Aerospace Engineering Commons^™

The Performance Of Quadrilateral Element With Rotational Degrees Of Freedom In Statics And Dynamics Analysis And Optimization, Xingzhi Wang

Mechanical and Aerospace Engineering Theses - Archive

Finite Element Method (FEM) is widely used in structural analysis, and the standard approach to increase the accuracy of analysis is increasing the total degrees of freedom (DOFs), namely, refine the mesh. By introducing the rotational DOFs, better accuracy can be achieved without change the mesh. The objective of this study was to investigate the performance of elements with rotational DOFs in statics and dynamics analysis and applying these elements to optimization. The implementation of three representative elements with rotational DOFs for statics analysis is reproduced. Also, this work implements these elements to dynamics analysis and optimization. The results show …

Computational Study Of Form Factor Of 3rd Generation Open Compute Servers Using Different Dielectric Fluids For Single-Phase Immersion Cooling, Pranavi Rachamreddy

Mechanical and Aerospace Engineering Theses - Archive

Computer system dependency has been increased in the modern world and that has encouraged the rapid growth of data centers in leading business units like banking, education, transportation, social media and many more. Data center is a facility that incorporates an organisation’s IT operations and equipment, as well as where it stores, processes, and manages the data. To fulfil the demands of data storage and data processing, corresponding increase in power density of servers are needed. The data center energy efficiency largely depends on the thermal management of servers. Currently, air cooling is the most widely used thermal management technique …

A New Adaptive Multiscale Approach For The Dynamic Modeling And Simulation Of Biomolecular Systems, Ashley Chase Guy

Mechanical and Aerospace Engineering Dissertations - Archive

This dissertation presents three developments in the simulation of sub-micron dynamical systems. First, a new thermostat formulation is shown to strictly enforce the constant temperature constraint necessary in many thermodynamic ensembles. This formulation also allows the system to quickly evolve to a low-potential state. Next, this new thermostat formulation is leveraged to extend a continuum-regime multiscale formulation to the atomistic regime allowing for equivalent time histories to be generated in significantly less computation time. Finally, an adaptive multiscale formulation allows for potential forces with time varying magnitudes to contribute to the overall dynamics similarly resulting in equivalent time histories in …

Robust Predictive Analytics For Determining Acclimation Parameter Of It Equipment, Premsanth Sadasivam

Mechanical and Aerospace Engineering Theses - Archive

Acclimation is the process in which an IT equipment adjusts to a change in its environment such as a change in temperature and humidity, allowing it to maintain performance across a range of environmental conditions. In commissioning of a new cold shipped IT equipment in data centers, environmental acclimation is an important step. Proper acclimation also minimizes the risk of powering on a machine that may still be wet due to moisture condensation. An experimental study is carried out to find how the acclimation occurs and the factors influencing it. These experiments are designed with various temperature ranges and using …

Vision-Aided Navigation Using Tracked Landmarks, Nicodemus Myhre

Doctoral Dissertations and Master's Theses

This thesis presents vision-based state estimation algorithms for autonomous vehicles to navigate within GPS-denied environments. To accomplish this objective, an approach is developed that utilizes a priori information about the environment. In particular, the algorithm leverages recognizable ‘landmarks’ in the environment, the positions of which are known in advance, to stabilize the state estimate. Measurements of the position of one or more landmarks in the image plane of a monocular camera are then filtered using an extended Kalman filter (EKF) with data from a traditional inertial measurement unit (IMU) consisting of accelerometers and rate gyros to produce the state estimate. …

Experimental Investigation Of Enhanced Damage Resistant Fiber Metal Laminates, Cannelle Metang Tefoung

Doctoral Dissertations and Master's Theses

Fiber metal laminates (FMLs) are hybrid composite structures made from fiber reinforced polymeric materials sandwiched between layers of thin metal alloy sheets. FMLs combine the advantages of metallic materials and fiber reinforced matrix systems. Some of these advantages include: lighter weight, enhanced impact tolerance, improved corrosion resistance, better fire resistance, longer fatigue life, greater tensile strength, easier repair ability and maintainability, etc. The most well-known commercially available FML is GLARE (Glass Laminate Aluminum Reinforced Epoxy), however there are ongoing issues, which include a very high fabrication cost compared to many competing material systems and substantial delamination upon impact and failure. …

Numerical Simulation Of Shock Wave Propagation In Ducts With Grooves, Seyed Mehdi Mortazawy

