• Computational modeling of barometric pressure fluctuation effects on explosive methane-air mixtures in a longwall mine gob

      Brune, Jürgen F.; Bogin, Gregory E.; Lolon, Samuel Atta; Grubb, John W.; Miller, Hugh B.; Sullivan, Neal P. (Colorado School of Mines. Arthur Lakes Library, 2017)
      The coal mining industry remains a major player in electrical power generation for the United States. The U.S. Energy Information Administration (EIA) reported that coal made up the second largest share after natural gas, approximately 30%, of the total electricity generated in 2016, further, it projected to remain significant for the next several decades together with natural gas and renewable sources (U.S. Energy Information Administration, 2017). Longwall mining has become more frequently used for extracting coal seams underground due to increased safety and higher productivity (EMFI, 2010) through improved mechanization and mining system automation. In the longwall method, the overlying strata are allowed to cave behind the working face after the coal is extracted, creating a porous zone known as gob. Due to its caving nature, the gob is inaccessible and presents a safety concern because of the potential methane and explosive mixture accumulation occurring in this zone. There have been a great number of mine fires and explosions in the United States and other countries that suggest the existence of an explosive mixture or Explosive Gas Zone (EGZ) in bleeder-ventilated longwall gob (Loane et al., 1975; Lynn et al., 1986; McKinney et al., 2001; Dziurzynski and Wasilewski, 2012; Brune, 2013). These events indicated that EGZs must have existed inside and around the perimeter of gobs. The risk of mine explosion will increase if these EGZs flow out from the gob to the surrounding mine entries. As mine pressure is influenced by atmospheric pressure, the fluctuation of outside pressure can disturb the pressure differential between the internal and external gob which consequently can either escalate or lessen the EGZ outgassing from the gob. A number of studies have related major mine explosions to abrupt barometric pressure changes in the United States, South Africa, Australia, and Poland (Hosler, 1948; Boyer, 1964; Kissell et al., 1973; Fauconnier, 1992; Hemp, 1994; Wasilewski, 2014; Belle, 2014; and Lolon et al., 2015). These disastrous mine explosions seem to happen frequently in stormy weather, which occur during late fall and winter seasons in the United States. Numerical modeling using computational fluid dynamics (CFD) is considered the best suited approach for simulating methane air flow and mixture in the gob due to its inaccessibility, which limits the availability of gob data. CFD modeling has been widely used for mine ventilation analysis around the globe (Brunner et al., 1995; Wala et al., 1997; Balusu et al., 2002; Calizaya et al., 2004; Lowndes et al., 2005; Yuan et al., 2006; and Ren, 2010). CFD models were developed in this research to analyze the formation of EGZ in the bleeder-ventilated gob, the effects of various magnitudes and rates of barometric pressure change on the EGZ and methane outgassing, and the potential location of the outgassing. The model was built based on an actual supercritical longwall mine in the western United States, characterized by the condition of no overlying strata hanging above the shields. The ventilation parameters and gob permeability characteristics were obtained from cooperating mines which had been studied by earlier researchers in this project (Worrall, 2012; Wachel, 2012; Marts, 2015; Gilmore, 2015). Other parameters not available in the cooperating mine such as location and operating pressure of methane source, and pressure drops of regulators and other ventilation controls were obtained from reliable references or similar studies, or calculated to be deemed reasonable. The outputs of CFD modeling indicated fringes of EGZ within the gob and several back-end crosscuts on the tailgate return under static atmospheric pressure condition, confirming an observation reported by several explosion investigations and studies of EGZ existence within the gob (Elkins et al., 2001; McKinney at al., 2001; Cario, 2006; Woodward and Sheffield, 2008; Page et al., 2011; Brune, 2013). The CFD models show that, under normal bleeder ventilation systems, it is very likely that EGZ is formed within the gob as a result of ventilation air ingressing into the gob and mixing with methane. The CFD models further identified that the methane and EGZ outgassing occurs in barometric pressure fall scenarios. The rise of atmospheric pressures is a preferable situation with respect to EGZ outgassing; CFD models demonstrated decreasing EGZ volumes within the gob and tailgate return crosscuts associated with barometric or external pressure increases. Therefore, this research focused more on the barometric fall scenarios than the cases where it increased. The hypotheses of gob breathing and outgassing under various scenarios of pressure changes were also proved by analyzing the modeling outputs. The amount of EGZ outflow depended on the magnitude of the pressure drop. The rate of outgassing was controlled by the rate of pressure fall. The location of EGZ outgassing was mainly in the tailgate and bleeder returns. Gob permeability is major assumption in this modeling, thus a parametric study is presented to discuss the effect of permeability on the base EGZ cases. The study shows larger EGZ volume within the gob with higher permeability. Higher permeable gob allowed more air ingression into the gob which, mixed with methane, resulted in larger EGZ. At the end, the results were validated against data provided by cooperating mines and also compared with published data. The main objective of this research is to provide the mining industry, its stakeholders, and the body of knowledge with a better understanding of gob breathing, EGZ outgassing and the methane explosion risk associated with barometric pressure changes and, ultimately, recommendations of best practices to prevent outgassing from resulting in a mine explosion. The best practices recommended include the risk matrix, a continuous monitoring system, and Gob Ventilation Borehole (GVB) application.
    • Solid-oxide fuel cells for unconventional oil and gas production

      Sullivan, Neal P.; Newman, Alexandra M.; Anyenya, Gladys A.; Braun, Robert J.; Jackson, Gregory; Maniloff, Peter (Colorado School of Mines. Arthur Lakes Library, 2017)
      This dissertation presents a novel, cost-effective, environmentally sustainable method for converting United States' vast oil shale reserves into crude oil. Geothermic Fuel Cells (GFC) are designed for in-situ oil-shale processing. When implemented, the GFC is placed underground within an oil-shale formation; the heat released by the high-temperature solid oxide fuel cells within the GFC during electricity generation is used to upgrade oil shale into “sweet” crude oil. The world's first Geothermic Fuel Cell prototypes were designed and built by Delphi Powertrain Systems; their performance was characterized at the Colorado Fuel Cell Center (Golden, CO, USA). Following indoor, laboratory operation and validation of two GFC modules, three multi-stack modules were assembled into a nine-stack GFC that was integrated with a natural gas fuel processor and ancillary components, and operated underground within the geology at the Colorado School of Mines campus. Extensive experimental data collected during GFC testing was used to calibrate a steady-state system model in Aspen Plus to predict the GFC stacks' electrochemical performance and the heat-rejection from the module. Following model validation, further simulations are performed for different values of current, fuel and air utilization to study their influence on system electrical and heating performance. The model is used to explore a wider range of operating conditions than can be experimentally tested, and provides insight into competing physical processes during Geothermic Fuel Cell operation. Results show that the operating conditions can be tuned to generate desired heat-flux conditions as needed across applications. A maximum combined-heat-and-power-efficiency of 90% is simulated in the parametric study. Using simulation data from the GFC model, a continuous, non-convex nonlinear multi-objective optimization model is developed in AMPL to optimize the design and dispatch of a single GFC heater well. The optimization model seeks to maximize the system heating and electrical efficiencies while minimizing costs. The optimal design and dispatch strategy obtained using the KNITRO 12.2.0 solver yielded a well-head cost of 37 $/bbl for the oil and gas produced using the GFC technology and a maximum combined-heat-and-power-efficiency of 79%.
    • Deepwater slope channels on active continental margins, Eocene forearc basin, California: architecture and Froude supercritical flow channel fills

