Si Deposition Rates in a Two‐Dimensional CVD Reactor and Comparisons with Model Calculations

1990 ◽  
Vol 137 (7) ◽  
pp. 2313-2319 ◽  
Author(s):  
William G. Breiland ◽  
Michael E. Coltrin
Keyword(s):  
Two Dimensional ◽  
Deposition Rates ◽  
Model Calculations

scholarly journals Anomalous spin correlations and excitonic instability of interacting 2D Weyl fermions

Science ◽  
2017 ◽  
Vol 358 (6369) ◽  
pp. 1403-1406 ◽  
Author(s):  
Michihiro Hirata ◽  
Kyohei Ishikawa ◽  
Genki Matsuno ◽  
Akito Kobayashi ◽  
Kazuya Miyagawa ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Nmr Relaxation ◽  
Spin Fluctuations ◽  
Two Dimensional ◽  
Marked Contrast ◽  
Metallic Behavior ◽  
Model Calculations ◽  
Spin Correlations ◽  
Zero Momentum ◽  
Weyl Fermions

The Coulomb interaction in systems of quasi-relativistic massless electrons has an unscreened long-range component at variance with conventional correlated metals. We used nuclear magnetic resonance (NMR) measurements to reveal unusual spin correlations of two-dimensional Weyl fermions in an organic material, causing a divergent increase of the Korringa ratio by a factor of 1000 upon cooling, in marked contrast to conventional metallic behavior. Combined with model calculations, we show that this divergence stems from an interaction-driven velocity renormalization that almost exclusively suppresses zero-momentum spin fluctuations. At low temperatures, the NMR relaxation rate shows an unexpected increase; numerical analyses show that this increase corresponds to internode excitonic fluctuations, a precursor to a transition from massless to massive quasiparticles.

scholarly journals Dispersal Distances for Airborne Spores Based on Deposition Rates and Stochastic Modeling

2007 ◽  
Vol 97 (10) ◽  
pp. 1325-1330 ◽  
Author(s):  
Anders Stockmarr ◽  
Viggo Andreasen ◽  
Hanne Østergård
Keyword(s):  
Fungal Spores ◽  
Two Dimensional ◽  
Airborne Spores ◽  
Modeling Framework ◽  
Deposition Rates ◽  
Spore Release ◽  
Special Cases ◽  
Release Height ◽  
Dispersal Distances ◽  
Parameter Values

A new modeling framework for particle dispersal is explored in the context of the particles being fungal spores dispersed within a field. The model gives rise to both exponentially decreasing and polynomially decreasing two-dimensional densities of deposited fungal spores. We reformulate the model in terms of time to deposition, and show how this concept is equivalent to the deposition rate for fungal spores. Special cases where parameter values for wind and gravitation lead to exponentially or polynomially decreasing densities are discussed, and formulas for one- and two-dimensional densities of deposited spores are given explicitly in terms of parameters for diffusion, wind, gravitation, and spore release height.

scholarly journals Position of Ice Divides and Ice Centers on Ice Sheets

1973 ◽  
Vol 12 (66) ◽  
pp. 353-360 ◽  
Author(s):  
J. Weertman
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Two Dimensional ◽  
Model Calculations ◽  
Accumulation Pattern ◽  
Rate Of Accumulation

Model calculations are made of the magnitude of the shift of the portion of an ice divide on a two dimensional ice sheet and of the “center” (the position of highest elevation) of a circular ice sheet when the rate of accumulation is different on different sides or in different sectors of an ice sheet. It is concluded that gross changes in the accumulation pattern are required to cause an appreciable shift of the position of ice divides or ice centers if the positions of the edge of the ice sheet are fixed.

Överlåtaren: a fast way to transfer and orthogonalize two-dimensional off-specular reflectivity data

2016 ◽  
Vol 49 (6) ◽  
pp. 2091-2099 ◽  
Author(s):  
F. A. Adlmann ◽  
G. K. Pálsson ◽  
J. C. Bilheux ◽  
J. F. Ankner ◽  
P. Gutfreund ◽  
...  
Keyword(s):  
Materials Science ◽  
Theoretical Modelling ◽  
Two Dimensional ◽  
Model Calculations ◽  
Full Characterization ◽  
Specular Scattering ◽  
Surfaces And Interfaces ◽  
Computational Performance ◽  
Reflectivity Data ◽  
Lateral Structures

