Matching Items (43,917)
Description
Chemical and mineralogical data from Mars shows that the surface has been chemically weathered on local to regional scales. Chemical trends and the types of chemical weathering products present on the surface and their abundances can elucidate information about past aqueous processes. Thermal-infrared (TIR) data and their respective models are essential for interpreting Martian mineralogy and geologic history. However, previous studies have shown that chemical weathering and the precipitation of fine-grained secondary silicates can adversely affect the accuracy of TIR spectral models. Furthermore, spectral libraries used to identify minerals on the Martian surface lack some important weathering products, including poorly-crystalline aluminosilicates like allophane, thus eliminating their identification in TIR spectral models. It is essential to accurately interpret TIR spectral data from chemically weathered surfaces to understand the evolution of aqueous processes on Mars. Laboratory experiments were performed to improve interpretations of TIR data from weathered surfaces. To test the accuracy of deriving chemistry of weathered rocks from TIR spectroscopy, chemistry was derived from TIR models of weathered basalts from Baynton, Australia and compared to actual weathering rind chemistry. To determine how specific secondary silicates affect the TIR spectroscopy of weathered basalts, mixtures of basaltic minerals and small amounts of secondary silicates were modeled. Poorly-crystalline aluminosilicates were synthesized and their TIR spectra were added to spectral libraries. Regional Thermal Emission Spectrometer (TES) data were modeled using libraries containing these poorly-crystalline aluminosilicates to test for their presence on the Mars. Chemistry derived from models of weathered Baynton basalts is not accurate, but broad chemical weathering trends can be interpreted from the data. TIR models of mineral mixtures show that small amounts of crystalline and amorphous silicate weathering products (2.5-5 wt.%) can be detected in TIR models and can adversely affect modeled plagioclase abundances. Poorly-crystalline aluminosilicates are identified in Northern Acidalia, Solis Planum, and Meridiani. Previous studies have suggested that acid sulfate weathering was the dominant surface alteration process for the past 3.5 billion years; however, the identification of allophane indicates that alteration at near-neutral pH occurred on regional scales and that acid sulfate weathering is not the only weathering process on Mars.
Contributors
Rampe, Elizabeth Barger (Author) / Sharp, Thomas G (Thesis advisor) / Christensen, Phillip (Committee member) / Hervig, Richard (Committee member) / Shock, Everett (Committee member) / Williams, Lynda (Committee member) / Arizona State University (Publisher)
Created
2011
Description
With the increasing focus on developing environmentally benign electronic packages, lead-free solder alloys have received a great deal of attention. Mishandling of packages, during manufacture, assembly, or by the user may cause failure of solder joint. A fundamental understanding of the behavior of lead-free solders under mechanical shock conditions is lacking. Reliable experimental and numerical analysis of lead-free solder joints in the intermediate strain rate regime need to be investigated. This dissertation mainly focuses on exploring the mechanical shock behavior of lead-free tin-rich solder alloys via multiscale modeling and numerical simulations. First, the macroscopic stress/strain behaviors of three bulk lead-free tin-rich solders were tested over a range of strain rates from 0.001/s to 30/s. Finite element analysis was conducted to determine appropriate specimen geometry that could reach a homogeneous stress/strain field and a relatively high strain rate. A novel self-consistent true stress correction method is developed to compensate the inaccuracy caused by the triaxial stress state at the post-necking stage. Then the material property of micron-scale intermetallic was examined by micro-compression test. The accuracy of this measure is systematically validated by finite element analysis, and empirical adjustments are provided. Moreover, the interfacial property of the solder/intermetallic interface is investigated, and a continuum traction-separation law of this interface is developed from an atomistic-based cohesive element method. The macroscopic stress/strain relation and microstructural properties are combined together to form a multiscale material behavior via a stochastic approach for both solder and intermetallic. As a result, solder is modeled by porous plasticity with random voids, and intermetallic is characterized as brittle material with random vulnerable region. Thereafter, the porous plasticity fracture of the solders and the brittle fracture of the intermetallics are coupled together in one finite element model. Finally, this study yields a multiscale model to understand and predict the mechanical shock behavior of lead-free tin-rich solder joints. Different fracture patterns are observed for various strain rates and/or intermetallic thicknesses. The predictions have a good agreement with the theory and experiments.
