bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing Methods to Assess Changes in Mechanical Properties of Shale Modified by Engineered Mineral Precipitation
Authors: Bedey K. , Cunningham A. B. , Phillips A. J. , Kirkland C. M. , Willett M. R. , Dobeck L. , Eldring J. , Crandall D. , Rutqvist J.
Published: September 2023

Fractures in subsurface shale formations serve multiple purposes, for example, in the recovery of resources in hydraulic fracturing or as potential harmful leakage passages through caprocks that may contribute undesired fluids to the atmosphere or functional groundwater aquifers. A proposed method to seal or influence fracture properties is Ureolysis-Induced Calcium Carbonate Precipitation (UICP), a bio-mineralization technology driven by the enzymatic hydrolysis of urea, resulting in the formation of calcium carbonate. The resulting calcium carbonate can bridge the gaps in fractured shale and reduce fluid flow through fractures. This study represents the first step toward determining the influence of UICP treatment on shale material and its subsequent mechanical strength properties. The goal of this preliminary work is twofold: first, we aim to identify a method to test tensile strength along a core axis and second, we seek to assess the effect of temperature on the tensile strength of intact, unfractured shale cores (2.54 cm (1 in) diameter, 5.08 cm (2 in) long for comparison with future fractured and UICP-treated cores. A modified Brazilian indirect tensile strength test successfully measured splitting tensile strength of shale cores from Eagle Ford and Wolfcamp formations at room temperature and 60°C.

INTRODUCTION

Hydraulic fracturing coupled with horizontal drilling has been an instrumental technology for extraction of natural gas reserves in subsurface rock formations such as sandstone and shale. Shale gas is the natural gas trapped within subsurface shale formations and has become a crucial unconventional energy source amid an evolving energy landscape. Hydraulic fracturing and horizontal drilling stimulated energy independence, lowered fuel prices, and promoted job creation in the United States (Q. Wang et al., 2014). While hydraulic fracturing created many positive economic impacts, it has also generated undesirable environmental effects. This research is aims at offsetting environmental costs by sealing fractured subsurface shale using a sustainable bio-mineralization technology known as Ureolysis-induced calcium carbonate precipitation (UICP) (Kirkland et al., 2021). If UICP can bridge the gap in fractured shale, and prove strong enough to seal fractures, UICP treatments may be used at the field scale to limit fracture propagation, better store carbon dioxide, and extend the life and efficiency of existing and future wells.
Impact of Proppant Distribution in Hydraulic Fracture on the Productivity of the Multi-Stage Fractured Marcellus Shale Horizontal Wells
Authors: El Sgher Mohamed , Aminian Kashy , Sattari Arya , Samuel Ameri
Published: September 2023

The impact of the proppant distribution within the hydraulic fracture on the productivity of the multi-stage fractured Marcellus shale horizontal well has been investigated. The available data from a Marcellus Shale horizontal well were compiled, analyzed using a fracture model to determine the fracture properties, and used to develop a reservoir model. Multipliers for permeability and conductivity were incorporated in the model to account for the dynamic net stress changes during the production. The model predictions were found to be in close agreement with the well production. The impact of the non-uniform fracture conductivity and stage spacing on gas production were then investigated. The non-uniform fracture conductivity has a significant impact on the initial gas production. Therefore, it is important to consider the impact of the non-uniform fracture conductivity in optimizing hydraulic fracturing treatments in Marcellus shale.

INTRODUCTION

The application of the horizontal drilling and hydraulic fracturing techniques have unlocked, significant natural gas reserves from shale gas reservoirs. Marcellus Shale is one of the most prolific and largest unconventional gas resources in US. There are approximately 95,000 square miles of Marcellus shale in Ohio, West Virginia, and Pennsylvania as well as areas in New York, Kentucky, Tennessee, and Maryland. Marcellus shale varies in thickness from 50 to 200 ft. The depth of the shale ranges from 4,000 to 8,500 ft. The average temperature of the Marcellus shale is 150°F. The total organic carbon (TOC) ranges from 2 to 20 percent in Marcellus Shale (Boyce et al., 2010).

Hydraulic fracture treatment involves injecting fluid into the wellbore in order to increase the downhole pressure to a level in excess of the fracturing pressure of the formation. In response to this increase in pressure, the formation cracks, allowing the injected fluid to enter and extend the crack further into the formation. To keep the crack open after injection, a solid proppant, such as sand, is mixed with the injected fluid. Proppant plays an important role in stopping fractures from closing under in-situ formation stress and maintaining the fracture conductivity. There is a greater degree of closure in the unpropped areas, and their conductivity is poorer than in the propped areas. The distribution of proppant within the fracture can significantly affect the productivity of the well. The Marcellus Shale is typically treated with 2,500 to 20,000 barrels of water and 25,000 to 75,000 pounds of sand proppant at a rate of 25 to 100 barrels per minute (Bruner and Smosna, 2011).
Enabling CO2 Plume Geothermal: Key Geological, Reservoir, and Operational Considerations
Authors: Okoroafor E. R. , Kang Y. , Elsayed T. , Indro A.
Published: September 2023

To investigate ways of advancing CO2 plume geothermal (CPG), we have examined key geological, reservoir, geomechanical, and operational considerations. We use a three-dimensional numerical reservoir simulator to model the impact of each parameter studied on the injectivity and productivity indices for CO2 plume geothermal systems. In addition, we use a coupled thermohydromechanical model to understand if the process might induce fracturing or seismicity. The result showed that the top of the reservoir, the formation porosity, and the formation thickness are the top three factors impacting the productivity index and injectivity index of CPG systems. We also note that produced CO2 is less than the injected CO2 due to trapping mechanisms and bypassed CO2. Lower permeability and anisotropy were more favorable for the given reservoir and well configuration. From a geological perspective, sensitivity analyses reveal the influence of dip on CO2 extraction and the need for optimal well placement. Elastic-brittle analysis suggests that reservoir fracturing and microseismicity may not occur during injection. However, microseismicity may occur during production, thus providing some guidance on how operators may want to optimize monitoring strategies.

