Engineering Commons^™

Anatomy Of A Nanoscale Conduction Channel Reveals The Mechanism Of A High-Performance Memristor, Feng Miao, John Strachan, Jianhua Yang, M Zhang, Ilan Goldfarb, Antonio Torrezan, Peter Eschbach, Ronald Kelley, Gilberto Medeiros-Ribeiro, R Stanley Williams

Electrical and Computer Engineering Faculty Publication Series

By employing a precise method for locating and directlyimaging the active switching region in a resistive random access memory (RRAM) device, a nanoscale conducting channel consisting of an amorphous Ta(O) solid solution surrounded by nearly stoichiometric Ta2O5 is observed. Structural and chemical analysis of the channel combined with temperature-dependent transport measurements indicate a unique resistance switching mechanism.

A Multicellular Model For Differential Regulation Of Circadian Signals In The Core And Shell Regions Of The Suprachiasmatic Nucleus, Christina Vasalou, Michael A. Henson

Michael A Henson

We developed a multicellular model of the mammalian circadian clock characterized by a high degree of heterogeneity with respect to single cell periodicity and behavior (intrinsic and driven oscillators), neurotransmitter release (VIP, GABA and glutamate synthesis) and spatial organization (core and shell regions), mimicking structural patterns within the SCN associated with distinct circadian functions. We simulated the SCN core and shell separately utilizing experimentally derived connectivity schemes for the two subdivisions as observed within the rat SCN. The core was modeled via a small world network characterized by VIP and GABA colocalization, whereas the shell was simulated as a nearest …

Evaluation Of Wind Load Integration In Disproportionate Collapse Analysis Of Steel Moment Frames For Column Loss, Simos Gerasimidis, C. Baniotopoulos

Civil and Environmental Engineering Faculty Publication Series

The design of steel structures, in most cases, depends majorly on the level of wind loads which are prescribed by codes and regulations and are used in the structural analysis due to the fact that steel structures being light and ductile systems are strongly affected from a slight difference in the values of wind loading. During the last decades, disproportionate collapse analysis has become of major interest mainly due to the increasing number of failures occurring in that pattern. Commonly accepted guidelines and methods of analysis have been produced, the most dominating of which being the Department of Defense Facilities …

Identification And Thermochemical Analysis Of High-Lignin Feedstocks For Biofuel And Biochemical Production, Venugopal Mendu, Anne E. Harman-Ware, Mark Crocker, Jungho Jae, Jozsef Stork, Samuel Morton, Andrew Placido, George W. Huber, Seth Debolt

George W. Huber

Background - Lignin is a highly abundant biopolymer synthesized by plants as a complex component of plant secondary cell walls. Efforts to utilize lignin-based bioproducts are needed. Results - Herein we identify and characterize the composition and pyrolytic deconstruction characteristics of high-lignin feedstocks. Feedstocks displaying the highest levels of lignin were identified as drupe endocarp biomass arising as agricultural waste from horticultural crops. By performing pyrolysis coupled to gas chromatography-mass spectrometry, we characterized lignin-derived deconstruction products from endocarp biomass and compared these with switchgrass. By comparing individual pyrolytic products, we document higher amounts of acetic acid, 1-hydroxy-2-propanone, acetone and furfural …

A Methodology To Estimate Capacity Impact Due To Connected Vehicle Technology, Daiheng Ni, Jia Li, Steven Andrews, Haizhong Wang

Daiheng Ni

Recent development in connected vehicle technology or equivalently vehicular ad hoc networks (VANET) has stimulated tremendous interests among decision makers, practitioners, and researchers due to the potential safety and mobility benefits provided by these technologies. A primary concern regarding the deployment of connected vehicle technology is the degree of market penetration required for effectiveness. This paper proposes a methodology to analyze the benefit of highway capacity gained from connected vehicle technology. To fulfill this purpose, a model incorporating the effects of connected vehicle technology on car following is formulated, building on which a rough estimate of the resulting capacity gain …

