College of Natural Scienceshttp://etd.aau.edu.et/handle/123456789/182021-04-21T04:16:56Z2021-04-21T04:16:56ZElectronic Structure of 2d-Gallium Arsenide as Studied Using First Principles Density Functional Theory (Dft)Amare, Andinethttp://etd.aau.edu.et/handle/123456789/261652021-04-19T06:56:14Z2020-08-23T00:00:00ZElectronic Structure of 2d-Gallium Arsenide as Studied Using First Principles Density Functional Theory (Dft)
Amare, Andinet
In this thesis we have calculated electronic structure of 2D-GaAs within the first
principles using Quantum ESPRESSO pacakage. We optimized lattice constant
and identified the nature and values of band gap of Zinc Blende structure gallium
aresnide (GaAs). Norm-conserving pseudopotential is used for the self-consistent
calculation, and the Generalized Gradient Approximation (GGA) for the exchange
correlation. An optimum lattice constant of 7.4Å, 6.1Å, and 5.7Å, respectively, is
obtained for 1D, 2D, and 3D, and in close agreement with the experimental value
5.65Å. 2-D GaAs is known to have a gap of 1.8 eV which is in close agreement with
previous observations [45], but has 25.9 % error to the experimental value 1.43 eV
[42]. This work clearly explains that lattice constant increases with decrease in
crystal size. Moreover, we could identify the charge transfer between the Ga and
As atoms. Generally we could make calculations and compare with its 1-D and 3-D
structures results.
2020-08-23T00:00:00ZGeotechnical Evaluation on Failed Section Along Felegeselam-Chida Road Project, Southwestern Ethiopia, Using Ps-Insar and Deterministic ApproachMitiku, Abayneshhttp://etd.aau.edu.et/handle/123456789/261642021-04-19T06:32:15Z2020-09-26T00:00:00ZGeotechnical Evaluation on Failed Section Along Felegeselam-Chida Road Project, Southwestern Ethiopia, Using Ps-Insar and Deterministic Approach
Mitiku, Abaynesh
The current study of geotechnical evaluation on failed section were conducted in Southwestern Ethiopia, Felegeselam-Chida road project. This research aims to evaluate the status and features of the landslides through Persistent Scattering- Interferometry Synthetic Aperture Radar (PS-InSAR) and deterministic analyses along Felegeselam-Chida road project, south-western Ethiopia. Database for the 10 selected landslides along the road project is generated from project thirteen Single Look Complex (SLC) radar images that are downloaded from Alaska satellite. These time series images cover from Nov 3, 2014 to Jan 6, 2020 and processed to define the rate of deformation on the failed sections. The deterministic analysis further defined the safety factor of each failed section from the input data obtained from DEM analysis, geological factors and field-laboratory investigation (both primary and secondary) data using Plaxis software package both 2D and 3D. The PS-InSAR analysis showed that the mean velocity of displacement rate is ranging from 47.4mm/yr to -54.4mm/yr in the entire study area starting from Nov, 2020 to date. Additional analysis made considering the vertical displacement from satellite line of sight (LOS) to define the deformations for each selected failed sections. Accordingly, the mean velocity displacements for each are calculated and ranges from 20 to -100mm/yr at Km 57; 40 to -120mm/yr at Km 63; 60 to -60mm/yr at Km 65; 50 to -60mm/yr at Km 68; 50 to -150 mm/yr at Km 78-79; 50 to -100 mm/yr at Km83; 20 to 100mm/yr at Km86;10 to -100 mm/yr at Km87; 30 to -90 mm/yr at Km 93; and 20 to -120 mm/yr at Km 94. The results also confirm that the landslides are happening prior to the road construction and further accelerated and reactivated afterwards. In the other hand, the deterministic safety factors (FS) of the failed sections showed that they are almost instable, with FS ranging from 0.73-1.11, to be easily triggered through saturation and slope cuts. The end result of both the factor of safety and displaced material on each failed sections are, at Km 57 is 1.05 and 50m; at Km 63 is 0.97 and 65m; at Km 68 is 1.1 and 52m, at Km 78-79 is 1 and 60m; at Km83 is 1 and 50m: at Km 86 is1 and 60m; at Km 87 is 1.08 and 40m; and at Km 93 is 0.73 and 45m respectively. Finally, the result determined at Km 94 is FOS 0.95 and 50m displacement. Besides, the deterministic analysis gave insight to the stress and pore pressure conditions at failure; and mobilized shear strength at failure to assist the remediation effort. In this sense, the deviatory stress results gave clues for the prominent cause of failure. When the deviator stress is as high as 883.6 KN/m2, like at Km 78-79, indicating loading or saturation is causing the failures. Whereas the low results obtained 80 KN/m2 at of Km 57 may indicate cutting is the main cause of the failure.
2020-09-26T00:00:00ZExplicit Finite Difference Scheme For 2d Parabolic Partial Differential EquationNegash, Habtemichaelhttp://etd.aau.edu.et/handle/123456789/261632021-04-17T22:48:14Z2020-06-25T00:00:00ZExplicit Finite Difference Scheme For 2d Parabolic Partial Differential Equation
Negash, Habtemichael
In this project report, explicit nite di erence scheme for 2D parabolic par-
tial di erential equations is considered. This method is used to solve the partial
derivatives in the partial di erential equations at each gride point that are de-
rived from neighbouring values by using Taylors theorem. The forward-time
centered-space(FTCS)and explicit schemes are developed. The MATLAB im-
plementation allows to experiment with the stability limit of the forward-time
centered-space(FTCS).
2020-06-25T00:00:00ZPenalty and Barriers Methods for Constrained Optimization ProblemsTefera, Liyahttp://etd.aau.edu.et/handle/123456789/261622021-04-17T22:24:51Z2020-05-20T00:00:00ZPenalty and Barriers Methods for Constrained Optimization Problems
Tefera, Liya
Constrained optimization problems are relatively more complex than uncon-
strained optimization problems. Some of these complexities are minimized
by penalty and barrier methods. Penalty and barrier methods are approx-
imating of constrained optimization problems by unconstrained optimiza-
tion problems or sequence of unconstrained optimization problem to _nd the
solution of a given constrained optimization problem. In penalty function
method the constrained problem is replace by unconstrained (sequence of
unconstrained) problem by adding a term to the objective function that pre-
scribes a high cost for violation of the constraints and in barrier method
the problem is replaced by unconstrained (sequence of unconstrained) prob-
lem through adding a term that favors points in the interior of the feasible
region over those near the boundary. Barrier requires that the interior of
the feasible sets must be nonempty and therefore, they are used with prob-
lems having only inequality constraints (there is no interior for equality con-
straints). Even though,these methods are fundamental, they have their own
series limitations to _nd its approximate solution to the constrained prob-
lem. In these methods we have to do with penalty parameter _, and this
certainly make problem of un-constraint optimization of the penalize objec-
tive function. With those limitations, method are very fundamentals to _nd
best solutions of constrained optimization problems with some restrictions.
2020-05-20T00:00:00Z