Incidents resulting in head injury generally involve components of both linear and rotational motion. The protection of the head from injury most often comes from the use of some form of helmet. Helmets currently are designed only to protect the head from linear accelerations. Recent research involving the analysis of concussion in professional football suggested that linear accelerations are more consistent in the prediction of concussion, with the resultant rotational accelerations correlating to the peak linear accelerations of the impact. This research proposes to determine if the situation of the head impact has an effect on the correlation of the linear and rotational accelerations, as well as to determine if the linear acceleration is consistent as the predominating factor of concussion in various linearinduced impact scenarios. Through the development of various impact test conditions using bicycle helmets on a biofidelic test headform and Hybrid III neck, it was determined that the correlation between the linear and rotational accelerations experienced by the head is affected in part by the impact situation. Additionally, while linear accelerations may be adequate predictors of concussion in some impact scenarios, it was determined that there are situations in which the rotational accelerations would be the more dominating factor in the expected probability of concussion.

A modern day airborne law enforcement helicopter is an exercise in compromise. Applying a Systems Engineering approach to selecting and outfitting a helicopter for airborne law enforcement can bring order to the process. The Suffolk County Police Aviation Section of New York was used as an example agency profile in analyzing mission requirements, establishing constraints, and analyzing alternatives. A benchmark survey was established for use in comparison. Benchmark trends indicated power margin and useful load as the primary performance requirements of an airborne platform with a primary mission of Emergency Medical Service (EMS) and a secondary mission of patrol. EMS requirements indicated the optimal airframe was a twin engine, while optimal for the patrol mission was single engine. Lack of mission systems integration with the airframe was the largest deficiency cited with reference to equipment. Thorough analysis of interfaces identified areas of systems integration that required special consideration. Current fleet deficiencies in power margin and useful load may be the result of over-laden aircraft, as opposed to underpowered airframes. Distinctions were made between goals and requirements. Analysis of subsystems resulted in suggestions of reduced mission profile weights for performance gains. Alternatives were examined by developing a grid analysis tool. A need was established for professional training of locallevel airborne law enforcement personnel in systems test and evaluation.

Hydrologic processes impact the functioning of aquatic ecosystems and influence fish population dynamics. The flow regime of a stream affects the structure, composition, and productivity of fish communities by regulating abiotic habitat conditions and biotic community processes. In the Great Smoky Mountains National Park (GRSM), native brook trout (Salvelinus fontinalis) populations have declined in some watersheds over the past decade, believed to be primarily due to episodic acidification. The potential affects long-term hydrologic patterns, temporal hydrologic trends, and hydrologic extremes have on brook and rainbow trout (Oncorhynchus mykiss) populations were explored in this study. The current GRSM fish sampling program began nearly two decades ago; a total of 69 streams, including 369 sites, are routinely sampled by GRSM fisheries biologists with standard methods. Detailed data is collected on the trout populations. The Nature Conservancy¡¯s Indicators of Hydrologic Alteration (IHA) was used to quantify the flow regime of each stream into 67 ecological relevant parameters. Because the trout sites were located in remote ungaged streams, the Hydrologic Simulation Program FORTRAN (HSPF) was used to simulate flows at each trout site for a study period lasting 18 years (1990-2007). Using local climate data the model was calibrated by adjusting parameters including storage, infiltration, runoff, and ground water for three elevation classes (low < 800 m ¡Ü middle ¡Ü 1,200 m < high) to observed stream flows from two USGS gaging stations and one NPS gaging station. The parameters defined by IHA included the a) magnitude, b) frequency, c) duration, d) time, and e) rate of change of hydrological events. IHAs were statistically compared to the surveyed trout populations. Results indicated the abundance of young-of-the-year (YOY) brook and rainbow trout significantly declined after extreme floods and droughts. In particular, low-flows during droughts significantly reduced recruitment for both brook and rainbow trout, which is likely due to decreased spawning habitat. Brook trout populations in larger low-elevation streams showed more stability compared to smaller headwater streams. The study provided GRSM resource managers a calibrated hydrology model with unique flow parameters characterizing GRSM watersheds, and possible influences hydrologic conditions may have on trout populations.

