Engineering Commons^™

Assessment Of Bridge Pier Response To Fire, Vehicle Impact, And Air Blast, Chen Fang, Qusai Alomari, Daniel G. Linzell

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Highway bridges exposed to intentional or unintentional fire followed by combined vehicle impact and air blast are at risk of significant damage and, possibly, collapse. Limited studies examining the complex effects of these extreme demands on bridge support elements and parametrizing their response and damage are found in the open literature. Research that is presented is part of an ongoing numerical investigation examining round, multi-column, reinforced concrete (RC), bridge pier behavior subject to multi-hazard scenarios involving fire, vehicle impact, and air blast. Detailed nonlinear finite element analysis models of single columns and multi-column piers supported by a pile foundation system …

Parametric Modeling Of Biomimetic Sharkskin For Wire Edm For Drag Reduction And Hydrophobicity, Joel Maxwell

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

This research sets out to demonstrate the viability of parametric modeling for biomimetic sharkskin in the effort to reduce drag and create a self-cleaning surface. Multiple designs were created to be machined by Wire EDM on stainless steel and titanium and were comparatively tested. Limitations of current manufacturing processes to economically produce naturally occurring structures such as sharkskin, emphasize the need to be able to calculate the most accurate design for a given manufacturing process. By designing a simplified but parametrically consistent model compared to an accurately depicted 3D model of sharkskin, the textured samples produced can be further tested …

Cybersecurity Of Agricultural Machinery: Exploring Cybersecurity Risks And Solutions For Secure Agricultural Machines, Mark Freyhof

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

Modern agriculture is reliant on agricultural machinery for the production of food, fuel, and other agricultural products. The need for producing large quantities of quality agricultural products while sustainably stewarding environmental resources has led to the integration of numerous digital technologies into modern agricultural machinery, such as the CAN bus and telematic control units (Liu et al., 2021). An unintended drawback of these integrated digital technologies is the opportunity for these components to become cyberattack vectors. Cyberattack instances have increasingly targeted critical infrastructures, with numerous reports from agencies such as the Federal Bureau of Investigation (FBI) and Department of Homeland …

Understanding The Nonlinear Dynamics Governing Vertical-Lift Vehicles With Variable-Speed, Fixed Rotors, Stephanie Vavra, Micah Busboom, Aleea Stanford, Keegan Moore

UNL Student Research Days Posters, Undergraduate

Problem: Traffic significantly limits travel in urban areas. • The NASA Urban Air Mobility Project is developing an air taxi as an alternative mean of transportation (Fig. 1).

Challenge: Operating rotors at different frequencies may cause the cabin to vibrate at high amplitudes. Such effects are currently unknown.

Objective: Understand the effect of variable speed rotors on passenger comfort.

From the reduced-order modeling simulations, it can be assumed that counteracting the rotor speed in-balances can reduce the displacement and vibrations experienced at the center of the wing. In other words, should a rotor not maintain its optimal operation speed, reducing …

Sources Of Variability And Uncertainty In Food-Energy-Water Nexus Systems, Heydi Calderon-Ambelis, Deepak R. Keshwani

Biological Systems Engineering: Papers and Publications

A nexus approach contributes to the strategic allocation of resources to secure food, energy, and water for the world population. Integrated models considering the complex interactions across food, energy, and water (FEW) enhance decision-making and strategic planning towards resilience. However, a significant number of the existing integrated models leave unaddressed the inherent variability and uncertainty present in the FEW sectors. Here, we review the importance of characterizing variability over spatial and temporal scales and the importance of decreasing the uncertainty present within a FEW nexus systems. The review also discusses existing modeling tools that address variability and uncertainty on single …

Creation And Application Of Various Tools For The Reconstruction, Curation, And Analysis Of Genome-Scale Models Of Metabolism, Wheaton L. Schroeder

Department of Chemical and Biomolecular Engineering: Theses and Student Research

Systems biology uses mathematics tools, modeling, and analysis for holistic understanding and design of biological systems, allowing the investigation of metabolism and the generation of actionable hypotheses based on model analyses. Detailed here are several systems biology tools for model reconstruction, curation, analysis, and application through synthetic biology. The first, OptFill, is a holistic (whole model) and conservative (minimizing change) tool to aid in genome-scale model (GSM) reconstructions by filling metabolic gaps caused by lack of system knowledge. This is accomplished through Mixed Integer Linear Programming (MILP), one step of which may also be independently used as an additional curation …

Predictive Modeling Of Fate And Transport Of Three Prevalent Contaminants In Midwest Agroecosystem Surface Waters: Nitrate-N, Atrazine, And Escherichia Coli, Samuel Hansen

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

The majority of streams and rivers in the United States (U.S.) are ecologically impaired, or threatened by anthropogenic stressors. Recent reports have found atrazine in drinking water to be associated with increased birth defects and incidences of Non-Hodgkin’s Lymphoma, with higher levels of significance from exposure to both atrazine and nitrate-N. In contrast, recent illnesses from E. coli contaminating vegetables that originated from irrigation water has increased awareness of identifying sources of E. coli entering irrigation reservoirs.

