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- Title
- Design and Simulation of Device Failure Models for Electrostatic Discharge (ESD) Event.
- Creator
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Miao, Meng, Sundaram, Kalpathy, Yuan, Jiann-Shiun, Gong, Xun, Jin, Yier, Salcedo, Javier, University of Central Florida
- Abstract / Description
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In this dissertation, the research mainly focused on discussing ESD failure event simulation and ESD modeling, seeking solutions for ESD issues by simulating ESD event and predict possible ESD reliability problem in IC design. The research involves failure phenomenon caused by ESD/ EOS stress, mainly on the thermal failure due to inevitable self-heating during an ESD stress. Standard Complementary Metal-Oxide-Semiconductor (CMOS) process and high voltage Doublediffusion Metal-Oxide...
Show moreIn this dissertation, the research mainly focused on discussing ESD failure event simulation and ESD modeling, seeking solutions for ESD issues by simulating ESD event and predict possible ESD reliability problem in IC design. The research involves failure phenomenon caused by ESD/ EOS stress, mainly on the thermal failure due to inevitable self-heating during an ESD stress. Standard Complementary Metal-Oxide-Semiconductor (CMOS) process and high voltage Doublediffusion Metal-Oxide-Semiconductor (DMOS) process are used for design of experiment. A multi-function test platform High Power Pulse Instrument (HPPI) is used for ESD event evaluation and device characterization. SPICE-like software ADICE is for back-end simulation.Electrostatic Discharges (ESD) is one of the hazard that may affect IC circuit function and cause serious damage to the chip. The importance of ESD protection has been raised since the CMOS technology advanced and the dimension of transistors scales down. On the other hand, the variety of applications of chips is also making corresponding ESD protection difficult to meet different design requirement. Aside from typical requirements such as core circuit operation voltage, maximum accepted leakage current, breakdown conditions for the process and overall device sizes, special applications like radio frequency and power electronic requires ESD to be low parasitic capacitance and can sustain high level energy. In that case, a proper ESD protection design demands not only a robust ESD protection scheme, but co-design with the inner circuit. For that purpose, it is necessary to simulate the results of ESD impact on IC and find out possible weak point of the circuit and improve it. The first step of the simulation is to have corresponding models available. Unfortunately, ESD models, especially there are lack of circuit-level ESD models that provide quick and accurate prediction of ESD event.In this dissertation paper, ESD models, especially ESD failure models for device thermal failure are introduced, with modeling methodology accordingly. First, an introduction for ESD event and typical ESD protection schemes are introduced. Its purpose is to give basic concept of ESD. For ESD failure models, two typical types can be categorized depends on the physical mechanisms that cause the ESD damage. One is the gate oxide breakdown, which is electric field related. The other is the thermal-related failure, which stems from the self-heating effect associated with the large current passing through the ESD protection structure. The first one has become increasingly challenging with the aggressive scaling of the gate dielectric in advanced processes and ESD protection for that need to be carefully designed. The second one, thermal failure widely exists in semiconductor devices as long as there is ESD current flow through the device and accumulate heat at junctions. Considering the universality of thermal failure in ESD device, it is imperative to establish a model to simulate ESD caused thermal failure.Several works related to ESD model can be done. One crucial part for a failure model is to define the failure criterion. As common solution for ESD simulation and failure prediction. The maximum current level or breakdown voltage is used to judge whether a device fails under ESD stresses. Such failure criteria based on measurable voltage or current values are straightforward and can be easy to implemented in simulation tools. However, the shortcoming of these failure criteria is each failure criterion is specifically designed for certain ESD stress condition. For example, the failure voltage level for Human Body Model and Charged Device Model are quite different, and it is hard to judge a device's ESD capability under standard test conditions based on its transmission line pulse test result. So it is necessary to look deeper into the physical mechanism of device failure under ESD and find a more universal failure criterion for various stress conditions.As one of the major failure mechanisms, thermal failure evaluated by temperature is a more universal failure criterion for device failure under ESD stress. Whatever the stress model is, the device will fail if a critical temperature is reached at certain part inside the device and cause structural damage. Then finding out that critical temperature is crucial to define the failure point for device thermal failure. One chapter of this dissertation will focus on discussing this issue and propose a simple method to give close estimation of the real failure temperature for typical ESD devices.Combined these related works, a comprehensive diode model for ESD simulation is proposed. Using existing ESD models, diode I-V characteristic from low current turn-on to high current saturation can be simulated. By using temperature as the failure criterion, the last point of diode operation, or the second breakdown point, can be accurately predicted. Additional investigation of ESD capability of devices for special case like vertical GaN diode is discussed in Chapter IV. Due to the distinct material property of GaN, the vertical GaN diode exhibits unique and interesting quasi-static I-V curves quite different from conventional silicon semiconductor devices. And that I-V curve varies with different pulse width, indicating strong conductivity modulation of diode neutral region that will delay the complete turn-on of the vertical GaN diode.
Show less - Date Issued
- 2017
- Identifier
- CFE0006626, ucf:51291
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006626
- Title
- Evaluation of Real World Toll Plazas Using Driving Simulation.
- Creator
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Carroll, Kali, Abdel-Aty, Mohamed, Lee, JaeYoung, Eluru, Naveen, University of Central Florida
- Abstract / Description
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Toll plazas are becoming an essential part of the highway system, especially within the state of Florida. Many crashes reported on highways occur at toll plazas. A primary reason for many vehicle collisions happening at these facilities is the fact that each toll plaza agency has different design, signage and marking criteria. This, in turn, causes driver confusion and possible last minute weaving maneuvers. Even though the varying design of toll plazas is a clear highway safety factor,...
Show moreToll plazas are becoming an essential part of the highway system, especially within the state of Florida. Many crashes reported on highways occur at toll plazas. A primary reason for many vehicle collisions happening at these facilities is the fact that each toll plaza agency has different design, signage and marking criteria. This, in turn, causes driver confusion and possible last minute weaving maneuvers. Even though the varying design of toll plazas is a clear highway safety factor, research in the field is very limited but expanding. This study focuses on one toll plaza, in particular the Dean Mainline Toll Plaza, located in Orlando, Florida. The toll plaza is located directly between two roads that are in close proximity of each other. Because of this, the toll plaza is very close to the on- and off- ramps, which can be even more confusing and stressful for a driver entering or leaving the highway. The purpose of this study is to evaluate the safety and efficiency of the Dean Mainline Toll Plaza in order to make recommendations to improve or maintain the current toll plaza design, as well as potentially contribute to a nationally set design standard for toll plazas. Using the NADS miniSimTM Simulator, 72 subjects were recruited, and each subject was asked to drive 3 scenarios that were randomly selected from a pool of 24 scenarios. The following factors were changed in order to study the driver's behavior: signage and their location, pavement markings, distances between the toll plaza and ramps, and traffic conditions. All of these factors were altered and observed on five of the eight possible routes than can be taken through the toll plaza. The subjects were asked to complete questionnaires before and after all of the scenarios, as well as in between each driving scenario. These questionnaires included demographic characteristics, such as age, education, income, E-PASS ownership, etc. The data that were collected by the driving simulator and questionnaires were analyzed by ANOVA and multinomial logistic regression models. A positive relationship was found between non-urgent lane changing and the current real-world sign conditions prior to the toll plaza. Relationships were also found between the subjects' speed in various locations and signage before the toll plaza and segment length after the toll plaza. Along with specified recommendations for future research in toll plaza safety, recommendations for the Dean Mainline Toll Plaza include maintaining the current signs and pavement markings, as they were found to be beneficial in drivers performing safe lane changing maneuvers.