      Plink-Björklund, Piret; Ono, Kenya; Benson, Robert D.; Anderson, Donna S.; Carr, Mary; Dykstra, Mason (Colorado School of Mines. Arthur Lakes Library, 2017)
      This dissertation focuses on the southern California active margin continental slopes, and tests the hypothesis that deepwater slope architectures on active continental margins differ from passive margins or foreland basins due to both the structurally-controlled steep gradients, and the narrowness of the shelf platform. These controlling factors allow the high-gradient hinterland to connect directly to the steep deepwater slope and are insusceptible to relative sea-level change. This high-gradient hinterland to deepwater slope margin causes the direct and sustained sediment supply from the river to the continental slope. To test this hypothesis, two main study regions were chosen in the Eocene forearc deepwater basins filled with the Great Valley Sequence Belt, which are the La Jolla Group, exposed north of San Diego, and the Juncal Formation in Frazier Park. Field work in these two regions allowed for a comparison between two types of deepwater slope systems. The La Jolla Group is composed of relatively lower aspect ratio channel complexes, which form a prograding upper slope. The Juncal Formation is composed of relatively higher-aspect ratio channel complexes, which form an intra-slope fan complex with a feeder channel on the middle slope. Both systems are highly channelized, as was hypothesized to be characteristic for active margins. The La Jolla prograding channel complexes demonstrate a highly channelized upper slope environment with considerably lower slope progradation rate, as compared to passive margins or foreland basins. The Juncal slope fan complex demonstrates that the majority of the fan volume is formed by avulsive channel complexes without lobe elements. The channel fills inboth systems span from heterolithic fine-grained channel fills, to sandy to heterolithic channel fill, and sandy fills with basal conglomerates. All the channel fills indicate an abundance of bypass signatures. This is especially remarkable for the heterolithic channel fills, which are different from the existing models for fine-grained channel fills that consider channel abandonment or passive infill. Furthermore, all channel fills are interpreted to be dominated by Froude supercritical flow deposits due to pervasive scour-and-fill structures with backsets. This suggests that the Froude supercritical flow may control the observed highly irregular shape and distribution of the sandstones (e.g., mounded shape and mosaic-like facies distribution) in the channel fills. The studied channel complexes provide an outcrop analog for modern sea-floor upslope migrating scour and fill structures that form crescent-shape bedforms in channels and submarine canyons. This work and the comparison to modern systems suggest that supercritical flow and bypassing turbidity currents are significant processes on active continental margins due to both high sediment supply, and the steep hinterland to continental margin slopes.
    • Understanding aggregation of solvating extractants in applied separations

      Shafer, Jenifer C.; Baldwin, Anna G.; Jensen, Mark; Williams, S. Kim R.; King, Jeffrey C.; Bridges, Nicholas J. (Colorado School of Mines. Arthur Lakes Library, 2017)
      Solvent extraction is an efficient and effective method for the industrial-scale recovery and purification of metals from mixed raw materials. Understanding the molecular-scale forces driving extraction remains an area of active research despite over 70 years of experience with industrial-scale solvent extraction processes. This thesis presents a series of studies on the extraction chemistry of two extractants relevant to applied separations. The extractant tributyl phosphate (TBP) is used in the Plutonium Uranium Reduction Extraction (PUREX) process for recovering uranium and plutonium from used nuclear fuel. The extractant N,N,N',N'-tetraoctyl diglycolamide (TODGA) is being considered for use in the Actinide Lanthanide Separation (ALSEP) process for separation and purification of lanthanides and minor actinides from PUREX process wastes. Distribution data collected for the extraction of trace amounts of fission and corrosion products by TBP in the presence of bulk uranium were mostly consistent with extraction through a traditional solvation mechanism. The exeception was the decreased extraction of low valence transition metals with increasing uranium concentration, which suggests another extraction mechanism such as reversed micelle formation. Distribution data collected for lanthanides in a TODGA solvent extraction system were also consistent with a traditional solvation mechanism. The selectivity trend for TODGA across the lanthanide series was found to follow the amount of water co-extracted with each lanthanide, suggesting that the extraction of lanthanides by TODGA is impacted by species in the outer coordination sphere of the extracted complexes. Diffusion NMR spectroscopy was used to determine the sizes and interactions of colloidal TBP aggregates in 20% TBP samples containing nitric acid, zirconium, and uranium. The aggregate sizes calculated from diffusion experiments were similar to those found previously using small angle neutron scattering (SANS). However, diffusion experiments suggested the presence of repulsive interactions between aggregates, while prior SANS experiments suggested attractive interactions. Diffusion NMR spectroscopy, rheology, and SANS experiments with 30% TBP samples containing nitric acid, zirconium, and uranium also produced conflicting results when the TBP aggregates were assumed to be colloidal particles. These results suggest that understanding the extraction of metals by TBP on a molecular-scale requires treating TBP aggregates as molecular species.
    • Benchmarking of neutron flux parameters at the USGS TRIGA reactor in Lakewood, Colorado

