Engineering Commons^™

Developing And Characterizing A Rapid Prototyping Stereo-Lithography Machine To Produce Interpenetrating Polymer Network Systems, Lena R. Butterfield

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Rapid prototyping and interpenetrating network systems (IPNs) ideas and technologies were studied in order to develop a rapid prototyping machine capable of producing IPNs. This work was done as collaboration between the University of Nebraska-Lincoln and the University of Rouen, France, and is part of a project of controlling material property distribution by means of gradient IPN production within a rapid prototyping machine.

A standard stereo-lithography rapid prototyping (RP) machine was built and then modified for the purpose of producing an IPN system composed of an acrylic component, bisphenol A propoxylate diacrylate (BPA-PDA) and an epoxy component, 3,4 epoxycyclohexyl-methyl 3,4 …

Solving The Search For Source Code, Kathryn T. Stolee

School of Computing: Dissertations, Theses, and Student Research

Programmers frequently search for source code to reuse using keyword searches. When effective and efficient, a code search can boost programmer productivity, however, the search effectiveness depends on the programmer's ability to specify a query that captures how the desired code may have been implemented. Further, the results often include many irrelevant matches that must be filtered manually. More semantic search approaches could address these limitations, yet existing approaches either do not scale, are not flexible enough to find approximate matches, or require complex specifications.

We propose a novel approach to semantic search that addresses some of these limitations and …

User Modeling Via Machine Learning And Rule-Based Reasoning To Understand And Predict Errors In Survey Systems, Leonard Cleve Stuart

School of Computing: Dissertations, Theses, and Student Research

User modeling is traditionally applied to systems were users have a large degree of control over their goals, the content they view, and the manner in which they navigate through the system. These systems aim to both recommend useful goals to users and to assist them in achieving perceived goals. Systems such as online or telephone surveys are different in that users have only a singular goal of survey completion, extremely limited control over navigation, and content is restricted to prescribed set of survey tasks; changing the user modeling problem to one in which the best means of assisting users …

Ideal Optimum Performance Of Propellers, Lifting Rotors And Wind Turbines, Ramin Modarres

All Theses and Dissertations (ETDs)

No abstract provided.

Stochastic Reconstruction Of Multiple Source Atmospheric Contaminant Dispersion Events, Derek Wade, Inanc Senocak

Mechanical and Biomedical Engineering Faculty Publications and Presentations

Reconstruction of intentional or accidental release of contaminants into the atmosphere using concentration measurements from a sensor network constitutes an inverse problem. An added complexity arises when the contaminant is released from multiple sources. Determining the correct number of sources is critical because an incorrect estimation could mislead and delay response efforts. We present a Bayesian inference method coupled with a composite ranking system to reconstruct multiple source contaminant release events. Our approach uses a multi-source data-driven Gaussian plume model as the forward model to predict the concentrations at sensor locations. Bayesian inference with Markov chain Monte Carlo (MCMC) sampling …

Public Perception Of Unmanned Aerial Systems (Uas): A Survey Of Public Knowledge Regarding Roles, Capabilities, And Safety While Operating Within The National Airspace System (Nas), Dennis Vincenzi, David Ison, Dahai Liu

Publications

A variety of challenges to the successful assimilation of Unmanned Aircraft Systems (UASs) into the National Airspace System (NAS) exists. Aside from technical and legislative challenges, another setback has recently surfaced when the FAA suspended its selection process for UAS test sites due to privacy concerns. This new obstacle has the potential to further delay UAS integration. Very little literature or coverage of UAS domestic operations and accidents have been published and made available to the public at large. As a result, the public has very little information upon which to form any realistic or reasonable opinions concerning the integration …

High-Resolution Low-Noise Polarization Imaging Sensor For Astronomical Applications, Radoslav Marinov

All Theses and Dissertations (ETDs)

Polarization imaging is useful to the field of astronomy because the polarization state caused by reflections, scattering events, and magnetic fields can be used to infer properties such as shape and index of refraction about celestial bodies. This work presents a low-noise high-resolution polarization imaging sensor consisting of a CCD imager overlaid with a nanowire linear polarizer filter array of four different orientations: 0°, 45°, 90°, and 135°) matched to the pixel pitch. Fabrication details and experimental setup for characterization are discussed. The performance of the sensor is assessed over a range of polarization states, light intensities, wavelengths, and incident …

End-To-End Delay Analysis For Wireless Control Networks Under Edf Scheduling, Chengjie Wu

All Theses and Dissertations (ETDs)

No abstract provided.

