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Engineering

Permanent URI for this collectionhttp://hdl.handle.net/10342/44

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    Application of Monin-Obukhov Similarity Theory to a Near Shore Atmospheric Acoustic Model: A Measurement Informed Evaluation
    (East Carolina University, May 2025) Stengrim, Matthew
    An understanding of sound propagation from industrial activities, airports, wind farms, and a variety of other sources can be assisted by acoustic modeling. Modeling airborne sound propagation over long distances usually requires making a number of assumptions pertaining to the state of the atmosphere and terrain in addition to those in the governing equations and numerical methods. One set of assumptions about the lower atmosphere is Monin-Obukhov Similarity Theory (MOST)–a system used to estimate vertical profiles of air temperature, humidity, and wind speed. In this work, MOST air temperature profiles are compared against long-term air temperature profile measurements up to seven meters in elevation over water and marsh grass surfaces. In addition, the Crank-Nicholson Parabolic Equation (CNPE) method is used to compare acoustic sound pressure level predictions between MOST-informed and air temperature measurement informed sound speed profiles. Applications of MOST meeting the conventional stability parameter condition for validity were found to be roughly as successful over land as over water. However, at night over the marsh, MOST was 35% less likely on average to meet the validity condition whereas over the water it was only 13% less likely. Acoustic model predictions using MOST temperature profiles diverge from those using measured profiles under negative temperature gradients as a result of a sharp increase in the predicted temperature below 1 m in elevation.
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    EXPERIMENTAL AND NUMERICAL STUDY ON THE COMPARISON OF POINT-ABSORBER WAVE ENERGY CONVERTERS
    (East Carolina University, December 2024) Cortez, Benjamin
    The objective of this thesis is to investigate how buoy geometry affects the performance of point absorber wave energy converters. Five different buoy geometries were designed, each with the same initial diameter and total height. These models were then tested using the same experimental conditions. The experimental phase was conducted in a lab scale wave tank and involved the use of a LVDT sensor to measure buoy displacement, wave height gauges to measure water height, and a high-speed camera to record the experiments. The models were tested completely perpendicular to the water as well as at different angles with the water. ANSYS AQWA was used for numerical analysis of the buoys. The buoy models were modeled perpendicular to the water using the wave conditions that were recorded in the wave tank as well as the wave conditions that were recorded at Jennette's Pier (Nags Head, NC) over five days. AQWA wave tank simulations output graphs depicting amplitude, radiation forces and gravitational forces for each buoy while the environmental simulations focused on amplitude only. Buoyancy forces were calculated for each model (perpendicular to the water only). The experimental results showed the overall trend that as angle of inclination increased, the buoy amplitude would decrease. The most likely reason why the ranges decreased as the angle of inclination increased was because as the LVDT sensor was inclined, the shield of the sensor began acting as an inclined plane creating friction between the sensor shield and armature. One model consistently outperformed the other models in both the wave tank and environmental simulations. The wave tank simulations also suggested a correlation between volume and buoy amplitude. There were differences between the experimental results and numerical wave tank results. This could have been because of friction between the sensor armature and shield, irregular wave shapes in the wave tank, certain parts not modeled in AQWA, and negative damping values in AQWA. Further studies into buoy geometry in point absorbers should examine performance changes when changing materials to examine the relationship between mass and buoy performance more thoroughly.