INTRODUCTION

The apparent high cost and lack of economic attractiveness of carbon capture utilization and storage (CCUS) projects have been perceived as a challenge for the large-scale deployment of numerous CO2 capture projects (Shen et al. 2022 and Gibbins et al. 2008). Budinis et al. (2018) suggest that the ability to utilize and sequester captured CO2 could enhance the economic viability of CCUS. Researchers such as Brown (2000), Pruess (2006), Luo and Jiang (2014), and Okoroafor et al. (2022) have investigated the thermal performance of an enhanced geothermal system (EGS) using supercritical CO2, which has shown promise for heat mining due to the favorable thermophysical properties of CO2 in its supercritical state. However, unlike the complex fracture system of the EGS model, the CO2 plume geothermal system takes advantage of CO2's greater compressibility, expansibility, and lower viscosity when injected into sedimentary rocks. Fluid loss in the system indirectly serves the purpose of CO2 geological storage, as Randolph et al. (2010, 2011) observed.
Machine Learning Based Predictive Models for UCS and Young's Modulus of the Dakota Sand Using Schmidt Hammer Rebound
Authors: Chellal H. A. K. , Egenhoff S. , Latrach A. , Bakelli O.
Published: September 2023

The Inyan Kara formation is a fluvial sandstone saline aquifer in the Williston basin that gained a lot of interest in the recent years due to it being the main saltwater disposal formation and one of the most promising CO2 storage formations in the basin. However very little is known about the geomechanical properties of this formation given the limited number of cored wells and other necessary data through this interval. Therefore, this study used a combination of well log data, routine geomechanical core data experiments and Schmidt hammer measurements to create a robust machine learning model that accurately predicts the deformability and strength of the Inyan Kara formation (i.e., the uniaxial confined stress (UCS) and Young's modulus) from Schmidt hammer rebound. The model performance was then compared to published empirical correlations and proved to be very accurate with near perfect predictions. Our model uses data from the Williston basin and therefore would be more suitable and perform much better on data from the same basin than the existing empirical relationships.

INTRODUCTION

The Inyan Kara formation in the Williston basin has gained a lot of interest in the recent years given the rising Drilling problems caused by the saltwater disposal activity in this formation (Basu et al., 2019) and the interest in this formation as a potential CO2 storage formation. However, this formation is a saline aquifer located at an average depth ranging between 4000 to 6000 feet with no potential hydrocarbon resources. Therefore, wireline logs and core data in this formation are very scarce (Basu et al., 2020) and this is the primary motivation for this study which aims to generate a machine learning model that correlates the Schmidt hammer rebound to the young's modulus and unconfined compressive strength of the different lithologies in this formation which are parameters usually measured through destructive laboratory tests. Given the importance of the mechanical properties of the rocks for geomechanical modeling (Chellal et al., 2022) as it relates to CO2 geological storage, wellbore stability and other problems related to saltwater disposal. This highlights the importance of finding a machine learning model that rely on non-destructive testing methods like the Schmidt hammer rebound to estimate the deformability and strength of the rock defined by young's modulus (YM) and unconfined compressive strength (UCS) (Malki et al., 2023).
Blast Movement Simulation Through a Hybrid Approach of Continuum, Discontinuum, and Machine Learning Modeling
Authors: Fu Wei , Furtney Jason , Valencia Jorge
Published: September 2023

Estimating and optimizing rock movement during blasting is important to prevent unnecessary material handling, reduce ore loss and dilution, and minimize environmental footprint. It has been challenging and computationally burdensome to model the whole dynamic process because rock blasting consists of a complex process that generally involves explosive detonation, gas expansion, stress wave propagation, rock fragmentation and throw, and muckpile formation. In this regard, we propose a hybrid approach that captures the first-order impacts on the rock movement due to blasting while achieving accelerated simulation. Specifically, a small-scale continuum model is established to represent an annulus of rock, with explosive in the center and gas pressure resulting from the detonation applied to the borehole surface, which reduces as the borehole deforms. The continuum model simulates the early-stage, near-field rock blasting process and forms a synthetic dataset based on realistic explosive data to train a machine learning model. Key parameters, such as expanded hole diameter, burden velocity, and time-dependent gas pressure, are readily obtained from the constructed machine learning model. Informed by the machine learning model, the subsequent discontinuum model simulates the dynamic rock movement and predicts the muckpile formation in the far field using the rolling resistance contact model. Our results demonstrate the efficacy of the proposed approach to capture the key physics of blast-induced rock movement and realize accelerated blast design optimization aided by machine learning.

