Engineering Commons^™

Computational And Experimental Investigations Into Aerospace Plasmas, William Thomas Bennett

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Investigations into two different fields of plasma research are presented here. These include the study of ion engine performance and the use of plasma discharges for flow control. In the area of ion engine performance, optimizing electron confinement is the primary goal of this work. The work of prior researchers was expanded through the study of the cathode emission location and the energy of the primary electrons. Cathode position was shown to have minimal effect on confinement length. For electron energy values greater than 20eV the effect on confinement length was also found to be very small. The strength of …

The Effects Of Chronic Hypoxia And Substance P On The Chemosensitive Response Of Individual Nucleus Tractus Solitarius (Nts) Neurons From Adult Rats, Nicole L. Nichols

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The chemosensitive responses of individual nucleus tractus solitarius (NTS) neurons from neonatal rats have been extensively studied, but few studies have examined the chemosensitive responses of NTS neurons from adult rats. In addition, environmental conditions have been used to mimic respiratory diseases/disorders in rats to study how the cellular responses of individual neurons change to regulate breathing during pathological conditions. Lastly, it has been shown that substance P release increases in response to hypoxia from peripheral afferents that primarily terminate in the caudal NTS. We studied the effect of chronic hypoxia (CHx) and substance P on the response to hypercapnia …

Design Of Pulse Output Direct Digital Synthesizer With An Analog Filter Bank, Aditya R. Pothuri

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Over the past two decades frequency synthesizer has progressed from a relatively crystal bank synthesizer to multi-loop phase locked loops. But in recent years direct digital synthesizers (DDS) have witnessed an increase in demand over their analog counterparts. The DDS offers a wide range of advantages over phase locked loops such as high frequency range, fast switching response, and sub-hertz frequency resolution. However, the conventional DDS suffers limitations due to its architecture involving digital-to-analog converter (DAC) and read-only-memory (ROM) with respect to high clock speeds.

The Pulse Output Direct Digital Synthesizer (PODDS) presented in this thesis eliminates the necessity for …

Gps Coarse Acquisition Using The Monobit Fft Algorithm In A Broadband Receiver, John Flynn

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The purpose of this research was to investigate the feasibility of using broadband electronic warfare (EW) receivers for Global Position System (GPS) tracking. These are pulse-oriented receivers, typically with input bandwidths of 1 Ghz or larger, and so by definition do not have the same characteristics and processing of continuous wave (CW) receivers like GPS devices, FM radios, etc. For example, the spectral output of the Fast Fourier Transform (FFT) used in broadband signal processing updates on the frequency of the FFT input sample size, versus a CW receiver which updates on a more continuous basis.

The foundation of this …

Evolutionary Methodology For Optimization Of Image Transforms Subject To Quantization Noise, Michael Ray Peterson

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Lossy image compression algorithms sacrifice perfect imagereconstruction in favor of decreased storage requirements. Modelossy compression schemes, such as JPEG2000, rely upon the discrete wavelet transform (DWT) to achieve high levels of compression while minimizing the loss of information for image reconstruction. Some compression applications require higher levels of compression than those achieved through application of the DWT and entropy coding. In such lossy systems, quantization provides high compression rates at the cost of increased distortion. Unfortunately, as the amount of quantization increases, the performance of the DWT for accurate image reconstruction deteriorates. Previous research demonstrates that a genetic algorithm can …

Mechanisms Of Nickel-Based Coatings For Fretting Wear Mitigation Of Ti6al4v Interfaces, Carl H. Hager Jr.

