Current Search: localization (x)
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- Title
- Improved Multi-Task Learning Based on Local Rademacher Analysis.
- Creator
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Yousefi, Niloofar, Mollaghasemi, Mansooreh, Rabelo, Luis, Zheng, Qipeng, Anagnostopoulos, Georgios, Xanthopoulos, Petros, Georgiopoulos, Michael, University of Central Florida
- Abstract / Description
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Considering a single prediction task at a time is the most commonly paradigm in machine learning practice. This methodology, however, ignores the potentially relevant information that might be available in other related tasks in the same domain. This becomes even more critical where facing the lack of a sufficient amount of data in a prediction task of an individual subject may lead to deteriorated generalization performance. In such cases, learning multiple related tasks together might offer...
Show moreConsidering a single prediction task at a time is the most commonly paradigm in machine learning practice. This methodology, however, ignores the potentially relevant information that might be available in other related tasks in the same domain. This becomes even more critical where facing the lack of a sufficient amount of data in a prediction task of an individual subject may lead to deteriorated generalization performance. In such cases, learning multiple related tasks together might offer a better performance by allowing tasks to leverage information from each other. Multi-Task Learning (MTL) is a machine learning framework, which learns multiple related tasks simultaneously to overcome data scarcity limitations of Single Task Learning (STL), and therefore, it results in an improved performance. Although MTL has been actively investigated by the machine learning community, there are only a few studies examining the theoretical justification of this learning framework. The focus of previous studies is on providing learning guarantees in the form of generalization error bounds. The study of generalization bounds is considered as an important problem in machine learning, and, more specifically, in statistical learning theory. This importance is twofold: (1) generalization bounds provide an upper-tail confidence interval for the true risk of a learning algorithm the latter of which cannot be precisely calculated due to its dependency to some unknown distribution P from which the data are drawn, (2) this type of bounds can also be employed as model selection tools, which lead to identifying more accurate learning models. The generalization error bounds are typically expressed in terms of the empirical risk of the learning hypothesis along with a complexity measure of that hypothesis. Although different complexity measures can be used in deriving error bounds, Rademacher complexity has received considerable attention in recent years, due to its superiority to other complexity measures. In fact, Rademacher complexity can potentially lead to tighter error bounds compared to the ones obtained by other complexity measures. However, one shortcoming of the general notion of Rademacher complexity is that it provides a global complexity estimate of the learning hypothesis space, which does not take into consideration the fact that learning algorithms, by design, select functions belonging to a more favorable subset of this space and, therefore, they yield better performing models than the worst case. To overcome the limitation of global Rademacher complexity, a more nuanced notion of Rademacher complexity, the so-called local Rademacher complexity, has been considered, which leads to sharper learning bounds, and as such, compared to its global counterpart, guarantees faster convergence rates in terms of number of samples. Also, considering the fact that locally-derived bounds are expected to be tighter than globally-derived ones, they can motivate better (more accurate) model selection algorithms.While the previous MTL studies provide generalization bounds based on some other complexity measures, in this dissertation, we prove excess risk bounds for some popular kernel-based MTL hypothesis spaces based on the Local Rademacher Complexity (LRC) of those hypotheses. We show that these local bounds have faster convergence rates compared to the previous Global Rademacher Complexity (GRC)-based bounds. We then use our LRC-based MTL bounds to design a new kernel-based MTL model, which enjoys strong learning guarantees. Moreover, we develop an optimization algorithm to solve our new MTL formulation. Finally, we run simulations on experimental data that compare our MTL model to some classical Multi-Task Multiple Kernel Learning (MT-MKL) models designed based on the GRCs. Since the local Rademacher complexities are expected to be tighter than the global ones, our new model is also expected to exhibit better performance compared to the GRC-based models.
Show less - Date Issued
- 2017
- Identifier
- CFE0006827, ucf:51778
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006827
- Title
- Online, Supervised and Unsupervised Action Localization in Videos.
- Creator
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Soomro, Khurram, Shah, Mubarak, Heinrich, Mark, Hu, Haiyan, Bagci, Ulas, Yun, Hae-Bum, University of Central Florida
- Abstract / Description
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Action recognition classifies a given video among a set of action labels, whereas action localization determines the location of an action in addition to its class. The overall aim of this dissertation is action localization. Many of the existing action localization approaches exhaustively search (spatially and temporally) for an action in a video. However, as the search space increases with high resolution and longer duration videos, it becomes impractical to use such sliding window...
Show moreAction recognition classifies a given video among a set of action labels, whereas action localization determines the location of an action in addition to its class. The overall aim of this dissertation is action localization. Many of the existing action localization approaches exhaustively search (spatially and temporally) for an action in a video. However, as the search space increases with high resolution and longer duration videos, it becomes impractical to use such sliding window techniques. The first part of this dissertation presents an efficient approach for localizing actions by learning contextual relations between different video regions in training. In testing, we use the context information to estimate the probability of each supervoxel belonging to the foreground action and use Conditional Random Field (CRF) to localize actions. In the above method and typical approaches to this problem, localization is performed in an offline manner where all the video frames are processed together. This prevents timely localization and prediction of actions/interactions - an important consideration for many tasks including surveillance and human-machine interaction. Therefore, in the second part of this dissertation we propose an online approach to the challenging problem of localization and prediction of actions/interactions in videos. In this approach, we use human poses and superpixels in each frame to train discriminative appearance models and perform online prediction of actions/interactions with Structural SVM. Above two approaches rely on human supervision in the form of assigning action class labels to videos and annotating actor bounding boxes in each frame of training videos. Therefore, in the third part of this dissertation we address the problem of unsupervised action localization. Given unlabeled videos without annotations, this approach aims at: 1) Discovering action classes using a discriminative clustering approach, and 2) Localizing actions using a variant of Knapsack problem.
Show less - Date Issued
- 2017
- Identifier
- CFE0006917, ucf:51685
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006917
- Title
- Planning and Control of Swarm Motion as Continua.