INTRODUCTION

Rock blasting is a highly effective technique employed for fracturing and moving rock mass with extensive applications in various fields such as mining, quarrying, tunneling, and civil engineering industries. The understanding of rock behaviors during blasting is critical for optimizing blasting design, reducing material loss and/or dilution, as well as minimizing environmental impact and safety hazards. While it is difficult to quantify rock blasting experimentally, numerical simulation approaches have been developed over the years to model the process. However, simulating rock blasting is still a challenging and computationally demanding task. One of the main challenges lies in the complex physical processes that occur during blasting, including non-ideal detonation, near-field rock crushing, fracturing, vibration, ore/waste movement, and muckpile formation. Simulating rock blasting movement is further complicated by the intrinsic heterogeneity of rock materials and variability in blasting conditions, which result in highly nonlinear and discontinuous behaviors. Moreover, the wide range of length and time scales involved in these sub-processes presents a significant computational burden.
Joule Heating of Brine Saturated Berea Sandstone: Observations from DC Electric Current
Authors: Smalls P. T. , Villamor-Lora R. , Germaine J. T. , Einstein H. H.
Published: September 2023

High-voltage electrical current can be utilized to increase rock permeability and can be a sustainable alternative to decrease water consumption associated with hydraulic fracturing. During previous applications of this technique, ion carriers, mainly brine water, evaporated as temperature increased during electrical resistive (joule) heating of the reservoir, limiting effectiveness of the technique. Understanding how electrical conductivity evolves as a function of applied electrical current is fundamental for developing methods to overcome previous limitations of the technique. In this study, we developed a first-of-its kind triaxial cell that allows one to apply electrical current, with temperature and pore pressure data collected during the joule heating process of a Berea Sandstone rock specimen. We investigated the relationships between pore fluid composition, pore pressure, and electrical conductivity evolution. The relationships between pore fluid composition, and joule heating evolution under variable electrical energy inputs are important to understand for analyzing the long-term effectiveness of electrical rock fracturing.

INTRODUCTION

Waterless permeability enhancement techniques including mechanical, gaseous, and electrical based methods have been previously investigated to address the environmental concerns associated with hydraulic fracturing (e.g., Gandossi 2013, Kumar et. al, 2017, Wang et. al, 2016). However, widespread adoption of these techniques has stalled due to limitations in stimulated reservoir volume, and environmental safety concerns associated with the exposure of hazardous gases as a fracturing fluid. Alternatively, electrical resistive heating has proven effective at stimulating petroleum reservoirs to increase production (e.g., Elder et. al, 1957, Rehman and Meribout, 2012).

Waterless permeability enhancement techniques including mechanical, gaseous, and electrical based methods have been previously investigated to address the environmental concerns associated with hydraulic fracturing (e.g., Gandossi 2013, Kumar et. al, 2017, Wang et. al, 2016). However, widespread adoption of these techniques has stalled due to limitations in stimulated reservoir volume, and environmental safety concerns associated with the exposure of hazardous gases as a fracturing fluid. Alternatively, electrical resistive heating has proven effective at stimulating petroleum reservoirs to increase production (e.g., Elder et. al, 1957, Rehman and Meribout, 2012).
Production of Ceramic from Sulfidic Mine Tailings and Investigation of Fracture Toughness Under Mode I Loading
Authors: Shabani F. , Asadizadeh M. , Hedayat A. , Tunstall L. , Gorman B. P. , Taboada Neira M. , Vega González J. A. , Verá Alvarado J. W.
Published: September 2023

Mine tailings (MTs) are the waste of mining operations after the valuable metals have been extracted. Given the significant quantities produced globally, the deposition of MTs causes problems including occupation of large areas of land and environmental contamination by toxic leachates. The production of sustainable construction materials from MTs is an environmentally friendly solution to reduce the consumption of natural resources and decrease their adverse impacts on the environment. This study investigates the feasibility of using sulfidic MTs in the production of ceramics. A targeted physical, mineralogical, and chemical characterization of the tailings resulted in the development of a production process that involved grinding the raw tailings, mixing with binders, pressing circular specimens, and then sintering. The properties of sintered ceramics, including crystalline phase, density, water absorption, and compressive strength, were investigated. The mode I fracture toughness of the ceramics was assessed by subjecting a notched semi-circular bending (NSCB) specimen to three-point bending loading. The full-field strains on the surface of the specimens were measured using Digital Image Correlation (DIC) technique, and as a result mode I fracture toughness of ceramics and crack propagation from the existing notch were successfully evaluated.

