Mines Repository (Colorado School of Mines)
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La Playa and El Banco claims, Nayarit, Mexico
No full textMine report no. 2057.Typescript (carbon copy).Title supplied by cataloger.Two letters of correspondence concerning La Playa and El Banco, dated 1923 -- Preliminary report on "La Playa" and "El Banco" claims, District of Ixtlan, State of Nayarit, Mexico, for the Cia. Exploradora de Minas de Mexico, S.A. / Alfredo Terrazas -- El Banco [map] -- Minas de la Playa [map]
Estimating historical concentrations of per- and polyfluoroalkyl substances with groundwater flow and transport models and iterative ensemble smoothing analysis
No full textIncludes bibliographical references.2025 Spring.Per- and polyfluoroalkyl substances (PFASs) are a class of contaminants of considerable concern due to their toxicity and persistence in the environment. The accurate prediction of PFAS transport in the subsurface remains a significant challenge in numerical modeling, due to uncertainty surrounding the processes that govern PFAS transport such as mass loading mechanisms from the vadose zone to groundwater. This research aims to address this uncertainty by exploring the simulated controls on PFAS fate and transport in the vadose zone, using the numerical model HYDRUS, and integrating simulated PFAS mass-loading to the water table into groundwater flow and transport models developed with MODFLOW 6 to investigate PFAS migration in groundwater. We use data from and downgradient of the Peterson Space Force Base, situated southeast of Colorado Springs in El Paso County, Colorado, USA. At Peterson, fire-fighting training activities using aqueous film-forming foams (AFFF) have resulted in PFAS contamination of the Fountain Aquifer groundwater, a vital source for the region’s drinking water, primarily with perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonate (PFHxS). To investigate this contamination, we built a HYDRUS-1D model for a 50-year period simulating variably saturated flow and PFAS fate and transport with a 30-year contamination period from 1970 to 2000, and a 20-year post-contamination period from 2000 to 2020. The purpose of this model is to create a simple yet representative simulation of variably saturated PFAS transport in the vadose zone at this site to gain a general understanding of PFAS loading to groundwater in the absence of clear records on AFFF-contamination events at the site (frequency, volume, mass, application area, etc.). This model is not intended to be a precise, predictive tool but rather a conceptual-deterministic model used to simulate an initial input of PFAS mass loading into the groundwater model. The resulting concentration profiles at the water table served as solute concentration boundary conditions for a MODFLOW 6-based groundwater flow and transport model. We calibrated hydraulic conductivities and recharge multipliers using observed head data and developed a solute-transport model for PFOS, PFOA, and PFHxS. Transport parameters—including bulk density, porosity, immobile porosity, distribution coefficient (Kd), and mass loading—were estimated and refined using Iterative Ensemble Smoothing (IES), a data assimilation approach that quantifies uncertainty and improves model fit. This integrated modeling framework successfully reproduced key spatial and temporal patterns of PFAS concentrations in downgradient municipal well fields and provided insight into the primary controls on PFAS fate in the subsurface. Although the model tended to underpredict observed concentrations, especially for PFOA and PFHxS, it offers a valuable approach for assessing PFAS exposure through groundwater pathways. The trend of under prediction for PFOA and PFHxS may be attributed to PFAS precursors whose transformations from precursor to PFOA or PFHxS were not captured in this model. By addressing vadose-zone transport, PFAS loading to the water table, and subsurface transport uncertainties, this work contributes to improving the understanding of historical PFAS contamination so that the impact of contamination on humans can be better quantified.
Annual reports of the Lucky Tiger-Combination Gold Mining Company
No full textMine report no. 2063.Includes annual reports of the Lucky Tiger-Combination Gold Mining Company for the following years: 1913, 1920, 1921, 1922, 1925, 1926, 1928.Includes maps.Title supplied by cataloger
Reheat cracking susceptibility in welds of creep resistant alloys for power generation applications
No full textIncludes bibliographical references.2025 Spring.Power generation industries utilize creep-resistant materials for elevated temperature components (>500°C) and various corrosive environments, e.g. molten salts. Transfer pipelines, pressure vessels, and thermal energy storage (TES) tanks may utilize austenitic stainless steel (SS) alloys, e.g. type 347H, 347AP (347LN), and Therma 4910 (316LNB). Higher temperature components(>720°C), such as supercritical CO2 primary heat exchangers (PHX), may require nickel base superalloys with superior creep strength, such as Haynes®282 (H282) and Inconel®740H (IN740H). Arc welds of these components may be susceptible to stress relaxation cracking (SRC) or strain age cracking (SAC) during post weld heat treatment (PWHT) or service. These reheat cracking (RC) phenomena are attributed to a combination of susceptible microstructures, sufficiently high tensile residual stress and reheating.
