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Articles 1 - 30 of 95
Full-Text Articles in Engineering
A Systems And Cost Analysis Of Human Rated Mars Entry, Descent, And Landing Vehicles, Paul Daniel Friz
A Systems And Cost Analysis Of Human Rated Mars Entry, Descent, And Landing Vehicles, Paul Daniel Friz
Doctoral Dissertations
"Cost is one of the biggest obstacles to sending humans to Mars. However, spacecraft costs are typically not taken into consideration until after the preliminary vehicle and mission concepts have been designed. Once costs have been estimated, managers and project teams often lack confidence that the final cost of the mission will match the preliminary estimates. The present work provides a robust methodology for using cost as a valid metric early in the design phase of future human Mars Entry, Descent, and Landing (EDL) vehicles. This is done in three parts. First, state of the art parametric costing methods are …
Solvent-Free Additive Manufacturing Of Electrodes For Li-Ion Batteries, Brandon Joshua Ludwig
Solvent-Free Additive Manufacturing Of Electrodes For Li-Ion Batteries, Brandon Joshua Ludwig
Doctoral Dissertations
"A new Li-ion battery electrode manufacturing process using a solvent free additive manufacturing method has been developed. Li-ion battery electrodes consist of active material particles, a binder additive, and a conductive additive. Traditionally, Li-ion battery electrodes are manufacturing using the "slurry casting" technique. In this method, the electrode materials are mixed with a solvent to create a slurry. Electrodes fabricated in this method are readily implemented for small platforms, such as portable electronics. However, this method isn't as economically viable in large platforms due to high material and manufacturing costs. High material and manufacturing costs are mostly attributed to the …
Plugging Performance Of Preformed Particle Gels In Fractures And Its Influencing Factors, Ze Wang
Plugging Performance Of Preformed Particle Gels In Fractures And Its Influencing Factors, Ze Wang
Doctoral Dissertations
"Preformed particle gels (PPG) has been successfully applied to combat the water channeling caused by fractures or fracture-like channels. Understanding the placement and plugging of PPG in fractures is crucial for gel treatment design. The objective of the dissertation is to explore the plugging performance of three PPG products in two types of fracture models, the partially and fully open fractures. The following studies has been conducted and conclusions have been drawn based on the results and analysis. First, the placement and plugging performance of conventional PPG was investigated using core flooding experiments conducted partially open fractures. The plugging efficiency …
Modeling Strategies For Estimating And Suppressing Electromagnetic Interference And Improving Power Integrity, Tamar Makharashvili
Modeling Strategies For Estimating And Suppressing Electromagnetic Interference And Improving Power Integrity, Tamar Makharashvili
Doctoral Dissertations
"Decoupling capacitors are used to suppress high-frequency noise in power distribution networks. The inductance associated with a mounted decoupling capacitor can vary by 26% depending on characteristics of the printed circuit board. Here, simple and accurate inductance models of 2- and 8-terminal capacitors including connections to the power and return plane are developed. Circuit models of the capacitors and layout are created using the partial equivalent element circuit method which provide options for circuit-level simulations as well as analytic estimation of inductance. The circuit solution matches results from the full-wave simulation model within 9% for the 8-terminal capacitor and within …
Biomaterials For Bone Regeneration, Youqu Shen
Biomaterials For Bone Regeneration, Youqu Shen
Doctoral Dissertations
"The purpose of this Ph.D. research is to investigate and improve two classes of hydroxyapatite (HA)-based biomaterials for bone repair: calcium phosphate microspheres and bioactive silicate glass scaffolds. These biomaterials were prepared with modified compositions and microstructures and then were evaluated for bone regeneration.
