Engineering Commons^™

Characterization, Classification, And Genesis Of Seismocardiographic Signals, Amirtaha Taebi

Electronic Theses and Dissertations

Seismocardiographic (SCG) signals are the acoustic and vibration induced by cardiac activity measured non-invasively at the chest surface. These signals may offer a method for diagnosing and monitoring heart function. Successful classification of SCG signals in health and disease depends on accurate signal characterization and feature extraction. In this study, SCG signal features were extracted in the time, frequency, and time-frequency domains. Different methods for estimating time-frequency features of SCG were investigated. Results suggested that the polynomial chirplet transform outperformed wavelet and short time Fourier transforms. Many factors may contribute to increasing intrasubject SCG variability including subject posture and respiratory …

Characterization Of Anisotropic Mechanical Performance Of As-Built Additively Manufactured Metals, Sanna Siddiqui

Electronic Theses and Dissertations

Additive manufacturing (AM) technologies use a 3D Computer Aided Design (CAD) model to develop a component through a deposition and fusion layer process, allowing for rapid design and geometric flexibility of metal components, for use in the aerospace, energy and biomedical industries. Challenges exist with additive manufacturing that limits its replacement of conventional manufacturing techniques, most especially a comprehensive understanding of the anisotropic behavior of these materials and how it is reflected in observed tensile, torsional and fatigue mechanical responses. As such, there is a need to understand how the build orientation of as-built additively manufactured metals, affects mechanical performance …

Fiber Optimization For Operation Beyond Transverse Mode Instability Limitations, Joshua Bradford

Electronic Theses and Dissertations

Transverse Mode Instabilities (TMIs) stand as a fundamental limitation to power and brightness scaling in laser systems based upon optical fiber technologies. This work comprises experimental and theoretical investigations into fiber laser design that should minimize the effects of Stimulated Thermal Rayleigh Scattering. Theoretical discussions and simulations focus on how fiber parameters affect transverse mode coupling. These include core geometry optimization, pump geometry optimization, in addition to the effects of HOM content and losses on the TMI threshold. Experimentally, a high-power laser facility is commissioned with beam quality diagnostics to quantify the thresholds of the onset of modal interferences and …

Non-Hermitian Optics, Absar Ulhassan

Electronic Theses and Dissertations

From the viewpoint of quantum mechanics, a system must always be Hermitian since all its corresponding eigenvalues must be real. In contrast, the eigenvalues of open systems-unrestrained because of either decay or amplification-can be in general complex. Not so long ago, a certain class of non-Hermitian Hamiltonians was discovered that could have a completely real eigenvalue spectrum. This special class of Hamiltonians was found to respect the property of commutation with the parity-time (PT) operator. Translated into optics, this implies a balance between regions exhibiting gain and loss. Traditionally, loss has been perceived as a foe in optics and something …

Power Scaling Of High Power Solid State Lasers., Bumjin Oh

Electronic Theses and Dissertations

The solid-state laser is one of the most widely used lasers in scientific research and industrial applications. This thesis describes detailed investigations of two modern architectures of high power cw solid-state lasers, a 20 W diode-pumped Yb:YAG thin disc laser and 300 W diode-pumped Nd:YAG rod laser. With the thin disc laser architecture, the signal beam must fit to the pump area on the disc defined by the multi-pass diode pump configuration. The beam propagation, beam diameter, phase and thermal effects for various cavity configurations are investigated theoretically and experimentally. In addition, the internal loss, small signal gain, and thermal …

Regolith-Based Construction Materials For Lunar And Martian Colonies, Kevin Grossman

Electronic Theses and Dissertations

Humankind's ambitions of exploring our solar system and parts beyond depend heavily on our ability to collect resources from local environments at our destinations rather than bringing materials on the journey. This is a concept known as in-situ resource utilization (ISRU) and it is one that has been understood by every explorer and settler in the history of humankind. Regolith on the moon and Mars has been shown to be a particularly useful resource and has the ability to provide humans with resources including water, oxygen, construction material, fabric, radiation shielding, metals, and may more. This dissertation focuses on construction …

Adiabatic Film Cooling Effectiveness Of A Transpiration-Cooled Leading Edge Fabricated By Laser Additive Manufacturing, Luisana Calderon