- Creator
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Rastgoftar, Hossein, Jayasuriya, Suhada, Das, Tuhin, Xu, Chengying, Qu, Zhihua, Simaan, Marwan, University of Central Florida
- Abstract / Description
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In this thesis, new algorithms for formation control of multi agent systems (MAS) based on continuum mechanics principles will be investigated. For this purpose agents of the MAS are treated as particles in a continuum, evolving in an n-D space, whose desired configuration is required to satisfy an admissible deformation function. Considered is a specific class of mappings that is called homogenous where the Jacobian of the mapping is only a function of time and is not spatially varying. The...
Show moreIn this thesis, new algorithms for formation control of multi agent systems (MAS) based on continuum mechanics principles will be investigated. For this purpose agents of the MAS are treated as particles in a continuum, evolving in an n-D space, whose desired configuration is required to satisfy an admissible deformation function. Considered is a specific class of mappings that is called homogenous where the Jacobian of the mapping is only a function of time and is not spatially varying. The primary objectives of this thesis are to develop the necessary theory and its validation via simulation on a mobile-agent based swarm test bed that includes two primary tasks: 1) homogenous transformation of MAS and 2) deployment of a random distribution of agents on to a desired configuration. Developed will be a framework based on homogenous transformations for the evolution of a MAS in an n-D space (n=1, 2, and 3), under two scenarios: 1) no inter-agent communication (predefined motion plan); and 2) local inter-agent communication. Additionally, homogenous transformations based on communication protocols will be used to deploy an arbitrary distribution of a MAS on to a desired curve. Homogenous transformation with no communication: A homogenous transformation of a MAS, evolving in an R^n space, under zero inter agent communication is first considered. Here the homogenous mapping, is characterized by an n x n Jacobian matrix Q(t) and an n x 1 rigid body displacement vector D(t), that are based on positions of n+1 agents of the MAS, called leader agents. The designed Jacobian Q(t) and rigid body displacement vector D(t) are passed onto rest of the agents of the MAS, called followers, who will then use that information to update their positions under a pre-defined motion plan. Consequently, the motion of MAS will evolve as a homogenous transformation of the initial configuration without explicit communication among agents. Homogenous Transformation under Local Communication: We develop a framework for homogenous transformation of MAS, evolving in R^n, under a local inter agent communication topology. Here we assume that some agents are the leaders, that are transformed homogenously in an n-D space. In addition, every follower agent of the MAS communicates with some local agents to update its position, in order to grasp the homogenous mapping that is prescribed by the leader agents. We show that some distance ratios that are assigned based on initial formation, if preserved, lead to asymptotic convergence of the initial formation to a final formation under a homogenous mapping.Deployment of a Random Distribution on a Desired Manifold: Deployment of agents of a MAS, moving in a plane, on to a desired curve, is a task that is considered as an application of the proposed approach. In particular, a 2-D MAS evolution problem is considered as two 1-D MAS evolution problems, where x or y coordinates of the position of all agents are modeled as points confined to move on a straight line. Then, for every coordinate of MAS evolution, bulk motion is controlled by two agents considered leaders that move independently, with rest of the follower agents motions evolving through each follower agent communicating with two adjacent agents.
Show less - Date Issued
- 2013
- Identifier
- CFE0004915, ucf:49640
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004915
- Title
- Nonlinear dispersive partial differential equations of physical relevance with applications to vortex dynamics.
- Creator
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VanGorder, Robert, Kaup, David, Vajravelu, Kuppalapalle, Nevai, Andrew, Mohapatra, Ram, Kassab, Alain, University of Central Florida
- Abstract / Description
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Nonlinear dispersive partial differential equations occur in a variety of areas within mathematical physics and engineering. We study several classes of such equations, including scalar complex partial differential equations, vector partial differential equations, and finally non-local integro-differential equations. For physically interesting families of these equations, we demonstrate the existence (and, when possible, stability) of specific solutions which are relevant for applications....
Show moreNonlinear dispersive partial differential equations occur in a variety of areas within mathematical physics and engineering. We study several classes of such equations, including scalar complex partial differential equations, vector partial differential equations, and finally non-local integro-differential equations. For physically interesting families of these equations, we demonstrate the existence (and, when possible, stability) of specific solutions which are relevant for applications. While multiple application areas are considered, the primary application that runs through the work would be the nonlinear dynamics of vortex filaments under a variety of physical models. For instance, we are able to determine the structure and time evolution of several physical solutions, including the planar, helical, self-similar and soliton vortex filament solutions in a quantum fluid. Properties of such solutions are determined analytically and numerically through a variety of approaches. Starting with complex scalar equations (often useful for studying two-dimensional motion), we progress through more complicated models involving vector partial differential equations and non-local equations (which permit motion in three dimensions). In many of the examples considered, the qualitative analytical results are used to verify behaviors previously observed only numerically or experimentally.
Show less - Date Issued
- 2014
- Identifier
- CFE0005272, ucf:50545
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005272
- Title
- Mathematical and Computational Methods for Freeform Optical Shape Description.
- Creator
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Kaya, Ilhan, Foroosh, Hassan, Rolland, Jannick, Turgut, Damla, Thompson, Kevin, Ilegbusi, Olusegun, University of Central Florida
- Abstract / Description
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Slow-servo single-point diamond turning as well as advances in computer controlled small lap polishing enable the fabrication of freeform optics, specifically, optical surfaces for imaging applications that are not rotationally symmetric. Freeform optical elements will have a profound importance in the future of optical technology. Orthogonal polynomials added onto conic sections have been extensively used to describe optical surface shapes. The optical testing industry has chosen to...
