Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Physical Sciences and Mathematics (11)
- Mechanical Engineering (7)
- Electrical and Computer Engineering (4)
- Engineering Science and Materials (4)
- Environmental Sciences (4)
-
- Materials Science and Engineering (4)
- Aerodynamics and Fluid Mechanics (3)
- Aerospace Engineering (3)
- Applied Mathematics (3)
- Artificial Intelligence and Robotics (3)
- Civil and Environmental Engineering (3)
- Computer Engineering (3)
- Computer Sciences (3)
- Oil, Gas, and Energy (3)
- Environmental Engineering (2)
- Medicine and Health Sciences (2)
- Chemistry (1)
- Civil Engineering (1)
- Electromagnetics and Photonics (1)
- Engineering Physics (1)
- Health and Medical Administration (1)
- Life Sciences (1)
- Mathematics (1)
- Medical Physiology (1)
- Medical Sciences (1)
- Other Physics (1)
- Physical Chemistry (1)
- Physics (1)
- Physiology (1)
- Keyword
-
- Hydrogel (2)
- Spectroscopy (2)
- A-Fib (1)
- AVNRT (1)
- AVRT (1)
-
- Air Pollution (1)
- Alkali treatment (1)
- Alternative buffer layer (1)
- Arrhythmias (1)
- Artificial intelligence (1)
- Atrazine (1)
- Automated (1)
- Bi-directional stiffness change (1)
- CFD (1)
- CIGS (1)
- CMU Masonry (1)
- COMSOL Multiphysics (1)
- Capture (1)
- Chalcopyrite (1)
- DTW (1)
- Data Augmentation (1)
- Database (1)
- Deep learning (1)
- Delamination (1)
- Dimensional Analysis (1)
- Disinfection by product (1)
- Dispersion (1)
- Dynamic Time Warping (1)
- Electroactive Polymers (EAPs) (1)
- Electrocardiogram monitoring (1)
Articles 1 - 22 of 22
Full-Text Articles in Engineering
Survey Of How Irregularities In The Electrical System Of The Human Heart Link To Different Heart Arrhythmias, Jazmine Boloor
Survey Of How Irregularities In The Electrical System Of The Human Heart Link To Different Heart Arrhythmias, Jazmine Boloor
UNLV Theses, Dissertations, Professional Papers, and Capstones
This thesis explores the circuital pathway that a signal takes within the heart throughout a full heartbeat and provides a timing analysis. It then surveys the different pathways that could arise in the electrical system of the heart, and the associated heart diseases linked to the location of each pathway. Common heart arrhythmias such as atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia, atrial flutter, and atrial fibrillation are surveyed, and their pathways are analyzed. Electrocardiograms are presented to aid in understanding of the timing analysis associated with irregularity in heart function. Finally, this thesis explores an avenue of the heartbeat …
An Avalanche Transistor-Based Pulse Generator Design For Infrared Laser Applications, Abraham Lopez
An Avalanche Transistor-Based Pulse Generator Design For Infrared Laser Applications, Abraham Lopez
UNLV Theses, Dissertations, Professional Papers, and Capstones
This thesis details the design and results of a circuit intended for infrared laser applications, specifically for transcranial infrared light simulation (TILS) experiments and for use as a range finder. The circuit itself is comprised of a transistor, high voltage power supply, laser diode, capacitor, resistor, diode, and low voltage pulse. The design of a range finder is also developed. The range finder design is the same as the circuit developed for TILs with the addition of a few more components for receiving the returned light pulse such as a photodiode, op-amp, and comparator. The techniques used for a successful …
Development Of Pre-Magnetized Magnetorheological Elastomer For Bidirectionally Variable Stiffness Applications, Choonghan Lee
Development Of Pre-Magnetized Magnetorheological Elastomer For Bidirectionally Variable Stiffness Applications, Choonghan Lee
UNLV Theses, Dissertations, Professional Papers, and Capstones
Magnetorheological elastomers (MREs) utilize magnetic forces between ferromagnetic particles to cause variable stiffness properties and damping with external magnetic fields. In the MREs, the particles are embedded in a cured elastomer matrix, and an external magnetic field makes the stiffness change due to induced magnetic forces among particles. A disadvantage of the conventional MREs is that they cannot be softened (reduced stiffness) under an external magnetic field. Considering that there are many engineering applications where fast changes of stiffness in both directions (stiffening and softening) are required, embedding magnetically biased particles in the MRE can provide potential solutions. In this …
