Control of the rate of heat generation and the resulting temperature variations during the processing of thermosets is very necessary both to achieve the desired ultimate properties of the final product and to conserve energy and time. With this motivation, theoretical and experimental studies on the kinetics and thermal characterization of the curing reaction of thermoset polyesters were accomplished, and a mathematical curing model was proposed for the casting operation of these plastics. Temperature distribution through the thickness of the polymer mass was obtained by monitoring thermocouples placed at known locations with the aid of PDP-11/40 computer. Both isothermal and dynamic techniques of differential scanning calorimetry (Du Pont DSC) were used to obtain the heats of reaction and a kinetic expression for the polymerization reaction. The proposed kinetic model can be utilized to obtain the rates of heat generation a different curing temperatures. The overall activation energy of the curing reaction was calculated as 17.0 kcal/mole and the overall reaction rate constant as 2.60X10⁹exp(-17,000/RT) min⁻¹. The thermal properties of the polyester were determined as a function of temperature, and also attempts were made to measure these properties as a function of extent of reaction. The specific heat of cured polyester samples was determined over the temperature range 60-180°C. A more or less linear increase in specific heat was observed with increasing temperature between 60° and 120°C where the values were 0.38 and 0.43 cal/g-°C, respectively. Thermal conductivity measurements were accomplished by using a Colora Thermoconductometer, but a new sample system had to be developed for use with this instrument for the measurements of uncured and partially cured samples. A linear increase in conductivity of cured polyester with increasing temperature from a value of 4.5 X 10⁻⁴ cal/cm-sec-°C at 40°C to 5.0 X 10⁻⁴ cal/cm-sec-°C at 94°C was observed. Simulation of the curing process was based upon differential equations describing one-dimensional unsteady-state conductive heat transfer through the casting and the rate of the crosslinking reaction. The numerical scheme that was presented predicts the temperature and concentration profiles during the curing process. Agreement between the simulated and experimental temperature profiles was very good. The proposed model can be readily utilized in characterizing the curing process, predicting curing performance, and establishing guidelines for better design of the casting and other reaction molding operations with most of the thermoset plastics. / Ph. D.

Wind tunnel tests were conducted in an effort to determine the magnitudes, power spectra and correlation of loads over the surface of a model of a tall building. The model was tested as a single element and also with an identical element upstream to provide an interfering flow. The work is presented in three parts which deal with the boundary layer simulation, the measurement technique using multiple transducers and the results of several model tests. A turbulent shear layer similar to that found in the atmospheric boundary layer under strong wind conditions was generated in a wind tunnel with a short test-section by using a combination of sp:i,res and floor roughness elements. Flow properties were measured in detail at the model location, seven meters downstream of the spires. Properties measured included the mean velocity and turbulence characteristics for all three velocity components. Turbulence properties included intensities, some co-variances, integral length scales and power spectra. The flow was found to be two-dimensional across the central third of the tunnel and to be reasonably homogeneous in the flow direction. Measured flow properties were compared with estimates of full-scale properties for winds over urban areas as reported in review papers. The model flow was determined to be an acceptable simulation of atmospheric shear layer winds over urban areas for geometric scale ratios (between model and prototype) ranging from 1/400 to 1/600. Resultant fluctuating loads were measured at several elevations throughout the height of a square cylinder having an aspect ratio of 8.33. Analog circuits using operational amplifiers were used to amplify and sum signals from numerous pressure transducers. The resultant signals directly represented resultant loads at the level where the transducers were located and consequently, simultaneous measurements of pressures at each transducer were not required. With this technique, fluctuating loads may be measured whether or not the model is moving, and it is the only method available for determining fluctuating twisting moments at various levels throughout the height of a model of a tall building. Tests were conducted for numerous model orientations and configurations. Measurements were made of fluctuating normal forces and twisting moments at six elevations throughout the model height. Mean properties of the loads are presented for all configurations while spectra and coherence functions are presented for four illustrative cases. Test configurations included those involving a single instrumented model as well as cases where an identical model was placed upstream of the instrumented model. Load coefficients were found to vary throughout the height of the model. Spectra of the fluctuating loads for cases involving the single model indicate both periodic and random types of loading depending on the load component measured and the angle of orientation of the model. Both the power spectra of the loads and the correlation of the loads throughout the height of the model could be altered by the interference of an upstream model. Results indicate that the placement and orientation of neighboring buildings is critical to the aerodynamic stability of a particular building. / Ph. D.

