Engineering Commons^™

Enhancing The Resolution Of Imaging Systems By Spatial Spectrum Manipulation, Wyatt Adams

Dissertations, Master's Theses and Master's Reports

Much research effort has been spent in the 21st century on superresolution imaging techniques, methods which can beat the diffraction limit. Subwavelength composite structures called ``metamaterials" had initially shown great promise in superresolution imaging applications in the early 2000s, owing to their potential for nearly arbitrary capabilities in controlling light. However, for optical frequencies they are often plagued by absorption and scattering losses which can decay or destroy their interesting properties. Similar issues limit the application of other superresolution devices operating as effective media, or metal films that can transfer waves with large momentum by supporting surface plasmon polaritons. In …

Electro-Optic Antenna Elements For Passive Phased Array Radar, Evan Gawron

Dissertations, Master's Theses and Master's Reports

Passive phased antenna arrays are utilized in military and civilian radar systems to determine the received signal origination. Phased array placement for optimal reception is challenging due to the required supporting electronic hardware and the associated coaxial cabling that typically accompanies each antenna channel. Low noise amplifiers and frequency conversion hardware add size and complexity, limiting possible positions for phased array placement. Eliminating required phased array electronic subcomponents without sacrificing function would allow placement onto smaller agile platforms, such as unmanned systems and rapid deployment networks. Electro-optic (EO) antenna elements utilize an optical waveguide embedded between the antenna and ground …

Community Detection In Complex Networks And Application To Dense Wireless Sensor Networks Localization, Sakineh Yazdanparast

Dissertations, Master's Theses and Master's Reports

Complex network analysis is applied in numerous researches. Features and characteristics of complex networks provide information associated with a network feature called community structure. Naturally, nodes with similar attributes will be more likely to form a community. Community detection is described as the process by which complex network data are analyzed to uncover organizational properties, and structure; and ultimately to enable extraction of useful information. Analysis of Wireless Sensor Networks (WSN) is considered as one of the most important categories of network analysis due to their enormous and emerging applications. Most WSN applications are location-aware, which entails precise localization of …

Estimation Of Multi-Directional Ankle Impedance As A Function Of Lower Extremity Muscle Activation, Lauren Knop

Dissertations, Master's Theses and Master's Reports

The purpose of this research is to investigate the relationship between the mechanical impedance of the human ankle and the corresponding lower extremity muscle activity. Three experimental studies were performed to measure the ankle impedance about multiple degrees of freedom (DOF), while the ankle was subjected to different loading conditions and different levels of muscle activity. The first study determined the non-loaded ankle impedance in the sagittal, frontal, and transverse anatomical planes while the ankle was suspended above the ground. The subjects actively co-contracted their agonist and antagonistic muscles to various levels, measured using electromyography (EMG). An Artificial Neural Network …

Online Learning Of The Spatial-Temporal Channel Variation In Underwater Acoustic Communication Networks, Wensheng Sun

Dissertations, Master's Theses and Master's Reports

Influenced by environmental conditions, underwater acoustic (UWA) communication channels exhibit spatial and temporal variations, posing significant challenges for UWA networking and applications. This dissertation develops statistical signal processing approaches to model and predict variations of the channel and relevant environmental factors. Firstly, extensive field experiments are conducted in the Great Lakes region. Three types of the freshwater river/lake acoustic channels are characterized in the aspects of statistical channel variations and sound propagation loss, including stationary, mobile and under-ice acoustic channels. Statistical data analysis shows that relative to oceanic channels, freshwater river/lake channels have larger temporal coherence, higher correlation among densely …

Optimal Power Flow Control Of Networked Dc Microgrids, Eddy H. Trinklein

Dissertations, Master's Theses and Master's Reports

The US military is moving toward the electrification of many weapon systems and platforms. Advanced weapon systems such as high energy radar, electro-magnetic kinetic weapons and directed energy pose significant integration challenges due to their pulsed power electrical load profile. Additionally, the weapons platforms, including ships, aircraft, and vehicles can be studied as a mobile microgrids with multiple generation sources, loads, and energy storage. There is also a desire to extend the mission profile and capabilities of these systems. Common goals are to increase fuel efficiency, maintaining system stability, and reduce energy storage size as typically required to enable pulsed …

