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Description
The recent years have witnessed a rapid development of mobile devices and smart devices. As more and more people are getting involved in the online environment, privacy issues are becoming increasingly important. People’s privacy in the digital world is much easier to leak than in the real world, because every action people take online would leave a trail of information which could be recorded, collected and used by malicious attackers. Besides, service providers might collect users’ information and analyze them, which also leads to a privacy breach. Therefore, preserving people’s privacy is very important in the online environment.
In this dissertation, I study the problems of preserving people’s identity privacy and loca- tion privacy in the online environment. Specifically, I study four topics: identity privacy in online social networks (OSNs), identity privacy in anonymous message submission, lo- cation privacy in location based social networks (LBSNs), and location privacy in location based reminders. In the first topic, I propose a system which can hide users’ identity and data from untrusted storage site where the OSN provider puts users’ data. I also design a fine grained access control mechanism which prevents unauthorized users from accessing the data. Based on the secret sharing scheme, I construct a shuffle protocol that disconnects the relationship between members’ identities and their submitted messages in the topic of identity privacy in anonymous message submission. The message is encrypted on the mem- ber side and decrypted on the message collector side. The collector eventually gets all of the messages but does not know who submitted which message. In the third topic, I pro- pose a framework that hides users’ check-in information from the LBSN. Considering the limited computation resources on smart devices, I propose a delegatable pseudo random function to outsource computations to the much more powerful server while preserving privacy. I also implement efficient revocations. In the topic of location privacy in location based reminders, I propose a system to hide users’ reminder locations from an untrusted cloud server. I propose a cross based approach and an improved bar based approach, re- spectively, to represent a reminder area. The reminder location and reminder message are encrypted before uploading to the cloud server, which then can determine whether the dis- tance between the user’s current location and the reminder location is within the reminder distance without knowing anything about the user’s location information and the content of the reminder message.
In this dissertation, I study the problems of preserving people’s identity privacy and loca- tion privacy in the online environment. Specifically, I study four topics: identity privacy in online social networks (OSNs), identity privacy in anonymous message submission, lo- cation privacy in location based social networks (LBSNs), and location privacy in location based reminders. In the first topic, I propose a system which can hide users’ identity and data from untrusted storage site where the OSN provider puts users’ data. I also design a fine grained access control mechanism which prevents unauthorized users from accessing the data. Based on the secret sharing scheme, I construct a shuffle protocol that disconnects the relationship between members’ identities and their submitted messages in the topic of identity privacy in anonymous message submission. The message is encrypted on the mem- ber side and decrypted on the message collector side. The collector eventually gets all of the messages but does not know who submitted which message. In the third topic, I pro- pose a framework that hides users’ check-in information from the LBSN. Considering the limited computation resources on smart devices, I propose a delegatable pseudo random function to outsource computations to the much more powerful server while preserving privacy. I also implement efficient revocations. In the topic of location privacy in location based reminders, I propose a system to hide users’ reminder locations from an untrusted cloud server. I propose a cross based approach and an improved bar based approach, re- spectively, to represent a reminder area. The reminder location and reminder message are encrypted before uploading to the cloud server, which then can determine whether the dis- tance between the user’s current location and the reminder location is within the reminder distance without knowing anything about the user’s location information and the content of the reminder message.
ContributorsZhao, Xinxin (Author) / Xue, Guoliang (Thesis advisor) / Ahn, Gail-Joon (Committee member) / Huang, Dijiang (Committee member) / Zhang, Yanchao (Committee member) / Arizona State University (Publisher)
Created2015
Description
This dissertation addresses the role of kinship and residential mobility during the transition from Final Neolithic to Early Bronze Age (ca. 3500 – 2500 BC) in Attica, Greece. It examines descent systems, ancestor formation, and the interplay between biological, social, and spatial structure in mortuary practices. It also evaluates the nature and degree of residential mobility and its potential role in the formation and maintenance of social networks. Archaeological hypotheses on the kin-based structure of formal cemeteries, the familial use of collective tombs, marriage practices and mate exchange, and relocation were tested focusing on the Early Helladic cemetery of Tsepi at Marathon. Tsepi constitutes the earliest formally organized cemetery on the Greek mainland and it has also contributed to enduring debates over the nature of the interaction between the eastern Attic coast and the central Aegean islands.