      Greife, Uwe; Alzaabi, Osama E.; Sarazin, Frederic; Shafer, Jenifer C.; Sellinger, Alan (Colorado School of Mines. Arthur Lakes Library, 2017)
      The USGS TRIGA Reactor (GSTR) located at the Denver Federal Center in Lakewood Colorado provides opportunities to Colorado School of Mines students to do experimental research in the field of neutron activation analysis. The scope of this thesis is to obtain precise knowledge of neutron flux parameters at the GSTR. The Colorado School of Mines Nuclear Physics group intends to develop several research projects at the GSTR, which requires the precise knowledge of neutron fluxes and energy distributions in several irradiation locations. The fuel burn-up of the new GSTR fuel configuration and the thermal neutron flux of the core were recalculated since the GSTR core configuration had been changed with the addition of two new fuel elements. Therefore, a MCNP software package was used to incorporate the burn up of reactor fuel and to determine the neutron flux at different irradiation locations and at flux monitoring bores. These simulation results were compared with neutron activation analysis results using activated diluted gold wires. A well calibrated and stable germanium detector setup as well as fourteen samplers were designed and built to achieve accuracy in the measurement of the neutron flux. Furthermore, the flux monitoring bores of the GSTR core were used for the first time to measure neutron flux experimentally and to compare to MCNP simulation. In addition, International Atomic Energy Agency (IAEA) standard materials were used along with USGS national standard materials in a previously well calibrated irradiation location to benchmark simulation, germanium detector calibration and sample measurements to international standards.
    • Advanced power theories and signal decomposition methods for controlling smart converters in smart grid applications

      Simões, M. Godoy; Harirchi, Farnaz; Al-Durra, Ahmed; Mohagheghi, Salman; Ammerman, Ravel F.; Steele, John P. H. (Colorado School of Mines. Arthur Lakes Library, 2017)
      During last two decades, the enormous level of aggregation of distributed generation units DGUs (widely known as the technology of Microgrids), in addition to increasing usage of nonlinear loads in power systems has raised new mathematical-conceptual challenges, specially in power electronics. Most of the traditional power theories and concepts therein, have been defined and formulated for simple balanced and linear systems. As a result, most of them are not directly applicable in case of new system structures with a considerable amount of uncertainty in the production and nonlinearity in the consumption. Due to uncertainties injected by the dynamic behavior of the DGUs (mostly renewable-based), the power components in the traditional power theories should be redefined under highly dynamic behavior of the power signals. Moreover, corresponding justifications need to be implemented to adapt all the related control strategies and compensation techniques. Renewable-based energies, such as wind and solar, are inherently uncertain power sources which can have unpredictable unwanted impacts on power flow, voltage regulation, and result in distribution losses. Microgrids that are quickly expanded through the power networks and power theories play a critical role in all the control strategies designed for these systems. When operating in the islanded mode, low-voltage Microgrids can exhibit considerable variation of amplitude and frequency of the voltage supplied to the loads, thus affecting power quality and network stability. Limited power capability in Microgrids can cause a voltage distortion which affects measurement accuracy, and possibly cause tripping of protections. Besides, the nonlinear and unbalanced loads obscure the traditional power definitions and equations. In such contexts, a reconsideration of power theories is required, since they form the basis for supply and load characterization and accountability. Moreover, developing new control techniques for harmonic and reactive compensators are mandatory, because they operate in a strongly interconnected environment and must perform cooperatively to face system dynamics, ensure power quality, and limit distribution losses. The main purpose of this research is to improve the quality, reliability and stability of future electrical power delivery by improving the overall performance of smart Microgrids through usage of advanced time-domain power theories (such as instantaneous power theory (PQ) and Conservative Power Theory (CPT)). Another major contribution of this work is the introduction of new mathematical power theory concepts (termed Enhanced Instantaneous Power Theory (EIPT)) in addition to implementation of adequate new control strategies. This work specially expanded based on a specific viewpoint which says that power theories can be interpreted as advanced signal decomposition techniques which are used as the initial step in electrical power signals analysis. This signal analysis step forms the fundamental headstock for power electronic interfaces controller design procedure. After describing the mathematical fundamentals of our modified power theory, EIPT; then this method is used as a time-domain signal decomposition approach for relevant applications. Exploiting the fine levels of information revealed through analysis of the power signals with the mentioned decomposition approaches, we provide more levels of freedom in the case of control frameworks. This research also investigate the interesting application of EIPT, besides other practical power theories such as CPT, in islanding detection problems, where a new instantaneous intelligent passive islanding detection strategy will be introduced. In a nutshell, developing new time-domain power theory concepts while exploiting the inherent capacities of the pre-existing power theories, the main goal of this work will be designing a reliable and smart multifunctional control scheme that can address all the aforementioned challenges.
    • Determination of hydrogen in low alloy steel by magnetoacoustic emission and Barkhausen noise

      Liu, Stephen; Olson, D. L. (David LeRoy); Poncelow, Jonathan A.; De Moor, Emmanuel; Yu, Zhenzhen; Steele, John P. H.; Vidal, Edgar E.; Meegan, Douglas (Colorado School of Mines. Arthur Lakes Library, 2017)
      This work serves to assess the viability of a nondestructive technique for the determi- nation of hydrogen in steel welds using variation in magnetic properties. To that end, the philosophical framework is established through a review of applicable theories and develop- ment of new models with regard to hydrogen mobility and ferromagnetism, where possible. Experimental methods and analytical algorithms are developed to determine variation in magnetoacoustic and Barkhausen emission character and changes in magnetization behav- ior. These techniques are then applied to a select number of low-alloy steel samples varied in microstructure by heat treatment and hydrogen concentration by electrolytic charging. Results of these tests are interpreted in the context of hydrogen trapping in ferrous metals and the impact of the solute on the ferromagnetic properties and magnetization dynamics of steel. Finally, the methods developed are evaluated for their robustness as nondestructive methods for hydrogen characterization in field and/or laboratory environments.
    • Faster isomer network generation

      Mehta, Dinesh P.; Thiagarajan, Dheivya; Han, Qi; Wu, Bo; Ciobanu, Cristian V. (Colorado School of Mines. Arthur Lakes Library, 2017)
      Isomer networks provide a mechanism to understand and interpret relationships between organic molecules with applications in medicinal chemistry and drug design. The extraction of isomer networks is a time and data-intensive computation. The contributions of this dissertation are a variety of techniques to more efficiently (with respect to time and memory) compute isomers networks. Specifically, we describe our efforts to improve the network extraction process by 1) Using the symmetry present in most molecules to reduce run time and memory and streamlining the algorithm used for the detection of duplicate canonical names, a key step in determining the bond count distances between pairs of isomers. Together, these techniques result in reductions in memory of up to 60% and improvements in runtime of up to a factor of 100. 2) Developing an optimal grouping algorithm to subdivide an all-all computation with large memory requirements. The algorithm provides a solution to sub divide the "big data" problem that arises in the construction of isomer networks into several independent "small data" problems. Our results show that using the grouping algorithm can help divide large data sets into independent smaller ones that can be processed in parallel. 3) Generating the isomer network for 1,050,125 isomers of Nicotine (with a preliminary analysis of the same) using the cloud computing capabilities of Amazon Web Services and Microsoft Azure. These techniques can also be employed to successfully compute isomers networks for other chemical compounds.
    • Qualitative risk assessment and identification of key drivers for consideration during selection of a copper tailings disposal technology, A

