Browsing by Subject "Interaction"

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Analytical, experimental, and field evaluations of soil-geosynthetic interaction under small displacements
(2016-08) Roodi, Gholam Hossein; Zornberg, Jorge G.; Stokoe, Kenneth H; Gilbert, Robert B; Prozzi, Jorge A; Taleff, Eric M
The increasing use of geosynthetics in stabilization of pavement systems under traffic loads and environmental changes requires proper understanding of the mechanisms that govern the soil-geosynthetic interaction. Significant research has already been conducted on the soil-geosynthetic interaction under ultimate conditions, which is relevant to reinforcement of retaining walls and steep slopes. However, little research has been undertaken to investigate the properties and mechanisms that govern the soil-geosynthetic interaction under small displacements, which is relevant to applications such as the geosynthetic stabilization of pavement layers. While characterization of the maximum geosynthetic strength (e.g., tensile strength or pullout resistance) is relevant for the design of soil-geosynthetic systems under ultimate conditions, proper design properties in systems where geosynthetics are used to control deformations should involve characterization of the stiffness of soil-geosynthetic composite. The objective of this research is to develop a better understanding of the soil-geosynthetic interaction under small displacements using analytical, experimental, and field evaluations. Three studies were conducted on different aspects of soil-geosynthetic interaction under small displacements: (1) Analytical and experimental evaluations of the soil-geosynthetic composite (SGC) model using large-scale soil-geosynthetic interaction tests, (2) analytical and experimental evaluations of soil-geosynthetic interaction using small-scale soil-geosynthetic interaction tests, and (3) field evaluation of soil-geosynthetic interaction under small displacements. Each study provides lessons and conclusions on specific aspects investigated in that study. Collectively, they suggest that the analytical model proposed in this study provides a good basis towards predicting the general performance of geosynthetic-stabilized pavements. The analytical formulation of the SGC model indicates that soil-geosynthetic interaction under small displacements can be characterized by the stiffness of soil-geosynthetic composite ( ), which is the slope of the linear relationship defined between the unit tension squared (T2) versus displacements (u) in each point along the active length of a geosynthetic. The linearity and uniqueness of the relationship between the unit tension squared (T2) and displacements (u) throughout the active length of specimens tested in a comparatively large soil-geosynthetic interaction device were experimentally confirmed. Overall, the experimental results from the large-scale soil-geosynthetic interaction tests were found to be in good agreement with the adopted constitutive relationships and with the analytical predictions of the SGC model. Evaluation of experimental results from tests conducted to assess repeatability indicated that the variability of the estimated values for the constitutive parameters ( and ) and the stiffness of soil-geosynthetic composite ( ) are well within the acceptable ranges when compared to variations of other soil and geosynthetic properties. Suitability of the assumptions and outcomes of the model was also confirmed for a variety of testing conditions and materials. Evaluation of the experimental data obtained from a subsequent experimental program involving small-scale soil-geosynthetic interaction tests indicates that although the assumptions of the analytical model do not fully conform to the conditions in a small-scale test, experimental results confirm the linearity and uniqueness of the relationship between the unit tension squared (T2) and the displacements (u) throughout the specimen. Evaluation of the results obtained from small- and large-scale interaction tests on five geosynthetics with a range of properties indicates that both large and small testing scales can be used for comparative evaluation of the stiffness of soil-geosynthetic composite among geosynthetics. However, since the stiffness values obtained from the two testing scales were found to be different, the stiffness values from the large-scale soil-geosynthetic interaction tests should be suitable for design purposes, while values from the small-scale interaction tests should be suitable for specification and comparison purposes. Evaluation of the long-term performance of full-scale paved test sections under both traffic and environmental loads indicates that stabilization with geosynthetics contributes to improving the road performance under both loading conditions. The benefits derived from using geosynthetics under traffic loads were realized by reducing the total length of rut or rutting depth. On the other hands, the benefits from using geosynthetics under environmental loads in roads founded on expansive subgrades were realized by mitigating the percentage of longitudinal cracks appears on the road surface. The latter benefits were found to be more pronounced towards the end of dry seasons, when longitudinal cracks tend to develop. Comparison among the performances of geosynthetic-stabilized test sections under environmental loads indicate that the benefit provided by geosynthetics correlates well with the stiffness of soil-geosynthetic composite ( ) characterized in the laboratory. Geosynthetic products with comparatively larger were found to lead to a comparatively better field performance.
Control-friendly scheduling algorithms for multi-tool, multi-product manufacturing systems
(2011-12) Bregenzer, Brent Constant; Qin, Joe; Hasenbein, John J.; Edgar, Thomas F.; Hwang, Gyeong S.; Kutanoglu, Erhan; Bonnecaze, Roger T.