Electronic Theses and Dissertations

Laser additive manufacturing (LAM) is an emerging technology capable of fabricating complex geometries not possibly made by investment casting methods for gas turbine applications. LAM techniques consist of building parts in a layer-by-layer process by selectively melting metal powders. In the present study, a mock leading edge segment of a turbine blade fabricated by LAM of Inconel 718 powders is investigated. For this particular design, the traditional showerhead film cooling holes have been replaced by two strips containing engineered-porous regions with the purpose of simulating the effect of transpiration cooling. Transpiration cooling has been considered a promising external convective cooling …

Development Of A Tabletop Coherent Soft X-Ray Source, Hanfu Kong

Electronic Theses and Dissertations

The goal of this thesis is to design a tabletop coherent soft X-ray source for attosecond high resolution imaging. We collect signals from gas cells with different length and lens with different focal length. A spectrometer with a grating and a CCD camera is applied to observe and measure the spectrum of the X-ray attosecond pulses. This thesis first introduces the theory background of ultrafast lasers, then mainly explains high harmonic generation, which is the key method for attosecond pulses generation, subsequently presents the experiment system and analyzes the results from the experiment, also compares different combinations of parameters of …

Fast Compressed Automatic Target Recognition For A Compressive Infrared Imager, Brian Millikan

Electronic Theses and Dissertations

Many military systems utilize infrared sensors which allow an operator to see targets at night. Several of these are either mid-wave or long-wave high resolution infrared sensors, which are expensive to manufacture. But compressive sensing, which has primarily been demonstrated in medical applications, can be used to minimize the number of measurements needed to represent a high-resolution image. Using these techniques, a relatively low cost mid-wave infrared sensor can be realized which has a high effective resolution. In traditional military infrared sensing applications, like targeting systems, automatic targeting recognition algorithms are employed to locate and identify targets of interest to …

An Engineering Analytics Based Framework For Computational Advertising Systems, Mengmeng Chen

Electronic Theses and Dissertations

Engineering analytics is a multifaceted landscape with a diversity of analytics tools which comes from emerging fields such as big data, machine learning, and traditional operations research. Industrial engineering is capable to optimize complex process and systems using engineering analytics elements and the traditional components such as total quality management. This dissertation has proven that industrial engineering using engineering analytics can optimize the emerging area of Computational Advertising. The key was to know the different fields very well and do the right selection. However, people first need to understand and be experts in the flow of the complex application of …

Influence Of Chitosan-Alginate Scaffold Stiffness On Bone Marrow Stromal Cell Differentiation, Isabel Arias Ponce

Electronic Theses and Dissertations

Tissue grafts are the gold standard for replacing large volume tissue defects. Yet, they present several risks, including infection, low functional outcomes, and reduced graft integrity. Tissue engineering (TE) combines cells and biomaterial scaffolds to foster tissue growth and remodeling. Bone marrow stromal cells (BMSCs) have been shown to respond to the stiffness of their microenvironment, resulting in differentiation into different lineages. 3D porous chitosan-alginate (CA) scaffolds have been previously demonstrated for bone TE with osteoblasts and BMSCs; however, only a single scaffold composition (4 wt%) was studied. Three CA scaffold compositions (2, 4, 6 wt% CA) were produced. Scanning …

Cell Printing: An Effective Advancement For The Creation Of Um Size Patterns For Integration Into Microfluidic Biomems Devices, Megan Aubin

Electronic Theses and Dissertations

The Body-on-a-Chip (BoaC) is a microfluidic BioMEMs project that aims to replicate major organs of the human body on a chip, providing an in vitro drug testing platform without the need to resort to animal model testing. Using a human model also provides significantly more accurate drug response data, and may even open the door to personalized drug treatments. Microelectrode arrays integrated with human neuronal or human cardiac cells that are positioned on the electrodes are essential components for BoaC systems. Fabricating these substrates relies heavily on chemically patterned surfaces to control the orientation and growth of the cells. Currently, …

Liquid Crystal Phase Modulation For Beam Steering And Near-Eye Displays, Yun-Han Lee

