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- Genre: Masters Thesis
- Creators: Arizona State University
- Creators: Chakraborty, Bijeta
- Member of: ASU Electronic Theses and Dissertations
Description
The Cave Creek Complex fires of June and July of 2005 north of Phoenix, Arizona, U.S.A. burned 248,310 acres of Sonoran desert, primarily on the Tonto National Forest, USFS. The fires consumed multiple stands of the keystone species Carnegiea gigantea, the saguaro cactus. Restoration efforts in late spring 2007 involved the monitoring of 200 transplanted saguaro cacti over a two year period for overall establishment and success. Observation of local saguaro distribution suggests that soil factors might influence saguaro growth. Therefore, soil samples were collected from each transplant location and analyzed for percentage coarse fragments, texture, pH and electrical conductivity as soil collection and analysis of these variables are relatively inexpensive and expedient. Regression analysis was used to determine which, if any of these soil characteristics significantly correlated with plant growth. The results of this study found significant correlation between saguaro transplant growth and the soil variables of clay content and pH, but no correlation between saguaro growth and coarse fragment percentages or electrical conductivity.
ContributorsElliott, Todd (Author) / Green, Douglas (Thesis advisor) / Steele, Kelly (Committee member) / Alford, Eddie (Committee member) / Arizona State University (Publisher)
Created2013
Description
Efficiency of components is an ever increasing area of importance to portable applications, where a finite battery means finite operating time. Higher efficiency devices need to be designed that don't compromise on the performance that the consumer has come to expect. Class D amplifiers deliver on the goal of increased efficiency, but at the cost of distortion. Class AB amplifiers have low efficiency, but high linearity. By modulating the supply voltage of a Class AB amplifier to make a Class H amplifier, the efficiency can increase while still maintaining the Class AB level of linearity. A 92dB Power Supply Rejection Ratio (PSRR) Class AB amplifier and a Class H amplifier were designed in a 0.24um process for portable audio applications. Using a multiphase buck converter increased the efficiency of the Class H amplifier while still maintaining a fast response time to respond to audio frequencies. The Class H amplifier had an efficiency above the Class AB amplifier by 5-7% from 5-30mW of output power without affecting the total harmonic distortion (THD) at the design specifications. The Class H amplifier design met all design specifications and showed performance comparable to the designed Class AB amplifier across 1kHz-20kHz and 0.01mW-30mW. The Class H design was able to output 30mW into 16Ohms without any increase in THD. This design shows that Class H amplifiers merit more research into their potential for increasing efficiency of audio amplifiers and that even simple designs can give significant increases in efficiency without compromising linearity.
ContributorsPeterson, Cory (Author) / Bakkaloglu, Bertan (Thesis advisor) / Barnaby, Hugh (Committee member) / Kiaei, Sayfe (Committee member) / Arizona State University (Publisher)
Created2013
Description
Class D Amplifiers are widely used in portable systems such as mobile phones to achieve high efficiency. The demands of portable electronics for low power consumption to extend battery life and reduce heat dissipation mandate efficient, high-performance audio amplifiers. The high efficiency of Class D amplifiers (CDAs) makes them particularly attractive for portable applications. The Digital class D amplifier is an interesting solution to increase the efficiency of embedded systems. However, this solution is not good enough in terms of PWM stage linearity and power supply rejection. An efficient control is needed to correct the error sources in order to get a high fidelity sound quality in the whole audio range of frequencies. A fundamental analysis on various error sources due to non idealities in the power stage have been discussed here with key focus on Power supply perturbations driving the Power stage of a Class D Audio Amplifier. Two types of closed loop Digital Class D architecture for PSRR improvement have been proposed and modeled. Double sided uniform sampling modulation has been used. One of the architecture uses feedback around the power stage and the second architecture uses feedback into digital domain. Simulation & experimental results confirm that the closed loop PSRR & PS-IMD improve by around 30-40 dB and 25 dB respectively.
