Matching Items (54)
Description
In this thesis I introduce a new direction to computing using nonlinear chaotic dynamics. The main idea is rich dynamics of a chaotic system enables us to (1) build better computers that have a flexible instruction set, and (2) carry out computation that conventional computers are not good at it. Here I start from the theory, explaining how one can build a computing logic block using a chaotic system, and then I introduce a new theoretical analysis for chaos computing. Specifically, I demonstrate how unstable periodic orbits and a model based on them explains and predicts how and how well a chaotic system can do computation. Furthermore, since unstable periodic orbits and their stability measures in terms of eigenvalues are extractable from experimental times series, I develop a time series technique for modeling and predicting chaos computing from a given time series of a chaotic system. After building a theoretical framework for chaos computing I proceed to architecture of these chaos-computing blocks to build a sophisticated computing system out of them. I describe how one can arrange and organize these chaos-based blocks to build a computer. I propose a brand new computer architecture using chaos computing, which shifts the limits of conventional computers by introducing flexible instruction set. Our new chaos based computer has a flexible instruction set, meaning that the user can load its desired instruction set to the computer to reconfigure the computer to be an implementation for the desired instruction set. Apart from direct application of chaos theory in generic computation, the application of chaos theory to speech processing is explained and a novel application for chaos theory in speech coding and synthesizing is introduced. More specifically it is demonstrated how a chaotic system can model the natural turbulent flow of the air in the human speech production system and how chaotic orbits can be used to excite a vocal tract model. Also as another approach to build computing system based on nonlinear system, the idea of Logical Stochastic Resonance is studied and adapted to an autoregulatory gene network in the bacteriophage λ.
ContributorsKia, Behnam (Author) / Ditto, William (Thesis advisor) / Huang, Liang (Committee member) / Lai, Ying-Cheng (Committee member) / Helms Tillery, Stephen (Committee member) / Arizona State University (Publisher)
Created2011
Description
The main objective of this study is to investigate the mechanical behaviour of cementitious based composites subjected dynamic tensile loading, with effects of strain rate, temperature, addition of short fibres etc. Fabric pullout model and tension stiffening model based on finite difference model, previously developed at Arizona State University were used to help study the bonding mechanism between fibre and matrix, and the phenomenon of tension stiffening due to the addition of fibres and textiles. Uniaxial tension tests were conducted on strain-hardening cement-based composites (SHCC), textile reinforced concrete (TRC) with and without addition of short fibres, at the strain rates ranging from 25 s-1 to 100 s-1. Historical data on quasi-static tests of same materials were used to demonstrate the effects including increases in average tensile strength, strain capacity, work-to-fracture due to high strain rate. Polyvinyl alcohol (PVA), glass, polypropylene were employed as reinforcements of concrete. A state-of-the-art phantom v7 high speed camera was setup to record the video at frame rate of 10,000 fps. Random speckle pattern of texture style was made on the surface of specimens for image analysis. An optical non-contacting deformation measurement technique referred to as digital image correlation (DIC) method was used to conduct the image analysis by means of tracking the displacement field through comparison between the reference image and deformed images. DIC successfully obtained full-filed strain distribution, strain versus time responses, demonstrated the bonding mechanism from perspective of strain field, and corrected the stress-strain responses.
