Engineering Commons^™

Effects Of Geometry And Phase On Material Damage Response Under High-Speed Impact, Rachel Waxman

Theses and Dissertations

Peridynamics, presented by Silling in 2000 [1], is a reformulation of the elastic theory from differential equations to integral equations, which are more equipped to handle discontinuities, such as crack initiation and propagation. Because of this, peridynamics is an effective tool to address many of the problems relevant to the aerospace and defense industries. For example, airborne sand particles and raindrops cause local damage to aircraft in flight. This damage manifests itself as radial and subsurface lateral cracking, as well as increased surface roughness. All of these damage morphologies may result in undesired degradation of mechanical and optical properties.

This …

Multi-Column Neural Networks And Sparse Coding Novel Techniques In Machine Learning, Ammar O. Hoori

Theses and Dissertations

Accurate and fast machine learning (ML) algorithms are highly vital in artificial intelligence (AI) applications. In complex dataset problems, traditional ML methods such as radial basis function neural network (RBFN), sparse coding (SC) using dictionary learning, and particle swarm optimization (PSO) provide trivial results, large structure, slow training, and/or slow testing. This dissertation introduces four novel ML techniques: the multi-column RBFN network (MCRN), the projected dictionary learning algorithm (PDL) and the multi-column adaptive and non-adaptive particle swarm optimization techniques (MC-APSO and MC-PSO). These novel techniques provide efficient alternatives for traditional ML techniques. Compared to traditional ML techniques, the novel ML …

Designing Biomimetic Implant Surfaces To Promote Osseointegration Under Osteoporotic Conditions By Revitalizing Mechanisms Coupling Bone Resorption To Formation, Ethan M. Lotz

Theses and Dissertations

In cases of compromised bone remodeling like osteoporosis, insufficient osseointegration occurs and results in implant failure. Implant retention relies on proper secondary fixation, which is developed during bone remodeling. This process is disrupted in metastatic bone diseases like osteoporosis. Osteoporosis is characterized low bone mass and bone strength resulting from either accelerated osteoclast-mediated bone resorption or impaired osteoblast-mediated bone formation. These two processes are not independent phenomena. In fact, osteoporosis can be viewed as a breakdown of the cellular communication connecting bone resorption to bone formation. Because bone remodeling occurs at temporally generated specific anatomical sites and at different times, …

Antennas And Wave Propagation In Wireless Body Area Networks: Design And Evaluation Techniques, Ala Alemaryeen

Theses and Dissertations

Recently, fabrication of miniature electronic devices that can be used for wireless connectivity becomes of great interest in many applications. This has resulted in many small and compact wireless devices that are either implantable or wearable. As these devices are small, the space for the antenna is limited. An antenna is the part of the wireless device that receives and transmits a wireless signal. Implantable and wearable antennas are very susceptible to harmful performance degradation caused by the human body and very difficult to integrate, if not designed properly. A designer need to minimize unwanted radiation absorption by the human …

Straintronic Nanomagnetic Devices For Non-Boolean Computing, Md Ahsanul Abeed

Theses and Dissertations

Nanomagnetic devices have been projected as an alternative to transistor-based switching devices due to their non-volatility and potentially superior energy-efficiency. The energy efficiency is enhanced by the use of straintronics which involves the application of a voltage to a piezoelectric layer to generate a strain which is ultimately transferred to an elastically coupled magnetostrictive nanomaget, causing magnetization rotation. The low energy dissipation and non-volatility characteristics make straintronic nanomagnets very attractive for both Boolean and non-Boolean computing applications. There was relatively little research on straintronic switching in devices built with real nanomagnets that invariably have defects and imperfections, or their adaptation …

Cell Type And Substrate Dependence Of Fibronectin Properties And Mechanotransduction, Navpreet S. Saini

Theses and Dissertations

Fibronectin is an important protein that is able to bind to other fibronectin molecules and to cell surface receptors. In doing so, the interactions fibronectin can perform is important for the processes of cell migration and tissue formation. Understanding the properties of fibronectin and fibril assembly is useful for areas such as wound healing, where fibronectin molecules are assembled to protect the tissue and to perform other tasks. Because of these reasons, it is important to understand how fibronectin is assembled and how its properties affect the fibril assembly, which in return affects the way the cell matrix operates. Previously …

