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- Title
- EMPIRICAL MODELING OF A MARIJUANA EXPECTANCY MEMORY NETWORK IN CHILDREN AS A FUNCTION OF AGE AND MARIJUANA USE.
- Creator
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Alfonso, Jacqueline, Dunn, Michael, University of Central Florida
- Abstract / Description
-
The present investigation modeled the expectancy memory organization and likely memory activation patterns of marijuana expectancies of children across age and marijuana use. The first phase of the study surveyed 142 children to obtain their first associate to marijuana use. From their responses, the Marijuana Expectancy Inventory for Children and Adolescents (MEICA) was developed. The second phase of the study administered the MEICA to a second sample of 392 children to model marijuana...
Show moreThe present investigation modeled the expectancy memory organization and likely memory activation patterns of marijuana expectancies of children across age and marijuana use. The first phase of the study surveyed 142 children to obtain their first associate to marijuana use. From their responses, the Marijuana Expectancy Inventory for Children and Adolescents (MEICA) was developed. The second phase of the study administered the MEICA to a second sample of 392 children to model marijuana expectancy organization and probable memory activation paths of marijuana users versus never-users. Results indicated that irrespective of age, adolescents who have used marijuana tend to emphasize positive-negative effects, whereas adolescents who have never used marijuana tend to emphasize psychological-physiological effects. Memory activation patterns also differed by marijuana use history such that users are more likely to begin their paths with short-term positive effects of marijuana, versus non-users who access long-term cognitive and physiological effects with more likelihood. This study is the first to examine specific marijuana outcome expectancies of children and adolescents as they relate to marijuana-using behavior. Implications for marijuana prevention and intervention programs, future research, and limitations of the current investigation are discussed.
Show less - Date Issued
- 2005
- Identifier
- CFE0000897, ucf:46629
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000897
- Title
- DECREASING ALCOHOL USE AMONG HIGH SCHOOL STUDENTS BY CHALLENGING ALCOHOL EXPECTANCIES.
- Creator
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Cruz, Iris, Dunn, Michael, University of Central Florida
- Abstract / Description
-
Altering alcohol expectancies has reduced alcohol use among college students and may lead to successful prevention of alcohol use among high school students. We randomly assigned 379 12th-grade students to an expectancy challenge, traditional alcohol information, or control condition, and used Individual Differences Scaling to map expectancies into memory network format with Preference Mapping to model likely paths of association. After expectancy and traditional alcohol interventions, higher...
Show moreAltering alcohol expectancies has reduced alcohol use among college students and may lead to successful prevention of alcohol use among high school students. We randomly assigned 379 12th-grade students to an expectancy challenge, traditional alcohol information, or control condition, and used Individual Differences Scaling to map expectancies into memory network format with Preference Mapping to model likely paths of association. After expectancy and traditional alcohol interventions, higher drinking male participants exhibited a greater likelihood to associate alcohol use with negative and sedating consequences and a decreased likelihood to associate alcohol with positive and arousing consequences. Drinking decreases paralleled the magnitude of changes in their likely path of expectancy activation. Children and adults who emphasize negative and sedating effects have been found to be less likely to use alcohol. Therefore, expectancy challenge interventions that have been successful at modifying expectancies and subsequently decreasing alcohol consumption among heavy drinking college students may be useful in the development of prevention curricula for high school students.
Show less - Date Issued
- 2006
- Identifier
- CFE0001232, ucf:46887
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001232
- Title
- A STUDY ON THE PERCEPTION OF BRAIN GAMES AND THEIR EFFECT ON MEMORY AND COGNITIVE SKILLS.
- Creator
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Heiman, Sheila, Smither, Janan, University of Central Florida
- Abstract / Description
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In this thesis, a literature review was conducted in order to analyze the numerous sources that investigated the effects memory games may have on participants. Each study covered different scopes and methods in the field of cognitive improvement, which gave way to a variety of results used to create a comprehensive literature review. The experiments included in the literature review gathered evidence to find the effect that "brain" games had on memory and cognitive skills. An explanation and...
Show moreIn this thesis, a literature review was conducted in order to analyze the numerous sources that investigated the effects memory games may have on participants. Each study covered different scopes and methods in the field of cognitive improvement, which gave way to a variety of results used to create a comprehensive literature review. The experiments included in the literature review gathered evidence to find the effect that "brain" games had on memory and cognitive skills. An explanation and analysis were made on the brain's deterioration as it ages and the varying amounts of plasticity it contains. The overall perspective gained from the literature review allowed for a better understanding of the results of the surveys conducted for this thesis. The distinctive ways to encourage and improve brain health were researched, and a particular focus was placed on memory games regarding brain health factors. Overall, the benefits identified covered an increase in working memory, skills, and processing speed. However, there was an indication that the improvements were only for the tasks at hand. When research was conducted on transferable activities, there was little to no proof of the transferability of measured improvements. During the research portion of the thesis, a survey was conducted that involved 90 participants from the age of 60 and older on their perception of brain games. The results of the 9-question survey showed statistically significant correlations between the amount of times individuals had played memory games and their perception of both the simplicity and effectiveness of these games. Participants who had played games more frequently viewed the games as both more effective and simpler. Similarly, participants with more education perceived the games as being simpler. The male participants in this study were found to play memory games more frequently than the women. Overall, the correlations drawn from the results of the survey promote the enriched discussion on the subject of memory games and cognitive improvement.
Show less - Date Issued
- 2014
- Identifier
- CFH0004607, ucf:45261
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004607
- Title
- LOW TEMPERATURE AND REDUCED LENGTH SCALE BEHAVIOR OF SHAPE MEMORY AND SUPERELASTIC NITI AND NITIFE ALLOYS.
