Engineering Commons^™

Hydrodynamic Wave Contributions To Combustion Instability In Rockets, Esam M. T. Abu-Irshaid

Doctoral Dissertations

Experimental measurements suggest that a new source of instability in rocket motors is due to hydrodynamic disturbances. These disturbances, if ignored, could impact our assessment of rocket motor performance. In this work, the corresponding problem of hydrodynamic instability is considered. A mathematical model for these disturbances is carried out by perturbing the continuity and momentum equations. A one dimensional model which represents the wave disturbances in time and space is implemented to quantify the amplification rate, in time or space, and the wave amplitude. The only available measurements of these disturbances arise in cold flow experiments that simulate the gas …

Studies Of The Mechanism Of Electron Beam Induced Deposition (Ebid), Young Ryong Choi

Doctoral Dissertations

The controlled deposition of metals resulting from the passage of an ion beam through an atmosphere of a suitable precursor gas is a well-established procedure for micro scale materials manipulation. While the ion beam technique is rapid and reliable it has the disadvantage that the beam itself can ablate and contaminate the target with Gallium or other materials, and the fact that ion optics are less widely accessible than electron optical columns. We have therefore been investigating the theory and practice of depositing metal using an electron beam and variety of precursor gases. The aim of this work is to …

A High Gain Multi-Stage Operational Amplifier Using Compound Transconductance Element, Chandra Sekhar Acharyulu Durisety

Doctoral Dissertations

The rapid increase in integrated circuit complexity attributed to the advancements in fabrication techniques combined with the increasing demand for consumer applications has created an immense demand for high performance analog systems. These analog systems include high-resolution (≥ 14-bit) and/or high-speed (≥ 1 GHz) ADCs, high- linearity filters and power management circuits. The fundamental limitations in these systems are tied to the constraints imposed by the basic design elements that tend to include amplifiers and reference generators (voltage/current). With continued technology scaling, innovative circuits and design techniques are necessary in achieving high performance analog/mixed-signal systems.

The goal of this research …

The Thermophysical Roll Of Nanoparticles In Nanofluidic Heat And Mass Transport, Chan Hee Chon

Doctoral Dissertations

Nanofluids are colloids that consist of a base fluid and nanometer sized metallic particles, which serve to improve the heat and mass transport characteristics of nanofluids over those of the base fluid. Many researchers, attracted to the highly enhanced thermal conductivity, have studied nanofluids, and yet have never been able to reveal the basic mechanisms of their characteristic improvements. This present work thus seeks to gain an understanding of the role of nanoparticles in nanofluidic heat and mass transport characteristics through three experimental measurements: 1) thermal conductivity measurement, 2) thermophoretic motion measurement, and 3) evaporation measurement.

Using thermal conductivity, thermophoresis, …

Efficient Image Processing In Resource-Constrained Visual Sensor Networks, Hongtao Du

Doctoral Dissertations

Visual sensor networks (VSNs) that employ content-rich 2-D images or image sequences as the basic media have been evolving rapidly in recent years. Besides the critical resource constraints that are already inherent in any micro-sensor networks, the development of VSNs also faces challenges from device design, image transmission, and onboard image processing, among which efficient onboard processing is the most difficult to tackle. The focus of this dis- sertation is to develop efficient image processing solutions from three aspects: to improve the time-consuming image processing algorithms using pipelined and parallel computing; to dis- tribute the computation more effectively through novel …

Development Of A Test Methodology For Determining The Efficacy Of One Atmosphere Uniform Glow Discharge Plasma Against Airborne Contaminants, Ronald Edward Domitrovic

Doctoral Dissertations

A method of analysis is developed for an atmospheric plasma reactor in a ducted air stream with the intent of enabling parametric analysis for the multi-variable problem. Industrial uses for atmospheric plasma are numerous and in this case, a particular type of plasma known as “One Atmosphere Uniform Glow Discharge Plasma” (OAUGDP™) was studied for its chemistry generation abilities and its microorganism efficacy properties. The system of an OAUGDP reactor positioned in an air duct of fully-developed turbulent flow is constructed of nineteen pertinent variables and dimensional analysis is applied according to the Buckingham Pi method, yielding fourteen dimensionless variable …