This study integrates osteological, biogeochemical, and archaeological data. Inherited dental and cranial features were used to examine biological relatedness and postmarital residence (biodistance analysis). Biochemical analysis of archaeological and modern samples was conducted to examine the geographic origins of the individuals buried in the cemetery and reconstruct mobility patterns. Osteological and biogeochemical data were interpreted in conjunction with archaeological and ethnographic/ethnohistoric data.
The results generally supported a relationship between spatial organization and biological relatedness based on phenotypic similarity at Tsepi. Postmarital residence analysis showed exogamous practices and tentatively supported higher male than female mobility. This practice, along with dietary inferences, could also be suggestive of maritime activities. Biogeochemical analysis showed a local character for the cemetery sample (96%). The common provenance of the three non-local individuals might reflect a link between Tsepi and a single locale. Burial location was not determined by provenance or solely by biological relatedness. Overall, the results point towards more nuanced reconstructions of mobility in prehistoric Aegean and suggest that burial location depended on a complex set of inter-individual relationships and collective identities. The contextualized bioarchaeological approach applied in this study added to the anthropological investigations of social practices such as kin relations (e.g., biological, marital, social kinship) and residential relocation as diachronic mechanisms of integration, adaptation, or differentiation.
This study integrates osteological, biogeochemical, and archaeological data. Inherited dental and cranial features were used to examine biological relatedness and postmarital residence (biodistance analysis). Biochemical analysis of archaeological and modern samples was conducted to examine the geographic origins of the individuals buried in the cemetery and reconstruct mobility patterns. Osteological and biogeochemical data were interpreted in conjunction with archaeological and ethnographic/ethnohistoric data.
The results generally supported a relationship between spatial organization and biological relatedness based on phenotypic similarity at Tsepi. Postmarital residence analysis showed exogamous practices and tentatively supported higher male than female mobility. This practice, along with dietary inferences, could also be suggestive of maritime activities. Biogeochemical analysis showed a local character for the cemetery sample (96%). The common provenance of the three non-local individuals might reflect a link between Tsepi and a single locale. Burial location was not determined by provenance or solely by biological relatedness. Overall, the results point towards more nuanced reconstructions of mobility in prehistoric Aegean and suggest that burial location depended on a complex set of inter-individual relationships and collective identities. The contextualized bioarchaeological approach applied in this study added to the anthropological investigations of social practices such as kin relations (e.g., biological, marital, social kinship) and residential relocation as diachronic mechanisms of integration, adaptation, or differentiation.
ContributorsPrevedorou, Eleni Anna (Author) / Buikstra, Jane E. (Thesis advisor) / Knudson, Kelly J. (Committee member) / Stojanowski, Chris M (Committee member) / Fox, Sherry C. (Committee member) / Rutter, Jeremy B. (Committee member) / Arizona State University (Publisher)
Created2015
Description
With the advent of Internet, the data being added online is increasing at enormous rate. Though search engines are using IR techniques to facilitate the search requests from users, the results are not effective towards the search query of the user. The search engine user has to go through certain webpages before getting at the webpage he/she wanted. This problem of Information Overload can be solved using Automatic Text Summarization. Summarization is a process of obtaining at abridged version of documents so that user can have a quick view to understand what exactly the document is about. Email threads from W3C are used in this system. Apart from common IR features like Term Frequency, Inverse Document Frequency, Term Rank, a variation of page rank based on graph model, which can cluster the words with respective to word ambiguity, is implemented. Term Rank also considers the possibility of co-occurrence of words with the corpus and evaluates the rank of the word accordingly. Sentences of email threads are ranked as per features and summaries are generated. System implemented the concept of pyramid evaluation in content selection. The system can be considered as a framework for Unsupervised Learning in text summarization.