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    Integration of Cervical Nervous Tissues into a Head-Neck Finite Element Model for the Investigation of Radiculopathy
    (East Carolina University, July 2024) Bruns, Rachel Elaine
    Radiculopathy of the spine is a prevalent chronic disorder caused by a wide number of pathologies, affecting up to 10% of individuals over the age of 50 (Mansfield et al., 2020). It is caused by compression of the nerve roots within the spinal column and intervertebral foramen of the spine as they travel from the spinal cord distally to the rest of the body. While cervical radiculopathy is prevalent within the common aging population, recent concern has been raised at the increasing incidence of reported neck pain in fighter pilots, helicopter pilots, and crewmen (Ang & Harms-Ringdahl, 2006; Harrison et al., 2015; Posch et al., 2019; Walters PL et al., 2012). Repetitive loading activities such as wearing heavy helmets can cause compression of the spine which could be contributing to chronic neck pain, decreasing quality of life and safety while operating aircraft (Mansfield et al., 2020; Van den Oord et al., 2012). Due to the ethical concerns of researching loading the neck in human experiments, mechanisms of nerve root pain and potential radiculopathy can be investigated using finite element (FE) modeling, which is a computational method that utilizes constitutive mathematical equations to simulate mechanical behavior of one or multiple components under loading conditions. While there has been development of many FE models of the cervical spine for different applications (Ah Shin et al., 2016; Khuyagbaatar et al., 2017, 2018; H.-J. Kim et al., 2009; Mihara, 2017; Xue et al., 2021, 2023), to our knowledge, no previous studies investigated cervical radiculopathy, nerve root compression, or the soft-tissue interaction within the spinal canal and intervertebral foramen (IVF). In this thesis, the focus was on the development and implementation of the nerve root geometry and surrounding ligaments into a full model of the cervical spine. The Nerve CSM (Cervical Spine Model) was developed in this thesis by adding nervous tissue to an existing head-neck model, the VIVA Open Human Body Model (OpenHBM) published by (Östh et al., 2017). The VIVA OpenHBM already contained a skull, vertebrae, intervertebral discs, vertebral ligaments, passive muscles, and surrounding soft tissues. The nervous tissue modeled and incorporated into the VIVA OpenHBM to create the new Nerve CSM in this thesis encompassed gray and white matter of the spinal cord, cerebrospinal fluid, dura mater, root sheaths, spinal nerves, nerve roots, dorsal root ganglions, nerve rootlets, denticulate ligaments, foraminal ligaments and epidural ligaments. Geometry was created in SolidWorks (SOLIDWORKS 2023, Dassault Systèmes-SolidWorks Corporation, Waltham, MA, USA) using anatomical measurements from the literature the part’s meshes were generated in ANSYS. These meshes were incorporated into the VIVA OpenHBM in LS-Prepost (LS-PrePost 4.10, © 2024 DYNAmore GmbH, an Ansys Company, Hauptniederlassung Stuttgart) , where the nerve rootlets, denticulate ligaments, foraminal ligaments, and epidural ligaments were created using discrete tension-only spring elements. Validation of the Nerve CSM’s global head and spinal cord kinematics was performed by replicating the 2.3 m/s whiplash simulation published by (Östh et al., 2017) and the flexion/extension simulations published by (Stoner et al., 2019). The global head kinematics of the Nerve CSM in the 2.3 m/s whiplash simulation did not change substantially compared to the VIVA OpenHBM. Additionally, the correlation score for the time response of the Nerve CSM compared to the experimental data was similar to the VIVA OpenHBM, thus, it is reasonable to conclude that the addition of the nerve geometry did not considerably alter the global kinematics of the VIVA OpenHBM. The results of the spinal cord kinematic validation of the Nerve CSM demonstrated that the spinal cord during flexion and extension of the head moved within the bounds of variation presented in the experimental data (Stoner et al., 2019), pointing to a conclusion that the Nerve CSM demonstrates suitable spinal cord kinematics for a healthy participant. Future work will encompass the integration of the Nerve CSM into subject-specific pilot neck models to investigate the effect of cervical spine compression and flight related loading conditions on the interaction between the nerve roots and surrounding tissues.
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    ANALYZING THE EFFECT OF REBAR HEATING ON BRIDGE STRUCTURES: SURFACE TEMPERATURE IMPLICATIONS
    (East Carolina University, July 2024) Nunez Hernandez, Pablo Andres
    This study presents a comprehensive simulation-based analysis aimed at enhancing the serviceability of bridge decks in cold climates by preventing ice formation through the application of an electrical power heat source (EPH) within transversal rebars. The objective is to identify the appropriate EPH capable of maintaining bridge surface temperatures above freezing under various climatic conditions. The study uses "Mean Minimum Temperature" data from the U.S. Climate Normals dataset (1991-2020) to ensure simulations are applicable across diverse regions. By systematically varying the power of the embedded heat source, the research identifies the minimum required EPH input to maintain the bridge deck surface at 3°C, preventing ice formation. Key findings indicate that the developed 3D FEA model effectively avoid ice formation on bridge surfaces by using an external electrical energy source connected to transverse steel rebars. Parameters such as outside temperature, wind speed, and EPH location significantly influence the performance of the heating system. A stress analysis confirms the feasibility of this method, providing guidelines for designers. The study concludes that maintaining a spacing of 12 inches (0.3048 meters) is optimal for the EPH placement and for ensuring structural integrity the EPH heat flow should not exceed 1.22kW.
