Matching Items (13)
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- Genre: Masters Thesis
- Creators: Arizona State University
- Creators: Chakraborty, Bijeta
- Member of: ASU Electronic Theses and Dissertations
Description
The increasing popularity of Twitter renders improved trustworthiness and relevance assessment of tweets much more important for search. However, given the limitations on the size of tweets, it is hard to extract measures for ranking from the tweet's content alone. I propose a method of ranking tweets by generating a reputation score for each tweet that is based not just on content, but also additional information from the Twitter ecosystem that consists of users, tweets, and the web pages that tweets link to. This information is obtained by modeling the Twitter ecosystem as a three-layer graph. The reputation score is used to power two novel methods of ranking tweets by propagating the reputation over an agreement graph based on tweets' content similarity. Additionally, I show how the agreement graph helps counter tweet spam. An evaluation of my method on 16~million tweets from the TREC 2011 Microblog Dataset shows that it doubles the precision over baseline Twitter Search and achieves higher precision than current state of the art method. I present a detailed internal empirical evaluation of RAProp in comparison to several alternative approaches proposed by me, as well as external evaluation in comparison to the current state of the art method.
ContributorsRavikumar, Srijith (Author) / Kambhampati, Subbarao (Thesis advisor) / Davulcu, Hasan (Committee member) / Liu, Huan (Committee member) / Arizona State University (Publisher)
Created2013
Description
Efficiency of components is an ever increasing area of importance to portable applications, where a finite battery means finite operating time. Higher efficiency devices need to be designed that don't compromise on the performance that the consumer has come to expect. Class D amplifiers deliver on the goal of increased efficiency, but at the cost of distortion. Class AB amplifiers have low efficiency, but high linearity. By modulating the supply voltage of a Class AB amplifier to make a Class H amplifier, the efficiency can increase while still maintaining the Class AB level of linearity. A 92dB Power Supply Rejection Ratio (PSRR) Class AB amplifier and a Class H amplifier were designed in a 0.24um process for portable audio applications. Using a multiphase buck converter increased the efficiency of the Class H amplifier while still maintaining a fast response time to respond to audio frequencies. The Class H amplifier had an efficiency above the Class AB amplifier by 5-7% from 5-30mW of output power without affecting the total harmonic distortion (THD) at the design specifications. The Class H amplifier design met all design specifications and showed performance comparable to the designed Class AB amplifier across 1kHz-20kHz and 0.01mW-30mW. The Class H design was able to output 30mW into 16Ohms without any increase in THD. This design shows that Class H amplifiers merit more research into their potential for increasing efficiency of audio amplifiers and that even simple designs can give significant increases in efficiency without compromising linearity.
ContributorsPeterson, Cory (Author) / Bakkaloglu, Bertan (Thesis advisor) / Barnaby, Hugh (Committee member) / Kiaei, Sayfe (Committee member) / Arizona State University (Publisher)
Created2013
Description
Class D Amplifiers are widely used in portable systems such as mobile phones to achieve high efficiency. The demands of portable electronics for low power consumption to extend battery life and reduce heat dissipation mandate efficient, high-performance audio amplifiers. The high efficiency of Class D amplifiers (CDAs) makes them particularly attractive for portable applications. The Digital class D amplifier is an interesting solution to increase the efficiency of embedded systems. However, this solution is not good enough in terms of PWM stage linearity and power supply rejection. An efficient control is needed to correct the error sources in order to get a high fidelity sound quality in the whole audio range of frequencies. A fundamental analysis on various error sources due to non idealities in the power stage have been discussed here with key focus on Power supply perturbations driving the Power stage of a Class D Audio Amplifier. Two types of closed loop Digital Class D architecture for PSRR improvement have been proposed and modeled. Double sided uniform sampling modulation has been used. One of the architecture uses feedback around the power stage and the second architecture uses feedback into digital domain. Simulation & experimental results confirm that the closed loop PSRR & PS-IMD improve by around 30-40 dB and 25 dB respectively.
