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Title: HYBRID PHOTONIC SIGNAL PROCESSING.
Creator: Ghauri, Farzan, Riza, Nabeel, University of Central Florida
Abstract / Description: This thesis proposes research of novel hybrid photonic signal processing systems in the areas of optical communications, test and measurement, RF signal processing and extreme environment optical sensors. It will be shown that use of innovative hybrid techniques allows design of photonic signal processing systems with superior performance parameters and enhanced capabilities. These applications can be divided into domains of analog-digital hybrid signal processing applications and free-space-...
Show moreThis thesis proposes research of novel hybrid photonic signal processing systems in the areas of optical communications, test and measurement, RF signal processing and extreme environment optical sensors. It will be shown that use of innovative hybrid techniques allows design of photonic signal processing systems with superior performance parameters and enhanced capabilities. These applications can be divided into domains of analog-digital hybrid signal processing applications and free-space--fiber-coupled hybrid optical sensors. The analog-digital hybrid signal processing applications include a high-performance analog-digital hybrid MEMS variable optical attenuator that can simultaneously provide high dynamic range as well as high resolution attenuation controls; an analog-digital hybrid MEMS beam profiler that allows high-power watt-level laser beam profiling and also provides both submicron-level high resolution and wide area profiling coverage; and all optical transversal RF filters that operate on the principle of broadband optical spectral control using MEMS and/or Acousto-Optic tunable Filters (AOTF) devices which can provide continuous, digital or hybrid signal time delay and weight selection. The hybrid optical sensors presented in the thesis are extreme environment pressure sensors and dual temperature-pressure sensors. The sensors employ hybrid free-space and fiber-coupled techniques for remotely monitoring a system under simultaneous extremely high temperatures and pressures.
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Date Issued: 2007
Identifier: CFE0001983, ucf:47423
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001983

Title: EFFECT OF COMPOSITION, MORPHOLOGY AND SEMICONDUCTING PROPERTIES ON THE EFFICIENCY OF CUIN1-XGAXSE2-YSY THIN-FILM SOLAR CELLS PREPARED BY RAPID THERMAL PROCESSING.
Creator: Kulkarni, Sachin, Dhere, Neelkanth, University of Central Florida
Abstract / Description: A rapid thermal processing (RTP) reactor for the preparation of graded CuIn1-xGaxSe2-ySy (CIGSeS) thin-film solar cells has been designed, assembled and is being used at the Photovoltaic Materials Laboratory of the Florida Solar Energy Center. CIGSeS films having the optimum composition, morphology, and semiconducting properties were prepared using RTP. Initially films having various Cu/(In+Ga) ratios were prepared. In the next step selenium incorporation in these films was optimized,...
Show moreA rapid thermal processing (RTP) reactor for the preparation of graded CuIn1-xGaxSe2-ySy (CIGSeS) thin-film solar cells has been designed, assembled and is being used at the Photovoltaic Materials Laboratory of the Florida Solar Energy Center. CIGSeS films having the optimum composition, morphology, and semiconducting properties were prepared using RTP. Initially films having various Cu/(In+Ga) ratios were prepared. In the next step selenium incorporation in these films was optimized, followed by sulfur incorporation in the surface to increase the bandgap at the surface. The compositional gradient of sulfur was fine-tuned so as to increase the conversion efficiency. Materials properties of these films were characterized by optical microscopy, SEM, AFM, EDS, XRD, GIXRD, AES, and EPMA. The completed cells were extensively studied by electrical characterization. Current-voltage (I-V), external and internal quantum efficiency (EQE and IQE), capacitance-voltage (C-V), and light beam induced current (LBIC) analysis were carried out. Current Density (J)-Voltage (V) curves were obtained at different temperatures. The temperature dependence of the open circuit voltage and fill factor has been estimated. The bandgap value calculated from the intercept of the linear extrapolation was ~1.1-1.2 eV. Capacitance-voltage analysis gave a carrier density of ~4.0 x 1015 cm-3. Semiconductor properties analysis of CuIn1-xGaxSe2-ySy (CIGSeS) thin-film solar cells has been carried out. The values of various PV parameters determined using this analysis were as follows: shunt resistance (Rp) of ~510 Ohms-cm2 under illumination and ~1300 Ohms-cm2 in dark, series resistance (Rs) of ~0.8 Ohms-cm2 under illumination and ~1.7 Ohms-cm2 in dark, diode quality factor (A) of 1.87, and reverse saturation current density (Jo) of 1.5 x 10-7A cm-2. The efficiency of 12.78% obtained during this research is the highest efficiency obtained by any University or National Lab for copper chalcopyrite solar cells prepared by RTP. CIGS2 cells have a better match to the solar spectrum due to their comparatively higher band-gap as compared to CIGS cells. However, they are presently limited to efficiencies below 13% which is considerably lower than that of CIGS cells of 19.9%. One of the reasons for this lower efficiency is the conduction band offset between the CIGS2 absorber layer and the CdS heterojunction partner layer. The band offset value between CIGS2 and CdS was estimated by a combination of ultraviolet photoelectron spectroscopy (UPS) and Inverse Photoemission Spectroscopy (IPES) to be -0.45 eV, i.e. a cliff is present between these two layers, enhancing the recombination at the junction, this limits the efficiency of CIGS2 wide-gap chalcopyrite solar cells.
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Date Issued: 2008
Identifier: CFE0002467, ucf:47728
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002467

