Engineering Commons^™

Characterization Of Porous Media And Refractory Materials, Xin Chen

Doctoral Dissertations

Because of its unique advantages on energy savings and casting complex shaper, Lost Foam Casting (LFC) has been widely used as a replacement to the conventional techniques (sand and investment castings). In order to continuously improve the quality of the Lost Foam Casting process for reducing scrap rate and increasing energy savings, the US Department of Energy through its National Industrial Competitiveness through Energy, Environment, and Economics (NICEEE) program sponsored the present study to develop new characterization techniques for enhancing the understanding of the fundamental properties of the refractory materials used in The Lost Foam Casting process. In this study, …

An Adaptive Tool-Based Telerobot Control System, Ge Zhang

Doctoral Dissertations

Modern telerobotics concepts seek to improve the work efficiency and quality of remote operations. The unstructured nature of typical remote operational environments makes autonomous operation of telerobotic systems difficult to achieve. Thus, human operators must always remain in the control loop for safety reasons. Remote operations involve tooling interactions with task environment. These interactions can be strong enough to promote unstable operation sometimes leading to system failures. Interestingly, manipulator/tooling dynamic interactions have not been studied in detail. This dissertation introduces a human-machine cooperative telerobotic (HMCTR) system architecture that has the ability to incorporate tooling interaction control and other computer assistance …

Convergence And Robustness Issues In Computational Fluids, Xiaoqiang Zeng

Doctoral Dissertations

The present research develops two methods to improve the convergence and robustness of CFL algorithm, the triple time method and error- limited time step ramping method.

A general formulation of the triple time scheme is developed by introducing three pseudo time-marching steps to control three preconditionings for artificial dissipation, non-linear equation iteration convergence and linear equation iteration convergence separately. It is proven that the triple time method can be degenerated to the single time method and the multiple DDLGS iteration method at special cases.

Stability analysis is used to choose the optimum combination of three preconditionings from the steady preconditioning, …

High Accuracy Distributed Target Detection And Classification In Sensor Networks Based On Mobile Agent Framework, Xiaoling Wang

Doctoral Dissertations

High-accuracy distributed information exploitation plays an important role in sensor networks. This dissertation describes a mobile-agent-based framework for target detection and classification in sensor networks. Specifically, we tackle the challenging problems of multiple- target detection, high-fidelity target classification, and unknown-target identification.

In this dissertation, we present a progressive multiple-target detection approach to estimate the number of targets sequentially and implement it using a mobile-agent framework. To further improve the performance, we present a cluster-based distributed approach where the estimated results from different clusters are fused. Experimental results show that the distributed scheme with the Bayesian fusion method have better performance …

Synthesis And Ordering Of Nanostructures Using Laser Light, Yingfeng Guan

Doctoral Dissertations

This dissertation focuses on the formation of 1-D and 2-D nanoscale structures induced by the KrF excimer UV laser irradiation of silicon (λ=248 nm). Relatively low laser energy density (E_d<=1 J/cm²) is required to produce nanostructures. Alignment of 2-D nanoripple structures and nanoprotrusions has been realized by using Lloyd’s mirror configuration.

Laser-generated silicon microcone arrays were used as templates for the growth of nanocolumns. The formation mechanism of the microstructure is reviewed, and the origin and growth of nanocolumns are discussed. The formation mechanism of nanocolumns requires highly localized melting, which explains why they fail to form on …

A Study Of The Evolution Of Laser-Induced Periodic Surface Microstructures On Silicon And Electronic Transport In Composite Carbon Nanotube Networks, Stephen Jesse

Doctoral Dissertations

This dissertation addresses two main topics, the formation of micron-scale surface structures on single crystal silicon by irradiation with a KrF (248 nm) pulsed excimer laser source, and an investigation into electronic transport through composites of polymer (PMMA) and single-walled carbon nanotubes. It is shown that the spacing between laser-generated surface structures is determined primarily by the melt time and that the crystal orientation of the substrate can determine whether surface structures will form at all and also influence the shape of individual surface structures. During the melt/solidification cycle, the shape of liquid-vapor interface in modified by surface tension, and …