Estimation And Prediction Of The Human Gait Dynamics For The Control Of An Ankle-Foot Prosthesis, Guilherme Aramizo Ribeiro

Dissertations, Master's Theses and Master's Reports

With the growing population of amputees, powered prostheses can be a solution to improve the quality of life for many people. Powered ankle-foot prostheses can be made to behave similar to the lost limb via controllers that emulate the mechanical impedance of the human ankle. Therefore, the understanding of human ankle dynamics is of major significance. First, this work reports the modulation of the mechanical impedance via two mechanisms: the co-contraction of the calf muscles and a change of mean ankle torque and angle. Then, the mechanical impedance of the ankle was determined, for the first time, as a multivariable …

Modeling And Control Of Maximum Pressure Rise Rate In Rcci Engines, Aditya Basina

Dissertations, Master's Theses and Master's Reports

Low Temperature Combustion (LTC) is a combustion strategy that burns fuel at lower temperatures and leaner mixtures in order to achieve high efficiency and near zero NOx emissions. Since the combustion happens at lower temperatures it inhibits the formation of NOx and soot emissions. One such strategy is Reactivity Controlled Compression Ignition (RCCI). One characteristic of RCCI combustion and LTC com- bustion in general is short burn durations which leads to high Pressure Rise Rates (PRR). This limits the operation of these engines to lower loads as at high loads, the Maximum Pressure Rise Rate (MPRR) hinders the use of …

Networked Microgrid Optimization And Energy Management, Robert S. Jane

Dissertations, Master's Theses and Master's Reports

Military vehicles possess attributes consistent with a microgrid, containing electrical energy generation, storage, government furnished equipment (GFE), and the ability to share these capabilities via interconnection. Many military vehicles have significant energy storage capacity to satisfy silent watch requirements, making them particularly well-suited to share their energy storage capabilities with stationary microgrids for more efficient energy management. Further, the energy generation capacity and the fuel consumption rate of the vehicles are comparable to standard diesel generators, for certain scenarios, the use of the vehicles could result in more efficient operation. Energy management of a microgrid is an open area of …

Lithium-Ion Battery Degradation Evaluation Through Bayesian Network Method For Residential Energy Storage Systems, Khalid Khan

Dissertations, Master's Theses and Master's Reports

Batteries continue to infiltrate in innovative applications with the technological advancements led by Li-ion chemistry in the past decade. Residential energy storage is one such example, made possible by increasing efficiency and decreasing the cost of solar PV. Residential energy storage, charged by rooftop solar PV is tied to the grid, provides household loads. This multi-operation role has a significant effect on battery degradation. These contributing factors especially solar irradiation and weather conditions are highly variable and can only be explained with probabilistic analysis. However, the effect of such external factors on battery degradation is approached in recent literature with …

Effect Of Sensor Errors On Autonomous Steering Control And Application Of Sensor Fusion For Robust Navigation, Shuvodeep Bhattacharjya

Dissertations, Master's Theses and Master's Reports

Autonomous steering control is one the most important features in autonomous vehicle navigation. The nature and tuning of the controller decides how well the vehicle follows a defined trajectory. A poorly tuned controller can cause the vehicle to oversteer or understeer at turns leading to deviation from a defined path. However, controller performance also depends on the state–feedback system. If the states used for controller input are noisy or has bias / systematic error, the navigation performance of the vehicle is affected irrespective of the control law and controller tuning. In this report, autonomous steering controller analysis is done for …

Development Of The Coil Volume Method For Time-Domain Simulation Of Internal Faults In Transformers, Elizaveta Egorova

Dissertations, Master's Theses and Master's Reports

A power transformer is a very important and expensive asset for a utility. As for any other power equipment, the transformer is subject to internal faults. The extent of transformer damage depends on the fault duration. Therefore, the protective relays should provide for sensitivity, selectivity, and speed of operation to minimize the effects of damaging conditions. High sensitivity of the relay allows it to identify internal faults quickly. However, the relay should not jeopardize the normal operation of the transformer. To determine desirable relay settings, a transformer model for simulation of internal faults is required.

Transformer models, shown in the …