Enhanced stability in CO2 of Ta doped BaCe0.9Y0.1O3−δ electrolyte for intermediate temperature SOFCs

The influence of Ta concentration on the stability of BaCe_0.9−xTa_xY_0.1O_3−δ (where x=0.01, 0.03 and 0.05) powders and sintered samples in CO₂, their microstructure and electrical properties were investigated. The ceramic powders were synthesized by the method of solid state reaction, uniaxially pressed and sintered at 1550 °C to form dense electrolyte pellets. A significant stability in CO₂ indicated by the X-ray analysis performed was observed for the samples with x≥0.03. The electrical conductivities determined by impedance measurements in the temperature range of 550–750 °C and in various atmospheres (dry argon, wet argon and wet hydrogen) increased with temperature but decreased with Ta concentration. The highest conductivities were observed in the wet hydrogen atmosphere, followed by those in wet argon, while the lowest were obtained in the dry argon atmosphere for each dopant concentration. The composition with Ta content of 3 mol% showed satisfactory characteristics: good resistance to CO₂ in extreme testing conditions, while a somewhat reduced electrical conductivity is still comparable with that of BaCe_0.9Y_0.1O_3−δ.     

Analysis of MWCNT/epoxy composites at microwave frequency: reproducibility investigation

A wide-band microwave characterization of nanocomposites based on commercial multiwalled carbon nanotubes (MWCNTs) and epoxy resin is presented. The sample preparation method is discussed in detail. Field emission scanning electron microscopy is used for morphological sample analysis of nanocomposites and MWCNTs. The complex permittivity is measured in a wide frequency band (3 to 18 GHz) using a commercial dielectric probe (Agilent 85070D) and a network analyzer (E8361A). A statistical analysis based on one-way analysis of variance (ANOVA) technique is performed. The aim of this statistical analysis is to investigate the influence of concentration of nanoparticles inside the polymer matrix on the complex permittivity. This can be significantly different in nanocomposites even if the samples have similar electrical properties.     

Flexible and configurable verification policies with Omnibus

The three main assertion-based verification approaches are: run-time assertion checking (RAC), extended static checking (ESC) and full formal verification (FFV). Each approach offers a different balance between rigour and ease of use, making them appropriate in different situations. Our goal is to explore the use of these approaches together in a flexible way, enabling an application to be broken down into parts with different reliability requirements and different verification approaches used in each part. We explain the benefits of using the approaches together, present a set of guidelines to avoid potential conflicts and give an overview of how the Omnibus IDE provides support for the full range of assertion-based verification approaches within a single tool.     

Scatter correction techniques in 3D PET: a Monte Carlo evaluation

In this work, a Monte Carlo software package, PET-EGS, designed to simulate realistic PET clinical studies, was used to assess three different approaches to scatter correction in 3D PET: analytical (gaussian fitting technique), experimental (dual energy window technique) and probabilistic (Monte Carlo technique). Phantom and clinical studies were carried out by 3D PET and simulated by PET-EGS. A clinical study (¹⁸F-FDG brain study) was simulated assuming PET emission/transmission multiple-volume images as a voxelised source object describing the distribution of both the radioactivity and attenuation coefficients and accounting for out-of-field activity and media. The accuracy of PET-EGS in modelling the physical response of a 3D PET scanner was assessed by statistical comparison between measured and total (scatter+unscatter) simulated distributions (probability for the two distributions to be the same distribution: p>0.95). The accuracy of the scatter models, for each scatter correction technique, was evaluated on sinograms by statistical comparison between the estimated and the simulated scatter distributions (agreement <1 σ). The accuracy of scatter correction was evaluated on sinograms by comparison between scatter corrected and simulated unscatter distributions, proving a comparable accuracy of all the considered scatter correction techniques for brainlike distributed sources     

Investigation of Thermophysical Properties of Thermal Degraded Biodiesels

Biofuels are an alternative to fossil fuels and can be made from many different raw materials. The use of distinct catalyst and production processes, feedstocks, and types of alcohol results in biofuels with different physical and chemical properties. Even though these diverse options for biodiesel production are considered advantageous, they may pose a setback when quality specifications are considered, since different properties are subject to different reactions during usage, storage and handling. In this work, we present a systematic characterization of biodiesels to investigate how accelerated thermal degradation affects fuel properties. Two different types of biodiesel, commercially obtained from distinct feedstocks, were tested. The thermal degradation process was performed by maintaining the temperature of the sample at \(140 \,^{\circ }\hbox {C}\) under constant air flux for different times: 0 h, 3 h, 6 h, 9 h, 12 h, 24 h and 36 h. Properties such as density, viscosity, activation energy, volumetric thermal expansion coefficient, gross caloric value, acid value, infrared absorption, and temperature coefficient of the refractive index were used to study the thermal degradation of the biodiesel samples. The results show a significant difference in fuel properties before and after the thermal degradation process suggesting the formation of undesirable compounds. All the properties mentioned above were found to be useful to determine whether a biodiesel sample underwent thermal degradation. Moreover, viscosity and acid value were found to be the most sensitive characteristics to detect the thermal degradation process.     

Enhanced biohydrogen production from microalgae by diesel engine hazardous emissions fixation

Microalgae cultivation has gained increased attention from research and industry sectors in recent years, due to the wide variety of applications for the produced biomass, such as biofuels and substances of high economic value. Indirect biophotolysis biohydrogen production from microalgae has been shown recently to be limited by the amount of accumulated biomass during the growth phase. As a result, this study focused on developing a strategy to increase biohydrogen generation via biomass production increase through microalgae cultivation using exhaust gases from diesel engines. In order to achieve that objective, four simultaneous cultures were conducted to compare the growth of microalgae under pure air and emissions injection, in different flow regimes. An indigenous microalgae strain was selected to be robust under different weather conditions and was identified as Acutodesmus obliquus through rDNA sequence analysis. The results indicate an increase in biomass production of about 2.8 times for the best case of cultivation with emissions in comparison to a compressed air condition. Besides the growth analyses, the potential for treating the hazardous emissions injected into the system was investigated and the data demonstrated that the CO₂ and NO_x content was substantially reduced, showing that no damage to the microalgae is caused by the diesel engine emissions. Numerical simulation results for the H₂ production indirect biophotolysis demonstrate that there is an optimal rhythm for maximum time averaged H₂ production rate, and that the stoichiometrically limited total H₂ production is augmented by a similar factor to microalgae biomass production increase.