Electronic Theses and Dissertations

Liquid crystal spatial phase modulator plays an important role in laser beam steering, wave-front shaping and correction, optical communication, optical computation and holography. One fundamental limitation lays in the response time of liquid crystal reorientation. To achieve fast response time, polymer-network liquid crystals are therefore proposed. By incorporating polymer network in a liquid crystal host, the response time can be reduced by a factor of 100. However, the polymer network introduces hysteresis, light scattering, and high voltage. The motivation for a fast-response liquid crystal phase modulator will be discussed in the first chapter. In the second chapter, we introduce our …

Some Aggregation Operators For Bipolar-Valued Hesitant Fuzzy Information, Florentin Smarandache, Tahir Mahmood, Kifayat Ullah, Qaisar Khan

Branch Mathematics and Statistics Faculty and Staff Publications

In this article we define some aggregation operators for bipolar-valued hesitant fuzzy sets. These operations include bipolar-valued hesitant fuzzy ordered weighted averaging (BPVHFOWA) operator, bipolar-valued hesitant fuzzy ordered weighted geometric (BPVHFOWG) operator and their generalized forms. We also define hybrid aggregation operators and their generalized forms and solved a decision-making problem on these operation.

Thermoresponsive, Redox-Polymerized Cellulosic Hydrogels Undergo In Situ Gelation And Restore Intervertebral Disc Biomechanics Post Discectomy, Devika Varma, H. A. Lin, R. G. Long, G. T. Gold, A. C. Hecht, J. C. Iadridis, Steven B. Nicoll

Publications and Research

Back and neck pain are commonly associated with intervertebral disc (IVD) degeneration. Structural augmentation of diseased nucleus pulposus (NP) tissue with biomaterials could restore degeneration-related IVD height loss and degraded biomechanical behaviors; however, effective NP replacement biomaterials are not commercially available. This study developed a novel, crosslinked, dual-polymer network (DPN) hydrogel comprised of methacrylated carboxymethylcellulose (CMC) and methylcellulose (MC), and used in vitro, in situ and in vivo testing to assess its efficacy as an injectable, in situ gelling, biocompatible material that matches native NP properties and restores IVD biomechanical behaviors. Thermogelling MC was required to enable consistent and timely …

Face Size Biases Emotion Judgment Through Eye Movement, Shuo Wang

Faculty & Staff Scholarship

Faces are the most commonly used stimuli to study emotions. Researchers often manipulate the emotion contents and facial features to study emotion judgment, but rarely manipulate low-level stimulus features such as face sizes. Here, I investigated whether a mere difference in face size would cause differences in emotion judgment. Subjects discriminated emotions in fear-happy morphed faces. When subjects viewed larger faces, they had an increased judgment of fear and showed a higher specificity in emotion judgment, compared to when they viewed smaller faces. Concurrent high-resolution eye tracking further provided mechanistic insights: subjects had more fixations onto the eyes when they …

Single-Site Catalyst Promoters Accelerate Metal- Catalyzed Nitroarene Hydrogenation, Liang Wang, Erjia Guan, Jian Zhang, Junhao Yang, Yihan Zhu, Yu Han, Ming Yang, Cheng Cen, Gang Fu, Bruce C. Gates, Feng-Shou Xiao

Faculty & Staff Scholarship

Atomically dispersed supported metal catalysts are drawing wide attention because of the opportunities they offer for new catalytic properties combined with efficient use of the metals. We extend this class of materials to catalysts that incorporate atomically dispersed metal atoms as promoters. The catalysts are used for the challenging nitroarene hydro- genation and found to have both high activity and selectivity. The promoters are single-site Sn on TiO2 supports that incorporate metal nanoparticle catalysts. Represented as M/Sn- TiO2 (M = Au, Ru, Pt, Ni), these catalysts decidedly outperform the unpromoted supported metals, even for hydrogenation of nitroarenes substituted with various …

Cm-Dii And Mcf-7 Breast Cancer Cell Responses To Chemotherapeutic Agents, Ashten M.C. Anderson