Thermal Stability Of Binary Cr-Cr3Si And Ternary Nial-Mo Eutectic Alloys, Aravind Gali

Doctoral Dissertations

The thermal stability of multiphase intermetallics at temperatures to 1400°C was investigated by studying two model eutectic systems: Cr-Cr₃Si having a lamellar microstructure and NiAl-Mo having a fibrous microstructure. In drop cast Cr-Cr₃Si, coarsening was found to be interface controlled. The coarsening rate could be significantly reduced by microalloying with Ce and Re, two elements which were chosen because they were expected to segregate to the Cr-Cr₃Si interfaces and decrease their energies. Similarly, directional solidification, which is also expected to lower the Cr- Cr₃Si interfacial energy, was found to dramatically decrease the …

Scheduling Algorithms For Scalable High-Performance Packet Switching Architectures, Xike Li

Doctoral Dissertations

Packet switching fabrics constitute a fundamental building block of all Internet routers. As a core technology, the switching engine is responsible for enabling multiple input (ingress) ports to be dynamically linked to output (egress) ports, thereby allowing packets to effectively traverse the router. Scheduling algorithms, which play a key role in switching fabrics, determine the dynamic configurations of the input-output matchings. The ever growing need for additional bandwidth and more sophisticated service provisioning in next- generation networks necessitates the introduction of scalable packet scheduling solutions that go beyond legacy schemes.

Switch architectures can be coarsely classified into two categories, in …

An Investigation Of The Deposition And Characterization Of Materials Formed By Electron Beam Induced Deposition, Wei Li

Doctoral Dissertations

This dissertation deals with EBID – Electron Beam Induced Deposition – a novel bottom up nanofabrication technique. Since EBID was first employed for nano-patterning, a number of empirical factors were investigated to control deposition process. Meanwhile a few theoretical models were proposed based on some fundamental assumptions. So far little work has been done to verify the validity of these assumptions. The main objective of my PhD study, therefore, was to answer whether these assumptions are valid so that unifying the empirical factors and theoretical models would be possible. Electrical resistivity of deposited materials was another interesting topic included in …

A Study Of The Relationship Between Indentation Creep And Uniaxial Creep, James Anthony Lamanna Jr.

Doctoral Dissertations

The purpose of this work is to further the scientific understanding of the relationship between indentation creep and uniaxial creep. The data for this study was obtained by conducting both indentation and uniaxial creep experiments on amorphous selenium. Experiments were designed to collect data over a wide range of creep rates. Specific temperatures were chosen to collect creep data above and below the glass transition temperature of 31°C. The indentation and uniaxial compression data was used to accomplish several objectives.

The first objective was to test the ability of the Oliver-Pharr stiffness equation to predict contact area. The current contact …

The Stability Analysis Of Linear Dynamical Systems With Time-Delays, Ajeet Ganesh Kamath

Doctoral Dissertations

Time-delay systems, which are also sometimes known as hereditary systems or systems with memory, aftereffects or time-lag, represent a class of infinite-dimensional systems, and are used to describe, among other types of systems, propagation and transport phenomena, population dynamics, economic systems, communication net- works and neural network models. A key method for the stability analysis of time- delay dynamical systems is the Lyapunov’s second method, applied to functional differential equations. Specifically, stability of a given linear time-delay dynamical system is typically shown using a Lyapunov-Krasovskii functional, which involves a quadratic part and an integral part. The quadratic part is usually …

Pseudoelasticity And Shape Memory Effect In Single Crystal Fe3Al, Saurabh Kabra

Doctoral Dissertations

Fe₃Al is an intermetallic compound which has shown some excellent engineering properties and has been widely studied for this reason. It also shows interesting mechanical phenomenon like yield stress anomaly and pseudoelasticity. Mechanical behavior and diffraction studies on the pseudoelastic aspect of Fe₃Al have been presented in this work.

Single crystalline, D0₃ ordered Fe₃Al is known to show pseudoelastic behavior at room temperature. Pseudoelastic behavior was seen in both tension and compression with a distinct tension-compression asymmetry. No strain hardening occurred under tension even at high applied strains as opposed to compression, …

Analysis And Control Of Nonnegative Systems, Jayanthy Ramakrishnan

Doctoral Dissertations

Nonnegative systems are dynamical systems with nonnegative states for random non- negative initial conditions. A subclass of nonnegative systems are compartmental systems characterized by conservation laws.Nonnegative and compartmental systems have widespread applications in biological systems, medical systems, thermodynamic systems, network systems, economic systems, etc.