Title: GREEN BUILDING: PUBLIC OPINION, SEMANTICS, AND HEURISTIC PROCESSING.
Creator: Webb, Christina, Schraufnagel, Scot, University of Central Florida
Abstract / Description: Research on public support for green building has, to date, been incomplete. Understanding the demographics of individuals that support green building has remained secondary to merely determining real opinions on the topic. The identity of supporters and the motivation behind their support is the focus of this research. Specifically, is support for green building dependent on the way in which the issue is framed? This research aims to focus on those that are spreading the message about green...
Show moreResearch on public support for green building has, to date, been incomplete. Understanding the demographics of individuals that support green building has remained secondary to merely determining real opinions on the topic. The identity of supporters and the motivation behind their support is the focus of this research. Specifically, is support for green building dependent on the way in which the issue is framed? This research aims to focus on those that are spreading the message about green building, industry experts, and the mass public. By exposing how green building experts talk about the issue, we may begin to understand why public support for green building has yet to reach the kind of mainstream acceptance other planning and design techniques have,such as New Urbanism. I predict that green building experts perceived low levels of public awareness, with the exception of those within the Northwest region, which I believ will perceive higher levels of awareness. In addition, I assume that industry experts will be most focused on energy efficiency as a primary concept of green building. As for the public, I hypothesize that those aware of green building and individuals age 50 and older will be more likely to support green building. With the introduction of source cues, I expect that support for green building will decrease when respondents received either an environmentalism cue or a government program cue. Using survey instruments, I was able to determine that all green building experts perceive public awareness as low and do, in fact, focus their efforts on energy efficiency. With regards to the public, support was highest among those that are aware, as well as those age 50 and older. In addition, insertion of source cues decreased support for green building, with the government program source cue providing the lowest levels of support for green building.
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Date Issued: 2005
Identifier: CFE0000600, ucf:46525
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000600

Title: INTERFEROMETRY-BASED FREE SPACE COMMUNICATION AND INFORMATION PROCESSING.
Creator: Arain, Muzamil, Riza, Nabeel, University of Central Florida
Abstract / Description: This dissertation studies, analyzes, and experimentally demonstrates the innovative use of interference phenomenon in the field of opto-electronic information processing and optical communications. A number of optical systems using interferometric techniques both in the optical and the electronic domains has been demonstrated in the filed of signal transmission and processing, optical metrology, defense, and physical sensors. Specifically it has been shown that the interference of waves in...
Show moreThis dissertation studies, analyzes, and experimentally demonstrates the innovative use of interference phenomenon in the field of opto-electronic information processing and optical communications. A number of optical systems using interferometric techniques both in the optical and the electronic domains has been demonstrated in the filed of signal transmission and processing, optical metrology, defense, and physical sensors. Specifically it has been shown that the interference of waves in the form of holography can be exploited to realize a novel optical scanner called Code Multiplexed Optical Scanner (C-MOS). The C-MOS features large aperture, wide scan angles, 3-D beam control, no moving parts, and high beam scanning resolution. A C-MOS based free space optical transceiver for bi-directional communication has also been experimentally demonstrated. For high speed, large bandwidth, and high frequency operation, an optically implemented reconfigurable RF transversal filter design is presented that implements wide range of filtering algorithms. A number of techniques using heterodyne interferometry via acousto-optic device for optical path length measurements have been described. Finally, a whole new class of interferometric sensors for optical metrology and sensing applications is presented. A non-traditional interferometric output signal processing scheme has been developed. Applications include, for example, temperature sensors for harsh environments for a wide temperature range from room temperature to 1000 degree C.
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Date Issued: 2005
Identifier: CFE0000598, ucf:46478
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000598

Title: PREPARATION AND CHARACTERIZATION OF CIGSS SOLAR CELLS AND PV MODULE DATA ANALYSIS.
Creator: Shirolikar, Jyoti, Dhere, Neelkanth, University of Central Florida
Abstract / Description: In this thesis, multiple activities have been carried out in order to improve the process of CIGSS solar cell fabrication on a 4" x 4" substrate. The process of CIGSS solar cell fabrication at FSEC's PV Materials Lab involves a series of steps that were all carried out manually in the past. A LABVIEW program has been written to carry out automated sputter deposition of Mo back contact, CuGa, In metallic precursors on a soda lime glass substrate using a stepper motor control for better...
Show moreIn this thesis, multiple activities have been carried out in order to improve the process of CIGSS solar cell fabrication on a 4" x 4" substrate. The process of CIGSS solar cell fabrication at FSEC's PV Materials Lab involves a series of steps that were all carried out manually in the past. A LABVIEW program has been written to carry out automated sputter deposition of Mo back contact, CuGa, In metallic precursors on a soda lime glass substrate using a stepper motor control for better uniformity. Further, selenization/ sulfurization of these precursors was carried out using rapid thermal processing (RTP). CIGS films were sulfurized using chemical bath deposition (CBD). ZnO:Al was deposited on the CIGSS films using RF sputtering. A separate LABVIEW program was written to automate the process of ZnO:Al deposition. Ni/Al contact fingers were deposited on the ZnO:Al layer using the e-beam evaporation technique. Further, in order to test these solar cells in-house, a simple current-voltage (IV) tracer was fabricated using LABVIEW. A quantum efficiency (QE) measurement setup was built with guidance from the National Renewable Energy Laboratory (NREL). Lastly, analysis of data from photovoltaic (PV) modules installed on the FSEC test site has been carried out using a LABVIEW program in order to find out their rate of degradation as time progresses. A 'C' program has also been written as an aid for keeping a daily log of errors in data and for troubleshooting of the same.
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Date Issued: 2005
Identifier: CFE0000859, ucf:46645
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000859