- Creator
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Manjeri, Radhakrishnan, Vaidyanathan, Raj, University of Central Florida
- Abstract / Description
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Shape memory and superelastic applications of NiTi based alloys have typically been limited to near room temperature or to bulk length scales. The objective of this work is two-fold: first, to investigate shape memory behavior at low temperatures in the context of the R-phase transformation in NiTiFe alloys by recourse to arc-melting, differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and mechanical testing at low temperatures; and second, to investigate...
Show moreShape memory and superelastic applications of NiTi based alloys have typically been limited to near room temperature or to bulk length scales. The objective of this work is two-fold: first, to investigate shape memory behavior at low temperatures in the context of the R-phase transformation in NiTiFe alloys by recourse to arc-melting, differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and mechanical testing at low temperatures; and second, to investigate superelasticity and two-way shape memory behavior at reduced length scales in the context of NiTi by recourse to micro-compression, micro-indentation and TEM studies. Selected compositions of ternary NiTiFe shape memory alloys were arc-melted and thermo-mechanically processed to investigate the influence of composition and processing parameters on the formation of the R-phase. The methodology used for the processing and characterization of the alloys was established and included microprobe analysis, DSC, TEM and mechanical testing. No phase transformation was observed in alloys with Fe content in excess of 4 at.%. Thermo-mechanical treatments facilitated the formation of the R-phase in Ni-rich alloys. The range of the transformation between the R-phase and austenite, and the hysteresis associated with it were influenced by the distribution and size of metastable Ni4Ti3 precipitates. The investigation of the microstructural, thermal and mechanical properties of the R-phase transformation in NiTiFe alloys revealed a complex dependence of these properties on processing parameters. The present work also highlighted the hitherto unexplored competition between the two inelastic deformation modes operating in the R-phase (detwinning and stress-induced transformation) and established the preference of one mode over the other in stress-temperature space. The complete micromechanical response of superelastic NiTi was examined by performing careful micro-compression experiments on single crystal pillars of known orientations using a nanoindenter tip. Specifically, the orientation dependence of the elastic deformation of austenite, the onset of its transformation to martensite, the gradient and the hysteresis in the stress-strain response during transformation, the elastic modulus of the stress-induced martensite and the onset of plasticity of the stress-induced martensite were analyzed in separate experiments. A majority of the results were explained by recourse to a quantitative determination of strains associated with austenite grains transforming to martensite variants or twinning in martensite. Microstructural studies were also performed on a micro-indentation trained NiTi shape memory alloy specimen to understand the mechanisms governing the two-way shape memory effect. In situ TEM studies at temperature on specimens obtained at different depths below the indent showed the presence of retained martensite along with the R-phase. Previously, while such two-way shape memory behavior has typically been associated with large dislocation densities, this work provides evidence of the role of retained martensite and the R-phase in cases with reduced dislocation densities. Funding support for this work from NSF (CAREER DMR-0239512), NASA (NAG3-2751) and SRI is acknowledged.
Show less - Date Issued
- 2009
- Identifier
- CFE0002825, ucf:48065
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002825
- Title
- CONSTRUCTING AFRICAN AMERICAN HISTORIES IN CENTRAL FLORIDA.
- Creator
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Parry, Katherine, Cassanello, Robert, University of Central Florida
- Abstract / Description
-
From the time of their occurrence up to the present, people have constructed and revised narratives about violent racial events in Florida. In the case of the racial violence in Ocoee and the lynching of July Perry, multiple accounts coexisted until one particular group in the 1990's contested earlier conservative white Southern narratives with new public memories containing African American perspectives of the events, demanding racial justice and memorialization of the events. A struggle...
Show moreFrom the time of their occurrence up to the present, people have constructed and revised narratives about violent racial events in Florida. In the case of the racial violence in Ocoee and the lynching of July Perry, multiple accounts coexisted until one particular group in the 1990's contested earlier conservative white Southern narratives with new public memories containing African American perspectives of the events, demanding racial justice and memorialization of the events. A struggle over the power to construct this narrative resulted in compromises between the two sets of memories. While some goals were attained, the landscape of memorization remains undeveloped. The construction of a narrative concerning the meaning of Harry T. Moore's life and death entered the public domain at his death and remained unchanging, carried forward by the collective memories of African Americans in Florida. Historians reassessed his role as a martyr for civil rights to the first martyr of the Civil Right's Movement. A group of African Americans in Brevard County were successful in attaining resources that included landscape and a memorial complex during the 1990's and the first decade of 2000. The construction of public memories and the power to gain landscape and resources for commemoration reflected the aims and power of each group. Because the public memories of July Perry were contested, the group could not attain commemorative landscapes. However, the narratives about Harry T. Moore had consensus, allowing significant commemorations.
Show less - Date Issued
- 2008
- Identifier
- CFE0002271, ucf:47836
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002271
- Title
- Cognitive and vascular risk factors for depression: Testing an integrated theoretical framework.
- Creator
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Scott, Rosanna, Paulson, Daniel, Rapport, Mark, Dvorak, Robert, Dangiolo, Mariana, University of Central Florida
- Abstract / Description
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Objective: Theoretical models that have guided the study of later-life depression include the vascular depression hypothesis, depression-executive dysfunction syndrome, and the CaR-FA-X model. Evidence suggests these can be integrated into a single developmental model of disordered mood (and its associated overgeneral memory feature) in later-life to delineate a mechanism of the vascular depression effect and identify modifiable intervention targets.Methods: In older adults, four serial...
