Engineering Commons^™

The Mechanical And Thick Section Bending Behavior Of Friction Stir Processed Aluminum Plate, D. Hilbert, C. Fuller, M. Mahoney, B. London

Materials Engineering

Friction stir processing (FSP) 2519-T87 aluminum plate results in enhanced ductility, 25% strain at fracture. However, the yield strength in the FSP zone drops to 175 MPa from ~400 MPa. Actively cooling the plate during FSP increases the yield strength to 185 MPa and decreases ductility to 20% strain at fracture. Thick bending of a plate of the alloy was demonstrated after the surface was subjected to FSP.

Leaching Properties Of Estuarine Harbor Sediment Before And After Electrodialytic Remediation, Kevin H. Gardner, Gunvor M. Nystroem, Deana A. Aulisio

Civil & Environmental Engineering

Electrodialytic remediation (EDR) can be used to extract heavy metals from a variety of different media. In this work, contaminated harbor sediments from two locations in the United States and one in Norway were subjected to EDR, and were compared with batch extractions conducted with the sediment. pH-dependent leaching tests were used to evaluate changes in leaching properties of treated and control sediments. Significant fractions of total concentrations were removed during treatment (35–95% with an average of 75% for all sediments and elements investigated). The release of elements in pH-dependent leaching tests, however, demonstrated equal or greater leaching from treated …

Improving Dc Power Supply Efficiency With Neural Network Controller, Weiming Li, Xiao-Hua Yu

Electrical Engineering

DC-DC converters can be found in almost every power electronics device. To improve the efficiency and controller response of a DC-DC converter to dynamical ~stem changes, neural network has been chosen as an alternative to classic methods. However, no prior work has been done in the neural network approach for control of a PSFB (phase-Shifted Full-Bridge) converter yet. In this research, a multi-layer feedforward neural network controller is proposed. The neural network based controller has the advantage of adaptive learning ability, and can work under the situation when the input voltage and load current fluctuate. Levenberg-Marquardt backpropagation training algorithm is …

An Experimental Evaluation Of Performance Variance For Internally Threaded Geometry Related To Extended Tap Wear In Low Carbon Steel, Todd E. Alberts

All-Inclusive List of Electronic Theses and Dissertations

The development of internal threads in a manufactured part is in many cases one of the final operations in the production workflow. Quality issues in thread form development can destroy a part that has previously undergone expensive machining. The issue of tap wear is one of the multi-faceted elements that have a direct correlation on the quality of threaded components. The purpose of this research centers on resultant mechanical pull performance for the stripping of internally threaded geometry in low carbon steel as measured over various increments of the tap cutting life cycle.

Linear And Non-Linear Control Of A Quadrotor Uav, Andrew Neff

All Theses

This thesis describes two controllers designed specifically for a quadrotor helicopter unmanned aerial vehicle (UAV). A linear controller and a non-linear controller are discussed for use on the quadrotor helicopter using feedback that is obtained from microelectromechanical systems and GPS.
The linear controller is an orientation based PID controller that controls the angles of the quadrotor UAV. The controller was first simulated and the results displayed graphically using FlightGear. Experiments were conducted using this controller on a DraganFlyer X-Pro quadrotor helicopter to prove the proposed method used for closing the feedback loop.
The non-linear controller is developed using Lyapunov stability …

Isomap Tracking With Particle Filter, Nikhil Rane

All Theses

The problem of tracking an object in an image sequence involves challenges like translation, rotation, scaling, varying ambient light and occlusions. A model of an object is built off-line by making a training set with images of the object with different poses. A dimensionality reduction technique is used to capture the variations in the training images. This gives a low-dimensional representation of the data. Isometric feature mapping is the dimensionality reduction technique used to capture the true degrees of freedom in the data. Once the data is reduced to low-dimensions it forms a part of the state-vector of the object. …

Computing Statistical Characteristics When We Know Probabilities With Interval Or Fuzzy Uncertainty: Computational Complexity, Gang Xiang, Jim W. Hall

Departmental Technical Reports (CS)

In traditional statistics, we usually assume that we know the exact probability distributions. In practice, we often only know the probabilities with interval uncertainty.