Methods to accurately predict atrazine and E. coli occurrence and potential sources in waterways continue to limit the identifying appropriate and effective prevention …

Developing An Integrated Model For The Corn, Ethanol, And Beef Systems Using A Loosely Coupled Web Framework, Ryan Anderson

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

With the global population approaching 9 billion people by the year 2050, the world’s food, energy, and water (FEW) resources must be used more intelligently to provide for everyone. While we understand how individual FEW systems behave using modeling, we cannot understand the full environmental and production impacts of decisions in each system without understanding how they are all linked together. An approach to coupling these systems is starting with identifying a few highly interconnected FEW systems. The corn, ethanol, and beef systems are large economic and agricultural drivers in the Midwest United States and are highly linked. Many individual …

Event And Time-Triggered Control Module Layers For Individual Robot Control Architectures Of Unmanned Agricultural Ground Vehicles, Tyler Troyer

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

Automation in the agriculture sector has increased to an extent where the accompanying methods for unmanned field management are becoming more economically viable. This manifests in the industry’s recent presentation of conceptual cab-less machines that perform all field operations under the high-level task control of a single remote operator. A dramatic change in the overall workflow for field tasks that historically assumed the presence of a human in the immediate vicinity of the work is predicted. This shift in the entire approach to farm machinery work provides producers increased control and productivity over high-level tasks and less distraction from operating …

Ls-Dyna® Modeling Enhancement Support, John D. Reid, Robert W. Bielenberg, Chaz Ginger

Nebraska Department of Transportation: Research Reports

The Pooled Fund Program member states provided funding for LS-DYNA modeling enhancements in Years 17 thru 22 (2006-2011), with a project period of 2006-2016. This report documents many of the modeling issues addressed throughout the project period. The funding has been effectively utilized to advance the current state-of-the-art for computer simulation and has provided the following benefits for the entire industry: (1) improved roadside safety hardware, (2) reduced development time and cost, (3) improved understanding of the behavior of roadside safety features, especially for impacts outside of normal crash test conditions, (4) improved LS-DYNA modeling techniques and procedures, and (5) …

Nres/Metr/Bsen 479/879: Hydroclimatology—A Peer Review Of Teaching Project Benchmark Portfolio, Francisco Munoz-Arriola

UNL Faculty Course Portfolios

Rising temperatures and extreme hydrometeorological and climate events are evidences of a changing climate. An increasing population together with their demands for food, energy and water make changes in climate evidence the need to train a new generation of multidisciplinary professionals with a clear understanding of the effects of a changing climate in their activities. Historically, climate sciences were used for scientific and weather operational contexts and engineers applied stationary assumptions for multi-term planning. My goal is to identify elements built from classroom experiences about (a) the suitability of a hydroclimatology course for engineers and scientists; (b) the multidisciplinary skills; …

Expedient Airfield Runway Repair Using Folded Fiberglass Mat, Christopher Y. Tuan, Willaim C. Dass

Department of Civil and Environmental Engineering: Faculty Publications

For expedient airfield runway repair, the US Air Force has developed a folded fiberglass mat to cover craters repaired with a well-compacted granular base material. The objective of this study was to evaluate the adequacy of using polymer plugs to anchor the mat to a repaired asphalt pavement for heavy aircraft operations. The effort consisted of materials testing, field experiments and analytical modeling. An 89,800-kg (198,000-pound) load cart having the footprint of a single C-5 main gear was pulled on a mat with wheels locked to simulate full braking forces. Anchor bushings were instrumented to measure anchor loads. A simplified …

Fabrication And Modeling Of Electrochemical Double-Layer Capacitors Using Carbon Nano-Onion Electrode Structures, Fabio Parigi

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Electrochemical capacitors or ultracapacitors (UCs) that are commercially available today overcome battery limitations in terms of charging time (from tens of minutes to seconds) and limited lifetime (from a few thousand cycles up to more than one million) but still lack specific energy and energy density (2-5% of a lithium ion battery). The latest innovations in carbon nanomaterials, such as carbon nanotubes as an active electrode material for UCs, can provide up to five times as much energy and deliver up to seven times more power than today’s activated carbon electrodes. Further improvements in UC power density have been achieved …

