Unsteady separation past moving surfaces

Unsteady boundary-layer development over moving walls in the limit of infinite Reynolds number is investigated using both the Eulerian and Lagrangian formulations. To illustrate general trends, two model problems are considered, namely the translating and rotating circular cylinder and a vortex convected in a uniform flow above an infinite flat plate. To enhance computational speed and accuracy for the Lagrangian formulation, a remeshing algorithm is developed. The calculated results show that unsteady separation is delayed with increasing wall speed and is eventually suppressed when the speed of the separation singularity approaches that of the local mainstream velocity. This suppression is also described analytically. Only 'upstream-slipping' separation is found to occur in the model problems. The changes in the topological features of the flow just prior to the separation that occur with increasing wall speed are discussed

The structure of a three-dimensional turbulent boundary layer

The three-dimensional turbulent boundary layer is shown to have a self-consistent two-layer asymptotic structure in the limit of large Reynolds number. In a streamline coordinate system, the streamwise velocity distribution is similar to that in two-dimensional flows, having a defect-function form in the outer layer which is adjusted to zero at the wall through an inner wall layer. An asymptotic expansion accurate to two orders is required for the cross-stream velocity which is shown to exhibit a logarithmic form in the overlap region. The inner wall-layer flow is collateral to leading order but the influence of the pressure gradient, at large but finite Reynolds numbers, is not negligible and can cause substantial skewing of the velocity profile near the wall. Conditions under which the boundary layer achieves self-similarity and the governing set of ordinary differential equations for the outer layer are derived. The calculated solution of these equations is matched asymptotically to an inner wall-layer solution and the composite profiles so formed describe the flow throughout the entire boundary layer. The effects of Reynolds number and cross-stream pressure gradient on the cross-stream velocity profile are discussed and it is shown that the location of the maximum cross-stream velocity is within the overlap region

The effect of response format and presentation conditions on comprehension assessments for students with and without a reading disability

Previous studies (Collins, 2015; Kennan & Meenan, 2014) have shown how variations in text and task factors and individual reader skills affect performance on reading comprehension assessments. The present study examined whether different presentation conditions (silent reading, watching a video) and response formats (open-ended vs. multiple-choice questions) influenced comprehension performance for students with and without reading disabilities. In addition, measures of word-level reading, vocabulary, working memory, listening comprehension, and prior knowledge were also assessed to determine the best predictors of performance on comprehension assessments. Participants were 32 fifth grade students, 17 with reading disabilities (RD) and 15 typically developing (TD) students. All students were initially administered measures of word-level reading, vocabulary, listening comprehension, working memory, and decoding. Students were then administered four passages. Two of the passages were read silently and two were presented with videos. For each condition (text and video), comprehension was assessed with open-ended and multiple-choice questions. All assessments were administered individually to each student across two 60-minute testing sessions. All students were found to perform significantly better on the multiple-choice questions than the open-ended questions. As expected, the TD group had significantly higher comprehension scores on all measures. Presentation condition did not significantly affect performance for either group. Listening comprehension, working memory, and prior knowledge contributed unique variance to performance on the different response formats. For the open-ended questions, 67% of the variance was explained by the measures of listening comprehension and prior knowledge. In contrast, only 38% of the variance was explained by working memory for the multiple-choice questions. Even though students performed better on the multiple-choice questions, the regression analyses indicated that the open-ended questions were better reflections of basic language abilities and prior knowledge. Open-ended questions appear to provide a better measure of reader and text factors than multiple-choice questions which are more influenced by task factors. Future studies should continue to examine how reader, text and task factors influence comprehension performance

Predictors of high risk teenage pregnancies

To identify variables that predict birthweight among teenagers participating in a prenatal program? data were analyzed from 25,945 women, including 5,270 teenagers. Of black teenagers in the program* 8 to 17%. had low birthweight births, compared to 8 to 10'/. of the white teenagers. The percentages were significantly different only at age 15. Whereas black teenage mothers more often were unmarried, had previous abortions, and used public prenatal care providers, white teenage mothers more often smoked and were employed. Birthweight was regressed on a number of variables selected from the medical histories of the pregnant women. To obtain a risk score, the standardized regression coefficients were used to calculate weights that could be summed for each woman. Women who scored 10 or more were considered at risk. Risk weights for teenagers and for young adult women (ages 20 and 21) were calculated and compared with the risk weights for women of all ages who were in the prenatal program

