Engineering Commons^™

The Rheology And Roll-To-Roll Processing Of Shear-Thickening Particle Dispersions, Sunilkumar Khandavalli

Doctoral Dissertations

Particle dispersions are ubiquitous in our daily lives ranging from food and pharmaceutical products to inks. There has been great interest in the recent years in formulation of functional inks to fabricate myriad flexible electronic devices through high-throughput roll-to-roll technologies. The formulations often contain several functional additives or rheological modifiers that can affect the microstructure, rheology and processing. Understanding the rheology of formulations is important for tuning the formulation for optimal processing. This thesis presents investigations on the rheology of particle dispersions and their impact on roll-to-roll technologies. Shear-thickening behavior is common in particle dispersions, particularly, concentrated particulate inks. We …

Aliovalent Dopants In Zno Nanocrystals: Synthesis To Electronic Structure, Dongming Zhou

Doctoral Dissertations

Semiconductor nanocrystal doping has stimulated broad interest for many applications including solar energy conversion, nanospintronics, and phosphors or optical labels. The study of the chemistry and physics of doped colloidal semiconductor nanocrystals has been dominated in the literature by isovalent dopants such as Mn²⁺ and Co²⁺ ions in II-VI semiconductors, in which the dopant oxidation state is the same as the cation ions. Until recently, aliovalent dopants has received much attention due to the plasmonic properties. Aliovalent is when the oxidation states of the dopant in the lattice differs from the cation ions. In the plasmonic semiconductor nanocrystals, …

Formal Analysis Of Arithmetic Circuits Using Computer Algebra - Verification, Abstraction And Reverse Engineering, Cunxi Yu

Doctoral Dissertations

Despite a considerable progress in verification and abstraction of random and control logic, advances in formal verification of arithmetic designs have been lagging. This can be attributed mostly to the difficulty in an efficient modeling of arithmetic circuits and datapaths without resorting to computationally expensive Boolean methods, such as Binary Decision Diagrams (BDDs) and Boolean Satisfiability (SAT), that require “bit blasting”, i.e., flattening the design to a bit-level netlist. Approaches that rely on computer algebra and Satisfiability Modulo Theories (SMT) methods are either too abstract to handle the bit-level nature of arithmetic designs or require solving computationally expensive decision or …

The Role Of Chain Configuration In Governing The Rational Design Of Polymers For Adhesion, Onyenkachi Wamuo

Doctoral Dissertations

ABSTRACT THE ROLE OF CHAIN CONFIGURATION IN GOVERNING THE RATIONAL DESIGN OF POLYMERS FOR ADHESION SEPTEMBER 2017 ONYENKACHI C. WAMUO, B.Eng., FEDERAL UNIVERSITY OF TECHNOLOGY, OWERRI (FUTO), NIGERIA M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Shaw Ling Hsu The chain configurational control of polymers used in adhesion can be utilized as a means of tuning the cohesive properties of hot melt adhesives (HMAs). The cohesive properties control the solidification, strength, setting speed. Propylene-Ethylene copolymers (PP-co-PE) and thermoplastic polyurethanes (TPUs) were studied. In the first project, the effects of sequence distribution of the two types …

Microbial Competition In Bioelectrochemical Systems, Varun Srinivasan

Doctoral Dissertations

Bioelectrochemical systems(BESs)/ microbial fuel fells (MFCs) are a well-studied potential technology for bioremediation and decentralized wastewater treatment. However, progress has been somewhat stalled at the bench-scale. In well controlled experiments electron recovery is high. In natural environments, wastewaters are complex and anode-respiring bacteria can be outcompeted in the presence of competing microorganisms, leading to a loss in electron-recovery and power production. Furthermore, the cathode of the MFC plays a vital role in providing flexibility for treatment options but is an understudied part of MFCs. Modelling Intracellular Competition in a Denitrifying Biocathode: One potential MFC configuration uses an organic-oxidizing anode biofilm …

Computational Studies Of Structure–Function Relationships Of Supported And Unsupported Metal Nanoclusters, Hongbo Shi

Doctoral Dissertations

Fuel cells have been demonstrated to be promising power generation devices to address the current global energy and environmental challenges. One of the many barriers to commercialization is the cost of precious catalysts needed to achieve sufficient power output. Platinum-based materials play an important role as electrocatalysts in energy conversion technologies. In order to improve catalytic efficiency and facilitate rational design and development of new catalysts, structure–function relationships that underpin catalytic activity must be understood at a fundamental level. First, we present a systematic analysis of CO adsorption on Pt nanoclusters in the 0.2-1.5 nm size range with the aim …

