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Interval contractor-based reference governor for a class of uncertain nonlinear systems
No full textThis paper proposes a novel interval contractor-based reference governor design for a class of nonlinear systems containing both polynomial terms and unknown constant parameters which are valued in known bounded intervals. The reference governor ensures that input and state polynomial constraints are satisfied, despite uncertainties in the model and constraints. Its synthesis computes a maximal output admissible set (or MOAS), and requires adding new components to the state vector. It also uses interval analysis methods to shrink the bounds for the uncertain parameters over time. The MOAS computations are performed offline using a grid of the uncertain parameter bounds. Then, the reference governor is computed online by combining bisection algorithms and interval contractors
Bounded Extremum Seeking for Static Quadratic Maps Using Nonlinear Transformation and Lyapunov Method
No full textWe present a new practical stability analysis for a bounded gradient based extremum seeking problem for two variable static quadratic maps that contain a time-varying additive measurement uncertainty. Instead of using earlier averaging-based approaches, we introduce a new state transformation, a time-varying quadratic Lyapunov function, and a comparison principle to obtain essentially less conservative bounds on the dither frequency and on the ultimate bound of the estimation error compared with earlier results. Our numerical example illustrates the efficiency of the method
The Color of Medical School Curriculum: African American Medical Students’ Experiences with Culturally Relevant Curriculum at Predominantly White Institutions
No full textThe research gap in narratives from African American medical students on the topic of culturally relevant curriculum at predominantly white institutions requires attention. The research on Black medical students’ experiences in medicine fails to distinguish the voices of the diaspora drowning out the most underrepresented group, Black/African Americans. As medical students prepare to serve patients from diverse backgrounds, a medical school curriculum that is culturally relevant and pays homage to the diversity of patient demographics is warranted. Using the multicultural education framework to guide this research, the researcher was able to amplify the voices of Black/African American medical students as they described their experiences with culturally relevant curriculum at predominantly white institutions. The study was guided by a central research question and three sub-questions to gain insight from participants. Thirteen semi-structed interviews were completed. From the narratives, six themes emerged: complicit administration: administration partial investment and the perpetuation of artificial culture; silence as a burden: the weight of faculty discomfort with conversations on race, culture, and ethnicity in medical education; one-size fails all: the pedagogical gap in self-directed resource learners; care disparities: faculty knowledge gaps in the treatment of patients from diverse backgrounds; biased diagnostics: the hidden curriculum of patient stereotypes in medical stem questions; and, this African American life as a medical textbook: personal journeys shaping culturally competent care. Findings from this study add to the dearth of research on the experiences of Black/African American medical students with culturally relevant curriculum
Patterns and Processes Behind Secretive Marshbird Movement, Abundance, and Distribution Across Southeastern Louisiana
Full text linkRestoration and conservation of coastal Louisiana hinges on understanding the patterns and processes underlying habitat heterogeneity on the landscape and therefore the species that inhabits this region, including secretive marshbirds. Elusive in nature, this guild of birds has evolved under dynamic hydroperiods, and myriad plant communities present within wetlands. Only recently, however, has research focused on the role of hydrologic dynamics and vegetative structure and distribution on abundance, movement and detection of marshbirds, specifically within southeastern Louisiana. This study aimed to quantify the ecological patterns and processes, particularly hydrologic processes and landscape structure, driving breeding secretive marshbird movement, abundance and distribution across southeastern Louisiana at different spatial and temporal scales. The effects of water depths and variability on temporary emigration and detection probability of marshbirds during surveys were also quantified. Different temporal water depth and water depth variability measurements demonstrated species-specific effects on displacement and home range with strong seasonal correlations apparent. Additionally, water depths, water depth variability, and vegetation structure affected abundance, but whether positively or negatively differed by species, specifically by where marshbirds occurred on the estuarine gradient. Availability for detection increased with water depth variability in fresh marshes but availability began to decrease as salinity increased. These findings underscore the importance of dynamic processes and patterns on the