Matching Items (380)
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Description
Current economic conditions necessitate the extension of service lives for a variety of aerospace systems. As a result, there is an increased need for structural health management (SHM) systems to increase safety, extend life, reduce maintenance costs, and minimize downtime, lowering life cycle costs for these aging systems. The implementation

Current economic conditions necessitate the extension of service lives for a variety of aerospace systems. As a result, there is an increased need for structural health management (SHM) systems to increase safety, extend life, reduce maintenance costs, and minimize downtime, lowering life cycle costs for these aging systems. The implementation of such a system requires a collaborative research effort in a variety of areas such as novel sensing techniques, robust algorithms for damage interrogation, high fidelity probabilistic progressive damage models, and hybrid residual life estimation models. This dissertation focuses on the sensing and damage estimation aspects of this multidisciplinary topic for application in metallic and composite material systems. The primary means of interrogating a structure in this work is through the use of Lamb wave propagation which works well for the thin structures used in aerospace applications. Piezoelectric transducers (PZTs) were selected for this application since they can be used as both sensors and actuators of guided waves. Placement of these transducers is an important issue in wave based approaches as Lamb waves are sensitive to changes in material properties, geometry, and boundary conditions which may obscure the presence of damage if they are not taken into account during sensor placement. The placement scheme proposed in this dissertation arranges piezoelectric transducers in a pitch-catch mode so the entire structure can be covered using a minimum number of sensors. The stress distribution of the structure is also considered so PZTs are placed in regions where they do not fail before the host structure. In order to process the data from these transducers, advanced signal processing techniques are employed to detect the presence of damage in complex structures. To provide a better estimate of the damage for accurate life estimation, machine learning techniques are used to classify the type of damage in the structure. A data structure analysis approach is used to reduce the amount of data collected and increase computational efficiency. In the case of low velocity impact damage, fiber Bragg grating (FBG) sensors were used with a nonlinear regression tool to reconstruct the loading at the impact site.
ContributorsCoelho, Clyde (Author) / Chattopadhyay, Aditi (Thesis advisor) / Dai, Lenore (Committee member) / Wu, Tong (Committee member) / Das, Santanu (Committee member) / Rajadas, John (Committee member) / Papandreou-Suppappola, Antonia (Committee member) / Arizona State University (Publisher)
Created2011
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Description
Many products undergo several stages of testing ranging from tests on individual components to end-item tests. Additionally, these products may be further "tested" via customer or field use. The later failure of a delivered product may in some cases be due to circumstances that have no correlation with the product's

Many products undergo several stages of testing ranging from tests on individual components to end-item tests. Additionally, these products may be further "tested" via customer or field use. The later failure of a delivered product may in some cases be due to circumstances that have no correlation with the product's inherent quality. However, at times, there may be cues in the upstream test data that, if detected, could serve to predict the likelihood of downstream failure or performance degradation induced by product use or environmental stresses. This study explores the use of downstream factory test data or product field reliability data to infer data mining or pattern recognition criteria onto manufacturing process or upstream test data by means of support vector machines (SVM) in order to provide reliability prediction models. In concert with a risk/benefit analysis, these models can be utilized to drive improvement of the product or, at least, via screening to improve the reliability of the product delivered to the customer. Such models can be used to aid in reliability risk assessment based on detectable correlations between the product test performance and the sources of supply, test stands, or other factors related to product manufacture. As an enhancement to the usefulness of the SVM or hyperplane classifier within this context, L-moments and the Western Electric Company (WECO) Rules are used to augment or replace the native process or test data used as inputs to the classifier. As part of this research, a generalizable binary classification methodology was developed that can be used to design and implement predictors of end-item field failure or downstream product performance based on upstream test data that may be composed of single-parameter, time-series, or multivariate real-valued data. Additionally, the methodology provides input parameter weighting factors that have proved useful in failure analysis and root cause investigations as indicators of which of several upstream product parameters have the greater influence on the downstream failure outcomes.
ContributorsMosley, James (Author) / Morrell, Darryl (Committee member) / Cochran, Douglas (Committee member) / Papandreou-Suppappola, Antonia (Committee member) / Roberts, Chell (Committee member) / Spanias, Andreas (Committee member) / Arizona State University (Publisher)
Created2011
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Description
Advancements in computer vision and machine learning have added a new dimension to remote sensing applications with the aid of imagery analysis techniques. Applications such as autonomous navigation and terrain classification which make use of image classification techniques are challenging problems and research is still being carried out to find

