ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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Description
Second-generation biofuel feedstocks are currently grown in land-based systems that use valuable resources like water, electricity and fertilizer. This study investigates the potential of near-shore marine (ocean) seawater filtration as a source of planktonic biomass for biofuel production. Mixed marine organisms in the size range of 20µm to 500µm were isolated from the University of California, Santa Barbara (UCSB) seawater filtration system during weekly backwash events between the months of April and August, 2011. The quantity of organic material produced was determined by sample combustion and calculation of ash-free dry weights. Qualitative investigation required density gradient separation with the heavy liquid sodium metatungstate followed by direct transesterification and gas chromatography with mass spectrometry (GC-MS) of the fatty acid methyl esters (FAME) produced. A maximum of 0.083g/L of dried organic material was produced in a single backwash event and a study average of 0.036g/L was calculated. This equates to an average weekly value of 7,674.75g of dried organic material produced from the filtration of approximately 24,417,792 liters of seawater. Temporal variations were limited. Organic quantities decreased over the course of the study. Bio-fouling effects from mussel overgrowth inexplicably increased production values when compared to un-fouled seawater supply lines. FAMEs (biodiesel) averaged 0.004% of the dried organic material with 0.36ml of biodiesel produced per week, on average. C16:0 and C22:6n3 fatty acids comprised the majority of the fatty acids in the samples. Saturated fatty acids made up 30.71% to 44.09% and unsaturated forms comprised 55.90% to 66.32% of the total chemical composition. Both quantities and qualities of organics and FAMEs were unrealistic for use as biodiesel but sample size limitations, system design, geographic and temporal factors may have impacted study results.
ContributorsPierre, Christophe (Author) / Olson, Larry (Thesis advisor) / Sommerfeld, Milton (Committee member) / Brown, Albert (Committee member) / Arizona State University (Publisher)
Created2011
Description
Photovoltaic (PV) systems are one of the next generation's renewable energy sources for our world energy demand. PV modules are highly reliable. However, in polluted environments, over time, they will collect grime and dust. There are also limited field data studies about soiling losses on PV modules. The study showed how important it is to investigate the effect of tilt angle on soiling. The study includes two sets of mini-modules. Each set has 9 PV modules tilted at 0, 5, 10, 15, 20, 23, 30, 33 and 40°. The first set called "Cleaned" was cleaned every other day. The second set called "Soiled" was never cleaned after the first day. The short circuit current, a measure of irradiance, and module temperature was monitored and recorded every two minutes over three months (January-March 2011). The data were analyzed to investigate the effect of tilt angle on daily and monthly soiling, and hence transmitted solar insolation and energy production by PV modules. The study shows that during the period of January through March 2011 there was an average loss due to soiling of approximately 2.02% for 0° tilt angle. Modules at tilt anlges 23° and 33° also have some insolation losses but do not come close to the module at 0° tilt angle. Tilt anlge 23° has approximately 1.05% monthly insolation loss, and 33° tilt angle has an insolation loss of approximately 0.96%. The soiling effect is present at any tilt angle, but the magnitude is evident: the flatter the solar module is placed the more energy it will lose.
ContributorsCano Valero, José (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Madakannan, Arunachalanadar (Committee member) / Macia, Narciso (Committee member) / Arizona State University (Publisher)
Created2011
Description
A primary motivation of research in photovoltaic technology is to obtain higher efficiency photovoltaic devices at reduced cost of production so that solar electricity can be cost competitive. The majority of photovoltaic technologies are based on p-n junction, with efficiency potential being much lower than the thermodynamic limits of individual technologies and thereby providing substantial scope for further improvements in efficiency. The thesis explores photovoltaic devices using new physical processes that rely on thin layers and are capable of attaining the thermodynamic limit of photovoltaic technology. Silicon heterostructure is one of the candidate technologies in which thin films induce a minority carrier collecting junction in silicon and the devices can achieve efficiency close to the thermodynamic limits of silicon technology. The thesis proposes and experimentally establishes a new theory explaining the operation of silicon heterostructure solar cells. The theory will assist in identifying the optimum properties of thin film materials for silicon heterostructure and help in design and characterization of the devices, along with aiding in developing new devices based on this technology. The efficiency potential of silicon heterostructure is constrained by the thermodynamic limit (31%) of single junction solar cell and is considerably lower than the limit of photovoltaic conversion (~ 80 %). A further improvement in photovoltaic conversion efficiency is possible by implementing a multiple quasi-fermi level system (MQFL). A MQFL allows the absorption of sub band gap photons with current being extracted at a higher band-gap, thereby allowing to overcome the efficiency limit of single junction devices. A MQFL can be realized either by thin epitaxial layers of alternating higher and lower band gap material with nearly lattice matched (quantum well) or highly lattice mismatched (quantum dot) structure. The thesis identifies the material combination for quantum well structure and calculates the absorption coefficient of a MQFl based on quantum well. GaAsSb (barrier)/InAs(dot) was identified as a candidate material for MQFL using quantum dot. The thesis explains the growth mechanism of GaAsSb and the optimization of GaAsSb and GaAs heterointerface.