ContributorsNadella, Sravan (Author) / Davulcu, Hasan (Thesis advisor) / Li, Baoxin (Committee member) / Sen, Arunabha (Committee member) / Arizona State University (Publisher)
Created2015
Description
Social influences are important determinants of drug initiation in humans, particularly during adolescence and early adulthood. My dissertation tested three hypotheses: 1) conditioned and unconditioned nicotine and social rewards elicit unique patterns of neural signaling in the corticolimbic neurocircuitry when presented in combination versus individually; 2) play behavior is not necessary for expression of social reward; and 3) social context enhances nicotine self-administration. To test the first hypothesis, Fos protein was measured in response to social and nicotine reward stimuli given alone or in combination and in response to environmental cues associated with the rewards in a conditioned place preference (CPP) test. Social-conditioned environmental stimuli attenuated Fos expression in the nucleus accumbens core. A social partner elevated Fos expression in the caudate-putamen, medial and central amygdala, and both nucleus accumbens subregions. Nicotine decreased Fos expression in the cingulate cortex, caudate-putamen, and the nucleus accumbens core. Both stimuli combined elevated Fos expression in the basolateral amygdala and ventral tegmental area, suggesting possible overlap in processing both rewards in these regions. I tested the second hypothesis with an apparatus containing compartments separated by a wire mesh barrier that allowed limited physical contact with a rat or object. While 2 pairings with a partner rat (full physical contact) produced robust CPP, additional pairings were needed for CPP with a partner behind a barrier or physical contact with an object (i.e., tennis ball). The results demonstrate that physical contact with a partner rat is not necessary to establish social-reward CPP. I tested the third hypothesis with duplex operant conditioning chambers separated either by a solid or a wire mesh barrier to allow for social interaction during self-administration sessions. Nicotine (0.015 and 0.03 mg/kg, IV) and saline self-administration were assessed in male and female young-adult rats either in the social context or isolation. Initially, a social context facilitated nicotine intake at the low dose in male rats, but suppressed intake in later sessions more strongly in female rats, suggesting that social factors exert strong sex-dependent influences on self-administration. These novel findings highlight the importance of social influences on several nicotine-related behavioral paradigms and associated neurocircuitry.
ContributorsPeartree, Natalie (Author) / Neisewander, Janet L (Thesis advisor) / Conrad, Cheryl D. (Committee member) / Nikulina, Ella M (Committee member) / Sanabria, Federico (Committee member) / Arizona State University (Publisher)
Created2015
Description
The Upper Verde River of central Arizona flows through a landscape of complex geology at the meeting of seven biotic communities and three physiographic provinces. This has resulted in notably diverse flora and fauna and a hub of rare and endemic plant species. The river has sustained cultures since pre-history, however current regional water use is predicted to diminish streamflow over the next century. Prior to this project, no floristic inventory had been conducted along any section of the Verde. The purpose of this study was to develop a Flora of the Upper Verde River, with the goals of documenting rare and endemic species, the composition and abundance of wetland plants, and the factors shaping plant diversity in the region.
I made a total of 1856 collections and reviewed past collections to produce a checklist of 729 vascular plant taxa in 403 genera and 98 families. The most species-rich family is the Poaceae, followed by Asteraceae and Fabaceae. The flora includes 159 wetland taxa, 47 endemics, and 26 taxa of conservation concern, eight of which are Federally listed. Several new populations were found in these categories and of rarely-collected taxa including one state record, three county records and several range extensions. I report on the local status of several endemics, wetland taxa with limited distributions, and relict populations of a tepary bean (Phaseolus acutifolius) that were likely transported to the region and cultivated by pre-Columbian cultures. I categorize thirteen distinct plant communities, the most abundant being Pinyon/Juniper Woodland, Chihuahuan/Apacherian Scrub, and Riparian Deciduous Forest.
Four primary factors influence floristic diversity of the Upper Verde region: 1) a location at the junction of three physiographic and floristic provinces—represented by co-occurrence of species with affinities to the Sonoran, Intermountain and Madrean regions, 2) geologic diversity—as distinct groups of species are associated with particular geologic types, 3) topographic and habitat complexity—allowing species adapted to disparate environments to co-occur, and 4) human introductions—since over 15% of the flora is composed of introduced species from Eurasia and several taxa were introduced to the region and cultivated by pre-Columbian cultures.
I made a total of 1856 collections and reviewed past collections to produce a checklist of 729 vascular plant taxa in 403 genera and 98 families. The most species-rich family is the Poaceae, followed by Asteraceae and Fabaceae. The flora includes 159 wetland taxa, 47 endemics, and 26 taxa of conservation concern, eight of which are Federally listed. Several new populations were found in these categories and of rarely-collected taxa including one state record, three county records and several range extensions. I report on the local status of several endemics, wetland taxa with limited distributions, and relict populations of a tepary bean (Phaseolus acutifolius) that were likely transported to the region and cultivated by pre-Columbian cultures. I categorize thirteen distinct plant communities, the most abundant being Pinyon/Juniper Woodland, Chihuahuan/Apacherian Scrub, and Riparian Deciduous Forest.