Design And Testing Of An Agonist-Antagonist Position-Impedance Controlled Myoelectric Prosthesis, Christopher Aymonin

Theses and Dissertations

Intuitive prosthetic control is limited by the inability to easily convey intention and perceive physical requirements of the task. Rather than providing haptic feedback and allowing users to consciously control every component of manipulation, relegating some aspects of control to the device may simplify operation. This study focuses on the development and testing of a control scheme able to identify object stiffness and regulate impedance. The system includes an algorithm to detect the apparent stiffness of an object, a proportional nonlinear EMG control algorithm for interpreting a user’s desired grasp aperture, and an antagonistically acting impedance controller. Performance of a …

Electric Load Forecasting Using Long Short-Term Memory Algorithm, Tianshu Yang

Theses and Dissertations

Abstract

Power system load forecasting refers to the study or uses a mathematical method to process

past and future loads systematically, taking into account important system operating

characteristics, capacity expansion decisions, natural conditions, and social impacts, to

meet specific accuracy requirements. Dependence of this, determine the load value at a

specific moment in the future. Improving the level of load forecasting technology is

conducive to the planned power management, which is conducive to rationally arranging

the grid operation mode and unit maintenance plan, and is conducive to formulating

reasonable power supply construction plans and facilitating power improvement, and

improve the …

Resonant Acoustic Wave Assisted Spin-Transfer-Torque Switching Of Nanomagnets, Austin R. Roe

Theses and Dissertations

We studied the possibility of achieving an order of magnitude reduction in the energy dissipation needed to write bits in perpendicular magnetic tunnel junctions (p-MTJs) by simulating the magnetization dynamics under a combination of resonant surface acoustic waves (r-SAW) and spin-transfer-torque (STT). The magnetization dynamics were simulated using the Landau-Lifshitz-Gilbert equation under macrospin assumption with the inclusion of thermal noise. We studied such r-SAW assisted STT switching of nanomagnets for both in-plane elliptical and circular perpendicular magnetic anisotropy (PMA) nanomagnets and show that while thermal noise affects switching probability in in-plane nanomagnets, the PMA nanomagnets are relatively robust to the …

Optically Transparent Antennas And Filters For Smart City Communication, Ryan B. Green

Theses and Dissertations

Incremental usage of mobile devices demand a new generation of wireless networks (5G) to provide faster data rates, more reliable coverage, monitor city infrastructure usage, and increase network capacity. The frequencies proposed for the upcoming 5G network would result in shorter broadcast distances and network dead zones, countered by incorporating transparent antennas into glass high rises. Transparent antennas possess, however a major challenge: low gain. This lower gain can be countered by means of employing antennas in an antenna array, boosting the gain and even giving the array the ability to beam form for the upcoming 5G network. The 5G …

Let’S Face It: The Effect Of Orthognathic Surgery On Facial Recognition Algorithm Analysis, Carolyn Bradford Dragon

Theses and Dissertations

Aim: To evaluate the ability of a publicly available facial recognition application program interface (API) to calculate similarity scores for pre- and post-surgical photographs of patients undergoing orthognathic surgeries. Our primary objective was to identify which surgical procedure(s) had the greatest effect(s) on similarity score.

Methods: Standard treatment progress photographs for 25 retrospectively identified, orthodontic-orthognathic patients were analyzed using the API to calculate similarity scores between the pre- and post-surgical photographs. Photographs from two pre-surgical timepoints were compared as controls. Both relaxed and smiling photographs were included in the study to assess for the added impact of facial pose on …

The Application Of Index Based, Region Segmentation, And Deep Learning Approaches To Sensor Fusion For Vegetation Detection, David L. Stone

Theses and Dissertations

This thesis investigates the application of index based, region segmentation, and deep learning methods to the sensor fusion of omnidirectional (O-D) Infrared (IR) sensors, Kinnect sensors, and O-D vision sensors to increase the level of intelligent perception for unmanned robotic platforms. The goals of this work is first to provide a more robust calibration approach and improve the calibration of low resolution and noisy IR O-D cameras. Then our goal was to explore the best approach to sensor fusion for vegetation detection. We looked at index based, region segmentation, and deep learning methods and compared them with a goal of …

