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Articles 31 - 58 of 58
Full-Text Articles in Engineering
Laboratory Study Of The Geotechnical Properties Of Abraded Railway Ballast With Natural And Clay Mix Fouling, Andrew Rohrman
Laboratory Study Of The Geotechnical Properties Of Abraded Railway Ballast With Natural And Clay Mix Fouling, Andrew Rohrman
Doctoral Dissertations
With 140,000 miles of active track, railroad freight is the largest method of transporting goods in the United States. An important component of the railroad substructure is the gravel-size aggregate placed below the tracks, called ballast. The ballast is responsible for draining water away from the track, resisting forces from traffic loading, maintaining track position, and reducing loads to acceptable pressures for the subgrade. Ballast is typically selected to be highly angular and uniformly graded, but these characteristics are constantly changing under dynamic traffic loading. As the ballast is loaded, the particles abrade against each other, grinding off stone dust …
Walking For Object Transport: An Examination Of The Coordinative Adaptations To Locomotor, Perceptual, And Manual Task Constraints, Avelino Amado
Walking For Object Transport: An Examination Of The Coordinative Adaptations To Locomotor, Perceptual, And Manual Task Constraints, Avelino Amado
Doctoral Dissertations
The goal of this dissertation was to understand how the intrinsic dynamics of gait adapt to support the performance of an ecologically relevant object transport task. A common object transport task is walking with a cup of water. Because the water can move relatively independent of the cup, the cup and water system is classified as a complex object. To model this task participants carried a cup with a wooden lid placed on top. On the lid there was a circular region with the same circumference as the cup and a ball. The object of the task was to keep …
Mechanical Performance Of Structural Systems With Missing Members: From Buildings To Architected Materials, Panagiotis Pantidis
Mechanical Performance Of Structural Systems With Missing Members: From Buildings To Architected Materials, Panagiotis Pantidis
Doctoral Dissertations
Structural systems are potentially subjected to damage initiating scenarios throughout the course of their service time. Depending on the nature and extent of the damaging event, they may experience significant reduction or even complete loss of their mechanical performance. This dissertation delves into the mechanics of structural systems under the notion of missing members from their domain, investigating types of structural systems: a) multi-story steel framed buildings, and b) materials with a truss-lattice microstructure. Part I of the dissertation investigates the performance of multi-story steel framed buildings under a column removal scenario, developing an analytical framework for their quasi-static robustness …
Power System Planning In Disparate Systems: Modeling Sustainability And Electricity Access, Destenie Nock
Power System Planning In Disparate Systems: Modeling Sustainability And Electricity Access, Destenie Nock
Doctoral Dissertations
Electricity goals around the world tend to focus on increasing social benefit through one of two avenues: (1) increasing overall system sustainability or (2) increasing access to electricity. These goals guide the transition of the power system. In pursuit of these goals decision makers will need modeling tools that can inform decisions, in a way that is flexible enough to include a wide range of preferences and goals. It is clear that the future generation mix of the power system will change, but the most sustainable solution, will change based on a country's goals. This dissertation will explore the various …
Equity And Efficiency In Multi-Modal Transportation Systems, Nicholas M. Fournier
Equity And Efficiency In Multi-Modal Transportation Systems, Nicholas M. Fournier
Doctoral Dissertations
The land-use pattern for many cities is a central business district surrounded by sprawling suburbs. This pattern can lead to an inefficient and congestion-prone transportation system due to a reliance on automobiles, because high-capacity transit is not efficient in low-density areas where insufficient travelers can access transit. This also poses an equity concern as the monetary cost of faster and more expensive travel disproportionately burdens low income travelers. This dissertation presents a deterministic approximation of a discrete choice model for mixed access and mainline transportation modes, meaning that travelers may use different modes to access a mainline system, such as …
Sparsity In Machine Learning: An Information Selecting Perspective, Siwei Feng
Sparsity In Machine Learning: An Information Selecting Perspective, Siwei Feng
Doctoral Dissertations
Today we are living in a world awash with data. Large volumes of data are acquired, analyzed and applied to tasks through machine learning algorithms in nearly every area of science, business, and industry. For example, medical scientists analyze the gene expression data from a single specimen to learn the underlying causes of disease (e.g. cancer) and choose the best treatment; retailers can know more about customers' shopping habits from retail data to adjust their business strategies to better appeal to customers; suppliers can enhance supply chain success through supply chain systems built on knowledge sharing. However, it is also …