Advancements in computer vision and machine learning have added a new dimension to remote sensing applications with the aid of imagery analysis techniques. Applications such as autonomous navigation and terrain classification which make use of image classification techniques are challenging problems and research is still being carried out to find better solutions. In this thesis, a novel method is proposed which uses image registration techniques to provide better image classification. This method reduces the error rate of classification by performing image registration of the images with the previously obtained images before performing classification. The motivation behind this is the fact that images that are obtained in the same region which need to be classified will not differ significantly in characteristics. Hence, registration will provide an image that matches closer to the previously obtained image, thus providing better classification. To illustrate that the proposed method works, naïve Bayes and iterative closest point (ICP) algorithms are used for the image classification and registration stages respectively. This implementation was tested extensively in simulation using synthetic images and using a real life data set called the Defense Advanced Research Project Agency (DARPA) Learning Applied to Ground Robots (LAGR) dataset. The results show that the ICP algorithm does help in better classification with Naïve Bayes by reducing the error rate by an average of about 10% in the synthetic data and by about 7% on the actual datasets used.
ContributorsMuralidhar, Ashwini (Author) / Saripalli, Srikanth (Thesis advisor) / Papandreou-Suppappola, Antonia (Committee member) / Turaga, Pavan (Committee member) / Arizona State University (Publisher)
Created2011
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Description
Underwater acoustic communications face significant challenges unprecedented in radio terrestrial communications including long multipath delay spreads, strong Doppler effects, and stringent bandwidth requirements. Recently, multi-carrier communications based on orthogonal frequency division multiplexing (OFDM) have seen significant growth in underwater acoustic (UWA) communications, thanks to their well well-known robustness against severely

Underwater acoustic communications face significant challenges unprecedented in radio terrestrial communications including long multipath delay spreads, strong Doppler effects, and stringent bandwidth requirements. Recently, multi-carrier communications based on orthogonal frequency division multiplexing (OFDM) have seen significant growth in underwater acoustic (UWA) communications, thanks to their well well-known robustness against severely time-dispersive channels. However, the performance of OFDM systems over UWA channels significantly deteriorates due to severe intercarrier interference (ICI) resulting from rapid time variations of the channel. With the motivation of developing enabling techniques for OFDM over UWA channels, the major contributions of this thesis include (1) two effective frequencydomain equalizers that provide general means to counteract the ICI; (2) a family of multiple-resampling receiver designs dealing with distortions caused by user and/or path specific Doppler scaling effects; (3) proposal of using orthogonal frequency division multiple access (OFDMA) as an effective multiple access scheme for UWA communications; (4) the capacity evaluation for single-resampling versus multiple-resampling receiver designs. All of the proposed receiver designs have been verified both through simulations and emulations based on data collected in real-life UWA communications experiments. Particularly, the frequency domain equalizers are shown to be effective with significantly reduced pilot overhead and offer robustness against Doppler and timing estimation errors. The multiple-resampling designs, where each branch is tasked with the Doppler distortion of different paths and/or users, overcome the disadvantages of the commonly-used single-resampling receivers and yield significant performance gains. Multiple-resampling receivers are also demonstrated to be necessary for UWA OFDMA systems. The unique design effectively mitigates interuser interference (IUI), opening up the possibility to exploit advanced user subcarrier assignment schemes. Finally, the benefits of the multiple-resampling receivers are further demonstrated through channel capacity evaluation results.
ContributorsTu, Kai (Author) / Duman, Tolga M. (Thesis advisor) / Zhang, Junshan (Committee member) / Tepedelenlioğlu, Cihan (Committee member) / Papandreou-Suppappola, Antonia (Committee member) / Arizona State University (Publisher)
Created2011
Description

Consider Steven Cryos’ words, “When disaster strikes, the time to prepare has passed.” Witnessing domestic water insecurity in events such as Hurricane Katrina, the instability in Flint, Michigan, and most recently the winter storms affecting millions across Texas, we decided to take action. The period between a water supply’s disruption

Consider Steven Cryos’ words, “When disaster strikes, the time to prepare has passed.” Witnessing domestic water insecurity in events such as Hurricane Katrina, the instability in Flint, Michigan, and most recently the winter storms affecting millions across Texas, we decided to take action. The period between a water supply’s disruption and restoration is filled with anxiety, uncertainty, and distress -- particularly since there is no clear indication of when, exactly, restoration comes. It is for this reason that Water Works now exists. As a team of students from diverse backgrounds, what started as an honors project with the Founders Lab at Arizona State University became the seed that will continue to mature into an economically sustainable business model supporting the optimistic visions and tenants of humanitarianism. By having conversations with community members, conducting market research, competing for funding and fostering progress amid the COVID-19 pandemic, our team’s problem-solving traverses the disciplines. The purpose of this paper is to educate our readers about a unique solution to emerging issues of water insecurity that are nested across and within systems who could benefit from the introduction of a personal water reclamation system, showcase our team’s entrepreneurial journey, and propose future directions that will this once pedagogical exercise to continue fulfilling its mission: To heal, to hydrate and to help bring safe water to everyone.

