Matching Items (24)
Filtering by
- All Subjects: engineering
- Creators: Goryll, Michael
Description
Color perception has been widely studied and well modeled with respect to combining visible electromagnetic frequencies, yet new technology provides the means to better explore and test novel temporal frequency characteristics of color perception. Experiment 1 tests how reliably participants categorize static spectral rainbow colors, which can be a useful tool for efficiently identifying those with functional dichromacy, trichromacy, and tetrachromacy. The findings confirm that all individuals discern the four principal opponent process colors, red, yellow, green, and blue, with normal and potential tetrachromats seeing more distinct colors than color blind individuals. Experiment 2 tests the moving flicker fusion rate of the central electromagnetic frequencies within each color category found in Experiment 1 as a test of the Where system. It then compares this to the maximum temporal processing rate for discriminating direction of hue change with colors displayed serially as a test of the What system. The findings confirm respective processing thresholds of about 20 Hz for Where and 2-7 Hz for What processing systems. Experiment 3 tests conditions that optimize false colors based on the spinning Benham’s Top illusion. Findings indicate the same four principal colors emerge as in Experiment 1, but at low saturation levels for trichromats that diminish further for dichromats. Taken together, the three experiments provide an overview of the common categorical boundaries and temporal processing limits of human color vision.
ContributorsKrynen, Richard Chandler (Author) / Mcbeath, Michael K (Thesis advisor) / Homa, Donald (Committee member) / Newman, Nathan (Committee member) / Stone, Greg (Committee member) / Arizona State University (Publisher)
Created2021
Description
A Microbial fuel cell (MFC) is a bio-inspired carbon-neutral, renewable electrochemical converter to extract electricity from catabolic reaction of micro-organisms. It is a promising technology capable of directly converting the abundant biomass on the planet into electricity and potentially alleviate the emerging global warming and energy crisis. The current and power density of MFCs are low compared with conventional energy conversion techniques. Since its debut in 2002, many studies have been performed by adopting a variety of new configurations and structures to improve the power density. The reported maximum areal and volumetric power densities range from 19 mW/m2 to 1.57 W/m2 and from 6.3 W/m3 to 392 W/m3, respectively, which are still low compared with conventional energy conversion techniques. In this dissertation, the impact of scaling effect on the performance of MFCs are investigated, and it is found that by scaling down the characteristic length of MFCs, the surface area to volume ratio increases and the current and power density improves. As a result, a miniaturized MFC fabricated by Micro-Electro-Mechanical System(MEMS) technology with gold anode is presented in this dissertation, which demonstrate a high power density of 3300 W/m3. The performance of the MEMS MFC is further improved by adopting anodes with higher surface area to volume ratio, such as carbon nanotube (CNT) and graphene based anodes, and the maximum power density is further improved to a record high power density of 11220 W/m3. A novel supercapacitor by regulating the respiration of the bacteria is also presented, and a high power density of 531.2 A/m2 (1,060,000 A/m3) and 197.5 W/m2 (395,000 W/m3), respectively, are marked, which are one to two orders of magnitude higher than any previously reported microbial electrochemical techniques.
ContributorsRen, Hao (Author) / Chae, Junseok (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Phillips, Stephen (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2016
Description
The coexistence of superconductivity and ferromagnetic orders has been the subject of study for many years. It well known that these materials possess two competing order parameters; however the two order parameters can coexist under special circumstances inducing interesting physical phenomena. In recent years the demand of ultra-low-power, high density cryogenic memories has brought considerable interest to integrate superconducting and magnetic thin films in one structure to produce novel memory elements. The operation of the device depends on the unusual electronic properties associated with the Superconductor (S) /Ferromagnetic (F) proximity effect.
Niobium (Nb) based Josephson junction devices were fabricated with barriers containing two ferromagnetic layers separated by a normal metal space layer. In device operation, electrons in the superconductor are injected into the ferromagnets, causing the superconductor wavefunction to shift its phase and decay in amplitude. Such devices have two different states that depend on the relative magnetization of their ferromagnetic barrier layers, parallel or antiparallel. In these different states, the junctions have different phase shifts and critical currents. Superconducting circuits containing these devices can be designed to operate as memory cells using either one of these outputs.
