Search Results (820)

To improve the durability of terahertz (THz) electromagnetic shielding materials in atomic oxygen environments relevant to low Earth orbit (LEO), two MXene/para-aramid nanofiber (ANF) composite architectures were designed, including a uniformly blended structure and a sandwich configuration. Ti₃C₂T_x MXene was used as the conductive phase, while ANF served as a protective matrix. Oxygen plasma treatment was employed to simulate atomic oxygen exposure. The results show that the plasma resistance of blended films strongly depends on MXene content. Increasing the MXene fraction enhances conductive network redundancy and reduces conductivity degradation. In contrast, the sandwich-structured film exhibits superior structural stability. The outer ANF layers effectively limit direct plasma–MXene interaction and undergo surface carbonization during plasma exposure, forming an additional diffusion barrier. As a result, the sandwich film maintains stable THz shielding performance, with the average shielding effectiveness increasing from 42.6 dB to 44.9 dB after plasma treatment. These results indicate that structural regulation of the internal conductive network, which limits plasma penetration, is essential for maintaining stable MXene-based THz shielding performance under oxidative plasma conditions. Full article

Sediment-derived turbidity, intensified by anthropogenic activities, is a widespread form of particulate pollution in aquatic ecosystems. Yet, its effects on planktonic crustaceans remain insufficiently quantified across particle types and disturbance regimes. We exposed five species (Daphnia magna, Leptodora kindtii, Eurytemora velox, Thermocyclops crassus, and T. oithonoides) to turbidity generated by red clay, diatomaceous earth (amorphous silica), and bentonite at three substrate loads (0.5, 1.5, and 3 g/100 mL) and three resuspension regimes (1, 12, and 24 disturbances per day) for 72 h. Particle size distributions and turbidity reduction under free sedimentation were measured using NTU and FAU. Survival decreased across all species, with substrate load as the most consistent predictor, while disturbance frequency showed taxon-dependent effects, particularly in D. magna and L. kindtii. Sensitivity differed among taxa, with L. kindtii and E. velox being the least tolerant, whereas cyclopoid copepods (Thermocyclops spp.) were comparatively resistant. Substrate identity also affected responses, with D. magna being particularly sensitive to amorphous silica relative to clay and bentonite. These findings indicate that survival under sediment-derived turbidity depends on both particle properties and exposure regime, suggesting that increasing sediment mobilization may act as an ecological filter shaping plankton communities. Full article

Physical-layer key generation (PLKG) is a technique that produces symmetric encryption keys by exploiting the inherent characteristics of wireless channels. It offers advantages including high physical-layer security, elimination of pre-shared keys, dynamic upgradability, and resistance to quantum attacks, making PLKG a promising security solution for next-generation (6G) networks. However, satellite communication channels exhibit high dynamics and long propagation delays. Characteristics such as large Doppler shifts, short coherence times, and orbital predictability pose severe challenges to PLKG, including reciprocity degradation, low key generation rate (KGR), and susceptibility to channel-prediction attacks. This work proposes a delay-Doppler domain time-hopping key generation scheme (KE-DD-TH) based on Orthogonal Time Frequency Space (OTFS) modulation for high-speed links between Low-Earth-Orbit (LEO)/Medium-Earth-Orbit (MEO) satellites and ground terminals in Ka/Ku bands. The scheme performs non-uniform sampling on the DD domain grid of OTFS symbols using an ephemeris-driven pseudo-random time-hopping sequence generated by cascaded linear feedback shift registers (LFSRs) and a nonlinear matrix transformation. Both legitimate parties estimate the channel only at time-hopping instants and multiply two adjacent estimates to construct an “equivalent channel” matrix, yielding a random source with high entropy, high reciprocity, and low predictability. The eavesdropper’s key disagreement rate (KDR) remains close to 0.5 under all signal-to-noise ratio (SNR) conditions, corresponding to the ideal random-guessing baseline. This indicates that Eve obtains negligible mutual information, i.e., $I(K_A;K_E)\approx 0$. By contrast, the conventional KE-DD scheme allows Eve’s KDR to degrade to 0.014 at 30 dB SNR, indicating near-complete key recovery. The generated keys pass all 12 randomness tests of the NIST SP 800-22 statistical test suite. Full article

