Surface microtopography affects a series of complex and dynamic hydrologic and environmental processes that are associated with both surface and subsurface systems, such as overland flow generation, infiltration, soil erosion, and sediment transport. Due to the influence of surface depressions, overland flow essentially features a series of progressive puddle-to-puddle (P2P) filling, spilling, merging, and splitting processes; and hydrologic systems often exhibit threshold behaviors in hydrologic connectivity and the associated overland flow generation process. It is inherently difficult to realistically simulate the discontinuous overland flow on irregular topographic surfaces and quantify the spatio-temporal variations in dynamic behaviors of topography-dominated hydrologic systems. This dissertation research aims to develop a hydrologic model to simulate the discontinuous, dynamic P2P overland flow processes under the control of surface microtopography for various rainfall and soil conditions, and propose new approaches to quantify hydrologic connectivity. In the developed P2P overland flow model, the depressions of a topographic surface are explicitly incorporated into a well-delineated, cascaded P2P drainage system as individual objects to facilitate the simulation of their dynamic behaviors and interactions. Overland flow is simulated by using diffusion wave equations for a DEM-derived flow drainage network for each puddle-dominated area. In addition, a P2P hydrologic connectivity concept is proposed to characterize runoff generation processes and the related spatio-temporal dynamics. Two modified hydrologic connectivity indices, time-varying connectivity function and connectivity length of the connected areas and ponded areas, are proposed to quantitatively describe the intrinsic spatio-temporal variations in hydrologic connectivity associated with overland flow generation. In addition, the effects of DEM resolution, surface topography, rainfall distribution, and surface slope on hydrologic connectivity are also evaluated in this dissertation research. The developed model can be applied to examine the spatio-temporally varying P2P dynamics for hydrologic systems. This model provides a means to investigate the effects of the spatial organization/heterogeneity of surface microtopography, rainfall, and soil on overland flow generation and infiltration processes. In addition, the two proposed hydrologic connectivity indices are able to bridge the gap between the structural and functional hydrologic connectivity and effectively reveal the variability and the threshold behaviors of overland flow generation. / National Science Foundation under Grant No. EAR-0907588 / Department of Civil and Environmental Engineering, North Dakota State University / North Dakota Water Resources Research Institute

Spatial characterization of surface microtopography is important in understanding the overland flow generation and the spatial distribution of surface runoff. In this study, fractal parameters (i.e., fractal dimension D and crossover length l) and three hydrotopographic parameters, random roughness (RR) index, maximum depression storage (MDS), and the number of connected areas (NCA), have been applied to characterize the spatial complexity of microtopography. Clear and meaningful relationships have been established between these parameters. The RR was calculated as the standard deviation of the processed elevation, and the fractal parameters were calculated with the semivariogram method. The puddle delineation program was applied in this study to spatially delineate soil surface and to accurately determine MDS and NCA. It has been found that fractal parameters can better characterize surface microtopography. More importantly, fractal and anisotropic analyses can help to better understand the overland flow generation process.

