Tribological Behaviour of Plasma-Functionalized Graphene as Low-Viscosity Oil Additive

The influence of plasma functionalization of multilayer graphene (MG) as an additive for low-viscosity polyolester (POE) oil in terms of dispersion stability and tribological behaviour was investigated. Pure MG and MG functionalized via N2 and NH3 plasma were analysed. The plasma functionalization significantly improved the substrate wettability and the dispersion stability of the nanofluids. The tribological behaviour of the nanofluids was investigated using a reciprocating cylinder on plane configuration. 0.05 wt% of the functionalized nanoparticles dramatically increased the scuffing resistance and significantly improved the anti-wear properties of the POE oil (over 60% wear reduction). Optical microscopy, white light interferometry, scanning electron microscopy and micro-Raman spectroscopy were used to identify the wear mechanisms. The functionalization provides a well-dispersed suspension, which contributes to the formation of a continuous and homogeneous anti-wear tribofilm. Once between the sliding surfaces, the MG improves the load-carrying capacity of the oil, avoiding the seizure of the tribolayer.     

The vulnerability of wind power to climate change in Brazil

The availability and reliability of wind power depend a great deal on current and future climate conditions, which may vary in light of possible global climate change (GCC). Long-term energy planning, however, does not normally take possible future GCC into consideration, which may turn out to be a risky exercise. In the case of Brazil, the untapped wind power potential is known to be impressive, provided that climate conditions remain the same over time. The focus of this study is to analyze some possible impacts of GCC on the wind power potential of Brazil, by simulating wind conditions associated with the IPCC A2 and B2 Scenarios. Results based on the HadCM3 general circulation model and the analysis of the country's wind database indicate that the wind power potential in Brazil would not be jeopardized in the future due to possible new climate conditions. On the contrary, improved wind conditions are expected, particularly in the Northeast coast of the country. Therefore, investments in wind power generation can be an interesting way to expand renewable energy production in Brazil. However, given the large uncertainties associated with GCC models and scenarios, the findings of this paper should be viewed as a possibility rather than as a projection.     

Adaptive Signal Modeling Based on Sparse Approximations for Scalable Parametric Audio Coding

This paper deals with the application of adaptive signal models for parametric audio coding. A fully parametric audio coder, which decomposes the audio signal into sinusoids, transients and noise, is here proposed. Adaptive signal models for sinusoidal, transient, and noise modeling are therefore included in the parametric scheme in order to achieve high-quality and low bit-rate audio coding. In this paper, a new sinusoidal modeling method based on a perceptual distortion measure is proposed. For transient modeling, a fast and effective method based on matching pursuit with a mixed dictionary is chosen. The residue of the previous models is analyzed as a noise-like signal. The proposed parametric audio coder allows high quality audio coding for one-channel audio signals at 16 kbits/s (average bit rate). A bit-rate scalable version of the parametric audio coder is also proposed in this work. Bit-rate scalability is intended for audio streaming applications, which are highly demanded nowadays. The performance of the proposed parametric audio coders (nonscalable and scalable coders) is assessed in comparison to widely used audio coders operating at similar bit rates.      

Serotonin‐transporter promoter polymorphism modulates the ability to control food intake: Effect on total weight loss

Scope

The biggest challenge for losing weight is the ability to control the amount of food eaten; the tendency to overeat is called disinhibition. Our aims were to determine whether (a) the SLC6A 4‐promoter variant (5‐HTTLPR) relates to disinhibition; (b) this association could affect total weight‐loss during a behavioral/dietary treatment for obesity.

Methods and results

A total of 2961 subjects attended voluntarily five weight‐loss clinics; a subsample (n = 624) was recruited for SLC6A4 genotyping. Total weight‐loss, emotional‐eating‐score and disinhibition‐score were examined. We observed that: (a) the reduced ability to control food intake (disinhibition) is implicated in the impairment to lose weight; (b) SLC6A 4‐promoter variant is implicated in disinhibition. S carriers (low‐expressing) of the SLC6A4‐promoter variant had a lower inhibition capacity and showed more failure (1.6 times) to control the amount of food eaten than LL (p < 0.05); other factors such as eating while bored, overeating after work at night, or craving for specific foods were associated to the SLC6A4 genotype (p < 0.05); (c) The combination of disinhibition (high disinhibition) and genetics (S carrier) had a higher impact on total weight loss than each factor separately.

Conclusions

SLC6A 4‐promoter variant is associated with the ability to control food intake and interacts with emotional eating to modulate total weight loss.

