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(1 - 9 of 9)
- Title
- Low Strain Rate Studies of Alumina Epoxy Composites using Piezospectroscopy.
- Creator
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Jones, Ashley, Raghavan, Seetha, Gordon, Ali, Vaidyanathan, Rajan, University of Central Florida
- Abstract / Description
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Particulate composites are widely used in many aerospace and military applications as energetic materials, armor materials or coatings and their behavior under dynamic loads have gained increasing significance. The addition of modifiers such as alumina nanoparticles generally facilitates the improvement of the mechanical strength to density ratio due to high specific area and particle rigidity. This allows for sufficient particle-matrix bonding and therefore improved stiffness and load...
Show moreParticulate composites are widely used in many aerospace and military applications as energetic materials, armor materials or coatings and their behavior under dynamic loads have gained increasing significance. The addition of modifiers such as alumina nanoparticles generally facilitates the improvement of the mechanical strength to density ratio due to high specific area and particle rigidity. This allows for sufficient particle-matrix bonding and therefore improved stiffness and load transfer in the composite. Photo-luminescent ?-alumina nanoparticles when embedded in an epoxy matrix allow for the added benefit of in situ measurements at low strain rates to provide stress-sensitive information using the particle piezospectroscopic (PS) property. To investigate the low strain rate behavior, cylindrical specimens of alumina-epoxy composites with varying volume fractions of alumina were fabricated using a casting process to ensure minimal surface finishing and reduced manufacturing time. The results illustrate the capability of alumina nanoparticles to act as diagnostic sensors to measure the stress-induced shifts of the spectral R-line peaks resulting from low compressive strain rates. The range of PS coefficients measured, -3.15 to -5.37 cm^-1/GPa for R1 and -2.62 to -5.39 cm^-1/GPa for R2, correlate well with static test results of similar volume fractions. Results reveal a general trend of increasing sensitivity of the PS coefficients with increasing strain rate when compared to similar materials under static conditions. In contrast to static results, at a given strain rate, the PS coefficients show varying degrees of sensitivity for each volume fraction. This information can be used to determine the time-dependent micro-scale stresses the nanoparticles sustain during composite loading. Additionally, this work facilitates failure prediction by monitoring upshifts in the PS information. Calibration of the in situ diagnostic stress sensing capabilities of varying volume fractions of alumina nanocomposites under quasi-static strain rates in this work sets the precedent for future studies at high strain rates.
Show less - Date Issued
- 2013
- Identifier
- CFE0005099, ucf:50728
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005099
- Title
- SYNTHESIS OF SELF-RESETTING STAGE LOGIC PIPELINES.
- Creator
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Oreifej, Rashad, Ejnioui, Abdel, University of Central Florida
- Abstract / Description
-
As designers began to pack multi-million transistors onto a single chip, their reliance on a global clocking signal to orchestrate the operations of the chip has started to face almost insurmountable difficulties. As a result, designers started to explore clockless circuits to avoid the global clocking problem. Recently, self-resetting circuits implemented in dynamic logic families have been proposed as viable clockless alternatives. While these circuits can produce excellent performances,...
Show moreAs designers began to pack multi-million transistors onto a single chip, their reliance on a global clocking signal to orchestrate the operations of the chip has started to face almost insurmountable difficulties. As a result, designers started to explore clockless circuits to avoid the global clocking problem. Recently, self-resetting circuits implemented in dynamic logic families have been proposed as viable clockless alternatives. While these circuits can produce excellent performances, they display serious limitations in terms of area cost and power consumption. A middle-of-the-road alternative, which can provide a good performance and avoid the limitations seen in dynamic self-resetting circuits, would be to implement self-resetting behavior in static circuits. This alternative has been introduced recently as Self-Resetting Stage Logic and used to propose three types of clockless pipelines. Experimental studies show that these pipelines have the potential to produce high throughputs with a minimum area overhead if a suitable synthesis methodology is available. This thesis proposes a novel synthesis methodology to design and verify clockless pipelines implemented in SRSL by taking advantage of the maturity of current CAD tools. This methodology formulates the synthesis problem as a combinatorial analytical problem for which a run-time efficient exact solution is difficult to derive. Consequently, a two-phase algorithm is proposed to synthesize these pipelines from gate netlists subject to user-specified constraints. The first phase is a heuristic based on the as-soon-as-possible scheduling strategy in which each gate of the netlist is assigned to a single pipeline stage without violating the period constraint of each pipeline stage. On the other hand, the second phase consists of a heuristic, based on the Kernighan-Lin partitioning strategy, to minimize the number of nets crossing each pair of adjacent pipeline stages. The objective of this optimization is to reduce the number of latches separating pipeline stages since these latches tend to occupy large areas. Experiments conducted on a prototype of the synthesis algorithm reveal that these self-resetting stage logic pipelines can easily reach throughputs higher than 1 GHz. Furthermore, these experiments reveal that the area overhead needed to implement the self-resetting circuitry of these pipelines can be easily amortized over the area of the logic embedded in the pipeline stages. In the overall, the synthesis methods developed for SRSL produce low area overhead pipelines for wide and deep gate netlists while it tends to produce high throughput pipelines for wide and shallow gate netlists. This shows that these pipelines are mostly suitable for coarse-grain datapaths.