Honors Theses

CM-DiI is a lipophilic, red fluorescent dye used for staining and tracking the migration of cells. CM-DiI makes it possible to visualize cells in histological regions and can therefore be very useful for the tracking of cancer cell proliferation and metastasis in vivo. The ability to track and quantitate cancer cell proliferation in vivo is essential for cancer drug discovery. If CM-DiI labeled cancer cells respond to chemotherapy agents similar to unlabeled cancer cells, it facilitates screening of potential anti-cancer compounds using CM-DiI labeled cells in a xenotransplanted, transgenic zebrafish model (Danio rerio). To investigate whether CM-DiI labeling would affect …

The Development And Optimization Of An Ethylbenzene Process, Aynslie Fritz

Honors Theses

The purpose of this thesis was to optimize a pre-existing vapor phase ethylbenzene process, and to develop a base case liquid phase ethylbenzene process. A brief introduction is included to present an overview of process optimization and suggest common strategies to employ. While optimizing the vapor phase process, discrete optimization was performed to determine the local optima for multiple unit operations by comparing their net present value to that of the base case. After optimization, an $81.5 million increase in net present value was obtained. When developing the liquid phase ethylbenzene process, Antoine's Equation, Raoult's Law, the first law of …

Effects Of Predation On The Biochemical Constituents Of The Bleached Soft Coral Sinularia Polydactyla, Carley Elizabeth Cole

Honors Theses

Climate change can indirectly affect the level of predation on soft corals. As sea temperatures rise, more and more bleaching events are occurring, which can affect the production of chemical defenses and the concentrations of the biochemical constituents that make up the soft corals. These changes may make the soft corals more attractive to predators. This phenomenon is suggested by the environmental stress theory (EST), which states that under stressful conditions, more of an organism's energy is allocated to survival rather than to other factors, such as reproduction or predator deterrence. To test the effect of predation on already bleached …

Technique For The Synthesis Of Difluorinated Organic Molecules Using Magnesium Bases, Cassidy S. Baldwin

Honors Theses

The presence of fluorine in organic molecules can confer biological advantages which are often exploited in drug development. For example, fluorine has been shown to limit drug metabolism and enhance drug distribution. However, the development of fluorinated pharmaceutics poses synthetic challenges. These challenges are especially pronounced when developing molecules with a difluoromethyl group. One difluoromethyl functional group of particular interest is the α,α-difluoro-β-amino carbonyl group, which has been seen in potential drug leads. The previous methods of accessing this group are inefficient and complex. The goal of this project was to develop a new technique to access this group by …

Product Realization Capstone: Safety Steps For The Willie Price Lab School, Christopher L. Sevigney

Honors Theses

The purpose of this document is to outline the engineering design and production development process for a safety step to be used in pre-schools. The team began by establishing customer need and moved through the design and prototyping phases. Once a design was selected, the team focused on developing a production process for the product. The project culminated in two one-hour long production runs in which the team carried out the production process to fill a customer order. The results of the first run indicated that adjustments needed to be made to the process, as the required number of pieces …

Nanopulse Stimulation (Nps) Induces Tumor Ablation And Immunity In Orthotopic 4t1 Mouse Breast Cancer: A Review, Stephen J. Beebe, Brittany P. Lassiter, Siqi Guo

Bioelectrics Publications

Nanopulse Stimulation (NPS) eliminates mouse and rat tumor types in several different animal models. NPS induces protective, vaccine-like effects after ablation of orthotopic rat N1-S1 hepatocellular carcinoma. Here we review some general concepts of NPS in the context of studies with mouse metastatic 4T1 mammary cancer showing that the postablation, vaccine-like effect is initiated by dynamic, multilayered immune mechanisms. NPS eliminates primary 4T1 tumors by inducing immunogenic, caspase-independent programmed cell death (PCD). With lower electric fields, like those peripheral to the primary treatment zone, NPS can activate dendritic cells (DCs). The activation of DCs by dead/dying cells leads to increases …

Aviation Outreach Model And Gap Analysis: Examining Solutions To Address Workforce Shortages, Rebecca K. Lutte

Aviation Institute Faculty Publications

The purpose of this research is to examine aviation outreach programs to identify best practices and areas for improvement in the endeavor to recruit youth to the aviation industry. The research includes creation of a model of aviation outreach and development and application of an aviation outreach gap analysis design. Three programs are analyzed, Women in Aviation Girls in Aviation Day, Experimental Aviation Association Young Eagles, and Aircraft Owners and Pilots Association High School Aviation Initiative. Each program takes a unique approach to recruiting youth and the strengths and weaknesses, based on the aviation outreach model, are discussed. Results of …

