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Articles 1 - 30 of 49
Full-Text Articles in Engineering
Development Of Dual-Cure Hybrid Polybenzoxazine Thermosets, Jananee Narayanan Sivakami
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 …
Application Of Starch-Based Nanoparticle Colloidal Dispersion In Curtain Coating, Ting Chen
Application Of Starch-Based Nanoparticle Colloidal Dispersion In Curtain Coating, Ting Chen
Dissertations
In this research, a conventional petro-based latex was partially replaced with a biobased latex in a curtain coating. A common petro-based rheology modifier used in curtain coatings, which is relatively costly and difficult to disperse, was also replaced with two inorganic rheology modifiers. The influence of these materials on coating rheology and curtain stability was thoroughly examined.
In the rheological study, the interactions between biopolymer nanoparticles and inorganic rheology modifiers were found to improve the rheological properties of the biobased latex coatings. Changes in the rheological properties of the coatings were found to depend on the type of rheology modifier …
Numerical Simulation And Modeling Of Combustion In Scramjets, Ryan James Clark
Numerical Simulation And Modeling Of Combustion In Scramjets, Ryan James Clark
Dissertations
In the last fifteen years the development of a viable scramjet has quickly approached the following long term goals: responsive sub-orbital space access; long-range, prompt global strike; and high-speed transportation. Nonetheless, there are significant challenges that need to be resolved. These challenges include high skin friction drag and high heat transfer rates, inherent to vehicles in sustained, hypersonic flight. Another challenge is sustaining combustion. Numerical simulation and modeling was performed to provide insight into reducing skin friction drag and sustaining combustion.
Numerical simulation was used to investigate boundary layer combustion, which has been shown to reduce skin friction drag. The …
Development Of A Capacity Deployment Model For Disrupted Supply Chain Networks, James D. Burns
Development Of A Capacity Deployment Model For Disrupted Supply Chain Networks, James D. Burns
Dissertations
The increasing complexity of modern supply chains is widely accepted as one of the many drivers of risk that can leave organizations vulnerable to the effects of a disruption. This acceptance has contributed to an emerging interest in Supply Chain Resilience in the literature. Resilient supply chains are able to both resist the effects of a disruption and recover efficiently if the disruption is severe. This new body of literature is still in a formative phase and has thus far focused on defining Supply Chain Resilience, proposing frameworks for its implementation, exploring factors that contribute to resilience, and investigating methods …
Effects Of Expected Service Life Exposures On The Functional Properties And Impact Performance Of An American Football Helmet Outer Shell Material, David E. Krzeminski
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
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
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 …
Face Recognition With Multi-Stage Matching Algorithms, Xianming Chen
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 …
Novel Software Defined Radio Architecture With Graphics Processor Acceleration, Lalith Narasimhan
Novel Software Defined Radio Architecture With Graphics Processor Acceleration, Lalith Narasimhan
Dissertations
Wireless has become one of the most pervasive core technologies in the modern world. Demand for faster data rates, improved spectrum efficiency, higher system access capacity, seamless protocol integration, improved security and robustness under varying channel environments has led to the resurgence of programmable software defined radio (SDR) as an alternative to traditional ASIC based radios. Future SDR implementations will need support for multiple standards on platforms with multi-Gb/s connectivity, parallel processing and spectrum sensing capabilities. This dissertation implemented key technologies of importance in addressing these issues namely development of cost effective multi-mode reconfigurable SDR and providing a framework to …
Studying The Optimum Design Of Automotive Thermoelectric Air Conditioning, Alaa Attar
Studying The Optimum Design Of Automotive Thermoelectric Air Conditioning, Alaa Attar
Dissertations
The remarkable amount of research being conducted on thermoelectrics gives the impression that this technology will have a bright future in power generation and temperature control systems. At the present time, thermoelectrics is applied widely for temperature control, but has not yet replaced conventional air-conditioning systems due to its lower performance. Currently, approximately 10% of annual vehicle fuel consumption corresponds to the air-conditioning system used to cool the vehicle cabin. Conventional air-conditioning systems cool the entire cabin; however, about 73% of a vehicle’s mileage occurs while the driver is the only occupant. These facts indicate the need for a single …
