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THE WAVE STRUCTURE FUNCTION AND TEMPORAL FREQUENCY SPREAD IN WEAK TO STRONG OPTICAL TURBULENCE
Title
THE WAVE STRUCTURE FUNCTION AND TEMPORAL FREQUENCY SPREAD IN WEAK TO STRONG OPTICAL TURBULENCE.
Creator
Masino, Aaron Joseph, Young, Cynthia Y., University of Central Florida
Abstract / Description
This paper presents analytic expressions for the wave structure function, frequency spread of the temporal frequency spectrum, and the temporal frequency spectrum of optical signals propagating through a random medium, specifically the Earth's atmosphere. The results are believed to be valid for all optical turbulence conditions. These expressions are developed using the Rytov approximation method. Generally, the validity of statistical quantities obtained via this method is restricted to...
Show moreThis paper presents analytic expressions for the wave structure function, frequency spread of the temporal frequency spectrum, and the temporal frequency spectrum of optical signals propagating through a random medium, specifically the Earth's atmosphere. The results are believed to be valid for all optical turbulence conditions. These expressions are developed using the Rytov approximation method. Generally, the validity of statistical quantities obtained via this method is restricted to conditions of weak optical turbulence. However, in this work, by using a modification of the effective atmospheric spectral model presented by Andrews et al. for scintillation index, wave structure function expressions have been derived that are valid in all turbulence conditions as evidenced by comparison to experimental data. Analytic wave structure function results are developed for plane, spherical, and Gaussian-beam waves for one-way propagation. For the special case of a spherical wave, comparisons are made with experimental data. The double pass case is also considered. Analytic expressions for the wave structure function are given that incorporate reflection from a smooth target for an incident spherical wave. Additionally, analytic expressions for the frequency spread of the temporal frequency spectrum and the temporal frequency spectrum itself, after one-way propagation for horizontal and slant paths, are derived for plane and spherical waves. These results are also based on the Rytov perturbation method . Expressions that are believed to be valid in all turbulence conditions are also developed by use of the effective atmospheric spectral model used in the wave structure function development. Finally, double pass frequency spread expressions are also presented. As in the case of the wave structure function, reflection from a smooth target with an incident spherical wave is considered.
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Date Issued
2004
Identifier
CFE0000073, ucf:46106
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000073
FADE STATISTICS FOR A LASERCOM SYSTEM AND THE JOINT PDF OF A GAMMA-GAMMA DISTRIBUTED IRRADIANCE AND ITS TIME DERIVATIVE
Title
FADE STATISTICS FOR A LASERCOM SYSTEM AND THE JOINT PDF OF A GAMMA-GAMMA DISTRIBUTED IRRADIANCE AND ITS TIME DERIVATIVE.
Creator
Stromqvist Vetelino, Frida, Young, Cynthia, University of Central Florida
Abstract / Description
The performance of lasercom systems operating in the atmosphere is reduced by optical turbulence, which causes irradiance fluctuations in the received signal. The result is a randomly fading signal. Fade statistics for lasercom systems are determined from the probability density function (PDF) of the irradiance fluctuations. The expected number of fades per second and their mean fade time require the joint PDF of the fluctuating irradiance and its time derivative. Theoretical integral...
Show moreThe performance of lasercom systems operating in the atmosphere is reduced by optical turbulence, which causes irradiance fluctuations in the received signal. The result is a randomly fading signal. Fade statistics for lasercom systems are determined from the probability density function (PDF) of the irradiance fluctuations. The expected number of fades per second and their mean fade time require the joint PDF of the fluctuating irradiance and its time derivative. Theoretical integral expressions, as well as closed form, analytical approximations, were developed for the joint PDF of a gamma-gamma distributed irradiance and its time derivative, and the corresponding expression for the expected number of fades per second. The new approximation for the conditional PDF of the time derivative of a gamma-gamma irradiance is a zero mean Gaussian distribution, with a complicated irradiance depending variance. Fade statistics obtained from experimental data were compared to theoretical predictions based on the lognormal and gamma-gamma distributions. A Gaussian beam wave was propagated through the atmosphere along a horizontal path, near ground, in the moderate-to-strong optical turbulence. To characterize the propagation path, a new method that infers atmospheric propagation parameters was developed. Scintillation theory combined with a numerical scheme was used to infer the structure constant, Cn2, the inner scale and the outer scale from the optical measurements. The inferred parameters were used in calculations for the theoretical PDFs. It was found that fade predictions made by the gamma-gamma and lognormal distributions provide an upper and lower bound, respectively, for the probability of fade and the number of fades per second for irradiance data collected in the moderate-to-strong fluctuation regime. Aperture averaging effects on the PDF of the irradiance fluctuations were investigated by comparing the irradiance distributions for the three receiver apertures at two different values of the structure parameter and, hence, different values of the coherence radius. For the moderate-to-strong fluctuation regime, the gamma-gamma distribution provides a good fit to the irradiance fluctuations collected by finite-sized apertures that are significantly smaller than the coherence radius. For apertures larger than or equal to the coherence radius, the irradiance fluctuations appear to be lognormally distributed.