The main emphasis on taking this uncertainty into account has been on situations in which we know a cumulative distribution function (cdf) with interval uncertainty. However, in some cases, we know the probability density function (pdf) with interval uncertainty. We show that in this situations, the exact range of some statistical characteristics can be efficiently computed. Surprisingly, for some other characteristics, similar statistical problems which are efficiently solvable for interval-valued cdf become computationally difficult (NP-hard) for …

Synthesis And Characterization Of Polythiophene Derivatives, Xin Chen

Material Science and Engineering Dissertations - Archive

In Chapter 1, the history of conducting polymers, especially polythiophene and its derivatives, was briefly reviewed. Different approaches of structural modifications to afford small bandgap polythiophene derivatives were discussed. The emergence of metal-containing polymers (metallopolymers) as functional materials has attracted tremendous attention around the world. Introducing metals into thiophene-based oligomers and polymers, whether the backbone or the side chain of the p-conjugated framework, the electronic, optical, or magnetic properties of the material are expected to by significantly affected by metals through various mechanisms. Synthesis methods to prepare poly(thienylene vinylene) were also briefly reviewed in this chapter. In Chapter 2, the …

Autonomous And Cooperative Multi-Uav Guidance In Adversarial Environment, Ugur Zengin

Mechanical and Aerospace Engineering Dissertations - Archive

The research presented in this dissertation is aimed at developing rule-based autonomous and cooperative guidance strategies for UAVs to perform missions such as path planning, target tracking and rendezvous while reducing their risk/threat exposure level, and avoiding threats and/or obstacles by utilizing measurement information provided by sensors. First, a mathematical formulation is developed to represent the area of operation that contains various types of threats, obstacles, restricted areas, in a single framework. Once constructed, there will be no need to distinguish between adversaries as the framework already contains the information on what needs to be avoided and the level of …

Design, Analysis And Development Of A Morphable Wing Structure For Unmanned Aerial Vehicle Performance Augmentation, Abhijit Hiraman Supekar

Mechanical and Aerospace Engineering Theses - Archive

In this research, we propose mechanisms to continuously morph a wing from a lower aspect ratio to a higher and to further extremities of a gull and an inverted-gull configuration. The mechanism comprises of a linear actuator for the extension of the wing and the servo motors to obtain the gull and inverted gull configurations. The initial design and preliminary finite element representation using 3D-beams and plates in ANSYS Classic were the benchmarks to proceed for the detailed structural analysis of the complete wing in ANSYS Workbench. An elliptical pressure distribution at the quarter cord is assumed for the linear …

Design And Implementation Of A Feedback Linearizing Controller And Kalman Filter For A Magnetic Levitation System, John Andrew Henley

Mechanical and Aerospace Engineering Theses - Archive

The principal investigation undertaken in this research is the development and subsequent implementation of a feedback linearizing nonlinear controller and extended Kalman filter for a laboratory-based Magnetic Levitation (Maglev) device. The Maglev hardware is both highly nonlinear and open-loop unstable in its dynamic response. The control and estimation scheme proposed in this work is first validated using an increasingly sophisticated level of simulations. The control and estimation algorithm had the sensor noise identified using hardware data. Then, the plant noise covariance is tuned using both on-line and off-line hardware data. Additionally, the output of the nonlinear controller is then mapped …

Experimental Study Of Laminated Composite Tubes Under Bending, Puneet Saggar

Material Science and Engineering Theses - Archive

Bending stiffness of laminated composite tubes was determined experimentally using four-point bending test. The experimental results were compared with the results obtained by the laminated plate and smear property approaches. The results indicate that experimental values are closer to prediction of the laminated plate approach compared to smear property approach. Effects of tube radius and stacking sequence and fiber orientation of the walled thickness laminate on bending stiffness and strength of composite tubes were studied. Fracture analysis was conducted to investigate the failure process of the tube. Both techniques of x-ray radiography and optical microscopy were used in this study. …