The fabrication of semiconductor devices is a highly competitive and capital intensive industry. Due to the high costs of building wafer fabrication facilities (fabs), it is expected that products should be made efficiently with respect to both time and material, and that expensive unit operations (tools) should be utilized as much as possible. The process flow is characterized by frequent machine failures, drifting tool states, parallel processing, and reentrant flows. In addition, the competitive nature of the industry requires products to be made quickly and within tight tolerances. All of these factors conspire to make both the scheduling of product flow through the system and the control of product quality metrics extremely difficult. Up to now, much research has been done on the two problems separately, but until recently, interactions between the two systems, which can sometimes be detrimental to one another, have mostly been ignored. The research contained here seeks to tackle the scheduling problem by utilizing objectives based on control system parameters in order that the two systems might behave in a more beneficial manner. A non-threaded control system is used that models the multi-tool, multi-product process in a state space form, and estimates the states using a Kalman filter. Additionally, the process flow is modeled by a discrete event simulation. The two systems are then merged to give a representation of the overall system. Two control system matrices, the estimate error covariance matrix from the Kalman filter and a square form of the system observability matrix called the information matrix, are used to generate several control-based scheduling algorithms. These methods are then tested against more tradition approaches from the scheduling literature to determine their effectiveness on both the basis of how well they maintain the outputs near their targets and how well they minimize the cycle time of the products in the system. The two metrics are viewed simultaneously through use of Pareto plots and merits of the various scheduling methods are judged on the basis of Pareto optimality for several test cases.
Electronic correlations in few layer graphene
(2011-12) Zhang, Fan, 1983-; MacDonald, Allan H.
In this thesis we investigate the electronic band structures and the correlations in chirally (ABC) stacked N-layer graphene with N ≥ 2. We use ab initio density-functional theory and k · p theory to fit the parameters of a p-band tightbinding model. External potential differences between top and bottom layers are strongly screened by charge transfer but still open an energy gap at overall neutrality. Perpendicular magnetic field drives the system into the quantum Hall region with 4N-fold zero energy Landau levels. We predict that Coulomb interactions spontaneously break the SU(4N) symmetry and drive quantum Hall effects at all integer fillings n from −2N to 2N with exotic spin and pseudospin polarizations. Based on mean-field theory and perturbative renormalization group analysis, we predict that the ground state of bilayer graphene spontaneously breaks inversion symmetry for arbitrarily weak electron-electron interactions and conclude that this instability is not suppressed by quantum fluctuations but that, because of trigonal warping, it may occur only in high quality suspended bilayers. Remarkably flat conduction and valence bands that touch at charge neutrality point and Bloch states with large pseudospin chirality combine to make the bilayer graphene gapless band state strongly susceptible to a family of broken symmetry states in which each spinvalley flavor spontaneously transfers charge between layers. We explain how these states are distinguished by their charge, spin, and valley Hall conductivities, by their orbital magnetizations, and by their edge state properties. We further analyze how these competing states are influenced by Zeeman fields that couple to spin and by interlayer electric fields that couple to layer pseudospin, and comment on the possibility of using response and edge state signatures to identify the character of the bilayer ground state experimentally. We demonstrate that similar insulating broken symmetry states and spontaneous topological orders also occur in bilayer’s thicker cousins, chirally stacked multilayer graphene systems.
Evaluation of soil-geogrid interaction at different load levels using pullout tests and transparent soil
(2013-08) Ferreira, Julio Antonio Zambrano; Zornberg, Jorge G.
Geogrids have been used for decades as reinforcement for mechanically stabilized earth retaining walls and base layers of pavements. However, literature on these applications is contradictory regarding the displacement and strain levels at which the bearing mechanism of interaction between soil and geogrid is developed along the transverse ribs of geogrids. No data are available on the deflections and displacement profiles of transverse ribs during loading of geogrids. Field and laboratory data on strain distributions along geogrids are limited. Accordingly, the objective of this study is to better understand the mechanisms of soil-geogrid interaction that develop at different stages of pullout tests, especially at small displacements and strains. Moreover, the behavior of transverse ribs throughout pullout testing is evaluated. Pullout loads were obtained from a load cell synchronized with two 5 MP cameras. Images of the geogrid were analyzed using the Particle Image Velocimetry (PIV) technique to obtain displacement profiles along the entire geogrid specimen throughout the duration of the test. Five transparent pullout tests were conducted using a confining pressure of 35 kPa (5 psi) on polypropylene geogrids with different configurations. Displacements along the polypropylene geogrid used in this study are well represented by an exponential equation. The bearing mechanism along transverse ribs was observed to develop at small viii displacements. The contribution of the bearing mechanism was first observed at 25 % of the maximum pullout force. Interference between transverse ribs was first observed at approximately 60 % of the maximum pullout force. High interference between transverse ribs was observed when the ratio of spacing between transverse ribs (S) over the thickness of the transverse ribs (B) was equal to 24. Negligible interference was observed when S/B was equal to 57. Displacements of soil particles were observed when the ratio distance from the soil-geogrid interface (d) over the D₅₀ of the soil was equal to 3, but they were orders of magnitude smaller than the displacements of the geogrid specimens. The observed boundary of the zone of influence of geogrids was for values of 3 < d/D₅₀ < 7 for the transparent soil used in this study.
