Engineering Commons^™

A Mathematical Framework For Unmanned Aerial Vehicle Obstacle Avoidance, Sorathan Chaturapruek

HMC Senior Theses

The obstacle avoidance navigation problem for Unmanned Aerial Vehicles (UAVs) is a very challenging problem. It lies at the intersection of many fields such as probability, differential geometry, optimal control, and robotics. We build a mathematical framework to solve this problem for quadrotors using both a theoretical approach through a Hamiltonian system and a machine learning approach that learns from human sub-experts' multiple demonstrations in obstacle avoidance. Prior research on the machine learning approach uses an algorithm that does not incorporate geometry. We have developed tools to solve and test the obstacle avoidance problem through mathematics.

Nonlinear Dynamics And Anisotropic Structure Of Rotating Sheared Turbulence, Abdelaziz Salhi, Frank G. Jacobitz, Kai Schneider, Claude Cambon

School of Engineering: Faculty Scholarship

Homogeneous turbulence in rotating shear flows is studied by means of pseudospectral direct numerical simulation and analytical spectral linear theory (SLT). The ratio of the Coriolis parameter to shear rate is varied over a wide range by changing the rotation strength, while a constant moderate shear rate is used to enable significant contributions to the nonlinear interscale energy transfer and to the nonlinear intercomponental redistribution terms. In the destabilized and neutral cases, in the sense of kinetic energy evolution, nonlinearity cannot saturate the growth of the largest scales. It permits the smallest scale to stabilize by a scale-by-scale quasibalance between …

Design And Evaluation Of A Propulsion System For Small, Compact, Low-Speed Maneuvering Underwater Vehicles, Florence M. Mbithi

Electronic Theses and Dissertations

Underwater vehicles used to perform precision inspection and non-destructive evaluation in tightly constrained or delicate underwater environments must be small, have low-speed maneuverability and a smooth streamlined outer shape with no appendages. In this thesis, the design and analysis of a new propulsion system for such underwater vehicles is presented. It consists primarily of a syringe and a plunger driven by a linear actuator and uses different inflow and outflow nozzles to provide continuous propulsive force. A prototype of the proposed propulsion mechanism is built and tested. The practical utility and potential efficacy of the system is demonstrated and assessed …

Sweeping Langmuir Probe (Slp) Of The Storms Sounding Rocket Mission, Padmashri Suresh, Charles Swenson

Browse all Datasets

On October 30, 2007 NASA launched rocket 36.218 carrying the mission: “Investigation of Mid Latitude Ionospheric Irregularities Associated with Terrestrial Weather Systems” also known as the STORMS Mission. The rocket was launched from Wallops Island, Virginia (37.95◦ N, 284.53◦ E, 67.5◦ dip angle) at twelve minutes past local midnight. It flew along an azimuth of 114◦ and reached apogee near 394 km. The rocket payload had a suite of instruments from Utah State University/Space Dynamic Lab (USU/SDL) and University of Texas, Dallas (UTD), for making in-situ electron density, wind and electric field measurements.

The Sweeping Langmuir Probe or SLP was …

Airmen With Mild Traumatic Brain Injury (Mtbi) At Increased Risk For Subsequent Mishaps, Casserly R. Whitehead, Timothy S. Webb, Timothy S. Wells, Kari L. Hunter

United States Air Force: Publications

Background: Little is known regarding long-term performance decrements associated with mild Traumatic Brain Injury (mTBI). The goal of this study was to determine if individuals with an mTBI may be at increased risk for subsequent mishaps. Methods: Cox proportional hazards modeling was utilized to calculate hazard ratios for 518,958 active duty U.S. Air Force service members (Airmen) while controlling for varying lengths of followup and potentially confounding variables. Two non-mTBI comparison groups were used; the second being a subset of the original, both without head injuries two years prior to study entrance. Results: Hazard ratios indicate that the causes of …

Thermal Conduction And Heat Generation Phenomena In Li-Ion Cells, Stephen Drake

Mechanical and Aerospace Engineering Dissertations - Archive

Cylindrical lithium ion (Li-ion) cells have demonstrated high power density and energy capacity among other energy storage devices. Despite their already widespread use, the thermal transport properties of cylindrical Li-ion batteries are not well documented and understood, while a sizable amount of work has been carried out for electrical, electrochemical, and materials optimization of Li-ion cells. These thermal phenomena are particularly important for high discharge rate batteries. With this uncertainty, if thermophysical properties are not accounted for in thermal models, the result may be a significant under-prediction or over-prediction of the temperature field in a Li-ion cell.Experimental techniques are described …

