952 resultados para electronic theses and dissertations


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China’s behavior as a near-monopolist of rare earths has come under increasing scrutiny in recent years. This thesis first examines the underlying causes behind China’s rise to the status of rare-earths near-monopolist, including government support; lax environmental controls; unregulated production; and relatively low costs compared to the rest of the world. Second, the thesis also examines the preeminent international and domestic factors influencing China’s behavior as a near-monopolist of rare earths. International factors include international demand; international trade pressure; international price-setting authority issues; and geopolitical factors. I next identify domestic factors that exert influence over China’s rare earths-related behavior: environmental protection; rare earth resource protection; rare earths industry regulation; and protecting and aiding China’s domestic rare earths industry. The study concludes with a synthesis of the factors influencing China’s rare-earths-related behavior in the overall context of support and direction by China’s Central Government.

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Research has found that children with autism spectrum disorders (ASD) show significant deficits in receptive language skills (Wiesmer, Lord, & Esler, 2010). One of the primary goals of applied behavior analytic intervention is to improve the communication skills of children with autism by teaching receptive discriminations. Both receptive discriminations and receptive language entail matching spoken words with corresponding objects, symbols (e.g., pictures or words), actions, people, and so on (Green, 2001). In order to develop receptive language skills, children with autism often undergo discrimination training within the context of discrete trial training. This training entails teaching the learner how to respond differentially to different stimuli (Green, 2001). It is through discrimination training that individuals with autism learn and develop language (Lovaas, 2003). The present study compares three procedures for teaching receptive discriminations: (1) simple/conditional (Procedure A), (2) conditional only (Procedure B), and (3) conditional discrimination of two target cards (Procedure C). Six children, ranging in age from 2-years-old to 5-years-old, with an autism diagnosis were taught how to receptively discriminate nine sets of stimuli. Results suggest that the extra training steps included in the simple/conditional and conditional only procedures may not be necessary to teach children with autism how to receptively discriminate. For all participants, Procedure C appeared to be the most efficient and effective procedure for teaching young children with autism receptive discriminations. Response maintenance and generalization probes conducted one-month following the end of training indicate that even though Procedure C resulted in less training sessions overall, no one procedure resulted in better maintenance and generalization than the others. In other words, more training sessions, as evident with the simple/conditional and conditional only procedures, did not facilitate participants’ ability to accurately respond or generalize one-month following training. The present study contributes to the literature on what is the most efficient and effective way to teach receptive discrimination during discrete trial training to children with ASD. These findings are critical as research shows that receptive language skills are predictive of better outcomes and adaptive behaviors in the future.

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Multiple linear regression model plays a key role in statistical inference and it has extensive applications in business, environmental, physical and social sciences. Multicollinearity has been a considerable problem in multiple regression analysis. When the regressor variables are multicollinear, it becomes difficult to make precise statistical inferences about the regression coefficients. There are some statistical methods that can be used, which are discussed in this thesis are ridge regression, Liu, two parameter biased and LASSO estimators. Firstly, an analytical comparison on the basis of risk was made among ridge, Liu and LASSO estimators under orthonormal regression model. I found that LASSO dominates least squares, ridge and Liu estimators over a significant portion of the parameter space for large dimension. Secondly, a simulation study was conducted to compare performance of ridge, Liu and two parameter biased estimator by their mean squared error criterion. I found that two parameter biased estimator performs better than its corresponding ridge regression estimator. Overall, Liu estimator performs better than both ridge and two parameter biased estimator.