Experimental investigation of geomechanical aspects of hydraulic fracturing unconventional formations
(2014-08) Alabbad, Emad Abbad; Olson, Jon E.
Understanding the mechanisms that govern hydraulic fracturing applications in unconventional formations, such as gas-bearing shales, is of increasing interest to the petroleum upstream industry. Among such mechanisms, the geomechanical interactions between hydraulic fractures and pre-existing fractures on one hand, and simultaneous multiple hydraulic fractures on the other hand are seen of high importance. Although the petroleum engineering and related literature contains a number of studies that discusses such topics of hydraulic fracture interactions, there still remain some aspects that require answers, validations, or further supporting data. Particularly, experimental evidence is fairly scarce and keenly needed to solidify the understanding of such complex applications. In this work, the investigation methodology uses a series of hydraulic fracturing laboratory tests performed on synthetic rocks made of gypsum-based cements such as hydrostone and plaster in various experimental set ups. Those laboratory tests aim to closely investigate hydraulic fracture intersection with pre-existing fractures by assessing some factors that govern its outcomes. Specifically, the roles of the pre-existing fracture cementation, aperture, and relative height on the intersection mode are examined. The results show dominant effect of the cement-fill type relative to the host-rock matrix in determining whether hydraulic fracture crossing the pre-existing interface may occur. Similarly, hydraulic fracture height relative to the height of the pre-existing fracture may dictate the intersection results. However, the intersection mode seems to be insensitive of the pre-existing fracture aperture. Moreover, simultaneous multi-fracture propagation is examined and found to be impacted by the interference of the stresses induced from each fracturing source on neighboring fracturing sources. Such stress interference increases as the number of the propagating hydraulic fractures increase. While hydraulic fractures initiating from fracturing sources located in the middle of the fracturing stage seem to have inhibited propagation, outer hydraulic fractures may continue propagating with outward curvatures. Overall, the experimental results and analyses offer more insights for understanding hydraulic fracture complexity in unconventional formations.
Feedback for language learning exercises on Livemocha.com
(2011-12) Allstrom, Grace Adelaide; Kelm, Orlando R., 1957-; Hughes, Joan
This report investigates the amount and types of feedback that are produced on the social language learning site Livemocha.com in response to learners’ written and oral productions. The data are 200 speaking and writing activity submissions with a total of 674 reviewer comments and 1,357 feedback tokens. Feedback is separated into 19 categories which take into account interpersonal communication as well as task-based and grammatical information. More than one-third of all feedback tokens consist of the reviewer encouraging, congratulating, or otherwise offering emotional support to the learner. This strongly indicates that Livemocha.com users are not solely focused on the mechanics of learning languages, but also are creating a welcoming community of practice.
Gaining literacy XP: uncovering semiotic resources in a digital game and exploring L2 learner gameplay as a multiliteracy practice
(2019-08) Schoen, Kristina Maren; Arens, Katherine, 1953-; Crane, Cori; Boas, Hans; Henry, Nicholas; Blyth, Carl; Sykes, Julie
Digital games create interactive, multimodal spaces for second language (L2) learners to engage with contextualized language. Scholarship on digital games for L2 learning has previously focused on the affordances of games as language learning tools, i.e. for vocabulary acquisition and communication (deHaan, Reed, & Kuwada, 2010; Peterson, 2012), overlooking their value as rich, semiotic texts and gameplay as multiliteracy practice. This dissertation explores the textuality of the digital game The Vanishing of Ethan Carter (The Astronauts, 2014) and the literacy practices of L2 learners of German as they engage in dyadic pairs with the game. Using Systemic Functional Linguistics (Halliday, 1978; Halliday & Matthiessen, 2004) and social semiotics (Kress, 2000) as analytical frameworks, an initial text analysis of the game focuses on the organization of narrative information in an orbital generic structure (White, 1997). Given the non-sequential narrative organization, a second analysis identifies lexical cohesive ties (Halliday & Hasan, 1976) that connect the different linguistic texts comprising the game’s narrative chapters. Adopting the lens of intermodality (Painter & Martin, 2011), a final analysis explores how narrative texts and the multimodal environment interface. The second half of this study analyzes L2 learners’ engagement with The Vanishing of Ethan Carter in order to understand the gameplay process as multifaceted literacy practices. Based on video and audio recordings of gameplay sessions, one gameplay analysis tracks communication patterns of L2 dyads across the game’s narrative chapters, focusing on utterance frequency in relation to puzzle-solving and text engagement. To contextualize the L2 dyad utterance patterns, a second analysis examines the substance of learners’ interactions, pointing to variation in puzzle-solving strategies and level of relative textual engagement. A final gameplay analysis describes how learner groups utilize supplementary materials—transcripts of in-game texts and walkthrough videos—as game-external tools for mediating the gameplay process. Results of the study contribute to the growing field of digital game-based language learning. In particular, the game and gameplay analyses frame L2 learners’ experiences playing a digital game as acts of multiliteracy engagement. Additionally, the research design offers a potential expansion to current research practices in a relatively young field of inquiry.
