Matching Items (1,026)
Description
This research is focused on two separate but related topics. The first uses an electroencephalographic (EEG) brain-computer interface (BCI) to explore the phenomenon of motor learning transfer. The second takes a closer look at the EEG-BCI itself and tests an alternate way of mapping EEG signals into machine commands. We test whether motor learning transfer is more related to use of shared neural structures between imagery and motor execution or to more generalized cognitive factors. Using an EEG-BCI, we train one group of participants to control the movements of a cursor using embodied motor imagery. A second group is trained to control the cursor using abstract motor imagery. A third control group practices moving the cursor using an arm and finger on a touch screen. We hypothesized that if motor learning transfer is related to the use of shared neural structures then the embodied motor imagery group would show more learning transfer than the abstract imaging group. If, on the other hand, motor learning transfer results from more general cognitive processes, then the abstract motor imagery group should also demonstrate motor learning transfer to the manual performance of the same task. Our findings support that motor learning transfer is due to the use of shared neural structures between imaging and motor execution of a task. The abstract group showed no motor learning transfer despite being better at EEG-BCI control than the embodied group. The fact that more participants were able to learn EEG-BCI control using abstract imagery suggests that abstract imagery may be more suitable for EEG-BCIs for some disabilities, while embodied imagery may be more suitable for others. In Part 2, EEG data collected in the above experiment was used to train an artificial neural network (ANN) to map EEG signals to machine commands. We found that our open-source ANN using spectrograms generated from SFFTs is fundamentally different and in some ways superior to Emotiv's proprietary method. Our use of novel combinations of existing technologies along with abstract and embodied imagery facilitates adaptive customization of EEG-BCI control to meet needs of individual users.
Contributorsda Silva, Flavio J. K (Author) / Mcbeath, Michael K (Thesis advisor) / Helms Tillery, Stephen (Committee member) / Presson, Clark (Committee member) / Sugar, Thomas (Committee member) / Arizona State University (Publisher)
Created2013
Description
Insulation aging monitoring is widely used to evaluate the operating condition of power equipment. One important monitoring method is detecting partial discharges (PD). PD is a localized breakdown of dielectric and its characteristics can give information about the insulation aging. Most existing test methods cannot identify different kinds of defects. Also, the practical application of PD detection in most existing test methods is restricted by weak PD signals and strong electric field disturbance from surroundings. In order to monitor aging situation in detail, types of PDs are important features to take into account. To classify different types of PDs, pulse sequence analysis (PSA) method is advocated to analyze PDs in the rod-plane model. This method can reflect cumulative effects of PDs, which are always ignored when only measuring PD value. It also shows uniform characteristics when different kinds of detecting system are utilized. Moreover, it does not need calibration. Analysis results from PSA show highly consistent distribution patterns for the same type of PDs and significant differences in the distribution patterns among types of PDs. Furthermore, a new method to detect PD signals using fiber bragg grating (FBG) based PD sensor is studied in this research. By using a piezoelectric ceramic transducer (PZT), small PD signals can be converted to pressure signal and then converted to an optical wavelength signal with FBG. The optical signal is isolated from the electric field; therefore its attenuation and anti-jamming performance will be better than traditional methods. Two sensors, one with resonant frequency of 42.7 kHz and the other 300 kHz, were used to explore the performance of this testing system. However, there were issues with the sensitivity of the sensors of these devices and the results have been communicated with the company. These devices could not give the results at the same level of accuracy as the conventional methods.
