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- Title
- TOWARD INCREASING PERFORMANCE AND EFFICIENCY IN GAS TURBINES FOR POWER GENERATION AND AERO-PROPULSION: UNSTEADY SIMULATION OF ANGLED DISCRETE-INJECTION COOLANT IN A HOT GAS PATH CROSSFLOW.
- Creator
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Johnson, Perry, Kapat, Jayanta, University of Central Florida
- Abstract / Description
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This thesis describes the numerical predictions of turbine film cooling interactions using Large Eddy Simulations. In most engineering industrial applications, the Reynolds-Averaged Navier-Stokes equations, usually paired with two-equation models such as k-[epsilon] or k-[omega], are utilized as an inexpensive method for modeling complex turbulent flows. By resolving the larger, more influential scale of turbulent eddies, the Large Eddy Simulation has been shown to yield a significant...
Show moreThis thesis describes the numerical predictions of turbine film cooling interactions using Large Eddy Simulations. In most engineering industrial applications, the Reynolds-Averaged Navier-Stokes equations, usually paired with two-equation models such as k-[epsilon] or k-[omega], are utilized as an inexpensive method for modeling complex turbulent flows. By resolving the larger, more influential scale of turbulent eddies, the Large Eddy Simulation has been shown to yield a significant increase in accuracy over traditional two-equation RANS models for many engineering flows. In addition, Large Eddy Simulations provide insight into the unsteady characteristics and coherent vortex structures of turbulent flows. Discrete hole film cooling is a jet-in-cross-flow phenomenon, which is known to produce complex turbulent interactions and vortex structures. For this reason, the present study investigates the influence of these jet-crossflow interactions in a time-resolved unsteady simulation. Because of the broad spectrum of length scales present in moderate and high Reynolds number flows, such as the present topic, the high computational cost of Direct Numerical Simulation was excluded from possibility.
Show less - Date Issued
- 2011
- Identifier
- CFH0004086, ucf:44798
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004086
- Title
- TWO CONCEPTIONS OF THE MIND.
- Creator
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Aguda, Benjamin, Gallagher, Shaun, University of Central Florida
- Abstract / Description
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Since the cognitive revolution during the last century the mind has been conceived of as being computer-like. Like a computer, the brain was assumed to be a physical structure (hardware) upon which a computational mind (software) was built. The mind was seen as a collection of independent programs which each have their own specific tasks, or modules. These modules took sensory input "data" and transduced it into language-like representations which were used in mental computations. Recently, a...
Show moreSince the cognitive revolution during the last century the mind has been conceived of as being computer-like. Like a computer, the brain was assumed to be a physical structure (hardware) upon which a computational mind (software) was built. The mind was seen as a collection of independent programs which each have their own specific tasks, or modules. These modules took sensory input "data" and transduced it into language-like representations which were used in mental computations. Recently, a new conception of the mind has developed, grounded cognition. According to this model, sensory stimulus is saved in the original format in which it was received and recalled using association mechanisms. Rather than representations being language-like they are instead multimodal. The manipulation of these multimodal representations requires processing distributed throughout the brain. A new holistic model for mental architecture has developed in which the concerted activity of the brain's modal systems produces functional systems which are intimately codependent with one another. The purpose of this thesis is to explore both the modular and multimodal theories of mental architecture. Each will be described in detail along with their supporting paradigms, cognitivism and grounded cognition. After my expositions I will offer support for my own position regarding these two theories before suggesting avenues for future research.
Show less - Date Issued
- 2011
- Identifier
- CFH0003784, ucf:44765
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0003784
- Title
- ON-CHIP SPIRAL INDUCTOR/TRANSFORMER DESIGN AND MODELING FOR RF APPLICATIONS.
- Creator
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Chen, Ji, Liou, Juin, University of Central Florida
- Abstract / Description
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Passive components are indispensable in the design and development of microchips for high-frequency applications. Inductors in particular are used frequently in radio frequency (RF) IC's such as low-noise amplifiers and oscillators. High performance inductor has become one of the critical components for voltage controlled oscillator (VCO) design, for its quality factor (Q) value directly affects the VCO phase noise. The optimization of inductor layout can improve its performance, but the...
Show morePassive components are indispensable in the design and development of microchips for high-frequency applications. Inductors in particular are used frequently in radio frequency (RF) IC's such as low-noise amplifiers and oscillators. High performance inductor has become one of the critical components for voltage controlled oscillator (VCO) design, for its quality factor (Q) value directly affects the VCO phase noise. The optimization of inductor layout can improve its performance, but the improvement is limited by selected technology. Inductor performance is bounded by the thin routing metal and small distance from lossy substrate. On the other hand, the in-accurate inductor modeling further limits the optimization process. The on-chip inductor has been an important research topic since it was first proposed in early 1990's. Significant amount of study has been accomplished and reported in literature; whereas some methods have been used in industry, but not released to public. It is of no doubt that a comprehensive solution is not exist yet. A comprehensive study of previous will be first address. Later author will point out the in-adequacy of skin effect and proximity effect as cause of current crowding in the inductor metal. A model method embedded with new explanation of current crowding is proposed and its applicability in differential inductor and balun is validated. This study leads to a robust optimization routine to improve inductor performance without any addition technology cost and development.
Show less - Date Issued
- 2006
- Identifier
- CFE0001364, ucf:46962
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001364
- Title
- CHARACTERIZATION OF AN ADVANCED NEURON MODEL.
- Creator
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Echanique, Christopher, Behal, Aman, University of Central Florida
- Abstract / Description
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This thesis focuses on an adaptive quadratic spiking model of a motoneuron that is both versatile in its ability to represent a range of experimentally observed neuronal firing patterns as well as computationally efficient for large network simulation. The objective of research is to fit membrane voltage data to the model using a parameter estimation approach involving simulated annealing. By manipulating the system dynamics of the model, a realizable model with linear parameterization (LP)...
