Academic literature on the topic 'LD5655.V855 1986.W444'

The purpose of this study was to determine the extent to which Tinto's model of the dropout process applied to a national sample of community college students. Strict definitions of persistence were used in applying a Tinto-based model to both 2- and 4-year student samples from the High School and Beyond (HSB) data set. The primary focus of the study was to determine the relative effects of social and academic integration, in relation to student background characteristics, on two measures of persistence: persistence in the institution, and persistence in higher education. The data were analyzed using path analyses procedures. Results only partially supported Tinto's theory. Major findings revealed that: 1) background variables directly affected persistence, no matter how defined, 2) the ability of Tinto's model to explain persistence may be highly dependent on the criteria used in defining persistence, 3) the model may better explain institutional persistence than persistence in the system of higher education, 4) student background characteristics may be more influential than institutional characteristics in explaining the long term persistence behavior of students, 5) results indicated that the Tinto model's ability to explain persistence was dependent upon the criteria used for defining persistence/dropout.
Ed. D.

The nighttime losses from an integral collector storage (ICS) system were investigated. The significance of the sky temperature, wind speed, and ambient temperature on the losses were examined. Outdoor data was taken on several nights to characterize the thermal performance of an ICS system under various environmental conditions. Indoor tests were then performed under an artificial "nighttime sky" environment, with a simulated wind, in an attempt to duplicate the heat losses which occurred outdoors. The standard rating procedure which specifies the conditions for the heat loss tests for ICS systems was analyzed to see how well it characterizes the collector performance at night. Experimental results indicate a synergistic effect between the sky temperature and wind speed. The effects of wind on the losses from the ICS system overshadow the effects of small changes in sky temperature, but larger changes of sky temperature, with a constant wind speed, have a pronounced effect. It is recommended that both of these parameters be taken into account in heat loss tests in standard rating procedures. Indoor tests can duplicate outdoor heat loss results within 8 per cent. The minimum requirement for SRCC rating tests should be to monitor, record, and report the sky temperature.
M.S.

A slender body theory method developed for a body moving parallel to a wall in shallow water is extended to include angular orientation of the body to the wall. The method satisfies only the zero normal velocity condition on the external boundaries but does not take into account the effect of induced flows on the body itself. A spheroid and a Series 60, block .80 hull were the bodies studied. The side force and yaw moment on each body were determined numerically for varying angular orientation with respect to either a single wall or canal bank. For both cases results for a range of depths and wall separation distances are presented. It is found that the method gives good qualitative side force predictions for a body moving parallel to a wall, but is unable to correctly predict the yaw moment or the side force due to angular orientation. This result dictates the need for a more complex mathematical model to properly represent the flow than the simple model and quasiâ steady method used here.

Master of Science

A theoretical study of convective heat transfer is presented for a laminar flow subjected to an axial variation in the external heat transfer coefficient (or dimensionless Biot number). Since conventional techniques fail for a variable boundary condition parameter, a variable eigenfunction approach is developed. An analysis is carried out for a periodic heat transfer coefficient, which serves as a model for heat transfer from a duct fitted with an array of evenly spaced fins. Three solution methods for the variable eigenfunction technique are examined: an Nth order approximation method, an iterative method and a stepwise periodic method. The stepwise periodic method provides the most convenient and accurate solution for a stepwise periodic Biot number. Graphical results match exactly to ones obtained by Charmchi and Sparrow from a finite-difference scheme. A connected region technique is also developed to provide limited exact results to test the validity of the three solution methods. The study of a finned duct by a stepwise periodic Biot number is carried out via a parametric study, an average (constant) Biot number approximation and an assumed velocity profile analysis. Results for the parametric study show that external finning yields substantial heat transfer enhancement over an unfinned duct, especially when the Biot number of the unfinned regions is low. A decrease in the interfin spacing causes increased enhancement. Variations of the period of the Biot number causes relatively small changes in enhancement as long as the ratio of finned to unfinned surface remains unchanged. An average (constant) Biot number approximation for a specified finned tube is compared to the stepwise periodic Biot number solution. The results show that the constant Biot number approximation provides accurate results. Finally, the results for the influence of the assumed velocity profile demonstrate that a constant velocity flow provides increased heat transfer and more effective enhancement by external finning than a laminar fully developed flow, especially at high Biot numbers. This study provides insight into heat transfer enhancement due to finning and also develops a solution methodology for problems involving variable boundary condition parameters.
M.S.

This paper evaluates the effectiveness of the institutional framework of the Commonwealth of Virginia in the implementation and enforcement of nonpoint source (NPS) pollution control measures in the state's urbanizing areas. The institutional framework is developed primarily around the existing governmental framework. The federal, state and local roles are examined in terms of the relevant legislative and executive NPS control activities already taking place. The judicial function is considered in terms of constitutional guarantees of protection of private property and the potential for liability stemming from the implementation of structural and nonstructural best management practices (BMP's). Three generic categories of BMP's are evaluated in light of this institutional environment: on-site BMP's, off-site BMP's and nonstructural BMP's. Where they are relevant, various subcategories of the institutional environment are examined: mechanisms and responsibility for financing and maintenance, managing future urban growth and mediating interjurisdictional arrangements. The introduction and first four chapters develop this material and the final chapter is an analysis of the existing state programs (the Erosion and Sediment Control Law and the State Water Control Board's voluntary Urban NPS Control and Abatement Program). The product of this analysis is the conclusion that both state programs analyzed are weak due to a lack of state oversight. In addition, the Erosion and Sediment Control Program could be strengthened by amending the law to add a viable "stop work" order and by defining violations as being civil rather than criminal (misdemeanors) violations.
M.S.

