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  Partner: UNT Libraries
 Decade: 2010-2019
 Language: English
 Collection: UNT Theses and Dissertations
1/F Baseband Noise Suppression in Ofdm Using Kalman Filter

1/F Baseband Noise Suppression in Ofdm Using Kalman Filter

Date: May 2012
Creator: Rodda, Lasya
Description: As the technology is advances the reduced size of hardware gives rise to an additive 1/f baseband noise. This additive 1/f noise is a system noise generated due to miniaturization of hardware and affects the lower frequencies. Though 1/f noise does not show much effect in wide band channels because of its nature to affect only certain frequencies, 1/f noise becomes a prominent in OFDM communication systems where narrow band channels are used. in this thesis, I study the effects of 1/f noise on the OFDM systems and implement algorithms for estimation and suppression of the noise using Kalman filter. Suppression of the noise is achieved by subtracting the estimated noise from the received noise. I show that the performance of the system is considerably improved by applying the 1/f noise suppression.
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9-Lipoxygenase Oxylipin Pathway in Plant Response to Biotic Stress

9-Lipoxygenase Oxylipin Pathway in Plant Response to Biotic Stress

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Date: May 2012
Creator: Nalam, Vamsi J.
Description: The activity of plant 9-lipoxygenases (LOXs) influences the outcome of Arabidopsis thaliana interaction with pathogen and insects. Evidence provided here indicates that in Arabidopsis, 9-LOXs facilitate infestation by Myzus persicae, commonly known as the green peach aphid (GPA), a sap-sucking insect, and infection by the fungal pathogen Fusarium graminearum. in comparison to the wild-type plant, lox5 mutants, which are deficient in a 9-lipoxygenase, GPA population was smaller and the insect spent less time feeding from sieve elements and xylem, thus resulting in reduced water content and fecundity of GPA. LOX5 expression is induced rapidly in roots of GPA-infested plants. This increase in LOX5 expression is paralleled by an increase in LOX5-synthesized oxylipins in the root and petiole exudates of GPA-infested plants. Micrografting experiments demonstrated that GPA population size was smaller on plants in which the roots were of the lox5 mutant genotype. Exogenous treatment of lox5 mutant roots with 9-hydroxyoctadecanoic acid restored water content and population size of GPA on lox5 mutants. Together, these results suggest that LOX5 genotype in roots is critical for facilitating insect infestation of Arabidopsis. in Arabidopsis, 9-LOX function is also required for facilitating infection by F. graminearum, which is a leading cause of Fusarium head ...
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161 Glass: Site Specific Music in an Artistic Context

161 Glass: Site Specific Music in an Artistic Context

Date: May 2010
Creator: Rusnak, Christina S.
Description: The composition 161 Glass is a 17-minute musical work with percussion, wind and brass instruments in which the intersection of mid-century architecture, and the art and culture of a dynamic city are inextricably linked. Through this paper, I explore the process of composing a musical work in relationship to the significance of site specific context. The paper begins by defining the concept of site specific art works; then reviews the discourse of the intersection of art, music and architecture. I then delve into the cultural and geographic context surrounding this project from the modern era through the present, and how those perspectives apply to the building and my piece. I reveal how the composition relates the musical ideas to the site. Finally, I describe the collaborative process between myself, the musicians and the Dallas Contemporary staff.
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3D Reconstruction Using Lidar and Visual Images

3D Reconstruction Using Lidar and Visual Images

Date: December 2012
Creator: Duraisamy, Prakash
Description: In this research, multi-perspective image registration using LiDAR and visual images was considered. 2D-3D image registration is a difficult task because it requires the extraction of different semantic features from each modality. This problem is solved in three parts. The first step involves detection and extraction of common features from each of the data sets. The second step consists of associating the common features between two different modalities. Traditional methods use lines or orthogonal corners as common features. The third step consists of building the projection matrix. Many existing methods use global positing system (GPS) or inertial navigation system (INS) for an initial estimate of the camera pose. However, the approach discussed herein does not use GPS, INS, or any such devices for initial estimate; hence the model can be used in places like the lunar surface or Mars where GPS or INS are not available. A variation of the method is also described, which does not require strong features from both images but rather uses intensity gradients in the image. This can be useful when one image does not have strong features (such as lines) or there are too many extraneous features.
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Absorptive Capacity:  An Empirical Examination of the Phenomenon and Relationships with Firm Capabilities