Show moreThis thesis focuses on an adaptive quadratic spiking model of a motoneuron that is both versatile in its ability to represent a range of experimentally observed neuronal firing patterns as well as computationally efficient for large network simulation. The objective of research is to fit membrane voltage data to the model using a parameter estimation approach involving simulated annealing. By manipulating the system dynamics of the model, a realizable model with linear parameterization (LP) can be obtained to simplify the estimation process. With a persistently excited current input applied to the model, simulated annealing is used to efficiently determine the best model parameters that minimize the square error function between the membrane voltage reference data and data generated by the LP model. Results obtained through simulation of this approach show feasibility to predict a range of different neuron firing patterns.
Show less - Date Issued
- 2012
- Identifier
- CFH0004259, ucf:44958
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004259
- Title
- HYSTERESIS EFFECTS IN DRIVING.
- Creator
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Morgan, Justin, Hancock, Peter, University of Central Florida
- Abstract / Description
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This dissertation presents two studies examining the interaction between workload history and driver mental workload. The first experiment focuses on testing for the presence of a hysteresis effect in the driving task. The second experiment examines the proposition that cueing impending periods of higher task demand can reduce the impact of any such potential hysteresis effects. Thirty-two licensed drivers served as participants and all served in both studies. Using the directions provided by...
Show moreThis dissertation presents two studies examining the interaction between workload history and driver mental workload. The first experiment focuses on testing for the presence of a hysteresis effect in the driving task. The second experiment examines the proposition that cueing impending periods of higher task demand can reduce the impact of any such potential hysteresis effects. Thirty-two licensed drivers served as participants and all served in both studies. Using the directions provided by a Heads-Up-Display navigation system, participants followed a pre-set route in the simulated environment. At specified points within the drive, the navigation system would purposefully fail which required drivers to relay a ten digit alphanumeric error code to a remote operator in order to reset the system. Results indicated that this increase in task demand from the navigation system's failure leads to a significant increase in perceived mental workload as compared to pre-failure periods. This increase in driver mental workload was not significantly reduced by the time the drive ended, indicating the presence of a hysteresis effect. In the second experiment, the navigation system provided a completely reliable visual warning before failure. Results indicate that cueing had neither an effect on perceived mental workload, nor any ameliorating effect on the hysteretic type effect seen in mental workload recovery. The conclusion of these findings being that the overall safety and efficiency of the surface transportation system would likely improve by designs which accommodate the periods immediately following a reduction in stress. Whether from leaving high demand areas such as work zones or in the period immediately after using a in-car information device such as a GPS or a cell phone, these post-high workload periods are associated with increased variability in driver inputs and levels of mental workload.
Show less - Date Issued
- 2008
- Identifier
- CFE0002169, ucf:47925
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002169
- Title
- UNIFIED LARGE AND SMALL SIGNAL STATE-SPACE BASED MODELING AND SYMBOLIC SIMULATION FOR PWM CONVERTERS.
- Creator
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Shoubaki, Ehab, Batarseh, Issa, University of Central Florida
- Abstract / Description
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In this Dissertation, which concentrates on discrete modeling for control purposes of DC/DC converters and simulation through symbolic techniques. A Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulation of the converter switches, and this approach results in a small signal discrete model. The Second approach is direct...
Show moreIn this Dissertation, which concentrates on discrete modeling for control purposes of DC/DC converters and simulation through symbolic techniques. A Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulation of the converter switches, and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulation, this approach yields both a large signal nonlinear discrete model and a linear small signal model. Harmonic analysis of the converter's states at steady-state is done for steady-state waveform acquisition, which increases the accuracy of the model especially for finding the control to inductor current frequency response. Also the harmonic Analysis technique is used to both obtain the response of the converter to a load transient and to finding the optimal duty cycle response that minimizes the disturbance. Finally the Discrete model is verified for the Half-Bridge DC/DC topology for its three main control schemes (Asymmetric, Symmetric, DCS). A GUI platform in MATLAB is presented as a wrapper that utilizes the models and analysis presented in this thesis. Symbolic simulation techniques are developed in general manner for linear piecewise circuits and then through State-Space formalism specialized for DC/DC converters. A general symbolic solver programmed in JAVA that implements said techniques is presented.
Show less - Date Issued
- 2009
- Identifier
- CFE0002836, ucf:48061
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002836
- Title
- Assessing the Impact of Multi-variate Steering-rate Vehicle Control on Driver Performance in a Simulation Framework.
- Creator
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Xynidis, Michael, Morrow, Patricia Bockelman, Karwowski, Waldemar, Martin, Glenn, O'Neal, Thomas, Xanthopoulos, Petros, Mouloua, Mustapha, University of Central Florida
- Abstract / Description
-
When a driver turns a steering-wheel, he or she normally expects the vehicle's steering system to communicate an equivalent amount of signal to the road-wheels. This relationship is linear and occurs regardless of the steering-wheel's position within its rotational travel. The linear steering paradigm in passenger vehicles has gone largely unchanged since mass production of passenger vehicles began in 1901. However, as more electronically-controlled steering systems appear in conjunction with...
