Engineering Commons^™

Modeling Long-Term Plutonium Transport In The Savannah River Site Vadose Zone, Deniz Demirkanli

All Dissertations

Improved understanding of flow and radionuclide transport in vadose zone sediments is fundamental to future planning involving radioactive materials. Long-term experiments were conducted at the Savannah River Site (SRS), where a series of lysimeters containing sources of different Pu oxidation states were placed in the shallow subsurface and exposed to the environment for 2 to 11 years. After the experiments, Pu activity concentrations were measured along vertical cores. The distributions were anomalous in nature, with irregular downward migration and unexpected upward migration. Previous studies suggested that surface-mediated, oxidation/reduction (redox) reactions may be responsible for the anomalies. This hypothesis is tested …

A Robust Conjugate Heat Transfer Methodology With Novel Turbulence Modeling Applied To Internally-Cooled Gas Turbine Airfoils, William York

All Dissertations

Computational fluid dynamics and heat transfer (CFD) has become a viable, physics-based analysis tool for complex flow and/or heat transfer problems in recent years due, in large part, to rapid advances in computing power. CFD based on the Reynolds-averaged Navier-Stokes (RANS) equations is starting to enter the mainstream design environment in certain industries where rapid and reliable predictive capability is necessary. One such application is the gas turbine industry, where thermal management of airfoils at extremely high temperatures is one of the most critical components in engine design for reliability. The problem is complicated by the need for advanced airfoil …

Optimizing The Project Team's Contribution To Business Objectives, Chad Rowland

All Theses

The traditional expectations of the project team are for the processes of engineering, procurement, construction, and start-up to be expertly administered. However, these performance criteria can be satisfied yet still not meet the ultimate business needs of the owner. The purpose of this thesis was to determine ways to improve the likelihood of achieving owner's business objectives. Fifty-one questionnaire survey forms were analyzed to obtain data for thirty-three pre-project planning activities. A data analysis concluded with a degree of statistical significance that for thirteen of the thirty-three activities, the more successful projects, as defined by the satisfaction of the business …

A Cross-Layer Approach To Increase Spatial Reuse And Throughput For Ad Hoc Networks, Steven Boyd

All Theses

Ad hoc networks employing adaptive-transmission protocols can alter transmission parameters to suit the channel environment. Channel-access mechanisms are used to govern temporal use of the transmission medium amongst nodes. Effective operation of a channel-access mechanism can improve the ability of an adaptive-transmission protocol to accommodate changing channel conditions. The interoperability of these two mechanisms motivates cross-layer design of adaptive-transmission protocols.
In this thesis we examine the integration of a new channel-access mechanism with a physical-layer adaptive-transmission protocol to create a cross-layer protocol with enhanced capabilities. We derive specific physical-layer measurements which are used to control channel-access behavior in a distributed …

Using A Spline To Model The Motion Of A 4-Man Fireteam During Building Clearing Exercises, Marshall Werner

All Theses

This paper examines the problem of tracking positions of a fireteam (4-5 men) as they perform building clearing exercises in order to predict future motion od the team. This was done by examining the team as a single entity rather than 4 or 5 separate entities. A team model was used under the assumption that the team stays together as a group and moves in specific patterns. The model chosen for this experiment was a spline curve. This spline curve allowed for movement in straight lines through hallways as well as curving around corners.

A Comparison Of The Zns(Ag) Scintillation Detector To The Silicon Semiconductor Detector For Quantification Of Alpha Radioactivity In Aqueous Solutions, Jennifer Foster

All Theses

A ZnS(Ag) detector was successfully used in the direct detection of alpha particles from aqueous solutions and the results were compared to the passivated ion implanted planar silicon (PIPS) continuous air monitor (CAM) detector. The ZnS(Ag) detector is recommended for on-line detection of gross alpha radioactivity from high-level liquid waste process streams; however, the detector suffers from limitations due to variations in detection efficiency with alpha energies. The beta and gamma interference did not significantly spillover into the alpha region of interest of the ZnS(Ag) detector which provided absolute detection efficiencies of 7.19 ± 0.13%, 5.37 ± 0.02%, and 4.21 …

Evaporation Estimation Using A Floating Pan, Michael Klink

All Theses

Almost all regions in the United States must accurately estimate evaporation to have effective water management programs. The purpose of this study is to develop a better method for measuring evaporation. Lake evaporation along with meteorological data are measured directly from a floating pan. The floating pan is specifically designed to account for one of the most sensitive parameters of evaporation, the water surface temperature, which the design achieves. However, other design factors such as air movement, solar radiation, stability, heat transfer, wave action, water level range, and site location were also taken into consideration. The evaporation measured from the …

Investigation Of The Effects Of Subgrid-Scale Turbulence On Resolvable-Scale Statistics, Qinglin Chen