Wachusett Reservoir Contaminant Spill Modeling Using Ce-Qual W2, Cory S. Devonis

Environmental & Water Resources Engineering Masters Projects

This research studies contaminant spills in the Wachusett Reservoir by two dimensional modeling utilizing CE-QUAL W2. The Wachusett Reservoir, located in central Massachusetts, has a capacity of 65 billion gallons and is the primary water source for the metropolitan Boston area. There are numerous inflows and outflows to and from the Wachusett Reservoir, with the Quabbin Aqueduct supplying approximately half of the total water entering the Wachusett. The Quabbin Aqueduct connects the Quabbin Reservoir (412 billion gallons) to the Wachusett Reservoir and supplies water to maintain desired water surface elevations in the Wachusett during time of high demand and low …

Perchlorate Reduction By Sulfur Oxidizing Bacteria, Amber R. Boles

Environmental & Water Resources Engineering Masters Projects

Perchlorate (ClO4-) contaminated water is becoming a wide-spread problem as more sites are being identified worldwide. Biological perchlorate reduction is a promising alternative to conventional physical/chemical treatment processes and has the advantage of reducing perchlorate to the benign products, chloride and oxygen. A number of bacteria are capable of reducing perchlorate using a variety of electron donors including organic carbon compounds, hydrogen, iron, and reduced sulfur compounds. Previous studies in our laboratory successfully used a novel, sulfur oxidizing bacterial consortium (SUPeRB) to reduce perchlorate in both batch culture and in packed bed reactors (PBR). There were two main objectives of …

Sub-Daily Multi-Objective Models For Optimizing Hydropower In The Deerfield River, Kelcy Adamec

Environmental & Water Resources Engineering Masters Projects

This document is part of the Connecticut River Watershed Project, a federally authorized collaborative project of the U.S. Army Corps of Engineers (US ACE), the Nature Conservancy (TNC), the University of Massachusetts Amherst (UMass), and the U.S. Geological Survey (USGS). The project began in September 2008 with Congressional funding for this project with TNC and the USACE as equal funding partners.

The Connecticut River Watershed Project will identify management modifications for more than seventy influential dams in the Connecticut River Basin to increase environmental benefits while maintaining beneficial human uses such as water supply, flood control, and hydropower generation. Key …

Investigating Estrogenic Endocrine Disrupting Compounds And Their Disinfection Byproducts Within Drinking Water Treatment, Kirsten E. Studer

Environmental & Water Resources Engineering Masters Projects

Emerging public health concerns relating to the epigenetic effects of EDCs, along with the

reconceptualization of dose response curves, provides a compelling rationale for addressing

estrogenically active contaminants in drinking water. These environmental health concerns are

now known to have long lasting impacts, especially on fetal development. For this drinking

water research, the estrogenic EDC byproducts were identified and the treatment processes were

compared using the dose applied, the number of byproducts formed and the relative

quantification of the treatment byproducts. The analytical optimized method presented and

implemented in this research successfully determined the percent degradation of the parent

compound …

Investigating Estrogenic Endocrine Disrupting Compounds And Their Disinfection Byproducts Within Drinking Water Treatment, Kirsten E. Studer

Environmental & Water Resources Engineering Masters Projects

Emerging public health concerns relating to the epigenetic effects of EDCs, along with the reconceptualization of dose response curves, provides a compelling rationale for addressing estrogenically active contaminants in drinking water. These environmental health concerns are now known to have long lasting impacts, especially on fetal development. For this drinking water research, the estrogenic EDC byproducts were identified and the treatment processes were compared using the dose applied, the number of byproducts formed and the relative quantification of the treatment byproducts. The analytical optimized method presented and implemented in this research successfully determined the percent degradation of the parent compound …

Queue Length Based Pacing Of Internet Traffic, Cai Yan

Open Access Dissertations

As the Internet evolves, there is a continued demand for high Internet bandwidth. This demand is driven partly by the widely spreading real-time video applications, such as on-line gaming, teleconference, high-definition video streaming. All-optical switches and routers have long been studied as a promising solution to the rapidly growing demand. Nevertheless, buffer sizes in all-optical switches and routers are very limited due to the challenges in manufacturing larger optical buffers. On the other hand, Internet traffic is bursty. The existence of burstiness in network traffic has been shown at all time scales, from tens of milliseconds to thousands of seconds. …

Phase Behavior Of Block Copolymers In Compressed Co2 And As Single Domain-Layer, Nanolithographic Etch Resists For Sub-10 Nm Pattern Transfer, Curran Matthew Chandler