Show less - Date Issued
- 2016
- Identifier
- CFE0006085, ucf:50960
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006085
- Title
- Coordinated Optimal Power Planning of Wind Turbines in an Offshore Wind Farm.
- Creator
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Vishwakarma, Puneet, Xu, Yunjun, Kapat, Jayanta, Kauffman, Jeffrey, Behal, Aman, University of Central Florida
- Abstract / Description
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Wind energy is on an upswing due to climate concerns and increasing energy demands on conventional sources. Wind energy is attractive and has the potential to dramatically reduce the dependency on non-renewable energy resources. With the increase in wind farms there is a need to improve the efficiency in power allocation and power generation among wind turbines. Wake interferences among wind turbines can lower the overall efficiency considerably, while offshore conditions pose increased...
Show moreWind energy is on an upswing due to climate concerns and increasing energy demands on conventional sources. Wind energy is attractive and has the potential to dramatically reduce the dependency on non-renewable energy resources. With the increase in wind farms there is a need to improve the efficiency in power allocation and power generation among wind turbines. Wake interferences among wind turbines can lower the overall efficiency considerably, while offshore conditions pose increased loading on wind turbines. In wind farms, wind turbines' wake affects each other depending on their positions and operation modes. Therefore it becomes essential to optimize the wind farm power production as a whole than to just focus on individual wind turbines. The work presented here develops a hierarchical power optimization algorithm for wind farms. The algorithm includes a cooperative level (or higher level) and an individual level (or lower level) for power coordination and planning in a wind farm. The higher level scheme formulates and solves a quadratic constrained programming problem to allocate power to wind turbines in the farm while considering the aerodynamic effect of the wake interaction among the turbines and the power generation capabilities of the wind turbines. In the lower level, optimization algorithm is based on a leader-follower structure driven by the local pursuit strategy. The local pursuit strategy connects the cooperative level power allocation and the individual level power generation in a leader-follower arrangement. The leader, could be a virtual entity and dictates the overall objective, while the followers are real wind turbines considering realistic constraints, such as tower deflection limits. A nonlinear wind turbine dynamics model is adopted for the low level study with loading and other constraints considered in the optimization. The stability of the algorithm in the low level is analyzed for the wind turbine angular velocity. Simulations are used to show the advantages of the method such as the ability to handle non-square input matrix, non-homogenous dynamics, and scalability in computational cost with rise in the number of wind turbines in the wind farm.
Show less - Date Issued
- 2015
- Identifier
- CFE0005899, ucf:50896
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005899
- Title
- Understanding the Capabilities and Limitations of Advanced Interactive M(&)S: A Cricothyroidotomy Simulation Case Study.
- Creator
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Campbell-Wynn, Lillian, Proctor, Michael, Kincaid, John, Crumpton-Young, Lesia, Liu, Alan, Burgess, Deborah, University of Central Florida
- Abstract / Description
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Simulation for surgical education and training is increasingly perceived as a valuable contribution to traditional teaching methods providing a structured learning experience. Surgical simulations allow surgeons to practice tactics, techniques and procedures numerous times without the cost, limitations and ethical problems of using cadaver-based models. The goal of this research is to advance the use of modeling and simulation in support of emergency medical training. This research explores...
Show moreSimulation for surgical education and training is increasingly perceived as a valuable contribution to traditional teaching methods providing a structured learning experience. Surgical simulations allow surgeons to practice tactics, techniques and procedures numerous times without the cost, limitations and ethical problems of using cadaver-based models. The goal of this research is to advance the use of modeling and simulation in support of emergency medical training. This research explores questions identified through a case study of two different modeling and simulation techniques (-) virtual reality and mannequins - in the support of combat emergency medical education and training. To reduce the scope to a manageable dissertation, the research focuses on CricSim as representative form of virtual reality simulation and HapMed as a form of mannequin simulation both with haptic-enabled capabilities. To further narrow the scope, the research focuses on training of a medical technique common to both simulation systems, which for this research was the cricothyroidotomy airway management technique. The U.S. Army expressed interest in training of combat medics in the cricothyroidotomy airway management technique and offered to support experimentation with both facilities and trained combat medics as the sample population. An experiment supporting this research took place at Fort Indiantown Gap, a National Guard Training Center located in Annville, Lebanon County, Pennsylvania and is the home of the Medical Battalion Training Site. An advanced airway management course is augmented with combat medics receiving training and evaluation on performing the cricothyroidotomy procedure using CricSim and HapMed with system experts provided by each respective developer. The NASA Task Load survey is used to collect participants' assessment of workload in terms of Mental Demand, Physical Demand, Temporal Demand, Level of Effort, Performance and Level of Frustration based on four primary tasks of the cricothyroidotomy. Additionally, the Technology Acceptance Model survey is used to provide insight into participant's assessment of usability. Professional trainers also provide their assessment of the virtual simulators suitability in support of the combat medics in performing their tasks based on their standards. The results of the participants' assessment of each virtual simulator take the form of a comparison study. To improve the advancement of medical simulation in the training of cricothyroidotomy procedure, a summary of findings, generalized conclusions, lessons learned and recommendations for future research are illuminated. The dissertation team is comprised of medical experts within the U.S. Air Force Education and Training Command, U.S. Army Research and Medical Command, and the Uniformed Services University of the Health Sciences as well as simulation subject matter experts from the University of Central Florida.
Show less - Date Issued
- 2013
- Identifier
- CFE0005142, ucf:50705
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005142
- Title
- An Integrated Framework for Automated Data Collection and Processing for Discrete Event Simulation Models.
- Creator
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Rodriguez, Carlos, Kincaid, John, Karwowski, Waldemar, O'Neal, Thomas, Kaup, David, Mouloua, Mustapha, University of Central Florida
- Abstract / Description
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Discrete Events Simulation (DES) is a powerful tool of modeling and analysis used in different disciplines. DES models require data in order to determine the different parameters that drive the simulations. The literature about DES input data management indicates that the preparation of necessary input data is often a highly manual process, which causes inefficiencies, significant time consumption and a negative user experience.The focus of this research investigation is addressing the manual...
