Engineering Commons^™

Modification And Evaluation Of Continuous Roll Prediction Model For Front Drive Mowers, Xinyan Wang

Doctoral Dissertations

The recently approved ASAE Standard S547 “Tip-Over Protective Structure (TOPS) for Front Wheel Drive Turf and Landscape Equipment” addressed a continuous roll prediction model for Roll-Over Protective Structure (ROPS) design. The existing model described in this Standard did not take into account the influence of the mower deck on the rollover behavior. In order to evaluate the accuracy of the original model, according to the ASAE S547 requirement, a 4.05 meters long and 3.42 meters wide slope of 35 degrees was constructed at the University of Tennessee. Lateral upset tests for Deere F925 front drive mower with regular and inverted …

Differential-Algebraic Approach To Speed And Parameter Estimation Of The Induction Motor, Mengwei Li

Doctoral Dissertations

This thesis considers a differential-algebraic approach to estimating the speed and rotor time constant of an induction motor using only the measured terminal voltages and currents. It is shown that the induction motor speed satisfies both a second-order and a third-order polynomial equation whose coefficients depend the stator voltages, stator currents, and their derivatives. Further, it is shown that as long as the stator electrical frequency is nonzero, the speed is uniquely determined by these polynomials. The speed so determined is then used to stabilize a dynamic (Luenberger type) observer to obtain a smoothed speed estimate. With full knowledge of …

Thermal And X-Ray Analysis On The Origin Of Double Melting Phenomena Of Poly(L-Lactic Acid) Films, Xiaoyun Ling

Doctoral Dissertations

Thermal analysis is one of the most commonly used techniques to characterize the structure and properties of semicrystalline polymers. Unfortunately, the interpretation of thermal events is not always straightforward, but can be quite complicated. However, the complexity involved is often overlooked, leading to erroneous or, at least, questionable results and interpretations. In the present study we carry out an extensive investigation of the thermal behavior of poly(L-lactic acid), PLLA, films prepared under a wide range of crystallization conditions, including isothermal and non-isothermal crystallization from both the glassy state and the melt. The primary techniques used were differential scanning calorimetry (DSC), …

High-Temperature Low-Cycle-Fatigue And Crack-Growth Behaviors Of Three Superalloys: Hastelloy ® X, Haynes ® 230, And Haynes ® 188, Yulin Lu

Doctoral Dissertations

Extensive smooth-bar low-cycle-fatigue (LCF) and fatigue crack growth (FCG) experiments on three solid-solution-strengthened superalloys HASTELLOY X, HAYNES 230, and HAYNES 188 have been conducted at 816 and 927 C. Limited tests were run at 649 C, 871 C, and 982 C to study the temperature effect. The LCF tests were performed under a total-strain-range-control mode at Solar Turbines Inc., Metcut Research Inc., and The University of Tennessee (UT). The FCG tests were done under both the constant-load-range and constant-stress-intensity-factor-range modes at Westmoreland Testing Inc. and UT. Various hold times were imposed at the maximum strain or load in both the …

Isolation And Thermodynamic Characterization Of Aminoglycoside Nucleotidyltransferase (2″)-Ia, Roger Edward Wright

Doctoral Dissertations

Aminoglycoside nucleotidyltransferase(2″)-Ia is one of the most important aminoglycoside-modifying enzymes. Because of the difficulties in isolating this enzyme with a high level of purity, very little work has been reported for this enzyme. A procedure for obtaining this enzyme with a purity level of greater than 95% from inclusion bodies was developed. The optimal conditions for isolating ANT(2″) were solubilizing the inclusion bodies in 8 M urea followed by direct dilution of the enzyme into 0.1 M Tris-HCl pH 8.5, 0.2 M KCl, 0.4 ML-arginine and 5 mM reduced glutathione at 4°C. The determination of an effective method of obtaining …

A Proposed Framework For Simultaneous Optimization Of Evacuation Traffic Distribution And Assignment, Fang Yuan

Doctoral Dissertations

In the conventional evacuation planning process, evacuees are assigned to fixed destinations based mainly on the criterion of geographical proximity. However, such pre-specified destinations (OD table) almost always lead to sub-optimal evacuation efficiencies due to uncertain road conditions such as congestion, road blockage, and other hazards associated with the emergency. By relaxing the constraint of assigning evacuees to pre-specified destinations, a one-destination evacuation (ODE) concept has the potential of greatly improving the evacuation efficiency. A framework for simultaneous optimization of evacuation traffic distribution and assignment is therefore proposed in this study. Based on the concept of ODE, the optimal destination …