How differences in interactions affect learning and development of design expertise in the context of biomedical engineering design
(2009-05) Svihla, Vanessa; Petrosino, Anthony J. (Anthony Joseph), 1961-
Authentic design commonly involves teams of designers collaborating on ill-structured problems over extended time periods. Nonetheless, design has been studied extensively in sequestered settings, limiting our understanding of design as process and especially of learning design process. This study addresses potential shortcomings of such studies by examining in-situ student team design. The participants of this study are three cohorts of a year-long capstone biomedical engineering design class at The University of Texas. Pilot research demonstrated advantages of a more authentic redesign task over a kit-based design task; students who chose devices to redesign were significantly better at representing perspective taking associated with customers' needs. Pilot research showed that there was no relationship between Early Efficiency (appropriate use of factual and conceptual knowledge) and Final Innovation of design products. I triangulated various methods for studying design: Qualitative research, Hierarchical Linear Modeling, and Social Network Analysis, the latter of which allowed me to generate team-level statistics of interaction (Cohesion), once I devised a practical method to account for missing data in a weighted network. Final Efficiency is a function of Early Innovation, early and late Cohesion, and team feasibility (factual and practical knowledge). Final Innovation is a function of Early Innovation, late Cohesion, and team Voice of the Customer (perspective-taking), with all relationships in both models positive. Measures of both design skills and interaction are required to explain variance in these outcomes. Narratives of team negotiation of design impasses --seemingly insurmountable barriers-- provide deeper understanding of relationships between design process and products. The case study teams spent a large percentage of their time engaged in problem scoping, but framed as engineering science rather than as engineering design. Only when they began prototyping did they transition towards being solution focused and frame the problem as engineering design. This left little time for iteration of the final design. Variance in timing of iteration may account for slight deviations of the case study teams from the statistical model. Recommendations include earlier opportunities to design and support for team collaboration. Social network analysis is recommended when learning is interactional and to support triangulation.
"How do you know god didn't start the universe and blow it up?" : using classroom talk and controversy to support scientific literacy
(2014-05) Freeman, Jennifer Lynn; Schallert, Diane L.
This study investigated the participant structure and content of discourse in five high-school science classrooms and their connection to scientifically literate practices for talking, reasoning, and evaluating claims. Through a detailed exploration of the way teachers introduced classes to the topic of evolution, I was able to examine how teachers used language to build a social framework for participation, examined the opportunities and challenges stemming from their various approaches, and explored how the structure and content of classroom talk contributed to framing science. This study used techniques from interactional sociolinguistics and conversational analysis to examine videos of interaction in five secondary biology classrooms on the day teachers introduced their students to lessons focused on the topic of evolution. Implications of this study focus on how teacher's discourse moves could open or close a discussion to student knowledge contributions, and emphasize how open discussions offer both challenges and opportunities to teachers wishing to facilitate scientifically literate discourse practices in their classroom.
The impact of the business-project interface on capital project performance
(2013-08) Yun, Sungmin; O'Brien, William J.; Mulva, Stephen Patrick
A capital project represents a significant investment by a firm to create future economic benefits. Since the global economic recession begun in 2008, corporate owners have paid increased attention to business-project interfaces with the aim of improving alignment between business strategy and capital project development. Despite its importance, the business-project interface has not been quantitatively measured and no empirical evidence exists about its effects on performance outcomes. This dissertation intends to identify and quantify the business-project interfaces in the development of a capital project in terms of personnel involvement and task interaction, and to investigate its effects on performance outcomes and the value of best practices. To achieve these objectives, a conceptual framework for assessing the involvement and interaction on business-project interfaces was developed. Based on the conceptual framework, a questionnaire including quantitative measures for the assessment of personnel involvement and task interaction was designed. Supplemental survey responses were received for several industrial capital projects that had initially provided capital project data to the CII Benchmarking & Metrics database. The effects of the business-project interface in terms of cost, schedule, change, and business performance were documented. Data analyses show that project groups with high involvement by business personnel and high interaction between business and project units tend to show remarkably improved project performance. Furthermore, this dissertation presents confirmation that projects with high involvement of business unit personnel and intensive implementation of best practices tend to show superior project performance. The primary contribution of this research is to provide a quantitative assessment tool to assess the business-project interface and to document the interface throughout project life cycle. Another contribution is empirical evidence of the benefits on project performance from implementing best practices that were supported by management.