NASICON-type Na₃V₂(PO₄)₃ (NVP) is widely regarded as a promising cathode for sodium-ion batteries owing to its robust three-dimensional framework and high operating voltage (~3.4 V vs. Na⁺/Na). However, NVP suffers severe capacity degradation under fast-charging conditions due to its intrinsically low electronic conductivity, which critically impedes its practical deployment. Herein, we systematically investigate the fast-charging failure mechanism of NVP and propose a trace Sm³⁺ doping strategy (x = 0.03) to address this limitation. Undoped NVP retains only 13.5% and 56.62% of its initial capacity after 1000 cycles at 5000 mA g⁻¹ and 1307 cycles at 2000 mA g⁻¹, respectively. Post-cycling scanning electron microscopy (SEM) reveals extensive crack formation and particle pulverization, providing direct morphological evidence for structural failure. To overcome this, Sm³⁺-doped Na₃V_1.97Sm_0.03(PO₄)₃/C (NVPSM) is synthesized via a sol–gel method. X-ray diffraction (XRD) confirms that the NASICON phase is preserved. Raman spectroscopy reveals an improved graphitization degree (I_D/I_G = 0.97 vs. 1.02 for NVP), and X-ray photoelectron spectroscopy (XPS) verifies the V³⁺ oxidation state and the incorporation of Sm³⁺. Electrochemically, NVPSM achieves capacity retentions of 60.3% after 2300 cycles at 5000 mA g⁻¹ and 83.89% after 1436 cycles at 2000 mA g⁻¹. Electrochemical impedance spectroscopy confirms reduced charge-transfer resistance, and post-cycling SEM shows markedly improved structural integrity. These results demonstrate that trace rare-earth doping effectively mitigates fast-charging-induced structural failure in NVP-based cathodes. Full article

The development of resin-regolith composites represents a promising In Situ Resource Utilization (ISRU) strategy for future lunar missions. While unsuitable for primary habitat construction due to the payload cost of transporting polymers from Earth, these composites offer a highly efficient solution for manufacturing non-structural, everyday items (e.g., containers, tools, and plant cultivation pots) directly on the Moon via mold–casting. This approach significantly reduces the volume and mass of pre-formed plastic payloads. In this work, the influence of the particle size distribution of a lunar highland simulant (LHS-1E) on the mechanical properties of epoxy-based composites was systematically investigated for such applications. First, the regolith-to-resin ratio was optimized for castability, establishing a maximum regolith content of 60 wt.%. Then, four different size fractions of the simulant were prepared by sieving (>200 µm, 200–100 µm, 100–50 µm, and <50 µm), and composite samples were cast maintaining this optimal ratio. X-ray microtomography revealed that using larger particles (>200 µm) increased composite porosity, whereas smaller fractions promoted more compact structures. Three-point bending tests showed that intermediate particle sizes (200–100 µm and 100–50 µm) led to enhanced flexural strength, while the smallest particles (<50 µm) decreased mechanical performance, likely due to a lower basalt content in this finer fraction. Finally, ball-on-disk tribological analyses highlighted that composites made with larger particles (>200 µm) exhibited superior wear resistance, whereas particle size had negligible effects on the coefficient of friction. Overall, the results demonstrate that both particle size and mineralogical composition significantly influence the performance of regolith–epoxy composites, providing essential guidelines for the in situ manufacturing of functional, non-structural objects for lunar outposts. Full article