Title: OFF-CHIP COMMUNICATIONS ARCHITECTURES FOR HIGH THROUGHPUT NETWORK PROCESSORS.
Creator: Engel, Jacob, Kocak, Taskin, University of Central Florida
Abstract / Description: In this work, we present off-chip communications architectures for line cards to increase the throughput of the currently used memory system. In recent years there is a significant increase in memory bandwidth demand on line cards as a result of higher line rates, an increase in deep packet inspection operations and an unstoppable expansion in lookup tables. As line-rate data and NPU processing power increase, memory access time becomes the main system bottleneck during data store/retrieve...
Show moreIn this work, we present off-chip communications architectures for line cards to increase the throughput of the currently used memory system. In recent years there is a significant increase in memory bandwidth demand on line cards as a result of higher line rates, an increase in deep packet inspection operations and an unstoppable expansion in lookup tables. As line-rate data and NPU processing power increase, memory access time becomes the main system bottleneck during data store/retrieve operations. The growing demand for memory bandwidth contrasts the notion of indirect interconnect methodologies. Moreover, solutions to the memory bandwidth bottleneck are limited by physical constraints such as area and NPU I/O pins. Therefore, indirect interconnects are replaced with direct, packet-based networks such as mesh, torus or k-ary n-cubes. We investigate multiple k-ary n-cube based interconnects and propose two variations of 2-ary 3-cube interconnect called the 3D-bus and 3D-mesh. All of the k-ary n-cube interconnects include multiple, highly efficient techniques to route, switch, and control packet flows in order to minimize congestion spots and packet loss. We explore the tradeoffs between implementation constraints and performance. We also developed an event-driven, interconnect simulation framework to evaluate the performance of packet-based off-chip k-ary n-cube interconnect architectures for line cards. The simulator uses the state-of-the-art software design techniques to provide the user with a flexible yet robust tool, that can emulate multiple interconnect architectures under non-uniform traffic patterns. Moreover, the simulator offers the user with full control over network parameters, performance enhancing features and simulation time frames that make the platform as identical as possible to the real line card physical and functional properties. By using our network simulator, we reveal the best processor-memory configuration, out of multiple configurations, that achieves optimal performance. Moreover, we explore how network enhancement techniques such as virtual channels and sub-channeling improve network latency and throughput. Our performance results show that k-ary n-cube topologies, and especially our modified version of 2-ary 3-cube interconnect - the 3D-mesh, significantly outperform existing line card interconnects and are able to sustain higher traffic loads. The flow control mechanism proved to extensively reduce hot-spots, load-balance areas of high traffic rate and achieve low transmission failure rate. Moreover, it can scale to adopt more memories and/or processors and as a result to increase the line card's processing power.
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Date Issued: 2005
Identifier: CFE0000734, ucf:46581
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000734

Title: SYNTAX-BASED CONCEPT EXTRACTION FOR QUESTION ANSWERING.
Creator: Glinos, Demetrios, Gomez, Fernando, University of Central Florida
Abstract / Description: Question answering (QA) stands squarely along the path from document retrieval to text understanding. As an area of research interest, it serves as a proving ground where strategies for document processing, knowledge representation, question analysis, and answer extraction may be evaluated in real world information extraction contexts. The task is to go beyond the representation of text documents as "bags of words" or data blobs that can be scanned for keyword combinations and word...
Show moreQuestion answering (QA) stands squarely along the path from document retrieval to text understanding. As an area of research interest, it serves as a proving ground where strategies for document processing, knowledge representation, question analysis, and answer extraction may be evaluated in real world information extraction contexts. The task is to go beyond the representation of text documents as "bags of words" or data blobs that can be scanned for keyword combinations and word collocations in the manner of internet search engines. Instead, the goal is to recognize and extract the semantic content of the text, and to organize it in a manner that supports reasoning about the concepts represented. The issue presented is how to obtain and query such a structure without either a predefined set of concepts or a predefined set of relationships among concepts. This research investigates a means for acquiring from text documents both the underlying concepts and their interrelationships. Specifically, a syntax-based formalism for representing atomic propositions that are extracted from text documents is presented, together with a method for constructing a network of concept nodes for indexing such logical forms based on the discourse entities they contain. It is shown that meaningful questions can be decomposed into Boolean combinations of question patterns using the same formalism, with free variables representing the desired answers. It is further shown that this formalism can be used for robust question answering using the concept network and WordNet synonym, hypernym, hyponym, and antonym relationships. This formalism was implemented in the Semantic Extractor (SEMEX) research tool and was tested against the factoid questions from the 2005 Text Retrieval Conference (TREC), which operated upon the AQUAINT corpus of newswire documents. After adjusting for the limitations of the tool and the document set, correct answers were found for approximately fifty percent of the questions analyzed, which compares favorably with other question answering systems.
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Date Issued: 2006
Identifier: CFE0000985, ucf:46711
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000985

