Digital Commons Network^™

Design And Evaluation Of High Efficiency Power Converters Using Wide-Bandgap Devices For Pv Systems, Fahad Almasoudi

Electronic Theses and Dissertations

The shortage of fossil resources and the need for power generation options that produce little or no environmental pollution drives and motivates the research on renewable energy resources. Power electronics play an important role in maximizing the utilization of energy generation from renewable energy resources. One major renewable energy source is photovoltaics (PV), which comprises half of all recently installed renewable power generation in the world. For a grid-connected system, two power stages are needed to utilize the power generated from the PV source. In the first stage, a DCDC converter is used to extract the maximum power from the …

Nanoengineering Of Next Generation Silicone Rubber Materials For Extreme Applications, Monika Bleszynski

Electronic Theses and Dissertations

Silicone rubber materials are frequently used in extreme environments, including aviation, space, high voltage and other applications. In service, however, complex and difficult to predict damage mechanisms in the rubbers can occur which can lead to severe failures of essential infrastructural components. For example, Non-Ceramic Insulators (NCIs), which support some of the most critical high voltage lines in the world, regularly exhibit severe polymer aging due to environmental pollution, ultra-violet (UV) radiation, and dry band and corona arcing. Designing silicone rubbers to resist aging in these demanding environments is difficult and requires an interdisciplinary approach, including correctly assessing the actual …

Ice Adhesion Analysis Of Severely Aged Pdms Rubbers, Theodore R. Woll

Electronic Theses and Dissertations

The goal of this study was to evaluate and optimize the ice adhesion test initially developed by the University of Denver and to examine Polydimethylsiloxane (PDMS) based silicone rubbers for their ice-phobicity as a function of their physical and chemistry properties, and under severe oxidative aging. The test is based on an ice block bonded to a silicone rubber substrate and subjected to shear. In its original state, the test had severe limitations that caused the ice to be dislodged through a mixture of shear and peeling. Several steps were taken in this research to improve the test, and the …

Improving The Accuracy Of Mobile Touchscreen Qwerty Keyboards, Amanda Kirk

Electronic Theses and Dissertations

In this thesis we explore alternative keyboard layouts in hopes of finding one that increases the accuracy of text input on mobile touchscreen devices. In particular, we investigate if a single swap of 2 keys can significantly improve accuracy on mobile touchscreen QWERTY keyboards. We do so by carefully considering the placement of keys, exploiting a specific vulnerability that occurs within a keyboard layout, namely, that the placement of particular keys next to others may be increasing errors when typing. We simulate the act of typing on a mobile touchscreen QWERTY keyboard, beginning with modeling the typographical errors that can …

Translating Data From The Laboratory Into Simulation: A Computational Framework For Subject-Specific Finite Element Musculoskeletal Simulation, Donald R. Hume

Electronic Theses and Dissertations

Computational modeling is a powerful tool which has been used to inform decisions made by engineers, scientists, and clinicians for decades. Musculoskeletal modeling has emerged as a computational modeling technique used to understand the interaction between the body and its surroundings. There are several common approaches used for musculoskeletal modeling which take advantage of different model formulations to obtain information of interest. Unfortunately, models with different joint formulations inherit disparities in representations of ligament, muscle, and cartilage at joints of interest. These differences affect the way the joint functions and limit the insight it provides through computational analysis. Musculoskeletal models …

A Bi-Encoder Lstm Model For Learning Unstructured Dialogs, Diwanshu Shekhar

Electronic Theses and Dissertations

Creating a data-driven model that is trained on a large dataset of unstructured dialogs is a crucial step in developing a Retrieval-based Chatbot systems. This thesis presents a Long Short Term Memory (LSTM) based Recurrent Neural Network architecture that learns unstructured multi-turn dialogs and provides implementation results on the task of selecting the best response from a collection of given responses. Ubuntu Dialog Corpus Version 2 (UDCv2) was used as the corpus for training. Ryan et al. (2015) explored learning models such as TF-IDF (Term Frequency-Inverse Document Frequency), Recurrent Neural Network (RNN) and a Dual Encoder (DE) based on Long …

Force-Canceling Mixer Algorithm For Vehicles With Fully-Articulated Radially Symmetric Thruster Arrays, Joseph Nicholas Casabona

Electronic Theses and Dissertations

A new type of fully-holonomic aerial vehicle is identified and developed that can optionally utilize automatic cancellation of excessive thruster forces to maintain precise control despite little or no throttle authority. After defining the physical attributes of the new vehicle, a flight control mixer algorithm is defined and presented. This mixer is an input/output abstraction that grants a flight control system (or pilot) full authority of the vehicle's position and orientation by means of an input translation vector and input torque vector. The mixer is shown to be general with respect to the number of thrusters in the system provided …