Show moreSlow-servo single-point diamond turning as well as advances in computer controlled small lap polishing enable the fabrication of freeform optics, specifically, optical surfaces for imaging applications that are not rotationally symmetric. Freeform optical elements will have a profound importance in the future of optical technology. Orthogonal polynomials added onto conic sections have been extensively used to describe optical surface shapes. The optical testing industry has chosen to represent the departure of a wavefront under test from a reference sphere in terms of orthogonal ?-polynomials, specifically Zernike polynomials. Various forms of polynomials for describing freeform optical surfaces may be considered, however, both in optical design and in support of fabrication. More recently, radial basis functions were also investigated for optical shape description. In the application of orthogonal ?-polynomials to optical freeform shape description, there are important limitations, such as the number of terms required as well as edge-ringing and ill-conditioning in representing the surface with the accuracy demanded by most stringent optics applications. The first part of this dissertation focuses upon describing freeform optical surfaces with ? polynomials and shows their limitations when including higher orders together with possible remedies. We show that a possible remedy is to use edge clustered-fitting grids. Provided different grid types, we furthermore compared the efficacy of using different types of ? polynomials, namely Zernike and gradient orthogonal Q polynomials. In the second part of this thesis, a local, efficient and accurate hybrid method is developed in order to greatly reduce the order of polynomial terms required to achieve higher level of accuracy in freeform shape description that were shown to require thousands of terms including many higher order terms under prior art. This comes at the expense of multiple sub-apertures, and as such computational methods may leverage parallel processing. This new method combines the assets of both radial basis functions and orthogonal phi-polynomials for freeform shape description and is uniquely applicable across any aperture shape due to its locality and stitching principles. Finally in this thesis, in order to comprehend the possible advantages of parallel computing for optical surface descriptions, the benefits of making an effective use of impressive computational power offered by multi-core platforms for the computation of ?-polynomials are investigated. The ?-polynomials, specifically Zernike and gradient orthogonal Q-polynomials, are implemented with a set of recurrence based parallel algorithms on Graphics Processing Units (GPUs). The results show that more than an order of magnitude speedup is possible in the computation of ?-polynomials over a sequential implementation if the recurrence based parallel algorithms are adopted.
Show less - Date Issued
- 2013
- Identifier
- CFE0005012, ucf:49993
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005012
- Title
- Routing, Localization and Positioning Protocols for Wireless Sensor and Actor Networks.
- Creator
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Akbas, Mustafa, Turgut, Damla, Boloni, Ladislau, Georgiopoulos, Michael, Brust, Matthias, Bassiouni, Mostafa, Zhao, Yue, University of Central Florida
- Abstract / Description
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Wireless sensor and actor networks (WSANs) are distributed systems of sensor nodes and actors that are interconnected over the wireless medium. Sensor nodes collect information about the physical world and transmit the data to actors by using one-hop or multi-hop communications. Actors collect information from the sensor nodes, process the information, take decisions and react to the events.This dissertation presents contributions to the methods of routing, localization and positioning in...
Show moreWireless sensor and actor networks (WSANs) are distributed systems of sensor nodes and actors that are interconnected over the wireless medium. Sensor nodes collect information about the physical world and transmit the data to actors by using one-hop or multi-hop communications. Actors collect information from the sensor nodes, process the information, take decisions and react to the events.This dissertation presents contributions to the methods of routing, localization and positioning in WSANs for practical applications. We first propose a routing protocol with service differentiation for WSANs with stationary nodes. In this setting, we also adapt a sports ranking algorithm to dynamically prioritize the events in the environment depending on the collected data. We extend this routing protocol for an application, in which sensor nodes float in a river to gather observations and actors are deployed at accessible points on the coastline. We develop a method with locally acting adaptive overlay network formation to organize the network with actor areas and to collect data by using locality-preserving communication.We also present a multi-hop localization approach for enriching the information collected from the river with the estimated locations of mobile sensor nodes without using positioning adapters. As an extension to this application, we model the movements of sensor nodes by a subsurface meandering current mobility model with random surface motion. Then we adapt the introduced routing and network organization methods to model a complete primate monitoring system. A novel spatial cut-off preferential attachment model and center of mass concept are developed according to the characteristics of the primate groups. We also present a role determination algorithm for primates, which uses the collection of spatial-temporal relationships. We apply a similar approach to human social networks to tackle the problem of automatic generation and organization of social networks by analyzing and assessing interaction data. The introduced routing and localization protocols in this dissertation are also extended with a novel three dimensional actor positioning strategy inspired by the molecular geometry. Extensive simulations are conducted in OPNET simulation tool for the performance evaluation of the proposed protocols.
Show less - Date Issued
- 2013
- Identifier
- CFE0005292, ucf:50564
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005292
- Title
- Photon Statistics in Disordered Lattices.
- Creator
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Kondakci, Hasan, Saleh, Bahaa, Abouraddy, Ayman, Christodoulides, Demetrios, Mucciolo, Eduardo, University of Central Florida
- Abstract / Description
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Propagation of coherent waves through disordered media, whether optical, acoustic, or radio waves, results in a spatially redistributed random intensity pattern known as speckle -- a statistical phenomenon. The subject of this dissertation is the statistics of monochromatic coherent light traversing disordered photonic lattices and its dependence on the disorder class, the level of disorder and the excitation configuration at the input. Throughout the dissertation, two disorder classes are...
Show morePropagation of coherent waves through disordered media, whether optical, acoustic, or radio waves, results in a spatially redistributed random intensity pattern known as speckle -- a statistical phenomenon. The subject of this dissertation is the statistics of monochromatic coherent light traversing disordered photonic lattices and its dependence on the disorder class, the level of disorder and the excitation configuration at the input. Throughout the dissertation, two disorder classes are considered, namely, diagonal and off-diagonal disorders. The latter exhibits disorder-immune chiral symmetry -- the appearance of the eigenmodes in skew-symmetric pairs and the corresponding eigenvalues in opposite signs. When a disordered photonic lattice, an array of evanescently coupled waveguides, is illuminated with an extended coherent optical field, discrete speckle develops. Numerical simulations and analytical modeling reveal that discrete speckle shows a set of surprising features, that are qualitatively indistinguishable in both disorder classes. First, the fingerprint of transverse Anderson localization -- associated with disordered lattices, is exhibited in the narrowing of the spatial coherence function. Second, the transverse coherence length (or speckle grain size) freezes upon propagation. Third, the axial coherence depth is independent of the axial position, thereby resulting in a coherence voxel of fixed volume independently of position.When a single lattice site is coherently excited, I discovered that a thermalization gap emerges for light propagating in disordered lattices endowed with disorder-immune chiral symmetry. In these systems, the span of sub-thermal photon statistics is inaccessible to the input coherent light, which -- once the steady state is reached -- always emerges with super-thermal statistics no matter how small the disorder level. An independent constraint of the input field for the chiral symmetry to be activated and the gap to be observed is formulated. This unique feature enables a new form of photon-statistics interferometry: by exciting two lattice sites with a variable relative phase, as in a traditional two-path interferometer, the excitation-symmetry of the chiral mode pairs is judiciously broken and interferometric control over the photon statistics is exercised, spanning sub-thermal and super-thermal regimes. By considering an ensemble of disorder realizations, this phenomenon is demonstrated experimentally: a deterministic tuning of the intensity fluctuations while the mean intensity remains constant.Finally, I examined the statistics of the emerging light in two different lattice topologies: linear and ring lattices. I showed that the topology dictates the light statistics in the off-diagonal case: for even-sited ring and linear lattices, the electromagnetic field evolves into a single quadrature component, so that the field takes discrete phase values and is non-circular in the complex plane. As a consequence, the statistics become super-thermal. For odd-sited ring lattices, the field becomes random in both quadratures resulting in sub-thermal statistics. However, this effect is suppressed due to the transverse localization of light in lattices with high disorder. In the diagonal case, the lattice topology does not play a role and the transmitted field always acquires random components in both quadratures, hence the phase distribution is uniform in the steady state.