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Date Issued
2006
Identifier
CFE0001440, ucf:47069
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001440
EFFECT OF INNER SCALE ATMOSPHERIC SPECTRUM MODELS ON SCINTILLATION IN ALL OPTICAL TURBULENCE REGIMES
Title
EFFECT OF INNER SCALE ATMOSPHERIC SPECTRUM MODELS ON SCINTILLATION IN ALL OPTICAL TURBULENCE REGIMES.
Creator
Mayer, Kenneth, Young, Cynthia, University of Central Florida
Abstract / Description
Experimental studies have shown that a "bump" occurs in the atmospheric spectrum just prior to turbulence cell dissipation.1,3,4 In weak optical turbulence, this bump affects calculated scintillation. The purpose of this thesis was to determine if a "non-bump" atmospheric power spectrum can be used to model scintillation for plane waves and spherical waves in moderate to strong optical turbulence regimes. Scintillation expressions were developed from an "effective" von Karman spectrum using...
Show moreExperimental studies have shown that a "bump" occurs in the atmospheric spectrum just prior to turbulence cell dissipation.1,3,4 In weak optical turbulence, this bump affects calculated scintillation. The purpose of this thesis was to determine if a "non-bump" atmospheric power spectrum can be used to model scintillation for plane waves and spherical waves in moderate to strong optical turbulence regimes. Scintillation expressions were developed from an "effective" von Karman spectrum using an approach similar to that used by Andrews et al.8,14,15 in developing expressions from an "effective" modified (bump) spectrum. The effective spectrum extends the Rytov approximation into all optical turbulence regimes using filter functions to eliminate mid-range turbulent cell size effects to the scintillation index. Filter cutoffs were established by matching to known weak and saturated scintillation results. The resulting new expressions track those derived from the effective bump spectrum fairly closely. In extremely strong turbulence, differences are minimal.
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Date Issued
2007
Identifier
CFE0001559, ucf:47141
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001559
COMPARING ASSESSMENT METHODS AS PREDICTORS OF STUDENT LEARNING IN UNDERGRADUATE MATHEMATICS
Title
COMPARING ASSESSMENT METHODS AS PREDICTORS OF STUDENT LEARNING IN UNDERGRADUATE MATHEMATICS.
Creator
Shorter, Nichole, Young, Cynthia, University of Central Florida
Abstract / Description
This experiment was designed to determine which assessment method: continuous assessment (in the form of daily in-class quizzes), cumulative assessment (in the form of online homework), or project-based learning, best predicts student learning (dependent upon posttest grades) in an undergraduate mathematics course. Participants included 117 university-level undergraduate freshmen enrolled in a course titled "Mathematics for Calculus". Initially, a multiple regression model was formulated to...
Show moreThis experiment was designed to determine which assessment method: continuous assessment (in the form of daily in-class quizzes), cumulative assessment (in the form of online homework), or project-based learning, best predicts student learning (dependent upon posttest grades) in an undergraduate mathematics course. Participants included 117 university-level undergraduate freshmen enrolled in a course titled "Mathematics for Calculus". Initially, a multiple regression model was formulated to model the relationship between the predictor variables (the continuous assessment, cumulative assessment, and project scores) versus the outcome variable (the posttest scores). However, due to the possibility of multicollinearity present between the cumulative assessment predictor variable and the continuous assessment predictor variable, a stepwise regression model was implemented and caused the cumulative assessment predictor variable to be forced out of the resulting model, based on the results of statistical significance and hypothesis testing. The finalized stepwise regression model included continuous assessment scores and project scores as predictor variables of students' posttest scores with a 99% confidence level. Results indicated that ultimately the continuous assessment scores best predicted students' posttest scores.