Modeling And Experimental Study Of Carbon Dioxide Absorption/Stripping In Gas Liquid Membrane Contactor, Nihmiya Abdul Rahim
Modeling And Experimental Study Of Carbon Dioxide Absorption/Stripping In Gas Liquid Membrane Contactor, Nihmiya Abdul Rahim
Dissertations
Natural gas consists primarily of methane (CH4) but it also contains considerable amounts of contaminating compounds mainly carbon dioxide (CO2). The presence of CO2 reduces the heating value of the gas and due to its acidic character causes several operational problems. Hence the removal of CO2 from natural gas is crucially important. The focus of this research work is to investigate the potential for the energy efficient and effective separation of CO2/CH4 gas mixture via lean solvent and regenerating of the rich solvent through absorption/stripping mechanism taking place in a hollow fiber gas liquid membrane contactor process (GLMC) which combines …
Production And Characterization Of Composite Nano/Micro Sized Particles By Rapid Expansion Of Supercritical Solutions (Ress) Co-Precipitation, Beidi He
Dissertations
Nanoscale composites of hexahydro-1, 3, 5-trinitro-1, 3, 5-triazine (RDX) and polymer binders were produced by co-precipitation using rapid expansion of supercritical solutions (RESS). The binders used in this study are poly (vinylidene fluoride-co-hexafluoropropylene) (VDF-HFP22), polystyrene (PS) and 7-amino-4-methyl coumarin (AMC). The RDX/VDF-HFP22 and RDX/PS co-precipitated nanoparticles were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM). The average size of produced nanoparticles is ca. 100 nm. TEM analysis of RDX/PS nano-composite shows a core-shell structure with RDX as the core material and the shell consisting of the polymeric binder. X-ray Powder Diffraction (XRPD) analysis …
Hydrodynamics, Dissolution, And Mass Transfer Effects In Different Dissolution Testing Apparatuses And Laboratory Systems, Bing Wang
Dissertations
Dissolution testing apparatuses and shaker flasks agitated by shaker tables are laboratory systems routinely found in many laboratories at most companies and agencies, and especially in pharmaceutical companies. These devices are commonly used in a number of applications, from drug development to quality control. Despite their common use, these systems have not been fully investigated from an engineering perspective in order to understand their operation characteristics. For example, the hydrodynamics of many of these systems have received little attention until relatively recently, and only over the last few years have some of these systems, such as the USP dissolution testing …
Recycling In A Lean Environment, Marylin N. Glass-Hedges
Recycling In A Lean Environment, Marylin N. Glass-Hedges
Dissertations
Lean Manufacturing and Green Manufacturing systems co-occur in many manufacturing facilities. This dissertation investigated the relationship between materials recycling—as an important green waste-reduction technique—and lean techniques, and their influence on lean outcomes, specifically 1) if a correlation exists between lean techniques and material recycling, as these two variables also influence lean outcomes; and 2) the mediating effect of materials recycling between lean techniques and lean outcomes. Exploratory factor analysis, confirmatory factor analysis, and structural equation modeling were the chosen statistical analysis methods utilized to explore and confirm the lean techniques and lean outcomes constructs, test the models’ hypotheses and answer …
Novel Stretchable Printed Wearable Sensor For Monitoring Body Movement, Temperature And Electrocardiogram, Along With The Readout Circuit, Ali Eshkeiti
Dissertations
Conformal and stretchable wearable sensors provide vital real time information about individual’s health conditions. In this work, Traditional printing methods are used for fabrication of stretchable and wearable sensors which can be mounted on the human skin for the purpose of health tracking. In addition, screen printing technology was utilized to develop printed and flexible electronic circuit board which can be used as a readout circuit along with fabricated wearable sensors. The dissertation is organized and pursued in three projects.
In the first project, screen printing was used to fabricate multi-layer PCBs using printed deposited materials on three distinct substrates. …
On The Selection Of A Good Shape Parameter For Rbf Approximation And Its Application For Solving Pdes, Lei-Hsin Kuo
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 …
Control Strategies For Improving The Performance Of Heaving Wave Energy Converters, Mohammed Abdi Jama.
Control Strategies For Improving The Performance Of Heaving Wave Energy Converters, Mohammed Abdi Jama.
