Search Results (766)

The irradiation of atomic oxygen (AO) severely restricts the application of polymeric lubricating coatings in low Earth orbit (LEO). Herein, octa- and mono-amino polyhedral oligomeric silsesquioxanes (POSSs) were chemically bonded onto polyimide/molybdenum disulfide (PI/MoS₂) composite coatings with a gradient structure based on Si density. The gradient coatings presented better wear resistance under different loads; notably, the wear rate decreased by 83.5%. Additionally, the effects of AO exposure on the surface morphologies, chemical structure, and tribological properties of the gradient coatings were investigated in detail. The results indicated that the mass loss and wear rates under AO irradiation decreased significantly, which can be attributed to the passivated network-like SiO₂ layer that covered the coating surface after AO irradiation. As a result, the addition of POSS significantly improved the tribological properties and AO resistance. Full article

Efficient soil conditioning is critical for controlling the mechanical behavior of sandy muck in earth pressure balance (EPB) shield tunneling. This study investigates the undrained shear response of sand conditioned with slurry, a newly developed bubble–slurry, and foam under vertical stresses of 0–300 kPa, considering different injection ratios and shear rates. Under atmospheric pressure, conditioning reduces both peak and residual shear strengths by more than 90% compared with untreated sand. Foam- and bubble–slurry-conditioned sands show stable strength within 6 h; after 24 h, peak strength increases from 0.39 to 4.67 kPa for foam-conditioned sand but only from 0.67 to 0.84 kPa for bubble–slurry-conditioned sand. Shear strength increases nearly linearly with shear rate, especially for residual strength. Pore-scale mechanisms were interpreted by considering bubble proportion and size, pore-fluid rheology, and surface tension. Rheology governs whether dynamic or viscous resistance dominates at different shear rates, while surface tension influences stress transmission through bubble stability and interparticle lubrication. The void ratio range of e/e_max = 1.00–1.36 was identified as achieving low shear strength and good flowability. Field application in Jinan Metro Line R2 confirmed that combined conditioning (25% foam + 13% slurry) reduced cutterhead torque by about 37% without spewing. Full article

In the construction of large-scale caissons, it is difficult to obtain accurate values of the end resistance. There are also inclination, sand boiling, and other issues. In this study, a simplified calculation model for the broken-line end-bearing capacity was proposed on the basis of the passive extrusion failure theory of foundations. Simplified calculation formulas for the bearing capacity under different soil support conditions were established, considering the impacts of excavation or burial depth on the failure slip surface and bearing capacity of the foundation. In addition, the impacts of different shapes of caisson components on the end resistance were analyzed. On the basis of this analysis, a bearing capacity correction coefficient was introduced that considers three-dimensional spatial effects; the calculation results of the end resistance method deviate from the on-site measured earth pressure values by no more than 10%. The dominant influences of the inclining moment and resisting moment on the caisson’s attitude varied progressively as the caisson continued to sink. In the construction of large-scale caissons, end resistance emerged as the primary factor governing the caisson’s orientation. Accordingly, a “stepped progressive” sinking control method was developed and implemented during the caisson sinking operations for Pier No. 5 of the Changzhou-Taixing Yangtze River Bridge. By actively controlling the width of the supporting soil at the end of the caisson and the burial depth, the verticality of the caisson throughout the construction process remained within 1/150. The verticality of the final sinking of the caisson exceeded 1/2000, and the torsional angle of the final sinking of the caisson was only 0.07°. This achieved the active control of the end resistance of the large caisson, the process of sinking, the attitude during the sinking, and the risk of sand boiling. Full article

This article presents an analysis of the impact of photovoltaic (PV) sources on the effectiveness and selectivity of earth fault protection in a 6 kV industrial distribution network. Simulations were conducted in the ATP-EMTP environment using a model of a generalized, real industrial network with an isolated neutral point. This model was based on data from real-world cases of earth faults with varying resistance. This study’s main objective was to determine how the power generated by PV sources affects the time and spectral waveforms of currents and zero-sequence voltages, in addition to the network’s overall response to disturbances. The results provide a quantitative assessment of the impact of distributed generation on the operational security of industrial power grids and form a basis for developing recommendations for coordinating protection in power systems integrated with renewable energy sources. Full article