Show moreObjective: Theoretical models that have guided the study of later-life depression include the vascular depression hypothesis, depression-executive dysfunction syndrome, and the CaR-FA-X model. Evidence suggests these can be integrated into a single developmental model of disordered mood (and its associated overgeneral memory feature) in later-life to delineate a mechanism of the vascular depression effect and identify modifiable intervention targets.Methods: In older adults, four serial mediation models evaluated the relationships between (1) vascular burden and depressive symptoms via executive control and rumination, and (2) vascular burden and autobiographical memory specificity (AMS) via executive control and rumination. In younger adults, four simple mediation models were conducted to compare results to older adults, including models assessing the relationships between (1) executive control and depressive symptoms via rumination, and (2) executive control and AMS via rumination. Bias-corrected bootstrapping was employed throughout.Results: Older adult n=56; younger adult n=63. Older adult serial mediation models demonstrated significant individual relationships between a working memory measure and depressive symptoms, as well as between rumination and depressive symptoms. The vascular depression effect neared significance. No other direct or indirect effects were supported. In younger adults, rumination was significantly associated with depressive symptoms; all other hypothesized relationships were not significant.Conclusions: Model 1, evaluating the impact of vascular burden on depressive symptoms in older adults via working memory and rumination, respectively, was the most effective in integrating vascular depression, DED, and CaR-FA-X. However, there was not support for a vascular depression mechanism. Null results in this sample could be attributable to inadequate power or measurement error. Clinically, results promote interventions that target older adults presenting with depression, executive dysfunction, or rumination, independently or combined.
Show less - Date Issued
- 2019
- Identifier
- CFE0007860, ucf:52759
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007860
- Title
- Civil War Memory and the Preservation of the Olustee Battlefield.
- Creator
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Trelstad, Steven, Gannon, Barbara, Walker, Ezekiel, Cassanello, Robert, University of Central Florida
- Abstract / Description
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This thesis explores the absence of a Union monument at the Olustee Battlefield one hundred and fifty-five years after the battle concluded though this field has a number of Confederate monuments. Moreover, after the Battle of Olustee in February 1864, the largest battle of the Civil War fought on Florida soil, the victorious Confederates killed wounded African American soldiers left behind after the Union retreat. This thesis examines why Olustee battlefield became a place of Confederate...
Show moreThis thesis explores the absence of a Union monument at the Olustee Battlefield one hundred and fifty-five years after the battle concluded though this field has a number of Confederate monuments. Moreover, after the Battle of Olustee in February 1864, the largest battle of the Civil War fought on Florida soil, the victorious Confederates killed wounded African American soldiers left behind after the Union retreat. This thesis examines why Olustee battlefield became a place of Confederate memory, enshrining the Lost Cause within its monuments for well over a half of a century that consciously excluded any commemoration of the Union dead. The lack of proper commemoration to the costly Union sacrifices at Olustee comes as a surprise, since some of the Union dead still rest in a mass grave on the battlefield. They remain on this field because after the war, federal soldiers reburied the Olustee dead in a mass grave and erected a temporary memorial that marked their final resting place. This neglect contradicted War department policy that mandated that the reinterred Union dead be in separate graves and marked by individual permanent headstones. When the temporary monument marking their presence disappeared, this also erased the memory of their presence and their sacrifice from the Olustee landscape. This left room for champions of the Confederate Lost Cause - Southern, Confederate Civil War memory - like the United Daughters of Confederacy (UDC) to build monuments to the Confederate cause. In fact, these women worked actively to ensure that the Union dead were not memorialized, particularly the African American casualties. The UDC managed the site until 1949, when the State of Florida assumed control of those grounds. Seventy years of direct control by the state of Florida failed to make a difference in the landscape of memory at Olustee: the Union dead have no monument to commemorate their sacrifice. This thesis explores why the markers, monuments, and policies still honor the Lost Cause memory of the battle, even as the park services in charge of the site promote a reconciliationist narrative and the resurgence of Union memory, including the sacrifice of black US soldiers. Sources used include Official Records of the Union and Confederate Armies, meeting minutes of the UDC, newspaper articles, official documents from the Florida Division of Parks and Recreation, documents from the National Park Service, private correspondences, and state legislature bills.
Show less - Date Issued
- 2019
- Identifier
- CFE0007869, ucf:52763
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007869
- Title
- How Much is Enough? Trauma Recall and the Exposure Therapy Process.
- Creator
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Morrison, Krystal, Beidel, Deborah, Bowers, Clint, Bohil, Corey, University of Central Florida
- Abstract / Description
-
Prevailing theoretical models of posttraumatic stress disorder (PTSD) as well as exposure therapy (EXP) methodology suggest that recall of a trauma is crucial to altering the conditioned fear response associated with PTSD (Benito (&) Walther, 2015; Craske et al., 2008; Foa (&) Kozak, 1986). However, it is unclear whether limited recall of the event impacts the EXP process and treatment outcomes. This study examined whether incomplete trauma recall affected pre-treatment PTSD severity, Initial...
Show morePrevailing theoretical models of posttraumatic stress disorder (PTSD) as well as exposure therapy (EXP) methodology suggest that recall of a trauma is crucial to altering the conditioned fear response associated with PTSD (Benito (&) Walther, 2015; Craske et al., 2008; Foa (&) Kozak, 1986). However, it is unclear whether limited recall of the event impacts the EXP process and treatment outcomes. This study examined whether incomplete trauma recall affected pre-treatment PTSD severity, Initial Fear Activation (IFA), Overall Fear Activation (OFA), Within-Session Habituation (WSH), Between-Session Habituation (BSH; overall extinction), average length of EXP sessions, number of EXP sessions, and post-treatment PTSD severity, in 166 veterans of Operation Enduring Freedom, Operation Iraqi Freedom, and Operation New Dawn, who completed EXP treatment. Contrary to predicted outcomes, the extent of recall did not attenuate veterans' participation in EXP as measured by IFA, OFA, WSH and BSH. Furthermore, less recall did not result in more severe pre-treatment PTSD, longer EXP sessions, more EXP sessions, or attenuated treatment response, as measured by the Clinician-Administered PTSD Scale for DSM-IV (CAPS; Weathers, Ruscio, (&) Keane, 1999) and PTSD Checklist Military Version (PCL-M; Weathers, Huska, (&) Keane, 1991) at pre- and post-treatment. This suggests that veterans who are unable to recall aspects of their traumatic experience can engage successfully and benefit equally from EXP akin to veterans who experience less difficulty recalling trauma details. This research is the first to examine trauma recall in the context of the EXP process and contributes to the current body of literature that aims to address the question: For whom do treatments work?