Four primary factors influence floristic diversity of the Upper Verde region: 1) a location at the junction of three physiographic and floristic provinces—represented by co-occurrence of species with affinities to the Sonoran, Intermountain and Madrean regions, 2) geologic diversity—as distinct groups of species are associated with particular geologic types, 3) topographic and habitat complexity—allowing species adapted to disparate environments to co-occur, and 4) human introductions—since over 15% of the flora is composed of introduced species from Eurasia and several taxa were introduced to the region and cultivated by pre-Columbian cultures.
ContributorsCoburn, Francis S (Author) / Stromberg, Juliet C. (Thesis advisor) / Landrum, Leslie R (Thesis advisor) / Makings, Elizabeth (Committee member) / Fertig, Walter F (Committee member) / Arizona State University (Publisher)
Created2015
Description
This research focuses upon the intersection of social complexity and leadership among commoners in complex societies as expressed through mortuary ritual. I study how ideology, materialized through treatment of the deceased body, was a potential source of power among commoners in ancient Maya society and how this materialization changed through time. Mortuary data are drawn from mid-level settlements of the Belize River Valley, located in western Belize within the eastern Maya lowlands. The primary research question addresses whether mid-level leaders in the Belize River Valley targeted certain human bodies for ancestral veneration through tomb re-entry and ritual interaction with skeletal remains. The ritual-political strategy of mid-level leaders is measured using archaeothanatology, an analysis of grave taphonomy based on forensic data, to reconstruct cultural beliefs about death based on treatment of deceased bodies, radiogenic strontium isotope analysis to reconstruct residential history, and analysis of dental metrics to assess biological kinship. While preservation of osseous material was poor, results indicate that the frequency of disarticulated and secondary burials was higher in eastern structures than in other locales, although eastern structures were not the only loci of these types of deposits. Overall, it does not seem like secondary burials were regularly and purposefully created for use as ritual objects or display. Radiogenic strontium isotope data enrich this analysis by showing that eastern structures were not a burial locale exclusive to individuals who spent their childhood in the Belize Valley. Data from upper-level eastern structures also suggests that within that part of society local birth did not guarantee interment in a local manner; perhaps the social network created during one's life shaped treatment in death more than residential origin. Biological distance analyses were inconclusive due to missing data. Comparison of mortuary practices to nearby regions shows distinct mortuary patterning across space and time. This is consistent with reconstructions of ancient Maya sociopolitical organization as regionally diverse and moderately integrated.
ContributorsNovotny, Anna (Author) / Buikstra, Jane E. (Thesis advisor) / Carr, Christopher (Committee member) / Robin, Cynthia (Committee member) / Astor-Aguilera, Miguel (Committee member) / Tiesler, Vera (Committee member) / Knudson, Kelly J. (Committee member) / Arizona State University (Publisher)
Created2015
Description
ABSTRACT
This interdisciplinary study examines the linguistic strategies that determine perception of female representation in Peruvian feminist narrative during the late XIX century. It uses as reference narratives that are considered representatives of the literary tendencies of Latin América feminine trajectory. The feminine subject was studied in two novels of Mercedes Cabello de Carbonera: Los amores de Hortensia (1886) and Blanca Sol (1889). The novels were selected with the aim of capturing the evolution and the development of the female characters as self-realizing subjects.
The theoretical framework is led by the speech act philosophy of John Austin, John Searle, and Victoria Escandell Vidal. The feminist literary theory is guided by the feminist principle of Judith Butler, Luce Irigaray and Julia Kristeva that relates to the development of female subjectivity; by Sandra Gilbert and Susan Gubar, and Virginia Woolf that reveals the dynamics of women’s creativity.
Through a close analysis of the speech acts, the research demonstrates that the female characters used their tactics to complain and request on their attempts to uproot the hegemonic normative social structures. The speech acts are presented as key instrument for a better understanding of the complex mechanisms of language, through which the feminist ideology of the nineteenth century is transmitted and reproduced. Within feminist theory the purpose is to show how the performative nature of language can be applied to the concept of power as subversive resistance. While the evolution of the female protagonists through the different spaces they move were traced, the investigation’s central idea that envisions the feminine subject as a process, was also examined.
After comparing and contrasting the portrayal of the protagonists, a thematic analysis was performed to capture the intricacies of meaning within the discourse. The analysis suggests that female representation in literature can be reexamined through historical, political, and socio-economic contexts, as well as through verbal expression.
