203435 research outputs found
Sort by
Rare Earth Element Recovery from Acid Mine Drainage Using Ion Exchange and Selective Precipitation Processes
No full textRare earth elements (REEs) are used in high-tech applications due to their electromagnetic and optical properties. As global demand for REEs surges, the limitation of primary mineral deposits has increased interest in alternative sources. One such source is acid mine drainage (AMD), which, although typically low in REE concentration, offers a promising avenue for recovery. Among the emerging recovery methods, ion exchange has shown promise due to its effectiveness at low concentrations and lower operational cost than conventional techniques such as acid leaching and solvent extraction.
This research focused on developing a recovery process by combining ion exchange with selective precipitation techniques. For this, 14 AMD samples were collected, and based on total REEs (TREEs) concentrations and other elemental compositions, one sample from Kanawha County, WV, was selected as the feedstock for process development.
The recovery process developed began with three sequential pH-dependent precipitation steps. Sodium hydroxide (NaOH) was added to the raw AMD to reach pH 4, removing 66% of iron and other impurities. A second adjustment to pH 5 facilitated the removal of 95% of aluminum and additional contaminants. After filtration, the pH increased from 5 to 9 to precipitate the majority of REEs. The resulting solids were redissolved in sulfuric acid (H₂SO₄), achieving a REE enrichment factor of 20 and producing a preconcentrated feedstock for ion exchange.
Ion exchange experiments employed 50WX8 cationic resin. Process parameters were optimized by evaluating REE recovery and selectivity at different flow velocities (1–10 L/h) and feedstock pH values (0.5–3). Optimal loading conditions were identified at pH 1.5 and 1 L/h flow rate, achieving 99% REE sorption. Elution studies used sulfuric acid at varying concentrations (1–3 M) and flow velocities (0.5–3 L/h). The best elution performance obtained 95% REE recovery and a REE enrichment factor of 148 with 2 M H₂SO₄ at 0.5 L/h.
The eluted solution was subjected to selective precipitation using oxalic acid. This step was optimized by varying the oxalate-to-REE molar ratio (1.5–17), precipitation pH (0.1–2), and reaction time (0–2 h). The highest REE precipitation recovery (98%) was achieved with a C₂O₄:REE ratio of 7, pH 1.5, and 1-hour reaction time. The resulting oxalates were washed with deionized water and calcined to produce REE oxides as the final product.
The overall process yielded REE oxides with a purity of 97% by weight, demonstrating the technical feasibility of recovering high-purity REEs AMD using an integrated ion exchange and selective precipitation approach
Searching for the Tender Places : Shoddy, Knowledge, and Material Culture in the Civil War Era
Get PDFIn the American Civil War era, shoddy was difficult to understand. It was simultaneously seen as evidence of advancing western civilization as well as a disgusting amalgamation of refuse and disease that threatened those who touched it. Made from shredding woolen rags and tailors’ clippings, the recycled woolen fibers could by applied in myriad woolen blends that came to dominate the ready-made clothing industry that developed through the first half of the nineteenth century. Its application could soften coarse blends and refine the appearance of cheap cloth. When the American Civil War erupted in 1861, however, shoddy came to define anything and everything that was inferior. Contracting scandals rocked Northern states, and complaints of rotten uniforms propelled shoddy into the wider American lexicon and inaugurated what this dissertation calls the “shoddy crisis”: the immediate, visceral response to early supply problems among Northerners and the continued vitriol through the war that generated public debate on issues of fraud, profiteering, and capitalism. Other historians have broadly examined shoddy’s “adjectification” by analyzing the ways that Civil War era Americans applied the term “shoddy” to things they saw as inferior in their society. This dissertation seeks to reframe the historical analysis of shoddy in the Civil War era by using material culture methodology. In doing so, it uncovers the ways that shoddy fibers impacted antebellum American clothing, wartime contracting, and the culture of the Civil War era North. Shoddy’s “adjectification” was spurred not only by early supply scandals, but knowledge Americans gained about shoddy through the popular press, and centered on the physical characteristics of shoddy in cloth. When used properly, shoddy was nearly invisible and even expert inspectors could not identify it. The contracting scandals and investigations called into question the expertise of inspectors, quartermasters, and clothiers. Questions of how to identify shoddy propelled its use in popular discourse through the Civil War, and the physical characteristics of shoddy learned by Americans through the popular press helped them identify the “shoddies” in their midst. In emphasizing the materiality of shoddy, this dissertation uncovers the myriad ways that simple woolen fibers transfixed a nation at war. Rather than a symptom of the early rush to clothe Union volunteers, shoddy fibers, in all their forms, continued to frustrate Quartermasters, Congressmen, and the American public through the entirety of the conflict