ContributorsChakraborty, Bijeta (Author) / Bakkaloglu, Bertan (Thesis advisor) / Garrity, Douglas (Committee member) / Ozev, Sule (Committee member) / Arizona State University (Publisher)
Created2012
Description
Human-robot interaction has expanded immensely within dynamic environments. The goals of human-robot interaction are to increase productivity, efficiency and safety. In order for the integration of human-robot interaction to be seamless and effective humans must be willing to trust the capabilities of assistive robots. A major priority for human-robot interaction should be to understand how human dyads have been historically effective within a joint-task setting. This will ensure that all goals can be met in human robot settings. The aim of the present study was to examine human dyads and the effects of an unexpected interruption. Humans’ interpersonal and individual levels of trust were studied in order to draw appropriate conclusions. Seventeen undergraduate and graduate level dyads were collected from Arizona State University. Participants were broken up into either a surprise condition or a baseline condition. Participants individually took two surveys in order to have an accurate understanding of levels of dispositional and individual levels of trust. The findings showed that participant levels of interpersonal trust were average. Surprisingly, participants who participated in the surprise condition afterwards, showed moderate to high levels of dyad trust. This effect showed that participants became more reliant on their partners when interrupted by a surprising event. Future studies will take this knowledge and apply it to human-robot interaction, in order to mimic the seamless team-interaction shown in historically effective dyads, specifically human team interaction.
ContributorsShaw, Alexandra Luann (Author) / Chiou, Erin (Thesis advisor) / Cooke, Nancy J. (Committee member) / Craig, Scotty (Committee member) / Arizona State University (Publisher)
Created2019
Description
Social scientists from many disciplines have examined trust, including trust between those with different religious affiliations, emotional antecedents of trust, and physiological correlates of trust. However, little is known about how all of these factors intersect to shape trust behaviors. The current study aimed to examine physiological responses while individuals engaged in a trust game with a religious in-group or out-group member. Participants were randomly assigned to one of four conditions in which they were presented with the target’s profile before playing the game. In each of the conditions the target was described as either Catholic or Muslim and as someone who engaged in either costly signaling or anti-costly signaling behavior. In addition to assessing the amount of money invested as a behavioral measure of trust, physiological responses, specifically cardiac interbeat interval (IBI) and respiratory sinus arrhythmia (RSA), were measured. I hypothesized that when playing the trust game with a Catholic target as opposed to a Muslim target, Christian participants would (1) report being more similar to the target, (2) trust the target more, (3) invest more money in the target, (4) have a more positive outlook on the amount invested, and (5) show greater cardiorespiratory down-regulation, reflected by increases in IBI and RSA. Findings revealed that Christian participants reported greater similarity and showed a non-significant trend toward reporting a more positive outlook on (greater confidence in/satisfaction with) their investment decision when playing a Catholic versus Muslim target. Additionally, Christian participants who played an anti-costly signaling Catholic target showed greater cardiorespiratory down-regulation (increases from baseline for IBI, reflecting slower heart rate, and increases in RSA) than Christian participants who played an anti-costly signaling Muslim target. Results from this study echo previous findings suggesting that perceived similarity may facilitate trust. Findings also are consistent with previous research suggesting that religious ingroup or outgroup membership may not be as influential in shaping trust decisions if the trustee is costly signaling; for anti-signaling, however, cardiorespiratory down-regulation to a religious ingroup member may be apparent. These physiological signals may provide interoceptive information about a peer’s trustworthiness.
ContributorsThibault, Stephanie A (Author) / Roberts, Nicole A. (Thesis advisor) / Burleson, Mary (Committee member) / Hall, Deborah (Committee member) / Arizona State University (Publisher)
Created2019
Description
Reading partners’ actions correctly is essential for successful coordination, but interpretation does not always reflect reality. Attribution biases, such as self-serving and correspondence biases, lead people to misinterpret their partners’ actions and falsely assign blame after an unexpected event. These biases thus further influence people’s trust in their partners, including machine partners. The increasing capabilities and complexity of machines allow them to work physically with humans. However, their improvements may interfere with the accuracy for people to calibrate trust in machines and their capabilities, which requires an understanding of attribution biases’ effect on human-machine coordination. Specifically, the current thesis explores how the development of trust in a partner is influenced by attribution biases and people’s assignment of blame for a negative outcome. This study can also suggest how a machine partner should be designed to react to environmental disturbances and report the appropriate level of information about external conditions.
