Matching Items (345)
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As the 3rd generation solar cell, quantum dot solar cells are expected to outperform the first 2 generations with higher efficiency and lower manufacture cost. Currently the main problems for QD cells are the low conversion efficiency and stability. This work is trying to improve the reliability as well as

As the 3rd generation solar cell, quantum dot solar cells are expected to outperform the first 2 generations with higher efficiency and lower manufacture cost. Currently the main problems for QD cells are the low conversion efficiency and stability. This work is trying to improve the reliability as well as the device performance by inserting an interlayer between the metal cathode and the active layer. Titanium oxide and a novel nitrogen doped titanium oxide were compared and TiOxNy capped device shown a superior performance and stability to TiOx capped one. A unique light anneal effect on the interfacial layer was discovered first time and proved to be the trigger of the enhancement of both device reliability and efficiency. The efficiency was improved by 300% and the device can retain 73.1% of the efficiency with TiOxNy when normal device completely failed after kept for long time. Photoluminescence indicted an increased charge disassociation rate at TiOxNy interface. External quantum efficiency measurement also inferred a significant performance enhancement in TiOxNy capped device, which resulted in a higher photocurrent. X-ray photoelectron spectrometry was performed to explain the impact of light doping on optical band gap. Atomic force microscopy illustrated the effect of light anneal on quantum dot polymer surface. The particle size is increased and the surface composition is changed after irradiation. The mechanism for performance improvement via a TiOx based interlayer was discussed based on a trap filling model. Then Tunneling AFM was performed to further confirm the reliability of interlayer capped organic photovoltaic devices. As a powerful tool based on SPM technique, tunneling AFM was able to explain the reason for low efficiency in non-capped inverted organic photovoltaic devices. The local injection properties as well as the correspondent topography were compared in organic solar cells with or without TiOx interlayer. The current-voltage characteristics were also tested at a single interested point. A severe short-circuit was discovered in non capped devices and a slight reverse bias leakage current was also revealed in TiOx capped device though tunneling AFM results. The failure reason for low stability in normal devices was also discussed comparing to capped devices.
ContributorsYu, Jialin (Author) / Jabbour, Ghassan E. (Thesis advisor) / Alford, Terry L. (Thesis advisor) / Yu, Hongbin (Committee member) / Arizona State University (Publisher)
Created2011
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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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Semiconductor nanowires are featured by their unique one-dimensional structure which makes them promising for small scale electronic and photonic device applications. Among them, III-V material nanowires are particularly outstanding due to their good electronic properties. In bulk, these materials reveal electron mobility much higher than conventional silicon based devices, for

Semiconductor nanowires are featured by their unique one-dimensional structure which makes them promising for small scale electronic and photonic device applications. Among them, III-V material nanowires are particularly outstanding due to their good electronic properties. In bulk, these materials reveal electron mobility much higher than conventional silicon based devices, for example at room temperature, InAs field effect transistor (FET) has electron mobility of 40,000 cm2/Vs more than 10 times of Si FET. This makes such materials promising for high speed nanowire FETs. With small bandgap, such as 0.354 eV for InAs and 1.52 eV for GaAs, it does not need high voltage to turn on such devices which leads to low power consumption devices. Another feature of direct bandgap allows their applications of optoelectronic devices such as avalanche photodiodes. However, there are challenges to face up. Due to their large surface to volume ratio, nanowire devices typically are strongly affected by the surface states. Although nanowires can be grown into single crystal structure, people observe crystal defects along the wires which can significantly affect the performance of devices. In this work, FETs made of two types of III-V nanowire, GaAs and InAs, are demonstrated. These nanowires are grown by catalyst-free MOCVD growth method. Vertically nanowires are transferred onto patterned substrates for coordinate calibration. Then electrodes are defined by e-beam lithography followed by deposition of contact metals. Prior to metal deposition, however, the substrates are dipped in ammonium hydroxide solution to remove native oxide layer formed on nanowire surface. Current vs. source-drain voltage with different gate bias are measured at room temperature. GaAs nanowire FETs show photo response while InAs nanowire FETs do not show that. Surface passivation is performed on GaAs FETs by using ammonium surfide solution. The best results on current increase is observed with around 20-30 minutes chemical treatment time. Gate response measurements are performed at room temperature, from which field effect mobility as high as 1490 cm2/Vs is extracted for InAs FETs. One major contributor for this is stacking faults defect existing along nanowires. For InAs FETs, thermal excitations observed from temperature dependent results which leads us to investigate potential barriers.
ContributorsLiang, Hanshuang (Author) / Yu, Hongbin (Thesis advisor) / Ferry, David (Committee member) / Tracy, Clarence (Committee member) / Arizona State University (Publisher)
Created2011
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A workload-aware low-power neuromorphic controller for dynamic power and thermal management in VLSI systems is presented. The neuromorphic controller predicts future workload and temperature values based on the past values and CPU performance counters and preemptively regulates supply voltage and frequency. System-level measurements from stateof-the-art commercial microprocessors are used to