      Nelson, Priscilla P.; Figueroa, Linda A.; Lammers, Heather; Spiller, D. Erik; Holley, Elizabeth A. (Colorado School of Mines. Arthur Lakes Library, 2017)
      Technologies utilized for the disposal of slurry, paste, thickened, and filtered tailings include containment within impoundments, open pit backfill, submarine placement, underground backfill, tailings and waste rock combined disposal, and dry stack placement. Each technology has inherent environmental, social, and economic drivers to be considered during mine planning. Geotechnical and geochemical properties of the tailings, and site-specific design constraints will also drive the selection of a disposal technology. Alternative technologies should be developed to address the increase in volume of tailings generated as lower grade ore is extracted, and to minimize risk associated with current technologies. Understanding the key drivers for selection of existing technologies is a necessary precursor to the future development of alternative technologies. This thesis presents a qualitative risk assessment of environmental, social, economic, geotechnical, geochemical, and site-specific elements utilized in selection of a tailings disposal technology. United States regulations and international guidelines for tailings disposal, and general industry accepted goals for current disposal technologies are summarized. Copper deposit geology, ore processing methods and available disposal technologies are described. Results of the qualitative assessment include the identification of critical, high, moderate, and low ranked drivers for the selection of each tailings disposal technology. Critical and high ranked elements are recognized as key drivers for consideration during the selection of each tailings disposal technology. Key drivers for all technologies include the political and regulatory climate, investor confidence, and the acid generation and neutralization potential of the tailings. Key drivers for consideration during the selection of all surface disposal technologies also include land disturbance, construction cost, and the availability of local materials for construction. Understanding the key drivers for each disposal technology will assist the selection of a suitable, site-specific technology, and is a necessary precursor to the future development of alternative technologies.
    • Probabilistic source-to-sink analysis of the provenance of the California paleoriver: implications for the early Eocene paleogeography of western North America

      Plink-Björklund, Piret; Jones, Evan Rhys; Anderson, Donna S.; Nummedal, Dag; Navarre-Sitchler, Alexis K.; Longman, Mark W.; Miskimins, Jennifer L. (Colorado School of Mines. Arthur Lakes Library, 2017)
      The Latest Paleocene to Early Eocene Colton and Wasatch Formations exposed in the Roan Cliffs on the southern margin of the Uinta Basin, UT make up a genetically related lobate wedge of dominantly fluvial deposits. Estimates of the size of the river that deposited this wedge of sediment vary by more than an order of magnitude. Some authors suggest the sediments are locally derived from Laramide Uplifts that define the southern margin of the Uinta Basin, the local recycling hypotheses. Other authors suggest the sediments were transported by a river system with headwaters 750 km south of the Uinta Basin, the California paleoriver hypothesis. This study uses source-to-sink analysis to constrain the size of the river system that deposited the Colton-Wasatch Fm. We pay particular attention to the what magnitude and recurrence interval of riverine discharge is preserved in the Colton-Wasatch Fm. stratigraphy, and consider the effects this has on scaling discharge to the paleo-catchment area of the system. We develop new scaling relationships between discharge and catchment area using daily gauging data from 415 rivers worldwide. Previous studies using a global database of rivers use average discharge in scaling relationships to catchment area. We demonstrate that average discharge is a flow of variable magnitude and recurrence interval in rivers with different hydrology, and that at higher magnitudes of discharge, especially 99th percentile discharge and higher, the discharge yields and recurrence intervals of flow events of given magnitude are similar across climates and hydrological regimes. These scaling relationships between 99th percentile and higher magnitudes of flow and catchment area have greatly improved predictive precision compared to existing relationships using average discharge. The discharge events our new scaling relationships are based on are also of similar magnitude and recurrence interval as bankfull flow in modern rivers. Bankfull flow is typically considered the flow state that is in geomorphic equilibrium with deposits of ancient river systems. We test our new scaling relationships between 99th percentile and larger discharge and catchment area in modern rivers on a dataset of six ancient rivers of variable size, climate, hydrology where the catchment size is constrained by other methods. We demonstrate that our new scaling relationships introduce less selection bias and upscaling issues than regional curves that are used in other source-to-sink studies. We also demonstrate the utility of a probabilistic approach to source-to-sink analysis of the catchment area of ancient river systems using a Monte Carlo simulator. Using this method we quantitatively evaluate the likelihood of multiple hypotheses of catchment area for the river systems of interest. We show that discharge events 99th percentile and higher have somewhat characteristic recurrence intervals across climatic and hydrological regimes, and that the higher the magnitude of the recurrence interval that characterizes it will be longer. Given that in modern systems rivers with highly variable hydrology have longer recurrence intervals of bankfull, or the channel-forming discharge, than in rivers with persistent hydrology, it then follows that these systems are in geomorphic equilibrium with higher magnitude discharge events. This has an important impact on our source-to-sink analysis as it predicts that given two river systems with the same catchment area, the trunk channel in the river with more variable hydrology will have larger equilibrium channel dimensions. Of our six ancient river systems studied using our probabilistic source-to-sink method, the Colton-Wasatch Fm. is the endmember of a flood-dominated fluvial style. The Colton-Wasatch Fm. was deposited concomitantly with the Paleocene-Eocene Thermal Maximum, a punctuated greenhouse climate change event associated with seasonal to flood and drought prone hydrology in mid-latitude continental interiors. The sedimentology of the Colton-Wasatch Fm. is dominated by Froude-supercritical and high-deposition rate sedimentary structures, downstream accreting barforms, in-channel pedogenically modified fine-grained deposits, and abundant in-channel continental bioturbation that suggest deposition during the waning stage of floods and long-term channel abandonment between depositional events. The river was highly avulsion prone due to the high variability in discharge and built a large fluvial fan system in its depositional terminus in the Uinta Basin. We statistically project the apex position of the fan in the lower part of the Colton-Wasatch Fm. based on paleocurrent measurements across the basin to a location ~250 km south of the Uinta Basin. The maximum progradation of the fan system is recorded in the middle part of the Colton-Wasatch Fm., and we interpret the fan apex was near Sunnyside, UT at this time. This suggests the fluvial fan prograded more than 100 km in response to punctuated climatic forcing from the lower to the middle part, and later back-stepped in the upper part of the Colton-Wasatch Fm. in what was likely a climatic recovery phase. We apply a scaling relationship to the ~25 m deep and ~750 m wide channel deposits in the Colton-Wasatch Fm. that implies the channels are in geomorphic equilibrium with a ~50-100 year flood event. This scaling relationship is based on the maximum recorded discharge in our dataset of gauging data for 415 modern rivers that has a median duration of 66 years. Of our scaling relationships based on 99th percentile discharge and higher, this relationship produces the most conservative estimates of catchment area. Our probabilistic evaluation of the two hypotheses as to the provenance of the Colton-Wasatch Fm. suggests the California paleoriver hypothesis is more than ten times as likely as the local recycling hypothesis. This is supported by our interpretation that the size of the fluvial fan that is the terminus of this river is larger than the catchment area predicted by the local recycling hypothesis. In this way, our source-to-sink and sedimentological/stratigraphic analyses are complimentary, and strongly support a far-traveled provenance for the Colton-Wasatch Fms. transported by an arid and flood-prone California paleoriver that was the dominant axial drainage system in the southwestern US during the Early Eocene.
    • Investigation of high-temperature and high-pressure steam gasification kinetics of a coal-derived char surrogate