Reflectivity measurements offer unique opportunities for the study of surfaces and interfaces, and specular reflectometry has become a standard tool in materials science to resolve structures normal to the surface of a thin film. Off-specular scattering, which probes lateral structures, is more difficult to analyse, because the Fourier space being probed is highly anisotropic and the scattering pattern is truncated by the interface. As a result, scattering patterns collected with (especially time-of-flight) neutron reflectometers are difficult to transform into reciprocal space for comparison with model calculations. A program package is presented for a generic two-dimensional transformation of reflectometry data intoqspace and back. The data are represented on an orthogonal grid, allowing cuts along directions relevant for theoretical modelling. This treatment includes background subtraction as well as a full characterization of the resolution function. The method is optimized for computational performance using repeatable operations and standardized instrument settings.

scholarly journals Two-Dimensional Thermo-Mechanical Modelling of Flow and Depth-Age Profiles Near the Ice Divide in Central Greenland

1989 ◽  
Vol 12 ◽  
pp. 31-36 ◽  
Author(s):  
Dorthe Dahl-Jensen
Keyword(s):  
Age Distribution ◽  
Ice Sheet ◽  
Surface Strain ◽  
Two Dimensional ◽  
Stress Distributions ◽  
Geothermal Heat ◽  
Last Glacial Period ◽  
Model Calculations ◽  
Pressure Melting ◽  
Time Invariant

The ice divide on an ice sheet is a special place on the ice sheet, where the velocity and stress distributions are different from those found just two ice thicknesses from the ice divide. A two-dimensional thermo-mechanical model has been used to model the flow near the ice divide in central Greenland. The results show that the surface strain-rates are increased by 50% of the values found 15 km down-stream and that the basal temperatures rise by 3°C. Estimates of a depth–age distribution in the vicinity of Crête show that the isochrones rise at the dome. The model calculations predict 1600 m of Holocene ice, 1000 m of Wisconsin ice, and 400 m of ice older than 115kyear. 15 km down-stream from the dome, the thickness of ice older than 115 kyear will be reduced by 50%. In these calculations it has been assumed that the ice thickness at the dome is time-invariant. The existence of the old ice depends on the basal temperature. The estimates of the basal temperature depend strongly on past accumulation rates and on the geothermal heat flux but the ice has most likely been below the pressure-melting point throughout the last glacial period.

scholarly journals A cloud chemistry module for the 3-D cloud-resolving mesoscale model Meso-NH with application to idealized cases

2013 ◽  
Vol 6 (4) ◽  
pp. 1275-1298 ◽  
Author(s):  
M. Leriche ◽  
J.-P. Pinty ◽  
C. Mari ◽  
D. Gazen
Keyword(s):  
Wet Deposition ◽  
Mesoscale Model ◽  
Three Dimensional ◽  
Chemical Species ◽  
Cloud Microphysics ◽  
Mixed Phase ◽  
Two Dimensional ◽  
Deposition Rates ◽  
Scavenging Efficiency ◽  
Ice Phase

Abstract. A complete chemical module has been developed for use in the Meso-NH three-dimensional cloud resolving mesoscale model. This module includes gaseous- and aqueous-phase chemical reactions that are analysed by a pre-processor generating the Fortran90 code automatically. The kinetic solver is based on a Rosenbrock algorithm, which is robust and accurate for integrating stiff systems and especially multiphase chemistry. The exchange of chemical species between the gas phase and cloud droplets and raindrops is computed kinetically by mass transfers considering non-equilibrium between the gas- and the condensed phases. Microphysical transfers of chemical species are considered for the various cloud microphysics schemes available, which are based on one-moment or two-moment schemes. The pH of the droplets and of the raindrops is diagnosed separately as the root of a high order polynomial equation. The chemical concentrations in the ice phase are modelled in a single phase encompassing the two categories of precipitating ice particles (snow and graupel) of the microphysical scheme. The only process transferring chemical species in ice is retention during freezing or riming of liquid hydrometeors. Three idealized simulations are reported, which highlight the sensitivity of scavenging efficiency to the choice of the microphysical scheme and the retention coefficient in the ice phase. A two-dimensional warm, shallow convection case is used to compare the impact of the microphysical schemes on the temporal evolution and rates of acid precipitation. Acid wet deposition rates are shown to be overestimated when a one-moment microphysics scheme is used compared to a two-moment scheme. The difference is induced by a better prediction of raindrop radius and raindrop number concentration in the latter scheme. A two-dimensional mixed-phase squall line and a three-dimensional mixed-phase supercell were simulated to test the sensitivity of cloud vertical transport to the retention efficiency of gases in the ice phase. The 2-D and 3-D simulations illustrate that the retention in ice of a moderately soluble gas such as formaldehyde substantially decreases its concentration in the upper troposphere. In these simulations, retention of highly soluble species in the ice phase significantly increased the wet deposition rates.

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