Engineering Commons^™

Modeling Plant Uptake Of Metal In Constructed Wetlands Supported By Experimentally Derived Uptake Rates, Michael B. Peake

Theses and Dissertations

Many communities and Air Force installations are using constructed wetlands to filter trace metals from their stormwater runoff. Constructed wetlands are attractive to industry for runoff mitigation because they are relatively cheap to build and operate and require little or no energy for operation. The purpose of this research project is to develop quantitative concepts for understanding the dynamics of metal uptake in constructed wetland plants by constructing a system dynamics model supported by experimental observation and offer environmental managers a tool to simulate, under a broad range of conditions, long term wetland exposure to stormwater runoff contaminated with trace …

The Effect Of University Characteristics On The Bicycle Transportation Mode And Helmet Usage, Carlton C. Urban

Masters Theses

By performing a statistical analysis on data collected from the Internet, this study sought to determine if designated characteristics of a university actually affect the bicycle transportation mode and helmet usage on college campuses. The focus group for this research experience involved bicycle commuters affiliated with universities in the United States. Through the establishment of a World Wide Web home page and on-line survey, the author obtained data concerning estimated bicycle and helmet usage percentages, and campus characteristic data from bicyclist responses. The Internet was used as an innovative approach to collecting data. Essentially the participant would simply locate the …

Habitat Suitability Mapping Through Integration Of Multicriteria Evaluation Techniques With A Geographic Information System (Gis), Anthony A. Ference

Theses and Dissertations

The presence of an endangered species, the Pacific Pocket Mouse (PPM), in critical Marine Corps training areas aboard Camp Pendleton may adversely affect training activities that are crucial to meeting the Marine Corps' mission. Camp Pendleton must focus limited budgetary assets for live trapping surveys of the PPM in the areas of best habitat suitability and the purpose of this study was to develop a PPM habitat suitability map of Camp Pendleton. Suitability maps were developed by integrating expert opinion with the Camp Pendleton Geographic Information System (GIS) database.

Study Of Desorption Of Contaminant From Synthetic Soil, Kung-Fu Hwang

Theses and Dissertations

A better understanding of sorption and desorption processes could improve estimates of time and cost required for remedial activities, exposure times and health risk, and bioavailability. Conventional rate-limited sorption models do not accurately define the diffusion domain at the grain scale. Heyse (1994) proposed the multiple sites in series (MSS) model, which allows more general description of the geometry of the sorption domain than the classical spherical or discrete distributions. A version of this model was tested by deVenoge (1996). The model was able to accurately simulate sorption rate data, but could not estimate unique geometry parameters. This research is …

Economic Valuation Of Air Force Environmental Resources: A Contingent Valuation Case Study, Timothy P. Haynie

Theses and Dissertations

The Air Force spends $1 billion each year to preserve, maintain, and restore environmental resources under its control (Budget of the United States Government, 1994). Assessing the benefit of this spending is a central issue in federal environmental management. As federal environmental management moves from a "clean it up at any cost" mentality to one which carefully considers the costs and benefits of spending, a fundamental question arises: What value of environmental resources does our environmental spending provide? As in any rational economic exchange benefits must exceed costs; the value of an environmental resource which benefits from public spending must …

A Comparative Analysis Of Two Alternatives To Chemical Aircraft Paint Stripping, George P. Joyce Ii

Theses and Dissertations

The Air Force must periodically strip and paint its aircraft to prevent the damaging effects of corrosion. The paint removal process typically involves the use of toxic chemicals such as methylene chloride which are soon to be banned as a result of impending environmental regulations and increased costs associated with handling and disposing of such material. The Air Force must choose an alternative to methylene chloride chemical stripping which complies with environmental regulations and reduces costs. This thesis compares the life cycle costs and environmental impacts of two alternatives to chemical aircraft stripping. Plastic Media Blasting (PMB) and Modified Medium …

Development Of Synthetic Soils For Sorption Mass Transfer Model Validation, Thomas P. De Venoge

Theses and Dissertations

Existing sorption models often fail to describe grain scale sorption because of an inability to define the diffusion domain. A proposed improved model required testing to determine model validity. The testing method used a synthetic media of known geometry such that the distribution of sorption sites was known. Sorption rate data was obtained using batch experiments with the media. Data was used in comparison against model predicted rates. Fined sorption site distributions were compared to real distributions obtained by controlling sorbent geometries. Comparison determined model performance in fitting known distributions. The focus of this study was to (1) determine what …

Environmental Restoration Project, Peer Review Process Assessment, Paul A. Schantz