In this work a study about the behavior of nanomaterial-based innovative transparent electrodes is presented, with a special focus on graphene, for space photovoltaic applications, in particular their transparency and the efficiency of the final device. The efficiency of a solar cell is characterized by referring to Power Conversion Efficiency and External/Internal Quantum Efficiency. Starting from the literature results, it is possible to observe that solar cells realized by innovative nanomaterial-based transparent electrodes show promising results in terms of efficiency in the Earth environment. It is known that the space environment is characterized by extreme conditions including high-energy radiation, strong temperature variations and high vacuum, which can damage materials and, consequentially, influence their performances. Among all the properties like transmittance and sheet resistance, which are the main requirements for a good transparent electrode, could change their value and, therefore, influence the efficiency of the solar cell adopting this kind of electrode. In this paper, a theoretical analysis on the effects of high-energy radiation on the transmittance of graphene layers is given, leading to the observation that in the UV frequency range, it shows a sharp fall. Moreover, the effect of temperature varying is studied by an theoretical analysis on the resistivity of the twisted graphene bilayer. It is possible to observe that, in this configuration, the system moves from a superconductor to a metal, according to temperature and twist angle. This represents a starting point to have good efficiency of solar devices in a space environment by keeping high the transparency of their electrodes. Full article

The rational design of electrode architectures is essential for advancing high-performance supercapacitors. In this study, Nd₂O₃ electrodes with controlled structural features were developed via a polyacrylic acid (PAA)-assisted hydrothermal approach. By systematically tuning PAA concentration, the growth mechanism of Nd₂O₃ was effectively regulated, leading to a distinct morphological transition from compact agglomerates to well-defined hierarchical structures. The optimized Nd₂O₃-P2 electrode exhibits a porous and interconnected architecture, providing enhanced electrolyte accessibility and shortened ion diffusion pathways. This structural optimization significantly improves electrochemical performance, delivering a high areal capacitance of 26.889 F/cm² at 10 mA/cm², along with excellent rate capability and reduced internal resistance. Kinetic analysis reveals that charge storage is predominantly governed by diffusion-controlled Faradaic processes, with the optimized structure facilitating rapid ion transport and efficient redox activity. Additionally, the electrode demonstrates excellent cycling durability, retaining 87.08% capacitance over 12,000 cycles. An asymmetric supercapacitor assembled using Nd₂O₃-P2 and activated carbon achieves stable operation up to 1.5 V, delivering good capacitance retention (81.2%) after 7000 cycles. This work highlights the effectiveness of PAA-induced structural tuning and provides a practical strategy for developing advanced rare earth oxide-based electrodes for energy storage applications. Full article

Wildland fire scientists have made substantial advances in measuring fire behavior, but properly collecting data is often beyond the capacity of prescribed fire managers and by definition all but impossible for wildfire events. While a method for the immediate assessment of burn severity has been developed around multispectral imagery from space-based Earth observation systems, there has been little comparison of these post hoc metrics to actual fire behavior. Meanwhile, the application of research results from experimental prescribed burns to rangeland affected by wildfire can be impeded by a lack of understanding of how immediate burn severity differs between wildfires and prescribed burns, especially in rangelands. Overall, much of what is known about wildland fire behavior, severity, and effects comes from forests, whereas rangelands are characterized by having lower fuel loads comprised of fine vegetation that promotes high rates of spread and brief residence time. This paper provides rangeland-specific information on the relationships between direct field-based fire behavior measurements and a space-based index of burn severity (differenced Normalized Burn Ratio, ΔNBR, from Sentinel-2 imagery), and uses those data to compare burn severity across 54 prescribed burns in North Dakota, USA, and 28 nearby wildfires in the US Northern Great Plains. In prescribed burns, remotely sensed burn severity increased with rate of spread and flame temperature 15 cm above the ground, but had no statistically significant relationship with soil surface temperature. In the semi-arid western zone of the Northern Great Plains, wildfires and prescribed burns had similar, low–moderate severity; wildfires in the eastern zone tended to be of moderately high severity and thus greater than the low severity of the experimental prescribed burns. By describing meaningful gradients in surface fire behavior in rangelands with ΔNBR, even those without the capacity to measure fire behavior in the field can monitor prescribed fire effectiveness and incorporate burn severity in adaptive management plans. Understanding the relationship between burn severity across wildfires and prescribed burns is a critical step in applying knowledge gained from research on prescribed fires to areas impacted by wildfire. Resistance to prescribed burning might be overcome by increasing livestock managers’ experience with post-fire forage resources through grazing areas burned in unintentional wildfires, but current practice and policy discourage or outright prevent ranchers from doing so. Future research ought to connect burn severity with ecosystem recovery metrics to ensure post-fire grazing does not impair rangeland sustainability. Full article

