View All Items

Title: EFFECT OF REPEATED FUNCTION ALLOCATION AND RELIABILITY ON AUTOMATION INDUCED MONITORING INEFFICIENCY.
Creator: Jones, Lauriann, Mouloua, Mustapha, University of Central Florida
Abstract / Description: The purpose of this study is to extend previous findings of Mouloua, Parasuraman, and Molloy (1993), Parasuraman, Mouloua, and Molloy (1996), Hilburn, Parasuraman, and Mouloua (1996), and Oakley, Mouloua, and Hancock (2003) by: 1) examining the effect of repeated adaptive function allocation to manual control of minimal length (5 minutes) to reduce of human error and minimize workload; 2) explore the placement or timing of adaptive function allocation intervals (approximately 20 minutes of...
Show moreThe purpose of this study is to extend previous findings of Mouloua, Parasuraman, and Molloy (1993), Parasuraman, Mouloua, and Molloy (1996), Hilburn, Parasuraman, and Mouloua (1996), and Oakley, Mouloua, and Hancock (2003) by: 1) examining the effect of repeated adaptive function allocation to manual control of minimal length (5 minutes) to reduce of human error and minimize workload; 2) explore the placement or timing of adaptive function allocation intervals (approximately 20 minutes of automation control to reduce the human operators' monitoring decrement between intervals, maintain adaptive recovery performance levels, and improve response times); 3) examine different levels of automation reliability (30%, 60%, and 90% reliable); 4) explore factors that may be manipulated to reduce automation-induced monitoring inefficiency, increase detection of automation malfunctions, improve situation awareness, reduce response/reaction times, and reduce workload in a simulated complex aviation system. The study was a 2 (non-adaptive control vs. adaptive group) x 3 (30%, 60%, and 90% automation reliability condition) x 4 (repeated 25 minute session) mixed factorial design. Fifty-four undergraduate participants' (i.e., 27 participants per group; 9 participants per condition; at least 18 yrs. of age) percentage of detected malfunctions, response times, and subjective workload were gathered from the Multi-Attribute Task Battery and the NASA TLX. Results indicated a significant improvement in detection of malfunctions and response times during adaptive-function allocation to manual control but without adaptive recovery. There was a significant effect for workload found between baseline measures and experimental sessions by group in the first session but not across experimental sessions. Theoretical and practical implications, limitations and future research are discussed.
Show less
Date Issued: 2007
Identifier: CFE0001874, ucf:47387
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001874

Title: THE EFFECTS OF DIFFERENTIAL ITEM FUNCTIONING ON PREDICTIVE BIAS.
Creator: Bryant, Damon, Stone-Romero, Eugene, University of Central Florida
Abstract / Description: The purpose of this research was to investigate the relation between measurement bias at the item level (differential item functioning, dif) and predictive bias at the test score level. Dif was defined as a difference in the probability of getting a test item correct for examinees with the same ability but from different subgroups. Predictive bias was defined as a difference in subgroup regression intercepts and/or slopes in predicting a criterion. Data were simulated by computer. Two...
Show moreThe purpose of this research was to investigate the relation between measurement bias at the item level (differential item functioning, dif) and predictive bias at the test score level. Dif was defined as a difference in the probability of getting a test item correct for examinees with the same ability but from different subgroups. Predictive bias was defined as a difference in subgroup regression intercepts and/or slopes in predicting a criterion. Data were simulated by computer. Two hypothetical subgroups (a reference group and a focal group) were used. The predictor was a composite score on a dimensionally complex test with 60 items. Sample size (35, 70, and 105 per group), validity coefficient (.3 or .5), and the mean difference on the predictor (0, .33, .66, and 1 standard deviation, sd) and the criterion (0 and .35 sd) were manipulated. The percentage of items showing dif (0%, 15%, and 30%) and the effect size of dif (small = .3, medium = .6, and large = .9) were also manipulated. Each of the 432 conditions in the 3 x 2 x 4 x 2 x 3 x 3 design was replicated 500 times. For each replication, a predictive bias analysis was conducted, and the detection of predictive bias against each subgroup was the dependent variable. The percentage of dif and the effect size of dif were hypothesized to influence the detection of predictive bias; hypotheses were also advanced about the influence of sample size and mean subgroup differences on the predictor and criterion. Results indicated that dif was not related to the probability of detecting predictive bias against any subgroup. Results were inconsistent with the notion that measurement bias and predictive bias are mutually supportive, i.e., the presence (or absence) of one type of bias is evidence in support of the presence (or absence) of the other type of bias. Sample size and mean differences on the predictor/criterion had direct and indirect effects on the probability of detecting predictive bias against both reference and focal groups. Implications for future research are discussed.
Show less
Date Issued: 2004
Identifier: CFE0000157, ucf:46160
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000157