Metallic Systems At The Nano And Micro Scale: Bimetallic Nanoparticles As Catalysts And Mcraly Bond Coats In Thermal Barrier Coatings, Kenneth Kane

Theses and Dissertations

The dissertation is split into two parts. The first part will be focused on changes in material properties found at the nanoscale, as miscibility and electronic structure can change significantly with size. The formation of classically-immiscible bimetallic nanoparticles (BNPs) becomes favorable at the nanoscale and novel catalytic properties can emerge from the bimetallic alloying. The formation of alloyed and non-alloyed BNPs is achieved through pulse laser ablation (PLA) and a significant increase in catalytic activity is observed for both. Recently discovered, the increased activity in the non-alloyed BNPs, deemed multicomponent photocatalysis, is examined and the proposed mechanism discussed. The second …

Compositional Analysis Of Cerium And Cesium In Rapid Setting Cement As An Immobilization Agent For Nuclear Waste, Riyadh M. Motny

Theses and Dissertations

A feasibility of rapid setting cement (RSC) as an agent of immobilization for certain elements such as fission products or radioactive materials was explored. Cerium (Ce) and cesium (Cs) have been selected as a surrogate for U and/or Pu and fission products, respectively, in this study in three phases. In Phase I, RSC was evaluated for physical properties (e.g., porosity, density, pH values, etc.) using two groups methods—the cement powder at different concentrations of Ce (2 – 10 wt%) with deionized water (DIW) and artificial seawater (ASW). The results showed that the final setting time and compressive strength of RSC …

The Role Of Kras In Mechanosensing In Non-Small Cell Lung Cancer, Krista M. Powell

Theses and Dissertations

Lung cancer is the number one cause of cancer related death worldwide, with more than 1.6 million fatalities each year. Non-small cell lung cancer (NSCLC) accounts for 80-85% of all lung cancers, with KRAS being one of the most prevalent oncogenic driver mutations. Therapeutic approaches for KRAS-mutated NSCLC have been extensively explored due to the US National Cancer Institute RAS Initiative, but methods of directly targeting KRAS or downstream effectors, such as MEK, still have poor results. Previous reports have shown that KRAS-mutated NSCLC activate distinct receptor tyrosine kinases (RTKs) depending on the epithelial or mesenchymal state. Epithelial-to-mesenchymal transition (EMT) …

Computational And Experimental Investigation On The Wetting Behavior Of Droplet-Fiber Systems, Hossain Aziz

Theses and Dissertations

Interaction of a liquid droplet and a fiber or layer of fibers is ubiquitous in nature and in a variety of industrial applications. It plays a crucial role in fog harvesting, coalescence filtration, membrane desalination, self-cleaning and fiber based microfluidics, among many others. This work presents a quantitative investigation on the interactions of a droplet with a fiber or layers of fibers. More precisely, the present work is focused on 1) predicting the effects of fiber’s size and material on its ability to withhold a droplet against external forces and on the liquid residue left on the fiber after the …

Au@Tio2 Nanocomposites Synthesized By X-Ray Radiolysis As Potential Radiosensitizers, Maria C. Molina Higgins

Theses and Dissertations

Radiosensitization is a novel targeted therapy strategy where chemical compounds are being explored to enhance the sensitivity of the tissue to the effects of ionizing radiation. Among the different radiosensitizers alternatives, nanomaterials have shown promising results by enhancing tumor injury through the production of free radicals and reactive oxygen species (ROS). In this work, Gold-supported titania (Au@TiO₂) nanocomposites were synthesized through an innovative strategy using X-ray irradiation, and their potential as radiosensitizers was investigated. Radiosensitization of Au@TiO₂ nanocomposites was assessed by monitoring the decomposition of Methylene Blue (MB) under X-ray irradiation in the presence of the nanomaterial. …

Group Decision-Making, Edward Cook

Theses and Dissertations

The present work explores improvements in group decision-making. It begins with a practical example using state-of-the-art techniques for a complex, high-risk decision. We show how these techniques can reveal a better alternative. Although we created an improved decision process, decision-makers were apt to protect their own organizations instead of the project. This tendency was reduced over the course of the decision-making process but inspired the first conceptual component of this work.