Interaction between proton pump inhibitors and clopidogrel
(2010-08) Oyetayo, Olaonipekun Oladoyin; Talbert, Robert L.; Bailey, Steven R.; Frei, Christopher R.; Ryan, Laurajo
Introduction: Proton pump inhibitors (PPI) may impair the biotransformation of clopidogrel leading to increased major adverse cardiac events (MACE). Available studies have focused solely on patients receiving clopidogrel following a cardiac event. Given the widespread use of this combination, (about 64% in a recent study), this represents a major interaction that deserves further study. The objective of this thesis was to determine if the potential interaction between PPIs and clopidogrel leads to an increase in MACE in high-risk atherosclerotic patients receiving clopidogrel and PPIs as compared to clopidogrel alone. Methods: We conducted a retrospective chart review of patients in the University Hospital System who received clopidogrel between January 1, 2007 and April 30, 2009. Patients were included if they were hospitalized for acute coronary syndromes, stroke/TIA, revascularization (coronary, cerebral or peripheral arteries), or aspirin allergy. The primary outcome was the composite of myocardial infarction (MI), stroke/transient ischemic attack (TIA), coronary artery revascularization, or death (all cause) during the first year following discharge. Secondary outcomes included the composite of MI, stroke /TIA, revascularization (coronary, cerebral or peripheral arteries), or death. Bivariate analyses were conducted using Student’s t test, Mann Whitney U and Chi-square tests where appropriate. Multivariate analysis was conducted to adjust for baseline differences. Results: Overall, 1700 charts were reviewed and 572 patients met study criteria. The median follow-up was 332 days. The most common indication for clopidogrel use was coronary artery revascularization (66%). There were 201 patients in the clopidogrel with PPI group and 371 patients in the clopidogrel without PPI group. Baseline characteristics were evenly matched between both groups except for smoking, liver disease, and prior receipt of a PPI. The primary endpoint occurred in 21 patients in the clopidogrel with PPI group and 38 patients in the clopidogrel without PPI group (10% vs. 10%, p = 0.9, OR 1.02, 95% CI 0.58 – 1.80). The primary endpoint was unchanged after multivariate adjustments for baseline differences (adjusted OR 0.98, 95% CI 0.54 – 1.75). Likewise, there was no difference in the secondary endpoint (14% vs. 15%, p = 0.8, OR 1.02; 95% CI 0.58 – 1.80). The secondary endpoint was also unchanged after multivariate adjustments for baseline differences (adjusted OR 1.04, 95% CI (0.61 – 1.75) Conclusion: Patients receiving clopidogrel with a PPI demonstrated similar rates of MACE when compared to patients receiving clopidogrel without a PPI.
Interaction effects in topological insulators
(2012-05) Wen, Jun, doctor of physics; Fiete, Gregory A; MacDonald, Allan H; Niu, Qian; Yao, Zhen; Chelikowsky, James R
In this thesis we employ various mean-field approaches to study the shortrange interaction effects in topological insulators. We start with the Kane-Mele model on the decorated honeycomb lattice and study the stability of topological insulator phase against different perturbations. We establish an adiabatic connection between a noninteracting topological insulator and a strongly interacting spin liquid in its Majorana fermion representation. We use the Hartree-Fock mean-field approach, slave-rotor approach and slave-boson approach to study correlation effects related to topological insulators. With the spontaneous symmetry breaking mechanism, we can have an interaction driven topological insulator with extended Hubbard models on the kagome lattice and decorated honeycomb lattice. For the interplay among spin-orbit coupling, distortion and correlation effect in transition metal oxides, we use the slave-rotor mean-field approach to study its phase transition. We identify regimes where a strong topological Mott insulator and a weak topological insulator reside due to the strong Coulomb interaction and distortion. This is relevant to experiments with the transition metal oxides as they hold promise to realize topological insulators. To study the doping effects and a possible spin liquid in Kane-Mele-Hubbard model on the honeycomb lattice, we employ the slave-boson mean-field approach which is appropriate for the intermediate interaction strength. We compare our results with those obtained from other methods.