Title: METACOGNITIVE COACHING AS A MEANS TO ENHANCE COLLEGE AND CAREER SUCCESS FOR STUDENTS WITH EXECUTIVE FUNCTION DISORDERS.
Creator: Parsons, Christine, Marino, Matthew, Ph.D., University of Central Florida
Abstract / Description: Preparing undergraduate students for careers in science, technology, engineering, and mathematics (STEM) fields continues to be a national priority. This project analyzed the effects of virtual metacognitive academic coaching between graduate student coaches and undergraduate STEM majors with Executive Function disorders at a large, four-year university. The project team analyzed the persistence of the undergraduate students in their major, as well as the graduate students' abilities to...
Show morePreparing undergraduate students for careers in science, technology, engineering, and mathematics (STEM) fields continues to be a national priority. This project analyzed the effects of virtual metacognitive academic coaching between graduate student coaches and undergraduate STEM majors with Executive Function disorders at a large, four-year university. The project team analyzed the persistence of the undergraduate students in their major, as well as the graduate students' abilities to transfer the coaching experiences to K-12 settings. A mixed-methods design evaluated qualitative (i.e. student/coaches' surveys and interviews) outcomes for undergraduate STEM majors and for graduate students. The goal of this project is to develop iteratively a model of scalable supports that can be utilized to support undergraduates with disabilities in STEM majors' at large universities such as UCF. Graduate student coaches paired with undergraduate STEM majors with Executive Function disorders (n=26) worked collaboratively throughout one semester to developed strategies that supported the success of the undergraduate students' coursework. Both coaches and students provided examples of positive effects of the academic coaching process that supported student course work and created experiences that the graduate students could use in a K-12 setting.
Show less
Date Issued: 2016
Identifier: CFH2000176, ucf:45947
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000176

Title: THE RELATIONSHIP OF PARENTS' WORK STRESS AND CHILD FUNCTIONING IN THE CONTEXT OF SPILLOVER EFFECTS, MARITAL AND PARENTING STRESS, AND PARENTS' PERCEPTIONS.
Creator: Hare, Megan, Renk, Kimberly, University of Central Florida
Abstract / Description: Given that working is something parents cannot avoid in our society, understanding the ramifications that work stress can have is an important tool in today's society. This study sought to investigate the impact of parents' work stress on young children in the context of work-family spillover, parenting stress, marital stress, and perceptions of parenting. As part of this study, 106 working parents of children who ranged in age from 1- to 5-years rated their stress levels across multiple...
Show moreGiven that working is something parents cannot avoid in our society, understanding the ramifications that work stress can have is an important tool in today's society. This study sought to investigate the impact of parents' work stress on young children in the context of work-family spillover, parenting stress, marital stress, and perceptions of parenting. As part of this study, 106 working parents of children who ranged in age from 1- to 5-years rated their stress levels across multiple domains (i.e., work, marriage, and parenting), their perceived parenting behaviors, and their young child's emotional and behavioral functioning. Correlational results of this study supported the hypothesis that these variables would be related significantly to young children's emotional and behavioral functioning. Further, hierarchical regression analyses revealed that a single variable did not predict significantly young children's internalizing and externalizing behaviors but that a combination of work stress, work-family spillover, parenting stress, marital stress, and perceptions of parenting were important in accounting for variance. The results of this study emphasized the importance of studying the selected variables collectively so that employers can evaluate current workplace policies and resources to help minimize work stress and work-family spillover.
Show less
Date Issued: 2014
Identifier: CFH0004645, ucf:45308
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004645

Title: THE EFFECTIVENESS OF FUNCTIONAL MOVEMENT SCREENING TESTING IN PREVENTION OF ANTERIOR CRUCIATE LIGAMENT INJURIES IN WOMEN'S COLLEGIATE SOCCER.
Creator: Ferrara, Morgan P, Fisher, Thomas, University of Central Florida
Abstract / Description: The Functional Movement Screen (FMS), invented in 1995, has been adopted among Division One sports programs across the country. Being a women's soccer player at the University of Central Florida (UCF), this particular topic had been of interest for years. The FMS is a series of seven tests evaluated at the beginning and end of each season. The UCF team's preventative rehabilitation was based upon the measurements from the FMS testing. The team engaged in preventative rehabilitation three...
Show moreThe Functional Movement Screen (FMS), invented in 1995, has been adopted among Division One sports programs across the country. Being a women's soccer player at the University of Central Florida (UCF), this particular topic had been of interest for years. The FMS is a series of seven tests evaluated at the beginning and end of each season. The UCF team's preventative rehabilitation was based upon the measurements from the FMS testing. The team engaged in preventative rehabilitation three times a week. Each year of my membership, the team of 28 to 30 players had no less than two anterior cruciate ligament tears each season. This research explored the effectiveness of the Functional Movement Screening, and its' predictive ability regarding injury to possibly prevent future injuries. The purpose of this study was to review literature of multiple studies exploring the Functional Movement Screen, the anterior cruciate ligament, and, specifically, the recent spike in women's collegiate soccer injuries. This study also examined and included findings from five years of FMS scoring data from the UCF women's soccer team. The study consisted of 43 participants, 29 in the control group and 14 in the test group (those who suffered and ACL tear). They were females, ages 18-23, and of fit manner. Multivariate analysis, independent and dependent T-Tests, and Leven's test ran these data. This study also investigated the reliability of the Functional Movement Screen and analyzed data about anterior cruciate ligament injuries among women's collegiate soccer players. Recommendations for future protocols and implications for coaches, trainers, and women soccer players are provided.
Show less
Date Issued: 2018
Identifier: CFH2000297, ucf:45774
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000297

