Engineering Commons^™

Analysis Of Noise Sources In Avalanche Region Of Reverse Biased P-N Junctions, Md Sakiul Islam Sudman

Electrical Engineering Theses - Archive

There is a need to understand the physical mechanisms for excess noise factor (F) in avalanche diodes for all regions of operation. The current classical theory accounts for F only for low carrier multiplication where single carrier injection starts the avalanche process. Our model fits the white noise exhibited by reverse-biased avalanche diodes in the entire operation region of four orders of current magnitude. In this sense, it is a first. The measured noise data was provided by Texas Instruments. We fitted the measured noise components with the calculated noise components where carrier multiplication takes place. The least …

Neural Net Estimation Of Discriminants Posterior Probability Vector, Harshvardhan Harshvardhan

Electrical Engineering Theses - Archive

Interpreting multi-layer perceptron (MLP) classifier outputs as posterior probabilities is a well-established practice in machine learning and is supported in the literature. However, several authors point out that MLP outputs are very poor estimates of the posterior probabilities. This is demonstrated for classifiers with and without nonlinear output activation. Achieving this reliability depends on key factors such as model complexity, sufficient training data availability, and optimization techniques' effectiveness. In practice, these requirements are not met, resulting in suboptimal probability estimates. Our approach introduces an innovative method based on the softmax output. The method aim to refine MLP discriminants into more …

A Learning-Based Framework For Autonomous Robotic Operations In Resource-Denied Environments, Joseph M. Cloud

Computer Science and Engineering Dissertations - Archive

Establishing a sustained human presence beyond Earth necessitates the development of autonomous systems capable of extracting and utilizing local resources. On the Moon, in-situ resource utilization (ISRU) is essential to reduce the dependency on Earth-based supplies. Leveraging lunar resources such as water ice for life support and fuel production or regolith for surface construction will enable long-term lunar missions and future deep space exploration. NASA's Artemis program is targeting the lunar south pole (LSP), an area with raw, yet abundant resources available. The harsh environmental conditions present significant challenges for humans operating and installing surface infrastructure. Autonomous robotic systems are …

Web-Based Visualization Of Spatial And Spatio-Temporal Data Using Integrated Datasets, Mohammad Shaito

Computer Science and Engineering Dissertations - Archive

Currently, spatial geographic data can be collected for many applications that involve data on the planet earth. These collected data typically have coordinates (x,y), or longitude and latitude in map space, and thus can be located and displayed on maps. Data alone represents facts and has no meaning on its own but becomes meaningful when it is associated with application knowledge, such as elections, crimes, disease, etc. For example, there is no meaning behind those numbers (1, 23, 125, 355, . . .), yet they are data that can gain meaning when correlated with the total number of cases of …

Bringing "Virtual" To "Reality": Enhancing Security And Usability On Vr System And Applications, Huadi Zhu

Computer Science and Engineering Dissertations - Archive

With the rapid advancements in computer science, electronics, optics, and related fields, virtual reality (VR) gradually penetrates into our daily lives, and is predicted to become a core technology in the near future. Despite its potentials, however, existing designs and solutions for VR applications remain at the infant stage, introducing limited usability and efficiency for real-world users. Besides, the increasing prevalence of VR presents new security and privacy threats due to the vast amount of information stored in or accessible through VR devices. To bridge this gap, we exploit and combine techniques from computer science and human biology, as well …

Termite Gut Microbe (Tav5) Application To Pulp & Paper Wastewater And Sugarcane Bagasse: Enhancing Lignin Degradation And Methane Generation During Anaerobic Digestion, Doreen Ntiamoah-Asare, Melanie Sattler Ph.D, P.E.

Civil Engineering Dissertations - Archive

TAV5 is a bacterium strain of the family Opitutaceae from Termite-Associated Verrucomicrobium isolated from the hindgut of Reticulitermes Flavipes, the most common subterranean termite in North America. The genome of TAV5 contains genes coding for enzymes that could structurally modify lignin.

Pulp & paper wastewater and Sugarcane bagasse contain high levels of cellulose (44-46%) and hemicellulose (27-32% ), as well as lignin (17-23%) which is recalcitrant to biodegradation. The lignin tend to shield the cellulose and hemicellulose making them inaccessible for biodegradation.

