Publications

Results 126–150 of 217
Skip to search filters

The impact of trade costs on rare earth exports : a stochastic frontier estimation approach

Vugrin, Eric D.; Brady, Patrick V.

The study develops a novel stochastic frontier modeling approach to the gravity equation for rare earth element (REE) trade between China and its trading partners between 2001 and 2009. The novelty lies in differentiating betweenbehind the border' trade costs by China and theimplicit beyond the border costs' of China's trading partners. Results indicate that the significance level of the independent variables change dramatically over the time period. While geographical distance matters for trade flows in both periods, the effect of income on trade flows is significantly attenuated, possibly capturing the negative effects of financial crises in the developed world. Second, the total export losses due tobehind the border' trade costs almost tripled over the time period. Finally, looking atimplicit beyond the border' trade costs, results show China gaining in some markets, although it is likely that some countries are substituting away from Chinese REE exports.

More Details
TYPE SAND Report YEAR 2013
OSTIDOI

Some logistical considerations in designing a system of deep boreholes for disposal of high-level radioactive waste

Brady, Patrick V.; Arnold, Bill W.

Deep boreholes could be a relatively inexpensive, safe, and rapidly deployable strategy for disposing Americas nuclear waste. To study this approach, Sandia invested in a three year LDRD project entitled %E2%80%9CRadionuclide Transport from Deep Boreholes.%E2%80%9D In the first two years, the borehole reference design and backfill analysis were completed and the supporting modeling of borehole temperature and fluid transport profiles were done. In the third year, some of the logistics of implementing a deep borehole waste disposal system were considered. This report describes what was learned in the third year of the study and draws some conclusions about the potential bottlenecks of system implementation.

More Details
TYPE SAND Report YEAR 2012
OSTIDOI

First-principles flocculation as the key to low energy algal biofuels processing

Hewson, John C.; Mondy, L.A.; Murton, Jaclyn K.; O'Hern, Timothy J.; Parchert, Kylea J.; Pohl, Phillip I.; Williams, Cecelia V.; Wyatt, Nicholas B.; Barringer, David A.; Pierce, Flint P.; Brady, Patrick V.; Dwyer, Brian P.; Grillet, Anne M.; Hankins, M.G.; Hughes, Lindsey G.; Lechman, Jeremy B.

This document summarizes a three year Laboratory Directed Research and Development (LDRD) program effort to improve our understanding of algal flocculation with a key to overcoming harvesting as a techno-economic barrier to algal biofuels. Flocculation is limited by the concentrations of deprotonated functional groups on the algal cell surface. Favorable charged groups on the surfaces of precipitates that form in solution and the interaction of both with ions in the water can favor flocculation. Measurements of algae cell-surface functional groups are reported and related to the quantity of flocculant required. Deprotonation of surface groups and complexation of surface groups with ions from the growth media are predicted in the context of PHREEQC. The understanding of surface chemistry is linked to boundaries of effective flocculation. We show that the phase-space of effective flocculation can be expanded by more frequent alga-alga or floc-floc collisions. The collision frequency is dependent on the floc structure, described in the fractal sense. The fractal floc structure is shown to depend on the rate of shear mixing. We present both experimental measurements of the floc structure variation and simulations using LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). Both show a densification of the flocs with increasing shear. The LAMMPS results show a combined change in the fractal dimension and a change in the coordination number leading to stronger flocs.

More Details
TYPE SAND Report YEAR 2012
OSTIDOI
Results 126–150 of 217
Results 126–150 of 217