Show moreDiscrete Events Simulation (DES) is a powerful tool of modeling and analysis used in different disciplines. DES models require data in order to determine the different parameters that drive the simulations. The literature about DES input data management indicates that the preparation of necessary input data is often a highly manual process, which causes inefficiencies, significant time consumption and a negative user experience.The focus of this research investigation is addressing the manual data collection and processing (MDCAP) problem prevalent in DES projects. This research investigation presents an integrated framework to solve the MDCAP problem by classifying the data needed for DES projects into three generic classes. Such classification permits automating and streamlining the preparation of the data, allowing DES modelers to collect, update, visualize, fit, validate, tally and test data in real-time, by performing intuitive actions. In addition to the proposed theoretical framework, this project introduces an innovative user interface that was programmed based on the ideas of the proposed framework. The interface is called DESI, which stands for Discrete Event Simulation Inputs.The proposed integrated framework to automate DES input data preparation was evaluated against benchmark measures presented in the literature in order to show its positive impact in DES input data management. This research investigation demonstrates that the proposed framework, instantiated by the DESI interface, addresses current gaps in the field, reduces the time devoted to input data management within DES projects and advances the state-of-the-art in DES input data management automation.
Show less - Date Issued
- 2015
- Identifier
- CFE0005878, ucf:50861
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005878
- Title
- Performance Evaluation of Two Silt Fence Geosynthetic Fabrics During and After Rainfall Event.
- Creator
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Dubinsky, Gregg, Chopra, Manoj, Randall, Andrew, Wang, Dingbao, Gogo-Abite, Ikiensinma, University of Central Florida
- Abstract / Description
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Silt fence is one of the most widely used perimeter control devices and is considered an industry standard for use in the control of sediment transport from construction sites. Numerous research studies have been conducted on the use of silt fence as a perimeter control, including a number of studies involving controlled laboratory flume tests and outdoor tests performed in the field on construction sites with actual monitored storm events. In field tests, due to the random and uncontrollable...
Show moreSilt fence is one of the most widely used perimeter control devices and is considered an industry standard for use in the control of sediment transport from construction sites. Numerous research studies have been conducted on the use of silt fence as a perimeter control, including a number of studies involving controlled laboratory flume tests and outdoor tests performed in the field on construction sites with actual monitored storm events. In field tests, due to the random and uncontrollable nature of real storm events and field conditions, studies have shown difficulty in evaluating silt fence performance. These field studies have shown the need for performance testing of silt fence in a more controlled environment, which can also simulate the actual use and performance in the field. This research, which is a continuation of ongoing research on silt fence fabrics at UCF Stormwater and Management Academy, was conducted in order to evaluate silt fence performance under simulated field conditions. Presented in this thesis are evaluation of two silt fence fabrics, a woven (ASR 1400) fabric and nonwoven (BSRF) fabric. Both fabrics were installed separately on a tilted test bed filled with a silty-sand soil and subjected to simulated rainfall.Previous field studies on the performance of silt fence fabrics have evaluated the turbidity and sediment removal efficiencies only after the rain event, with the assumption that the efficiency values represent the true overall performance of silt fence. The results of this study revealed that the turbidity and suspended sediment performance efficiencies of silt fence were significantly affected by the time of sampling. The performance efficiencies during rainfall remained less than 55 percent, however, after the rainfall event ended, the performance efficiencies increased over time, reaching performance efficiency upwards of 90 percent. The increase in efficiency after rainfall was due to the constant or decreasing ponding depth behind the silt fence, increased filtration due to fabric clogging, and sedimentation of suspended particles.The nonwoven fabric was found to achieve higher removal efficiencies and flow-through rates both during and after the rain event when compared with the woven fabric. However, over the entire test duration (during and after rainfall combined), the projected overall efficiencies of both fabrics were similar. The projected overall average turbidity performance efficiencies of the woven and nonwoven silt fence fabrics was 80 and 78 percent, respectively. Both fabric types also achieved comparable overall average suspended sediment concentration efficiencies of 79 percent. This result leads to the conclusion that silt fence performance in the field is dependent on three main processes: filtration efficiency occurring during the rain event, filtration and sedimentation efficiency occurring after the rainfall event, and flow-through rate of the silt fence fabrics. Decreases in the flow-through rate lead to increases in the overall efficiency. This thesis quantifies the different mechanisms by which these processes contribute to the overall efficiency of the silt fence system and shows how these processes are affected by different conditions such as the degree of embankment slope and rainfall intensity.
Show less - Date Issued
- 2014
- Identifier
- CFE0005158, ucf:50688
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005158
- Title
- A Generic Framework For Multi-Method Modeling and Simulation of Complex Systems Using Discrete Event, System Dynamics and Agent Based Approaches.
- Creator
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Mykoniatis, Konstantinos, Karwowski, Waldemar, Kincaid, John, Xanthopoulos, Petros, Akbas, Ilhan, University of Central Florida
- Abstract / Description
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Decisions about Modeling and Simulation (M(&)S) of Complex Systems (CS) need to be evaluated prior to implementation. Discrete Event (DE), System Dynamics (SD), and Agent Based (AB) are three different M(&)S approaches widely applied to enhance decision-making of complex systems. However, single type M(&)S approaches can face serious challenges in representing the overall multidimensional nature of CS and may result in the design of oversimplified models excluding important factors....
Show moreDecisions about Modeling and Simulation (M(&)S) of Complex Systems (CS) need to be evaluated prior to implementation. Discrete Event (DE), System Dynamics (SD), and Agent Based (AB) are three different M(&)S approaches widely applied to enhance decision-making of complex systems. However, single type M(&)S approaches can face serious challenges in representing the overall multidimensional nature of CS and may result in the design of oversimplified models excluding important factors. Conceptual frameworks are necessary to offer useful guidance for combining and/or integrating different M(&)S approaches. Although several hybrid M(&)S frameworks have been described and are currently deployed, there is limited guidance on when, why and how to combine, and/or integrate DE, SD, and AB approaches. The existing hybrid frameworks focus more on how to deal with specific problems rather than to provide a generic way of applicability to various problem situations.The main aim of this research is to develop a generic framework for Multi-Method Modeling and Simulation of CS, which provides a practical guideline to integrated deployment or combination of DE, SD, and AB M(&)S methods. The key contributions of this dissertation include: (1) a meta-analysis literature review that identifies criteria and generic types of interaction relationships that are served as a basis for the development of a multi-method modeling and simulation framework; (2) a methodology and a framework that guide the user through the development of multi-method simulation models to solve CS problems; (3) an algorithm that recommends appropriate M(&)S method(s) based on the user selected criteria for user defined objective(s); (4) the implementation and evaluation of multi method simulation models based on the framework's recommendation in diverse domains; and (5) the comparison of multi-method simulation models created by following the multi-method modeling and simulation framework.It is anticipated that this research will inspire and motivate students, researchers, practitioners and decision makers engaged in M(&)S to become aware of the benefits of the cross-fertilization of the three key M(&)S methods.
Show less - Date Issued
- 2015
- Identifier
- CFE0005980, ucf:50762
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005980
- Title
- Driving performance adaptation through practice with and without distracters in a simulated environment.