Title: INVESTIGATING THE MECHANISMS THAT DRIVE IMPLICIT COORDINATION IN TEAMS.
Creator: Hoeft, Raegan, Jentsch, Florian, University of Central Florida
Abstract / Description: The purpose of this study was to empirically test the oft-noted hypothesis that shared mental models lead to implicit coordination. Specifically, this dissertation investigated the underlying mechanisms of implicit coordination and how different aspects of shared mental models affect the process. The research questions tested in this study were (a)how perceptions of sharedness affect the initiation of implicit coordination, (b) how actual levels of sharedness affect the process of implicit...
Show moreThe purpose of this study was to empirically test the oft-noted hypothesis that shared mental models lead to implicit coordination. Specifically, this dissertation investigated the underlying mechanisms of implicit coordination and how different aspects of shared mental models affect the process. The research questions tested in this study were (a)how perceptions of sharedness affect the initiation of implicit coordination, (b) how actual levels of sharedness affect the process of implicit coordination, and (c) how quality of task mental models affects successful implicit coordination. Sixty same-gender, two-person teams engaged in a complex military reconnaissance planning task in which the team members were required to work together by exchanging information to plan routes for one unmanned aerial vehicle (UAV) and one unmanned ground vehicle (UGV). The results provided partial support for the influence of different facets of shared mental models on the process of implicit coordination. Specifically, individual mental model quality, not perceptions of sharedness or actual mental model sharedness, was the biggest predictor of the initiation of implicit coordination. Additionally, perceptions of sharedness and actual mental model sharedness interacted with one another, such that teams in mismatched conditions (high perceptions of sharedness but low actual sharedness [false consensus], or low perceptions of sharedness and high actual sharedness, [pluralistic ignorance]) tended to increase their communications. The implications and recommendations for future research on implicit coordination and shared mental models are discussed. Additionally, the implications for operators of unmanned vehicles are also discussed.
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Date Issued: 2006
Identifier: CFE0001181, ucf:46857
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001181

Title: THE PSYCHOLOGICAL BASIS OF THREAT PERCEPTION AND ITS EFFECT ON THE USE OF FORCE BY US PRESIDENTS.
Creator: Kazazis, Collin J., Schafer, Mark, University of Central Florida
Abstract / Description: This thesis creates a new variable for threat perception built upon psychological concepts and then applies this new variable to the question of why leaders use military force in certain situations. The concept of threat perception has a long history in the field in terms of its effect on leaders choosing to use military force. However, while the concept of threat perception is inherently psychological, previous proxies for the variable have included only situational factors, which is highly...
Show moreThis thesis creates a new variable for threat perception built upon psychological concepts and then applies this new variable to the question of why leaders use military force in certain situations. The concept of threat perception has a long history in the field in terms of its effect on leaders choosing to use military force. However, while the concept of threat perception is inherently psychological, previous proxies for the variable have included only situational factors, which is highly problematic. By utilizing the Operational Code, this study creates a new threat-perception variable based on cognitive constructs. Using a sample of US presidents, this new variable is tested in two different ways. The first examines three psychological characteristics (need for power, in-group bias, and distrust) from Leadership Trait Analysis that are thought to influence the level of threat perception in a leader. The second examines threat perception as an explanatory variable for the use of force alongside three other important control variables (economic violence, presidential popularity, and US power). The use of force variable is derived from Meernik's Use of Force dataset with each case in the dataset representing an opportunity to use force. The psychological data are derived from the verbal material of US presidents using at-a-distance methods found in the literature. OLS regression and probit are used to model the research questions. The project finds that levels of threat perception are indeed affected by a leader's level of distrust, in-group bias, and need for power. In addition, the new psychologically-derived threat-perception variable is a very good predictor of a president's use of force: presidents with higher levels of threat perception have a much higher probability of using force when the situation presents an opportunity.
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Date Issued: 2019
Identifier: CFH2000559, ucf:45649
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000559

Title: ITERCHANGING DISCRETE EVENT SIMULATIONPROCESS INTERACTION MODELSUSING THE WEB ONTOLOGY LANGUAGE - OWL.
Creator: Lacy, Lee, Sepulveda, Jose, University of Central Florida
Abstract / Description: Discrete event simulation development requires significant investments in time and resources. Descriptions of discrete event simulation models are associated with world views, including the process interaction orientation. Historically, these models have been encoded using high-level programming languages or special purpose, typically vendor-specific, simulation languages. These approaches complicate simulation model reuse and interchange. The current document-centric World Wide Web is...
Show moreDiscrete event simulation development requires significant investments in time and resources. Descriptions of discrete event simulation models are associated with world views, including the process interaction orientation. Historically, these models have been encoded using high-level programming languages or special purpose, typically vendor-specific, simulation languages. These approaches complicate simulation model reuse and interchange. The current document-centric World Wide Web is evolving into a Semantic Web that communicates information using ontologies. The Web Ontology Language – OWL, was used to encode a Process Interaction Modeling Ontology for Discrete Event Simulations (PIMODES). The PIMODES ontology was developed using ontology engineering processes. Software was developed to demonstrate the feasibility of interchanging models from commercial simulation packages using PIMODES as an intermediate representation. The purpose of PIMODES is to provide a vendor-neutral open representation to support model interchange. Model interchange enables reuse and provides an opportunity to improve simulation quality, reduce development costs, and reduce development times.
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Date Issued: 2006
Identifier: CFE0001353, ucf:46977
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001353