Show less - Date Issued
- 2006
- Identifier
- CFE0001196, ucf:46866
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001196
- Title
- LOW REYNOLDS NUMBER WATER FLOW CHARACTERISTICS THROUGH RECTANGULAR MICRO DIFFUSERS/NOZZLES WITH A PRIMARY FOCUS ON MAJOR/MINOR PRESSURE LOSS, STATIC PRESSURE RECOVERY, AND FLOW SEPARATION.
- Creator
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Hallenbeck, Kyle, Chew, Larry, University of Central Florida
- Abstract / Description
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The field of microfluidics has recently been gathering a lot of attention due to the enormous demand for devices that work in the micro scale. The problem facing many researchers and designers is the uncertainty in using macro scaled theory, as it seems in some situations they are incorrect. The general idea of this work was to decide whether or not the flow through micro diffusers and nozzles follow the same trends seen in macro scale theory. Four testing wafers were fabricated using PDMS...
Show moreThe field of microfluidics has recently been gathering a lot of attention due to the enormous demand for devices that work in the micro scale. The problem facing many researchers and designers is the uncertainty in using macro scaled theory, as it seems in some situations they are incorrect. The general idea of this work was to decide whether or not the flow through micro diffusers and nozzles follow the same trends seen in macro scale theory. Four testing wafers were fabricated using PDMS soft lithography including 38 diffuser/nozzle channels a piece. Each nozzle and diffuser consisted of a throat dimension of 100μm x 50μm, leg lengths of 142μm, and half angles varying from 0o – 90o in increments of 5o. The flow speeds tested included throat Reynolds numbers of 8.9 – 89 in increments of 8.9 using distilled water as the fluid. The static pressure difference was measured from the entrance to the exit of both the diffusers and the nozzles and the collected data was plotted against a fully attached macro theory as well as Idelchik's approximations. Data for diffusers and nozzles up to HA = 50o hints at the idea that the flow is neither separating nor creating a vena contracta. In this region, static pressure recovery within diffuser flow is observed as less than macro theory would predict and the losses that occur within a nozzle are also less than macro theory would predict. Approaching a 50o HA and beyond shows evidence of unstable separation and vena contracta formation. In general, it appears that there is a micro scaled phenomenon happening in which flow gains available energy when the flow area is increased and looses available energy when the flow area decreases. These new micro scaled phenomenon observations seem to lead to a larger and smaller magnitude of pressure loss respectively.
Show less - Date Issued
- 2008
- Identifier
- CFE0002391, ucf:47772
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002391
- Title
- Point Cloud Technology for Analysis of Existing Structures.
- Creator
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Cano, Jacob, Catbas, Necati, Apostolakis, Georgios, Zaurin, Ricardo, Walters, Lori, University of Central Florida
- Abstract / Description
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For this thesis, a study was completed on two different structures on the UCF Orlando campus through the use of both structural plans and point cloud technology. The results sought to understand the viability of point cloud technology as an accurate tool for the static and dynamic modal analysis of existing structures. For static analysis, a portion of the framing of Spectrum Stadium was rendered, modeled, analyzed and compared to a previous case study. The results emphasized how different...
Show moreFor this thesis, a study was completed on two different structures on the UCF Orlando campus through the use of both structural plans and point cloud technology. The results sought to understand the viability of point cloud technology as an accurate tool for the static and dynamic modal analysis of existing structures. For static analysis, a portion of the framing of Spectrum Stadium was rendered, modeled, analyzed and compared to a previous case study. The results emphasized how different users can render dissimilar member sizes and lengths due to human judgment on point cloud visuals. The study also found that structural plans cannot always be relied upon as the most accurate source for analysis as the new point cloud produced more accurate results than the structural plans when compared to the control model. For the pedestrian bridge, the structure was scanned, rendered and modeled for both static and dynamic modal analysis. The point cloud produced from scanning the bridge was modified twice in order to have three distinct point clouds with varying densities: fine, medium and coarse. These three cases were compared to structural plans in a static analysis. The fine point cloud produced the most accurate displacement results with an accuracy above 96%. The data sources were also compared to experimental data under dynamic modal analysis to discover how lessening the density of point clouds affect the accuracy of results. The analysis showed that point cloud technology can give you an accuracy of 88% and above for frequency while also producing MAC values exceeding 0.9 consistently. Also, changes in density were found to change the accuracy of results but the numeric values stayed within close proximity by not differing more than 10%. This thesis shines a light on the accuracy point cloud technology can ascertain and the potential it has within engineering.