The open HA microspheres with dense convex surfaces and rough and porous concave surfaces were obtained by sectioning closed hollow HA microspheres. Bone regeneration with the open HA microspheres was greater than with the closed HA microsphere at 12 weeks. Hollow biphasic calcium phosphate (BCP) microspheres have been prepared with different fractions of HA and β-TCP …
Build Strategy Investigation Of Ti-6al-4v Produced Via A Hybrid Additive Manufacturing Process, Lei Yan
Build Strategy Investigation Of Ti-6al-4v Produced Via A Hybrid Additive Manufacturing Process, Lei Yan
Doctoral Dissertations
“Till now, laser metal deposition (LMD) has been developed with the capability of near-net shape high-performance metal parts fabrication, especially complicated titanium alloys, nickel alloys, and aluminum alloys. However, LMD processed parts usually do not meet end-use requirements without post treatments. In-process part quality inspection and inner features machining are impossible within a single LMD process. Hybrid additive manufacturing (HAM), which integrates additive and subtractive manufacturing in one process, has been proposed to increase the feasibility of complex parts fabrication. This dissertation aims to improve the applications of Ti-6Al-4V parts fabricated via a HAM technique. The first research topic is …
Hardware Architectures For Compact Microwave And Millimeter Wave Cameras, Matthew Jared Horst
Hardware Architectures For Compact Microwave And Millimeter Wave Cameras, Matthew Jared Horst
Doctoral Dissertations
"Millimeter wave SAR imaging has shown promise as an inspection tool for human skin for characterizing burns and skin cancers. However, the current state-of-the-art in microwave camera technology is not yet suited for developing a millimeter wave camera for human skin inspection. Consequently, the objective of this dissertation has been to build the necessary foundation of research to achieve such a millimeter wave camera. First, frequency uncertainty in signals generated by a practical microwave source, which is prone to drift in output frequency, was studied to determine its effect on SAR-generated images. A direct relationship was found between the level …
Novel Insights Into Low Salinity Water Flooding Enhanced Oil Recovery In Sandstone Reservoirs, Hasan N. Al-Saedi
Novel Insights Into Low Salinity Water Flooding Enhanced Oil Recovery In Sandstone Reservoirs, Hasan N. Al-Saedi
Doctoral Dissertations
"Ever growing global energy demand and the natural decline in oil production from mature oil fields have been the main incentives to search for methods to increase recovery efficiency for several decades. Water flooding is extensively applied worldwide to improve oil recovery. The recent drop in oil prices has turned the oil industry to the cheapest improved oil recovery (IOR) techniques, such as low salinity (LS) waterflooding. Also, the reduction in reservoir energy and the friendly environmental aspects of low salinity water flooding (LSWF) provide additional incentives for its use. That LS water requires decreasing only the active divalent cations …
Scaleable Nanomanufacturing Of Metasurfaces Using Microsphere Photolithography, Chuang Qu
Scaleable Nanomanufacturing Of Metasurfaces Using Microsphere Photolithography, Chuang Qu
Doctoral Dissertations
“The cost-effective manufacturing of metasurfaces over large areas is a critical issue that limits their implementations. Microsphere photolithography (MPL) uses a scalable self-assembled microsphere array as an optical element to focus collimated light to nanoscale photonic jets in a photoresist layer. This dissertation investigates the fabrication capabilities, process control, and potential applications of MPL. First, the MPL concept is applied to the fabrication of metasurfaces with engineered IR absorption (e.g. perfect absorption with multiband/broadband and wavelength/polarization dependences). Improving the patterning of the photoresist requires a fundamental understanding the photochemical photonic jet interactions. The dissertation presents a model of the MPL …
