An ongoing debate persists of the value of computerized delivery of instructional material. At the center of this debate about the value of computer-assisted-instruction (CAI) is (1) the lack of a theoretical base and (2) the question of whether CAI influences the learner. Research begun by Brunswik allows the value of accommodation of individual learning preferences to be applied. CAI also has the capacity to supplement the presentation of textbook content and support educators using a multimodal approach to teaching that accommodates individual preferences. This study examined the development of an environment to presented stimulation which could add to the motivation of learners. This study investigated the relationship between the creation of a CAI learning environment based on Brunswik’s psychology and 102 master and doctoral students' cognitive styles. The study investigated the ability of two cognitive measures to predict the CAI presentation method best suited for an individual's cognitive ability. Two different cognitive measures were regressed against three different CAI presentation methods (text only, text and static graphics, and text and animated graphics). These three different methods were used for delivery of a basic instructional design since they were simple for the user to follow and easily created via a multimedia environment for the designer. Instruction using these methods was limited to three content areas: random sampling, systematic sampling, and skewness of distribution. An Aptitude-Treatment-Interaction (ATI) analysis was used to study the interaction between participants' cognitive attributes and CAI presentation types. While a significant effect was not found in most of the recall tests, many disordinal interactions demonstrated tendencies that warranted further study. An ANCOVA was also performed using the total immediate recall scores showing significant differences among the CAI presentation types. The results of a one-way ANOVA found that participants assigned to the text only CAI presentation method tested better than their counterparts using the graphic additions to the textual instruction. / Ph. D.

The purposes of this study were to examine how teachers responded to ethical issues in the workplace and to prepare materials for use in teacher training and staff development programs. To determine teacher responses to certain ethical situations, twenty open-ended scenarios describing ethical situations were developed. Twenty social studies teachers from school divisions with 25,000 students or more and twenty social studies teachers from school divisions with 3,500 students or less were selected and on-site interviews were conducted with each teacher responding to four randomly selected scenarios. Responses were transcribed, analyzed, and distilled. The twenty scenarios and the teachers' responses were then used as a basis for the development of materials for teacher preparation programs for one college and staff development programs for one school division. All but two scenarios reflected a difference between what teachers perceived to be the action most taken by teachers and the action perceived to be the most ethical. Responses by teachers to ethical situations revealed that potential and practicing teachers would benefit by the study of professional ethics in their professional preparation program. / Ed. D.

School boards are the governing bodies for school divisions. Their successful operation is essential to the success of the school division. "Best practice", as indicated in the literature, calls for school boards to recognize the need to examine or assess their own performance and to set the criteria or goals by which they will evaluate their performance and to create a composite of strengths and weaknesses in relation to the criteria they set for themselves. Boards should design or select evaluation instruments which reflect local performance criteria and instruments that are open ended so that other items may be included as board members desire. The development of objectives for the improvement of the boards' performance should be based on an evaluation of themselves discussed and agreed to in a regularly scheduled annual meeting with a facilitator and site for the event predetermined. Finally, the process should be focused on the board as a body; not on the individual board members. This study solicited information describing the practices of school boards in Virginia relative to evaluation of themselves as boards and compared those practices with literature-based "best practice." Defining "best practice" was accomplished by reviewing educational literature on the practice of board evaluation. The literature was screened for components recommended as required in effective school board self-evaluation. Components recommended as effective practice were determined to be "best practice." The questionnaire was designed in two sections. The first grouping of questions on the survey was to identify the divisions where school boards practiced self-evaluation. Subsequent queries, in section two, gathered information that would allow description of the practices used by school boards who practiced self-evaluation. Section two, also, posed questions regarding the boards' use of procedures that were determined to be components of "best practice". A survey questionnaire was mailed to the superintendents of all 132 school divisions in Virginia inquiring about their board's practices of evaluating their own performance. Responses were received from 128 of the 132 divisions, a 97% rate of return. Only forty-one (32%) of the responding school divisions reported having school boards that evaluate themselves. Are school boards in the Commonwealth evaluating their own performance? The major findings of this study indicate that most school boards in Virginia, more than two out of three, do not practice school board evaluation. School boards in Virginia that allege participation in the practice of school board evaluation do not use many of the components of self-evaluation recommended as "best practice". School board evaluation is used less often in those divisions of medium size than in other divisions and less often in those divisions associated with counties as their governing units than in other divisions associated with other types of governing units. / Ed. D.

