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

The base test method provides a means of determining the load-carrying capacity of multiple spans, multiple purlin line standing seam roof systems. The method uses results from a single span, simply supported, two purlin line experimental tests, the 1986 American Iron and Steel Institute Specifications, and stiffness analysis of the actual design system. Currently, a base test must be conducted for each combination of purlins, deck panels, and clips that a manufacturer uses. The objective of this thesis is to investigate the possibility of eliminating the size of purlins, the orientation of purlins, length of span, and the presence or absence of insulation from a manufacturer’s required base test matrix. The findings of the investigation are based on the results of four different series of gravity load base tests. It was found that a linear relationship exists between the percentage of through-fastened capacity obtained by the purlins and their effective section moduli. This relationship was found to exist regardless of the purlin type. / Master of Science

A method for predicting the unsteady, subsonic, aeroservoelastic response of a wing has been developed. The air, wing, and control surface are considered to be a single dynamical system. All equations are solved simultaneously in the time domain by a predictor-corrector method. The scheme allows nonlinear aerodynamic and structural models to be used and subcritical, critical, and supercritical aeroelastic behavior may be modeled without restrictions to small disturbances or periodic motions. A vortex-lattice method is used to model the aerodynamics. This method accounts for nonlinear effects associated with high angles of attack, unsteady behavior, and deformations of the wing. The vortex-lattice method is valid as long as separation or vortex bursting does not occur. Two structural models have been employed: a linear model and a nonlinear model which accounts for large curvature. Both models consider the flexural-torsional motion of an inextensional wing. / Master of Science

A fast response method for detection of ignition and extinction of liquid spray flames has been improved. Also, a method of determining fuel-to-air ratios and temperatures of pre-mixed, gaseous flames has been developed. Both methods utilize chemiluminescent signals from an OH system centered at 309 nm and a CH system centered at 431 nm. The ignition and extinction method was improved by replacing an optical system composed of lenses and a monochromator by a system composed of a fiber optic cable and band pass interference filters. The use of a solid-state photodiode instead of a photomultiplier tube was investigated. Transient histories of the OH and CH signals were recorded by performing light-off ignition and intermittent ignition flame tests. These signal histories were compared to histories obtained using the original apparatus. The fuel-to-air ratio and temperature detection method was investigated by recording the spectra of laminar, pre-mixed methane flames of known stoichiometry with a lens, monochromator, and photomultiplier tube set-up and measuring the flame temperatures with a high-temperature Pt-10%Rh thermocouple. Various combinations of signal characteristics were found to be functions of fuel-to-air ratio and temperature. Optimum signals for monitoring with a detector were determined. Recommendations for future work in this area are discussed. / Master of Science

This thesis is concerned with the analysis of a Rectilinear Distance Location Allocation Problem, where the costs are directly proportional to rectilinear distances and the amount shipped. The problem is formulated as a Mixed Integer Bilinear Programming Problem and as a Discrete Location Allocation Problem. Using linear programming relaxations constructed via the Reformulation-Linearization Technique (RLT), the latter formulation is shown to provide stronger lower bounds and is therefore adopted for implementation. In addition, cutting planes are developed to further strengthen the linear programming relaxation. The special structure of the resulting linear program is exploited in order to get a quick lower bound via a suitable Lagrangian dual formulation. This lower bounding scheme is embedded within a finitely convergent Branch and Bound algorithm that enumerates over the location decision variable space. An illustrative example and computational experience are provided to demonstrate the efficacy of the proposed algorithm. / Master of Science

Analytical expressions describing the input current spectrum of the flyback Pulse-Width-Modulated, Zero-Current-Switched Quasi-Resonant-Converter, and Zero-Voltage-Switched Quasi-Resonant-Converter are derived in terms of normalized circuit parameters. These analytical results are tested against experimental results. The same numerical example is presented for these three converters in which the input current spectrum is computed for various line/load conditions and the results are mutually compared. Detailed experimental results are presented for the same three converters as well as for the flyback Zero-Voltage-Switched Multi-Resonant-Converter. The effects of any parasitic oscillations in the experimental circuit are also considered. / Master of Science

New ventilation fans for Navy ships need to filter chemical agents from the supply air. This requires much greater pressure ratios than in earlier fans. This research was conducted to understand the performance of these new fans. LDV measurements of axial and tangential velocities were made in a Navy fan from upstream stations, throughout the blade row, and downstream into the stator. Data were collected two ways: (1) averaged over the entire rotor cycle and (2) averaged at each rotation angle. Upstream bimodal probability densities of the axial velocity component were found in the cycle-averaged data. Bimodal distributions indicate instabilities in the stagnation or separation lines or vortex shedding. The phase-averaged data show there to be a dependency of velocity on rotor positions. Downstream profiles mapped the large separation region downstream of the rotor. The downstream region shows recirculating flow and reattachment as the flow moves into the stator section. Phase-averaged profiles in the stator inlet plane show the periodic rotor wake as it enters the stator. The resulting flow angle does not match the stator angle. In the blade row, the phase-averaged velocity profiles show negative tangential velocities near the leading edge and separation occurring near midchord. The region influenced by the separation extends across most of the blade passage as the fluid approaches the exit plane of the rotor. The separation in the blade row contributes to the poor performance of the fan and low pressure recovery. / Master of Science

Rudbeckia hirta is a tender perennial or self-sowing annual which is becoming increasingly popular as a garden flower and a component of wildflower meadow mixes. It may also have -considerable potential for use as a potted crop. R. hirta has a defined juvenility period but preliminary unpublished results suggested that plants originating from different latitudes may possess unequal juvenile periods and exhibit dissimilar sensitivities to photoperiod. Seven R. hirta ecotypes originating from latitudes ranging from 30.l0oN to 45.l0oN were exposed to long days (LD) at different leaf numbers to determine juvenile phase length and speed of floral initiation. Ecotypes from northern latitudes had fewer leaves at maturity and, overall, there was a quadratic relationship between latitude of origin and number of days to first flower from start of LD. Once plants were mature, the speed of floral initiation and development also varied among ecotypes. / Master of Science

The calculation of electromechanical forces that are present in a machine due to the magnetic field set up by current-carrying conductors and coils, especially when in the presence of permeable iron, is one of the most important and difficult problems in the vast field of the theory and design of electrical machines. It is a problem, moreover, which is usually dealt with by empirical methods based upon test results or by the use of numerical techniques such as Finite Element Analysis (FEA). In this thesis, analytical formulas are developed to evaluate the electromechanical forces and torques involved in brushless surface-mounted permanent magnet machines directly from, design parameters. In the first model, a slotless stator design is assumed while in the second model, the conductors are considered as being embedded in the stator iron. Both the models thus developed are then tested by means of a numerical method (FEA) and their utility in performing parametric studies is demonstrated in the case of the first model. / Master of Science

The "zonal grid method" is widely used to alleviate the difficulties for flow field calculations with complex geometry. In the present study, a patched grid method is employed in the computation of flow fields behind a two-ring flameholder which forms a multiple-connected region. A standard K - ε model is used to close the system. The calculation is performed by using a SIMPLE type algorithm in two subdomains in a body-fitted coordinate system With nonstaggered grid arrangements. The concept of conservative interpolation technique is applied to treat the flux conservation across the interface. The effect of the distance between these two rings on the flow pattern is studied. It is found the distance of the rings either in the axial direction or in the radial direction does not change the strength of the recirculation zone, but alters the flow pattern. The predicted streamlines, the turbulence kinetic energy K, and the reverse mass flow rate are presented. / Master of Science