- Creator
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Gentzler, Marc, Smither, Janan, Neider, Mark, Rinalducci, Edward, Mcconnell, Daniel, Ray, Roger, University of Central Florida
- Abstract / Description
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A preponderance of research points to the detrimental effects of distraction on driving performance. An interesting question is whether practice can improve distracted driving. The results from the few longitudinal simulator-based research studies conducted on driving distraction have been inconclusive. This may be because practice effects could be confounded with participants adapting to driving in the simulator. Therefore, participants in the current studies were trained until performance...
Show moreA preponderance of research points to the detrimental effects of distraction on driving performance. An interesting question is whether practice can improve distracted driving. The results from the few longitudinal simulator-based research studies conducted on driving distraction have been inconclusive. This may be because practice effects could be confounded with participants adapting to driving in the simulator. Therefore, participants in the current studies were trained until performance reached a steady state prior to introducing the distracters.In this dissertation, two single-subject design studies were used to investigate the effects of training on distracted driving. The first study included two participants who experienced several different types of distracters. In the second study distracters were introduced before and after the training phase. The two distracters selected for Study 2 included conversing on a handheld phone and texting on a touchscreen phone continuously while driving in a city scenario. Previous research has not compared texting to phone, has had relatively littleexamination of texting and driving alone, and has primarily focused on hands-free phones and on highway settings. Participants drove on a city route which they had previously memorized to add realism to the driving task. Measures collected included speed maintenance, lane deviations/position errors, stop errors, and turn errors in both studies. In Study 2, subjective workload and reaction time were also collected.Findings indicated that training improved performance substantially for all participants in both studies compared to the initial baseline. Participants who experienced six and even nine sessions of the initial baseline did not necessarily improve more than those who only had three sessions. Performance for some participants did not improve in the initial baseline. The lower error levels in training remained fairly stable in subsequent baselines showing that actual learning did occur. Texting had higher error levels than phone both pre and post-training. There were no practice effects noticed for the distracters post-training for any of the participants, and in fact errors increased across sessions for phone and especially texting in Study 2. Training helped improve performance during the phone distraction more so than texting overall, although this varied for different dependent measures. Although errors were reduced after training in the distracter phases, the data actually showed that the performance difference between the baselines and the distracters pre-training was smaller than the differences post-training. Based on these findings, it is recommended that researchers conducting driving simulation research systematically train their participants on driving the simulator before they begin data collection.
Show less - Date Issued
- 2014
- Identifier
- CFE0005169, ucf:50658
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005169
- Title
- Agent-Based and System Dynamics Hybrid Modeling and Simulation Approach Using Systems Modeling Language.
- Creator
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Soyler Akbas, Asli, Karwowski, Waldemar, Geiger, Christopher, Kincaid, John, Mikusinski, Piotr, University of Central Florida
- Abstract / Description
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Agent-based (AB) and system dynamics (SD) modeling and simulation techniques have been studied and used by various research fields. After the new hybrid modeling field emerged, the combination of these techniques started getting attention in the late 1990's. Applications of using agent-based (AB) and system dynamics (SD) hybrid models for simulating systems have been demonstrated in the literature. However, majority of the work on the domain includes system specific approaches where the...
Show moreAgent-based (AB) and system dynamics (SD) modeling and simulation techniques have been studied and used by various research fields. After the new hybrid modeling field emerged, the combination of these techniques started getting attention in the late 1990's. Applications of using agent-based (AB) and system dynamics (SD) hybrid models for simulating systems have been demonstrated in the literature. However, majority of the work on the domain includes system specific approaches where the models from two techniques are integrated after being independently developed. Existing work on creating an implicit and universal approach is limited to conceptual modeling and structure design. This dissertation proposes an approach for generating AB-SD hybrid models of systems by using Systems Modeling Language (SysML) which can be simulated without exporting to another software platform. Although the approach is demonstrated using IBM's Rational Rhapsody(&)#174; it is applicable to all other SysML platforms. Furthermore, it does not require prior knowledge on agent-based or system dynamics modeling and simulation techniques and limits the use of any programming languages through the use of SysML diagram tools. The iterative modeling approach allows two-step validations, allows establishing a two-way dynamic communication between AB and SD variables and develops independent behavior models that can be reused in representing different systems. The proposed approach is demonstrated using a hypothetical population, movie theater and a real(-)world training management scenarios. In this setting, the work provides methods for independent behavior and system structure modeling. Finally, provides behavior models for probabilistic behavior modeling and time synchronization.
Show less - Date Issued
- 2015
- Identifier
- CFE0006399, ucf:51517
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006399
- Title
- Forced Convection Cooling of Electric Motors Using Enhanced Surfaces.
- Creator
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Almaghrabi, Mohammed, Chow, Louis, Kassab, Alain, Das, Tuhin, University of Central Florida
- Abstract / Description
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Electric motors are extensively engaged in industrial and commercial applications such as electrical cars, energy-conversion systems, elevators, and actuators for aircrafts. Due to the significant internal heat generation, it is usually a challenge to design and manufacture high power density, high reliability, and low cost electric motors with superior performance. One of the efficient ways to dissipate the heat generated in the electrical motor is by using extended surfaces (i.e. heat sinks...
Show moreElectric motors are extensively engaged in industrial and commercial applications such as electrical cars, energy-conversion systems, elevators, and actuators for aircrafts. Due to the significant internal heat generation, it is usually a challenge to design and manufacture high power density, high reliability, and low cost electric motors with superior performance. One of the efficient ways to dissipate the heat generated in the electrical motor is by using extended surfaces (i.e. heat sinks). These surfaces are extruded from the motor casing and air is forced though them by a cooling fan. This cooling approach is simple to be implemented and has zero carbon emission to the environment. Adding ribs on the motor extended surface enhances the heat dissipation rate. This project is intended to study numerically the effect of varying ribs spacing and ribs heights on heat removal efficiency, accounting for the relative change in heat transfer coefficient and pressure drop compared to those for a smooth flow channel. The study is conducted to simulate the airflow field, and heat transfer for a plate heat sink using ANSYS V.16.The domain considered in the present work is a simple design of an electric motor annulus. The electric motor annulus consists of an array of ribbed fins. Heat source is represented as a uniform heat flux of 12250 W/m2 at the bottom surface of the heat sink base. Through the simulations, the rib heights (e=0.05, 0.1, 0.2, in mm) and spacing (p=1, 2,3,4,5, in mm) between the ribs, the channel width (Wch= 2 and 6 in mm), and the rib configuration (continues and inline ribs) are varied to study their effect on the performance of the heat sink for a Reynolds number range from 3133 to 12532. To assess which rib configuration is best, a figure of merit (named as thermal-hydraulic performance) is used which is defined as the ratio of heat transfer enhancement to the increase in pumping power due to the presence of the ribs. The highest thermal-hydraulic performance value out of all the transverse cases at Wch=2 mm in this study was 1.07 at e=0.05 mm, p=4 mm, and Re=3133 which means only a 7% enhancement is obtained. These set of cases are suitable for increasing the rate of heat transfer while ignoring the pressure drop penalty. Changing the channel width to 6 mm increases the thermal-hydraulic performance by about 23%. Therefore, this channel width is used for the inline ribs configurations with seven different opening ratios (10% to 70%). The inline ribs are investigated at two different Reynolds number (3133 and 12532). At an opening ratio of 50% the highest thermal-hydraulic performance of 1.18 and 1.22 were found at Re=3133 and p=5 mm, and at Re=3133 and p=1 mm, respectively. These simulation results show that with proper channel and ribs configuration, one can achieve about 22% increase in the thermal-hydraulic performance ratio over that of the smooth channel.