ContributorsChakraborty, Bijeta (Author) / Bakkaloglu, Bertan (Thesis advisor) / Garrity, Douglas (Committee member) / Ozev, Sule (Committee member) / Arizona State University (Publisher)
Created2012
Description
Aboveground net primary production (ANPP) is an important ecosystem process that, in drylands, is most frequently limited by water availability. Water availability for plants is in part controlled by the water holding capacity of soils. Available water holding capacity (AWHC) of soils is strongly influenced by soil texture and depth. This study drew upon localized rain gauge data and four data-sets of cover-line and biomass data to estimate ANPP and to determine annual precipitation (PPT). I measured soil depth to caliche and texture by layer of 112 plots across the four landscape units for which estimation of ANPP were available. A pedotransfer function was used to estimate AWHC from soil depth increments to depth of caliche measurements and texture analysis. These data were analyzed using simple and multivariate regression to test the effect of annual precipitation and available water holding capacity on aboveground net primary production. Soil texture remained constant among all plots (sandy loam) and depth to caliche varied from 15.16 cm to 189 cm. AWHC and the interaction term (PPT*AWHC) were insignificant (p=0.142, p=0.838) and annual PPT accounted for 18.4% of the variation in ANPP. The y-intercept was significantly different for ANPP ~ annual PPT when considering AWHC values either above or below 3 cm. Shrub ANPP was insensitive to precipitation regardless of AWHC (R2=-0.012, R2=0.014). Results from this study indicate that a model incorporating annual PPT and AWHC may not serve as a good predictor for ANPP at a site level where there is little variation in soil texture.
ContributorsWagner, Svenja K (Author) / Sala, Osvaldo E. (Thesis advisor) / Cease, Arianne (Committee member) / Hall, Sharon (Committee member) / Peters, Debra (Committee member) / Arizona State University (Publisher)
Created2019
Description
The public has expressed a growing desire for more sustainable and green technologies to be implemented in society. Bio-cementation is a method of soil improvement that satisfies this demand for sustainable and green technology. Bio-cementation can be performed by using microbes or free enzymes which precipitate carbonate within the treated soil. These methods are referred to as microbial induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP). The precipitation of carbonate is the formation of crystalline minerals that fill the void spaces within a body of soil.
This thesis investigates the application of EICP in a soil collected from the Arizona State University Polytechnic campus. The surficial soil in the region is known to be a clayey sand. Both EICP and MICP have their limitations in soils consisting of a significant percentage of fines. Fine-grained soils have a greater surface area which requires the precipitation of a greater amount of carbonate to increase the soil’s strength. EICP was chosen due to not requiring any living organisms during the application, having a faster reaction rate and size constraints.
To determine the effectiveness of EICP as a method of improving a soil with a significant amount of fines, multiple comparisons were made: 1) The soil’s strength was analyzed on its own, untreated; 2) The soil was treated with EICP to determine if bio-cementation can strengthen the soil; 3) The soil had sand added to reduce the fines content and was treated with EICP to determine how the fines percentage effects the strength of a soil when treated with EICP.
While the EICP treatment increased the strength of the soil by over 3-fold, the strength was still relatively low when compared to results of other case studies treating sandy soils. More research could be done with triaxial testing due to the samples of the Polytechnic soil’s strength coming from capillarity.
This thesis investigates the application of EICP in a soil collected from the Arizona State University Polytechnic campus. The surficial soil in the region is known to be a clayey sand. Both EICP and MICP have their limitations in soils consisting of a significant percentage of fines. Fine-grained soils have a greater surface area which requires the precipitation of a greater amount of carbonate to increase the soil’s strength. EICP was chosen due to not requiring any living organisms during the application, having a faster reaction rate and size constraints.
To determine the effectiveness of EICP as a method of improving a soil with a significant amount of fines, multiple comparisons were made: 1) The soil’s strength was analyzed on its own, untreated; 2) The soil was treated with EICP to determine if bio-cementation can strengthen the soil; 3) The soil had sand added to reduce the fines content and was treated with EICP to determine how the fines percentage effects the strength of a soil when treated with EICP.
