Matching Items (97)
Description
Attitudes and habits are extremely resistant to change, but a disruption of the magnitude of the COVID-19 pandemic has the potential to bring long-term, massive societal changes. During the pandemic, people are being compelled to experience new ways of interacting, working, learning, shopping, traveling, and eating meals. Going forward, a critical question is whether these experiences will result in changed behaviors and preferences in the long term. This paper presents initial findings on the likelihood of long-term changes in telework, daily travel, restaurant patronage, and air travel based on survey data collected from adults in the United States in Spring 2020. These data suggest that a sizable fraction of the increase in telework and decreases in both business air travel and restaurant patronage are likely here to stay. As for daily travel modes, public transit may not fully recover its pre-pandemic ridership levels, but many of our respondents are planning to bike and walk more than they used to. These data reflect the responses of a sample that is higher income and more highly educated than the US population. The response of these particular groups to the COVID-19 pandemic is perhaps especially important to understand, however, because their consumption patterns give them a large influence on many sectors of the economy.
ContributorsConway, Matthew Wigginton (Author) / Salon, Deborah (Author) / da Silva, Denise Capasso (Author) / Mirtich, Laura Christine (Author)
Created2020-09-03
Description
Adaptation to climate change is a core sustainability challenge across the Global South. Development and government organizations conceptualize and govern climate adaptation by creating national and sub-national action plans and implementing projects. This dissertation confronts the inherent tensions that arise when formal planned adaptation interventions encounter the complex, often messy realities of the implementation context. In doing so, this research examines how planned adaptation—with its incentives, provisioned resources, prescribed behaviors, and expectations of commitment from target beneficiaries —interacts with individuals and communities already balancing diverse risks while pursuing their livelihood aspirations. Two broad questions guide this dissertation: 1) how is adaptation envisioned by planners and practitioners? and, 2) how do project beneficiaries engage with, and experience planned adaptation interventions? The research employs an exploratory and inductive qualitative research design. Using Foucault’s lens of governmentality, this research utilises document analysis to examine how the first wave of Indian adaptation projects envision goals, conceptualize problems, delineate roles, and frame expectations of intended beneficiaries. Next, using a case study of an adaptation project implemented in Uttarakhand, India, the study examines the motivations and associated trade-offs behind the engagement and disengagement of the intended beneficiaries: smallholder farmers. Insights from gender-differentiated focus group discussions guide this analysis. Both inquiries are supplemented with findings from semi-structured interviews with Indian adaptation experts and project implementers. The analysis finds that: 1) project reports construct identities of the climate vulnerable beneficiary, implicitly assigning roles and transferring responsibilities for sustaining adaptation efforts beyond project timelines, 2) project participants are not default beneficiaries, but instead exercise agency in decision-making by either opting-in or opting-out of planned initiatives, and 3) the implicit and explicit costs of engaging in planned adaptation interventions are substantial, encompassing significant contributions of time, physical labor, and active participation during and post the project period. This dissertation challenges existing notions of whom planned adaptation serves, and to what end, offering new insights into its design and effectiveness. Furthermore, this research suggests that for planned adaptation to be sustainable, a concerted effort to align with evolving needs, aspirations and livelihood shifts of those on the frontlines of climate change is essential.
ContributorsYogya, Yamini (Author) / Eakin, Hallie (Thesis advisor) / Aggarwal, Rimjhim (Committee member) / York, Abigail (Committee member) / Agrawal, Arun (Committee member) / Arizona State University (Publisher)
Created2024
Description
Given increasing frequency and intensity of extreme weather events and disparities in socio-economic conditions, managing flood risks has become ever more challenging. Building a community flood resilience becomes an essential strategy to reduce flood risks and achieve sustainable development. However, enhancing community flood resilience presents numerous obstacles and potential downsides. To address such a challenge, this dissertation investigates the interactions among natural, built environment, and actor systems using a case study of flooding in Jakarta, Indonesia, focusing on the Ciliwung river watershed. The study first develops a conceptual framework for community flood resilience by integrating concepts from disaster, flood, and community resilience research to represent how water, structural elements, and actors are connected and can contribute to hazards and vulnerabilities. Building on the framework, the study utilizes a mixed-methods approach, combining stakeholder interviews with network and heatmap analysis to identify the roles and interconnections of relevant actors in Jakarta’s flooding. Next, the study employs a hybrid of agent-based and system dynamics modeling to explore the complex interactions among the watershed’s physical and actor systems. The model evaluates how the level of collaboration among government agencies affects flood management interventions and community resilience under various scenarios concerning weather patterns and land-use change.