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    IDENTIFYING A RELATIONSHIP BETWEEN DESIGN CONCEPT REPRESENTATION STYLE AND CONSUMER PRODUCT PREFERENCE
    (East Carolina University, 2023-05-03) Echerd, Jonathan O
    Product designers are constantly seeking insight into the mind of the consumer in efforts to get a better idea as to what the market demands. Feedback from consumers informs designers on changes that need to be made to a product and can provide information about what end-users expect. To explore possible improvements to the design process, a study was conducted on concept representation style and its effects on consumer preferences. The study employed statistical testing to identify a relationship between representation style and consumer preference consistency, lending insight into the best practices for conveying critical information throughout the design process. The study described in this thesis consists of conducting a series of surveys, introducing hand drawings, solid models, and realistic renderings as representations of eyeglass frames to participants, eliciting preference data from those participants, and comparing their preference ratings to those of physical models of the same frames. This study was supplemented with an eye-tracking system to establish a connection of where the effective details lie in the design representations, as well as suggest some decision-making strategies at play. Results indicate that a significant difference in consistency between representation styles does exist, and that CAD solid models are inconsistent with preferences of physical models. When only participants with an engineering background were evaluated however, this relationship did not exist, suggesting that a familiarity with a particular design practice may impact how individuals judge a particular representation style. It is also suggested by eye-tracking analysis that participants were more likely to give semantic responses when observing physical models.
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    Graph Theoretic analysis of the Human Brain's Functional Connectivity Alteration Due to Sleep Restriction
    (East Carolina University, 2023-05-03) Antar, Marwa
    Sleep plays a vital role in learning and memory consolidation. Several studies used brain models of sleep deprivation (SD) and insomnia to study the association between sleep deficiency and cognitive decline conditions. SD was found to cause similar, albeit subtle, cognitive decline symptoms displayed by dementia patients affecting attentional functions, decision making, working and long-term memory. This study examines the effect of sleep restriction (SR) on brain networks and utilizes Functional Connectivity (FC) analysis to identify patterns of information processing between different brain regions. It particularly applies weighted phase-lag index (wPLI) to quantify brain signals synchronization levels during a visual oddball paradigm task that evokes event-related potentials (ERPs) associated with face recognition. This study also examines the viability of graph theoretic analysis (GTA), which provides a holistic view on the brain network topology. GTA quantifies the brain connectivity features to assess the global efficiency and local efficiency of information processing, pre- and post- SR intervention. Significant alterations were found in all graph indices mainly in [alpha]-, [mu]- and [beta]- frequency bands due to induced mental fatigue. The obtained results reveal significantly lower local connections (p [less-than] 0.05) and lower global efficiency (p [less-than] 0.001), particularly in the [alpha]- band as a result of mental fatigue, reflecting the impact of sleep loss on attention and memory processing.
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    Simulating and Optimizing a Zero-Waste Wave-To-Water Desalination System
    (East Carolina University, 2023-04-28) Glosson, Gabriel
    Current methods of producing clean water are not capable of meeting growing demands. One method of producing clean water is through a process called desalination, which is the process of removing salt and other minerals from seawater. However, traditional desalination methods can be energy-intensive and generate significant amounts of waste. To help address these issues, a hybrid wave-to-water desalination system that combines reverse osmosis (RO) with supercritical water desalination (SCWD) can produce freshwater from seawater. SCWD treats the brine produced by RO, while RO produces freshwater at a lower energy cost. The system utilizes an oscillating surge wave energy converter (OSWEC) to harness the energy of ocean waves to directly pressurize the seawater feeding into the RO system. Using ocean waves as an energy source makes the system renewable and reduces the carbon footprint of the desalination process. This thesis presents the development of a simulation for a small-scale zero-waste desalination system powered by off-grid renewable energy. The model of the system was developed using MATLAB Simulink along with WEC-Sim. A sensitivity analysis was performed on the model to determine the optimal configuration of key system parameters. The sensitivity analysis was conducted using an irregular wave pattern with a significant wave height of 0.117 m and a period of 1.68 s. The parameters investigated in the sensitivity analysis were the system's power take-off (PTO) volumetric displacement, accumulator size, and RO membrane type. The results of the sensitivity analysis showed that the optimized system was the one that used an SW30HR-380 RO membrane, a PTO volumetric displacement of 1975 cm³/rad, and a 10-gallon accumulator. The average water production rate for the optimized system was 32.644 gpm.
