Research has been conducted in recent years to determine the dynamic behavior of aircraft in unusual flight attitudes, particularly at very high angle-of-attack or post-stall conditions. The possibility that future advanced fighter aircraft will have the ability to perform controlled maneuvers at such attitudes is indicated by the current military aircraft flying qualities specification, MIL-STD-1797. As it becomes more important to understand the dynamics of aircraft at such flight conditions, the need for a meaningful and useful assessment of aircraft departure resistance in varying attitudes will increase proportionally. This thesis surveys some of the measures of departure susceptibility currently in use and examines a candidate for a new departure resistance criterion which offers distinct advantages over the traditional metrics. The new departure resistance criterion, called DP_SSV is essentially a measure of how much uncertainty the nominally stable plant can tolerate before being driven unstable. DP_SSV is calculated using structured singular values. In this thesis, DP_SSV is calculated over various flight conditions for a typical high-performance fighter aircraft which is represented by a full six degree of freedom, nonlinear simulation. The results are compared with those obtained by using a traditional departure susceptibility metric and by examining the eigenvalues of linearized forms of the aircraft model. The new criterion DP_SSV is shown to provide more information about the departure susceptibility of an aircraft than C_{ηβ_DYN} traditional metric, and to produce results in good agreement with the eigenvalue analysis of the stability of the aircraft for the conditions studied. The interpretation of DP_SSV is discussed, and suggestions for future investigation are also presented. / Master of Science

Grain sorghum is the principal food crop in Botswana. It is often grown in low fertility, coarse-textured soils. It is a common practice within some ethnic groups in Botswana to remove the primary panicle with the expectation that this will increase the grain yield by promoting tillers. A factorial experiment was conducted in the greenhouse to investigate the effect of panicle removal at anthesis and N on growth and yield of grain sorghum. Two N rates (25 or 100 kg/ha), three cultivars (Segaolane, Northrup King 2660, and Korwane), two main panicle treatments (present or removed), and five replications were used. Panicle removal increased the number of tillers and kernel weight but decreased yield (by reducing kernel number) in Segaolane and NK 2660. The kernel weight in Korwane did not respond to panicle treatments, but grain yield was reduced by panicle removal. In all cultivars, photosynthesis was reduced when the main panicle was removed. Korwane invested more assimilates in vegetative material (harvest index = 0.15), while Segaolane and NK 2660 partitioned more photosynthates into grain yield (harvest index = 0.5). Nitrogen application increased total dry matter, tillers, grain yield, and number of kernels in each variety except that Korwane was not responsive in kernel number. Nitrogen fertilization decreased kernel weight in two of the varieties but not Korwane. Kernel weight of Korwane was not affected by any of the treatments in this test. In summary, panicle removal appeared not to be a positive management practice for increasing grain yield of any of the varieties studied. On the other hand, N fertilization was beneficial to yield. / Master of Science

The purpose of this research was to determine consumers’ satisfaction with cooking systems commonly available in the United States. Five types of cooktops (conventional electric coil, gas flame, solid element, and halogen and electric coil under glass ceramic) and six types of cookware (glass ceramic, porcelain enamel-on-aluminum nonstick, stainless steel with an aluminum disk, heavy gauge aluminum, thin gauge aluminum, and heavy gauge aluminum with non-stick finish) formed 30 cooking systems. Fifteen consumers prepared one menu that represented four cooking operations (frying, boiling, thermalization, and waterless) with each of the 30 cooking systems. They also completed a three-part questionnaire to determine their knowledge and practices regarding the interaction between cooktops and cookware at the beginning, to assess their satisfaction with each cooking system, and to test their knowledge and preferences after completing the 30 cooking systems. Statistical analysis included repeated measures ANOVA, T-test, and General Linear Model (GLM). Statistically significant findings include: (1) Knowledge was different before and after completing the 30 cooking systems; (2) There was a relationship between consumers’ knowledge and overall satisfaction; (3) There was a relationship between optimum compatibility and consumers’ satisfaction; (4) There were differences among cookware of different gauges with respect to evenness of heating; (5) The cooking systems required different levels of user interaction; (6) There were differences in consumers’ satisfaction with cookware cleaning and frying due to the interior finish of the cookware. However, there was no significant difference in consumers’ overall satisfaction with the cooking systems. / Master of Science

A novel oligomer was synthesized for the purpose of investigating the effects of ultraviolet, thermal, and microwave polymerization. The synthesis involved an anionic ring-opening equilibration reaction to produce poly(dimethylsiloxane) which was then endcapped with an acid chloride to result in a material which was linear, flexible, had a functionality of four, and a strong dipole moment. Acrylamide terminated poly(dimethylsiloxane) was the end product and was cured with ultraviolet radiation, thermal energy, and microwaves. Characterization of the cured materials demonstrated interesting findings. Microwave cured materials resulted in higher degrees of cure than thermal or ultraviolet cured samples, despite using the best match for the heating rate-sample temperature profiles for each cure process. Several characterization techniques were employed and the procedures and results may be useful for others interested in finding the most efficient cure mode for their material. / Master of Science

