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- All Subjects: Civil Engineering
- Creators: Arizona State University
Description
Entering a new market in the construction industry is a complex task. Although many contractors have experienced the benefits of expanding their market offerings, many more have had unsuccessful experiences causing hardship for the entire organization. Standardized decision-making processes can help to increase the likelihood of success, but few specialty contractors have taken the time to develop a formal procedure. According to this research, only 6 percent of survey respondents and 7 percent of case study participants from the sheet metal industry have a formal decision process. Five sources of data (existing literature, industry survey, semi-structured interviews, factor prioritization workshops, and expert panel discussions) are consulted to understand the current market entry decision-making practices and needs of the sheet metal industry. The data help to accomplish three study objectives: (1) determine the current processes and best practices used for market entry decision-making in the sheet metal industry, (2) identify motivations leading to market entry by sheet metal contractors, and (3) develop a standardized decision process that improves market entry decision outcomes. Grounded in a firm understanding of industry practices, a three-phased decision-making framework is created to provide a structured approach to guide contractors to an informed decision. Four industry leaders with over 175 years of experience in construction reviewed and applied every step of the framework to ensure it is practical and easy to use for contractors.
ContributorsSullivan, Jera J (Author) / El Asmar, Mounir (Thesis advisor) / Gibson, G Edward (Committee member) / Sullivan, Kenneth (Committee member) / Arizona State University (Publisher)
Created2016
Description
Higher plant Rubisco activase (Rca) is a stromal ATPase responsible for reactivating Rubisco. It is a member of the AAA+ protein superfamily and is thought to assemble into closed-ring hexamers like other AAA+ proteins belonging to the classic clade. Progress towards modeling the interaction between Rca and Rubisco has been slow due to limited structural information on Rca. Previous efforts in the lab were directed towards solving the structure of spinach short-form Rca using X-ray crystallography, given that it had notably high thermostability in the presence of ATP-γS, an ATP analog. However, due to disorder within the crystal lattice, an atomic resolution structure could not be obtained, prompting us to move to negative stain electron microscopy (EM), with our long-term goal being the use of cryo-electron microscopy (cryo-EM) for atomic resolution structure determination. Thus far, we have screened different Rca constructs in the presence of ATP-γS, both the full-length β-isoform and truncations containing only the AAA+ domain. Images collected on preparations of the full-length protein were amorphous, whereas images of the AAA+ domain showed well-defined ring-like assemblies under some conditions. Procedural adjustments, such as the use of previously frozen protein samples, rapid dilution, and minimizing thawing time were shown to improve complex assembly. The presence of Mn2+ was also found to improve hexamer formation over Mg2+. Calculated class averages of the AAA+ Rca construct in the presence of ATP-γS indicated a lack of homogeneity in the assemblies, showing both symmetric and asymmetric hexameric rings. To improve structural homogeneity, we tested buffer conditions containing either ADP alone or different ratios of ATP-γS to ADP, though results did not show a significant improvement in homogeneity. Multiple AAA+ domain preparations were evaluated. Because uniform protein assembly is a major requirement for structure solution by cryo-EM, more work needs to be done on screening biochemical conditions to optimize homogeneity.
ContributorsHernandez, Victoria Joan (Author) / Wachter, Rebekka (Thesis director) / Chiu, Po-Lin (Committee member) / Redding, Kevin (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Nonlinear responses in the dynamics of climate system could be triggered by small change of forcing. Interactions between different components of Earth’s climate system are believed to cause abrupt and catastrophic transitions, of which anthropogenic forcing is a major and the most irreversible driver. Meantime, in the face of global climate change, extreme climatic events, such as extreme precipitations, heatwaves, droughts, etc., are projected to be more frequent, more intense, and longer in duration. These nonlinear responses in climate dynamics from tipping points to extreme events pose serious threats to human society on a large scale. Understanding the physical mechanisms behind them has potential to reduce related risks through different ways. The overarching objective of this dissertation is to quantify complex interactions, detect tipping points, and explore propagations of extreme events in the hydroclimate system from a new structure-based perspective, by integrating climate dynamics, causal inference, network theory, spectral analysis, and machine learning. More specifically, a network-based framework is developed to find responses of hydroclimate system to potential critical transitions in climate. Results show that system-based early warning signals towards tipping points can be located successfully, demonstrated by enhanced connections in the network topology. To further evaluate the long-term nonlinear interactions among the U.S. climate regions, causality inference is introduced and directed complex networks are constructed from climatology records over one century. Causality networks reveal that the Ohio valley region acts as a regional gateway and mediator to the moisture transport and thermal transfer in the U.S. Furthermore, it is found that cross-regional causality variability manifests intrinsic frequency ranging from interannual to interdecadal scales, and those frequencies are associated with the physics of climate oscillations. Besides the long-term climatology, this dissertation also aims to explore extreme events from the system-dynamic perspective, especially the contributions of human-induced activities to propagation of extreme heatwaves in the U.S. cities. Results suggest that there are long-range teleconnections among the U.S. cities and supernodes in heatwave spreading. Findings also confirm that anthropogenic activities contribute to extreme heatwaves by the fact that causality during heatwaves is positively associated with population in megacities.
ContributorsYang, Xueli (Author) / Yang, Zhihua (Thesis advisor) / Lai, Ying-Cheng (Committee member) / Li, Qi (Committee member) / Xu, Tianfang (Committee member) / Zeng, Ruijie (Committee member) / Arizona State University (Publisher)
Created2023
Description
Waste plastic is considered an environmental pollutant because it is not biodegradable. Therefore, there is increased interest in the use of recycled plastic in pavement construction. Polyethylene terephthalate (PET) is a thermoplastic polymer that is commonly used in the manufacturing of containers and bottles. Waste PET is a durable material that has shown enhancement in performance when introduced into asphalt binder and asphalt mixtures. However, PET particles tend to separate from asphalt because of differences in density, molecular structure, molecular weight, and viscosity, leading to inadequate dispersion of PET particles in the asphalt. This incompatibility between PET and asphalt causes segregation, where storage stability becomes an issue. To solve this problem, applying a surface activation on the PET using another abundant urban waste (waste vegetable oil) was examined in this study, showing this method can be effective to enhance PET-asphalt interactions and consequently the storage stability of PET-modified asphalt. To ensure proper surface activation, it is important to thoroughly understand the chemo-mechanics of asphalt containing PET particles as well as the underlying interaction mechanism at the molecular level. Therefore, this study integrates a multi-scale approach using computational modeling based on density functional theory along with laboratory experiments to provide an in-depth understanding of the mechanisms of interaction between surface-activated PET and asphalt. To do so, the efficacy of bio-oil treatment was examined in terms of both the surface-activation capability and the durability of the resulting PET-modified asphalt. It was found that the grafted bio-oil on the PET particles can make a strong interaction with bituminous composites, leading to enhancing the durability and extending the service life of asphalt pavement by reducing the diffusion of free radicals and moisture into the bulk. The study was further extended to study the effect of coating the PET with biochar, showing the latter coating can improve the mechanical properties of the PET-modified asphalt and the adsorption behavior of the PET for volatile organic compounds. The performance of the waste PET was compared with another widely used modifier, crumb rubber.
ContributorsAldagari, Sand (Author) / Fini, Elham (Thesis advisor) / Kaloush, Kamil (Committee member) / Ozer, Hasan (Committee member) / Arizona State University (Publisher)
Created2024