In a form of controlled electromagnetic suspension, a permanent magnetic is levitated by a magnetic field; the field is produced by electrical currents passing through coils. These currents are the control input. In a Large-Gap system the coils are at some distance from the suspended body; in general, there is no closed form expression relating the currents to the flux at the point of the suspended body. Thus, in the general case, it is not possible to establish control-theoretic results for this kind of Large-Gap suspension system. It is shown, however, that if the coil placement configuration exhibits a particular cylindrically symmetric structure, expressions can be found relating the coil positions to the flux. These expressions are used to show the existence of a unique equilibrium point and controllability, in five dimensions of control, for a generic form of Large-Gap system. The results are shown to remain true if the suspended body is rotated about a particular axis. Closed form expressions are found for the currents required to suspend the body at these variable orientations. An inequality between difference classes of experimental inputs is shown to be a necessary condition for suspension of the body. It is demonstrated that the addition of coils to the system cannot lead to six dimensions of controllability. Let the system be given by the standard control equation 𝑥̇=𝐴𝑥+𝐵𝑢 Closed form expressions are found for the eigenvalues of 𝐴. In the course of proving that some coil placement restrictions may be relaxed, 𝐵 is shown to be related to the Vandermonde matrix. / Ph. D.

As a result of tireless and well directed efforts from its professional communities, geography as a field of study experienced a tremendous revitalization during the past few decades. Collegiate geography educators, however, cannot afford to become satisfied; additional needs in both research and application persist if the discipline is to continue its evolutionary resurgence. One continuing question is: now that they have careers as professional geographers, how do collegiate geography graduates view their program experiences? Specifically, for this investigation questions for selected topics and sub-topics (or areas) were: what was the extent of their initial exposure to these during their programs; how relevant were these to their current jobs; and what was the utility of including these in degree programs? Also, what types of expertise did they develop since graduation? The topics of interest were: other disciplines, geography, business, education, computers, and communications. A collection of 181 academic and non-academic professional geographers provided their opinions about these questions. Their answers indicated that: (1) by far, communication, education, and computers had the highest ratings for utility, relevance, and expertise gained after graduation; (2) ratings for exposure during degree programs were comparably lower for all topics; and (3) the academics and non-academics, although from different occupational environments, agreed most of the time. The discussion includes further detail about the ratings and focuses on how the two groups responded. Additional attention focuses on implications of the results in terms of the impacts on collegiate geography programs. The presentation concludes with recommendations for future research and application. / Ph. D.

The purpose of this study was to investigate differences in academic performance and persistence among freshman participating in fraternities, corps of cadets, and athletics in comparison to matched samples of non-members. The study showed that, on average, students were adversely affected by participation in athletics and fraternities when sex, race, college, major, and academic ability were controlled. There was no evidence to conclude that participation in these organizations had any consistent effect on persistence. / Ph. D.

"I was sitting here trying to think if some of the comments that we are sitting here making were unique to blacks in the tenure and promotion process, and I think that for the most part they are. I was trying to figure out why, and one thing that came to mind was the level of fear or trust that we have in the system that tends to be dominated by white male mentality and thought. Whereas, our contemporaries who are not black are faced with a lot of similar types of concerns, I think they’re inclined to trust the system more in that they are not necessarily fearful of how this subjectivity or discussion will be turned against them, merely because of their color, because that is not an issue..." This study was conducted to discover and explore perceived factors that influence the achievement of tenure for African American faculty at two predominantly white institutions. Data for this study were collected by conducting focus group interviews with African American faculty. A total of 22 faculty participated in one of four focus group interviews. Data were analyzed by the constant comparative and axial coding method of analysis. The findings of this study indicate that progression towards tenure for African American faculty is related to how they experience the institutional environment and to structural factors related to the tenure process. Three major themes characterize their experience: (a) issues related to the traditional criteria for tenure, (b) value of tenure, and (c) interaction with the academic environment, that is, the institutional culture. The following are common threads underpinning the factors identified: (a) institutional fit, (b) double standards, (c) racism, (d) prejudicial attitudes and perceptions, and (e) trust and dishonesty. The challenge to attain tenure, despite the obstacles are viewed by the participants in this study as an intrinsic motivation to stay and “play the game”. / Ph. D.