This thesis outlines the application of Computational Fluid Dynamics to the characterization of the gas distribution process inherent in automotive gas generators. The gas distribution process is important to understand as it greatly influences the overall performance of the device and its competitiveness in the marketplace. Presently, there is limited analysis that has been conducted on the gas generators. The current method involves conducting experiments using prototype hardware and high speed video to capture the flow field. This approach has proven to be useful; however, it lacks the ability to thoroughly study the fluid dynamics. Furthermore, the analysis has to be conducted on actual hardware and lacks the freedom inherent to computer CAD models and CFD where changes can be implemented and studied at a lower cost and in less time. The thesis details the general background on gas generators, the existing analysis methods, the construction of the CFD model, and a detailed look at the simulation results.

Among river engineers there is growing recognition that the success of a stream restoration project is dependent on the accurate prediction of sediment transport along a reach. To aid the design process, several numerical one- and multi-dimensional models have been developed to quantify in-stream sediment transport and hydraulic characteristics, and multiple sampling techniques have been proposed to establish the upstream sediment supply. However, the governing physical boundaries and variables (i.e., Manning’s ‘n’ variable, energy slope, and upstream sediment supply) required to initiate a sediment transport simulation are time consuming and difficult to measure in the field, and the estimation of these variables based on best professional judgment can lead to inaccurate predictions of sediment transport, resulting in the design of unstable projects. Thus, there exists a demand to understand the model sensitivity to key input parameters (i.e., Manning’s n value and sediment rating curves), and their effects on sediment transport simulations, especially when input parameters must be estimated and results can not be verified easily. The goal of this study was to evaluate the performance of CCHE2D, a twodimensional sediment transport model, in a Cumberland Plateau mountainous stream reach with complex morphology and coarse substrate. The model was utilized to simulate sediment transport through a single hydrograph. Bed elevation change along a reach (100-m scale), was evaluated by comparing the deviation between simulated and measured elevations at multiple monitoring points before and after the simulated flood event. The study objective included testing the sensitivity of overall bed change at a reach, local, and point scales to two key model inputs parameters, the Manning’s n value and sediment supply. Despite the relative stability observed along the site, simulated results show the model overestimated aggradation at a reach, local, and point scales. Statistical analysis of simulated results showed that bed elevation change was most sensitive to the bedload rating curve and Manning’s n value input parameters. Importantly, the site-specific bedload rating curve and measured roughness coefficient have the potential to reduce the error between simulated and measured results if accurate simulations of sediment transport can be achieved by a computational model.

The thesis objective is to safeguard power electronics used in modular converter applications. A new fault current limiting and protection circuit is proposed. The system level fault mitigation assemblies take a long time to remove a fault and within this time the IGBTs used in the Flexible AC Transmission System (FACTS) application will undergo high thermal and mechanical stress. Exposure to such conditions over a prolonged period of time will reduce the device lifetime, which is one of the major reasons why power electronics are not very popular in utility applications. Modular converter approach will reduce the device ratings required to mitigate the fault at power electronics level. The fault current limiting and protection circuit is tested using PSPICE simulation tool. The test set up is simple comprising of two IGBTs, one which acts as device under test (DUT) and another which acts as switch regulating fault seen by DUT. The test voltage is 480 Volt and R-L is varied over a range of L – 20nanoHenry, 2microHenry, and 10microHenry and R – 20Ohm, 50Ohm, and 100Ohm. The fault current limiting (FCL) and protection circuit worked accurately in each of the cases described above, thereby safely turning OFF the device within the short circuit withstand capacity (10microseconds) of IGBTs. The FCL and protection circuit can mitigate both Hard Switched Fault and Fault Under Load seen by the IGBT during short circuit condition. The circuit developed is different from the conventional protection gate drives available in the market and there is the possibility of customizing it further for modular blocks.

