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Description
Metal hydride materials have been intensively studied for hydrogen storage applications. In addition to potential hydrogen economy applications, metal hydrides offer a wide variety of other interesting properties. For example, hydrogen-dominant materials, which are hydrides with the highest hydrogen content for a particular metal/semimetal composition, are predicted to display high-temperature

Metal hydride materials have been intensively studied for hydrogen storage applications. In addition to potential hydrogen economy applications, metal hydrides offer a wide variety of other interesting properties. For example, hydrogen-dominant materials, which are hydrides with the highest hydrogen content for a particular metal/semimetal composition, are predicted to display high-temperature superconductivity. On the other side of the spectrum are hydrides with small amounts of hydrogen (0.1 - 1 at.%) that are investigated as viable magnetic, thermoelectric or semiconducting materials. Research of metal hydride materials is generally important to gain fundamental understanding of metal-hydrogen interactions in materials. Hydrogenation of Zintl phases, which are defined as compounds between an active metal (alkali, alkaline earth, rare earth) and a p-block metal/semimetal, were attempted by a hot sintering method utilizing an autoclave loaded with gaseous hydrogen (< 9 MPa). Hydride formation competes with oxidative decomposition of a Zintl phase. The oxidative decomposition, which leads to a mixture of binary active metal hydride and p-block element, was observed for investigated aluminum (Al) and gallium (Ga) containing Zintl phases. However, a new phase Li2Al was discovered when Zintl phase precursors were synthesized. Using the single crystal x-ray diffraction (SCXRD), the Li2Al was found to crystallize in an orthorhombic unit cell (Cmcm) with the lattice parameters a = 4.6404(8) Å, b = 9.719(2) Å, and c = 4.4764(8) Å. Increased demand for materials with improved properties necessitates the exploration of alternative synthesis methods. Conventional metal hydride synthesis methods, like ball-milling and autoclave technique, are not responding to the demands of finding new materials. A viable alternative synthesis method is the application of high pressure for the preparation of hydrogen-dominant materials. Extreme pressures in the gigapascal ranges can open access to new metal hydrides with novel structures and properties, because of the drastically increased chemical potential of hydrogen. Pressures up to 10 GPa can be easily achieved using the multi-anvil (MA) hydrogenations while maintaining sufficient sample volume for structure and property characterization. Gigapascal MA hydrogenations using ammonia borane (BH3NH3) as an internal hydrogen source were employed in the search for new hydrogen-dominant materials. Ammonia borane has high gravimetric volume of hydrogen, and additionally the thermally activated decomposition at high pressures lead to a complete hydrogen release at reasonably low temperature. These properties make ammonia borane a desired hydrogen source material. The missing member Li2PtH6 of the series of A2PtH6 compounds (A = Na to Cs) was accessed by employing MA technique. As the known heavier analogs, the Li2PtH6 also crystallizes in a cubic K2PtCl6-type structure with a cell edge length of 6.7681(3) Å. Further gigapascal hydrogenations afforded the compounds K2SiH6 and Rb2SiH6 which are isostructural to Li2PtH6. The cubic K2SiH6 and Rb2SiH6 are built from unique hypervalent SiH62- entities with the lattice parameters of 7.8425(9) and 8.1572(4) Å, respectively. Spectroscopic analysis of hexasilicides confirmed the presence of hypervalent bonding. The Si-H stretching frequencies at 1550 cm-1 appeared considerably decreased in comparison with a normal-valent (2e2c) Si-H stretching frequencies in SiH4 at around 2200 cm-1. However, the observed stretching modes in hypervalent hexasilicides were in a reasonable agreement with Ph3SiH2- (1520 cm-1) where the hydrogen has the axial (3e4c bonded) position in the trigoal bipyramidal environment.
ContributorsPuhakainen, Kati (Author) / Häussermann, Ulrich (Thesis advisor) / Seo, Dong (Thesis advisor) / Kouvetakis, John (Committee member) / Wolf, George (Committee member) / Arizona State University (Publisher)
Created2013
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Description
Wind measurements are fundamental inputs for the evaluation of potential energy yield and performance of wind farms. Three-dimensional scanning coherent Doppler lidar (CDL) may provide a new basis for wind farm site selection, design, and control. In this research, CDL measurements obtained from multiple wind energy developments are analyzed and