Show less - Date Issued
- 2015
- Identifier
- CFE0005968, ucf:50786
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005968
- Title
- Social Media Usage by Municipal Elected Officials for Open Government Community Engagement.
- Creator
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Stoeckel, Sarah, Bryer, Thomas, Mitchell, David, Hu, Qian, Brown, Tim, University of Central Florida
- Abstract / Description
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As public administration has evolved with the technological advances in today's society, it can be challenging to ensure the demands of the public are being met in terms of efficiency, effectiveness, and engagement. Nonetheless, a focus on community remains at the forefront of public administration. When looking at technology and the community, the tool known as social media emerges. Social media has allowed people to interact in new ways and therefore, has allowed the government to interact...
Show moreAs public administration has evolved with the technological advances in today's society, it can be challenging to ensure the demands of the public are being met in terms of efficiency, effectiveness, and engagement. Nonetheless, a focus on community remains at the forefront of public administration. When looking at technology and the community, the tool known as social media emerges. Social media has allowed people to interact in new ways and therefore, has allowed the government to interact with citizens in ways they have not been able to in the past. In addition to attempting to modernize public administration, there has been an increased focus on building citizen trust through providing a more open government structure. The Open Government Directive issued by President Barack Obama focused on three tenets, which included transparency, participation, and collaboration. One of the ways government entities within the United States are strengthening these areas is through the implementation of various social media sites as a means to stay connected with citizens. With an increase of users utilizing social media tools for both information and connection, many government departments and agencies have incorporated social media use into their workplace as a function for their department. However, it is elected officials that are the ones who represent the citizens from their governmental role and thus, can aid in bridging the gap between citizens and government. Yet, there is little research on how elected officials, specifically in municipalities, are utilizing social media to connect with their constituents. This study discusses social media use by municipal elected officials and how it relates to open government community engagement. Open government community engagement is defined in terms of the three tenets of the Open Government Directive: transparency, participation, and collaboration encompassing the rungs of Arnstein's ladder of citizen participation. For this qualitative study, fifty-seven Florida municipal elected officials were interviewed regarding their social media use or lack thereof in terms of engagement with citizens. The interviews are followed-up with content analysis of social media sites. An ethnographic approach is utilized to uncover and develop common themes related to open government community engagement. The findings suggest while some municipal elected officials are utilizing social media well in terms of open government community engagement, there is a lack of clear understanding of social media use within the context of the Sunshine Law, as well as other barriers prohibiting utilizing social media for more of the participation and collaboration components. There are several reasons municipal elected officials opt to avoid social media altogether, while additional concepts related to open government limited engagement and closed government community engagement are explored. The concept of avoidance was addressed, especially as it pertained to the practical implications for both city administrators and elected officials.
Show less - Date Issued
- 2018
- Identifier
- CFE0007377, ucf:52083
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007377
- Title
- Local Health Department Adoption of Health Information Technology and Its Impact on Population Health.
- Creator
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Yeung, Tina, Wan, Thomas, Cortelyou-Ward, Kendall, Liu, Albert Xinliang, Dziegielewski, Sophia, University of Central Florida
- Abstract / Description
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Since the enactment of the HITECH Act in 2009, the US has invested billions in building a robust health information technology (HIT) infrastructure that is secure, capable of the electronic transfer of data and allows for real-time access of patient medical data, among others. This empirical study explored the driving forces (coercive, mimetic, and normative) in the adoption of HIT (i.e. EHRs and HIEs) by local health departments (LHDs) and how it has impacted the population health of...
Show moreSince the enactment of the HITECH Act in 2009, the US has invested billions in building a robust health information technology (HIT) infrastructure that is secure, capable of the electronic transfer of data and allows for real-time access of patient medical data, among others. This empirical study explored the driving forces (coercive, mimetic, and normative) in the adoption of HIT (i.e. EHRs and HIEs) by local health departments (LHDs) and how it has impacted the population health of counties in the US. The researcher conducted a cross-sectional, quantitative study using secondary data sources. The study included data on 505 local health departments and 433 counties' population health data. Institutional theory guided this research and generalized estimating equations, logistic regression, and multiple linear regression were utilized to analyze health IT adoption by LHDs and its impact on county-level health outcomes. Results showed that normative forces, measured by the employment of IS specialists was most impactful in the adoption of both EHRs and HIEs. Mimetic forces, measured by the completion of a CHA and coercive forces measured by the implementation of the HITECH Act were not found to be statistically significant in the adoption of EHRs or HIEs. Finally, EHR adoption was statistically significant at improving population health at the county level. This research study has contributed in three areas: 1) to fill a knowledge gap on the impact of health IT adoption by LHDs on health outcomes; 2) to formulate a theoretically grounded framework to study population health and its variability; and 3) to identify target areas for public health interventions. In conclusion, a substantial amount of resources dedicated in creating a robust health IT infrastructure requires close analysis of the impact health IT has on the population health of our nation.