Show less - Date Issued
- 2018
- Identifier
- CFE0007347, ucf:52116
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007347
- Title
- Impulsivity and Attention-Deficit/Hyperactivity Disorder (ADHD): Testing competing predictions from the working memory and behavioral inhibition models of ADHD.
- Creator
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Raiker, Joseph, Rapport, Mark, Beidel, Deborah, Mouloua, Mustapha, University of Central Florida
- Abstract / Description
-
Impulsivity is a hallmark of two of the three DSM-IV ADHD subtypes and is associated with myriad adverse outcomes. Limited research, however, is available concerning the mechanisms and processes that contribute to impulsive responding by children with ADHD. The current study tested predictions from two competing models of ADHD (-) working memory (WM) and behavioral inhibition (BI) (-) to examine the extent to which ADHD-related impulsive responding was attributable to model-specific...
Show moreImpulsivity is a hallmark of two of the three DSM-IV ADHD subtypes and is associated with myriad adverse outcomes. Limited research, however, is available concerning the mechanisms and processes that contribute to impulsive responding by children with ADHD. The current study tested predictions from two competing models of ADHD (-) working memory (WM) and behavioral inhibition (BI) (-) to examine the extent to which ADHD-related impulsive responding was attributable to model-specific mechanisms and processes. Children with ADHD (n = 21) and typically developing children (n = 20) completed laboratory tasks that provided WM (domain-general central executive [CE], phonological/visuospatial storage/rehearsal) and BI indices (stop-signal reaction time [SSRT], stop-signal delay, mean reaction time). These indices were examined as potential mediators of ADHD-related impulsive responding on two diverse laboratory tasks used commonly to assess impulsive responding (CPT: continuous performance test; VMTS: visual match-to-sample). Bias-corrected, bootstrapped mediation analyses revealed that CE processes significantly attenuated between-group impulsivity differences, such that the initial large-magnitude impulsivity differences were no longer significant on either task after accounting for ADHD-related CE deficits. In contrast, SSRT partially mediated ADHD-related impulsive responding on the CPT but not VMTS. This partial attenuation was no longer significant after accounting for shared variance between CE and SSRT; CE continued to attenuate the ADHD-impulsivity relationship after accounting for SSRT. These findings add to the growing literature implicating CE deficits in core ADHD behavioral and functional impairments, and suggest that cognitive interventions targeting CE rather than storage/rehearsal or BI processes may hold greater promise for alleviating ADHD-related impairments.
Show less - Date Issued
- 2011
- Identifier
- CFE0004155, ucf:49070
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004155
- Title
- ADHD BEHAVIOR PROBLEMS AND NEAR- AND LONG-TERM SCHOLASTIC ACHIEVEMENT: DIFFERENTIAL MEDIATING EFFECTS OF VERBAL AND VISUOSPATIAL MEMORY.
- Creator
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Sarver, Dustin, Rapport, Mark, University of Central Florida
- Abstract / Description
-
The current study examined verbal and visuospatial memory abilities as potential mediators of the relationship among ADHD behavior problems and near- and long-term scholastic achievement. Scholastic achievement was measured initially and at 4-year follow-up in an ethnically diverse sample of children (N = 325). Nested composite (reading, math, language) and domain-specific reading structural equation models revealed that ADHD behavior problems exerted a negative influence on scholastic...
Show moreThe current study examined verbal and visuospatial memory abilities as potential mediators of the relationship among ADHD behavior problems and near- and long-term scholastic achievement. Scholastic achievement was measured initially and at 4-year follow-up in an ethnically diverse sample of children (N = 325). Nested composite (reading, math, language) and domain-specific reading structural equation models revealed that ADHD behavior problems exerted a negative influence on scholastic achievement measures, both initially and at follow-up. Much of this influence, however, was mediated by verbal memory's contribution to near-term achievement, whereas visuospatial memory contributed more robustly to long-term achievement. For the domain-specific math achievement model, the collective influence of verbal and visuospatial memory fully mediated the direct influence of ADHD behavior problems on near-term math achievement, and visuospatial memory alone contributed to both near- and long-term achievement. In all models, measured intelligence made no contribution to later achievement beyond its initial influence on early achievement. The results contribute to the understanding of the developmental trajectory of scholastic achievement, and have potential implications for developing remedial programs targeting verbal and visual memory deficits in children with ADHD behavior problems.
Show less - Date Issued
- 2010
- Identifier
- CFE0003502, ucf:48950
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003502
- Title
- THE MEMORY OF FORGOTTEN THINGS.
- Creator
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Metz, Brittany, Poindexter, Carla, University of Central Florida
- Abstract / Description
-
This thesis investigates my lack of childhood memories and documents how my artwork stands in as a substitute for that lost memory. The first part of the thesis analyzes my early life and influences; the second part analyzes my art making and process. The narrative style of writing is intentionally autobiographical to mimic the narrative style and structure of the thesis installation. My upbringing, interests, creative process, access to materials, and inspiration are fully explored. The...
