This study concerns the effect of column temperature on selectivity in gas chromatography (GC). Reversal of peak elution order at different temperatures is observed when selectivity is sufficiently changed by changing the temperature. A study of homologous functional groups and the elution order of a test mixture was made at several temperatures, by keeping constant operating chromatographic parameters such as column head pressure, split ratio, sample concentration, injector and detector temperature. The homologous series studied were esters, carboxylic acids, ketones and alkanes. The stationary phases used were Carbowax (Supelcowax 10), and 5% diphenyl and 95% dimethyl silicone ( HP Ultra 2). The identification of each compound was confirmed by two methods : comparing retention times, and spiking the sample. The results of an investigation for accurately determining the dead time is also presented. The experimental results of using 10% methane in helium and the results of a theoretical model based on Poiseuille's equation were studied and compared. It is concluded that dead time calculations are a major source of error for the calculations in this work. In addition, a derived thermodynamic equation based on the Van't Hoff equation was obtained and used to calculate the molar enthalpy and entropy of compounds over a range of temperatures. The experimental thermodynamic values were compared with the theoretical values obtained from the Clausius- Clapeyron equation. From the data obtained, a graph of In k' (retention factor) versus 1/ temperature for a homologous series, known as a Van't Hoff plot, predicts a reversal of elution order where an intersection of two lines occur. Selectivity of the stationary phase has changed solely due to temperature effects. This can only occur when different solute/solvent interactions are present. This work is an attempt to predict when peak inversion should occur based on the Van Hoff's plot. Experimental result are presented that confirm the prediction. / Master of Science

The behavior of composite steel joists with various degrees of shear connection is investigated. The results of eight full-size composite joist tests, conducted as a portion of the study, are presented. Joist spans range from 24 ft. to 30 ft. and depths from 8 in. to 18 in. Six types of mechanical connectors provide horizontal shear transfer capacity. Steel deck supported slabs, from 3 in. to 4 in. thick, are used for all tests. The results of the experiments are used to evaluate the flexural strength and associated failure modes of partially composite and fully composite joists. The results of each test are compared to theoretical calculations based on an ultimate strength flexural model. The joists are classified by how the provided amount of shear connection compares to the bottom chord yield force and by how the provided amount of shear connection in conjunction with the top chord capacity compares to the bottom chord yield force. Behavior typical of each classification is discussed. Correlation with previously conducted composite joist tests of similar configuration is also discussed. / Master of Science

One of the difficulties in solving E:MI problems is the lack of diagnostic tools available. In this thesis work, a tool, called Noise Separator, is developed, which can be used to decipher the differential-mode (DM) noise and the common-mode (CM) noise from the total noise. A noise separator hardware is built and tested. The results show that at least 50 dB rejection to either DM or CM noise is achieved for frequency ranging from 10 KHz to 30 MHz. With the aid of the Noise Separator, EMI filter design is made easier. / Master of Science

There is a critical need for materials with very high dielectric constant to be integrated in the next generation of 64- and 256-Mb ULSI DRAMs. Materials in the Pb-based perovskite family have high relative permittivities and have consequently attracted a world wide attention. Cubic Lead Lanthanum Titanate (PLT) is one of the prime candidates in this respect and its structure and properties in the thin film form were investigated in the present study, for potential application in the ULSI DRAMs. Thin films of Lead Lanthanum Titanate corresponding to 28 atomic percentage of lanthanum were prepared by metalorganic decomposition (MOD) process. Solutions were prepared from lead acetate, lanthanum acetate and titanium iso-propoxide and thin films were then spin-coated from these solutions on PtlTilSi0₂/Si and sapphire substrates. The films were fabricated from two solutions of different compositions. The composition of the first solution was determined assuming that the incorporation of La³⁺ in the PbTi0₃ structure gives rise to A-site or Pb vacancies whereas for the composition of the other solution the creation of B-site or Ti vacancies was assumed. The effect of excess lead on the structure and the properties was also studied for 0% to 20% of excess PbO. The x-ray diffraction patterns of all films at room temperature indicated a cubic structure with lattice constant of 3.92 A. Optical and electrical measurements showed that the films made assuming B-site vacancies had better properties. In general, excess PbO was found to improve the optical as well as the electrical properties of films. However, in films with Bsite vacancies this improvement occurred only up to 5-10% of excess PbO, while higher PbO additions had a deleterious effect. The films had high resistivity, good relative permittivity, low loss, very low leakage current density, and high charge storage density. A type-B film with 10 % excess Pb had a permittivity of 1336 at 100 kHz. It also had a charge storage density at room temperature of around 16.1 μC/cm² at a field of 200 kV/cm and no sign of polarization loss or breakdown was observed up to 10¹⁰ cycles under the accelerated degradation breakdown test. / Master of Science