Theses and Dissertations

Installation Restoration Program (IRP) projects often cost over $250 thousand, and projects over $1.5 million are common. To ensure these projects are risk based, technically sound, and cost effective, the Air Force instituted a peer review program in 1992. The objective of this research is to describe and analyze the peer review process. Through triangulation of data from interviews, observations, official and academic documents, and surveys, seven constructs were discovered: focus, agenda, facilitator, written preparation, oral presentation, team characteristics, and reviewer characteristics. A questionnaire was used to gather perceptions of peer review effectiveness--the criterion variable--and of the seven constructs. A …

Investigation Of Sorption Mass Transfer Models Using Synthetic Soils, Karla K. Mika

Theses and Dissertations

Grain-scale sorption mass transfer is an important process that must be considered when predicting clean-up time and choosing remediation techniques for subsurface hazardous waste contamination. Rate-limited sorption is responsible for the rebound effect, where remediated groundwater is recontaminated by desorption. Sorbed contaminants are not available for microbial degradation, and the desorption rate may govern the effectiveness of natural attenuation by biodegradation. Grain-scale sorption nonequilibrium is generally attributed to diffusive transport, either in SOM or in mineral micropores. Typically used sorption mass transfer models either fail to reproduce long-term slow desorption (first-order models), or are based on diffusion in assumed (often …

Development Of Site Characterization Simulator Specifications, Jeffrey L. Heiderscheidt

Theses and Dissertations

The purpose of this study was to develop a tool for evaluating data quality when characterizing a potentially contaminated groundwater aquifer, and to provide a basis for developing a simulator to allow environmental managers and engineers to practice and learn about the site characterization process. Specifically, this study characterized the uncertainty, estimation block size, and cost for the various methods of determining the value of each geological, hydrological, and contaminant parameter necessary to characterize a site. Research entailed identifying site characterization objectives and identifying parameters necessary to obtain those objectives. Methods of estimating each parameter were identified, then research was …

Fracture Mechanics Of High Strength Concrete Members, Rajendra K. Navalurkar

Dissertations

This study investigates the behavior of High Strength Concrete (HSC) under uniaxial state of stresses. Emphasis is placed on experimental evaluation of important mechanical and fracture properties. Owing to high brittleness of HSC, experimental results especially on tensile behavior have been largely limited and scarce. In this research, direct uniaxial tension tests are employed for determination of the post-peak tensile softening characteristics of HSC. The softening characteristics of high strength concrete is found to be considerably different than that of normal strength concrete (NSC). Fracture energies evaluated form the descending branch of the stress softening reveal significant drop in the …

Biodegradation And Landfill Settlement, Shailesh Pisolkar

Theses

The most widely used method for the final disposal of solid waste is landfilling, which is also economical and simpler than most other disposal systems. Long term settlement in a landfill occurs mainly due to biodegradation of the refuse which is a very slow microbiological process. However, if the rate of biodegradation is enhanced, it may be possible to achieve early stabilization, faster settlement, consequently more capacity of the landfill to handle waste.

The objective of this research is to study the effects of enhanced biodegradation on settlement and to compare these results to other models used for predicting landfill …

Relationship Between Precipitation, Surface Runoff, And Shallow Water-Table, Manoj Patel

Theses

In this study, a model was developed to describe the relationship between precipitation, surface runoff, and shallow groundwater table in a watershed that is subjected to groundwater extraction and urbanization. Regression analysis of fourteen years (1976-1989) of time series data for precipitation, stream discharge, ground water elevation, and groundwater extraction yielded good correlation between these parameters.

Analysis of the data associated with groundwater recharge and discharge events that occurred in the watershed from 1976 to 1989 yielded a high correlation between the above cited parameters. Regression analysis utilized to predict monthly variations in groundwater elevations showed a fair correlation between …

Solidification/Stabilization Of Petroleum Contaminated Soils With Cold Mix Asphalt Concrete, Nazhat Aboobaker

Theses

In this research Petroleum Contaminated Soils (PCSs) are recycled in Cold Mix Asphalt (CMA), to produce a useful product that can control potential environmental threats. The stability, durability, and hydraulic conductivity are three important engineering parameters that need to be considered when using petroleum contaminated soils (PCSs) in cold mix asphalt (CMA). In this research, stability, durability, and hydraulic conductivity due to the addition of six different PCSs into CMA is investigated. The stability test were performed to determine if cold mix asphalt made with petroleum contaminated soil can withstand heavy traffic. The freeze-thaw, and wet-dry tests were performed to …

Comprehensive Conjunctive-Use Management Of Connected Surface Water Groundwater Systems Using Stochastic Inputs And Uncertainties, Seshadri Suryanarayana

Civil & Environmental Engineering Theses & Dissertations

A comprehensive conjunctive-use management model is developed. The dynamics of flow and solute transport processes in connected surface water groundwater systems are integrated by a dual programming management model. The governing aquifer flow parameters and streamflows are treated as stochastic random processes. Multiple realizations of the random field are generated and are explicitly incorporated in a non-linear optimization model along with other system, environmental, and management constraints. To facilitate management of large aquifer systems, a linked simulation-optimization approach is used. The simulation program generates the response matrices for flow and transport processes. The management model then determines optimal well discharges …

The Constant Fracture Angle Model For Cementitious Materials, Suk Ki Kim

Dissertations

Fracture mechanics of concrete has been investigated for the past two decades using linear elastic and nonlinear fracture mechanics concepts. The models proposed so far remain questionable largely due to specimen dependency of the proposed fracture parameters.