Development And Characterization Of Lead & Lead-Free Perovskite Solar Cell Materials, Rubaiya Murshed
Development And Characterization Of Lead & Lead-Free Perovskite Solar Cell Materials, Rubaiya Murshed
UNLV Theses, Dissertations, Professional Papers, and Capstones
In recent years, perovskite photovoltaic technology has offered enormous viability and dimensionality in solar cell research. As a light-harvesting active layer, Perovskite generated remarkable development in device efficiency of 25.7% for the single-junction solar cell, and over 33% for the perovskite/silicon tandem solar cell. Also, perovskite-perovskite tandem solar cell (also called all-perovskite tandem solar cell) shows great potential in device performance and achieved a power conversion efficiency (PCE) of 26.4%. Transitioning photovoltaic technology from the laboratory to commercial products, high PCE, low cost, long lifetime, and low toxicity are some of the critical factors to consider during material selection. Pb-halide …
Towards Cfd Investigations Into Particulate Air Pollution Of A Desert Urban Environment, Prosun Roy
Towards Cfd Investigations Into Particulate Air Pollution Of A Desert Urban Environment, Prosun Roy
UNLV Theses, Dissertations, Professional Papers, and Capstones
This dissertation has explored computational fluid dynamics (CFD) techniques for studying particulate air quality in the Las Vegas urban area. The dissertation is based on three research tasks: • High time-resolution fenceline air quality sensing and dispersion modeling for environmental justice-centered source attribution. (Chapter 2) • Pollen dispersion and deposition in real-world urban settings: A computational fluid dynamic study. (Chapter 3) • Effects of urban canopy parameterizations on modeling pollen dispersion and exposure. (Chapter 4) In Chapter 2, we investigate the facilitation of low-cost air quality sensors (LCAQS) and CFD technique on exposure assessment of environmental justice (EJ) communities and …
Facial Expression Recognition Using Convolutional Neural Networks (Cnns) And Generative Adversarial Networks (Gans) For Data Augmentation And Image Generation, Shekhar Singh
UNLV Theses, Dissertations, Professional Papers, and Capstones
Facial expressions play a crucial role in human communication, serving as a powerful means to convey emotions. However, classifying facial expressions using artificial intelligence (AI) can be challenging, especially with small datasets and images. Facial Expression Recognition (FER) is an active area of research, with Convolutional Neural Networks (CNNs) being widely employed for classification. In this research, we propose a CNN-based approach for FER that utilizes both original and augmented datasets to enhance classification accuracy. Experimental results on the FER2013 dataset show test accuracies of 63.39% and 64.59% for the original and augmented datasets, respectively, in a seven-class classification task. …
Non-Destructive Means Of Predicting Masonry Prism Strength Using Ultrasonic Pulse Velocity (Upv), Connor J. Barlow
Non-Destructive Means Of Predicting Masonry Prism Strength Using Ultrasonic Pulse Velocity (Upv), Connor J. Barlow
UNLV Theses, Dissertations, Professional Papers, and Capstones
Current ASTM standards call for grouted masonry prisms to be tested for compressive strength at 28-days to ensure compliance with the structural design. In the event of failing tests, the subject samples may require redesign or reconstruction which can pose problems due to ongoing development around and including the prisms between the time of placement and obtaining test results. The purpose of this research is to determine if the use of ultrasonic pulse velocity (UPV) testing can be utilized to determine a correlation between prism composite strength of the masonry prism with ultrasound readings as to provide preliminary means of …
Trajectory Analysis For Driving Safety Quantification, Michael I. Chang
Trajectory Analysis For Driving Safety Quantification, Michael I. Chang
UNLV Theses, Dissertations, Professional Papers, and Capstones
In order to evaluate the efficacy of the skid recovery exercise in the Driver’s Edge teenage driving program, a process is established to determine the trajectories of vehicles from recorded videos, compare them in terms of similarity through dynamic time warping (DTW), and then analyze the similarity measurements to assess whether the program has a significant effect on driving ability by repeated measures analysis of variance (rANOVA). The video is analyzed by Harris corner detection and Lucas-Kanade optical flow method to ascertain the vehicle trajectories. A homography is then estimated to translate coordinates from video into real-world. The instructor and …