INTRODUCTION

The disposal of vast amounts of MTs is considered one of the most significant environmental concerns in the mining industry. The presence of contaminated materials after extracting valuable metals such as gold, silver, and copper can lead to harmful environmental consequences. MTs occupy an extensive area of land in the form of mud-like material in tailing ponds or behind storage dams (Barrie et al., 2015; Kossoff et al., 2014). Exposure of sulfide minerals to water and air typically leads to acid mine drainage which is a widespread environmental hazard resulting from seepage and dam failure. This process can impact groundwater and surface water leading to high levels of iron, aluminum, metals, and sulfates (Kinnunen et al., 2018; Nordstrom, 1999). Over the past few years, a number of researchers studied the potential risks to human health and the harm caused by soils that have been contaminated with heavy metal mine tailings (Ngole-Jeme and Fantke, 2017; Ogola et al., 2002; Olobatoke and Mathuthu, 2016).
Investigation of Mode II Fracture Behavior of Alkali-Activated Mine Tailings
Authors: Asadizadeh M. , Hedayat A. , Tunstall L. , Taboada Neira M. , Vega González J. A. , Verá Alvarado J. W.
Published: September 2023

Reuse of mine tailings (MTs) rich in aluminum oxide and silicon dioxide to produce a geopolymer using an alkali activator is a sustainable approach to reduce the MTs’ environmental hazard. The fracturing behavior of mine tailing-based alkali activated materials under mode II loading has been largely unexplored. In this study, the mode II fracture tests have been adopted to examine the double-edge notched Brazilian disk (DNBD) geopolymer specimens under diametral loading. A mixture of MTS (85% wt.), class F fly ash (FA) (15% wt.), and 10 M NaOH solution with solid/liquid ratio of 14% was prepared, and using a cylindrical mold, specimens were cast and then cured at 70 °C. Mode II fracture toughness, the evolution of the crack tip opening and sliding displacement and the shear and minimum principal strain behavior were examined through strain mapping using the Digital Image Correlation (DIC) technique. The results showed that although DNBD is intended to provide pure mode II loading, mixed mode fracturing was observed, as there was still some crack surface opening. The study highlights the need for further investigation to fully understand the nature of mixed-mode fracture behavior in DNBD specimens and its implications for material characterization.

With the rise in demand for mineral excavation and processing, significant quantities of mine tailings (MTs) are produced annually around the world. MTs are the waste rocks that are left over after the extraction of valuable metals has been completed during the mineral processing. As a result, there is a growing concern on how to manage the increasing amounts of MTs that are generated, and how to utilize them effectively. Based on the different phases, MTs can be stored either in impounding lakes for slurries or waste piles for solids (Kiventerä et al., 2018). Given their abundance and potential impact on the environment, it is important to explore ways to reuse these materials. MTs that contain sufficient quantities of aluminosilicates can be efficiently transformed into sustainable building materials by subjecting them to the process of alkaline activation and geopolymerization. The geopolymerization process creates a strong and durable material that can be used in various construction applications, including the manufacturing of bricks, tiles, and concrete (Davidovits, 2020; Muñoz Velasco et al., 2014; Provis & Van Deventer, 2009). Therefore, the utilization of MTs as a resource for construction materials can offer economic and environmental advantages (Singh et al., 2015; Zhang, Hedayat, Bolaños Sosa, Huamani Bernal, et al., 2021; Zhang, Hedayat, Han, et al., 2022; Zhang, Hedayat, Perera-Mercado, et al., 2022).
An Optimized Deep Neural Network for Rockburst Damage Potential Modelling
Authors: Toksanbayev N. K. , Adoko A. C.
Published: September 2023

Managing ground prone to rockburst is challenging, especially in seismically active underground mines. Over the past few decades, numerous studies have been conducted on predicting rockburst damage potential. However, in most cases, only fair model performance was achieved due to the complex nature of rockburst as a seismic event and the non-linearity of data. To overcome these limitations, this paper presents a more reliable model for predicting rockburst damage potential (RDP). An Artificial Neural Network was established, and its parameters were optimized using the Adam optimizer. Rockburst data consisting of 254 case histories were compiled and used to model the RDP scale. The dataset was divided into two parts: a training set, which accounted for 80% of the dataset, and a separate test set, which accounted for the remaining 20%. Cross-validation technique was applied to the training set to avoid overfitting. The input parameters for the model included the capacity of the ground support system, stress conditions, presence of geological structure, excavation span, and peak particle velocity. Several performance indices were used to evaluate the model, and the overall results indicate good performance. In conclusion, this study could help engineers adequately assess rockburst damage in seismically active mines.

INTRODUCTION

Rockburst refers to the damage that occurs on rock excavation surfaces as a result of a seismic event (Ortlepp and Stacey, 1994). It is characterized by a sudden release of strain energy stored within a specific volume of rock (Kaiser and Cai, 2012). Rockbursts are known for their unpredictable and violent nature, representing a significant threat to workers’ safety, mining productivity, and operational costs. Rockbursts and mine seismicity are responsible for a large number of accidents and casualties in many parts of the world every year, as reported in Europe (Ptáček, 2017; Heib, 2018), China (Cai, 2016; Jian-Po Liu, 2018; Linming Dou, 2018; Xia-Ting Feng, 2018), India (Panthi, 2018), South Africa (Aswegen, 2018), and Canada (Leveille et al., 2017; Simser, 2019). Furthermore, with the depletion of near-surface mineral resources caused by the rising demand for minerals, there is a shift towards exploiting deeper deposits, often in high-stress and unfavorable geo-engineering conditions. This results in an increased likelihood of rockburst incidents and makes mining-induced seismic activity a significant concern for the mining sector. It is, thus, evident that the ability to forecast and manage rockburst occurrences is becoming increasingly important.
Alternation Injection Induced Thermal Performance of a Heterogeneous Fracture in Geothermal Reservoirs
Authors: Chen Yuedu , Liang Weiguo
Published: September 2023