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Since 2004 the Colombian Ministry of Education has been implementing the Programa Nacional de Bilingüismo (PNB) with the goal of having bilingual high school graduates in English and Spanish by 2019. However, implementation of the PNB has been criticized by English Language Teaching (ELT) specialists in the country who say, among other things, that the PNB introduced a discourse associated exclusively with bilingualism in English and Spanish. This study analyzed interviews with 15 participants of a public school of the Colombian Escuela Nueva, a successful model of community-based education that has begun a process of internationalization, regarding the participants’ perceptions of foreign language education and the policies of the PNB. Six students, five teachers, and four administrators were each interviewed twice using semi-structured interviews. To offer a critique of the PNB, this study tried to determine to what extent the school implemented the elements of Responsible ELT, a model developed by the researcher incorporating the concepts of hegemony of English, critical language-policy research, and resistance in ELT. Findings included the following: (a) students and teachers saw English as the universal language whereas most administrators saw English imposed due to political and economic reasons; (b) some teachers misinterpreted the 1994 General Law of Education mandating the teaching of a foreign language as a law mandating English; and (c) some teachers and administrators saw the PNB’s adoption of competence standards based on the Common European Framework of Reference for languages as beneficial whereas others saw it as arbitrary. Conclusions derived from this study of this Escuela Nueva school were: (a) most participants found the goal of the PNB unrealistic; (b) most teachers and administrators saw the policies of the PNB as top-down policies without assessment or continuity; and (c) teachers and administrators mentioned a disarticulation between elementary and high school ELT policies that may be discouraging students in public schools from learning English. Thus, this study suggests that the policies of the PNB may be contributing to English becoming a gatekeeper for higher education and employment thereby becoming a tool for sustaining inequality in Colombia.

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Long-span bridges are flexible and therefore are sensitive to wind induced effects. One way to improve the stability of long span bridges against flutter is to use cross-sections that involve twin side-by-side decks. However, this can amplify responses due to vortex induced oscillations. Wind tunnel testing is a well-established practice to evaluate the stability of bridges against wind loads. In order to study the response of the prototype in laboratory, dynamic similarity requirements should be satisfied. One of the parameters that is normally violated in wind tunnel testing is Reynolds number. In this dissertation, the effects of Reynolds number on the aerodynamics of a double deck bridge were evaluated by measuring fluctuating forces on a motionless sectional model of a bridge at different wind speeds representing different Reynolds regimes. Also, the efficacy of vortex mitigation devices was evaluated at different Reynolds number regimes. One other parameter that is frequently ignored in wind tunnel studies is the correct simulation of turbulence characteristics. Due to the difficulties in simulating flow with large turbulence length scale on a sectional model, wind tunnel tests are often performed in smooth flow as a conservative approach. The validity of simplifying assumptions in calculation of buffeting loads, as the direct impact of turbulence, needs to be verified for twin deck bridges. The effects of turbulence characteristics were investigated by testing sectional models of a twin deck bridge under two different turbulent flow conditions. Not only the flow properties play an important role on the aerodynamic response of the bridge, but also the geometry of the cross section shape is expected to have significant effects. In this dissertation, the effects of deck details, such as width of the gap between the twin decks, and traffic barriers on the aerodynamic characteristics of a twin deck bridge were investigated, particularly on the vortex shedding forces with the aim of clarifying how these shape details can alter the wind induced responses. Finally, a summary of the issues that are involved in designing a dynamic test rig for high Reynolds number tests is given, using the studied cross section as an example.

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The importance of checking the normality assumption in most statistical procedures especially parametric tests cannot be over emphasized as the validity of the inferences drawn from such procedures usually depend on the validity of this assumption. Numerous methods have been proposed by different authors over the years, some popular and frequently used, others, not so much. This study addresses the performance of eighteen of the available tests for different sample sizes, significance levels, and for a number of symmetric and asymmetric distributions by conducting a Monte-Carlo simulation. The results showed that considerable power is not achieved for symmetric distributions when sample size is less than one hundred and for such distributions, the kurtosis test is most powerful provided the distribution is leptokurtic or platykurtic. The Shapiro-Wilk test remains the most powerful test for asymmetric distributions. We conclude that different tests are suitable under different characteristics of alternative distributions.

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In line with Wittgenstein's axiom that "what the solipsist means is quite correct; only it cannot be said, but makes itself manifest," this thesis aims to demonstrate how the gulf between analytic and continental philosophy can best be bridged through the mediation of art. The present thesis brings attention to Markson's work, lauded in the tradition of Faulkner, Joyce, and Lowry, as exemplary of the shift from modernity to postmodernity, wherein the human heart is not only in conflict with itself, but with the language out of which it is necessarily constituted. Markson limns the paradoxical condition of the subject severed from intersubjectivity, and affected not only by the grief of bereavement, which can be defined in Heideggarian terms as anxiety for the ontic negation of a being (i.e., death), but by loss, which I assert is the ontological ground for how Dasein encounters the nothing in anxiety proper.

