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At least 631 records · Page 35

Ultra-High Operation Temperature SiC-matrix Solar Thermal Air Receiver (HOTSSTAR) enabled by additive manufacturing: Test Facility & Performance Evaluations

Solar Heat for Industrial Processes (SHIP) cavity receivers are capable of generating electricity or industrial process heat by absorbing thermal energy from solar radiation, focused on a small area. The concentration of solar radiation on the small area of the receiver enables the achievement of high temperatures (ranging from 400°C to 1,100°C) of a working fluid, thus making the SHIP technology thermodynamically comparable with conventional power plants. A volumetric receiver consists of a porous structure-generally made of silicon carbide or metal, which absorbs solar radiation and converts it into heat energy. Heat energy from the porous materials is then transferred to the fluid following through them. A volumetric receiver acts as a convective heat exchanger, transferring heat to the fluid through convection. Open-loop volumetric receivers work with air at atmospheric pressure and are suitable for single-cycle or multi-cycle energy plants. A Model Based Systems Engineering (MBSE) approach was used to develop a test bed at Sandia national Laboratories (SNL) capable of demonstrating an open-loop volumetric air receiver developed by General Electric Aerospace (GE Aerospace). This paper presents the development of the various MBSE methods, test bed, and testing operations for the GE air receiver, which was experimentally demonstrated to achieve 1,350°C for over 3 hours of operation and an approximate 70% receiver efficiency. By being able to achieve such high temperatures >1,000°C, this work provides the potential to support many SHIP industrial use cases.

14 SOLAR ENERGY↗

Kinetic Simulations of Microstructural Evolution (KSOME)

"Kinetic simulations of microstructural evolution" (KSOME) is an object Kinetic Monte Carlo (OMKC) simulation code. It is developed to simulate microstructural evolution in materials during irradiation. KSOME is developed from ground up with priority given to the flexibility, ease of upgradability, and computation efficiency, in that order. With previously developed simulation codes, various processes (more precisely, the diffusion-reaction processes) that can occur in a system were hardwired into the code. Hence, to perform higher fidelity simulations, a significant coding effort was required every time to incorporate either a more accurate description of existing processes or new processes. With KSOME, the necessity for frequent code upgrades whenever there is a need to perform higher fidelity simulations is either eliminated or reduced significantly. In KSOME, the categories of various diffusion-reaction processes and the data-management system are hardwired, while the execution of the diffusion-reaction processes specific to a system is specified via input files. In the present version of KSOME, the analytical expression required to calculate defect interaction radii are inputted via a text file. However, the ability to parse mathematical expressions from a text file can be extended to input the analytical expression to calculate other defect properties; including the expressions to calculate the change in the migration barriers of mobile defects due to long-range interaction with extended defects

Nandipati, Giridhar [Pacific Northwest National La↗

Baseplate Temperature–Dependent Vertical Composition Gradient in Pseudo–Bilayer Films for Printing Non–Fullerene Organic Solar Cells

Numerous previous reports on the sequential deposition (SD) technique have demonstrated that this approach can achieve a p–i–n active layer architecture with an ideal vertical composition gradient, which is one of the critical factors that can influence the physical processes that determine the photovoltaic performance of organic solar cells. Herein, a commonly used photovoltaic system comprised of PM6 as a donor and Y6 as an acceptor is investigated with respect to sequential blade–processing deposition to comprehensively explore the morphology characteristics as a function of baseplate temperature. A systematic study of the temperature–dependent blend morphology elucidates the SD–processed configuration merits and device physics behind temperature–controlled degree of vertical composition gradient, and constructs the temperature–microstructure–property relationship for the corresponding photovoltaic parameters. The result shows, as the temperature increases, the morphology of the active layer has undergone a distinct evolution from the pseudo–bulk heterojunction to a pseudo–planar heterojunction and then to a pseudo–planar bilayer, leading to a non–monotonic correlation between baseplate temperature and device performance. Further, this investigation not only reveals the importance of precisely controlling baseplate temperature for gaining vertical morphology control, but also provides a path toward rational optimization of device performance in the lab–to–fab transition.

