Matching Items (43,913)
Description
In-situ environmental transmission electron microscopy (ETEM) is a powerful tool for following the evolution of supported metal nanoparticles under different reacting gas conditions at elevated temperatures. The ability to observe the events in real time under reacting gas conditions can provide significant information on the fundamental processes taking place in catalytic materials, from which the performance of the catalyst can be understood. The first part of this dissertation presents the application of in-situ ETEM studies in developing structure-activity relationship in supported metal nanoparticles. In-situ ETEM studies on nanostructures in parallel with ex-situ reactor studies of conversions and selectivities were performed for partial oxidation of methane (POM) to syngas (CO+H2) on Ni/SiO2, Ru/SiO2 and NiRu/SiO2 catalysts. During POM, the gas composition varies along the catalyst bed with increasing temperature. It is important to consider these variations in gas composition in order to design experiments for in-situ ETEM. In-situ ETEM experiments were performed under three different reacting gas conditions. First in the presence of H2, this represents the state of the fresh catalyst for the catalytic reaction. Later in the presence of CH4 and O2 in 2:1 ratio, this is the composition of the reacting gases for the POM reaction and this composition acts as an oxidizing environment. Finally in the presence of CH4, this is the reducing gas. Oxidation and reduction behavior of Ni, Ru and NiRu nanoparticles were followed in an in-situ ETEM under reacting gas conditions and the observations were correlated with the performance of the catalyst for POM. The later part of the dissertation presents a technique for determining the gas compositional analysis inside the in-situ ETEM using electron energy-loss spectroscopy. Techniques were developed to identify the gas composition using both inner-shell and low-loss spectroscopy of EELS. Using EELS, an "operando TEM" technique was successfully developed for detecting the gas phase catalysis inside the ETEM. Overall this research demonstrates the importance of in-situ ETEM studies in understanding the structure-activity relationship in supported-metal catalysts for heterogeneous catalysis application.
ContributorsChenna, Santhosh (Author) / Crozier, Peter A. (Thesis advisor) / Carpenter, Ray (Committee member) / Sieradzki, Karl (Committee member) / Petuskey, William (Committee member) / Arizona State University (Publisher)
Created2011
Description
This study investigated the link between the cognitive clusters from the Woodcock–Johnson III Tests of Cognitive Ability (WJ III COG) and Broad Math, Math Calculation Skills, and Math Reasoning clusters of the Woodcock–Johnson III Tests of Achievement (WJ III ACH) using data collected over seven years by a large elementary school district in the Southwest. The students in this study were all diagnosed with math learning disabilities. Multiple regression analyses were used to predict performance on the Broad Math, Math Calculation Skills, and Math Reasoning clusters from the WJ III ACH. Fluid Reasoning (Gf), Comprehension–Knowledge (Gc), Short–Term Memory (Gsm), and Long–term Retrieval (Glr) demonstrated strong relations with Broad Math and moderate relations with Math Calculation Skills. Auditory Processing (Ga) and Processing Speed (Gs) demonstrated moderate relations with Broad Math and Math Calculation Skills. Visual–Spatial Thinking (Gv) and Processing Speed (Gs) demonstrated moderate to strong relations with the mathematics clusters. The results indicate that the specific cognitive abilities of students with math learning disabilities may differ from their peers.
ContributorsBacal, Emily (Author) / Caterino, Linda (Thesis advisor) / Stamm, Jill (Committee member) / Sullivan, Amanda (Committee member) / Arizona State University (Publisher)
Created2010
Description
Processed pyro-gel contains castor oil with solid component of boehmite (Al-OOH). The pyro-gel is synthesized by heat to convert boehmite to gamma-Al2O3 and to a certain extent alpha-Al2O3 nano-particles and castor oil into carbon residue. The effect of heat on pyro-gel is analyzed in a series of experiments using two burning chambers with the initial temperature as the main factor. The obtained temperature distribution profiles are studied and it is observed that the gel behaves very close to the theoretical prediction under heat. The carbon residue with Al2O3 is then processed for twelve hours and then analyzed to obtain the pore distribution of the Al2O3 nano-particles and the relation between the pore volume and the pre-heat temperature is analyzed. The obtained pore distribution shows the pore volume of Al2O3 nano-particles has direct relation to the pre-heat temperature. The experimental process involving the cylindrical reactor is simulated by using a finite rate chemistry eddy-dissipation model in a non-premixed and a porous mesh. The temperature distribution profile of the processed gel for both the meshes is obtained and a comparison is done with the data obtained in the experimental analysis. The temperature distribution obtained from the simulations show they follow a very similar profile to the temperature distribution obtained from experimental analysis, thus confirming the accuracy of both the models. The variation in numerical values between the experimental and simulation analysis is discussed. A physical model is proposed to determine the pore formation based on the temperature distribution obtained from experimental analysis and simulation.
