Matching Items (151)
Description
We studied the microbial community structure of pilot two-stage membrane biofilm reactors (MBfRs) designed to reduce nitrate (NO[subscript 3]–) and perchlorate (ClO[subscript 4]–) in contaminated groundwater. The groundwater also contained oxygen (O[subscript 2]) and sulfate (SO[2 over 4]–), which became important electron sinks that affected the NO[subscript 3]– and ClO[subscript 4]– removal rates. Using pyrosequencing, we elucidated how important phylotypes of each “primary” microbial group, i.e., denitrifying bacteria (DB), perchlorate-reducing bacteria (PRB), and sulfate-reducing bacteria (SRB), responded to changes in electron-acceptor loading. UniFrac, principal coordinate analysis (PCoA), and diversity analyses documented that the microbial community of biofilms sampled when the MBfRs had a high acceptor loading were phylogenetically distant from and less diverse than the microbial community of biofilm samples with lower acceptor loadings. Diminished acceptor loading led to SO[2 over 4]– reduction in the lag MBfR, which allowed Desulfovibrionales (an SRB) and Thiothrichales (sulfur-oxidizers) to thrive through S cycling. As a result of this cooperative relationship, they competed effectively with DB/PRB phylotypes such as Xanthomonadales and Rhodobacterales. Thus, pyrosequencing illustrated that while DB, PRB, and SRB responded predictably to changes in acceptor loading, a decrease in total acceptor loading led to important shifts within the “primary” groups, the onset of other members (e.g., Thiothrichales), and overall greater diversity.
ContributorsOntiveros-Valencia, Aura (Author) / Tang, Youneng (Author) / Zhao, Heping (Author) / Friese, David (Author) / Overstreet, Ryan (Author) / Smith, Jennifer (Author) / Evans, Patrick (Author) / Rittmann, Bruce (Author) / Krajmalnik-Brown, Rosa (Author) / Biodesign Institute (Contributor) / Swette Center for Environmental Biotechnology (Contributor) / Julie Ann Wrigley Global Institute of Sustainability (Contributor) / School of Sustainability (Contributor)
Created2014-07-01
Residential Choice’s Impact on Sustainable Transportation Options: A Study in the Phoenix Metro Area
Description
This study adds to the literature about residential choice and sustainable transportation. Through the interviews and the personal stories gathered, there was diversity shown in the residential location choice process. We also noticed that “commute” means different things to different households, and that many people did not consider their commute to work to be a primary factor determining their final home location. Moreover, many people were willing to increase their commute time, or trade access to desirable amenities for a longer commute. Commuting time to work was one example of the tradeoffs that homeowners make when choosing a home, but there were also others such as architectural type and access to neighborhood amenities. Lastly, time constraints proved to be a very significant factor in the home buying process. Several of our households had such strict time constraints that limited their search to a point of excluding whole areas. Overall, our study sheds light on transportation’s role in residential choice and underscores the complexity of the location choice process.
ContributorsKats, Elyse Nicole (Author) / Salon, Deborah (Thesis director) / Kuminoff, Nicolai (Committee member) / School of Sustainability (Contributor) / School of Geographical Sciences and Urban Planning (Contributor) / School of Community Resources and Development (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Since 1979, Phoenix has been organized into 15 theoretically self-contained urban villages in order to manage rapid growth. The major objective of the village plan was to decrease demand for personal vehicle use by internalizing travel to the closest village core, or an adjacent village core, instead of expanding travel to one metropolitan core. Phoenix’s transition from a monocentric urban structure to a more polycentric structure has yet to be studied for its efficacy on this goal of turning personal vehicle travel inward. This paper pairs more conventional measures of automobile dependence, such as, use of alternative modes of transportation in place of private vehicle use and commute times, with more nuanced measures of internal travel between work and home, job housing ratio, and job industry breakdowns to describe Phoenix’s reliance on automobiles. Phoenix’s internal travel ratios were higher when compared to adjacent cities and either on-par or lower when compared to non-adjacent cities that were comparable to Phoenix in population density and size.
ContributorsCuiffo, Kathryn Victoria (Author) / King, David (Thesis director) / Salon, Deborah (Committee member) / Dean, W.P. Carey School of Business (Contributor) / Department of Psychology (Contributor) / Department of Economics (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Transit ridership is declining in most cities throughout America. Public transportation needs to be improved in order for cities to handle urban growth, reduce carbon footprint, and increase mobility across income groups. In order to determine what causes changes in transit ridership, I performed a descriptive analysis of five metro areas in the United States. I studied changes in transit ridership in Dallas, Denver, Minneapolis, Phoenix, and Seattle from 2013 through 2017 to determine where public transportation works and where it does not work. I used employment, commute, and demographic data to determine what affects transit ridership. Each metro area was studied as a separate case because the selected cities are difficult to compare directly. The Seattle metro area was the only metro to increase transit ridership throughout the period of the study. The Minneapolis metro area experienced a slight decline in transit ridership, while Phoenix and Denver declined significantly. The Dallas metro area declined most of the five cities studied. The denser metro areas fared much better than the less dense areas. In order to increase transit ridership cities should increase the density of their city and avoid sprawl. Certain factors led to declines in ridership in certain metro areas but not all. For example, gentrification contributed to ridership decline in Denver and Minneapolis, but Seattle gentrified and increased ridership. Dallas and Phoenix experienced low-levels of gentrification but experienced declining ridership. Therefore, organizations such as the American Public Transportation Association (APTA) who attempt to find the single factor causing the decline in transit ridership, or the one factor that will increase ridership are misguided. Above all, this thesis shows that there is no single factor causing the ridership decline in each metro area, and it is wise to study each metro area as a separate case.
