Engineering Commons^™

Hard-Switching And Soft-Switching Two-Switch Flyback Pwm Dc-Dc Converters And Winding Loss Due To Harmonics In High-Frequency Transformers, Dakshina S. Murthy Bellur

Browse all Theses and Dissertations

The flyback pulse-width modulated (PWM) DC-DC power converter is a very important circuit in switching mode power supply (SMPS) converters for low power applications. The main drawback of the conventional single-switch flyback converter is the high turn-off voltage stress suffered by the switch. The high voltage transients are caused by the resonant behavior of the transformer leakage inductance and the transistor output capacitance, resulting in ringing superimposed on the steady-state switch voltage level. This requires a transistor with higher voltage rating. However, a transistor with higher voltage rating has higher on-resistance causing higher conduction loss. The high voltage ringing also …

A Human-Computer Integrated Approach Towards Content Based Image Retrieval, Phani Nandan Kidambi

Browse all Theses and Dissertations

Digital photography technologies permit quick and easy uploading of any image to the web. Millions of images being are uploaded on the World Wide Web every day by a wide range of users. Most of the uploaded images are not readily accessible as they are not organized so as to allow efficient searching, retrieval, and ultimately browsing. Currently major commercial search engines utilize a process known as Annotation Based Image Retrieval (ABIR) to execute search requests focused on retrieving an image. Even though the information sought is an image, the ABIR technique primarily relies on textual information associated with an …

Analysis Of Amputee Gait Using Virtual Reality Rehabilitation Techniques, Maurissa S. D'Angelo

Browse all Theses and Dissertations

This research shows promise in becoming a standard practice for long term amputee rehabilitation. Exceptional rehabilitation is not universally available to all disabled individuals due to circumstances which limit patient care such as a limited number of trained personnel, limited access to therapy in remote areas, limited patient feedback, limited visits under insurance policies and differing expertise of personnel. Providing real-time, objective feedback will help to continuously improve the quality of life of amputee individuals and provide standardized baseline techniques. The research described in this dissertation expands the use of virtual reality systems to amputee rehabilitation. A virtual reality system …

Design And Validation Of A Sensor Integration And Feature Fusion Test-Bed For Image-Based Pattern Recognition Applications, Hrishikesh Karvir

Browse all Theses and Dissertations

We integrated a sensor hardware test-bed using scientific grade, commercial off-the-shelf (COTS) technology and developed supporting software to enable rapid prototyping. The validity of this test-bed and associated software was demonstrated through the delivery of a ground-based multispectral visual surveillance prototype for improvised explosive devices (IED) detection using electro-optical (EO) and short-wave infrared (SWIR) cameras. Software developed to support the test-bed included modules for image acquisition, preconditioning, segmentation, feature extraction, data regularization and pattern recognition. To provide spatially co-aligned data, we optimized a mutual information-based image registration algorithm to improve its convergence rate and benchmarked it against the established simplex …

The History, Philosophy, And Practice Of Agent-Based Modeling And The Development Of The Conceptual Model For Simulation Diagram, Brian L. Heath

Browse all Theses and Dissertations

This research advances ABM as a generic analysis tool such that ABM can reach its full potential as a revolution in modeling and simulation. To achieve this goal, the field of ABM is examined from many perspectives. The first perspectives examined are complex systems, the historical emergence of ABM, and philosophical issues related to ABM. These topics establish some clear foundations for the field across multiple disciplines. Next the current practice of ABM is investigated. Through a comprehensive 279 article survey some current deficiencies and opportunities in ABM are identified. Based on these opportunities, a new diagramming technique called the …

Uncertainty Quantification Of Residual Stresses Induced By Laser Peening Simulation, Hemanth Amarchinta

Browse all Theses and Dissertations

Advanced mechanical surface enhancement techniques have been used successfully to increase the fatigue life of metallic components. These techniques impart deep compressive residual stresses into the component to counter potentially damage-inducing tensile stresses generated under service loading. Laser Peening (LP) is an advanced mechanical surface enhancement technique used predominantly in the aircraft industry. To reduce costs and make the technique available on a large-scale basis for industrial applications, simulation of the LP process is required. Accurate simulation of the LP process is a challenging task, because the process has many parameters such as laser spot size, pressure profile, and material …