Forensic Characterization and Comparison of Modern Nail Polish Products by Their Physical Features and Chemical Composition
Get PDFNail polish can serve as valuable evidence in forensic investigations as it is often found on the hands and feet of individuals. Nail polish can break off and transfer easily during self-defense actions or forceful contact, such as in cases of kidnapping, sexual assault, or homicide. These residues can provide clues about who was at the scene, as well as where, when, and how the event evolved. However, compared to other types of paints commonly analyzed in forensic laboratories, limited forensic research has been conducted on the chemical composition and discrimination capabilities of popular nail products. The lack of information makes it challenging to interpret nail polish evidence because the forensic scientist cannot accurately evaluate how common or rare the evidence’s features are within the relevant population context.
This project expanded the knowledge base on nail polishes from various angles, enabling the forensic community to use nail polish evidence to its full potential. First, the study compiled a collection of over one hundred sources of nail polish chemistry, formulations, and industry regulations, through a comprehensive literature review on cosmetics textbooks, patents, webpages, and scientific articles, with a forensic perspective in mind. The findings of this repository have been organized into detailed documents and supporting figures to provide an overview of the complexity of nail polish chemistry for nitrocellulose-based (NC), UV-curable gels (gel), and dip powder (DP) products.
Following an investigation of supporting literature, the project produced a dataset of 164 nail polishes, comprising NC, Gel, and DP polishes from five brands and eleven colors, for examination. When possible, the set included matching brands and colors across all three types of polish. Characterization and classification of these main polish types were performed using physical and chemical properties, as determined by macroscopical and microscopical examination, micro-solubility testing, Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), and Scanning Electron Microscopy with Energy Dispersive X-Ray Spectrometry (SEM-EDS). Visually, DP samples were distinguishable from NC and Gel samples by microscopical examination alone, due to the distinct presence of micro-polymeric beads. The NC and Gel polishes were distinguished from one another using micro-solubility tests, where NC is soluble in acetone and produces a deep blue color reaction in the presence of diphenylamine in sulfuric acid, while Gels do not react to these solvents. The microscopic examination and micro-solubility steps, in conjunction with macroscopical examination (color comparison), discriminated all comparison pairs except 33 of them, all of which were samples of the same nail polish type and color. Rapid confirmation of the nail polish type (NG, Gel, or DP) can be achieved using ATR-FTIR, as all three classes contain binders’ functional groups with distinctive IR peaks. Physical and chemical features were documented for each nail polish layer, which may include clear top coats, color coat(s), and, in some products, base coats. In addition to the multi-layered coat system, nail polish traces can also contain residues of the nail substrate, adding significance to the evidence. Therefore, this study also evaluates a subset of natural and artificial nails. The analysis by ATR-FTIR reveals that the characterization of the unknown substrate is possible, providing key insights into the potential preservation and use of biological and chemical evidence on the same item of interest.
Finally, the thesis reports the informative power of each technique, both alone and when combined. Across 13,366 pairwise comparisons, the complete analytical workflow achieved a 99.99% discrimination power, resulting in only one pair that was indistinguishable (IN). The results support the proposed workflow as an adequate sequence for the forensic comparison of nail polish products. Across all techniques, the most discriminating method was microscopical examination, providing a 99.7% discrimination (38 IN pairs), followed by elemental analysis using SEM-EDS (99.5% discrimination, 62 IN pairs). Through the examination of extenders and ratios of main binder constituents, ATR-FTIR alone resulted in a 97.9% discrimination power, with 285 indistinguishable pairs falling in within-group comparisons (i.e., Gel to Gel, DP to DP).