The continuous and alternation injection-production operation modes through three injection wells and three production wells towards the single fracture was considered numerically to evaluate its effect on flow patterns and thermal performance, including aperture evolution, flow rates, production temperature. The anisotropic fracture aperture distributions studied were generated follow a log-normal distribution. The results show that, when fluid is injected into a fracture zone, the local fracture permeability will be enhanced, which in turn promotes the migration of fluid along the fracture. Initial heterogeneous fracture aperture attracts more fluid and promotes directional development of the fracture aperture during the thermal extraction process. The continuous injection is associated with a more pronounced directional aperture increase within the heterogeneous fracture, which generally exacerbates flow channeling and causes decreases in production temperature with the injection time. By contrast, the alternation operation avoiding the formation of concentrated channeling flow and effectively promote fluid migration across the entire fracture surface and achieve a larger heat exchange area compared to continuous operation. The average of the temperature and production heat of the three production wells during alternation operation is found to be overall larger than that of the continuous operation. The results of this study suggest that alternation operation through multi-wells is helpful to result in favorable thermal performance.

INTRODUCTION

Geothermal energy is widely regarded as a sustainable and fully renewable energy(Tester et al. 2006). The efficient extraction of thermal energy from subsurface geothermal reservoirs necessitates the creation or access of an interconnected fracture system, often achieved through hydraulic fracturing or shearing(Park et al. 2020). The fluid circulation within the fractures or faults, which is heated upon contact with hot rocks, carries the heat to the surface(Detournay et al. 2022). The flow pattern and evolution of the fluid within individual fractures and the resulting heat exchange between the fluid and the surrounding rock are key factors in heat production(Guo et al. 2016). Understanding and optimizing these processes are crucial for efficient and sustainable geothermal energy production.
Innovative Approach for Monitoring Underground Excavations at San Xavier Underground Mine Laboratory
Authors: Akbulut Nilufer B. , Anani Angelina , Brown Leonard D. , Wellman Edward C.
Published: September 2023

Assessing and making decisions in underground mines is crucial and is difficult due to the harsh environment and the limitation of accessibility. Monitoring plays an important role in assessing ground conditions to ensure safety and efficiency. Through consistent monitoring, a safe interoperable underground mine can be achieved, but to ensure coherent and valid monitoring, there are factors that need to be considered. The approach taken for monitoring with technologies used in it can highly impact the safety, productivity, and understanding of ground conditions. Visualizations designed with principles of Human-Computer Interaction (HCI), can improve knowledge, and aid situational awareness. Focusing on monitoring systems and interfaces that are user-friendly and reliable can help improve overall underground conditions. This paper proposes a monitoring framework that uses desktop and Virtual Reality (VR) to display rock movement in the San Xavier (SX) Underground Mine Laboratory through a digital twin.

INTRODUCTION

Continuous monitoring is required to enhance assessment and situational awareness (SA) in engineering projects such as mining. Monitoring creates a safer workplace, ensuring efficient and continuous production that meets production and profit goals. An optimal monitoring system for large-scale projects would be a system understood by different subject matter experts with varying levels of expertise. Continuous and efficient monitoring plays a foundational role in harsh and uncertain underground mine conditions. The data obtained from monitoring the rock mass in underground mine operations improves decision-making process, enhances the understanding of the current state of the mine, and helps make predictions. With the overwhelming flow of data, there is a higher possibility of having false positives and uninformative data representation, leading to serious cognitive burden (Zhou et al., 2017). The display of data and information and monitoring network design is crucial to overcoming cognitive burden. A monitoring system that emphasizes user-friendly methods, such as visual analytics (VA), would help engineers and workers gain insight from large and complex data sets resulting in enhanced overall SA (Zhou et al., 2017). Having a monitoring system that considers the display of information at an underground mine could secure the safety of the workers and minimize risks, help to plan better designs, and evaluate current designs, and improve the advancement at the mine.
Numerical Modelling of the Influence of Tidal Stresses on Qualitative Fracture Patterns on the Surface of Europa
Authors: Walding J. C. , Paluszny A. , Zimmerman R. W.
Published: September 2023

The ice crust of Jupiter's Galilean satellite Europa exhibits a number of large-scale lineae features, as well as numerous regions with smaller scale lineae patterns. In this work, a three-dimensional finite-element simulator is used to model lineae as fractures in the crust that nucleate, grow, and interact. The medium is assumed to be isotropic and linearly elastic. Fractures are assumed to grow primarily in tension due to tidal stresses in the ice crust, and a damage criterion is used to model the weakening of the ice matrix that occurs concurrently with fracturing. The growth of multiple fractures is modelled geometrically as a function of multi-modal stress intensity factors computed at the fracture tips. The tidal forces that drive this fracturing process are computed according to the model of Wahr et al. (2009), and fracturing is evaluated over multi-scale periods from days to millions of years. Fracture nucleation and growth are modelled within the span of the satellite, with emphasis on characterizing the fracture patterns in the equatorial region. Multiple three-dimensional non-planar fractures are seen to grow and interact within each region. The simulated patterns are qualitatively compared against images obtained by NASA's Galileo mission.