Title: SEX DETERMINATION USING DISCRIMINANT FUNCTION ANALYSIS OF CARPALS FROM MAYA SITES IN BELIZE FROM PRE-CLASSIC TO SPANISH COLONIAL PERIOD.
Creator: Labbe, Michelle D, Williams, Lana, University of Central Florida
Abstract / Description: The sexing of human skeletal remains is important for identification and demographic purposes. It is made more difficult when elements such as the skull and pelvis are not recovered or are in too poor of a condition to assess. Previous studies have used carpal (wrist) bones of contemporary populations to assess the viability of these skeletal elements exhibiting sexual dimorphism, as these bones are small, compact elements that are usually recovered in good condition. This study evaluates the...
Show moreThe sexing of human skeletal remains is important for identification and demographic purposes. It is made more difficult when elements such as the skull and pelvis are not recovered or are in too poor of a condition to assess. Previous studies have used carpal (wrist) bones of contemporary populations to assess the viability of these skeletal elements exhibiting sexual dimorphism, as these bones are small, compact elements that are usually recovered in good condition. This study evaluates the use of carpal bones recovered from an ancient Maya population from Belize to determine the biological sex of individuals. The study sample is part of the Maya Archaeological Skeletal Collection (MASC), which contains individuals from the sites of Lamanai, San Pedro, Altun Ha, and Marco Gonzalez and dates from the Late Maya Pre-Classic (400 BC-AD 250) to the Spanish Colonial period (AD 1521-1821). Multiple measurements were taken on 36 capitate, 34 lunate, 34 scaphoid, 27 trapezium, 24 hamate, 22 triquetral, 22 trapezoid, and 16 pisiform bones from several individuals. Discriminant function analysis was used to determine if sexual dimorphism is measurable in this population using these elements. Previous studies used populations with known identities, assessing individuals from crypts, graveyards, or medical collections from the last few centuries. This study varies from previous studies as it utilizes archaeological remains, making this study one of the first to evaluate non-contemporary remains with unknown sex. Results of this study demonstrate that this population exhibits sexual dimorphism and discriminant function analysis can be used to distinguish between two groups. This demonstrates that carpals could be used to help determine biological sex of archaeological populations as well as a tool to help with identification in forensic cases.
Show less
Date Issued: 2019
Identifier: CFH2000562, ucf:45645
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000562

Title: GOLD NANOPARTICLES: SYNTHESIS, PROPERTY STUDY AND APPLCICATIONS FORBIOMOLECULAR DETECTION AND PHOTOTHERMAL THERAPY.
Creator: liu, xiong, Huo, Qun, University of Central Florida
Abstract / Description: This dissertation presents a systematic study on gold nanoparticles: from their chemical synthesis, modification of surface functionalities, optical properties studies with emphasis on the absorption and scattering properties, to applications of gold nanoparticles in biomolecular detection, imaging and photothermal therapy. In chapter 2, we studied the kinetics of gold nanoparticle growth under Brust-Shiffrin reaction conditions. In chapter 3, we further examined the reaction mechanism and...
Show moreThis dissertation presents a systematic study on gold nanoparticles: from their chemical synthesis, modification of surface functionalities, optical properties studies with emphasis on the absorption and scattering properties, to applications of gold nanoparticles in biomolecular detection, imaging and photothermal therapy. In chapter 2, we studied the kinetics of gold nanoparticle growth under Brust-Shiffrin reaction conditions. In chapter 3, we further examined the reaction mechanism and growth kinetics of gold nanoparticles using oleylamine as both a reducing reagent and particle growth passivation ligand. From these two projects, important understanding was revealed on gold nanoparticle formation and growth mechanism. Chapter 4 describes the synthesis of a monofunctional gold nanoparticle through a solid phase place exchange reaction. From Chapter 5, we moved to the optical property study of gold nanoparticles, particularly the absorption and scattering phenomenon. In this work a systematic analysis on the extinction coefficient of gold nanoparticles was performed, providing meaningful references for applications based on optical absorption properties of gold nanoparticles. In Chapter 6 and Chapter 7, we developed a one-step homogeneous immunoassay for protein detection and analysis based on the strong light scattering of gold nanoparticles and dynamic light scattering detection technique. In Chapter 8, we further improved the stability of gold nanoparticle bioconjugates using a poly(ethylene glycol)-coated gold nanoparticles and further tested this nanoparticle in the one-step homogeneous immunoassay. Finally in Chapter 9, we demonstrated the application of gold nanoparticles for in vitro bioimaging and photothermal therapy of a lung cancer cell. In summary, this dissertation presents a comprehensive study on the synthesis, surface modification, property study of gold nanoparticles and their applications in biomolecular imaging and analysis.
Show less
Date Issued: 2009
Identifier: CFE0002874, ucf:48020
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002874

