Publications

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Design and operation of the electric power grid (EPG) relies heavily on computational models. High-fidelity, full-order models are used to study transient phenomena on only a small part of the network. Reduced-order dynamic and power flow models are used when analysis involving thousands of nodes are required due to the computational demands when simulating large numbers of nodes. The level of complexity of the future EPG will dramatically increase due to large-scale deployment of variable renewable generation, active load and distributed generation resources, adaptive protection and control systems, and price-responsive demand. High-fidelity modeling of this future grid will require significant advances in coupled, multi-scale tools and their use on high performance computing (HPC) platforms. This LDRD report demonstrates SNL's capability to apply HPC resources to these 3 tasks: (1) High-fidelity, large-scale modeling of power system dynamics; (2) Statistical assessment of grid security via Monte-Carlo simulations of cyber attacks; and (3) Development of models to predict variability of solar resources at locations where little or no ground-based measurements are available.

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We present the results of a one year LDRD program that has focused on evaluating the use of newly developed deep ultraviolet LEDs in water purification. We describe our development efforts that have produced an LED-based water exposure set-up and enumerate the advances that have been made in deep UV LED performance throughout the project. The results of E. coli inactivation with 270-295 nm LEDs are presented along with an assessment of the potential for applying deep ultraviolet LED-based water purification to mobile point-of-use applications as well as to rural and international environments where the benefits of photovoltaic-powered systems can be realized.

Parallel microscopic experimentation (the combinatorial approach often used in solid-state science) was applied to characterize atmospheric copper corrosion behavior. Specifically, this technique permitted relative sulfidation rates to be determined for copper containing different levels of point defects and impurities (In, Al, O, and D). Corrosion studies are inherently difficult because of complex interactions between material interfaces and the environment. The combinatorial approach was demonstrated using micron-scale Cu lines that were exposed to a humid air environment containing sub-ppm levels of H{sub 2}S. The relative rate of Cu{sub 2}S growth was determined by measuring the change in resistance of the line. The data suggest that vacancy trapping by In and Al impurities slow the sulfidation rate. Increased sulfidation rates were found for samples containing excess point defects or deuterium. Furthermore, the sulfidation rate of 14 {micro}m wide Cu lines was increased above that for planar films.

The electronic properties of heavily and orderly Si-doped nipi structures in GaAs are studied theoretically using the ab-initio self-consistent pseudopotential method within the local density approximation. Two nipi configurations are considered. Besides investigating the nature of the impurity-related band edge states, the xy-planar-averaged local ionic and self-consistent potentials are also analyzed. The screening effect of the host crystal on the doping induced potential is found to be small. The effects of the doping induced electric field and the strain due to dopings are also examined. 13 refs., 9 figs., 2 tabs.