All Dissertations

The effects of the subgrid-scale (SGS) turbulence on the resolvable-scale statistics and the effects of SGS models on large-eddy simulation (LES) are studied. It is shown that the SGS turbulence evolves the resolvable-scale joint probability density function (JPDF) through the conditional means of the SGS stress, the SGS scalar flux, and their production rate, which must be reproduced by the SGS model for LES to predict correctly the one-point resolvable-scale statistics, a primary goal of LES. This necessary condition is used as the basis for studying SGS physics and for testing SGS models. Theoretical predictions, measurements data obtained in a …

Stabilization Of Vascular Elastin By Treatment With Tannins, Jason Isenburg

All Dissertations

Elastin is an important component of the extracellular matrix that endows cardiovascular tissue with the ability to extend and recoil repetitively. It has been shown that elastin may be vulnerable to enzymatic degradation and calcification in certain pathological cases. As a result, elastin degeneration may be associated with the failure of tissue-derived cardiovascular devices, such as bioprosthetic heart valves, as well as the development and progression of aortic aneurysms, a disease associated with progressive connective tissue degeneration of the arterial wall. Therefore, an elastin stabilizing agent may be beneficial for both applications. As such, our objectives for elastin stabilization are …

Investigation Into Compatibility Between Repair Material And Substrate Concrete Using Experimental And Finite Element Method, Rashmi Pattnaik

All Dissertations

The failure of concrete repairs is mainly due to improper selection of repair material based on individual repair material properties, without investigating the compatibility between repair material and substrate concrete. In this dissertation the compatibility between eight repair materials and substrate concrete was investigated in three stages. First, individual properties of the repair materials such as setting time, flow, compressive strength, flexural strength, split tensile strength, bond strength, drying shrinkage, freeze-thaw resistance, and permeability, were determined using standard ASTM test procedures. Second, the compatibility was investigated using a composite beam under third point loading. Third, the correlation of repair material …

Modeling And Simulation Of Friction-Limited Continuously Variable Transmissions, Nilabh Srivastava

All Dissertations

Over the last few decades, a lot of research effort has increasingly been directed towards developing vehicle transmissions that accomplish the government imperatives of increased vehicle efficiency and lower exhaust (greenhouse gaseous) emissions. These exhaust emissions can be regulated or lowered by increasing the fuel economy of a vehicle, and CVTs (continuously variable transmissions), indubitably, play a crucial role in this plan to improve the fuel economy. A continuously variable transmission is an emerging automotive transmission technology that offers a continuum of gear ratios between desired limits. A CVT offers numerous advantages over the conventional multi-step gear transmissions such as …

Channel-Access And Routing Protocols For Wireless Ad Hoc Networks With Directional Antennas, Arvind Swaminathan

All Dissertations

Medium-access control (MAC) and multiple-hop routing protocols are presented that exploit the presence of directional antennas at nodes in a wireless ad hoc network. The protocols are designed for heterogeneous networks in which an arbitrary subset use directional antennas. It is shown that the new protocols improvement the network`s performance substantially in a wide range of scenarios.
A new MAC protocol is presented that employs the RTS/CTS mechanism. It accounts for the constraints imposed by a directional antenna system, and it is designed to exploit the capabilities of a directional antenna. It is shown that the receiver blocking problem is …

Shear-Wave Velocity Model Of Near-Surface Sediments, Site Response, And Building Damage: 1886 Charleston, South Carolina Earthquake, Cedric Fairbanks

All Dissertations

An updated small-strain shear wave velocity (Vs) model of near-surface sediments is constructed using measurements from over 90 investigation sites in the greater Charleston area. It is constructed by separating the Vs measurements into six major geologic units. The six units are: 1) man-made fills, 2) Holocene and late Pleistocene deposits, 3) the Wando Formation, 4) the Ten Mile Hill beds, 5) the Penholoway Formation and the Daniel Island beds, and 6) Tertiary deposits. Median Vs values for these units in the top 25 m are 145 m/s, 111 m/s, 189 m/s, 176 m/s, 285 m/s and 399 m/s, respectively. …

The Effects Of Viscoelastic Behavior On The Operation Of A Delayed Resonator Vibration Absorber, John Cowans

All Theses

Delayed resonators have proven to be effective vibration absorbers (VAs) for tracking and canceling the effects of harmonic excitations on a structure. The Delayed Resonator (DR) is selfcontained, as no information from outside of its substructure is required for proper operation. It adjusts for variations in frequency using time-delay and gain as control parameters.
This thesis examines the relationship between viscoelastic (VE) loss mechanisms in systems with DR and the choice of modeling method used to calculate control parameters and determine system stability. It is hypothesized that a VE loss mechanism approximated by a single viscous dashpot may lead to …