Fundamental Studies Of X-Ray And Secondary Electron Spectroscopy, Staya Prasad Mulapudi

Doctoral Dissertations

Microanalysis of submicron particles in the Scanning Electron Microscope (SEM) is only possible by using low incident electron beam energies due to smaller interaction volume and suppressed beam induced charging. Such low beam energies must use L- and M- lines rather than the familiar K-lines. The information about the fundamental parameters of X-ray emission and transport at low energies is limited, so the use of L- and M- lines is problematic. The rate of generation of X-rays from an element irradiated at some energy E depends on the product of the ionization cross-section (E) and the fluorescent yield . Unfortunately …

Modeling And Source Apportionment Of Primary And Secondary Pm2.5 In The Atmosphere, Prakash Doraiswamy

Doctoral Dissertations

Source apportionment of PM_2.5 is important to identify the source categories that are responsible for the concentrations observed at a particular receptor. Although receptor models have been used to do source apportionment, they do not fully take into account the chemical reactions (including photochemical reactions) involved in the formation of secondary fine particles. Secondary fine particles are formed from photochemical and other reactions involving precursor gases such as sulfur dioxide (SO₂), oxides of nitrogen (NO_x), ammonia (NH₃) and volatile organic compounds (VOC). The purpose of this research work was to model primary and …

Developing A Lean Based Model For A Hospital Pharmacy Environment, Jason North

Masters Theses

Lean strategies have become necessary in healthcare due primarily to two factors: a demand for efficiency and a need to reduce medical error. The case for the necessity of a lean program is based on trends of increasing costs and decreasing revenues resulting from government intervention. Profit margin per patient has been reduced, and therefore more patients per time period must be seen in order to meet profitability goals. Preventable medical error is shown to be a leading cause of death.

Current research in the area of hospital and healthcare efficiency proves that a parallel exists between healthcare efficiency today …

The Design Of Medium Access Control (Mac) Protocols For Energy Efficient And Qos Provision In Wireless Sensor Networks, Yang Liu

Masters Theses

This thesis work focuses on innovative design of media access control (MAC) protocols in wireless sensor networks (WNSs). The characteristics of the WSN inquire that the network service design considers both energy efficiency and the associated application requirement. However, most existing protocols address only the issue of energy efficiency.

In this thesis, a MAC protocol has been proposed (referred to as Q-MAC) that not only minimized the energy consumption in multi-hop WSNs, but also provides Quality of Service (QoS) by differentiating network services based on priority levels prescribed by different applications. The priority levels reflect the state of system resources …

Automated Grid Generator For Mhd Flow Simulations Made With The Gems Code, Konstantin Kolokolnikov

Masters Theses

Numerical simulations for Hypersonic Vehicle Power System (HVEPS) Project were based on a multi-domain, general Navier-Stokes Solver Code called the GEMS® Code. The GEMS® Code was in the process of being extended to solve for plasma flows with both self-induced as well as externally-applied magnetic fields. GEMS® is also capable of simulating both laminar and turbulent flow in unbounded as well as ducted flows. For application to the ducted Plasma flows generated experimentally in the HVEPS program, GEMS® was set up to calculate turbulent flow in 1-3D (dimensional) duct geometries in general and in 2D, 3D ones for purposes of …

Hardware Acceleration Of The Embedded Zerotree Wavelet Algorithm, Suresh S. Polisetty

Masters Theses

The goal of this project was to gain experience in designing and implementing a microelectronic system to acclerate the execution of a time-consuming software algorithm, the Embedded Zerotree Wavelet (EZW), which is used in multimedia applications. The algorithm was implemented using MATLAB to be certain it was fully understood and to serve as a validation reference. Then, the algorithm was mapped into a hardware description language, VHDL, and its resulting implementation verified with the golden reference. The hardware description was then targeted to a field-programmable gate array (FPGA). Significant acceleration was achieved since the hardware implementation in a FPGA (Xilinx …

