Engineering Commons^™

Long-Term Trends In Air Temperature Distribution And Extremes, Growing Degree-Days, And Spring And Fall Frosts For Climate Impact Assessments On Agricultural Practices In Nebraska, Kari E. Skaggs, Suat Irmak

Biological Systems Engineering: Papers and Publications

Air temperature influences agricultural practices and production outcomes, making detailed quantifications of temperature changes necessary for potential positive and negative effects on agricultural management practices to be exploited or mitigated. Temperature trends of long-term data for five agricultural locations, ranging from the subhumid eastern to the semiarid western parts of Nebraska, were studied to determine local temperature changes and their potential effects on agricultural practices. The study quantified trends in annual and monthly average maximum and minimum air temperature (T_max and T_min), daily temperature range (DTR), total growing degree-days, extreme temperatures, growing-season dates and lengths, and …

Developing A Restorable Wetland Index For Rainwater Basin Wetlands In South-Central Nebraska: A Multi-Criteria Spatial Analysis, Zhenghong Tang, Xu Li, Nan Zhao, Ruopu Li, F. Edwin Harvey

Community and Regional Planning Program: Faculty Scholarly and Creative Activity

It is always challenging for decision makers to prioritize wetland conservation programs at the landscape scale. This study employed a GIS-based multi-criteria spatial decision support tool that identified locations with the highest restoration potential for wetland conservation programs in the Rainwater Basin in south-central Nebraska. Five indicators were considered to assess wetland restoration potential: (1) Vegetation characteristics; (2) Soil characteristics; (3) Water volume released from hydrological modification of agricultural irrigation pits; (4) Topographical depression status; and (5) Habitat condition. The results suggested 192 (1.6% of the total) hydric soil footprints as the highest prioritized locations for future wetland restoration programs. …

Initial Changes In Species Cover Following Savanna Restoration Treatments In Western Iowa, David A. Mckenzie, Thomas B. Bragg, David M. Sutherland

Great Plains Research: A Journal of Natural and Social Sciences

Study areas in the Iowa Loess Hills were used to evaluate short-term responses of understory species to three treatment methods designed to facilitate restoration of Quercus macrocarpa savanna. Treatments included burning alone, burning with thinning, and burning with clear-cutting. Plant abundance and diversity were compared before treatment and one year after treatment. Ninety-nine plant species were identified during the study, of which 40 were new following treatment, although most of these were forest associates. Increases in diversity of understory species were observed after treatment, particularly in plots with combined burning and thinning. The forb group was most consistent in response …

Hydrologic Evaluation Of Established Rain Gardens In Lincoln, Nebraska, Andrew R. Anderson, Thomas G. Franti, David P. Shelton

Biological Systems Engineering: Papers and Publications

Increased urbanization has resulted in water quality and flooding problems for many receiving waters in the United States. Rain gardens are one type of best management practice commonly used in low impact development (LID). Many studies have evaluated large engineered bioretention cells in research settings. There is little information on the effectiveness of homeowner-maintained rain gardens that rely on deep percolation as the method for water exfiltration. Repeatable controlled experiments are very rare in hydrologic studies due to the inherent variability of weather data. The objective of this study was to evaluate the hydrologic properties of twelve established rain gardens …

Dynamics Of Depression Storage During Sprinkler Irrigation And Precipitation Events, Michael B. Mckinney

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

Surface depression storage (D_s) is the volume of precipitation excess which is stored by surface microrelief features of soils. The volume of water stored in surface depressions when precipitation rate exceeds infiltration rate reduces the amount of runoff generated. Because Ds is dependent on soil microrelief, land slope, and crop residue, tillage and management practices can have a considerable impact on the magnitude of this value.

When modeling irrigation systems and surface hydrology, depression storage is often treated as a static abstraction, meaning that maximum storage volume must be filled before runoff occurs. However, several researchers have documented …

Life Cycle Boundaries And Greenhouse Gas Emissions From Beef Cattle, Quentin M. Dudley

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

Beef cattle are estimated to directly contribute 26% of U.S. agricultural greenhouse gas (GHG) emissions, and future climate change policy may target reducing these emissions. Life cycle assessment (LCA) of GHG emissions from U.S. feedlot beef cattle was conducted to compare methods of the U.S. Environmental Protection Agency (EPA) with a more complete evaluation of emissions. The inclusion of emissions from crop production for feed, associated land use change, and other minor factors nearly doubled GHG emissions associated with beef feedlots from the EPA Annual Inventory estimate of 1611 kgCO₂e hd^-1 yr^-1 to 3182 ± 167 …