Atomistic Simulations Of Deformation In Metallic Nanolayered Composites, Sixie Huang
Atomistic Simulations Of Deformation In Metallic Nanolayered Composites, Sixie Huang
Doctoral Dissertations
"The mechanical behavior of Metallic Nanolayered Composites (MNCs) is governed by their underlying microstructure. In this dissertation, the roles of the interlayer spacing (grain size, d) and the intralayer biphase spacing (layer thickness, h) on mechanical response of Cu/Nb MNCs are examined by Molecular Dynamics (MD) simulations. The study of the strength of MNCs show that small changes in both d and h play a profound role in the relative plastic contributions from grain boundary sliding and dislocation glide. The interplay of d and h leads to a very broad transition region from grain boundary sliding dominated flow, where the …
Efficient Estimation And Mitigation For Radio-Frequency Interference, Qiaolei Huang
Efficient Estimation And Mitigation For Radio-Frequency Interference, Qiaolei Huang
Doctoral Dissertations
"With rapid innovations in Internet of Things (IoT) and wireless technology, more and more consumer electronic devices around the world are now connected to the internet. In a small form factor electronic device, there are plenty of potential noise sources such as System On Chip (SoC), high speed traces, flexible cables and power converters, etc. Those noise sources can possibly introduce radio frequency interference (RFI) issues. In this dissertation, a transfer function based calculation method is proposed to estimate radio frequency interference (RFI) problems. The derived equations can clearly decompose the RFI problem into two parts: the noise source and …
Development Of Stage-I Tempered High Strength Cast Steel For Ground Engaging Tools, Viraj Ashok Athavale
Development Of Stage-I Tempered High Strength Cast Steel For Ground Engaging Tools, Viraj Ashok Athavale
Doctoral Dissertations
"Ground Engaging Tools (GET) are the expendable replacement parts used in heavy machinery used with mining or construction equipment. GET’s protect the expensive machine components from the wear and tear found common in high-impact or high-abrasion environments. The goal of this project is to develop advanced next-generation alloy choices that outperforms the existing GET materials. A method of predicting tempered hardness of mixed microstructures was formulated. Using this model, two alloy series viz. Cr-Ni-Mo and Mn-Si-Mo-V were proposed and experimented with the goal of obtaining a high strength and impact resistant cast steel. Cast iterations of Cr-Ni-Mo alloy series were …
Applications Of Machine Learning In Nuclear Imaging And Radiation Detection, Shaikat Mahmood Galib
Applications Of Machine Learning In Nuclear Imaging And Radiation Detection, Shaikat Mahmood Galib
Doctoral Dissertations
"The main focus of this work is to use machine learning and data mining techniques to address some challenging problems that arise from nuclear data. Specifically, two problem areas are discussed: nuclear imaging and radiation detection. The techniques to approach these problems are primarily based on a variant of Artificial Neural Network (ANN) called Convolutional Neural Network (CNN), which is one of the most popular forms of 'deep learning' technique.
The first problem is about interpreting and analyzing 3D medical radiation images automatically. A method is developed to identify and quantify deformable image registration (DIR) errors from lung CT scans …
Mass Spectrometry Analysis Of Contaminants Of Emerging Concern: Nanoparticles, Algal Toxins, And Cyanotoxins In Natural Waters And Their Potential Health Impacts, Ariel R. Donovan
Mass Spectrometry Analysis Of Contaminants Of Emerging Concern: Nanoparticles, Algal Toxins, And Cyanotoxins In Natural Waters And Their Potential Health Impacts, Ariel R. Donovan
Doctoral Dissertations
“The analysis of contaminants of emerging concern is critical to protecting environmental health. In the presented dissertation, two groups of contaminants of emerging concern were assessed using mass spectrometry methods: nanoparticles and algal and cyanotoxins.