The decomposition of silicates in sulfuric acid to extract rare earth elements (REE) is typically characterized by the formation of an amorphous silica layer surrounding the receding crystal that may act as a passivation barrier limiting the rate of mineral dissolution. In this context, sulfuric acid treatment experiments coupled with detailed characterization of the evolution of the decomposition reaction were performed on natural allanite (CaREEAl₂Fe²⁺Si₃O₁₁O[OH]), as well as synthetic neodymium disilicate (Nd₂Si₂O₇), orthosilicate (Ca₂Nd₈(SiO₄)₆O₂), and orthophosphate (NdPO₄) phases in order to investigate if there are key factors, operating on a wide range of silicates, that negatively impact REE recovery. While, as expected, the acid strength is the driver in promoting the decomposition of the orthophosphate, for the silicates investigated, no matter their crystalline structure and chemical resistance, there is a severe passivation mechanism at play in concentrated H₂SO₄. However, in all cases, this effect can be minimized by water dilution, which strongly enhances sulfate-forming cation transfer across the produced amorphous silica layer. Taking into consideration this distinct characteristic of the mode of decomposition of silicates in sulfuric acid should help in defining optimal extraction strategies. Full article

The 6xxx-series Al alloys have been used for decades because of their favorable strength-to-weight ratio, corrosion resistance, and fatigue performance. However, conventional welding techniques often induce localized weakening, as thermal effects modify the microstructure and compromise structural integrity. For nearly 70 years, AA4043 welding wire has been the primary choice for joining 6xxx-series Al alloys. Nevertheless, microstructural and mechanical property mismatches between the base metal and weld region remain key factors contributing to premature failure, while welding-induced defects further increase rupture susceptibility. Microalloying has emerged as an effective strategy for enhancing both the mechanical and thermal properties of aluminum alloys. In this study, rare-earth (RE) elements La and Ce were introduced into the AA4043 system to exploit their grain refining and mechanical strengthening capabilities. In addition, the effects of Sr modification were examined and compared with La-Ce addition. This work aims to elucidate the strengthening mechanisms associated with La-Ce-Ti microalloying in AA4043 welding wire, a topic that has rarely been systematically investigated. With 0.019Ti-0.02La-0.03Ce additions, the modified wire exhibited significant performance improvements, achieving an UTS of 204 MPa and a YS of 191 MPa—representing increases of 10.3% and 18.6%, respectively. Full article

To investigate the performance of horizontally reinforced composite foundations in resisting surface rupture of normal faults, this study designed and conducted a series of physical model tests. A systematic comparative analysis was performed on the fracture resistance of sites with three-layer sand, five-layer sand, and three-layer clay geogrid horizontally reinforced composite foundations under 70° normal fault dislocation. The results indicate that significant changes in earth pressure serve as a precursor indicator of fault rupture, and their evolution process reveals the internal energy accumulation and release mechanism. Increasing the number of geogrid layers significantly enhances the lateral confinement of the foundation, resulting in a narrower macro-rupture zone located farther from the structure in sand sites, and promotes the formation of a step-fault scarp deformation mode at the surface, which is more conducive to structural safety. Under identical reinforcement conditions, the clay site exhibited comprehensively superior fracture resistance compared to the sand site due to the soil cohesion and stronger interfacial interaction with the geogrids, manifested as more significant deviation of the rupture path, and lower microseismic accelerations and structural strains transmitted to the building. Comprehensive analysis confirms that employing geogrid-reinforced composite foundations can effectively guide the surface rupture path and improve the deformation pattern, representing an effective engineering measure for mitigating disaster risk for buildings spanning active faults. Full article

Permanent magnet synchronous machines (PMSMs) are the preferred choice for electric vehicles (EVs), hybrid EVs, and wind turbines because of their high torque density, efficiency, and wide constant-power speed range. Conventional PMSMs rely heavily on rare-earth (RE) permanent magnets like Nd-Fe-B, which offers high remanence and coercivity but comes with high costs, supply chain issues, and environmental concerns. To address these challenges, this paper explores the potential of tetragonal Fe₂Ni₂N, a newly developed RE-free permanent magnet, as a replacement for commercial Nd-Fe-B (N35) in high-performance PMSMs. Fe₂Ni₂N shows a remanent flux density of 1.2 T and coercivity of 0.957 MA/m, closely matching those of commercial N35 magnets. Finite element analysis (FEA) in Ansys Maxwell was performed on both surface-mounted (SPM) and interior-mounted (IPM) PMSMs under EV-representative operating conditions. Results demonstrate that Fe₂Ni₂N-based machines have similar demagnetization resistance, torque, and efficiency to those with N35 magnets, with slight performance advantages at low speeds and nearly identical performance at high speeds. Furthermore, system-level parameters such as DC bus voltage and stator current were analyzed, showing that increased voltage extends the constant torque region while higher current enhances torque output but can slightly reduce efficiency at elevated speeds. These findings confirm that Fe₂Ni₂N is a promising RE-free alternative to Nd-Fe-B for sustainable, high-performance PMSMs. Results show that Fe₂Ni₂N-based machines have similar demagnetization resistance, torque, and efficiency to those with N35 magnets, with slight performance benefits at low speeds and nearly identical results at high speeds. Furthermore, system-level parameters, such as DC bus voltage and stator current, were analyzed. The results show that increased voltage extends the constant-torque region, while higher current enhances torque output but can slightly reduce efficiency at elevated speeds. These findings confirm that Fe₂Ni₂N is a promising RE-free alternative to Nd-Fe-B for sustainable, high-performance PMSMs. Full article