Controlling Steam Flood Migration With Air Injection Wells, Rex Hodges

All Dissertations

Steam flooding is an aggressive remediation technology for removing volatile organic chemical (VOC) sources that slowly dissolve into passing groundwater. Plume concentrations can be reduced, accelerating cleanup, and decreasing plume management costs. Steam injected in wells surrounding the source spreads outward and develops into a front that drives contamination to a system of groundwater pumping wells in the saturated zone and soil vapor extraction wells in the vadose zone. The process can be modeled with the non-isothermal multi-phase flow simulator T2VOC to include operation designs and factors at individual sites.
A pilot field-scale test at the Savannah River Site (SRS) …

Soccer Headgear Effects On Impact Profiles During A Heading Scenario, Ryan Posey

All Theses

The risk of head injuries in the sport of soccer has recently become a topic of concern, particularly with youth players whom may suffer long-lasting or even permanent effects from a severe head injury. In response to these worries, headguards have been developed specifically for use in soccer. These headguards have been studied using crash test dummy heads mounted with various electronic instruments - accelerometers, gyroscopes, etc. The headgear-mounted dummy heads have been struck with various objects (soccer ball, another dummy head, pole, etc) to test for changes in head acceleration response.
Testing of soccer headgear has previously been limited …

Internal Combustion Engine Cooling Strategies: Theory And Test, John Chastain

All Theses

Advanced internal combustion engine thermal management systems can enhance overall engine performance through the use of computer controlled cooling system actuators. Existing ground vehicle cooling systems generally have performance limitations due to the fixed behavior of the wax-based thermostat valve and crankshaft dependent operation of the coolant pump and radiator fan. Upgrading the traditional thermostat valve, water pump, and radiator fan with actuators permit real time computer control for improved temperature tracking and reduced power consumption. In this paper, the benefits associated with advanced automotive cooling systems are experimentally investigated. A 4.6L engine with a real-time data acquisition and control …

Unsupervised Neural Pattern Classifiers For Oral Vowel Pronunciation Of Foreign-Accented Speech, Joseph Hecker

All Theses

This thesis describes the development of unsupervised neural-based pattern classifiers for the training of vowel pronunciations for students learning a foreign language. This paper examines American learners of the French language. A corpus of single word utterances is compiled from a group of native French speakers. Cepstral features are used to train two unsupervised neural pattern classifiers: a self-organizing map and a growing neural gas. The development and justification for the use of these classifiers is presented. The output from the classifier is translated to a bar graph for visual assessment. The degree to which the utterance sounds native is …

The Effects Of Calcium Magnesium Acetate Deicers On Portland Cement Mortar Bars, Jeffrey Davis

All Theses

This thesis involves the investigation of the effects of Calcium Magnesium Acetate (CMA) deicers on Portland cement mortar bars. In addition to mass-loss, length change, pulse velocity and soak solution pH, the thesis also contains a rigorous chemical analysis of the mortar completed at the National Institute of Standards and Technology (NIST) in Gaithersburg, MD. The research completed at NIST was done using a technique known as X-ray Mapping. The X-ray techniques were employed to determine the exact nature of the damage caused by CMA. The thesis is a combination of two papers, on the physical effects of CMA and …

Investigation Of Corrosion Effects On Bond-Slip And Tensile Strength Of Reinforced Concrete Members, M. A. Shayanfar, Amir Safiey, M. Ghalehnovi

Publications

The corrosion effect on tensile strength of RC members is very important to region with high corrosion conditions. In this article a study on finding bond behaviour, crack pattern, crack spacing, and tensile strength of RC members is presented. For this purpose a comprehensive experimental program including reinforced concrete cylanders with different concrete covers and reinforcement ratios under various corrosion rates is conducted. The specimens are located in large tub containing water and salt (5% salt solution) with a devich for accelerated corrosion production. For each specimen, the variation of total tensile strength versus its average strain is plotted and …

Real-Time Identification Of Sliding Friction Using Labview Fpga, Laine Mears, Jeannie S. Falcon, Thomas R. Kurfess

Publications

Friction is present in all mechanical systems, and can greatly affect system stability and control in precision motion applications. In this paper, we present application of a frictional model to trajectory planning of a part centering system with real-time identification of model parameters through system force and position response. This identification is carried out using LabVIEW motion control software and digital signal processing (DSP) and field-programmable gate array (FPGA) hardware. A comparison of hardware performance for force measurement is also made.

