Engineering Commons^™

A Globally Stable Attractor That Is Locally Unstable Everywhere, Phanindra Tallapragada, Senbagaraman Sudarsanam

Publications

We construct two examples of invariant manifolds that despite being locally unstable at every point in the transverse direction are globally stable. Using numerical simulations we show that these invariant manifolds temporarily repel nearby trajectories but act as global attractors. We formulate an explanation for such global stability in terms of the ‘rate of rotation’ of the stable and unstable eigenvectors spanning the normal subspace associated with each point of the invariant manifold. We discuss the role of this rate of rotation on the transitions between the stable and unstable regimes.

Graphene Field Effect Transistors For Highly Sensitive And Selective Detection Of K+ Ions, Hongmei Li, Yihao Zhu, Md. Sayful Islam, Md. Anisur Rahman, Kenneth B. Walsh, Goutam Koley

Publications

Graphene-based ion sensitive field effect transistors (GISFETs) with high sensitivity and selectivity for K+ ion detection have been demonstrated utilizing valinomycin based ion selective membrane. The performance of the GISFETs for K+ ion detection was studied in various media over a concentration range of 1 μM–2 mM. The sensitivity of the sensor was found to be >60 mV/decade, which is comparable to the best Si-based commercial ISFETs, with negligible interference found from Na+ and Ca2+ ions in high concentration. The sensor performance did not change significantly in Tris–HCl solution or with repeated testing over a period of two months highlighting …

Increase In The Reduction Potential Of Uranyl Upon Interaction With Graphene Oxide Surfaces, V. N. Bliznyuk, N. Conroy, Y. Xie, R. Podila, A. Rao, Brian A. Powell

Publications

Coordination of uranyl (U(VI)) with carboxylate groups on functionalized graphene oxide (GO) surfaces has been shown to alter the reduction potential of the sorbed uranium ion. A quantitative measure of the reduction potential and qualitative estimation of sorption/desorption processes were conducted using cyclic voltammetry, and the proposed coordination environment was determined using the surface sensitive attenuated total reflection mode of infrared spectroscopy (ATR-FTIR). GO is a nanostructured material possessing a large amount of oxygen-containing functional groups both on basal planes and at the edges, which can form strong surface complexes with radionuclides. The presence of these functional groups on the …

Extended Lamer Synthesis Of Cobalt Doped Ferrite, Benjamin D. Fellows, Sarah Sandler, Jacob Livingston, Kristin Fuller, Lotanna Nwandu, Sarah Timmis, Kayla A. Lantz, Morgan Stefik, O. Thompson Mefford

Publications

Nonstoichiometric cobalt ferrite nanoparticles have drawn interest in magnetically mediated energy delivery due to their high magnetocrystalline anisotropy and their high peak loss frequency. The use of an extended LaMer synthesis allows for size control of the doped particles up to a threshold core diameter of 18 nm. Above this diameter, particles become unstable and drop out of suspension, allowing for further nucleation events to occur. This leads to a cyclic nucleation, growth, and destabilization regime seen during the course of the reaction. Using the size control of the extended LaMer synthesis technique, we examine the specific absorption rate (SAR) …

An Investigation Of Information Sought By Caregivers Of Alzheimer’S Patients On Online Peer-Support Groups, Emma Scharett, Kapil Chalil Madathil, Snehal Lopes, Hunter Rogers, Sruthy Agnisarman, Shraddhaa Narasimha, Aparna Ashok, Cheryl Dye

Publications

Alzheimer’s caregivers seek social support through online communities to deal with their issues. The research team conducted a content analysis of ALZConnected.org to investigate the characteristics of information searched by caregivers and responses received. Two-hundred fifty posts and related responses were randomly selected and analyzed using a classification tool derived from the analysis of 500 posts and related responses spanning a yearlong period. The Linguistic Inquiry and Word Count (LIW C) generated an average tone rating of 25.94 for the posts and 52.69 for the responses. The findings highlighted the caregiver’s need for emotional support (59.6%), and confusion about Alzheimer’s …

A Comparative Study On The Durability Of Geopolymer Mortars Produced With Ground Glass Fiber, Fly Ash, And Glass-Powder In Sodium Sulfate Solution, Hassan Rashidian-Dezfouli, Prasada Rao Rangaraju