A Discrete-Time Technique For Linearity Enhancement Of Wideband Receivers, Mohammad Ghadiri Sadrabadi
A Discrete-Time Technique For Linearity Enhancement Of Wideband Receivers, Mohammad Ghadiri Sadrabadi
Doctoral Dissertations
A new signal processing technique is introduced to enhance the linearity performance of wideband radio frequency (RF) receivers. The proposed technique combines the advancements in mixer first architectures with a library of binary sequences as local oscillator signals to enable wide instantaneous bandwidth and high linearity for the RF receiver. To do so, N-bit pseudo-random-binary-sequences (PRBS) are used as local oscillator signals. The RF input signal is multiplied with the PRBS at the mixer and then averaged over the full sequence. This in effect reduces the amplitude of the signal and improves the overall linearity of the system. In order …
Rheological Investigations Of Self-Assembled Block Copolymer Nanocomposites With Complex Architectures, Benjamin Yavitt
Rheological Investigations Of Self-Assembled Block Copolymer Nanocomposites With Complex Architectures, Benjamin Yavitt
Doctoral Dissertations
The self-assembly of block copolymers (BCP) into microphase separated structures is an attractive route to template and assemble functional nanoparticles (NP) into highly ordered nanocomposites and is central to the “bottom up” fabrication of future materials with tunable electronic, optical, magnetic, and mechanical properties. The optimization of the co-assembly requires an understanding of the fundamentals of phase behavior, intermolecular interactions and dynamics of the polymeric structure. Rheology is a novel characterization tool to investigate these processes in such systems that are not accessible by other means. With the combination of X-ray scattering techniques, structure-property relationships are determined as a function …
Direct Printing/Patterning Of Key Components For Biosensor Devices, Yiliang Zhou
Direct Printing/Patterning Of Key Components For Biosensor Devices, Yiliang Zhou
Doctoral Dissertations
Recently, biosensor devices, especially wearable devices for monitoring human health, have attracted significant interests and meanwhile, they have a huge market. These wearable biosensor devices usually consist of several key components, including microfluidics, biosensing elements and power supply. Though advanced sensing platforms have been extensively explored, high manufacturing fee and lack of practical functions are the main reasons that most of devices and techniques are still out of reach for potential users. This dissertation focuses on fabricating these key components for biosensor devices via advanced printing/patterning techniques, such as inkjet-printing and nanoimprinting. These fabrication techniques can be potentially extended to …
Quantitative Probing Of Vacancies And Ions Dynamics In Electroactive Oxide Materials, Jiaxin Zhu
Quantitative Probing Of Vacancies And Ions Dynamics In Electroactive Oxide Materials, Jiaxin Zhu
Doctoral Dissertations
Oxygen vacancy and ion dynamics in functional oxides are critical factors influencing electrical conductivity and electrochemical activity of oxides assemblies. The recent advancements in deposition and fabrication of oxide heterostructured films with atomic-level precision has led to discovery of intriguing physical properties and new artificial materials. While still under debate, researchers most often attribute these observed behaviors to unique oxygen vacancy distributions in the substrate near heterointerfaces. In electroactive oxides devices such as solid oxide cells (SOCs), oxygen vacancy and ion transport at the triple-phase boundary determines the performance of the device. This complex process motivates numerous remaining questions regarding …
Improving And Understanding Data Quality In Large-Scale Data Systems, Xiaolan Wang
Improving And Understanding Data Quality In Large-Scale Data Systems, Xiaolan Wang
Doctoral Dissertations
Systems and applications rely heavily on data, which makes data quality a critical factor for their function. In turn, low quality data can be incredibly costly and disruptive, leading to loss of revenue, incorrect conclusions, and misguided policy decisions. Improving data quality is far more than purging datasets of errors; it is more important to improve the processes that produce the data, to collect good data sources that are used for generating the data, and to truly understand the quality of the data. Therefore, the objective of this thesis is to improve and understand data quality from the above aspects. …
Targeted Design Of Co-Continuous Nanostructures In Copolymers, Di Zeng
Targeted Design Of Co-Continuous Nanostructures In Copolymers, Di Zeng
Doctoral Dissertations