Show moreThis thesis investigates my lack of childhood memories and documents how my artwork stands in as a substitute for that lost memory. The first part of the thesis analyzes my early life and influences; the second part analyzes my art making and process. The narrative style of writing is intentionally autobiographical to mimic the narrative style and structure of the thesis installation. My upbringing, interests, creative process, access to materials, and inspiration are fully explored. The impact my early life has on my current work is evident. Real memory is combined with created memory in the thesis multi-media installation. I wish to transport the viewer into the dreamlike space I have constructed with found objects and multi-media materials by offering an immersive experience into my world.
Show less - Date Issued
- 2011
- Identifier
- CFE0003649, ucf:48814
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003649
- Title
- Deformation and Phase Transformation Processes in Polycrystalline NiTi and NiTiHf High Temperature Shape Memory Alloys.
- Creator
-
Benafan, Othmane, Vaidyanathan, Rajan, Gordon, Ali, Notardonato, William, Kapat, Jayanta, University of Central Florida
- Abstract / Description
-
The unique ability of shape memory alloys (SMAs) to remember and recover their original shape after large deformation offers vast potential for their integration in advanced engineering applications. SMAs can generate recoverable shape changes of several percent strain even when opposed by large stresses owing to reversible deformation mechanisms such as twinning and stress-induced martensite. For the most part, these alloys have been largely used in the biomedical industry but with limited...
Show moreThe unique ability of shape memory alloys (SMAs) to remember and recover their original shape after large deformation offers vast potential for their integration in advanced engineering applications. SMAs can generate recoverable shape changes of several percent strain even when opposed by large stresses owing to reversible deformation mechanisms such as twinning and stress-induced martensite. For the most part, these alloys have been largely used in the biomedical industry but with limited application in other fields. This limitation arises from the complexities of prevailing microstructural mechanisms that lead to dimensional instabilities during repeated thermomechanical cycling. Most of these mechanisms are still not fully understood, and for the most part unexplored. The objective of this work was to investigate these deformation and transformation mechanisms that operate within the low temperature martensite and high temperature austenite phases, and changes between these two states during thermomechanical cycling. This was accomplished by combined experimental and modeling efforts aided by an in situ neutron diffraction technique at stress and temperature. The primary focus was to investigate the thermomechanical response of a polycrystalline Ni49.9Ti50.1 (in at.%) shape memory alloy under uniaxial deformation conditions. Starting with the deformation of the cubic austenitic phase, the microstructural mechanisms responsible for the macroscopic inelastic strains during isothermal loading were investigated over a broad range of conditions. Stress-induced martensite, retained martensite, deformation twinning and slip processes were observed which helped in constructing a deformation map that contained the limits over which each of the identified mechanisms was dominant. Deformation of the monoclinic martensitic phase was also investigated where the microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were captured and compared to the bulk macroscopic response of the alloy. This isothermal deformation was found to be a quick and efficient method for creating a strong and stable two-way shape memory effect.The evolution of inelastic strains with thermomechanical cycling of the same NiTi alloy, as it relates to the alloy stability, was also studied. The role of pre-loading the material in the austenite phase versus the martensite phase as a function of the active deformation modes (deformation processes as revealed in this work) were investigated from a macroscopic and microstructural perspective. The unique contribution from this work was the optimization of the transformation properties (e.g., actuation strain) as a function of deformation levels and pre-loading temperatures. Finally, the process used to set actuators, referred to as shape setting, was investigated while examining the bulk polycrystalline NiTi and the microstructure simultaneously through in situ neutron diffraction at stress and temperature. Knowledge gained from the binary NiTi study was extended to the investigation of a ternary Ni-rich Ni50.3Ti29.7Hf20 (in at.%) for use in high-temperature, high-force actuator applications. This alloy exhibited excellent dimensional stability and high work output that were attributed to a coherent, nanometer size precipitate phase that resulted from an aging treatment. Finally, work was initiated as part of this dissertation to develop sample environment equipment with multiaxial capabilities at elevated temperatures for the in situ neutron diffraction measurements of shape memory alloys on the VULCAN Diffractometer at Oak Ridge National Laboratory. The developed capability will immediately aid in making rapid multiaxial measurements on shape memory alloys wherein the texture, strain and phase fraction evolution are followed with changes in temperature and stress.This work was supported by funding from the NASA Fundamental Aeronautics Program, Supersonics Project including (Grant No. NNX08AB51A). This work has also benefited from the use of the Lujan Neutron Scattering Center at LANSCE, which is funded by the Office of Basic Energy Sciences DOE. LANL is operated by Los Alamos National Security LLC under DOE Contract No. DE-AC52-06NA25396.
Show less - Date Issued
- 2012
- Identifier
- CFE0004496, ucf:49288
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004496
- Title
- DESIGN, FABRICATION AND TESTING OF A LOW TEMPERATURE HEAT PIPE THERMAL SWITCH WITH SHAPE MEMORY HELICAL ACTUATORS.
- Creator
-
Benafan, Othmane, Vaidyanathan, Raj, University of Central Florida
- Abstract / Description
-
This work reports on the design, fabrication and testing of a thermal switch wherein the open and closed states are actuated by shape memory alloy elements while heat is transferred by a heat-pipe. The motivation for such a switch comes from NASA's need for thermal management in advanced spaceport applications associated with future lunar and Mars missions. For example, as the temperature can approximately vary between 40 K to 400 K during lunar day/night cycles, such a switch can reject...
