Digital Commons Network^™

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 …

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 …

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 …

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 …

Laboratory Evaluation Of Unbound Rap As A Pavement Base Material, Wenbin He

Masters Theses

More than 50 million tons of asphalt pavements are milled every year in the United States (Taha 1999). The economical benefit attracts the recycling practice of utilizing RAP as paving materials.

In unbound RAP material, aged asphalt wraps aggregates. It is believed that unbound RAP performs differently from usual unbound material due to the existence of asphalt wrap. In the present study, triaxial tests were conducted for the unbound RAP under different temperatures. In addition, limestone and gravel were tested in order to compare with RAP. The resilient modulus, triaxial static creep behavior and hysteresis loops were obtained to compare …

Microprocessor Implementation Of Autoregressive Analysis Of Process Sensor Signals, Swetha Priyanka Pakala

Masters Theses

Automated signal analysis can help for effective system surveillance and also to analyze the dynamic behavior of the system such as impulse response, step response etc. Autoregressive analysis is a parametric technique widely used for system surveillance and diagnosis. The main aim objective of this research work is to develop an embedded system for autoregressive analysis of sensor signals in an online fashion for monitoring system parameters. This thesis presents the algorithm, data representation and performance of the optimized microprocessor implementation of autoregressive analysis.

In this work an autoregressive (AR) model is generated as a solution to a linear system …

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 …

Design And Optimization Of A Wind Deflector For Round-Nose Md-500 Series Helicopters, James Joseph Wright

Masters Theses

This thesis examines the problem experienced by the numerous rotary wing operators whose operations require flight with personnel seated outside the fuselage or with doors off. This investigation is specific to the round nose configured MD-500 series aircraft due to test aircraft availability and the wide range of missions it conducts worldwide. During cruise flight, personnel exposed to the aircraft slipstream are subjected to high wind loads and extreme wind chill effects, compromising their ability to perform required tasks. External passengers also add to the overall helicopter parasite drag, decreasing its performance as well as interfering with the crew through …

“Design, Development And Characterization Of A Thermal Sensor Brick System For Modular Robotics, Nikhil Arun Naik

Masters Theses

This thesis presents the work on thermal imaging sensor brick (TISB) system for modular robotics. The research demonstrates the design, development and characterization of the TISB system. The TISB system is based on the design philosophy of sensor bricks for modular robotics. In under vehicle surveillance for threat detection, which is a target application of this work we have demonstrated the advantages of the TISB system over purely vision-based systems. We have highlighted the advantages of the TISB system as an illumination invariant threat detection system for detecting hidden threat objects in the undercarriage of a car. We have compared …

Integrated Corridor Management: Operational Strategies Under Interstate Diversion Scenarios, Shaun Michael Quayle

Masters Theses

This thesis looks at operational strategies to increase capacity within the context of Integrated Corridor Management (ICM) under a non-recurring Interstate incident scenario. This incident scenario creates lengthy queues and increased delay and travel times on the Interstate, forcing a portion of Interstate traffic to utilize alternate routes throughout the corridor, changing the network traffic patterns. Particular operational strategies are tested under this premise to qualify and mildly quantify the benefits of relaying incident and diversion routing information to corridor drivers, mimicking ITS information dissemination elements such as changeable message signs, highway advisory radio, in vehicle navigation systems and etc. …

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 …

Outside The Fence,' The Threat To The U.S. Aviation Industry, David Thomas Ramsey

Masters Theses

The purpose of this thesis was to examine the threat to the Aviation Industry from within the United States. The overall investigation starts with one assumption “that there will at some time in the near future be a covert operative group that desires to attack or engage the United States in war on its home land.” The principles of war will be analyzed resulting in covert cell guidance specifically; “economy of force” will require the covert units to be as small as possible to affect as many nodes as possible. Endurance will require the covert team to restrict any tactics …

Installing A Night Vision Imaging System In The Cf-188 Hornet: Compatibility Of Warning And Caution Lights, Andrew John Soundy

Masters Theses

The purpose of this thesis was to investigate the NVIS compatibility of fire warning lights as installed during a NVIS upgrade of the CF-188 Hornet for operation with Generation 3 AN/AVS-9 night vision goggles. Data was gathered and compared to the specifications listed in MIL-STD-3009 to determine suitability of the implemented design. Of particular concern during the execution of this project was the compatibility of fire warning lights for operation in both day-time and night-time conditions with respect to NVIS radiance. The initial design placed the NVIS radiance of cockpit warning lights at a level commensurate with that suggested by …

An Experimental Study Of Incompressible Axisymmetric Cavity Flow With Swirl, Lee Charles Wendell

Masters Theses

A systematic study was performed of the flow phenomena in an axisymmetric cavity. Axial flow Reynolds numbers ranged from 100,000 to 530,000 for cavity L/D range of 0.25 to 1.65. Working medium for this study was water reflecting that only incompressible domain of cavity flow was covered in this study. Previous results of axisymmetric flow investigations were reproduced and extended to lower L/D values, with the modified test article. Introduction of swirl in the cavity flow was studied in detail for its effects on the enhancement or suppression of cavity modes that have been measured.

The axial apparatus tested here …

Processing And Characterization Of A Novel Bioabsorbable Polymer For Biomedical Applications, Katherine Atchley

Masters Theses

A series of amino acid based bioanalogous polymers have been synthesized by Dr. C. C. Chu at Cornell University for future use in biomedical applications. These poly(ester amide)s have been designed to be bioabsorbable, with particular interest in internal fixation and drug delivery applications. The polymers PEA 4-Phe-4, 4-Phe-Das, and 8-Phe-Das were studied; however, due to better material properties, the focus mainly centered on 4-Phe-4. Since these are new polymers, processing conditions needed to be determined and the structure and properties characterized. The fibers were also processed post-extrusion in an effort to induce orientation and crystallinity within the polymer chains. …

A Resource Efficient Localized Recurrent Neural Network Architecture And Learning Algorithm, Daniel Borisovich Budik

Masters Theses

Recurrent neural networks (RNNs) are widely acknowledged as an effective tool that can be employed by a wide range of applications that store and process temporal sequences. The ability of RNNs to capture complex, nonlinear system dynamics has served as a driving motivation for their study. RNNs have the potential to be effectively used in modeling, system identification and adaptive control applications, to name a few, where other techniques fall short. Most of the proposed RNN learning algorithms rely on the calculation of error gradients with respect to the network weights. What distinguishes recurrent neural networks from static, or feedforward …