Analysis Of Vehicle Use Patterns During Military Field Exercises To Identify Potential Roads, Chunxia Wu

Doctoral Dissertations

Military training is an intensive land use and can cause negative environmental effects. Many studies conducted under Integrated Training Area Management (ITAM) for quantifying the impact resulted from the military training exercise found that off-road vehicular activities during training exercises cause the major impact to the training land. Vehicle land use patterns at a certain location affect the impact severity: concentrated and repeated traffic create more serious damage to the land compared to the dispersed offroad vehicle movements. Those areas heavily disturbed by off-road traffic may require a longer period of time or special treatments for the land to return …

Evaluation Of Heavy-Duty Diesel Vehicle Emissions During Cold-Start And Steady-State Idling Conditions And Reduction Of Emissions From A Truck-Stop Electrification Program, James A. Calcagno

Doctoral Dissertations

Cold-start and extended-idling emissions of carbon monoxide (CO), oxides of nitrogen (NOx) and particulate matter (PM) were measured from 24, class-8B, heavy-duty diesel vehicles (HDDV8B) using portable emission monitoring equipment. The ratio of nitrogen dioxide (NO₂) to NOx and the ratio of PM_2.5 to total PM were reported. Truck model years ranged from 1992 to 2004. All vehicles were tested in the field during summer and fall months under ambient environmental conditions at low (600-800 rpm) and high (1000 rpm) engine idling speeds with the truck cab air-conditioner operating at “on” and “off” modes. Sampling data thus …

Health Risk Assessment Posed By The Mobile Source Air Toxics On An Urban To Regional Area, Luis Alonso Díaz Robles

Doctoral Dissertations

Air toxics are important health concern. The purpose of this research was to develop a protocol to predict exposure concentrations of air toxics and inhalation cancer and noncancer risk that come from different gasoline and diesel-fueled sources. The protocol was developed by linking the U.S. EPA’s Models-3/CMAQ model as the exposure model and toxicological and epidemiological evidence functions. The NEI version 3 for the year 1999 was used in this analysis for point, area, and non-road sources, whereas NMIM was used to create the on-road emissions. The year 2003 was used for meteorological data and as reference to compare the …

Liquid Crystals Confined In Nanoporous Silica, Yang Gao

Doctoral Dissertations

Confinement has a nontrivial effect on a condensed matter system due to the finite size effect, the surface effect and the induced disorder. Different techniques such as calorimetric measurement, dielectric spectroscopy, dynamic light scattering, X-ray scattering and quasi-elastic neutron scattering have been widely used to study this important topic. Confined liquid crystals (LCs) have attracted great attention in particular because they are a soft system and their physical properties are more easily affected by the geometrical confinement (entropic) effect and the surface interaction (energetic) effect. In this paper, we study the phase transitions and dynamic behavior of LCs, 5CB and …

Adaptive Nonlinear Optimization Methodology For Installed Capacity Decisions In Distributed Energy/Cooling Heat And Power Applications., Carl Randolph Hudson

Doctoral Dissertations

Evaluation of potential cooling, heating and power (CHP) applications requires an assessment of the operations and economics of a particular system in meeting the electric and thermal demands of a specific end-use facility. Given the electrical and thermal load behavior of a facility, the tariff structure for grid-supplied electricity, the price of primary fuel (e.g., natural gas), the operating strategy and characteristics of the CHP system, and an assumed set of installed CHP system capacities (e.g., installed capacity of prime mover and absorption chiller), one can determine the cost of such a system as compared to reliance solely on traditional, …

The Rrnat/Rdna Ratio As A Measure Of Nitrite Oxidizing Activity, Shawn A. Hawkins

Doctoral Dissertations

A bench scale nitrification reactor (BSNR) containing nitrite oxidizing bacteria (NOB) of the genus Nitrobacter (» 1 × 10¹⁰/L; 5 - 22% of bacteria) was used to assess the ribosomal RNA transcript (rRNAt) to ribosomal RNA gene (rDNA) ratio as an in-situ nitrite oxidizing activity metric. A quantitative PCR detection system was developed that amplified a 143 base pair sequence within the Nitrobacter spp. 16S - 23S intergenenic spacer region. The resulting real-time PCR (rDNA) and real-time RT-PCR (rRNAt) assays were specific, accurate, and sensitive, requiring three replicate nucleic acid extracts to reliably detect a true 2-fold concentration …