Show less - Date Issued
- 2016
- Identifier
- CFE0006433, ucf:51484
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006433
- Title
- Internet of Things Business Modeling and Analysis using Agent-Based Simulation.
- Creator
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Basingab, Mohammed, Rabelo, Luis, Elshennawy, Ahmad, Lee, Gene, Rahal, Ahmad, University of Central Florida
- Abstract / Description
-
Internet of Things (IoT) is a new vision of an integrated network covering physical objects that are able to collect and exchange data. It enables previously unconnected devices and objects to become connected using equipping devices with communication technology such as sensors and radio frequency identification tags (RFID). As technology progresses towards new paradigm such as IoT, there is a need for an approach to identify the significance of these projects. Conventional simulation...
Show moreInternet of Things (IoT) is a new vision of an integrated network covering physical objects that are able to collect and exchange data. It enables previously unconnected devices and objects to become connected using equipping devices with communication technology such as sensors and radio frequency identification tags (RFID). As technology progresses towards new paradigm such as IoT, there is a need for an approach to identify the significance of these projects. Conventional simulation modeling and data analysis approaches are not able to capture the system complexity or suffer from a lack of data needed that can help to build a prediction. Agent-based Simulation (ABM) proposes an efficient simulation scheme to capture the structure of this dimension and offer a potential solution.Two case studies were proposed in this research. The first one introduces a conceptual case study addressing the use of agent-based simulations to verify the effectiveness of the business model of IoT. The objective of the study is to assess the feasibility of such application, of the market in the city of Orlando (Florida, United States). The second case study seeks to use ABM to simulate the operational behavior of refrigeration units (7,420) in one of largest retail organizations in Saudi Arabia and assess the economic feasibility of IoT implementation by estimating the return on investment (ROI).
Show less - Date Issued
- 2017
- Identifier
- CFE0006855, ucf:51756
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006855
- Title
- A Framework for Measuring Return on Investment for Healthcare Simulation-Based Training.
- Creator
-
Bukhari, Hatim, Rabelo, Luis, Elshennawy, Ahmad, Goldiez, Brian, Andreatta, Pamela, University of Central Florida
- Abstract / Description
-
In the healthcare sector, providing high-quality service in a safe environment for both patient and staff is an obvious and ultimate major objective. Training is an essential component for achieving this important objective. Most organizations acknowledge that employee simulation-based training programs are an important part of the human capital strategy, yet few have effectively succeeded in quantifying the real and precise ROI of this type of investment. Therefore, if the training is...
Show moreIn the healthcare sector, providing high-quality service in a safe environment for both patient and staff is an obvious and ultimate major objective. Training is an essential component for achieving this important objective. Most organizations acknowledge that employee simulation-based training programs are an important part of the human capital strategy, yet few have effectively succeeded in quantifying the real and precise ROI of this type of investment. Therefore, if the training is perceived as a waste of resources and its ROI is not clearly recognized, it will be the first option to cut when the budget cut is needed.The various intangible benefits of healthcare simulation-based training are very difficult to quantify. In addition, there was not a unified way to count for the different cost and benefits to provide a justifiable ROI. Quantifying the qualitative and intangible benefits of medical training simulator needed a framework that helps to identify and convert qualitative and intangible benefits into monetary value so it can be considered in the ROI evaluation.This research is a response to the highlighted importance of developing a comprehensive framework that has the capability to take into consideration the wide range of benefits that simulation-based training can bring to the healthcare system taking into consideration the characteristics of this specific field of investment. The major characteristics of investment in this field include the uncertainty, the qualitative nature of the major benefits, and the diversity and the wide range of applications.This comprehensive framework is an integration of several methodologies and tools. It consists of three parts. The first part of the framework is the benefits and cost structure, which pays special attention to the qualitative and intangible benefits by considering the Value Measurement methodology (VMM) and other previously existing models. The second part of the framework is important to deal with the uncertainty associated with this type of investment. Monte Carlo simulation is a tool that considered multiple scenarios of input sets instead of a single set of inputs. The third part of the framework considers an advanced value analysis of the investment. It goes beyond the discounted cash flow (DCF) methodologies like net present value (NPV) that consider a single scenario for the cash flow to Real Options Analysis that consider the flexibility over the lifetime of the investment when evaluating the value of the investment. This framework has been validated through case studies.
Show less - Date Issued
- 2017
- Identifier
- CFE0006859, ucf:51750
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006859
- Title
- Assessment of Tattoo and Silicone Wounds in Terms of Time of Treatment and Perceived Treatment Quality.
- Creator
-
Pettitt, M, Karwowski, Waldemar, Shumaker, Randall, Cendan, Juan, Sottilare, Robert, University of Central Florida
- Abstract / Description
-
At the point of injury, critical medical tasks include locating and identifying an injury as well as applying the appropriate initial care. Over the past decade, to increase the fidelity of wound representation and ultimately the quality of medical care, a considerable amount of research and development has occurred to improve simulated wounds during training, primarily at the point of injury. As material and techniques mature and as more relevant data is collected on tissue properties,...
Show moreAt the point of injury, critical medical tasks include locating and identifying an injury as well as applying the appropriate initial care. Over the past decade, to increase the fidelity of wound representation and ultimately the quality of medical care, a considerable amount of research and development has occurred to improve simulated wounds during training, primarily at the point of injury. As material and techniques mature and as more relevant data is collected on tissue properties, examining what fidelity is required for training at the point of injury is crucial. The main objective of this effort was to assess a three dimensional silicone wound versus a two dimensional tattoo wound for training and to examine differences in user perceptions and treatment time. This was accomplished with a test population of 158 City of Orlando Fire Department First Responders which were randomly assigned to each group (three dimensional silicone wound group versus a two dimensional tattoo wound group). The data analyses incorporated the use of non-parametric statistics (Mann-Whitney U Test) to compare the differences between the two groups on depth perception, sense of urgency, immersion, and time on task. Other factors that were examined included the costs for the average tattoo wound and silicone wound as well as the number of uses before the synthetic wound is visibly damaged. The data results indicated that at the point of injury, there were relatively few statistically significant differences in the survey data or time on task between the silicone and tattoo wounds. Additionally, the cost analysis revealed that the silicone wound is significantly more expensive than the tattoo wound. Supporting the military and civilian first responder communities, the results of this study provides statistically reliable data on the use of trauma tattoos as a tool for mastering point of injury treatment during training exercises.
