Matching Items (43,913)
Description
A numerical study of incremental spin-up and spin-up from rest of a thermally- stratified fluid enclosed within a right circular cylinder with rigid bottom and side walls and stress-free upper surface is presented. Thermally stratified spin-up is a typical example of baroclinity, which is initiated by a sudden increase in rotation rate and the tilting of isotherms gives rise to baroclinic source of vorticity. Research by (Smirnov et al. [2010a]) showed the differences in evolution of instabilities when Dirichlet and Neumann thermal boundary conditions were applied at top and bottom walls. Study of parametric variations carried out in this dissertation confirmed the instability patterns observed by them for given aspect ratio and Rossby number values greater than 0.5. Also results reveal that flow maintained axisymmetry and stability for short aspect ratio containers independent of amount of rotational increment imparted. Investigation on vorticity components provides framework for baroclinic vorticity feedback mechanism which plays important role in delayed rise of instabilities when Dirichlet thermal Boundary Conditions are applied.
ContributorsKher, Aditya Deepak (Author) / Chen, Kangping (Thesis advisor) / Huang, Huei-Ping (Committee member) / Herrmann, Marcus (Committee member) / Arizona State University (Publisher)
Created2011
Description
Building Applied Photovoltaics (BAPV) form an essential part of today's solar economy. This thesis is an effort to compare and understand the effect of fan cooling on the temperature of rooftop photovoltaic (PV) modules by comparing two side-by-side arrays (test array and control array) under identical ambient conditions of irradiance, air temperature, wind speed and wind direction. The lower operating temperature of PV modules due to fan operation mitigates array non uniformity and improves on performance. A crystalline silicon (c-Si) PV module has a light to electrical conversion efficiency of 14-20%. So on a cool sunny day with incident solar irradiance of 1000 W/m2, a PV module with 15% efficiency, will produce about only 150 watts. The rest of the energy is primarily lost in the form of heat. Heat extraction methods for BAPV systems may become increasingly higher in demand as the hot stagnant air underneath the array can be extracted to improve the array efficiency and the extracted low-temperature heat can also be used for residential space heating and water heating. Poly c-Si modules experience a negative temperature coefficient of power at about -0.5% /o C. A typical poly c-Si module would experience power loss due to elevation in temperature, which may be in the range of 25 to 30% for desert conditions such as that of Mesa, Arizona. This thesis investigates the effect of fan cooling on the previously developed thermal models at Arizona State University and on the performance of PV modules/arrays. Ambient conditions are continuously monitored and collected to calculate module temperature using the thermal model and to compare with actually measured temperature of individual modules. Including baseline analysis, the thesis has also looked into the effect of fan on the test array in three stages of 14 continuous days each. Multiple Thermal models are developed in order to identify the effect of fan cooling on performance and temperature uniformity. Although the fan did not prove to have much significant cooling effect on the system, but when combined with wind blocks it helped improve the thermal mismatch both under low and high wind speed conditions.
ContributorsChatterjee, Saurabh (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Rogers, Bradley (Committee member) / Macia, Narciso (Committee member) / Arizona State University (Publisher)
Created2011
Description
This study investigated the internal factor structure of the English language development Assessment (ELDA) using confirmatory factor analysis. ELDA is an English language proficiency test developed by a consortium of multiple states and is used to identify and reclassify English language learners in kindergarten to grade 12. Scores on item parcels based on the standards tested from the four domains of reading, writing, listening, and speaking were used for the analyses. Five different factor models were tested: a single factor model, a correlated two-factor model, a correlated four-factor model, a second-order factor model and a bifactor model. The results indicate that the four-factor model, second-order model, and bifactor model fit the data well. The four-factor model hypothesized constructs for reading, writing, listening and speaking. The second-order model hypothesized a second-order English language proficiency factor as well as the four lower-order factors of reading, writing, listening and speaking. The bifactor model hypothesized a general English language proficiency factor as well as the four domain specific factors of reading, writing, listening, and speaking. The Chi-square difference tests indicated that the bifactor model best explains the factor structure of the ELDA. The results from this study are consistent with the findings in the literature about the multifactorial nature of language but differ from the conclusion about the factor structures reported in previous studies. The overall proficiency levels on the ELDA gives more weight to the reading and writing sections of the test than the speaking and listening sections. This study has implications on the rules used for determining proficiency levels and recommends the use of conjunctive scoring where all constructs are weighted equally contrary to current practice.