University Of Nebraska At Omaha 2018-2019 Course Catalog, University Of Nebraska At Omaha

Undergraduate Catalogs

Located in one of America’s best cities to live, work and learn, the University of Nebraska at Omaha (UNO) is Nebraska’s premier metropolitan university. With more than 15,000 students enrolled in 200-plus programs of study, UNO is recognized nationally for its online education, graduate education, military friendliness, and community engagement efforts.Founded in 1908, UNO has served learners of all backgrounds for more than 100 years and is dedicated to another century of excellence both in the classroom and in the community.

The Design, Test And Evaluation Of A Sensing System For Process Analytical Technology (Pat), Trevor Murphy

Theses

Increased globalisation and competitiveness has given rise to a more dynamic and diverse global market that has begun to place incredible strain on manufacturing supply chains. Conventional manufacturing methods such as the batch manufacturing methods employed largely by the materials processing industries i.e. pharmaceuticals, polymers and magnesium processing plants are ill-suited to cope with the demands of today. As products evolve with technological advancements they become more complex to produce and require alternative approaches to manufacturing to ensure product quality while reducing costs and increasing manufacturing efficiencies.

A potential solution to the growing demands on today's supply chain is process …

Hosting Capacity Optimization In Modern Distribution Grids, Mansoor T. Alturki

Electronic Theses and Dissertations

The availability of distributed renewable energy resources and the anticipated increase in new types of loads are changing the way electricity is being produced and supplied to consumers. This shift is moving away from a network delivering power solely from centralized power plants towards a decentralized network which supplements its power production by incorporating local distributed generators (DGs). However, the increased integration of DGs into existing distribution networks is impacting their behavior in terms of voltage profile, reliability, and power quality. To determine the maximum amount of DG that distribution grids can accommodate the concept of hosting capacity is introduced. …

Automated Cfd Optimization To Maximize Wind Farms Performance And Land Use, Rafael Valotta Rodrigues

Electronic Theses and Dissertations

In this research, a computational system was designed to analyze and optimize the layout of wind farms under variable operational conditions. At first, a wind turbine computational fluid dynamic (CFD) model was developed covering the near wake. The near wake flow field was validated against near wake velocity data from the MEXICO experiment. The CFD simulation demonstrated that the tip speed ratio and the pitch angle greatly influence the near wake behavior, affecting the velocity deficit and the turbulence intensity profile in this region. The CFD model was extended to cover the far wake, aiming to become a computational tool …

Adrenergic Stimulation In Acute Hyperglycemia: Effects On Cellular And Tissue Level Murine Cardiac Electrophysiology, Sridevi Thyagarajan

Theses and Dissertations--Biomedical Engineering

Cardiovascular complications associated with elevated levels of glucose in the blood (Hyperglycemia, HG) is a growing health concern. HG is known to be associated with a variety of cardiovascular morbidities including higher incidence of electrical disturbances. Although effects of chronic HG have been widely investigated, electrophysiological effects of acute hyperglycemia are relatively less known. Further, hyperglycemic effects on adrenergic response is not widely investigated. We used excised ventricular tissues from mice to record trans-membrane potentials during a variety of pacing protocols to investigate cellular/tissue level electrophysiological effects of acute hyperglycemia and adrenergic stimulation (1µM Isoproterenol, a β-adrenergic agonist). A custom …

Effects Of Lumbar Spinal Fusion On Lumbopelvic Rhythm During Activities Of Daily Living, Cameron G. Slade

Theses and Dissertations--Biomedical Engineering

Abnormalities in lumbopelvic rhythm (LPR) play a role in occurrence/recurrence of low back pain (LBP). The LPR before spinal fusion surgery and its changes following the surgery are not understood. A repeated measure study was designed to investigate timing and magnitude aspects of LPR in a group of patients (n = 5) with LBP before and after a spinal fusion surgery. Participants completed a forward bending and backward return task at their preferred pace in the sagittal plane. The ranges of thoracic and pelvic rotations and lumbar flexion (as the magnitude aspects of LPR) as well as the mean absolute …