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Articles 91 - 105 of 105
Full-Text Articles in Physical Sciences and Mathematics
A 3-D Model Of The Auroral Ionosphere, Yishi Lee
A 3-D Model Of The Auroral Ionosphere, Yishi Lee
Doctoral Dissertations and Master's Theses
A new 3-D model of the high latitude ionosphere is developed to study the coupling of the ionosphere with the magnetosphere and neutral atmosphere. The model consists of equations describing conservations of mass, momentum and energy for the six ionospheric constituents (O+, NO+, N+2 , O+2 , N+ and e-) and an electrostatic potential equation. This 3-D model is used to examine interrelated processes of ion heating, plasma structuring due to perpendicular transport, ion upflow, molecular ion generation, and neutral wave forcing. It is first validated by comparisons with a 2-D model, which uses similar mathematical and numerical approaches, and …
Relating Air Quality In The Work Environment To Occupational Health Disease, Hussien Awad Alumar
Relating Air Quality In The Work Environment To Occupational Health Disease, Hussien Awad Alumar
Doctoral Dissertations and Master's Theses
Comprehensive knowledge of the air pollutants effects on the human health generally is a crucial requirement in developing effective policies for reducing such adverse effects related to ambient air pollution. Such knowledge would be essential in helping various affected countries, including the less developed countries (LDCs), to develop effective regulatory frameworks for assessing and managing air quality in the workplaces. Developed and developing countries therefore need to develop effective techniques or strategies focused towards improving the workplace monitoring competence in diverse industrial environments. Such initiatives are essential in reducing or eliminating the industrial pollutants within the workplaces while also helping …
Investigation Of A Lagrangian-Point Propellant Depot Rendezvous Approach For An Interplanetary Mission To Mars, Joshua W. Ehrlich
Investigation Of A Lagrangian-Point Propellant Depot Rendezvous Approach For An Interplanetary Mission To Mars, Joshua W. Ehrlich
Doctoral Dissertations and Master's Theses
This thesis investigates the feasibility of a refueling station for a beyond Earth orbit (BEO) mission. The propellant depot is located at the L2 -Lagrangian point within the Earth-Moon system. This investigation determines if a refueling mission will reduce propulsive energy requirements necessary for Earth departure of a BEO-vehicle to achieve an interplanetary transfer to Mars. Furthermore, this research presents a trade study which identifies approximate total requirements for a direct and rendezvous mission to Mars as well as the necessary fuel masses to complete each approach. This analysis provides conclusive information in determining the benefits in utilizing a …
Numerical Modeling Of Anti-Icing Using An Array Of Heated Synthetic Jets, Nikisha Maria Nagappan
Numerical Modeling Of Anti-Icing Using An Array Of Heated Synthetic Jets, Nikisha Maria Nagappan
Doctoral Dissertations and Master's Theses
A novel approach to icing control using an array of thermally activated synthetic jet actuators (SJAs) embedded in a wedge surface subject to a super-cooled flow is investigated numerically. The effects of SJA actuation with and without jet heating on ice accretion are studied using the FENSAP-ICE software. It is shown that the heated actuating SJAs can lead to a significant reduction in the amount of ice accreted on the surface. Additional parametric studies on several icing and SJA parameters are analyzed for their influence on the amount of ice accretion.