Design of Fault Tolerant Control systems

This research designs a Fault Tolerant Control (FTC) approach that compensates for both actuator and sensor faults by using multiple observers. This method is shown to work for both linear time-variant and linear time-invariant systems. This work takes advantage of sensor redundancy to compensate for sensor faults. A method to calculate the rank of available sensor redundancy is developed to determine how many independent sensors can fail without losing observability. This rank is the upper bound on the number of simultaneous sensor failures that the system can tolerate. Based on this rank, a series of reduced order Kalman observers are created to remove sensors presumed faulty from the internal feedback of the estimators. Actuator redundancy is examined as a potential way to compensate for actuator faults. A method to calculate the available actuator redundancy is designed. This redundancy would allow for the correction of partial and full actuator failures, but few systems exhibit sufficient actuator redundancy. Actuator faults are instead tolerated by replacing the Kalman estimators with Augmented State Observers (ASO). The ASO adds estimates of the actuator faults as additional states of the system in order to isolate and estimate the actuator faults. Then a supervisor is designed to select the observer that correctly identifies the sensor fault set. From that observer, the supervisor collects state estimates and calculates estimates of the sensors and faults. These estimates are then used in feedback with a controller that performs pole placement on the original system

A case study of the supports that foster teachers’ awareness of students with disabilities experiencing homelessness

Students with disabilities experiencing homelessness are a growing and vulnerable population in the United States (Bassuk et al., 2014). They have a myriad of unique and complex needs, many of which teachers are ill prepared to meet. In this study, the researcher conducted a case study (Yin, 2014), set within the context of Ecological Systems Theory (EST; Bronfenbrenner, 1979), to investigate existing school and district level supports for teachers of students with disabilities experiencing homelessness, and teachers’ and other school personnel’s perceptions of those supports. The researcher interviewed six school and district level personnel, and analyzed several school and district level documents and web resources regarding homeless education to triangulate the data. Data were coded at three levels, the first two employing deductive logic and a priori codes based on the EST theoretical framework (Level I) and extant literature (Level II; Fereday & Muir-Cochrane, 2006). The third level of analysis was conducted using an inductive process, during which codes emerged from the data (Leech & Onwuegbuzie, 2007). Results from Level I coding indicated microsystem supports (to students and families) were provided most frequently, followed by exosystem supports (to teachers and other school professionals). Level II coding revealed teachers and other school professionals have drastically different perceptions of the absence or presence of teacher supports. Furthermore, the roles of teachers and other school professionals are concentrated on providing supports to students and families far more frequently than providing them to teachers. Level III analysis resulted in four overarching themes: homeless education norms, perceptions of the experience of homelessness, assumptions about teacher awareness and supports, and culture of support. While other school professionals often worked together formally and informally, they rarely involved teachers in their teams, but reported they provide adequate teacher support. The special educator’s perceptions indicated a lack of knowledge and support as well as a desire to improve both. Although the majority of participants held a deficit perspective of students with and without disabilities experiencing homelessness, overall they conveyed the importance of establishing a culture of support for those students and their families. Implications for future research include an investigation of the descriptive (the way things are done) and injunctive (the way things ought to be done) norms (Cialdini et al., 1990) within schools and districts. Specifically, the siloed nature of homeless education appears to be an emerging descriptive norm, when existing research supports homeless education ought to be carried out in a coordinated, team-based manner (i.e., injunctive). Professionals from other systems must be included in future research, as the norms from various systems can result in further contradictions. Similarly, additional investigations of rural homeless education are warranted to further unveil norms that impact the education of rural students with disabilities experiencing homelessness. Finally, considerations for practice include overhauling professional development to include teacher leadership and coaching as valid and sustainable options for improving the supports for teachers of students with and without disabilities experiencing homelessness

The status of elementary school general music programs in selected elementary schools in the Charlotte-Mecklenburg County school system in North Carolina