Part 1. Discotic liquid crystals are a relatively new class of mesogens in which the molecules self assemble in the melt state to form highly ordered columnar stacks. The ability of the molecules to display this type of mesomorphic behavior is a function of their shape; a semi-rigid core with flexible "arms" gives the necessary flatness and broad diameter conducive to columnar stacking. We first set out to make discotic liquid crystals by synthesizing a series of three-armed aryloxy-s-triazines with aromatic Schiff's base moieties at the molecular periphery and investigate the thermal and optical behavior of these compounds. We discovered that these molecules were in fact rigid rod, or calamitic, liquid crystals based on the optical textures and X-ray diffraction patterns in the mesophase. This is in direct conflict with published but unsubstantiated reports of the "discotic” behavior of similar compounds. The failure of these compounds to give crystals suitable for X-ray crystal structural analysis prompted us to utilize electron microscopy to look at the microstructures formed when dilute solutions were evaporated onto different substrates. Surprisingly, these aryloxy-s-triazines in several different solvents formed well defined microtubules of varying dimensions on both copper and polymeric substrates. Hole diameters of up to 10³ Å and lengths of up to 0.5 cm were commonly seen using both transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Finally, we understood via molecular modeling studies that the aryloxy-s-triazines adopted a rod shape in the mesophase due to the inherent flexibility of the ether linkages at the triazine core. By substituting 1,3,5-triphenylbenzene cores in place of the s-triazine we hoped to rigidify the molecules and prompt them to stack in a discotic or columnar fashion in the melt state. This plan was successful based on the X-ray diffraction patterns and optical textures observed with these compounds in the mesophase. Part 2. α-Aminonitriles and their derivatives have played an important role in the synthesis of enantiomerically pure and racemic α-amino acids for almost ninety years. Much less studied is the alkylation behavior of this particular class of compounds. The ability of the aminonitrile moiety to be deprotonated with a base and reacted with various electrophiles allows for the placement of carbonyl functionalities virtually anywhere in a synthetic system through hydrolysis of this aminonitrile group after alkylation. Using this "umpolung”, or reversed polarity, approach we have demonstrated the utility of this class of compounds by reacting them with several activated aromatic dihalides and aliphatic dihalides to produce high molecular weight poly(bis-α-aminonitrile)s which were in turn hydrolyzed under mild conditions to afford the corresponding polymeric ketones. This ability to form both wholly aromatic and mixed aliphatic/aromatic polyketones is extremely powerful and unprecedented in the literature to date. During the course of this research, it was also discovered that some of these α-aminonitriles underwent side reactions which were undesirable for polymerization but which produced interesting compounds in their own right. These enaminonitriles and quinodimethanes which resulted from dehydrocyanation were studied extensively in order to exploit the possible polymerization of these reactive intermediates. Finally, another route to ketones is through the reaction of enamines with appropriate electrophiles followed by acid hydrolysis. Research towards polymeric ketones was Carried out using monomeric di(enamine)s and aromatic diacid chlorides with the hope of producing high molecular weight polymeric 1,3-diketones. Unfortunately, the extent of reaction was not high enough to produce high molecular weight polymers. / Ph. D.

The emergence of new data models requires further research into federated database systems. A federated database system (FDBS) provides uniform access to multiple heterogeneous databases. Most FDBS's provide access to only the older data models such as relational, hierarchical, and network models. A federated system requires a meta data model. The meta model is a uniform data model through which users access data regardless of the data model of the data's native database. This dissertation examines the question of meta models for use in an FDBS that provides access to relational, object oriented, and rule based databases. This dissertation proposes Cyrano, a hybrid of object oriented and rule based data models. The dissertation demonstrates that Cyrano is suitable as a meta model by showing that Cyrano satisfies the following three criteria: 1) Cyrano fully supports relational, object oriented, and rule based member data models. 2) Cyrano provides sufficient capabilities to support integration of heterogeneous databases. 3) Cyrano can be implemented as the meta model of an operational FDBS. This dissertation describes four primary products of this research: 1) The dissertation presents Cyrano, a meta model designed as part of this research that supports both the older and the newer data models. Cyrano is an example of analytic object orientation. Analytic object orientation is a conceptual approach that combines elements of object oriented and rule based data models. 2) The dissertation describes Roxanne, a proof-of-concept FDBS that uses Cyrano as its meta model. 3) The dissertation proposes a set of criteria for the evaluation of meta models. The dissertation uses these criteria to demonstrate Cyrano's Suitability as a meta model. 4) The dissertation presents an object oriented FDBS reference architecture suitable for use in describing and designing an FDBS. / Ph. D.