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    OSCILLATING SURGE WAVE ENERGY CONVERTER GEOMETRY OPTIMIZATION FOR DIRECT SEAWATER DESALINATION
    (East Carolina University, 2023-05-03) McMorris, Jason
    Having a reliable supply of fresh water is a problem that affects nations around the world. Saltwater desalination is one of the best methods for fulfilling this need, but it is an energy-intensive process that is expensive to maintain. Wave energy can be utilized to increase the efficiency of seawater desalination using a wave energy converter (WEC) to lower the external energy requirement. This thesis presents an analysis of scaled down flap-type oscillating surge wave energy converter (OSWEC) geometries and their effects on the power output. The performance of the OSWEC was tested using different flap shapes in addition to different configurations of thickness, density, and center of mass. The tested wave conditions were based on scaled down wave conditions at Jennette's Pier in Nag's Head, North Carolina, and used a significant wave height of 0.117m and a natural period of 1.68s. The system's power take-off (PTO) was also manipulated using different damping and stiffness coefficients to maximize the power generated from the OSWEC. The results of the wave simulations showed that the thinnest configuration of the variable thickness cylindrical flap shape, with the highest tested density and center of mass, produced the most power using the given wave conditions with an average power output of 30.11W.
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    An Error Prediction Model for Construction Bulk Measurements Using a Customized Low-Cost UAS-LIDAR System
    (2022-07-19) Guan, Shanyue; Huang, Yilei; Wang, George; Sirianni, Hannah; Zhu, Zhen
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    Towards a Multi-Scale Computer Modeling Workflow for Simulation of Pulmonary Ventilation in Advanced COVID-19
    (2022) Middleton, Shea; Dimbath, Elizabeth; Pant, Anup; George, Stephanie M.; Vahdati, Ali; Peach, M. Sean; Yang, Kaida; Ju, Andrew W.; Maddipati, Veeranna
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    Investigating the Use of Virtual Reality Headsets for Postural Control Assessment: Instrument Validation Study
    (2021) Sylcott, Brian; Lin, Chia-Cheng; Williams, Keith; Hinderaker, Mark
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    Preprocessing Techniques’ Effect On Overfitting for VGG16 Fast-RCNN Pistol Detection
    (2021-03) Wu, Rui; Li, Jiahao; Ablan, Charles; Guan, Shanyue; Yao, Jason
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    Characterization and Biomimetic Fabrication Study of Fetal Membranes for Understanding and Prevention of Preterm Birth
    (East Carolina University, 2022-04-25) Wheeler, Mackenzie L
    Preterm birth is defined as a baby being born before 37 weeks gestation and is a large problem, affecting 10% of all pregnancies in the United States and world annually. Preterm birth can result in lifelong complications for the infant or even death, considering the fetus continues developing vital organs throughout the last few weeks of pregnancy. Over the course of pregnancy, several layers and sub-layers are formed in order to protect the fetus from the external environment. Two of the most crucial layers that were heavily focused on throughout this project were the amnion and the chorion layers, which combine to make the placental membrane that surrounds the fetus. Preterm birth most often occurs due to mechanical failure of the membranes. Collagen proteins make up the strength and elasticity of the fetal membranes, supporting the fetus. If these proteins fail, this increases the chance of preterm birth occurring. A degrading enzyme, known as collagenase, often affects the membranes through bacteria and infections, breaking down the collagen fibers and leading to premature rupture of membranes or preterm pre-labor rupture of membranes. To study this process, a few different routes were taken. Artificial gels were tested on a nanoindentation machine to gather preliminary data to compare nanoindentation on real tissue. Artificial biomimetic membranes were also electrospun and mechanically tested on a macroscale. The goal of the biomimetic electrospun fiber mat is to be used to patch the woman's rupture site after pre-labor rupture of membranes occurs. Four different mat categories were fabricated: not treated crosslinked (NX), not treated uncrosslinked (NU), treated crosslinked (TX), and treated uncrosslinked (TU). Treatment indicates that they were placed in the oven. Human fetal membranes were also mechanically tested on a macroscale after being submerged and incubated at two different set times in a control solution and varying levels of collagenase concentrations, including 45 U/mL and 135 U/mL. Fourier transform infrared spectroscopy of natural tissues was then used to analyze the integrity of the collagen molecules. The results for this study indicate that through nanoindentation, the elastic modulus of two different types of hydrogels were consistently lower than anticipated. In regard to electrospinning, the uncrosslinked fiber mats have significantly greater strength than the crosslinked fiber mats. The fetal membrane results showed that overall, there was significant decrease in elastic modulus when membranes were submerged in a high collagenase concentration. Strength of the fetal membranes decreased significantly as collagenase concentration and incubation time increased. These findings suggest that collagenase buildup within the human body can potentially lead to preterm birth. Overall, this work sought to study the biomechanical properties of fetal membranes. In current literature, there have been strength and elastic modulus values of placental membranes obtained through different modes of testing, but never through biaxial puncture testing. This project focused on a new approach of mechanically testing placental membranes.