Title: Cognitive and vascular risk factors for depression: Testing an integrated theoretical framework.
Creator: Scott, Rosanna, Paulson, Daniel, Rapport, Mark, Dvorak, Robert, Dangiolo, Mariana, University of Central Florida
Abstract / Description: 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: Impulsivity and Attention-Deficit/Hyperactivity Disorder (ADHD): Testing competing predictions from the working memory and behavioral inhibition models of ADHD.
Creator: 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: TRANSPLANTATION OF IPS CELLS REDUCES APOPTOSIS AND FIBROSIS AND IMPROVES CARDIAC FUNCTION IN STREPTOZOTOCIN-INDUCED DIABETIC RATS.
Creator: Neel, Sarah, Singla, Dinender, University of Central Florida
Abstract / Description: Background: Streptozotocin (STZ) induced diabetes leads to various complications including cardiomyopathy. Recent data suggests transplanted bone marrow stem cells improve cardiac function in diabetic cardiomyopathy. However, whether modified ES, iPS cells, or factors released from these cells can inhibit apoptosis and fibrosis remains completely unknown. The present study was designed to determine the effects of transplanted ES cells overexpressing pancreatic transcription factor 1 a (Ptf1a)...
Show moreBackground: Streptozotocin (STZ) induced diabetes leads to various complications including cardiomyopathy. Recent data suggests transplanted bone marrow stem cells improve cardiac function in diabetic cardiomyopathy. However, whether modified ES, iPS cells, or factors released from these cells can inhibit apoptosis and fibrosis remains completely unknown. The present study was designed to determine the effects of transplanted ES cells overexpressing pancreatic transcription factor 1 a (Ptf1a), a pro-pancreatic endodermal transcription factor, iPS cells, or their respective conditioned media (CM) on diabetic cardiomyopathy. Methods: Experimental diabetes was induced in male Sprague Dawley rats (8-10 weeks old) by intraperitoneal STZ injections (65 mg/kg body weight for 2 consecutive days). Animals were divided into six experimental groups including control, treated with sodium citrate buffer IP, STZ, STZ + ES-Ptf1a cells, STZ + iPS cells, STZ + ES-Ptf1a CM and STZ + iPS CM. Following STZ injections, appropriate cells (1 X 106/mL/injection/day) or CM (2 mL injection/day) were given intravenously for 3 consecutive days. Animals were sacrificed and hearts were harvested at day 28. Histology, TUNEL staining, and Caspase-3 activity were used to assess apoptosis and fibrosis. ERK1/2 phosphorylation was quantified using ELISAs. M-mode echocardiography fractional shortening was used to assess cardiac function. Results: Animals transplanted with ES cells, iPS cells, or both CMs showed a significant (p<0.05) reduction in interstitial fibrosis, and apoptosis compared with STZ group. ERK expression was not significantly different compared with STZ. Echocardiography showed a significant (p<0.05) improvement in fractional shortening in cell and media transplanted groups compared with STZ. Conclusions: Our data suggest that ES cells, iPS cells, and/or CMs inhibit apoptosis, reduce fibrosis, and improve cardiac function in STZ-treated diabetic rats.
Show less
Date Issued: 2010
Identifier: CFE0003512, ucf:48964
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003512

Title: Multicultural Personality and Psychological Functioning.
Creator: Trottier, Lauren, Negy, Charles, Cassisi, Jeffrey, Renk, Kimberly, University of Central Florida
Abstract / Description: As the U.S. becomes increasingly diverse, individuals will need to interact effectively with a wide range of people. The theory of multicultural personality refined by Ponterotto (2010) proposes that some individuals may be better suited than others to adapt to the changing demographic landscape. Individuals with a multicultural personality are theorized to have the ability to interact effectively within a wide range of contexts and draw on diverse experiences and resources to solve everyday...
Show moreAs the U.S. becomes increasingly diverse, individuals will need to interact effectively with a wide range of people. The theory of multicultural personality refined by Ponterotto (2010) proposes that some individuals may be better suited than others to adapt to the changing demographic landscape. Individuals with a multicultural personality are theorized to have the ability to interact effectively within a wide range of contexts and draw on diverse experiences and resources to solve everyday problems in multiple ways as well as seek out diversity in their lives. Because of their skills and disposition, Ponterotto (2010) suggests that those with a multicultural personality may experience better psychological functioning than their non-multicultural counterparts. The current study utilized Structural Equation Modeling to test the hypothesis that individuals who endorse greater multicultural personality also exhibit less prejudice, greater ethnic identity, and better psychological functioning, defined as a combination of subjective well-being and clinical symptomology. Results indicated moderate fit to the data and examination of specific paths within the model suggests that the relationship between multicultural personality and subjective well-being may be stronger than that between multicultural personality and clinical symptomology. Differences by ethnicity were also found on measures of ethnic identity and mental health. These results highlight the need to further refine the concept of multicultural personality as well as examine the complex relationships between multicultural personality, subjective well-being, and clinical symptomology.
Show less
Date Issued: 2013
Identifier: CFE0004950, ucf:49567
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004950