Show less - Date Issued
- 2017
- Identifier
- CFE0006825, ucf:51801
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006825
- Title
- Spatial and Temporal Compressive Sensing for Vibration-based Monitoring: Fundamental Studies with Beam Vibrations.
- Creator
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Ganesan, Vaahini, Das, Tuhin, Kauffman, Jeffrey L., Raghavan, Seetha, University of Central Florida
- Abstract / Description
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Vibration data from mechanical systems carry important information that is useful for characterization and diagnosis. Standard approaches rely on continually streaming data at a fixed sampling frequency. For applications involving continuous monitoring, such as Structural Health Monitoring (SHM), such approaches result in high data volume and require powering sensors for prolonged duration. Furthermore, adequate spatial resolution, typically involves instrumenting structures with a large...
Show moreVibration data from mechanical systems carry important information that is useful for characterization and diagnosis. Standard approaches rely on continually streaming data at a fixed sampling frequency. For applications involving continuous monitoring, such as Structural Health Monitoring (SHM), such approaches result in high data volume and require powering sensors for prolonged duration. Furthermore, adequate spatial resolution, typically involves instrumenting structures with a large array of sensors. This research shows that applying Compressive Sensing (CS) can significantly reduce both the volume of data and number of sensors in vibration monitoring applications. Random sampling and the inherent sparsity of vibration signals in the frequency domain enables this reduction. Additionally, by exploiting the sparsity of mode shapes, CS can also enable efficient spatial reconstruction using fewer spatially distributed sensors than a traditional approach. CS can thereby reduce the cost and power requirement of sensing as well as streamline data storage and processing in monitoring applications. In well-instrumented structures, CS can enable continuous monitoring in case of sensor or computational failures. The scope of this research was to establish CS as a viable method for SHM with application to beam vibrations. Finite element based simulations demonstrated CS-based frequency recovery from free vibration response of simply supported, fixed-fixed and cantilever beams. Specifically, CS was used to detect shift in natural frequencies of vibration due to structural change using considerably less data than required by traditional sampling. Experimental results using a cantilever beam provided further insight into this approach. In the experimental study, impulse response of the beam was used to recover natural frequencies of vibration with CS. It was shown that CS could discern changes in natural frequencies under modified beam parameters. When the basis functions were modified to accommodate the effect of damping, the performance of CS-based recovery further improved. Effect of noise in CS-based frequency recovery was also studied. In addition to incorporating damping, formulating noise-handling as a part of the CS algorithm for beam vibrations facilitated detecting shift in frequencies from even fewer samples. In the spatial domain, CS was primarily developed to focus on image processing applications, where the signals and basis functions are very different from those required for mechanical beam vibrations. Therefore, it mandated reformulation of the CS problem that would handle related challenges and enable the reconstruction of spatial beam response using very few sensor data. Specifically, this research addresses CS-based reconstruction of deflection shape of beams with fixed boundary conditions. Presence of a fixed end makes hyperbolic terms indispensable in the basis, which in turn causes numerical inconsistencies. Two approaches are discussed to mitigate this problem. The first approach is to restrict the hyperbolic terms in the basis to lower frequencies to ensure well conditioning. The second, a more systematic approach, is to generate an augmented basis function that will combine harmonic and hyperbolic terms. At higher frequencies, the combined hyperbolic terms will limit each other's magnitude, thus ensuring boundedness. This research thus lays the foundation for formulating the CS problem for the field of mechanical vibrations. It presents fundamental studies and discusses open-ended challenges while implementing CS to this field that will pave way for further research.
Show less - Date Issued
- 2017
- Identifier
- CFE0007120, ucf:51954
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007120
- Title
- Electing or Appointing School District Superintendents in the State of Florida: A Comparison of Characteristics and Performance of Districts Led by Elected Superintendents Versus Districts Led by Appointed Superintendents.
- Creator
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Smith, Timothy, Johnson, Jerry, Doherty, Walter, Vitale, Thomas, Fritz, Ronald, University of Central Florida
- Abstract / Description
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Florida and Alabama are the only two states in the United States of America with school districts led by either elected superintendents or appointed superintendents. The other 48 states only have appointed superintendent-led school districts. The current study was conducted to examine the impact of the superintendent governance structure on student learning by analyzing differences in student achievement between Florida school districts led by elected superintendents and Florida school...
Show moreFlorida and Alabama are the only two states in the United States of America with school districts led by either elected superintendents or appointed superintendents. The other 48 states only have appointed superintendent-led school districts. The current study was conducted to examine the impact of the superintendent governance structure on student learning by analyzing differences in student achievement between Florida school districts led by elected superintendents and Florida school districts led by appointed superintendents. The conceptual framework of the study was the tension between democratic localism and professionalism. Dynamics associated with the conceptual framework are relevant to the current debate.This quantitative study included cross-tabulations of the superintendent governance structure by regions and by locale codes. Descriptive statistics were used to define differences between school districts with elected or appointed superintendents in the areas of enrollment, free/reduced lunch, ELL populations, test scores, and graduation rates. An independent samples t-test was used to further analyze the demographic variables. A one-way ANCOVA was employed to determine if the superintendent governance structure or the demographic variables were associated with variances in student achievement.Research findings indicated that appointed superintendent-led school districts performed slightly higher than elected superintendent-led school districts. However, the superintendent governance structure did not have a statistically significant relationship with student achievement. Instead, poverty, as measured by free/reduced lunch rates, had a statistically significant relationship with student achievement.
Show less - Date Issued
- 2019
- Identifier
- CFE0007727, ucf:52416
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007727
- Title
- Assessing the Impact of Economies of Scale and Uncontrollable Factors on the Performance of U.S. Cities.
- Creator
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Allaf, Mamoon, Martin, Lawrence, Wan, Thomas, Kapucu, Naim, Baker, Paul, University of Central Florida
- Abstract / Description
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Despite the increased interest among local governments in collecting data on performance measurement, empirical evidence is still limited regarding the extent to which these data are utilized to assess the impact on efficiency of economies of scale and uncontrollable factors. Data envelopment analysis (DEA) is a linear programming method designed to estimate the relative efficiency of decision-making units. In addition to assessing relative efficiency, DEA can estimate scale efficiency and...