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    Increasing Creative Output by Visually Enhancing Engineering Design Tools
    (East Carolina University, 2022-05-02) Harr, David D
    Innovation does not come about by random chance but is intentionally cultivated by the efforts of a designer. Many strategies exist for approaching design, ranging from the instinctual and intuitive to the more technical or analytical methods. When it comes to design, engineers are continually striving to improve the effectiveness of the design process. One area of the engineering design process deserving of attention is the ideation phase. Ideation refers to the brainstorming and idea generating activities that usually happen early in the design process. When faced with a problem engineers work to gather as many potential solutions as possible. Having a large body of initial ideas helps designers converge on an optimum final solution. Engineers have developed numerous analytical ideation tools to guide cognitive design processes and increase ideation productivity. This research investigates the effects of enhancing conceptual design tools in accordance with recommendations from the field of cognitive science. Pedagogy and learning theory literature frequently advocate for the use of multimodal representation. This refers to using multiple sensory avenues like text, sound, and visuals to communicate more effectively. A common application of this multimodal principle is to supplement text with visuals. This research investigates the impact of such a recommendation within the context of design ideation. An experiment was organized to evaluate the effect of adding visual icons to an analytical ideation tool. Using a panel of expert graders, the ideation results of engineering students were graded. This data was then statistically analyzed to look for correlations between the merit of the ideation outcomes and the presence/absence of visual icons. Ultimately, no correlation was found between increased merit in ideation outputs and the presence of visuals in the ideation tool. Upon reflection, it was proposed that there are simply other factors which had a bigger impact on the ideation results in the context of this experiment. Finally, the investigation added insight into the use of different parameters for measuring ideation effectiveness including quality, quantity, novelty, feasibility, and variety. The statistical analysis revealed that in this experiment a positive correlation existed between all five metrics. This implies that in certain applications researchers may be able to justify only using one criterion for evaluating creative ideation output.
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    Experimental Studies of Flow-Structure Interactions in Blast/Shock-Driven Complex Flows
    (East Carolina University, 2022-04-29) Zieg, Parker
    Blast waves, which are generated by the sudden energy release in a finite space, are encountered in various situations. As the blast/shock waves propagate, any object in its path can be damaged by the combination of significant compression behind the shock front and the subsequent complex flow-structure interactions. Insufficient protection from blast loads has led to a significant loss of human lives and enormous structural damage and economic loss, highlighting the importance of developing effective blast/shock mitigation technologies. However, due to the lack of fundamental knowledge in the flow-structure interactions in various blast/shock conditions, the conventional methods of mitigating blast/shock have relied on the brutal use of various cladding rigid/soft materials where the coupling between the flow and structures is usually ignored. Challenges remain in understanding the complex flow-structure interactions driven by the rapidly-evolving nonlinear blast/shock waves. In this thesis, a series of experiments were carried out in the East Carolina University Advanced Blast Wave Simulator (ECU-ABWS) to characterize the flow-structure interactions (particularly the flow-airfoil interactions) under various blast/shock conditions. While the incident (side-on) pressures at multiple locations along the blast propagation were measured by using a temporally-resolved multi-point pressure sensing system, the time-evolutions of blast-airfoil interactions were also qualitatively revealed by using a high-speed Schlieren imaging system. A high-accuracy force/moment measurement system was also developed and used to determine the aerodynamic responses of the airfoil structure under various blast conditions. The understanding of these interactions allows for the further development of more efficient blast/shock mitigation techniques.