14 SOLAR ENERGY↗

Results of the Analyses of SMECT Mercury Sample Collected During Mercury Pump (MB1) Functional Check

A pump added to remove mercury from the sump of the Slurry Mix Evaporator Condensate Tank (SMECT) in DWPF was successfully tested in 2020, resulting in a sample of contaminated mercury obtained from the Mercury Purification Process (MPP) cell. The mercury in the sump of the SMECT was present as a result of steam stripping of sludge slurry in the Sludge Receipt and Adjustment Tank (SRAT) at DWPF. A schematic of the MPP system provided by DWPF personnel is shown in Appendix A. DWPF personnel supplied the following detailed description of the Hg sampling: “The sample provided is the result of DWPF extraction of mercury by means of the Mercury Pump-Water Cart. The Mercury Pump extracted the sample from the SMECT mercury sump. The pump uses pressurized water to transfer a small amount of mercury to a leachate bucket located at the Lab Mercury cell. The mercury and water were allowed to be self separated, and mercury was gravity decanted from the leachate bucket.” DWPF personnel indicate that the leachate bucket is equipped with both a top stopcock/drain and a lower/bottom stopcock/drain from which the mercury was decanted or drained out, while the separated water layer remained above the mercury during draining. The DWPF customer requested SRNL to analyze the sample for the following: gross alpha/nonvolatile beta analysis and perform a Toxicity Characteristic Leaching Procedure (TCLP) per the Environmental Protection Agency's Test Methods for Evaluating Solid Waste: Physical/Chemical Methods, SW-846. While the TCLP was preferred, a Total Metals analysis of the eight Resource Conservation and Recovery Act (RCRA) metals was deemed acceptable.2 The analytical data collected on this mercury sample will be used in planning for sample disposition as well to start a profile for future Hg disposition of Hg collected from steam stripping.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

A Comparative Analysis of Lithium-Ion Battery Chemistries for Cold-Climate Maritime Applications

Energy storage, primarily in the form of electrochemical batteries, is critical for enabling integration of marine energy (e.g., power from waves and currents) with end-use applications at sea due to the periodicity of the resources and requirement of consistent, smooth power delivery. Powering high-latitude coastal or ocean-based observing systems has been identified as a high value-proposition use case, exemplifying the concept of Powering the Blue Economy. An existing power system implementation for such a platform uses solar panels coupled to rechargeable lithium-ion batteries, augmented by a non-rechargeable backup bank used to power heaters in winter months. As wave energy is a potential resource for powering this and similar use cases and is strongest when solar power is most limited, it was hypothesized that integration of wave power would alleviate some of the challenges in cold climates related to energy storage. In this work, we investigate the use case scenario in simulation and perform a comparative test of commercially-available lithium-ion battery chemistry formulations to determine the most appropriate choice for the application. The experiment compared the most commonly-used lithium-based battery types (NCM, NCA, and LFP) in laboratory conditions emulating a battery enclosure thermally coupled to freezing seawater using an industrial battery performance tester in PNNL's arctic simulation lab. Battery strings were repeatedly cycled (i.e., charged, discharged, rested) and their usable capacity was measured. Both NCM and NCA strings exhibited degradation upon cycling, while the LFP string maintained stable operation through over 700 complete cycles. Though lower in baseline capacity, LFP are recommended for this and similar low-temperature applications with access to high levels of bulk charging current (e.g., from high-energy wave events) and their use may reduce the cost and complexity of battery conditioning and protection apparatus.