Show moreWhen a driver turns a steering-wheel, he or she normally expects the vehicle's steering system to communicate an equivalent amount of signal to the road-wheels. This relationship is linear and occurs regardless of the steering-wheel's position within its rotational travel. The linear steering paradigm in passenger vehicles has gone largely unchanged since mass production of passenger vehicles began in 1901. However, as more electronically-controlled steering systems appear in conjunction with development of autonomous steering functions in vehicles, an opportunity to advance the existing steering paradigms arises. The following framework takes a human-factors approach toward examining and evaluating alternative steering systems by using Modeling and Simulation methods to track and score human performance.Present conventional steering systems apply a linear relationship between the steering-wheel and the road wheels of a vehicle. The rotational travel of the steering-wheel is 900(&)deg; and requires two-and-a-half revolutions to travel from end-stop to opposite end-stop. The experimental steering system modeled and employed in this study applies a dynamic curve response to the steering input within a shorter, 225(&)deg; rotational travel. Accommodation variances, based on vehicle speed and steering-wheel rotational position and acceleration, moderate the apparent steering input to augment a more-practical, effective steering rate. This novel model follows a paradigm supporting the full range of steering-wheel actuation without necessitating hand repositioning or the removal of the driver's hands from the steering-wheel during steering maneuvers.In order to study human performance disparities between novel and conventional steering models, a custom simulator was constructed and programmed to render representative models in a test scenario. Twenty-seven males and twenty-seven females, ranging from the ages of eighteen to sixty-five were tested and scored using the driving simulator that presented two successive driving test vignettes: One vignette using conventional 900(&)deg; steering with linear response and the other employing the augmented 225(&)deg; multivariate, non-linear steering.The results from simulator testing suggest that both males and females perform better with the novel system, supporting the hypothesis that drivers of either gender perform better with a system augmented with 225(&)deg; multivariate, non-linear steering than with a conventional steering system. Further analysis of the simulated-driving scores indicates performance parity between male and female participants, supporting the hypothesis positing no significant difference in driver performance between male and female drivers using the augmented steering system. Finally, composite data from written questionnaires support the hypothesis that drivers will prefer driving the augmented system over conventional steering.These collective findings support justification for testing and refining novel steering systems using Modeling and Simulation methods. As a product of this particular study, a tested and open-sourced simulation framework now exists such that researchers and automotive designers can develop, as well as evaluate their own steering-oriented products within a valid human-factors construct. The open-source nature of this framework implies a commonality by which otherwise disparate research and development work can be associated.Extending this framework beyond basic investigation to reach applications requiring more-specialized parameters may even impact drivers having special needs. For example, steering-system functional characteristics could be comparatively optimized to accommodate individuals afflicted with upper-body deficits or limited use of either or both arms. Moreover, the combined human-factors and open-source approaches distinguish the products of this research as a common and extensible platform by which purposeful automotive-industry improvements can be realized(-)contrasted with arbitrary improvements that might be brought about predominantly to showcase technological advancements.
Show less - Date Issued
- 2018
- Identifier
- CFE0007420, ucf:52706
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007420
- Title
- Assessing Pedestrian Safety Conditions on Campus.
- Creator
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Morris, Morgan, Abdel-Aty, Mohamed, Hasan, Samiul, Wu, Yina, University of Central Florida
- Abstract / Description
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Pedestrian-related crashes are a significant safety issue in the United States and cause considerable amounts of deaths and economic cost. Pedestrian safety is an issue that must be uniquely evaluated in a college campus, where pedestrian volumes are dense. The objective of this research is to identify issues at specific locations around UCF and suggest solutions for improvement. To address this problem, a survey that identifies pedestrian safety issues and locations is distributed to UCF...
Show morePedestrian-related crashes are a significant safety issue in the United States and cause considerable amounts of deaths and economic cost. Pedestrian safety is an issue that must be uniquely evaluated in a college campus, where pedestrian volumes are dense. The objective of this research is to identify issues at specific locations around UCF and suggest solutions for improvement. To address this problem, a survey that identifies pedestrian safety issues and locations is distributed to UCF students and staff, and an evaluation of drivers reactions to pedestrian to vehicle (P2V) warning systems is studied through the use of a NADS MiniSim driving simulator. The survey asks participants to identify problem intersections around campus and other issues as pedestrians or bicyclists in the UCF area. Univariate probit models were created from the survey data to identify which factors contribute to pedestrian safety issues, based off the pedestrian's POV and the driver's POV. The models indicated that the more one is exposed to traffic via walking, biking, and driving to campus contributes to less safe experiences. The models also show that higher concerns with drivers not yielding, unsafety of crossing the intersections, and the number of locations to cross, indicate less safe pedestrian experiences from the point of view of pedestrians and drivers. A promising solution for pedestrian safety is Pedestrian to Vehicle (P2V) communication. This study simulates P2V connectivity using a NADS MiniSim Driving Simulator to study the effectiveness of the warning system on drivers. According to the results, the P2V warning system significantly reduced the number of crashes in the tested pre-crash scenarios by 88%. Particularly, the P2V warning system can help decrease the driver's reaction time as well as impact velocity if the crash were to occur.
Show less - Date Issued
- 2019
- Identifier
- CFE0007839, ucf:52818
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007839
- Title
- A System Dynamics Approach on Sustainability Assessment of the United States Urban Commuter Transportation.
- Creator
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Ercan, Tolga, Tatari, Omer, Oloufa, Amr, Eluru, Naveen, Xanthopoulos, Petros, University of Central Florida
- Abstract / Description
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Transportation sector is one of the largest emission sources and is a cause for human health concern due to the high dependency on personal vehicle in the U.S. Transportation mode choice studies are currently limited to micro- and regional-level boundaries, lacking of presenting a complete picture of the issues, and the root causes associated with urban passenger transportation choices in the U.S. Hence, system dynamics modeling approach is utilized to capture complex causal relationships...