To quantify the shift in phase and amplitude decay of the wavefunction through a common ferromagnet, permalloy, a series of Nb/permalloy/Nb Josephson junctions with varying ferromagnetic layer thicknesses were fabricated. Data have shown that the optimal thickness of a fixed layer composed of permalloy is 2.4 nm, as it shifts the wavefunction phase to π/2, its “pivot point.” If set to precisely this value, the free layer in SFNF'S junctions will switch the junction into either the 0 or π state depending on its magnetic orientation. To minimize the free-layer switching energy dilute Cu-permalloy alloy [Cu0.7(Ni80Fe20)0.3] with a low magnetic saturation (Ms of ~80 emu/cm3) was used as the free layer. These devices exhibit switching energies at small magnetic fields, demonstrating their potential use for low power non-volatile memory for superconductor circuits.
Lastly, to study the proximity effect using other potentially-useful ferromagnetic layers, measurements were performed on Nb/F bilayers and Nb/F/AlOx/Al tunnel junctions with ferromagnets Ni8Fe19, Ni65Fe15Co20, and Pd1-xNix. The dependence of the critical temperature of the bilayers and density of states that propagated through the ferromagnetic layer were studied as a function of thickness. From this study, crucial magnetic and electrical parameters like magnetic coherence lengths (ξF), exchange energy (Eex), and the rate of shift in the wavefunction’s phase and amplitude as a function of thickness were determined.
Niobium (Nb) based Josephson junction devices were fabricated with barriers containing two ferromagnetic layers separated by a normal metal space layer. In device operation, electrons in the superconductor are injected into the ferromagnets, causing the superconductor wavefunction to shift its phase and decay in amplitude. Such devices have two different states that depend on the relative magnetization of their ferromagnetic barrier layers, parallel or antiparallel. In these different states, the junctions have different phase shifts and critical currents. Superconducting circuits containing these devices can be designed to operate as memory cells using either one of these outputs.
To quantify the shift in phase and amplitude decay of the wavefunction through a common ferromagnet, permalloy, a series of Nb/permalloy/Nb Josephson junctions with varying ferromagnetic layer thicknesses were fabricated. Data have shown that the optimal thickness of a fixed layer composed of permalloy is 2.4 nm, as it shifts the wavefunction phase to π/2, its “pivot point.” If set to precisely this value, the free layer in SFNF'S junctions will switch the junction into either the 0 or π state depending on its magnetic orientation. To minimize the free-layer switching energy dilute Cu-permalloy alloy [Cu0.7(Ni80Fe20)0.3] with a low magnetic saturation (Ms of ~80 emu/cm3) was used as the free layer. These devices exhibit switching energies at small magnetic fields, demonstrating their potential use for low power non-volatile memory for superconductor circuits.
Lastly, to study the proximity effect using other potentially-useful ferromagnetic layers, measurements were performed on Nb/F bilayers and Nb/F/AlOx/Al tunnel junctions with ferromagnets Ni8Fe19, Ni65Fe15Co20, and Pd1-xNix. The dependence of the critical temperature of the bilayers and density of states that propagated through the ferromagnetic layer were studied as a function of thickness. From this study, crucial magnetic and electrical parameters like magnetic coherence lengths (ξF), exchange energy (Eex), and the rate of shift in the wavefunction’s phase and amplitude as a function of thickness were determined.
ContributorsAbd El Qader, Makram (Author) / Newman, Nathan (Thesis advisor) / Rowell, John (Committee member) / Rizzo, Nick (Committee member) / Yu, Hongbin (Committee member) / Arizona State University (Publisher)
Created2016
Description
This report summarizes the development of a test stand used to measure the thrust or impulse of pulsed plasma thrusters (PPT). Currently, there is a lack of accessible, cost-efficient methods for measuring thrust in the market due to the difficulties associated with developing a test stand for extremely low thrust outputs. Despite the difficulties, there is an ever-growing need to develop new methods of measuring thrust as the increased demand for small satellites has prompted investors from the government and private sectors to conduct further research into the development of better propulsion systems for space applications. A part of the developmental process of making propulsion systems is being able to test the thrust of these propulsion systems under vacuum conditions that simulate a space environment. This report details the research conducted on existing test stands as well as the process of designing, manufacturing, and testing a thrust measurement device.
ContributorsYu, Finley (Author) / Goryll, Michael (Thesis director) / Sharp, Thomas (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2024-05