Show less - Date Issued
- 2017
- Identifier
- CFE0006904, ucf:51733
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006904
- Title
- Improving Safety under Reduced Visibility Based on Multiple Countermeasures and Approaches including Connected Vehicles.
- Creator
-
Wu, Yina, Abdel-Aty, Mohamed, Lee, JaeYoung, Eluru, Naveen, University of Central Florida
- Abstract / Description
-
The effect of low visibility on both crash occurrence and severity is a major concern in the traffic safety field. Different approaches were utilized in this research to analyze the effects of fog on traffic safety and evaluate the effectiveness of different fog countermeasures. First, a (")Crash Risk Increase Indicator (CRII)(") was proposed to explore the differences of crash risk between fog and clear conditions. A binary logistic regression model was applied to link the increase of crash...
Show moreThe effect of low visibility on both crash occurrence and severity is a major concern in the traffic safety field. Different approaches were utilized in this research to analyze the effects of fog on traffic safety and evaluate the effectiveness of different fog countermeasures. First, a (")Crash Risk Increase Indicator (CRII)(") was proposed to explore the differences of crash risk between fog and clear conditions. A binary logistic regression model was applied to link the increase of crash risk with traffic flow characteristics. Second, a new algorithm was proposed to evaluate the rear-end crash risk under fog conditions. Logistic and negative binomial models were estimated in order to explore the relationship between the potential of rear-end crashes and the reduced visibility together with other traffic parameters. Moreover, the effectiveness of real-time fog warning systems was assessed by quantifying and characterizing drivers' speed adjustments through driving simulator experiments. A hierarchical assessment concept was suggested to explore the drivers' speed adjustment maneuvers. Two linear regression models and one hurdle beta regression model were estimated for the indexes. Also, another driving simulator experiment was conducted to explore the effectiveness of Connected-Vehicles (CV) crash warning systems on the drivers' awareness of the imminent situation ahead to take timely crash avoidance action(s). Finally, a micro-simulation experiment was also conducted to evaluate the safety benefits of a proposed Variable Speed limit (VSL) strategy and CV technologies. The proposed VSL strategy and CV technologies were implemented and tested for a freeway section through the micro-simulation software VISSIM. The results of the above mentioned studies showed the impact of reduced visibility on traffic safety, and the effectiveness of different fog countermeasures.
Show less - Date Issued
- 2017
- Identifier
- CFE0006928, ucf:51704
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006928
- Title
- Network Partitioning in Distributed Agent-Based Models.
- Creator
-
Petkova, Antoniya, Deo, Narsingh, Hughes, Charles, Bassiouni, Mostafa, Shaykhian, Gholam, University of Central Florida
- Abstract / Description
-
Agent-Based Models (ABMs) are an emerging simulation paradigm for modeling complex systems, comprised of autonomous, possibly heterogeneous, interacting agents. The utility of ABMs lies in their ability to represent such complex systems as self-organizing networks of agents. Modeling and understanding the behavior of complex systems usually occurs at large and representative scales, and often obtaining and visualizing of simulation results in real-time is critical.The real-time requirement...
Show moreAgent-Based Models (ABMs) are an emerging simulation paradigm for modeling complex systems, comprised of autonomous, possibly heterogeneous, interacting agents. The utility of ABMs lies in their ability to represent such complex systems as self-organizing networks of agents. Modeling and understanding the behavior of complex systems usually occurs at large and representative scales, and often obtaining and visualizing of simulation results in real-time is critical.The real-time requirement necessitates the use of in-memory computing, as it is dif?cult and challenging to handle the latency and unpredictability of disk accesses. Combining this observation with the scale requirement emphasizes the need to use parallel and distributed computing platforms, such as MPI-enabled CPU clusters. Consequently, the agent population must be "partitioned" across different CPUs in a cluster. Further, the typically high volume of interactions among agents can quickly become a signi?cant bottleneck for real-time or large-scale simulations. The problem is exacerbated if the underlying ABM network is dynamic and the inter-process communication evolves over the course of the simulation. Therefore, it is critical to develop topology-aware partitioning mechanisms to support such large simulations.In this dissertation, we demonstrate that distributed agent-based model simulations bene?t from the use of graph partitioning algorithms that involve a local, neighborhood-based perspective. Such methods do not rely on global accesses to the network and thus are more scalable. In addition, we propose two partitioning schemes that consider the bottom-up individual-centric nature of agent-based modeling. The ?rst technique utilizes label-propagation community detection to partition the dynamic agent network of an ABM. We propose a latency-hiding, seamless integration of community detection in the dynamics of a distributed ABM. To achieve this integration, we exploit the similarity in the process flow patterns of a label-propagation community-detection algorithm and self-organizing ABMs.In the second partitioning scheme, we apply a combination of the Guided Local Search (GLS) and Fast Local Search (FLS) metaheuristics in the context of graph partitioning. The main driving principle of GLS is the dynamic modi?cation of the objective function to escape local optima. The algorithm augments the objective of a local search, thereby transforming the landscape structure and escaping a local optimum. FLS is a local search heuristic algorithm that is aimed at reducing the search space of the main search algorithm. It breaks down the space into sub-neighborhoods such that inactive sub-neighborhoods are removed from the search process. The combination of GLS and FLS allowed us to design a graph partitioning algorithm that is both scalable and sensitive to the inherent modularity of real-world networks.
Show less - Date Issued
- 2017
- Identifier
- CFE0006903, ucf:51706
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006903
- Title
- Determining the Feasibility of using Micro Simulation to asses safety of Pedestrian Crossings.
- Creator
-
Darius, Jenner, Radwan, Essam, Abou-Senna, Hatem, Abdel-Aty, Mohamed, University of Central Florida
- Abstract / Description
-
For the past several decades, pedestrian safety has been an oncoming issue that has thrown the area of transportation engineering into a frenzy. Pedestrian safety has become predominantly one of the leading causes of fatalities in traffic accidents. Florida has been reported as one of the leading states in pedestrian fatalities with 2.56 fatality rate per 100,000 population and about 20 percent of all traffic fatalities in the state of Florida. Nonetheless, as research is being done and...