Open Access Dissertations

Diblock copolymers have many interesting properties, which first and foremost include their ability to self-assemble into various ordered, regularly spaced domains with nanometer-scale feature sizes. The work in this dissertation can be logically divided into two parts - the first and the majority of this work describes the phase behavior of certain block copolymer systems, and the second discusses real applications possible with block copolymer templates. Many compressible fluids have solvent-like properties dependent on fluid pressure and can be used as processing aids similar to liquid solvents. Here, compressed CO₂ was shown to swell several thin homopolymer films, including …

Electrostatic Effects In Aggregation Of Crystallin Proteins, Deniz Elizabeth Civay

Open Access Dissertations

The three projects utilized polymer physics theories to investigate polymer aggregation mechanics. Dynamic light scattering (DLS), static light scattering (SLS) and small angle light scattering (SALS) were the primary characterization tools. The goal of the first project was to study the aggregation of bovine βL-crystallin and apply that knowledge towards cataract formation, which is caused by aggregation of the crystallins. The first series of experiments characterized the kinetics of α-crystallin and βL-crystallin in water at room temperature. α-crystallin’s equilibrium hydrodynamic radius value was kinetically independent. βL-crystallin formed an aggregate with an Rh that was kinetically dependent. The packing structure of …

Aspects Of Network Formation And Property Evolution In Glassy Polymer Networks, Andrew Thomas Detwiler

Open Access Dissertations

Experimental and theoretical characterization techniques are developed to illuminate relationships between molecular architecture, processing strategies, and physical properties of several model epoxy-amine systems. Just beyond the gel point partially cured networks are internally antiplasticized by unreacted epoxy and amine which leads to enhanced local chain packing and strain localization during deformation processes. Additional curing causes the antiplasticization to be removed, resulting in lower modulus, density, yield stress, and less strain localization. Physical and mechanical probes of network formation are discussed with respect to several different partially cured model epoxy-amine chemistries. The non-linear fracture energy release rate and the molecular architecture …

Organic Photovoltaics Based On P3ht/Pcbm: Correlating Efficiency And Morphology, Dian Chen

Open Access Dissertations

Controlling the morphology of thin films is key in optimizing the efficiency of polymer-based photovoltaic (PV) devices. The morphology and interfacial behavior of the multicomponent active layers confined between electrodes are strongly influenced by the preparation conditions. Results obtained in this work quantitatively show the photovoltaic device performance is strongly affected by the nanoscopic morphology, crystal orientation, composition distribution and the interdiffusion behavior of the photoactive layer. To better understand the physics of the photoactive layer in the organic photovoltaic devices, it is necessary to gain a quantitative understanding of the morphology and the manner in which it develops. A …

Role Of Strongly Interacting Additives In Tuning The Structure And Properties Of Polymer Systems, Vikram Kumar Daga

Open Access Dissertations

Block copolymer (BCP) nanocomposites are an important class of hybrid materials in which the BCP guides the spatial location and the periodic assembly of the additives. High loadings of well-dispersed nanofillers are generally important for many applications including mechanical reinforcing of polymers. In particular the composites shown in this work might find use as etch masks in nanolithography, or for enabling various phase selective reactions for new materials development. This work explores the use of hydrogen bonding interactions between various additives (such as homopolymers and non-polymeric additives) and small, disordered BCPs to cause the formation of well-ordered morphologies with small …

Clock Generation And Distribution For Enhancing Immunity To Power Supply Noise, Jinwook Jang

Open Access Dissertations

Clock generation and distribution are getting difficult due to increased die size and increased number of cores in a microprocessor. Clock frequencies of microprocessors have been increased and expected to trend 4GHz in near future. This increased clock frequency requires to limit the clock skew and jitter to 5~10% of clock frequency, which is 12.5~25ps. On top of this, non-ideal power supply behavior (supply droops) is worsening available timing margin to the critical paths. This dissertation presents three types of interrelated works: 1) analytical modeling of period jitter of global clock distribution induced by power supply droop, 2) circuit design …

Effects Of Molecular Architecture On Crystallization Behavior Of Pol(Lactic Acid) And Ethylene-Vinyl Acetate, Jeffrey Paul Kalish

