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Air Force Institute of Technology

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Articles 121 - 150 of 186

Full-Text Articles in Applied Mathematics

Feature Guided Image Registration Applied To Phase And Wavelet-Base Optic Flow, Kate R. Duffy Mar 2003

Feature Guided Image Registration Applied To Phase And Wavelet-Base Optic Flow, Kate R. Duffy

Theses and Dissertations

Optic Flow algorithms are useful in problems such as computers vision, navigational systems, and robotics. However, current algorithms are computationally expensive or lack the accuracy to be effective compared with traditionally navigation systems. Recently, lower accuracy inertial navigation systems (INS) based on Microelectromechanical systems (MEMS) technology have been proposed to replace more accurate traditional navigation systems.

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Shortest Path Problems In A Stochastic And Dynamic Environment, Jae Il Cho Mar 2003

Shortest Path Problems In A Stochastic And Dynamic Environment, Jae Il Cho

Theses and Dissertations

In this research, we consider stochastic and dynamic transportation network problems. Particularly, we develop a variety of algorithms to solve the expected shortest path problem in addition to techniques for computing the total travel time distribution along a path in the network. First, we develop an algorithm for solving an independent expected shortest path problem. Next, we incorporate the inherent dependencies along successive links in two distinct ways to find the expected shortest path. Since the dependent expected shortest path problem cannot be solved with traditional deterministic approaches, we develop a heuristic based on the K-shortest path algorithm for this …

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Finite Extinction Time For Non-Linear Absorption-Diffusion Equations, Jacob B. Goldberg Sep 2002

Finite Extinction Time For Non-Linear Absorption-Diffusion Equations, Jacob B. Goldberg

Theses and Dissertations

In this thesis, we develop a numerical method in order to approximate the solutions of one-dimensional, non-linear absorption-diffusion equations. We test our method for accuracy against a linear diffusion equation with a solution that can be written in closed form. We then test various types of diffusion and absorption terms to determine which ones produce extinction in finite time. We also develop a numerical method to computationally solve diffusion-free equations. We compare the numerical solutions of the one-dimensional, non-linear absorption-diffusion equation and the diffusion-free equation and we find that for the cases tested, the numerical absorption-diffusion solutions are always less …

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Comparing Clustering Algorithms For Use With Genomic And Proteomic Data, Rebecca A. Olson Sep 2002

Comparing Clustering Algorithms For Use With Genomic And Proteomic Data, Rebecca A. Olson

Theses and Dissertations

The Human Genome Project and related projects have resulted in the development of a number of new experimental and analytic tools for use in genomic and proteomic research. In the area of toxicogenomics, researchers are concerned with how genes react to exposure to certain chemicals. The United States Air Force is interested in the effect of exposure to mission-essential chemicals. Although military personnel may come into contact with chemicals such as hydrazine, risk assessment is usually very limited. On the genomic level, risk assessment is a multi-stop and multi-disciplinary process. The process begins with an experiment that exposes cells to …

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An Analysis Of Mutually Dispersive Brown Symbols For Non-Linear Ambiguity Suppression, Matthew J. Papaphotis Mar 2002

An Analysis Of Mutually Dispersive Brown Symbols For Non-Linear Ambiguity Suppression, Matthew J. Papaphotis

Theses and Dissertations

This thesis significantly advances research towards the implementation of optimal Non-linear Ambiguity Suppression (NLS) waveforms by analyzing the Brown theorem. The Brown theorem is reintroduced with the use of simplified linear algebraic notation. A methodology for Brown symbol design and digitization is provided, and the concept of dispersive gain is introduced. Numerical methods are utilized to design, synthesize, and analyze Brown symbol performance. The theoretical performance in compression and dispersion of Brown symbols is demonstrated and is shown to exhibit significant improvement compared to discrete codes. As a result of this research a process is derived for the design of …

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Modeling And Analysis Of Multicommodity Network Flows Via Goal Programming, Matthew A. Scott Mar 2002