Title: DENSITY FUNCTIONAL THEORY STUDY OF MOLECULES AND CRYSTALS CONTAINING D AND F METALS.
Creator: Gangopadhyay, Shruba, Masunov, Artem, University of Central Florida
Abstract / Description: Density Functional Theory (DFT) method is applied to study the crystal structure of transition metal and lanthanide oxides, as well as molecular magnetic complexes. DFT is a widely popular computational approach because it recasts a many-body problem of interacting electrons into an equivalent problem of non-interacting electrons, greatly reducing computational cost. We show that for certain structural properties like phase stability, lattice parameter and oxygen migration energetics pure DFT...
Show moreDensity Functional Theory (DFT) method is applied to study the crystal structure of transition metal and lanthanide oxides, as well as molecular magnetic complexes. DFT is a widely popular computational approach because it recasts a many-body problem of interacting electrons into an equivalent problem of non-interacting electrons, greatly reducing computational cost. We show that for certain structural properties like phase stability, lattice parameter and oxygen migration energetics pure DFT can give good agreement with experiments. But moving to more sensitive properties like spin state energetic certain modifications of standard DFT are needed. First we investigated mixed ionic-electronic conducting perovskite type oxides with a general formula ABO3 (where A =Ba, Sr, Ca and B = Co, Fe, Mn). These oxides often have high mobility of the oxygen vacancies and exhibit strong ionic conductivity. They are key materials that nd use in several energy related applications, including solid oxide fuel cell (SOFC), sensors, oxygen separation membranes, and catalysts. Different cations and oxygen vacancies ordering are examined using plane wave pseudopotential density functional theory. We nd that cations are completely disordered, whereas oxygen vacancies exhibit a strong trend for aggregation in L-shaped trimer and square tetramer structure. On the basis of our results, we suggest a new explanation for BSCF phase stability. Instead of linear vacancy ordering, which must take place before the phase transition into brownmillerite structure, the oxygen vacancies in BSCF prefer to form the nite clusters and preserve the disordered cubic structure. This structural feature could be found only in the rst-principles simulations and cannot be explained by the effect of the ionic radii alone. In order to understand vacancy clustering and phase stability in oxygen-deficient barium strontium cobalt iron oxide (BSCF), we predict stability and activation energies for oxygen vacancy migration. Using symmetry constrained search and Nudged Elastic Band method, we characterize the transition states for an oxygen anion moving into a nearby oxygen vacancy site that is surrounded by different cations and find the activation energies to vary in the range 30-50 kJ/mol in good agreement with experimental data. Next we study spin alignments of single molecule magnets (SMM). SMMs are a class of polynuclear transition metal complexes, which characterized by a large spin ground state and considerable negative anisotropy. These properties lead to a barrier for the reversal of magnetization. For these reasons SMM are expected to be promising materials for molecular spintronics and quantum computing applications. To design SMM for quantum computation, we need to accurately predict their magnetic properties. The most important property is, Heisenberg exchange coupling constant (J). This constant appears in model Heisenberg Hamiltonian that can be written in general form as here Jij represents the coupling between the two magnetic centers i and j with the spin states Si and Sj. The positive J values indicate the ferromagnetic ground state and the negative ones indicate the antiferromagnetic ground state. We found pure DFT is not accurate enough to predict J values. We employ density functionals with a Hubbard U term that helps to counteract the unphysical delocalization of electrons due to errors in pure exchange-correlation functionals. Unlike most previous DFT+U studies, we calibrate U parameters for both metal and ligand atoms using five binuclear manganese complexes as the benchmarks. We note delocalization of the spin density onto acetate ligands due to À-back bonding, inverting spin-polarization of the acetate oxygen atoms relative to that predicted from superexchange mechanism. This inversion may affect performance of the models assuming strict localization of the spins on magnetic centers for the complexes with bridging acetate ligands. Next, we apply DFT+U methodology for Mn12(mda) and Mn12(ada) complexes to calculate all six nearest neighbor Jij value. Our result shows both qualitative and quantitative agreement with experiments unlike other DFT studies. Using the optimized geometry of the ground spin state instead of less accurate experimental geometry was found to be crucial for this good agreement. The protocol tested in this study can be applied for the rational design of single-molecule magnets for molecular spintronics and quantum computing applications. Finally we apply hybrid DFT methodology to calculate geometrical parameters for cerium oxides. We review the experimental and computational studies on the cerium oxide nanoparticles, as well as stoichiometric phases of bulk ceria. Electroneutral and nonpolar pentalayers are identified as building blocks of type A sesqioxide structure. The idealized structure of the nanoparticles is described as dioxide covered by a single pentalayer of sesquioxide, which explains the exceptional stability of subsurface vacancies in nanoceria. The density functional theory (DFT) predictions of the lattice parameters and bulk moduli for the Ce(IV) and Ce(III) oxides at the hybrid DFT level are also presented. The calculated values for both compounds agree with experiment and allow to predict changes in the lattice parameter with decreasing size of the nanoparticles. The results validate hybrid DFT as a promising method for future study the structure of oxygen vacancies and catalytic properties of ceria nanoparticles.
Show less
Date Issued: 2011
Identifier: CFE0003741, ucf:48762
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003741

Title: SIMULATION OF PHOTOCHROMIC COMPOUNDS USING DENSITY FUNCTIONAL THEORY METHODS.
Creator: Patel, Pansy, Masunov, Artem, University of Central Florida
Abstract / Description: This Thesis describes the systematic theoretical study aimed at prediction of the essential properties for the functional organic molecules that belong to diarylethene (DA) family of compounds. Diarylethenes present the distinct ability to change color under the influence of light, known as photochromism. This change is due to ultrafast chemical transition from open to closed ring isomers (photocyclization). It can be used for optical data storage, photoswitching, and other photonic...
Show moreThis Thesis describes the systematic theoretical study aimed at prediction of the essential properties for the functional organic molecules that belong to diarylethene (DA) family of compounds. Diarylethenes present the distinct ability to change color under the influence of light, known as photochromism. This change is due to ultrafast chemical transition from open to closed ring isomers (photocyclization). It can be used for optical data storage, photoswitching, and other photonic applications. In this work we apply Density Functional Theory methods to predict 6 of the related properties: (i) molecular geometry; (ii) resonant wavelength; (iii) thermal stability; (iv) fatigue resistance; (v) quantum yield and (vi) nanoscale organization of the material. In order to study sensitivity at diode laser wavelengths, we optimized geometry and calculated vertical absorption spectra for a benchmark set of 28 diarylethenes. Bond length alternation (BLA) parameters and maximum absorption wavelengths (λmax) are compared to the data presently available from X-ray diffraction and spectroscopy experiments. We conclude that TD-M05/6-31G*/PCM//M05-2X/6-31G*/PCM level of theory gives the best agreement for both the parameters. For our predictions the root mean square deviation (RMSD) are below 0.014 ÃƒÂ… for the BLAs and 25 nm for λmax. The polarization functions in the basis set and solvent effects are both important for this agreement. Next we consider thermal stability. Our results suggest that UB3LYP and UM05-2X functionals predict the activation barrier for the cycloreversion reaction within 3-4 kcal/mol from experimental value for a set of 7 photochromic compounds. We also study thermal fatigue, defined as the rate of undesirable photochemical side reactions. In order to predict the kinetics of photochemical fatigue, we investigate the mechanism of by-product formation. It has been established experimentally that the by-product is formed from the closed isomer; however the mechanism was not known. We found that the thermal by-product pathway involves the bicyclohexane (BCH) ring formation as a stable intermediate, while the photochemical by-product formation pathway may involve the methylcyclopentene diradical (MCPD) intermediate. At UM05-2X/6-31G* level, the calculated barrier between the closed form and the BCH intermediate is 51.2 kcal/mol and the barrier between the BCH intermediate and the by-product 16.2 kcal/mol. Next we investigate two theoretical approaches to the prediction of quantum yield (QY) for a set of 14 diarylethene derivatives at the validated M05-2X/6-31G* theory level. These include population of ground-state conformers and location of the pericycylic minimum on the potential energy surface 2-A state. Finally, we investigate the possibility of nanoscale organization of the photochromic material based on DNA template, as an alternative to the amorphous polymer matrix. Here we demonstrate that Molecular Dynamic methods are capable to describe the intercalation of π-conjugated systems between DNA base pairs and accurately reproduced the available photophysical properties of these nanocomposites. In summary, our results are in good agreement with the experimental data for the benchmark set of molecules we conclude that Density Functional Theory methods could be successfully used as an important component of material design strategy in prediction of accurate molecular geometry, absorption spectra, thermal stability of isomers, fatigue resistance, quantum yield of photocyclization and photophysical properties of nanocomposites.
Show less
Date Issued: 2010
Identifier: CFE0003136, ucf:48633
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003136