INTRODUCTION

Europa is the fourth largest Galilean moon of Jupiter; with a radius of 1560 km (Nimmo et al., 2007), and is the sixth closest to its parent planet. It has a rocky core that is entirely surrounded by an ice shell, which is estimated to be between 1 and 30 km thick (Billings and Kattenhorn, 2005), where the lower estimates arise from mechanical flexure analysis (Figueredo et al., 2002; Nimmo et al., 2007), and the higher estimates arise from thermodynamic analysis (Hussmann et al., 2002; McKinnon, 1999; Ojakangas and Stevenson, 1989). Estimates based on impact cratering tend to lie between these two bounds (Greeley et al., 1998; Moore et al., 1998; Schenk, 2002). Encased between the silicate core and the ice shell is thought to be a vast liquid water ocean, approximately 100 km thick (Pappalardo et al., 1999). This ocean, and therefore Europa as a whole, is the object of great scientific curiosity, due to its viability as a habitat for extra-terrestrial life (Schulze-Makuch and Irwin, 2000; Kargel et al., 2000).
In-Situ X-Ray Measurements of Grain Stress and Strain During Uniaxial Compaction of Miniature Sandstone Samples
Authors: Hurley R. C. , Shahin G.
Published: September 2023

Laboratory rock deformation has been extensively studied using in-situ optical and X-ray imaging and acoustic emissions (AE) measurements. These measurements have revealed rich kinematics across scales during sandstone compaction, from grain-scale breakage to sample-scale shear and compaction bands. Nevertheless, much progress remains in understanding the connection between rock deformation and grain-scale stress evolution before and after yielding and during the onset and progression of sample-scale strain localization. Such an understanding may offer opportunities for new mechanism-based constitutive models and estimation of grain-scale properties such as intra- and inter-granular bond strength. In this work, we describe the first-known simultaneous application of in-situ X-ray tomography and 3D X-ray diffraction to make strain and stress measurements in miniature samples of Nugget and Berea sandstones. This data provides a first quantification of grain-scale stress heterogeneity, grain-scale and inter-granular bond strength, and larger-scale stress heterogeneity during sandstone compaction. We discuss challenges in X- ray tomography and diffraction analyses for sandstones, which are related to challenges in identification of individual grains in tomographic images featuring minimal contrast at grain boundaries and challenges in performing diffraction microscopy from non-ideal diffraction spots generated by natural quartz crystals. We propose methods for examining the strength of inter-granular bonds and relating AE activity to stress fluctuations using our experimental data.

INTRODUCTION

Sandstone accommodates macroscopic deformation by a combination of microscopic mechanisms including cement bridge breakage, Hertzian particle fractures, particle crushing and pore collapse, and grain rearrangements (Paterson & Wong, 2005; Wong & Baud, 2012). Heterogeneous structures emerge at all length scales during sandstone compaction – from the contact-scale through cement-bridge breakage and chipping, to the grain-scale through breakage and pulverization, to the bulk-scale through shear and compaction band development. The evolution of these structures as a function of microscopic and macroscopic stress states and evolution is a key pursuit of rock mechanics. Success in this pursuit may enable development of robust mechanism-based constitutive models and progress in evaluating long standing questions related to associativity and other aspects of plasticity laws for rocks (Menéndez et al., 1996; Tengattini et al., 2014; Wong et al., 1997).
Shales: From the Atomic Scale to the Rock-Mass Scale
Authors: Rodriguez-Hernandez C. D. , Liu M. , Volkova E. , Yan B. , Turkiyyah G. , Santamarina J. C.
Published: September 2023

Fine-grained sediments, mudrocks and shales have unique fabric and pore topology that reflect their mineral composition and formation history. Atomic-scale clay-clay electrical interactions coexist with the micron-scale mechanical interactions between silicate and carbonate grains, clay tactoids and organic matter; layering adds cm-scale vertical heterogeneity. The resulting strata define the performance of km-scale natural and engineering systems including oil and gas reservoirs and the long-term geological storage of CO2 and nuclear waste. This study presents the building blocks and physical evidence that support a new multi-scale numerical simulation approach for fine-grained sediments, mudrocks and shales. Atomic-scale studies show the effect of isomorphic substitution and adsorbed water molecules on clay tactoid stiffness. Pore-scale analyses based on SEM images reveal spherical pores in organic matter and elongated/aligned pores bound by clay tactoids. Particle-scale simulations capture fabric evolution including tactoid alignment facilitated by organic matter deformation to accommodate to the evolving mineral fabric. The resulting tactoid and organic matter alignment gives rise to shale fissility.

INTRODUCTION

Fine-grained sediments develop unique fabrics related to sedimentation environment and mineralogical composition. Eventually, porosity decreases with depth while diagenetic processes overprint new characteristics as fine-grained sediments become mudrocks and shales. Their ensuing hydro-thermo-chemo-mechanical properties affect the performance of near-surface infrastructures (e.g., foundations, pavements, tunnels), hydraulic fracturing and shale gas recovery (Speight, 2013), and the seal capacity for CO2 geological storage (Kang et al., 2011; Heller and Zoback, 2014; Espinoza and Santamarina, 2017). Despite the economic and social importance of these formations, the structure of mudrocks and shales remains poorly understood in part due to their complex topology, associated heterogeneity, anisotropy and wide range of scales (Arif et al., 2021).