Microphase separated copolymers with nano-scale morphologies are critically important in designing next generation materials. Cocontinuous nanoscale structures, in which domains of multiple different phases each simultaneously percolate in three dimensions, provide opportunities to synergistically combine properties of the constituent polymers in a wide variety of contexts. While cocontinuous nanostructures are fabricated through equilibrium self-assembly of block or graft copolymers and kinetically trapped phase separation of polymer blends or crosslinked copolymer networks, their formation is highly sensitive to changes in chemical details, synthesis and/or processing conditions, bringing practical challenges to generalization to multiple systems. In this dissertation, we focus on transforming …
Probing Quantized Excitations And Many-Body Correlations In Transition Metal Dichalcogenides With Optical Spectroscopy, Shao-Yu Chen
Probing Quantized Excitations And Many-Body Correlations In Transition Metal Dichalcogenides With Optical Spectroscopy, Shao-Yu Chen
Doctoral Dissertations
Layered transition metal dichalcogenides (TMDCs) have attracted great interests in recent years due to their physical properties manifested in different polytypes: Hexagonal(H)-TMDC,which is semiconducting, exhibits strong Coulomb interaction and intriguing valleytronic properties; distorted octahedral(T’)-TMDC,which is semi-metallic, is predicted to exhibit rich nontrivial topological physics. In this dissertation,we employ the polarization-resolved micron-Raman/PL spectroscopy to investigate the optical properties of the atomic layer of several polytypes of TMDC. In the first part for polarization-resolved Raman spectroscopy, we study the lattice vibration of both H and T’-TMDC, providing a thorough understanding of the polymorphism of TMDCs. We demonstrate that Raman spectroscopy is a …
Synthesis And Molecular Transport Studies In Zeolites And Nanoporous Membranes, Vivek Vattipalli
Synthesis And Molecular Transport Studies In Zeolites And Nanoporous Membranes, Vivek Vattipalli
Doctoral Dissertations
The advent of nanoporous materials such as zeolites and nanoporous membranes has provided cost-effective solutions to some of the most pressing problems of the 20th century such as the conversion of crude oil into fuels and valuable chemicals. Hierarchical zeolites and mesoporous inorganic membranes are showing great promise in addressing new problems such as the conversion of biomass into value-added chemicals and development of energy-efficient separation processes. The synthesis and fundamental aspects of molecular transport in these new materials with hierarchical porosities need to be better understood in order to rationally develop them for these desired applications. Pore narrowing …
Development Of Functional Biomaterials Using Protein Building Blocks, Li-Sheng Wang
Development Of Functional Biomaterials Using Protein Building Blocks, Li-Sheng Wang
Doctoral Dissertations
Proteins have intrinsic molecular properties that are highly useful for materials applications, especially for biomaterials. My research has focused on translating these molecular properties to materials surface behavior. In one approach, I developed a fluorous-based thermal treatment strategy to generate stable thin films from a variety of naturally abundant proteins. The different surface properties generated from the choice of protein were utilized to modulate cell-surface interactions, prevent bacterial adhesions, and control drug loading/release. I have used nanoimprint lithography to generate patterned protein films for cell alignment. Coupling with inkjet printing deposition, I have fabricated mixed protein films with spatial and …
Chemical Stability And Performance Influence Of Choice Substituents And Core Conjugation Of Organic Semiconductors, Jack Ly
Doctoral Dissertations
Realizing organic based active materials for electronic devices, such as thin film transistors and photovoltaics, has been long sought after. Advancement in the field driven by chemists, engineers, and physicists alike have bolstered organic based semiconductor performance levels to rival those of traditional inorganic amorphous silicon-based devices. Within the field of organic semiconductors (OSC), two categories of active materials may be generalized: (1) polymer and (2) small molecule semiconductors. Each class of OSC inherently have their own advantages and disadvantages. Polymer semiconductors (PSC) allow a wide range in tunability via choice monomers and side chain engineering to illicit desirable energy …
Building The Outer Membrane Protein G (Ompg) Nanopore Library: From The Discrimination Of Biotin-Binding Proteins In Serum To Resolving Human Carbonic Anhydrase From Human Red Blood Cells, Bib Yang
Doctoral Dissertations
The use of pore-forming proteins (PFPs) in nanopore sensing has been fruitful largely due to their nanoscale size and the ease with which protein nanopores can be manipulated and consistently reproduced at a large scale. Nanopore sensing relies heavily on a steady ionic current afforded by rigid nanopores, as the change in current is indicative of analyte detection, revealing characteristics of the analyte such as its relative size, concentration, and charge, as well as the nanopore:analyte interaction. Rigid PFPs have been used in applications such as DNA sequencing, kinetic studies, analyte discrimination, and protein conformation dynamics at the single-molecule level. …