Title: Error Rates in Narrow-band Digital FM Systems Operating Various Interference Environments.
Creator: Rodriguez, Arthur M., Mathews, B.E., Engineering
Abstract / Description: Florida Technological University College of Engineering Thesis
Date Issued: 1975
Identifier: CFR0004778, ucf:52971
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFR0004778

Title: An Exploration of the Feasibility of Functional Near-Infrared Spectroscopy as a Neurofeedback Cueing System for the Mitigation of the Vigilance Decrement.
Creator: Hancock, Gabriella, Szalma, James, Mouloua, Mustapha, Bohil, Corey, Hoffman, Robert, Matthews, Gerald, University of Central Florida
Abstract / Description: Vigilance is the capacity for observers to maintain attention over extended periods of time, and has most often been operationalized as the ability to detect rare and critical signals (Davies (&) Parasuraman, 1982; Parasuraman, 1979; Warm, 1984). Humans, however, have natural physical and cognitive limitations that preclude successful long-term vigilance performance and consequently, without some means of assistance, failures in operator vigilance are likely to occur. Such a decline in...
Show moreVigilance is the capacity for observers to maintain attention over extended periods of time, and has most often been operationalized as the ability to detect rare and critical signals (Davies (&) Parasuraman, 1982; Parasuraman, 1979; Warm, 1984). Humans, however, have natural physical and cognitive limitations that preclude successful long-term vigilance performance and consequently, without some means of assistance, failures in operator vigilance are likely to occur. Such a decline in monitoring performance over time has been a robust finding in vigilance experiments for decades and has been called the vigilance decrement function (Davies (&) Parasuraman, 1982; Mackworth, 1948). One of the most effective countermeasures employed to maintain effective performance has been cueing: providing the operator with a reliable prompt concerning signal onset probability. Most protocols have based such cues on task-related or environmental factors. The present dissertation examines the efficacy of cueing when nominally based on operator state (i.e., blood oxygenation of cortical tissue) in a novel vigilance task incorporating dynamic displays over three studies. Results pertaining to performance outcomes, physiological measures (cortical blood oxygenation and heart rate variability), and perceived workload and stress are interpreted via Signal Detection Theory and the Resource Theory of vigilance.
Show less
Date Issued: 2017
Identifier: CFE0006599, ucf:51286
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006599

Title: Content-based Information Retrieval via Nearest Neighbor Search.
Creator: Huang, Yinjie, Georgiopoulos, Michael, Anagnostopoulos, Georgios, Hu, Haiyan, Sukthankar, Gita, Ni, Liqiang, University of Central Florida
Abstract / Description: Content-based information retrieval (CBIR) has attracted significant interest in the past few years. When given a search query, the search engine will compare the query with all the stored information in the database through nearest neighbor search. Finally, the system will return the most similar items. We contribute to the CBIR research the following: firstly, Distance Metric Learning (DML) is studied to improve retrieval accuracy of nearest neighbor search. Additionally, Hash Function...
Show moreContent-based information retrieval (CBIR) has attracted significant interest in the past few years. When given a search query, the search engine will compare the query with all the stored information in the database through nearest neighbor search. Finally, the system will return the most similar items. We contribute to the CBIR research the following: firstly, Distance Metric Learning (DML) is studied to improve retrieval accuracy of nearest neighbor search. Additionally, Hash Function Learning (HFL) is considered to accelerate the retrieval process.On one hand, a new local metric learning framework is proposed - Reduced-Rank Local Metric Learning (R2LML). By considering a conical combination of Mahalanobis metrics, the proposed method is able to better capture information like data's similarity and location. A regularization to suppress the noise and avoid over-fitting is also incorporated into the formulation. Based on the different methods to infer the weights for the local metric, we considered two frameworks: Transductive Reduced-Rank Local Metric Learning (T-R2LML), which utilizes transductive learning, while Efficient Reduced-Rank Local Metric Learning (E-R2LML)employs a simpler and faster approximated method. Besides, we study the convergence property of the proposed block coordinate descent algorithms for both our frameworks. The extensive experiments show the superiority of our approaches.On the other hand, *Supervised Hash Learning (*SHL), which could be used in supervised, semi-supervised and unsupervised learning scenarios, was proposed in the dissertation. By considering several codewords which could be learned from the data, the proposed method naturally derives to several Support Vector Machine (SVM) problems. After providing an efficient training algorithm, we also study the theoretical generalization bound of the new hashing framework. In the final experiments, *SHL outperforms many other popular hash function learning methods. Additionally, in order to cope with large data sets, we also conducted experiments running on big data using a parallel computing software package, namely LIBSKYLARK.
Show less
Date Issued: 2016
Identifier: CFE0006327, ucf:51544
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006327