Asymmetric friction, that is, different friction forces resisting sliding in opposing directions, works as a rectifier, transferring the applied oscillations into unidirectional motion. Locomotion of devices based on asymmetric friction is investigated by considering a model system consisting of an asymmetric friction block connected to a symmetric friction block by a spring. The symmetric friction block models the resistance to the movement by the environment. It is found that under harmonic oscillation, the system displays two distinct types of motion: Recurrent Movement (stick-slip-type movement) and Sub-Frictional Movement. The Recurrent Movement occurs when the inertia force is sufficient to overcome the frictional force. In this case, the system with asymmetric friction exhibits unidirectional locomotion, while the system with only symmetric friction oscillates about a fixed point. The Sub-Frictional Movement occurs when the inertia is insufficient to overcome the frictional force. Then the symmetric friction block moves against the asymmetric friction block and sufficiently loads the spring to enable some movement of the system. Thus, motion is generated even when the external forces are below the static friction threshold. These types of motion have been found to exhibit different types of spectral fallout: while the Recurrent Movement produces a typically observed frictional fallout 1/ω, where ω is the frequency, the Sub-Frictional Movement produces a stronger 1/ω² fallout, only observed in the development of an oblique fracture in rocks under compression. This discovery can shed light on mechanisms of rock failure in compression. Understanding of the unidirectional movement induced by asymmetric friction can be instrumental in designing novel locomotion devices that can move in narrow channels or fractures in the Earth’s crust or in extraterrestrial bodies utilising the (renewable) energy of external vibrations. Full article

Gallium nitride (GaN) has emerged as one of the most promising wide-bandgap semiconductors for next-generation space photovoltaics. In contrast to conventional III–V compounds such as GaAs and InP, which are highly efficient under terrestrial conditions but suffer from radiation-induced degradation and thermal instability, GaN offers an exceptional combination of intrinsic material properties ideally suited for harsh orbital environments. Its wide bandgap, high thermal conductivity, and strong chemical stability contribute to superior resistance against high-energy protons, electrons, and atomic oxygen, while minimizing thermal fatigue under repeated cycling between extreme temperatures. Recent progress in epitaxial growth—spanning metal–organic chemical vapor deposition, molecular beam epitaxy, hydride vapor phase epitaxy, and atomic layer deposition—has enabled unprecedented control over film quality, defect densities, and heterointerface sharpness. At the device level, InGaN/GaN heterostructures, multiple quantum wells, and tandem architectures demonstrate outstanding potential for spectrum-tailored solar energy conversion, with modeling studies predicting efficiencies exceeding 40% under AM0 illumination. In this review article, the current state of knowledge on GaN materials and device architectures for space photovoltaics has been summarized, with emphasis placed on recent progress and persisting challenges. Particular focus has been given to defect management, doping strategies, and bandgap engineering approaches, which define the roadmap toward scalable and radiation-hardened GaN-based solar cells. With sustained interdisciplinary advances, GaN is anticipated to complement or even supersede traditional III–V photovoltaics in space, enabling lighter, more durable, and radiation-hard power systems for long-duration missions beyond Earth’s magnetosphere. Full article

In this article, I argue that the climate crisis is a symptom of dissonant eco-subjects and relations that are, in part, produced by Abrahamic religious/spiritual traditions—traditions that function as apparatuses of the ontological rift between human and other-than-human animals. The argument begins by addressing the relation between Abrahamic traditions and apparatuses of the ontological rift. This sets the stage for explicating what is meant by spiritualities of eco-dissonant subjects. To further understand the features of eco-dissonant spiritualities, I turn to the philosophical notion of self-deception and the psychoanalytic notion of weak dissociation, which help explain our resistance to becoming aware of our contributions to the sufferings of other species and the wounding of the Earth, as well as our resistance to change. Full article