ContributorsCui, Longfei (Author) / Gorur, Ravi (Thesis advisor) / Vittal, Vijay (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2013
Description
The future grid will face challenges to meet an increased power demand by the consumers. Various solutions were studied to address this issue. One alternative to realize increased power flow in the grid is to use High Temperature Low Sag (HTLS) since it fulfills essential criteria of less sag and good material performance with temperature. HTLS conductors like Aluminum Conductor Composite Reinforced (ACCR) and Aluminum Conductor Carbon Composite (ACCC) are expected to face high operating temperatures of 150-200 degree Celsius in order to achieve the desired increased power flow. Therefore, it is imperative to characterize the material performance of these conductors with temperature. The work presented in this thesis addresses the characterization of carbon composite core based and metal matrix core based HTLS conductors. The thesis focuses on the study of variation of tensile strength of the carbon composite core with temperature and the level of temperature rise of the HTLS conductors due to fault currents cleared by backup protection. In this thesis, Dynamic Mechanical Analysis (DMA) was used to quantify the loss in storage modulus of carbon composite cores with temperature. It has been previously shown in literature that storage modulus is correlated to the tensile strength of the composite. Current temperature relationships of HTLS conductors were determined using the IEEE 738-2006 standard. Temperature rise of these conductors due to fault currents were also simulated. All simulations were performed using Microsoft Visual C++ suite. Tensile testing of metal matrix core was also performed. Results of DMA on carbon composite cores show that the storage modulus, hence tensile strength, decreases rapidly in the temperature range of intended use. DMA on composite cores subjected to heat treatment were conducted to investigate any changes in the variation of storage modulus curves. The experiments also indicates that carbon composites cores subjected to temperatures at or above 250 degree Celsius can cause permanent loss of mechanical properties including tensile strength. The fault current temperature analysis of carbon composite based conductors reveal that fault currents eventually cleared by backup protection in the event of primary protection failure can cause damage to fiber matrix interface.
ContributorsBanerjee, Koustubh (Author) / Gorur, Ravi (Committee member) / Karady, George G. (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2014
Description
Although research has documented robust prospective relationships between externalizing symptomatology and subsequent binge drinking among adolescents, the extent to which internalizing symptoms increase risk for drinking remains controversial. In particular, the role of anxiety as a predictor of binge drinking remains unclear. Recent evidence suggests that one possible reason for these mixed findings is that separate dimensions of anxiety may differentially confer risk for alcohol use. The present study tested two dimensions of anxiety - worry and physiological anxiety -- as predictors of binge drinking in a longitudinal study of juvenile delinquents. Overall, results indicate that worry and physiological anxiety showed differential relations with drinking behavior. In general, worry was protective against alcohol use, whereas physiological anxiety conferred risk for binge drinking, but both effects were conditional on levels of offending. Implications for future research examining the role of anxiety in predicting drinking behavior among youth are discussed.
ContributorsNichter, Brandon (Author) / Chassin, Laurie (Thesis advisor) / Barrera, Manuel (Committee member) / Presson, Clark (Committee member) / Arizona State University (Publisher)
Created2014
Description
Fibromyalgia (FM) is a chronic musculoskeletal disorder characterized by widespread pain, fatigue, and a variety of other comorbid physiological and psychological characteristics, including a deficit of positive affect. Recently, the focus of research on the pathophysiology of FM has considered the role of a number of genomic variants. In the current manuscript, case-control analyses did not support the hypothesis that FM patients would differ from other chronic pain groups in catechol-O-methyltransferase (COMT) and mu-opioid receptor (OPRM1) genotype. However, evidence is provided in support of the hypothesis that functional single nucleotide polymorphisms on the COMT and OPRM1 genes would be associated with risk and resilience, respectively, in a dual processing model of pain-related positive affective regulation in FM. Forty-six female patients with a physician-confirmed diagnosis of FM completed an electronic diary that included once-daily assessments of positive affect and soft tissue pain. Multilevel modeling yielded a significant gene X environment interaction, such that individuals with met/met genotype on COMT experienced a greater decline in positive affect as daily pain increased than did either val/met or val/val individuals. A gene X environment interaction for OPRM1 also emerged, indicating that individuals with at least one asp allele were more resilient to elevations in daily pain than those homozygous for the asn allele. In sum, the findings offer researchers ample reason to further investigate the contribution of the catecholamine and opioid systems, and their associated genomic variants, to the still poorly understood experience of FM.