Background: The continued success of Lean thinking beyond manufacturing has led to an increasing interest to utilize it in software engineering (SE). Value Stream Mapping (VSM) had a pivotal role in the operationalization of Lean thinking. However, this has not been recognized in SE adaptations of Lean. Furthermore, there are two main shortcomings in existing adaptations of VSM for an SE context. First, the assessments for the potential of the proposed improvements are based on idealistic assertions. Second, the current VSM notation and methodology are unable to capture the myriad of significant information flows, which in software development go beyond just the schedule information about the flow of a software artifact through a process. Objective: This thesis seeks to assess Software Process Simulation Modeling (SPSM) as a solution to the first shortcoming of VSM. In this regard, guidelines to perform simulation-based studies in industry are consolidated, and the usefulness of VSM supported with SPSM is evaluated. To overcome the second shortcoming of VSM, a suitable approach for capturing rich information flows in software development is identified and its usefulness to support VSM is evaluated. Overall, an attempt is made to supplement existing guidelines for conducting VSM to overcome its known shortcomings and support adoption of Lean thinking in SE. The usefulness and scalability of these proposals is evaluated in an industrial setting. Method: Three literature reviews, one systematic literature review, four industrial case studies, and a case study in an academic context were conducted as part of this research. Results: Little evidence to substantiate the claims of the usefulness of SPSM was found. Hence, prior to combining it with VSM, we consolidated the guidelines to conduct an SPSM based study and evaluated the use of SPSM in academic and industrial contexts. In education, it was found to be a useful complement to other teaching methods, and in the industry, it triggered useful discussions and was used to challenge practitioners’ perceptions about the impact of existing challenges and proposed improvements. The combination of VSM with FLOW (a method and notation to capture information flows, since existing VSM adaptions for SE are insufficient for this purpose) was successful in identifying challenges and improvements related to information needs in the process. Both proposals to support VSM with simulation and FLOW led to identification of waste and improvements (which would not have been possible with conventional VSM), generated more insightful discussions and resulted in more realistic improvements. Conclusion: This thesis characterizes the context and shows how SPSM was beneficial both in the industrial and academic context. FLOW was found to be a scalable, lightweight supplement to strengthen the information flow analysis in VSM. Through successful industrial application and uptake, this thesis provides evidence of the usefulness of the proposed improvements to the VSM activities.

<p>Positron Emission Tomography, PET, is a noninvasive medical imaging technique to get functional information of the kinetics of radioactive compound injected in the body. The data used in this thesis comes from a total of five H₂¹⁵O PET studies of one patient. This was done in order to study the blood flow in liver metastasis of the patient, before and after treatment.</p><p>A one compartment model was used to do the ROI based analyses. With a least square method in Matlab the unknown parameters in the model, such as the kinetic rate constants, the dispersion and the fraction of blood in the tissue, was extracted. Also a brief analysis of different parts of the metastases, edge and center, was done to see the variations within the metastases. The results show some increase of the blood flow after the treatment, and two of the three studied metastases showed a distinct difference of the activity in the center versus the edge. Given in the thesis are also some basic PET and compartmental modeling theory.</p> / <p>Positronemissionstomografi, PET, är en icke-invasiv medicinsk bildteknik för att få funktionell information om kinetiken av radioaktiva föreningar injicerade i kroppen. Det data som används i denna kandidatuppsats kommer från totalt fem H₂¹⁵O PET-studier av en patient. Detta gjordes för att studera blodflödet i levermetastaser hos patienten före och efter behandling.</p><p>En 1-kompartmentmodell användes för att göra ROI-baserade analyser. Med en minsta kvadrat-metod i Matlab kunde de okända parametrarna i modellen, såsom den kinetiska hastighetskonstanten, spridningen och andelen blod i vävnaden, fås ut. En kort analys gjordes också av olika delar av metastaserna, kanten och mitten, för att se variationerna inuti metastaserna. Resultaten visar en viss ökning av blodflödet efter behandlingen, och två av de tre studerade metastaser visade en tydlig skillnad av aktiviteten i mitten jämfört med kanten. I rapporten ges också grundläggande teori om bland annat PET och kompartmentmodellering.</p>

Positron Emission Tomography, PET, is a noninvasive medical imaging technique to get functional information of the kinetics of radioactive compound injected in the body. The data used in this thesis comes from a total of five H215O PET studies of one patient. This was done in order to study the blood flow in liver metastasis of the patient, before and after treatment. A one compartment model was used to do the ROI based analyses. With a least square method in Matlab the unknown parameters in the model, such as the kinetic rate constants, the dispersion and the fraction of blood in the tissue, was extracted. Also a brief analysis of different parts of the metastases, edge and center, was done to see the variations within the metastases. The results show some increase of the blood flow after the treatment, and two of the three studied metastases showed a distinct difference of the activity in the center versus the edge. Given in the thesis are also some basic PET and compartmental modeling theory. / Positronemissionstomografi, PET, är en icke-invasiv medicinsk bildteknik för att få funktionell information om kinetiken av radioaktiva föreningar injicerade i kroppen. Det data som används i denna kandidatuppsats kommer från totalt fem H215O PET-studier av en patient. Detta gjordes för att studera blodflödet i levermetastaser hos patienten före och efter behandling. En 1-kompartmentmodell användes för att göra ROI-baserade analyser. Med en minsta kvadrat-metod i Matlab kunde de okända parametrarna i modellen, såsom den kinetiska hastighetskonstanten, spridningen och andelen blod i vävnaden, fås ut. En kort analys gjordes också av olika delar av metastaserna, kanten och mitten, för att se variationerna inuti metastaserna. Resultaten visar en viss ökning av blodflödet efter behandlingen, och två av de tre studerade metastaser visade en tydlig skillnad av aktiviteten i mitten jämfört med kanten. I rapporten ges också grundläggande teori om bland annat PET och kompartmentmodellering.