     

Comparison between externally fired gas turbine and gasifier-gas turbine system for the olive oil industry

The olive oil industry generates during the extraction process several solid wastes as olive tree leaves and prunings, exhausted pomace and olive pits. These renewable wastes could be used for power and heat applications. The aim of this paper is to compare the performance of two small-scale CHP systems: a gasification- gas turbine system and an EFGT (externally fired gas turbine system). For this reason, several parameters have been calculated: generated heat and power, electric and overall efficiencies, biomass consumption, exergy efficiency, optimum pressure ratio, etc. These systems provide 30 kW_e and about 60kW_th. Simulation results show that the electrical and overall efficiencies achieved in EFGT system (19.1% and 59.3%, respectively) are significantly higher than those obtained in the gasification plant (12.3% and 45.4%). The proposed CHP systems have been modeled using Cycle-Tempo^® software.     

Propagation by stem cuttings and root system structure of Jatropha curcas

Scarce knowledge about the propagation of Jatropha curcas is one of the limitations for the growth of cultivated area with this oilseed crop. The effect of stem cuttings length, basal area, and position on the branch on sprouting and early growth of jatropha plants were evaluated, and the effect of the propagation method on the structure of root system of adult plants was studied. The growth and development of Jatropha curcas plants were influenced by length and basal area of stem cuttings. Short cuttings favor early sprouting, but long and thick cuttings promote more shoot and root growth. Plants originated from stem cuttings obtained from the base of the branch grew more shoot structures (buds, stems, and leaves) than stem cutting from middle and apex of the branch. Leaf area at 75 days after planting was not influenced by the dimensions of stem cutting. The most vigorous root system was observed in the plants that originate from direct seeding, without any transplanting. Propagation using bag or root plug interferes with the formation of a deep tap root. Propagation through stem cuttings resulted in a very different root system structure, with predominance of superficial and thin roots. When the cap of a tap root is lost, the plant was able to regenerate a new root.     

Comparison of seven numerical methods for determining Weibull parameters for wind energy generation in the northeast region of Brazil

This paper deals with the analysis and comparison of 7 (seven) numerical methods for the assessment of effectiveness in determining the parameters for the Weibull distribution, using wind speed data collected in Camocim and Paracuru cities, State of Ceará, in the northeast region of Brazil, in the period from August 2004 to April 2006, obtained by the Department of Infrastructure of the State of Ceará. One method is not well known, namely the equivalent energy method, and its performance is compared to the others. By using the methods of analysis of variance, RMSE (root mean square error), and chi-square tests to compare the proposed methods, this study aims to determine which ones are effective in determining the parameters of the Weibull distribution for the available data, in an attempt to establish acceptable criteria to a better utilization of wind power in the State of Ceará, which is a national prominence in the use of renewable sources for electricity generation in Brazil.     

An experimental comparison between LPG and engine exhaust gas as energy source for an absorption refrigeration system

This paper presents an experimental analysis of an absorption refrigeration system, comparing two different energy sources. The exhaust gas from an internal combustion engine was evaluated against the original energy source, liquefied petroleum gas (LPG). The experiments were performed in a domestic refrigerator, monitoring the air temperature and humidity inside the equipment. A production engine was tested with 25% and wide‐open throttle valve (WOT), mounted on a bench dynamometer. The energy demand, cooling capacity and coefficient of performance (COP) were determined for both energy sources. The results showed that engine exhaust gas is a potential source for absorption refrigeration systems. When the engine exhaust gas was used as energy source, the energy available for the refrigerator was higher with 25% throttle valve opening. Copyright © 2011 John Wiley & Sons, Ltd.     

Ambient Protection of Few‐Layer Black Phosphorus via Sequestration of Reactive Oxygen Species

Few‐layer black phosphorous (BP) has emerged as a promising candidate for next‐generation nanophotonic and nanoelectronic devices. However, rapid ambient degradation of mechanically exfoliated BP poses challenges in its practical deployment in scalable devices. To date, the strategies employed to protect BP have relied upon preventing its exposure to atmospheric conditions. Here, an approach that allows this sensitive material to remain stable without requiring its isolation from the ambient environment is reported. The method draws inspiration from the unique ability of biological systems to avoid photo‐oxidative damage caused by reactive oxygen species. Since BP undergoes similar photo‐oxidative degradation, imidazolium‐based ionic liquids are employed as quenchers of these damaging species on the BP surface. This chemical sequestration strategy allows BP to remain stable for over 13 weeks, while retaining its key electronic characteristics. This study opens opportunities to practically implement BP and other environmentally sensitive 2D materials for electronic applications.