16 TIDAL AND WAVE POWER↗

Transforming U.S. Particle Physics Education: A Snowmass 2021 Study

The pursuit of knowledge in particle physics requires constant learning. As new tools become available, new theories are developed, and physicists search for new answers with ever-evolving methods. However, it is the case that formal educational systems serve as the primary training grounds for particle physicists. Graduate school (and undergraduate school to a lesser extent) is where researchers learn most of the technical skills required for research, develop scientific problem-solving abilities, learn how to establish themselves in their field, and begin developing their career. It is unfortunate, then, that the skills gained by physicists during their formal education are often mismatched with the skills actually required for a successful career in physics. We performed a survey of the U.S. particle physics community to determine the missing elements of graduate and undergraduate education and to gauge how to bridge these gaps. In this contributed paper, part of the 2021-22 Snowmass Community Planning Exercise, we report the results of this survey. We also recommend several specific community actions to improve the quality of particle physics education; the "community" here refers to physics departments, national labs, professional societies, funding agencies, and individual physicists.

Bitter, O.↗

Search for a Singly Strange Hexaquark Using Polarization Data From CLAS12 at Jefferson Lab Virginia

Recently hadron spectroscopy has seen a lot of success. There has been a large number of baryon and meson resonances discovered over the last two decades. There have also been several tetra and pentaquark candidates with experimental evidence but not confirmed. The first serious candidate was the X(3872), a potential tetraquark, leading to this rise in success for exotic hadron physics. This has brought about improvements in Quantum Chromo Dynamics (QCD), our current best description of interactions between quarks and gluons. QCD predicts the existence of hexaquark states, and then the d*(2380) was discovered. This thesis explores the rest of the d* Jp =3+ anti-decuplet by searching for experimental evidence of the ds hexaquark. This is the first analysis of the e'd ¿e'K+d0 s ¿e'K+¿n channel using the Py' measurements of the ¿ as a lens to perform this search. This observable was extracted from ¿ electroproduction events off a liquid deuterium target. From this an upper limit of the Breit-Wigner peak strength was extracted. This was done with the use of the CLAS12 detector system housed at Thomas Jefferson Laboratory in Virginia, USA. These polarization measurements are the first to be made on this data, and this is the first time the ds has been searched for in such a way.

Clash, Geraint↗

Numerical simulation of coupled THM behaviour of full-scale EBS in backfilled experimental gallery in the Horonobe URL

Bentonite-based engineered barrier system (EBS) is a key component of many repository designs for the geological disposal of high-level radioactive waste. Given the complexity and interaction of the phenomena affecting the barrier system, coupled thermo-hydro-mechanical (THM) numerical analyses are a potentially useful tool for a better understanding of their behaviour. In this context, a Task (the Horonobe EBS experiment) was undertaken to study, using numerical analyses, the thermo-hydro-mechanical (and thermo-hydro) interactions in bentonite based engineered barriers within the international cooperative project DECOVALEX 2023. One full-scale in-situ experiment and four laboratory experiments, largely complementary, were selected for modelling. The Horonobe EBS experiment is a temperature-controlled non-isothermal experiment combined with artificial groundwater injection. The Horonobe EBS experiment consists of the heating and cooling phases. Six research teams performed the THM or TH (depended on research team approach) numerical analyses using a variety of computer codes, formulations and constitutive laws. Finally, for each experiment, the basic features of the analyses are described and the comparison between calculations and laboratory experiments and field observations are presented and discussed.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Evaluation of Acoustic Channel Capacity for Complex Piping Topology