The first objective of this work is to analyze the influence of weld-induced residual stress/strain and temperature on RC susceptibility of the three abovementioned creep-resistant stainless steels, including their heat-affected zones (HAZs), and fusion zone (FZ) made with matching fillers and alternative filler E16.8.2 FZ. The influence of PWHT, service environment and repair welds on RC susceptibility is evaluated as well. Stress relaxation tests (SRT) are primarily conducted with a Gleeble® 3500 to simulate RC in these various microstructures and provide a susceptibility ranking based on stress thresholds and time to failure as a function of temperature. Residual stress measurements, using the high intensity diffractometer for residual stress analysis (HIDRA) beamline at Oak Ridge National Laboratory (ORNL), were performed to understand the influence of PWHT, repair welding, and weld filler on residual stress in 347H SS weldments. A combination of metallurgical characterization techniques is used to assist in failure mechanism analysis. In 347H SS weldments, it is observed that the matching filler E347 FZ in as-welded (AW) condition is more susceptible to RC than single pass 347H HAZ and AW E16.8.2 FZ based on stress- and time-to-fracture at 750-1050°C test temperatures. Lower tortuous grain boundaries in E347 FZ could explain lower critical stress threshold compared to 347H HAZ, but E16.8.2 filler with leaner composition (no Nb (C, N)) is observed to be more RC resistant. PWHT with properly designed parameters not only reduces residual stress and strain reductions, but it also reduces RC susceptibility in E347 FZ microstructure compared to AW E347 FZ. SRT of ex-serviced 347H SS welds generally indicate similar failure times and cracking susceptibility to fresh welds. For repair welds, the FZ longitudinal residual stress using E16.8.2 filler is observed to be lower than that with E347 filler, although the transverse residual stress increased in the previous HAZ that is further away from the repair. Repair welds with alternative E16.8.2 filler exhibit better RC resistance in the FZ compared to repair welds with matching E347 filler at 800-850°C test temperatures, due to a more creep ductile E16.8.2 FZ in contrast to adjacent 347H HAZ. Microcracks in adjacent E347 FZ (HAZ of repair) show δ-ferrite dissolution laced with interdendritic Nb (C, N) precipitates. The impurity segregation of sulfur to γ/γ boundaries because of δ-ferrite dissolution can lower the grain boundary surface energy and facilitate easier cracking. These SRT results of failure in adjacent HAZs correlate with increased transverse tensile residual stresses after repair welding, regardless of the weld filler used. 347AP and Therma 4910 SS HAZs using similar SRT techniques demonstrate higher RC resistance (longer times to failure) compared to 347H HAZ. Using matching fillers, FZ of 347AP outperforms E347. All samples that failed by RC at temperature reveal intergranular/interdendritic fracture characteristics. Despite residual stress, the lack or reduction of Nb carbonitrides (contributing to grain deformation resistance during creep or stress relaxation in 347H) in 347 AP HAZ and FZ, Therma 4910 HAZ, and E16.8.2 FZ could explain the enhanced RC resistance in alternative materials. More creep resistance in AW 347H HAZ and E347 FZ attributed to the Nb carbonitrides strengthening may explain the high RC compared to alternative HAZ and FZ microstructures with higher creep strains but no RC failure.
The second objective of this work is to use the SRT methodology developed above to investigate SAC susceptibility of the welded H282 and IN740H laser-powder bed fusion (L-PBF) components. The influence of weld HAZ of L-PBF (and additive manufacturing) components has not been studied in literature. The impacts of heating rate during post weld aging treatment and build orientation on HAZ cracking susceptibility are evaluated. Overall, the vertically built components are more resistant to cracking than horizontal build components for both alloys due to grain morphology difference. Intergranular SAC failures are observed along migrating grain boundaries (MGBs) distinguished by stress-assisted elongation of grain boundary secondary phases (γ’ or carbides). IN740H HAZ shows extensively wider precipitate denuded zones within MGB region compared to H282 HAZ, likely explaining higher SAC susceptibility in IN740H HAZs. Fast heating rates (3480°C/h and above) for both H282 and IN740H L-PBF HAZ microstructures exhibit low SAC susceptibility, manifested by no failure in H282 microstructure and extended failure times in IN740H compared to slower heating rates. The shortest time-to-failure, or worst SAC resistance, is observed during the intermediate heating rates (100-333°C/h) for H282 and slow heating rates (40-100°C/h) in IN740H. The competing mechanism between strengthening by phase transformation and stress relaxation as a function of time at temperature determines the SAC susceptibility. Non-isothermal CALPHAD simulations show higher γ’ volume fraction development during heating with slower heating rates, which could inhibit further bulk stress relaxation prior to reaching aging temperature at 800°C and cause faster strain accumulation along MGBs and γ’ denuded zones
General description of the general conditions at Ely, White Pine County, Nevada
No full textMine report no. 1808.Typescript (carbon copy) and handwritten version of report
Gold Pan Mining Company
No full textMine report no. 2113.Includes maps and illustrations.Includes one stock certificate.Physical copy held in the Russell L. & Lyn Wood Mining History Archive is a gift of the Russell L. & Lyn Wood Mining History Archive Fund
Park Rangers' Problem: motion planning for sequential visibility requirements
No full textIncludes bibliographical references.2025 Spring.Many robot tasks may involve achieving visibility (such as to observe areas of interest) or maintaining occlusion (such as to avoid disturbing other agents). We generally formulate such sequential visibility tasks for 3D worlds, termed the Park Rangers' Problem, and we develop an approach to solve such tasks offering completeness under certain requirements. Our approach constructs an abstraction based on an exact test for visibility between areas, and multiple tests and relaxations for the nonconvex problem of determining occlusions between areas. We apply a constraint-based planning approach and iteratively refine the abstraction. Finally, we evaluate the approach on simulated visibility scenarios
Colloid assembly and actuation under magnetic and electric fields
No full textIncludes bibliographical references.2025 Spring.Active colloidal particles, typically ranging from 10 nms to 10 µms in size, have attracted significant attention over the past few decades for their ability to be controlled by external fields. In this thesis, we investigate the assembly of colloidal particles into three systems of increasing complexity, the first two manipulated with applied magnetic fields and the third with combined magnetic and electric fields.