Focusing on the R&D demand for green earthen building materials in coastal high-temperature and high-humidity areas, this study explores the biocolonization control mechanism of raw earth–rubble walls, taking the traditional raw earth–rubble walls of ancient buildings in Sanfang Qixiang, Fuzhou, as the research subject. FTIR, XRD, Raman, and SEM-EDS combined technologies were employed for characterization. The results show that the raw earth is rich in proteins, amino acids, and other nutrients, which provide the nutritional basis for plant growth. The raw earth and rubble share homologous mineral components. The rubble is fired from raw earth mixed with iron minerals such as hematite, with carbonaceous substances generated during the firing process. Iron, carbon, and potassium released from the weathered rubble may inhibit the growth of plant roots. The raw earth is relatively looser than the rubble, and the two form a dense–loose alternating structure. Combined with the secondary calcification mechanism in the raw earth, this structure resists the expansion and cracking of the wall and improves the viscosity and hardness of the wall. It is concluded that in a high-temperature and high-humidity environment, the raw earth first releases nutrients to promote plant growth. As time progresses, the relevant substances released by the rubble continuously inhibit root growth. Combined with the structural characteristics of the wall with high firmness and crack resistance, plants growing on the wall will not damage the wall structure. This finding provides a theoretical basis for the biocolonization control mechanism of raw earth–rubble walls and also offers practical references for the protection and sustainable reuse of raw earth buildings in similar areas. Full article

This article contends that Western philosophical traditions and Abrahamic spiritualities, while different, are entangled in the sense that together they represent distinct discursive performative epistemologies regarding how individuals inhabit the world. More specifically, what they share are social imaginaries that are founded on epistemologies of deficiency that radically separate human beings from other species and the Earth. It is argued further that these epistemologies are implicated in Western subjects’ instrumental, reifying, and exploitative dispositions and behaviors toward other species and the Earth, which the climate crisis makes apparent. Psychoanalysis can provide reasons for the emergence of these social imaginaries and their attendant resistance to changing how we dwell with other species and the Earth. In psychoanalytic parlance, epistemologies of deficiency entail projecting onto other species existential impermanence, which accompanies weak dissociation that assuages anxiety and fear regarding the impermanence of ourselves and our significations. Once persons become aware of this, they are ideally faced with deciding whether to take accountability and to change. Quantum physics/philosophy can provide a corrective lens for both psychoanalysis and Western spiritualities—a lens that accompanies more capacious epistemologies that invite ecologically inclusive, caring, and ethical ways of inhabiting a biodiverse world upon which matter–life–consciousness depend. Full article

This study explains how an extremely low electrical earthing resistance was achieved in challenging gravelly soil conditions. In the existing soil, a resistance of 5 ohms was measured using traditional earthing techniques. After excavating and removing the granular soil, it was replaced with fine-grained, sandy-silty clay, then compacted after moistening, reducing earthing resistance to 2.5 ohms. The goal was to achieve a resistance below 0.5 ohms, which is necessary for the precise operation of robotic welding machines. To achieve this, a hybrid strategy was employed, combining deep earthing by drilling with ground-enhancing compounds in the gravelly soil. In İzmir-Torbalı, a 40 m-deep borehole was drilled to install a copper electrode in water-saturated clay below the groundwater level. To increase the conductivity of the granular soil and ensure contact with the electrode, the borehole was filled with graphite powder. As a result, the earthing resistance reached only 0.28 ohms, proving the effectiveness of this method in high-resistance soils. Full article