Retrieval Of Nano-Size Particles From A Solid Substrate, Krishna Prasad Podila

Masters Theses

The retrieval of nano-size particles from suspects and crime scenes can significantly enhance surveillance and crime investigation. The Thesis deals with extensive study of free surface energy coupled with Hertzian contact energy under different conditions between a nano-sized particle and a substrate and the various methods of dislodging the particle. Using the Johnson-Kendall-Roberts (JKR) theory, a physical spring-mass-damper model is defined. Mathematical equations are formulated and solved with non-linear equations simulating the real world situation. Using Newmark’s β method, the system is solved for response of free and forced vibrations taking moisture to be responsible for damping. Key assumptions such …

Curvature Variation As Measure Of Shape Information, Sreenivas Rangan Sukumar

Masters Theses

In this thesis, we present the Curvature Variation Measure (CVM) as our informational approach to shape description. We base our algorithm on shape curvature, and extract shape information as the entropic measure of the curvature. We present definitions to estimate curvature for both discrete 2D curves and 3D surfaces and then formulate our theory of shape information from these definitions.

With focus on reverse engineering and under vehicle inspection, we document our research efforts in constructing a scanning mechanism to model real world objects. We use a laser-based range sensor for the data collection and discuss view-fusion and integration to …

Investigation Of Fiber Splitting In Side-By-Side Bicomponent Meltblown Nonwoven Webs By Additive Applications, Jihua Xiao

Masters Theses

Ever since the potential applications of superfine fibers were realized, bicomponent fibers have received considerable commercial interest. Webs containing microfine bicomponent fibers, such as bicomponent meltblown webs, have found great opportunities in production of finer fibers by subsequent fiber splitting, though technical problems still exist due to special features of the meltblown fibers, including low molecular orientation, low crystallinity and low strength.

In this research, the mechanics of polymeric interfacial adhesion in side-by-side bicomponent meltblown fibers was discussed and the method of enhancing the fiber splitting in bicomponent meltblown webs by additive application prior to the extrusion process was proposed …

Computational Aerodynamic Analysis Of Converging Free Jets, George Wayman Hatcher

Masters Theses

The aerodynamics of converging free jets was studied to determine the characteristics of the flow field involved in the manufacture of meltblown fibers. The two-dimensional computational fluid dynamic analysis was validated through comparison to boundary layer theory. The converging jet geometry consisted of two symmetric rectangular channels 30º from the axis of symmetry, 0.013 inches wide, converging toward a free expansion region at standard atmospheric conditions. The two channels were 0.015 inches apart at the exit, and the perpendicular wall region between them was flush with the upper and lower plate faces of the meltblowing die. Upstream boundary conditions of …

Cure Behavior Study And Elastic Modulus Characterization Of Resin System Of A Quasi Poloidal Stellarator Modular Coil, Hariharanath Kavuri

Masters Theses

Composites materials are increasingly becoming choice materials because of their tremendous strength-to-weight properties and impressive design flexibility. A more recent application of composites is in nuclear fusion reactors. One such reactor is the Quasi-Poloidal Stellarator (QPS) being developed by Oak Ridge National laboratory. QPS, with a non-axisymmetric, near-poloidally symmetric magnetic configuration, has stranded copper/epoxy composite coils, used for magnetic confinement of plasma. CTD- 404 and CTD-101K are the resins under consideration for the modular coils with copper fiber as reinforcement. Structural integrity of the modular coils over wide range of temperatures, including liquid nitrogen temperature, is of vital importance and …

A Two-Phase Cooling Method Using R134a Refrigerant To Cool Power Electronics Devices, Jeremy Bryant Campbell

Masters Theses

Power electronics are vital to the operation and performance of hybrid-electric vehicles (HEVs) because they provide the interface between the energy sources and the traction drive motor. As with any “real” system, power electronic devices have losses in the form of heat energy during normal switching operation, which has the potential ability to damage or destroy the device. Thus, to maintain reliability of the PE system, the heat energy produced must be removed. Present HEV cooling methods provide adequate cooling effects, but lack sufficient junction temperature control to maintain long-term reliability. This thesis is based on using the automobile’s air …

The Synthesis And Characterization Of Mesoporous Uranium Oxide Catalysts For Oxidative Destructions Of Volatile Organic Compounds And Clean Air Protection, Cyrus Khezr Riahi-Nezhad

Masters Theses

The overall goal of this research was to investigate a new class of mesoporous uranium oxide catalyst used to destroy a range of volatile organic compounds (VOCs), including aromatics and chlorinated organic compounds under conditions which are applicable for U.S. Department of Energy (DOE) facilities and U.S. industries.