Natural attenuation of trichloroethene (TCE) and technetium (99Tc) was studied for five consecutive seasons (from January 2002 to January 2003) in Little Bayou Creek. The stream receives ground water discharge from an aquifer contaminated by past waste disposal activities at the Paducah Gaseous Diffusion Plant (PGDP), a uranium enrichment facility near Paducah, Kentucky. Results from stream gaging, contaminant monitoring, tracer tests (with bromide, nitrate, rhodamine WT and propane) and simulation modeling indicate the TCE is naturally attenuated by volatilization and dilution, with volatilization rates related to the ambient temperature and surface discharge rate. The only apparent mechanism of 99Tc attenuation is dilution. Travel times of non-gaseous tracers were found to be similar and have highest values in October and lowest in June. It was also estimated from modeling that the transport of the solutes in the stream was mostly one-dimensional with insignificant secondary storage.

AN ABSTRACT OF THE DISSERTATION OFSUMAN SAURABH, for the Doctor of Philosophy degree in Engineering Science, presented on August 30, 2019, at Southern Illinois University Carbondale.TITLE: GEOMECHANICAL STATE OF ROCKS WITH DEPLETION IN UNCONVENTIONAL COALBED METHANE RESERVOIRSMAJOR PROFESSOR: Dr. Satya HarpalaniOne of the major reservoir types in the class of unconventional reservoirs is coalbed methane. Researchers have treated these reservoirs as isotropic when modeling stress and permeability, that is, mechanical properties in all directions are same. Furthermore, coal is a highly sorptive and stress- sensitive rock. The focus of this dissertation is to characterize the geomechanical aspects of these reservoirs, strain, stresses, effective stress and, using the information, establish the dynamic flow/permeability behavior with continued depletion. Several aspects of the study presented in this dissertation can be easily extended to shale gas reservoirs. The study started with mechanical characterization and measurement of anisotropy using experimental and modeling work, and evaluation of how the sorptive nature of coal can affect the anisotropy. An attempt was also made to characterize the variation in anisotropy with depletion. The results revealed that the coals tested were orthotropic in nature, but could be approximated as transversely isotropic, that is, the mechanical properties were isotropic in the horizontal plane, but significantly different in vertical direction. Mechanical characterization of coal was followed by flow modeling. Stress data was used to characterize the changes in permeability with depletion. This was achieved by plotting stress path followed by coal during depletion. The model developed was used to successfully predict the permeability variation in coal with depletion for elastic deformations. As expected, the developed model failed to predict the permeability variation resulting from inelastic deformation given that it was based on elastic constitutive equations. Hence, the next logical step was to develop a generalized permeability model, which would be valid for both elastic and inelastic deformations. Investigation of the causes of coal failure due to anisotropic stress redistribution during depletion was also carried out as a part of this study. It was found that highly sorptive rocks experience severe loss in horizontal stresses with depletion and, if their mechanical strength is not adequate to support the anisotropic stress redistribution, rock failure can result. In order to develop a generalized permeability model based on stress data, stress paths for three different coal types were established and the corresponding changes in permeability were studied. Stress path plotted in an octahedral mean stress versus octahedral shear stress plane provided a signal for changes in the permeability for both elastic as well as inelastic deformations. This signal was used to develop a mechanistic model for permeability modeling, based on stress redistribution in rocks during depletion. The model was able to successfully predict the permeability variation for all three coal types. Finally, since coal is highly stress- sensitive, changes in effective stresses were found to be the dictating factor for deformations, changes in permeability and possible failure with depletion. Hence, the next step was to develop an effective stress law for sorptive and transversely isotropic rocks. For development of an effective stress law for stress sensitive, transversely isotropic rocks, previously established constitutive equations were used to formulate a new analytical model. The model was then used to study changes in the variation of Biot’s coefficient of these rocks. It was found that Biot’s coefficient, typically less than one, can take values larger than one for these rocks, and their values also change with depletion. The study provides a methodology which can be used to estimate the Biot’s coefficient of any rock. As a final step, preliminary work was carried out on the problem of under-performing coal reservoirs in the San Juan basin, where coal is extremely tight with very low permeability. An extension of the work presented in this dissertation is to use the geomechanical characterization techniques to unlock these reservoirs and improve their performance. The experimental data collected during this preliminary study is included in the last chapter of the dissertation.