ContributorsFinan, Patrick Hamilton (Author) / Zautra, Alex (Thesis advisor) / Davis, Mary (Committee member) / Lemery-Chalfant, Kathryn (Committee member) / Presson, Clark (Committee member) / Arizona State University (Publisher)
Created2011
Description
When people pick up the phone to call a telephone quitline, they are taking an important step towards changing their smoking behavior. The current study investigated the role of a critical cognition in the cessation process--self-efficacy. Self-efficacy is thought to be influential in behavior change processes including those involved in the challenging process of stopping tobacco use. By applying basic principles of self-efficacy theory to smokers utilizing a telephone quitline, this study advanced our understanding of the nature of self-efficacy in a "real-world" cessation setting. Participants received between one and four intervention calls aimed at supporting them through their quit attempt. Concurrent with the initiation of this study, three items (confidence, stress, and urges) were added to the standard telephone protocol and assessed at each call. Two principal sets of hypotheses were tested using a combination of ANCOVAs and multiple regression analyses. The first set of hypotheses explored how self-efficacy and changes in self-efficacy within individuals were associated with cessation outcomes. Most research has found a positive linear relation between self-efficacy and quit outcomes, but this study tested the possibility that excessively high self-efficacy may actually reflect an overconfidence bias, and in some cases be negatively related to cessation outcomes. The second set of hypotheses addressed several smoking-related factors expected to affect self-efficacy. As predicted, higher baseline self-efficacy and increases in self-efficacy were associated with higher rates of quitting. However, contrary to predictions, there was no evidence that overconfidence led to diminished cessation success. Finally, as predicted, shorter duration of quit attempts, shorter time to relapse, and stronger urges all were associated with lower self-efficacy. In conclusion, understanding how self-efficacy and changes in self-efficacy affect and are affected by cessation outcomes is useful for informing both future research and current quitline intervention procedures.
ContributorsGoesling, Jenna (Author) / Barrera, Manuel (Thesis advisor) / Shiota, Lani (Committee member) / Enders, Craig (Committee member) / Presson, Clark (Committee member) / Arizona State University (Publisher)
Created2011
Description
This paper presents a theoretical model for evaluating flashover performance of insulators under contaminated conditions. The model introduces several new features when compared with existing models such as, the formation of dry bands, variations in insulator geometry and surface wettability. The electric field distribution obtained from software for 3-Dimensional models along with form factor are used to determine the dimensions of the dry bands and the onset of arcing. The model draws heavily from experimental measurements of flashover voltage and surface resistance under wet conditions of porcelain and composite insulators. The model illustrates the dominant role played by the insulator shape and housing material on the flashover performance.
ContributorsBo, Lin (Author) / Gorur, Ravi (Thesis advisor) / Vittal, Vijay (Committee member) / Farmer, Richard (Committee member) / Arizona State University (Publisher)
Created2012
Description
This research presents potential and electric field calculations on medium voltage (MV) epoxy insulated outdoor current transformers (CTs) using a numeri-cal calculation approach. Two designs of MV dry-type epoxy insulated CTs were modeled using 3D field simulation software COULOMB® 9.0. Potential and elec-tric fields were calculated based on boundary element method. Different condi-tions such as dry exterior surface, wet exterior surface and internal voids were considered. The research demonstrates that the presence of internal conductors in CTs results in a less severe surface electric field distribution when compared to outdoor insulators of the same voltage range and type. The high electric field near the exited end triple-point of the CT reduces. This remained true even under wet conditions establishing better outdoor performance of CTs than outdoor insulators which have no internal conductors. The effect of internal conductors on voids within the insulation structure was also established. As a down side, internal voids in CTs experience higher electric field stress than in conductor-less insulators. The work recognizes that internal conducting parts in dry type CTs improves their outdoor performance when compared to electrical equipment without internal conductors.