Show moreTransportation sector is one of the largest emission sources and is a cause for human health concern due to the high dependency on personal vehicle in the U.S. Transportation mode choice studies are currently limited to micro- and regional-level boundaries, lacking of presenting a complete picture of the issues, and the root causes associated with urban passenger transportation choices in the U.S. Hence, system dynamics modeling approach is utilized to capture complex causal relationships among the critical system parameters affecting alternative transportation mode choices in the U.S. as well as to identify possible policy areas to improve alternative transportation mode choice rates for future years up to 2050. Considering the high degree of uncertainties inherent to the problem, multivariate sensitivity analysis is utilized to explore the effectiveness of existing and possible policy implications in dynamic model in the terms of their potential to increase transit ridership and locating critical parameters that influences the most on mode choice and emission rates. Finally, the dissertation advances the current body of knowledge by integrating discrete event simulation (multinomial fractional split model) and system dynamics for hybrid urban commuter transportation simulation to test new scenarios such as autonomous vehicle (AV) adoption along with traditional policy scenarios such as limiting lane-mile increase on roadways and introducing carbon tax policy on vehicle owners. Overall, the developed simulation models clearly indicate the importance of urban structures to secure the future of alternative transportation modes in the U.S. as the prevailing policy practices fail to change system behavior. Thus, transportation system needs a paradigm shift to radically change current impacts and the market penetration of AVs can be one of the reforms to provoke this transition since it is expected to revolutionize mode choice, emission trends, and the built environment.
Show less - Date Issued
- 2019
- Identifier
- CFE0007626, ucf:52554
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007626
- Title
- MECHANICAL CHARACTERIZATION AND NUMERICAL SIMULATION OF A LIGHT-WEIGHT ALUMINUM A359 METAL-MATRIX COMPOSITE.
- Creator
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DeMarco, James, Gordon, Ali, University of Central Florida
- Abstract / Description
-
Aluminum metal-matrix composites (MMCs) are well positioned to replace steel in numerous manufactured structural components, due to their high strength-to-weight and stiffness ratios. For example, research is currently being conducted in the use of such materials in the construction of tank entry doors, which are currently made of steel and are dangerously heavy for military personnel to lift and close. However, the manufacture of aluminum MMCs is inefficient in many cases due to the loss of...
Show moreAluminum metal-matrix composites (MMCs) are well positioned to replace steel in numerous manufactured structural components, due to their high strength-to-weight and stiffness ratios. For example, research is currently being conducted in the use of such materials in the construction of tank entry doors, which are currently made of steel and are dangerously heavy for military personnel to lift and close. However, the manufacture of aluminum MMCs is inefficient in many cases due to the loss of material through edge cracking during the hot rolling process which is applied to reduce thick billets of as-cast material to usable sheets. In the current work, mechanical characterization and numerical modeling of as-cast aluminum A359-SiCp-30% is employed to determine the properties of the composite and identify their dependence on strain rate and temperature conditions. Tensile and torsion tests were performed at a variety of strain rates and temperatures. Data obtained from tensile tests were used to calibrate the parameters of a material model for the composite. The material model was implemented in the ANSYS finite element software suite, and simulations were performed to test the ability of the model to capture the mechanical response of the composite under simulated tension and torsion tests. A temperature- and strain rate-dependent damage model extended the constitutive model to capture the dependence of material failure on testing or service conditions. Trends in the mechanical response were identified through analysis of the dependence of experimentally-obtained material properties on temperature and strain rate. The numerical model was found to adequately capture strain rate and temperature dependence of the stress-strain curves in most cases. Ductility modeling allowed prediction of stress and strain conditions which would lead to rupture, as well as identification of areas of a solid model which are most likely to fail under a given set of environmental and load conditions.
Show less - Date Issued
- 2011
- Identifier
- CFE0004007, ucf:49177
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004007
- Title
- The Effectiveness of Virtual Humans vs Pre-Recorded Humans in a Standardized Patient Performance Assessment.
- Creator
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Palathinkal, Joel, Kincaid, John, Shumaker, Randall, Allred, Kelly, Smith, Roger, University of Central Florida
- Abstract / Description
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A Standardized Patient (SP) is a trained actor who portrays a particular illness to provide training to medical students and professionals. SPs primarily use written scripts and additional paper-based training for preparation of practical and board exams. Many institutions use various methods for training such as hiring preceptors for reenactment of scenarios, viewing archived videos, and computer based training. Currently, the training that is available can be enhanced to improve the level...
Show moreA Standardized Patient (SP) is a trained actor who portrays a particular illness to provide training to medical students and professionals. SPs primarily use written scripts and additional paper-based training for preparation of practical and board exams. Many institutions use various methods for training such as hiring preceptors for reenactment of scenarios, viewing archived videos, and computer based training. Currently, the training that is available can be enhanced to improve the level of quality of standardized patients. The following research is examining current processes in standardized patient training and investigating new methods for clinical skills education in SPs. The modality that is selected for training can possibly affect the performance of the actual SP case.This paper explains the results of a study that investigates if there is a difference in the results of an SP performance assessment. This difference can be seen when comparing a virtual human modality to that of a pre-recorded human modality for standardized patient training. The sample population navigates through an interactive computer based training module which provides informational content on what the roles of an SP are, training objectives, a practice session, and an interactive performance assessment with a simulated Virtual Human medical student. Half of the subjects interact with an animated virtual human medical student while the other half interacts with a pre-recorded human. The interactions from this assessment are audio-recorded, transcribed, and then graded to see how the two modalities compare. If the performance when using virtual humans for standardized patients is equal to or superior to pre-recorded humans, this can be utilized as a part task trainer that brings standardized patients to a higher level of effectiveness and standardization. In addition, if executed properly, this tool could potentially be used as a part task trainer which could provide savings in training time, resources, budget, and staff to military and civilian healthcare facilities.
Show less - Date Issued
- 2011
- Identifier
- CFE0004149, ucf:49037
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004149
- Title
- Numerical Simulation of Conventional Fuels and Biofuels Dispersion and Vaporization Process in Co-flow and Cross-flow Premixers.