Lava flow hazards are one of the few constant themes across the wide spectrum of volcanic research in the solar system. These dynamic hazards are controlled by the location of the eruption, the topography and material properties of the land upon which the flow spreads, and the properties of the lava (e.g., volume, temperature, and rheology). Understanding the influences on eruption location and how lava flows modify the landscape are important steps to accurately forecast volcanic hazards. Three studies are presented in this dissertation that address di˙erent aspects of modeling and assessing vent opening and lava flow hazards. The first study uses hierarchical clustering to explore the distribution of activity at Craters of the Moon (COM) lava field on the eastern Snake River Plain (ESRP). Volcanism at COM is characterized by 53 mapped eruptive vents and 60+ lava flows over the last 15 ka. Temporal, spatial, and spatio-temporal clustering methods that examine different aspects of the distribution of volcanic vents are introduced. The sensitivity of temporal clustering to different criteria that capture the age range of magma generation and ascent is examined Spatial clustering is dictated by structures on the ESRP that attempt to capture the footprint of an emplacing dike. A combined spatio-temporal is the best approach to understanding the distribution of linked eruptive centers and can also provide insight into the evolution of volcanism for the region. Spatial density estimation is used to visualize the differences between these models. The goal of this work is to improve vent opening forecasting tools for use in assessing lava flow hazards. The second study presents a new probabilistic lava flow hazard assessment for the U.S. Department of Energy’s Idaho National Laboratory (INL) nuclear facility that (1) explores the way eruptions are defined and modeled, (2) stochastically samples lava flow parameters from observed values for use in MOLASSES, a lava flow simulator, (3) calculates the likelihood of a new vent opening within the boundaries of INL, (4) determines probabilities of lava flow inundation for INL through Monte Carlo simulation, and (5) couples inundation probabilities with recurrence rates to determine the annual likelihood of lava flow inundation for INL. Results show a 30% probability of partial inundation of the INL given an e˙usive eruption on the ESRP, with an annual inundation probability of 8.4×10^−5 to 1.8×10^−4. An annual probability of 6.2×10^−5 to 1.2×10^−4 is estimated for the opening of a new eruptive center within INL boundaries. The third study models thermo-mechanical erosion of a pyroclastic substrate by flow-ing lava on Volcán Momotombo, Nicaragua. It describes the unique morphology of a lava flow channel using TanDEM-X/TerraSAR-X and terrestrial radar digital elevation models. New methods for modeling paleotopography on steep-sided cones are introduced to mea-sure incision depths and document cross-channel profiles. The channel is incised ~35 m into the edifice at the summit and transitions into a constructional feature halfway down the ~1,300 m high cone. An eroded volume of ~4×10^5 m3 was calculated. It is likely that a lava flow eroded into the cone as it emplaced during an eruption in 1905. There is not suÿcient energy to thermally erode this volume, given the observed morphology of the flow. Models are tested that explore the relationship of shearing and material properties of the lava and substrate against measured erosion depths and find that thermo-mechanical erosion is the most likely mode of channel formation. Additionally, it is likely that all forms of erosion via lava flow are impacted by thermal conditions due to the relationship between temperature and substrate hardness. The evolution of these structures (their creation and subsequent infilling) plays an important role in the growth of young volcanoes and also controls future lava flows hazards, as seen by the routing of the 2015 flow into the 1905 channel.

