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A review of artificial intelligence (AI)-based applications to nanocomposites
No full textRecent progress in artificial intelligence (AI) techniques has attracted interest from researchers in various engineering fields, including materials science and engineering. AI has enabled materials researchers to explore vast materials design spaces, which were previously inaccessible due to the inherent limitations of conventional techniques (viz., experiments and physics-based computational models). This is particularly true for the design of nanocomposites because of the many degrees of freedom associated with both material composition and manufacturing parameters. The primary motivation of this review is to report how AI techniques are being used in nanocomposite materials design, with special attention given to the manufacturing and property prediction of nanocomposites using AI techniques
A controlled-source physical model for long period seismic events
Get PDFLong-period seismic events (LPs) are observed within active volcanoes, hydrothermal systems and hydraulic fracturing. The prevailing model for LP seismic events suggests that they result from pressure disturbances in fluid-filled cracks that generate slow, dispersive waves known as Krauklis waves. These waves oscillate within the crack, causing it to act as a seismic resonator whose far-field radiations are known as LP events. Since these events are generated from fluid-filled cracks, they have been used to analyse fluid transport and fracturing in geological settings. Additionally, they are deemed precursors to volcanic eruptions. However, other mechanisms have been proposed to explain LP seismicity. Thus, a robust interpretation of these events requires understanding all parameters contributing to LP seismicity. To achieve this, for the first time, we have developed a physical model to investigate LP seismicity under controlled-source conditions. The physical model consists of a 30 cm × 15 cm × 0.2 cm crack embedded within a concrete slab with dimensions of 3 m × 3 m × 0.24 m. Using this apparatus, we investigate fundamental factors affecting long-period seismic signals, including crack stiffness, fluid density and viscosity, radiation patterns and triggering location. Our findings are consistent with the theoretical model for Krauklis waves within a fluid-filled crack. In this study, we examine the interplay between fluid properties and characteristics of waves within and radiated from the crack model. Records from a pressure transducer within the crack model have the same frequency characteristics as the surface sensors, indicating that the surface sensors are recording the crack waves. Because the crack stiffness parameters for all the fluids are relatively high, fluid density variations have a larger effect on the crack wave frequency, with higher density fluids yielding lower resonance frequencies. Similarly, the quality factor (Q) decreases with increasing fluid density. We also find that an increase in fluid viscosity along with the increased fluid density results in a decrease in resonance frequency and Q. Trigger locations at the middle of the crack length and width most effectively resonated the first and second transverse modes. Thus, this physical model can offer new horizons in understanding LP seismicity and bridge the gap between theoretical models and observed LP signals
Wind Shear and the Role of Eddy Vapor Transport in Driving Water Convection on Jupiter
Get PDFRecent observations of convection in the Jovian atmosphere have demonstrated that convection is strongly concentrated at specific locations on the planet. For instance, observations of lightning show that the cyclonic features (e.g., belts and folded filamentary regions) show increased convective activity compared to anticyclonic regions. Meanwhile, the distribution of ammonia and water vapor shows a large enrichment near the equator, which is also suggestive of strong upwelling and convective activity. Marrying these different observations is challenging owing to a lack of data concerning the characteristics of the deep Jovian atmosphere and a resulting inability to observe the true deep source of the various convective phenomena. To understand the nature of these convective events and the role of the structure of the deep atmosphere in driving convective events, we run simulations of cloud formation and convection using the Explicit Planetary hybrid-Isentropic Coordinate General Circulation Model. We vary the dynamics of the atmosphere by parameterizing the deep wind shear and studying the resulting effect on the strength, frequency, and distribution of convective storms. We find that convection in our model is strongly tied to the local dynamics and the deep wind shear. We further decompose the generation of convective available potential energy into three components (thermal, mechanical, and moist/chemical) and find that the chemical mechanism is the strongest component, working to advect water vapor from moisture-rich regions to moisture-poor regions and to drive convection along a “moisture front.