ContributorsKuriakose, Anju Susan (Author) / Macswan, Jeff (Thesis advisor) / Haladyna, Thomas (Thesis advisor) / Thompson, Marilyn (Committee member) / Arizona State University (Publisher)
Created2011
Description
The purpose of this study was to examine the effects of an after-school music program on music underachievers' musical achievement, social development and self-esteem. A true-experimental pretest-posttest design was used and included 14 hours of treatment time. The subjects (N = 66), fifth-grade students were randomly selected from the lowest quartile of scores on Colwell's Music Achievement Test (MAT), which was administered to all fifth-grade students (N = 494) in three Korean elementary schools. The treatment group (n =33) experienced a movement-based after-school music program (MAMP); the control group (n = 33) did not receive the after-school music program. Measurements included sections of Colwell's Music Achievement Test (MAT), Kim's Social Development Scale (SDS), and Hare's Self-Esteem Scale (HSS). The researcher and music teachers of each school administered all measurements. Fourteen treatment lessons occurred over fourteen weeks. One-way analyses of covariance tests were used to test for post-test differences between groups. A significant difference was found in music achievement total scores of the MAT with the treatment group scoring higher scores than the control group. There were no significant differences for interval and meter discrimination tests of MAT. There were no significant differences between treatment and control groups in the post-test scores of the Social Development Scale (SDS) and the Self-Esteem Scale (HSS). However, for both tests, mean scores increased for the treatment group and decreased for the control group. Results from this study suggest that a movement-based after-school music program promotes music underachievers' musical growth and may also support music underachievers' social development and self-esteem.
ContributorsYun, Gwan Ki (Author) / Stauffer, Sandra L (Thesis advisor) / Bush, Jeffrey B (Committee member) / Schmidt, Margaret T (Committee member) / Sullivan, Jill M (Committee member) / Tobias, Evan (Committee member) / Arizona State University (Publisher)
Created2011
Description
The current study employs item difficulty modeling procedures to evaluate the feasibility of potential generative item features for nonword repetition. Specifically, the extent to which the manipulated item features affect the theoretical mechanisms that underlie nonword repetition accuracy was estimated. Generative item features were based on the phonological loop component of Baddelely's model of working memory which addresses phonological short-term memory (Baddeley, 2000, 2003; Baddeley & Hitch, 1974). Using researcher developed software, nonwords were generated to adhere to the phonological constraints of Spanish. Thirty-six nonwords were chosen based on the set item features identified by the proposed cognitive processing model. Using a planned missing data design, two-hundred fifteen Spanish-English bilingual children were administered 24 of the 36 generated nonwords. Multiple regression and explanatory item response modeling techniques (e.g., linear logistic test model, LLTM; Fischer, 1973) were used to estimate the impact of item features on item difficulty. The final LLTM included three item radicals and two item incidentals. Results indicated that the LLTM predicted item difficulties were highly correlated with the Rasch item difficulties (r = .89) and accounted for a substantial amount of the variance in item difficulty (R2 = .79). The findings are discussed in terms of validity evidence in support of using the phonological loop component of Baddeley's model (2000) as a cognitive processing model for nonword repetition items and the feasibility of using the proposed radical structure as an item blueprint for the future generation of nonword repetition items.
ContributorsMorgan, Gareth Philip (Author) / Gorin, Joanna (Thesis advisor) / Levy, Roy (Committee member) / Gray, Shelley (Committee member) / Arizona State University (Publisher)
Created2011
Description
During the twentieth-century, the dual influence of nationalism and modernism in the eclectic music from Latin America promoted an idiosyncratic style which naturally combined traditional themes, popular genres and secular music. The saxophone, commonly used as a popular instrument, started to develop a prominent role in Latin American classical music beginning in 1970. The lack of exposure and distribution of the Latin American repertoire has created a general perception that composers are not interested in the instrument, and that Latin American repertoire for classical saxophone is minimal. However, there are more than 1100 works originally written for saxophone in the region, and the amount continues to grow. This Modern Latin American Repertoire for Classical Saxophone: Recording Project and Performance Guide document establishes and exhibits seven works by seven representative Latin American composers.The recording includes works by Carlos Gonzalo Guzman (Colombia), Ricardo Tacuchian (Brazil), Roque Cordero (Panama), Luis Naón (Argentina), Andrés Alén-Rodriguez (Cuba), Alejandro César Morales (Mexico) and Jose-Luis Maúrtua (Peru), featuring a range of works for solo alto saxophone to alto saxophone with piano, alto saxophone with vibraphone, and tenor saxophone with electronic tape; thus forming an important selection of Latin American repertoire. Complete recorded performances of all seven pieces are supplemented by biographical, historical, and performance practice suggestions. The result is a written and audio guide to some of the most important pieces composed for classical saxophone in Latin America, with an emphasis on fostering interest in, and research into, composers who have contributed in the development and creation of the instrument in Latin America.