Modeling And Analysis Of Multicommodity Network Flows Via Goal Programming, Matthew A. Scott

Theses and Dissertations

In this research we focused on the mobility system modeled by the AMC mobility planner's calculator (AMPCALC). We developed AMPCALC as a user-friendly tool and allow the user to easily carry out strategic airlift, air refueling and aeromedical evacuation calculations that are covered in Air Force Pamphlet 10-1403. In this study, Excel software and its macro language, Visual Basic for Application, are our two main tools. In the methodology of the thesis we examined fundamental aspects of the mobility system in AMPCALC. We discussed formulation logic of the mobility cycle. We presented ramp use optimization and tanker optimization processes. We …

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Selecting Salient Features In High Feature To Exemplar Ratio Conditions, Ismail Aslan Mar 2002

Selecting Salient Features In High Feature To Exemplar Ratio Conditions, Ismail Aslan

Theses and Dissertations

A key tenet to the Air Force's vision of Global Vigilance, Reach, and Power is the ability to project power via the use of aerial refueling. Scheduling of limited tanker resources is a major concern for Air Mobility Command (AMC). Currently the Combined Mating and Ranging Planning System (CMARPS) is used to plan aerial refueling operations, however due to the complex nature of the program and the length of time needed to run a scenario, the need for a simple tool that runs in much shorter time is desired. Ant colony algorithms are recently developed heuristics for finding solutions to …

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Identifying Enlisted Stay And Leave Population Characteristics With Discriminant Analysis, Zabrina Y. Hoggard Mar 2002

Identifying Enlisted Stay And Leave Population Characteristics With Discriminant Analysis, Zabrina Y. Hoggard

Theses and Dissertations

The research contribution of this thesis is the first known integrated architecture and feature selection algorithm for Radial Basis Neural Networks (RBNNs). The objective is to apply the network iteratively to determine the final architecture and feature set used to evaluate a problem. Additionally, this thesis compares three different classification techniques, Discriminant Analysis (DA), Feed-Forward Neural Networks (FFN) and RBNNs against several hard to solve problems. These problems were used to evaluate general classifier performance as well as the performance of the feature selection techniques. This thesis describes the classification techniques as well as the measures used to evaluate them. …

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Analysis And Numerical Solution Of An Integral Equation Method For Electromagnetic Scattering From A Cavity In A Ground Plane, Eric T. Howe Sep 2001

Analysis And Numerical Solution Of An Integral Equation Method For Electromagnetic Scattering From A Cavity In A Ground Plane, Eric T. Howe

Theses and Dissertations

In this research the electromagnetic scattering of a plane wave from a two-dimensional cavity embedded in an infinite, perfectly conducting ground plane is investigated. The plane wave is assumed to be under transverse electric (TE) polarization with respect to the x-axis. The cavity may be empty or filled with an arbitrary homogeneous, lossy material. A coupled set of scalar integral equations that govern the electromagnetic scattering is implemented. An approximate solution to the scalar integral equations is found via a Method of Moments (MoM) algorithm. The algorithm is implemented in a computer code, and approximations to the total magnetic field …

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A Low Power Application-Specific Integrated Circuit (Asic) Implementation Of Wavelet Transform/Inverse Transform, Daniel N. Harvala Mar 2001

A Low Power Application-Specific Integrated Circuit (Asic) Implementation Of Wavelet Transform/Inverse Transform, Daniel N. Harvala

Theses and Dissertations

A unique ASIC was designed implementing the Haar Wavelet transform for image compression/decompression. ASIC operations include performing the Haar wavelet transform on a 512 by 512 square pixel image, preparing the image for transmission by quantizing and thresholding the transformed data, and performing the inverse Haar wavelet transform, returning the original image with only minor degradation. The ASIC is based on an existing four-chip FPGA implementation. Implementing the design using a dedicated ASIC enhances the speed, decreases chip count to a single die, and uses significantly less power compared to the FPGA implementation. A reduction of RAM accesses was realized …