The Virginia Department of Education suggested that its school divisions adopt an Evaluation by Objectives (EBO) teacher evaluation system as a means for its school divisions to satisfy the personnel evaluation section of the Standards of Quality mandate. This study surveyed Virginia's principals as to their use of and perceptions of the efficacy of the suggested EBO model. In addition, the study examined specific personal (age, years of administrative experience, membership in a teacher organization) variables and institutional (number of teachers in the school, number of teachers evaluated, EBO training, hours of EBO training) variables as possible predictors of the dependent variable, principal's perceived effectiveness of the suggested EBO procedures. The survey results indicated that 95.5 percent of the principals used or modified the procedures. The majority of these principals (86.8 percent) perceived the procedures to be effective, in improving teacher performance. Multiple regression analysis (MRA) was used to test the predictive strength of the independent variables identified in this study. The variables, although significant at the .01 level, were not meaningful as predictors of principals' perceived effectiveness of EBO. The adjusted R² coefficient of determination was only 5.9 percent. / Ed. D.

This thesis stresses the semantic aspect of the environment in an attempt to generate design alternatives for the redevelopment of the O Street Market site in Washington, D.C. The intention in presenting, as a conclusion to the study, an alternative image of the site that stands in stark contrast to that proffered by a potential developer is to stimulate the search for and discussion of additional alternatives. The alternative image presented arises from a redefinition of the problem based on an analysis of the time cycles that affect the project and on an exploration of the message-giving potential of physical objects and configurations in relation to the social, political, economic and behavioral context of the site. Resulting from this redefinition of parameters is an object whose feasibility is founded, not in traditional economic analyses, but in stability and evolutionary potential rooted in diversity and adaptability within its context. The bias of the writer is that the only supportable design solution for the problem will be generated in collaboration with the existing and potential residents and users. The schematic design, therefore, is presented as an object for redefinition and translation, in such an interactive forum, rather than as a solution to the problem. / Master of Architecture

An elastic plane stress finite element analysis of the stress distributions in four flat test specimens for in-plane shear response of composite materials subjected to mechanical or thermal loads is presented. The shear test specimens investigated include: slotted coupon, cross beam, Iosipescu, and rail shear. Results are presented in the form of normalized stress contour plots for all three in-plane stress components. The slotted specimen is studied for three graphite-epoxy laminates ([0], [90], [±45]_S); the cross beam is studied for two graphite-epoxy laminates ([0/90]_S, [±45]_S); the Iosipescu and rail shear specimens are studied with several materials (steel, graphite-epoxy, and graphite-polyimide) and several laminates ([0], [90], [0/90]_S, [±45]_S, [0/90/±45]_S) with rigid and elastic fixtures loaded mechanically or thermally. Geometric alterations are also investigated. The study shows that the cross beam, Iosipescu, and rail shear specimens have stress distributions which are more than adequate for determining linear shear behavior of composite materials. Laminate properties, core effects, and fixture configurations are among the factors which were found to influence the stress distributions. / Master of Science

This thesis seeks to identify the potential for the unconstrained minimization algorithms of mathematical programming to be cost-effective with the conventional techniques of nonlinear structural analysis. With this in mind, the author has attempted to critically evaluate a few of the more commonly used algorithms for their effectiveness in solving structural problems involving geometric and/or material nonlinearities. The algorithms have been categorized as being zeroth order requiring only function evaluations, first order requiring evaluation of both the function and the gradient or second order requiring in addition a variable metric. The sensitivity of the first and second order algorithms to the accuracy of derivatives derived on the basis of finite difference operations clearly suggests using analytically derived derivatives in order to obtain better control of the computational effort required for convergence to the exact solution. The thesis concludes by attempting to identify the algorithm which promises to be most effective in predicting nonlinear structural response and suggests improvements that could be made to make it even more cost-effective when compared with other well known techniques of nonlinear structural analysis. / Master of Science