Title: Childhood Maltreatment and Mother-Young Child Attachment: Examining Interactions among Attachment, Depression, Reflective Functioning, Parenting Behaviors, and Young Children's Outcomes in Mothers with Histories of Childhood Maltreatment.
Creator: Khan, Maria, Renk, Kimberly, Paulson, Daniel, Sims, Valerie, University of Central Florida
Abstract / Description: Although previous research identified mothers who experienced childhood maltreatment as exhibiting an especially heightened risk for attachment difficulties with their own young children, evidence regarding the mechanisms of action driving this relationship have been lacking. Thus, the current study introduced mothers' depressive symptoms and the novel construct of reflective functioning as potential mediators to help explain the relationship between mothers' childhood maltreatment...
Show moreAlthough previous research identified mothers who experienced childhood maltreatment as exhibiting an especially heightened risk for attachment difficulties with their own young children, evidence regarding the mechanisms of action driving this relationship have been lacking. Thus, the current study introduced mothers' depressive symptoms and the novel construct of reflective functioning as potential mediators to help explain the relationship between mothers' childhood maltreatment experiences and patterns of insecure (i.e., anxious, avoidant, and disorganized) mother-young child attachment. The current study included a community sample of 146 mothers with children who ranged in age from 1(&)#189;-to 5-years. Mothers provided ratings of their own childhood maltreatment experiences, attachment with their young children, depressive symptoms, reflective functioning, parenting behaviors and attributions, and young children's problems. Correlational analyses displayed significant associations among the variables of interest. Additionally, mediational analyses indicated that mothers' depressive symptoms mediated the relationship between mothers' childhood maltreatment experiences and patterns of insecure mother-young child attachment. Given that mothers' childhood maltreatment experiences failed to predict reflective functioning, the mediational role of reflective functioning was unsupported. Further, mothers' reflective functioning mediated the relationship between mothers' depressive symptoms and patterns of mother-young child insecure attachment. Finally, hierarchical regression analyses showed that mothers' adverse childhood experiences and depressive symptoms uniquely predicted their young children's internalizing and externalizing problems. These data suggested that the psychological consequences resulting from adverse childhood experiences may be more damaging to mothers' attachment with their young children than mothers' adverse childhood experiences alone. Moreover, these findings suggested that mothers' depressive symptoms and reflective functioning work together in predicting mother-young child attachment. Altogether, these results demonstrated the importance for promoting trauma-informed parenting interventions for facilitating secure emotional connections between mothers and young children, especially in mothers with childhood traumatic experiences themselves.
Show less
Date Issued: 2017
Identifier: CFE0006753, ucf:51860
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006753

Title: Childhood Trauma, Reflective Functioning and Attributions, Self-Efficacy, and Perceived Parenting Competence: What Happens When the Traumatized Child Grows Up and Becomes a Mother?.
Creator: Cunningham, Annelise, Renk, Kimberly, Paulson, Daniel, Sims, Valerie, University of Central Florida
Abstract / Description: Previous research documented the relationship between self-efficacy and perceived parenting competence. Further, previous evidence supported the cognitive, emotional, and behavioral consequences of early exposure to trauma. To build on these previously noted relationships, the present study examined the relationships among reflective functioning and attributions, self-efficacy, and perceived parenting competence, with self-efficacy serving as a mediating variable. Specifically, this study...
Show morePrevious research documented the relationship between self-efficacy and perceived parenting competence. Further, previous evidence supported the cognitive, emotional, and behavioral consequences of early exposure to trauma. To build on these previously noted relationships, the present study examined the relationships among reflective functioning and attributions, self-efficacy, and perceived parenting competence, with self-efficacy serving as a mediating variable. Specifically, this study sought to focus on the cognitive variables associated with mothers' perceived self-efficacy and parenting competence and how those variables interact differently when early exposure to trauma is present. As part of this study, a national community sample of 126 culturally diverse mothers of young children who were between the ages of 1(&)#189;- to 5-years rated their own reflective functioning, attributions, self-efficacy, and perceived parenting competence as well as their young children's emotional and behavioral functioning. Correlational analyses showed significant relationships among the variables of interest. Further, mediation analyses indicated that, for the overall sample, mothers' self-efficacy mediated the relationship between both mothers' reflective functioning and attributions and perceived parenting competence. Interestingly, a varying relationship among reflective functioning was found among mothers with a trauma history in comparison to the total sample. Additionally, hierarchical regression analyses demonstrated that, for both samples, mothers' reflective functioning, attributions, self-efficacy, and perceived parenting competence collectively predicted young children's emotional and behavioral functioning. Lastly, through an auxiliary hypothesis, a curvilinear relationship was identified between mothers' perceived self-efficacy and parenting competence. Overall, this study contributed information regarding the importance of self-efficacy as a mechanism through which reflective functioning and attributions may potentially be related to perceived parenting competence. Accordingly, these findings suggested that mothers' perceptions about their own abilities may be a potentially important point of intervention.
Show less
Date Issued: 2016
Identifier: CFE0006092, ucf:51191
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006092

