Engineering Commons^™

Luminescence Of Defects In The Structural Transformation Of Layered Tin Dichalcogenides, Peter Sutter, H.P. Komsa, A. V. Krasheninnikov, Y Huang, Eli A. Sutter

Department of Electrical and Computer Engineering: Faculty Publications

Layered tin sulfide semiconductors are both of fundamental interest and attractive for energy conversion applications. Sn sulfides crystallize in several stable bulk phases with different Sn:S ratios (SnS2, Sn2, S3, and SnS), which can transform into phases with a lower sulfur concentration by introduction of sulfur vacancies (VS). How this complex behavior affects the optoelectronic properties remains largely unknown but is of key importance for understanding light-matter interactions in this family of layered materials. Here, we use the capability to induce VS and drive a transformation between few-layer SnS2 and SnS by electron beam irradiation, combined with in-situ cathodoluminescence spectroscopy …

Femtosecond Laser Micromachining Of Low-Temperature Co-Fired Ceramic And Glass Fiber Reinforced Polymer Printed Circuit Boards Materials, Raif Farkouh

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

Low-temperature co-fired ceramic (LTCC), and glass fiber reinforced polymer (GFRP) printed circuit boards (PCBs) are two materials used for the packaging of electronics. The excellent mechanical and electrical properties of LTCC, combined with the ability to embed passive components offer superior radio frequency (RF) performance and device miniaturization for high-frequency applications. Due to its unique properties, LTCC provides superior performance in applications as diverse as military radar, imaging systems, advanced automotive sensing, telecommunications, and satellites. The use of LTCC in these applications has created a demand for the micromachining of holes, channels, and cavities with specific geometries and structures. Likewise, …

Harmonics Elimination In Three Phase Cascade H-Bridge Multilevel Inverter Using Virtual Stage Pwm, Amro Quedan

Durham School of Architectural Engineering and Construction: Dissertations, Thesis, and Student Research

The multilevel inverters are one of the great solutions that are proposed to satisfy the demand for high-power application and the significant integration of renewable energy. The conversion process from DC to AC must be done at high efficiency to decrease the energy loss and to ensure the electric grid power quality. The Total Harmonic Distortion (THD) is the most important feature that indicates the efficiency of the conversion process. In this research, due to the advantages of the cascade H-bridge inverter over other topologies, it has been used with the virtual stage PWM technique to investigate two different methods …

High Throughput Phenotyping Of Sorghum For The Study Of Growth Rate, Water Use Efficiency, And Chemical Composition, Piyush Pandey

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

Plant phenotyping using digital images has increased the throughput of the trait measurement process, and it is considered to be a potential solution to the problem of the phenotyping bottleneck. In this study, RGB images were used to study relative growth rate (RGR) and water use efficiency (WUE) of a diverse panel of 300 sorghum plants of 30 genotypes, and hyperspectral images were used for chemical analysis of macronutrients and cell wall composition. Half of the plants from each genotype were subjected to drought stress, while the other half were left unstressed. Quadratic models were used to estimate the shoot …

Setback Distance Requirements For Removal Of Swine Slurry Constituents In Runoff, John E. Gilley, Shannon L. Bartelt-Hunt, Kent M. Eskridge, Xu Li, Amy M. Schmidt, Daniel D. Snow

Biological Systems Engineering: Papers and Publications

The use of setback distances for manure application on cropland areas adjacent to surface water bodies could serve a function similar to vegetative filter strips. However, little information currently exists to identify the setback distances necessary to effectively reduce the transport of contaminants in runoff. The objective of this study was to determine the effects of setback distance and runoff rate on concentrations of selected constituents in runoff following land application of swine slurry to a no-till cropland area in southeast Nebraska. The study site had a residue cover of 7.73 Mg ha-1 and a slope gradient of 4.9%. The …

Meeting Real-Time Constraint Of Spectrum Management In Tv Black-Space Access, Zhongyuan Zhao

CSE Technical Reports

The TV set feedback feature standardized in the next generation TV system, ATSC 3.0, would enable opportunistic access of active TV channels in future Cognitive Radio Networks. This new dynamic spectrum access approach is named as black-space access, as it is complementary of current TV white space, which stands for inactive TV channels. TV black-space access can significantly increase the available spectrum of Cognitive Radio Networks in populated urban markets, where spectrum shortage is most severe while TV whitespace is very limited. However, to enable TV black-space access, secondary user has to evacuate a TV channel in a timely manner …