Predicting Hospital Patients' Admission To Reduce Emergency Department Boarding, Mohammadmahdi Moqri

Graduate Masters Theses

Emergency Department (ED) boarding - the inability to transfer emergency patients to inpatient beds- is a key factor contributing to ED overcrowding. This paper presents a novel approach to improving hospital operational efficiency and, therefore, to decreasing ED boarding. Using the historic data of 15,000 patients, admission results and patient information are correlated in order to identify important admission predictor factors. For example, the type of radiology exams prescribed by the ED physician is identified as among the most important predictors of admission. Based on these factors, a real-time prediction model is developed which is able to correctly predict the …

Evaluation Of Broiler Litter Heat Production During Windrowing & Nitrogen Based Gas Emission Mitigation Using Biofilter, Min Lei

Graduate Theses and Dissertations

Ammonia emission from animal feeding operations (AFOs) has negative effects on environment and animals' health. Thus measuring and mitigating ammonia emission from AFOs is important for environmental protection. In chapter I, different ammonia measurements were discussed and a mitigation technology- biofilter was represented.

In-house windrowing of built-up litter has been used by broiler producers to reduce pathogen loads and rejuvenate litter for the next flock. When litter is piled up for an extended period during downtime, heat generated by the litter pile can become a substantial heat source due to the metabolism of microorganisms. In chapter II, heat production rates …

Controlling Bacterial Persister Cells And Biofilms By Synthetic Brominated Furanones, Jiachuan Pan

Biomedical and Chemical Engineering - Dissertations

Bacteria are well known to obtain tolerance to antibiotics by forming multicellular structures, known as biofilms, and by entering dormancy and forming persister cells. Both mechanisms allow bacteria to tolerate antibiotics at concentrations hundreds to thousands of times higher than the lethal dose for regular planktonic cells of the same genotype. Persister formation increases in biofilms; thus, effective control of persister cells, especially those in biofilms is critically important to infection control. Over the past decades, a bacterial signaling system based on cell density, named quorum sensing (QS), has been found to regulate biofilm formation and, in Pseudomonas aeruginosa, the …

Common Information And Decentralized Inference With Dependent Observations, Ge Xu

Electrical Engineering and Computer Science - Dissertations

Wyner's common information was originally defined for a pair of dependent discrete random variables. This thesis generalizes its definition in two directions: the number of dependent variables can be arbitrary, so are the alphabets of those random variables. New properties are determined for the generalized Wyner's common information of multiple dependent variables. More importantly, a lossy source coding interpretation of Wyner's common information is developed using the Gray-Wyner network. It is established that the common information equals to the smallest common message rate when the total rate is arbitrarily close to the rate distortion function with joint decoding if the …

Experimental And Analytical Investigation Of The Transient Thermal Response Of Air Cooled Data Centers, Hamza Salih Erden

Dissertations - ALL

This work investigates the transient response of the thermal environment in air cooled data centers through experiments, analytical and computational tools. The key thermal characteristics of the various data center components were extracted from a set of experiments. This includes the development of practical experimental procedures for the thermal characterization of servers solely based on air temperature measurements and the transient response of the computer room air handlers. The knowledge of thermal characteristics paves the way for the physics-based lumped-capacitance models. A CFD-based transient simulation of the air temperature field, in which the transient thermal response of the servers was …

Comparison Of Methods To Evaluate Chitosan As An Antimicrobial Against Listeria Spp. Cultures, Scott Hartley