ContributorsGhosha, Kuṇāla (Author) / Bowden, Stuart (Thesis advisor) / Honsberg, Christiana (Thesis advisor) / Vasileska, Dragica (Committee member) / Goodnick, Stephen (Committee member) / Arizona State University (Publisher)
Created2011
Description
Strong communities are important for society. One of the most important community builders, making friends, is poorly supported online. Dating sites support it but in romantic contexts. Other major social networks seem not to encourage it because either their purpose isn't compatible with introducing strangers or the prevalent methods of introduction aren't effective enough to merit use over real word alternatives. This paper presents a novel digital social network emphasizing creating friendships. Research has shown video chat communication can reach in-person levels of trust; coupled with a game environment to ease the discomfort people often have interacting with strangers and a recommendation engine, Zazzer, the presented system, allows people to meet and get to know each other in a manner much more true to real life than traditional methods. Its network also allows players to continue to communicate afterwards. The evaluation looks at real world use, measuring the frequency with which players choose the video chat game versus alternative, more traditional methods of online introduction. It also looks at interactions after the initial meeting to discover how effective video chat games are in creating sticky social connections. After initial use it became apparent a critical mass of users would be necessary to draw strong conclusions, however the collected data seemed to give preliminary support to the idea that video chat games are more effective than traditional ways of meeting online in creating new relationships.
ContributorsSorensen, Asael (Author) / VanLehn, Kurt (Thesis advisor) / Liu, Huan (Committee member) / Burleson, Winslow (Committee member) / Arizona State University (Publisher)
Created2011
Description
To address sustainability issues in wastewater treatment (WWT), Siemens Water Technologies (SWT) has designed a "hybrid" process that couples common activated sludge (AS) and anaerobic digestion (AD) technologies with the novel concepts of AD sludge recycle and biosorption. At least 85% of the hybrid's AD sludge is recycled to the AS process, providing additional sorbent for influent particulate chemical oxygen demand (PCOD) biosorption in contact tanks. Biosorbed PCOD is transported to the AD, where it is converted to methane. The aim of this study is to provide mass balance and microbial community analysis (MCA) of SWT's two hybrid and one conventional pilot plant trains and mathematical modeling of the hybrid process including a novel model of biosorption. A detailed mass balance was performed on each tank and the overall system. The mass balance data supports the hybrid process is more sustainable: It produces 1.5 to 5.5x more methane and 50 to 83% less sludge than the conventional train. The hybrid's superior performance is driven by 4 to 8 times longer solid retention times (SRTs) as compared to conventional trains. However, the conversion of influent COD to methane was low at 15 to 22%, and neither train exhibited significant nitrification or denitrification. Data were inconclusive as to the role of biosorption in the processes. MCA indicated the presence of Archaea and nitrifiers throughout both systems. However, it is inconclusive as to how active Archaea and nitrifiers are under anoxic, aerobic, and anaerobic conditions. Mathematical modeling confirms the hybrid process produces 4 to 20 times more methane and 20 to 83% less sludge than the conventional train under various operating conditions. Neither process removes more than 25% of the influent nitrogen or converts more that 13% to nitrogen gas due to biomass washout in the contact tank and short SRTs in the stabilization tank. In addition, a mathematical relationship was developed to describe PCOD biosorption through adsorption to biomass and floc entrapment. Ultimately, process performance is more heavily influenced by the higher AD SRTs attained when sludge is recycled through the system and less influenced by the inclusion of biosorption kinetics.