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Fretting wear is an accumulation of damage that occurs at component interfaces that are subjected to high contact stresses coupled with low amplitude oscillation. The key to fretting wear reduction in metallic contacts is the mitigation of galling at the interface, followed by the control of debris production and the rheology of active wear debris. Once the thin surface species of the metallic interfaces is dispersed, adhesion between the contacting nascent surfaces causes the inception of severe surface deformation and material transfer or removal. This is extremely apparent in the fretting wear of aerospace materials such as titanium alloy and …

Novel Redox And Dna-Dependent Conformational Changes In Human Ku, A Dna-Double Strand Break Repair Protein, Jason Alexander Lehman

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Ionizing radiation (IR) and radiomimetic drugs used in cancer chemotherapy cause DNA double-strand breaks which are repaired by the nonhomologous end joining (NHEJ) pathway. Ku is a heterodimeric protein comprised of 70 and 80 kDa subunits and recognizes free DNA ends. Once Ku is bound to DNA, it binds to the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), and forms a heterotrimeric DNA-PK complex for repair and damage signaling.

We have analyzed the Ku protein using multiple biochemical techniques and uncovered a novel reversible redox change (Andrews, Lehman and Turchi, (2006) JBC 281(19):13596-603). From this data, we hypothesized that a redox-dependent …

Costas Pll Loop System For Bpsk Detection, Rajesh Kumar Keregudadhahalli

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A 2GHz carrier recovery Costas Loop based BPSK detector is designed using CMOS 0.18μm technology. The designed BPSK detector consists of single to differential conversion circuit, phase/frequency detector, Voltage Controlled Oscillator, differential to single conversion circuit, first order loop filter and a third multiplier. Different architectures available for each block have been discussed along with the design methodology adopted. The schematics were simulated in analog design environment.

The Costas loop presented in this work can sense both 0° and 180° phases at its input. Thus the Costas loop carrier recovery circuit overcomes the 180° phase ambiguity presented by the conventional …

Ici Reduction Methods For Mc-Cdma Systems, Meng Wu

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Multi-carrier code-division multiple-access (MC-CDMA) is an important multiple access candidate for 4G wireless communication system. While MC-CDMA provides high performance and high capacity in frequency selective fading channels, it is very sensitive to the signal distortion, especially the Inter Carrier Interference (ICI). We apply self-cancelation and a frequency transmission paradigm to MC-CDMA system to improve the sytem performance in an ICI rich environment. Furthermore, we combine the frequency transmission paradigm FD-MC-CDMA with ICI cancelation. Also, we apply all these three schemes into non-contiguous OFDM and non-contiguous MC-CDMA systems in simple Cognitive Radio communication environments and present the simulation results. Theoretical …

Automotive Battery State-Of-Health Monitoring Methods, Ryan J. Grube

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Effective vehicular power management requires accurate knowledge of battery state, including state-of-charge (SOC) and state-of-health (SOH). An essential functionality of automotive batteries is delivering high power in short periods to crank the engine. A well-known approach to battery SOH monitoring is to infer battery state-of-health from battery impedance or resistance, which is not robust to variation of battery types. The research and development of more reliable battery state-of-health monitoring methods to ensure vehicle start-up ability are presented in this thesis. The methods include a battery cranking voltage based method, a parity-relation based method using battery voltage and cranking current signals, …

Performance Analysis Of Quantitative Bone Measurement With Spiral, Multi-Detector Ct Scanners, Shruti Gupta

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The measure of bone strength and fracture risk assessment is based primarily on bone mineral density (BMD). Computed tomography (CT), a frequently used radiographic technique that provides cross-sectional images, can be used for BMD quantification. Called quantitative computed tomography (QCT), it determines true volumetric density and also differentiates between trabecular and cortical bone. As a result, QCT improves the ability to detect early changes in trabecular BMD accurately and precisely.