Developing An Affect-Aware Rear-Projected Robotic Agent, Ali Mollahosseini

Electronic Theses and Dissertations

Social (or Sociable) robots are designed to interact with people in a natural and interpersonal manner. They are becoming an integrated part of our daily lives and have achieved positive outcomes in several applications such as education, health care, quality of life, entertainment, etc. Despite significant progress towards the development of realistic social robotic agents, a number of problems remain to be solved. First, current social robots either lack enough ability to have deep social interaction with human, or they are very expensive to build and maintain. Second, current social robots have yet to reach the full emotional and social …

Optimal Planning Of Microgrid-Integrated Battery Energy Storage, Ibrahim S. Alsaidan

Electronic Theses and Dissertations

Battery energy storage (BES) is a core component in reliable, resilient, and cost-effective operation of microgrids. When appropriately sized, BES can provide the microgrid with both economic and technical benefits. Besides the BES size, it is found that there are mainly three planning parameters that impact the BES performance, including the BES integration configuration, technology, and depth of discharge.

In this dissertation, the impact of each one of these parameters on the microgrid-integrated BES planning problem is investigated. Three microgrid-integrated BES planning models are developed to individually find the optimal values for the aforementioned parameters. These three microgrid-integrated BES planning …

Study Of Optical Ofdm System For Wireless Lan Applications, Salih Mohamed S. Kenshil

Electronic Theses and Dissertations

The advantages of optical fiber make it possible to extend the data rate transmission and propagation distance. Orthogonal frequency division multiplexing (OFDM) as a multicarrier technique (MC) is used in hybrid optical-wireless system designs because it has the best spectral efficiency to radio frequency (RF) interference and lower multipath distortion. In this dissertation, a study and evaluation of optical OFDM based wireless local area network (W-LAN) systems are presented. The baseband of the OFDM signal is fully transmitted and up-converted to a radio frequency signal. Also, to reduce system costs, simple base stations (BSs) are interconnected to a central office …

Robust Distributed Stabilization Of Interconnected Multiagent Systems, Vahid Rezaei

Electronic Theses and Dissertations

Many large-scale systems can be modeled as groups of individual dynamics, e.g., multi-vehicle systems, as well as interconnected multiagent systems, power systems and biological networks as a few examples. Due to the high-dimension and complexity in configuration of these infrastructures, only a few internal variables of each agent might be measurable and the exact knowledge of the model might be unavailable for the control design purpose. The collective objectives may range from consensus to decoupling, stabilization, reference tracking, and global performance guarantees. Depending on the objectives, the designer may choose agent-level low-dimension or multiagent system-level high-dimension approaches to develop distributed …

Studying Facial Expression Recognition And Imitation Ability Of Children With Autism Spectrum Disorder In Interaction With A Social Robot, Farzaneh Askari

Electronic Theses and Dissertations

Children with Autism Spectrum Disorder (ASD) experience limited abilities in recognizing non-verbal elements of social interactions such as facial expressions [1]. They also show deficiencies in imitating facial expressions in social situations. In this Master thesis, we focus on studying the ability of children with ASD in recognizing facial expressions and imitating the expressions using a rear-projected expressive humanoid robot, called Ryan. Recent studies show that social robots such as Ryan have great potential for autism therapy. We designed and developed three studies, first to evaluate the ability of children with ASD in recognizing facial expressions that are presented to …

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. …

Optimal Operation Of Integrated Microgrids, Abdullah Albaker

Electronic Theses and Dissertations

Microgrids' deployments are increasing and projected to increase even more in future due to the significant advantages that are provided by this technology for end-use customers. However, microgrids can be connected to each other to create integrated microgrids system, which can further promote the anticipated and desired benefits. An integrated operation of microgrids can potentially improve the local power system reliability and resilience, increase the individual microgrids' economic benefits, and promote further utilization of renewable energy resources. Integrating microgrids, to achieve a microgrid network or cluster, is expected be an essential application towards smarter power grids and a key operational …

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 …

Motivations, Team Dynamics, Development Practices And How They Impact The Success Of Open Source Software: A Study Of Projects Of Code For America Brigades, Le Chang

Electronic Theses and Dissertations

Open data movement has nurtured the growth of civic open source software (OSS) in the recent decade. This emerging phenomenon has demonstrated a way that a community can collectively utilize technology to solve its problems.

This study is based on software projects in brigades of Code for America, which is a network of organizations that group volunteers to create digital solutions to community problems. In this study, we analyze the software engineering practices of current civic open source software development, participants' motivations and perceptions of the projects, and provide insights on the antecedents of success of the application development.

A …

Algorithmic Music Generation For Pedagogy Of Sight Reading, Ryan Stephen Davis

Electronic Theses and Dissertations

Autodeus is the name of the program that has been developed and was designed to aid guitar students in the attainment and betterment of musical notation sight reading skills. Its primary goal is to provide a very flexible tool that has the ability to generate virtually endless types of sight reading exercises at many various skill levels.