Absorptive Capacity: An Empirical Examination of the Phenomenon and Relationships with Firm Capabilities

Date: May 2012
Creator: Daspit, Josh
Description: The field of strategic management addresses challenges that firms encounter in an attempt to remain competitive. The ability to explain variation in firm success through examination of knowledge flows has become a prominent focus of research in the strategic management literature. Specifically, researchers have sought to further examine how firms convert knowledge, a phenomenon conceptualized as absorptive capacity. Absorptive capacity is the firm’s ability to acquire, assimilate, transform, and exploit knowledge. Few studies have captured the richness and multi-dimensionality of absorptive capacity, and it remains to be understood how the dimensions of the phenomenon convert knowledge. Furthermore, how absorptive capacity influences the firm remains to be understood. To address these research gaps, this dissertation seeks to (1) determine how absorptive capacity converts knowledge, and (2) determine how absorptive capacity influences firm capabilities. The research questions are investigated using structural modeling techniques to analyze data collected from software-industry firms. The findings offer contributions to the absorptive capacity and capability literatures. For example, absorptive capacity is hypothesized to consist of complex relationships among its internal dimensions. However, findings of this study suggest the relationships among the dimensions are linear in nature. This finding is in line with the theoretical foundations of and ...
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Accomplished Teachers' Instructional Decisions About Shakespeare

Accomplished Teachers' Instructional Decisions About Shakespeare

Date: May 2013
Creator: Parris, Sheri Rene’
Description: Teachers' decisions are a powerful influence on student learning and it is important to fully document accomplished teachers' instructional decisions, as well as to investigate possible influences on those decisions. Shakespearean dramas are central to high school curricula across the U.S. and pose particular instructional challenges, therefore teachers' decisions about teaching these texts are of particular interest. There is limited empirical research, however, about these instructional decisions. Thus, the purpose of this study was to describe how four accomplished high school English teachers working on a single campus make instructional decisions about teaching a Shakespearean play. Specifically, research questions addressed teachers' decisions regarding the teaching of a Shakespearean play and various influences on those decisions (self-reports and inferences from the data). Case study methodology was used, including an inductive analysis of individual teacher interviews, classroom observations, focus group, instructional artifacts, and researcher's journal. The findings revealed that instructional activities described by these teachers addressed support for meaning-making during four stages of reading instruction: (a) before, during, and after; (b) before; (c) during; and (d) after. Comparison of these cases suggests that, although each teacher brings personal preferences and unique background knowledge to her instructional decisions, all make decisions to promote ...
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Accreditation Facilitation Projects:  Supporting High Quality Early Childhood Education and Care

Accreditation Facilitation Projects: Supporting High Quality Early Childhood Education and Care

Date: May 2013
Creator: Reinke, Stephanie L.
Description: High-quality early childhood education and care (ECEC) are linked to positive developmental outcomes for children. Systems have been created to define, measure and promote high-quality ECEC. National accreditation status is deemed the gold standard of a high-quality program, yet many centers are unable to achieve this without assistance. With the help of Accreditation Facilitation Projects (AFPs), many low-income centers are able to achieve accreditation. Centers collaborating with an AFP reap many benefits including financial support, ongoing training and mentoring, and guidance through the accreditation process. AFPs invest greatly in the centers they collaborate with and the longer the center takes to achieve accreditation, the more resources an AFP must expend. The purposes of this study were to understand if the educational level of center director, the total enrollment of a center, or the percentage of children receiving government subsidies could predict the time it takes for a center to complete the accreditation process while receiving assistance from an AFP, and to determine if there are differences in attitudes about program accreditation between center directors and early learning specialists who serve as accreditation mentors to the directors. Findings revealed that a) the higher educational level of program directors is associated with ...
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Acculturation, Acculturative Stress, and Anxiety Among Hispanic Undergraduates

