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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 14 (1977), S. 141-147 
    ISSN: 1432-0630
    Keywords: 82.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have determined by direct molecular beam velocity measurements that translational energy accommodation of O2 molecules scattered from a hot polycrystalline tungsten target is inefficient at high surface temperatures. Translational energy accommodation is inefficient whether the surface is clean or covered with oxygen to a varying extent, even though in the latter case the scattering is diffuse. On a clean tungsten surface the scattering of the O2 was approximately specular and the reaction probability of O2 was constant and greater than 90% over the temperature range 1000K to 2800 K. It was shown by simultaneous helium scattering that atomic surface roughness of an oxygen chemilayer, rather than trapping, is a major cause of the observed diffuse scattering of oxygen. At the lowest surface temperature of 1000 K, with an oxygen chemilayer present, the velocity of the most probable number density of the scattered O2 was lower than in the incoming beam or than that expected for complete equilibration with the surface.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 14 (1977), S. 411-413 
    ISSN: 1432-0630
    Keywords: 82.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A direct first step in the mechanism for the initial oxidation of a polycrystalline tungsten surface, the catalyzed dissociation of O2 on it, or the formation of WO X by O2 at intermediate temperatures is shown to occur in ∼10−13 s. Molecular beam experiments demonstrated that the reactivity was greater than 90%, the unreacted O2 was substantially unaccommodated in translational energy to the surface temperature, and the reaction probability was nearly independent of surface temperature from 2800 to 415 K although there was a small increase at 415 K. The general conditions when no molecular surface precursor state contributes to the surface reactivity are discussed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-2967
    Keywords: carbon dioxide ; plume ; pH ; random walk ; diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A method to evaluate aquatic mortality given a pollutant distribution is presented and applied to several sample low pH plumes representing various ocean CO2 disposal schemes. The method is an improvement over current analysis because it integrates the mortality due to time‐varying exposure to low pH with the probabilistic experiences of passive organisms subject to turbulent lateral diffusion as they pass through the plume. For the examples presented, the plume was discretized laterally into lanes and longitudinally by time steps, and a random walk model accounting for the scale‐dependent nature of relative diffusion was used to simulate the organism pathways over one time step. From these simulations, the probability that an organism will be in a given lane, $$\dot \jmath $$ , one time step after it starts from an initial lane, $$i$$ , was determined for all combinations of $$i$$ and $$\dot \jmath $$ . These probabilities were used to find the number of organisms following each of the possible pathways, and the mortality to the organisms due to their time varying exposure to low pH was determined by using the toxicity model described in part I of this paper. The integrated method allows the impact of the plume to be described in terms of total organism mortality as well as spatial deficit of organisms.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-2967
    Keywords: carbon dioxide ; sequestration ; plume ; pH ; toxicity ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Feasibility studies suggest that the concept of capturing CO2 from fossil fuel power plants and discharging it to the deep ocean could help reduce atmospheric CO2 concentrations. However, the local reduction in seawater pH near the point of injection is a potential environmental impact. Data from the literature reporting on toxicity of reduced pH to marine organisms potentially affected by such a plume were combined into a model expressing mortality as a function of pH and exposure time. Since organisms exposed to real plumes would experience a time‐varying pH, methods to account for a variable exposure were reviewed and a new method developed based on the concept of isomortality. In part II of this paper, the method is combined with a random‐walk model describing the transport of passive organisms through a low pH plume leading to a Monte‐Carlo‐like risk assessment which is applied to several candidate CO2 injection scenarios.
    Type of Medium: Electronic Resource
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