The coal gasification process yields coarse slag (GFS), a byproduct composed predominantly of amorphous aluminosilicate minerals. GFS, with its low carbon content and its ground powder's demonstrated pozzolanic activity, is a promising supplementary cementitious material (SCM) for use in cement. An investigation into the ion dissolution characteristics, initial hydration kinetics, hydration reaction process, microstructure evolution, and mechanical strength development of GFS-blended cement pastes and mortars was undertaken. Elevated temperatures and heightened alkalinity levels can amplify the pozzolanic activity inherent in GFS powder. Methotrexate The cement's reaction mechanism was impervious to changes in the specific surface area and content of the GFS powder. Crystal nucleation and growth (NG), phase boundary reaction (I), and diffusion reaction (D) constituted the three distinct stages of the hydration process. The enhanced specific surface area of GFS powder might augment the chemical kinetic efficiency within the cement system. A positive relationship exists between the reaction extent of GFS powder and the blended cement's reactivity. Cement's activation and enhancement of late-stage mechanical properties were most prominent when utilizing a low GFS powder content (10%) coupled with its high specific surface area (463 m2/kg). The findings indicate that GFS powder, characterized by its low carbon content, is applicable as a supplementary cementitious material.
Falls have a detrimental impact on the quality of life for senior citizens, underscoring the benefit of fall detection systems, especially for those living alone and incurring injuries. Beyond that, the detection of near falls, or moments of imbalance or stumbling, provides a significant opportunity to prevent the occurrence of a fall. A wearable electronic textile device, designed and engineered for fall and near-fall monitoring, was the central focus of this project, which employed a machine learning algorithm to analyze the gathered data. A significant goal behind this study was crafting a wearable device that individuals would find comfortable and hence, use. A pair of over-socks, each equipped with a unique motion-sensing electronic yarn, were conceived. The trial, including thirteen participants, saw the implementation of over-socks. Three categories of daily activities, namely ADLs, were performed, in addition to three different fall types onto a crash mat, and a single near-fall was also observed. Data from the trail was visually analyzed to find patterns; a machine learning algorithm was then applied for the categorization process. The developed over-socks, augmented by a bidirectional long short-term memory (Bi-LSTM) network, have demonstrated the ability to differentiate between three distinct categories of activities of daily living (ADLs) and three different types of falls, achieving an accuracy of 857%. The system exhibited exceptional accuracy in distinguishing solely between ADLs and falls, with a performance rate of 994%. Lastly, the model's performance in recognizing stumbles (near-falls) along with ADLs and falls achieved an accuracy of 942%. The study additionally concluded that the motion-sensing electronic yarn is required in only one overlying sock.
In recently developed lean duplex stainless steel 2101, oxide inclusions were observed in welded areas following flux-cored arc welding using an E2209T1-1 flux-cored filler metal. These oxide inclusions are directly responsible for the observed variations in the mechanical properties of the welded metal. Therefore, a correlation, requiring verification, has been established between oxide inclusions and mechanical impact toughness. This study, therefore, leveraged scanning electron microscopy and high-resolution transmission electron microscopy to examine the relationship between oxide inclusions and resistance to mechanical shock. Examination of the spherical oxide inclusions within the ferrite matrix phase showed a mix of oxides, with these inclusions situated in close proximity to intragranular austenite. The observed oxide inclusions, resulting from the deoxidation of the filler metal/consumable electrodes, consisted of titanium- and silicon-rich amorphous oxides, MnO (cubic), and TiO2 (orthorhombic/tetragonal). Our study indicated no substantial correlation between the type of oxide inclusion and the amount of energy absorbed, and no cracks were initiated near them.