- Creator
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Gu, Xin, Kumar, Ranganathan, Basu, Saptarshi, Kapat, Jayanta, Chow, Louis, Shivamoggi, Bhimsen, University of Central Florida
- Abstract / Description
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In order to follow increasingly strict regulation of pollutant emissions, a new concept of Lean Premixed pre-vaporized (LPP) combustion has been proposed for turbines. In LPP combustion, controlled atomization, dispersion and vaporization of different types of liquid fuel in the pre-mixer are the key factors required to stabilize the combustion process and improve the efficiency. A numerical study is conducted for the fundamental understanding of the liquid fuel dispersion and vaporization...
Show moreIn order to follow increasingly strict regulation of pollutant emissions, a new concept of Lean Premixed pre-vaporized (LPP) combustion has been proposed for turbines. In LPP combustion, controlled atomization, dispersion and vaporization of different types of liquid fuel in the pre-mixer are the key factors required to stabilize the combustion process and improve the efficiency. A numerical study is conducted for the fundamental understanding of the liquid fuel dispersion and vaporization process in pre-mixers using both cross-flow and co-flow injection methods. First, the vaporization model is validated by comparing the numerical data to existing experiments of single droplet vaporization under both low and high convective air temperatures. Next, the dispersion and vaporization process for biofuels and conventional fuels injected transversely into a typical simplified version of rectangular pre-mixer are simulated and results are analyzed with respect to vaporization performance, degree of mixedness and homogeneity. Finally, collision model has been incorporated to predict more realistic vaporization performance. Four fuels, Ethanol, Rapeseed Methyl Esters (RME), gasoline and jet-A have been investigated. For mono-disperse spray with no collision model, the droplet diameter reduction and surface temperature rise were found to be strongly dependent on the fuel properties. The diameter histogram near the pre-mixer exit showed a wide droplet diameter distribution for all the fuels. In general, pre-heating of the fuels before injection improved the vaporization performance. An improvement in the drag model with Stefan flow correction showed that a low speed injection and high cone angle improved performance. All fuels achieved complete vaporization under a spray cone angle of 140(&)deg;. In general, it was found that cross-flow injection achieved better vaporization performance than co-flow injection. A correlation is derived for jet-A's total vaporization performance as a function of non-dimensional inlet air temperature and fuel/air momentum flux ratio. This is achieved by curve-fitting the simulated results for a broad range of inlet air temperatures and fuel/air momentum flux ratios. The collision model, based on no-time-counter method (NTC) proposed by Schmidt and Rutland, was implemented to replace O'Rourke's collision algorithm to improve the results such that the unphysical numerical artifact in a Cartesian grid was removed and the results were found to be grid-independent. The dispersion and vaporization processes for liquid fuel sprays were simulated in a cylindrical pre-mixer using co-flow injection method. Results for jet-A and Rapeseed Methyl Esters (RME) showed acceptable grid independence. At relatively low spray cone angle and injection velocity, it was found that the collision effect on the average droplet size and the vaporization performance were very high due to relatively high coalescence rate induced by droplet collisions. It was also found that the vaporization performance and the level of homogeneity of fuel-air mixture could be significantly improved when the dispersion level is high, which can be achieved by increasing the spray cone angle and injection velocity. In order to compare the performance between co-flow and cross-flow injection methods, the fuels were injected at an angle of 40(&)deg; with respect to the stream wise direction to avoid impacting on the wall. The cross-flow injection achieved similar vaporization performance as co-flow because a higher coalescence rate induced by droplet collisions cancelled off its higher heat transfer efficiency between two phases for cross-flow injections.
Show less - Date Issued
- 2012
- Identifier
- CFE0004192, ucf:49004
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004192
- Title
- AN INTERVAL BASED APPROACH TO MODEL INPUT UNCERTAINTY IN DISCRETE-EVENT SIMULATION.
- Creator
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Batarseh, Ola, Wang, Yan, University of Central Florida
- Abstract / Description
-
The objective of this research is to increase the robustness of discrete-event simulation (DES) when input uncertainties associated models and parameters are present. Input uncertainties in simulation have different sources, including lack of data, conflicting information and beliefs, lack of introspection, measurement errors, and lack of information about dependency. A reliable solution is obtained from a simulation mechanism that accounts for these uncertainty components in simulation. An...
Show moreThe objective of this research is to increase the robustness of discrete-event simulation (DES) when input uncertainties associated models and parameters are present. Input uncertainties in simulation have different sources, including lack of data, conflicting information and beliefs, lack of introspection, measurement errors, and lack of information about dependency. A reliable solution is obtained from a simulation mechanism that accounts for these uncertainty components in simulation. An interval-based simulation (IBS) mechanism based on imprecise probabilities is proposed, where the statistical distribution parameters in simulation are intervals instead of precise real numbers. This approach incorporates variability and uncertainty in systems. In this research, a standard procedure to estimate interval parameters of probability distributions is developed based on the measurement of simulation robustness. New mechanisms based on the inverse transform to generate interval random variates are proposed. A generic approach to specify the required replication length to achieve a desired level of robustness is derived. Furthermore, three simulation clock advancement approaches in the interval-based simulation are investigated. A library of Java-based IBS toolkits that simulates queueing systems is developed to demonstrate the new proposed reliable simulation. New interval statistics for interval data analysis are proposed to support decision making. To assess the performance of the IBS, we developed an interval-based metamodel for automated material handling systems, which generates interval performance measures that are more reliable and computationally more efficient than traditional DES simulation results.