Contributors
Fei, Huiyang (Author) / Jiang, Hanqing (Thesis advisor) / Chawla, Nikhilesh (Thesis advisor) / Tasooji, Amaneh (Committee member) / Mobasher, Barzin (Committee member) / Rajan, Subramaniam D. (Committee member) / Arizona State University (Publisher)
Created
2011
Description
As pointed out in the keynote speech by H. V. Jagadish in SIGMOD'07, and also commonly agreed in the database community, the usability of structured data by casual users is as important as the data management systems' functionalities. A major hardness of using structured data is the problem of easily retrieving information from them given a user's information needs. Learning and using a structured query language (e.g., SQL and XQuery) is overwhelmingly burdensome for most users, as not only are these languages sophisticated, but the users need to know the data schema. Keyword search provides us with opportunities to conveniently access structured data and potentially significantly enhances the usability of structured data. However, processing keyword search on structured data is challenging due to various types of ambiguities such as structural ambiguity (keyword queries have no structure), keyword ambiguity (the keywords may not be accurate), user preference ambiguity (the user may have implicit preferences that are not indicated in the query), as well as the efficiency challenges due to large search space. This dissertation performs an expansive study on keyword search processing techniques as a gateway for users to access structured data and retrieve desired information. The key issues addressed include: (1) Resolving structural ambiguities in keyword queries by generating meaningful query results, which involves identifying relevant keyword matches, identifying return information, composing query results based on relevant matches and return information. (2) Resolving structural, keyword and user preference ambiguities through result analysis, including snippet generation, result differentiation, result clustering, result summarization/query expansion, etc. (3) Resolving the efficiency challenge in processing keyword search on structured data by utilizing and efficiently maintaining materialized views. These works deliver significant technical contributions towards building a full-fledged search engine for structured data.
Contributors
Liu, Ziyang (Author) / Chen, Yi (Thesis advisor) / Candan, Kasim S (Committee member) / Davulcu, Hasan (Committee member) / Jagadish, H V (Committee member) / Arizona State University (Publisher)
Created
2011
Description
Phosphorus (P), an essential element for life, is becoming increasingly scarce, and its global management presents a serious challenge. As urban environments dominate the landscape, we need to elucidate how P cycles in urban ecosystems to better understand how cities contribute to — and provide opportunities to solve — problems of P management. The goal of my research was to increase our understanding of urban P cycling in the context of urban resource management through analysis of existing ecological and socio-economic data supplemented with expert interviews in order to facilitate a transition to sustainable P management. Study objectives were to: I) Quantify and map P stocks and flows in the Phoenix metropolitan area and analyze the drivers of spatial distribution and dynamics of P flows; II) examine changes in P-flow dynamics at the urban agricultural interface (UAI), and the drivers of those changes, between 1978 and 2008; III) compare the UAI's average annual P budget to the global agricultural P budget; and IV) explore opportunities for more sustainable P management in Phoenix. Results showed that Phoenix is a sink for P, and that agriculture played a primary role in the dynamics of P cycling. Internal P dynamics at the UAI shifted over the 30-year study period, with alfalfa replacing cotton as the main locus of agricultural P cycling. Results also suggest that the extent of P recycling in Phoenix is proportionally larger than comparable estimates available at the global scale due to the biophysical characteristics of the region and the proximity of various land uses. Uncertainty remains about the effectiveness of current recycling strategies and about best management strategies for the future because we do not have sufficient data to use as basis for evaluation and decision-making. By working in collaboration with practitioners, researchers can overcome some of these data limitations to develop a deeper understanding of the complexities of P dynamics and the range of options available to sustainably manage P. There is also a need to better connect P management with that of other resources, notably water and other nutrients, in order to sustainably manage cities.
Contributors
Metson, Genevieve (Author) / Childers, Daniel (Thesis advisor) / Aggarwal, Rimjhim (Thesis advisor) / Redman, Charles (Committee member) / Arizona State University (Publisher)
Created
2011
Description
The majority of chronic myeloid leukemia (CML) and some of acute lymphocytic leukemia (ALL) cases are associated with possessing the BCR-Abl fusion protein from an oncogenic translocation, resulting in a constantly active form of Abl and rapid proliferation. CML and ALL cells that possess the BCR-Abl fusion protein are known as Philadelphia chromosome positive (Ph+). Currently, Imatinib (selective Abl inhibitor) is used as therapy against CML and ALL. However, some patients may have malignancies which show resistance to Imatinib. Previous work displays that the transformation of progenitor B cells with the v-Abl oncogene of Abelson murine leukemia virus results in cell cycle progression, rapid proliferation, and potentially malignant transformation while preventing any further differentiation. Progenitor B cells transformed with the temperature-sensitive form of the v-Abl oncogene have served as a model to study cellular response to Imatinib treatment. After some manipulation, very few cells were forced to progress to malignancy, forming tumor in vivo. These cells were no long sensitive to v-Abl inactivation, resembling the Imatinib resistant ALL. Autophagy is the process by which proteins and organelles are broken-down and recycled within the eukaryotic cell and has been hypothesized to play a part in cancer cell survival and drug-resistance. LC3 processing is a widely accepted marker of autophagy induction and progression. It has also been shown that Imatinib treatment of Ph+ leukemia can induce autophagy. In this study, we examined the autophagy induction in response to v-Abl inactivation in a Ph+-B-ALL cell model that shows resistance to Imatinib. In particular, we wonder whether the tumor cell line resistant to v-Abl inactivation may acquire a high level of autophagy to become resistant to apoptosis induced by v-Abl inactivation, and thus become addicted to autophagy. Indeed, this tumor cell line displays a high basal levels of LC3 I and II expression, regardless of v-Abl activity. We further demonstrated that inhibition of the autophagy pathway enhances the tumor line's sensitivity to Imatinib, resulting in cell cycle arrest and massive apoptosis. The combination of autophagy and Abl inhibitions may serve as an effective therapy for BCR-Abl positive CML.
