Engineering Commons^™

Development And Characterization Of Perovskite Solar Cells For Tandem Device Configuration, Angel Moiseis De La Rosa

Open Access Theses & Dissertations

Photovoltaic devices based on perovskite materials are constantly progressing towards more applicability in large-area panels. In order for perovskite-based photovoltaics to reach reliable and stable commercialization, common issues with the use of perovskite still need to be resolved, including the need to identify fabrication processes that can yield optimal material parameters for better photovoltaic performance. Defining an optimal fabrication process requires that researchers and manufacturers alike come to an agreement regarding perovskite characteristics that result from device operation and material processing. This work focuses on characterizing physical, electrical, and electronic properties of a FAxCs1-xPb(IyBr1-y)3 perovskite, and how some of these …

Tram System Automation For Environmental Spectroscopy And Vegetation Monitoring, Enrique Anguiano Chavez

Open Access Theses & Dissertations

Spectroscopy is the science of studying the interactions of matter and electromagnetic radiation (EMR). In particular, field spectroscopy takes place in a natural environment with a natural source of EMR. The paper presents progress towards the development and automation of a tram cart system. The new system in development collects high resolution, hyperspectral images and data from a spectrometer. Alternatives for a sensor cover mechanism to provide cover for the sensors mounted while the system is not operating are discussed, analyzing and comparing the benefits and disadvantages. An implementation for a charging station in an environment isolated from the electric …

Development Of The Payload System And Obc Microcontroller Coding For A Cubic Satellite Performing An Additive Self-Repair Experiment In Space, Eduardo Macias-Zugasti

Open Access Theses & Dissertations

Additive manufacturing, which is also known as three-dimensional printing, in space is one of the most promising technologies advancing current capabilities for in-orbit space manufacturing and assembly. Additive manufacturing contributes to the reduction of cost per kilogram and number of launches, thus facilitating extraterrestrial colonization and deep-space exploration. The state of the art includes advancing efforts inside the International Space Station (ISS). However, the ISS is a controlled environment and, to the best of our knowledge, no spacecraft or satellite has performed additive manufacturing tasks in the extreme environment of outer space. In this work a 1U CubeSat named Orbital …

Testing The Reliability And Flexibility Of Digitizers Adapting The Rf/If Signals Over Ip Applications Using A Testbed Platform, Jose Carlos Sandoval

Open Access Theses & Dissertations

As physical constraints can be challenging for Radio Frequency (RF) telemetry, a new solution has been exploited to support the demand for RF transmissions. As frequency spectrum gets crowded with more technologies, a solution to a reliable transmission is needed. Digitizers can mitigate many of the physical constraints in order to achieve a successful RF transmission. The method includes the conversion of the RF signals to be sent over IP networks, transmit and de-convert the signal. IP networks will mitigate many disadvantages over a regular signal transmission. The authority in charge to allocate frequency bands is the Federal Communications Commission …

Mathematical Modeling, Optimal Control And Stability Analysis For Dynamic Supply Chains, Yasser Alberto Davizon

Open Access Theses & Dissertations

Dynamic supply chains (SC) are important to reduce inventory, to enable the flow of materials, and maximize profits. By this, dynamic SC require proper decision-making with effective performance and synchronization. In operations and production planning processes, decision-makers develop convenient and suitable decisions, to validate their hypoThesis about which decisions incorporate more profit while reducing costs on enterprise operations. Based on this, inventory management plays a crucial point in the supply chain analysis. In general, SC processes raw material, cash, and information flows, taking into account the demand profile of the system. This research work presents the mathematical modeling, optimal control, …

Development Of A Mems Fabrication Process On Soi To Study High Strain In Transition-Metal Dichalcogenides, Edgar Acosta

Open Access Theses & Dissertations

Over the recent years there has been an increasing demand of better performing electronics. However, as the semiconductor industry keeps on improving and scaling the technology to the nanometer regime, the passive power density has overcome the overall power consumption of transistors. The inability to reduce the power alongside the scaling of transistors has led the scientific community in the search for alternatives or different solutions to overcome this power crisis. The use of two-dimensional Transition-Metal Dichalcogenides (TMDCS) and Micro-Electro-Mechanical System (MEMS) actuators, in conjunction, has been proposed as an alternative solution [1]. Recent studies of TMDCS have shown a …