The purpose of this research is to validate a method of determining viscosity of highly viscous liquids with known surface tension in which is not confined by solid wall. The major part of the work involves comparing and analyzing the data from the Fluid Merging Viscosity Measurement experiments (FMVM), conducted onboard the ISS, with results from numerical analysis codes. In these experiments, two different size or equal size droplets are deployed and allowed to merge under the action of the known surface tension without any external forcing. The drop merging process is performed in the zero gravity environment of space on board the ISS. Simultaneously, computer codes are used to determine the viscosity by producing the matching curves of the experimentally measured contact radius speed with theoretical calculation for the model experimental data. Using this technique, the value of viscosity was determined with reasonable accuracy for several liquids tested.

A Natural Media Filter (NMF) and Constructed Treatment Wetland (CTW) pilot study was performed on an industrial landfill leachate site. The pilot study was designed to test if a NMF and CTW could be a low cost replacement option for the current wastewater treatment system. The main contaminates of concern for the leachate were poly-chlorinated biphenyls (PCBs) and ammonia. The pilot unit consisted of two systems, a subsurface flow CTW and an up-flow NMF that utilize mushroom compost as a media. The two units were run in parallel and were both supplied with untreated leachate. The CTW was operated at a flow rate of 0.3 gpm with a 2.2 day retention time. The goal of the study was to operate the NMF at 0.2 gpm with a half-day retention time, but due to operational issues this flow rate varied throughout the study. The Influent concentration of ammonia varied from non-detectable to 17 mg/l as nitrogen, with effluent concentration from the CTW fluctuating from non-detectable to 16 mg/l. For PCBs, influent concentrations during the majority of the study were non detectable, but during the last few months of the study large spikes in PCBs were recorded. The natural media filter was able to remove PCBs below limits of detection for most of the study, but breakthrough occurred towards the end of the study. For the constructed treatment wetland, removal of ammonia and nitrate/nitrite were modeled using the both the Plug Flow Model and the Tank-in-Series Model. The CTW was considered to be a Plug Flow unit and was oxygen limited. For the Natural Media Filter, the data collected did not allow for a proper evaluation of the adsorption capacity of the unit. A PCB mass balance was performed on the NMF from data collected from core samples of the compost. The unit was successful in removing PCB loading nine times higher than its designed capacity and the failure of the unit is attributed to short circuiting caused by the unit freezing.

A study to assess the utility of an aircraft referenced 3D audio display was undertaken to determine if there could be any improvements to pilot performance when operating under high workload conditions. Test subjects flew a general aviation light twin-engine aircraft under simulated single-pilot instrument flight rule conditions. Workload was elevated by ensuring each test subject had to execute an unexpected missed approach procedure and simultaneously handle a simulated engine failure. Subjective data was gathered using the NASA Task Load Index and a post-flight questionnaire on perceived performance, workload and situational awareness. Objective data on pilot performance was gathered using the research aircraft’s onboard instrumentation system. Within the limitations of having a low number (5) of test subjects available, subjective data results showed a perceived increase in situational awareness, performance, and a statistically significant reduction in workload. Although not statistically significant, the only objective impact to performance was a slight increase in heading control and course intercept. There was no corresponding performance increase in airspeed control, angle of bank control, or improvements to aircraft track. Overall, the results indicate that a 3D audio display would have utility and pilot acceptance as a supplemental navigational display, but would not result in any substantial improvements to pilot performance.

Precision op amps are widely used in instrumentation, automotive, and industrial applications. This thesis presents the design and characterization of a low-power precision operational amplifier that uses “ping-pong” autozero architecture for automatic offset correction. The op amp is designed for extreme environment applications, operating across a wide temperature range (minus 180 degree Celsius to plus 120 degree Celsius) with low offset, low drift and low power consumption. This design has been fabricated in a SiGe BiCMOS 0.5-micron process and the measured results demonstrate that the op amp is fully functional and achieves less than 40 microvolt input-referred offset voltage with 0.1 microvolt per degree offset voltage drift and 1 microwatt power consumption.