Show moreFor the past several decades, pedestrian safety has been an oncoming issue that has thrown the area of transportation engineering into a frenzy. Pedestrian safety has become predominantly one of the leading causes of fatalities in traffic accidents. Florida has been reported as one of the leading states in pedestrian fatalities with 2.56 fatality rate per 100,000 population and about 20 percent of all traffic fatalities in the state of Florida. Nonetheless, as research is being done and hypotheses are being calibrated and produced, there has to be a way of measuring and determining the number of pedestrian-to-vehicle conflicts without having to yet apply the system on the field without further validation. Moreover, pedestrian-to-vehicle conflicts have been a rising issue in correlation to the pedestrian fatalities. The fact that the highway safety manual has limited information about crash modification functions for pedestrian and that pedestrian fatality is a rare event, it is worthwhile identifying and adopting surrogate safety measures for pedestrian. Thus, having the capability to analyze various surrogate safety measures within the confines of micro simulation would be a great contribution to real-world application. As a result, the purpose of this thesis is to determine the feasibility of using micro simulation to assess safety of pedestrian crossings using specifically VISSIM and SSAM. During this study, a great deal of data extraction was taken from videotapes collected at nine various intersections, each with its own environmental and geometrical factors. Various parameters were taken from the different sites in order to calibrate and validate VISSIM and SSAM. The parameters included traffic and pedestrian volumes, walking speeds, crossing times, signal timings, and pedestrian-to-vehicle conflicts. During this study, an extensive amount of analysis testing was done in order to obtain the optimum threshold within various combinations of thresholds that would define the pedestrian-to-vehicle conflicts. The analysis was initiated for the time to collision (TTC) and post encroachment time (P.E.T) thresholds. This is done so that the typical scenario of an intersection can be analyzed and comparisons can be made efficiently between observed and simulated conflicts. There were 55 combinations of TTC and PET thresholds produced that were also statistically calculated using the mean absolute percent error (MAPE) in order to determine the most efficient threshold for all 9 intersections. Calibration also was done for parameters in VISSIM that included the safety distance factor (SDF) and the Add-stop distance to assess the sensitivity of these parameters in computing the number of pedestrian-to-vehicle conflicts. These thresholds and factors were used for further validation and assessment of the feasibility of the SSAM and VISSIM model. Data results displayed that the simulated conflicts and the observed conflicts illustrated reasonable correlation. However, even with the feasibility of VISSIM and SSAM being validated, there still are questions that arise pertaining to whether VISSIM and other micro simulation can assess real-world driver behavior and the unpredictability of driver maneuvering. More research with more intersections are recommended to be done.
Show less - Date Issued
- 2016
- Identifier
- CFE0006526, ucf:51379
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006526
- Title
- Analysis of Driving Behavior at Expressway Toll Plazas using Driving Simulator.
- Creator
-
Saad, Moatz, Abdel-Aty, Mohamed, Eluru, Naveen, Lee, JaeYoung, University of Central Florida
- Abstract / Description
-
The objective of this study is to analyze the driving behavior at toll plazas by examining multiple scenarios using a driving simulator to study the effect of different options including different path decisions, various signs, arrow markings, traffic conditions, and extending auxiliary lanes before and after the toll plaza on the driving behavior. Also, this study focuses on investigating the effect of drivers' characteristics on the dangerous driving behavior (e.g. speed variation, sudden...
Show moreThe objective of this study is to analyze the driving behavior at toll plazas by examining multiple scenarios using a driving simulator to study the effect of different options including different path decisions, various signs, arrow markings, traffic conditions, and extending auxiliary lanes before and after the toll plaza on the driving behavior. Also, this study focuses on investigating the effect of drivers' characteristics on the dangerous driving behavior (e.g. speed variation, sudden lane change, drivers' confusion). Safety and efficiency are the fundamental goals that transportation engineering is always seeking for the design of highways. Transportation agencies have a crucial challenging task to accomplish traffic safety, particularly at the locations that have been identified as crash hotspots. In fact, toll plaza locations are one of the most critical and challenging areas that expressway agencies have to pay attention to because of the increasing traffic crashes over the past years near toll plazas.Drivers are required to make many decisions at expressway toll plazas which result in drivers' confusion, speed variation, and abrupt lane change maneuvers. These crucial decisions are mainly influenced by three reasons. First, the limited distance between toll plazas and the merging areas at the on-ramps before the toll plazas. In additional to the limited distance between toll plazas and the diverging areas after the toll plazas at the off-ramps. Second, it is also affected by the location and the configuration of signage and pavement markings. Third, drivers' decisions are affected by the different lane configurations and tolling systems that can cause drivers' confusion and stress. Nevertheless, limited studies have explored the factors that influence driving behavior and safety at toll plazas. There are three main systems of the toll plaza, the traditional mainline toll plaza (TMTP), the hybrid mainline toll plaza (HMTP), and the all-electronic toll collection (AETC). Recently, in order to improve the safety and the efficiency of the toll plazas, most of the traditional mainline toll plazas have been converted to the hybrid toll plazas or the all-electronic toll collection plazas. This study assessed driving behavior at a section, including a toll plaza on one of the main expressways in Central Florida. The toll plaza is located between a close on-ramp and a nearby off-ramp. Thus, these close distances have a significant effect on increasing driver's confusion and unexpected lane change before and after the toll plaza. Driving simulator experiments were used to study the driving behavior at, before and after the toll plaza. The details of the section and the plaza were accurately replicated in the simulator. In the driving simulator experiment, Seventy-two drivers with different age groups were participated. Subsequently, each driver performed three separate scenarios out of a total of twenty-four scenarios. Seven risk indicators were extracted from the driving simulator experiment data by using MATLAB software. These variables are average speed, standard deviation of speed, standard deviation of lane deviation, acceleration rate, standard deviation of acceleration (acceleration noise), deceleration rate, and standard deviation of deceleration (braking action variation). Moreover, various scenario variables were tested in the driving simulator including different paths, signage, pavement markings, traffic condition, and extending auxiliary lanes before and after the toll plaza. Divers' individual characteristics were collected from a questionnaire before the experiment. Also, drivers were filling a questionnaire after each scenario to check for simulator sickness or discomfort. Nine variables were extracted from the simulation questionnaire for representing individual characteristics including, age, gender, education level, annual income, crash experience, professional drivers, ETC-tag use, driving frequency, and novice international drivers. A series of mixed linear models with random effects to account for multiple observations from the same participant were developed to reveal the contributing factors that affect driving behavior at toll plazas. The results uncovered that all drivers who drove through the open road tolling (ORT) showed higher speed and lower speed variation, lane deviation, and acceleration noise than other drivers who navigate through the tollbooth. Also, the results revealed that providing adequate signage, and pavement markings are effective in reducing risky driving behavior at toll plazas. Drivers tend to drive with less lane deviation and acceleration noise before the toll plaza when installing arrow pavement markings. Adding dynamic message sign (DMS) at the on-ramp has a significant effect on reducing speed variation before the toll plaza. Likewise, removing the third overhead sign before the toll plaza has a considerable influence on reducing aggressive driving behavior before and after the toll plaza. This result may reflect drivers' desire to feel less confusion by excessive signs and markings. Third, extending auxiliary lanes with 660 feet (0.125 miles) before or after the toll plaza have an effect on increasing the average speed and reducing the lane deviation and the speed variation at and before the toll plaza. It also has an impact on increasing the acceleration noise and the braking action variation after the toll plaza. Finally, it was found that in congested conditions, participants drive with a lower speed variation and lane deviation before the toll plaza but with a higher acceleration noise after the toll plaza. On the other hand, understanding drivers' characteristics is particularly important for exploring their effect on risky driving behavior. Young drivers (18-25) and old drivers (older than 50 years) consistently showed a higher risk behavior than middle age drivers (35 to 50). Also, it was found that male drivers are riskier than female drivers at toll plazas. Drivers with high education level, drivers with high income, ETC-tag users, and drivers whose driving frequency is less than three trips per day are more cautious and tend to drive at a lower speed.