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Finite Element Model Updating Using Antiresonant Frequencies, Keith W. Jones Mar 2000

Finite Element Model Updating Using Antiresonant Frequencies, Keith W. Jones

Theses and Dissertations

The applications of antiresonant frequencies to finite element (FE) model updating are few and usually limited to numerical examples. This work uses antiresonant frequencies in the model updating of an experimental structure and analyzes the physical correctness of the updated model by using it to detect damage. Antiresonant frequencies were used in the FE model updating of a six-meter aluminum truss. The model used rigid links to model welded and bolted joints. Rigid link dimensions were used as parameters in an iterative update based on eigenvalue and antiresonance sensitivities. The first update used 11 natural frequencies and 21 antiresonant frequencies …

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Evaporation Of Jet Fuels, Charles Eric Hack Dec 1999

Evaporation Of Jet Fuels, Charles Eric Hack

Theses and Dissertations

Determining the fate and transport of JP-8 jet fuel is a complex and important problem. As part of the startup procedures for jet engines, fuel is passed through aircraft engines before combustion is initiated. Because of the extremely low temperatures at northern tier Air Force bases, the unburned fuel does not evaporate readily and may come into contact with ground crew. To determine the amount and duration of contaminant contact, the evaporation of the emitted fuel must be modeled. The amount and composition of the fuel upon reaching the ground crew may be determined by droplet evaporation models that have …

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Multiple Comparison Pruning Of Neural Networks, Donald E. Duckro Sep 1999

Multiple Comparison Pruning Of Neural Networks, Donald E. Duckro

Theses and Dissertations

Reducing a neural network's complexity improves the ability of the network to be applied to future examples. Like an overfitted regression function, neural networks may miss their target because of the excessive degrees of freedom stored up in unnecessary parameters. Over the past decade, the subject of pruning networks has produced non-statistical algorithms like Skeletonization, Optimal Brain Damage, and Optimal Brain Surgery as methods to remove connections with the least salience. There are conflicting views as to whether more than one parameter can be removed at a time. The methods proposed in this research use statistical multiple comparison procedures to …

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Estimation And Goodness-Of-Fit In The Case Of Randomly Censored Lifetime Data, David M. Reineke Jun 1999

Estimation And Goodness-Of-Fit In The Case Of Randomly Censored Lifetime Data, David M. Reineke

Theses and Dissertations

A new continuous distribution function estimator for randomly censored data is developed, discussed, and compared to existing estimators. Minimum distance estimation is shown to be effective in estimating Weibull location parameters when random censoring is present. A method of estimating all 3 parameters of the 3-parameter Weibull distribution using a combination of minimum distance and maximum likelihood is also given. Cramer-von Mises and Anderson-Darling goodness-of-fit test statistics are modified to measure the discrepancy between the maximum likelihood estimate and the Kaplan-Meier product-limit estimate of the distribution function of the random variable of interest. These modified test statistics are used to …

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Three-Dimensional Calculation Of Contaminant Transport In Groundwater At A Dover Afb Site, Tariq O. Hashim Dec 1998

Three-Dimensional Calculation Of Contaminant Transport In Groundwater At A Dover Afb Site, Tariq O. Hashim

Theses and Dissertations

Macroscale rate-limited sorption modeling was tested using a production transport code, the GMS/FEMWATER ground-water modeling package. The code (Version 1.1 of FEMWATER. dated 1 August 1995) was applied to a 3D conceptual model developed from a field site at Dover AFB, DE. A simulation was performed of a 200 hour contaminant injection pulse followed by clean water flushing. A moment analysis performed on the resulting breakthrough curve validated code self-consistency. Another injection pulse simulation showed that retardation temporally delays the breakthrough peak. Transport simulations of pulsed clean water pumping of the test cell with a prescribed initial contaminant distribution demonstrated …

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Trigonometric Transforms For Image Reconstruction, Thomas M. Foltz Jun 1998