ContributorsYao, Yiming (Author) / Barzin, Mobasher (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Neithalath, Narayanan (Committee member) / Arizona State University (Publisher)
Created2013
Description
Complex dynamical systems consisting interacting dynamical units are ubiquitous in nature and society. Predicting and reconstructing nonlinear dynamics of units and the complex interacting networks among them serves the base for the understanding of a variety of collective dynamical phenomena. I present a general method to address the two outstanding problems as a whole based solely on time-series measurements. The method is implemented by incorporating compressive sensing approach that enables an accurate reconstruction of complex dynamical systems in terms of both nodal equations that determines the self-dynamics of units and detailed coupling patterns among units. The representative advantages of the approach are (i) the sparse data requirement which allows for a successful reconstruction from limited measurements, and (ii) general applicability to identical and nonidentical nodal dynamics, and to networks with arbitrary interacting structure, strength and sizes. Another two challenging problem of significant interest in nonlinear dynamics: (i) predicting catastrophes in nonlinear dynamical systems in advance of their occurrences and (ii) predicting the future state for time-varying nonlinear dynamical systems, can be formulated and solved in the framework of compressive sensing using only limited measurements. Once the network structure can be inferred, the dynamics behavior on them can be investigated, for example optimize information spreading dynamics, suppress cascading dynamics and traffic congestion, enhance synchronization, game dynamics, etc. The results can yield insights to control strategies design in the real-world social and natural systems. Since 2004, there has been a tremendous amount of interest in graphene. The most amazing feature of graphene is that there exists linear energy-momentum relationship when energy is low. The quasi-particles inside the system can be treated as chiral, massless Dirac fermions obeying relativistic quantum mechanics. Therefore, the graphene provides one perfect test bed to investigate relativistic quantum phenomena, such as relativistic quantum chaotic scattering and abnormal electron paths induced by klein tunneling. This phenomenon has profound implications to the development of graphene based devices that require stable electronic properties.
ContributorsYang, Rui (Author) / Lai, Ying-Cheng (Thesis advisor) / Duman, Tolga M. (Committee member) / Akis, Richard (Committee member) / Huang, Liang (Committee member) / Arizona State University (Publisher)
Created2012
Description
What can classical chaos do to quantum systems is a fundamental issue highly relevant to a number of branches in physics. The field of quantum chaos has been active for three decades, where the focus was on non-relativistic quantumsystems described by the Schr¨odinger equation. By developing an efficient method to solve the Dirac equation in the setting where relativistic particles can tunnel between two symmetric cavities through a potential barrier, chaotic cavities are found to suppress the spread in the tunneling rate. Tunneling rate for any given energy assumes a wide range that increases with the energy for integrable classical dynamics. However, for chaotic underlying dynamics, the spread is greatly reduced. A remarkable feature, which is a consequence of Klein tunneling, arise only in relativistc quantum systems that substantial tunneling exists even for particle energy approaching zero. Similar results are found in graphene tunneling devices, implying high relevance of relativistic quantum chaos to the development of such devices. Wave propagation through random media occurs in many physical systems, where interesting phenomena such as branched, fracal-like wave patterns can arise. The generic origin of these wave structures is currently a matter of active debate. It is of fundamental interest to develop a minimal, paradigmaticmodel that can generate robust branched wave structures. In so doing, a general observation in all situations where branched structures emerge is non-Gaussian statistics of wave intensity with an algebraic tail in the probability density function. Thus, a universal algebraic wave-intensity distribution becomes the criterion for the validity of any minimal model of branched wave patterns. Coexistence of competing species in spatially extended ecosystems is key to biodiversity in nature. Understanding the dynamical mechanisms of coexistence is a fundamental problem of continuous interest not only in evolutionary biology but also in nonlinear science. A continuous model is proposed for cyclically competing species and the effect of the interplay between the interaction range and mobility on coexistence is investigated. A transition from coexistence to extinction is uncovered with a non-monotonic behavior in the coexistence probability and switches between spiral and plane-wave patterns arise. Strong mobility can either promote or hamper coexistence, while absent in lattice-based models, can be explained in terms of nonlinear partial differential equations.
ContributorsNi, Xuan (Author) / Lai, Ying-Cheng (Thesis advisor) / Huang, Liang (Committee member) / Yu, Hongbin (Committee member) / Akis, Richard (Committee member) / Arizona State University (Publisher)
Created2012
Description
This thesis examines Care Not Cash, a welfare reform measure that replaced traditional cash General Assistance program payments for homeless persons in San Francisco with in-kind social services. Unlike most welfare reform measures, proponents framed Care Not Cash as a progressive policy, aimed at expanding social services and government care for this vulnerable population. Drawing on primary and secondary documents, as well as interviews with homelessness policy experts, this thesis examines the historical and political success of Care Not Cash, and explores the potential need for implementation of a similar program in Phoenix, Arizona.