<u>Taphrocerus schaefferi</u> is a leaf miner of yellow nutsedge, a serious weed of many agronomic and horticultural crops. Beetles begin egg-laying in early June; the eggs have an incubation period of 16 days. There are three larval instars, the first two of which consume only the chlorenchyma and upper epidermal cells of the infested leaf. The third instar is responsible for most of the tissue destruction. Approximately one half of the vascular bundles are destroyed. Larvae are cannibalistic and only one larva per leaf can develop. The larval and pupal stadia are 20 and 11 days, respectively. Adults emerge in late July and August. The immature stages are described and illustrated. The life cycle of <u>T. schaefferi</u> is well synchronized with that of its host. The primary mortality factor of the immature stages is two larval and pupal chalcid parasites which account for 74% of the total larval mortality. The total dry weight of plants without leaf miners is significantly greater at the P< 0.05 level than those plants with 5-8 leaf miners present. However, the development of <u>T. schaefferi</u> causes only minimal damage to the host. Mining occurs only in mature leaves, the first and second instar mine is superficial, and the third instar mine occurs near the onset of leaf senescence. As a consequence, the biocontrol potential of <u>T. schaefferi</u> is limited. A survey to detect the presence of <u>Elliponeura debilis</u> Loew (Diptera), a seed feeding chloropid, and <u>Glyphipteryx impigritella</u> Clemens (Lepidoptera, Glyphipterygidae), a leaf miner, was conducted. / Master of Science

This study was designed to identify factors influencing relocation to retirement communities. Participants were residents of two New Jersey retirement communities which offered single family detached dwelling units with common grounds, community recreational facilities, and security guards. Residents paid monthly maintenance fees to cover operation of the common areas. Total sample size was residents of 160 dwelling units. Specifically, respondents were from 40 units, or a 40 percent sample, in an Ocean County community and from 120 units, or a 10 percent sample, in a Burlington County community. The researcher developed a test instrument designed to ascertain reasons for relocation. Data were collected October 11-17, 1976, by the researcher who contacted the subjects at their homes. First, it was found that no significant differences existed between the samples and that only three items relating to influences upon mobility were significantly different between communities. These items were the large size of one's last dwelling unit, high property taxes on the last dwelling unit, and the value of one's new dwelling unit for the money. Second, no one factor precipitated relocation; rather, it was a combination of factors within the old and new near environments. Last, dwelling unit and neighborhood factors for the old and new near environments were influences, but community factors were only an influence as they relate to the new near environment. / Master of Science

A procedure is developed to examine the parameters affecting the accuracy of the vortex-lattice method when applied to a nonlinear lifting surface problem with leading edge separation. Among the factors investigated are the extensions of the bound vortex segments off the sharp edges of the wing, modifications of the Biot-Savart law to damp out near singularities, the length of the free vortex segments, the placement of the control points on the surface of the wing, and methods of applying the no-penetration boundary condition and spatial conservation of circulation. Two methods of force and pressure calculations are considered and an interpolation procedure is introduced to represent the pressure distribution as a continuous function over the surface of the wing. Delta, arrowhead, and cropped delta wings are presented as numerical examples. Parametric studies are made for the delta wing of aspect ratio one. It is found that the parameter which has the greatest influence on the solution is the extension of the bound vortex segments adjoining the leading edge off the leading edge. / Master of Science

Five states were chosen for the study: New York, Massachusetts, California, Oregon and Washington. The author visited each of the five states and Washington, D.C. in 1976 to collect writings, published and informal, and to interview persons concerning the historical background and implementation of the states' forest practice acts. The changing national attitudes toward the use and abuse of forest resources was traced as historical background. For each state, the political forces involved with forests were examined to determine how they contributed to the development and current form of the forest practice act. The purposes for which the states' acts were passed were analyzed. Available information on costs and benefits were included to illustrate what a state might expect if it decides such a program is desirable. Criteria were developed for evaluating the success of a state's forest practice act. A list of apparently successful features of selected administrative and regulatory systems was included to illustrate what form a model forest practice act might take. The criteria for success that were developed are: (1) improvement in existing conditions; (2) financial impacts on the timber operator, forest landowner and the state; and (3) the administrative development of regulations. Successful administrative and enforcement systems were: (1) part-time, independent forest practice boards promulgating regulations based on legislative policy; (2) single agency enforcement; (3) classification of forest practices according to their potential for environmental damage; and (4) a priority inspection system. / Master of Science