Contributors
Arkus, Nohea (Author) / Chang, Yung (Thesis advisor) / Kusumi, Kenro (Committee member) / Lake, Douglas (Committee member) / Jacobs, Bertram (Committee member) / Arizona State University (Publisher)
Created
2011
Description
Reliable extraction of human pose features that are invariant to view angle and body shape changes is critical for advancing human movement analysis. In this dissertation, the multifactor analysis techniques, including the multilinear analysis and the multifactor Gaussian process methods, have been exploited to extract such invariant pose features from video data by decomposing various key contributing factors, such as pose, view angle, and body shape, in the generation of the image observations. Experimental results have shown that the resulting pose features extracted using the proposed methods exhibit excellent invariance properties to changes in view angles and body shapes. Furthermore, using the proposed invariant multifactor pose features, a suite of simple while effective algorithms have been developed to solve the movement recognition and pose estimation problems. Using these proposed algorithms, excellent human movement analysis results have been obtained, and most of them are superior to those obtained from state-of-the-art algorithms on the same testing datasets. Moreover, a number of key movement analysis challenges, including robust online gesture spotting and multi-camera gesture recognition, have also been addressed in this research. To this end, an online gesture spotting framework has been developed to automatically detect and learn non-gesture movement patterns to improve gesture localization and recognition from continuous data streams using a hidden Markov network. In addition, the optimal data fusion scheme has been investigated for multicamera gesture recognition, and the decision-level camera fusion scheme using the product rule has been found to be optimal for gesture recognition using multiple uncalibrated cameras. Furthermore, the challenge of optimal camera selection in multi-camera gesture recognition has also been tackled. A measure to quantify the complementary strength across cameras has been proposed. Experimental results obtained from a real-life gesture recognition dataset have shown that the optimal camera combinations identified according to the proposed complementary measure always lead to the best gesture recognition results.
Contributors
Peng, Bo (Author) / Qian, Gang (Thesis advisor) / Ye, Jieping (Committee member) / Li, Baoxin (Committee member) / Spanias, Andreas (Committee member) / Arizona State University (Publisher)
Created
2011
Description
Belief affects behavior and rhetoric has the potential to bring about action. This paper is a critical content analysis of the ideology and rhetoric of key Islamist intellectuals and the Islamist organization Hizb ut-Tahrir, as stated on the website http://english.hizbuttahrir.org. The responses of specific Muslim Reformers are also analyzed. The central argument underlying this analysis centers on the notion that such Islamist ideology and its rhetorical delivery could be a significant trigger for the use of violence; interacting with, yet existing independently of, other factors that contribute to violent actions. In this case, a significant aspect of any solution to Islamist rhetoric would require that Muslim Reformers present a compelling counter-narrative to political Islam (Islamism), one that has an imperative to reduce the amount of violence in the region. Rhetoric alone cannot solve the many complicated issues in the region but we must begin somewhere and countering the explicit and implicit calls to violence of political Islamist organizations like Hizb ut-Tahrir seems a constructive step.
Contributors
Boyer, Paul Daniel (Author) / Mean, Lindsey (Thesis advisor) / Waldron, Vincent (Committee member) / Carter, Heather (Committee member) / Arizona State University (Publisher)
Created
2010
Description
The purpose of this study was to examine compulsory schooling in the United States and its potential to provide an inconsistent avenue to employment for students from neighborhoods of differing socioeconomic status. Specifically, this study asked why do students from privileged neighborhoods typically end up in positions of ownership and management while those from impoverished urban or rural neighborhoods end up in working-class positions or involved in cycles of incarceration and poverty? This research involved the use of qualitative methods, including participant observation and interview, as well as photography, to take a look at a reputable private day school in the southwest. Data was collected over the span of eight weeks and was then analyzed and compared with preexisting data on the schooling experience of students from impoverished urban and rural neighborhoods, particularly data focused on juvenile detention centers. Results showed that compulsory schooling differs in ways that contribute to the preexisting hierarchical class structure. The research suggests that schooling can be detrimental to the future quality of life for students in impoverished neighborhoods, which questions a compulsory school system that exists within the current hierarchical class system.