Analysis of metal oxide nanoparticles in environmental matrices has been a challenging issue, as most traditional methods require complicated sample preparation methods or that can alter or destroy the nanoparticles in the system. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) methods were used to detect metal oxide nanoparticles in surface waters and their removal through drinking water treatment simulations while retaining all information regarding …
Design And Performance Of Fiber-Reinforced Concrete With Adapted Rheology For Construction And Repair Of Bridge Structures, Ahmed Abdelrazik
Design And Performance Of Fiber-Reinforced Concrete With Adapted Rheology For Construction And Repair Of Bridge Structures, Ahmed Abdelrazik
Doctoral Dissertations
“The objective of this document is to design high-performance fiber-reinforced self-consolidating concrete (FR-SCC) for infrastructure repair and fiber-reinforced super-workable concrete (FR-SWC) for bridge construction. The investigated fibers included propylene synthetic fibers, hooked steel fibers, double and triple hooked steel fibers, hybrid crimped steel fiber and polypropylene multifilament fibers, and micro-macro steel fibers. The fiber volume varied between 0 and 0.75%. An expansive agent (EA) was incorporated to compensate for shrinkage and induce compression in the concrete at early age. Two types of EA (G and K) were employed at 0 to 8%, by mass of binder. The investigated FRSCC and …
Three-Dimensional Nanotube Arrays For Solar Energy Harvesting And Production Of Solar Fuels, Wipula P. R. Liyanage
Three-Dimensional Nanotube Arrays For Solar Energy Harvesting And Production Of Solar Fuels, Wipula P. R. Liyanage
Doctoral Dissertations
"Over the past decade extensive research has been carried out on photovoltaic semiconductors to provide a solution towards a renewable energy future. Fabricating high-efficiency photovoltaic devices largely rely on nanostructuring the photoabsorber layers due to the ability of improving photoabsorption, photocurrent generation and transport in nanometer scale. Vertically aligned, highly uniform nanorods and nanowire arrays for solar energy conversion have been explored as potential candidates for solar energy conversion and solar-fuel generation owing to their enhanced photoconversion efficiencies.
However, controlled fabrication of nanorod and especially nanotube arrays with uniform size and shape and a pre-determined distribution density is still a …
Characterization Of Aerosols In An Underground Mine, Arash A. Habibi
Characterization Of Aerosols In An Underground Mine, Arash A. Habibi
Doctoral Dissertations
“Diesel-powered engines are a common source of submicron carbon-rich particles. Characterizing morphological and physical attributes of diesel agglomerates is therefore of great importance to be able to identify the source and improve removal technology. Size-segregated sampling was conducted in two phases of underground experiments. Scanning transmission electron microscopy and fast mobility particle sizers were used to determine the size distribution of agglomerates based on particle mobility and projected area diameter. Controlled zone sampling test results were used to determine the morphological characteristics of agglomerates for specific types of diesel equipment both with and without removal strategies. Changes in fractal dimension, …
Time-Dependent Reliability Methodologies With Saddlepoint Approximation, Zhangli Hu
Time-Dependent Reliability Methodologies With Saddlepoint Approximation, Zhangli Hu
Doctoral Dissertations
"Engineers always encounter time-dependent uncertainties that ubiquitously exist, such as the random deterioration of material properties and time-variant loads. Therefore the reliability of engineering systems becomes time-dependent. It is crucial to predict the time-dependent reliability in the design stage, given possible catastrophic consequences of a failure. Although extensive research has been conducted on reliability analysis, estimating the reliability accurately and efficiently is still challenging. The objective of this work is to develop accurate and efficient reliability methodologies for engineering design. The basic idea is the integration of traditional reliability methods with saddlepoint approximation (SPA), which can accurately approximate the tail …
Military Applications Of Geological Engineering, Stephen H. Tupper
Military Applications Of Geological Engineering, Stephen H. Tupper
Doctoral Dissertations
"This work examines the premise that military engineering and geological engineering are intellectually paired and overlapped in practice to a significant extent. Geological engineering is an established, albeit young, academic discipline that enjoys wide industry and civil demand and is supported by many professional organizations. In contrast, military engineering is an ancient, empirically derived training or "OJT" program with practice-based trade-associations that has narrow government-only utility. The premise is formed by decades-long observation of U. S. Army military engineer officers completing a Master of Science degree in geological engineering as a complement to their practice-based training in military engineering at …
Nanomorphology Dependent Optical And Mechanical Properties Of Aerogels, Chandana Mandal
Nanomorphology Dependent Optical And Mechanical Properties Of Aerogels, Chandana Mandal
Doctoral Dissertations
"Aerogels are very low density, light weight open pore materials. A hypothesis that is under intense current investigation by the scientific community states that the mechanical properties of nanostructured polymers depend on their nanomorphology. Aerogels are nanostructured ultra-lightweight nanoporous materials with skeletal frameworks that can display a wide range of nanomorphologies. Thereby aerogels comprise a suitable platform for testing not only that hypothesis but also a wide range of other properties such as light scattering for applications, for example, in thermally insulating windows.
