Matching Items (1,578)
Description
The wide adoption and continued advancement of information and communications technologies (ICT) have made it easier than ever for individuals and groups to stay connected over long distances. These advances have greatly contributed in dramatically changing the dynamics of the modern day workplace to the point where it is now commonplace to see large, distributed multidisciplinary teams working together on a daily basis. However, in this environment, motivating, understanding, and valuing the diverse contributions of individual workers in collaborative enterprises becomes challenging. To address these issues, this thesis presents the goals, design, and implementation of Taskville, a distributed workplace game played by teams on large, public displays. Taskville uses a city building metaphor to represent the completion of individual and group tasks within an organization. Promising results from two usability studies and two longitudinal studies at a multidisciplinary school demonstrate that Taskville supports personal reflection and improves team awareness through an engaging workplace activity.
ContributorsNikkila, Shawn (Author) / Sundaram, Hari (Thesis advisor) / Byrne, Daragh (Committee member) / Davulcu, Hasan (Committee member) / Olson, Loren (Committee member) / Arizona State University (Publisher)
Created2013
Description
In this dissertation, combined photo-induced and thermionic electron emission from low work function diamond films is studied through low energy electron spectroscopy analysis and other associated techniques. Nitrogen-doped, hydrogen-terminated diamond films prepared by the microwave plasma chemical vapor deposition method have been the most focused material. The theme of this research is represented by four interrelated issues. (1) An in-depth study describes combined photo-induced and thermionic emission from nitrogen-doped diamond films on molybdenum substrates, which were illuminated with visible light photons, and the electron emission spectra were recorded as a function of temperature. The diamond films displayed significant emissivity with a low work function of ~ 1.5 eV. The results indicate that these diamond emitters can be applied in combined solar and thermal energy conversion. (2) The nitrogen-doped diamond was further investigated to understand the physical mechanism and material-related properties that enable the combined electron emission. Through analysis of the spectroscopy, optical absorbance and photoelectron microscopy results from sample sets prepared with different configurations, it was deduced that the photo-induced electron generation involves both the ultra-nanocrystalline diamond and the interface between the diamond film and metal substrate. (3) Based on results from the first two studies, possible photon-enhanced thermionic emission was examined from nitrogen-doped diamond films deposited on silicon substrates, which could provide the basis for a novel approach for concentrated solar energy conversion. A significant increase of emission intensity was observed at elevated temperatures, which was analyzed using computer-based modeling and a combination of different emission mechanisms. (4) In addition, the electronic structure of vanadium-oxide-terminated diamond surfaces was studied through in-situ photoemission spectroscopy. Thin layers of vanadium were deposited on oxygen-terminated diamond surfaces which led to oxide formation. After thermal annealing, a negative electron affinity was found on boron-doped diamond, while a positive electron affinity was found on nitrogen-doped diamond. A model based on the barrier at the diamond-oxide interface was employed to analyze the results. Based on results of this dissertation, applications of diamond-based energy conversion devices for combined solar- and thermal energy conversion are proposed.
ContributorsSun, Tianyin (Author) / Nemanich, Robert (Thesis advisor) / Ponce, Fernando (Committee member) / Peng, Xihong (Committee member) / Spence, John (Committee member) / Treacy, Michael (Committee member) / Arizona State University (Publisher)
Created2013
Description
Group III-nitride semiconductors have attracted much attention for applications on high brightness light-emitting diodes (LEDs) and laser diodes (LDs) operating in the visible and ultra-violet spectral range using indium gallium nitride in the active layer. However, the device efficiency in the green to red range is limited by quantum-confined Stark effects resulting from the lattice mismatch between GaN and InGaN. In this dissertation, the optical and micro-structural properties of GaN-based light emitting structures have been analyzed and correlated by utilizing cathodoluminescence and transmission electron microscopy techniques. In the first section, optimization of the design of GaN-based lasers diode structures is presented. The thermal strain present in the GaN underlayer grown on sapphire substrates causes a strain-induced wavelength shift. The insertion of an InGaN waveguide mitigates the mismatch strain at the interface between the InGaN quantum well and the GaN quantum barrier. The second section of the thesis presents a study of the characteristics of thick non-polar m-plane InGaN films and of LED structures containing InGaN quantum wells, which minimize polarization-related electric fields. It is found that in some cases the in-plane piezoelectric fields can still occur due to the existence of misfit dislocations which break the continuity of the film. In the final section, the optical and structural properties of InGaAlN quaternary alloys are analyzed and correlated. The composition of the components of the film is accurately determined by Rutherford backscattering spectroscopy.