Wind measurements are fundamental inputs for the evaluation of potential energy yield and performance of wind farms. Three-dimensional scanning coherent Doppler lidar (CDL) may provide a new basis for wind farm site selection, design, and control. In this research, CDL measurements obtained from multiple wind energy developments are analyzed and a novel wind farm control approach has been modeled. The possibility of using lidar measurements to more fully characterize the wind field is discussed, specifically, terrain effects, spatial variation of winds, power density, and the effect of shear at different layers within the rotor swept area. Various vector retrieval methods have been applied to the lidar data, and results are presented on an elevated terrain-following surface at hub height. The vector retrieval estimates are compared with tower measurements, after interpolation to the appropriate level. CDL data is used to estimate the spatial power density at hub height. Since CDL can measure winds at different vertical levels, an approach for estimating wind power density over the wind turbine rotor-swept area is explored. Sample optimized layouts of wind farm using lidar data and global optimization algorithms, accounting for wake interaction effects, have been explored. An approach to evaluate spatial wind speed and direction estimates from a standard nested Coupled Ocean and Atmosphere Mesoscale Prediction System (COAMPS) model and CDL is presented. The magnitude of spatial difference between observations and simulation for wind energy assessment is researched. Diurnal effects and ramp events as estimated by CDL and COAMPS were inter-compared. Novel wind farm control based on incoming winds and direction input from CDL's is developed. Both yaw and pitch control using scanning CDL for efficient wind farm control is analyzed. The wind farm control optimizes power production and reduces loads on wind turbines for various lidar wind speed and direction inputs, accounting for wind farm wake losses and wind speed evolution. Several wind farm control configurations were developed, for enhanced integrability into the electrical grid. Finally, the value proposition of CDL for a wind farm development, based on uncertainty reduction and return of investment is analyzed.
ContributorsKrishnamurthy, Raghavendra (Author) / Calhoun, Ronald J (Thesis advisor) / Chen, Kangping (Committee member) / Huang, Huei-Ping (Committee member) / Fraser, Matthew (Committee member) / Phelan, Patrick (Committee member) / Arizona State University (Publisher)
Created2013
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Description
This dissertation investigates the long-term consequences of human land-use practices in general, and in early agricultural villages in specific. This pioneering case study investigates the "collapse" of the Early (Pre-Pottery) Neolithic lifeway, which was a major transformational event marked by significant changes in settlement patterns, material culture, and social markers.

This dissertation investigates the long-term consequences of human land-use practices in general, and in early agricultural villages in specific. This pioneering case study investigates the "collapse" of the Early (Pre-Pottery) Neolithic lifeway, which was a major transformational event marked by significant changes in settlement patterns, material culture, and social markers. To move beyond traditional narratives of cultural collapse, I employ a Complex Adaptive Systems approach to this research, and combine agent-based computer simulations of Neolithic land-use with dynamic and spatially-explicit GIS-based environmental models to conduct experiments into long-term trajectories of different potential Neolithic socio-environmental systems. My analysis outlines how the Early Neolithic "collapse" was likely instigated by a non-linear sequence of events, and that it would have been impossible for Neolithic peoples to recognize the long-term outcome of their actions. The experiment-based simulation approach shows that, starting from the same initial conditions, complex combinations of feedback amplification, stochasticity, responses to internal and external stimuli, and the accumulation of incremental changes to the socio-natural landscape, can lead to widely divergent outcomes over time. Thus, rather than being an inevitable consequence of specific Neolithic land-use choices, the "catastrophic" transformation at the end of the Early Neolithic was an emergent property of the Early Neolithic socio-natural system itself, and thus likely not an easily predictable event. In this way, my work uses the technique of simulation modeling to connect CAS theory with the archaeological and geoarchaeological record to help better understand the causes and consequences of socio-ecological transformation at a regional scale. The research is broadly applicable to other archaeological cases of resilience and collapse, and is truly interdisciplinary in that it draws on fields such as geomorphology, computer science, and agronomy in addition to archaeology.
ContributorsUllah, Isaac (Author) / Barton, C. Michael (Thesis advisor) / Banning, Edward B. (Committee member) / Clark, Geoffrey (Committee member) / Arrowsmith, J. Ramon (Committee member) / Arizona State University (Publisher)
Created2013
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Description