Robust Control Methods For Nonlinear Systems With Uncertain Dynamics And Unknown Control Direction, Chau T. Ton
Robust Control Methods For Nonlinear Systems With Uncertain Dynamics And Unknown Control Direction, Chau T. Ton
Doctoral Dissertations and Master's Theses
Robust nonlinear control design strategies using sliding mode control (SMC) and integral SMC (ISMC) are developed, which are capable of achieving reliable and accurate tracking control for systems containing dynamic uncertainty, unmodeled disturbances, and actuator anomalies that result in an unknown and time-varying control direction. In order to ease readability of this dissertation, detailed explanations of the relevant mathematical tools is provided, including stability denitions, Lyapunov-based stability analysis methods, SMC and ISMC fundamentals, and other basic nonlinear control tools. The contributions of the dissertation are three novel control algorithms for three different classes of nonlinear systems: single-input multipleoutput (SIMO) systems, …
Nonlinear Control For Dual Quaternion Systems, William D. Price
Nonlinear Control For Dual Quaternion Systems, William D. Price
Doctoral Dissertations and Master's Theses
The motion of rigid bodies includes three degrees of freedom (DOF) for rotation, generally referred to as roll, pitch and yaw, and 3 DOF for translation, generally described as motion along the x, y and z axis, for a total of 6 DOF. Many complex mechanical systems exhibit this type of motion, with constraints, such as complex humanoid robotic systems, multiple ground vehicles, unmanned aerial vehicles (UAVs), multiple spacecraft vehicles, and even quantum mechanical systems. These motions historically have been analyzed independently, with separate control algorithms being developed for rotation and translation. The goal of this research is to study …
Identification And Classification Of Stratospheric Sudden Warming Events, Thomas S. Ehrmann
Identification And Classification Of Stratospheric Sudden Warming Events, Thomas S. Ehrmann
Doctoral Dissertations and Master's Theses
Analysis of northern hemisphere stratospheric data from 1978-2011 is used to identify and classify Stratospheric Sudden Warming events. A total of 41 events are identified during this 33 year period, resulting in an average occurrence rate of 1.24 events/year. No significant variation in the rate is observed during the period analyzed. The average temperature increase during an SSW event is 12 K and the average duration is 32 days. Each identified event is classified as either a vortex displacement or split event and the ratio of displacement to split events is found to be 0.86.
A Gap Analysis Of Meteorological Requirements For Commercial Space Operators, Nicholas Stapleton
A Gap Analysis Of Meteorological Requirements For Commercial Space Operators, Nicholas Stapleton
Doctoral Dissertations and Master's Theses
Commercial space companies will soon be the primary method of launching people and supplies into orbit. Among the critical aspects of space launches are the meteorological concerns. Laws and regulations pertaining to meteorological considerations have been created to ensure the safety of the space industry and those living around spaceports; but, are they adequate? Perhaps the commercial space industry can turn to the commercial aviation industry to help answer that question. Throughout its history, the aviation industry has dealt with lessons learned from mishaps due to failures in understanding the significance of weather impacts on operations. Using lessons from the …
Identifying Signatures Of Plasma Waves And Reconnection Associated With Kelvin-Helmholtz Activity, Thomas Wesley Moore
Identifying Signatures Of Plasma Waves And Reconnection Associated With Kelvin-Helmholtz Activity, Thomas Wesley Moore
Doctoral Dissertations and Master's Theses
The magnetopause marks the boundary between the shocked solar wind and magnetospheric plasma. Understanding the dynamics of the plasma processes at the magnetopause boundary is crucial to the study of plasma transport into the magnetosphere. Previous studies have shown that there exists a temperature asymmetry in the plasma sheet. During northward IMF, the cold component ions are 30-40% hotter in the dawn flank plasma sheet compared to the dusk flank. However, the mechanisms responsible are still not entirely clear. Recent work has shown that reconnection in Kelvin-Helmholtz vortices can transport plasma into the magnetosphere. Previous studies have also shown that …
Evaluating The Effect Of Smart Parking Technology On Campus Parking System Efficiency Using Discrete Event Simulation, Glenn Phillip Surpris
Evaluating The Effect Of Smart Parking Technology On Campus Parking System Efficiency Using Discrete Event Simulation, Glenn Phillip Surpris
Doctoral Dissertations and Master's Theses