In this dissertation we have investigated the applications of nonnegative systems in biological and network systems. The specific focus in biological systems has been in the area of pharmacokinetics and we have addressed the consensus problem in network systems. We have specifically focused on the time-delay present in compartmental systems and have investigated the behavior of …

Methylsilane Derived Sic Particle Coatings Produced By Fluid-Bed Chemical Vapor Deposition, James Henry Miller

Doctoral Dissertations

This report describes the research effort that was undertaken to develop and understand processing techniques for the deposition of both low and high density SiC coatings from a non-halide precursor, in support of the Generation IV Gas-Cooled Fast Reactor (GFR) fuel development program.

The research was conducted in two phases. In the first phase, the feasibility of producing both porous SiC coatings and dense SiC coatings on surrogate fuel particles by fluidized bed chemical vapor deposition (FBCVD) using gas mixtures of methylsilane and argon was demonstrated. In the second phase, a combined experimental and modeling effort was carried out in …

Effects Of Temperature And Grain Size On The Transformation And The Deformation Behaviors Of The Trip (Transformation Induced Plasticity) Steels, Kaixiang Tao

Doctoral Dissertations

Two types of TRIP steels, a commercial 304L stainless steel and an Fe-10%Cr-5%Ni-8%Mn steel, have been used to investigate the effects of temperature and grain size on the transformation and mechanical behaviors. 304L SS was used to investigate the effects of temperature ranging from 300K to 77K, while the Fe-10%Cr-5%Ni-8%Mn steel was used for the investigation of the effects of the grain size at 300K.

At 203K, the fcc grains of the 304L SS with {200} plane normal parallel to the loading direction are preferred for the fcc to bcc transformation and the {200} plane normals of the newly-formed bcc …

A Lifetime-Prediction Approach To Understanding Corrosion: The Corrosion-Fatigue And The Corrosion Behavior Of A Nickel-Based Superalloy And A Nanocrystalline Alloy, Rejanah Vernice Steward

Doctoral Dissertations

Lifetime-prediction models are useful for simulating a material’s in-service behavior or outcome. Perhaps the greatest advantage of these models is the ability to use the predicted results to help optimize engineering designs and reduce costs. The Hastelloy^® C-2000^® superalloy is a single-phase material and face-centered cubic in structure at all temperatures. The C-2000^® alloy is a commercially designed alloy manufactured to function in both reducing and oxidizing solutions. C-2000^® is used as a fabrication material for heat exchangers, piping for chemical refineries, and storage repositories. The corrosion properties of C-2000^® are excellent, and the ductility …

Ex-Situ Epitaxial Yba2Cu3O7-Δ Films: Precursor Conversion And Film Characterization, Yifei Zhang

Doctoral Dissertations

BaF₂-based precursors were deposited on various substrates by electron beam co- evaporation and trifluoroactates-involved metal organic deposition (TFA-MOD) for fabricating biaxially-textured YBa₂Cu₃O_7-δ (YBCO) films. A low-pressure processing system was established for the conversion of the precursors. High critical current densities near 4 MA/cm² (77 K, self field) were obtained for the first time through the ex-situ conversion under the total pressures as low as 10 mTorr. The viability of the low- pressure conversion may enable a large-scale, cost-effective batch production of YBCO- based high temperature superconductor (HTS) wires.

The effects of the …

A Kinetic Study Of Indentation Pop-Out In Si, Songqing Wen

Doctoral Dissertations

The kinetics of the phenomenon of pop-out during nanoindentation of silicon were studied by a variety of mechanical and structural characterization techniques. Pop- out is commonly viewed to result from the reversal of a unique pressure-induced, volume reducing phase transformation that occurs in silicon and germanium.