THERMIONIC EMISSION COMPUTATIONAL DESIGN OF RARE-EARTH HEXABORIDE CATHODES IN AN OXYGEN ENVIRONMENT
Get PDFThis project seeks to optimize a rare-earth hexaboride cathode material for thermionic emission Hall-effect thruster in an air breathing electric propulsion system for the very low earth orbit (VLEO). The main atmospheric constituents in VLEO are nitrogen and atomic oxygen. The presence of oxygen causes the Hall-effect thruster cathode to poison, sharply decreasing its electron emission, thus reducing thrust. Two cathodes used for thermionic emission are dispenser cathodes and lanthanum hexaboride (LaB6) cathodes, with the LaB6 cathodes having better resistance to oxygen poisoning. It is desired to develop a cathode that can better tolerate the oxygen environment than LaB6, so the alloys of LaB6 and other rare-earth hexaborides are explored with respect to their: Work function, determined via the Hashimoto approximation Stable oxide formation at operation temperature and pressure, assessed with Ellingham diagrams Pilling-Bedworth ratio using the most stable oxide to evaluate the oxide’s protectiveness of the cathode surface
Resist!: Sustaining forest carbon sequestration and wood production after insect disturbance
No full textDisturbances from insect pests threaten ecologically and economically important goods and services supplied by forests, including wood production and carbon sequestration. We highlight the factors that influence these services’ resistance, a term quantifying the initial response to disturbance. Insects inflict damage through a range of mechanisms, prompting distinct plant physiological responses that scale to influence ecosystem processes and, with time, goods and services. The degree and timing of tree mortality and defoliation affect the amount of residual vegetation available to support compensatory wood production and influence carbon sequestration by changing rates of detritus-fueled decomposition. Compounding, or sequential, insect attacks may prime a forest for additional disturbance, further eroding wood production and carbon sequestration. Forest management practices that promote biological and structural diversity, and augment or retain limiting biological and nutrient resources, may buffer against the effects of insect pests on wood production and carbon sequestration
Mycorrhiza-assisted phytoremediation of spiked chromium-contaminated soil: Assessing AMF-vetiver symbiosis for Cr accumulation and soil quality enhancement
No full textChromium (Cr) is a hazardous pollutant in industrial and mining areas and threatens soil ecosystems. Mycorrhiza-assisted phytoremediation serves as an eco-friendly and effective approach to mitigate Cr contamination from soil. In this investigation, varying Cr dosages (100 mg kg−1, 500 mg kg−1, and 1000 mg kg−1) were applied into the soil alongside vetiver plants (Chrysopogon zizanioides L.) inoculated with three different AMF species (Claroideoglomus claroideum, Glomus hoi, and Claroideoglomus etunicatum). The results indicated that AMF inoculation enhanced Cr accumulation (1.96 folds, 1.63 folds) in the root tissue of vetiver compared to the control. Among the AMF species, Glomus hoi demonstrated the highest effectiveness in reducing Cr bioavailability (P10: 0.247 mg kg−1, P11: 1.117 mg kg−1, and P12: 4.789 mg kg−1) in the soil, followed by Claroideoglomus claroideum and Claroideoglomus etunicatum at post-harvest. Additionally, microbial and enzymatic activity improved in the presence of AMF compared to the control, as AMF alleviated Cr-induced stress by stimulating antioxidant activity. AMF enhanced soil glomalin-related proteins and colonization percentage, thereby promoting plant growth. The correlation and principal component analysis depict a positive association between Cr accumulation in vetiver (root and shoot) and the different Cr phases. Interestingly, in the presence of Glomus hoi, the VTF (\u3c 1) and VBCF (\u3e1) indicate that this symbiotic association is well-suited for phytoremediation applications. Hence, AMF-assisted phytoremediation emerges as a viable and sustainable approach, offering advantages over other remediation techniques and providing potential solutions for managing soil Cr contamination
Defoliation frequency outweighs timing as a driver of tree mortality related to drought-defoliation interaction