Energy Management And Control Of Smart Power Distribution Systems, Eric Galvan

Open Access Theses & Dissertations

With the development of distributed energy resources (DERs) and advancements in technology, microgrids (MGs) appear primed to become an even more integral part of the future distribution grid. In this transition to the smart power grid of the future, MGs must be properly managed and controlled to allow efficient integration of DERs. Over the past years, there has been rapid adoption of roof-top solar photovoltaic (PV) and battery electric vehicles (BEVs). Although roof-top solar PV and BEVs can provide environmental benefits (e.g., reduction of emissions), they also create various challenges for power system operators. For example, roof-top solar PV generation …

Artificial Intelligence In The Assessment Of Transmission And Distribution Systems Under Natural Disasters Using Machine Learning And Deep Learning Techniques In A Knowledge Discovery Framework, Rossana Villegas

Open Access Theses & Dissertations

Warming trends and increasing temperatures have been observed and reported by federal agencies, such as the National Oceanic and Atmospheric Administration (NOAA). Extreme-weather events, especially hurricanes, tornadoes and winter storms, are among the highly devastating natural disasters responsible for massive and prolonged power outages in Electrical Transmission and Distribution Systems (ETDS). Moreover, the failure rate probability of any system component under extreme-weather tends to increase in the impacted geographic area. This Dissertation proposes an Artificial Intelligence (AI) Decision Support System that can predict damage in the ETDS and allow operators to mitigate disastrous extreme weather events. The document reports the …

Characterization And Quality Assessment Of Smart Polymer Systems Fabricated By Using 3d Printing Technique, Carlos Alejandro Garcia Rosales

Open Access Theses & Dissertations

Shape memory polymers (SMPs) are classified as smart materials due to their inherent stimulus-induced response. SMP is capable of recovering its original shape from a high degree of deformation by applying an external stimulus such as thermal energy. Other stimuli are electricity, light, chemical, and magnetic field. Shape memory polymers (SMPs) and its fabrication process has recently attracted much attention as a result of their potential application as soft active materials. Demonstration of SMP systems fabricated via 3D printing technologies has been one of the most popular attempts. This Dissertation presents an integration of two commercial SMP materials (DiAPLEX and …

Microstructure Evolution Of Chalcogenide Materials Via Molecular Dynamics, Sharmin Abdullah

Open Access Theses & Dissertations

The properties of a material are defined by its granular microstructure which is determined by its grain evolution and the types of grain boundaries present in the structure. For example, the performance of Cadmium Sulfide/Cadmium Telluride (CdS/CdTe) solar cells can be affected by the presence of grain boundaries which makes the study of grain structure evolution a very important part of solar cell performance optimization. Grain boundary mobilities are important properties in material science and engineering as they determine grain structures under given processing and operating conditions.

In this thesis, several computational tools were used to analyze the formation and …

Material Characterizations Of Organic-Inorganic Halide Perovskites Using Various Deposition Techniques For Planar Perovskite Solar Cell, Shaimum Shahriar

Open Access Theses & Dissertations

Organic-inorganic halide perovskites have rapidly become emerging materials for photovoltaic applications. Strong characterization methods are needed to fully comprehend the chemistry and composition of perovskite solar cells. Understanding the interaction between layers inside a cell and how they react with the environment is important to achieve optimum manufacturing processes, and improve the efficiency of perovskite solar cells. The present work demonstrates the material characterizations of organic-inorganic halide perovskites using (i) one-step deposition, (ii) two-steps deposition, (iii) solvent-to-solvent extraction, and (iv) mixed-cation solution processing. Investigations by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) have been undertaken …

Conductivity Modulation In Strained 2d Transition- Metal- Dichalcogenides Via Micro- Electro- Mechanical Actuation, Aldo Ivan Vidaña

Open Access Theses & Dissertations

In this thesis, strain-induced conductivity modulation in bi-layer molybdenum disulfide (MoS2) flakes is experimentally investigated and modeled. Uniaxial tensile strain in the MoS2 flakes is achieved using a micro-electro-mechanical (MEM) actuator. Conductivity ratios up to 400 are demonstrated. Theoretical predictions of conductivity versus applied voltage in the MEMS-MoS2 device match experimental data reasonably well using only the effective width of the TMDC flakes as the sole fitting parameter. The amount of strain induced in the MoS2 flakes was determined to be as high as 2.7% for one flake using the model fitted to the experiment data. The switching energy required …

