The composition of the population of undergraduate students in the U. S. has changed dramatically in recent years. A number of factors including societal transformations, a changing economy and demographic trends of the past decade have had particular impact. The cohort of students over age 30 is now the fastest growing segment of students who are entering or returning to colleges and universities. At this age the mature student is generally well established in work, community and family. While much of the research has focused on individual student needs, it has failed to investigate family and education interactions among older married reentry students. This is despite the reality that family concerns are often cited as the primary reason a reentry student withdraws from school. In this study, stepwise multiple regression was used to determine the extent to which gender, demographic background, and family issues explain the variance in reentry student perception of reentry student problems. This analysis yielded results which support the thesis that regardless of the student's gender, family problems are the strongest predicator of reentry student problems. Implications from this study may provide invaluable information to counselors, student service professionals, administrators, educators, and other professionals who work with reentry students and their families. This information can help to dispel myths and to aid reentry student and family adjustments. / Master of Science

A piezoceramic actuator used for structural control behaves electrically as a nearly pure capacitance. When conventional amplifiers are used to drive these actuators, the current and voltage is close to 90 degrees out of phase. This causes the power factor (PF) of the load to be close to zero and results in excessive power requirements. This thesis reports the results of a study of the following question: What effect does applying power factor correction methods to piezoceramic actuators have on their power consumption characteristics? A subproblem we explored was to detennine the qualitative relationship between the power consumption of a piezoceramic actuator and the damping that actuator added to a structure. To address the subproblem, a feedback control experiment was built which used a ceramic piezoceramic actuator and a strain rate sensor configured to add damping to a cantilevered beam. A disturbance was provided by a shaker attached to the beam. The power consumption of the actuator was determined by measuring the current and voltage of the signal to the actuator. The energy dissipated in the beam by the feedback control loop was assumed to be modeled by an ideal structural damping model. A model relating structural damping as a function of the apparent power consumed by the actuator was developed, qualitatively verified, and physically justified. Power factor correction methods were employed by adding an inductor in both parallel to and in series with the piezoceramic actuator. The inductance values were chosen such that each inductor-capacitor (LC) circuit was in resonance at the second natural frequency of the beam. Implementing the parallel LC circuit reduced the current consumption of the piezoceramic actuator by 75% when compared to the current consumption of the actuator used without an inductor. Implementing the series LC circuit produced a 300% increase in the voltage applied to the actuator compared to the case when no inductor was used. In both cases, employing power factor correction methods corrected the power factor to near unity and reduced the apparent power by 12 dB. A theoretical model of each circuit was developed. The analytical and empirical results are virtually identical. The results of this study can be used to synthesize circuits to modify piezoceramic actuators, reducing the voltage or current requirements of the amplifiers used to drive those actuators / Master of Science

The incorporation of reliability theory into a fatigue analysis program is studied. A thorough background in probabilistic methods and metal fatigue is presented, allowing a full understanding of these processes. An automotive wheel assembly is then introduced as an example of the applications of this durability/reliability design package. A detailed step-by-step procedure is utilized to develop the basic information needed to analyze the wheel assembly: material properties, geometry, and loading; the relationship between applied load and stress; and the degree of variation in specific material properties, wheel thickness, and service loading. An in depth documentation of the effect of these “real world” variations on wheel reliability is then presented in graphical form. Several different approaches in altering the design variables are used in order to thoroughly illustrate the resulting component reliability. Such information is particularly relevant where product quality and warranty formulation are concerned. / Master of Science

This thesis presents the results of a study done on the damage accumulation process in poly(ether ketone ketone) and its AS4 carbon fiber reinforced composites. The damage accumulation process was studied as a function of applied heat treatment. This study is the result of a project funded by duPont and was done in part to explain the dramatic change in fatigue properties observed at duPont as the applied heat treatment is changed. The mechanical properties were characterized using a battery of tests. The quenched composite systems have lower moduli, but higher toughness and elongations. The quenched systems also have the best fatigue performance and therefore, it can be concluded that the quenched composite systems have the best potential as far as industrial applications are concerned. Quenching has other advantages in industrial applications. These include decreased chances of operator error, and decreased processing times. The damage accumulation process was characterized using the acoustic emission method and also the drop in stiffness during flexure testing. It has been observed that the ultimate mechanical properties show a weak dependence on the applied heat treatment, whereas the damage accumulation process changes dramatically. A model has been developed to simulate the damage accumulation process. This model has then been used to predict the fatigue S-N curve in stroke control and to qualitatively relate it to the available fatigue data in stress control. / Master of Science