Show less - Date Issued
- 2010
- Identifier
- CFE0003343, ucf:48441
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003343
- Title
- IMPROVING THROUGHPUT AND PREDICTABILITY OF HIGH-VOLUME BUSINESS PROCESSES THROUGH EMBEDDED MODELING.
- Creator
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DeKeyrel, Joseph, Malone, Linda, University of Central Florida
- Abstract / Description
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Being faster is good. Being predictable is better. A faithful model of a system, loaded to reflect the system's current state, can then be used to look into the future and predict performance. Building faithful models of processes with high degrees of uncertainty can be very challenging, especially where this uncertainty exists in terms of processing times, queuing behavior and re-work rates. Within the context of an electronic, multi-tiered workflow management system (WFMS) the author builds...
Show moreBeing faster is good. Being predictable is better. A faithful model of a system, loaded to reflect the system's current state, can then be used to look into the future and predict performance. Building faithful models of processes with high degrees of uncertainty can be very challenging, especially where this uncertainty exists in terms of processing times, queuing behavior and re-work rates. Within the context of an electronic, multi-tiered workflow management system (WFMS) the author builds such a model to endogenously quote due dates. A WFMS that manages business objects can be recast as a flexible flow shop in which the stations that a job (representing the business object) passes through are known and the jobs in the stations queues at any point are known. All of the other parameters associated with the flow shop, including job processing times per station, and station queuing behavior are uncertain though there is a significant body of past performance data that might be brought to bear. The objective, in this environment, is to meet the delivery date promised when the job is accepted. To attack the problem the author develops a novel heuristic algorithm for decomposing the WFMS's event logs exposing non-standard queuing behavior, develops a new simulation component to implement that behavior, and assembles a prototypical system to automate the required historical analysis and allow for on-demand due date quoting through the use of embedded discrete event simulation modeling. The developed software components are flexible enough to allow for both the analysis of past performance in conjunction with the WFMS's event logs, and on-demand analysis of new jobs entering the system. Using the proportion of jobs completed within the predicted interval as the measure of effectiveness, the author validates the performance of the system over six months of historical data and during live operations with both samples achieving the 90% service level targeted.
Show less - Date Issued
- 2011
- Identifier
- CFE0003580, ucf:48913
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003580
- Title
- Modeling Transport and Protein Adsorption in Microfluidic Systems.
- Creator
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Finch, Craig, Hickman, James, Kincaid, John, Lin, Kuo-Chi, Behal, Aman, Cho, Hyoung, University of Central Florida
- Abstract / Description
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This work describes theoretical advances in the modeling and simulation of microfluidic systems and demonstrates the practical application of those techniques. A new multi-scale model of the adsorption of hard spheres was formulated to bridge the gap between simulations of discrete particles and continuum fluid dynamics. A whispering gallery mode (WGM) biosensor was constructed and used to measure the kinetics of adsorption for two types of proteins on four different surfaces. Computational...
Show moreThis work describes theoretical advances in the modeling and simulation of microfluidic systems and demonstrates the practical application of those techniques. A new multi-scale model of the adsorption of hard spheres was formulated to bridge the gap between simulations of discrete particles and continuum fluid dynamics. A whispering gallery mode (WGM) biosensor was constructed and used to measure the kinetics of adsorption for two types of proteins on four different surfaces. Computational fluid dynamics was used to analyze the transport of proteins in the flow cell of the biosensor. Kinetic models of protein adsorption that take transport limitations into account were fitted to the experimental data and used to draw conclusions about the mechanisms of adsorption. Transport simulations were then applied to the practical problem of optimizing the design of a microfluidic bioreactor to enable (")plugs(") of fluid to flow from one chamber to the next with minimal dispersion. Experiments were used to validate the transport simulations. The combination of quantitative modeling and simulation and experiments led to results that could not have been achieved using either approach by itself. Simulation tools that accurately predict transport and protein adsorption will enable the rational design of microfluidic devices for biomedical applications.
Show less - Date Issued
- 2011
- Identifier
- CFE0004474, ucf:49313
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004474
- Title
- Bleeding Control Using Multiple Amputee Trauma Trainer in Medical Simulation: Comparison of Movement Versus Non-Movement in Training.
- Creator
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Allen, Christine, Kincaid, John, Schatz, Sarah, Allred, Kelly, Talbert, Steven, Sotomayor, Teresita, University of Central Florida
- Abstract / Description
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Army first responders, specifically Combat Medics and Combat Lifesavers, provide medical intervention while in the field. Didactic as well as hands-on training helps to prepare these first responders, and one module they receive involves bleeding control. First responders are taught to use the Combat Application Tourniquet(&)#174; (CAT(&)#174;) to stop bleeding from limbs subjected to severe injury such as amputation, gunshot, or severe lacerations. A training aid like the Multiple Amputee...
