The Geoscience Laser Altimeter System (GLAS) is a waveform Lidar system carried on board the Ice, Cloud, and Elevation Satellite (ICESat). This study tested the use of GLAS data, from the L3e and L3g campaigns, to estimate total canopy height. GLAS footprint locations were sampled for ground truth. The GLAS-derived and field-derived canopy heights portrayed good correlation (R2= 0.8354). This study examined two representative fire fuel models within forests in East-Central Mississippi. GLAS waveforms were compared with field data for fire fuel models 9 and 10 of the fire fuel models described by Anderson (1982). GLAS data intensities were extracted and averaged to create predictive variables. Two variables were applied in Logistic regression to predict the probability of belonging to either fuel model (overall accuracy = 0.6875).

Stringent government mandates for the fuel economy and emissions of light-duty consumer vehicles have forced manufacturers to focus on improvements in these areas. Increased consumer pressure has also shifted the automobile market towards higher efficiency vehicles. This study investigates the use of intelligent engine peripheral control to improve fuel efficiency and reduce vehicle emissions. The conventional automotive alternator control strategy contributes to higher overall vehicle losses and increased fuel consumption through indiscriminate loading of the engine. The improved method focuses on the selective reduction of engine loading and the recapture of vehicle energy during braking using intelligent control of the alternator system. The concept was demonstrated on the Mississippi State University Challenge X hybrid vehicle. The fuel economy and NOx emissions of the vehicle were improved by 6.6% and 10.5% respectively over the drive cycle developed by the 2006 Mississippi State University Challenge X team to evaluate emissions.

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No description available.

No description available.

No description available.

Ceramic and refractory metal foams have a potential for use in extreme environments, such as in fuel elements within nuclear reactors both in space and terrestrial applications. In addition, infiltrating an open-cell ceramic foam with a continuous second phase can create an interpenetrating phase composite (IPC), consisting of a three-dimensional reinforcement structure. One aspect of investigation within this study was the influence of foam pore/strut size, foam composition, and foam density on neutronic and mechanical properties. Neutron transmission through open-cell tantalum carbide foams was measured using experimental techniques and modeled with Monte Carlo N-Particle (MCNP) transport code. Neutron transmission decreased linearly within tantalum carbide (TaC)/reticulated vitreous carbon (RVC) foams as areal TaC density increased. All MCNP modeling runs predicted slightly higher neutron transmission than what was experimentally measured, potentially indicating that the foam structure had a small influence on neutron transmission. Compressive strength and Young's moduli of tantalum carbide foams were measured for foam specimens that were exposed to thermal cycling and thermal shock, as well as for baseline specimens. Extensive micro-cracking was observed in the foams after 18 thermal cycles to 2100°C. However, thermal shock in liquid nitrogen did not produce observable micro-cracking in the TaC foams. The average strengths of baseline TaC/RVC foams ranged from 1.97 MPa - 3.82 MPa. The baseline TaC/PyC/RVC foams exhibited strengths ranging from 4.57 MPa - 12.60 MPa. The compressive strength of thermally cycled foams tended to be 1/3-1/2 that of baseline specimens. Another aspect of this study investigated the infiltration of RVC foams with tungsten powder in an attempt to form a tungsten-ceramic foam interpenetrating phase composite (IPC). It was found that tungsten particle size influenced infiltrated densities more than foam pore size. Significantly lower infiltrated densities were obtained using sub-micron tungsten than with 5-10 micron tungsten as a result of particle agglomeration. Infiltrated 5-10 micron tungsten achieved densities ranging from 23-25% theoretical within RVC foams, whereas sub-micron tungsten densities ranged from 11-16% theoretical. Constrained densification was observed during sintering of tungsten-infiltrated foams. / Ph. D.