The Effect Of Ultrasonic Vibration On The Solidification Of Light Alloys, Xiaogang Jian

Doctoral Dissertations

This exposition presents the novel thermodynamical and microstructural modification to light alloys, such as aluminum alloys and magnesium alloys, by ultrasonic vibrations during their solidification processes. Ultrasonic vibration has proven to be effective in controlling columnar dendritic structure, reducing the size of equiaxed grains, and under some conditions, producing globular non-dendritic grains. Despite this, the solidification process under the effect of ultrasonic vibration was not clear. Not only was there no such research on how ultrasonic vibration affected its solidification thermodynamically, but also its effects on the as-cast microstructure, including the primary fcc phase, the eutectics, and the secondary phases, …

Experimental, Theoretical, And Device Application Development Of Nanoscale Focused Electron-Beam-Induced Deposition, Steven Jeffrey Randolph

Doctoral Dissertations

To elucidate the effects of beam heating in electron beam-induced deposition (EBID), a Monte-Carlo electron-solid interaction model has been employed to calculate the energy deposition profiles in bulk and nanostructured SiO₂. Using these profiles, a finite element model was used to predict the nanostructure tip temperatures for standard experimental EBID conditions. Depending on the beam energy, beam current, and nanostructure geometry, the heat generated can be substantial. This heat source can subsequently limit the EBID growth by thermally reducing the mean stay time of the precursor gas. Temperature dependent EBID growth experiments qualitatively verified the results of the …

Suppliers Evaluation And Selection: A Comprehensive Model To Minimize The Risk Associated With Quality And Delivery, Ammar Mohamed Aamer

Doctoral Dissertations

This research focuses on one of the main steps in outsourcing, supplier
evaluation and selection. The main contributions of this research were twofold.
First, best practices in the supplier’s value stream were identified that directly or
indirectly impact a supplier’s quality and delivery. Second, a comprehensive
supplier evaluation and selection model was developed based on the value
stream concept to minimize the risk associated with two very critical supplierselection factors, quality and on-time delivery.

A survey was conducted to identify best practices. The outcome of the survey
was used to develop a computer based supplier evaluation model, which could
be …

Manufacturing System And Supply Chain Analyses Related To Product Complexity And Sequenced Parts Delivery, Hui Sun

Doctoral Dissertations

Mixed model assembly has been widely used in many industries. It is applied in order to effectively deal with increasing product complexity. Sequencing and resequencing on a mixed-model assembly line is also complicated by high product complexity. To improve the performance of a mixed-model assembly system and the supply chain, one can develop efficient sequencing rules to address sequencing problems, and manage product complexity to reduce its negative impact on the production system. This research addresses aspects of sequence alteration and restoration on a mixed-model assembly line for the purpose of improving the performance of a manufacturing system and its …

A Methodology For Solving The Equations Arising In Nonlinear Parameter Identification Problems: Application To Induction Machines, Kaiyu Wang

Doctoral Dissertations

This dissertation presents a method that can be used to identify the parameters of a class of systems whose regressor models are nonlinear in the parameters. The technique is based on classical elimination theory, and it guarantees that the solution for the parameters which minimize a least-squares criterion can be found in a finite number of steps. The proposed methodology begins with an input-output linear overparameterized model whose parameters are rationally related. After making appropriate substitutions that account for the overparameterization, the problem is transformed into a nonlinear least-squares problem that is not overparameterized. The extrema equations are computed, and …

Integration Of Micro Nano And Bio Technologies With Layer -By -Layer Self -Assembly, Dinesh Shankar Kommireddy

Doctoral Dissertations

In the past decade, layer-by-layer (LbL) nanoassembly has been used as a tool for immobilization and surface modification of materials with applications in biology and physical sciences. Often, in such applications, LbL assembly is integrated with various techniques to form functional surface coatings and immobilized matrices. In this work, integration of LbL with microfabrication and microfluidics, and tissue engineering are explored. In an effort to integrate microfabrication with LbL nanoassembly, microchannels were fabricated using soft-lithography and the surface of these channels was used for the immobilization of materials using LbL and laminar flow patterning. Synthesis of poly(dimethyldiallyl ammonium chloride)/poly(styrene sulfonate) …