The purpose of this research study was to describe the status of public elementary school general music programs of Charlotte and Mecklenburg County, North Carolina. Specifically, the goals of the investigation were: (1) to describe the current status of elementary general music programs in selected public schools of the Charlotte- Mecklenburg School System; (2) to compare music goals, objectives, and criteria for each elementary grade as documented by the Charlotte-Mecklenburg School System with those of the North Carolina Department of Public Instruction; and (3) to determine the extent to which music goals, objectives, and criteria of the Char1otte-Meck1enburg School System have been implemented in the selected schools. Data collection instruments for the study included the "Elementary Music Teachers' Questionnaire" and the Silver Burdett Music Competency Tests (1979). A comparison was also made between the state (North Carolina) and local (Charlotte-Mecklenburg)elementary music curriculum guides

Djuna Barnes and experimental narration : a study of character-narration in the poetry, fiction, and drama of Djuna Barnes with a detailed analysis of its use in her novel, Nightwood

"For years one has dreamed of Paris," wrote Djuna Barnes In 1922, "...thinking in my heart of all unknown churches... Paris evenings...and children trying not to grow out of their clothes before they can get around the corner and home, and a slow haze, while at regulated Intervals, water can be heard dripping, dripping, dripping."1 And I say to myself, shall I tell the world what Paris meant to me, or shall I let it sit In its clubs, and Its libraries and its homes with Mark Twain and Arthur Symons on Its knee, and such desultory sketches as may have fallen from the reeking pens of women, while learning all that Americans failed to notice, on some garden urn?"

The effects of predation by threadfin shad, dorosoma petenense, and competition on body length of diaptomus in Piedmont North Carolina lakes

The species diversity of diaptomid copepods in piedmont North Carolina lakes has increased since these lakes were surveyed by McKee and Coker in 1940. This has been due, in large part, to the introduction of the vertebrate predator threadfin shad (Dorosoma petenense) and its effect on the only two diaptomid copepods present at that time, Diaptomus birgei and Diaptomus reighardi. These two copepods were never found together at the time of McKee and Coker’s survey, one or the other occupying the entire "Diaptomus niche" in any given lake. Ecological maturation of these lakes coupled with predation by Dorosoma petenense has enabled ether diaptomid copepods such as D. pallidus and D). mississippiensis to enter these lakes and also has allowed the coexistence of D. birgei and D. reighardi. Study of seasonal fluctuations in copepod population densities has shown that in shad-inhabited lakes the larger species tend to be dominant during times of low shad predation and the smaller species become dominant when shad activity is high (Beavers and Stavn 1975) . To test the degree of size selectivity of prey by shad, measurements were made of a single species (D. reighardi) over a one-year period in two lakes, one lake with and the other lake without shad. Seasonal variation in mean length was found to be similar in the two lakes during winter and early spring; however, from late spring through fall mean length of D. reighardi dropped below the yearly average to a greater degree in the shad-inhabited lake. This latter time period corresponded to the time of the year when shad were active in the shad-inhabited lake

Fourier-based image sharpness sensor for adaptive optics correction

Adaptive optics reduces undesirable turbulence effects present during propagation and imaging through the atmosphere or another random medium. Within an adaptive optics system, wavefront sensing determines the incoming wavefront errors. Image sharpening is one method of wavefront sensing where the sharpness value is measured from the image intensity based on a given sharpness metric. The wavefront correction device is then perturbed until the sharpness value is maximized. The key to image sharpening is defining sharpness with a sharpness metric that reaches a maximum when wavefront error is zero. Present image sharpness metrics often use the image intensity. In contrast, this dissertation introduces four novel sharpness metrics based on the Fourier transform of the image. Since high spatial frequencies carry information about the image’s edges and fine details, taking the Fourier transform and maximizing the high spatial frequencies sharpens the image. Coherence of the illumination source and the sharpness metric choice determine which of the presented optical system configurations to use. Performances of the Fourier-based sharpness metrics are observed and compared by measuring the sharpness value while adding defocus to the system. If the sharpness value reaches a maximum with zero wavefront error then the sharpness metric is successful. This investigation continues by adding astigmatism, coma, and spherical aberration and measuring the sharpness value to see the affect of these higher order aberrations. The sharpness metrics are then implemented into a simple manual closed-loop correction system. This dissertation presents successful performance results of these novel Fourier-based sharpness metrics showing great promise for use in adaptive optics correction