Unsteady Thrust Measurement Techniques For Pulse Detonation Engines, Dibesh Dhoj Joshi

Mechanical and Aerospace Engineering Dissertations - Archive

Thrust is a critical performance parameter and its correct determination is necessary to characterize an engine. Many conventional thrust measurement techniques prevail. However, further developments are required for correct measurement of thrust in the case of a pulse detonation engine (PDE), since the entire thrust generation process is intermittent. The significant effect of system dynamics in the form of inertial forces, stress wave propagation and reflections initiated in the structure due to detonations and pulse-to-pulse interaction in a fast operating PDE further complicate the thrust measurement process. These complications call for a further, detailed study of the unsteady thrust characteristics. …

Experimental Investigation Of Nucleate Boiling And Thin-Film Evaporation On Enhanced Silicon Surfaces, Shailesh Malla

Mechanical and Aerospace Engineering Dissertations - Archive

The present work consists of two major studies. The first study investigates the effects of surface energy or wettability on nucleate pool boiling and the second study investigates the thin-film evaporative cooling for near junction thermal management. For the first study, effects of surface energy or wettability on critical heat flux (CHF) and boiling heat transfer (BHT) of smooth heated surfaces was studied in saturated pool boiling of water at 1 atm. For this purpose hydrophilic and hydrophobic surfaces were created on one side of 1cm x 1cm double-side polished silicon substrates. A resistive heating layer was applied on the …

Degradation Mechanics Of Bone And Bone Like Materials Via Multiscale Analysis, Md Farzad Sarker

Mechanical and Aerospace Engineering Dissertations - Archive

Bone fracture is a common health risk for older people suffering from bone disease like osteoporosis. The more severe the osteoporosis is the more structural degradation in bones occurs, which eventually makes bones more fracture prone. The mechanical behavior of bone depends on the structural response of bone constituents over a broad range of length scales spanning from the nanoscale collagen fibril level to the macroscale trabeculae level. As such, in order to understand bone fracture, it is important to know the structure-property relations of bone material over the entire length of scale. Surprisingly, a quantitative understanding of bone fracture …

Wind Field Estimation And Its Utilization In Trajectory And Input Prediction, Jane-Wit Kampoon

Mechanical and Aerospace Engineering Dissertations - Archive

This dissertation work develops a method for onboard estimation of wind field with spatial and temporal variation based on local wind vector estimation and/or measurements from multiple aircraft flying in the same airspace. Aircraft flying in the same airspace of operation are considered airborne wind sensors scattered over the airspace because of the fact that aircraft carry along with them wind information inherent in their dynamics and kinematics. The onboard wind field estimation is formulated in the framework of parameter estimation based on various wind field models, which are different function of position and time. The online wind field estimation …

Electrowetting On Dielectric Digital Microfluidics For 3-Dimensional Cell Culture And Chemical Screening, Subin Mac George

Mechanical and Aerospace Engineering Dissertations - Archive

Microfluidic devices have allowed improved cell culture studies to be carried out by allowing greater spatiotemporal control over the cell environment while at the same time providing greater throughput, increased automation capabilities and reagent savings. To improve the relevancy of such studies, 3-dimensional (3D) cell culture has been attempted in microfluidic devices. 3D cell culture is known to better mimic and recreate the environment that cells in the body experience as compared to conventional 2-dimensional cell culture. However, incorporating 3D cell culture into conventional channel based microfluidic devices have proven to be challenging. Hydrogels which provide the 3D environment in …

Modeling, Estimation, And Analysis Of Unresolved Space Object Tracking And Identification, Laura Suarez Henderson

Mechanical and Aerospace Engineering Dissertations - Archive

The problem of orbit determination along with shape determination is significant. The orbit determination problem has been tackled for centuries by some of the greatest mathematicians and physicists. The issue of shape determination of space objects, although more recent, has also been addressed quite extensively. Nevertheless, these problems remain of great interest in the scientific and engineering community, and are addressed in this work. The greatest motivation for the tracking and identification of Earth orbiting objects is the ever-increasing population of space assets and man-made debris. It is of interest to implement new and better techniques to track and identify …