Mainly, the comventional norms that limited women to some social places and that oblige them to maintain proper conducts did not silence them entirely, as we can observe in the petitions and complaints that became transcendent acts of defiance.
ABSTRACTO
Este trabajo de investigación interdisciplinario examina las estrategias lingüísticas que condicionan la percepción de la representación femenina y feminista en la narrativa peruana de finales del siglo XIX. El sujeto femenino se ha estudiado en dos novelas de Mercedes Cabello de Carbonera Los amores de Hortensia (1886) y Blanca Sol (1889), éstas se seleccionaron con el objetivo de entender la evolución de los personajes femeninos como sujetos que se auto-realizan.
El marco teórico para este estudio es guiado por la filosofía hermeneútica de John Austin, John Searle y Victoria Escandell que se basan en la naturaleza performativa de las expresiones lingüísticas. El análisis de género se basa en la teoría de Judith Butler Luce Irigaray y Julia Kristeva que se relacionan con el desarrollo de la subjetividad femenina; en la ideología de Sandra Gilbert y Susan Gubar y Virginia Woolf que exponen las dinámicas de creatividad de la escritora.
A través del análisis de los actos de habla, la investigación sugiere que los personajes femeninos usan estrategias de quejas y de pedidos con el intento de eliminar las estructuras sociales hegemónicas. Los actos de habla se presentan como un instrumento necesario para un mejor entendimiento de los mecanismos del lenguaje, por medio de los cuales se transmite la idea feminista del siglo XIX. La teoría feminista tiene como objetivo, explicar cómo la naturaleza performativa del lenguaje se puede adaptar al concepto de poder como resistencia subversiva. Se investiga la idea central de nuestra pesquisa que percibe al sujeto femenino como un sujeto en proceso. Después de comparar y contrastar el perfil de los personajes protagónicos, se lleva a cabo el análisis temático para captar las complejidades del sentido en el discurso. Esta investigación propone que la representación femenina puede ser reevaluada por medio de contextos históricos, políticos y socio-económicos y de expresiones verbales.¬
En general, las normas convencionales del siglo XIX que limitaron a la mujer a ciertas esferas sociales y que requerían de ésta una conducta discreta, no las silenciaron totalmente como se puedo apreciar en los pedidos y quejas que resultaron ser medios trascendentes de actos de desafío.
This interdisciplinary study examines the linguistic strategies that determine perception of female representation in Peruvian feminist narrative during the late XIX century. It uses as reference narratives that are considered representatives of the literary tendencies of Latin América feminine trajectory. The feminine subject was studied in two novels of Mercedes Cabello de Carbonera: Los amores de Hortensia (1886) and Blanca Sol (1889). The novels were selected with the aim of capturing the evolution and the development of the female characters as self-realizing subjects.
The theoretical framework is led by the speech act philosophy of John Austin, John Searle, and Victoria Escandell Vidal. The feminist literary theory is guided by the feminist principle of Judith Butler, Luce Irigaray and Julia Kristeva that relates to the development of female subjectivity; by Sandra Gilbert and Susan Gubar, and Virginia Woolf that reveals the dynamics of women’s creativity.
Through a close analysis of the speech acts, the research demonstrates that the female characters used their tactics to complain and request on their attempts to uproot the hegemonic normative social structures. The speech acts are presented as key instrument for a better understanding of the complex mechanisms of language, through which the feminist ideology of the nineteenth century is transmitted and reproduced. Within feminist theory the purpose is to show how the performative nature of language can be applied to the concept of power as subversive resistance. While the evolution of the female protagonists through the different spaces they move were traced, the investigation’s central idea that envisions the feminine subject as a process, was also examined.
After comparing and contrasting the portrayal of the protagonists, a thematic analysis was performed to capture the intricacies of meaning within the discourse. The analysis suggests that female representation in literature can be reexamined through historical, political, and socio-economic contexts, as well as through verbal expression.
Mainly, the comventional norms that limited women to some social places and that oblige them to maintain proper conducts did not silence them entirely, as we can observe in the petitions and complaints that became transcendent acts of defiance.
ABSTRACTO
Este trabajo de investigación interdisciplinario examina las estrategias lingüísticas que condicionan la percepción de la representación femenina y feminista en la narrativa peruana de finales del siglo XIX. El sujeto femenino se ha estudiado en dos novelas de Mercedes Cabello de Carbonera Los amores de Hortensia (1886) y Blanca Sol (1889), éstas se seleccionaron con el objetivo de entender la evolución de los personajes femeninos como sujetos que se auto-realizan.