Contributors
Theodoropoulos, Eftyhia (Author) / Margolis, Eric (Thesis advisor) / Nakagawa, Kathryn (Committee member) / Appleton, Nicholas (Committee member) / Arizona State University (Publisher)
Created
2011
Description
Growers and the USDA showed increasing favor for agricultural chemicals over cultural and biological forms of pest control through the first half of the twentieth century. With the introduction of DDT and other synthetic chemicals to commercial markets in the post-World War II era, pesticides became entrenched as the primary form of pest control in the industrial agriculture production system. Despite accumulating evidence that some pesticides posed a threat to human and environmental health, growers and government exercised path-dependent behavior in the development and implementation of pest control strategies. As pests developed resistance to regimens of agricultural chemicals, growers applied pesticides with greater toxicity in higher volumes to their fields with little consideration for the unintended consequences of using the economic poisons. Consequently, pressure from non-governmental organizations proved a necessary predicate for pesticide reform. This dissertation uses a series of case studies to examine the role of non-governmental organizations, particularly environmental organizations and farmworker groups, in pesticide reform from 1962 to 2011. For nearly fifty years, these groups served as educators, communicating scientific and experiential information about the adverse effects of pesticides on human health and environment to the public, and built support for the amendment of pesticide policies and the alteration of pesticide use practices. Their efforts led to the passage of more stringent regulations to better protect farmworkers, the public, and the environment. Environmental organizations and farmworker groups also acted as watchdogs, monitoring the activity of regulatory agencies and bringing suit when necessary to ensure that they fulfilled their responsibilities to the public. This dissertation will build on previous scholarly work to show increasing collaboration between farmworker groups and environmental organizations. It argues that the organizations shared a common concern about the effects of pesticides on human health, which enabled bridge-builders within the disparate organizations to foster cooperative relationships. Bridge-building proved a mutually beneficial exercise. Variance in organizational strategies and the timing of different reform efforts limited, but did not eliminate, opportunities for collaboration. Coalitions formed when groups came together temporarily, and then drifted apart when a reform effort reached its terminus, leaving future collaboration still possible.
Contributors
Tompkins, Adam (Author) / Hirt, Paul (Thesis advisor) / Rome, Adam (Committee member) / Adamson, Joni (Committee member) / Rosales, F (Committee member) / Arizona State University (Publisher)
Created
2011
Description
This dissertation examines the factors related to the success of host country field offices established by international Non-Governmental Organizations (NGOs). Further, this dissertation examines NGO field office mission success in the context of working with foreign host governments and clients. This dissertation is a case of the field offices of The Nature Conservancy in South and Central America. The principal research aim is to identify the primary factors that are related to success of field offices. Success is identified as a multidimensional concept. A conceptual model for success is developed. The conceptual model derived causal factors from the literature and captured categories of variables such as: (1) managerial tactics and techniques dictated by the NGO and adopted by field office leaders; (2) the distance between cultural features of the host country and those of the country of origin of the field office manager and personnel; and, (3) characteristics of the host country government. The dissertation: (1) utilizes a working definition of NGO drawn from the scholarly literature in the field; (2) describes the role of field offices (located in host countries) in the calculus of "home office" goal achievement; (3) discusses the types of "change"--delivery of goods, delivery of services, changes in behavior, changes in norms or attitudes--that field offices may have and how they differ in the challenges they create for field office managers; and, (4) develops a conceptual definition for success. This dissertation is concerned with the factors associated with success in the international NGO's field office. A model of success predictors is tested in this work. The findings suggest that the field offices mission success may be affected by local culture but this was not an issue for the organization studied. Mission success as perceived by the field seems to be a product of organizational culture. The contribution of the research to academic literature is that this study is both an exploratory and descriptive study of how NGO mission is carried out in the field and the impacts of national and organizational culture on mission success.
Contributors
Kraeger, Patsy (Author) / Cayer, N. Joseph (Thesis advisor) / Yoshioka, Carlton A. (Committee member) / Lan, Zhiyong (Committee member) / Arizona State University (Publisher)
Created
2011