The relatively recent success of the aquarium as a tourist destination has promoted a National interest in marine life. In the past twenty years cities have built aquariums that draw millions annually to various locations, justifying financial maintenance of delicate underwater life systems and increasing local tourism. Some successful aquariums such as the Monterey and Boston city aquariums have not only effectively drawn large numbers of visitors, but also have gained architectural recognition with award winning designs, therefore adding a new dimension to the recent trend in museum design. Still, with the emphasis on tourism, an issue that has yet to be addressed is the function of the aquarium as resource center of marine life. This proposal for the Jacksonville city aquarium endeavors to address the function of the aquarium as an institute for research and education, while utilizing the unique marine ecology setting to promote awareness of local underwater ecosystems. In this way, educational research and wildlife awareness set a new standard for aquarium design. Tourism can simultaneously emphasize inner-city urban development and promote the wealth of its existing ecology. This educational focus, in conjunction with the three states of marine habitat, establishes the basis for the aquarium design. By integrating the building design into the existing fabric of the city and focusing the research on the local rivers and habitats, the aquarium design will achieve the integrity needed to support this ambitious venture.
Master of Architecture

A new numerical procedure has been developed for the finite-volume solution of the Euler equations on unstructured, triangular meshes using a flux-difference split, upwind method. The procedure uses a dual mesh system to implement the finite-volume scheme using conserved variables stored at the vertices of the triangles. The vertices of the triangles are located approximately in the center of the dual mesh cells and conservation is enforced about each dual mesh finite-volume. Techniques are developed for implementing Roe's approximate Riemann solver on unstructured grids. Higher order accuracy is achieved by using MUSCL-differencing. MUSCL-differencing is implemented on an unstructured grid by interpolating the values stored at the vertices of triangular elements to find the value at the outermost point of the three-point MUSCL-differencing formula. Flow solutions are computed using a four-stage Runge-Kutta time integration. Convergence is accelerated using non-standard weighting of the Runge-Kutta stages, variable time-steps, residual smoothing and residual min- imization. Applications and comparisons with structured grid solutions are made for a supersonic shock reflection problem, the supersonic flow over a blunt body, flow through a simple wedge inlet, and several AGARD 07 working group transonic airfoils. In general, the solutions computed by the upwind solver on the unstructured grids were as accurate as upwind solutions on a structured mesh. The blunt body solution, and some of the transonic airfoil solutions on the unstructured meshes, appeared to be less accurate than the structured mesh solutions. Fortuitously, the structured meshes used in these solutions tended to line up with the shock waves present in the flow-field. The upwind flux-differencing scheme captured the shock wave with greatest accuracy when it was applied normal to the discontinuity, as was done in these test cases.
Ph. D.

The quality of whole-tree wood chips has been the focus of much attention during the past few years because of the increased use of lower grade wood über in pulp production. The need to up-grade the quality has resulted in the use of some form of screening system to separate acceptable wood chips from unwanted material at most pulp mills. In order to upgrade the chip quality, a study was conducted to determine the effect of selected parameters of a separation system with an inclined, vibrating screen on screening efficiency. The parameters studied included screen aperture size and frequency of oscillation. Two screen sizes (3/8 and 1/4 inch apertures) and four different frequencies (1.25, 1.50, 1.75, and 2.00 Hertz) were considered. All other shaker unit parameters were held constant. Statistical analysis revealed that the lowest frequency resulted in the highest screening efficiencies for both the pin chips and fines categories. Screening efficiencies were higher with 3/8 inch screen as opposed to 1/4 inch screen, for all frequencies considered, but at 1.25 Hertz, the screening efficiency of fines was only 6 percent better with 3/8 inch screen. This analysis revealed that the lowest acceleration vectors produced the best screening efficiencies. Velocity and acceleration vectors were directly related to frequency of oscillation since all other parameters were held constant for this study. A Programmer’s Hierarchical Interactive Graphics System (PHIGS) program was developed to graphically simulate the screen motion and to analyze the maximum velocity and acceleration vectors of the upper swing arm (input link). By interactively changing the shaker unit parameters, the screen motion was animated and viewed, with the calculated vectors used in the statistical analysis.
Master of Science

The uses for wideband antennas include wideband measurement systems, spread spectrum communications systems, feeds for reflectors and elements in wideband arrays. Here, wideband antennas are discussed and Archimedean spiral antennas are found to be appropriate elements for use in a new type of wideband array referred to as the wideband switched array. The design of an Archimedean spiral and a necessary wideband balun transformer feed structure are presented. To aid in the design, the Electromagnetic Surface Patch Code (ESP) developed by Ohio State University is used. The spiral and feed structure are constructed and measured results are compared to predictions obtained by ESP.

Master of Science