The introduction of helical CT for quantitative analysis introduces new complexities. Even though using multi-detector helical CT for BMD assessment is being suggested, a detailed analysis of its validity is …

Information Presentation On Mobile Device For Plant Operations, Raghavendra Rao Polakonda

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Process control and maintenance systems have been used in the petrochemical and refining industry for long time for improving operator performance and workforce efficiency. However, there is a need to integrate these systems with current technological innovations in a systematic and meaningful manner. Advances in mobile computing, sensor technologies, software algorithms, and computational methods provide the possibility for easy access to information anytime-anywhere. The issues associated with retrieving and reviewing this information directly affects the ability to make timely and quality decisions in high stakes environments like a petrochemical plant where time critical decisions are involved. This research investigates the …

New Heuristic And Metaheuristic Approaches Applied To The Multiple-Choice Multidimensional Knapsack Problem, Chaitr Hiremath

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The knapsack problem has been used to model various decision making processes. Industrial applications find the need for satisfying additional constraints and these necessities lead to the variants and extensions of knapsack problems which are complex to solve. Heuristic algorithms have been developed by many researchers to solve the variants of knapsack problems. Empirical analysis has been done to compare the performance of these heuristics. Little research has been done to find out why certain algorithms perform well on certain test problems while not so well on other test problems. There has been little work done to gain knowledge of …

The Development Of A Nonlinear Phase-Lock Loop With Adaptive Gain Control Based On Modern Control Theory, Michael D. Myers

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As the performance of integrated circuits (IC) improve, a more precise clock-signal is needed to regulate their actions. The primary objective of this dissertation is to improve the phase-lock loop (PLL), which is the most common type of clock-generator. A nonlinear phase-lock loop (NPLL) was developed by adding a nonlinear-gain unit to a standard PLL. The NPLL implementation improves performance compared to existing PLLs by demonstrating faster acquisition times and superior jitter performance. The nonlinear-gain is achieved by the use of a fuzzy controller. The fuzzy controller takes in a value and generates outputs based upon the rules that are …

Broad Bandwidth High Resolution Analog To Digital Converters: Theory, Architecture And Implementation, Saiyu Ren

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Analog to digital converters (ADCs) translate analog quantities, which are characteristic of most phenomena in the "real world" to digital language for a variety of applications including information processing, computing, communication and control systems. The performance of the digital signal processing and communication systems is generally limited by the speed and precision of the digital input signal which is achieved at the interface between analog and digital information. The analog to digital converter (ADC) has become a critical component for advanced telecommunication systems. The desire to move the analog to digital interface closer to the sensor has resulted in more …

Risk Based Analysis And Design Af Stiffened Plates, Heather B. Dwire

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The traditional Risk Based Design (RBD) process involves designing a structure based on risk estimates obtained during several iterations of an optimization routine. This approach is computationally expensive for large-scale aircraft structural systems. The main objective of this research is to establish a RBD algorithm and produce RBD plots for stiffened plates. Basic steps to check functionality will be done by first analyzing a flat plate for which closed formed equations are available and then moving to more complex geometries like stiffened plates.

Therefore, the concept of RBD plots that can be used for both structural sizing and risk assessment …

Design And Analysis Of A Mach 3 Dual Mode Scramjet Combustor, Christopher Ryan Corbin

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Low speed operation of a dual mode scramjet engine is important to the development of a two stage to orbit reusable launch vehicle. This study investigates the Mach 3 operation of a dual mode scramjet engine. SRGULL, a one-dimensional cycle code for scramjet engines, and VULCAN, a computational fluid dynamics code capable of solving reacting flows, are used in this study. Staged injection is investigated to allow more heat release at a low flight Mach number condition so that more thrust can be achieved and inlet unstart is avoided. The nominal case has one injector located 1.067 meters downstream of …

Improved Structural Health Monitoring Using Random Decrement Signatures, Oleg V. Shiryayev

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Detection of structural damage phenomena such as cracks, delaminations, or loose fasteners is important because it increases safety and may allow significant reduction in operational costs. Many structural health monitoring techniques are based on detecting changes in vibration features obtained from the measured response. The technique presented in this work is based on the random decrement signatures calculated from the random response. No knowledge of input signal is required. Random decrement signatures have been used for damage detection purposes in the past. The significance of this work is that it explores the possibility of identifying the type of damage and …