High-Yield Bioinspired Atmospheric Water Capture Through Hydrogels, Yiwei Gao
High-Yield Bioinspired Atmospheric Water Capture Through Hydrogels, Yiwei Gao
UNLV Theses, Dissertations, Professional Papers, and Capstones
Water scarcity is a global issue affecting billions of people, and atmospheric water harvesting (AWH) technology has been identified as a potential solution. However, existing single-material AWH approaches have limited water harvesting yields due to alternated water capture, storage, and release stages, and only function within a high relative humidity range. In my doctoral research project, we developed a bio-inspired, hydrogel-based multi-layer AWH approach that allows for segregated capture, storage, and release stages, and is envisioned to have higher daily water harvesting efficiency even in low-humidity areas. My research began with understanding the relations between hydrogel mechanical stiffness, hydraulic permeability, …
Time-Dependent Wetting Behavior Of Hydrogels, Amir Kashani
Time-Dependent Wetting Behavior Of Hydrogels, Amir Kashani
UNLV Theses, Dissertations, Professional Papers, and Capstones
Hydrogels are 3-D polymers with hygroscopic properties that enable them to absorb and retain large amounts of water. In many applications such as biomedical applications, including drug delivery, wound healing, tissue engineering, biosensors, and contact lenses, agriculture, food and beverage, cosmetics, and environmental, hydrogels also need to maintain a high degree of wetting in order to ensure effective functionality and interaction with surrounding fluids or tissues in desired applications. The combination of wetting and absorptive behavior of hydrogels that are often encountered in biomedical, biological, industrial and the mentioned applications presents a challenging physical problem that is not completely understood. …
Enhanced Iot-Based Electrocardiogram Monitoring System With Deep Learning, Jian Ni
Enhanced Iot-Based Electrocardiogram Monitoring System With Deep Learning, Jian Ni
UNLV Theses, Dissertations, Professional Papers, and Capstones
Due to the rapid development of computing and sensing technologies, Internet of Things (IoT)-based cardiac monitoring plays a crucial role in providing patients with cost-efficient solutions for long-term, continuous, and pervasive electrocardiogram (ECG) monitoring outside a hospital setting. In a typical IoT-based ECG monitoring system, ECG signals are picked up by sensors located on the edge, and then uploaded to the remote cloud servers. ECG interpretation is performed for the collected ECGs in the cloud servers and the analysis results can be made instantly available to the patients as well as their healthcare providers.In this dissertation, we first examine the …
A One-Dimensional Analysis Of A Microbial Fuel Cell For Efficient Acetate Removal And Power Density Output, David Rouhani
A One-Dimensional Analysis Of A Microbial Fuel Cell For Efficient Acetate Removal And Power Density Output, David Rouhani
UNLV Theses, Dissertations, Professional Papers, and Capstones
Microbial fuel cells (MFCs) are electrochemical devices that utilize microorganisms to convert organic matter into electrical energy. MFCs have been discussed to have potential application for sustainable wastewater treatment due to their ability to generate electricity while simultaneously treating contaminated water. To optimize MFC performance, numerical models can be used to understand the complex electrochemical and biological processes occurring in the system. In this study, a numerical model was developed to simulate the performance of MFCs under varying operating conditions and to investigate the performance of a MFC for treating wastewater fuel. More specifically, the MFC was modeled to oxidize …
Development Of An Automated Gpib System For Characterization Of Sige Avalanche Photodiodes, David A. Santiago
Development Of An Automated Gpib System For Characterization Of Sige Avalanche Photodiodes, David A. Santiago
UNLV Theses, Dissertations, Professional Papers, and Capstones