Multifunctional material systems are systems that contain individual materials or components which are capable of performing multiple functions. The combination of functions into single entities allows for system-level benefits that are not possible through the optimization of subsystems independently. Benefits enabled through multifunctional designs include increased system efficiency through mass and or volume savings as well as part count reductions. Fiber reinforced polymer (FRP) composite materials are lightweight, high-strength materials that can be tailored to achieve a unique set of properties. These characteristics make composites ideal materials for multifunctional designs. The current research focuses on the production, optimization, and characterization of a multifunctional fuel cell system. This product combines fuel cell technology with composite materials technology to achieve a design that produces electrical power while also providing specific load carrying capability. The study investigates new system designs and new processing techniques, including vacuum assisted resin transfer molding (VARTM) and pultrusion. A metric which allows for the characterization of multifunctional fuel cell systems is developed and applied to three fuel cell designs. This metric uses Frostig's Higher Order Theory to analyze the mechanical behavior of the cells while the electrical performance of each device is based on its specific power output. For the cells investigated here, multifunctional efficiencies between 22% and 69% are achieved. The multifunctional efficiency is highly dependent on the transverse pressure applied to the fuel cell components, as this pressure determines ohmic resistances, mass transfer properties, and sealing abilities of the systems. The mechanical pressures at the GDL/Polar Plate interface of a model fuel cell system are explored via experiments with pressure-sensitive film as well as FEA studies, and an optimum structural pressure of approximately 200 psi is identified. Additionally, the effects that concentrated, bending loads have on the electrochemical performance of a model multifunctional cell are explored. The results indicate that one must give generous consideration to the out of plane loads which the fuel cell system will be subjected to (both inherent, structural loads resulting from processing conditions and external, applied loads encountered during operation) in order to achieve optimal multifunctional efficiency. / Ph. D.

This thesis describes a procedure to measure the transient effects in a fuel cell air delivery system. These methods were applied to model the 20 kW automotive fuel cell system that was used in Animul H2, a fuel cell-battery hybrid sedan developed by a group of engineering students at Virginia Tech. The air delivery system included the air compressor, the drive motor for the compressor, the motor controller, and any plumbing between the fuel cell inlet and the compressor outlet. The procedure was to collect data from a series of tests of the air delivery system with no load (zero outlet pressure) and at several loads. The air compressor speed, outlet pressure, and motor controller current were measured in response to a variety of speed requests. This data was fit to transfer functions relating the compressor speed, outlet pressure, or motor controller current to the speed request. The fits were found using a least squares optimization technique. After the experimental model was developed, it was augmented with an analytical model of the rest of the fuel cell system. The mass flow of the air was determined from the air compressor speed and outlet pressure with the compressor map. The fuel cell current was found by assuming a constant stoichiometric ratio. The power out of the fuel cell was calculated from the fuel cell current and the pressure with the polarization curve. The model of the fuel cell system was implemented in Matlab/Simulink. Several open and closed loop simulations were run to test the functionality of the fuel cell system model. The gross and net powers of the fuel cell system were found as a function of the compressor operating speed. The time it took for the system to come up to power as a function of idle speed was also found. A PID controller was implemented to allow the system to track a reference power request. The key contributions of this work were to develop a method to test the air delivery system to determine the dynamics of the system, to develop a model based on these tests and some analytical knowledge of fuel cells, and to use the model to simulate the operation and control of a fuel cell system. / Master of Science

The catalyst layer of a proton exchange membrane (PEM) fuel cell is a mixture of polymer, carbon, and platinum. The characteristics of the catalyst layer play a critical role in determining the performance of the PEM fuel cell. This research investigates the role of catalyst layer composition using a Central Composite Design (CCD) experiment with two factors which are Nafion content and carbon loading while the platinum catalyst surface area is held constant. For each catalyst layer composition, polarization curves are measured to evaluate cell performance at common operating conditions, Electrochemical Impedance Spectroscopy (EIS), and Cyclic Voltammetry (CV) are then applied to investigate the cause of the observed variations in performance. The results show that both Nafion and carbon content significantly affect MEA performance. The ohmic resistance and active catalyst area of the cell do not correlate with catalyst layer composition, and observed variations in the cell resistance and active catalyst area produced changes in performance that were not significant relative to compositions of catalyst layers. / Master of Science