To study the mechanical properties of nanostructured matter as a function of nanomorphology, various shape-memory polyurethane aerogels …
Microstructural Evolution Of Zirconium Carbide (Zrcₓ) Ceramics Under Irradiation Conditions, Raul Florez
Microstructural Evolution Of Zirconium Carbide (Zrcₓ) Ceramics Under Irradiation Conditions, Raul Florez
Doctoral Dissertations
A comprehensive understanding of the microstructural evolution of Zirconium Carbide (ZrC2) ceramics under irradiation conditions is required for their successful implementation in advanced Gen-IV gas-cooled nuclear reactors. The research presented in this dissertation focusses on elucidating the ion and electron irradiation response of ZrC2 ceramics. In the first part of the research, the microstructural evolution was characterized for ZrC2 ceramics irradiated with 10 MeV Au3+ ions up to doses of 30 displacement per atom (dpa) at 800 ºC. Coarsening of the defective microstructure, as a function of dose, was revealed by transmission electron microscopy analysis. …
Deep Understanding Of Degradation In Lithium Ion Batteries Through Experimental And First-Principles Study, Yufang He
Doctoral Dissertations
"The growing interests in Lithium-ion Batteries (LIBs) have significantly accelerated the development of active materials. However, the key challenge is that electrode materials suffer from degradation, which include transition metal dissolution, solid electrolyte interphase (SEI) layer formation, and mechanical fracture. To address these issues, applying an ultrathin coating onto active materials via Atomic Layer Deposition (ALD) is an efficient way. Although numerious works have been done for active material performance improvement via ALD technology, the fundamental enhancement mechanisms of ALD coating on battery performance improvement are not yet known. Therefore, this dissertation consists of four papers, which focused on the …
Design And Prototyping Of A Real-Time Millimeter Wave Imaging System, Zahra Manzoor
Design And Prototyping Of A Real-Time Millimeter Wave Imaging System, Zahra Manzoor
Doctoral Dissertations
"The goal of this work is to design, prototype and test an innovative millimeter wave imaging system that operates in the frequency range of 33-35 GHz and is capable of producing rapid images of various diverse scenes. In particular, the imaging system includes two main sections, one is related to the hardware design of the system, and the other focuses on the development of a novel comprehensive image reconstruction algorithm. The hardware design includes custom transmitter and receiver sub-systems, and a sparse switched array which was optimized for 320 mm x 220 mm aperture plane, and also included an improved …
Characterization And Modeling Of Esd Events And Near-Field Scanning Calibration Structures, Shubhankar Kashinath Marathe
Characterization And Modeling Of Esd Events And Near-Field Scanning Calibration Structures, Shubhankar Kashinath Marathe
Doctoral Dissertations
"This research is divided into three papers that cover, two major topics. The first topic, system-level electrostatic discharge (ESD), is discussed over the course of two papers. The second topic, a calibration structure for near-field scanning probe calibration application, is discussed in the last paper. In the first paper, software-assisted detection methods are proposed for secondary ESD discharges. The measured waveforms are analyzed with respect to waveform parameters, such as the vertical threshold of the rising edge, the derivative of the current waveform, and total charge delivered. These parameters enable automatic detection of secondary ESD while monitoring the discharge waveform …
The Effects Of Fatigue And Weathering On The Failure Behavior Of Commercial Soda-Lime-Silicate Glass, Erica Ann Ronchetto
The Effects Of Fatigue And Weathering On The Failure Behavior Of Commercial Soda-Lime-Silicate Glass, Erica Ann Ronchetto
Doctoral Dissertations
"The principle objective of this research is to advance our understanding of the effects of humid conditions on the strength and susceptibility to fatigue of soda-lime silicate (SLS) glass. The two-point bend method was used to evaluate the fatigue characteristics and the degradation of failure strain of fibers drawn from melts of commercial soda-lime silicate glass and exposed to various environmental conditions. Soda lime silicate glasses from two commercial products but with similar nominal compositions were examined. One glass had pristine failure strains about 10% greater than the other, but both had similar fatigue parameters. The fatigue parameter increased from …