Title: LEARNING TECHNIQUES FOR INFORMATION RETRIEVAL AND MINING IN HIGH-DIMENSIONAL DATABASES.
Creator: Cheng, Hao, Hua, Kien A., University of Central Florida
Abstract / Description: The main focus of my research is to design effective learning techniques for information retrieval and mining in high-dimensional databases. There are two main aspects in the retrieval and mining research: accuracy and efficiency. The accuracy problem is how to return results which can better match the ground truth, and the efficiency problem is how to evaluate users' requests and execute learning algorithms as fast as possible. However, these problems are non-trivial because of the...
Show moreThe main focus of my research is to design effective learning techniques for information retrieval and mining in high-dimensional databases. There are two main aspects in the retrieval and mining research: accuracy and efficiency. The accuracy problem is how to return results which can better match the ground truth, and the efficiency problem is how to evaluate users' requests and execute learning algorithms as fast as possible. However, these problems are non-trivial because of the complexity of the high-level semantic concepts, the heterogeneous natures of the feature space, the high dimensionality of data representations and the size of the databases. My dissertation is dedicated to addressing these issues. Specifically, my work has five main contributions as follows. The first contribution is a novel manifold learning algorithm, Local and Global Structures Preserving Projection (LGSPP), which defines salient low-dimensional representations for the high-dimensional data. A small number of projection directions are sought in order to properly preserve the local and global structures for the original data. Specifically, two groups of points are extracted for each individual point in the dataset: the first group contains the nearest neighbors of the point, and the other set are a few sampled points far away from the point. These two point sets respectively characterize the local and global structures with regard to the data point. The objective of the embedding is to minimize the distances of the points in each local neighborhood and also to disperse the points far away from their respective remote points in the original space. In this way, the relationships between the data in the original space are well preserved with little distortions. The second contribution is a new constrained clustering algorithm. Conventionally, clustering is an unsupervised learning problem, which systematically partitions a dataset into a small set of clusters such that data in each cluster appear similar to each other compared with those in other clusters. In the proposal, the partial human knowledge is exploited to find better clustering results. Two kinds of constraints are integrated into the clustering algorithm. One is the must-link constraint, indicating that the involved two points belong to the same cluster. On the other hand, the cannot-link constraint denotes that two points are not within the same cluster. Given the input constraints, data points are arranged into small groups and a graph is constructed to preserve the semantic relations between these groups. The assignment procedure makes a best effort to assign each group to a feasible cluster without violating the constraints. The theoretical analysis reveals that the probability of data points being assigned to the true clusters is much higher by the new proposal, compared to conventional methods. In general, the new scheme can produce clusters which can better match the ground truth and respect the semantic relations between points inferred from the constraints. The third contribution is a unified framework for partition-based dimension reduction techniques, which allows efficient similarity retrieval in the high-dimensional data space. Recent similarity search techniques, such as Piecewise Aggregate Approximation (PAA), Segmented Means (SMEAN) and Mean-Standard deviation (MS), prove to be very effective in reducing data dimensionality by partitioning dimensions into subsets and extracting aggregate values from each dimension subset. These partition-based techniques have many advantages including very efficient multi-phased pruning while being simple to implement. They, however, are not adaptive to different characteristics of data in diverse applications. In this study, a unified framework for these partition-based techniques is proposed and the issue of dimension partitions is examined in this framework. An investigation of the relationships of query selectivity and the dimension partition schemes discovers indicators which can predict the performance of a partitioning setting. Accordingly, a greedy algorithm is designed to effectively determine a good partitioning of data dimensions so that the performance of the reduction technique is robust with regard to different datasets. The fourth contribution is an effective similarity search technique in the database of point sets. In the conventional model, an object corresponds to a single vector. In the proposed study, an object is represented by a set of points. In general, this new representation can be used in many real-world applications and carries much more local information, but the retrieval and learning problems become very challenging. The Hausdorff distance is the common distance function to measure the similarity between two point sets, however, this metric is sensitive to outliers in the data. To address this issue, a novel similarity function is defined to better capture the proximity of two objects, in which a one-to-one mapping is established between vectors of the two objects. The optimal mapping minimizes the sum of distances between each paired points. The overall distance of the optimal matching is robust and has high retrieval accuracy. The computation of the new distance function is formulated into the classical assignment problem. The lower-bounding techniques and early-stop mechanism are also proposed to significantly accelerate the expensive similarity search process. The classification problem over the point-set data is called Multiple Instance Learning (MIL) in the machine learning community in which a vector is an instance and an object is a bag of instances. The fifth contribution is to convert the MIL problem into a standard supervised learning in the conventional vector space. Specially, feature vectors of bags are grouped into clusters. Each object is then denoted as a bag of cluster labels, and common patterns of each category are discovered, each of which is further reconstructed into a bag of features. Accordingly, a bag is effectively mapped into a feature space defined by the distances from this bag to all the derived patterns. The standard supervised learning algorithms can be applied to classify objects into pre-defined categories. The results demonstrate that the proposal has better classification accuracy compared to other state-of-the-art techniques. In the future, I will continue to explore my research in large-scale data analysis algorithms, applications and system developments. Especially, I am interested in applications to analyze the massive volume of online data.
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Date Issued: 2009
Identifier: CFE0002882, ucf:48022
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002882