landscape and the need to incorporate metrics of temporary emigration into detection probability for marshbird abundance estimates. Habitat heterogeneity in the form of proportion of temporary water, proportion of edge, flooding heterogeneity and vegetation denseness were the most informative predictors of the presence of marshbirds, outperforming salinity values for all species except clapper rail. Dynamic hydrological processes and habitat structure on the landscape play important roles in marshbird movement, abundance, and distribution but the dynamic and fluctuating landscape of southeastern Louisiana makes modeling difficult within the region, highlighting the need for multi-temporal and spatial scale variables to better understand the patterns and processes influencing marshbird use and needs
A PERFORMANCE GUIDE TO CHRISTOS HATZIS’ SONGS ON POEMS BY SAPPHO
Full text linkAbstract
Christos Hatzis’ Three Songs of Poems by Sappho (1999) represents a compelling yet understudied contribution to contemporary art song repertoire. This study examines Hatzis’ settings of Sappho’s Fragments 1, 16, and 44, offering both scholarly analysis and practical performance guidance to make the cycle more accessible to singers and scholars. Through musical and textual analysis, this project reveals how Hatzis bridges ancient Greek lyric poetry with modern compositional techniques. The study demonstrates his innovative approach to word painting, rhythmic flexibility, and extended tonality, showing how these elements honor Sappho’s intimate first-person voice while creating a distinctive 20th-century art song idiom. Performance practice recommendations address technical and interpretive suggestions, include an International Phonetic Alphabet guide in modern Greek, as well as insight into the textual changes rendered by Dr. Christos Hatzis. The study synthesizes historical research on the legend of Sappho with analysis of Hatzis’ compositional philosophy to provide a multifaceted understanding of the work. Designed as both a scholarly resource and practical guide, this project aims to encourage more frequent performances of Three Songs of Poems by Sappho while establishing its importance in the art song canon. It offers singers concrete tools for interpretation while suggesting directions for future research on comparative Sappho settings, as well as an examination of Hatzis’ evolved approach to text setting
Chemical Design and Modulation of the Self-Assembly of Sequence-Defined Ionic Polypeptoids in Aqueous Solution: Investigating Micellar Structure and Polymer Conformations
No full textThis dissertation aims to uncover the effect of coronal charge patterning on the structure of aqueous micellar assemblies of ionic, sequence-defined peptoid multiblock copolymers in dilute and semi-dilute regime. This work involves a multifaceted approach involving molecular dynamics (MD) simulations, contrast-variation small-angle neutron scattering (CVSANS), other analytical methods (DLS, TEM, etc.). Biomolecules such as polysaccharides and intrinsically disordered proteins use charge patterning to modulate their structure, dynamics, intra/inter-molecular interactions, and biological functions. The unique opportunity for tailored morphologies in synthetic polymer assemblies, tuned only by the charge sequence of molecularly equivalent chains, is attractive for many applications. Polypeptoids are N-substituted polyglycine backbones are structural biomimetics of polypeptides. The absence of backbone hydrogen bonding and stereogenic centers of peptoids results in flexible backbone conformations with a diminished propensity to form secondary structures. The backbone conformations and polymer interaction with solvents can be tailored by the chemical identity of N-substituents on peptoids. Therefore, peptoids are a well-suited platform to investigate the effect of sequence-encoded electrostatic interactions on the resulting micellar structures, intramicellar conformations, and self-assembly behavior in aqueous solutions due to the possibility of precisely controlling the number and positions of the ionizable monomers along the chains. The central hypothesis of this work is that sequence-defined electrostatic monomers encoded in the peptoid backbone dictate micelle structure and dynamics by balancing electrostatic repulsion, hydration, and interfacial energetics.
These studies underscore the critical role of charge patterning in shaping the structure and behavior of synthetic self-assemblies, providing design rules for advanced polymeric materials, and deepening our understanding of biomimetic nanostructure formation in aqueous media
Examining Leadership Practices of Athletic Directors and Its Impact on Student-Athlete Academic Progress Rates (APR’s) at Historically Black Colleges and University’s (HBCU’s)
No full textHistorically Black Colleges and Universities (HBCUs) face persistent challenges in meeting NCAA Academic Progress Rate (APR) requirements, with nearly one-third of HBCU football programs falling below the 930 threshold. This correlational study examined whether leadership styles of athletic directors at HBCUs predict APR compliance outcomes using Full Range Leadership Theory (FRLT) as a theoretical framework, specifically focusing on transformational and transactional leadership approaches.