Overall, this project exposes the relevant physical features and chemical information of three contemporary nail polish products and provides recommendations for the examination, characterization, and comparison of these traces. The findings are anticipated to provide critical context and background for forensic examiners to expand the use of modern nail products in investigations and assess their significance to a courtroom audience
Investigation Of Spalling Effects on The Brittle Behavior of Rectangular Pillars in Underground Stone Mines
No full textRecent catastrophic collapses in U.S. limestone mines have exposed the limitations of traditional empirical design formulas for brittle rock masses. These events, especially those involving slender pillars, underscore that traditional methods often fail to account for progressive, spalling-dominated failure, highlighting a crucial gap in our understanding. This research addresses this issue by conducting a comprehensive investigation into the mechanics of spalling in rectangular stone mine pillars, utilizing advanced three-dimensional numerical modeling with FLAC3D combined with LiDAR-based geometric modeling.
The stability of a pillar is governed by a complex interaction between the in-situ stress field, rock mass properties, and pillar geometry. In shallow to moderate depths typical of stone mines, the horizontal stress component is often much higher than the vertical component, resulting in high tangential compressive stresses on the pillar walls that lead to spalling failure. The failure process is primarily determined by the pillar\u27s shape, especially the width-to-height ratio. Slender pillars (w/h \u3c 1.5) lack a significantly confined inner core and are prone to sudden, brittle collapse with little warning. In contrast, squat pillars (with a high w/h ratio) develop a confined core, which allows for a more ductile, strain-softening response even after the outer surface has failed. To simulate this behavior accurately, a constitutive model should reflect the progressive nature of brittle fracture. Classical failure criteria, such as the Mohr-Coulomb model, are conceptually flawed for this purpose because they assume the simultaneous mobilization of cohesion and friction, which is physically impossible since friction can only be mobilized on a surface that has already formed after the loss of cohesion.
To overcome this limitation, this research employs the Cohesion-Weakening Friction-Strengthening (CWFS) theory. The CWFS model describes a more physically realistic, sequential failure process: (1) as the rock is loaded beyond its damage initiation threshold, micro-cracks form and merge, resulting in a gradual reduction of the rock\u27s cohesive strength; (2) only after significant damage and the development of fracture surfaces can the frictional component of strength activate and increase as fragments interlock under confinement. This framework is conceptually better suited for modeling spalling, a cohesion-loss-focused process that occurs at the low-confinement pillar surface.
The core of this thesis comprises a series of three-dimensional numerical simulations using FLAC3D, which incorporates both idealized block models and realistic pillar shapes derived from LiDAR scans processed with CloudCompare and Rhino 3D software. The models are designed to analyze the initiation and development of spalling under realistic geomechanical conditions. The CWFS behavior is implemented using the built-in strain-softening Mohr-Coulomb model, with parameters selected and calibrated based on a comprehensive review of published case studies for brittle rocks.
The numerical simulations successfully captured the brittle nature of the stone pillars. The results provided a detailed, mechanistic view of how failure initiates and leads to a critical stress redistribution into a confined inner core. The modeling clarified the critical role of the w/h ratio in determining the failure mode. It provided insight into the length benefit of rectangular pillars by mechanistically exploring the concept behind the effective pillar width formula. This analysis will enhance understanding of the failure mechanisms of stone mine pillars
Evaluation of Manufacturing Processes and Firearm Examiners Assessment of Subclass Characteristics
No full textDue to criticisms towards the firearm and tool mark examiner community by several reports and other scientists, especially in regards to subclass characteristics, there was an apparent need for a study to provide deeper insight into (1) the manufacturing processes and the produced marks; (2) transfer of those marks to cartridge cases, if applicable; (3) into examiner assessment of the identification of subclass and individual characteristics. These needs were addressed, in part, by the objectives of this research study: characterize different manufacturing methods and the breech faces thus produced to evaluate the presence of subclass characteristics, reproducibility of subclass characteristics on spent cartridge cases of various ammunition brands, and to evaluate the consistency of firearm examiners in distinguishing subclass characteristics from individual characteristics.