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Date Issued
2008
Identifier
CFE0002432, ucf:47704
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002432
THE SCINTILLATION INDEX IN MODERATE TO STRONG TURBULENCE FOR THE GAUSSIAN BEAM WAVE ALONG A SLANT PATH
Title
THE SCINTILLATION INDEX IN MODERATE TO STRONG TURBULENCE FOR THE GAUSSIAN BEAM WAVE ALONG A SLANT PATH.
Creator
Thomas, Fredrick, Young, Cynthia, University of Central Florida
Abstract / Description
Scintillation is one of the most common statistics in the literature of mathematical modeling of laser propagation through random media. One approach to estimating scintillation is through the Rytov approximation, which is limited to weak atmospheric turbulence. Recently, an improvement of the Rytov approximation was developed employing a linear filter function technique. This modifies the Rytov approximation and extends the validity into the moderate to strong regime. In this work, an...
Show moreScintillation is one of the most common statistics in the literature of mathematical modeling of laser propagation through random media. One approach to estimating scintillation is through the Rytov approximation, which is limited to weak atmospheric turbulence. Recently, an improvement of the Rytov approximation was developed employing a linear filter function technique. This modifies the Rytov approximation and extends the validity into the moderate to strong regime. In this work, an expression governing scintillation of a Gaussian beam along an uplink slant path valid in all regimes of turbulence is presented, as well as results for the limiting cases of a plane wave and a spherical wave.
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Date Issued
2005
Identifier
CFE0000670, ucf:46509
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000670
Improving Student Learning in Undergraduate Mathematics
Title
Improving Student Learning in Undergraduate Mathematics.
Creator
Rejniak, Gabrielle, Young, Cynthia, Brennan, Joseph, Martin, Heath, University of Central Florida
Abstract / Description
The goal of this study was to investigate ways of improving student learning, par-ticularly conceptual understanding, in undergraduate mathematics courses. This studyfocused on two areas: course design and animation. The methods of study were thefollowing: Assessing the improvement of student conceptual understanding as a result of teamproject-based learning, individual inquiry-based learning and the modied empo-rium model; and Assessing the impact of animated videos on student learning with...
Show moreThe goal of this study was to investigate ways of improving student learning, par-ticularly conceptual understanding, in undergraduate mathematics courses. This studyfocused on two areas: course design and animation. The methods of study were thefollowing: Assessing the improvement of student conceptual understanding as a result of teamproject-based learning, individual inquiry-based learning and the modied empo-rium model; and Assessing the impact of animated videos on student learning with the emphasis onconcepts.For the first part of our study (impact of course design on student conceptual understanding) we began by comparing the following three groups in Fall 2010 and Fall2011:1. Fall 2010: MAC 1140 Traditional Lecture (&) Fall 2011: MAC 1140 Modied Empo-rium2. Fall 2010: MAC 1140H with Project (&) Fall 2011: MAC 1140H no Project3. Fall 2010: MAC 2147 with Projects (&) Fall 2011: MAC 2147 no ProjectsAnalysis of pre-tests and post-tests show that all three courses showed statistically significant increases, according to their respective sample sizes, during Fall 2010. However, in Fall 2011 only MAC 2147 continued to show a statistically significant increase. Therefore in Fall 2010, project-based learning - both in-class individual projects and out-of-class team projects - conclusively impacted the students' conceptual understanding. Whereas, in Fall 2011, the data for the Modified Emporium model had no statistical significance and is therefore inconclusive as to its effectiveness. In addition the difference in percent ofincrease for MAC 1140 between Fall 2010 - traditional lecture model - and Fall 2011 -modified emporium model - is not statistically significant and we cannot say that either model is a better delivery mode for conceptual learning. For the second part of our study, the students enrolled in MAC 1140H Fall 2011 and MAC 2147 Fall 2011 were given a pre-test on sequences and series before showing them an animated video related to the topic. After watching the video, students were then given the same 7 question post test to determine any improvement in the students' understanding of the topic. After two weeks of teacher-led instruction, the students tookthe same post-test again. The results of this preliminary study indicate that animated videos do impact the conceptual understanding of students when used as an introduction into a new concept. Both courses that were shown the video had statistically significant increases in the conceptual understanding of the students between the pre-test and the post-animation test.