Modeling Performance, Cost, Delivery, And Trip Distribution Of Demand Responsive Transit Systems With Zoning, Mahour Rahimi

Doctoral Dissertations

Demand responsive transit (DRT) services are expensive to operate, so it is crucial to understand the factors that drive the agency costs and be able to investigate and predict the effect of possible changes in specific operating parameters as well as demand and service coverage areas on total costs. In this research, we adopt the concept of the analytical model proposed by Daganzo (1978) to present continuum approximation (CA) models that can estimate important service related factors. As the first step, we propose three analytical models to approximate the operation related variables of DRT services; Fleet Size, Vehicle Hours Traveled …

Theory And Practice Of Supply Chain Synchronization, Michael Prokle

Doctoral Dissertations

In this dissertation, we develop strategies to synchronize component procurement in assemble-to-order (ATO) production and overhaul operations. We focus on the high-tech and mass customization industries which are not only considered to be very important to create or keep U.S. manufacturing jobs, but also suffer most from component inventory burden. In the second chapter, we address the deterministic joint replenishment inventory problem with batch size constraints (JRPB). We characterize system regeneration points, derive a closed-form expression of the average product inventory, and formulate the problem of finding the optimal joint reorder interval to minimize inventory and ordering costs per unit …

Analyses Of Densely Crosslinked Phenolic Systems Using Low Field Nmr, Jigneshkumar Patel

Doctoral Dissertations

A uniform dispersion of reactants is necessary to achieve a complete reaction involving multi-components, especially for the crosslinking of rigid high-performance materials. In these reactions, miscibility is crucial for curing efficiency. This miscibility is typically enhanced by adding a third component, a plasticizer. For the reaction of the highly crystalline crosslinking agent hexamethylenetetramine (HMTA) with a strongly hydrogen-bonded phenol formaldehyde resin, furfural has been traditionally used as the plasticizer. However, the reason for its effectiveness is not clear. In this doctoral thesis work, miscibility and crosslinking efficiency of plasticizers in phenolic curing reactions are studied by thermal analysis and spectroscopic …

Protein-Nanoparticle Co-Engineering: Self-Assembly, Intracellular Protein Delivery, And Crispr/Cas9-Based Gene Editing, Rubul Mout

Doctoral Dissertations

Direct cytoplasmic delivery of gene editing nucleases such CRISPR/Cas9 systems and therapeutic proteins provides enormous opportunities in curing human genetic diseases, and assist research in basic cell biology. One approach to attain such a goal is through engineering nanotechnological tools to mimic naturally existing intra- and extracellular protein delivery/transport systems. Nature builds transport systems for proteins and other biomolecules through evolution-derived sophisticated molecular engineering. Inspired by such natural assemblies, I employed molecular engineering approaches to fabricate self-assembled nanostructures to use as intracellular protein delivery tools. Briefly, proteins and gold nanoparticles were co-engineered to carry complementary electrostatic recognition elements. When these …

Fabrication Of Functional Nano-Structured Materials And Devices Using Supercritical Fluids, Shengkai Li

Doctoral Dissertations

Nano-structured materials possess unconventional properties and enable miniaturization of devices. However, fabrications of such materials and devices are challenging and in many cases cumbersome, and development of nanofabrication techniques are essential to realizing novel designs and commercializing scientific ideas. Supercritical fluids possess a unique combination of gas-like diffusion properties and liquid-like dissolution power, and are suitable reaction media for fabricating materials at the nanometer scale. This dissertation focuses on developing supercritical fluids-related techniques for fast and large-scale fabrication of novel composite materials and devices. Using supercritical fluid deposition (SFD) technique, cobalt thin films were deposited on a variety of substrates, …

Bio-Based Wind Turbine Blades: Renewable Energy Meets Sustainable Materials For Clean, Green Power, Rachel Koh