Four manufacturing processes were used to consecutively manufacture breech face inserts for a Thompson/Center® (T/C®) Contender® G2 pistol as the firearm of choice because of its capability of interchangeable breech face inserts which allows the manufacturing of consecutive breech face inserts to simulate different firearms. One hundred and ten breech faces were manufactured in two phases (Group A and B). A Sensofar® S neox 3D optical profiler was used to collect the 3D topographical scans of the breech faces and their resultant test fires which provided a total of 220 breech face scans and 3,000 cartridge case scans (includes before and after finishing method). The congruent matching cells algorithm (CMC) developed by the National Institute of Standards and Technology (NIST) was used to pairwise compare all breech faces and test fires within their respective group by manufacturing processes. These results were used to assess the presence of subclass characteristics from the manufacturing processes. It was found that the broached and plunge milled manufacturing methods produced some subclass characteristics on the breech faces, whereas the turned and face milled manufacturing methods did not. The marks from the manufacturing methods transferred some of the subclass characteristics to their respective cartridge cases. Once finishing methods were applied, some, if not all, of the subclass characteristics were removed and therefore reduced the amount transferred to the cartridge cases. The glass bead blasting finishing method was a more abrasive finishing method compared to the tumbling method.
Five primer brands were compared to assess the effect they had on the transfer and presence of subclass characteristics from the broached breech faces, both unfinished and finished. A total of 5,000 cartridge cases were collected and inter- and intra-brand comparisons were performed using the CMC algorithm. Performance was determined by receiver operating characteristic (ROC) curves and area under the curve (AUC) analysis. The Federal Match primers marked and performed the best when compared to the other primer brands. The order of performance by primer brand was Federal Match, Winchester, CCI, Sellier & Bellot, and Remington. Several error rates and the equal error rates were also calculated to assess the performance of each primer brand.
Lastly, firearm examiners were evaluated by labeled images of cartridge cases that contained different characteristic types (i.e. class, subclass, and individual). Eight firearm examiners participated and were qualitatively assessed for both reproducibility and repeatability. Generated heatmaps of each mark type within each group were performed. It was found there was consensus within each group for most images. The areas which were marked subclass and individual characteristics were overlaid and it was noted that the experimental group had more areas that were labeled as both characteristic types compared to the control group. The repeatability images demonstrated that each participant performed relatively well replicating their mark up on the repeated images. More formal and practical training in identification of subclass characteristics by firearm examiners is suggested from the results of this study
Apostrophes and Archimedes
No full textThis thesis explores how digital collage and printmaking can be used to develop images through acts of subjective response, intentional and unintentional acts of appropriation, and parodic re-use and comparison pushed to absurd extremes. It looks at the history of creating art for parodic re-use and examines “Pataphysics”, developed by and for art appropriation of pattern, form, and process. These concepts are explained and related to visual artwork that was made for the thesis exhibition Apostrophes and Archimedes Cast Shadow Puppets. The exhibition invites viewers to experience the phenomenon of observation, automatic transformation, and creation using multiple modalities of exaggerated and absurd reprographic image making techniques to compare our memory and creativity to similar devices
Towards Reliable Defect Detection in Laser Additive Manufacturing: AI-Driven Solutions for Domain-Specific and Interconnected Challenges
No full textLaser Additive Manufacturing (LAM) has emerged as a transformative technology in the aerospace and biomedical industries due to its ability to fabricate and repair high-value components with high precision. However, the intricate laser-material interactions involved in LAM processes, such as Directed Energy Deposition (DED) and Powder Bed Fusion (PBF-L), can lead to defects like porosity, which compromise the structural integrity of the final parts. Traditional non-destructive evaluation methods, such as high-resolution X-ray Computed Tomography (XCT), are commonly used to identify internal defects. But the process is very time-consuming and requires labor-intensive manual inspection. In contrast, in-situ thermal monitoring of melt pool dynamics presents a promising alternative, offering