Modeling Temporal Structures In Time-Varying Networks, Kun Tu
Modeling Temporal Structures In Time-Varying Networks, Kun Tu
Doctoral Dissertations
A dynamic network is a network whose structure changes because of the emergence and disappearance of node or edges. It can be used to study complex systems where individuals in a system are represented as nodes and their relations/interactions are represented as edges. Studying dynamic network structures helps to better understand changes in relationships. Considerable work has been conducted on learning network structure. However, due to the complexity of dynamic networks, there is considerable room for improvement to obtain better analysis results. This thesis studies different aspects of characteristic and dynamics of a network, focusing on their application in link …
Direct Patterning Of Nature-Inspired Surfaces For Biointerfacial Applications, Feyza Dundar
Direct Patterning Of Nature-Inspired Surfaces For Biointerfacial Applications, Feyza Dundar
Doctoral Dissertations
There are three major challenges for the design of patterned surfaces for biointerfacial applications: (i) durability of antibacterial/antifouling mechanisms, (ii) mechanical durability, and (iii) lifetime of the master mold for mass production of patterned surfaces. In this dissertation, we describe our contribution for the development of each of these challenges. The bioinspired surface, Sharklet AFTM, has been shown to reduce bacterial attachment via a biocide-free structure-property relationship effectively. Unfortunately, the effectiveness of polymer-based sharkskin surfaces is challenged over the long term by both eventual bacteria accumulation and a lack of mechanical durability. To address these common modes of …
Direct Printing Of Conductive Inks For Organic Electronics And Wearable Microfluidics, Aditi Naik
Direct Printing Of Conductive Inks For Organic Electronics And Wearable Microfluidics, Aditi Naik
Doctoral Dissertations
This dissertation examines the direct printing of conductive inks on polymeric substrates for applications in organic electronics, microfluidic valving systems, and wearable sweat sensors. The inexpensive production of solution-based electrodes with high electrical conductivity is necessary to enable the next-generation of printed, flexible, and organic electronics. Specifically, the optimization and printing of liquid-phase graphene ink and nanoparticle-based silver ink by soft nanoimprint lithography and inkjet-printing is discussed to achieve printed functional devices. Using scalable low-cost patterning systems, these flexible applications are compatible with roll-to-roll processing, enabling large-scale manufacturing. This research expands the knowledge of high-resolution printing optimization for the direct …
The Investigation Of Surface Barrier During Molecular Transport In Hierarchical Zeolites, Xiaoduo Qi
The Investigation Of Surface Barrier During Molecular Transport In Hierarchical Zeolites, Xiaoduo Qi
Doctoral Dissertations
Hierarchical zeolites with micropore lengths on the order of nanometers have been synthesized with the aim of reducing mass transfer limitation. However, due to large external surface to volume ratios, the mass transport in these materials can be hindered by a secondary rate limitation step imposed on the external surface of the zeolites. This has led to the general phenomenon referred to as “surface barriers”, which cause the enhancement in mass transport being far lower than expected. In order to fully unlock the potential of hierarchical zeolites, it is imperative to fundamentally understand the molecular transport in these new types …
Modeling And Optimizing Routing Decisions For Travelers And On-Demand Service Providers, Xinlian Yu
Modeling And Optimizing Routing Decisions For Travelers And On-Demand Service Providers, Xinlian Yu
Doctoral Dissertations
This thesis investigates the dynamic routing decisions for individual travelers and on-demand service providers (e.g., regular taxis, Uber, Lyft, etc). For individual travelers, this thesis models and predicts route choice at two time-scales: the day-to-day and within-day. For day-to-day route choice, methodological development and empirical evidences are presented to understand the roles of learning, inertia and real-time travel information on route choices in a highly disrupted network based on data from a laboratory competitive route choice game. The learning of routing policies instead of simple paths is modeled when real-time travel information is available, where a routing policy is defined …
A Multiline Anchor Concept For Floating Offshore Wind Turbines, Casey Fontana
A Multiline Anchor Concept For Floating Offshore Wind Turbines, Casey Fontana
Doctoral Dissertations