In recent years, an increase of environmental temperature in urban areas has raised many concerns. These areas are subjected to higher temperature compared to the rural surrounding areas. Modification of land surface and the use of materials such as concrete and/or asphalt are the main factors influencing the surface energy

In recent years, an increase of environmental temperature in urban areas has raised many concerns. These areas are subjected to higher temperature compared to the rural surrounding areas. Modification of land surface and the use of materials such as concrete and/or asphalt are the main factors influencing the surface energy balance and therefore the environmental temperature in the urban areas. Engineered materials have relatively higher solar energy absorption and tend to trap a relatively higher incoming solar radiation. They also possess a higher heat storage capacity that allows them to retain heat during the day and then slowly release it back into the atmosphere as the sun goes down. This phenomenon is known as the Urban Heat Island (UHI) effect and causes an increase in the urban air temperature. Many researchers believe that albedo is the key pavement affecting the urban heat island. However, this research has shown that the problem is more complex and that solar reflectivity may not be the only important factor to evaluate the ability of a pavement to mitigate UHI. The main objective of this study was to analyze and research the influence of pavement materials on the near surface air temperature. In order to accomplish this effort, test sections consisting of Hot Mix Asphalt (HMA), Porous Hot Mix asphalt (PHMA), Portland Cement Concrete (PCC), Pervious Portland Cement Concrete (PPCC), artificial turf, and landscape gravels were constructed in the Phoenix, Arizona area. Air temperature, albedo, wind speed, solar radiation, and wind direction were recorded, analyzed and compared above each pavement material type. The results showed that there was no significant difference in the air temperature at 3-feet and above, regardless of the type of the pavement. Near surface pavement temperatures were also measured and modeled. The results indicated that for the UHI analysis, it is important to consider the interaction between pavement structure, material properties, and environmental factors. Overall, this study demonstrated the complexity of evaluating pavement structures for UHI mitigation; it provided great insight on the effects of material types and properties on surface temperatures and near surface air temperature.

ContributorsPourshams-Manzouri, Tina (Author) / Kaloush, Kamil (Thesis advisor) / Wang, Zhihua (Thesis advisor) / Zapata, Claudia E. (Committee member) / Mamlouk, Michael (Committee member) / Arizona State University (Publisher)
Created2013
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Description
The dynamics of urban water use are characterized by spatial and temporal variability that is influenced by associated factors at different scales. Thus it is important to capture the relationship between urban water use and its determinants in a spatio-temporal framework in order to enhance understanding and management of urban

The dynamics of urban water use are characterized by spatial and temporal variability that is influenced by associated factors at different scales. Thus it is important to capture the relationship between urban water use and its determinants in a spatio-temporal framework in order to enhance understanding and management of urban water demand. This dissertation aims to contribute to understanding the spatio-temporal relationships between single-family residential (SFR) water use and its determinants in a desert city. The dissertation has three distinct papers to support this goal. In the first paper, I demonstrate that aggregated scale data can be reliably used to study the relationship between SFR water use and its determinants without leading to significant ecological fallacy. The usability of aggregated scale data facilitates scientific inquiry about SFR water use with more available aggregated scale data. The second paper advances understanding of the relationship between SFR water use and its associated factors by accounting for the spatial and temporal dependence in a panel data setting. The third paper of this dissertation studies the historical contingency, spatial heterogeneity, and spatial connectivity in the relationship of SFR water use and its determinants by comparing three different regression models. This dissertation demonstrates the importance and necessity of incorporating spatio-temporal components, such as scale, dependence, and heterogeneity, into SFR water use research. Spatial statistical models should be used to understand the effects of associated factors on water use and test the effectiveness of certain management policies since spatial effects probably will significantly influence the estimates if only non-spatial statistical models are used. Urban water demand management should pay attention to the spatial heterogeneity in predicting the future water demand to achieve more accurate estimates, and spatial statistical models provide a promising method to do this job.
ContributorsOuyang, Yun (Author) / Wentz, Elizabeth (Thesis advisor) / Ruddell, Benjamin (Thesis advisor) / Harlan, Sharon (Committee member) / Janssen, Marcus (Committee member) / Arizona State University (Publisher)
Created2013
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Description
Farmers' markets are a growing trend both in Arizona and the broader U.S., as many recognize them as desirable alternatives to the conventional food system. As icons of sustainability, farmers' markets are touted as providing many environmental, social, and economic benefits, but evidence is mounting that local food systems primarily