A Generic Stability And Control Tool For Flight Vehicle Conceptual Design: Aeromech Software Development, Gary John Coleman

Mechanical and Aerospace Engineering Theses - Archive

During the conceptual design (CD) phase, various solution concepts must, and should, be explored to select the best flight vehicle size and configuration in order to meet the mission requirements. As the aerospace industry advances novel aerospace flight vehicle configurations promising larger operational performance and overall efficiency, demanding integrated flight vehicles like the flying wing configuration (FWC) or blending wing body (BWB) are under investigation. Some of these novel configurations rely on novel control effectors (CE) and complex flight control systems in order to obtain the desired performance objectives. Clearly, stability and control plays an important roll in the design …

Experimental Studies To Address Strengths Of Limestone Cores, Sulfate Heave Problems In Limestone Cores And Tunnel Lining, Vivekananda Chikyala

Civil Engineering Theses - Archive

Sulfate induced heave is a common scenario in tunnels located on sedimentary rocks containing Pyrites. Pyrite oxidation produces Gypsum which is a major source of natural sulfates. DART NC -1B tunnel is located in Dallas, north Texas. Dallas is located on sedimentary rocks with high Pyrite content and has a history of sulfate induced heave problems in several projects. In spring 2005 & 2006, the shotcrete liner in DART NC-1B tunnel showed cracking associated with water leaks. Considering the local geology and the history of the tunnel, researchers at The University of Texas at Arlington (UTA) suspected probable occurrence of …

Performance Studies On Rigid Pavement Sections Built On Stabilized Sulfate Soils, Deepti Vasudev

Civil Engineering Theses - Archive

Soils of Southeast Arlington are highly expansive and rich in sulfates. They undergo sulfate induced heaving when traditional calcium based stabilizers are used for soil stabilization (Puppala et al. 1998). Traditional stabilizers do not provide effective solution since they are known to induce heaving, termed in the literature as sulfate induced heaving (Hunter, 1988). Both swelling and softening of these soils rich in sulfates induce considerable damage to overlying pavement infrastructure. Typically, high sulfate soils treated with calcium based stabilizers form ettringite mineral. Ettringite undergoes heaving when hydrated (Hunter, 1988; Puppala et al. 2001). Since this sulfate-induced heave is caused …

Tissue And Vascular Oxygenation Dynamics Determined By Optical Approaches And Mri, Mengna Xia

Bioengineering Dissertations - Archive

Tumor oxygenation is a crucial factor to determine the efficiency of non-surgery therapy, such as radiotherapy and chemotherapy. Therefore, various approaches have been applied to tumor in order to improve the tumor oxygen level. Breathing oxygenrich gas with normobaric or hyperbaric pressure has been demonstrated to overcome hypoxia, but with marginal success. Therefore, the outcome would be improved greatly, if the responsive tumors were identified a priori. Two non-invasive techniques were applied to monitor tumor oxygenation dynamics simultaneously when rats were exposed to hyperoxic gas intervention. 19F MRI provides tumor tissue oxygen tension (pO2) images, while Near Infrared Spectroscopy (NIRS) …

Effects Of A Debonding Flaw Size And Location On The Flexural Performance Of Cfrp Retrofitted Steel Sections, Sharad C. Choudhary

Civil Engineering Theses - Archive

In US there are several thousand steel bridges at present. Out of them many bridges are at various level of advance deteriorations due to many years of service life and environmental factors. These bridges cannot be fully replaced so retrofitting is the best choice .Earlier steel plates were used. With introduction of FRP in 1960.It is replacing the steel plates as they are lighter in weight and can be made stronger than steel. While installation of these FRP some kinds of Flaws are encountered. The variation of strength of carbon fiber reinforced laminate used for structural repair or strengthening containing …

Wireless Sensor Network Testbed: Measurement And Analysis, Rahul Pramod Sawant

Electrical Engineering Theses - Archive

Energy conservation is critical in Wireless Sensor Networks. Replacing or recharging batteries is not an option for sensors deployed in hostile environments. Generally communication electronics in the sensor utilizes most energy. This thesis studies the effect of changing the transmission power and baud rate on transmission distance. Using Shannon channel capacity formula and Log - Distance Path Loss Model, transmission distance is shown to be related to transmit power and baud rate. Extensive empirical readings are taken to confirm the above relation. The path loss exponent got as a result of data fitting is within the acceptable range for wireless …

A Performance-Based Incentive Program For Asphalt Pavement, Tim Wentz, Satya Peruri, Wayne Jensen, Bruce Fischer

Nebraska Department of Transportation: Research Reports

No abstract provided.

