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ESTIMATION OF TANGENTIAL MOMENTUM ACCOMMODATION COEFFICIENT USING MOLECULAR DYNAMICS SIMULATION
Title
ESTIMATION OF TANGENTIAL MOMENTUM ACCOMMODATION COEFFICIENT USING MOLECULAR DYNAMICS SIMULATION.
Creator
Finger, George, Kapat, Jayanta, University of Central Florida
Abstract / Description
The Tangential Momentum Accommodation Coefficient (TMAC) is used to improve the accuracy of fluid flow calculations in the slip flow regime. Under such conditions (indicated by Knudsen number greater than 0.001), the continuum assumption that a fluid velocity at a solid surface is equal to the surface velocity is inaccurate because relatively significant fluid "slip" occurs at the surface. Prior work has not led to a method to quickly estimate a value for TMAC - it is frequently assumed. In...
Show moreThe Tangential Momentum Accommodation Coefficient (TMAC) is used to improve the accuracy of fluid flow calculations in the slip flow regime. Under such conditions (indicated by Knudsen number greater than 0.001), the continuum assumption that a fluid velocity at a solid surface is equal to the surface velocity is inaccurate because relatively significant fluid "slip" occurs at the surface. Prior work has not led to a method to quickly estimate a value for TMAC - it is frequently assumed. In this work, Molecular Dynamics techniques are used to study the impacts of individual gas atoms upon solid surfaces to understand how approach velocity, crystal geometry and interatomic forces affect the scattering of the gas atoms, specifically from the perspective of tangential momentum. It is a logical step in the development of a comprehensive technique to estimate total coefficient values to be used by those investigating flows in micro- and nano-channels or on orbit spacecraft where slip flow occurs. TMAC can also help analysis in transitional or free molecular regimes of flow. The gas – solid impacts were modeled using Lennard Jones potentials. Solid surfaces were modeled with approximately 3 atoms wide by 3 atoms deep by 40 or more atoms long. The crystal surface was modeled as a Face Centered Cubic (100). The gas was modeled as individual free gas atoms. Gas approach angles were varied from 10° to 70° from normal. Gas speed was either specified directly or by way of a ratio relationship with the Lennard-Jones energy potential (Energy Ratio). In order to adequately model the trajectories and maintain conservation of energy, very small time steps (on the order of 0.0005 ô , where ô is the natural time unit) were used. For each impact the initial and final tangential momenta were determined and after a series of many impacts, a value of TMAC was calculated for those conditions. The modeling was validated with available experimental data for He gas atoms at 1770 m/s impacting Cu over angles ranging from 10° to 70°. The model agreed within 3% of the experimental values and correctly predicted that the coefficient changes with angle of approach. Molecular Dynamics results estimate TMAC values from a high of 1.2 to a low of 0.25, generally estimating a higher coefficient at the smaller angles. TMAC values above 1.0 indicate backscattering, which has been experimentally observed in numerous instances. The ratio of final to initial momenta, when plotted for a given sequence of gas atoms spaced across a lattice cycle typically follows a discontinuous curve, with continuous portions indicating forward and back scattering and discontinuous portions indicating multiple bounces. Increasing the Energy Ratio above a value of 5 tends to decrease the coefficient at all angles. Adsorbed layers atop a surface influence the coefficient similar to their Energy Ratio. The results provide encouragement to develop the model further, so as to be able in the future to evaluate TMAC for gas flows with Maxwell temperature distributions involving numerous impact angles simultaneously.
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Date Issued
2005
Identifier
CFE0000760, ucf:46567
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000760
Advanced castes at the outset of eusociality in wasps (Vespidae)
Title
Advanced castes at the outset of eusociality in wasps (Vespidae).
Creator
Piekarski, Patrick, Sharanowski, Barbara, Carpenter, James, Hoffman, Eric, University of Central Florida
Abstract / Description
A dominating and widespread view is that evolutionary change is gradual and waits upon mutation. Likewise, it is thought that workers and queens of eusocial insects diverged gradually and stepwise. That is, rudimentary castes preceded advanced castes. This paradigm hinges on eusociality having evolved once in Vespidae, and primitively eusocial paper wasps lacking ontogenetic caste biasing (differentiation of castes during larval development). Using a phylogenomic approach this study shows...
Show moreA dominating and widespread view is that evolutionary change is gradual and waits upon mutation. Likewise, it is thought that workers and queens of eusocial insects diverged gradually and stepwise. That is, rudimentary castes preceded advanced castes. This paradigm hinges on eusociality having evolved once in Vespidae, and primitively eusocial paper wasps lacking ontogenetic caste biasing (differentiation of castes during larval development). Using a phylogenomic approach this study shows strong evidence for two origins of eusociality in vespid wasps, wherein one origin is likely characterized by the sudden appearance of castes with physiological, and perhaps even morphological, differences established before adulthood (i.e. advanced castes). Ontogenetic caste biasing was likely present at the outset of eusociality in the most recent common ancestor of paper wasps, yellowjackets and hornets. This suggests that the definitive, non-temporal castes of eusocial wasps evolved from interactions between mothers and daughters, rather than same generation females. These results challenge the idea that castes began with only rudimentary differences. A model of stepwise caste divergence, which assumes an independent mutation event for each phenotypic caste difference, is unwarranted. It is hypothesized that phenotypic plasticity and cryptic genetic variation may explain how some eusocial societies emerged, and began with advanced castes. The results suggest that evolution can produce alternative phenotypes with many aspects of the phenotype being discrete at the outset. Thus, the emergence and divergence of castes in eusocial vespids was not necessarily a gradual process.