Farmers' markets are a growing trend both in Arizona and the broader U.S., as many recognize them as desirable alternatives to the conventional food system. As icons of sustainability, farmers' markets are touted as providing many environmental, social, and economic benefits, but evidence is mounting that local food systems primarily serve the urban elite, with relatively few low-income or minority customers. However, the economic needs of the market and its vendors often conflict with those of consumers. While consumers require affordable food, farmers need to make a profit. How farmers' markets are designed and governed can significantly influence the extent to which they can meet these needs. However, very little research explores farmers' market design and governance, much less its capacity to influence financial success and participation for underprivileged consumers. The present study examined this research gap by addressing the following research question: How can farmers' markets be institutionally designed to increase the participation of underprivileged consumers while maintaining a financially viable market for local farmers? Through a comparative case study of six markets, this research explored the extent to which farmers' markets in Central Arizona currently serve the needs of farmer-vendors and underprivileged consumers. The findings suggest that while the markets serve as a substantial source of income for some vendors, participation by low-income and minority consumers remains low, and that much of this appears to be due to cultural barriers to access. Management structures, site characteristics, market layout, community programs, and staffing policies are key institutional design features, and the study explores how these can be leveraged to better meet the needs of the diverse participants while improving the markets' financial success.
ContributorsTaylor, Carissa (Author) / Aggarwal, Rimjhim (Thesis advisor) / York, Abigail (Committee member) / Wharton, Christopher (Christopher Mack), 1977- (Committee member) / Arizona State University (Publisher)
Created2013
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Description
Topological insulators with conducting surface states yet insulating bulk states have generated a lot of interest amongst the physics community due to their varied characteristics and possible applications. Doped topological insulators have presented newer physical states of matter where topological order co&ndashexists; with other physical properties (like magnetic order). The

Topological insulators with conducting surface states yet insulating bulk states have generated a lot of interest amongst the physics community due to their varied characteristics and possible applications. Doped topological insulators have presented newer physical states of matter where topological order co&ndashexists; with other physical properties (like magnetic order). The electronic states of these materials are very intriguing and pose problems and the possible solutions to understanding their unique behaviors. In this work, we use Electron Energy Loss Spectroscopy (EELS) – an analytical TEM tool to study both core&ndashlevel; and valence&ndashlevel; excitations in Bi2Se3 and Cu(doped)Bi2Se3 topological insulators. We use this technique to retrieve information on the valence, bonding nature, co-ordination and lattice site occupancy of the undoped and the doped systems. Using the reference materials Cu(I)Se and Cu(II)Se we try to compare and understand the nature of doping that copper assumes in the lattice. And lastly we utilize the state of the art monochromated Nion UltraSTEM 100 to study electronic/vibrational excitations at a record energy resolution from sub-nm regions in the sample.
ContributorsSubramanian, Ganesh (Author) / Spence, John (Thesis advisor) / Jiang, Nan (Committee member) / Chen, Tingyong (Committee member) / Chan, Candace (Committee member) / Arizona State University (Publisher)
Created2013
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Description
This dissertation explores the unique role schools play in contributing toward a sustainable future for their communities. This was undertaken by first conducting a thorough review and analysis of the literature on the current utilization of schools as agents of sustainable development, along with an evaluation of schools engaging in

This dissertation explores the unique role schools play in contributing toward a sustainable future for their communities. This was undertaken by first conducting a thorough review and analysis of the literature on the current utilization of schools as agents of sustainable development, along with an evaluation of schools engaging in this model around the United States. Following this, a framework was developed to aid in the assessment of school-community engagements from the perspective of social change. Sustainability problem solving tools were synthesized for use by schools and community stakeholders, and were tested in the case study of this dissertation. This case study combined methods from the fields of sustainable development, transition management, and social change to guide two schools in their attempts to increase community sustainability through addressing a shared sustainability problem: childhood obesity. The case study facilitated the creation of a sustainable vision for the Phoenix Metropolitan Area without childhood obesity, as well as strategic actions plans for each school to utilize as they move forward on addressing this challenge.
ContributorsLawless, Tamara Hope (Author) / Golub, Aaron (Thesis advisor) / Redman, Charles (Committee member) / Schugurensky, Daniel (Committee member) / Arizona State University (Publisher)
Created2013
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Description
Current policies subsidizing or accelerating deployment of photovoltaics (PV) are typically motivated by claims of environmental benefit, such as the reduction of CO2 emissions generated by the fossil-fuel fired power plants that PV is intended to displace. Existing practice is to assess these environmental benefits on a net life-cycle basis,