Here, we report a highly efficient and stable catalytic system based on monometallic oxides supported on HY zeolites for the catalytic oxidation of chlorobenzene (CB). Among the transition and rare-earth metal oxides screened, the 30Cu/HY catalyst demonstrates exceptional performance, achieving near 100% CB conversion at 300 °C (500 ppm CB, 10,000 h⁻¹) alongside outstanding 24 h continuous stability without deactivation. Quantitative Py-IR analysis reveals that this superior activity is fundamentally driven by extensive solid-state ion exchange, forming robust Lewis acid centers (Cu-Y structures) that synergize with zeolitic Brønsted acid sites to efficiently polarize and cleave C-Cl bonds. Through an integrated approach combining in situ DRIFTS, real-time mass spectrometry, TGA, and NLDFT pore size analysis, we elucidate that the exceptional deep-oxidation capability of Cu/HY continuously mineralizes carbonaceous intermediates. This property minimizes coke deposition (2.91 wt%) and preserves the hierarchical pore architecture, preventing the coverage of active sites and severe pore blockage by partially oxidized intermediates (such as phenolic, aldehydic, and quinonic species) and stable carbonate species responsible for the deactivation of other metal oxides. These insights provide a mechanistic framework for the rational design of robust, chlorine-resistant catalysts for the sustainable abatement of persistent organic pollutants. Full article

Besides filled skutterudites with a high figure of merit, unfilled skutterudites also play an important role as thermoelectric materials; furthermore, they are easier to produce and do not need expensive rare earths as fillers. In the present review, thermoelectric properties (at 300 K and at the highest measured temperature) of more than 600 compositions from more than 230 publications between 1957 and 2025 were collected and evaluated. In various figures, the dependence of the peak ZT on the electrical resistivity, Seebeck coefficient, the power factor and the thermal conductivity is displayed for (i) binary CoSb₃, for (ii) CoSb₃ substituted at the Co-site, for (iii) substitution at the Sb-site or at both sites as well as for (iv) unfilled skutterudites without Co or Sb or Co and Sb. In most cases, the peak ZT equals the ZT at the highest measured temperature. Thermoelectric data are listed (i) to comply with the periodic chart and publishing year as well as (ii) in the form of a graphical overview of all discussed skutterudites. In this respect, this review will support the search for the ideal TE material for practical use. Full article

Global interest in sustainable building materials is increasing due to growing concerns regarding the environmental impacts of conventional construction materials, particularly fired clay bricks. Compressed Stabilized Earth Blocks (CSEBs) have emerged as a viable, cost-effective, and environmentally sustainable alternative for building construction. The incorporation of waste-derived additives in CSEBs not only addresses waste management challenges but also enhances the functional performance of earthen materials. This study presents a comprehensive synthesis of existing research on the influence of fibers, binders, stabilizers, and production processes on the performance characteristics of CSEBs. A systematic literature review was conducted following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020 guidelines, resulting in the identification and analysis of 256 relevant studies. The selected literature was synthesized using the Theories, Contexts, Characteristics, and Methodologies (TCCM) framework to map research trends and methodological approaches. The review indicates that fiber reinforcement primarily improves flexural strength and thermal performance, while binders significantly enhance compressive strength and erosion resistance. The findings also demonstrate that selected waste materials can partially replace natural soil, provided minimum material and performance standards are satisfied. The study highlights the need for standardized manufacturing guidelines and testing protocols to improve the reliability, scalability, and wider adoption of CSEBs in sustainable building applications. Full article

The continuous drive for higher efficiency in gas turbines has led to increased combustion temperatures, making the thermal shock resistance of thermal insulation tiles a critical factor limiting performance. Corundum–mullite multiphase ceramics are widely used in such applications; however, their performance is often constrained by an inherent trade-off between mechanical strength and thermal shock resistance. In this work, a synergistic modification strategy based on rare-earth disilicate phases was developed, wherein Y₂O₃ and SiC were incorporated into a corundum–mullite matrix to enable in situ formation and controlled distribution of Y₂Si₂O₇ via gel casting. During sintering, Y₂Si₂O₇ acts as a transient liquid phase, facilitating densification and grain boundary strengthening; upon thermal shock, it migrates to fill and heal grain boundaries and microcracks, thereby significantly enhancing thermal shock resistance. The optimized sample S5, sintered at 1400 °C, exhibited a bulk density of 2.12 g/cm³ and a bending strength of 68.43 MPa. Notably, after 30 thermal shock cycles (air cooling from 1000 °C to RT), its bending strength increased to 79.71 MPa, corresponding to a 16.48% enhancement. This work provides an effective strategy for incorporating rare-earth disilicates into multiphase ceramics and offers valuable guidance for the development of high-performance components for gas turbines. Full article