ContributorsHuang, Yu (Author) / Ponce, Fernando A. (Thesis advisor) / Tsen, Kong-Thon (Committee member) / Treacy, Michael (Committee member) / Drucker, Jeffery (Committee member) / Culbertson, Robert (Committee member) / Arizona State University (Publisher)
Created2011
Raman spectroscopy characterization of anharmonicity and alloying effects in semiconductor materials
Description
The chemical sensitivity and spatial resolution of Raman spectroscopy, combined with the sensitivity of modern systems that can easily detect single atomic layers, have made this technique a preferred choice for the strain characterization of complex systems such as nanoscale complementary metal-oxide-semiconductor - CMOS - devices. A disadvantage of Raman spectroscopy, however, is that the shifts associated with strain are not related to the geometrical deformations in any obvious way, so that careful calibrations are needed to determine the anharmonic coefficients (p, q and r) that relate strain to Raman shifts. A new set of measurements of the Raman shift in strained Ge films grown on relaxed SiGe buffer layers deposited on Si substrates is presented, and thereby, a new consistent set of values for the parameters p and q for Ge has been proposed. In this dissertation the study of the vibrational properties of Ge1-xSnx alloys has also been reported. The temperature dependence of the Raman spectrum of Ge-rich Ge1-x Snx and Ge1-x-ySi xSny alloys has been determined in the 10 K - 450 K range. The Raman line shift and width changes as a function of temperature are found to be virtually identical to those observed in bulk Ge. This result shows that the anharmonic decay process responsible for the temperature dependence is extremely robust against the alloy perturbation.
ContributorsBagchi, Sampriti (Author) / Menéndez, Jose (Thesis advisor) / Treacy, Michael (Committee member) / Ponce, Fernando (Committee member) / Tsen, Kong-Thon (Committee member) / Rez, Peter (Committee member) / Arizona State University (Publisher)
Created2011
Description
ABSTRACT Group III-nitride semiconductor materials have been commercially used in fabrication of light-emitting diodes (LEDs) and laser diodes (LDs) covering the spectral range from UV to visible and infrared, and exhibit unique properties suitable for modern optoelectronic applications. Great advances have recently happened in the research and development in high-power and high-efficiency blue-green-white LEDs, blue LDs and other optoelectronic applications. However, there are still many unsolved challenges with these materials. In this dissertation, several issues concerning structural, electronic and optical properties of III-nitrides have been investigated using a combination of transmission electron microscopy (TEM), electron holography (EH) and cathodoluminescence (CL) techniques. First, a trend of indium chemical inhomogeneity has been found as the indium composition increases for the InGaN epitaxial layers grown by hydride vapor phase epitaxy. Second, different mechanisms contributing to the strain relaxation have been studied for non-polar InGaN epitaxial layers grown on zinc oxide (ZnO) substrate. Third, various structural morphologies of non-polar InGaN epitaxial layers grown on free-standing GaN substrate have been investigated. Fourth, the effect of the growth temperature on the performance of GaN lattice-matched InAlN electron blocking layers has been studied. Finally, the electronic and optical properties of GaN nanowires containing a AlN/GaN superlattice structure have been investigated showing relatively small internal electric field and superlattice- and defect-related emissions along the nanowires.
ContributorsSun, Kewei (Author) / Ponce, Fernando (Thesis advisor) / Smith, David (Committee member) / Treacy, Michael (Committee member) / Drucker, Jeffery (Committee member) / Schmidt, Kevin (Committee member) / Arizona State University (Publisher)
Created2011
Description
This research compares shifts in a SuperSpec titanium nitride (TiN) kinetic inductance detector's (KID's) resonant frequency with accepted models for other KIDs. SuperSpec, which is being developed at the University of Colorado Boulder, is an on-chip spectrometer designed with a multiplexed readout with multiple KIDs that is set up for a broadband transmission of these measurements. It is useful for detecting radiation in the mm and sub mm wavelengths which is significant since absorption and reemission of photons by dust causes radiation from distant objects to reach us in infrared and far-infrared bands. In preparation for testing, our team installed stages designed previously by Paul Abers and his group into our cryostat and designed and installed other parts necessary for the cryostat to be able to test devices on the 250 mK stage. This work included the design and construction of additional parts, a new setup for the wiring in the cryostat, the assembly, testing, and installation of several stainless steel coaxial cables for the measurements through the devices, and other cryogenic and low pressure considerations. The SuperSpec KID was successfully tested on this 250 mK stage thus confirming that the new setup is functional. Our results are in agreement with existing models which suggest that the breaking of cooper pairs in the detector's superconductor which occurs in response to temperature, optical load, and readout power will decrease the resonant frequencies. A negative linear relationship in our results appears, as expected, since the parameters are varied only slightly so that a linear approximation is appropriate. We compared the rate at which the resonant frequency responded to temperature and found it to be close to the expected value.