Current policies subsidizing or accelerating deployment of photovoltaics (PV) are typically motivated by claims of environmental benefit, such as the reduction of CO2 emissions generated by the fossil-fuel fired power plants that PV is intended to displace. Existing practice is to assess these environmental benefits on a net life-cycle basis, where CO2 benefits occurring during use of the PV panels is found to exceed emissions generated during the PV manufacturing phase including materials extraction and manufacture of the PV panels prior to installation. However, this approach neglects to recognize that the environmental costs of CO2 release during manufacture are incurred early, while environmental benefits accrue later. Thus, where specific policy targets suggest meeting CO2 reduction targets established by a certain date, rapid PV deployment may have counter-intuitive, albeit temporary, undesired consequences. Thus, on a cumulative radiative forcing (CRF) basis, the environmental improvements attributable to PV might be realized much later than is currently understood. This phenomenon is particularly acute when PV manufacture occurs in areas using CO2 intensive energy sources (e.g., coal), but deployment occurs in areas with less CO2 intensive electricity sources (e.g., hydro). This thesis builds a dynamic Cumulative Radiative Forcing (CRF) model to examine the inter-temporal warming impacts of PV deployments in three locations: California, Wyoming and Arizona. The model includes the following factors that impact CRF: PV deployment rate, choice of PV technology, pace of PV technology improvements, and CO2 intensity in the electricity mix at manufacturing and deployment locations. Wyoming and California show the highest and lowest CRF benefits as they have the most and least CO2 intensive grids, respectively. CRF payback times are longer than CO2 payback times in all cases. Thin film, CdTe PV technologies have the lowest manufacturing CO2 emissions and therefore the shortest CRF payback times. This model can inform policies intended to fulfill time-sensitive CO2 mitigation goals while minimizing short term radiative forcing.
ContributorsTriplican Ravikumar, Dwarakanath (Author) / Seager, Thomas P (Thesis advisor) / Fraser, Matthew P (Thesis advisor) / Chester, Mikhail V (Committee member) / Sinha, Parikhit (Committee member) / Arizona State University (Publisher)
Created2013
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Description
Sustainable development in an American context implies an ongoing shift from quantitative growth in energy, resource, and land use to the qualitative development of social-ecological systems, human capital, and dense, vibrant built environments. Sustainable urban development theory emphasizes locally and bioregionally emplaced economic development where the relationships between people, localities,

Sustainable development in an American context implies an ongoing shift from quantitative growth in energy, resource, and land use to the qualitative development of social-ecological systems, human capital, and dense, vibrant built environments. Sustainable urban development theory emphasizes locally and bioregionally emplaced economic development where the relationships between people, localities, products, and capital are tangible to and controllable by local stakeholders. Critical theory provides a mature understanding of the political economy of land development in capitalist economies, representing a crucial bridge between urban sustainability's infill development goals and the contemporary realities of the development industry. Since its inception, Phoenix, Arizona has exemplified the quantitative growth paradigm, and recurring instances of land speculation, non-local capital investment, and growth-based public policy have stymied local, tangible control over development from Phoenix's territorial history to modern attempts at downtown revitalization. Utilizing property ownership and sales data as well as interviews with development industry stakeholders, the political economy of infill land development in downtown Phoenix during the mid-2000s boom-and-bust cycle is analyzed. Data indicate that non-local property ownership has risen significantly over the past 20 years and rent-seeking land speculation has been a significant barrier to infill development. Many speculative strategies monopolize the publicly created value inherent in zoning entitlements, tax incentives and property assessment, indicating that political and policy reforms targeted at a variety of governance levels are crucial for achieving the sustainable development of urban land. Policy solutions include reforming the interconnected system of property sales, value assessment, and taxation to emphasize property use values; replacing existing tax incentives with tax increment financing and community development benefit agreements; regulating vacant land ownership and deed transfers; and encouraging innovative private development and tenure models like generative construction and community land trusts.
ContributorsStanley, Benjamin W (Author) / Boone, Christopher G. (Thesis advisor) / Redman, Charles (Committee member) / Bolin, Robert (Committee member) / Arizona State University (Publisher)
Created2013