Show moreArmy first responders, specifically Combat Medics and Combat Lifesavers, provide medical intervention while in the field. Didactic as well as hands-on training helps to prepare these first responders, and one module they receive involves bleeding control. First responders are taught to use the Combat Application Tourniquet(&)#174; (CAT(&)#174;) to stop bleeding from limbs subjected to severe injury such as amputation, gunshot, or severe lacerations. A training aid like the Multiple Amputee Trauma Trainer(TM) (MATT(TM)) simulator provides tourniquet training using a lifelike bilateral lower limb amputee. In addition, MATT(TM) combines movement and resistance while the first responder applies the tourniquet, mimicking conditions one would see in a real situation. This research describes tourniquet history, appropriate usage, field tourniquet review, surgical tourniquet, CAT(&)#174; bleeding intervention procedures, bleeding physiology and complications, prehospital tourniquet use in recent conflicts, medical simulation fidelity, and a review of the value of animatronic movement during tourniquet simulation-based training. I then evaluate the effectiveness of animatronic movement during tourniquet training using the Advanced MATT in an experiment using Army first responders. The control group experienced no movement while the experimental group experienced movement when applying a tourniquet during the lab-training. Each group then alternately experienced Advanced MATT movement during an immersive scenario along with fog, strobe lights, and battle sounds. It was hypothesized that 1) In the immersive scenario, the experimental groups (i.e., those who were trained on a moving simulator) would have a faster reaction time as compared to those participants who did not receive training on the moving Advanced MATT simulator; 2) In the lab-based training, the experimental groups would have a slower reaction time; 3) In the immersive scenario, the experimental groups would have a faster tourniquet application time when subjected to movement while in the lab-based training, but the experimental groups would also have a slower tourniquet application time when initially subjected to movement in the laboratory-based training; finally, 4, 5, and 6) Participants who completed lab-based tourniquet training on the Advanced MATT simulation with animatronic movement would report higher perceived realism scores than participants who complete the training on a static version of the Advanced MATT and participants who completed a tourniquet training immersive scenario on the Advanced MATT simulation with movement would report higher perceived realism, presence, and self-efficacy scores than participants who complete the training on a static version of the Advanced MATT. The empirical results show a significant overall training effect of the Advanced MATT simulator (with or without movement). For reaction time and tourniquet application time, involving simulator movement was significant over varying scenarios. A small reduction in reaction and tourniquet application time on the battlefield may be extremely beneficial on the battlefield. Participants who received movement generally gave more positive reactions than those who did not received movement, although these results failed to reach statistical significance. Participants who received movement, followed by a scenario without movement rated the subjective ratings the lowest, suggestive of the lack of movement. Furthermore, despite the order movement was received, no large drops in performance occurred in any condition, indicating that negative training was avoided.
Show less - Date Issued
- 2011
- Identifier
- CFE0004468, ucf:49316
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004468
- Title
- A Production and Cost Modeling Methodology of 2nd Generation Biofuel in the United States.
- Creator
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Poole, David, Kincaid, John, Mollaghasemi, Mansooreh, Geiger, Christopher, University of Central Florida
- Abstract / Description
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The use of biofuels in the United States has increased dramatically in the last few years. The largest source of feedstock for ethanol to date has been corn. However, corn is also a vitally important food crop and is used commonly as feed for cattle and other livestock. To prevent further diversion of an important food crop to production of ethanol, there is great interest in developing commercial-scale technologies to make ethanol from non-food crops, or other suitable plant material. This...
Show moreThe use of biofuels in the United States has increased dramatically in the last few years. The largest source of feedstock for ethanol to date has been corn. However, corn is also a vitally important food crop and is used commonly as feed for cattle and other livestock. To prevent further diversion of an important food crop to production of ethanol, there is great interest in developing commercial-scale technologies to make ethanol from non-food crops, or other suitable plant material. This is commonly referred to as biomass. A review is made of lignocellulosic sources being considered as feedstocks to produce ethanol. Current technologies for pretreatment and hydrolysis of the biomass material are examined and discussed. Production data and cost estimates are culled from the literature, and used to assist in development of mathematical models for evaluation of production ramp-up profiles, and cost estimation. These mathematical models are useful as a planning tool, and provide a methodology to estimate monthly production output and costs for labor, capital, operations and maintenance, feedstock, raw materials, and total cost. Existing credits for ethanol production are also considered and modeled. The production output in liters is modeled as a negative exponential growth curve, with a rate coefficient providing the ability to evaluate slower, or faster, growth in production output and its corresponding effect on monthly cost. The capital and labor costs per unit of product are determined by dividing the monthly debt service and labor costs by that month?s production value. The remaining cost components change at a constant rate in the simulation case studies. This methodology is used to calculate production levels and costs as a function of time for a 25 million gallon per year capacity cellulosic ethanol plant. The parameters of interest are calculated in MATLAB with a deterministic, continuous system simulation model. Simulation results for high, medium, and low cost case studies are included. Assumptions for the model and for each case study are included and some comparisons are made to cost estimates in the literature. While the cost per unit of product decreases and production output increases over time, some reasonable cost values are obtained by the end of the second year for both the low and medium cost case studies. By the end of Year 2, total costs for those case studies are $0.48 per liter and $0.88 per liter, respectively. These cost estimates are well within the reported range of values from the reviewed literature sources. Differing assumptions for calculations made by different sources make a direct cost comparison with the outputs of this modeling methodology extremely difficult. Proposals for reducing costs are introduced. Limitations and shortcomings of the research activity are discussed, along with recommendations for potential future work in improving the simulation model and model verification activities. In summary, the author was not able to find evidence?within the public domain?of any similar modeling and simulation methodology that uses a deterministic, continuous simulation model to evaluate production and costs as a function of time. This methodology is also unique in highlighting the important effect of production ramp-up on monthly costs for capital (debt service) and labor. The resultant simulation model can be used for planning purposes and provides an independent, unbiased estimate of cost as a function of time.
Show less - Date Issued
- 2012
- Identifier
- CFE0004424, ucf:49321
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004424
- Title
- Towards Scalable Nanomanufacturing: Modeling the Interaction of Charged Droplets from Electrospray using GPU.
- Creator
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Yang, Weiwei, Deng, Weiwei, Chen, Ruey-Hung, Ilie, Marcel, University of Central Florida
- Abstract / Description
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Electrospray is an atomization method subject to intense study recently due to its monodispersity and the wide size range of droplets it can produce, from nanometers to hundreds of micrometers. This thesis focuses on the numerical and theoretical modeling of the interaction of charged droplets from the single and multiplexed electrospray. We studied two typical scenarios: large area film depositions using multiplexed electrospray and fine pattern printings assisted by linear electrostatic...