While the EICP treatment increased the strength of the soil by over 3-fold, the strength was still relatively low when compared to results of other case studies treating sandy soils. More research could be done with triaxial testing due to the samples of the Polytechnic soil’s strength coming from capillarity.
ContributorsRoss, Johnathan (Author) / Kavazanjian, Edward (Thesis advisor) / Zapata, Claudia (Committee member) / Hamdan, Nasser (Committee member) / Arizona State University (Publisher)
Created2018
Description
As a result of growing populations and uncertain resource availability, urban areas are facing pressure from federal and state agencies, as well as residents, to promote conservation programs that provide services for people and mitigate environmental harm. Current strategies in US cities aim to reduce the impact of municipal and household resource use, including programs to promote water conservation. One common conservation program incentivizes the replacement of water-intensive turfgrass lawns with landscapes that use less water consisting of interspersed drought-tolerant shrubs and trees with rock or mulch groundcover (e.g. xeriscapes, rain gardens, water-wise landscapes). A handful of previous studies in experimental landscapes have shown that converting a turfgrass yard to a shrub-dominated landscape has the potential to increase rates of nitrate (NO3-) leaching. However, no studies have examined the drivers or patterns across diverse management practices. In this research, I compared soil nutrient retention and cycling in turfgrass and lawn-alternative xeriscaped yards along a chronosequence of time since land cover change in Tempe, Arizona, in the semi-arid US Southwest. Soil inorganic extractable nitrogen (N) pools were greater in xeriscapes compared to turfgrass lawns. On average xeriscapes contained 2.5±0.4 g NO3--N/m2 in the first 45 cm of soil, compared to 0.6±0.7 g NO3--N/m2 in lawns. Soil NO3--N pools in xeriscaped yards also varied significantly with time: pools were largest 9-13 years after cover change and declined to levels comparable to turfgrass at 18-21 years. Variation in soil extractable NO3--N with landscape age was strongly influenced by management practices that control soil water availability, including shrub cover, the presence of sub-surface plastic sheeting, and the frequency of irrigation. This research is the first to explore the ecological outcomes and temporal dynamics of an increasingly common, ‘sustainable’ land use practice that is universally promoted in US cities. Our findings show that transitioning from turfgrass to water-efficient residential landscaping can lead to an accumulation of NO3--N that may be lost from the soil rooting zone over time, through leaching following irrigation or rainfall. These results have implications for best management practices to optimize the benefits of water-conserving residential yards.
ContributorsHeavenrich, Hannah (Author) / Hall, Sharon J (Thesis advisor) / Larson, Kelli L (Committee member) / Potaki, Diane E (Committee member) / Arizona State University (Publisher)
Created2015
Description
In this thesis, a digital input class D audio amplifier system which has the ability
to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress the power supply noise and harmonic distortions. The design is using global foundry 0.18um technology.
Based on simulation, the power supply rejection at 200Hz is about -49dB with
81dB dynamic range and -70dB THD+N. The full scale output power can reach as high as 27mW and still keep minimum -68dB THD+N. The system efficiency at full scale is about 82%.
to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress the power supply noise and harmonic distortions. The design is using global foundry 0.18um technology.
Based on simulation, the power supply rejection at 200Hz is about -49dB with
81dB dynamic range and -70dB THD+N. The full scale output power can reach as high as 27mW and still keep minimum -68dB THD+N. The system efficiency at full scale is about 82%.