In this study, a new approach for modeling the fracture characteristics of concrete and fiber reinforced concrete is proposed. The model depends on the load CMOD relationship rather than the traditional load-deflection principle. Although energy consumed during fracture is definitely a direct function of the load displacement response, it was observed that traditional displacement measurement included an extraneous and erratic portion due to …

Development Of A Traffic Safety Index For Urban Intersections, Jae-Hong Kang

Dissertations

Conventional safety analysis focuses on the accident environment at specific locations or a limited segment of highways or arterials, and attempts to identify the effects of accident contributing factors. The development of a safety index in the past was based on a statistical summary for county or statewide areas, using general indicators such as population, number of registered vehicles, vehicle miles traveled and so on. This research effort presents a state-of-the-art procedural analytical approach for the safety analysis of Manhattan intersections that are exposed to a unique urban environment. The computed index provides safety ratings that can identify potential safety …

Development Of A Multivariate Qsar Model To Predict Desorption Of Halogenated Aliphatic Hydrocarbons From Activated Sludge Solids, Sudhi Ranjan Mukherjee

Dissertations

Data collected from different wastewater treatment processes have provided statistically significant evidence that many toxic organic contaminants on EPA's list of priority pollutants concentrate several orders of magnitude greater than influent concentrations in industrial and municipal wastewater sludges. Because of the reversibility of sorption processes, it is possible for sorbed organic compounds to desorb at a later time, hence making disposal of these sludges a potential problem. Although a number of models have been developed to predict sorption parameters, they have all been based on empirically derived descriptors whose validity is seriously compromised by the variation in available data for …

Discrete Element Modeling Of Dry Granular Material Using A Massively Parallel Supercomputer, David W. Washington

Dissertations

It is the state-of -the-art within Geotechnical Engineering to model soils as systems of particles rather than using the traditional continuum approach. Simulating these systems of particles for geotechnical boundary value problems results in systems which are of necessity large, motivating the application of massively parallel supercomputers. This thesis pursues such an approach.

The following work describes numerical experiments using a Discrete Element Method (DEM) paradigm for soils (Trubal) together with massively parallel computers with Single Instruction Multiple Data (SIMD) architecture. The discrete element method describes the behavior of granular assemblies using the classical mechanics of discrete bodies. The computational …

Development Of A Fiber Optic Polarimetric Sensor For Concrete, Insang Lee

Theses

Development of a fiber optic sensor for embedment in cementitious composites and measurement of displacements associated with the opening of microcracks is described. The sensor can be employed as a transducer for measurement of crack tip opening displacements during fracture tests. A polarization maintaining fiber is used as the sensing element, and transduction mechanism is similar to those of other polarimetric type based sensors. However, the deformation resolving power of the sensor is increased by way of increasing the effective length of the optical fiber. This is done by winding the optical fiber into a coil. A direct relationship between …

Separation Of Polycyclic Aromatic Hydrocarbons By Using Micellar Electrokinetic Chromatography, Patricia Simmons

Theses

In this work, the use of micellar electrokinetic chromatography (MEKC) for the separation of five polycyclic aromatic hydrocarbon (PAH) compounds is investigated. All of the compounds studied are listed by the United States Environmental Protection Agency as priority pollutants.

In micellar electrokinetic chromatography, solutes partition between the aqueous phase and the micellar phase. This partition is based on the hydrophobicity of each compound. In some cases, organic modifiers are added to the electrophoretic solution to enhance the separation efficiency. The organic modifier used in this study is y-cyclodextrin (y-CD), and sodium dodecyl sulfate (SDS) is used as the micellar phase. …

Advanced Characterization And Leaching Behavior Of Hexavalent And Trivalent Chromium From Waste Material, Erik Moerman

Theses

In this thesis we employed advanced characterization techniques such as XRF, XRD, XPS, SEM, and EDS to provide detailed information about the chromium waste _ specifically chromium valence states (Cr(VI) and Cr(III)), and their chemical association with other phases in the waste matrix.

The removal of Cr(VI) was accomplished by leaching with aqueous solutions containing inorganic anions such as Cl^-, SO₄^2-, PO₄^3- and others. Cr(VI) can be released from the waste by a combination of desorption and ion exchange processes. The efficiency and kinetics of displacing CrO₄^2- from the waste by …

Effect Of River Impoundment On Its Water Salinity And Associated Environmental Impacts, Ayat Ahmed Soliman

Archived Theses and Dissertations

No abstract provided.