Investigation Of Wetting States On Microstructures After Liquid Drops Contact Groove Base, Mingming Xiang

Mechanical and Aerospace Engineering Dissertations - Archive

Wetting properties of roughness surfaces have attracted a considerable attention because of both the scientific insight and the practical applications. One of the most intriguing topics of wetting is the so-called Cassie-Baxter and Wenzel transition. Recently, theoretical and experimental works have been done to explore this transition on microstructure-formed surfaces. One of the criteria that most commonly used to judge such transition is whether a liquid drop contacts the base of a roughness groove. It is expected that, after the contact, liquid immediately fills the roughness groove, and subsequently the wetting state is changed from Cassie-Baxter state to that of …

Thermal Design Of Lithium Bromide-Water Solution Vapour Absorption Cooling System For Indirect Evaporative Cooling For It Pod, Digvijay Ramkrishna Sawant

Mechanical and Aerospace Engineering Theses - Archive

Supervising Professor: Dereje Agonafer Nowadays with increase use of internet, mobile there is increase in heat which ultimately increases the efficient cooling system of server room or IT POD. Use of traditional ways of cooling system has ultimately increased CO? emission and depletion of CFC's are serious environmental issues which led scientific people to improve cooling techniques and eliminate use of CFC's. To reduce dependency on fossil fuels and 4environmental friendly system needed to be design. For being utilizing low grade energy source such as solar collector and reducing dependency on fossil fuel vapour absorption cooling system has shown a …

Finite Element Based Methodology For Prediction Of Matrix-Dominated Failure In Composites, Guillaume Seon

Mechanical and Aerospace Engineering Dissertations - Archive

The objective of this work is to develop a computational failure prognosis methodology applicable to virtual testing of composites. The major motivation for the establishment of virtual testing is the ability to reduce actual testing of composite structures, which is oftentimes expensive and time consuming, by numerical simulations. A successful virtual test methodology should be applicable to monotonic and fatigue loading, account for strong anisotropy of composite materials and capture the effects of manufacturing irregularities. This work proposes to use three-dimensional finite element modelling for predicting the onset and progression of matrix-dominated failures modes, such as matrix cracks and delaminations, …

Improving Ducting To Increase Cooling Performance Of High-End Web Servers Subjected To Signicant Thermal Shadowing -An Experimental And Computational Study, Divya Mani

Mechanical and Aerospace Engineering Theses - Archive

Ensuring that all the critical components like CPU's receive sufficient amount of flow as per their requirement is an vital importance in implementing air cooling for IT equipments. In addition to that the overall system resistance varies with the component location with in the chassis. In this study, parametric improvement in chassis ducting system is made to counteract the effects of thermal shadowing in a open compute air cooled server in which a CPU thermally shadows the other. Commercially available computational fluid dynamics codes have permitted simulation of server models to predict efficiency of the servers with every changes made …

Analytical And Experimental Investigation Of Thermal Transport In Three-Dimensional Integrated Circuits (3d Ics), Leila Choobineh

Mechanical and Aerospace Engineering Dissertations - Archive

Thermal management of three-dimensional integrated circuits (3D ICs) is recognized to be one of the foremost technological and research challenges currently blocking the widespread adoption of this promising technology. The computation of steady-state temperature fields in a 3D IC is critical for determining the thermal characteristics of a 3D IC and for evaluating any candidate thermal management technology. An analytical solution for the three-dimensional temperature field in a 3D IC based on solution of the governing energy equations using Fourier series expansion for steady-state temperature fields is studied. Comparison of the predicted temperature fields with finite-element simulation shows excellent agreement. …

Effect Of Warm Water Cooling For An Isolated Hybrid Liquid Cooled Server, Alekhya Addagatla

Mechanical and Aerospace Engineering Theses - Archive

Data center cooling strategies have changed overtime due to increases in power densities and ever increasing server cooling power requirement. Traditionally, most data centers adopt air cooling where the Computer Room Air Conditioning (CRAC) units pump volumes of chilled air to cool information technology (IT) equipment and dispose the heat from the servers to the ambient. With demand for energy-efficient and cost-effective data centers growing, alternative methods to both provide electrical power and cooling systems are the subject of active investigation. As data centers increase in size and current air-cooling systems reach their limitations, cooling technology will inevitably evolve towards …