Effectiveness Of Chain Link Turtle Fence And Culverts In Reducing Turtle Mortality And Providing Connectivity Along U.S. Hwy 83, Valentine National Wildlife Refuge, Nebraska, Usa, Marcel P. Huijser, Kari E. Gunson, Elizabeth R. Fairbank

Nebraska Department of Transportation: Research Reports

We evaluated the effectiveness of existing turtle fences through collecting and analyzing turtle mortality data along U.S. Hwy 83, in and around Valentine National Wildlife Refuge, Nebraska, USA. We also investigated the level of connectivity for turtles provided through the culverts that were originally designed to pass water through a capture-mark-recapture experiment. While fenced valley sections had 33.1% fewer turtle observations than unfenced valley sections, the difference was not significant. However, we think that the effectiveness of the fence can be improved through fence repairs, other modifications of the fences, vegetation maintenance, and extending the length of the fences. Four …

An Unmanned Aerial System For Prescribed Fires, Evan M. Beachly

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

Prescribed fires can lessen wildfire severity and control invasive species, but some terrains may be difficult, dangerous, or costly to burn with existing tools. This thesis presents the design of an unmanned aerial system that can ignite prescribed fires from the air, with less cost and risk than with aerial ignition from a manned aircraft. The prototype was evaluated in-lab and successfully used to ignite interior areas of two prescribed fires. Additionally, we introduce an approach that integrates a lightweight fire simulation to autonomously plan safe flight trajectories and suggest effective fire lines. Both components are unique in that they …

Design And Implementation Of A Stand-Alone Tool For Metabolic Simulations, Milad Ghiasi Rad

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

In this thesis, we present the design and implementation of a stand-alone tool for metabolic simulations. This system is able to integrate custom-built SBML models along with external user’s input information and produces the estimation of any reactants participating in the chain of the reactions in the provided model, e.g., ATP, Glucose, Insulin, for the given duration using numerical analysis and simulations. This tool offers the food intake arguments in the calculations to consider the personalized metabolic characteristics in the simulations. The tool has also been generalized to take into consideration of temporal genomic information and be flexible for simulation …

Education Leadership Perspectives: Positve Ways, Iwasan D. Kejawa Ed.D

Department of Educational Administration: Faculty Publications

Are outdated traditional education, information technological infrastructure, problematic issues in providing quality leadership education in many of our instittutions today? With this into considerations, are these issues vital in order to stabilize the political and economic embroidery of our institutions or organizations, and its psychological and sociological awareness? What are really to be taught in our institutions to educate the present and the future leaders in the society? It is found that education may be the training of the mind to perform desire functions or to perpetuate the modality of obtaining an end or result. Actually, the accessibility of leadership …

Evaluation Of Opportunities And Challenges Of Using Inrix Data For Real-Time Performance Monitoring And Historical Trend Assessment, Anuj Sharma, Vesal Ahsani, Sandeep Rawat

Nebraska Department of Transportation: Research Reports

In recent years there has been a growing desire for the use of probe vehicle technology for congestion detection and general infrastructure performance assessment. Unlike costly traditional data collection by loop detectors, wide-area detection using probe-sourced traffic data is significantly different in terms of measurement technique, pricing, coverage, etc. This affects how the new technology is applied and used to solve current traffic problems such as traffic incident management and roadway performance assessment. This report summarizes the experiences and lessons learned while using probe data for traffic operations and safety management in the state of Nebraska and makes recommendations for …

Use Of Long Term Weather Data And Spatially Delineated Field Attributes To Predict Water And Energy Conservation From Variable Rate Irrigation, Sahil Sharma

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

The declining levels of the Ogallala aquifer calls for more judicious use of water. Studies have shown that VRI has the potential for water savings. But adoption of VRI is still very low. The major reason is lack of information on the returns from the VRI systems and its feasibility in different fields. Also, a quantification of the required reduction in prices of VRI is necessary. So, an economic return analysis of VRI strategies was done to compare it to uniform irrigation management (UIM) using a water balance model based on long term weather data and field properties for a …