      Porter, Jason M.; Kelley, Madison A.; Bogin, Gregory E.; Braun, Robert J.; Brune, Jürgen F. (Colorado School of Mines. Arthur Lakes Library, 2017)
      Gasification is technology that has seen increasing international interest through its ability to convert solid, carbonaceous feedstocks (i.e., coal or biomass) into energy, fuels, and chemicals. Additionally, gasification is considered a ``clean'' technology as harmful emissions and greenhouse gases are readily sequestered. The gasification of a carbonaceous material proceeds in two primary steps: the devolatilization of the feedstock followed by the gasification reactions of the remaining carbon (char). As the gasification reactions are significantly slower than combustion reactions or the devolatilization step, these reactions are rate limiting. While most modern commercial petrochemical processes are designed with a fundamental understanding of the reactions involved, the complex nature of gasification has prevented this for being true of gasification processes --- the coupled heterogeneous and homogeneous kinetics, multi-mode heat transfer, fluid dynamics, and variability in feedstocks, among other factors, makes measuring or modeling these conversion rates challenging. In this study, we focus solely on char reactions with steam at high temperature and pressure (i.e., conditions that are applicable to entrained-flow gasification). The feedstock used in this study was a char ``surrogate'' (a coal-derived activated carbon) which was thoroughly characterized to provide data regarding its composition, physical structure, and reactivity. Activated carbon was identified as a potential surrogate for char as it is physically consistent, has characteristics similar to that of traditional char, and is available for other researchers to acquire. Thorough characterization of the feedstock used in a study is critical as the gasification rate is heavily dependent on the feedstock properties (such as composition, surface area, pore size distribution, etc.) and it allows for the results from different studies to be compared. In order to perform detailed char gasification measurements, a novel experimental setup was designed to allow for single, macro char particles (nominally 2 mm) to be inserted into our reactor, exposed to a high temperature and high pressure steam environment, and then removed all while operating at elevated temperatures and pressures. This setup is unique as it allows for a single particle to be exposed to steam in a controlled environment with known boundary conditions that can be readily modeled. Additionally, the mass of the particles were measured before and after exposure to the steam environment using a microbalance and thermogravimetric analysis providing accurate measurement of the extent of carbon conversion. Experiments were conducted at temperatures of 1000 \degree C to 1400 \degree C and pressures between 1 bar and 15 bar. The resulting conversion data was analyzed using the random pore model, shrinking core model, and volumetric model, of which the random pore model provided the best fit. Apparent activation energy, frequency factor, and reaction order were calculated and agree well with literature values and trends. Finally, the conversion data from this study were compared against two studies in the literature that were performed under similar conditions and general agreement was found after considering the differences in experimental setup.
    • Zinc silicon phosphide as a wide band gap semiconductor for integration with silicon

      Toberer, Eric; Tamboli, Adele C.; Martinez, Aaron D.; Stradins, Paul; Ohno, Timothy R.; Gorman, Brian P. (Colorado School of Mines. Arthur Lakes Library, 2017)
      There has been a longstanding need for optically-active materials that can be integrated with Si, both for tandem photovoltaics and for other optoelectronic applications. We focus on ZnSiP2, a ternary III-V analog with 0.5% lattice mismatch with Si and a 2.1 eV band gap, nearly ideal for a top cell on a Si-based tandem device. We have shown that ZnSiP2 has many properties suitable for applications to Si-based tandem photovoltaics using bulk single crystals grown in a Zn flux. Here, we report the first photovoltaic measurements of ZnSiP2 using photoeletrochemistry. We show that ZnSiP2 has excellent photoresponse and high open circuit voltage of 1.3 V, as measured in a photoelectrochemical configuration. The high voltage and low band gap-voltage offset are on par with much more mature wide band gap III-V materials. Photoluminescence data combined with theoretical defect calculations illuminate the defect physics underlying this high voltage, showing that the intrinsic defects in ZnSiP2 are shallow and the minority carrier lifetime is 7 ns. The favorable results obtained from characterization of bulk material encourage the development of ZnSiP2 as a photovoltaic absorber. To pursue this development, we have constructed a thin film growth reactor. This reactor employs a combination of chemical vapor deposition, using silane and phosphine as precursor gases, and physical vapor deposition, using an effusion cell to evaporate elemental Zn. We will present the results of ZnSiP2 film growth on (100) Si substrates. The composition, structure, and morphology of these films have been characterized by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, X-ray diffraction and transmission electron diffraction, and electron microscopy, respectively. These promising results represent significant advancement towards implementing ZnSiP2 as a top cell material on Si-based tandem photovoltaics.
    • Machine learning for the automatic detection of anomalous events