A complimentary 2 year-long comprehensive guitar sight-reading course syllabus can be implemented via Autodeus as it is capable of generating all the necessary exercises. It is able to generate these exercises quickly and efficiently through the use of a back tracking algorithm that …

Patient-Specific Quantification Of The Relationship Between The Left Atrium Pressure And The Ostial Diameter Of The Left Atrial Appendage, Sky Tianqi Gao

Electronic Theses and Dissertations

The left atrial appendage has been a historically understudied region of the heart until fairly recently with the new understanding of its role in the stroke pathway of patients with atrial fibrillation. The goal of this study is to take a look at the biomechanical behavior of the left atrium and left atrial appendage under normal physiological loading conditions using material properties taken from biaxial stretch tests. Several different options for material properties models were tested and biaxial stretch test data of cadaveric human tissue samples for the left atrium and appendage were fit to a Fung-type strain-energy function for …

Computational Modeling Of Transcatheter Aortic Valves, Mostafa Abbasi

Electronic Theses and Dissertations

Transcatheter aortic valve replacement (TAVR) is an established therapy alternative to surgical valve replacement in high-risk and intermediate-risk patients with severe aortic stenosis. Currently, although TAVR is an alternative and less-invasive treatment for high-risk and intermediate-risk patients, surgical aortic valves replacement (SAVR) was still considered as the gold standard for low-risk patients. TAVR could potentially be applied to lower-risk younger patients if the indications can be safely expanded to the patients and transcatheter aortic valve (TAV) long-term durability can match with that of surgical bioprostheses. In contrast to surgical aortic valves (SAVs), there have been limited clinical data on the …

Development Of A Locomotion And Balancing Strategy For Humanoid Robots, Emile Bahdi

Electronic Theses and Dissertations

The locomotion ability and high mobility are the most distinguished features of humanoid robots. Due to the non-linear dynamics of walking, developing and controlling the locomotion of humanoid robots is a challenging task. In this thesis, we study and develop a walking engine for the humanoid robot, NAO, which is the official robotic platform used in the RoboCup Spl. Aldebaran Robotics, the manufacturing company of NAO provides a walking module that has disadvantages, such as being a black box that does not provide control of the gait as well as the robot walk with a bent knee. The latter disadvantage, …

Predictive Modeling Of Hip Dislocation: Assessment Of Surgical And Patient Factors To Reduce The Occurrence Of Hip Instability And Adverse Clinical Outcomes, Daniel N. Huff

Electronic Theses and Dissertations

Instability and dislocation remain leading indications for revision of primary Total Hip Arthroplasty (THA). Many studies have addressed the links between implant design and propensity for dislocation, however a comprehensive review of the ability of modern THA constructs to protect against joint instability is needed.

Accordingly, the objective of this study is to provide objective data about THA risks to be considered in the treatment algorithm to protect against adverse joint loading conditions and joint instability. Adverse loading conditions were assessed in a population of activities of daily living using data from telemetric hip implant representation in an FE simulation …

Cementless Tibial Base Micromotion During Activities Of Daily Living, Hayden Wilson

Electronic Theses and Dissertations

Initial stability of cementless total knee replacement (TKR) components is directly related to long-term fixation and success, as excess motion hinders bony ingrowth. To assess implant stability, there is a need for more physiologically accurate loading conditions, incorporating forces and displacements in all 6 degrees-of-freedom found in the knee joint, as well as understanding the impact of femoral flexion on conformity of tibiofemoral articulation. Understanding how different activities of daily living generate tibial micromotion yields insight into surgical technique considerations, and rehabilitation strategies post-operatively. ASTM F3141-15, which specifies knee flexion, Internal-External moment, Medial-Lateral, Anterior-Posterior and Superior-Inferior forces during gait and …

Rnn-Based Generation Of Polyphonic Music And Jazz Improvisation, Andrew Hannum

Electronic Theses and Dissertations

This paper presents techniques developed for algorithmic composition of both polyphonic music, and of simulated jazz improvisation, using multiple novel data sources and the character-based recurrent neural network architecture char-rnn. In addition, techniques and tooling are presented aimed at using the results of the algorithmic composition to create exercises for musical pedagogy.

Design Of Power Switched-Capacitor Converters And Their Performance Analysis In A Soft-Charging Operation, Ayoob Alateeq

Electronic Theses and Dissertations

Switched-capacitor (SC) converters have gained more interest due to their high power density and appropriateness for small circuit integration. Building a SC DC-to-DC converter with only capacitors and switches is the main reason to seek a higher power density achievement. However, the SC converters suffer dominant losses related to their capacitors and switches. These losses can be determined and optimized by calculating the converter's output impedance in its two asymptotic limits.

We proposed a high voltage gain and a very low output impedance power switched-capacitor converter (PSC) with a lower number of components compared to other step-up switched-capacitor topologies. The …