Title: LOW NOISE, HIGH REPETITION RATE SEMICONDUCTOR-BASED MODE-LOCKED LASERS FOR SIGNAL PROCESSING AND COHERENT COMMUNICATIONS.
Creator: Quinlan, Franklyn, Delfyett, Peter, University of Central Florida
Abstract / Description: This dissertation details work on high repetition rate semiconductor mode-locked lasers. The qualities of stable pulse trains and stable optical frequency content are the focus of the work performed. First, applications of such lasers are reviewed with particular attention to applications only realizable with laser performance such as presented in this dissertation. Sources of timing jitter are also reviewed, as are techniques by which the timing jitter of a 10 GHz optical pulse train may be...
Show moreThis dissertation details work on high repetition rate semiconductor mode-locked lasers. The qualities of stable pulse trains and stable optical frequency content are the focus of the work performed. First, applications of such lasers are reviewed with particular attention to applications only realizable with laser performance such as presented in this dissertation. Sources of timing jitter are also reviewed, as are techniques by which the timing jitter of a 10 GHz optical pulse train may be measured. Experimental results begin with an exploration of the consequences on the timing and amplitude jitter of the phase noise of an RF source used for mode-locking. These results lead to an ultralow timing jitter source, with 30 fs of timing jitter (1 Hz to 5 GHz, extrapolated). The focus of the work then shifts to generating a stabilized optical frequency comb. The first technique to generating the frequency comb is through optical injection. It is shown that not only can injection locking stabilize a mode-locked laser to the injection seed, but linewidth narrowing, timing jitter reduction and suppression of superfluous optical supermodes of a harmonically mode-locked laser also result. A scheme by which optical injection locking can be maintained long term is also proposed. Results on using an intracavity etalon for supermode suppression and optical frequency stabilization then follow. An etalon-based actively mode-locked laser is shown to have a timing jitter of only 20 fs (1Hz-5 GHz, extrapolated), optical linewidths below 10 kHz and optical frequency instabilities less than 400 kHz. By adding dispersion compensating fiber, the optical spectrum was broadened to 2 THz and 800 fs duration pulses were obtained. By using the etalon-based actively mode-locked laser as a basis, a completely self-contained frequency stabilized coupled optoelectronic oscillator was built and characterized. By simultaneously stabilizing the optical frequencies and the pulse repetition rate to the etalon, a 10 GHz comb source centered at 1550 nm was realized. This system maintains the high quality performance of the actively mode-locked laser while significantly reducing the size weight and power consumption of the system. This system also has the potential for outperforming the actively mode-locked laser by increasing the finesse and stability of the intracavity etalon. The final chapter of this dissertation outlines the future work on the etalon-based coupled optoelectronic oscillator, including the incorporation of a higher finesse, more stable etalon and active phase noise suppression of the RF signal. Two appendices give details on phase noise measurements that incorporate carrier suppression and the noise model for the coupled optoelectronic oscillator.
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Date Issued: 2008
Identifier: CFE0002252, ucf:47878
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002252

Title: Gee, Officer Krupke: An Actor's Casebook.
Creator: Eichenlaub, Eric, Brotherton, Mark, Ingram, Kate, Niess, Christopher, University of Central Florida
Abstract / Description: In 2016, I was cast as Officer Krupke in a production of West Side Story at Orlando Shakespeare Theater in Partnership with UCF. Even though Krupke can be thought of as a minor character in the play, bringing him to life required a great deal of research and imagination. In order to ground myself in the reality of the role, I researched the effects of implicit bias in modern policing, applied that research to Uta Hagen's Nine Questions, and brought that knowledge into the rehearsal hall and...
Show moreIn 2016, I was cast as Officer Krupke in a production of West Side Story at Orlando Shakespeare Theater in Partnership with UCF. Even though Krupke can be thought of as a minor character in the play, bringing him to life required a great deal of research and imagination. In order to ground myself in the reality of the role, I researched the effects of implicit bias in modern policing, applied that research to Uta Hagen's Nine Questions, and brought that knowledge into the rehearsal hall and onto the stage. I examined how my character's interactions with Lieutenant Schrank influenced his actions and attitudes toward both street gangs in the play and reflected on how my research and these performances changed my point of view and helped me recognize my own biases. This thesis reflects that process and will serve as a tool available to any actor seeking to create his or her own interpretation of Officer Krupke.
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Date Issued: 2018
Identifier: CFE0007327, ucf:52140
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007327

Title: A Decision Support Model for Autonomous Trucks Strategies.
Creator: Mohamed, Ahmad Saeid Ammar, Yun, Hae-Bum, Chopra, Manoj, Sallam, Amr, University of Central Florida
Abstract / Description: We examined the potential to improve the movement of freight using Truck PlatooningLane strategies on limited access highways in the State of Florida. In the First part of thisresearch, we investigated the potential benefits from dedicating one lane from existinglanes for autonomous trucks only. In this regard, a general framework tool was developedto evaluate and compare different measurements (e.g., travel tim and emissions) to betterassist decision makers to determine the most effective...
Show moreWe examined the potential to improve the movement of freight using Truck PlatooningLane strategies on limited access highways in the State of Florida. In the First part of thisresearch, we investigated the potential benefits from dedicating one lane from existinglanes for autonomous trucks only. In this regard, a general framework tool was developedto evaluate and compare different measurements (e.g., travel tim and emissions) to betterassist decision makers to determine the most effective freight transportation strategy.Additionally, the travel time, level of service and emissions on Florida Strategic IntermodalSystem (SIS) were systematically analyzed using a VISSIM and MOVES simulation todetermine if it can be improved. For the scenarios simulated in this investigation, the inputincluded different patterns with a variety of peak hour volumes, truck percentages, speeds,and number of lanes. Additionally, the various total values of the resultant travel time,emissions and level of service for each SIS corridor were determined and calculated usinga General Linear Model and then tabulated to reveal input patterns. The results showed thata truck platooning lane can significantly reduce the travel time and emissions of trucks. Inthe second part, we proposed using a The Analytic Hierarchy Process (AHP) method toevaluate the potential benefits of building a new lane for autonomous trucks. The AHPmethod was developed to include all possible measurements that can assist decision makersto select the best autonomous truck policy. The results of the AHP model showed that thesafety criterion was significantly the most influential perspective per experts' opinions. Theresults showed that experts were more concerned about safety and environmentalconsiderations than the initial cost associated with building a new lane.
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Date Issued: 2018
Identifier: CFE0007056, ucf:51983
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007056