Publications

An experimental investigation was conducted to investigate the performance of geopolymers made with three different precursors consisting of fly ash, Ground Glass Fiber (GGF), and Glass-Powder (GLP) exposed to sodium sulfate solution. Precursors were activated using either sodium hydroxide solution or combinations of sodium hydroxide and sodium silicate solution with varying levels of sodium and silica content. Among the mixtures with each of the three precursors, mortar mixtures with the highest compressive strength were selected to test their resistance against exposure to a 5% sodium sulfate solution. Changes in the weight and compressive strength of the specimens were monitored up …

Multiscale Modeling Of Cardiovascular Flows, Alison Marsden, Ethan Kung

Publications

Simulations of blood flow in the cardiovascular system offer investigative and predictive capabilities to augment current clinical tools. Using image-based modeling, the Navier-Stokes equations can be solved to obtain detailed 3-dimensional hemodynamics in patient-specific anatomical models. Relevant parameters such as wall shear stress and particle residence times can then be calculated from the 3D results and correlated with clinical data for treatment planning and device evaluation. Reduced-order models such as open or closed loop 0D lumped-parameter models can simulate the dynamic behavior of the circulatory system using an analogy to electrical circuits. When coupled to 3D simulations as boundary conditions, …

A Sustainable Approach For Tungsten Carbide Synthesis Using Renewable Biopolymers, Monsur Islam, Rodrigo Martinez-Duarte

Publications

Here we present a sustainable, environment-friendly and energy-efficient approach for synthesis of porous tungsten carbide (WC). A biopolymer-metal oxide composite featuring iota-carrageenan, chitin and tungsten trioxide (WO3) was used as the precursor material. The reaction mechanism for the synthesis of WC was estimated using the results from X-ray diffraction characterization (XRD). A synthesis temperature of 1300 °C and dwell time of 3 h were found to be the optimum process parameters to obtain WC>98% pure. The grain size, porosity and Brunauer–Emmett–Teller (BET) surface area of the synthesized WC were characterized using field emission scanning electron microscopy, high resolution transmission …

Convergence Of The Fast State Estimation For Power Systems, Md Ashfaqur Rahman, Ganesh Kumar Venayagamoorthy

Publications

Power system state estimation is a fundamental computational process that requires both speed and reliability. To meet the needs, some variants of the constant Jacobian methods have been used in the industry over the last several decades. The variants work very well under normal operating conditions with nominal values of the states. However, the convergence of the methods are not analysed mathematically and it may contain pitfalls. In this study, the convergence of the constant Jacobian methods are analysed and it is shown that the methods fail under high variations of the states. To increase the reliability of the processes, …

Forces And Disease: Electrostatic Force Differences Caused By Mutations In Kinesin Motor Domains Can Distinguish Between Disease-Causing And Non-Disease-Causing Mutations, Lin Li, Yunhui Peng, Subash Godar, Ivan Getov, Shaolei Teng, Joshua Alper, Emil Alexov

Publications

The ability to predict if a given mutation is disease-causing or not has enormous potential to impact human health. Typically, these predictions are made by assessing the effects of mutation on macromolecular stability and amino acid conservation. Here we report a novel feature: the electrostatic component of the force acting between a kinesin motor domain and tubulin. We demonstrate that changes in the electrostatic component of the binding force are able to discriminate between disease-causing and non-disease-causing mutations found in human kinesin motor domains using the receiver operating characteristic (ROC). Because diseases may originate from multiple effects not related to …

Lb3d: A Parallel Implementation Of The Lattice-Boltzmann Method For Simulation Of Interacting Amphiphilic Fluids, S. Schmieschek, L. Shamardin, S. Frijters, T. Krüger, U. D. Schiller, J. Harting, P. V. Coveney

Publications

We introduce the lattice-Boltzmann code LB3D, version 7.1. Building on a parallel program and supporting tools which have enabled research utilising high performance computing resources for nearly two decades, LB3D version 7 provides a subset of the research code functionality as an open source project. Here, we describe the theoretical basis of the algorithm as well as computational aspects of the implementation. The software package is validated against simulations of meso-phases resulting from self-assembly in ternary fluid mixtures comprising immiscible and amphiphilic components such as water–oil–surfactant systems. The impact of the surfactant species on the dynamics of spinodal decomposition are …

Real-Time Traffic State Estimation With Connected Vehicles, Sakib Mahmud Khan, Kaken Dey, Mashrur Chowdhury