ContributorsSagi, Varun (Author) / Lee, Taewoo (Thesis advisor) / Phelan, Patrick (Committee member) / Chen, Kangping (Committee member) / Arizona State University (Publisher)
Created2010
Description
Mid-Century ranch house architecture and design is significant to the architectural landscape of the Phoenix Metropolitan Area. The increasing age of the city's post-WWII properties is creating a need for renovation and rehabilitation, and new technologies have created modern conveniences for today's homeowners, changing interior space plan requirements. These homeowners will need guidance to alter these properties correctly and to preserve the home's essential features. This thesis analyzes the design trends and materials used during the mid-twentieth century, and demonstrates methods for applying them to a current renovation project. The research outlined in this document proves that it is possible to maintain historic integrity, include "Green" design strategies, and apply contemporary technology to a modern ranch renovation.
ContributorsSimmons, Rachel (Author) / Brandt, Beverly (Thesis advisor) / Warren-Findley, Janelle (Committee member) / Boradkar, Prasad (Committee member) / Arizona State University (Publisher)
Created2009
Description
Advanced composites are being widely used in aerospace applications due to their high stiffness, strength and energy absorption capabilities. However, the assurance of structural reliability is a critical issue because a damage event will compromise the integrity of composite structures and lead to ultimate failure. In this dissertation a novel homogenization based multiscale modeling framework using semi-analytical micromechanics is presented to simulate the response of textile composites. The novelty of this approach lies in the three scale homogenization/localization framework bridging between the constituent (micro), the fiber tow scale (meso), weave scale (macro), and the global response. The multiscale framework, named Multiscale Generalized Method of Cells (MSGMC), continuously bridges between the micro to the global scale as opposed to approaches that are top-down and bottom-up. This framework is fully generalized and capable of modeling several different weave and braids without reformulation. Particular emphasis in this dissertation is placed on modeling the nonlinearity and failure of both polymer matrix and ceramic matrix composites.
ContributorsLiu, Guang (Author) / Chattopadhyay, Aditi (Thesis advisor) / Mignolet, Marc (Committee member) / Jiang, Hanqing (Committee member) / Li, Jian (Committee member) / Rajadas, John (Committee member) / Arizona State University (Publisher)
Created2011
Description
Ever reducing time to market, along with short product lifetimes, has created a need to shorten the microprocessor design time. Verification of the design and its analysis are two major components of this design cycle. Design validation techniques can be broadly classified into two major categories: simulation based approaches and formal techniques. Simulation based microprocessor validation involves running millions of cycles using random or pseudo random tests and allows verification of the register transfer level (RTL) model against an architectural model, i.e., that the processor executes instructions as required. The validation effort involves model checking to a high level description or simulation of the design against the RTL implementation. Formal techniques exhaustively analyze parts of the design but, do not verify RTL against the architecture specification. The focus of this work is to implement a fully automated validation environment for a MIPS based radiation hardened microprocessor using simulation based approaches. The basic framework uses the classical validation approach in which the design to be validated is described in a Hardware Definition Language (HDL) such as VHDL or Verilog. To implement a simulation based approach a number of random or pseudo random tests are generated. The output of the HDL based design is compared against the one obtained from a "perfect" model implementing similar functionality, a mismatch in the results would thus indicate a bug in the HDL based design. Effort is made to design the environment in such a manner that it can support validation during different stages of the design cycle. The validation environment includes appropriate changes so as to support architecture changes which are introduced because of radiation hardening. The manner in which the validation environment is build is highly dependent on the specifications of the perfect model used for comparisons. This work implements the validation environment for two MIPS simulators as the reference model. Two bugs have been discovered in the RTL model, using simulation based approaches through the validation environment.
ContributorsSharma, Abhishek (Author) / Clark, Lawrence (Thesis advisor) / Holbert, Keith E. (Committee member) / Shrivastava, Aviral (Committee member) / Arizona State University (Publisher)
Created2011
Description
In this project, a novel method is presented for measuring the resistivity of nanoscale metallic conductors (nanowires) using a variable-spacing 2-point method with a modified ultrahigh vacuum scanning tunneling microscope. An auxiliary field emission imaging method that allows for scanning insulating surfaces using a large gap distance (20nm) is also presented. Using these methods, the resistivity of self-assembled endotaxial FeSi2 nanowires (NWs) on Si(110) was measured. The resistivity was found to vary inversely with NW width, being rhoNW = 200 uOhm cm at 12 nm and 300 uOhm cm at 2 nm. The increase at small w is attributed to boundary scattering, and is fit to the Fuchs-Sondheimer model, yielding values of rho0 = 150 uOhm cm and lambda = 2.4 nm, for specularity parameter p = 0.5. These results are attributed to a high concentration of point defects in the FeSi2 structure, with a correspondingly short inelastic electron scattering length. It is remarkable that the defect concentration persists in very small structures, and is not changed by surface oxidation.