ContributorsReitzel, Gage Alexander (Co-author) / Filipek, Marina (Co-author) / Sadiasa, Aira (Co-author) / Byrne, Jared (Thesis director) / Sebold, Brent (Committee member) / Historical, Philosophical & Religious Studies (Contributor) / School of Human Evolution & Social Change (Contributor, Contributor) / Historical, Philosophical & Religious Studies, Sch (Contributor) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description

The Constitution is a document that was made over 200 years ago by a population that could have never imagined the type of technology or social advances made in the 21st century. This creates a natural rift between governing ideals between then and now, that needs to be addressed. Rather

The Constitution is a document that was made over 200 years ago by a population that could have never imagined the type of technology or social advances made in the 21st century. This creates a natural rift between governing ideals between then and now, that needs to be addressed. Rather than holding the values of the nation to a time when people were not considered citizens because of the color of their skin, there need to be updates made to the Constitution itself. The need for change and the mechanisms were both established by the Framers while creating and advancing the Constitution. The ideal process to go about these changes is split between the formal Article V amendment process and judicial activism. The amendment process has infinite scope for changes that can be done, but due to the challenge involved in trying to pass any form of the amendment through both State and Federal Congresses, that process should be reserved for only fundamental or structural changes. Judicial activism, by way of Supreme Court decisions, is a method best applied to the protection of people’s rights.

Created2021-05
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The thesis analyzes the apathetic youth turnout myth and researches to see if voter suppression can explain the reason behind low youth turnout. This thesis is a study done with Arizona State University students to assess their level of voter turnout, their levels of political engagement, and if they have

The thesis analyzes the apathetic youth turnout myth and researches to see if voter suppression can explain the reason behind low youth turnout. This thesis is a study done with Arizona State University students to assess their level of voter turnout, their levels of political engagement, and if they have experienced voter suppression. Respondents were also asked about the support given by ASU in terms of helping with the voting process. Results indicate that Arizona State students have high levels of political engagement, and that 1 in 5 ASU students have experienced voter suppression. Furthermore, ASU students on a whole are uncertain about the role ASU should play in supporting students with the voting process.

Created2021-05
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As political campaigning becomes increasingly digital and data-driven, data privacy has become a question of democratic governance. Yet, Congress has yet to pass a comprehensive federal data privacy law and even the strongest subnational data privacy laws exempt political campaigns from regulation. <br/><br/>This thesis examines how data privacy laws impact

As political campaigning becomes increasingly digital and data-driven, data privacy has become a question of democratic governance. Yet, Congress has yet to pass a comprehensive federal data privacy law and even the strongest subnational data privacy laws exempt political campaigns from regulation. <br/><br/>This thesis examines how data privacy laws impact data-driven and digital political campaigning. Specifically, it investigates what information is incorporated into the political data ecosystem, how data privacy laws regulate the collection of this data, and how actors in the political data ecosystem respond to these laws. It examines both sector-specific federal law and subnational data protection regulation through a case study of California. This research suggests that although the California Consumer Privacy Act and California Privacy Rights Act are landmark steps in American data protection, subnational data privacy law remains inhibited by the federal market-based approach.

ContributorsScovil, Daiva Julija (Author) / Gary, Marchant (Thesis director) / K, Royal (Committee member) / Historical, Philosophical & Religious Studies (Contributor, Contributor) / School of Politics and Global Studies (Contributor, Contributor) / Historical, Philosophical & Religious Studies, Sch (Contributor, Contributor) / Watts College of Public Service & Community Solut (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Disinformation has long been a tactic used by the Russian government to achieve its goals. Today, Vladimir Putin aims to achieve several things: weaken the United States’ strength on the world stage, relieve Western sanctions on himself and his inner circle, and reassert dominant influence over Russia’s near abroad (the

Disinformation has long been a tactic used by the Russian government to achieve its goals. Today, Vladimir Putin aims to achieve several things: weaken the United States’ strength on the world stage, relieve Western sanctions on himself and his inner circle, and reassert dominant influence over Russia’s near abroad (the Baltics, Ukraine, etc.). This research analyzed disinformation in English, Spanish, and Russian; noting the dominant narratives and geopolitical goals Russia hoped to achieve by destabilizing democracy in each country/region.

Created2021-05
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For my project, I delve into the relationships of Victor and the Monster as well as the relationships Victor shares with other characters that were underdeveloped within the original novel by Mary Shelley in the novel Franeknstein. I examine their relationships in two components. The first through my own interpretation

For my project, I delve into the relationships of Victor and the Monster as well as the relationships Victor shares with other characters that were underdeveloped within the original novel by Mary Shelley in the novel Franeknstein. I examine their relationships in two components. The first through my own interpretation of Victor and the Monster’s relationship within a creative writing piece that extends the novel as if Victor had lived rather than died in the arctic in order to explore the possibilities of a more complex set of relationships between Victor and the Monster than simply creator-creation. My writing focuses on the development of their relationship once all they have left is each other. The second part of my project focuses on an analytical component. I analyze and cite the reasoning for my creative take on Victor and the Monster as well as their relationship within the novel and Mary Shelley’s intentions.

ContributorsHodge Smith, Elizabeth Ann (Author) / Fette, Don (Thesis director) / Hoyt, Heather (Committee member) / Historical, Philosophical & Religious Studies (Contributor, Contributor) / Historical, Philosophical & Religious Studies, Sch (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05