Lyotropic and thermotropic high strength liquid crystalline polymers have become an important area of research and development in polymeric, high performance materials. These materials have afforded excellent high temperature stability and high strength in the oriented direction, but not in the transverse direction. Hence, "balancing" the properties in both directions is an important area of research. Segmented polymers composed of an amorphous, glassy engineering thermoplastic, and an anisotropic, liquid crystalline polymer were synthesized and investigated. The isotropic phase is based upon a ductile poly(arylene ether sulfone), while the anisotropic segment is based on a rigid poly(arylate) moiety. The difunctionally terminated, controlled molecular weight poly(sulfone) oligomers were synthesized via a nucleophilic aromatic substitution reaction. Functional end groups included phenolic, acetate and carboxyl. The structure and reactivity of these oligomers was characterized by analytical techniques, including FT-IR, NMR, and polymer physical characterization methods such as, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and thermal mechanical analysis (TMA), and dynamic mechanical thermal analysis (DMTA). The well characterized, difunctionally terminated poly(sulfone) oligomers were then utilized along with ester forming monomers in a subsequent melt acidolysis reaction to form segmented poly(sulfone)-poly(arylate) co- or terpolymers. Earlier work by Lambert (281-283) showed that solution and interfacial techniques could only be utilized to synthesize segmented polymers with low poly(arylate) contents. The melt acidolysis technique allowed the synthesis of poly(sulfone)- poly(arylate) polymers with poly(arylate) contents as high as 90 weight percent. Along with a high degree of agitation, the melt acidolysis technique utilized chlorobenzene as a solvent in the initial stage of the reaction to enhance the mixing of the poly(sulfone) oligomers and ester forming monomers, allowing true segmented polymers to be formed. This was proven by FT-IR and extraction studies, which determined that very little of the original poly(sulfone) oligomer was extracted by refluxing chloroform. The morphology of these polymers was studied by polarized optical microscopy, and wide angle X-ray scattering. Low weight fraction poly(arylate) co- and terpolymers were determined to be amorphous, while higher poly(arylate) weight fraction polymers (15 weight percent or greater) were found to be semi-crystalline or liquid crystalline. Thermal analysis (DSC) also gave evidence that these materials were semi-crystalline or liquid crystalline. Also, as the weight fraction of poly(arylate) was increased, a significant improvement in solvent resistance was observed as well as an improvement in the modulus and tensile strength. / Ph. D.

Waterproofing membranes have been used on bridge decks for almost three decades in order to prevent chloride ingress into concrete. However, the performance of these membranes have yet to be adequately evaluated. Therefore, this research was carried out primarily to evaluate the integrity and effectiveness of standard preformed membranes placed on concrete bridge decks. The actual conditions of a bridge deck were simulated in the laboratory using scaled-down reinforced concrete specimens. Forty-eight outdoor and twelve indoor specimens were cast. Three types of standard preformed membranes (Bithuthene 5000, Royston lOA, and Protecto Wrap M400-A), punctured with holes of various sizes and frequencies per unit area, were placed on the specimens. All of the specimens were overlaid with 2.5 inches of hot-mix asphalt, except four outdoor (control) specimens and three indoor specimens. / Master of Science

A l0-kW horizontal axis wind turbine was studied to determine the effects of wind shear and gravity on rotor blade bending moments. A drag sphere based wind measuring system was designed to measure rapid fluctuations in wind velocity at two different heights. However, severe power line noise problems with the low level signals forced the use of standard rotating cup anemometry. Rotor blade bending moments were obtained with strain gages mounted on blade extenders near the root of the instrumented blade. Rotor angular position data were obtained with a photocell arrangement. The one per revolution primary bending moment frequency was caused mostly by gravity-induced bending. Also present is the 6 Hz blade natural frequency. A logarithmic atmospheric boundary layer (ABL) profile was used to estimate wind conditions at the upper level. Examination of the bending moment data revealed good agreement with values predicted from the ABL profile (within 4% in the mean) indicating the profile was a good mean approximation. A logarithmic atmospheric boundary layer (ABL) profile was used to estimate wind conditions at the upper level. Examination of the bending moment data revealed good agreement with values predicted from the ABL profile (within 4% in the mean) indicating the profile was a good mean approximation. / Master of Science

The effects of time-dependent electron density fluctuations on a synthesized time domain reflectometry response of a one-dimensional cold plasma sheath are considered. Numerical solutions of the Helmholtz wave equation, which describes the electric field of a normally incident plane wave in a specified static electron density profile, are used. Included in this work is a study of the effects of Doppler shifts resulting from moving density fluctuations in the electron density profile of the sheath. / Master of Science