This thesis presents the algorithms and methods to represent the skin of an engineering model with non-uniform, hierarchical B-spline surfaces. Non-uniform, hierarchical B-splines offer the mechanical designer many advantages: parametrically defined components may be added to a surface while maintaining C² surface continuity; detailed features may be added to a surface without globally affecting the B-spline control net; and an appropriate geometric basis for finite element meshing and analysis in the conceptual design phase can be established. These algorithms are applied to ASCYNT, a conceptual aircraft design code, to verify and validate the algorithms. A single-surface definition of an aircraft skin, appropriate for computational fluid dynamic and radar and infrared cross-section analysis, is designed using non-uniform hierarchical B-spline surfaces. / Master of Science

Problems related to estimating soil ingestion by wildlife species from analysis of feces were examined. Soil ingestion was investigated as a means by which wildlife may be exposed to environmental contaminants, particularly Pb. Titanium (Ti) and acid-insoluble residue (AIR) tracer methods for estimating soil ingestion were compared. The two methods were not significantly (P > 0.05) different when diet consisted of 10% (dry weight, d.w.) soil. When diet contained 5% soil, soil ingestion was more accurately estimated using the Ti method. Digestibility of soil can be ignored in the equation for quantifying soil ingestion from analysis of feces. Soil ingestion, as percentage dry matter intake (% DMI), by five wildlife species was estimated from analysis of feces or intestinal contents using the Ti tracer method. Soil ingestion by mourning doves (Zenaida macroura) was estimated using AIR analysis of crop contents. Mean (± S.E.) soil ingestion by Canada geese (Branta canadensis) and mallards (Anas platyrhynchos) were 4.92 (± 0.60) and 11.73 (± 1.54), respectively. Diets of short-tailed shrews (Blarina brevicauda) consisted of 5.20 (± 1.87)% soil, white-footed mice (Peromyscus leucopus) 16.21 (± 4.85)%, meadow voles (Microtus pennsylvanicus) 2.01 (± 0.34)%, and mourning doves 0.83 (± 0.41)% soil. Mallards collected from Killarney Lake, northern Idaho were analyzed for free erythrocyte protoporphyrin, fecal, liver, and kidney Pb concentrations, and soil/sediment ingestion. Sediment from the area contained 4485 ppm Pb (d.w.). Protoporphyrin was a poor indicator of Pb contamination at this level of exposure and/or under these conditions. Soil/sediment ingestion by mallards averaged 7.5% DMI. Tissue Pb concentrations indicated mallards were suffering from chronic exposure to low concentrations of Pb. Sediment collected from Killarney Lake (4485 ppm Pb) was fed to northern bobwhites (Colinus virginianus) at 8% DMI for 21 dad. Lead concentrations in blood, liver, and kidneys were determined and compared to control values. Treated and control birds showed no significant decline (P > 0.05) in feed intake and body mass did not change by greater than ± 1% over time. Lead in treated birds averaged 7 ppm (d.w.) in liver, 30 ppm (d.w.) in kidneys, and 126 ppb (wet weight, w.w.) in blood. Liver and kidney Pb concentrations of controls were < 0.1 ppm (d.w.) and averaged 630 ppm (w.w.) in blood. / Master of Science

This thesis presents the development, analysis, and design of a new low-ripple coupled-inductor boost topology. This topology is proposed for applications in which the conventional boost requires an input filter and two-stage output filter. One "zero-ripple" coupled magnetic provides both energy storage and second-order filtering of the input and output currents. Dc analysis is presented along with design guidelines. A novel magnetic structure is proposed which simplifies design and manufacture, while improving reliability. Small signal models for the proposed topology are presented along with hardware verification. It is found that, with proper damping, the small signal characteristics of the coupled-inductor topology are very similar to those of the conventional boost. This new boost topology offers a compact alternative to the conventional boost without sacrificing performance. / Master of Science

An interesting stability property, as fascinating as that of spinning tops and gyroscopes, is observable in the motion of an unbalanced ring spinning on a rough horizontal surface. An analytical and numerical study is performed to investigate the general motion of an unbalanced ring modeled as a thin ring with a particle attached to its rim. The translational motion is represented by the rectangular coordinates of the ring geometric center. The rotational motion is represented by a 1-2-3 set of Euler angles. The kinetic motion equations are derived with the use of Newton's second law and Euler's rotational motion equations. The types of motion considered are the pure-rolling and rolling-with-slipping motions. Given favorable initial conditions, ring properties, and a sufficiently large constraint force in the form of friction, the ring undergoes a pure-rolling motion. For other conditions, however, limitations on the magnitude of the friction force render the pure the mathematical model to allow switching from pure-rolling to rolling-with-slipping motion and vice versa. The general motions of the unbalanced ring, obtained by numerically integrating the governing equations with the use of the seventh-eighth order Runge-Kutta method, are in very good qualitative agreement to those observed during an experiment performed with the use of a high-speed video camera. / Master of Science