      Camp, Tracy; Fisher, Wendy D.; Wang, Hua; Krzhizhanovskaya, Valeria; Zhang, Hao; Navidi, William Cyrus; Stone, Kerri (Colorado School of Mines. Arthur Lakes Library, 2017)
      In this dissertation, we describe our research contributions for a novel approach to the application of machine learning for the automatic detection of anomalous events. We work in two different domains to ensure a robust data-driven workflow that could be generalized for monitoring other systems. Specifically, in our first domain, we begin with the identification of internal erosion events in earth dams and levees (EDLs) using geophysical data collected from sensors located on the surface of the levee. As EDLs across the globe reach the end of their design lives, effectively monitoring their structural integrity is of critical importance. The second domain of interest is related to mobile telecommunications, where we investigate a system for automatically detecting non-commercial base station routers (BSRs) operating in protected frequency space. The presence of non-commercial BSRs can disrupt the connectivity of end users, cause service issues for the commercial providers, and introduce significant security concerns. We provide our motivation, experimentation, and results from investigating a generalized novel data-driven workflow using several machine learning techniques. In Chapter 2, we present results from our performance study that uses popular unsupervised clustering algorithms to gain insights to our real-world problems, and evaluate our results using internal and external validation techniques. Using EDL passive seismic data from an experimental laboratory earth embankment, results consistently show a clear separation of events from non-events in four of the five clustering algorithms applied. The results from experimenting with our BSR data, using various system information (SI) and system information blocks (SIBs), show we can make a clear distinction between commercial and non-commercial scans in both Universal Mobile Telephone System (UMTS) and Long Term Evolution (LTE); more work is needed to understand whether non-commercial BSRs can be discovered in the Global System for Mobile Communications (GSM) analysis. We also investigate and provide results on using ASN.1 encoded LTE data as input to our machine learning algorithms; we use encoded data to eliminate the need for extensive feature selection and manual analysis that could potentially introduce bias. Chapter 3 uses a multivariate Gaussian machine learning model to identify anomalies in our experimental data sets. For the EDL work, we used experimental data from two different laboratory earth embankments. Additionally, we explore five wavelet transform methods for signal denoising. The best performance is achieved with the Haar wavelets. We achieve up to 97.3% overall accuracy and less than 1.4% false negatives in anomaly detection. Using the BSR scans, we continue to see that the GSM broadcast messages are not suitable for our anomaly detection system. However, the multivariate Gaussian approach with the UMTS, LTE, and ANS.1 encoded LTE scans were successful in separating commercial from non-commercial BSRs with 100% overall accuracy. In Chapter 4, we research using two-class and one-class support vector machines (SVMs) for an effective anomaly detection system. We again use the two different EDL data sets from experimental laboratory earth embankments (each having approximately 80% normal and 20% anomalies) to ensure our workflow is robust enough to work with multiple data sets and different types of anomalous events (e.g., cracks and piping). We apply Haar wavelet-denoising techniques and extract nine spectral features from decomposed segments of the time series data. The two-class SVM with 10-fold cross validation achieved over 94% overall accuracy and 96% F1-score. The F1-score is a measure of the algorithms predictive performance and the harmonic mean of precision and recall. Experiments with the one-class SVM (no labeled data for anomalies) using the top features selected by our automatic feature selection algorithm increase our overall results from 83% accuracy and 89% F1-score to over 91% accuracy and 95% F1-score. The two-class SVM experiments with our BSR detection workflow, using the top two features for each data set, highlight the ability to make a distinction between commercial and non-commercial BSRs with 83.3% overall accuracy and 89.8% F1-score for GSM and an impressive 100% overall accuracy for UMTS, LTE, and the ASN.1 encoded LTE data. As expected, using labels for only normal data, the one-class SVM resulted in a lower overall performance. The overall accuracy for GSM, UMTS, and LTE dropped to 73.3%, 74.5%, and 91.1%, with F1-scores of 81.0%, 82.2%, and 95.0%, respectively. Our approach provides a means for automatically identifying anomalous events using various machine learning techniques. Detecting internal erosion events in aging EDLs, earlier than is currently possible, can allow more time to prevent or mitigate catastrophic failures. Results show that we can successfully separate normal from anomalous data observations in passive seismic data, and provide a step towards techniques for continuous real-time monitoring of EDL health. Our lightweight non-commercial BSR detection system also has promise in separating commercial from non-commercial BSR scans without the need for prior geographic location information, extensive time-lapse surveys, or a database of known commercial carriers.
    • Field testing for Extreme Universe Space Observatory aboard a Super Pressure Balloon (EUSO-SPB): logistics and first results

      Wiencke, Lawrence; Cummings, Austin; Casolino, Marco; Leach, Kyle; Sarazin, Frederic (Colorado School of Mines. Arthur Lakes Library, 2017)
      Extreme Universe Space Observatory aboard a Super Pressure Balloon (EUSO-SPB) is a prototype cosmic ray detector that will, for the first time, record cosmic rays from above. It is planned to fly for nearly 100 days at an altitude of \unit[33]{km}, looking downward onto Earth's atmosphere, and measure the ultraviolet light emitted by ultra-high energy cosmic ray extensive air showers. It is the primary scientific payload aboard the 2017 NASA super pressure balloon flight launched from Wanaka, NZ. \\ It was necessary to perform an end-to-end characterization of the instrument, as post test recovery is not guaranteed. A laser underflight study for EUSO-SPB is planned to occur to evaluate the assembled instrument's response to realistic optical tracks. In case of failure, it was necessary to conduct ground-to-ground testing, where laser test beams at "flight-like" distances through Earth's atmosphere would be provided.\\ The Black Rock Mesa (BRM) Telescope Array (TA) test site in Delta, Utah was chosen as the location for the instrument field testing. The assembled and working EUSO-SPB instrument was transported using a ground loading, weather-sealed, air-suspension trailer and a custom "vibration-proof" dolly. During transportation, the maximum acceleration experienced by the instrument was \unit[1.2]{g's}. Test beams were provided by a fixed energy, vertical laser at \unit[21]{km} and by a steerable, variable energy, laser at \unit[24]{km}. Hundreds of thousands of pulsed, UV laser shots were successfully recorded during the six nights of operation, with various energies, directions, and triggering methods. Energy sweeps were performed with a $45^{\circ}$ tilted away laser at \unit[24]{km} to determine the nominal energy threshold of EUSO-SPB in a balloon simulated geometry for two different lens configurations.\\ First results show that the 2 lens configuration of EUSO-SPB was approximately twice as sensitive as the 3 lens configuration to laser light, with $50\%$ energy thresholds of \unit[1]{mJ} and \unit[2]{mJ}, respectively. Cloud coverage and aerosols were ruled out as potential causes of the lens configuration energy threshold discrepancy. A preliminary conversion to equivalent cosmic ray energy was performed using custom laser and cosmic ray simulations. For EUSO-SPB in flight configuration, the $50\%$ energy threshold was estimated to be \unit[$3*10^{18}$]{eV} and \unit[$7*10^{18}$]{eV} for the 2 and 3 lens configurations, respectively, assuming aerosol content of $\alpha$=\unit[$5*10^{-5}$]{$\mathrm{m}^{-1}$} and $\mathrm{H}_{\mathrm{scale}}$=\unit[2]{km} during the laser data collection. The estimated event rate for EUSO-SPB was updated using the results of this work, and found to be 4.5 events per week.
    • Fe-Zn phase evolution and cracking behavior in Zn-coated press-hardened steel