Show moreElectrospray is an atomization method subject to intense study recently due to its monodispersity and the wide size range of droplets it can produce, from nanometers to hundreds of micrometers. This thesis focuses on the numerical and theoretical modeling of the interaction of charged droplets from the single and multiplexed electrospray. We studied two typical scenarios: large area film depositions using multiplexed electrospray and fine pattern printings assisted by linear electrostatic quadrupole focusing. Due to the high computation power requirement in the unsteady n-body problem, graphical processing unit (GPU) which delivers 10 Tera flops in computation power is used to dramatically speed up the numerical simulation both efficiently and with low cost. For large area film deposition, both the spray profile and deposition number density are studied for different arrangements of electrospray and electrodes. Multiplexed electrospray with hexagonal nozzle configuration can not give us uniform deposition though it has the highest packing density. Uniform film deposition with variation (<) 5% in thickness was observed with the linear nozzle configuration combined with relative motion between ES source and deposition substrate. For fine pattern printing, linear quadrupole is used to focus the droplets in the radial direction while maintaining a constant driving field at the axial direction. Simulation shows that the linear quadrupole can focus the droplets to a resolution of a few nanometers quickly when the inter-droplet separation is larger than a certain value. Resolution began to deteriorate drastically when the inter-droplet separation is smaller than that value. This study will shed light on using electrospray as a scalable nanomanufacturing approach.
Show less - Date Issued
- 2012
- Identifier
- CFE0004463, ucf:49333
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004463
- Title
- A Framework for Process Data Collection, Analysis, and Visualization in Construction Projects.
- Creator
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Akhavian, Reza, Behzadan, Amir, Oloufa, Amr, Tatari, Mehmet, University of Central Florida
- Abstract / Description
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Automated data collection, simulation and visualization can substantially enhance the process of designing, analysis, planning, and control of many engineering processes. In particular, managing processes that are dynamic in nature can significantly benefit from such techniques. Construction projects are good examples of such processes where a variety of equipment and resources constantly interact inside an evolving environment. Management of such settings requires a platform capable of...
Show moreAutomated data collection, simulation and visualization can substantially enhance the process of designing, analysis, planning, and control of many engineering processes. In particular, managing processes that are dynamic in nature can significantly benefit from such techniques. Construction projects are good examples of such processes where a variety of equipment and resources constantly interact inside an evolving environment. Management of such settings requires a platform capable of providing decision-makers with updated information about the status of project entities and assisting site personnel making critical decisions under uncertainty. To this end, the current practice of using historical data or expert judgments as static inputs to create empirical formulations, bar chart schedules, and simulation networks to study project activities, resource operations, and the environment under which a project is taking place does not seem to offer reliable results.The presented research investigates the requirements and applicability of a data-driven modeling framework capable of collecting and analyzing real time field data from construction equipment. In the developed data collection scheme, a stream of real time data is continuously transferred to a data analysis module to calculate the input parameters required to create dynamic 3D visualizations of ongoing engineering activities, and update the contents of a discrete event simulation (DES) model representing the real engineering process. The generated data-driven simulation model is an effective tool for projecting future progress based on existing performance. Ultimately, the developed framework can be used by project decision-makers for short-term project planning and control since the resulting simulation and visualization are completely based on the latest status of project entities.
Show less - Date Issued
- 2012
- Identifier
- CFE0004347, ucf:49419
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004347
- Title
- Application of Modeling and Simulation to Reduce Costs of Acquisition within Triple Constraints.
- Creator
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Mohammad, Syed, Kincaid, John, Shumaker, Randall, Wiegand, Rudolf, Richardson, Paul, University of Central Florida
- Abstract / Description
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A key component of defense acquisition programs operating using the Integrated Defense Acquisition, Technology, and Logistics Life Cycle Management System is the reliance on the triple constraints of cost, schedule, and performance. While the use of Modeling and Simulation tools and capabilities is prevalent and well established in the Research and Development, Analysis, and Training domains, acquisition programs have been reluctant to use Modeling and Simulation in any great depth due to...
Show moreA key component of defense acquisition programs operating using the Integrated Defense Acquisition, Technology, and Logistics Life Cycle Management System is the reliance on the triple constraints of cost, schedule, and performance. While the use of Modeling and Simulation tools and capabilities is prevalent and well established in the Research and Development, Analysis, and Training domains, acquisition programs have been reluctant to use Modeling and Simulation in any great depth due to inaccessibility of tools, Subject Matter Experts, and implications to cost and schedule. This presents a unique Simulation Management challenge which requires an in-depth understanding of the technical capabilities available within an organization, their applicability to support immediate needs, and the flexibility to utilize these capabilities within the programmatic environment to provide a value added service. The focus of this dissertation is to study the use of Modeling and Simulation in the Defense arena, and to review the applicability of Modeling and Simulation within programmatic acquisition environments which are constrained by cost, schedule, and performance. This research draws comparisons between Modeling and Simulation to other Process Improvement initiatives, such as Lean and Six Sigma, and reviews case studies involving the application of Modeling and Simulation within triple constrained environments. The development of alternate scenarios allows cost benefit analysis to be conducted for each scenario and alternate scenario, developing a case for whether or not the application of Modeling and Simulation within the triple constrained environment delivered any consequential benefit to the acquisition process. Observations are made regarding the level of Modeling and Simulation as applied within each case study, and generalized recommendations are made for the inclusion of cost benefit analysis methodologies for analyzing proposed Modeling and Simulation activities within acquisition programs. Limitations and shortcomings of the research activity are discussed, along with recommendations for potential future work in the Simulation Management field, both with respect to the specific case studies reviewed in this study and the general field.
Show less - Date Issued
- 2012
- Identifier
- CFE0004415, ucf:49396
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004415