The study addressed three research questions examining: (1) whether athletic directors\u27 leadership styles predict the likelihood of meeting APR compliance; (2) to what extent these leadership styles predicted average APR scores; and (3) how leadership styles influenced athletic directors\u27 ability to foster academic progress within HBCU athletic programs. Data was collected using the Multifactor Leadership Questionnaire (MLQ-5X short) administered to athletic directors from 46 institutions across four HBCU athletic conferences (SWAC, MEAC, CIAA, and SIAC). Binary logistic regression was employed to analyze the relationship between leadership styles (interval measures) and APR compliance (dichotomous pass/fail outcome).
This research addresses a critical gap in understanding effective leadership practices at HBCUs facing unique challenges including limited resources, underprepared student-athletes, and financial constraints. Findings will inform leadership training initiatives and institutional strategies to improve academic outcomes for student-athletes at HBCUs, contributing to broader conversations about equity and social justice in intercollegiate athletics
THE LEGACY OF PLACE: A LOUISIANA CASE STUDY FOR THE PAST AND ITS DYNAMIC IMPACT ON CONTEMPORARY SOCIAL AND ENVIRONMENTAL LANDSCAPES
No full textMany scholars have suggested that the current environmental justice literature does not address the historically-informed social underpinnings of what creates and upholds environmental inequality (Park and Pellow 2004; Pellow 2006; Teelucksingh 2007; Kurtz 2009; Holifield et al. 2009; Pellow 2016; Pulido 2017). To fully understand the breadth of environmental inequality, the current study aims to understand how place, theorized according to Gieryn (2000) as a culmination of space, material, and cultural meaning assigned to it by those within and without, informs and upholds the environmental inequality within. The first objective aims to understand how slavery informs contemporary Black-White TRI distribution inequality. This aim is approached using spatial regression methods, spatial mapping, and quantitative data obtained from EPA and Census databases. The second objective aims to capture how environmental justice community leaders confront collective memories of injustice and use them to inform collective action. Other social dynamics influencing collective action are uncovered and applied to practical implications for the future of Louisiana environmental land use planning, and management. Aim 1 findings suggest that environmental inequality is a more contemporary outcome, given that racialized environmental inequality persists contemporarily in places with greater Black presence. Aim 2 findings indicate memorial connections between historical injustices and contemporary environmental inequality, resulting in environmental justice collective action outcomes. Decisions to organize EJ collective action were often initiated by a series of place-based factors: 1) historical racial inequality, 2) strong place attachment, 3) contemporary environmental inequality mirroring history and elders as historians 4) government distrust and historically perceived governmental inadequacies, 5) industrial distrust and historical wrongdoing by industry, and 6) sharing of history from community historians and members’ bodies. Collective action was also influenced by social dynamics within place, which included: 1) trust responses and 2) spiritual faith and religion, both found to have guided collective action in EJ movements. Results of these collective memories include organizing collective action to ensure historic inequalities are not replicated, collective action to protect their community, its values, and its inhabitants, and collective action to engage civic spheres to empower change
Improving Fertilizer Efficiency in Containerized Nursery Production Through Substrate Temperature Management Techniques
Full text linkResource efficiency, particularly regarding mineral nutrients, is a critical factor in the long-term success of the nursery industry. Fertilizer release is controlled by water and temperature in container-grown ornamental nursery production systems. Thus, it was hypothesized that pragmatic management of substrate temperature and moisture could extend the longevity of controlled-release fertilizer (CRF) in a container system. This study was conducted to determine the effect of irrigation scheduling, container color, and stratified substrates on substrate temperature and the subsequent use and longevity of CRF in a crop production setting. ‘Limelight’ Hydrangea (Hydrangea paniculata) liners were planted in either black or white colored 3-gal containers and grouped in sixteen rows of 10 plants. Rows were subjected to a single or cyclic irrigation application, in which irrigation was split into three irrigations at three minutes daily. Hydrangeas grown in white containers with cyclic irrigation increased plant growth by up to 50% compared to those grown in black containers with single-application irrigation. Root health and fertilizer efficiency were improved with substrate temperature management strategies. The results from this thesis provide insight into the methods that growers can use to mitigate root zone temperatures to enhance crop growth and salability, increase fertilizer use and efficiency, and decrease phosphorus leaching from nursery containers