Nutrient Losses In Runoff From Feedlot Surfaces As Affected By Unconsolidated Surface Materials, John E. Gilley, Jason R. Vogel, Roger A. Eigenberg, David B. Marx, Brian L. Woodbury

Biological Systems Engineering: Papers and Publications

Beef cattle feedlots contain unconsolidated surface materials (loose manure pack) that accumulate during a feeding cycle. The effects of varying amounts of unconsolidated surface materials on runoff nutrient losses are not well understood. The objectives of this study were to (1) compare runoff nutrient losses from feedlot surfaces containing varying amounts of unconsolidated surface materials, (2) determine if differences in runoff nutrient losses exist among rainfall simulation runs, (3) relate runoff nutrient losses to selected feedlot soil characteristics, and (4) identify the effects of varying runoff rate on nutrient loss rates from feedlot surfaces. This study was conducted on 0.75 …

Mapping Spatially Interpolated Precipitation, Reference Evapotranspiration, Actual Crop Evapotranspiration, And Net Irrigation Requirements In Nebraska: Part I. Precipitation And Reference Evapotranspiration, Vivek Sharma, Suat Irmak

Biological Systems Engineering: Papers and Publications

Precipitation and reference evapotranspiration are two important variables in hydrologic analyses, agricultural crop production, determining actual crop evapotranspiration and irrigation water requirements, and irrigation management. Both variables vary in space and time, and the weather networks that measure or quantify and report both variables are too sparse for practical applications by water resources planners, managers, and irrigators. Long-term (1986- 2009) average annual (January to December), seasonal (growing season, May to September), and monthly (May, June, July, August, and September) precipitation and Penman-Monteith-estimated alfalfa-reference evapotranspiration (ET_ref) were spatially interpolated and mapped for all 93 counties in Nebraska using the …

Effects Of Manure Handling And Application Method On Odor And Gas Emission Potential Of Swine Manure, Rick R. Stowell

Biological Systems Engineering: Papers and Publications

Manure composition and emissions potential of swine manure were investigated in opposing contexts of desired and undesired methane generation. In the main study, the full-scale treatment effects of anaerobic digestion on the air emissions potential of swine manure were investigated. Manure slurry and digester effluent samples were collected from a pork production facility in eastern Nebraska that utilizes a complete-mix anaerobic digester to treat the manure and produce biogas for use in generating electricity. Samples were collected from three sites in the manure stream (below-barn pit, digester outlet, and holding pond) from 9/22/08 through 12/2/09 in order to observe changes …

Evaluation Of The Bank Stability And Toe Erosion Model (Bstem) For Predicting Lateral Retreat On Composite Streambanks, Taber L. Midgley, Garey A. Fox, Derek M. Heeren

Biological Systems Engineering: Papers and Publications

Streambank erosion is known to be a major source of sediment in streams and rivers. The Bank Stability and Toe Erosion Model (BSTEM) was developed in order to predict streambank retreat due to both fluvial erosion and geotechnical failure. However, few, if any, model evaluations using long-term streambank retreat data have been performed. The objectives of this research were to (1) monitor long-term composite streambank retreat during a hydraulically active period on a rapidly migrating stream, (2) evaluate BSTEM’s ability to predict the measured streambank retreat, and (3) assess the importance of accurate geotechnical, fluvial erosion, and near-bank pore-water pressure …

Chemical Modification Of Polysaccharides Using Reactive Extrusion, Pratik Bhandari

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

The objective of this dissertation was to study the use of reactive extrusion for the chemical modifications of starch and cellulose. A carboxymethyl derivative of starch and carboxymethyl and acetate derivatives of cellulose were prepared using reactive extrusion.

Carboxymethyl starch with rapid swelling properties in water was prepared using reactive extrusion. This was achieved by controlling the gelatinization and through the use of NaOH by controlling the water/ethanol ratio. The effects of NaOH, H₂O, temperature, ethanol, sodium mono chloro acetate, sodium tripolyphosphate, citric acid, epichlorohydrin and extruder screw configuration on the degree of substitution of carboxymethyl starch were …

Wheat Strip Effects On Nutrient Loads Following Variable Manure Applications, Chance Thayer, John E. Gilley, Lisa M. Durso, David B. Marx

Biological Systems Engineering: Papers and Publications

Vegetative filters have been found to significantly reduce nutrient loads in runoff. This study was conducted to: (1) evaluate the effects of a narrow wheat strip, varying manure application rates, and different overland flow rates on runoff nutrient loads following application of beef cattle manure; (2) determine the upper capacity of a narrow wheat strip to reduce nutrient loads by applying excessive amounts of manure; and (3) compare the effectiveness of narrow wheat strips and grass hedges in reducing runoff nutrient loads. A 1.4 m wide strip of actively growing winter wheat was located at the bottom of selected 0.75 …