Trigonometric Transforms For Image Reconstruction, Thomas M. Foltz

Theses and Dissertations

This dissertation demonstrates how the symmetric convolution-multiplication property of discrete trigonometric transforms can be applied to traditional problems in image reconstruction with slightly better performance than Fourier techniques and increased savings in computational complexity for symmetric point spread functions. The fact that the discrete Fourier transform a circulant matrix provides an alternate way to derive the symmetric convolution-multiplication property for discrete trigonometric transforms. Derived in this manner, the symmetric convolution-multiplication property extends easily to multiple dimensions and generalizes to multidimensional asymmetric sequences. The symmetric convolution-multiplication property allows for linear filtering of degraded images via point-by-point multiplication in the transform domain …

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Solving Geometric Knapsack Problems Using Tabu Search Heuristics, Christopher A. Chocolaad Mar 1998

Solving Geometric Knapsack Problems Using Tabu Search Heuristics, Christopher A. Chocolaad

Theses and Dissertations

An instance of the geometric knapsack problem occurs in air lift loading where a set of cargo must be chosen to pack in a given fleet of aircraft. This paper demonstrates a new heuristic to solve this problem in a reasonable amount of time with a higher quality solution then previously reported in literature. We also report a new tabu search heuristic to solve geometric knapsack problems.

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Neural Network Modeling Of The Head-Related Transfer Function, Damion Reinhardt Mar 1998

Neural Network Modeling Of The Head-Related Transfer Function, Damion Reinhardt

Theses and Dissertations

Battlefield synthesis of 3-D audio may require the interpolation and compression of head-related transfer function (HRTF) data. This thesis is an implementation of a functional model of the HRTF using artificial neural networks (ANNs), the model provides both compression and interpolation.

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A New Sequential Goodness Of Fit Test For The Three-Parameter Weibull Distribution With Known Shape Based On Skewness And Kurtosis, Jonathan C. Clough Mar 1998

A New Sequential Goodness Of Fit Test For The Three-Parameter Weibull Distribution With Known Shape Based On Skewness And Kurtosis, Jonathan C. Clough

Theses and Dissertations

The Weibull distribution finds wide applicability across a broad spectrum of disciplines and is very prevalent in reliability theory. Consequently, numerous statistical tests have been developed to determine whether sample data can be adequately modeled with this distribution. Unfortunately, the majority of these goodness-of-fit tests involve a substantial degree of computational complexity. The study presented here develops and evaluates a new sequential goodness-of-fit test for the three-parameter Weibull distribution with a known shape that delivers power comparable to popular procedures while dramatically reducing computational requirements. The new procedure consists of two distinct tests, using only the sample skewness and sample …

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Calibrated Probabilistic Quantitative Precipitation Forecasts Based On The Mrf Ensemble, Frederick Anthony Eckel Mar 1998

Calibrated Probabilistic Quantitative Precipitation Forecasts Based On The Mrf Ensemble, Frederick Anthony Eckel

Theses and Dissertations

Probabilistic quantitative precipitation forecasts (PQPF) based on the medium range forecast (MRF) ensemble are currently in operational use below their full potential quality (i.e., accuracy and reliability). This unfulfilled potential is due to the MRF ensemble being adversely affected by systematic errors which arise from an imperfect model and less than ideal ensemble initial perturbations. This thesis sought to construct a calibration to account for these systematic errors and thus produce higher quality PQPF. Systematic errors were explored with the use of the verification rank histogram, which tracks the performance of the ensemble. The information in these histograms was then …

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Improved Mathematical Modeling For Gps Based Navigation, Salvatore Nardi Mar 1998

Improved Mathematical Modeling For Gps Based Navigation, Salvatore Nardi

Theses and Dissertations

This thesis is concerned with the development of new closed form GPS position determination algorithms that work in the presence of pseudorange measurement noise. The mathematical derivation of two closed form algorithms, based on stochastic modeling and estimation techniques, is presented. The algorithms provide an estimate of the GPS solution parameters (viz., the user position and the user clock bias) as well as the estimation error covariance. The experimental results are analyzed by comparison to the baseline results from the conventional Iterative Least Squares (ILS) algorithm. In typical GPS scenarios, the closed form algorithms are extremely sensitive to noise, making …