Rare-earth oxide (REO) nanoparticles (NPs)—such as cerium (CeO₂), samarium (Sm₂O₃), neodymium (Nd₂O₃), terbium (Tb₄O₇), and praseodymium (Pr₂O₃)—have demonstrated strong antimicrobial activity against multidrug-resistant bacteria. Their effectiveness is attributed to unique physicochemical properties, including oxygen vacancies and redox cycling, which facilitate the generation of reactive oxygen species (ROS) that damage microbial membranes and biomolecules. Additionally, electrostatic interactions with microbial surfaces and sustained ion release contribute to membrane disruption and long-term antimicrobial effects. REOs also inhibit bacterial enzymes, DNA, and protein synthesis, providing broad-spectrum activity against Gram-positive, Gram-negative, and fungal pathogens. However, dose-dependent cytotoxicity to mammalian cells—primarily due to excessive ROS generation—and nanoparticle aggregation in biological media remain challenges. Surface functionalization with polymers, peptides, or metal dopants (e.g., Ag, Zn, and Cu) can mitigate cytotoxicity and enhance selectivity. Scalable and sustainable synthesis remains a challenge due to high synthesis costs and scalability issues in industrial production. Green and biogenic routes using plant or microbial extracts can produce REOs at lower cost and with improved safety. Advanced continuous flow and microwave-assisted synthesis offer improved particle uniformity and production yields. Biomedical applications include antimicrobial coatings, wound dressings, and hybrid nanozyme systems for oxidative disinfection. However, comprehensive and intensive toxicological evaluations, along with regulatory frameworks, are required before clinical deployment. Full article

Coal fly ash (CFA) is a promising secondary resource for rare earth element (REE) recovery. This study characterized CFA using XRF, SEM-EDS, ICP-MS, and XRD, revealing critical REE concentrations of 26.3 ppm (Nd), 4.84 ppm (Dy), 2.89 ppm (Er), 1.69 ppm (Eu), and 0.85 ppm (Tb). REEs are distributed in Al-Si-Mg-Ca-rich aluminosilicates, except Dy, which is associated with Fe-rich phases. Leaching optimization using response surface methodology (RSM) with a central composite design (CCD) identified optimal conditions at 59.5% HCl:40.5% citric acid, 85 °C, and 720 min, achieving recoveries of 94.8% (Dy), 85.2% (Er), 73.1% (Eu), 79.1% (Nd), and 85.7% (Tb). These conditions provided the best balance between recovery, acid use, and selectivity, demonstrating potential scalability for industrial applications. The quadratic model accurately predicted REE recoveries, with accuracies of 95.61% (Dy), 97.76% (Er), 97.30% (Eu), 99.07% (Nd), and 99.17% (Tb). Thermodynamic analysis showed that mineral dissolution influenced REE selectivity, with anorthite (ΔG₃₅₈K = −348.1 kJ·mol⁻¹) dissolving readily, while ankerite (ΔG₃₅₈K = 5.49 × 10⁶ kJ·mol⁻¹) contributed to high selectivity, particularly for Mg. Element selectivity followed Mg > Al > Si > Fe ≥ Ca, indicating Mg- and Al-bearing phases were more susceptible, while Fe- and Ca-bearing minerals remained more resistant under mixed-acid conditions. Full article

This study examines the behavior and control of zero-sequence parameters in IT-type electrical networks under conditions of capacitive insulation asymmetry and complex asymmetric faults on the power receiver side. Existing methods of zero-sequence analysis typically address either symmetrical network conditions or single-phase earth faults in isolation, and they often neglect the combined effects of conductor breakage, transient fault resistance, and capacitive unbalance. To overcome these limitations, this work develops an analytical model based on the general theory of electrical engineering and symmetrical components, enabling a unified description of zero-sequence voltages and currents that incorporates both insulation asymmetry and compound fault scenarios. The model establishes closed-form relationships linking zero-sequence quantities to network parameters, power receiver characteristics, and transient resistances at the fault point. The results demonstrate several previously unreported effects, including a 180° vector shift and nearly 50% reduction in zero-sequence voltage and current magnitudes during simultaneous conductor breakage and earth faults compared with conventional single-phase faults—phenomena that critically influence the correct setting of protection devices. The study further shows that capacitive insulation asymmetry alone may generate zero-sequence voltages sufficient to trigger earth-fault protection regardless of the neutral grounding mode. These findings reveal increased risks of fault escalation, misoperation of existing protection systems, and prolonged unsafe touch voltages. Overall, the derived dependencies provide a new analytical basis for improving the design and coordination of protection systems in IT-type networks. Full article

This article presents the programme for the characterisation of earth mortars stabilised with experimental pozzolanic material from fluid catalytic cracking (FCC). This study aims to establish the optimal ratio for adding pozzolan to stabilise earth mortars. Ash may be used in conservation processes, as it presents suitable pozzolanic properties. Based on the starting premise that its application does not cause chromatic variations in the final mortar and displays resistance to damage from chlorides and extreme temperatures, it can be considered ideal for this purpose. The process of transformation into ash is linked to the production of naphthas and refined petroleum products, where the mineral is a catalyst for the reaction. With use, the mineral tends to shrink, losing the necessary properties for this process. Over the last decade, this process, which is widely used in the petrochemical industry, has generated a volume of waste of up to 3000 tons per day. The amount of waste generated is of interest for its reuse, and a rise is observed in preliminary studies, which confirm that this material is pozzolanic and non-toxic. This offers the possibility of studying this addition to stabilise materials and constructions manufactured with earth. Full article