High-Power Energy Scavenging For Portable Devices, Simon J. Tritschler

Browse all Theses and Dissertations

Portable electronic devices and crafts such as unmanned aerial vehicles (UAV's) may benefit greatly from the ability to extract power from overhead distribution power lines on a temporary basis to power electronics or charge on-board batteries. However, most of the current literature on the subject of energy scavenging is focused on micropower and other small-scale applications. Several high-power energy scavenging methods are investigated here with an emphasis on relating physical sensor dimensions with output power. A novel power scavenging mechanism is introduced that shows excellent correlation between theoretical and experimental performance. In addition, a universal power supply is proposed which …

Relative Stability Of The Inner-Current Loop Of Peak Current-Mode Controlled Pwm Dc-Dc Converters In Ccm, Nisha Kondrath

Browse all Theses and Dissertations

Current-mode control is a commonly adopted method of regulation for pulse-width modulated (PWM) dc-dc power converters in industry, but is not well understood. The advantages of current-mode control over the voltage-mode control include inherent overload and short circuit protection, faster response, line-noise rejection, and multiple converter paralleling. Current-mode controlled system consists of (1) an inner-current loop and (2) an outer-voltage loop, which sets the reference voltage to the inner loop. To ensure stable operation of the multi-loop converter, all the sequential loops in the circuit should be stable with sufficient degree of stability. The research in this dissertation is focused …

Fusion Of Video And Doppler Radar For Traffic Surveillance, Arunesh Roy

Browse all Theses and Dissertations

Current Continuous Wave (CW) Doppler radar speed measurement systems lack the ability to distinguish multiple targets. Most systems can only identify the strongest (closest) target or the fastest target.

This dissertation is related to a fusion algorithm for a VIdeo-Doppler-radAR (Vidar) traffic surveillance system. The Vidar systems uses a robust matching algorithm which iteratively matches the information from a video camera and multiple Doppler radars corresponding to the same moving vehicle, and a stochastic algorithm which fuses the matched information from the video camera and Doppler radars to derive the vehicle velocity and angle information.

We use two heterogeneous sensors …

Development Of An Unsteady Aeroelastic Solver For The Analysis Of Modern Turbomachinery Designs, Timothy James Leger

Browse all Theses and Dissertations

Developers of aircraft gas turbine engines continually strive for greater efficiency and higher thrust-to-weight ratio designs. To meet these goals, advanced designs generally feature thin, low aspect airfoils, which offer increased performance but are highly susceptible to flow-induced vibrations. As a result, High Cycle Fatigue (HCF) has become a universal problem throughout the gas turbine industry and unsteady aeroelastic computational models are needed to predict and prevent these problems in modern turbomachinery designs. This research presents the development of a 3D unsteady aeroelastic solver for turbomachinery applications. To accomplish this, a well established turbomachinery Computational Fluid Dynamics (CFD) code called …

Design, Modeling, Fabrication And Characterization Of Three-Dimensional Ferromagnetic-Core Solenoid Inductors In Su-8 Interposer Layer For Embedded Passive Component Integration With Active Chips, Robert Carl Fitch Jr.

Browse all Theses and Dissertations

Integrated circuit technology continually presses toward higher transistor density and thus smaller dimensions, yet passive components which remain the bulk of the circuit area, surprisingly receive sideline attention. This work addresses a niche area of inductor design as it applies to the 3-dimensional (3-D) integration of active transistors and passive components. Hybrid, 3-D circuits residing on inexpensive silicon substrates can be fashioned using a photosensitive epoxy known as SU-8 serving as the interposer layer between the substrate and in which the passive components are embedded. The active components, which are known-good-chips, are secured with epoxy into deep reactive ion etched …

Structural Health Monitoring Of A Thermal Protection System For Fastener Failure With A Validated Model, Randy Joseph Tobe

Browse all Theses and Dissertations

Air vehicles flying at hypersonic speeds encounter extreme thermal, aerodynamic and acoustic loads. To maintain the structural integrity of the flight vehicle, a thermal protection system shields the main structure from these loads. Therefore, maintaining the health of the thermal protection system is critical for a successful mission and vehicle safety. One of the more common types of failure in a mechanically attached thermal protection system is fastener failure. Since reducing vehicle turnaround between flights is desired, creating an automated system to perform structural health monitoring on the fastener health of the thermal protection system is needed. This can be …