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During the past two decades, many researchers have developed methods for the detection of structural defects at the early stages to operate the aerospace vehicles safely and to reduce the operating costs. The Surface Response to Excitation (SuRE) method is one of these approaches developed at FIU to reduce the cost and size of the equipment. The SuRE method excites the surface at a series of frequencies and monitors the propagation characteristics of the generated waves. The amplitude of the waves reaching to any point on the surface varies with frequency; however, it remains consistent as long as the integrity and strain distribution on the part is consistent. These spectral characteristics change when cracks develop or the strain distribution changes. The SHM methods may be used for many applications, from the detection of loose screws to the monitoring of manufacturing operations. A scanning laser vibrometer was used in this study to investigate the characteristics of the spectral changes at different points on the parts. The study started with detecting a load on a plate and estimating its location. The modifications on the part with manufacturing operations were detected and the Part-Based Manufacturing Process Performance Monitoring (PbPPM) method was developed. Hardware was prepared to demonstrate the feasibility of the proposed methods in real time. Using low-cost piezoelectric elements and the non-contact scanning laser vibrometer successfully, the data was collected for the SuRE and PbPPM methods. Locational force, loose bolts and material loss could be easily detected by comparing the spectral characteristics of the arriving waves. On-line methods used fast computational methods for estimating the spectrum and detecting the changing operational conditions from sum of the squares of the variations. Neural networks classified the spectrums when the desktop – DSP combination was used. The results demonstrated the feasibility of the SuRE and PbPPM methods.

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Reactive oxygen species are a normal consequence of life in an aerobic environment. However when they deviate from the narrow permissible range in cells, oxidative damage can occur. Dictyostelium discoideum is a model organism ideal for the study of cell signaling events such as those affected by oxidative stress. It was previously shown that Ras signaling in Dictyostelium is affected by genetic inactivation of the antioxidant enzyme Superoxide dismutase C (SodC) and in vitro data suggests that the NKCD motif of Ras is the redox target of superoxide. The main objective of this project was to determine the mechanism of superoxide mediated Ras regulation in vivo. To accomplish the main objective, we cloned, and in some cases, mutated different Ras proteins and later determined their activity in wild type and sodC- cells. RasC and RasD showed normal activation in sodC- cells, however RasG and RasS displayed high Ras activity. These last two Ras proteins contain the NKC118D motif inside the nucleotide binding region. A mutation of cysteine118 to alanine in RasG rendered the protein less active in sodC- than the wild type RasG protein and a mutation alanine118 to cysteine in RasD conferred redox sensitivity to this small GTPase. Additionally, the propensity of RasG to be targeted by superoxide was evident when the environment of wild type cells was manipulated to induce the internal generation of superoxide through changes in the extracellular ion levels mainly magnesium. Lack of magnesium ions increased the intracellular level of superoxide and severely hampered directional cell migration. Chemotaxis of cells expressing RasG was negatively impacted by the absence of magnesium ions; however rasG- cells did not seem to be affected in their ability to perform chemotaxis. The last experiment implies that RasG is an important mediator of cell signaling during oxidative stress, responsible for preventing cells from continuing their developmental program. Our study suggests that the cysteine residue in the NKCD motif is essential for mediating the redox sensitivity of Ras proteins in Dictyostelium and that RasG is an essential mediator of the response to oxidative stress in this organism.

