364 research outputs found
Recommended from our members
Phreatic seepage flow through an earth dam with an impeding strip
New mathematical models are developed and corresponding boundary value problems are analytically and numerically solved for Darcian flows in earth (rock)âfilled dams, which have a vertical impermeable barrier on the downstream slope. For saturated flow, a 2-D potential model considers a free boundary problem to Laplaceâs equation with a traveling-wave phreatic line generated by a linear drawup of a water level in the dam reservoir. The barrier re-directs seepage from purely horizontal (a seepage face outlet) to purely vertical (a no-flow boundary). An alternative model is also used for a hydraulic approximation of a 3-D steady flow when the barrier is only a partial obstruction to seepage. The Poisson equation is solved with respect to Strackâs potential, which predicts the position of the phreatic surface and hydraulic gradient in the dam body. Simulations with HYDRUS, a FEM-code for solving Richardsâ PDE, i.e., saturated-unsaturated flows without free boundaries, are carried out for both 2-D and 3-D regimes in rectangular and hexagonal domains. The Barenblatt and Kalashnikov closed-form analytical solutions in non-capillarity soils are compared with the HYDRUS results. Analytical and numerical solutions match well when soil capillarity is minor. The found distributions of the Darcian velocity, the pore pressure, and total hydraulic heads in the vicinity of the barrier corroborate serious concerns about a high risk to the structural stability of the dam due to seepage. The modeling results are related to a âforensicâ review of the recent collapse of the spillway of the Oroville Dam, CA, USA
A pH-based pedotransfer function for scaling saturated hydraulic conductivity reduction: improved estimation of hydraulic dynamics in HYDRUS
Hydraulic conductivity is a key soil property governing agricultural production and is thus an important parameter in hydrologic modeling. The pH scaling factor for saturated hydraulic conductivity (Ks) reduction in the HYDRUS model was reviewed and evaluated for its ability to simulate Ks reduction. A limitation of the model is the generalization of Ks reduction at various levels of electrolyte concentration for different soil types, i.e., it is not soil specific. In this study, a new generalized linear regression model was developed to estimate Ks reduction for a larger set of Australian soils compared with three American soils. A nonlinear pedotransfer function was also produced, using the LevenbergâMarquardt optimization algorithm, by considering the pH and electrolyte concentration of the applied solution as well as the soil clay content. This approach improved the estimation of the pH scaling factor relating to Ks reduction for individual soils. The functions were based on Ks reduction in nine contrasting Australian soils using two sets of treatment solutions with Na adsorption ratios of 20 and 40; total electrolyte concentrations of 8, 15, 25, 50, 100, 250, and 500 mmolc Lâ1; and pH values of 6, 7, 8, and 9. A comparison of the experimental data and model outputs indicates that the models performed objectively well and successfully described the Ks reduction due to the pH. Further, a nonlinear function provided greater accuracy than the generalized function for the individual soils of Australia and California. This indicates that the nonlinear model provides an improved estimation of the pH scaling factor for Ks reduction in specific soils in the HYDRUS model and should therefore be considered in future HYDRUS developments and applications
Characteristic emotional intelligence and emotional well-being
Both theory and previous research suggest a link between emotional intelligence and emotional well-being. Emotional intelligence includes the ability to understand and regulate emotions; emotional well-being includes positive mood and high self-esteem. Two studies investigated the relationship between emotional intelligence and mood, and between emotional intelligence and self-esteem. The results of these studies indicated that higher emotional intelligence was associated with characteristically positive mood and higher self-esteem. The results of a third study indicated that higher emotional intelligence was associated with a higher positive mood state and greater state self-esteem. The third study also investigated the role of emotional intelligence in mood and self-esteem regulation and found that individuals with higher emotional intelligence showed less of a decrease in positive mood and self-esteem after a negative state induction using the Velten method, and showed more of an increase in positive mood, but not in self-esteem, after a positive state induction. The findings were discussed in the light of previous work on emotional intelligence, and recommendations were made for further study
Electronic structure of wurtzite and zinc-blende AlN
The electronic structure of AlN in wurtzite and zinc-blende phases is studied
experimentally and theoretically. By using x-ray emission spectroscopy, the Al
3p, Al 3s and N 2p spectral densities are obtained. The corresponding local and
partial theoretical densities of states (DOS), as well as the total DOS and the
band structure, are calculated by using the full potential linearized augmented
plane wave method, within the framework of the density functional theory. There
is a relatively good agreement between the experimental spectra and the
theoretical DOS, showing a large hybridization of the valence states all along
the valence band. The discrepancies between the experimental and theoretical
DOS, appearing towards the high binding energies, are ascribed to an
underestimation of the valence band width in the calculations. Differences
between the wurtzite and zinc-blende phases are small and reflect the slight
variations between the atomic arrangements of both phases
- âŠ