TAV5 can breakdown lignin, making the cellulose and hemicellulose accessible to microorganisms for biodegradation into methane generation for …

Development Of A Real-Time Warning System For Bridge Icing Using Time Domain Reflectometry, Taryn Dilorenzo

Civil Engineering Dissertations - Archive

Treacherous driving conditions are a safety concern during the winter season where icing on roadways and bridges is of particular concern. The use of sensors to detect the presence or potential of surface ice formation is essential for efficient and effective winter road maintenance. However, there is a lack of ice detection systems that combine robust sensors, active warning signs and an ice detection algorithm that is reliable and economical. This study presents an innovative sensor that uses dielectric sensing to detect the onset of ice formation on a bridge deck. The sensor combines an automatic algorithm for ice detection …

Streamlining Public Engagement In Transportation Projects Using Text Analytics, Alireza Shamshiri

Civil Engineering Dissertations - Archive

Infrastructure projects impact a broad range of stakeholders, particularly local communities, whose engagement is critical for successful outcomes. Despite the importance of public engagement in these projects, traditional methods of capturing and analyzing public opinion often fail to fully represent the diverse, genuine perspectives involved. This has led to conflicts between community members and project sponsors. On the other hand, despite advancements in text analytics, including natural language processing (NLP) and its subfields such as topic modeling, sentiment analysis, and neural networks, their functionalities and effectiveness in analyzing public opinion in the domain of infrastructure projects have not been fully …

Roles Of Vegetation On Soil Moisture Dynamics In Transitional Climates- Lessons From Improving Phenology Representation In Land Surface Model And Retrieval Algorithm, Farhad Hassani

Civil Engineering Dissertations - Archive

Soil moisture is a critical component of the terrestrial water and energy cycles, influencing key hydrological and atmospheric processes such as infiltration, runoff generation, evapotranspiration, and atmospheric boundary layer dynamics. Accurate representation of soil moisture is essential for reliable hydrological modeling, drought monitoring, and seasonal to sub-seasonal (S2S) weather forecasting. Vegetation significantly affects soil moisture dynamics through processes like transpiration, canopy interception, and root water uptake, especially in transitional climates where conditions fluctuate between arid and humid states. However, errors in vegetation phenology representation can lead to substantial biases in soil moisture estimates within land surface models (LSMs) and satellite …

Polymeric Spray-Applied Pipe Lining Selection, Evaluation And System Design, Sanaz Ghalambor

Civil Engineering Dissertations - Archive

POLYMERIC SPRAY-APPLIED PIPE LINING SELECTION, EVALUATION

AND SYSTEM DESIGN

Sanaz Ghalambor, PhD

The University of Texas at Arlington, 2024

Supervising Professor: Dr. Mohammad Najafi

Numerous pipes are considerably aged, and most are no longer functional. Immediate attention is required to either restore or replace these pipelines. To avoid digging up and replacing underground pipes, the Spray-Applied Pipe Lining (SAPL) rehabilitation technology, also known as Spray-In-Place-Pipe (SIPP) lining, can be used for pipe rehabilitation. This approach lowers expenses and downtime while preserving landscapes and structures and enhancing hydraulic characteristics. Although lining water pipes through spray application is the oldest pipeline rehabilitation …

Development And Application Of Teems (Telecommuting Expectation Models): Predicting Post-Pandemic Telecommuting Choice And Frequency Using Machine Learning Models, Aiswarya Acharath Mohanakrishnan

Civil Engineering Dissertations - Archive

Telecommuting, increasingly prevalent in today's workforce, has gained significant momentum amid the pandemic-induced shift towards remote work. It altered the travel behavior of workers and their travel patterns. This evolution prompts a reevaluation of worker travel behavior, necessitating adjustments in travel demand modeling to optimize transportation planning and service provision. Using the commuter’s data from a typical pre-pandemic workday to model the travel demand of weeks or years in the future is outdated. In designing transportation systems for the future, Metropolitan Planning Organizations (MPOs) will thus need to account for change in work trips due to telecommuting, and how this …

Advanced Network And Graph Theoretical Approaches To Urban Traffic Control And Optimization, Peirong Wang

Civil Engineering Dissertations - Archive

This article-based dissertation consists of four complete manuscripts related to using proposed advanced network and graph theoretical approaches to optimize traffic control. Manuscript One addresses the integration of Connected Automated Vehicles (CAVs) and human-driven vehicles in heterogeneous traffic networks. Traditional models assume uniform driving behaviors, which are now inadequate. To address this, an integer programming formulation for a vehicle-oriented traffic dynamics model in space-time networks is introduced. This model distinguishes between individual vehicles and their unique driving behaviors, capturing diverse attributes of heterogeneous traffic flow. The manuscript demonstrates how the model can estimate the propagation of backward shockwaves for scheduled …

Experimental And Numerical Analyses Of Percussion Driven Earth Anchors Under Monotonic Pullout Tests, Mehran Azizian

Civil Engineering Dissertations - Archive

This dissertation provides a thorough investigation into the behavior and performance of Percussion-Driven Earth Anchors (PDEAs) during monotonic pullout tests. PDEAs are becoming more commonly utilized in geotechnical engineering because of their effectiveness in installation, ability to bear loads immediately, and minimal disruption to the environment. Despite their advantages, a detailed understanding of their pullout capacity and failure mechanisms remains limited.

