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- Asadzadeh, Mohammad, 1952
(author)
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Streamline diffusion methods for the Fermi and Fokker-Planck equations
- 1997
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In: Transport Theory and Statistical Physics. ; 26:3, s. 319-340
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Journal article (peer-reviewed)abstract
- e derive error estimates in certain weighted L2-norms for the streamline diffusion and discontinuous Galerkin finite element methods for steady state, energy dependent, Fermi and Fokker-Planck equations in two space dimensions, giving error bounds of order O(hk+1/2), for the weighted current function J, as in the convection dominated convection-diffusion problems, with J ε Hk+1(Ω) and h being the quasi-uniform mesh size in triangulation of our three dimensional phase-space domain Ω = Iz, times Iy times Iz, with z corresponding to the velocity variable. Our studies, in this paper, contain a priori error estimates for Fermi and Fokker-Planck equations with both piecewise continuous and piecewise discontinuous (in x and xy-directions) trial functions. The analyses are based on stability estimates which relay on an angular symmetry (not isotropy!) assumption. A continuation of this paper, the a posteriori error estimates for Fermi and Fokker-Planck equations, is the subject of a future work.
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- Asadzadeh, Mohammad, 1952, et al.
(author)
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The discrete ordinates method for the neutron transport equation in an infinite cylindrical domain
- 1992
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In: Mathematical Models and Methods in Applied Science. ; 2:3, s. 317-338
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Journal article (peer-reviewed)abstract
- We prove a regularity result for a Fredholm integral equation with weakly singular kernel, arising in connection with the neutron transport equation in an infinite cylindrical domain. The theorem states that the solution has almost two derivatives in L1, and is proved using Besov space techniques. This result is applied in the error analysis of the discrete ordinates method for the numerical solution of the neutron transport equation. We derive an error estimate in the L1-norm for the scalar flux, and as a consequence, we obtain an error bound for the critical eigenvalue.
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45. |
- Ashwin, M.J., et al.
(author)
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The bonding of CAs acceptors in InxGa1-xAs grown by chemical beam epitaxy using carbon tetrabromide as the source of carbon
- 1996
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 80:12, s. 6754-6760
-
Journal article (peer-reviewed)abstract
- InxGa1-xAs layers (0≤x≤0.37) doped with carbon (>1020 cm-3) were grown on semi-insulating GaAs substrates by chemical beam epitaxy using carbon tetrabromide (CBr4) as the dopant source. Hall measurements imply that all of the carbon was present as CAs for values x up to 0.15. The C acceptors were passivated by exposing samples to a radio frequency hydrogen plasma for periods of up to 6 h. The nearest-neighbor bonding configurations of CAs were investigated by studying the nondegenerate antisymmetric hydrogen stretch mode (A-1 symmetry) and the symmetric XH mode (A+1 symmetry) of the H-CAs pairs using IR absorption and Raman scattering, respectively. Observed modes at 2635 and 450 cm-1 had been assigned to passivated Ga4CAs clusters. New modes at 2550 and 430 cm-1 increased in strength with increasing values of x and are assigned to passivated InGa3CAs clusters. These results were compared with ab initio local density functional theory. Modes due to AlInGaCAs clusters were detected in samples containing grown in Al and In. These results demonstrate that for InGaAs, CBr4 is an efficient C doping source since both In-CAs bonds as well as Ga-CAs bonds are formed, whereas there is no evidence for the formation of In-CAs bonds in samples doped with C derived from trimethylgallium or solid sources
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