ContributorsOcampo Cardona, Javier Andrés (Author) / McAllister, Timothy (Thesis advisor) / Spring, Robert (Committee member) / Hill, Gary (Committee member) / Pilafian, Sam (Committee member) / Rogers, Rodney (Committee member) / Gardner, Joshua (Committee member) / Arizona State University (Publisher)
Created2011
Description
S-Taliro is a fully functional Matlab toolbox that searches for trajectories of minimal robustness in hybrid systems that are implemented as either m-functions or Simulink/State flow models. Trajectories with minimal robustness are found using automatic testing of hybrid systems against user specifications. In this work we use Metric Temporal Logic (MTL) to describe the user specifications for the hybrid systems. We then try to falsify the MTL specification using global minimization of robustness metric. Global minimization is carried out using stochastic optimization algorithms like Monte-Carlo (MC) and Extended Ant Colony Optimization (EACO) algorithms. Irrespective of the type of the model we provide as an input to S-Taliro, the user needs to specify the MTL specification, the initial conditions and the bounds on the inputs. S-Taliro then uses this information to generate test inputs which are used to simulate the system. The simulation trace is then provided as an input to Taliro which computes the robustness estimate of the MTL formula. Global minimization of this robustness metric is performed to generate new test inputs which again generate simulation traces which are closer to falsifying the MTL formula. Traces with negative robustness values indicate that the simulation trace falsified the MTL formula. Traces with positive robustness values are also of great importance because they indicate how robust the system is against the given specification. S-Taliro has been seamlessly integrated into the Matlab environment, which is extensively used for model-based development of control software. Moreover the toolbox has been developed in a modular fashion and therefore adding new optimization algorithms is easy and straightforward. In this work I present the architecture of S-Taliro and its working on a few benchmark problems.
ContributorsAnnapureddy, Yashwanth Singh Rahul (Author) / Fainekos, Georgios (Thesis advisor) / Lee, Yann-Hang (Committee member) / Gupta, Sandeep (Committee member) / Arizona State University (Publisher)
Created2011
Description
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
Description
The AIDS epidemic has tremendously impacted the population of Mozambique. The rate of newly infected young women continues to grow disproportionately which is why consideration of health interventions specific to this population to combat the spread of the disease is critical. The Health Belief Model emphasizes the importance of self efficiency in the process of health related behavioral changes. Previous research has found that low levels of autonomy increase one's risk of contracting HIV/AIDS. This research uses data from a study conducted in 2006 in Mozambique to test whether higher levels of autonomy are associated with the practice of self protective behaviors related to the contraction of HIV/AIDS. Results suggest that some measures of autonomy such as education are positively associated with the practice of self protective behaviors. However, higher levels of decision making powers were negatively associated with the practice of self protective behaviors.
ContributorsWilliams, Kelli (Author) / Hayford, Sarah (Thesis advisor) / Agadjanian, Victor (Committee member) / Yabiku, Scott (Committee member) / Arizona State University (Publisher)
Created2011
Description
There are many wireless communication and networking applications that require high transmission rates and reliability with only limited resources in terms of bandwidth, power, hardware complexity etc.. Real-time video streaming, gaming and social networking are a few such examples. Over the years many problems have been addressed towards the goal of enabling such applications; however, significant challenges still remain, particularly, in the context of multi-user communications. With the motivation of addressing some of these challenges, the main focus of this dissertation is the design and analysis of capacity approaching coding schemes for several (wireless) multi-user communication scenarios. Specifically, three main themes are studied: superposition coding over broadcast channels, practical coding for binary-input binary-output broadcast channels, and signalling schemes for two-way relay channels. As the first contribution, we propose an analytical tool that allows for reliable comparison of different practical codes and decoding strategies over degraded broadcast channels, even for very low error rates for which simulations are impractical. The second contribution deals with binary-input binary-output degraded broadcast channels, for which an optimal encoding scheme that achieves the capacity boundary is found, and a practical coding scheme is given by concatenation of an outer low density parity check code and an inner (non-linear) mapper that induces desired distribution of "one" in a codeword. The third contribution considers two-way relay channels where the information exchange between two nodes takes place in two transmission phases using a coding scheme called physical-layer network coding. At the relay, a near optimal decoding strategy is derived using a list decoding algorithm, and an approximation is obtained by a joint decoding approach. For the latter scheme, an analytical approximation of the word error rate based on a union bounding technique is computed under the assumption that linear codes are employed at the two nodes exchanging data. Further, when the wireless channel is frequency selective, two decoding strategies at the relay are developed, namely, a near optimal decoding scheme implemented using list decoding, and a reduced complexity detection/decoding scheme utilizing a linear minimum mean squared error based detector followed by a network coded sequence decoder.
ContributorsBhat, Uttam (Author) / Duman, Tolga M. (Thesis advisor) / Tepedelenlioğlu, Cihan (Committee member) / Li, Baoxin (Committee member) / Zhang, Junshan (Committee member) / Arizona State University (Publisher)
Created2011