Identification And Characterization Of Mtoa: A Decaheme C-Type Cytochrome Of The Neutrophilic Fe(Ii)-Oxidizing Bacterium Sideroxydans Lithotrophicus Es-1, Juan Liu, Zheming Wang, Sara M. Belchik, Marcus J. Edwards, Chongxuan Liu, David W. Kennedy, Eric D. Merkley, Mary S. Lipton, Julea N. Butt, David J. Richardson, John M. Zachara, James K. Fredrickson, Kevin M. Rosso, Liang Shi

US Department of Energy Publications

The Gram-negative bacterium Sideroxydans lithotrophicus ES-1(ES-1) grows on FeCO₃ or FeS at oxic–anoxic interfaces at circumneutral pH, and the ES-1-mediated Fe(II) oxidation occurs extracellularly. However, the molecular mechanisms underlying ES-1’s ability to oxidize Fe(II) remain unknown. Survey of the ES-1 genome for candidate genes formicrobial extracellular Fe(II) oxidation revealed that it contained a three-genecluster encoding homologs of Shewanella oneidensis MR-1(MR-1) MtrA, MtrB, and CymA that are involved in extracellular Fe(III) reduction. Homologs of MtrA and MtrB were also previously shown to be involved in extracellular Fe(II) oxidation by Rhodopseudomonas palustris TIE-1. To distinguish them from those found in MR-1, …

Methane And Carbon Dioxide Production From Simulated Anaerobic Degradation Of Cattle Carcasses, Qi Yuan, Samuel Saunders, Shannon L. Bartelt-Hunt

Department of Civil and Environmental Engineering: Faculty Publications

Approximately 2.2 million cattle carcasses require disposal annually in the United States. Land burial is a convenient disposal method that has been widely used in animal production for disposal of both daily mortalities as well as during catastrophic mortality events. To date, greenhouse gas production after mortality burial has not been quantified, and this study represents the first attempt to quantify greenhouse gas emissions from land burial of animal carcasses. In this study, anaerobic decomposition of both homogenized and unhomogenized cattle carcass material was investigated using bench-scale reactors. Maximum yields of methane and carbon dioxide were 0.33 and 0.09 m …

Field Performance Evaluation Of A Ventilation System: A Swine Case Study, Jay D. Harmon, Michael C. Brumm, Larry D. Jacobson, Stephen H. Pohl, David R. Stender, Richard R. Stowell

Biological Systems Engineering: Papers and Publications

Swine finishing facility ventilation has become relatively complex and is often mismanaged as a system. One of the few ways to truly understand these systems is to spend time systematically going through the many components of the building and how they work as a system. To learn to help producers better, a team of university Extension specialists that included agricultural engineers and animal scientists spent an extended period carefully documenting conditions in a deep‐pit swine finishing building with two 1,000‐head rooms. Exhaust fans connected to the manure pit and wall fans were operated at various stages as a negative‐pressure ventilation …

An Investigation Of Reflective Mulches For Use Over Capillary Mat Systems For Winter-Time Greenhouse Strawberry Production, George E. Meyer, Ellen T. Paparozzi, Elizabeth Walter-Shea, Erin E. Blankenship, Stacy A. Adams

Department of Agronomy and Horticulture: Faculty Publications

Photosynthethically active radiation (PAR) is a principle environmental variable used by horticultural specialists, agronomists and ecosystem modelers to characterize the quantity and quality of light conducive to plant growth and development. Spatial distribution of PAR in a greenhouse can be quite variable and diffuse throughout the day time photoperiod, especially at low sun angles in northern regions of the United States. Four colors of reflective plastic mulches (white, red, olive, and black) were evaluated for winter-time strawberry (Fragaria × ananassa Duch.) production based on their reflectance and transmittance properties in a double-polyethylene, plastic-glazed Quonset greenhouse inNebraska. The spectral properties …

P95. In Vivo Loads In The Cervical Spine: A Preliminary Investigation Using A Force-Sensing Implant, Rebecca A. Wachs, Mary Beth M. Grabowsky, Joseph C. Glennon, Eric H. Ledet

Biological Systems Engineering: Papers and Publications

BACKGROUND CONTEXT: It is estimated that up to 80% of the general population will experience at least one significant bout of low back pain in their lifetime. The leading known cause of low back pain is degenerative disc disease (DDD). Many established risk factors for low back pain and DDD are mechanical in nature and are often related to occupational activities, such as poor posture and frequent/heavy lifting. Altered mechanical loading in the spine has been shown to be a potential stimulus for disc degeneration. However, a link between occupational/environmental factors and intervertebral loading has never been demonstrated in vivo. …