Show less - Date Issued
- 2019
- Identifier
- CFE0007438, ucf:52724
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007438
- Title
- A Compiler-based Framework for Automatic Extraction of Program Skeletons for Exascale Hardware/Software Co-design.
- Creator
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Rudraiah Dakshinamurthy, Amruth, Dechev, Damian, Heinrich, Mark, Deo, Narsingh, University of Central Florida
- Abstract / Description
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The design of high-performance computing architectures requires performance analysis of large-scale parallel applications to derive various parameters concerning hardware design and software development. The process of performance analysis and benchmarking an application can be done in several ways with varying degrees of fidelity. One of the most cost-effective ways is to do a coarse-grained study of large-scale parallel applications through the use of program skeletons. The concept of a `...
Show moreThe design of high-performance computing architectures requires performance analysis of large-scale parallel applications to derive various parameters concerning hardware design and software development. The process of performance analysis and benchmarking an application can be done in several ways with varying degrees of fidelity. One of the most cost-effective ways is to do a coarse-grained study of large-scale parallel applications through the use of program skeletons. The concept of a ``program skeleton'' that we discuss in this paper is an abstracted program that is derived from a larger program where source code that is determined to be irrelevant is removed for the purposes of the skeleton. In this work, we develop a semi-automatic approach for extracting program skeletons based on compiler program analysis. We demonstrate correctness of our skeleton extraction process by comparing details from communication traces, as well as show the performance speedup of using skeletons by running simulations in the SST/macro simulator. Extracting such a program skeleton from a large-scale parallel program requires a substantial amount of manual effort and often introduces human errors. We outline a semi-automatic approach for extracting program skeletons from large-scale parallel applications that reduces cost and eliminates errors inherent in manual approaches. Our skeleton generation approach is based on the use of the extensible and open-source ROSE compiler infrastructure that allows us to perform flow and dependency analysis on larger programs in order to determine what code can be removed from the program to generate a skeleton.
Show less - Date Issued
- 2013
- Identifier
- CFE0004743, ucf:49795
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004743
- Title
- Reasoning Tradeoffs in Implicit Invocation and Aspect Oriented Languages.
- Creator
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Sanchez Salazar, Jose, Leavens, Gary, Turgut, Damla, Jha, Sumit, Martin, Heath, University of Central Florida
- Abstract / Description
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To reason about a program means to state or conclude, by logical means, some properties the program exhibits; like its correctness according to certain expected behavior. The continuous need for more ambitious, more complex, and more dependable software systems demands for better mechanisms to modularize them and reason about their correctness. The reasoning process is affected by the design decisions made by the developer of the program and by the features supported by the programming...
Show moreTo reason about a program means to state or conclude, by logical means, some properties the program exhibits; like its correctness according to certain expected behavior. The continuous need for more ambitious, more complex, and more dependable software systems demands for better mechanisms to modularize them and reason about their correctness. The reasoning process is affected by the design decisions made by the developer of the program and by the features supported by the programming language used. Beyond Object Orientation, Implicit Invocation and Aspect Oriented languages pose very hard reasoning challenges. Important tradeoffs must be considered while reasoning about a program: modular vs. non-modular reasoning, case-by-case analysis vs. abstraction, explicitness vs. implicitness; are some of them. By deciding a series of tradeoffs one can configure a reasoning scenario. For example if one decides for modular reasoning and explicit invocation a well-known object oriented reasoning scenario can be used.This dissertation identifies various important tradeoffs faced when reasoning about implicit invocation and aspect oriented programs, characterize scenarios derived from making choices regarding these tradeoffs, and provides sound proof rules for verification of programs covered by all these scenarios. Guidance for program developers and language designers is also given, so that reasoning about these types of programs becomes more tractable.
Show less - Date Issued
- 2015
- Identifier
- CFE0005706, ucf:50133
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005706
- Title
- FINITE ELEMENT METHOD MODELING OF ADVANCED ELECTRONIC DEVICES.
- Creator
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Chen, Yupeng, Wu, Thomas, University of Central Florida
- Abstract / Description
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In this dissertation, we use finite element method together with other numerical techniques to study advanced electron devices. We study the radiation properties in electron waveguide structure with multi-step discontinuities and soft wall lateral confinement. Radiation mechanism and conditions are examined by numerical simulation of dispersion relations and transport properties. The study of geometry variations shows its significant impact on the radiation intensity and direction. In...