A data acquisition and control system (DACS) has been designed and constructed for use during propagation experiments with the OLYMPUS satellite. OLYMPUS is a European Space Agency experimental satellite that broadcasts coherent at 12, 20 and 30 GHz and is viewed from Blacksburg, Virginia at an elevation angle of 13.9°. This low elevation angle yields a relatively long atmospheric path which serves to accentuate propagation effects. The DACS is a custom design which collects propagation, environmental and status information and periodically calibrates external equipment. Beacon signal strength is measured via a hybrid analog/digital receiver. The analog portion the receiver utilizes the coherency of the satellite beacons to track 20 and 30 GHz signals to the noise floor. The digital portion of the receiver is contained within the DACS and consists of a stand-alone microprocessor which filters the beacon signal to determine the power in a 3 Hz bandwidth. Additional DACS circuitry collects analog and digital input channels and controls external through digital output channels. Digital outputs are used to reference the collected to known by performing periodic calibrations on external equipment. Analog input channels are used to measure quantities including external temperature, wind speed wind direction, while digital inputs monitor alarm conditions. The VIEW program utility permits an operator to graphically view data in real time. In addition, collected data is stored to tape without an interruption in data collection. DACS operation has been virtually continuous since data collection was started on August 3, 1990. / Master of Science

Master of Science

When diaphragm action is considered in the design of post-frame buildings, the endwalls may require supplemental reinforcement to replace lost strength and stiffness, due to placement of large doors and openings in the endwalls. The diaphragm design standard, ASAE EP484, does not provide guidelines concerning such endwall reinforcement. Flat steel strapping 1s proposed for use as supplemental reinforcement to replace this lost strength and stiffness. An analysis procedure was developed, with the intention of serving as input to endwall diaphragm design. Using PPSA 3.00 and calibrated endwall data, a computer structural analog was developed that “mimics” the deflection of an actual solid endwall. Sections of the structural analog were removed to represent a centered door opening. Fictitious members representing steel-strap bracing were added to the remaining endwall diaphragm to restore the endwall deflection to that of the same endwall with no door openings. Large corner post uplift values were observed for tall endwalls. For purposes of endwall analysis, it is necessary to distribute corner post uplift forces to the other posts along the adjacent endwall and sidewall. Along with the tabulated results in this research, this analysis procedure provides building designers a tool that will enable them to analyze virtually any endwall-door combination. All that is required is PPSA 3.00 software (or equivalent), a personal computer, and endwall stiffness data. / Master of Science

This thesis describes an adaptive protection scheme that performs the collection of the voltage and current phasors during post-fault period, tracking the power swing phenomena, identifying the onset of instability, and then issuing a stabilizing command. In this work, the protection system is to maintain the reliability! ensure the secure operation, and prevent total collapse of the power system. The work is based upon methods of clustering for meter placement in a bulk power system, and selecting the pilot points for installing the phasor measurement units (PMU) to measure the bus voltage phasors and associated branch current phasors. According to the network law, fast calculation of state estimation can be made from these measurements. Because the on-line assessment of transient stability has to provide a quick and approximate result, the direct method which determines stability without explicit integration techniques is applicable in this study. The results of the system stability prediction in real-time by digital computer simulation under stable and unstable operating conditions are presented. / Master of Science

The use of a microchannel plate as an optical encoding device has many advantages. These include large surface area and large-scale signal averaging. This instrument was designed to obtain and interpret the information generated by the optical transform of a microchannel plate. It will be shown that a large amount of information about solution interactions and properties can be obtained from such an instrument. / Master of Science

The study evaluates widely used slope estimation algorithms with the aim of determining similarities or differences between results obtained by each, the accuracy of methods in modelling actual slope, and the suitability of these methods for site-specific and non-site specific applications. The data used in the study comprise of 24 artificial surfaces generated from mathematical equations and a natural surface represented by a USGS Digital Elevation Model of the Salem Quadrangle, Virginia. The concept of using artificial surfaces was to enable determination of accuracy without the requirement for field observations. The gradient calculated from partial derivatives of the equations was used to compare results from different methods. The natural surface was used to validate the findings of the study on artificial surfaces. The results were then statistically evaluated using ANOVA and regression analysis. It was found that the methods could be used interchangeably for non-site-specific applications while for site-specific applications the differences could be very significant. / Master of Science