Doctoral Dissertations

Wood, once the material of choice for wind turbine blades, was phased out in the late 20th century as the growing size of blades imposed stricter material requirements and glass- and carbon-fiber composites gained industry popularity. However, the last several years have seen great advances in bio-based composite materials technology, including flax, hemp, and wood composites and laminates. These materials are increasingly utilized in high-performance, structurally demanding applications, largely because they are a more sustainable choice than many other engineering materials. Today, as the first glass-fiber wind turbine blades are ready to retire, wind developers are presented with an enormous …

Tissue-Guided Engineering Of Polyethylene Glycol Hydrogels, Lauren Jansen

Doctoral Dissertations

Polyethylene glycol (PEG) hydrogels are tunable cell culture platforms that recapitulate tissue geometry, water content, and bulk modulus. Despite these benefits, PEG hydrogels elicit an acute immune response, limiting their use in regenerative medicine, and they critically underrepresent the cell-instructive proteins found in the extracellular matrix (ECM). Here, I developed a new class of tissue-specific PEG-based materials and provided biocompatible strategies to improve the user handling and cell viability post-encapsulation when using these hydrogels. I also demonstrated that decreasing the protein fouling to PEG does not decrease the foreign body response to implanted hydrogels, a common misconception in the field. …

Nanocomposite Polymer Networks For Reconfigurable Materials, Adam W. Hauser

Doctoral Dissertations

This thesis broadly aims to design reconfigurable materials through complementary combinations of nanoparticles and polymers. Understanding nanoparticle dispersion pathways and mechanisms is a critical first step in any polymer nanocomposite work as it continues to be a non-trivial subject. To this end, Chapter 2 describes a simple method to control nanoparticle dispersion within polymer melts by photografting random copolymers to selectively reactive nanoparticle ligands. The chapters following focus on harnessing the functionality of well dispersed nanocomposite networks to elicit macro-scale responses. Chapter 3 exploits the unique optical properties of gold nanoparticles in combination with thermally responsive hydrogels and liquid crystalline …

Decision Analytical Methods For Robust Water Infrastructure Planning Under Deep Uncertainty, Mehmet Umit Taner

Doctoral Dissertations

Deep uncertainties resulting from climate change, demographic pressures, and rapidly evolving socioeconomic conditions are challenging the way that water planners design and operate large-scale infrastructure systems. Conventionally, water infrastructures have been developed using stationary methods, assuming that the underlying uncertainties can be derived from historical data or experience. However, these methods are less useful under deeply uncertain climate and socioeconomic conditions, in which the future can be substantially different from the past and cannot be expressed by well-defined probability distributions. The recognition of deep uncertainties in long-term water resources planning has led to the development of “decision-analytical” frameworks that do …

Adaft: A Resource-Efficient Framework For Adaptive Fault-Tolerance In Cyber-Physical Systems, Ye Xu

Doctoral Dissertations

Cyber-physical systems frequently have to use massive redundancy to meet application requirements for high reliability. While such redundancy is required, it can be activated adaptively, based on the current state of the controlled plant. Most of the time the physical plant is in a state that allows for a lower level of fault-tolerance. Avoiding the continuous deployment of massive fault-tolerance will greatly reduce the workload of CPSs. In this dissertation, we demonstrate a software simulation framework (AdaFT) that can automatically generate the sub-spaces within which our adaptive fault-tolerance can be applied. We also show the theoretical benefits of AdaFT, and …

Polyorganosiloxanes: Molecular Nanoparticles, Nanocomposites And Interfaces, Daniel H. Flagg

Doctoral Dissertations

Five research projects described. First, a reproducible, lab-scale synthesis of MQ silicone copolymers is presented. MQ copolymers are commercially important materials that have been ignored by the academic community. One possible reason for this is the difficulty of controlling and reproducing the preparative copolymerizations that have been reported. A reproducible method for lab-scale preparation was developed that controls molecular weight by splitting the copolymerization into the discrete steps of sol growth from silicate precursor and end-capping by trimethylsiloxy groups. Characterization of MQ products implicates that they are composed of highly condensed, polycyclic structures. The MQ copolymers prepared in the first …

Microbial Dynamics And Design Considerations For Decentralized Microbial Fuel Cell Applications, Cynthia Castro

Doctoral Dissertations

The purpose of this dissertation was to assess the practicality of using microbial fuel cells (MFCs) as alternative sanitation systems for wastewater treatment and energy recovery, focusing on identifying key design considerations for treating high strength wastewater and managing alternative metabolic pathways. We evaluated the energetic outputs of a lab-based pilot MFC designed to treat complex organics present in both synthetic feces and municipal wastewater. The pilot MFC produced two energetic products, methane and electricity, when treating two types of complex wastewaters. The energetic products associated with anode respiration and methanogenesis were simultaneously observed and yielded a combined energy ouput …