Title: Nonparametric and Empirical Bayes Estimation Methods.
Creator: Benhaddou, Rida, Pensky, Marianna, Han, Deguang, Swanson, Jason, Ni, Liqiang, University of Central Florida
Abstract / Description: In the present dissertation, we investigate two different nonparametric models; empirical Bayes model and functional deconvolution model. In the case of the nonparametric empirical Bayes estimation, we carried out a complete minimax study. In particular, we derive minimax lower bounds for the risk of the nonparametric empirical Bayes estimator for a general conditional distribution. This result has never been obtained previously. In order to attain optimal convergence rates, we use a wavelet...
Show moreIn the present dissertation, we investigate two different nonparametric models; empirical Bayes model and functional deconvolution model. In the case of the nonparametric empirical Bayes estimation, we carried out a complete minimax study. In particular, we derive minimax lower bounds for the risk of the nonparametric empirical Bayes estimator for a general conditional distribution. This result has never been obtained previously. In order to attain optimal convergence rates, we use a wavelet series based empirical Bayes estimator constructed in Pensky and Alotaibi (2005). We propose an adaptive version of this estimator using Lepski's method and show that the estimator attains optimal convergence rates. The theory is supplemented by numerous examples. Our study of the functional deconvolution model expands results of Pensky and Sapatinas (2009, 2010, 2011) to the case of estimating an $(r+1)$-dimensional function or dependent errors. In both cases, we derive minimax lower bounds for the integrated square risk over a wide set of Besov balls and construct adaptive wavelet estimators that attain those optimal convergence rates. In particular, in the case of estimating a periodic $(r+1)$-dimensional function, we show that by choosing Besov balls of mixed smoothness, we can avoid the ''curse of dimensionality'' and, hence, obtain higher than usual convergence rates when $r$ is large. The study of deconvolution of a multivariate function is motivated by seismic inversion which can be reduced to solution of noisy two-dimensional convolution equations that allow to draw inference on underground layer structures along the chosen profiles. The common practice in seismology is to recover layer structures separately for each profile and then to combine the derived estimates into a two-dimensional function. By studying the two-dimensional version of the model, we demonstrate that this strategy usually leads to estimators which are less accurate than the ones obtained as two-dimensional functional deconvolutions. Finally, we consider a multichannel deconvolution model with long-range dependent Gaussian errors. We do not limit our consideration to a specific type of long-range dependence, rather we assume that the eigenvalues of the covariance matrix of the errors are bounded above and below. We show that convergence rates of the estimators depend on a balance between the smoothness parameters of the response function, the smoothness of the blurring function, the long memory parameters of the errors, and how the total number of observations is distributed among the channels.
Show less
Date Issued: 2013
Identifier: CFE0004814, ucf:49737
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004814

Title: Optimization problem in single period markets.
Creator: Jiang, Tian, Yong, Jiongmin, Qi, Yuanwei, Shuai, Zhisheng, University of Central Florida
Abstract / Description: There had been a number of researches that investigated on the security market without transactioncosts. The focus of this research is in the area that when the security market with transaction costsis fair and in such fair market how one chooses a suitable portfolio to optimize the financial goal.The research approach adopted in this thesis includes linear algebra and elementary probability.The thesis provides evidence that we can maximize expected utility function to achieve our goal...
Show moreThere had been a number of researches that investigated on the security market without transactioncosts. The focus of this research is in the area that when the security market with transaction costsis fair and in such fair market how one chooses a suitable portfolio to optimize the financial goal.The research approach adopted in this thesis includes linear algebra and elementary probability.The thesis provides evidence that we can maximize expected utility function to achieve our goal(maximize expected return under certain risk tolerance). The main conclusions drawn from thisstudy are under certain conditions the security market is arbitrage-free, and we can always find anoptimal portfolio maximizing certain expected utility function.
Show less
Date Issued: 2013
Identifier: CFE0004696, ucf:49875
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004696

Density Functional Theory (5)	+ -
density functional theory (5)	+ -
Empirical Bayes (4)	+ -
Highway Safety Manual (4)	+ -
working memory (4)	+ -

Executive Function (3)	+ -
Safety Performance Functions (3)	+ -
executive function (3)	+ -
fNIRS (3)	+ -
meshless methods (3)	+ -
Aging (2)	+ -
Bootstrap (2)	+ -
CaR-FA-X (2)	+ -
Catalysis (2)	+ -
Crash Modification Factors (2)	+ -
Functional Near-Infrared Spectroscopy (2)	+ -
Functions (2)	+ -
Lyapunov functions (2)	+ -
Parenting (2)	+ -
Phospholipase A2 (2)	+ -
Rumination (2)	+ -
Transferability (2)	+ -
atmospheric turbulence (2)	+ -
discriminant function analysis (2)	+ -
executive functions (2)	+ -
functional near-infrared spectroscopy (2)	+ -
global stability (2)	+ -
gold nanoparticles (2)	+ -
meta-analysis (2)	+ -
neuropsychology (2)	+ -

ETD Collection (104)	+ -
Honors Collection (15)	+ -

English (117)	+ -
Engilsh (2)	+ -

University of Central Florida (118)	+ -
Abdel-Aty, Mohamed (8)	+ -
Rapport, Mark (7)	+ -
Lee, JaeYoung (6)	+ -
Paulson, Daniel (6)	+ -

Search In

Pages

Pages

Sort Results By:

Narrow results by:

Topical Subject

Collection

Type of Resource

Language

Creator

Format

Owner