All Theses

The antimicrobial properties of a chitosan-coated vacuum-packaged pouch were tested against Listeria monocytogenes (LM) inoculated on frankfurters. A 1.5% chitosan solution was successfully coated onto a corona-treated poly/nylon based film and then heat-sealed to form a pouch. An initial 5 log CFU/mL population of LM was used to inoculate a frankfurter in the pouch, which was then vacuum-sealed and stored at 4¡ and 13¡ C for a period of 8 weeks, with bacteria enumeration performed on weekly intervals. An uncoated pouch was tested as a control. It was found that the chitosan-coated pouches did not exhibit any antimicrobial properties against …

Evaluation Of Anaerobic Biodegradation Of High Concentrations Of Halogenated Methanes, Priya Rachel Jacob

All Theses

Removal of the chlorinated methanes, carbon tetrachloride (CT), chloroform (CF) and dichloromethane (DCM), and the halogenated methane, trichlorofluoromethane (commonly known as CFC-11 or Freon-11) from contaminated soil and groundwater remains challenging. Releases to the environment resulted from historically poor disposal practices, as well as spills and leaks from underground storage tanks. Among these three compounds, CF is considered the benchmark for evaluating the feasibility of bioremediation, due to its typically high level of toxicity towards most anaerobic prokaryotes. However, inhibitory effects of low concentrations of CFC-11 on anaerobes have been reported as well. Bioremediation is an attractive option for clean-up, …

An Optimization Model For Class Scheduling At A Dance Studio, Chirag Ojha

All Theses

Scheduling has been a large area of research for decades. A substantial amount of work has been done to express, classify, and solve scheduling problems. Most of these problems are computationally difficult to solve and require complex algorithms. In this thesis, we develop a mixed-integer linear program for a real world optimization problem at a dance studio. Similar to a university, the students in this studio request a particular class and instructors teach the classes under constrained resources such as a limited number of classrooms. The priorities of instructors as well as dancers are included to further mimic reality. Experimental …

Development Of A Rating System To Measure The Vulnerability Of Residential Homes To Natural Hazards, Corey Cattano

All Dissertations

Hurricanes and tropical storms continue to damage the United States coastline where population migration increases and tourism thrives. Extended dry spells, high winds, and hot summers in the Mountain and Pacific West regions promote ideal conditions for seemingly uncontrollable wildfires. Additionally, the increased frequency of unstable climate conditions foretells signs of Mother Nature not letting up. With recent events such as Superstorm Sandy and the Waldo Canyon wildfires in mind, there is a strong need to improve hazard mitigation techniques in residential homes and encourage resilient building methods. Research within this field is challenging due to the lack of descriptive …

Miniature Concrete Prism Test - A New Test Method For Evaluating The Asr Potential Of Aggregates, The Effectiveness Of Asr Mitigation And The Job Mixture, Enamur Latifee

All Dissertations

Existing test methods to characterize ASR potential of aggregates and mitigation ability of supplementary cementing materials such as the Accelerated Mortar Bar Test (AMBT) and the Concrete Prism Test (CPT) are widely accepted in the industry. Although, the AMBT is a rapid test, the results from this test can be unreliable, particularly with certain types of aggregates. The CPT is considered as a more reliable test; however, the duration of this test method renders it impractical for routine usage in the industry to screen deleterious materials or inefficient ASR mitigation measures. This research presents a new test method-Miniature Concrete Prism …

A Simplified Approach To Thermomechanical Fatigue And Application To V-Shaped Notches, Thomas Bouchenot

HIM 1990-2015

A vast array of high value parts in land- and air-based turbomachinery are subjected to non-isothermal cycling in the presence of mechanical loading. Crack initiation, growth and eventual failure more significantly reduce life in these components compared to isothermal conditions. More accurate simulation of the stress and strain evolution at critical locations of components, as well as test specimens, can lead to a more accurate prediction of remaining life to a structural integrity specialists. The focus of this thesis is to characterize the effects of thermomechanical fatigue (TMF) on generic turbomachinery alloy. An expression that can be used to estimate …