Learning through interaction and embodied practice in a scientific laboratory
(2012-05) Mey, Inger Hansen, 1941-; Keating, Elizabeth Lillian; Sherzer, Joel; Streeck, Jürgen; Hartigan, John; Walters, Keith
This study purports to explore how apprentices in microbiology, through interaction and multimodal activities, acquire the knowledge and skills that are necessary for doing scientific experiments. It aims to examine the ways novices learn to scrutinize and discuss the data under investigation, how experts communicate scientific knowledge about microbes to novices, and how experts and novices together create new scientific knowledge during the apprenticeship. Furthermore, this study aims at explaining the various ways narratives contribute to the socialization of the apprentice into the workplace and the scientific field, and how stories help retain knowledge, gained in one situation, to be used in other contexts and situations. To achieve this aim, I videotaped daily activities in a small microbiology lab, focusing on detailed observations of experts and novices as they engaged in teaching and learning. I was especially interested in what kinds of innovative symbolic communication resources would be invoked during such educational activities. In addition, I collected data pertaining to how the apprentice was socialized into this particular community of practice. I applied a ‘situated learning’ approach to the analysis of the instructional data, as well as discourse analytic and social semiotic methods of analyzing verbal and nonverbal, embodied interaction. I found that researchers, by using embodied and semiotic resources, created moments of shared participation between themselves and their scientific objects. Likewise I found that gestures shaped objects and concepts, and brought these into an intersubjective space where researchers, tools, instruments, and concepts interacted in a collaborative architecture. I named the specific literacy prevalent in scientific experimentation (reading and understanding graphs, diagrams, pictures, etc.) as ‘science literacy’, to distinguish it from the term ‘scientific literacy’, a general understanding of popularized scientific topics. Blurred boundaries were discovered between the living organisms and their semiotic representations whenever the expert and the novice referred to the living organisms in their discussions concerning graphs and diagrams. The researchers changed their terminology, depending on the bacteria changing from animate to inanimate status. Finally, I discovered the significance of contextual tellability in narratives functioning both as introduction to the workplace and as memory devices.
Mechanisms driving species interactions and community structure on the phytochemical landscape
(2023-04-20) Morrison, Colin Richard; Gilbert, Lawrence E.; Sedio , Brian E; Wolf, Amelia A; Smiley, John T
Identifying how variation in abiotic factors and species traits influence the outcome of ecological interactions is fundamental to our understanding of which processes affect community assembly and structure. My goal in this PhD was to describe how nutrient dynamics, plant physical traits, and chemistry affect plant-insect and plant-plant interactions. I pursued this goal in three different systems with natural history observations, comparative field studies, manipulative greenhouse experiments, analytical chemistry, and bioinformatics. I found that investing nitrogen in one tropical passion vine survival strategy did not come at the cost of strategies. Rather, increased soil nitrogen resulted in richer metabolomes, higher leaf toxin concentrations, longer vines, greater biomass, and more leaves with a superior ability to capture sunlight. Next, I investigated how plant traits facilitate the spread of invasive species in Texas, and what consequences their spread has for local communities. I found that lack of variation among native prickly pear nutritional qualities makes them suitable resources to an invasive cactus moth (Cactoblastis cactorum) that recently established in Texas. These findings have serious implications for prickly pear, and their associated food webs that will soon interact with the expanding invasive moth population. I also studied how competition and allelochemical weapons interact to facilitate spread of Guinea grass, a globally distributed invasive pasture grass, in Texas. I found that shading and allelochemistry by Guinea grass interacted to significantly reduce the recruitment and growth of native plants which results in communities with significantly reduced plant diversity. Finally, I compared passion vine phylogenetic, metabolomic, and quantitative traits to describe the drivers of host specialization by sympatric beetles and caterpillars in Costa Rica. I found that passion vine relatedness correlated with host usage in both groups, and different plant characteristics explained how similar each herbivore assemblage was among available hosts. These studies demonstrated the effects of resource availability on plant trait expression and specialized trophic interactions in different environments. Moreover, this dissertation showcased how the mechanisms which govern individual species interactions scale up to influence community structure on a mosaic phytochemical landscape.
Mitigation in Spanish discourse : social and cognitive motivations, linguistic analyses, and effects on interaction and interlocutors
(2010-05) Czerwionka, Lori Ann; Koike, Dale April; Streeck, J�; Beaver, David; Kelm, Orlando; Hensey, Fritz
Mitigation is the modification of language in response to social or cognitive challenges (stressors) in contexts of linguistic interaction (Martinovski, Mao, Gratch, & Marsella 2005). Previous mitigation research has been largely from social perspectives, addressing the word or utterance levels of language. This dissertation presents an empirical study of mitigating language resulting from both a cognitive stressor (degree of uncertainty) and social stressor (degree of imposition) in Spanish discourse, and the impacts of mitigation on interaction and interlocutors. The tripartite approach includes a: (1) quantitative analysis of discourse markers associated with mitigation (speaker-discourse, speaker-listener, and epistemic markers); (2) qualitative discourse analysis, relying on concepts from the Conversation Analysis framework; and (3) qualitative analysis of interlocutors’ perceptions of mitigation, using metalinguistic conversations. The results are discussed considering prior research on mitigation, politeness theories, and Clark’s (2006) model of ‘language use’ to address information types, interlocutor roles, and mutual knowledge. In addition, Caffi and Janney’s (1994) ‘anticipatory schemata’ and Pinker’s (2007) social psychological perspective of indirect language inform the theoretical framework. Results indicate that: (1) Mitigation devices vary depending on contextual factors prompting mitigation, significantly fewer speaker-listener markers are shown as evidence of mitigation, and epistemic markers, which are commonly analyzed mitigation devices, are infrequent overall in these data. These results provide evidence against the assumption that mitigation is associated with increased use of linguistic devices; (2) Two mitigating discourse structures were found, depending on the degree of uncertainty. Within contexts of high-imposition, the Co-reconstruction structure (CRS) is found in contexts with uncertainty and the Non-linear structure (NLS) is in contexts with certainty; and (3) The listeners’ metalinguistic comments indicate that the CRS, compared to the NLS, is preferred. Also, the results indicate how interlocutors address cognitive, social, and emotional stressors in interaction. Considering all analyses, a unifying definition of mitigation in discourse is provided. This phenomenon is characterized as the postponement of both confirmed knowledge and negotiation of the interlocutor relationship. This research contributes the first experimental investigation of mitigation as the result of cognitive and social stressors, and also the first systematic analysis of mitigation in Spanish discourse.