Modeling Of Power Semiconductor Devices, Tanya Kirilova Gachovska

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

One of the requirements for choosing a proper power electronic device for a converter is that it must possess a low specific on-resistance. The specific on-resistance of a bipolar device is related to the base width and doping concentration of the lightly doped drift region. This means that the doping concentration and the width of the low-doped base region in a bipolar device must be carefully considered to achieve a desired avalanche breakdown voltage and on-resistance. In order to determine the technological parameters of a semiconductor device, a one dimensional analysis is used to calculate the minimum depletion layer width, …

Numerical Simulation Of Expansion And Charring Of Carbon-Epoxy Laminates In Fire Environments, Matthew Mcgurn, Paul Desjardin, Amanda Dodd

US Department of Energy Publications

A thermal model is developed for the response of carbon-epoxy composite laminates in fire environments. The model is based on a porous media description that includes the effects of gas transport within the laminate along with swelling. Model comparisons are conducted against the data from Quintiere et al. [34]. Verifications are conducted for both coupon level and intermediate scale one-sided heating tests. Comparisons of the heat release rate (HRR) and time-to-ignition as well as the final products (mass fractions, volume percentages, porosity, etc.) are conducted. Overall, the agreement between available the data and model is good considering the simplified approximations …

Coupled Electromagnetic And Heat Transfer Model For Microwave Heating In Domestic Ovens, Krishnamoorthy Pitchai, Sohan Birla, Jeyamkondan Subbiah, D. D. Jones, Harshanardhan Thippareddi

Department of Food Science and Technology: Faculty Publications

Microwave ovens are used extensively for heating a variety of not-ready-to-eat food products. Non-uniform heating of foods in microwave ovens is a major concern in assuring microbiological safety of such products. The non-uniform heating of foods is attributed by complex interaction of microwaves with foods. To understand this complex interaction, a comprehensive model was developed to solve coupled electromagnetic and heat transfer equations using finite-difference time-domain based commercial software. The simulation parameters, cell size, heating time step, and number of iterations for steady state electromagnetic field were optimized. The model was validated by 30 s heating profile of a cylindrical …

A Novel Telecommunications-Based Approach To Mathematical Modeling Of Hiv Infection, Aaron T. Sharp

Computer and Electronics Engineering: Dissertations, Theses, and Student Research

It is well known that biological systems utilize communication in some form, one prolific example of this is the propagation of HIV (Human Immunodeficiency Virus) in the human body. By modeling HIV infection as a communication system, we hope to gain a unique insight into HIV and biological communication systems in general. Such a model would provide researchers a platform for experimenting and simulating various biological communication systems. We have previously developed a layered communication protocol for interpreting biological communication systems using telecommunications paradigms and will apply said model to HIV proliferation. We will also demonstrate the effectiveness of the …

Electromagnetic And Heat Transfer Modeling Of Microwave Heating In Domestic Ovens, Krishnamoorthy Pitchai

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Microwave (MW) ovens are used extensively for heating a variety of not-ready-to-eat food products. It is vital to achieve target temperature uniformly throughout the food to inactivate foodborne pathogens to assure safety. Non-uniform heating of foods in microwave ovens is the major concern in assuring microbiological safety of such products. The non-uniform heating of foods in domestic microwave ovens is due to complex interactions of microwaves with foods. A comprehensive coupled electromagnetic and heat transfer model was developed using finite-difference time-domain based numerical method to understand the complex interaction of microwaves with foods. Simulation parameters such as cell size, heating …

Modeling Heat Transfer During Cooling Of Ready-To-Eat Meat And Poultry Products Using Three-Dimensional Finite Element Analysis And Web-Based Simulation, Jihan F. Cepeda Jimenez

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

The meat industry is required to comply with processing performance standards for preventing the growth of foodborne pathogens in products. These performance standards, established by the United States Department of Agriculture - Food Safety and Inspection Service (USDA-FSIS) require a reduction of Salmonella spp (lethality standard) and limit the growth of sporeforming bacteria (stabilization standard) in certain processed meat products. In general, strategies used to comply with these standards are associated with thermal processing. Meat processors have difficulties complying with these performance standards. Moreover, thermal processing deviations are an issue in the meat industry that generate uncertainty regarding the safety …

Effect Of Magnetron Frequency On Heating Pattern In Domestic Oven, Sohan Birla, Krishnamoorthy Pitchai, Jeyamkondan Subbiah, David D. Jones

Department of Biological Systems Engineering: Conference Presentations and White Papers