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Flight Test And Handling Qualities Analysis Of A Longitudinal Flight Control System Using Multiobjective Techniques, John R. Anderson Mar 1998

Flight Test And Handling Qualities Analysis Of A Longitudinal Flight Control System Using Multiobjective Techniques, John R. Anderson

Theses and Dissertations

This thesis addresses the application of optimal, multiobjective control theory control theory to flight control design for the approach and landing phase of flight. Five flight control systems were designed using classical, H2, H infinity, and Mixed H2/H infinity methods. The MATLAB™ MUTOOLS™ and AFIT MXTOOLS toolboxes were used to produce the optimal, multiobjective designs. These designs were implemented for flight test on the Calspan VSS I Learjet, simulating the unstable longitudinal dynamics of an F-16 type aircraft. A limited handling qualities investigation was performed. Model following was used in the design phase to meet handling qualities specifications. The designs …

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An Investigation Of Plume Rise From Titan Iv Rocket Launches, Joseph D. Brands Dec 1997

An Investigation Of Plume Rise From Titan Iv Rocket Launches, Joseph D. Brands

Theses and Dissertations

Space launches at Cape Canaveral Air Station (CCAS) and Vandenberg Air Force Base (vAFB) produce exhaust ground clouds from the solid rocket boosters and liquid hypergolic fuels containing several toxic substances. In order to estimate the health effects that would be imposed upon the public by scheduled launches, range safety officials rely on the Rocket Exhaust Effluent Diffusion Model to predict ground level concentrations of these substances. A drawback to the REEDM is its underprediction of the initial ground clouds stabilization height. This underprediction causes an overprediction of the ground level toxic substance concentrations. This thesis focused on increasing the …

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The Rational Resolution Analysis: A Generalization Of Multi-Resolution Analyses With Application To To The Specific Emitter Identification Problem, Bruce P. Anderson Dec 1997

The Rational Resolution Analysis: A Generalization Of Multi-Resolution Analyses With Application To To The Specific Emitter Identification Problem, Bruce P. Anderson

Theses and Dissertations

The rational resolution analysis RRA is introduced and developed as a generalization of the integer, dilation multiresolution analyses MRA developed by Mallat and Meyer. Rational dilation factors are achieved by relaxing the condition on MRAs that successive approximation spaces be embedded. Conditions for perfect reconstruction are discussed and it is shown that perfect reconstruction is possible with specific constraints on the scaling function the scaling filter must have its roots on the unit circle. Furthermore, the required arrangement of the roots indicate the scaling function must be derived from a B-spline of some degree. It is proven the only compactly …

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Optimal Pulsed Pumping For Remediation Of Aquifers When Sorption Is Rate-Limited, Lawrence J. Schmitt Dec 1997

Optimal Pulsed Pumping For Remediation Of Aquifers When Sorption Is Rate-Limited, Lawrence J. Schmitt

Theses and Dissertations

A variational optimization technique is developed to acquire an optimal schedule of pulsed pumping operations for use at existing pump-and-treat aquifer remediation sites. The optimization problem is stated as a minimization of a generic management objective functional, constrained by the contaminant transport equations in two-dimensional or three-dimensional flow models which account for rate-limited sorption. The two-dimensional case is fully developed and a first-order rate equation is used to describe the transport of sorbing contaminant. The first variation provides necessary optimality conditions that must be met by any optimal solution, in turn leading to a pulsed pumping schedule of operation. The …

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The Fate And Transport Of Airborne Jp-4 And Jp-8 Aerosol During Cold Startup, Bradford Eugene Buckman Dec 1997

The Fate And Transport Of Airborne Jp-4 And Jp-8 Aerosol During Cold Startup, Bradford Eugene Buckman

