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Emission Model (emission + model)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Start-Up Transient in a Hall Thruster

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 10 2006
F. Taccogna
Abstract For the first time a two dimensional axisymmetric fully kinetic Particle-in-Cell/Monte Carlo Collision (PICMCC) model is used to describe the start-up transient of the acceleration channel in a Hall thruster. The Poisson equation and a secondary electron emission model are invoked for the description of the plasma dynamic phase. Numerical results have been used to see the formation and evolution of the discharge inside the channel. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Subsurface addition emission model

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2005
Allen Hatfield PhD
Subsurface addition is commonly used in the chemical industry as a means of ensuring that the incoming reagent is distributed uniformly within a batch as the addition proceeds. The difference between subsurface addition and the typical above-surface addition is in how the inlet liquid stream enters the vessel. When calculating the process vent emissions for an above-surface addition one considers the partial pressure of the inlet stream components along with the batch components. This is because both mixtures have direct exposure to the vessel headspace during the addition process. For subsurface addition, volatile compounds that are contained in the inlet stream are exposed to the headspace only as they appear in the batch during the addition process. The purpose of this paper is to present a model for estimating the vent emissions for subsurface addition processes based on the integrated average liquid-phase composition. © 2004 American Institute of Chemical Engineers Environ Prog, 2004 [source]

Contribution of N2O to the greenhouse gas balance of first-generation biofuels

GLOBAL CHANGE BIOLOGY, Issue 1 2009
EDWARD M. W. SMEETS
Abstract In this study, we analyze the impact of fertilizer- and manure-induced N2O emissions due to energy crop production on the reduction of greenhouse gas (GHG) emissions when conventional transportation fuels are replaced by first-generation biofuels (also taking account of other GHG emissions during the entire life cycle). We calculate the nitrous oxide (N2O) emissions by applying a statistical model that uses spatial data on climate and soil. For the land use that is assumed to be replaced by energy crop production (the ,reference land-use system'), we explore a variety of options, the most important of which are cropland for food production, grassland, and natural vegetation. Calculations are also done in the case that emissions due to energy crop production are fully additional and thus no reference is considered. The results are combined with data on other emissions due to biofuels production that are derived from existing studies, resulting in total GHG emission reduction potentials for major biofuels compared with conventional fuels. The results show that N2O emissions can have an important impact on the overall GHG balance of biofuels, though there are large uncertainties. The most important ones are those in the statistical model and the GHG emissions not related to land use. Ethanol produced from sugar cane and sugar beet are relatively robust GHG savers: these biofuels change the GHG emissions by ,103% to ,60% (sugar cane) and ,58% to ,17% (sugar beet), compared with conventional transportation fuels and depending on the reference land-use system that is considered. The use of diesel from palm fruit also results in a relatively constant and substantial change of the GHG emissions by ,75% to ,39%. For corn and wheat ethanol, the figures are ,38% to 11% and ,107% to 53%, respectively. Rapeseed diesel changes the GHG emissions by ,81% to 72% and soybean diesel by ,111% to 44%. Optimized crop management, which involves the use of state-of-the-art agricultural technologies combined with an optimized fertilization regime and the use of nitrification inhibitors, can reduce N2O emissions substantially and change the GHG emissions by up to ,135 percent points (pp) compared with conventional management. However, the uncertainties in the statistical N2O emission model and in the data on non-land-use GHG emissions due to biofuels production are large; they can change the GHG emission reduction by between ,152 and 87 pp. [source]

Wind direction azimuthal signature in the Stokes emission vector from the ocean surface at microwave frequencies

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2001
A. J. Camps
Abstract An ocean polarimetric emission model is presented. It is found that skewness and upwind/cross-wind rms slopes are responsible for the first and second azimuthal harmonic, respectively. Atmospheric effects contribute significantly at low wind speeds, and at horizontal polarization at certain observation angles. Simulation results compare favorably with reported JPL,WINDRAD measurements. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 426,432, 2001. [source]