Show moreDespite the increased interest among local governments in collecting data on performance measurement, empirical evidence is still limited regarding the extent to which these data are utilized to assess the impact on efficiency of economies of scale and uncontrollable factors. Data envelopment analysis (DEA) is a linear programming method designed to estimate the relative efficiency of decision-making units. In addition to assessing relative efficiency, DEA can estimate scale efficiency and incorporate the impact of uncontrollable factors. Using data from the International City/County Association (ICMA), this study utilized DEA to evaluate the impact of economies of scale and uncontrollable factors on the relative efficiency of municipal service delivery in the United States. The findings from this doctoral dissertation show that uncontrollable variables such as population density, unemployment, and household income suppress the relative efficiency of local governments. Moreover, the findings imply that the prevalence of economies of scale in city governments depends on the types of services these governments provide.
Show less - Date Issued
- 2012
- Identifier
- CFE0004201, ucf:49002
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004201
- Title
- The Effect of the Great Recession on Local Goverment Policy in Florida.
- Creator
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Levey, Richard, Martin, Lawrence, Zhang, Ning, Lawther, Wendell, Hawkins, Christopher, University of Central Florida
- Abstract / Description
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The length and depth of the Great Recession of 2008 provides an opportunity to examine the policy behavior of local governments unlike any window since the 1930's post Depression era. Utilizing Peterson's (1981) City Limits typology as a framework for local government policy allows for an evaluation of whether or not the economic downturn caused local governments to change their relative expenditures between policy categories. The City Limits typology has been widely used in the literature to...
Show moreThe length and depth of the Great Recession of 2008 provides an opportunity to examine the policy behavior of local governments unlike any window since the 1930's post Depression era. Utilizing Peterson's (1981) City Limits typology as a framework for local government policy allows for an evaluation of whether or not the economic downturn caused local governments to change their relative expenditures between policy categories. The City Limits typology has been widely used in the literature to explain how expenditures define a local government's role in economic development. The typology has had limited use in a pre-post natural experimental research design to determine if a local government has 'shifted' policy priorities as measured by changes in expenditures among and between policy categories. This research design and the use Peterson's framework combine for a study that has not yet been conducted under similar conditions.Most of the existing literature, including the research from the 1980's, failed to account for inter-state differences that directly affect local government expenditures and policy. Concentrating solely on Florida local governments, this study eliminates the confounding nature of a national study and ensures that the unit of analysis is comparable for research purposes. The study utilizes actual expenditure data for all cities and counties in Florida from FY2006 through FY2011. The research tests for the relationships between changes in policy priorities from pre- to post-recession, and the type of government, form of government, and various socio-economic factors.The research contributes to a new body of knowledge that is just beginning to emerge in the literature about how local governments respond to periods of extreme fiscal stress. The findings suggest that cities and counties had an inverse response from pre- to post-recession with cities shifting toward developmental expenditures and counties prioritizing allocational spending. Differences were also found between forms of government. In addition, the density of population was found to contribute differently to shifts in expenditures for cities and counties. The study identifies emerging patterns that can help local governments understand past behavior and better anticipate future economic downturns.
Show less - Date Issued
- 2015
- Identifier
- CFE0005971, ucf:50782
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005971
- Title
- Development of a nano-sensing approach and a portable prototype for real-time detection and quantification of free mercury in stream-flow: combining science and engineering in pro of the environment.
- Creator
-
Chemnasiri, Warinya, Hernandez, Florencio, Kuebler, Stephen, Zou, Shengli, Uribe Romo, Fernando, Huo, Qun, University of Central Florida
- Abstract / Description
-
Mercury (Hg) is a well-known hazardous environmental contaminant existing in several forms, but all are toxic to human in one way or the others. Since Hg usually settles into water polluting the environment and accumulating in living organisms, it is crucial to monitor Hg levels in the aquatic ecosystem. Although there are many well established techniques currently used to detect Hg, most of them require elaborate and time-consuming sample preparation and pre-concentration procedures, as well...
Show moreMercury (Hg) is a well-known hazardous environmental contaminant existing in several forms, but all are toxic to human in one way or the others. Since Hg usually settles into water polluting the environment and accumulating in living organisms, it is crucial to monitor Hg levels in the aquatic ecosystem. Although there are many well established techniques currently used to detect Hg, most of them require elaborate and time-consuming sample preparation and pre-concentration procedures, as well as costly and bulky equipment that limit their practical application in the field. In order to overcome the existent limitations in Hg determination methods, Hernandez and co-workers proposed the first surface Plasmon resonance (SPR) (-) based Hg sensor using gold nanorods (AuNRs) that offers high sensitivity and selectivity, attributed to the strong affinity between Au and Hg. In this dissertation, I first present my contribution to the understanding of the effect of size and aspect ratio of AuNRs on the limit of detection (LOD) and the dynamic range (DR) of the SPR-based Hg sensor using the qualitative model. In this part I demonstrate how both sensitivity and DR can be improved simultaneously via a modified wet chemistry procedure. Then, I show our approach towards the immobilization of AuNRs silane coated glass slides to expand the application of the SPR-based Hg sensor to stream-flow. Finally, I present the design and fabrication of the first real prototype of the SPR-based Hg sensor, and its application in stream-flow detection and speciation of mercury in the environment. The outcomes of my research have resulted in an innovative real-time portable Hg sensor apparatus with the desired high sensitivity, selectivity and DR to be used in stream-flow applications in Oak Ridge National Labs sites.
Show less - Date Issued
- 2015
- Identifier
- CFE0006283, ucf:51589
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006283
- Title
- Quasi-Gorenstein Modules.
- Creator
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York, Alexander, Brennan, Joseph, Martin, Heath, Ismail, Mourad, Kuebler, Stephen, University of Central Florida
- Abstract / Description
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This thesis will study the various roles that quasi-Gorenstein modules and their properties play in the study of homological dimensions and linkage of modules. To that effect we begin by studying these modules in their own right. An $R$-module $M$ of grade $g$ will be quasi-Gorenstein if $\Ext_R^i(M,R)=0$ for $i\neq g$ and there is an isomorphism $M\cong\Ext_R^g(M,R)$. Such modules have many nice properties which we will explore throughout this thesis. We will show they help extend a...