Uranium oxides are known to have high efficiency and long-term stability when used to destroy volatile organic compounds (VOCs) when compared with some of the commercial catalysts, such as precious metals, TiO₂, and Co₃O₄ catalysts. Two key factors limiting catalytic activities of uranium oxides prepared by conventional …

Analysis Of Pilot Performance Using Precision Visual Flight Rules, Thomas Morrissey

Masters Theses

Precision Visual Flight Rules (PVFR) seeks to allow helicopter pilots to fly predetermined routes in high density traffic areas with greater precision by using a Global Positioning System (GPS). An analysis of the cross-track error during the PVFR developmental testing is presented. The primary objective is to determine the dominant factors which effect pilot performance using this higher standard of precision. Factors which are investigated include: total flight time, recent helicopter flight time, pilot ratings, and experience with the particular aircraft and GPS model. A conclusion is presented on which factors need to be addressed before opening up PVFR routes …

An Alternative Medium For The Measurement Of Soil Suction By The Filter Paper Method, Lori Ann Mcdowell

Masters Theses

Soil suction is the negative pressure within soil particles, which is a function of the moisture content. It plays an important role in agriculture, civil engineering, and geology. Suction is used in practice to identify expansive soils, to locate heave areas, to develop moisture requirements for arid land plants, to measure for collapse of soils around a footing, and to monitor flow movement of moisture. Soil suction varies with moisture content, and the relationship between suction and water content is known as the soil-moisture characteristic curve of a soil. There are several laboratory tests available to measure suction, but the …

Nanoscale Materials Processing: Electron Beam-Induced Etching Of Silicon And Silicon Dioxide, Steven Jeffrey Randolph

Masters Theses

Both silicon and silicon dioxide can be etched with an electron beam in the presence of a xenon difluoride atmosphere in a process known as electron beam-induced etching (EBIE). In order to study the EBIE process, a Hitachi S-3500N scanning electron microscope (SEM) was modified to accept a vapor delivery system. Evidence has been presented regarding the fundamental mechanisms by which EBIE occurs, as well as the microscope variables that effect the etch process.

The effects of beam current and beam energy on the EBIE process were examined for both materials. On silicon, it was observed that the increased current …

X-Ray Image Processing And Visualization For Remote Assistance Of Airport Luggage Screeners, Yue Zheng

Masters Theses

X-ray technology is widely used for airport luggage inspection nowadays. However, the ever-increasing sophistication of threat-concealment measures and types of threats, together with the natural complexity, inherent to the content of each individual luggage make x-ray raw images obtained directly from inspection systems unsuitable to clearly show various luggage and threat items, particularly low-density objects, which poses a great challenge for airport screeners.

This thesis presents efforts spent in improving the rate of threat detection using image processing and visualization technologies. The principles of x-ray imaging for airport luggage inspection and the characteristics of single-energy and dual-energy x-ray data are …

Microstrain Pattern Analysis Of The Canine Patellar Tendon Following A Tibial Plateau Leveling Osteotomy, Joshua Paul Stapleton

Masters Theses

This study investigates the change in strain patterns of the canine patellar tendon following a Tibial Plateau Leveling Osteotomy (TPLO). The TPLO is a procedure used to minimize anterior tibial translation in canines following a cranial cruciate rupture. A noted clinical deficiency randomly seen with the TPLO is an inflammation of the patellar tendon. In some instances, the inflammation results in material damage resulting in a calcification of the tendon and in worst cases, a fracture of the patella.