Polymeric diphenylmethane diisocyanate, pMDI, has become an important wood binder in recent years, due to its excellent performance in wood-based composites. However, much still remains unknown about the nature of their bonding mechanism. This research describes efforts to learn more molecular information about the pMDI-wood bondline, and to further improve the bonding performance. In order to correlate molecular phenomena with macroscopic performance of wood-adhesive bondline, low frequency molecular motions in wood were probed using dynamic mechanical analysis (DMA) and ¹³C cross-polarization, magic-angle spinning (CP/MAS) NMR. A correlation between the CP time constant <T_c_h* and the dynamic storage modulus E’ was established for dry wood, but was not valid for wet wood samples. Two types of pMDI with properties similar to commercial resins, except for isomer ratio, was synthesized. The one with isomer ratio similar to commercial resins was analyzed with ¹⁵N CP/MAS NMR. The results show that the pMDI-wood bondline is a heterogeneous complex of urethanes, polyureas, residual isocyanates and biurets. The network structure is controlled by the curing variables such as temperature and time. Urethane formation was detected under relatively mild cure conditions. Thermal decomposition of urethanes (120°C) and polyurets (185°C) were detected. ¹⁵N NMR was demonstrated as a powerful technique, but suffers from signal overlap which prevents a clear evaluation of the relative contributions of urethane and urea formation. Another type of pMDI with higher 2,4’- isomer content was used to investigate the effects of isomer ratio on bonding mechanism. The chemical species found in the heterogeneous bondline are similar, except that urethane formation is less evident here. Relaxation studies show very different behaviors, in which the bondline with higher 2,4’- isomers may have a higher molecular mobility. A fracture toughness test method, contoured double cantilever beams (CDCB), was developed to evaluate the macroscopic performance. They both showed strong bonding, and there was no significant difference found. To explain the strong bonding of pMDI and wood, an interpenetrating polymer network (IPN) theory was hypothesized. ¹³C CP/MAS NMR and DMA were used to evaluate this hypothesis. The results were inconclusive due the limitations of the techniques. / Ph. D.

In this research, photochemical molecular devices were designed to perform photoinitiated electron collection. These devices were synthesized, characterized and their spectroscopic, photochemical and electrochemical properties investigated. The general formula for these systems is {[(bpy)₂Ru(BL)]₂MCl₂}⁵⁺ (M = Ir^III and BL = dpq (2,3-bis(2- pyridyl)quinoxaline) or dpb (2,3-bis(2-pyridyl)benzoquinoxaline), or M = Rh^III, BL = dpp (2,3-bis(2-pyridyl)pyrazine)). The functioning of these devices as photoinitiated electron collectors was determined. Through the use of a sacrificial electron donor in a photolysis experiment, the functioning of the {[(bpy)₂Ru(dpb)]₂IrCl₂}⁵⁺ trimetallic complex as a photochemical molecular device for photoinitiated electron collection was established. The interaction of the electron donor with the trimetallic complex was also investigated through a Stern-Volmer quenching study. To tune the properties of the chromophoric units, [Ru₂(bpy)(BL)]²⁺, the bridging ligand was varied. The dpq bridging ligand was modified through the incorporation of electron donating and electron withdrawing substituents. The 6,7-dimethyl-2,3-bis(2’- pyridyl)quinoxaline and 6,7-chloro-2,3-bis(2’-pyridyl)quinoxaline bridging ligands were synthesized and characterized. The ruthenium mono- and bimetallic complexes utilizing these bridging ligands, as well as dpb, were synthesized and investigated. It was shown that the light absorbing and electrochemical properties of these [Ru(bpy)₂(BL)]²⁺ chromophores can be varied by altering the π-acceptor nature of the bridging ligand. / Ph. D.

Dynamic route guidance systems which are products of the Intelligent Transportation Systems (ITS) Technology have been reasonably useful in guiding motorists from their origins to destinations. In general, transportation networks could be used more efficiently if dynamic route guidance information could be provided to motorists at all relevant locations along freeway corridors. This is however not possible, particularly because of financial constraints. It is therefore imperative that information be provided to motorists at locations where it will be of maximum benefit. The objective of this research is to develop methodologies and computer models for estimating utility of motorist information at different locations along freeway corridors. Such models will be very useful in guiding transportation professionals to optimize resources when providing guidance information to motorists. The methodologies have been developed based on both recurrent and non recurrent traffic congestion situations. The methodologies assume that motorists behave rationally and will divert from congested freeways to uncongested arterials based on the user equilibrium traffic assignment criteria. The utility of information estimation has however been based on total system time savings. Computer models have been developed based on the methodologies using the C++ programming language. Nonetheless, because the computer models have been developed based on historical traffic data, they have been validated using real time simulation models developed with the SIMSCRIPT II.5 programming language. The validation process proved reasonably successful. Many factors which include traffic volumes on alternate arterial routes to a given freeway link, the number of alternate routes to the freeway link especially under recurrent traffic congestion conditions, link lengths, volume of traffic on the freeway link and incident history in the case of non recurrent congestions influence the utility of information. With the particular networks investigated in this research however, the results indicate volume of traffic on the freeway links as the most influencing factor, since freeway links with relatively high traffic volumes tend to have relatively high utility values. The reason for this is probably because of the small size nature of the networks used, hence as a result all the freeway links tend to have only one or two alternate routes and the traffic volumes on the arterial links also do not differ significantly. The freeway link volumes therefore become the dominating factor in influencing the information utilities. / Ph. D.