real-time insights into defect formation. Despite recent advances, accurately interpreting melt pool thermal gradients remains a challenge for conventional analytical methods. This research proposes a domain-informed artificial intelligence (AI) framework that addresses three interconnected challenges in LAM, namely large amounts of unlabeled data with limited labels and severe class imbalance by performing (i) unsupervised porosity segmentation in unlabeled XCT scan datasets using the Segment Anything Model (SAM) guided by prompts created through unsupervised clustering, (ii) semi-supervised classification of limited-labeled melt pool thermal images by combin- ing a self-supervised Masked Autoencoders (MAE) and Vision Transformers (ViT) classifier, and (iii) handling severe class imbalance by generating synthetic minority samples using a domain-aware class- conditioned diffusion model with high fidelity samples with mode coverage. The proposed methodologies are validated on in-house experimental datasets, highlighting real-world applicability for limited labeled or unlabeled datasets. The research was divided into two main parts: in-house experimentation- tion with data acquisition and labeling, and customized modeling to address key challenges and perform downstream tasks. Overall, this work demonstrates the potential of customizing state-of-the-art AI techniques for complex and label-scarce manufacturing datasets, contributing towards robust, scalable, and efficient defect detection frameworks in the LAM domain
Analysis of shotshell breech face impressions using a computer-based algorithm
Get PDFForensic firearm analysis involves the comparison of test fires from a suspect firearm to an unknown sample, typically collected from a crime scene. Test fires and the unknown sample are examined for agreement in class characteristics and sufficient agreement in individual characteristics using a comparison microscope. The forensic analysis of firearms has been challenged both in court and by governmental organizations for its subjective nature and the inability to accurately report error rates.
To combat these challenges, the National Institute of Standards and Technology (NIST) has proposed using computer-based algorithms, such as Congruent Matching Cells (CMC). These CMC algorithm calculates the degree of similarity between samples using topography measurements. Instead of using the Association of Firearm and Tool Mark (AFTE) Theory of Identification, the number of congruent matching cells determines if the unknown sample and test fires were discharged by the same firearm.
Two shotguns, a Mossberg® 500® and a Remington® 870TM each discharged 405 shotshells with varying pellet weight, pellet size, and charge weight. Shotshells were then scanned with a confocal microscope prior to being imported into the CMC algorithm for cropping and comparisons. Comparisons were only performed within the same firearm and were analyzed to determine applicability of the CMC algorithm in regard to shotshell comparisons as well as to determine if there was any influence by pellet weight, pellet size, and charge weight on the breech face impressions.
The results of this study demonstrated that the CMC algorithm can be applied to shotshell comparisons. In order to improve the utility of the algorithm the congruency thresholds need to be optimized for such firearms. The area of the firing pin impressions on shotshells are very large in comparison to area of the primer surface. This resulted in high false negative rates for both firearms (FNR Mossberg®500® = 48.4% and FNR Remington®870TM = 38.9%) when using the CMC threshold of six (the threshold determined for pistols). The results show that charge weight, pellet size, and pellet weight all affect the CMC count and CMCpercentages due to the variation in breech face impressions as a result of their role in the cycle of fire
The Effect of Carrier Type and Material Used on Results of 1,1,1,2-Tetrafluoroethane Application to Teeth
Get PDFIntroduction: The formulation of a pulpal diagnosis is crucial to prescribe appropriate treatment recommendations for endodontics. The application of a cold stimulus to the tooth’s surface utilizing the refrigerant 1,1,1,2-Tetrafluoroethane (R-134a) is a common way to obtain a pulpal diagnosis. Cotton as a form of applicator is used to absorb the R-134a and create a temperature change in the pulp. There is limited research if there is a better material than cotton to generate this cold response. No studies to date have been found to determine if a sponge as an applicator would generate a more significant cold response than a form of cotton.
The research hypothesis is that the e-Dx® sponge will create a greater temperature drop in an extracted tooth than the other carriers tested over time.
The null hypothesis is there will be no significant difference in the temperature change registered in an extracted tooth depending upon the nature of the applicator (e-Dx® sponge (Jordco®), #2 cotton pellet, or cotton swab) to transfer R-134a.