A Framework To Support Spatial, Temporal And Thematic Analytics Over Semantic Web Data, Matthew Steven Perry

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Spatial and temporal data are critical components in many applications. This is especially true in analytical applications ranging from scientific discovery to national security and criminal investigation. The analytical process often requires uncovering and analyzing complex thematic relationships between disparate people, places and events. Fundamentally new query operators based on the graph structure of Semantic Web data models, such as semantic associations, are proving useful for this purpose. However, these analysis mechanisms are primarily intended for thematic relationships. This dissertation proposes a framework built around the RDF data model for analysis of thematic, spatial and temporal relationships between named entities. …

Effect Of A Graded Layer On The Plastic Dissipation During Mixed-Mode Fatigue Crack Growth On Plastically Mismatched Interfaces, Craig M. Baudendistel

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Recent work has proposed a dissipated energy theory of fatigue crack growth in layered materials under mixed-mode loading. An inherent assumption of this prior work is that a perfect crack exists along the interface joining the top and bottom layers. The current work extends the approach of previous studies to incorporate a grading of plastic properties between the two layers through parametric finite element modeling with ABAQUS. An elastic-plastic 2D model using 8-node biquadratic elements was used to map the plastic dissipation of a two layer specimen with a grading of plastic properties parallel to the crack face. This property …

Global Optimization Of An Aircraft Thermal Management System Through Use Of A Genetic Algorithm, Christopher T. Allen

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Optimization algorithms utilize known information about the system to identify solutions that are more efficient and meet the requirements of the user. The algorithms require an objective function, or formula (linear or nonlinear) that models what the user is looking to optimize, in order to begin the search for a more feasible solution. Because optimization problems can involve either linearor non-linear functions, various algorithms have been created that can locate optimum solutions faster depending on the type of objective function being optimized.

This research focuses on optimizing an aircrafts thermal management system by using one such algorithm. This was performed …

Study Of Multi-Modal And Non-Gaussian Probability Density Functions In Target Tracking With Applications To Dim Target Tracking, Peter V. Hlinomaz

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The majority of deployed target tracking systems use some variant of the Kalman filter for their state estimation algorithm. In order for a Kalman filter to be optimal, the measurement and state equations must be linear and the process and measurement noises must be Gaussian random variables (or vectors). One problem arises when the state or measurement function becomes a multi-modal Gaussian mixture. This typically occurs with the interactive multiple model (IMM) technique and its derivatives and also with probabilistic and joint probabilistic data association (PDA/JPDA) algorithms. Another common problem in target tracking is that the target's signal-to-noise ratio (SNR) …

Real-Time Hilbert Transform And Autocorrelation For Digital Wideband Communication Applications, Murthy, Dilip Srinivasa

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Digital wideband receiver plays a key role in communication and radar systems, and it is used detect and analyze wide range of radio frequency (RF) signals. A digital Instantaneous Frequency Measurement (IFM) receiver is designed, where implementation of a real-time architecture of a Hilbert transform and autocorrelation algorithm is presented. Real-time architecture performs continuous monitoring and processing of the incoming signal. Prior to the previous one bit design, the input data fed to the Hilbert transform is 8-bit wide at a clock rate of 320 MHz with the input data rate is increased by a factor of eight, an 8-bit …

The Influence Of Thickness On The Complex Modulus Of Air Plasma Sprayed Ceramic Blend Coatings, Jason Edgar Hansel

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Previous research suggests that damping of metallic beams that have a hard ceramic coating applied on them is proportional to the coating thickness. This indicates that the damping is a volume dependent material property. Since thickness variations are likely in an actual application, it is essential to understand the role that coating thickness plays in damping effectiveness. For this research, a series of tests were conducted using substrate beams of 90 mil Ti-6Al-4V, coated with 3 mils of an air plasma sprayed NiCrAlY bond coat followed by a Titania-Alumina ceramic blend coating applied via air plasma spray in one of …