No full textClimate change is expected to increase the frequency and severity of forest disturbance, making it more likely that multiple forms of disturbance will occur simultaneously. The resulting disturbance interactions could have compounding effects on tree mortality. Between 2016 and 2018, southern New England experienced both severe drought and spongy moth defoliation resulting in widespread tree mortality. The frequency and timing of defoliation varied substantially across the region, while drought conditions were relatively uniform. Our goal was to assess the influence of variable defoliation frequency and timing (relative to the preceding drought) on variation in tree mortality rates using a combination of remotely sensed data on defoliation patterns and field data on forest stand characteristics and tree mortality. Stand-level tree basal area mortality associated with the drought-defoliation interaction averaged 19 % across all study sites, with a maximum level of 50 %. Based on our analysis, mortality rates were most strongly explained by combinations of defoliation severity, frequency, and stand characteristics (R2 = 0.52–0.60). Sites experiencing only drought but no defoliation or drought and a single year of defoliation had comparably low mortality rates, while sites experiencing drought and multi-year defoliation had higher mortality rates. Our research suggests that defoliation frequency was an important factor in predicting tree mortality, while defoliation timing and drought itself had less importance in this interaction
Derivation and Experimental Validation of a Parameterized Nonlinear Froude–Krylov Force Model for Heaving-Point-Absorber Wave Energy Converters
Get PDFWave energy converters (WECs) have gained significant attention as a promising renewable energy source. Optimal control strategies, crucial for maximizing energy extraction, have traditionally relied on linear models based on small motion assumptions. However, recent studies indicate that these models do not adequately capture the complex dynamics of WECs, especially when large motions are introduced to enhance power absorption. The nonlinear Froude–Krylov (FK) forces, particularly in heaving-point-absorbers with varying cross-sectional areas, are acknowledged as key contributors to this discrepancy. While high-fidelity computational models are accurate, they are impractical for real-time control applications due to their complexity. This paper presents a parameterized approach for expressing nonlinear FK forces across a wide range of point-absorber buoy shapes inspired by implementing real-time, model-based control laws. The model was validated using measured force data for a stationary spherical buoy subjected to regular waves. The FK model was also compared to a closed-form buoyancy model, demonstrating a significant improvement, particularly with high-frequency waves. Incorporating a scattering model further enhanced force prediction, reducing error across the tested conditions. The outcomes of this work contribute to a more comprehensive understanding of FK forces across a broader range of buoy configurations, simplifying the calculation of the excitation force by adopting a parameterized algebraic model and extending this model to accommodate irregular wave conditions
The Influence of Extrusion Geometry and Ratio on Extrudate Mechanical Properties for a 6005A Alloy Containing Either Sc and Zr or Cr and Mn Dispersoid Formers
Get PDFThere is a demand for a 6005A series extrusion alloy with improved strength that maintains good extrudability. Replacing Mn and Cr dispersoid formers with Sc and Zr is expected to increase the room temperature mechanical properties while not affecting extrudability. Al3X dispersoids with a Sc core surrounded by a Zr shell are stable at higher temperatures and enhance recrystallization resistance and precipitation strengthening. However, there is little information on how the Sc and Zr additions affect the properties of an extrudate as a function of extrusion geometry and ratio. A 6005A series alloy with Cr and Mn additions is compared to an alloy with Sc and Zr additions with rod and flat cross-sections at extrusion ratios of 25 and 92. The results show that Sc and Zr additions increased yield strength and ultimate tensile strength while maintaining ductility compared to Cr and Mn additions. Rod shapes performed significantly better than flat shapes, but there was no significant effect of extrusion ratio
Support for the US Endangered Species Act Is High and Steady Over the Past Three Decades
Get PDFConservation professionals expect increased attempts to weaken the US Endangered Species Act (ESA) during the second Trump administration. As such, it is important to understand Americans’ level of support for the ESA. Prior research indicates that support for the ESA remained consistently strong across four studies conducted over a two-decade period, 1996–2015. The research presented here extends those observations to six studies conducted over a three-decade period, 1996–2025. We find that support of the ESA over that period has remained consistently high, at about 84%, and opposition has remained consistently low, at about 12%. We also report on other trends and patterns in support for the ESA, highlighting high and growing support for the ESA among politically conservative people and the absence of any rural–urban divide in support for the ESA