The first concept describes the “Cost of Conflict” that can arise in a group decision, using game theory to represent the non-cooperative approach and comparing the outcome to the …

Modeling Cascading Failures In Power Systems In The Presence Of Uncertain Wind Generation, Mir Hadi Athari

Theses and Dissertations

One of the biggest threats to the power systems as critical infrastructures is large-scale blackouts resulting from cascading failures (CF) in the grid. The ongoing shift in energy portfolio due to ever-increasing penetration of renewable energy sources (RES) may drive the electric grid closer to its operational limits and introduce a large amount of uncertainty coming from their stochastic nature. One worrisome change is the increase in CFs.

The CF simulation models in the literature do not allow consideration of RES penetration in studying the grid vulnerability. In this dissertation, we have developed tools and models to evaluate the impact …

Multiphase Droplet Interactions With A Single Fiber, Noor M. Farhan

Theses and Dissertations

Abstract

Multiphase Droplet Interactions with a Single Fiber

By: Noor M. Farhan

A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University.

Virginia Commonwealth University, 2019

Director: Hooman V. Tafreshi,

Professor, Department of Mechanical and Nuclear Engineering

Formulating the physics of droplet adhesion to a fiber is interesting intellectually and important industrially. A typical example of a droplet–fiber system in nature is the dew droplets on spider webs, where droplets first precipitate and grow on the fibers, but they eventually fall when they become too heavy. Obviously, quantifying the force …

A Computational Assessment Of Lisfranc Injuries And Their Surgical Repairs, Michael Perez

Theses and Dissertations

While Lisfranc injuries in the mid foot are less common than other ankle and mid foot injuries, they pose challenges in both properly identifying them and treating them. When Lisfranc injuries are ligamentous and do not include obvious fractures, they are very challenging for clinicians to identify unless weight bearing radiographs are used. The result is that 20%-40% of Lisfranc injuries are missed in the initial evaluation. Even when injuries are correctly identified the outcomes of surgical procedures remain poor. Existing literature has compared the different surgical procedures but has not had a standard approach or procedures across studies. This …

Load Scheduling With Maximum Demand And Time Of Use Pricing For Microgrids, Hayder O. Alwan

Theses and Dissertations

Several demand side management (DSM) techniques and algorithms have been used in the literature. These algorithms show that by adopting DSM and Time-of-Use (TOU) price tariffs; electricity cost significantly decreases, and optimal load scheduling is achieved. However, the purpose of the DSM is to not only lower the electricity cost, but also to avoid the peak load even if the electricity prices low. To address this concern, this dissertation starts with a brief literature review on the existing DSM algorithms and schemes. These algorithms can be suitable for Direct Load Control (DLC) schemes, Demand Response (DR), and load scheduling strategies. …

The Role Of The Mechanical Environment On Cd117+ Endothelial Cell Angiogenesis, Patrick Link

Theses and Dissertations

Angiogenesis is a complex process coordinating cell migration, proliferation, and lumen formation. Changes to the microenvironment regulate angiogenesis through mechanotransduction and cytokine signals. In pulmonary hypertension, something in the process becomes abnormal, resulting in changes to the microenvironment and the formation of a glomerulus of dysfunctional capillaries, called a plexiform lesion. Endothelial cells, expressing CD117 (CD117+ EC clones) increase in the plexiform lesions of pulmonary hypertension, independent of pro-angiogenic VEGF signaling. We hypothesize that the mechanical environment and the macromolecular composition of the extracellular matrix, both, contribute to the aberrant angiogenesis. When we changed the mechanical environment, we changed the …

Engineering The Alveolar Gas Exchange Barrier With Extracellular Matrix Coatings For Bioengineered Lungs, Bethany M. Young

Theses and Dissertations

Lower respiratory diseases are currently the third leading cause of death worldwide. For many end-stage patients with these diseases, there is no cure and a shortage of donor organs available for transplant. A promising solution is to design regenerative scaffolds or complete bioengineered lungs, using decellularized lung tissues as a template for regeneration. Recent advances in the field have made significant strides towards developing a transplantable lung. However, the current technology has not produced a functional lung for in vivo transplant due to immature gas exchange barriers. The mechanisms driving alveolar barrier maturation and role that extracellular matrix (ECM) plays …