El marco teórico para este estudio es guiado por la filosofía hermeneútica de John Austin, John Searle y Victoria Escandell que se basan en la naturaleza performativa de las expresiones lingüísticas. El análisis de género se basa en la teoría de Judith Butler Luce Irigaray y Julia Kristeva que se relacionan con el desarrollo de la subjetividad femenina; en la ideología de Sandra Gilbert y Susan Gubar y Virginia Woolf que exponen las dinámicas de creatividad de la escritora.
A través del análisis de los actos de habla, la investigación sugiere que los personajes femeninos usan estrategias de quejas y de pedidos con el intento de eliminar las estructuras sociales hegemónicas. Los actos de habla se presentan como un instrumento necesario para un mejor entendimiento de los mecanismos del lenguaje, por medio de los cuales se transmite la idea feminista del siglo XIX. La teoría feminista tiene como objetivo, explicar cómo la naturaleza performativa del lenguaje se puede adaptar al concepto de poder como resistencia subversiva. Se investiga la idea central de nuestra pesquisa que percibe al sujeto femenino como un sujeto en proceso. Después de comparar y contrastar el perfil de los personajes protagónicos, se lleva a cabo el análisis temático para captar las complejidades del sentido en el discurso. Esta investigación propone que la representación femenina puede ser reevaluada por medio de contextos históricos, políticos y socio-económicos y de expresiones verbales.¬
En general, las normas convencionales del siglo XIX que limitaron a la mujer a ciertas esferas sociales y que requerían de ésta una conducta discreta, no las silenciaron totalmente como se puedo apreciar en los pedidos y quejas que resultaron ser medios trascendentes de actos de desafío.
ContributorsAtencia-Oliden, Elizabeth Miriam (Author) / Urioste-Azcorra, Carmen (Thesis advisor) / Cerron-Palomino, Alvaro (Committee member) / Rosales, Jesus (Committee member) / Arizona State University (Publisher)
Created2015
Description
Li He (790-816), an outstanding poet full of literary talent in
classical Chinese poem history, his poignant words, incredible literary construction, nether artistic conception and nuanced peculiar poem style owned him the reputation of “ghostly, demonic genius” 鬼才. Scholars demonstrated that his ghostly and demonic style has much to do with the special imagery and allusion in his poetry. However, this kind of ghostly appeal of literature exactly have much to do with the large quantity of sensory vocabulary that the poet is expert in using in his poems, which evokes resonance from the readers/audiences. Li He fuses visual, auditory, olfactory, gustatory and tactile sensation in his poems, building up his special writing style, evoking and creating a sensorial space for readers. The thesis concentrates on analyzing the sensory vocabulary in Li He’s poetry, sonic depiction in particular, which are rarely discussed before, based on which making further conclusion about the artistic conception and the special style of Li He’s poetry.
classical Chinese poem history, his poignant words, incredible literary construction, nether artistic conception and nuanced peculiar poem style owned him the reputation of “ghostly, demonic genius” 鬼才. Scholars demonstrated that his ghostly and demonic style has much to do with the special imagery and allusion in his poetry. However, this kind of ghostly appeal of literature exactly have much to do with the large quantity of sensory vocabulary that the poet is expert in using in his poems, which evokes resonance from the readers/audiences. Li He fuses visual, auditory, olfactory, gustatory and tactile sensation in his poems, building up his special writing style, evoking and creating a sensorial space for readers. The thesis concentrates on analyzing the sensory vocabulary in Li He’s poetry, sonic depiction in particular, which are rarely discussed before, based on which making further conclusion about the artistic conception and the special style of Li He’s poetry.
ContributorsWen, Yu (Author) / West, Stephen H. (Thesis advisor) / Ling, Xiaoqiao (Committee member) / Oh, Young Kyun (Committee member) / Arizona State University (Publisher)
Created2015
Towards high-efficiency thin-film solar cells: from theoretical analysis to experimental exploration
Description
GaAs single-junction solar cells have been studied extensively in recent years, and have reached over 28 % efficiency. Further improvement requires an optically thick but physically thin absorber to provide both large short-circuit current and high open-circuit voltage. By detailed simulation, it is concluded that ultra-thin GaAs cells with hundreds of nanometers thickness and reflective back scattering can potentially offer efficiencies greater than 30 %. The 300 nm GaAs solar cell with AlInP/Au reflective back scattering is carefully designed and demonstrates an efficiency of 19.1 %. The device performance is analyzed using the semi-analytical model with Phong distribution implemented to account for non-Lambertian scattering. A Phong exponent m of ~12, a non-radiative lifetime of 130 ns, and a specific series resistivity of 1.2 Ω·cm2 are determined.
