Engineering Commons^™

Effects Of Expected Service Life Exposures On The Functional Properties And Impact Performance Of An American Football Helmet Outer Shell Material, David E. Krzeminski

Dissertations

The purpose of this dissertation is to gain a greater scientific understanding of the changes in functional material properties and impact performance of an American football helmet outer shell material under expected service life exposures. The research goals are to (i) quantify chemical, physical, thermal, and mechanical degradation of an American football outer shell material under expected environmental conditions and (ii) develop a linear drop test impact protocol to employ expected on-field impact conditions to American football helmet components and a plaque-foam (i.e., shell-liner) surrogate. Overall, a step-wise progression of analysis was demonstrated to concurrently quantify and understand changes in …

Hybrid Aryl-Ether-Ketone And Hyperbranched Epoxy Networks, John Misasi

Dissertations

In this dissertation, relationships between chemical structures, cure kinetics and network architectures are correlated to bulk mechanical properties for novel, hybrid epoxy-amine networks. The work is split into two primary sections: the first is the synthesis and characterization of multifunctional glassy networks based on aryl-ether-ketone diamine curatives, while the second is based on the synthesis and characterization of hyperbranched epoxy polymers and their resulting networks.

Three aryl-ether-ketone (AEK) diamines of increasing molecular weights were synthesized and used to cure 4,4’-tetraglycidylether of diaminodiphenylmethane (TGDDM); the resulting networks were compared to 4,4’-diaminodiphenyl sulfone cured TGDDM. Architectural differences were created by varying cure …

Polyacrylonitrile Copolymers: Effects Of Molecular Weight, Polydispersity, Composition, And Sequencing On Thermal Ring-Closing Stabilization, Jeremy D. Moskowitz

Dissertations

Controlled polyacrylonitrile (PAN)-based carbon fiber precursors with defined molecular weights, polydispersities, compositions, and architectures have been prepared for their study on thermal ring-closing stabilization behavior. PAN and its copolymers of number average molecular weights exceeding 170,000 g/mol were successfully synthesized via low temperature reversible addition-fragmentation chain transfer (RAFT) polymerization. RAFT polymerizations of PAN-based precursors were compared to conventional free radical solution polymerizations with a focus on the effects of molecular weight and polydispersity on structural evolution and cyclization efficiency. When RAFT polymerization was extended to copolymers, it was found that RAFT copolymers achieved greater cyclization intensities and improved thermal stability …

Development Of Dual-Cure Hybrid Polybenzoxazine Thermosets, Jananee Narayanan Sivakami

Dissertations

Polybenzoxazines are potential high performance thermoset replacements for traditional phenolic resins that can undergo an autocatalytic, thermally initiated ring - opening polymerization, and possess superior processing advantages including excellent shelf-life stability, zero volatile loss and limited volumetric shrinkage. The simplistic monomer synthesis and availability of a wide variety of inexpensive starting materials allows enormous molecular design flexibility for accessing a wide range of tailorable material properties for targeted applications. Despite the fact, once fully cured, benzoxazines are difficult to handle due to their inherent brittleness, leaving a very little scope for any modifications. The motivation of this dissertation is directed …

Face Recognition With Multi-Stage Matching Algorithms, Xianming Chen

Dissertations

For every face recognition method, the primary goal is to achieve higher recognition accuracy and spend less computational costs. However, as the gallery size increases, especially when one probe image corresponds to only one training image, face recognition becomes more and more challenging. First, a larger gallery size requires more computational costs and memory usage. Meanwhile, that the large gallery sizes degrade the recognition accuracy becomes an even more significant problem to be solved.

A coarse parallel algorithm that equally divides training images and probe images into multiple processors is proposed to deal with the large computational costs and huge …

On The Selection Of A Good Shape Parameter For Rbf Approximation And Its Application For Solving Pdes, Lei-Hsin Kuo

Dissertations

Meshless methods utilizing Radial Basis Functions~(RBFs) are a numerical method that require no mesh connections within the computational domain. They are useful for solving numerous real-world engineering problems. Over the past decades, after the 1970s, several RBFs have been developed and successfully applied to recover unknown functions and to solve Partial Differential Equations (PDEs).
However, some RBFs, such as Multiquadratic (MQ), Gaussian (GA), and Matern functions, contain a free variable, the shape parameter, c. Because c exerts a strong influence on the accuracy of numerical solutions, much effort has been devoted to developing methods for determining shape parameters which provide …

Cure Kinetics, Morphologies, And Mechanical Properties Of Thermoplastic/Mwcnt Modified Multifunctional Glassy Epoxies Prepared Via Continuous Reaction Methods, Xiaole Cheng

Dissertations

The primary goal of this dissertation is to develop a novel continuous reactor method to prepare partially cured epoxy prepolymers for aerospace prepreg applications with the aim of replacing traditional batch reactors. Compared to batch reactors, the continuous reactor is capable of solubilizing and dispersing a broad range of additives including thermoplastic tougheners, stabilizers, nanoparticles and curatives and advancing epoxy molecular weights and viscosities while reducing energy consumption.

In order to prove this concept, polyethersulfone (PES) modified 4, 4’-diaminodiphenylsulfone (44DDS)/tetraglycidyl-4, 4’-diaminodiphenylmethane (TGDDM) epoxy prepolymers were firstly prepared using both continuous reactor and batch reactor methods. Kinetic studies confirmed the chain …

Novel Bioinformatic Approaches For Analyzing Next-Generation Sequencing Data, Yan Peng

Dissertations

In general, DNA reconstruction is deemed as the key of molecular biology since it makes people realize how genotype affects phenotypes. The DNA sequencing technology emerged exactly towards this and has greatly promoted molecular biology’s development. The traditional method, "Sanger," is effective but extremely expensive on a cost-per-base basis. This shortcoming of Sanger method leads to the rapid development of next-generation sequencing technologies. The NGS technologies are widely used by virtue of their low-cost, high-throughput, and fast nature. However, they still face major drawbacks such as huge amounts of data as well as relatively short read length compared with traditional …

Secure And Reliable Routing Protocol For Transmission Data In Wireless Sensor Mesh Networks, Nooh Adel Bany Muhammad

Dissertations

Abstract

Sensor nodes collect data from the physical world then exchange it until it reaches the intended destination. This information can be sensitive, such as battlefield surveillance. Therefore, providing secure and continuous data transmissions among sensor nodes in wireless network environments is crucial. Wireless sensor networks (WSN) have limited resources, limited computation capabilities, and the exchange of data through the air and deployment in accessible areas makes the energy, security, and routing major concerns in WSN. In this research we are looking at security issues for the above reasons. WSN is susceptible to malicious activities such as hacking and physical …