ContributorsBai, Jing (Author) / Bakkaloglu, Bertan (Thesis advisor) / Arizona State University (Publisher)
Created2015
Description
The advantages and challenges of combining zero-valent iron (ZVI) and microbial reduction of trichloroethene (TCE) and perchlorate (ClO4-) in contaminated soil and groundwater are not well understood. The objective of this work was to identify the benefits and limitations of simultaneous application of ZVI and bioaugmentation for detoxification of TCE and ClO4- using conditions relevant to a specific contaminated site. We studied conditions representing a ZVI-injection zone and a downstream zone influenced Fe (II) produced, for simultaneous ZVI and microbial reductive dechlorination applications using bench scale semi-batch microcosm experiments. 16.5 g L-1 ZVI effectively reduced TCE to ethene and ethane but ClO4- was barely reduced. Microbial reductive dechlorination was limited by both ZVI as well as Fe (II) derived from oxidation of ZVI. In the case of TCE, rapid abiotic TCE reduction made the TCE unavailable for the dechlorinating bacteria. In the case of perchlorate, ZVI inhibited the indigenous perchlorate-reducing bacteria present in the soil and groundwater. Further, H2 generated by ZVI reactions stimulated competing microbial processes like sulfate reduction and methanogenesis. In the microcosms representing the ZVI downstream zone (Fe (II) only), we detected accumulation of cis-dichloroethene (cis-DCE) and vinyl chloride (VC) after 56 days. Some ethene also formed under these conditions. In the absence of ZVI or Fe (II), we detected complete TCE dechlorination to ethene and faster rates of ClO4- reduction. The results illustrate potential limitations of combining ZVI with microbial reduction of chlorinated compounds and show the potential that each technology has when applied separately.
ContributorsMohana Rangan, Srivatsan (Author) / Krajmalnik-Brown, Rosa (Thesis advisor) / Delgado, Anca G (Committee member) / Lowry, Gregory V. (Committee member) / Arizona State University (Publisher)
Created2017
Description
The United States Department of Agriculture provides requirements for a farm operation to become certified organic, but how do these regulations influence nutrient
management on organic farms? There is insufficient evidence to show if the current
regulations on nutrient sourcing and application are feasible and effective. An online
survey was administered to owners and operators of organic farms. Survey respondents
were offered a free soil test as an incentive to participate and to compare their practices
and soil quality. Assessing the current nutrient management under organic regulations
provides information to help assess the sustainability of their nutrient management
practices. Early data suggest that organic farmers may most often be overapplying and
creating legacy sources with this key resource.
ContributorsBonham, Emma Eileen (Author) / Muenich, Rebecca (Thesis advisor) / Zanin, Alaina (Committee member) / Williams, Clinton (Committee member) / Arizona State University (Publisher)
Created2022
Description
Advanced technology has increased access to Antarctica; consequently, there has been an increase in research and tourism. The production of the new technology and the increased number of individuals visiting can increase the presence of persistent organic pollutants and microplastic within Antarctic soil. Studies have focused primarily on identifying these pollutants in high human impact areas with perhaps an assumption that low human impact areas would have lower concentrations of pollutants. The object of this paper, therefore, was to test the hypothesis that higher concentrations of persistent organic pollutants and microplastic are found in soils collected near research stations and tourist areas, as opposed to sites that are further from stations and have less direct human impact. Soil samples were collected along a 1,500 km transect of the Scotia Arch and Antarctic Peninsula from three high human impact sites and three low human impact sites to compare the concentration of contaminates identified within the soil. The presence and quantities of microplastic were identified using Nile Red and fluorescence microscopy, while gas chromatography-mass spectrometry was used to detect polychlorinated biphenyls, pesticides, polycyclic aromatic hydrocarbons, n-alkane, and phthalates. Although varying contaminate concentration levels were found at all six sights, counter to the hypothesis, there were no clear patterns of increasing pollutants with increasing human activities. These findings could imply that global sources of pollutants can increase local pollutants indicating the best way to solve any pollution problem is through a global lens.
ContributorsCarroll, Kenneth Charles (Author) / Polidoro, Beth (Thesis advisor) / Kinzig, Ann (Thesis advisor) / Ball, Becky (Committee member) / Arizona State University (Publisher)
Created2022