Open Access Dissertations

The relationship between polymer chain architecture, crystallization behavior, and morphology formation was investigated. The structures formed are highly dependent on chain configuration and crystallization kinetics. Poly(lactic acid) (PLA) and Poly(ethylene-co-vinyl acetate) (EVA) random copolymers were studied. Sample characterization was performed using a variety of techniques, including spectroscopy, scattering, and calorimetry. In PLA, structural differences between α’ and α crystalline phases were analyzed using cryogenic infrared and Raman spectroscopy. Compared to the  crystal, the ’ crystal has slightly looser packing and weaker intermolecular interactions involving carbonyl and methyl functional groups. Simulations in conjunction with Raman scattering analyzed the …

Modeling And Simulation Of Nanoparticle Formation In Microemulsion Droplets, Sreekumar R. Kuriyedath

Open Access Dissertations

Semiconductor nanocrystals, also known as quantum dots (QDs), are an important class of materials that are being extensively studied for a wide variety of potential applications, such as medical diagnostics, photovoltaics, and solid-state lighting. The optical and electronic properties of these nanocrystals are different from their bulk properties and depend on the size of the QDs. Therefore an important requirement in their synthesis is a proper control on the final nanoparticle size. Recently, a technique has been developed for synthesizing zinc selenide (ZnSe) QDs using microemulsion droplets as templates. In these systems, a fixed amount of a reactant is dissolved …

A Numerical Study Of Droplet Formation And Behavior Using Interface Tracking Methods, Sandeep Menon

Open Access Dissertations

An adaptive remeshing algorithm has been developed for multiphase flow simulations using the moving-mesh interface tracking (MMIT) technique. The edge-swapping algorithm uses the Delaunay criterion (in 2D) and a dynamic programming technique (in 3D) to maximize the quality of mesh primitives surrounding edges in the mesh, and performs local remeshing to minimize interpolation errors. Edge bisection and contraction operations are also performed to adjust the mesh resolution around important features like fluid-interfaces, driven by a local length scale estimation algorithm that is efficient and easily parallelized. Flow-field interpolation after reconnection is achieved using a conservative, second-order accurate remapping scheme that …

Structural Applications Of Metal Foams Considering Material And Geometrical Uncertainty, Mohammadreza Moradi

Open Access Dissertations

Metal foam is a relatively new and potentially revolutionary material that allows for components to be replaced with elements capable of large energy dissipation, or components to be stiffened with elements which will generate significant supplementary energy dissipation when buckling occurs. Metal foams provide a means to explore reconfiguring steel structures to mitigate cross-section buckling in many cases and dramatically increase energy dissipation in all cases. The microstructure of metal foams consists of solid and void phases. These voids have random shape and size. Therefore, randomness ,which is introduced into metal foams during the manufacturing processes, creating more uncertainty in …

Separation Of Carboxylic Acids From Aqueous Fraction Of Fast Pyrolysis Bio-Oils Using Nanofiltration And Reverse Osmosis Membranes, Achyuta Vara Prasada Rao Teella

Open Access Dissertations

There has been a growing interest in renewable sources of energy due to an increase in demand and potential shortages and environmental problems associated with fossil fuels. Bio-oils, complex liquid fuels produced from fast pyrolysis of biomass, have been recognized as one potential source of renewable energy. However, they cannot be utilized directly due to their high viscosity, corrosiveness, and high char content. Bio-oils readily phase separate into aqueous phase and organic phase upon addition of water. The aqueous fraction of bio oil (AFBO) is convenient to process and contains sugars, organic acids, hydroxyacetone, hydroxyacetaldehyde, furfural, phenols and other organic …

Low-Profile, Modular, Ultra-Wideband Phased Arrays, Steven S. Holland

Open Access Dissertations

Ultrawideband (UWB) phased antenna arrays are critical to the success of future multi-functional communication, sensing, and countermeasure systems, which will utilize a few UWB phased arrays in place of multiple antennas on a platform. The success of this new systems approach relies in part on the ability to manufacture and assemble low-cost UWB phased arrays with excellent radiation characteristics.This dissertation presents the theory and design of a new class of UWB arrays that is based on unbalanced fed tightly-coupled horizontal dipoles over a ground plane. Practical implementation of this concept leads to two inexpensive wideband array topologies, the Banyan Tree …