Show moreThis thesis will study the various roles that quasi-Gorenstein modules and their properties play in the study of homological dimensions and linkage of modules. To that effect we begin by studying these modules in their own right. An $R$-module $M$ of grade $g$ will be quasi-Gorenstein if $\Ext_R^i(M,R)=0$ for $i\neq g$ and there is an isomorphism $M\cong\Ext_R^g(M,R)$. Such modules have many nice properties which we will explore throughout this thesis. We will show they help extend a characterization of diagonalizable matrices over principal ideal domains to more general rings. We will use their properties to help lay a foundation for a study of homological dimensions, helping to generalize the concept of Gorenstein dimension to modules of larger grade and present a connection to these new dimensions with certain generalized Serre conditions.We then give a categorical construction to the concept of linkage. The main motivation of such a construction is to generalize ideal and module linkage into one unified theory. By using the defintion of linkage presented by Nagel \cite{NagelLiaison}, we can use categorical language to define linkage between categories. One of the focuses of this thesis is to show that the history of linkage has been wrought with a misunderstanding of which classes of objects to study. We give very compelling evidence to suggest that linkage is a tool to gain information about the even linkage classes of objects. Further, scattered among the literature is a wide array of results pertaining to module linkage, homological dimensions, duality, and adjoint functor pairs and for which we show that these fall under the umbrella of this unified theory. This leads to an intimate relationship between associated homological dimensions and the linkage of objects in a category. We will give many applications of the theory to modules allowing one to cover vast grounds from Gorenstein dimensions to Auslander and Bass classes to local cohomology and local homology. Each of these gives useful insight into certain classes of modules by applying this categorical approach to linkage.
Show less - Date Issued
- 2018
- Identifier
- CFE0007268, ucf:52202
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007268
- Title
- Evolution and distribution of phenotypic diversity in the venom of Mojave Rattlesnakes (Crotalus scutulatus).
- Creator
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Strickland, Jason, Savage, Anna, Parkinson, Christopher, Hoffman, Eric, Rokyta, Darin, University of Central Florida
- Abstract / Description
-
Intraspecific phenotype diversity allows for local adaption and the ability for species to respond to changing environmental conditions, enhancing survivability. Phenotypic variation could be stochastic, genetically based, and/or the result of different environmental conditions. Mojave Rattlesnakes, Crotalus scutulatus, are known to have high intraspecific venom variation, but the geographic extent of the variation and factors influencing venom evolution are poorly understood. Three primary...
Show moreIntraspecific phenotype diversity allows for local adaption and the ability for species to respond to changing environmental conditions, enhancing survivability. Phenotypic variation could be stochastic, genetically based, and/or the result of different environmental conditions. Mojave Rattlesnakes, Crotalus scutulatus, are known to have high intraspecific venom variation, but the geographic extent of the variation and factors influencing venom evolution are poorly understood. Three primary venom types have been described in this species based on the presence (Type A) or absence (Type B) of a neurotoxic phospholipase A2 called Mojave toxin and an inverse relationship with the presence of snake venom metalloproteinases (SVMPs). Individuals that contain both Mojave toxin and SVMPs, although rare, are the third, and designated Type A + B. I sought to describe the proteomic and transcriptomic venom diversity of C. scutulatus across its range and test whether diversity was correlated with genetic or environmental differences. This study includes the highest geographic sampling of Mojave Rattlesnakes and includes the most venom-gland transcriptomes known for one species. Of the four mitochondrial lineages known, only one was monophyletic for venom type. Environmental variables poorly correlated with the phenotypes. Variability in toxin and toxin family composition of venom transcriptomes was largely due to differences in transcript expression. Four of 19 toxin families identified in C. scutulatus account for the majority of differences in toxin number and expression variation. I was able to determine that the toxins primarily responsible for venom types are inherited in a Mendelian fashion and that toxin expression is additive when comparing heterozygotes and homozygotes. Using the genetics to define venom type is more informative and the Type A + B phenotype is not unique, but rather heterozygous for the PLA2 and/or SVMP alleles. Intraspecific venom variation in C. scutulatus highlights the need for fine scale ecological and natural history information to understand how phenotypic diversity is generated and maintained geographically through time.
Show less - Date Issued
- 2018
- Identifier
- CFE0007252, ucf:52198
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007252
- Title
- The Response of American Police Agencies to Digital Evidence.
- Creator
-
Yesilyurt, Hamdi, Wan, Thomas, Potter, Roberto, Applegate, Brandon, Lang, Sheau-Dong, University of Central Florida
- Abstract / Description
-
Little is known about the variation in digital forensics practice in the United States as adopted by large local police agencies. This study investigated how environmental constraints, contextual factors, organizational complexity, and organizational control relate to the adoption of digital forensics practice. This study integrated 3 theoretical perspectives in organizational studies to guide the analysis of the relations: institutional theory, contingency theory, and adoption-of-innovation...