Synthesis And Structure-Property Relationships Of Polymeric Membranes For Small Molecule Transport, Haomiao Yuan

Doctoral Dissertations

One key challenge for alkaline anion exchange membrane fuel cells is the lack of alkaline stable polycations. The synthesis of random, crosslinked and block copolymers based on the cobaltocenium phenylene norbornene (NPC) monomer is described. The polymers were synthesized from ring-opening metathesis polymerization (ROMP) of the NPC monomer showed excellent thermo-alkaline and thermo-oxidative stability. Random copolymers, crosslinked networks and amphiphilic diblock copolymers were prepared by copolymerizing NPC with different hydrophobic monomers: norbornene for random copolymers, dicyclopentadiene for crosslinked networks and a norbornene dibenzyl ether monomer for amphiphilic diblock copolymers. Mechanical robust membranes were prepared from all these copolymers. Polymers with …

Modeling Of Nanoscale Transport In Mesoporous Membranes, Ashutosh Rathi

Doctoral Dissertations

Mesoporous membranes with pore sizes in the range 2-50 nm provide an energy efficient alternative for separation of mixtures such as CO₂ from stack effluents and volatile organic compounds (VOC) from air. Transport mechanisms such as capillary condensation, Knudsen diffusion and surface adsorption help in enrichment of a more condensable component based on the bulk mixture thermodynamics, surface chemistry and geometry of the mesopores. Despite the progress in synthesis techniques, design of better mesoporous materials for targeted separations is still a challenge due to the absence of clear design rules. Modeling techniques can be used to quantify the relevant …

Metabolic Modeling And Engineering Of Gas Fermentation In Bubble Column Reactors, Jin Chen

Doctoral Dissertations

Gas fermentation is an attractive route to produce alternative fuels and chemicals from non-food feedstocks, such as waste gas streams from steel mills and synthesis gas (mainly CO and H₂) produced from municipal solid waste through gasification. While commercial development of gas fermentation technology is underway, many research problems must be addressed to further advance the technology towards economic competitiveness. A particularly important challenge is to develop integrated metabolic and transport models that describe gas fermentation in industrially relevant bubble column reactors. I have developed and evaluated a spatiotemporal metabolic model for bubble column reactors with the syngas …

Three-Dimensional Memristor Integrated Circuits And Applications, Peng Lin

Doctoral Dissertations

New computing paradigms are highly demanded in the “Big Data” era to efficiently process, store and extract useful information from overwhelmingly rich amount of data. New computing systems based on large scale memristor circuits emerges as a very promising candidate due to its capability to both store and process information, thus eliminating the von Neumann bottleneck in the conventional complementary metal oxide semiconductor (CMOS) based computers. As the lateral scaling of the device geometry approaching its physical limit, three-dimensional stacking of multiple device layers becomes necessary to further increase the packing density. Moreover, innovations in the 3D circuits design can …

Solution-Based Assembly Of Conjugated Polymers Into Nanofibers For Organic Electronics, Daniel E. Acevedo Cartagena

Doctoral Dissertations

Solution-based crystallization of conjugated polymers offers a scalable and attractive route to develop hierarchical structures for electronic devices. The introduction of well-defined nucleation sites into metastable solutions provides a way to regulate the crystallization behavior, and therefore the morphology of the material. A crystallization method for generating metastable solutions of poly(3-hexylthiophene) (P3HT) was established. These metastable solutions allow P3HT to selectively crystallize into nanofibers (NFs) on graphene-coated surfaces. It was found that the crystallization kinetics is faster with increasing P3HT molecular weight and concentration. Through in situ atomic force microscopy, it was confirmed that NFs grow vertically in a face-on …

Guiding The Self-Assembly Of Block Copolymers In 2d And 3d With Minimal Patterning, Jaewon Choi