Dissertations
The main objective of this study is to develop control strategies to enhance the performance of single-body heaving wave energy converters (WECs). Maximizing the energy captured from sea waves while respecting the physical and thermal limitations of the WEC is of a paramount importance for any control strategy to be effective. In addition, it is desirable for the controller to be less vulnerable to model uncertainties and external disturbances. A complete wave-to-wire dynamic model has been derived for the heaving WEC. This includes models that describe the system hydrodynamic forces using the linear wave theory and models that describe the …
Implementation Of Traditional Printing Techniques For The Development Of Flexible Printed Sensors, Sai Guruva Reddy Avuthu
Implementation Of Traditional Printing Techniques For The Development Of Flexible Printed Sensors, Sai Guruva Reddy Avuthu
Dissertations
Printed electronics has gained a remarkable interest over the past decade for the fabrication of cost efficient electronic devices, with a major focus on the development of flexible sensors. This dissertation focuses on the fabrication of flexible sensors using traditional printing processes such as screen, inkjet and gravure printing.
A flexible organic thin film transistor (OTFT) was successfully fabricated on a polyethylene terephthalate (PET) substrate and employed as a humidity sensor. Aluminum gate electrode was thermally evaporated on PET and UV clear dielectric layer was spin coated. Source and drain silver interdigitated electrodes were screen printed. 6,13-bis(triisopropylsilylethynyl) pentacene, a humidity …
Exploration Of Stimulus Current Energy Reduction And Bifurcation Dynamics In Conductance-Based Neuron Models Using Optimal Control Theory, Michael E. Ellinger
Exploration Of Stimulus Current Energy Reduction And Bifurcation Dynamics In Conductance-Based Neuron Models Using Optimal Control Theory, Michael E. Ellinger
Dissertations
Hodgkin-Huxley type conductance-based models can simulate the effect of time-varying injected stimulus currents on the neuron membrane voltage. The dynamics simulated by these model types enables investigation of the biophysical basis of neuronal activity which is fundamental to higher level function. Broadened understanding the basis of nervous system function could lead to development of effective treatment for related diseases, disorders, and the effects of trauma. In this dissertation, optimal control is used with conductance-based neuron models to develop a "Reduced Energy Input Stimulus Discovery Method." Within the method, an objective function balances two competing criteria: tracking a reference membrane voltage …
Analysis Of Vibroacoustic Properties Of Dimpled Beams Using A Boundary Value Model, Kyle R. Myers
Analysis Of Vibroacoustic Properties Of Dimpled Beams Using A Boundary Value Model, Kyle R. Myers
Dissertations
Attention has been given recently to the use of dimples as a means of passively altering the vibroacoustic properties of structures. Because of their geometric complexity, previous studies have modeled dimpled structures using the finite element method. However, the dynamics of dimpled structures are not completely understood. The goal of this study is to provide a better understanding of these structures through the development of a boundary value model (BVM) using Hamilton's Variational Principle. The focus of this study is on dimpled beams, which represent the simplest form of a dimpled structure.
A general model of a beam with N …
New Screening Methodology For Selection Of Polymeric Materials For Transdermal Drug Delivery Devices, Roberto P. Falcone
New Screening Methodology For Selection Of Polymeric Materials For Transdermal Drug Delivery Devices, Roberto P. Falcone
Dissertations
As medical advances extend the human lifespan, the level of chronic illnesses will increase and thus straining the needs of the health care system that, as a result, governments will need to balance expenses without upsetting national budgets.
Therefore, the selection of a precise and affordable drug delivery technology is seen as the most practical solution for governments, health care professionals, and consumers.
Transdermal drug delivery patches (TDDP) are one of the best economical technologies that are favored by pharmaceutical companies and physicians alike because it offers fewer complications when compared to other delivery technologies. TDDP provides increased efficiency, safety …
High Frequency Field Potentials Of The Cerebellar Cortex, Jonathan David Groth
High Frequency Field Potentials Of The Cerebellar Cortex, Jonathan David Groth
Dissertations
The cerebellum plays a crucial role in motor coordination along with basal ganglia and the motor areas of the cerebral cortex. Both somatosensory and the cerebro-cerebral pathways bring in massive amounts of neural information to the cerebellum. The output of the cerebellar cortex projects to various motor cortices as well as down to the spinal cord to make its contributions to the motor function.