ContributorsBarro, Joshua Andrew (Co-author) / Barro, Joshua (Co-author) / King, David (Thesis director) / Salon, Deborah (Committee member) / School of Politics and Global Studies (Contributor) / Walter Cronkite School of Journalism & Mass Comm (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
The growing urban heat island (UHI) phenomenon is having detrimental effects on urban populations and the environment, and therefore, must be addressed. The purpose of this research is to investigate possible strategies that could be utilized to reduce the effects of the urban heat island for the city of Phoenix. Current strategies, case studies, and the ENVI-Met modeling software were used to finalize conclusions and suggestions to further progress Phoenix's goals in combating its urban heat island. Results from the studies found that there is much potential in reducing daytime and evening temperatures through improving infrastructure by means of increased vegetation in the forms of green roofs and walls, reducing anthropogenic heat release, improving artificial surface coverage, and implementing lasting policies for further development. Results from the ENVI-met microclimate program shows areas for further research in urban heat island mitigation strategies.
ContributorsShqalsi, Ema (Author) / Pijawka, David (Thesis director) / Middel, Ariane (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / School of Geographical Sciences and Urban Planning (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
The City of Phoenix Street Transportation Department partnered with the Rob and Melani Walton Sustainability Solutions Service at Arizona State University (ASU) and researchers from various ASU schools to evaluate the effectiveness, performance, and community perception of the new pavement coating. The data collection and analysis occurred across multiple neighborhoods and at varying times across days and/or months over the course of one year (July 15, 2020–July 14, 2021), allowing the team to study the impacts of the surface treatment under various weather conditions.
ContributorsMiddel, Ariane (Author) / Vanos, Jennifer K. (Author) / Hondula, David M. (Author) / Kaloush, Kamil (Author) / Sailor, David (Author) / Medina, Jose R. (Jose Roberto) (Author) / Schneider, Florian (Author) / Ortiz, Johny Cordova (Author) / Campbell, Bill (Author) / Epel, Erin (Contributor) / Rice, Brendan (Contributor) / Garcia, Ruth (Contributor) / Phoenix (Ariz.). Street Transportation Department (Contributor) / City of Phoenix (Funder) / Industrial Development Authority of the County of Maricopa (Funder) / Julie Ann Wrigley Global Institute of Sustainability (Funder) / Arizona State University. Healthy Urban Environments Program (Contributor)
Created2021-09
Description
Traditional Reinforcement Learning (RL) assumes to learn policies with respect to reward available from the environment but sometimes learning in a complex domain requires wisdom which comes from a wide range of experience. In behavior based robotics, it is observed that a complex behavior can be described by a combination of simpler behaviors. It is tempting to apply similar idea such that simpler behaviors can be combined in a meaningful way to tailor the complex combination. Such an approach would enable faster learning and modular design of behaviors. Complex behaviors can be combined with other behaviors to create even more advanced behaviors resulting in a rich set of possibilities. Similar to RL, combined behavior can keep evolving by interacting with the environment. The requirement of this method is to specify a reasonable set of simple behaviors. In this research, I present an algorithm that aims at combining behavior such that the resulting behavior has characteristics of each individual behavior. This approach has been inspired by behavior based robotics, such as the subsumption architecture and motor schema-based design. The combination algorithm outputs n weights to combine behaviors linearly. The weights are state dependent and change dynamically at every step in an episode. This idea is tested on discrete and continuous environments like OpenAI’s “Lunar Lander” and “Biped Walker”. Results are compared with related domains like Multi-objective RL, Hierarchical RL, Transfer learning, and basic RL. It is observed that the combination of behaviors is a novel way of learning which helps the agent achieve required characteristics. A combination is learned for a given state and so the agent is able to learn faster in an efficient manner compared to other similar approaches. Agent beautifully demonstrates characteristics of multiple behaviors which helps the agent to learn and adapt to the environment. Future directions are also suggested as possible extensions to this research.