Show less - Date Issued
- 2016
- Identifier
- CFE0006492, ucf:51391
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006492
- Title
- Light Trapping in Thin Film Crystalline Silicon Solar Cells.
- Creator
-
Boroumand Azad, Javaneh, Chanda, Debashis, Peale, Robert, Del Barco, Enrique, Flitsiyan, Elena, Schoenfeld, Winston, University of Central Florida
- Abstract / Description
-
This dissertation presents numerical and experimental studies of a unified light trapping approach that is extremely important for all practical solar cells. A 2D hexagonal Bravais lattice diffractive pattern is studied in conjunction with the verification of the reflection mechanisms of single and double layer anti-reflective coatings in the broad range of wavelength 400 nm - 1100 nm. By varying thickness and conformity, we obtained the optimal parameters which minimize the broadband...
Show moreThis dissertation presents numerical and experimental studies of a unified light trapping approach that is extremely important for all practical solar cells. A 2D hexagonal Bravais lattice diffractive pattern is studied in conjunction with the verification of the reflection mechanisms of single and double layer anti-reflective coatings in the broad range of wavelength 400 nm - 1100 nm. By varying thickness and conformity, we obtained the optimal parameters which minimize the broadband reflection from the nanostructured crystalline silicon surface over a wide range of angle 0(&)deg;-65(&)deg;. While the analytical design of broadband, angle independent anti-reflection coatings on nanostructured surfaces remains a scientific challenge, numerical optimization proves a viable alternative, paving the path towards practical implementation of the light trapping solar cells. A 3 (&)#181;m thick light trapping solar cell is modeled in order to predict and maximize combined electron-photon harvesting in ultrathin crystalline silicon solar cells. It is shown that the higher charge carrier generation and collection in this design compensates the absorption and recombination losses and ultimately results in an increase in energy conversion efficiency. Further, 20 (&)#181;m and 100 (&)#181;m thick functional solar cells with the light trapping scheme are studied. The efficiency improvement is observed numerically and experimentally due to photon absorption enhancement in the light trapping cells with respect to a bare cell of same thickness.
Show less - Date Issued
- 2017
- Identifier
- CFE0006936, ucf:51654
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006936
- Title
- Quantitative Framework For Social Cultural Interactions.
- Creator
-
Bhatia, Taranjeet, Boloni, Ladislau, Turgut, Damla, Sukthankar, Gita, Fiore, Stephen, University of Central Florida
- Abstract / Description
-
For an autonomous robot or software agent to participate in the social life of humans, it must have a way to perform a calculus of social behavior. Such a calculus must have explanatory power (it must provide a coherent theory for why the humans act the way they do), and predictive power (it must provide some plausible events from the predicted future actions of the humans).This dissertation describes a series of contributions that would allow agents observing or interacting with humans to...
Show moreFor an autonomous robot or software agent to participate in the social life of humans, it must have a way to perform a calculus of social behavior. Such a calculus must have explanatory power (it must provide a coherent theory for why the humans act the way they do), and predictive power (it must provide some plausible events from the predicted future actions of the humans).This dissertation describes a series of contributions that would allow agents observing or interacting with humans to perform a calculus of social behavior taking into account cultural conventions and socially acceptable behavior models. We discuss the formal components of the model: culture-sanctioned social metrics (CSSMs), concrete beliefs (CBs) and action impact functions. Through a detailed case study of a crooked seller who relies on the manipulation of public perception, we show that the model explains how the exploitation of social conventions allows the seller to finalize transactions, despite the fact that the clients know that they are being cheated. In a separate study, we show that how the crooked seller can find an optimal strategy with the use of reinforcement learning.We extend the CSSM model for modeling the propagation of public perception across multiple social interactions. We model the evolution of the public perception both over a single interaction and during a series of interactions over an extended period of time. An important aspect for modeling the public perception is its propagation - how the propagation is affected by the spatio-temporal context of the interaction and how does the short-term and long-term memory of humans affect the overall public perception.We validated the CSSM model through a user study in which participants cognizant with the modeled culture had to evaluate the impact on the social values. The scenarios used in the experiments modeled emotionally charged social situations in a cross-cultural setting and with the presence of a robot. The scenarios model conflicts of cross-cultural communication as well as ethical, social and financial choices. This study allowed us to study whether people sharing the same culture evaluate CSSMs at the same way (the inter-cultural uniformity conjecture). By presenting a wide range of possible metrics, the study also allowed us to determine whether any given metric can be considered a CSSM in a given culture or not.
Show less - Date Issued
- 2016
- Identifier
- CFE0006262, ucf:51047
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006262
- Title
- A Holistic Framework for Effective Engineering Leadership Development Using 3D Virtual World Simulation.
- Creator
-
Almalki, Hamed, Rabelo, Luis, Elshennawy, Ahmad, Lee, Gene, Ferreras, Ana, University of Central Florida
- Abstract / Description
-
Problems associated with the limited success of traditional engineering leadership development are the absence of embedded real-life industry case studies in leadership development and incorrect applications of leadership strategies in the various contexts. Though recommended programs for enhancing leadership development exist, they lack an examined framework, especially when it comes to leadership development of undergraduate engineering students. In this research effort, the impact of a...
Show moreProblems associated with the limited success of traditional engineering leadership development are the absence of embedded real-life industry case studies in leadership development and incorrect applications of leadership strategies in the various contexts. Though recommended programs for enhancing leadership development exist, they lack an examined framework, especially when it comes to leadership development of undergraduate engineering students. In this research effort, the impact of a framework using 3D virtual world simulation and the 4-D Leadership System to enhance the leadership abilities of undergraduate engineering students at the individual and team levels based on industrial leadership case studies was investigated. The 3D virtual world simulation was used to provide experiential learning by replacing human beings with avatars that could be managed or dramatized by real people. This framework was examined and validated by a randomized pretest-posttest control group design. Paired and two-sample t-tests revealed a significant development in the average team leadership skills of the experimental group, but no significant change occurred in the control group teams. There was a reduction in the mean of individuals' tests which indicated there was a small enhancement in an individual's leadership skills; however, the change was small and not statistically significant. Also, the administration of the 3D virtual world leadership simulation on the undergraduate engineering students had a significant effect on a team's average leadership skills. There was a small, but insignificant effect of the 3D virtual world simulation for individuals. The findings of the study supported simulation as having potential to strengthen the leadership development of undergraduate engineering students, thereby preparing them to meet industry's demands for engineering leadership.
Show less - Date Issued
- 2016
- Identifier
- CFE0006248, ucf:51087
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006248