      Speer, J. G.; Ghanbari, Zahra N.; Matlock, David K.; Van Tyne, C. J.; Bourne, Gerald; Stebner, Aaron P. (Colorado School of Mines. Arthur Lakes Library, 2017)
      Zinc coated press-hardened steel (PHS) sheet used for the production of strong, corrosion resistant parts is of interest to the automotive community, but concerns about liquid metal embrittlement (LME) remain. Specifically, mitigation of the cracking associated with LME, via better understanding of the alloyed coating microstructural features and interaction with the substrate sheet during deformation, is desired. The objective of this work was to relate the microstructural evolution in the Fe Zn coatings heat treated under single or two step thermal processing to the cracking response in specimens deformed in uniaxial tension at elevated temperature. A Gleeble® 3500 was used to heat treat galvanized 22MnB5 samples at hold times and temperatures relevant to new processes recently implemented in some hot stamping lines. The alloying achieved during heating and isothermal holding of specimens was assessed, and used to interpret the cracking response in the coating (and substrate) of specimens deformed at high temperature. Heat treatments using systematic heating rates were conducted to investigate the Fe Zn phase development during heating to elevated temperatures relevant to press-hardening. The specimen heated at the slowest rate (2 ºC/s) was comprised of the most Fe rich phases (Γ and αFe(Zn)). Comparison of the compositions of these phases to the Fe Zn phase diagram at elevated temperature (775 ºC), suggested that this coating was mostly solid at elevated temperature, and thus may also have had little Zn rich liquid upon reaching target temperature. The minimized Zn-rich liquid at elevated temperature indicated that minimal soak time would have been necessary to eliminate Zn rich liquid in the coating prior to deformation at this temperature. Specimens were also heat treated via single or two step isothermal profiles (with and without deformation), and the phases were identified and quantified to understand the state of the coating microstructure at each room and elevated temperature. Fractions of the phases developed in the alloyed coating were measured using quantitative image analysis. The fraction of δ (most Zn rich phase identified in the coatings) appeared to decrease, while the fraction of Γ and αFe(Zn) appeared to increase, with increased soak time and temperature. The δ phase was not observed in specimens heat treated at the highest time/temperature combinations (850 °C for 60-120 s), suggesting that the greatest degree of alloying occurred in these specimens. The fraction of the δ+Γ1 phases present in each specimen are suggested to contribute to the amount of Zn rich liquid present at the highest deformation temperature (700 °C), and thereby used to estimate the amount of Zn rich liquid available during elevated temperature tensile tests. The thickness of the αFe(Zn) layer also increased with increased hold time and temperature. The αFe(Zn) layer thickness in undeformed versus deformed specimens and composition gradient across the layer were measured and compared to cracking behavior of the layer. At the highest deformation temperature (700 °C), the αFe(Zn) layer exhibited cracks after intermediate and extended hold times (60 and 120 s); these specimens also exhibited the higher αFe(Zn) layer thicknesses and slightly narrower composition gradients compared to specimens deformed at the same temperature after shorter soak times. The cracking behavior observed in the deformed specimens was related to the microstructural evolution of the coating based on the inferred amount of liquid present at elevated temperature and the relative plasticity of the αFe(Zn) layer. In most cases, deep cracking into the substrate sheet associated with LME was avoided. Crack mitigation during deformation was proposed to be a result of: reduction of Zn rich liquid via increased alloying or reduced deformation temperature, or retention of a continuous αFe(Zn) layer between the alloyed coating and substrate, that served as a barrier layer to prevent contact between the Zn rich liquid and Fe-substrate.
    • Open pit mine planning with stockpiling

      Newman, Alexandra M.; Rezakhah, Mojtaba; Newman, Alexandra M.; Eggert, Roderick G.; Moreno, Eduardo; Mehta, Dinesh P.; Kaunda, Rennie (Colorado School of Mines. Arthur Lakes Library, 2017)
      This dissertation consists of three papers; the first is published in European Journal of Operational Research, the second is nearing submission to it Optimization and Engineering, and the third is nearing submission to International Journal of Mining, Reclamation and Environment. These papers apply operations research techniques to open pit mine production scheduling with stockpiling (OPMPS+S). The first paper, "Linear Models for Stockpiling in Open-pit Mine Production Scheduling Problems," reviews existing models to solve OPMPS+S and shows that a nonlinear-integer model provides an exact solution but is intractable even for medium-size data sets. Then, we present an approximation to that nonlinear-integer model, solve the nonlinear-integer and proposed models for multiple data sets and show that the latter model provides solutions very close to those provided by the nonlinear-integer model. By pairing this novel formulation with recently developed linear programming algorithms and heuristics, we demonstrate a dramatic decrease in solution time. The second paper, "Comparison of an Improved Open Pit Mine Stockpiling Model with Commercial Software," introduces an extension to the model presented in the first paper to blend material with multiple grades and a contaminant in the stockpile. Existing state-of-the-art algorithms which exploit the problem structure produce integer solutions with associated net present value at least 18.7% higher than that provided by commercial of-the-shelf software. The third paper, "Open Pit Mine Planning with Degradation Due to Stockpiling," presents three new models that consider degradation due to stockpiling, compare them with models without degradation, and show that degradation has a major impact on the value a stockpile provides.
    • Experimental measurement and numerical modeling of multiphase flow in Middle Bakken

      Yin, Xiaolong; Kazemi, Hossein; Cho, Younki; Illangasekare, T. H.; Prasad, Manika; Sonnenberg, Stephen A.; Tutuncu, Azra (Colorado School of Mines. Arthur Lakes Library, 2017)
      Relative permeability is an extremely useful measure of complex multiphase fluid flow in a porous media, and much effort has been devoted by researchers to determine the factors that control relative permeability. Nevertheless, detailed experimental data especially for unconventional cores is scant in literature, which motivated this research. Specifically, this dissertation addresses and presents the relative permeability end points measured in two Middle Bakken formation cores for three different processes: oil-displacing-water, water-displacing-oil, and gas-displacing-oil using a steady-state method. The Middle Bakken petrophysical properties measured by Weatherford Labs and by the author are also presented. Finally, two conceptual models were proposed to explain the measured end-point relative permeability, and a 2-D lattice Boltzmann simulator was developed to obtain relative permeability curves of a two-dimensional pore geometry generated using Voronoi grid. The contributions of this work include measurements of relative permeability in a tight shale, interpretation of experimental results using pore-scale features of the cores, and lattice Boltzmann simulation.
    • Joint interpretation of time-lapse gravity data and production data for a gas reservoir