Transmission of information using elastic waves on existing metallic pipes provides an alternative communication option for a nuclear facility. The advantages of this approach consist of transmitting information through physical barriers, such as the containment building wall. In addition, this approach provides physical cybersecurity since the pipe becomes an analog communication channel which is difficult to eavesdrop on and difficult to sever. In prior work, a laboratory bench-scale system consisting of a six foot-long straight section of nuclear grade stainless steel pipe and high-temperature ultrasonic LiNbO 3 transducers was assembled. The lab systems was used for communication protocol development and preliminary data transmission demonstration. Next phase of project development involves deployment of the ultrasonic communication system in a representative environment. Mechanisms Engineering Test Loop (METL) facility at ANL was chosen as a viable candidate for communication system demonstration. Analysis of piping manifolds at METL has shown that in a typical scenario, ultrasonic signals have to be transmitted over straight and bent piping sections. This report describes preliminary studies on transmission of information with ultrasonic shear waves across bent piping sections. A test article consisting of a stainless steel pipe bent at 90° was developed for laboratory analysis of ultrasonic signal transmission. The bent piping test article developed by welding two straight pipes to an elbow. For consistency, the diameter and wall thickness of the bent pipe is the same as that of the straight pipe utilized in prior studies. COMSOL computer simulations were performed to study ultrasonic refracted shear wave coupling and transmission across bent piping. Preliminary evaluations of ultrasonic shear wave transmission were conducted with piezoelectric (PZT) and LiNbO 3 transducers, with the signals recorded with previously developed LabView interface. Preliminary results have shown significant dispersion of transmitted signals, most likely due to reflections and scattering by piping welds. Signal distortion compensation algorithm based on time reversal modulation (TRM) was initially investigated for transmission through solids, and demonstrated for signals transmitted over the bent pipe. Using TRM, it was shown that communication bitrates of 100Kbps were achievable, in principle.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Rheological Properties of Enzymatically Hydrolyzed Corn Stover Pretreated via Deacetylation and Mechanical Refining

Lignocellulosic biomass is a feedstock for fuels and chemicals that does not compete with food resources and has less contaminants than refuse-derived biomass feedstocks. To convert lignocellulosics to biofuels or value-added products, multiple processing steps are typically necessary. One method of producing biofuels from lignocellulosic biomass utilizes a deacetylation and mechanical refining pretreatment and an enzymatic hydrolysis reaction to produce fermentable sugars from cellulose and hemicellulose. The rheological properties of biomass, such as yield stress and plastic viscosity, change during enzymatic hydrolysis and alter the energy requirements for pumping and mixing, an important consideration for the design of processing equipment. The dynamic changes in rheological properties that occur in a corn stover feedstock undergoing enzymatic hydrolysis are characterized in this work, and the influence on pressure losses in piping systems is estimated. Two rheometer geometries were fabricated with stereolithography 3D printing to reduce wall slip and sample ejection. The slurries have complex rheological behaviors that include shear-thinning behavior. Shear stress ramps were performed on samples at 20 and 50 degrees C using the custom geometries, and the Herschel-Bulkley model was fit to the data. The dynamic nature of the rheological properties is correlated with changes in the average fiber length at various extents of reaction, and the influence of solids concentration on the observed rheology and piping pressure losses is discussed.

09 BIOMASS FUELS↗

Enabling Entrained-Flow Gasification of Blends of Coal, Biomass and Plastics (Final Report)