The research provides an exploratory tool and a strategic guide for enhancing community flood resilience. The stakeholder analysis reveals the complexity of stakeholder relationships and challenges such as imbalance in resource allocation, authority overlap, and low engagement. These insights highlight the need for trust-building, community involvement, and strategic alignment in flood management efforts. Systems modeling to derive policy recommendations bridges the gap between theoretical frameworks and governance challenges, offering empirical evidence of the critical role of governmental collaboration in reducing exposure to floods. The systems modeling results suggest that under conditions of uncertainties, enhancing community flood resilience requires a coordinated approach among stakeholders.
ContributorsSulistyo, Sinta Rahmawidya (Author) / Agusdinata, Datu Buyung (Thesis advisor) / Aggarwal, Rimjhim (Committee member) / Brundiers, Katja (Committee member) / Arizona State University (Publisher)
Created2024
ContributorsForgey, Sydney (Performer) / Hickman, Miriam, 1955- (Performer) / Smith, David (Performer) / ASU Library. Music Library (Publisher)
Created2020-03-25
Description
A piezoelectric transducer, comprised of electroded and active pad PZT layer atop a backing PZT layer and protected with an acoustic matching layer, and operating under a pulse-echo technique for longitudinal ultrasonic imaging, acts as both source and detector.
Ultrasonic transducer stacks (modules), which had failed or passed during pulse-echo sensitivity testing, were received from Consortium X. With limited background information on these stacks, the central theme was to determine the origin(s) of failure via the use of thermal and physicochemical characterization techniques.
The optical and scanning electron microscopy revealed that contact electrode layers are discontinuous in all samples, while delaminations between electrodes and pad layer were observed in failed samples. The X-ray diffraction data on the pad PZT revealed an overall c/a ratio of 1.022 ratio and morphotropic boundary composition, with significant variations of the Zr to Ti ratio within a sample and between samples. Electron probe microanalysis confirmed that the overall Zr to Ti ratio of the pad PZT was 52/48, and higher amounts of excess PbO in failed samples, whereas, inductively coupled plasma mass spectrometry revealed the presence of Mn, Al, and Sb (dopants) and presence of Cu (sintering aid) in in this hard (pad) PZT. Additionally, three exothermic peaks during thermal analysis was indicative of incomplete calcination of pad PZT. Moreover, transmission electron microscopy and scanning transmission electron microscopy revealed the presence of parylene at the Ag-pad PZT interface and within the pores of pad PZT (in failed samples subjected to electric fields). This further dilutes the electrical, mechanical, and electromechanical properties of the pad PZT, which in turn detrimentally influences the pulse echo sensitivity.
Ultrasonic transducer stacks (modules), which had failed or passed during pulse-echo sensitivity testing, were received from Consortium X. With limited background information on these stacks, the central theme was to determine the origin(s) of failure via the use of thermal and physicochemical characterization techniques.
The optical and scanning electron microscopy revealed that contact electrode layers are discontinuous in all samples, while delaminations between electrodes and pad layer were observed in failed samples. The X-ray diffraction data on the pad PZT revealed an overall c/a ratio of 1.022 ratio and morphotropic boundary composition, with significant variations of the Zr to Ti ratio within a sample and between samples. Electron probe microanalysis confirmed that the overall Zr to Ti ratio of the pad PZT was 52/48, and higher amounts of excess PbO in failed samples, whereas, inductively coupled plasma mass spectrometry revealed the presence of Mn, Al, and Sb (dopants) and presence of Cu (sintering aid) in in this hard (pad) PZT. Additionally, three exothermic peaks during thermal analysis was indicative of incomplete calcination of pad PZT. Moreover, transmission electron microscopy and scanning transmission electron microscopy revealed the presence of parylene at the Ag-pad PZT interface and within the pores of pad PZT (in failed samples subjected to electric fields). This further dilutes the electrical, mechanical, and electromechanical properties of the pad PZT, which in turn detrimentally influences the pulse echo sensitivity.
ContributorsPeri, Prudhvi Ram (Author) / Dey, Sandwip (Thesis advisor) / Smith, David (Committee member) / Alford, Terry (Committee member) / Arizona State University (Publisher)
Created2018
Description
Computer assisted language learning (CALL) has become increasingly common as a means of helping learners develop essential skills in a second or foreign language. However, while many CALL programs claim to be based on principles of second language acquisition (SLA) theory and research, evaluation of design and learning outcomes at the level of individual CALL exercises is lacking in the existing literature. The following proposed study will explore the design of computer-based vocabulary matching exercises using both written text and images and the effects of various design manipulations on learning outcomes. The study will use eye-tracking to investigate what users attend to on screen as they work through a series of exercises with different configurations of written words and images. It will ask whether manipulation of text and image features and combinations can have an effect on learners’ attention to the various elements, and if so, whether differences in levels of attention results in higher or lower scores for measures of learning. Specifically, eye-tracking data will be compared to post-test scores for recall and recognition of target vocabulary items to look for a correlation between levels of attention to written forms in-task and post-test gains in scores for vocabulary learning.