ContributorsMcCutcheon, Zachary Ryan (Author) / Lucio, Joanna (Thesis director) / Williams, David (Committee member) / Bretts-Jamison, Jake (Committee member) / School of Public Affairs (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
ABSTRACTWith the National Aeronautics and Space Administration (NASA) Psyche Mission, humans will soon have the first opportunity to explore a new kind of planetary body: one composed mostly of metal as opposed to stony minerals or ices. Identifying the composition of asteroids from Earth-based observations has been an ongoing challenge. Although optical reflectance spectra, radar, and orbital dynamics can constrain an asteroid’s mineralogy and bulk density, in many cases there is not a clear or precise match with analogous materials such as meteorites. Additionally, the surfaces of asteroids and other small, airless planetary bodies can be heavily modified over geologic time by exposure to the space environment. To accurately interpret remote sensing observations of metal-rich asteroids, it is therefore necessary to understand how the processes active on asteroid surfaces affect metallic materials. This dissertation represents a first step toward that understanding. In collaboration with many colleagues, I have performed laboratory experiments on iron meteorites to simulate solar wind ion irradiation, surface heating, micrometeoroid bombardment, and high-velocity impacts. Characterizing the meteorite surface’s physical and chemical properties before and after each experiment can constrain the effects of each process on a metal-rich surface in space. While additional work will be needed for a complete understanding, it is nevertheless possible to make some early predictions of what (16) Psyche’s surface regolith might look like when humans observe it up close. Moreover, the results of these experiments will inform future exploration beyond asteroid Psyche as humans attempt to understand how Earth’s celestial neighborhood came to be.
ContributorsChristoph, John Morgan M. (Author) / Elkins-Tanton, Linda (Thesis advisor) / Williams, David (Committee member) / Dukes, Catherine (Committee member) / Sharp, Thomas (Committee member) / Bell III, James (Committee member) / Arizona State University (Publisher)
Created2023
Description
Breast cancer is one of the leading causes of cancer-related deaths among women in the United States. Uninsured women are less likely to receive breast cancer screenings, more likely to be diagnosed at an advanced stage, and more likely to have poorer outcomes following a breast cancer diagnosis (Abdelsattar et al., 2016; Akinlotan et al., 2021; Ko et al., 2020; & Ntiri et al., 2018). Women in underserved communities often experience socioeconomic barriers which impact obtaining preventative screenings, such as mammograms. Lack of patient navigation, transportation, and financial concerns interfere with obtaining breast cancer screening (Akinlotan et al., 2021 & Miller et al., 2019). Through the intervention of mobile mammography, uninsured women in underserved communities can be reached and access to screening mammograms can be achieved (Stanley et al., 2017 & Vang et al., 2018). Two mobile mammography events were hosted at the project site which provided 35 women with screening mammograms. All scheduled mammogram time slots at the events were filled and completed. Offering mobile mammography to this population has the potential to increase breast cancer surveillance.