ContributorsDiaz, Heriberto Chacon (Author) / Mauskopf, Philip (Thesis director) / McCartney, Martha (Committee member) / Department of Physics (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
This paper considers what factors influence student interest, motivation, and continued engagement. Studies show anticipated extrinsic rewards for activity participation have been shown to reduce intrinsic value for that activity. This might suggest that grade point average (GPA) has a similar effect on academic interests. Further, when incentives such as scholarships, internships, and careers are GPA-oriented, students must adopt performance goals in courses to guarantee success. However, performance goals have not been shown to correlated with continued interest in a topic. Current literature proposes that student involvement in extracurricular activities, focused study groups, and mentored research are crucial to student success. Further, students may express either a fixed or growth mindset, which influences their approach to challenges and opportunities for growth. The purpose of this study was to collect individual cases of students' experiences in college. The interview method was chosen to collect complex information that could not be gathered from standard surveys. To accomplish this, questions were developed based on content areas related to education and motivation theory. The content areas included activities and meaning, motivation, vision, and personal development. The developed interview method relied on broad questions that would be followed by specific "probing" questions. We hypothesize that this would result in participant-led discussions and unique narratives from the participant. Initial findings suggest that some of the questions were effective in eliciting detailed responses, though results were dependent on the interviewer. From the interviews we find that students value their group involvements, leadership opportunities, and relationships with mentors, which parallels results found in other studies.
ContributorsAbrams, Sara (Author) / Hartwell, Lee (Thesis director) / Correa, Kevin (Committee member) / Department of Psychology (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
This study estimates the capitalization effect of golf courses in Maricopa County using the hedonic pricing method. It draws upon a dataset of 574,989 residential transactions from 2000 to 2006 to examine how the aesthetic, non-golf benefits of golf courses capitalize across a gradient of proximity measures. The measures for amenity value extend beyond home adjacency and include considerations for homes within a range of discrete walkability buffers of golf courses. The models also distinguish between public and private golf courses as a proxy for the level of golf course access perceived by non-golfers. Unobserved spatial characteristics of the neighborhoods around golf courses are controlled for by increasing the extent of spatial fixed effects from city, to census tract, and finally to 2000 meter golf course ‘neighborhoods.’ The estimation results support two primary conclusions. First, golf course proximity is found to be highly valued for adjacent homes and homes up to 50 meters way from a course, still evident but minimal between 50 and 150 meters, and insignificant at all other distance ranges. Second, private golf courses do not command a higher proximity premia compared to public courses with the exception of homes within 25 to 50 meters of a course, indicating that the non-golf benefits of courses capitalize similarly, regardless of course type. The results of this study motivate further investigation into golf course features that signal access or add value to homes in the range of capitalization, particularly for near-adjacent homes between 50 and 150 meters thought previously not to capitalize.
ContributorsJoiner, Emily (Author) / Abbott, Joshua (Thesis director) / Smith, Kerry (Committee member) / Economics Program in CLAS (Contributor) / School of Sustainability (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The objective of this paper is to provide an educational diagnostic into the technology of blockchain and its application for the supply chain. Education on the topic is important to prevent misinformation on the capabilities of blockchain. Blockchain as a new technology can be confusing to grasp given the wide possibilities it can provide. This can convolute the topic by being too broad when defined. Instead, the focus will be maintained on explaining the technical details about how and why this technology works in improving the supply chain. The scope of explanation will not be limited to the solutions, but will also detail current problems. Both public and private blockchain networks will be explained and solutions they provide in supply chains. In addition, other non-blockchain systems will be described that provide important pieces in supply chain operations that blockchain cannot provide. Blockchain when applied to the supply chain provides improved consumer transparency, management of resources, logistics, trade finance, and liquidity.
ContributorsKrukar, Joel Michael (Author) / Oke, Adegoke (Thesis director) / Duarte, Brett (Committee member) / Hahn, Richard (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / Department of Economics (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The Super Catalan numbers are a known set of numbers which have so far eluded a combinatorial interpretation. Several weighted interpretations have appeared since their discovery, one of which was discovered by William Kuszmaul in 2017. In this paper, we connect the weighted Super Catalan structure created previously by Kuszmaul and a natural $q$-analogue of the Super Catalan numbers. We do this by creating a statistic $\sigma$ for which the $q$ Super Catalan numbers, $S_q(m,n)=\sum_X (-1)^{\mu(X)} q^{\sigma(X)}$. In doing so, we take a step towards finding a strict combinatorial interpretation for the Super Catalan numbers.
ContributorsHouse, John Douglas (Author) / Fishel, Susanna (Thesis director) / Childress, Nancy (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05