Publications

A novel framework is developed in this paper, to increase the real-time roadway traffic condition assessment accuracy, which integrates connected vehicle technology (CVT) with artificial intelligence (AI) paradigm forming a CVT-AI method. Traffic density is a major indicator of traffic conditions. In this paper, the traffic operational condition is assessed based on traffic density. A simulated network of Interstate 26 in South Carolina is developed to investigate the effectiveness of the method. The assumption is that the vehicle onboard units will forward the CV generated data to the edge devices (e.g., roadside units) for further processing. CV generated distance headway …

The Soil Moisture Velocity Equation, Fred L. Ogden, Myron B. Allen, Wencong Lai, Jianting Zhu, Mookwon Seo, Craig C. Douglas, Cary A. Talbot

Publications

Numerical solution of the one-dimensional Richards' equation is the recommended method for coupling groundwater to the atmosphere through the vadose zone in hyperresolution Earth system models, but requires fine spatial discretization, is computationally expensive, and may not converge due to mathematical degeneracy or when sharp wetting fronts occur. We transformed the one-dimensional Richards' equation into a new equation that describes the velocity of moisture content values in an unsaturated soil under the actions of capillarity and gravity. We call this new equation the Soil Moisture Velocity Equation (SMVE). The SMVE consists of two terms: an advection-like term that accounts for …

Enhancing Anaerobic Digestion Of Food Waste Through Biochemical Methane Potential 1 Assays At Different Substrate: Inoculum Ratios, Shakira R. Hobbs, Amy E. Landis, Bruce E. Rittmann, Michelle N. Young, Prathap Parameswaran

Publications

Food waste has a high energy potential that can be converted into useful energy in the form of methane via anaerobic digestion. Biochemical Methane Potential assays (BMPs) were conducted to quantify the impacts on methane production of different ratios of food waste. Anaerobic digester sludge (ADS) was used as the inoculum, and BMPs were performed at food waste:inoculum ratios of 0.42, 1.42, and 3.0 g chemical oxygen demand/g volatile solids (VS). The 1.42 ratio had the highest CH4-COD recovery: 90% of the initial total chemical oxygen demand (TCOD) was from food waste, followed by ratios 0.42 and 3.0 at 69% …

Further Cost Reduction Of Battery Manufacturing, Amir A. Asif, Rajendra Singh

Publications

The demand for batteries for energy storage is growing with the rapid increase in photovoltaics (PV) and wind energy installation as well as electric vehicle (EV), hybrid electric vehicle (HEV) and plug-in hybrid electric vehicle (PHEV). Electrochemical batteries have emerged as the preferred choice for most of the consumer product applications. Cost reduction of batteries will accelerate the growth in all of these sectors. Lithium-ion (Li-ion) and solid-state batteries are showing promise through their downward price and upward performance trends. We may achieve further performance improvement and cost reduction for Li-ion and solid-state batteries through reduction of the variation in …

Data‐Enabled Cognitive Modeling: Validating Student Engineers’ Fuzzy Design‐Based Decision‐Making In A Virtual Design Problem, Golnaz Arastoopour Irgens, Naomi C. Chesler, Jeffrey Linderoth, David Williamson Shaffer

Publications

The ability of future engineering professionals to solve complex real‐world problems depends on their design education and training. Because engineers engage with open‐ended problems in which there are unknown parameters and multiple competing objectives, they engage in fuzzy decision‐making, a method of making decisions that takes into account inherent imprecisions and uncertainties in the real world. In the design‐based decision‐making field, few studies have applied fuzzy decision‐making models to actual decision‐making process data. Thus, in this study, we use datasets on student decision‐making processes to validate approximate fuzzy models of student decision‐making, which we call data‐enabled cognitive modeling. The results …

Cancer Cell Redirection Biomarker Discovery Using A Mutual Information Approach, Kimberly Roche, F. Alex Feltus, Jang Pyo Park, Marie-May Coissieux, Chenyan Chang, Vera B.S. Chan, Mohamed Bentires-Alj, Brian W. Booth

Publications

Introducing tumor-derived cells into normal mammary stem cell niches at a sufficiently high ratio of normal to tumorous cells causes those tumor cells to undergo a change to normal mammary phenotype and yield normal mammary progeny. This phenomenon has been termed cancer cell redirection. We have developed an in vitro model that mimics in vivo redirection of cancer cells by the normal mammary microenvironment. Using the RNA profiling data from this cellular model, we examined high-level characteristics of the normal, redirected, and tumor transcriptomes and found the global expression profiles clearly distinguish the three expression states. To identify potential redirection …

Current Understanding And Future Research Directions At The Onset Of The Next Century Of Sintering Science And Technology, Rajendra K. Bordia, Suk-Joong L. Kang, Eugene A. Olevsky