Development Of Palladium Nanowires, Chuanding Cheng

Doctoral Dissertations

Inherent limitations of traditional lithography have prompted the search for means of achieving self-assembly of nano-scale structures and networks for the next generation of electronic and photonic devices. The nanowire, the basic building block of a nanocircuit, has recently become the focus of intense research. Reports on nanowire synthesis and assembly have appeared in the scientific literature, which include Vapor-Liquid-Solid mechanism, template-based electrochemical fabrication, solvothermal or wet chemistry, and assembly by fluid alignment or microchannel networks. An ideal approach for practical application of nanowires would circumvent technical and economic constraints of templating. Here we report on the self-assembly of highly-ordered …

A Fe-Fd Hybrid Scheme For Solving Parabolic Two-Step Micro Heat Transport Equations In Irregularly Shaped Three Dimensional Double -Layered Thin Films Exposed To Ultrashort -Pulse Lasers, Brian R. Barron

Doctoral Dissertations

Multi-layer thin films are important components in many micro-electronic devices. These films are often used when a single film layer is insufficient to meet devices specifications. The continued reduction in component size has the side effect of increasing the thermal stress on these films and consequently the devices they comprise. Understanding the transfer of heat-energy at the micro-scale is important for thermal processing using a pulse-laser. Often, micro-voids may be found in processed devices. This is due to thermal expansion. Such defects may cause an amplification of neighboring defects resulting in severe damage and consequently the failure of the device. …

Application Of Polyelectrolyte Layer-By-Layer Nano-Assembly For Surface Modification, Encapsulation And Controlled Release, Nikhil Anil Pargaonkar

Doctoral Dissertations

In this study, we applied the traditional Electrostatic layer-by-layer (ELBL) assembly procedure to fabricate nanothin films over flat surfaces, and modify particle surfaces to influence the drug particle size, and drug release. The ELBL assembly has previously been applied to fabricate multilayer nano-scale thin films, but its ability to instantaneously influencing particle size is unique. Other unique observations such as influence on drug release as a result of polymer complexation, and thermal changes occurring during layer fabrication are recorded.

The ELBL self-assembly process was applied to produce dexamethasone particles layered with various polyelectrolyte layer combinations. These combinations were further applied …

Design And Development Of Poly -(3 -Hexylthiophene) Field Effect Transistors, Fengliang Xue

Doctoral Dissertations

Organic field effect transistors (OFETs) with poly(3-hexylthiophene) (P3HT) as the active layer are developed and studied. The device characteristics are significantly affected by source/drain contact resistance, and P3HT-SiO 2 interface and the traps. These results are verified by the numerical device simulations. The temperature dependence of device mobility is studied, which indicates that the carrier transport is either heat-assisted or heat-limited at different temperature ranges. The on/off ratio and threshold voltage are found to be dependent on the temperature. Hysteresis effect due to gate electric stress is investigated. The silanol groups present at the SiO2 surface are thought to be …

Fatigue Behavior Of A Zirconium-Based Bulk Metallic Glass, William Hutchison Peter

Doctoral Dissertations

Although the mechanical behavior of Zr-based bulk metallic glasses (BMGs) has been studied, fatigue studies in controlled environments and testing conditions have not been adequately performed or understood. Early fatigue examinations of rectangular bar specimens tested in bending had resulted in fatigue strengths substantially lower than anticipated [1,2,3,4,5]. Preliminary work performed by Peter et al. and Wang et al. on uniaxial button-head specimens have yielded in very different fatigue behavior with fatigue-endurance limits comparable to conventional high-strength, crystalline alloys [6,7,8,9,10]. Between all S-N results studied, the fatigue-endurance limits for Zr-based BMGs have been observed to range from 150 MPa to …

The Mechanical And Electrochemical Properties Of Bulk Metallic Glasses, Mark Lee Morrison

Doctoral Dissertations

Bulk metallic glasses (BMGs) represent an emerging class of materials with an amorphous structure and a unique combination of properties. Some of these outstanding properties include exceptionally high strength, large elastic deformation, near-net-shape formability, and superplasticity. However, these materials are not commonly used in structural applications because of a lack of plasticity and a lack of clarity in terms of deformation and failure mechanisms. Furthermore, the electrochemical behavior of these materials with and without loading is not well defined. Thus, the objectives of this study were to define and model the electrochemical and mechanical behaviors of BMGs, in addition to …