One Butterfly : understanding interface and interaction design for multitouch environments in museum contexts
(2010-05) Whitworth, Erin Casey; Geisler, Gary; Francisco-Revilla, Luis
Museums can be perceived as stuffy and forbidding; web technologies can enable museums to expand access to their collections and counterbalance these perceptions. Museums are searching for new ways to communicate with the public to better make a case for their continued relevance in the digital information age. With the emergence of multitouch computing, other diverse forms of digital access and the popularization of the user experience, challenge museum design professionals to synthesize the information seeking experience that occurs on multiple computing platforms. As a means of addressing these issues, this Master’s Report summarizes the One Butterfly design project. The project's goal was to create a design for a multitouch interface for federated search of Smithsonian collections. This report describes the project’s three major phases. First, an idea for an interface was developed and designs based on that idea were captured and clarified. Second, a formal review of related research was undertaken to ground these designs in the museum informatics, user interface design, and multitouch interaction design literatures. Finally, the report concludes with a review and reflection on the designs and their underlying ideas in light of things learned in the previous phases.
Recasts in the EFL classroom : a comparison of native and nonnative teachers
(2010-05) Yang, Yi-Chun Christine; Blyth, Carl S. (Carl Stewart), 1958-; Schallert, Diane; Horwitz, Elaine K.; Abrams, Zsuzsanna; Svinicki, Marilla
Recasting (i.e., corrective feedback in which the teacher paraphrases a learner's incorrect utterance without explicitly labeling it as erroneous) is a frequent phenomenon in classroom discourse. Despite its frequency and naturalness, educators continue to debate its efficacy. At issue is whether learners notice such implicit feedback in order to make use of it. This on-going debate centers on the following question: What makes a teacher's recast noticeable to a student? While most of the studies in the recast literature have emphasized student factors such as working memory and/or developmental readiness (e.g., Havranek & Cesnik, 2001), few studies have explored how teacher factors affect learner perceptions of and receptivity to recasts. This study fills this gap by employing qualitative methods to investigate student perceptions of their teacher recasts. Six classes in Applied English Departments at three different institutes of technology in mid-southern Taiwan participated in this study. Different methods were employed to gather student and teacher data in order to arrive at a more complete understanding of classroom recasts: classroom observations, individual student interviews, group stimulated recall interviews, and teacher interviews. According to student interview data, seven teacher categories (e.g., nativeness, teacher language use, teacher affect, etc.) were found to have a significant impact on students’ noticing of and receptivity to recasts. In particular, the findings indicate that EFL student perceptions of recasts are profoundly affected by teachers’ language use (e.g. phonetic and syntactic features) and teachers' nativeness (e.g., native vs. nonnative). Other factors such as teacher-student rapport also mediate students’ attention to and understanding of feedback. In addition to the student self-report data, classroom observation data of teachers' behavior indicated striking differences as well--native teachers tended to correct more grammatical errors while nonnative teachers corrected more phonological errors. In light of these findings, suggestions for improving student awareness of corrective recasts are given to both native and nonnative teachers. It is hoped that the qualitative categories uncovered in this study will lead to more rigorous, testable hypotheses for future quantitative analysis.
Review of anti-stigma social media interventions for mental illness
(2018-08-17) Li, Siyan; Stout, Patricia A.
