710,214 research outputs found

    Development of a land use regression model for black carbon using mobile monitoring data and its application to pollution-avoiding routing

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    Black carbon is often used as an indicator for combustion-related air pollution. In urban environments, on-road black carbon concentrations have a large spatial variability, suggesting that the personal exposure of a cyclist to black carbon can heavily depend on the route that is chosen to reach a destination. In this paper, we describe the development of a cyclist routing procedure that minimizes personal exposure to black carbon. Firstly, a land use regression model for predicting black carbon concentrations in an urban environment is developed using mobile monitoring data, collected by cyclists. The optimal model is selected and validated using a spatially stratified cross-validation scheme. The resulting model is integrated in a dedicated routing procedure that minimizes personal exposure to black carbon during cycling. The best model obtains a coefficient of multiple correlation of R = 0.520. Simulations with the black carbon exposure minimizing routing procedure indicate that the inhaled amount of black carbon is reduced by 1.58% on average as compared to the shortest-path route, with extreme cases where a reduction of up to 13.35% is obtained. Moreover, we observed that the average exposure to black carbon and the exposure to local peak concentrations on a route are competing objectives, and propose a parametrized cost function for the routing problem that allows for a gradual transition from routes that minimize average exposure to routes that minimize peak exposure

    Reducing Black Carbon from Wood Burning in Fairbanks, Alaska

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    Fairbanks, Alaska has been home to air quality concerns for years. Heat sources like wood boilers emit black carbon, a pollutant akin to soot. In Fairbanks\u27s harsh winters, black carbon is trapped close to the earth and creates health problems for residents. Black carbon has a more global effect as well, however, and climate scientists have recently begun to consider reducing black carbon emissions as a viable way to slow the pace of climate change. Fairbanks is uniquely situated to react to this call for action. Reducing black carbon emissions from wood burning in Fairbanks would not only contribute to the greater fight against climate change, but would alleviate significant local air quality and health concerns. This Comment summarizes the issue of black carbon in Fairbanks, and proposes several legal approaches to mitigate its negative environmental and health effects, including public nuisance claims, local regulations, and stricter compliance with federal environmental laws

    Sources of uncertainties in modelling black carbon at the global scale

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    Our understanding of the global black carbon (BC) cycle is essentially qualitative due to uncertainties in our knowledge of its properties. This work investigates two source of uncertainties in modelling black carbon: those due to the use of different schemes for BC ageing and its removal rate in the global Transport-Chemistry model TM5 and those due to the uncertainties in the definition and quantification of the observations, which propagate through to both the emission inventories, and the measurements used for the model evaluation. The schemes for the atmospheric processing of black carbon that have been tested with the model are (i) a simple approach considering BC as bulk aerosol and a simple treatment of the removal with fixed 70% of in-cloud black carbon concentrations scavenged by clouds and removed when rain is present and (ii) a more complete description of microphysical ageing within an aerosol dynamics model, where removal is coupled to the microphysical properties of the aerosol, which results in a global average of 40% in-cloud black carbon that is scavenged in clouds and subsequently removed by rain, thus resulting in a longer atmospheric lifetime. This difference is reflected in comparisons between both sets of modelled results and the measurements. Close to the sources, both anthropogenic and vegetation fire source regions, the model results do not differ significantly, indicating that the emissions are the prevailing mechanism determining the concentrations and the choice of the aerosol scheme does not influence the levels. In more remote areas such as oceanic and polar regions the differences can be orders of magnitude, due to the differences between the two schemes. The more complete description reproduces the seasonal trend of the black carbon observations in those areas, although not always the magnitude of the signal, while the more simplified approach underestimates black carbon concentrations by orders of magnitude. The sensitivity to wet scavenging has been tested by varying in-cloud and below-cloud removal. BC lifetime increases by 10% when large scale and convective scale precipitation removal efficiency are reduced by 30%, while the variation is very small when below-cloud scavenging is zero. Since the emission inventories are representative of elemental carbon-like substance, the model output should be compared to elemental carbon measurements and if known, the ratio of black carbon to elemental carbon mass should be taken into account when the model is compared with black carbon observation

    Separation of Carbon from Deinking Waste by Means of Flotation

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    The technique of froth flotation, as practiced in the separation of mineral ores, has been applied to the separation of carbon black from the deinking waste of the paper industry. On the theory that carbon black (from ink) has a positive charge in water, and clay and cellulose fibers have negative charges in water, experiments were of two types. First, it was attempted to float the carbon from the clay and cellulose fibers. Second, it was attempted to float the clay and cellulose fibers from the carbon. Several possible formulas were found for separating carbon black from deinking waste. Favorable results were obtained in both types of experiments

    Effective conductivity in association with model structure and spatial inhomogeneity of polymer/carbon black composites

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    The relationship between effective conductivity and cell structure of polyethylene/carbon composites as well as between effective conductivity and spatial distribution of carbon black are discussed. Following Yoshida's model both structures can, in a way, be said to be intermediate between the well known Maxwell-Garnett (MG) and Bruggeman (BR) limiting structures. Using TEM photographs on composites with various carbon blacks we have observed that the larger is Garncarek's inhomogeneity measure H of two-dimensional (2D) representative distribution of the carbon black, the smaller is the effective conductivity of the composite.Comment: 7 pages, 9 figure

    Theoretical and experimental aspects of carbon formation in thermal plasma

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    Formation of carbon black from Freons was studied in RF thermal plasma conditions. Equilibrium compositions of the products were calculated by computer code ASTRA 4.0. The experiments on thermal decomposition were performed in an RF thermal plasma reactor. By comparing the calculated and experimental results a model was constructed on carbon black formation in RF thermal plasma reactor

    Laser ignition of an optically sensitised secondary explosive by a diode laser

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    As a green technology, laser ignition of a relatively insensitive secondary explosive has been experimentally investigated. The explosive, hexanitrostilbene (HNS), was doped with one of two optical sensitizers, carbon black or a laser absorbing dye, and a continuous-wave (CW) infrared diode laser was used as the igniting source. The ignition sensitivities of HNS with each of the two optical sensitizers were analysed and compared in terms of: optical power threshold for ignition, ignition delay and full burn delay at various laser powers. The results have shown that both the chemical dye and carbon black optically sensitize the explosive with similar efficiencies. In contrast to the carbon black, the dye provides wavelength specificity and selectivity in the laser ignition process and its solubility in some specific solvents improves the coating of the explosive material. It was therefore concluded that the laser absorbing dye is a better candidate for optical sensitization in laser ignition than the commonly used carbon black. The combination of laser ignition sensitivity with wavelength selectivity potentially offers higher reliability and safety at a low optical power for future ignitors of secondary explosives

    Indentation toughness of Al2O3-CNT nanocomposites

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    In the last few years new ceramic/carbon nanotube composites have been developed and a number of authors have reported improved mechanical and functional properties in the case of ceramic/CNT composites compared to the monolithic materials. according to the results reinforcing by CNTs in many cases improved the fracture toughness of Al2O3, however, this toughening is not evident, and some of the variations may purely arise from using different testing techniques. The improvement in fracture toughness is due to bridging of the crack surfaces by CNTs during the crack propagation by CNT pullout mechanism, which strongly depends on the interfacial bonding between CNTs and the matrix. The aim of the present work is to investigate the effect of addition of carbon nanotubes and carbon black on the indentation toughness of alumina-CNT and alumina-carbon black nanocomposites