Methods: A single mandibular incisor was selected after confirming canal space radiographically. The apical 3mm of the root was sectioned, a size #15 K-file used to remove impediments, and a thermocouple wire threaded into the canal to the full coronal extent of the canal. The tooth was embedded in acrylic, and the wire closed into place with composite resin. To simulate intraoral conditions, the tooth was placed in an incubator at 37°C prior to sample collecting. The e-Dx® sponge, #2 cotton pellet, and cotton swab were used for sample collection after saturation of R-134a for 5s onto the applicator. The application of R-134a was repeated for 10 samples with each applicator, discarding the applicator after each use. Temperature change from baseline was recorded at 5s, 10s, and 15s. A linear mixed model was used to assess the data over time for each group. Statistical inferences were based on ANOVA at a significance level of p \u3c 0.05. Mean temperature changes at 5s, 10s, and 15s were recorded relative to baseline.
Results: ANOVA analysis showed the e-Dx® sponge performed better than the cotton pellet, cotton swab, and control (p\u3c 0.0001), the #2 cotton pellet maintained cold better than the cotton swab and control (p\u3c 0.0001), and the cotton swab performed the worst, having little effect on temperature change on the simulated pulp of the extracted tooth (p\u3c 0.0526). Mean temperature changes at 5s, 10s, and 15s were 0.69, 3.82, and 6.97 for the sponge; 0.69, 2.64, 4.31 for the #2 cotton pellet; and 0.17, 0.45, and 1.08 for the cotton swab.
Conclusion: Within the limitations of this in-vitro study, it is suggested that the e-Dx® sponge applicator would provide for a better transfer of cold from R-134a than a #2 cotton pellet or cotton swab during sensibility testing
MINERALOGICAL AND GEOCHEMICAL ASSESSMENT OF RARE EARTH ELEMENT AND OTHER CRITICAL MINERAL OCCURRENCES IN COAL-DERIVED MATERIALS FOR RESOURCE RECOVERY POTENTIAL
Get PDFRare earth elements (REEs) and other critical minerals (CMs) are indispensable to modern clean energy, electronics, and defense sectors due to their unique physical and chemical properties. The increasing global demand for these elements—combined with concerns about supply chain disruptions and the environmental impact of conventional mining—has heightened the urgency to identify alternative, sustainable sources. Among various secondary resources, coal-derived wastes such as coal refuse, fly ash, bottom ash, and coal acid mine drainage sludge have emerged as promising feedstocks for REE and CM recovery within the United States.
In this study, a comprehensive mineralogical and geochemical assessment was performed on selected coal-derived materials sourced from diverse U.S. coal basins. A suite of advanced analytical techniques was utilized, including X-ray Diffraction (XRD) for crystalline phase identification, Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) for microstructural and elemental mapping, Transmission Electron Microscopy (TEM) for nanoscale examination of mineral-hosting phases, and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for quantitative determination of REE and CM concentrations. Furthermore, a sequential extraction protocol was applied to delineate the chemical speciation and extractability of REEs across operationally defined geochemical fractions.
The results reveal that all coal-derived samples contained significant concentrations of REEs and CMs, with measured total rare earth element (TREE) values ranging from approximately 323 to over 1,000 ppm depending on sample type and thermal treatment. Sequential extraction showed that the acid-soluble fraction accounted for the majority of extractable REEs in each material, indicating substantial potential for recovery via hydrometallurgical leaching. Carbonate-bound and organically associated REEs were also detected, suggesting some mobility under moderate chemical conditions. In contrast, the ion-exchangeable fraction consistently exhibited the lowest REE recoveries, implying limited surface adsorption or weak binding in these materials. Importantly, a strong correlation was observed between REE distribution and the presence of aluminosilicate phases—particularly in fly ash—supporting the conclusion that a substantial portion of REEs is structurally incorporated within amorphous or poorly crystalline silicate matrices formed during coal combustion. This finding underscores the necessity of aggressive chemical or thermal activation strategies for efficient REE mobilization. Critical elements such as lithium, cobalt, nickel, and aluminum were also identified at notable concentrations, particularly in fly ash and AMD sludge, underscoring the potential of coal by-products as multi-element resources.
Overall, the study demonstrates that coal-derived wastes represent viable secondary sources of critical elements, provided that their complex mineralogical contexts are fully understood and appropriately leveraged. By integrating mineralogical, microstructural, and chemical speciation analyses, this research provides a robust foundation for the development of sustainable recovery technologies, ultimately contributing to enhanced environmental stewardship and the resilience of the domestic REE and other critical mineral supply chain