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Chapter 1: Patents and Entry Competition in the Pharmaceutical Industry: The Role of Marketing Exclusivity Effective patent length for innovation drugs is severely curtailed because of extensive efficacy and safety tests required for FDA approval, raising concern over adequacy of incentives for new drug development. The Hatch-Waxman Act extends patent length for new drugs by five years, but also promotes generic entry by simplifying approval procedures and granting 180-day marketing exclusivity to a first generic entrant before the patent expires. In this paper we present a dynamic model to examine the effect of marketing exclusivity. We find that marketing exclusivity may be redundant and its removal may increase generic firms' profits and social welfare. Chapter 2: Why Authorized Generics?: Theoretical and Empirical Investigations Facing generic competition, the brand-name companies some-times launch generic versions themselves called authorized generics. This practice is puzzling. If it is cannibalization, it cannot be profitable. If it is divisionalization, it should be practiced always instead of sometimes. I explain this phenomenon in terms of switching costs in a model in which the incumbent first develops a customer base to ready itself against generic competition later. I show that only sufficiently low switching costs or large market size justifies launch of AGs. I then use prescription drug data to test those results and find support. Chapter 3: The Merger Paradox and R&D Oligopoly theory says that merger is unprofitable, unless a majority of firms in industry merge. Here, we introduce R&D opportunities to resolve this so-called merger paradox. We have three results. First, when there is one R&D firm, that firm can profitably merge with any number of non-R&D firms. Second, with multiple R&D firms and multiple non-R&D firms, all R&D firms can profitably merge. Third, with two R&D firms and two non-R&D firms, each R&D firms prefer to merge with a non-R&D firm. With three or more than non-R&D firms, however, the R&D firms prefer to merge with each other.

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To stay competitive, many employers are looking for creative and innovative employees to add value to their organization. However, current models of job performance overlook creative performance as an important criterion to measure in the workplace. The purpose of this dissertation is to conduct two separate but related studies on creative performance that aim to provide support that creative performance should be included in models of job performance, and ultimately included in performance evaluations in organizations. Study 1 is a meta-analysis on the relationship between creative performance and task performance, and the relationship between creative performance and organizational citizenship behavior (OCB). Overall, I found support for a medium to large corrected correlation for both the creative performance-task performance (ρ = .51) and creative performance-OCB (ρ = .49) relationships. Further, I also found that both rating-source and study location were significant moderators. Study 2 is a process model that includes creative performance alongside task performance and OCB as the outcome variables. I test a model in which both individual differences (specifically: conscientiousness, extraversion, proactive personality, and self-efficacy) and job characteristics (autonomy, feedback, and supervisor support) predict creative performance, task performance, and OCB through engagement as a mediator. In a sample of 299 employed individuals, I found that all the individual differences and job characteristics were positively correlated with all three performance criteria. I also looked at these relationships in a multiple regression framework and most of the individual differences and job characteristics still predicted the performance criteria. In the mediation analyses, I found support for engagement as a significant mediator of the individual differences-performance and job characteristics-performance relationships. Taken together, Study 1 and Study 2 support the notion that creative performance should be included in models of job performance. Implications for both researchers and practitioners alike are discussed.

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Students with specific learning disabilities (SLD) typically learn less history content than their peers without disabilities and show fewer learning gains. Even when they are provided with the same instructional strategies, many students with SLD struggle to grasp complex historical concepts and content area vocabulary. Many strategies involving technology have been used in the past to enhance learning for students with SLD in history classrooms. However, very few studies have explored the effectiveness of emerging mobile technology in K-12 history classrooms. This study investigated the effects of mobile devices (iPads) as an active student response (ASR) system on the acquisition of U.S. history content of middle school students with SLD. An alternating treatments single subject design was used to compare the effects of two interventions. There were two conditions and a series of pretest probesin this study. The conditions were: (a) direct instruction and studying from handwritten notes using the interactive notebook strategy and (b) direct instruction and studying using the Quizlet App on the iPad. There were three dependent variables in this study: (a) percent correct on tests, (b) rate of correct responses per minute, and (c) rate of errors per minute. A comparative analysis suggested that both interventions (studying from interactive notes and studying using Quizlet on the iPad) had varying degrees of effectiveness in increasing the learning gains of students with SLD. In most cases, both interventions were equally effective. During both interventions, all of the participants increased their percentage correct and increased their rate of correct responses. Most of the participants decreased their rate of errors. The results of this study suggest that teachers of students with SLD should consider a post lesson review in the form of mobile devices as an ASR system or studying from handwritten notes paired with existing evidence-based practices to facilitate students’ knowledge in U.S. history. Future research should focus on the use of other interactive applications on various mobile operating platforms, on other social studies subjects, and should explore various testing formats such as oral question-answer and multiple choice.