Floating offshore wind turbines (FOWTs) hold great potential for the renewable energy industry, but capital costs remain high. In efforts to increase FOWT substructure efficiency and reduce costs, this thesis investigates a novel multiline anchor concept in which FOWTs share anchors instead of being moored separately. The goal of this thesis is to evaluate the force dynamics, design, and potential cost reduction of the system. Anchor forces are simulated using the NREL 5 MW reference turbine and OC4-DeepCwind semisubmersible platform, and multiline anchor force is computed as the vector sum of the contributing mooring line tensions. The use of a …
Sequence Design Via Semidefinite Programming Relaxation And Randomized Projection, Dian Mo
Sequence Design Via Semidefinite Programming Relaxation And Randomized Projection, Dian Mo
Doctoral Dissertations
Wideband is a booming technology in the field of wireless communications. The receivers in wideband communication systems are expected to cover a very wide spectrum and adaptively extract the parts of interest. The literature has focused on mixing the input spectrum to baseband using a pseudorandom sequence modulation and recovering the received signals from linearly independent measurements by parallel branches to mitigate the pressures from required extreme high sampling frequency. However, a pseudorandom sequence provides no rejection for the strong interferers received together with weak signals from distant sources. The interferers cause significant distortion due to the nonlinearity of the …
Applications Of Machine Learning Methods In Macroscopic Crash Analysis For Transportation Safety Management, Somaye Garmroudi Dovirani
Applications Of Machine Learning Methods In Macroscopic Crash Analysis For Transportation Safety Management, Somaye Garmroudi Dovirani
Doctoral Dissertations
Transportation Safety Planning (TSP) is a statewide-scale tool and combines transportation planning processes with safety aims to increase safety and reduce transportation fatalities and injuries. Traffic safety, which continues to remain a critical issue worldwide, has led to a myriad of modeling techniques to improve analytical capabilities with respect to crash modeling and prediction. State and metropolitan transportation planning processes must be consistent with Strategic Highway Safety Plans. This research aims to identify models and methods to improve the ability to capture variables that have the most significant impact on traffic safety through crash prediction modeling. In order to achieve …
Thermodynamic And Economic Analysis Of Several Hybrid Multigeneration Cycles And Waste Heat Recovery Systems Driven By Concentrated Solar Tower, Kasra Mohammadi
Thermodynamic And Economic Analysis Of Several Hybrid Multigeneration Cycles And Waste Heat Recovery Systems Driven By Concentrated Solar Tower, Kasra Mohammadi
Doctoral Dissertations
In recent decades, growth in the world population, economic and living standards have been responsible for substantial increases in global energy consumption. Moreover, exploitation of fossil fuels to supply energy demands has led to global climate change, which is expected to have far-reaching and long-lasting consequences on the planet. These factors have motivated the importance and necessity of developing more efficient ways for energy conservation and generation that avoid the production of greenhouse gases that contribute to climate change. One method to address these issues is to develop combined production such as multigeneration for simultaneous production of electricity, cooling, fresh …
Fundamental Limits Of Covert Communication In Packet Channels, Ramin Soltani
Fundamental Limits Of Covert Communication In Packet Channels, Ramin Soltani
Doctoral Dissertations
This dissertation focuses on covert communication in channels where the communication takes place by the transmission of packets. Consider a channel where authorized transmitter Jack sends packets to authorized receiver Steve according to a Poisson process with rate $\lambda$ packets per second for a time period $T$. Jack's transmitted packet visit Alice, Willie, Bob and Steve, respectively. Suppose that covert transmitter Alice wishes to communicate information to covert receiver Bob without being detected by a watchful adversary Willie. We consider three sets of assumptions for this channel. For each set of assumptions, we present a technique for establishing covert communication …
Application Of Ground Penetrating Radar For Use In Thermal Conductivity Site Investigations, Aaron J. Rubin
Application Of Ground Penetrating Radar For Use In Thermal Conductivity Site Investigations, Aaron J. Rubin
Doctoral Dissertations
Measurement of soil thermal conductivity in-situ is important for many practical geotechnical and civil engineering applications. However, for a variety of reasons it can be difficult to measure in-situ. A novel method to estimate the thermal conductivity of sands based on electrical relative permittivity (dielectric constant) measurements and GPR data is presented. First, an analytical model to estimate thermal conductivity of soils was developed and validated using a database of thermal conductivity measurements. The new thermal conductivity model was then compared to existing models using a larger database of new and pervious thermal conductivity measurements conducted on a wide range …