Microscopic Surface Textures Created By Interfacial Flow Instabilities, Jing Gu

HIM 1990-2015

In nature, microscopic surface textures impact useful function, such as the drag reduction of shark skin (Dean & Bhushan, 2010) and superhydrophobicity of the lotus leaf(Pan, Kota, Mabry, & Tuteja, 2013). In this study, we explore these phenomena by re-creating microscopic surface textures via the method of interfacial flow instability in drying polyvinylidene fluoride (PVDF) acetone solutions. In general, PVDF films can be made using either spin coating or electrospray deposition with various weight concentrations in acetone. In order to study the morphology of the porous structure of PVDF films, wet deposition samples were fabricated by spin coating or near-field …

Volatile Organic Compound Emissions From Surface Coating Facilities: Characterization Of Facilities, Estimation Of Emission Rates, And Dispersion Modeling Of Off-Site Impacts, Annabrabha Athappan, Sulak Sumitsawan, Roja Haritha Gangupomu, Ketwalee Kositkanawuth, Parthen Parikh, Benjamin Nmai Afotey, Neelesh Sule, Sahithi Raj Kalidindi, Melanie L. Sattler, Yvette Pearson Weatherton

Civil Engineering Faculty Publications - Archive

Surface coating facilities are major sources of volatile organic compounds (VOCs) in urban areas. These VOCs can contribute to ground-level ozone formation, and many are hazardous air pollutants (HAPs), including xylene, ethylbenzene, and toluene. This project was conducted in order to provide information for updating the Texas Commission on Environmental Quality (TCEQ), USA, permit by rule for Surface Coating Facilities. Project objectives were: 1) To develop a database of information regarding surface coating facilities in Texas; 2) To estimate maximum emission rates for various VOC species from surface coating facilities in Texas; 3) To conduct dispersion modeling to estimate off-site …

Post Weld And Epoxy Anchorage Variations For W-Beam Guardrail Attached To Low-Fill Culverts, Scott K. Rosenbaugh, Ronald K. Faller, Dean L. Sicking, Robert W. Bielenberg, Craig W. Price, John D. Reid

Nebraska Department of Transportation: Research Reports

No abstract provided.

Chomp: Covariant Hamiltonian Optimization For Motion Planning, Matthew A. Zucker, N. Ratliff, A. D. Dragan, M. Pivtoraiko, M. Klingensmith, C. M. Dellin, J. A. Bagnell, S. S. Srinivasa

Engineering Faculty Works

In this paper, we present CHOMP (covariant Hamiltonian optimization for motion planning), a method for trajectory optimization invariant to reparametrization. CHOMP uses functional gradient techniques to iteratively improve the quality of an initial trajectory, optimizing a functional that trades off between a smoothness and an obstacle avoidance component. CHOMP can be used to locally optimize feasible trajectories, as well as to solve motion planning queries, converging to low-cost trajectories even when initialized with infeasible ones. It uses Hamiltonian Monte Carlo to alleviate the problem of convergence to high-cost local minima (and for probabilistic completeness), and is capable of respecting hard …

Analysis Of Parameter Tuning On Energy Efficiency In Asynchronous Circuits, Justin Thomas Roark

Graduate Theses and Dissertations

Power and energy consumption are the primary concern of the digital integrated circuit (IC) industry. Asynchronous logic, in the past several years, has increased in popularity due to its low power nature. This thesis analyzes a collection of array multipliers with different parameters to compare two asynchronous design paradigms, NULL Convention Logic (NCL) and Multi-Threshold NULL Convention Logic (MTNCL). Several commercially available pieces of software and custom scripts are used to analyze the asynchronous circuits and their components to provide the energy consumption estimation on various parts of each circuit. The analysis of the software results revealed that MTNCL circuits …

Finite Element Analysis And Validation Of Hip Joints With The Main Types Of Femoroacetabular Impingement, Kevin Lucas Mitchell

