scholarly journals Numerical predictions of aerosol charging and electrical conductivity of the lower atmosphere of Mars

2007 ◽  
Vol 34 (4) ◽  
Author(s):  
M. Michael ◽  
M. Barani ◽  
S. N. Tripathi
Keyword(s):  
Electrical Conductivity ◽  
Lower Atmosphere ◽  
Numerical Predictions ◽  
Aerosol Charging

scholarly journals Thermally driven circulation in a region of complex topography: comparison of wind-profiling radar measurements and MM5 numerical predictions

2006 ◽  
Vol 24 (6) ◽  
pp. 1537-1549 ◽  
Author(s):  
L. Bianco ◽  
B. Tomassetti ◽  
E. Coppola ◽  
A. Fracassi ◽  
M. Verdecchia ◽  
...  
Keyword(s):  
Land Surface ◽  
Central Italy ◽  
Surface Wind ◽  
Lower Atmosphere ◽  
Complex Topography ◽  
Model Errors ◽  
Data Set ◽  
Near Surface ◽  
Numerical Predictions ◽  
Thermally Driven

Abstract. The diurnal variation of regional wind patterns in the complex terrain of Central Italy was investigated for summer fair-weather conditions and winter time periods using a radar wind profiler. The profiler is located on a site where interaction between the complex topography and land-surface produces a variety of thermally and dynamically driven wind systems. The observational data set, collected for a period of one year, was used first to describe the diurnal evolution of thermal driven winds, second to validate the Mesoscale Model 5 (MM5) that is a three-dimensional numerical model. This type of analysis was focused on the near-surface wind observation, since thermally driven winds occur in the lower atmosphere. According to the valley wind theory expectations, the site – located on the left sidewall of the valley (looking up valley) – experiences a clockwise turning with time. Same characteristics in the behavior were established in both the experimental and numerical results. Because the thermally driven flows can have some depth and may be influenced mainly by model errors, as a third step the analysis focuses on a subset of cases to explore four different MM5 Planetary Boundary Layer (PBL) parameterizations. The reason is to test how the results are sensitive to the selected PBL parameterization, and to identify the better parameterization if it is possible. For this purpose we analysed the MM5 output for the whole PBL levels. The chosen PBL parameterizations are: 1) Gayno-Seaman; 2) Medium-Range Forecast; 3) Mellor-Yamada scheme as used in the ETA model; and 4) Blackadar.

scholarly journals Pore-scale modeling of electrical and fluid transport in Berea sandstone

Geophysics ◽  
2010 ◽  
Vol 75 (5) ◽  
pp. F135-F142 ◽  
Author(s):  
Xin Zhan ◽  
Lawrence M. Schwartz ◽  
M. Nafi Toksöz ◽  
Wave C. Smith ◽  
F. Dale Morgan
Keyword(s):  
Electrical Conductivity ◽  
Transport Properties ◽  
Electrical Transport ◽  
Fluid Transport ◽  
Sample Volume ◽  
Image Resolution ◽  
Hydraulic Permeability ◽  
Sandstone Sample ◽  
Numerical Predictions ◽  
Surface Conduction

The purpose of this paper is to test how well numerical calculations can predict transport properties of porous permeable rock, given its 3D digital microtomography [Formula: see text] image. For this study, a Berea 500 sandstone sample is used, whose [Formula: see text] images have been obtained with resolution of [Formula: see text]. Porosity, electrical conductivity, permeability, and surface area are calculated from the [Formula: see text] image and compared with laboratory-measured values. For transport properties (electrical conductivity, permeability), a finite-difference scheme is adopted. The calculated and measured properties compare quite well. Electrical transport in Berea 500 sandstone is complicated by the presence of surface conduction in the electric double layer at the grain-electrolyte boundary. A three-phase conductivity model is proposed to compute surface conduction on the rock [Formula: see text] image. Effects of image resolution and computation sample size on the accuracy of numerical predictions are also investigated. Reducing resolution (i.e., increasing the voxel dimensions) decreases the calculated values of electrical conductivity and hydraulic permeability. Increasing computation sample volume gives a better match between laboratory measurements and numerical results. Large sample provides a better representation of the rock.

Removing Substrate Background in TEM Microanalysis

1974 ◽  
Vol 32 ◽  
pp. 568-569
Author(s):  
John C. Russ ◽  
Nicholas C. Barbi
Keyword(s):  
Electrical Conductivity ◽  
Rapid Growth ◽  
Organic Film ◽  
Absolute Concentration ◽  
Background Signal ◽  
X Ray ◽  
Elemental Concentrations ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
The Continuum

The rapid growth of interest in attaching energy-dispersive x-ray analysis systems to transmission electron microscopes has centered largely on microanalysis of biological specimens. These are frequently either embedded in plastic or supported by an organic film, which is of great importance as regards stability under the beam since it provides thermal and electrical conductivity from the specimen to the grid.Unfortunately, the supporting medium also produces continuum x-radiation or Bremsstrahlung, which is added to the x-ray spectrum from the sample. It is not difficult to separate the characteristic peaks from the elements in the specimen from the total continuum background, but sometimes it is also necessary to separate the continuum due to the sample from that due to the support. For instance, it is possible to compute relative elemental concentrations in the sample, without standards, based on the relative net characteristic elemental intensities without regard to background; but to calculate absolute concentration, it is necessary to use the background signal itself as a measure of the total excited specimen mass.

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