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Date Issued
2012
Identifier
CFE0004320, ucf:49481
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004320
The Effects of a Loving-Kindness Meditation Intervention on Positive Emotions, Social Connectedness, and Problem Behaviors in Second and Third Grade Students.
Title
The Effects of a Loving-Kindness Meditation Intervention on Positive Emotions, Social Connectedness, and Problem Behaviors in Second and Third Grade Students.
Creator
Collinsmchugh, Doreen, Gill, Michele, Allen, Kay, Hutchinson, Cynthia, Young, Mark, University of Central Florida
Abstract / Description
Concerns about K-12 students' mental health and social, emotional, and ethical development have prompted some schools to implement programs designed to promote student well-being and healthy social and emotional functioning. Most of these programs are distinguished as social and emotional learning (SEL) programs and/or character education programs. Although there is growing empirical support for the potential of school-based mindfulness interventions to positively influence students' well...
Show moreConcerns about K-12 students' mental health and social, emotional, and ethical development have prompted some schools to implement programs designed to promote student well-being and healthy social and emotional functioning. Most of these programs are distinguished as social and emotional learning (SEL) programs and/or character education programs. Although there is growing empirical support for the potential of school-based mindfulness interventions to positively influence students' well-being, the number of school-based mindfulness studies is limited, and the majority of the investigations have focused on students' cognitive rather than affective capacities. Loving-Kindness Meditation (LKM), a mindfulness- and compassion-based practice, is garnering recent attention as an effective intervention for positively affecting numerous factors related to well-being. For instance, research has demonstrated LKM's effectiveness in enhancing positive emotions, empathy, and social connectedness, and improving problem behaviors in adult populations. Although LKM is a component of the Mindfulness-Based Stress Reduction (MBSR) program, and a number of mindfulness-based school programs are MBSR- adapted, to date LKM has not been studied with children or youth populations. With this in mind, the purpose of this active comparison trial investigation was to examine the effects of a loving-kindness meditation intervention on positive emotions, empathy, social connection, and problem behaviors in second- and third- grade students. Findings suggest LKM may be more appropriately used in school settings as a sequential part of a comprehensive mindfulness program and introduced after a solid mindfulness practice has been established.
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Date Issued
2016
Identifier
CFE0006286, ucf:51584
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006286
The Influence of a Career Planning STEM Explorations Course on Vocational Maturity, Career Decidedness and Career Thoughts for Undergraduate Students
Title
The Influence of a Career Planning STEM Explorations Course on Vocational Maturity, Career Decidedness and Career Thoughts for Undergraduate Students.
Creator
Prescod, Diandra, Daire, Andrew, Van Horn, Stacy, Butler, Sylvester, Young, Cynthia, University of Central Florida
Abstract / Description
According to the National Academy of Sciences (NAS), innovation that accompanies careers in science, technology engineering, and math (STEM) create a driving force in the economy and the creation of jobs, yet many positions remain open due to the lack of qualified individuals to fill them (NAS, 2011). Continuing research and innovation proves to be important, yet not enough students graduate with STEM degrees and enter into STEM careers. Career planning courses for undergraduate students...
Show moreAccording to the National Academy of Sciences (NAS), innovation that accompanies careers in science, technology engineering, and math (STEM) create a driving force in the economy and the creation of jobs, yet many positions remain open due to the lack of qualified individuals to fill them (NAS, 2011). Continuing research and innovation proves to be important, yet not enough students graduate with STEM degrees and enter into STEM careers. Career planning courses for undergraduate students increase student confidence about their abilities to make career decisions (Grier-Reed (&) Skaar, 2010: Scott (&) Ciani 2008). Vocational maturity and career decision making skills also improve as a result of these courses (Reese (&) Miller, 2006; Scott (&) Ciani, 2008). Although research provides evidence of the impact of career planning courses that are specific to certain disciplines (Heffner, Macera (&) Cohen, 2006), the need for research exists on examining the role career planning courses have in STEM recruitment and retention. This study aimed to investigate the influence of career development intervention in STEM recruitment and retention efforts by examining career decidedness, career thoughts and vocational maturity. Furthermore, the influence of the class was examined by using demographics such as gender, ethnicity, SAT scores, and algebra math placements scores. The Career Development Inventory (CDI) and Career Thoughts Inventory (CTI) provided measures of career thoughts, career decidedness and vocational maturity for this study. The results provided clarity as to the influence of the career planning course. Vocational maturity and career decidedness increase by the end of the career planning course and negative career thoughts decreased. Implications of the findings include counselor education, career development, practice and future research. In a time when billions of dollars are spent on STEM initiative, the current study provided an economically viable career development STEM initiative. The research reveals millions are dollars invested into updating lab equipment, purchasing new materials for students, and training teachers. The current study utilized a career planning course allowing students to explore their likes, dislikes, and abilities and how the aforementioned are connected to career interests. This study also provides insight into how the STEM effort can more specifically recruit students who will excel in STEM disciplines. ?