The Use Of Capacity And Inventory In A Rate-Based Planning And Scheduling System To Achieve Strategic Goals In Industrial Applications, Chad Aaron Toney

Doctoral Dissertations

In pull or lean manufacturing, the final production schedule is in the form of takt time (drumbeat). All internal and external suppliers are driven by pull signals to feed the production rate. However, variability can be a problem for this drumbeat as the plan should not change more than the ability of the suppliers’ capability to respond. The supply chain should have sufficient flexibility to react quickly to changes in demand, while minimizing week-to-week production variability.

Current planning and scheduling systems do not produce a plan that minimizes fluctuations. If the schedule is frozen for several periods, they are slow …

Low-Voltage Analog Circuit Design Using The Adaptively Biased Body-Driven Circuit Technique, Stephen Christopher Terry

Doctoral Dissertations

The scaling of MOSFET dimensions and power supply voltage, in conjunction with an increase in system- and circuit-level performance requirements, are the most important factors driving the development of new technologies and design techniques for analog and mixed-signal integrated circuits. Though scaling has been a fact of life for analog circuit designers for many years, the approaching 1-V and sub-1-V power supplies, combined with applications that have increasingly divergent technology requirements, means that the analog and mixed-signal IC designs of the future will probably look quite different from those of the past. Foremost among the challenges that analog designers will …

Studies In Rheology: Molecular Simulation And Theory, Chunggi Baig

Doctoral Dissertations

With an enormous advance in the capability of computers during the last few
decades, the computer simulation has become an important tool for scientific researches in many areas such as physics, chemistry, biology, and so on. In particular, moleculardynamics (MD) simulations have been proven to be of a great help in understanding the rheology of complex fluids from the fundamental microscopic viewpoint. There are two important standard flows in rheology: shear flow and elongational flow. While there exist suitable nonequilibrium MD (NEMD) algorithms of shear flows, such as the Lees-Edwards purely boundary-driven algorithm and the so-called SLLOD algorithm as a …

Floating Wim Threshold Concept For Truck Weight Enforcement, Zhongren Gu

Doctoral Dissertations

Weigh stations are the primary weight compliance checkpoints for commercial trucks. In the past several decades, states have used weigh-in-motion (WIM) technology to reduce delay and increase enforcement on overweight vehicles. This study offers a detailed analysis of weigh station systems and presents floating-threshold algorithms to improve the efficiency of WIM equipped weigh stations.

This research evaluates weigh station design and operational parameters using queueing theory and found that WIM technology not only enhances the effectiveness and efficiency of weigh station operations but also largely reduces travel delay for trucking companies. The effects of truck demand, truck weight distribution, static …

Application Of Statistical Methods And Process Models For The Design And Analysis Of Activated Sludge Wastewater Treatment Plants (Wwtps), Jinsheng Huo

Doctoral Dissertations

The purpose of this study is to investigate statistical procedures to qualify uncertainty, and explicitly evaluate its impact on wastewater treatment plants (WWTPs). The goal is to develop a statistical-based procedure to design WWTPs that provide reliable protection of water quality, instead of making overly conservative assumptions and adopting empirical safety factors. An innovative Monte Carlo based procedure was developed to quantify the risk of violating effluent as a function of various design decisions. A simulation program called StatASPS was developed to conduct Monte Carlo simulations combined with the ASM1 model.

A random influent generator was developed to describe the …

Study Of Rheological Properties Of Polymeric Liquids By Using Multiple-Mode Models, Bangwu Jiang

Doctoral Dissertations

Knowledge of the rheological properties of non-Newtonian fluids is critical for modeling in polymer-processing equipment such as injection molders, extruders, and blow molders. Rheological measurements can be obtained through standard flows, such as shear flow and elongational flow. In our research, we modeled the rheological properties of polymeric fluids in several types of experiments: transient and steady shear flow, small amplitude oscillatory shear flow, transient elongational flow, and step-strain shear flow.

The accuracy of modeling calculations depends critically on the performance of the rheological model used. Differential constitutive models with a single relaxation time can be used for exploratory fluid …