Assessed the contribution of demographic, illness, and psychosocial parameters to the psychological adjustment of 64 caregivers of children with or at risk for HIV infection. As a group, caregivers reported a significantly greater level of psychological distress than the general population while the level of well-being reported by caregivers was similar to that of the general population. Illness and demographic parameters failed to significantly predict aspects of caregiver adjustment, together accounting for only six and nine percent of the variance in caregiver psychological distress and well-being, respectively. Psychosocial variables, however, contributed significant increments in the variance of both domains of caregiver adjustment. Specifically, higher levels of caregiver psychological distress were associated with poorer caregiver health status, greater number of coping strategies reported, and higher levels of family conflict. Higher levels of caregiver well-being were associated with perceptions of less impact of negative life events, lower levels of family conflict, and greater perceptions of emotional support. Implications for future research and intervention are discussed. / Ph. D.

An atomic force microscope (AFM) was used to measure surface forces between a glass sphere and a flat fused silica plate under a number of conditions. Hydrophobic surfaces exhibiting contact angles ranging from 0 to 109° were prepared by reacting silica with octadecyltrichlorosilane (OTS). Contact angles, AFM images, and infrared transmission spectra showed that OTS forms clusters on the silica surface. The presence of water in the reaction was shown to greatly influence the formation of these clusters. Forces were measured between surfaces coated with identical (symmetric) and different (asymmetric) amounts of OTS to determine contributions from hydrophobic forces. The results showed that the hydrophobic force parameters of the asymmetric interactions, K132, can be predicted from those of the symmetric interactions, K131 and K232, using a geometric mean combining rule. Asymmetric force measurements were conducted between a hydrophobized glass sphere and a bare silica plate in dodecylamine hydrochloride (DARCl) solutions as a function of pH in an effort to simulate the forces involved in bubble-particle interactions for the quartz-amine flotation system. The appearance of the hydrophobic force in these measurements correlates well with the pH range of maximum flotation recoveries for quartz-amine flotation system. / Ph. D.

An efficient design formulation for feedforward Active Structural Acoustic Control (ASAC) systems for complex structures and disturbances is presented. The approach consists in a multi-level optimization procedure. The upper level part is carried out in the modal domain, where the optimum modal control forces and modal error sensor components which minimize the total radiated power are obtained. These optimum modal parameters are then used in a set of lower level optimization problems to find the physical characteristics of the actuators and sensors to be implemented. In this work, the developed formulations are demonstrated in three systems of increasing complexity. First, a simply supported plate excited by at a single frequency is presented. The study of this relatively simple case serves as a benchmark for more complex systems permitting the evaluation of the performance of the design approach. Then, the formulation is implemented for the case of a simply supported cylinder under multiple frequency excitations. In this case numerical techniques are used to obtain the structural and acoustic responses showing the capabilities of the formulations to be implemented to complex structures. In both cases (i.e., the simply supported plate and cylinder), the results show that the optimum configurations yield significant reductions in the total radiated acoustic power depending on the number of control channels and allowed control effort. Moreover, it is demonstrated that the proposed design approach gives a clear insight into the relative contributions of the modes to the sound field providing a better understanding of how they have to be controlled in order to minimize sound radiation. Finally, the design approach is validated in an experimental arrangement for the attenuation of sound radiation from and enclosed box structure under a realistic periodic disturbance. Up to 36dB of attenuation in the acoustic power is obtained in the experiment demonstrating the effectiveness of the proposed design approach for practical applications. / Ph. D.

A comprehensive study including modeling and control of aeroelastic instabilities in free flying aircraft with flexible wings has been completed. The structural model of the wing consists of a trapezoidal composite plate rigidly attached to a fuselage with rigid-body degrees of freedom. Both quasi-steady and quasi-static aerodynamic strip theories were used to analyze several different flutter mechanisms for a variety of low aspect ratio wing configurations. The most critical flutter mechanism was found to be body-freedom flutter, a coupling of aircraft pitching and wing bending motions, for wings in a forward-sweep configuration. In addition, a modal approximation to the flutter eigenvalue problem was used to substantially reduce computation cost, making the resulting model very attractive for use in larger multiobjective design packages. Composite ply angle tailoring was investigated as a passive method of increasing the body-freedom flutter airspeed of an aircraft model. In addition, wing mounted piezoelectric sensor and induced-strain actuator patches were used in conjunction with active feedback control laws to increase the airspeed at which body-freedom flutter occurs. Two control laws were tested, coupled and independent modal position feedback, to delay frequency coalescence and thus increase the flutter airspeed. / Ph. D.