The research encompasses both experimental and numerical analyses to bridge this knowledge gap. Experimental tests were conducted using Digital Image Correlation (DIC) techniques to obtain precise measurements of soil and anchor interaction and figure out the failure mechanism. Photogrammetry …

Moisture And Glass Transition Temperature Kinetics From Long Term Hygrothermal Aging Of Carbon/Epoxy Composites, Behnaz Hassanpour

Civil Engineering Dissertations - Archive

The durability of fiber reinforced polymer composites used in civil infrastructure rehabilitation has become increasingly critical, especially under long-term hygrothermal aging conditions. This study focuses on the results of long-term (up to 6 years) hygrothermal aging of wet layup carbon/epoxy composites and investigates the effects of moisture, as well as accelerated aging at elevated temperatures with varying thicknesses and fabric areal weights. The primary objective is to establish a comprehensive understanding of moisture uptake kinetics and its subsequent effects on the glass transition temperature (T_g), mechanical performance, and the resulting implications for material durability. Four papers form …

Analytical And Simulation Modelling Of The Thermal Runaway Phenomenon In Mosfet Semiconductors, Arun Narasimhan

Mechanical and Aerospace Engineering Theses - Archive

MOSFETS (Metal Oxide Semiconductor Field Effect Transistors) are a popular type of active current carrying device. The need for higher performance and faster switching times has led to designs which use low gate source voltage where heat conduction is dominated by charge carriers. The concentration of charge carriers increases with an increase in temperature, causing more current to flow as the temperature increases. As a result, the device draws more current as temperature increases, causing further temperature rise. As the device temperature increased, it would draw more current and cause further temperature rise. This is a positive feedback loop which …

Cooperative Pursuit Nonlinear Guidance And Control Laws To Surround Intruder Swarms, Rishab Rijal

Mechanical and Aerospace Engineering Theses - Archive

In this thesis, an integrated guidance and control architecture to enable a group of n quadcopters, which are connected to each other by a rope line, to perform cooperative pursuit with the objective to surround a swarm of intruder UAVs (possibly flying in restricted airspaces) is presented. The UAVs in the intruder swarm may maneuver and sometimes get closer to each other, and sometimes further apart, and the pursuing UAVs need to adjust their formation appropriately to achieve the surround objective. A nonlinear controller is developed for the quadcopters so as to effectively execute the guidance laws, thereby ensuring precise …

Design And Development Of Supersonic Free Jet Facility, Gowtham Sai Somaroutu

Mechanical and Aerospace Engineering Theses - Archive

High-speed wind tunnels are essential facilities for conducting research and testing in external and internal flows. This thesis details the design and development of a blow-down supersonic free-jet facility with a 3-inch square nozzle in the Mach number range of and unit Reynolds number ranging. Key aspects of the facility development include the detailed design of the gas supply system, control valve selection, plenum, nozzle, test section, and the selection of an exhaust silencer. CAD designs for all the components of the facility were also generated in this effort.

A new analytical approach was developed to design supersonic contoured nozzles …

Numerical Simulation And Optimization Of Fin Configurations For Enhanced Heat Sink Performance In Aluminum And Copper Materials, Rimpy Singh

Mechanical and Aerospace Engineering Theses - Archive

The constant evolution of data centers and high-power electronic systems has raised critical challenges in heat dissipation and thermal management. Single-phase immersion cooling, where electronic components are submerged in a thermally conductive but non-electrically conductive liquid (dielectric liquid), offers improved heat dissipation capabilities and emerges as a promising alternative to traditional air-cooling methods, which often fail to meet the thermal demands of densely packed, high-power systems. This study investigates and compares the thermal performance of aluminum and copper heat sinks with fin thicknesses of 0.33 mm and 0.54 mm, respectively, using finite element analysis based on computational fluid dynamics (CFD) …

Semiconductor Photonic Crystal Surface Emitting Lasers For High Power, High Brightness And High Speed Applications, Chhabindra Gautam