A structural health monitoring technique, developed at the Center for Intelligent Material Systems and Structures, employs piezoelectric (PZT) materials for tracking the structural impedance to qualitatively identify damage. The mechanical impedance of a structure is a function of the structure's mass, stiffness, damping, and structural boundary conditions. Changes in any of the above-mentioned properties lead to a change in the mechanical impedance of the structure and a change in the impedance pattern of the structure. The mechanical impedance of a structure can be measured by coupling the electrical and mechanical impedances via PZT patches. Therefore any change in the mechanical impedance leads to a change in the electrical impedance of the PZT bonded to the structure of interest. However, change of the electrical impedance can also occur due to changes in temperature. Piezoelectric materials have been known to have temperature dependency regarding their basic properties, such as the dielectric constant and the piezoelectric coefficient. In this thesis, this temperature dependency will be investigated. The motivation of this work is linked to the impedance-based nondestructive evaluation (NDE) technique which employs PZT sensors for tracking changes in the structural impedance, by measuring the electrical impedance, to qualitatively identify damage. However, for this NDE technique to be successful in all types of environments, it must be insensitive to temperature variations. As mentioned earlier, piezoelectric materials have strong temperature dependency and a temperature compensation procedure is necessary. Therefore, two software correction techniques were developed to eliminate the effects of temperature in the electrical impedance measurements of PZT sensors. (NDE) technique which employs PZT sensors for tracking changes in the structural impedance, by measuring the electrical impedance, to qualitatively identify damage. However, for this NDE technique to be successful in all types of environments, it must be insensitive to temperature variations. As mentioned earlier, piezoelectric materials have strong temperature dependency and a temperature compensation procedure is necessary. Therefore, two software correction techniques were developed to eliminate the effects of temperature in the electrical impedance measurements of PZT sensors. The second correction technique is based on the sensor output. Through experimental investigation, it was found that temperature will have the effect of shifting the electrical impedance magnitude of the piezoelectric sensor, while leaving the impedance phase unaffected. To characterize the temperature effects in PZT materials, a temperature coefficient which is independent of frequency has defined. Finally, based on the defined temperature coefficient, a simple temperature compensation technique has been implemented successfully, eliminating the effects of temperature on PZT sensors while not eliminating the effects of temperature on the structure. / Master of Science

The pales weevil, Hylobius pales (Herbst), and the deodar weevil, Piss odes nemorensis Germar, are regeneration pests of pine plantations in the eastern United States. Attempts to sample regeneration weevils in Virginia have met with little success. Two trap types were field tested to determine their effectiveness in sampling H. pales and P. nemorensis populations in Virginia Christmas tree plantations. Labor intensive pit traps, using natural host materials and synthetic volatiles, caught significantly more weevils than PVC pitfall traps baited with synthetic volatiles alone. No differences in trap catches were observed between stationary and rotated traps. Vegetation management had no effect on trap catch. However, it was observed that newly planted white pine seedlings (Pinus strobus L.) were fed upon by H. pales at Significantly higher rates in plots not managed for competing vegetation than in herbicide treated plots. Feeding activity in mowed plots was intermediate. Trap catch did not correlate with seedling damage within or among sampling periods, or between years. The seasonal activity of both species is reviewed in detail. Mark-and-recapture techniques used to assess trap efficacy showed traps baited with pine material were most effective, irrespective of trap type. The response of H. pales adults to different ethanol-and-turpentine ratios in a laboratory bioassay did not vary with respect to gender or age. No gender differences in response to treatments were observed in these studies. / Master of Science

Research on Dynamic Visual Acuity (DVA) to date has conventionally used visual targets originating from a single fixation point and moving in a single, predictable linear direction. These procedures (presumably dictated by apparatus constraints) ensured the observer knew when and from where the target would appear. A computerized test for DVA was developed and used to test DVA under viewing conditions not testable with conventional apparatuses. Two target direction conditions were compared over 3 durations (170, 370, 570 ms) and 5 velocities (0, 22, 45, 70, and 100 deg/s): fixed target direction (target originated from single fixation point, and moved horizontally from the observer’s left to the observer’s right, as has been the convention in DVA research over the past 57 years ) and random target direction (the target emanated randomly from one of six screen locations and move linearly across the screen to a point 180 deg opposite its origin). As hypothesized, the random direction condition, which may more closely represent DVA as applied in the real world, proved to be significantly more difficult relative to the fixed direction condition. Contrary to expectations of the current research as well as the general consensus in the DVA literature, data were also presented indicating that the generally accepted relationship between increased target velocity and increased DVA thresholds, may be in part the consequence of conventional apparatuses and procedures. The effect training was also investigated on under both fixed and random target direction conditions. No significant effect of training was demonstrated over four sessions, which may be a result inadequate sensitivity of the test. Strengths and weaknesses of a computer testing platform to test DVA are discussed. / Master of Science

Specialty magazines play a role in shaping how females of all ages view the world and themselves. This world for teens is often focused on dating, fashion and the evolving and conflicting issues of self-confidence and body image. Home, health and career messages predominate women's magazines. A young woman retains the opportunity to increase her bone density through her late twenties at which time bone density holds steady until the onset of menopause. The 1989 calcium Recommended Dietary Allowances (RDA) were increased from 800 mg/d to 1200 mg/d for only one female age group: 19-22 y, which was extended to 19-24 y to maximize the opportunity for peak bone accretion. In recognition of this change and the inverse relationship that exists between bone mass and body weight, the frequency of calcium and weight loss content was compared between teen-focused magazines (Seventeen and Mademoiselle) and women's magazines (Good Housekeeping and Ladies Home Journal) for two four-year periods (1986-89 and 1991- 94). Women's magazines were found to have 20 times the calcium coverage in overall area (ads, articles and columns) and 40 times the number of calcium ads as found in teen-focused magazines. In contrast, teen-focused magazines published 1.4 times more weight loss area than was found in women's magazines. The calcium message has primarily been offered to women past their best opportunity to affect bone mass. There was no impact on calcium coverage for either magazine type due to the release of the 1989 RDAs. / Master of Science