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Date Issued
2017
Identifier
CFE0006640, ucf:51240
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006640
Analyzing Faculty Attitudes and Actions Surrounding Distance Education Accommodations and Inclusiveness Based On UDL Principles
Title
Analyzing Faculty Attitudes and Actions Surrounding Distance Education Accommodations and Inclusiveness Based On UDL Principles.
Creator
Cash, Catherine, Cox, Thomas, Vitale, Thomas, Preston, Michael, Hahs-Vaughn, Debbie, University of Central Florida
Abstract / Description
As distance education continues to increase, it is vital that postsecondary institutions contribute time and resources towards upholding inclusive teaching practices that decrease barriers and increase opportunities for diverse student populations. This study examined faculty attitudes and actions surrounding online accommodations and inclusive teaching practices that were based on Universal Design for Learning (UDL) principles using the Inclusive Teaching Strategies Inventory (ITSI), which...
Show moreAs distance education continues to increase, it is vital that postsecondary institutions contribute time and resources towards upholding inclusive teaching practices that decrease barriers and increase opportunities for diverse student populations. This study examined faculty attitudes and actions surrounding online accommodations and inclusive teaching practices that were based on Universal Design for Learning (UDL) principles using the Inclusive Teaching Strategies Inventory (ITSI), which was adapted into the Inclusive Teaching Strategies Inventory-Distance Education (ITSI-DE) to focus on faculty teaching fully online courses. The ITSI-DE measured the following seven constructs: (a) Accommodations, (b) Accessible Course Materials, (c) Course Modifications, (d) Inclusive Lecture Strategies, (e) Inclusive Classroom, (f) Inclusive Assessment, and (g) Disability Law and Concepts (Lombardi et al., 2015). Exploratory factor analyses (EFA) affirmed a five-factor structure for action subscales, and seven-factor structure for attitudinal subscales for the ITSI-DE. The internal consistency calculated for the ITSI-DE was consistent with prior values reported for the ITSI, which ranged from .70 to .85 (Lombardi et al., 2013). A Pearson product moment correlation was performed, which confirmed a statistically significant correlation between faculty attitudes and actions. Next, a multivariate analyses of variance (MANOVA) was performed to examine if significant differences existed between faculty attitudes and actions based on instructional rank, college, age, or gender. Results affirmed statistically significant differences between faculty attitudes and actions based on gender. Lastly, no significant findings were associated with the three chi square test of association that were performed to identify if college, age, or gender influenced preferred methods of training on inclusive teaching practices. Descriptive statistics indicated the largest percentage of faculty preferred to receive information and training on inclusive teaching practices via online methods (46.8%) versus face-to-face methods (34.3%) and hard copy print methods (18.9%).
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Date Issued
2018
Identifier
CFE0007747, ucf:52399
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007747
Determinants of Satisfaction and EWOM in Collaborative Consumption and the Sharing Economy: Timeshare Stays Versus Peer-to-Peer Accommodations
Title
Determinants of Satisfaction and EWOM in Collaborative Consumption and the Sharing Economy: Timeshare Stays Versus Peer-to-Peer Accommodations.
Creator
Redditt, Jennifer, Fyall, Alan, Gregory, Amy, Ro, Heejung, Orlowski, Marissa, Altinay, Levent, University of Central Florida
Abstract / Description
Considered a disrupter in the lodging industry, sharing economy accommodations have become an emergent field in hospitality literature. While this literature predominantly addresses peer-to-peer accommodations such as Airbnb, it has not considered timeshares, one of the sharing economy pioneers. However, consumer behavior literature has integrated timeshares into the sharing economy due to the shared resource of accommodations between consumers. This study examined the determinants of...
Show moreConsidered a disrupter in the lodging industry, sharing economy accommodations have become an emergent field in hospitality literature. While this literature predominantly addresses peer-to-peer accommodations such as Airbnb, it has not considered timeshares, one of the sharing economy pioneers. However, consumer behavior literature has integrated timeshares into the sharing economy due to the shared resource of accommodations between consumers. This study examined the determinants of Satisfaction (Amenities, Community Belonging, Economic Benefits, Trust, and Vacation Counselor/Host) for consumers of two different types of sharing economy lodging products, timeshares and peer-to-peer accommodations, and their electronic word-of-mouth (eWOM) behavior. Considered a critical travel information source, eWOM has been attributed to affecting purchase decisions in hospitality literature. Current research has revealed a gap in peer-to-peer accommodation studies related to eWOM. This study extended eWOM research by exploring the role of Satisfaction as a mediator between the determinants and eWOM. In addition, accommodation type (timeshare vs. peer-to-peer accommodation) was investigated as a moderator to the relationship between the determinants and Satisfaction, and to the relationship between Satisfaction and eWOM. The study employed the two-step approach of confirmatory factor analysis (CFA) and structural equation modelling (SEM). The results indicated that Amenities, Community Belonging, Economic Benefits, Trust, and Vacation Counselor/Host had a positive impact on sharing economy lodging Satisfaction. Amenities, Economic Benefits, and Trust demonstrated an indirect effect on eWOM behavior through sharing economy lodging satisfaction. The model also revealed that Community Belonging had a direct effect on eWOM. Multiple group SEM revealed that accommodation type moderated the effect of Community Belonging's impact on sharing economy lodging Satisfaction, as well as the effect of sharing economy lodging Satisfaction on eWOM behavior. Satisfaction did not mediate any relationships for peer-to-peer accommodations. This study extends eWOM literature and provides competitive advantage insights between two sharing economy accommodation types.