This project demonstrated the technical feasibility of gasifying blends of coal, biomass and mixed waste plastics in a high pressure entrained-flow gasifier for production of hydrogen. This was achieved by creating slurries of coal, biomass pyrolysis liquids and liquefied plastic oil. Specific objectives of the project included (1) determining compositions of coal-biomass-plastic mixtures that produce a stable slurry suitable for pumping to high pressure, (2) designing and testing a novel burner to effectively atomize the mixed feedstock slurry in a pressurized gasifier, and (3) acquiring first-of-a-kind performance data for pressurized, oxygen-blown entrained-flow gasification of slurried blends of coal, biomass and plastic. A key focus of the project was preparation of mixtures of coal, biomass and plastic. To facilitate easy pumping to high pressure, slurries were created using (i) bioliquid resulting from a well-established rapid thermal treatment pyrolysis process, (ii) oil produced from waste plastic via an available thermal conversion process, and (iii) ground coal. Lab-scale tests were conducted to evaluate viscosity and stability/propensity for the mixtures to separate over time. Larger batches of the most promising slurry compositions were prepared and subjected to pumping studies. It was found that mixtures containing less than about 40% coal and less than about 30% plastic oil were stable and of low enough viscosity to facilitate pumping to high pressure. A high-performance hot oxygen burner (HOB) was designed and fabricated for use in an existing 1 ton/day pressurized entrained-flow gasifier. Ex-situ testing demonstrated that the HOB provides excellent atomization of the slurries and creates a very uniform and robust flame. Performance of the HOB in the gasifier was exceptional and resulted in better conversion to syngas than any previous generation of burner. Fabricating the HOB for this project was challenging due to the relatively small scale of the gasifier. Performance in larger-scale systems is expected to be even better. Gasification of mixtures of coal, bioliquid and plastic oil proved to be relatively easy. The gasifier was able to be started up, pressurized and transitioned to the blended slurry feedstock with no technical difficulty. Syngas rich in CO and H 2 , with relatively low concentrations of CO 2 , was produced. During startup and at low gasification temperatures, soot formation was observed, as is typical for gasification of petroleum-based feedstocks. No slag buildup was observed under the conditions tested. The project was successful in demonstrating the technical feasibility of the concept. Future development should broaden the range of feedstocks under consideration, more deeply explore performance of the gasifier, and evaluate scale-up and implementation strategies.

08 HYDROGEN↗

Integrating Crack Detection and Pipe Shape Optimization for Enhanced Sewage System Durability

Crack detection in underground reinforced concrete pipes has been essential in determining the state of stormwater infrastructure. Detection models have been implemented for detecting cracks and other defects in pipes using CCTV footage for stormwater drainage systems. In addition, Finite element models have been used to determine optimum shapes and pipe thickness for different boundary conditions such as header pipes in power plants. The concept of shape optimization emerges as a crucial factor in power plant design and operation, with the potential to maximize performance while minimizing the use of materials. Shape optimization not only enhances efficiency but also contributes to reducing the environmental footprint. This paper discusses the integration of both topics by using the cracks detected in underground pipes as boundary conditions for shape optimization of the pipes. A machine learning model has been developed which uses limited data for training and outlines the location of detected cracks. A shape optimization methodology is proposed in which ANSYS modules are used to analyze fluid flow and then optimize the shape of the pipe. The crack detection model developed has been applied to a crack detected in lab setting and machine learning model used has an accuracy of 98% using a random forest algorithm.

20 FOSSIL-FUELED POWER PLANTS↗

High-throughput investigation of structural evolution upon solid-state in Cu–Cr–Co combinatorial multilayer thin-film

Cu-Cr-Co combinatorial multilayer thin-films were prepared by a high-throughput ion beam sputtering system. Based on the thickness ratio among the individual nanoscale monolayers (Cu, Cr, Co), the resulting stoichiometry covered the entire phase diagram. The chemical composition and structure of Cu-Cr-Co combinatorial chip upon solid-state reaction were studied by lab-based micro-X-ray fluorescence (mu-XRF) and high-throughput synchrotron X-ray diffraction (XRD), respectively. A composition-structure map for Cu-Cr-Co combinatorial chip was developed through automated data analysis employing hierarchical clustering techniques. The structural evolution of Cu-Cr-Co combinatorial chip as a function of heat-treatment temperature, time, and modulation period were studied systematically. Furthermore, the effect of the elemental distribution in-depth direction was investigated to gain more insights regarding phase transformation. This work provides an efficient method and new perspectives for the design and optimization of the composition and structure of high-performance thin-films.