This study was conducted to investigate the effect of smart parking systems (SPS) on parking search times (PST) in large parking lots. SPSs are systems that disseminate real-time parking spot availability to drivers searching for parking. The literature review revealed discrete event simulation (DES) to be a suitable tool for studying the dynamic behavior in parking lots. The parking lot selected for data collection was a university parking lot with 234 spaces. The data collected included arrival rates, departure rates, the geometric properties of the parking lot, preferred parking search strategies, and driving speeds. Arena 13.9, by Rockwell Automation, Inc, …
Assessing The Effects Of Climate Change And Addressing Solutions At L. F. Wade International Airport, Bermuda, Sebastian Romeo Phillip Brisson
Assessing The Effects Of Climate Change And Addressing Solutions At L. F. Wade International Airport, Bermuda, Sebastian Romeo Phillip Brisson
Doctoral Dissertations and Master's Theses
The purpose of this thesis was to find how past trends and future predictions of climate change and associated factors would affect airport operations at the L. F. Wade International Airport. The Government of Bermuda's plans to build a new terminal were also analyzed to determine potential impacts. Predicted future trends of sea level rise and hurricane activity were assessed by analyzing previous occurrences and studies and depicted using GIS mapping data. Risk of storm surge to the L. F. Wade International Airport has become apparent, especially after Hurricane Fabian of 2003. The results of this study suggest that the …
The Effects Of Eye Gaze Based Control On Operator Performance In Monitoring Multiple Displays, Allison Popola
The Effects Of Eye Gaze Based Control On Operator Performance In Monitoring Multiple Displays, Allison Popola
Doctoral Dissertations and Master's Theses
This study investigated the utility and efficacy of using eye tracking technology as a method for selecting control of a camera within a multiple display configuration. A task analysis with a Keystroke-Level-Model (KLM) was conducted to acquire an estimated time for switching between cameras. KLM estimates suggest that response times are faster using an eye tracker than manual control -indicating a time savings. To confirm these estimates, and test other hypotheses a 2 × 2 within-subjects factorial design was used to examine the effects of Control (Using an eye tracker, or manual) under different Task Loads (Low, High). Dependent variables …
Fabry-Perot Observations Of Midlatitude Neutral Winds And Atmospheric Gravity Wave Activity, Marjory Anne Katon
Fabry-Perot Observations Of Midlatitude Neutral Winds And Atmospheric Gravity Wave Activity, Marjory Anne Katon
Doctoral Dissertations and Master's Theses
The mesosphere and lower thermosphere displays a wide range of dynamical phenomena resulting in a complex and variable regions. Governed primarily by fluid dynamics, the motion of the upper atmosphere is modulated by a number of atmospheric waves propagating upward from various sources in the lower atmosphere. Among these are atmospheric gravity waves which have been recognized as a major source of momentum and energy in the mesosphere and lower thermosphere as well as a major factor in the dynamic coupling between the troposphere and lower thermosphere. A Fabry-Perot interferometer possessed by the Space Physics Research Laboratory at the Embry-Riddle …
Identifying An Optimal Dining Plan System For The Entertainment Industry, Joseph Crimi
Identifying An Optimal Dining Plan System For The Entertainment Industry, Joseph Crimi
Doctoral Dissertations and Master's Theses
The Disney Dining Plan (DDP) is a pre-paid meal plan guests can purchase when they make their reservation at Walt Disney World (WDW). Under the current system, the information provided to guests explaining the program is unclear which leads to confusion for guests. For example, guests are not sure what food they can purchase using the DDP or at which dining locations they can use the DDP. Given these problems, the present study evaluated a new information system for the DDP. The independent variables in this study were symbol type, the symbols used in the current DDP and new symbols …
Translational And Rotational Control Of An Asteroid Orbiting Satellite, Takahiro Kuhara
Translational And Rotational Control Of An Asteroid Orbiting Satellite, Takahiro Kuhara
Doctoral Dissertations and Master's Theses
The objective of this thesis is to analyze an effective control scheme for an asteroid orbiting satellite. The thesis first summarizes the progress made in the dynamics formulation of such satellites and then provides a theoretical framework for the control system design. The control objective is to maintain a nadir pointing attitude on a circular equatorial orbit. Using established control design techniques, feedback laws are constructed to control both rotational and translational motion of the satellite so that the control objective is achieved. Computer simulations are carried out to illustrate the effectiveness of the control laws.