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Date Issued
2014
Identifier
CFE0005232, ucf:50592
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005232
Practical Implementations of the Active Set Method for Support Vector Machine Training with Semi-definite Kernels
Title
Practical Implementations of the Active Set Method for Support Vector Machine Training with Semi-definite Kernels.
Creator
Sentelle, Christopher, Georgiopoulos, Michael, Anagnostopoulos, Georgios, Kasparis, Takis, Stanley, Kenneth, Young, Cynthia, University of Central Florida
Abstract / Description
The Support Vector Machine (SVM) is a popular binary classification model due to its superior generalization performance, relative ease-of-use, and applicability of kernel methods. SVM training entails solving an associated quadratic programming (QP) that presents significant challenges in terms of speed and memory constraints for very large datasets; therefore, research on numerical optimization techniques tailored to SVM training is vast. Slow training times are especially of concern when...
Show moreThe Support Vector Machine (SVM) is a popular binary classification model due to its superior generalization performance, relative ease-of-use, and applicability of kernel methods. SVM training entails solving an associated quadratic programming (QP) that presents significant challenges in terms of speed and memory constraints for very large datasets; therefore, research on numerical optimization techniques tailored to SVM training is vast. Slow training times are especially of concern when one considers that re-training is often necessary at several values of the model's regularization parameter, C, as well as associated kernel parameters.The active set method is suitable for solving SVM problem and is in general ideal when the Hessian is dense and the solution is sparse-the case for the l1-loss SVM formulation. There has recently been renewed interest in the active set method as a technique for exploring the entire SVM regularization path, which has been shown to solve the SVM solution at all points along the regularization path (all values of C) in not much more time than it takes, on average, to perform training at a single value of C with traditional methods. Unfortunately, the majority of active set implementations used for SVM training require positive definite kernels, and those implementations that do allow semi-definite kernels tend to be complex and can exhibit instability and, worse, lack of convergence. This severely limits applicability since it precludes the use of the linear kernel, can be an issue when duplicate data points exist, and doesn't allow use of low-rank kernel approximations to improve tractability for large datasets. The difficulty, in the case of a semi-definite kernel, arises when a particular active set results in a singular KKT matrix (or the equality-constrained problem formed using the active set is semi-definite). Typically this is handled by explicitly detecting the rank of the KKT matrix. Unfortunately, this adds significant complexity to the implementation; and, if care is not taken, numerical instability, or worse, failure to converge can result. This research shows that the singular KKT system can be avoided altogether with simple modifications to the active set method. The result is a practical, easy to implement active set method that does not need to explicitly detect the rank of the KKT matrix nor modify factorization or solution methods based upon the rank. Methods are given for both conventional SVM training as well as for computing the regularization path that are simple and numerically stable. First, an efficient revised simplex method is efficiently implemented for SVM training (SVM-RSQP) with semi-definite kernels and shown to out-perform competing active set implementations for SVM training in terms of training time as well as shown to perform on-par with state-of-the-art SVM training algorithms such as SMO and SVMLight. Next, a new regularization path-following algorithm for semi-definite kernels (Simple SVMPath) is shown to be orders of magnitude faster, more accurate, and significantly less complex than competing methods and does not require the use of external solvers. Theoretical analysis reveals new insights into the nature of the path-following algorithms. Finally, a method is given for computing the approximate regularization path and approximate kernel path using the warm-start capability of the proposed revised simplex method (SVM-RSQP) and shown to provide significant, orders of magnitude, speed-ups relative to the traditional (")grid search(") where re-training is performed at each parameter value. Surprisingly, it also shown that even when the solution for the entire path is not desired, computing the approximate path can be seen as a speed-up mechanism for obtaining the solution at a single value. New insights are given concerning the limiting behaviors of the regularization and kernel path as well as the use of low-rank kernel approximations.
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Date Issued
2014
Identifier
CFE0005251, ucf:50600
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005251