Doctoral Dissertations

Directed self-assembly (DSA) of block copolymers (BCPs) based on topographic patterns is one of the most promising strategies for overcoming resolution limitations in the current lithographic process and fabricating the next generation data storage devices. While the DSA of BCPs with deep topographic patterning has been extensively studied both experimentally and theoretically over the past two decades, less attention has been paid to the development of the DSA process using minimal topographic patterning. This dissertation focuses on understanding the effect of minimal topographic patterning on guiding the self-assembly of BCPs in 2D and 3D. We demonstrate that minimal trench patterns …

Interactions At The Aqueous Interface Of Large-Area Graphene: Colloidal-Scale And Protein Adsorption, Aaron Chen

Doctoral Dissertations

This thesis addresses the interactive interfacial character of large-area supported graphene in an aqueous environment near neutral pH. Studies of molecular bio-interactions with proteins and colloidal interactions with microparticles probe the role of hydrophobicity, van der Waals, and electrostatic contributions with varied ionic strength. The respective roles of the silica support and the graphene itself are identified. Results are benchmarked against other systems directly in experiments, and against published behavior with other materials, especially self-assembled monolayers. The adhesive and adsorption behavior of supported graphene is also put into context by calculations of surface and interaction potentials. Interest in graphene is …

Autoplug: An Automated Metadata Service For Smart Outlets, Lurdh Pradeep Reddy Ambati

Masters Theses

Low-cost network-connected smart outlets are now available for monitoring, controlling, and scheduling the energy usage of electrical devices. As a result, such smart outlets are being integrated into automated home management systems, which remotely control them by analyzing and interpreting their data. However, to effectively interpret data and control devices, the system must know the type of device that is plugged into each smart outlet. Existing systems require users to manually input and maintain the outlet metadata that associates a device type with a smart outlet. Such manual operation is time-consuming and error-prone: users must initially inventory all outlet-to-device mappings, …

Analyzing Spark Performance On Spot Instances, Jiannan Tian

Masters Theses

Amazon Spot Instances provide inexpensive service for high-performance computing. With spot instances, it is possible to get at most 90% off as discount in costs by bidding spare Amazon Elastic Computer Cloud (Amazon EC2) instances. In exchange for low cost, spot instances bring the reduced reliability onto the computing environment, because this kind of instance could be revoked abruptly by the providers due to supply and demand, and higher-priority customers are first served.

To achieve high performance on instances with compromised reliability, Spark is applied to run jobs. In this thesis, a wide set of spark experiments are conducted to …

Numerical Simulation Of Multi-Phase Core-Shell Molten Metal Drop Oscillations, Kaushal Sumaria

Masters Theses

The surface tension of liquid metals is an important and scientifically interesting parameter which affects many metallurgical processes such as casting, welding and melt spinning. Conventional methods for measuring surface tension are difficult to use for molten metals above temperatures of 1000 K. Containerless methods are can be used to measure the surface tension of molten metals above 1000 K. Oscillating drop method is one such method where a levitated droplet is allowed to undergo damped oscillations. Using the Rayleigh’s theory for the oscillation of force-free inviscid spherical droplets, surface tension and viscosity of the sample can be calculated from …

Effects Of Malformed Or Absent Valves To Lymphatic Fluid Transport And Lymphedema In Vivo In Mice, Akshay S. Pujari

Masters Theses

Lymph is primarily composed of fluid and proteins from the blood circulatory system that drain into the space surrounding cells, interstitial space. From the interstitial space, the fluid enters and circulates in the lymphatic system until it is delivered into the venous system. In contrast to the blood circulatory system, the lymphatic system lacks a central pumping organ dictating the predominant driving pressure and velocity of lymph. Transport of lymph via capillaries, pre-collecting and collecting lymphatic vessels relies on the synergy between pressure gradients, local tissue motion, valves and lymphatic vessel contractility. The direction of lymph transport is regulated by …

Non-Equispaced Fast Fourier Transforms In Turbulence Simulation, Aditya M. Kulkarni

Masters Theses

Fourier pseudo-spectral method on equispaced grid is one of the approaches in turbulence simulation, to compute derivative of discrete data, using fast Fourier Transform (FFT) and gives low dispersion and dissipation errors. In many turbulent flows the dynamically important scales of motion are concentrated in certain regions which requires a coarser grid for higher accuracy. A coarser grid in other regions minimizes the memory requirement. This requires the use of Non-equispaced Fast Fourier Transform (NFFT) to compute the Fourier transform, by solving a system of linear equations.

To achieve similar accuracy, the NFFT needs to return more Fourier coefficients than …