ContributorsLakshmichand Jain, Sandeep Kumar (Author) / Gorur, Ravi (Thesis advisor) / Karady, George G. (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2012
Description
In the United States, especially in metropolitan areas, transmission infra-structure is congested due to a combination of increasing load demands, declining investment, and aging facilities. It is anticipated that significant investments will be required for new construction and upgrades in order to serve load demands. This thesis explores higher phase order systems, specifically, six-phase, as a means of increasing power transfer capability, and provides a comparison with conventional three-phase double circuit transmission lines. In this thesis, the line parameters, electric and magnetic fields, and right of way are the criteria for comparing six-phase and three-phase double circuit lines. The calculations of the criteria were achieved by a program developed using MATLAB. This thesis also presents fault analysis and recommends suitable pro-tection for six-phase transmission lines. This calculation was performed on 4-bus, 9-bus, and 118-bus systems from Powerworld® sample cases. The simulations were performed using Powerworld® and PSCAD®. Line parameters calculations performed in this thesis show that line imped-ances in six-phase lines have a slight difference, compared to three-phase double circuit line. The shunt capacitance of compacted six phase line is twice of the value in the three-phase double circuit line. As a consequence, the compacted six-phase line provides higher surge impedance loadings. The electric and magnetic fields calculations show that, ground level electric fields of the six-phase lines decline more rapidly as the distance from center of the lines increase. The six-phase lines have a better performance on ground level magnetic field. Based on the electric and magnetic field results, right of way re-quirements for the six-phase lines and three-phase double circuit line were calcu-lated. The calculation results of right of way show that six-phase lines provide higher power transfer capability with a given right of way. Results from transmission line fault analysis, and protection study show that, fault types and protection system in six-phase lines are more complicated, com-pared to three-phase double circuit line. To clarify the concern about six-phase line protection, a six-phase line protection system was designed. Appropriate pro-tection settings were determined for a six-phase line in the 4-bus system.
ContributorsDeng, Xianda (Author) / Gorur, Ravi (Thesis advisor) / Heydt, Gerald (Committee member) / Vittal, Vijay (Committee member) / Arizona State University (Publisher)
Created2012
Description
This purpose of this thesis study was to examine variables of the "War on Cancer" frame, loss-gain prime, and patient gender on treatment decision for advanced cancer patients. A total of 291 participants (141 females) participated in an online survey experiment and were randomly assigned to one of eight possible conditions, each of which were comprised of a combination of one of two levels for three total independent variables: war frame ("War on Cancer" frame or neutral frame), loss-gain prime (loss prime or gain prime), and patient gender (female or male). Each of the three variables were operationalized to determine whether or not the exposure to the war on cancer paradigm, loss-frame language, or male patient gender would increase the likelihood of a participant choosing a more aggressive cancer treatment. Participants read a patient scenario and were asked to respond to questions related to motivating factors. Participants were then asked to report preference for one of two treatment decisions. Participants were then asked to provide brief demographic information in addition to responding to questions about military history, war attitudes, and cancer history. The aforementioned manipulations sought to determine whether exposure to various factors would make a substantive difference in final treatment decision. Contrary to the predicted results, participants in the war frame condition (M = 3.85, SD = 1.48) were more likely to choose the pursuit of palliative care (as opposed to aggressive treatment) than participants in the neutral frame condition (M = 3.54, SD = 1.23). Ultimately, these significant findings suggest that there is practical information to be gained from treatment presentation manipulations. By arming healthcare providers with a more pointed understanding of the nuances of treatment presentation, we can hope to empower patients, their loved ones, and healthcare providers entrenched in the world of cancer treatment.
ContributorsKnowles, Madelyn Ann (Author) / Kwan, Virginia S. Y. (Thesis director) / Presson, Clark (Committee member) / Salamone, Damien (Committee member) / Department of Psychology (Contributor) / School of Human Evolution and Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05