36 MATERIALS SCIENCE↗

Summer 2017 Microfluidics Research Report

Liquid-liquid Extraction (LLE), also known as solvent extraction, represents a large subset of chemistry where one or more solutes are transferred across an interface between two immiscible liquids. This type of chemistry is used in industrial scale processes to purify solvents, refine ore, process petroleum, treat wastewater, and much more. Although LLE has been successfully employed at the macroscale, where many liters/kgs of species are processed at large flow rates, LLE stands to benefit from lab-on-a-chip technology, where reactions take place quickly and efficiently at the microscale. A device, called a screen contactor, has been invented at Los Alamos National Laboratory (LANL) to perform solvent extraction at the microscale. This invention has been submitted to LANL’s Feynman Center for Innovation, and has been filed for provisional patent under U.S. Patent Application No. 62/483,107 1. The screen contactor consists of a housing that contains two different screen materials, flametreated stainless steel and polyether ether ketone (PEEK) thermoplastic, that are uniquely wetted by either an aqueous or an organic liquid phase, respectively. Liquids in this device flow longitudinally through the screens. The fine pore size of the screens (tens of microns) provide large capillary/adhesional forces while maintaining small hydraulic pressure drops. These physical characteristics are paramount to efficient microscale liquid phase separation. To demonstrate mass transfer using the screen contactor, a well-known chemical system 2 consisting of water and n-decane as solvents and trimethylamine (TEA) as a solute was selected. TEA is basic in water so its concentration can easily be quantified using a digital pH meter and an experimentally determined base dissociation constant. Characterization of this solvent system and its behavior in the screen contactor have been the focus of my research activities this summer. In the following sections, I have detailed experimental results that have been gathered.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Thermomechanical design optimization for low metal footprint in hybrid metal-polymer heat exchanger

Material and maintenance costs of metal-based heat exchangers surpass profits in waste heat recovery (WHR) from ultra-low temperature (<100C) sources [1]. A low-cost alternative like polymer pipes suffer from poor thermal conductivity (~0.2 W/mK), and a low overall heat transfer coefficient. Polymers’ thermal conductivity have previously been enhanced through systematic molecular alignment by stretching [2], chemical vapor deposition of extended polymers [3], surface grating [4], etc. However, these approaches suffer from scalability issues for WHR heat exchangers in terms of cost [3], and thermomechanical considerations [5]. In this work, we propose novel hybrid metal-polymer heat exchangers that are made from polymer-copper strips. Through finite element method (FEM) simulations, we first optimize the placement of copper around polymer strips to enhance the transverse thermal conductivity of the strips. The copper cladded polymer strips are wound helically in a roll-to-roll system to form the pipes for a heat exchanger. We then optimize the design of helically wound pipes to reduce thermomechanical strains to < 0.2 % at 100C and 40 psi working conditions. At 25 % volume fraction of copper in the pipe, we predict up to 20 % enhancement in overall heat transfer from a base polymer with a thermal conductivity of 0.2 W/mK. We also compare and contrast the thermomechanical performance of the optimized metal-polymer strips to random metal matrix composites. Finally, we experimentally verify the thermal conductivity of the optimized strips through bulk thermal conductivity and thermal interface resistance measurement setup. By systematically improving the design through FEM and experimental measurements, we provide an optimized design of hybrid metal-polymer pipes that provides a low metal footprint and cost-effective means for harvesting waste heat from ultra-low temperature sources. Thekdi, Arvind, and Sachin U. Nimbalkar. Oak Ridge National Lab, 2015 Shen, Sheng, et al. Nature nanotechnology 5.4 (2010): 251. Xu, Yanfei, et al. Science advances 4.3 (2018): 3031. Smith, M. K., Singh, V., Kalaitzidou, K., & Cola, B. A. (2015). ACS nano, 9(2), 1080-1088. Aymonier, C., Bortzmeyer, D., Thomann, R., & M&uuml;lhaupt, R. (2003). Chemistry of Materials, 15(25), 4874-4878.