In order to investigate the strain patterns, four fresh frozen canine cadaver stifles were used. The cadavers were mounted for stabilization …

Investigation Of Zircaloy-4 Doped With Metallic Burnable Poisons, Chrysostomes K. Kahambwe

Masters Theses

Burnable poisons are used in all commercial reactors to level the power distribution and to reduce the requirements for an excessively large control system. It has been proposed that metallic rare earth elements, serving as burnable poisons, might be alloyed with the fuel cladding rather than mixed with fuel in the form of compounds. This research project studies the effect of such additions on the ductility.and the corrosion resistance of three such alloys.

Alloys of Zircaloy-4 with 0.5 % Gd, 2.0 % Dy, and 2.0 % Er, chosen to represent the maximum likely concentrations of the absorbing elements to be …

A Computer Modeling Approach Using Critical Resource Diagramming Network Analysis In Project Scheduling, Vincent Gilles Delgado

Masters Theses

The problem of resource constrained project scheduling (RCPSP) continues to be an important topic in project management. Different scheduling processes have been introduced to solve cases of RCPSP. Most of the developed methods are based on a network analysis approach. The two main technique of project network analysis used for planning, scheduling, and control are PERT and CPM. These approaches assume unlimited resource availability in project network analysis. In realistic projects, both the time and resource requirements of activities should be considered in developing network schedules. Another particularity of the methods created, so far, is the focus on activities during …

Implementation Of Critical Path Method And Critical Resource Diagramming Using Arena Simulation Software, Jamie Ehresman Gunter

Masters Theses

A relatively new resource management tool, which considers both time and resource requirements, is Critical Resource Diagramming (CRD). CRD is a simple extension to the CPM technique developed for resource management purposes. It is a graphical tool used mainly for resource scheduling.

The purpose of this study is to use the Arena simulation software and CRD to solve problems. This will be accomplished by setting up an example problem in the simulation program, Arena, and the CRD approach will be used as a deterministic and probabilistic problem.

The Arena output results for the deterministic parts of the example were compared …

Effects Of Pressure And Equivalence Ratio On Minimum Ignition Energies Of Methane-Air Mixtures And Effect Of Pressure On Breakdown Threshold Energies Of Methane And Air, Sameer Vidyadhar Bondre

Masters Theses

An experimental investigation is conducted to determine the effect of pressure on breakdown threshold energies of methane and air. In addition the effect of pressure and equivalence ratios on minimum ignition energies of methane-air mixtures are also investigated. The pressures for the breakdown threshold energy experiments are varied from 0.02 to 1.17 MPa, and pressures and equivalence ratios for minimum ignition energy experiments are varied from 0.1 to 1.04 MPa and 0.6 to 1.2, respectively. The gas breakdown and the ignition of the methane-air mixture is achieved using a laser-induced spark from a 5.5 ns pulse Q-switched Nd:YAG laser at …

Use Of The Gps Reciprocal Heading Method For Determining Pitot-Static Position Error In Helicopter Flight Testing, Rucie James Moore

Masters Theses

This thesis is an evaluation of using the Global Positioning System (GPS) reciprocal heading method to determine pitot-static position errors in helicopter flight testing. Determination of position error is a fundamental flight test task that must occur early in a test program, as all other results with regard to airspeed rely on the data. The test determines errors of the pitot-static system that cause inaccurate indication of airspeed to the pilot. The measured course, a currently approved method, provides a measure of the helicopter’s groundspeed by flying the helicopter over a known distance and converting elapsed time into the speed …

Causal Analysis Of Fatal Trenching Accidents, John Patrick Wagner

Masters Theses

A study was performed by the Construction Industry Research and Policy Center at The University of Tennessee, Knoxville to identify causation for U.S. trench collapse fatalities in the construction industry that occurred during the years 1997-1999. Of the 1217 fatality case files analyzed, 44 were categorized as trench collapse fatalities. The 44 trench collapse case files were analyzed and the contributed factors of the fatalities were identified in an effort to determine the causation of collapses. The results of the study showed a large number of trenches without any type of protective devices being used. The findings of the fatal …