We begin by demonstrating that a single applied magnetic field can be used to assemble simple spheres into uniform colloidal chains. These chains can be varied from two to four to eight monomers in length and serve as the building blocks for more complex superstructures.
For our second study, we demonstrate that simple colloidal spheres can be assembled into microbots using an applied magnetic field. We determine, however, that these active devices are rigid and face challenges such as limited biocompatibility, inefficient drug loading, and surface slip. To address these issues, we introduce magnetically controlled soft microbots based on emulsion droplets decorated with simple magnetic colloidal spheres at their outer surface. Soft microbots can roll like deflated tires under magnetic fields, which change the lubrication layer and increase the contact area of soft robots. This inherent deformability can enhance traction significantly, supported by numerical simulations and theoretical analysis.
Finally, we extend control over motion and functionality using a hybrid actuation strategy like combined electric and magnetic fields. This method enables fine-tuning of interparticle interactions, leading to more complex and novel structures. One such structure is the dodecagonal quasicrystal, which displays “forbidden” symmetries and long-range orientational order without periodicity, first discovered in synthetic alloys and later in Nature. When the quasicrystal building blocks are colloidal particles, the formation processes slow dramatically, allowing for real-time, in-situ observation and providing a valuable platform for studying the dynamics
Analysis of nitrogen oxide emissions produced during combustion of cracked-ammonia fuels
No full textIncludes bibliographical references.2024 Spring.Ammonia has emerged as a chemical with the potential to bridge the gap in the global initiative to replace organic fuels with hydrogen. While hydrogen boasts high energy density and zero carbon emissions, it is difficult to store, transport, and utilize directly. Ammonia is a hydrogen-dense chemical that is an excellent hydrogen carrier, thus presenting a means to overcome the storage and transportation challenges associated with hydrogen. Ammonia also provides a means for safe and timely utilization of hydrogen through ammonia-hydrogen combustion. Pure ammonia is difficult to ignite and burn. In contrast, pure hydrogen is extremely flammable and difficult to control. However, ammonia-hydrogen blends have proven to burn efficiently in a myriad of combustion-based power generation systems including gas turbines, compression engines, and spark ignition engines. An advantage of ammonia is that it can produce ammonia/hydrogen blends directly through cracking, which is the decomposition of ammonia to produce hydrogen and nitrogen.
Conventional ammonia cracking produces NH3/H2/N2 fuel mixtures. Our research group has developed a catalytic membrane reformer that rejects nitrogen, and produces NH3/H2 blends. To date, little attention has been paid to the potential differences of the two blends in terms of combustion. This work compares the flame stability and NOx production of the two mixtures (with and without additional nitrogen). The range of operating conditions (equivalence ratio, fuel-hydrogen mole fraction, axial velocity) at which laminar burner-stabilized flames exist is defined. Experimental NOx measurements are compared to Chemkin simulated NOx concentrations, revealing the potential occurrence of selective catalytic reduction.
In this work we built a laminar, 1-dimensional flat flame apparatus to study NOx emissions produced from the two mixtures. It was found that rejection of nitrogen improved flame stability, particularly at low fuel-hydrogen mole fractions. However, rejection of nitrogen has negligible effect on the production of NOx. Initial experiments contradicted expectations based on theoretical modeling in terms of NOx production. It was determined that the NOx analyzers used do not function properly in the high humidity environments resulting from ammonia combustion. This issue was partially resolved by providing additional dilution to the post flame sampling region. Under these conditions, very good qualitative agreement between data and model expectations were observed. However, the experimental NOx concentrations remained below model expectations, which was attributed in part to catalytic reduction of NOx in the sampling line. This might be a promising avenue for NOx reduction in the future