As a global health concern, mental illness mental illness is a leading cause of mortality and morbidity worldwide. The stigma attached to mental illness leads the delay of treatment as well as decrease the quality of life. Therefore, reducing stigma for mental illness is extremely urgent. Mass media shows the potential of many interventions for decreasing mental illness stigma. As a new form of mass media, social media can be more promising in stigma reduction. The benefits of social media include cost-efficiency, privacy-protection, high-accessibility, broad-coverage, and no limitations for time and geography. The most important benefit is the enrichment of interactions. 10 research studies were selected by screening titles, abstracts, and full texts from a database search that yielded 145 results. The research data were collected from two databases on 26 July 2018. The publication date ranges from 2011-2018. By comparing and analyzing these 10 research studies, three questions are answered: (1) What kinds of social media were used? (2) How was social media used in the interventions? (3) What was the effect of social media? As expected, social media interventions are effective at reducing stigma. The effects are more significant in females than in males. Future research and interventions should explore new ways to use the interactive functions of social media and exploit more types of social media platforms. Additionally, the endeavor should also be made to deconstruct social media to find its inner logic and mechanism, in order to develop precise models and techniques to assess its effects on reducing mental illness stigma.
Social presence, interaction, and participation in asynchronous creative writing workshops
(2011-12) Williams, James Patrick; Bias, Randolph G.; Dillon, Andrew; Doty, Philip; Rice-Lively, Mary Lynn; Keating, Elizabeth
Trends in user-generated content on the Web are shifting the role of online course materials, student work, and communications channels in instructional settings. Evidence of users’ interaction with content has been brought into the foreground through interface elements which reflect and encourage interaction, including comments, ratings, tags, “likes”, view statistics, and others. This research considers such features "interaction traces" and explores their use and interpretation by student learners. This research investigates the use and perception of these features by students within a particular type of asynchronous learning environment, the creative writing workshop. Within the two courses studied, a poetry course and a fiction course, two forms of interaction traces were presented: peer criticism posted as comments on creative work and visible view counts for all comments posted in the course. Informed by the Community of Inquiry framework and using a case study methodology, this dissertation investigates whether interaction traces affect perceptions of social presence among students and how students respond to this evidence of the interaction and critique. Data were collected from course discussion transcripts, course management system usage statistics, and participant responses to six surveys. Discussion thread transcripts were subjected to content analysis for indicators of social presence. Additionally, the researcher performed individual interviews with the instructor and a subset of students. Analysis of participants' social presence, interaction with others, and participation in the class revealed evidence that peer criticism was mediated by social presence, that students engaged in a variety of individual relationships based on perceptions developed through interaction traces, and that participant reading and writing activities affected how they perceived the course and their peers. Social presence in comments served not only to humanize participants and to resolve conflict but led to confusion and frustration in some cases. The instructor's high level of social presence in the courses influenced participants and provided a model for some participants' approaches to coursework. Based on the themes which emerged from the case reports, this dissertation suggests some implications for online course planning and course management system design with regard to interaction traces.
Spatiotemporal analysis of animal movement and interactions
(2020-05) Hoover, Brendan Arthur; Miller, Jennifer A. (Jennifer Anne); Arima, Eugenio; Keitt, Timothy; Long, Jed; Middleton, Richard S; Young, Kenneth R
The spatiotemporal aspects of animal telemetry data, collected using technologies such as global positioning systems (GPS) and acoustic sensors, has become a critical area of ecological research. This dissertation contributes to the computational analysis of animal movement by analyzing and introducing methods to facilitate the analysis and interpretation of animal movement, specifically their use of space and their interactions. In Chapter 2, time-based home range methods were evaluated for accuracy in terms of area, shape, and location in response to sample size and common wildlife GPS-point patterns. These characteristics of home range estimation are important for inferring animal habitat and resource use. Despite the improved accuracy of time-based methods compared to traditional point-based methods, location was often inaccurate for all GPS-point patterns, as were shape and area for GPS-point patterns with perforations (common for areas with large physical barriers like mountains or lakes). Therefore, future research should focus on methods aimed at improving home range accuracy. Animal interactions are an important aspect of animal behavioral ecology that impacts processes like predation, mating, and disease spread. Interactions are spatially and temporally variable and can occur either through direct contact or at asynchronous spaces and/or times. Chapter 3 introduces a method, termed the temporally-asynchronous joint potential path area (ta-jPPA), that maps potential areas of spatially-synchronous-temporally-asynchronous interactions in order to link interactions to landscape features or other environmental variables. Given the spatiotemporal nature of animal movements, analysis metrics that quantify interaction often use subjective thresholds to subset or classify telemetry data. In Chapter 4, an unsupervised learning technique is presented as an exploratory data analysis tool that uses the spatiotemporal properties of two animal trajectories to uncover spatiotemporal analysis thresholds. These thresholds are not meant to replace expert knowledge of a species being studied, but to be used when no knowledge exists, as well as to explore different spatiotemporal scales of interaction. Using simulated data, the method was able to distinguish interactions from random movement, found appropriate thresholds based on derived models, and with empirical data the method was able to find patterns that were consistent with previously observed behavior.