Title: Computer Simulation of 911 Emergency Telephone System for Orange County, Florida.
Creator: Veillette, Ronald J., null, null, Engineering
Abstract / Description: Florida Technological University College of Engineering Thesis; The State of Florida has mandated that a statewide 911 system be implemented, and the Department of General Services, Division of Communications, has performed a study of possible 911 system configurations for Orange County based on the findings of a study performed by the Stanford Research Institute for the whole of the State of Florida. The Orange County study determined operator manning levels of the primary law enforcement...
Show moreFlorida Technological University College of Engineering Thesis; The State of Florida has mandated that a statewide 911 system be implemented, and the Department of General Services, Division of Communications, has performed a study of possible 911 system configurations for Orange County based on the findings of a study performed by the Stanford Research Institute for the whole of the State of Florida. The Orange County study determined operator manning levels of the primary law enforcement agencies involved in the system and response times to citizen calls for each of the configurations proposed. This research generated computer simulation models of the two most likely to be implemented configurations for handling citizen calls. The models were run sing the input parameters defined in the Orange County study, and the results compared favorably. Additional runs were made with varying resource assignments to evaluate call service with respect to the level of performance and response time. The models were designed in modular form, such that they can easily be structured to conform to other operational configurations. This will allow evaluation of prosed systems prior to actual start up and analysis of resource requirements based on population predictions.
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Date Issued: 1977
Identifier: CFR0004777, ucf:52962
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFR0004777

Title: STOCHASTIC OPTIMIZATION AND APPLICATIONS WITH ENDOGENOUS UNCERTAINTIES VIA DISCRETE CHOICE MODELSl.
Creator: Chen, Mengnan, Zheng, Qipeng, Boginski, Vladimir, Vela, Adan, Yayla Kullu, Muge, University of Central Florida
Abstract / Description: Stochastic optimization is an optimization method that solves stochastic problems for minimizing or maximizing an objective function when there is randomness in the optimization process. In this dissertation, various stochastic optimization problems from the areas of Manufacturing, Health care, and Information Cascade are investigated in networks systems. These stochastic optimization problems aim to make plan for using existing resources to improve production efficiency, customer...
Show moreStochastic optimization is an optimization method that solves stochastic problems for minimizing or maximizing an objective function when there is randomness in the optimization process. In this dissertation, various stochastic optimization problems from the areas of Manufacturing, Health care, and Information Cascade are investigated in networks systems. These stochastic optimization problems aim to make plan for using existing resources to improve production efficiency, customer satisfaction, and information influence within limitation. Since the strategies are made for future planning, there are environmental uncertainties in the network systems. Sometimes, the environment may be changed due to the action of the decision maker. To handle this decision-dependent situation, the discrete choice model is applied to estimate the dynamic environment in the stochastic programming model. In the manufacturing project, production planning of lot allocation is performed to maximize the expected output within a limited time horizon. In the health care project, physician is allocated to different local clinics to maximize the patient utilization. In the information cascade project, seed selection of the source user helps the information holder to diffuse the message to target users using the independent cascade model to reach influence maximization. \parThe computation complexities of the three projects mentioned above grow exponentially by the network size. To solve the stochastic optimization problems of large-scale networks within a reasonable time, several problem-specific algorithms are designed for each project. In the manufacturing project, the sampling average approximation method is applied to reduce the scenario size. In the health care project, both the guided local search with gradient ascent and large neighborhood search with Tabu search are developed to approach the optimal solution. In the information cascade project, the myopic policy is used to separate stochastic programming by discrete time, and the Markov decision process is implemented in policy evaluation and updating.
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Date Issued: 2019
Identifier: CFE0007792, ucf:52347
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007792

Title: Coming to a full stop: An investigation of menstrual period stigmas in college students.
Creator: O'Toole, Mary, Sellnow, Deanna, Sandoval, Jennifer, Dodd, Melissa, University of Central Florida
Abstract / Description: The focus of this study was to understand perceptions college students have regarding menstruation and if viewing a normalized media message may influence these perceptions. A treatment group of participants was randomly assigned to view an episode of the hit family sitcom Blackish that focused on menstruation and then answer survey questions. A control group of participants only answered the survey questions. A mixed methods analysis revealed three primary conclusions. First, these results...
Show moreThe focus of this study was to understand perceptions college students have regarding menstruation and if viewing a normalized media message may influence these perceptions. A treatment group of participants was randomly assigned to view an episode of the hit family sitcom Blackish that focused on menstruation and then answer survey questions. A control group of participants only answered the survey questions. A mixed methods analysis revealed three primary conclusions. First, these results contradict existing research in that the college students surveyed generally do not hold negative perceptions that may stigmatize menstruation. Second, the treatment that viewed the normalized media message intervention did not report significantly more positive perceptions about menstruation as a natural bodily function than their counterparts in the control group. Third, many participants acknowledged menstruation is a stigmatized topic and media messages not only currently contribute to these attitudes but could be used as a catalyst for guiding society toward normalizing it. These results extend existing research on how people perceive menstruation and on mass media effect research as a means to address stigmatized topics.
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Date Issued: 2018
Identifier: CFE0007066, ucf:51970
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007066