Master's Theses

Current research suggests that femoroacetabular impingement can be a cause of osteoarthritis. Femoroacetabular impingement is a condition that can affect both the femur and the pelvis of an individual. Femoroacetabular impingement can cause damage to the hip joint and its surrounding tissues. The articular cartilage and the labrum are both affected by this condition. A cam impingement is where a bony protrusion develops at the femoral head/neck junction. A pincer impingement is where a bony protrusion develops at the acetabular rim. Often, patients are seen with a combination of both impingements. The main goal of this study was to computationally …

Smart Superhydrophobic Materials, Adetoun Taiwo

Theses and Dissertations

Superhydrophobicity refers to surfaces with extremely large water droplet contact angles (usually greater than 150°). This phenomenon requires a hydrophobic material with micro or nano-scale roughness. Superhydrophobic surfaces exist in nature (e.g. the lotus leaf) and can be produced synthetically. This project focuses on the development and characterization of superhydrophobic materials with tunable wettability (i.e. smart superhydrophobic materials). In this study, surfaces were prepared by electrospinning thin, aligned polystyrene fibers onto a piezoelectric unimorph substrate. Results showed electric field induced changes in substrate curvature, which produced corresponding changes in surface wettability. From experiments, an average change in water contact angle …

Accuracy Analysis Of Parallel Method Based On Non-Overlapping Domain Decomposition Method, Moonho Tak, Yooseob Song, Hye-Kwan Jeon, Taehyo Park

Civil Engineering Faculty Publications

In this paper, an accuracy analysis of parallel method based on non-overlapping domain decomposition method is carried out. In this approach, proposed by Tak et al.(2013), the decomposed subdomains do not overlap each other and the connection between adjacent subdomains is determined via simple connective finite element named interfacial element. This approach has two main advantages. The first is that a direct method such as gauss elimination is available even in a singular problem because the singular stiffness matrix from floating domain can be converted to invertible matrix by assembling the interfacial element. The second is that computational time and …

The Assignment Problem With Dependent Costs., Ghazal Tariri

Electronic Theses and Dissertations

Assigning workers, each with their own skill set, to tasks which demand different skills in an efficient manner is a challenging problem that often requires workers to receive additional training. The training of workers is very costly with Training Magazine’s Annual Industry Report stating 58.5 billion dollars were spent in 2007 on employee training in the United States. Therefore assigning workers to tasks in such a way as to minimize the overall training costs is an important problem in many organizations. In this research, the assignment problem with dependent cost is considered, i.e. the training cost associated with assigning a …

Interleukin Expression After Injury And The Effects Of Interleukin-1 Receptor Antagonist, Connie S. Chamberlain, Ellen M. Leiferman, Kayt E. Frisch, Stacey L. Brickson, William L. Murphy, Geoffrey S. Baer, Ray Vanderby

Faculty Work Comprehensive List

Ligament healing follows a series of complex coordinated events involving various cell types, cytokines, as well as other factors, producing a mechanically inferior tissue more scar-like than native tissue. Macrophages provide an ongoing source of cytokines to modulate inflammatory cell adhesion and migration as well as fibroblast proliferation. Studying interleukins inherent to ligament healing during peak macrophage activation and angiogenesis may elucidate inflammatory mediators involved in subsequent scar formation. Herein, we used a rat healing model assayed after surgical transection of their medial collateral ligaments (MCLs). On days 3 and 7 post-injury, ligaments were collected and used for microarray analysis. …

Optimization Problem Formulation For Predicting Knee Muscle And Contact Forces During Gait, Gil Serrancolí, Jonathan P. Walter, Allison Kinney, Benjamin J. Fregly, Josep M. Font-Llagunes

Mechanical and Aerospace Engineering Faculty Publications

The human body has more muscles than degrees of freedom (DOF), which leads to indeterminacy in the muscle force calculation. In this study, an optimization problem to estimate the lower-limb muscle forces during a gait cycle of a patient wearing an instrumented knee prosthesis is formulated. It consists of simulating muscle excitations in a physiological way while muscle parameters are calibrated.