Hfo Detector Based On Eeg Mean Energy Change Detection, Raul Ontiveros

Open Access Theses & Dissertations

The main goal of this work is to support automated seizure prediction by identifying preictal states using multiple detectors of high-frequency oscillations (HFOs). Assessment of HFOs from a seizure onset zone may be facilitated using automatic HFO detectors. However, studies have shown that HFOs can be generated by physiological or pathological brain processes. Distinguishing between pathological and physiological HFOs is challenging due to a lack of discriminant information in signals' morphology and other characteristics. Other complicating factors include a lack of consistency in definitions of HFO frequency ranges, the need for expert verification of HFO detection, and lack of robustness …

Hybrid 3d Printing Demonstrated By Arbitrary 3d Meandering Transmission Lines, Ubaldo Robles

Open Access Theses & Dissertations

This Dissertation focuses on the automation of multi-material direct write three-dimensional (3D) manufacturing of arbitrary metal-dielectric structures. The technology was demonstrated by manufacturing 3D meandering interconnects and transmission lines (TLs). Manufacturing 3D functional electronics with multiple materials required pushing the current state of 3D printing (3DP) technology to utilize simultaneous multi-material processes combined with sophisticated slicing and bonding under one process. Multi material 3DP is known as hybrid 3DP. This research pioneered the process for producing meandering transmission lines, starting with design and manufacturing, using hybrid 3DP through micro-dispensing and fuse deposition modeling. The research starts by 3DP magnetic and …

Assessing Performance Of Detectors Of High Frequency Oscillations In Eeg Signals, Deeksha Seetharama Bhat

Open Access Theses & Dissertations

Attempts to perform epileptic seizure prediction have been made for decades, but there is no solution yet that is generally effective, though some progress in this area has been reported. Interictal epileptic spikes were considered as the only biomarkers of seizure-generating brain tissue until the recent discovery of high-frequency oscillations (HFOs) in electroencephalographic (EEG) signals, with frequency contents in the range from 80 Hz to 800 Hz. HFOs are now considered as biomarkers of epileptogenic tissue and the seizure onset zone. However, there are challenges in the definition and detection of HFO events which complicate this perspective. In studies about …

People Detection From Time-Of-Flight Imagery With Inpainting-Based Preprocessing, Basavarajaiah Totada

Open Access Theses & Dissertations

The Thesis describes a method of detection and tracking of people using depth images captured by a Time-of-Flight (ToF) camera, such as those obtained with a Microsoft Kinect V2. Key advantages of this approach are that the identity of people is not disclosed, and the system can operate in low-light conditions. The automated approach developed here is inspired by cell-tracking methods as implemented in the well-known biomedical imaging software called CellProfiler. Our approach involves significant preprocessing of the depth images by a combination of adaptive center weighted median filtering and iterative inpainting. The next step is detection of each person's …

Superpixel-Based Unsupervised Hyperspectral Unmixing, Jiarui Yi

Open Access Theses & Dissertations

Recently, superpixel-based approaches have been proposed for hyperspectral unmixing. The basic assumption of this approach is that the superpixel over-segmentation segments the image into small homogeneous areas. A low-dimensional (LD) image representation is obtained by using the average of the superpixels, which are then used in other image processing tasks up the processing chain. Due to superpixel-segmentation algorithm limitations, the region inside a superpixel may not be homogeneous. Therefore, the average may not be an adequate representation for the superpixel, leading to inaccuracies in the low dimensional representation resulting in errors in the image processing tasks or analysis. Here we …

Improving Time-Of-Flight And Other Depth Images: Super-Resolution And Denoising Using Variational Methods, Salvador Canales Andrade

Open Access Theses & Dissertations

Depth information is a new important source of perception for machines, which allow them to have a better representation of the surroundings. The depth information provides a more precise map of the location of every object and surfaces in a space of interest in comparison with conventional cameras. Time of flight (ToF) cameras provide one of the techniques to acquire depth maps, however they produce low spatial resolution and noisy maps. This research proposes a framework to enhance and up-scale depth maps by using two different regularization terms: Total Generalized Variation (TGV) and Total Generalized Variation with a Structure Tensor …