Title: Predictors of hospital quality and efficiency.
Creator: Fotovvat, Hoda, Wan, Thomas, Liu, Albert Xinliang, Ramirez, Bernardo, Yu, Chia-Yuan, University of Central Florida
Abstract / Description: American hospitals have made serious efforts to implement and expand their health information technology capabilities and to integrate different specialized care or high-tech services in order to maximize the efficiency and quality of care. In providing a variety of HIT-related services, these hospitals expanded their national reputation in line with integrated care goals. As a result, hospitals are encouraged to establish effective communication channels to facilitate patient-physician...
Show moreAmerican hospitals have made serious efforts to implement and expand their health information technology capabilities and to integrate different specialized care or high-tech services in order to maximize the efficiency and quality of care. In providing a variety of HIT-related services, these hospitals expanded their national reputation in line with integrated care goals. As a result, hospitals are encouraged to establish effective communication channels to facilitate patient-physician sharing of the patient care experience, to enhance effective pain management, and to transform patient-centered care modalities to solidify the adequacy of patient care processes. By analyzing national data sets publicly available, this investigation explored the relationship of acute-care hospitals' performance to the contextual, organizational and patient characteristics, using a cross-sectional study design. This study developed and evaluated the quality and efficiency of hospitals with respects to the structural complexity, process adequacy, efficiency, and quality of care. The structure-process-outcome theory in quality of care developed by Donabedian (1980), is adopted for this investigation. Statistical methods such as confirmatory factor analysis (CFA) and covariance structure model are employed. The population surveyed by the American Hospital Association (AHA) are acute care hospitals throughout the United States, including more than 3000 acute care hospitals of all types of ownership. The data provided by HIMSS Analytics and AHA are available for 2015 and the data provided CMS quality indicators are available for 2016. The key finding of this research is that process adequacy mediates the relationship between hospital structure and performance variables. The efficiency variable played an important role in shaping quality. The location and hospital teaching status have a moderate impact in determining hospital performance by affecting the structure and process of hospitals.
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Date Issued: 2019
Identifier: CFE0007888, ucf:52796
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007888

Title: Crossing Literate Worlds: Exploring How Students With Rich Identities as Writers Negotiate Multiple Writing Contexts.
Creator: Shrum, Autumn, Wardle, Elizabeth, Wallace, David, Scott, John, University of Central Florida
Abstract / Description: This study investigated the literate identities of college students who engage in various school and non-school writing practices simultaneously. In case studies of three student writers, the researcher seeks to explore how the discourse community roles, self-perceptions, negotiation of multiple writing processes and development of authority impacted the students' identities as writers. Triangulated research methods included weekly interviews with the student participants, observation of the...
Show moreThis study investigated the literate identities of college students who engage in various school and non-school writing practices simultaneously. In case studies of three student writers, the researcher seeks to explore how the discourse community roles, self-perceptions, negotiation of multiple writing processes and development of authority impacted the students' identities as writers. Triangulated research methods included weekly interviews with the student participants, observation of the students in their writing classrooms and analysis of the students' school and non-school texts over one semester. Students experienced several conflicts and synergies between contexts. Main findings indicated that writing across many academic and extra-academic settings during a short time period may alter self-perceptions, encourage or discourage the repurposing of writing processes, and limit the development of authority. Implications for teachers and researchers of college-level writing center on awareness of the literate lives of students beyond classroom walls. Future research questions are raised regarding the transfer of writing-related knowledge as it may occur in students with strong literate identities.
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Date Issued: 2011
Identifier: CFE0004167, ucf:49061
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004167

Title: STUDY OF DESIGN FOR RELIABILITY OF RF AND ANALOG CIRCUITS.
Creator: Tang, Hongxia, Yuan, Jiann-Shiun, Wu, Xinzhang, Sundaram, Kalpathy, Chow, Lee, University of Central Florida
Abstract / Description: Due to continued device dimensions scaling, CMOS transistors in the nanometer regime have resulted in major reliability and variability challenges. Reliability issues such as channel hot electron injection, gate dielectric breakdown, and negative bias temperature instability (NBTI) need to be accounted for in the design of robust RF circuits. In addition, process variations in the nanoscale CMOS transistors are another major concern in today's circuits design.An adaptive gate-source biasing...
Show moreDue to continued device dimensions scaling, CMOS transistors in the nanometer regime have resulted in major reliability and variability challenges. Reliability issues such as channel hot electron injection, gate dielectric breakdown, and negative bias temperature instability (NBTI) need to be accounted for in the design of robust RF circuits. In addition, process variations in the nanoscale CMOS transistors are another major concern in today's circuits design.An adaptive gate-source biasing scheme to improve the RF circuit reliability is presented in this work. The adaptive method automatically adjusts the gate-source voltage to compensate the reduction in drain current subjected to various device reliability mechanisms. A class-AB RF power amplifier shows that the use of a source resistance makes the power-added efficiency robust against threshold voltage and mobility variations, while the use of a source inductance is more reliable for the input third-order intercept point.A RF power amplifier with adaptive gate biasing is proposed to improve the circuit device reliability degradation and process variation. The performances of the power amplifier with adaptive gate biasing are compared with those of the power amplifier without adaptive gate biasing technique. The adaptive gate biasing makes the power amplifier more resilient to process variations as well as the device aging such as mobility and threshold voltage degradation. Injection locked voltage-controlled oscillators (VCOs) have been examined. The VCOs are implemented using TSMC 0.18 (&)#181;m mixed-signal CMOS technology. The injection locked oscillators have improved phase noise performance than free running oscillators.A differential Clapp-VCO has been designed and fabricated for the evaluation of hot electron reliability. The differential Clapp-VCO is formed using cross-coupled nMOS transistors, on-chip transformers/inductors, and voltage-controlled capacitors. The experimental data demonstrate that the hot carrier damage increases the oscillation frequency and degrades the phase noise of Clapp-VCO.A p-channel transistor only VCO has been designed for low phase noise. The simulation results show that the phase noise degrades after NBTI stress at elevated temperature. This is due to increased interface states after NBTI stress. The process variability has also been evaluated.
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Date Issued: 2012
Identifier: CFE0004223, ucf:49000
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004223

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