Sexual Conflict Over Egg Allocation: A Dynamic Programming Approach To Modeling The Evolution Of Male Harm And Female Resistance, David Kelley

Renée Crown University Honors Thesis Projects - All

Sexual conflict, which is expected to be ubiquitous among polygamous species, is known to occasionally result in male adaptations that are harmful to females. One theoretical model indicates that males may benefit from physically harming their mates by triggering a “terminal investment” reproductive response by them. Using dynamic programming, we explore how females optimize their lifetime egg allocation, how selection acts on males to exploit such allocation, and how females respond to resist this exploitation. The model reveals alternative female response pathways; one of the most effective of which is simply to forgo plasticity in egg allocation. By switching to …

Electromagnetically Actuated Devices For Optical Coherence Tomography Applications, Hans P. Hu

Electrical Engineering Dissertations - Archive

A fast optical scanning device has always been desired for numerous applications such as biomedical imaging, optical communications, and variety of sensing and actuating applications. This dissertation presents a new scanning device operated using external magnetic field with low cost, high function versatility, low field strength, and low power consumption. The design architecture of this device shows its potential for in vivo application with an advantage that addresses the concern of safety. Materials properties are examined using alternating gradient magnetometer(AGM) to verify its performance. Pressure and temperature invariant fabrication processes are implemented to make this device without complicated equipments. The …

Discrete-Time Control Algorithms And Adaptive Intelligent Systems Designs, Asma Azmi Al-Tamimi

Electrical Engineering Dissertations - Archive

In this work, approximate dynamic programming (ADP) designs based on adaptive critic structures are developed to solve the discrete-time optimal control problems in which the state and action spaces are continuous. This work considers linear discrete-time systems as well as nonlinear discrete-time systems that are affine in the input. This research resulted in forward-in-time reinforcement learning algorithms that converge to the solution of the Generalized Algebraic Riccati Equation (GARE) for linear systems. For the nonlinear case, a forward-in-time reinforcement learning algorithm is presented that converges to the solution of the associated Hamilton-Jacobi Bellman equation (HJB). The results in the linear …

Performance Analysis Of Dpsk Systems With Mimo Employing Egc Over Wireless Fading Channels, Iyad Al Falujah

Electrical Engineering Dissertations - Archive

The proliferation of digital wireless communication services has increased the congestion of the available radio spectrum. In addition to that, wireless communications are encountered by multipath channel fading. To alleviate the scarcity of the radio spectrum and multipath channel fading, attention in this dissertation is placed on differentially coherent phase shift keying (DPSK) systems with equal gain combining (EGC) diversity reception. DPSK systems are capable of achieving high spectral efficiency with adequate performance over wireless fading channels. Several wireless communication systems have adopted DPSK such as the time division multiple access (TDMA) version of the North American Digital Cellular (NADC) …

Investigation Of Information Processing And Cognitive Performance Capacities With Different Instrumentation Configurations, Saju John Mathew

Bioengineering Theses - Archive

The focus of this thesis is the investigation of two new performance capacity tests related to a concept known as "situational awareness": 1) Visual Motor Multitask Performance Capacity (VMMPC) and 2) Visual Auditory Information Processing Dexterity (VAIPD). These represent major components of human information processing and are therefore important in situations ranging from driving and other activities of daily living to occupational and sport tasks. These tests have been recently designed and implemented on a laboratory-based instrument called the BEP I. In the present project, they are implemented on a different, more portable platform that is under development and known …

An Evaluation Of Using Component Mode Synthesis For Structural Models, Richard Lynn Scott

