UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item The demands, constraints, and instructional leadership choices of elementary principals implementing the Common Core State Standards(2013) Sirgo, Sarah; Mawhinney, Hanne; Education Policy, and Leadership; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Common Core State Standards (CCSS) placed unique demands and constraints on principals. Principals did not always make similar instructional leadership choices in how to spend their time, how to lead, and what to emphasize as a result of perceptions about their role, job demands, and the priorities for individual schools. Rosemary Stewart's job demands, constraints and choices model (1982) was integrated with Hoy and Miskel's (2008) social systems of schools framework to describe and analyze principal perceptions and instructional leadership choices. Demands, constraints, and choices were used to categorize perceptions about what exists and paired with the four frames of open systems. Instructional leadership was examined through the use of the Maryland Instructional Leadership Framework (MILF). This research was designed as a qualitative case study to answer three research questions. 1) What are the current demands that elementary principals perceive in their work? 2) What are the constraints that impact implementation of the CCSS? 3) How does a principal make instructional leadership choices in implementing the CCSS? The study used purposeful sampling and included six elementary principals within one district. Principals were with 3 to 30 years of experience and led medium sized schools with low levels of poverty and second language learner populations. Data was collected through semi-structured interviews, document, and memo review. Findings indicated that principals experienced a range of expected demands including supporting school climate, meeting district expectations for adherence to policies, managing the school building, and navigating the power structures of the district and community. Constraints included time, attitude, the distribution of power, attending to community needs, and the organizational hierarchy of the district. Instructional leadership priorities centered on supporting school conditions to facilitate collaboration and directing the professional development of staff. The results of this study provided a portrait of the challenges that principals faced, areas of possible influence, and how instructional leadership choices unfolded in a reform environment. In addition, the research served as an influential starting point for evaluating whether the instructional leadership practices utilized are sufficient to achieve the expected outcomes for CCSS implementation.Item A Theory of Cramer-Rao Bounds for Constrained Parametric Models(2010) Moore, Terrence Joseph; Kedem, Benjamin; Mathematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A simple expression for the Cram'er-Rao bound (CRB) is presented for the scenario of estimating parameters $\theta$ that are required to satisfy a differentiable constraint function $f(\theta)$. A proof of this constrained CRB (CCRB) is provided using the implicit function theorem, and the encompassing theory of the CCRB is proven in a similar manner. This theory includes connecting the CCRB to notions of identifiability of constrained parameters; the linear model under a linear constraint; the constrained maximum likelihood problem, it's asymptotic properties and the method of scoring with constraints; and hypothesis testing. The value of the tools developed in this theory are then presented in the communications context for the convolutive mixture model and the calibrated array model.Item Numerical studies of constraints and gravitational wave extraction in general relativity(2004-08-04) Fiske, David Robert; Misner, Charles W; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Within classical physics, general relativity is the theory of gravity. Its equations are non-linear partial differential equations for which relatively few closed form solutions are known. Because of the growing observational need for solutions representing gravitational waves from astrophysically plausible sources, a subfield of general relativity, numerical relativity, has a emerged with the goal of generating numerical solutions to the Einstein equations. This dissertation focuses on two fundamental problems in modern numerical relativity: (1) Creating a theoretical treatment of the constraints in the presence of constraint-violating numerical errors, and (2) Designing and implementing an algorithm to compute the spherical harmonic decomposition of radiation quantities for comparison with observation. On the issue of the constraints, I present a novel and generic procedure for incorporating the constraints into the equations of motion of the theory in a way designed to make the constraint hypersurface an attractor of the evolution. In principle, the prescription generates non-linear corrections for the Einstein equations. The dissertation presents numerical evidence that the correction terms do work in the case of two formulations of the Maxwell equations and two formulations of the linearized Einstein equations. On the issue of radiation extraction, I provide the first in-depth analysis of a novel algorithm, due originally to Misner, for computing spherical harmonic components on a cubic grid. I compute explicitly how the truncation error in the algorithm depends on its various parameters, and I also provide a detailed analysis showing how to implement the method on grids in which explicit symmetries are enforced via boundary conditions. Finally, I verify these error estimates and symmetry arguments with a numerical study using a solution of the linearized Einstein equations known as a Teukolsky wave. The algorithm performs well and the estimates prove true both in simulations run on a uniform grid and in simulations that make use of fixed mesh refinement techniques.