The Reactivity Of Dissolved Organic Matter For Disinfection By-Product Formation, Mehmet Kitis, Tanju Karanfil, James E. Kilduff

Publications

Dissolved organic matter (DOM) in 6 water samples collected from 4 surface waters were fractionated using some or all of 5 physicochemical separation processes (activated carbon and XAD-8 batch adsorption, alum coagulation, ultrafiltration (UF), and XAD-8 column fractionation). Activated carbon, XAD-8 batch adsorption and alum coagulation processes fractionated DOM by preferentially removing high-SUVA components from solution. The XAD-8 column method fractionated DOM into hydrophobic and hydrophilic components while UF separated DOM into different size fractions. Over 40 DOM fractions, characterized using carbon-normalized (specific) ultraviolet absorbance (SUVA), were obtained for each water. Trihalomethane (THM) and haloacetic acid (HAA_9) formation after chlorination …

A Multi-Objective Decision-Making Framework For Transportation Investments, Mashrur Chowdhury, Pulin Tan

Publications

This paper presents a framework based on multi-objective optimization that can be used to generate and analyze the most desirable transportation investment options based on their objectives and constraints. The framework, which is based on the surrogate worth trade-off analysis, could be applied to both discrete or continuous decision-problem scenarios. In a discrete problem, a predefined set of alternatives is available, whereas continuous problems are not characterized by a predefined set of alternatives. This framework was applied with the data generated for a Capital Beltway Corridor investment study. The multi-objective decision-making framework was found to be adaptable to this typical …

The Synthesis, Characterization, And Cell Seeding Of A Collagen/Hydroxyapatite Porous Scaffold For Treatment Of Osseous Defects, Kim Rachel Patterson

All Theses

The need for finding a bone graft substitute stems from the fact that approximately 200,000 bone grafting procedures are performed annually in the U.S. alone. Although biological grafting options (i.e. autografts & allografts) exist, they do suffer from inherent problems. These include limited resources, costly processing, and potential for pathogen transfer. Thus, investigators have sought synthetic alternatives.

The objective of this research was to utilize hydroxyapatite (HA) and collagen, both analogues to the major constituents of bone, to fabricate an optimal synthetic osteoconductive/osteoinductive bone scaffold. Current attempts by other investigators to combine the two materials have been met with some …

Theoretical And Empirical Investigation Into Polymer Blend Morphology In Fiber Spinning, Ajay D. Padsalgikar

All Dissertations

A promising way of developing new fiber forming materials is by utilization of polymer blends. The morphology of polymer blends has a significant effect on the properties of the resultant fiber. Morphological studies have shown that immiscible additives remain dispersed in the matrix as suspended droplets and that the droplets are elongated into fibrils under the action of shear or extensional forces during processing. The deformability of the dispersed phase is a controlling factor in deciding the resultant morphology and thereby the fiber properties. We report the results of a study of droplet deformation in uniaxial elongational flow under non …

Effect Of Unbalance On Power System Components In The Presence Of Harmonics, Jessica Williams

All Theses

No abstract provided.

A Theoretical Nonlinear Dynamical Model Of Coupled Heat And Momentum Transfer In Forced Convection Film Boiling, Jolie Ann Long

All Theses

In film boiling, a layer of vapor completely blankets the heated surface and prevents liquid contact with the surface. Film boiling is usually considered undesirable because it is an inefficient mode of heat transfer and can lead to temperatures in excess of those allowed for many materials. Because film boiling may inhibit desired heat transfer in several processes including metals manufacturing, cryogenic engineering, and electronic cooling, it is useful to consider how the film boiling vapor layer may be destabilized or altered such that time-averaged heat transfer is improved.

Predicting The Future Fate Of Pcbs In Lake Hartwell, Alan W. Elzerman, Kevin J. Farley, Frank M. Dunnivant, Craig Cooper

Publications

No abstract provided.

Modeling Of Algal Productivity And Diel Oxygen Profiles In The Partitioned Aquaculture System, Caye M. Drapcho

All Dissertations

Fish production in pond culture systems is often limited by the dissolved oxygen (DO) concentration. Algal biomass and productivity, which greatly impact the DO concentration, are difficult to control in traditional pond systems. The Partitioned Aquaculture System (PAS) was designed to increase fish production by managing algal productivity and DO through control of algal cell retention time, water depth, and mixing. The objectives of this study were 1) to determine impact of culture conditions on algal productivity, 2) develop a model of algal productivity and diel DO levels, and 3) to predict the maximum fish production attainable with the PAS. …

Study Of Parameters Affecting Performance Of Automotive Transmission Filters, Debra Cauthen

All Theses

Modified isocyanate binders have been introduced as a possible alternative to phenolic resins for bonding nonwovens in automatic transmission filtration. The Occupational Safety and Health Administration (OSHA) and the American Conference of Governmental Industrial Hygienists (ACGIH) have placed restrictions on worker exposure to phenol-formaldehyde due to toxicological and ecological concerns. Modified isocyanates are unproven for bonding needlefelts in this application.