Show moreThis work reports on the design, fabrication and testing of a thermal switch wherein the open and closed states are actuated by shape memory alloy elements while heat is transferred by a heat-pipe. The motivation for such a switch comes from NASA's need for thermal management in advanced spaceport applications associated with future lunar and Mars missions. For example, as the temperature can approximately vary between 40 K to 400 K during lunar day/night cycles, such a switch can reject heat from a cryogen tank in to space during the night cycle while providing thermal isolation during the day cycle. By utilizing shape memory alloy elements in the thermal switch, the need for complicated sensors and active control systems are eliminated while offering superior thermal isolation in the open state. Nickel-Titanium-Iron (Ni-Ti-Fe) shape memory springs are used as the sensing and actuating elements. Iron (Fe) lowers the phase transformation temperatures to cryogenic regimes of operation while introducing an intermediate, low hysteretic, trigonal R-phase in addition to the usual cubic and monoclinic phases typically observed in binary NiTi. The R-phase to cubic phase transformation is used in this application. The methodology of shape memory spring design and fabrication from wire including shape setting is described. Heat transfer is accomplished via heat acquisition, transport and rejection in a variable length heat pipe with pentane and R-134a as working fluids. The approach used to design the shape memory elements, quantify the heat transfer at both ends of the heat pipe and the pressures and stresses associated with the actuation are outlined. Testing of the switch is accomplished in a vacuum bell jar with instrumentation feedthroughs using valves to control the flow of liquid nitrogen and heaters to simulate the temperature changes. Various performance parameters are measured and reported under both transient and steady-state conditions. Funding from NASA Kennedy Space Center for this work is gratefully acknowledged.
Show less - Date Issued
- 2009
- Identifier
- CFE0002810, ucf:48142
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002810
- Title
- DIRECT, HANDS-ON OR INQUIRY INSTRUCTION: A STUDY OF INSTRUCTIONAL SEQUENCING AND MOTIVATION IN THE SCIENCE CLASSROOM.
- Creator
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Vander Wiede, Jamie, Gill, Michele, University of Central Florida
- Abstract / Description
-
Currently, a debate exists between the strengths and weaknesses of direct and inquiry instruction. Inquiry instruction is related to positive effect on learner motivation whereas supporters of direct instruction point to its ability to adequately support learners' working memories (Hmelo-Silver, Duncan, & Chinn, 2007; Kirschner, Sweller, & Clark, 2006; Kuhn, 2007; Sweller, 1988). This study examined the possibility of combining the best features of both inquiry and direct instruction by...
Show moreCurrently, a debate exists between the strengths and weaknesses of direct and inquiry instruction. Inquiry instruction is related to positive effect on learner motivation whereas supporters of direct instruction point to its ability to adequately support learners' working memories (Hmelo-Silver, Duncan, & Chinn, 2007; Kirschner, Sweller, & Clark, 2006; Kuhn, 2007; Sweller, 1988). This study examined the possibility of combining the best features of both inquiry and direct instruction by sequencing them together. A two-part lesson on electrical circuits was presented in three separate sequences of instruction to middle school students to determine if differences in student motivation and academic achievement emerge depending on whether a guided inquiry lab followed or preceded direct instruction. Results indicated equal levels of perceived competence by students across all instructional sequences and greater interest/enjoyment and perceived autonomy support when the instructional sequence began with a guided inquiry lesson. No significant differences in achievement were reported among the sequences.
Show less - Date Issued
- 2011
- Identifier
- CFE0003902, ucf:48737
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003902
- Title
- Conceptualization and Fabrication of a Bioinspired Mobile Robot Actuated by Shape Memory Alloy Springs.
- Creator
-
Richardson, Lietsel, Das, Tuhin, Pal, Sudeshna, Huang, Helen, University of Central Florida
- Abstract / Description
-
This work is an experimental study and fabrication of design concepts to validate the feasibility of smart materials and their applications in bio-inspired robotics. Shape-Memory Alloy (SMA) springs are selected as the smart material actuators of interest to achieve locomotion in the proposed mobile robot. Based on a previous design of the robot, this work focuses on both implementing a new locomotion concept and reducing size and weight of the previous design, both using SMA based actuators....
Show moreThis work is an experimental study and fabrication of design concepts to validate the feasibility of smart materials and their applications in bio-inspired robotics. Shape-Memory Alloy (SMA) springs are selected as the smart material actuators of interest to achieve locomotion in the proposed mobile robot. Based on a previous design of the robot, this work focuses on both implementing a new locomotion concept and reducing size and weight of the previous design, both using SMA based actuators. Objectives are met in consideration of the conceptual mechanics of circular robot locomotion. The first prototype is a variation of the original design. It consists of a soft, rubber outer shell with three intrinsically attached diametric SMA springs that deform the outer shell during contraction and relaxation. The springs were provided with electrical current in patterns to produce deformation needed to generate momentum and allow the robot to tumble and roll. This design was further improved to provide more stability while rolling.The second design concept is a modification of our previous design leading to reduction in size and weight while maintaining essentially the same mechanism of locomotion. In this case, the SMA springs were externally configured between the end of equi-spaced spokes and the circular core. Upon actuation, the spokes function as diametrically translating legs to generate locomotion. These design concepts are fabricated and experimented on, to determine their feasibility, i.e. whether rolling/tumbling motion is achieved. The scope of the project was limited to demonstration of basic locomotion, which was successful. Future work on this project will address the design of automatic control to generate motion using closed-loop sensor-based actuation.
Show less - Date Issued
- 2019
- Identifier
- CFE0007524, ucf:52589
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007524
- Title
- Development of 3D Vision Testbed for Shape Memory Polymer Structure Applications.