Thermodynamic Limitations To Agricultural Productivity And Food Security: Livestock In Sub-Saharan Africa, Calvin Harman

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

By 2050, to feed a nearly tripling and more urbanized population in sub-Saharan Africa (SSA) will require significant increases in crop productivity throughout the region’s agricultural systems, if a greater reliance on imports is to be avoided. Increases in crop yields to maximum potential productivity (closure of crop yield gaps) can produce more calories and protein, but may be insufficient to sustain the burgeoning human population according to recent analysis (van Ittersum et al., 2016). In this thesis, alternative management options (i.e. crop allocation and crop substitutions) are found to increase total energy productivity and the thermodynamic efficiency of food …

Performance Assessment Of Electromagnetic Soil Water Sensors In Different Soil Textural, Temperature, And Salinity Conditions, Jasreman Singh

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

Determination of accurate and continuous measurements of volumetric water content (θ_v) is extremely valuable for irrigation management and other agronomic decisions. Lately, electromagnetic (EM) sensors are being widely used to monitor θ_v continuously which also offer the benefits of ease of installation, fewer regulatory and safety concerns, and cost effectiveness. However, the accuracy of parameters [soil temperature, electrical conductivity (EC_a), dielectric permittivity (ε_ra), and θ_v] reported by EM sensors need to be evaluated for them to be utilized for agricultural water management. In the current study, the accuracy of a wide …

Cultivation Of Chlorella Sorokiniana Using Beef Feedlot Runoff Holding Pond Effluent, Mitchell Klaus Goedeken

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

A study was conducted to test the suitability of utilizing beef feedlot runoff holding pond effluent for cultivating algae. The algae strain used, Chlorella sorokiniana, was previously identified as a potential energy feedstock for cattle. The previous research was initiated in pursuit of a goal to develop a cycle of utilizing nutrients from beef manure to cultivate algae and then utilizing dewatered algae as a feed supplement for beef cattle.

Runoff holding pond effluent samples were collected from commercial beef production operations in Nebraska during spring 2016. Equal portions of samples from each cooperating farm were composited and then aliquoted …

Life Cycle Assessment In Foundry Sand Reclamation – Comparison Of Secondary Reclamation Processes, Samuel Keith Ghormley

Department of Environmental Engineering: Theses and Student Research

Foundries represent a significant part of the base of the world’s economy and as a sector are one of the largest consumers of energy and producers of solid waste in the United States. Sand casting foundries use approximately 5-10% of their total energy on sand handling processes. By adding a secondary sand reclamation process, foundries can expect to become more energy efficient as well as reducing solid waste from the foundry. To measure the broader environmental impacts, life cycle assessment (LCA) can be used. The goal of the current research was to examine a medium-sized foundry in the United States …

Generalized Ellipsometry On Complex Nanostructures And Low-Symmetry Materials, Alyssa Mock

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

In this thesis, complex anisotropic materials are investigated and characterized by generalized ellipsometry. In recent years, anisotropic materials have gained considerable interest for novel applications in electronic and optoelectronic devices, mostly due to unique properties that originate from reduced crystal symmetry. Examples include white solid-state lighting devices which have become ubiquitous just recently, and the emergence of high-power, high-voltage electronic transistors and switches in all-electric vehicles. The incorporation of single crystalline material with low crystal symmetry into novel device structures requires reconsideration of existing optical characterization approaches. Here, the generalized ellipsometry concept is extended to include applications for materials with …

Anti-Icing Properties Of Femtosecond Laser Surface Processed Material, Ryan James Bell

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

In this thesis, the use of femtosecond laser surface processing (FLSP) to enhance the anti-icing properties of a commonly used aircraft alloy, Al 7075-O Clad is described. By changing the surface morphology through FLSP and the surface chemistry through siloxane vapor deposition, the wettability of Al 7075-O Clad was altered.