ContributorsGlessner-Vallee, Paula (Author) / Santerre, Jennifer (Thesis advisor) / College of Nursing and Health Innovation (Contributor)
Created2023-04-26
Description
Introduction: The objective of this study is to emphasize the significance of exclusive breastfeeding (EB) and investigate methods to encourage and sustain it within a hospital environment. Using the self-efficacy theory, the study seeks to improve the current support system for breastfeeding mothers and their families. Methods: The project was approved by the university IRB and facility IRB; guidelines were maintained. The project takes place in a non-profit organization in the southwestern United States. Education was conducted at a required staff meeting for Women and Infant Services (WIS) floor about supporting breastfeeding mothers. A pre- and post-education Breastfeeding Knowledge Scale (BKS) survey was performed, effectiveness was measured using a two-tailed t-test. The reliability of the BKS scale is 0.83 and the validity of the scale is reported to be strong. The hospital measures the EB rates of patients that are greater than 37 weeks gestation without need for neonatal intensive unit care and the mom requests to breastfeed. Results: The goal was 42% rate of EB in the first 48 hours after birth. After education the average rate of EB was 39.6%, lower than the goal but higher than the 33.7% rate before education. A two-tailed paired sample t-test (n=27) was used for BKS and the results were significant based on an alpha value; thus, showing significant knowledge gain. Conclusion: Consistent staff education improves breastfeeding support for moms in the hospital, leading to successful exclusive breastfeeding. This project benefits various settings, such as pediatric, postpartum, labor and delivery, and pediatric offices.
ContributorsHudson, Jennifer (Author) / Esperas, Amanda (Thesis advisor) / College of Nursing and Health Innovation (Contributor)
Created2023-04-26
Description
Introduction: Depression screening in the pediatric setting is a crucial part of the adolescent's examination. A standardized screening tool and protocol streamlines the process of assessing adolescents and minimizes the chances of serious mental health disorders going undetected and untreated. Evaluation of current evidence demonstrates the use of a standardized tool improves detection, diagnosis, and management of depression and other mental health illnesses.
Method: The Patient Health Questionnaire—modified for adolescents (PHQ9-A) was administered to all eligible adolescents, ages 12-18, during an annual well visit for a period of 6 weeks. Lewin's Change Theory guided a system change in the electronic health record, and the questionnaire results were documented and provided to the pediatric provider at the time of the appointment. A chart review was conducted to determine whether all eligible patients were administered the questionnaire and if a depression diagnosis or mental health referral had been made.
Results: Out of 76 eligible well visits, 65 (86%) patients completed the PHQ9-A. The average score was 5.29 (SD = 6.49) with a maximum score of 25. Out of those that completed screening, 11 (17%) had a positive PHQ9-A score resulting in 8 referrals to mental health services and 2 mental health diagnoses in the clinic.
ContributorsCoomer, Meagan (Author) / Rauton, Monica (Thesis advisor) / College of Nursing and Health Innovation (Contributor)
Created2023-04-27
Description
Background: There is growing evidence that persistent exposure to the adverse effects of stressful work conditions, abuse, and re-traumatization without proper intervention leads to compassion fatigue (CF) and reduced compassion satisfaction (CS). Without appropriate intervention, the outcome of CF affects the patient, staff, and the organization. Despite proposed self-care measures, mental health (MH) workers continue to struggle with CF and lack the resources to combat the issue.
Objectives: Ongoing awareness on the implications of trauma and its impact on one's behavior, supports the use of Trauma-informed care (TIC) skills in creating a conducive work environment. This quality improvement project examines the efficacy of TIC education as an intervention for CF pre/post-one-hour education session among MH workers.
Methods: MH nurses (n=8) from diverse backgrounds in a Phoenix inpatient psychiatric hospital gave consent for the study. Participation was sought via flyers and entailed attending the one-hour education session, filling out a demographic, and pre/post-professional quality of life (ProQol) surveys. The ProQol standardized tool measures CF, CS, and burnout with reliability >0.70. Expected outcomes include a reduction in CF and an improvement in CS. Data analysis using intellectus software involved descriptive analysis and paired t-tests to compare outcomes.
Results: Pre/post data analysis was statistically significant, P = 0.003, which shows a reduction in CF and an improvement in CS.
Conclusion: TIC as an intervention for CF looks promising. MH nurses can manage their stress symptoms and that of their patients using TIC skills.
ContributorsOnyia, Nneka (Author) / Guthery, Ann (Thesis advisor) / College of Nursing and Health Innovation (Contributor)
Created2023-04-29