Engineering Commons^™

Fabrication And Mass Transport Analysis Of Tape Cast Nano-Silver High Temperature Solder, Jared Ray Mccoppin

Browse all Theses and Dissertations

The principal objective in this research was to develop a die attach method to facilitate the use of wide band gap semiconductors in high-temperature environments, and study fundamental mass transport in nano-initiated die attach microstructure at high temperature. Low temperature sintering silver-nano-pastes have been demonstrated as an effective method for die attach by other groups. Fabrication and optimization of the die attach method in this work was accomplished via tape casting. A novel binder system and a bimodal particle distribution were utilized. The tape casting method allowed die attach materials to be pre-stressed. Fundamental understanding of creep deformation process and …

Effect Of A Graded Layer On The Plastic Dissipation During Mixed-Mode Fatigue Crack Growth On Ductile Bimaterial Interfaces, Craig M. Baudendistel

Browse all Theses and Dissertations

An energy-based theory for predicting mode I fatigue crack growth rates in ductile metals based on the total plastic dissipation ahead of a crack tip was proposed in 2003. Since then, this theory has been extended to layered material systems that typically include mixed-mode loading and elastic/plastic mismatch. Previous research by the author first extended this theory to include a graded layer (i.e., no step change in material properties across the crack plane) with which to more accurately model a crack interface between two materials with a mismatch in plastic properties only. In the current research, the graded layer model …

Integrity Monitoring For Multiple Errors In Vision Navigation Systems, Nicholas Allen Baine

Browse all Theses and Dissertations

In aviation applications, navigation integrity is paramount. Integrity of GPS systems is well established with set standards. Vision-based navigation systems have been found to be an adequate substitute for GPS when it is unavailable but are unlikely to be utilized until there is a measure for system integrity. Work has been done to detect the effect of a single measurement pair being corrupted with a bias; however, the measurement geometry varies greatly with the environment. The environment could be sparse in visual features to track, or the environment could be rich with features. With more features, there is a greater …

Computational Analysis Of Vortex Structures In Flapping Flight, Zongxian Liang

Browse all Theses and Dissertations

Vortex structures and vortical formation in flapping flight are directly related to the force production. To analyze the connection between vortex structures and aerodynamic performance of flapping flight, we have developed highly efficient algorithms for large-scale flow simulations with moving and deforming bodies. To further understand the underlying mechanisms of force generation caused by the coherent structures of the vortex formation, a new analysis method has been developed to measure the influence of Proper Orthogonal Decomposition (POD) modes on aerodynamic forces.

It is challenging to finish three-dimensional Direct Numerical Simulations (DNS) of insect flight in a limited amount of time. …

Spectrally Modulated Spectrally Encoded Framework Based Cognitive Radio In Mobile Environment, Xue Li

Browse all Theses and Dissertations

Radio spectrum has become a precious resource, and it has long been the dream of wireless communication engineers to maximize the utilization of the radio spectrum. Dynamic Spectrum Access (DSA) and Cognitive Radio (CR) have been considered promising to enhance the efficiency and utilization of the spectrum. Since some of the spectrum bands are occupied by primary users (PUs), the available spectrum for secondary users (SUs) are non-contiguous, and multi-carrier transmission technologies become the natural solution to occupy those non-contiguous bands. Non-contiguous multi-carrier based modulations, such as NC-OFDM (non-contiguous Orthogonal Frequency Division Multiplexing), NC-MC-CDMA (non-contiguous multi-carrier code division multiple access) …

A Semantic Situation Awareness Framework For Indoor Cyber-Physical Systems, Pratikkumar Desai

Browse all Theses and Dissertations

Recently, the domain of cyber-physical systems (CPSs) has emerged as a successor to the traditional embedded systems and the wireless sensor networks. The relatively new cyber-physical domain offers tight integration of control, communication and computation components to develop advanced web based application in various heterogeneous domains such as health care, disaster management, automation and environment monitoring. The applications of indoor CPSs include remote patient monitoring, smart home, etc. with focus on situation awareness via event identification from context information. The principal challenges associated with the development of situation awareness applications include uncertainty in contextual data, incomplete domain knowledge, interoperability between …