Condensation and the subsequent freezing of condensates on FLSP Al 7075-O Clad was studied. Both structure height and surface wettability were shown to play a role in the delay of freezing. Freezing occurred on the FLSP superhydrophilic surface faster than on the unprocessed Al 7075-O Clad surface, however, freezing was …

Design And Validation Of An Experimental Setup To Study Single Phase Heat Transfer Enhancement Of Femtosecond Laser Processed Metallic Surfaces, Sarah Jane Wallis

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

In the present work, a single phase flow heat transfer experimental loop was designed with the intention of studying the effects of femtosecond laser surface processing (FLSP) on metallic surfaces with the specific goal of enhancing heat transfer in compact heat exchangers currently in use by NASA. This experimental setup went through two major design iterations which are detailed in this thesis. The first iteration consisted of a counterflow fluid-to-fluid heat exchanger, which measured overall heat transfer coefficients and pressure drops, where the overall heat transfer coefficient is defined in terms of the total thermal resistance to heat transfer between …

Condensation And Subsequent Freezing Delays As A Result Of Using A Femtosecond Laser Functionalized Surface, Chongji Huang

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

Femtosecond laser surface processing (FLSP) enhances the anti-icing properties of a commonly used aircraft alloy, Al 7075-O Clad. The wettability of Al 7075-O Clad was altered by changing the surface morphology through FLSP and the surface chemistry through siloxane vapor deposition. Tall mound and short mound FLSP functionalized surfaces were created through two sets of laser parameters. Atmospheric condensation and subsequent freezing of condensates on FLSP Al 7075-O Clad was studied. Results indicate that both structure height and surface wettability play a role in the delay of freezing. Freezing occurred on the FLSP superhydrophilic surface faster than on a unprocessed …

Analytical Modeling Of A Communication Channel Based On Subthreshold Stimulation Of Neurobiological Networks, Alireza Khodaei

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

The emergence of wearable and implantable machines manufactured artificially or synthesized biologically opens up a new horizon for patient-centered health services such as medical treatment, health monitoring, and rehabilitation with minimized costs and maximized popularity when provided remotely via the Internet. In particular, a swarm of machines at the scale of a single cell down to the nanoscale can be deployed in the body by the non-invasive or minimally invasive operation (e.g., swallowing and injection respectively) to perform various tasks. However, an individual machine is only able to perform basic tasks so it needs to exchange data with the others …

Sustainable Clean Coal Technology With Power And Methanol Production, Xiaomeng Wang

Department of Chemical and Biomolecular Engineering: Theses and Student Research

The coal-based chemical process is still indispensable in modern society due to the worldwide vast reserves and popular price of coal. Power generation and chemical production from coal still play an important role in the global chemical industrial market. Electricity generation and chemical production from coal is still the trend as long as the coal is plentiful and inexpensive. Modern chemical industry aims at sustainability and hence the development of clean coal technologies is critical.

Coal-based methanol economy, as an attractive liquid transportation fuel as well as an essential intermediate chemical feedstock, can fill a possible gap between declining fossil …

Quantifying Effectiveness Of Streambank Stabilization Practices On Cedar River, Nebraska, Naisargi Dave, Aaron R. Mittelstet

Biological Systems Engineering: Papers and Publications

Excessive sediment is a major pollutant to surface waters worldwide. In some watersheds, streambanks are a significant source of this sediment, leading to the expenditure of billions of dollars in stabilization projects. Although costly streambank stabilization projects have been implemented worldwide, long-term monitoring to quantify their success is lacking. There is a critical need to document the long-term success of streambank restoration projects. The objectives of this research were to (1) quantify streambank retreat before and after the stabilization of 18 streambanks on the Cedar River in North Central Nebraska, USA; (2) assess the impact of a large flood event; …

Synthesis Of Graphene And Graphene-Based Composite Membrane, Yuanjun Fan

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

Vibration membrane equipped for earphone requires high performance in both mechanical properties and electronic properties. With extraordinary properties on both, graphene and graphene-based composite materials appear as a promising candidate for this application. Chemical vapor deposition (CVD) is believed to be the most convenient way to synthesize a large area (on scale of square centimeters) as well as a homogeneous thickness for the membrane. The thesis focuses on applying control variable experiment method to analyze different effects on mechanical property of the two CVD setting parameters: cooling rate, and hydrocarbon precursor. For isolating the specimens efficiently, a modified electrochemical method …

Method For Single Crystal Growth Of Photovoltaic Perovskite Material And Devices, Jinsong Huang, Qingfeng Dong

Department of Mechanical and Materials Engineering: Faculty Publications

Systems and methods for perovskite single crystal growth include using a low temperature solution process that employs a temperature gradient in a perovskite solution in a container , also including at least one small perovskite single crystal , and a substrate in the solution upon which substrate a perovskite crystal nucleates and grows , in part due to the temperature gradient in the solution and in part due to a temperature gradient in the substrate . For example , a top portion of the substrate external to the solution may be cooled .