ContributorsTobler, Samuel (Author) / Bennett, Peter (Thesis advisor) / McCartney, Martha (Committee member) / Tao, Nongjian (Committee member) / Doak, Bruce (Committee member) / Chen, Tingyong (Committee member) / Arizona State University (Publisher)
Created2011
Description
This study compared a stimulus fading (SF) procedure with a constant time delay (CTD) procedure for identification of consonant-vowel-consonant (CVC) nonsense words for a participant with autism. An alternating treatments design was utilized through a computer-based format. Receptive identification of target words was evaluated using a computer format and the researcher conducted a generalization probe for expressive identification evaluation. Neither treatment condition resulted in consistent gains on the receptive identification measure. Both treatment conditions resulted in gains on the expressive identification assessment. The SF treatment condition was more efficient due to 1) accuracy in identifying all of the SF target words in fewer sessions than the CTD target words and 2) incidental learning that occurred as a result of exposure to additional SF words as distracter choices and in receptive identification assessments. Implications are discussed.
ContributorsRedhair, Emily (Author) / McCoy, Kathleen (Thesis advisor) / Mathur, Sarup (Committee member) / Zucker, Stanley (Committee member) / Caterino, Linda (Committee member) / Arizona State University (Publisher)
Created2011
Description
Female infertility can present a significant challenge to quality of life. To date, few, if any investigations have explored the process by which women adapt to premature ovarian insufficiency (POI), a specific type of infertility, over time. The current investigation proposed a bi-dimensional, multi-factor, model of adjustment characterized by the identification of six latent factors representing personal attributes (resilience resources and vulnerability), coping (adaptive and maladaptive) and outcomes (distress and wellbeing). Measures were collected over the period of one year; personal attributes were assessed at Time 1, coping at Time 2 and outcomes at Time 3. It was hypothesized that coping factors would mediate associations between personal attributes and outcomes. Confirmatory Factor Analysis (CFA), simple regressions and single mediator models were utilized to test study hypotheses. Overall, with the exception of coping, the factor structure was consistent with predictions. Two empirically derived coping factors, and a single standalone strategy, avoidance, emerged. The first factor, labeled "approach coping" was comprised of strategies directly addressing the experience of infertility. The second was comprised of strategies indicative of "letting go /moving on." Only avoidance significantly mediated the association between vulnerability and distress.
ContributorsDriscoll, Mary (Author) / Davis, Mary C. (Thesis advisor) / Aiken, Leona S. (Committee member) / Luecken, Linda J. (Committee member) / Zautra, Alex J. (Committee member) / Arizona State University (Publisher)
Created2011
Description
Over recent decades, euthanasia has been a topic of increasing debate. With legalization of euthanasia in the states of Oregon and Washington and attempted reform in several other U.S. states and nations worldwide, it has become increasingly important to understand the roles and values of helping professionals who might be working with clients considering this option. The current study targeted 85 undergraduate students, 54 doctoral students in counseling psychology, and 53 doctoral-level professionals in psychology to assess both their personal values regarding euthanasia and their willingness to allow a client the autonomy to make a decision about euthanasia. Several factors were analyzed in regards to their relation to client autonomy and attitudes toward euthanasia, including age of client and sex of client. These variables were manipulated in vignettes to create four scenarios: a 24 year old male, 24 year old female, 80 year old male, 80 year old female. Other factors included level of education of the participant, spirituality and strength of religiosity of the participant, and personal experiences with deaths of friends or family members. Results indicated that more education was associated with greater support for euthanasia and that stronger religiosity and spirituality were related to less support for euthanasia. This study also found that participants did not exhibit differential levels of support based solely on the age or the sex of the client depicted in the vignette. Results further indicated that for doctoral students and professionals the loss of a loved one, regardless of cause of death, did not have a significant effect on their attitudes toward euthanasia. It is important for training programs to be aware of these findings in order to monitor trainees in terms of personal biases in the therapy relationship. With objectivity a high priority while working with clients, it is necessary to be aware of outside factors potentially influencing one's work with clients surrounding this value-laden issue.
ContributorsBevacqua, Frank (Author) / Robinson-Kurpius, Sharon (Thesis advisor) / Kinnier, Richard (Committee member) / Homer, Judy (Committee member) / Arizona State University (Publisher)
Created2011