The response of foals to the stress of weaning was examined in terms of a behavioral protocol and the responses of plasma ascorbate, serun1 cortisol, and the serum cortisol response to an ACTH challenge. Behavior scores (1 to 10) as an index of stress were assigned to each foal daily, with high scores indicating less stress and better adjustment. The experimental plan was a 2 X 2 factorial of pre-weaning diet and stall weaning method. Foals were raised on pasture supplemented with hay and a pelleted concentrate (PHC) or pasture supplemented with hay only (PH). Foals were placed in stalls singly or in pairs for weaning. Gender influences were also examined. The foals exhibited characteristic behavioral and physiological responses to the social dislocative stress of weaning. Behavior scores were lower in paired than in single foals (p = .008) and tended to be lower in PH than PHC foals (p = .15). No differences in post-weaning plasma ascorbate concentrations were found among treatments. Responses of serum cortisol to an ACTH challenge were lower in PH than PHC foals (p = .001) and in paired than single foals (p = .058), and lower responses were taken to represent adrenal depletion arising from stress. Behavior scores were positively correlated with the response of serum cortisol to ACTH. Both behavioral data and the serum cortisol response to ACTH indicate that foals were better able to cope with weaning stress when supplemented with concentrate prior to weaning and when weaned singly. / Master of Science

Bioindicators were used to assess degradation to fish resident to the Clinch River drainage. Species studied were rock bass (<i>Ambloplites rupestris</i>), northern hogsucker (<i>Hypentelium nigricans</i>) and striped shiner (<i>Luxilus chrysocephalus</i>). The data were collected in parallel with a study of the index of biotic integrity (IBI) on fish communities also in the Clinch River drainage. Sites selected for this study were identical to those used for IBI. Data obtained from fish sampled at relatively pristine sites (i.e., high IBI) were used as references to be compared with data obtained from fish sampled at sites suspected of human impact (low IBI). Results demonstrated variable bioindicator response to degraded sites. While bioindicators were elevated at certain sites, others were not significantly different from corresponding reference values. Furthermore, results showed a number of correlations between certain bioindicators and IBI and several IBI components, implying a possible relationship between these initial individual-level responses (biondicators) and eventual longer term population- and community-level effects (i.e., IBI and its components). However, these results also varied between impacted sites. Future field application of bioindicators in the presence of such a multiplicity of potential stressors was discussed. / Master of Science

Most work in knowledge acquisition and manipulation has focused on expert systems. Expert systems solve one kind of problem: heuristic classification. This thesis extends some advances in knowledge engineering to a broader class of problem: design. Design is examined as a generic activity, found in many fields of professional practice. A theoretical framework is developed that supports the refinement of design from high-level concepts through implementation. This framework includes a computational model that is shown to be completely general (Turing-equivalent). Therefore, the theory and model are suitable for representing any design project. They are applied specifically to software development. Practical support for software designers is offered in a prototype software design system. Existing work in automated knowledge acquisition is used to transfer knowledge about a design from the designer to the automated tool. Consistent support for refinement of design choices at any level of detail makes design a maintainable activity. This opens new possibilities for automated code generation, automated maintenance, and the nlore effective management of software at a higher-level design representation. / Master of Science

The study of human-environment interactions by geography is traditionally conceptualized as the "man-land" theme in geographic analysis. Feminists and other post-structuralists criticize that conceptualization. Following those critiques, this study evaluates ecofeminism as a possible alternative to a "man-land" formulation. Ecofeminism is presented and analyzed as a school of thought that also studies human-environment interactions. Vandan Shiva's discourse and treatment of Chipko provide the central ecofeminist case study. The thesis elucidates ecofeminism's sensitivity to the geographic concept of place in order to determine whether or not ecofeminism is adequate as a geographic theory. Analysis of Vandana Shiva's texts reveals that ecofeminism universalizes and fails to accommodate the geographic concept of place. / Master of Science

The design, performance, and analysis of a soil vapor extraction system to identify zones most conductive to air transport and quantify kair in sequential soil layers is presented. A multi-level extraction well, with alternating solid and screened sections, was utilized to characterize multi-layered media. The field site, located in the Carolina Slate Belt within the physiographic region known as the Piedmont, is comprised of alternating layers of different soil types of varying kair, including thin bands of clay, silt, and sand. The pneumatic test consisted of one multi-level extraction well and four multi-level pressure monitoring wells. Screen locations were based on previous site characterization. Vapors were extracted at one screen while pressure, temperature, and volumetric flow rate were monitored using a computer data acquisition system. Data was analyzed by both steady-state and transient solution techniques using pressure drawdown versus time data collected at various locations. Results from vapor extraction tests indicate that the multi-level approach is advantageous when dealing with heterogenous media, since the most permeable layer was identified. Transient and steady-state solutions indicate that a k_air= 2.0 X 10⁻⁷ cm² is representative of the located permeable layer within the subsurface. Vacuum system, formation, and extraction well characteristics are evaluated to determine pressure as a function of volumetric flow rate. / Master of Science

Periodic gratings in waveguides act as frequency selective mirrors making them very useful as spectral filters for wavelength division multiplexing applications and as end mirrors for narrow linewidth lasers. A study of the spectral characteristics of both single and double gratings in planar dielectric waveguides is presented. The analysis of light propagation in a planar dielectric waveguide with sinusoidal boundary perturbations is carried out using coupled-mode theory. Power reflection and transmission coefficients are calculated for single gratings as well as two gratings of the same period and depth but arbitrary lengths and separated by a specified distance. The spectral response is examined for several cases. The influence of grating period, depth, and length in the single-grating case as well as separation of the gratings in the case of a double grating is investigated. Numerical results for example cases are presented. The results of this study are valuable for designing grating devices which are becoming increasingly attractive to broadband fiber-optic communication systems. / Master of Science