A New Multiscale Approach For Dynamic Modeling And Simulation Of Micro-Nano Biomolecular Systems Characterized By A Low Reynolds Number, Mahdi Haghshenas-Jaryani

Mechanical and Aerospace Engineering Dissertations - Archive

In this dissertation, a new multiscale computational framework was developed in order to model and simulate motility of micro-nano-sized objects in fluid environments, characterized with a low Reynolds number. Especially, it has been used for studying the dynamic behavior of biomolecular systems such as motor proteins inside cells.Long simulation run time is one of the most important issues in modeling of cellular and biomolecular systems at the nanoscale due to the multiple time and length scales involved in the dynamics of these systems. These multiscale features are caused by either structure-structure (e.g. flexibility in biological structure or contact) or structure-fluid …

Factors Affecting The Performance Characteristics Of Wet Cooling Pads For Data Center Applications, Vishnu Sreeram

Mechanical and Aerospace Engineering Theses - Archive

The energy consumption of data centers in the current US market is fast growing in large numbers by every day. It was reported that in 2013, US data centers almost consumed 91 billion kilowatt-hours of electricity significant enough to power the whole of New York city twice a year [1]. Ever since the explosion of cloud computing, digital content and others the energy consumed by data centers has taken a steep increase and will continue in the coming years.As a result, there is a growing need to reduce the energy consumption of data centers by employing different cooling techniques which …

Experimental And Computational Study Of An It Pod And Its Cooling System, Suhas Sathyanarayan

Mechanical and Aerospace Engineering Theses - Archive

Conventional data centers are extremely large buildings that have complex power distribution and cooling systems. These data centers employ relatively expensive cooling systems which are inefficient. These inefficiencies of traditional data centers can be overcome by partitioning the server load into modular sections which can be deployed, powered and cooled depending on availability and requirement. Modular data centers are increasingly being developed instead of using large data centers to save huge amount of capital investment. High energy efficiency is a priority and measures have been taken to increase it. Cooling techniques such as air-side economization and evaporative cooling are proving …

Elimination Of Surface Tension Effect On A Small Plate By Developing Superwetting Surfaces, Varun Garg

Mechanical and Aerospace Engineering Theses - Archive

In this work, we explored the possibility of creating superwetting surfaces, which are defined here as the ones with apparent contact angles less than 5°, using roughness structures for the purpose of eliminating surface tension effect on a floating small plate. It is often considered that the ratio of the actual roughness surface over the projected one plays a critical role in generating superwetting surfaces. However, we found that the ratio of the top surfaces of roughness structures over the projected one had more influence on apparent contact angles. As this ratio was less than 0.013, the resulting apparent contact …

Design And Multifidelity Analysis Of Dual Mode Scramjet Compression System Using Coupled Npss And Fluent Simulation, Nandakumar Vijayakumar

Mechanical and Aerospace Engineering Theses - Archive

Hypersonic airbreathing engines provide many potential opportunities for future aerospace applications and immense efforts have been taken in gaining knowledge in them for the past decades .The physical phenomenon occurring in the hypersonic flow regime makes the design and performance prediction of a scramjet engine difficult. Though the cutting edge simulation tool development fights its way towards accurate prediction of the environment, the time consumed by the entire process in designing and analyzing a scramjet engine and its component, can be excessive. A multi-fidelity approach for designing a scramjet with a cruising Mach number of 6 is detailed in this …

Computational Study Of Behavior Of Gas Absorption In Data Center Equipment And Its Effects On The Rate Of Corrosion/Contamination, Tejeshkumar Vasantrao Bagul

Mechanical and Aerospace Engineering Theses - Archive

The reliability of the data center equipment is being compromised as the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) recommendable psychrometric limits are stretched outside the recommendable zones. When the ambient conditions are conducive enough the humidity and the gaseous contaminants present in the data centers react with the elements of Printed Circuit Boards (PCB) at various temperatures. The products of the reaction may lead to short circuit or extra resistance to the passage of current. This poses an increased threat to the reliability of the PCB.Contamination has become a serious problem in the developing nations like …