Analysis Of High Performance Scientific Programming Workflows, Withana Kankanamalage Umayanganie Klaassen

Open Access Theses & Dissertations

Substantial time is spent on building, optimizing and maintaining large-scale software that is run on supercomputers. However, little has been done to utilize overall resources efficiently when it comes to including expensive human resources. The community is beginning to acknowledge that optimizing the hardware performance such as speed and memory bottlenecks contributes less to the overall productivity than does the development lifecycle of high-performance scientific applications. Researchers are beginning to look at overall scientific workflows for high performance computing. Scientific programming productivity is measured by time and effort required to develop, configure, and maintain a simulation experiment and its constituent …

Parallelization And Scalability Analysis Of The \\[1pc] 3d Spatially Variant Lattice Algorithm, Henry Roger Moncada Lopez

Open Access Theses & Dissertations

The purpose of this research is to design a faster implementation of an algorithm to generate 3D spatially variant lattices (SVL) and improve its performance when it is running on a parallel computer system. The algorithm is used to synthesize a SVL for a periodic structure. The algorithm has the ability to spatially vary the unit cell, the orientation of the unit cells, lattice spacing, fill fraction, material composition, and lattice symmetry. The algorithm produces a lattice that is smooth, continuous and free of defects. The lattice spacing remains strikingly uniform even when the lattice is spatially varied. This is …

Interference Analysis And Mitigation Of Telemetry (Tm) And 4g Long-Term Evolution (Lte) Systems In Adjacent Spectrum Bands, Juan Francisco Gonzalez

Open Access Theses & Dissertations

Currently, the telecommunications, radio systems, and many other wireless services in the United States are using the spectrum from the 6 kHz to the 300 GHz frequencies. Although it may seem enough for said systems, as more users and devices are being introduced into the market, the spectrum is limiting the faster introduction of these devices and/or systems. The radio frequency spectrum is home to many transmissions, from amateur radio to cellphone applications, which all share similar frequency bands. By sharing, the number of applications can be increased in a single band, but their performance may be affected. Herein, experiments …

Advances In Chemical Vapor Deposition Growth Of Molybdenum Disulfide For Photodetectors And Flexible Electronics, Carlos Francisco De Anda Orea

Open Access Theses & Dissertations

The conversion of light into electrical signals is at the basis of technologies that affect our daily lives. Applications, including video imaging, optical communications, biomedical imaging, security, night-vision, gas sensing and motion detection have reached a high level of maturity due to the development of high-performance materials, large-scale production, and integration technologies. Currently conventional photodetectors made of Silicon (Si) or III-V compounds are about to reach their maximum efficiency, and every time it is harder to get a noticeable improvement in performance of sensors based on these materials, not to mention the complicated fabrication methods to achieve just a few …

Image Data Mining For Quality Control Of Nanofiber Reinforced Piezoelectric Nanocomposites Based On Sem Images, Zhonghua Hu

Open Access Theses & Dissertations

Recently, portable and wireless nano-scaled devices have been widely used in environmental monitoring, medical implants, defense technology, industrial safety, and personal electronics, such as the nanowire-based gas and chemical sensors and programmable nanowire circuit for nano-processors. There has been an increasing demand for high energy density capacitors that can be engineered for various applications in advanced devices. In it, piezoelectric nanofiber materials play critical role in producing new products. A piezo-ceramic polymer composite contains a polymer of high dielectric strength and high permittivity ceramic inclusions, making it well suited as a high energy density capacitor. Furthermore, the research shows that …

Organic-Inorganic Graphite And Transition Metal Dichalcogenide Based Composites For 3d Printing, Jorge Alfredo Catalan Gonzalez

Open Access Theses & Dissertations

This project was multipronged to help fuse together topics of additive manufacturing and two-dimensional (2D) layered materials, and studying the mechanical and electrical properties of the composites produced. The composites are made from the thermoplastic polymer acting as a matrix and the graphite and 2D transition metal dichalcogenides (TMDs) serving as the filler or reinforcement. Different concentrations of TMD's were added to the matrix to study the effect of composition on the mechanical and electrical properties. To shed insights into the mechanical properties, test coupons were produced as "dog bone" structures for tensile testing using the ASTM D638 type 5 …