Publications

Sintering and accompanying microstructural evolution is inarguably the most important step in the processing of ceramics and hard metals. In this process, an ensemble of particles is converted into a coherent object of controlled density and microstructure at an elevated temperature (but below the melting point) due to the thermodynamic tendency of the particle system to decrease its total surface and interfacial energy. Building on a long development history as a major technological process, sintering remains among the most viable methods of fabricating novel ceramics, including high surface area structures, nanopowder-based systems, and tailored structural and functional materials. Developing new …

Do Single-Use Medical Devices Containing Biopolymers Reduce The Environmental Impacts Of Surgical Procedures Compared With Their Plastic Equivalents?, Scott R. Unger, Troy A. Hottle, Shakira R. Hobbs, Cassandra L. Thiel, Nicole Campion, Melissa M. Bilec, Amy E. Landis

Publications

Background: While petroleum-based plastics are extensively used in health care, recent developments in biopolymer manufacturing have created new opportunities for increased integration of biopolymers into medical products, devices and services. This study compared the environmental impacts of single-use disposable devices with increased biopolymer content versus typically manufactured devices in hysterectomy.

Methods: A comparative life cycle assessment of single-use disposable medical products containing plastic(s) versus the same single-use medical devices with biopolymers substituted for plastic(s) at Magee-Women’s Hospital (Magee) in Pittsburgh, PA and the products used in four types of hysterectomies that contained plastics potentially suitable for biopolymer substitution. Magee is …

Assessing The Importance Of The Root Mean Square (Rms) Value Of Different Waveforms To Determine The Strength Of A Dielectrophoresis Trapping Force, Jordan Gilmore, Monsur Islam, Josie Duncan, Rucha Nato, Rodrigo Martinez-Duarte

Publications

No abstract provided.

Assessing The Importance Of The Root Mean Square (Rms) Value Of Different Waveforms To Determine The Strength Of A Dielectrophoresis Trapping Force, Jordon Gilmore, Monsur Islam, Josie Duncan, Rucha Natu, Rodrigo Martinez-Duarte

Publications

No abstract provided.

High Performance Computing Simulations To Identify Process Parameter Designs For Profitable Titanium Machining, Mathew Kuttolamadom, Joshua Jones, Laine Mears, James Von Oehsen, Thomas Kurfess, John Ziegert

Publications

The objective of this paper was to conduct a study of the multi-level multi-variable design space in titanium machining through high performance computing (HPC) simulations that was otherwise too vast to be explored by physical experiments alone. For tool wear-based performance metrics, this resulted in a validated set of machining parameters for achieving profitable material removal rates (MRR) (optimized cost of processing and tooling) across multiple operational configurations, alloys, tool geometries, and process conditions. The approach was to include all machining-related variables and their distributions available within the software as inputs to finite-element models (FEM) of the machining process. The …

Fabrication Challenges And Perspectives On The Use Of Carbon-Electrode Dielectrophoresis In Sample Preparation, Rodrigo Martinez-Duarte

Publications

The focus of this review is to assess the current status of three-dimensional (3D) carbon-electrode dielectrophoresis (carbonDEP) and identify the challenges currently preventing it from its use in high-throughput applications such as sample preparation for diagnostics. The use of 3D electrodes over more traditional planar ones is emphasised here as a way to increase the throughput of DEP devices. Glass-like carbon electrodes are derived through the carbonisation of photoresist structures made using photolithography. These biocompatible carbon electrodes are not ideal electrical conductors but are more electrochemically stable than noble metals such as gold and platinum. They are also significantly less …

Changes In Temporal Variability Of Precipitation Over Land Due To Anthropogenic Forcings, Goutam Konapala, Ashok Mishra, L. Ruby Leung

Publications

This study investigated the anthropogenic influence on the temporal variability of annual precipitation for the period 1950–2005 as simulated by the CMIP5 models. The temporal variability of both annual precipitation amount (PRCPTOT) and intensity (SDII) was first measured using a metric of statistical dispersion called the Gini coefficient. Comparing simulations driven by both anthropogenic and natural forcing (ALL) with simulations of natural forcing only (NAT), we quantified the anthropogenic contributions to the changes in temporal variability at global, continental and sub-continental scales as a relative difference of the respective Gini coefficients of ALL and NAT. Over the period of 1950–2005, …