ContributorsYoung, Michelle Nichole (Author) / Rittmann, Bruce E. (Thesis advisor) / Fox, Peter (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Arizona State University (Publisher)
Created2011
Description
The photovoltaic (PV) modules are primarily characterized for their performance with respect to incident irradiance and operating temperature. This work deals with data collection and automation of data processing for the performance and thermal characterizations of PV modules. This is a two-part thesis: The primary part (part-1) deals with the software automation to generate performance matrix as per IEC 61853-1 standard using MPPT (maximum power point tracking) data at the module or system level; the secondary part (part-2) deals with the software automation to predict temperature of rooftop PV modules using the thermal model coefficients generated in the previous studies of the Photovoltaic Reliability Laboratory (PRL). Part 1: The IEC 61853-1 standard published in January 2011 specifies the generation of a target performance matrix of photovoltaic (PV) modules at various temperatures and irradiance levels. In a conventional method, this target matrix is generated using all the data points of several measured I-V curves and the translation procedures defined in IEC 60891 standard. In the proposed method, the target matrix is generated using only three commonly field measured parameters: Module temperature, Incident irradiance and MPPT (Maximum Peak Power Tracking) value. These parameters are loaded into the programmed Excel file and with a click of a button, IEC 61853-1 specified Pmppt matrix is displayed on the screen in about thirty seconds. Part 2: In a previous study at PRL, an extensive thermal model to predict operating temperature of rooftop PV modules was developed with a large number of empirical monthly coefficients for ambient temperature, irradiance and wind speed. Considering that there is large number of coefficients for each air gap of rooftop modules, it became necessary to automate the entire data processing to predict the temperature of rooftop PV modules at different air gaps. This part of the work was dedicated to automatically predict the temperature of rooftop modules at different air gaps for any month in a year just using only four input parameters: Month, Irradiance, Ambient temperature and Wind speed.
ContributorsKoka, Kartheek (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Rogers, Bradley (Committee member) / Macia, Narciso F. (Committee member) / Arizona State University (Publisher)
Created2011
Description
The failure to withhold inappropriate behavior is a central component of most impulse control disorders, including Attention Deficit Hyperactivity Disorder (ADHD). The present study examined the effects of housing environment and methylphenidate (a drug often prescribed for ADHD) on the performance of rats in two response inhibition tasks: differential reinforcement of low rate (DRL) and fixed minimum interval (FMI). Both tasks required rats to wait a fixed amount of time (6 s) before emitting a reinforced response. The capacity to withhold the target response (volitional inhibition) and timing precision were estimated on the basis of performance in each of the tasks. Paradoxically, rats housed in a mildly enriched environment that included a conspecific displayed less volitional inhibition in both tasks compared to rats housed in an isolated environment. Enriched housing, however, increased timing precision. Acute administration of methylphenidate partially reversed the effects of enriched housing. Implications of these results in the assessment and treatment of ADHD-related impulsivity are discussed.
ContributorsHill, Jade C (Author) / Sanabria, Federico (Thesis advisor) / Killeen, Peter (Committee member) / Neisewander, Janet (Committee member) / Arizona State University (Publisher)
Created2011
Description
This study evaluates two photovoltaic (PV) power plants based on electrical performance measurements, diode checks, visual inspections and infrared scanning. The purpose of this study is to measure degradation rates of performance parameters (Pmax, Isc, Voc, Vmax, Imax and FF) and to identify the failure modes in a "hot-dry desert" climatic condition along with quantitative determination of safety failure rates and reliability failure rates. The data obtained from this study can be used by module manufacturers in determining the warranty limits of their modules and also by banks, investors, project developers and users in determining appropriate financing or decommissioning models. In addition, the data obtained in this study will be helpful in selecting appropriate accelerated stress tests which would replicate the field failures for the new modules and would predict the lifetime for new PV modules. The study was conducted at two, single axis tracking monocrystalline silicon (c-Si) power plants, Site 3 and Site 4c of Salt River Project (SRP). The Site 3 power plant is located in Glendale, Arizona and the Site 4c power plant is located in Mesa, Arizona both considered a "hot-dry" field condition. The Site 3 power plant has 2,352 modules (named as Model-G) which was rated at 250 kW DC output. The mean and median degradation of these 12 years old modules are 0.95%/year and 0.96%/year, respectively. The major cause of degradation found in Site 3 is due to high series resistance (potentially due to solder-bond thermo-mechanical fatigue) and the failure mode is ribbon-ribbon solder bond failure/breakage. The Site 4c power plant has 1,280 modules (named as Model-H) which provide 243 kW DC output. The mean and median degradation of these 4 years old modules are 0.96%/year and 1%/year, respectively. At Site 4c, practically, none of the module failures are observed. The average soiling loss is 6.9% in Site 3 and 5.5% in Site 4c. The difference in soiling level is attributed to the rural and urban surroundings of these two power plants.