C Rajagopal, Manjunath↗

LHCspin: a Polarized Gas Target for LHC

The goal of the LHCspin project is to develop innovative solutions for measuring the 3D structure of nucleons in high-energy polarized fixed-target collisions at LHC, exploring new processes and exploiting new probes in a unique, previously unexplored, kinematic regime. A precise multi-dimensional description of the hadron structure has, in fact, the potential to deepen our understanding of the strong interactions and to provide a much more precise framework for measuring both Standard Model and Beyond Standard Model observables. This ambitious task poses its basis on the recent experience with the successful installation and operation of the SMOG2 unpolarized gas target in front of the LHCb spectrometer. Besides allowing for interesting physics studies ranging from astrophysics to heavy-ion physics, SMOG2 provides an ideal benchmark for studying beam-target dynamics at the LHC and demonstrates the feasibility of simultaneous operation with beam-beam collisions. With the installation of the proposed polarized target system, LHCb will become the first experiment to simultaneously collect data from unpolarized beam-beam collisions at $\sqrt{s}$=14 TeV and polarized and unpolarized beam-target collisions at $\sqrt{s_{NN}}\sim$100 GeV. LHCspin has the potential to open new frontiers in physics by exploiting the capabilities of the world's most powerful collider and one of the most advanced spectrometers. This document also highlights the need to perform an R&D campaign and the commissioning of the apparatus at the LHC Interaction Region 4 during the Run 4, before its final installation in LHCb. This opportunity could also allow to undertake preliminary physics measurements with unprecedented conditions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Chemistry imaging and distribution analysis of rare earth elements in coal using LIBS and LA-ICP-MS instruments

Currently, demand for rare earth elements (REEs) increased significantly. Coal is actively evaluated as potential economic sources for extraction of REEs. Here, in this work, laser-induced breakdown spectroscopy (LIBS) was evaluated for rapid estimation of REEs content and their distribution in the natural coal samples. The results were compared with similar laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) measurements. Thirteen coal samples (nine standard samples and five natural samples) were used in this study. Powder samples were pressed into pellets while coal chunks were directly ablated for data recording. Pellets of the powder standard samples were used to optimize the data acquisition system and then data recorded with this optimized system was used to identify the proper data acquisition and analysis models. After establishing the proper data acquisition system and analysis model using the standard samples, natural coal samples in powder form and their chunks were utilized to record LIBS and LA-ICP-MS spectra. Multivariate calibration models were developed using four of the natural samples, which were evaluated by predicting the REE content in the fifth sample. Principal component analysis was performed on the LIBS data obtained from the natural samples and it classified all the samples with high accuracy. Two-dimensional (2D) elemental mapping on coal chunk samples was also performed using both LIBS and LA-ICP-MS to study the distribution of REEs in the samples. The resulting elemental images and their correlations can be used to infer mineral distributions.

01 COAL, LIGNITE, AND PEAT↗

Intermittent Criticality Multi‐Scale Processes Leading to Large Slip Events on Rough Laboratory Faults

Abstract We discuss data of three laboratory stick‐slip experiments on Westerly Granite samples performed at elevated confining pressure and constant displacement rate on rough fracture surfaces. The experiments produced complex slip patterns including fast and slow ruptures with large and small fault slips, as well as failure events on the fault surface producing acoustic emission bursts without externally‐detectable stress drop. Preparatory processes leading to large slips were tracked with an ensemble of ten seismo‐mechanical and statistical parameters characterizing local and global damage and stress evolution, localization and clustering processes, as well as event interactions. We decompose complex spatio‐temporal trends in the lab‐quake characteristics and identify persistent effects of evolving fault roughness and damage at different length scales, and local stress evolution approaching large events. The observed trends highlight labquake localization processes on different spatial and temporal scales. The preparatory process of large slip events includes smaller events marked by confined bursts of acoustic emission activity that collectively prepare the fault surface for a system‐wide failure by conditioning the large‐scale stress field. Our results are consistent overall with an evolving process of intermittent criticality leading to large failure events, and may contribute to improved forecasting of large natural earthquakes.

Geochemistry & Geophysics↗