Effects Of Microstructure On The Strain Rate Sensitivity Of Advanced Steels, Rakan Alturk, Steven Mates, Zeren Xu, Fadi Abu-Farha

Publications

The dependence of the strain rate sensitivity of advanced ~1 GPa tensile strength steels on the phases present in their microstructures was studied by testing different steels at 0.005 and 500 s−¹. The high strain rate tests were performed using a Kolsky bar setup, while the quasi-static tests were performed using a universal testing machine. The two main steels of interest were the Ferrite-Martensite DP980 and the Ferrite-Martensite-Austenite QP980; the latter being a transformation induced plasticity (TRIP) assisted steel. For comparison, ferritic CR5 mild steel and austenitic stainless steel 201 were also tested under the same conditions. Though …

Superior Performance Of Continuous Over Pulsatile Flow Ventricular Assist Devices In The Single Ventricle Circulation: A Computational Study, Tyler Schmidt, David Rosenthal, Olaf Reinhartz, Kirk Riemer, Fei He, Tain-Yen Hsia, Alison Marsden, Ethan Kung

Publications

This study compares the physiological responses of systemic-to-pulmonary shunted single ventricle patients to pulsatile and continuous flow ventricular assist devices (VADs). Performance differences between pulsatile and continuous flow VADs have been clinically observed, but the underlying mechanism remains poorly understood. Six systemic-to-pulmonary shunted single ventricle patients (mean BSA=0.30 m2) were computationally simulated using a lumped-parameter network tuned to match patient specific clinical data. A first set of simulations compared current clinical implementation of VADs in single ventricle patients. A second set modified pulsatile flow VAD settings with the goal to optimize cardiac output (CO). For all patients, the best-case continuous …

Analytical Content Vulnerability Assessment Methodology For Earthquake Catastrophe Models, Keivan Rokneddin, Amir Safiey, Mohammad Javanbarg, Vijay Manghnani, Weichiang Pang

Publications

The scarcity of detailed claims data for building contents (Coverage C) from historical earthquake events poses a significant challenge for property insurance catastrophe models to reliably estimate the losses associated to building contents. To develop content vulnerability functions empirically, one would need to have access to data from a multitude of historical events; however, loss disaggregation by coverage is rarely reported even when claims data become available from recent significant events such as Maule (2010) and Tohoku (2011). While damage to the building structure (Coverage A) can be estimated analytically using simulation-based fragility functions to amend sparse historical observations, the …

Development Of Earthquake Vulnerability Functions And Risk Curves For Low And Mid-Rise Hotel Buildings Using A Performance-Based Loss Estimation Framework, Amir Safiey, Weichiang Pang, Mohammad Javanbarg, Keivan Rokneddin, Ershad Ziaei

Publications

The concept of performance-based earthquake engineering has gained significant attentions in both the research and engineering communities. The development of a performance-based seismic loss assessment framework, known as the FEMA P-58 method, allows one to estimate the potential financial losses of a building using performance-based engineering method. This research employs a seismic loss estimation framework derived using the P-58 method to estimate the monetary loss of a mid-rise wood-frame hotel building which is assumed to be located in Napa Valley, California. A 3D structural model representative of the dynamic behavior of the wood-frame hotel was created and subjected to Incremental …

Role Of Ground Glass Fiber As A Pozzolan In Portland Cement Concrete, Hassan Rashidian-Dezfouli, Prasad Rao Rangaraju

Publications

Millions of tons of fiberglass are produced annually for a variety of applications. Because of stringent quality requirements and operational characteristics of the manufacturing plants, a significant quantity of fiberglass that does not meet required specifications of the industry ends up as waste in landfills. This study investigated the use of ground glass fiber (GGF) that had been discarded by plants because it did not meet prescribed standards, as a supplementary cementitious material (SCM) for portland cement. Three replacement levels (10%, 20%, and 30% by mass) for portland cement in paste, mortar, and concrete mixtures were studied. Mechanical and durability …

Demisting Using An Ultrasonic Standing Wave Field, T. M. Merrell, John Saylor

Publications

Removing drops from an air flow can be challenging, particularly, for small drops. Herein a method for demisting is presented that employs ultrasonics to force small drops to combine. Specifically, a cylindrical ultrasonic standing wave field is established in a tube, forming pressure nodes that take the form of cylinders located within the tube and having the same axis as the tube. Droplets are driven toward these pressure nodes by the acoustic radiation force, forcing smaller drops to combine to form larger drops, which eventually fall due to gravity, thereby demisting the flow. Experiments presented herein show that, for the …