ContributorsHsiung, Chi-Ping (M.S.) (Author) / Chiou, Erin (Thesis advisor) / Cooke, Nancy J. (Thesis advisor) / Zhang, Wenlong (Committee member) / Arizona State University (Publisher)
Created2019
Description
In this thesis, a digital input class D audio amplifier system which has the ability
to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress the power supply noise and harmonic distortions. The design is using global foundry 0.18um technology.
Based on simulation, the power supply rejection at 200Hz is about -49dB with
81dB dynamic range and -70dB THD+N. The full scale output power can reach as high as 27mW and still keep minimum -68dB THD+N. The system efficiency at full scale is about 82%.
to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress the power supply noise and harmonic distortions. The design is using global foundry 0.18um technology.
Based on simulation, the power supply rejection at 200Hz is about -49dB with
81dB dynamic range and -70dB THD+N. The full scale output power can reach as high as 27mW and still keep minimum -68dB THD+N. The system efficiency at full scale is about 82%.
ContributorsBai, Jing (Author) / Bakkaloglu, Bertan (Thesis advisor) / Arizona State University (Publisher)
Created2015
Description
With the growth of autonomous vehicles’ prevalence, it is important to understand the relationship between autonomous vehicles and the other drivers around them. More specifically, how does one’s knowledge about autonomous vehicles (AV) affect positive and negative affect towards driving in their presence? Furthermore, how does trust of autonomous vehicles correlate with those emotions? These questions were addressed by conducting a survey to measure participant’s positive affect, negative affect, and trust when driving in the presence of autonomous vehicles. Participants’ were issued a pretest measuring existing knowledge of autonomous vehicles, followed by measures of affect and trust. After completing this pre-test portion of the study, participants were given information about how autonomous vehicles work, and were then presented with a posttest identical to the pretest. The educational intervention had no effect on positive or negative affect, though there was a positive relationship between positive affect and trust and a negative relationship between negative affect and trust. These findings will be used to inform future research endeavors researching trust and autonomous vehicles using a test bed developed at Arizona State University. This test bed allows for researchers to examine the behavior of multiple participants at the same time and include autonomous vehicles in studies.
ContributorsMartin, Sterling (Author) / Cooke, Nancy J. (Thesis advisor) / Chiou, Erin (Committee member) / Gray, Robert (Committee member) / Arizona State University (Publisher)
Created2019
Description
Human-robot teams (HRTs) have seen more frequent use over the past few years,specifically, in the context of Search and Rescue (SAR) environments. Trust is an important factor in the success of HRTs. Both trust and reliance must be appropriately calibrated for the human operator to work faultlessly with a robot teammate. In highly complex and time restrictive environments, such as a search and rescue mission following a disaster, uncertainty information may be given by the robot in the form of confidence to help properly calibrate trust and reliance. This study seeks to examine the impact that confidence information may have on trust and how it may help calibrate reliance in complex HRTs. Trust and reliance data were gathered using a simulated SAR task environment for participants who then received confidence information from the robot for one of two missions. Results from this study indicated that trust was higher when participants received confidence information from the robot, however, no clear relationship between confidence and reliance were found. The findings from this study can be used to further improve human-robot teaming in search and rescue tasks.
ContributorsWolff, Alexandra (Author) / Cooke, Nancy J (Thesis advisor) / Chiou, Erin (Committee member) / Gray, Rob (Committee member) / Arizona State University (Publisher)
Created2022
Description
Food-sharing is central to the human experience, involving biological and sociocultural functions. In small-scale societies, sharing food reduces variance in daily food-consumption, allowing effective risk-management, and creating networks of interdependence. It was hypothesized that trust and interdependence would be fostered between people who shared food. Recruiting 221 participants (51% Female, Mage = 19.31), sharing food was found to decrease trust and interdependence in a Trust Game with $3.00 and a Dictator Game with chocolates. Participants trusted the least and gave the fewest chocolates when sharing food. Contrary to lay beliefs about sharing food, breaking bread with strangers may hinder rather than foster trust and giving in situations where competition over limited resources is salient, or under one-shot scenarios where people are unlikely to see each other again in the future.
ContributorsGuevara Beltran, Diego Guevara (Author) / Aktipis, Athena C (Thesis advisor) / Kenrick, Douglas T. (Committee member) / Varnum, Michael C (Committee member) / Arizona State University (Publisher)
Created2020