Theses and Dissertations

During cold startup (engine warm-up) procedures at northern tier bases, fuel aerosol (JP-4 and JP-8) is emitted before complete combustion of the fuel occurs. The time necessary for complete combustion to occur may be as long as 10 minutes. Hence, during these first few minutes, aerosol is emitted at relatively high concentrations. This research investigates the principle behavior of the emitted aerosol: advection, dispersion, evaporation, and settling. Using previous work in fuel jettisoning and evaporation as a foundation, this thesis investigates the physical factors affecting the airborne concentration of fuel aerosol at different times, the amount of fuel aerosol reaching …

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Parameter Estimation For Real Filtered Sinusoids, Daniel R. Zahirniak Sep 1997

Parameter Estimation For Real Filtered Sinusoids, Daniel R. Zahirniak

Theses and Dissertations

This research develops theoretical methods for parameter estimation of filtered, pulsed sinusoids in noise and demonstrates their effectiveness for Electronic Warfare EW applications. Within the context of stochastic modeling, a new linear model, parameterized by a set of Linear Prediction LP coefficients, is derived for estimating the frequencies of filtered sinusoids. This model is an improvement over previous modeling techniques since the effects of the filter and the coefficients upon the noise statistics are properly accounted for during model development. From this linear model, a relationship between LP coefficient estimation and Maximum Likelihood ML frequency estimation is derived and several …

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An Investigation Of Instantaneous Plume Rise From Rocket Exhaust, Paul F. Sand Dec 1996

An Investigation Of Instantaneous Plume Rise From Rocket Exhaust, Paul F. Sand

Theses and Dissertations

Rocket launches at Vandenburg Air Force Base and Cape Canaveral Air Station produce exhaust clouds containing several toxic by-products, including HC1 and A12O3. These clouds rise to atmospheric stabilization heights, and then start dispersing and diffusing through the air. Upon reaching the ground, concentration levels of the toxins may present a human health risk. To predict these risks and concentration levels, range officials use a computer program titled the Rocket Effluent Exhaust Diffusion Model (REEDM). The version currently in use has been shown to underpredict the stabilization height of the exhaust cloud. This thesis examines the theory and algorithms used …

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Characteristic Spatial Quadratures For Discrete Ordinates Neutral Particle Transport On Arbitrary Tetrahedral Meshes, Charles R. Brennan Jun 1996

Characteristic Spatial Quadratures For Discrete Ordinates Neutral Particle Transport On Arbitrary Tetrahedral Meshes, Charles R. Brennan

Theses and Dissertations

Characteristic spatial quadratures for discrete ordinates calculations on meshes of arbitrary tetrahedra are derived and tested, including the step (SC), linear (LC), and exponential (EC) characteristic quadratures and variants that assume constant distributions on cell faces. Tetrahedral meshes accurately model curved surfaces with few cells. A split cell approach subdivides tetrahedra along the streaming direction, reducing the transport to one dimension. Assumed forms of the cell source and entering flux distributions have sufficient parameters to match the zeroth and first spatial moments. These parameters are determined by analytically inverting a linear system (LC), or by numerical inversion using Newton's method …

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A Point Model Of Aquifer Cleanup With A Distribution Of First-Order Rate Parameters, Jon E. Hodge Dec 1995

A Point Model Of Aquifer Cleanup With A Distribution Of First-Order Rate Parameters, Jon E. Hodge

Theses and Dissertations

Many try modeling groundwater contaminant transport to predict it. Is this possible with rate-limited processes, and under what conditions? On occasion, cleanups go slower than predicted (tailing) and hazardous concentrations reappear after cleanup is thought complete (rebound). Rate-limited transport is blamed by many. When immobile water is present, diffusion from varied sizes and shapes of immobile regions can cause varied rate limitations (due to varied diffusion path lengths). Although known, most modelers represent these varied rate-limiting processes with a single 'representative' rate-parameter. This can yield poor predictions for long-term experiments, and the parameter is generally time and pump-rate dependent. This …

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