The Transmission Control Protocol (TCP) has successfully governed the Internet congestion control for two decades. It is by now, however, widely recognized that TCP has started to reach its limits and that new congestion control protocols are needed in the near future. This has spurred an intensive research effort searching for new congestion control designs that meet the demands of a future Internet scaled up in size, capacity and heterogeneity. In this thesis we derive network fluid flow models suitable for analysis and synthesis of window based congestion control protocols such as TCP. In window based congestion control the transmission rate of a sender is regulated by: (1) the adjustment of the so called window, which is an upper bound on the number of packets that are allowed to be sent before receiving an acknowledgment packet (ACK) from the receiver side, and (2) the rate of the returning ACKs. From a dynamical perspective, this constitutes a cascaded control structure with an outer and an inner loop. The first contribution of this thesis is a novel dynamical characterization and an analysis of the inner loop, generic to all window based schemes and formed by the interaction between the, so called, ACK-clocking mechanism and the network. The model is based on a fundamental integral equation relating the instantaneous flow rate and the window dynamics. It is verified in simulations and testbed experiments that the model accurately predicts dynamical behavior in terms of system stability, previously unknown oscillatory behavior and even fast phenomenon such as traffic burstiness patterns present in the system. It is demonstrated that this model is more accurate than many of the existing models in the literature. In the second contribution we consider the outer loop and present a detailed fluid model of a generic window based congestion control protocol using queuing delay as congestion notification. The model accounts for the relations between the actual packets in flight and the window size, the window control, the estimator dynamics as well as sampling effects that may be present in an end-to-end congestion control algorithm. The framework facilitates modeling of a quite large class of protocols. The third contribution is a closed loop analysis of the recently proposed congestion control protocol FAST TCP. This contribution also serves as a demonstration of the developed modeling framework. It is shown and verified in experiments that the delay configuration is critical to the stability of the system. A conclusion from the analysis is that the gain of the ACK-clocking mechanism dramatically increases with the delay heterogeneity for the case of an equal resource allocation policy. Since this strongly affects the stability properties of the system, this is alarming for all window based congestion control protocols striving towards proportional fairness. While these results are interesting as such, perhaps the most important contribution is the developed stability analysis technique. / QC 20100813

Accurate modeling of current flow and network parameter extraction in 2-D and 3-D conductors has an important application in signal integrity of high-speed interconnects. In this thesis, we propose a new rigorous single-source Surface-Volume-Surface Electric Field Integral Equation (SVS-EFIE) for magnetostatic analysis of 2-D transmission lines and broadband resistance and inductance extraction in 3-D interconnects. Furthermore, the novel integral equation can be used for the solution of full-wave scattering problems on penetrable 2-D cylinders of arbitrary cross-section under transverse magnetic polarization. The new integral equation is derived from the classical Volume Electric Field Integral Equation (V-EFIE) by representing the electric field inside a conductor or a scatterer as a superposition of the cylindrical waves emanating from the conductor’s surface. This converts the V-EFIE into a surface integral equation involving only a single unknown function on the surface. The novel equation features a product of integral operators mapping the field from the conductor surface to its volume and back to its surface terming the new equation the Surface-Volume-Surface EFIE. The number of unknowns in the proposed SVS-EFIE is approximately the square root of the number of degrees of freedom in the traditional V-EFIE; therefore, it allows for substantially faster network parameter extraction and solutions to 2-D scattering problems without compromising the accuracy. The validation and benchmark of the numerical implementation of the Method of Moment discretization of the novel SVS-EFIE has been done via comparisons against numerical results obtained by using alternative integral equations, data found in literature, simulation results acquired from the CAD software, and analytic formulas.