ContributorsPatchin, Colleen (Author) / Smith, David (Thesis advisor) / Ross, Andrew (Committee member) / James, Mark (Committee member) / Arizona State University (Publisher)
Created2019
Description
This dissertation describes fundamental studies of hollow carbon nanostructures, which may be used as electrodes for practical energy storage applications such as batteries or supercapacitors. Electron microscopy is heavily utilized for the nanoscale characterization. To control the morphology of hollow carbon nanostructures, ZnO nanowires serve as sacrificial templates. The first part of this dissertation focuses on the optimization of synthesis parameters and the scale-up production of ZnO nanowires by vapor transport method. Uniform ZnO nanowires with 40 nm width can be produced by using 1100 °C reaction temperature and 20 sccm oxygen flow rate, which are the two most important parameters.
The use of ethanol as carbon source with or without water steam provides uniform carbonaceous deposition on ZnO nanowire templates. The amount of as-deposited carbonaceous material can be controlled by reaction temperature and reaction time. Due to the catalytic property of ZnO surface, the thicknesses of carbonaceous layers are typically in nanometers. Different methods to remove the ZnO templates are explored, of which hydrogen reduction at temperatures higher than 700 °C is most efficient. The ZnO templates can also be removed under ethanol environment, but the temperatures need to be higher than 850 °C for practical use.
Characterizations of hollow carbon nanofibers show that the hollow carbon nanostructures have a high specific surface area (>1100 m2/g) with the presence of mesopores (~3.5 nm). The initial data on energy storage as electrodes of electrochemical double layer capacitors show that high specific capacitance (> 220 F/g) can be obtained, which is related to the high surface area and unique porous hollow structure with a thin wall.
The use of ethanol as carbon source with or without water steam provides uniform carbonaceous deposition on ZnO nanowire templates. The amount of as-deposited carbonaceous material can be controlled by reaction temperature and reaction time. Due to the catalytic property of ZnO surface, the thicknesses of carbonaceous layers are typically in nanometers. Different methods to remove the ZnO templates are explored, of which hydrogen reduction at temperatures higher than 700 °C is most efficient. The ZnO templates can also be removed under ethanol environment, but the temperatures need to be higher than 850 °C for practical use.
Characterizations of hollow carbon nanofibers show that the hollow carbon nanostructures have a high specific surface area (>1100 m2/g) with the presence of mesopores (~3.5 nm). The initial data on energy storage as electrodes of electrochemical double layer capacitors show that high specific capacitance (> 220 F/g) can be obtained, which is related to the high surface area and unique porous hollow structure with a thin wall.
ContributorsSong, Yian (Author) / Liu, Jingyue (Committee member) / Smith, David (Committee member) / McCartney, Martha (Committee member) / Chen, Tingyong (Committee member) / Arizona State University (Publisher)
Created2016
Description
This dissertation presents research findings regarding the exploitation of localized surface plasmon (LSP) of epitaxial Ag islands as a means to enhance the photoluminescence (PL) of Germanium (Ge) quantum dots (QDs). The first step of this project was to investigate the growth of Ag islands on Si(100). Two distinct families of Ag islands have been observed. “Big islands” are clearly faceted and have basal dimensions in the few hundred nm to μm range with a variety of basal shapes. “Small islands” are not clearly faceted and have basal diameters in the 10s of nm range. Big islands form via a nucleation and growth mechanism, and small islands form via precipitation of Ag contained in a planar layer between the big islands that is thicker than the Stranski-Krastanov layer existing at room-temperature.
The pseudodielectric functions of epitaxial Ag islands on Si(100) substrates were investigated with spectroscopic ellipsometry. Comparing the experimental pseudodielectric functions obtained for Si with and without Ag islands clearly identifies a plasmon mode with its dipole moment perpendicular to the surface. This observation is confirmed using a simulation based on the thin island film (TIF) theory. Another mode parallel to the surface may be identified by comparing the experimental pseudodielectric functions with the simulated ones from TIF theory. Additional results suggest that the LSP energy of Ag islands can be tuned from the ultra-violet to the infrared range by an amorphous Si (α-Si) cap layer.