Individual And Community Well-Being In Nonmetropolitan Nebraska: 2017 Nebraska Rural Poll Results, Rebecca J. Vogt, Cheryl A. Burkhart-Kriesel, Randolph L. Cantrell, Bradley Lubben, L. J. Mcelravy, T. L. Meyer

Rural Futures Institute: Publications

Conclusion

By many different measures, rural Nebraskans are positive about their community. Many rural Nebraskans rate their community favorably on its social dimensions: as friendly, trusting and supportive. Most rural Nebraskans say it would be difficult to leave their community and have a positive attachment to their community. And, most rural Nebraskans disagree that their community is powerless to control its future.

Across all years of this study, rural Nebraskans’ views about the change in their community have generally been positive. The proportion believing their community has changed for the better during the past year has usually been greater than …

Techno-Economic Implications Of Fed-Batch Enzymatic Hydrolysis, Ellen Emanuel

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

As ethanol production continues to increase in the United States, cellulosic ethanol continues to gain traction as a viable option for meeting ethanol demands. In this work, a literature review of techno-economic analyses for cellulosic ethanol was conducted. It was found that pretreatment methods greatly affect the ethanol production costs. There is a lack of techno-economic data comparing a batch enzymatic hydrolysis to a fed-batch enzymatic hydrolysis for a separate hydrolysis and fermentation production process. Consequently, a techno-economic analysis comparing cellulosic ethanol production using batch versus fed-batch enzymatic hydrolysis was conducted. SuperPro Designer software (Intelligen, Scotch Plains, New Jersey), a …

Oct-Based Three Dimensional Modeling Of Stent Deployment, Pengfei Dong, David Prabhu, David L. Wilson, Hiram G. Bezerra, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Stent deployment has been widely used to treat narrowed coronary artery. Its acute outcome in terms of stent under expansion and malapposition depends on the extent and shape of calcifications. However, no clear understanding as to how to quantify or categorize the impact of calcification. We have conducted ex vivo stenting characterized by the optical coherence tomography (OCT). The goal of this work is to capture the ex vivo stent deployment and quantify the effect of calcium morphology on the stenting. A three dimensional model of calcified plaque was reconstructed from ex vivo OCT images. The crimping, balloon expansion and …

Anchoring And Stiffening Techniques For Portable Concrete Barriers, Surajkumar Bhakta

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

Portable concrete barrier (PCB) systems are utilized on federal and state highways in circumstances such as placing adjacent to vertical drop-offs and in construction zones. PCB systems are most commonly used in a free-standing configuration, which are known to have relatively large deflections when impacted. Large deflections are undesirable when dealing with limited space. In order to allow PCBs to be used in space restricted locations, seven PCB anchoring and stiffening techniques were tested and evaluated as per Manual for Assessing Safety Hardware (MASH) testing standards. Results will allow the New Jersey Department of Transportation to update guidance for their …

Development Of Cardiac Atrial Kick Shear Wave Elastography To Assess Myocardial Stiffness, Aaron J. Engel

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

Increased myocardial stiffness, which is characteristic of many cardiovascular diseases, leads to a loss of diastolic function and is a cause of diastolic heart failure. Current methods to estimate myocardial stiffness rely on pressure-volume relationships derived from invasive cardiac catheter measurements. Noninvasive methods to estimate myocardial stiffness include ultrasound-based and magnetic resonance-based shear wave elastography, where the stiffness of the tissue is related to the propagation speed of a shear wave. Currently, ultrasound-based cardiac shear wave elastography includes acoustic radiation force based methods; however, the in vivo generation and detection of the shear waves in myocardium is significantly degraded due …