A workload-aware low-power neuromorphic controller for dynamic power and thermal management in VLSI systems is presented. The neuromorphic controller predicts future workload and temperature values based on the past values and CPU performance counters and preemptively regulates supply voltage and frequency. System-level measurements from stateof-the-art commercial microprocessors are used to get workload, temperature and CPU performance counter values. The controller is designed and simulated using circuit-design and synthesis tools. At device-level, on-chip planar inductors suffer from low inductance occupying large chip area. On-chip inductors with integrated magnetic materials are designed, simulated and fabricated to explore performance-efficiency trade offs and explore potential applications such as resonant clocking and on-chip voltage regulation. A system level study is conducted to evaluate the effect of on-chip voltage regulator employing magnetic inductors as the output filter. It is concluded that neuromorphic power controller is beneficial for fine-grained per-core power management in conjunction with on-chip voltage regulators utilizing scaled magnetic inductors.
ContributorsSinha, Saurabh (Author) / Cao, Yu (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Yu, Hongbin (Committee member) / Christen, Jennifer B. (Committee member) / Arizona State University (Publisher)
Created2011
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Description

Within the pediatric hospitalization experience, fear and anxiety are two emotions commonly felt by children of all ages. Hospitalized children can greatly benefit from interventions designed to help them cope with these emotions throughout their medical experiences. This study draws on each of our clinical experiences as volunteers at Phoenix

Within the pediatric hospitalization experience, fear and anxiety are two emotions commonly felt by children of all ages. Hospitalized children can greatly benefit from interventions designed to help them cope with these emotions throughout their medical experiences. This study draws on each of our clinical experiences as volunteers at Phoenix Children’s Hospital, and uses a qualitative analysis of three semi-structured interviews with currently employed Child Life Specialists to understand and analyze the use of medical play, a form of play intervention with a medical theme or medical equipment. We explore the goals and benefits of medical play for hospitalized pediatric patients, the process of using medical play as an intervention, including the activity design process, the assessments and adjustments made throughout the child’s hospitalization, and the considerations and limitations to implementing medical play activities. Ultimately, we found that the element of fun that defines play can be channeled into medical play activities implemented by skilled Child Life Specialists, who are experts in their field, in clinical settings to promote several different and beneficial goals, including pediatric patient coping.

ContributorsGarciapena, Danae (Co-author) / Aguiar, Lara (Co-author) / Loebenberg, Abby (Thesis director) / Swanson, Jodi (Committee member) / College of Health Solutions (Contributor) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Veterans are approximately 30% more likely than non-veterans to suffer from severe hearing impairment. Tinnitus, or ringing in the ears, which is increasingly common among military service men and women, has been linked to significant cognitive and psychological impairment and can be worsened by the same sounds that trigger post-traumatic

Veterans are approximately 30% more likely than non-veterans to suffer from severe hearing impairment. Tinnitus, or ringing in the ears, which is increasingly common among military service men and women, has been linked to significant cognitive and psychological impairment and can be worsened by the same sounds that trigger post-traumatic stress disorder (PTSD). In fact, tinnitus and PTSD often present as comorbidities, and recent studies suggest these two disorders may share a common neurological pathway. Additional studies are required to better understand the connection between hearing loss and impaired cognitive function such as that observed in with PTSD. Here, we use the fruit fly, Drosophila melanogaster, to explore the relationship between hearing loss and cognitive function. Negative geotaxis climbing assays and courtship behavior analysis were used to examine neurobehavioral changes induced by prolonged, intense auditory stimulation. Preliminary results suggest that exposure to loud noise for an extended period of time significantly affected Drosophila behavior, with males being more sensitive than females. Based on our results, there appears to be a potential connection between noise exposure and behavior, further suggesting that Drosophila could be an effective model to study the link between hearing loss and PTSD.

ContributorsMichael, Allison Faye (Author) / Hackney-Price, Jennifer (Thesis director) / Sellner, Erin (Committee member) / School of Social and Behavioral Sciences (Contributor) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Socioeconomic differences have driven society and laid the foundation for the types of opportunities and resources one is eligible to receive. Higher socioeconomic status provides individuals the chance of obtaining an overall better education, occupation, and income. We see this with particular clarity when we examine healthcare. The World Health

Socioeconomic differences have driven society and laid the foundation for the types of opportunities and resources one is eligible to receive. Higher socioeconomic status provides individuals the chance of obtaining an overall better education, occupation, and income. We see this with particular clarity when we examine healthcare. The World Health Organization has regarded healthcare as a fundamental human right, except socioeconomically disadvantaged individuals not only do not have equal access to healthcare, but they also often receive a lower quality of care. These socioeconomic differences are often paired with racial differences, resulting in one group, or set of groups, having social advantage over the others. Although this problem has been discussed throughout the past century, it has not been properly addressed materially and practically. Unequal access to quality healthcare is especially highlighted throughout the COVID-19 pandemic, where there has been evidence that minorities, in particular Black communities, have received inadequate care. Quality healthcare has become unaffordable and a luxury that only certain groups get the privilege of receiving. Not only that, but the ongoing inequalities in the healthcare system have gone so far that they have instilled hostility and mistrust towards the healthcare system.