Heterostructures were grown that incorporated Ge QDs, an epitaxial Si cap layer and Ag islands grown atop the Si cap layer. Optimum growth conditions for distinct Ge dot ensembles and Si cap layers were obtained. The density of Ag islands grown on the Si cap layer depends on its thickness. Factors contributing to this effect may include the average strain and Ge concentration on the surface of the Si cap layer.
The effects of the Ag LSP on the PL of Ge coherent domes were investigated for both α-Si capped and bare Ag islands. For samples with low-doped substrates, the LSPs reduce the Ge dot-related PL when the Si cap layer is below some critical thickness and have no effect on the PL when the Si cap layer is above the critical thickness. For samples grown on highly-doped wafers, the LSP of bare Ag islands enhanced the PL of Ge QDs by ~ 40%.
The pseudodielectric functions of epitaxial Ag islands on Si(100) substrates were investigated with spectroscopic ellipsometry. Comparing the experimental pseudodielectric functions obtained for Si with and without Ag islands clearly identifies a plasmon mode with its dipole moment perpendicular to the surface. This observation is confirmed using a simulation based on the thin island film (TIF) theory. Another mode parallel to the surface may be identified by comparing the experimental pseudodielectric functions with the simulated ones from TIF theory. Additional results suggest that the LSP energy of Ag islands can be tuned from the ultra-violet to the infrared range by an amorphous Si (α-Si) cap layer.
Heterostructures were grown that incorporated Ge QDs, an epitaxial Si cap layer and Ag islands grown atop the Si cap layer. Optimum growth conditions for distinct Ge dot ensembles and Si cap layers were obtained. The density of Ag islands grown on the Si cap layer depends on its thickness. Factors contributing to this effect may include the average strain and Ge concentration on the surface of the Si cap layer.
The effects of the Ag LSP on the PL of Ge coherent domes were investigated for both α-Si capped and bare Ag islands. For samples with low-doped substrates, the LSPs reduce the Ge dot-related PL when the Si cap layer is below some critical thickness and have no effect on the PL when the Si cap layer is above the critical thickness. For samples grown on highly-doped wafers, the LSP of bare Ag islands enhanced the PL of Ge QDs by ~ 40%.
ContributorsKong, Dexin (Author) / Drucker, Jeffery (Thesis advisor) / Chen, Tingyong (Committee member) / Ros, Robert (Committee member) / Smith, David (Committee member) / Arizona State University (Publisher)
Created2015
Description
Photocatalytic water splitting is a promising technique to produce H2 fuels from water using sustainable solar energy. To better design photocatalysts, the understanding of charge transfer at surfaces/interfaces and the corresponding structure change during the reaction is very important. Local structural and chemical information on nanoparticle surfaces or interfaces can be achieved through characterizations on transmission electron microscopy (TEM). Emphasis should be put on materials structure changes during the reactions in their “working conditions”. Environmental TEM with in situ light illumination system allows the photocatalysts to be studied under light irradiation when exposed to H2O vapor. A set of ex situ and in situ TEM characterizations are carried out on typical types of TiO2 based photocatalysts. The observed structure changes during the reaction are correlated with the H2 production rate for structure-property relationships.
A surface disordering was observed in situ when well-defined anatase TiO2 rhombohedral nanoparticles were exposed to 1 Torr H2O vapor and 10suns light inside the environmental TEM. The disordering is believed to be related to high density of hydroxyl groups formed on surface oxygen vacancies during water splitting reactions.
Pt co-catalyst on TiO2 is able to split pure water producing H2 and O2. The H2 production rate drops during the reaction. Particle size growth during reaction was discovered with Z-contrast images. The particle size growth is believed to be a photo-electro-chemical Ostwald ripening.
Characterizations were also carried out on a more complicated photocatalyst system: Ni/NiO core/shell co-catalyst on TiO2. A decrease of the H2 production rate resulting from photo-corrosion was observed. The Ni is believed to be oxidized to Ni2+ by OH• radicals which are intermediate products of H2O oxidation. The mechanism that the OH• radicals leak into the cores through cracks on NiO shells is more supported by experiments.
Overall this research has done a comprehensive ex situ and in situ TEM characterizations following some typical TiO2 based photocatalysts during reactions. This research has shown the technique availability to study photocatalyst inside TEM in photocatalytic conditions. It also demonstrates the importance to follow structure changes of materials during reactions in understanding deactivation mechanisms.
A surface disordering was observed in situ when well-defined anatase TiO2 rhombohedral nanoparticles were exposed to 1 Torr H2O vapor and 10suns light inside the environmental TEM. The disordering is believed to be related to high density of hydroxyl groups formed on surface oxygen vacancies during water splitting reactions.