Mechanical and Aerospace Engineering Theses - Archive

Structural analysts have used component mode synthesis (CMS), also known as substructuring, for decades to divide large structural models into smaller, more manageable models, and to reduce the size of the associated mathematical problem. Applying CMS can also reduce the front-end effort to build models, even models that are smaller than those for which CMS has typically been applied. This paper presents an evaluation of the accuracy of two smaller substructured models so that analysts might feel confident in applying CMS to gain the benefits. The evaluation starts with an introduction to CMS. Then, CMS is applied to a small, …

Control And Simulation Of Relative Motion For Aerial Refueling In Racetrack Maneuver, Eunyoung Kim

Mechanical and Aerospace Engineering Theses - Archive

This thesis addresses the problem of controlling the receiver aircraft to achieve a successful aerial refueling. For the performance verification of the controller, a new set of nonlinear, 6-DOF, rigid body equations of motion for the receiver aircraft has been used. The equations are written in terms of state variables that are relative to the reference frame that is attached to, translates and rotates with the tanker aircraft. Furthermore, the nonlinear equations contain the wind effect terms and their time derivatives to represent the aerodynamic coupling involved between the two aircraft. These wind terms are obtained using an averaging technique …

Analysis Of Ride Quality Of Tractor Semi-Trailers, Christopher Spivey

All Theses

This thesis develops parameter variation techniques for calculating the set of vehicle parameters that result in the best ride comfort for the driver. The model is a fifteen degree-of-freedom (15 DOF) tractor semi-trailer vertical dynamic ride model. The modeling and simulation techniques used in this thesis are extensions of the research performed by Trangsrud and Vaduri. Features of the model include suspension characteristics for (a) each of the five axles (tractor steer axle, two tractor drive axles, and two trailer axles), (b) tires, (c) a flexible engine mount, (d) the tractor cab, (e) the driver's seat, and (f) a fifth …

1/F Noise In Carbon Nanotube Devices - On The Impact Of Contacts And Device Geometry, Joerg Appenzeller, Yu-Ming Lin, Joachim Knoch, Zhihong Chen, Phaedon Avouris

Other Nanotechnology Publications

We report on the 1/f noise in various ballistic carbon nanotube devices. A common means to characterize the quality of a transistor in terms of noise is to evaluate the ratio of the noise amplitude A and the sample resistance R. By contacting semiconducting tubes with different metal electrodes we are able to show that a small A/R value by itself is no indication of a suitable metal/tube combination for logic applications. We discuss how current in a nanotube transistor is determined by the injection of carriers at the electrode/nanotube interface, while at the same time excess noise is related …

Voluntary And Confidential Reporting Systems As A Means Of Reducing The Accident Rate In Shadow 200 Flight Operations, William Lawrence Jagnow

Master's Theses - Daytona Beach

Although effective, the United States Army's Shadow 200 Unmanned Aerial Vehicle has suffered an unacceptably high accident rate. Errors committed by operators have significantly contributed to this accident rate. The voluntary and confidential Aviation Safety Reporting System and Aviation Safety Action Program have been successful in identifying and addressing errors committed by air carrier pilots. This study has explored the implementation of voluntary and confidential reporting systems in Shadow 200 flight operations. Mixed methods research combined quantitative survey data and qualitative interview data as a means of determining attitudes relevant to the implementation of such systems. Identified deficiencies included: (a) …

Prediction Of Fatigue Life In 7075-T6 Aluminum From Neural Network Analysis Of Acoustic Emission Data, Nicholas S. Spivey

Master's Theses - Daytona Beach

Through the use of an acoustic emission (AE) data acquisition system, a Kohonen self-organizing map, and a back-propagation neural network, AE data from 7075-T6 aluminum specimens were used to classify failure mechanisms and predict the number of fatigue cycles to failure. AE waveforms were captured from 40 notched tensile specimens during the low-cycle fatiguing process. A Kohonen self-organizing map and initial data filters were used to classify the data into two distinct failure mechanisms, plane strain and plane stress fracture, plus a third less prevalent mechanism. These results were employed to construct a back-propagation neural network to predict the number …