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Date Issued
2019
Identifier
CFE0007854, ucf:52785
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007854
THE IMPACT OF MEDITATION AND MINDFULNESS IN THE ELEMENTARY CLASSROOM: A REVIEW OF RESEARCH LITERATURE ACROSS FIVE DISCIPLINES
Title
THE IMPACT OF MEDITATION AND MINDFULNESS IN THE ELEMENTARY CLASSROOM: A REVIEW OF RESEARCH LITERATURE ACROSS FIVE DISCIPLINES.
Creator
Routhier-Martin, Kayli, Killingsworth Roberts, Sherron, University of Central Florida
Abstract / Description
Mindfulness meditation programs, benefits, and outcomes were examined through research previously conducted and published by professionals within five differing disciplines: health and wellness, psychology, elementary education, exceptional education, and medicine. The goal was to find common themes within the differing disciplines in order to gather information about the effectiveness of a mindfulness meditation program to be used in an elementary classroom. In this thesis, the chapter of...
Show moreMindfulness meditation programs, benefits, and outcomes were examined through research previously conducted and published by professionals within five differing disciplines: health and wellness, psychology, elementary education, exceptional education, and medicine. The goal was to find common themes within the differing disciplines in order to gather information about the effectiveness of a mindfulness meditation program to be used in an elementary classroom. In this thesis, the chapter of Health and Wellness is a review of literature that tells the benefits found within meditators, which are not found within non-meditators. The chapter of Psychology explains the social-emotional needs of students, the causes of stress and anxieties amongst students, and the benefits that meditation provides in order to counter the negative effects of stress, anxiety, poverty, etc. The chapter of Elementary Education reviews research literature on the existing mindfulness meditation programs within the United States. This chapter also describes the implementation of such a program in an elementary school, as well as the documented data of the outcomes of the programs. The chapter of Exceptional Education is a review of the research literature on the benefits mindfulness meditation has on students with exceptionalities, such as specific learning disabilities, attention deficit hyperactivity disorder, and autism spectrum disorder. The chapter of Medicine is a retelling of previously published scholarly articles that list the neurological benefits of meditation, and also references the negative side effects to the currently prescribed medications that are being used in the treatment of ADHD.
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Date Issued
2015
Identifier
CFH0004877, ucf:45424
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH0004877
Role Ambiguity: Defining the Elusive Role of the Special Education Teacher Who Works in Inclusive Settings
Title
Role Ambiguity: Defining the Elusive Role of the Special Education Teacher Who Works in Inclusive Settings.
Creator
Slanda, Dena, Little, Mary, Martin, Suzanne, Pearl, Cynthia, Boote, David, University of Central Florida
Abstract / Description
This phenomenological study examined the lived experiences of special education teachers who worked in inclusive settings. Given the increasing number of students with disabilities receiving special education services in the general education classroom (U.S. Department of Education, 2016), there is a critical need to understand the dynamic role of a special education teacher who works in inclusive settings. Federal mandates have required special education teachers working in inclusive...
Show moreThis phenomenological study examined the lived experiences of special education teachers who worked in inclusive settings. Given the increasing number of students with disabilities receiving special education services in the general education classroom (U.S. Department of Education, 2016), there is a critical need to understand the dynamic role of a special education teacher who works in inclusive settings. Federal mandates have required special education teachers working in inclusive settings to rethink their roles (McLeskey, Landers, Hoppey, (&) Williamson, 2011) and restructure their approach to providing specially-designed services. Further, these roles are dependent on those who interpret and implement policy and access to finite resources. This study used a phenomenological research method to examine the roles and responsibilities of special education teachers. Semi-structured interviews were conducted with seven participants (N = 7). A thematic analysis resulted in five overarching themes. The five themes included: (a) supporting students with disabilities within a support facilitation model; (b) role ambiguity of the special education teacher; (c) the lack of roles and responsibilities of the special education teacher within the MTSS framework; (d) the changing role of collaboration and communication; and (e) the challenges impacting the inclusion of students with disabilities in the general education setting. This study exposed the multiple facets of school and district policies that directly affected special educators' roles and responsibilities, as well as the emergence of a new role as a support facilitator.
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Date Issued
2017
Identifier
CFE0006796, ucf:51821
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006796