Modeling Training Effects On Task Performance Using A Human Performance Taxonomy, Douglas P. Meador

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There is little argument that modern military systems are very complex, both in terms of the resources in time and money to develop them and the infrastructure that is required to produce trained operators. To properly execute human systems integration during the acquisition process, systems built to train operators must be developed that optimize training. Consequently, the training system community would benefit from simulation models that provide the ability to make accurate predictions of training processes, and allow the decision maker to specify an optimum combination of operator performance after training and the cost of that training. The goal of …

The Effect Of Variable Gravity On The Cooling Performance Of A 16-Nozzle Spray Array, Levi J. Elston

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The objective of this thesis was to investigate the cooling performance of a 16-nozzle spray array, using FC-72 as the working fluid, in variable gravity conditions with additional emphasis on fluid management and flow stability. A flight test experiment was modified to accommodate a 16-nozzle spray array, which was then tested in the parabolic flight trajectory environment of NASA's C-9 reduced gravity aircraft. The 16-nozzle array was designed to cool a 25.4 x 25.4 [mm] area on a thick film resistive heater used to simulate electronic components. Data was taken and reduced as a result of flight tests conducted over …

Implementation Of Simulation For Network Service Delivery Point Capacity Analysis, Tiffany Jill Harper

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As businesses consolidate and modernize their operations, the impact on their network and computing infrastructure is a major consideration. In this thesis, discrete event simulation is used to show how implementation of an Enterprise Resource Planning (ERP) system can impact network performance and ultimately affect end-users. More specifically, the model simulates the flow of data packets across a network, through a Service Delivery Point (SDP), which is comprised of routers, switches, and firewalls that connect a Local Area Network to a Wide Area Network.

The model was used to run to determine the affect of more network traffic and additional …

Integrated Inductors, Mandar Dilip Kavimandan

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Integrated inductors, also called spiral inductors, on-chip inductors, or planarinductors, are inseparable part in radio frequency integrated circuits (RFICs). Increasing growth in RFICs from the past few decades has forced study of these components in greater detail. Apart from IC inductors, there are several components mounted on a chip - namely capacitors, resistors, MOSFETs, diodes etc. It is extremely important to understand the electrical and magnetic behavior of all these components. Electrical behavior of these components is easy to understand. However, the real challenge lies in realizing and predicting the magnetic behavior of components, namely, inductors and capacitors. Capacitors have …

Influence Of Voltage Source Pulse Width Modulated Switching And Induction Motor Circuit On Harmonic Current Content, Martin T. Lange

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The purpose of this research is to present analysis of the harmonic content present in the phase current of a three phase induction motor while being powered by a voltage source pulse-width modulated (PWM) variable speed drive (VSD). First, the topology and circuit of the drive, its operational fundamentals and waveform appearance are presented and discussed. Next, the three-phase induction motor circuit model and operational characteristics are discussed. Finally, the harmonic content present in the induction motor phase current is determined by use of the PSPICE model. The ability of the PSICE simulation to determine harmonic content is established. It …

Microstructural Stability And Thermomechanical Processing Of Boron Modified Beta Titanium Alloys, Balakrishna Cherukuri

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One of the main objectives during primary processing of titanium alloys is to reduce the prior beta grain size. Producing an ingot with smaller prior beta grain size could potentially eliminate some primary processing steps and thus reduce processing cost. Trace additions of boron have been shown to decrease the as-cast grain size in alpha + beta titanium alloys. The primary focus of this dissertation is to investigate the effect of boron on microstructural stability and thermomechanical processing in beta titanium alloys.

Two metastable beta titanium alloys: Ti-15Mo-2.6Nb-3Al-0.2Si (Beta21S) and Ti-5Al-5V-5Mo-3Cr (Ti5553) with 0.1 wt% B and without boron additions …