The mechanical characteristics were examined by standard nanoindentation methods using a number of triangular pyramidal indenters with centerline-to-face angles varying in the range 35°-85°. The load at which pop-out occurs was systematically measured as a function of indenter angle, loading/unloading rate, and maximum load. Nanoindentation tests were conducted both at a constant loading rate …

Studying The Fatigue Behavior Of Zr-Based Bulk-Metallic Glasses And Composites, Gongyao Wang

Doctoral Dissertations

As excellent candidates for structural materials, the mechanical behavior of bulk metallic glasses (BMGs) is being widely studied. Although their fatigue behavior is very important for engineering applications, there are few studies on their fatigue behavior. Moreover, the understanding of the fatigue behavior is pretty limited.

High-cycle fatigue experiments were conducted on notched Zr-based BMGs under tension-tension loading in air and vacuum at room temperature. A sparking phenomenon was found by infrared camera at the final fracture moment of Zr₅₀Al₁₀Cu₃₀Ni₁₀ in air. The fatigue-endurance limit (983 MPa) of Zr₅₀Cu₃₇Al …

Computer Modeling Of Tennessee Valley Authority’S Coal Based Power Plant At Kingston To Predict The Effluent To Emory River, Bratendu Bagchi

Doctoral Dissertations

In the wake of stringent environmental regulations, this research studies ash pond discharge to the river by Kingston Power plant. Currently 1296 MGD of fresh water from the Emory river via plant intake is used in condenser cooling. 40 MGD of ash sluice water containing ammonium compounds, mercury compounds, phosphates, Arsenic, Selenium, etc, is discharged to the plant intake via the ash pond for recycle back as sluice water into the plant. Ammonia slip from SCR unit is responsible for the ammonia and mercury comes from the coal. The research addresses the methodology to predict pollutants in the ash pond …

Severe Plastic Deformation Using Friction Stir Processing, And The Characterization Of Microstructure And Mechanical Behavior Using Neutron Diffraction, Wanchuck Woo

Doctoral Dissertations

Friction-stir welding (FSW) is a solid-state joining process, which utilizes a cylindrical rotating tool consisting of a concentric threaded tool pin and tool shoulder. The strong metallurgical bonding during the FSW is accomplished through: (1) the severe plastic deformation caused by the rotation of the tool pin that plunges into the material and travels along the joining line; and (2) the frictional heat generated mainly from the pressing tool shoulder. Recently, a number of variations of the FSW have been applied to modify the microstructure, for example, grain refinements and homogenization of precipitate particles, namely friction-stir processing (FSP). Applications of …

Surface Composition And Interaction Of Thermally Treated White Oak With White Sprits, Roy Douglas Wilcox

Doctoral Dissertations

The surface composition and energy of two thermally treated white oak stave sources and the acidic composition of their white spirit extracts were studied to determine whether composition of the maturing extract could be attributed to variability in surface composition due to degradation of lignin, cellulose, and extractives with thermal treatment and extraction. The sources were from the Ozarks and Appalachia. Surface composition was determined by X-Ray photoelectron spectroscopy (XPS). Surface energy was obtained from the wicking method of contact angle determination with probe liquids and application of the van Oss geometric mean equation. Acid-base properties and composition of the …

A Distributed Solution For Visual Sensor Networks To Detect Targets In Crowds, Cheng Qian

Masters Theses

Visual sensor networks (VSNs), a novel concept about fulfilling vision tasks by a network of collaborative visual sensors, has been attracting more and more attentions these days. This thesis introduces some pioneering research on developing a distributed algorithm for VSNs to detect targets in a cluttered scene. The algorithm is aimed to achieve excellent performances on both detection accuracy and energy efficiency.

Based on a statistical model of the cluttered scene, the development starts with a centralized version where all the nodes send visual data to a central node and the central node invokes an iterative prioritization strategy (IPS) to …

Experimental Analyses Of An Atmospheric Pressure Electrical Plasma Decontaminator, Eric Pius Pradeep

Masters Theses

Electrical Gas Plasmas have been widely utilized in the frontiers of sterilization and disinfection of hazardous chemicals and unsafe microorganisms. In this research Atmospheric Pressure Non-thermal Plasma has been employed using various working gases such as air, helium and nitrogen to study its decontamination effects. Focus is given to analyze the constituents of the plasma such as UV light, charged particles, and chemical components produced during the operation of the discharge which influences the incapacitation of the exposed entities, in this specific study, only bacteria and bacteriophages were exposed. Biological tests involved the cultivation of bacteria and bacteriophages on Petri …