Safety Airway For Small Unmanned Aerial Vehicles Using A Gas Particles Behavior Analogy, Pablo Rangel

Open Access Theses & Dissertations

The United States Federal Aviation Administration (FAA) implemented the Part 107 legislation to allow the flight of Unmanned Aerial Vehicles (UAV) for commercial use (i.e. package deliveries, power transmission line inspections, etc.) in the National Airspace System (NAS). As a consequence of the newly introduced rules, there is an increased risk for accidents involving injured bystanders or damaged to property. The work within this document defines a UAV to UAV safety distance model that acts as a range sensor enabled "elastic bubble". The length of the UAV safety bubble contracts and expands upon changing airway wind speed conditions. It also …

Bragg Gratings In Polarization Maintaining Optical Fiber As Three Dimensional Strain Sensor, Joel Quintana

Open Access Theses & Dissertations

Fiber-Bragg Gratings (FBG) for Structural Health Monitoring (SHM) have been studied extensively as they offer electrically passive operation, electromagnetic interference (EMI) immunity, high sensitivity and multiplexing as compared to conventional electric strain sensors. FBG sensors written within polarization maintaining (PM) optical fiber offer ad- ditional dimensions of strain measurement, greatly reducing the number of sensors needed to properly monitor a structure. This reduction however, adds complexity to the dis- crimination of the sensorâ??s optical response to its corresponding applied strains. This Dissertation defines the set of algorithms needed to measure planar strain using PM-FBGs exclusively. It defines the minimum number …

Compressive Vector Reconstruction: Hypothesis For Blind Image Deconvolution, Alonso Orea Amador

Open Access Theses & Dissertations

Alternative imaging devices propose to acquire and compress images simultaneously. These devices are based on the compressive sensing (CS) theory. A reduction in the measurement required for reconstruction without a post-compression sub-system allows imaging devices to become simpler, smaller, and cheaper. In this research, we propose a new algorithm to compress and reconstruct blurred images for CS imaging devices. Blur effect in images is common due to relative motion, lens, limited aperture dimensions, lack of focus, and/or atmospheric turbulence. Our intention is to compress a blurred image with CS techniques and then reconstruct a blur-free version using the proposed algorithm. …

Optimization Of Neural Network Architecture For Classification Of Radar Jamming Fm Signals, Alberto Soto

Open Access Theses & Dissertations

Radar jamming signal classification is valuable when situational awareness of radar systems is sought out for timely deployment of electronic support measures. Our Thesis shows that artificial neural networks can be utilized for effective and efficient signal classification. The goal is to optimize an artificial Neural Network (NN) approach capable of distinguishing between two common radar waveforms, namely bandlimited white Gaussian jamming noise (BWGN) and the ubiquitous linearly frequency modulated (LFM) signal. This is made possible by creating a theoretical framework for NN architecture testing that leads to a high probability of detection (PD) and a low probability of false …

Automatic Patch Classification And Diffusion In Adaptive, Luis Alonso Ponce

Open Access Theses & Dissertations

Multi-Frame image restoration is a form of Super-Resolution (SR) which consists of combining multiple Low-Resolution (LR) images in order to reconstruct a single High Resolution (HR) image. In this Thesis we improved a spatially-adaptive SR scheme, based on the framework of Optimal Recovery (OR), whereby the block-by-block processing is done based on the properties of the corresponding local LR image data patches. The bandwidth parameter is adapted based on the local variance of each corresponding block from all LR images that contribute to the HR image block to be reconstructed. Also, an optimal regularization parameter needs to be chosen for …

Structural And Electrical Characterization Of Tin Oxide Resistive Switching, Arka Talukdar

Open Access Theses & Dissertations

Resistive switching in metal oxide is a phenomenon in which the metal oxide changes its resistance upon application of electric field and thus giving two states; high resistance state (HRS) and low resistance state (LRS). Many metal oxides have been investigated however very little is known about unipolar resistive switching in SnO2 though it has shown excellent resistive switching characteristics. Defects in the material play a vital role in resistive switching of the metal oxides. In this work, the role of defects in resistive switching of SnO2 are investigated in Ti/SnO2/Au structures. Two methods were used to control the concentration …