Electrical Engineering Dissertations - Archive

Photonic Crystal Surface Emitting Laser (PCSEL) is the promising third generation semiconductor laser technology as it addresses the challenges of the conventional semiconductor lasers (EEL/VCSEL) by providing single mode high power output with good beam quality (thus high brightness). The large area in plane coupling resulting from the multiple Bragg’s diffraction conditions in the periodic 2D photonic crystal cavities in the lasing cladding region leads to single mode operation over very large area. By model design engineering, such in plane lasing cavity can leak the light out of the plane, which result in surface emission. The ability to scale the …

Advanced Thermal Management Solutions For High-Powered Chips: A Comprehensive Study On Immersion Cooling And Electrochemical Additive Manufacturing-Based Cold Plates, Gautam Gupta

Mechanical and Aerospace Engineering Dissertations - Archive

This dissertation investigates advanced thermal management strategies for high-performance computing systems to address the escalating thermal challenges posed by increasing power densities and computational demands. Chapter 1 evaluates the efficacy of forced convection Single-Phase Immersion Cooling (SPIC) with a dielectric fluid (EC-110) compared to traditional air cooling for a 776 W server. Computational Fluid Dynamics (CFD) simulations demonstrate significant reductions in chip junction temperatures, maximum Dual In-line Memory Module (DIMM) temperatures, and server pressure drop with immersion cooling, highlighting its superior heat dissipation capabilities.

Chapter 2 delves into the comparative analysis of forced and natural convection Single-Phase Immersion Cooling techniques. …

Reliability Assessment Of 2.5d Heterogenous Integrated Circuits, Cu-Cu Hybrid Bonded Interconnects & Thermo-Mechanical Assessment Of Substrates In Two-Phase Immersion Cooling, Akshay Boovanahally Lakshminarayana

Mechanical and Aerospace Engineering Dissertations - Archive

Moore’s law has predicted the growth of semiconductor industry for the last 50 years by providing a template for silicon scaling and homogenous system on chip integration of multiple circuits. Lately, this trend has been declining due to the increased power density and functionality and increasing chip size to accommodate this. Moving forward, heterogeneous integration of chiplets will improve the silicon yield by integrating multiple multi-functional chiplets that are of smaller area onto an interposer or a substrate in 2.5D, 3D or 3.5 D architectures. In this study, computational analysis is done on the impact of design parameters and material …

Towards The Development Of A Unified Synthesis System Framework: Advancement Of Avds Towards A Generic, Multi-Disciplinary, And Multi-Fidelity Aerospace Vehicle Design Environment, Ian Wesley Maynard

Mechanical and Aerospace Engineering Dissertations - Archive

At the start of any design program for the development of a novel aerospace vehicle, there can be millions of design, mission, and technology trades to be explored. Design software is needed that can modularly adapt itself such that it can be generically applied to a wide variety of aerospace applications. It needs to be automated such that it can ‘stitch’ together and generate synthesis codes using a wide variety of disciplinary methods including geometry, aerodynamics, propulsion, trajectory, weights, stability and control, cost, etc. It should also be able to modularly switch the multi-disciplinary synthesis execution process in the synthesis …

Analysis And Detection Of Cyber Attacks In Multi Vehicle Systems Using Macroscopic Models, Abhishek Kashyap

Mechanical and Aerospace Engineering Dissertations - Archive

The study of potential cyber-attacks in different domains is an active area of research. Given that systems are becoming more and more interconnected, cyber physical systems that operate infrastructure and/or plants can make these assets more vulnerable and open to different attack vectors. The primary focus of this research is the modeling, analysis and detection of cyber-attacks on platoons of autonomous cars and swarms of UAVs. In this work, we consider scenarios wherein an attacker may hack into a subset of vehicles in a multi-vehicle system and make subtle modifications in their parameters. Due to the interconnected nature of the …

Assessment Of Drainage Characteristics Of Recycled Crushed Concrete Aggregate (Rcca) And Plastic Mix Pavement Base, Amena Begum

Civil Engineering Theses - Archive

Recycled Crushed Concrete Aggregate (RCCA) offers a sustainable alternative to natural aggregate in construction, reducing reliance on natural resources and diverting construction and demolition debris from landfills. Similarly, the escalating global plastic waste crisis highlights the need for innovative solutions to address non-biodegradable waste disposal challenges and create opportunities for recycling plastics into value-added applications. This study explores the potential of RCCA mixed with plastic waste, such as HDPE and PP, as a viable substitute for natural aggregates in flexible pavement base layers, with a focus on hydraulic properties and drainage performance to enhance pavement durability.