Thin-film CdTe solar cells have also attracted lots of attention due to the continuous improvements in their device performance. To address the issue of the lower efficiency record compared to detailed-balance limit, the single-crystalline Cd(Zn)Te/MgCdTe double heterostructures (DH) grown on InSb (100) substrates by molecular beam epitaxy (MBE) are carefully studied. The Cd0.9946Zn0.0054Te alloy lattice-matched to InSb has been demonstrated with a carrier lifetime of 0.34 µs observed in a 3 µm thick Cd0.9946Zn0.0054Te/MgCdTe DH sample. The substantial improvement of lifetime is due to the reduction in misfit dislocation density. The recombination lifetime and interface recombination velocity (IRV) of CdTe/MgxCd1-xTe DHs are investigated. The IRV is found to be dependent on both the MgCdTe barrier height and width due to the thermionic emission and tunneling processes. A record-long carrier lifetime of 2.7 µs and a record-low IRV of close to zero have been confirmed experimentally.
The MgCdTe/Si tandem solar cell is proposed to address the issue of high manufacturing costs and poor performance of thin-film solar cells. The MBE grown MgxCd1-xTe/MgyCd1-yTe DHs have demonstrated the required bandgap energy of 1.7 eV, a carrier lifetime of 11 ns, and an effective IRV of (1.869 ± 0.007) × 103 cm/s. The large IRV is attributed to thermionic-emission induced interface recombination. These understandings can be applied to fabricating the high-efficiency low-cost MgCdTe/Si tandem solar cell.
Thin-film CdTe solar cells have also attracted lots of attention due to the continuous improvements in their device performance. To address the issue of the lower efficiency record compared to detailed-balance limit, the single-crystalline Cd(Zn)Te/MgCdTe double heterostructures (DH) grown on InSb (100) substrates by molecular beam epitaxy (MBE) are carefully studied. The Cd0.9946Zn0.0054Te alloy lattice-matched to InSb has been demonstrated with a carrier lifetime of 0.34 µs observed in a 3 µm thick Cd0.9946Zn0.0054Te/MgCdTe DH sample. The substantial improvement of lifetime is due to the reduction in misfit dislocation density. The recombination lifetime and interface recombination velocity (IRV) of CdTe/MgxCd1-xTe DHs are investigated. The IRV is found to be dependent on both the MgCdTe barrier height and width due to the thermionic emission and tunneling processes. A record-long carrier lifetime of 2.7 µs and a record-low IRV of close to zero have been confirmed experimentally.
The MgCdTe/Si tandem solar cell is proposed to address the issue of high manufacturing costs and poor performance of thin-film solar cells. The MBE grown MgxCd1-xTe/MgyCd1-yTe DHs have demonstrated the required bandgap energy of 1.7 eV, a carrier lifetime of 11 ns, and an effective IRV of (1.869 ± 0.007) × 103 cm/s. The large IRV is attributed to thermionic-emission induced interface recombination. These understandings can be applied to fabricating the high-efficiency low-cost MgCdTe/Si tandem solar cell.
ContributorsLiu, Shi (Author) / Zhang, Yong-Hang (Thesis advisor) / Johnson, Shane R (Committee member) / Vasileska, Dragica (Committee member) / Yu, Hongbin (Committee member) / Arizona State University (Publisher)
Created2015
Description
Gender disparity in sentencing outcomes has a long tradition in sentencing literature, with a substantial body of evidence indicating that women offenders are treated with greater leniency over male counterparts. The prior literature on gender and sentencing, however, has ignored broader social contexts within which judicial decision-making occurs. This dissertation attempts to address this limitation by dissecting the nature of gender disparity through ecological lenses. Using federal sentencing data for FY 2001 through 2010 and other complementary data sets, this dissertation, divided into two major sub-studies, has examined the roles of two social contextual variables, such as religioius and political conservatism, in producing gender differentials in sentencing outcomes.
ContributorsKim, Byung Bae (Author) / Spohn, Cassia (Thesis advisor) / Wang, Xia (Committee member) / Wright, Kevin (Committee member) / Arizona State University (Publisher)
Created2015