Application Of Energy Analysis To The Problem Of Propulsion Driven Nutation Instability Of Spin Stabilized Spacecraft, Tina Morina Rice

Masters Theses

Propulsion driven nutation instability in spin stabilized spacecraft was first observed in the late nineteen seventies. It’s often referred to as the PAM-D coning anomaly, as it first occurred in the McDonnell Douglas Payload Assist Module (PAM-D). Propulsion driven nutation instability is a performance degrading phenomenon that occurs in spin-stabilized spacecraft used for the raising of satellite payloads to geosynchronous orbit. It is characterized by a coning (wobbling) motion that grows to a large degree during the final seconds of motor burn. The instability is clearly related to the increased size of the rocket needed to support the increasing …

The Functional Application Of The Propeller Load Curve For Fixed Pitch Propellers, Rebecca Barnett Speas

Masters Theses

This thesis attempts to help the flight test community by using the propeller load curve (also known as prop load) to find brake horsepower (BHP) easily with only a propeller tachometer. This thesis also covers the equation for the propeller load curve.

The flight test was done using a Piper Cherokee 180 equipped with a Lycoming 0-360-A3A engine. The flight test data were collected at University of Tennessee Space Institute (UTSI). This data were then compared to the prop load from the engine manufacturer.

Based on the result of this flight test, using the prop load equation from the Lycoming …

Controlling The Dispersion Of Nanoparticles In Polymer Matrices, Chang-Uk Lee

Masters Theses

The dispersion of nanoparticles in a polymer matrix is a critical parameter to design and realize targeted morphologies and properties of a final polymer-based nanocomposite. This thesis presents experimental studies to investigate the dispersion of nanoparticles is polymer matrices using specific intermolecular hydrogen bonding between the nanoparticles and polymer matrices under two main topics.

The first topic is the impact of sample preparation processes on the properties of polymer carbon nanotube nanocomposites. Polymer nanocomposites composed of poly(styrene-co-vinyl phenol) (PSVPh) copolymers and 5 wt % multi-walled carbon nanotubes (MWNTs) were prepared from three different methods, including melt-mixing and solution casting. The …

Lignin Composites With Phenol-Acrylates Cured By Electron Beam, Seth N. Bowman

Masters Theses

As the major by-product of the pulp and paper industry, determining a use for lignin represents a key priority to almost any bio-materials research organization. The purpose of this study is to investigate the interaction with and effects of lignin within phenol- acrylate composites cured by electron beam, characterizing changes to both physical and chemical properties. In order to more fully characterize the effects of lignin, results of pure lignin as well as cellulose samples subjected to electron beam radiation and tested by FT-IR are presented. For the composite material, results of both DMA and FT-IR spectroscopy will be presented. …

Retrofit Reconfigurable Flight Control System And The F/A-18c, Matthew E. Doyle

Masters Theses

The United States Navy has completed the initial flight test of a Reconfigurable Control Law System (RCLAWS) on the F/A-18C. The purpose of reconfigurable control is to allow for the safe operation of an aircraft that has experienced a sudden change in aircraft dynamics resulting from aircraft damage or flight control effector damage. The RCLAWS utilized during this flight test are novel in that they are designed to augment the production flight control system instead of replacing it. In order to reduce verification and certification requirements, this retrofit reconfigurable methodology supplements pilot commands to compensate for undesirable aircraft dynamics instead …

An Evaluation Of The Ah-64 Night Vision Systems For Use In 21st Century Urban Combat, John Kevin Heinecke

Masters Theses

Currently one of the most arduous and dangerous aviation missions for the military attack helicopter pilot is the night combat mission. The mission entails flight at close proximity to the ground and obstacles such as wires, trees, and buildings in an effort to avoid detection by enemy air defense and insurgent small arms fire. Night flight requires the use of augmented vision systems and enhanced aircraft stability and control systems to allow pilots to effectively see and negotiate those hazards that would otherwise be visible during daylight.

The U.S. Army currently fields two variants of augmented visionics, the Aviator Night …