Eralpha Isoforms Modulate The Tumorigenicity Of 24r,25(Oh)2d3 In Estrogen-Responsive Cancer, Anjali Verma

Theses and Dissertations

Over 200,000 cases of breast cancer are diagnosed every year. Nearly 20% of these patients supplement their diets with some form of vitamin D. This high frequency of vitamin D supplement use may be due in part to research suggesting that cancer patients with higher serum vitamin D₃ levels have better prognoses than patients with low serum vitamin D_3. However, double-blind clinical trials on the efficacy of vitamin D₃ supplementation in breast cancer have been inconclusive. A recent meta-analysis showed evidence of reduced cancer recurrence in patients taking vitamin D₃ supplements who had ‘estrogen receptor positive’ …

Sensor Placement For Damage Localization In Sensor Networks, Fereshteh Firouzi

Theses and Dissertations

The objective of this thesis is to formulate and solve the sensor placement problem for damage localization in a sensor network. A Bayesian estimation problem is formulated with the time-of-flight (ToF) measurements. In this model, ToF of lamb waves, which are generated and received by piezoelectric sensors, is the total time for each wave to be transmitted, reflected by the target, and received by the sensor. The ToF of the scattered lamb wave has characteristic information about the target location. By using the measurement model and prior information, the target location is estimated in a centralized sensor network with a …

Mechanochemical Regulation Of Epithelial Tissue Remodeling: A Multiscale Computational Model Of The Epithelial-Mesenchymal Transition Program, Lewis Scott

Theses and Dissertations

Epithelial-mesenchymal transition (EMT) regulates the cellular processes of migration, growth, and proliferation - as well as the collective cellular process of tissue remodeling - in response to mechanical and chemical stimuli in the cellular microenvironment. Cells of the epithelium form cell-cell junctions with adjacent cells to function as a barrier between the body and its environment. By distributing localized stress throughout the tissue, this mechanical coupling between cells maintains tensional homeostasis in epithelial tissue structures and provides positional information for regulating cellular processes. Whereas in vitro and in vivo models fail to capture the complex interconnectedness of EMT-associated signaling networks, …

Energy Efficient Spintronic Device For Neuromorphic Computation, Md Ali Azam

Theses and Dissertations

Future computing will require significant development in new computing device paradigms. This is motivated by CMOS devices reaching their technological limits, the need for non-Von Neumann architectures as well as the energy constraints of wearable technologies and embedded processors. The first device proposal, an energy-efficient voltage-controlled domain wall device for implementing an artificial neuron and synapse is analyzed using micromagnetic modeling. By controlling the domain wall motion utilizing spin transfer or spin orbit torques in association with voltage generated strain control of perpendicular magnetic anisotropy in the presence of Dzyaloshinskii-Moriya interaction (DMI), different positions of the domain wall are realized …

Modeling The Peak Absorption Of Meh-Ppv In Various Solvents Using Density Functional Theory, Corell H. Moore

Theses and Dissertations

Density Functional Theory (DFT) and time-dependent Density Functional Theory (TD-DFT) are powerful tools for modeling orbital energy in conjugated molecules and have been useful tools for research in organic photovoltaics. In this work, DFT is first used to explain the red shift in the absorption spectrum and increased absorption observed in MEH-PPV. Initially, the modeling of the red-shift in the absorption peak of MEH-PPV is studied using Gaussian 03 software with the global hybrid functional B3LYP for exchange-correlation and the 6-31G basis set. DFT and TD-DFT are used to separately study the effects of polymer chain length, carbon-carbon double-bond stretching, …

Differential Mobility Classifiers In The Non-Ideal Assembly, Thamir Alsharifi

Theses and Dissertations

The differential mobility classifier (DMC) is one of the core components in electrical mobility particle sizers for sizing sub-micrometer particles. Designing the DMC requires knowledge of the geometrical and constructional imperfection (or tolerance). Studying the effects of geometrical imperfection on the performance of the DMC is necessary to provide manufacturing tolerance and it helps to predict the performance of geometrically imperfect classifiers, as well as providing a calibration curve for the DMC. This thesis was accomplished via studying the cylindrical classifier and the parallel plate classifier. The numerical model was built using the most recent versions of COMSOL Multiphysics^{® …}