Show moreLittle is known about the variation in digital forensics practice in the United States as adopted by large local police agencies. This study investigated how environmental constraints, contextual factors, organizational complexity, and organizational control relate to the adoption of digital forensics practice. This study integrated 3 theoretical perspectives in organizational studies to guide the analysis of the relations: institutional theory, contingency theory, and adoption-of-innovation theory. Institutional theory was used to analyze the impact of environmental constraints on the adoption of innovation, and contingency theory was used to examine the impacts of organizational control on the adoption of innovation. Adoption of innovation theory was employed to describe the degree to which digital forensics practice has been adopted by large municipal police agencies having 100 or more sworn police officers.The data set was assembled primarily by using Law Enforcement Management and Administrative Statistics (LEMAS) 2003 and 1999. Dr. Edward Maguire`s survey was used to obtain 1 variable. The joining up of the data set to construct the sample resulted in 345 large local police agencies. The descriptive results on the degree of adoption of digital forensics practice indicate that 37.7% of large local police agencies have dedicated personnel to address digital evidence, 32.8% of police agencies address digital evidence but do not have dedicated personnel, and only 24.3% of police agencies have a specialized unit with full-time personnel to address digital evidence. About 5% of local police agencies do nothing to address digital evidence in any circumstance. These descriptive statistics indicate that digital evidence is a matter of concern for most large local police agencies and that they respond to varying degrees to digital evidence at the organizational level. Agencies that have not adopted digital forensics practice are in the minority. The structural equation model was used to test the hypothesized relations, easing the rigorous analysis of relations between latent constructs and several indicator variables. Environmental constraints have the largest impact on the adoption of innovation, exerting a positive influence. No statistically significant relation was found between organizational control and adoption of digital forensic practice. Contextual factors (task scope and personnel size) positively influence the adoption of digital forensics. Structural control factors, including administrative weight and formalization, have no significant influence on the adoption of innovation. The conclusions of the study are as follows. Police agencies adopt digital forensics practice primarily by relying on environmental constraints. Police agencies exposed to higher environmental constraints are more frequently expected to adopt digital forensics practice. Because organizational control of police agencies is not significantly related to digital forensics practice adoption, police agencies do not take their organizational control extensively into consideration when they consider adopting digital forensics practice. The positive influence of task scope and size on digital forensics practice adoption was expected. The extent of task scope and the number of personnel indicate a higher capacity for police agencies to adopt digital forensics practice. Administrative weight and formalization do not influence the adoption of digital forensics practice. Therefore, structural control and coordination are not important for large local police agencies to adopt digital forensics practice.The results of the study indicate that the adoption of digital forensics practice is based primarily on environmental constraints. Therefore, more drastic impacts on digital forensics practice should be expected from local police agencies' environments than from internal organizational factors. Researchers investigating the influence of various factors on the adoption of digital forensics practice should further examine environmental variables. The unexpected results concerning the impact of administrative weight and formalization should be researched with broader considerations.
Show less - Date Issued
- 2011
- Identifier
- CFE0004181, ucf:49081
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004181
- Title
- Intercultural Communication in the Global Age: Lessons Learned from French Technical Communicators.
- Creator
-
Tallman, Nicole, Flammia, Madelyn, Bowdon, Melody, Jones, Daniel, University of Central Florida
- Abstract / Description
-
This thesis explores the cultural considerations American technical communicators must address when working with French colleagues and when creating technical documentation for French audiences. A review of the literature on intercultural communication theory was conducted, along with a review of the limited research on technical communication in France and the needs of French audiences. A qualitative online survey of French technical communicators was also conducted. Through this survey,...
Show moreThis thesis explores the cultural considerations American technical communicators must address when working with French colleagues and when creating technical documentation for French audiences. A review of the literature on intercultural communication theory was conducted, along with a review of the limited research on technical communication in France and the needs of French audiences. A qualitative online survey of French technical communicators was also conducted. Through this survey, French technical communicators reported on their intercultural beliefs, experiences, and practices, and information, language, and cultural needs.Survey responses were analyzed using inductive thematic analysis. Two main themes were developed as a result of this analysis: the importance of adapting content to French audiences, and the cultural differences between French and American information needs and communication styles. Survey findings were combined with theoretical and practical literature to offer American technical communicators guidance for successful intercultural interactions. This thesis concludes with suggestions for future practice and research in intercultural technical communication.
Show less - Date Issued
- 2013
- Identifier
- CFE0004944, ucf:49604
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004944
- Title
- Visuo-spatial abilities in remote perception: A meta-analysis of empirical work.
- Creator
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Fincannon, Thomas, Jentsch, Florian, Sims, Valerie, Bowers, Clint, Chen, Jessie, University of Central Florida
- Abstract / Description
-
Meta-analysis was used to investigate the relationship between visuo-spatial ability and performance in remote environments. In order to be included, each study needed to examine the relationship between the use of an ego-centric perspective and various dimensions of performance (i.e., identification, localization, navigation, and mission completion time). The moderator analysis investigated relationships involving: (a) visuo-spatial construct with an emphasis on Carroll's (1993)...
Show moreMeta-analysis was used to investigate the relationship between visuo-spatial ability and performance in remote environments. In order to be included, each study needed to examine the relationship between the use of an ego-centric perspective and various dimensions of performance (i.e., identification, localization, navigation, and mission completion time). The moderator analysis investigated relationships involving: (a) visuo-spatial construct with an emphasis on Carroll's (1993) visualization (VZ) factor; (b) performance outcome (i.e., identification, localization, navigation, and mission completion time); (c) autonomy to support mission performance; (d) task type (i.e., navigation vs. reconnaissance); and (e) experimental testbed (i.e., physical vs. virtual environments). The process of searching and screening for published and unpublished analyses identified 81 works of interest that were found to represent 50 unique datasets. 518 effects were extracted from these datasets for analyses.Analyses of aggregated effects (Hunter (&) Schmidt, 2004) found that visuo-spatial abilities were significantly associated with each construct, such that effect sizes ranged from weak (r = .235) to moderately strong (r = .371). For meta-regression (Borenstein, Hedges, Figgins, (&) Rothstein, 2009; Kalaian (&) Raudenbush, 1996; Tabachnick (&) Fidell, 2007), moderation by visuo-spatial construct (i.e., focusing on visualization) was consistently supported for all outcomes. For at least one of the outcomes, support was found for moderation by test, the reliability coefficient of a test, autonomy (i.e. to support identification, localization, and navigation), testbed (i.e., physical vs. virtual environment), intended domain of application, and gender. These findings illustrate that majority of what researchers refer to as (")spatial ability(") actually uses measures that load onto Carroll's (1993) visualization (VZ) factor. The associations between this predictor and all performance outcomes were significant, but the significant variation across moderators highlight important issues for the design of unmanned systems and the external validity of findings across domains. For example, higher levels of autonomy for supporting navigation decreased the association between visualization (VZ) and performance. In contrast, higher levels of autonomy for supporting identification and localization increased the association between visualization (VZ) and performance. Furthermore, moderation by testbed, intended domain of application, and gender challenged the degree to which findings can be expected to generalize across domains and sets of participants.
Show less - Date Issued
- 2013
- Identifier
- CFE0004680, ucf:49858
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004680