Pt co-catalyst on TiO2 is able to split pure water producing H2 and O2. The H2 production rate drops during the reaction. Particle size growth during reaction was discovered with Z-contrast images. The particle size growth is believed to be a photo-electro-chemical Ostwald ripening.
Characterizations were also carried out on a more complicated photocatalyst system: Ni/NiO core/shell co-catalyst on TiO2. A decrease of the H2 production rate resulting from photo-corrosion was observed. The Ni is believed to be oxidized to Ni2+ by OH• radicals which are intermediate products of H2O oxidation. The mechanism that the OH• radicals leak into the cores through cracks on NiO shells is more supported by experiments.
Overall this research has done a comprehensive ex situ and in situ TEM characterizations following some typical TiO2 based photocatalysts during reactions. This research has shown the technique availability to study photocatalyst inside TEM in photocatalytic conditions. It also demonstrates the importance to follow structure changes of materials during reactions in understanding deactivation mechanisms.
ContributorsZhang, Liuxian (Author) / Crozier, Peter (Thesis advisor) / Smith, David (Committee member) / Chan, Candace (Committee member) / Liu, Jingyue (Committee member) / Arizona State University (Publisher)
Created2015
Description
Diarrheal diseases caused by poor water, sanitation and hygiene continue to kill more children in Sub-Saharan Africa's burgeoning informal urban settlements than in any other part of the world. In recent years, Delegated Management Model (DMM), a partnership in which a utility delegates service management to slum residents have been promoted as new models to improve services.
This dissertation examines the benefits of DMM by comparing water services in three informal settlements in Kisumu city, Kenya: two slums where DMM has been implemented, and one, a control, where it has not. In addition, the research examined how school-based hygiene interventions could be designed to improve safe water and hygiene knowledge in urban informal settlements. This study compared outcomes of two approaches to hygiene education, one which combined messages with participatory water testing; the second used hygiene messages alone.
Results of the DMM study showed that DMM implementation had lowered water cost and improved provider accountability. However, unhygienic water collection and handling practices on the part of the service users could contaminate drinking water that was clean at the delivery point, thus preventing the intended health outcomes of DMM from being realized. Results of the hygiene education intervention showed that one week after the inventions, hygiene knowledge among students who received the intervention that combined hygiene messages with participatory water testing was significantly improved. Evaluation of the intervention 12 months after implementation showed that the hygiene knowledge gained was sustained.
The research findings suggest that: i) regular monitoring of water quality at the kiosks is essential to ensure that the DMM model achieves intended health outcomes, ii) sanitation conditions at kiosk sites need to be regulated to meet minimum hygiene standards, and iii) customers need to be educated on safe water collection and storage practices. Finally, school-based hygiene education could be made more effective by including hands-on water testing by students. Making sustainable impact on health and wellbeing of slum residents requires not only building effective partnerships for water delivery, but also paying close attention to the other points of intervention within the water system.
This dissertation examines the benefits of DMM by comparing water services in three informal settlements in Kisumu city, Kenya: two slums where DMM has been implemented, and one, a control, where it has not. In addition, the research examined how school-based hygiene interventions could be designed to improve safe water and hygiene knowledge in urban informal settlements. This study compared outcomes of two approaches to hygiene education, one which combined messages with participatory water testing; the second used hygiene messages alone.
Results of the DMM study showed that DMM implementation had lowered water cost and improved provider accountability. However, unhygienic water collection and handling practices on the part of the service users could contaminate drinking water that was clean at the delivery point, thus preventing the intended health outcomes of DMM from being realized. Results of the hygiene education intervention showed that one week after the inventions, hygiene knowledge among students who received the intervention that combined hygiene messages with participatory water testing was significantly improved. Evaluation of the intervention 12 months after implementation showed that the hygiene knowledge gained was sustained.
The research findings suggest that: i) regular monitoring of water quality at the kiosks is essential to ensure that the DMM model achieves intended health outcomes, ii) sanitation conditions at kiosk sites need to be regulated to meet minimum hygiene standards, and iii) customers need to be educated on safe water collection and storage practices. Finally, school-based hygiene education could be made more effective by including hands-on water testing by students. Making sustainable impact on health and wellbeing of slum residents requires not only building effective partnerships for water delivery, but also paying close attention to the other points of intervention within the water system.
ContributorsNzengya, Daniel (Author) / Aggarwal, Rimjhim (Thesis advisor) / Hartwell, Leland (Committee member) / Boone, Christopher (Committee member) / Arizona State University (Publisher)
Created2014