The origin and function of the field potential oscillations in the cerebellum, especially in the high frequencies, have not been explored sufficiently. The primary objective of this study was to investigate the spatio-temporal characteristics of high …
Accounting For Midblock Pedestrian Activity In The Hcm 2010 Urban Street Segment Analysis, Albert Forde
Accounting For Midblock Pedestrian Activity In The Hcm 2010 Urban Street Segment Analysis, Albert Forde
Dissertations
The Urban Street segment analysis Chapter of the 2010 Highway Capacity Manual (HCM 2010) provides a methodology for analyzing automobile performance on signalized roadway segments within an urban roadway network. The methodology involves applying a platoon dispersion model to: a) predict the vehicle arrival flow profiles at a downstream signalized intersection; b) use the predicted arrivals to compute the proportion of vehicle arrivals on green; and c) subsequently estimate the delay, travel speed and Level of Service (LOS) under which the segment operates. Vehicles arriving during the red interval at a signalized intersection generally accumulate and form a platoon. When …
Optimization Methods For Active And Passive Localization, Nil Garcia
Optimization Methods For Active And Passive Localization, Nil Garcia
Dissertations
Active and passive localization employing widely distributed sensors is a problem of interest in various fields. In active localization, such as in MIMO radar, transmitters emit signals that are reflected by the targets and collected by the receive sensors, whereas, in passive localization the sensors collect the signals emitted by the sources themselves. This dissertation studies optimization methods for high precision active and passive localization.
In the case of active localization, multiple transmit elements illuminate the targets from different directions. The signals emitted by the transmitters may differ in power and bandwidth. Such resources are often limited and distributed uniformly …
Collaborative Rescheduling Of Flights In A Single Mega-Hub Network, Sufian Ikhmeis
Collaborative Rescheduling Of Flights In A Single Mega-Hub Network, Sufian Ikhmeis
Dissertations
Traditionally, airlines have configured flight operations into a Hub and Spoke network design. Using connecting arrival departure waves at multiple hubs these networks achieve efficient passenger flows. Recently, there has been much growth in the development of global single mega-hub (SMH) flight networks that have a significantly different operating cost structure and schedule design. These are located primarily in the Middle East and are commonly referred to as the ME3. The traditionalist view is that SMH networks are money losers and subsidized by sovereign funds.
This research studies and analyzes SMH networks in an attempt to better understand their flight …
System Design And Performance Analysis Of Asymmetrically And Symmetrically Clipped Optical (Asco)-Ofdm For Im/Dd Optical Wireless Communications, Nan Wu
Dissertations
As the quantity of mobile communication devices, such as cellphones, tablets, and laptops, dramatically increase, the demand for high speed wireless service has been growing. Optical wireless communications (OWCs), which offer unlimited transmission bandwidth, have received a lot of attention and been studied in recent decades. They can be an effective alternative to radio frequency communications (RFCs) for indoor high speed data transmission. Intensity modulation direct detection (IM/DD) is a simple way to realize the transmission of optical wireless signals in an indoor environment. Information data streams are modulated into the intensity of optical carriers and transmitted by light emitting …
Piezoelectric Scaffolds For Osteochondral Defect Repair, Sita Mahalakshmi Damaraju
Piezoelectric Scaffolds For Osteochondral Defect Repair, Sita Mahalakshmi Damaraju
Dissertations
Osteoarthritis is one of the most prevalent causes of disability affecting nearly 27 million Americans. Osteoarthritis is caused when extensive damage occurs to the articular cartilage later spreading to the underlying subchondral bone, resulting in osteochondral defects. The current clinical therapies aim at regenerating the hyaline cartilage, but instead fibrocartilage forms at the osteochondral defect site, which is inferior in structure and function and fails to integrate with the surrounding tissue. A biomimetic scaffold, which can provide cues similar to the native extracellular matrix, may facilitate osteochondral defect repair. Articular cartilage and bone extracellular matrix have been shown to produce …
Secure And Reliable Routing Protocol For Transmission Data In Wireless Sensor Mesh Networks, Nooh Adel Bany Muhammad
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 …
Modeling Of Environmentally Assisted Fatigue Crack Growth Behavior, Sree Phani Chandar Reddy
Modeling Of Environmentally Assisted Fatigue Crack Growth Behavior, Sree Phani Chandar Reddy
Dissertations
The formation of fatigue cracks and their propagation due to cyclic loading in metals have been a concern for more than hundred years. Since fatigue failure were first reported by the railroad industry in 1840s, tremendous progress has been achieved in understanding fatigue behavior of metals. But fatigue damage is still a concern due to its complex dependency on various environmental variable like humidity, temperature, time and corrosive environment. Although numerous theories and models have been proposed in the past, the effects of environment on fatigue crack growth (FCG) is not completely understood. This dissertation aims to shed light on …
Novel Bioinformatic Approaches For Analyzing Next-Generation Sequencing Data, Yan Peng
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 …