A comprehensive experimental program …

Flood Frequency Analyses Using Depth-Area Reduction Factors (Darfs) In Texas, Mohamad Ahmadzadeh

Civil Engineering Dissertations - Archive

The increasing frequency and severity of flood events globally necessitate more accurate and reliable hydrologic models to inform flood risk management and mitigation strategies. Traditional hydrologic models have often relied on the simplification of uniformly distributed rainfall across watersheds, a method that fails to account for the spatial variability inherent in real-world storm events. This dissertation addresses this critical gap by applying Depth-Area Reduction Factors (DARFs) in hydrologic modeling, specifically focusing on the Trinity and Neches River Basins in Texas. DARFs are used to adjust point rainfall data to reflect the reduction in rainfall intensity as storm areas increase, thereby …

Degree Of Dispersion/Exfoliation And Surface Functionalization Of 1d And 2d Carbon Nanostructured Materials: Interface Interactions And Effects On Mechanical Properties, Michail Margas

Material Science and Engineering Dissertations - Archive

The development of advanced cementitious nanocomposites relies heavily on understanding the interfacial interactions between carbon-based nanomaterials and the cement matrix, which significantly influence the material’s performance. The goal of this dissertation is to investigate the effect of dispersion/exfoliation and surface functionalization of 1D multiwall carbon nanotubes (MWCNTs), carbon nanofibers (CNFs), and 2D graphene nanoplatelets (GNPs) in aqueous suspensions on the interface interactions of nanoengineered cementitious composites. The first objective of this dissertation is to quantitatively evaluate the degree of nanomaterial dispersion for MWCNT and CNF suspensions, in a converging manner for cement-based materials applications using spectroscopic techniques, such as UV-vis …

An In-Vitro Model For Visualizing Intraocular Lens And Lens Capsule Interaction In Posterior Capsule Opacification, Amjad Chatila

Bioengineering Dissertations - Archive

Posterior Capsule Opacification (PCO) is a common complication post cataract surgery. It is believed that Intraocular Lens (IOL) physical and chemical properties would affect their PCO potential. The tight binding between IOL and posterior lens capsule (PLC) is believed to have a negative impact on PCO formation, as suggested in the “No space, no cell, no PCO” hypothesis. To test the hypothesis, we have recently developed an in vitro 3D system to simulate IOL and PLC physical interaction. To expand the function and capability of this system, one objective of my work was to develop the next generation adhesion force …

Novel Engineering Approaches For Orthopedic Injury Treatment And Infection Diagnosis, Cynthia Co

Bioengineering Dissertations - Archive

Bioengineering has made significant contributions to the treatment of orthopedic injury through interdisciplinary approaches. Central to these advancements are many orthopedic implants, including anchors and joint replacements, which have been designed to restore mobility. Despite their functional efficacy, these products have limited lifespan and are associated with many complications, such as implant-associated infection. The success of implant design and function, both in the short and long term, is paramount for enhancing patient outcomes and overall well-being. Therefore, my thesis work is dedicated to addressing these critical challenges, aiming to maximize their treatment effect while minimizing the implant-associated complications.

Long-term patient …

3d Point Cloud Sensing And Analytics With Applications In Process Mining And Quality Control Of Additive Manufacturing, Zehao Ye

Industrial, Manufacturing, and Systems Engineering Dissertations - Archive

The rapid advancement in Additive Manufacturing (AM) technologies has developed significant innovations in various sectors, including medical, aerospace, and automotive industries. Despite these benefits, the adoption of AM is often hindered by quality inconsistencies related to the surface defects and geometrical inaccuracies in the fabricated products. These defects can significantly undermine the mechanical properties of the products, leading to material waste and potential safety issues. This dissertation addresses the critical challenges in quality control of AM processes through the integration of 3D point cloud data and machine learning techniques, aiming to enhance the reliability and efficiency of AM systems. The …

A Human Factors Approach To Improve Layout Design For A Virtual Reality-Based Training Platform, Md Humaun Kobir, Taufiq Rahman, Yiran Yang, Shuchisnigdha Deb

SAGE Open Access Agreement Publications-Archive

In manufacturing industries, equipment arrangement, and layout design are critical factors that directly influence productivity, workplace safety, and workers’ performance. Link analysis, as a human factors approach, has been widely used in industries for many years to improve layout design and machinery arrangement. This approach considers humans' physical and cognitive capabilities and movement limitations to find an optimal design. Virtual reality significantly impacts our society from product design to worker training. Hence, effective virtual training platforms require the same attention to layout design as manufacturing work settings which offer efficient testing of multiple layouts. This research focuses on developing a …