Engineering Modeling, Analysis And Optimal Design Of Custom Foot Orthotic, Lieselle Enid Trinidad

Open Access Dissertations

This research details a procedure for the systematic design of custom foot orthotics based on simulation models and their validation through experimental and clinical studies. These models may ultimately be able to replace the use of empirical tables for designing custom foot orthotics and enable optimal design thicknesses based on the body weight and activities of end-users. Similarly, they may facilitate effortless simulation of various orthotic and loading conditions, changes in material properties, and foot deformities by simply altering model parameters. Finally, these models and the corresponding results may also form the basis for subsequent design of a new generation …

Ion Mobility Studies Of Functional Polymeric Materials For Fuel Cells And Lithium Ion Batteries, Shilpi Sanghi

Open Access Dissertations

The research presented in this thesis focuses on developing new functional polymeric materials that can conduct ions, H⁺, or OH^- or Li⁺. The motivation behind this work was to understand the similarities and/or differences in the structure property relationships between polymer membranes and the conductivity of H⁺ and OH^- ions, and between polymer membranes and the anhydrous conductivity of H⁺ and Li⁺ ions. This understanding is critical to developing durable polymer membranes with high H⁺, OH^- and Li⁺ ion conductivity for proton exchange membrane fuel cells (PEMFCs), …

Development Of Plant Cell Culture Processes To Produce Natural Product Pharmaceuticals: Characterization, Analysis, And Modeling Of Plant Cell Aggregation, Martin Kolewe

Open Access Dissertations

Plant derived natural products represent some of the most effective anti-cancer and anti-infectious disease pharmaceuticals available today. However, uncertainty regarding the feasibility of commercial supply due to the limited availability of many plants in nature has resulted in a dramatic reduction in the use of natural products as leads in modern drug discovery. Plant cell suspension culture, consisting of dedifferentiated plant cells grown in vitro and amenable to large scale industrial biotechnology processes, is a production alternative which promises renewable and economical supply of these important drugs. The widespread application of this technology is limited by low product yields, slow …

In Situ Reinforced Polymers Using Low Molecular Weight Compounds, Onur Sinan Yordem

Open Access Dissertations

The primary objective of this research is to generate reinforcing domains in situ during the processing of polymers by using phase separation techniques. Low molecular weight compounds were mixed with polymers where the process viscosity is reduced at process temperatures and mechanical properties are improved once the material system is cooled or reacted. Thermally induced phase separation and thermotropic phase transformation of low molar mass compounds were used in isotactic polypropylene (iPP) and poly(ether ether ketone) (PEEK) resins. Reaction induced phase separation was utilized in thermosets to generate anisotropic reinforcements. A new strategy to increase fracture toughness of materials was …

A Systematic Method To Evaluate And Develop Renewable Energy Technologies, George W. Huber, A. A. Upadhye, W. Qi

George W. Huber

No abstract provided.

On Co-Optimization Of Constrained Satisfiability Problems For Hardware Software Applications, Kunal Ganeshpure

Doctoral Dissertations 1896 - February 2014

Manufacturing technology has permitted an exponential growth in transistor count and density. However, making efficient use of the available transistors in the design has become exceedingly difficult. Standard design flow involves synthesis, verification, placement and routing followed by final tape out of the design. Due to the presence of various undesirable effects like capacitive crosstalk, supply noise, high temperatures, etc., verification/validation of the design has become a challenging problem. Therefore, having a good design convergence may not be possible within the target time, due to a need for a large number of design iterations.

Capacitive crosstalk is one of the …

Flow Cytometry Of Cultured Plant Cells For Characterization Of Culture Heterogeneity And Cell Sorting Applications, Vishal Gaurav

Open Access Dissertations

Plant cells culture provides a production source for plant-derived pharmaceuticals in which environmental conditions can be more easily controlled, manipulated, and optimized to yield high quantities of these valuable natural products. The Roberts Laboratory focuses on development and optimization of bio-processes for production of the anti-cancer agent paclitaxel (Taxol®) in Taxus cell suspension cultures with an emphasis on understanding cellular metabolism at both the molecular and cellular level. Most studies concerning metabolite production via cell culture technology rely on culture-average parameters, which are often insufficient to describe culture heterogeneity. There are several limitations associated with this non-model system; and adapting …