Doctoral Dissertations and Master's Theses

The pressure attenuation of moving shocks when they propagate in ducts, is of great importance in a wide variety of applications, such as health, safety, and transportation. The objective of this research is to simulate the propagation of shock waves in ducts with roughness. The roughness is added in the form of grooves as in an existing experiment. Different shapes are considered in order to better understand the physics behind the evolution of the complex shock patterns resulting from diffraction, reflection and refraction of the primary moving shock. The contribution of grooves and duct shape on these phenomena and pressure …

Research Of A Non-Linearity Control Algorithm For Uav Target Tracking Based On Fuzzy Logic Systems, Chaoying Pei, Jingjuan Zhang, Xueyun Wang, Qian Zhang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Target tracking is one of the most widely used applications of UAVs and visual based tracking is the main method for non-cooperative tracking. In non-cooperative tracking missions, the UAV circles around the target and the gimbal rotates to keep the optic axis of the onboard camera pointing to the target. Compared with the biaxial gimbal, the single-axis gimbal system consists of only one torque motor, forming a great lightweight sensor suite, which also increases the requirement of the control accuracy. In the process of tracking moving target using a UAV with single-axis gimbal, there are still several challenges: (1) The …

2018 Spring Graduate Recognition Program, Propulsion Research Center, Robert Frederick

PRC Graduate Recognition

This program includes the graduate recognition program for spring 2018. Includes photographs, upcoming events, recent publications, and student profiles.

Ultrasonic Nondestructive Evaluation Of Metal Additive Manufacturing., Venkata Karthik Nadimpalli

Electronic Theses and Dissertations

Metal Additive Manufacturing (AM) is increasingly being used to make functional components. One of the barriers for AM components to become mainstream is the difficulty to certify them. AM components can have widely different properties based on process parameters. Improving an AM processes requires an understanding of process-structure-property correlations, which can be gathered in-situ and post-process through nondestructive and destructive methods. In this study, two metal AM processes were studied, the first is Ultrasonic Additive Manufacturing (UAM) and the second is Laser Powder Bed Fusion (L-PBF). The typical problems with UAM components are inter-layer and inter-track defects. To improve the …

The Future Of Construction As It Applies To The Colonization Of The Moon And Mars, Julian Prestia

UNLV Theses, Dissertations, Professional Papers, and Capstones

The goals of this research are:

1. To compile a comprehensive list of all the viable known solutions (and early stage potential solutions) to the issues related to constructing permanent, sustainable, and safe structures for human colonies on our moon and Mars,

2. Determine the most effective potential solutions, and

3. Further develop these ideas as to assist in further space endeavors.

This proposed paper will assist space experts in determining the best next steps in the development of deep-space travel and colonization technologies. Preliminary research has identified several key problems associated with establishing space colonies. They are as follows: …

Thrust Augmented Nozzle For A Hybrid Rocket With A Helical Fuel Port, Joel H. Marshall

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A thrust augmented nozzle for hybrid rocket systems is investigated. The design lever-ages 3-D additive manufacturing to embed a helical fuel port into the thrust chamber of a hybrid rocket burning gaseous oxygen and ABS plastic as propellants. The helical port significantly increases how quickly the fuel burns, resulting in a fuel-rich exhaust exiting the nozzle. When a secondary gaseous oxygen flow is injected into the nozzle downstream of the throat, all of the remaining unburned fuel in the plume spontaneously ignites. This secondary reaction produces additional high pressure gases that are captured by the nozzle and significantly increases the …

A Novel Magnetorheological Fluid Damper For A Small Spacecraft With Flexible Appendages, Robert Waelchli

Doctoral Dissertations and Master's Theses

Small satellites have become increasingly popular over the past thirty years, particularly since the adoption of the common CubeSat architecture early this century. Because of their restricted volume and electrical budgets however, there are practical limits to the missions that small satellites may adopt. One potential near-term solution to the problem of limited electrical power may be the adoption of larger, flexible solar arrays. However, spacecraft with flexible appendages have historically presented attitude control challenges relating to platform stability given the dynamic response of the flexible components to applied torques. These challenges may be particularly disruptive to a small spacecraft …

Propulsive Battery Packs Sizing For Aviation Applications, Tianyuan Zhao

Doctoral Dissertations and Master's Theses

This thesis derives analytical methods for sizing the propulsive battery packs for designing an electric-driven aircraft. Lithium-Ion (Li-Ion) battery is the primary choice of battery cell chemistry in this thesis research due to its superior specific energy and market availability. The characteristics of Lithium-Ion battery cells are first determined and studied using experimental test results and manufacturers published data. Based on the design requirement to the battery system, the battery sizing will fall into one of the two sizing categories. The first category is power sizing, which requires the battery’s ability to deliver full power demanded by the electric motor. …