Quantification And Heterogeneity Of Infiltration And Transport In Alluvial Floodplains, Derek M. Heeren, Garey A. Fox, Daniel E. Storm, Peter Q. Storm, Brian E. Haggard, Todd Halihan, Ronald B. Miller

Biological Systems Engineering: Papers and Publications

In order to protect drinking water systems and aquatic ecosystems, all critical nutrient source areas and transport mechanisms need to be characterized. It is hypothesized that hydrologic heterogeneities (e.g., macropores and gravel outcrops) in the subsurface of floodplains play an integral role in impacting flow and contaminant transport between the soil surface and shallow alluvial aquifers which are intricately connected to streams. Infiltration is often assumed to be uniform at the field scale, but this neglects the high spatial variability common in anisotropic, heterogeneous alluvial floodplain soils. In the Ozark ecoregion, for example, the erosion of carbonate bedrock (primarily limestone) …

Dielectric Function Spectra And Critical-Point Energies Of Cu2znsnse4 From 0.5 To 9.0 Ev, S. . G. Choi, H. . Y. Zhao, C. Persson, C. L. Perkins, A Donohue, B To, A. G. Norman, J Li, I. L. Repins

US Department of Energy Publications

We present dielectric function e=e₁+ie₂spectra and critical-point energies of Cu₂ZnSnSe₄ determined by spectroscopic ellipsometry from 0.5 to 9.0 eV. We reduce artifacts from surface overlayers to the maximum extent possible by performing chemical-mechanical polishing and wet-chemical etching of the surface of a Cu₂ZnSnSe₄ thin film. Ellipsometric data are analyzed by the multilayer model and the e spectra are extracted. The data exhibit numerous spectral features associated with critical points, whose energies are obtained by fitting standard lineshapes to second energy derivatives of the data. The experimental results are in good …

The Sintering Behavior Of Close-Packed Spheres, R. Bjørk, V. Tikare, H. L. Frandsen, N. Pryds

US Department of Energy Publications

The sintering behavior and microstructural evolution of a powder compact is influenced strongly by initial properties, such as the relative density, the particle and pore size distribution, and the powder packing. While the influence of the former parameters on the microstructural evolution has been investigated in some detail, the impact of the initial packing of the powder has been mostly overlooked. However, research has shown that the sintering behavior of a powder can be significantly improved if the powder is regularly packed.

This has been shown for monodisperse spherical TiO2 particles [1], which sintered 10 times faster and exhibited almost …

The Hardness And Strength Of Metal Tribofilms: An Apparent Contradiction Between Nanoindentation And Pillar Compression, Corbett C. Battaile, Brad L. Boyce, Christopher Weinberger, Somuri Prasad, Joseph R. Michael, Blythe G. Clark

US Department of Energy Publications

After sliding contact of a hard spherical counterface on a metal surface, the resulting wear scar possesses a complex microstructure consisting of dislocations, dislocation cells, ultrafine or nanocrystalline grains, and material that has undergone dynamic recovery. There remains a controversy as to the mechanical properties of the tribolayer formed in this wear scar. To investigate the properties of this thin layer of damaged material in single crystal nickel, we employed two complementary techniques: pillar compression and nanoindentation. In both techniques, the tests were tailored to characterize the near surface properties associated with the top 500 nm of material, where the …

Sparse Pseudospectral Approximation Method, Paul G. Constantine, Michael Eldred, Eric Phipps

US Department of Energy Publications

Multivariate global polynomial approximations – such as polynomial chaos or stochastic collocation methods – are now in widespread use for sensitivity analysis and uncertainty quantification. The pseudospectral variety of these methods uses a numerical integration rule to approximate the Fourier-type coefficients of a truncated expansion in orthogonal polynomials. For problems in more than two or three dimensions, a sparse grid numerical integration rule offers accuracy with a smaller node set compared to tensor product approximation. However, when using a sparse rule to approximately integrate these coefficients, one often finds unacceptable errors in the coefficients associated with higher degree polynomials.