The stability of the Yangzong tunnel, especially during excavation and long-term maintenance, is strongly influenced by the instantaneous mechanical properties and creep behaviors of the surrounding dolomitic limestone, the primary rock material. Four conventional triaxial compression tests were implemented to ascertain the limestone's instantaneous mechanical behavior and failure mechanisms. Subsequently, the creep behavior of the limestone under multi-stage incremental axial loading was studied, utilizing a state-of-the-art rock mechanics testing system (MTS81504) and confining pressures of 9 MPa and 15 MPa. The results of the investigation disclose the following. The curves of axial, radial, and volumetric strain against stress, under varied confining pressures, share a similar trend. The stress drop after peak load, however, is less pronounced with increasing confining pressure, indicative of a transition from brittle to ductile rock behavior. The confining pressure plays a specific role in managing the cracking deformation present in the pre-peak stage. Besides, the quantities of compaction and dilatancy-related components in the volumetric strain-stress diagrams vary noticeably. Besides the shear-dominated fracture, the failure mode of the dolomitic limestone is also influenced by the confining pressure. With the loading stress reaching the creep threshold stress, the primary and steady-state creep stages arise successively, and an augmented deviatoric stress is directly associated with a larger creep strain. Tertiary creep, followed by creep failure, occurs when the accelerated creep threshold stress is overcome by a greater deviatoric stress. Beyond this, the threshold stresses at a 15 MPa confinement are greater than the values recorded at 9 MPa confinement. This clearly suggests a notable influence of confining pressure on the threshold values, with a higher confining pressure correlating to a larger threshold stress. In the case of the specimen's creep failure, the mode is one of immediate shear-driven fracturing, exhibiting parallels to the failure mode under high confining pressure in a conventional triaxial compression test. By linking a suggested visco-plastic model in series with a Hookean component and a Schiffman body, a multi-element nonlinear creep damage model is established that precisely characterizes the full range of creep behaviors.
Varying concentrations of TiO2-MWCNTs are incorporated within MgZn/TiO2-MWCNTs composites, which are synthesized through a combination of mechanical alloying, a semi-powder metallurgy process, and spark plasma sintering, as investigated in this study. The study of these composites also includes exploring their mechanical, corrosion, and antibacterial attributes. Compared to the MgZn composite material, the MgZn/TiO2-MWCNTs composites demonstrated a notable improvement in both microhardness (79 HV) and compressive strength (269 MPa). Cell culture and viability experiments on the TiO2-MWCNTs nanocomposite demonstrated an increase in osteoblast proliferation and attachment, leading to better biocompatibility. Methotrexate The corrosion resistance of the magnesium-based composite, upon the addition of 10 wt% TiO2-1 wt% MWCNTs, was demonstrably improved, reducing the corrosion rate to roughly 21 millimeters per year. In vitro testing, lasting up to two weeks, demonstrated a slower degradation rate when TiO2-MWCNTs were added to a MgZn matrix alloy. Antibacterial tests on the composite revealed activity against Staphylococcus aureus, characterized by an inhibition zone of 37 mm. Orthopedic fracture fixation devices possess a substantial potential enhancement when incorporating the MgZn/TiO2-MWCNTs composite structure.
Magnesium-based alloys produced using mechanical alloying (MA) are noted for their specific porosity, a fine-grained microstructure, and isotropic properties. Moreover, metallic combinations including magnesium, zinc, calcium, and the esteemed element gold are biocompatible and, thus, appropriate for use in biomedical implants. Selected mechanical properties and structural analysis of Mg63Zn30Ca4Au3 are presented in this paper as part of its evaluation as a potential biodegradable biomaterial. The presented findings encompass X-ray diffraction (XRD), density, scanning electron microscopy (SEM), particle size distribution, Vickers microhardness, and electrochemical characterization via electrochemical impedance spectroscopy (EIS) and potentiodynamic immersion testing. These properties are examined for an alloy developed via mechanical synthesis (13-hour milling) and spark-plasma sintering (SPS) at 350°C, 50 MPa, with a 4-minute hold and varying heating rates. The experimental results show a compressive strength of 216 MPa coupled with a Young's modulus of 2530 MPa. The structure is characterized by MgZn2 and Mg3Au phases, originating from the mechanical synthesis, and Mg7Zn3, the product of the sintering process. While MgZn2 and Mg7Zn3 enhance the corrosion resistance of magnesium-based alloys, the double layer formed upon contact with Ringer's solution proves an ineffective barrier, necessitating further data collection and optimization strategies.
Numerical techniques are commonly used to simulate crack propagation in concrete, a quasi-brittle material, when subjected to monotonic loads. Subsequent research and action are required for a more profound grasp of the fracture behavior when subjected to cyclic loading. Methotrexate Numerical simulations of mixed-mode crack propagation in concrete, specifically using the scaled boundary finite element method (SBFEM), are explored in this study. A cohesive crack approach, integrated with a thermodynamically-based constitutive concrete model, underpins the development of crack propagation. For model verification, two illustrative crack scenarios were simulated under monotonic and alternating stress.