Underwater Acoustic Communications And Adaptive Signal Processing, Mohammadhossein Behgam
Underwater Acoustic Communications And Adaptive Signal Processing, Mohammadhossein Behgam
Doctoral Dissertations
"This dissertation proposes three new algorithms for underwater acoustic wireless communications. One is a new tail-biting circular MAP decoder for full tail-biting convolution (FTBC) codes for very short data blocks intended for Internet of Underwater Things (IoUT). The proposed algorithm was evaluated by ocean experiments and computer simulations on both Physical (PHY) and Media access control (MAC) layers. The ocean experimental results show that without channel equalization, the full tail-biting convolution (FTBC) codes with short packet lengths not only can perform similarly to zero-tailing convolution (ZTC) codes in terms of bit error rate (BER) in the PHY layer. Computer simulation …
Deep Neural Network Learning-Based Classifier Design For Big-Data Analytics, Krishnan Raghavan
Deep Neural Network Learning-Based Classifier Design For Big-Data Analytics, Krishnan Raghavan
Doctoral Dissertations
"In this digital age, big-data sets are commonly found in the field of healthcare, manufacturing and others where sustainable analysis is necessary to create useful information. Big-data sets are often characterized by high-dimensionality and massive sample size. High dimensionality refers to the presence of unwanted dimensions in the data where challenges such as noise, spurious correlation and incidental endogeneity are observed. Massive sample size, on the other hand, introduces the problem of heterogeneity because complex and unstructured data types must analyzed. To mitigate the impact of these challenges while considering the application of classification, a two step analysis approach is …
Intelligent Data-Driven Decision-Making To Mitigate Or Stop Lost Circulation, Husam Hasan Alkinani
Intelligent Data-Driven Decision-Making To Mitigate Or Stop Lost Circulation, Husam Hasan Alkinani
Doctoral Dissertations
”Lost circulation is a challenging problem in the oil and gas industry. Each year, millions of dollars are spent to mitigate or stop this problem. The aim of this work is to utilize machine learning and other intelligent solutions to help to make better decision to mitigate or stop lost circulation. A detailed literature review on the applications of decision tree analysis, expected monetary value, and artificial neural networks in the oil and gas industry was provided. Data for more than 3000 wells were gathered from many sources around the world. Detailed economics and probability analyses for lost circulation treatments’ …
Improving Base Metal Electrowinning, Charles Ebenezer Abbey
Improving Base Metal Electrowinning, Charles Ebenezer Abbey
Doctoral Dissertations
"In zinc electrowinning, Mn oxidizes to form MnO2 on Pb-Ag anodes, cell walls and pipes. MnO2 reduces anode corrosion but also leads to short circuits and maintenance issues. MnO2 is thought to interact with chloride ions and produce oxidized chlorine species. The interactions between Mn and Cl are not well understood. Bench scale experiments were conducted to investigate the effects of the manganese to chloride ratio on anode corrosion rate and electrolyte chemistry using rolled Pb-Ag anodes. Increasing the average Mn/Cl- ratio from ~7:1 to ~11:1 reduced the anode corrosion rate. Anode scales produced with Mn/Cl …
Transient Multiphase Flow Simulation For Unloading Of Frac Hit Gas Wells, Miguel Angel Cedeno Moreno
Transient Multiphase Flow Simulation For Unloading Of Frac Hit Gas Wells, Miguel Angel Cedeno Moreno
Doctoral Dissertations
"This work seeks to develop a fully step-by-step transient multiphase flow simulation valid for unloading gas wells using nitrogen. It studies the behavior of nitrogen for unloading horizontal gas wells with gas injection in the annulus. The work investigates unloading non-Newtonian fluids such as those which invade offset wells when a frac hit occurs during hydraulic fracturing operations in unconventional wells. The effect of varying tubing depth and injection pressure are included in the study.
Results show that as the plastic viscosity increases, the nitrogen volume and time to unload will be increased. As tubing depth increases, the nitrogen volume …