By …

Pore Scale Analysis Of The Impact Of Mixing-Induced Reaction Dependent Viscosity Variations, S.M. Davison, H. Yoon, M. J. Martinez

US Department of Energy Publications

Expanding interest in enhanced subsurface natural resource recovery and carbon sequestration motivates study of reacting flows in porous media. In this work, we examine the case of reaction products that increase or decrease the viscosity of the fluid. Parallel reactant streams flow through porous media and react transversely along the centerline. We utilize a pore scale, finite element numerical method that couples the reaction with fluid flow through two arrangements of porous media at three Damkohler (Da) numbers and two viscosity conditions. When the product increases the fluid viscosity, the flow velocity is reduced and higher amounts of …

Raman/Rayleigh Scattering And Co-Lif Measurements In Laminar And Turbulent Jet Flames Of Dimethyl Ether, Frederik Fuest, Robert S. Barlow, Jyh-Yuan Chen, Andreas Dreizler

US Department of Energy Publications

To reduce the impact of combustion of fossil fuels on air quality and climate change, dimethyl ether (DME) is a promising alternative diesel fuel candidate. Technical combustion processes, including formation of pollutants, are influenced by turbulence–chemistry interaction. Therefore, accurate prediction by computational combustion models of combustion systems burning DME must account for multiple scalars and scalar gradients. The testing of such models requires detailed experiments. Here a study is presented on the feasibility of simultaneous species and temperature measurements in turbulent dimethyl ether flames, using line-imaged Raman/Rayleigh scattering of the major species H₂, O₂, N_{2 …}

The Fundamental Equation Of Eddy Covariance And Its Application In Flux Measurements, Lianhong Gu, William J. Massman, Ray Leuning, Stephen Pallardy, Tilden Meyers, Paul Hanson, Jeffery Riggs, Kevin Hosman, Bai Yang

US Department of Energy Publications

A fundamental equation of eddy covariance (FQEC) is derived that allows the net ecosystem exchange (NEE) N̅s of a specified atmospheric constituent s to be measured with the constraint of conservation of any other atmospheric constituent (e.g. N2, argon, or dry air). It is shown that if the condition │N̅s│ ˃˃ │X̅s│ │N̅co2│is true, the conservation of mass can be applied with the assumption of no net ecosystem source or sink of dry air and the FQEC is reduced to the following equation and its approximation for horizontally homogeneous mass fluxes:

N̅_s = c̅_dw’X’_{s …}

A Non-Premixed Combustion Model Based On Flame Structure Analysis At Supercritical Pressures, Guilhem Lacaze, Joseph Oefelein

US Department of Energy Publications

This work presents a study of non-premixed flames at supercritical-pressure conditions. Emphasis is placed on flame stability in liquid rocket engines fueled with liquid oxygen and gaseous hydrogen. The flame structure sensitivity to strain, pressure, temperature and real-fluid effects was investigated in detailed opposed-jet flames calculations. It is shown that the flame is very robust to strain, that the flamelet assumption is valid for the conditions of interest, and that real-fluid phenomena can have a significant impact on flame topology. At high-pressure supercritical conditions, small pressure or temperature variations can induce strong changes of thermodynamic properties across the flame. A …

Field Ion Source Development For Neutron Generators, B. Bargsten Johnson, P. R. Schwoebel, C. E. Holland, P. J. Resnick, K L. Hertz, D L. Chichester

US Department of Energy Publications

An ion source based on the principles of electrostatic field desorption is being developed to improve the performance of existing compact neutron generators. The ion source is an array of gated metal tips derived from field electron emitter array micro fabrication technology. A comprehensive summary of development and experimental activities is presented. Many structural modifications to the arrays have been incorporated to achieve higher tip operating fields, while lowering fields at the gate electrode to prevent gate field electron emission which initiates electrical breakdown in the array. The latest focus of fabrication activities has been on rounding the gate electrode …

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 …

Saturated–Unsaturated Flow In A Compressible Leaky-Unconfined Aquifer, Phoolendra Mishra, Velimir Vesselinov, Kristopher Kuhlman

US Department of Energy Publications

An analytical solution is developed for three-dimensional flow towards a partially penetrating largediameter well in an unconfined aquifer bounded below by a leaky aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage due to Neuman. We extend the theory of leakage in unconfined aquifers by (1) including water flow and storage in the unsaturated zone above the water table, and (2) allowing the finite-diameter pumping well to partially penetrate the aquifer. The …

Combined Finite Element And Peridynamic Analyses For Predicting Failure In A Stiffened Composite Curved Panel With A Central Slot, Erkan Oterkus, Erdogan Madenci, Olaf Weckner, Stewart Silling, Philip Bogert, Alexander Tessler

US Department of Energy Publications

This study presents an analysis approach based on a merger of the finite element method and the peridynamic theory. Its validity is established through qualitative and quantitative comparisons against the test results for a stiffened composite curved panel with a central slot under combined internal pressure and axial tension. The predicted initial and final failure loads, as well as the final failure modes, are in close agreement with the experimental observations. This approach demonstrates the capability of the PD approach to assess the durability of complex composite structures.