ContributorsMartinez Castro, Karen (Author) / Sturgess, Jessica (Thesis director) / Sellner, Erin (Committee member) / School of Social and Behavioral Sciences (Contributor) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Collective human attitudes influenced by macro-forces that impact environmental issues are partially correlated to our behaviors for the good and the harm of the planet. In this thesis, I will explore how collective human attitudes contribute to pro-environmental behaviors, common and pre-existing frames of mind on major conservation dilemmas, and

Collective human attitudes influenced by macro-forces that impact environmental issues are partially correlated to our behaviors for the good and the harm of the planet. In this thesis, I will explore how collective human attitudes contribute to pro-environmental behaviors, common and pre-existing frames of mind on major conservation dilemmas, and finally suggest future directions on how humans could be inclined to take on more environmental responsibility through an increase in human-environmental connectivity. It is found that humans are largely driven by institution structures, education, and social influence. In conclusion, more efforts should be placed to further analyze these structural incentives for pro-environmental behaviors and use them to make environmental stewardship more accessible for all people and diverse circumstances. This can be done by evaluating the human dimensions of what influences human attitudes and behaviors, how to use these forces to systematically influence pro-environmental choices, applying these structural forces to main conservation issues, and further incorporating moral discourse into the environmental research in order to appeal correctly to all aspects and perspectives. Only when human connectivity is understood in relation to the natural sciences will we be able to make positive change in the direction of a healthier Earth.

ContributorsCheek, Alana C (Author) / Vargas, Perla (Thesis director) / Keahey, Jennifer (Committee member) / School of Humanities, Arts, and Cultural Studies (Contributor) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Forensic entomology is an important field of forensic science that utilizes insect evidence in criminal investigations. Blow flies (Diptera: Calliphoridae) are among the first colonizers of remains and are therefore frequently used in determining the minimum postmortem interval (mPMI). Blow fly development, however, is influenced by a variety of factors

Forensic entomology is an important field of forensic science that utilizes insect evidence in criminal investigations. Blow flies (Diptera: Calliphoridae) are among the first colonizers of remains and are therefore frequently used in determining the minimum postmortem interval (mPMI). Blow fly development, however, is influenced by a variety of factors including temperature and feeding substrate type. Unfortunately, dietary fat content remains an understudied factor on the development process, which is problematic given the relatively high rates of obesity in the United States. To study the effects of fat content on blow fly development we investigated the survivorship, adult weight and development of Lucilia sericata (Meigen; Diptera: Calliphoridae) and Phormia regina (Meigen; Diptera: Calliphoridae) on ground beef with a 10%, 20%, or 27% fat content. As fat content increased, survivorship decreased across both species with P. regina being significantly impacted. While P. regina adults were generally larger than L. sericata across all fat levels, only L. sericata demonstrated a significant (P < 0.05) difference in weight by sex. Average total development times for P. regina are comparable to averages published in other literature. Average total development times for L. sericata, however, were nearly 50 hours higher. These findings provide insight on the effect of fat content on blow fly development, a factor that should be considered when estimating a mPMI. By understanding how fat levels affect the survivorship and development of the species studied here, we can begin improving the practice of insect evidence analysis in casework.

ContributorsNoblesse, Andrew (Author) / Weidner, Lauren (Thesis director) / Parrott, Jonathan (Committee member) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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The ongoing Global Coronavirus Pandemic has been upheaving social norms for over a<br/>year at this point. For countless people, our lives look very different at this point in time<br/>then they did before the pandemic began. Quarantine, Shelter in Place, Work from<br/>Home, and Online classes have led global populations to become

The ongoing Global Coronavirus Pandemic has been upheaving social norms for over a<br/>year at this point. For countless people, our lives look very different at this point in time<br/>then they did before the pandemic began. Quarantine, Shelter in Place, Work from<br/>Home, and Online classes have led global populations to become less active leading to<br/>an increase in sedentary lifestyles. The final impact of this consequence is unknown,<br/>but emerging studies have led to concrete evidence of decreased physical and mental<br/>wellbeing, particularly in children. VirusFreeSports was the brainchild of three ASU<br/>Honors students who sought to remedy these devastating consequences by creating<br/>environments where children can participate in sports and exercise safely, free of the<br/>threat COVID-19 or other transmissible illnesses. The ultimate goal for the project team<br/>was to build traction for their idea, which culminated in a video pitch sent to potential<br/>investors. Although largely created as an exercise and we did not create a full<br/>certification course, merely a prototype through a website with sample questions to<br/>gauge interest, the project was a success as a large target market for this product was<br/>identified that showed great promise. Our team believes that early entrance to the<br/>market, as well as the lack of any other competitors would give the team a tremendous<br/>advantage in creating an impactful and influential service.

ContributorsTanveer, Samad (Co-author) / Israel, Natasha (Co-author) / Vrbanac, Matthew (Co-author) / Byrne, Jared (Thesis director) / Lee, Chris (Committee member) / Kunowski, Jeff (Committee member) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05