Design Methodology For Composite Structures Consisting Of Reinforced Hollow Brick Walls And Concrete Beams Connected At A Joint With Flashing And Subject To In-Plane Bending, John Kennedy Mccall

Doctoral Dissertations

Due to waterproofing requirements, a flashing joint is generally used at the base of a brick wall to facilitate transport of moisture from the back of a brick wall to the outside of the building. The flashing results in a loss of bond and reduced friction between the reinforced brick wall and the supporting structure. This loss of strength is of little consequence to veneer; however, it may impact wall behavior for reinforced hollow brick. This research, which uses hollow Suprking bricks as manufactured by the General Shale Co., develops data to assess the in-plane shear behavior of the flashing …

Organic Matter Characterization Of Virginia Rivers And Reservoirs, Susanne Margaret Lockhart

Civil & Environmental Engineering Theses & Dissertations

Research was conducted on characterizing the DOC characteristics and to discern whether spatial and temporal variations exist in these characteristics as impacted by seasonal, hydrologic or other factors. Data was cumulative of two studies: the State-Wide Survey in which water samples were taken in March and July 1995 from surface waters in four physiographic regions of Virginia and the James River Peninsula Survey concentrating on reservoirs and rivers on the James River Peninsula.

Results illustrate that the two largest fractions of DOC were the hydrophilic and hydrophobic acid fractions. An increase in DOC was observed between the mountains and the …

Discharge Coefficient Scale Effects Analysis For Weirs, Michael Clyde Johnson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Much work has been published regarding discharge coefficients for various weir structures. What has not been published to the same extent are the effects of model scale associated with the weirs being studied. If laboratory weirs are too small, scale effects can affect the magnitude of the discharge coefficient. These errors may be significant if the weir serves as a control structure for an emergency spillway. It is imperative that discharge be accurately predicted to enable safe design and operation.

Numerical and physical means were employed to analyze the effects of scale associated with Froude Modeling of weirs with sharp …

Implementation Of Alf Results To Designing Flexible Pavements In Louisiana, Ludfi Djakfar

Doctoral Dissertations

The Louisiana Transportation Research Center (LTRC) recently conducted a research effort using the Accelerated Loading Facility (ALF). The objective of the research was to evaluate a limited number of alternative base materials and construction techniques envisioned to provide a significant reduction in the occurrence of shrinkage and reflected block cracking in the cement-stabilized bases. Nine test sections were constructed for this research, using the same wearing course material but having different thicknesses of crushed stone and soil cement bases and subbases. The soil cement base is the most commonly used base material in Louisiana, whereas crushed stone is a preferred …

The Progressive Failure Analysis Of Cut Slope In Anisotropic Strain Softening Soils, Jong Woon Choi

Civil & Environmental Engineering Theses & Dissertations

The failure phenomena in earth structures such as slopes and embankments on clay foundations are a consequence of the formation of failure surfaces.

A finite difference computer code, FLAC (Itasca Consulting Group, 1993), with the isotropic Mohr-Coulomb plasticity model, is used to analyze the undrained progressive failure of a strain softening soil during a slope excavation process. The focus of the study is on the short-term stability of slopes. In the first series of analyses, which are aimed at the evaluation of anisotropic strength effect on slope stability, the isotropic Mohr-Coulomb plasticity model is slightly modified to implement the anisotropic …

A One-Dimensional Model For Storm Breaching Of Barrier Islands, Cheol Shik Shin

Civil & Environmental Engineering Theses & Dissertations

A set of numerical models is developed for simulating the four stages of barrier breaching characterized by one horizontal spatial dimension.

The SBEACH model is employed for the first stage of dune/beach erosion. The Lax-Wendroff two-step explicit scheme for Stage II is developed to simulate initiation of ocean flood propagation on initially dry barrier islands and the method of characteristics (MOC), is employed to compute additional boundary data. The development of the Preissmann implicit scheme for water motion and a forward time centered space explicit scheme for sediment motion in Stages III and IV provide a tool to study the …

Anaerobic Digestion And Acid Hydrolysis Of Nitrocellulose, Fong-Jung Tai

Dissertations

In this investigation, studies were conducted to evaluate the biodegradation of nitrocellulose in anaerobic batch reactors with and without the supplemental carbon inducers, such as cellulose, cellobiose, and lactose. Results from the anaerobic study show that degradation of nitrocellulose alone is difficult and that nitrocellulose degradative enzymes could be induced by the three inducers tested. As high as 48.91% conversion could be obtained at Cellulose/Nitrocellulose ratio of 1 to I. Studies also indicated that type 20 and 50 celluloses would be more effective and optimum pH was about 6.4 in biodegradation of nitrocellulose. Three testing systems, namely, single-stage, two-stage, and …