Show moreIn this dissertation, we use finite element method together with other numerical techniques to study advanced electron devices. We study the radiation properties in electron waveguide structure with multi-step discontinuities and soft wall lateral confinement. Radiation mechanism and conditions are examined by numerical simulation of dispersion relations and transport properties. The study of geometry variations shows its significant impact on the radiation intensity and direction. In particular, the periodic corrugation structure exhibits strong directional radiation. This interesting feature may be useful to design a nano-scale transmitter, a communication device for future nano-scale system. Non-quasi-static effects in AC characteristics of carbon nanotube field-effect transistors are examined by solving a full time-dependent, open-boundary Schrödinger equation. The non-quasi-static characteristics, such as the finite channel charging time, and the dependence of small signal transconductance and gate capacitance on the frequency, are explored. The validity of the widely used quasi-static approximation is examined. The results show that the quasi-static approximation overestimates the transconductance and gate capacitance at high frequencies, but gives a more accurate value for the intrinsic cut-off frequency over a wide range of bias conditions. The influence of metal interconnect resistance on the performance of vertical and lateral power MOSFETs is studied. Vertical MOSFETs in a D2PAK and DirectFET package, and lateral MOSFETs in power IC and flip chip are investigated as the case studies. The impact of various layout patterns and material properties on RDS(on) will provide useful guidelines for practical vertical and lateral power MOSFETs design.
Show less - Date Issued
- 2006
- Identifier
- CFE0001389, ucf:46987
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001389
- Title
- THE EFFECTS ADVERTISING PLAYS ON COLLEGE STUDENTS' MORAL INTENTIONS BEYOND PURCHASE BEHAVIOR.
- Creator
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Crockett, William, Massiah, Carolyn, University of Central Florida
- Abstract / Description
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Advertisements affect our daily lives and as technology and the practice of marketing has developed over the course of history, we have become exposed to greater amounts of product and service campaigns. The purpose of advertisements is to educate the consumer with the goal of ultimately selling the product, and many companies and organizations would not be able to survive without the use of advertisements. Ultimately, it is a necessity for a business to prosper in a competitive market, but...
Show moreAdvertisements affect our daily lives and as technology and the practice of marketing has developed over the course of history, we have become exposed to greater amounts of product and service campaigns. The purpose of advertisements is to educate the consumer with the goal of ultimately selling the product, and many companies and organizations would not be able to survive without the use of advertisements. Ultimately, it is a necessity for a business to prosper in a competitive market, but there are possible side-effects for the consumer that are beyond the intentions to buy. The purpose of this thesis is to explore the effects advertisements play on the college student in particular. Different static/multi media advertisements have been shown to various college students ranging in gender and background to discover the comprehensive ramifications of specific promotions to study the moral and ethical impact that advertisements play on students' moral intent. An analysis and conclusion will be given, along with ideas for possible future studies. Recommendations will also be stated for marketers to be morally responsible for the advertisements they portray so the audience is not effected in a way that can lead to unwanted consequences. Ultimately, the results did not support the original hypotheses, leading to thought- provoking questions concerning our current marketing practices and the effectiveness of static and multimedia advertisements on college students. Future studies need to take place to reveal the accuracy of the study and to ultimately answer the question, "Are current advertisements influencing the audience at hand?"
Show less - Date Issued
- 2012
- Identifier
- CFH0004250, ucf:44899
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004250
- Title
- DISTANCE.
- Creator
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Kosik, Jonathan, Neal, Darlin, University of Central Florida
- Abstract / Description
-
Distance is a collection of short fiction that explores the spaces between us. Sometimes it's emotional, sometimes it's physical; it lies before us like a cross-country journey, dragging us through emotional terrain fraught with countless dangers and rare rewards. A convict returns to his childhood home. A lonely man documents the unexpected damage of an oil spill in the Gulf of Mexico. A teenager learns that some boots are not made for walking. These stories are the long and short of it....
Show moreDistance is a collection of short fiction that explores the spaces between us. Sometimes it's emotional, sometimes it's physical; it lies before us like a cross-country journey, dragging us through emotional terrain fraught with countless dangers and rare rewards. A convict returns to his childhood home. A lonely man documents the unexpected damage of an oil spill in the Gulf of Mexico. A teenager learns that some boots are not made for walking. These stories are the long and short of it. They examine the way we struggle to understand love, lust, disappointment and the kind of detachment that can develop where we least expect it. We all know the distance between two people differs by degree, but in the end, where that space exists, an inescapable question awaits: Should we sever the tie or bridge the gap?
Show less - Date Issued
- 2011
- Identifier
- CFE0003715, ucf:48783
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003715