A wetland was constructed near Norton, VA by Westmoreland Coal Company to treat acid mine drainage (AMD) from an inactive coal refuse pile. The AMD had an average inflow pH of 7.0, and average inflow concentrations measuring 4 mg/L total Fe, 3 mg/L total Mn and 450 mg/L dissolved sulfate. An 18 month field study of water quality improvement and sulfate-reducing bacterial (SRB) populations revealed that the wetland was effectively treating the AMD. Iron and Mn both met compliance standards set by the EPA requiring an instream Fe concentration of 3 mg/L and an instream Mn concentration of 2 mg/L. SRB averaged 8.7 x 10⁴ through the 18 month study period as determined by the Most Probable Number (MPN) method. The concentration of sulfate was decreased by an average of 360 mg/L as the AMD passed through the wetland. In a separate laboratory study, the effect of carbon addition, pH and Fe concentration on microbial sulfate reduction and the subsequent precipitation of Fe and Mn was determined in mesocosms built to simulate a wetland. Mesocosms were constructed with plexiglass sheets and measured 6" x 6" x 24". Each mesocosm was filled with a 4-inch layer of limestone gravel beneath 17 inches of weathered pine bark mulch. A perforated PVC pipe was installed within the limestone layer to act as an underground drain. With mulch as the only source of available carbon, a 15% decrease in total sulfate concentration occurred in AMD containing initial concentrations of 1500, 750 and 375 mg/L sulfate. The population of SRB averaged 10⁵/ g dry mulch. The addition of 300 mg/L carbon as lactate resulted in an a 3 log₁₀ increase in SRB population. Following the addition of carbon as lactate, the concentration of sulfate decreased 95%. Total Fe decreased 90% from inflow concentrations prior to the addition of lactate, and decreased 96% following the addition of lactate to the AMD. The effect of varying the influent pH of AMD was studied using wetland mesocosms, and a pH of 3.5 adversely affected microbial sulfate reduction and water quality improvement. Populations of SRB decreased by 3 log₁₀ from an initial population of 10⁸ SRB/g dry mulch. Iron and Mn concentrations decreased 70 and 37% respectively. Hydrogen ion concentration increased to 7.0 and above when inflow pH was 4.5 and 6.0, but increased to an average of 6.4 when inflow pH was 3.5. The effect of different concentrations of Fe within AMD was investigated using wetland mesocosms, and total inflow Fe concentrations of 155 and 301 mg/L resulted in a greater percent decrease in sulfate concentrations than at a lessor Fe concentration averaging 85 mg/L. Total Mn decreased 12% at an inflow Fe concentration of 85 mg/L, and decreased 43% at an inflow Fe concentration of 301 mg/L. The results generated from both the analysis of the Pine Branch wetland and the laboratory mesocosm experiments demonstrate that subsurface flow constructed wetlands are a viable form for treatment of AMD. 2197820b-4775-4425-b667-55393f34b513,"This thesis deals with the deliberate insertion of nonlinear elements in second-order linear control systems for the purpose of improving their transient response. The main body consists of a method of obtaining a desired step response by placing a nonlinear computer in the forward loop. This computer fixes the system trajectory in the phase plane by determining the required output velocity for the error present at any time. An inner control loop adjusts the output velocity to agree with the computed signal in an extremely short time, thus giving a very close agreement between actual and desired responses. Several examples are presented to show the application of this method, and experimental verification is obtained with an analog computer. Areas of future study and practical limitations are discussed in the final sections of the thesis. / Master of Science

The objective of this thesis is to develop an analysis approach for formulation of transduction or input/output representations for magnetostrictive actuators. This transduction model is developed through application of an electro-magneto-mechanical impedance modeling approach which combines both the mechanical dynamics and coupled behavior of the actuator device. Lumped and continuous mechanical impedance elements model the actuator dynamics and the constitutive relationships for Terfenol-D characterize the electro-magneto-mechanical interaction. Experimental analysis of a Terfenol-D actuator serves to verify the developed models and provides an indication of actuator non-linearity. The developed transduction model allows for various device behavior analysis including dissipative power consumption, force and stroke output, and efficiency as a transducer. An actuator design strategy based upon the dynamics of the actuator and a driven external system is presented and allows for analysis of various actuator behaviors in terms of device parameters. The Terfenol-D actuator as a collocated actuator/sensor is also made possible with the transduction model. / Master of Science