The ectomycorrhizal communities of three aspen-covered sites in southwestern Montana and southeastern Idaho with varying stand age, conditions, and soil types were compared. In all, 39 species of ectomycorrhizal fungi were associated with P. tremuloides. Dominant fungal species varied by site. Species reported on acidic soils in Europe and other species reported to be "early colonizers" were found exclusively on the acidic soils of the Butte site. Many "late stage" fungi such as Amanitas and Cortinarii were found on the older and more productive sites. Nine isolates of ectomycorrhizal fungi were tested for their ability to form mycorrhizae with P. tremuloides. Amanita muscaria v. formosa, A. pantherina, Paxillus vernalis, and Pisolithus tinctorius formed mantles and Hartig nets. Inocybe lacera and Piloderma croceum formed mantles but no Hartig nets. Dry weight, stem diameter, height and number of roottips increased in the young aspen seedlings inoculated with a majority of the fungi listed above. The implications for aspen survival and growth are discussed. / Master of Science

The flowfields of two axial-flow fans and one core compressor are studied in this thesis. The research data, previously gathered by other researchers, was obtained by means of a high-response dual hot wire aspirating probe. The probe measures total pressure and total temperature (and thereby isentropic efficiency) at several radial locations downstream of each rotor. The main objective of this research was to attain a heightened knowledge of sirbomachine losses and their source. To this end, two different methods of ensemble averaging the data are used in conjunction with data from the three rotors. Also, randomness calculations are performed for each rotor. The flowfield randomness of the two fans is shown to correlate well with their respective high tip losses. The core compressor is shown to have a very random flowfield, with no identifiable blade wakes, that extends across the entire blade span. This observation for the core compressor is supported by both contour plots and randomness calculations. Endwall boundary layer effects are thought to be much more predominant for the core compressor than for the two fans and are thereby the cause of the extent of the randomness in the core compressor flowfield. The randomness and losses for each rotor are expressed as a function of their inlet relative Mach numbers to see if shock losses are responsible for the randomness or losses. All three rotors are shown to have high tip losses. The high tip losses for the TS-30 rotor and Rotor 37 are shown not to be a function of inlet relative Mach number, while the TS-33 rotor has high tip losses that are thought to be partially due to a shock/boundary layer interaction. Aperiodicity, one category of randomness, is shown to increase with increasing inlet relative Mach number for the two axial-flow fans. Nonuniformity, another category of randomness, is shown to be independent of inlet relative Mach number for the two fans. / Master of Science

A laser Doppler anemometer was used to measure the axial and radial velocity components of hydrogen-air counterflow diffusion flames (CFDF). An axisymmetric opposed jet burner (OJB) used seeded air in one cylindrical tube, and a hydrogen-nitrogen mixture in the opposing cylindrical tube. Velocity measurements were made at four different operating flow rates, and were used to compute the associated strain rate fields. The results were used to qualitatively assess current CFDF modeling schemes, and to expand the knowledge of the fluid velocity field behavior within these flames. The data show behavior qualitatively consistent with most models and experimental studies: the radial velocity is essentially linear with radial position, and the velocity data collapse to functions of axial position only for regions away from the stagnation plane. However, the data also show a variable strain rate field and a relatively thick reaction zone, which are both inconsistent with CFDF models. The axial velocity fields also behaved unexpectedly as the operating flow rates were increased, transitioning from the characteristic N -shaped profile to an asymptotically-approaching profile. / Master of Science