Photon counting is a technique in many modern technologies such as medical imaging and LiDAR systems. Photon counting is needed in many aspects of the development process for these technologies from photodetector characterization to operation of the finished product. This thesis will serve to solve the challenge of quantifying photodetector performance using automating test equipment with known software packages such as MATLAB to be able tocharacterize photodetectors in an efficient manner. A custom MATLAB program has been developed to interface with various instrumentation using a General-Purpose Interface Bus (GPIB) and a Prologix GPIB-USB controller that will be able to send …
Monitoring And Classification Of Tissue Perfusion Through The Combined Use Of Thermal, Rgb, And Laser Speckle Contrast Imaging, Ivan Soto
UNLV Theses, Dissertations, Professional Papers, and Capstones
In cooperation with the UNLV School of Medicine, this thesis is part of a bigger project aimed at developing a post-op surgery device for the constant unattended monitoring of a patient’s tissue. This device is intended to monitor areas of surgical sites and detect any complications without the need for continuous supervision by medical professionals. One such complication includes inadequate tissue perfusion, or a lack of blood flow reaching a patient’s tissue. The role of this thesis is to fit a convolutional neural network model to the available data gathered from voluntary participants and attempt to classify the data as …
Information-Theoretic Model Diagnostics (Infomod), Armin Esmaeilzadeh
Information-Theoretic Model Diagnostics (Infomod), Armin Esmaeilzadeh
UNLV Theses, Dissertations, Professional Papers, and Capstones
Model validation is a critical step in the development, deployment, and governance of machine learning models. During the validation process, the predictive power of a model is measured on unseen datasets with a variety of metrics such as Accuracy and F1-Scores for classification tasks. Although the most used metrics are easy to implement and understand, they are aggregate measures over all the segments of heterogeneous datasets, and therefore, they do not identify the performance variation of a model among different data segments. The lack of insight into how the model performs over segments of unseen datasets has raised significant challenges …
Investigating Haloacetonitrile (Han) Formation Potential From Nitrogenous Antibiotics And Agrochemicals, Kazi Shafayet Haider
Investigating Haloacetonitrile (Han) Formation Potential From Nitrogenous Antibiotics And Agrochemicals, Kazi Shafayet Haider
UNLV Theses, Dissertations, Professional Papers, and Capstones
Disinfection can promote safe drinking water. Chlorine and chloramines are the two most used disinfectants. While these disinfectants are effective in inactivating disease-causing pathogens, they also produce hazardous byproducts when they react with organic compounds (precursors). Nitrogenous disinfection byproducts (N-DBPs) are more toxic than their counterparts. The increased use of nitrogen-based agrochemicals and antibitics has led to their detection in different water sources. The presence of secondary amine and aniline in these compounds can act as a source of reactive nitrogen to form N-DBPs. In addition, the increased concentration of bromide in water systems due to anthropogenic activities can enhance …
Simulating Condensation In The Theory Of Classical Nucleation, David Vallet
Simulating Condensation In The Theory Of Classical Nucleation, David Vallet
UNLV Theses, Dissertations, Professional Papers, and Capstones
The scope of this thesis is to numerically investigate condensation that occurs in transonic and supersonic flows. Condensation shocks are a phenomenon that occurs within converging-diverging nozzles. There are many applications forconverging-diverging nozzles, such as thermovapour compressors (TVC), which are largely used for desalination. As water resources become more precious within the western United States there is a need to develop cost effective solutions for cleaning water. Steam generator power stations are another application where enhanced simulations and accuracy of design could improve efficiency and save on carbon emissions. Traditionally, numerical designs of transonic flows have been conducted with either …
An Investigation Of Soft Electrohydraulic Actuators: Theory, Characterization, And Conceptual Applications, Alexandrea Washington
An Investigation Of Soft Electrohydraulic Actuators: Theory, Characterization, And Conceptual Applications, Alexandrea Washington
UNLV Theses, Dissertations, Professional Papers, and Capstones
