Computational Simulation of Explosively Generated Pulsed Power Devices

Technology and size constraints have limited the development of the end game mechanisms of today\u27s modern military weapons. A smaller, more efficient means of powering these devices is needed, and explosive pulsed power devices could be that answer. While most prior research has been in the experimental field, there is a need for more theory-based research and a computer modeling capability. The objective of this research was to use experimental data collected by the US Army at Redstone Arsenal from their ferroelectric generator (FEG) design in combination with the ALEGRA-EMMA code to develop a computer model that can accurately represent an FEG and that can be verified against experimental data and used to predict future experiments. While the ALEGRA code is not capable of simulating the breakdown phenomenon seen in the open circuit cases, the model can accurately reproduce the peak values for the current but has problems reproducing the peak values for the voltage. Overall, the developed model provides a good baseline simulation capability that can be used as a springboard for future development with further research

Stability and Evolution of Planar and Concave Slopes under Unsaturated and Rainfall Conditions

Natural slopes are often observed to have a concave, convex, or a combination concave/convex profile, yet constructed slopes are traditionally designed with planar cross-sectional geometry. In this paper, the stability of two planar slopes was compared with that of companion concave slopes, designed to have similar factors of safety (FOS) under gravity loading. The stability of these slopes was then investigated in response to a suction event followed by a precipitation event, and it was shown that both the planar and the concave slopes experienced similar changes in stability. Additional analyses were conducted with a simulated erosion mechanism to investigate how the planar and concave shapes would evolve under a sequence of three similar suction/precipitation/erosion cycles. The results suggest that for these slopes, the second and third simulated weather cycles reduced the stability of the slopes, yet had a lesser effect on the concave slopes than the planar slopes. This is in spite of the fact that the planar slopes became more “concave-like” due to the simulated erosion, and suggests slopes designed to be concave may perform better than the planar slopes

Seminary Training, Role Demands, Family Stressors and Strategies for Alleviation of Stressors in Pastors’ Families

This is a report from a study of the stressors faced by Seventh-day Adventist pastors and their families in the North American Division.https://digitalcommons.andrews.edu/hrsa/1231/thumbnail.jp

Through Christ Alone?: Adventists’ Beliefs about Salvation

This presentation examines how Adventists from four world divisions view the issue of salvation. Using data from the 2018 and 2023 Global Church Member’s Surveys, we compare and contrast members’ stated beliefs over time about how one receives salvation. The analysis includes cultural factors that may be influencing these outcomes

Effective mass theory of monolayer \delta-doping in the high-density limit

Monolayer \delta-doped structures in silicon have attracted renewed interest with their recent incorporation into atomic-scale device fabrication strategies as source and drain electrodes and in-plane gates. Modeling the physics of \delta-doping at this scale proves challenging, however, due to the large computational overhead associated with ab initio and atomistic methods. Here, we develop an analytical theory based on an effective mass approximation. We specifically consider the Si:P materials system, and the limit of high donor density, which has been the subject of recent experiments. In this case, metallic behavior including screening tends to smooth out the local disorder potential associated with random dopant placement. While smooth potentials may be difficult to incorporate into microscopic, single-electron analyses, the problem is easily treated in the effective mass theory by means of a jellium approximation for the ionic charge. We then go beyond the analytic model, incorporating exchange and correlation effects within a simple numerical model. We argue that such an approach is appropriate for describing realistic, high-density, highly disordered devices, providing results comparable to density functional theory, but with greater intuitive appeal, and lower computational effort. We investigate valley coupling in these structures, finding that valley splitting in the low-lying \Gamma band grows much more quickly than the \Gamma-\Delta band splitting at high densities. We also find that many-body exchange and correlation corrections affect the valley splitting more strongly than they affect the band splitting

Thermodynamic stability of neutral Xe defects in diamond

Optically active defect centers in diamond are of considerable interest, and ab initio calculations have provided valuable insight into the physics of these systems. Candidate structures for the Xe center in diamond, for which little structural information is known, are modeled using density functional theory. The relative thermodynamic stabilities were calculated for two likely structural arrangements. The split-vacancy structure is found to be the most stable for all temperatures up to 1500 K. A vibrational analysis was also carried out, predicting Raman- and IR-active modes which may aid in distinguishing between center structures

Ab initio calculation of energy levels for phosphorus donors in silicon

The s manifold energy levels for phosphorus donors in silicon are important input parameters for the design and modeling of electronic devices on the nanoscale. In this paper we calculate these energy levels from first principles using density functional theory. The wavefunction of the donor electron’s ground state is found to have a form that is similar to an atomic s orbital, with an effective Bohr radius of 1.8 nm. The corresponding binding energy of this state is found to be 41 meV, which is in good agreement with the currently accepted value of 45.59 meV. We also calculate the energies of the excited 1s(T 2) and 1s(E) states, finding them to be 32 and 31 meV respectively