Metallic Hydrides I: Hydrogen Storage and Other Gas-Phase Applications

A brief survey is given of the various classes of metal alloys and compounds that are suitable for hydrogen-storage and energy-conversion applications. Comparisons are made of relevant properties including hydrogen absorption and desorption pressures, total and reversible hydrogen-storage capacity, reaction-rate kinetics, initial activation requirements, susceptibility to contamination, and durability during long-term thermal cycling. Selected applications are hydrogen storage as a fuel, gas separation and purification, thermal switches, and sorption cryocoolers

Sand dune field paleoenvironment, paleoecology, and human environmental interaction in the middle Tanana River Valley near the Gerstle River, subarctic Alaska: the late glacial to the middle Holocene

Thesis (M.A.) University of Alaska Fairbanks, 2017This study was conducted to explore paleoenvironmental change within the Gerstle-Sawmill Dune Field (GSDF), located just west of the Gerstle River in the middle Tanana River valley, Interior Alaska from the late Glacial to the middle Holocene. Specifically, this study was undertaken to document human-environment interaction on the landscape. Geoarchaeological methods were used in order to determine the history of sand dune development across the area, how the local ecological systems changed through time, and determine prehistoric human use of environment and response to environmental and ecological change. The data collected from these locations was used to create a model for sand dunes and human land use regarding local ecological stability and dynamic sand dune deposition. Patterns of human land use within the GSDF were then compared with data collected from sites in proximity to the GSDF to determine how this portion of the environment operated within the larger geographic area. This geoarchaeological research aids in understanding ecological patterning within terrestrial lowland systems from the Late Glacial to the Middle Holocene, with regard to human land use dynamics within a changing geomorphological system

Solid State NMR Characterization of Complex Metal Hydrides systems for Hydrogen Storage Applications

Solid state NMR is widely applied in studies of solid state chemistries for hydrogen storage reactions. Use of ^(11)B MAS NMR in studies of metal borohydrides (BH_4) is mainly focused, revisiting the issue of dodecaborane formation and observation of ^(11)B{^1H} Nuclear Overhauser Effect

Hydrogenation of Magnesium Nickel Boride for Reversible Hydrogen Storage

We report that a ternary magnesium nickel boride (MgNi_(2.5)B_2) mixed with LiH and MgH_2 can be hydrogenated reversibly forming LiBH_4 and Mg_2NiH_4 at temperatures below 300 °C. The ternary boride was prepared by sintering a mechanically milled mixture of MgB_2 and Ni precursors at 975 °C under inert atmosphere. Hydrogenation of the ternary, milled with LiH and MgH_2, was performed under 100 to 160 bar H_2 at temperatures up to 350 °C. Analysis using X-ray diffraction, Fourier transform infrared, and ^(11)B magic angle spinning NMR confirmed that the ternary boride was hydrogenated forming borohydride anions. The reaction was reversible with hydrogenation kinetics that improved over three cycles. This work suggests that there may be other ternary or higher order boride phases useful for reversible hydrogen storage

A parametric shell analysis of the shuttle 51-L SRB AFT field joint

Following the Shuttle 51-L accident, an investigation was conducted to determine the cause of the failure. Investigators at the Langley Research Center focused attention on the structural behavior of the field joints with O-ring seals in the steel solid rocket booster (SRB) cases. The shell-of-revolution computer program BOSOR4 was used to model the aft field joint of the solid rocket booster case. The shell model consisted of the SRB wall and joint geometry present during the Shuttle 51-L flight. A parametric study of the joint was performed on the geometry, including joint clearances, contact between the joint components, and on the loads, induced and applied. In addition combinations of geometry and loads were evaluated. The analytical results from the parametric study showed that contact between the joint components was a primary contributor to allowing hot gases to blow by the O-rings. Based upon understanding the original joint behavior, various proposed joint modifications are shown and analyzed in order to provide additional insight and information. Finally, experimental results from a hydro-static pressurization of a test rocket booster case to study joint motion are presented and verified analytically

Can magnetic susceptibility data separate archaeological palimpsests? A case study from the Hess Creek site in interior Alaska with archaeological prospection implications

Magnetic Susceptibility (MS) is applied at a high latitude Interior Alaskan site. MS is implemented in breaking apart cultural palimpsests. MS acts as a proxy for assigning archaeological traditions and complexes. MS functions as a prospection tool for site excavation expansion

Hybrid Dealiased Convolutions

This paper proposes a practical and efficient solution for computing convolutions using hybrid dealiasing. It offers an alternative to explicit or implicit dealiasing and includes an optimized hyperparameter tuning algorithm that uses experience to find the optimal parameters. Machine learning algorithms and efficient heuristics are also developed to estimate optimal parameters for larger convolution problems using only small squares/rectangles.Comment: Undergraduate Thesi