Interaction Of Growing Cracks In Hydraulic Fracturing, Li Wei Lo

Mechanical and Aerospace Engineering Theses - Archive

Recently, hydraulic fracturing has been utilized to extract natural gas and oil from low-permeability shale rocks. This technique has been studied in hundreds of papers. A deep understanding of the fracture network formation in hydraulic fracturing is essential to advancing the technology, e.g., to enhance the quality of fracking, and to keep aquifers from being contaminated. In the present study, the Linear Elastic Fracture Mechanics (LEFM) is applied to approach the crack extension behaviors in brittle rocks under hydraulic loading. The boundary element method is used to carry out the simulation where numerical treatment is only needed upon the cracks …

Influence Of Variation In Cpu Utilization On The Rack Level Fan Configuration As A Cooling Technique For High End Servers, Shreyas Nagaraj

Mechanical and Aerospace Engineering Theses - Archive

The data center industry has experienced significant growth over the past decade with the introduction and explosion of online banking, social networking and entertainment services. As a result, power consumption of such facilities continues to grow at a rapid pace. It has become imperative that energy savings and efficiencies be pursued in these components at various levels within the data center facility. This project aims to achieve the same by replacing internal server fans with larger, more-efficient fan units at the rear face of the rack. This study will be conducted by using a cluster of 1.5U Intel based Open …

Microwave-Based Navigation Of Femtosatellites Using On-Off Keying, Namrata J. Kamte

Mechanical and Aerospace Engineering Theses - Archive

The objective of this research is to validate that a custom-built microchip-scale satellite transmitting a signal modulated with a Pseudo Random Noise code using On-Off Keying, can be tracked. The weak GPS satellite signal is modulated with a Pseudo Random Noise (PRN) code that provides a mathematical gain. Our signal is modulated with the same PRN code using On-Off Keying (OOK) unlike Phase Shift Keying used in GPS satellites. Our goal is to obtain timing and positioning information from the microchip-scale satellite via a ground station using the concepts of PRN encoding and the OOK modulation technique.Decimeter scale satellites, with …

Use Of Nanoparticle Enhanced Phase Change Material (Nepcm) For Data Center Cooling Application, Harshal Gujarathi

Mechanical and Aerospace Engineering Theses - Archive

This study attempts to take advantage of nanoparticles with high thermal conductivity and the latent heat capacity of phase change materials together to enhance heat transfer rate. The main difficulty in using PCM for energy application is its low thermal conductivity in solid state. So, when solidification starts it makes it hard for evacuation of energy. A paraffin-based nanoparticle containing various volume fractions of Cu was applied. The suspended nanoparticles caused an increase in thermal conductivity of nanoparticles enhanced phase change material (NEPCM) compared to conventional PCM, resulting in heat transfer enhancement and a higher melting rate. The higher temperature …

Improving Air Cooling Efficiency Of 2ou High-End Web Server By Using Bigger Rack Level Fans And Controlling Flow Using Bimetallic Strips, Ravi Teja Mutyala

Mechanical and Aerospace Engineering Theses - Archive

Due to the doubling of processing power ever so often, designing an efficient thermal management system for database centers is becoming more and more difficult. Two studies have been done, one on air cooling using bigger rack level fans and another in liquid cooling minimizing the size of flow control devices. Fans are one of the most inefficient and power hungry devices used in an air cooled database center. Study has been done to improve the air cooling efficiency using larger rack level fans on 2OU open compute server. Simulations have been done using commercial computational fluid dynamic (CFD) software …

Composite Materials Equivalent Properties In Lamina, Laminate, And Structure Levels, Kamran Tavakoldavani

Mechanical and Aerospace Engineering Theses - Archive

Increasing use of thick composite structures requires a large model for structural analysis. In the analysis, equivalent properties of composites are often used. The equivalent properties of a composite are defined as the properties of a homogeneous orthotropic composite to representative an anisotropic heterogeneous composite material.A set of equations for equivalent mechanical and thermal properties in lamina and laminate as well as structures was developed. The developed model for lamina and laminate of composite was based upon the equivalent structural characteristics of 0? lamina and homogenized 0? laminate for lamina and laminate level, respectively. The concept of narrow beam was …