualidades comerciais dos frutos. Quando o tratamento hidrotérmico foi conduzido juntamente com aplicação de cera de carnaúba houve prolongamento significativo da vida útil dos frutos. Com este procedimento verificouse manutenção da boa aparência externa e interna dos frutos após os 12 dias de testes