- Creator
-
Thompson, Kenneth, Xu, Yunjun, Gou, Jihua, Lin, Kuo-Chi, University of Central Florida
- Abstract / Description
-
As applications for shape memory polymers (SMPs) become more advanced, it is necessary to have the ability to monitor both the actuation and thermal properties of structures made of such materials. In this paper, a method of using three stereo pairs of webcams and a single thermal camera is studied for the purposes of both tracking three dimensional motion of shape memory polymers, as well as the temperature of points of interest within the SMP structure. The method used includes a stereo...
Show moreAs applications for shape memory polymers (SMPs) become more advanced, it is necessary to have the ability to monitor both the actuation and thermal properties of structures made of such materials. In this paper, a method of using three stereo pairs of webcams and a single thermal camera is studied for the purposes of both tracking three dimensional motion of shape memory polymers, as well as the temperature of points of interest within the SMP structure. The method used includes a stereo camera calibration with integrated local minimum tracking algorithms to locate points of interest on the material and measure their temperature through interpolation techniques. The importance of the proposed method is that it allows a means to cost effectively monitor the surface temperature of a shape memory polymer structure without having to place intrusive sensors on the samples, which would limit the performance of the shape memory effect. The ability to monitor the surface temperatures of a SMP structure allows for more complex configurations to be created while increasing the performance and durability of the material. Additionally, as compared to the previous version, both the functionalities of the testbed and the user interface have been significantly improved.
Show less - Date Issued
- 2015
- Identifier
- CFE0005893, ucf:50860
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005893
- Title
- High-Performance Composable Transactional Data Structures.
- Creator
-
Zhang, Deli, Dechev, Damian, Leavens, Gary, Zou, Changchun, Lin, Mingjie, University of Central Florida
- Abstract / Description
-
Exploiting the parallelism in multiprocessor systems is a major challenge in the post ``power wall'' era. Programming for multicore demands a change in the way we design and use fundamental data structures. Concurrent data structures allow scalable and thread-safe accesses to shared data. They provide operations that appear to take effect atomically when invoked individually.A main obstacle to the practical use of concurrent data structures is their inability to support composable operations,...
Show moreExploiting the parallelism in multiprocessor systems is a major challenge in the post ``power wall'' era. Programming for multicore demands a change in the way we design and use fundamental data structures. Concurrent data structures allow scalable and thread-safe accesses to shared data. They provide operations that appear to take effect atomically when invoked individually.A main obstacle to the practical use of concurrent data structures is their inability to support composable operations, i.e., to execute multiple operations atomically in a transactional manner. The problem stems from the inability of concurrent data structure to ensure atomicity of transactions composed from operations on a single or multiple data structures instances. This greatly hinders software reuse because users can only invoke data structure operations in a limited number of ways.Existing solutions, such as software transactional memory (STM) and transactional boosting, manage transaction synchronization in an external layer separated from the data structure's own thread-level concurrency control. Although this reduces programming effort, it leads to significant overhead associated with additional synchronization and the need to rollback aborted transactions. In this dissertation, I address the practicality and efficiency concerns by designing, implementing, and evaluating high-performance transactional data structures that facilitate the development of future highly concurrent software systems.Firstly, I present two methodologies for implementing high-performance transactional data structures based on existing concurrent data structures using either lock-based or lock-free synchronizations. For lock-based data structures, the idea is to treat data accessed by multiple operations as resources. The challenge is for each thread to acquire exclusive access to desired resources while preventing deadlock or starvation. Existing locking strategies, like two-phase locking and resource hierarchy, suffer from performance degradation under heavy contention, while lacking a desirable fairness guarantee. To overcome these issues, I introduce a scalable lock algorithm for shared-memory multiprocessors addressing the resource allocation problem. It is the first multi-resource lock algorithm that guarantees the strongest first-in, first-out (FIFO) fairness. For lock-free data structures, I present a methodology for transforming them into high-performance lock-free transactional data structures without revamping the data structures' original synchronization design. My approach leverages the semantic knowledge of the data structure to eliminate the overhead of false conflicts and rollbacks.Secondly, I apply the proposed methodologies and present a suite of novel transactional search data structures in the form of an open source library. This is interesting not only because the fundamental importance of search data structures in computer science and their wide use in real world programs, but also because it demonstrate the implementation issues that arise when using the methodologies I have developed. This library is not only a compilation of a large number of fundamental data structures for multiprocessor applications, but also a framework for enabling composable transactions, and moreover, an infrastructure for continuous integration of new data structures. By taking such a top-down approach, I am able to identify and consider the interplay of data structure interface operations as a whole, which allows for scrutinizing their commutativity rules and hence opens up possibilities for design optimizations.Lastly, I evaluate the throughput of the proposed data structures using transactions with randomly generated operations on two difference hardware systems. To ensure the strongest possible competition, I chose the best performing alternatives from state-of-the-art locking protocols and transactional memory systems in the literature. The results show that it is straightforward to build efficient transactional data structures when using my multi-resource lock as a drop-in replacement for transactional boosted data structures. Furthermore, this work shows that it is possible to build efficient lock-free transactional data structures with all perceived benefits of lock-freedom and with performance far better than generic transactional memory systems.
Show less - Date Issued
- 2016
- Identifier
- CFE0006428, ucf:51453
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006428
- Title
- From Ashes To Ash(&)#233;: Memorializing Traumatic Events Through Participatory Digital Archives.
- Creator
-
Carlton, Patricia, Kamrath, Mark, Janz, Bruce, Mauer, Barry, Underberg-Goode, Natalie, Bedwell, Jeffrey, University of Central Florida
- Abstract / Description
-
Traumatic, cataclysmic events, whether caused by man-made or natural forces, threaten the safety, stability, and resilience of a community or state. Additionally, massive media exposure given to documenting and providing information, place the media consumers at psychological risk. As an alternative to broadcast news reports, online memorials and disaster archives provide the public the means and central locations for witnessing catastrophic events, as well as collectively commemorating and...