A fast response method for the determination of temperature and equivalence ratio has been developed for turbulent premixed flames. This method utilizes chemiluminescent signals to make correlations with flame temperature and equivalence ratio. Emissions from two radical groups are used for the correlations: an OH system at 309 nm and a CH system at 431 nm. The experimental apparatus consists of a turbulent burner, an optical system (lenses, monochromator, and photomultiplier tube), and a data collection system (digital oscilloscope and computer). An optical system using fiber optics and band pass interference filters was also investigated. The spectra of turbulent, premixed methane flames of known stoichiometry were recorded. A high temperature Pt-Pt10%Rh thermocouple was used to establish flame temperature. The ratio of signal width to signal height of the OH spectra was used to correlate flame temperature. The ratio of OH to CH signal heights was used to correlate equivalence ratio. Turbulent correlations were compared to laminar correlations developed in previous studies. The effect of increasing turbulence on correlations was investigated. Applications for this technology and recommendations for future work are discussed. / Master of Science

This study is a geophysical investigation that uses reflection seismic and potential field data to contribute to the development of a structural model of the North American Atlantic Passive Margin beneath the Atlantic Coastal Plain of northeastern Virginia. Specifically, this study focuses between 37.5° and 38.5° north latitude and 75.5° and 77.5° west longitude. The geophysical data include two seismic lines that were reprocessed at the Regional Geophysics Laboratory at Virginia Polytechnic Institute and State University. In addition, gravity modelling is performed in order to test the model developed from the seismic data. Several important results have been achieved from this study. Lower Cretaceous fluvial sediments are less reflective than the overlying marine sequence. This observation is most obvious toward the east, particularly on line CF-1. Reverse faulting, which might be related to movement within the basement, is observed in at least one location on line NAB-11A, near Loretto, VA. Curiously, the dip is in the opposite direction of other reverse faults observed within the coastal plain. The thickness of Triassic strata in the Taylorsville basin is constrained by seismic reflection data and gravity modelling. Results indicate that the basin is approximately 3 km deep. The strata within the basin appear to be poorly reflective except where they locally onlap the bottom of the basin, which is marked by a prominent reflector that is interpreted to be a diabase sill associated with Jurassic magmatism. In addition, the basin appears to be intruded by moderately dipping dikes that were fed by the sill. The occurrence of basaltic material within the basin is confirmed by well log data. Probably the most important result of this study is the tectonic implications of prominent, arcuate potential field anomalies and their relationships to changes in midcrustal reflectivity observed on the east side of line NAB-11A. Gravity modelling confirms the likelihood of a nearvertical, anomalous, mafic mass that extends to the Moho. This observation is supported by the loss of contiguous reflections in this area. A similar observation was made along the southern extension of the same anomaly by Coruh and others (1988) who proposed that this feature is a dike swarm associated with Mesozoic rifting. It is proposed here that this body also could be an ancient Mesozoic magma chamber that collapsed during cooling after the Atlantic margin passed into the drift sequence. / Master of Science

The effects of a prerigor CaCl₂ injection and blade tenderization on several sensory and physical characteristics of beef infraspinatus and longissimus muscles were determined. Blade tenderization resulted in increased tenderness (P<0.05) of postrigor infraspinatus muscle as measured by sensory panel, and numerically higher, though insignificant (P>0.05), sensory scores for postrigor longissimus muscle. However, no improvements (P>0.05) in tenderness of prerigor CaCl₂ injected muscles were observed due to blade tenderization. Objective and subjective measurements revealed that prerigor CaCl₂ injected muscles were less tender (P<0.05) than postrigor muscles independent of blade tenderization. Furthermore, steaks from prerigor CaCl₂ injected cuts had lower (P<0.05) texture scores for both muscles and flavor scores for infraspinatus samples, as well as higher microbial counts (P<0.05) than samples from postrigor muscles. Increased aging from 3 days to 7 days resulted in improved (P<0.05) tenderness, but also resulted in decreased (P<0.05) flavor, texture, color, and overall appearance scores, as well as increased (P<0.05) TBA values and microbial load. / Master of Science