Previous analytical and numerical studies focused on atomic-scale interactions (molecular dynamics – Liu et al., 2015; Han et al., 2019; Faisal et al., 2021, density functional theory – Zartman et al., 2010), particle-level analyses (discrete elements – Anandarajah, 2000; Yao and Anandarajah, 2003; Pagano et al., 2020; de Bono and McDowell, 2022) and macro-scale constitutive models (Schofield and Wroth, 1968; Sanchez et al., 2005) to account for the effect of scale in fine-grained sediments.
Pengaruh Gaya Hidup Konsumtif Dan Hedonisme Terhadap Keputusan Konsumen Dalam Pembelian Barang Di Shopee Perspektif Ekonomi Islam
Authors: Cahyani Anisa Binar
Published: September 2023

The purpose of this study was to determine the effect of a consumptive lifestyle and hedonism on consumer decisions in purchasing goods at shopee according to an Islamic economic perspective. The data used is primary data. Furthermore, the data collection technique used in this study was distributing questionnaires to respondents who used the Google form to collect data. In this study the researchers used the t test method and coefficient test with the help of the smart pls program version 3. Based on the results of the research the R² value lies at 0 R² 1, an R² value close to one which means the model is getting better. Meanwhile, the value of R² which is zero means that there is no relationship between the dependent variable and the explanatory variable. From the table where R² 1 with a value of 0 1,000 1, this means that the variance of the consumptive lifestyle and hedonism is able to explain the variance of consumer decisions by 100%. Keywords : Consumptive Lifestyle, Hedonism, and Consumer Decisions
Mehr Fokus auf die Strukturen. Wie Medien verantwortungsvoll(er) über die Gewalt gegen Frauen berichten können
Authors: Meltzer Christine E.
Published: September 2023

Die Berichterstattung über Gewalt gegen Frauen in den Medien kann eine wichtige Rolle bei der Sensibilisierung für dieses gesellschaftliche Problem und bei der Suche nach Lösungen spielen. Vor diesem Hintergrund greift der vorliegende Beitrag Leitlinien und Empfehlungen auf und entwickelt diese schrittweise weiter. Dadurch werden neue praxisnahe Impulse erarbeitet, die bei der Frage helfen, wie Medien verantwortungsvoll über Gewalt gegen Frauen berichten können. Die am häufigsten genannten Aspekte sind eine sensible Sprache, die Einordnung von Gewalt als alltägliches und strukturelles Problem, Hinweise auf Hilfsreinrichtungen sowie die Thematisierung marginalisierter Gruppen. Diese werden in Bezug zur aktuellen medi- alen Berichterstattung in Deutschland gesetzt.
Magnetic Resonance Spectroscopy Findings of Intracranial Chondroma and Chondrosarcoma with a Non-skull Base Origin: A Report of Two Cases
Authors: Amanpour-Gharaei Behzad , Haghshenas Bilehsavar Shirin , Pour-Rashidi Ahmad , Izanlou Mohsen , Bastanipour Yasaman , Hashemi Hassan , Oghabian Mohammad Ali , Nazar Elham , Raminfard Samira
Published: September 2023

Introduction: Intracranial chondroma and chondrosarcoma are very rare tumors that mainly originate from the base of the skull. Advanced neuroimaging studies, including magnetic resonance spectroscopy (MRS), play a pivotal role in both tumor diagnosis and presurgical planning. Case Presentation: We present two cases of intracranial cartilaginous tumors, including a chondroma and a chondrosarcoma, both of which presented with severe headaches. Due to inconclusive conventional MRI and MRS results, they were both primarily diagnosed as intra-axial brain tumors. However, pathological reports later confirmed the diagnosis of a chondroma and a chondrosarcoma. Conclusion: Based on the present findings, the use of advanced neuroimaging techniques, such as MRS, may improve diagnostic accuracy. We believe that MRS can play a significant role in the surgical planning of similar cases. Also, reporting rare cases worldwide can contribute to the improvement of radiographic diagnosis.
Anàlisi i control de cianurs i productes relacionats presents en aigües residuals i dissolucions de processos industrials mitjançant electroforesi capil.lar
Authors:   , Martí i  Gregorio Vicenç
Published: September 2023

Esta tesis consiste en la aplicación de la electroforesis capilar (CE) a la separación y cuantificación de especies cianuradas y al estudio del comportamiento de estas especies y de su destino final. Como material de estudio se han seleccionado distintos procesos industriales (lixiviación de minerales y arenas auriferas, disoluciones de proceso en industrias de recubrimientos electrolíticos, lixiviación intensiva en autoclave de convertidores de automóvil) donde los cianuros tienen aplicación.

En la primera parte de la tesis se ha realizado un estudio detallado de las características de la técnica CE, y posteriormente se ha optimizado una metodología para aplicarla a los distintos problemas que se recogen en el resto de la memoria.

La segunda parte de la tesis se ha dedicado a la aplicación de la ce al estudio de la lixiviación con NaCN de los metales preciosos y estratégicos presentes en minerales auriferos (Au, Ag) y en convertidores de automóviles (PT, PD, RH), obteniendo finalmente un método analítico capaz de ser utilizado para el seguimiento de este tipo de procesos.

 En la tercera parte de la tesis se ha realizado la determinación del cianuro libre, del débilmente ligado y del total en aguas procedentes de la industria de los recubrimientos electrolíticos y en disoluciones de cianuros oxidadas con hipoclorito, que es el método mas extendido para tratar las aguas industriales. Para analizar estas formas de cianuros, se han planteado dos soluciones, basadas en la detección indirecta y en la derivatización.