The Warehouse-Inventory-Transportation Problem For Multi-Echelon Supply Chains, Bhanuteja Sainathuni

Browse all Theses and Dissertations

Warehouses play a vital role in mitigating variations in supply and demand, and providing value-added services in a supply chain. However, our observation of supply chain practice reveals that warehousing decisions are not included when developing a distribution plan for the supply chain. This lack of integration has resulted in substantial variation in workload (42%-220%) at our industry partner's warehouse costing them millions of dollars. We address this real-world challenge by investigating the interdependencies between warehouse, inventory, and transportation decisions, integrate them in a mathematical programming model, and develop managerial insights based on solutions of industry-sized problem instances. Our three …

Distributed Fault Diagnosis Of Interconnected Nonlinear Uncertain Systems, Qi Zhang

Browse all Theses and Dissertations

Fault diagnosis is crucial in achieving safe and reliable operations of interconnected control systems. This dissertation presents a distributed fault detection and isolation (FDI) method for interconnected nonlinear uncertain systems. The contributions of this dissertation include the following: First, the detection and isolation problem of process faults in a class of interconnected input-output nonlinear uncertain systems is investigated. A novel fault detection and isolation scheme is devised, and the fault detectability and isolability conditions are rigorously investigated, characterizing the class of faults in each subsystem that are detectable and isolable by the proposed distributed FDI method. Second, a distributed sensor …

Computational Modeling Of Nanosensors Based On Graphene Nanoribbons Including Electron-Phonon Effects, Kirti Kant K. Paulla

Browse all Theses and Dissertations

We investigate detection mechanisms of real time sensors, based on ultra-thin (single and bi-atomic layer thick) and ultra-narrow (~1nm) graphene nanoribbons (GNRs), using first principle based theoretical methods. In the first part of this study we study the electronic and magnetic structures of bilayer graphene nanoribbons (BGNRs) beyond the conventional AA and AB stackings, by using density functional theory within both local density and generalized gradient approximations (LDA and GGA). Our results show that, irrespective of the method chosen, stacking arrangements other than the conventional ones are most stable, and result in significant modification of BGNRs characeristics. The most stable …

A Computational Study Of Linking Solid Oxide Fuel Cell Microstructure Parameters To Cell Performance, Chao Wang

Browse all Theses and Dissertations

Solid Oxide Fuel Cell (SOFC) has been considered as a promising technology to replace the traditional fossil fuels due to high efficiency, low emission, and silent operation. The configuration of microstructures throughout the electrodes plays a significant role in improving cell performance. However, current research did not capture the connections of the microstructure parameters, which is vital to simulate the SOFC behavior under practical circumstances. This study explored the correlations of microstructure parameters from a micro scale level, together with mass transfer and electrochemical reactions inside the electrodes, providing a novel approach to predict the SOFC performance numerically. The results …

Fundamental Understanding Of Blisk Analytical Response, Joseph A. Beck

Browse all Theses and Dissertations

This effort seeks to increase the reduced-order model fidelity for mistuned Integrally Bladed Rotor (IBR) and Dual Flow-path Integrally Bladed Rotor (DFIBR) response prediction by explicitly accounting for blade geometric and material property deviations. These methods are formulated in a component mode synthesis (CMS) framework utilizing secondary modal reductions in a cyclic symmetry format. The resulting reduced-order models (ROMs) capture perturbations to both blade natural frequencies and mode shapes resulting from geometric deviations. Furthermore, the secondary modal reductions and cyclic symmetry format offer significant computational savings over traditional component mode synthesis methods that give a further reduction in model size. …

Modeling And Minimization Of Integrated Circuit Packaging Parasitics At Radio Frequencies, Christopher Benedik

Browse all Theses and Dissertations

Many integrated circuits are connected to their packaging pins through bondwires. Due to the low cost of bondwires, there is interest in extending operating frequencies or negating their effects in order to keep the price of packaged integrated circuits as low as possible. Bondwires function as lumped circuits consisting of inductors, capacitors, and resistors which can be modeled based on wire geometry. Knowing this, models can be created which approximate the effects of bondwires. With the knowledge of these models, compensation techniques can be implemented which will match the bondwire impedance to the signal line impedance. The effects of these …