Electroactive polymer (EAP) materials are a novel soft electromechanical device that exploits the inherent electrical and mechanical advantages of flexible polymer materials. Within this groundbreaking field there are various actuator and sensor devices that have been developed for a variety of applications, from medical devices to artificial biological systems. This research focuses on electrohydraulic actuators, which are comprised of a flexible conductive medium, a dielectric fluid, and a compliant film material to encapsulate the dielectric fluid. This specific study centers around the electrohydraulic EAP actuator known as the Hydraulically Amplified Self-Healing Electrostatic (HASEL) actuator, first introduced by the Keplinger group …
Metastability And Degradation In Cu(In,Ga)Se2 Thin-Film Solar Cells, Mohsen Jahandardoost
Metastability And Degradation In Cu(In,Ga)Se2 Thin-Film Solar Cells, Mohsen Jahandardoost
UNLV Theses, Dissertations, Professional Papers, and Capstones
Cu(In,Ga)(S,Se)2 or CIGS is a thin-film semiconductor that has shown a device efficiency of 23.35% and 24.2% for single-junction and perovskite/CIGS tandem solar cells, respectively. CIGS offers promising properties such as tunable bandgap and ease of processing making them great candidates for thin-film tandem devices. However, knowledge of the effect of material defects, buffer materials, and post-deposition treatment (PDT) on degradation and metastability behavior in these devices is not well understood.In this dissertation, metastability and long-term degradation of CIGS thin-film solar cells have been investigated under combinatorial stress factors of heat, light, and voltage bias to systematically understand the effect …
Mathematical Modeling: Finite Element Analysis And Computations Arising In Fluid Dynamics And Biological Applications, Jorge Reyes
Mathematical Modeling: Finite Element Analysis And Computations Arising In Fluid Dynamics And Biological Applications, Jorge Reyes
UNLV Theses, Dissertations, Professional Papers, and Capstones
It is often the case when attempting to capture real word phenomena that the resulting mathematical model is too difficult and even not feasible to be solved analytically. As a result, a computational approach is required and there exists many different methods to numerically solve models described by systems of partial differential equations. The Finite Element Method is one of them and it was pursued herein.This dissertation focuses on the finite element analysis and corresponding numerical computations of several different models. The first part consists of a study on two different fluid flow models: the main governing model of fluid …
Analysis And Application Of Finite Element And High-Order Finite Difference Methods For Maxwell’S Equations In Complex Media, Li Zhu
UNLV Theses, Dissertations, Professional Papers, and Capstones
The Perfectly Matched Layer (PML) technique is an effective tool introduced by B´erenger [13] to reduce the unbounded wave propagation problem to a bounded domain problem. This dissertation focuses on two different PML models and their applications to wave propagation problems with Maxwell’s equation in complex media. We investigate these models using two popular numerical methods: the Finite Difference Method (FDM) in Chapters 2 and 3, and the Finite Element Method (FEM) in Chapters 4 and 5.In Chapter 2, we focus on analyzing the stability of a PML developed by B’ecache et al. [10] for simulating wave propagation in the …
Spectroscopic Studies On Silicon And Chalcopyrite Materials For Solar Energy Applications, Amandee Hua
Spectroscopic Studies On Silicon And Chalcopyrite Materials For Solar Energy Applications, Amandee Hua
UNLV Theses, Dissertations, Professional Papers, and Capstones
In this dissertation, silicon-based materials for photovoltaics and chalcopyrite-based materials for photoelectrochemical water splitting are investigated using various spectroscopic and microscopic techniques. Although silicon dominates the photovoltaic market, further improvement can be made by using an alternative low temperature passivation approach. Currently, thermally grown SiO2 passivation is commonly used for silicon solar cells. However, this technique requires high processing temperatures (>800 °C), which increases the thermal budget, potentially decreases the bulk quality of Si, and can lead to difficulties in implementing in production lines. Here, a S-based passivation approach is studied that require lower processing temperatures of ~550 °C. …