      Li, Yaoguo; Balza Morales, Andrea; Trainor-Guitton, Whitney; Benson, Robert D. (Colorado School of Mines. Arthur Lakes Library, 2017)
      Time-lapse gravity is commonly used to monitor fluid movement and is especially useful when monitoring water encroachment in a gas reservoir. Although time-lapse gravity has considerable resolution, it is beneficial to integrate different types of data to complement the time-lapse gravity interpretation. When monitoring water-influx in a reservoir, an increase in water yield in some wells may indicate increasing saturation values and suggest areas of fluid movement and density contrast change with time. These data can complement the time-lapse gravity analysis, the question to address is how to integrate these data appropriately to enhance the monitoring of the edgewater in a reservoir. The objective of this thesis is to develop a workflow to invert a time-lapse gravity data set and production data in the Sebei Gas field located in Western China and monitor the edgewater encroachment. Three time-lapse gravity surveys were conducted between 2011 and 2013 and were processed to estimate the error associated with the data set. Consequently, production data collected from 286 wells, was evaluated and plotted to determine its feasibility as complementary data for the time-lapse gravity inversion. To jointly interpret these two independent data sets, I converted the sparse production data into a time-lapse reference model that is subsequently incorporated as a guide into a generalized density inversion. To constrain the inversion result to a similar lithologic setting of the reservoir, I imposed spatially varying upper and lower density bound constraints for different depths of the model. Through this approach, I construct a set of density contrast models that are guided by the measured changes in gas/water yield, and whose distribution fits the time-lapse gravity data. The results of this work demonstrate that integrating the production data and setting lithology dependent bound constraints produced an improved definition of density changes. By doing a first order estimation of the porosity in the reservoir, I verified that the porosity estimated using the recovered density contrast of the improved model are more representative of the known porosity of the gas reservoir.
    • Understanding structure-property relations in β-eucryptite under pressure and at elevated temperature

      Reimanis, Ivar E. (Ivar Edmund); Chen, Yachao; Ciobanu, Cristian V.; Packard, Corinne E.; Gorman, Brian P. (Colorado School of Mines. Arthur Lakes Library, 2017)
      β-eucryptite (LiAlSiO4) has received widespread attention from both industry and academia due to its negative coefficient of thermal expansion (CTE) and one-dimensional Li ionic conductivity. Additionally, β-eucryptite undergoes a pressure-induced phase transformation at relatively low pressures. These various behaviors arise because the crystal structure is open and highly anisotropic. The present study uses several experimental methods to better understand the relation between the structure and the electrical and mechanical behavior of β-eucryptite. Synthesis and processing methods were developed to make pure β-eucryptite and β-eucryptite doped with Mg of varying particle sizes. In-situ diamond anvil cell - x-ray diffraction was performed to study the pressure induced phase transformation from β-eucryptite to the high pressure phase β-eucrypite. With the assistance of Rietveld refinement and atomistic modeling, the crystal structure of the β-eucrypite was determined to be an orthorhombic with space group Pna21. This is the first time that both space group and atomic positions of the high pressure phase have been reported. It is also observed that Mg-doped β-eucryptite undergoes the pressure induced transformation at slightly higher pressures than pure β-eucryptite (2.47 GPa compared with 1.8 GPa hydrostatic stress), implying that Mg stabilizes β-eucryptite. Furthermore, the presence of Mg leads to a state in which two high pressure phases coexist. It was observed that the critical pressure for transformation to the high pressure phase decreases with increasing β-eucryptite grain size, up to a critical grain size beyond which grain size does not play a role. The experimental results were described by a nucleation and growth model for transformation. The effect of structural changes in β-eucryptite from low to high temperature was examined by measuring the Li ionic conductivity with electrochemical impedance spectroscopy (EIS). The conductivity is strongly influenced by the Li order-disorder transition at ~500 ºC where the activation energy dramatically increases. It is shown that the conductivity depends on whether or not the Li ions motion is correlated or uncorrelated, leading to three activation energies: at low temperatures it is correlated, at ~500 ºC it is uncorrelated and at high temperatures it is correlated again. The present study focuses on measuring the material properties under pressure and at high temperature, separately. These measurements provide the first step towards elucidating the relation between mechanical and electrical properties. The order-disorder transition is caused by the rearrangement of Li ions at evaluated temperature, an event which is expected to influence the pressure-induced phase transformation. Specifically, a change in the size of the Li channels resulting from Li redistribution, is expected to modify the phase transformation pressure.
    • Central Laser Facility at the Pierre Auger Observatory. Studies of the atmospheric vertical aerosol optical depth and other applications to cosmic ray measurements, The

      Wiencke, Lawrence; Medina Hernandez, Carlos Francisco; Sarazin, Frederic; Squier, Jeff A.; Dreyer, Christopher B.; Wakin, Michael B. (Colorado School of Mines. Arthur Lakes Library, 2017)
      The two largest observatories in the world dedicated to the study of Ultra High Energy Cosmic Rays (UHECR) are the Pierre Auger Observatory (Auger) in Mendoza, Argentina and the Telescope Array (TA) in Utah, USA. The measurements of the cosmic ray flux by Auger and TA present a discrepancy at the highest part of the energy spectrum. In this thesis, I study if this discrepancy can be attributed to instrumental effects related to the measurements of the atmospheric aerosol contents in Auger. The Auger Fluorescence Detector (FD) measures the scattered light from laser tracks generated by the Central Laser Facility (CLF) and the eXtreme Laser Facility (XLF) located near the center of Auger, to estimate the vertical aerosol optical depth (τ (z,t)). A good knowledge of τ (z,t) is needed to obtain unbiased and reliable FD measurements of the energy of the UHECR primary particle. The CLF was upgraded substantially in 2013 to improve laser reliability. A substantial part of my Ph.D work is dedicated to building, maintaining and analyzing data from this upgraded facility. The upgraded CLF includes a backscatter Raman LIDAR which independently measures τ (z,t). For the first time in a cosmic ray experiment, two years of measurements of τ (z,t) obtained with the Raman LIDAR are compared with the measurements obtained with the FD. Based on these comparisons, an alternative atmospheric database was created to study its effects on the measurements of the flux as a function of energy. The resulting energy spectrum plot is found to be more compatible with the energy spectrum plot released by TA.