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The purpose of this thesis was to explore the boundary between human and other created by virtual worlds in contemporary science fiction novels. After a close reading of the three novels: Surface Detail, Existence, and Lady of Mazes, and the application of contemporary literary theories, the boundary presented itself and led to the discovery of where the human becomes other. The human becomes other when it becomes lost to the virtual world and no longer exists or interacts with material reality. Each of the primary texts exhibits both virtual reality and humanity in different ways, and each is explored to find where humanity falls apart. Overall, when these theories are applied to real life there is no real way to avoid the potential for fully immersive virtual worlds, but there are ways to avoid their alienating effects.

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Many systems and applications are continuously producing events. These events are used to record the status of the system and trace the behaviors of the systems. By examining these events, system administrators can check the potential problems of these systems. If the temporal dynamics of the systems are further investigated, the underlying patterns can be discovered. The uncovered knowledge can be leveraged to predict the future system behaviors or to mitigate the potential risks of the systems. Moreover, the system administrators can utilize the temporal patterns to set up event management rules to make the system more intelligent. With the popularity of data mining techniques in recent years, these events grad- ually become more and more useful. Despite the recent advances of the data mining techniques, the application to system event mining is still in a rudimentary stage. Most of works are still focusing on episodes mining or frequent pattern discovering. These methods are unable to provide a brief yet comprehensible summary to reveal the valuable information from the high level perspective. Moreover, these methods provide little actionable knowledge to help the system administrators to better man- age the systems. To better make use of the recorded events, more practical techniques are required. From the perspective of data mining, three correlated directions are considered to be helpful for system management: (1) Provide concise yet comprehensive summaries about the running status of the systems; (2) Make the systems more intelligence and autonomous; (3) Effectively detect the abnormal behaviors of the systems. Due to the richness of the event logs, all these directions can be solved in the data-driven manner. And in this way, the robustness of the systems can be enhanced and the goal of autonomous management can be approached. This dissertation mainly focuses on the foregoing directions that leverage tem- poral mining techniques to facilitate system management. More specifically, three concrete topics will be discussed, including event, resource demand prediction, and streaming anomaly detection. Besides the theoretic contributions, the experimental evaluation will also be presented to demonstrate the effectiveness and efficacy of the corresponding solutions.

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Conjugated polymers (CPs) are intrinsically fluorescent materials that have been used for various biological applications including imaging, sensing, and delivery of biologically active substances. The synthetic control over flexibility and biodegradability of these materials aids the understanding of the structure-function relationships among the photophysical properties, the self-assembly behaviors of the corresponding conjugated polymer nanoparticles (CPNs), and the cellular behaviors of CPNs, such as toxicity, cellular uptake mechanisms, and sub-cellular localization patterns. Synthetic approaches towards two classes of flexible CPs with well-preserved fluorescent properties are described. The synthesis of flexible poly(p-phenylenebutadiynylene)s (PPBs) uses competing Sonogashira and Glaser coupling reactions and the differences in monomer reactivity to incorporate a small amount (~10%) of flexible, non-conjugated linkers into the backbone. The reaction conditions provide limited control over the proportion of flexible monomer incorporation. Improved synthetic control was achieved in a series of flexible poly(p-phenyleneethynylene)s (PPEs) using modified Sonogashira conditions. In addition to controlling the degree of flexibility, the linker provides disruption of backbone conjugation that offers control of the length of conjugated segments within the polymer chain. Therefore, such control also results in the modulation of the photophysical properties of the materials. CPNs fabricated from flexible PPBs are non-toxic to cells, and exhibit subcellular localization patterns clearly different from those observed with non-flexible PPE CPNs. The subcellular localization patterns of the flexible PPEs have not yet been determined, due to the toxicity of the materials, most likely related to the side-chain structure used in this series. The study of the effect of CP flexibility on self-assembly reorganization upon polyanion complexation is presented. Owing to its high rigidity and hydrophobicity, the PPB backbone undergoes reorganization more readily than PPE. The effects are enhanced in the presence of the flexible linker, which enables more efficient π-π stacking of the aromatic backbone segments. Flexibility has minimal effects on the self-assembly of PPEs. Understanding the role of flexibility on the biophysical behaviors of CPNs is key to the successful development of novel efficient fluorescent therapeutic delivery vehicles.