In this study a computer model was developed to simulate microwave heating of a model food with a range of magnetron frequencies. The range was decided upon performing the frequency spectrum analysis of microwave leakage from the microwave oven. Simulation results showed that the magnetron input as sinusoidal frequency from 2.44 GHz to 2.48 GHz generates different heating profiles. The simulated heating profiles were compared with experimental heating profiles obtained by using an IR camera. None of simulations with individual frequency exactly matches with experimental temperature profile. The closet match between simulated and observed temperature profiles was found with 2.46 …

Development Of Novel Microwave Cooking Model For Not-Ready-To Eat Foods, Sohan Birla, Krishnamoorthy Pitchai, Jeyamkondan Subbiah, David D. Jones

Department of Biological Systems Engineering: Conference Presentations and White Papers

Recently safety of microwave cooked food has come under scrutiny because of recent outbreak and recalls associated with some of these not-ready-to-eat (NRTE) frozen foods. Heating uniformity of these foods is paramount in rendering the foods safe for consumption. Degree of uneven microwave heating is influenced by both microwave oven and characteristics of food load which decides the electric field distribution within the food load. Given the complexity of parameters, a computer model is always desirable to optimize heating uniformity by proper selection of food shape, proportions, plating, packaging selection and more. Earlier many researchers have made one or more …

An Adaptive Neuro-Fuzzy Inference System For Modeling Mechanical Properties Of Tapioca Starch-Poly(Lactic Acid) Nanocomposite Foams, Siew-Yoong Lee, Milford Hanna, David D. Jones

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

Tapioca starch, poly(lactic acid) and Cloisite 30B nanocomposites foams, with clay contents of 1, 3, 5 and 7% (w/w), were prepared by a meltintercalation method. Multiple inputs single output models were developed to predict radial expansion ratio, unit density, bulk compressibility and spring index of the nanocomposite foams. An individual ANFIS model was developed for each mechanical property using clay content, temperature, pressure and torque as input parameters. All models preformed well with R² values > 0.71. All models had very low root mean squared error values.

Proposed Beef Cattle Manure Excretion And Characteristics Standard For Asae, Galen E. Erickson, B. Auvermann, R. A. Eigenberg, L. W. Greene, Terry J. Klopfenstein, Richard K. Koelsch

Department of Biological Systems Engineering: Conference Presentations and White Papers

A committee was formed consisting of both animal scientists and agricultural engineers to evaluate and update current ASAE standards. An intake minus retention model was developed to estimate nutrient excretion. This approach allows users (producers, engineers, etc.) to develop site specific information based on known variables such as protein or phosphorus content of diets and cattle performance. This approach illustrates the importance of nutrition on nutrient excretion in livestock operations. Our focus is for feedlot cattle and updates excretion of dry matter (DM or total solids), organic matter (OM or volatile solids), N, P, Ca, K, Na, Mg, S, Cu, …

Task Specific Uncertainty In Coordinate Measurement, R. G. Wilhelm, R. Hocken, H. Schwenke

Department of Mechanical and Materials Engineering: Faculty Publications

Task specific uncertainty is the measurement uncertainty associated with the measurement of a specific feature using a specific measurement plan. This paper surveys techniques developed to model and estimate task specific uncertainty for coordinate measuring systems, primarily coordinate measuring machines using contacting probes. Sources of uncertainty are also reviewed.

Simulation Modeling Presentations: The Life Cycle, Edward Yellig, Paul Savory

Department of Industrial and Management Systems Engineering: Faculty Publications

A typical large scale simulation modeling project spans many months and encompasses activities such as problem definition, data collection, model development, experimentation, and scenario analysis. During the life cycle of a simulation project, numerous presentations are made to many different types of audiences. The purpose of these presentations will vary from seeking project approval, requesting information, discussing simulation model features, verifying the model, validating the model, presenting the experimental results, and offering model conclusions. This paper will discuss presentation techniques we used during a year-long simulation-modeling project. We will highlight techniques used for defining the purpose of each presentation, identifying …

Testing Of A Water Loss Distribution Model For Moving Sprinkler Systems, Allen L. Thompson, Derrel L. Martin, John M. Norman, Judy A. Tolk, James R. Gilley, Arlan D. Schneider

Biological Systems Engineering: Papers and Publications

Field water balance measurements using monolithic lysimeters were used in validating the Cupid-DPE model for predicting water loss partitioning during sprinkler irrigation from a moving lateral system fitted with impact sprinklers and spray nozzles. The model combines equations governing water droplet evaporation and droplet ballistics with a comprehensive plant-environment energy balance model. Comparisons indicate good agreement between measured and modeled transpiration, and the measured and modeled soil evaporation during the day of irrigation. Total predicted evapotranspiration during the day of irrigation was greater than measured totals using the monolithic lysimeters. However, part of this difference was because the lysimeters could …