Development Of A Small Unmanned Aerial Vehicle Longitudinal Model For Future Flutter Testing, Said S. Hamada

Doctoral Dissertations and Master's Theses

This thesis presents the system identification of the longitudinal motion of a small unmanned aerial vehicle with flexible characteristics. The unmanned aerial vehicle of study is an off-the-shelf aircraft with limited knowledge about the dynamic model. The first task in obtaining a model for flutter testing is determining the rigid body model. Specifically, this thesis will focus in the development of the aircraft and obtaining the longitudinal rigid body model. This involves the assembly and configuration of the avionics and sensors, performing experiments to determine mass and inertia properties and using software tools for aerodynamic analysis to get preliminary values …

An Underwater Vehicle Navigation System Using Acoustic And Inertial Sensors, Khalid M. Alzahrani

Doctoral Dissertations and Master's Theses

Unmanned Underwater Vehicles (UUVs) have become an essential tool for different underwater tasks. Compared with other unmanned systems, the navigation and localization for UUVs are particularly challenging due to the unavailability of Global Positioning System (GPS) signals underwater and the complexity of the unstable environment. Alternative methods such as acoustic positioning systems, Inertial Navigation Systems (INS), and the geophysical navigation approach are used for UUV navigation. Acoustic positioning systems utilize the characteristics of acoustic signals that have a lower absorption rate and a more extended propagation distance than electromagnetic signals underwater. The significant disadvantage of the INS is the “drift,” …

Homography-Based State Estimation For Autonomous Exploration In Unknown Environments, Andres S. Chavez Armijos

Doctoral Dissertations and Master's Theses

This thesis presents the development of vision-based state estimation algorithms to enable a quadcopter UAV to navigate and explore a previously unknown GPS denied environment. These state estimation algorithms are based on tracked Speeded-Up Robust Features (SURF) points and the homography relationship that relates the camera motion to the locations of tracked planar feature points in the image plane. An extended Kalman filter implementation is developed to perform sensor fusion using measurements from an onboard inertial measurement unit (accelerometers and rate gyros) with vision-based measurements derived from the homography relationship. Therefore, the measurement update in the filter requires the processing …

Feasibility Study Of A Multi-Purpose Aircraft Concept With A Leading-Edge Cross-Flow Fan, Stanislav Karpuk

Doctoral Dissertations and Master's Theses

A wing-embedded Cross-Flow Fan (CFF) was first proposed as an active flow control (AFC) device nearly 40 years ago. The CFF can be employed as a propulsion device as well as a high-lift system. This thesis research focuses on investigating the use of CFF as a high-lift device for an Extremely Short Take-off and Landing (ESTOL) aircraft. The wing-embedded CFF performance analysis is mostly addressed from an aerodynamic perspective and focuses on using such AFC technology in the conceptual aircraft design process. In particular, the design trade study of an aircraft featuring CFF as a high-lift device applied to a …

The Measurement Of The Adhesion Of Glaze Ice., Andrew Hardesty Work Jr.

Electronic Theses and Dissertations

Icing is a lethal and costly aviation hazard affecting aircraft of all sizes ranging from small UAVs to large commercial craft such as the Boeing 787, resulting in hundreds of deaths over the last century and resulting in billions of dollars of economic impact. Three predominant types of icing, namely, airframe icing, engine icing, and rotorcraft icing, dominate aircraft icing research. Each type poses unique challenges. In the case of rotor icing, attention needs to give to the rotating environment with large oscillatory loads and icing conditions. In the case of airframe icing, special attention needs to be paid to …

Modeling And Control Of A 6-Dof Multi-Rotorcraft: Air-Ball, Jerry Ja Wang

Theses and Dissertations

The Air-Ball project seeks to develop an omnidirectional, unmanned aerial vehicle with six degrees of freedom. The Air-Ball vehicle uses six propellers powered by six independent electric motors for propulsion and control. Each motor is attached to a hollow shaft that can rotate ±360° actuated by electric servos. Four of these propulsion shafts are configured in an orientation resembling a quad-copter, where the shafts are 90° apart. The other two propulsion shafts extrude perpendicular from each side of the plane of the quadcopter configuration. Under this unique configuration, Air-Ball is capable of decoupling the motion in the translational and rotational …