Acculturation, Acculturative Stress, and Anxiety Among Hispanic Undergraduates

Date: May 2011
Creator: Durón, Kelly M.
Description: First generation college students face some unique challenges in the pursuit of higher education. Aside from academic stressors, there are stressors related to social and cultural transitions which may exacerbate pre-existing emotional or psychological distress. Research suggests that acculturation influences psychological well-being and development. The current study examined the relationships between acculturation, acculturative stress, socio-economic status, and symptoms of anxiety among first-generation college students of Hispanic origin. Participants (N = 125) included those who were first in their family to attend college and were primarily female, of traditional college age, and of Mexican heritage. All measures were self-report and were completed online. Overall, this study was inconclusive as most analyses were underpowered. The present study failed to support a relationship between style of acculturation and symptoms of anxiety, although, experiencing Anglo marginality was related to high levels of acculturative stress and anxiety. Finally, regression analysis revealed that acculturative stress, age, and Anglo marginalization were significant predictors of anxiety and accounted for 31% of variance in anxiety. Implications of the present study were discussed. Further study with adequate power is highly recommended.
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Acculturation and Depression in Older Mexican American Adults: the Role of Social Support

Acculturation and Depression in Older Mexican American Adults: the Role of Social Support

Date: August 2012
Creator: Caballero, Daniela
Description: Despite socioeconomic disadvantages, less acculturated Mexican Americans tend to exhibit better mental health than their more acculturated counterparts. However, in the case of older Mexican American adults, research has demonstrated the opposite to be true (Gonzalez, Haan, & Hinton, 2001). A variable of interest potentially responsible for this difference is social support. Thus, the current study proposed to investigate the mediation and moderation effects that social support has on the relationship between acculturation and depression in older Mexican American adults age 60 or older. Data from the Health and Retirement Study (HRS) was analyzed. Results showed that the mediating effect of contact with one’s children (-.109*) and the moderating effect of total social support and contact with one’s children (-.127*; -.103*) were statistically significant in the relationship between acculturation and depression. Although these effects are small they may still hold important implications for better understanding this population.
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Accuracy and Efficiency in Computational Chemistry: The Correlation Consistent Composite Approach

Accuracy and Efficiency in Computational Chemistry: The Correlation Consistent Composite Approach

Date: August 2011
Creator: Wilson, Brent R.
Description: One of the central concerns of computational chemistry is that of efficiency (i.e. the development of methodologies which will yield increased accuracy of prediction without requiring additional computational resources – RAM, disk space, computing time). Though the equations of quantum mechanics are known, the solutions to these equations often require a great deal of computing power. This dissertation primarily concerns the theme of improved computational efficiency (i.e. the achievement of greater accuracy with reduced computational cost). Improvements in the efficiency of computational chemistry are explored first in terms of the correlation consistent composite approach (ccCA). The ccCA methodology was modified and this enhanced ccCA methodology was tested against the diverse G3/05 set of 454 energetic properties. As computational efficiency improves, molecules of increasing size may be studied and this dissertation explored the issues (differential correlation and size extensivity effects) associated with obtaining chemically accurate (within 1 kcal mol-1) enthalpies of formation for hydrocarbon molecules of escalating size. Two applied projects are also described; these projects concerned the theoretical prediction of a novel rare gas compound, FKrOH, and the mechanism of human glutathione synthetase’s (hGS) negative cooperativity. The final work examined the prospect for the parameterization of the modified embedded atom ...
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