ContributorsMallineni, Jaya Krishna (Author) / Govindasamy, Tamizhmani (Thesis advisor) / Devarajan, Srinivasan (Committee member) / Narciso, Macia (Committee member) / Arizona State University (Publisher)
Created2013
Description
Chronic restraint stress impairs hippocampal-mediated spatial learning and memory, which improves following a post-stress recovery period. Here, we investigated whether brain derived neurotrophic factor (BDNF), a protein important for hippocampal function, would alter the recovery from chronic stress-induced spatial memory deficits. Adult male Sprague-Dawley rats were infused into the hippocampus with adeno- associated viral vectors containing the coding sequence for short interfering (si)RNA directed against BDNF or a scrambled sequence (Scr), with both containing the coding information for green fluorescent protein to aid in anatomical localization. Rats were then chronically restrained (wire mesh, 6h/d/21d) and assessed for spatial learning and memory using a radial arm water maze (RAWM) either immediately after stressor cessation (Str-Imm) or following a 21-day post-stress recovery period (Str-Rec). All groups learned the RAWM task similarly, but differed on the memory retention trial. Rats in the Str-Imm group, regardless of viral vector contents, committed more errors in the spatial reference memory domain than did non-stressed controls. Importantly, the typical improvement in spatial memory following recovery from chronic stress was blocked with the siRNA against BDNF, as Str-Rec-siRNA performed worse on the RAWM compared to the non-stressed controls or Str-Rec-Scr. These effects were specific for the reference memory domain as repeated entry errors that reflect spatial working memory were unaffected by stress condition or viral vector contents. These results demonstrate that hippocampal BDNF is necessary for the recovery from stress-induced hippocampal dependent spatial memory deficits in the reference memory domain.
ContributorsOrtiz, J. Bryce (Author) / Conrad, Cheryl D. (Thesis advisor) / Olive, M. Foster (Committee member) / Taylor, Sara (Committee member) / Bimonte-Nelson, Heather A. (Committee member) / Arizona State University (Publisher)
Created2013
Description
Within the media there is an abundance of reports that claim tourists are being harassed, kidnapped and even killed in some instances as a result of their representation of their country's political ideology and international relations. A qualitative study was undertaken in Bolivia to determine how a tourist avoids or copes with the fear of severe political retribution or harassment in a country whose political environment is largely opposed to that of the traveler's home country. Interviews were conducted in multiple regions of Bolivia, and the data were coded. The results show that tourists experience political retribution on a much smaller scale than initially thought, usually through non-threatening social encounters. The overall themes influencing traveler behaviors are the (Un)Apologetic American, the George W. Bush foreign policy era, avoiding perceived unsafe countries or regions, and Bolivian borders. Respondents, when asked to reflect upon their behavioral habits, do not usually forthrightly deny their country of origin but merely adapt their national identities based on their familial origins, dual citizenship, language abilities or lack thereof, familiarity with the world/regional politics or lack thereof and associating oneself with a popular region in the United States (e.g. New York), rather than the US as a whole. Interestingly, none of the Americans interviewed candidly deny their American nationality or express future intention to deny their nationality. The Americans did express feeling "singled out" at the Bolivian borders which leads to the management implication to implement an automated receipt when purchasing a Bolivian visa and improving the Ministry of Tourism website that would more clearly state visa requirements. Additionally, the image of Bolivia as a culturally and politically homogeneous country is discussed.
ContributorsCastellanos, Cassandra (Author) / Timothy, Dallen J. (Thesis advisor) / Catlaw, Thomas J (Committee member) / Nyaupane, Gyan P (Committee member) / Arizona State University (Publisher)
Created2013