La problemática de la detección del cianuro libre (CN- y HCN (aq)) y de especies relacionadas (CNO-, SCN-, NO3, CI-, SO42- y CIO-) resuelto con la utilización de la fluorescencia indirecta con un detector prototipo con fuente láser.

La determinación de cianuros en muestras reales de disoluciones de recubrimientos electrolíticos se ha conseguido mediante su derivatizacion a NI(CN)42- utilizando una disolución de NI(II)-NH3.
Study of nanocomposites prepared from polyamides and biodegradable polyesters and poly(ester amide)s
Authors:   , Morales Gámez Laura Teresa
Published: September 2023

Polymer clay nanocomposites of polyamides and biodegradable polymers with three kinds of organomodified clays were prepared by different techniques (in situ polymerization, solution casting, and melt mixing). The polymers used in this
research were nylons 56, 65 and 47 and the biodegradable polymers: poly (glycolic acid-alt-6-hydrohexanoic acid) and
poly(glycolic acid-alt-6-aminohexanoic acid). The development of biodegradable nanocomposites with improved or modified material properties is an interesting topic since these new materials are expected to replace already existing biodegradable
and non-biodegradable commodity plastics in some specific applications.This project aims to study the influence of clay particles incorporated in a polymer matrix on the crystallization processes, the study of the in situ polymerization kinetics of
mixtures of clays and monomers of biodegradable polymers, as well as the influence of nanoparticles on the thermal behavior and morphologic parameters.
Even-odd, and odd-even polyamides were chosen to study the Brill transition and to prepare nanocomposites with organomodified clays. These polyamides have a peculiar structure where hydrogen bonds are established along two
different directions. X-ray diffraction as well as SAXS-WAXD synchrotron experiments were employed to study the structural changes induced by temperature, during heating and cooling. Different organomodified clays were used to prepare nanocomposites, which final structure was found to be dependent on the preparation method.
Nanocomposites derived from biodegradable polymers were characterized by means of X-ray diffraction and transmission electron microscopy. Morphological studies showed that the extent of clay dispersion depended on the clay type and on the preparation technique. Hence, exfoliated and intercalated nanocomposites could be obtained. The final nanocomposite structure was found to have a great influence on both cold and hot crystallization processes. Hence, the crystallization rate increased and decreased with respect to the neat polymer when intercalated and exfoliated structures were respectively obtained. The kinetics of the polymerization process was also studied by means of FTIR and SAXS-WAXD. The results
indicate that the presence of the organomodified clay had a remarkable effect on the kinetic parameters.
Contribució a l'estudi de la protecció contra incendis en instal·lacions de procés
Authors:   , Planas Cuchi Eulàlia
Published: September 2023

Esta tesis se ha estructurado en cuatro partes principales: 1) Introducción. Se ha hecho un repaso de la bibliografía existente referente a incendios de charcos de líquido y equipo sujeto a la acción directa de la llama. Se ha realizado también un análisis histórico basado en incendios. 2) Experimentación. Se describe la instalación experimental utilizada para llevar a cabo experimentos a gran escala (charcos de 4 y 12 m2 bajo un depósito de 3m de longitud y 1’2m de diámetro)3) Análisis de los resultados. Se ha analizado la reproducibilidad de las pruebas, el calor total y de convección emitidos, y la evolución de las temperaturas del depósito durante el estado transitorio. Se ha definido un parámetro llamado “Factor de obstaculización” , para cuantificar el efecto que un obstáculo produce sobre el calor total emitido.4) Modelización. Se ha desarrollado una modelización para calcular la medida de la llama en la altura y tiempo. Se ha propuesto un modelo matemático que permite determinar la radiación incidente sobre la superficie del depósito, así como la temperatura alcanzada por este.
Penerapan Pendekatan Rebt (Rational Emotif Behavior Therapy) Dalam Meningkatkan Rasa Percaya Diri Siswa Di SMK Negeri 1 Tomohon Melalui Konseling Individu
Authors: Soreh Frengky , Mambu Melky , Ginting Clara , Sahabat Eugenia , Pontoh Injilia , Dongkilat Meyvi , Kasenda Rinna Yunita , Wantah Mario Erick
Published: September 2023

Rasa percaya diri sangatlah membantu bagi semua Individu, selain dapat berinteraksi dengan lebih mudah, percaya diri juga dapat membantu individu untuk dapat berbaur dengan hal yang berkaitan pendidikan. Percaya diri yang rendah dapat mempengaruhi individu dalam mengungkapkan perasaan atau hal yang ingin disampaikan, sering merasa malu karena takut gagal dalam berbagai hal. Contohnya takut gagal sebelum mencoba dan merasa malu memberikan pendapat. Peran guru dalam membimbing dan membantu anak dalam memenuhi tugas dan perkembangan anak agar terpenuhi. Dalam memenuhi tugas dan perkembangan anak yang kurang percaya diri maka perlunya guru bimbingan konseling dalam menangani anak dan membantu untuk meningkatkan rasa kepercayaan anak. Salah satu layanan dalam membangaun rasa percaya diri anak yaitu menggunakan teknik REBT atau (Rational Emotive Behavior Theraphy ) dengan menerapkan layanan konseling individu.