Thin-Film Nanotechnology for Power Sources

Russian Engineering Research - Thin-film vacuum technology permits the creation of new electrode materials on the basis of a flexible carbon matrix with a highly developed surface. Supercapacitor...     

Human responses to high levels of carbon dioxide and air temperature

In this study, 30 subjects were exposed to different combinations of air temperature (T_a: 24, 27, and 30°C) and CO₂ level (8000, 10 000, and 12 000 ppm) in a high-humidity (RH: 85%) underground climate chamber. Subjective assessments, physiological responses, and cognitive performance were investigated. The results showed that as compared with exposure to T_a = 24°C, exposure to 30°C at all CO₂ levels caused subjects to feel uncomfortably warm and experience stronger odor intensity, while increased mental effort and greater intensity of acute health symptoms were reported. However, no significant effects of T_a on task performance or physiological responses were found. This indicated that subjects had to exert more effort to maintain their performance in an uncomfortably warm environment. Increasing CO₂ from 8000 to 12 000 ppm at all T_a caused subjects to report higher rates of headache, fatigue, agitation, and feeling depressed, although the results were statistically significant only at 24 and 27°C. The text typing performance and systolic blood pressure (SBP) decreased significantly at this exposure, whereas diastolic blood pressure (DBP) and thermal discomfort increased significantly. These effects suggest higher arousal/stress. No significant interaction effect of T_a and CO₂ concentration on human responses was identified.     

Preparation and characterization of calcium phosphate cement with enhanced tissue adhesion for bone defect repair

Anti-washout and tissue adhesion properties are essential for the clinical application of injectable bone materials. In this study, we prepared calcium phosphate cement (CPC) with anti-washout and tissue adhesion properties and attempted to build covalent bonds between CPC and the amino groups in bone tissue under a self-regulating pH system in the CPC (acidic to basic). The results of push-out tests demonstrated that a significant enhancement (from 6.42 ± 0.76 N to 61.5 ± 4.09 N) in tissue adhesion was obtained with the addition of 6% (w/w) oxidized sodium alginate (OSA) in CPC. The FTIR, XRD, anti-washout test, XPS, pH test, and SEM results suggested that the synergistic effect of OSA-citric acid (CA) led to the formation of a three-dimensional gel network structure in the CPC, and the Schiff base reaction between aldehyde and amino groups induced adhesion between CPC and the bone tissue. Further, the addition of less OSA had no significant negative effect on the hydration properties of CPC. Our work aims to promote the development of injectable bone material in clinical applications.     

Performance investigation on a novel 3D wave flow channel design for PEMFC

Flow field structure can largely determine the output performance of Polymer electrolyte membrane fuel cell. Excellent channel configuration accelerates electrochemical reactions in the catalytic layer, effectively avoiding flooding on the cathode side. In present study, a three-dimensional, multi-phase model of PEMFC with a 3D wave flow channel is established. CFD method is applied to optimize the geometry constructions of three-dimensional wave flow channels. The results reveal that 3D wave flow channel is overall better than straight channel in promoting reactant gases transport, removing liquid water accumulated in microporous layer and avoiding thermal stress concentration in the membrane. Moreover, results show the optimal flow channel minimum depth and wave length of the 3D wave flow channel are 0.45 mm and 2 mm, respectively. Due to the periodic geometric characteristics of the wave channel, the convective mass transfer is introduced, improving gas flow rate in through-plane direction. Furthermore, when the cell output voltage is 0.4 V, the current density in the novel channel is 23.8% higher than that of conventional channel.     

Insights into low-carbon hydrogen production methods: Green,blue and aqua hydrogen

The primary aim of this study is to provide insights into different low-carbon hydrogen production methods. Low-carbon hydrogen includes green hydrogen (hydrogen from renewable electricity), blue hydrogen (hydrogen from fossil fuels with CO₂ emissions reduced by the use of Carbon Capture Use and Storage) and aqua hydrogen (hydrogen from fossil fuels via the new technology). Green hydrogen is an expensive strategy compared to fossil-based hydrogen. Blue hydrogen has some attractive features, but the CCUS technology is high cost and blue hydrogen is not inherently carbon free. Therefore, engineering scientists have been focusing on developing other low-cost and low-carbon hydrogen technology. A new economical technology to extract hydrogen from oil sands (natural bitumen) and oil fields with very low cost and without carbon emissions has been developed and commercialized in Western Canada. Aqua hydrogen is a term we have coined for production of hydrogen from this new hydrogen production technology. Aqua is a color halfway between green and blue and thus represents a form of hydrogen production that does not emit CO₂, like green hydrogen, yet is produced from fossil fuel energy, like blue hydrogen. Unlike CCUS, blue hydrogen, which is clearly compensatory with respect to carbon emissions as it captures, uses and stores produced CO₂, the new production method is transformative in that it does not emit CO₂ in the first place. In order to promote the development of the low-carbon hydrogen economy, the current challenges, future directions and policy recommendations of low-carbon hydrogen production methods including green hydrogen, blue hydrogen, and aqua hydrogen are investigated in the paper.     

Flame characteristics of premixed H2-air mixtures explosion venting in a spherical container through a duct

The explosion venting duct can effectively reduce the hazard degree of a gas explosion and conduct the venting energy to the safe area. To investigate the flame quantitative propagation law of explosion venting with a duct, the effects of hydrogen fraction and explosion venting duct length on jet flame propagation characteristics of premixed H₂-air mixtures were analyzed through experiment and simulation. The experiment results under initial conditions of room temperature and 1 atm show that when hydrogen fraction was high enough, part of the unburned hydrogen was mixed with air again to reach an ignitable concentration, resulting in the secondary combustion was easier produced and the duration of the secondary flame increased. With the increase of venting duct length, the flame front distance and propagation velocity increased. Meanwhile, the spatial distribution of pressure field and temperature field, and the propagation process and mechanism of the flame venting with a duct were analyzed using FLUENT software. The variation of the pressure wave and the pressure reflection oscillation law in the explosion venting duct was captured. Therefore, in the industrial explosion venting design with a duct, the hazard caused by the coupling of venting pressure and venting flame under different fractions should be considered comprehensively.     

The impacts of cattle access points on deposited sediment levels in headwater streams in Ireland

Cattle access to streams has been linked globally with degradation of stream water quality, driven largely by bank erosion and resultant instream, fine sediment deposition. The majority of evidence on such effects is however based in arid and semiarid regions of the United States and Australia, with few studies relating to cool temperate climates such as Northwest Europe. In this study, “Quorer” resuspendable sediment samples were taken from riffle geomorphic units upstream (control) and at two points downstream (pressure and recovery) of cattle access points in headwater streams in agricultural catchments in Ireland to assess levels of deposited stream sediment. Samples were taken in April/May (2016) prior to the grazing season and in October (2016) at the end of the grazing season. Sites in good‐high ecological status catchments and less than good ecological status catchments were included in the study. Higher levels of sediment were found downstream of cattle access points in both good‐high status and less than good status catchments; however, the impacts of access points were spatially confined to, in most cases, the area immediately downstream of the point of access. There was a strong correlation between deposited sediment mass and organic matter (OM) mass, with levels of OM increasing linearly with deposited sediment mass. Levels of measured sediment were negatively correlated with riparian habitat health (measured using a qualitative habitat assessment). The results of this study highlight the need for measures to prevent cattle access to headwater streams where access points can be many in order to manage local habitat quality and downstream water quality issues.