ContributorsVora, Kevin Jatin (Author) / Zhang, Yu (Thesis advisor) / Yang, Yezhou (Committee member) / Praharaj, Sarbeswar (Committee member) / Arizona State University (Publisher)
Created2021
Description
This dissertation consists of three chapters that investigate the rapid adoption and complex implementation of city commitments to transition to 100% renewable energy (100RE). The first paper uses a two-stage, mixed methods approach to examine 100RE commitments across the US, combining a multivariate regression of demographic, institutional, and policy factors in adoption and six interview-based state case studies to discuss implementation. Adoption of this non-binding commitment progressed rapidly for city councils around the US. Results show that many cities passed 100RE commitments with no implementation plan and minimal understanding of implementation challenges. This analysis highlights that many cities will need new institutions and administrative capacities for successful implementation of these ambitious new policies. While many cities abandoned the commitment soon after adoption, collaboration allowed cities in a few states to break through and pursue implementation, examined further in the next two studies. The second paper is a qualitative case study examining policymaking for the Utah Community Renewable Energy Act. Process tracing methods are used to identify causal factors in enacting this legislation at the state level and complementary resolutions at the local level. This Act was passed through the leadership and financial backing of major cities and committed the investor-owned utility to fulfill any city 100RE resolutions passed through 2019. Finally, the third paper is a mixed-methods, descriptive case study of the benefits of Community Choice Aggregation (CCA) in California, which many cities are using to fulfill their 100RE commitments. Cities have adopted CCAs to increase their local voice in the energy process, while fulfilling climate and energy goals. Overall, this research shows that change in the investor-owned utility electricity system is in fact possible from the city scale, though many cities will need institutional innovation to implement these policies and achieve the change they desire. While cities with greater resources are better positioned to make an impact, smaller cities can collaborate to similarly influence the energy system. Communities are interested in lowering energy costs for customers where possible, but the central motivations in these cases were the pursuit of sustainability and increasing local voice in energy decision-making.
ContributorsKunkel, Leah Christine (Author) / Breetz, Hanna L (Thesis advisor) / Parker, Nathan (Committee member) / Salon, Deborah (Committee member) / Arizona State University (Publisher)
Created2022
Description
Infrastructure systems are facing non-stationary challenges that stem from climate change and the increasingly complex interactions between the social, ecological, and technological systems (SETSs). It is crucial for transportation infrastructures—which enable residents to access opportunities and foster prosperity, quality of life, and social connections—to be resilient under these non-stationary challenges. Vulnerability assessment (VA) examines the potential consequences a system is likely to experience due to exposure to perturbation or stressors and lack of the capacity to adapt. Post-fire debris flow and heat represent particularly challenging problems for infrastructure and users in the arid U.S. West. Post-fire debris flow, which is manifested with heat and drought, produces powerful runoff threatening physical transportation infrastructures. And heat waves have devastating health effects on transportation infrastructure users, including increased mortality rates. VA anticipates the potential consequences of these perturbations and enables infrastructure stakeholders to improve the system's resilience. The current transportation climate VA—which only considers a single direct climate stressor on the infrastructure—falls short of addressing the wildfire and heat challenges. This work proposes advanced transportation climate VA methods to address the complex and multiple climate stressors and the vulnerability of infrastructure users. Two specific regions were chosen to carry out the progressive transportation climate VA: 1) the California transportation networks’ vulnerability to post-fire debris flows, and 2) the transportation infrastructure user’s vulnerability to heat exposure in Phoenix.
ContributorsLi, Rui (Author) / Chester, Mikhail V. (Thesis advisor) / Middel, Ariane (Committee member) / Hondula, David M. (Committee member) / Pendyala, Ram (Committee member) / Arizona State University (Publisher)
Created2022
Description
With rapid advances in technology development and public adoption, it is crucial to understand how these services will shape the future of travel depending on the extent to which people will use these services; impact the transportation and infrastructure systems such as changes in the use of transit and active modes of travel; and influence how technology developers create and update these transportation technologies to better serve people’s mobility needs. This dissertation explores how two major emerging services, namely ridehailing services and autonomous vehicles (AVs), will be used in the future when they are widely available and vastly used, and how they may impact the transportation infrastructure and societal travel patterns. The four proposed chapters use comprehensive quantitative and qualitative methods to explore the status of these technologies from theory, through robust modeling frameworks, to practice, by investigating the recent AV pilot deployments in real-world settings. In the second chapter, it was found that increased frequency of ridehailing use is significantly associated with a decrease in bus usage, suggesting that ridehailing functions more as a substitute for buses than as a complement and implying that transit agencies should explore ways to incorporate ridehailing services in their plans to enhance transit usage. Next, the third chapter showed that interest in using AVs for running errands had a positive and significant effect on AV ownership intent, even after accounting for a host of variables. The fourth chapter depicted how ridehailing experiences have a considerable effect on the willingness to ride AV-based services in both private and shared modes, suggesting that experience is crucial for future adoption of these services. Then, two recent real-world AV experiences are explored in the fifth chapter. Lessons learned from these experiments reinforced the importance of first-hand experiences in promoting AV awareness and trustworthiness, potentially leading to greater degrees of adoption. Finally, the results and discussions presented in this dissertation strengthen the body of literature on key emerging transportation technologies and inform policymakers and stakeholders to properly prepare cities and the public to welcome these technologies into our transportation system in an efficient, equitable, and complementary way.
ContributorsMagassy, Tassio Bezerra (Author) / Pendyala, Ram M (Thesis advisor) / Khoeini, Sara (Committee member) / Polzin, Steven E (Committee member) / Salon, Deborah (Committee member) / Arizona State University (Publisher)
Created2023