Show moreTraumatic, cataclysmic events, whether caused by man-made or natural forces, threaten the safety, stability, and resilience of a community or state. Additionally, massive media exposure given to documenting and providing information, place the media consumers at psychological risk. As an alternative to broadcast news reports, online memorials and disaster archives provide the public the means and central locations for witnessing catastrophic events, as well as collectively commemorating and mourning the tragic losses. According to psychological and ethnographic research, narrativizing the trauma through shared memories and artifacts of mourning produce multiple therapeutic benefits, including the likely development of cognitive awareness, empathy, and catharsis.Complicating these benefits, however, are psychological risks of secondary trauma resulting from archiving and curating disaster collections, and the potential for economic and political exploitation. The participatory disaster archives are embedded in trauma culture, serving as public witnesses to survivors of trauma and reinforcing the medical, social, and civic infrastructures associated with a community's recovery from and resilience to calamities. Ironically, the confluence of public archive/memorials with medical and other socio-technical institutions that facilitate recovery from crises, also contribute to trauma culture's sustenance. This dissertation investigates the effects of digitally archiving and memorializing traumatic events through an interdisciplinary methodology of critical cultural studies and ethnography. I argue that participatory disaster archives may both mitigate psychological risks and augment social benefits through adopting protocols of best practice.
Show less - Date Issued
- 2016
- Identifier
- CFE0006277, ucf:51599
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006277
- Title
- Images of Nostalgia: An Exploration of the Creation of Recollection Through Visual Media.
- Creator
-
Dickerson, Allyson, Harris, Christopher, Danker, Elizabeth, Shults, Katherine, Perez, Jonathan, University of Central Florida
- Abstract / Description
-
I create innovative artistic works in which the experiential consciousness of the viewer drifts between objects, images, and the auditory narrative. The work approaches the visualization of memory and the catharsis of the loss felt from death. The projection of light onto lifeless entomological specimens mimics the projection of memory as a means to return to what has been lost. The digital copy of the specimen flickers across their bodies as a tribute to the movement that once possessed them...
Show moreI create innovative artistic works in which the experiential consciousness of the viewer drifts between objects, images, and the auditory narrative. The work approaches the visualization of memory and the catharsis of the loss felt from death. The projection of light onto lifeless entomological specimens mimics the projection of memory as a means to return to what has been lost. The digital copy of the specimen flickers across their bodies as a tribute to the movement that once possessed them. A List of Things that Quicken the Heart is a body of multimedia installation and single channel work that has been completed as part of my candidacy for an Emerging Media: Entrepreneurial Digital Cinema M.F.A. at the University of Central Florida.The single channel video work is created in the essay film mode. The visual elements of the piece are a blend of the effect of contextualizing disparate images and subjects. It is the means by which the audience is led to draw connections to the subject of memory without making any specific inferences. As the assembly of images takes place, so too does the assembly of theoretical and observational threads in the essay narration. As the filmmaker, I am speaking directly to the viewer about the implications of my experiences and observations. The editorial rhythm is such that the viewer is allowed brief pauses in the flow of information to meditate on the subject of nostalgia, and how the film incites them to consider the notion. There will also be an ambient audio component designed with the idea of creating a subtle, auditory contrast between familiar and uncanny ambient sounds.The correlating installations will serve as artifacts of memory, the physical objects relevant to my own nostalgia, which will help to serve as a recollection of the narration. In order to integrate them with the tone of the essay film, the narration will be played as a separate component through speakers that surround the space, so that it will envelope the viewer.
Show less - Date Issued
- 2017
- Identifier
- CFE0006735, ucf:51858
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006735
- Title
- Hyperactivity in attention-deficit/hyperactivity disorder (ADHD): Testing functional relationships with phonological working memory performance and attention.
- Creator
-
Sarver, Dustin, Rapport, Mark, Beidel, Deborah, Mouloua, Mustapha, Vasquez, Eleazar, University of Central Florida
- Abstract / Description
-
Excessive gross motor activity is currently considered a ubiquitous and disruptive feature of attention-deficit/hyperactivity disorder (ADHD); however, an alternative model challenges this premise and hypothesizes a functional relationship between activity level, attention, and working memory. The current study investigated whether, and the extent to which, particular forms of gross motor activity are functionally related to children's attention and phonological working memory performance....
Show moreExcessive gross motor activity is currently considered a ubiquitous and disruptive feature of attention-deficit/hyperactivity disorder (ADHD); however, an alternative model challenges this premise and hypothesizes a functional relationship between activity level, attention, and working memory. The current study investigated whether, and the extent to which, particular forms of gross motor activity are functionally related to children's attention and phonological working memory performance. Objective observations of children's gross motor movements and attention by independent observers were conducted while children with ADHD (n = 29) and typically developing children (n = 23) completed multiple counterbalanced tasks entailing low and high phonological working memory demand. The tasks were then sequenced hierarchically to reflect the lowest to highest activity level condition for each child. Results revealed that (a) ADHD-related phonological working memory performance deficits are moderated by increases in intra-individual activity level, (b) heightened activity level impacts performance independently of changes in observed attention, and (c) increases in particular forms of movement (foot movement and out-of-chair movement) contribute to greater phonological working memory performance within the context of attentive behavior. The findings collectively indicate that phonological working memory deficits in children with ADHD are associated with an inability to up-regulate motor activity to facilitate optimal task performance, and that behavioral treatments targeting reductions in certain forms of hyperactivity may have unintended consequences on working memory functioning in ADHD.
Show less - Date Issued
- 2013
- Identifier
- CFE0004930, ucf:49630
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004930
